a. Formulation of water glass sand casting coating for impeller
In order to ensure that the surface roughness of impeller water glass sand casting meets the technical requirements, prevent the occurrence of sand sticking casting defects and increase the absorption and release resistance of water glass mold, a certain thickness of zircon powder alcohol-based coating is applied on the surface of impeller water glass sand mold and sand core. The water glass sand casting coating of impeller is organic solvent coating, The coating is hardened or self dry hardened after ignition without drying in the kiln. In this way, it not only shortens the production cycle, saves energy and reduces equipment investment, but also improves the surface quality of water glass sand casting of impeller, but also improves the moisture absorption resistance of water glass sand. The formula is shown in the table.
| Zircon powder | Bauxite | Resin | Polyvinyl butyral | Na based boron bentonite | Clay | Urotropine | Ethanol | Water |
| 70 | 30 | 1.2-2.0 | 1-4 | 1-5 | 0.5-1.5 | 8 | Appropriate amount | 3.4-3.5 |
b. Coating technology of water glass sand casting for impeller
Due to mass production and strong moisture absorption of sodium silicate molding sand (core), brush coating method is used in the experiment. When brushing, the coating thickness is generally between 0.3mm ~ 1mm. If the quality cannot be guaranteed at one time, it can be applied twice ~ 3 times. When brushing, the coating is easy to penetrate into the pores on the surface of the mold and core, and the combination with the water glass sand casting core of the impeller is also firm.