| 摘要 |
PROBLEM TO BE SOLVED: To prevent the generation of cracking in a sintered body and to obtain a sintered member of high quality by subjecting a sintered body obtd. by subjecting a sintering material to compacting and sintering and premolding it under hydrostatic pressure to improve its relative density and executing forging to form its shape into the product shape. SOLUTION: For example, at the time of producing an engine valve, metal and an organic substance are mixed, and a powdery sintering material A is compacted to form a cylindrical extruding material B, which is thereafter sintered to control its relative density to about >=90%. This sintered extruding material B is set to a pressing machine, the molding temp. of the sintered body is controlled to a temp. range in which its forgeability is made sufficiently high by high frequency induction heating or the like to improve its ductility and forgeability, and compression molding is executed while hydrostatic pressure is applied thereto to control the relative density of the extruded material B to about >=99%. Next, this extruded material B is subjected to forging at about 70 to 80% draft and, if required, may be subjected to the modification of strains, heat treatment, machining, oxidizing treatment or the like as well.
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