Q1: Which of the following heat treatment processes is used for softening the hardened material ?

ANS:B - Tempering

The heat treatment process used for softening hardened materials is tempering. Explanation:

• Tempering is a heat treatment process typically applied to hardened materials, such as steel, to reduce their hardness and increase their toughness.
• After the material has been hardened through processes such as quenching, it often becomes too brittle for practical use in many applications.
• Tempering involves reheating the hardened material to a temperature below its critical point and holding it at that temperature for a specified period, followed by controlled cooling.
• During tempering, the internal stresses in the material are relieved, and the microstructure undergoes changes that result in a reduction in hardness while improving toughness and ductility.
• The specific temperature and duration of tempering determine the final mechanical properties of the material, with higher temperatures typically resulting in softer and tougher materials.
• Normalizing and annealing are other heat treatment processes, but they are not specifically used for softening hardened materials like tempering. Normalizing is primarily used to refine the grain structure and relieve internal stresses, while annealing is used to achieve specific microstructures and properties, such as increased ductility or improved machinability.