Low yield ratio high toughness thick steel plate excellent in low temperature impact toughness and method for producing the same

摘要

Provided is a low-yield-ratio high-strength-toughness thick steel plate with excellent low-temperature impact toughness, which comprises: 0.05%-0.11% of C, 0.10%-0.40% of Si, 1.60%-2.20% of Mn, S0.003%, 0.20-0.70% of Cr, 0.20%-0.80% of Mo, 0.02%-0.06% of Nb, 3.60%-5.50% of Ni, 0.01%-0.05% of Ti, 0.01%-0.08% of Al, 0 N‰¤0.0060%, 0 O‰¤0.0040%, and 0 Ca‰¤0.0045%, with the balance being Fe and inevitable impurities; in addition, Ni + Mn ‰¥ 5.5 is also satisfied. The manufacturing method for the above-mentioned steel plate comprises smelting, casting, heating, two-stage rolling, quenching, cooling after quenching, and tempering.