Manufacturing process and process of alumina ceramics
One powder preparation: The alumina powder is prepared into powder materials according to different product requirements and different molding processes. When extrusion molding or injection molding is used, a binder and a plasticizer need to be introduced into the powder, generally a thermoplastic plastic or resin organic binder with a weight ratio of 10-30% should be at 150-200 ° C with alumina powder. Mix uniformly at temperature to facilitate molding operations. The powder raw material formed by the hot pressing process does not need to add a binder. If semi-automatic or full-automatic dry pressing is used, the powder has special process requirements, and the powder needs to be processed by spray granulation to make it spherical, so as to improve the fluidity of the powder and facilitate automatic filling of the mold during molding. wall. In addition, in order to reduce the friction between the powder and the mold wall, it is necessary to add 1 to 2% of lubricants such as stearic acid and binder PVA.
Two molding methods: Alumina ceramic products are molded by dry pressing, grouting, extrusion, cold isostatic pressing, injection, casting, hot pressing and hot isostatic pressing. In recent years, domestic and foreign countries have developed molding technology methods such as filter press molding, direct solidification injection molding, gel injection molding, centrifugal grouting, and solid free molding.
Three firing technology: The technical method of densifying the granular ceramic body and forming a solid material is called sintering. Sintering is a method of removing voids between particles in the body, excluding a small amount of gas and impurity organic matter, and making the particles grow and combine with each other to form a new substance. The most widely used heating device for firing is an electric furnace. In addition to atmospheric sintering, there are also hot-pressing and hot-isostatic sintering, microwave sintering, arc plasma sintering, and self-propagating sintering.
Four finishing and packaging processes:
Some alumina ceramic materials require finishing after sintering. The hardness of alumina ceramic materials is higher, and it is necessary to use harder abrasive polishing brick materials for finishing. Such as SiC, B4C or diamond. Usually use coarse to fine grinding step by step, the final surface polishing. Generally, Al2O3 micron powder or diamond paste can be used for grinding and polishing. In addition, laser processing and ultrasonic processing can be used for grinding and polishing. Some alumina ceramic parts need to be packaged with other materials