MINING AND PROCESSING PLANTS SELECT STEEL GRINDING BALLS

Sometimes we face a situation where our clients consider the possibility of using cast-iron (chromium-alloyed) balls in ball mills at mining and processing plants. Our specialists have studied this topic and we wish to share the results with you.

The highly chromium balls are mainly used exclusively in cement milling in Ukraine, the Russian Federation and practically all over the world today. This is due to the nature of the shredding process in the industry: dry grinding, stopping of the mill, usually once every 3-4 months, low hardness (abrasiveness) of the ground material. However, in the processing industry, where wet milling is used, the situation is fundamentally different.

The last attempt to use chromium balls in Ukraine was in July 2016. We have tried to gather as much information as possible about all tests of this type of grinding balls. For the sake of objectivity, we averaged the results (specific consumption) of each test and multiplied by the current value of cast-iron (chromium-doped) balls. Thus, we obtained a universal measure of shredder cost per ton of ore with cast-iron balls. Below are the results of our calculations:

1. During the period 2014-2016, several industrial tests were conducted at Ukrainian mining and processing plants. Omitting all intermediate calculations, we observe the following:

• For balls with a diameter of 25-50mm, the cost of grinding one ton of ore varies from 0.317 U.E. to 0.347 U.E. The average cost of grinding one ton of ore is 0.330 U.E.
• For large diameters (120-125mm), the dilution of the grinding cost per ton of ore ranges from 0.634 u.e. to 0.687 u.e. The average is 0.660 u.e.

2. At the same time, Energosteel tested the steel grinding balls of the sixth hardness grade (HRC more than 65). These tests showed a 10-30 per cent decrease in the specific consumption depending on the specifics of the shredding process for each specific client.

Below is the cost of milling one ton of ore using steel grinding balls of the sixth hardness group (HRC more than 65) of LLC «Energosteel Plant» production:

• For balls 25-60mm – 0.260 U.E. The variation in value ranges from 0.248 to 0.295 U.E.
• For balls 100-120mm, the cost of shredding one tonne of ore is 0.537 u.e.

As seen, on average, the cost of grinding one ton of ore on chromium balls of small diameter is 27% higher than the cost of grinding on roller balls of the 6th hardness group, produced by Energosteel. Grinding balls of large diameter of 6 group are  more efficient than chromium in money equivalent by 23%.

In addition to the economic effect, we provide you with a number of factors that show the advantage of using steel grinding balls in ore processing plants:

• Limited number of chromium ball manufacturers, the manufacturer can dictate monopoly conditions;
• The location specificity of the production facilities in the third world countries, which creates a long transport route, risk of delivery delays, exchange rate risks;
• The need to keep an extra volume of grinding balls in stock to minimize logistical risks;
• The myth that chromium balls in mills are less corrosive, physical wear is significantly higher than corrosion, so the latter can be neglected;
• If a chromium ball is used, the mill shall be fitted with a lining (and other metallic components) made of the same material;
• High cost of chromium cast iron lining.

We hope this information will be useful to our readers and help them make the right choice when searching for the manufacturer of grinding balls in 2022.