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Sealing surface is the most critical working face of the valve, the quality of the sealing surface directly affects the service life of the valve, and the material of the sealing surface is an important factor to ensure the quality of the sealing surface.
Therefore, the following factors should be considered when selecting valve sealing surface materials:
① Corrosion resistance.
"Corrosion" is the process in which the sealing surface is damaged under the action of the medium. If the surface is damaged in this way, the tightness cannot be guaranteed, therefore, the sealing surface material must be resistant to corrosion. The corrosion resistance of the material mainly depends on the 10,000 of the material and its chemical stability.
② Abrasion resistance.
"Abrasion" refers to the damage caused by friction in the process of relative movement of the sealing surface. This kind of damage will inevitably cause the damage of the sealing surface, so the sealing surface material must have good abrasion resistance, especially the gate valve. The abrasion resistance of a material is often determined by the internal properties of the material.
③ Erosion resistance.
"Erosion" is the process of destroying the sealing surface when the medium flows through it at high speed. This kind of damage is more obvious in the throttle valve and safety valve used in the high temperature and high pressure steam medium, which has a great impact on the sealing failure, therefore, erosion resistance is also one of the important requirements of the sealing surface material.
④ There should be a certain hardness, and the hardness will decrease greatly under the specified working temperature.
⑤ The linear expansion coefficient of the sealing surface and the body material should be similar, which is more important for the structure of the sealing ring, so as to avoid additional stress and cause loosening at high temperatures.
⑥ When used under high temperature conditions, there should be enough oxidation resistance, thermal fatigue resistance and thermal cycling.
Under the current circumstances, it is difficult to find a sealing surface material that fully meets the above requirements, and it can only meet the requirements of certain aspects according to different valve types and uses. For example, valves used in high-speed media should pay special attention to the erosion resistance requirements of the sealing surface; When the medium contains solid impurities, the sealing surface material with higher hardness should be selected.