Transactions . ieve that I can representit, under the special conditions of quenching already dennedby_the diagram here given in Fig. 1. This is, however, a some- * Comptes rendus, vol. cxxi., p. 684, November 11, 1895. MICROSTRUCTURE OF STEEL AND THEORIES OF HARDENING. what crude approximation, and should be rendered more accu-rate by numerous experiments. For the same steel, with per cent, of carbon, the microstructural compositionwould be represented in terms of temperature of quenchingby a diagram such as Fig. 2. In other words, the proportionof segregated cementite, which shou
Transactions . ieve that I can representit, under the special conditions of quenching already dennedby_the diagram here given in Fig. 1. This is, however, a some- * Comptes rendus, vol. cxxi., p. 684, November 11, 1895. MICROSTRUCTURE OF STEEL AND THEORIES OF HARDENING. what crude approximation, and should be rendered more accu-rate by numerous experiments. For the same steel, with per cent, of carbon, the microstructural compositionwould be represented in terms of temperature of quenchingby a diagram such as Fig. 2. In other words, the proportionof segregated cementite, which should be some 13 per the steel in question, quenched above Ar3i2,i, may vary fromabout 13 per cent, to almost none. This shows that the ce-mentite continues to be dissociated, or at least to be dissolvedprogressively, when the temperature is progressively raisedabove the critical point. As I see absolutely nothing among the observations of which is in contradiction with my own, I hold the latter. 400 500 600 TOO S00 Temperatures (degrees Microstructural Composition of Steel Containing to per cent, of Carbon,and Quenched at Various Temperatures. valid; and I conclude that the changes of structure, not beingnecessarily restrained at the critical points, are not the causeof these points. The opinions of Mr. Sauveur, moreover, from the triplepoint of view of chemistry, physics and mechanics, raise diffi-culties which he has been the first to recognize and very frankly to point out. From the chemical point of view the minute state of divisionof the carbide Fe3C explains sufficiently well the readiness withwhich it could be attacked by hydracids, because plates of di-mensions which do admit of measurement appear to be a littleattacked. But in the colorimetric estimation of carbon byEggertzs method, why is it that in hardened steel there is acertain amount of carbon which is apparently lost? The fine MICROSTRUCTURE OF STEEL AND THEORIES OF HARDENING. 881
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