Spring steel wire needs high elastic limit, yield strength and tensile strength because spring is working in the elastic range and should not have permanent deformation. If the spring is going to work in an environment of high temperature, the same spring steel wire needs more requirements of good heat resistance, and heat treatment can increase the heat resistance of spring steel wire.
The spring steel wire after different heat treatment can be produced to different springs.
Heat treatment of hot forming spring – this heat treatment of spring steel wire is quenching and tempering in the middle temperature. The organization is tempering troostite after heat treatment. This kind of organization is of high elastic limit and yield limit, and certain toughness.
Heat treatment of cold formed spring – for the spring which made of cold drawn spring steel wire or cold rolled steel, has reach the performance that spring required due to the material hardening by cold plastic deformation. So after the spring forming, it just needs the distressing of keeping temperature in 30min in the range of about 250degrees, to eliminate the internal stress produced by cold forming.
Heat treatment of heat-resistant spring steel wire - valve springs of internal combustion engine work at higher temperatures, some of which exists corrosive atmosphere, we must use a special spring steel wire and appropriate specifications of heat treatment.