Patent ID: 8273191

Claim:
A high-strength stainless steel material having a composition comprising, as essential components thereof, greater than 0.00 mass % but not greater than 0.15 mass % of C, greater than 0.0 mass % but not greater than 2.0 mass % of Si, greater than 0.0 mass % but not greater than 4.0 mass % of Mn, greater than 0.00 mass % but not greater than 0.04 mass % of P, greater than 0.00 mass % but not greater than 0.03 mass % of S, greater than 0.0 mass % but not greater than 4.0 mass % of Ni, from 10.0 to 20.0 mass % of Cr, and greater than 0.00 mass % but not greater than 0.12 mass % of N with a balance of Fe and inevitable impurities; having a metal microstructure composed of two phases, one of the phases being a ferrite phase and the other of the phases being a martensite phase; having a γ max of from 50 to 85, the γ max being represented by the following equation (1): γ max =420W c +470W N +23W Ni +7W Mn −11.5W Cr −11.5W Si +189 (1) (in the equation (1), W c , W N , W Ni , W Mn , W Cr and W Si represent contents (unit: mass %) of C, N, Ni, Mn, Cr, and Si relative to the total mass of the stainless steel material, respectively; and having a difference of 300 HV or less in hardness between the ferrite phase and the martensite phase and wherein the high-strength steel material has a hardness of 397 HV or less.