Introduction

Some figures to introduce the subject

Successively for coarse and fine grinding

How grinding balls are wearing How grinding balls are wearing

Parameters to take into account concerning the impacts

Deformation of grinding balls

Grinding balls of tomorrow

Several words about metallurgy

Quality criteria of grinding balls

(Generations of grinding balls)

Maintenance of grinding ball charges

Diameter Weigth Surface Nbr balls Specific surface

(mm) (inch) (gr) (cm2) per mt m

2/mt

90 31/2"

2,916.841 254.469 342.837 8.724

80 2,048.590 201.062 488.141 9.815

77 3" 1,826.658 186.265 547.448 10.197

70 1,372.396 153.938 728.653 11.217

64 21/2" 1,048.878 128.680 953.400 12.268

60 864.249 113.097 1,157.074 13.086

Figures

60 864.249 113.097 1,157.074 13.086

50 2" 500.144 78.540 1,999.424 15.703

40 256.074 50.265 3,905.121 19.629

38 11/2" 219.551 45.365 4,554.750 20.662

35 171.549 38.485 5,829.238 22.434

31.75 11/4" 128.061 31.669 7,808.779 24.730

30 108.031 28.274 9,256.602 26.172

25 1" 62.518 19.635 15,995.393 31.407

23 48.682 16.619 20,541.473 34.138

22.22 7/8" 43.895 15.511 22,781.638 35.336

20 3/4" 32.009 12.566 31,241.213 39.259

17 5/8" 19.658 9.079 50,869.875 46.186

15 13.504 7.069 74,052.133 52.344

The composition of the ball charges

plays a major role in the

grinding energy consumption:

particle size distribution of the feed

Figures

particle size distribution of the feed

hardness of the feed

other factors like motion of the charge

% of moisture

% of slag, pozzolana, ...

open/closed circuit

grinding media consumption

Costs related to grinding media

Figures

energy consumption

grinding media charges removing and sorting

Figures

Characteristics and quality of the media :

excellent wear resistance

adapted impact resistance

excellent resistance to deformation

manufacturing quality irreproachable and constant

BALL CHARGES

FOR

COARSECOARSE

GRINDING CHAMBERS

Reduction

from feed size between 0 and 5 to 100 mm

down to product size 100 % < 1 to 2 mm

Ball diameter

Working conditions

110 mm - 50 mm

Medium to high abrasivity

Medium to high impact level

NORMAL

1. Abrasion of ground material

2. Friction between balls

3. Fatigue due to repeated impacts

Wear factors

3. Fatigue due to repeated impacts

4. Dry corrosion

5. DeformationABNORMAL

6. Excessive work hardening

7. Internal foundry defects

3. Fatigue due to repeated impacts

causes

Wear

factors

causes

MICRO-CHIPPING

slight chipping at the surface

of the grinding media due to

the hardness of the material

GRINDING BALLS WEAR

ABRASION + CHIPPING

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Violence of impacts

6. Excessive work hardening

causes

Wear

factors

causes

SCALING

chipping on an important depth

at the surface of the balls leading

to the destruction of the balls

1. Abrasion of material to be ground

2. Friction between balls

3. Dry corrosion

4. Fatigue due to repeated impacts

Wear

factors

martensitic

matrix Chromium

carbides

High Cr cast iron grinding ball

unstable

phase

Hardness of

ground material

Hardness of

balls

Grinding balls wear Abrasion

ground material

high wear of balls

balls>

Mohs Scale Other

minerals

Knoop

Hardness

(+Shore)

Vickers

Hardness

(HV)

Metallic structures Rc

Hardness

HB

(3T30)

1 Talc Coal 20

35

2 Gypsum 40 36

124 110 110

3 Calcite 136 140 200

216 (32) 200

4 Fluorite 175 190 (11)

235 70-200 Ferrite (13)

305 170-230 Austenite (12%Mn) (5-18)

300-460 Pearlite (alloyed) 30-45

(58) 318 301

423 43 400

5 Apatite 435 440 44

300-600 Austenite (Cr. 30-55

Glas 455 cast iron) 48

Hardness scales

related to the

Mohsscale

Glas 455 cast iron) 48

~ 550 (72) 544 51 500

6 Orthoclase Clinker 620 640 600

(84) 740 60

500-800 500-1010 Martensite fx(C) (48)65

Silex 820 950

(98) 1020 68 (712)

7 Quartz Fondu ~ 840

1025 Fe3C

8 Topaz Grenat 1330 1430

1735 1200-1600 (FeCr)7C3

1800 1500 Mo2C

9 Corundum 2020 1800

1500-2000 (FeCr)23C6

1800 2400 WC

2800 3700 B4C/NbC

10 Diamond 7575 10000

WEAR as a relation of the ratio existing between the hardness

of the ABRASIVE (material to be ground) and

the WEAR RESISTING MATERIAL

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Mohsscale

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Ha/Hm

GRINDING BALLS WEAR ABRASION

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Ground product hardness scale / Mohsscale

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GRINDING BALLS WEAR ABRASION

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6 7Ground product hardness scale

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90 mm

~ 3000 gr

Impacts

According to

the volume of

the ball

30 mm~ 3000 gr

~ 100 gr

IMPACT energy of a ball

according to its diameter and the diameter of the mill

15.00

20.00

25.00

dia 110 mm

dia 100 mm

dia 90 mm

dia 80 mm

Impacts

0.00

5.00

10.00

1 2 3 4 5 6

Mill diameter

k

g

m

dia 77 mm

dia 70 mm

dia 64 mm

dia 60 mm

dia 50 mm

dia 40 mm

MARTENSISTIC

MATRIX

CHROMIUM

WHAT IS A PROPER

GRINDING BALL ?martensitic

matrixChromium

carbides

Quality

CHROMIUM

CARBIDES

AUSTENITE

a PERFECT

SOUNDNESS austenite

Metallurgy

Depth of penetration of the

deformation according to the

impact force

Metallurgy

Depending of the force

yield deformation

plastic deformation

TENSILE

strength

neutral fiber

Metallurgy

strength

Importance of tensile - compression

stresses induced by impacts according

to the quantity of residual austenite

after quenching

Metallurgy

LESS MORE

High hardness throughoutmartensitic matrix

Cr carbides

Low potential of work-hardeningcontrolled low quantity of

CHARACTERISTICS OF THE

MAGOTTEAUX GRINDING BALLS

FOR COARSE MILLING

martensitic

matrixChromium

carbides

controlled low quantity of

unstable metallurgical phase

Identical and homogeneous

metallurgical characteristics

for all the specimens

Regular shape

Perfect physical soundness unstablephase

High hardness throughout

Low potential of

work-hardening

martensitic

matrixChromium

carbides

unstable

phase

Same hardness and same

homogeneous metallurgical

structure are obtained

Identical and homogeneous

metallurgical characteristics

for all the specimens

martensitic

matrixChromium

carbides

structure are obtained

thanks to :

precise

chemical composition

oil quenching

additional heat treatment

clean manufacturing conditionsunstable

phase

BALL CHARGES

FOR

FINISHINGFINISHING

GRINDING CHAMBERS

Reduction

from feed size 60% > 90 microns

down to product size 10 - 20 % > 90 microns (C.C.)

5 % > 90 microns (O.C.)

Ball diameter

Working conditions

5 % > 90 microns (O.C.)

60 mm - 15 mm

Generally smooth conditions

No strong lifting effect

Limited impacts

1. Abrasion of the material to be ground

Wearing factors

1. Abrasion of the material to be ground

2. Friction of ball against ball

3. Deformation

CHARACTERISTICS OF THE

MAGOTTEAUX GRINDING BALLS

FOR FINE MILLING

High hardness throughoutmartensitic matrix

Cr carbides

Controlled potential of work-hardeningcontrolled low quantity of

martensitic

matrixChromium

carbides

controlled low quantity of

unstable metallurgical phase

Identical and homogeneous

metallurgical characteristics

for all the specimens

Perfect physical soundness

Regular shape unstablephase

Same hardness and same

homogeneous metallurgical

structure are obtained

Identical and homogeneous

metallurgical characteristics

for all the specimens

martensitic

matrixChromium

carbides

thanks to :

precise

chemical composition

high carbon content

oil quenching

clean manufacturing conditions unstablephase

High hardness throughout

Controlled potential of

work-hardeningmartensitic

matrixChromium

carbides

unstable

phase

Molding in cluster

Metallurgy

Sketch of a mould

filled up with

liquid metal

Metallurgy

Shrinkage

after

solidification

Metallurgy

Magotteaux yearly produces more than

200.000 Tons of Grinding Media

Magotteaux production

of which 65.000 tons for the cement

industry in 10 factories Worldwide

All these grinding balls are produced

according to the same

Magotteaux production

manufacturing procedure

quality control standards

securing a same high level of constant

quality

Besides the activity of

producing excellent grinding balls,

Magotteaux also offers the

Magotteaux production

services of Process Engineers

Magotteaux has a permanent

program of research for new more

cost effective grinding ball materials

Quality Insurance

C

Gas holes,

sand and slag holes,

cracks,

appearing on surface, or after light fettling

Above big shrinkage

which caused breakage

Destructive and

non destructive

visual examination

Quality

Hereunder little shrinkage

appearing after cutting and grinding.

YSphericity

check up

Quality

X Y

Swelling

phenomenon

Quality

real

And tomorrow ...

GRINDING MEDIA

cost

waste ENERGY

cost