Materials for making valve parts are selected based on the following factors:
1. The pressure, temperature and characteristics of the working medium.
2. The force of the part and its role in the valve structure.
3. Good craftsmanship.
4. In the case of meeting the above conditions, there must be a lower cost.
During the valve opening and closing process, the valve stem is subjected to tensile, compressive and torsional forces, and is in direct contact with the medium. At the same time, there is a relative frictional movement between the valve stem and the packing. Therefore, the valve stem material must ensure that it has sufficient Strength and impact toughness, certain corrosion resistance and scratch resistance, and good processability.
Commonly used valve stem materials are as follows.
1. Carbon steel
When used in water and steam medium with low pressure and medium temperature not exceeding 300 ℃, A5 ordinary carbon steel is generally used.
35 high-quality carbon steel is generally used for medium pressure and water and steam medium with medium temperature not exceeding 450 °C.
2. Alloy steel
40Cr (chromium steel) is generally used for medium pressure and high pressure, and the medium temperature does not exceed 450 ℃ for water, steam, petroleum and other media.
38CrMoALA nitrided steel can be selected for use in high pressure and medium temperature not exceeding 540℃ such as water and steam.
25Cr2MoVA chrome-molybdenum-vanadium steel is generally used when it is used in high-pressure steam medium with medium temperature not exceeding 570℃.
3. Stainless and acid-resistant steel
It is used for non-corrosive media and weakly corrosive media with medium pressure and high pressure, and the medium temperature does not exceed 450 ℃. 1Cr13, 2Cr13, 3Cr13 chromium stainless steel can be selected.
When used in corrosive media, Cr17Ni2, 1Cr18Ni9Ti, Cr18Ni12Mo2Ti, Cr18Ni12Mo3Ti and other stainless acid-resistant steel and PH15-7Mo precipitation hardening steel can be selected.
4. Heat-resistant steel
When used for high temperature valves with medium temperature not exceeding 600℃, 4Cr10Si2Mo martensitic heat-resistant steel and 4Cr14Ni14W2Mo austenitic heat-resistant steel can be selected.