| 摘要 |
PROBLEM TO BE SOLVED: To increase the time strength of steel in a sour environment by allowing it to have a specified compsn. contg. C, Si, Mn, S, P, Mo, V, Al, N, and the balance Fe with inevitable impurities and allowing it to have a steel structure composed of a martensitic one. SOLUTION: This steel contains, by mass, 0.10 to 0.35% C, <=0.5% Si, 0.1 to 1.0% Mn, <=0.005% S, <=0.015% P, 0.15 to 1.0% Mo, 0.3 to 3.0% V, <=0.1% Al and <=0.01% N. The steel may moreover contain, at need, one or more kinds among <=0.3% Nb, <=0.1% Ti, <=0.003% B, <=1.5% Cr and <=1% Co. The steel may furthermore contain one or more kinds among <=0.02% Ca, <=0.05% rare earth metals, <=0.1% Zr and <=0.01% Mg. The steel has high hardenability, whose structure can be formed into a martensitic one and is suitable for a steel pipe for oil well use in particular.
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