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AssigneeHitachi Construction Machinery Co., Ltd.
InventorsKazuyoshi Hatano, Ken Ichiryu, Morio Tamura, Eiji Kometani, Yasuharu Gotoh, Nobuyoshi Hidao
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A sliding member is sulphonitride by heating at 480.degree.-600.degree. C. in the presence of both 10-500 ppm of a hydrogen sulfide gas and a 20-70 vol % ammonia gas, or by a method which comprises performing a primary heat treatment on the sliding member at 450.degree.-540.degree. C. in the presence of 50-200 ppm of a hydrogen sulfide gas and a 10-70 vol % ammonia gas, then ceasing the supply of the ammonia gas, slowly reducing the temperature to a level of 200.degree.-350.degree. C., and performing a secondary heat treatment at that temperature level. By the either method, the sliding member having a FeS.sub.2 on its topmost surface can be obtained.
In a gas sulphonitriding method which comprises sulphonitriding a steel member with a sulphurizing gas and a nitriding gas, the improvement which comprises supplying a predetermined concentration of the sulphurizing gas together with a predetermined concentration of the nitriding gas and the carrier gas into a reaction furnace containing the steel member to be treated, performing a primary heat treatment at a temperature in the range of 450.degree.-540.degree. C., then ceasing the supply of the nitriding gas, slowly reducing the temperature in the reaction furnace to a level in the range of 200.degree.-350.degree. C., and performing a secondary heat treatment at that temperature.
In a gas sulphurization method that comprises sulphurizing a steel member at least with a hydrogen sulfide gas, the improvement wherein said hydrogen sulfide gas is used for sulphurization at a concentration in the range of 50-200 ppm and the sulphurizing treatment is performed at a temperature in the range of 200.degree.-350.degree. C.
Dependencies are inferred from the claim text.