| 摘要 |
PURPOSE:To form easily a metallic blank material into the shape of a diaphragm, by heating an super-plastic metallic blank material having a crystal structure with the crystal grain diameter of the metal below a specified value to obtain a super-plastic state. CONSTITUTION:A super-plastic metal plate of aluminum alloy is preheated to a temperature 0.4-0.7 times the melting point (658.8 deg.C) of aluminum, e.g., 350 deg.C, so as to bring a metallic plate into the super-plastic state, i.e., a softening state. Further, the softened super-plastic metallic plate is put in metal die of cone shaped diaphragm form to obtain the diaphragm of a cone form by the press forming or one processing of press forming using the vacuum forming method. In providing an annular corrugation around the die in the circumferential direction, the diaphragm 1 having the corrugation 2 for reinforcement is obtained as shown in Fig. A. Further, in providing plural ribs in the radial direction of the diaphragm, the plural ribs 3, 3 incorporated for the reinforcement are obtained for the diaphragm 1 as shown in Fig. B. |
