EP1425121B1 - Method for producing castings, molding sand and its use for carrying out said method - Google Patents

Method for producing castings, molding sand and its use for carrying out said method Download PDF

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Publication number
EP1425121B1
EP1425121B1 EP02772298A EP02772298A EP1425121B1 EP 1425121 B1 EP1425121 B1 EP 1425121B1 EP 02772298 A EP02772298 A EP 02772298A EP 02772298 A EP02772298 A EP 02772298A EP 1425121 B1 EP1425121 B1 EP 1425121B1
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EP
European Patent Office
Prior art keywords
casting
moulding material
casting mould
cited
binding agent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP02772298A
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German (de)
French (fr)
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EP1425121A1 (en
Inventor
Bernhard Stauder
Walter Gintner
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Hydro Aluminium Mandl and Berger GmbH
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Hydro Aluminium Mandl and Berger GmbH
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Filing date
Publication date
Priority claimed from DE10145417A external-priority patent/DE10145417A1/en
Priority claimed from DE10209224A external-priority patent/DE10209224A1/en
Priority claimed from DE10209183A external-priority patent/DE10209183A1/en
Application filed by Hydro Aluminium Mandl and Berger GmbH filed Critical Hydro Aluminium Mandl and Berger GmbH
Publication of EP1425121A1 publication Critical patent/EP1425121A1/en
Application granted granted Critical
Publication of EP1425121B1 publication Critical patent/EP1425121B1/en
Anticipated expiration legal-status Critical
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
    • B22C1/08—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives for decreasing shrinkage of the mould, e.g. for investment casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
    • B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/10—Cores; Manufacture or installation of cores
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/12—Treating moulds or cores, e.g. drying, hardening

Definitions

  • the invention relates to a method for producing castings from a molten metal, in particular a light metal melt, such as molten aluminum.
  • the invention relates to a molding material and its use for the production of moldings, which are used for the casting of molten metal, in particular light metal melt, such as molten aluminum.
  • mold parts may be, for example, by casting cores through which cavities in the interior of the be formed to be produced casting.
  • casting mold parts according to the invention may be components from which a multi-part casting mold is assembled, by means of which the outer shape of the casting to be produced is determined.
  • such casting parts can be casting cores, through which cavities are formed in the interior of the casting to be produced, or casting mold elements that make up a multi-part casting mold is composed, which determines the outer shape of the casting to be produced.
  • molding material systems are generally used, which are composed of a molding material and a binder. These two components are mixed together, shaped and processed into a compact body in a suitable curing process.
  • the molding material used is usually quartz sand, which is bound in the majority of applications with an organic binder.
  • quartz sand as a raw material for the production of mold parts has proven itself in many ways, especially in the field of casting of light metal materials.
  • quartz sand can be obtained inexpensively and is characterized by a simple processability and a good quality in the image of the mold elements of each mold part to be produced.
  • the molding material used for the production of the moldings must have high strength and dimensional accuracy, which is maintained even when occurring during the construction of the mold and the casting of the melt loads.
  • the molding material should be removed easily after pouring. The latter proves to be particularly important when casting cores are used, which form in the casting complex shaped interiors.
  • the molding materials should be so regenerable after use that the mold base material as high a rate of reuse is achieved. This can be achieved in a manner known per se by using inorganic binders which release low emissions during the production of the moldings and can be incinerated almost without residue after the end of the casting process by the action of sufficiently high temperatures.
  • DE 44 46 352 A discloses a casting core composition
  • a casting core composition comprising refractory grains consisting essentially of mullite, which have a substantially spherical shape, and a binder for binding the refractory grains.
  • the binder used in the known casting core composition is an organic binder, in particular a thermosetting resin such as phenolic resin.
  • From JP 54 004817 A is a self-hardening molding sand, consisting of quartz sand and, as a binder, water glass known.
  • the known molding sand further contains fireclay particles, in particular mullite fireclay particles.
  • JP 07 164102 A discloses a casting mold, in particular a casting core, which is produced from a molding base material and a thermosetting resin.
  • a casting mold in particular a casting core, which is produced from a molding base material and a thermosetting resin.
  • existing free spaces are then filled under pressure with a filler between the sand and resin binder components.
  • the filling material may in particular consist of a refractory material and an inorganic liquid material of water glass. In this way, the temperature and pressure resistance of the known mold to the molten metal to be increased.
  • JP 55 084251 A a casting method is known in which a molded part is produced using an organic binder.
  • the parts of the casting mold which depict regions of the casting of large thickness, are replaced by a molding material of a molding sand and a water glass binder. In this way, high temperature cracks due to different cooling rates in the casting should be avoided.
  • the known molding material systems regardless of whether they contain organic or inorganic binders, have the properties required for an optimum working result under normal conditions Especially with thin-walled moldings, as used for example for the casting of engine blocks or cylinder heads as forming cores for oil channels, it may come as a result of unavoidable thermal expansion that the requirements for dimensional accuracy of the casting are no longer met.
  • Another problem with casting complex molded castings using conventionally made mold parts is that the sand is difficult to remove from the casting after cooling.
  • the casting is shaken or subjected to shocks that cause disintegration of the casting cores located in the interior of the casting and the outside adhering to the casting moldings and promote trickling out of the resulting molding material particles.
  • these mechanical methods of removing the moldings involve the risk of damaging the casting. This can lead to cracking, especially with filigree or thin-walled components.
  • the object of the invention was to provide a method by which can produce high quality, complex molded castings and in which after completion of the casting process, the mold parts can be removed easily and safely from or from the casting.
  • a molding material should be provided, with which moldings can be produced which are suitable for producing high-quality, complex-shaped castings and can be removed after completion of the casting process in a simple manner and safely from or from the casting.
  • the invention is based on the recognition that it is possible by the choice of a suitable molding material to produce casting moldings which optimally combine the properties required for the simple, safe and environmentally friendly production of high-quality, dimensionally stable castings.
  • the molding material according to the invention contains a granular or comparable particle-like form present and as such free-flowing base material, which exhibits a significantly low thermal expansion compared to conventionally used quartz sand during its warming unavoidably occurring during the casting.
  • the molding material thus ensures a high dimensional stability in the production of complex molded castings even with low material thickness.
  • the free-flowing in the unbound state base material is mixed with a binder, which has a different from the base expansion behavior when heated. Due to the different thermal expansion of mold base and binder occurs after the heat input from the casting heat to detach the binder from the grains of the molding material. As a result, therefore, when the binder expands more than the base, the binder breaks up so that it loses its solid shape and can be easily removed from the casting. Conversely, the expansion behavior of the molding base material can be such that the binding to the binder is broken by a change in volume associated with the heating and the base material again becomes free-flowing. It is essential that it comes along with the heating to break up the core or mold component, so that this has decayed after cooling of the casting in easily removable, loose items.
  • the thermal expansion behavior of the molding material according to the invention in accordance with the invention is adapted to the thermal expansion behavior of the molten metal to be cast and by simultaneously this molding material based on a produced free-flowing base material, it is achieved that after cooling of the casting each of the casting at least partially encompassed or adjacent to the casting molding is broken due to the forces occurring in the course of cooling into loose individual pieces that can be easily removed.
  • the fracture of the mold parts is effected by the forces occurring as a result of the different expansion of cast metal and mold material.
  • the invention affects the casting of components made of aluminum melts.
  • Aluminum has a high coefficient of thermal expansion, so that in the course of pouring and solidification of the melt on the molded parts in contact with the molded parts so high forces are exerted that the relevant molding safely breaks into smaller parts. This proves to be particularly favorable when the molding is a core mold.
  • a further feature of the molding material obtained and used according to the invention which is favorable for the invention is that the binder and mold base material are coordinated so that the particles of the base material are thermally stable and not elastically bound by the binder in the molded parts produced from the molding material.
  • the molded part produced from a molded base material of this kind behaves brittle over the entire temperature interval during the casting of the melt, which promotes the breaking of the molded parts which is desirable according to the invention.
  • the binder of the moldings is preferably chosen so that it does not decompose by the action of heat. In this way it is avoided that volumes are released in the core, which could lead to a according to the invention undesirable flexibility of the molding in question.
  • a further advantageous embodiment of the invention consists in that the particles of the molding base material have a substantially round, spherical shape.
  • the spherical shape of the molding material and the associated prevalence of point contacts between the mold base particles promotes the automatic disintegration of the moldings as a result of the mechanical forces occurring during casting and solidification of the melt.
  • a molding material that meets this requirement particularly well is synthetically produced mullite.
  • a further advantageous embodiment of the invention provides that the mold base material more than 50%, preferably more than 70% of the quartz sand subsituierende alumina sand (mullite) has.
  • Mullite has a round grain shape and a density comparable to quartz sand.
  • the moldings produced therefrom are much easier to process than, for example, known ZrO 2 sands.
  • the spherical spherical shape of the mullite particles in practice leads to a simplified processability of the molded materials produced from such molding base materials and concomitantly to a reduced wear of the tools and machines used for the production of moldings , About it owns a molding material with high Due to its low thermal expansion, mullite has a high degree of dimensional stability in the production of complex shaped castings even with low material thickness.
  • molding material composed according to the invention is particularly suitable for the production of casting cores. These can be removed after casting without the risk of damaging the finished casting.
  • a molding base material composed of a mullite quartz sand mixture and a molding material produced therefrom have a rather insulating effect. Therefore, these substances can be used specifically for such casting applications, where it comes to a temperature above the critical for quartz sands temperature of 573 ° C warming, but in which the thermal conductivity of the molded parts produced from the substances concerned plays a minor role or the heat conduction should be deliberately restricted.
  • molding material binder and base material are also preferably matched to one another such that a molded part produced from the molding material has a low thermal conductivity. This property causes that after the casting of the molten metal, the temperature difference between the casting material and the molded part remains large, so that the risk of premature thermally or chemically induced decomposition of the molded part is reduced to a minimum.
  • the disintegration of the casting cores can be assisted by matching the constituents of the molding material so that the molding base and binder expand differently when heated, with the result that the bonds between them break during a heating associated with the casting of the melt.
  • the invention can be realized in a particularly practical manner by processing a molding material which consists of a mixture of one in granular or comparable particle-like form and as such free-flowing base material and an inorganic binder is formed.
  • inorganic binders are their better environmental compatibility and the fact that the moldings produced with such binders can be easily recycled into the cycle of the molding material.
  • molding materials which have been mixed out of a water glass-based binder and a molding base material composed according to the invention have proven particularly suitable. It is essential, however, that the expansion behavior of the mixed components sufficiently different from each other.
  • mold base material and binder expand differently. In this case, it comes after the heat input from the casting heat to detach the binder from the grains of the molding material. For example, if the binder expands more than the base material, it breaks up the molding so that it loses its solid shape and breaks up into fragments. These can easily be shaken off or from the casting without the risk of mechanical damage.
  • the binder expands more than the base material, it breaks up the molding so that it loses its solid shape and breaks up into fragments. These can easily be shaken off or from the casting without the risk of mechanical damage.
  • essential for the fact that it comes in this variant to the inventively desired automatic disintegration of the molding consequently, the different thermal expansion of mold base and binder in the way that under the action of Gietihitze the binder as a result of resulting between mold base and binder thermal stresses from the mold base particles flakes off or breaks in itself.
  • the respective casting mold part is also produced in the process according to the invention by injecting a molding material mixture composed according to the invention into the core box of a core molding machine in a known manner. Subsequently, the molding material is cured, for example, according to the method described in DE 196 32 293 Al, by applying to the mold of the core box heated to a temperature of 100 ° C to 160 ° C, a negative pressure and the core molding over a period of 20 to 30 seconds is heated by the core box.
  • the mold part becomes so strong that it can be taken out of the core box and set in a heater outside the core box, for example, a microwave oven.
  • a heater outside the core box, for example, a microwave oven.
  • it is heated sufficiently with sufficient heat output that it is withdrawn sufficient for complete curing amount of water.
  • the removal of water can also be achieved by sufficient heating of the core box itself or by hot-air gassing respectively. These measures can each be combined with a heating taking place outside the core box. It is likewise possible to effect the removal of water by means of microwave heating acting directly on the core molding still located in the core box.
  • the respective molded part can be sprayed with binder liquid to increase the core surface strength.
  • the moldings treated in this way have an increased stability with likewise increased abrasion resistance, so that they can be stored without problems and meet the highest demands on their dimensional accuracy. This proves to be particularly favorable with regard to an optimized quality of the casting to be produced when a water glass binder is used.
  • Two recesses are formed in the underside of the camshaft core at a distance from one another in the longitudinal direction, by means of which the shape of the bearing blocks of the cylinder head to be produced for the purpose of supporting the camshaft is determined.
  • the recesses extends in each case a branch of an extending with its main portion parallel and at a distance from the camshaft core ⁇ lkanalkerns.
  • the length of the branches is many times bigger than theirs Diameter.
  • the length of the main portion of the oil channel core is many times greater than its diameter.
  • the oil channel core has been prepared in a conventional manner in a conventional form-casting machine from a molding material according to the invention, which has been produced by mixing a molding material consisting of mullite sand and quartz sand with a Wasserglaabinder. Due to the proportion of mullite sand is ensured that the Olkanalkern evenly and thus clearly unambiguously expands even when it rises in the course of the casting of the cylinder head to above 573 ° C heating.
  • the casting cores deform due to the invention in accordance with wise matched characteristics of mold base and binder only slightly.
  • the low thermal expansion of Formgrunastoffs thus supports the process reliable achievement of the dimensional requirements of the casting.
  • the respective casting core is subjected to high mechanical stresses as a result of the considerably higher solid contraction of the casting metal compared with the casting cores.
  • the treatment of the G confusekernbruch Swisse may include a gentle breaking into granular particles. Then, the obtained granular particles may be subjected to metal deposition and dedusting to restore the condition necessary for their reuse. Subsequently, the molded parts recycled to granular material are again used as the base material for the molding material composed according to the invention.
  • molding materials are used in accordance with the invention which consist of mold base material mixed with waterglass binder, such as synthetic mullite, no appreciable emissions occur during the production of the moldings. This can be avoided in conventional procedure as a result of gas formation recurring casting defects, extensive provisions for the extraction of gases and complex tool cleaning. Pollution of the environment and the operating staff are reduced to a minimum.
  • mullite or a comparable inert refractory material is used as the base material of the molding material system according to the invention
  • another advantage of the invention is the chemical resistance of the molding material to binder and melt. This feature ensures that in the inventive procedure, a casting is obtained, the surface of which, after the emptying of the fragments of the mandrels and moldings without additional cleaning measures is completely free of Restsandanhaftept.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mold Materials And Core Materials (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
  • Powder Metallurgy (AREA)

Abstract

The invention provides a method with which high-quality complex-shaped castings can be manufactured and with which, after the end of the casting process, the casting mould parts can be easily removed out of or from the casting without any risk. To achieve this the following steps are carried out: Manufacture of a mould material by mixing of a basic mould material, inert in comparison with the molten metal and pourable, which under heating expands less than quartz sand, and a binding agent, which under heating expands differently in comparison with the basic mould material, the manufacture of a casting mould part from the mould material, assembly of a casting mould making use of the casting mould part, pouring of the molten metal into the casting mould to form a casting, cooling of the casting over a solidification and cooling period, in which the casting mould part disintegrates self-actingly into fragments, removal of the fragments of the casting mould part from or out of the casting, and reprocessing of the fragments of the mould material to form a pourable basic mould material.

Description

Die Erfindung betrifft ein Verfahren zum Herstellen von Gussstücken aus einer Metallschmelze, insbesondere einer Leichtmetallschmelze, wie Aluminiumschmelze.The invention relates to a method for producing castings from a molten metal, in particular a light metal melt, such as molten aluminum.

Darüber hinaus betrifft die Erfindung einen Formstoff und seine Verwendung für die Herstellung von Gießformteilen, die für das Abgießen von Metallschmelze, insbesondere von Leichtmetallschmelze, wie Aluminiumschmelze, eingesetzt werden- Bei derartigen Gießformteilen kann es sich beispielsweise um Gießkerne handeln, durch welche Hohlräume im Innern des zu erzeugenden Gussteils ausgebildet werden. Ebenso kann es sich bei erfindungsgemäßen Gießformteilen um Bauelemente handeln, aus denen eine mehrteilige Gießform zusammengesetzt wird, durch die die Außenform des zu erzeugenden Gussteils bestimmt wird.In addition, the invention relates to a molding material and its use for the production of moldings, which are used for the casting of molten metal, in particular light metal melt, such as molten aluminum. Such mold parts may be, for example, by casting cores through which cavities in the interior of the be formed to be produced casting. Likewise, casting mold parts according to the invention may be components from which a multi-part casting mold is assembled, by means of which the outer shape of the casting to be produced is determined.

Bei der gießtechnischen Herstellung von Bauteilen aus Metall werden Gießformteile benötigt, durch die einerseits die innere und andererseits die äußere Form des zu gießenden Werkstücks bestimmt wird. Bei derartigen Gießformteilen kann es sich dementsprechend um Gießkerne, durch welche Hohlräume im Innern des zu erzeugenden Gussteils ausgebildet werden, oder um Gießformelemente handeln, aus denen eine mehrteilige Gießform zusammengesetzt wird, welche die Außenform des zu erzeugenden Gussteils bestimmt.In the casting production of components made of metal casting moldings are required by the one hand, the inner and on the other hand, the outer shape of the workpiece to be cast is determined. Accordingly, such casting parts can be casting cores, through which cavities are formed in the interior of the casting to be produced, or casting mold elements that make up a multi-part casting mold is composed, which determines the outer shape of the casting to be produced.

Zur Herstellung von Gießformteilen werden in der Regel Formstoffsysteme eingesetzt, die aus einem Formgrundstoff und einem Bindemittel zusammengesetzt sind. Diese beiden Komponenten werden miteinander vermischt, geformt und in einem geeigneten Aushärteprozess zu einem kompakten Körper verarbeitet. Als Formgrundstoff kommt dabei üblicherweise Quarzsand zum Einsatz, der in der überwiegenden Zahl der Anwendungen mit einem organischen Bindemittel gebunden wird.For the production of moldings molding material systems are generally used, which are composed of a molding material and a binder. These two components are mixed together, shaped and processed into a compact body in a suitable curing process. The molding material used is usually quartz sand, which is bound in the majority of applications with an organic binder.

Die verwendung von Quarzsand als Grundstoff für die Herstellung von Gießformteilen hat sich insbesondere im Bereich des Vergießens von Leichtmetallwerkstoffen in mehrfacher Hinsicht bewährt. So lässt sich derartiger Quarzsand kostengünstig beschaffen und zeichnet sich durch eine einfache Verarbeitbarkeit und eine gute Qualität bei der Abbildung der Formelemente des jeweils zu erzeugenden Gießformteils aus.The use of quartz sand as a raw material for the production of mold parts has proven itself in many ways, especially in the field of casting of light metal materials. Thus, such quartz sand can be obtained inexpensively and is characterized by a simple processability and a good quality in the image of the mold elements of each mold part to be produced.

Als umweltverträglichere Alternative zu organischen Bindern ist die verwendung von Bindern auf Wasserglasbasis vorgeschlagen worden. Dieser Wasserglasbinder wird mit dem Formsand vermischt. Das erhaltene Gemisch wird dann in den Formkasten einer Formmaschine geschossen, in dem ein die Form des herzustellenden Formteils abbildender Hohlraum ausgebildet ist. Anschließend wird dem in die Form gegebenen Gemisch durch Wärmezufuhr Wasser entzogen. Die Wärmezufuhr kann dabei über eine entsprechende Beheizung des Formkastens oder durch eine direkt auf das Gemisch wirkende Mikrowellenheizung erfolgen (WO-A-86/00033, EP 0 917 499 B1, DE 196 32 293 A1).As a more environmentally acceptable alternative to organic binders, the use of water glass based binders has been proposed. This water glass binder is mixed with the molding sand. The resulting mixture is then shot into the molding box of a molding machine in which a cavity forming the shape of the molded article is formed. Subsequently, the mixture introduced into the mold is deprived of water by the addition of heat. The heat can be through a corresponding heating of the mold box or by a direct on the mixture acting microwave heating done (WO-A-86/00033, EP 0 917 499 B1, DE 196 32 293 A1).

Um ein optimales Arbeitsergebnis beim Abgießen der Metallschmelze zu gewährleisten, muss der zur Herstellung der Gießformteile eingesetzte Formstoff eine hohe Festigkeit und Maßtreue besitzen, die auch bei während des Baus der Gießform und dem Abgießen der Schmelze auftretenden Belastungen erhalten bleibt. Darüber hinaus soll sich der Formstoff nach dem Abgießen auf einfache Weise entfernen lassen. Letzteres erweist sich insbesondere dann als besonders wichtig, wenn Gießkerne eingesetzt werden, die in dem Gussteil komplex geformte Innenräume ausbilden.In order to ensure an optimal work result when pouring the molten metal, the molding material used for the production of the moldings must have high strength and dimensional accuracy, which is maintained even when occurring during the construction of the mold and the casting of the melt loads. In addition, the molding material should be removed easily after pouring. The latter proves to be particularly important when casting cores are used, which form in the casting complex shaped interiors.

Schließlich sollen die Formstoffe nach Gebrauch so regenerierbar sein, dass beim Formgrundstoff eine möglichst hohe Quote der Wiederverwendung erreicht wird. Dies lässt sich in an sich bekannter Weise durch Verwendung von anorganischen Bindern erreichen, die während der Herstellung der Formteile geringe Emissionen freisetzen und nach Beendigung des Gießvorgangs durch Einwirken von ausreichend hohen Temperaturen annähernd rückstandslos verbrannt werden können.Finally, the molding materials should be so regenerable after use that the mold base material as high a rate of reuse is achieved. This can be achieved in a manner known per se by using inorganic binders which release low emissions during the production of the moldings and can be incinerated almost without residue after the end of the casting process by the action of sufficiently high temperatures.

Aus der DE 44 46 352 A ist eine Gießkernzusammensetzung mit.im Wesentlichen aus Mullit bestehenden feuerfesten Körnern, die eine im Wesentlichen sphärische Gestalt besitzen und einem Bindemittel zum Binden der feuerfesten Körner bekannt. Als Bindemittel kommt bei der bekannten Gießkernzusammensetzung ein organisches Bindemittel, insbesondere ein wärmehartbares Harz, wie Phenolharz, zum Einsatz.DE 44 46 352 A discloses a casting core composition comprising refractory grains consisting essentially of mullite, which have a substantially spherical shape, and a binder for binding the refractory grains. The binder used in the known casting core composition is an organic binder, in particular a thermosetting resin such as phenolic resin.

Aus der JP 54 004817 A ist ein selbsthärtender Formsand, bestehend aus Quarzsand und, als Binder, Wasserglas bekannt. Um eine Reaktion des Siliciumoxids des Quarzsands mit dem Natriumoxid des wasserglases zu Glas zu verhindern, enthält der bekannte Formsand weiterhin Schamotteteilchen, insbesondere Mullit-Schamotteteilchen.From JP 54 004817 A is a self-hardening molding sand, consisting of quartz sand and, as a binder, water glass known. In order to prevent a reaction of the silica of the quartz sand with the sodium oxide of the water glass to glass, the known molding sand further contains fireclay particles, in particular mullite fireclay particles.

Weiterhin ist aus der JP 07 164102 A eine Gießform, insbesondere ein Gießkern, bekannt, der aus einem Formgrundstoff und einem wärmehärtbaren Harz hergestellt wird. Bei der bekannten Gießform werden zwischen den Sand- und Harzbinderkomponenten bestehende Freiräume anschließend unter Druck mit einem Füllmaterial gefüllt. Das Füllmaterial kann insbesondere aus einem feuerfesten Material und einem anorganischen flüssigen Material aus Wasserglas bestehen. Auf diese Weise soll die Temperatur- und Druckbeständigkeit der bekannten Gießform gegenüber der Metallschmelze erhöht werden.Furthermore, JP 07 164102 A discloses a casting mold, in particular a casting core, which is produced from a molding base material and a thermosetting resin. In the known mold existing free spaces are then filled under pressure with a filler between the sand and resin binder components. The filling material may in particular consist of a refractory material and an inorganic liquid material of water glass. In this way, the temperature and pressure resistance of the known mold to the molten metal to be increased.

Schließlich ist aus der JP 55 084251 A ein Gießverfahren bekannt, bei dem ein Gießformteil unter Verwendung eines organischen Binders hergestellt wird. Dabei werden die Teile der Gießform, die Bereiche des Gussstücks großer Dicke abbilden, durch einen Formstoff aus einem Formsand und einem wasserglasbinder ersetzt. Auf diese weise sollen Hochtemperaturrisse aufgrund unterschiedlicher Abkühlraten in dem Gussstück vermieden werden.Finally, from JP 55 084251 A, a casting method is known in which a molded part is produced using an organic binder. In this case, the parts of the casting mold, which depict regions of the casting of large thickness, are replaced by a molding material of a molding sand and a water glass binder. In this way, high temperature cracks due to different cooling rates in the casting should be avoided.

In der praktischen Anwendung zeigt sich, dass die bekannten Formstoffsysteme unabhängig davon, ob organische oder anorganische Binder enthalten, unter üblichen Bedingungen die für ein optimales Arbeitsergebnis erforderlichen Eigenschaften besitzen-Doch besonders bei dünnwandigen Formteilen, wie sie beispielsweise für das Gießen von Motorblöcken oder Zylinderköpfen als Formkerne für ölkanäle eingesetzt werden, kann es in Folge unvermeidbarer Wärmeausdehnung dazu kommen, dass die Anforderungen an die Maßhaltigkeit des Gussteils nicht mehr erfüllt werden.In practical application, it can be seen that the known molding material systems, regardless of whether they contain organic or inorganic binders, have the properties required for an optimum working result under normal conditions Especially with thin-walled moldings, as used for example for the casting of engine blocks or cylinder heads as forming cores for oil channels, it may come as a result of unavoidable thermal expansion that the requirements for dimensional accuracy of the casting are no longer met.

Ein weiteres Problem beim Abgießen von komplex geformten Gussstücken unter Verwendung von konventionell hergestellten Gießformteilen besteht darin, dass sich der Sand nach der Abkühlung nur schwer aus dem Gussteil entfernen lässt. Üblicherweise wird das Gussteil dazu geschüttelt oder Schlägen ausgesetzt, die einen Zerfall der im Innern des Gussteils befindlichen Gießkerne und der Außen an dem Gussteil haftenden Formteile bewirken und das Herausrieseln der erhaltenen Formstoffpartikel fördern sollen. Diese mechanischen Verfahren zum Entfernen der Formteile bringen jedoch die Gefahr einer Beschädigung des Gussteils mit sich. So kann es insbesondere bei filigran geformten oder dünnwandigen Bauteilen zu Rissbildungen kommen.Another problem with casting complex molded castings using conventionally made mold parts is that the sand is difficult to remove from the casting after cooling. Usually, the casting is shaken or subjected to shocks that cause disintegration of the casting cores located in the interior of the casting and the outside adhering to the casting moldings and promote trickling out of the resulting molding material particles. However, these mechanical methods of removing the moldings involve the risk of damaging the casting. This can lead to cracking, especially with filigree or thin-walled components.

Es ist daher vorgeschlagen worden, anstelle mechanisch auf das Gussteil einwirkender Maßnahmen das Gussstück so stark zu erhitzen, dass der Binder verbrennt bis allein der Formgrundstoff zurückbleibt und als rieselfähiges Material leicht aus und von dem Gussteil entfernt werden kann. Der dazu erforderliche apparative Aufwand ist erheblich. Darüber hinaus sind die für das Verbrennen des Binders erforderlichen Temperaturen so hoch, dass mit der Erwärmung unvermeidbar auch eine Änderung der Eigenschaften des metallischen Gussstücks verursacht wird.It has therefore been proposed, instead of mechanically acting on the casting measures the casting to heat so much that the binder burns until the mold base material alone remains and can be easily removed as a free-flowing material and from the casting. The required equipment is considerable. In addition, the temperatures required for burning the binder are so high that the heating inevitably causes a change in the properties of the metallic casting.

Aufgabe der Erfindung war es, ein Verfahren anzugeben, mit welchem sich qualitativ hochwertige, komplex geformte Gussstücke herstellen lassen und bei dem nach Beendigung des Gießvorgangs die Gießformteile auf einfache Weise und gefahrlos aus bzw. von dem Gussstück entfernt werden können. Darüber hinaus sollte ein Formstoff zur Verfügung gestellt werden, mit welchem sich Formteile herstellen lassen, die zur Erzeugung qualitativ hochwertiger, komplex geformter Gussstücke geeignet sind und sich nach Beendigung des Gießvorgangs auf einfache Weise und gefahrlos aus bzw. von dem Gussstück entfernen lassen.The object of the invention was to provide a method by which can produce high quality, complex molded castings and in which after completion of the casting process, the mold parts can be removed easily and safely from or from the casting. In addition, a molding material should be provided, with which moldings can be produced which are suitable for producing high-quality, complex-shaped castings and can be removed after completion of the casting process in a simple manner and safely from or from the casting.

Diese Aufgabe wird in Bezug auf das Verfahren erfindungsgemäß durch ein Verfahren gemäß Patentanspruch 1 gelöst.This object is achieved in relation to the method according to the invention by a method according to claim 1.

In Bezug auf die vorrichtung wird die voranstehend genannte Aufgabe durch einen Formstoff gemäß Patentanspruch 6 gelöst.With respect to the device, the above object is achieved by a molding material according to claim 6.

Die Erfindung basiert auf der Erkenntnis, dass sich durch die Wahl eines geeigneten Formstoffs Gießformteile erzeugen lassen, die in optimaler Weise die für die einfache, sichere und umweltfreundliche Herstellung von hochwertigen, maßhaltigen Gussteilen erforderlichen Eigenschaften miteinander verbinden.The invention is based on the recognition that it is possible by the choice of a suitable molding material to produce casting moldings which optimally combine the properties required for the simple, safe and environmentally friendly production of high-quality, dimensionally stable castings.

Erfindungsgemäßer Formstoff verbindet in optimaler Weise die Eigenschaften, welche Voraussetzung für die Herstellung eines qualitativ hochwertigen Gussteils bei gleichzeitig einfacher Herstellweise sind. Zu diesem Zweck enthält der erfindungsgemäße Formstoff einen in körniger oder vergleichbar partikelartiger Form vorliegenden und als solcher rieselfähigen Grundstoff, der bei seiner während des Abgusses unvermeidbar eintretenden Erwärmung eine gegenüber konventionell verwendetem Quarzsand deutlich geringe Wärmeausdehnung zeigt. Der Formgrundstoff gewährleistet so auch bei geringer Materialstärke eine hohe Maßhaltigkeit bei der Herstellung komplex geformter Gussstücke.Inventive molding material optimally combines the properties which are the prerequisite for the production of a high-quality casting with a simultaneously simple manufacturing method. For this purpose, the molding material according to the invention contains a granular or comparable particle-like form present and as such free-flowing base material, which exhibits a significantly low thermal expansion compared to conventionally used quartz sand during its warming unavoidably occurring during the casting. The molding material thus ensures a high dimensional stability in the production of complex molded castings even with low material thickness.

Der im ungebundenen Zustand rieselfähige Grundstoff ist mit einem Binder vermischt, der ein von dem Grundstoff unterschiedliches Ausdehungsverhalten bei Erwärmung besitzt. Aufgrund der unterschiedlichen Wärmeausdehnung von Formgrundstoff und Bindemittel kommt es nach dem wärmeeintrag aus der Gießhitze zur Ablösung des Binders von den Körnern des Formgrundstoffs. Im Ergebnis sprengt daher der Binder dann, wenn er sich stärker ausdehnt als der Grundstoff, das Formteil so auf, dass es seine feste Form verliert und leicht aus bzw. von dem Gussteil entfernt werden kann. Umgekehrt kann das Ausdehnungsverhalten des Formgrundstoffes so beschaffen sein, dass durch eine mit der Erwärmung einhergehende volumenänderung die Bindung zu dem Binder gebrochen und der Grundstoff wieder rieselfähig wird. Wesentlich ist, dass es einhergehend mit der Erwärmung zum Aufbrechen des Kern- bzw. Formbauteils kommt, so dass dieses nach der Abkühlung des Gussteils in leicht entfernbare, lose Einzelteile zerfallen ist.The free-flowing in the unbound state base material is mixed with a binder, which has a different from the base expansion behavior when heated. Due to the different thermal expansion of mold base and binder occurs after the heat input from the casting heat to detach the binder from the grains of the molding material. As a result, therefore, when the binder expands more than the base, the binder breaks up so that it loses its solid shape and can be easily removed from the casting. Conversely, the expansion behavior of the molding base material can be such that the binding to the binder is broken by a change in volume associated with the heating and the base material again becomes free-flowing. It is essential that it comes along with the heating to break up the core or mold component, so that this has decayed after cooling of the casting in easily removable, loose items.

Indem das thermische Ausdehnungsverhalten des erfindungsgemäßen Formstoffs in erfindungsgemäßer Weise auf das thermische Ausdehnungsverhalten der zu vergießenden Metallschmelze abgestimmt ist und indem gleichzeitig dieser Formstoff auf Basis eines rieselfähigen Grundstoffs hergestellt ist, wird erreicht, dass nach dem Abkühlen des Gussteils das von dem Gussteil jeweils zumindest teilweise umfasste bzw. an das Gussteil angrenzende Formteil aufgrund der im Zuge des Abkühlens auftretenden Kräfte in lose Einzelstücke zerbrochen ist, die leicht entfernt werden können. Der Bruch der Gießformteile wird dabei durch die in Folge der unterschiedlichen Ausdehnung von Gießmetall und Formmaterial auftretenden Kräfte bewirkt.By the thermal expansion behavior of the molding material according to the invention in accordance with the invention is adapted to the thermal expansion behavior of the molten metal to be cast and by simultaneously this molding material based on a produced free-flowing base material, it is achieved that after cooling of the casting each of the casting at least partially encompassed or adjacent to the casting molding is broken due to the forces occurring in the course of cooling into loose individual pieces that can be easily removed. The fracture of the mold parts is effected by the forces occurring as a result of the different expansion of cast metal and mold material.

Besonders günstig wirkt sich die Erfindung beim Gießen von Bauteilen aus Aluminiumschmelzen aus. Aluminium weist einen hohen thermischen Ausdehnungskoeffizienten auf, so dass die im Zuge des Abgießens und Erstarrens der Schmelze auf die mit dem abgegossenen Teil in Berührung stehenden Formteile so hohe Kräfte ausgeübt werden, dass das betreffende Formteil sicher in kleinere Teile zerbricht. Als besonders günstig erweist sich dies, wenn es sich bei dem Formteil um eine Kernform handelt.Particularly favorable, the invention affects the casting of components made of aluminum melts. Aluminum has a high coefficient of thermal expansion, so that in the course of pouring and solidification of the melt on the molded parts in contact with the molded parts so high forces are exerted that the relevant molding safely breaks into smaller parts. This proves to be particularly favorable when the molding is a core mold.

Eine weitere für die Erfindung günstige Eigenschaft des erfindungsgemäß beschaffenen und verwendeten Formstoffs besteht darin, dass Binder und Formgrundstoff so aufeinander abgestimmt sind, dass bei den aus dem Formstoff erzeugten Formgussteilen die Partikel des Grundstoffs thermisch stabil und nicht elastisch von dem Binder gebunden sind. Das aus einem derart beschaffenen Formgrundstoff erzeugte Formgussteil verhält sich über das gesamte beim Abgießen der Schmelze durchlaufene Temperaturintervall spröde, wodurch das gemäß der Erfindung erwünschte Zerbrechen der Formteile gefördert wird.A further feature of the molding material obtained and used according to the invention which is favorable for the invention is that the binder and mold base material are coordinated so that the particles of the base material are thermally stable and not elastically bound by the binder in the molded parts produced from the molding material. The molded part produced from a molded base material of this kind behaves brittle over the entire temperature interval during the casting of the melt, which promotes the breaking of the molded parts which is desirable according to the invention.

Das Bindemittel der Formteile ist bevorzugt so gewählt, dass es sich durch die Einwirkung von Wärme nicht zersetzt. Auf diese Weise wird vermieden, dass im Kern volumina freigegeben werden, die zu einer gemäß, der Erfindung unerwünschten Nachgiebigkeit des betreffenden Formteils führen könnten.The binder of the moldings is preferably chosen so that it does not decompose by the action of heat. In this way it is avoided that volumes are released in the core, which could lead to a according to the invention undesirable flexibility of the molding in question.

Eine weitere vorteilhafte Ausgestaltung der Erfindung besteht darin, dass die Partikel des Formgrundstoffs eine im Wesentlichen runde, kugelige Form aufweisen. Die Kugelform des Formgrundstoffes und das damit verbundene Vorherrschen von Punktkontakten zwischen den Formgrundstoffpartikeln fördert den selbsttätigen Zerfall der Formteile in Folge der beim Abgießen und Erstarren der Schmelze auftretenden mechanischen Kräfte. Ein Formgrundstoff der diese Anforderung besonders gut erfüllt, ist synthetisch erzeugter Mullit. Dementsprechend sieht eine weitere vorteilhafte Ausgestaltung der Erfindung vor, dass der Formgrundstoff mehr als 50 %, vorzugsweise mehr als 70 % des Quarzsandes subsituierende Aluminiumoxid-Sand (Mullit) aufweist. Mullit weist eine runde Kornform und eine mit Quarzsand vergleichbare Dichte auf. Daher sind die daraus hergestellten Formstoffe wesentlich einfacher zu verarbeiten als beispielsweise bekannte ZrO2-Sande. Neben den Vorteilen in Bezug auf den erfindungsgemäß angestrebten mechanisch ausgelösten Zerfall der Formteile führt die runde Kugelform der Mullitpartikel in der Praxis zu einer vereinfachten Verarbeitbarkeit der aus solchen Formgrundstoffen erzeugten Formstoffe und damit einhergehend zu einem verminderten verschleiß der für die Herstellung der Formteile verwendeten werkzeuge und Maschinen. Darüber besitzt ein Formstoff mit hohen Gehalten an Mullit auf Grund seiner geringen Wärmeausdehnung auch bei geringer Materialstärke eine hohe Maßhaltigkeit bei der Herstellung komplex geformter Gussstücke.A further advantageous embodiment of the invention consists in that the particles of the molding base material have a substantially round, spherical shape. The spherical shape of the molding material and the associated prevalence of point contacts between the mold base particles promotes the automatic disintegration of the moldings as a result of the mechanical forces occurring during casting and solidification of the melt. A molding material that meets this requirement particularly well is synthetically produced mullite. Accordingly, a further advantageous embodiment of the invention provides that the mold base material more than 50%, preferably more than 70% of the quartz sand subsituierende alumina sand (mullite) has. Mullite has a round grain shape and a density comparable to quartz sand. Therefore, the moldings produced therefrom are much easier to process than, for example, known ZrO 2 sands. In addition to the advantages with respect to the inventively desired mechanically induced disintegration of the molded parts, the spherical spherical shape of the mullite particles in practice leads to a simplified processability of the molded materials produced from such molding base materials and concomitantly to a reduced wear of the tools and machines used for the production of moldings , About it owns a molding material with high Due to its low thermal expansion, mullite has a high degree of dimensional stability in the production of complex shaped castings even with low material thickness.

Überraschend hat sich gezeigt, dass der Zerfall der aus erfindungsgemäß zusammengesetztem Formstoff hergestellten Formteilen soweit zeitverzögert gegenüber dem Abgießen der Metallschmelze selbsttätig eintritt, dass er keinen negativen Einfluss mehr auf die Qualität des zu diesem Zeitpunkt schon ausreichend erstarrten Gussteils hat.Surprisingly, it has been found that the disintegration of the molded parts produced from the molding material according to the invention occurs as far as time-delayed against the casting of the molten metal, that it no longer has a negative influence on the quality of the already sufficiently solidified casting at this time.

Aufgrund seiner besonderen Eigenschaften ist erfindungsgemäß zusammengesetzter Formstoff besonders zur Herstellung von Gießkernen geeignet. Diese können nach dem Gießen ohne die Gefahr einer Beschädigung des fertigen Gussstücks entfernt werden.Due to its special properties, molding material composed according to the invention is particularly suitable for the production of casting cores. These can be removed after casting without the risk of damaging the finished casting.

Wärmetechnisch wirkt ein aus einem Mullit-Quarzsandgemisch zusammengesetzter Formgrundstoff und ein daraus erzeugter Formstoff eher isolierend. Daher können diese Stoffe gezielt für solche gießtechnische Anwendungen genutzt werden, in denen es zwar zu einer über die für Quarzsande kritische Temperatur von 573 °C hinausgehenden Erwärmung kommt, bei denen die Wärmeleitfähigkeit der aus den betreffenden Stoffen erzeugten Formteile jedoch eine untergeordnete Rolle spielt bzw. die Wärmeleitung bewusst eingeschränkt werden soll.From a thermal point of view, a molding base material composed of a mullite quartz sand mixture and a molding material produced therefrom have a rather insulating effect. Therefore, these substances can be used specifically for such casting applications, where it comes to a temperature above the critical for quartz sands temperature of 573 ° C warming, but in which the thermal conductivity of the molded parts produced from the substances concerned plays a minor role or the heat conduction should be deliberately restricted.

Praktische Versuche haben ergeben, dass durch das Zumischen einer ausreichenden Menge von Mullit-Sand zu einem Quarzsand die Probleme der spontanen Geometrieveränderungen abgefangen werden können, die bei alleiniger Verwendung von Quarzsand als Formgrundstoff für die Herstellung von schlanken, filigranen Gussteilen auftreten. Wesentlich ist dabei, dass der Anteil des Al2SiO5-Sands jeweils ausreichend hoch ist, um die bei Quarzsand andernfalls mit der Erwärmung über die kritische Temperatur einhergehende Längenänderung des Quarzes ausgleichen zu können.Practical experiments have shown that by adding a sufficient amount of mullite sand to a quartz sand the problems of the spontaneous Geometric changes can be intercepted, which occur with the sole use of quartz sand as a molding material for the production of slender, filigree castings. It is essential that the proportion of Al 2 SiO 5 sand is sufficiently high in each case in order to be able to compensate for the change in length of the quartz associated with the heating above the critical temperature in the case of quartz sand.

Bei erfindungsgemäß beschaffenem Formstoff sind Binder und Grundstoff darüber hinaus bevorzugt derart aufeinander abgestimmt, dass ein aus dem Formstoff erzeugtes Gießformteil eine geringe Wärmeleitfähigkeit besitzt. Diese Eigenschaft bewirkt, dass nach dem Abgießen der Metallschmelze der Temperaturunterschied zwischen Gussmaterial und dem Formteil groß bleibt, so dass die Gefahr einer vorzeitigen thermisch bzw. chemisch ausgelösten Zersetzung des Formteils auf ein Minimum reduziert ist.In accordance with the invention obtained molding material binder and base material are also preferably matched to one another such that a molded part produced from the molding material has a low thermal conductivity. This property causes that after the casting of the molten metal, the temperature difference between the casting material and the molded part remains large, so that the risk of premature thermally or chemically induced decomposition of the molded part is reduced to a minimum.

Zusätzlich lässt sich der Zerfall der Gießkerne dadurch unterstützen, dass die Bestandteile des Formstoffs so aufeinander abgestimmt werden, das sich Formgrundstoff und Binder bei Erwärmung unterschiedlich ausdehnen mit der Folge, dass die Bindungen zwischen ihnen bei einer mit dem Abgießen der Schmelze einhergehenden Erwärmung aufbrechen.In addition, the disintegration of the casting cores can be assisted by matching the constituents of the molding material so that the molding base and binder expand differently when heated, with the result that the bonds between them break during a heating associated with the casting of the melt.

Besonders praxisgerecht lässt sich die Erfindung dadurch verwirklichen, dass ein Formstoff verarbeitet wird, der aus einer Mischung eines in körniger oder vergleichbar partikelartiger Form vorliegenden und als solcher rieselfähigen Grundstoffs und einem anorganischen Binder, gebildet ist.The invention can be realized in a particularly practical manner by processing a molding material which consists of a mixture of one in granular or comparable particle-like form and as such free-flowing base material and an inorganic binder is formed.

Der Vorteil der Verwendung von anorganischen Bindern besteht in ihrer besseren Umweltverträglichkeit und dem Umstand, dass sich die mit derartigen Bindern hergestellten Formteile problemlos in den Kreislauf des Formstoffs zurückführen lassen. Als besonders geeignet haben sich in diesem Zusammenhang Formstoffe erwiesen, die aus einem auf Wasserglas basierenden Binder und einem erfindungsgemäß zusammengesetzten Formgrundstoff gemischt sind. Wesentlich ist dabei jedoch, dass das Ausdehnungsverhalten der miteinander vermischten Komponenten in ausreichender weise voneinander unterscheidet.The advantage of using inorganic binders is their better environmental compatibility and the fact that the moldings produced with such binders can be easily recycled into the cycle of the molding material. In this context, molding materials which have been mixed out of a water glass-based binder and a molding base material composed according to the invention have proven particularly suitable. It is essential, however, that the expansion behavior of the mixed components sufficiently different from each other.

Besonders vorteilhaft ist es in diesem Zusammenhang, wenn sich Formgrundstoff und Bindemittel unterschiedlich ausdehnen. In diesem Fall kommt es nach dem wärmeeintrag aus der Gießhitze zur Ablösung des Binders von den Körnern des Formgrundstoffs. So sprengt der Binder, wenn er sich stärker ausdehnt als der Grundstoff, das Formteil so auf, dass es seine feste Form verliert und in Bruchstücke zerfällt. Diese können ohne die Gefahr mechanischer Beschädigung leicht aus bzw. von dem Gussteil abgeschüttelt werden. Wesentlich dafür, dass es bei dieser Variante zum erfindungsgemäß angestrebten selbsttätigen Zerfall des Formteils kommt, ist folglich die unterschiedliche Wärmeausdehnung von Formgrundstoff und Bindemittel in der Art, dass unter Einwirkung der Gietihitze das Bindemittel in Folge der zwischen Formgrundstoff und Binder entstehenden thermischen Spannungen von den Formgrundstoffteilchen abplatzt oder in sich bricht. Durch dieses nach dem Aushärten des Formteils spröde Bruchverhalten des Bindemittels wird die Bindung zwischen den einzelnen Partikeln des Formgrundstoffs äufgebrochen und das Formteil zerfällt. Das verbleibende lose Gemisch aus Formgrundstoff- und Bindemittelbruchstücken ist rieselfähig und kann einfach aus bzw. von dem Gussstück entfernt werden.It is particularly advantageous in this context if mold base material and binder expand differently. In this case, it comes after the heat input from the casting heat to detach the binder from the grains of the molding material. For example, if the binder expands more than the base material, it breaks up the molding so that it loses its solid shape and breaks up into fragments. These can easily be shaken off or from the casting without the risk of mechanical damage. Essential for the fact that it comes in this variant to the inventively desired automatic disintegration of the molding, consequently, the different thermal expansion of mold base and binder in the way that under the action of Gietihitze the binder as a result of resulting between mold base and binder thermal stresses from the mold base particles flakes off or breaks in itself. By this after curing of the molding brittle fracture behavior of the binder, the bond between the individual particles of the molding material is broken and breaks down the molding. The remaining loose mixture of Formgrundstoff- and binder fragments is free-flowing and can be easily removed from or from the casting.

Das jeweilige Gießformteil wird auch beim erfindungsgemäßen Verfahren dadurch hergestellt, dass eine erfindungsgemäß zusammengesetzte Formstoffmischung in bekannter Weise in den Kernkasten einer Kernformmaschine eingeschossen wird. Anschließend wird der Formstoff beispielsweise gemäß dem in der DE 196 32 293 Al beschriebenen Verfahren gehärtet, indem an die Hohlform des auf eine Temperatur von 100 °C bis 160 °C erwärmten Kernkastens ein Unterdruck angesetzt und der Kernformling über eine Zeit von 20 bis 30 Sekunden von dem Kernkasten erwärmt wird.The respective casting mold part is also produced in the process according to the invention by injecting a molding material mixture composed according to the invention into the core box of a core molding machine in a known manner. Subsequently, the molding material is cured, for example, according to the method described in DE 196 32 293 Al, by applying to the mold of the core box heated to a temperature of 100 ° C to 160 ° C, a negative pressure and the core molding over a period of 20 to 30 seconds is heated by the core box.

Während dieser Zeit wird das Gießformteil so fest, dass es aus dem Kernkasten entnommen werden und in eine außerhalb des Kernformkastens angeordnete Heizeinrichtung, beispielsweise einen Mikrowellenofen, gesetzt werden kann. In dieser Heizeinrichtung wird es bei ausreichender Wärmeleistung soweit erwärmt, dass ihm eine für die vollständige Aushärtung ausreichende Menge an Wasser entzogen wird.During this time, the mold part becomes so strong that it can be taken out of the core box and set in a heater outside the core box, for example, a microwave oven. In this heater, it is heated sufficiently with sufficient heat output that it is withdrawn sufficient for complete curing amount of water.

Alternativ oder ergänzend zu einer außerhalb des Kernformkastens angeordneten Mikrowellenheizung kann der Wasserentzug auch durch eine ausreichende Beheizung des Kernkastens selbst oder durch eine Heißluftbegasung erfolgen. Diese Maßnahmen können jeweils mit einer außerhalb des Kernkastens erfolgenden Beheizung kombiniert werden. Ebenso ist es möglich, den wasserentzung durch eine direkt auf den noch im Kernkasten befindlichen Kernformling einwirkende Mikrowellenbeheizung zu bewirken.As an alternative or in addition to a microwave heating arranged outside the core-molding box, the removal of water can also be achieved by sufficient heating of the core box itself or by hot-air gassing respectively. These measures can each be combined with a heating taking place outside the core box. It is likewise possible to effect the removal of water by means of microwave heating acting directly on the core molding still located in the core box.

Wird für die Aushärtung eine Beheizung des Formteils außerhalb des Kernkastens vorgenommen, so kann das jeweilige Formteil zur Steigerung der Kernoberflächenfestigkeit mit Binderflüssigkeit besprüht werden. Die so behandelten Formteile weisen eine erhöhte Stabilität bei ebenso erhöhter Abriebfestigkeit auf, so dass sie problemlos gelagert werden können und höchsten Anforderungen an ihre Maßhaltigkeit gerecht werden. Dies erweist sich insbesondere dann als günstig im Hinblick auf eine optimierte Qualität des zu erzeugenden Gussstücks, wenn ein Wasserglasbinder eingesetzt wird.If a heating of the molded part outside the core box is carried out for curing, then the respective molded part can be sprayed with binder liquid to increase the core surface strength. The moldings treated in this way have an increased stability with likewise increased abrasion resistance, so that they can be stored without problems and meet the highest demands on their dimensional accuracy. This proves to be particularly favorable with regard to an optimized quality of the casting to be produced when a water glass binder is used.

Nachfolgend wird die Erfindung anhand eines Nockenwellenkerns einer Gießform für das Gießen eines Zylinderkopfes aus einer Aluminiumgusslegierung näher erläutert.The invention will be explained in more detail with reference to a camshaft core of a casting mold for casting a cylinder head from an aluminum casting alloy.

In die Unterseite des Nockenwellenkerns sind in Längsrichtung beabstandet zueinander zwei Ausnehmungen eingeformt, durch welche jeweils die Form der zur Lagerung der Nockenwelle vorgesehenen Lagerböcke des herzustellenden Zylinderkopfes bestimmt ist. In die Ausnehmungen reicht jeweils ein Ast eines sich mit seinem Hauptabschnitt parallel und in einem Abstand zum Nockenwellenkern erstreckenden Ölkanalkerns. Die Länge der Äste ist dabei um ein Vielfaches größer als ihr Durchmesser. Ebenso ist die Länge des Hauptabschnitts des ölkanalkerns um ein vielfaches größer als sein Durchmesser.Two recesses are formed in the underside of the camshaft core at a distance from one another in the longitudinal direction, by means of which the shape of the bearing blocks of the cylinder head to be produced for the purpose of supporting the camshaft is determined. In the recesses extends in each case a branch of an extending with its main portion parallel and at a distance from the camshaft core Ölkanalkerns. The length of the branches is many times bigger than theirs Diameter. Likewise, the length of the main portion of the oil channel core is many times greater than its diameter.

Der Ölkanalkern ist in an sich bekannter Weise in einer konventionellen Formschießmaschine aus einem erfindungsgemäßen Formstoff hergestellt worden, der durch Mischung eines aus Mullit-Sand und Quarzsand bestehenden Formgrundstoffs mit einem Wasserglaabinder erzeugt worden ist. Aufgrund des Anteils an Mullit-Sand ist gewährleistet, dass der Olkanalkern auch bei seiner im Zuge des Abgießens des herzustellenden Zylinderkopfes auf bis über 573 °C ansteigenden Erwärmung sich gleichmäßig und infolgedessen eindeutig vorausbestimmbar ausdehnt.The oil channel core has been prepared in a conventional manner in a conventional form-casting machine from a molding material according to the invention, which has been produced by mixing a molding material consisting of mullite sand and quartz sand with a Wasserglaabinder. Due to the proportion of mullite sand is ensured that the Olkanalkern evenly and thus clearly unambiguously expands even when it rises in the course of the casting of the cylinder head to above 573 ° C heating.

Brüche im Bereich der Äste Dehnungen des Hauptabschnitts im Bereich zwischen den Ästen sowie Krümmungen im Bereich der freien Enden des Hauptabschnitts, wie sie bei in konventioneller Weise basierend auf reinen Quarzsand enthaltenden Formgrundstoffen hergestellten ölkanalkernen festgestellt werden, werden auf diese weise sicher vermieden. Durch Verwendung eines in erfindungsgemäßer weise zusammengesetzten Formstoffs lassen sich somit Zylinderköpfe und vergleichbare Gussstücke, die dünne, sich über große Länge erstreckende Kanäle aufweisen, mit hoher Präzision in großen Stückzahlen im Leichmetallguss zuverlässig herstellen.Branches in the region of the branches Extensions of the main section in the area between the branches as well as curvatures in the area of the free ends of the main section, as found in oil channel cores produced in a conventional manner based on pure quartz sand-containing molding materials, are reliably avoided in this way. By using a compound according to the invention in the molding material thus cylinder heads and comparable castings, which have thin, extending over long lengths channels can be produced reliably with high precision in large numbers in Leichmetallguss.

Während des Abgusses der Metallschmelze, bei der es sich bevorzugt um eine Aluminiumschmelze oder eine andere Leichtmetallschmelze handelt, und der Zeit, in der das Metall des Gusssstücks noch fließfähig ist, verformen sich die Gießkerne aufgrund der in erfindungsgemäßer weise aufeinander abgestimmten Eigenarten von Formgrundstoff und Binder nur unwesentlich. Die geringe Wärmeausdehnung des Formgrunastoffs unterstützt so das prozesssichere Erreichen der Maßanforderungen des Gussstücks.During the casting of the molten metal, which is preferably an aluminum melt or another molten light metal, and the time in which the metal of the cast piece is still flowable, the casting cores deform due to the invention in accordance with wise matched characteristics of mold base and binder only slightly. The low thermal expansion of Formgrunastoffs thus supports the process reliable achievement of the dimensional requirements of the casting.

Nach einer Erstarrungs- und Abkühlzeit, in der das Gussstück eine für die Weiterverarbeitung ausreichende Festigkeit erreicht, werden die Bruchstücke, in die der jeweilige Gießkern in Folge der Einwirkung der Gießhitze und auf Grund des unterschiedlichen Wärmeausdehnungsverhaltens des Formgrundstoffs und des Binders selbsttätig zerfällt, aus dem Gussstück entleert und aufbereitet. Im Zuge des Erstarrungsvorgangs und in der Abkühlphase nach vollständiger Erstarrung des Metalls wird durch die verglichen mit den Gießkernen erheblich höhere Festkörperkontraktion des Gussmetalls der jeweilige Gießkern hohen mechanischen Spannungen unterworfen. Diese führen aufgrund der spröden, unelastischen Beschaffenheit der Gießkerne dazu, dass die Gießkerne zu knollenartigen Bruchstücken zerspringen. Deren Volumen und Festigkeit ist so gering, dass die Gussteile alleine durch Einbringen von Schwingungsenergie entsandet werden können, da sämtlicher Kernaltsand losgelöst vom Gussteil vorliegt. Durch Presslufthämmer ausgeübte Hammerschläge, wie sie beim Stand der Technik noch erforderlich sind, werden für die Entsandung nicht benötigt.After a solidification and cooling time, in which the casting reaches a sufficient for further processing strength, the fragments into which the respective casting core due to the action of the casting heat and due to the different thermal expansion behavior of the mold base material and the binder decomposes automatically, from the Casting emptied and prepared. In the course of the solidification process and in the cooling phase after complete solidification of the metal, the respective casting core is subjected to high mechanical stresses as a result of the considerably higher solid contraction of the casting metal compared with the casting cores. These lead due to the brittle, inelastic nature of the casting cores to the casting cores shatter into bulbous fragments. Their volume and strength is so low that the castings can be sanded by introducing vibrational energy alone, since all the core solutand is detached from the casting. Hammer blows exerted by pneumatic hammers, which are still required in the prior art, are not required for desanding.

Die Aufbereitung der Gießkernbruchstücke kann ein schonendes Brechen zu körnigen Partikeln umfassen. Dann können die erhaltenen körnigen Partikel einer Metallabscheidung und einer Entstaubung unterzogen werden, um den für ihre Wiederverwendung notwendigen Zustand herzustellen. Anschließend werden die zu körnigem Material recycleten Gießformteile wieder als Grundstoff für erfindungsgemäß zusammengesetzten Formstoff verwendet.The treatment of the Gießkernbruchstücke may include a gentle breaking into granular particles. Then, the obtained granular particles may be subjected to metal deposition and dedusting to restore the condition necessary for their reuse. Subsequently, the molded parts recycled to granular material are again used as the base material for the molding material composed according to the invention.

Werden in erfindungsgemäßer Weise Formstoffe verwendet, die aus mit Wasserglasbinder vermischtem Formgrundstoff, wie synthetischem Mullit, bestehen, so treten bei der Herstellung der Gießformteile keine nennenswerten Emissionen auf. Dadurch können bei konventioneller vorgehensweise in Folge von Gasbildung immer wieder auftretende Gussfehler, umfangreiche Vorkehrungen für das Absaugen von Gasen und aufwendige Werkzeugreinigungen vermieden werden. Belastungen der Umwelt und des Bedienpersonals sind so auf ein Minimum reduziert.If molding materials are used in accordance with the invention which consist of mold base material mixed with waterglass binder, such as synthetic mullite, no appreciable emissions occur during the production of the moldings. This can be avoided in conventional procedure as a result of gas formation recurring casting defects, extensive provisions for the extraction of gases and complex tool cleaning. Pollution of the environment and the operating staff are reduced to a minimum.

Wird Mullit oder ein vergleichbar inerter Feuerfestwerkstoff als Grundstoff des erfindungsgemäßen Formstoffsystems verwendet, so besteht ein weiterer Vorteil der Erfindung in der chemischen Beständigkeit des Formgrundstoffs gegenüber Binder und Schmelze. Diese Eigenschaft stellt sicher, dass bei erfindungsgemäßer vorgehensweise ein Gussstück erhalten wird, dessen Oberfläche nach dem Entleeren der Bruchstücke der Formkerne und Formteile ohne zusätzliche Reinigungsmaßnahmen völlig frei von Restsandanhaftungen ist.If mullite or a comparable inert refractory material is used as the base material of the molding material system according to the invention, another advantage of the invention is the chemical resistance of the molding material to binder and melt. This feature ensures that in the inventive procedure, a casting is obtained, the surface of which, after the emptying of the fragments of the mandrels and moldings without additional cleaning measures is completely free of Restsandanhaftungen.

Claims (15)

  1. A method for producing cast parts from a metal melt, particularly a light metal melt, including the following steps:
    - production of a casting mould element from a moulding material, which is made from a base moulding material that is inert with respect to the metal melt, pourable, and includes a content of more than 50% synthetic mullite and a remainder content of silica sand, and that consists of essentially spherical particles and is mixed with an inorganic binding agent, wherein the thermal expansion behaviours of the base moulding material and the binding agent are adjusted with respect to one another such that the coefficient of thermal expansion of the metal melt is greater than the coefficient of thermal expansion of the casting mould element made from the moulding material,
    - constituting a casting mould using the casting mould element,
    - pouring off the metal melt into the casting mould to form a cast part,
    - cooling the cast part for a solidification and cooling period, during which the casting mould element crumbles to fragments without further intervention,
    - removing the fragments of the casting mould element from the surface or the interior of the cast part,
    - processing the fragments of the moulding material to produce a pourable base moulding material.
  2. The method as cited in one of the preceding claims,
    characterised in that
    the production of the casting mould element includes injecting the moulding material into a hollow shape formed in a core box, prehardening the moulding material that has been injected into the core box to form the casting mould element by the application of heat, and hardening the casting mould element in a heating installation arranged outside of the core box.
  3. The method as cited in claim 2,
    characterised in that
    the heating installation includes a microwave heating device.
  4. The method as cited in either of claims 2 or 3,
    characterised in that
    the binding agent is drizzled onto the casting mould element before the hardening step.
  5. The method as cited in any of the preceding claims,
    characterised in that
    the processing of the fragments of the moulding material includes the steps of breaking up the fragments, segregating the metal, sorting the grains and/or dedusting.
  6. A moulding material for producing casting mould elements for pouring off of metal melt, particularly light metal melt, made from a mixture of a base moulding material that is inert with respect to the metal melt, pourable, and includes a content of more than 50% synthetic mullite and a remainder content of silica sand, and that consists of essentially spherical particles, and an inorganic binding agent mixed with the base moulding material, wherein the thermal expansion behaviours of the base moulding material and the binding agent are adjusted with respect to one another such that the coefficient of thermal expansion of the metal melt is greater than the respective coefficient of thermal expansion of each casting mould element that is made from the moulding material.
  7. The moulding material as cited in claim 6,
    characterised in that
    the binding agent expands differently than the base moulding material upon heating.
  8. The moulding material as cited in either of claims 6 or 7,
    characterised in that
    the binding agent is stable under the effects of the casting heat.
  9. The moulding material as cited in any of claims 6 to 8,
    characterised in that
    the binding agent is a water glass binding agent.
  10. The moulding material as cited in any of claims 6 to 9,
    characterised in that
    the base moulding material is made entirely from mullite.
  11. The moulding material as cited in any of claims 7 to 10,
    characterised in that
    the metal melt is an aluminium melt.
  12. The moulding material as cited in any of claims 7 to 11,
    characterised in that
    its thermal conductivity is lower than that of the metal to be cast.
  13. A use of a base moulding material produced as cited in any of claims 6 to 12 in order to carry out the method constituted by any of claims 1 to 5.
  14. The use as cited in claim 13,
    characterised in that
    the casting mould element products from the moulding material is a foundry core.
  15. The use as cited in claim 14,
    characterised in that
    the length of the casting mould element is a larger than its diameter by a multiple thereof.
EP02772298A 2001-09-14 2002-09-13 Method for producing castings, molding sand and its use for carrying out said method Expired - Lifetime EP1425121B1 (en)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
DE10145417 2001-09-14
DE10145417A DE10145417A1 (en) 2001-09-14 2001-09-14 Production of cast pieces from a molten metal comprises forming a cast molded part, forming a molded part from the molding material, pouring the molten bath into the casting mold, cooling, removing the fragments of the mold part
DE10209224A DE10209224A1 (en) 2002-03-04 2002-03-04 Production of cast pieces from a molten metal comprises forming a cast molded part, forming a molded part from the molding material, pouring the molten bath into the casting mold, cooling, removing the fragments of the mold part
DE10209224 2002-03-04
DE10209183 2002-03-04
DE10209183A DE10209183A1 (en) 2002-03-04 2002-03-04 Production of cast pieces from a molten metal comprises forming a cast molded part, forming a molded part from the molding material, pouring the molten bath into the casting mold, cooling, removing the fragments of the mold part
PCT/EP2002/010301 WO2003024642A1 (en) 2001-09-14 2002-09-13 Method for producing castings, molding sand and its use for carrying out said method

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EP1425121A1 EP1425121A1 (en) 2004-06-09
EP1425121B1 true EP1425121B1 (en) 2006-04-19

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EP (1) EP1425121B1 (en)
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AT (1) ATE323563T1 (en)
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CA (1) CA2461797A1 (en)
DE (1) DE50206490D1 (en)
ES (1) ES2262845T3 (en)
HU (1) HUP0401547A2 (en)
MX (1) MXPA04002424A (en)
PL (1) PL367736A1 (en)
WO (1) WO2003024642A1 (en)

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DE10321106A1 (en) * 2003-05-09 2004-12-23 Hydro Aluminium Deutschland Gmbh Molded material, molded part and method for the production of moldings for a casting mold
WO2007036039A1 (en) 2005-09-30 2007-04-05 Nortel Networks Limited Initial access channel for scalable wireless mobile communication networks
CN1319669C (en) * 2005-12-20 2007-06-06 金啸海 Moulding sand used for casting and its preparation method
EP2216112A1 (en) * 2009-02-10 2010-08-11 Siemens Aktiengesellschaft Nickel based moulded component with a compensation body and method for producing same
EP3041623B1 (en) * 2013-09-04 2017-06-07 Nemak, S.A.B. de C.V. Method for removing a cast part cast from a light metal melt from a casting mould
DE102014110826A1 (en) 2014-07-30 2016-02-04 Fritz Winter Eisengiesserei Gmbh & Co. Kg Method for casting castings
KR101663084B1 (en) * 2016-03-18 2016-10-06 박성제 Faucet manufacturing method
CN111822677A (en) * 2019-04-11 2020-10-27 上海航天精密机械研究所 Light metal casting method based on composite casting mold
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CA2461797A1 (en) 2003-03-27
CN1599651A (en) 2005-03-23
ATE323563T1 (en) 2006-05-15
CN1298456C (en) 2007-02-07
US20040261969A1 (en) 2004-12-30
ES2262845T3 (en) 2006-12-01
PL367736A1 (en) 2005-03-07
JP2005502473A (en) 2005-01-27
EP1425121A1 (en) 2004-06-09
KR20040070330A (en) 2004-08-07
BR0212534A (en) 2004-10-19
MXPA04002424A (en) 2005-04-11
WO2003024642A1 (en) 2003-03-27
HUP0401547A2 (en) 2005-08-29
DE50206490D1 (en) 2006-05-24

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