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• Time of issue:2023-01-04 14:59
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(Summary description)The investment casting process contains various residues in the aluminum liquid sucked out by the electrostatic precipitator, so purification is required before casting. In industrial production, purification methods such as clarification, flux, and vapor are mainly used, and some also use fixed solidification and filtration methods for purification. 1. Flux purification: Flux purification is the application of a slimy discharge composed of many fluxes involved in aluminum liquid, allowing the metal oxides in the aluminum liquid to be absorbed and dissolved by this discharge, forming a new discharge that rises to the surface, and after cooling, forms a sludge to be removed. The flux used for purification is composed of salts with low melting point, low relative density, low surface support, high vitality, and strong adsorption on air oxidation slag. When applying, a small piece of flux is first loaded into a cage, and then stabbed into the bottom of the mixing furnace to stir back and forth. Alloy steel precision castings can be cast by removing the cage after the flux is melted, and stopping for 5-10 minutes to remove the surface sludge. According to requirements, the flux can also be removed from the surface to provide a covering effect. 2. Vapor purification gas purification is a major raw aluminum purification method, commonly used as chlorine gas, nitrogen gas, or a mixture of chlorine and nitrogen gas. (1) Chlorine purification. Previously, active vapor chlorine was used as purifying agent (Chloride process). In the Chloride process process, when chlorine gas enters the aluminum liquid, many abnormally thin AlCl3 and bubbles are formed, which are fully mixed in the aluminum liquid. The hydrogen dissolved in the aluminum liquid, along with some alloy aluminum precision casting equipment impurities, are adsorbed on the AlCl3 bubble, followed by the AlCl3 bubble rising to the surface of the aluminum liquid and discharged. When entering chlorine gas, it can also chlorinate some elements that are more negatively charged than aluminum, such as calcium, sodium, magnesium, etc., which generate corresponding chlorides due to entering chlorine gas and are separated. Therefore, Chloride process is a very effective method for purifying primary aluminum. The amount of chlorine used is 500-700g per ton of aluminum, but because O2 is harmful and precious, in order to avoid gas damage and reduce the cost of waste aluminum production, it has been gradually replaced by Noble gas nitrogen purification method in the contemporary aluminum industry. (2) Nitrogen purification method. It is also known as the continuous purification method without smoke, using alumina balls (418mm) as the filtering material. N2 immediately enters the aluminum liquid. The aluminum liquid is continuously fed into the purification furnace, passed through the alumina ball filter layer, and subjected to nitrogen flushing. Therefore, the non-metallic material impurities and their dissolved hydrogen in the aluminum liquid are removed, and then continuously discharged, resulting in even distribution of slender nitrogen bubbles in the solved aluminum liquid, which has purification effect. Nitrogen has zero air pollution and a large purification output, which can solve 200-600kg of aluminum liquid per minute. The amount of aluminum loss generated during the entire purification process is relatively reduced, so it is now widely used. But unlike chlorine gas, it can remove calcium, sodium, and magnesium from aluminum liquid.