What is the Normalizing (Heat Treatment)?
In normalizing heat treatment process, the metal is heated to rise to a temperature (which will always be above its critical temperature), then kept for some time long enough for transformation to occur, and finally air cooled. Note that it is not quenched but cooled slowly in air.
Suppose if the steel is heated (to normalize it) then the result will be a mixture of ferrite and cementite which has a higher strength and hardness, but lower ductility.
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Normalization is done to,
- Relive its internal stresses.
- To get uniform grain size.
- To regain the ductility and softness.
Normalizing Heat Treatment & Process
Below are some important points to remember.
- Normalizing is only done for Ferrous or Iron alloys.
- It can refine the crystal structure of the part and produces a more uniform grain structure.
- Steel is heated in a furnace to rich above the austenitic temperature until the ferrite completely converted into austenite. During this high energy, grain shapes to come together. This transformation is called grain refinement. Usually, it takes less than 2 hours of time with 50 to 55 degrees of temperature. The values will change as the carbon percentage and object dimension changes.
- The cooling is done at room temperature in still air. It is the final step in the process.
- The method is normally used after the metal is forged or cast, to put steel in the best condition for machining.