Alumina ceramics two different molding methods
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, at home and abroad have developed a filter molding, direct solidification injection molding, gel injection molding, centrifugal injection molding and solid free molding technology. Different product shapes, sizes, complex shapes and precision products require different molding methods
Alumina ceramic plate
Two commonly used molding methods of alumina ceramics are introduced:
1, dry press molding: alumina ceramic dry press molding technology is limited to simple shape and inner wall thickness of more than 1mm, length and diameter ratio is not greater than 4:1 objects. The molding methods are uniaxial or bidirectional. The press has two kinds of hydraulic type and mechanical type, which can be semi-automatic or automatic forming method. The maximum press pressure is 200Mpa. The output can reach 15 ~ 50 pieces per minute. Because of the uniform stroke pressure of the hydraulic press, the height of the pressing parts is different when the powder filling is different. The size of the pressure applied by the mechanical press varies due to the amount of powder filling, which is easy to lead to the difference in the size shrinkage after sintering and affect the quality of the product. Therefore, the uniform distribution of powder particles in the dry pressing process is very important for mold filling. Whether the filling amount is accurate or not has a great influence on the dimensional accuracy control of manufactured alumina ceramic parts. Powder particles with more than 60μm, between 60 ~ 200 mesh can obtain the maximum free flow effect, to achieve the best pressure molding effect.
2, grouting molding method: grouting molding is the earliest molding method used for alumina ceramics. Due to the use of gypsum mold, the cost is low and it is easy to form large size and complex shape parts. The key of grouting molding is the preparation of alumina slurry. Usually water is used as the flux medium, and then the degumming agent and the binder are added, after full grinding, the gas is discharged, and then the plaster mold is poured backwards. Due to the absorption of water by the capillaries of the plaster mold, the slurry is solidified in the mold. In hollow grouting, the excess slurry should be poured out when the slurry adsorbed on the mold wall reaches the required thickness. In order to reduce the shrinkage of the body, high concentration slurry should be used as far as possible.
Organic additives should also be added to the alumina ceramic slurry to form a double electric layer on the surface of the slurry particles so that the slurry is stably suspended without settling. In addition, binders such as vinyl alcohol, methyl cellulose, alginate amine and dispersants such as polyacrylamide and gum Arabic are added to make the slurry suitable for grouting molding operation.
