Valve fitting stem nuts can be made of different materials for different application requirements. For example, plastics can be used, and the plastics for the stem nut are nylon 66 and nylon 1010, which have the advantages of corrosion resistance, low friction coefficient, good processability and low cost. However, because it is lower in strength than metal, it is usually only used on low pressure, small diameter valves.
Copper alloy can also be used to make valve fitting stem nut. This material will not rust, and has a small coefficient of friction and a certain strength and toughness. It is a commonly used material for stem nuts. Low-pressure valves with a nominal pressure not exceeding 1.6 MPa are made of 2CuZn38MnPb2 cast brass; valves with a nominal pressure of 6.4 MPa or less often use ZCuA110Fe3 tin-free bronze; high-pressure valves with a nominal pressure of 6.4 MPa or more often use ZCuZn25A16Fe3Mn3 cast brass.
Steel fittings can also be used to make valve fitting stem nuts. For example, for some media that require high hardness or corrosion to copper, steel is used to replace copper. Under the condition that the stem is not killed, 35, 40 high-quality carbon steel and 1Cr13, 1Cr18Ni9, Cr17Ni2 and other stainless steel are often used to make the stem nut. In the selection, the general rule that the hardness of the stem nut is lower than the hardness of the stem should be observed to avoid premature wear and seizure.http://www.dmgcastings.com/