In “the source of metal material outgassing in vacuum system”, screw vacuum pump manufacturer introduced that metal waste gas in vacuum system mainly comes from two aspects. Next, let’s look at degassing methods for general purpose metal parts.
Usually, the metal parts and the vacuum chamber shell in the vacuum system can be degassed by vacuum baking. In addition, it is easy to remove the residual organic pollutants in the vacuum and reduce the content of the volatile organic compounds in the vacuum. With the increase of temperature, the amount of desorption gas on the metal surface and the gas diffusion from the metal surface will increase. The body will increase. Therefore, metal materials are usually heated to the highest temperature that can withstand degassing.
Before the vacuum baking and degassing of metal parts, the surface must be degreased to remove the oxide layer and other pollutants on the surface, and then heated in vacuum for degassing. Vacuum baking degassing is usually carried out under the pressure of 10 ^ – 2 ^ – 3PA. At the same time, the highest baking temperature is usually chosen as the annealing temperature. This not only ensures good vacuum performance, but also eliminates metal parts. Internal stress during machining. But for different materials of metal parts, baking temperature and time will be different. For prestressed parts such as brackets and springs, the baking temperature needs to be lower than the annealing temperature.
Aluminum parts cannot be baked due to their low melting point. For parts with thick wall or larger diameter, the baking time should be extended appropriately.
In addition, for stainless steel and aluminum or aluminum alloy materials commonly used in vacuum engineering, the effects of vacuum baking degassing and glow discharge degassing are roughly the same, but the composition of desorption materials is different. The residual gas of vacuum baking degassing is mainly composed of carbon dioxide, carbon monoxide, water and hydrogen, while that of glow discharge degassing is mainly hydrogen.
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