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
