What is meant by i) quenching of steel. ii) annealing of steel. GROUP: B Short answer questions 5 × 5 = 25

i) Quenching of steel Quenching is a heat treatment process in which steel is heated to a high temperature (above its upper critical point) and then rapidly cooled in water, oil, or brine. This rapid cooling converts austenite into martensite, a hard and brittle structure. Quenching increases the hardness and strength of steel but makes it more brittle. It is commonly used for tools, blades, and springs where hardness is required.

ii) Annealing of steel Annealing involves heating steel to a suitable temperature (typically 723–910°C) and then slowly cooling it in a furnace. This process relieves internal stresses, refines the grain structure, and converts martensite into a softer, more ductile form called pearlite + ferrite. Annealing improves machinability and reduces brittleness, making steel easier to work with. It is used for wires, sheets, and components requiring formability.