The oxide film and impurity particles suspended in the molten aluminum are difficult to completely remove in a furnace with a wide open surface. The effect of applying the flux with the powder spraying machine is better, but it is still difficult to achieve the purpose of comprehensively purifying the molten aluminum. Therefore, in addition to using the flux in the large-capacity furnace to remove some contaminated impurities, the modern melting and casting workshop also uses an on-line purification device outside the furnace to comprehensively purify the molten aluminum flowing out of the holding furnace, and completely remove the remaining gas and slag in the molten aluminum. AdTech offers On-line Purification Device, includes online degassing unit and CFF filtering system.
The principle of the on-line purification device outside the furnace is to allow the molten aluminum to fully contact the inert gas in a small purification furnace equipped with a heater, so that the hydrogen present in the molten aluminum diffuses into the inert bubbles with zero hydrogen partial pressure and escapes. Liquid level. The solid slag suspended in the molten aluminum will also be adsorbed on the surface of the bubbles and removed together. After the online purification process, the hydrogen content of the molten aluminum can be reduced to half of the original value. The particle diameter of non-metallic inclusions below 50μm can be removed 50%, and those above 100μm can be removed 90%. Adding 0.5%-3% refining agent in the inert gas can increase the hydrogen removal rate from 50% to 65%, and can also remove 60%-75% of Na and Li. It is very important when extracting molten aluminum to produce aluminum.
Inert gas can be dispersed into tiny bubbles into lambda aluminum liquid through rotating nozzle, atomizing nozzle or porous ceramic plate. The purification device outside the furnace has the patent name of the inventor. In order to prevent the secondary pollution of the molten aluminum in the purification furnace, some devices also cover the surface of the molten aluminum with inert gas. The inert gas can be nitrogen or argon. Nitrogen must be high-purity nitrogen with a purity greater than 99.995%, and the purity of argon should be greater than 99.98%. The cost of argon is higher than that of nitrogen, but its advantage is that it will not react with molten aluminum to form compounds at high temperatures. After the aluminum liquid is purified online, the hydrogen content should reach 0.12mL/100g (below A. For products with strict quality requirements, the hydrogen content should reach 0.10m/100g (Al) or less.
The time for the molten aluminum to pass through the purification device is very short. After processing, it is difficult to completely separate the smaller slag and inclusions from the molten aluminum in such a short time. In order to ensure the cleanliness of the molten aluminum, all purification devices outside the furnace are equipped with There is a filtering device to remove suspended impurities. The shape of the impurities in the molten aluminum is a film or a particle, the film thickness is 0.1-0.5μm, the length or width is 10-5000μm, and the particle diameter is 0.1-50um. There are oxides such as Al2O3, SiO2, MgO, and non-oxides such as AlF3, Al4C3, and AlN.