If you are already happy with your milling processes, this article can be informative and of course your comments will add value to the subject. But if you are stuck in forged vs cast grinding balls dilemma and wonder if you are using the most optimum grinding media for your ball mills, we highly recommend reading it. To avoid redundancy, forged and roll-forged grinding balls are collectively called forged grinding balls in this article.
We do not want to compare apples and oranges here. Of course chromium cast balls undergo lower wear rates. As the chromium content increases, wear rate will be reduced. Experience with our grinding balls shows that medium-chromium cast grinding balls (7-12% Cr) will have around 10% lower wear rate compared to 70Cr2 forged grinding balls of the same size that enjoy a small chromium content. But that’s not the whole story!
In our forging plant, we use highest quality round bars which are either produced in our hot-rolling mill or supplied from the most renowned producers in the market. Consequently, after passing through the strictest QC tests, standard and consistent quality round bars will be introduced to forging plant in a continuous process. In another words, round bars composition will be similar in 0.01 percent accuracy. But in casting, there is no such possibility. The cast material is made ready batch by batch, where there is no possibility of precise controls due to nature of casting process. As a result, when grinding balls are made from standard round bars in a fully automatic continuous process where all parameters, e.g. temperatures, are constantly controlled by microprocessors, sensors, and PLCs you can be more confident of final product quality. By the same token, forging heat treatment is also much more reliable, being both continuous and controllable. Unlike casting heat treatment which happens batch by batch.
Shape always matter when we are talking about milling. Spalling and parting lines increase breakage in cast balls, which is more felt in case of larger-sized impact balls. Additionally, casting defects and specially shrinkage defects are inevitable for large size balls.
To sum up, while medium-chromium cast balls have lower wear rates, forged grinding balls are some 20-30% cheaper, more spherical in shape, have more predictable wear patterns and enjoy more controllable continuous production processes. Today several wet milling plants are turning into forged grinding balls to optimize their processes and minimize their costs. Costs in grinding media is a correlation between grinding media consumption, power consumption and product grade. Therefore, we believe that forged vs cast grinding balls is a decision that is not easy to make and demands careful analysis of several parameters.
