| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method for a high strength steel sheet in a grade of API X65 or higher which exhibits excellent resistance to HIC (hydrogen induced cracking) in a central segregated part, and that occurring in the vicinity of a surface and from inclusions, and has excellent weld toughness. SOLUTION: Steel having a composition containing, by mass, 0.02 to 0.08% C, 0.01 to 0.50% Si, 0.5 to 1.8% Mn,≤0.01% P,≤0.002% S, 0.05 to 0.50% Mo, 0.005 to 0.04% Ti, 0.01 to 0.07% Al, 0.005 to 0.05% Nb and/or 0.005 to 0.10% V is subjected to hot rolling at a heating temperature of 1,000 to 1,250°C and at a rolling finishing temperature of 750 to 950°C, and is thereafter cooled to 600 to 700°C at a cooling rate of≥2°C/s. The steel sheet is subjected to heating to 600 to 700°C for one or more times, and the time in which the average temperature of the steel sheet lies in 600 to 700°C is controlled to≥3 min. COPYRIGHT: (C)2003,JPO
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