| 摘要 |
PROBLEM TO BE SOLVED: To produce a steel for a seamless steel pipe having high strength of >=110 ksi yield stress, excellent in toughness and producible by inline heat treatment. SOLUTION: This steel for a seamless steel pipe has a composition containing, by mass, as fundamental components, 0.15 to 0.35% C, 0.1 to 1.5% Si, 0.3 to 1.5% Mn, <=0.005% S, 0.05 to 1.5% Cr and 0.001 to 0.2% sol.Al, and furthermore, either of <0.015% P, <0.003% N and a trace amount of Ti.
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