LOW-YIELD-RATIO HIGH-STRENGTH-TOUGHNESS THICK STEEL PLATE WITH EXCELLENT LOW-TEMPERATURE IMPACT TOUGHNESS AND MANUFACTURING METHOD THEREFOR

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, S≦0.003%, 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, 0N≦0.0060%, 0O≦0.0040%, and 0Ca≦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.