COLD COIL SPRING HEAT TREATMENT METHOD FOR IMPROVEMENT OF INNER SIDE RESIDUAL STRESS AND FATIGUE LIFE

摘要

The present invention relates to a heat treatment method to improve an inner compressive residual stress and a service life of a cold spring, which is provided to enhance the service life of the coil spring by removing most of the tensile residual stress generated inside the coil spring in a formation process of the cold spring during a heat treatment process. To achieve this, the present invention comprises: (S10) a step of injecting a cold-formed coil spring into tempering equipment, and thermally treating the coil spring as the coil spring is maintained to be compressed in the tempering process; and (S20) a step of naturally cooling the coil spring in the air after releasing the compression of the coil spring coming from the tempering equipment.