Provided is a method of producing foamed sand (s) for forming a sand mold. The foamed sand (s) includes sand particles (p) and foam (f) adhering to surfaces of the sand particles (p). The foam (f) contains water glass (b), water (w), and a surfactant (c). According to the method, an aqueous surfactant solution (e) in which the surfactant (c) is dissolved is frothed to generate froth (d) from the aqueous surfactant solution (e). Then, the generated froth (d), the water glass (b), and the water (w) are kneaded with the sand constituted by the sand particles (p).

Provided is a method of producing foamed sand (s) for forming a sand mold. The foamed sand (s) includes sand particles (p) and foam (f) adhering to surfaces of the sand particles (p). The foam (f) contains water glass (b), water (w), and a surfactant (c). According to the method, an aqueous surfactant solution (e) in which the surfactant (c) is dissolved is frothed to generate froth (d) from the aqueous surfactant solution (e). Then, the generated froth (d), the water glass (b), and the water (w) are kneaded with the sand constituted by the sand particles (p).

The invention relates to a method for more quickly producing molds (2) or cores (2) for foundry purposes by adapting the specific electrical resistance in the selection of the core box to the mixture (9) of a molding material and of a water-containing binder, which binder, when dissolved, forms an electrolyte and has a sufficient electrical conductivity. It is essential to the invention that an electrically conductive material (7) for holding the mixture (9) is introduced into an electrically non-conductive housing (3), wherein the specific electrical conductivity of the material (7) at operating temperature (7) at least approximately corresponds to the specific electrical conductivity of the mixture (9) at temperatures between 100 C. and 130 C., and that electrical energy and thus heat are supplied to the material (7) via electrodes (10) arranged in/on the housing (3) (resistance heating principle), leading to curing of the mixture (9). Depending on the sand core, up to 30% shorter cycle times can be achieved.

The invention relates to a method for more quickly producing molds (2) or cores (2) for foundry purposes by adapting the specific electrical resistance in the selection of the core box to the mixture (9) of a molding material and of a water-containing binder, which binder, when dissolved, forms an electrolyte and has a sufficient electrical conductivity. It is essential to the invention that an electrically conductive material (7) for holding the mixture (9) is introduced into an electrically non-conductive housing (3), wherein the specific electrical conductivity of the material (7) at operating temperature (7) at least approximately corresponds to the specific electrical conductivity of the mixture (9) at temperatures between 100 C. and 130 C., and that electrical energy and thus heat are supplied to the material (7) via electrodes (10) arranged in/on the housing (3) (resistance heating principle), leading to curing of the mixture (9). Depending on the sand core, up to 30% shorter cycle times can be achieved.

The present invention provides a curing agent for casting a water glass, including an ester and an amorphous silicon dioxide obtained by a thermal decomposition of ZrSiO.sub.4; and the curing agent for casting the water glass does not contain water. According to the present invention, the curing agent for casting the water glass has a strong adhesion-enhancing effect and a long shelf life, and is easy to use.

The present invention provides a curing agent for casting a water glass, including an ester and an amorphous silicon dioxide obtained by a thermal decomposition of ZrSiO.sub.4; and the curing agent for casting the water glass does not contain water. According to the present invention, the curing agent for casting the water glass has a strong adhesion-enhancing effect and a long shelf life, and is easy to use.

The subject matter of the invention is mold material mixtures for producing molds or cores for metal casting, consisting of at least one refractory base mold material, a binder and an additive based on factice. The invention also relates to a component system, a method for producing molds and cores using the mold material mixtures or the component system respectively, and to molds and cores produced by said method.

A foundry mixture for making molds used for molding cast metal parts includes foundry sand, a non-aqueous binder, and a cleaning agent that includes calcium oxide. Residual foundry mixture remaining on the cast part after removal from the mold is removed by electrolytic cleaning of the cast part.

A foundry mixture for making molds used for molding cast metal parts includes foundry sand, a non-aqueous binder, and a cleaning agent that includes calcium oxide. Residual foundry mixture remaining on the cast part after removal from the mold is removed by electrolytic cleaning of the cast part.

A method of casting an article from a molten metal including: admitting molten metal to a mould formed from a foundry sand comprising a blend of silica sand and a zircon aggregate, the zircon aggregate exhibiting a sharp rise in linear thermal expansion coefficient in a temperature band above 1200 C. and up to 1600 C.; and cooling the mould and molten metal to solidify the molten metal and form a cast article, wherein one or more surfaces of the mould, or of a portion of the mould, in contact with the molten metal are uncoated.