The process of heating steels to the suitable temperature according to the kind of steels, followed by still-air cooling to remove the thermal influence of forging or hot rolling. This treatment refines the grain size and enhances the uniformity of the micro-structure. In some instances, this treatment will improve machinability. A previously cold worked part will soften when normalized. An annealed part will harden when normalized.

Normalizing involves heating the steel to about 50°C above its upper critical temperature, generally 900°C. The component is then held at this temperature until the temperature is uniform throughout the part (generally one hour per inch of thickness), and then cooled in air.

The micro-structure produced by normalizing, depending upon the carbon content of the steel, is Pearlite (Eutectoid), Pearlite in a Ferrite Matrix (Hypoeutectoid), or Pearlite in a Commentate Matrix (Hypereutectoid). Cooling in air results in a fine Pearlite with improved mechanical properties compared to the full annealing process described above.

Normalizing is used to refine the grain structure and to create a more homogeneous structure when a steel is to be reheated for hardening and quenching or full annealing, or to unify the micro-structure of the heat effected zone of weldments, segregation in castings and forgings and provide a more uniform structure, and also to provide moderate hardening.