Evaluation of the protective C2S layer in the corrosion process of doloma-C refractories

The performance of doloma-C refractory bricks during the steel refining step is essential for a cost effective production of steel and should be well understood. Occasionally, in special runs, the industrial practice requires a fast adjust of slag composition to fulfill the metallurgical requirements. This procedure can lead to active corrosion of the refractories, which decrease dramatically their overall life. This work aims to investigate the phenomena involving the protective layer of dicalcium silicate (C2S), which is formed through the reaction between silica slag and dolomitic refractories. C2S layer samples were characterized by analyzing their chemical composition, phase formation and microstructure. C2S was observed as the main phase, but the presence of cuspidine, a silicate-based phase with low melting point, promoted the mechanism of C2S layer dissolution by a slag with a high content of fluorspar. This work was completed with a case study in which C2S/slag samples were taken from different points of the ladle in order to evaluate the effect of fluorspar on C2S layer dissolution. Post mortem doloma-C refractory brick samples were also analyzed to verify the influence of fluorspar on the corrosion process.