Abstract: Martensitic mixed phase stainless steel, which has in well balance between excellent strength and formability and excellent fatigue properties, and is inexpensive, and suitable for spring members, has: a chemical composition comprising C: 0.1-0.4%, Si: at most 2.0%, Mn: 0.1-6.0%, Cr: 10.0-28.0%, N: at most 0.17%, the remainder of Fe and impurities, and a metallurgical structure which includes a ferrite phase and a martensitic phase, and also a retained austenite phase of 5 volume % or less if necessary, and which satisfies a relationship of CM/CF?5.0 where an average value CF of C content existing in the ferrite phase, and an average value CM of C content existing in the martensite.

Abstract: Martensitic mixed phase stainless steel, which has in well balance between excellent strength and formability and excellent fatigue properties, and is inexpensive, and suitable for spring members, has: a chemical composition comprising C: 0.1-0.4%, Si: at most 2.0%, Mn: 0.1-6.0%, Cr: 10.0-28.0%, N: at most 0.17%, the remainder of Fe and impurities, and a metallurgical structure which includes a ferrite phase and a martensitic phase, and also a retained austenite phase of 5 volume % or less if necessary, and which satisfies a relationship of CM/CF?5.0 where an average value CF of C content existing in the ferrite phase, and an average value CM of C content existing in the martensite.