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A Design Study in Austempered Ductile Iron - Smith Foundry Drive Wheel

Austempering Heat-Treatment

A controlled and tailored austempering heat treatment is essential to produce the required metal microstructure for the desired mechanical properties in the cast iron component.

The austempering process consists of two specific treatment regimes --


As-Cast Wheel

  1. Austenitizing -- The cast component is heated to temperatures between 1560F/850C and 1740F/950C and held for 15 to 120 minutes.  The austenitizing temperature determines the matrix carbon content, because carbon solubility in austenite increases with temperature.

  2. Austempering -- After austenitizing, the cast component is quenched in a molten salt bath at a temperature between 460F/238C and 752F/400C and held 30 to 240 minutes, followed by cooling to room temperature.  (A rapid quenching rate is important to avoid the formation of pearlite in the matrix.)

The actual temperatures and times for the different heat treatment steps depend on the iron composition, the section thickness of the part, and the desired ADI grade.
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That is why the actual heat-treatment  conditions are tailored for a given component design to promote uniform and controlled microstructure through the thickness of the part.


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Copyright 2005 by the American Foundry Society. All rights reserved.
Address Comments to: jss@afsinc.org
Last Modified:May, 2005 by STG

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In cooperation with
Smith Foundry Co