2.10.2 Normalizing
It is the process of heating the steel to the temperature 50°C or more above the critical
temperature 723°C. Then the steel is held at this temperature for a considerable period
which results in complete transformation. This is followed by air cooling of steel. In
normalizing, complete phase recrystallization takes place and fine grained structure is
obtained.
Here in cooling, rate of cooling is faster than furnace cooling. During air cooling,
austenite transforms into finer and more abundant pearlite structure in comparison to
annealing. Properties obtained by normalizing depend on the size and composition of
steel. As the smaller pieces cool more rapidly because of more exposure area, fine pearlite
is formed and thus they are harder than larger pieces.
The object of normalizing is to refine the structure of steel and remove strains which
may have been caused by cold working. When steel is cold worked the crystal structure
is distorted and the metal may be brittle and unrealistic.
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