Patent ID: 7862666

Claim:
A highly corrosion resistant high strength stainless seamless steel pipe for linepipe having a composition comprising: 0.001 to 0.015% C, 0.01 to 0.5% Si, 0.1 to 1.8% Mn, 0.03% or less P, 0.005% or less S, 15.7 to 18% Cr, 0.5% or more and less than 5.5% Ni, 0.5 to 3.5% Mo, 0.02 to 0.2% V, 0.001 to 0.015% N, and 0.006% or less O, by mass, to satisfy the formulae (1), (2), and (3), and optionally further comprising by mass: 0.002 to 0.05% Al, 3.5% or less Cu, at least one element selected from the group consisting of 0.2% or less Nb, 0.3% or less Ti, 0.2% or less Zr, 0.01% or less B, and 3.0% or less W; and/or 0.01% or less Ca; and balance of Fe and impurities: Cr+0.65Ni+0.6Mo+0.55Cuâˆ’20Câ‰§18.5â€ƒâ€ƒ(1) Cr+Mo+0.3Siâˆ’43.5Câˆ’0.4Mnâˆ’Niâˆ’0.3Cuâˆ’9Nâ‰§11.5â€ƒâ€ƒ(2) C+Nâ‰§0.025â€ƒâ€ƒ(3) where C, Ni, Mo, Cr, Si, Mn, Cu, and N signify the content of the respective elements, and a microstructure comprising a residual austenite phase that is present in an amount of 4.1% to about 40%, and about 10 to about 60% ferrite and about 25% or more tempered martensite by volume, in a ferrite and martensite dual-phase as a base phase.