Fused aluminum oxides show a value of 9 on the Mohs scale of hardness close to diamond (Mohs 10), the hardest known substance. Besides their superior hardness, the characteristics of fused aluminum oxides include sharp-edged grains, great load bearing capacity, a high degree of shock resistance and thermal and chemical stability.
Chemical & Physical Properties
Crystal Form
Alpha alumina trigonal system
Chemical nature
Amphoteric
Reaction with acids
Subject to mild attack by aqua and hydrofluoric acid
Reaction with Alkalies
Very slight with strong hot solution only
Oxidation-reduction effects
None
True Density(g/cm3)
3.97
Hardness
Knoop(kg/cm2)
2000-2200
Moh’s
9
Colour
Dark Brown
Colour after firing
Light blue
Melting point
2000°C
Max Usable temperature
1900°C
Specific heat (cal/g.°C)
0.26(20-29°C)
Coefficient of thermal conductivity
Room temperature
900°C
(cal/cm2.sec.°C)
0.047
0.013
Electrical resistivity (Wcm)
30°C
300°C
900°C
1600°C
1016
1013
105
104
Coefficient of linear expansion (x10-6)
7-9(0-1600°C)
Grit No.
Micron
Grit No.
Micron
Grit No.
Micron
10
2360 ~ 2000
30
710 ~ 600
80
212 ~ 180
12
2000 ~ 1700
36
600 ~ 500
90
180 ~ 150
14
1700 ~ 1400
40
500 ~ 425
100
150 ~ 125
16
1400 ~ 1180
46
425 ~ 355
120
125 ~ 106
20
1180 ~ 1000
54
355 ~ 300
150
106 ~ 75
22
1000 ~ 850
60
300 ~ 250
180
90 ~ 63
24
850 ~ 710
70
250 ~ 212
220
75 ~ 53
Available micron powder sizes
China GB 2477-83
JIS
FEPA(84) / DIN(70)
ISO(77)
Grit No.
Standard size range(µm)
Grit No.
ds50 value (µm)
Grit No.
ds50 value (µm)
Grit No.
ds50 value (µm)
Standard werte der Mikro-F-Reihe
Serigraph 5000D
240
60.0±4.0
P240
58.5±2.0
280
52.0±3.0
P280
52.2±2.0
W63
63 – 50
320
46.0±2.5
F230/53
53±3.0
50.0±3.0
P320
46.2±1.5
W50
50 – 40
360
40.0±2.0
F240/45
44.5±2.0
42.0±2.0
P360
40.5±1.5
400
34.0±2.0
P400
35.0±1.5
W40
40 – 28
500
28.0±2.0
F280/37
36.5±1.5
34.5±1.5
P500
30.2±1.5
600
24.0±1.5
F320/29
29.2±1.5
27.7±1.5
P600
25.8±1.0
W28
38 – 20
700
21.0±1.3
F360/23
22.8±1.5
21.6±1.5
P800
21.8±1.0
800
18.0±1.0
F400/17
17.3±1.0
16.5±1.0
P1000
18.3±1.0
W20
20 – 14
1000
15.5±1.0
F500/13
12.8±1.0
12.3±1.0
P1200
15.3±1.0
W14
14-10
1200
13.0±1.0
1500
10.5±1.0
F600/9
9.3±1.0
9.0±1.0
W10
10-7
2000
8.5±0.7
W7
7-5
2500
7.0±0.7
F800/7
6.5±1.0
6.3±1.0
W5
5 – 3.5
3000
5.7±0.5
F1000/5
4.5±0.8
4.5±0.8
F1200/3
3.1±0.5
3.1±0.5
for general purposes
for general purposes
for bonded abrasives
for coated abrasives
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