HIGH-STRENGTH SEAMLESS STAINLESS STEEL PIPE FOR OIL WELLS

Abstract

To provide a high-strength seamless stainless steel pipe for oil wells that has high strength, excellent hot workability, excellent resistance to carbon dioxide gas corrosion, and excellent resistance to SSC in a low-temperature environment. A high-strength seamless stainless steel pipe for oil wells having a composition containing the particular components, the remainder being Fe and unavoidable impurities, and satisfying the following expression (1) and the following expression (2), having a number density of an inclusion having a major axis of 5 µm or more and 0.5 < Ti / (Ti+Al+Mg+Ca) < 1.0 of 0.5 per mm² or more and 3 per mm² or less, and having a yield strength of 655 MPa or more, where 0.5 < Ti / (Ti+Al+Mg+Ca) < 1.0, Ti, Al, Mg and Ca represent the contents (% by mass) of the elements in the inclusion, and an element that is not contained is designated as 0, Cr+0.65Ni+0.6Mo+0.55Cu-20C = 15.0 (1) Cr+Mo+0.3Si-43.3C-0.4Mn-Ni-0.3Cu-9N = 11.0 (2) where Cr, Ni, Mo, Cu, C, Si, Mn and N represent the contents (% by mass) of the elements, and an element that is not contained is designated as 0.