The valve stem is not only a moving part, a force part, but also a sealing part in the valve opening and closing process. At the same time, it is affected by the impact and corrosion of the medium, and also produces friction with the filler. 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 wearing part, and the mechanical processing properties and heat treatment properties of the material should also be paid attention to when selecting.
The general selection of the brand is QA19-2, HPb59-1-1. It is suitable for low pressure valves with nominal pressure less than or equal to 1.6MPa and temperature less than or equal to 200℃.
Generally selected A5, 35 steel, after nitriding treatment, suitable for nominal pressure less than or equal to 2.5MPa ammonia valve, water, steam and other medium low and medium pressure valves. A5 steel is suitable for valves whose temperature does not exceed 300℃; 35 steel is suitable for valves whose temperature does not exceed 450℃. (Note: The actual route proves that the valve stem made of carbon steel nitriding can not solve the corrosion resistance problem well, and should be avoided.)
Generally use 40Cr, 38CrMoA1A, 20CrMo1V1A and other materials. After chrome plating, 40Cr is suitable for water, steam, petroleum and other media with nominal pressure less than or equal to 32MPa and temperature less than or equal to 450℃. After nitriding treatment, 38CrMoA1A can withstand 10MPa pressure at the operating temperature of 540 ° C, and is often used in power station valves. 20CrMo1V1A can withstand 14MPa pressure at an operating temperature of 570 ° C after nitriding treatment, and is often used on power station valves.
Generally choose 2Cr13, 3Cr13, 1Cr17Ni2, 1Cr18Ni12Mo2Ti and other materials. 2Cr13, 3Cr13 stainless steel is suitable for water, steam and weakly corrosive media with nominal pressure less than or equal to 32MPa and temperature less than or equal to 450℃, and the surface can be strengthened by chromium plating, high-frequency quenching and other methods. 1Cr17Ni2 stainless steel valve, low temperature valve, resistant to corrosive media. 1Cr18Ni9Ti, 1Cr18Ni12Mo2Ti stainless acid-resistant steel is used in high temperature valves with nominal pressure less than or equal to 6.4MPa and temperature less than or equal to 600℃, and can also be used in stainless steel valves with temperature less than or equal to -100℃ and low temperature valves. 1Cr18Ni9Ti is resistant to corrosive media such as nitric acid. 1Cr18Ni12Mo2Ti is resistant to corrosive media such as acetic acid. When 1Cr18Ni9Ti and 1Cr18Ni12Mo2Ti are used in high temperature valves, they can be nitrided to improve the abrasion resistance.
Bearing chromium steel
GCr15 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 more materials used to make the valve stem, as well as 4Cr10Si2Mo martensitic heat-resistant steel, 4Cr14Ni14W2Mo austenitic heat-resistant steel.