Silica sol has the advantages of good adhesion, high temperature strength and low shrinkage. It is widely respected by precision casting enterprises and has become the industry recommended product of China Foundry Association. Special S series for precision casting is divided into surface-specific S-830 silica sol and back layer-specific S-1430 silica sol according to different high-temperature strength properties. At the same time, according to customer demand, Huihe developed SJ series with 2 varieties, SJ. -25 surface layer enhanced silica sol, which can improve the surface finish and high temperature strength, improve the yield of castings, reduce the time and cost of sand cleaning; SJ-30 polymer modified silica sol can greatly improve the shell The efficiency and stability of the shell mold quality are more suitable for the application in the automatic shell production line; the drying speed of the shell film can be greatly improved, the construction period is shortened, and the cost is saved.