Austempering kinetics of a Mn-Mo-Cu ductile iron with a high nodule count

Austempering kinetic measurements and mechanical property measurements are reported for a ductile iron containing 3.7%C, 2.6%Si, 0.16%Mn, 0.2%Mo and 0.5%Cu for austenitising temperatures of 860 and 890 degrees C and austempering temperatures of 320, 355, 380 and 400 degrees C, The nodule count of the iron was 215 mm(-2). It is shown that the austempering kinetics show a similar dependence on austempering parameters to those of irons with a lower nodule count, The processing window is open for all austempering conditions studied. The mechanical properties of the iron austempered at 380 degrees C attain optimum values, which satisfy the ASTM A897:1990 and BS EN 1564:1997 standards, within the processing window. This suggests that the same criteria can be used to define the processing window in irons with different nodule counts.