| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength steel sheet of a grade of API X80 or above which exhibits excellent resistance to HIC (hydrogen induced cracking) in a central segregated part, and HIC occurring from the vicinity of the surface and inclusions without undergoing the addition of large quantities of alloy elements. SOLUTION: The high strength steel sheet has 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, >0.04 to 0.10% Ti and 0.01 to 0.07% Al, and the balance substantially Fe, and in which C/(Mo+Ti) as the ratio of the C content to the total content of Mo and Ti by atomic % is 0.5 to 3.0, and has a metallic structure substantially consisting of a ferritic single phase, and in which precipitates containing Ti and Mo are dispersedly precipitated.
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