NON-MAGNETIC AUSTENITIC STAINLESS STEEL MATERIAL AND PRODUCTION METHOD THEREFOR

To provide a non-magnetic austenitic stainless steel material having excellent strength and corrosion resistance, suitable for machine members to be used in a corrosive environment, and a production method therefor.SOLUTION: The present invention relates to a non-magnetic austenitic stainless steel material having a predetermined component composition, satisfying (40[N]+1.2[Cr]+0.07exp(0.3[Ni]+0.3[Cu]))×1.5[Mo]^(-0.18)≤60, in which the content of an element M is represented by [M]% in terms of mass%, consisting of an austenite single phase structure, and having a critical pitting temperature of 50°C or higher, and a 0.2% proof stress of 970 MPa or more at a position at a depth of 1 inch from the surface (or, at a depth of T/4 or D/4 from the surface if the thickness T or the diameter D is less than 4 inches). A method for producing the steel material includes subjecting a steel ingot to hot working and then cooling treatment, and performing warm working at an area reduction rate of 15% to 50% in a temperature range of 800°C to 300°C during the cooling treatment.SELECTED DRAWING: None 【課題】 腐食環境で用いられる機械部材の用途に好適な、強度及び耐食性に優れた非磁性のオーステナイト系ステンレス鋼材及びその製造方法の提供。【解決手段】 所定の成分組成を有するとともに、元素Ｍの含有量を質量％で［Ｍ］％とすると、（４０［Ｎ］＋１．２［Ｃｒ］＋０．０７ｅｘｐ（０．３［Ｎｉ］＋０．３［Ｃｕ］））×１．５［Ｍｏ］＾（－０．１８）≦６０を満たし、オーステナイト単相組織であって、臨界孔食発生温度（ＣＰＴ）が５０℃以上であり、表面から深さ１インチ（但し、４インチ未満の厚さＴ又は直径Ｄの場合は表面から深さＴ／４又はＤ／４）の位置における０．２％耐力が９７０ＭＰａ以上である。かかる鋼材の製造方法は、鋼塊を熱間加工に続いて冷却処理し、この冷却過程の８００～３００℃の温度範囲において、減面率で１５～５０％の温間加工を施す。【選択図】 なし