EVALUATION OF WEAR AND IMPACT PROPERTIES OF GRINDING BALLS USED IN SARCHESHMEH COPPER PLANT

Ball mills are used in the last stage ofore processing for grinding raw materials. forged70cr2 alloy steel and austempered ductile iron (adi) balls are materials from which grindingballs are made for sarcheshm eh copper plant (scp) ball mills. in the present study wear andimpact properties of these two kinds of balls have been investigated. some balls randomly wereselected as samples. they were cut to investigate the cross section under optical and scanningelectron microscopes. the microstructure of the sample balls was studied and quantitativemeasurements ofmicrostructural f eatures were performed. the hardness ofdifferent parts ofcrosssections of balls was measured. the wear resistance of the balls was measured by pin on discmethod. repeated dropt test was employed to evaluate impact resistance of the balls. themicrostructure of adi balls consisted of bianitic matrix with graphite nodules and some retainedaustenite and martensite. micro cracks and porosities in the cast structure were frequentlyobserved. in the case offorged steel balls the microstructure composed oftempered martensite inouter area and bianitic structure with some tempered martensite in central areas. the wear andimpact resistance of forged steel balls were markedly higher than those of adi balls. thedifference was consistent with the differences between the microstructures ofthe two kinds of balls.cast structure with microcracks and shrinkage porosities in adi balls gives rise to lower impactresistanc e.