Alumina ceramics have been widely used in many industries because of their excellent properties. Alumina ceramics is a general term for ceramic products made of calcined alumina as the main raw material. Due to the different content of alumina, it is divided into 75 ceramics, 85 ceramics, 90 ceramics, 95 ceramics, and 99 ceramics.
The raw material processing methods of alumina ceramics mainly include a dry method and a wet method. The dry method mainly uses a roller ball mill for dry grinding, and the wet method mainly uses a roller ball mill, stirring mill, and sand mill for wet grinding.
There are many molding methods for alumina ceramics, but the most important ones are grouting, hot die casting, film rolling, dry pressing, isostatic pressing, casting, injection and gel injection molding, etc. Different molding methods correspond to different processes.
The raw material processing methods of hot die casting and rolling film are mainly dry grinding, and the raw material processing methods of grouting, dry pressing, and isostatic pressing are mainly wet grinding. Hot die-casting, rolling film and gel injection molding, and other molding methods also need to mix organic matter into the processed powder, and dry-pressed and isostatic-pressed powders need to be granulated after wet grinding. The current granulation The equipment mainly includes a pressure spray drying tower and a centrifugal spray drying tower.
Different molding methods use different molds. The grouting method uses plaster molds, the hot die casting method and dry pressing method uses metal molds, and isostatic pressing mainly uses rubber molds.
The above-mentioned various molding methods have different molding principles and processes, so their characteristics are also different, and each has its own advantages and disadvantages. The choice of ceramic molding method should be comprehensively determined according to the performance requirements, shape, size, output, and economic benefits of the product. Grouting molding uses cheap plaster molds, simple equipment, and low cost, and is suitable for the manufacture of complex-shaped ceramic parts and large-sized ceramic products.
Dry pressing can form ceramic products with complex shapes, with high dimensional accuracy and almost no need for follow-up processing. It is the main molding process for making special-shaped ceramic products; it is especially suitable for the preparation of various ceramic products with small cross-sectional thicknesses, such as ceramic sealing rings, Ceramic water valves, ceramic liners, ceramic lining, etc.
The formed body is dried or degreased and loaded into a kiln for sintering. The corresponding sintering system is formulated according to the different alumina content. Theoretically, the higher the alumina content, the higher the sintering temperature required. Sintering equipment mainly includes a pusher kiln, tunnel kiln, roller kiln, shuttle kiln, and bell kiln.
After the fired alumina ceramic products are cleaned and selected, those with low requirements on dimensional tolerance and surface roughness can be directly packaged, and those with high requirements on the above two indicators must be ground and polished.
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