STAINLESS STEEL FOR OIL WELL, STAINLESS STEEL TUBE FOR OIL WELL, AND METHOD OF MANUFACTURING STAINLESS STEEL FOR OIL WELL.

摘要

stainless steel for oil well, stainless steel tube for oil well, and method of making stainless steel for oil well is chemical composition of a stainless steel according to the present invention consisting of c: no more than 0.05%, si: no more than 0.5%, mn: 0.01 to 0.5%, p: no more than 0.04%, s: no more than 0.01% , cr: more than 16.0 and not more than 18.0%, ni: more than 4.0 and not more than 5.6%, mo: 1.6 to 4.0%, cu: · 1.5 to 3.0%, ai: 0.001%, 10%, en: no more than 0.050%, the balance being femal and impure, and satisfies formulas (1) and (2). furthermore, the microstructure of the same contains a martensitic phase and a ferritic phase that has a volume ratio of 1 to 40%, and the distribution ratio of the ferritic phase is higher than 85%. cr + cu + ni + mo ~ 25.5 (1) -8 s 30 (c + n) + 0.5 nm + ni + cu / 2 + 8.2 - 1.1 (cr + mo) s -4 (2 )