Assessment of Magnesia Refractories Corrosion by Iron-Rich Slags

Abstract

High purity magnesia refractories have been tested for their resistance to iron-rich converter slags of ferronickel production. Laboratory tests were performed using crucibles made from magnesia refractories filled with slag at temperatures up to 1700 °C and contact times of 1, 2, 4, or 8 h. SEM observations and microanalyses performed on both refractories and slag indicated the progressive substitution of Mg in magnesia refractories by iron and production of magnesiowustite ((Mg, Fe)O), thus forming an affected intermediate zone with a depth depending on contact time and temperature. At the most aggressive conditions investigated, i.e., temperature 1700 °C and 8 h contact time, the maximum depth of the intermediate affected zone measured was 1.57 mm. Thermodynamic simulation of the system with FactSage 7.0 confirmed the formation of magnesiowustite with progressively higher rates of Mg substitution by Fe that decreases the melting point of (Mg, Fe)O, resulting in the progressive corrosion of the converters’ lining.

Keywords

• refractories
• magnesia
• ferronickel
• FeNi
• corrosion
• slags