Tempering aims to obtain a microstructure that provides high hardness and mechanical strength properties. The part to be tempered is heated to the austenitizing temperature and then subjected to a suddeen cooling, resulting in an increase in hardness. During cooling, the drop in temperature promotes structural transformations that lead to the emergence of internal stresses.

A wide range of applications is made possible by tempering.

Quench hardening is a mechanical process by which steel and cast iron alloys are increased in hardness. This is done vy heating the material to a certain temperature. which depends on the material, and then cooling it. This produces a harder material, either through surface or deep hardening, varying with the cooling rate. It is common for the material to undergo a tempering process to reduce stresses and brittleness resulting from the tempering process. Normally hardened partes are, among others, gears, shafts and wear blocks.