Effect of Austempering Temperature on Properties

Gray iron usually is quenched in salt or oil at a temperature between 230 and 425°C (840 and 900°F) for austempering. The quench bath usually is held at a temperature between 230 and 290°C (450 and 550°F) when high hardness and wear resistance are the ultimate aim of the treatment. The required holding time to achieve maximum transformation is determined by the temperature of the quenching bath and the chemical composition of the iron. The effect of chemical composition on the holding time can be considerable, and alloy additions such as Ni, Cr, and Mo increase the time required for transformation. Casting shape and section thickness determine the amounts of the added hardenability agents (Ni, Cu, Mo), because cooling must be fast enough to prevent any transformation of austenite until the casting reaches the temperature of the bath.



May 18, 2007 One Minute Mentor