Water glass casting is not an independent casting process. Water glass is widely used in the field of casting, and it is mainly used to make the adhesives in sand mold or sand shell.

Water glass castings have low production costs, short production cycle, and the product surface quality is poor, so it is mainly used for carbon steel and low alloy steel castings; The surface quality of silica sol product is good, but it needs long production cycle, high costs, so it is mainly used for high-alloy steel and stainless steel products.

Water glass casting refers to the process in which water glass is added into the molding materials in proportion (usually silica sand) and then gets stirred and mixed for 6-8 min, and then grinded into “sodium silicate-bonded sand”. Then the sand is put into the mould boxes in which CO2 has been much blown into. CO2 starts the chemical reaction with the water glass to form the silica gel which hardens the sodium silicate-bonded sand. Then the whole casting process is complete after drawing, mould assembling and pouring procedures.

Sodium silicate [Na2SiO3 or (Na2O)(SiO2)] is a high strength binder used with silica molding sand. To cure the binder carbon dioxide gas is used, which creates the following reaction:

Na_2 O (SiO_2) + CO_2 \rightleftharpoons Na_2 CO_3 + 2SiO_2 + Heat

The advantage to this binder is that it can be used at room temperature and it's fast. The disadvantage is that its high strength leads to shakeout difficulties and possibly hot tears in the casting.

Water glass casting is widely applied throughout all kinds of departments of the national economy such as automobile castings, engineering machinery castings, agricultural machinery castings, motor castings, elevator castings, fire control, metal castings and ship castings. As for the agricultural machinery castings, there are a lot of machines and accessories made through the water glass casting like the principal axis of draught fans and parts of the tractors. Water glass casting can reduce costs of making general agricultural mechanical parts especially with low production precision and surface finish degree like carbon steel castings such as shifting fork, pin roll, blunt extension, boxes, chain wheel, etc.