Which of the following property is affected by heat treatment?
Explanation: Heat treatment involves changes in the micro structure and hence all the internal properties are effected.
Annealing involves heating the component to a temperature
Explanation: In annealing, component is heated to a temperature above than critical temperature.
Which of the following is true?
Explanation: In annealing, the furnace is switched off and component cools slowly. In normalising, component is air cooled.
Explanation: During quenching, component is rapidly cooled which leads to formation of martensite. Hence hardness increases.
Explanation: Tempering involves reheating the quenched product to a temperature less than transformation range. It improves ductility and reduces brittleness.
Silicon addition in spring steel increases its toughness.
Explanation: Silicon addition increases strength without lowering the ductility.
Nickel addition in alloys
Explanation: Nickel addition increases toughness by limiting grain growth.
Flame hardening involves
Explanation: Flame Hardening is a process of heating the surface with a flame above critical temperature and then quenching it.
Induction hardening process involves
Explanation: Heating can only be done in presence of alternating current and not constant current.
Case carburising involves
Explanation: Case carburising involves introducing carbon at surface layer. Medium can be liquid, solid or gas and high case depths are possible.