Influence of the furan moulding sand on the ductile iron casting surface quality

摘要

The results of investigations of the influence of molding sand with furan resin, prepared both with fresh sand and reclaimed matrix, on the formation of microstructure and surface quality of ductile iron castings are presented in the paper. Different furan moulding sands were used within the studies: moulding sand prepared with fresh sand and moulding sands prepared with reclaimed sands of different purification degree, determined by loss of ignition value. A series of experimental heats of ductile iron in molds made of molding sand characterized by different levels of surface-active elements (sulfur) were performed. Various concentrations of sulfur, which is considered as a unfavourable element from the spheroidisation point of view, in the moulding sands as a function of the loss on ignition has been shown in the paper. Investigations carried out by means of scanning electron microscopy (EDS), showed a concentration gradient profiles of surface-active elements in the surface layer of castings which are responsible for their quality. Moreover an analysis is shown of the effect of the wall thickness, and the initial temperature of the metal in the mould cavity on the formation of the graphite degeneration nodules in the surface layer of the casting.