1. Isothermal heat treatment of spring machine
For spring machines with small diameters or sufficient cutting performance, isothermal heat treatment can be used, which can not only reduce empathy, but also increase strong ductility. It is best to carry out another quenching after isothermal heat treatment to increase the ductility limit. The quenching temperature is the same as the isothermal heat treatment temperature.
2. Deformation and tempering treatment
The deformation and quenching and tempering treatment combines the deformation strengthening of the steel and the quenching and tempering treatment to improve the compressive strength and ductility of the steel in an all-round way. The deformation and tempering treatment can be divided into high temperature, medium and soft ultra-low temperature. The high-temperature deformation quenching and tempering treatment is the heat treatment immediately after the deformation caused by the stable ferrite, and it can also be combined with forging or hot rolling, that is, the heat treatment is immediately after the hot forming. The trolley leaf spring produced by 60Si2Mn steel is subjected to high temperature deformation and tempering treatment (930℃+ thermal independent variable 18%, oil quenching), and then quickly quenched at a high temperature of 650℃×3.25min. Its compressive strength and fatigue life Both have been greatly improved.
3. The spring machine should be relaxed after heat treatment and quenching
When the spring machine is working under external force for a long time, due to the stress relaxation, it will cause permanent (plastic deformation) deformation in the microanalysis. The degree is reduced, which is not allowable for the usual precision spring machines. Therefore, this kind of spring machine should be relaxed after heat treatment and quenching. Heat treatment method: load the spring machine in advance so that its deformation exceeds the deformation that will be caused when the spring machine is in operation. Then it is heated under the standard of 20℃ higher than the operating temperature, and the heat insulation is 8~24h.
4. Shot blasting solution
The spring machine requires high process performance, and surface defects such as scratches, expansion, and air oxidation carbonization will usually become stress areas and fatigue and rupture sources during the work of the spring machine. Shot blasting is one of the most common ways to improve the process performance of spring machines at this stage. If a fine steel ball is used to spray the surface of the spring machine at a high speed and carry out shot blasting, it will not only improve the process performance of the spring machine, increase the compressive strength of the surface layer, and make the surface under compressive stress, thereby increasing the fatigue limit and service life of the spring machine.
5. Ultra-low temperature carbonitriding
For the coil spring, the close combination of quenching and ultra-low temperature carbonitriding (soft nitriding) is selected, which can significantly improve the fatigue life and corrosion resistance of the spring machine.