These following factors will have an influence on how to choose the material of valve components.
1. The pressure, temperature and feature of working medium.
2. The force situation of this component and the role it plays in valve structure.
3. Good manufacturability.
4. When meeting the conditions above, a low price is required.
Materials of valve stem
When opening and closing the valves, valve stems have to bear tension, pressure and torsional forces and contact with medium directly. Also there is relative friction movement between stems and padding. So, the material of valve stems must have sufficient strength, good impact ductility, great manufacturability in the specified temperature with some degree corrosion and abrasion resistance.
Common materials are as follows:
1. Carbon steel
If the temperature of water or steam doesn’t exceed 300 Celsius degrees and the pressure is low, we normally choose A5 (common carbon steel).
If the temperature of water or steam doesn’t exceed 450 Celsius degrees and the pressure is medium, we normally choose 35 (high quality carbon steel).
2. Alloy steel
If the temperature of water, steam, oil and other media doesn’t exceed 450 Celsius degrees and the pressure is in medium or high situation, we normally choose 40Cr (chrome steel).
If the temperature of water, steam and other media doesn’t exceed 540 Celsius degrees and the pressure is high, we can choose 38CrMoALA (nitriding steel).
If the temperature of steam doesn’t exceed 570 Celsius degrees and the pressure is high, we normally choose 25Cr2MoVA (vanadium steel).
3. Stainless acid resistance steel
If the temperature of non-corrosive medium or weak corrosive medium doesn't exceed 450 Celsius degrees and the pressure is in medium or high situation, we can choose 1Cr13、2Cr13 and 3Cr13 (chromium stainless steel).
If it is used for corrosive medium, we can choose Cr17Ni2、1Cr18Ni9Ti、Cr18Ni12Mo2Ti、Cr18Ni12Mo3Ti and other stainless acid resistance steels and PH15-7Mo (precipitation hardening steel).
4. Heat resistance steel
When it is used for high temperature valves (the medium temperature doesn’t exceed 600 Celsius degrees), we can choose 4Cr10Si2Mo heat resistance steel or 4Cr14Ni14W2Mo heat resistance steel.