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

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.

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.