Tempering is the reheating of quenched steel to a suitable temperature for an appropriate period of time and cooling back to room temperature.

• A. Heating steel above transformation temperature and slow cooling
• B. Reheating quenched steel to a suitable temperature and cooling
• C. Quenching steel rapidly in water
• D. Cold working steel

Answer: (B)

Tempering follows quenching and is a heat treatment that sits between hardening and full annealing. It involves reheating the quenched steel to a moderate temperature, holding it for a while, and then cooling it back to room temperature. This relieves the internal stresses created during quenching and reduces brittleness, while keeping much of the hardness. The description given matches this process exactly: reheating the quenched steel to a suitable temperature for an appropriate period and then cooling to room temperature. Heating above the transformation temperature with slow cooling would push the material toward softer, more ductile structures (annealing/normalizing) rather than tempering. Quenching rapidly in water is the hardening step that produces martensite, not tempering. Cold working deforms the metal at room temperature and isn’t a heat treatment to relieve stresses.