Hardening, annealing, and tempering are three of the most well-known processes for the heat treatment of steel. Depending on the treatment used, the material may become more or less fragile, harder or softer, or stronger or weaker. The method chosen depends on the desired characteristics of the material. If steel is being treated, one may end up with a material with high tensile strength but a relatively low degree of brittleness. main difference between hardening, annealing, and tempering process in steel.
Annealing is a process in which a metal is heated to a particularly high temperature, held there for a period of between several hours then and allowed to cool slowly. Tempering is the process of heating a substance to a temperature below its critical range and then cooling rapidly. Hardening is a process when steel is heated to very high temperature and quickly cooled by quenching (cooling steel rapidly to obtain desired properties). The speed of cooling is a critical difference between annealing, tempering and hardening.
Properties of Steel:
Annealing is used to soften materials or to obtain other desired physical and chemical properties such as machinability, electrical properties, dimensional stability, increase toughness and homogeneity of metals and restore ductility to the metal prior to further working. Hardening(quenching) is used for increasing the hardness of a metal. Tempering increases ductility and toughness of steel, reduce brittleness, minimizes cracking, and increases workability.
The main applications of these heat treatment processes are: Annealing is used for metals and metal alloys, whereas Hardening is used for metal alloys containing sufficient carbon and alloy content and Tempering is used mainly for steel and spring steel.