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℃.

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 valve stems made of carbon steel nitrided cannot solve the corrosion resistance problem well and should be avoided.)

Generally, materials such as 40Cr, 38CrMoA1A, and 20CrMo1V1A are selected. After chrome plating, 40Cr is suitable for media such as water, steam, and oil with a nominal pressure of 32MPa or less and a temperature of 450℃ or less. 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.

Generally, materials such as 2Cr13, 3Cr13, 1Cr17Ni2, and 1Cr18Ni12Mo2Ti are used. 2Cr13 and 3Cr13 stainless steels 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.

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.

The valve stem nut is matched with the valve stem by threads, directly bearing the axial force of the valve stem, and is in the friction between the valve plate and the bracket and other valve parts. Therefore, in addition to having a certain strength, the valve stem nut is also required to have a small friction coefficient, no rust, and no bite with the valve stem.

The following materials are often used for valve stem nuts:

The plastics used to make valve stem nuts are nylon 66 and nylon 1010, which have the advantages of corrosion resistance, small friction coefficient, good processability and low cost. However, since its strength is lower than that of metal, it is only used on low-pressure and small-diameter valves.

Copper alloy does not rust, has a low friction coefficient, and has a certain strength and toughness. It is currently the material commonly used for valve stem nuts. Low-pressure valves with a nominal pressure of less than or equal to 1.6MPa often use 2CuZn38MnPb2 cast brass; valves with a nominal pressure of less than or equal to 6.4MPa often use ZCuA110Fe3 Wuxi bronze; high-pressure valves with a nominal pressure greater than 6.4MPa often use ZCuZn25A16Fe3Mn3 cast brass.

When the valve stem nut of the electric valve needs to have high hardness and the ammonia medium corrodes copper, steel is used instead of copper. Under the condition that the valve stem does not bite, 35, 40 high-quality carbon steel and 1Cr13, 1Cr18Ni9, Cr17Ni2 and other stainless steels are often used to make valve stem nuts. When selecting, the general rule should be followed that the hardness of the stem nut should be lower than the hardness of the stem to avoid premature wear and seizure.