K. Monma, S. Uemura and M. Hirata
It is well known that the resistivity of quenched steel is much higher than that of annealed one. Especially in the cases of high speed steel and K. S. magneto-steel, the values of quenched state are remarkably high.
Hitherto it has not been throughly explained in what process such high resistivity condition was accompanied by Ar'' transformation.
The authors measured the electrical resistance change during Ar'' transformation of high speed steel and some other special steels. And the following results were obtained: (1) The resistivity increased remarkably in Ar'' transformation, (2) but even in the case of Ar'' transformation, when the occurring temperature was some what higher than a certain critical value,—which varies with the kind of steels—, the resistivity showed a remarkable decrease with the transformation.
The transformation of type (2) was notationed Art''. The main cause of resistivity increase accompanied by Ar'' transformation may be explained as being due to the high resistivity of supersaturated α -solid solution. In the case of Art'' the transformation temperature was so high that the transformed supersaturated α -solution could not hold its own state, consequently, the carbide precipitated out of it. This is the reason why the resistivity decreased in Art'' transformation.
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