In the operation of the core machine, the sand core is used to meet the following conditions.
1. The low moisture absorption and moisture absorption of the sand wick will reduce the strength of the sand core and increase the air volume of the core, so as to cause the defects such as stoma. In order to reduce the production of gas, the sand core is required to have low moisture absorption and air volume.
2, good air permeability in the process of casting, casting sand mold and sand core temperature will rise sharply, moisture to evaporate quickly, combustion, decomposition of organic matter, volatile, inorganic chemical reactions occur, these will produce large amounts of gas. If these gases cannot be discharged successfully, they must break into the metal fluid to make the casting hole. Therefore, the sand core is required to have good air permeability.
3. Good ductile casting will produce great stress during cooling. If the sand core is not strong, the casting may produce deformation and even crack.
4. High degree of refractoriness in the pouring process, the sand core is roasted by the high temperature metal liquid for a long time, which makes the casting surface produce sticky sand easily. Therefore, the sand core is required to have a high degree of refractoriness, so as to avoid the defects such as sticky sand.
5. Good sanding ability will reduce the cleaning load and improve the surface quality of the casting.
6. The high dimensional precision sand core mainly forms the inner cavity and hole of the casting, and these places are generally no longer machined. Therefore, the sand core is required to have high dimensional accuracy.
7. Good stability and balance only have good stability and balance, so as to ensure that the sand core is easy to operate and stable and reliable when it is suspended and removed.