NON-TEMPERED STEEL PLATE HAVING EXCELLENT LARGE HEAT INPUT WELDING HAZ TOUGHNESS AND TOUGHNESS AFTER HEATING AND WORKING

摘要

PURPOSE:To provide the steel plate satisfying the severe requirement for toughness by incorporating specific % of C, Si, Mn, Al, Ti, N, and B into this steel plate in such a manner that the ratios of the B, N and Ti satisfy specific relations and constituting the balance of iron. CONSTITUTION:The non-tempered steel is constituted by incorporating 0.02 to 0.12% C, =0.40% Si, 0.5 to 1.60% Mn, 0.01 to 0.04% Al, 0.005 to 0.012% Ti, 0.002 to 0.005% N, and 0.0005 to 0.0015% B into the steel plate, and consisting the balance of iron and unavoidable impurities. The conditions of formula I are satisfied. Further, one or two kinds of =1.00% Cu and =1.00% Ni may be incorporated therein. The non-tempered steel plate having the excellent large heat input welding HAZ toughness and toughness after heating and working for large-sized welded structures, such as ocean structures, ships and storage tanks, is provided in this way.