| 摘要 |
PURPOSE:To increase the rigidity with simplie constitution by heating and processing under a prescribed temperature in air, and forming the hardening layer of an oxidizing membrane at the surface after a diaphragm substrate using titanium as the substrate is molded into a diaphragm shape. CONSTITUTION:A titanium foil extended in a sheet shape is pressured and molded with a necessary die and made into a diaphragm substrate 31 including the part to come to be a diaphragm having a spherical protruded surface. The diaphragm substrate 31 is heated by a heating furnace 32. For heating, 300-500 deg.C are suitable in order to form a good quality oxidizing membrane at the surface. Next, the diaphragm substrate 31 is removed from the heating furnace 32, the part, which comes to be the diaphragm is cut with a press and trimmed, thereby, being able to obtain a diaphragm 33 having the oxidizing hardening layer at the surface.
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