The history of Austempering begines in 1930's. The word Austempering means - uniform structure. Austempering is a heat treatment that is applied on the ferrous metal, especially on steel. Mainly it is used to improve the mechanical properties or eliminate/reduce distortion. It offers many performance and manufacturing advantages over the traditional process combinations. It may be applied to a number of materials and each combination has it's own advantages. By adjusting the manufacturing process, it can be translated into significant cost savings. The most frequent cost savings are realized by machining before the heat treatment. When speaking about the improvements of performance, the austempered materials are typically compared to traditionally tempered and quenched materials with a micro-structure of tempered Martensite. It is an isothermal process of heat treatment and when it applied on the correct material, it produces a tougher and stronger structure than comparable with traditional heat treatment. This process was used during second world war in the extensive production of guns parts.
However, the equipments that were used in this process were inefficient and so thius process was very expensive. Routinely, this process was applied to malleable iron parts and steel. The high cost of this process limited it's use only to the parts of high performance. This heat treating process when applied to the metals produce metallurgical structure that is called Bainite. The parts are heated to high temperature, then cooled rapidly enough to a temperature to produce the required micro-structure. The typical parameters of Austemperin process applied on an unsuitable material will not result in a proper formation and so the final product will not be called austempered.
It is a hardening process for the metals which yields required mechanical properties including: -
1. Toughness
2. Higher Ductility
3. Strength for Hardness
4. Resistance to Shock
5. Reduced distortion particularly with thin parts.
6. Increase Fatigue strength.
7. Environmental embrittlement and resistance to Hydrogen.
This Austempering process is widely used in automotive industry where the maximum toughness and flexibility is required and for the clips. Generally the range of it's applications, encompasses parts fabricated from strip of small cross section or from sheet. It is applicable particularly on the parts of thin carbon steel, requiring some exceptional toughness. It is most effective on medium to high carbon alloys. This process utilize a salt bath at a high temperature to quench parts, generally in the range of 600 degrees Fahrenheits depending on the required hardness. The advantage of this process is usually the distortion is reduced due to the higher quenching temperature of salt bath. It is a great alternative to the traditional heat treating process, especially for stampings and springs that need precise control of dimensions.
