Design requirements for metal vacuum flanges

    The basic requirements for designing metal flanges are:

    ①It is required to provide an airtight interface with good performance, usually by high-strength metal extruding soft metal to form a reliable airtight;

    ②It can meet the mechanical strength and sealing pressure of the flange connection, and can maintain a proper sealing pressure in the subsequent operation and baking.

    In addition, it is also necessary to consider the protection of the surface of the flange assembly positioning flange plane seal or groove seal during assembly, as well as the baking resistance and corrosion resistance in the atmospheric environment.

    At present, most of the metal connecting flanges are made of stainless steel and soft metal (copper, aluminum, nickel, gold, etc.) gaskets. When it is baked out, the temperature and the creep properties of the material should be paid enough attention in the design work. For example, copper can produce significant creep at a temperature of 300 to 400°C, while aluminum has a lower creep temperature, and indium will creep at room temperature. Creep is the most prone to air leakage in the cooling stage after repeated baking.

    The method to overcome creep is to design the metal flange structure to have sufficient resilience after baking, so that even if creep occurs at high temperature, the stainless steel flange still has enough sealing force after the baking is finished and returns to room temperature. Ensure air tightness. In addition, you should also pay attention to other problems caused by high temperature, such as indium will corrode stainless steel at a sufficiently high temperature, ultra-high vacuum clean metal surfaces, and troubles caused by mutual diffusion welding under high temperature and high pressure.

(Huiputech)