Influence of Ferrosilicon Addition on Silicon-oxygen Equilibria in High-silicon Steels

Abstract

The role of impurities introduced to the steel melt through ferrosilicon addition is of considerable importance in determining the steel cleanness of Si-killed, Si-alloyed steel grades. The silicon requirement is often met with ferrosilicon (FeSi) addition at the industrial scale. In the present study, a detailed investigation of commercial purity ferrosilicon (FeSi) alloy has been conducted to assess its impurity content. Aluminium and titanium were found to be the main impurities among others. Si–O equilibria in liquid steel has been established at 1873 K using FeSi alloy for a wide range of silicon concentration to examine the influence of its impurities. The actual Si–O equilibria established through FeSi addition was compared with true Si–O equilibria which was established using High-purity silicon (HPS) addition. It has been observed that impurities (mainly aluminium and titanium) from FeSi perturbed the true Si–O equilibria. Thermodynamic and kinetic considerations pertaining to this deviation have been elaborated in the present study.