Hitachi Powdered Metals Co., Ltd.

Other

Yoshimi Sugaya

Makoto Iwakiri

Yutaka Mabuchi

Akira Fujiki

Masato Yamaguchi

Yukihiro Maekawa

Takeshi Oba

Katsuhiko Ueda

Masakazu Wada

Disclosed is a die for compacting a powdered material. The die has a die body having a penetrating die cavity to which a couple of punches are adapted to apply for pressing the powdered material to be supplied to form a compact, and a die holder having a bore into which the die body is shrink fitted. The die cavity is provided with a coating composed of a material which is selected from the group consisting of titanium carbide, titanium nitride, alumina, titanium cyanide, hafnium nitride, chromium nitride, tungsten carbide and DLC, and the die holder is composed of a steel material which is prepared by tempering at a temperature higher than a treatment temperature at which the coating is provided on the die cavity. The die cavity is tapered at a ratio within a range of 1/5,000 to 1/1,000.

Die for die compacting of powdered material

A sintered metal sprocket for a silent chain is produced by the following steps. A base mixture is prepared, which contains a powder metallurgical iron powder, a lubricant and a graphite powder. Then, the base mixture is subjected to a compression molding while being heated at above approximately 100&deg; C. thereby to produce a green compact. Then, the green compact is subjected to a sintering at a temperature above approximately 1180&deg; C. For much improving the mechanical performance of the sprocket thus sintered, the same may be subjected to a carbonizing hardening or an induction hardening.

Method of producing sintered metal sprocket and sprocket produced by the method

There is disclosed a method for forming compacts having a hole extending along a direction crossing the compressing direction. In the method, a powder or a pre-compressed compact and a core for forming a hole are assembled in a cavity. The core and a die are set in a condition that the core can move in the compressing direction. The punch compresses the powder and forms a compact. The core does not engage with the die, whereby the core is not exerted with load. Therefore, the method does not need control of compressing for avoiding exertion of load on the core, and can prevent transformation or break of the core. The compact in which the core is inserted is drawn out from the die, so that damages such as break or crumble of the compact is prevented in drawing out.

Method for forming compacts

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Chiba, Japan

Yoshimi Sugaya