Ceramics--16 Molding Processes

Ceramics are divided into advanced ceramics, modern ceramics, new ceramics, high-performance ceramics, high-tech ceramics and fine ceramics, breaking through the boundaries of traditional ceramics with clay as the main raw material, mainly oxides, carbides, nitrides, silicides, etc. Raw materials, and sometimes can be compounded with metals to form ceramic-metal composite materials, which are ceramic materials with unique and excellent properties prepared by modern material technology.

Ceramic molding is to make ceramic raw materials into green bodies with specified shape, size and certain strength according to the actual production requirements. The molding process depends on the properties of the ceramic raw materials and the molding process. There are various methods for creating the shape of ceramic products, but in general, they can be divided into dry forming and wet forming.

The following Avant will briefly introduce the 16 process methods of ceramic molding.

1. Dry Pressing.

Dry pressing is to add a certain amount of organic additives (binders, lubricants, plasticizers, defoamers, water reducers, etc.) to the ceramic powder to form it in the mold under the action of external pressure.

Advantages: Easy to automate.

Disadvantages: During the molding process, the delamination of the green body is often caused by uneven radial and axial pressure distribution, and cracking and uneven density also often occur.

2. Isostatic Pressing.

Isostatic pressing is a method of compressing powder by applying isotropic pressure. According to the different molding temperature, isostatic pressing is divided into hot isostatic pressing and cold isostatic pressing. Cold isostatic pressing is an isostatic pressing method for forming workpieces at room temperature. Hot isostatic pressing refers to the isostatic pressing method in which the workpiece is isostatically formed and sintered under high temperature and high pressure.

Advantages: can press parts with concave, hollow, slender and other complex shapes; small friction loss, low forming pressure; pressure is transmitted from all aspects, uniform density distribution of green compact, high compact strength, convenient mold making, long life long and low cost.

Disadvantages: The size and shape of the green compact are not easy to precisely control, the productivity is low, the investment is large, the operation is more complicated, the molding is operated under high pressure, and the container and other high-pressure components need special protection.

3. Ultra-high Pressure Molding.

Ultra-high pressure molding is a rapidly developing molding method, which is mostly used in the molding of nano-ceramics. The particle size of nano-ceramics is greatly affected by the sintering temperature. The lower the sintering temperature, the smaller the particle size, and the easier it is to obtain nano-ceramics; and by increasing the molding pressure and increasing the initial density of the green body, the sintering temperature of the nano-ceramics can be reduced. Therefore, ultra-high pressure forming came into being. Ultra-high pressure molding significantly changes the sintering properties of the green body, making it easier to obtain nano-ceramics.

4. Powder Electromagnetic Molding.

Powder electromagnetic pressing is a new high-efficiency molding process that utilizes strong pulsed electromagnetic force to act on powder to densify it. This method is usually used for the forming of metal materials and can achieve very high densities. The densities of the samples formed by the powder electromagnetic pressing method all reach more than 95%, and they have good piezoelectric and dielectric properties.

5. Extrusion.

Mix the powder, adhesive, lubricant, etc. with water evenly and fully knead, and then use the hydraulic press to push the piston to extrude the plasticized billet from the extrusion nozzle. As the inner shape of the extrusion nozzle gradually shrinks, the piston exerts a great extrusion force on the mud mass, so that the billet is dense and formed.

Advantages: The ceramic membrane tube obtained by extrusion molding has large porosity, density and compressive strength, and the pore size distribution is concentrated, the gas permeation flux is large, and it is an excellent ceramic membrane tube. It is suitable for making pipes or bars with round, oval, polygonal and other special-shaped fracture surfaces.

Disadvantages: The material has low strength and is easy to deform, and may produce surface pits and blistering, cracking and internal cracks and other defects.

6. Injection Molding.

Injection molding is also known as hot die casting. This technology gives metal powder, ceramic powder and polymer similar fluidity by adding a certain amount of polymer and additive components and heating, and filling the slurry into the metal mold under pressure. , after cooling, the blank is obtained by de-blanking. It is listed as an important "national key technology" by developed countries such as the United States.

Advantages: high utilization rate of raw materials, fast and automatic mass production; special-shaped parts with small volume, complex shape and high dimensional accuracy can be prepared; due to the flow punching die, the density of the green body is uniform, and the sintered product performance is superior; the production cost is low.

In the next article, we will continue to share another 6 kinds of ceramic molding process methods.

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Shanddong Avant New Material Technology, focus on alumina materials 13 years.