Plastic Grinding Media (sp.gr. 1.0 to 1.2)

Various alloys available (low carbon, high carbon, chrome steel, stainless steel, etc.) in a variety of forms:

Ball bearings Good wear, very round but will result in metallic contamination. Cost directly related to material and inversely proportional to size. 1/16″ to 6″.

Shot Irregular shapes with lumps and bumps, but only cost effective alternative for steel in sizes less than 1mm. Inexpensive, sizes from 90 microns to 3mm.

Other forms Steel wire can be cut and formed to produce diagonals, ballcones (looks like a flattened ice cream cone), pins (rods), oval balls and other shapes.

Alumina Grinding Media (sp.gr. 2.8 to 3.9)

Available in a range of specific gravities which rises as the alumina (Al2O3) content increases. The grinding media is actually alumina particles held in place by an SiO2 glass phase. Sizes from 400 microns to over 1 inch in beads, balls, satellites (ball with bands) and cylinders. Low to medium cost, small sizes are more costly.

Fused Zirconium oxide Grinding Media (sp.gr. 3.8) Smooth surface leads to low mill wear and longevity. Sizes from 200 microns to 2.5mm. Medium cost.

Sintered Zirconium silicate Grinding Media (sp.gr. 4.0-4.6) ZrO2 + SiO2 + Al2O3, with and without Y2O3 stabilizer. Tight size spreads from 200 microns to 2.6mm. Low to medium cost.

High density Zirconium oxide Grinding Media (sp.gr. 5.5) 95% ZrO2 + MgO stabilizer. Beads from 400 microns to 3.35mm. Cylinders and satellites to 1-1/4″. Medium cost.

Rare Earth stabilized Zirconium oxide Grinding Media (sp.gr. 5.8 to 6.1) ZrO2 + CeO. Yellow or black, very hard. Sizes from 400 microns to 2″. Medium cost.

Yttrium stabilized Zirconium oxide Grinding Media (sp.gr. 6.0) 95% ZrO2 + 5% Y2O3. Best wear properties of all grinding media, very round and very smooth, narrow size spreads. High cost is offset by low wear and minimal contamination.