HIGH STRENGTH STEEL FOR WELDED STRUCTURE HAVING EXCELLENT SURFACE CRACK RESISTANCE AND METHOD FOR PR

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PROBLEM TO BE SOLVED : To provide a high strength steel for a welded structure having excellent surface crack resistance, and to provide a method for producing the same. SOLUTION : The high strength steel for a welded structure having excellent surface crack resistance has a composition containing, by mass, 0.01 to 0.20% C, 0.02 to 0.50% Si, 0.3 to 2.5% Mn, ≤0.03% P, 0.001 to 0.03% S, 0.01 to 1.0% Cu, 0.005 to 0.05% Nb, 0.001 to 0.05% Al, 0.005 to 0.05% Ti, 0.001 to 0.01% N, 0.0005 to 0.01% rare earth metals, 0.0001 to 0.003% Ca, and the balance iron with inevitable impurities, and in which the grain size of γ in the surface layer of the slab is ≤1, 200 μm. COPYRIGHT : (C)2009, JPO&INPIT