| 摘要 |
PROBLEM TO BE SOLVED: To make a part of the thickness of a diameter expansion part of an intermediate product easy to flow in the downward direction of a die hole by improving a forming process of the intermediate product through upsetting forging in the case of forming an engine valve. SOLUTION: On a lower electrode 7 of an electric forge reducing device 6, a forming guide 8 reducing its diameter gradually in a tapered shape to the downward and in a nearly funnel shape is provided and in an expansion process of a diameter expansion part 2a in an intermediate product 2, by regulating free expansion through bringing the lower outer circumferential face of the diameter expansion part 2a into contact with the inner surface of the forming guide 8, the lower surface 2b linked with a shaft part 2c in the diameter expansion part 2a is made into the inclined surface which is gradually reduced into a tapered shape in the diameter.
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