| 摘要 |
PROBLEM TO BE SOLVED: To produce a ferrite-martensite duplex stainless welded steel pipe exhibiting excellent SSC resistance and toughness in in oil well environment even without executing quenching and tempering heat treatment and annealing heat treatment for a long time to a hot rolled steel sheet as the stock and a steel pipe after pipe making by welding. SOLUTION: This ferrite-martensite duplex stainless welded steel pipe has a composition containing, by mass, <=0.02% C, <=0.04% P, <=0.01% S, 2 to 8% Ni, 11.5 to 15% Cr, 1.5 to 4% Mo, 0 to 1% Si, 0 to 1 % Mn, 0 to 0.1% sol.Al, 0 to 1.2% Cu, 0 to 0.2% Ti, <=0.02% N, 0.1% V, and the balance Fe with impurities, and in which the content of ferrite in the metallic structure is 15 to 40 volume %.
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