| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a high strength/high toughness thick steel plate preventing the generation of cracking on the cutting-off surface at cutting off time with a shearing work and having excellent DWTT (Drop Weight Tear Test) characteristics. SOLUTION: This production method is performed as the followings, by which after reheating at 1,000-1,200°C to a steel composed by mass% of 0.03-0.12% C,≤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 and further, one or two or more kinds of Cu, Ni, Cr, Mo, V, B and if necessary, one or two or more kinds of Ca, REM, Zr, Mg and the balance Fe with inevitable impurities, the hot-rolling is performed so as to become≥67% accumulating rolling reduction ratio in the temperature zone of≤950°C and the cooling is started at 20-80°C/s cooling velocity from the temperature zone of≥700°C after completing the rolling, and the reheating of performed to≥300°C to <500°C at≥5°C/s temperature-rising velocity just after stopping the cooling in the temperature zone of <250°C. COPYRIGHT: (C)2006,JPO&NCIPI
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