SE317617B - - Google Patents

Abstract

The invention comprises abrasive grain formed of a plurality of sintered microcrystalline particles of bauxite, the grain being of elongated shape and controlled grit size and having a uniform cross-section and an average transverse to longitudinal dimensional ratio of less than 1:1. The grain is prepared by comminuting bauxite into microcrystalline particles, forming the comminuted material directly into grain, each grain being composed of many of said particles, and firing the grain until sintered. The invention also comprises a grinding wheel comprising said abrasive grain and a thermosetting resin bond therefor. The wheel is prepared by adding a thermosetting phenolic resin bond to said grain, and forming the grain and the bond into a wheel under pressure and heat.ALSO:The invention comprises abrasive grain formed of a plurality of sintered microcrystalline particles of bauxite, the grain being of elongated shape and controlled grit size and having a uniform cross-section and an average transverse to longitudinal dimensional ratio of less than 1:1. Preferably the bauxite particles are each not more than about 2.5 microns in size prior to sintering, and in the sintered grain are each not more than about 5 microns in size. The abrasive grain is prepared by comminuting bauxite into microcrystalline particles, forming the comminuted material directly into grain of uniform cross-section and controlled grit size with an average transverse to longitudinal dimensional ratio of less than 1:1, each grain being composed of many of said particles, and firing the grain until sintered. Sintering is preferably carried out at 1300 DEG C. to 1600 DEG C. The comminuted material may be mixed with a binder prior to forming it into grain, and the grain fired at 700 DEG C. to 1100 DEG C. in an oxidizing atmosphere until the binder is removed. The comminuted material is preferably formed into grain by extruding it into rods and severing the rods.