heattreat

Heat treatment, or heat treating, is a group of industrial processes that alter the properties of metals by heating and cooling them in a controlled manner. The aim is to produce specific microstructures that improve hardness, strength, toughness, ductility, or wear resistance without changing the overall shape significantly.

Common processes include annealing, which softens metal and relieves internal stresses; normalizing, which refines grain structure through air cooling after austenitizing; quenching and tempering, which hardens steel through rapid cooling followed by reheating to a lower temperature to balance hardness and toughness; and case hardening methods such as carburizing, nitriding, and carbonitriding, which enrich the surface with alloying elements for a hard exterior while maintaining a tougher core.

Heat treatment is performed in furnaces, including batch and continuous furnaces, vacuum, gas, oil, or water quenching. Atmospheres are controlled to prevent oxidation and to supply reducing or reactive gases. Solutions heat treatment and aging are used for aluminum and some precipitation-hardened alloys.

TTT and CCT diagrams guide schedules; results depend on material, alloy composition, and cooling rate. The practice is applied across industries such as automotive, aerospace, tooling, and construction components. Quality control includes hardness testing, microstructure observation, and residual stress assessment to ensure the desired properties are achieved.