| 摘要 |
PROBLEM TO BE SOLVED: To provide a method capable of connecting high-strength oil well steel pipes having excellent mechanical properties in addition to excellent corrosion resistance under a severe corrosive environment containing CO2, Cl-, etc. SOLUTION: The high-strength martensitic stainless steel pipes for oil wells containing <=0.03% C, 0.70% Si, 0.30 to 2.00% Mn, <=0.03% P, <=0.005% S, 10.5 to 15.0% Cr, <=7.0% Ni, <=0.05% Al, <=0.2 % N and <=0.01% O and further containing one or >=2 kinds among Nb, V, Mo, Cu, Ti, Zr, W, B and Ca at prescribed ratios or below and consisting of the balance Fe and inevitable impurities are welded and connected in such a manner that the maximum hardness of a welded joint part attains <=380 HV and the difference between the average hardness of the weld metal and the maximum hardness of a weld heat effected part attains <=100 HV. |
