HOT ROLLED HIGH STRENGTH STEEL PLATE FOR WORKING, EXCELLENT IN FATIGUE CHARACTERISTIC AND HAVING THERMAL SOFTENING RESISTANCE, AND ITS PRODUCTION

摘要

PURPOSE: To stably produce a hot rolled high strength steel plate for working, excellent in fatigue characteristic and having thermal softening resistance, at a low cost. ;CONSTITUTION: This steel has a composition consisting of, by weight ratio, 0.03-0.20% C, 1.0-5.0% Al, 0.5-3.5% Mn, ≤5.0% Si, ≤0.05% P, ≤0.01% S, and the balance Fe with inevitable components. Moreover, this steel is constituted, as a microstructure, of ferrite as a primary phase and a secondary phase, and further, the volume occupancy of ferrite is ≤50% and the ratio of Vickers microhardness between the ferrite and the secondary phase (secondary-phase hardness/ferrite hardness) is regulated to ≤1.5. As characteristics, this steel has ≥400MPa tensile strength (TS), ≥18000 (MPa.%) strength-and-(total elongation) balance (tensile strength × total elongation), ≥12000(MPa.%) strength- and-(uniform elongation) balance (tensile strength ×(uniform elongation), and ≥0.50 fatigue limit value. By this method, the hot rolled high strength steel plate for working, excellent in fatigue characteristic and having thermal softening resistance, can be obtained.;COPYRIGHT: (C)1996,JPO