IMPROVEMENTS IN OR RELATING TO ZIRCONIUM CORUNDUM

1,209,515. Zirconium corundum. DYNAMIT NOBEL A.G. 4 Sept., 1968 [5 Sept., 1967], No. 42098/68. Heading C1J. A substantially eutectic mixture of zirconium dioxide and of bauxite having a silicon dioxide content of not more than 5 wt. per cent is shaped and sintered either in a reducing atmosphere at 1250-1500‹ C. or in an oxidizing atmosphere at 1400-1600‹ C. At least 70% of the zirconium dioxide and at least 70% of the aluminium oxide have grain sizes below 5 Á and the mixture contains 56 to 60 parts by weight of aluminium oxide per 44 to 40 parts of zirconium dioxide. The mixture can also contain 4-5% CaO, 6-7% MgO or 8-9% YtO 2 , based upon the weight of zirconium dioxide plus the weight of aluminium oxide, as a stabilizer, and organic binders. The shapes made are bricks which are crushed to provide abrasive granules, pebble shapes suitable for blasting and grinding balls, and extruded shapes, such as tubes, thread guides and drawing dies for wires.