The butterfly valve will have problems such as low elasticity and fracture after being used for a long time. What are the methods to make the service life of butterfly valve longer?
1、 Shot peening
Shot peening is one of the widely used methods to improve the surface quality of butterfly valves. The butterfly valve is required to have high surface quality. Surface defects such as scratches, folds, oxidation and decarburization will cause fatigue and fracture sources where the stress concentration occurs during operation. If small steel shot is used to blast the surface of the butterfly valve at high speed, shot peening can improve the surface quality of the butterfly valve, improve the surface strength, and the surface is in a compressive stress state, thus improving the fatigue strength and service life of the butterfly valve.
2、 Isothermal quenching of butterfly valve
The butterfly valve with small diameter or sufficient hardenability can use isothermal quenching, which can not only reduce the center change, but also improve the strength and toughness. After isothermal quenching, it is better to conduct another tempering to improve the elasticity limit. The tempering temperature is the same as that of isothermal quenching.
3、 Thermomechanical treatment
The thermomechanical treatment is to combine the deformation strengthening and heat treatment strengthening of steel to further improve the strength and toughness of steel. Thermomechanical treatment can be divided into high temperature, moderate temperature and low temperature. High temperature thermomechanical treatment refers to quenching immediately after deformation in the undisturbed austenite state, or it can be combined with casting or hot rolling, that is, quenching immediately after hot forming.
4、 Relaxation treatment of butterfly valve
The butterfly valve works under the external force for a long time, because of the stress relaxation, it will produce a small amount of permanent (plastic) deformation. Especially for the butterfly valve working at high temperature, the stress relaxation phenomenon is more severe at high temperature, which will reduce the precision of the butterfly valve, which is not allowed for general precision butterfly valves. Therefore, this type of butterfly valve shall be subject to relaxation treatment after quenching and tempering. The working principle of the electric butterfly valve is to fill the closed pressure cylinder with inert gas or oil gas mixture, so that the pressure in the cavity is several times or dozens of times higher than the atmospheric pressure. The movement of the piston rod is realized by using the pressure difference generated by the cross-sectional area of the piston rod being less than the cross-sectional area of the piston. It is widely used in self-adjusting air suspension of commercial cars, buses, rail vehicles, machinery and building bases.
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