1. The spring cannot be tempered by increasing the temperature and shortening the time.

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

3. Reducing diameter: the outer diameter of carbon steel spring will be reduced when tempering, so some dimensions should be reserved when winding the spring.

4. Spring return color: the return color is related to the temperature and the residue on the steel wire surface, and the uneven color is related to the temperature distribution or the air flow in the furnace. If the color is expected to be uniform, the furnace and charging method should be well managed; If there is oil or fingerprints locally, it will change color after tempering.

5. Tempering temperature: the tempering temperature generally used is 250-280 ¡æ. If the steel wire is treated at 200-250 ¡æ, although the strength can be improved, the plasticity and toughness will also be lost, which can lead to fracture when the tension spring is used as hook or torsion spring bending leg.

6. Compression spring: mild tempering at low temperature after hammering can reduce deformation.

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

8. Torsion spring: 280 ¡æ tempering treatment shall be carried out after coiling spring. If it needs to be processed again after coiling spring, the low temperature tempering temperature shall be 250 ¡æ.

9. Hook of tension spring and arm of torsion spring: the position will change after tempering. If there is an accurate position requirement, the change amount should be mastered.