3', 9,4 ,3“1,«?.2 . _A_ ll! HIll HI ‘ H 'K \ 3 I1! h m I, A PHYSICO - CHEMICAL STUDY .OF HOT-WORK TOOL STEELS WEEKS FEE THE DEGREE 0F MET. ENG.‘ Edwin A. Brophy . 1934 A Physico — Chemicel Study Of Hot - fork Tool Steele Theisie Submitted To The Faculty Of michigan State College In Partial Fulfillment Of The Recuirements For The Degree C) H) Metallurgical Engineer .a\ b v. ~IV , l . f . Q V' ¢’ Edwin A.Ernnhy ‘.\\L'X \(i. \ June 1934 f7) ’1‘ A C K N O W L D G M E N T S —--.---—_--—----‘---_--D—-~.I-- and gratitude to Professor Henry E. P"hlow for his kindness and helpful suggestions, also for his part in making this theisis possible. Also my appreciation and thanks to Tr Korean I. Stotz, Superintendent and Er John A. Nelson, Metallurgist, Breeburn Alloy Steel Corporation for samples, tests, and numerous suggestions. Their help cannot be stressed too highly. 94313 Hot Work Tool Steels A B S T R A C T --—--——-———-.~-.—--—- This thesis consists of: N 03 0 01 Typical analysis as used to-day. Discussion of the general factors to be considered in the application of such steels. Effects induced by the major alloying elements. A very comprehensive study of the physical prop— erties at normal (room) and elevated temperatures. Dilatometric change study by the Chevenard Dil- atometer. Photomicrographic study of the important types. The heat-treatment and particular application each type is best suited for. Hot work tool steels have been developed through industrial research over a long period of time. Therefore, the analysis involved seem to be legion. This of course is a decided disadvantage to menu- facturer as well as consumer. Each type developed seems to carry with it, in the natural course of time, several off-spring. The off-spring fortunately frequently means the death of the parent-analysis. The main types of analysis (13) are listed on the following page. It is to be noted that tungsten or chromium, usually both, are the main alloying elements in hot work steels. The effect of these elements is discussed separately. Nickel seems to have been somewhat neglected as an alloying element in hot work steels, but it is my opinion that future research will show the possibilities of both nickel and molybdenum for this class of work. Each analysis presents certain advantages for particular applications, but the large tonnage consumption is held to six or seven grades of steel. Therefore, these main types have been selected, and will be described in de— tail. Of the other grades the important points only will be mentioned. o.m\m.H OM\om. . u t - OM\mH. = om\om.flaasvoa. ma . n u u . o.M\om.m mM\om. = o~\om. om\oa. ms . n u n . o.ma\oo.ms ma\oa. = om\0m. mM\om. as - u I .o.aa\o.mfl cm.\om. om.m\oo.m OM\mH. = OM\mH.. ma\oas OH . u . o.W\oo.m om.\0m. oo.w\oo.m mM\om. . OM\mH. oa\mm. o : o.H\mm. . o.m\ms.a om\om. ms.a\mm.a om\0m. = mm\ma. om\ma. m . QM\mH. .om.\oa. o.m\ms.e mm\ma. oo.m\mn.a o.H\ow. g mM\om. oa\om. N z u - o.m\m.H QM\om. om.H\0m.H o.H\ow. = 0m\om. Om\o:.. m s a n u u om.a\om.m oa\mm. = oa\om. mo.H\om m u I . o.mH\o.OH om\o~. om.M\oo.m mM\om. = OM\mH. mm\om. : u o.H\m~. m.a\o.: m.ma\m.sa o.H\mw. mm.:\m~.m OM\mH. = QM\mH. mm\om. m n OM\mH. - m.mfi\m.~H o.H\mm. mm.a\ms.m om.\ma. = QM\mH. mm\om. m u u a m.mfi\m.sa o.a\mm. mm.:\ms.m cm.\ma. mmo. OM\mH. m~\mm. H .................................................................. hmmmw--------------------- .sz .os .00 .a .p .Ho .Hm .msm .es .0 mass .mewafififi I mammaw A009 Mmoa Box Carbon: l$----- In plain carbon steel the effect is to 1 war the critical range, that is, the hardening; increase the tensile strength with a corresponding increase in brittleness. With the presence of alloys, especially tungsten, inherent 'brittleness is present, and usually develops as checks or cracks on the edges of the rolled or forged sections. In the iron-tungsten alloys a carbon content of .55 to .75% seems to forge with much greater ease and less loss than either low or high carbon percentages. Then the carbon falls much below .55% there is no particular trouble with exterior cracking, but there is a tendency for the internal structure to become stringy or fibrous. This type of structure is usually referred to as a woody structure, and it is possible that it is due to rejection of excess tungsten (Fe when an insufficiency of carbon W 3 2) is present to form the noreal tungsten carbides, - Fe W C 4 2 When higher carbon— greater than .75% — is present, there is an excess of large carbide globules, which mi ht account for the characteristic brittleness. It should be noted, that according to the research work of Sykes, a carbonless tungsten alloy of this type is hardenable, and vet is without allctropic modifications. The hardening in such cases is purely by particle pre- cipitation. When carbon is present it assumes the characteristics of steel and hardens by the regular martensitic method, that is, by cuenching. Without carbon the matrix is wholly ferrite. ACCOTd1W6.to Sykes these carbonless tungsten and molybd- denum alloys possess red-hardness after quenching and reheating t0 13000F, (2000 above the tempering temperature of high speed steel). The percentage of carbon in hot work steels has a decided effect on the Ar critical points. With approximately .7% carbon and 18% tungsten we have two well defired points on cooling, namely, Arl— 710°C and Ar 41000. (see dil- 8- atometric curve). With the same tungsten content and the carbon reduced to approximately .SOT there are stall two critical points on cooling; but the Arlis the more intense, whereas with the higher carbon the Ar2 showed the greater intensity. The Ar change is the point of transformation 2 to the martensitic phase, and of course is accompanied by a tremendous expansion. There does not seem to be any very positive or definite facts concerning the presence of vanadium in steel. It forms solid solutions with alpha iron, but less than 2% will completely eliminate the gamma form of iron. The presence of vanadium has little or no effect on the critical points. Vanadium, like silicon and manganese, has always been a benefit to steel in helping to cleanse and degasify it. It has also the marked tendency to control or nreven excessive grain growth while steel is at elevated temper- atures during working or heat treating. For this reason it is common practice, when extreme hardness is reouired, 1 (and vanadium is present) to increase toe tenperature for hardening. The depth of the case hardness is considerably increased by a small addition of vanadium. It is to be noted that large additions of this element are not necessary. In most, perhaps all steels, the percentage rarely exceeds 2%. This higher percentage is used only in a few special high speed steels. It is usually 1% or less. It is thouiht by many that the addition of a small amount of vanadium lends strength and endurance to working edges of the tools. This is undoubtedly true, but it is probably Yaiiéiee_£9223§i due to the limiting of the grain growth and increasing the homoyeneity, rather than any particular character- istic of vanadium. The forging and rolling of alloy steels containing vanadium is not affected to any appreciable degree by vanadium up to percentages of 2?. Vany mill men are of the Opinion that it helps forging, due to aiding solution of carbides at hiph temperatures. This is very problem- atical. EFFECTS OF ALLOYIJG ELE ENTS This element has gained much greater use of late in hot work and high speed steels. It is capable of lending strength and resistance at elevated temperatures. It forms a solid solution with alpha and gamma iron, and therefore, renders solid solution hardness to steels containing it. The effect on the critical points is very slight. Cf late the percentages used have greatly increased; some high speed steels containing up to 2?. The presence of cobalt in steels prose ts much trouble with decarburized soft skins. For some unknown reason the presence of cobalt enhances decarburization during working operations, especially when many reheatines are necessary. Depths of decarburization up to 1/16" are not uncommon. The evidence is that cobalt is not oxidized, but tungsten is oxidized and forms a yellow powder (W03?) on the forging tools. None of the salts of cobalt are yellow, whereas the color of tungstic acid (W01)1g an orange yellow. This condition never occurs in the absence of cobalt. Therefore, it might be likened to a catalytic action, - The cobalt acting as the catalytic agent. Cobalt (contd) The outside skin freouently runs as low as .10? carbon, and presents a problem for heat treating. This alloy is structurally weak, and while not much difficulty is encountered in forging, yet the outside decarburized skin when subjected to rolling, particular— ly in squares and flats, tears away at the corners, due to its absolute lack of tensile strength. This is why is it important to grind away the decarburized skin from the billets after h rdening and before rolling. (ll This element, like tungsten and chromium, offers much hardness at elevated temperatures. kolybdenum is gradually, but surely, destined to play a large roll in hot Bork and high speed steels of the future. In Syke's research he worked with iron-molygdenum and iron-tungsten alloys, and he found the behavior of molybdenum not unlike that of tungsten. much work has been done on substituting molybdenum for tungsten in high Speed and similar steels. It has been found that one part of molybdenum is equivalent to 2.5 parts tung- sten. The resulting steels are not quite the eoual of the tungsten steels for resistance to wear, but if need be they could be substituted. Molybdenum is better when used as an adjunct to tungsten and chromium. The increase in red hardness is ouite pronounced. The same decarburization trouble experienced in forging cobalt steels is presented with the working of molybdenum steels, only to a greater extent. Some think the soft skin Tie the result of oxidation of molybdenum to $00, k Molybdenum (5ontd) and its subsequent volatili7ation. I think the molybdenum acts similarly to the cobalt, that is, as a catalytic agent, and causes decarburi7ation. To prevent this "soft skin" forming it is necessary to forge under a neutral gas condition, or under a film of borax melted across the ingot. Teither of these methods are very practical in a steel mill. So until some method is found vhereby the soft skin can be prevented, it is hardly likely that molybdenum will ever disolace tungsten except, perhaps, as a war-time emergency owing to the scarcity of doxestic tungsten. EFFECTS OF ALL‘YIEG ELEE HTS --_--~_.‘.—-- ~——-—- -— _ - _- —._. Chromium There is nothing very definite on the action or effect of Chromium in hot work steels. It is, however, a valuable adjunct to tungsten in giving resistance to heat at elevated temperatures, sepecially the resistance to softening and erosive wear. It also increases the toughness somewhat. It is quite commonly thought that the presence of chromium has a tendency toward greater carbide solution, and in- creases the homogeneity of the grains. microscopic ex- amination of varying percentages of chromium shows a great change in the nature of the austenite grains. The critical points are not materially effected by high or low chromium percentages,- any change is simply due to sluggishness and atomic immobility induced by this element. In the working of steels containing chromium the effect is noticed with .50%, — it has a decided stiffening effect. This is due, as with tungsten, to atomic sluggishness. Chromium acts like tungsten in many respects,and a high chromium steel without tungsten resists heat effects re- markably well. It also induces air-hardening properties. A steel with 13% chromium (high carbon) air herdens to a (0213331 UL“. <0 0:139 > Rockwell C — 82, and resists exposure to high temoeratures reasonably well. Stainless steel at one tire was used extensively for hot work purposes. With chromium,es with tungsten, the forging is carried on very SlOle and cautiously to get the metal to "flow", and also is closely watched to prevent temperature from fall— ing to the air hardening range, - about l7OOOF. When the percentage of Or is above 8% with normal carbop the actual abrasive hardness of the chromium, together with its air hardening features, begin to present them- selves. The presence of Cr necessitates a much longer soaking temperature for forging and heat treating. This is probably due to the high specific heat of the alloy, and also the induced sluggishness from the Cr. Chromium, like tungsten, contributes deep hardening characteristics to the steel. The sluggishness of Cr alloys enables the steels to Tith- stand considerable heat due to its tendency, owing to atomic immobility, to inhibit the breaking down of the martensitic grains. EFFECTS OF ALLOYING ELEIEKTS ——-“‘---------.a-----’-—----- Tungsten The solubility of tungsten in iron varies with the % seems to temperature. At low temperatures 8 to 10? be the limit of solubility, while at elevated temp- eratures, approaching the melting point, the solubil- itv rises to nearly 35%. The tungsten that fails to v dissolve is precipitated as FeSWZ' When Csrbcn is 4320. The major element in present day hot work steels is present the tungsten forms the compound Fe tungsten, and it is also of major importance in develop- ing red—hardness and heat resistance. It forms a solid solution with iron. It has the ability of retaining its hardness at elevated temperatures, and for this reason is common in hot work tool steels. It has little or no effect on the critical points, although it is commonly thousht to raise them. Any change in the critical points is due to sluggishness caused by the highly alloyed condition of the steel, setting up atomic immobility. Also the diffusion of carbon is very slow, and frequently sufficient time is not allowed after the Ac manifestation before cooling. This results in a low carbon martensitic phase and a critical change at an Tungsten (contd.) elevated temperature. But this is not a normal condition; - the steel is not in equilibrium. Time has been denied for complete solution of the carbon. It is fairly well conceded, however, that tungsten does lower the carbon of the eutectoid point. Owing to the atomic immobility and sluggishness of the elements caused largely by the presence of tungsten, it is necessary to use hardening temperatures much in excess of that used for regular steels (this applies to steels with a tungsten content greater than 7%) to give ample time for the solution of compounds of tungsten such as Feswzand Fe4W C. A steel containing 10% tungsten requires a temperature greater than ZlOOOF to insure complete sol- ution of the tungsten compounds. Just as the presence of tungsten raises the temperature necessary for hardening, it likewise raises the forging and rolling temperatures. This, also, is due to the atomic immobility of its compounds. The element tungsten induces in steel the property of air- hardening and deep penetration hardness. With high tungsten steels, say above 12%, the hardness obtained from air-hard— ening is practically the same as that obtained from oil quenching. This characteristic property of air-hardening Tungsten (contd) presents difficulties in forging and rolling opporations, and if the temperature of the steel falls much below l7OOOF the metal stiffens perceptibly. Int the forging operations frequent reheatings are necessary, due to this hardening effect as the temperature drops. At quenching temperatures high tungsten steels are entirely- austenitic, which is retained on quenching. The presence of tungsten increases the tempering temperature at which austenite is transformed into the hard martensitic phase. Tungsten also gives deep hardening properties to steel. The requirements demanded and the factors involved in destroying dies should be given careful study before recommending or applying any particular type of hot — work analysis. The application of the correct ty‘e of analysis and the proper heat-treatment are the all deciding factors in the life of hot-work dies. The main factors to study before applying any steel are: temperature involved (maximum and minimum), length of time die is in contact with heat, temperature to which die rises, cooling or lack of cooling conditions, contact or lack of contact with water or oil, lubrication, sudden changes of temperature, physical stresses such as torsion or impact, etc. If careful thought were always given to these salient factors fewer failures would be experienced in the application of hot work tool steel. The heat treatment of course is vital, as too much stress cannot be placed on this subject. Carefulness and preper furnace control is always a requisite. The Rockwell hardness is of great importance, and it has been my experience that heat treaters and shop men are prone to consider extreme hardness necessary to the life of the die. In the vast majority of cases the exact opposite is true. Rarely in hot work application is a hardness exceeding Rockwell 0-50 necessary for long life. In most cases much less than this value is desirable. ‘The lowest hardness that will withstand erosion is best, as the extreme iardness sets up a marked susceptibility to heat—checking which soon causes the breakdown of the die. C "’ .65- .75 En - .15— .30 Si - .15- .30 Cr - 3.75- 4.25 Va - .85— 1.00 W — 17.50- 18.50 As shown by the analysis, this is an 18:4:1 type of high speed steel. At one time this analysis was widely used for hot work purposes. The high tungsten - chromium content offers much resistance to erosion and elevated temperatures; but with the high carbon percentage the alloy is prone to set up heat-checks when in contact with high temperatures for any length of time. The high carbon - tungsten content also induces extreme brittleness that preven 8 its use on work where any shock is in— volved. When used it is necessary to temper at a very high temperature to increase the ductility and impact values. Of late years this analysis has found very little use for purposes other than cutting tools where red—hardness is required. From this analysis, however, most tungsten hot work steels have evolved; hence its inclusion. TYPE I _......I --.4-.- Heat Treatment: Forging - 17500 — 2100 Q) *1; Annealing - 1600 — 16500 Brinell — 207 — 288 Rockwell Hardness after Oil Cooling: 28500 F - 011 24000 F - Oil ~-”"‘~-~-“~- —-_-—~¢—----- we Draw - c — 66 c - 67 10000F — 65 66 11000 _ 65 66 12000 - 62 63 13000 - 61 61 Recommended Hardening Treatment: Preheat - ISOOOF Quench — 22500 Oil or Air Draw - 1150O — 12500 (according to requirements) Charpy Impact Values in Foot Pounds Heat Treatment Charpy Rockwell Quench Temp.°F Draw 0F Values Hardness 011 2250 1100 3.14 C 61 ' ' 1150 3.37 59 ' 2380 1050 2.02 64 “ 2000 1200 2.90 49 ' 2150 ” ' 57 ” 2250 - ' 59 ' ' 1100 2.62 58 ' ' 1200 ' 55 Air ' ' 2.50 54 011 2300 ' 2.62 61 Tensile Yield Strength Strength lb/SqIn. 1b/Sqln Red. of Hardness Heat Treatment 322750 YSlTS 330860 275000 175600 - 145020 - 2.0 6.0 Are? Rock. Shore 6 0 C 59 81 .56 55 73 23000F Oil 1100 Draw 23000F Oil 1200 Draw At Elevated Temperatures -*---—*—‘---~---—~-~-- 14.8 _ - 21000? Air 1250 Drew 21000? Air 1250 Draw I EQYT -M- exudateqmer moofl 3A — satireQth eItaaeT A—— —— - .——— A‘— _ ‘ __ _.— — -" :atavfsnA &OVQ - o tseH eeenbrsfl to .beH 1-3noIE bIetY eIIaneT snemreetr erode .ioofi 691A sorts d33n9138 diametta a e nIp8\dI .aIp8\d£ -—— _ w— vfiv — — —v—- — —— 110 100088 18 ea 0 0 V8.I BTIBY OEYSS8 I310 OOII , I10 100088 8? aa 88. 83.0 OOOEVS 088088 word 0081 eerutereqme? beravefl :A tIevtrerIex IOOOII has 0009 «In 100013 - so o 3.1 0.3 - ooaavr weIG 0381 11A 1°oors - — 8.&I 0.3 - osoabr weIG 068! TYPE I Typical Ueee - Hot Work Automobile Valve Seats Plunglrl for Upeetting Inchinee Shear Blades Heading Dies _—.------ Automobile Valve Seats Plungers for Upsetting Machines Sheer Blades Heading Dies C - .69 in - .23 Cr — 4.01 We - . 98 I — 17.96 Nearly any type of curve can be obtained from this type of steel. The normal heating and cooling curve is as shown in this chart. Time and temperature are factors in the position of the critical points. The test specimen was heated to 97000 and showed a crit- ical transformation (Ac) at 8000 - 95020. The specimen was carried to a temperature of 97000, before starting cooling, to insure the complete solution of the carbides. Two definite cooling transformations are shown; Arl - 7250—70090 and Arg — 4200-31090. The intensity of the Arl point is very slight, but the Arg point shows a very large expansion over a wide range of temperature. This latter point of course is the martensitic hardening range of high speed steel. The eXpansion being due to the formation of martensite, This specim n shows some contraction at the point where cooling was discontinued, due probably to retained austenite. Tampering would eliminate this condition. It should be mentioned that if cooling of Specimen commences after the Ac transformation, before suff- icient time has been given for the complete solution of carbides, the martensite will be of low carbon content and will result in raising the Ar point, and cause a greater intensity of the Arl point. This, however, is not a normal condition. This steel is not in equilibrium. totetric nvw ..1.3 L»; 9 TC? 7\ 1.. , _.-_. -. >Ls . , .-. '0- ___..- '5 INCH X 10 e INCHES PER IN EXPANSION 12 13. 11 10 (‘7' 040/0 " 9706‘. o o I I I I II I I o o '0 I I I l O O 0/ I I O I a j I / o I / / o II He «600.6. I e / fir. - 725 C. I 10"} 1° ’7'? ' 420 C . ° P ‘. I I, X I I o I .0 ‘\ 1 I x u 9 a 4 5 8 10 TEMPERATURE. 12 °C. Two photomicrographs are shown at high magnification, (x2400). Photomicrograph 1 shows this steel in the annealed condition, and is a very good example of the large excess grains of tungsten compounds. Photomicrograph 2 depicts the steel in the hardened untempered condition. The large austenitic grains are very pronounced. The matrix shows a slightly martensitic condition with globules of tungsten car- bide interspersed throughout the matrix. These are the excess compounds of tungsten that failed to go into solution. .11. co 4.... 0;. A... C. K Fig. Analysis: as ______ C — .50 — .55 Mn — .15 — .30 Si — .15 — .30 Cr _. 3.75 —4.25 Va - .85 -1.00 W — 17.50 - 18.50 Mo — .15 - .30 In recent years this analysis has gradually found a much wider application for hot work purposes. With the exception of the reduction cf carbon to .505 and a small addition of molybdenum, this steel is the same chemically as Type 1. The lowering of the carbon removes most of the brittle— ness; see comparative tensile tests, inherent to high tungsten — high carbon steels. By lowering the carbon the tensile strength is not greatly reduced, yet the elongation is increased four fold, while the reduction of area is trebled. The lower carbon content of course gives considerably lower hardness figures after quench- ing, but this is helpful in preventing heat-checking. For certain applications Rockwell hardnesses as low as C 35 are frequ ntly necessary. With high carbon steel, fine hair-line heat checks set up quickly from contact with high temperatures, - this is not the case when the carbon percentage is lower with corresponding lower Rockwell hardn 38 figures. This type of steel does not always con— tain a percentage of molybdenum, but the addition of a small amount (.50t) is a decided improvement in the life of the steel. I have seen gripper dies working against Silcrome valves produce 35,000 valves without the molybdenum addition, and better than 200,000 valves with the addition of .35% molybdenum. TYPE 2 Heat Treatment: Forging — 18500-20000? Annealing — 15500—1600O Brinell - 817 — 835 Rockwell Hardness after Oil and Air Cooling: ~--~--—"fl_~—-~~-‘~-—fl—d~ No Draw — C 49 C 55 C 59 lOOOOF - 51 55 59 1100 - 48 53 58 1150 - 48 52 56 1200 - 47 50 54 1250 - 38 40 45 1300 - 37 38 43 Recommended Hardening Treatment: Preheat - 1500°F Quench - 20000—81500F (oil or air ) Draw - According to hardness desired. A long draw is very important. Analysis: 0 _ Cr - Va — w _ Charpy Impact Values in Foot .50 4.05 0.97 18.36 Pounds -’—----------—‘--—O'~~————— -‘-----‘_--.‘ Draw Charpy Values Rockwell Hardness -__——---—'—-—-fi-_--—~-—~-—-—-_—---—-——- —__._ Quench Temp 5F Oil 2000 " 2153 " 2250 " 2250 " 2250 " 8300 Tensile Yield Strength Strength 1b/SqIn. lb/SqIn. 245,130 195,000 N O) {\J ()1 N O) Red.of Area Hardness Vest Rock. Shore Treat ent 50 ”9 r"250“" €11 1°00 Draw Nut Dies, Large Size - harden in Forge Fire, Face only. Nut Dies, Small Size 23500F Air 1200 Drew Gripper Die Valves 20500F(packed) Air 1000-11500 Draw Brass Extrusion Dies 21000F(packed) Air 1200—1250O Draw Brinell 285-302(Before Machining) Brass Extrusion Dies 2200°F(packed) Air 1300 Draw Brinell 285-302 Rockwell C 42-45 Hot Press Dies, Axle Flange 21500F Air 1290 Draw C 46 -.‘_.. .- TYPE 2 Hot Press Punches, Axle Flange 2150°r 011 1250 Draw 0 4O Gaining Dies, Upsetting BISOOF Air (packed) 1200 Draw C 46-48 Analysis: C — .53 En - .14 bl ~ .15 Cr — 3.87 Va - .98 W - 18.29 The analysis of this steel is not unlike that of Type 1, but the critical transformations exhibit a marked constitutional difference. The heating was carried to 90000 and showed a critical transformation (Ac) at 7900 — 84000. Sufficient time and temperature were given after this transformation to ensure complete solution of carbides. Cooling was started slowly and two critical points were recorded; Arl - 8000—70000 and Arg - 3500- 25000. It will be observed that opposite to Type 1 TYPE 2 the Arl point in this steel shows the greater volume change. This condition is due to the low carbon percentage in the steel, resulting in martensite of low carbon analysis, which naturally raises the critical point. The Ara point is very small, but shows considerable expansion, indicating a marten- sitic change. The steel shows a slight expansion at the point where cooling was discontinued. '5 x K). 10 INCHES nalNCH EXPANSION IN 15. 12 0 ac amt. (OI ,' an - 800°C. P ’0 F7”: ' 350T. 1‘12 | l l 11 4 6 a w 12°C. TEMPERATURE. Two photouicrotrsphs at high :r;n?£ication,(x2200) are shown. Iigure 3 is in the annealed condition and is not unlike Fiaure 1 of Type 1. It shows the large globules of excess alloy that hrs been precipitated. o o 0 1 7- w 1 a. . (a, -— ‘0 Figure 4 38 in the hardened conOiticn, r250 F 511, with excess tungsten carbide globules tut failed to go into solution. J 5 t.‘ '.v. D t. ‘f ' I, . . O . .1. v p .... o. ”v.4,K n x saoo TYPE 3 Analysis: C - .50-55 MU - .15—30 81 - .15-30 Cr - 3.75—4.25 V - .85—l.00 W - 17.50-18.5 Co - 4.00- 4.5 This type is similar chemically to the regular 18:4:1 analysis with the addition of approximately 4% cobalt and 1% molybdenum. At first it was thought that this analysis g (D vs great at resistance to erosion at elevated temperatures. There are many drawbacks and disadvantages with this -ype of analysis. The first and foremost is the lack of uniform— ity of results obtained in practice; second, the marked tendency to develop a decarburized case at 22509F, which rapidly increases up to 24000F. It is safe to say that there is no hot work application that cannot be done equally as well, or perhaps better, with Type 2 analysis previously described. Some very phenomenal results have been obtained with Type 3 steel in extruding hard non—ferrous alloys such as brass, but owing to lack of uniformity, it does not average over a long period of time as well as other compositions. Forging - 1850 - aoooor Annealing - 1550 - 1500O Brinell — 235 - 255 Rockwell Hardness after Oil and Air Cooling: —-—---——_———.—-~-—--——--—-—_-_-—~-—--_—---—..--— PlOOOF 225005 25000? No Draw 0 54 c 55 c 58 1000 54 55 5a 1100 52 55 55 1200 44 54 57 1253 as so 51 1300 53 48 4a Reconmended Hardening Treatment: Preheat _ 15000F. Quench - 20000 _ -?l5OOF (packed) Air Draw - ’According to hardness desired) Tensile Properties - At Elevated Temperatures ----‘-_---—---_“-—~‘_--‘_--—‘-——----—‘---I_----- Temperatures, 9000, 9000 and llOOOF respectively. Tensile Yield Flong— Red of Rockwell Heat Strength Strength ation lb/Sqln. lb/SqIn. 4 Area Hardness Treatment ".0 148,170 - 5.0 191,520 — 0 128,030 — 8.0 Typical Uses 15.4 0 41 21000 Air 1300 Draw 0 4a 22500 Air 1200 Draw 18.8 45 22500 Air 1350 Drew - Hot Work Extrusion Dies — Brass, Gripper Dies, 21000? Air (packed) 1300 Draw Rockwell C 42—44 21500? Air (packed) 1250 Drew Rockwell C 42-45 -—--—-.‘ Analysis: C — .30 - .35 Lil“) — .15 " .30 Si - .20 - .35 Cr - 3.00 - 3 50 Va — .30 — .50 W — 10.00 12.00 This type of steel is probably more widely used for i0 l/sis so f:r U ther an s S1) not work purposes than any 0 *3 developed. The analysis differs widely for diffs ent consumers and manufacturers, but they are all funds- mentally the same basic type. The most common range is given in the analysis chart. Bowever, it is common to have the chromium 3.0/8.0? and the tungsten 5.0/14.0?; the carbon of course will vary between .30/45? with thee, elements,- the higher the alloying elements the lower the carbon content. For example the C — .40/45, Cr —6.0, W - 6.0 type is ouite commonly used. This steel presents much ease and latitude in heat trest— ing, and can be quenched in air or oil with equally good results. It is to be noted that with a very high pene- 'J) teel h C) 0') tration hardnes-, this ,s a very hi“h yield poin., and shows considerable ductility with a reduction of area of 14.04. The heat resistance - as shown in tempering chart - is (D .54 O (D "G c+ H. 0 L5 in ,__J '1-4 ‘<‘. ’10 O O Q. 0 a {3‘ (D (3‘ H . D {‘0 W 0.. L) E: :3 Ho :3 :J‘ .1) H O. 73 -‘D :7) if) H. (D <: D r '3 s: not susceptible to brittleness with impact or heat checking when properly hardened. Forging — 1750'O - 19000? Annealing - 1553 - 1800 Brinell - 207 - 228 1950 F 2150 F 5250 F To Draw C 48 C E9 C 56 1000 4a 59 55 1050 4a 52 5a 1100 4a 52 54 1150 46 51 53 1200 44 47 43 1250 $5 43 45 1300 20 as 59 Recommended Hardening Treatment: Preheat -—lSOOOF Quench — 2150O - 22500? Air or 011. Drew - According to hardness desired. haroy Imoact Heat Treatment: 10.63 ”ct wounds Charoy Erato? Values 1200 8.43 1225 3.05 1200 9.38 1100 3.20 1200 5.88 2.62 1200 Rockwell ?ardness --——---.—--—‘.-c---c.--~—n--‘---——--a——_-——--- -------- Va - .39 VI? -' 1.0073 Tensile Yield Elong— Red 0f Hardness Heat Strength Strength ation Ares Rock. Shore Treatment lb/Sqln. lb/Sqln. ~$ -% -------‘-_-—--‘-‘-—-‘----—---—------------——-------—---- 252,370 222,000 6.15 13.8 C 49 62 20500? Oil 1180 Drew At Elevated Temperatures 247,390 210,000 9.0 31.7 C 48 62 21502? 011 1150 Drew 208,770 188,000 10.0 52. 185,540 167,560 11.0 51. 144,515 128,500 12.0 19.8 - - 1‘ u --—-———-----—-—---—----~-‘ Brass Forming Dies, 21500? 011 1200 Draw 0 4 on I 4:- D Aluminium Extrusion Dies, 215OOF Oil 1180 Draw 0 1270 Drew 0 38-42 (Before machining) Sizing Ring Steel .402 Carbon, 21000? Air 1250 Draw C 40 (Before Vachining) Gripper Dies — Upsetting Pivots, 2100°F Air 1250 Drew 0 40 Insert Dies — Ford Valves 21500? 011 1150 Draw C 48-50 Rotary Shears - Skelp Mill, 21500? Air 1225 Draw 0 42 Formin, Dies - Boiler Shop ! 2lOOOF Air 1200 Draw C) 43- 0) Typical Uses (contd.) Extruding Brass — Bods, 2250°F Air 1100 Draw 0 42—45 Extruding Brass - Sections, 1175 Drew C 40—42 Hot Shears — Morgan Flying Shear 2" Billets, 21500? Air 1250 Draw 0 41 Hot Shears — Morgan Flying Shear- Sheet Ear, 215OOF Air 1250 Draw 0 41 ----‘_--------d'-‘---- -- ----—.-_-.-- C — .36 En — .16 Si - .19 Cr — 3.19 Va - .42 W — 10.15 Two exceptionally well difinde points of considerable intensity are shown, - Ac - 8100-86000 and Ar _ 7750- 69000. The intensity of the point on heating is slight— ly greater than the cooling transformation. It is to be noted that the Ar transformation of this steel occurs at a much higher temperature than is usual for high tungsten steels. This is due to the low carbon contained in the precipitated martensite, the steel only containing .365 carbon originally. The shrinkage shown where cooling was discontinued is very slight, and would be entirely removed if test specimen had been cooled to atmospheric temperature. L . ,Jw r a v LIT V F? Diletoeetric Tyne 4 .r. _ _ _ _ 3 m .OHx mil 0 k roz_ S. .c. .e w w 6 7. C r aw P: o I [OI /I/I o ’I’o’ /°”/’ /0/ o o m n .V D N mmIoZ_ Z. ZodmZ< '11 >4 \2 ’0 ‘.\3 C) O N 0%" r. (I) Analysis: C — .40 - .50 Mn - .20 ~ .30 Si - .80 — 1.0 Cr - 1.30 - 1.5 W — 1.50 — 2.0 Va - .20 - .30 This type of steel has found extremely wide application; especially where any degree of shock is present. It is suitable for both hot and cold work purposes, probably finding greater use for the latter than the former pur— pose. It is a very highly alloyed analysis, and on a cursory view might be thought to be brittle; but the opposite is true. It is probably one of the toughest and most ductile tool steels manufactured. There is a very large tonnage of this steel used in the form of shear blades; - hot and cold. The analysis used in this type is nearly fool-proof in heat treatment, which is a very desirable feature. A disagreeable characteristic is the tendency to harden with a soft skin. This condition is much more pro- nounced when the steel is hardened in an electric fur- nace. In a gas fired furnace it can be controlled fairly well. When hardened in a coke forge there is no evidence of this condition. The contact with the carbonaceous material probably acts as car- burizing agent. Due to this characteristic, it is advisable to pack-harden small sections, — punches, or sections that are not later to be ground. The Rockwell hardness of this steel is not a very great factor in the life of the tools. Forging - 15500 _ 17500v Annealing - 14500? Brinell — 196 - 217 Rockwell Hardness after Oil Quench: --_----“—~---—----—------_------. 17000? Oil 17500? Oil No Draw 0 56 C 58 700°? 55 54 900 47 50 1000 48 4a 1100 47 48 1200 40 45 Recommended Hardening Treatment: Quench - 1850O — 17500F 0i1 Draw - As desired. Heat Treatment Charpy Rockwell Quench Temp.OF Draw Values Hardness 0i1 1700 - 17.7 C 56 011 1700 450 22.0 54 Oil 1700 1050 31.3 48 011 1700 1200 62.1 34 Tensile Properties — At Room Temperature Tensile Yield Elong- Red of Hardness Heat Strength Strength ation Area Rock. Shore Treatment lb/Sqln. lb/Sqln. 4 a 307,260 195,000 2.65 .91 C 54 69 17000? 0i1 Ho Draw 507,750 250,000 4.51 8.81 52 69 17000? Oil 800 Draw 287,880 258,000 4.51 8.87 51 85 1700°F Oil 750 Draw 244,880 201,000 6.67 13.30 46 60 17000? Oil 1050 Draw Tensile Properties — At Elevated Temperatures Temperatures, 750, 7000, 9000, 11000, 11500, 9000 and llOOOF respectively. Tensile Yield Elong- Red of Hardness Heat Strength Strength ation Area Rock. Shore Treatment lb/SQIn. lb/Scln. 5 4 227,740 208,000 10.0 58.1 0 48 80 16750? 0i1 194,080 188,000 15.0 57.1 48 80 " " 151,805 155,000 20.5 84.1 48 60 n " 82,810 88,000 44.0 85.5 48 80 u u 72,850 58,000 55.0 88.1 48 60 n u 175,8000 — 2.0 1.2 42 - 175005 011 1250 Draw 145,020 - ' 8.0 14.8 n - n n Analysis Used For Charpy And Tensile Tests: (not including —-.-~----— Aluminium Extrusion Dies, 17500F 1250 Aluminium Extrusion Dies, 1750°F 975 Header Rivets, 17500F 1150 Shear Knives - Bar Hill, 17500F 550 Aluminium Die Castings, 17500F 1050 Bull Riveter, 17500? 1225 Shear Knives - Rotary Hot 175005 450 Oil Draw Oil Draw Oil Draw Oil Draw Oil Draw Oil Draw M1118 Oil Draw C 38-37 (Before Machining) Shore 63—68 55-60 Shore Shore Brinell 444 Shore 50-55 3/16" thick, Shore 72—77 Typical Uses (contd) Shear Knives - Billet and Bloom, 17500F 011 1050 Drew Shore 60 Shear Knives 9" Blooms, 17500? 011 1250 Drew Shore 55 Dummy Blocks - Extrusion of Brass, 17500? 011 1100 Draw C 42-44 Dilatometric Observation ---—---_-_-_—------‘--—- Analysis: 0 — .47 Mn - .29 Si — .92 Cr — 1.22 Val - .23 W — 1.90 This curve shows a well defined Ac critical point 0 at 7850 — 850°C, with the Ar point at 7250 — 680 0 equally well defined and of about the same intensity. The noticeable thing about this curve is how ouickly and closely it returns to normal dimensions after the completion of the Ar transformation. Being an oil hardening steel accounts for some of the lack of distortion, but the analysis is such as to elim— inate any great amount of movement in the steel. F’I -3 x10, IN INCHE3 PER INCH EXPANSION 12. 11 ‘10 o.’o / I. I I 0 O I I I ’l \\ P, 9' ‘32" - Ila I II ,I I o‘ / I 3 I / {’5 7. fit - 7552:. m- — 7252:. 4 6 8 10 TEMPERATURE. 12. .C- -------- Two photomicrographs, showing this steel annealed and hardened, are shown at 2200 diameters magnif— ication. Figure 9 shows the annealed structure of the steel. It is a normal structure for a complex alloy such as this steel. Figure 10 is hardened, l75OOF — Oil, structure and shows the rejected excess constituents in a decided laminated or banded condition. fl 1 0» fix. C 9...u .1 a «H. VA .rl TYPE 7 and 8 Analysis: Type 7 Type 8 C - 0:30 - 040 045 "" .50 Si - .80 - 1.00 .30 — .50 Cr - 4.75 — 6.00 4.25 — 4.75 ‘Ia — o 20 "' 030 o 20 - o 3.”) W — 4.75 - 6.00 1.75 — 2.00 00 - .40 - .60 — — — MO - 015 _ 030 .85 - 1.00 This type of steel was developed primarilv for the non- ferrous industry. It found its first application in pressure die casting the hard aluminum alloys. It proved much superior for this type of work than anything prev— iously used. Since that time it has found a much wider application. This steel, although not generally considered as suitable for extruding the hard non-ferrous metals such as brass, proves very good for such work, if care is used in pre- paring the dies and is properly heat treated. It does not offer the same resistance to abrasion and erosion at elevated temperatures as Types 2 and 4; but it is certain— ly warrants use in such times as these when the volume being extruded is not great. It probably averages three— fourths the life of the high tungsten steels on this work. TYPE 7 and 8 This steel offers great ease in heat treating, - being air hardening, and shows little or no tendency to scale with a minimum of warpage. It withstands breakdown from heat up to llOOOF, before any sudden change of hardness is apparent. Forging _ 19000 _ 20000? Annealing — 15500 ~ 16000 Brinell - 217 - 235 Rockwell After Oil and Air Cooling: No Draw 8000 1000 1050 1100 1200 _—----—----‘---- Recommended Hardening Treatment: Quench Draw - 18000-18509F (Air) Pack Harden. - 9000-11309? (According to hardness desired) ---—----.—-—.---—-—.......---—-_—...---.-..——~-.-—— (3 K0 — .22 Va - .50 W - 5.54 Charpy Impact Values in Foot Pounds ---- -"---‘--.-—-—---~-__----~-——----“- Heat Treatment Charpy Rockwell Quench Temp.OF Draw Values Hardness Air 1825 - 18.90 C 55 " 1885 1000 18.90 54 " 1825 1100 19.46 49 " 1825 1200 30.67 40 Oil 1825 1000 18.90 54 Tensile Yield Elong- Red of Hardness Heat Strength Strength ation Area Rock. Shore Treatment 1b/SQIn. 1b/Scln. % a 259,390 217,000 8.43 17.8 0 49 62 18250? Air 1000 Drew 161,460 126,000 13.50 37.3 55 46 18259? Air 1150 Draw At Elevated Temperatures Temperatures, 750, 7000, 9000, 11000 and 11000? respectively. 269,470 207,000 5.0 8.6 50 67 241,115 192,500 9.4 25.0 - — 217,045 172,000 10.0 30.5 - - 112,950 85,000 23.8 69.9 - - 196,550 - 11.0 41.9 50 67 18250? Air 1100 Drew II H H H H 11 18250? Air 1100 Drew TYPE 7 Typical Uses - Hot Work Aluminum Die Casting, 18250? Air 1100 Draw Brinell 444 Shear Blades - Rotary Sheet Bar, Shear Blades — 35" Aluminum Extrusion 1825°F Air 1050 Draw C 52 Blooming Mill, iasaor Air 1150 Draw Shore 60 Dies, 18250F Air 1100 Draw Shore 65 1200 Drew C 38—40 (Before Machining) Brass Extrusion Dies, 18500F Air 1150—1175 Draw 0 4O —.-—--—-_ Dilatometric Observation Analysis: 0 - .39 Mn - .21 Si — .97 Cr - 4.78 Va - .30 W — 5.54 Co - .53 ‘o — .22 This curve shows two well defined transformations; Ac, 810O - 870°C and Ar, 350O - 300°C. Both tran8~ formations are of considerable magnitude and about the same intensity. At the point where cooling was discontinued the spec— imen showed a small amount of shrinkage, but nothing very great, and it is quite likely that had cooling continued to room temperature, the heating and cool- ing curves would have closely approached each other. 9-.l' | II [1 If, _ a _ _ _ _1 'fic 43/02 Hr 550 C .9“ NH 3 “-2 x 2 6 Q N. m 102— a: nmIOZ_ Z. ZQ~WZ