Effect of Temperature on the Properties and Microstructures of Carbon Refractories for Blast Furnace

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 β-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-μm 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.