Water glass sand is a kind of molding sand which is a mixture of raw sand and water glass (sometimes with other auxiliary materials) in appropriate proportions and is used for casting. It has significant advantages in ensuring casting quality, reducing production costs, recycling resources, and being eco-friendly.
Pure water glass is a colorless, transparent, viscous liquid. When it contains oxides of iron, manganese, aluminum, and calcium, it has various colors such as yellow-green, blue-gray, and milky white.
Water glass can be hardened by physical and chemical-physical methods, and can adapt to the diversity of molding and core making processes. The wide range of production applications is the greatest advantage and feature of water glass. In terms of molding sand technology, there are self-hardening sand process, cold core box core shooting process, and precision casting process (investment casting process) that are suitable for large-scale mechanized assembly lines, as well as CO2 blowing hardening technology that is suitable for various scales and manual operation, and can even be used for special, three-dimensional rapid direct molding technology without molds;
In terms of products, it can be applied to various types of castings such as stainless steel castings, alloy steel castings, and carbon steel castings. It has been successfully applied to the production of small precision castings with a mass of grams to super-large steel castings with a mass of 400t.
Sodium silicate has a low melting point and softens at high temperatures, which makes the sand mold have better yield at high temperatures and can reduce the thermal cracking defects of castings. However, since water glass melts at high temperatures and can promote the sintering of silica sand, the initial CO2 blowing hardened water glass molding sand has high residual strength and poor collapsibility after pouring due to the high amount of water glass added. The processes such as organic ester water glass self-hardening sand, vacuum replacement hardening (VRH) method and microwave drying method developed in the mid-to-late 20th century have greatly reduced the amount of water glass added to the molding sand and significantly improved the collapsibility of the molding sand. After that, the regeneration of old sand of organic ester water glass self-hardening sand has also been improved through several stages of improvement such as dry method, hot method and wet method.
With the rapid development of science and technology in modern society and the significant improvement of people's awareness of environmental protection, the use of green and clean production technology in casting production has gradually become a consensus among the majority of foundry workers. The molding sand and core sand process with water glass as a binder has basically achieved harmlessness, low cost and resource recycling, becoming a green, clean and sustainable casting production technology.
Compared with many organic binders, water glass has two major advantages:
① It is environmentally friendly and harmless to the human body. It does not produce any harmful gases to the human body during the production process of sand mixing, molding, pouring, and old sand regeneration, and can achieve clean and harmless production.
② Rich resources and low prices.
Post time: Jun-10-2025