Annealing is a method of softening steel and relieving the internal stresses.  The steel is heated to about 50 degrees C above the austenitic temperature.  It is held at that temperature for sometime.  Then, it is gradually cooled to the ambient temperature. 

Annealing increases the ductility and increases its workability of steel.  The hardness of the steel is reduced by annealing.  Metals like copper, brass and gold can also be annealed. 

At high temperatures, the metal is susceptible to oxidation.  This can be preventing by conducting the heating in an inert atmosphere of special gases such as forming gas ( a mixture of hydrogen and nitrogen) or  endothermic gas ( a mixture of carbonmonoxide, nitrogen and hydrogen).

Glass is also annealed to remove internal stresses and increase the strength.