Refining aluminium-alloy melts with graphite rotors

Abstract

The presented paper is focused on the study of refining aluminium-alloy melts. The quality of castings is determined by the basic material, i.e., the input material (furnace charge), its subsequent melting and subsequent metallurgical modifications. To allow the profitability of production, low-quality input materials are currently used, which, although they have the required chemical composition, may contain a large amount of impurities, coming not only from the original input materials, but also from their processing. To allow a cost reduction, in addition to rejected castings, the residues of gating and chipping from the machining are used as charge materials in foundries. However, the melt thus prepared is heavily contaminated with gases and inclusions.The aim of the research was, therefore, to verify the use of graphite rotors functioning as degassing units for refining aluminium melts. The experiments were conducted under laboratory and pilot-plant conditions using the plant equipment. The refining efficiency was monitored with respect to the type and shape of the graphite rotor and the refining medium used. The achieved purity of the resulting melt was evaluated to establish the density index and the final cast microstructure.