1. Reducing the brittleness, eliminating or reducing the internal stress. Steel parts are with great internal stress and brittleness after quenching. If not tempered in time, the steel often deform or even crack.

2. To obtain the required mechanical properties. After tempering, the hardness of the workpiece is high and brittle. In order to meet different performance requirements, the hardness can be adjusted by tempering to reduce the brittleness and obtain the required toughness and plasticity.

3. Stabilizing parts size.

4. For some alloy steels which are difficult to soften after annealing, high temperature tempering is often used after quenching (or normalizing) to make the carbides in the steels gather properly and reduce the hardness so as to facilitate cutting.