PRODUCTION OF CORROSIONPROOF SPRING FOR SUSPENSION

PURPOSE:To produce a corrosionproof spring for suspension where the occurrence of pitting corrosion to be the origin of spring breakage and also the occurrence of delayed fracture are prevented and which is free from deterioration in strength. CONSTITUTION:The suspension spring can be produced by performing treatments, such as the stages of soaking, hot forming, hardening, tempering, shot peening, and coating or the stages of cold forming, soaking, hardening, tempering, shot peening, and coating. In this method, at least a part of the surface of the steel material for spring, before soaking or before cold forming, is electroplated with manganese, and, at the time of soaking treatment, hydrogen in the steel material is released and manganese is diffused and penetrated. By this method, the suspension spring free from delayed fracture can be produced, and further, the occurrence of pitting corrosion to be the origin of corrosion fatigue.breakage in a salt damage environment can be prevented.