Five methods can help manufacturers improve the service life of springs

There are the following aspects to improve the service life of the spring:

(1) Austempering of spring

Austempering can be used for springs with small diameter or sufficient hardenability, which can not only reduce decentering, but also improve strength and toughness. It is best to perform another tempering after austempering to increase the elastic limit. The tempering temperature is the same as the austempering temperature.

(2) Deformation heat treatment

Deformation heat treatment is a combination of steel deformation strengthening and heat treatment strengthening to further improve the strength and toughness of steel. Thermomechanical treatment is divided into high temperature, medium temperature and low temperature. High temperature deformation heat treatment is quenching immediately after deformation occurs in a stable austenite state, and can also be combined with forging or hot rolling, that is, quenching immediately after hot forming. The automobile leaf spring made of 60Si2Mn steel is subjected to high temperature deformation heat treatment (930℃+thermal variable 18%, oil quenching), and adopts high temperature rapid tempering at 650℃ for 3.25min, and its strength and fatigue life have been greatly improved.

(3) Relaxation treatment of spring

The spring works under the action of external force for a long time, due to the stress relaxation, it will produce a small amount of permanent (plastic) deformation, especially the spring working at high temperature, the stress relaxation phenomenon is more serious at high temperature, which reduces the accuracy of the spring. It is not allowed for general precision springs. Therefore, this type of spring should undergo relaxation treatment after quenching and tempering. Heat treatment process: pre-load the spring so that its deformation exceeds the deformation that may occur when the spring is working. Then heat it at 20℃ higher than the working temperature for 8~24h.

(4) Shot peening

Shot peening is one of the most widely used methods to improve the surface quality of springs. Springs require high surface quality, and surface defects such as scratches, folds, and oxidative decarburization tend to become stress concentrations and fatigue fracture sources during spring operation. If small steel shots are used to spray the surface of the spring at high speed for shot peening, it will not only improve the surface quality of the spring, increase the surface strength, and put the surface in a state of compressive stress, thereby increasing the fatigue strength and service life of the spring.

(5) Low temperature carbonitriding

The combined process of tempering and low-temperature carbonitriding (nitrocarburizing) is used for coil springs, which can significantly improve the fatigue life and corrosion resistance of the spring.