Strengthening technology of spring

(1) Heat treatment strengthening technology of spring
1) Heat treatment in protective atmosphere. In China, the heat treatment of spring with wire less than 15mm, oil quenched tempered steel wire and toughened steel are all heat treated in protective atmosphere. Protective atmosphere heat treatment can eliminate surface decarburization and oxidation, and improve the surface quality of the materials.

2) Induction heating or protective atmosphere induction heating heat treatment. This process is usually carried out on the wire rod before the coil spring is formed. Some spring factories put the heat treatment of the wire material together with the spring production to reduce the cost. Induction heating treatment has good strengthening effect and high speed of induction heating, which helps to refine grains and reduce surface decarburization, which 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 spring also adopts surface nitriding technology. Now, the more advanced technology is low temperature gas nitriding technology. Generally, the nitriding temperature is (450-470) ℃, and the gas nitriding time is (5-20) H.

(2) Shot peening strengthening technology of spring
1) Combined shot peening technology. Combined shot peening, also known as multiple shot peening process. Most economical processes are secondary shot peening. It is realized by shot peening with different diameters. For the first time, larger pellets were used to obtain residual compressive stress and surface finish.
2) Stress shot peening process. Stress shot peening is also a classic shot peening process, but it is difficult to be used in mass production. However, due to the rapid development of stress peening equipment, it has been greatly developed in the mass production of high stress automobile suspension spring in recent years. In particular, the combination of stress enhanced 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 shot blasting, the peak value of residual stress can reach (1200 ~ 1500) MPa, so as to obtain high fatigue strength.

(3) The hot pressing process of spring is mainly used in the spiral spring with high requirements of permanent deformation resistance, which is a high-level stabilization process to prevent permanent deformation. The hot pressing process can not only significantly improve the permanent deformation resistance, but also increase the fatigue life.