Alumina (Al203) is neutral in nature. Among the three lining materials, it has the highest negative free energy of formation. Hence it is the most stable oxide. Alumina refractories are produced form bauxite. These are produced to different levels of purity – form 80% Al203. Different grades are used on the basis of maximum operational temperature during melting.
The commonly used binders are either silica (for use with acidic slags) or magnesia (for use with basis slag). Additional binders may be added to promote sintering at a lower temperature. The size grading is somewhat coarser to that of silica ramming mass.
Advantage: Alumina has high refractoriness, and is more inert to many metal-slag reactions.
Limitations: Its thermal shock resistance is somewhat poorer than that of silica. It is relatively very costly.