GB868734A - Casting hollow ingots of non-ferrous metals - Google Patents

Abstract

868,734. Cores. ALUMINUM CO. OF AMERICA. Aug. 5, 1958 [Aug. 16, 1957], No. 25023/58. Class 83 (1). Hollow ingots of non-ferrous metals melting below 2000‹ F. except the alkali, alkaline earth, rare earth or radioactive metals, are cast in a liquid-cooled mould with a permeable, gypsum plaster core. The core acts as a heat insulator and substantially all the heat is removed through the mould or outer surface of the ingot beneath the mould, or the interior wall of the casting is smooth and free from defects. The core may be solid or comprise a plaster coating on a perforated tubular metal or plastic support. In a continuous casting process the core is inserted in sections 34, 36, which may be threaded on a steel rod, guided by adjustable arms 14 and initially located on a protuberance 32 on the movable mould bottom 30 and weighted by a weight 20. The metal is poured from a trough 6 having outlets controlled by valves 8. In an ingot mould, Fig. 4, the core is held by a pivoted weight 50. Mould and core materials.-The core material may be all gypsum plaster, but up to 1% of additives such as sodium-, sulphate-, chloride-, citrate and citric acid may be added to accelerate or retard setting. Up to 50% by volume of fillers such as talc, asbestos, glass fibre and sand may also be added. For magnesium &c. casting oxygen inhibitors such as sulphur, boric acid, alkali metal borofluorides or silicofluorides, 0.5-5% by weight may be added, together with a small amount of urea formaldehyde to suppress efflorescence of the water-soluble inhibitors. The permeable properties of the plaster are imparted by the known processes of recrystallization and rehydration, or aeration of a slurry of the semi-hydrate and water and foaming agents. Extracting cores.-The core may be cut out by mechanical means or washed out by a jet of water or compressed air or both, before or after thermal treatment of the casting. Specification 696,169 is referred to.