To provide a steel heat treatment method, a manufacturing method of machine parts, machine parts and a rolling bearing including the machine parts capable of suppressing degradation of the hardness and enhancing the dimensional stability in a quasi-high temperature environment, and improving the hardness level.
The steel heat treatment method comprises a step of preparing steel containing, by mass, 0.1% and 0.4% carbon, 0.1% and 1.1% silicon, 0.5% and 1.5% manganese, and the balance iron with impurities, a step of forming a nitrogen-enriched layer in an area including the surface of steel by executing the carbonitriding of the steel at the temperature of A1 point or above, and a step of executing the bainite transformation of the nitrogen-enriched layer so that the amount of the retained austenite in the nitrogen-enriched layer is 5 vol.% by keeping the steel at the temperature exceeding the MS point of the nitrogen-enriched layer and the temperature equal to or higher than the MS point by 50C.
Toshio Morita
Yoshihei Nakamura
Yutaka Horii
Hisato Noda
Masayuki Sakai
Nobuo Arakawa