Oxidation and Diffusion in Selected Pitch‐Bonded Magnesia Refractories

A conventional and an improved (Mg‐containing) BOF refractory, of commercial pitch‐bonded magnesia type, were evaluated to determine their Mg diffusion and carbon oxidation characteristics. MgO dense‐zone formation was characterized experimentally for various firing times at 1650°C, from which Mg diffusion coefficients in the range 1.4x10 ‐9 to 8.13x10 ‐10 cm 2 /s were determined. The data indicate that the Mg diffusion in the system is of the extrinsic type, controlled by the impurities in the MgO, such as Al 3+ , Fe 3+ , and Cr 3+ . The effects of Mg vaporization and MgO condensation, preceding dense‐zone formation, were observed to initiate at 1200°C. The dense‐zone thickness and the amount of unoxidized carbon were greatest for the Mg‐containing refractory.