1.2C-1Si-17Cr-2.5Mo-0.8V工具鋼の経年ひずみ

概要

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The effects of tempering temperature on distortion in service of a 1.2C-1Si-17Cr-2.5Mo-0.8V, mass%, tool steel which was developed for precision molding die of semi-conductors such as LSI were investigated. When tempered at 490℃ after quenched from 1125℃ followed by subzero treating, the steel possessed a very small distortion in service less than 1×10^<-5> under cooling-heating cyclic test, in accompany with a significant hardness above 62HRC. The small distortion in service was associated with an increase in retained austenite stability against the martensite transformation which was evaluated by lattice parameter of the retained austenite and its increment on tempering. It was expected that the stabilization of the retained austenite was resulted from dissolution of M_3C carbides and suppression of M_<23>C_6 alloy carbide precipitation.