PRODUCTION METHOD FOR CASE HARDENING STEEL FOR COLD FORGING AND CASE HARDENING STEEL FOR COLD FORGING PRODUCED THEREBY

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a case hardening steel for cold forging which can be cold forged in as-rolled state without being annealed, does not cause abnormal grain growth in the carburization treatment after cold forging, and is excellent in fatigue properties.;SOLUTION: The steel containing 0.10-0.25 wt.% C, 0.15 wt.% or lower Si, 0.50 wt.% or lower Mn, 0.035 wt.% or lower P, 0.035 wt.% or lower S, 1.20-2.00 wt.% Cr, 0.35 wt.% or lower Mo, 0.10-0.30 wt.% Al, 0.0080-0.0250 wt.% N, 0.005-0.10 wt.% Nb, 0.0010-0.0050 wt.% B, 0.0020 wt.% or lower O, if necessary at least either 0.005-0.10 wt.% Ti or 0.005-0.10 wt.% V, and the balance being iron and unavoidable impurities is heated to 1,200-1,350°C and rolled to obtain a steel bloom, which is heated to 800-900°C and rolled at 900°C or lower to obtain a steel bar or a wire rod.;COPYRIGHT: (C)2003,JPO