FRITSCH PULVERISETTE 5/4 classic line - Manual (Page 29)

6.1 Choice of grinding bowls and grinding balls
CAUTION!
If the grinding elements used are not genuine accessories,
we assume no guarantee and exclude all liability for
damage to the device or for personal injury.
The hardness and density (specific weight) of the grinding bowl and
grinding balls used must be greater than that of the material used to pre-
vent excessive wear by abrasion.
Material
(bowl and balls)
Main components of
the material
Density in g/cm 3
High density means
high impact energy!
Abrasion resistance Use for grinding
stock
Agate (99.9% SiO
2
) 2.65 Good Soft to medium-hard
samples
Silicon nitride (90% Si
3
N
4
) 3.25 Extremely good Abrasive samples,
metal-free grinding
Sintered corundum (99.7% Al
2
O
3
) 3.9 Fairly good Medium-hard,
fibrous samples
Zirconium oxide (96,2% ZrO
2
) 5.7 Very good Fibrous, abrasive
samples
Stainless steel Bowl:
(17-19% Cr + 8-10%
Ni)
Balls:
(12.5-14.5% Cr + 1%
Ni)
7.8 Fairly good Medium-hard, brittle
samples
Tempered steel Bowl: (11-12% Cr)
Balls: (1.0-1.65% Cr) 7.9 Good Hard, brittle samples
Tungsten carbide (93% WC+6% Co) 14.9 Very good Hard, abrasive sam-
ples
The grinding bowls and grinding balls made of zirconium oxide are
resistant to acids - apart from hydrofluoric acid.
Normally choose a grinding bowl and grinding balls that are made of the
same material.
Exception: Tungsten carbide balls (<20 mm) may be temporarily (a few
minutes) combined with grinding bowls made of tempered steel.
Using the device
- 29 -