Selecting Grinding Media For Mine Milling: Size, Material And Wear

Grinding balls become smaller with use as they repeatedly hit the ore and rub against each other. How long they last depends on the ore being processed and the conditions inside the mill. Operators add new balls as needed to replace those lost through wear.

Ball diameter should match the feed size and the required grinding fineness. Larger balls are generally used for coarse grinding, while smaller balls are more suited to finer material. Forged and rolled carbon steel balls and low-alloy steel balls are available in diameters from 20 mm to 125 mm. Cylpebs, a cylindrical form of grinding media, are also used in certain milling applications.

Forged and rolled balls are commonly used where the media must withstand repeated impact. High-chromium cast balls with 11%–26% chromium are used in cement grinding, dry milling and other applications involving heavy abrasion. If corrosion is also present, the operating environment should be considered when choosing the material grade.

The cost of grinding media is not limited to the initial purchase. Rapid wear means more frequent replenishment, while broken balls can add to media losses. Comparing media consumption per ton of ore with mill output helps show how well a particular size and material perform in actual operation.