heattreater

A heat treater is a person or facility that performs heat treatment of metal parts to alter mechanical properties such as hardness, strength, ductility, and wear resistance. Heat treaters operate either in-house within manufacturing plants or as independent service providers. The goal is to achieve predictable, repeatable properties through controlled heating and cooling, while maintaining traceability and process safety.

Common processes include annealing, which softens metal and relieves stresses; normalizing, which refines the grain structure by air cooling after heating above the critical temperature; hardening, which increases hardness through austenitizing and quenching; and tempering, which adjusts hardness and toughness after hardening. Surface hardening methods such as carburizing, carbonitriding and nitriding create a hard outer layer while preserving a tougher core. Specialized routes like austempering or martempering modify cooling paths to achieve different microstructures. Aging or precipitation hardening strengthens certain alloys by forming dispersed particles.

Equipment used by heat treaters includes various furnaces such as box, batch, pit, and vacuum furnaces, with precise temperature control and atmosphere management. Quenching media may be oil, water, polymer, or gas, and quenchants are chosen to control distortion and carbide formation. Modern operations emphasize furnace uniformity, controlled heating cycles, and appropriate post-quench tempering or aging steps.

Quality and standards are central to heat treatment. Work is documented with process specifications and lot traceability. Standards from AMS, ASTM, and ISO cover materials, heat treatment procedures, and testing methods. Many facilities pursue certifications such as ISO 9001 and, where applicable, Nadcap accreditation. Quality control often includes hardness testing, microstructure analysis, and nondestructive testing after treatment.