Annealing basically can be referred as the process of reducing stress within metal by heating the metal to a prescribed temperature. Annealing is a process of heating the steel slightly above the critical temperature of steel (723 degrees Centigrade) then allows it to cool down very slowly.Annealing can induce ductility;it can soften material, relieve internal stresses of the metal, refine the structure by making it homogeneous, and improve cold working properties.
Normalization is an annealing process which is applied to ferrous alloys to give the material a uniform fine grained structure and make the material less brittle. It is used on steels of less than 0.4% carbon to transform austenite into ferrite, pearlite and sorbet. It particularly involves heating of the steel to 20-50 kelvin above its upper critical point. It is soaked for a short period at that temperature and then allowed to cool in air. Smaller grains form that produce a tougher, more ductile material. It eliminates columnar grains and dendritic segregation that sometimes occurs during casting. Normalizing improves machinability of a component and provides dimensional stability if subjected to further heat treatment processes.
It is the process basically performed on steels. The process consists of heating the material up to a temperature above 1950°F and holding it long enough for the carbon to go into solution. After this, the material is quickly cooled to prevent the carbon from coming out of solution. Solution- annealed material is in its most corrosion-resistant and ductile condition.
Large castings or structures that are welded tend to possess internal stresses caused mainly during their manufacture and also because of uneven cooling. These internal stresses cause brittleness at isolated locations in the castings or structures, which can than lead to sudden breakage or failure of the metal. This process involves heating the casting or structure to almost 650 Degree centigrade. The temperature is maintained constantly for a few hours and allowed to cool down slowly. This process hence relieves the internal stress of the metal helping it prevent from breakage.