,,the ,,working ,,of ,,steel ,,annealing1 ,,heat ,,treating ,,and ,,hardening ,,of ,,carbon ,,and ,,alloy ,,steel ,,by ,,fred ,h4 ,,colvin ,member ,american ,society of ,mechanical ,engineers and ,franklin ,institute2 ,editor of the ,american ,machinist1 ,author of ,machine ,shop ,arithmetic1 ,machine ,shop ,calculations1 ,american ,machinists' ,hand ,book4 ,,and ,k4 ,a4 ,,juthe1 ,m4,e4 ,chief ,engineer1 ,american ,metallurgical ,corp4 ,member ,american ,society ,mechanical ,engineers1 ,american ,society ,testing ,materials1 ,heat ,treatment ,association1 ,etc4 ,,second ,,edition ,,third ,,impression ,mc,g,r,a,w-,,hill ,,book ,,company1 ,inc4 ,,new ,,york3 #cgj ,,seventh ,,avenue ,,london3 #f #h ,,bouverie ,,st41 ,e4 ,c4 #d ,,preface ,,to ,,second ,,edition ,advantage has been taken of a reprinting to revise1 extensively1 the portions of the book relating to the modern science of metallography4 ,considerable of the matter relating to the influence of chemical composition upon the properties of alloy steels has been rewritten4 ,furthermore1 opportunity has been taken to include some brief notes on methods of physical testing--whereby the metallurgist judges of the excellence of his metal in advance of its actual performance in service4 ,,new ,,york1 ,n4 ,y41 ,august1 #aibb4 ,,preface ,,to ,,first ,,edition ,the ever increasing uses of steel in all industries and the necessity of securing the best results with the material used1 make a knowledge of the proper working of steel more important than ever before4 ,for it is not alone the quality of the steel itself or the alloys used in its composition1 but the proper working or treatment of the steel which determines whether or not the best possible use has been made of it4 ,with this in mind1 the authors have drawn1 not only from their own experience but from the best sources available1 information as to the most approved methods of working the various kinds of steel now in commercial use4 ,these include low carbon1 high carbon and alloy steels of various kinds1 and from a variety of industries4 ,the automotive field has done much to develop not only new alloys but efficient methods of working them and has been drawn on liberally so as to show the best practice4 ,the practice in government arsenals on steels used in fire arms is also given4 ,while not intended as a treatise on steel making or metallurgy in any sense1 it has seemed best to include a little information as to the making of different steels and to give considerable general information which it is believed will be helpful to those who desire to become familiar with the most modern methods of working steel4 ,it is with the hope that this volume1 which has endeavored to give due credit to all sources of information1 may prove of value to its readers and through them to the industry at large4 ,july1 #aiba4 ,,the ,,authors4 ,,contents ,,preface ,,introduction ,,chapter ,i4 ,,steel ,,making ,,ii4 ,,composition ,,and ,,properties ,,of ,,steels ,,iii4 ,,alloys ,,and ,,their ,,effect ,,upon ,,steel ,,iv4 ,,application ,,of ,,liberty ,,engine ,,materials ,,to ,,the ,,automotive ,,industry ,v4 ,,the ,,forging ,,of ,,steel ,,vi4 ,,annealing ,,vii4 ,,case-,,hardening ,,or ,,surface-,,carburizing ,,viii4 ,,heat ,,treatment ,,of ,,steel ,,ix4 ,,hardening ,,carbon ,,steel ,,for ,,tools ,x4 ,,high ,,speed ,,steel ,,xi4 ,,furnaces ,,xii4 ,,pyrometry ,,and ,,pyrometers ,,appendix ,,index ,,introduction ,,the ,,abc ,,of ,,iron ,,and ,,steel ,in spite of all that has been written about iron and steel there are many hazy notions in the minds of many mechanics regarding them4 ,it is not always clear as to just what makes the difference between iron and steel4 ,we know that high-carbon steel makes a better cutting tool than low-carbon steel4 ,and yet carbon alone does not make all the difference because we know that cast iron has more carbon than tool steel and yet it does not make a good cutting tool4 ,pig iron or cast iron has from #c to #e per cent carbon1 while good tool steel rarely has more than #a-a_/d per cent of carbon1 yet one is soft and has a coarse grain1 while the other has a fine grain and can be hardened by heating and dipping in water4 ,most of the carbon in cast iron is in a form like graphite1 which is almost pure carbon1 and is therefore called graphitic carbon4 ,the resemblance can be seen by noting how cast-iron borings blacken the hands just as does graphite1 while steel turnings do not have the same effect4 ,the difference is due to the fact that the carbon in steel is not in a graphitic form as well as because it is present in smaller quantities4 ,in making steel in the old way the cast iron was melted and the carbon and other impurities burned out of it1 the melted iron being stirred or puddled1 meanwhile4 ,the resulting puddled iron1 also known as wrought iron1 is very low in carbon2 it is tough1 and on being broken appears to be made up of a bundle of long fibers4 ,then the iron was heated to redness for several days in material containing carbon 7charcoal7 until it absorbed the desired amount1 which made it steel1 just as case-hardening iron or steel adds carbon to the outer surface of the metal4 ,the carbon absorbed by the iron does not take on a graphitic form1 however1 as in the case of cast iron1 but enters into a chemical compound with the iron1 a hard brittle substance called cementite by metallurgists4 ,in fact1 the difference between the hard1 brittle cementite and the soft1 greasy graphite1 accounts for many of the differences between steel and gray cast iron4 ,wrought iron1 which has very little carbon of any sort in it1 is fairly soft and tough4 ,the properties of wrought iron are the properties of pure iron4 ,as more and more carbon is introduced into the iron1 it combines with the iron and distributes itself throughout the metal in extremely small crystals of cementite1 and this brittle1 hard substance lends more and more hardness and strength to the steel1 at the expense of the original toughness of the iron4 ,as more and more carbon is contained in the alloy--for steel is a true alloy--it begins to appear as graphite1 and its properties counteract the remaining brittle cementite4 ,eventually1 in gray cast iron1 we have properties which would be expected of wrought iron1 whose tough metallic texture was shot through with flakes of slippery1 weak graphite4 ,but to return to the methods of making steel tools in use #ajj years ago4 ,the iron bars1 after heating in charcoal1 were broken and the carbon content judged by the fracture4 ,those which had been in the hottest part of the furnace would have the deepest case and highest carbon4 ,so when the steel was graded1 and separated into different piles1 a few bars of like kind were broken into short lengths1 melted in fire-clay crucibles at an intense white heat1 cast carefully into iron molds1 and the resulting ingot forged into bars under a crude trip hammer4 ,this melting practice is still in use for crucible steel1 and will be described further on page #d4 ,,the ,,working ,,of ,,steel ,,annealing1 ,,heat ,,treating ,,and ,,hardening ,,of ,,carbon ,,and ,,alloy ,,steel ,,chapter ,i ,,steel ,,making ,there are four processes now used for the manufacture of steel4 ,these are3 ,the ,bessemer1 ,open ,hearth1 ,crucible and ,electric ,furnace ,methods4 ,,bessemer ,,process ,the bessemer process consists of charging molten pig iron into a huge1 brick-lined pot called the bessemer converter1 and then in blowing a current of air through holes in the bottom of the vessel into the liquid metal4 ,the air blast burns the white hot metal1 and the temperature increases4 ,the action is exactly similar to what happens in a fire box under forced draft4 ,and in both cases some parts of the material burn easier and more quickly than others4 ,thus it is that some of the impurities in the pig iron--including the carbon--burn first1 and if the blast is shut off when they are gone but little of the iron is destroyed4 ,unfortunately sulphur1 one of the most dangerous impurities1 is not expelled in the process4 ,a bessemer converter is shown in ,fig4 #a1 while ,fig4 #b shows the details of its construction4 ,this shows how the air blast is forced in from one side1 through the trunnion1 and up through the metal4 ,where the steel is finished the converter is tilted1 or swung on its trunnions1 the blast turned off1 and the steel poured out of the top4 ,,open ,,hearth ,,process ,the open hearth furnace consists of a big brick room with a low arched roof4 ,it is charged with pig iron and scrap through doors in the side walls4 ,illustration3 ,,fig4 #a4--;,a typical ,bessemer converter4 ,through openings at one end of the furnace come hot air and gas1 which burn in the furnace1 producing sufficient heat to melt the charge and refine it of its impurities4 ,lime and other nonmetallic substances are put in the furnace4 ,these melt1 forming a slag which floats on the metal and aids materially in the refining operations4 ,in the bessemer process air is forced through the metal4 ,in the open-hearth furnace the metal is protected from the flaming gases by a slag covering4 ,therefore it is reasonable to suppose that the final product will not contain so much gas4 ,illustration3 ,,fig4 #b4--;,action of ,bessemer converter4 ,illustration3 ,,fig4 #c4--,regenerative open hearth furnace4 ,a diagram of a modern regenerative furnace is shown in ,fig4 #c4 ,air and gas enter the hearth through chambers loosely packed with hot fire brick1 burn1 and exit to the chimney through another pair of chambers1 giving to them some of the heat which would otherwise waste4 ,the direction is reversed about every twenty minutes by changing the position of the dampers4 ,,crucible ,,steel ,crucible steel is still made by melting material in a clay or graphite crucible4 ,each crucible contains about #dj lb4 of best puddled iron1 #dj lb4 of clean mill scrap--ends trimmed from tool steel bars--and sufficient rich alloys and charcoal to make the mixture conform to the desired chemical analysis4 ,the crucible is covered1 lowered into a melting hole 7,fig4 #d7 and entirely surrounded by burning coke4 ,in about four hours the metal is converted into a quiet white hot liquid4 ,several crucibles are then pulled out of the hole1 and their contents carefully poured into a metal mold1 forming an ingot4 ,illustration3 ,,fig4 #d4--,typical crucible furnace4 ,if modern high-speed steel is being made1 the ingots are taken out of the molds while still red hot and placed in a furnace which keeps them at this temperature for some hours1 an operation known as annealing4 ,after slow cooling any surface defects are ground out4 ,ingots are then reheated to forging temperature1 hammered down into billets of about one-quarter size1 and #aj to #bj per cent of the length cut from the top4 ,after reheating the billets are hammered or rolled into bars of desired size4 ,finished bars are packed with a little charcoal into large pipes1 the ends sealed1 and annealed for two or three days4 ,after careful inspection and testing the steel is ready for market4 ,,the ,,electric ,,process ,the fourth method of manufacturing steel is by the electric furnace4 ,these furnaces are of various sizes and designs2 their size may be sufficient for only #ajj lb4 of metal--on the other hand electric furnaces for making armor-plate steel will hold #dj tons of steel4 ,designs vary widely according to the electrical principles used4 ,a popular furnace is the #f-ton ,heroult furnace illustrated in ,fig4 #e4 ,it is seen to be a squat kettle1 made of heavy sheet steel1 with a dished bottom and mounted so it can be tilted forward slightly and completely drained4 ,this kettle is lined with special fire brick which will withstand most intense heat and resist the cutting action of hot metal and slag4 ,for a roof1 a low dome of fire brick is provided4 ,the shell and lining is pierced in front for a pouring spout1 and on either side by doors1 through which the raw material is charged4 ,two or three carbon electrodes--#ah-;in4 cylinders of specially prepared coke or graphite--extend through holes in the roof4 ,electrical connections are made to the upper ends1 and a very high current sent through them4 ,this causes tremendous arcs to form between the lower ends of the electrodes and the metal below1 and these electric arcs are the only source of heat in this style of furnace4 ,electric furnaces can be used to do the same work as is done in crucible furnaces--that is to say1 merely melt a charge of carefully selected pure raw materials4 ,on the other hand it can be used to produce very high-grade steel from cheap and impure metal1 when it acts more like an open-hearth furnace4 ,it can push the refining even further than the latter furnace does1 for two reasons3 first the bath is not swept continuously by a flaming mass of gases2 second1 the temperature can be run up higher1 enabling the operator to make up slags which are difficult to melt but very useful to remove small traces of impurities from the metal4 ,electric furnaces are widely used1 not only in the iron industry1 but in brass1 copper and aluminum works4 ,it is a useful melter of cold metal for making castings4 ,it can be used to convert iron into steel or vice versa4 ,its most useful sphere1 however1 is as a refiner of metal1 wherein it takes either cold steel or molten steel from open hearth or bessemer furnaces1 and gives it the finishing touches4 ,illustration3 ,,fig4 #e4--,slagging off an electric furnace4 ,illustration3 ,,fig4 #f4--,pouring the ingots4 ,as an illustration of the furnace reactions that take place the following schedule is given1 showing the various stages in the making of a heat of electric steel4 ,the steel to be made was a high-carbon chrome steel used for balls for ball bearings3 #f-,,ton ,,heroult ,,furnace #aa3ej ,a4,m4--,material charged3 ,boiler plate #e1ihj lb4 ,stampings #e1iia lb4 ----------- #aa1iga lb4 ,limestone #gjj lb4 #ab3bi ,p4,m4--,completed charging 7current switched on74 #c3bj ,p4,m4--,charge melted down4 ,preliminary analysis under black slag4 ,analysis3 ,carbon ,silicon ,sulphur ,phosphorus ,manganese #j4jf #j4jad #j4jcb #j4jji #j4jh ,note the practical elimination of phosphorus4 #c3dj ,p4,m4--,the oxidizing 7black7 slag is now poured and skimmed off as clean as possible to prevent rephosphorizing and to permit of adding carburizing materials4 ,for this purpose carbon is added in the form of powdered coke1 ground electrodes or other forms of pure carbon4 ,the deoxidizing slag is now formed by additions of lime1 coke and fluorspar 7and for some analyses ferrosilicon74 ,the slag changes from black to white as the metallic oxides are reduced by these deoxidizing additions and the reduced metals return to the bath4 ,a good finishing slag is creamy white1 porous and viscous4 ,after the slag becomes white1 some time is necessary for the absorption of the sulphur in the bath by the slag4 ,the white slag disintegrates to a powder when exposed to the atmosphere and has a pronounced odor of acetylene when wet4 ,further additions of recarburizing material are added as needed to meet the analysis4 ,the further reactions are shown by the following3 #c3dj ,p4,m4--,recarburizing material added3 #acj lb4 ground electrodes4 #be lb4 ferromanganese4 ,analysis3 ,carbon ,silicon ,sulphur ,phosphorus ,manganese #j4gf #j4jaa #j4jcj #j4jjh #j4bf ,to form white slag there was added3 #bbe lb4 lime4 #ge lb4 powdered coke4 #ee lb4 fluorspar4 #d3ej ,p4,m4-- ,analysis3 ,carbon ,silicon ,sulphur ,phosphorus ,manganese #j4ge #j4jad #j4jab #j4jjh #j4bh ,note reduction of the sulphur content4 ,during the white-slag period the following alloying additions were made3 #ejj lb4 pig iron4 #hj lb4 ferrosilicon4 #i lb4 ferromanganese4 #adf lb4 #f per cent carbon ferrochrome4 ,the furnace was rotated forward to an inclined position and the charge poured into the ladle1 from which in turn it was poured into molds4 #e3dj ,p4,m4--,heat poured4 ,analysis3 ,carbon ,silicon ,sulphur ,phosphorus ,manganese ,chromium #j4ig #j4be #j4jad #j4jac #j4cc #j4gj ,ingot weight poured #id4j per cent ,scull #b4g per cent ,loss #c4c per cent ,total current consumption for the heat1 #d1gjj k,w4-hr4 or #gaj kw4-hr4 per ton4 ,electric steel1 in fact1 all fine steel1 should be cast in big-end-up molds with refractory hot tops to prevent any possibility of pipage in the body of the ingot4 ,in the further processing of the ingot1 whether in the rolling mill or forge1 special precautions should be taken in the heating1 in the reduction of the metal and in the cooling4 ,no attempt is made to compare the relative merits of open hearth and electric steel2 results in service1 day in and day out1 have1 however1 thoroughly established the desirability of electric steel4 ,ten years of experience indicate that electric steel is equal to crucible steel and superior to open hearth4 ,the rare purity of the heat derived from the electric are1 combined with definite control of the slag in a neutral atmosphere1 explains in part the superiority of electric steel4 ,commenting on this recently ,dr4 ,h4 ,m4 ,howe stated that in the open hearth process you have such atmosphere and slag conditions as you can get1 and in the electric you have such atmosphere and slag conditions as you desire4 ,another type of electric furnace is shown in ,figs4 #g and #h4 ,this is the ,ludlum furnace1 the illustrations showing a #aj-ton size4 ,figure #g shows it in normal1 or melting position1 while in ,fig4 #h it is tilted for pouring4 ,in melting1 the electrodes first rest on the charge of material in the furnace4 ,after the current is turned on they eat their way through1 nearly to the bottom4 ,by this time there is a pool of molten metal beneath the electrode and the charge is melted from the bottom up so that the roof is not exposed to the high temperature radiating from the open arc4 ,the electrodes in this furnace are of graphite1 #i in4 in diameter and the current consumed is about #ejj kw4-hr4 per ton4 ,illustration3 ,,fig4 #g4--,ludlum electric furnace4 ,illustration3 ,,fig4 ,s4--,the furnace tilted for pouring4 ,one of the things which sometimes confuse regarding the contents of steel is the fact that the percentage of carbon and the other alloys are usually designated in different ways4 ,carbon is usually designated by points and the other alloys by percentages4 ,the point is one ten-thousandth while #a per cent is one one-hundredth of the whole4 ,in other words1 one hundred point carbon is steel containing #a per cent carbon4 ,twenty point carbon1 such as is used for carbonizing purposes is #j4bj per cent4 ,tool steel varies from one hundred to one hundred and fifty points carbon1 or from #a4jj to #a4ej per cent4 ,nickel1 chromium1 etc41 are always given in per cent1 as a #c4e per cent nickel1 which means exactly what it says--#c-a_/b parts in #ajj4 ,bearing this difference in mind all confusion will be avoided4 ,,classifications ,,of ,,steel ,among makers and sellers1 carbon tool-steels are classed by grade and temper4 ,the word grade is qualified by many adjectives of more or less cryptic meaning1 but in general they aim to denote the process and care with which the steel is made4 ,temper of a steel refers to the carbon content4 ,this should preferably be noted by points1 as just explained2 but unfortunately1 a #ec-point steel 7containing #j4ec per cent carbon7 may locally be called something like ,no4 #c temper4 ,a widely used method of classifying steels was originated by the ,society of ,automotive ,engineers4 ,each specification is represented by a number of #d digits1 the first figure indicating the class1 the second figure the approximate percentage of predominant alloying element1 and the last two the average carbon content in points4 ,plain carbon steels are class #a1 nickel steels are class #b1 nickel-chromium steels are class #c1 chromium steels are class #e1 chromium-vanadium steels are class #f1 and silico-manganese steels are class #i4 ,thus by this system1 steel #bcdj would be a #c per cent nickel steel with #j4dj per cent carbon2 or steel #ajbe would be a #j4be plain carbon steel4 ,steel makers have no uniform classification for the various kinds of steel or steels used for different purposes4 ,the following list shows the names used by some of the well-known makers3 ,air-hardening steel ,chrome-vanadium steel ,alloy steel ,circular saw plates ,automobile steel ,coal auger steel ,awl steel ,coal mining pick or cutter steel ,axe and hatchet steel ,coal wedge steel ,band knife steel ,cone steel ,band saw steel ,crucible cast steel ,butcher saw steel ,crucible machinery steel ,chisel steel ,cutlery steel ,chrome-nickel steel ,drawing die steel 7,wortle7 ,drill rod steel ,patent1 bush or hammer steel ,facing and welding steel ,pick steel ,fork steel ,pivot steel ,gin saw steel ,plane bit steel ,granite wedge steel ,quarry steel ,gun barrel steel ,razor steel ,hack saw steel ,roll turning steel ,high-speed tool steel ,saw steel ,hot-rolled sheet steel ,scythe steel ,lathe spindle steel ,shear knife steel ,lawn mower knife steel ,silico-manganese steel ,machine knife steel ,spindle steel ,magnet steel ,spring steel ,mining drill steel ,tool holder steel ,nail die shapes ,vanadium tool steel ,nickel-chrome steel ,vanadium-chrome steel ,paper knife steel ,wortle steel ,passing to the tonnage specifications1 the following table from ,tiemann's excellent pocket book on ,iron and ,steel1 will give an approximate idea of the ordinary designations now in use3 ,approximate ,grades carbon range ,common uses ,extra soft #j4jh-j4ah ,pipe1 chain and other welding purposes2 7dead soft7 case-hardening purposes2 rivets2 pressing and stamping purposes4 ,structural 7soft7 #j4ae-j4be ,structural plates1 shapes and bars for 7medium7 bridges1 buildings1 cars1 locomotives2 boiler 7flange7 steel2 drop forgings2 bolts4 ,medium #j4bj-j4ce ,structural purposes 7ships72 shafting2 automobile parts2 drop forgings4 ,medium hard #j4ce-j4fj ,locomotive and similar large forgings2 car axles2 rails4 ,hard #j4fj-j4he ,wrought steel wheels for steam and electric railway service2 locomotive tires2 rails2 tools1 such as sledges1 hammers1 pick points1 crowbars1 etc4 ,spring #j4he-a4je ,automobile and other vehicle springs2 tools1 such as hot and cold chisels1 rock drills and shear blades4 ,spring #j4ij-a4ae ,railway springs2 general machine shop tools4 ,,chapter ,,ii ,,composition ,,and ,,properties ,,of ,,steel ,it is a remarkable fact that one can look through a dozen text books on metallurgy and not find a definition of the word steel4 ,some of them describe the properties of many other irons and then allow you to guess that everything else is steel4 ,if it was difficult a hundred years ago to give a good definition of the term when the metal was made by only one or two processes1 it is doubly difficult now1 since the introduction of so many new operations and furnaces4 ,we are in better shape to know what steel is than our forefathers4 ,they went through certain operations and they got a soft malleable1 weldable metal which would not harden2 this they called iron4 ,certain other operations gave them something which looked very much like iron1 but which would harden after quenching from a red heat4 ,this was steel4 ,not knowing the essential difference between the two1 they must distinguish by the process of manufacture4 ,to-day we can make either variety by several methods1 and can convert either into the other at will1 back and forth as often as we wish2 so we are able to distinguish between the two more logically4 ,we know that iron is a chemical element--the chemists write it ,fe for short1 after the ,latin word ferrum1 meaning iron--it is one of those substances which cannot be separated into anything else but itself4 ,it can be made to join with other elements2 for instance1 it joins with the oxygen in the air and forms scale or rust1 substances known to the chemist as iron oxide4 ,but the same metal iron can be recovered from that rust by abstracting the oxygen2 having recovered the iron nothing else can be extracted but iron2 iron is elemental4 ,we can get relatively pure iron from various minerals and artificial substances1 and when we get it we always have a magnetic metal1 almost infusible1 ductile1 fairly strong1 tough1 something which can be hardened slightly by hammering but which cannot be hardened by quenching4 ,it has certain chemical properties1 which need not be described1 which allow a skilled chemist to distinguish it without difficulty and unerringly from the other known elements--nearly #ajj of them4 ,carbon is another chemical element1 written ,c for short1 which is widely distributed through nature4 ,carbon also readily combines with oxygen and other chemical elements1 so that it is rarely found pure2 its most familiar form is soot1 although the rarer graphite and most rare diamond are also forms of quite pure carbon4 ,it can also be readily separated from its multitude of compounds 7vegetation1 coal1 limestone1 petroleum7 by the chemist4 ,with the rise of knowledge of scientific chemistry1 it was quickly found that the essential difference between iron and steel was that the latter was iron plus carbon4 ,consequently it is an alloy1 and the definition which modern metallurgists accept is this3 ,steel is an iron-carbon alloy containing less than about #b per cent carbon4 ,of course there are other elements contained in commercial steel1 and these elements are especially important in modern alloy steels1 but carbon is the element which changes a soft metal into one which may be hardened1 and strengthened by quenching4 ,in fact1 carbon1 of itself1 without heat treatment1 strengthens iron at the expense of ductility 7as noted by the percentage elongation an #h-;in4 bar will stretch before breaking74 ,this is shown by the following table3 ---------------------------------------- ---------------------------------- ,elastic ,ultimate,percentage4 ,class by use4 ,class by ,per cent limit strengthelongation hardness4 carbon4 lb4 per lb4 per in #h inches4 sq4 in4 sq4 in4 ---------------------------------------- ----------------------------- ,boiler rivet steel,dead soft #j4jh to #j4ae #be1jjj #ej1jjj #cj ,struc4 rivet steel,soft #j4ae to #j4bb #cj1jjj #ee1jjj #cj ,boiler plate steel,soft #j4jh to #j4aj #cj1jjj #fj1jjj #be ,structural steel ,medium #j4ah to #j4cj #ce1jjj #fe1jjj #be ,machinery steel ,hard #j4ce to #j4fj #dj1jjj #ge1jjj #bj ,rail steel ,hard #j4ce to #j4ee #dj1jjj #ge1jjj #ae ,spring steel ,high carbon#a4jj to #a4ej #fj1jjj #abe1jjj #aj ,tool steel ,high carbon#j4ij to #a4ej #hj1jjj #aej1jjj #e ---------------------------------------- ---------------------------------- ,just why a soft material like carbon 7graphite71 when added to another soft material like iron1 should make the iron harder1 has been quite a mystery1 and one which has caused a tremendous amount of study4 ,the mutual interactions of these two elements in various proportions and at various temperatures will be discussed at greater length later1 especially in ,chap4 ,,viii1 p4 #aje4 ,but we may anticipate by saying that some of the iron unites with all the carbon to form a new substance1 very hard1 a carbide which has been called cementite4 ,the compound always contains iron and carbon in the proportions of three atoms of iron to one atom of carbon2 chemists note this fact in shorthand by the symbol ,fe#c;,c 7a definite chemical compound of three atoms of iron to one of carbon74 ,many of the properties of steel1 as they vary with carbon content1 can be linked up with the increasing amount of this hard carbide cementite1 distributed in very fine particles through the softer iron4 ,,sulphur is another element 7symbol ,s7 which is always found in steel in small quantities4 ,some sulphur is contained in the ore from which the iron is smelted2 more sulphur is introduced by the coke and fuel used4 ,sulphur is very difficult to get rid of in steel making2 in fact the resulting metal usually contains a little more than the raw materials used4 ,only the electric furnace is able to produce the necessary heat and slags required to eliminate sulphur1 and as a matter of fact the sulphur does not go until several other impurities have been eliminated4 ,consequently1 an electric steel with extremely low sulphur 7#j4jb per cent7 is by that same token a well-made metal4 ,sulphur is of most trouble to rolling and forging operations when conducted at a red heat4 ,it makes steel tender and brittle at that temperature--a condition known to the workmen as red-short4 ,it seems to have little or no effect upon the physical properties of cold steel--at least as revealed by the ordinary testing machines--consequently many specifications do not set any limit on sulphur1 resting on the idea that if sulphur is low enough not to cause trouble to the manufacturer during rolling1 it will not cause the user any trouble4 ,tool steel and other fine steels should be very low in sulphur1 preferably not higher than #j4jc per cent4 ,higher sulphur steels 7#j4jf per cent1 and even up to #j4aj per cent7 have given very good service for machine parts1 but in general a high sulphur steel is a suspicious steel4 ,screw stock is purposely made with up to #j4ab per cent sulphur and a like amount of phosphorus so it will cut freely4 ,manganese counteracts the detrimental effect of sulphur when present in the steel to an amount at least five times the sulphur content4 ,,phosphorus is an element 7symbol ,p7 which enters the metal from the ore4 ,it remains in the steel when made by the so-called acid process1 but it can be easily eliminated down to #j4jf per cent in the basic process4 ,in fact the discovery of the basic process was necessary before the huge iron deposits of ,belgium and the ,franco-,german border could be used4 ,these ores contain several per cent phosphorus1 and made a very brittle steel 7cold short7 until basic furnaces were used4 ,basic furnaces allow the formation of a slag high in lime1 which takes practically all the phosphorus out of the metal4 ,not only is the resulting metal usable1 but the slag makes a very excellent fertilizer1 and is in good demand4 ,,silicon is a very widespread element 7symbol ,si71 being an essential constituent of nearly all the rocks of the earth4 ,it is similar to carbon in many of its chemical properties2 for instance it burns very readily in oxygen1 and consequently native silicon is unknown--it is always found in combination with one or more other elements4 ,when it bums1 each atom of silicon unites with two atoms of oxygen to form a compound known to chemists as silica 7,si,o#b71 and to the small boy as sand and agate4 ,iron ore 7an oxide of iron7 contains more or less sand and dirt mixed in it when it is mined1 and not only the iron oxide but also some of the silicon oxide is robbed of its oxygen by the smelting process4 ,pig iron--the product of the blast furnace--therefore contains from #a to #c per cent of silicon1 and some silicon remains in the metal after it has been purified and converted into steel4 ,however1 silicon1 as noted above1 burns very readily in oxygen1 and this property is of good use in steel making4 ,at the end of the steel-making process the metal contains more or less oxygen1 which must be removed4 ,this is sometimes done 7especially in the so-called acid process7 by adding a small amount of silicon to the hot metal just before it leaves the furnace1 and stirring it in4 ,it thereupon abstracts oxygen from the metal wherever it finds it1 changing to silica 7,si,o#b7 which rises and floats on the surface of the cleaned metal4 ,most of the silicon remaining in the metal is an excess over that which is required to remove the dangerous oxygen1 and the final analysis of many steels show enough silicon 7from #j4bj to #j4dj7 to make sure that this step in the manufacture has been properly done4 ,,manganese is a metal much like iron4 ,its chemical symbol is ,mn4 ,it is somewhat more active than iron in many chemical changes--notably it has what is apparently a stronger attraction for oxygen and sulphur than has iron4 ,therefore the metal is used 7especially in the so-called basic process7 to free the molten steel of oxygen1 acting in a manner similar to silicon1 as explained above4 ,the compound of manganese and oxygen is readily eliminated from the metal4 ,sufficient excess of elemental manganese should remain so that the purchaser may be sure that the iron has been properly deoxidized1 and to render harmless the traces of sulphur present4 ,no damage is done by the presence of a little manganese in steel1 quite the reverse4 ,consequently it is common to find steels containing from #j4c to #a4e per cent4 ,,alloying ,,elements4--,commercial steels of even the simplest types are therefore primarily alloys of iron and carbon4 ,impurities and their remedies are always present3 sulphur1 phosphorus1 silicon and manganese--to say nothing of oxygen1 nitrogen and carbon oxide gases1 about which we know very little4 ,it has been found that other metals1 if added to well-made steel1 produce definite improvements in certain directions1 and these alloy steels have found much use in the last ten years4 ,alloy steels1 in addition to the above-mentioned elements1 may commonly contain one or more of the following1 in varying amounts3 ,nickel 7,ni71 ,chromium 7,cr71 ,vanadium 7,va71 ,tungsten 7,w71 ,molybdenum 7,mo74 ,these steels will be discussed at more length in ,chapters ,,iii and ,,iv4 ,,properties ,,of ,,steel ,steels are known by certain tests4 ,early tests were more or less crude1 and depended upon the ability of the workman to judge the grain exhibited by a freshly broken piece of steel4 ,the cold-bend test was also very useful--a small bar was bent flat upon itself1 and the stretched fibers examined for any sign of break4 ,harder stiff steels were supported at the ends and the amount of central load they would support before fracture1 or the amount of permanent set they would acquire at a given load noted4 ,files were also used to test the hardness of very hard steel4 ,these tests are still used to a considerable extent1 especially in works where the progress of an operation can be kept under close watch in this way1 the product being periodically examined by more precise methods4 ,the chief furnace-man1 or melter1 in a steel plant1 judges the course of the refining process by casting small test ingots from time to time1 breaking them and examining the fracture4 ,cutlery manufacturers use the bend test to judge the temper of blades4 ,file testing of case-hardened parts is very common4 ,however there is need of standardized methods which depend less upon the individual skill of the operator1 and which will yield results comparable to others made by different men at different places and on different steels4 ,hence has grown up the art of testing materials4 ,,tensile ,,properties ,strength of a metal is usually expressed in the number of pounds a #a-;in4 bar will support just before breaking1 a term called the ultimate strength4 ,it has been found that the shape of the test bar and its method of loading has some effect upon the results1 so it is now usual to turn a rod #e-a_/b in4 long down to #j4eje in4 in diameter for a central length of #b-c_/h in41 ending the turn with #a_/b-;in4 fillets4 ,the area of the bar equals #j4b sq4 in41 so the load it bears at rupture multiplied by #e will represent the ultimate strength in pounds per square inch4 ,such a test bar is stretched apart in a machine like that shown in ,fig4 #i4 ,the upper end of the bar is held in wedged jaws by the top cross-head1 and the lower end grasped by the movable head4 ,the latter is moved up and down by three long screws1 driven at the same speed1 which pass through threads cut in the corners of the cross-head4 ,when the test piece is fixed in position the motor which drives the machine is given a few turns1 which by proper gearing pulls the cross-head down with a certain pull4 ,this pull is transmitted to the upper cross-head by the test bar1 and can be weighed on the scale arm1 acting through a system of links and levers4 ,thus the load may be increased as rapidly as desirable1 always kept balanced by the weighing mechanism1 and the load at fracture may be read directly from the scale beam4 ,this same test piece may give other information4 ,if light punch marks are made1 #b in4 apart1 before the test is begun1 the broken ends may be clamped together1 and the distance between punch marks measured4 ,if it now measures #c in4 the stretch has been #a in4 in #b1 or #ej per cent4 ,this figure is known as the elongation at fracture1 or briefly1 the elongation1 and is generally taken to be a measure of ductility4 ,when steel shows any elongation1 it also contracts in area at the same time4 ,often this contraction is sharply localized at the fracture2 the piece is said to neck4 ,a figure for contraction in area is also of much interest as an indication of toughness2 the diameter at fracture is measured1 a corresponding area taken out from a table of circles1 subtracted from the original area 7#j4bjj sq4 in47 and the difference divided by #j4b to get the percentage contraction4 ,illustration3 ,,fig4 #i4--,olsen testing machine4 ,quite often it is desired to discover the elastic limit of the steel1 in fact this is of more use to the designer than the ultimate strength4 ,the elastic limit is usually very close to the load where the metal takes on a permanent set4 ,that is to say1 if a delicate caliper 7extensometer1 so called7 be fixed to the side of the test specimen1 it would show the piece to be somewhat longer under load than when free4 ,furthermore1 if the load had not yet reached the yield point1 and were released at any time1 the piece would return to its original length4 ,however1 if the load had been excessive1 and then relieved1 the extensometer would no longer read exactly #b4j in41 but something more4 ,soft steels give very quickly at the yield point4 ,in fact1 if the testing machine is running slowly1 it takes some time for the lower head to catch up with the stretching steel4 ,consequently at the yield point1 the top head is suddenly but only temporarily relieved of load1 and the scale beam drops4 ,in commercial practice1 the yield point is therefore determined by the drop of the beam4 ,for more precise work the calipers are read at intervals of #ejj or #a1jjj lb4 load1 and a curve plotted from these results1 a curve which runs straight up to the elastic limit1 but there bends off4 ,a tensile test therefore gives four properties of great usefulness3 ,the yield point1 the ultimate strength1 the elongation and the contraction4 ,compression tests are seldom made1 since the action of metal in compression and in tension is closely allied1 and the designer is usually satisfied with the latter4 ,,impact ,,tests ,impact tests are of considerable importance as an indication of how a metal will perform under shock4 ,some engineers think that the tensile test1 which is one made under slow loading1 should therefore be supplemented by another showing what will happen if the load is applied almost instantaneously4 ,this test1 however1 has not been standardized1 and depends to a considerable extent upon the type of machine1 but more especially the size of the specimen and the way it is nicked4 ,the machine is generally a swinging heavy pendulum4 ,it falls a certain height1 strikes the sample at the lowest point1 and swings on past4 ,the difference between the downward and upward swing is a measure of the energy it took to break the test piece4 ,,fatigue ,,tests ,it has been known for fifty years that a beam or rod would fail at a relatively low stress if only repeated often enough4 ,it has been found1 however1 that each material possesses a limiting stress1 or endurance limit1 within which it is safe1 no matter how often the loading occurs4 ,that limiting stress for all steels so far investigated causes fracture below #aj million reversals4 ,in other words1 a steel which will not break before #aj1jjj1jjj reversals can confidently be expected to endure #ajj1jjj1jjj1 and doubtless into the billions4 ,about the only way to test one piece such a large number of times is to fashion it into a beam1 load it1 and then turn the beam in its supports4 ,thus the stress in the outer fibers of the bar varies from a maximum stretch through zero to a maximum compression1 and back again4 ,a simple machine of this sort is shown in ,fig4 #aj1 where ,b and ,e are bearings1 ,a the test piece1 turned slightly down in the center1 ,c and ,d ball bearings supporting a load ,w4 ,k is a pulley for driving the machine and ,n is a counter4 ,illustration3 ,,fig4 #aj4--,sketch of rotating beam machine for measuring endurance of metal4 ,,hardness ,,testing ,the word hardness is used to express various properties of metals1 and is measured in as many different ways4 ,scratch hardness is used by the geologist1 who has constructed ,moh's scale as follows3 ,talc has a hardness of #a ,rock ,salt has a hardness of #b ,calcite has a hardness of #c ,fluorite has a hardness of #d ,apatite has a hardness of #e ,feldspar has a hardness of #f ,quartz has a hardness of #g ,topaz has a hardness of #h ,corundum has a hardness of #i ,diamond has a hardness of #aj ,a mineral will scratch all those above it in the series1 and will be scratched by those below4 ,a weighted diamond cone drawn slowly over a surface will leave a path the width of which 7measured by a microscope7 varies inversely as the scratch hardness4 ,cutting hardness is measured by a standardized drilling machine1 and has a limited application in machine-shop practice4 ,rebounding hardness is commonly measured by the ,shore scleroscope1 illustrated in ,fig4 #aa4 ,a small steel hammer1 #a_/d in4 in diameter1 #c_/d in4 in length1 and weighing about #a_/ab oz4 is dropped a distance of #aj in4 upon the test piece4 ,the height of rebound in arbitrary units represents the hardness numeral4 ,illustration3 ,,fig4 #aa4--,shore scleroscope4 ,should the hammer have a hard flat surface and drop on steel so hard that no impression were made1 it would rebound about #ij per cent of the fall4 ,the point1 however1 consists of a slightly spherical1 blunt diamond nose #j4jb in4 in diameter1 which will indent the steel to a certain extent4 ,the work required to make the indentation is taken from the energy of the falling body2 the rebound will absorb the balance1 and the hammer will now rise from the same steel a distance equal to about #ge per cent of the fall4 ,a permanent impression is left upon the test piece because the impact will develop a force of several hundred thousand pounds per square inch under the tiny diamond-pointed hammer head1 stressing the test piece at this point of contact much beyond its ultimate strength4 ,the rebound is thus dependent upon the indentation hardness1 for the reason that the less the indentation1 the more energy will reappear in the rebound2 also1 the less the indentation1 the harder the material4 ,consequently1 the harder the material1 the more the rebound4 ,indentation hardness is a measure of a material's resistance to penetration and deformation4 ,the standard testing machine is the ,brinell1 ,fig4 #ab4 ,a hardened steel ball1 #aj mm4 in diameter1 is forced into the test piece with a pressure of #c1jjj kg4 7#c-a_/c tons74 ,the resulting indentation is then measured4 ,illustration3 ,,fig4 #ab4--;,hydraulic testing machine4 7,brinell principle47 ,while under load1 the steel ball in a ,brinell machine naturally flattens somewhat4 ,the indentation left behind in the test piece is a duplicate of the surface which made it1 and is usually regarded as being the segment of a sphere of somewhat larger radius than the ball4 ,the radius of curvature of this spherical indentation will vary slightly with the load and the depth of indentation4 ,the ,brinell hardness numeral is the quotient found by dividing the test pressure in kilograms by the spherical area of the indentation4 ,the denominator1 as before1 will vary according to the size of the sphere1 the hardness of the sphere and the load4 ,these items have been standardized1 and the following table has been constructed so that if the diameter of the identation produced by a load of #c1jjj kg4 be measured the hardness numeral is found directly4 ,,table ,,for ,,brinell ,,ball ,,test ---------------------------------------- -------------------------------- ,diameter of ,ball ,hardness ,number ,diameter of ,ball ,hardness ,number ,impression1 mm4 for a ,load of ,impression1 mm4 for a ,load of #c1jjj kg4 #c1jjj kg4 ---------------------------------------- ----------------------------- #b4j #idf #d4e #agi #b4a #heg #d4f #agj #b4b #ghb #d #g #afc #b4c #gac #d4h #aef #b4d #feb #d4i #adi #b4e #fjj #e4j #adc #b4f #eee #e4a #acg #b4g #eab #e4b #aca #b4h #dgg #e4c #abf #b4i #ddd #e4d #aba #c4j #dah #e4e #aaf #c4a #chg #e4f #aab #c4b #cfd #e4g #ajg #c4c #cdj #e4h #ajc #c4d #cba #e4i #ii #c4e #cjb #f4j #ie #c4f #bhf #f4a #ib #c4g #bfi #f4b #hi #c4h #bee #f4c #hf #c4i #bda #f4d #hc #d4j #bbh #f4e #hj #d4a #bag #f4f #gg #d4b #bjg #f4g #gd #d4c #aif #f4h #ga4e #d4d #ahg #f4i #fi ---------------------------------------- -------------------------------- ,,chapter ,,iii ,,alloys ,,and ,,their ,,effect ,,upon ,,steel ,in view of the fact that alloy steels are coming into a great deal of prominence1 it would be well for the users of these steels to fully appreciate the effects of the alloys upon the various grades of steel4 ,we have endeavored to summarize the effect of these alloys so that the users can appreciate their effect1 without having to study a metallurgical treatise and then1 perhaps1 not get the crux of the matter4 ,,nickel ,nickel may be considered as the toughest among the non-rare alloys now used in steel manufacture4 ,originally nickel was added to give increased strength and toughness over that obtained with the ordinary rolled structural steel and little attempt was made to utilize its great possibilities so far as heat treatment was concerned4 ,the difficulties experienced have been a tendency towards laminated structure during manufacture and great liability to seam1 both arising from improper melting practice4 ,when extra care is exercised in the manufacture1 particularly in the melting and rolling1 many of these difficulties can be overcome4 ,the electric steel furnace1 of modern construction1 is a very important step forward in the melting of nickel steel2 neither the crucible process nor basic or acid open-hearth furnaces give such good results4 ,great care must be exercised in reheating the billet for rolling so that the steel is correctly soaked4 ,the rolling must not be forced2 too big reduction per pass should not be indulged in1 as this sets up a tendency towards seams4 ,nickel steel has remarkably good mechanical qualities when suitably heat-treated1 and it is preeminently adapted for case-hardening4 ,it is not difficult to machine low-nickel steel1 consequently it is in great favor where easy machining properties are of importance4 ,nickel influences the strength and ductility of steel by being dissolved directly in the iron or ferrite2 in this respect differing from chromium1 tungsten and vanadium4 ,the addition of each #a per cent nickel up to #e per cent will cause an approximate increase of from #d1jjj to #f1jjj lb4 per square inch in the tensile strength and elastic limit over the corresponding steel and without any decrease in ductility4 ,the static strength of nickel steel is affected to some degree by the percentage of carbon2 for instance1 steel with #j4be per cent carbon and #c4e per cent nickel has a tensile strength1 in its normal state1 equal to a straight carbon steel of #j4e per cent with a proportionately greater elastic limit and retaining all the advantages of the ductility of the lower carbon4 ,to bring out the full qualities of nickel it must be heat-treated1 otherwise there is no object in using nickel as an alloy with carbon steel as the additional cost is not justified by increased strength4 ,nickel has a peculiar effect upon the critical ranges of steel1 the critical range being lowered by the percentage of nickel2 in this respect it is similar to manganese4 ,nickel can be alloyed with steel in various percentages1 each percentage having a very definite effect on the microstructure4 ,for instance1 a steel with #j4b per cent carbon and #b per cent nickel has a pearlitic structure but the grain is much finer than if the straight carbon were used4 ,with the same carbon content and say #e per cent nickel1 the structure would still be pearlitic1 but much finer and denser1 therefore capable of withstanding shock1 and having greater dynamic strength4 ,with about #j4b per cent carbon and #h per cent nickel1 the steel is nearing the stage between pearlite and martensite1 and the structure is extremely fine1 the ferrite and pearlite having a very pronounced tendency to mimic a purely martensite structure4 ,steel with #j4b per cent carbon and #ae per cent nickel is entirely martensite4 ,higher percentages of nickel change the martensitic structure to austenite1 the steel then being non-magnetic4 ,the higher percentages1 that is #cj to #ce per cent nickel1 are used for valve seats1 valve heads1 and valve stems1 as the alloy is a poor conductor of heat and is particularly free from any tendency towards corrosion or pitting from the action of waste gases of the internal-combustion engine4 ,nickel steels having #c-a_/b per cent nickel and #j4ae to #j4bj per cent carbon are excellent for case-hardening purposes1 giving hard surfaces and tough interiors4 ,to obtain the full effect of nickel as an alloy1 it is essential that the correct percentage of carbon be used4 ,high nickel and low carbon will not be more efficient than lower nickel and higher carbon1 but the cost will be much greater4 ,generally speaking1 heat-treated nickel alloy steels are about two to three times stronger than the same steel annealed4 ,this point is very important as many instances have been found where nickel steel is incorrectly used1 being employed when in the annealed or normal state4 ,,chromium ,chromium when alloyed with steel1 has the characteristic function of opposing the disintegration and reconstruction of cementite4 ,this is demonstrated by the changes in the critical ranges of this alloy steel taking place slowly2 in other words1 it has a tendency to raise the ,ac range 7decalescent points7 and lower the ,ar range 7recalescent points74 ,chromium steels are therefore capable of great hardness1 due to the rapid cooling being able to retard the decomposition of the austenite4 ,the great hardness of chromium steels is also due to the formation of double carbides of chromium and iron4 ,this condition is not removed when the steel is slightly tempered or drawn4 ,this additional hardness is also obtained without causing undue brittleness such as would be obtained by any increase of carbon4 ,the degree of hardness of the lower-chrome steels is dependent upon the carbon content1 as chromium alone will not harden iron4 ,the toughness so noticeable in this steel is the result of the fineness of structure2 in this instance1 the action is similar to that of nickel1 and the tensile strength and elastic limit is therefore increased without any loss of ductility4 ,we then have the desirable condition of tough hardness1 making chrome steels extremely valuable for all purposes requiring great resistance to wear1 and in higher-chrome contents resistance to corrosion4 ,all chromium-alloy steels offer great resistance to corrosion and erosion4 ,in view of this1 it is surprising that chromium steels are not more largely used for structural steel work and for all purposes where the steel has to withstand the corroding action of air and liquids4 ,bridges1 ships1 steel building1 etc41 would offer greater resistance to deterioration through rust if the chromium-alloy steels were employed4 ,prolonged heating and high temperatures have a very bad effect upon chromium steels4 ,in this respect they differ from nickel steels1 which are not so affected by prolonged heating1 but chromium steels will stand higher temperatures than nickel steels when the period is short4 ,chromium steels1 due to their admirable property of increased hardness1 without the loss of ductility1 make very excellent chisels and impact tools of all types1 although for die blocks they do not give such good results as can be obtained from other alloy combinations4 ,for ball bearing steels1 where intense hardness with great toughness and ready recovery from temporary deflection is required1 chromium as an alloy offers the best solution4 ,two per cent chromium steels2 due to their very hard tough surface1 are largely used for armor-piercing projectiles1 cold rolls1 crushers1 drawing dies1 etc4 ,the normal structure of chromium steels1 with a very low carbon content is roughly pearlitic up to #g per cent1 and martensitic from #h to #bj per cent2 therefore1 the greatest application is in the pearlitic zone or the lower percentages4 ,,nickel-,,chromium ,a combination of the characteristics of nickel and the characteristics of chromium1 as described1 should obviously give a very excellent steel as the nickel particularly affects the ferrite of the steel and the chromium the carbon4 ,from this combination1 we are able to get a very strong ferrite matrix and a very hard tough cementite4 ,the strength of a strictly pearlitic steel over a pure iron is due to the pearlitic being a layer arrangement of cementite running parallel to that of a pure iron layer in each individual grain4 ,the ferrite i4e41 the iron is increased in strength by the resistance offered by the cementite which is the simple iron-carbon combination known to metallurgists as ,fe#c;,c4 ,the cementite1 although adding to the tensile strength1 is very brittle and the strength of the pearlite is the combination of the ferrite and cementite4 ,in the event of the cementite being strengthened1 as in the case of strictly chromium steels1 an increased tensile strength is readily obtained without loss of ductility and if the ferrite is strengthened then the tensile strength and ductility of the metal is still further improved4 ,nickel-chromium alloy represents one of the best combinations available at the present time4 ,the nickel intensifies the physical characteristics of the chromium and the chromium has a similar effect on the nickel4 ,for case-hardening1 nickel-chromium steels seem to give very excellent results4 ,the carbon is very rapidly taken up in this combination1 and for that reason is rather preferable to the straight nickel steel4 ,with the mutually intensifying action of chromium and nickel there is a most suitable ratio for these two alloys1 and it has been found that roughly #b-a_/b parts of nickel to about #a part of chromium gives the best results4 ,therefore1 we have the standard types of #c4e per cent nickel with #a4e per cent chromium to #a4e per cent nickel with #j4f per cent chromium and the various intermediate types4 ,this ratio1 however1 does not give the whole story of nickel-chromium combinations1 and many surprising results have been obtained with these alloys when other percentage combinations have been employed4 ,,vanadium ,vanadium has a very marked effect upon alloy steels rich in chromium1 carbon1 or manganese4 ,vanadium itself1 when combined with steel very low in carbon1 is not so noticeably beneficial as in the same carbon steel higher in manganese1 but if a small quantity of chromium is added1 then the vanadium has a very marked effect in increasing the impact strength of the alloy4 ,it would seem that vanadium has the effect of intensifying the action of chromium and manganese1 or that vanadium is intensified by the action of chromium or manganese4 ,vanadium has the peculiar property of readily entering into solution with ferrite4 ,if vanadium contained is considerable it also combines with the carbon1 forming carbides4 ,the ductility of carbon-vanadium steels is therefore increased1 likewise the ductility of chrome-vanadium steels4 ,the full effect of vanadium is not felt unless the temperatures to which the steel is heated for hardening are raised considerably4 ,it is therefore necessary that a certain amount of soaking takes place1 so as to get the necessary equalization4 ,this is true of all alloys which contain complex carbides1 i4e41 compounds of carbon1 iron and one or more elements4 ,chrome-vanadium steels also are highly favored for case hardening4 ,when used under alternating stresses it appears to have superior endurance4 ,it would appear that the intensification of the properties due to chromium and manganese in the alloy steel accounts for this peculiar phenomenon4 ,vanadium is also a very excellent scavenger for either removing the harmful gases1 or causing them to enter into solution with the metal in such a way as to largely obviate their harmful effects4 ,chrome-vanadium steels have been claimed1 by many steel manufacturers and users1 to be preferable to nickel-chrome steels4 ,while not wishing to pass judgment on this1 it should be borne in mind that the chrome-vanadium steel1 which is tested1 is generally compared with a very low nickel-chromium alloy steel 7the price factor entering into the situation71 but equally good results can be obtained by nickel-chromium steels of suitable analysis4 ,where price is the leading factor1 there are many cases where a stronger steel can be obtained from the chrome and vanadium than the nickel-chrome4 ,it will be safe to say that each of these two systems of alloys have their own particular fields and chrome-vanadium steel should not be regarded as the sole solution for all problems1 neither should nickel-chromium4 ,,manganese ,manganese adds considerably to the tensile strength of steel1 but this is dependent on the carbon content4 ,high carbon materially adds to the brittleness1 whereas low-carbon1 pearlitic-manganese steels are very tough and ductile and are not at all brittle1 providing the heat-treating is correct4 ,manganese steel is very susceptible to high temperatures and prolonged heating4 ,in low-carbon pearlitic steels1 manganese is more effective in increasing ultimate strength than is nickel2 that is to say1 a #j4de carbon steel with #a4be per cent manganese is as strong as a #j4de carbon steel with #a4e per cent nickel4 ,the former steel is much used for rifle barrels1 and in the heat-treated condition will give #hj1jjj to #ij1jjj lb4 per square inch elastic limit1 #aae1jjj to #abe1jjj lb4 per square inch tensile strength1 #bc per cent elongation1 and #ee per cent reduction in area4 ,manganese when added to steel has the effect of lowering the critical range2 #a per cent manganese will lower the upper critical point #fj;,f4 ,the action of manganese is very similar to that of nickel in this respect1 only twice as powerful4 ,as an instance1 #a per cent nickel would have the effect of lowering the upper critical range from #be to #cj;,f4 ,low-carbon pearlitic-manganese steel1 heat-treated1 will give dynamic strength which cannot be equaled by low-priced and necessarily low-content nickel steels4 ,in many instances1 it is preferable to use high-grade manganese steel1 rather than low-content nickel steel4 ,high-manganese steels or austenite manganese steels are used for a variety of purposes where great resistance to abrasion is required1 the percentage of manganese being from #aa to #ad per cent1 and carbon #a to #a4e per cent4 ,this steel is practically valueless unless heat-treated2 that is1 heated to about yellow red and quenched in ice water4 ,the structure is then austenite and the air-cooled structure of this steel is martensite4 ,therefore this steel has to be heated and very rapidly cooled to obtain the ductile austenite structure4 ,manganese between #b and #g per cent is a very brittle material when the carbon is about #a per cent or higher and is1 therefore1 quite valueless4 ,below #b per cent manganese steel low in carbon is very ductile and tough steel4 ,the high-content manganese steels are known as the ,hadfield manganese steels1 having been developed by ,sir ,robert ,hadfield4 ,small additions of chrome up to #a per cent increase the elastic limit of low-carbon pearlitic-manganese steels without affecting the steel in its resistance to shock1 but materially decrease the percentage of elongation4 ,vanadium added to low-carbon pearlitic manganese steel has a very marked effect1 increasing greatly the dynamic strength and changing slightly the susceptibility of this steel to heat treatments1 giving a greater margin for the hardening temperature4 ,manganese steel with added vanadium is most efficient when heat-treated4 ,,tungsten ,tungsten1 as an alloy in steel1 has been known and used for a long time4 ,the celebrated and ancient damascus steel being a form of tungsten-alloy steel4 ,tungsten and its effects1 however1 did not become generally realized until ,robert ,mushet experimented and developed his famous mushet steel and the many improvement made since that date go to prove how little ,mushet himself understood the peculiar effects of tungsten as an alloy4 ,tungsten acts on steel in a similar manner to carbon1 that is1 it increases its hardness1 but is much less effective than carbon in this respect4 ,if the percentage of tungsten and manganese is high1 the steel will be hard after cooling in the air4 ,this is impossible in a carbon steel4 ,it was this combination that ,mushet used in his well-known air-hardening steel4 ,the principal use of tungsten is in high-speed tool steel1 but here a high percentage of manganese is distinctly detrimental1 making the steel liable to fire crack1 very brittle and weak in the body1 less easily forged and annealed4 ,manganese should be kept low and a high percentage of chromium used instead4 ,tools of tungsten-chromium steels1 when hardened1 retain their hardness1 even when heated to a dark cherry red by the friction of the cutting or the heat arising from the chips4 ,this characteristic led to the term red-hardness1 and it is this property that has made possible the use of very high cutting speeds in tools made of the tungsten-chromium alloy1 that is1 high-speed steel4 ,tungsten steels containing up to #f per cent do not have the property of red hardness any more than does carbon tool steel1 providing the manganese or chromium is low4 ,when chromium is alloyed with tungsten1 a very definite red-hardness is noticed with a great increase of cutting efficiency4 ,the maximum red-hardness seems to be had with steels containing #ah per cent tungsten1 #e4e per cent chromium and #j4gj per cent carbon4 ,very little is known of the actual function of tungsten1 although a vast amount of experimental work has been done4 ,it is possible that when the effect of tungsten with iron-carbon alloys is better known1 a greater improvement can be expected from these steels4 ,tungsten has been tried and is still used by some steel manufacturers for making punches1 chisels1 and other impact tools4 ,it has also been used for springs1 and has given very good results1 although other less expensive alloys give equally good results1 and are in some instances1 better4 ,tungsten is largely used in permanent magnets4 ,in this1 its action is not well understood4 ,in fact1 the reason why steel becomes a permanent magnet is not at all understood4 ,theories have been evolved1 but all are open to serious questioning4 ,the principal effect of tungsten1 as conceded by leading authorities1 is that it distinctly retards separation of the iron-carbon solution1 removing the lowest recalescent point down to atmospheric temperature4 ,a peculiar property of tungsten steels is that if a heating temperature of #a1gej;,f4 is not exceeded1 the cooling curves indicate but one critical point at about #a1cej;,f4 ,but when the heating temperature is raised above #a1hej;,f41 this critical point is nearly if not quite suppressed1 while a lower critical point appears and grows enormously in intensity at a temperature between #ffj and #gej;,f4 ,the change in the critical ranges1 which is produced by heating tungsten steels to over #a1hej;,f41 is the real cause of the red-hard properties of these alloys4 ,its real nature is not understood1 and there is no direct evidence to show what actually happens at these high temperatures4 ,it may readily be understood that an alloy containing four essential elements1 namely3 iron1 carbon1 tungsten and chromium1 is one whose study presents problems of extreme complexity4 ,it is possible that complex carbides may be formed1 as in chromium steels1 and that compounds between iron and tungsten exist4 ,behavior of these combinations on heating and cooling must be better known before we are able to explain many peculiarities of tungsten steels4 ,,molybdenum ,molybdenum steels have been made commercially for twenty-five years1 but they have not been widely exploited until since the war4 ,very large resources of molybdenum have been developed in ,america1 and the mining companies who are equipped to produce the metal are very active in advertising the advantages of molybdenum steels4 ,it was early found that #a part molybdenum was the equivalent of from #b to #b-a_/b parts of tungsten in tool steels1 and magnet steels4 ,it fell into disrepute as an alloy for high-speed tool steel1 however1 because it was found that the molybdenum was driven out of the surface of the tool during forging and heat treating4 ,within the last few years it has been found that the presence of less than #a per cent of molybdenum greatly enhances certain properties of heat-treated carbon and alloy steels used for automobiles and high-grade machinery4 ,in general1 molybdenum when added to an alloy steel1 increases the figure for reduction of area1 which is considered a good measure of toughness4 ,molybdenum steels are also relatively insensible to variations in heat treatment2 that is to say1 a chromium-nickel-molybdenum steel after quenching in oil from #a1dej;,f4 may be drawn at any temperature between #ijj and #a1ajj;,f4 with substantially the same result 7static tensile properties and hardness74 ,,silicon ,silicon prevents1 to a large extent1 defects such as gas bubbles or blow holes forming while steel is solidifying4 ,in fact1 steel after it has been melted and before it has been refined1 is wild and gassy4 ,that is to say1 if it would be cast into molds it would froth up1 and boil all over the floor4 ,a judicious amount of silicon added to the metal just before pouring1 prevents this action--in the words of the steel maker1 silicon kills the steel4 ,if about #a4ge per cent metallic silicon remains in a #j4fe carbon steel1 it makes excellent springs4 ,,phosphorus ,phosphorus is one of the impurities in steel1 and it has been the object of steel makers for years to eliminate it4 ,on cheap grades of steel1 not subject to any abnormal strain or stress1 #j4a per cent phosphorus is not objectionable4 ,high phosphorus makes steel cold short1 i4e41 brittle when cold or moderately warm4 ,,sulphur ,sulphur is another impurity and high sulphur is even a greater detriment to steel than phosphorus4 ,high sulphur up to #j4ji per cent helps machining properties1 but has a tendency to make the steel hot short1 i4e41 subject to opening up cracks and seams at forging or rolling heats4 ,sulphur should never exceed #j4jf per cent nor phosphorus #j4jh per cent4 ,steel used for tool purposes should have as low phosphorus and sulphur contents as possible1 not over #j4jb per cent4 ,we can sum up the various factors something as follows for ready reference4 ,the ingredient ,its effect ,iron ,the basis of steel ,carbon ,the determinative ,sulphur ,a strength sapper ,phosphorus ,the weak link ,oxygen ,a strength destroyer ,manganese ,for strength ,nickel ,for strength and toughness ,tungsten ,hardener and heat resister ,chromium ,for resisting shocks ,vanadium ,purifier and fatigue resister ,silicon ,impurity and hardener ,titanium ,removes nitrogen and oxygen ,molybdenum ,hardener and heat resister ,aluminum ,kills or deoxidizes steel ,,properties ,,of ,,alloy ,,steels ,the following table shows the percentages of carbon1 manganese1 nickel1 chromium and vanadium in typical steel alloys for engineering purposes4 ,it also gives the elastic limit1 tensile strength1 elongation and reduction of area of the various alloys1 all being given the same heat treatment with a drawing temperature of #a1ajj;,f4 7#fjj;,c474 ,the specimens were one inch rounds machined after heat treatment4 ,tungsten is not shown in the table because it is seldom used in engineering construction steels and then usually in combination with chromium4 ,tungsten is used principally for the magnets of magnetos1 to some extent in the manufacture of hacksaws1 and for special tool steels4 ,,table ,i4--,,properties ,,of ,,alloy ,,steels ---------------------------------------- -------------------------------------- ,manganese1_/ ,chromium1_/ ,elastic,tensile ,elongation,reduction ,carbon1 per _/,nickel1 per _/,vanadium1limit1 ,strength1in #b in41 of area1 per cent per cent per cent lb4 perlb4 per per cent per cent cent cent sq4 in4sq4 in4 ---------------------------------------- ------------------------------ #j4bg #j4ee #di1jjj #hj1jjj #cj #fe #j4bg #j4dg #j4bf #ff1jjj #ih1jjj #be #eb #j4cf #j4db #eh1jjj #ij1jjj #bg #fj #j4cd #j4hg #j4ac #hb1ejj #ajc1jjj #bb #eg #j4de #j4ej #fe1jjj #if1jjj #bb #eb #j4dc #j4fj #j4cb #if1jjj #abb1jjj #ba #eb #j4dg #j4ij #j4ae #ajb1jjj #abg1ejj #bc #eh #j4cj #j4fj #c4dj #ge1jjj #aje1jjj #be #fg #j4cc #j4fc #c4fj #j4be #aah1jjj #adb1jjj #ag #eg #j4cj #j4di #c4fj #a4gj #aai1jjj #adi1ejj #ba #fj #j4be #j4dg #c4dg #a4fj #j4ae #aci1jjj #agj1jjj #ah #ec #j4be #j4ej #b4jj #a4jj #ajb1jjj #abd1jjj #be #gj #j4ch #j4cj #b4jh #a4af #abj1jjj #acd1jjj #bj #eg #j4db #j4bb #b4ad #a4bg #j4bf #ade1jjj #afa1ejj #af #ec #j4cf #j4fa #a4df #j4fd #aag1fjj #acb1ejj #af #eh #j4cf #j4ej #a4cj #j4ge #j4af #adj1jjj #aeg1ejj #ag #ed #j4cj #j4ej #j4hj #ij1jjj #aje1jjj #bj #ej #j4bc #j4eh #j4hb #j4ag #ajf1jjj #abd1jjj #ba #ff #j4bf #j4dh #j4ib #j4bj #aab1jjj #acg1jjj #bj #fa #j4ce #j4fd #a4jc #j4bb #acb1ejj #adi1ejj #af #ed #j4ej #j4ib #a4jb #j4bj #agj1jjj #ahf1jjj #ae #de ---------------------------------------- -------------------------------------- ,,non-,,shrinking1 ,,oil-,,hardening ,,steels ,certain steels have a very low rate of expansion and contraction in hardening and are very desirable for test plugs1 gages1 punches and dies1 for milling cutters1 taps1 reamers1 hard steel bushings and similar work4 ,it is recommended that for forging these steels it be heated slowly and uniformly to a bright red1 but not in a direct flame or blast4 ,harden at a dull red heat1 about #a1cjj;,f4 ,a clean coal or coke fire1 or a good muffle-gas furnace will give best results4 ,fish oil is good for quenching although in some cases warm water will give excellent results4 ,the steel should be kept moving in the bath until perfectly cold4 ,heated and cooled in this way the steel is very tough1 takes a good cutting edge and has very little expansion or contraction which makes it desirable for long taps where the accuracy of lead is important4 ,the composition of these steels is as follows3 ,per cent ,manganese #a4dj to #a4fj ,carbon #j4hj to #j4ij ,vanadium #j4bj to #j4be ,illustration3 ,,fig4 #ac4--;,effect of copper in steel4 ,,effect ,,of ,a ,,small ,,amount ,,of ,,copper ,,in ,,medium-,,carbon ,,steel ,this shows the result of tests by ,c4 ,r4 ,hayward and ,a4 ,b4 ,johnston on two types of steel3 one containing #j4cj per cent carbon1 #j4jab per cent phosphorus1 and #j4hfj per cent copper1 and the other #j4cfe per cent carbon1 #j4jec per cent phosphorus1 and #j4jcj per cent copper4 ,the accompanying chart in ,fig4 #ac shows that high-copper steel has decided superiority in tensile strength1 yield point and ultimate strength1 while the ductility is practically the same4 ,hardness tests by both methods show high-copper steel to be harder than low-copper1 and the ,charpy shock tests show high-copper steel also superior to low-copper4 ,the tests confirm those made by ,stead1 showing that the behavior of copper steel resembles that of nickel steel4 ,the high-copper steels show finer grain than the low-copper4 ,the quenched and drawn specimens of high-copper steel were found to be slightly more martensitic4 ,,high-,,chromium ,,or ,,rust-,,proof ,,steel ,high-chromium1 or what is called stainless steel containing from #aa to #ad per cent chromium1 was originally developed for cutlery purposes1 but has in the past few years been used to a considerable extent for exhaust valves in airplane engines because of its resistance to scaling at high temperatures4 ,percentage ,carbon #j4bj to #j4dj ,manganese1 not to exceed #j4ej ,phosphorus1 not to exceed #j4jce ,sulphur1 not to exceed #j4jce ,chromium #aa4ej to #ad4jj ,silicon1 not to exceed #j4cj ,the steel should be heated slowly and forged at a temperature above #a1gej;,f4 preferably between #a1hjj and #b1bjj;,f4 ,if forged at temperatures between #a1fej and #a1gej;,f4 there is considerable danger of rupturing the steel because of its hardness at red heat4 ,owing to the air-hardening property of the steel1 the drop-forgings should be trimmed while hot4 ,thin forgings should be reheated to redness before trimming1 as otherwise they are liable to crack4 ,the forgings will be hard if they are allowed to cool in air4 ,this hardness varies over a range of from #bej to #ejj ,brinell1 depending on the original forging temperature4 ,,annealing can be done by heating to temperatures ranging from #a1bij to #a1chj;,f4 and cooling in air or quenching in water or oil4 ,after this treatment the forgings will have a hardness of about #bjj ,brinell and a tensile strength of #ajj1jjj to #aab1jjj lb4 per square inch4 ,if softer forgings are desired they can be heated to a temperature of from #a1efj to #a1fej;,f4 and cooled very slowly4 ,although softer the forgings will not machine as smoothly as when annealed at the lower temperature4 ,,hardening4--,the forgings can be hardened by cooling in still air or quenching in oil or water from a temperature between #a1fej and #a1gej;,f4 ,the physical properties do not vary greatly when the carbon is within the range of composition given1 or when the steel is hardened and tempered in air1 oil1 or water4 ,when used for valves the following specification of physical properties have been used3 ,yield point1 pounds per square inch #gj1jjj ,tensile strength1 pounds per square inch #ij1jjj ,elongation in #b in41 per cent #ah ,reduction of area1 per cent #ej ,the usual heat treatment is to quench in oil from #a1fej;,f4 and temper or draw at #a1ajj to #a1bjj;,f4 ,one valve manufacturer stated that valves of this steel are hardened by heating the previously annealed valves to #a1fej;,f4 and cooling in still air4 ,this treatment gives a scleroscope hardness of about #ej4 ,in addition to use in valves this steel should prove very satisfactory for shafting for water-pumps and other automobile parts subject to objectionable corrosion4 ,,table #b4--;,,comparison ,,of ,,physical ,,properties ,,for ,,high-,,chromium ,,steels ,,of ,,different ,,carbon ,,content ---------------------------------------- ---------------------------------- ,c #j4bj ,c #j4bg ,c #j4ej ,mn #j4de ,mn #j4ej ,cr #ab4ef ,cr #ab4bd ,cr #ad4hd ---------------------------------------- ------------------------------- ,quenched in oil from degrees ,fahrenheit #a1fjj #a1fjj #a1fej ,tempered at degrees ,fahrenheit #a1afj #a1jhj #a1ajj ,yield point1 pounds per square inch #gh1cjj #ge1jjj #ia1faf ,tensile strength1 pounds per square inch #ajd1fjj #ajd1bej #abc1fdh ,elongation in #b in41 per cent #be4j #bc4e #ad4e ,reduction of area1 per cent #eb4e #ea4d #cc4e ---------------------------------------- ---------------------------------- ,,table #c4--;,,comparison ,,of ,,physical ,,properties ,,between ,,air1 ,,oil ,,and ,,water-,,hardened ,,steel ,,having ,,chemical ,,analysis ,,in ,,percentage ,,of ---------------------------------------- --------------------------------- ,carbon #j4bd ,manganese #j4cj ,phosphorus #j4jce ,sulphur #j4jce ,chromium #ab4he ,silicon #j4bj ---------------------------------------- --------------------------------- ,hardened ,elastic ,tensile ,hardening from1 ,tempered limit1 strength1,elongation,reduction medium degrees at1 degrees per lb4 lb4 ,per in #b in4 of area1 ,fahrenheit,fahrenheit sq4 in4 sq4 in4 per cent per cent ---------------------------------------- --------------------------- #icj #aeh1hae #aib1dae #ac4j #dj4e #a1ajj #ii1fhj #abj1jfe #ba4j #ei4b ,air #a1fej #a1cjj #gj1ghe #aja1bej #bf4j #fd4f #a1chj #ff1jhj #ih1cce #bh4j #fc4f #a1dgj #gj1ghe #if1iij #bg4j #fd4g ---------------------------------------- --------------------------- #icj #afc1jgj #bjb1gbj #h4j #ah4b ,oil #a1fej #a1ajj #hh1bee #aaf1dhj #bj4j #ef4i #a1cjj #gg1iej #aje1eje #be4e #fc4h #a1chj #hh1bee #ih1ghe #bg4j #ff4c ---------------------------------------- --------------------------- #icj #aeh1hae #bjb1jej #ab4j #cd4b ,water #a1fej #a1ajj #ij1bgj #abj1gce #bb4j #ei4h #a1cjj #ff1jhj #ajb1eij #be4h #fd4h #a1chj #fg1bjj #ig1hij #bg4j #fe4b ---------------------------------------- --------------------------------- ,this steel can be drawn into wire1 rolled into sheets and strips and drawn into seamless tubes4 ,,corrosion4--,this steel like any other steel when distorted by cold working is more sensitive to corrosion and will rust4 ,rough cut surfaces will rust4 ,surfaces finished with a fine cut are less liable to rust4 ,ground and polished surfaces are practically immune to rust4 ,when chromium content is increased to #af to #ah per cent and silicon is added1 from #b to #d per cent1 this steel becomes rust proof in its raw state1 as soon as the outside surface is removed4 ,it does not need to be heat-treated in any way4 ,these compositions are both patented4 ,s4 ,a4 ,e4 ,,standard ,,steels ,the following steel specifications are considered standard by the ,society of ,automotive ,engineers and represents automobile practice in this country4 ,these tables give the ,s4 ,a4 ,e4 number1 the composition of the steel and the heat treatment4 ,these are referred to by letter--the heat treatments being given in detail on pages #acd to #acg in ,chap4 #h4 ,it should be noted that the percentage of the different ingredients desired is the mean1 or halfway between the minimum and maximum4 ,,table #d4--;,,carbon ,,steels ---------------------------------------- -------------------------------------- ,s4 ,a4 ,e4 ,carbon ,manganese ,specification7minimum and 7minimum and ,phosphorus ,sulphur ,heat no4 maximum7 maximum7 7maximum7 7maximum7 treatment ---------------------------------------- --------------------------------- #a1jaj #j4je to #j4ae #j4cj to #j4fj #j4jde #j4je ,quench at #a1ejj #a1jbj #j4ae to #j4be #j4cj to #j4fj #j4jde #j4je ,a or ,b #a1jbe #j4bj to #j4cj #j4ej to #j4hj #j4jde #j4je ,h #a1jce #j4cj to #j4dj #j4ej to #j4hj #j4jde #j4je ,h1 ,d or ,e #a1jde #j4dj to #j4ej #j4ej to #j4hj #j4jde #j4je ,h1 ,d or ,e #a1jie #j4ij to #a4je #j4be to #j4ej #j4jdj #j4je ,f ---------------------------------------- -------------------------------------- ,,table #e4--,,screw ,,stock ---------------------------------------- ----------------------------------- ,s4 ,a4 ,e4 ,carbon ,manganese ,phosphorus ,sulphur ,specification no4 7maximum7 ---------------------------------------- ------------------------------- #a1aad #j4jh to #j4bj #j4cj to #j4hj #j4ab #j4jf to #j4ab ---------------------------------------- ----------------------------------- ,,table #f4--,,nickel ,,steels ---------------------------------------- ------------------------------------- ,s4 ,a4 ,e4 ,phosphorus ,specification 7maximum7 no4 ---- _/ ,carbon ,manganese ,sulphur ,nickel ,heat 7minimum and7minimum and 7maximum77minimum andtreatment maximum7 maximum7 maximum7 ---------------------------------------- ------------------------------- #b1cae #j4aj to #j4bjj4ej to #j4hj #j4jd #j4jde #c4be to #c4ge;,g1 ,h or ,k #b1cbj #j4ae to #j4bej4ej to #j4hj #j4jd #j4jde #c4be to #c4ge;,g1 ,h or ,k #b1ccj #j4be to #j4cej4ej to #j4hj #j4jd #j4jde #c4be to #c4ge ,h or ,k #b1cce #j4cj to #j4djj4ej to #j4hj #j4jd #j4jde #c4be to #c4ge ,h or ,k #b1cdj #j4ce to #j4dej4ej to #j4hj #j4jd #j4jde #c4be to #c4ge ,h or ,k #b1cde #j4dj to #j4ejj4ej to #j4hj #j4jd #j4jde #c4be to #c4ge ,h or ,k ---------------------------------------- ------------------------------------- ,,table #g4--,,nickel-,,chromium ,,steels ---------------------------------------- --------------------------------------- ,s4 ,a4 ,e4 ,phosphorus ,sulphur ,specification 7maximum77maximum7 ,heat no4 ------ ------ ---- treatment ,carbon ,manganese ,nickel ,chromium 7minimum and7minimum and 7minimum and7minimum and maximum7 maximum7 maximum7 maximum7 ---------------------------------------- -------------------------------- #c1abjj4ae to #j4bej4ej to #j4hjj4jdj4jdea4jj to #a4ejj4de to #j4ge99;,g1,h or ,d #c1abej4bj to #j4cjj4ej to #j4hjj4jdj4jdea4jj to #a4ejj4de to #j4ge99;,h1,d or ,e #c1acjj4be to #j4cej4ej to #j4hjj4jdj4jdea4jj to #a4ejj4de to #j4ge99;,h1,d or ,e #c1acej4cj to #j4djj4ej to #j #hjj4jdj4jdea4jj to #a4ejj4de to #j #ge99;,h1,d or ,e #c1adjj4ce to #j4dej4ej to #j4hjj4jdj4jdea4jj to #a4ejj4de to #j4ge99;,h1,d or ,e #c1bbjj4ae to #j4bej4cj to #j4fjj4jdj4jdja4ej to #b4jjj4ij to #a4be ,g1,h or ,d #c1bcjj4be to #j4cej4cj to #j4fjj4jdj4jdja4ej to #b4jjj4ij to #a4be ,h or ,d #c1bdjj4ce to #j4dej4cj to #j4fjj4jdj4jdja4ej to #b4jjj4ij to #a4be ,h or ,d #c1bejj4de to #j4eej4cj to #j4fjj4jdj4jdja4ej to #b4jjj4ij to #a4be ,m or ,q ,x#c1caej4aj to #j4bjj4de to #j4gej4jdj4jdjb4ge to #c4bej4fj to #j4ie ,g ,x#c1ccej4cj to #j4djj4de to #j4gej4jdj4jdjb4ge to #c4bej4fj to #j4ie ,p or ,r ,x#c1cejj4de to #j4eej4de to #j4gej4jdj4jdjb4ge to #c4bej4fj to #j4ie ,p or ,r #c1cbjj4ae to #j4bej4cj to #j4fjj4jdj4jdjc4be to #c4gea4be to #a4ge ,l #c1ccjj4be to #j4cej4cj to #j4fjj4jdj4jdjc4be to #c4gea4be to #a4ge ,p or ,r #c1cdjj4ce to #j4dej4cj to #j4fjj4jdj4jdjc4be to #c4gea4be to #a4ge ,p or ,r ---------------------------------------- --------------------------------------- 99 ,another grade of this type of steel is available with chromium content of #j4ae per cent to #de per cent4 ,it has somewhat lower physical properties4 ,,table #h4--;,,chromium ,,steels ---------------------------------------- --------------------------------------- ,s4 ,a4 ,e4 ,specification no4 --- ,carbon ,manganese ,chromium 7minimum and7minimum and,phosphorus,sulphur 7minimum and ,heat maximum7 maximum7 7maximum7 7maximum7 maximum7 treatment ---------------------------------------- --------------------------------- #e1abj #j4ae to #j4be 99 #j4jd #j4jde #j4fe to #j4he ,b #e1adj #j4ce to #j4de 99 #j4jd #j4jde #j4fe to #j4he ,h or ,d #e1afe #j4fj to #j4gj 99 #j4jd #j4jde #j4fe to #j4he ,h or ,d #e1aie #j4ij to #a4jej4bj to #j4de #j4jc #j4jc #j4ij to #a4aj,m1 ,p or ,r #ea1abj #a4aj to #a4cjj4bj to #j4de #j4jc #j4jc #j4ij to #a4aj,m1 ,p or ,r #e1bie #j4ij to #a4jej4bj to #j4de #j4jc #j4jc #a4aj to #a4cj,m1 ,p or ,r #eb1abj #a4aj to #a4cjj4bj to #j4de #j4jc #j4jc #a4aj to #a4cj,m1 ,p or ,r ---------------------------------------- --------------------------------------- --,two types of steel are available in this class1 one with manganese #j4be to #j4ej per cent 7#j4ce per cent desired71 and silicon not over #j4bj per cent2 the other with manganese #j4fj to #j4hj per cent 7#j4gj per cent desired71 and silicon #j4ae to #j4ej per cent4 ,,table #i4--;,,chromium-,,vanadium ,,steels ---------------------------------------- --------------------------------------- ,s4 ,a4 ,e4 ,phosphorus ,sulphur ,vanadium ,specification 7maximum77maximum7 7minimum7 no4 ------ -- _/ - ,carbon ,manganese ,chromium ,heat 7minimum and7minimum and 7minimum and treatment maximum7 maximum7 maximum7 ---------------------------------------- -------------------------------- #f1abj #j4ae to #j4bej4ej to #j4hj #j4jd #j4jd #j4hj to #a4aj #j4ae ,s #f1abe #j4bj to #j4cjj4ej to #j4hj #j4jd #j4jd #j4hj to #a4aj #j4ae ,s or ,t #f1acj #j4be to #j4cej4ej to #j4hj #j4jd #j4jd #j4hj to #a4aj #j4ae ,t or ,u #f1ace #j4cj to #j4djj4ej to #j4hj #j4jd #j4jd #j4hj to #a4aj #j4ae ,t or ,u #f1adj #j4ce to #j4dej4ej to #j4hj #j4jd #j4jd #j4hj to #a4aj #j4ae ,t or ,u #f1ade #j4dj to #j4ejj4ej to #j4hj #j4jd #j4jd #j4hj to #a4aj #j4ae ,u #f1aej #j4de to #j4eej4ej to #j4hj #j4jd #j4jd #j4hj to #a4aj #j4ae ,u #f1aie #j4ij to #a4jej4bj to #j4de #j4jc #j4jc #j4hj to #a4aj #j4ae ,u ---------------------------------------- --------------------------------------- ,,table #aj4--,,silico-,,manganese ,,steels ---------------------------------------- ------------------------------------- ,s4 ,a4 ,e4 ,specification no4 ----- ,carbon ,manganese ,silicon 7minimum and7minimum and,phosphorus,sulphur 7minimum and ,heat maximum7 maximum7 7maximum7 7maximum7 maximum7 treatment ---------------------------------------- ------------------------------- #i1bej #j4de to #j4eej4fj to #j4hj #j4jde99 #j4jde #a4hj to #b4aj ,v #i1bfj #j4ee to #j4fej4ej to #j4gj #j4jde99 #j4jde #a4ej to #a4hj ,v ---------------------------------------- ------------------------------------- 99 ,steel made by the acid process may contain maximum #j4je phosphorus4 ,,liberty ,,motor ,,connecting ,,rods ,the requirements for materials for the ,liberty motor connecting rods are so severe that the methods of securing the desired qualities will be of value in other lines4 ,the original specifications called for chrome-nickel but the losses due to the difficulty of handling caused the ,lincoln ,motor ,company to suggest the substitution of chrome-vanadium steel1 and this was accepted by the ,signal ,corps4 ,the rods were accordingly made from chromium-vanadium steel1 containing carbon1 #j4cj to #j4dj per cent2 manganese1 #j4ej to #j4hj per cent2 phosphorus1 not over #j4jd per cent2 sulphur1 not over #j4jd per cent2 chromium1 #j4hj to #a4aj per cent2 vanadium1 not less than #j4ae per cent4 ,this steel is ordinarily known in the trade as #j4ce carbon steel1 ,s4 ,a4 ,e41 specification #f1ace1 which provides a first-rate quality steel for structural parts that are to be heat-treated4 ,the fatigue resisting or endurance qualities of this material are excellent4 ,it has a tensile strength of #aej1jjj lb4 minimum per square inch2 elastic limit1 #aae1jjj lb4 minimum per square inch2 elongation1 #e per cent minimum in #b in42 and minimum reduction in area1 #be per cent4 ,the original production system as outlined for the manufacturers had called for a heat treatment in the rough-forged state for the connecting rods1 and then semi-machining the rod forgings before giving them the final treatment4 ,the ,lincoln ,motor ,company insisted from the first that the proper method would be a complete heat treatment of the forging in the rough state1 and machining the rod after the heat treatment4 ,after a number of trial lots1 the ,signal ,corps acceded to the request and production was immediately increased and quality benefited by the change4 ,this method was later included in a revised specification issued to all producers4 ,the original system was one that required a great deal of labor per unit output4 ,the ,lincoln organization developed a method of handling connecting rods whereby five workmen accomplished the same result that would have required about #cj or #cb by the original method4 ,even after revising the specification so as to allow complete heat treatments in the rough-forged state1 the ordinary methods employed in heat-treating would have required #ab to #ae men4 ,with the fixtures employed1 five men could handle #a1cjj connecting rods1 half of which are plain and half1 forked1 in a working period of little over #g hr4 ,illustration3 ,fig4 #ad4--,rack for holding rods4 ,illustration3 ,fig4 #ae4--,sliding rods into tank4 ,the increase in production was gained by devising fixtures which enabled fewer men to handle a greater quantity of parts with less effort and in less time4 ,in heat-treating the forgings were laid on a rack or loop ,a1 ,fig4 #ad1 made of #a-a_/d-;in4 double extra-heavy pipe1 bent up with parallel sides about #i in4 apart1 one end being bent straight across and the other end being bent upward so as to afford an easy grasp for the hook4 ,fifteen rods were laid on each loop1 there being four loops of rods charged into a furnace with a hearth area of #cf by #ff in4 ,the rods were charged at a temperature of approximately #ijj;,f4 ,they were heated for refining over a period of #c hr4 to #a1fbe;,f41 soaked #ae min1 at this degree of heat and quenched in soluble quenching oil4 ,in pulling the heat to quench the rods1 the furnace door was raised and the operator pulls one of the loops ,a1 ,fig4 #ae forward to the shelf of the furnace1 supporting the straight end of the loop by means of the porter bar ,b4 ,they swung the loop of rods around from the furnace shelf and set the straight end of the loop on the edge of the quenching tank1 then raise the curved end ,c1 by means of their hook ,d so that all the rods on the loop slide into the oil bath4 ,before the rods cooled entirely1 the baskets in the quenching tank were raised and the oil allowed to partly drain off the forgings1 and they were stacked on curved-end loops or racks and charged into the furnace for the second or hardening heat4 ,the temperature of the furnace was raised in #a-a_/b hr4 to #a1eej;,f41 the rods soaked for #ae min4 at this degree of heat and quenched in the same manner as above4 ,they were again drained while yet warm1 placed on loops and charged into the furnace for the third or tempering heat4 ,the temperature of the furnace was brought to #a1ajj;,f4 in #a hr41 and the rods soaked at this degree of heat for #a hr4 ,they were then removed from the furnace the same as for quenching1 but were dumped onto steel platforms instead of into the quenching oil1 and allowed to cool on these steel platforms down to the room temperature4 ,,pickling ,,the ,,forgings ,the forgings were then pickled in a hot solution of either niter cake or sulphuric acid and water at a temperature of #agj;,f41 and using a solution of about #be per cent4 ,the solution was maintained at a constant point by taking hydrometer readings two or three times a day1 maintaining a reading of about #a4age4 ,sixty forked or one hundred single rods were placed in wooden racks and immersed in a lead-lined vat #cj by #cj by #e ft4 long4 ,the rack was lowered or lifted by means of an air hoist and the rods were allowed to stay in solution from #a_/b to #a hr41 depending on the amount of scale4 ,the rods were then swung and lowered in the rack into running hot water until all trace of the acid was removed4 ,the rod was finally subjected to ,brinell test4 ,this shows whether or not the rod has been heat-treated to the proper hardness4 ,if the rods did not read between #bda and #bgg1 they were re-treated until the proper hardness is obtained4 ,,chapter ,,iv ,,application ,,of ,,liberty ,,engine ,,materials ,,to ,,the ,,automotive ,,industry#a ,footnote #a3 ,paper presented at the summer meeting of the ,s4 ,a4 ,e4 at ,ottawa ,beach in ,june1 #aiai4 ,the success of the ,liberty engine program was an engineering achievement in which the science of metallurgy played an important part4 ,the reasons for the use of certain materials and certain treatments for each part are given with recommendations for their application to the problems of automotive industry4 ,the most important items to be taken into consideration in the selection of material for parts of this type are uniformity and machineability4 ,it has been demonstrated many times that the ordinary grades of bessemer screw stock are unsatisfactory for aviation purposes1 due to the presence of excessive amounts of unevenly distributed phosphorus and sulphide segregations4 ,for this reason1 material finished by the basic open hearth process was selected1 in accordance with the following specifications3 ,carbon1 #j4aej to #j4bej per cent2 manganese1 #j4ejj to #j4hjj per cent2 phosphorus1 #j4jde maximum per cent2 sulphur1 #j4jfj to #j4jij per cent4 ,this material in the cold-drawn condition will show3 ,elastic limit1 #ej1jjj lb4 per square inch1 elongation in #b in41 #aj per cent1 reduction of area1 #ce per cent4 ,this material gave as uniform physical properties as ,s4 ,a4 ,e4 ,no4 #ajbj steel and at the same time was sufficiently free cutting to produce a smooth thread and enable the screw-machine manufacturers to produce1 to the same thread limits1 approximately #ge per cent as many parts as from bessemer screw stock4 ,there are but seven carbon-steel carbonized parts on the ,liberty engine4 ,the most important are the camshaft1 the camshaft rocker lever roller and the tappet4 ,the material used for parts of this type was ,s4 ,a4 ,e4 ,no4 #a1jbj steel1 which is of the following chemical analysis3 ,carbon #j4aej to #j4bej per cent2 manganese1 #j4cjj to #j4fjj per cent2 phosphorus1 #j4jde maximum per cent2 sulphur1 #j4jej maximum per cent4 ,the heat treatment consisted in carbonizing at a temperature of from #a1fej to #a1gjj;,f4 for a sufficient length of time to secure the proper depth of case1 cool slowly or quench2 then reheat to a temperature of #a1chj to #a1dcj;,f4 to refine the grain of the case1 and quench in water4 ,the only thing that should limit the rate of cooling from the carbonizing heat is distortion4 ,camshaft rocker lever rollers and tappets1 as well as gear pins1 were quenched directly from the carbonizing heat in water and then case-refined and rehardened by quenching in water from a temperature of from #a1chj to #a1dcj;,f4 ,the advantage of direct quenching from the carbonizing heat is doubtless one of economy1 and in many cases will save the cost of a reheating4 ,specifications for case hardening1 issued by the ,society of ,automotive ,engineers1 have lately been revised2 whereas they formerly called for a slow cooling1 they now permit a quenching from the pot4 ,doubtless this is a step in advance4 ,warpage caused by quenching can be reduced to a minimum by thoroughly annealing the stock before any machine work is done on it4 ,another advantage obtained from rapid cooling from the carbonizing heat is the retaining of the majority of the excess cementite in solution which produces a less brittle case and by so doing reduces the liability of grinding checks and chipping of the case in actual service4 ,in the case of the camshaft1 it is not possible to quench directly from the carbonizing heat because of distortion and therefore excessive breakage during straightening operations4 ,all ,liberty camshafts were cooled slowly from carbonizing heat and hardened by a single reheating to a temperature of from #a1chj to #a1dcj;,f4 and quenching in water4 ,considerable trouble has always been experienced in obtaining uniform hardness on finished camshafts4 ,this is caused by insufficient water circulation in the quenching tank1 which allows the formation of steam pockets to take place1 or by decarbonization of the case during heating by the use of an overoxidizing flame4 ,another cause1 which is very often overlooked1 is due to the case being ground off one side of cam more than the other and is caused by the roughing master cam being slightly different from the finishing master cam4 ,great care should be taken to see that this condition does not occur1 especially when the depth of case is between #a_/cb and #c_/fd in4 ,,carbon-,,steel ,,forgings ,low-stressed1 carbon-steel forgings include such parts as carbureter control levers1 etc4 ,the important criterion for parts of this type is ease of fabrication and freedom from over-heated and burned forgings4 ,the material used for such parts was ,s4 ,a4 ,e4 ,no4 #a1jcj steel1 which is of the following chemical composition3 ,carbon1 #j4bej to #j4cej per cent2 manganese1 #j4ejj to #j4hjj per cent2 phosphorus1 #j4jde maximum per cent2 sulphur1 #j4jej maximum per cent4 ,to obtain good machineability1 all forgings produced from this steel were heated to a temperature of from #a1ege to #a1fbe;,f4 to refine the grain of the steel thoroughly and quenched in water and then tempered to obtain proper machineability by heating to a temperature of from #a1jjj to #a1ajj;,f4 and cooled slowly or quenched4 ,forgings subjected to this heat treatment are free from hard spots and will show a ,brinell hardness of #agg to #bag1 which is proper for all ordinary machining operations4 ,great care should be taken not to use steel for parts of this type containing less than #j4be per cent carbon1 because the lower the carbon the greater the liability of hard spots1 and the more difficult it becomes to eliminate them4 ,the only satisfactory method so far in commercial use for the elimination of hard spots is to give forgings a very severe quench from a high temperature followed by a proper tempering heat to secure good machine ability as outlined above4 ,the important carbon-steel forgings consisted of the cylinders1 the propeller-hubs1 the propeller-hub flange1 etc4 ,the material used for parts of this type was ,s4 ,a4 ,e4 ,no4 #a1jde steel1 which is of the following chemical composition3 ,carbon1 #j4djj to #j4ejj per cent2 manganese1 #j4ejj to #j4hjj per cent2 phosphorus1 #j4jde maximum per cent2 sulphur1 #j4jej maximum per cent4 ,all forgings made from this material must show1 after heat treatment1 the following minimum physical properties3 ,elastic limit1 #gj1jjj2 lb4 per square inch1 elongation in #b in41 #ah per cent1 reduction of area1 #de2 per cent1 ,brinell hardness1 #bag to #bee4 ,to obtain these physical properties1 the forgings were quenched in water from a temperature of #a1ejj to #a1eej;,f41 followed by tempering to meet proper ,brinell requirements by heating to a temperature of #a1aej to #a1bjj;,f4 and cooled slowly or quenched4 ,no trouble of any kind was ever experienced with parts of this type4 ,the principal carbon-steel pressed parts used on the ,liberty engine were the water jackets and the exhaust manifolds4 ,the material used for parts of this type was ,s4 ,a4 ,e4 ,no4 #a1jaj steel1 which is of the following chemical composition3 ,carbon1 #j4je to #j4ae per cent2 manganese1 #j4cj to #j4fj per cent2 phosphorus1 #j4jde maximum per cent2 sulphur1 #j4jde maximum per cent4 ,no trouble was experienced in the production of any parts from this material with the exception of the water jacket4 ,due to the particular design of the ,liberty cylinder assembly1 many failures occurred in the early days1 due to the top of the jacket cracking with a brittle fracture4 ,it was found that these failures were caused primarily from the use of jackets which showed small scratches or die marks at this joint and secondarily by improper annealing of the jackets themselves between the different forming operations4 ,by a careful inspection for die marks and by giving the jackets #a1djj;,f4 annealing before the last forming operation1 it was possible to completely eliminate the trouble encountered4 ,,highly ,,stressed ,,parts ,the highly stressed parts on the ,liberty engine consisted of the connecting-rod bolt1 the main-bearing bolt1 the propeller-hub key1 etc4 ,the material used for parts of this type was selected at the option of the manufacturer from standard ,s4 ,a4 ,e4 steels1 the composition of which are given in ,table #aa4 ,,table #aa4--;,,composition ,,of ,s4 ,a4 ,e4 ,,steels ,nos4 #b1ccj1 #c1ace ,,and #f1acj ,steel ,no #b1ccj #c1ace #f1acj ,carbon1 minimum #j4bej #j4cjj #j4bej ,carbon1 maximum #j4cej #j4djj #j4dej ,manganese1 minimum #j4ejj #j4ejj #j4ejj ,manganese1 maximum #j4hjj #j4hjj #j4hjj ,phosphorus1 maximum #j4jde #j4jdj #j4jdj ,sulphur1 maximum #j4jde #j4jde #j4jde ,nickel1 minimum #c4bej #a4jjj ,nickel1 maximum #c4gej #a4ejj ,chromium1 minimum #j4dej #j4hjj ,chromium1 maximum #j4gej #a4ajj ,vanadium1 minimum #j4aej ,all highly stressed parts on the ,liberty engine must show1 after heat treatment1 the following minimum physical properties3 ,elastic limit1 #ajj1jjj lb4 per square inch2 elongation in #b in41 #af per cent2 reduction of area1 #de per cent2 scleroscope hardness1 #dj to #ej4 ,the heat treatment employed to obtain these physical properties consisted in quenching from a temperature of #a1ebe to #a1ege;,f41 in oil1 followed by tempering at a temperature of from #ibe to #ige;,f4 ,due to the extremely fine limits used on all threaded parts for the ,liberty engine1 a large percentage of rejection was due to warpage and scaling of parts4 ,to eliminate this objection1 many of the ,liberty engine builders adopted the use of heat-treated and cold-drawn alloy steel for their highly stressed parts4 ,on all sizes up to and including #c_/h in4 in diameter1 the physical properties were secured by merely normalizing the hot-rolled bars by heating to a temperature of from #a1ebe to #a1ege;,f41 and cooling in air1 followed by the usual cold-drawing reductions4 ,for parts requiring stock over #c_/h in4 in diameter1 the physical properties desired were obtained by quenching and tempering the hot-rolled bars before cold-drawing4 ,it is the opinion that the use of heat-treated and cold-drawn bars is very good practice1 provided proper inspection is made to guarantee the uniformity of heat treatment and1 therefore1 the uniformity of the physical properties of the finished parts4 ,the question has been asked many times by different manufacturers1 as to which alloy steel offers the best machineability when heat-treated to a given ,brinell hardness4 ,the general consensus of opinion among the screw-machine manufacturers is that ,s4 ,a4 ,e4 ,no4 #f1acj steel gives the best machineability and that ,s4 ,a4 ,e4 ,no4 #b1ccj steel would receive second choice of the three specified4 ,in the finishing of highly stressed parts for aviation engines1 extreme care must be taken to see that all tool marks are eliminated1 unless they are parallel to the axis of strain1 and that proper radii are maintained at all changes of section4 ,this is of the utmost importance to give proper fatigue resistance to the part in question4 ,,gears ,the material used for all gears on the ,liberty engine was selected at the option of the manufacturer from the following standard ,s4 ,a4 ,e4 steels1 the composition of which are given in ,table #ab1 ,,table #ab4--;,,composition ,,of ,,steels ,,nos4 ,x-#c1cdj ,,and #f1adj ,steel ,no ,x-#c1cdj #f1adj ,carbon1 minimum #j4cej #j4cej ,carbon1 maximum #j4dej #j4dej ,manganese1 minimum #j4dej #j4ejj ,manganese1 maximum #j4gej #j4hjj ,phosphorus1 maximum #j4jdj #j4jdj ,sulphur1 maximum #j4jde #j4jde ,nickel1 minimum #b4gej ,nickel1 maximum #c4bej ,chromium1 minimum #j4gjj #j4hjj ,chromium1 maximum #j4iej #a4ajj ,vanadium1 minimum #j4aej ,all gears were heat-treated to a scleroscope hardness of from #ee to #ee4 ,the heat treatment used to secure this hardness consisted in quenching the forgings from a temperature of #a1eej to #a1fjj;,f4 in oil and annealing for good machineability at a temperature of from #a1cjj to #a1cej;,f4 ,forgings treated in this manner showed a ,brinell hardness of from #agg to #bag4 ,,rate ,,of ,,cooling ,at the option of the manufacturer1 the above treatment of gear forgings could be substituted by normalizing the forgings at a temperature of from #a1eej to #a1fjj;,f4 ,the most important criterion for proper normalizing1 consisted in allowing the forgings to cool through the critical temperature of the steel1 at a rate not to exceed #ej;,f4 per hour4 ,for the two standard steels used1 this consisted in cooling from the normalizing temperature down to a temperature of #a1ajj;,f41 at the rate indicated4 ,forgings normalized in this manner will show a ,brinell hardness of from #agg to #bag4 ,the question has been repeatedly asked as to which treatment will produce the higher quality finished part4 ,in answer to this ,i will state that on simple forgings of comparatively small section1 the normalizing treatment will produce a finished part which is of equal quality to that of the quenched and annealed forgings4 ,however1 in the case of complex forgings1 or those of large section1 more uniform physical properties of the finished part will be obtained by quenching and annealing the forgings in the place of normalizing4 ,the heat treatment of the finished gears consisted of quenching in oil from a temperature of from #a1dbj to #a1ddj;,f4 for the ,no4 ,x-#c1cdj steel1 or from a temperature of from #a1ejj to #a1edj;,f4 for ,no4 #f1adj steel1 followed by tempering in saltpeter or in an electric furnace at a temperature of from #fej to #gjj;,f4 ,the question has been asked by many engineers1 why is the comparatively low scleroscope hardness specified for gears8 ,the reason for this is that at best the life of an aviation engine is short1 as compared with that of an automobile1 truck or tractor1 and that shock resistance is of vital importance4 ,a sclerescope hardness of from #ee to #fe will give sufficient resistance to wear to prevent replacements during the life of an aviation engine1 while at the same time this hardness produces approximately #ej per cent greater shock-resisting properties to the gear4 ,in the case of the automobile1 truck or tractor1 resistance to wear is the main criterion and for that reason the higher hardness is specified4 ,great care should be taken in the design of an aviation engine gear to eliminate sharp corners at the bottom of teeth as well as in keyways4 ,any change of section in any stressed part of an aviation engine must have a radius of at least #a_/cb in4 to give proper shock and fatigue resistance4 ,this fact has been demonstrated many times during the ,liberty engine program4 ,,connecting ,,rods ,the material used for all connecting rods on the ,liberty engine was selected at the option of the manufacturer from one of two standard ,s4 ,a4 ,e4 steels1 the composition of which are given in ,table #ac4 ,,table #ac4--;,,composition ,,of ,,steels ,,nos4 ,x-#c1cce ,,and #f1ace ,steel ,no4 ,x-#c1cce #f1ace ,carbon1 minimum #j4cjj #j4cjj ,carbon1 maximum #j4djj #j4djj ,manganese1 minimum #j4dej #j4ejj ,manganese1 maximum #j4gej #j4hjj ,phosphorus1 maximum #j4jdj #j4jdj ,sulphur1 maximum #j4jde #j4jde ,nickel1 minimum #b4gej ,nickel1 maximum #c4bej ,chromium1 minimum #j4gjj #j4hjj ,chromium1 maximum #j4iej #a4ajj ,vanadium minimum #j4aej ,all connecting rods were heat-treated to show the following minimum physical properties2 ,elastic limit1 #aje1jjj lb4 per square inch3 elongation in #b in41 #ag4e2 per cent1 reduction of area #ej4j2 per cent41 ,brinell hardness1 #bda to #bgg4 ,the heat treatment used to secure these physical properties consisted in normalizing the forgings at a temperature of from #a1eej to #a1fjj;,f41 followed by cooling in the furnace or in air4 ,the forgings were then quenched in oil from a temperature of from #a1dbj to #a1ddj;,f4 for the ,no4 ,x-#c1cce steel1 or from a temperature of from #a1ejj to #a1ebe;,f4 for ,no4 #f1ace steel1 followed by tempering at a temperature of from #a1jge to #a1aej;,f4 ,at the option of the manufacturer1 the normalizing treatment could be substituted by quenching the forgings from a temperature of from #a1eej to #a1fjj;,f41 in oil1 and annealing for the best machineability at a temperature of from #a1cjj to #a1cej;,f4 ,the double quench1 however1 did not prove satisfactory on ,no4 ,x-#c1cce steel1 due to the fact that it was necessary to remove forgings from the quenching bath while still at a temperature of from #cjj to #ejj;,f4 to eliminate any possibility of cracking4 ,in view of the fact that this practice is difficult to carry out in the average heat-treating plant1 considerable trouble was experienced4 ,the most important criterion in the production of aviation engine connecting rods is the elimination of burned or severely overheated forgings4 ,due to the particular design of the forked rod1 considerable trouble was experienced in this respect because of the necessity of reheating the forgings before they are completely forged4 ,as a means of elimination of burned forgings1 test lugs were forged on the channel section as well as on the top end of fork4 ,after the finish heat treatment1 these test lugs were nicked and broken and the fracture of the steel carefully examined4 ,this precaution made it possible to eliminate burned forgings as the test lugs were placed on sections which would be most likely to become burned4 ,there is a great difference of opinion among engineers as to what physical properties an aviation engine connecting rod should have4 ,many of the most prominent engineers contend that a connecting rod should be as stiff as possible4 ,to produce rods in this manner in any quantity1 it is necessary for the final heat treatment to be made on the semi-machined rod4 ,this practice would make it necessary for a larger percentage of the semi-machined rods to be cold-straightened after the finish heat treatment4 ,the cold-straightening operation on a part having important functions to perform as a connecting rod is extremely dangerous4 ,in view of the fact that a connecting rod functions as a strut1 it is considered that this part should be only stiff enough to prevent any whipping action during the running of the engine4 ,the greater the fatigue-resisting property that one can put into the rod after this stiffness is reached1 the longer the life of the rod will be4 ,this is the reason for the ,brinell limits mentioned being specified4 ,in connection with the connecting rod1 emphasis must be laid on the importance of proper radii at all changes of section4 ,the connecting rods for the first few ,liberty engines were machined with sharp corners at the point where the connecting-rod bolt-head fits on assembly4 ,on the first long endurance test of a ,liberty engine equipped with rods of this type1 failure resulted from fatigue starting at this point4 ,it is interesting to note that every rod on the engine which did not completely fail at this point had started to crack4 ,the adoption of a #a_/cb-;in4 radius at this point completely eliminated fatigue failures on ,liberty rods4 ,,crankshaft ,the crankshaft was the most highly stressed part of the entire ,liberty engine1 and1 therefore1 every metallurgical precaution was taken to guarantee the quality of this part4 ,the material used for the greater portion of the ,liberty crankshafts produced was nickel-chromium steel of the following chemical composition3 ,carbon1 #j4cej to #j4dej per cent2 manganese1 #j4cjj to #j4fjj per cent2 phosphorus1 #j4jdj maximum per cent2 sulphur1 #j4jde maximum per cent2 nickel1 #a4gej to #b4bej per cent2 chromium1 #j4gjj to #j4ijj per cent4 ,each crankshaft was heat-treated to show the following minimum physical properties3 ,elastic limit1 #aaf1jjj lb4 per square inch2 elongation in #b in41 #af per cent1 reduction of area1 #ej per cent1 ,izod impact1 #cd ft4-lb42 ,brinell hardness1 #bff to #cba4 ,for every increase of #d1jjj lb4 per square inch in the elastic limit above #aaf1jjj lb4 per square inch1 the minimum ,izod impact required was reduced #a ft4-lb4 ,the heat treatment used to produce these physical properties consisted in normalizing the forgings at a temperature of from #a1eej to #a1fjj;,f41 followed by quenching in water at a temperature of from #a1dge to #a1ebe;,f4 and tempering at a temperature of from #a1jjj to #a1ajj;,f4 ,it is absolutely necessary that the crankshafts be removed from the quenching tank before being allowed to cool below a temperature of #ejj;,f41 and immediately placed in the tempering furnace to eliminate the possibility of quenching cracks4 ,a prolongation of not less than the diameter of the forging bearing was forged on one end of each crankshaft4 ,this was removed from the shaft after the finish heat treatment1 and physical tests were made on test specimens which were cut from it at a point half way between the center and the surface4 ,one tensile test and one impact test were made on each crankshaft1 and the results obtained were recorded against the serial number of the shaft in question4 ,this serial number was carried through all machining operations and stamped on the cheek of the finished shaft4 ,in addition to the above tensile and impact tests1 at least two ,brinell hardness determinations were made on each shaft4 ,all straightening operations on the ,liberty crankshaft which were performed below a temperature of #ejj;,f4 were followed by retempering at a temperature of approximately #bjj;,f4 below the original tempering temperature4 ,another illustration of the importance of proper radii at all changes of section is given in the case of the ,liberty crankshaft4 ,the presence of tool marks or under cuts must be completely eliminated from an aviation engine crankshaft to secure proper service4 ,during the duration of the ,liberty program1 four crankshafts failed from fatigue1 failures starting from sharp corners at bottom of propeller-hub keyway4 ,two of the shafts that failed showed torsional spirals running more than completely around the shaft4 ,as soon as this difficulty was removed no further trouble was experienced4 ,one of the most important difficulties encountered in connection with the production of ,liberty crankshafts was hair-line seams4 ,the question of hair-line seams has been discussed to greater length by engineers and metallurgists during the war than any other single question4 ,hair-line seams are caused by small non-metallic inclusions in the steel4 ,there is every reason to believe that these inclusions are in the greater majority of cases manganese sulphide4 ,there is a great difference of opinion as to the exact effect of hair-line seams on the service of an aviation engine crankshaft4 ,it is the opinion of many that hair-line seams do not in any way affect the endurance of a crankshaft in service1 provided they are parallel to the grain of the steel and do not occur on a fillet4 ,of the #bj1jjj ,liberty engines produced1 fully #ej per cent of the crankshafts used contain hair-line seams but not at the locations mentioned4 ,there has never been a failure of a ,liberty crankshaft which could in any way be traced to hair-line seams4 ,it was found that hair-line seams occur generally on high nickel-chromium steels4 ,one of the main reasons why the comparatively mild analysis nickel-chromium steel was used was due to the very few hair-line seams present in it4 ,it was also determined that the hair lines will in general be found near the surface of the forgings4 ,for that reason1 as much finish as possible was allowed for machining4 ,a number of tests have been made on forging bars to determine the depths at which hair-line seams are found1 and many cases came up in which hair-line seams were found #c_/h in4 from the surface of the bar4 ,this means that in case a crankshaft does not show hair-line seams on the ground surface this is no indication that it is free from such a defect4 ,one important peculiarity of nickel-chromium steel was brought out from the results obtained on impact tests4 ,this peculiarity is known as blue brittleness4 ,just what the effect of this is on the service of a finished part depends entirely upon the design of the particular part in question4 ,there have been no failures of any nickel-chromium steel parts in the automotive industry which could in any way be traced to this phenomena4 ,whether or not nickel-chromium-steel forgings will show blue brittleness depends entirely upon the temperature at which they are tempered and their rate of cooling from this temperature4 ,the danger range for tempering nickel-chromium steels is between a temperature of from #djj to #a1ajj;,f4 ,from the data so far gathered on this phenomena1 it is necessary that the nickel-chromium steel to show blue brittleness be made by the acid process4 ,there has never come to my attention a single instance in which basic open hearth steel has shown this phenomena4 ,just why the acid open hearth steel should be sensitive to blue brittleness is not known4 ,all that is necessary to eliminate the presence of blue brittleness is to quench all nickel-chromium-steel forgings in water from their tempering temperature4 ,the last #bj1jjj ,liberty crankshafts that were made were quenched in this manner4 ,,piston ,,pin ,the piston pin on an aviation engine must possess maximum resistance to wear and to fatigue4 ,for this reason1 the piston pin is considered1 from a metallurgical standpoint1 the most important part on the engine to produce in quantities and still possess the above characteristics4 ,the material used for the ,liberty engine piston pin was ,s4 ,a4 ,e4 ,no4 #bcae steel1 which is of the following chemical composition3 ,carbon1 #j4ajj to #j4bjj per cent2 manganese1 #j4ejj to #j4hjj per cent2 phosphorus1 #j4jdj maximum per cent2 sulphur1 #j4jde maximum per cent2 nickel1 #c4bej to #c4gej per cent4 ,each finished piston pin1 after heat treatment1 must show a minimum scleroscope hardness of the case of #gj1 a scleroscope hardness of the core of from #ce to #ee and a minimum crushing strength when supported as a beam and the load applied at the center of #ce1jjj lb4 ,the heat treatment used to obtain the above physical properties consisted in carburizing at a temperature not to exceed #a1fge;,f41 for a sufficient length of time to secure a case of from #j4jb to #j4jd in4 deep4 ,the pins are then allowed to cool slowly from the carbonizing heat1 after which the hole is finish-machined and the pin cut to length4 ,the finish heat treatment of the piston pin consisted in quenching in oil from a temperature of from #a1ebe to #a1ege;,f4 to refine the grain of core properly and then quenching in oil at a temperature of from #a1cdj to #a1chj;,f4 to refine and harden the grain of the case properly1 as well as to secure proper hardness of core4 ,after this quenching1 all piston pins are tempered in oil at a temperature of from #cge to #djj;,f4 ,a #ajj per cent inspection for scleroscope hardness of the case and the core was made1 and no failures were ever recorded when the above material and heat treatment was used4 ,,application ,,to ,,the ,,automotive ,,industry ,the information given on the various parts of the ,liberty engine applies with equal force to the corresponding parts in the construction of an automobile1 truck or tractor4 ,we recommend as first choice for carbon-steel screw-machine parts material produced by the basic open hearth process and having the following chemical composition2 ,carbon1 #j4aej to #j4bej per cent2 manganese1 #j4ejj to #j4hjj per cent2 phosphorus1 #j4jde maximum per cent2 sulphur1 #j4jge to #j4aej per cent4 ,this material is very uniform and is nearly as free cutting as bessemer screw stock4 ,it is sufficiently uniform to be used for unimportant carburized parts1 as well as for non-heat-treated screw-machine parts4 ,a number of the large automobile manufacturers are now specifying this material in preference to the regular bessemer grades4 ,as second choice for carbon-steel screw-machine parts we recommend ordinary bessemer screw stock1 purchased in accordance with ,s4 ,a4 ,e4 specification ,no4 #aaad4 ,the advantage of using ,no4 #aaad steel lies in the fact that the majority of warehouses carry standard sizes of this material in stock at all times4 ,the disadvantage of using this material is due to its lack of uniformity4 ,the important criterion for transmission gears is resistance to wear4 ,to secure proper resistance to wear a ,brinell hardness of from #eab to #efj must be obtained4 ,the material selected to obtain this hardness should be one which can be made most nearly uniform1 will undergo forging operations the easiest1 will be the hardest to overheat or burn1 will machine best and will respond to a good commercial range of heat treatment4 ,it is a well-known fact that the element chromium1 when in the form of chromium carbide in alloy steel1 offers the greatest resistance to wear of any combination yet developed4 ,it is also a well-known fact that the element nickel in steel gives excellent shock-resisting properties as well as resistance to wear but not nearly as great a resistance to wear as chromium4 ,it has been standard practice for a number of years for many manufacturers to use a high nickel-chromium steel for transmission gears4 ,a typical nickel-chromium gear specification is as follows3 ,carbon1 #j4dgj to #j4ebj per cent2 manganese1 #j4ejj to #j4hjj per cent2 phosphorus1 #j4jdj maximum per cent2 sulphur1 #j4jde maximum per cent2 chromium1 #j4gjj to #j4iej per cent4 ,there is no question but that a gear made from material of such an analysis will give excellent service4 ,however1 it is possible to obtain the same quality of service and at the same time appreciably reduce the cost of the finished part4 ,the gear steel specified is of the air-hardening type4 ,it is extremely sensitive to secondary pipe1 as well as seams1 and is extremely difficult to forge and very easy to overheat4 ,the heat-treatment range is very wide1 but the danger from quenching cracks is very great4 ,in regard to the machineability1 this material is the hardest to machine of any alloy steel known4 ,,composition ,,of ,,transmission-,,gear ,,steel ,if the nickel content of this steel is eliminated1 and the percentage of chromium raised slightly1 an ideal transmission-gear material is obtained4 ,this would1 therefore1 be of the following composition3 ,carbon1 #j4dgj to #j4ebj per cent2 manganese1 #j4ejj to #j4hjj per cent2 phosphorus1 #j4jdj maximum per cent2 sulphur1 #j4jde maximum per cent2 chromium1 #j4hjj to #a4ajj per cent4 ,the important criterion in connection with the use of this material is that the steel be properly deoxidized1 either through the use of ferrovanadium or its equivalent4 ,approximately #b1ejj sets of transmission gears are being made daily from material of this analysis and are giving entirely satisfactory results in service4 ,the heat treatment of the above material for transmission gears is as follows3 ,normalize forgings at a temperature of from #a1e4ej to #a1fjj;,f4 ,cool from this temperature to a temperature of #a1ajj;,f4 at the rate of #ej per hour4 ,cool from #a1ajj;,f41 either in air or quench in water4 ,forgings so treated will show a ,brinell hardness of from #agg to #bag1 which is the proper range for the best machineability4 ,the heat treatment of the finished gears consists of quenching in oil from a temperature of #a1ejj to #a1edj;,f41 followed by tempering in oil at a temperature of from #cge to #dbe;,f4 ,gears so treated will show a ,brinell hardness of from #eab to #efj1 or a scleroscope hardness of from #gb to #hj4 ,one tractor builder has placed in service #bj1jjj sets of gears of this type of material and has never had to replace a gear4 ,taking into consideration the fact that a tractor transmission is subjected to the worst possible service conditions1 and that it is under high stress #ij per cent of the time1 it seems inconceivable that any appreciable transmission trouble would be experienced when material of this type is used on an automobile1 where the full load is applied not over #a per cent of the time1 or on trucks where the full load is applied not over #ej per cent of the time4 ,the gear hardness specified is necessary to reduce to a minimum the pitting or surface fatigue of the teeth4 ,if gears having a ,brinell hardness of over #efj are used1 danger is encountered1 due to low shock-resisting properties4 ,if the ,brinell hardness is under #eab1 trouble is experienced due to wear and surface fatigue of the teeth4 ,for ring gears and pinions material of the following chemical composition is recommended3 ,carbon1 #j4ajj to #j4bjj per cent2 manganese1 #j4cej to #j4fej per cent2 phosphorus1 #j4jdj maximum per cent2 sulphur1 #j4jde maximum per cent2 chromium1 #j4eej to #j4gej per cent2 nickel1 #j4djj to #j4fjj per cent4 ,care should be taken to see that this material is properly deoxidized either by the use of ferrovanadium or its equivalent4 ,the advantage of using a material of the above type lies in the fact that it will produce a satisfactory finished part with a very simple treatment4 ,the heat treatment of ring gears and pinions is as follows3 ,carburize at a temperature of from #a1fej to #a1gjj;,f4 for a sufficient length of time to secure a depth of case of from #a_/cb to #c_/fd in41 and quench directly from carburizing heat in oil4 ,reheat to a temperature of from #a1dcj to #a1dfj;,f4 and quench in oil4 ,temper in oil at a temperature of from #cge to #dbe;,f4 ,the final quenching operation on a ring gear should be made on a fixture similar to the ,gleason press to reduce distortion to a minimum4 ,one of the largest producers of ring gears and pinions in the automotive industry has been using this material and treatment for the last #b years1 and is of the opinion that he is now producing the highest quality product ever turned out by that plant4 ,on some designs of automobiles a large amount of trouble is experienced with the driving pinion4 ,if the material and heat treatment specified will not give satisfaction1 rather than to change the design it is possible to use the following analysis material1 which will raise the cost of the finished part but will give excellent service3 ,carbon1 #j4ajj to #j4bjj per cent2 manganese1 #j4cej to #j4fej per cent2 phosphorus1 #j4jdj maximum per cent2 sulphur1 #j4jde maximum per cent2 nickel1 #d4gej to #e4bej per cent4 ,the heat treatment of pinions produced from this material consists in carburizing at a temperature of from #a1fjj to #a1fej;,f4 for a sufficient length of time to secure a depth of case from #a_/cb to #c_/fd in4 ,the pinions are then quenched in oil from a temperature of #a1ejj to #a1ebe;,f4 to refine the grain of the core and quenched in oil from a temperature of from #a1cdj to #a1cfj;,f4 ,to refine and harden the case4 ,the use of this material however1 is recommended only in an emergency1 as high-nickel steel is very susceptible to seams1 secondary pipe and laminations4 ,the main criterion on rear-axle and pinion shafts1 steering knuckles and arms and parts of this general type is resistance to fatigue and torsion4 ,the material recommended for parts of this character is either ,s4 ,a4 ,e4 ,no4 #face or ,no4 #cace steel1 which have the chemical composition given in ,tables #i and #g4 ,,heat ,,treatment ,,of ,,axles ,parts of this general type should be heat-treated to show the following minimum physical properties3 ,elastic limit1 #aae1jjj lb4 per square inch2 elongation in #b in41 #af per cent2 reduction of area1 #ej per cent2 ,brinell hardness1 #bgg to #cba4 ,the heat treatment used to secure these physical properties consists in quenching from a temperature of from #a1ebj to #a1edj;,f4 in water and tempering at a temperature of from #ige to #a1jbe;,f4 ,where the axle shaft is a forging1 and in the case of steering knuckles and arms1 this heat treatment should be preceded by normalizing the forgings at a temperature of from #a1eej to #a1fjj;,f4 ,it will be noted that these physical properties correspond to those worked out for an ideal aviation engine crankshaft4 ,if parts of this type are designed with proper sections1 so that this range of physical properties can be used1 the part in question will give maximum service4 ,one of the most important developments during the ,liberty engine program was the fact that it is not necessary to use a high-analysis alloy steel to secure a finished part which will give proper service4 ,this fact should save the automotive industry millions of dollars on future production4 ,if the proper authority be given the metallurgical engineer to govern the handling of the steel from the time it is purchased until it is assembled into finished product1 mild-analysis steels can be used and the quality of the finished product guaranteed4 ,it was only through the careful adherence to these fundamental principles that it was possible to produce #bj1jjj ,liberty engines1 which are considered to be the most highly stressed mechanism ever produced1 without the failure of a single engine from defective material or heat treatment4 ,,making ,,steel ,,balls ,steel balls are made from rods or coils according to size1 stock less than #i_/af-;in4 comes in coils4 ,stock #e_/h-;in4 and larger comes in rods4 ,ball stock is designated in thousandths so that #e_/h-;in4 rods are known as #j4fbe-;in4 stock4 ,steel for making balls of average size is made up of3 ,carbon #j4ie to #a4je per cent ,silicon #j4bj to #j4ce per cent ,manganese #j4cj to #j4de per cent ,chromium #j4ce to #j4de per cent ,sulphur and phosphorus not to exceed #j4jbe per cent ,for the larger sizes a typical analysis is3 ,carbon #a4jb per cent ,silicon #j4ba per cent ,manganese #j4dj per cent ,chromium #j4fe per cent ,sulphur #j4jbf per cent ,phosphorus #j4jad per cent ,balls #e_/h in4 and below are formed cold on upsetting or heading machines1 the stock use is as follows3 ,,table #ad4--,,sizes ,,of ,,stock ,,for ,,forming ,,balls ,,on ,,header ---------------------------------------- --------------- ,diameter of ,diameter of ,diameter of ,diameter of ball1 inch stock inch ball1 inch stock1 inch ---------------------------------------- ------------ #a_/h #j4ajj #e_/af #j4bce #e_/cb #j4abj #c_/h #j4bge #c_/af #j4ade #g_/af #j4cbj #g_/cb #j4agj #a_/b #j4cfe #a_/d #j4aij #i_/af #j4cie #i_/cb #j4bbj #e_/h #j4ddj ---------------------------------------- --------------- ,for larger balls the blanks are hot-forged from straight bars4 ,they are usually forged in multiples of four under a spring hammer and then separated by a suitable punching or shearing die in a press adjoining the hammer4 ,the dimensions are3 ---------------------------------------- ------------------- ,diameter of ball1 ,diameter of die1 ,diameter of stock1 inch inch inch ---------------------------------------- ----------------- #c_/d #j4gge #j4fbe #g_/h #j4ije #j4gbi #a #a4jce #j4hbc ---------------------------------------- ------------------- ,before hardening1 the balls are annealed to relieve the stresses of forging and grinding1 this being done by passing them through a revolving retort made of nichrome or other heat-resisting substance4 ,the annealing temperature is #a1cjj;,f4 ,the hardening temperature is from #a1dbe to #a1dge;,f4 according to size and composition of steel4 ,small balls1 #e_/af and under1 are quenched in oil1 the larger sizes in water4 ,in some special cases brine is used4 ,quenching small balls in water is too great a shock as the small volume is cooled clear through almost instantly4 ,the larger balls have metal enough to cool more slowly4 ,balls which are cooled in either water or brine are boiled in water for #b hr4 to relieve internal stresses1 after which the balls are finished by dry-grinding and oil-grinding4 ,the ball makers have an interesting method of testing stock for seams which do not show in the rod or wire4 ,the ,hoover ,steel ,ball ,company cut off pieces of rod or wire #g_/af in4 long and subject them to an end pressure of from #bj1jjj to #ej1jjj lb4 ,a pressure of #bj1jjj lb4 compresses the piece to #c_/af in4 and the #ej1jjj lb4 pressure to #c_/cb in4 ,this opens any seam which may exist but a solid bar shows no seam4 ,another method which has proved very successful is to pass the bar or rod to be tested through a solenoid electro-magnet4 ,with suitable instruments it is claimed that this is an almost infallible test as the instruments show at once when a seam or flaw is present in the bar4 ,,chapter ,v ,,the ,,forging ,,of ,,steel ,so much depends upon the forging of steel that this operation must be carefully supervised4 ,this is especially true because of the tendency to place unskilled and ignorant men as furnace-tenders and hammer men4 ,the main points to be supervised are the slow and careful heating to the proper temperature2 forging must be continued at a proper rate to the correct temperature4 ,the bar of stock from which a forging was made may have had a fairly good structure1 but if the details of the working are not carefully watched1 a seamy1 split article of no value may easily result4 ,,heating4--,although it is possible to work steels cold1 to an extent depending upon their ductility1 and although such operations are commonly performed1 forging usually means working heated steel4 ,heating is therefore a vital part of the process4 ,heating should be done slowly in a soaking heat4 ,a soft lazy flame with excess carbon is necessary to avoid burning the corners of the bar or billet1 and heavily scaling the surface4 ,if the temperature is not raised slowly1 the outer part of the metal may be at welding heat while the inner part is several hundred degrees colder and comparatively hard and brittle4 ,the above refers to muffle furnaces4 ,if the heating is done in a small blacksmith's forge1 the fire should be kept clean1 and remade at intervals of about two hours4 ,ashes and cinders should be cleaned from the center down to the tuyere and oily waste and wood used to start a new fire4 ,as this kindles a layer of coke from the old fire is put on top1 and another layer of green coal 7screened and dampened blacksmiths' coal7 as a cover4 ,when the green coal on top has been coked the fire is ready for use4 ,as the fuel burns out in the center1 the coke forming around the edge is pushed inward1 and its place taken by more green coal4 ,thus the fire is made up of three parts2 the center where coke is burning and the iron heating2 a zone where coke is forming1 and the outside bank of green coal4 ,,steel ,,worked ,,in ,,austenitic ,,state4--,as a general rule steel should be worked when it is in the austenitic state4 7,see page #ajh47 ,it is then soft and ductile4 ,as the steel is heated above the critical temperature the size of the austenite crystals tends to grow rapidly4 ,when forging starts1 however1 these grains are broken up4 ,the growth is continually destroyed by the hammering1 which should consequently be continued down to the upper critical temperature when the austenite crystals break up into ferrite and cementite4 ,the size of the final grains will be much smaller and hence a more uniform structure will result if the mother austenite was also fine grained4 ,a final steel will be composed of pearlite2 ferrite and pearlite2 or cementite and pearlite1 according to the carbon content4 ,the ultimate object is to secure a fine1 uniform grain throughout the piece and this can be secured by uniform heating and by thoroughly rolling it or working it at a temperature just down to its critical point4 ,if this is correctly done the fracture will be fine and silky4 ,steel which has been overheated slightly and the forging stopped at too high a temperature will show a granular fracture4 ,a badly overheated or burned steel will have iridescent colors on a fresh fracture1 it will be brittle both hot and cold1 and absolutely ruined4 ,,steel ,,can ,,be ,,worked ,,cold4--,as noted above1 steel can be worked cold1 as in the case of cold-rolled steel4 ,heat treatment of cold-worked steel is a very delicate operation4 ,cold working hardens and strengthens steel4 ,it also introduces internal stresses4 ,heat-treatments are designed to eliminate the stresses without losing the hardness and strength4 ,this is done by tempering at a low heat4 ,avoid the blue range 7#cej to #gej;,c474 ,tempering for a considerable time just under the critical is liable to cause great brittleness4 ,annealing 7reheating through the critical7 destroys the effect of cold work4 ,,forging ,,high-,,speed ,,steel4--,heat very slowly and carefully to from #a1hjj to #b1jjj;,f4 and forge thoroughly and uniformly4 ,if the forging operation is prolonged do not continue forging the tool when the steel begins to stiffen under the hammer4 ,do not forge below #a1gjj;,f4 7a dark lemon or orange color74 ,reheat frequently rather than prolong the hammering at the low heats4 ,after finishing the forging allow the tool to cool as slowly as possible in lime or dry ashes2 avoid placing the tool on the damp ground or in a draught of air4 ,use a good clean fire for heating4 ,do not allow the tool to soak at the forging heat4 ,do not heat any more of the tool than is necessary in order to forge it to the desired shape4 ,,carbon ,,tool ,,steel4--,heat to a bright red1 about #a1ejj to #a1eej;,f4 ,do not hammer steel when it cools down to a dark cherry red1 or just below its hardening point1 as this creates surface cracks4 ,,oil-,,hardening ,,steel4--,heat slowly and uniformly to #a1dej;,f4 and forge thoroughly4 ,do not under any circumstances attempt to harden at the forging heat4 ,after cooling from forging reheat to about #a1dej;,f4 and cool slowly so as to remove forging strains4 ,,chrome-,,nickel ,,steel4--,forging heat of chrome-nickel steel depends very largely on the percentage of each element contained in the steel4 ,steel containing from #a_/b to #a per cent chromium and from #a-a_/b to #c-a_/b per cent nickel1 with a carbon content equal to the chromium1 should be heated very slowly and uniformly to approximately #a1fjj ,f41 or salmon color4 ,after forging1 reheat the steel to about #a1dej and cool slowly so as to remove forging strains4 ,do not attempt to harden the steel before such annealing4 ,a great deal of steel is constantly being spoiled by carelessness in the forging operation4 ,the billets may be perfectly sound1 but even if the steel is heated to a good forging heat1 and is hammered too lightly1 a poor forging results4 ,a proper blow will cause the edges and ends to bulge slightly outwards--the inner-most parts of the steel seem to flow faster than the surface4 ,light blows will work the surface out faster2 the edges and ends will curve inwards4 ,this condition in extreme cases leaves a seam in the axis of the forging4 ,steel which is heated quickly and forging begun before uniform heat has penetrated to its center will open up seams because the cooler central portion is not able to flow with the hot metal surrounding it4 ,uniform heating is absolutely necessary for the best results4 ,figure #af shows a sound forging4 ,the bars in ,fig4 #ag were burst by improper forging1 while the die1 ,fig4 #ah1 burst from a piped center4 ,figure #ai shows a piece forged with a hammer too light for the size of the work4 ,this gives an appearance similar to case-hardening1 the refining effect of the blows reaching but a short distance from the surface4 ,while it is impossible to accurately rate the capacity of steam hammers with respect to the size of work they should handle1 on account of the greatly varying conditions1 a few notes from the experience of the ,bement works of the ,niles-,bement-,pond ,company will be of service4 ,illustration3 ,,fig4 #af4--;,a sound forging4 ,illustration3 ,,fig4 #ag4--;,burst from improper forging4 ,for making an occasional forging of a given size1 a smaller hammer may be used than if we are manufacturing this same piece in large quantities4 ,if we have a #f-;in4 piece to forge1 such as a pinion or a short shaft1 a hammer of about #a1ajj-lb4 capacity would answer very nicely4 ,but should the general work be as large as this1 it would be very much better to use a #a1ejj-lb4 hammer4 ,if1 on the other hand1 we wish to forge #f-;in4 axles economically1 it would be necessary to use a #g1jjj- or #h1jjj-lb4 hammer4 ,the following table will be found convenient for reference for the proper size of hammer to be used on different classes of general blacksmith work1 although it will be understood that it is necessary to modify these to suit conditions1 as has already been indicated4 ,illustration3 ,,fig4 #ah4--;,burst from a piped center4 ,illustration3 ,,fig4 #ai4--,result of using too light a hammer4 ,diameter of stock ,size of hammer #c-a_/b in4 #bej to #cej lb4 #d in4 #cej to #fjj lb4 #d-a_/b in4 #fjj to #hjj lb4 #e in4 #hjj to #a1jjj lb4 #f in4 #a1ajj to #a1ejj lb4 ,steam hammers are always rated by the weight of the ram1 and the attached parts1 which include the piston and rod1 nothing being added on account of the steam pressure behind the piston4 ,this makes it a little difficult to compare them with plain drop or tilting hammers1 which are also rated in the same way4 ,illustration3 ,,fig4 #bj4--;,good and bad ingots4 ,steam hammers are usually operated at pressures varying from #ge to #ajj lb4 of steam per square inch1 and may also be operated by compressed air at about the same pressures4 ,it is cheaper1 however1 in the case of compressed air to use pressures from #fj to #hj lb4 instead of going higher4 ,forgings must1 however1 be made from sound billets if satisfactory results are to be secured4 ,figure #bj shows three cross-sections of which ,a is sound1 ,b is badly piped and ,c is worthless4 ,,plant ,,for ,,forging ,,rifle ,,barrels ,the forging of rifle barrels in large quantities and heat-treating them to meet the specifications demanded by some of the foreign governments led ,wheelock1 ,lovejoy ,company to establish a complete plant for this purpose in connection with their warehouse in ,cambridge1 ,mass4 ,this plant1 designed and constructed by their chief engineer1 ,k4 ,a4 ,juthe1 had many interesting features4 ,many features of this plant can be modified for other classes of work4 ,illustration3 ,,fig #ba4--;,cutting up barrels4 ,illustration3 ,,fig4 #bb4--,upsetting the ends4 ,the stock1 which came in bars of mill length1 was cut off so as to make a barrel with the proper allowances for trimming 7,fig4 #ba74 ,they then pass to the forging or upsetting press in the adjoining room4 ,this press1 which is shown in more detail in ,fig4 #bb1 handled the barrels from all the heating furnaces shown4 ,the men changed work at frequent intervals1 to avoid excessive fatigue4 ,illustration3 ,,fig4 #bc4--;,continuous heating furnace4 ,then the barrels were reheated in the continuous furnace1 shown in ,fig4 #bc1 and straightened before being tested4 ,the barrels were next tested for straightness4 ,after the heat-treating1 the ends are ground1 a spot ground on the enlarged end and each barrel tested on a ,brinell machine4 ,the pressure used is #c1jjj kg41 or #f1fad lb41 on a #aj-millimeter ball1 which is standard4 ,hardness of #bdj was desired4 ,the heat-treating of the rifle blanks covered four separate operations3 7#a7 ,heating and soaking the steel above the critical temperature and quenching in oil to harden the steel through to the center2 7#b7 reheating for drawing of temper for the purpose of meeting the physical specifications2 7#c7 reheating to meet the machine ability test for production purposes2 and 7#d7 reheating to straighten the blanks while hot4 ,a short explanation of the necessity for the many heats may be interesting4 ,for the first heat1 the blanks were slowly brought to the required heat1 which is about #aej;,f4 above the critical temperature4 ,they are then soaked at a high heat for about #a hr4 before quenching4 ,the purpose of this treatment is to eliminate any rolling or heat stresses that might be in the bars from mill operations2 also to insure a thorough even heat through a cross-section of the steel4 ,this heat also causes blanks with seams or slight flaws to open up in quenching1 making detection of defective blanks very easy4 ,the quenching oil was kept at a constant temperature of #ajj;,f41 to avoid subjecting the steel to shocks1 thereby causing surface cracks4 ,the drawing of temper was the most critical operation and was kept within a #aj fluctuation4 ,the degree of heat necessary depends entirely on the analysis of the steel1 there being a certain variation in the different heats of steel as received from the mill4 ,,machineability ,reheating for machine ability was done at #ajj less than the drawing temperature1 but the time of soaking is more than double4 ,after both drawing and reheating1 the blanks were buried in lime where they remain1 out of contact with the air1 until their temperature had dropped to that of the workroom4 ,for straightening1 the barrels were heated to from #ijj to #a1jjj;,f4 in an automatic furnace #be ft4 long1 this operation taking about #b hr4 ,the purpose of hot straightening was to prevent any stresses being put into the blanks1 so that after rough-turning1 drilling or rifling operations they would not have a tendency to spring back to shape as left by the quenching bath4 ,a method that produces an even better machining rifle blank1 which practically stays straight through the different machining operations1 was to rough-turn the blanks1 then subject them to a heat of practically #a1jjjj for #d hr4 ,production throughout the different operations is materially increased1 with practically no straightening required after drilling1 reaming1 finish-turning or rifling operations4 ,illustration3 ,,fig4 #bd4 ,,fig4 #be4 ,,figs4 #bd and #be4--,roof system of cooling quenching oil4 ,this method was tested out by one of the largest manufacturers and proved to be the best way to eliminate a very expensive finished gun-barrel straightening process4 ,illustration3 ,,fig4 #bf4--;,details of the cooler4 ,the heat-treating required a large amount of cooling oil1 and the problem of keeping this at the proper temperature required considerable study4 ,the result was the cooling plant on the roof1 as shown in ,figs4 #bd1 #be and #bf4 ,the first two illustrations show the plant as it appeared complete4 ,figure #bf shows how the oil was handled in what is sometimes called the ebulator system4 ,the oil was pumped up from the cooling tanks through the pipe ,a to the tank ,b4 ,from here it ran down onto the breakers or separators ,c1 which break the oil up into fine particles that are caught by the fans ,d4 ,the spray is blown up into the cooling tower ,e1 which contains banks of cooling pipes1 as can be seen1 as well as baffies ,f4 ,the spray collects on the cool pipes and forms drops1 which fall on the curved plates ,g and run back to the oil-storage tank below ground4 ,the water for this cooling was pumped from #aj artesian wells at the rate of #fj gal4 per minute and cooled #ij gal4 of oil per minute1 lowering the temperature from #acj or #adj to #ajj;,f4 ,the water as it came from the wells averaged around #eb;,f4 ,the motor was of a #g-a_/b-;hp4 variable-speed type with a range of from #gjj to #a1bjj r4p4m41 which could be varied to suit the amount of oil to be cooled4 ,the plant handled #cjj gal4 of oil per minute4 ,,chapter ,,vi ,,annealing ,there is no mystery or secret about the proper annealing of different steels1 but in order to secure the best results it is absolutely necessary for the operator to know the kind of steel which is to be annealed4 ,the annealing of steel is primarily done for one of three specific purposes3 ,to soften for machining purposes2 to change the physical properties1 largely to increase ductility2 or to release strains caused by rolling or forging4 ,proper annealing means the heating of the steel slowly and uniformly to the right temperature1 the holding of the temperature for a given period and the gradual cooling to normal temperature4 ,the proper temperature depends on the kind of steel1 and the suggestions of the maker of the special steel being used should be carefully followed4 ,for carbon steel the temperatures recommended for annealing vary from #a1dej to #a1fjj;,f4 ,this temperature need not be long continued4 ,the steel should be cooled in hot sand1 lime or ashes4 ,if heated in the open forge the steel should be buried in the cooling material as quickly as possible1 not allowing it to remain in the open air any longer than absolutely necessary4 ,best results1 however1 are secured when the fire does not come in direct contact with the steel4 ,good results are obtained by packing the steel in iron boxes or tubes1 much as for case-hardening or carbonizing1 using the same materials4 ,pieces do not require to be entirely surrounded by carbon for annealing1 however4 ,do not remove from boxes until cold4 ,steel to be annealed may be classified into four different groups1 each of which must be treated according to the elements contained in its particular analysis4 ,different methods are therefore necessary to bring about the desired result4 ,the classifications are as follows3 ,high-speed steel1 alloy steel1 tool or crucible steel1 and high-carbon machinery steel4 ,,annealing ,,of ,,high-,,speed ,,steel ,for annealing high-speed steel1 some makers recommend using ground mica1 charcoal1 lime1 fine dry ashes or lake sand as a packing in the annealing boxes4 ,mixtures of one part charcoal1 one part lime and three parts of sand are also suggested1 or two parts of ashes may be substituted for the one part of lime4 ,to bring about the softest structure or machine ability of high-speed steel1 it should be packed in charcoal in boxes or pipes1 carefully sealed at all points1 so that no gases will escape or air be admitted4 ,it should be heated slowly to not less than #a1dej;,f4 and the steel must not be removed from its packing until it is cool4 ,slow heating means that the high heat must have penetrated to the very core of the steel4 ,when the steel is heated clear through it has been in the furnace long enough4 ,if the steel can remain in the furnace and cool down with it1 there will be no danger of air blasts or sudden or uneven cooling4 ,if not1 remove the box and cover quickly with dry ashes1 sand or lime until it becomes cold4 ,too high a heat or maintaining the heat for too long a period1 produces a harsh1 coarse grain and greatly increases the liability to crack in hardening4 ,it also reduces the strength and toughness of the steel4 ,steel which is to be used for making tools with teeth1 such as taps1 reamers and milling cutters1 should not be annealed too much4 ,when the steel is too soft it is more apt to tear in cutting and makes it more difficult to cut a smooth thread or other surface4 ,moderate annealing is found best for tools of this kind4 ,,tool ,,or ,,crucible ,,steel ,crucible steel can be annealed either in muffled furnace or by being packed4 ,packing is by far the most satisfactory method as it prevents scaling1 local hard spots1 uneven annealing1 or violent changes in shape4 ,it should be brought up slowly to just above its calescent or hardening temperature4 ,the operator must know before setting his heats the temperature at which the different carbon content steels are hardened4 ,the higher the carbon contents the lower is the hardening heat1 but this should in no case be less than #a1dej;,f4 ,,annealing ,,alloy ,,steel ,the term alloy steel1 from the steel maker's point of view1 refers largely to nickel and chromium steel or a combination of both4 ,these steels are manufactured very largely by the open-hearth process1 although chromium steels are also a crucible product4 ,it is next to impossible to give proper directions for the proper annealing of alloy steel unless the composition is known to the operator4 ,nickel steels may be annealed at lower temperatures than carbon steels1 depending upon their alloy content4 ,for instance1 if a pearlitic carbon steel may be annealed at #a1dej;,c41 the same analysis containing #b-a_/b per cent nickel may be annealed at #a1cfj;,c4 and a #e per cent nickel steel at #a1bgj4 ,in order that high chromium steels may be readily machined1 they must be heated at or slightly above the critical for a very long time1 and cooled through the critical at an extremely slow rate4 ,for a steel containing #j4i to #a4a per cent carbon1 under #j4ej per cent manganese1 and about #a4j per cent chromium1 ,bullens recommends the following anneal3 #a4 ,heat to #a1gjj or #a1gej;,f4 #b4 ,air cool to about #hjj;,f4 #c4 ,soak at #a1dbe to #a1dej;,f4 #d4 ,cool slowly in furnace4 ,,high-,,carbon ,,machinery ,,steel ,the carbon content of this steel is above #cj points and is hardly ever above #fj points or #j4fj per cent4 ,annealing such steel is generally in quantity production and does not require the care that the other steels need because it is very largely a much cheaper product and a great deal of material is generally removed from the outside surface4 ,the purpose for which this steel is annealed is a deciding factor as to what heat to give it4 ,if it is for machineability only1 the steel requires to be brought up slowly to just below the critical and then slowly cooled in the furnace or ash pit4 ,it must be thoroughly covered so that there will be no access of cool air4 ,if the annealing is to increase ductility to the maximum extent it should be slowly heated to slightly over the upper critical temperature and kept at this heat for a length of time necessary for a thorough penetration to the core1 after which it can be cooled to about #a1bjj;,f41 then reheated to about #a1cfj;,f41 when it can be removed and put in an ash pit or covered with lime4 ,if the annealing is just to relieve strains1 slow heating is not necessary1 but the steel must be brought up to a temperature not much less than a forging or rolling heat and gradually cooled4 ,covering in this case is only necessary in steel of a carbon content of more than #dj points4 ,,annealing ,,in ,,bone ,steel and cast iron may both be annealed in granulated bone4 ,pack the work the same as for case-hardening except that it is not necessary to keep the pieces away from each other4 ,pack with bone that has been used until it is nearly white4 ,heat as hot as necessary for the steel and let the furnace cool down4 ,if the boxes are removed from furnace while still warm1 cover boxes and all in warm ashes or sand1 air slaked lime or old1 burned bone to retain heat as long as possible4 ,do not remove work from boxes until cold4 ,,annealing ,,of ,,rifle ,,components ,,at ,,springfield ,,armory ,in general1 all forgings of the components of the arms manufactured at the ,armory and all forgings for other ordnance establishments are packed in charcoal1 lime or suitable material and annealed before being transferred from the forge shop4 ,except in special cases1 all annealing will be done in annealing pots of appropriate size4 ,one fire end of a thermo-couple is inserted in the center of the annealing pot nearest the middle of the furnace and another in the furnace outside of but near the annealing pots4 ,the temperatures used in annealing carbon steel components of the various classes used at the ,armory vary from #hjj;,c4 ,to #hhj;,c4 or #a1dge to #a1fae;,f4 ,the fuel is shut off from the annealing furnace gradually as the temperature of the pot approaches the prescribed annealing temperature so as to prevent heating beyond that temperature4 ,the forgings of the rifle barrel and the pistol barrel are exceptions to the above general rule4 ,these forgings will be packed in lime and allowed to cool slowly from the residual heat after forging4 ,,chapter ,,vii ,,case-,,hardening ,,or ,,surface-,,carburizing ,carburizing1 commonly called case-hardening1 is the art of producing a high-carbon surface1 or case1 upon a low carbon steel article4 ,wrenches1 locomotive link motions1 gun mechanisms1 balls and ball races1 automobile gears and many other devices are thereby given a high-carbon case capable of assuming extreme hardness1 while the interior body of metal1 the core1 remains soft and tough4 ,the simplest method is to heat the piece to be hardened to a bright red1 dip it in cyanide of potassium 7or cover it by sprinkling the cyanide over it71 keep it hot until the melted cyanide covers it thoroughly1 and quench in water4 ,carbon and nitrogen enter the outer skin of the steel and harden this skin but leave the center soft4 ,the hard surface or case varies in thickness according to the size of the piece1 the materials used and the length of time which the piece remains at the carburizing temperature4 ,cyanide case-hardening is used only where a light or thin skin is sufficient4 ,it gives a thickness of about #j4jjb in4 ,in some cases of cyanide carburizing1 the piece is heated in cyanide to the desired temperature and then quenched4 ,for a thicker case the steel is packed in carbon materials of various kinds such as burnt leather scraps1 charcoal1 granulated bone or some of the many carbonizing compounds4 ,machined or forged steel parts are packed with case-hardening material in metal boxes and subjected to a red heat4 ,under such conditions1 carbon is absorbed by the steel surfaces1 and a carburized case is produced capable of responding to ordinary hardening and tempering operations1 the core meanwhile retaining its original softness and toughness4 ,such case-hardened parts are stronger1 cheaper1 and more serviceable than similar parts made of tool steel4 ,the tough core resists breakage by shock4 ,the hardened case resists wear from friction4 ,the low cost of material1 the ease of manufacture1 and the lessened breakage in quenching all serve to promote cheap production4 ,for successful carburizing1 the following points should be carefully observed3 ,the utmost care should be used in the selection of pots for carburizing2 they should be as free as possible from both scaling and warping4 ,these two requirements eliminate the cast iron pot1 although many are used1 thus leaving us to select from malleable castings1 wrought iron1 cast steel1 and special alloys1 such as nichrome or silchrome4 ,if first cost is not important1 it will prove cheaper in the end to use pots of some special alloy4 ,illustrations3 ,,figs4 #bg to #cj4--;,case-hardening or carburizing boxes4 ,illustration3 ,,fig4 #ca4--;,a lid that is easily luted4 ,the pots should be standardized to suit the product4 ,pots should be made as small as possible in width1 and space gained by increasing the height2 for it takes about #a-a_/b hr4 to heat the average small pot of #d in4 in width1 between #c and #d hr4 to heat to the center of an #h-;in4 box1 and #e to #f hr4 to heat to the center of a #ab-;in4 box2 and the longer the time required to heat to the center1 the more uneven the carburizing4 ,the work is packed in the box surrounded by materials which will give up carbon when heated4 ,it must be packed so that each piece is separate from the others and does not touch the box1 with a sufficient amount of carburizing material surrounding each4 ,figures #bg to #ca show the kind of boxes used and the way the work should be packed4 ,figure #ca shows a later type of box in which the edges can be easily luted4 ,figure #cj shows test wires broken periodically to determine the depth of case4 ,figure #bh shows the minimum clearance which should be used in packing and ,fig4 #bi the way in which the outer pieces receive the heat first and likewise take up the carbon before those in the center4 ,this is why a slow1 soaking heat is necessary in handling large quantities of work1 so as to allow the heat and carbon to soak in equally4 ,while it has been claimed that iron below its critical temperature will absorb some carbon1 ,giolitti has shown that this absorption is very slow4 ,in order to produce quick and intense carburization the iron should preferably be above its upper critical temperature or #a1fjj;,f41--therefore the carbon absorbed immediately goes into austenite1 or solid solution4 ,it is also certain that the higher the temperature the quicker will carbon be absorbed1 and the deeper it will penetrate into the steel1 that is1 the deeper the case4 ,at ,sheffield1 ,england1 where wrought iron is packed in charcoal and heated for days to convert it into blister steel1 the temperatures are from #a1gej to #a1hcj;,f4 ,charcoal by itself carburizes slowly1 consequently commercial compounds also contain certain energizers which give rapid penetration at lower temperatures4 ,the most important thing in carburizing is the human element4 ,most careful vigilance should be kept when packing and unpacking1 and the operator should be instructed in the necessity for clean compound free from scale1 moisture1 fire clay1 sand1 floor sweepings1 etc4 ,from just such causes1 many a good carburizer has been unjustly condemned4 ,it is essential with most carburizers to use about #be to #ej per cent of used material1 in order to prevent undue shrinking during heating2 therefore the necessity of properly screening used material and carefully inspecting it for foreign substances before it is used again4 ,it is right here that the greatest carelessness is generally encountered4 ,don't pack the work to be carburized too closely2 leave at least #a in4 from the bottom1 #c_/d in4 from the sides1 and #a in4 from the top of pots1 and for a #f-;hr4 run1 have the pieces at least #a_/b in4 apart4 ,this gives the heat a chance to thoroughly permeate the pot1 and the carburizing material a chance to shrink without allowing carburized pieces to touch and cause soft spots4 ,good case-hardening pots and annealing tubes can be made from the desired size of wrought iron pipe4 ,the ends are capped or welded1 and a slot is cut in the side of the pot1 equal to one quarter of its circumference1 and about #g_/h of its length4 ,another piece of the same diameter pipe cut lengthwise into thirds forms a cover for this pot4 ,we then have a cheap1 substantial pot1 non-warping1 with a minimum tendency to scale1 but the pot is difficult to seal tightly4 ,this idea is especially adaptable when long1 narrow pots are desired4 ,when pots are packed and the carburizer thoroughly tamped down1 the covers of the pot are put on and sealed with fire clay which has a little salt mixed into it4 ,the more perfect the seal the more we can get out of the carburizer4 ,the rates of penetration depend on temperature and the presence of proper gas in the required volume4 ,any pressure we can cause will1 of course1 have a tendency to increase the rate of penetration4 ,if you have a wide furnace1 do not load it full at one time4 ,put one-half your load in first1 in the center of the furnace1 and heat until pots show a low red1 about #a1cbe to #a1cej;,f4 ,then fill the furnace by putting the cold pots on the outside or1 the section nearest the source of heat4 ,this will give the work in the slowest portion of the furnace a chance to come to heat at the same time as the pots that are nearest the sources of heat4 ,to obtain an even heating of the pots and lessen their tendency to warp and scale1 and to cause the contents of the furnace to heat up evenly1 we should use a reducing fire and fill the heating chamber with flame4 ,this can be accomplished by partially closing the waste gas vents and reducing slightly the amount of air used by the burners4 ,a short flame will then be noticed issuing from the partially closed vents4 ,thus1 while maintaining the temperature of the heating chamber1 we will have a lower temperature in the combustion chamber1 which will naturally increase its longevity4 ,sometimes it is advisable to cool the work in the pots4 ,this saves compound1 and causes a more gradual diffusion of the carbon between the case and the core1 and is very desirable condition1 inasmuch as abrupt cases are inclined to chip out4 ,the most satisfactory steel to carburize contains between #j4aj and #j4bj per cent carbon1 less than #j4ce per cent manganese1 less than #j4jd per cent phosphorus and sulphur1 and low silicon4 ,but steel of this composition does not seem to satisfy our progressive engineers1 and many alloy steels are now on the market1 these1 although more or less difficult to machine1 give when carburized the various qualities demanded1 such as a very hard case1 very tough core1 or very hard case and tough core4 ,however1 the additional elements also have a great effect both on the rate of penetration during the carburizing operation1 and on the final treatment1 consequently such alloy steels require very careful supervision during the entire heat treating operations4 ,,rate ,,of ,,absorption ,according to ,guillet1 the absorption of carbon is favored by those special elements which exist as double carbides in steel4 ,for example1 manganese exists as manganese carbide in combination with the iron carbide4 ,the elements that favor the absorption of carbon are3 manganese1 tungsten1 chromium and molybdenum those opposing it1 nickel1 silicon1 and aluminum4 ,guillet has worked out the effect of the different elements on the rate of penetration in comparison with steel that absorbed carbon at a given temperature1 at an average rate of #j4jce in4 per hour4 ,his tables show that the following elements require an increased time of exposure to the carburizing material in order to obtain the same depth of penetration as with simple steel3 ,when steel contains ,increased time of exposure #b4j per cent nickel #bh per cent #g4j per cent nickel #cj per cent #a4j per cent titanium #ab per cent #b4j per cent titanium #bh per cent #j4e per cent silicon #ej per cent #a4j per cent silicon #hj per cent #b4j per cent silicon #abb per cent #e4j per cent silicon ,no penetration #a4j per cent aluminum #abb per cent #b4j per cent aluminum #cej per cent ,the following elements seem to assist the rate of penetration of carbon1 and the carburizing time may therefore be reduced as follows3 ,when steel contains ,decreased time of exposure #j4e per cent manganese #ah per cent #a4j per cent manganese #be per cent #a4j per cent chromium #aj per cent #b4j per cent chromium #ah per cent #j4e per cent tungsten #j #a4j per cent tungsten #j #b4j per cent tungsten #be per cent #a4j per cent molybdenum #j #b4j per cent molybdenum #ah per cent ,the temperature at which carburization is accomplished is a very important factor4 ,hence the necessity for a reliable pyrometer1 located so as to give the temperature just below the tops of the pots4 ,it must be remembered1 however1 that the pyrometer gives the temperature of only one spot1 and is therefore only an aid to the operator1 who must use his eyes for successful results4 ,the carbon content of the case generally is governed by the temperature of the carburization4 ,it generally proves advisable to have the case contain between #j4ij per cent and #a4aj carbon2 more carbon than this gives rise to excess free cementite or carbide of iron1 which is detrimental1 causing the case to be brittle and apt to chip4 ,t4 ,g4 ,selleck gives a very useful table of temperatures and the relative carbon contents of the case of steels carburized between #d and #f hrs4 using a good charcoal carburizer4 ,this data is as follows3 ,,table #ae4--;,,carbon ,,content ,,obtained ,,at ,,various ,,temperatures ,at #a1ejj;,f41 the surface carbon content will be #j4ij per cent ,at #a1fjj;,f41 the surface carbon content will be #a4jj per cent ,at #a1fej;,f41 the surface carbon content will be #a4aj per cent ,at #a1gjj;,f41 the surface carbon content will be #a4be per cent ,at #a1gej;,f41 the surface carbon content will be #a4dj per cent ,at #a1hjj;,f41 the surface carbon content will be #a4ge per cent ,to this very valuable table1 it seems best to add the following data1 which we have used for a number of years4 ,we do not know the name of its author1 but it has proved very valuable1 and seems to complete the above information4 ,the table is self-explanatory1 giving depth of penetration of the carbon of the case at different temperatures for different lengths of time3 ---------------------------------------- ----------------- ,temperature ,penetration ----------------------------- #a1eej #a1fej #a1hjj ---------------------------------------- -------------- ,penetration after #a_/b hr4 #j4jjh #j4jab #j4jcj ,penetration after #a hr4 #j4jah #j4jbf #j4jde ,penetration after #b hr4 #j4jce #j4jdh #j4jfj ,penetration after #c hr4 #j4jde #j4jee #j4jge ,penetration after #d hr4 #j4jeb #j4jfa #j4jib ,penetration after #f hr4 #j4jef #j4jge #j4aaj ,penetration after #h hr4 #j4jfb #j4jhc #j4acj ---------------------------------------- ----------------- ,from the tables given1 we may calculate with a fair degree of certainty the amount of carbon in the case1 and its penetration4 ,these figures vary widely with different carburizers1 and as pointed out immediately above1 with different alloy steels4 ,,carburizing ,,material ,the simplest carburizing substance is charcoal4 ,it is also the slowest1 but is often used mixed with something that will evolve large volumes of carbon monoxide or hydrocarbon gas on being heated4 ,a great variety of materials is used1 a few of them being charcoal 7both wood and bone71 charred leather1 crushed bone1 horn1 mixtures of charcoal and barium carbonate1 coke and heavy oils1 coke treated with alkaline carbonates1 peat1 charcoal mixed with common salt1 saltpeter1 resin1 flour1 potassium bichromate1 vegetable fibre1 limestone1 various seed husks1 etc4 ,in general1 it is well to avoid complex mixtures4 ,h4 ,l4 ,heathcote1 on analyzing seventeen different carburizers1 found that they contained the following ingredients3 ,per cent ,moisture #b4fh to #bf4ag ,oil #j4ag to #bj4gf ,carbon 7organic7 #f4gj to #ed4ai ,calcium phosphate #j4cb to #gd4ge ,calcium carbonate #a4bj to #aa4eg ,barium carbonate nil to #db4jj ,zinc oxide nil to #ad4ej ,silica nil to #h4ad ,sulphates 7,,so#c7 trace to #c4de ,sodium chloride nil to #g4hh ,sodium carbonate nil to #dj4jj ,sulphides 7,s7 nil to #b4hj ,carburizing mixtures1 though bought by weight1 are used by volume1 and the weight per cubic foot is a big factor in making a selection4 ,a good mixture should be porous1 so that the evolved gases1 which should be generated at the proper temperature1 may move freely around the steel objects being carburized2 should be a good conductor of heat2 should possess minimum shrinkage when used2 and should be capable of being tamped down4 ,many secret mixtures are sold1 falsely claimed to be able to convert inferior metal into crucible tool steel grade4 ,they are generally nothing more than mixtures of carbonaceous and cyanogen compounds possessing the well-known carburizing properties of those substances4 ,,quenching ,it is considered good practice to quench alloy steels from the pot1 especially if the case is of any appreciable depth4 ,the texture of carbon steel will be weakened by the prolonged high heat of carburizing1 so that if we need a tough core1 we must reheat it above its critical range1 which is about #a1fjj;,f4 for soft steel1 but lower for manganese and nickel steels4 ,quenching is done in either water1 oil1 or air1 depending upon the results desired4 ,the steel is then very carefully reheated to refine the case1 the temperature varying from #a1cej to #a1dej;,f41 depending on whether the material is an alloy or a simple steel1 and quenched in either water or oil4 ,illustration3 ,,fig4 #cb4--;,case-hardening depths4 ,there are many possibilities yet to be developed with the carburizing of alloy steels1 which can produce a very tough1 tenacious austenitic case which becomes hard on cooling in air1 and still retains a soft1 pearlitic core4 ,an austenitic case is not necessarily file hard1 but has a very great resistance to abrasive wear4 ,the more carbon a steel has to begin with the more slowly will it absorb carbon and the lower the temperature required4 ,low-carbon steel of from #ae to #bj points is generally used and the carbon brought up to #hj or #he points4 ,tool steels may be carbonized as high as #bej points4 ,in addition to the carburizing materials given1 a mixture of #dj per cent of barium carbonate and #fj per cent charcoal gives much faster penetration than charcoal1 bone or leather4 ,the penetration of this mixture on ordinary low-carbon steel is shown in ,fig4 #cb1 over a range of from #b to #ab hr4 ,,effect ,,of ,,different ,,carburizing ,,material ,illustrations3 ,,figs4 #cc to #cg4 ,each of these different packing materials has a different effect upon the work in which it is heated4 ,charcoal by itself will give a rather light case4 ,mixed with raw bone it will carburize more rapidly1 and still more so if mixed with burnt bone4 ,raw bone and burnt bone1 as may be inferred1 are both quicker carbonizers than charcoal1 but raw bone must never be used where the breakage of hardened edges is to be avoided1 as it contains phosphorus and tends to make the piece brittle4 ,charred leather mixed with charcoal is a still faster material1 and horns and hoofs exceed even this in speed2 but these two compounds are restricted by their cost to use with high-grade articles1 usually of tool or high-carbon steel1 that are to be hardened locally--that is1 pack-hardened4 ,cyanide of potassium or prussiate of potash are also included in the list of carbonizing materials2 but outside of carburizing by dipping into melted baths of this material1 their use is largely confined to local hardening of small surfaces1 such as holes in dies and the like4 ,dr4 ,federico ,giolitti has proven that when carbonizing with charcoal1 or charcoal plus barium carbonate1 the active agent which introduces carbon into the steel is a gas1 carbon monoxide 7,,co71 derived by combustion of the charcoal in the air trapped in the box1 or by decomposition of the carbonate4 ,this gas diffuses in and out of the hot steel1 transporting carbon from the charcoal to the outer portions of the metal3 ,if energizers like tar1 peat1 and vegetable fiber are used1 they produce hydrocarbon gases on being heated--gases principally composed of hydrogen and carbon4 ,these gases are unstable in the presence of hot iron3 it seems to decompose them and sooty carbon is deposited on the surface of the metal4 ,this diffuses into the metal a little1 but it acts principally by being a ready source of carbon1 highly active and waiting to be carried into the metal by the carbon monoxide--which as before1 is the principal transfer agent4 ,animal refuse when used to speed up the action of clean charcoal acts somewhat in the same manner1 but in addition the gases given off by the hot substance contain nitrogen compounds4 ,nitrogen and cyanides 7compounds of carbon and nitrogen7 have long been known to give a very hard thin case very rapidly4 ,it has been discovered only recently that this is due to the steel absorbing nitrogen as well as carbon1 and that nitrogen hardens steel and makes it brittle just like carbon does4 ,in fact it is very difficult to distinguish between these two hardening agents when examining a carburized steel under the microscope4 ,one of the advantages of hardening by carburizing is the fact that you can arrange to leave part of the work soft and thus retain the toughness and strength of the original material4 ,figures #cc to #cg show ways of doing this4 ,the inside of the cup in ,fig4 #cd is locally hardened1 as illustrated in ,fig4 #cd1 spent or used bone being packed around the surfaces that are to be left soft1 while cyanide of potassium is put around those which are desired hard4 ,the threads of the nut in ,fig4 #ce are kept soft by carburizing the nut while upon a stud4 ,the profile gage1 ,fig4 #cf1 is made of high-carbon steel and is hardened on the inside by packing with charred leather1 but kept soft on the outside by surrounding it with fireclay4 ,the rivet stud shown in ,fig4 #cg is carburized while of its full diameter and then turned down to the size of the rivet end1 thus cutting away the carburized surface4 ,after packing the work carefully in the boxes the lids are sealed or luted with fireclay to keep out any gases from the fire4 ,the size of box should be proportioned to the work4 ,the box should not be too large especially for light work that is run on a short heat4 ,if it can be just large enough to allow the proper amount of material around it1 the work is apt to be more satisfactory in every way4 ,pieces of this kind are of course not quenched and hardened in the carburizing heat1 but are left in the box to cool1 just as in box annealing1 being reheated and quenched as a second operation4 ,in fact1 this is a good scheme to use for the majority of carburizing work of small and moderate size4 ,material is on the market with which one side of the steel can be treated2 or copper-plating one side of it will answer the same purpose and prevent that side becoming carburized4 ,,quenching ,,the ,,work ,in some operations case-hardened work is quenched from the box by dumping the whole contents into the quenching tank4 ,it is common practice to leave a sieve or wire basket to catch the work1 allowing the carburizing material to fall to the bottom of the tank where it can be recovered later and used again as a part of a new mixture4 ,for best results1 however1 the steel is allowed to cool down slowly in the box after which it is removed and hardened by heating and quenching the same as carbon steel of the same grade4 ,it has absorbed sufficient carbon so that1 in the outer portions at least1 it is a high-carbon steel4 ,,the ,,quenching ,,tank ,the quenching tank is an important feature of apparatus in case-hardening--possibly more so than in ordinary tempering4 ,one reason for this is because of the large quantities of pieces usually dumped into the tank at a time4 ,one cannot take time to separate the articles themselves from the case-hardening mixture1 and the whole content of the box is droped into the bath in short order1 as exposure to air of the heated work is fatal to results4 ,unless it is split up1 it is likely to go to the bottom as a solid mass1 in which case very few of the pieces are properly hardened4 ,illustration3 ,,fig4 #ch4--;,combination cooling tank for case-hardening4 ,a combination cooling tank is shown in ,fig4 #ch4 ,water inlet and outlet pipes are shown and also a drain plug that enables the tank to be emptied when it is desired to clean out the spent carburizing material from the bottom4 ,a wire-bottomed tray1 framed with angle iron1 is arranged to slide into this tank from the top and rests upon angle irons screwed to the tank sides4 ,its function is to catch the pieces and prevent them from settling to the tank bottom1 and it also makes it easy to remove a batch of work4 ,a bottomless box of sheet steel is shown at ,c4 ,this fits into the wire-bottomed tray and has a number of rods or wires running across it1 their purpose being to break up the mass of material as it comes from the carbonizing box4 ,below the wire-bottomed tray is a perforated cross-pipe that is connected with a compressed-air line4 ,this is used when case-hardening for colors4 ,the shop that has no air compressor may rig up a satisfactory equivalent in the shape of a low-pressure hand-operated air pump and a receiver tank1 for it is not necessary to use high-pressure air for this purpose4 ,when colors are desired on case-hardened work1 the treatment in quenching is exactly the same as that previously described except that air is pumped through this pipe and keeps the water agitated4 ,the addition of a slight amount of powdered cyanide of potassium to the packing material used for carburizing will produce stronger colors1 and where this is the sole object1 it is best to maintain the box at a dull-red heat4 ,illustration3 ,,fig4 #ci4--,why heat treatment of case-hardened work is necessary4 ,the old way of case-hardening was to dump the contents of the box at the end of the carburizing heat4 ,later study in the structure of steel thus treated has caused a change in this procedure1 the use of automobiles and alloy steels probably hastening this result4 ,the diagrams reproduced in ,fig4 #ci show why the heat treatment of case-hardened work is necessary4 ,starting at ,a with a close-grained and tough stock1 such as ordinary machinery steel containing from #ae to #bj points of carbon1 if such work is quenched on a carbonizing heat the result will be as shown at ,b4 ,this gives a core that is coarse-grained and brittle and an outer case that is fine-grained and hard1 but is likely to flake off1 owing to the great difference in structure between it and the core4 ,reheating this work beyond the critical temperature of the core refines this core1 closes the grain and makes it tough1 but leaves the case very brittle2 in fact1 more so than it was before4 ,,refining ,,the ,,grain ,this is remedied by reheating the piece to a temperature slightly above the critical temperature of the case1 this temperature corresponding ordinarily to that of steel having a carbon content of #he points1 ,when this is again quenched1 the temperature1 which has not been high enough to disturb the refined core1 will have closed the grain of the case and toughened it4 ,so1 instead of but one heat and one quenching for this class of work1 we have three of each1 although it is quite possible and often profitable to omit the quenching after carburizing and allow the piece or pieces and the case-carburizing box to cool together1 as in annealing4 ,sometimes another heat treatment is added to the foregoing1 for the purpose of letting down the hardness of the case and giving it additional toughness by heating to a temperature between #cjj and #ejj4 ,usually this is done in an oil bath4 ,after this the piece is allowed to cool4 ,it is possible to harden the surface of tool steel extremely hard and yet leave its inner core soft and tough for strength1 by a process similar to case-hardening and known as pack-hardening4 ,it consists in using tool steel of carbon contents ranging from #fj to #hj points1 packing this in a box with charred leather mixed with wood charcoal and heating at a low-red heat for #b or #c hr41 thus raising the carbon content of the exterior of the piece4 ,the article when quenched in an oil bath will have an extremely hard exterior and tough core4 ,it is a good scheme for tools that must be hard and yet strong enough to stand abuse4 ,raw bone is never used as a packing for this class of work1 as it makes the cutting edges brittle4 ,,case-,,hardening ,,treatments ,,for ,,various ,,steels ,plain water1 salt water and linseed oil are the three most common quenching materials for case-hardening4 ,water is used for ordinary work1 salt water for work which must be extremely hard on the surface1 and oil for work in which toughness is the main consideration4 ,the higher the carbon of the case1 the less sudden need the quenching action take hold of the piece2 in fact1 experience in case-hardening work gives a great many combinations of quenching baths of these three materials1 depending on their temperatures4 ,thin work1 highly carbonized1 which would fly to pieces under the slightest blow if quenched in water or brine1 is made strong and tough by properly quenching in slightly heated oil4 ,it is impossible to give any rules for the temperature of this work1 so much depending on the size and design of the piece2 but it is not a difficult matter to try three or four pieces by different methods and determine what is needed for best results4 ,the alloy steels are all susceptible of case-hardening treatment2 in fact1 this is one of the most important heat treatments for such steels in the automobile industry4 ,nickel steel carburizes more slowly than common steel1 the nickel seeming to have the effect of slowing down the rate of penetration4 ,there is no cloud without its silver lining1 however1 and to offset this retardation1 a single treatment is often sufficient for nickel steel2 for the core is not coarsened as much as low-carbon machinery steel and thus ordinary work may be quenched on the carburizing heat4 ,steel containing from #c to #c4e per cent of nickel is carburized between #a1fej and #a1gej;,f4 ,nickel steel containing less than #be points of carbon1 with this same percentage of nickel1 may be slightly hardened by cooling in air instead of quenching4 ,chrome-nickel steel may be case-hardened similarly to the method just described for nickel steel1 but double treatment gives better results and is used for high-grade work4 ,the carburizing temperature is the same1 between #a1fej and #a1gej;,f41 the second treatment consisting of reheating to #a1djj and then quenching in boiling salt water1 which gives a hard surface and at the same time prevents distortion of the piece4 ,the core of chrome-nickel case-hardened steel1 like that of nickel steel1 is not coarsened excessively by the first heat treatment1 and therefore a single heating and quenching will suffice4 ,,carburizing ,,by ,,gas ,the process of carburizing by gas1 briefly mentioned on page #hh1 consists of having a slowly revolving1 properly heated1 cylindrical retort into which illuminating gas 7a mixture of various hydrocarbons7 is continuously injected under pressure4 ,the spent gases are vented to insure the greatest speed in carbonizing4 ,the work is constantly and uniformly exposed to a clean carbonizing atmosphere instead of partially spent carbonaceous solids which may give off very complex compounds of phosphorus1 sulphur1 carbon and nitrogen4 ,originally this process was thought to require a gas generator but it has been discovered that city gas works all right4 ,the gas consists of vapors derived from petroleum or bituminous coal4 ,sometimes the gas supply is diluted by air1 to reduce the speed of carburization and increase the depth4 ,,preventing ,,carburizing ,,by ,,copper-,,plating ,copper-plating has been found effective and must have a thickness of #j4jjje in4 ,less than this does not give a continuous coating4 ,the plating bath used has a temperature of #agj;,f4 ,a voltage of #d4a is to be maintained across the terminals4 ,regions which are to be hardened can be kept free from copper by coating them with paraffin before they enter the plating tank4 ,the operation is as follows3 ,operation ,no4 ,contents of bath ,purpose #a ,gasoline ,to remove grease #b ,sawdust ,to dry #c ,warm potassium hydroxide solution ,to remove grease and dirt #d ,warm water ,to wash #e ,warm sulphuric acid solution ,to acid clean #f ,warm water ,to wash #g ,cold water ,additional wash #h ,cold potassium cyanide solution ,cleanser #i ,cold water ,to wash #aj ,electric cleaner1 warm sodium ,cleanser to give good hydroxide case-iron anode plating surface #aa ,copper plating bath of copper ,plating bath sulphate and potassium cyanide solution warm ,there are also other methods of preventing case-hardening1 one being to paint the surface with a special compound prepared for this purpose4 ,in some cases a coating of plastic asbestos is used while in others thin sheet asbestos is wired around the part to be kept soft4 ,,preparing ,,parts ,,for ,,local ,,case-,,hardening ,at the works of the ,dayton ,engineering ,laboratories ,company1 ,dayton1 ,ohio1 they have a large quantity of small shafts1 ,fig4 #dj1 that are to be case-hardened at ,a while the ends ,b and ,c are to be left soft4 ,formerly1 the part ,a was brush-coated with melted paraffin but1 as there were many shafts1 this was tedious and great care was necessary to avoid getting paraffin where it was not wanted4 ,illustration3 ,,fig4 #dj4--,shaft to be coated with paraffin4 ,to insure uniform coating the device shown in ,fig4 #da was made4 ,melted paraffin is poured in the well ,a and kept liquid by setting the device on a hot plate1 the paraffin being kept high enough to touch the bottoms of the rollers4 ,the shaft to be coated is laid between the rollers with one end against the gage ,b1 when a turn or two of the crank ,c will cause it to be evenly coated4 ,illustration3 ,,fig4 #da4--;,device for coating the shaft4 ,,the ,,penetration ,,of ,,carbon ,carburized mild steel is used to a great extent in the manufacture of automobile and other parts which are likely to be subjected to rough usage4 ,the strength and ability to withstand hard knocks depend to a very considerable degree on the thoroughness with which the carburizing process is conducted4 ,many automobile manufacturers have at one time or another passed through a period of unfortunate breakages1 or have found that for a certain period the parts turned out of their hardening shops were not sufficiently hard to enable the rubbing surfaces to stand up against the pressure to which they were subjected4 ,so many factors govern the success of hardening that often this succession of bad work has been actually overcome without those interested realizing what was the weak point in their system of treatment4 ,as the question is one that can create a bad reputation for the product of any firm it is well to study the influential factors minutely4 ,,introduction ,,of ,,carbon ,the matter to which these notes are primarily directed is the introduction of carbon into the case of the article to be hardened4 ,in the first place the chances of success are increased by selecting as few brands of steel as practicable to cover the requirements of each component of the mechanism4 ,the hardener is then able to become accustomed to the characteristics of that particular material1 and after determining the most suitable treatment for it no further experimenting beyond the usual check-test pieces is necessary4 ,although a certain make of material may vary in composition from time to time the products of a manufacturer of good steel can be generally relied upon1 and it is better to deal directly with him than with others4 ,in most cases the case-hardening steels can be chosen from the following3 7#a7 ,case-hardening mild steel of #j4bj per cent carbon2 7#b7 case-hardening #c-a_/b per cent nickel steel2 7#c7 case-hardening nickel-chromium steel2 7#d7 case-hardening chromium vanadium4 ,after having chosen a suitable steel it is best to have the sample analyzed by reliable chemists and also to have test pieces machined and pulled4 ,to prepare samples for analysis place a sheet of paper on the table of a drilling machine1 and with a #c_/h-;in4 diameter drill1 machine a few holes about #c_/h in4 deep in various parts of the sample bar1 collecting about #c oz4 of fine drillings free from dust4 ,this can be placed in a bottle and dispatched to the laboratory with instructions to search for carbon1 silicon1 manganese1 sulphur1 phosphorus and alloys4 ,the results of the different tests should be carefully tabulated1 and as there would most probably be some variation an average should be made as a fair basis of each element present1 and the following tables may be used with confidence when deciding if the material is reliable enough to be used4 ,,table #af4--;,,case-,,hardening ,,mild ,,steel ,,of #j4bj ,,per ,,cent ,,carbon ,carbon #j4ae to #j4be per cent ,silicon ,not over #j4bj per cent ,manganese #j4cj to #j4fj per cent ,sulphur ,not over #j4jd per cent ,phosphorus ,not over #j4jd per cent ,a tension test should register at least #fj1jjj lb4 per square inch4 ,,table #ag4--;,,case-,,hardening #c-a_/b ,,per ,,cent ,,nickel ,,steel ,carbon #j4ab to #j4bj per cent ,manganese #j4fe per cent ,sulphur ,not over #j4jde per cent ,phosphorus ,not over #j4jd per cent ,nickel #c4be to #c4ge per cent ,,table #ah4--;,,case-,,hardening ,,nickel ,,chromium ,,steel ,carbon #j4ae to #j4be per cent ,manganese #j4ej to #j4hj per cent ,sulphur ,not over #j4jde per cent ,phosphorus ,not over #j4jd per cent ,nickel #a to #a4e per cent ,chromium #j4de to #j4ge per cent ,,table #ai4--;,,case-,,hardening ,,chromium ,,vanadium ,,steel ,carbon ,not over #j4be per cent ,manganese #j4ej to #j4he per cent ,sulphur ,not over #j4jd per cent ,phosphorus ,not over #j4jd per cent ,chromium #j4hj to #a4aj per cent ,vanadium ,not less than #j4ae per cent ,having determined what is required we now proceed to inquire into the question of carburizing1 which is of vital importance4 ,,using ,,illuminating ,,gas ,the choice of a carburizing furnace depends greatly on the facilities available in the locality where the shop is situated and the nature and quantity of the work to be done4 ,the furnaces can be heated with producer gas in most cases1 but when space is of value illuminating gas from a separate source of supply has some compensations4 ,when the latter is used it is well to install a governor if the pressure is likely to fluctuate1 particularly where the shop is at a high altitude or at a long distance from the gas supply4 ,many furnaces are coal-fired1 and although greater care is required in maintaining a uniform temperature good results have been obtained4 ,the use of electricity as a means of reaching the requisite temperature is receiving some attention1 and no doubt it would make the control of temperature comparatively simple4 ,however1 the cost when applied to large quantities of work will1 for the present at least1 prevent this method from becoming popular4 ,it is believed that the results obtainable with the electric furnace would surpass any others2 but the apparatus is expensive1 and unless handled with intelligence would not last long4 ,the most elementary medium of carburization is pure carbon1 but the rate of carburization induced by this material is very low1 and other components are necessary to accelerate the process4 ,many mixtures have been marketed1 each possessing its individual merits1 and as the prices vary considerably it is difficult to decide which is the most advantageous4 ,absorption from actual contact with solid carbon is decidedly slow1 and it is necessary to employ a compound from which gases are liberated1 and the steel will absorb the carbon from the gases much more readily4 ,both bone and leather charcoal give off more carburizing gases than wood charcoal1 and although the high sulphur content of the leather is objectionable as being injurious to the steel1 as also is the high phosphorus content of the bone charcoal1 they are both preferable to the wood charcoal4 ,by mixing bone charcoal with barium carbonate in the proportions of #fj per cent of the former to #dj per cent of the latter a very reliable compound is obtained4 ,the temperature to which this compound is subjected causes the liberation of carbon monoxide when in contact with hot charcoal4 ,many more elaborate explanations may be given of the actions and reactions taking place1 but the above is a satisfactory guide to indicate that it is not the actual compound which causes carburization1 but the gases released from the compound4 ,until the temperature of the muffle reaches about #a1cjj;,f4 carburization does not take place to any useful extent1 and consequently it is advisable to avoid the use of any compound from which the carburizing gases are liberated much before that temperature is reached4 ,in the case of steel containing nickel slightly higher temperatures may be used and are really necessary if the same rate of carbon penetration is to be obtained1 as the presence of nickel resists the penetration4 ,at higher temperatures the rate of penetration is higher1 but not exactly in proportion to the temperature1 and the rate is also influenced by the nature of the material and the efficiency of the compound employed4 ,the so-called saturation point of mild steel is reached when the case contains #j4ij per cent of carbon1 but this amount is frequently exceeded4 ,should it be required to ascertain the amount of carbon in a sample at varying depths below the skin this can be done by turning off a small amount after carburizing and analyzing the turnings4 ,this can be repeated several times1 and it will probably be found that the proportion of carbon decreases as the test piece is reduced in diameter unless decarburization has taken place4 ,illustration3 ,,fig4 #db4--;,chart showing penetration of carbon4 ,the chart1 ,fig4 #db1 is also a good guide4 ,in order to use the chart it is necessary to harden the sample we desire to test as we would harden a piece of tool steel1 and then test by scleroscope4 ,by locating on the chart the point on the horizontal axis which represents the hardness of the sample the curve enables one to determine the approximate amount of carbon present in the case4 ,should the hardness lack uniformity the soft places can be identified by etching4 ,to accomplish this the sample should be polished after quenching and then washed with a weak solution of nitric acid in alcohol1 whereupon the harder points will show up darker than the softer areas4 ,the selection of suitable boxes for carburizing is worthy of a little consideration1 and there can be no doubt that in certain cases results are spoiled and considerable expense caused by using unsuitable containers4 ,as far as initial expense goes cast-iron boxes are probably the most expedient1 but although they will withstand the necessary temperatures they are liable to split and crack1 and when they get out of shape there is much difficulty in straightening them4 ,the most suitable material in most cases is steel boiler plate #c_/h or #a_/b in4 thick1 which can be made with welded joints and will last well4 ,the sizes of the boxes employed depend to a great extent on the nature of the work being done1 but care should be exercised to avoid putting too much in one box1 as smaller ones permit the heat to penetrate more quickly1 and one test piece is sufficient to give a good indication of what has taken place4 ,if it should be necessary to use larger boxes it is advisable to put in three or four test pieces in different positions to ascertain if the penetration of carbon has been satisfactory in all parts of the box1 as it is quite possible that the temperature of the muffle is not the same at all points1 and a record shown by one test piece would not then be applicable to all the parts contained in the box4 ,it has been found that the rate of carbon penetration increases with the gas pressure around the articles being carburized1 and it is therefore necessary to be careful in sealing up the boxes after packing4 ,when the articles are placed within and each entirely surrounded by compound so that the compound reaches to within #a in4 of the top of the box a layer of clay should be run around the inside of the box on top of the compound4 ,the lid1 which should be a good fit in the box1 is then to be pressed on top of this1 and another layer of clay run just below the rim of the box on top of the cover4 ,a ,,satisfactory ,,luting ,,mixture ,a mixture of fireclay and sand will be found very satisfactory for closing up the boxes1 and by observing the appearance of the work when taken out we can gage the suitability of the methods employed1 for unless the boxes are carefully sealed the work is generally covered with dark scales1 while if properly done the articles will be of a light gray4 ,by observing the above recommendations reliable results can be obtained1 and we can expect uniform results after quenching4 ,,gas ,,consumption ,,for ,,carburizing ,although the advantages offered by the gas-fired furnace for carburizing have been generally recognized in the past from points of view as close temperature regulation1 decreased attendance1 and greater convenience1 very little information has been published regarding the consumption of gas for this process4 ,it has therefore been a matter of great difficulty to obtain authentic information upon this point1 either from makers or users of such furnaces4 ,in view of this1 the details of actual consumption of gas on a regular customer's order job will be of interest4 ,the ,revergen furnace1 manufactured by the ,davis ,furnace ,company1 ,luton1 ,bedford1 ,england1 was used on this job1 and is provided with regenerators and fired with illuminating gas at ordinary pressure1 the air being introduced to the furnace at a slight pressure of #c to #d in4 water gage4 ,the material was charged into a cold furnace1 raised to #a1feb;,f41 and maintained at that temperature for #h hr4 to give the necessary depth of case4 ,the work consisted of automobile gears packed in six boxes1 the total weight being #gac lb4 ,the required temperature of #a1feb;,f4 was obtained in #gj min4 from lighting up1 and a summary of the data is shown in the following table3 ,cubic ,foot ,total ,per ,pound ,number of of ,load ,cubic ,foot ,gas to raise furnace and charge from cold to #a1feb;,f41 #gj min4 #a4bi #ibe ,gas to maintain #a1feb;,f4 for #ast hour #j4ch #bge ,gas to maintain #a1feb;,f4 for #bnd hour #j4db #cjj ,gas to maintain #a1feb;,f4 for #crd hour #j4ch #bge ,gas to maintain #a1feb;,f4 for #dth hour #j4db #cjj ,gas to maintain #a1feb;,f4 for #eth hour #j4di #cej ,gas to maintain #a1feb;,f4 for #fth hour #j4di #cej ,gas to maintain #a1feb;,f4 for #gth hour #j4de #cbe ,gas to maintain #a1feb;,f4 for #hth hour #j4de #cbe ,the overall gas consumption for this run of #i hr4 #aj min4 was only #d4h cu4 ft4 per pound of load4 ,,the ,,care ,,of ,,carburizing ,,compounds ,of all the opportunities for practicing economy in the heat-treatment department1 there is none that offers greater possibilities for profitable returns than the systematic cleaning1 blending and reworking of artificial carburizers1 or compounds4 ,the question of whether or not it is practical to take up the work depends upon the nature of the output4 ,if the sole product of the hardening department consists of a #a4aj carbon case or harder1 requiring a strong highly energized material of deep penetrative power such as that used in the carburizing of ball races1 hub-bearings and the like1 it would be best to dispose of the used material to some concern whose product requires a case with from #j4gj to #j4ij carbon1 but where there is a large variety of work the compound may be so handled that there will be practically no waste4 ,this is accomplished with one of the most widely known artificial carburizers by giving all the compound in the plant three distinct classifications3 ,new1 being direct from the maker2 half and half1 being one part of new and one part first run2 and #b to #a1 which consists of two parts of old and one part new4 ,,separating ,,the ,,work ,,from ,,the ,,compound ,during the pulling of the heat1 the pots are dumped upon a cast-iron screen which forms a table or apron for the furnace4 ,directly beneath this table is located one of the steel conveyor carts1 shown in ,fig4 #dc1 which is provided with two wheels at the rear and a dolly clevis at the front1 which allows it to be hauled away from beneath the furnace apron while filled with red-hot compound4 ,a steel cover is provided for each box1 and the material is allowed to cool without losing much of the evolved gases which are still being thrown off by the compound4 ,illustration3 ,,fig4 #dc4--,the cooling carts4 ,illustration3 ,,fig4 #dd4--,machine for blending the mixture4 ,as this compound comes from the carburizing pots it contains bits of fireclay which represent a part of the luting used for sealing1 and there may be small parts of work or bits of fused material in it as well4 ,after cooling1 the compound is very dusty and disagreeable to handle1 and1 before it can be used again1 must be sifted1 cleaned and blended4 ,some time ago the writer was confronted with this proposition for one of the largest consumers of carburizing compound in the world1 and the problem was handled in the following manner3 ,the cooled compound was dumped from the cooling cars and sprinkled with a low-grade oil which served the dual purposes of settling the dust and adding a certain percentage of valuable hydrocarbon to the compound4 ,in ,fig4 #dd is shown the machine that was designed to do the cleaning and blending4 ,,blending ,,the ,,compound ,essentially1 this consists of the sturdy1 power-driven separator and fanning mill which separates the foreign matter from the compound and elevates it into a large settling basin which is formed by the top of the steel housing that incloses the apparatus4 ,after reaching the settling basin1 the compound falls by gravity into a power-driven rotary mixing tub which is directly beneath the settling basin4 ,here the blending is done by mixing the proper amount of various grades of material together4 ,after blending the compound1 it is ready to be stored in labeled containers and delivered to the packing room4 ,it will be seen that by this simple system there is the least possible loss of energy from the compound4 ,the saving commences the moment the cooling cart is covered and preserves the valuable dust which is saved by the oiling and the settling basin of the blending machine4 ,then1 too1 there is the added convenience of the packers who have a thoroughly cleaned1 dustless1 and standardized product to work with4 ,of course1 this also tends to insure uniformity in the case-hardening operation4 ,with this outfit1 one man cleans and blends as much compound in one hour as he formerly did in ten4 ,,chapter ,,vii ,,heat ,,treatment ,,of ,,steel ,heat treatment consists in heating and cooling metal at definite rates in order to change its physical condition4 ,many objects may be attained by correct heat treatment1 but nothing much can be expected unless the man who directs the operations knows what is the essential difference in a piece of steel at room temperature and at a red heat1 other than the obvious fact that it is hot4 ,the science of metallography has been developed in the past #be years1 and aided by precise methods of measuring temperature1 has done much to systematize the information which we possess on metallic alloys1 and steel in particular4 ,,critical ,,points ,one of the most important means of investigating the properties of pure metals and their alloys is by an examination of their heating and cooling curves4 ,such curves are constructed by taking a small piece and observing and recording the temperature of the mass at uniform intervals of time during a uniform heating or cooling4 ,these observations1 when plotted in the form of a curve will show whether the temperature of the mass rises or falls uniformly4 ,the heat which a body absorbs serves either to raise the temperature of the mass or change its physical condition4 ,that portion of the heat which results in an increase in temperature of the body is called sensible heat1 inasmuch as such a gain in heat is apparent to the physical senses of the observer4 ,if heat were supplied to the body at a uniform rate1 the temperature would rise continuously1 and if the temperature were plotted against time1 a smooth rising curve would result4 ,or1 if sensible heat were abstracted from the body at a uniform rate1 a time-temperature curve would again be a smooth falling curve4 ,such a curve is called a cooling curve4 ,however1 we find that when a body is melting1 vaporizing1 or otherwise suffering an abrupt change in physical properties1 a quantity of heat is absorbed which disappears without changing the temperature of the body4 ,this heat absorbed during a change of state is called latent heat1 because it is transformed into the work necessary to change the configuration and disposition of the molecules in the body2 but it is again liberated in equal amount when the reverse change takes place4 ,from these considerations it would seem that should the cooling curve be continuous and smooth1 following closely a regular course1 all the heat abstracted during cooling is furnished at the expense of a fall in temperature of the body2 that is to say1 it disappears as sensible heat4 ,these curves1 however1 frequently show horizontal portions or arrests which denote that at that temperature all of the heat constantly radiating is being supplied by internal changes in the alloy itself2 that is1 it is being supplied by the evolution of a certain amount of latent heat4 ,in addition to the large amount of heat liberated when a metal solidifies1 there are other changes indicated by the thermal analysis of many alloys which occur after the body has become entirely solidified4 ,these so-called transformation points or ranges may be caused by chemical reactions taking place within the solid1 substances being precipitated from a solid solution1 or a sudden change in some physical property of the components1 such as in magnetism1 hardness1 or specific gravity4 ,it may be difficult to comprehend that such changes can occur in a body after it has become entirely solidified1 owing to the usual conception that the particles are then rigidly fixed4 ,however1 this rigidity is only comparative4 ,the molecules in the solid state have not the large mobility they possess as a liquid1 but even so1 they are still moving in circumscribed orbits1 and have the power1 under proper conditions1 to rearrange their position or internal configuration4 ,in general1 such rearrangement is accompanied by a sudden change in some physical property and in the total energy of the molecule1 which is evidenced by a spontaneous evolution or absorption of latent heat4 ,cooling curves of the purest iron show at least two well-defined discontinuities at temperatures more than #a1jjj;,f41 below its freezing-point4 ,it seems that the soft1 magnetic metal so familiar as wrought iron1 and called alpha iron or ferrite by the metallurgist1 becomes unstable at about #a1djj;,f4 and changes into the so-called beta modification1 becoming suddenly harder1 and losing its magnetism4 ,this state in turn persists no higher than #a1gjf;,c41 when a softer1 non-magnetic gamma iron is the stable modification up to the actual melting-point of the metal4 ,these various changes occur in electrolytic iron1 and therefore cannot be attributed to any chemical reaction or solution2 they are entirely due to the existence of allotropic modifications of the iron in its solid state4 ,illustration3 ,,fig4 #de4--;,inverse ,rate ,cooling ,curve of #j4ch ,c ,steel4 ,steels1 or iron containing a certain amount of carbon1 develop somewhat different cooling curves from those produced by pure iron4 ,figure #de shows1 for instance1 some data observed on a cooling piece of #j4ch per cent carbon steel1 and the curve constructed therefrom4 ,it will be noted that the time was noted when the needle on the pyrometer passed each dial marking4 ,if the metal were not changing in its physical condition1 the time between each reading would be nearly constant2 in fact for a time it required about #ej sec4 to cool each unit4 ,when the dial read about #cb4e 7corresponding in this instrument to a temperature of #gge;,c4 or #a1dbg;,f47 the cooling rate shortened materially1 #ee sec4 then #fe1 then #ajj1 then #ajj2 showing that some change inside the metal was furnishing some of the steadily radiating heat4 ,this temperature is the so-called upper critical for this steel4 ,further down1 the lower critical is shown by a large heat evolution at #fie;,c4 or #a1bhc;,f4 ,just the reverse effects take place upon heating1 except that the temperatures shown are somewhat higher--there seems to be a lag in the reactions taking place in the steel4 ,this is an important point to remember1 because if it was desired to anneal a piece of #j4ch carbon steel1 it is necessary to heat it up to and beyond #a1dgf ,f4 7#a1dbg;,f4 plus this lag1 which may be as much as #ej74 ,it may be said immediately that above the upper critical the carbon exists in the iron as a solid solution1 called austenite by metallographers4 ,that is to say1 it is uniformly distributed as atoms throughout the iron2 the atoms of carbon are not present in any fixed combination1 in fact any amount of carbon from zero to #a4g per cent can enter into solid solution above the upper critical4 ,however1 upon cooling this steel1 the carbon again enters into combination with a definite proportion of iron 7the carbide cementite1 ,fe#c;,c71 and accumulates into small crystals which can be seen under a good microscope4 ,formation of all the cementite has been completed by the time the temperature has fallen to the lower critical1 and below that temperature the steel exists as a complex substance of pure iron and the iron carbide4 ,it is important to note that the critical points or critical range of a plain steel varies with its carbon content4 ,the following table gives some average figures3 ,carbon ,content4 ,upper ,critical4 ,lower ,critical4 #j4jj #a1gjf;,f4 #a1ccj;,f4 #j4bj #a1fjj;,f4 #a1ccj;,f4 #j4dj #a1dhj;,f4 #a1ccj;,f4 #j4fj #a1djj;,f4 #a1ccj;,f4 #j4hj #a1cej;,f4 #a1ccj;,f4 #j4ij #a1ccj;,f4 #a1ccj;,f4 #a4jj #a1dgj;,f4 #a1ccj;,f4 #a4bj #a1fej;,f4 #a1ccj;,f4 #a4dj #a1hcj;,f4 #a1ccj;,f4 #a4fj #b1jjj;,f4 #a1ccj;,f4 ,it is immediately noted that the critical range narrows with increasing carbon content until all the heat seems to be liberated at one temperature in a steel of #j4ij per cent carbon4 ,beyond that composition the critical range widens rapidly4 ,note also that the lower critical is constant in plain carbon steels containing no alloying elements4 ,illustration3 ,,fig4 #df4--,microphotograph of steel used in ,s4 ,k4 ,f4 bearings1 polished and etched with nitric acid and magnified #a1jjj times4 ,made by ,h4 ,o4 ,walp4 ,this steel of #j4ij carbon content is an important one4 ,it is called eutectoid steel4 ,under the microscope a properly polished and etched sample shows the structure to consist of thin sheets of two different substances 7,fig4 #df74 ,one of these is pure iron1 and the other is pure cementite4 ,this structure of thin sheets has received the name pearlite1 because of its pearly appearance under sunlight4 ,pearlite is a constituent found in all annealed carbon steels4 ,pure iron1 having no carbon1 naturally would show no pearlite when examined under a microscope2 only abutting granules of iron are delicately traced4 ,the metallographist calls this pure iron ferrite4 ,as soon as a little carbon enters the alloy and a soft steel is formed1 small angular areas of pearlite appear at the boundaries of the ferrite crystals 7,fig4 #dg74 ,with increasing carbon in the steel the volume of iron crystals becomes less and less1 and the relative amount of pearlite increases1 until arriving at #j4ij per cent carbon1 the large ferrite crystals have been suppressed and the structure is all pearlite4 ,higher carbon steels show films of cementite outlining grains of pearlite 7,fig4 #dh74 ,this represents the structure of annealed1 slowly cooled steels4 ,it is possible to change the relative sizes of the ferrite and cementite crystals by heat treatment4 ,large grains are associated with brittleness4 ,consequently one must avoid heat treatments which produce coarse grains4 ,illustration3 ,,fig4 #dg4--,structure of low carbon steel1 polished1 etched and viewed under #ajj magnifications4 ,tiny white granules of pure iron 7ferrite7 have small accumulations of dark-etching pearlite interspersed between them4 ,photograph by ,h4 ,s4 ,rawdon4 ,illustration3 ,,fig4 #dh4--,slowly cooled high-carbon steel1 polished1 etched and viewed at #ajj magnifications4 ,the dark grains are pearlite1 separated by white films of iron carbide 7cementite74 ,photograph by ,h4 ,s4 ,rawdon4 ,in general it may be said that the previous crystalline structure of a steel is entirely obliterated when it passes just through the critical range4 ,at that moment1 in fact1 the ferrite1 cementite or pearlite which previously existed has lost its identity by everything going into the solid solution called austenite4 ,if sufficient time is given1 the chemical elements comprising a good steel distribute themselves uniformly through the mass4 ,if the steel be then cooled1 the austenite breaks up into new crystals of ferrite1 cementite and pearlite2 and in general if the temperature has not gone far above the critical1 and cooling is not excessively slow1 a very fine texture will result4 ,this is called refining the grain2 or in shop parlance closing the grain4 ,however1 if the heating has gone above the critical very far1 the austenite crystals start to grow2 a very short time at an extreme temperature will cause a large grain growth4 ,subsequent cooling gives a coarse texture1 or an arrangement of ferrite1 cementite and pearlite grains which is greatly coarsened1 reflecting the condition of the austenite crystals from which they were born4 ,it maybe noted in passing that the coarse crystals of cast metal cannot generally be refined by heat treatment unless some forging or rolling has been done in the meantime4 ,heat treatment alone does not seem to be able to break up the crystals of an ingot structure4 ,,hardening ,steel is hardened by quenching from above the upper critical4 ,apparently the quick cooling prevents the normal change back to definite and sizeable crystals of ferrite and cementite4 ,hardness is associated with this suppressed change4 ,if the change is allowed to continue by a moderate reheating1 like a tempering1 the hardness decreases4 ,if a piece of steel could be cooled instantly1 doubtless austenite could be preserved and examined4 ,in the ordinary practice of hardening steels1 the quenching is not so drastic1 and the transformation of austenite back to ferrite and cementite is more or less completely effected1 giving rise to certain transitory forms which are known as martensite1 troostite1 sorbite1 and finally1 pearlite4 ,austenite has been defined as a solid solution of cementite 7,fe#c;,c7 in gamma iron4 ,it is stable at various temperatures dependent upon its carbon content1 which may be any amount up to the saturated solution containing #a4g per cent4 ,austenite is not nearly as hard as martensite1 owing to its content of the soft gamma iron4 ,fig4 #di shows austenite to possess the typical appearance of any pure1 crystallized substance4 ,in the most quickly quenched high carbon steels1 austenite commonly forms the ground mass which is interspersed with martensite1 a large field of which is illustrated in ,fig4 #ej4 ,martensite is usually considered to be a solid solution of cementite in beta iron4 ,it represents an unstable condition in which the metal is caught during rapid cooling4 ,it is very hard1 and is the chief constituent of hardened high-carbon steels1 and of medium-carbon nickel-steel and manganese-steel4 ,troostite is of doubtful composition1 but possibly is an unstable mixture of untransformed martensite with sorbite4 ,it contains more or less untransformed material1 as it is too hard to be composed entirely of the soft alpha modification1 and it can also be tempered more or less without changing in appearance4 ,its normal appearance as rounded grains is given in ,fig4 #ea2 larger patches show practically no relief in their structure1 and a photograph merely shows a dark1 structureless area4 ,illustration3 ,,fig4 #di4--;,coarse-grained martensite1 polished and etched with nitric acid and magnified #ej times4 ,made by ,prof4 ,chas4 ,y4 ,clayton4 ,sorbite is believed to be an early stage in the formation of pearlite1 when the iron and iron carbide originally constituting the solid solution 7austenite7 have had an opportunity to separate from each other1 and the iron has entirely passed into the alpha modification1 but the particles are yet too small to be distinguishable under the microscope4 ,it also1 possibly1 contains some incompletely transformed matter4 ,sorbite is softer and tougher than troostite1 and is habitually associated with pearlite4 ,its components are tending to coagulate into pearlite1 and will do so in a fairly short time at temperatures near the lower critical1 which heat will furnish the necessary molecular freedom4 ,the normal appearance1 however1 is the cloudy mass shown in ,fig4 #eb4 ,pearlite is a definite conglomerate of ferrite and cementite containing about six parts of the former to one of the latter4 ,when pure1 it has a carbon content of about #j4ie per cent4 ,it represents the complete transformation of the eutectoid austenite accomplished by slow-cooling of an iron-carbon alloy through the transformation range4 7,see ,fig4 #df47 ,illustration3 ,,fig4 #ej4--,quenched high-carbon steel1 polished1 etched and viewed at #ajj magnifications4 ,this structure is called martensite and is desired when maximum hardness is essential4 ,photograph by ,h4 ,s4 ,rawdon4 ,illustration3 ,,fig4 #ea4--,martensite 7light needles7 passing into troosite 7dark patches74 #acj ,x4 ,from a piece of eutectoid steel electrically welded4 ,illustration3 ,,fig4 #eb4--,sorbite 7dark patches7 passing into pearlite 7wavy striations74 ,light ,areas are ,patches of ,ferrite4 #bbj ,x4 ,from a piece of hypo-eutectoid steel electrically welded4 ,these observations are competent to explain annealing and toughening practice4 ,a quickly quenched carbon steel is mostly martensitic which1 as noted1 is a solid solution of beta iron and cementite1 hard and brittle4 ,moderate reheating or annealing changes this structure largely into troostite1 which is a partly transformed martensite1 possessing much of the hardness of martensite1 but with a largely increased toughness and shock resistance4 ,this toughness is the chief characteristic of the next material in the transformation series1 sorbite1 which is merely martensite wholly transformed into a mixture of ultramicroscopic crystals of ferrite 7alpha iron7 and cementite 7,fe#c;,c74 ,tempering or drawing should be restricted to mean moderate reheating1 up to about #cej ,c41 forming troostitic steel4 ,toughening represents the practice of reheating hardened carbon steels from #cej ,c4 up to just below the lower critical1 and forms sorbitic steel2 while annealing refers to a heating for grain size at or above the transformation ranges1 followed by a slow cooling4 ,any of these operations not only allows the transformations from austenite to pearlite to proceed1 but also relieves internal stresses in the steel4 ,normalizing is a heating like annealing1 followed by a moderately rapid quench4 ,,judging ,,the ,,heat ,,of ,,steel ,while the use of a pyrometer is of course the only way to have accurate knowledge as to the heat being used in either forging or hardening steels1 a color chart will be of considerable assistance if carefully studied4 ,these have been prepared by several of the steel companies as a guide1 but it must be remembered that the colors and temperatures given are only approximate1 and can be nothing else4 ,illustration3 ,,fig4 #ec4--;,finding hardening heats with a magnet4 ,the ,magnet ,test4--,the critical point can also be determined by an ordinary horse-shoe magnet4 ,touch the steel with a magnet during the heating and when it reaches the temperature at which steel fails to attract the magnet1 or in other words1 loses its magnetism1 the critical point has been reached4 ,figures #ec and #ed show how these are used in practice4 ,the first 7,fig4 #ec7 shows the use of a permanent horse-shoe magnet and the second 7,fig4 #ed7 an electro-magnet consisting of an iron rod with a coil or spool magnet at the outer end4 ,in either case the magnet should not be allowed to become heated but should be applied quickly4 ,illustration3 ,,fig4 #ed4--,using electro-magnet to determine heat4 ,the work is heated up slowly in the furnace and the magnet applied from time to time4 ,the steel being heated will attract the magnet until the heat reaches the critical point4 ,the magnet is applied frequently and when the magnet is no longer attracted1 the piece is at the lowest temperature at which it can be hardened properly4 ,quenching slightly above this point will give a tool of satisfactory hardness4 ,the method applies only to carbon steels and will not work for modern high-speed steels4 ,,heat ,,treatment ,,of ,,gear ,,blanks ,this section is based on a paper read before the ,american ,gear ,manufacturers' ,association at ,white ,sulphur ,springs1 ,w4 ,va41 ,apr4 #ah1 #aiah4 ,great advancement has been made in the heat treating and hardening of gears4 ,in this advancement the chemical and metallurgical laboratory have played no small part4 ,during this time1 however1 the condition of the blanks as they come to the machine shop to be machined has not received its share of attention4 ,there are two distinct types of gears1 both types having their champions1 namely1 carburized and heat-treated4 ,the difference between the two in the matter of steel composition is entirely in the carbon content1 the carbon never running higher than #be-point in the carburizing type1 while in the heat-treated gears the carbon is seldom lower than #ce-point4 ,the difference in the final gear is the hardness4 ,the carburized gear is file hard on the surface1 with a soft1 tough and ductile core to withstand shock1 while the heat-treated gear has a surface that can be touched by a file with a core of the same hardness as the outer surface4 ,,annealing ,,work4--,with the exception of several of the higher types of alloy steels1 where the percentages of special elements run quite high1 which causes a slight air-hardening action1 the carburizing steels are soft enough for machining when air cooled from any temperature1 including the finishing temperature at the hammer4 ,this condition has led many drop-forge and manufacturing concerns to consider annealing as an unnecessary operation and expense4 ,in many cases the drop forging has only been heated to a low temperature1 often just until the piece showed color1 to relieve the so-called hammer strains4 ,while this has been only a compromise it has been better than no reheating at all1 although it has not properly refined the grain1 which is necessary for good machining conditions4 ,annealing is heating to a temperature slightly above the highest critical point and cooling slowly either in the air or in the furnace4 ,annealing is done to accomplish two purposes3 7#a7 to relieve mechanical strains and 7#b7 to soften and produce a maximum refinement of grain4 ,,process ,,of ,,carburizing4--,carburizing imparts a shell of high-carbon content to a low-carbon steel4 ,this produces what might be termed a dual steel1 allowing for an outer shell which when hardened would withstand wear1 and a soft ductile core to produce ductility and withstand shock4 ,the operation is carried out by packing the work to be carburized in boxes with a material rich in carbon and maintaining the box so charged at a temperature in excess of the highest critical point for a length of time to produce the desired depth of carburized zone4 ,generally maintaining the temperature at #a1fej to #a1gjj ,f4 for #g hr4 will produce a carburized zone #a_/cb in4 deep4 ,heating to a temperature slightly above the highest critical point and cooling suddenly in some quenching medium1 such as water or oil hardens the steel4 ,this treatment produces a maximum refinement with the maximum strength4 ,drawing to a temperature below the highest critical point 7the temperature being governed by the results required7 relieves the hardening strains set up by quenching1 as well as the reducing of the hardness and brittleness of hardened steel4 ,,effects ,,of ,,proper ,,annealing4--,proper annealing of low-carbon steels causes a complete solution or combination to take place between the ferrite and pearlite1 producing a homogeneous mass of small grains of each1 the grains of the pearlite being surrounded by grains of ferrite4 ,a steel of this refinement will machine to good advantage1 due to the fact that the cutting tool will at all times be in contact with metal of uniform composition4 ,while the alternate bands of ferrite and pearlite are microscopically sized1 it has been found that with a ,gleason or ,fellows gear-cutting machine that rough cutting can be traced to poorly annealed steels1 having either a pronounced banded structure or a coarse granular structure4 ,,temperature ,,for ,,annealing4--,theoretically1 annealing should be accomplished at a temperature at just slightly above the critical point4 ,however1 in practice the temperature is raised to a higher point in order to allow for the solution of the carbon and iron to be produced more rapidly1 as the time required to produce complete solution is reduced as the temperature increases past the critical point4 ,for annealing the simpler types of low-carbon steels the following temperatures have been found to produce uniform machining conditions on account of producing uniform fine-grain pearlite structure3 #j4ae to #j4be per cent carbon1 straight carbon steel4--,heat to #a1fej;,f4 ,hold at this temperature until the work is uniformly heated2 pull from the furnace and cool in air4 #j4ae to #j4be per cent carbon1 #a-a_/b per cent nickel1 #a_/b per cent chromium steel4--,heat to #a1fjj;,f4 ,hold at this temperature until the work is uniformly heated2 pull from the furnace and cool in air4 #j4ae to #j4be per cent carbon1 #c-a_/b per cent nickel steel4--,heat to #a1ege;,f4 ,hold at this temperature until the work is uniformly heated2 pull from the furnace and cool in air4 ,,care ,,in ,,annealing4--,not only will benefits in machining be found by careful annealing of forgings but the subsequent troubles in the hardening plant will be greatly reduced4 ,the advantages in the hardening start with the carburizing operation1 as a steel of uniform and fine grain size will carburize more uniformly1 producing a more even hardness and less chances for soft spots4 ,the holes in the gears will also close in more uniformly1 not causing some gears to require excessive grinding and others with just enough stock4 ,also all strains will have been removed from the forging1 eliminating to a great extent distortion and the noisy gears which are the result4 ,with the steels used1 for the heat-treated gears1 always of a higher carbon content1 treatment after forging is necessary for machining1 as it would be impossible to get the required production from untreated forgings1 especially in the alloy steels4 ,the treatment is more delicate1 due to the higher percentage of carbon and the natural increase in cementite together with complex carbides which are present in some of the higher types of alloys4 ,where poor machining conditions in heat-treated steels are present they are generally due to incomplete solution of cementite rather than bands of free ferrite1 as in the case of case-hardening steels4 ,this segregation of carbon1 as it is sometimes referred to1 causes hard spots which1 in the forming of the tooth1 cause the cutter to ride over the hard metal1 producing high spots on the face of the tooth1 which are as detrimental to satisfactory gear cutting as the drops or low spots produced on the face of the teeth when the pearlite is coarse-grained or in a banded condition4 ,in the simpler carburized steels it is not necessary to test the forgings for hardness after annealing1 but with the high percentages of alloys in the carburizing steels and the heat-treated steels a hardness test is essential4 ,to obtain the best results in machining1 the microstructure of the metal should be determined and a hardness range set that covers the variations in structure that produce good machining results4 ,by careful control of the heat-treating operation and with the aid of the ,brinell hardness tester and the microscope it is possible to continually give forgings that will machine uniformly and be soft enough to give desired production4 ,the following gives a few of the hardness numerals on steel used in gear manufacture that produce good machining qualities3 #j4bj per cent carbon1 #c per cent nickel1 #a-a_/d2 per cent chromium--,brinell #aef to #agj4 #j4ej per cent carbon1 #c per cent nickel1 #a per cent chromium--,brinell #agi to #ahg4 #j4ej per cent carbon chrome-vanadium--,brinell #agj to #agi4 ,,the ,,influence ,,of ,,size ,the size of the piece influences the physical properties obtained in steel by heat treatment4 ,this has been worked out by ,e4 ,j4 ,janitzky1 metallurgical engineer of the ,illinois ,steel ,company1 as follows3 ,illustration3 ,,fig4 #ee4--;,effect of size on heating4 ,with an increase in the mass of steel there is a corresponding decrease in both the minimum surface hardness and depth hardness1 when quenched from the same temperature1 under identical conditions of the quenching medium4 ,in other words1 the physical properties obtained are a function of the surface of the metal quenched for a given mass of steel4 ,keeping this primary assumption in mind1 it is possible to predict what physical properties may be developed in heat treating by calculating the surface per unit mass for different shapes and sizes4 ,it may be pointed out that the figures and chart that follow are not results of actual tests1 but are derived by calculation4 ,they indicate the mathematical relation1 which1 based on the fact that the physical properties of steel are determined not alone by the rate which heat is lost per unit of surface1 but by the rate which heat is lost per unit of weight in relation to the surface exposed for that unit4 ,the unit of weight has for the different shaped bodies and their sizes a certain surface which determines their physical properties4 ,for example1 the surface corresponding to #a lb4 of steel has been computed for spheres1 rounds and flats4 ,for the sphere with a unit weight of #a lb4 the portion is a cone with the apex at the center of the sphere and the base the curved surface of the sphere 7surface exposed to quenching74 ,for rounds1 a unit weight of #a lb4 may be taken as a disk or cylinder1 the base and top surfaces naturally do not enter into calculation4 ,for a flat1 a prismatic or cylindrical volume may be taken to represent the unit weight4 ,the surfaces that are considered in this instance are the top and base of the section1 as these surfaces are the ones exposed to cooling4 ,the results of the calculations are as follows3 ,,table #bj4--,,sphere ,diameter ,surface per of sphere pound of steel ,x ,y #h in4 #b4fdh sq4 in4 #f in4 #c4eca sq4 in4 #d in4 #e4bid sq4 in4 #c in4 #g4jfb sq4 in4 #b in4 #aj4fa sq4 in4 ,,xy #ba4ahe4 ,,table #ba4--,,round ,diameter ,surface per of round pound of steel ,x ,y #h4j in4 #a4gfe sq4 in4 #f4j in4 #b4ced sq4 in4 #e4j in4 #b4hbi sq4 in4 #d4j in4 #c4eca sq4 in4 #c4j in4 #d4gjh sq4 in4 #b4j in4 #g4jfb sq4 in4 #a4j in4 #ad4abe sq4 in4 #j4e in4 #bh4be sq4 in4 #j4be in4 #ef4e sq4 in4 ,,xy #ad4abd4 ,,table #bb4--;,,flat ,thickness ,surface per of flat pound of steel ,x ,y #h4j in4 #j4hhbh sq4 in4 #f4j in4 #a4agg sq4 in4 #e4j in4 #a4dab sq4 in4 #d4j in4 #a4gfe sq4 in4 #c4j in4 #b4cde sq4 in4 #b4j in4 #c4eca sq4 in4 #a4j in4 #g4jfb sq4 in4 #j4e in4 #ad4abd sq4 in4 #j4be in4 #bh4bdh sq4 in4 ,,xy #g4jfb4 ,having once determined the physical qualities of a certain specimen1 and found its position on the curve we have the means to predict the decrease of physical qualities on larger specimens which receive the same heat treatment4 ,when the surfaces of the unit weight as outlined in the foregoing tables are plotted as ordinates and the corresponding diameters as absciss1 the resulting curve is a hyperbola and follows the law ,,xy ,c4 ,in making these calculations the radii or one-half of the thickness need only to be taken into consideration as the heat is conducted from the center of the body to the surface1 following the shortest path4 ,the equations for the different shapes are as follows3 ,for flats ,,xy #g4jfb ,for rounds ,,xy #ad4abd ,for spheres ,,xy #ba4ahe ,it will be noted that the constants increase in a ratio of #a1 #b1 and #c1 and the three bodies in question will increase in hardness on being quenched in the same ratio1 it being understood that the diameter of the sphere and round and thickness of the flat are equal4 ,relative to shape1 it is interesting to note that rounds1 squares1 octagons and other three axial bodies1 with two of their axes equal1 have the same surface for the unit weight4 ,for example3 ,size ,length ,surface ,weight ,surface for #a lb4 #b in4 ,sq4 #ab in4 #if4j sq4 in4 #ac4fj lb4 #g4jf sq4 in4 #b in4 ,round #ab in4 #ge4d sq4 in4 #aj4fh lb4 #g4jf sq4 in4 ,although this discussion is at present based upon mathematical analysis1 it is hoped that it will open up a new field of investigation in which but little work has been done1 and may assist in settling the as yet unsolved question of the effect of size and shape in the heat treatment of steel4 ,,heat-,,treating ,,equipment ,,and ,,methods ,,for ,,mass ,,production ,the heat-treating department of the ,brown-,lipe-,chapin ,company1 ,syracuse1 ,n4 ,y41 runs day and night1 and besides handling all the hardening of tools1 parts of jigs1 fixtures1 special machines and appliances1 carburizes and heat-treats every month between #aej1jjj and #bjj1jjj gears1 pinions1 crosses and other components entering into the construction of differentials for automobiles4 ,the treatment of the steel really begins in the mill1 where the steel is made to conform to a specific formula4 ,on the arrival of the rough forgings at the ,brown-,lipe-,chapin factory1 the first of a long series of inspections begins4 ,,annealing ,,method4--,forgings which are too hard to machine are put in pots with a little charcoal to cause a reducing atmosphere and to prevent scale4 ,the covers are then luted on and the pots placed in the furnace4 ,carbon steel from #ae to #be points is annealed at #a1fjj;,f4 ,nickel steel of the same carbon and containing in addition #c-a_/b per cent nickel is annealed at #a1dej;,f4 ,when the pots are heated through1 they are rolled to the yard and allowed to cool4 ,this method of annealing gives the best hardness for quick machining4 ,the requirements in the machine operations are very rigid and1 in spite of great care and probably the finest equipment of special machines in the world1 a small percentage of the product fails to pass inspection during or at the completion of the machine operations4 ,these pieces1 however1 are not a loss1 for they play an important part in the hardening process1 indicating as they do the exact depth of penetration of the carburizing material and the condition of both case and core4 ,,heat-,,treating ,,department4--,the heat-treating department occupies an ,l-shaped building4 ,the design is very practical1 with the furnace and the floor on the same level so that there is no lifting of heavy pots4 ,fuel oil is used in all the furnaces and gives highly satisfactory results4 ,the consumption of fuel oil is about #b gal4 per hour per furnace4 ,the work is packed in the pots in a room at the entrance to the heat-treatment building4 ,before packing1 each gear is stamped with a number which is a key to the records of the analysis and complete heat treatment of that particular gear4 ,should a question at any time arise regarding the treatment of a certain gear1 all the necessary information is available if the number on the gear is legible4 ,for instance1 date of treatment1 furnace1 carburizing material1 position of the pot in the furnace1 position of gear in pot1 temperature of furnace and duration of treatment are all tabulated and filed for reference4 ,after marking1 all holes and parts which are to remain uncarburized are plugged or luted with a mixture of kaolin and ,mellville gravel clay1 and the gear is packed in the carburizing material4 ,bohnite1 a commercial carburizing compound is used exclusively at this plant4 ,this does excellent work and is economical4 ,broadly speaking1 the economy of a carburizing compound depends on its lightness4 ,the space not occupied by work must be filled with compound2 therefore7 other things being equal1 a compound weighing #be lb4 would be worth more than twice as much as one weighing #fj lb4 per cubic foot4 ,it has been claimed that certain compounds can be used over and over again1 but this is only true in a limited way1 if good work is required4 ,there is1 of course1 some carbon in the compound after the first use1 but for first-class work1 new compound must be used each time4 ,,the ,,packing ,,department4--,in ,fig4 #ef is shown the packing pots where the work is packed4 ,these are of malleable cast iron1 with an internal vertical flange around the hole ,a4 ,this fits in a bell on the end of the cast-iron pipe ,b1 which is luted in position with fireclay before the packing begins4 ,at ,c is shown a pot ready for packing4 ,the crown gears average #aj to #ab in4 in diameter and weigh about #aa lb4 each4 ,when placed in the pots1 they surround the central tube1 which allows the heat to circulate4 ,each pot contains five gears4 ,two complete scrap gears are in each furnace 7i4e41 gears which fail to pass machining inspection71 and at the top of front pot are two or more short segments of scrap gear1 used as test pieces to gage depth of case4 ,illustration3 ,,fig4 #ef4--,packing department and special pots4 ,after filling to the top with compound1 the lid ,d is luted on4 ,ten pots are then placed in a furnace4 ,it will be noted that the pots to the right are numbered #a1 #b1 #c1 #d1 indicating the position they are to occupy in the furnace4 ,the cast-iron ball shown at ,e is small enough to drop through the pipe ,b1 but will not pass through the hole ,a in the bottom of the pot4 ,it is used as a valve to plug the bottom of the pot to prevent the carburizing compound from dropping through when removing the carburized gears to the quenching bath4 ,without detracting from the high quality of the work1 the metallurgist in this plant has succeeded in cutting out one entire operation and reducing the time in the hardening room by about #bd hr4 ,formerly1 the work was carburized at about #a1gjj;,f4 for #i hr4 ,the pots were then run out into the yard and allowed to cool slowly4 ,when cool1 the work was taken out of the pots1 reheated and quenched at #a1fjj;,f4 to refine the core4 ,it was again reheated to #a1dbe;,f4 and quenched to refine the case4 ,finally1 it was drawn to the proper temper4 ,,short ,,method ,,of ,,treatment4--,in the new method1 the packed pots are run into the case-hardening furnaces1 which are heated to #a1fjj;,f4 ,on the insertion of the cold pots1 the temperature naturally falls4 ,the amount of this fall is dependent upon a number of variables1 but it averages nearly #ejj;,f4 as shown in the pyrometer chart1 ,fig4 #fa4 ,the work and furnace must be brought to #a1fjj;,f4 ,within #b-a_/b hr42 otherwise1 a longer time will be necessary to obtain the desired depth of case4 ,on this work1 the depth of case required is designated in thousandths1 and on crown gears1 the depth in #j4jbh in4 ,having brought the work to a temperature of #a1fjj;,f4 the depth of case mentioned can be obtained in about #e-a_/b hr4 by maintaining this temperature4 ,as stated before1 at the top of each pot are several test pieces consisting of a whole scrap gear and several sections4 ,after the pots have been heated at #a1fjj;,f4 for about #e-a_/d hr41 they are removed1 and a scrap-section test-piece is quenched direct from the pot in mineral oil at not more than #ajj;,f4 ,the end of a tooth of this is then ground and etched to ascertain the depth of case4 ,as these test pieces are of exactly the same cross-section as the gears themselves1 the carburizing action is similar4 ,when the depth of case has been found from the etched test pieces to be satisfactory1 the pots are removed4 ,the iron ball then is dropped into the tube to seal the hole in the bottom of the pot2 the cover and the tube are removed1 and the gears quenched direct from the pot in mineral oil1 which is kept at a temperature not higher than #ajj;,f4 ,,the ,,effect4--,the heating at #a1fjj;,f4 gives the first heat treatment which refines the core1 which under the former high heat 7#a1gjj;,f47 was rendered coarsely crystalline4 ,all the gears1 including the scrap gears1 are quenched direct from the pot in this manner4 ,the gears then go to the reheating furnaces1 situated in front of a battery of ,gleason quenching machines4 ,these furnaces accommodate from #ab to #af crown gears4 ,the carbon-steel gears are heated in a reducing atmosphere to about #a1dbe;,f4 7depending on the carbon content7 placed in the dies in the ,gleason quenching machine1 and quenched between dies in mineral oil at less than #ajj;,f4 ,the test gear receives exactly the same treatment as the others and is then broken1 giving a record of the condition of both case and core4 ,,affinity ,,of ,,nickel ,,steel ,,for ,,carbon4--,the carbon- and nickel-steel gears are carburized separately owing to the difference in time necessary for their carburization4 ,practically all printed information on the subject is to the effect that nickel steel takes longer to carburize than plain carbon steel4 ,this is directly opposed to the conditions found at this plant4 ,for the same depth of case1 other conditions being equal1 a nickel-steel gear would require from #bj to #cj min4 less than a low carbon-steel gear4 ,from the quenching machines1 the gears go to the sand-blasting machines1 situated in the wing of the heat-treating building1 where they are cleaned4 ,from here they are taken to the testing department4 ,the tests are simple and at the same time most thorough4 ,,testing ,,and ,,inspection ,,of ,,heat ,,treatment4--,the hard parts of the gear must be so hard that a new mill file does not bite in the least4 ,having passed this file test at several points1 the gears go to the center-punch test4 ,the inspector is equipped with a wooden trough secured to the top of the bench to support the gear1 a number of center punches 7made of #c_/d-;in4 hex-steel having points sharpened to an angle of #abj deg47 and a hammer weighing about #d oz4 ,with these simple tools1 supplemented by his skill1 the inspector can feel the depth and quality of the case and the condition of the core4 ,the gears are each tested in this way at several points on the teeth and elsewhere1 the scrap gear being also subjected to the test4 ,finally1 the scrap gear is securely clamped in the straightening press shown in ,fig4 #eg4 ,with a #c-a_/b-lb4 hammer and a suitable hollow-ended drift manipulated by one of ,sandow's understudies1 teeth are broken out of the scrap gear at various points4 ,these give a record confirming the center-punch tests1 which1 if the angle of the center punch is kept at #abj deg4 and the weight of the hammer and blow are uniform1 is very accurate4 ,after passing the center-punch test the ends of the teeth are peened lightly with a hammer4 ,if they are too hard1 small particles fly off4 ,such gears are drawn in oil at a temperature of from #cjj to #cej;,f41 depending on their hardness4 ,some builders prefer to have the extreme outer ends of the teeth drawn somewhat lower than the rest4 ,this drawing is done on gas-heated red-hot plates1 as shown at ,a in ,fig4 #eh4 ,illustration3 ,,fig4 #eg4--,press for holding test gears for breaking4 ,nickel steel1 in addition to all the tests given to carbon steel1 is subjected to a ,brinell test4 ,for each steel1 the temperature and the period of treatment are specific4 ,for some unknown reason1 apparently like material with like treatment will1 in isolated cases1 not produce like results4 ,it then remains for the treatment to be repeated or modified1 but the results obtained during inspection form a valuable aid to the metallurgist in determining further treatment4 ,,temperature ,,recording ,,and ,,regulation4--,each furnace is equipped with pyrometers1 but the reading and recording of all temperatures are in the hands of one man1 who occupies a room with an opening into the end of the hardening department4 ,the opening is about #ae ft4 above the floor level4 ,on each side of it1 easily legible from all of the furnaces1 is a board with the numbers of the various furnaces1 as shown in ,figs4 #ei and #fj4 ,opposite each furnace number is a series of hooks whereon are hung metal numbers representing the pyrometer readings of the temperature in that particular furnace4 ,within the room1 as shown in ,fig4 #fj1 the indicating instrument is to the right1 and to the left is a switchboard to connect it with the thermo-couples in the various furnaces4 ,the boards shown to the right and the left swing into the room1 which enables the attendant easily to change the numbers to conform to the pyrometer readings4 ,readings of the temperatures of the carburizing furnaces are taken and tabulated every ten minutes4 ,these1 numbered #a to #aj1 are shown on the board to the right in ,fig4 #ei4 ,the card shown in ,fig4 #fa gives such a record4 ,these records are filed away for possible future reference4 ,illustration3 ,,fig4 #eh4--;,gas heated drawing plate for tooth ends4 ,the temperatures of the reheating furnaces1 numbered from #a to #bf and shown on the board to the left in ,fig4 #ei1 are taken every #e min4 ,each furnace has a large metal sign on which is marked the temperature at which the furnace regulator is required to keep his heat4 ,as soon as any variation from this is posted on the board outside the pyrometer room1 the attendant sees it and adjusts the burners to compensate4 ,illustration3 ,,fig4 #ei4--,pyrometer recording room4 ,illustration3 ,,fig4 #fj4--;,inside of ,pyrometer switch room4 ,,dies ,,for ,,gleason ,,tempering ,,machines4--,in ,fig4 #fb is shown a set of dies for the ,gleason tempering machine4 ,these accurately made dies fit and hold the gear true during quenching1 thus preventing distortion4 ,illustration3 ,,fig4 #fa4--;,carburizing furnace record4 ,referring to ,fig4 #fb1 the die ,a has a surface ,b which fits the face of the teeth of the gear ,c4 ,this surface is perforated by a large number of holes which permit the quenching oil to circulate freely4 ,the die ,a is set in the upper end of the plunger ,a of the tempering machine1 shown in ,fig4 #fc1 a few inches above the surface of the quenching oil in the tank ,n4 ,inside the die ,a are the centering jaws ,d1 ,fig4 #fb1 which are an easy fit for the bore of the gear ,c4 ,the inner surface of the centering jaws is in the shape of a female cone4 ,the upper die is shown at ,e4 ,in the center 7separate from it1 but a snug sliding fit in it7 is the expander ,g1 which1 during quenching1 enters the taper in the centering jaws ,d1 expanding them against the bore of the gear ,c4 ,the faces ,f of the upper die ,e fit two angles at the back of the gear and are grooved for the passage of the quenching oil4 ,the upper die ,e is secured to the die carrier ,b1 shown in ,fig4 #i1 and inside the die is the expander ,g1 which is backed up by compression springs4 ,illustration3 ,,fig4 #fb4--;,dies for ,gleason gear-hardening machine4 ,,hardening ,,operation4--,hardening a gear is accomplished as follows3 ,the gear is taken from the furnace by the furnaceman and placed in the lower die1 surrounding the centering jaws1 as shown at ,h in ,fig4 #fb and ,c in ,fig4 #fc4 ,air is then turned into the cylinder ,d1 and the piston rod ,e1 the die carrier ,b1 the top die ,f and the expander ,g descend4 ,the pilot ,h enters a hole in the center of the lower die1 and the expander ,g enters the centering jaws ,i1 causing them to expand and center the gear ,c in the lower die4 ,on further advance of the piston rod ,e1 the expander ,g is forced upward against the pressure of the springs ,j and the upper die ,f comes in contact with the upper surface of the gear4 ,further downward movement of the dies1 which now clamp the work securely1 overcomes the resistance of the pressure weight ,k 7which normally keeps up the plunger ,a71 and the gear is submerged in the oil4 ,the quenching oil is circulated through a cooling system outside the building and enters the tempering machine through the inlet pipe ,l4 ,when the machine is in the position shown1 the oil passes out through the ports ,m in the lower plunger to the outer reservoir ,n1 passing to the cooling system by way of the overflow ,o4 ,when the lower plunger ,a is forced downward1 the ports ,m are automatically closed and the cool quenching oil from the inlet pipe ,l1 having no other means of escape1 passes through the holes in the lower die and the grooves in the upper1 circulating in contact with the surfaces of the gear and passes to the overflow4 ,when the air pressure is released1 the counterweights return the parts to the positions shown in ,fig4 #fc1 and the operator removes the gear4 ,illustration3 ,,fig4 #fc4--;,gleason tempering machine4 ,the gear comes out uniformly hard all over and of the same degree of hardness as when tempered in an open tank4 ,the output of the machine depends on the amount of metal to be cooled1 but will average from #h to #af per hour4 ,each machine is served by one man1 two furnaces being required to heat the work4 ,a slight excess of oil is used in the firing of the furnaces to give a reducing atmosphere and to avoid scale4 ,illustration3 ,,fig4 #fd4--;,hardening and shrinking sleeves4 ,,carburizing ,,low-,,carbon ,,sleeves4--,low-carbon sleeves are carburized and pushed on malleable-iron differential-case hubs4 ,formerly1 these sleeves were given two treatments after carburization in order to refine the case and the core1 and then sent to the grinding department1 where they were ground to a push fit for the hubs4 ,after this they were pushed on the hubs4 ,by the method now employed1 the first treatment refines the core1 and on the second treatment1 the sleeves are pushed on the hub and at the same time hardened4 ,this method cuts out the internal grinding time1 pressing on hubs1 and haulage from one department to another4 ,also1 less work is lost through splitting of the sleeves4 ,the machine for pushing the sleeves on is shown in ,fig4 #fd4 ,at ,a is the stem on which the hot sleeve ,b is to be pushed4 ,the carburized sleeves are heated in an automatic furnace1 which takes them cold at the back and feeds them through to the front1 by which time they are at the correct temperature4 ,the loose mandrel ,c is provided with a spigot on the lower end1 which fits the hole in the differential-case hub4 ,the upper end is tapered as shown and acts as a pilot for the ram ,d4 ,the action of pushing on and quenching is similar to the action of the ,gleason tempering machine1 with the exception that water instead of oil is used as a quenching medium4 ,the speed of operation depends on a number of variables1 but from #cej to #ejj can be heated and pressed on in #aa hr4 ,,cyanide ,,bath ,,for ,,tool ,,steels4--,all high-carbon tool steels are heated in a cyanide bath4 ,with this bath1 the heat can be controlled within #c deg4 ,the steel is evenly heated without exposure to the air1 resulting in work which is not warped and on which there is no scale4 ,the cyanide bath is1 of course1 not available for high-speed steel because of the very high temperatures necessary4 ,,drop ,,forging ,,dies ,the kind of steel used in the die of course influences the heat treatment it is to receive1 but this also depends on the kind of work the die is to perform4 ,if the die is for a forging which is machined all over and does not have to be especially close to size1 where a variation of #a_/af in4 is not considered excessive1 a low grade steel will be perfectly satisfactory4 ,in cases of fine work1 however1 where the variation cannot be over #j4jje to #j4ja in4 we must use a fine steel and prevent its going out of shape in the heating and quenching4 ,a high quality crucible steel is suggested with about the following analysis3 ,carbon #j4ge per cent1 manganese #j4be per cent1 silicon #j4ae per cent1 sulphur #j4jae per cent1 and phosphorus #j4jae per cent4 ,such a steel will have a decalescent point in the neighborhood of #a1cee;,f4 and for the size used1 probably in a die of approximately #h in41 it will harden around #a1dej;,f4 ,to secure best results care must be taken at every step4 ,the block should be heated slowly to about #a1djj;,f41 the furnace closed tight and allowed to cool slowly in the furnace itself4 ,it should not soak at the high temperature4 ,after machining1 and before it is put in the furnace for hardening1 it should be slowly preheated to #hjj or #ijj;,f4 ,this can be done in several ways1 some putting the die block in front of the open door of a hardening furnace and keeping the furnace at about #a1jjj;,f4 ,the main thing is to heat the die block very slowly and evenly4 ,the hardening heat should be very slow1 #g hr4 being none too long for such a block1 bringing the die up gradually to the quenching temperature of #a1dej4 ,this should be held for #a_/b hr4 or even a little more1 when the die can be taken out and quenched4 ,there should be no guess work about the heating1 a good pyrometer being the only safe way of knowing the correct temperature4 ,the quenching tank should be of good size and have a spray or stream of water coming up near the surface4 ,dip the die block about #c in4 deep and let the stream of water get at the face so as to play on the forms4 ,by leaving the rest of the die out of the water1 moving the die up and down a trifle to prevent a crack at the line of immersion1 the back of the block is left tough while the face is very hard4 ,to overcome the tendency to warp the face it is a good plan to pour a little water on the back of the die as this tends to even up the cooling4 ,the depth to which the die is dipped can be easily regulated by placing bars across the tank at the proper depth4 ,after the scleroscope shows the die to be properly hardened1 which means from #ih to #aja1 the temper should be drawn as soon as convenient4 ,a lead pot in which the back of the die can be suspended so as to heat the back side1 makes a good method4 ,or the die block can be placed back to the open door of a furnace4 ,on a die of this size it may take several hours to draw it to the desired temper4 ,this can be tested while warm by the scleroscope method1 bearing in mind that the reading will not be the same as when cold4 ,if the test shows from #gf to #gh while warm1 the hardness when cold will be about #hc1 which is about right for this work4 ,s4 ,a4 ,e4 ,,heat ,,treatments ,the ,society of ,automotive ,engineers have adopted certain heat treatments to suit different steels and varying conditions4 ,these have already been referred to on pages #ci to #da in connection with the different steels used in automobile practice4 ,these treatments are designated by letter and correspond with the designations in the table4 ,,heat ,,treatments ,heat ,treatment ,a ,after forging or machining3 #a4 ,carbonize at a temperature between #a1fjj;,f4 and #a1gej;,f4 7#a1fej-a1gjj;,f4 desired47 #b4 ,cool slowly or quench4 #c4 ,reheat to #a1dej-a1ejj;,f4 and quench4 ,heat ,treatment ,b ,after forging or machining3 #a4 ,carbonize between #a1fjj;,f4 and #a1gej;,f4 7#a1fej-a1gjj;,f4 ,desired47 #b4 ,cool slowly in the carbonizing mixture4 #c4 ,reheat to #a1eej-a1fbe;,f4 #d4 ,quench4 #e4 ,reheat to #a1djj-a1dej;,f4 #f4 ,quench4 #g4 ,draw in hot oil at #cjj to #dej;,f41 depending upon the degree of hardness desired4 ,heat ,treatment ,d ,after forging or machining3 #a4 ,heat to #a1ejj-a1fjj;,f4 #b4 ,quench4 #c4 ,reheat to #a1dej-a1ejj;,f4 #d4 ,quench4 #e4 ,reheat to #fjj-a1bjj;,f4 and cool slowly4 ,heat ,treatment ,e ,after forging or machining3 #a4 ,heat to #a1ejj-a1eej;,f4 #b4 ,cool slowly4 #c4 ,reheat to #a1dej-a1ejj;,f4 #d4 ,quench4 #e4 ,reheat to #fjj-a1bjj;,f4 and cool slowly4 ,heat ,treatment ,f ,after shaping or coiling3 #a4 ,heat to #a1dbe-a1dge;,f4 #b4 ,quench in oil4 #c4 ,reheat to #djj-ijj;,f41 in accordance with temper desired and cool slowly4 ,heat ,treatment ,g ,after forging or machining3 #a4 ,carbonize at a temperature between #a1fjj;,f4 and #a1gej;,f4 7#a1fej-a1gjj;,f4 desired74 #b4 ,cool slowly in the carbonizing mixture4 #c4 ,reheat to #a1ejj-a1eej;,f4 #d4 ,quench4 #e4 ,reheat to #a1cjj-a1djj;,f4 #f4 ,quench4 #g4 ,reheat to #bej-ejj;,f4 7in accordance with the necessities of the case7 and cool slowly4 ,heat ,treatment ,h ,after forging or machining3 #a4 ,heat to #a1ejj-a1fjj;,f4 #b4 ,quench4 #c4 ,reheat to #fjj-a1bjj;,f4 and cool slowly4 ,heat ,treatment ,k ,after forging or machining3 #a4 ,heat to #a1ejj-a1eej;,f4 #b4 ,quench4 #c4 ,reheat to #a1cjj-a1djj;,f4 #d4 ,quench4 #e4 ,reheat to #fjj-a1bjj;,f4 and cool slowly4 ,heat ,treatment ,l ,after forging or machining3 #a4 ,carbonize between #a1fjj;,f4 and #a1gej;,f4 7#a1fej-a1gjj;,f4 desired74 #b4 ,cool slowly in the carbonizing mixture4 #c4 ,reheat to #a1djj-a1ejj;,f4 #d4 ,quench4 #e4 ,reheat to #a1cjj-a1djj;,f4 #f4 ,quench4 #g4 ,reheat to #bej-ejj;,f4 and cool slowly4 ,heat ,treatment ,m ,after forging or machining3 #a4 ,heat to #a1dej-a1ejj;,f4 #b4 ,quench4 #c4 ,reheat to #ejj-a4bej;,f4 and cool slowly4 ,heat ,treatment ,p ,after forging or machining3 #a4 ,heat to #a1dej-a1ejj;,f4 #b4 ,quench4 #c4 ,reheat to #a1cge-a1dej;,f4 slowly4 #d4 ,quench4 #e4 ,reheat to #ejj-a1bej;,f4 and cool slowly4 ,heat ,treatment ,q ,after forging3 #a4 ,heat to #a1dge-a1ebe;,f4 7,hold at this temperature one-half hour1 to insure thorough heating47 #b4 ,cool slowly4 #c4 ,machine4 #d4 ,reheat to #a1cge-a1dbe;,f4 #e4 ,quench4 #f4 ,reheat to #bej-eej;,f4 and cool slowly4 ,heat ,treatment ,r ,after forging3 #a4 ,heat to #a1ejj-a1eej;,f4 #b4 ,quench in oil4 #c4 ,reheat to #a1bjj-a1cjj;,f4 7,hold at this temperature three hours47 #d4 ,cool slowly4 #e4 ,machine4 #f4 ,reheat to #a1cej-a1dej;,f4 #g4 ,quench in oil4 #h4 ,reheat to #bej-ejj;,f4 and cool slowly4 ,heat ,treatment ,s ,after forging or machining3 #a4 ,carbonize at a temperature between #a1fjj and #a1gej;,f4 7#a1fej-a1gjj;,f4 ,desired47 #b4 ,cool slowly in the carbonizing mixture4 #c4 ,reheat to #a1fej-a1gej;,f4 #d4 ,quench4 #e4 ,reheat to #a1dge-a1eej;,f4 #f4 ,quench4 #g4 ,reheat to #bej-eej;,f4 and cool slowly4 ,heat ,treatment ,t ,after forging or machining3 #a4 ,heat to #a1fej-a1gej;,f4 #b4 ,quench4 #c4 ,reheat to #ejj-a1cjj;,f4 and cool slowly4 ,heat ,treatment ,u ,after forging3 #a4 ,heat to #a1ebe-a1fjj;,f4 7,hold for about one-half hour47 #b4 ,cool slowly4 #c4 ,machine4 #d4 ,reheat to #a1fej-a1gjj;,f4 #e4 ,quench4 #f4 ,reheat to #cej-eej;,f4 and cool slowly4 ,heat ,treatment ,v ,after forging or machining3 #a4 ,heat to #a1fej-a1gej;,f4 #b4 ,quench4 #c4 ,reheat to #djj-a1bjj;,f4 and cool slowly4 ,,restoring ,,overheated ,,steel ,the effect of heat treatment on overheated steel is shown graphically in ,fig4 #fe to the series of illustrations on pages #acg to #add4 ,this was prepared by ,thos4 ,firth ,sons1 ,ltd41 ,sheffield1 ,england4 ,illustration3 ,,fig4 #fe4--;,chart of changes due to heating and cooling4 ,the center piece ,fig4 #fe represents a block of steel weighing about #be lb4 ,the central hole accommodated a thermo-couple which was attached to an autographic recorder4 ,the curve is a copy of the temperature record during heating and cooling4 ,into the holes in the side of the block small pegs of overheated mild steel were inserted4 ,one peg was withdrawn and quenched at each of the temperatures indicated by the numbered arrows1 and after suitable preparation these pegs were photographed in order to show the changes in structure taking place during heating and cooling operations4 ,the illustrations here reproduced are selected from those photographs with the object of presenting pictorially the changes involved in the refining of overheated steel or steel castings4 ,figures #ff to #gi with their captions show much that is of value to steel users4 ,illustration3 ,,fig4 #ff4--,the structure of overheated mild steel from which all the pegs were made 7magnified #be diameters74 ,the pegs withdrawn at #gbj;,c41 or earlier1 had this structure and were quite soft4 ,illustration3 ,,fig4 #fg4--,peg withdrawn at #gej;,c4 7magnified #be diameters74 ,the structure is apparently unaltered1 but the peg was hard and1 unlike the earlier ones1 would not bend double4 ,illustration3 ,,fig4 #fh4--;,a portion of #ff magnified #bjj diameters to show that the dark 7pearlite7 areas are laminated4 ,illustration3 ,,fig4 #fi4--;,a portion of #fg magnified #bjj diameters1 showing that pearlite areas are no longer laminated and providing reason for observed hardness4 ,illustration ,,fig4 #gj4--,peg withdrawn at #ghj;,c4 7magnified #be diameters71 showing inter-diffusion of transformed pearlite and ferrite areas4 ,illustration3 ,,fig4 #ga4--,peg withdrawn at #hjj;,c4 7magnified #be diameters71 showing inter-diffusion so far advanced that the original outline of the crystals is now only faintly suggested4 ,illustration3 ,,fig4 #gb4--,peg withdrawn at #hej;,c4 7magnified #ajj diameters7 after inter-diffusion was completed4 ,note the regular outlines and the small size of the crystals as compared with #fg4 ,illustration3 ,,fig4 #gc4--,to facilitate comparison #fg was enlarged to the same magnification as #fb1 and the one superimposed on the other4 ,the single large crystal occupied as much space as #h1jjj of the smaller ones4 ,illustration3 ,,fig4 #gd4--,the peg withdrawn on cooling at #hjj;,c4 7magnified #ajj diameters7 shows the first reappearance of free ferrite4 ,all pegs withdrawn at higher temperatures were like ,fig4 #gb4 ,illustration3 ,,fig4 #ge4--,peg withdrawn after cooling to #gfj;,c4 ,the increased amount of free ferrite arranges itself about the crystals as envelopes4 ,illustration3 ,,fig4 #gf4-,peg withdrawn after cooling to #gdj;,c4 ,illustration3 ,,fig4 #gg4--,peg withdrawn after cooling to #fgj;,c4 7magnified #hjj diameters74 ,just at this moment the lamination of pearlite1 which now occupied its original area1 was taking place4 ,in some parts the lamination was perfect1 in other parts the iron and iron-carbide were still dissolved in each other4 ,illustration3 ,,fig4 #gh4--;,any peg withdrawn after #fgj;,c4 on cooling 7magnified #ajj diameters74 ,illustration3 ,,fig4 #gi4--,structure of overheated steel before 7left7 and after refining 7right74 ,,chapter ,,ix ,,hardening ,,carbon ,,steel ,,for ,,tools ,for years the toolmaker had full sway in regard to make of steel wanted for shop tools1 he generally made his own designs1 hardened1 tempered1 ground and usually set up the machine where it was to be used and tested it4 ,most of us remember the toolmaker during the sewing machine period when interchangeable tools were beginning to find their way2 rather cautiously at first4 ,the bicycle era was the real beginning of tool making from a manufacturing standpoint1 when interchangeable tools for rapid production were called for and toolmakers were in great demand4 ,even then1 jigs1 and fixtures were of the toolmaker's own design1 who practically built every part of it from start to finish4 ,the old way1 however1 had to be changed4 ,instead of the toolmaker starting his work from cutting off the stock in the old hack saw1 a place for cutting off stock was provided4 ,if1 for instance1 a forming tool was wanted1 the toolmaker was given the master tool to make while an apprentice roughed out the cutter4 ,the toolmaker1 however1 reserved the hardening process for himself4 ,that was one of the particular operations that the old toolmaker refused to give up4 ,it seemed preposterous to think for a minute that any one else could possibly do that particular job without spoiling the tools1 or at least warp it out of shape 7most of us did not grind holes in cutters #ae to #bj years ago72 or a hundred or more things might happen unless the toolmaker did his own hardening and tempering4 ,that so many remarkably good tools were made at that time is still a wonder to many1 when we consider that the large shop had from #cj to #dj different men1 all using their own secret compounds1 heating to suit eyesight1 no matter if the day was bright or dark1 and then tempering to color4 ,but the day of the old toolmaker has changed4 ,now a tool is designed by a tool designer1 ,o4,k4'd1 and then a print goes to the foreman of the tool department1 who specifies the size and gets the steel from the cutting-off department4 ,after finishing the machine work it goes to the hardening room1 and this is the problem we shall now take up in detail4 ,,the ,,modern ,,hardening ,,room4--,a hardening room of today means a very different place from the dirty1 dark smithshop in the corner with the open coal forge4 ,there1 when we wanted to be somewhat particular1 we sometimes shoveled the coal cinders to one side and piled a great pile of charcoal on the forge4 ,we now have a complete equipment2 a gas- or oil-heating furnace1 good running water1 several sizes of lead pots1 and an oil tank large enough to hold a barrel of oil4 ,by running water1 we mean a large tank with overflow pipes giving a constant supply4 ,the ordinary hardening room equipment should consist of3 ,gas or oil muffle furnace for hardening4 ,gas or oil forge furnace4 ,a good size gas or oil furnace for annealing and case-hardening4 ,a gas or oil furnace to hold lead pots4 ,oil tempering tank1 gas- or oil-heated4 ,pressure blower4 ,large oil tank to hold at least a barrel of oil4 ,big water tank with screen trays connected with large pipe from bottom with overflow4 ,straightening press4 ,the furnace should be connected with pyrometers and tempering tank with a thermometer4 ,beside all this you need a good man4 ,it does not make much difference how completely the hardening department is fitted up1 if you expect good work1 a small percentage of loss and to be able to tackle anything that comes along1 you must have a good man1 one who understands the difference between low- and high-carbon steel1 who knows when particular care must be exercised on particular work4 ,in other words1 a man who knows how his work should be done1 and has the intelligence to follow directions on treatments of steel on which he has had no experience4 ,jewelers' tools1 especially for silversmith's work1 probably have to stand the greatest punishment of any all-steel tools and to make a spoon die so hard that it will not sink under a blow from an #a1hjj-lb4 hammer with a #d-;ft4 drop1 and still not crack1 demands careful treatment4 ,to harden such dies1 first cover the impression on the die with paste made from bone dust or lampblack and oil4 ,place face down in an iron box partly filled with crushed charcoal1 leaving back of die uncovered so that the heat can be seen at all times4 ,heat slowly in furnace to a good cherry red4 ,the heat depends on the quality and the analysis of steel and the recommended actions of the steel maker should be carefully followed4 ,when withdrawn from the fire the die should be quenched as shown in ,fig4 #hj with the face of die down and the back a short distance out of the water4 ,when the back is black1 immerse all over4 ,illustration3 ,,fig4 #hj4--,quenching a die1 face down4 ,if such a tank is not at hand1 it would pay to rig one up at once1 although a barrel of brine may be used1 or the back of the die may be first immersed to a depth of about #a_/b in4 ,when the piece is immersed1 hold die on an angle as in ,fig4 #ha4 ,illustration3 ,,fig4 #ha4--;,hold die at angle to quench4 ,this is for the purpose of expelling all steam bubbles as they form in contact with hot steel4 ,we are aware of the fact that a great many toolmakers in jewelry shops still cling to the overhead bath1 as in ,fig4 #hb1 but more broken pieces and more dies with soft spots are due to this method than to all the others combined1 as the water strikes one spot in force1 contracting the surface so much faster than the rest of the die that the results are the same as if an uneven heating had been given the steel4 ,,take ,,time ,,for ,,hardening4--,uneven heating and poor quenching has caused loss of many very valuable dies1 and it certainly seems that when a firm spends from #ge to #dej in cutting a die that a few hours could be spared for proper hardening4 ,but the usual feeling is that a tool must be hurried as soon as the hardener gets it1 and if a burst die is the result from either uneven or overheated steel and quenching same without judgment1 the steel gets the blame4 ,illustration3 ,,fig4 #hb4--;,an obsolete method4 ,give the steel a chance to heat properly1 mix a little common sense with your #cj years experience on the other fellows steel4 ,remember that high-carbon steel hardens at a lower heat than low-carbon steel1 and quench when at the right heat in the two above ways1 and #ii per cent of the trouble will vanish4 ,when a die flies to pieces in quenching1 don't rush to the superintendent with a poor-steel story1 but find out first why it broke so that the salesman who sold it will not be able to harden piece after piece from the same bar satisfactorily4 ,if you find a cold short1 commonly called a pipe1 you can lay the blame on the steelmaker4 ,if it is a case of overheating and quenching when too hot1 you will find a coarse grain with many bright spots like crystals to the hardening depth4 ,if uneven heating is the cause1 you will find a wider margin of hardening depth on one side than on the other1 or find the coarse grain from over-heating on one side while on the other you will find a close grain1 which may be just right4 ,if you find any other faults than a pipe1 or are not able to harden deep enough1 then take the blame like a man and send for information4 ,the different steel salesmen are good fellows and most of them know a thing or two about their own business4 ,for much work a cooling bath at from #ej to #ge;,f4 is very good both for small hobs1 dies1 cutter plates or plungers4 ,some work will harden best in a barrel of brine1 but in running cold water1 splendid results will be obtained4 ,cutter plates should always be dipped corner first and if any have stripper holes1 they should first be plugged with asbestos or fire clay cement4 ,in general it may be said that the best hardening temperature for carbon steel is the lowest temperature at which it will harden properly4 ,,carbon ,,in ,,tool ,,steel ,carbon tool steel1 or tool steel as it is commonly called1 usually contains from #hj to #abe points 7or from #j4hj to #a4be per cent7 of carbon1 and none of the alloys which go to make up the high speed steels4 ,this was formerly known also as crucible or cast steel1 or crucible cast steel1 from the way in which it was made4 ,this was before the days of steel castings4 ,the advent of these caused so much confusion that the term was soon dropped4 ,when we say tool steel1 we nearly always refer to carbon-tool steel1 high-speed steel being usually designated by that name4 ,for many purposes carbon-steel cutters are still found best1 although where a large amount of material is to be removed at a rapid rate1 it has given way to high-speed steels4 ,,carbon ,,steels ,,for ,,different ,,tools ,all users of tool steels should carefully study the different qualities of the steels they handle4 ,different uses requires different kinds of steel for best results1 and for the purpose of designating different steels some makers have adopted the two terms temper1 and quality1 to distinguish between them4 ,in this case temper refers to the amount of carbon which is combined with the iron to make the metal into a steel4 ,the quality means the absence of phosphorous1 sulphur and other impurities1 these depending on the ores and the methods of treatment4 ,steel makers have various ways of designating carbon steels for different purposes4 ,some of these systems involve the use of numbers1 that of the ,latrobe ,steel ,company being given herewith4 ,it will be noted that the numbers are based on #bj points of carbon per unit4 ,the names given the different tempers are also of interest4 ,other makers use different numbers4 ,the temper list follows3 ,,latrobe ,,temper ,,list ,,of ,,carbon ,,tool ,,steels ,no4 #c temper #j4fj to #j4fi per cent carbon ,no4 #c-a_/b temper #j4gj to #j4gi per cent carbon ,no4 #d temper #j4hj to #j4hi per cent carbon ,no4 #d-a_/b temper #j4ij to #j4ii pet cent carbon ,no4 #e temper #a4jj to #a4ji per cent carbon ,no4 #e-a_/b temper #a4aj to #a4ai per cent carbon ,no4 #f temper #a4bj to #a4bi per cent carbon ,no4 #f-a_/b temper #a4cj to #a4ci per cent carbon ,no4 #g temper #a4dj to #a4di per cent carbon ,,uses ,,of ,,the ,,various ,,tempers ,,of ,,carbon ,,tool ,,steel ,,die ,,temper4--,no4 #c3 ,all kinds of dies for deep stamping1 pressing and drop forgings4 ,mining drills to harden only4 ,easily weldable4 ,,smiths' ,,tool ,,temper4--,no4 #c-a_/b3 ,large punches1 minting and rivet dies1 nailmakers' tools1 hammers1 hot and cold sets1 snaps and boilermakers' tools1 various smiths' tools1 large shear blades1 double-handed chisels1 caulking tools1 heading dies1 masons' tools and tools for general welding purposes4 ,,shear ,,blade ,,temper4--,no4 #d3 ,punches1 large taps1 screwing dies1 shear blades1 table cutlery1 circular and long saws1 heading dies4 ,weldable4 ,,general ,,purpose ,,temper4--,no4 #d-a_/b3 ,taps1 small punches1 screwing dies1 sawwebs1 needles1 etc41 and for all general purposes4 ,weldable4 ,,axe ,,temper4--,no4 #e3 ,axes1 chisels1 small taps1 miners' drills and jumpers to harden and temper1 plane irons4 ,weldable with care4 ,,cutlery ,,temper4--,no4 #e-a_/b3 ,large milling cutters1 reamers1 pocket cutlery1 wood tools1 short saws1 granite drills1 paper and tobacco knives4 ,weldable with very great care4 ,,tool ,,temper4--,no4 #f3 ,turning1 planing1 slotting1 and shaping tools1 twist drills1 mill picks1 scythes1 circular cutters1 engravers' tools1 surgical cutlery1 circular saws for cutting metals1 bevel and other sections for turret lathes4 ,not weldable4 ,,hard ,,tool ,,temper4--,no4 #f-a_/b3 ,small twist drills1 razors1 small and intricate engravers' tools1 surgical instruments1 knives4 ,not weldable4 ,,razor ,,temper4--,no4 #g3 ,razors1 barrel boring bits1 special lathe tools for turning chilled rolls4 ,not weldable4 ,,steel ,,for ,,chisels ,,and ,,punches ,the highest grades of carbon or tempering steels are to be recommended for tools which have to withstand shocks1 such as for cold chisels or punches4 ,these steels are1 however1 particularly useful where it is necessary to cut tempered or heat-treated steel which is more than ordinarily hard1 for cutting chilled iron1 etc4 ,they are useful for boring1 for rifle-barrel drilling1 for fine finishing cuts1 for drawing dies for brass and copper1 for blanking dies for hard materials1 for formed cutters on automatic screw machines and for roll-turning tools4 ,steel of this kind1 being very dense in structure1 should be given more time in heating for forging and for hardening1 than carbon steels of a lower grade4 ,for forging it should be heated slowly and uniformly to a bright red and only light blows used as the heat dies out4 ,do not hammer at all at a black heat4 ,reheat slowly to a dark red for hardening and quench in warm water4 ,grind on a wet grindstone4 ,where tools have to withstand shocks and vibration1 as in pneumatic hammer work1 in severe punching duty1 hot or cold upsetting or similar work1 tool steels containing vanadium or chrome-vanadium give excellent results4 ,these are made particularly for work of this kind4 ,,chisels-,,shapes ,,and ,,heat ,,treatment#a ,footnote #a3 ,abstract of paper by ,,henry ,,fowler1 chief mechanical engineer of the ,midland ,ry41 ,england1 before the ,institution of ,mechanical ,engineers4 ,in the chief mechanical engineer's department of the ,midland ,ry41 after considerable experimenting1 it was decided to order chisel steel to the following specifications3 carbon1 #j4ge to #j4he per cent1 the other constituents being normal4 ,this gives a complete analysis as follows3 carbon1 #j4ge to #j4he2 manganese1 #j4cj2 silicon1 #j4aj2 sulphur1 #j4jbe2 phosphorus1 #j4jbe4 ,the analysis of a chisel which had given excellent service was as follows3 carbon1 #j4ge2 manganese1 #j4ch2 silicon1 #j4af2 sulphur1 #j4jbh2 phosphorus1 #j4jbf4 ,the heat treatment is unknown4 ,illustration3 ,,fig4 #hc4--;,forms of chisels standardized for the locomotive shops of the ,midland ,ry41 ,england4 ,at the same time that chisel steel was standardized1 the form of the chisels themselves was revised1 and a standard chart of these as used in the locomotive shops was drawn up4 ,figure #hc shows the most important forms1 which are made to stock orders in the smithy and forwarded to the heat-treatment room where the hardening and tempering is carried out on batches of fifty4 ,a standard system of treatment is employed1 which to a very large extent does away with the personal element4 ,since the chemical composition is more or less constant1 the chief variant is the section which causes the temperatures to be varied slightly4 ,the chisels are carefully heated in a gas-fired furnace to a temperature of from #gcj to #gdj;,c4 7#a1cdj to #a1cfd;,f47 according to section4 ,in practice1 the first chisel1 is heated to #gcj;,c42 and the second to #gce;,c4 7#a1cee;,f472 and a #a in4 half round chisel to #gdj;,c41 because of their varying increasing thickness of section at the points4 ,upon attaining this steady temperature1 the chisels are quenched to a depth of #c_/h to #a_/b in4 from the point in water1 and then the whole chisel is immersed and cooled off in a tank containing linseed oil4 ,the oil-tank is cooled by being immersed in a cold-water tank through which water is constantly circulated4 ,after this treatment1 the chisels have a dead hard point and a tough or sorbitic shaft4 ,they are then tempered or the point let down4 ,this is done by immersing them in another oil-bath which has been raised to about #bae;,c4 7#dai;,f74 ,the first result is1 of course1 to drop the temperature of the oil1 which is gradually raised to its initial point4 ,on approaching this temperature the chisels are taken out about every #b;,c4 rise and tested with a file1 and at a point between #bae and #bbj;,c4 7#dbh;,f471 when it is found that the desired temper has been reached1 the chisels are removed1 cleaned in sawdust1 and allowed to cool in an iron tray4 ,no comparative tests of these chisels with those bought and treated by the old rule-of-thumb methods have been made1 as no exact method of carrying out such tests mechanically1 other than trying the hardness by the ,brinell or scleroscope method1 are known2 any ordinary test depends so largely upon the dexterity of the operator4 ,the universal opinion of foremen and those using the chisels as to the advantages of the ones receiving the standard treatment described is that a substantial improvement has been made4 ,the chisels were not normalized4 ,tests of chisels normalized at about #ijj;,c4 7#a1feb;,f47 showed that they possessed no advantage4 ,tools or pieces which have holes or deep depressions should be filled before heating unless it is necessary to have the holes hard on the inside4 ,in that case the filling would keep the water away from the surface and no hardening would take place4 ,where filling is to be done1 various materials are used by different hardeners4 ,fireclay and common putty seem to be favored by many4 ,every mechanic who has had anything to do with the hardening of tools knows how necessary it is to take a cut from the surface of the bar that is to be hardened4 ,the reason is that in the process of making the steel its outer surface has become decarbonized4 ,this change makes it low-carbon steel1 which will of course not harden4 ,it is necessary to remove from #a_/af to #a_/d in4 of diameter on bars ranging from #a_/b to #d in4 ,this same decarbonization occurs if the steel is placed in the forge in such a way that unburned oxygen from the blast can get at it4 ,the carbon is oxidized1 or burned out1 converting the outside of the steel into low-carbon steel4 ,the way to avoid this is to use a deep fire4 ,lack of this precaution is the cause of much spoiled work1 not only because of decarbonization of the outer surface of the metal1 but because the cold blast striking the hot steel acts like boiling hot water poured into an ice-cold glass tumbler4 ,the contraction sets up stresses that result in cracks when the piece is quenched4 ,,preventing ,,decarbonization ,,of ,,tool ,,steel ,it is especially important to prevent decarbonization in such tools as taps and form cutters1 which must keep their shape after hardening and which cannot be ground away on the profile4 ,for this reason it is well to put taps1 reamers and the like into pieces of pipe in heating them4 ,the pipe need be closed on one end only1 as the air will not circulate readily unless there is an opening at both ends4 ,even if used in connection with a blacksmith's forge the lead bath has an advantage for heating tools of complicated shapes1 since it is easier to heat them uniformly and they are submerged and away from the air4 ,the lead must be stirred frequently or the heat is not uniform in all parts of the lead bath4 ,covering the lead with powdered charcoal will largely prevent oxidization and waste of lead4 ,such a bath is good for temperatures between #fbj and #a1aej;,f4 ,at higher temperatures there is much waste of lead4 ,,annealing ,,to ,,relieve ,,internal ,,stresses ,work quenched from a high temperature and not afterward tempered will1 if complex in shape1 contain many internal stresses which may later cause it to break4 ,they may be eased off by slight heating without materially lessening the hardness of the piece4 ,one way to do this is to hold the piece over a fire and test it with a moistened finger4 ,another way is to dip the piece in boiling water after it has first been quenched in a cold bath4 ,such steps are not necessary with articles which will afterward be tempered and in which the strains are thus reduced4 ,in annealing steels the operation is similar to hardening1 as far as heating is concerned4 ,the critical temperatures are the proper ones for annealing as well as hardening4 ,from this point on there is a difference1 for annealing consists in cooling as slowly as possible4 ,the slower the cooling the softer will be the steel4 ,annealing may be done in the open air1 in furnaces1 in hot ashes or lime1 in powdered charcoal1 in burnt bone1 in charred leather and in water4 ,open-air annealing will do as a crude measure in cases where it is desired to take the internal stresses out of a piece4 ,care must be taken in using this method that the piece is not exposed to drafts or placed on some cold substance that will chill it4 ,furnace annealing is much better and consists in heating the piece in a furnace to the critical temperature and then allowing the work and the furnace to cool together4 ,when lime or ashes are used as materials to keep air away from the steel and retain the heat1 they should be first heated to make sure that they are dry4 ,powdered charcoal is used for high-grade annealing1 the piece being packed in this substance in an iron box and both the work and the box raised to the critical temperature and then allowed to cool slowly4 ,machinery steel may be annealed in spent ground-bone that has been used in casehardening2 but tool steel must never be annealed in this way1 as it will be injured by the phosphorus contained in the bone4 ,charred leather is the best annealing material for high-carbon steel1 because it prevents decarbonizing taking place4 ,,double ,,annealing ,water annealing consists in heating the piece1 allowing it to cool in air until it loses its red heat and becomes black and then immediately quenching it in water4 ,this plan works well for very low-carbon steel2 but for high-carbon steel what is known as the double annealing treatment must be given1 provided results are wanted quickly4 ,the process consists in heating the steel quickly to #bjj or more above the upper critical1 cooling in air down through the recalescence point1 then reheating it to just above the critical point and again cooling slowly through the recalescence1 then quenching in oil4 ,this process retains in the steel a fine-grained structure combined with softness4 ,,quenching ,,tool ,,steel ,to secure proper hardness1 the cooling of quenching of steel is as important as its heating4 ,quenching baths vary in nature1 there being a large number of ways to cool a piece of steel in contrast to the comparatively few ways of heating it4 ,plain water1 brine and oil are the three most common quenching materials4 ,of these three the brine will give the most hardness1 and plain water and oil come next4 ,the colder that any of these baths is when the piece is put into it the harder will be the steel2 but this does not mean that it is a good plan to dip the heated steel into a tank of ice water1 for the shock would be so great that the bar would probably fly to pieces4 ,in fact1 the quenching bath must be sometimes heated a bit to take off the edge of the shock4 ,brine solutions will work uniformly1 or give the same degree of hardness1 until they reach a temperature of #aej;,f4 above which their grip relaxes and the metals quenched in them become softer4 ,plain water holds its grip up to a temperature of approximately #ajj;,f42 but oil baths1 which are used to secure a slower rate of cooling1 may be used up to #ejj or more4 ,a compromise is sometimes effected by using a bath consisting of an inch or two of oil floating on the surface of water4 ,as the hot steel passes through the oil1 the shock is not as severe as if it were to be thrust directly into the water2 and in addition1 oil adheres to the tool and keeps the water from direct contact with the metal4 ,the old idea that mercury will harden steel more than any other quenching material has been exploded4 ,a bath consisting of melted cyanide of potassium is useful for heating fine engraved dies and other articles that are required to come out free from scale4 ,one must always be careful to provide a hood or exhaust system to get rid of the deadly fumes coming from the cyanide pot4 ,the one main thing to remember in hardening tool steel is to quench on a rising heat4 ,this does not mean a rapid heating as a slow increase in temperature is much better in every way4 ,,the ,,theory ,,of ,,tempering4--,steel that has been hardened is generally harder and more brittle than is necessary1 and in order to bring it to the condition that meets our requirements a treatment called tempering is used4 ,this increases the toughness of the steel1 i4e41 decrease the brittleness at the expense of a slight decrease in hardness4 ,there are several theories to explain this reaction1 but generally it is only necessary to remember that in hardening we quench steel from the austenite phase1 and1 due to this rapid cooling1 the normal change from austenite to the eutectoid composition does not have time to take place1 and as a consequence the steel exists in a partially transformed1 unstable and very hard condition at atmospheric temperatures4 ,but owing to the internal rigidity which exists in cold metal the steel is unable to change into its more stable phase until atoms can rearrange themselves by the application of heat4 ,the higher the heat1 the greater the transformation into the softer phases4 ,as the transformation takes place1 a certain amount of heat of reaction1 which under slow cooling would have been released in the critical range1 is now released and helps to cause a further slight reaction4 ,if a piece of steel is heated to a certain temperature and held there1 the tempering color1 instead of remaining unchanged at this temperature1 will advance in the tempering-color scale as it would with increasing temperature4 ,this means that the tempering colors do not absolutely correspond to the temperatures of steels1 but the variations are so slight that we can use them in actual practice4 7,see ,table #bc1 page #aeh47 ,,temperatures ,,to ,,use4--,as soon as the temperature of the steel reaches #ajj;,c4 7#bab;,f47 the transformation begins1 increasing in intensity as the temperature is raised1 until finally when the lower critical range is reached1 the steel has been all changed into the ordinary constituents of unhardened steels4 ,if a piece of polished steel is heated in an ordinary furnace1 a thin film of oxides will form on its surface4 ,the colors of this film change with temperature1 and so1 in tempering1 they are generally used as an indication of the temperature of the steel4 ,the steel should have at least one polished face so that this film of oxides may be seen4 ,an alternative method to the determination of temper by color is to temper by heating in an oil or salt bath4 ,oil baths can be used up to temperatures of #ejj;,f42 above this1 fused-salt baths are required4 ,the article to be tempered is put into the bath1 brought up to and held at the required temperature for a certain length of time1 and then cooled1 either rapidly or slowly4 ,this takes longer than the color method1 but with low temperatures the results are more satisfactory1 because the temperature of the bath can be controlled with a pyrometer4 ,the tempering temperatures given in the following table are taken from a handbook issued by the ,midvale ,steel ,company4 ,,table #bc4--,,tempering ,,temperatures ,,for ,,steels ---------------------------------------- ------------------------------------ ,temperature ,temperature for #a hr4 for #h min4 --------------- ,color --------------- ,uses ,deg4 ,f4,deg4 ,c4 ,deg4 ,f4,deg4 ,c4 ---------------------------------------- ------------------------------- #cgj #ahh ,faint yellow #dfj #bch ,scrapers1 brass-turning tools1 reamers1 taps1 milling cutters1 saw teeth4 #cij #aii ,light straw #eaj #bfe ,twist drills1 lathe tools1 planer tools1 finishing tools #daj #baj ,dark straw #efj #bic ,stone tools1 hammer faces1 chisels for hard work1 boring cutters4 #dcj #bba ,brown #faj #cba ,trephining tools1 stamps4 #dej #bcb ,purple #fdj #ccg ,cold chisels for ordinary work1 carpenters' tools1 picks1 cold punches1 shear blades1 slicing tools1 slotter tools4 #dij #bed ,dark blue #ffj #cdc ,hot chisels1 tools for hot work1 springs4 #eaj #bfe ,light blue #gaj #cgf ,springs1 screw drivers4 ---------------------------------------- ------------------------------------ ,it will be noted that two sets of temperatures are shown1 one being specified for a time interval of #h min4 and the other for #a hr4 ,for the finest work the longer time is preferable1 while for ordinary rough work #h min4 is sufficient1 after the steel has reached the specified temperature4 ,the rate of cooling after tempering seems to be immaterial1 and the piece can be cooled at any rate1 providing that in large pieces it is sufficiently slow to prevent strains4 ,,knowing ,,what ,,takes ,,place4--,how are we to know if we have given a piece of steel the very best possible treatment8 ,the best method is by microscopic examination of polished and etched sections1 but this requires a certain expense for laboratory equipment and upkeep1 which may prevent an ordinary commercial plant from attempting such a refinement4 ,it is highly recommended that any firm that has any large amount of heat treatment to do1 install such an equipment1 which can be purchased for from #bej to #ejj4 ,its intelligent use will save its cost in a very short time4 ,the other method is by examination of fractures of small test bars4 ,steel heated to its correct temperatures will show the finest possible grain1 whereas underheated steel has not had its grain structure refined sufficiently1 and so will not be at its best4 ,on the other hand1 overheated steel will have a coarser structure1 depending on the extent of overheating4 ,to determine the proper quenching temperature of any particular grade of steel it is only necessary to heat pieces to various temperatures not more than #bj;,c4 7#cf;,f47 apart1 quench in water1 break them1 and examine the fractures4 ,the temperature producing the finest grain should be used for annealing and hardening4 ,similarly1 to determine tempering temperatures1 several pieces should be hardened1 then tempered to various degrees1 and cooled in air4 ,samples1 say six1 reheated to temperatures varying by #ajj from #cjj to #hjj;,c4 will show a considerable range of properties1 and the drawing temperature of the piece giving the desired results can be used4 ,for drawing tempers up to #ejj;,f4 oil baths of fresh cotton seed oil can be safely and satisfactorily used4 ,for higher temperature a bath of some kind of fused salt is recommended4 ,,hints ,,for ,,tool ,,steel ,,users ,do not hesitate to ask for information from the maker as to the best steel to use for a given purpose1 mentioning in as much detail as possible the use for which it is intended4 ,do not heat the steel to a higher degree than that fixed in the description of each class4 ,never heat the steel to more than a cherry red without forging it or giving it a definite heat treatment4 ,heating steel at even moderate temperature is liable to coarsen the grain which can only be restored by forging or by heat treating4 ,let the forging begin as soon as the steel is hot enough and never let tool steel soak in the fire4 ,continue the hammering vigorously and constantly1 using lighter blows as it cools off1 and stopping when the heat becomes a very dull red or a faint brown4 ,should welding be necessary care should be taken not to overheat in order to make an easy weld4 ,keep it below the sparkling point as this indicates that the steel is burnt4 ,begin to forge as soon as the welds are put together1 taking care to use gentle strokes at first increasing them as the higher heat falls1 but not overdoing the hammering when the steel cools4 ,the hammering should be extended beyond the welding point and should continue until the dull red or brown heat is reached4 ,,preventing ,,cracks ,,in ,,hardening ,the blacksmith in the small shop1 where equipment is usually very limited1 often consisting of a forge1 a small open hard-coal furnace1 a barrel of water and a can of oil must have skill and experience4 ,with this equipment the smith is expected to1 and usually can1 produce good results if proper care is taken4 ,in hardening carbon tool steel in water1 too much cannot be said in favor of slow1 careful heating1 nor against overheating if cracks are to be avoided4 ,it is not wise to take the work from the hardening bath and leave it exposed to the air if there is any heat left in it1 because it is more liable to crack than if left in the bath until cold4 ,in heating1 plenty of time is taken for the work to heat evenly clear through1 thus avoiding strains caused by quick and improper heating1 ,in quenching in water1 contraction is much more rapid than was the expansion while heating1 and strains begin the moment the work touches the water4 ,if the piece has any considerable size and is taken from the bath before it is cold and allowed to come to the air1 expansion starts again from the inside so rapidly that the chilled hardened surface cracks before the strains can be relieved4 ,many are most successful with the hardening bath about blood warm4 ,when the work that is being hardened is nearly cold1 it is taken from the water and instantly put into a can of oil1 where it is allowed to finish cooling4 ,the heat in the body of the tool will come to the surface more slowly1 thus relieving the strain and overcoming much of the danger of cracking4 ,some contend that the temper should be drawn as soon as possible after hardening3 but that if this cannot be done for some hours1 the work should be left in the oil until the tempering can be done4 ,it is claimed that forming dies and punch-press dies that are difficult to harden will seldom crack if treated in this way4 ,small tools or pieces that are very troublesome because of peculiar shape should be made of steel which has been thoroughly annealed4 ,it is often well to mill or turn off the outer skin of the bar1 to remove metal which has been cold-worked4 ,then heat slowly just through the critical range and cool in the furnace1 in order to produce a very fine grain4 ,tools machined from such stock1 and hardened with the utmost care1 will have the best chance to survive without warping1 growth or cracking4 ,,shrinking ,,and ,,enlarging ,,work ,steel can be shrunk or enlarged by proper heating and cooling4 ,pins for forced fits can be enlarged several thousandths of an inch by rapid heating to a dull red and quenching in water4 ,the theory is that the metal is expanded in heating and that the sudden cooling sets the outer portion before the core can contract4 ,in dipping the piece is not held under water till cold but is dipped1 held a moment and removed4 ,then dipped again and again until cold4 ,rings and drawing dies are also shrunk in a similar way4 ,the rings are slowly heated to a cherry red1 slipped on a rod and rolled in a shallow pan of water which cools only the outer edge4 ,this holds the outside while the inner heated portion is forced inward1 reducing the hole4 ,this operation can be repeated a number of times with considerable success4 ,,tempering ,,round ,,dies ,a number of circular dies of carbon tool steel for use in tool holders of turret lathes were required4 ,no proper tempering oven was available1 so the following method was adopted and proved quite successful4 ,after the dies had been hardened dead hard in water1 they were cleaned up bright4 ,a pair of ordinary smiths' tongs was made with jaws of heavy material and to fit nicely all around the outside of the die1 leaving a #c_/cb-;in4 space when the jaws were closed around the die4 ,the dies being all ready1 the tongs were heated red hot1 and the dies were picked up and held by the tongs4 ,this tempered them from the outside in1 left the teeth the temper required and the outside slightly softer4 ,the dies held up the work successfully and were better than when tempered in the same bath4 ,,the ,,effect ,,of ,,tempering ,,on ,,water-,,quenched ,,gages ,the following information has been supplied by ,automatic and ,electric ,furnaces1 ,ltd41 #f1 ,queenstreet1 ,london1 ,s4 ,w43 ,two gages of #c_/d in4 diameter1 #ab threads per inch1 were heated in a ,wild-,barfield furnace1 using the pyroscopic detector1 and were quenched in cold water4 ,they were subsequently tempered in a salt bath at various increasing temperatures1 the effective diameter of each thread and the scleroscope hardness being measured at each stage4 ,the figures are in #aj1jjjths of an inch1 and indicate the change or - with reference to the original effective diameter of the gages4 ,the results for the two gages have been averaged4 ,,table #bd4--;,,changes ,,due ,,to ,,quenching ---------------------------------------- ------------------------ ,after ,tempering temperature1 degrees ,centigrade ,thread quenching------------------------------- ---------- #bbj #bfj #cjj #cdj #chj #dbj ---------------------------------------- ----------------- #a #be #ai #ag #ae #ac #aa #aa #b #ah #ab #aa #i #f #e #e #c #ab #f #e #c #j #j #j #d #aj #d #d #b 444 #j - #a #e #i #d #d #b #j #j #j #f #i #d #c #b #j #j #j #g #aj #e #e #c #b #a #b #h #h #d #c #b #j #j #a #i #i #d #c #b #a #a #a #aj #i #e #e #c #b #b #b #aa #g #d #d #b #a #a #a #ab #i #e #e #e #d #d #c ,scleroscope #hj #gj #gj #fb #ef #ec #eb ---------------------------------------- ------------------------ ,had these gages been formed with a plain cylindrical end projecting in front of the screw1 the first two threads would have been prevented from increasing more than the rest4 ,the gages would then have been fairly easily corrected by lapping after tempering at #bbj;,c4 ,practically no lapping would be required if they were tempered at #cdj;,c4 ,there seems to be no advantage in going to a higher temperature than this4 ,the same degree of hardness could have been obtained with considerably less distortion by quenching directly in fused salt4 ,it is interesting to note that when the swelling after water quenching does not exceed #j4jjab in41 practically the whole of it may be recovered by tempering at a sufficiently high temperature1 but when the swelling exceeds this amount the steel assumes a permanently strained condition1 and at the most only #j4jjad in4 can be recovered by tempering4 ,,tempering ,,colors ,,on ,,carbon ,,steels ,opinions differ as to the temperature which is indicated by the various colors1 or oxides1 which appear on steel in tempering4 ,the figures shown are from five different sources and while the variations are not great1 it is safer to take the average temperature shown in the last column4 ,,table #be4--;,,colors1 ,,temperatures1 ,,degrees ,,fahrenheit ---------------------------------------- ------------------ ,a ,b ,c ,d ,e ,average ---------------------------------------- ------------ ,faint yellow #dcj #dcj #dcj #dcj #dcj #dcj ,light straw #dge #dfj #dej 444 #dej #deh ,dark straw #ejj #ejj #dgj #dej #dgj #dgh ,purple 7reddish7 #ebe #ecj #ebj #ecj #eaj #ebc ,purple 7bluish7 444 #eee #eej #eej #eej #eea ,blue #ege #ehe #efj #ehj #efj #egb ,gray blue 444 #fjj 444 #fjj #faj #fjc ,greenish blue 444 #fbe 444 444 #fcj #fbg ---------------------------------------- ------------------ ,,table #bf4--;,,another ,,color ,,table ---------------------------------------- ------------------ ,degrees ,fahrenheit ,high temperatures judged by color ---------------------------------------- ----------------- #dcj ,very pale yellow #dfj ,straw-yellow #dhj ,dark yellow #ejj ,brown-yellow ,visible in full daylight #ebj ,brown-purple #edj ,full purple #efj ,full blue #fjj ,very dark blue _/ #geb ,red heat1 visible in the dark #hhe ,red heat1 visible in the twilight #ige ,red heat1 visible in the daylight #a1bib ,dark red #a1feb ,cherry-red #a1hcb ,bright cherry-red #b1jab ,orange-red #b1aib ,orange-yellow #b1cgb ,yellow-white #b1eeb ,white welding heat #b1gcb ,brilliant white #b1iab ,dazzling white 7bluish-white7 ---------------------------------------- ------------------ ,these differences might easily be due to the difference in the light at the time the colors were observed4 ,it must also be remembered that even a thin coating of oil will make quite a difference and cause confusion4 ,it is these possible sources of error1 coupled with the ever present chance of human error1 that makes it advisable to draw the temper of tools in an oil bath heated to the proper temperature as shown by an accurate high-temperature thermometer4 ,another table1 by ,gilbert and ,barker1 runs to much higher temperatures4 ,beyond #b1bjj1 however1 the eye is very uncertain4 ,,table #bf4--;,,colors ,,for ,,tempering ,,tools ---------------------------------------- ------------------------------- ,approximate color and ,kind of tool temperature ---------------------------------------- ------------------------------ ,yellow ,thread chasers1 hollow mills 7solid type7 twist drills #dcj to #dej;,f4 centering tools1 forming tools1 cut-off tools1 profile cutters1 milling cutters1 reamers1 dies1 etc4 ---------------------------------------- ------------------------------ ,straw-yellow ,thread rolling dies1 counterbores1 countersinks4 ,shear #dfj;,f4 blades1 boring tools1 engraving tools1 etc4 ---------------------------------------- ------------------------------ ,brown-yellow ,taps1 ,thread dies1 cutters1 reamers1 etc4 #ejj;,f4 ---------------------------------------- ------------------------------ ,light purple ,taps1 dies1 rock drills1 knives1 punches1 gages1 etc4 #ecj;,f4 ---------------------------------------- ------------------------------ ,dark purple ,circular saws for metal1 augers1 dental and surgical #eej;,f4 instruments1 cold chisels1 axes4 ---------------------------------------- ------------------------------ ,pale blue ,bone saws1 chisels1 needles1 cutters1 etc4 #ehj;,f4 ---------------------------------------- ------------------------------ ,blue ,hack saws1 wood saws1 springs1 etc4 #fjj;,f4 ---------------------------------------- ------------------------------- ,,chapter ,x ,,high-,,speed ,,steel ,for centuries the secret art of making tool steel was handed down from father to son4 ,the manufacture of tool steel is still an art which1 by the aid of science1 has lost much of its secrecy2 yet tool steel is today made by practical men skilled as melters1 hammer-men1 and rollers1 each knowing his art4 ,these practical men willingly accept guidance from the chemist and metallurgists4 ,a knowledge of conditions existing today in the manufacture of high-speed steel is essential to steel treaters4 ,it is well for the manufacturer to have steel treaters understand some of his troubles and difficulties1 so that they will better comprehend the necessity of certain trade customs and practices1 and1 realizing the manufacturer's desire to cooperate with them1 will reciprocate4 ,the manufacturer of high-speed steel knows and appreciates the troubles and difficulties that may sometimes arise in the heat-treating of his product4 ,his aim is to make a uniform steel that will best meet the requirements of the average machine shop on general work1 and at the same time allow the widest variation in heat treatment to give desired results4 ,high speed steel is one of the most complex alloys known4 ,a representative steel contains approximately #bd per cent of alloying metals1 namely1 tungsten1 chromium1 vanadium1 silicon1 manganese1 and in addition there is often found cobalt1 molybdenum1 uranium1 nickel1 tin1 copper and arsenic4 ,,standard ,,analysis ,the selection of a standard analysis by the manufacturer is the result of a series of compromises between various properties imparted to the steel by the addition of different elements and there is a wide range of chemical analyses of various brands4 ,the steel1 to be within the range of generally accepted analysis1 should contain over #af per cent and under #bj per cent tungsten2 if of lower tungsten content it should carry proportionately more chromium and vanadium4 ,the combined action of tungsten and chromium in steel gives to it the remarkable property of maintaining its cutting edge at relatively high temperature4 ,this property is commonly spoken of as red-hardness4 ,the percentages of tungsten and chromium present should bear a definite relationship to each other4 ,chromium imparts to steel a hardening property similar to that given by carbon1 although to a less degree4 ,the hardness imparted to steel by chromium is accompanied by brittleness4 ,the chromium content should be between #c4e and #e per cent4 ,vanadium was first introduced in high-speed steel as a scavenger1 thereby producing a more homogeneous product1 of greater density and physical strength4 ,it soon became evident that vanadium used in larger quantities than necessary as a scavenger imparted to the steel a much greater cutting efficiency4 ,recently1 no less an authority than ,prof4 ,j4 ,o4 ,arnold1 of the ,university of ,sheffield1 ,england1 stated that high-speed steels containing vanadium have a mean efficiency of #ajh4i1 as against a mean efficiency of #fa4i obtained from those without vanadium content4 ,a wide range of vanadium content in steel1 from #j4e to #a4e per cent1 is permissible4 ,an ideal analysis for high-speed steel containing #ah per cent tungsten is a chromium content of approximately #c4he per cent2 vanadium1 #j4he to #a4aj per cent1 and carbon1 between #j4fb and #j4gg per cent4 ,,detrimental ,,elements4--,sulphur and phosphorus are two elements known to be detrimental to all steels4 ,sulphur causes red-shortness and phosphorus causes cold-shortness4 ,the detrimental effects of these two elements counteract each other to some extent but the content should be not over #j4jb sulphur and #j4jbe phosphorus4 ,the serious detrimental effect of small quantities of sulphur and phosphorus is due to their not being uniformly distributed1 owing to their tendency to segregate4 ,the manganese and silicon contents are relatively unimportant in the percentages usually found in high-speed steel4 ,the detrimental effects of tin1 copper and arsenic are not generally realized by the trade4 ,small quantities of these impurities are exceedingly harmful4 ,these elements are very seldom determined in customers' chemical laboratories and it is somewhat difficult for public chemists to analyze for them4 ,in justice to the manufacturer1 attention should be called to the variations in chemical analyses among the best of laboratories4 ,generally speaking1 a steel works' laboratory will obtain results more nearly true and accurate than is possible with a customer's laboratory1 or by a public chemist4 ,this can reasonably be expected1 for the steel works' chemist is a specialist1 analyzing the same material for the same elements day in and day out4 ,the importance of the chemical laboratory to a tool-steel plant cannot be over-estimated4 ,every heat of steel is analyzed for each element1 and check analyses obtained2 also1 every substance used in the mix is analyzed for all impurities4 ,the importance of using pure base materials is known to all manufacturers despite chemical evidence that certain detrimental elements are removed in the process of manufacture4 ,the manufacture of high-speed steel represents the highest art in the making of steel by tool-steel practice4 ,some may say1 on account of our increased knowledge of chemistry and metallurgy1 that the making of such steel has ceased to be an art1 but has become a science4 ,it is1 in fact an art2 aided by science4 ,the human element in its manufacture is a decided factor1 as will be brought in the following remarks3 ,the heat treatment of steel in its broad aspect may be said to commence with the melting furnace and end with the hardening and tempering of the finished product4 ,high-speed steel is melted by two general types of furnace1 known as crucible and electric4 ,steel treaters1 however1 are more vitally interested in the changes that take place in the steel during the various processes of manufacture rather than a detailed description of those processes1 which are more or less familiar to all4 ,in order that good high-speed steel may be furnished in finished bars1 it must be of correct chemical analysis1 properly melted and cast into solid ingots1 free from blow-holes and surface defects4 ,sudden changes of temperature are to be guarded against at every stage of its manufacture and subsequent treatment4 ,the ingots are relatively weak1 and the tendency to crack due to cooling strains is great4 ,for this reason the hot ingots are not allowed to cool quickly1 but are placed in furnaces which are of about the same temperature and are allowed to cool gradually before being placed in stock4 ,good steel can be made only from good ingots4 ,steel treaters should be more vitally interested in the important changes which take place in high-speed steel during the hammering operations than that of any other working the steel receives in the course of its manufacture4 ,,quality ,,and ,,structure ,the quality of high-speed steel is dependent to a very great extent upon its structure4 ,the making of the structure begins under the hammer1 and the beneficial effects produced in this stage persist through the subsequent operations1 provided they are properly carried out4 ,the massive carbides and tungstides present in the ingot are broken down and uniformly distributed throughout the billet4 ,to accomplish this the reduction in area must be sufficient and the hammer blows should be heavy1 so as to carry the compression into the center of the billet2 otherwise1 undesirable characteristics such as coarse structure and carbide envelopes will exist and cause the steel treater much trouble4 ,surface defects invisible in the ingot may be opened up under the hammering operation1 in which event they are chipped from the hot billet4 ,ingots are first hammered into billets4 ,these billets are carefully inspected and all surface defects ground or chipped4 ,the hammered billets are again slowly heated and receive a second hammering1 known as cogging4 ,the billet resulting therefrom is known as a cogged billet and is of the proper size for the rolling mill or for the finishing hammer4 ,although it is not considered good mill practice1 some manufacturers who have a large rolling mill perform the very important cogging operation in the rolling mill instead of under the hammer4 ,cogging in a rolling mill does not break up and distribute the carbides and tungstides as efficiently as cogging under the hammer2 another objection to cogging in the rolling mill is that there is no opportunity to chip surface defects developed as they can be under the trained eye of a hammer-man1 thereby eliminating such defects in the finished billet4 ,the rolling of high-speed steel is an art known to very few4 ,the various factors governing the proper rolling are so numerous that it is necessary for each individual rolling mill to work out a practice that gives the best results upon the particular analysis of steel it makes4 ,important elements entering into the rolling are the heating and finishing temperatures1 draft1 and speed of the mill4 ,in all of these the element of time must be considered4 ,high-speed steel should be delivered from the rolling mill to the annealing department free from scale1 for scale promotes the formation of a decarbonized surface4 ,in preparation of bars for annealing1 they are packed in tubes with a mixture of charcoal1 lime1 and other material4 ,the tubes are sealed and placed in the annealing furnace and the temperature is gradually raised to about #a1fej;,f41 and held there for a sufficient length of time1 depending upon the size of the bars4 ,after very slow cooling the bars are removed from the tubes4 ,they should then show a ,brinnell number of between #bce and #bge4 ,the inspection department ranks with the chemical and metallurgical departments in safeguarding the quality of the product4 ,it inspects all finished material from the standpoint of surface defects1 hardness1 size and fracture4 ,it rejects such steel as is judged not to meet the manufacturer's standard4 ,the inspection and metallurgical departments work hand in hand1 and if any department is not functioning properly it will soon become evident to the inspectors1 enabling the management to remedy the trouble4 ,the successful manufacture of high-speed steel can only be obtained by those companies who have become specialists4 ,the art and skill necessary in the successful working of such steel can be attained only by a man of natural ability in his chosen trade1 and trained under the supervision of experts4 ,to become an expert operator in any department of its manufacture1 it is necessary that the operator work almost exclusively in the production of such steel4 ,as to the heat treatment1 it is customary for the manufacturer to recommend to the user a procedure that will give to his steel a high degree of cutting efficiency4 ,the recommendations of the manufacturer should be conservative1 embracing fairly wide limits1 as the tendency of the user is to adhere very closely to the manufacturer's recommendations4 ,unless one of the manufacturer's expert service men has made a detailed study of the customer's problem1 the manufacturer is not justified in laying down set rules1 for if the customer does a little experimenting he can probably modify the practice so as to produce results that are particularly well adapted to his line of work4 ,the purpose of heat-treating is to produce a tool that will cut so as to give maximum productive efficiency4 ,this cutting efficiency depends upon the thermal stability of the complex hardenites existing in the hardened and tempered steel4 ,the writer finds it extremely difficult to convey the meaning of the word hardenite to those that do not have a clear conception of the term4 ,the complex hardenites in high-speed steel may be described as that form of solid solution which gives to it its cutting efficiency4 ,the complex hardenites are produced by heating the steel to a very high temperature1 near the melting point1 which throws into solution carbides and tungstides1 provided they have been properly broken up in the hammering process and uniformly distributed throughout the steel4 ,by quenching the steel at correct temperature this solid solution is retained at atmospheric temperature4 ,it is not the intention to make any definite recommendations as to heat-treating of high-speed steel by the users4 ,it is recognized that such steel can be heat-treated to give satisfactory results by different methods4 ,it is1 however1 believed that the ,american practice of hardening and tempering is becoming more uniform4 ,this is due largely to the exchange of opinions in meetings and elsewhere4 ,the trend of ,american practice for hardening is toward the following3 ,first1 slowly and carefully preheat the tool to a temperature of approximately #a1ejj;,f41 taking care to prevent the formation of excessive scale4 ,second1 transfer to a furnace1 the temperature of which is approximately #b1bej to #b1djj;,f41 and allow to remain in the furnace until the tool is heated uniformly to the above temperature4 ,third1 cool rapidly in oil1 dry air blast1 or lead bath4 ,fourth1 draw back to a temperature to meet the physical requirements of the tool1 and allow to cool in air4 ,it was not very long ago that the desirability of drawing hardened high-speed steel to a temperature of #a1ajj was pointed out1 and it is indeed encouraging to learn that comparatively few treaters have failed to make use of this fact4 ,many treaters at first contended that the steel would be soft after drawing to this temperature and it is only recently1 since numerous actual tests have demonstrated its value1 that the old prejudice has been eliminated4 ,high-speed steel should be delivered only in the annealed condition because annealing relieves the internal strains inevitable in the manufacture and puts it in vastly improved physical condition4 ,the manufacturer's inspection after annealing also discloses defects not visible in the unannealed state4 ,the only true test for a brand of high-speed steel is the service that it gives by continued performance month in and month out under actual shop conditions4 ,the average buyer is not justified in conducting a test1 but can well continue to purchase his requirements from a reputable manufacturer of a brand that is nationally known4 ,the manufacturer is always willing to cooperate with the trade in the conducting of a test and is much interested in the information received from a well conducted test4 ,a test1 to be valuable1 should be conducted in a manner as nearly approaching actual working conditions in the plant in which the test is made as is practical4 ,in conducting a test a few reputable brands should be allowed to enter4 ,all tools entered should be of exactly the same size and shape4 ,there is much difference of opinion as to the best practical method of conducting a test1 and the decision as to how the test should be conducted should be left to the customer1 who should cooperate with the manufacturers in devising a test which would give the best basis for conclusions as to how the particular brands would perform under actual shop conditions4 ,the value of the file test depends upon the quality of the file and the intelligence and experience of the person using it4 ,the file test is not reliable1 but in the hands of an experienced operator1 gives some valuable information4 ,almost every steel treater knows of numerous instances where a lathe tool which could be touched with a file has shown wonderful results as to cutting efficiency4 ,modern tool-steel practice has changed from that of the past1 not by the use of labor-saving machinery1 but by the use of scientific devices which aid and guide the skilled craftsman in producing a steel of higher quality and greater uniformity4 ,it is upon the intelligence1 experience1 and skill of the individual that quality of tool steel depends4 ,,hardening ,,high-,,speed ,,steels ,we will now take up the matter of hardening high-speed steels4 ,the most ordinary tools used are for lathes and planers4 ,the forging should be done at carbon-steel heat4 ,rough-grind while still hot and preheat to about carbon-steel hardening heat1 then heat quickly in high-speed furnace to white heat1 and quench in oil4 ,if a very hard substance is to be cut1 the point of tool may be quenched in kerosene or water and when nearly black1 finish cooling in oil4 ,tempering must be done to suit the material to be cut4 ,for cutting cast iron1 brass castings1 or hard steel1 tempering should be done merely to take strains out of steel4 ,on ordinary machinery steel or nickel steel the temper can be drawn to a dark blue or up to #ijj;,f4 ,if the tool is of a special form or character1 the risk of melting or scaling the point cannot be taken4 ,in these cases the tool should be packed1 but if there is no packing equipment1 a tool can be heated to as high heat as is safe without risk to cutting edges1 and cyanide or prussiate of potash can be sprinkled over the face and then quenched in oil4 ,some very adverse criticism may be heard on this point1 but experience has proved that such tools will stand up very nicely and be perfectly free from scales or pipes4 ,where packing cannot be done1 milling cutters1 and tools to be hardened all over1 can be placed in muffled furnace1 brought to #b1bbj and quenched in oil4 ,all such tools1 however1 must be preheated slowly to #a1djj to #a1ejj then placed in a high-speed furnace and brought up quickly4 ,do not soak high-speed steel at high heats4 ,quench in oil4 ,we must bear in mind that the heating furnace is likely to expand tools1 therefore provision must be made to leave extra stock to take care of such expansion4 ,tools with shanks such as counter bores1 taps1 reamers1 drills1 etc41 should be heated no further than they are wanted hard1 and quench in oil4 ,if a forge is not at hand and heating must be done1 use a muffle furnace and cover small shanks with a paste from fire clay or ground asbestos4 ,hollow mills1 spring threading dies1 and large cutting tools with small shanks should have the holes thoroughly packed or covered with asbestos cement as far as they are wanted soft4 ,,cutting-,,off ,,steel ,,from ,,bar ,to cut a piece from an annealed bar1 cut off with a hack saw1 milling cutter or circular saw4 ,cut clear through the bar2 do not nick or break4 ,to cut a piece from an unannealed bar1 cut right off with an abrasive saw2 do not nick or break4 ,if of large cross-section1 cut off hot with a chisel by first slowly and uniformly heating the bar1 at the point to be cut1 to a good lemon heat1 #a1hjj to #a1hej;,f4 and cut right off while hot2 do not nick or break4 ,allow the tool length and bar to cool before reheating for forging4 ,,lathe ,,and ,,planer ,,tools ,,forging4--,gently warm the steel to remove any chill1 is particularly desirable in the winter1 then heat slowly and carefully to a scaling heat1 that is a lemon heat 7#a1hjj to #b1jjj;,f471 and forge uniformly4 ,reheat the tool for further forging directly the steel begins to stiffen under the hammer4 ,under no circumstances forge the steel when the temperature falls below a dark lemon to an orange color about #a1gjj;,f4 ,reheat as often as is necessary to finish forging the tool to shape4 ,allow the tool to cool after forging by burying the tool in dry ashes or lime4 ,do not place on the damp ground or in a draught of air4 ,the heating for forging should be done preferably in a pipe or muffle furnace but if this is not convenient use a good clean fire with plenty of fuel between the blast pipe and the tool4 ,never allow the tool to soak after the desired forging heat has been reached4 ,do not heat the tool further back than is necessary to shape the tool1 but give the tool sufficient heat4 ,see that the back of the tool is flatly dressed to provide proper support under the nose of the tool4 ,,hardening ,,high-,,speed ,,steel4--,slowly reheat the cutting edge of the tool to a cherry red1 #a1djj;,f41 then force the blast so as to raise the temperature quickly to a full white heat1 #b1bjj to #b1bej;,f41 that is1 until the tool starts to sweat at the cutting face4 ,cool the point of the tool in a dry air blast or preferably in oil1 further cool in oil keeping the tool moving until the tool has become black hot4 ,to remove hardening strains reheat the tool to from #ejj to #a1ajj;,f4 ,cool in oil or atmosphere4 ,this second heat treatment adds to the toughness of the tool and therefore to its life4 ,,grinding ,,tools4--,grind tools to remove all scale4 ,use a quick-cutting1 dry1 abrasive wheel4 ,if using a wet wheel1 be sure to use plenty of water4 ,do not under any circumstances force the tool against the wheel so as to draw the color1 as this is likely to set up checks on the surface of the tool to its detriment4 ,,for ,,milling ,,cutters ,,and ,,formed ,,tools ,,forging4--,forge as before4--,,annealing4--,place the steel in a pipe1 box or muffle4 ,arrange the steel so as to allow at least #a in4 of packing1 consisting of dry powder ashes1 powdered charcoal1 mica1 etc41 between the pieces and the walls of the box or pipe4 ,if using a pipe close the ends4 ,heat slowly and uniformly to a cherry red1 #a1cge to #a1dej;,f4 according to size4 ,hold the steel at this temperature until the heat has thoroughly saturated through the metal1 then allow the muffle box and tools to cool very slowly in a dying furnace or remove the muffle with its charge and bury in hot ashes or lime4 ,the slower the cooling the softer the steel4 ,the heating requires from #b to #aj hr4 depending upon the size of the piece4 ,,hardening ,,and ,,tempering4--,it is preferable to use two furnaces when hardening milling cutters and special shape tools4 ,one furnace should be maintained at a uniform temperature from #a1cge to #a1dej;,f4 while the other should be maintained at about #b1bej;,f4 ,keep the tool to be hardened in the low temperature furnace until the tool has attained the full heat of this furnace4 ,a short time should be allowed so as to be assured that the center of the tool is as hot as the outside4 ,then quickly remove the tool from this preheating furnace to the full heat furnace4 ,keep the tool in this furnace only as long as is necessary for the tool to attain the full temperature of this furnace4 ,then quickly remove and quench in oil or in a dry air blast4 ,remove before the tool is entirely cold and draw the temper in an oil bath by raising the temperature of the oil to from #ejj to #gej;,f4 and allow this tool to remain1 at this temperature1 in the bath for at least #cj min41 insuring uniformity of temper2 then cool in the bath1 atmosphere or oil4 ,if higher drawing temperatures are desired than those possible with oil1 a salt bath can be used4 ,a very excellent bath is made by mixing two parts by weight of crude potassium nitrate and three parts crude sodium nitrate4 ,these will melt at about #dej;,f4 and can be used up to #a1jjj;,f4 ,before heating the steel in the salt bath1 slowly preheat1 preferably in oil4 ,reheating the hardened high-speed steel to #a1jjj;,f4 will materially increase the life of lathe tools1 but milling and form cutters1 taps1 dies1 etc41 should not be reheated higher than #ejj to #fej;,f41 unless extreme hardness is required1 when #a1ajj to #a1jjj;,f41 will give the hardest edge4 ,,instructions ,,for ,,working ,,high-,,speed ,,steel ,owing to the wide variations in the composition of high-speed steels by various makers1 it is always advisable to follow the directions of each when using his brand of steel4 ,in the absence of specific directions the following general suggestions from several makers will be found helpful4 ,the ,ludlum ,steel ,company recommend the following3 ,,cutting-,,off4--,to cut a piece from an annealed bar1 cut off with a hack saw1 milling cutter or circular saw4 ,cut clear through the bar2 do not nick or break4 ,to cut a piece from an unannealed bar1 cut right off with an abrasive saw2 do not nick or break4 ,if of large cross-section1 cut off hot with a chisel by first slowly and uniformly heating the bar1 at the point to be cut1 to a good lemon heat1 #a1hjj-a1hej;,f4 and cut right off while hot2 do not nick or break4 ,allow the tool length and bar to cool before reheating for forging4 ,,lathe ,,and ,,planer ,,tools ,,to ,,forge4--,gently warm the steel to remove any chill is particularly desirable in the winter4 ,then heat slowly and carefully to a scaling heat1 that is a lemon heat 7#a1hjj-b1jjj;,f471 and forge uniformly4 ,reheat the tool for further forging directly the steel begins to stiffen under the hammer4 ,under no circumstances forge the steel when the temperature falls below a dark lemon to an orange color3 about #a1gjj;,f4 ,reheat as often as is necessary to finish forging the tool to shape4 ,allow the tool to cool after forging by burying the tool in dry ashes or lime4 ,do not place on the damp ground or in a draught of air4 ,the heating for forging should be done preferably in a pipe or muffle furnace1 but if this is not convenient use a good clean fire with plenty of fuel between the blast pipe and the tool4 ,never allow the tool to soak after the desired forging heat has been reached4 ,do not heat the tool further back than is necessary to shape the tool1 but give the tool sufficient heat4 ,see that the back of the tool is flatly dressed to provide proper support under the nose of the tool4 ,,hardening4--,slowly reheat the cutting edge of the tool to a cherry red1 #a1djj;,f41 then force the blast so as to raise the temperature quickly to a full white heat1 #b1bjj-b1bej;,f41 that is1 until the tool starts to sweat at the cutting face4 ,cool the point of the tool in a dry air blast or preferably in oil2 further cool in oil1 keeping the tool moving until the tool has become black hot4 ,to remove hardening strains reheat the tool to from #ejj to #a1ajj;,f4 ,cool in oil or atmosphere4 ,this second heat treatment adds to the toughness of the tool and therefore to its life4 ,,grinding4--,grind tools to remove all scale4 ,use a quick cutting1 dry1 abrasive wheel4 ,if using a wet wheel1 be sure to use plenty of water4 ,do not under any circumstances force the tool against the wheel so as to draw the color1 as this is likely to set up checks on the surface of the tool to its detriment4 ,the ,firth-,sterling ,steel ,company say3 ,,instead ,,of ,,printing ,,any ,,rules ,,on ,,the ,,hardening ,,and ,,tempering ,,of ,,firth-,,sterling ,,steels ,,we ,,wish ,,to ,,say ,,to ,,our ,,customers3 ,,trust ,,the ,,steel ,,to ,,the ,,skill ,,and ,,the ,,judgement ,,of ,,your ,,toolsmith ,,and ,,tool ,,temperer4 ,the steel workers of today know by personal experience and by inheritance all the standard rules and theories on forging1 hardening and tempering of all fine tool steels4 ,they know the importance of slow1 uniform heating1 and the danger of overheating some steels1 and underheating others4 ,the tempering of tools and dies is a science taught by heat1 muscle and brains4 ,the tool temperer is the man to hold responsible for results4 ,the tempering of tools has been his life work4 ,he may find suggestions on the following pages interesting1 but we are always ready to trust the treatment of our steels to the experienced man at the fire4 ,,heat ,,treatment ,,of ,,lathe1 ,,planer ,,and ,,similar ,,tools ,,fire4--,for these tools a good fire is one made of hard foundry coke1 broken in small pieces1 in an ordinary blacksmith forge with a few bricks laid over the top to form a hollow fire4 ,the bricks should be thoroughly heated before tools are heated4 ,hard coal may be used very successfully in place of hard coke and will give a higher heat4 ,it is very easy to give ,blue ,chip the proper heat if care is used in making up the fire4 ,,forging4--,heat slowly and uniformly to a good forging heat4 ,do not hammer the steel after it cools below a bright red4 ,avoid as much as possible heating the body of the tool1 so as to retain the natural toughness in the neck of the tool4 ,,hardening4--,heat the point of the tool to an extreme white heat 7about #b1bjj;,f47 until the flux runs4 ,this heat should be the highest possible short of melting the point4 ,care should be taken to confine the heat as near to the point as possible so as to leave the annealing and consequent toughness in the neck of the tool and where the tool is held in the tool post4 ,,cool in an air blast1 the open air or in oil1 depending upon the tools or the work they are to do4 ,for roughing tools temper need not be drawn except for work where the edge tends to crumble on account of being too hard4 ,for finishing tools draw the temper to suit the purpose for which they are to be used4 ,,grind thoroughly on dry wheel 7or wet wheel if care is used to prevent checking74 ,,heat ,,treatment ,,of ,,milling ,,cutters1 ,,drills1 ,,reamers1 ,,etc4 ,,the ,,fire4--,gas and electric furnaces designed for high heats are now made for treating high-speed steels4 ,we recommend them for treating all kinds of ,blue ,chip tools and particularly the above class4 ,after tools reach a yellow heat in the forge fire they must not be allowed to touch the fuel or come in contact with the blast or surrounding air4 ,,heating4--,tools of this kind should be heated to a mellow white heat1 or as hot as possible without injuring the cutting edges 7#b1jjj to #b1bjj;,f474 ,for most work the higher the heat the better the tool4 ,where furnaces are used1 we recommend preheating the tools to a red heat in one furnace before putting them in a white hot furnace4 ,,cooling4--,we recommend quenching all of the above tools in oil when taken from the fire4 ,we have found fish oil1 cottonseed oil1 ,houghton's ,no4 #b soluble oil and linseed oil satisfactory4 ,the high heat is the important thing in hardening ,blue ,chip tools4 ,if a white hot tool is allowed to cool in the open air it will be hard1 but the air scales the tool4 ,,drawing ,,the ,,temper4--,tools of this class should be drawn considerably more than water-hardening steel for the same purpose4 ,,heat ,,treatment ,,of ,,punches ,,and ,,dies1 ,,shears1 ,,taps1 ,,etc4 ,,heating4--,the degree to which tools of the above classes should be heated depends upon the shape1 size and use for which they are intended4 ,generally1 they should not be heated to quite as high a heat as lathe tools or milling cutters4 ,they should have a high heat1 but not enough to make the flux run on the steel 7by pyrometer #a1ijj to #b1ajj;,f474 ,,cooling4--,depending on the tools1 some should be dipped in oil all over1 some only part way1 and others allowed to cool down in the air naturally1 or under air blast4 ,in cooling1 the toughness is retained by allowing some parts to cool slowly and quenching parts that should be hard4 ,,drawing ,,the ,,temper4--,as in cooling1 some parts of these tools will require more drawing than others1 but1 on the whole1 they must be drawn more than water hardening tools for the same purpose or to about #ejj;,f4 all over1 so that a good file will just touch the cutting or working parts4 ,,barium ,,chloride ,,process4--,this is a process developed for treating certain classes of tools1 such as taps1 forming tools1 etc4 ,it is being successfully used in many large plants4 ,briefly the treatment is as follows3 ,in this treatment the tools are first preheated to a red heat1 but small tools may be immersed without preheating4 ,the barium chloride bath is kept at a temperature of from #b1jjj to #b1ajj;,f41 and tools are held in it long enough to reach the same temperature4 ,they are then dipped in oil4 ,the barium chloride which adheres to the tools is brushed off1 leaving the tools as dean as before heating4 ,a ,,chromium-,,cobalt ,,steel ,the ,latrobe ,steel ,company make a high-speed steel without tungsten1 its red-hardness properties depending on chromium and cobalt instead of tungsten4 ,it is known as ,p4 ,r4 ,k-#cc steel4 ,it does not require the high temperature of the tungsten steels1 hardening at #a1hcj to #a1hej;,f4 instead of #b1bjj or even higher1 as with the tungsten4 ,this steel is forged at #a1ijj to #b1jjj;,f4 and must not be worked at a lower temperature than #a1fjj;,f4 ,it requires soaking in the fire more than the tungsten steels4 ,it can be normalized by heating slowly and thoroughly to #a1dge;,f41 holding this for from #aj to #bj min4 according to the size of the piece and cooling in the open air1 protected from drafts4 ,a peculiarity of this steel is that it becomes non-magnetic at or above #a1ifj;,f4 and the magnetic quality is not restored by cooling4 ,normalizing as above1 however1 restores the magnetic qualities4 ,this enables the user to detect any tools which have been overheated1 with a horseshoe magnet4 ,it is sometimes advantageous to dip tools1 before heating for hardening1 in ordinary fuel or quenching oil4 ,the oil leaves a thin film of carbon which tends to prevent decarbonization1 giving a very hard surface4 ,for other makes of high-speed steel used in lathe and planer tools the makers recommend that the tools be cut from the bar with a hack saw or else heated and cut with a chisel4 ,the heating should be very slow until the steel reaches a red after which it can be heated more rapidly and should only be forged at a high heat4 ,it can be forged at very high heats but care should be taken not to forge at a low heat4 ,the heating should be uniform and penetrate clear to the center of the bar before forging is begun4 ,reheat as often as necessary to forge at the proper heat4 ,after forging cool in lime before attempting to harden4 ,do not attempt to harden with the forging heat as was sometimes done with the carbon tools4 ,for hardening forged tools1 heat slowly up to a bright red and then rapidly until the point of the tool is almost at a melting heat4 ,cool in a blast of cold1 dry air4 ,for large sizes of steel1 cool in linseed oil or in fish oil as is most convenient4 ,if the tools are to be used for finishing cuts heat to a bright yellow and quench in oil4 ,grind for use on a sand wheel or grindstone in preference to an emery or an artificial abrasive wheel4 ,for hardening milling and similar cutters1 preheat to a bright red1 place the cutter on a round bar of suitable size1 and revolve it quickly over a very hot fire4 ,heat as high as possible without melting the points of the teeth and cool in a cold blast of dry air or in fish oil4 ,light fragile cutters1 twist drills1 taps and formed cutters may be heated almost white and then dipped in fish oil for hardening4 ,where possible it is better to give an even higher heat and cool in the blast of cold1 dry air as previously recommended4 ,,suggestions ,,for ,,handling ,,high-,,speed ,,steels ,the following suggestions for handling high-speed steels are given by a maker whose steel is probably typical of a number of different makes1 so that they will be found useful in other cases as well4 ,these include hints as to forging as well as hardening1 together with a list of dont's which are often very useful4 ,this applies to forging1 hardening of lathe1 slotting1 planing and all similar tools4 ,illustration3 ,,fig4 #hd4--;,all-steel1 #e_/h in4 square1 #a_/b ,x #a in41 and larger is usually mild finished1 and can be cut in a hack saw4 ,if cut off hot1 be sure to heat the butt end slowly and thoroughly in a clean fire4 ,rapid and insufficient heating invariably cracks the steel4 ,if you want to stamp the end with the name of the steel1 it is necessary that this is done at a good high orange color heat1 as it is otherwise apt to split the steel4 7,take your time1 do not hurry47 ,,hardening ,,high-,,speed ,,steel ,in forging use coke for fuel in the forge4 ,heat steel slowly and thoroughly to a lemon heat4 ,do not forge at a lower heat4 ,do not let the steel cool below a bright cherry red while forging4 ,after the tool is dressed1 reheat to forging heat to remove the forging strain1 and lay on the floor until cold4 ,then have the tool rough ground on a dry emery wheel4 ,illustration3 ,,fig4 #he4--;,be sure to have a full yellow heat at the dotted line4 ,remember this is a boring mill tool and will stand out in the tool-post1 and if you do not have a high thorough lemon heat1 your tool will snap off at the dotted line4 7,ninety-five per cent of all tools which break1 have been forged at too low a heat or at a heat not thorough to the center47 ,illustration3 ,,fig4 #hf4--,keep your high lemon forging heat up4 ,if you forge under a steam hammer1 take light blows4 ,do not jam your tool into shape4 ,put frequently back into the fire4 ,never let the high lemon color go down and beyond the dotted line4 ,for built-up and bent tools special care should be taken that the forging heat does not go below a bright cherry4 ,for tools #c_/d by #a-a_/b or larger where there is a big strain in forging1 such as bending at angles of about #de deg4 and building the tools up1 they should be heated to at least #a1gjj;,f4 ,slowly and without much blast4 ,for a #c_/d by #a-a_/b tool it should take about #aj min4 with the correct blast in a coke fire4 ,larger tools in proportion4 ,they can then be bent readily1 but no attempt should be made to forge the steel further without reheating to maintain the bright cherry red4 ,this is essential1 as otherwise the tools crack in hardening or while in use4 ,illustration3 ,,fig4 #hg4--;,be sure that the tool is absolutely straight at the bottom1 so as to lie flat in the tool-post4 ,illustration3 ,,fig4 #hh4--,this is the finished forged tool1 and let this grow cold by itself1 the slower the better4 ,it is well to cool the tool slowly in hot ashes1 to remove all forging strain4 ,you can now grind the tool dry on a sharp emery wheel4 ,the more you now finish the tool in grinding1 the less there is to come off after hardening4 ,in hardening place the tool in a coke fire 7hollow fire if possible7 with a slow blast and heat gradually up to a white welding heat on the nose of the tool4 ,then dip the white hot part only into thin oil or hold in a strong cold air blast4 ,when hardening in oil do not hold the tool in one place but keep it moving so that it cools as quickly as possible4 ,it is not necessary to draw the temper after hardening these tools4 ,illustration3 ,,fig4 #hi4--,this tool is ground1 ready for hardening4 ,never harden from the forging heat4 ,illustration3 ,,fig4 #ij4--;,heat the nose of the tool only up to dotted line1 very slowly and thoroughly to an absolutely white welding heat1 so that it shows a trifle fused around the edges1 and be very sure that this fusing has gone thoroughly through the nose1 otherwise the fusing effect will be taken off after the second grinding4 ,note the difference of the nose between this and ,fig4 #hf4 ,illustration3 ,,fig4 #ia4--,shows unnecessary roasting and drossing4 ,such hardening requires a great amount of grinding and is not good4 ,after hardening grind carefully on a wet emery wheel1 and be sure that the wheel is sharp with a plentiful supply of water4 ,do not force the grinding1 otherwise the cold water striking the steel heated up by friction1 will crack the nose4 ,be sure that the grinding wheel is sharp4 ,in grinding all tools should be ground as lightly as possible on a soft wet sandstone or on a wet emery wheel1 and care should be taken not to create any surface cracks1 which are invariably the result of grinding too forcibly4 ,the foregoing illustrations1 ,figs4 #hd to #ia1 with their captions1 will be found helpful4 ,special points of caution to be observed when hardening high-speed steel4 ,,don',t use a green coal fire2 use coke1 or build a hollow fire4 ,,don',t have the bed of the fire free from coal4 ,,don',t hurry the heating for forging4 ,the heating has to be done very slowly and the forging heat has to be kept very high 7a full lemon color7 heat and the tool has to be continually brought back into the fire to keep the high heat up4 ,when customers complain about seams and cracks1 in #i cases out of #aj1 this has been caused by too low a forging heat1 and when the blacksmith complains about tools cracking1 it is necessary to read this paragraph to him4 ,,don',t try to jam the tool into shape under a steam hammer with one or two blows2 take easy blows and keep the heat high4 ,,don',t have the tool curved at the bottom2 it must lie perfectly flat in the tool post4 ,,don',t harden from your forging heat2 let the tool grow cold or fairly cold4 ,after forging you can rough grind the tool dry1 but not too forcibly4 ,,don',t1 for hardening1 get more than the nose white hot4 ,,don',t get the white heat on the surface only4 ,,don',t hurry your heating for hardening2 let the heat soak thoroughly through the nose of the tool4 ,,don',t melt the nose of the tool4 ,,don',t1 as a rule1 dip the nose into water2 this should be done only for extremely hard material4 ,it is dangerous to put the nose into water for fear of cracking and when you do put the nose into water put just #a_/b in4 only of the extreme white hot part into the water and don't keep it too long in the water2 just a few seconds1 and then harden in oil4 ,we do not recommend water hardening4 ,,don',t grind too forcibly4 ,,don',t grind dry after hardening4 ,,don',t discolor the steel in grinding4 ,,don',t give too much clearance on tools for cutting cast iron4 ,,don',t start on cast iron with a razor edge on the tool4 ,take an oil stone and wipe three or four times over the razor edge4 ,,don',t use tool holder steel from bars without hardening the nose of each individual tool bit4 ,,air-,,hardening ,,steels4--,these steels are recommended for boring1 turning and planing where the cost of high-speed seems excessive4 ,they are also recommended for hard wood knives1 for roughing and finishing bronze and brass1 and for hot bolt forging dies4 ,this steel cannot be cut or punched cold but can be shaped and ground on abrasive wheels of various kinds4 ,it should be heated slowly and evenly for forging and kept as evenly heated at a bright red as possible4 ,it should not be forged after it cools to a dark red4 ,after the tool is made1 heat it again to a bright red and lay it down to cool in a dry place or it can be cooled in a cold1 dry air blast4 ,water must be kept away from it while it is hot4 ,,chapter ,,xi ,,furnaces ,there are so many standard furnaces now on the market that it is not necessary to go into details of their design and construction and only a few will be illustrated4 ,oil1 gas and coal or coke are most common but there is a steady growth of the use of electric furnaces4 ,illustration3 ,,fig4 #ib4--,standard lead pot furnace4 ,,typical ,,oil-,,fired ,,furnaces4--,several types of standard oil-fired furnaces are shown herewith4 ,figure #ib is a lead pot furnace1 ,fig4 #ic is a vertical furnace with a center column4 ,this column reduces the cubical contents to be heated and also supports the cover4 ,illustration3 ,,fig4 #ic4--;,furnace with center column4 ,a small tool furnace is shown in ,fig4 #id1 which gives the construction and heat circulation4 ,a larger furnace for high-speed steel is given in ,fig4 #ie4 ,the steel is supported above the heat1 the lower flame passing beneath the support4 ,for hardening broaches and long reamers and taps1 the furnace shown in ,fig4 #if is used4 ,twelve jets are used1 these coming in radially to produce a whirling motion4 ,illustration3 ,,fig4 #id4--;,furnace for cutting tools4 ,illustration3 ,,fig4 #ie4--;,high-speed steel furnace4 ,oil and gas furnaces may be divided into three types3 the open heating chamber in which combustion takes place in the chamber and directly over the stock2 the semimuffle heating chamber in which combustion takes place beneath the floor of the chamber from which the hot gases pass into the chamber through suitable openings2 and the muffle heating chamber in which the heat entirely surrounds the chamber but does not enter it4 ,the open furnace is used for forging1 tool dressing and welding4 ,the muffle furnace is used for hardening dies1 taps1 cutters and similar tools of either carbon or high-speed steel4 ,the muffle furnace is for spring hardening1 enameling1 assaying and work where the gases of combustion may have an injurious effect on the material4 ,illustration3 ,,fig4 #if4--;,furnace for hardening broaches4 ,illustration3 ,,fig4 #ig4--;,forging and welding furnace4 ,illustration3 ,,fig4 #ih4--,semi-muffle furnace4 ,illustration3 ,,fig4 #ii4--,muffle furnace4 ,furnaces of these types of oil-burning furnaces are shown in ,figs4 #ig1 #ih1 and #ii2 these being made by the ,gilbert ,barker ,manufacturing ,company4 ,the first has an air curtain formed by jets from the large pipe just below the opening1 to protect the operator from heat4 ,illustration3 ,,fig4 #ajj4--;,gas fired furnace4 ,illustration3 ,,fig4 #aja4--;,car door type of annealing furnace4 ,oil furnaces are also made for both high- and low-pressure air1 each having its advocates4 ,the same people also make gas-fired furnaces4 ,several types of furnaces for various purposes are illustrated in ,fig4 #ajj and #aja4 ,the first is a gas-fired hardening furnace of the surface-combustion type4 ,a large gas-fired annealing furnace of the ,maxon system is shown in ,fig4 #aja4 ,this is large enough for a flat car to be run into as can be seen4 ,it shows the arrangement of the burners1 the track for the car and the way in which it fits into the furnace4 ,these are from the designs of the ,industrial ,furnace ,corporation4 ,before deciding upon the use of gas or oil1 all sides of the problem should be considered4 ,gas is perhaps the nearest ideal but is as a rule more expensive4 ,the tables compiled by the ,gilbert ,barker ,manufacturing ,company and shown herewith1 may help in deciding the question4 ,,table #bg4--,,showing ,,comparison ,,of ,,oil ,,fuel ,,with ,,various ,,gaseous ,,fuels ,heat units per thousand cubic feet ,natural gas #a1jjj1jjj ,air gas 7gas machine7 #bj cp #hae1ejj ,public illuminating gas1 average #fej1jjj ,water gas 7from bituminous coal7 #cgg1jjj ,water and producer gas1 mixed #age1jjj ,producer gas #aej1jjj ,since a gallon of fuel oil 7#g lb47 contains #acc1jjj heat units1 the following comparisons may evidently be made4 ,at #e cts4 a gallon1 the equivalent heat units in oil would equal3 ,per thousand cubic feet ,natural gas at #j4cge ,air gas1 #bj cp at #j4cjg ,public illuminating gas1 average at #j4bdd ,water gas 7from bituminous coal7 at #j4adb ,water and producer gas1 mixed at #j4jfe ,producer gas at #j4jeg ,comparing oil and coal is not always simple as it depends on the work to be done and the construction of the furnaces4 ,the variation rises from #ge to #bjj gal4 of oil to a ton of coal4 ,for forging and similar work it is probably safe to consider #ajj gal4 of oil as equivalent to a ton of coal4 ,then there is the saving of labor in handling both coal and ashes1 the waiting for fires to come up1 the banking of fires and the dirt and nuisance generally4 ,the continuous operation possible with oil adds to the output4 ,when comparing oil and gas it is generally considered that #d-a_/b gal4 of fuel oil will give heat equivalent to #a1jjj cu4 ft4 of coal gas4 ,the pressure of oil and air used varies with the system installed4 ,the low-pressure system maintains a pressure of about #h oz4 on the oil and draws in free air for combustion4 ,others use a pressure of several pounds1 while gas burners use an average of perhaps #a-a_/b lb4 of air to give best results4 ,the weights and volumes of solid fuels are3 ,anthracite coal1 #ee to #fe lb4 per cubic foot or #cd to #da cubic feet per ton2 bituminous coal1 #ej to #ee lb4 per cubic foot or #da to #de cubic feet per ton2 coke1 #bh lb4 per cubic foot or #hj cubic feet per ton--the ton being calculated as #b1bdj lb4 in each case4 ,a novel carburizing furnace that is being used by a number of people1 is built after the plan of a fireless cooker4 ,the walls of the furnace are extra heavy1 and the ports and flues are so arranged that when the load in the furnace and the furnace is thoroughly heated1 the burners are shut off and all openings are tightly sealed4 ,the carburization then goes on for several hours before the furnace is cooled below the effective carburizing range1 securing an ideal diffusion of carbon between the case and the core of the steel being carburized4 ,this is particularly adaptable where simple steel is used4 ,,protective ,,screens ,,for ,,furnaces ,workmen needlessly exposed to the flames1 heat and glare from furnaces where high temperatures are maintained suffer in health as well as in bodily discomfort4 ,this shows several types of shields designed for the maximum protection of the furnace worker4 ,bad conditions are not necessary2 in almost every case means of relief can be found by one earnestly seeking them4 ,the larger forge shops have adopted flame shields for the majority of their furnaces4 ,years ago the industrial furnaces 7particularly of the oil-burning variety7 were without shields1 but the later models are all shield-equipped4 ,these shields are adapted to all of the more modern1 heat-treating furnaces1 as well as to those furnaces in use for working forges2 and attention should be paid to their use on the former type since the heat-treating furnaces are constantly becoming more numerous as manufacturers find need of them in the many phases of munitions making or similar work4 ,the heat that the worker about these furnaces must face may be divided in general into two classes3 there is first that heat due to the flame and hot gases that the blast in the furnaces forces out onto a man's body and face4 ,in the majority of furnaces this is by far the most discomforting1 and care must be taken to fend it and turn it behind a suitable shield4 ,the second class is the radiant heat1 discharged as light from the glowing interior of the furnace4 ,this is the lesser of the two evils so far as general forging furnaces are concerned1 but it becomes the predominating feature in furnaces of large door area such as in the usual case-hardening furnaces4 ,here the amount of heat discharged is often almost unbearable even for a moment4 ,this heat can be taken care of by interposing suitable1 opaque shields that will temporarily absorb it without being destroyed by it1 or becoming incandescent4 ,should such shields be so constructed as to close off all of the heat1 it might be impossible to work around the furnace for the removal of its contents1 but they can be made movable1 and in such a manner as to shield the major portion of the worker's body4 ,first taking up the question of flame shields1 the illustration1 ,fig4 #ajb1 is a typical installation that shows the main features for application to a forging machine or drop-hammer1 oil-burning furnace1 or for an arched-over1 coal furnace where the flame blows out the front4 ,this shield consists of a frame covered with sheet metal and held by brackets about #f in4 in front of the furnace4 ,it will be noted that slotted holes make this frame adjustable for height1 and it should be lowered as far as possible when in use1 so that the work may just pass under it and into the furnace openings4 ,immediately below the furnace openings1 and close to the furnace frame will be noted a blast pipe carrying air from the forge-shop fan4 ,this has a row of small holes drilled in its upper side for the entire length1 and these direct a curtain of cold air vertically across the furnace openings1 forcing all of the flame1 or a greater portion of it1 to rise behind the shield4 ,since the shield extends above the furnace top there is no escape for this flame until it has passed high enough to be of no further discomfort to the workman4 ,in this case fan-blast air is used for cooling1 and this is cheaper and more satisfactory because a great volume may be used4 ,however1 where high-pressure air is used for atomizing the oil at the burner1 and nothing else is available1 this may be employed--though naturally a comparatively small pipe will be needed1 in which minute holes are drilled1 else the volume of air used will be too great for the compressor economically to supply4 ,steam may also be employed for like service4 ,illustration3 ,,figs4 #ajb to #ajh4--,protective devices for furnace fronts4 ,the latest shields of this type are all made double1 as illustrated1 with an inner sheet of metal an inch or two inside of the front4 ,in the illustration1 ,a1 ,fig4 #ajb1 this inner sheet is smaller1 but some are now built the same size as the front and bolted to it with pipe spacers between4 ,the advantage of the double sheet is that the inner one bears the brunt of the flame1 and1 if needs be1 burns up before the outer2 while1 if due to a heavy fire it should be heated red at any point1 the outer sheet will still be much cooler and act as an additional shield to the furnace man4 ,,heavy ,,forging ,,practice4--,in heavy forging practice where the metal is being worked at a welding heat1 the amount of flame that will issue from an open-front furnace is so great that a plain1 sheet-steel front will neither afford sufficient protection nor stand up in service4 ,for such a place a water-cooled front is often used4 ,the general type of this front is illustrated in ,fig4 #ajc1 and appears to have found considerable favor1 for numbers of its kind are scattered throughout the country4 ,in this case the shield is placed at a slight angle from the vertical1 and along the top edge is a water pipe with a row of small holes through which sprays of water are thrown against it4 ,this water runs down in a thin sheet over the shield1 cooling it1 and is collected in a trough connected with a run-off pipe at the bottom4 ,the lower blast-pipe arrangement is similar to the one first described4 ,there are several serious objections to this form of shield that should lead to its replacement by a better type2 the first is that with a very hot fire1 portions in the center may become so rapidly heated that the steam generated will part the sheet of water and cause it to flow from that point in an inverted ,v1 and that section will then quickly become red hot4 ,another feature is that after the water and fire are shut down for the night the heat of the furnace can be great enough to cause serious warping of the surface of the shield so that the water will no longer cover it in a thin1 uniform sheet4 ,after rigging up a big furnace with a shield of this type several years ago1 its most serious object was found in the increase of the water bill of the plant4 ,this was already of large proportions1 but it had suddenly jumped to the extent of several hundred dollars4 ,investigation soon disclosed the fact that this water shield was one of the main causes of the added cost of water4 ,a little estimating of the amount of water that can flow through a #a_/b-;in4 pipe under #cj-lb4 pressure1 in the course of a day1 will show that this amount at #aj cts4 per #a1jjj gal41 can count up rather rapidly4 ,figure #ajc is a section through a portion of the furnace front and shield showing all of the principal parts4 ,this shield consists essentially of a very thin tank1 about #b-a_/b in4 between walls1 and filled with water4 ,like other shields it is fitted with an adjustment1 that it may be raised and lowered as the work demands4 ,the tank having an open top1 the water as it absorbs heat from the flame will simply boil away in steam2 and only a small amount will have to be added to make up for that which has evaporated4 ,the water-feed pipe shown at ,f ends a short distance above the top of the tank so that just how much water is running in may readily be seen4 ,an overflow pipe is provided at ,o which aids in maintaining the water at the proper height1 as a sufficient quantity can always be permitted to run in1 to avoid any possibility of the shield ever boiling dry2 at the same time the small excess can run off without danger of an overflow4 ,the shield illustrated in ,fig4 #ajd has been in constant use for over two years1 giving greater satisfaction than any other of which the writer has known4 ,it might also be noted that this shield was made with riveted joints1 the shop not having a gas-welding outfit4 ,to flange over the edges and then weld them with an acetylene torch would be a far more economical procedure1 and would also insure a tight and permanent joint4 ,the water-cooled front shown in ,fig4 #aje is an absurd effort to accomplish the design of a furnace that will provide cool working conditions4 ,this front was on a bolt-heating furnace using hard coal for fuel2 and it may be seen that it takes the place of all of the brickwork that should be on that side4 ,had this been nothing more than a very narrow water-cooled frame1 with brickwork below and supporting bricks above1 put in like the tuyeres in a foundry cupola1 the case would have been somewhat different1 for then it would have absorbed a smaller proportion of the heat4 ,a blacksmith who knows how a piece of cold iron laid in a small welding furnace momentarily lowers the temperature1 will appreciate the enormous amount of extra heat that must be maintained in the central portion of this furnace to make up for the constant chilling effect of the cold wall4 ,moreover1 since there would have been serious trouble had steam generated in this front1 a steady stream of water had to be run through it constantly to insure against an approach to the boiling point4 ,this is illustrated because of its absurdity1 and as a warning of something to avoid4 ,water-cooled1 tuyere openings1 as mentioned above1 which support brick side-walls of the furnace1 have proved successful for coal furnaces used for forging machine and drop-hammer heating1 since they permit a great amount of work to be handled through their openings without wearing away as would a brick arch4 ,great care should be exercised properly to design them so that a minimum amount of the cold tuyere will be in contact with the interior of the furnace1 and all interior portions possible should be covered by the bricks4 ,however1 a discussion of these points will hardly come in the flame-shield class1 although they can be made to do a great deal toward relieving the excessive heat to be borne by the furnace worker4 ,,flange ,,shields ,,for ,,furnaces4--,such portable flame shields as the one illustrated in ,fig4 #ajf may prove serviceable before furnaces required for plate work1 where the doors are often only opened for a moment at a time4 ,this shield can be placed far enough in front of the furnace1 that it will be possible to work under it or around it1 in removing bulky work from the furnace1 and yet it will afford the furnace tender some relief from the excessive glare that will come out the wide-opened door4 ,to have this shield of light weight so that it may be readily pushed aside when not wanted1 the frame may be made up of pipe and fittings1 and a piece of thin sheet steel fastened in the panel by rings about the frame4 ,about the most disagreeable task in a heat-treating shop is the removal of the pots from the case-hardening furnaces2 these must be handled at a bright red heat in order that their contents may be dumped into the quenching tank with a minimum-time contact with the air1 and before they have cooled sufficiently to require reheating4 ,facing the heat before the large open doors of the majority of these furnaces1 in a man-killing task even when the weather is moderately cool4 ,the boxes soon become more or less distorted1 and then even the best of lifting devices will not remove a hot pot without several minutes labor in front of the doors4 ,in ,fig4 #ajg is shown a method of arranging a shield on one type of charging and removing truck4 ,this shield cannot afford more than a partial protection to the body of the furnace tender1 because he must be able to see around it1 and in some cases even push it partly through the door of the furnace1 but even small as it is it may still afford some welcome protection4 ,the great advantage in this case of having the shield on the truck instead of stationary in front of the furnace1 is that it still affords protection as long as the hot pot is being handled through the shop on its way to the quenching tank4 ,it might be interesting to many engaged in the heat-treating or case hardening of steel parts1 to make a special note of the design of the truck that is illustrated in connection with the shield2 the general form is shown although the actual details for the construction of such a truck are lacking2 these being simple1 may be readily worked out by anyone wishing to build one4 ,this is considered to be one of the quickest and easiest operated devices for the removal of this class of work from the furnace4 ,to be sure it may only be used where the floor of the furnace has been built level with the floor of the room1 but many of the modern furnaces of this class are so designed4 ,the pack-hardening pots are cast with legs1 from two to three inches high1 to permit the circulation of the hot gases1 and so heat more quickly4 ,between these legs and under the body of the pot1 the two forward prongs of the truck are pushed1 tilting the outer handle to make these prongs as low as possible4 ,the handle is then lowered and1 as it has a good leverage1 the pot is easily raised from the floor1 and the truck and its load rolled out4 ,,heating ,,of ,,manganese ,,steel4--,another form of heat-treating furnace is that which is used for the heating of manganese and other alloy steels1 which after having been brought to the proper heat are drawn from the furnace into an immediate quenching tank4 ,with manganese steel in particular1 the parts are so fragile and easily damaged while hot that it is frequent practice to have a sloping platform immediately in front of the furnace door down which the castings may slide into a tank below the floor level4 ,such a furnace with a quenching tank in front of its door is shown in ,fig4 #ajh4 ,these tanks are covered with plates while charging the furnace and the cold castings are placed in a moderately cool furnace4 ,since some of these steels must not be charged into a furnace where the heat is extreme but should be brought up to their final heat gradually1 there is little discomfort during the charging process4 ,when quenching1 however1 from a temperature of #a1hjj to #a1ijj1 it is extremely unpleasant in front of the doors4 ,the swinging shield is here adapted to give protection for this work4 ,as will be noted it is hung a sufficient distance in front of the doors1 that it may not interfere with the castings as they come from the furnace1 and slide down into the tank4 ,to facilitate the work1 and avoid the necessity of working with the bars outside the edges of the shield1 the slot-like hole is cut in the center of the shield1 and through this the bars or rakes for dragging out the castings are easily inserted and manipulated4 ,the advantage of such a swinging shield is that it may be readily moved from side to side1 or forward and back as occasion requires4 ,,furnace ,,data ,in order to give definite information concerning furnaces1 fuels etc41 the following data is quoted from a paper by ,seth ,a4 ,moulton and ,w4 ,h4 ,lyman before the ,steel ,heat ,treaters ,society in ,september1 #aibj4 ,this considers a factory producing #cj1jjj lb4 of automobile gears per #bd hr4 ,the transmission gears will be of high-carbon steel and the differential of low-carbon steel1 carburized4 ,the heat-treating equipment required is3 #a4 ,annealing furnaces #a1djj to #a1fjj;,f4 #b4 ,carburizing furnaces #a1gjj to #a1hjj;,f4 #c4 ,hardening furnaces #a1dej to #a1eej;,f4 #d4 ,drawing furnaces #cej to #iej;,f4 ,all of the forging blanks are annealed before machining1 about three-quarters of the machined gears and parts are carburized1 all the carburized gears are given a double treatment for core and case1 all gears and parts are hardened and all parts are drawn4 ,the possible sources of heat supply and their values are as follows3-- #a4 ,oil #adj1jjj ,b4t4u4 per gallon #b4 ,natural gas #a1ajj ,b4t4u4 per cubic foot #c4 ,city gas #fej ,b4t4u4 per cubic foot #d4 ,water gas #cjj ,b4t4u4 per cubic foot #e4 ,producer gas #agj ,b4t4u4 per cubic foot #f4 ,coal #ab1jjj ,b4t4u4 per pound #g4 ,electric current #c1dab ,b4t4u4 per kilowatt-hour ,for the heat treatment specified only comparatively low temperatures are required4 ,no difficulty will be experienced in attaining the desired maximum temperature of #a1hjj;,f4 with any of the heating medium above enumerated2 but it should be noted that the producer gas with a ,b4t4u4 content of #agj per cubic foot and the electric current would require specially designed furnaces to obtain higher temperatures than #ahjj;,f4 ,,table #bh4--;,,comparattve ,,operating ,,costs ,assuming ,cost of oil- and gas-fired furnaces installed as #ajj4jj per square foot of hearth ,cost of coal-fired furnace installed as #aej4jj per square foot of hearth ,cost of electric furnace #ajj kw4 capacity installed as #ij4jj per kilowatt ,cost of electric furnace #aej kw4 capacity installed as #gj4jj per kilowatt ,output #c1jjj lb4 charge1 #h hr4 heat carburizing1 #b hr4 heating only4 ,annual service #g1bjj hr4 ,fixed charges including interest1 depreciation1 taxes1 insurance and maintenance #ae per cent4 ,extra operating labor for coal-fired furnace #fj cts4 per hour1 one man four furnaces4 ,,cost ,,of ,,various ,,types ,,of ,,furnaces ---------------------------------------- --------------------------------------- ,class fuel ,fuel per ,unit fuel,installation,efficiency ,fixed ,cost per charge cost cost per cent charges charge ---------------------------------------- -------------------------------- #a #b #c #d #e #f #g ---------------------------------------- -------------------------------- ,carburizing ---------------------------------------- -------------------------------- #a,oil #eb4j gal4 #j4ae gal4 #b1djj4jj #ab4f 4#dj #h4bj #b,natural gas #d4d ,m #j4ej ,m #b1djj4jj #ah4h #j4dj #b4fj #c;,city gas #h4c ,m #j4hj ,m #b1djj4jj #ag4j #j4dj #g4jd #d,water gas #ah4g ,m #j4dj #b1djj4jj #af4d #j4dj #g4hh #e,producer gas #cg4c ,m #j4aj ,m #b1djj4jj #ad4e #j4dj #d4ac #f;,coal #had4j lb4 #f4jj ton #c1fjj4jj #i4d #j4fj #c4ih #g;,electricity #ejj4j kw-hr4 #j4jae kw4 #i1jjj4jj #ec4j #a4ej #i4jj ---------------------------------------- -------------------------------- ,heating ---------------------------------------- -------------------------------- #a,oil #cj4h gal4 #j4ae gal4 #b1djj4jj #ba4d #j4aj #d4gb #b,natural gas #b4fa ,m #j4ej ,m #b1djj4jj #cb4j #j4aj #a4dj #c;,city gas #d4i ,m #j4hj ,m #b1djj4jj #bh4h #j4aj #d4jb #d,water gas #aa4a ,m #j4dj ,m #b1djj4jj #bg4f #j4aj #d4ed #e,producer gas #bb4a ,m #j4aj ,m #b1djj4jj #bd4f #j4aj #b4ca #f;,coal #cdh4j lb4 #f4jj ton #c1fjj4jj #bb4j #j4ae #a4ch #g;,electricity #cbi4j kw-hr4 #j4jae kw4 #aj1ejj4jj #ha4ge #j4dd #e4ch ---------------------------------------- --------------------------------------- ,this shows but two of the operations and for a single furnace4 ,the total costs for all operations on the #cj1jjj lb4 of gears per #bd hr4 is shown in ,table #bi4 ,,table #bi4--;,,comparative ,,annual ,,production ,,costs ,,for #cj1jjj ,,pounds ,,output ,,in #bd ,,hours ---------------------------------------- ------------------ ,no4 ,equipment ,installation cost ---------------------------------------- ---------------- #a #b #c ,i ,oil #agi1jjj4jj ,,ii ,oil and electric #bac1jjj4jj ,,iii ,natural gas #aag1jjj4jj ,,iv 7,a7 ,natural gas containing furnaces #abj1jjj4jj ,v ,natural gas and electric #aha1jjj4jj ,,vi ,city gas #abb1jjj4jj ,,vii ,city gas and electric #ahb1jjj4jj ,,viii ,water gas #bad1jjj4jj ,,ix ,water gas and electric #bch1jjj4jj ,x ,producer gas #bdf1jjj4jj ,,xi ,producer gas and electric #bee1jjj4jj ,,xii ,coal and electric #aid1jjj4jj ,,xiii ,electric #beg1jjj4jj ---------------------------------------- ------------------ ---------------------------------------- ----------------------------- ,annual operating expenses ,cost ,no4 ---------------------------------------- ,total per lb4 ,fixed ,heat ,labor metal1 charges cents ---------------------------------------- ------------------------ #a #d #e #f #g #h ,i #bf1hej4jj #aef1jjj4jj #aje1jjj4jj #bhg1hej4jj #c4ai ,,ii #ca1iej4jj #adb1ggj4jj #ig1jjj4jj #bga1gbj4jj #c4jb ,,iii #ag1eej4jj #dd1bej4jj #ig1jjj4jj #aeh1hjj4jj #a4gh ,,iv #ah1jjj4jj #da1jjj4jj #id1jjj4jj #aec1jjj4jj #a4gj ,v #bg1aej4jj #gc1hbj4jj #ij1jjj4jj #aij1igj4jj #b4ac ,,vi #ah1cjj4jj #abc1bjj4jj #id1jjj4jj #bce1ejj4jj #b4fb ,,vii #bg1cjj4jj #abh1hbj4jj #ij1jjj4jj #bdf1jbj4jj #b4gd ,,viii #ah1fjj4jj #ajd1jjj4jj #id1jjj4jj #baf1fjj4jj #b4da ,,ix #bg1dej4jj #aag1dbj4jj #ij1jjj4jj #bcd1hgj4jj #b4fb ,x #ah1ijj4jj #fi1cjj4jj #ij1jjj4jj #agh1bjj4jj #a4ih ,,xi #bg1gej4jj #ib1ebj4jj #ij1jjj4jj #baj1bgj4jj #b4cd ,,xii #bi1ajj4jj #hg1bbj4jj #ij1jjj4jj #bjf1cbj4jj #b4cj ,,xiii #ch1eej4jj #ace1jjj4jj #hd1jjj4jj #beg1eej4jj #b4hf ---------------------------------------- ----------------------------- ,,note4--,producer plant fixed charges are included in the cost of gas and are charged as heat in column #e1 so they are omitted from column #d4 ,,chapter ,,xii ,,pyrometry ,,and ,,pyrometers ,a knowledge of the fundamental principles of pyrometry1 or the measurement of temperatures1 is quite necessary for one engaged in the heat treatment of steel4 ,it is only by careful measurement and control of the heating of steel that the full benefit of a heat-treating operation is secured4 ,before the advent of the thermo-couple1 methods of temperature measurement were very crude4 ,the blacksmith depended on his eyes to tell him when the proper temperature was reached1 and of course the color appeared different on light or dark days4 ,cherry to one man was orange to another1 and it was therefore almost impossible to formulate any treatment which could be applied by several men to secure the same results4 ,one of the early methods of measuring temperatures was the iron ball method4 ,in this method1 an iron ball1 to which a wire was attached1 was placed in the furnace and when it had reached the temperature of the furnace1 it was quickly removed by means of the wire1 and suspended in a can containing a known quantity of water2 the volume of water being such that the heat would not cause it to boil4 ,the rise in temperature of the water was measured by a thermometer1 and1 knowing the heat capacity of the iron ball and that of the water1 the temperature of the ball1 and therefore the furnace1 could be calculated4 ,usually a set of tables was prepared to simplify the calculations4 ,the iron ball1 however1 scaled1 and changed in weight with repeated use1 making the determinations less and less accurate4 ,a copper ball was often used to decrease this change1 but even that was subject to error4 ,this method is still sometimes used1 but for uniform results1 a platinum ball1 which will not scale or change in weight1 is necessary1 and the cost of this ball1 together with the slowness of the method1 have rendered the practice obsolete1 especially in view of modern developments in accurate pyrometry4 ,,pyrometers ,armor plate makers sometimes use the copper ball or ,siemens' water pyrometer because they can place a number of the balls or weights on the plate in locations where it is difficult to use other pyrometers4 ,one of these pyrometers is shown in section in ,fig4 #aji4 ,,siemens' ,,water ,,pyrometer4--,it consists of a cylindrical copper vessel provided with a handle and containing a second smaller copper vessel with double walls4 ,an air space a separates the two vessels1 and a layer of felt the two walls of the inner one1 in order to retard the exchange of temperature with the surroundings4 ,the capacity of the inner vessel is a little more than one pint4 ,a mercury thermometer b is fixed close to the wall of the inner vessel1 its lower part being protected by a perforated brass tube1 whilst the upper projects above the vessel and is divided as usual on the stem into degrees1 ,fahrenheit or ,centigrade1 as desired4 ,at the side of the thermometer there is a small brass scale c1 which slides up and down1 and on which the high temperatures are marked in the same degrees as those in which the mercury thermometer is divided2 on a level with the zero division of the brass scale a small pointer is fixed1 which traverses the scale of the thermometer4 ,illustration3 ,,fig4 #aji4--,siemens' copper-ball pyrometer4 ,short cylinders d1 of either copper1 iron or platinum1 are supplied with the pyrometer1 which are so adjusted that their heat capacity at ordinary temperature is equal to one-fiftieth of that of the copper vessel filled with one pint of water4 ,as1 however1 the specific heat of metals increases with the temperature1 allowance is made on the brass sliding scales1 which are divided according to the metal used for the pyrometer cylinder d4 ,it will therefore be understood that a different sliding scale is required for the particular kind of metal of which a cylinder is composed4 ,in order to obtain accurate measurements1 each sliding scale must be used only in conjunction with its own thermometer1 and in case the latter breaks a new scale must be made and graduated for the new thermometer4 ,the water pyrometer is used as follows3 ,exactly one pint 7#j4efh liter7 of clean water1 perfectly distilled or rain water1 is poured into the copper vessel1 and the pyrometer is left for a few minutes to allow the thermometer to attain the temperature of the water4 ,the brass scale c is then set with its pointer opposite the temperature of the water as shown by the thermometer4 ,meanwhile one of the metal cylinders has been exposed to the high temperature which is to be measured1 and after allowing sufficient time for it to acquire that temperature1 it is rapidly removed and dropped into the pyrometer vessel without splashing any of the water out4 ,the temperature of the water will rise until1 after a little while1 the mercury of the thermometer has become stationary4 ,when this is observed the degrees of the thermometer are read off1 as well as those on the brass scale c opposite the top of the mercury4 ,the sum of these two values together gives the temperature of the flue1 furnace or other heated space in which the metal cylinder had been placed4 ,with cylinders of copper and iron1 temperatures up to #a1hjj;,f4 7#a1jjj;,c47 can be measured1 but with platinum cylinders the limit is #b1gjj;,f4 7#a1ejj;,c474 ,for ordinary furnace work either copper or wrought-iron cylinders may be used4 ,iron cylinders possess a higher melting point and have less tendency to scale than those of copper1 but the latter are much less affected by the corrosive action of the furnace gases2 platinum is1 of course1 not subject to any of these disadvantages4 ,the weight to which the different metal cylinders are adjusted is as follows3 ,copper #acg4j grams ,wrought-iron #aab4j grams ,platinum #djb4f grams ,in course of time the cylinders lose weight by scaling2 but tables are provided giving multipliers for the diminished weights1 by which the reading on the brass scale should be multiplied4 ,,the ,,thermo-,,couple ,with the application of the thermo-couple1 the measurement of temperatures1 between1 say1 #gjj and #b1ejj;,f41 was made more simple and precise4 ,the theory of the thermo-couple is simple2 it is that if two bars1 rods1 or wires of different metals are joined together at their ends1 when heated so that one junction is hotter than the other1 an electromotive force is set up through the metals1 which will increase with the increase of the difference of temperature between the two junctions4 ,this electromotive force1 or voltage1 may be measured1 and1 from a chart previously prepared1 the temperature determined4 ,in most pyrometers1 of course1 the temperatures are inscribed directly on the voltmeter1 but the fact remains that it is the voltage of a small electric current1 and not heat1 that is actually measured4 ,there are two common types of thermo-couples1 the first making use of common1 inexpensive metals1 such as iron wire and nichrome wire4 ,this is the so-called base metal couple4 ,the other is composed of expensive metals such as platinum wire1 and a wire of an alloy of platinum with #aj per cent of rhodium or iridium4 ,this is called the rare metal couple1 and because its component metals are less affected by heat1 it lasts longer1 and varies less than the base metal couple4 ,the cold junction of a thermo-couple may be connected by means of copper wires to the voltmeter1 although in some installations of base metal couples1 the wires forming the couple are themselves extended to the voltmeter1 making copper connections unnecessary4 ,from the foregoing1 it may be seen that accurately to measure the temperature of the hot end of a thermo-couple1 we must know the temperature of the cold end1 as it is the difference in the temperatures that determines the voltmeter readings4 ,this is absolutely essential for precision1 and its importance cannot be over-emphasized4 ,when pyrometers are used in daily operation1 they should be checked or calibrated two or three times a month1 or even every week4 ,where there are many in use1 it is good practice to have a master pyrometer of a rare metal couple1 which is used only for checking up the others4 ,the master pyrometer1 after calibrating against the melting points of various substances1 will have a calibration chart which should be used in the checking operation4 ,it is customary now to send a rare metal couple to the ,bureau of ,standards at ,washington1 where it is very carefully calibrated for a nominal charge1 and returned with the voltmeter readings of a series of temperatures covering practically the whole range of the couple4 ,this couple is then used only for checking those in daily use4 ,pyrometer couples are more or less expensive1 and should be cared far when in use4 ,the wires of the couple should be insulated from each other by fireclay leads or tubes1 and it is well to encase them in a fireclay1 porcelain1 or quartz tube to keep out the furnace gases1 which in time destroy the hot junction4 ,this tube of fireclay1 or porcelain1 etc41 should be protected against breakage by an iron or nichrome tube1 plugged or welded at the hot end4 ,these simple precautions will prolong the life of a couple and maintain its precision longer4 ,sometimes erroneous temperatures are recorded because the cold end of the couple is too near the furnace and gets hot4 ,this always causes a temperature reading lower than the actual1 and should be guarded against4 ,it is well to keep the cold end cool with water1 a wet cloth1 or by placing it where coal air will circulate around it4 ,best of all1 is to have the cold junction in a box1 together with a thermometer1 so that its temperature may definitely be known4 ,if this temperature should rise #bj;,f4 on a hot day1 a correction of #bj;,f4 should be added to the pyrometer reading1 and so on4 ,in the most up-to-date installations1 this cold junction compensation is taken care of automatically1 a fact which indicates its importance4 ,optical pyrometers are often used where it is impracticable to use the thermo-couple1 either because the temperature is so high that it would destroy the couple1 or the heat to be measured is inaccessible to the couple of ordinary length4 ,the temperatures of slag or metal in furnaces or running through tap-holes or troughs are often measured with optical pyrometers4 ,in one type of optical pyrometer1 the observer focuses it on the metal or slag and moves an adjustable dial or gage so as to get an exact comparison between the color of the heat measured with the calor of a lamp or screen in the pyrometer itself4 ,this1 of course1 requires practice1 and judgment1 and brings in the personal equation4 ,with care1 however1 very reliable temperature measurements may be made4 ,the temperatures of rails1 as they leave the finishing pass of a rolling mill1 are measured in this way4 ,another type of optical pyrometer is focused on the body1 the temperature of which is to be measured4 ,the rays converge in the telescope on metal cells1 heating them1 and thereby generating a small electric current1 the voltage of which is read an a calibrated voltmeter similar to that used with the thermo-couple4 ,the best precision is obtained when an optical pyrometer is used each time under similar conditions of light and the same observer4 ,where it is impracticable to use either thermo-couples or optical pyrometers1 sentinels may be used4 ,there are small cones or cylinders made of salts or other substances of known melting points and covering a wide range of temperatures4 ,if six of these sentinels1 melting respectively at #a1cjj1 #a1cej1 #a1djj1 #a1dej1 #a1ejj1 and #a1eej;,f41 were placed in a row in a furnace1 together with a piece of steel to be treated1 and the whole heated up uniformly1 the sentinels would melt one by one and the observer1 by watching them through an opening in the furnace1 could tell when his furnace is at say #a1ejj or between #a1ejj and #a1eej1 and regulate the heat accordingly4 ,a very accurate type of pyrometer1 but one not so commonly used as those previously described1 is the resistance pyrometer4 ,in this type1 the temperature is determined by measuring the resistance to an electric current of a wire which is at the heat to be measured4 ,this wire is usually of platinum1 wound around a quartz tube1 the whole being placed in the furnace4 ,when the wire is at the temperature of the furnace1 it is connected by wires with a ,wheatstone ,bridge1 a delicate device for measuring electrical resistance1 and an electric current is passed through the wire4 ,this current is balanced by switching in resistances in the ,wheatstone ,bridge1 until a delicate electrical device shows that no current is flowing4 ,the resistance of the platinum wire at the heat to be measured is thus determined on the ,bridge1 and the temperature read off on a calibration chart1 which shows the resistance at various temperatures4 ,these are the common methods used to-day for measuring temperatures1 but whatever method is used1 the observer should bear in mind that the greatest precision is obtained1 and hence the highest efficiency1 by keeping the apparatus in good working order1 making sure that conditions are the same each time1 and calibrating or checking against a standard at regular intervals4 ,,the ,,pyrometer ,,and ,,its ,,use ,in the heat treatment of steel1 it has become absolutely necessary that a measuring instrument be used which will give the operator an exact reading of heat in furnace4 ,there are a number of instruments and devices manufactured for this purpose but any instrument that will not give a direct reading without any guess work should have no place in the heat-treating department4 ,a pyrometer installation is very simple and any of the leading makers will furnish diagrams for the correct wiring and give detailed information as to the proper care of1 and how best to use their particular instrument4 ,there are certain general principles1 however1 that must be observed by the operators and it cannot be too strongly impressed upon them that the human factor involved is always the deciding factor in the heat treatment of steel4 ,a pyrometer is merely an aid in the performance of doing good work1 and when carefully observed will help in giving a uniformity of product and act as a check on careless operators4 ,the operator must bear in mind that although the reading on the pyrometer scale gives a measure of the temperature where the junction of the two metals is located1 it will not give the temperature at the center of work in the furnace1 unless by previous tests1 the heat for penetrating a certain bulk of material has been decided on1 and the time necessary for such penetration is known4 ,each analysis of plain carbon or alloy steel is a problem in itself4 ,its critical temperatures will be located at slightly different heats than for a steel which has a different proportion of alloying elements4 ,furthermore1 it takes time for metal to acquire the heat of the furnace4 ,even the outer surface lags behind the temperature of the furnace somewhat1 and the center of the piece of steel lags still further4 ,it is apparent1 therefore1 that temperature1 although important1 does not tell the whole story in heat treatment4 ,time is also a factor4 ,time at temperature is also of great importance because it takes time1 after the temperature has been reached1 for the various internal changes to take place4 ,hence the necessity for soaking1 when annealing or normalizing4 ,therefore1 a clock is as necessary to the proper pyrometer equipment as the pyrometer itself4 ,for the purpose of general work where a wide range of steels or a variable treatment is called for1 it becomes necessary to have the pyrometer calibrated constantly1 and when no master instrument is kept for this purpose the following method can be used to give the desired results3 ,,calibration ,,of ,,pyrometer ,,with ,,common ,,salt ,an easy and convenient method for standardization and one which does not necessitate the use of an expensive laboratory equipment is that based upon determining the melting point of common table salt 7sodium chloride74 ,while theoretically salt that is chemically pure should be used 7and this is neither expensive nor difficult to procure71 commercial accuracy may be obtained by using common table salt such as is sold by every grocer4 ,the salt is melted in a clean crucible of fireclay1 iron or nickel1 either in a furnace or over a forge-fire1 and then further heated until a temperature of about #a1fjj to #a1fej;,f4 is attained4 ,it is essential that this crucible be clean because a slight admixture of a foreign substance might noticeably change the melting point4 ,the thermo-couple to be calibrated is then removed from its protecting tube and its hot end is immersed in the salt bath4 ,when this end has reached the temperature of the bath1 the crucible is removed from the source of heat and allowed to cool1 and cooling readings are then taken every #aj sec4 on the milli-voltmeter or pyrometer4 ,a curve is then plotted by using time and temperature as cordinates1 and the temperature of the freezing point of salt1 as indicated by this particular thermocouple1 is noted1 i4e41 at the point where the temperature of the bath remains temporarily constant while the salt is freezing4 ,the length of time during which the temperature is stationary depends on the size of the bath and the rate of cooling1 and is not a factor in the calibration4 ,the melting point of salt is #a1dgb;,f41 and the needed correction for the instrument under observation can be readily applied4 ,it should not be understood from the above1 however1 that the salt-bath calibration cannot be made without plotting a curve2 in actual practice at least a hundred tests are made without plotting any curve to one in which it is done4 ,the observer1 if awake1 may reasonably be expected to have sufficient appreciation of the lapse of time definitely to observe the temperature at which the falling pointer of the instrument halts4 ,the gradual dropping of the pointer before freezing1 unless there is a large mass of salt1 takes place rapidly enough for one to be sure that the temperature is constantly falling1 and the long period of rest during freezing is quite definite4 ,the procedure of detecting the solidification point of the salt by the hesitation of the pointer without plotting any curve is suggested because of its simplicity4 ,,complete ,,calibration ,,of ,,pyrometers4--,for the complete calibration of a thermo-couple of unknown electromotive force1 the new couple may be checked against a standard instrument1 placing the two bare couples side by side in a suitable tube and taking frequent readings over the range of temperatures desired4 ,if only one instrument1 such as a millivoltmeter1 is available1 and there is no standard couple at hand1 the new couple may be calibrated over a wide range of temperatures by the use of the following standards3 ,water1 boiling point #bab;,f4 ,tin1 under charcoal1 freezing point #dej;,f4 ,lead1 under charcoal1 freezing point #fba;,f4 ,zinc1 under charcoal1 freezing point #ghf;,f4 ,sulphur1 boiling point #hcb;,f4 ,aluminum1 under charcoal1 freezing point #a1baf;,f4 ,sodium chloride 7salt71 freezing point #a1dgd;,f4 ,potassium sulphate1 freezing point #a1ieh;,f4 ,a good practice is to make one pyrometer a standard2 calibrate it frequently by the melting-point-of-salt method1 and each morning check up every pyrometer in the works with the standard1 making the necessary corrections to be used for the day's work4 ,by pursuing this course systematically1 the improved quality of the product will much more than compensate for the extra work4 ,the purity of the substance affects its freezing or melting point4 ,the melting point of common salt is given in one widely used handbook at #a1dba;,f41 although chemically pure sodium chloride melts at #a1dgd;,f4 as shown above4 ,a sufficient quantity for an extended period should be secured4 ,test the melting point with a pyrometer of known accuracy4 ,knowing this temperature it will be easy to calibrate other pyrometers4 ,,placing ,,of ,,pyrometers4--,when installing a pyrometer1 care should be taken that it reaches directly to the point desired to be measured1 that the cold junction is kept cold1 and that the wires leading to the recording instrument are kept in good shape4 ,the length of these lead wires have an effect2 the longer they are1 the lower the apparent temperature4 ,when pyrometers placed in a number of furnaces are connected up in series1 and a multiple switch is used for control1 it becomes apparent that pyrometers could not be interchanged between furnaces near and far from the instrument without affecting the uniformity of product from each furnace4 ,calibration can best be done without disturbing the working pyrometer1 by inserting the master instrument into each furnace separately1 place it alongside the hot junction of the working pyrometer1 and compare the reading given on the indicator connected with the multiple switch4 ,protection tubes should be replaced when cracked1 as it is important that no foreign substance is allowed to freeze in the tube1 so that the enclosed junction becomes a part of a solid mass joined in electrical contact with the outside protecting tube4 ,wires over the furnaces must be carefully inspected from time to time1 as no true reading can be had on an instrument1 if insulation is burned off and short circuits result4 ,if the standard calibrating instrument used contains a dry battery1 it should be examined from time to time to be sure it is in good condition4 ,,the ,,leeds ,,and ,,northrup ,,potentiometer ,,system ,the potentiometer pyrometer system is both flexible and substantial in that it is not affected by the jar and vibration of the factory or the forge shop4 ,large or small couples1 long or short leads can be used without adjustment4 ,the recording instrument may be placed where it is most convenient1 without regard to the distance from the furnace4 ,,its ,,fundamental ,,principle4--,the potentiometer is the electrical equivalent of the chemical balance1 or balance arm scales4 ,measurements are made with balance scales by varying known weights until they equal the unknown weight4 ,when the two are equal the scales stand at zero1 that is1 in the position which they occupy when there is no weight on either pan2 the scales are then said to be balanced4 ,measurements are made with the potentiometer by varying a known electromotive force until it equals the unknown2 when the two are equal the index of the potentiometer1 the galvanometer needle1 stands motionless as it is alternately connected and disconnected4 ,the variable known weights are units separate from the scales1 but the potentiometer provides its own variable known electromotive force4 ,the potentiometer provides1 first1 a means of securing a known variable electromotive force and1 second1 suitable electrical connections for bringing that electromotive force to a point where it may be balanced against the unknown electromotive force of the couple4 ,the two are connected with opposite polarity1 or so that the two e4m4f4s oppose one another4 ,so long as one is stronger than the other a current will flow through the couple2 when the two are equal no current will flow4 ,figure #ajg shows the wiring of the potentiometer in its simplest form4 ,the thermo-couple is at ,h1 with its polarity as shown by the symbols and -4 ,it is connected with the main circuit of the potentiometer at the fixed point ,d and the point ,g4 ,illustration3 ,,fig4 #aaj4--,simple potentiometer4 ,a current from the dry cell ,ba is constantly flowing through the main1 or so-called potentiometer circuit1 ,,abcdgef4 ,the section ,,dge of this circuit is a slide wire1 uniform in resistance throughout its length4 ,the scale is fixed on this slide wire4 ,the current from the cell ,ba as it flows through ,,dge1 undergoes a fall in potential1 setting up a difference in voltage1 that is1 an electromotive force1 between ,d and ,e4 ,there will also be electromotive force between ,d and all other points on the slide wire4 ,the polarity of this is in opposition to the polarity of the thermo-couple which connects into the potentiometer at ,d and at ,g4 ,by moving ,g along the slide wire a point is found where the voltage between ,d and ,g in the slide wire is just equal to the voltage between ,d and ,g generated by the thermo-couple4 ,a galvanometer in the thermo-couple circuit indicates when the balance point is reached1 since at this point the galvanometer needle will stand motionless when its circuit is opened and closed4 ,illustration3 ,,fig4 #aaa4--,standard cell potentiometer4 ,the voltage in the slide wire will vary with the current flowing through it from the cell ,ba and a means of standardizing this is provided4 ,,sc1 ,fig4 #aaa1 is a cadmium cell whose voltage is constant4 ,it is connected at two points ,c and ,d to the potentiometer circuit whenever the potentiometer current is to be standardized4 ,at this time the galvanometer is thrown in series with ,,sc4 ,the variable rheostat ,r is then adjusted until the current flowing is such that as it flows through the standard resistance ,,cd1 the fall in potential between ,c and ,d is just equal to the voltage of the standard cell ,,sc4 ,at this time the galvanometer will indicate a balance in the same way as when it was used with a thermo-couple4 ,by this operation the current in the slide wire ,,dge has been standardized4 ,illustration3 ,,fig4 #aab4--;,hand adjusted cold-end compensator4 ,,development ,,of ,,the ,,wiring ,,scheme ,,of ,,the ,,cold-,,end ,,compensator4--,the net voltage generated by a thermo-couple depends upon the temperature of the hot end and the temperature of the cold end4 ,therefore1 any method adopted for reading temperature by means of thermo-couples must in some way provide a means of correcting for the temperature of the cold end4 ,the potentiometer may have either of two very simple devices for this purpose4 ,in one form the operator is required to set a small index to a point on a scale corresponding to the known cold junction temperature4 ,in the other form an even more simple automatic compensator is employed4 ,the principle of each is described in the succeeding paragraphs1 in which the assumption is made that the reader already understands the potentiometer principle as described above4 ,as previously explained the voltage of the thermo-couple is measured by balancing it against the voltage drop ,,dg in the potentiometer4 ,as shown in ,fig4 #aaa1 the magnitude of the balancing voltage is controlled by the position of ,g4 ,make ,d movable as shown in ,fig4 #aab and the magnitude of the voltage ,,dg may be varied either from the point ,d or the point ,g4 ,this gives a means of compensating for cold end changes by setting the slider ,d4 ,as the cold end temperature rises the net voltage generated by the couple decreases1 assuming the hot end temperature to be constant4 ,to balance this decreased voltage the slider ,d is moved along its scale to a new point nearer ,g4 ,in other words1 the slider ,d is moved along its scale until it corresponds to the known temperature of the cold end and then the potentiometer is balanced by moving the slider ,g4 ,the readings of ,g will then be direct4 ,illustration3 ,,fig4 #aac4--;,another type of compensator4 ,the same results will be obtained if a slide wire upon which ,d bears is in parallel with the slide wire of ,g1 as shown in ,fig4 #aac4 ,,automatic ,,compensator4--,it should be noted that the effect of moving the contact ,d1 ,fig4 #aac1 is to vary the ratio of the resistances on the two sides of the point ,d in the secondary slide wire4 ,in the recording pyrometers1 an automatic compensator is employed4 ,this automatic compensator varies the ratio on the two sides of the point ,d in the following manner3 ,the point ,d1 ,fig4 #aad1 is mechanically fixed2 on one side of ,d is the constant resistance coil ,m1 on the other the nickel coil ,n4 ,n is placed at or near the cold end of the thermo-couple 7or couples74 ,nickel has a high temperature coefficient and the electrical proportions of ,m and ,n are such that the resistance change of ,n1 as it varies with the temperature of the cold end1 has the same effect upon the balancing voltage between ,d and ,g that the movement of the point ,d1 ,fig4 #aad1 has in the hand-operated compensator4 ,instruments embodying these principles are shown in ,figs4 #aae to #aag4 ,the captions making their uses clear4 ,illustration3 ,,fig4 #aad4--;,automatic cold-end compensator4 ,,placing ,,the ,,thermo-,,couples ,the following illustrations from the ,taylor ,instrument ,company show different applications of the thermo-couples to furnaces of various kinds4 ,figure #aah shows an oil-fired furnace with a simple vertical installation4 ,figure #aai shows a method of imbedding the thermo-couple in the floor of a furnace so as to require no space in the heating chamber4 ,illustration3 ,,fig4 #aae4--,potentiometer ready for use4 ,various methods of applying a pyrometer to common heat-treatment furnaces are shown in ,figs4 #abj to #abb4 ,illustration3 ,,fig4 #aaf4--;,eight-point recording pyrometer-,carpenter ,steel ,co4 ,,leeds ,,and ,,northrup ,,optical ,,pyrometer ,the principles of this very popular method of measuring temperature are sketched in ,fig4 #abc4 ,illustration3 ,,fig4 #aag4--,multiple-point thermocouple recorder--,bethlehem ,steel ,co4 ,illustration3 ,,fig4 #aah4--,tycos pyrometer in oil-fired furnace4 ,the instrument is light and portable1 and can be sighted as easily as an opera glass4 ,the telescope1 which is held in the hand1 weighs only #be oz42 and the case containing the battery1 rheostat and milliammeter1 which is slung from the shoulder1 only #aj lb4 ,illustration3 ,,fig4 #aai4--,thermocouple in floor of furnace4 ,illustration3 ,,fig4 #abj4--,pyrometer in gas furnace4 ,a large surface to sight at is not required4 ,so long as the image formed by the objective is broader than the lamp filament1 the temperature can be measured accurately4 ,illustration3 ,,fig4 #aba4--,tycos multiple indicating pyrometer and recorder4 ,illustration3 ,,fig4 #abb4--,pyrometer in galvanizing tank4 ,distance does not matter1 as the brightness of the image formed by the lens is practically constant1 regardless of the distance of the instrument from the hot object4 ,illustration3 ,,fig4 #abc4--,leeds ,northrup optical pyrometer4 ,the manipulation is simple and rapid1 consisting merely in the turning of a knurled knob4 ,the setting is made with great precision1 due to the rapid change in light intensity with change in temperature and to the sensitiveness of the eye to differences of light intensity4 ,in the region of temperatures used for hardening steel1 for example1 different observers using the instrument will agree within #c;,c4 ,illustration3 ,,fig4 #abd4--,too low4 ,,fig4 #abe4--,too high4 ,,fig4 #abf4--;,correct4 ,only brightness1 not color1 of light is matched1 as light of only one color reaches the eye4 ,color blindness1 therefore1 is no hindrance to the use of this method4 ,the use of the instrument is shown in ,fig4 #abg4 ,,optical ,,system ,,and ,,electrical ,,circuit ,,of ,,the ,,leeds ,,northrup ,,optical ,,pyrometer4--,for extremely high temperature1 the optical pyrometer is largely used4 ,this is a comparative method4 ,by means of the rheostat the current through the lamp is adjusted until the brightness of the filament is just equal to the brightness of the image produced by the lens ,l1 ,fig4 #abc1 whereupon the filament blends with or becomes indistinguishable in the background formed by the image of the hot object4 ,this adjustment can be made with great accuracy and certainty1 as the effect of radiation upon the eye varies some twenty times faster than does the temperature at #a1fjj;,f41 and some fourteen times faster at #c1djj;,f4 ,when a balance has been obtained1 the observer notes the reading of the milliammeter4 ,the temperature corresponding to the current is then read from a calibration curve supplied with the instrument4 ,illustration3 ,,fig4 #abg4--,using the optical pyrometer4 ,as the intensity of the light emitted at the higher temperatures becomes dazzling1 it is found desirable to introduce a piece of red glass in the eye piece at ,r4 ,this also eliminates any question of matching colors1 or of the observer's ability to distinguish colors4 ,it is further of value in dealing with bodies which do not radiate light of the same composition as that emitted by a black body1 since nevertheless the intensity of radiation of any one color from such bodies increases progressively in a definite manner as the temperature rises4 ,the intensity of this one color can therefore be used as a measure of temperature for the body in question4 ,figures #abd to #abf show the way it is read4 ,,correction ,,for ,,cold-,,junction ,,errors ,the voltage generated by a thermo-couple of an electric pyrometer is dependent on the difference in temperature between its hot junction1 inside the furnace1 and the cold junction1 or opposite end of the thermo-couple to which the copper wires are connected4 ,if the temperature or this cold junction rises and falls1 the indications of the instrument will vary1 although the hot junction in the furnace may be at a constant temperature4 ,a cold-junction temperature of #ge;,f41 or #be;,c41 is usually adopted in commercial pyrometers1 and the pointer on the pyrometer should stand at this point on the scale when the hot junction is not heated4 ,if the cold-junction temperature rises about #ge;,f41 where base metal thermo-couples are used1 the pyrometer will read approximately #a low for every #a rise in temperature above #ge;,f4 ,for example1 if the instrument is adjusted for a cold-junction temperature of #ge1 and the actual cold-junction temperature is #ij;,f41 the pyrometer will read #ae low4 ,if1 however1 the cold-junction temperature falls below #ge;,f41 the pyrometer will read high instead of low1 approximately #a for every #a drop in temperature below #ge;,f4 ,with platinum thermo-couples1 the error is approximately #a_/b for #a change in temperature4 ,,correction ,,by ,,zero ,,adjustment4--,many pyrometers are supplied with a zero adjuster1 by means of which the pointer can be set to any actual cold-junction temperature4 ,if the cold junction of the thermo-couple is in a temperature of #ajj;,f41 the pointer can be set to this point on the scale1 and the readings of the instrument will be correct4 ,,compensating ,,leads4--,by the use of compensating leads1 formed of the same material as the thermo-couple1 the cold junction can be removed from the head of the thermo-couple to a point #aj1 #bj or #ej ft4 distant from the furnace1 where the temperature is reasonably constant4 ,where greater accuracy is desired1 a common method is to drive a #b-;in4 pipe1 with a pointed closed end1 some #aj to #bj ft4 into the ground1 as shown in ,fig4 #abh4 ,the compensating leads are joined to the copper leads1 and the junction forced down to the bottom of the pipe4 ,the cold junction is now in the ground1 beneath the building1 at a depth at which the temperature is very constant1 about #gj;,f41 throughout the year4 ,this method will usually control the cold-junction temperature within #e;,f4 ,where the greatest accuracy is desired a compensating box will overcome cold-junction errors entirely4 ,it consists of a case enclosing a lamp and thermostat1 which can be adjusted to maintain any desired temperature1 from #ej to #aej;,f4 ,the compensating leads enter the box and copper leads run from the compensating box to the instrument1 so that the cold junction is within the box4 ,figure #abi shows a ,brown compensating box4 ,illustration3 ,,fig4 #abh4--;,correcting cold-junction error4 ,if it is desired to maintain the cold junction at #ajj3 the thermostat is set at this point1 and the lamp1 being wired to the #aaj- or #bbj-volt lighting circuit1 will light and heat the box until #ajj is reached1 when the thermostat will open the circuit and the light is extinguished4 ,the box will now cool down to #ih1 when the circuit is again closed1 the lamp lights1 the box heats up1 and the operation is repeated4 ,illustration3 ,,fig4 #abi4--;,compensating box4 ,,brown ,,automatic ,,signaling ,,pyrometer ,in large heat-treating plants it has been customary to maintain an operator at a central pyrometer1 and by colored electric lights at the furnaces1 signal whether the temperatures are correct or not4 ,it is common practice to locate three lights above each furnace-red1 white and green4 ,the red light burns when the temperature is too low1 the white light when the temperature is within certain limits--for example1 #bj;,f4 of the correct temperature--and the green light when the temperature is too high4 ,illustration3 ,,fig4 #acj4--;,brown automatic signaling pyrometer4 ,instruments to operate the lights automatically have been devised and one made by ,brown is shown in ,fig4 #acj4 ,the same form of instrument is used for this purpose to automatically control furnace temperatures1 and the pointer is depressed at intervals of every #aj sec4 on contacts corresponding to the red1 white and green lights4 ,illustration3 ,,fig4 #aca4--;,automatic temperature control4 ,,an ,,automatic ,,temperature ,,control ,,pyrometer ,automatic temperature control instruments are similar to the ,brown indicating high resistance pyrometer with the exception that the pointer is depressed at intervals of every #aj sec4 upon contact-making devices4 ,no current passes through the pointer which simply depresses the upper contact device tipped with platinum1 which in turn comes in contact with the lower contact device1 platinum-tipped1 and the circuit is completed through these two contacts4 ,the current is very small1 about #a_/aj amp41 as it is only necessary to operate the relay which in turn operates the switch or valve4 ,a small motor is used to depress the pointer at regular intervals4 ,the contact-making device is adjustable throughout the scale range of the instrument1 and an index pointer indicates the point on the instrument at which the temperature is being controlled4 ,the space between the two contacts on the high and low side1 separated by insulating material1 is equivalent to #a per cent of the scale range4 ,a control of temperature is therefore possible within #a per cent of the total scale range4 ,figure #aca shows this attached to a small furnace4 ,illustration3 ,,fig4 #acb4--,portable thermocouple testing molten brass4 ,,pyrometers ,,for ,,molten ,,metal ,pyrometers for molten metal are connected to portable thermocouples as in ,fig4 #acb4 ,usually the pyrometer is portable1 as shown in this case1 which is a ,brown4 ,other methods of mounting for this kind of work arc shown in ,figs4 #acc and #acd4 ,the bent mountings are designed for molten metal1 such as brass or copper and are supplied with either clay1 graphite or carborundum tubes4 ,fifteen feet of connecting wire is usually supplied4 ,the angle mountings1 ,fig4 #acd1 are recommended for baths such as lead or cyanide4 ,the horizontal arm is usually about #ad in4 long1 and the whole mounting is easily taken apart making replacements very easy4 ,details of the thermo-couple shown in ,fig4 #acb are given in ,fig4 #ace4 ,this is a straight rod with a protector for the hand of the operator4 ,the lag in such couples is less than one minute4 ,these are ,englehard mountings4 ,,protectors ,,for ,,thermo-,,couples ,thermo-couples must be protected from the danger of mechanical injury4 ,for this purpose tubes of various refractory materials are made to act as protectors4 ,these in turn are usually protected by outside metal tubes4 ,pure wrought iron is largely used for this purpose as it scales and oxidizes very slowly4 ,these tubes are usually made from #b to #d in4 shorter than the inner tubes4 ,in lead baths the iron tubes often have one end welded closed and are used in connection with an angle form of mounting4 ,illustration3 ,,fig4 #acc4--;,bent handle thermocouple with protector4 ,where it is necessary for protecting tubes to project a considerable distance into the furnace a tube made of nichrome is frequently used4 ,this is a comparatively new alloy which stands high temperatures without bending4 ,it is more costly than iron but also much more durable4 ,when used in portable work and for high temperatures1 pure nickel tubes are sometimes used4 ,there is also a special metal tube made for use in cyanide4 ,this metal withstands the intense penetrating characteristics of cyanide4 ,it lasts from six to ten months as against a few days for the iron tube4 ,the inner tubes of refractory materials1 also vary according to the purposes for which they are to be used4 ,they are as follows3 ,,marquardt ,,mass ,,tubes for temperatures up to #c1jjj;,f41 but they will not stand sudden changes in temperature1 such as in contact with intermittent flames1 without an extra outer covering of chamotte1 fireclay or carborundum4 ,illustration3 ,,fig4 #acd4--,other styles of bent mounting4 ,,fused ,,silica ,,tubes for continuous temperatures up to #a1hjj;,f4 and intermittently up to #b1djj;,f4 ,the expansion at various temperatures is very small1 which makes them of value for portable work4 ,they also resist most acids4 ,,chamotte ,,tubes are useful up to #b1hjj;,f4 and are mechanically strong4 ,they have a small expansion and resist temperature changes well1 which makes them good as outside protectors for more fragile tubes4 ,they cannot be used in molten metals1 or baths of any kind nor in gases of an alkaline nature4 ,they are used mainly to protect a ,marquardt mass or silica tube4 ,,carborundum ,,tubes are also used as outside protection to other tubes4 ,they stand sudden changes of temperature well and resist all gases except chlorine1 above #a1gej;,f4 ,especially useful in protecting other tubes against molten aluminum1 brass1 copper and similar metals4 ,,clay ,,tubes are sometimes used in large annealing furnaces where they are cemented into place1 forming a sort of well for the insertion of the thermo-couple4 ,they are also used with portable thermo-couples for obtaining the temperatures of molten iron and steel in ladles4 ,used in this way they are naturally short-lived1 but seem the best for this purpose4 ,illustration3 ,,fig4 #ace4--,straight thermocouple and guard4 ,,corundite ,,tubes are used as an outer protection for both the ,marquardt mass and the silica tubes for kilns and for glass furnaces4 ,graphite tubes are also used in some cases for outer protections4 ,,calorized ,,tubes are wrought-iron pipe treated with aluminum vapor which often doubles or even triples the life of the tube at high temperature4 ,these tubes come in different sizes and lengths depending on the uses for which they are intended4 ,heavy protecting outer tubes may be only #a in4 in inside diameter and as much as #c in4 outside diameter1 while the inner tubes1 such as the ,marquardt mass and silica tubes are usually about #c_/d in4 outside and #c_/h in4 inside diameter4 ,the length varies from #ab to #dh in4 in most cases4 ,special terminal heads are provided1 with brass binding posts for electrical connections1 and with provisions for water cooling when necessary4 ,,appendix ,,table #cb4--,temperature ,conversion ,tables4 ,,table #cc4--;,comparison ,between ,degrees ,centigrade and ,degrees ,fahrenheit4 ,,table #cd4--,weight of ,round1 ,octagon and ,square ,carbon ,tool ,steel per ,foot4 ,,table #ce4--,weight of ,round ,carbon ,tool ,steel #ab ,in4 in ,diameter and ,larger1 per ,foot4 ,,table #cf4--;,decimal ,equivalents of a foot4 ,,temperature ,,conversion ,,tables ,by ,,albert ,,sauveur ---------------------------------------- ---------------------------------- -#dei4d to #j #j to #ajj #ajj to #ajjj ---------------------------------------- -------------------------------- ,c4 ,f4 ,c4 ,f4 ,c4 ,f4 ,c4 ,f4 ,c4 ,f4 ---------------------------------------- ------------------------------ -#bgc -#dei4d -#ag4h #j #cb #aj4j #ej #abb4j #ch #ajj #babbfj #ejj #icb -#bfh -#dej -#ag4b #a #cc4haj4f #ea #abc4h #dc #aaj #bcjbff #eaj #iej -#bfb -#ddj -#af4g #b #ce4faa4a #eb #abe4f #di #abj #bdhbga #ebj #ifh -#beg -#dcj -#af4a #c #cg4daa4g #ec #abg4d #ed #acj #bffbgg #ecj #ihf -#bea -#dbj -#ae4f #d #ci4bab4b #ed #abi4b #fj #adj #bhdbhb #edj #ajjd -#bdf -#daj -#ae4j #e #da4jab4h #ee #aca4j #ff #aej #cjbbhh #eej #ajbb -#bdj -#djj -#ad4d #f #db4hac4c #ef #acb4h #ga #afj #cbjbic #efj #ajdj -#bcd -#cij -#ac4i #g #dd4fac4i #eg #acd4f #gg #agj #ccfbii #egj #ajeh -#bbi -#chj -#ac4c #h #df4dad4d #eh #acf4d #hb #ahj #cehcjd #ehj #ajgf -#bbc -#cgj -#ab4h #i #dh4bae4j #ei #ach4b #hh #aij #cgdcaj #eij #ajid -#bah -#cfj -#ab4b #aj #ej4jae4f #fj #adj4j #ic #bjj #cibcaf #fjj #aaab -#bab -#cej -#aa4g #aa #ea4haf4a #fa #ada4h #ii #baj #dajcba #faj #aacj -#bjg -#cdj -#aa4a #ab #ec4faf4g #fb #adc4fajj #bab #daccbg #fbj #aadh -#bja -#ccj -#aj4f #ac #ee4dag4b #fc #ade4dajd #bbj #dbhccb #fcj #aaff -#aif -#cbj -#aj4j #ad #eg4bag4h #fd #adg4baaj #bcj #ddfcch #fdj #aahd -#aij -#caj -#i4dd #ae #ei4jah4c #fe #adi4jaaf #bdj #dfdcdc #fej #abjb -#ahd -#cjj -#h4hi #af #fa4hah4i #ff #aej4haba #bej #dhbcdi #ffj #abbj -#agi -#bij -#h4cc #ag #fc4fai4d #fg #aeb4fabg #bfj #ejjced #fgj #abch -#agc -#bhj -#g4gh #ah #fe4dbj4j #fh #aed4dacb #bgj #eahcfj #fhj #abef -#afi -#bgc -#dei4d -#g4bb #ai #fg4bbj4f #fi #aef4bach #bhj #ecfcff #fij #abgd -#afh -#bgj -#ded -#f4fg #bj #fh4jba4a #gj #aeh4jadc #bij #eedcga #gjj #abib -#afb -#bfj -#dcf -#f4aa #ba #fi4hba4g #ga #aei4hadi #cjj #egbcgg #gaj #acaj -#aeg -#bej -#dah -#e4ef #bb #ga4fbb4b #gb #afa4faed #caj #eijchb #gbj #acbh -#aea -#bdj -#djj -#e4jj #bc #gc4dbb4h #gc #afc4dafj #cbj #fjhchh #gcj #acdf -#adf -#bcj -#chb -#d4dd #bd #ge4bbc4c #gd #afe4baff #ccj #fbfcic #gdj #acfd -#adj -#bbj -#cfd -#c4hi #be #gg4jbc4i #ge #afg4jaga #cdj #fddcii #gej #achb -#acd -#baj -#cdf -#c4cc #bf #gh4hbd4d #gf #afh4hagg #cej #ffbdjd #gfj #adjj -#abi -#bjj -#cbh -#b4gh #bg #hj4fbe4j #gg #agj4fahb #cfj #fhjdaj #ggj #adah -#abc -#aij -#caj -#b4bb #bh #hb4dbe4f #gh #agb4dahh #cgj #fihdaf #ghj #adcf -#aah -#ahj -#bib -#a4fg #bi #hd4bbf4a #gi #agd4baic #chj #gafdba #gij #aded -#aab -#agj -#bgd -#a4aa #cj #hf4jbf4g #hj #agf4jaii #cij #gcddbg #hjj #adgb -#ajg -#afj -#bef -#j4ef #ca #hg4hbg4b #ha #agg4hbjd #djj #gebdcb #haj #adij -#aja -#aej -#bch #j #cb #hi4fbg4h #hb #agi4fbaj #daj #ggjdch #hbj #aejh -#ie4f -#adj -#bbj #j4ef #cc #ia4dbh4c #hc #aha4dbaf #dbj #ghhddc #hcj #aebf -#ij4j -#acj -#bjb #a4aa #cd #ic4bbh4i #hd #ahc4bbba #dcj #hjfddi #hdj #aedd -#hd4d -#abj -#ahd #a4fg #ce #ie4jbi4d #he #ahe4jbbg #ddj #hbdded #hej #aefb -#gh4i -#aaj -#aff #b4bb #cf #if4hcj4j #hf #ahf4hbcb #dej #hdbdfj #hfj #aehj -#gc4c -#ajj -#adh #b4gh #cg #ih4fcj4f #hg #ahh4fbch #dfj #hfjdff #hgj #aeih -#fg4h -#ij -#acj #c4cc #ch #ajj4dca4a #hh #aij4dbdc #dgj #hghdga #hhj #afaf -#fb4b -#hj -#aab #c4hi #ci #ajb4bca4g #hi #aib4bbdi #dhj #hifdgg #hij #afcd -#ef4g -#gj -#id #d4dd #dj #ajd4jcb4b #ij #aid4jbed #dij #iaddhb #ijj #afeb -#ea4a -#fj -#gf #e4jj #da #aje4hcb4h #ia #aie4h #dhh #iaj #afgj -#de4f -#ej -#eh #e4ef #db #ajg4fcc4c #ib #aig4f #dic #ibj #afhh -#dj4j -#dj -#dj #f4aa #dc #aji4dcc4i #ic #aii4d #dii #icj #agjf -#cd4d -#cj -#bb #f4fg #dd #aaa4bcd4d #id #bja4b #ejd #idj #agbd -#bh4i -#bj #d #g4bb #de #aac4jce4j #ie #bjc4j #eaj #iej #agdb -#bc4c -#aj #ad #g4gh #df #aad4hce4f #if #bjd4h #eaf #ifj #agfj -#ag4h #j #cb #h4cc #dg #aaf4fcf4a #ig #bjf4f #eba #igj #aggh #h4hi #dh #aah4dcf4g #ih #bjh4d #ebg #ihj #agif #i4dd #di #abj4bcg4b #ii #baj4b #ecb #iij #ahad #cg4h #ajj #bab4j #ech #ajjj #ahcb ---------------------------------------- ---------------------------------- ---------------------------------------- ------------------------ #ajjj to #bjjj #bjjj to #cjjj ---------------------------------------- ----------------------- ,c4 ,f4 ,c4 ,f4 ,c4 ,f4 ,c4 ,f4 ---------------------------------------- --------------------- #ech #ajjj #ahcb #haf #aejj #bgcb #ajic #bjjj #cfcb #acga #bejj #decd #edc #ajaj #ahej #hba #aeaj #bgej #ajii #bjaj #cfej #acgg #beaj #deeb #edi #ajbj #ahfh #hbg #aebj #bgfh #aajd #bjbj #cffh #achb #bebj #defj #eed #ajcj #ahhf #hcb #aecj #bghf #aaaj #bjcj #cfhf #achh #becj #dehh #efj #ajdj #aijd #hch #aedj #bhjd #aaaf #bjdj #cgjd #acic #bedj #dfjf #eff #ajej #aibb #hdc #aeej #bhbb #aaba #bjej #cgbb #acii #beej #dfbb #ega #ajfj #aidj #hdi #aefj #bhdj #aabg #bjfj #cgdj #adjd #befj #dfdj #egg #ajgj #aieh #hed #aegj #bheh #aacb #bjgj #cgeh #adaj #begj #dfeh #ehb #ajhj #aigf #hfj #aehj #bhgf #aach #bjhj #cggf #adaf #behj #dfgf #ehh #ajij #aiid #hff #aeij #bhid #aadc #bjij #cgid #adba #beij #dfid #eic #aajj #bjab #hga #afjj #biab #aadi #bajj #chab #adbg #bfjj #dgab #eii #aaaj #bjcj #hgg #afaj #bicj #aaed #baaj #chcj #adcb #bfaj #dgcj #fjd #aabj #bjdh #hhb #afbj #bidh #aafj #babj #chdh #adch #bfbj #dgdh #faj #aacj #bjff #hhh #afcj #biff #aaff #bacj #chff #addc #bfcj #dgff #faf #aadj #bjhd #hic #afdj #bihd #aaga #badj #chhd #addi #bfdj #dghd #fba #aaej #bajb #hii #afej #cjjb #aggg #baej #cijb #aded #bfej #dhjb #fbg #aafj #babj #ijd #affj #cjbj #aahb #bafj #cibj #adfj #bffj #dhbj #fcb #aagj #bach #iaj #afgj #cjch #aahh #bagj #cich #adff #bfgj #dhch #fch #aahj #baef #iaf #afhj #cjef #aaic #bahj #cief #adga #bfhj #dhed #fdc #aaij #bagd #iba #afij #cjgd #aaii #baij #cigd #adgg #bfij #dhgf #fdi #abjj #baib #ibg #agjj #cjib #abjd #bbjj #ciib #adhb #bgjj #dhib #fed #abaj #bbaj #icb #agaj #caaj #abaj #bbaj #djaj #adhh #bgaj #diaj #ffj #abbj #bbbh #ich #agbj #cabh #abaf #bbbj #djbh #adic #bgbj #dibh #fff #abcj #bbdf #idc #agcj #cadf #abba #bbcj #djdf #adii #bgcj #didf #fga #abdj #bbfd #idi #agdj #cafd #abbg #bbdj #djfd #aejd #bgdj #difd #fgg #abej #bbhb #ied #agej #cahb #abcb #bbej #djhb #aeaj #bgej #dihb #fhb #abfj #bcjj #ifj #agfj #cbjj #abch #bbfj #dajj #aeaf #bgfj #ejjj #fhh #abgj #bcah #iff #aggj #cbah #abdc #bbgj #daah #aeba #bggj #ejah #fic #abhj #bccf #iga #aghj #cbcf #abdi #bbhj #dacf #aebg #bghj #ejcf #fii #abij #bced #igg #agij #cbed #abed #bbij #daed #aecb #bgij #ejed #gjd #acjj #bcgb #ihb #ahjj #cbgb #abfj #bcjj #dagb #aech #bhjj #ejgb #gaj #acaj #bcij #ihh #ahaj #cbij #abff #bcaj #daij #aedc #bhaj #ejij #gaf #acbj #bdjh #iic #ahbj #ccjh #abga #bcbj #dbjh #aedi #bhbj #eajh #gba #accj #bdbf #iii #ahcj #ccbf #abgg #bccj #dbbf #aeed #bhcj #eabf #gbg #acdj #bddd #ajjd #ahdj #ccdd #abhb #bcdj #dbdd #aefj #bhdj #eadd #gcb #acej #bdfb #ajaj #ahej #ccfb #abhh #bcej #dbfb #aeff #bhej #eafb #gch #acfj #bdhj #ajaf #ahfj #cchj #abic #bcfj #dbhj #aega #bhfj #eahj #gdc #acgj #bdih #ajba #ahgj #ccih #abii #bcgj #dbih #aegg #bhgj #eaih #gdi #achj #beaf #ajbg #ahhj #cdaf #acjd #bchj #dcaf #aehb #bhhj #ebaf #ged #acij #becd #ajcb #ahij #cdcd #acaj #bcij #dccd #aehh #bhij #ebcd #gfj #adjj #beeb #ajch #aijj #cdeb #acaf #bdjj #dceb #aeic #bijj #ebeb #gff #adaj #begj #ajdc #aiaj #cdgj #acba #bdaj #dcgj #aeii #biaj #ebgj #gga #adbj #behh #ajdi #aibj #cdhh #acbg #bdbj #dchh #afjd #bibj #ebhh #ggg #adcj #bfjf #ajed #aicj #cejf #accb #bdcj #ddjf #afaj #bicj #ecjf #ghb #addj #bfbd #ajfj #aidj #cebd #acch #bddj #ddbd #afaf #bidj #ecbd #ghh #adej #bfdb #ajff #aiej #cedb #acdc #bdej #dddb #afba #biej #ecdb #gic #adfj #bffj #ajga #aifj #cefj #acdi #bdfj #ddfj #afbg #bifj #ecfj #gii #adgj #bfgh #ajgg #aigj #cegh #aced #bdgj #ddgh #afcb #bigj #ecgh #hjd #adhj #bfif #ajhb #aihj #ceif #acfj #bdhj #ddif #afch #bihj #ecif #haj #adij #bgad #ajhh #aiij #cfad #acff #bdij #dead #afdc #biij #edad #ajic #bjjj #cfcb #afdi #cjjj #edcb ---------------------------------------- ----------------------- ,,note4--,the numbers in bold face type refer to the temperature either in degrees ,centigrade or ,fahrenheit which it is desired to convert into the other scale4 ,if converting from ,fahrenheit degrees to ,centigrade degrees the equivalent temperature will be found in the left column1 while if converting from degrees ,centigrade to degrees ,fahrenheit1 the answer will be found in the column on the right4 ,these tables are a revision of those by ,sauveur ,boylston1 metallurgical engineers1 ,cambridge1 ,mass4 ,copyright1 #aibj4 ,,interpolation ,,factors ,c4 ,f4 ,c4 ,f4 #j4ef #a #a4h #c4cc #f #aj4h #a4aa #b #c4f #c4hi #g #ab4f #a4fg #c #e4d #d4dd #h #ad4d #b4bb #d #g4b #e4jj #i #af4b #b4gh #e #i4j #e4ef #aj #ah4j ,those using pyrometers will find this and the preceding conversion table of great convenience3 ,,table #cc4--;,,comparison ,,between ,,degrees ,,centigrade ,,and ,,degrees ,,fahrenheit ---------------------------------------- --------------------------------- ,degrees ,degrees ,degrees ,degrees ,degrees ,degrees ,degrees ---------------------------------------- --------------------------- ,f4 ,c4 ,f4 ,c4 ,f4 ,c4 ,f4 ,c4 ,f4 ,c4 ,f4 ,c4 ,f4 ,c4 ---------------------------------------- -------------------- -#dj-dj4j #c-af4a #df #g4g #hi #ca4facb #ee4eage #gi4d #bge #ace4j -#ci-ci4d #d-ae4e #dg #h4c #ij #cb4bacc #ef4aagf #hj4j #cjj #adh4h -#ch-ch4h #e-ae4j #dh #h4h #ia #cb4gacd #ef4fagg #hj4e #cbe #afb4g -#cg-ch4c #f-ad4d #di #i4c #ib #cc4cace #eg4bagh #ha4a #cej #agf4f -#cf-cg4g #g-ac4h #ej #aj4j #ic #cc4iacf #eg4gagi #ha4f #cge #aij4e -#ce-cg4b #h-ac4c #ea #aj4e #id #cd4dacg #eh4cahj #hb4b #djj #bjd4d -#cd-cf4f #i-ab4g #eb #aa4a #ie #ce4jach #eh4haha #hb4g #dbe #bah4c -#cc-cf4a #aj-ab4b #ec #aa4f #if #ce4eaci #ei4dahb #hc4c #dej #bcb4b -#cb-ce4e #aa-aa4f #ed #ab4b #ig #cf4aadj #fj4jahc #hc4h #dge #bdf4a -#ca-ce4j #ab-aa4a #ee #ab4g #ih #cf4fada #fj4eahd #hd4d #ejj #bfj4j -#cj-cd4d #ac-aj4e #ef #ac4c #ii #cg4badb #fa4aahe #he4j #ebe #bgc4h -#bi-cc4i #ad-aj4j #eg #ac4hajj #cg4gadc #fa4fahf #he4e #eej #bhg4g -#bh-cc4c #ae -#i4c #eh #ad4daja #ch4cadd #fb4bahg #hf4a #ege #cja4f -#bg-cb4g #af -#h4h #ei #ae4jajb #ch4hade #fb4gahh #hf4f #fjj #cae4e -#bf-cb4b #ag -#h4c #fj #ae4eajc #ci4dadf #fc4cahi #hg4b #fbe #cbi4d -#be-ca4f #ah -#g4g #fa #af4aajd #dj4jadg #fc4haij #hg4g #fej #cdc4c -#bd-ca4a #ai -#g4b #fb #af4faje #dj4eadh #fd4daia #hh4c #fge #ceg4b -#bc-cj4e #bj -#f4f #fc #ag4bajf #da4aadi #fe4jaib #hh4h #gjj #cga4a -#bb-cj4j #ba -#f4a #fd #ag4gajg #da4faej #fe4eaic #hi4d #gbe #che4j -#ba-bi4d #bb -#e4e #fe #ah4cajh #db4baea #ff4aaid #ij4j #gej #cih4h -#bj-bh4h #bc -#e4j #ff #ah4haji #db4gaeb #ff4faie #ij4e #gge #dab4g -#ai-bh4c #bd -#d4d #fg #ai4daaj #dc4caec #fg4baif #ia4a #hjj #dbf4f -#ah-bg4g #be -#c4h #fh #bj4jaaa #dc4haed #fg4gaig #ia4f #hbe #ddj4e -#ag-bg4b #bf -#c4c #fi #bj4eaab #dd4daee #fh4caih #ib4b #hej #ded4d -#af-bf4f #bg -#b4g #gj #ba4aaac #de4jaef #fh4haii #ib4g #hge #dfh4c -#ae-bf4a #bh -#b4b #ga #ba4faad #de4eaeg #fi4dbjj #ic4c #ijj #dhb4b -#ad-be4e #bi -#a4f #gb #bb4baae #df4aaeh #gj4jbja #ic4h #ibe #dif4a -#ac-be4j #cj -#a4a #gc #bb4gaaf #df4faei #gj4ebjb #id4d #iej #eaj4j -#ab-bd4d #ca -#j4e #gd #bc4caag #dg4bafj #ga4abjc #ie4j #ige #ebc4h -#aa-bc4h #cb -#j4j #ge #bc4haah #dg4gafa #ga4fbjd #ie4ea1jjj #ecg4g -#aj-bc4c #cc #j4e #gf #bd4daai #dh4cafb #gb4bbje #if4aa1ajj #eic4c -#i-bb4g #cd #a4a #gg #be4jabj #dh4hafc #gb4gbjf #if4fa1bjj #fdh4h -#h-bb4b #ce #a4f #gh #be4eaba #di4dafd #gc4cbjg #ig4ba1cjj #gjd4d -#g-ba4f #cf #b4b #gi #bf4aabb #ej4jafe #gc4hbjh #ig4ga1djj #gfj4j -#f-ba4a #cg #b4g #hj #bf4fabc #ej4eaff #gd4dbji #ih4ca1ejj #hae4e -#e-bj4e #ch #c4c #ha #bg4babd #ea4aafg #ge4jbaj #ih4ha1fjj #hga4a -#d-bj4j #ci #c4h #hb #bg4gabe #ea4fafh #ge4ebaa #ii4da1gjj #ibf4f -#c-ai4d #dj #d4d #hc #bh4cabf #eb4bafi #gf4ababajj4ja1hjj #ihb4b -#b-ah4h #da #e4j #hd #bh4habg #eb4gagj #gf4fbacajj4ea1ijja1jcg4g -#a-ah4c #db #e4e #he #bi4dabh #ec4caga #gg4bbadaja4ab1jjja1jic4c #j-ag4g #dc #f4a #hf #cj4jabi #ec4hagb #gg4gbaeaja4fb1ajja1adh4h #a-ag4b #dd #f4f #hg #cj4eacj #ed4dagc #gh4cbbeajg4bb1bjja1bjd4d #b-af4f #de #g4b #hh #ca4aaca #ee4jagd #gh4hbejaba4ab1cjja1bfj4j ---------------------------------------- --------------------------------- #i x degrees ,c4 ,degrees ,fahrenheit -------------- #cb #e #e x 7degrees ,f4 - #cb7 ,degrees ,centigrade --------------------- #i ,three other useful tables are also given on the following pages4 ,,table #cd4--,,weight ,,of ,,round1 ,,octagon ,,and ,,square ,,carbon ,,tool ,,steel ,,per ,,foot ---------------------------------------- -------------------------------- ,size ,size in ,round ,octagon ,square in ,round ,octagon ,square inches inches ---------------------------------------- ------------------------- #a_/af #j4jaj #j4jaa #j4jac #b-a_/b #af4gi #ag4ga #ba4cg #a_/h #j4jdb #j4jdd #j4jec #b-e_/h #ah4ea #ai4eb #bc4ef #c_/af #j4jid #j4jii #j4abj #b-c_/d #bj4ca #ba4db #be4hf #a_/d #j4afh #j4agg #j4bad #b-g_/h #bb4bj #bc4da #bh4bg #e_/af #j4bfb #j4bgg #j4ccd #c #bd4ag #be4ej #cj4gh #c_/h #j4cgh #j4cih #j4dha #c-a_/h #bf4bc #bg4ff #cc4dj #g_/af #j4ead #j4edb #j4fee #c-a_/d #bh4cg #bi4ib #cf4ab #a_/b #j4fga #j4gjh #j4hee #c-c_/h #cj4ei #cb4bg #ch4ie #i_/af #j4hej #j4hif #a4jhb #c-a_/b #cb4ij #cd4gj #da4hi #e_/h #a4jdi #a4ajg #a4ccf #c-e_/h #ce4bi #cg4bc #dd4id #aa_/af #a4bgj #a4cci #a4faf #c-c_/d #cg4gg #ci4hd #dh4ji #c_/d #a4eaa #a4eid #a4ibd #c-g_/h #dj4cc #db4ed #ea4ce #ac_/af #a4ggc #a4hgj #b4beh #d #db4ig #de4cd #ed4gb #g_/h #b4jef #b4afi #b4fah #d-a_/d #dh4ea #ea4ag #fa4gg #ae_/af #b4cfa #b4dij #c4jjf #d-a_/b #ed4ci #eg4cg #fi4be #a #b4fhf #b4hcc #c4dbj #d-c_/d #fj4fj #fc4ib #gg4af #a-a_/h #c4cii #c4ehe #d4cbh #e #fg4ae #gj4hc #he4ej #a-a_/d #d4aig #d4dbg #e4cdd #e-a_/d #gd4jc #gh4jh #id4bf #a-c_/h #e4jgh #e4cef #f4fdf #e-a_/b #ha4be #he4gj #ajc4de #a-a_/b #f4jdd #f4cgd #g4fie #e-c_/d #hh4hj #ic4fg #aac4jg #a-e_/h #g4jic #g4dha #i4jca #f #if4fi #aja4ii #abc4ab #a-c_/d #h4bbf #h4fgd #aj4dgd #g #aca4fa #ach4hb #afg4eh #a-g_/h #i4ddc #i4ifj #ab4jbc #h #aga4ij #aha4cb #bah4hh #b #aj4gdd #aa4ccb #ac4fhj #i #bag4eg #bbi4dh #bgg4jb #b-a_/h #ab4abi #ab4gic #ae4ddc #aj #bfh4fj #bhc4ca #cdb4jj #b-a_/d #ac4eih #ad4cdc #ag4cad #aa #cbe4ja #cdb4hj #dac4hb #b-c_/h #ae4aea #ae4iha #ai4bia #ab #chf4gi #djg4ig #dib4dh ---------------------------------------- -------------------------------- ,high-speed steel1 being more dense than carbon steel1 weighs from #aj to #aa per cent more than carbon steel4 ,this should be added to figures given in the table4 ,,table #ce4--,,weight ,,of ,,round1 ,,carbon ,,tool ,,steel #ab ,,in4 ,,in ,,diameter ,,and ,,larger1 ,,per ,,foot ---------------------------------------- ---------------------------- ,diameter1 ,weight ,diameter1 ,weight ,diameter1 ,weight inches per foot inches per foot inches per foot ---------------------------------------- ----------------------- #ab #chf4gij #ae-g_/h #fgg4ebg #ai-c_/d #a1jdi4jaj #ab-a_/h #cie4eah #af #fhg4fjj #ai-g_/h #a1jfa4gje #ab-a_/d #djd4bdf #af-a_/h #fii4jag #bj #a1jgd4djj #ab-c_/h #dab4igd #af-a_/d #gaj4dce #bj-a_/h #a1jhh4ejb #ab-a_/b #dba4gjb #af-c_/h #gba4heb #bj-a_/d #a1ajb4fje #ab-e_/h #dcj4dcj #af-a_/b #gcc4bgj #bj-c_/h #a1aaf4gjg #ab-c_/d #dci4aeh #af-e_/h #gdd4fhg #bj-a_/b #a1acj4haj #ab-g_/h #ddg4hhf #af-c_/d #gef4aje #bj-e_/h #a1add4iab #ac #def4fae #af-g_/h #gfg4ebb #bj-c_/d #a1aei4jae #ac-a_/h #dfe4cdc #ag #ggh4idj #bj-g_/h #a1agc4aah #ac-a_/d #dgd4jga #ag-a_/h #gij4ceh #ba #a1ahg4bbj #ac-c_/h #dhb4gii #ag-a_/d #hja4ggg #ba-a_/h #a1bja4cbb #ac-a_/b #dia4ebg #ag-c_/h #hac4aie #ba-a_/d #a1bae4dbe #ac-e_/h #ejj4bee #ag-a_/b #hbd4fad #ba-c_/h #a1bbi4ebg #ac-c_/d #ejh4ihc #ag-e_/h #hcf4jcj #ba-a_/b #a1bdc4fcj #ac-g_/h #eag4gaa #ag-c_/d #hdg4ddg #ba-e_/h #a1beg4gcb #ad #ebf4ddj #ag-g_/h #heh4hfc #ba-c_/d #a1bga4hce #ad-a_/h #ecf4eab #ah #hgj4bhj #ba-g_/h #a1bhe4icg #ad-a_/d #edf4ehe #ah-a_/h #hhc4aje #bb #a1cjj4jdj #ad-c_/h #eef4feg #ah-a_/d #hie4ibj #bb-a_/h #a1cae4dhe #ad-a_/b #eff4gcj #ah-c_/h #ijh4gdj #bb-a_/d #a1ccj4icj #ad-e_/h #egf4hjb #ah-a_/b #iba4efj #bb-c_/h #a1cdf4cge #ad-c_/d #ehf4hge #ah-e_/h #icd4chj #bb-a_/b #a1cfa4hbj #ad-g_/h #eif4idg #ah-c_/d #idg4bjj #bb-e_/h #a1cgg4bfe #ae #fjg4jbj #ah-g_/h #ifj4jbj #bb-c_/d #a1cib4gaj #ae-a_/h #fag4jib #ai #igb4hdj #bb-g_/h #a1djh4aee #ae-a_/d #fbg4afe #ai-a_/h #ihe4jce #bc #a1dbc4fjj #ae-c_/h #fcg4bcg #ai-a_/d #iih4bcj #bc-a_/h #a1ded4dij #ae-a_/b #fdg4caj #ai-c_/h #a1jaj4ibe #bc-a_/d #a1dhe4chj #ae-e_/h #feg4chb #ai-a_/b #a1jbc4fbj #bc-c_/h #a1eaf4bgj #ae-c_/d #ffg4dee #ai-e_/h #a1jcf4cae #bd #a1edg4afj ---------------------------------------- ---------------------------- ,to find the weight of discs made of carbon steel1 in diameters up to and including #ab in41 without any allowance for finishing multiply the per foot weight of round bar steel1 shown herewith by the decimal equivalent of a foot given in the following table3 ,,table #cf4--;,,decimal ,,equivalents ,,of ,a ,,foot ---------------------------------------- ----------------------------- ,in4 #j #a_/h #a_/d #c_/h #a_/b #e_/h #c_/d #g_/h ---------------------------------------- --------------------- #j #j4jjj #j4jaj #j4jba #j4jca #j4jdb #j4jeb #j4jfc #j4jgc #a #j4jhc #j4jid #j4ajd #j4aae #j4abe #j4ace #j4adf #j4aef #b #j4afg #j4agg #j4ahh #j4aih #j4bjh #j4bai #j4bbi #j4bdj #c #j4bej #j4bfj #j4bgj #j4bha #j4bib #j4cjb #j4cac #j4cbc #d #j4ccc #j4cdd #j4ced #j4cfd #j4cge #j4che #j4cif #j4djf #e #j4daf #j4dbg #j4dcg #j4ddh #j4deh #j4dfi #j4dgi #j4dhj #f #j4ejj #j4eaj #j4ebj #j4eca #j4edb #j4eeb #j4efc #j4egc #g #j4ehc #j4eid #j4fjd #j4fae #j4fbe #j4fce #j4fdf #j4fef #h #j4fff #j4fgg #j4fhg #j4fih #j4gjh #j4gai #j4gbi #j4gdj #i #j4gej #j4gfj #j4ggj #j4gha #j4gib #j4hjb #j4hac #j4hbc #aj #j4hcc #j4hdd #j4hed #j4hfe #j4hge #j4hhe #j4hif #j4ijf #aa #j4iaf #j4ibg #j4icg #j4idh #j4iec #j4ifi #j4igi #j4iij ---------------------------------------- ----------------------------- ,,example4--,if the weight of a carbon steel disc #g in4 diameter1 #a-e_/h in4 thick is desired1 turn to page #bcc1 where the per foot weight of #g in4 round is given as #aca4f lb4 ,multiply this by the decimal equivalent of #a-e_/h in41 or #j4ace1 as shown in the above table1 and the product will be the net weight of the disc4 #aca4fa lb4 the weight of #a ft4 of #g in4 round4 #j4ace the per foot decimal equivalent of #a-e_/h in3 ------------ #fehje #cidhc #acafa ------------ #ag4gfgce lb4 weight of disc #g in4 diam4 #a-e_/h in4 thick without any allowance for finishing4 ,,authorites ,,quoted ,a ,,addis1 ,w ,h4 ,,american ,,machinists' ,,handbook ,,american ,,steel ,,trearers' ,,society ,,american ,,gear ,,mfrs4 ,,asso4 ,,automatic ,,and ,,electric ,,furnaces ,,ltd4 ,,arnold1 ,,prof4 ,j4 ,o4 ,b ,,burleigh1 ,r4 ,w4 ,,borden1 ,b4 ,,boker1 ,,herman ,co4 ,,brown ,,instrument ,co4 ,,brown-,,lipe-,,chaplin ,co4 ,c ,,campbell1 ,h4 ,h4 ,,carhart1 ,h4 ,a4 ,,clayton1 ,c4 ,y4 ,,curtis ,,airplane ,co4 ,e ,,englehard1 ,,charles ,,ensaw1 ,,howard ,f ,,firth-,,sterling ,,steel ,co4 ,,firth1 ,,thomas ,,sons ,,fowler1 ,,henry ,g ,,gilbert ,,barker ,h ,,haywahd1 ,c4 ,r4 ,,howe1 ,,dr4 ,h4 ,m4 ,,hoover ,,steel ,,ball ,,co4 ,,heathcote1 ,h4 ,l4 ,,harris1 ,,matthew ,,hunter1 ,j4 ,v4 ,j ,,janitzky1 ,e4 ,j4 ,,johnston1 ,a4 ,b4 ,,juthe1 ,k4 ,a4 ,l ,,latrobe ,,steel ,,co4 ,,ludlum ,,steel ,,co4 ,,leeds ,,northrup ,,co4 ,,lyman1 ,w4 ,h4 ,m ,,mansfield1 ,c4 ,a4 ,,midvale ,,steel ,co4 ,mc,k,e,n,n,a1 ,,roy ,c4 ,,moulton1 ,,seth ,a4 ,n ,,niles1 ,,bement1 ,,pond ,p ,,parker1 ,s4 ,w4 ,,poole1 ,c4 ,r4 ,r ,,rawdon1 ,h4 ,s4 ,s ,s4 ,a4 ,e4 7,,society ,,automotive ,,engineers7 ,,sauveur1 ,,albert ,,springfield ,,armory ,,sellack1 ,t4 ,g4 ,,smith1 ,a4 ,j4 ,,shirley1 ,,alfred ,j4 ,t ,,taylor ,,instrument ,co4 ,,thum1 ,e4 ,e4 ,,tiemann1 ,h4 ,p4 ,u ,u4 ,s4 ,,ball ,,bearing ,co4 ,,united ,,steel ,co4 ,,underwood1 ,,charles ,n4 ,v ,,van ,,de ,,venter1 ,,john ,h4 ,w ,,walp1 ,h4 ,o4 ,,wood1 ,,harold ,f4 ,,wheelock1 ,,lovejoy ,co4 ,,index ,a ,,abc of iron and steel ,absorption of carbon1 rate of ,air hardening steels ,analysis of high speed steel ,allotropic modifications ,alloy steel1 annealing properties of ,alloys and their effect in high speed steel in steel1 value of upon steel ,alpha iron ,annealing care in furnace high-chromium steel high speed tools in bone methods proper rifle components rust-proof steel steels temperature ,arrests ,austentite ,automotive industry1 application of ,liberty engine materials to temperature control ,axles1 heat treatment of ,b ,balls1 making steel ,barium chloride process ,baths for tempering ,bessemer converter ,beta iron ,blending compounds ,blister steel ,blue brittleness ,bone1 annealing in ,boxes for case hardening or carburizing ,breaking test gears ,brinell hardness ,broach hardening furnace ,brown automatic pyrometer ,burning ,c ,calorized tubes ,carbon content at various temperatures content of case hardened work in cast iron1 ix in tool steel introduction of penetration of steel steel forgings1 ,liberty engine steel tools steels1 ,s4 ,a4 ,e4 steels1 temper colors strengthens iron tool steel1 forging ,carbonizing1 see ,carburizing ,carborundum tubes ,carburization1 preventing ,carburizing by gas boxes compounds gas consumption by local material nickel steel or case hardening pots for ,carburizing1 process of short method sleeves with charcoal ,see ,case hardening ,car door type of furnace ,case1 depth of ,case hardening boxes cast iron local or surface carburizing treatments for various steels see ,carburizing ,cast iron1 carbon in case hardening ,cementite ,center column furnace ,centigrade table ,chamotte tubes ,chart of carbon penetration heat treatment shape ,chrome steel ,chrome-nickel steel steel1 forging ,chrome-vanadium steel ,chromium steels1 ,s4 ,a4 ,e4 ,chromium-cobalt steel ,chromium-vanadium steel1 ,s4 ,a4 ,e4 ,classification of steel ,clay tubes ,cold end compensator junction errors shortness worked steel ,color in tempering ,colors on carbon steels ,combination tank ,comparison of fuels ,compensating leads ,compensator for cold ends automatic ,composition of steel ,compound1 blending separating from work ,compounds for carburizing ,connecting rods1 ,liberty motor ,continuous heating furnace ,converter1 ,bessemer ,cooling curves ,cooling quenching oil1 roof system rate of1 for gear-forgings ,copper1 effect of1 in medium carbon steel ,copper-plating to prevent carburizing ,corrosion of high-chromium steel of rust-proof steel ,corundite tubes ,cost of operating furnaces ,cracks in hardening1 preventing ,crankshaft1 ,liberty motor ,critical point ,crucible or tool steel ,cutting off high speed steel ,cyanide bath for tool steel ,d ,decarbonizing of outer surface preventing ,depth of case ,detrimental elements in steel ,dies1 drop forging quenching soft spots in tempering round ,drawing ends of gear teeth ,drop forging dies ,ductility ,e ,effect of alloys of different carburizing material of size of piece of copper in medium carbon steel ,elastic limit ,electric process of steel making ,electrode ,elements1 chemical ,elongation ,endurance limit ,energizer1 #ha ,enlarging steel ,equipment for heat treating ,eutectoid ,f ,fahrenheit temperature table ,fatigue test ,ferrite ,file test ,flame shields ,flange shields for furnaces ,forging furnace high speed tools improper of steel practice1 heavy rifle barrels ,forgings1 carbon steel ,liberty engine ,formed tools1 high speed ,fractures1 examining by ,furnace1 continuous heating crucible data electric ,heroult open hearth records ,furnaces annealing broach hardening car door type center column cost of operating data on forging1 heavy fuels for gas fired high speed steel lead pot manganese steel muffle oil fired operating costs screens for tool ,furnaces1 water cooled fronts ,fuels1 comparison of for furnaces ,g ,gages1 changes due to quenching tempering ,gamma iron ,gas1 carburizing by consumption for carburizing fired furnace illuminating1 for carburizing ,gear blanks1 heat treatment of forgings1 rate of cooling for ,liberty engine hardening machine steel1 transmission teeth1 drawing ends of ,gears1 ,liberty engine ,gleason tempering machine ,grade of steel ,grain1 refining size ,graphitic carbon ,grinding high speed steel ,h ,hair lines in forgings ,hardening carbon steel for tools cracks1 preventing dies gears high speed steel high speed tools of high-chromium steel of rust-proof steel room1 modern ,hardness tests ,heating1 effect of size for forging ,heat1 judging by color treating departments equipment forgings inspection of ,liberty motor ,heat treating1 of axles of chisels of gears of high speed steel of steel ,s4 ,a4 ,e4 ,heat treatment ,heroult furnace ,high-chromium steel annealing of corrosion of hardening of ,highly stressed parts of ,liberty engine ,high speed steel1 analysis of annealing cutting off forging furnace hardening heat treatment of instructions for manufacture pack hardening structure of ,hints for steel users ,i ,illuminating gas for carburizing ,impact test ,improper forging ,influence of size on heating ,inspection of heat treatment ,internal stresses1 relieving ,introduction of carbon ,j ,jewelers' tools ,judging heat of steel by color ,l ,latent heat ,lathe and planer tools tools1 high speed ,latrobe temper list ,lead bath pot furnace ,leeds ,northrup potentiometer optical pyrometer ,liberty engine1 highly stressed parts of ,liberty engine materials1 application to automotive industry motor connecting rods motor1 crankshaft motor piston pin ,local case hardening ,luting mixture ,m ,machineability of steel ,machinery steel1 annealing ,magnet test ,making steel in electric furnace ,manganese steel furnace ,manufacture of high speed steel ,marquardt mass tubes ,martensite ,medium carbon steel1 effect of copper on ,metallography ,microphotographs ,microscopic examination ,milling cutters1 high speed ,mixture for luting ,modern hardening room ,molten metal pyrometers ,molybdenum ,muffle furnace ,n ,nickel ,nickel-chromium steel steels1 ,s4 ,a4 ,e4 ,nickel1 influence of1 on steel steel affinity for carbon steels1 ,s4 ,a4 ,e4 ,non-homogeneous melting ,non-shrinking steels ,normalizing ,o ,oil bath for tempering cooling on roof fired furnace hardening steel1 forging steels temperature of quenching ,open hearth furnace ,operating costs of furnaces ,outer surface decarbonizer ,over-heated steel1 restoring ,overheating dies ,p ,pack-hardening high speed steel ,packing work for carburizing ,paste for hardening dies ,pearlite ,penetration of carbon carbon1 chart of in case hardening ,phosphorus ,pickling ,liberty motor forgings ,pig iron ,piston pin1 ,liberty motor ,placing pyrometers ,planer tools1 high speed ,points of carbon in steel ,potentiometer1 ,leeds ,northrup ,pots for carburizing ,press for testing gears ,preventing carburization cracks in hardening ,properties of alloy steels of alloy steels1 table of steel ,protective screens for furnaces ,puddled iron ,punches and chisels1 steels for ,pyrometers calibration copper ball indicating inspection iron ball molten metal optical placing recording ,siemens testing water ,q ,quality and structure of high speed steel of steel ,quenching1 after carburizing dies in tank obsolete method oil1 temperature of tank tool steel ,r ,rate of absorption of carbon ,recording temperatures ,red shortness ,refining the grain ,regenerative open hearth furnace ,restoring overheated steel ,rifle barrels1 forging components1 annealing ,roof system of cooling oil ,rust-proof steel annealing of corrosion of hardening of ,s ,s4 ,a4 ,e4 carbon steels chromium steels chromium-vanadium heat treatments nickel-chromium steels nickel steels screw stock silico-manganese steel standard steels ,salt bath for tempering ,scleroscope test ,scratch hardness ,screens for furnaces ,screw stock1 ,s4 ,a4 ,e4 ,sensible heat ,sentinels1 melting of ,separating work from compound ,shields for furnace doors ,shore ,scleroscope ,short method of carburizing ,shrinking steel ,silica tubes ,silico-manganese steels1 ,s4 ,a4 ,e4 ,silicon ,silversmiths' tools ,size of piece1 effect of ,slags ,sleeves1 carburizing hardening and shrinking shrinking ,solid solution ,sorbite ,specimens1 test ,standard ,s4 ,a4 ,e4 steels ,steel1 balls1 stock for bolts1 making composition of deoxidation for chisels and punches forging of give it a chance heat treatment of high speed making ,bessemer process crucible process electric furnace process open hearth tools1 carbon1 in users' hints ,structure of high speed steel ,sulphur ,t ,tables1 air1 oil and water hardened steel alloy steels1 properties of carbon content carbon steels case hardening changes due to quenching chromium steels chromium-vanadium steels colors and temperature composition of steels cost of furnaces effect of size fuels1 comparison of high-chromium steel nickel-chromium steels nickel steels operating cost of furnaces production cost of furnaces ,s4 ,a4 ,e4 steels screw stock silico-manganese steels stock for balls temperature conversion tempering temperatures weight of steel ,tank for quenching dies ,taylor instruments ,temper1 colors of list1 ,latrobe of steel ,temperature recorders tables ,temperatures for tempering ,tempering colors on carbon steels gages high speed tools machine1 ,gleason round dies temperatures theory of ,tempers of carbon steel ,tensile test ,testing heat treatment ,tests of steel ,test specimens ,theory of tempering ,thermocouple base metal cold end placing protectors rare metal ,time for hardening ,tool furnace1 small ,tool or crucible steel1 annealing ,tool steel1 cyanide bath for quenching ,tools1 carbon in different carbon steel of high speed steel sulphur in tempers of various transformation points ,transmission gear steel ,treatments for various steels ,troosite ,tubes1 calorized carborundum ,chamotte clay ,marquardt mass silica ,tungsten steel ,u ,ultimate strength ,users of steel1 hints for ,v ,vanadium steel ,w ,water annealing cooled furnace fronts ,weight of steel bars ,working instructions for high speed steel ,wrought iron1 ix ,y ,yield ,point