Annealing is made to increase machining abilities and to soften the metal. Generally the purpose of annealing is as follows.
To refine the grain size.
To increase mechanical properties such as strength and ductility.
During casting, to remove those holes that are trapped in metal.
To make changes to the magnetic and electrical properties.
Annealing are processed in two types
Full Annealing
To soften the metal, Full annealing to refine the grain structure and relieve the strain.
In this process hypoeutectoid steel heated over 32 to 50 degree above than the upper critical temperature and for hypereutectoid steel heated over the 32 to 50 degree above than the lower critical temperature.
Hold this temperature until internal structure is not change, this maturation period is 1 mm per thickness square area 3 to 4 minutes.
And in the furnace it slowly cools down.
Process Annealing
Process annealing is used to remove internal stress due to previous setup.
In this process, the steel is heated to a lower temperature than the lower critical temperature. Keeping it cool for a while at a temperature, it is cooled gradually.
This process increases in machinability.
It happens a recrystallization in steel.
