Normalizing refers to a heat treatment process that is used to regulate internal material stress. Normalizing reduces the rate of corrosion that may be experienced by a metallic surface and also increases the strength and hardness of the steel.
Normalizing permits the refinement of a metal's grain size and improves the metal's mechanical properties. Normalizing gives steel a uniform and fine-grained structure. This uniformity in the chemical and physical properties of an alloy is most important after it has been casted, forged, hot rolled or cold rolled. This is due to the greater amount of deformation that is possible in the metal after such manipulation.
Normalizing involves heating a metal to a temperature that is roughly equivalent to its hardening temperature, which initiates the formation of austenitic grain boundaries. The material is then cooled, forming ferritic grains, which are the most fine-textured structures with predictable physical, corrosion and machinability responses.
During this process the metal's stress must be controlled because too much leads to metal failure.
Low-carbon steels usually do not need normalizing.