Austempering is a heat treatment applied to medium- to high-carbon iron alloys that produces a metallurgical structure called bainite. It is used to increase strength and toughness and to reduce distortions. The parts are brought to the hardening temperature during the process, then cooled quickly enough to a temperature above the martensite initial temperature and held at this temperature for a sufficient time until the desired bainite structure is achieved.
Austempering is mostly used for medium and high carbon steels with 35-55 HRC hardness, where toughness is required as well as low distortion. The process is widely used in the automotive industry for clips and parts where maximum flexibility and toughness are required. The field of application of austemper generally covers parts produced from small section sheets and strips. Austempering is particularly applied to thin-section carbon steel parts that require very high toughness. Austempering is applied to iron-based alloys such as SAE 1045 and 1095, 4130, 4140, 5160, 6150 (C45 to C100, 25CrMo4, 42CrMo4, 50CrV4) and nodular cast irons that require 38-52 HRC hardness and contain medium and high levels of carbon.