Dry pressing forming process of zirconia ceramics

There are many methods for forming zirconia ceramics, all of which are based on powder as raw material. Dry pressing forming belongs to dry forming, in addition to isostatic pressing forming. Below, Kezhong Ceramic Factory will focus on introducing dry pressing forming to everyone.

The so-called dry compression molding is formed using powder, a mixture of solid particles and air, as the raw material. In order to reduce friction and increase the strength of the formed body, the powder may contain a small amount of liquid wrapped around the particles, such as pesticides, adhesives, lubricants, etc. In order to densify, it is usually necessary to expel the air between particles as much as possible. Generally, pressure is used to force particles to approach each other and expel the air. According to the method of pressurization during the forming process, the dry forming of zirconia ceramics can be divided into dry pressing forming and isostatic pressing forming. Due to the different compression methods, the quality of the billets prepared by these two molding methods varies greatly.

Dry pressing forming, also known as molding, is the process of placing the granulated powder into a steel mold and pressing it onto a press to form a certain shape of the billet. In the production process of advanced ceramic solid materials, dry compression molding is commonly used: the characteristic of dry compression molding is low binder content, usually 7% -8%, which can be directly sintered without drying. It has many advantages such as simple production process, high efficiency, small shrinkage of the body, and can be automated production. It can be widely used for the production of various functional ceramics and electronic components in circular and thin sheets, especially suitable for pressing at a height of 0 Simple shaped products with a diameter of 3-60mm and a diameter of 5-50mm.

During dry pressing, pressing mode, pressure, such as pressing speed and holding time, and other technological parameters will have an important impact on the density of green body, especially the uneven pressure distribution will cause the inconsistent density distribution inside the green body, which will affect the performance.

In dry compression molding, there are unidirectional and bidirectional compression methods. Due to different compression methods, the distribution and transmission of pressure within the mold are also different. During unidirectional compression, there will be a significant pressure gradient. The greater the pressure difference between the green bodies, the greater the density of the green bodies above, while the density of the central part below is smaller. This is mainly due to the fact that when pressure is transmitted to the billet through the indenter, a group of particles in the billet layer near the indenter separates the fine and ultrafine particles in that layer, making them not only close to each other vertically but also horizontally. Then, the indenter further advances, and the pressure is transmitted to the inner layer through the dense layer near the indenter, And gradually decrease. Part of the pressure is also transmitted to the mold wall by the pressure head, so the green body has different densities at different heights and cross-sections.

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