Why does the spring need stress relief annealing?
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The spring stress is generated during the rolling spring process. The original straight steel wire is wound into a spring shape, so the spring will generate stress at each point, and the residual stress after heat treatment. For these stresses, heat treatment should be performed again. Remove the internal stress, otherwise the spring will break easily during work.
The coil spring rolled by the cold coil process generally uses a lead bath austempered cold drawn steel wire (carbon spring steel wire, piano wire) and oil quenched and tempered spring steel wire. Springs made from these steel wire cold rolls do not require quenching, but must be subjected to stress relief annealing. Stress relief annealing is often referred to simply as tempering, sometimes referred to as stress relief tempering or stress relief tempering.
The purpose of stress relief annealing is to:
1) Eliminate the internal stress of wire cold drawing and spring cold roll forming;
2) Stabilizing the size of the spring, the spring that has not been subjected to the stress relief annealing will have an increase in the outer diameter and dimensional instability during the subsequent processing and during use;
3) Increase the tensile strength and elastic limit of the wire;
4) Use stress relief annealing to control the spring size. For example, the spring is sometimes placed on the fixture for stress relief annealing to adjust the height of the spring.