Fused cast corundum series can be divided into three groups according to differing alumina crystal forms and quantities: α corundum block with the main crystal phase of α-Al2O3; α-β corundum block with the main crystal phases of α-Al2O3 and β-Al2O3 (with their ratio being 1:1 and the α phase slightly higher); β corundum block with the main crystal phase of β-Al2O3. Fused cast corundum products are made by melting alumina in an arc furnace and casting into designed moulds, then annealing and insulating, and finally processing with diamond abrasive tools.