Granular abrasive material

Claim 1

A method for producing granular abrasive material including the steps of: forming a dispersion of solid materials containing alumina, compounds containing silica, and other additives selected from compounds of the metals; silicon, zirconium, titanium, chromium, iron, magnesium, zinc, cobalt or nickel, in water and/or an organic compound, said dispersion containing sufficient alumina to provide a content of at least fifty-five weight percent alpha-aluminum oxide in the produced granular abrasive materials; grinding said solid materials of said dispersion until said solid materials of said dispersion are reduced to particles of which substantially all have a particle size of less than 0.1 micrometer to produce a sinterable slip; drying the ground dispersion of said solid material; and subjecting said dried dispersion to at least a two stage heat treatment including a first stage wherein said dried dispersion is preheated to between 250° and 600° C. for the expulsion of chemically bound water and/or organic compounds, and a subsequent stage wherein said preheated dried dispersion is heated to between 1400° and 1700° C. to sinter it to a density of more than eighty-five percent of the theoretical density of corundum such as to produce said granular abrasive material comprising both alpha-aluminum oxide and a silicate material and wherein the diameters of the crystals of said alpha-aluminum oxide are less than one micrometer.

Claim 2

A method for producing granular abrasive material including the steps of: forming a dispersion of solid materials containing alumina, compounds containing silica, and other additives selected from compounds of the metals; silicon, zirconium, titanium, chromium, iron, magnesium, zinc, cobalt or nickel, in water and/or an organic compound, said dispersion containing sufficient alumina to provide a content of at least fifty-five weight percent alpha-aluminum oxide in the produced granular abrasive materials; grinding said solid materials of said dispersion until said solid materials of said dispersion are reduced to particles of which substantially all have a particle size of less than 0.1 micrometer to produce a sinterable slip; drying the ground dispersion of said solid material; and subjecting said dried dispersion to at least a two stage heat treatment including a first stage wherein said dried dispersion is preheated to between 250° and 600° C. for the expulsion of chemically bound water and/or organic compounds, and a subsequent stage wherein said preheated dried dispersion is heated to between 1400° and 1700° C. to sinter it to a density of more than eighty-five percent of the theoretical density of corundum such as to produce said granular abrasive material comprising both alpha-aluminum oxide and a silicate material and wherein the diameters of the crystals of said alpha-aluminum oxide are less than one micrometer.