Molten metal filtration with ceramic foam filters is a proven method in order to remove the inclusions. This paper develops a new approach for the production of ceramic foam filters.
In the conventional method of ceramic foam filter production, polyurethane sponges are used. In this work, a ceramic foam filter was produced by using expanded polystyrene. Polystyrene is expanded in a specially designed mold by steam to form polystyrene patterns. Various ceramic slurries are then poured into the polystyrene cell and allowed to air dry.
After the shaping operation, filters are subjected to a sintering process under various conditions. By this new method, filter channel sizes can be controlled and traps with desired configurations can be formed. Some tests were applied to the produced filters. Thermal shock tests ensured that the filters could withstand temperatures of 1450 °C. The water absorption test showed that bauxite based material absorbed water more than the others.
Silicon carbide ceramic foam filter is a special technology. It has a foam porous structure of ceramic products, and its lightweight, chemical stability, large surface area through-hole rate, corrosion resistance to molten metal erosion, high temperature, high strength, high pass rate, and good thermal shock resistance characteristics.
Molten metal filtration is mainly used in the field of metallurgy and casting metal liquid filtration and purification. Ceramic foam filters can be made of different pore sizes and porosity, in order to obtain a satisfactory filtration effect.
A process for producing a silicon carbide ceramic foam filter includes the steps of preparing raw material becoming silicon carbide from a mixture of silicon carbide powder, alumina, zirconium silicate, talc, and kaolin clay; adding the foaming agents into the raw materials for silicon carbide generation, mixing the forming agents and the raw materials to obtain a raw material batch, shaping a foam structural body from the resulting mixture by extrusion, hydraulic press machine or mold for slip casting; drying the formed body, and sintering the formed body after drying. The structure and property of the silicon carbide ceramic foam filter were investigated by X-ray diffraction (XRD), Scanning Electronic Microscopy (SEM).