A steel-induced cracking

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PROBLEM TO BE SOLVED : To provide a steel material excellent in hydrogen-induced crack resistance which can prevent generation of an internal inclusion defect, and to provide a method for producing the same. SOLUTION : The steel material excellent in hydrogen-induced crack resistance is obtained by rolling a steel cast piece including, by mass, 0.03 to 0.10% C, 0.1 to 0.5% Si, 0.8 to 2.0% Mn, 0.030% or less P, 0.0025% or less S, 0.005% or less N, 0.010 to 0.11% sol. Al, 0.0004 to 0.0040% Ca, and 0.0003 to 0.0060% of a rare earth element (REM), with the balance being Fe and inevitable impurities. The percentage of the number of the following inclusions present in the steel material is 50% or more : (i) the maximum circle equivalent diameter of the inclusions present in the steel material is 30 μm; and (ii) in the cross sectional view in the rolling direction of the steel material, the average composition is %Al2O3+%CaO+%REM2O3≥80%, and the area of the region of (%REM)/(%Al+%Ca+%REM)≥0.5 is 40% or more of the total area. COPYRIGHT : (C)2012, JPO&INPIT