1. Chemical composition

Grinding media can be divided into glass beads, ceramic beads (including zirconium silicate beads, alumina beads, rare earth metal stabilized zirconium oxide beads, etc.), steel beads, etc. according to different materials. The crystal structure of grinding beads is determined by the differences in chemical composition and manufacturing process. The dense crystal structure ensures the high strength, high wear resistance and low ink absorption rate of the beads. The different percentages of various components determine the specific gravity of the grinding beads. The high specific gravity provides a guarantee for high grinding efficiency. The natural wear of the chemical composition of the grinding beads during the grinding process will have a certain impact on the performance of the slurry. Therefore, in addition to considering the low wear rate, the chemical elements to be considered are also factors to be considered. For example, when grinding magnetic tape powder or other electronic component slurries, metal elements such as Fe and Cu should be avoided, and grinding beads containing components such as Fe2O3 or CuSO4 are not among the choices, so the selection of zirconium beads is often a common choice in this industry; for example, in the grinding of pesticides, medicines and biochemicals, heavy metals are considered as elements of concern, and PbO is the most common component. In short, some physical properties (hardness, density, wear resistance) determined by the chemical composition of the beads and the contamination of the slurry by their own wear are factors to be considered when selecting grinding media.

2. Physical properties:

1. Density of grinding media

Density is usually expressed in specific gravity (true specific gravity) and bulk weight (false specific gravity). The molecular weight and percentage composition of various oxides determine the density of grinding. The density of commonly used grinding media is shown in Table 1. Under normal circumstances, the larger the specific gravity of the grinding beads, the greater the impulse and the higher the grinding efficiency, while the wear on the contact parts of the sand mill (inner cylinder, dispersion disk, etc.) is relatively large, so the viscosity and flow rate of the slurry become the key. Low-density grinding beads are suitable for low-viscosity slurries, and high-density grinding beads are suitable for high-viscosity slurries.

2. Particle size of grinding media

The size of grinding beads determines the number of contact points between grinding beads and materials. The more contact points beads with smaller particle size have in the same volume, the higher the grinding efficiency in theory. On the other hand, when grinding materials with relatively large initial particles, such as 100 micron slurry, beads with D=1mm may not be effective because the impulse of small beads cannot reach the energy for full grinding and dispersion. In this case, beads with larger particle size should be used.

3. Hardness of grinding media

Mohs hardness and Vickers hardness are commonly used indicators. The higher the hardness of grinding beads, the lower the wear rate of beads. For example, from the wear of grinding beads on the contact parts of the sand mill (dispersion disc, rod pin and inner cylinder, etc.), grinding beads with greater hardness have greater wear on the contact parts, but the best optimization point can be achieved by adjusting the filling amount of beads, the viscosity of the slurry, flow rate and other parameters.