Core tips:

1. Protective atmosphere heat treatment. In our country, the heat treatment of springs with wire less than 15mm, oil-quenched and tempered steel wire and toughened steel all use protective atmosphere heat treatment. Protective atmosphere heat treatment can eliminate surface decarburization and oxidation, and improve the surface quality of the material.　　

2. Induction heating or protective atmosphere induction heating heat treatment. This process is generally performed on the wire before the coil spring is formed. Some spring factories combine the heat treatment of the wire material with the spring production to reduce costs. Induction heating treatment has a good strengthening effect, and the induction heating speed is fast, which helps to refine the crystal grains and reduce surface decarburization, and can give full play to and improve the strength and toughness of the material.

(1) Heat treatment strengthening process technology of spring

　　1) Protective atmosphere heat treatment. In our country, the heat treatment of springs with wire less than 15mm, oil-quenched and tempered steel wire and toughened steel all use protective atmosphere heat treatment. Protective atmosphere heat treatment can eliminate surface decarburization and oxidation, and improve the surface quality of the material.

　　 2) Induction heating or protective atmosphere induction heating heat treatment. This process is generally performed on the wire before the coil spring is formed. Some spring factories combine the heat treatment of the wire material with the spring production to reduce costs. Induction heating treatment has a good strengthening effect, and the induction heating speed is fast, which helps to refine the crystal grains and reduce surface decarburization, and can give full play to and improve the strength and toughness of the material.

　　3) Surface nitriding heat treatment technology. In recent years, high-stress valve springs or other high-stress clutch springs have also adopted surface nitriding technology in order to achieve reliable fatigue life. Now the more advanced technology is low-temperature gas nitriding technology, and the general nitriding temperature is (450～470) ℃, the gas nitriding time is (5～20)h.

(2) Shot peening process of spring

　　1) Combined shot peening technology. Combined shot peening is generally called multiple shot peening process. Most economical processes use secondary shot peening. This is achieved by shot peening with pellets of different diameters. For the first time, larger pellets were used to obtain residual compressive stress and surface finish.

　　 2) Stress shot peening process. The stress shot peening process is also a relatively classic shot peening process, just because it is difficult to apply to mass production, but in recent years, due to the rapid development of stress shot peening equipment, it has been greatly improved in the mass production of high-stress automobile suspension springs. development of. Especially the combined application of stress-strengthening shot peening and other shot peening processes has a very good strengthening effect. The pre-stress of stress shot peening is generally set at (700-800) MPa. After stress blasting, the peak value of residual stress can reach (1200-1500) MPa, thereby obtaining high fatigue strength.

　　 (3) Hot-pressing process of springs The hot-pressing process is mainly applied to coil springs that require high resistance to permanent deformation, as an advanced anti-deformation stabilization process. The hot pressing process can not only significantly improve the deformation resistance, but also increase the fatigue life.