Thermo-Mechanical-Chemical Characterization of High-Carbon-Containing Refractory Castables

摘要

Over the last decades, the technological advance in the refractory castable area shows a clear trend for using denser materials presenting good hot mechanical properties and high corrosion resistance. High-carbon-containing refractories castables (HCCC) are used in steel making processes including lining for blast furnace troughs. Adding carbon leads to attractive properties for the castable: (a) high refractoriness; (b) thermal shock resistance enhancement; (c) low wettability by molten slag and steel and (d) better thermal conductivity. These castables usually contain high alumina cement (GaO content in the range between 0.2 and 1 mass%), brown fused alumina with low TiO_2 content, 10-30 mass% of silicon carbide, microsilica, carbon sources and additives. Microsilica addition helps to control rheology during installation and can improve properties at high temperatures due to the formation of needlelike mullite grains. Silicon carbide enhances the castable resistance to blast furnace slag corrosion, but has a limited resistance to iron. Thus, its amount is optimized with respect to these constraints3'. Moreover, SiC is commonly used to increase the thermal conductivity and decrease the thermal expansion coefficient of high-alumina castables, enhancing their resistance to thermal shock failure. Carbon sources (pitch, cokes, carbon black, graphite, etc.), on the other hand, have a similar effect on these properties, as well as improving the castable work of fracture and inhibiting the metal and slag corrosion because of its low wetting features.