Porous abrasive articles with agglomerated abrasives and method for making the agglomerated abrasives

A vitrified bonded abrasive tool, having a structure permeable to fluid flow, the tool comprising:

• a) about 5-75 volume % sintered agglomerates of a plurality of abrasive grain with a binding material, the binding material being characterized by a viscosity A at the binding material melting temperature;
• b) a vitrified bond characterized by a viscosity B at the binding material melting temperature, viscosity B being at least 33% lower than viscosity A;
• and
• c) about 35-80 volume % porosity, including at least 30 volume % interconnected porosity.

A vitrified bonded abrasive tool, having a structure permeable to fluid flow, the tool comprising:

• a) about 5-60 volume % sintered agglomerates of a plurality of abrasive grain with a binding material, the binding material being characterized by a melting temperature A;
• b) a vitrified bond characterized by a melting temperature B, melting temperature B being at least 150° C. lower than melting temperature A;
• and
• c) about 35-80 volume % porosity, including at least 30 volume % interconnected porosity.

A bonded abrasive tool, having a structure permeable to fluid flow, the tool comprising:

• a) about 34-56 volume % abrasive grain;
• b) about 3-25 volume % bond;
• and
• c) about 35-80 volume % total porosity, including at least 30 volume % interconnected porosity;
• wherein the interconnected porosity has been created without the addition of porosity inducing media and without the addition of elongated shaped materials having a length to cross-sectional width aspect ratio of at least 5:1.

An abrasive tool comprising 5 to 75 volume % abrasive grain agglomerates, made by a method comprising the steps:

• a) feeding abrasive grain and a binding material, selected from the group consisting essentially of vitrified bond materials, vitrified materials, ceramic materials, inorganic binders, organic binders and combinations thereof, into a rotary calcination kiln at a controlled feed rate;
• b) rotating the kiln at a controlled speed;
• c) heating the mixture at a heating rate determined by the feed rate and the speed of the kiln to temperatures from about 145 to 1,300° C.,
• d) tumbling the mixture in the kiln until the binding material adheres to the grain and a plurality of grains adhere together to create a plurality of sintered agglomerates;
• e) recovering the sintered agglomerates from the kiln, the sintered agglomerates consisting of a plurality of abrasive grains bonded together by the binding material and having an initial three-dimensional shape and a loose packing density of ≦1.6 g/cc;
• f) molding the sintered agglomerates into a shaped composite body;
• and
• g) thermally treating the shaped composite body to form the abrasive tool.

A method of grinding, comprising the steps of:

• a) providing a bonded abrasive tool, having a structure permeable to fluid flow, the tool comprising:
• 1) 5 to 75 volume % sintered agglomerates comprising a plurality of abrasive grains held with a binder material, the binder material being characterized by a melting temperature between 500 and 1400° C., and the sintered agglomerates having a three dimensional shape and having an initial size distribution prior to manufacture of the tool;
• 2) a bond;
• and
• 3) about 35-80 volume % total porosity, including at least 30 volume % interconnected porosity;
• wherein at least 50%, by weight, of the sintered agglomerates within the bonded abrasive tool retain a plurality of abrasive grains held in a three-dimensional shape after manufacture of the tool;
• b) bringing the bonded abrasive tool into contact with a workpiece;
• and
• c) abrading the surface of the workpiece with the bonded abrasive tool.

A method of grinding, comprising the steps of:

• a) providing a bonded abrasive tool, having a structure permeable to fluid flow, the tool comprising:
• 1) about 34-56 volume % abrasive grain;
• 2) about 3-25 volume % bond;
• and
• 3) about 35-80 volume % total porosity, including at least 30 volume % interconnected porosity;
• wherein the interconnected porosity has been created without the addition of porosity inducing filler material and without the addition of elongated shaped materials having an aspect ratio of at least 5:1;
• b) bringing the bonded abrasive tool into contact with a workpiece;
• and
• c) abrading the surface of the workpiece with the bonded abrasive tool.

A method of agglomerating abrasive grain, comprising the steps:

• a) feeding the grain and a binding material, selected from the group consisting essentially of vitrified bond materials, vitrified materials, ceramic materials, inorganic binders, organic binders, water, solvent and combinations thereof, into a rotary calcination kiln at a controlled feed rate;
• b) rotating the kiln at a controlled speed;
• c) heating the mixture at a heating rate determined by the feed rate and the speed of the kiln to temperatures from about 145 to 1,300° C.,
• d) tumbling the grain and the binding material in the kiln until the binding material adheres to the grain and a plurality of grains adhere together to create a plurality of sintered agglomerates;
• and
• e) recovering the sintered agglomerates from the kiln, whereby the sintered agglomerates have an initial three-dimensional shape, a loose packing density of ≦1.6 g/cc and comprise a plurality of abrasive grains.

Sintered agglomerates of abrasive grain, made by a method comprising the steps:

• a) feeding abrasive grain with a binding material into a rotary calcination kiln at a controlled feed rate;
• b) rotating the kiln at a controlled speed;
• c) heating the mixture at a heating rate determined by the feed rate and the speed of the kiln to temperatures from about 145 to 1,300° C.,
• d) tumbling the grain and the binding material in the kiln until the binding material adheres to the grain and a plurality of grains adhere together to create a plurality of sintered agglomerates;
• and
• e) recovering the sintered agglomerates from the kiln, whereby the sintered agglomerates have an initial three-dimensional shape, a loose packing density of ≦1.6 g/cc and contain a plurality of abrasive grains.