The effects of temperature on phase composition, microstructure, and properties of silicon-containing blast furnace (BF) carbon refractories after firing in coke breeze packing at 1000°C to 1600°C were studied with the aid of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray, mercury porosimetry, and a laser thermal conductivity meter. The results showed that silicon played a dominant role in the evolution of phase, microstructure, and properties. The amount of SiC whiskers increased with temperature. The phase in the outer part of the specimen was cristobalite balls, and its content decreased and b-SiC whisker increased in the inner part of the specimen. The phase and microstructure development with firing temperature influenced the properties. The bulk density, strength, and <1-lm micropore volume of open pores were highest, whereas the apparent and total porosity, mean pore size, and thermal conductivity were lowest for specimens fired at 1400°C. Moreover, the thermal conductivity was affected by pore structure and phases formed after firing.

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The effect of carbon aggregates on the carbon refractory properties for a blast furnace was studied with X-ray diffraction (XRD), scanning electron microscopy (SEM), an energydispersive X-ray, mercury porosimetry, a resistivity instrument, and a laser thermal conductivity meter. The results showed that the microporous structure of a sample was determined by the amount of b-SiC whiskers. The thermal conductivity was controlled by the thermal conductivity of the corresponding carbon aggregate, and the alkali and molten-iron attack was decided mainly by the pore and the graphitization degree of aggregate, respectively. For samples using calcined anthracites as aggregates, the microporous structure became worse, the thermal conductivity increased, and the molten-iron as well as the alkali attack became more severe with an increase in the anthracite calcining temperature. For all samples, microcrystalline graphite possessed the best microporous structure and the least alkali and molten-iron attack, whereas the graphite electrode scraps had the highest thermal conductivity and the most severe alkali and molten-iron attack.

Microstructures and properties of carbon refractories specimens for blast furnaces with SiO 2 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. SiO 2 additions decreased the mean pore diameter and tremendously increased <1-lm 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 Al 4 C 3 , AlN, and SiC whiskers. With double addition of SiO 2 + Al, not only the mean pore diameter decreased but also the thermal conductivity;<1-lm 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.

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