Gas composition in the vacuum chamber

    (1) Atmosphere in the vacuum chamber

    (2) The surface degassing in the vacuum chamber is also called surface desorption gas. The degassing amount is related to factors such as material type, temperature, pressure, and pumping time. The outgassing rate data of the material obtained from the experiment can be used for approximate calculation.

    (3) Leakage is mainly the amount of gas leaking through the dynamic seal and static seal of the vacuum chamber. The air leakage rate is generally expressed by the pressure growth rate, that is, the pressure rise rate.

    (4) For the gas release of refractory insulation materials, the gas release volume can be calculated with experimental data according to the type and amount of insulation materials.

    (5) The outgassing of the processed material during the process. The outgassing amount is often the main gas load for the exhaust of the vacuum system. Therefore, it is necessary to understand the characteristics of the gas generated during the process. Outgassing in the process is mainly produced by the following processes:

    ① The gas dissolved in the metal is directly discharged (for example, nitrogen and hydrogen are discharged from the molten metal, and hydrogen is discharged from the solid titanium). The reason is that the indoor temperature rises and the pressure decreases, and the solubility of the gas in the metal decreases. Productivity is related to time. The release rate is affected by the metal smelting and processing methods.

    ②The chemical reaction generates gaseous compounds and discharges them. For example, carbon and dissolved oxygen generate carbon oxide gas, or carbon reduces metal oxides to generate carbon oxide gas and is discharged. The gas produced in this way is related to pressure, temperature, time and productivity.

    ③The decomposition of the compound produces gas and discharges it. For example, hydrides, nitrides, oxides, etc. decompose to produce gaseous hydrogen, nitrogen and oxygen. The decomposed gas is related to temperature, pressure, time and productivity.

    In addition, the gas introduced in order to control the metal smelting process also needs to be pumped out. Such as the introduction of helium, argon or other gases as a means of stirring the molten metal.

    The calculation of material outgassing during the process is more complicated, and it cannot be accurately calculated at present, and can only be calculated approximately based on experimental values.

(Huiputech)