Casting molding first involves adding ceramic powder and dispersant into a solvent, which is then ball milled or ultrasonically oscillated to open up particle aggregation and wet the powder with the solvent. Then, binders and plasticizers are added again, and a stable and uniform slurry is obtained through secondary ball milling; Re form the slurry on the casting machine to obtain a green body; Then, moisture is applied to evaporate the solvent, and a mesh structure is formed between the binder and the ceramic powder to obtain a green film; Product types: Ceramic plungers, ceramic pump cores, ceramic valve cores, ceramic pistons, ceramic shaft sleeves, ceramic suction cups, microporous ceramics, etc; Materials: alumina, zirconia, silicon nitride, silicon carbide. Next, the green film is machined to obtain the desired specific shape; Finally, the desired finished product is obtained through rubber extrusion and sintering treatment.
Under the unremitting efforts of materials science workers, a new water-based casting method has been developed based on the original casting method, such as gel casting process, isostatic pressing casting process, and UV induced polymerization process.
1. Gel casting process
Gel casting utilizes the principle of polymerization of organic monomers for casting. This method involves adding ceramic powder, dispersant, and plasticizer to a mixed solution of organic monomers and crosslinking agents to prepare a low viscosity and high solid volume fraction (volume fraction greater than 50%) concentrated suspension. After adding the initiator and catalyst, the temperature is controlled and the monomer undergoes polymerization reaction, which increases the viscosity of the suspension and then undergoes in-situ solidification, ultimately preparing a green body with certain strength and suitable for machining.
The gel tape casting process not only significantly reduces the amount of organics in the slurry, but also increases the solid volume fraction and product density and strength, which is more and more conducive to the construction of a resource-saving and environment-friendly society.
2. Isostatic pressure casting process
The solid volume fraction of the slurry formed by casting is quite high, and during the wet process, solvent evaporation also occurs, leaving pores in the green body. Therefore, the green film obtained by casting is usually structurally textured and has a relatively high density, making it very easy to indirectly obtain a hard green body through casting.
Although the cast film blank obtained by extrusion molding is hard and has a loose structure, it has relatively good ductility. Therefore, the density of the blank can be improved by isostatic pressing secondary molding. However, the isostatic pressing casting equipment is relatively cheap, so it will make the process simpler and increase costs.
3. UV induced polymerization molding process
In response to the shortcomings of water-based casting technology, researchers have adopted the in-situ polymerization mechanism triggered by ultraviolet light, adding ultraviolet photosensitive monomers and ultraviolet polymerization initiators to the slurry and triggering ultraviolet in-situ polymerization reactions to solidify the slurry in situ. Compared to the traditional casting process, the UV induced casting process can be completed by adding a UV light source to a general casting machine, eliminating the most difficult wet process that causes material forming failure.
