In the 1960s, silica sol began to be used in the field of casting, mainly as binder.It has been widely used in foundry industry because of its simple preparation process, low pollution low cost.At present, silica sol is often used as binder in investment precision casting, which can guarantee the quality of investment precision casting.In the field of precision casting, the related research of silica sol has been gradually launched, the different properties of silica sol were studied in detail, then to determine the different properties of silica sol in the use of investment precision casting types, then promote the rapid development of investment precision casting industry.Silicone sol in investment precision casting is mainly used in the process of shell mold preparation of castings. Due to the use of Silicone sol as a binder with special properties, the quality of shell mold of castings has been greatly improved, which also makes the Silicone sol more widely used in investment precision casting.

The characteristics of silica sol its advantages as binder

1. Related properties of silica sol

Silica sol is a kind of appearance is milky white translucent colloidal solution, most of the stable alkaline, a few cases appear acidic.Silica sol has low viscosity, good dispersion performance, can be fully into the need to fill the solid material, can guarantee the smooth surface of the solid material.Silicol hydroxyl group adsorbed water are on the surface of silica sol particles, which can effectively improve the wettability of silica sol.Silica sol can effectively improve the mechanical chemical properties of the mixture after homogeneous mixing with organic resin.

2. the advantages of silica sol as binder

Silica sol is widely used as binder in investment precision casting, replacing the water solution of sodium silicate ethyl silicate which has complicated preparation process, serious pollution high cost.The advantages of this kind of binder widely used in investment precision casting mainly lie in that the preparation process of silica sol is relatively simple there is no complicated procedure.After its coating needs to adjust composition only can be used, make its keep in storage rises more convenient.Easy to operate during dipping coating process.

Preparation method classification of silica sol

1. Preparation method of silica sol

(1) direct acid neutralization method: using direct acid neutralization method to prepare silica sol, the use of ion exchange method to remove sodium ions in the raw material, which will get dilute sol containing less sodium ions, then the dilute sol is heated after stopping for a period of time, after the acidification reaction;(2) One-step dissolution method of elemental silicon: it mainly uses silicon powder to react with water under the catalysis of alkaline substances to generate hydrated silicate acid, which will be polymerized in water medium;(3) colloidal method: colloidal method in the process of preparing silica sol, the first use of acid solution to neutralize the sodium silicate solution, the formation of gel.

2. Classification of silica sol

There are mainly alkaline silica sol, acid silica sol neutral silica sol.

Application of silica sol in investment precision casting

Silica sol has been widely used as binder in investment precision casting.The application of silica sol in investment precision casting only improves the quality of casting, but also reduces the production cost.In the process of shell drying, the moisture in the shell will be transferred the inside of the shell to the surface of the shell coating, which will affect the surface quality of the shell. Because the silica sol is coated on the surface of the shell, the silica sol will solidify at a certain temperature, once solidified, it will be dissolved in other substances again.Therefore, although the moisture inside the shell will be transferred to the surface of the shell, it will affect the quality of the shell surface.In addition, in the process of drying, water will absorb a lot of heat in the process of evaporation, which will make the temperature of wax touch drop, then the size of the phenomenon, resulting in defects on the surface of the shell. Therefore, the drying process should be accelerated, so as to ensure the quality of the shell.