In what context is tempering applied to metals?

• A. Before casting
• B. After hardening
• C. During welding
• D. Before machining

Answer: (B)

Tempering is a heat treatment process applied to metals, particularly steels, after the hardening process. During hardening, steel is typically heated to a high temperature and then rapidly cooled, usually by quenching in water or oil. This makes the steel hard but can also make it brittle and susceptible to cracking.

Tempering involves reheating the hardened steel to a lower temperature, which reduces brittleness while retaining some degree of hardness. This step is crucial as it enhances the toughness of the metal, allowing it to withstand stress without fracturing. By carefully controlling the tempering temperature and duration, various mechanical properties can be achieved to suit specific applications.

The process is essential in many engineering and manufacturing applications where tough, durable materials are necessary. The option indicating tempering is applied after hardening accurately captures this integral phase in metal treatment.