| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength steel sheet for a sour-resistant line pipe excellent in material uniformity in the steel sheet which is suitable for use in a field, such as a line pipe, and a method for producing the same.SOLUTION: The steel sheet includes, in mass%, 0.02-0.08% of C, 0.01-0.5% of Si, 0.5-1.8% of Mn, 0.01% or less of P, 0.001% or less of S, 0.01-0.08% of Al, 0.0005-0.005% of Ca, and if necessary, one or two or more of Cu, Ni, Cr, Mo, Nb, V, and Ti, with the balance of Fe and unavoidable impurities, wherein metal structure is bainite structure, variation of hardness in the through-thickness direction is &Dgr;H25 or less, the variation of hardness in the sheet width direction is &Dgr;H25 or less in Vickers hardness, and the maximum hardness in the steel sheet surface layer part is &Dgr;H220 or less in Vickers hardness. The steel with the component composition is heated to a specific temperature, and is subjected to hot rolling, then accelerated cooling, and reheat treatment. |
