Corrosion mechanism and microstructure evolution of industrial used Al2O3-ZrO2-C slide plates

Abstract

Slide plates are one of the most important functional refractories that control the flow of molten steel from the steel ladle to the tundish. In order to improve the service performance of slide plates and accelerate continuous production of the steel industry, a detailed post-mortem analysis was necessary. In this study, the corrosion behaviors of the high-temperature heated Al2O3-ZrO2-C slide plate used one heat for a 200 tons steel ladle in industry were investigated. The results showed that the thermo-mechanical properties' mismatch led the formation of radial cracks, which was the main factor limiting the service life of the slide plates. Besides, corrosion microstructure revealed the dissociation of mullite-zirconia aggregates and the loss of graphite provided a channel for the penetration of molten steel. The penetration of molten steel could react with Al2O3 in the slide plates, which accelerated corrosion in the early stage and formed a composite spinel layer in the later stage to block corrosion. Also, acicular CaAl12O19 was formed behind the composite spinel layer, further blocking the penetration of molten steel. Furthermore, the ZrO2 from mullite-zirconia had an interlocking structure to prevent corrosion. Finally, the content and viscosity of the liquid phase at different positions of the used slide plates were calculated, which indicated that the area near the casting hole had more liquid phase and lower viscosity. This would further optimize the service performance of the slide plates.