Fused Refractories

materials that are produced by casting molten refractories in molds or by sawing apart cast blocks. Fused refractories also include various powders of different particle size that are produced by the crushing and particle-size reduction of solidified melts. The refractory charges are usually fused in arc furnaces, although sometimes induction, oxygen-gas, or plasma furnaces are used. The melt is cast in sand, graphite, or cast-iron molds. Refractories are classified by composition, for example, baddeleyite-corundum, corundum, and mullite-zirconia.

Cast fused refractories have an apparent porosity of 1–3 percent; a compression strength of 400–700 meganewtons/m², or 4,000–7,000 kilograms-force/cm²; and a high heat of deformation. They are quite stable against aggressive melts, but their thermal stability is usually not very high. Cast fused refractories are used in glass-fusion and heating furnaces and in the most vulnerable sections of open-hearth furnace linings and of oxygen-Bessemer converter linings. Powdered fused refractories are used to make critical parts and as fillers in linings of many furnaces, including induction furnaces.