| 摘要 |
PROBLEM TO BE SOLVED: To shorten a forming time required until the engine valve is formed from a bar shape stock, and to enhance the precision of a product shape after forming. SOLUTION: Performing is performed to an intermediate base stock consisting of a large diameter part, an intermediate diameter shaft part and small diameter shaft part. In the preforming, the large diameter part is formed to an onion shape almost the same as an umbrella part which is a final product shape, and also its shaft part is made to the same diameter by drawing the intermediate diameter shaft part. By performing the large diameter part into the onion shape, an upsetting limit rate is improved.
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