The present invention refers to a stable sodium and iron silicate solution that has a weight ratio of SiO.sub.2 to Na.sub.2O from 1.5 to 2.5 and a total percentage of solids, expressed by the sum of SiO.sub.2 and Na.sub.2O, from 20% to 55%. Said solution also has a soluble iron content, expressed by Fe, from 0.1% to 7%, and a water content from 38% to 79.9%. The present invention also refers to the process for preparing said stable solution of sodium and iron silicate, which comprises the steps of: (a) providing a siliceous material containing iron; (b) submitting said siliceous material containing iron to a hydrothermal treatment with caustic soda under high temperature and controlled pressure; and (c) filtering said reacted solution to separate the reacted portion of the hydrothermal treatment from the unreacted portion. Additionally, the present invention refers to the uses of said stable sodium and iron silicate solution.

The invention relates to a binder, which contains water glass and further a phosphate or a borate or both. The invention further relates to a method for constructing molds and cores layer by layer, the molds and cores comprising a construction material mixture, which at least comprises a refractory molding base material, and the binder. In order to produce the molds and cores layer by layer in 3-D printing, the refractory molding base material is applied layer by layer and is selectively printed with the binder layer by layer, and consequently a body corresponding to the molds or cores is constructed and the molds or cores are released after the unbonded construction material mixture has been removed.

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 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.

A surfactant composition for a formed sand including 80 to 99.8 mass % of a compound (A) represented by formula (1); 0.1 to 10 mass % of a compound (B) represented by formula (2); and 0.1 to 10 mass % of an amphoteric surfactant (C):

R.sup.1O-(EO).sub.n—SO.sub.3M.sup.1  (1)

wherein R.sup.1 represents a hydrocarbon group having 6 to 22 carbons, EO represents oxyethylene group, n is 1 to 10, and M.sup.1 represents an alkali metal, an alkaline earth metal, ammonium or an organic ammonium;

R.sup.2O—SO.sub.3M.sup.2  (2)

wherein R.sup.2 represents a hydrocarbon group having 6 to 22 carbons, and M.sup.2 represents an alkali metal, an alkaline earth metal, ammonium or an organic ammonium.

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.

The invention relates to a composition for forming a casting mold, the composition containing heat-resistant inorganic particles; a waterglass-based binder; a surfactant; a silicon-containing compound; activated carbon powder and grain; and water; and the silicon-containing compound contains at least one of metal silicon and ferrosilicon.

What is described is a process for producing an article for use in the foundry industry, selected from the group consisting of molds, cores, feeder elements and molding material mixtures, comprising the following steps: (S1) producing or providing a binder system comprising the following components in three spatially separate vessels: a component (A) comprising particulate amorphous silicon dioxide, a first liquid component (B) comprising waterglass, and a second liquid component (C) comprising aluminate ions dissolved in an aqueous phase, (S2) contacting a mold base material (D) and constituents of all the said components (A), (B) and (C) of the binder system in predetermined ratios in one or more steps, so as to result in a molding material mixture in which the aluminate ions and the particulate amorphous silicon dioxide are mixed wholly or partly into the waterglass, wherein steps (S1) and (S2) are conducted in a facility for producing molding material mixtures. Also described are a corresponding molding material mixture and apparatuses and uses

The present invention refers to a stable sodium and iron silicate solution that has a weight ratio of SiO.sub.2 to Na.sub.2O from 1.5 to 2.5 and a total percentage of solids, expressed by the sum of SiO.sub.2 and Na.sub.2O, from 20% to 55%. Said solution also has a soluble iron content, expressed by Fe, from 0.1% to 7%, and a water content from 38% to 79.9%. The present invention also refers to the process for preparing said stable solution of sodium and iron silicate, which comprises the steps of: (a) providing a siliceous material containing iron; (b) submitting said siliceous material containing iron to a hydrothermal treatment with caustic soda under high temperature and controlled pressure; and (c) filtering said reacted solution to separate the reacted portion of the hydrothermal treatment from the unreacted portion. Additionally, the present invention refers to the uses of said stable sodium and iron silicate solution.