Corrosion of the refractory zirconia metering nozzle due to molten steel and slag

Abstract

This paper presents a study on the phase composition and microstructure changes of a sintered Mg-stabilized zirconia metering nozzle exposed to the corrosive effect of the molten steel and slag in a tundish for continuous casting for 30 h. A macroscopic observation of the corroded material showed cracks and two zones that were distinguished with respect to colour. An X-ray diffraction analysis showed that the dark layer was richer in stabilized ZrO2 than the light layer. After the corrosion test, the nozzle had higher contents of MgO, SiO2, CaO, Al2O3 and Fe2O3 than the reference sample as evidenced by an X-ray fluorescence analysis. Moreover, during the corrosion process, liquid steel and slag infiltrated the zirconia material, which was confirmed with a SEM investigation. Along the hot face of the metering nozzle, the grains of zirconium oxide recrystallized with a high-temperature structure of ZrO2 and dissolved MgO and CaO derived from the slag, stabilizing this phase.