1. Copper alloy
The general brand name is qa19-2, hpb59-1-1.Suitable for low pressure valves with nominal pressure less than or equal to 1.6MPa and temperature less than or equal to 200 degrees.
2. Carbon steel
A5 and 35 steels are generally selected for nitrification. They are suitable for ammonia valves with nominal pressure less than or equal to 2.5MPa and low and medium pressure valves for water, steam and other media.A5 steel for valves with temperature not exceeding 300 degrees;35 steel is suitable for temperatures not exceeding 450 degrees.(note: the actual route proves that the valve stem made of carbon steel nitriding is not a good solution to corrosion resistance and should be avoided.)
3. Alloy steel
Materials such as 40Cr, 38CrMoA1A and 20CrMo1V1A are generally selected.After chromium-plated treatment, 40Cr is applicable to water, steam, petroleum and other media with nominal pressure less than or equal to 32MPa and temperature less than or equal to 450 degrees.The 38CrMoA1A, nitrided, can withstand pressure of 10MPa at a working temperature of 540 degrees and is commonly used in power station valves.20CrMo1V1A can be nitrided to bear 14MPa pressure at working temperature of 570 degrees, which is commonly used in power plant valves.
Materials such as 2Cr13, 3Cr13, 1Cr17Ni2 and 1Cr18Ni12Mo2Ti are generally selected.2Cr13 and 3Cr13 stainless steel are suitable for water, steam and weak corrosive medium with nominal pressure less than or equal to 32MPa and temperature less than or equal to 450 degrees.1Cr17Ni2 stainless steel valve, low temperature valve, corrosion resistant medium.1Cr18Ni9Ti, 1Cr18Ni12Mo2Ti stainless 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 degrees, or in stainless steel valves with temperature less than or equal to -100 degrees and in low-temperature valves.1Cr18Ni9Ti can withstand corrosive media such as nitric acid;1Cr18Ni12Mo2Ti can resist corrosive medium such as acetic acid.When 1Cr18Ni9Ti and 1Cr18Ni12Mo2Ti are used in high-temperature valve, nitrogen treatment can be adopted to improve the performance of anti-abrasion.
5. Bearing chrome steel
GCr15 is selected for use in ultra-high pressure valves with nominal pressure less than or equal to 300MPa and temperature less than or equal to 300 degrees.
There are many materials used for making valve stem, such as 4Cr10Si2Mo martensite heat resistant steel, 4Cr14Ni14W2Mo austenite heat resistant steel, etc.
The stem nut, in combination with the stem screw, directly bears the axial force of the stem and the friction between the plate and the bracket.Therefore, in addition to a certain strength, stem nuts are also required to have a small coefficient of friction, not rust, and not bite dead stem performance.