| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of a steel plate which has high strength and high toughness and which is prevented from cracking due to shearing. SOLUTION: After steel consisting of, by mass, 0.03-0.12% C, 0.01-0.5% Si, 1.5-3.0% Mn, 0.01-0.08% Al, 0.01-0.08% Nb, 0.005-0.025% Ti, 0.001-0.01% N, 0.0005-0.003% B, furthermore, 0.01-2% Cu, 0.01-3% Ni, 0.01-1% Cr, 0.01-0.1% Mo, 0.01-0.1% V, as necessary, one kind or two or more kinds of Ca, REM, Zr, Mg and the balance Fe with inevitable impurities is heated to 1,000-1,200°C, rolling is performed at≤950°C and at the cumulative rolling reduction of≥70% and, after finishing the rolling at≥800°C, the accelerated cooling of 20-80°C/s is started at≥700°C to < 800°C, the cooling is stopped at < 250°C and reheating is immediately performed at 5°C/s to 300-500°C. COPYRIGHT: (C)2007,JPO&INPIT
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