Selection of temperature and time during baking and degassing

    In all high vacuum systems, especially in the application of ultra-high vacuum systems, it is very important to release and exclude gas from the materials constituting the vacuum system. Under ultra-high vacuum conditions, the surface of the vessel wall is not actually in equilibrium with the ambient atmosphere, but is covered with a layer of condensable gas whose content far exceeds the content in the equilibrium state, so in the ultra-high vacuum area, The rate of deflation of the wall depends only on the pumping time and surface experience, and has nothing to do with the total pressure of the system.

    Under normal circumstances, the ultimate baking temperature of the stainless steel ultra-high vacuum system is about 450 ℃, but some experimental studies have shown that: in the degassing process of the system, the baking temperature does not need to be particularly strictly regulated, and the temperature of the system is uniform. Sex is much more important than baking temperature. The best way is to bake the entire system as evenly as possible, and the bake temperature is more appropriate at 150~250℃.

    If a certain material inside the system cannot withstand the temperature of 150°C or the thermal expansion of some important parts may cause trouble, a lower baking temperature should be selected, but all parts of the system must be as uniform as possible Bake, and the duration of baking should be lengthened.

    If a substance with high binding energy is attached to the surface of the system, a higher baking temperature is required to have an ideal outgassing rate. When the whole system cannot be baked uniformly, for example, when flanges with large heat capacity or heat-insulating devices are installed in the vacuum chamber, it is very difficult to uniformly bake them, so you need to choose a higher baking temperature.

(Huiputech)