The compression spring is a type of hardware component formed into a helical geometric shape by wire, so the hardening process for it is generally more difficult than that for flat hardware components (such as stamped parts). Additionally, strict control of the hardening effect on the cross-section of the compression spring is required to fully understand its resistance to fatigue fracture after use.

The hardening of compression springs typically adopts two methods:

• shot peening
• heat treatment

For shot peening treatment of compression springs: to process a batch of compression springs, they can be transported individually on a conveyor belt to the shot peening chamber, which is equipped with a set of parallel rolls. While being reinforced, the springs roll and rotate forward, allowing high-speed shot flow to pass between the coils of the compression springs and strike the metallic surface of the inner coils, which is where the stress is most concentrated.

Shot peening is a good reinforcement method for suspension springs; after appropriate shot peening, the fatigue life of high-stress springs can be increased by more than four times.