Quality Control and Hardness Measurement
In the long term, the effectiveness of grinding media must be measured by the final cost per tonne of product efficiently ground.
The Steel Ball Company’s advanced manufacturing methods and materials guarantee the maintenance of the geometrical tolerances and correct structures vital to reliable, consistent performance and long life. The Steel Ball Company’s products are rigorously tested to ensure that they meet the agreed specifications.
BALL HARDNESS: ‘THRU HARD’ OR ‘TOUGH CORE’
The Steel Ball Company’s expertise will ensure that you specify the most suitable grinding media for your particular application. The Steel Ball Company’s ‘thru hard’ ball has a uniform high hardness from surface to core, thus maintaining very good wear properties down to very small diameters.
The ‘tough core’ ball has a hard outer layer for long life, coupled with a tough, resilient core giving good impact resistance.
Presenting the Hard Facts on Average Volumetric Hardness
How hard is hard? The illustrations shown below tell an interesting story. Illustration ‘A’ shows an analysis of the cross sectional hardness of The Steel Ball Company’s ‘thru hard’ ball. Illustration ‘B’ below shows the same analysis carried out on a ball from another major grinding media manufacturer. The ball in illustration ‘B’ has the same AVH figure as The Steel Ball Company’s ball and will wear out at the same time. Yet there the similarity ends. After three quarters of the radius, the hardness of the ‘B’ ball dips below that of The Steel Ball Company’s ball. This brings into focus the area of greatest discussion about using AVH values. Over 72% of the final value is made up from the surface and 3/4 radius hardness readings. So AVH tells us relatively little about how a ball is going to perform once it has worn past that stage. The cross sectional hardness profile tells the full ‘inside story’.
Q What kind of performance will the ball in illustration ‘B’ below give?
A Once the ball has worn down to approximately 2/3 diameter, the remainder will wear away very quickly.
Q How will this affect the mill output?
A The rapidly wearing grinding media will give rise to an unstable and imbalanced ball charge, resulting in the possibility of more than one top up size being required to ensure the correct mesh of grind.
Q How will The Steel Ball Company’s ball perform?
A The cross sectional hardness profile shows that The Steel Ball Company’s ‘thru hard’ ball will wear evenly throughout its life. This will give a better size distribution in the mill, and avoid ‘dead zone grinding’. The shape of the ball will be preserved for much longer, giving a far more efficient grind.
AVH = 0.289 x Surface Hardness (S) + 0.437 x Hardness 3⁄4 R + 0.203
Hardness 1⁄2 R + 0.063 x Hardness 1⁄4 R + 0.008 x Centre Hardness (C)
The conclusions are obvious. High quality such as The Steel Ball Company offers always saves money in the long run.
Hardness Conversion Table
|Brinell Hardness Number||10mm Ball. 3000 kg Load|
|Rockwell C Scale Hardness Number||Standard Ball||Tungsten Carbide Ball||Vickers Hardness Number|