slag

Grinding sound use to be quite smooth. Crushing jaws made of hardmetal tungsten carbide does not seem to be necessary for grinding.

Within 60s, all sample has been ground. Few particles with a length up to 10 mm can be found afterwards. Majority of sample seems to be ground to < 6mm and finer.

A grinding of higher amounts is still plausible.

After pre grinding in result 1, sample can be fed to the grinding set of Vibration Cup Mill PULVERISETTE 9. About maximum 500g of sample might fit into the 250ml grinding set. After 1 minute of grinding, all sample has been ground to < 1mm. After 5 minutes, a small portion has been taken out to determine the fineness by sieving with Vibratory Sieve Shaker ANALYSETTE 3. We already found 61,6% < 63µm.

After 10 minutes, a further aliquot has been taken out and sieved. We found 77,8% < 63µm. After 15 minutes of dry grinding, already 87,3% of sample is able passing a 63µm mesh test sieve.

After totally 30 minutes of grinding, we reached 98,4% < 63µm. No sample is sticking to puck or ring, even longer grinding times can be set to improve the fineness. Because the grinding set will become constantly hotter, we reached about 65°C; even with several breaks for sieving.

To improve speed of grinding, a separation of desired fraction by sieving or sifting (classifying) and only proceed grinding the coarse fraction is possible.

Probably a batch wise grinding of smaller amounts (e.g. 250g) might be plausible as well (see result 3).

With this trail, we wanted to testify grinding result, when less will be used for grinding. Only 250g of sample has been fed. A much faster grinding result is expected to be found.

After 15 minutes of grinding, sample has been packed completely. An aliquot has been used for sieving with Vibratory Sieve Shaker ANALYSETTE 3 Pro.

About 95,7% of sample is able passing a 63µm mesh test sieve. Sample is not sticking, longer grinding times are still possible.

In our last trial we wanted to demonstrate grinding with a planetary ball mill. By using a Planetary Mill PULVERISETTE 5 classic line, up to 4 bowls can be ground simultaneously.

Bowls made of hardmetal tungsten carbide are only available up to 250ml volume. For a grinding of higher amounts, also steel or zirconium oxide bowls might be usable (depending on tolerable abrasion).

With a bowl of 500ml and 20mm Ø balls, 300-350g of sample can be ground in one batch.

After 5 minutes of dry grinding, an aliquot has been sieved out with our Vibratory Sieve Shaker ANALYSETTE 3 Pro. Already 78,1% of sample is able passing a 63µm mesh test sieve. After 15 minutes of grinding, sample starts sticking partly to bowl and balls. A longer dry grinding time might cause stronger sticking of sample.

We found 95,1% of sample, which is able passing a 63µm test sieve.

For a better fineness, still a grinding in suspension is possible.