Heat Treatment - The term ‘Heat Treatment’ may be defined as an operation or a combination of operations, in the manufacturing process of machine parts and tools. As a matter of fact, the heat treatment of a metal or an alloy is carried out first by heating it in solid state and then cooling it. It is possible to impart the required or desirable mechanical properties to steel or alloys for normal operations by heat treatment. Objectives of Heat Treatment - Though there are innumerable purposes, which are achieved by heat treatment yet the following are important :- To relieve internal stresses, which are set up in the metal due to cold or hot working . To soften the metal. To improve hardness of the metal surface. To improve machinability. To refine grain structure To improve mechanical properties like tensile strength, ductility and shock resistance, etc. To improve electrical and magnetic properties. To increase the resistance to wear, tear, heat and corrosion, etc.