GRK 2802: Interaction of Ladle Slag With Varying SiO2 Content and Recyclate-Based MgO–C Refractories

Abstract

Industrial MgO–C refractories fabricated from either pure fuzed magnesia (R0) or 50 wt% recycled MgO–C (R50) were exposed to ladle slags (C/A = 1) with varying SiO2 content (1–20 wt%). Wetting and infiltration behaviors were investigated using the sessile drop method at 1600°C under an Ar atmosphere for different dwell times. Quenched slag–refractory interfaces were characterized by SEM-EDX and compared with phase equilibrium simulations using FactSage 8.1. Increasing SiO2 content at 1600°C reduced slag density and surface tension, increased viscosity, and shifted saturation from MgO to MgAl2O4 spinel. During heating, R50 samples exhibited more intense gas formation. This delayed wetting and significantly slowed the initial stage of slag infiltration. Upon contact with recycled-based refractories, the high-SiO2 slag formed a dense, 195 μm-thick MgAl2O4-rich layer, entrapping residual calcium-silicate slag and serving as an in situ protective barrier against further oxidation and corrosion. These results demonstrate that well-processed MgO–C recyclate can inhibit slag attack, first by delaying infiltration via transient gas release, and subsequently by promoting a protective spinel layer under suitable slag compositions. Furthermore, the findings highlight the influence of substrate carbon content and open porosity on the slag’s melting and infiltration behavior.