The Iron Age 1924-09-11: Vol 114 Iss 11

THE IRON AGE _New York, September I'l, 1924 ESTABLISHED 1855 ~ VOL. 114, No. 11 Gases Evolved During Carburization Chemical Study of the Behavior of Five Solid Commercial Compounds—Theory of the Process BY VICTOR E. HILLMAN* modern pack hardening. The early procedure con- sisted in carburizing the steel throughout. Modern case hardening or partial cementation, however, im- plies that a high carbon layer of metal is superimposed upon a core of lesser carbon content. The operation is arrested after a suitable sansa case is formed. The pur- pose of the process is to manufacture steel objects with an outer zone or skin capable of heing hardened, and still retaining a soft and tough center or core. The process of ce- mentation had its incep- tion during the middle ages. The manufacturers of daggers, arms and needles were familiar with the art. The technique of their procedure, however, was slow to enter indus- trial channels. Each ar- tificer boasted the supe- riority of his own practice. The only secrets trans- mitted were those com- municated from father to son. The carburization of steel was given further impetus during the early part of the eighteenth cen- tury, when the French sci- entist Réaumer conducted a series of elaborate ce- mentation experiments. He detected the formation of an outer zone, capable dike total cementation process is a forerunner of of being hardened. More- 91 oth Fr over, he observed that the transformation proceeded gradually from the surface the metallic mass, and that the steel increased in weight as the result of carburization. Réaumur’s memoirs were communicated to the Academy of Sciences of Paris during the years 1720 to 1722. The results of his investigations gave rise to clear and precise rules for the effective technical application of the process of cementation. Subsequently, the art be- eame possible in all establishments. 81 es pan reeees coe on *Director of research, Crompton & Knowles Loom Works, Worcester, Mass. Arrangement of the Apparatus Used in the Investigation of the Gases Evolved During Carburization 100 1009 SNM CNN CONE OF + ce neDbAMNEREE! bi 086: HeAss kone RTEERORee The cements recommended by Réaumur were capricious mixtures of organic substances such as hoofs, hides, dung, etc. These complex substances were quickly abandoned and powdered charcoal was adopted as a carburizing medium. It is a well recognized fact that pure carbon will carburize steel, providing it is ~oormmormmnnnmnmnmnmmn Kept in contact with it for a sufficiently long time and at a sufficiently high temperature. From the standpoint of industrial heat treating, however, pure carbon wil! not act simply by contact without the intervention of any gas or vapor. Carburization is at- tained by heating the steel, protected from con- tact with air, to 1600 deg. Fahr. or thereabouts. The surface of the object is kept intimately associated with a carburizing com- pound which slowly de- composes under the appli- cation of heat. The car- bonaceous gases which are evolved gradually pen- etrate or diffuse into the mass of the steel. The gases enter the pores of the metal dilated by heat. Steel heated to a high temperature is easily per- meable to various gases. Modern carburizing com- pounds contain carbon as a 7 base either in the form of : eharred leather, charcoal, coal or coke, to which has been added salts. Briefly, they are built up from car- bonaceous dust, binder and energizer. Calcium carbonate is co used as an ener- gizer. It yields all of its CO, between 1000 and 1600 deg. Fahr. Magnesium carbonate has some merit. Its advantage lies in the readiness with which it is com- pletely dissociated, namely, at 1375 deg. Fahr. Sodium carbonate, on the other hand, does not dissociate to any appreciable extent at cementation temperatures. Scheerer noted that sodium carbonate loses 0.5 per cent of its weight due to the evolution of CO, when the salt is heated to 1832 deg. Fahr. However, when 611 cee ae 1 612 THE IRON AGE rt if sodium carbonate is used in combination with calcium, barium or magnesium carbonates, a complex mixture is formed which gives off its CO, at lower tempera- tures. Moreover hydrogen, whose presence will be hereinafter noted, accelerates the decomposition of a carbonate and thereby assists in the evolution of CO,. By the same token, barium carbonate will not rer te T 60 = —} | 50 nt 5 40 4 a & 30 a 20 Fa ot ail 10 . + oe ne j 0100 1200 1800 140015001 600 Temperature, Degrees Fahr. k= 15 — rhe 60 ~- rhe = 45 Pi 15 - >A >} Sample No. 1.—The following gases were evolved at the several temperatures adopted: 1100°F. 1200°F. 1300°F. 1400°F. 1500°F. 1550°F. CO, 60.6 22.0 12.0 5.0 2.4 2.0 Illuminants 0.0 0.0 0.4 0.3 0.2 0.2 Ov 1.0 1.0 0.6 0.7 0.8 1.0 ® co 14.6 31.0 41.0 63.6 57.6 57.6 CH, 8.3 11.6 7.4 2.2 2.1 1.6 He 7.1 27.7 32.1 23.0 29.8 28.5 Ns 8.4 6.7 6.5 5.2 i.1 6.6 1 snake vin one +c (OLETEED NA CREAET EDAUELABEROGAULA 18 1 OUORDOUED GARDE AONNDLEOGLL\\4ndA4s CONE LNO Sa LENAPEL OSD OMBAA LANE Hcaee tthe ct aneeneNnMaT TUL evolve CO, at the temperature of ordinary pack hardening. Mellor records the report of an observa- tion which states that the CO, evolved from barium carbonate at 1826 deg. Fahr. has a partial pressure of zero millimeters. This signifies that the quantity of gas given off is less than a measurable amount. Therefore, the evolution of CO, when a barium car- bonate energizer is used is due to a substance whose Per Cent 100 (200 1300 1400 1500 1600 Temperature, Degrees Fahr. K-15 ~ he 60 - rhe - 45 -- whe —- 15 —— hes Sample No. 2.—The following gases were evolved at the several temperatures adopted: 1100°F, 1200°F. 1300°F. 1400°F. 1500°F. 1550°F. 21.0 b 6.4 CO, 11.2 : 8.2 4.4 3.2 Illuminants 1.0 0.3 0.6 0.2 Q. 0.0 Oz 0.6 0.9 0.6 0.2 0.3 0.3 co 16.6 18.8 34.0 54.7 68.4 66.6 CH, 30.9 25.9 12.8 3.7 0.4 0.9 He 21.9 33.2 37.8 27.1 20.1 22.9 Ne 8.0 9.7 1.8 5.9 6.3 6.1 enene nana tanta tt reputed formula is Na:Ba (CO,),. In other words, the presence of sodium carbonate is necessary to effect dissociation. Carburizing substances or cements may be either solid, liquid or gaseous. The object of the author’s in- vestigation is to set forth the gaseous behavior of a number of the solid commercial compounds that are September 11, 1924 found on the market today. Five well known com- pounds were selected for experimentation. Uncharred bone was adopted as a standard ‘due to its superior carburizing properties. The essential nature of the manufactured compounds was similar. They con- tained calcium, barium, magnesium or sodium salts in the form of carbonates. It might be mentioned that the calcium and sodium salts predominated. The base was of a carbonaceous nature. The constitution of the substances, which experience has shown to be most efficient in producing cementation, are carbon and the carbonates of the alkali or alkaline earth metals. A weighed quantity (% lb.) of carburizing com- pound was introduced into an air tight compartment which was equipped with an exit tube and thermo- couple. Sketch No. 1 illustrates the arrangement of the apparatus. The gas sampling tube is shown in the foreground. The interior of the carburizing box— 12 x 5 x 3 in—was gradually heated from room tem- verature to 1550 deg. Fahr. The total time consumed in each instance was 5 hr. The rate of heating was immaterial. Concordant results were obtained for both slow and accelerated heating velocities. The maximum working temperature used in the investiga- tion was 1550 deg. Fahr. The flow of gas became negligible beyond that point save for the appearance of approximately 5 cc. of gas per min. The total volume of gas given off ranged from 65 to 85 liters. No appreciable quantities of gas were evolved after Mn 1200 1300 1400 1500 1600 l Temperature, Degrees Fahr. | eB = -— eG 0-= le == 15 -— fA Sample No. 3.—The following gases were evolved at the several temperatures adopted: 1100°F. 1200°F. 1300°F. i. oe" ra: ' 1100 COs 17.1 9.6 6.0 4 1 6 Illuminants 0.9 0.2 0.0 0.2 0.2 0.2 Os 1.2 1.2 0.0 0.8 1.0 0.5 co 14,2 16.8 26.1 47.2 43.3 36.6 , 34.0 25.9 17.2 5.2 2.4 2.3 He 24.3 42.5 43.1 33.7 43.0 48.3 Ne 8.3 3.8 7.6 5.5 7.0 10.5 one hour at 1700 deg. Fahr. An attempt was made to collect gas samples at 5, 10, 15, 20 and 25 hr. in- tervals with little or no success. All compounds manifested traces of ammonia and hydrogen sulphide between 500 and 1300 deg. Fahr. This result is probably due to the decomposition of organic matter. Moreover, the gases issuing from the exit tube could be ignited, when the interior of the carburizing box reached 1100 deg. Fahr. The maxi- mum volume of carburizing gas was evolved between 1300 and 1450 deg. Fahr. Beyond 1450 deg. Fahr., the rate of flow steadily decreased until at 1550 deg. Fahr. the quantity of gases evolved was almost negligible. The results obtained from samples Nos. 1, 2, 3, 4, 5, 6, and No. 1 reheated are hereinafter set forth. The action of the important gases, i. e. carbon dioxide, carbon monoxide, hydrogen and-methane, are presented in graphic form. Gas samples were taken at 15, 45, and 60-min. intervals as shown beneath the abscissae. It will be observed that the percentage of carbon dioxide predominates in the early stages of heating. The CO. is produced by the dissociation of the car- bonates. As the temperature increases, the percentage of CO, rapidly declines. With the decline of CO: there is a corresponding increase in CO. The car- burizing action of a case-hardening compound is due to the evolution of carbon dioxide which is subse- September 11, 1924 quently reduced to carbon monoxide. The maximum percentage of CO is reached between 1400 and 1500 deg. Fahr. Cemented zones occasioned by this gas are characterized by the fact that in them the con- centration of the carbon does not exceed 0.90 per cent. The action of carbon monoxide is “gradual,” giving cemented zones of the hypo-eutectic type. The gas yields one half of its carbon tothe steel, again pass- ing over into carbon dioxide which is again immedi- ately reduced to carbon monoxide by the action of the hot carbon base. The cycle of reactions is reproduced indefinitely. The carbon monoxide acts as a carrier or vehicle. CO, CO, + CE 2co 2CO + 3 Fe = Fe,C + CO, Methane is present in small amounts. This gas exerts carburizing action. Giolitti states that “the ad- dition of small quantities of volatile hydrocarbons to carbon monoxide merely raises the concentration of the carbon in the external layers of the cemented zones above the value which would result from the use of pure carbon monoxide under identical experimental conditions.” The cemented zones produced by CH, are characterized by a highly carburized external layer in L Temperature, Degrees Fahr. w= [5 = Ae 60 ~~ rhe 4S = dhe & --r Ao} Sample No. 4.—The following gases were evolved at the several temperatures adopted: 1100°F. 1200°F. 1300°F. 1400°F. 1500°F. 1550°F. 24. 12.6 6 . 2. COs 0 2 6.6 2.8 8.0 [lluminants 0.2 0.0 0.2 0.0 0.3 0.0 1.6 1.4 0.8 0.0 0.5 0.0 co 19.2 19.4 35.4 56.0 71.6 70.4 CH, 7.3 19.4 9.8 3.4 1.3 0.0 He 23.2 36.8 41.5 26.3 17.4 15.1 Ns 24.5 10.4 7.7 7.7 6.1 6.5 \H0HUFUO Ro oeDs eseNNUOUUPDERDENERELA ATTYEEPUNYT TN sienTrEAsHteCrDE. tnsDOOERLA CREDO TEEN: DeUrene es HOMEDOOED. OD ORONDE OS CERMERIRORED ORE TIOTDECTIONED: 6 FRROUESOLOTETRNOPERCRT ANTS «rpeeREREE which the concentration of the carbon surpasses 0.90 per cent. Steel carburized with this cement would be characterized by a layer or zone of hyper-eutectoid steel consisting of free cementite and pearlite. An undue amount of this gas would cause the case to chip or flake from the remainder of the steel. The hydro- carbons function by virtue of decomposition. They cause carbon to be deposited on the metal, which in turn produces carburization by direct contact. The larger the proportion of hydrocarbons contained in the gaseous mixture, the greater the concentration of carbon in the outer zone. The hydrocarbons are known as “sudden” cements. They will cement steel at 1300 deg. Fahr. Illuminants are classified as unsaturated hydro- earbons. The series includes ethylene and acetylene. The manner in which they act is controversial. The reactions which take place are extremely complex. Some investigators contend that the gases diffuse into the steel and there yield carbon. Others maintain that the gases owe their carburizing action essentially to the deposition of solid carbon which is assimilated into the metal by direct contact. Suffice it to say that small quantities of these gases have a tendency to raise the concentration of the carbon in the external layers of the cemented zones. THE IRON AGE 613 The presence of hydrogen may or may not be of importance. It is consistently present in all of the compounds investigated. It is a well known fact that the brittleness of cemented steels is not due entirely to the heating which accompanies cementation. A dif- ference exists between carburized bars and those simply heated. It is likely that the presence of hydrogen con- AEP ONERES EE NEN HENDRADODNRES (1 90) 0STNRRERORNRBO NEEL UTES wu URE TC FURL EOE | Temperature, Degrees Fahr. ; IS ->«-- 60 - oe 45 - e- hace Sample No. 5.—The following gases were evolved at the several temperatures adopted: 1100°F. 1200°F. 1300°F. 1400°F. 1500°F. — 5.6 . ’ CO, 17.2 6.4 3.5 2.2 Illuminants 0.3 0.8 0.5 0.6 0.4 0.2 Os 1.9 0.4 0.4 0.3 0.4 0.8 co 14.0 19.2 24.6 51.4 63.1 54.0 CH, 35.3 28.3 19.9 5.0 2.5 1.7 He 22.6 42.8 42.2 31.6 25.5 35.3 Ng 8.7 2.1 8.9 5.5 5.9 8.0 HNNLUONIRD DENA OERHPY \ERBBDEEDU OUNBEOSOYO OED DOSEONUEOESLDACOLIOAN/ORPLT E's GEDRORODEEDO, #OQRRERDED (ONSERRED reREOONDS. SUOROROOOTERERS tributes to the brittleness of carburized work. Precise investigations have not been undertaken, however. The action of nitrogen in the process of cementation has been studied by Braune. His interesting re- searches, a summary of which was published in Stahl 90 - 7, | A Temperature, Degrees Fahr. J. J ~ [F =" he 60 = AE Oe IS —- Sample No. 6—Bone.—The following gases were evolved at the several temperatures adopted: 1100°F. 1200°F. 1300°F. 1400°F. 1600°F. 1550°F. 11. 11. 2 4.6 2.2 1. CO, 8 1.6 7 6 INuminants 0.7 1.0 0.2 0.6 0.4 0.6 Oy 1.6 0.4 0.2 0.0 0.4 0.7 CO 22.3 41.8 55.8 66.8 $1.6 75.1 CH, 41.6 18.7 7.7 2.4 6.9 0.0 He 12.2 18.1 19.3 14.3 8.9 14.9 N2 9.8 8.4 9.6 11.3 5.6 71 en TT tt ee ee eee EE ee enna. 88 und Eisen, 1907, show that steel which has been sub- jected to cementation undergoes an absorption of nitro- gen. Minute quantities of the gas diffuse into the steel. Le Chatelier suggested that the phenomenon may account for the brittleness of the “heart” or “core” of cemented steels. Moreover, nitrogen has a tendency Ca NE tk pe one ere et ye i " te eens meet ee ate x eng pb ~ 614 THE IRON AGE to reduce the cementing action of CO by acting as a diluent. Sample No. 1 was exposed to the air for two days, whereupon it increased in weight. The compound was then reheated to 1550 deg. Fahr. and its chemical be- havior noted. No appreciable quantity of gas was evolved until 1875 deg. Fahr. The total volume given off was one half that evolved by a fresh compound. The hydrocarbons were practically negligible. The predominating gases were carbon monoxide and carbon Wmsiocpevens eons onseeransarrnnceisiny ctpersersnpeneepecvenevennpevenpen est iene: SEODHEC SUPDODELEGEDENEDODETDOOENGONENT Or Ri BEAnENERLD.EDAADDODNODOUODe BEDHULNOeNOEAALIGaNORE DE HEUG 1350 1400 1450 1500 1550 Temperature, Degrees Fahr. | AS ~ henna a fGnnn = hes Sample No. 1—Reheated.—The following gases were evolved at the se veral temperatures adopted: 1375°F. 1400°F. 1450°F. 1500°F. 1550°F. ‘ 8.2 6. of COg 18.2 12.6 0 6.2 Illuminants 0.0 0.2 0.0 0.2 0.1 Or 1.2 0.8 0.8 0.8 0.9 co 73.0 81.2 86.0 88.0 87.8 CH, 0.0 0.0 0.4 0.0 0.0 He 3.1 1.7 1.1 1.3 0.4 Ne 4.5 3.5 3.5 3.7 4.6 UASAGE NE VERE TROT ATTA) RAEN ERE HE TLL THE NUNTRT LL ETI E FEC MED) HERON 'TEC COREE SHEDETD GALS OEDE LOS EODE ORIEL DATED DADO EDOOADIE. BOAO ROP EDERELI DL DOCDONED EG FOSGE RO ROR ROTA DEO EE OE OROOE TENE: dioxide. As in other instances, the gases ceased to be evolved at 1550 deg. Fahr. Cements possess the property of being “regener- ated” when left exposed to the air. Regeneration is based upon the absorption of CO, The oxides formed during cementation by the dissociation of the carbon- ates absorb CO. again forming the carbonate. The presence of moisture is necessary. The hydroxide is first formed and subsequently converted to the carbonate. Obermayer Prize for Foundry Ideas The third Obermayer prize contest of the American Foundrymen’s Association will be held at the Milwau- kee convention during the week of Oct. 13 to 17. This prize will be given to a person connected with a foundry submitting a device, drawing or model of some jig or method which, in the opinion of the judges, embodies the best ideas for the economical production of castings. Entries for this contest must be for a jig or a piece of equipment that can be constructed in any foundry and used in the production of castings, in core mak- ing, molding or handling operations and should be accompanied by a written statement setting forth the merits of the particular device and methods of appli- cation. The judges’ decision will be announced at the gen- eral business meeting on Wednesday, Oct. 15, at which time the John A. Penton and J. H. Whiting gold medals of the association will be presented to Enrique Touceda and John Howe Hall. The winner of the Obermayer prize contest will be given a valuable prize and a cer- tificate from the association. Foundry executives are invited to bring this con- test to the attention of any persons in their employ who are eligible and urge them to compete. Any one con- templating entering this contest should write imme- diately to the secretary of the association, 140 South Dearborn Street, Chicago. September 11, 1924 Conclusions 1. Slow or accelerated heating does not alter the analysis of the gas evolved at the several temperatures adopted. 2. For a given temperature, there is a definite -maximum concentration of carbon monoxide. 3. At highet temperatures the activity of the cements investigated is due essentially to CO. 4. The evolution of carburizing gases prac- tically ceases at 1550 deg. Fahr. This value is nearly consistent with the complete dissociation temperature of calcium carbonate. 5. The maximum percentage of carbon mon- oxide is found within the range 1400 to 1500 deg. Fahr. The upper value is nearly consistent with the best temperature for cementation. The mechanical properties of the steel, ie., brittle- ness of “core” or “heart,” are less affected at 1550 deg. Fahr. than at any other carburizing temperature. 6. Prolonging the time at 1550 deg. Fahr. does not give rise to appreciable volumes of gas. Herein lies the advantage of luting carburizing boxes. Boxes sealed with fire clay prevent the escape of the active gases which are in the car- burizing box at 1550 deg. Fahr. If the car- burizing gases were not entrapped, heating above 1550 deg. Fahr. and prolonging the time would be futile toward appreciably increasing the depth of cementation. 7. All of the compounds investigated gave rise to a_ saturated hydrocarbon, namely, methane. Sufficient methane is evolved at 1100 deg. Fahr. to effect some degree of carburization. Charpy maintains that he obtained true cementa- tion as low as 1050 deg. Fahr. with this gas. 8. The illuminants or unsaturated hydro- carbons were at all times less than 1 per cent. The literature search embraced the following references: Stahl und Eisen Revue de Metallurgie Giolliti Sauveur Harry Brearley—“The Case Hardening of Steel” 3ullens H. B. Knowlton—Forging and Heat Treating—Dec., 1921 Cc. E. Carpenter—Forging and Heat Treating—Dec., 1921 H. B. Knowlton—Forging and Heat Treating—March, 1922 J. W. Mellor—‘“Inorganic and Theoretical Chemistry” The author wishes to acknowledge the work which was done by T. L. Counihan and E. D. Clark of the Crompton & Knowles research staff. Pittsburgh Steel Treaters The Pittsburgh chapter of the American Society for Steel Treating held its first meeting of the 1924-1925 season in the blue room of the William Penn Hotel on Tuesday, Sept. 2. The meeting, which was well at- tended, was addressed by Dr. N. B. Hoffman, metallur- gist, Colonial Steel Co., who spoke on “Some Phases of the Metallurgy of Tool Steel.” The paper brought out a very interesting discussion, the main points being graphitization through the breaking down of iron car- bide, and the causes of decarburization during anneal- ing. The chapter has formed an “On to Boston” club, and expects to send a large representation to the annual convention at Boston, Sept. 22 to 26. Arrangements are being made to have special cars attached to Boston trains. Officers of the chapter are: DuRay Smith, chair- man, Union Spring & Mfg. Co., New Kensington, Pa., O. B. McMillan, vice-chairman, Pittsburgh Rolls Cor- poration, Pittsburgh, and H. L. Walker, secretary- treasurer, 1102 Linden Place, N. S. Pittsburgh. The Crucible Steel Co., Syracuse, N. Y., is increas- ing production at its Holeomb Works, and has started up three 6-ton melting furnaces which have been idle throughout the summer. The Structure of Troostite and Sorbite Method of Etching Which Develops the Actual and Com- plex Constituents of Carbon Steels at High Magnifications BY 0. V. GREENE and numerous requests for information led to the institution of this investigation. It had for its purpose the development of the actual structures of the complex constituents of carbon. steels. The steels used were quenched and drawn at various tem- peratures that had been arranged with a view of pro- ducing troostite and sorbite in them. Physical tests were used to correlate the microstructure with the physical properties. | ACK of adequate information in technical literature The Scope of the Investigation The steel used for this investigation had the follow- ing composition: Carbon, Manganese, Phosphorus, Sulphur, Silicon, Per Cent Per Cent Per Cent Per Cent Per Cent 0.824 0.330 0.036 0.014 .106 Nickel and chromium were also present in small amounts. The heat treatment was as follows’: The stock, On DeLSHEWRSUEDOL ONEOHORDEDERTEGRONDEDDDLTLANONN oHOnHNNONHOE ENON DIDO IUNENNND ONS /LineREEseLDD LUFT DONE OON INU OMPECRDEFON (0 PO D)SETIEDOUD RT AEDRORAUAREORERDOONEDTEDEETT EE DEDDERDED sHUDEROE HOT HRDEURDLDTPLENT REN DDE Fr reenrapenneTy ry freshly prepared 1 per cent picric acid in ethyl alcohol. After the specimen was etched for perhaps 5 or 10 min. in this solution it was then removed and the car- bonaceous smudge rubbed off on moist broadcloth. The precautions to use against tarnishing and over-etching have been given in a previous article’, They are briefly summarized as follows: Care should be exercised against over etching, be- cause the structure will be obliterated or deeply pitted if the specimen remains only 30 seconds over the time necessary to develop the desired results. This is best controlled by examining the specimen at various times during the etching, until the desired condition is ob- tained. Tarnishing is even more serious and difficult to overcome than over etching. It will always take place unless the specimen is washed with alcohol upon its removal from the etching solution and kept wet with alcohol while being rubbed on the broadcloth. The specimen must then be washed in hot water and HU GPLEUUTDNEDEO ODEON OD BG OREY 900 #REQOO NEN AON pED EEERERSENRENNDEFUBED ED {488 /EDERRROEDENRE YTHENET DORE ETDDSEERONARREDERRDTERIOPETREDEIET® Fig. 1—Troostite (Dark) and Martensite (Light) x 500, Etched in Two Per Cent Nitric Acid in Ethyl Alcohol TETEOEEDO TH FEET TE DEERE REDE EMRENEON HHT 1 in. round, was normalized by heating to 1650 deg. Fahr. during 4 hr., soaking at 1650 deg. Fahr. during 4 hr., and then quenched in oil. The stock was then reheated to 1450 deg. Fahr., held 1 hr., with half of the specimens quenched in oil and half in water. The pieces were then drawn at 100-deg. intervals from 600 to 1300 deg. Fahr. The physical properties were characteristic of car- bon steel with these heat treatments. For example: Draw Elastic Ultimate Red. Temper- Limit, Strength, Elong., of Area, ature, Lb. per Lb. per Per Per Deg. Fahr. Sq. In. Sq. In. Cent Cent Brinell 600 134,500 187,500 11.0 32.4 388 900 127,500 169,000 13.5 36.5 342 1,100 90,500 129,000 20.0 47.8 249 1,300 75,250 101,000 23.5 54.7 198 A modification of Archer’s* method was employed for etching the specimens. The solution used was WORST REPRE TNA UTRRD AULA MSHLGLILA'ATTUCULNONACESSMCSUSASTOSOTUOECTSRIER ESET EERE TOE TOONS CUED RDU TSUNT TYE Fig. 2—Troostite (Light) and Martensite (Darker with Characteristic Acicular Structure), x 500, Etched in One Per Cent Picric Acid in Alcohol EEN TEN Ce MEO UTNMRAEBEMUTEFEN IE) COC OFEOER COC UHENL LEE TOU UE TEDIEC COPE OEODEOSEEEEL LOBUREREREEEDRE® DEDEPIRE SLES PEEREPEDEPUOEM 1000000501 600007 101111 eee ei; dried in an air blast. It should be photographed as soon as possible, for tarnish will appear quickly even in a dessicator. Explanation of Photomicrographs Two widely different methods of preparing a troosti- tic structure for examination are shown in Figs. 1 and 2. Fig. 1 shows troostite dark and martensite light, X 500, etched in 2 per cent nitrie acid in alcohol. The troostite with this method of etching becomes dark, structureless masses. This structure is char- acteristic of troostite as given in any textbook. When, however, the same specimen is etched by the method described in this article the treostite will lose its dark, structureless appearance and assume a very definite granularity, even at magnifications as low as 500 dia., as can bt seen from Fig. 2. Fig. 2 is the same speci- [HE author of this article is metallurgist for the Philadelphia & cea Railway constitu- Co., Reading, Pa. The results of recent -ray analyses of the ha ents of carbon steel are substantiated microscopically in this investigation, says the author. As nothing has appeared previously in this country in the technical literature on the true microscopic portrayal of troostite and sorbite, the author feels that this contribution should be particularly interesting. = Ne Ain ar aekie > bn ex © ope eees SS re ey ne ar | motte © thine 5 go ey me Resour ss ree Cnet i ree ee ee eres fork eer’ OER Semeaes 1 nas Ate nem amene 616 THE IRON AGE CURA UNanaeAMmDE MNES LA NUNNCHEEENEENDTONELUNNELANDURONDNNETEOUNONNE NCAT GOLENadt Oe FL SUENODRAUMNEODACE TDN” DUNNE ANRC CRORE EtHLOntANNEnEAENnEaOe . eet entiation Teo Ne . i mA Fig. 3—Troostite (Light) and a Small Spot of Marten- site (Dark), x 1000, Etched in One Per Cent Picric Acid in Alcohol. Drawn at 600 deg. Fahr. The mini- mum amount of free FesC is present AEUDHeDeLTONUPENDCRNONED au I UNELINODO pEEDEDNODU ADDO PNROASNAAOSAOUNNOIIIED men as Fig. 1, etched in 1 per cent picric acid in alcohol, X 500, showing troostite light with grain markings distinguishable, surrounded by martensite slightly darker with its characteristic acicular structure. The structure of the troostite at higher magnifica- tions will be given the other photomicrographs. They show troostite to be an agglomerate formed from the finely dispersed ferrite and cementite that was present in the martensite. The ferrite is no longer in a finely divided state, due to the fact that the network of the cementite lattice has been broken down, which allows the ferrite to agglomerate in large masses, forming a solid suspended solution with the cementite. Some of the cementite has become isolated particles of free Fe,C instead being in solid solution with the ferrite. These increase in number and size with the drawing temperature. Fig. 3 shows troostite light and martensite dark, X 1000, etched in 1 per cent picric acid, drawn at 600 deg. Fahr. The martensite remaining in the specimen is in isolated spots completely surrounded by troostite. A minimum amount of free Fe,C as nodules is present in this specimen. Fig. 4 shows troostite, X 1000, etched in 1 per cent picric acid, drawn at 600 deg. Fahr. This is the char- acteristic structure of troostite for this drawing tem- perature, showing its grain boundaries and few nodules of Fe,C. Fig. 5 shows troostite light and martensite dark, X 1000, etched in 1 per cent picric acid, drawn at 800 deg. Fahr. In this specimen the process of the growth of troostite through the martensite can be seen. In the lower right hand corner of the troostite may still be seen a shadow-like marking caused by a recent or incomplete growth of troostite in the martensite. Fig. 5—Troostite (Light) and Martensite (Dark), x 1000, Etched in One Per Cent Picric Acid in Alcohol. Drawn at 800 deg. Fahr. HLA 11 HHNELDLD LETHTS ATTN OHNNHDENTRETNODOCENeNeaoN seeURECOGRODONSEONINOA OND LONESUONEDEDNU DORREEONT SHOUD UIE SDEDEEUONERONORELEEODONNCH TONED NOE STONEOIOEODDENEIDERDODOEDNOORONNETON® September 11, 1924 !o4eot O44 eAEEUER114 SEEDUMAREBUEMANERREEDAANANED ULL UEAREREUOUORERERLEDA AT OERAEDOO UU AEERRUOOMEROURE UN OEGERDUEL YO nEOREEUOUTCONEEEDUOU HHANERBOUHOMRNSEEEOOMOAASaboOMNAnRaocansssgnnetxscse . Fig. 4—Troostite, Showing Characteristic Grain Bound- aries, x 1000, Etched in One Per Cent Picrie Acid in Alcohol. Drawn at 600 deg. Fahr. The minimum amount of free FesC is present NHQU cOAOOHO NDEs APLENUERAAABOOOAHLAs (104058808. SDLUUSETLUNELUCHREOAIERLONSRDLENDOA GAEL UONNOTUDELONEDDONNGSLLCOLDOANNOLENG CHUL CDOODEEDERS DODOADEDEESDODARESOEBAAUGREROEEAOOSAD ALAN UNEASY //)800 11 Fig. 6 shows troostite light and martensite dark, X 1000, etched in 1 per cent picric acid, drawn at 900 deg. Fahr. The troostite is shown growing through and surrounding the remaining martensite. The free Fe,C is appearing here in larger amounts than in Figs. 3 to 5 inclusive. Fig. 7 shows troostite light and martensite dark, X 1000, etched in 1 per cent picric acid, drawn at 1000 deg. Fahr. The nodules of free Fe,C have increased here more than Nos. 3 to 6 inclusive. The last of the martensite is being broken down into troostite here. No martensite appears in the following specimens. Fig. 8 shows troostite, X 1000, etched in 1 per cent picric acid, drawn at 1160 deg. Fahr. There was no martensite present in this specimen. The troostite is losing its grain size here and contains more of the free Fe,C than in previous specimens. In the last two photomicrographs, Figs. 9 and 10, the result of applying this method of etching to a sorbitic steel is shown. Using this method of attack, sorbite is seen to have a definite structure composed of ferrite still containing some Fe,C in solid solution and disperse spheroidal particles of free Fe,C. The cementite nodules are in a greater number and are slightly larger than in the previous specimens. There- fore, sorbite is simply a little more of a progression in the agglomeration from the martensite than the troostite was. Fig. 9 shows sorbite, X 1000, etched in 1 per cent picric acid, drawn at 1200 deg. Fahr., showing sorbite as a finely divided pearlite, most of the constituents of which are present as a conglomerate. Fig. 10 shows sorbite, X 1000, etched in 1 per cent picrie acid, drawn at 1300 deg. Fahr. The cementite nodules are slightly larger here than in Fig. 9. LHC dbOLDOCEUCEOOADANAUACOOAUSERROCUERADELUOEDONOUERDASUOELLELAUAODOUASEUAEDDENTHOUOAUERESOELAUERLORLEDLAAEGOEETDORECUREEN 1+ CGEDUMDEREEAERAAREARSEOREANAAPLEN” Rte RAAETTHET Fig. 6—Troostite (Light) and Martensite (Dark), x 1000, Etched in One Per Cent Picric Acid in Alcohol. Drawn at 900 deg. Fahr. SUCCUUCMRDEEEDALODODAVEDUNRBG EG ebtGAA0404L GADONUEENCATOUOBORDELLOELDONDAAYD, SUCLEDDOERAEROEDNGELEEUOCEE ELOOAUEDUOOLOEDEDEED DOC UADLESPTERSURDEDSDOSUURLEEOEERDERD LURE URRSELASDEORDOONA R11 1 September 11, 1924 ave eveGeRETTTE ry reTsDERT-EEDeEES HEN EToOEt HN OapeRRET TOO VET DOREY. OTTDOF SHEN rreREETDOREEENT Fig. 7—Troostite (Light) and Martensite 1000, Etched in One Per Cent Picric Acid in Alcohol Drawn at 1000 deg. Fahr. (Dark), x NUH OUNEDETDOHEREY CHEHERDDORERONNE PE EPOTEOD NEC ONAL LEDeREEDHRN NEG re enoUCDCarenPHNELeNsEenNNREScrtery It is interesting to note that in the development of technique in microscopy and etching of steels very little work has been directed along the lines of the common constituents of hardened carbon steels. Be- cause of this the appearance of troostite (Fig. 1) and sorbite as structureless dark etching masses has been taken more or less for granted, and technical writers present them in this manner, with the exception of an article printed in Stahl und Eisen about April 26, 1924, which appeared over a year after the completion of this investigation. As a consequence nearly every con- ceivable hypothesis has been suggested for the true nature of their structures. However, if the method of etching described in this article be used the troostite will lose its structureless appearance, and easily dis- tinguishable grain boundaries within the troostitic masses will be seen at magnifications as low as 500 dia. (Fig. 2). The sorbite also is seen to have a definite structure (Figs. 9 and 10). Various authors have suggested that the composi- tion of these constituents may be: Iron in the alpha, beta or gamma forms, or in two or in all three of these forms, while the carbon may be present as carbide in solution or free crystallized Fe,C, or both. Arnold, Rosenhain and Benedicks, as quoted by Rosen- hain, all agree fairly closely that troostite and sorbite are simply pearlites, the constituents of which are so small that they cannot be detected by the microscope. These investigators, in the order named, think they are emulsified pearlites, an alpha or beta iron in which the separated Fe,C is present in slightly larger masses than in the martensite, or a colloidal suspension of the cementite in iron. Sauveur writes that the constituents of troostite Fig. 9—Sorbite, x 1000, Etched in One Per Cent Picric Acid in Alcohol. Drawn at 1200 deg. Fahr. Showing finely divided ferrite and cementite SUPUTDERY TRDEF HERES! Leone FERUTERINRG DE HELORSHD, cRrmDERNEED peHer? THE IRON 1+ OTR CreneTtae vemenuaeTaTeNHERNT ERT SeTDNTNINNT LTTE AGE 617 CALNE Gee ane RMRNRT TED ETTEED TONE FETED rer ERRFERLERUENEOORES ETT: UPNTEEEN PERETEED, HYDE NE STO EDPS OT CUTPOERERNEDERE “ETE ORE 17 Pr LeR>E DONEREOPE: POERERERORO: F: HORBEATERENS:OBOEONERRSEL SUEPRRRSROETINTENBEL /1)) / OT rHERLU FOTN Fig. 8—Troostite, x 1000, Btched in One Per Cent Picric Acid in Alcohol. Drawn at 1100 deg. Fahr More of the free FegC appears here than was present in the previous photo micrographs SUPDPROMBETEN POT HEAOREND.EPND) DHETS ORBDNEDL "S000080! POREBED FER ®D "URI PUNDOFRORRS ODED FREBERDEDRERD F>s pr rn oneee and sorbite are: Free crystallized Fe,C, carbide in solu- tion, beta iron because of its hardness, and alpha iron because of its magnetism. However, in the author's estimation, the beta iron theory of hardness is obsolete. Maurer‘ refutes this theory probably better than any one. He states that effective hardening takes place when the alpha particles, arising from the gamma iron particles, are constrained to take up a greater volume than is normal to them, by the greater volume of the carbon in solution. The hardness is the re- sultant of the effort of the alpha particles to assume their ordinary volumes and the effort of the carbon in solution to compel them to assume volumes suitable for it. If the process takes place rapidly the alpha par- ticles will be in a cold worked condition, which explains the similarity in properties of cold worked and har- dened materials. Recent X-Ray Work The results of recent X-ray work on the structures of the hardened constituents of carbon steels coincide with the results of this investigation, which are as “ea follows: Cs X-ray investigation shows martensite to be alpha ta iron split up into cells by the Fe,C lattice. The par- + ticles are so finely divided that they may be regarded a as having colloidal dimensions. A disperse system, at; such as this, has properties that are similar to the io properties of cold worked materials. This is a slightly ai different point of view from the one given by Maurer # above. fe i It follows that an aggregate of larger particles of oh ssceesvesrtveocer nex creee1er nev 0100-1 EERO poreereerraeseernonepremeneetesents vas (Concluded on page 670) G ‘! Fig. 10—Sorbite, x 1000, Etched in One Per Cent Picric Acid in Alcohol. Drawn at 1300 deg. Fahr., showing finely divided ferrite and cementite with the cementite nodules slightly larger heré than in Fig. 9 1100 PROS MMORAMEERS oe MTS rEd cee RR: etn eRENRER IRC NRT Someones 180g Growth of American Alloy Steel Industry Large Expansion in Last Two Years—Statistics Since 1909 Reviewed—Pronounced Increase in Electric Alloy Steels BY EDWIN F. CONE United States was made in 1923. More alloy steels of all kinds, in proportion to the total steel output of the country, were made last year than in any year since alloy steel came into use commercially. From their introduction on a small scale, such steels have advanced in importance year by year until today they are indispensable to many industries. Prior to 1909 practically only simple carbon steels were made, either as ingots or castings. The quantity of alloy steels was so small that they were not recog- nized previous to that in annual statistics. Of course, high-speed steels were an exception to this statement, but in tonnage these did not mount up. This article presents a review of the progress of the American alloy steel industry in general, based on an analysis of the data of the American Iron and Steel Institute. It supplements a similar article, published in THE IRON AGE, Sept. 28, 1922, and covers developments of the years 1922 and 1923. The alloy steel casting in- dustry is discussed, particularly the progress made in the output, year by year, of electric alloy steels as a whole and electric alloy steel castings. \ NEW record in the alloy steel industry of the Expansion of the Entire Alloy Steel Industry The feature of the development of the alloy steel in- dustry in the last two years has been the expansion in production. In 1923 more alloy steel of all kinds was 0.0 wT fmm dA a od NA Fray a Ty | INE co nm oO ei ye PEE Hesse: er Tita eee ae of Gross Tons and Percentage How the Proportion of Alloy Steel to the Total Steel Produced Has Been Gradually Increasing. The use of the ratio chart makes the rates of fluctuation truly comparable made than in any previous year—2,106,489 gross tons. The next largest production was 1,787,852 tons in the war year, 1918. The next largest peace-time output was 1,673,496 tons in 1922. The striking fact, however, is that in 1923, as well as in 1922, the percentage of alloy steel of the total ingot and castings output of the coun- ANNEYECUITEVETONOREANNEENECEDOENEENYTUNDONE™YFRETOOEEONNHROTEAERE RUT EOODODERDHENL ENN FTITYTERNEFDICONTLONTTTNrNED OLEOUETDOUNETEETORTYORESDOOEOENEG>G couRRE TERE *y1t( Hy rr HonenE Table 1—Production of Steel Ingots and Castings and of Alloy Steel Ingots and Castings in the United States Tons of Total Alloy Alloy Steel Total Steel Steel, Steel, ofthe Total, tol Ton Gross Tons Gross Tons Per Cent Alloy Steel SD aan 5.6% 23,955,021 181,980 0.75 131.6 Rass ses 26,094,919 567.819 2.17 45.9 |) ae 23,676,106 481,459 2.03 49.1 Re % 4.60 31,251,303 792,501 2.53 39.4 Sa 31,300,874 714,357 2.28 43.8 are 23,513,030 646,953 2.75 36.3 i) ee 1,021,147 3.17 31.4 Rs 6 6.05% 42,773,680 1,362,615 3.18 31.3 BE Wks aoa 45,060,607 1,644,335 3.65 27.4 64h 44,462,432 1,787,852 4.02 24.8 Ns c's wa a 34 ‘671,232 1,481,188 4.27 23.4 BOs vate 42,132,934 1,660,292 3.94 25.3 EE oh ko a 2 19,783,797 809,548 4.10 24.3 ee 35°602'926 1,673,496 4.70 21.2 SU <4 44,943,696 2,106,489 4.70 21.3 try expanded to 4.70 per cent, as compared with the best previous record of 4.27 per cent in 1919. The increase in the proportion of alloy steels pro- duced has been gradual but steady since 1909. The actual figures are given in Table 1 and the development is shown graphically by one of the charts. In its in- fancy, or in 1909, the alloy steel production was only 0.75 per cent of the total steel output. This had ex- panded about threefold by 1913 and over six and one- quarter times by 1923, or in 15 years. Expressed otherwise, the rate of production of total steel to alloy steel in 1909 was over 130 to 1, or there were about 130 tons of steel ingots and castings made HUET UUEPEVENTUEPULUNED EAT ELEEEFRY CEE ITER TERLEON /UDONREL ETERS CRO VENETOTEEOONATUNROSROCRERNT Table 2—Production of Total Alloy Steel and of Alloy Steel Castings in the United States Total Alloy Total Alloy Steel, Castings, Percentage of Gross Tons Gross Tons Castings of Total Desens asus ; 23,002 12.64 29,357 5.17 56,290 11.69 103,109 13.01 88,927 12.44 69,846 10.79 97,896 9.58 56,458 4.14 67,529 4.10 66,485 3.71 45,372 3.06 68,353 4.11 40,255 4.97 59,104 3.53 92,220 4.37 COC OPE UPN UPTITPT PEIN FEET DETTE) CEEOL cena ORR NEN ERECT ONE for every ton of alloy steel. The last column of Table 1, giving these ratios, shows that the alloy steel indus- try received its impetus in 1910. The Alloy Steel Casting Industry An interesting phase of this analysis is the extent to which alloy steels have been incorporated in castings. This development is shown in Table 2, which, based on the same statistics, gives the total alloy steel and the total alloy steel castings output during the last 15 years. If the record of 1921 is eliminated, which was an abnormal year in many respects, 1923 recorded a sub- 618 September 11, 1924 stantial advance in the proportion of alloy castings to the total alloy steel. In 1923 this was 4.37 per cent, or the largest since 1915, excepting 1921. In this field of the alloy industry an unusual com- parison between present and pre-war tendencies exists. With the exception of 1910, during each year from 1909 to 1915 inclusive, a much larger tonriage and percentage of alloy castings was made than for any year since. A much smaller proportion has been made as castings from 1916 to the present time. For the six years (omitting 1910) prior to 1916, this percentage of alloy steel castings of the total alloy steel averaged 11.69 per cent, while from 1916 to 1923 inclusive this average has been about 4 per cent. Singularly in the depres- sion of 1921 the percentage was 4.97 per cent, the largest of any of recent years. The explanation offered when this subject was dis- cussed two years ago is unchanged now: In the few years just prior to 1915 a very large quantity of cast steel frames for locomotives was made containing vanadium. Many of the railroads ordered them, partly as an experiment and partly as regular equipment. This, of course, ran the total of alloy castings into large figures as each engine frame was very heavy. While this practice by the railroads still continues, it possibly does not represent so large a tonnage as formerly. This may account in part for the difference referred to. The more reasonable con- clusion is, however, that the increased use of alloy steels has been in rolled and forged material which has consequently cut down the proportion of castings in the total. OOGCULLLIUAEOOEAD AA OMMAA DOE RELEDUAADRSAOEDUNE CUOGEEE. © LMdUHSHRLILLAb4ASGLONSA PAAELELAUOGS FEAMOAL LOADLOSOROEOCE OA RAMOS LOMOSEDERA* GANA ALISON) 04 0UN( 4 CNN DNRLEAE) DNRDEONEL /AELLAC LE Table 3—Production of Total Alloy Steel and of Alloy Steel in Electric Furnaces in the United States Electric Total Electric Alloy Steel Alloy Steel, Alloy Steel, of Total Alloy Gross Tons Gross Tons Steel, Per Cent 1) eee Be.) Sy, sos ees niet BN ies a earn 567,819 608 0.11 BORED ga eden ua Sean 8.92 Seeees ad Bs oa cad oe 792,501 9,619 1,21 |) SS ae 714,357 11,264 1.57 Renee se veee ea 646,953 9,344 1.44 BOD vic dn pO Ge 1,021,147 27,944 2.73 L926 candied 1,362,615 71,129 5.22 ROLF os. cnwenns 1,644,335 130,578 7.94 19233 ..0 sw a.kelvs 1,787,852 290,961 16.26 ict ere 1,481,188 181,632 12.26 LGR rinses valet 1,660,292 245,572 14.78 BODE scene snes 809,548 63,246 7.81 19Ras cacketbas 1,673,496 125,419 7.49 1988s bs ve weee 2,106,489 194,976 9.25 OnE Hs A0td4bsn ERO DNADEANRDODO RAAELLOE DOVGEE HYDE» 00800E0UE NOU 1ENOONNAI NORD LOG LO) 4NDIAED ULES LENA LESERDOALAOREDBEROADUTIOD EIEERY cOTBUOTDD © OTC ORUD AROEUEEUOASAIATEDOECEON LIVERS ARERIVED In the light of recent developments the 1924 record will probably show a marked change from that of the past eight years, as the tendency to use heavy castings of alloy steel is increasing considerably. Alloy Steels from Electric Furnaces The electric furnace phase of the American alloy steel industry presents some interesting features. Tak- ing electric alloy steels as a whole and comparing the output with the total alloy steel made, the record for the last 15 years is arranged in Table 3, according to of- ficial data. The feature is the decided expansion in 1923, when 9.25 per cent of the total alloy steel production was made in electric furnaces, the increase over 1921 and 1922 being considerable. Ten years ago the percentage was only 1.57 per cent. The country’s electric steel industry did not assume any real prominence until 1912, since which time the growth has been rapid. A significant fact in this growth, however, is that the ex- pansion in electric alloy steel output has been larger in the years immediately following the war than during the war period, except possibly in 1918. Just why the years 1919 and 1920 should show a better record than the years since is difficult to explain. That a percentage of 7.81 per cent of electric alloy steel should have been made in such a poor economic year as 1921 is inter- esting. Electric Alloy Steel Castings Two years ago the rapid growth of the production of alloy steel castings in electric furnaces was character- ized as the most remarkable development up to that THE IRON AGE 619 ESRF EER B ee Ded 1 PL AE es Hb LR Hundreds of Gross Tons and Percentage bs eed Castings of Electric Alloy Steel Have Rapidly Been Increasing in Tonnage and in the Percentage of All Alloy Steel Made in Electric Furnaces time. It appeared first in 1921. Developments since have shown that this was not spasmodic. The real facts are brought out in Table 4 and in the second chart. While the percentages in 1922 and 1923 are not quite so large as in 1921, or 14.20 per cent and 14.90 per cent respectively, against 15.94 per cent in 1921, they are so much larger than in any years previous to 1921 that it is safe to say that the increase registered in 1921 has become an established one. During the war the relative tonnage of electric alloy steel castings was even smaller than bef. the war, but by 1918 such castings came into demand and from 3.33 per cent of electric alloy castings made in 1919 the expansion has continued until in the last three ES bEUED EGE VAUNSUBALL ERE U/ LOLOL DUNENOANDRETUEDOEDNGONRDS HTL OG YERDERANRD ND //CDEERL). /L4H0) PI LDO MENS HINRL HrRRbOMRRONIBEBS HL FEFNDOREDI NERS AI ERDD Hoes Femi" Table 4—Production of Total Alloy Steel and of Alloy Bteel Castings from Electric Furnaces in the United States Electric Total Electric Dlectric Alloy Castings Alloy Steel, Alloy Castings, of Total Alloy Gross Tons Gross Tons Steel, Per Cent BPO. chwed ove. +. 36eRe Os tuts eee one BEETS 3 ks os 608 8 1.32 PREG 6 8 cesin Ll Shs SU ee eae ENG e case 9,619 402 4.18 Ess sos ae % 11,264 443 3.93 Beets 65 Rs 9,344 340 3.64 BEA ail abies aie 27,944 96 0.34 ) ” BAe ees 71,129 926 1.30 Si 130,578 1,296 0.99 hy ie oie ve wa 290,961 3,076 1.05 BOGS. « cauebe « 181,632 6,057 3.33 RR Sere 245,572 11,710 4.77 BOR ccc cubes 63,246 10,084 15.94 > Re se 125,419 17,760 14.20 SOs «bere as 194,976 29,054 14.99 D0 LULET ET Onan RN. cee ENORDEROERDED COO LEPPEDORRDE HL Dee pe: /eerR cot eUmERCDSREN years an average proportion ef about 15 per cent has been reached. In 1923 the quantity of such material reached 29,0564 tons. The fact that this total is more than that of any previous two successive years emphasizes the growth in use of electric alloy steel castings. One cause has been, and is, the constantly greater use of heat-treated elec- tric alloy steel castings in place of regular forgings. Another factor is the production of manganese steel castings in the electric furnace instead of the converter. tS Rr oe Ret Lig a: - saad ae VaPeaaET" ao me 5 as i gt en NE ar ee ae tm Petia Reply Femme 620 In the last three or four years several plants have been erected for the electric production of manganese steel castings. Two Vital Factors The history of the last two years emphasizes the statement miade in this review two years ago—that two modern developments have made the alloy steel in- dustry possible: First, the electric furnace, and, second, the art of heat treatment. Before the advent of the former most ferroalloys were non-existent; now they are a common commercial product of electric furnaces with new ones developed. frequently, These in turn are making possible the production of new alloy steels. In the field of heat treatment, so rapid has heen the devel- opment of processes and of knowledge concerning actual reactions and effects as well as the perfection of equipment that not only are alloy steels brought to the highest efficiency, but even carbon steels are being im- proved. No better evidence of the importance of both the electric furnace and of heat treatment to the alloy : steel industry in particular and to the steel industry in general is at hand than the phenomena! growth of the American Society for Steel Treating. Progress in the development of alloy iron castings has been rapid in the last two years and should be men- } tioned here. The field is a broad one and full of im- portant possible developments. Details as to the extent of the expansion in this realm are not now at hand, but it is certain that considerable attention ha