Views: 0 Author: Site Editor Publish Time: 2022-03-29 Origin: Site
Ceramic ball grinding medium has experienced several great changes from early to modern, especially in the development trend of particle size, specific gravity and particle size deviation.
1. The smaller the particle size of ceramic ball is, the smaller it is
The grinding equipment has developed from attritor, the world's first agitated ball mill with larger particle size grinding ball, to vertical and horizontal sand mills with smaller particle size ceramic ball grinding beads, as well as various ultra-fine grinding new generation sand mills with improved functions. The particle size of ceramic ball grinding medium is getting smaller and smaller. There are two main reasons for this:
◆ micronization of final grinding fineness of materials: since the materials in the grinder are dispersed and ground through the contact of moving ceramic ball grinding medium, the smaller the particle size of ceramic ball grinding medium is, the more contact points are, and finally achieve higher grinding effect and smaller grinding fineness. For example, a brand of zirconium silicate beads with a particle size of 2mm is about 20000 per liter, while the particles with a particle size of 1mm reach about 80000, which is four times that of the former. When a product is ground with zirconium beads with larger particle size, the particle size of the material fails to meet the required fineness no matter how many sand grinding passes; When the ceramic ball grinding beads with smaller particle size are used, the effect is obviously improved.
◆ the improvement of the separation device of the sand mill makes it possible to use ultra-fine ceramic ball grinding beads: the allowable minimum grinding bead particle size has become an important index to evaluate the quality star grade of the sand mill. Every revolution in the design and manufacture of separation devices and materials has brought a leap in the use of grinding beads. From the static traditional flat nicke1 net to Johnson Net with triangular beam and to the dynamic ring separator and sleeve cartridge net, the particle size of the grinding medium that can be used is getting smaller and smaller in addition to prolonging the service life, without significantly affecting the flow of materials. The minimum bead used by the representative of the sleeve cartridge net (such as the speedball mill of premier in the United States) is 0.2mm; Representatives of ring separators (such as dyno mill laboratory type in Switzerland) can also use beads with a particle size of 0.2mm. The centrifugal separation device developed by Buhler company in Switzerland has changed the separation principle from distinguishing the size of beads to distinguishing the density of beads, and pushed the minimum particle size of grinding beads to a new limit.
2. The greater the specific gravity of ceramic balls
The specific gravity of common grinding beads such as glass beads, stone beads, zirconium silicate beads, pure zirconium beads and chromium steel balls increases in turn, and their hardness, compressive strength and wear resistance also increase in turn in addition to chromium steel balls. From the dynamic formula P = MV, it can be seen that the impulse P of the bead is directly proportional to the mass m of the bead. The greater the density, the greater the motion energy of the bead and the higher the grinding efficiency.
Because inorganic pigments with high toughness (such as carbon black, phthalocyanine blue, iron oxide, etc.) need ultra-fine grinding, and in order to pursue higher grinding efficiency and ideal gloss, the use of high-density grinding beads has become a solution. The sand mill manufacturer has complied with this requirement, which is mainly made possible by the following two reasons:
◆ production of high input energy density sanding mill: one of the development trends of modern sanding mill is that the volume of grinding cylinder becomes smaller, while the configured motor power becomes larger, and the input energy density increases sharply. Relevant control parameters are shown in the table below.
The energy density of modern sand mill is 4 times or more than that of traditional sand mill. This makes it possible to effectively drive high-density grinding beads (such as pure zirconium beads). At the same time, due to the high energy distribution in the grinding area, only grinding media with high compressive strength and wear resistance (such as pure zirconium beads) can be used.
◆ improvement of the material quality of the contact parts of the sand mill: the contact parts of the sand mill (such as inner cylinder, dispersion disc, rod pin and separation device) are made of hard and wear-resistant cemented carbide (such as tungsten carbide) and high-performance materials such as ceramics (such as silicon carbide and zirconia), which can resist the wear caused by the impact and friction of the height energy and high hardness of pure zirconium beads.
3. The particle size deviation of ceramic balls is getting smaller and smaller
For the sand mill, the ceramic ball grinding beads with uniform particle size reflect their advantages. On the one hand, they contribute to the narrow distribution of material fineness. On the other hand, they greatly reduce the generation of broken beads, reduce the wear of the contact parts of the sand mill and avoid the pollution to the products. Nowadays, the particle size deviation of Sanxin ceramic ball grinding medium commonly used in the market is maintained at 0.2mm. The market price of uniform beads is relatively high due to the complex manufacturing process.