Annealing: A kind of heat treatment of steel to make steel soft, less brittle, and elastic. in this process, steel is heated to redness and cooled slowly.
Hardening: It is another kind of heat treatment of steel. In this process, the steel is heated to redness and cooled suddenly to make the steel hard and brittle.
Tempering: it is another process of heat treatment of steel in order to get steel that is neither too hard nor too brittle. in this condition, hardened steel is heated to a temperature much below redness and cooled slowly.