Carbon sources for alumina–carbon functional refractories: an overview

Alumina (Al₂O₃)–carbon (C) refractories are widely used in the continuous-casting process of steel production, particularly in flow-control devices, because of their excellent thermal, thermomechanical and corrosion properties. These functional refractories in steel-casting operations are carbon-containing and carbon-bonded alumina refractories containing ∼30% residual carbon after coking. The main drawback associated is the oxidation of carbon at elevated temperatures, which leads to a loose and weak structure and deterioration of properties. Again, chances of ‘carbon pickup’ by steel during casting are also high due to the greater presence of carbon in refractories. Deep-decarburized-processed steel has the tendency to absorb carbon from contact refractory linings, which has an adverse impact on their properties. All of these concerns lead to a reduction in the carbon content of refractories. However, reducing the carbon content may deteriorate the comprehensive properties of refractories due to an increase in thermal stress associated with a decrease in the thermal conductivity and reduced non-wetting character. Thus, it is a global concern to reduce the carbon content of refractories without affecting much of their properties. This paper reviews scientific attempts to make low-carbon alumina–carbon-based functional refractories using different sources and their effect on the properties.