Heat treatment. Tempering of steel

Playlist “Materials science“ The purpose of tempering is to increase ductility of the quenched steel, reduce hardness and brittleness, and decrease internal stresses in hardened steels. Essencially, structural transformations that take place during tempering are decomposition of thermodynamically unstable martensite. As the heating temperature rises, the strength of the steel usually decreases, while the ductility increases. Tempering is classified in three categories: low-temperature, medium-temperature and high-temperature tempering. The tempering temperature range depends on the required strength of a particular part.