SEAMLESS DUPLEX STAINLESS STEEL TUBE

Claims

A seamless duplex stainless steel tube is provided that has high strength, excellent crevice corrosion resistance in a supercritical corrosive environment, and excellent hot workability. A seamless duplex stainless steel tube according to this disclosure has a chemical composition as described in the description, satisfies formula (1), and has a yield strength of 550 MPa or more.In the seamless duplex stainless steel tube according to the present disclosure, additionally, the microstructure is composed of ferrite and austenite, a ferrite volume ratio FX in a central portion of a wall thickness of the seamless duplex stainless steel tube is 35.0 to 65.0%, and a ferrite volume ratio FY in a region from the outer surface of the seamless duplex stainless steel tube to 100 µm in the depth direction is 0.90 FX or more: Cr + 3.3 (Mo + 0.5 W) + 16 N - Mn ≥ 30.0 (1) where, in formula (1) each element symbol is replaced by a corresponding element content in mass percent, and if a corresponding element is not contained, the corresponding element symbol is replaced by “0”.