. Transactions. ffect of a very high annealing temperature and a heavywall section. Notes on Mechanics of Graphitization of Normal White Cast Iron as Observed in Specimens Quenched AT Approximately 800° C. Briefly stated, the completely cooled normal white iron consists ofpearlite and cementite. There are, however, four kinds (from the view- ^ Bean. Highriter and Davenport: Fractures and Microstructures of AmericanMalleable Cast Iron. Trans. Amer. Foundrymens Assn. (1920) 29. VOL. LXVII.—31 482 MALLEAl^LEIZING OF WHITE CAST IRON point of origin and state of aggregation) of cementite, namely: m
. Transactions. ffect of a very high annealing temperature and a heavywall section. Notes on Mechanics of Graphitization of Normal White Cast Iron as Observed in Specimens Quenched AT Approximately 800° C. Briefly stated, the completely cooled normal white iron consists ofpearlite and cementite. There are, however, four kinds (from the view- ^ Bean. Highriter and Davenport: Fractures and Microstructures of AmericanMalleable Cast Iron. Trans. Amer. Foundrymens Assn. (1920) 29. VOL. LXVII.—31 482 MALLEAl^LEIZING OF WHITE CAST IRON point of origin and state of aggregation) of cementite, namely: massivepro-eutectic cementite, eutectic cementite, pro-eutectoid cementite,eutectoid cementite (pearlite). In some instances, it is possible to distinguish all of these elementswithin a rather limited area; more often, however, we are unable to makethese deductions with any degree of assurance. The massive pro-eutectic cementite results from supercooling as indicated by the pro-longation of line AB in Fig. 3X> Pi^CiSiit Carhan SO O Id Fig. 27.—Iron-carbon equilibrium diagram. Fig. 1 is typical of the structure of rapidly cooled cast iron. Theledeburite (eutectic) in the lower right-hand corner is small in amountbecause of the large amounts of structurally free cementite resultingfrom supercooHng; the pro-eutectoid cementite is in the form of needlelikeareas. The dark areas consist of pearlite formed by the transformationof the austenite at the Ai point. Much has been written on the general subject of the graphitizationof gray and malleable iron. The earlier investigators in this fieldapparently believed that it is essentially the structurally free and meta-stable cementite that decomposes at the higher temperatures to form ARTHUR PHILLIPS AND E. S. DAVENPORT 483 ferrite and graphite, or temper carbon. ]\Iore recentlj, however, severalinvestigators, notably Storey, Archer,^ and ]Merica° have suggestedthe possibility of graphitization direct from solid soluti
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