How many types of material of valve body are there ?The valve body, bonnet and gate (disc) are one of the main parts of the valve, which directly bear the medium pressure. The materials used must meet the requirements of “pressure and temperature rating of the valve”. Common materials are as follows:
1、 Gray cast iron: gray cast iron is suitable for water, steam, air, gas, oil and other media with nominal pressure of PN ≤ 1.0MPa and temperature of – 10 ℃ ~ 200 ℃. The common grades of gray cast iron are: HT200, HT250, HT300, ht350.
2、 Malleable cast iron: suitable for water, steam, air and oil medium with nominal pressure of PN ≤ 2.5MPa and temperature of – 30-300 ℃. Common brands include kth300-06, kth330-08 and kth350-10.
3、 Ductile iron: suitable for water, steam, air, oil and other media with PN ≤ 4.0Mpa and temperature of – 30 ~ 350 ℃. Common brands are: QT400-15, QT450-10, QT500-7.
In view of the current domestic technology level, the factories are uneven, and users are often difficult to test. According to experience, it is recommended that PN ≤ 2.5MPa, and steel valve is still used as safety valve.
4、 Acid resistant high silicon ductile iron: suitable for corrosive medium with nominal pressure of PN ≤ 0.25MPa and temperature lower than 120 ℃.
5、 Carbon steel: suitable for water, steam, air, hydrogen, ammonia, nitrogen and petroleum products with nominal pressure of PN ≤ 32.0mpa and temperature of – 30 ～ 425 ℃. Common brands are WC1, WCB, ZG25, high quality steel 20, 25, 30 and Low Alloy Structural Steel 16Mn.
6、 Copper alloy: suitable for water, sea water, oxygen, air, oil and other media with PN ≤ 2.5MPa, as well as steam media with temperature of – 40-250 ℃. The common brands are zgnsn10zn2 (tin bronze), H62, HPb59-1 (brass), qaz19-2, qa19-4 (aluminum bronze).
7、 High temperature copper: suitable for steam and petroleum products with nominal pressure PN ≤ 17.0mpa and temperature ≤ 570 ℃. Common brands include ZGCr5Mo, 1Cr5Mo, zg20 CrMoV, zg15gr1mo1v, 12CrMoV, wc6, wc9, etc. The specific selection must be in accordance with the valve pressure and temperature specifications.
8、 Low temperature steel: suitable for medium such as nominal pressure PN ≤ 6.4Mpa, temperature ≥ – 196 ℃ ethylene, propylene, liquid natural gas, liquid nitrogen, etc., common brands) ZG1Cr18Ni9, 0Cr18Ni9, 1Cr18Ni9Ti, zg0cr18ni9
9、 Stainless acid resistant steel, suitable for medium of nominal pressure PN ≤ 6.4Mpa, temperature ≤ 200 ℃ nitric acid, acetic acid, etc., common brands are zg0cr18ni9ti, zg0cr18ni10 < nitric acid resistance >, zg0cr18ni12mo2ti, zg1cr18ni12mo2ti < acid resistance and urea >