According to different product requirements and different molding processes, alumina powder is made into powder material. If the particle size of the powder is less than 1m, ultrafine pulverization is required to make the particle size distribution uniform. When using extrusion molding or injection molding, binders and plasticizers should be introduced into the powder, usually a thermoplastic or resin with a weight ratio of ten to thirty percent. The powder material for hot pressing does not need to add a binder. If semi-automatic or fully automatic dry pressing is used, the powder has special process requirements, so it is necessary to use spray granulation to process the powder to make it into a spherical shape to improve the fluidity of the powder and facilitate the automatic mold wall during molding. filling. In addition, in order to reduce the friction between the powder and the mold wall, a small amount of lubricants such as stearic acid and binder polyvinyl alcohol should be added.
For dry pressing, the powder should be sprayed and granulated, and polyvinyl alcohol is introduced as a binder. The water-soluble paraffin developed by a research institute in Shanghai is used as a binder for Al203 spray granulation. Al203 has good fluidity under heating. The powder after spray granulation should have good fluidity, bulk density and friction temperature less than 30. The ratio of particle grades is ideal to obtain a larger green density. The forming methods of alumina ceramic products include dry pressing, grouting, extrusion, cold isostatic pressing, injection, casting, hot pressing and hot isostatic pressing.
In recent years, some molding technology methods have been developed, such as press molding, direct solidification injection molding, gel injection molding, centrifugal grouting molding, and solid-free molding. Different shapes, sizes, complex shapes and precision products require different modeling methods.
