. Transactions. ommittee,Proc. Inst. Mech. Eng. (1905) Pt. 4, 857. ^ Portevin: Rev. de Met. (1917) 14, 707; also Preprint Iron and Steel Inst., Sept.,1919. Chevenard: Ibid., 610. Scott: Trans. (1920), 62, 689. Also U. S. Bureau of Standards Sci. Paper 335.» Dejean: Compt. Rend. (1917) 165, 429. 104 CRITICAL RANGES OF SOME COMMERCIAL NICKEL STEELS microstructure of the same steels air-cooled from above Acz- A fewcorrections have been made to their values from the curves so that thetabulated results would be comparable on the basis of observations takenfrom derived differential or inverse-rate c
. Transactions. ommittee,Proc. Inst. Mech. Eng. (1905) Pt. 4, 857. ^ Portevin: Rev. de Met. (1917) 14, 707; also Preprint Iron and Steel Inst., Sept.,1919. Chevenard: Ibid., 610. Scott: Trans. (1920), 62, 689. Also U. S. Bureau of Standards Sci. Paper 335.» Dejean: Compt. Rend. (1917) 165, 429. 104 CRITICAL RANGES OF SOME COMMERCIAL NICKEL STEELS microstructure of the same steels air-cooled from above Acz- A fewcorrections have been made to their values from the curves so that thetabulated results would be comparable on the basis of observations takenfrom derived differential or inverse-rate curves. Unfortunately, the tem-perature of the Ac I transformation cannot be estimated with any degreeof certainty from the curves given. In Fig. 4, the limits over which both martensite and troostite are foundin the air-cooled samples have been indicated by dotted lines. SinceCarpenter, Hadfield, and Longmuir did not examine microscopicallytheir samples used for thermal study, it is impossible to set accurately. 0 5 10 Per Cent Nickel Fig. 4.—Effect of nickel on the thermal critical ranges of to per CENT, carbon steels FROM DATA OF CaRPENTER, HaDFIELD, AND LONGMUIR. the limits of the range of nickel content over which, for the rate of coolingadopted, both martensite and troostite will be found and also the com-position at which ferrite no longer separates out, but this latter is probablysomewhere within the former region. The sharp temperature differencebetween Ar and Ari occurring between and 9 per cent, nickel contentsthe author believes to be quite significant and to correspond to the for-mation of appreciable amounts of troostite, for the marked structuraldifference between troostite and pearlite would indicate a similar thermaldifference. Besides these investigations of the changes in the physical propertiesof nickel steels, Meyer^ has studied microscopically the effect of nickel » Meyer: Stahlu. Eisen (1914) 34, 1395, 1456. HOWARD SCOTT 105 and manganese
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