24 April 2017

Difference between annealing and normalizing

What is annealing?

The heat treatment process that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness and making it more reliable and workable is called annealing.

What is normalizing?

Normalizing is also heat treatment process that mainly considered for thermal and microstructure properties used to relieve internal stresses, refine the grain size and improve mechanical properties. 

Let us have a deep insight into the comparison between annealing vs normalizing. 

Basic Difference :

Annealing: It is the process of heating metal in a furnace above its. recrystallization temperature and allows it to cool inside the furnace. 

Normalizing: The process is similar to that of annealing, but after soaking stage the material is taken out from the furnace and allowed to cool in the atmosphere.

Definition :
Annealing: It is a method of heat treatment used to make metals ductile and less hard.

Normalizing: It is a type of annealing process which is only specific to ferrous alloys.

Cooling process :

Annealing: The metals can be cooled down after heating either by cooling them in the air or quenching them in water.

Normalizing: It is important that the cooling process takes place slowly in this process so that it is always cooled in air and not quenched in water.

Grain Size : 

Annealing: It is not crucial to achieving a uniform grain size during the process.

Normalizing: Obtaining a uniform grain size is important for the process.

The hardness of the final product : 

Annealing: The metals are made to be less hard and ductile after annealing.

Normalizing: The alloys remain harder after normalizing when compared to a full annealing process.

Purpose :

Annealing: To increase some of the properties like ductility, softness, toughness, fine grain size and machineability so this reduces the hardness. 

Normalizing: To increase machinability, hardness to attain fine grain size than attained during annealing less softness and ductility.

Process :

Annealing: Heating the steel to a defined temperature and cooling it in a conditioned atmosphere like in furnace. 

Normalizing: Heating the steel to the above austenitic range and cooling in air.

Internal Stresses : 

Annealing: Internal stresses are least.

Normalizing: Internal stresses are slightly more.

Pearlite design : 

Annealing: Pearlite is coarse.

Normalizing: Pearlite is fine.

Cost :

Annealing: More expensive as it uses ovens.

Normalizing: Less expensive than annealing.