Electrocorundum normal (13A, 14A, 15A)

Normal (grades: 16a, 15a, 14a, 13a, containing (93-96)% Al2O3 and smelted with reduction of bauxite).Due to the high content of aluminum oxides and a small number of impurities in corundum, its crystals are larger. It has increased the viscosity, therefore used in the manufacture of abrasive tools for grinding of viscous materials with a high tensile strength, for abrasive machining with variable loads, as well as for heavy grinding and sanding work sanding.Depending on the amount and composition of the impurities, color of electrocorundum changes (from light to dark brown in color). Sizes of smelted corundum crystals are (0.6-0.8) mm. For example, for making grinding discs ones use a normal polycrystalline electrocorundum crystals with dimensions of about 50 microns.