Heat treatment is a group of industrial, heat treatment and metalworking processes used to alter the physical and sometimes chemical properties of materials. The most common application is metallurgy. Heat treatment is also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or cooling, often to extreme temperatures, to achieve a desired result, such as hardening or softening of a material. Heat treatment techniques include
annealing, case hardening, precipitation strengthening, tempering, carburizing, normalizing and quenching. Although the term heat treatment applies only to processes in which heating and cooling are applied for the specific purpose of intentionally changing properties, heating and cooling often occur incidentally during other manufacturing processes such as thermoforming or welding.