GB1099095A - Abrasives - Google Patents

Abstract

An abrasive article e.g. a grinding wheel, comprising cubic crystal structure silicon carbide grains, predominantly of hexagonal shape, the grains being coated with a thin layer of bonding material with spaced areas of the coating of adjacent grains merged and bonded together to provide a strong porous abrasive article. The grains can be coated with a layer of thermosetting resin e.g. phenolformaldehyde of 1 to 2 mils thickness. A vitreous bonding agent can also be used.ALSO:Cubic crystal structure silicon carbide grains predominately of hexagonal shape are made by heating equimolar mixtures of silicon and carbon in a non-oxidizing atmosphere to a temperature of from 1300 DEG to 2175 DEG C. until the reaction between the silicon and carbon to produce silicon carbide is complete. The silicon carbide at a temperature above 1300 DEG C. is then cooled to 1300 DEG C. at a rate not exceeding 100 DEG C. drop in temperature per minute. In a preferred embodiment a silicon and graphite mixture is heated in a non-oxidizing atmosphere to a temperature of 1800 DEG to 2175 DEG C. over a period of at least 15 minutes, and held at this temperature for at least 10 minute until the silicon and carbon have completely reacted, and then cooled to 1300 DEG C. over a period of at least 10 minutes. The silicon carbide grains are coated with a thin layer of thermosetting resin, e.g. phenolformaldehyde, with spaced areas of the coating of adjacent grains being merged and bonded together to provide a strong porous abrasive article. A vitreous bonding agent may be used.