| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a hollow valve capable of improving the strength of a head part. Ž<P>SOLUTION: Diameter of a pipe material 20 is reduced with a part of the pipe material 20 left by ironing to form a base section 11a of a stem part 11 and a head part form part 12a in the method for manufacturing the hollow valve 10. An inner diameter of a part of the head part form part 12a is expanded, upsetting of the section of which inner diameter is expanded is repeated to gradually increase an inner diameter of the head part form part 12a and to gradually thicken the inner diameter, and a thick wall part 21 in a shape widened toward an end is formed at the head part form part 12a. The thick wall part 21 is formed in an umbrella shape by hot forging to form the head part 12. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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