The valve stem is not only a moving part and a force-bearing part, but also a sealing part during the opening and closing of the valve. At the same time, it is impacted and corroded by the medium, and also produces friction with the packing. Therefore, when selecting the valve stem material, it must be ensured that it has sufficient strength, good impact toughness, abrasion resistance, and corrosion resistance at the specified temperature. The valve stem is a consumable part, and the mechanical processing performance and heat treatment performance of the material should also be paid attention to when selecting it. BAND Valve introduces the commonly used materials for valve stems!
Copper alloy
Generally, the grades used are QA19-2 and HPb59-1-1. It is suitable for low-pressure valves with a nominal pressure of less than or equal to 1.6MPa and a temperature of less than or equal to 200℃.
Carbon steel
Generally, A5 and 35 steels are selected. After nitriding, they are suitable for ammonia valves with a nominal pressure of less than or equal to 2.5MPa, and low and medium pressure valves for media such as water and steam. A5 steel is suitable for valves with a temperature not exceeding 300℃; 35 steel is suitable for valves with a temperature not exceeding 450℃. (Note: Practical experience has shown that the use of carbon steel nitriding to manufacture valve stems cannot solve the corrosion resistance problem well and should be avoided.)
Alloy steel
Generally, materials such as 40Cr, 38CrMoA1A, and 20CrMo1V1A are selected. After chrome plating, 40Cr is suitable for water, steam, oil and other media with a nominal pressure of less than or equal to 32MPa and a temperature of less than or equal to 450℃. After nitriding, 38CrMoA1A can withstand a pressure of 10MPa at an operating temperature of 540℃ and is often used in power station valves. After nitriding, 20CrMo1V1A can withstand a pressure of 14MPa at an operating temperature of 570℃ and is often used in power station valves.
Stainless steel
Generally, materials such as 2Cr13, 3Cr13, 1Cr17Ni2, and 1Cr18Ni12Mo2Ti are selected. 2Cr13 and 3Cr13 stainless steel are suitable for water, steam and weakly corrosive media with a nominal pressure of 32MPa or less and a temperature of 450℃ or less. The surface can be strengthened by chrome plating, high-frequency quenching and other methods. 1Cr17Ni2 stainless steel valves and cryogenic valves can resist corrosive media. 1Cr18Ni9Ti and 1Cr18Ni12Mo2Ti stainless acid-resistant steels are used in high-temperature valves with a nominal pressure of 6.4MPa or less and a temperature of 600℃ or less. They can also be used in stainless steel valves and cryogenic valves with a temperature of -100℃ or less. 1Cr18Ni9Ti can resist corrosive media such as nitric acid; 1Cr18Ni12Mo2Ti can resist corrosive media such as acetic acid. When 1Cr18Ni9Ti and 1Cr18Ni12Mo2Ti are used in high-temperature valves, nitriding treatment can be used to improve the anti-scratch performance.
Chromium steel for bearings
GCr15 is selected, which is suitable for ultra-high pressure valves with nominal pressure less than or equal to 300MPa and temperature less than or equal to 300℃.
There are many materials used to make valve stems, including 4Cr10Si2Mo martensitic heat-resistant steel, 4Cr14Ni14W2Mo austenitic heat-resistant steel, etc.