heattreats

Heat treatments, or heattreats, are controlled heating and cooling processes applied to metals and alloys with the goal of altering their microstructure and, consequently, their mechanical properties. These procedures are used to tailor hardness, strength, ductility, and toughness to specific applications.

Common processes include annealing (softens metal and relieves internal stresses), normalizing (refines grain structure by air cooling after heating to austenite), quenching and tempering (hardens steel by rapid cooling followed by a tempering heat to improve toughness), and surface hardening methods such as carburizing and nitriding (increase surface hardness while maintaining a tougher core). Precipitation hardening, or age hardening, increases strength by forming finely dispersed precipitates after solution treatment and aging.

Heat treatments depend on variables such as heating temperature, soaking time, cooling rate, and the atmosphere inside the furnace or bath. The resulting changes affect hardness, strength, ductility, and toughness, and can also influence residual stresses and dimensional stability. The choice of process is guided by material type and the desired balance of properties.

Materials commonly treated include steel, cast irons, aluminum and copper alloys. Equipment ranges from electric resistance and gas furnaces to quench media and, in some cases, specialized baths. Modern practices emphasize energy efficiency, environmental controls, and process repeatability. Applications span automotive components, gears, springs, aircraft parts, and tooling.

During heat treatment, distortion and cracks are potential risks; proper fixturing, temperature control, and quench media selection are essential. Standards and process specifications help guide procedures in industries such as aerospace and automotive.