Transactions . ar black spots indi-cate temperatures at which we found unreabsorbed ferrite, the white-centered circles those at which we found none. Note that the verypure electrolytic steel of carbon agrees with the slightly less pure 4 Cf. Benedicks, Proceedings of the Institution of Mechanical Engineers, Mav, 1910. 592 POSITION OF AE3 IN CARBON-IRON ALLOYS. steel of about carbon. The thermal results of Messrs. Burgessand Crowe with these same steels are shown by means of St. An-drews crosses, X, and plus marks, + . In view of the probability that the eutectoid point is at
Transactions . ar black spots indi-cate temperatures at which we found unreabsorbed ferrite, the white-centered circles those at which we found none. Note that the verypure electrolytic steel of carbon agrees with the slightly less pure 4 Cf. Benedicks, Proceedings of the Institution of Mechanical Engineers, Mav, 1910. 592 POSITION OF AE3 IN CARBON-IRON ALLOYS. steel of about carbon. The thermal results of Messrs. Burgessand Crowe with these same steels are shown by means of St. An-drews crosses, X, and plus marks, + . In view of the probability that the eutectoid point is at carbon and 725°, and that the break at L probably occursat about 760°, representing Ae2, the line HLM represents ourresults closely. Thus in 6 out of our 9 hypo-eutectoid steels, thisline lies within the 10° step in which we found that the reabsorptionof ferrite became complete; in two of the remaining steels it lies 2°or 3° outside this step; and in the last one it lies 7° below this step. 950. carbon, per cent. legend: , No Ferrite (or cementite)present\ MicrographioFerrite (or cementite) present f results End of Ac 3 ) Burgess and Crowes Thermal Beginning of Ar 3\ results Fig. 1.—The Authors Micrographic Reabsorption Determinations of Ac3 inLow-Manganese Steels, Together with the Thermal Determinations ofA3 by Burgess and Crowe on the Same Steels. The agreement is closer than is to be expected under our conditions,in view of the many sources of error, (1) decarburization, (2) persist-ence of solidificational segregation, (3) persistence of transforma-tional segregation, (4) precipitation of quenching ferrite,5 (5) failureto detect the last traces of unreabsorbed ferrite, and (6) tempera-ture errors from various sources. The first four of these act cumu-latively to raise the observed temperature of A3, and the sixth mayact in the same direction. (See § 31, p. 624.) 5 Ferrite which precipitates during the quenching, ;is distingui
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