The Iron and steel magazine . mass of metal. Roozeboom lays down the line ofthese retardations in alloys with a higher per cent of carbon than2 per cent as horizontal from 10000 C. and assumes that thetime of the formation of the cementite does not, therefore, be-come visible in the cooling curves because the evolution ofheat is too slight to be noticeable on thorough retardations inthe decrease of temperature. ig8 The Iron and Steel Magazine Through recent experiments * small developments of heathave been proved at about iooo° C, at least in a number ofcases; still Osmond f draws attention to
The Iron and steel magazine . mass of metal. Roozeboom lays down the line ofthese retardations in alloys with a higher per cent of carbon than2 per cent as horizontal from 10000 C. and assumes that thetime of the formation of the cementite does not, therefore, be-come visible in the cooling curves because the evolution ofheat is too slight to be noticeable on thorough retardations inthe decrease of temperature. ig8 The Iron and Steel Magazine Through recent experiments * small developments of heathave been proved at about iooo° C, at least in a number ofcases; still Osmond f draws attention to the fact that in takingdown cooling curves uncontrollable variations may take placein the decrease of temperature very easily on account of surfaceoxidation. Throughout the present experiments between 11300and 7000 no delays were noted; the one case (at 8oo° C), Curve7, might be traced to a mistake in observation. Hence the conjecture of Osmond f and Heyn J that theformation of cementite takes place at 11350 C, gains more. Fig. 15. Magnified 500 diameters probability. At this temperature during solidification carbidewould separate out of white iron, while in gray iron the forma-tion of graphite would occur, both processes being accompaniedby considerable evolutions of heat. It is Avorth noticing thatthe stop or retardation in the fall of temperature often extendsover an interval of only io° C, and it will be reserved for laterinvestigations to throw light on its exact meaning by extendingthe interval as much as possible. * Carpenter and Keeling, Journal of the Iron and Steel Institute,May, 1904. t Revue de Metallurgie, July, 1904, p. Heyn: Article already cited. Iron ( ai bon . \ Hoys i pn The further course of the cooling brings at 7000 anotherconsiderable delay; as we shall sec from the metallographicinvestigation, this point corresponds to the temperature wh< carbide is insoluble1 in iron and consequently the entire massof solid solution is divided into an intim
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