Graphite nodule count and size distribution in thin-walled ductile cast iron

Graphite nodule count and size distribution have been analysed in thin-walled ductile cast iron. The 2-D nodule counts have been converted into 3-D nodule counts by using a finite difference method (FDM). Particles having a diameter smaller than 5 μm should be neglected in the nodule count as these are inclusions and microporosities that do not influence the solidification morphology. If there are many small graphite nodules, as in thin-walled castings, only 3-D nodule counts calculated by FDM will give reliable results. 2-D nodule counts and 3-D nodule counts calculated by simple equations will give low results. The 3-D size distribution showed the presence of primary graphite nodules in hypereutectic castings. In thin plates the nodule count is similar in both eutectic and hypereutectic plates. In thicker plates the hypereutectic casting has the higher nodule count.