There are many purifying methods for molten aluminum in the furnace, including flux refining, and online degassing and filtration. Practice has proved that nitrogen refining in the production process that uses molten aluminum as the furnace charge has an excellent effect on the purification of molten aluminum and does not leave too many impurities in the molten aluminum.
However, the cleaning in the furnace can only be used to eliminate the molten aluminum itself and the added impurities during the smelting process, and cannot eliminate the pollution received during the casting process. Secondly, the furnace area is large and the molten pool is shallow, and the molten aluminum falling on each corner cannot be sufficiently cleaned. Third, the use of molten aluminum as a furnace material determines that it is extremely difficult to purify and is ideally cleaned. Therefore, in order to ensure the purity of molten aluminum before casting and rolling, large aluminum plants have adopted degassing equipment and filtering equipment.
The degassing equipment completes the purification, diversion, and temperature preservation of the aluminum liquid from the outlet of the static furnace to the front box; it is mainly composed of five parts: launder, degassing box, filter box, heating system, and main engine. The equipment uses high-purity nitrogen with a purity of 9.95% or more as the refining gas, and the degassing efficiency can reach more than 60 %. The gas content in the processed aluminum liquid is about 0.12 and below. The filter system uses ceramic filter plates with a filtration efficiency of 9% or more and a filtration accuracy of 3 μm.
When the degassing equipment is working, nitrogen can enter the pneumatic control box from the gas source through the gas flow meter. The flow meter can adjust the amount of nitrogen flowing into the aluminum liquid from the graphite rotor, and at the same time, the nitrogen is dispersed into fine bubbles through the high-speed rotating rotor And evenly distributed in the entire melt, hydrogen and non-metallic slag are adsorbed by fine nitrogen bubbles and brought to the surface of the liquid.
Purifying methods for molten aluminum is important for aluminum processing. In order to reduce the slag and gas content, it must be strictly controlled during the process of furnace installation and melting. The solid material in the furnace charge must be clean and dry, try to avoid or reduce the addition of oxide film, oil stains, plastics, sundries, etc., and remove the scum on the surface before the aluminum liquid enters the furnace. Try to melt quickly at high temperatures to reduce the generation of aluminum slag and gas. When operating in the furnace, ensure that the materials and tools used are clean and dry. All operations must be completed quickly according to the process requirements. Do not leave the furnace door open for a long time and air into the furnace.