Enamel frit is a glass with a complex oxide composition, which cools very quickly after melting and fragments in water. One of the key parts of enamel production is the grinding of the frit with additives that enable the subsequent preparation of the enamel suspension. When grinding, we want to obtain enamel in powder form, which can then be applied to a metal substrate.
At the industrial level, enamel frits are most often ground in drum mills lined with aluminum oxide and filled with balls of the same material. When grinding, we must pay attention to many parameters, such as: mill speed, size and quantity of grinding balls, moisture and product filling. The grinding process is difficult to monitor, as we do not have a good insight into what is happening in the mill itself, but by changing individual variables, we can observe their influence on the final properties of the enamel.
By systematically changing only one of the parameters of the mill, we wanted to find the optimal conditions for grinding the selected enamel frit. We focused on moisture, size and quantity of grinding balls and quantity of the frit. In addition to the search for optimal conditions, we also examined which grinding law the grinding of the selected material follows and how this affects the properties of the final product, specifically the adhesion of the enamel layer to the steel sheet and resistance to boiling water, steam and alkaline solution.
We experimentally proved that it is optimal if 40% of the mill is filled with balls that have enough energy during grinding to achieve the desired fineness of the product. We also noticed that the frit grinds fastest when it is almost completely dry. When grinding in mills of different dimensions, it has been shown that the energy input during grinding strongly follows Rittinger's law. Regarding the final properties of the product, it was shown that samples with smaller particle sizes performed better.
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