Samples (365e720 g) were ground under different experimental
conditions in a laboratory ball mill (drum mill) with 6e18 kg ball
(mixing of 0.5, 0.75 and 1 inch ball in diameter with equal weights)
at grinding time,10e15 min and rotation speed, 70e80 rpm such as
70% of particles were less than 75 mmin diameter. The ball mill used
was included a stainless steel pipe with 21 cm of diameter and
length of 30 cm with a wall thickness of 0.7 cm.
In determining the ball mass losses through total wear, 15 steel
balls were handpicked and marked and then before and after each
grinding experiment were weighted to calculate the ball losses.
Then, the wear rate in mils penetration per year (mpy) was calculated
according to using the following formula.