Interaction of Ladle Slag With Varying SiO ₂ Content and Recyclate‐Based MgO–C Refractories

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 SiO 2 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 SiO 2 content at 1600°C reduced slag density and surface tension, increased viscosity, and shifted saturation from MgO to MgAl 2 O 4 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‐SiO 2 slag formed a dense, 195 µm‐thick MgAl 2 O 4 ‐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.