DUPLEX STAINLESS STEEL

摘要

Provided is a duplex stainless steel that can suppress precipitation of a .sigma. phase at the time of high heat input welding, is excellent in SCC resistance under high-temperature chloride environments, and has a high strength. The duplex stainless steel according to the present invention includes a chemical composition containing, in mass percent, C: at most 0.030%, Si: 0.20 to 1.00%, Mn: at most 8.00%, P: at most 0.040%, S: at most 0.0100%, Cu: more than 2.00% and at most 4.00%, Ni: 4.00 to 8.00%, Cr: 20.0 to 28.0%, Mo: 0.50 to 2.00%, N: 0.100 to 0.350%, and sol. Al: at most 0.040%, the balance being Fe and impurities, and satisfying Expression (1) and Expression (2); a structure having a ferrite rate of at least 50%; and a yield strength of at least 550 MPa or more: 2.2Cr + 7Mo + 3Cu > 66 (1) Cr + 11Mo + 10Ni < 12(Cu + 30N) (2)