Tips to improve the service life of tension spring

In daily life, tension springs can be seen everywhere, so how to improve the service life of tension springs?

(1) Isothermal quenching of Tension Spring

Isothermal quenching can be used for springs with smaller diameters or sufficient hardenability, which can not only reduce center change, but also improve strength resistance. It is best to perform tempering again after isothermal quenching to increase the elastic limit. The tempering temperature is the same as the isothermal quenching temperature.

(2)Deformation heat treatment

Deformation heat treatment combines the deformation strengthening and heat treatment strengthening of steel to further improve the strength and resistance of steel. Deformation heat treatment can be divided into high temperature, medium temperature and low temperature. High temperature deformation heat treatment is quenching immediately after deformation in a stable austenite state. It can also be combined with casting or hot rolling, that is, quenching immediately after hot forming. Automobile leaf springs made of 60Si2Mn steel are subjected to high-temperature deformation heat treatment (930°C + thermal variable 18%, oil quenching), and then use high-temperature rapid tempering at 650°C × 3.25 minutes, and their strength and fatigue life are greatly improved.

(3) The tension spring should be relaxed after quenching and tempering.

When the spring is operated under the action of external force for a long time, due to stress relaxation, it will produce a small amount of permanent (plastic) deformation. Especially for springs operated at high temperatures, the stress relaxation phenomenon is more serious at high temperatures, which reduces the accuracy of the spring. This is not suitable for general precision springs. is not allowed. Therefore, this type of spring should be relaxed after quenching and tempering. Heat treatment process: preload the spring so that its deformation exceeds the deformation that may occur during operation of the spring. Then heat it at 20°C higher than the operating temperature and keep it warm for 8 to 24 hours.

(4) Shot peening

Spring is required to have high surface quality, and surface defects such as scratches, folds, oxidation and decarburization often become stress concentration points and sources of fatigue cracking during spring operation. Shot peening is one of the most widely used methods to improve the surface quality of springs. If the surface of the spring is blasted with fine steel shots at high speed and shot peened, it will not only improve the surface quality of the spring, increase the surface strength, put the surface in a compressive stress state, and then increase the fatigue strength and service life of the spring.

(5) Low temperature carbonitriding

Regarding the coil spring, the combined process of tempering and low-temperature carbonitriding (soft nitriding) can significantly improve the fatigue life and corrosion resistance of the Wire forming spring.