Silica sol (colloidal silica), also known as silicic acid solution, is a colloidal dispersion of amorphous silica aggregate particles in water. Silica sol has a wide water loss temperature range, which not only destroys its bonding strength, but also makes its three-dimensional structure more stable, resulting in higher bonding strength. It is a good inorganic binder for precision casting.
In the 1960s, silica sol began to be used as a binder for precision casting. Since the 1990s, due to the increasing pressure of environmental protection, silica sol has gradually replaced the widely used highly polluted and expensive ethyl silicate hydrolyzate. At present, polymer-enhanced quick-drying silica sol is widely used as a binder in the world investment casting industry.
Precision casting refers to the general term for the process of obtaining castings with precise dimensions. Investment casting is also known as lost wax casting. Its products are precise and complex, close to the final shape of the part, and can be used directly without machining or a small amount of machining. This is an advanced near-net-shape process. The process includes: selecting a suitable investment material (such as paraffin) to make the investment; repeating the steps of dipping the refractory coating (the main component is silica sol) and spraying the refractory sand on the investment, hardening the outer shell and drying; melting the inner investment, Obtain the mold cavity; bake the shell to obtain sufficient strength and burn off the remaining investment material; pour the required metal material; solidify, cool, shell, and clean the sand to obtain a high-precision finished product.
Silica sol is used for precision casting. Due to its good bonding ability and filling performance, the fabricated shell has high strength, high gloss and easy demoulding, and is widely used in this field. According to the specific use requirements, it is divided into surface silica sol and back silica sol, which consumes a lot of money.
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