The sealing surface is the key working surface 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 the sealing surface material of the valve:
1.Corrosion resistance."Corrosion" refers to 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, and therefore the sealing surface material must be resistant to corrosion.The corrosion resistance of the material mainly depends on its chemical stability.
2.Scratch-resistant."Scratch" refers to the damage caused by friction of the material during the relative movement of the sealing surface.This damage will inevitably cause the damage of the sealing surface. Therefore, the sealing surface material must have good anti-scratch performance, 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 a process in which the sealing surface is damaged when the medium flows through the sealing surface at high speed.This 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 damage. Therefore, erosion resistance is also one of the important requirements of sealing surface materials.
4.Should have a certain hardness, and in the specified working temperature under the hardness of a large decline.
5.The linear expansion coefficient of the sealing surface and the body material should be similar, which is more important for the structure with the sealing ring, so as to avoid extra stress and loosening at high temperature.
6.When used under high temperature conditions, there should be sufficient oxidation resistance, thermal fatigue resistance and thermal cycling and other problems.
At present, it is difficult to find the sealing surface material that fully meets the above requirements. It can only meet the requirements of some aspects according to different valve classes and uses.For example, the valve used in high speed media should pay special attention to the sealing surface erosion resistance requirements;When the medium contains solid impurities, the sealing surface material with higher hardness should be selected.