Method for reducing carbonaceous emissions and / or carbonaceous casting defects during molding cycles of molding materials comprising smectite-containing clay, the molding cycles including two or more molding cycles

Abstract

A method for reducing carbonaceous emissions and / or carbonaceous casting defects during a molding cycle of a molding material comprising smectite-containing clay, the molding cycle comprising two or more molding cycles, is provided. Described is a method for reducing carbonaceous emissions and / or carbonaceous casting defects during a molding material cycle that includes two or more loops through a molding material that includes smectite-containing clay.

Description

[Technical Field]

[0001] The present invention relates to a method for reducing carbonaceous emissions and / or carbonaceous casting defects during a molding material cycle that includes two or more loops with a molding material that includes smectite-containing clay. [Background technology]

[0002] The clay used to bind the molding material typically contains smectite. An example of such a smectite-containing clay is bentonite, especially sodium and calcium bentonite, which contains sodium and calcium in addition to magnesium, aluminum, and silicon elements. Other smectite-containing clays are hectorite, saponite, nontronite, beidellite, or sauconite. Clays such as kaolinite or illite can be used as clay-containing binders in a mixture with smectite-containing clay.

[0003] The smectite-containing clay preferably has a montmorillonite content of 50% by weight or more, more preferably 60% by weight or more, and even more preferably 70% by weight or more. If the montmorillonite content in naturally occurring smectite-containing clay is too low, it can be increased by refining. This is particularly applicable to bentonite.

[0004] For example, sodium bentonite may contain 70% to 95% by weight of montmorillonite, with the resulting residual components including quartz, opal, cristobalite, feldspar, biotite, clinoptilite, calcite, gypsum, and the like.

[0005] Thus, the terms "smectite-containing clays" and "bentonite" are used herein to refer to both the corresponding clays obtained from natural sources and to clays produced by refining natural clays.

[0006] The term "clay-bonded molds" is used herein, where appropriate, to refer to casting molds bonded with smectite-containing clays. This always means casting molds bonded with smectite-containing clays. In the foundry industry, it is preferred to use smectite-containing clays in the form of sodium or calcium bentonite and / or mixtures thereof, which mixtures are optionally produced in situ by the addition of salts and subsequent ion exchange.

[0007] Useful mold substrates are any sands that can be used to construct molds, retain their shape at high temperatures, and can be in contact with hot metals. Typical sands are silica sand, olivine sand, chromite sand, zirconium sand, and also synthetically produced ceramic sands or mixtures of these sands. Typically, molds contain at least 40% sand, preferably more than 50% sand, more preferably more than 60% sand, and most preferably more than 70% sand.

[0008] In industrial practice, clay-bonded molds are generally produced from molding materials containing smectite-containing clay as a binder and a mold substrate, as well as additives and water. Such molding materials are also called "green sand" or "wet casting sand." Compression of the molding material leads to compaction, thus ensuring sufficient dimensional stability.

[0009] In industrial practice, molding materials with smectite-containing clays as binders are typically used in molding material cycles.

[0010] For the purposes of this disclosure, what is meant by molding material cycle is that molding material from molds used for casting (also called used sand "casting material") is processed and used to produce new molding material, from which molds are again made and used for casting. Thus, the mold substrate present in the molding material forms, at least in part, a component of the processed molding material from at least one clay-bonded mold already used for casting.

[0011] In the context of this disclosure, a molding material cycle consists of at least two consecutive loops over time. Thus, two loops (not necessarily directly consecutive) of a molding material cycle can be distinguished as an earlier loop and a later loop. If a molding material cycle consists of only two loops, the first loop in the time series is the earlier loop, and the second loop in the time series is the later loop.

[0012] One loop of this molding material cycle can be described by the following characteristic steps (see FIG. 1 for a description of the following steps): (Step 1) Producing a molding material, i.e., a molding material comprising processed molding material and aggregates from a previous loop (see below); (Step 2) preparing a mold, i.e., preparing a smectite-containing clay-bonded mold from the molding material prepared in step (1); (Step 3) Casting, i.e., producing a casting by casting in the mold produced in step (2); (Step 4) Separating the casting produced in step (3) from the mold, i.e., separating to obtain a molding material that is used for casting and that includes material from the mold used for casting; (Step 5) A step of processing the molding material used for casting, i.e., a step of processing the molding material used for casting from step (4) to obtain a first processed molding material for producing a new molding material in step (1) of a later loop.

[0013] In certain cases, it may be preferred that one, more than one or all loops of the molding material cycle include further steps and / or that individual steps among those mentioned have further features, details of which will become apparent from the following description and the accompanying claims and drawings.

[0014] In each loop of the molding material cycle described above, in step (3), the mold prepared in step (2) is cast to produce a casting. This causes significant physical changes in the molding material due to the thermal and chemical stresses of the casting process (step (3) of the loop). To enable the molding material cycle, the molding material used for casting must be processed.

[0015] In some cases, particularly for the production of castings with complex geometries, in step (3), a casting is produced by casting the mold produced in step (2) with one or more inserted cores (see FIG. 3). Cores used in clay-bonded molds are typically not clay-bonded. Such cores are typically produced using organic binders, such as polyurethane or phenolic resins, or non-clay-containing inorganic binders, such as water glass-containing binders. When the casting produced in step (3) is separated from the mold and cores in step (4), the result is typically the molding material used in the casting, including material from the cores used in the casting (used core sand).

[0016] The processing of the molding material used for casting in step (5) results in processed molding material remaining in the molding material cycle, so that a portion of the mold substrate used (typically quartz sand) remains as a component of the processed molding material used for casting in the molding material cycle.

[0017] Processing typically involves the comminution (single grain) of the molding material used in the casting and the substantial removal of contaminants in the form of metal residues and by-products from the casting process, for example (core marks, feeder residues, etc.).

[0018] The thermal, mechanical and possibly also chemical stresses during the casting process give rise to wear products such as sand fines, inert clay fractions, decomposition products of additives, especially glassy carbon formers, reaction products of the core binder and oiled particles of the mold substrate.

[0019] To prevent such wear products from accumulating in the molding material cycle and / or to prevent the molding material properties from being adversely affected or the necessary active components of the binder (smectite-containing clay) and additives from being reduced to too low a level, agglomerates are added in each subsequent loop of step (1) in the manufacturing process of the molding material, i.e., the processed molding material is refreshed with agglomerates. To keep the mass of the molding material constant during the cycle, a corresponding amount of molding material is discharged from the molding material cycle. This can be done before refreshing with agglomerates (i.e., in step (5)) or after refreshing with agglomerates.

[0020] The aggregates are typically made of smectite-containing clay, water, additives (see below), and - new mould substrate (new sand), - a second processed moulding material produced by processing moulds and / or cores and / or parts thereof that have not been used for casting; - Third processed moulding materials produced by processing moulds and / or cores and / or parts thereof that were produced and used for casting outside the moulding material cycle in question. and one or more ingredients from the group consisting of:

[0021] The aggregates (especially bentonite) preferably also contain water.

[0022] The molds and cores from which the second and third processing molding materials are obtained do not need to be clay-bonded. In particular, the cores are typically not clay-bonded but are instead made with conventional organic binders, such as polyurethanes, particularly polyurethanes formed in the cold box process, or phenolic resins in the form of resols, particularly resols or novolaks used in the hot box or warm box process, particularly novolaks used in the cloning or mask-forming process.

[0023] In every loop of an industrial molding compound cycle, the objective in casting is to achieve essentially uniform quality of the casting. By controlling the supply and removal of the components of the molding compound, it is possible to achieve essentially constant optimal molding compound properties in the molding compound cycle (molding compound adjustment). In each loop, the molding compound is adjusted, i.e., optimized, by determining the required addition rates of smectite-containing clay (optional), additives, water, and new sand or the second and third processed molding compounds as defined above, and also by determining the amount of used sand to be removed, and by determining machine parameters such as mixing time or cooling intensity.

[0024] Molding materials for the production of clay-bonded molds in industrial practice typically contain additives in the form of so-called glassy carbon formers.

[0025] Glassy carbon formers (also called glassy carbon carriers, see https: / / www.giesserei-praxis.de / giesserei-lexikon / glossar / glanzkohlenstoff) are molding compound additives capable of forming hydrocarbon-based gases that carbonize during casting in the reducing atmosphere of the molding compound cavity. This produces glassy carbon. Examples of commonly used glassy carbon formers include hard coal dust, pitch, bitumen, resins, oils, plastics, and mixtures thereof.

[0026] Glassy carbon formers are added to clay-bonded molding materials, particularly for iron casting. The glassy carbon prevents wetting by the liquid casting material at the metal / mold interface. Furthermore, glassy carbon formers in the molding material can buffer quartz expansion and prevent sand expansion defects. However, increasing the proportion of hard coal dust or other glassy carbon formers in the processed molding material and increasing the proportion of glassy carbon former decomposition products (coke) increases the water demand of the molding material. An increased amount of water in the molding material can lead to casting defects, such as explosion intrusion.

[0027] Since the glassy carbon former is thermally decomposed and carbonized during the casting process, the corresponding loss in the molding material cycle must be periodically replaced in industrial practice by supplying new glassy carbon former. For this purpose, new glassy carbon former is added in at least some loops, preferably all loops, of the molding material cycle.

[0028] The main drawback of using glassy carbon formers is that they contain, for example, CO, CO2, NO x The emissions are in the form of polycyclic aromatics, as well as volatile organic compounds, particularly aromatic hydrocarbons such as benzene, toluene, and xylenes ("BTX emissions"). Furthermore, because glassy carbon formers often contain sulfur and / or sulfur-containing impurities, volatile sulfur-containing compounds are also commonly emitted. Another problem is the significant risk of dust explosions and spontaneous combustion when handling glassy carbon formers. Therefore, in industrial foundry operations, it is common for glassy carbon formers to be used in the production of clay-bonded molds in the form of a mixture with smectite-containing clays, especially bentonite, produced by the supplier.

[0029] For the reasons stated above, it is desirable and necessary to limit the use of glassy carbon formers or to replace them, at least in significant proportions, with suitable alternatives.

[0030] U.S. Patent No. 5,372,636A discloses a molding material containing sand, sodium smectite clay (especially sodium bentonite), and at least one oxide, salt (especially carbonate), or hydroxide of a metal, such as aluminum, calcium, iron, sodium, magnesium, boron, or zinc. There is no disclosure regarding the recycling of the molding material. Therefore, this document does not provide any information on whether such molding material is suitable for use in a molding material recycling.

[0031] WO 03 / 066253 A1 describes a process for producing molding materials, in particular for cycled casting purposes, according to which a non-water-swellable material is added to a mixture of granular masses and aggregates, for example a binder, for example bentonite, and water. The non-swellable porous materials used are in particular framework silicates or tectosilicates, such as zeolites, pumice or pumice stones, allophanes, imogolite, diatomaceous earth, polygarsite, sepiolite, diatomaceous earth or (acid- and / or thermally processed) clays.

[0032] Chinese Patent No. 108356214 discloses a molding material mixture containing sand, water, bentonite and additives having the following composition: SiO250~85% by weight Al2O39~45% by weight MgO 0.2~3wt% Fe2O31~8wt% CaO 1~7% by weight Fe3O40.4~8wt%

[0033] The additive is manufactured by mixing individual oxides. It is intended to replace glassy carbon formers. Molding materials containing this additive should have good recyclability. An exemplary molding material was used for 2-4 months. Summary of the Invention [Problem to be solved by the invention]

[0034] A primary objective of the present invention is to reduce carbonaceous emissions and / or carbonaceous casting defects. Carbonaceous emissions include, for example, emissions in the form of CO, CO2, and volatile organic compounds, particularly aromatic hydrocarbons such as benzene, toluene, and xylenes ("BTX emissions"), but also polycyclic aromatics.

[0035] This object is achieved by a method for reducing carbonaceous emissions and / or carbonaceous casting defects during a molding material cycle involving two or more loops with a molding material comprising smectite-containing clay, said method comprising: - reducing the carbon content of the molding material so that the molding material produced in the subsequent loop has a lower carbon content than the molding material produced in the previous loop; - adding an additive containing at least one dehydratable inorganic compound that removes water at a temperature of 150°C or higher in one or more subsequent loops of the molding material cycle; Includes.

[0036] According to the method of the present invention, it is possible to reduce carbon-based emissions and / or carbon-based casting defects during a molding material cycle that includes two or more loops of a molding material containing smectite-containing clay, i.e., during operation, without requiring interruption of the molding material cycle and / or sudden and significant changes to the molding material formulation. Instead, the method of the present invention allows the carbon content in the molding material to be gradually reduced during operation while continuing to use existing plants. Thus, a production line that uses a conventional molding material containing a glassy carbon former can be gradually switched to using a molding material with a significantly reduced carbon content.

[0037] In this way, the method of the present invention solves the problem of converting an existing (first) stable molding material cycle system into another (second) molding material cycle system, which is characterized by reduced carbonaceous emissions and / or reduced carbonaceous casting defects. Here, "stable" means that in the first and second molding material cycle systems, the molding materials cycled always have the property profile required for each application, including an acceptable distribution for the application. The parameters related to the property profile are, in particular, the compression moldability, unfired compressive strength, wet tensile strength, gas permeability, active clay content and flowability of the molding material.

[0038] The method of the present invention (as defined above and in claim 1) includes operating means for achieving the objectives: the aforementioned front loop is part of a first stable molding material cycle system, and the aforementioned back loop is part of a second stable molding material cycle system.

[0039] The present invention does not require that the carbon content of all molding materials produced in subsequent loops be lower than the carbon content of the molding materials produced in the preceding loops. What is important is that the carbon content of the molding materials is reduced so that carbon-based emissions decrease from the preceding loop to the following loop during a molding material cycle that includes two or more loops.

[0040] The molding material cycle to which the method of the present invention relates is preferably an industrial molding material cycle for foundry, preferably a foundry with at least one production line integrated into the molding material cycle, and optionally at least one further production line in which clay-free molds and / or cores are produced and / or used for casting.

[0041] The additives defined above do not necessarily have to be added in all loops of the molding compound cycle, and the molding compound cycle of the present invention may also consist of individual loops in which this additive is not added.

[0042] Further features, details, advantages and preferred embodiments of the method of the present invention will become apparent from the following description and the accompanying claims and drawings.

[0043] The carbon content of the molding material is determined by elemental analysis and includes carbon from organic carbon carriers and inorganic carbon carriers. The organic carbon carriers are, in particular, glassy carbon formers, organic binders, organic additives, and residues or decomposition products of glassy carbon formers, organic binders, and organic additives. The inorganic carbon carriers are, in particular, carbonates, which may be present in the molding material.

[0044] In molding materials having smectite-containing clays as binders, the carbon content can be reduced, in particular by reducing or avoiding the use of glassy carbon formers.

[0045] The reduction or even avoidance of the use of glassy carbon formers saves fossil resources.A further object achieved by the present invention is therefore to provide a resource-saving molding material cycle.

[0046] By reducing or even avoiding the use of glassy carbon formers, the risk of dust explosions and spontaneous combustion during the transportation, storage, and handling of the glassy carbon formers is reduced or even eliminated. Thus, a further object achieved by the present invention is to reduce the risk of dust explosions and spontaneous combustion during the transportation, storage, and handling of the glassy carbon formers.

[0047] Reducing or even avoiding the use of glassy carbon formers results in the formation of lower levels of pyrolysis products during the casting process that contaminate the molding material used for casting or the molding material discharged from the molding material cycle. The lower levels of carbon and sulfur in the molding material used for casting, associated with the reduced use of glassy carbon formers, are also advantageous for landfill deposition of non-reusable molding material fractions. Therefore, a further object achieved by the present invention is to facilitate further use or landfill deposition of the molding material used for casting.

[0048] A further object achieved by the present invention is to reduce sulfur-based and NOx emissions during a molding material cycle that includes two or more loops.

[0049] The objective of reducing sulfur-based emissions is achieved by the method defined above, and further - Reducing the sulfur content in the molding material so that the molding material produced in the subsequent loop has a lower sulfur content than the molding material produced in the previous loop.

[0050] The present invention does not require that the sulfur content of all molding materials produced in subsequent loops be lower than that of the molding materials produced in the preceding loops. What is important is that the sulfur content of the molding materials is reduced so that sulfur-based emissions decrease from the preceding loop to the following loop during a molding material cycle that includes two or more loops.

[0051] A further object achieved by the present invention is to reduce odors emitted during the casting process.

[0052] The reduction in the proportion of glassy carbon does not have an unacceptable effect on the properties of the molding material, the molds produced therefrom and the castings produced therewith.

[0053] The achievement of the above-defined objectives is based on the use of an additive that has the same effectiveness as the glassy carbon formers used in the prior art in preventing mold expansion defects, separating the metal and molding material, and accelerating mold collapse. Surprisingly, it has been found that a dehydratable inorganic compound that removes water at temperatures above 150°C can have the same effectiveness as the glassy carbon formers used in the prior art in preventing mold expansion defects and accelerating mold collapse.

[0054] Dehydration refers to the removal of water that is chemically (eg, in the form of hydroxide ions) or physically (eg, as water of crystallization in hydrates) bound by heating.

[0055] Preferably, the dehydratable inorganic compound contained in the additive used according to the present invention is a compound from the group of hydroxides and hydrate salts of metals. The term "hydroxide" as used herein also includes hydroxide oxides. Hydroxides and hydrate salts of metals in the +II or +III oxidation state are preferred, particularly hydroxides of metals in the +II or +III oxidation state. Magnesium hydroxide (especially in the form of brucite) and aluminum hydroxide are particularly preferred. Most preferred is aluminum trihydroxide Al(OH)3. Aluminum trioxide can be in various modifications, especially in the form of gibbsite, bayerite or nordstrandite, and can also be a mineral combined with other hydroxides or oxides.

[0056] Preferably, the additive used in accordance with the present invention does not contain carbon or a carbon carrier.

[0057] A preferred embodiment of the method of the present invention comprises the following steps: - in a previous loop of the two or more loops of the molding material cycle, a step of casting in a mold containing a smectite-containing clay-bonded molding material to obtain a molding material used for casting; - processing the molding material used for casting in the previous loop so that the processed molding material contains carbon and a first processed molding material is obtained; In a latter loop of the two or more loops of the molding material cycle, (i) First processed molding material and (ii) an aggregate, an additive as defined above, and -below: -Mold substrate - a second processed molding material produced by processing molding material from a mold and / or core and / or part thereof that was not used for casting, - a third processed molding material produced by processing a mold and / or a core and / or a part thereof used for casting outside the molding material cycle; and - optionally smectite-containing clay, preferably bentonite One or more raw materials from the group consisting of Aggregates containing producing a molding material comprising: a method comprising: Here, the molding material is produced so as to have a lower carbon concentration than the molding material produced in the previous loop.

[0058] In this preferred embodiment of the method of the present invention, a smectite-containing clay-bonded mold is used for casting in the first loop of two or more loops of the molding material cycle to produce a casting. The use of the mold for casting results in a molding material used for casting. The molding material used for casting is processed in the above-mentioned manner to become a first processed molding material. In order to keep the mass of the cycled molding material constant, a portion of the molding material used for casting is optionally discharged during the process, becoming the discharged molding material.

[0059] However, it is not necessary to discharge the processed molding material in every loop of the molding material cycle, and the molding material cycle of the present invention may include individual loops in which the processed molding material is not discharged.

[0060] In the subsequent loop of the molding material cycle, a molding material is produced that includes (i) the first processed molding material as defined above, and (ii) agglomerates. These agglomerates are an additive as defined above, and -below: -Mold substrate, especially quartz sand - A second processed molding material produced by processing molding material from molds and / or cores and / or parts thereof that have not been used for casting. - a third processed molding material produced by processing the molding material from the molds and / or cores and / or parts thereof used for casting outside the molding material cycle. - preferably smectite-containing clay, preferably bentonite One or more raw materials from the group consisting of Including, The agglomerates preferably also contain water.

[0061] If a portion of the molding material used for casting has not yet been discharged after processing, it is possible to discharge a portion of the molding material produced to become the discharged molding material in order to keep the mass of the cycled molding material constant. However, this is not necessarily required. The molding material cycle of the present invention may also include individual loops in which the molding material is not discharged.

[0062] The molding material produced in the subsequent loop of the molding material cycle comprises one or more or all of the above raw materials. The mold substrate used as raw material preferably comprises fresh quartz sand (new sand) or quartz sand, olivine sand, chromite sand, zirconium sand or synthetically produced ceramic sand or a mixture of these sands.

[0063] The smectite-containing clay is preferably a bentonite, in particular a bentonite from the group consisting of sodium bentonite and calcium bentonite and mixtures thereof.

[0064] The second processed molding material defined above is produced by processing molding material from unused molds and / or cores and / or parts thereof, which are not used for casting for various reasons, such as due to processing defects or lack of dimensional accuracy.

[0065] The third processed molding material defined above is produced, for example, by processing molding material from molds and / or cores and / or parts thereof that have been used for casting outside the molding material cycle in question, i.e. molds and cores that have been used for casting in another production line.

[0066] As defined above, the molds and cores from which the second and third processed molding materials are obtained do not necessarily need to be clay-bound. In particular, the cores are generally not clay-bound. Typically, the second processed molding material is produced by processing molding material from molds and / or cores and / or parts thereof that have not been used for casting, and the molds and cores are not clay-bound. Typically, the third processed molding material is produced by processing molding material from molds and / or cores and / or parts thereof that are used for casting outside the molding material cycle, and the molds and cores are not clay-bound. In these cases, the molds or cores contain a conventional organic binder, such as a phenolic resin or polyurethane formed in a cold box process, and / or its reaction product formed during the casting process; or an inorganic binder, such as a water glass-containing binder, and / or its reaction product formed during the casting process.

[0067] The molding material is produced in the subsequent loop so that it has a lower carbon concentration than the molding material produced in the previous loop. This is achieved, in particular, by adding a smaller amount of glassy carbon former compared to the previous loop, preferably by largely or completely eliminating the addition of glassy carbon former. This is made possible by using the additives described above, which have the same effect as the glassy carbon formers used in the prior art in terms of preventing mold expansion defects and promoting mold collapse. The additives preferably include one or both of the compounds of the group consisting of aluminum hydroxide and magnesium hydroxide. The molding material is preferably produced in the subsequent loop so that the produced molding material contains a higher total concentration of aluminum hydroxide and magnesium hydroxide than the first processed molding material from the previous loop.

[0068] The processed molding material of the previous loop from the molding material cycle to which the method of the present invention is applied (the first processed molding material defined above) typically contains at least one glassy carbon former and / or its carbonaceous reaction product formed during the casting process.

[0069] Preferably, according to the present invention, no glassy carbon is added in the subsequent loop to produce the molding material. Alternatively, according to the present invention, the additional mixture added to the subsequent loop to produce the molding material is one or more glassy carbon formers, and the total mass of carbon supplied together with the glassy carbon formers is less than the total mass of carbon removed in the previous loop by the discharge of the discharge and the molding material. Therefore, the amount of glassy carbon former introduced into the molding material in the subsequent loop is not sufficient to make the carbon concentration in the molding material produced in the subsequent loop equal to the carbon concentration in the molding material produced in the previous loop.

[0070] It will be apparent to those skilled in the art that omitting the addition of a glassy carbon former or reducing the dosage of the glassy carbon former should not be overcompensated by excessive dosage of the organic binder and its reaction products via the first, second, or third processing molding material.

[0071] The method of the present invention is preferred, in which the carbon content in the molding material is gradually reduced over 2 loops, preferably over at least 10 loops, more preferably over at least 20 loops.

[0072] If no new carbon is introduced over several loops, the carbon concentration in the molding material decreases with each loop, and as the number of loops increases, the decrease in carbon concentration becomes slower and the carbon concentration decreases asymptotically.

[0073] In one embodiment of the method of the present invention, the casting in the previous loop is performed in a mold with at least one inserted core. Thus, the molding material used for casting and the resulting first processed molding material resulting from the previous loop of the molding material cycle include material from at least one mold used for casting and at least one core used for casting in the same casting process. The material of the core used for casting includes a reaction product of the binder formed during casting.

[0074] Cores used in clay-bonded molds are generally not clay-bonded and are typically made with organic binders, such as cold box binders or phenolic resins, or with clay-free inorganic binders, such as binders containing water glass.

[0075] In this embodiment of the method of the present invention, it is possible to use a second processed molding material containing material from the mold and / or core and / or part thereof that has not been used for casting, and / or a third processed molding material containing material from the mold and / or core and / or part thereof that has been used for casting, where the mold and core may in each case be made with an organic binder, such as a low-temperature box binder or a phenolic resin, or a clay-free inorganic binder, such as a water glass-containing binder. In such cases, the molding material produced in the subsequent loop of the molding material cycle contains the used core sand.

[0076] In this embodiment of the method of the invention, it is preferred to use an additive comprising aluminium hydroxide, the proportion of aluminium hydroxide being at least 80%, preferably at least 90%, more preferably at least 95%, most preferably 99%, based on the total mass of aluminium hydroxide and magnesium hydroxide in the additive.

[0077] If the molding material produced in the subsequent loop contains carbon, at least 70% by weight, preferably at least 80% by weight, particularly preferably at least 90% by weight, and most preferably at least 95% of the carbon comes from the organic binder and reaction products of the binder of the cores used and unused in the casting.

[0078] In another embodiment of the method of the present invention, in the previous loop, casting is carried out in a mold without an inserted core so that the first processed molding material does not contain material from the core used for casting.

[0079] The second processed molding material used in this embodiment of the method of the present invention is preferably produced by processing molding material from only clay-bonded molds and / or cores and / or portions thereof that have not been used for casting. The third processed molding material used in this embodiment of the method of the present invention is preferably produced by processing molding material from only clay-bonded molds and / or cores and / or portions thereof that have been used for casting outside the molding material cycle in question.

[0080] In this embodiment of the method of the present invention, it is preferred to use an additive comprising one or both compounds from the group consisting of aluminum hydroxide and magnesium hydroxide, the proportion of magnesium hydroxide being between 0% and 100% based on the total mass of aluminum hydroxide and magnesium hydroxide in the additive.

[0081] In the method of the present invention, the cycle molding material is preferably used to manufacture iron casting molds.

[0082] In the method of the present invention, the front loop and the rear loop, preferably all loops, of the method of the present invention preferably comprise the following steps (see FIG. 2, further features of which shall have no limiting effect):

[0083] (Step 1) Producing a molding material, i.e., (i) a first processed molding material produced by processing a molding material used for casting resulting from a previous loop of the molding material cycle, as defined above; (ii) aggregates as defined above; producing a molding material comprising: (Step 2) preparing a mold, i.e., preparing a smectite-containing clay-bonded mold from the molding material prepared in step (1); (Step 3) Casting, i.e., producing a casting by casting in the mold produced in step (2); (Step 4) Separating the casting produced in step (3) from the mold, i.e., dividing it to obtain the molding material used for casting; (Step 5) A step of processing the molding material used for casting from step (4) to obtain a first processed molding material for producing a new molding material in step (1) of a subsequent loop, and, if necessary, discharging a portion of the molding material used for casting to discharge the molding material.

[0084] During the processing of step (5), if some of the molding material used for casting has not yet been discharged, in order to keep the mass of the cycle molding material constant, some of the molding material produced in step (1) of the next loop is discharged to discharge the molding material.

[0085] In a particular embodiment of the method of the invention, the previous and later, preferably all, loops of the method of the invention preferably comprise the following steps (see FIG. 4, further features of which are not intended to have a limiting effect): (Step 1) Producing a molding material, i.e., (i) a processed molding material produced by processing a molding material used for casting resulting from a previous loop of the molding material cycle, as defined above; (ii) aggregates as defined above; producing a molding material comprising: (Step 1a) Producing a core molding material, i.e., producing or providing a molding material for producing at least one core; (Step 2) preparing a mold, i.e., preparing a smectite-containing clay-bonded mold from the molding material prepared in step (1); (Step 2a) manufacturing a core, i.e., manufacturing or providing at least one core and inserting the at least one core into the mold manufactured in step (2); (Step 3) Casting, i.e., producing a casting by casting using the mold produced in step (2) having at least one core inserted in step (2a); (Step 4) separating the casting produced in step (3) from the mold and at least one core to provide a molding material used for casting, the molding material including material from the mold used for casting and the core used for casting; (Step 5) A step of processing the molding material used for casting from step (4) to obtain a first processed molding material for producing new molding material in step (1) of a subsequent loop, and optionally discharging a portion of the molding material used for casting to discharge the molding material.

[0086] During the processing of step (5), if some of the molding material used for casting has not yet been discharged, in order to keep the mass of the cycle molding material constant, some of the molding material produced in step (1) of the next loop is discharged to discharge the molding material.

[0087] In certain cases, it may be preferred that one, more than one or all loops of the molding material cycle include further steps and / or that individual steps among those mentioned have further features, details of which will become apparent from the following description and the accompanying claims and drawings.

[0088] In the production of the molding material, particularly in step (1) of the molding material cycle, it is preferred to mix the processed molding material with an agglomerate, which preferably also contains water.

[0089] The mold is preferably cooled together with the casting and, if present, at least one core, prior to separation in step (4).

[0090] The molding material used in casting is preferably cooled before processing.

[0091] Processing typically involves substantial removal of metal residues and other contaminants, such as contaminants by-products from the casting process (core residues, feeder residues, etc.), and grinding (particle isolation) of the molding material used for casting.

[0092] Thermal, mechanical and possibly chemical stresses give rise to wear products such as sand fines, inert clay fractions, decomposition products of additives and / or glassy carbon formers or reaction products of the core binder and oiled particles of the mold substrate.

[0093] To prevent such wear products from accumulating in the molding material cycle, and / or to prevent the molding material properties from being adversely affected, and / or to prevent the required active ratio of the binder (smectite-containing clay) and additives used according to the present invention from being reduced to too low a level, in the production of the molding material, particularly in step (1), aggregates are added to the molding material in each subsequent loop, i.e., the processed molding material is refreshed with aggregates. In order to keep the mass of the molding material constant during the cycle, a corresponding amount of molding material is discharged from the molding material cycle. This can be done before refreshing with aggregates (i.e., particularly in step (5)) or after refreshing with aggregates, i.e., after the production of the molding material in the subsequent loop. In the latter case, the amount of aggregates added is kept as small as possible.

[0094] Therefore, step (5) may optionally include the mandatory discharge of the molding material used for casting in an amount equal to the refreshment of step (1) of the next loop with the agglomerates containing the additives used according to the invention, thus making it possible to achieve a uniform profile of properties.

[0095] Preferably, in step (5), 0.5% to 20% by weight, preferably 2% to 15% by weight, more preferably 5% to 10% by weight of the molding material used for casting is discharged (sand discharge), and in step (1) of the subsequent loop, a corresponding amount of aggregate is added to keep the mass of the cycle molding material constant.

[0096] In step (5), if a portion of the molding material used in casting has not yet been discharged, 0.5% by weight to 20% by weight, preferably 2% by weight to 15% by weight, and more preferably 5% by weight to 10% by weight of the molding material produced in step (1) is discharged in order to keep the mass of the molding material constant after the cycle.

[0097] The molding material discharged during the treatment process in step (5) should meet the requirements for landfill class DKI according to Annex 3 of the German Ordinance on Landfills and Long-Term Disposal (Deponieverordnung-DepV) of 27 April 2009.

[0098] Preferably, the molding material cycle to which the method of the present invention relates comprises at least 10 loops, preferably at least 15 loops, more preferably at least 30 loops.

[0099] Preferably, the additives mentioned above are added to each loop of the molding material cycle.

[0100] The additives (as defined above) used according to the present invention are preferably free-flowing and / or pourable. The additives are preferably in the form of a powder or granular material. More preferably, the additives are in the form of particles having a particle size of 20 μm to 200 μm as measured by laser granulometry.

[0101] The proportion of the dehydratable inorganic compound that removes water at a temperature of 150°C or higher is preferably 1% to 100% based on the total mass of the additive defined above. The proportion of the dehydratable inorganic compound that removes water at a temperature of 150°C or higher is more preferably 20% to 100% based on the total mass of the additive defined above. The proportion of the dehydratable inorganic compound that removes water at a temperature of 150°C or higher is most preferably 30% to 100% based on the total mass of the additive defined above. The proportion of the dehydratable inorganic compound that removes water at a temperature of 150°C or higher is particularly preferably 50% to 100% based on the total mass of the additive defined above.

[0102] In certain cases, the additive used according to the invention may contain, in addition to said dehydratable inorganic compound or compounds, - inorganic carbonates, - Glassy carbon former It is preferred that the composition comprises one or more components from the group consisting of:

[0103] It will be clear to those skilled in the art that the amount of carbon supplied to the molding material via the additive should be limited so that the molding material produced in the subsequent loop has a lower carbon content than the molding material produced in the previous loop.

[0104] The additive preferably contains aluminum hydroxide, and the aluminum hydroxide present in the additive may have a water content in the range of 0.01% to 20%, preferably 0.01% to 12%. Particularly preferred is aluminum hydroxide having a water content of less than 1% (i.e., a water content of less than 1%), as confirmed by thermogravimetric analysis in a temperature range up to 105°C. Therefore, there is no need to expend special resources on drying the aluminum hydroxide.

[0105] In the additive, the aluminum hydroxide may be present in a mixture with iron oxide and / or iron hydroxide, the proportion of aluminum hydroxide being greater than 40% based on the total mass of aluminum hydroxide, iron oxide and / or iron hydroxide.

[0106] The additives used according to the invention preferably have a pH in the range of 7 to 14, measured according to DIN 19747:2009-07 (sample preparation), DIN EN 12457-1:2003-01 (leaching) and DIN EN ISO 10523:2012-04 (pH determination).

[0107] The additive used according to the present invention preferably contains one or more dehydratable inorganic compounds that remove water in the temperature range of 150°C to 850°C.

[0108] Preferably, the total proportion of elements from the group consisting of Pb, Cd, Cr, Co, Cu, Mo, Ni, Hg, Se, Zn, P, As, F, Br and Cl is less than or equal to 1% by weight, preferably less than or equal to 0.5% by weight, more preferably less than or equal to 0.1% by weight, most preferably less than or equal to 0.05% by weight, based on the total mass of the additive.

[0109] When producing the molding compound, the order in which the individual components are combined is flexible.

[0110] For example, the aggregates may be provided as a mixture.

[0111] Alternatively, the additive and the smectite-containing clay aggregate can be provided as a mixture, and the other aggregate can be provided separately. This approach is consistent with the current standard of providing glassy carbon formers in a prepared mixture with the smectite-containing clay. Thus, it is possible to continue using existing equipment for storage and dosing at the foundry.

[0112] Alternatively, the additive may be provided separately from the other aggregates.

[0113] Alternatively, the additive and optionally the smectite-containing clay or a premix of the additive and the smectite-containing clay can be mixed with the first processing material first, and then the additional ingredients can be added as described above.

[0114] Preferably, - a mold substrate, - a second processed moulding material produced by processing the mould and / or core used for casting and / or parts thereof outside the moulding material cycle, - Third processed molding materials produced by processing molding materials from molds and / or cores and / or parts thereof that have not been used for casting. The total mass of the raw materials introduced from the group consisting of is 0.5 to 10% by weight, preferably 1 to 8% by weight, more preferably 1.5 to 7% by weight, based on the total mass of the molding material to be produced.

[0115] The mass of the smectite-containing clay aggregate is preferably 0.1 to 1.5% by weight, more preferably 0.3 to 1.2% by weight, and even more preferably 0.5 to 1% by weight, based on the total mass of the molding material to be produced.

[0116] The total mass of the dehydratable inorganic compound that introduces the additive (defined above) as an aggregate and removes water at a temperature of 150°C or higher is 0.1% by weight to 1% by weight, preferably 0.3% by weight to 0.8% by weight, and more preferably 0.4% by weight to 0.7% by weight, based on the total mass of the molding material produced.

[0117] The smectite-containing clay used in the process of the present invention is preferably a bentonite selected from the group consisting of sodium bentonite, calcium bentonite and mixtures thereof.

[0118] The mold substrate is preferably selected from the group consisting of quartz sand, olivine sand, chromite sand, zirconium sand, synthetic ceramic sand, and mixtures of these sands. Typically, the mold contains at least 40% sand, preferably more than 50% sand, more preferably more than 60% sand, and most preferably more than 70% sand.

[0119] The method is preferably designed so that during casting at least 90% by weight of the molding material is exposed to temperatures of at most 1000° C. At temperatures above 1000° C., the aluminum hydroxide is irreversibly converted into corundum (α-aluminum hydroxide) and cannot be converted back to aluminum hydroxide by adding water in a downstream loop, and therefore can no longer function as an additive for use according to the invention as defined above.

[0120] It is therefore preferred that less than 50% by weight of the Al2O3 present in the moulding material is in the form of corundum, preferably less than 25% by weight, more preferably less than 10% by weight.

[0121] Preferably, the molding material produced in the downstream loop of the method of the invention has the following parameters: - a compressibility in the range of 25% to 55%, measured according to VDG Merkblatt P37 (April 1997), and / or - 8 N / cm, measured according to VDG Merkblatt P38 (May 1997) 2 ~35N / cm 2 and / or - 0.10 N / cm measured according to VDG Merkblatt P38 (May 1997) 2 ~0.50N / cm 2 Wet tensile strength and / or - a gas permeability of 70 to 200, measured according to BDG-Richtlinie P41 (October 2013) and / or - an active clay content of 4.5% to 16%, determined by the methylene blue method according to VDG Merkblatt P035 (October 1999), and / or -20% to 90% flowability as measured according to the Morek Multiserw Electric Ram Unit Model LUA-2e technical documentation, page 7.

[0122] More preferably, the molding material produced in the downstream loop of the method of the invention has the following parameters: - a compressibility in the range of 35% to 55%, measured according to VDG Merkblatt P37 (April 1997), and / or - 15 N / cm, measured according to VDG Merkblatt P38 (May 1997) 2 ~30N / cm 2 and / or - 0.20 N / cm measured according to VDG Merkblatt P38 (May 1997) 2 ~0.50N / cm 2 Wet tensile strength and / or - a gas permeability of 100 to 200, measured according to BDG-Richtlinie P41 (October 2013) and / or - an active clay content of 6% to 14%, determined by the methylene blue method according to VDG Merkblatt P035 (October 1999), and / or -30% to 90% flowability as measured according to the Morek Multiserw Electric Drive Ram Unit Model LUA-2e technical documentation, page 7.

[0123] Preferably, all the stated parameters of the molding material are within the above-mentioned preferred ranges, in particular within the above-mentioned particularly preferred ranges.

[0124] Typically, the molding material used in the front loop of the method of the invention has one or more of the following parameters: Carbon concentration of 2% to less than 5% by mass of molding material as determined by elemental analysis - Nitrogen concentration of less than 0.05% to 0.1% based on the mass of the molding material, as determined by elemental analysis - A sulfur concentration of less than 0.02% to 0.07% by mass of the molding material, as determined by elemental analysis - Loss on ignition of not more than 3% to 6%, determined in accordance with VDG Merkblatt P33 (April 1997).

[0125] More preferably, the molding material produced in the post-loop of the method of the present invention has one or more of the following parameters: a carbon concentration of less than 4%, preferably less than 3%, based on the mass of the molding material, as determined by elemental analysis Nitrogen concentration of less than 0.2%, preferably less than 0.1%, based on the mass of the molding material, as determined by elemental analysis a sulfur concentration of less than 0.05%, preferably less than 0.03%, based on the mass of the molding material, as determined by elemental analysis Loss on ignition of less than 5%, preferably less than 4%, measured according to VDG-Merkblatt P33 (April 1997) The carbon content of the molding material produced in the subsequent loop of the inventive process is lower than the carbon content of the molding material used in the previous loop of the inventive process. Preferably, the nitrogen content, sulfur content and ignition loss of the molding material produced in the subsequent loop of the inventive process are also lower than the molding material used in the previous loop of the inventive process. Preferably, all of the stated parameters of the molding material are within the above-mentioned preferred ranges, in particular the above-mentioned particularly preferred ranges.

[0126] A further aspect of the present disclosure relates to the use of the additives defined above in the method of the present invention for reducing carbonaceous emissions and / or carbonaceous casting defects during a molding material cycle comprising two or more loops with a molding material comprising smectite-containing clay. The above embodiments are applicable with respect to the additives preferably used and the preferred process design.

[0127] A further aspect of the present disclosure relates to the use of the additive defined above as a replacement or partial replacement for glassy carbon formers in smectite-containing clay-bonded molds for iron casting. The above embodiments are applicable with regard to the additives preferably used and the preferred process design.

[0128] The invention will now be described in detail with reference to the accompanying schematic drawings. [Brief explanation of the drawings]

[0129] [Figure 1]1 shows a molding material cycle (casting in a coreless mold) according to the prior art. [Figure 2] 1 shows a molding material cycle (casting in a coreless mold) according to the method of the present invention. [Figure 3] 1 shows a molding material cycle (casting in a mold with a core) according to the prior art. [Figure 4] 1 shows a molding material cycle (casting in a mold with a core) according to the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0130] According to Figures 1 and 2, one loop of the molding material cycle, excluding the core into which the mold used for casting in step (3) is inserted, includes at least steps (1) to (5) as defined above.

[0131] In step (1), (i) a first processed molding material produced by processing the molding material used for casting, which originates from a previous loop of the molding material cycle and does not include material from the core used for casting; (ii) Aggregates and A molding material comprising:

[0132] The aggregates are - one or more ingredients, - New mold base material (new sand), and - at least one processing molding material, - a second processed moulding material produced by processing moulds and / or cores and / or parts thereof that have not been used for casting; - a third processed moulding material produced by processing moulds and / or cores and / or parts thereof which have been produced and used for casting outside the moulding material cycle shown in Figures 1 and 2. At least one processing molding material selected from the group consisting of one or more ingredients from the group consisting of: optionally a smectite-containing clay, preferably bentonite, - water Includes.

[0133] In this case, the second processed molding material comprises material and / or cores and / or parts thereof from a mold not used for casting, and / or the third processed molding material comprises material and / or cores and / or parts thereof from a mold used for casting.

[0134] In a method not according to the invention (FIG. 1), at least one glassy carbon former is added as further aggregates in step (1) during the production of the molding material.

[0135] In the method of the invention (FIG. 2), the additives defined above are added as further aggregates in step (1) in the production of the molding material. The additives preferably contain or consist of magnesium hydroxide and / or aluminum trihydroxide.

[0136] The addition of glassy carbon formers is not completely excluded in the process of the present invention, but the amount of carbon supplied to the molding material must be limited so that the molding material produced in the subsequent loop has a lower carbon content than the molding material produced in the previous loop.

[0137] In step (2), the molding material produced in step (1) is used to produce a smectite-containing clay-bonded mold.

[0138] In step (3), a casting is produced by casting using the mold produced in step (2). The mold does not include an inserted core.

[0139] In step (4), the casting produced in step (3) is separated from the mold and used for casting, resulting in a molding material containing material from the mold used for casting but not containing material from the core used for casting. Preferably, the mold is cooled together with the casting before being separated in step (4).

[0140] In step (5), the molding material used for casting from step (4) is processed to obtain a first processed molding material for producing a new molding material in a subsequent loop, particularly step (1) of the next loop. Prior to processing in step (5), the molding material used for casting is preferably cooled. During the processing, a portion of the molding material used for casting can be ejected, resulting in an ejected molding material.

[0141] During the processing of step (5), if some of the molding material used for casting has not yet been discharged, in order to keep the mass of the cycle molding material constant, some of the molding material produced in step (1) of the next loop is discharged to discharge the molding material.

[0142] In a subsequent loop, in particular step (1) of the subsequent loop, the first processed molding material resulting from the previous loop, in particular step (5) of the previous loop, is used to produce new molding material as described above.

[0143] According to Figures 3 and 4, the molding material cycle loop in which the mold used for casting in step (3) contains at least one inserted core includes at least steps (1), (1a), (2), (2a), (3), (4) and (5) as defined above.

[0144] In step (1), (i) a first processed molding material produced by processing the molding material used for casting, resulting from a previous loop of the molding material cycle and including material from the core used for casting; (ii) Aggregates and A molding material comprising:

[0145] The aggregates are - one or more ingredients, - New mold base material (new sand), and - at least one processing molding material, - a second processed moulding material produced by processing moulds and / or cores and / or parts thereof that have not been used for casting; - a third processed molding material produced by processing a mold and / or core and / or part thereof that was produced and used for casting outside the molding material cycle shown in Figures 3 and 4. At least one processing molding material selected from the group consisting of one or more ingredients from the group consisting of: optionally a smectite-containing clay, preferably bentonite, - water Includes.

[0146] In a method not according to the invention (FIG. 3), at least one glassy carbon former is added as further aggregates in step (1) during the production of the molding material.

[0147] In the method of the present invention (FIG. 4), the additive defined above is added as further aggregates in step (1) in the production of the molding material. The additive preferably contains or consists of aluminum trihydroxide.

[0148] The addition of glassy carbon formers is not completely excluded in the process of the present invention, but the amount of carbon supplied to the molding material must be limited so that the molding material produced in the subsequent loop has a lower carbon content than the molding material produced in the previous loop.

[0149] In step (1a), a molding material (core molding material) for producing at least one core is produced or provided. This molding material comprises a mold substrate, a clay-free binder, and optionally additives. Additives suitable for molding materials for producing cores are known in the prior art. The binder is a conventional organic binder, such as a cold box binder or a phenolic resin, or a clay-free inorganic binder, such as a binder containing water glass.

[0150] In step (2), the molding material produced in step (1) is used to produce a smectite-containing clay-bonded mold.

[0151] In step (2a), at least one core is produced using the molding material (core molding material) produced or provided in step (1a), and this is inserted into the mold produced in step (2).

[0152] In step (3), a casting is produced by casting using the mold produced in step (2) and containing at least one inserted core.

[0153] In step (4), the casting produced in step (3) is separated from the mold and used for casting, and a molding material containing material from the mold used for casting and material from the core used for casting is obtained. Before being separated in step (4), it is preferable to cool the mold together with the casting.

[0154] In step (5), the molding material used for casting from step (4) is processed to obtain a first processed molding material for producing a new molding material in a subsequent loop, particularly step (1) of the next loop. Prior to processing in step (5), the molding material used for casting is preferably cooled. During the processing, a portion of the molding material used for casting can be ejected, resulting in an ejected molding material.

[0155] During the processing of step (5), if some of the molding material used for casting has not yet been discharged, in order to keep the mass of the cycle molding material constant, some of the molding material produced in step (1) of the next loop is discharged to discharge the molding material.

[0156] In a subsequent loop, in particular step (1) of the subsequent loop, the first processed molding material resulting from the previous loop, in particular step (5) of the previous loop, is used to produce new molding material as described above. [Example]

[0157] The invention will now be further illustrated by the following non-limiting examples.

[0158] 0. Test methods and molding materials 0.1 Test Method The following test methods (measurement methods) were used (Table 1).

[0159] [Table 1]

[0160] [Table 2]

[0161] The sleeve and fin model setup was fabricated as described in (https: / / www.researchdisclosure.com / database / RD705032) and used in the following tests.

[0162] 0.2 Materials used All figures for raw material inputs refer in each case to pure raw materials, i.e. dry materials, meaning that no moisture or hydrates are present.

[0163] During the research, molding materials from the conditioned molding material cycle system of the brake disc casting (hereinafter also referred to as the starting molding material) were used as starting materials for conversion tests of molding material cycle systems containing glassy carbon formers. The molding materials can be represented by the following data (Table 2).

[0164] [Table 3]

[0165] During the experimental work, a processed material from core sand was used (the second processed material defined above). For this purpose, cores were produced using organic or inorganic binders and then grated using a Webac circular vibrating screen.

[0166] The starting material for the organic binder-based molding compounds was a core produced by the cold box process using Biocure 8568P1 / Silcure 8431P2 binders sold by Huettenes-Albertus Chemische Werke GmbH in an LL20 core shooter from Laempe. For this purpose, Quarzwerke H32 molding sand was used, with a dosage of 0.7 parts by weight of each binder component per 100 parts by weight of sand. The cores were produced at an injection pressure of 450 kPa (4.5 bar) and an injection time of 1.5 seconds, and then cured by passing 10 g of dimethylpropylamine (N,N-dimethylpropylamine, GH6 catalyst, Huettenes-Albertus Chemische Werke GmbH) through the cores for 45 seconds at a sparging pressure of 200 kPa (2 bar).

[0167] The starting material for the molding compounds produced using inorganic binders was a core produced using the Cordis 9477 / Anorgit 9476 binder system sold by Huettenes-Albertus Chemische Werke GmbH in an LL20 core shooter from Laempe. For this purpose, Quarzwerke H32 molding sand was used, with a dosage of 2.2 parts by weight of Cordis 9477 and 1.15 parts by weight of Anorgit 9476 per 100 parts by weight of sand. The cores were produced in a core box at a controlled temperature of 180°C, with an injection pressure of 450 kPa (4.5 bar) and an injection time of 1.5 seconds. The cores were cured for 1 minute with a flow of hot air at 120°C with a sparging pressure of 200 kPa (2 bar).

[0168] The core is grated on a circular vibrating screen (Circular Vibrating Screen - 175056 Pilot Plant, manufactured by Webac). The resulting molding material has the properties shown in Table 3.

[0169] [Table 4]

[0170] The starting materials for the cores that do not decompose under the experimental conditions (i.e., cores that do not decompose during the splitting process (step (4)), see point 3, Experimental Series A below) were quartz sand of the HAP 0.20 / 0.315 / 0.40 type manufactured by HA Polska and water glass of the Steinex 48 / 50 type combined with Silica Fume Q1-Plus manufactured by RW Silicium, Huettenes-Albertus Chemische Werke GmbH, an inorganic binder. 100 parts by weight of quartz sand were mixed with 1.1 parts by weight of Silica Fume Q1-Plus and 3.4 parts by weight of Steinex 48 / 50 and molded into cores in a bulk core box. The cores were then sparged with hot CO2 at 100°C and a sparging pressure of 150 kPa (1.5 bar) for 60 seconds in a Morek laboratory core injection machine, thus curing the cores.

[0171] 1. Screening tests to identify suitable excipients Six kilograms of quartz sand (H32, manufactured by Quarzwerke) was mixed with 120 ml of water in a mixer (LM-2e pan mill mixer, manufactured by Morek MULTISERW) at 40 rpm for 2 minutes. Then, 0.48 kg of bentonite (dry weight) (Natroben 25F, manufactured by Clariant) and 0.30 kg of additives (dry weight) were added and mixed at 40 rpm for 7 minutes. The mixture thus obtained was manually sieved through a 3 mm mesh sieve, and then the compactability (CPB) (Tester type: PVG; ID number: 1501, Year: 2000) was determined. If the CPB was greater than 46.0%, the mixture was screened again and the CPB measurement was repeated. This process was repeated until the CPB was less than 46.0%. If the CPB was less than 44.0%, 7 to 12 ml of water was added, followed by mixing for 1 minute, and then the screening and CPB measurement were repeated. Water addition is repeated until the CPB exceeds 44.0%.

[0172] As a benchmark for the molding material properties, three different mixtures with glassy carbon formers according to the prior art are used. 1) A commercial premix of 25% glassy carbon former ("Sea Charcoal") and 75% sodium bentonite (NEMIR 2575) from HA Italia SpA 2) 5 parts by weight of ground coke (metallurgical coke) from LuxCarbon GmbH and 8 parts by weight of bentonite (Natroben 25F, Clariant) as glassy carbon formers 3) 5 parts by weight of Carboraxone 100 / P from Huettenes-Albertus France as a commercially available glassy carbon former and 8 parts by weight of bentonite (Natroben 25F, Clariant).

[0173] In addition to the molding material index, casting quality is also an important criterion for selecting the appropriate additive. To this end, i.e., to verify casting quality, castings were performed using the sleeve model setup described in (https: / / www.researchdisclosure.com / database / RD705032), i.e., molds manufactured according to the sleeve model setup described in (https: / / www.researchdisclosure.com / database / RD705032) were used for casting. The castings were then blasted and their surface roughness measured in accordance with DIN EN ISO 4287 (R_ISO). Two castings in each case were inspected. This involved inspecting the surfaces of the star-arranged fins with small, medium, and large separations three times each over a measuring distance of 8 mm using a Mitutoyo SJ-500P surface measuring instrument. Because there was no consistent trend regarding the spacing of the fins relative to one another and the surface roughness, the evaluation was simplified by using the average of all measurements performed. This indicated that the surface roughness of all the resulting castings was within a range that allowed for commercial use.

[0174] 1.1 Different types of aluminum and magnesium hydroxide as additives For the study of aluminum hydroxide, Al(OH)3 of the SH500 type (SH500 nuance-00, Alteo) and SH950 type (SH950 nuance-00, Alteo) are used.

[0175] For the testing of magnesium hydroxide, type 1 brucite, type 2 brucite and type 3 brucite from Ziegler & Co. GmbH are used (all values ​​according to Ziegler technical data sheet, Table 4, 10 / 2020).

[0176] [Table 5]

[0177] Table 5 shows the molding material properties and roughness of the castings made using various hydroxides and glassy carbon formers 1) to 3) used as references. 2 Dry compressive strength (DCS) of and moisture content of <2.8% are considered particularly positive, while >50N / cm 2 The dry compressive strength of 2000 to 30000 sinters is negative, as is the case for moisture contents of >3.2%. Hydroxides, especially aluminum hydroxide Al(OH)3 and magnesium hydroxide Mg(OH)2, allow the production of molds and show good molding material indices (see Table 5).

[0178] [Table 6]

[0179] 1.2 Study of aluminum hydroxide Al(OH)3 as an additive containing a glassy carbon former The good values ​​of hydroxides, especially aluminum hydroxide Al(OH)3, can be further improved by the addition of glassy carbon formers such as Carboraxone 100 / P, see Table 6. In particular, the surface roughness of the castings is reduced by the use of Carboraxone 100 / P, although the values ​​found when using pure aluminum hydroxide are also suitable.

[0180] [Table 7]

[0181] 1.3 Testing different carbonates as comparative additives Huntite (trade name UltraCarb D98, supplied by LKAB Minerals) does not achieve sufficiently good molding compound values, whereas dolomite and manganese carbonate (supplied by TROPAG GmbH) show perfectly acceptable molding compound values ​​(Table 7).

[0182] The dolomites used were Ziegler's Bianco Zandobbio 0 / 50 micron and Possehl Erzkontor's PE-DOL 90. Overall, the molding material index is somewhat worse than when using the hydroxides mentioned above. Nevertheless, this value allows the material to be used as a replacement for traditional glass-like carbon formers. However, carbonates have the disadvantage of containing carbon.

[0183] [Table 8]

[0184] The molding material properties can be improved by mixing carbonates and hydroxides (Table 8). In this context, Mixmag is a 50% / 50% mixture of brucite (93% Mg(OH)2) and raw magnesite (92% MgCO3), supplied by Possehl Erzkontor GmbH & Co. KG, and Dolomag is a 50% / 50% mixture of brucite (93% Mg(OH)2) and dolomite (95% CaMg(CO3)2), also supplied by Possehl Erzkontor.

[0185] [Table 9]

[0186] Further addition of a prior art glassy carbon former such as Carboraxone 100 / P to the hydroxide and carbonate mixture can further improve the molding compound values ​​(Table 9).

[0187] [Table 10]

[0188] 1.4 Emissions of bentonite and additives used Table 10 shows the emission measurements of the bentonites used and the additives used. The emission measurements were carried out at the Foundry Institute of the University of Freiberg. For this purpose, the materials were introduced into a tube furnace at 900 °C and the resulting emission was measured by online FT-IR and calibrated with test gases.

[0189] The emissions of additives used in accordance with the present invention are significantly lower than those of conventional glassy carbon formers, such as the aforementioned ground coke from LuxCarbon or Carboraxone 100 / P products. Carbonates (not according to the present invention), such as manganese carbonate, reduce hydrocarbon emissions, particularly benzene, toluene, and xylene, but are expected to significantly increase CO2 emissions compared to hydroxides, such as Al(OH)3. Therefore, according to the present invention, carbonates are preferably used in combination with hydroxides.

[0190] [Table 11]

[0191] 2. Production and testing of molding materials in cycles These tests are intended to repeatedly use a specific amount of molding material for casting and reprocessing. As is customary in industrial casting practice, the molding material is cycled. Additives are supplied each time the molding material is processed and accumulate with each loop. Components present in the starting molding material but no longer added are depleted, meaning that the proportion of components no longer added in subsequent loops decreases. The total amount of molding material during the cycle remains constant, approximately 8 kg. Two molds per loop are produced and used for casting, according to the sleeve model setup described in (https: / / www.researchdisclosure.com / database / RD705032).

[0192] For the explanation of the experimental procedure, reference is made to the molding material cycle in FIG.

[0193] The molding material cycle loop includes the following steps: Preparation of molding material (step (1), first loop) Experiment series 2.1, 2.2.1, 2.2.2, 2.3.1, 2.3.2 below In the first loop, 6 kg of quartz sand of type H32 manufactured by Quarzwerke is used. The mold base material is then mixed with 480 g of sodium bentonite (Natroben 25F, HA ITALIA SpA, a Na bentonite produced by activating natural Ca bentonite) and 300 g of the respective additives and 120 ml of water in a pan mill mixer manufactured by Morek Multiserw without water for 1 minute, and then mixed again after adding water for 7 minutes. For this purpose, the mold base material is first mixed with 120 ml of water in a pan mill mixer manufactured by Morek Multiserw for 1 minute, and then 480 g of sodium bentonite (Natroben 25F, HA ITALIA SpA) and 300 g of the respective additives are added, and then mixed in a pan mill mixer manufactured by Morek Multiserw for another 7 minutes.

[0194] Experiment series 2.4 to 2.6 below In the first loop, 3.7 kg of quartz sand of type H32 manufactured by Quarzwerke is used. The mold base material is then mixed with 322 g of Volclay (naturally occurring Na-bentonite, GEKO™ V foundry bentonite manufactured by Clariant Deutschland GmbH), 207 g of each additive, and 130 ml of water in a pan mill mixer manufactured by Morek Multiserw without water for 1 minute, and then mixed again after adding water for 7 minutes. For this purpose, the mold base material is first mixed with 130 ml of water in a pan mill mixer manufactured by Morek Multiserw for 1 minute, and then 322 g of Volclay and 207 g of each additive are added, and then mixed in a pan mill mixer manufactured by Morek Multiserw for another 7 minutes.

[0195] Further details are applicable to all experimental series 2.1-2.6 (unless otherwise stated).

[0196] Each time a molding material is produced (step (1)), additives are added and accumulated in each loop. The discharge of a portion of the molding material used for casting in step (5) or step (1) of the next loop (see FIG. 2) reduces the proportion of components present in the starting molding material but no longer added.

[0197] Mold Fabrication (Step (2) in All Loops) For this purpose, the molding material is introduced into the mold of a sleeve model device 3 minutes after mixing and compressed in two pressing operations (fill, pressurize, refill, pressurize). The process is completed within another 3 minutes. Two molds are made for each experiment.

[0198] Casting (Step (3) in every loop) After a 30-minute waiting period, the molds are used for casting one after the other. The molds are used to cast liquid metal of GJL 250 alloy at 1450°C using a ladle. The molds used for casting are left overnight before being split. At the same time, the castings are cooled, and the molding material is first heated and cooled in the molds overnight.

[0199] Split (step (4) in full loop) The casting material and the molding material used for casting are separated.

[0200] Processing (Full Loop Step (5)) The molding material is poured into a storage container, and the mass of molding material is crushed. Metal residue is removed.

[0201] Manufacturing molding material (Step (1) from the second loop onwards) New molding material is produced by refreshing processed molding material from a previous loop (first processed molding material) by mixing bentonite, water, additives (as defined above) and fresh mold base material (new sand), or by refreshing a second processed molding material by processing cores (see below for details).

[0202] The second processed molding material (see below for details) produced by fresh mold substrates or processed cores is added to the processed molding material from the previous loop and mixed with 120 ml of water for 1 minute, followed by the addition of sodium bentonite (Natroben 25F, HA ITALIA SpA, Experimental Series 2.1, 2.2.1, 2.2.2, 2.3.1, 2.3.2) or Volclay (GEKO™ V casting bentonite from Clariant Deutschland GmbH, Experimental Series 2.4, 2.5 and 2.6) and the respective additives (see below for the amounts of bentonite and additives) and then mixing for a further 7 minutes in a pan mill mixer from Morek Multiserw.

[0203] The increase in the amount of molding material due to addition to the mixer, i.e., the increase in the amount of molding material due to the mixture defined above, is controlled by drawing off the same amount of prepared molding material in each loop.

[0204] Each time the molding material is produced (step (1)), additives are added to each loop and accumulated. The discharge of a portion of the molding material used for casting reduces the proportion of components present in the starting molding material that are no longer added in subsequent loops.

[0205] 2.1 Mixture of Al(OH)3 or Mg(OH)2 additives with fresh mold substrate in subsequent loops Ten loops (0-9) are performed in each case using the sleeve model settings described in (in the first experiment, 100% fresh mold substrate of type H32 from Quarzwerke is used, https: / / www.researchdisclosure.com / database / RD705032).

[0206] In all subsequent loops 1 to 9, 4 kg of used molding material from the previous casting is used and refreshed with 400 g of mold base material (fresh mold base material) as well as 64 g of bentonite and 20 g of the respective additive.

[0207] The aluminum hydroxide Al(OH)3 additive used is SH950 Nuance-00 manufactured by Alteo. The results of the experiments with Al(OH)3 are shown in Table 11.

[0208] The magnesium hydroxide Mg(OH)2 additive used is Type 3 Brucite manufactured by Ziegler & Co. GmbH. The results of the experiments with Mg(OH)2 are shown in Table 12.

[0209] Both additives exhibit good moulding properties and comparable surface quality when fresh mould substrate is used as the agglomerate (see Figure 2, step (1)), which can be seen from the measured roughness of the castings.

[0210] Al(OH)3 as an additive results in a higher active clay content and a significantly lower ignition loss. For both Al(OH)3 and Mg(OH)2, the molding compound properties and castings are of good quality. The surface roughness of the castings is correspondingly low.

[0211] [Table 12]

[0212] [Table 13]

[0213] 2.2 Mixture of Al(OH)3 and Mg(OH)2 with cold box core sand in subsequent loops Thirty-one loops (0-30) were performed using the sleeve model setup described in (https: / / www.researchdisclosure.com / database / RD705032). The experimental procedures and measurements of molding material and casting properties were as described in Section 2.1, except that in subsequent loops, instead of fresh mold substrate, a second processed molding material was added by processing a core produced with cold box binder ("cold box core sand") that had not been used for casting (see Tables 13 or 16 for the proportion of mold material produced). (See Figure 2, step (1)).

[0214] 2.2.1 Mixture of aluminum hydroxide Al(OH)3 and subsequent cold box core sand in the loop When aluminum hydroxide Al(OH)3 was used, the molding compound properties were stable enough at a 5% mixture of cold box core sand, and the mixture was increased to 10% cold box core sand from loop 15 onwards (Tables 13 and 14). The molding compound properties remained stable.

[0215] [Table 14]

[0216] [Table 15]

[0217] [Table 16]

[0218] [Table 17]

[0219] Data from CNS analysis of the molding materials from different loops show an increase in carbon and nitrogen content resulting from the incorporation of cold box core sand. The surface roughness of the castings is improved compared to the experimental series in which new sand (see 2.1 above) was mixed in instead of cold box core sand. This is due to the incorporation of core sand (Table 15).

[0220] [Table 18]

[0221] 2.2.2 Mixture of Mg(OH)2 and subsequent cold box core sand in the loop It is clear that the use of magnesium hydroxide Mg(OH)2 in the form of type 3 brucite as an additive does not allow the properties of the molding compound to remain stable even after several loops. Thus, in loops 8 and 14, the bentonite content of the molding compound increases (Table 16). Nevertheless, there is no stabilization of the molding compound indices (Table 17). In particular, the wet tensile strength decreases as the number of loops increases, a trend that can only be counteracted in the short term by adding more fresh bentonite.

[0222] [Table 19]

[0223] [Table 20]

[0224] As expected, the incorporation of cold-box core sand increases the carbon content of the molding compound and, to a limited extent, the nitrogen content (Table 18). The surface roughness of the castings is good and not adversely affected. However, in contrast to aluminum hydroxide Al(OH) (see Experimental Series 2.2.1 above), the incorporation of magnesium hydroxide Mg(OH) with organic core sand (i.e., cold-box core sand, see above) does not allow molding compound cycles with stable molding compound properties (Table 17).

[0225] [Table 21]

[0226] 2.3 Mixtures of inorganically bonded core sand containing Al(OH)3 and Mg(OH)2 in subsequent loops Thirty-one loops (0-30) were run using the sleeve model setup described in (https: / / www.researchdisclosure.com / database / RD705032). The experimental procedures and measurements of molding material and casting properties were as described in Section 2.1, except that in subsequent loops, instead of fresh mold substrate, a second processed molding material (see Figure 2, step (1)) was added, which was produced by processing a core made with an inorganic binder (water glass) ("IOB core sand") that had not been used for casting (see Tables 19 or 22 for the proportion in the produced molding material). Therefore, this is an inorganic molding material cycle for all binders used.

[0227] 2.3.1 Aluminum hydroxide Al(OH)3 as an additive with inorganically bonded core sand mixtures in subsequent loops Even in the case of IOB core sand incorporation, the use of aluminum hydroxide Al(OH)3 results in a molding compound cycle with stable molding compound properties, so the incorporation of IOB core sand starting from loop 15 is increased to 10% (Tables 19 and 20).

[0228] [Table 22]

[0229] [Table 23]

[0230] [Table 24]

[0231] [Table 25]

[0232] Analysis of the molding material (Table 21) shows that there is no significant accumulation of carbon, nitrogen, or sulfur in the molding material. C-containing components from the inorganic binder (e.g., surfactant) are not very significant. The low C loading is one of the main advantages of this inorganic molding material cycle, as only very low emissions are expected (see below). Despite the relatively low carbon content, the obtained surface roughness (Table 21) is very close to that of the cold box core sand mixing experiment (Experimental Series 2.2.1).

[0233] [Table 26]

[0234] 2.3.2 Magnesium hydroxide Mg(OH)2 containing inorganically bonded core sand mixture in subsequent loops It is clear that the use of magnesium hydroxide Mg(OH)2 in the form of type 3 brucite as an additive does not allow the properties of the molding compound to remain stable even after several loops. Therefore, the bentonite content of the molding compound increases in loops 8 and 15 (Table 22). Nevertheless, there is no stabilization of the molding compound indices. In particular, the wet tensile strength decreases as the number of loops increases, a trend that can only be counteracted in the short term by adding more fresh bentonite (Table 23).

[0235] Thus, as with the cold box core sand mixture (Experimental Series 2.2.2), the addition of Mg(OH)2 as an additive did not result in a molding compound cycle with stable molding compound properties; the water demand of the mixture increased significantly, and other molding compound indices also showed instability (Table 23). The water demand of the molding compound corresponds to the water content of the molding compound mixture in a moldable state (target moldability). The active clay content and wet tensile strength showed significant decreases as the number of loops increased. This could be compensated for by adding bentonite, but no molding compound cycle had stable properties overall.

[0236] [Table 27]

[0237] [Table 28]

[0238] Analysis of selected molding material samples (Table 24) shows a slight increase in carbon content in many loops, likely due to the addition of bentonite. Ca bentonite is processed with carbonate during activation. The surface roughness of the castings is always acceptable, i.e., good to very good.

[0239] [Table 29]

[0240] 2.4 Mixture of Al(OH)3 additive and fresh mold substrate in subsequent loops Eleven loops (0-10) are performed using the sleeve model setup described (in the first experiment: https: / / www.researchdisclosure.com / database / RD705032) with 100% fresh mold substrate of type H32 manufactured by Quarzwerke.

[0241] In all subsequent loops 1 to 10, 3.7 kg of used molding material from the previous casting was used and refreshed with 185 g of mold base (fresh mold base) as well as 26 g of bentonite and 23 g of each additive (Table 25). The aluminum hydroxide Al(OH)3 additive used was SH950 Nuance-00 from Alteo. Stable molding material properties were achieved (Table 26).

[0242] When fresh mold substrate is used as the aggregate (see Figure 2, step (1)), good mold properties and good to very good surface quality are achieved, as can be seen from the measured roughness of the casting. As expected, since only inorganic materials were used, CNS analysis after 11 loops shows no significant levels of carbon and nitrogen (see Table 27).

[0243] [Table 30]

[0244] [Table 31]

[0245] [Table 32]

[0246] 2.5 Al(OH)3 and subsequent mixture of cold box core sand in the loop Eleven loops (0-10) were performed using the sleeve model setup described in (https: / / www.researchdisclosure.com / database / RD705032). The experimental procedures and measurements of molding material and casting properties were as described in Section 2.4, except that in subsequent loops, instead of fresh mold substrate, a second processed molding material (see Figure 2, step (1)) was added, which was not used for casting (see Table 28 for the proportion of molding material produced) and was produced by processing the core produced with the cold box binder ("cold box core sand"). Stable molding material properties were achieved (Table 29).

[0247] [Table 33]

[0248] [Table 34]

[0249] Data from CNS analysis of the molding material after 11 loops shows significant carbon and nitrogen levels resulting from the addition of cold box core sand, especially compared to the series of experiments with fresh sand feed (Table 30).

[0250] [Table 35]

[0251] 2.6 Al(OH)3 containing inorganically bonded core sand mixtures in subsequent loops Eleven loops (0-10) were run using the sleeve model setup described in (https: / / www.researchdisclosure.com / database / RD705032). Test procedures and measurements of molding material and casting properties were as described in Section 2.4, except that in subsequent loops, instead of fresh mold substrate, a second processed molding material (see Figure 2, step (1)) was added, which was produced by processing a core made with an inorganic binder (water glass) ("IOB core sand") that had not been used for casting (see Table 31 for the proportion in the produced molding material). This was therefore an inorganic molding material cycle for all binders used. Stable molding material properties were achieved (Table 32).

[0252] [Table 36]

[0253] [Table 37]

[0254] Analysis of the molding material (Table 33) shows that there is no significant accumulation of carbon, nitrogen, or sulfur in the molding material. C-containing components from the inorganic binder (e.g., surfactant) are not very significant. The low C loading is one of the main advantages of this inorganic molding material cycle, as only very low emissions are expected (see below). Despite the relatively low carbon content, the resulting surface roughness (Table 33) is comparable to that of the experiments using the cold box core sand mix (Experiment Series 2.5).

[0255] [Table 38]

[0256] 3. A molding material cycle that gradually reduces the carbon content in the molding material The purpose of these tests is to repeatedly cast and reprocess a certain amount of processed molding material, particularly while gradually reducing the carbon content in the molding material. As is customary in industrial casting practice, the molding material is one cycle. Additives are added each time the molding material is processed and accumulate with each loop. Components present in the starting molding material but no longer added are depleted, meaning that the proportion of components no longer added in subsequent loops decreases. The total amount of molding material is constant, approximately 1200 kg. Four molds are produced per loop and used for casting according to the fin model settings described (https: / / www.researchdisclosure.com / database / RD705032).

[0257] For the explanation of the experimental procedure, reference is made to the molding material cycle in FIG.

[0258] The molding material cycle loop includes the following steps:

[0259] Preparation of molding material (step (1), first loop) In the first loop, the processed mould material (starting mould material) from the mould material cycle of the brake disc casting is used (see point 0.2 above).

[0260] Using a BigBag removal station and two conveyor belts, the processed molding material is transferred from the BigBag to a bunker upstream of the Eirich mixer (Eirich Intensive Mixer R09, capacity: 150 liters, maximum 240 kg, batchwise operation under normal atmosphere). Pre-weighed additives (aggregates), bentonite, mold substrate or core material, and additives are fed onto the bunker extraction belt. The additive used is Al(OH)3, type SH950 (SH950 Nuance 00, Alteo).

[0261] Each time a molding material is produced (step (1), see FIG. 4), additives are added and accumulate with each loop. The discharge of a portion of the molding material used for casting in step (1) or step (5) of the next loop (see FIG. 4) reduces the proportion of components present in the starting molding material but no longer added.

[0262] The molding material is removed from the bunker and transported together with the aggregate into the mixer. The mixing process begins, water is automatically added, and after the mixing process is completed, the finished molding material is emptied from the mixer into a transport container. The transport container is then transported to the molding system.

[0263] The mixer program selected depending on the situation (depending on the water content of the mix) is either a mixing sequence without intermediate stops (Table 35) or a mixing sequence with intermediate stops (Table 34), with the desired compaction set at 40% + / - 5% by monitoring the water content. The desired compaction is established by monitoring the compressibility. Moldability varies with the water content of the molding material. The water content of each mix was confirmed. Because the water addition required to achieve the target compactability is unknown, intermediate stops in the mixing sequence make it easier to determine the amount of water required, and subsequent mixes can be produced without intermediate stops.

[0264] [Table 39]

[0265] [Table 40]

[0266] Mold Fabrication (Step (2) in All Loops) For this purpose, part of the volume of the bottom box of the mold is first filled with a layer of sieved molding material from a transport container, sieving enough molding material so that the outline of the fin model is no longer visible (this corresponds to a bottom box height of 80 mm and a top box height of 50 mm). The remaining volume of the bottom box is then filled with unsieved molding material. The screen has a transparent mesh size of 2 mm.

[0267] The bottom box (i.e., the molding material in the bottom box) is compressed in the HWS HSP-1D molding system using the Seiatsu airflow compression molding process with the specified parameters (Table 36, mold box size: 700 x 500 x 200 / 200 mm, model plate size: 650 x 450 x 30 mm). The time required for passing airflow through the molding material in the mold to fluidize it is called the Seiatsu time. The Seiatsu time can be set independently for the top and bottom boxes. The molding material is then compressed.

[0268] [Table 41]

[0269] The bottom box is manually flattened and removed and transported by crane to the assembly station. The top box is filled, compacted, removed, and transported in the same way. A pre-fabricated core (step (1a), see Figure 4) is inserted into the bottom box (step (2a), see Figure 4). The mold is assembled, supported, and transported to the casting station.

[0270] Casting (Step (3) in every loop) The mould is used to cast liquid metal of GJL 250 alloy at 1450°C using a ladle in an iron frame with a shear on one side.

[0271] The following molds are manufactured (steps (2), (2a)) and used for casting:

[0272] The mold used for casting is left to stand for four hours before being split, during which time the casting cools and the molding material heats up.

[0273] Split (step (4) in full loop) The upper and lower boxes are separated. The casting material and molding material used for casting are separated. The core sand is processed differently in the three molding material cycles examined.

[0274] 1. In Experiment Series A, where new sand is used as additional mould substrate, cores bonded with CO2-hardened water glass (see point 0.2 above) are used, which do not disintegrate during splitting and are completely discharged into the loop at this point.

[0275] 2. In Experiment Series B, where a cold box core was used, the central core was completely destroyed and could no longer be separated from the molding material. The core mark was not destroyed, nor could it simply be crushed. Therefore, the core mark was discharged into the loop at this point.

[0276] 3. In experiment series C, which used inorganically bonded cores (binder: Cordis 9477 / Anorgit 9476; see point 0.2), these only disintegrate at the edge layers, but can be very easily crushed by hand. Therefore, the IOB core sand is not discharged.

[0277] Processing (Full Loop Step (5)) The compound is spread on the floor and the compound lumps are broken up using a shovel. Metal residues are removed. The compound is left to cool on the hall floor for at least 3 hours. After cooling, the compound is filled into BigBags with a shovel.

[0278] Manufacturing molding material (Step (1) from the second loop onwards) New molding materials are produced by refreshing the processed molding material from the previous loop (first processed molding material) with the second processed molding material by mixing bentonite, water, additives (as defined above), and fresh mold substrate (new sand, Experimental Series A) or processed cores (Experimental Series B and C; see below for details). For the sequence of the mixing process, see details of step (1) of the first loop above.

[0279] The increase in the amount of molding material due to addition to the mixer, i.e., the increase in the amount of molding material due to the mixture defined above, is controlled by drawing off the same amount of prepared molding material in each loop.

[0280] Each time the molding material is produced (step (1)), additives are added to each loop and accumulated. The discharge of a portion of the molding material used for casting reduces the proportion of components present in the starting molding material that are no longer added in subsequent loops.

[0281] 3.1 Experimental series with mixing of fresh mold substrate (new sand) in step (1) (Experimental series A) When producing the mold (see step (2) above), a waterglass bonded core is used which is not destroyed after casting (see point 0.2 above) and which is removed as described above in step (4).

[0282] In an experimental series of 30 loops (A1-A30, see Table 37), the processed molding material from the previous loop (first processed molding material) was refreshed in each subsequent loop using a mold substrate from Grudzen Laz. Quarzwerke 0.20 / 0.315 / 0.40 type (1K class coarse quartz sand).

[0283] [Table 42]

[0284] [Table 43]

[0285] [Table 44]

[0286] [Table 45]

[0287] [Table 46]

[0288] As expected, as the number of loops increases, a gradual decrease in the loss on ignition of the samples can be observed, as less organic material is present in the molding compound. This is also indicated by a gradual decrease in the levels of carbon, nitrogen, and sulfur (Table 39), while the molding compound properties remain essentially unchanged (Table 38).

[0289] Despite the reduction in carbon content, no casting defects are observed and the surface roughness of the castings does not change significantly as a result of the reduction in carbon content (Table 40).

[0290] [Table 47]

[0291] 3.2 Experimental series with the incorporation of organically bonded core sand (Experimental series B) When the mold is manufactured (see step (2) above), a cold box core (see point 0.2 above) is inserted, which is completely broken in the center and can no longer be separated from the molding material.

[0292] In this experimental series with 30 loops (B1-B30, see Table 41), proceeding from the processed starting material from the brake disc foundry, a second processed molding material (see Figure 4) produced by processing a core produced with a cold box binder was added. In other words, in each subsequent loop, the processed molding material from the previous loop (first processed molding material) was refreshed with the second processed molding material produced by processing a core produced with a cold box binder.

[0293] [Table 48]

[0294] [Table 49]

[0295] [Table 50]

[0296] [Table 51]

[0297] [Table 52]

[0298] Molding material analysis (Table 43) shows that the loss on ignition of the molding material decreases as the number of loops increases. At the same time, the carbon (C), sulfur, and nitrogen (N) levels decrease, with the C and N levels approaching the limits determined by the mixing of the cold box bonded core sand. Here, the molding material properties remain essentially unchanged (Table 42).

[0299] In this series of experiments, the surface roughness of the castings is also determined (Table 44). It is observed that a good surface is obtained despite the reduced proportion of carbon in the molding material. No casting defects are observed.

[0300] [Table 53]

[0301] 3.3 Experimental series with inorganic bond core sand admixture (Experimental series C) When producing the mold (see step (2) above), inorganically bonded cores (binders Cordis 9477 / Anorgit 9476, see point 0.2 above) are used, which only disintegrate at the edge layers but can be crushed very easily by hand.

[0302] In this 30-loop experimental series (C1-C30, see Table 45), a second processed molding material (see Figure 4) produced by processing a core made with a water-glass binder (Anorgit / Cordis system) was added to the processed starting molding material from the brake disc casting (point 0.2). In other words, in each subsequent loop, the processed molding material from the previous loop (first processed molding material) was refreshed with the second processed molding material produced by processing a core made with a water-glass binder (Anorgit / Cordis system).

[0303] [Table 54]

[0304] [Table 55]

[0305] [Table 56]

[0306] [Table 57]

[0307] [Table 58]

[0308] The experiments clearly show that as the exchange of molding material increases, the ignition loss and the carbon, nitrogen and sulfur levels gradually decrease (Table 47), while the molding material properties remain essentially unchanged (Table 46).

[0309] Despite the reduced carbon content, no casting defects are observed and the surface roughness of the castings does not change as a result of the reduced carbon content (Table 48).

[0310] [Table 59]

[0311] 3.4 Landfill Class of Processing Molding Materials The processed molding materials from all three experimental series were examined after the 30th loop (A-30, B-30 or C-30), and the obtained values ​​were compared with those of the starting molding materials (Table 49; the abbreviation NG indicates that the measured value is below the detection limit). The findings were as follows:

[0312] Under the German Ordinance on Landfill and Long-Term Storage (Deponieverordnung) of July 4, 2020, processed starting molding material (starting sand) should be classified as Landfill Class II based on its loss on ignition, TOC (total organic carbon), and its phenolic index. The processed molding material from Experimental Series B cannot be classified as Landfill Class I because its TOC is only slightly too high and should therefore be classified as Landfill Class II, although further reduction of the TOC is possible by continuous replacement or use of different cold box binders.

[0313] The processed molding materials from Experimental Series A and C are covered by Landfill Class I.

[0314] [Table 60]

[0315] [Table 61]

[0316] 3.5 BTX release potential of processed molding materials The starting molding materials from the conditioned molding material loops of the brake disc castings and the molding materials from loops A-30, B-30, and C-30 were investigated for their BTX release potential. For this purpose, the samples were dried at 105 ° C and then ground in a planetary ball mill (Retsch Planetary Ball Mill PM100CM) at 300 rpm for 2 minutes under low-temperature conditions (container: 150 ml stainless steel cup with stainless steel balls). Cooled at -20 ° C for at least 12 hours; i.e., the grinding cup of the planetary ball mill was stored at -20 ° C for at least 12 hours before use to avoid excessive heating of the sample during the grinding operation. Then, 10 mg of sample was weighed into a pyrolysis tube. Each sample was determined in duplicate. Measurements were performed using the following equipment: GERSTEL MPS GERSTEL TDU 2 with pyrolysis module Agilent 8890B gas chromatograph with Agilent 5977 mass spectrometer RESTEK 13868 RXI-624Sil MS Capillary Column, -60°C to 300°C (320°C): 30m x 250µm x 1.4 0.25mm 150ml stainless steel grinding beaker and stainless steel grinding balls Hamilton Electronic Holder (VWR Technology Number HAMIDS86200) Hamilton 1 μl syringe (VWR Technical No. 549-1224) Carbotrap B filled glass inlet liner (up to 450°C) (Gerstel Technology No. 013248-005-00) ·Quartz pyrolysis tube (Gerstel equipment number 018437-020-00) Carbopack™ B, 60-80 net sorbent matrix (VWR Technology No. SUPL20273) Glass wool, silane treated (VWR technical number SERA22367.01)

[0317] The following conditions are observed:

[0318] Gas Chromatography (GC) Parameters

[0319] [Table 62]

[0320] PTV parameters (PTV = Programmed Temperature Vaporization System - i.e. the sample is pyrolyzed, the pyrolysis gases are condensed and then vaporized for GC analysis)

[0321] [Table 63]

[0322] Calibration Method: MSD parameters (MSD = Mass Spectrometric Detector)

[0323] [Table 64]

[0324] TDU parameters (TDU = Thermal Desorption Unit)

[0325] [Table 65]

[0326] Pyrolysis parameters

[0327] [Table 66]

[0328] Calibration was performed using standards based on benzene, toluene; m- and p-xylene; styrene; o-xylene; ethylbenzene, cumene.

[0329] Sample Method: MSD parameters

[0330] [Table 67]

[0331] TDU Parameters

[0332] [Table 68]

[0333] Pyrolysis parameters

[0334] [Table 69]

[0335] Method indicators

[0336] [Table 70]

[0337] The evaluation was performed using MassHunter software.

[0338] The results shown in Table 50 clearly demonstrate that the use of the additives of the present invention can significantly reduce pollutant emissions. The emission potential is significantly reduced, especially in combination with inorganic cores or when fresh mold substrate (new sand) is fed into the molding material cycle. A clear effect is also seen when cold box core sand is fed. In the model, the emission potential is reduced by more than 45%.

[0339] [Table 71]

[0340] In Table 50, "<..." means that the content of the BTEX compound of interest is below its detection limit.

[0341] Regarding the range of values ​​for the "BTEX at 900°C" row: The lower limit corresponds to the sum of the contents of BTEX compounds above the respective detection limit, a value which could be determined (in the case of the starting molding material these are benzene, toluene, ethylbenzene and m-, p-xylene).

[0342] The upper limit corresponds to the sum of the lower limit and the detection limit of each BTEX compound having a content below the respective detection limit (in the starting molding material these are o-xylene, styrene and cumene).

Claims

1. 1. A method for reducing carbonaceous emissions and / or carbonaceous casting defects in a molding material cycle comprising two or more loops having a molding material comprising a smectite-containing clay, comprising: - reducing the carbon content in the molding material produced in the subsequent loop so that the molding material has a lower carbon content than the molding material produced in the previous loop; - adding, in one or more subsequent loops of the two or more loops of the molding material cycle, an additive containing at least one dehydratable inorganic compound that removes water at a temperature of 150°C or higher; A method comprising:

2. Steps below: - in a previous loop of the two or more loops of the molding material cycle, a step of casting in a mold containing the smectite clay-bonded molding material to obtain a molding material used for casting; - processing the molding material used for casting in the previous loop so that the processed molding material contains carbon and a first processed molding material is obtained; In the latter loop of the two or more loops of the molding material cycle: (i) First processed molding material and (ii) an aggregate, - the additive as defined in claim 1, and -below: - Mold substrate - a second processed molding material produced by processing molding material from molds and / or cores and / or parts thereof that were not used for casting, - a third processed molding material produced by processing the mold and / or core and / or part thereof used for casting outside the molding material cycle; - optionally smectite-containing clays, One or more raw materials selected from the group consisting of Aggregates containing producing a molding material comprising: a method comprising:

10. The method of claim 1, wherein the molding material is produced to have a lower carbon concentration than the molding material produced in the previous loop.

3. the additive comprises one or both of a compound selected from the group consisting of aluminum hydroxide and magnesium hydroxide; 3. The method according to claim 1 or 2, wherein the molding material is preferably produced in the subsequent loop such that the produced molding material contains a higher total concentration of aluminum hydroxide and / or magnesium hydroxide than the first processed molding material from the previous loop.

4. 4. The method of claim 1, wherein the processed molding material from the previous loop comprises at least one glassy carbon former and / or the carbonaceous reaction product formed during casting.

5. 5. The method according to claim 1, wherein the further mixture added to the subsequent loop for producing the molding material is carbon in the form of one or more glassy carbon formers, and the total mass of carbon supplied together with the glassy carbon formers is less than the total mass of carbon removed in the previous loop by evacuation and evacuation of the molding material.

6. 6. The method according to any one of claims 1 to 5, wherein the carbon content in the molding material is gradually reduced over two loops, preferably over at least 10 loops, more preferably over at least 15 loops.

7. 7. The method according to claim 1, wherein the casting in the front loop is carried out in a mold having at least one inserted core.

8. The method of claim 7, wherein the core is made with an organic binder or made with an inorganic binder.

9. the core used for casting in the previous loop is manufactured using an organic binder; 9. The method according to claim 7, wherein the molding material produced in the subsequent loop comprises carbon, with at least 70% by weight, preferably at least 80% by weight, more preferably at least 90% by weight, and most preferably at least 95% of the carbon being from the organic binder of the cores used and unused in the casting.

10. 10. The method according to any one of claims 1 to 9, wherein the proportion of aluminium hydroxide is at least 80%, preferably at least 90%, more preferably at least 95%, and most preferably 99%, based on the total mass of aluminium hydroxide and magnesium hydroxide in the additive.

11. 7. The method according to claim 1, wherein the casting is carried out in the former loop in a mold without a core inserted therein.

12. The method according to any one of claims 1 to 11, wherein the recycled molding material is used for the production of iron casting molds.

13. 13. The method according to claim 1, comprising a step of reducing the sulfur content in the molding material so that the molding material produced in a subsequent loop has a lower sulfur content than the molding material produced in a previous loop.

14. Use of an additive as defined in claim 1 in a method according to any one of claims 1 to 13.

15. 10. Use of an additive as defined in claim 1 as a replacement for glassy carbon formers in smectite clay-bonded molds for iron casting.

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