The normalizing heat treatment of steel is carried out in the case of superheated steel from rolling, steels tensioned by cold plastic deformations or hot shaping of complex shape, and on steel welded by carpentry in cases where particularly high mechanical characteristics are required.
The structures and hardnesses obtained in normalized steel depend on both the type of material and the dimensions.
During the normalization treatment the homogenization of the structure is obtained and in the subsequent cooling the austenitic grain is refined.
It is carried out on hypoutectoid construction steels, on cast iron and on some aluminum alloys: the most common case is that of steel which is brought to a heating temperature higher than AC3, reaching about 880 °.
In this way a ferritic-pearlitic structure is created; as the content of alloying elements increases, the structures become harder comparable to bainite or martensite in the case of steels with low critical hardening speed.
Useful preparation for subsequent hardening or carburizing.
The normalization of the steels is obtained by heating the material to a temperature slightly higher (about 50-70 ° C more) than that of austenitization to allow to reach a microstructural balance