Waste foundry sand mineralogical characterisation: The impact of cast alloy, casting temperature and molding additive on the nature waste foundry sand

The metal casting industry discharges huge volumes of waste foundry sand yearly. It was estimated to be 250 thousand tons of spent silica foundry sand for the existing 200 casting facilities in South Africa. Even though, establish documents exist in regards to the foundry sand composition, few well documented theories are available in regards to changes or mutations taking place after casting process. Four waste silica casting sands were qualitatively analyzed for they mineralogical phases composition using the X-ray diffraction (XRD). The investigation was conducted on various waste casting sand alloy including aluminum, cast iron, high chrome and steel. The result revealed a significant compositional difference related to the molding binder and casting temperature. Different silica phase’s polymorph, related to the various alloy casting temperature, were observed in waste sand samples. Theses phases included alpha quartz, tridymite, and alpha cristobelite. The molding binder favored the crystalisation of bentonite related mineral such as periclase, microcline and wustite, within the greensand system. The chemically bonded sand exposed the presence of anorthite as the only existing mineralized phase in the resin sand. The mineralogical content of the waste foundry sand provides information on the molding binder used. In addition to that, silica polymorph it informs about the pouring temperature related to the cast alloy.