An Investigation on Reduction of Insoluble Build-ups in the ‎Inductor of Ductile Iron Pouring Machine

The pile-up of insoluble build-ups in induction pressure pouring machines has been one of the important problems in casting of ductile iron. The main constituent of these build-ups is magnesium oxide (MgO). The formation of MgO is resulted by oxidation of the magnesium which was used for graphite spheroidisation. In this research, the effectiveness of two solutions has been studied to overcome this problem in pouring machines of a casting plant. The solutions were the addition of a flux into the melt and applying nitrogen atmosphere instead of air. The chemical analysis of the melt, slag and build-ups were done using X-ray diffraction (XRD), wet chemistry method and quantometery technique. For the first approach, the best efficiency was obtained with addition of 900 g/ton flux into the ladle before inoculation. Without flux addition, the electrical current drop was drastic (~350 A in 16 days). However, the flux addition resulted in a slight drop in the electrical current (~50 A in 28 days). Moreover, the flux addition has changed the main constituent of build-ups from MgO to iron oxide (Fe2O3). The using of nitrogen atmosphere resulted in a significant decrement in the fading rate of magnesium from 0.017% in 36 min to 0.0146 % in 50 min.