The molten aluminum ceramic foam filter plate is composed of an aggregated mesh member made of refractory material and a coating formed on the surface of the mesh member. The coating has sodium silicate, which can be softened or sticky at the temperature of molten aluminum or molten aluminum alloy.
The casting of aluminum alloy includes the following steps: melting aluminum raw materials to obtain molten aluminum alloy; removing the inclusions from the molten aluminum alloy by adsorbing the inclusions with ceramic foam filter, thereby filtering the molten aluminum alloy.
The molten aluminum ceramic filter filtering ability depends mostly on the mesh roughness (mesh number) formed in the aggregate meshed member. Therefore, in order to remove small inclusion particles of about 10 to 25 μm as mentioned above, it is preferable that the refractory aggregate meshed member according to the present invention has a fine mesh, specifically having 2 openings or more per inch, more preferably having 6 openings or more per inch. However, in case that there are a large amount of inclusions, too fine mesh may give a practical problem that the filter is clogged up within a relatively short-term operation, thereby shortening the filter lifetime. Accordingly, the fineness of the mesh is preferably 10 openings or less per inch in order to prevent decreasing the filter life.
As the refractory material for the aggregate meshed member, used can be any refractory materials from which the meshed member can be formed. The conventional refractory materials can be chosen as appropriate from alumina, magnesia, silica, mullite, silicon carbide, and mixtures thereof. Then, a clay or slurry of these ceramics are formed and baked into a porous body of a suitable shape having a desired meshed size, such as noodle, honeycomb and tube shapes, to form the meshed member. The suitable shape of the meshed member allows the obtained filter to have a required strength for resisting thermal shocks and abrasion caused by the molten Al.
