To enable a reducing tube stock to be pressed in an axial direction from the tube end thereof.
Tube end holding dies 12a, 12b are arranged in one end part of die main bodies 11a, 11b. A sealing tool 13 on the side of the tube end holding die is inserted between the tube end holding dies 12a, 12b to hold one end part of the reducing tube stock TP2 together with the tube end holding dies 12a, 12b. A sealing tool 14 on the side of the die main bodies is inserted between the other end parts of the die main bodies 11a, 11b to hold the other end part of the reducing tube stock TP2 together with the die main bodies 11a, 11b. An elastic member 15 for imparting thrust force in the direction of one end part of the tube end holding dies 12a, 12b is provided between the die main bodies 11a, 11b and the tube end holding dies 12a, 12b. The injection hole 14a of working fluid is provided on the sealing tool 14 on the side of the die main bodies. The internal space of the die is made to be changeable in accordance with movement in the axial direction of the sealing tool 13 on the side of the tube end holding dies. In this way, a high expansion ratio is obtained and also the latitude of the forming is remarkably enhanced when applying the hydrostatic bulging to the reducing tube stock.
MITSUBISHI MOTORS CORP
SUMITOMO PIPE & TUBE CO LTD
Tetsuya Mizogami
Yoshinori Iwahara
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