Normalising Normalizing

Normalising involves heating the steel to about 40^oC above its upper critical limit. The steel is then held at this temperature for a period of time and is then cooled in air. It is desireable that the temperature of the steel shall be maintained for a time period more than 2 minutes per mm of section thickness and shall not exceed the upper critical temperature by more than 50^oC.

The structure produced by this process is pearlite (eutectoid) or pearlite in a ferrite matrix (hypoeutectoid) or pearlite in a cementite matrix (hypereutectoid). Because the steel is cooled in air the process results in a fine pearlite formation with improved mechanical properties compared to the full annealing process below

Normalising is used to

To refine the grain structure and to create a more homogeneous austenite when a steel is to be reheated for quench hardening or full annealing
To encourage reduced grain segregation in castings and forgings and provide a more uniform structure
To provide moderate hardening

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Metals Engineering