The steel parts is heated up to the austenitic region and then quenched into an isothermal salt-bath. Through the cooling agent in the salt-bath, the processing temperature is controlled to be below the pearlitic transformation temperature and above the martensitic transformation temperature. Depending on the temperature of the salt-bath, we can form upper bainite or lower bainite microstructures in the steels parts.
Benefits:
Compared with the mechanical properties of that of tempered martensite, the bainite phases not only has the comparable strength but also possess better toughness, elongation, and impact strength. So the austempered parts also don’t need to undergo further tempering process. In addition, unlike conventional quenching process, there are also no cracking or distortion problems in this case.