PRODUCTION OF CARBURIZED CASE HARDENING STEEL HAVING EXCELLENT DELAYED FRACTURE RESISTANCE

摘要

PURPOSE:To improve the delayed fracture resistance of the carburized case hardening steel by executing tempering after the hydrogen content attains a specific value or below after carburization hardening in the gas carburization treatment of the carburized case hardening steel. CONSTITUTION:The carburized case hardening steel is rested for =20 days without executing the tempering right after carburization hardening in the gas carburization treatment (excluding vacuum carburization and plasma carburization) of the carburized case hardening steel. The tempering is executed after the hydrogen content attains =0.3ppm by completely diffusing the infiltered hydrogen in this way. The delayed fracture resistance of the carburized case hardening steel is greatly improved by this method.