HIGH STRENGTH HOT ROLLED STEEL SHEET EXCELLENT IN FATIGUE PROPERTY OF BLANKING EDGE FACE AND STRETCH-FLANGING PROPERTY, AND ITS PRODUCTION METHOD

摘要

PROBLEM TO BE SOLVED: To provide a high strength hot rolled steel sheet which is excellent in the fatigue properties of blanking edge faces and stretch-flanging properties.;SOLUTION: The high strength hot rolled steel sheet excellent in the fatigue properties of blanking edge faces and stretch-flanging properties has a composition comprising, by mass, 0.03 to 0.10% C, 0.05 to 1.5% Si, 1.0 to 2.2% Mn, ≤0.05% P, ≤0.01% S, 0.001 to 0.006% N, 0.06 to 0.24% Ti, 0.002 to 0.009% Ce and 0.001 to 0.006% O, and the balance Fe with inevitable impurities, and in which the concentration product of Ce and O also satisfies the inequality (1) of [Ce][O]≤3.8×10^-9, and a bainitic ferrite phase is the structure with the maximum area ratio. If required, Cu, Ni, Nb, Mo and V can further be incorporated therein.;COPYRIGHT: (C)2005,JPO&NCIPI