Annealing of steel is called heat-treated when it is heated at the appropriate speed of the material and then held at a suitable temperature in the austenitic range. With proper cooling after holding at temperature, we want to achieve state of microstructure as balanced as possible. The purpose of annealing is to improve dimensional stability, machinability, working, achieve mechanical properties and reduce hardness.
Quenching is a type of heat treatment where the steel is heated in the austenite area. Then follows accordingly to steel grade rapid cooling in various hardening agents. The most used agents are water, oil, salt bath and air. This increases the hardness, making the steel more brittle and less tough. Temperature differences occur between the surface and the inside of material, which increase with the higher cooling rate. These differences can lead to the fault of the material or even to the cracks, so it is important to provide a certain steel with the appropriate hardening agent.