With the increase of industrial products, spring products are more and more rich, the number of springs gradually increased, and spring related technology is gradually mature. How to improve the service life of medical spring is the problem faced by spring manufacturers.

(1) Deformation heat treatment

Deformation heat treatment is a combination of deformation and heat treatment to further improve the strength and toughness of steel. Deformation heat treatment can be divided into high temperature, moderate temperature and low temperature three stages. High temperature deformation heat treatment to stabilize austenite state can be quenched immediately after deformation, or combined with forging or hot rolling, i.e. quenched immediately after hot forming. The strength and fatigue life of 60Si2Mn steel automobile leaf springs are greatly improved under the condition of rapid tempering at 650℃×3.25min after high temperature deformation heat treatment (930℃+ variable temperature 18, oil quenching).

(2) spring isothermal quenching

For springs with small diameter or adequate hardenability, isothermal quenching can be used, which can not only reduce the change, but also improve the strength and toughness. It is tempered again after isothermal quenching to improve the elastic limit. Tempering temperature is the same as isothermal quenching.

(3) Shot peening

Shot peening is one of the common methods to change the surface quality of spring. Springs need high surface quality. Surface defects such as scratches, folding, oxidation and decarbonization often become stress concentration sites and fatigue fracture sources. High-speed shot peening of fine steel shot on the spring surface can not only improve the surface quality of the spring, improve the surface strength, make the surface in the state of compressive stress, so as to improve the fatigue strength and service life of the spring.

(4) spring treatment

When a spring is operated for a long period of time under external force, a small amount of long-term (plastic) deformation will occur due to stress. Especially for the spring working at high temperature, the stress phenomenon at high temperature is more serious, reducing the precision of the spring, which is not allowed by the general fine spring. Therefore, such springs should be relaxed after quenching and tempering. Heat treatment process: preload the spring so that it deforms beyond the deformation that can occur when the spring is working. It is then heated at a temperature 20℃ above the operating temperature for 8 to 24 hours.

(5) Low temperature carbonitriding

The combination of tempering and low temperature carnitriding (soft nitriding) can significantly improve the fatigue life and corrosion resistance of the spring.