1. The tempering treatment of tension spring shall not be stopped by the method of advancing temperature and shortening time.

2. Hardness: with the increase of tempering temperature, the hardness increases slightly and then decreases. The temperature with the best fatigue function is slightly lower than the temperature with the largest hardness.

3. Diameter reduction: the outer diameter of carbon steel tension spring will be reduced during tempering, so some dimensions should be reserved during spring winding.

4. Tension spring return fire color: the return fire color is related to the temperature and the residue on the surface of the steel wire. The uneven color is related to the temperature distribution or the air flow in the furnace. If you want the color to be uniform, you should manage the furnace and charging method; If there is oil or fingerprint in the part, it will change color after tempering.

5. Tempering temperature: the commonly used tempering temperature is 250-280 ℃. If the steel wire is treated at 200-250 ℃, it can advance the strength, but the plastic toughness will also be lost, which can cause cracking when the tension spring is used as the hook or the torsion spring is bent.

6. Compression spring: hammering and mild low-temperature tempering in the future can reduce deformation.

7. Tension spring: the initial stress will be lost after tempering, and the allowable loss should be considered when setting the deviation.

8. Torsion spring: 280 ℃ tempering treatment shall be suspended after winding the spring. If the spring is to be reprocessed after winding, the low-temperature tempering temperature is 250 ℃.

9. Hook of tension spring and arm of torsion spring: the orientation will change after tempering. If there is a request for accurate orientation, the amount of change should be controlled.