| 主权项 |
1. A coated abrasive grain comprising a fused base grain at least partially covered with a coating obtained from a colloidal suspension of silica, the coating being 100% hydrophilic silica by weight based on the weight of the coating, the base grain comprising more than 40% of alumina, as a percentage by weight based on the weight of the base grain; the coated grain having a size of greater than 45 μm, and the coated grain being obtained by a method comprising the following steps in succession:
1) obtaining or producing fused base grains comprising more than 40% of alumina, as a percentage by weight based on the weight of the base grain; 2) at least partially coating the base grains with a suspension containing hydrophilic silica to form base grains wetted by the suspension; 3) drying the base grains wetted by the suspension in order to form said coating on the base grains, the base grains not undergoing any intermediate steps between step 2) and step 3), the base grain having one of the following chemical analyses, as percentages by weight for a total of 100%:
Al2O3: 45-65%ZrO2+HfO2: 35-50%Others: 0-12%, or
Al2O3: 65-80%ZrO2+HfO2: 15-30%Others: 0-12.0%, or
Al2O3: 92.0-98.5%MgO: 1.5-6.5%Others: <2.0%. |
