Production manner null of steel for crystal granularity stabilization superficial charring

摘要

PURPOSE: To provide the method for manufacturing case hardening steel for machine parts to be subjected to working under very severe conditions for their grain size such as spheroidizing annealing and cold forging. ;CONSTITUTION: The method for manufacturing grain size stabilized case hardening steel in which steel contg., by weight, 0.08 to 0.30% C, 0.05 to 1.0% Si, 0.3 to 2.0% Mn, 0.015 to 0.050% Al, 0.02 to 0.10% Nb and 0.015 to 0.030% N as well as in the range of N(%) ≥0.52×Al(%)+0.15×Nb(%) and the balance Fe with inevitable impurities is heated to ≥1150°C, is thereafter subjected to hot rolling in such a manner that its finishing temp. is regulated to 950 to 800°C and is thereafter cooled to the A1 transformation point or below at 0.3 to 0.05°C/sec is provided.;COPYRIGHT: (C)1993,JPO&Japio