(1) Heat treatment strengthening process technology of spring
1) Protective atmosphere heat treatment. In our country, the heat treatment of springs with wires 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 carried out 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. 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 gained a lot 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 good strengthening effect. The pre-stress of stress shot peening is generally set at (700-800) MPa. After stress blasting, the peak value of the residual stress can reach (1200-1500) MPa, thereby obtaining high fatigue strength.
(3) The hot pressure process of the spring The hot pressure process is mainly applied to the coil springs that require high permanent deformation resistance, as an advanced anti-permanent deformation stabilization process. In addition to significantly improving the resistance to permanent deformation, the hot pressing process can also increase the fatigue life.