An aggregate mixture for a mold, the aggregate mixture including an aggregate, a water-soluble binder, a water-soluble foaming agent, an aqueous mold release agent, and water.

The present invention relates to the selection of materials for methods for producing moulds (2) or cores (2) for foundry purposes. When selecting the core box material, a special ceramic, such as for example silicon carbide or silicon nitride, is used instead of metals such as steel or aluminium. It is essential for the inventionthat a material (7) for receiving the mixture (9) is introduced into a housing (3), the material consisting of silicon carbide or silicon nitride, that electrical energy is supplied to the material (7) by way of electrodes (10) arranged in/on the housing (3) and in this way heat is supplied, leading to curing of the mixture (9). This allows longer service lives to be achieved for the core boxes as a result of low abrasive wear.

Provided are: a coated sand having improved fluidity and being capable of improving a filling rate of a casting mold to be obtained; and a coated sand for advantageously manufacturing a casting mold having excellent strength, which coated sand provides a casting mold with good mold-releasability and collapsibility, gives cast products a favorable casting surface, and effectively improves sand adhesion on cast products. The coated sand is formed as a dry granular material having fluidity at room temperature, in which the surface of a refractory aggregate is coated with a solid layer of a water-soluble inorganic binder, and spherical particles of silicone resin having binder-repellency exist on the surface of the binder layer, or form a layer on the surface of the binder layer, a part of the spherical particles being not covered with the water-soluble inorganic binder and being exposed.

A moulding material mixture with at least one refractory material and water glass as an inorganic binding agent is used for producing casting moulds. The binding agent is cured with the aid of a carbonyl compound that has a molecular weight greater than 88 g/mol and less than 200 g/mol and a boiling point at 1013 hPa greater than 20 C. and less than 200 C. The at least one carbonyl compound is introduced into the gas phase, or carried with the gas phase. The at least one carbonyl compound has the formula R.sup.1R.sup.2CO, where R.sup.1 is H or a C1 or C2 alkyl and R.sup.2 is a carboxyl group RC(O)O bonded via the oxygen atom, where R is a C1 to C3 hydrocarbon.

A method of reusing core sand includes crushing a core used for casting into granules, the core includes water glass as a binder, and the water glass includes water-soluble water glass and water-insoluble water glass; heating the core; detaching the water glass from the core sand; and separating and collecting the core sand from a mixture of the water glass and the core sand.

A method for inorganic binder casting, comprising: selecting a Shape-Forming Material based on pre-determined manufacturing and shape characteristics, selecting a casting shape based on pre-determined design characteristics, and forming the Shape-Forming Material into a mold. The mold is coated with an inorganic binder solution at a pre-defined weight ratio and is dehydrated the Shape-Forming Material. The method further comprises pouring a hot liquid metal into the mold and allowing said hot liquid metal to cool to form a molded part. The Shape-Forming Material may be washed from said molded part with a solvent, the inorganic material and Shape-Forming Material reclaimed, reused, and the Shape-Forming Material reformed to a mold. The method further comprises recreating a liquid inorganic binder solution using the reclaimed inorganic material and recoating the Shape-Forming Material with the reclaimed inorganic binder solution.

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.

To provide a binder composition for molding, by which a mold made of aggregate has an excellent resistance to moisture. The binder composition for molding contains a water-soluble binder and at least one kind of lithium salt that is selected from a group of lithium silicate, lithium oxide, lithium hydroxide, lithium carbonate, lithium bromide, lithium chloride, lithium nitrate, and lithium nitrite.

A method of reusing core sand includes crushing a core used for casting into granules; heating the granules at a temperature of 300 C. to 550 C.; causing the heated granules to collide against each other such that water glass used as a binder detaches from the core sand; and blowing air into a mixture of the water glass and the core sand, which are detached from each other, such that the core sand is separated and collected from the mixture due to a difference in specific gravity between the water glass and the core sand.

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.