COLD-ROLLED STEEL SHEET OR HOT-ROLLED STEEL SHEET HAVING EXCELLENT HARDENABILITY IN COATING/BAKING AND COLD AGING RESISTANCE, AND ITS PRODUCTION METHOD

摘要

PROBLEM TO BE SOLVED: To provide a steel sheet having good hardenability in coating/baking and cold aging resistance. SOLUTION: This steel sheet has a composition containing, by mass, 0.0001 to 0.20% C, =2.0% Si, =3.0% Mn, =0.15% P and =0.015% S, containing Al and N so as to satisfy =0.10% Al, 0.001 to 0.10% N and 0.52 Al/N,; 5 and also containing one or more kinds selected from among Cr, Mo and V respectively so as to satisfy =2.5% Cr, =1.0% Mo, =0.1% V and (Cr+3 5Mo+39V)=0.1, and the balance Fe with inevitable impurities, in which BH170 evaluated by being heat-treated at 170 deg.C for 20 min after 2% tensile deformation is =45 MPa, also BH160 evaluated by being heat-treated at 160 deg.C for 10 min after 2% tensile deformation and BH150 evaluated by being heat-treated at 150 deg.C for 10 min after 2% tensile deformation are =35 MPa in both cases, and further, yield point elongation in a tensile test after being heat-treated at 100 deg.C for 1 hr is =0.6%.