MX2014012219A

MX2014012219A - Salt-based cores, method for the production thereof and use thereof.

Info

Publication number: MX2014012219A
Application number: MX2014012219A
Authority: MX
Inventors: Thorsten Hartig
Original assignee: Emil Müller GmbH
Priority date: 2012-04-10
Filing date: 2013-04-10
Publication date: 2015-06-05
Also published as: EP2836318A2; CN104428082A; US20150060005A1; WO2013152851A2; DE102013006135A1; WO2013152851A3; RU2014144721A

Abstract

Cores that are inserted into the mould during the die casting of workpieces from metal in order to keep the cavities provided in the workpieces free during the filling of the moulds with the melt have to meet demanding requirements with regard to their dimensional stability and suitability for removal from the cavities. Therefore, salt-based cores which can be produced by moulding and compressing a core material mixture are provided according to the invention, the core materials thereof being selected from at least one salt, at least one binder system comprising a combination of binder/binding agent and possibly auxiliary substances such as additives, fillers, wetting agents and catalysts, wherein the salt, the binder system and the possibly used auxiliary substances of the core material mixture are inorganic and these core materials are soluble with water as the solvent.

Description

SALINE BASE NUCLEI, METHOD FOR THE PRODUCTION OF SAME AND USE OF THESE The invention relates to salt-based nuclei, with methods for producing the salt-based nuclei, and with the use of such nuclei as indicators of the cavity in the production of cast metal parts, preferably in the emptying technology in permanent molds, which can be completely and easily removed from the workpieces using solvents, without any remaining solid residue.

The cores that are inserted into the molds when workpieces made of metal are emptied, to maintain the cavities provided in the free workpieces when the molds are filled with the cast iron are subjected to demanding requirements. The cores must be easy to produce, dimensionally stable and have precise contours, and the materials used to produce them and the solvents that dissolve them should not adversely affect the quality of the emptying or the environment, and should not they must cause no danger to health.

If special demands are placed on the accuracy of the surface and contour of the workpiece cavities, the surface of the cores must be particularly smooth, and have precise contours, and the Nuclei should be completely dissolved in a suitable solvent and be easy to remove from the cavities of the workpieces, without any remaining solid residue. Waste from cores that contain insoluble components, such as silica sand, can result in damage to the surfaces to be terminated, or cause the units to fail, for example, when the core residue results in the blockage of a injection nozzle in the common rail system of a diesel engine.

Saline-based cores that withstand both extreme thermal stresses and mechanical stresses that occur during overvading with meltable metals, and cores that not only have high strength, but can also be easily removed from the emptied part after the emptying process, and leave the smooth surface finish as best as possible in the emptied part; they can now be produced using the so-called dry pressing process, without a subsequent sintering or recrystallization process.

It is the object of the present invention to produce salt-based cores having low porosity, a good surface quality and the highest possible strength, and that can be removed easily and completely from the work pieces after the pieces of work have been emptied.

It is a further object of the present invention producing such cores in a formation method, which is as simple and as cost effective as possible, preferably using the so-called dry pressing method.

It is a further object of the present invention to improve this method of dry pressing and to provide cores that have a considerably improved strength, and yet, are easily removed from the cast part after casting, and which leave a smooth smooth finish in the part emptied.

According to the invention, these objects are achieved by the main claim and by the method according to claim 31. Advantageous embodiments of the invention are characterized in the dependent claims.

The cores according to the invention are composed of a salt, with which a special binder system can be mixed, and optionally auxiliary substances such as fillers, additives, wetting agents and catalysts. These cores are preferably intended for workpieces that are emptied of non-ferrous metals, such as aluminum, brass or copper, using the permanent casting method. The cores according to the invention are composed of substances that can be removed from the cavities of the work pieces without leaving any residue, using water, which is usually preferred for reasons of environmental protection.

The cores according to the invention have the advantage that they are composed of substances (core materials) which, when properly handled, do not have reactions that release gas that could harm the environment, neither during the production of the same nor during the emptying process. Furthermore, since cracking products of an organic binder do not develop during casting, the quality of the cast parts is improved due to the fact that defects of the casting such as holes, pores of the gas or the like resulting from the Released core gases can be avoided. No waste is created that requires special waste during the removal of the cores from the work pieces. Depending on the composition, substances can be recovered from the liquid phase using appropriate methods; for example, salt can be recovered by spray drying or concentration.

All the compositions of the core materials can be processed in conventional mechanical or hydraulic presses by compaction. The complexity of the geometry of the cores determines the manufacturing parameters, as well as the configuration and design of the tool used to produce the cores and the press.

Suitable materials for the cores according to the invention are salts of alkaline elements and alkaline earth elements, such as, in particular, sodium chloride, potassium chloride and magnesium chloride, sulfates and nitrates of the alkali elements and alkaline earth elements , such as in particular, potassium sulfate, magnesium sulfate, as well as ammonium salts, such as, in particular, ammonium sulfate. Water-soluble compounds of these core materials are preferred. These substances can be used individually or as mixtures, provided that they do not react with each other, and therefore adversely affect the desired properties, since the core material must not undergo any transformation of the substance during the core production, which would adversely affect the waste-free removal of the core material. In general, all readily soluble salts having a decomposition or melting point above the temperature of the liquid molten metal are suitable. Similar to sand, core materials can be easily and simply divided into the desired particle size or grain size classes. The distribution of the selected grain size and the selected degree of compaction influence, in particular, the surface finish of the cores. The smaller the grain size, the smoother It will be the surface. In general, since the highest degree of compaction is desirable, which can be achieved by mixing different salts, and optionally additional substances, having different distribution curves, for example, by a bimodal or trimodal grain size distribution in the mixture.

According to the invention, grain sizes in the range of 0.01 mm to 2 mm are preferred, depending on the core material and the quality of the desired surface, and the accuracy of the contour of the workpiece to be emptied. Depending on the degree of compaction, the grain size fractions of 0.01 mm to 0.29 mm, 0.3 mm to 1.3 mm and / or 1.31 mm to 2.0 mm, are mixed in different proportions.

Fillers, which can likewise be completely removed without leaving any residue when water is used as the solvent, can optionally replace a portion of the salt, to the extent that the density and strength are not adversely affected. According to the invention, it has been shown that as much as 30% by weight of the salt can be replaced with appropriate fillers. The grain size of the filling coincides advantageously with the grain size or the grain size distribution of the salt.

Therefore, to ensure the necessary stability of the nuclei after the training process, less an adequate binder system is added to the salt before compaction.

The approach according to the invention to achieve the object underlying the invention provides for the use of a special binder system comprising a binder / agglutination agent and a drying agent adapted thereto.

Essentially, all the binding / binding agents which after the curing process can be removed without leaving any residue, use water as the solvent, and wet the salt and optionally additional substances, can be used in this binder system according to the invention , where the mixture of these substances must be moldable in the loose nuclei by means of compaction. In general, inorganic phosphates, inorganic borates, silicate compounds or mixtures of these binding agents are suitable as binders / agglutination agents, if they can be removed without leaving any residue, using water as the solvent. For example, alkaline phosphate or monoaluminum ammonium phosphate phosphate, boron phosphate, trisodium phosphate, tetrapotassium pyrophosphate or sodium polyphosphate can be used as the inorganic phosphate.

Agglutination / agglutination agents made of water-soluble silicates, such as sodium silicate Water soluble, having a sodium silicate module of 1 to 5, are preferably used, wherein the sodium silicates having different sodium silicate modules, can also be present as a mixture. The amount added depends on the sodium silicate module that is used and, depending on the wetting behavior, is between 0.5% by weight and 15% by weight, preferably between 5% by weight and 8% by weight. Therefore, to achieve the properties necessary for the subsequent pouring process, such as strength and dimensional stability, it is also possible to use special binder blends.

For further processing of the core material to form the useful core, the manner in which the core material is present is of essential importance. If solid core materials are required, as in the case of the present invention, it is crucially important that the core materials are present in agglomerated or deagglomerated form, and that they are present in free flowing form. Only the mixtures of the free-flowing core materials are capable of filling independently and completely the so-called filling shoes used in the dry pressing method, the preferred forming method according to the invention. Only the free-flowing mixtures that comprise the salt, the binder system that is used, and the other mixed substances, are therefore useful as the core material for use in the dry pressing method.

However, in order to substantially improve the core materials useful for the dry pressing method in the manner according to the invention, it is also important to improve the ability to flow freely of the core materials, in particular, when the binder agents are used / of agglutination mentioned above.

This is achieved surprisingly according to the invention, by adding suitable drying agents in appropriate amounts, as a function of the selected binding / binding agents. The combination of binder / agglutination agents and the drying agent forms the special binder system, provided according to the invention. This binder system allows, surprisingly, that the underlying object of the invention be achieved.

All hydrophilic substances which are capable of reversibly binding to water, ie, which are capable of releasing the water absorbed through suitable treatment, are suitable as drying agents which can be used according to the invention. According to the invention, for example, finely dispersions, such as Aerosil, silica gel, zeolites, anhydrous sodium sulfate and / or magnesium sulfate can be used. Due to the chemical and structural properties of these drying agents, they trap water molecules and subsequently change their physical molecular structure due to intermolecular forces. The water molecules therefore can not escape from the structure and remain together during the preparation of the core materials. The bound water can be released again by the application of heat.

According to the invention, the amount of the aggregate drying agents is always dependent on the type and amount of binder / agglutination agents used, and can be easily determined by simple experimentation. A slight overdosing of the drying agent can be tolerated.

For example, when 1 to 5% by weight of sodium silicate is used as the binder / agglutination agent, based on the amount of salt used, 0.3 to 1.5% by weight of Aerosil, based on the amount of salt which is used, it is sufficient as the drying agent that can be used according to the invention, not only to ensure the ability to flow freely from the core material, but also to allow an improvement in the ability to flow freely from the core material, in comparison with core materials comprising from 1 to 5% by weight of sodium silicate as the binder / agglutination agent, based on the amount of salt used, but not comprising the drying agent.

By using the special binder system according to the invention, which comprises the combination of the binder / agglutination agent and the drying agent, it is also possible, for the first time, to use binders / agglutination agents in liquid form, in the preparation of the core materials. The wetting of the constituents of the core material with the binder / agglutination agent is considerably improved due to the use of liquid binders / agglutination agents. The constituents of the core material, in particular the salt grains which are surrounded by the binder / agglutination agent, are therefore coated. The result is a finished salt core that has considerably improved strength. According to the invention, for example, an aqueous 60% tetrapotassium pyrophosphate solution can be used as the liquid binder. Based on the amount of salt used, 1 to 5% by weight, preferably 2 to 4% by weight, and particularly preferably 2.5% by weight, of an aqueous 60% tetrapotassium pyrophosphate solution is added in this variant. To still ensure the ability to freely desired flow of the core material, the drying agent that is provided according to the invention, is added in a sufficient amount to the central material coated in this way with the binder. A slight overdosing of the drying agent can be tolerated in this case as well.

It is particularly advantageous when the tetrapotassium pyrophosphate in solid form is additionally added to the 60% tetrapotassium pyrophosphate aqueous solution in the same amount, or also in a larger amount.

The properties of the mixture according to the invention comprising the salt, optionally auxiliary substances such as additives, fillers, wetting agents and / or catalysts, and the special binder system according to the invention, can be influenced by the selected addition of additives . Here also, the prerequisite is that these additives, or the reaction products of these additives, can be completely removed from the cavity of a workpiece without difficulty and without leaving any residue, using water as the solvent, and that during emptying, no gases are released that damage the emptying process, which could result in defects in the emptying. Depending on the composition of the core materials, these additives can be selected from: wetting agents, for example, surfactants, additives that influence the consistency of the mixture, lubricants, additives for deagglomeration, gelling agents, additives that modify the thermophysical properties of the core, for example, thermal conductivity, additives that prevent the metal from adhering to the cores, additives that result in a homogenization and Improved miscibility, additives that increase shelf life, additives that prevent premature curing, additives that prevent the formation of smoke and condensates during emptying, and additives that result in accelerated curing. These additives are known to a person with experience in the production of conventional cores. The amount added depends on the type and composition of the core material.

Therefore, to further improve the strength required after dry pressing, it may be necessary, depending on the composition of the core material, to employ catalysts which adapt to the core material and which initiate and accelerate the curing of the core material.

It has been surprisingly shown that the addition of a particular fine grain salt, and preferably the addition of a powder salt having a particle size of less than 100 nm, acts as a catalyst for curing.

If gaseous catalysts are used in accordance with In the invention, the gas influencing the core material, preferably CO2 or air, can be blown into the mold while it is still closed after dry pressing, in particular to cure and dry the cores. The pressure can be as high as 5 bar.

It is also possible to carry out the thermal after-treatment of the cores at temperatures of up to 600 ° C, preferably at temperatures between 500 ° C and 600 ° C, and particularly preferably at temperatures of 580 ° C.

The central material is composed of the salt and the binder system and, if necessary, the additional substances such as fillers, additives and catalysts, where the fillers and binder system are inorganic. All substances can be mixed homogeneously using known mixing units. The aggregate amounts of the binder system and the additional substances should be selected as a function of the intended purpose of the cores, and determine the quality of the surface, as well as the density and strength of the cores.

The preparation of the core materials takes place separately from the manufacturing process, where optionally suitable protective measures may have to be provided to prevent agglomeration and premature curing. For example, depending on the composition of the Central material, preparation, transport and storage can also have logar under a protective gas or vacuum.

The composition and properties of a core decisively influence the quality of the cast part.

The salt-based sodium chloride cores produced according to the invention typically have a density of 1.5 g / cm3 to 1.9 g / cm3, and preferably 1.2 g / cm3 to 1.8 g / cm3, determined in accordance with the flotation method. This corresponds to a porosity of 10% to 35%, and preferably, 5% to 25%. The resistance to bending, measured in accordance with Technical Bulletin P73 of the VDG (German Association of Foundry Experts), is between 400 N / cm2 and 1500 N / cm2.

The most important properties are therefore, discussed below, based on an exemplary embodiment. The described properties refer to nuclei that are not coated with a black wash.

A core made of NaCl is used, which comprises additional substances such as sodium silicate binder, Aerosil as the drying agent, and additional added substances, such as release agents, retarding agents, wetting agents and the like. The core was formed at a pressure of 50 to 120 bar in a hydraulic press. The core was subjected to thermal after-treatment for 60 minutes at 580 ° C for curing. The present core is particularly suitable for use in casting permanent aluminum mold. The core must be dimensionally stable in order to be able to withstand the temperatures and forces that occur during emptying. The mechanical properties of the core were determined using a sample of 180 mm long, 22 mm wide and 22 mm high. The resistance to bending, measured according to Technical Bulletin P73 of the VDG (February 1996), was between 400 N / cm2 and 1500 N / cm2.

The core surface should not be removed from damage when the metal flows. For this reason, the core must have an appropriate surface resistance. Porosity also plays a vital role. The porosity in the present exemplary embodiment is 30%.

After the emptied part has solidified completely, the core must be removed. It is important that the core dissolves immediately, completely and easily without leaving any solid residue. (Note: If, within the scope of the present invention, the terms "water soluble", "dissolve" or "completely dissolve" are mentioned, this does not necessarily refer to the chemical concept of dissolving.) The decisive factor is that the constituents of the cores according to the invention can be removed from the cavity of a workpiece easily, completely, and without leaving any residue, using water as the solvent). By nature, the dissolution rate of the core depends on the core materials and the pretreatment of the core, as well as the size of the core. For pure salt, the rate of dissolution can deviate from that of a composition comprising binders and fillers. Experiments performed with a test part have shown that a core having the dimensions of 22 mm x 22 mm x 180 mm can be completely removed from the part emptied with hot water in the course of 1 minute to 2 minutes.

Based on the above discussion, the teachings according to the invention relate to salt-based nuclei > which can be produced by forming and compacting a mixture of core material, the core materials of which are selected from at least one salt, at least one binder system comprising a binder / agglutination agent and a drying agent, and optionally auxiliary substances such as additives, fillers, wetting agents and catalysts, where the salt, the binder system and the auxiliary substances optionally used are inorganic, these core materials can be dissolved using water as the solvent, and the mixture of core material is formed into cores and compact in a dry pressing method.

The preferred cores are those made from a mixture of core materials > in which salts are used that have a point of decomposition or melting above the temperature of the liquid metal that is poured around the nuclei; > in which the salts used are chlorides of the alkali elements and alkaline earth elements, in particular sodium chloride, potassium chloride and / or magnesium chloride, sulfates and nitrates of the alkali elements and alkaline earth elements, in particular potassium sulphate and / or magnesium sulfate, ammonium salts, in particular ammonium sulfate, or mixtures of these salts; > in which the salt is sodium chloride; > in which the grain sizes of the salt used varies from 0.01 mm to 2 mm; > in which the salt used is present in a bimodal or trimodal grain size distribution; > in which the salt used is present in a grain size distribution ranging from 0.01 to 0.29 mm, 0.3 to 1.3 mm and / or 1.31 to 2.0 mm; > in which binders / binders agglutination used in the binder system are inorganic phosphates, inorganic borates or silicate compounds, which can be removed without leaving any residue, using water, or mixtures of these binding / binding agents; > in which the agglutination / agglutination agents used in the binder system are alkaline phosphate or ammonium phosphate, monoaluminium phosphate, boron phosphate, trisodium phosphate, tetrapotassium pyrophosphate or sodium polyphosphate, which can be removed without leaving any residue, using water , or mixtures of these agglutination / binding agents; > wherein the binder / agglutination agents used in the binder system are water soluble silicate compounds, and preferably, sodium silicates; > wherein the binder in the binder system is a sodium silicate having a sodium silicate module of 1 to 5, and / or a mixture of sodium silicates having different sodium silicate modules; > in which the binder / agglutination agent content is between 0.5% by weight and 15% by weight, based on the salt that is used; > in which the content of the agent binder / agglutination is between 0.5% by weight and 15% by weight, based on the salt that is used, as a function of the wetting behavior and the sodium silicate module; > in which the sodium silicate is present as the binder / agglutination agent in a content of 0.5% by weight to 15% by weight, based on the salt used, as a function of the grain size distribution and adapted to the sodium silicate module; > in which the binder in the binder system is tetrapotassium pyrophosphate; > in which the binder used in the binder system is tetrapotassium pyrophosphate in liquid form; > in which the binder used in the binder system is tetrapotassium pyrophosphate in a 60% aqueous solution; > in which the binder used in the binder system is tetrapotassium pyrophosphate in a 60% aqueous solution, and in amounts of 1 to 5% by weight, preferably in amounts of 2 to 4% by weight, and particularly of preferred way, in amounts of 2.5% by weight, based on the amount of salt that is used; > in which the binder used in the binder system is tetrapotassium pyrophosphate in a 60% aqueous solution and in amounts of 1 to 5% by weight, preferably in amounts of 2 to 4% by weight, and particularly preferably, in amounts of 2.5% by weight, based on the amount of salt it is used, and in addition, tetrapotassium pyrophosphate is used in solid form, in the same amount or also in a larger amount; > wherein the binder is present in the binder system at a content of 1 to 15% by weight, based on the amount of salt that is used, and the drying agent is present at a content of 0.3 to 4.5% by weight , based on the amount of salt used; > in which hydrophilic substances which are capable of reversibly binding with water are used in the binder system as drying agents; > in which finely dispersed silicic acids, such as Aerosil, silica gel, zeolites, anhydrous sodium sulfate and / or magnesium sulfate are used in the binder system as drying agents; > in which a catalyst is added as an auxiliary substance; > wherein the catalyst is particularly a fine-grained salt, and preferably, a pulverized salt having a particle size of less than 100 nm; > in which the salt is sodium chloride, which it is preferably present in a bimodal or trimodal grain size distribution, particularly preferably in a grain size distribution of 0.01 to 0.29 mm, 0.3 to 1.3 mm and / or 1.31 to 2.0 mm, the binder system is composed of the combination of sodium silicate as the binder and Aerosil as the drying agent, the catalyst is particularly a fine-grained salt and preferably, pulverized salt having a particle size of less than 100 nm, optionally, are present additional auxiliary substances, such as additives, fillers, wetting agents and / or additional catalysts, and the mixture of the core materials flows freely; > in which the nuclei are treated with heat after forming; > in which, after forming, the cores are heat treated at a temperature of up to 600 ° C, preferably at temperatures of 500 to 600 ° C, and preferably at a temperature of 580 ° C; > wherein the cores formed have a density of 1.5 g / cm3 to 2.1 g / cm3, and preferably 1.2 g / cm3 to 1.8 g / cm3; > in which the formed cores have a porosity of 10% to 40%, and preferably 5% to 25%; > in which the nuclei formed have a Flexural strength of between 400 N / cm2 and 1500 N / cm2.

The teachings according to the invention are further related to: > methods for producing salt-based cores, wherein a mixture of core material, core materials selected from at least one salt, at least one binder system comprising a combination of a binder / agglutination agent and a drying agent, and optionally auxiliary substances such as additives, fillers, wetting agents and / or catalysts, mixed homogeneously, formed in a core, compacted in a dry pressing method, and optionally, heat treated.

The preferred methods are those in which > a salt is used and mixed has grain sizes with different distribution curves, preferably, in a bimodal or trimodal grain size distribution; > the salts are selected from chlorides of the alkali elements and alkaline earth elements, in particular sodium chloride, potassium chloride and / or magnesium chloride, sulfates and nitrates of the alkali elements and alkaline earth elements, in particular potassium sulphate and / or or magnesium sulfate, and ammonium salts, in particular ammonium sulfate, or mixtures of these salts, - > The binders / agglutination agents used in the binder system are inorganic phosphates, inorganic borates or silicate compounds which can be removed without leaving any residue, using water, or mixtures of these binding / agglutinating agents; > The agglutination / agglutination agents used in the binder system are alkaline phosphate or ammonium phosphate, monoaluminium phosphate, boron phosphate, trisodium phosphate, tetrapotassium pyrophosphate or sodium polyphosphate, which can be removed without leaving any residue, using water, or mixtures of these agglutination / binding agents; > The binder / agglutination agents used in the binder system are water-soluble silicate compounds, and preferably sodium silicates; > the binder in the binder system is a sodium silicate having a sodium silicate module of 1 to 5, and / or a mixture of sodium silicates having different sodium silicate modules; > the content of binding agents / agglutination is between 0.5% by weight and 15% by weight, based on the salt that is used; > the binder / agglutination agent content is between 0.5% by weight and 15% by weight, based on the salt that is used, as a function of the wetting behavior and the sodium silicate module; > the sodium silicate is present as the binder / agglutination agent in a content of 0.5% by weight to 15% by weight, based on the salt that is used, as a function of the grain size distribution and adapted to the module of the sodium silicate; > Hydrophilic substances that are capable of reversibly binding with water are used in the binder system as drying agents; > the drying agents used in the binder system are finely dispersed silicas, such as Aerosil, silica gel, zeolites, anhydrous sodium sulfate and / or magnesium sulfate; > a catalyst is added as an auxiliary substance; > the catalyst is particularly a fine-grained salt, and preferably, pulverized salt having a particle size of less than 100 nm; > the salt is sodium chloride, which is preferably present in a bimodal or trimodal grain size distribution, particularly preferably in a grain size distribution of 0.01 to 0.29 mm, 0.3 to 1.3 mm and / or 1.31 a 2.0 mm, the binder system is composed of the combination of sodium silicate as the binder and Aerosil as the drying agent, the catalyst is particularly a fine-grained salt, and preferably, pulverized salt having a particle size less than 100 nm, optionally, additional auxiliary substances are present, such as additives, fillers, wetting agents and / or additional catalysts, and the mixture of the core materials flows freely; > the core materials are mixed homogeneously, formed in the core, and compacted in a dry pressing method; > The core materials, depending on the material, the quality of the desired surface and the accuracy of the contour of the workpiece to be emptied of the metal, are used in grain sizes ranging from 0.01 mm to 2 mm, are formed in the core , and are compacted in the dry pressing method; > the nuclei are treated with heat after forming; > after forming, the cores are heat treated at a temperature of up to 600 ° C, preferably at temperatures of 500 to 600 ° C, and preferably at a temperature of 580 ° C.

The cores according to the invention can be used, for example, as indicators of the cavity in the production of cast metal parts, preferably in the technology of casting in permanent mold.

Claims

1. Saline-based cores, which can be produced by forming and compacting a mixture of core material, the core materials of which are selected from at least one salt, at least one binder system comprising a binder / agglutination agent and a drying agent, and optionally auxiliary substances such as additives, fillers, wetting agents and catalysts, wherein the salt, the binder system and the auxiliary substances optionally used, are inorganic, these core materials can be dissolved using water as the solvent, and the mixture of core material It is formed into cores and compacted in a dry pressing method.

2. The salt-based cores according to claim 1, wherein salts are used that have a point of decomposition or melting above the temperature of the liquid metal that is poured around the cores.

3. The salt-based nuclei according to claim 1 or 2, wherein the salts used are chlorides of the alkali elements and alkaline earth elements, in particular sodium chloride, potassium chloride and / or magnesium chloride, sulfates and nitrates of alkaline elements and alkaline earth elements, in particular potassium sulfate and / or magnesium sulfate, ammonium salts, in particular ammonium sulfate, or mixtures of these salts.

4. The salt-based nuclei according to one or more of the preceding claims, wherein the salt is sodium chloride.

5. The salt-based cores according to one or more of the preceding claims, wherein the grain sizes of the salt used vary from 0.01 mm to 2 mm.

6. The salt-based cores according to one or more of the preceding claims, wherein the salt that is used is present in a bimodal or trimodal grain size distribution.

7. The salt-based cores according to one or more of the preceding claims, wherein the salt used is present in a grain size distribution of 0.01 to 0.29 mm, 0.3 to 1.3 mm and / or 1.31 to 2.0 mm.

8. The salt-based cores according to one or more of the preceding claims, wherein the binding / binding agents used in the binder system are inorganic phosphates, inorganic borates or silicate compounds which can be removed without leaving any residue, using water, or mixtures of these binding / agglutination agents.

9. The salt-based cores according to one or more of the preceding claims, wherein the binding / agglutination agents used in the binder system are alkali phosphate or ammonium phosphate, monoaluminium phosphate, boron phosphate, trisodium phosphate, tetrapotassium pyrophosphate. or sodium polyphosphate, which can be removed without leaving any residue, using water, or mixtures of these agglutination / binding agents.

10. The salt-based cores according to one or more of the preceding claims, wherein the binding / binding agents used in the binder system are water-soluble silicate compounds, and preferably sodium silicates.

11. The salt-based cores according to one or more of the preceding claims, wherein the binder in the binder system is a sodium silicate having a sodium silicate module of 1 to 5, and / or a mixture of silicates of sodium that have different sodium silicate modules.

12. The salt-based cores according to one or more of the preceding claims, wherein the content of binding agents / agglutination is between 0.5% by weight and 15% by weight, based on the salt that is used.

13. The salt-based nuclei in accordance with one or more of the preceding claims, wherein the content of the binder / agglutination agent is between 0.5% by weight and 15% by weight, based on the salt that is used, as a function of the wetting behavior and the silicate modulus of sodium.

14. The salt-based cores according to one or more of the preceding claims, wherein the sodium silicate is present as the binder / agglutination agent in a content of 0.5% by weight to 15% by weight, based on the salt that it is used, as a function of the grain size distribution and adapted to the sodium silicate module.

15. The salt-based nuclei according to one or more of the preceding claims, wherein the binder in the binder system is tetrapotassium pyrophosphate.

16. The salt-based cores according to one or more of the preceding claims, wherein the binder used in the binder system is tetrapotassium pyrophosphate in liquid form.

17. The salt-based cores according to one or more of the preceding claims, wherein the binder used in the binder system is tetrapotassium pyrophosphate in a 60% aqueous solution.

18. The salt-based nuclei in accordance with one or more of the preceding claims, wherein the binder used in the binder system is tetrapotassium pyrophosphate in a 60% aqueous solution and in amounts of 1 to 5% by weight, preferably in amounts of 2 to 4% by weight. weight, and particularly preferably in amounts of 2.5% by weight, based on the amount of salt that is used.

19. The salt-based cores according to one or more of the preceding claims, wherein the binder used in the binder system is tetrapotassium pyrophosphate in a 60% aqueous solution and in amounts of 1 to 5% by weight, preferably in amounts of 2 to 4% by weight, and particularly preferably in amounts of 2.5% by weight, based on the amount of salt that is used, and in addition, tetrapotassium pyrophosphate is used in solid form, in the same amount or also in a greater amount.

20. The salt-based cores according to one or more of the preceding claims, wherein the binder is present in the binder system at a content of 1 to 15% by weight, based on the amount of salt that is used, and the The drying agent is present in a content of 0.3 to 4.5% by weight, based on the amount of salt that is used.

21. The salt-based nuclei in accordance with one or more of the preceding claims, wherein hydrophilic substances that are capable of reversibly binding with water are used in the binder system as drying agents.

22. The salt-based cores according to one or more of the preceding claims, wherein the finely dispersed silicas, such as Aerosil, silica gel, zeolites, anhydrous sodium sulfate and / or magnesium sulfate are used in the binder system. as drying agents.

23. The salt-based nuclei according to one or more of the preceding claims, wherein a catalyst is added as an auxiliary substance.

24. The salt-based cores according to one or more of the preceding claims, wherein the catalyst is particularly a fine-grained salt, and preferably, pulverized salt having a particle size of less than 100 nm.

25. The salt-based nuclei according to one or more of the preceding claims, wherein the salt is sodium chloride, which is preferably present in a bimodal or trimodal grain size distribution, particularly preferably in a distribution From the grain size of 0.01 to 0.29 mm, 0.3 to 1.3 mm and / or 1.31 to 2.0 mm, the binder system is composed of combination of sodium silicate as the binder and Aerosil as the drying agent, the catalyst is particularly a fine-grained salt and preferably a pulverized salt having a particle size less than 100 nm, optionally, auxiliary substances are present additional, such as additives, fillers, wetting agents and / or additional catalysts, and the mixture of core materials flows freely.

26. The salt-based cores according to one or more of the preceding claims, wherein the cores are heat treated after forming.

27. The salt-based cores according to one or more of the preceding claims, wherein, after forming, the cores are heat-treated at a temperature of up to 600 ° C, preferably at temperatures of 500 to 600 ° C, and preferably at a temperature of 580 ° C.

28. The salt-based cores according to one or more of the preceding claims, wherein the cores formed have a density of 1.5 g / cm3 to 2.1 g / cm3, and preferably 1.2 g / cm3 to 1.8 g / cm3.

29. The salt-based cores according to one or more of the preceding claims, wherein the cores formed have a porosity of 10% to 40%, and preferably 5% to 30%.

30. The salt-based cores according to one or more of the preceding claims, wherein the formed cores have a flexural strength of between 400 N / cm2 and 1500 N / cm2.

31. A method for producing salt-based cores, wherein a mixture of core material, the core materials of which are selected from at least one salt, at least one binder system comprising a combination of a binder / agglutination agent and a drying agent, and optionally auxiliary substances, such as additives, fillers, wetting agents and / or catalysts, is mixed homogeneously, formed into a core, compacted in a dry pressing method, and optionally, is treated with hot.

32. The method according to claim 31, wherein a salt having grain sizes with different distribution curves is used and mixed, preferably in a bimodal or trimodal grain size distribution.

33. The method according to claim 31 or 32, wherein the salts are selected from chlorides of the alkali elements and alkaline earth elements, in particular sodium chloride, potassium chloride and / or magnesium chloride, sulfates and nitrates of the elements alkaline and alkaline-earth elements, in particular sulphate potassium and / or magnesium sulfate, and ammonium salts, in particular ammonium sulfate, or mixtures of these salts.

34. The method according to one or more of the preceding method claims, wherein the binder / agglutination agents used in the binder system with inorganic phosphates, inorganic borates or silicate compounds that can be removed without leaving any residue, using water, or mixtures of these agglutination / binding agents.

35. The method according to one or more of the preceding method claims, wherein the binder / agglutination agents used in the binder system are alkaline phosphate or ammonium phosphate, monoaluminium phosphate, boron phosphate, trisodium phosphate, tetrapotassium pyrophosphate or sodium polyphosphate which can be removed without leaving any residue, using water, or mixtures of these binding / binding agents.

36. The method according to one or more of the preceding method claims, wherein the binder / agglutination agents used in the binder system are water-soluble silicate compounds, and preferably sodium silicates.

37. The method according to one or more of the preceding method claims, wherein the binder in the binder system is sodium silicate having a sodium silicate module from 1 to 5, and / or a mixture of sodium silicates having different sodium silicate modules.

38. The method according to one or more of the preceding method claims, wherein the hydrophilic substances which are capable of reversibly binding with water are used in the binder system as drying agents.

39. The method according to one or more of the preceding method claims, wherein finely dispersed silicas, such as Aerosil, silica gel, zeolites, anhydrous sodium sulfate and / or magnesium sulfate are used in the special binder system as drying agents.

40. The method according to one or more of the preceding method claims, wherein a catalyst is added as an auxiliary substance.

41. The method according to one or more of the preceding method claims, wherein the catalyst is particularly a fine-grained salt, and preferably, pulverized salt having a particle size of less than 100 nm.

42. The method according to one or more of the preceding method claims, wherein the salt is sodium chloride, which is preferably present in a bimodal or trimodal grain size distribution, particularly preferably in a grain size distribution of 0.01 to 0.29 mm, 0.3 to 1.3 mm and / or 1.31 to 2.0 mm, the binder system is composed of the silicate combination of sodium as the binding agent and Aerosil as the drying agent, the catalyst is particularly a fine-grained salt, and preferably, pulverized salt having a particle size of less than 100 nm, optionally, additional auxiliary substances are present, as additives, fillers, wetting agents and / or additional catalysts, and the mixture of the core materials flows freely.

43. The method according to one or more of the preceding method claims, wherein the core materials are mixed homogeneously, formed in a core and compacted in a dry pressing method.

44. The method according to one or more of the preceding method claims, wherein the core materials, depending on the material, the quality of the desired surface and the accuracy of the contour of the workpiece to be emptied of the metal, are used in Grain sizes ranging from 0.01 mm to 2 mm are formed in a core and compacted in a dry pressing method.

45. The method of compliance with one or more of the claims of the above method, wherein the cores are heat treated after forming.

46. The method according to one or more of the preceding method claims, wherein, after forming, the cores are heat treated at a temperature of up to 600 ° C, preferably at temperatures of 500 to 600 ° C, and preferably at a temperature of 580 ° C.

47. The use of the salt-based nuclei according to one or more of claims 1 to 20, as indicators of the cavity in the production of cast metal parts, preferably in the technology of permanent mold casting.