The application of magnetic moulding in casting of a ductile iron valve

Abstract

Impeding problems experienced in the valve manufacturing industry has resulted in the cost of locally manufactured valves to be up to 60% more expensive than imported products. The overall cost of manufactured products may be reduced by increasing the efficiency of manufacturing methods. A review and investigation of various manufacturing methods have led to the selection of the magnetic moulding process for further investigation. It was determined that due to the traditional mould materials used for the casting of cast irons, variation and control of the microstructure, determined by cooling rate, is limited. If the thermal conductivity of the mould material can be varied or controlled, substantial microstructural variation becomes possible that can substantially improve the strength of the cast product and lower the overall cost of local valve manufacturing. The feasibility of the magnetic moulding process on the casting of a ductile iron valve was tested by implementing this casting method. A casting was performed with an additive manufactured PMMA pattern and due to inconclusive results, a wire-cut EPS pattern with a square geometry was cast successfully with this method. The results of both castings were analysed by means of microstructural inspection and the testing of mechanical properties. Ultimately, it was concluded that the magnetic moulding casting process is a feasible manufacturing method with the potential to increase the affordability of locally manufactured valves if a low-density pattern material, such as EPS, is used. Additionally, it is a viable method that offers a vast amount of opportunities to vary the microstructural properties of cast iron if it is to be further implemented in valve casting.