Post on 23-Oct-2015
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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
C
l
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k
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r
W
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a
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a
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i
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m
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1
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10.9
W
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n
m
m
/
1
0
0
h
0.01
0.1
0.03
0.05
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
G
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Ha/Hm
F
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C
0 1 2 3 4 5 6 7 8 9 10
Mohsscale
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Ha/Hm
GRINDING BALLS WEAR ABRASION
G
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Ground product hardness scale / Mohsscale
W
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0.05
GRINDING BALLS WEAR ABRASION
C
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6 7Ground product hardness scale
W
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m
m
/
1
0
0
h
0.01
0.1
0.03
0.05
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