GB745668A - Improvements in and relating to the casting of metals - Google Patents

Abstract

An exothermic material for use in the casting of metals, contains aluminium, a metallic oxide, e.g. iron or manganese oxide, capable of reduction by the aluminium, a powerful oxidising agent and a fluoride, and is characterised by the inclusion of the fluoride salt in proportion not exceeding 0,75 per cent by weight of the material and also not exceeding 3-75 per cent of the aluminium content of the material. The content of the powerful oxidising agent in the material is preferably 0-5-12 per cent and consists of e.g. sodium chlorate and/or nitrate, neither in excess of 10 per cent thereof. A binder, e.g. colloidal clay such as bentonite, and/or refractory, such as silica sand or fire-brick, may be added to the exothermic material if it is to be used for producing mouldable shapes such as riser sleeves. The material may be used in the casting of steel, cast iron and nonferrous alloys as long as an ignition temperature of less than 600 DEG C. is not required. The following composition is given by way of example: aluminium powder 20-55 per cent, metallic oxide 5-55 per cent, powerful oxidising agent 0,5-12 per cent, fluoride salt, e.g. fluorspan, cryolite, sodium or potassium fluoride, 0,1-0,75 per cent, binder 3-6 per cent, refractory remainder.