On some problems of producing grinding media by cross wedge rolling combined with upsetting

Balls for ball mills can be produced by die forging, rolling and casting methods. The rolling of balls can be realized as skew or cross rolling. This paper describes a new method for producing balls by cross wedge rolling combined with upsetting. Special emphasis is put on failure modes occurring in this process. Typical defects in balls produced by the new technique are described. Causes of these defects are discussed, and methods for their prevention are proposed. Both overfill and underfill are analyzed. Emphasis is put on ball surface defects such as scratches and sharp edges, and the problem of internal cracking in balls is discussed. The problem of correct separation of balls is examined. Effects of the rolling temperature on the rolling process and quenching of balls are investigated. Finally, abrasive wear of tools in the cross wedge rolling of balls is described.