Mechanisms of carbon transport between magnesia-graphite ladle refractories and ultra-low carbon (ULC) steel were investigated using laboratory dip tests with commercial ladle refractories in a vacuum induction furnace. Refractories with carbon contents between 4-12 wt% were evaluated to observe the effect of carbon content on the rate of carbon transfer to the steel. The influence of slag was also examined by comparing slag free experiments with experiments performed with industrial slag compositions of varying MgO content. The reacted refractories were examined by SEM-EDX analysis to observe changes in the refractory that influenced the rate of carbon pickup to the steel. The mechanism for carbon transfer when refractories of 10 wt%C and 12 wt%C were in contact with ULC steel without slag was dissolution of carbon by steel penetrating into the refractory. There was no penetration and no carbon pickup when 4 wt%C and 6 wt%C refractories were in contact with ULC steel without slag. The presence of slag changed the pickup mechanism to corrosion of the refractory at the slag line. A slag closer to MgO saturation lessened the extent of that corrosion.
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