Study of the Oxidation of an Al-5Mg Alloy in Various Industrial Melting Furnace Atmospheres

In an industrial furnace, fired with a hydrocarbon-based fuel, the furnace atmosphere will essentially consist of a mixture of the four species: CO2, H2O, O2 and N2, all of which thermodynamically will react with aluminium. Earlier publications have addressed the question of the thermodynamic versus the kinetic driving forces for oxidation and dross formation of liquid aluminium alloys. Most of these studies have been performed in a laboratory environment with samples in the order of magnitude of 1 g or less. This paper describes a series of tests, where 10 kg samples of an Al-5Mg alloy were molten in a pilot scale furnace, using burners fired with LPG and LNG and with controlled flows of gas components to produce various mixtures of the four gaseous species. The weight gain of the samples were monitored to determine the degree of oxidation and dross formation.