| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength martensitic stainless steel oil well pipe having excellent corrosion resistance and high strength even under a severe environment containing CO2, Cl-, etc., capable of being connected by welding, and excellent in weldability. SOLUTION: This steel pipe has a composition containing, by mass, 10.5-15.0% Cr, 0.30-2.00%; Mn, <=7.0% Ni, <=0.20% Nb, and <=0.20% V, also containing C, N, Si, S, Al and O limited to <=0.03% C, <=0.03% N, <=0.70% Si, <=0.005% S, <=0.05% Al and <=0.01% O, and further containing alloying elements under the condition satisfying C+N<=0.04, 0.01<=0.8Nb+0.5V<=0.20, Cr+Mo+16N+0.5 Ni-5C>=11.5, and 1.1(Cr+1.5Si+Mo)-Ni-0.5(Mn+Cu)-30(C+N)<=11 (where C, N, Nb, V, Cr, Ni, Si, Mo, Mn and Cu represent the contents (mass %) of respective elements).
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