HEAT TREATMENT
*Heat Treatment is the controlled heating and cooling of metals for the purpose of altering their properties.
*The heat treatment process can greatly alter the mechanical and physical properties of metals and alloys, therefore it is the most important and widely used manufacturing processes.
*The heat treatment usually provides a simple and low-cost means of achieving desired properties.
*The properties of metals and alloys can be changed as desired by the heat treatment process.
TYPES OF HEAT TREATMENT PROCESS
1. Annealing
i) Full Annealing
ii) Process Annealing
iii) Stress itself Annealing
iv) Recrystallisation Annealing
2. Normalising
3. Hardening
4. Tempering
5. Austempering
6. Martempering
7. Case hardening
1. Annealing
*The term Annealing refers to a heat treatment in which a material is exposed to an elavated temperature for an extended time period and then slowly cooled.
*Annealing is one of the most widely used processes in the heat treatment of iron and steel.
*It is employed in casting, forging, rolled stock and press work.
2. Normalizing
Normalizing Heat Treatmentprocess is heating a steel above the critical temperature, holding for a period of time long enough for transformation to occur, and air cooling.
3. Quenching
quenching is the rapid cooling of a workpiece in water, oil or air to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, such as phase transformations, from occurring.
4. Tempering
Tempering is a heat treatment technique applied to ferrous alloys, such as steel or cast iron, to achieve greater toughness by decreasing the hardness of the alloy. The reduction in hardness is usually accompanied by an increase in ductility, thereby decreasing the brittleness of the metal.
5. Austempering
Austempering is heat treatment that is applied to ferrous metals, most notably steel and ductile iron. Austempering isdefined by both the process and the resultant microstructure.