AUSTEMPERING PROCESS IN HEAT TREATMENT :

In austempering or Isothermal quenching the steel part is heated to the required hardening temperature and then quenched in a molten salt or lead bath usually at a high temperature, i.e, from 300*C to 350*C, than that is prescribed for martempering. The steel is held in the bath for as long a time as is needed for isothermal transformation of the austenite , i.e, until transformation to bainite (acicular troosite) and not martensite is complete.

Although the steel is of same hardness as that of martensite, it is tougher and more ductile than other quenched and temper steels. Tempering is rarely needed after austempering.

The foundation for the austempering process in based upon the austenitic transformation at constant temperature and is represented diagrammatically by TTT - curves.

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Mechinopedia For Mechanical Engineers

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