Alkali metals removal is also important in aluminum smelting and casting process. Alkali metals and alkaline earth metals in aluminum melt mainly come from alkali metals and alkaline earth metal elements in the aluminum electrolysis process, such as Na, Li, Ca, etc., and also from aluminum alloy fluxes. Aluminum alloy fluxes are generally composed of alkali metals and alkaline earth metals. The main components of chloride and fluoride are KCl, NaCl, NaF, CaF, Na3A1F6, Na2SiF6, etc. The alkali metals and alkaline earth metals mentioned above will remain in the melt after the flux is used.
Experiments have proved that the alkali metals removal in the aluminum melt is to use chlorine, chlorine-containing refining agent (such as hexachloroethane, carbon tetrachloride, etc.) or fluoride-containing refining agent in the holding furnace. Perform refining treatment. However, in the process of using chlorine, chloride or fluoride, there will be chlorine gas floating out of aluminum melt, chlorine gas and hydrogen fluoride generated after the reaction with alkali metals, hexachloroethane and tetrachloride gasified by heating The production of carbon gas will seriously damage the furnace lining and shorten the life of the furnace; secondly, it will cause occupational hazards to production operators.
An environmentally friendly and efficient way of alkali metal/alkaline earth metal is realized by substitution reaction. The basic principle is to use the characteristics of active wave of alkali metal/alkaline earth metal chemical characteristics according to the order of metal activity, and add other metal salts with relatively inactive cations. , And then removed by other physical methods.
At present, high-performance alloys are developing in the direction of large specifications, and the size requirements of casting billets are gradually increasing. The hazards of residual gas, impurities, slag and alkali metals/alkaline earth metals in the aluminum alloy melt during the casting billet processing will be further highlighted.