| 摘要 |
PURPOSE:To improve and uniformize the hardenability of a steel material contg. specified weight percentages of C, Si, Mn, Cr, Al and N by heating the steel material to a prescribed temp., forging, it, and carrying out hardening at a specified temp. CONSTITUTION:A steel material having a composition contg. 0.26-0.50% C, <=0.50% Si, 0.30-1.8% Mn, <=0.020% P, 0.01-0.2% S, <=0.006% Al and <=0.005% N or further contg. <=1.2% Cr and/or <=0.3% Mo is heated at 990-1,200 deg.C and forged, and direct hardening is carried out at >=850 deg.C. Since the steel material having said regulated Al and N contents is heated at 990-1,200 deg.C and forged, the formation of soft spots during the hardening is prevented owing to mixed austenite grains and the hardenability is improved and uniformized. |
