Annealing, Normalizing, Quenching & Tempering of Steel

#Annealing

It is the process of heating a metal in a furnace above it's recrystallization temperature and allow it to cool inside the furnace. First the temperature of the material is raised (say 912–915°C for cast iron or steel). Secondly the material is soaked in that temperature for few hours. Third, the temperature is lowered and the material is allowed to cool inside the furnace. Annealing improves ductility, strength and good elongation properties.

#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 atmosphere. The properties of the material are bit lower than that of annealing because of different cooling areas in the material.

#Quenching

It is the process of heating the material above the recrystallization temperature and cooling it suddenly in a water bath or oil bath or in polymers. Type of quenchant depends upon the application. Martensite matrix structure is seen in case of quenched materials. The material becomes so hard, more brittle and has the ability to withstand wear, vibrations. Abrasive resistance is more but can't handle creep and impact loads.

#Tempering:

It is the heat treatment process which is done usually after quenching. In the process the material is heated to a temperature below the recrystallization value and hold for few hours. This process removes internal stress and improve a bit of ductility to the hard material. Usually tool steels undergo this process to improve tool life.

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