The company “Energosteel” produced an experimental batch (110 tn) the 40mm grinding balls of high carbon steel alloyed by Chromium in January 2017. The batch showed highest hardness values throughout cross section of grinding ball with a surface hardness 65-69HRC and volumetric hardness – 64-66 HRC. Thus, these products comply with the fifth group of hardness (according to both DSTU 3499-97 and DSTU 8538: 2015).
Grinding balls have been successfully tested for the impact resistance. 100 balls have been selected from a batch for the experiment. Each selected ball sustained the total impact energy of 64 312 J without destruction.
At hardness check of batch grinding balls we have faced with the problem of surface preparation for measurement. Polishing surface by fine-grained stone with coolant even with a minimum machine infeed gave a “tan” on the surface and polishing micro-cracks which distort hardness result of grinding balls to 3-5 HRC measured on a stationary hardness tester. The problem was solved by ultrasonic hardness tester T-UD2 for measuring hardness. Using a suitable method, we achieved increase measurement accuracy, increase productivity control and ensure a high results reliability.