Editing Steel (section)

===Heat treatment===
{{Main|Heat treating}}
There are many types of [[heat treatment|heat treating]] processes available to steel. The most common are [[annealing (metallurgy)|annealing]], [[quenching]], and [[tempering (metallurgy)|tempering]].

Annealing is the process of heating the steel to a sufficiently high temperature to relieve local internal stresses. It does not create a general softening of the product but only locally relieves strains and stresses locked up within the material. Annealing goes through three phases: [[recovery (metallurgy)|recovery]], [[recrystallization (metallurgy)|recrystallization]], and [[grain growth]]. The temperature required to anneal a particular steel depends on the type of annealing to be achieved and the alloying constituents.<ref>{{harvnb|Smith|Hashemi|2006|p=249}}.</ref>

Quenching involves heating the steel to create the austenite phase then quenching it in water or [[oil]]. This rapid cooling results in a hard but brittle martensitic structure.<ref name="smith&hashemi" /> The steel is then tempered, which is just a specialized type of annealing, to reduce brittleness. In this application the annealing (tempering) process transforms some of the martensite into cementite, or [[spheroidite]] and hence it reduces the internal stresses and defects. The result is a more ductile and fracture-resistant steel.<ref>{{harvnb|Smith|Hashemi|2006|p=388}}.</ref>