Abstract. 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.

There has been reluctance from many iron foundries to adopt naturally pressurized gating systems due to the lack of knowledge on the application of the theories set out by Dr. John Campbell. The applications of naturally pressurized gating systems are still evolving and, in many cases, are counterintuitive to foundry engineers. This research tested proposed gating system behavior during filling, and from the resulting data, velocity losses (friction coefficients) through ceramic foam filters were measured. The verification of the velocity by modeling and simulation of these systems proved relatively accurate in most cases studied. The research concluded that a vertical vortex sprue system had the highest velocity reduction, reducing it by 37% (friction coefficient of 0.63), but had some initial air bubbles travel through the gate before steady-state flow occurred. The most effective gating system tested was a bottom gate and ceramic foam filter combination utilizing a bypass for the initial damaged metal and initial velocity reduction. The in-line gating using 10PPI and 20 PPI ceramic foam filters had a reduction in velocity of 16% and 28%, respectively, but caused major bubbles and jetting of the initial metal at the gate. When using filters in-line with the runner, the filter print and the bypass should be vented and the bypass have sufficient volume to counteract the initial high-velocity metal entering from the sprue. A bypass of sufficient size, reduced the initial velocity of metal through the gate, allowed priming of the filter, eliminated jetting, and reduced the chance of damaged metal from entering the mold.

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The South African foundry industry is in a state of decline. From 2010 to 2020, almost 37 foundries were closed, resulting in 123 operational foundries from 160 foundries. A benchmarking study was done using analytical factors to determine how competitive SA (South Africa) foundries were compared to those in other countries. Notably, an attempt was made to map the analytical factors, such as capacity utilisation, labour productivity, process yield, and energy cost, of SA foundries and compare them to Chinese foundries. Questionnaires were formulated to acquire primary data from SA foundries and China. In South Africa, 11 out of 14 foundries responded to the questionnaires administered through face-to-face interviews, whereas in China, one out of three foundries responded through email. On average, data from SA foundries indicate that they are uncompetitive in gating systems, scrap casting, labour productivity, capacity utilisation, and energy costs. In conclusion, based on these analytical factors, Chinese foundry has a competitive edge over SA foundries and the EU; consequently, buyers may prefer to acquire casting from china due to lower production cost, which translates into cheaper casting. It is recommended that SA foundries invest in upskilling their workforces, adopt casting simulation software, and participate in energy efficiency programmes to improve their competitiveness.