The development history of silica sol application in precision casting

The binders commonly used in investment casting are mainly silicic acid colloidal solutions, including silica sol, water glass and ethyl silicate hydrolyzate. Silica sol and water glass are alkaline silicic acid colloids with water as the carrier, and ethyl silicate hydrolyzate is acidic silicic acid colloid with ethanol as the carrier, which is essentially silicic acid colloid.

Silica sol Silica sol was introduced into the investment casting process in the 1960s. First, Na+is used as a stabilizer, and the diameter of the colloidal particles is 12to14nm. In the 1970s, silica sol with a small particle size of 7to8 nm appeared on the surface layer, and in the 1970s, enhanced silica sol appeared. In themid1990s, quickdrying silica sol was developed abroad to replace ethyl silicate vinegar, which improved the problem of long shellmaking cycle of silica

sol. The largescale use of silica sol in our country began in the 1990s. The preparation method is mainlyion exchange and dissolution, that is, the impurities such as Na+ in water glass are replaced by ion exchange, and industrial pure silicon is dissolved in water and filtered.