METAL GASKET AND ITS LAW MATERIAL AND METHODS FOR PRODUCTION OF THEM

摘要

A method for producing a stainless steel gasket, which comprises subjecting a steel having a chemical composition, in mass %: C: 0.03 % or less, Si: 1.0 % or less, Mn: 2 % or less, Cr: 16.0 to 18.0 %, Ni: 6.0 to 8.0 %, N: 0.25 % or less, optinally Nb: 0.30 % or less and balance: Fe and inevitable impurities, to a cold rolling, followed by final annealing, to thereby form a structure containing 50 to 100 area % of recrystallized grains having an average grain diameter of 5 mu m or less and 0 to 50 area % of unrecrystallized portions, subjecting the product to a temper rolling in a rolling reduction of 30 % or more, to form a strain induced martensite phase in an area % of 40 % or more, forming the product, and subjecting the formed article to a heat treatment at a 200 to 350 DEG C. The gasket produced by the above method has a plural phase structure composed of 40 % or more of martensite having chromium nitride precipitates and the balanced amount of austenite, or a single phase structure composed of martensite having chromium nitride precipitates, and has a Hv of 500 or more. The gasket is markedly improved in strength and fatigue characteristics through precipitation strengthening.