The surface crack resisting properties and high strength steel with a manufacturing method therefor

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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. ŽSOLUTION : 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 1.8% Mn, ≤0.03% P, 0.001 to 0.03% S, 0.01 to 1.0% Cu, 0.001 to 0.05% Al, 0.005 to 0.05% Ti, 0.001 to 0.01% N and 0.0005 to 0.01% rare earth metals, and the balance iron with inevitable impurities, and in which the grain size of γ in the surface layer of the slab is ≤1, 500 μm. ŽCOPYRIGHT : (C)2009, JPO&INPIT Ž