Whether it is electrolytic raw aluminum liquid or remelted aluminum liquid, they all contain alumina and hydrogen. These two non-metallic impurities are the main impurities that affect the process performance, physical properties and mechanical properties of aluminum. Therefore, molten aluminium purification is mainly to remove these two impurities. Alumina exists in the state of suspension of fine particles in the aluminum liquid, and hydrogen exists in the state of free atoms in the aluminum liquid. Hydrogen has a certain solubility in molten aluminum, and as the temperature of molten aluminum increases, its solubility also increases.
The purpose of molten aluminium purification is to use various methods to reduce the gas content (mainly hydrogen) in molten aluminum, reduce non-metallic inclusions and various harmful metals. In the process of aluminum alloy melting and casting, there are different degrees of gas, non-metallic and other metal inclusions, which make the ingot loose, pores, slag inclusion and other defects, which have a significant negative impact on the performance of the product. The same is true for wire rod continuous casting and rolling. Since the aluminum wire rod will be subsequently processed into aluminum with a smaller diameter and cross-sectional area, the significance of aluminum liquid purification is greater.
The aluminum liquid mechanical purification method is an auxiliary to the bubble method. It is suitable for purification outside the furnace, that is, it is used in the tundish of the launder during the casting process. The materials used mainly filter cloth, ceramic foam filter, and alumina ball. This method can be used in conjunction with the bubble method.
The ceramic foam filter is a sheet filter, which is installed online between the metal processing system and the casting equipment. It has the dual functions of filtering and heating molten aluminum liquid. The principle of filtration is that the molten metal aluminum liquid passes through two ceramic filter plates to capture the impurities in the aluminum liquid. The effect of filtration depends on the selection of the number of holes in the filter medium; the flow rate of the filter depends on the size, number and number of holes of the filter plate. The resistance is installed in the lid on the box body during heating, and its purpose is to keep the metal temperature between the two castings at the temperature set by the operator, and to increase the metal temperature when the spoon is continuously cast.
