Sumitomo Metal Industries, Inc.

Honda Motor Co., Ltd.

Honda Giken Kogyo Kabushiki Kaisha

Nippon Steel Sumitomo Metal Corporation

Nippon Leakless Industry Co., Ltd.

Takashi Katsurai

Naoto Sato

Kazuhiko Adachi

Yasunori Murakami

Kenichi Goshokubo

Masaru Abe

Tadao Nishiyama

Seishi Ishiyama

Shigeki Muroga

Takashi c/o Nippon Leakless Ind Co Ltd Yajima

Hiromitsu c/o Nippon Leakless INDCOLTD Sasaki

Norifumi c/o Nippon Leakless Ind COLTD Misumi

Masabumi Miyashita

A high-performance stainless steel sheet which has a high strength which is optimal for a gasket for use in high-performance engines of automobiles and motorcycles and which also has excellent workability and fatigue properties and a method for its manufacture are provided. At least in a region from the surface of the sheet up to 3 &#x3bc;m in the thickness direction, nitrogen compounds of at least 10 nm and at most 200 nm are present in an amount of at least 200 per 100 &#x3bc;m. The number of nitrogen compounds of at least 10 nm and at most 200 nm in a region from the sheet surface up to 3 &#x3bc;m in the thickness direction of the sheet is at least 2 times the number of nitrogen compounds of this size in the central portion of the sheet thickness.

Stainless steel sheet for a gasket

This invention relates to a stainless steel gasket having markedly improved strength and fatigue properties due to precipitation strengthening. Its composition comprises C: at most 0.03%, Si: at most 1.0%, Mn: at most 2%, Cr: 16.0%-18.0%, Ni: 6.0%-8.0%, N: at most 0.25%, if necessary Nb: at most 0.30%, and a remainder of Fe and unavoidable impurities. After cold rolling, final annealing is carried out, and after a structure is formed of recrystallized grains with an average grain diameter of at most 5 &#x3bc;m having an area ratio of 50-100% and an unrecrystallized portion having an area ratio of 0-50%, a metal gasket is formed by steps including temper rolling with a reduction of at least 30% to make the area ratio of a strain induced martensite phase at least 40%, and forming and heat treatment at 200-350&#xb0; C. The metal gasket has a duplex phase structure of at least 40% martensite in which chromium nitride is precipitated and a remainder of austenite, or it has a single phase structure of martensite in which chromium nitride is precipitated, and it has Hv of at least 500.

Metal gasket and a material for its manufacture and a method for their manufacture

An austenitic stainless steel for use in engine gaskets having a high fatigue strength and resistance to settlement and method of manufacture thereof. The austenitic stainless steel is prepared by cold rolling at least 40%, annealing at a temperature of 700&deg; C. to 900&deg; C. followed by temper rolling with a reduction of at least 40%. The metal structure obtained by annealing is a recovered unrecrystallized structure or a mixed structure of a recovered unrecrystallized structure and a recrystallized structure. The austenitic stainless steel includes at most 0.03% C, at most 1.0% Si, at most 2.0% Mn, 16.0% to 18.0% Cr, 6.0% to 8.0% Ni and up to 0.20% N.

Stainless steel for use in engine gaskets and a method for manufacturing thereof

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Utsunomiya, Japan

Takashi Katsurai