1. Copper alloy
Generally, the brands selected are QA19-2 and HPb59-1-1. Applicable to low pressure valves with nominal pressure less than or equal to 1.6 MPa and temperature less than or equal to 200 degrees.
2. Carbon steel
Generally used A5, 35 steel, after nitriding treatment, suitable for low pressure and medium pressure valves of ammonia valve, water, steam and other medium with nominal pressure less than or equal to 2.5MPa. A5 steel is suitable for valves with a temperature not exceeding 300 degrees; 35 steel is suitable for temperatures not exceeding 450 degrees. (Note: The actual route proves that the valve stem is made of carbon steel and nitrided, which can not solve the corrosion problem well and should be avoided.)
3. Alloy steel
Generally, 40Cr, 38CrMoA1A, 20CrMo1V1A and other materials are selected. After being chrome-plated, 40Cr is suitable for water, steam, petroleum and other media with a nominal pressure of 32 MPa or less and a temperature of 450 degrees or less. The 38CrMoA1A is nitrided and can withstand a pressure of 10 MPa at a working temperature of 540 °C. It is commonly used on power station valves. 20CrMo1V1A can withstand a pressure of 14MPa at a working temperature of 570 degrees after nitriding, and is often used on power station valves.
4. Generally choose 2Cr13, 3Cr13, 1Cr17Ni2, 1Cr18Ni12Mo2Ti and other materials. 2Cr13 and 3Cr13 stainless steels are suitable for water, steam and weak corrosive media with a nominal pressure of 32 MPa or less and a temperature of 450 deg or less. The surface can be strengthened by chrome plating or high-frequency quenching. Corrosion-resistant medium on 1Cr17Ni2 stainless steel valve and cryogenic valve. 1Cr18Ni9Ti, 1Cr18Ni12Mo2Ti stainless acid-resistant steel is used in high-temperature valves with a nominal pressure of 6.4MPa or less and a temperature of 600 degrees or less. It can also be used in stainless steel valves with a temperature less than or equal to -100 degrees. 1Cr18Ni9Ti can resist corrosive medium such as nitric acid; 1Cr18Ni12Mo2Ti can resist corrosive medium such as acetic acid. When 1Cr18Ni9Ti and 1Cr18Ni12Mo2Ti are used for high temperature valves, nitriding treatment can be used to improve the scratch resistance.