Resin coated Ceramic sand as core sand for investment casting
Resin coated Ceramic sand is a modeling sand with a layer of resin binder on the surface of ceramsite sand. In the investment casting process, the shell mold outside the wax mold usually adopt materials such as mullite, corundum, and zircon sand. For the hollow parts of the casting, coated sand is suitable for core moulding. Using ceramic coated sand as core sand for investment casting has the following advantages:
1. Regular shape
Baozhu sand is spherical and has a smooth surface. This regular shape allows it to be tightly packed when filling the mold, thereby increasing the density of the sand core. Compared with irregularly shaped sand particles, the gaps between spherical Baozhu sand are smaller, which can reduce the penetration of molten metal during the pouring process, thereby reducing the possibility of mechanical sand sticking to the casting and improving the surface quality of the casting.
2. High strength
Baozhu sand coated sand is matched with a reasonable amount of resin addition, and the coated sand has good compressive strength and bending strength. It is beneficial to improve the mechanical strength of the core sand.
3 Reasonable particle size distribution
The particle size distribution of foundry ceramic sand compliance with specific casting requirements. The particle size of ceramic coated sand is usually 70-140 mesh, 100-200 mesh, etc. Appropriate particle size distribution can ensure that the sand core has good air permeability and compactness. In investment casting, good air permeability helps to discharge the gas generated during the solidification process of the casting and prevent the generation of defects such as pores; and sufficient compactness can ensure that the sand core maintains a stable shape during the casting process without deformation or collapse.
4. Low thermal expansion coefficient
Ceramsite sand has a small thermal expansion coefficient. During the casting process, when it is subjected to the action of high-temperature molten metal, its volume change is relatively small. This feature enables the sand core to maintain good dimensional stability in a high temperature environment. In this way, reduce the dimensional deviation and deformation of the casting caused by the expansion of the sand core, and improve the dimensional accuracy of the casting.
5. Good chemical stability
Ceramic sand has high chemical stability and is not easy to react chemically with molten metal. In investment casting, when in contact with various metal liquids (such as aluminum alloys, stainless steel, etc.), it can maintain its own chemical properties unchanged, avoiding surface defects of castings caused by chemical reactions, such as chemical sticking sand, inclusions, etc., and improving the purity and quality of castings.
6. Low acid consumption value
The acid consumption value of ceramsite sand is low, which means that it reacts weakly to acidic substances. When using acidic binders such as phenolic resin for coating, ceramic sand with low acid consumption value can better combine with the binder, improve the bonding strength, ensure the strength and hardness of the sand core, and thus facilitate the smooth casting process.
7. Good fluidity
Due to its spherical shape and smooth surface, Resin coated ceramic sand has good fluidity. During the core making process, it can be easily filled into every corner of the mold, even complex-shaped sand cores can be filled completely. It can reduce the voids and looseness in the sand core. In the meantime, improves the quality and integrity of the sand core.
8. Good demoulding performance
The smooth surface makes it easy for the ceramic coated sand to be removed from the mold after the sand core is formed. It reduces the possibility of sand core damage during demoulding. As a result, it can improve production efficiency and sand core yield. At the same time, good demoulding performance also helps to clean and reuse the mold, reducing production costs.
9. Improve casting accuracy
The above-mentioned characteristics of low thermal expansion coefficient and good dimensional stability enable the sand core made of ceramsite coated sand to better ensure the dimensional accuracy of castings. In investment casting, for some parts with high dimensional accuracy requirements, such as aerospace parts, precision machinery parts, etc., Ceramic coated sand can meet their high-precision casting requirements.
