Q1: The increase in hardness of metal due to its cold working is termed as the __________ hardening.

ANS:C - induction

• Induction hardening is a surface heat treatment process used to increase the hardness and wear resistance of metal components, typically steel.
• It involves heating the surface of the component locally using electromagnetic induction, followed by rapid quenching to achieve a hardened surface layer while maintaining a relatively softer core.
• The process is commonly applied to components such as gears, shafts, and other critical wear parts that require increased hardness and wear resistance in their working surfaces.
• The induction heating is achieved by placing the component within a high-frequency alternating magnetic field generated by an induction heating coil.
• The rapidly alternating magnetic field induces eddy currents within the surface layer of the component, causing it to heat up due to the resistance of the material to the flow of electric current (Joule heating).
• The surface temperature increases rapidly, typically to above the transformation temperature where the steel undergoes phase transformation to form austenite.
• Once the desired temperature is reached, the component is quenched using a suitable medium such as water or oil to rapidly cool the surface, causing martensitic transformation and hardening.
• The hardened surface layer provides increased wear resistance, while the softer core maintains toughness and ductility, reducing the risk of brittle fracture.
• Induction hardening offers several advantages over conventional heat treatment methods, including rapid heating, precise control of heating patterns, localized treatment, and minimal distortion of the component.