Effects of Heat Treatment on Microstructure and Properties of 18CrNiMo7-6 Steel
Effect of two heat treatment process(quenching and low temperature tempering,double quenching and low temperature tempering)on microstructure and cryogenic impact toughness of 18CrNiMo7-6 steels was studied.The results show that the microstructure of the steel samples after quenching is mainly lath martensite and retained austenite,the microstructure of the steel samples after double quenching is mainly martensite,retained austenite and fine ferrites,the ferrites is beneficial to improve toughness.The grain size of the steel samples after double quenching is finer and more uniform than that of the steel samples after quenching.The finer and more uniform grain and microstructure make the steel samples after double quenching exhibit better impact toughness at-20 ℃.
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