Abstract
Commercially available aluminum ConFlat® (CF) flanges produce the plastic deformation by pressing the knife edge deep into a soft aluminum gasket. Plastic deformation begins to occur after only 3 μm of penetration and produces enough work hardening to achieve an ultrahigh vacuum seal long before the flange faces actually touch. Deeper penetration merely widens the area of the seal reacting against the gasket hardness but does not significantly increase the effective sealing pressure. Commercially available metal C-rings have relatively wide seal widths. The use of a collapsible knife edge on the C-ring, made of soft gasket material, has also been used to produce high sealing pressure by concentrating sealing force. For long life, the yield strength of the sealing surface must be substantially higher than the hardness of the gasket material. Commercially available aluminum CF flanges have yield strength of 40 Kgf/mm2. However, the 6061 alloy widely used as a chamber material has yield strength of only 28 Kgf/mm2, which may be insufficient for long life.
Published Version
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