Stem nut material stem nut directly bears the axial force of the stem during the opening closing process of the valve, so it must have certain strength. At the same time, it is screw driven with the valve rod, which requires small friction coefficient, no rust avoid the phenomenon of seizure.
1、 Copper alloy is one of the most widely used materials because of its small friction coefficient no rust. Zhmn58-2-2 cast brass can be used for the low pressure valve with PG ＜ 1.6Mpa. ZQAl9-4 Wuxi bronze can be used for medium pressure valve of pg16-6.4mpa in excavator casting factory. For high pressure valves, zhal66-6-3-2 cast brass can be used.
2、 When copper alloy is allowed to be used for steel under working conditions, high-quality carbon steel such as 35 40, stainless acid resistant steel such as 2Cr13, 1Cr18Ni9 Cr17Ni2 can be used. Working conditions are allowed to refer to the following situations.
1. Excavator casting processing is used for electric valve, stem nut with melon clutch needs heat treatment to obtain high hardness surface hardness.
2. When the working medium surrounding environment is suitable for selecting copper alloy, such as ammonia medium which corrodes copper. When selecting the steel stem nut, pay special attention to the thread seizure.