| 摘要 |
PROBLEM TO BE SOLVED: To secure sufficient sealing performance even used at a low fastening pressure by forming a metal C ring gasket frequently used for an ultra-high vacuum appliance into an approximately crescent cross section and specifying the ratio of the wall thickness of a part in contact with a mated surface by fastening to the wall thickness of the central part. SOLUTION: The cross section of a metal C ring gasket G1 is formed into a crescent shape gradually and stepwisely thickening the thickness from a B portion and D portion toward a C portion. It is so formed that the ratio of the wall thickness t1 of a part in contact with a counter-part by fastening to the wall thickness t2 of the central part is 1.2 or more. The material of the metal C ring gasket G1 is preferably austenitic stainless steel not to react with gas and the machining method for forming it into C shape is that it is pressed in multi-stages possibly so as not to cause work hardening and normalized under the anoxia atmosphere to the surface hardness less than 300 Hv, thereby providing a superior sealing performance. This constitution can hold the superior sealing performance for a long period.
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