Effect of Refractories on Contamination Behavior of Molten Al-7%Si Alloy

Abstract

  This paper investigates the effect of refractory on phosphorous (P) contamination in molten Al-7%Si alloy. Four types of refractories with different aggregates and binder contents were prepared for the experiments. The refractories were formed into crucibles, filled with a molten Al-7%Si-0.0001%P alloy, and contamination experiments were carried out. The mechanism of P contamination into the molten alloy was examined by analyzing the P content of the alloy compound, observing the microstructure of the interface between the crucible and alloy, and applying thermogravimetric-differential thermal analysis (TG-DTA) to the refractories. When phosphate was used as the binder, P contamination of the molten alloy occurred between 800 and 900℃. From the TG-DTA results, the cause of this phenomenon was identified as dissolution of the binder. Furthermore, the amount of P elution rose as the ratio of non-alumina in the aggregate increased. Based on these results, it was concluded that a complex refractory material matrix causes localized reductions in the melting point, leading to pronounced increases in P contamination.