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
x
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
68 940
67 900
66 865
65 739 832
64 722 800
63 705 772
62 688 746
61 670 720
60 654 697
59 634 674
58 615 653
57 595 633
56 577 613
55 560 595
54 543 577
53 525 560
52 500 515 544
51 487 496 528
50 475 481 513
49 464 469 498
48 451 455 484
47 442 443 471
46 432 432 458
45 421 421 446
44 409 409 434
43 400 400 423
42 390 390 412
41 381 381 402
40 371 371 392
39 362 362 382
38 353 353 372
37 344 344 363
36 336 336 354
35 327 327 345
34 319 319 336
33 311 311 327
32 301 301 318
31 294 294 310
30 286 286 302
29 279 279 294
28 271 271 286
27 264 264 279
26 258 258 272
25 253 253 266