Abstract
The Japanese Industrial Standards Committee recommends the Ball Mill Test for evaluation of abrasive grain toughness; but it may be the grindability rather than the toughness that is assessed by this method, i. e. the ability how finely to be crushed. The authors, from the viewpoint that the term toughness means the energy for fracture, measured the fracture energy of abrasive grains in a drop-hammer type friability test. Main results obtained are summarized as follows: (1) Fracture energy has no significant correlation to hammer speeds ranging from 0.3-1.1 m/s. (2) Fracture energy becomes very large because of repeated impacts on the abrasive grain when the clearance between platens of hammer and anvil is too small compared to the grain size. (3) Fracture energy is directly proportional to the third power of the mean diameter of abrasive grains. (4) Fracture energy of abrasive materials recommended for heavy grinding is extremely high, followed by conventional aluminium oxide and silicon carbide abrasives. (5) Roasting at 1 300°C is valuable for improving the toughness of aluminium oxide grains.
