Microstructures and Properties of Carbon Refractories for Blast Furnaces with SiO2 and Al Additions

Abstract

Microstructures and properties of carbon refractories specimens for blast furnaces with SiO2 and Al additions were investigated after coking for 3 hours at 1400 °C with the aid of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray, mercury porosimetry, and a thermal properties analyzer. Additives can influence the matrix structures and improve the properties of specimens. SiO2 additions decreased the mean pore diameter and tremendously increased <1-μm pore volume by filling in the pores and matrix, resulting in an increased particle packing density. Addition of Al improved the thermal conductivity by the in-situ formation of well-developed Al4C3, AlN, and SiC whiskers. With double addition of SiO2 + Al, not only the mean pore diameter decreased but also the thermal conductivity; <1-μm pore volume and cold crushing strength increased by combining the above mentioned superiority of single additive; and more SiC formed, providing greater assistance to improve such material properties.