Production of silumins using silicon production waste

Abstract

The paper presents a review of existing methods to produce silumins. The possibility of obtaining foundry alloys using amorphous microsilica is shown. Different methods of adding SiO 2 particles into molten aluminum are studied: in the form of aluminum powder — SiO 2 master alloy tablets, particle mixing in the melt at the liquidus temperature and introducing SiO 2 together with a stream of argon. The paper provides calculations of Gibbs energy formation and change enthalpy for silicon reduction by aluminum from its oxide. Calculations demonstrated the thermodynamic possibility of silumin production using amorphous microsilica. The effect of alloying additives and impurities on the silicon reduction behavior is determined. It is found that magnesium can be used as a surface-active additive to remove oxygen from dispersed particle surfaces and reduce silicon from its oxide. It is determined that the method of aluminum-silicon alloy production by introducing amorphous microsilica preheated to 300 °С into the aluminum melt (t = = 900 °С) together with argon stream (with subsequent intensive mixing) features higher efficiency since it ensures producing aluminum-silicon alloys containing more than 6 wt.% of silicon and microstructure of pre-eutectic foundry silumins. Industrial application of the proposed method will improve the efficiency of the existing silumin production process due to savings on purchasing commercial crystalline silicon. Moreover, this technology will minimize the environmental impact by reducing the volume and subsequent eliminating sludge fields used as landfills for storing dust from silicon gas treatment systems containing up to 95 wt.% of amorphous microsilica.