Why do you think the different heating process result in different softness or hardness of the steel? Think about what steel is made of and how the atoms move .

Explanation:

Different heating process affect the microstructure of the steel in different ways. Thus, imparting different properties to the steel. For example, annealing is done is done to impart softness to steel, hardening is done to hardened the steel( eg: carburizing, nitriding, cyaniding) whereas tempering is done to improve the ductility of the steel.

Steel mainly contains iron and carbon. This percentage of carbon and iron decides the property of the steel. It is the % of carbon which is altered in different heating process that to obtained the desire microstructure in steel.