General characteristics of metal seals

    The main disadvantages of rubber seals are that they are not resistant to baking and have a large amount of outgassing at room temperature, so many require high-temperature baking (>200℃) and only use low vapor pressure (vapor pressure at room temperature <10^-10Pa). The vacuum system device cannot be sealed with rubber, but needs to be sealed with a metal sealing ring.

    The metal sealing ring has two outstanding advantages: ①The outgassing is much less than that of rubber; ②The system and device sealed with it can be baked and degassed at high temperature, so it can meet the requirements of ultra-high vacuum.

    Metal seals also have many disadvantages:

    ①The elasticity of the metal sealing ring is poor, and a great sealing force is required to ensure a reliable vacuum seal;

    ②The reusability is very poor, and some metal sealing rings can only be used once;

    ③The roughness and matching accuracy of the flange sealing surface and the knife edge are required to be high, and small scars can damage the seal, especially the processing of large-size flanges is very difficult;

    ④The thermal expansion coefficient of the sealing ring and the flange material is quite different. Uneven heating or incorrect sealing structure design will cause local deformation and cause air leakage.

(huiputech)