There are hundreds of valve materials, but only half of them are commonly used. We will classify the commonly used materials and clarify their scope of usage as follows so that we can have a deeper understanding of them.
Commonly used materials are as follows:
It is suitable for media such as water, steam, air, and oil with PN≤4.0MPa and a temperature range of -30～350℃.
It is suitable for media such as water, steam, air, hydrogen, ammonia, nitrogen, and petroleum products with nominal pressure PN≤32.0MPa and a temperature range of -30～425℃.
Forge-able Cast Iron
It is suitable for water, steam, air, and oil medium with nominal pressure PN≤2.5MPa and a temperature range of -30～300℃.
Gray Cast Iron
It is suitable for media such as water, steam, air, gas, and oil with nominal pressure PN≤1.0MPa and a temperature range of -10℃～200℃.
It is suitable for water, seawater, oxygen, air, oil, and other media with PN≤2.5MPa, as well as steam media with a temperature range of -40~250℃.
Acid-resistant and high-silicon Ductile Iron
It is suitable for corrosive media with nominal pressure PN≤0.25MPa and a temperature lower than 120℃.
Stainless acid-resistant steel
It is suitable for medium with nominal pressure PN≤6.4Mpa, temperature≤200℃ nitric acid, acetic acid, and so on.
It is suitable for media such as nominal pressure PN≤6.4Mpa, temperature≥-196℃ ethylene, propylene, liquid natural gas, liquid nitrogen, and so on.
It is suitable for steam and petroleum products with nominal pressure PN≤17.0MPA and temperature≤570℃.
Material of the Sealing surface
The sealing surface is the most critical working surface of the valve, and the quality of the sealing surface is closely related to the service life of the valve. Usually, the sealing surface material should consider the corrosion resistance, the scratch resistance, the erosion resistance, the oxidation resistance, and other factors, such as rubber (including nitrile rubber, fluorine rubber, etc.), plastic (PTFE, nylon, etc.), copper alloy (for low-pressure valve), chrome stainless steel (for ordinary high and medium pressure valves), Stellite alloy (for high temperature and high-pressure valves and strong corrosion valves), nickel-based alloys (for corrosive media)
Material of Valve Stem
During the opening and closing process of the valve, the valve stem is subjected to the tension, compression, and torsion forces, and it is directly in contact with the medium, and at the same time, there is a relative friction movement with the packing material. Therefore, the valve stem must ensure sufficient strength and impact toughness at the specified temperature, with certain corrosion resistance and scratch resistance, and have very good manufacturability.
When it is under low pressure or water and steam medium temperature not exceeding 300 ℃, A5 ordinary carbon steel is generally used. And 35 high-quality carbon steel is generally used in the medium which is the middle pressure and water and steam under the temperature of not exceeding 450 °C.
40Cr (chromium steel) is generally used for medium and high-pressure media such as water, steam, and petroleum with medium temperatures not exceeding 450 °C. 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 a high-pressure steam medium with a medium temperature not exceeding 570℃.
Acid-resistant stainless Steel
For medium and high pressure, non-corrosive medium and weakly corrosive medium with medium temperature not exceeding 450 ℃, 1Cr13, 2Cr13, 3Cr13 chromium stainless steel can be selected. When used in corrosive media, stainless acid-resistant steel such as Cr17Ni2, 1Cr18Ni9Ti, Cr18Ni12Mo2Ti, Cr18Ni12Mo3Ti, and PH15-7Mo precipitation hardening steel can be selected.