Feeding Against Gravity with Spot Feeders in High Silicon Ductile Iron

Abstract

A test pattern, with three different moduli castings was developed to investigate methods to optimise feeding of high silicon ductile cast irons. Different feeder types, modulus, and locations were investigated using both an insulating and an exothermal sleeve material. Porosities were analysed and classified using X-ray imaging and ultrasound analysis. The effect of the different feeder configurations were classified in reference to defect location, sleeve material, and feeder type, modulus, and location. The analysis showed that exothermal feeder sleeves with the right configurations can feed uphill against gravity. This effect may contribute to the thermal expansion created by the exothermal reaction. It was also found that the optimum feeder size does not scale linearly with the casting modulus but that larger casting modulus requires relatively smaller modulus feeders. The thermal gradient created by the feeders made with the insulating sleeve material was not sufficient to significantly improve feeding.