Liquid metal filtration technology was developed in the 1970s and was first used in aluminum alloys. Due to the low melting point of aluminum alloy, the density of alloy and oxide is almost the same, and inclusions are difficult to float. The first generation product is woven filter, the second generation product is extruded straight hole filter, the third generation product foam ceramic filter.
Ceramic foam filter is called “CFF” (ceramic foam filter). Usually, polyurethane foam is filled with ceramic slurry, and then the pulp is extruded. The ceramic material is wrapped around the foam fiber, then baked and sintered at high temperature, then the polyurethane is decomposed by heating, leaving the foam ceramic product – ceramic foam filter.
The research shows that the foam ceramic filter can also reduce the hydrogen content in molten aluminum while removing slag. Due to its good slag removal effect, simple operation, easy matching with other parts, and low cost, it has become a conventional purification method in aluminum processing industry. With the continuous improvement of the quality requirements of aluminum products, the requirements of the filter plate are also higher and higher.
Inclusions are the most common type of casting defects. There are many process steps in foundry production to reduce casting inclusions, such as selecting furnace material, removing metal slag before casting, and covering ladle with slag collector. The pouring ladle is bottom pouring type or teapot type, the gating system is closed type, and the horizontal runner is equipped with slag collecting bag and slag collecting trough.
The ceramic filter can be used in liquid metal filtration and the product has been commercialized. This liquid metal filtration process has been widely used in developed countries, and has become the simplest and most effective method to improve the mechanical properties of castings and reduce porosity and inclusions.
Foam ceramic castings filter has many advantages, such as good chemical stability, high specific strength, high temperature resistance, good thermal shock resistance, and large specific surface area. They are widely used in metallurgy, chemical industry, environmental protection, and other fields. In metallurgy, the use of ceramic foam filter plates can remove heterogeneous impurities in aluminum melt, such as slag and inclusions, which is one of the most effective ways to purify the melt.