| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To solve a problem that finished accuracy is insufficient in hot forging of a seat valve of a hollow engine valve and materials to be treated are limited in cold forging and that the number of processes of drawing is increased in the cold forging and a conventional warm forging to repeatingly require a process for intermediate heat-treatment such as annealing so that work efficiency is insufficient. <P>SOLUTION: A semifinished product having a hollow hole and a diameter enlargement part is manufactured (first step) and the drawing is carried out centered on the trunk part of the semifinished product (second step). The drawing is performed in constant-temperature atmosphere at any temperature between a normal temperature and 870°C, so that an entire die set of a press device is surrounded by a heat insulating material. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
