Effect of NaCl, KCl e Na3AlF6 on the refining process of aluminium alloys

To maximize the efficiency of the fluxes during the refining of the aluminium alloy scrap, a proper balance of the salts is required. This study preliminarily investigates the influence of different concentrations of NaCl, KCl and Na3AlF6 on the chemical and physical properties of the fluxes used during the refining process of the aluminium alloys. The melting temperature and the viscosity of the flux at different concentrations of NaCl, KCl and Na3AlF6 were analysed, as well as the ability to dissolve the aluminium oxide. Furthermore, the dissolution of the flux in water was investigated. The results showed how the melting temperature of the flux decreases, while the viscosity increases as the cryolite content increases. The attitude of dissolving the Al oxide is favoured by the addition of Na3AlF6, even at low concentrations and reduced time of treatment. The dissolution of the oxide allows the liquid aluminium entrapped in the scrap to be released and to return into the molten bath, thus increasing the yield of the refining process. On the contrary, the dissolution of the flux in water is reduced after the addition of cryolite.