| 摘要 |
A bottomed tubular blank or a blank having an open end and a closed end is formed into a valve body whose shape is defined by a pair of dies and the ends of pistons incorporated in the dies. Pressure oil is introduced into the blank through one of the pistons to bulge the blank to the shape thus defined. There are provided upper and lower pressing dies between which the blank is disposed and pistons extending into the dies in four directions, with the piston for pressing the opening of the blank being provided with an inlet for supplying the pressure oil into the blank and an outlet for discharging the pressure oil. When required, the blank is pressed by the dies for preliminary forming and then subjected to the hydraulic bulge forming.
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