EFFECT OF Nb ON THE PROPERTIES OF A LARGE-SIZED GRINDING BALL

Grinding balls are widely used in the mining industry due to their favorable properties; however, poor hardenability of large-sized grinding balls is a limitation in wide applications. The hardenability and hardness of large-sized grinding balls can be affected by microalloying elements. In this work, Nb microalloying was used to improve the mechanical properties of large-sized grinding balls. The microstructures and mechanical properties of Nb-containing grinding balls were studied in contrast to the Nb-free steel. Typical microstructures were observed with OM and SEM, respectively. The hardness was obtained with a Rockwell hardness tester. The results show that the typical microstructure of a large-sized grinding ball was mainly martensite and that the fracture surface consisted of dimples of different sizes. The prior-austenite grain size (PAGS) was decreased from 31.5 mu m to 22.6 mu m by adding 0.04 % Nb with a refined microstructure.