1. After the compression spring coil is formed by recrystallization annealing, recrystallization annealing must be carried out to stabilize the geometric size of the spring and reduce the deformation during quenching. The recrystallization annealing temperature is 550~650℃, the temperature is 1~ 1.5h, and then it is air-cooled. A small amount can be carried out in a salt bath furnace, and a large number of continuous resistance furnaces are used to control the atmosphere.

2. Quenching When quenching and heating in a salt bath furnace, the spring should be fastened evenly with iron wire or heated on the mandrel. When heating, ensure that the surface of the spring is oxidized and decarburized. The salt bath should be carefully deoxygenated. It can also be heated in a box furnace with controlled atmosphere, the heating temperature is 850℃ 10℃, the temperature is kept at 10~ 15min, and the oil is quenched from the furnace and completely cooled.

3. After tempering and quenching, tempering can be carried out twice. Corrective tempering is carried out first, and the temperature of corrective tempering is generally about 20℃ lower than the final tempering temperature, and the temperature is kept for 10 ~ 15 minutes, and then it is discharged from the furnace for air cooling. Then the final tempering is carried out, and after the size of the spring is corrected, the spring is installed on the tempering fixture for final tempering. Tempering fixture shall ensure that the pitch and free length of the spring meet the requirements. Tempering temperature 420℃ 10℃, heat preservation for 30 ~ 35 minutes, and water cooling.

4. Shot peening is needed to improve the fatigue strength of the spring. The diameter of the shot is φ 0.3 ~ 0.5 mm, when the compressed air is used for injection, the compressed air pressure is 0.4 ~ 0.5MPa, and the shot blasting is carried out by a centrifuge, and the linear speed of the shot is 70m/s, so the service life of the compression spring can be more than doubled after shot blasting.