Effect of C/MgAl₂O₄ composite powders on properties of low-carbon MgAl₂O₄-C refractories

With the increasing demand for low-carbon and ultra-low-carbon steel smelting, low-carbon spinel-carbon refractories for continuous casting are subject to more rigorous requirements for slag corrosion resistance and thermal shock resistance. This study systematically investigates the effect of nano-carbon/magnesium aluminate spinel（C/MgAl₂O₄） composite powder content on the properties of low-carbon magnesia-alumina spinel-carbon（MgAl₂O₄-C） refractories for stopper rods. The results indicate that the composite powder consists primarily of irregularly shaped particles with rough surfaces, in which nano-carbon is distributed between MgAl₂O₄ grains and adhered to spinel particle surfaces, forming a unique clustered morphology. The optimal performance of MgAl₂O₄-C refractories was achieved with 6.3% composite powder addition（sample C/MA-2）, showing 15.4%, 19.6%, and 45% enhancements in the cold modulus of rupture（CMOR）, the cold crushing strength（CCS）, and the hot modulus of rupture（HMOR）, respectively, compared to the composite-free sample（C/MA-0）. Sample C/MA-2 exhibited the best thermal shock resistance, showing a 11.9% higher the thermal shock resistance of than C/MA-0. Furthermore, the erosion depth of C/MA-2 was reduced by 19.6% relative to C/MA-0, demonstrating superior slag corrosion resistance.