Iryna Z. Increasing the uniformity of diamond grinding powders by strength and grain size through the selective choice of imperfect crystals by means of sieve, magnetic and electrical methods

The thesis is devoted to the study of increasing the uniformity by strength and grain size of diamond grinding powders produced with ferroalloys use through the selective choice of imperfect crystals by means of sieve, magnetic and electrical methods. It made possible to increase the uniformity by strength of diamond grinding powders up to by 1.6 times and the uniformity by grain size of the powders approximately in 2.0 times and results in uprating the working efficiency of crown drill bits fitted out with diamond grinding powders of higher uniformity in drilling hard rock. It was proved the first time that amplification of electrical properties (pА+e.p.) of diamond grains due to the adhesive bonding fine dispersed electroconductive metal particles on the diamond grain surface makes it possible to vary electrical resistance of the grains over the range 10^-7 ohm·m to 10^-3 ohm·m. This effect, by-turn, makes it possible to carry out the grain selection by strength and to increase the uniformity of powder by strength considerably. It ascertained that the additional sieve grading with R-20 sieves and selection of narrow classes of grain size of diamond result in increasing the main fraction of powders as well as grain size uniformity. Selection of fraction of 400/355 grain size led to increasing portion of main fraction of diamond powders of AC125 - AC65 grades, 400/315 grain size on 25-10 % and increases the uniformity by grain size of the powders. Industrial test showed that increasing of strength uniformity coefficient from 64 % to 76 % results in raising an average height of diamond protrusion in the matrix from 65 µm to 75 µm and lead to reduce the intensity of wear of crown drill bit more than 20 %.