THE USE OF ALUMINUM SLAG RECYCLING PRODUCTS IN INVESTMENT CASTING TECHNOLOGIES

The studies of fractional, chemical and phase compositions of aluminum-containing slags of different origin found that slags are multi-component systems consisting of metal and non-metal parts. The non-metal part contains water-soluble and water-insoluble components. A practical scheme for recycling aluminum-containing slags was proposed in order to isolate the water-insoluble component to be further used a secondary refractory dusting material. It was found that the secondary refractory dusting material has a positive effect on the quality of refractory ceramic molds in investment casting and the surface finish of experimental aluminum castings. This material improves the strength of refractory ceramic molds by 9 times in comparison with silica sand molds and increases gas permeability by 15 % to 33 % in comparison with fused alumina and silica sand molds, respectively. The study covers the processes used to produce refractory ceramic molds based on the secondary refractory dusting material. The mechanism of interaction between dusting material particles and suspension is theoretically justified in terms of colloid chemistry. Negatively charged aluminum hydroxide micelles appear when ceramic mold layers are formed using the secondary refractory dusting material. Interaction between differently charged Al(OH)3 and SiO2 micelles makes secondary refractory dusting material particles come in close contact with each other. The theoretically justified processes of ceramic mold layer formation with the secondary refractory dusting material make it possible to explain the reduction in the surface roughness of castings made of AK9ch aluminum casting alloy using investment casting by 3.7 times compared with standard production processes.