THERMO-MECHANICAL EXTRACTION OF ALUMINIUM FROM THE DROSS OF MELTING Al AND AlMg SCRAP

The thermodynamic properties of aluminium make its oxidation by various reactant gases an important side-reaction of melting. Magnesium, as a major alloying component, plays a further important role in determining the properties of the heterogeneous dross formed during the melting of aluminium alloys. The formed dross may entrap significant amounts of the metal, whose specific amount can be determined by a method including a thermo-mechanical treatment in an induction furnace with no special provisions, allowing most of the entrapped metal to be cast into blocks. Further significant portions of the contained metal are obtained by grinding and physical classification. These steps also aid in the modeling of the industrial dross treatment. The remaining metal content in the fine residue was determined by a special chemical method. The metal content of the dross obtained from melting Al alloys with varying Mg concentrations typically ranges between 70 - 85%. Magnesium was found to play an important role in determining the mass and metal content of the dross. The beneficial effect of using simple NaCl as a melting additive was also noted.