1. Protective atmosphere heat treatment. In China, springs with wire less than 15mm, oil quenched and tempered steel wires, and toughened steel are all treated with protective atmosphere heat treatment. Protective atmosphere heat treatment can eliminate surface decarburization and oxidation, and improve the surface quality of materials.  
2. Induction heating or protective atmosphere induction heating heat treatment. This process is generally carried out on the wire before the formation of the spiral spring. Some spring factories combine the heat treatment of the wire material with the production of the spring to reduce costs. Induction heating treatment has good strengthening effect, fast induction heating speed, helps refine grains and reduce surface decarburization, and can fully exert and improve the strength and toughness of materials.    
3. Surface nitriding heat treatment technology. In recent years, high stress valve butterfly springs or other high stress clutch springs have also adopted surface nitriding technology to achieve reliable fatigue life. The most advanced technology now is low-temperature gas nitriding technology, with a general nitriding temperature of (450-470) ℃ and a gas nitriding time of (5-20) h.
Characteristics of disc spring
1. High stiffness, strong buffering and vibration absorption ability, able to withstand large loads with small deformations, suitable for situations with small axial space requirements.
2. This spring has variable stiffness characteristics and a wide range of nonlinear properties.
3. Using the same disc spring in different combinations can result in a wide range of variations in spring characteristics. It can be combined by combining or stacking, or by combining different thicknesses and numbers of pieces.