Waterglass or “water glass” casting is also called “sodium silicate” casting because additives are used as binders in ceramic casting shells.
Sodium silicate was developed in the 17th century and is widely used in industry. The waterglass casting process originated in Russia. Waterglass precision casting is widely used in the machinery industry for grinding wheel manufacturing, metal corrosion protection, etc.
In the 1950s, the carbon dioxide blowing waterglass process was widely used. The waterglass addition amount in this process was large, the disintegration was poor, the old sand could not be reused, the silica sand resources were wasted, a large amount of solid waste was discharged, and the ecological environment was damaged, and it was facing elimination.
In 1999, a new type of ester-based hardened waterglass non-hardened sand was launched. The waterglass addition amount was 1.8-3.0%, with high strength and good disintegration. The old sand can be recycled and reused, and the recovery rate is 80-90%. It can be used for mechanized molding production lines and single-piece small-batch production. It can produce various castings from a few kilograms to hundreds of tons. It has been promoted and applied in dozens of enterprises such as railway vehicles, metallurgical machinery, heavy machinery, mining machinery, and general machinery plants. It is known as a green and environmentally friendly casting binder that meets sustainable development. It has become one of the most common investment casting processes in China, with about 75% of foundries using this process.
In water glass casting, sodium silicate is added to sand to form a ceramic slurry, which is then used to produce a ceramic shell mold. High temperature firing of the shell sintered the ceramic elements together to form a high-strength shell suitable for receiving molten metal charges. The advantages of adding sodium silicate are:
- It can be used in high temperature molds (so materials such as iron and ductile iron can be cast using this method)
- It dissolves in water, so it is clean and easy to remove
- Suitable for shelling heavy parts
