Normalization

Normalization is a heat treatment process used primarily on steel to give the material a uniform, fine-grained structure, thereby improving its strength, toughness, and machinability.

After, for example, hot forging, hot rolling, and casting of steel, the microstructure is not homogeneous but may consist of excessively large, but also small, grains and contain undesirable structural components, such as bainite and carbide precipitates. Such a microstructure is detrimental to both strength and toughness, as well as to processing properties.

Normalization begins with heating to a temperature in the austenite range, 800 – 920°C, with a short holding time, where new and smaller austenite grains are formed from the original, usually ferrite-pearlitic, structure. This is followed by cooling at a controlled and sufficiently high rate, whereby a ferrite-pearlitic microstructure is formed. This structure is more fine-grained and has a more homogeneous grain size distribution than the previous one.

Ref. Steel and Heat Treatment – A Handbook (8.2.1)

Applications
Carbon steel and low-alloy steels: Most common for improving the structure after forging, casting, or rolling.

Preparation for hardening: Normalization can be used as a step before hardening to create a uniform structure.

Industrial components: Machine parts, tools, and construction materials that require a balance between strength and machinability.