What are three low temperature heat treatments?

What are three low temperature heat treatments?

• A. Preheat, tempering and stress relieving
• B. Normalizing, hardening and annealing
• C. Quenching, case hardening, aging
• D. Aging, carburizing, nitriding

Answer: (A)

Low temperature heat treatments are done well below the steel’s transformation range to modify properties without forming new microstructures. Preheating before welding keeps heat input in check, reducing thermal shock, distortion, and cracking. Tempering follows hardening to lower brittleness and adjust hardness, while still preserving most of the strength. Stress relieving heats the metal to a moderate temperature to ease residual stresses from forming or machining, again without a major structural change. The other options mix processes that require higher temperatures or have different aims (like full austenitizing, rapid quenching, or surface-only treatments), so they aren’t grouped as true low‑temperature heat treatments.

Low temperature heat treatments are done well below the steel’s transformation range to modify properties without forming new microstructures. Preheating before welding keeps heat input in check, reducing thermal shock, distortion, and cracking. Tempering follows hardening to lower brittleness and adjust hardness, while still preserving most of the strength. Stress relieving heats the metal to a moderate temperature to ease residual stresses from forming or machining, again without a major structural change. The other options mix processes that require higher temperatures or have different aims (like full austenitizing, rapid quenching, or surface-only treatments), so they aren’t grouped as true low‑temperature heat treatments.