Impurity removal is an important step for aluminum casting process. More than 90% of the non-metallic inclusions in aluminum alloys are alumina inclusions, including the oxide film on the surface of aluminum ingots or scrap aluminum furnace charge, and the oxidation of aluminum during the smelting process. Other oxide inclusions are mainly oxides produced by the reduction of the lining material by aluminum, chlorides, nitrides and carbides produced during the purification of aluminum melt.
The impurity removal purification process of aluminum alloy is divided into two steps: furnace refining and online refining. There are three methods to remove gas inclusions: inert gas diffusion method, chlorine mixed gas purification method, flux and inert gas jet refining method. The methods to remove non-metallic inclusions mainly include media filtration, adsorption and dissolution methods. Media filtration methods include glass cloth filtration, foam ceramic filter plate filtration, tubular filter and alumina ball filtration. Due to the accompanying mechanism of slag gas and the principle of tension adsorption, some fine particles of non-metallic inclusions can also be removed during the process of degassing with inert gas. The cryolite in the refining flux can dissolve Al2O3, bring out the molten aluminum, and also achieve the purpose of impurity removal.
AdTech specially solves the problem of aluminum liquid impurities. AdTech offers refining flux, degassing unit, ceramic foam filter, and CFF filtering unit for impurity removal. The on-line degassing equipment and filtering equipment produced by AdTech are installed between the furnace and the casting machine, so as to eliminate hydrogen and other residues contained in molten aluminum and its alloys that affect its quality and mechanical properties.
The ceramic foam filter can effectively trap liquid metal inclusions and purify molten metal. Regarding the research on the mechanism of metal filtration and purification, there are mainly the following viewpoints: screening-cake-deep-bed filtration mechanism; floating separation mechanism; adsorption mechanism and rectification mechanism.