The addition of fluxing material (flux) in connection with metal casting techniques is known. Flux can be used to assist in removing impurities that might otherwise be entrapped in the cast metal. The flux may form a slag to contain the impurities.
The use of flux also serves to minimize or eliminate lamination defects. A lamination defect results from the sinking of solid oxidized metal films from an inside surface of a wall. When this solid metal film sinks into the molten metal, due to its greater density, the deoxidizers in the metal attack the oxygen on the surface of the solidified metal film. The result of this reaction is a plane of inclusions and porosity, which is typically called a lamination defect. The solidified metal film also traps inclusions which are attempting to float to the surface. The use of flux may also serve to reduce cold shuts, laps, and surface oxidation. Flux may also provide improved thermal insulation, especially at the top of molten metal.
By forming a fluid slag which may float on the surface of the molten metal, the flux may reduce oxidation of the molten metal and insulates the molten metal surface, minimizing heat loss to the air. This tends to prevent the formation of a solidified metal film caused by excessive heat loss at the surface of the molten metal. Additionally, fluid slag which is formed by the flux can contain the impurities which might otherwise be resident in the molten metal.
The prior art introduction of flux into molten metal can produce quality control problems, especially when a time released flux is desired. Liquid fluxes can be difficult to use in a time released manner and may further require additional agitation of the molten metal. Solid fluxes start to liquify along their outer surface immediately upon contact with molten metal. Solid fluxes may also move to float in the molten metal to locations which can alter the composition of the metal being cast, especially at the surfaces. Furthermore, the introduction of certain fluxes into certain molten metal may cause unwanted emissions. Thus, there exists a need in the art for better controlling of the positioning and the time release of flux material in molten metal.