Question

The process of heating and suddenly cooling of steel is known as :

• A. tempering
• B. annealing
• C. hardening
• D. nitriding

Answer 1

Answer: (C)

hardening

Answer 2

Quenching or hardening is heating up of steel article to redness $(1123\, K)$ and then cooling it suddenly by plunging it in water or oil to make steel hard and brittle Annealing is heating of steel well below red hot and then cooling it suddenly to make it soft. Tempering is heating the quenched steel at around $550\, K$ and then cooling it slowly to make it quite hard but less brittle Nitriding is heating of steel in atmosphere of nitrogen to make its surface hard