Described is a method of preparing a particulate refractory composition for use in the manufacture of foundry moulds and cores from spent foundry moulds or cores formed of refractory material and a binder containing water glass, the method comprising the following steps: providing broken material from spent foundry moulds or cores or preparing broken material from spent foundry moulds or cores, wherein the broken material comprises particles and/or aggregates of particles of refractory material having hardened water glass binder on their surface, mixing the broken material with particulate amorphous oxide comprising silicon dioxide in an amount of 85% by weight or more, based on the total amount of the particulate amorphous oxide, to give a mixture and subjecting the mixture to a heat treatment at a temperature of 400° C. or higher. Also described are a corresponding use, a reclamation mixture, and a method of making a foundry mould or core.

A method of preparing a unique foundry premix composition that has a low bulk density of 30-45 lbs/ft.sup.3 and contains fine particles with an average particle size of 85-100 μm is described. The unique foundry premix composition is produced by using specially designed assemblies of mechanical equipment with improved efficiency so that the premix can be prepared at a site closer to a foundry. As a result, increase in premix density caused by handling and shipping across a long distance from a traditional premix manufacturing facility to a foundry can be suppressed; transportation cost can be saved; and safety would be of less concern. The use of the foundry premix composition to prepare a sand molding medium for casting molded articles is also described.

A method of preparing a unique foundry premix composition that has a low bulk density of 30-45 lbs/ft.sup.3 and contains fine particles with an average particle size of 85-100 μm is described. The unique foundry premix composition is produced by using specially designed assemblies of mechanical equipment with improved efficiency so that the premix can be prepared at a site closer to a foundry. As a result, increase in premix density caused by handling and shipping across a long distance from a traditional premix manufacturing facility to a foundry can be suppressed; transportation cost can be saved; and safety would be of less concern. The use of the foundry premix composition to prepare a sand molding medium for casting molded articles is also described.

A casting core for casting moulds can include a central core and a core shroud arranged around the central core. The core shroud containing contains or consists of ceramic particles bound to a binder. The central core contains ceramic particles bound to a binder, wherein the ceramic particles of the central core contain at least one component, which exhibits, at a temperature in a range from 100° C. to 1500° C., a thermally induced phase transformation, and/ or at least two components, the thermal expansion coefficients of which at 20° C. differ by at least 5.Math.10.sup.−6K.sup.−1.

A casting core for casting moulds can include a central core and a core shroud arranged around the central core. The core shroud containing contains or consists of ceramic particles bound to a binder. The central core contains ceramic particles bound to a binder, wherein the ceramic particles of the central core contain at least one component, which exhibits, at a temperature in a range from 100° C. to 1500° C., a thermally induced phase transformation, and/ or at least two components, the thermal expansion coefficients of which at 20° C. differ by at least 5.Math.10.sup.−6K.sup.−1.

Provided are: a mold material having improved fluidity and being capable of improving a filling rate of a forming mold during formation of a casting mold; and a mold material that gives cast products a favorable casting surface, effectively improves sand adhesion on cast products, and advantageously provides a casting mold having excellent strength. The mold material is formed as a coated sand in a wet state with spherical particles of silicone resin having binder repellency existing on its surface, by at least mixing a water-soluble inorganic binder in the liquid state having a viscosity of not more than 1000 cP, and the spherical particles of silicone resin, with a refractory aggregate.

Provided are: a mold material having improved fluidity and being capable of improving a filling rate of a forming mold during formation of a casting mold; and a mold material that gives cast products a favorable casting surface, effectively improves sand adhesion on cast products, and advantageously provides a casting mold having excellent strength. The mold material is formed as a coated sand in a wet state with spherical particles of silicone resin having binder repellency existing on its surface, by at least mixing a water-soluble inorganic binder in the liquid state having a viscosity of not more than 1000 cP, and the spherical particles of silicone resin, with a refractory aggregate.

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.

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 casting mould comprising: an inorganic or refractory mould, wherein the mould is configured to receive feedstock; wherein the feedstock is configured to be heated in situ. A reusable mould, reusable susceptor, and/or release agent may be incorporated. Method of manufacturing a mould, and casting a part employing 5 in situ heating, are also provided.