GB610922A - Improvements relating to bonded abrasive bodies - Google Patents

Abstract

The grinding-elements of a ball mill are formed of hard sintered tungsten carbide bonded with cobalt or of a composition formed by finely dividing and intimately mixing, preferably in a wet condition, alumina and a clay such as bentonite with or without a flux such as fluorspar, drying, moulding under pressure with or without preliminary granulation, and sintering for several hours at a temperature of 1450-1700 DEG C. preferably about 1550 DEG C. (see Group V). Specification 575,753, [Group V] is referred to.ALSO:An abrasive body is obtained by mixing diamonds with a bonding medium formed of alumina intimately mixed with silica either alone or in the form of clay or other alumina-silica compound, the total amount of silica being 1 1/2 -10 per cent of the bonding mass, and sintering under heat and pressure. A flux such as fluorspar, not exceeding 10 per cent by weight of the bonding mass may be included. The diamonds may be incorporated only in the operative surfaces of the body, the remainder being constructed of another material. A mixture of alumina and bentonite, to which fluorspar may be added, is ground in a ball mill using balls of a hard alumina product or of tungsten carbide bonded with cobalt, in which case the product may contain up to 12 per cent of mixed tungsten carbide and cobalt. When grinding, which has preferably been effected wet, is complete, the mix is dried, preferably in a vacuum oven, mixed with diamond particles after previous pressing and granulation if desired, and sintered under heat and pressure in a graphite mould. A temperature of 1450-1700 DEG C., preferably about 1550 DEG C., and a pressure of 100-2000 lbs. per square inch are employed. Specification 575,753 is referred to.