Normalizing

It is the heat treatment process which is given to a product, which are subjected to relatively higher stress, the process consist of heating steel to a temperature 40 – 50°C above the line where austenite is stable, holding at that temperature for a short period and subsequently cooling in air at room temperature. This is known as air quenching, normalizing produces microstructure consisting of ferrite and pearlite for hypo eutectic steel and pearlite and cementite for hypereutectoid steel. Normalizing increase impact strength in steels. Normalized steel are harder and stronger but less ductile than annealed steels with the same composition.

Normalising is extensively used for improving the properties of steel castings.

Comparison between Normalizing and Annealing :

1. Normalizing require a heating range which is about 40° C above that of annealing.
2. Mechanical properties of steels are better than those produced by annealing.
3. Heat treatment process is of short duration due to increased rate of cooling of the metal in air.
4. If mechanical properties is not the main concern of the heat treatment, better machinability and removal of internal stresses is possible in annealing than obtained by normalizing.