(1) heat treatment technology for strengthening springs.
1) protective atmosphere heat treatment. In our country, protective atmosphere heat treatment is adopted in spring, oil quenched and tempered steel wire and toughened steel whose wire rod is less than 15mm. Heat treatment in protective atmosphere can remove surface decarbonization and oxidation and improve the surface quality of materials.
2) induction heating or protective atmosphere induction heating heat treatment. This process is usually carried out on the wire before forming the coil spring. Some spring factories combine heat treatment of wire materials with spring making to reduce costs. Induction heating treatment has better strengthening effect, rapid induction heating speed, help to refine grain and reduce surface decarbonization, can give full play to and improve the strength and toughness of materials.
3) surface nitriding heat treatment technology. In recent years, in order to achieve reliable fatigue life, high stress valve spring or other high stress clutch springs also use surface nitriding technology. Now the more advanced technology is low temperature gas nitriding technology, the general nitriding temperature is (450-470) C, gas nitriding time is (5-20) H.
(2) shot peening technology for spring
1) combined shot peening technology. Combined shot peening is also commonly called shot peening. Most economic processes are made of two shot peening. The pellets were shot with different diameters. For the first time, a larger pellet was used to obtain residual compressive stress and surface finish.
2) stress shot peening process. Stress shot peening technology is also a classical shot peening technology, just because it is difficult to be applied to mass production, but in recent years, due to the rapid development of stress shot peening equipment, the large-scale production of high-stress automotive suspension spring has been greatly developed. In particular, the combined application of stress enhanced shot peening and other shot peening processes has a very good reinforcement effect. The prestress of stress shot peening is generally set at (700-800) MPa. After stress shot peening, the peak value of residual stress can reach (1200-1500) MPa, and the high fatigue strength can be obtained.
(3) Spring hot compression technology is mainly used in the high demand of anti-permanent deformation of the coil spring, as a high-grade anti-permanent deformation of the stabilization process. Besides, it can significantly improve the resistance to permanent deformation, and also improve the fatigue life.