The invention relates to a casting core for casting moulds, wherein the casting core comprises a central core and a core shroud arranged around the central core. The core shroud contains or consists of ceramic particles bound to a binder. The central core contains or consists of ceramic particles bound to a binder, wherein the ceramic particles of the central core contain or consist of 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.10−6 K−1. The invention further relates to a method for producing the casting core according to the invention and the use of the casting core according to the invention.

The invention relates to a method for producing core sand and/or molding sand for casting purposes. A granular mineral mold base material is mixed with at least one inorganic binder and additionally an inorganic expanding additive. Water glass may be used as the binder and expandable graphite may be used as the expandable additive.

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 high-temperature-resistant casting system comprises following casting elements in a connection relationship: a sprue cup (1) and a down sprue (2) connected with a lower end of the sprue cup, wherein the other end of the down sprue is connected with one end of a filtering element (6), the other end of the filtering element is connected with a three-way pipe (3), openings in two sides of the three-way pipe are connected with one end of an inlet section of a runner (4), and one end of an outlet section of the runner is connected with a tapered elbow (5). The casting elements comprise the following components in percentage by weight:41-51% of a refractory fiber, 40-51% of a silicate fiber and 5-19% of a binder. A preparation method of the high-temperature-resistant casting system is further provided.

A high-temperature-resistant casting system comprises following casting elements in a connection relationship: a sprue cup (1) and a down sprue (2) connected with a lower end of the sprue cup, wherein the other end of the down sprue is connected with one end of a filtering element (6), the other end of the filtering element is connected with a three-way pipe (3), openings in two sides of the three-way pipe are connected with one end of an inlet section of a runner (4), and one end of an outlet section of the runner is connected with a tapered elbow (5). The casting elements comprise the following components in percentage by weight:41-51% of a refractory fiber, 40-51% of a silicate fiber and 5-19% of a binder. A preparation method of the high-temperature-resistant casting system is further provided.

What is described is the use of a particulate material comprising, as its sole constituent or as one of multiple constituents, a particulate synthetic amorphous silicon dioxide having a particle size distribution with a median in the range from 0.1 to 0.4 μm, determined by means of laser scattering, as additive for a molding material mixture at least comprising: a refractory mold base material having an AFS grain fineness number in the range from 30 to 100, particulate amorphous silicon dioxide having a particle size distribution with a median in the range from 0.7 to 1.5 μm, determined by means of laser scattering, and water glass, for increasing the moisture resistance of a molding producible by hot curing of the molding material mixture. Also described are corresponding processes, mixtures and kits.

What is described is the use of a particulate material comprising, as its sole constituent or as one of multiple constituents, a particulate synthetic amorphous silicon dioxide having a particle size distribution with a median in the range from 0.1 to 0.4 μm, determined by means of laser scattering, as additive for a molding material mixture at least comprising: a refractory mold base material having an AFS grain fineness number in the range from 30 to 100, particulate amorphous silicon dioxide having a particle size distribution with a median in the range from 0.7 to 1.5 μm, determined by means of laser scattering, and water glass, for increasing the moisture resistance of a molding producible by hot curing of the molding material mixture. Also described are corresponding processes, mixtures and kits.

A chemical regeneration method of water glass used sand is provided in the present disclosure, which belongs to the field of resource recycling in the casting industry. The present disclosure adopts a two-component reagent composed of calcium oxide and tap water, emulsion composed of sucrose and calcium oxide, and calcium chloride aqueous solution to process the regeneration of the used sand, and prepares the sample of the reclaimed sand obtained after the reagent mixed with the used sand is sealed and placed for 0 to 24 hours respectively, and tests the properties of the sample including: initial strength, final strength and collapsibility, and sodium carbonate content, and compares the properties of raw sand and used sand after the tests. Among several regeneration methods, each property index of the reclaimed sand obtained by using calcium oxide and tap water to regenerate for 12 hours is the best.

A chemical regeneration method of water glass used sand is provided in the present disclosure, which belongs to the field of resource recycling in the casting industry. The present disclosure adopts a two-component reagent composed of calcium oxide and tap water, emulsion composed of sucrose and calcium oxide, and calcium chloride aqueous solution to process the regeneration of the used sand, and prepares the sample of the reclaimed sand obtained after the reagent mixed with the used sand is sealed and placed for 0 to 24 hours respectively, and tests the properties of the sample including: initial strength, final strength and collapsibility, and sodium carbonate content, and compares the properties of raw sand and used sand after the tests. Among several regeneration methods, each property index of the reclaimed sand obtained by using calcium oxide and tap water to regenerate for 12 hours is the best.