1. Press molding
This is a common molding method for ceramic large-size grinding media. There are mainly dry pressing molding (the water content of the powder or additives is 3%-7%) and isostatic pressing (the water content of the powder or additives is less than 3%). Dry pressing molding has the characteristics of convenient and simple operation method and low technology and capital investment. However, due to uneven pressure distribution, the internal distribution of the blank is inconsistent, which affects the overall performance of the product. In order to increase the density of the blank, it is often used in actual production. A way to keep building up the pressure. But the bigger the pressure, the better. When it exceeds the ultimate pressure, the pressure will actually reduce the density of the blank. The reason is caused by spallation. The green body formed by isostatic pressing has high strength, high density and uniformity, and can prepare high-performance and high-quality grinding media balls. Therefore, two methods can be used in industry to produce high-performance ceramic balls.
Brief description of the process: The powder and various additives are mixed and then sprayed and granulated. The powder is then added to a metal mold to preform balls, and then the demoulded green body is subjected to cold isostatic pressing. The ball green body is obtained through this process. The green body prepared by this process has high density, and the fired ceramic balls have high density and good quality. The isostatic pressing method has a large investment in processing equipment and high post-processing costs. It is generally used to produce large-sized and high-quality grinding balls with a diameter greater than 10mm.
2. Rolling into balls
In addition to the cold isostatic pressing molding process, rolling into balls is also an important molding method for ceramic balls. This method has production equipment, It has the characteristics of raw materials, simple operation, good sphericity and easy sintering. Although the balling strength is not as strong as cold isostatic pressing, the preparation cost is lower, and balls of various sizes ranging from 0.1mm to 60mm can be produced according to requirements. Rolling into balls is done by rolling mud segments into balls. The process is as follows: add powder and water, binders, plasticizers, lubricants, etc. into a mud mill to knead into mud and then age to form plastic mud. , put it into a mud extruder to extrude it into mud strips, and cut it into mud segments with a length equal to the diameter, and then put it into a ball rolling machine to roll it into a ball blank. This molding method mainly controls the diameter and diameter of the die head of the mud extruder. By cutting the segments into shorter lengths, you can obtain mud segments with better consistency, and the roundness of the rolled ball blanks is also easy to control. However, due to the relatively low density of the ball blanks, it is necessary to increase the sintering temperature to obtain a denser porcelain body, resulting in abnormal grain growth. , it is difficult to produce microcrystalline zirconia with excellent wear resistance. There is also a method of direct rolling of powder. The process is as follows: using a simple and cheap rotating ball machine, first adding prefabricated ball seed crystals, and then adding ceramic powder while rotating and spraying water mist, so that the powder continues to stick. It is attached to the surface of the seed crystal and gradually grows, and finally a ball blank of the required size is obtained. By controlling appropriate roll forming process parameters, ball blanks with high volume density, good roundness and uniform size can be obtained. The principle of rolling into balls is somewhat similar to that of making glutinous rice balls, but it is not done by hands, but by machines.
3. Dropping liquid into balls
For grinding small zirconia Dielectric beads (0.05mm to a few tenths of a millimeter) can be formed into green ceramic beads using the titration method. For example, South Korea's Sano uses the company's self-made hydrothermally synthesized 6nm high-purity ultra-fine zirconia as raw material, and produces oxidized zirconia through the titration method. Zirconium ceramic microbeads can be sintered at low temperature and have no pores inside. They have high density, high strength, high toughness, low wear and other properties. It can be used for dispersing and grinding high-performance materials such as electrode materials, multilayer ceramic capacitors, paints, and coatings.