Heat Treatment is defined as an operation or combination of operation, involving heating and cooling of a metal or alloy in its solid state with the object of changing the characteristics of the material.
The amount of carbon present in plain carbon steel has a pronounced effect on the properties of steel and on the selection of suitable heat treatments to attain certain desired properties. Steels can be heat treated to produce a great variety of microstructures and properties. Generally, heat treatment uses phase transformation during heating and cooling to change a microstructure in a solid state.
you have easy understand the concepts of heat treatment processes