GAS CARBURIZING METHOD

Japanese Patent JP3486506

B2

PROBLEM TO BE SOLVED: To improve carburizability, to reduce the variation of carburizing concentration and carburized depth, and to improve quality by applying heating, at the gas carburizing, to a material to be carburized in an oxidizing atmosphere to modify its surface by oxidation and then performing carburizing.
SOLUTION: Prior to carburizing treatment, a material to be treated is heated to 200-750°C in an oxidizing atmosphere to undergo surface modification by oxidation. Further, by regulating the partial pressure of oxygen in the oxidizing atmosphere to 10-20 to 10-5MPa at this time, oxidation is uniformized and modification is efficiently performed. The object in performing this pretreatment for carburizing is to efficiently modify surface state into a carburizable state, because, in general, machining is previously applied to the material to be carburized and, as a result, compositional changes are brought about in the surface to be carburized, and, in many cases, the surface is in a state unsuitable for carburizing treatment, e.g. a composition different from that of the base material is formed or a passivity layer is formed. Further, because of modification by oxidation, uniform carburizing can be done, independently, e.g. of adhesion of cutting oil, etc., and also carburizing velocity can be improved.

Mikio Takei
Nobutaka Takeoka
Yoshiro Takebayashi

JP16383796A

January 13, 2004

June 03, 1996

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Koyo Seiko Co., Ltd.
Koyo Thermo Systems Co., Ltd.

C23C8/02; C23C8/14; C23C8/22; (IPC1-7): C23C8/02; C23C8/14; C23C8/22

JP501930A
JP657400A
JP760314A
JP551714A
JP3104852A

Takafumi Watanabe

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