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Alumina ceramics are currently divided into two types: high purity type and common type.Alumina ceramic dry pressing technology is used for simple shapes with inner wall thickness of more than 1mm and the ratio of length to diameter of not more than 4:1.Because the stroke pressure of hydraulic press is uniform, the height of pressing parts is different when the powder filling is different.However, the pressure exerted by the mechanical press varies with the amount of powder filling, which easily leads to the difference of size shrinkage after sintering and affects the product quality.
Injection molding is an early molding method for alumina ceramics.Due to the use of gypsum mold, low cost and easy to shape large size, complex shape parts.The key of grouting is the preparation of alumina slurry.Usually with water as the flux medium, then add the gel and binder, after fully grinding exhaust, and then pour into the gypsum mold.The slurry solidified in the mold due to the adsorption of water by the gypsum capillary.When hollow grouting, when the mold wall adsorption slurry to the required thickness, but also need to pour out the excess slurry.
The technique of densifying a granular ceramic billet to form a solid material is called sintering.Sintering is to remove the cavity between the particles in the billet, remove a small amount of gas and impurities and organic matter, so that the particles grow and combine with each other, forming a new material method.
Although continuous hot pressing sintering increases the output, but the cost of equipment and mould is too high. In addition, because of axial heating, the length of products is limited.Hot isostatic burning adopts high temperature and high pressure gas as pressure transfer medium, and has the advantages of uniform heating in all directions, so it is suitable for sintering complicated products.Due to the uniform structure, the material properties are improved by 30 ~ 50% compared with cold pressing sintering.10 ~ 15% higher than normal hot pressing sintering.
Some alumina ceramic materials after the completion of sintering, because of the higher hardness of alumina ceramic materials, need to be more hard polishing brick material for its finishing.Usually from coarse to fine abrasive step by step grinding, final surface polishing.In addition laser and ultrasonic machining grinding and polishing methods may also be used.Some alumina ceramic parts need to be packaged with other materials.