Mechanisms of corrosive wear of steel balls in grinding hematite ore

Abstract

Much work has. been done on wear of grinding media in ball mills; however, infornlation available is mostly related to abrasive wear, and data concerning corrosive wear are rather limited. Norman and Loeb (1) conducted wear tests on grinding balls. They found that during wet grinding of ore, steel balls showed an increase in rate of wear when the mill atmosphere was changed from air to pure oxygen. When the mill was operated in air atmosphere with pulp that had been Inade alkaline, a reduction in rate of wear was obtained. They reported that this variation in wear rate was due to the influence of an oxide film. Bond (2) attributed the increase in wear when changing from dry to wet grinding to dissolution of iron from active metal surfaces produced in grinding. Sobering and Carlson (3) also found that by converting from wet grinding to dry grinding of hematite ore at their Wabush Mines Plant, ball consumption was reduced by as much as 60% by avoiding the corrosive wear during wet grinding. In a similar manner, Bombled (4) concluded from his wear mechanism studies that the total wear of grinding media in ball mills is equal to the sum of surface abrasion, mass impact and corrosion by oxygen and moisture. By a different approach, Hoey (5) demonstrated the important role played by corrosive wear in the total wear of steel balls during wet grinding of ores in laboratory ball mills. Corrosion inhibitors were used in sulphide ore and iron ore slurries, and corrosive wear was reduced significantly. The role of corrosive wear in the total wear of steel balls was recognized both in the plant and in the laboratory; however, the corrosive wear mechanism has not been investigated. In this paper, ~. mechanism of corrosive wear of steel balls during wet grinding of hematite ore and an extrapolation method for the estin1ation of corrosive wear are presente~J