IMPROVED UNDERSTANDING OF THE MELTING BEHAVIOUR OF FUSED MAGNESIUMCHLORIDE-POTASSIUM CHLORIDE BASED REFINING FLUXES

摘要

Fused magnesium chloride-potassium chloride refining fluxeshave become widely adopted as a more environmentallyacceptable means for removing alkali metals and oxides frommolten aluminium than injection of chlorine gas. Refining fluxeswere initially designed based on the binary system magnesiumchloride-potassium chloride which exhibits two low melting pointeutectics; one at about 60% and one at about 40% mole %magnesium chloride. In a further development productscontaining 25% magnesium chloride have found widespreadadoption exhibiting equal removal efficiencies and satisfactorymelting behavior. The objective of the current work was toreconcile the observed performance with the phase equilibria byconducting differential thermal analysis on industrialcompositions and relating data collected to known binary andternary systems. The findings indicate a significant beneficialeffect from fluoride addition and the existence of a third lowmelting point eutectic at about 30 mole %.