EP0917499B1 - Method for the production of core preforms and recycling core sand for foundry - Google Patents

Method for the production of core preforms and recycling core sand for foundry Download PDF

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Publication number
EP0917499B1
EP0917499B1 EP97934549A EP97934549A EP0917499B1 EP 0917499 B1 EP0917499 B1 EP 0917499B1 EP 97934549 A EP97934549 A EP 97934549A EP 97934549 A EP97934549 A EP 97934549A EP 0917499 B1 EP0917499 B1 EP 0917499B1
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Prior art keywords
core
sand
core box
bonding agent
mixture
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EP97934549A
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German (de)
French (fr)
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EP0917499A2 (en
Inventor
Thomas Steinhäuser
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Vaw Aluminium AG
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Vereinigte Aluminium Werke AG
Vaw Aluminium AG
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    • 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
    • B22C1/186—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 contaming ammonium or metal silicates, silica sols
    • B22C1/188—Alkali metal silicates
    • 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 core moldings for foundry technology, whereby a mixture of an inorganic, fireproof molding sand and an inorganic Binder made of water glass, which The mixture is poured into a tempered core box, which is in the Water contained in the mixture is physically extracted and the core preform is removed from the core box and a Process for the production of circulating core sand.
  • test samples consisted of a compressed sand-sodium silicate mixture.
  • a vacuum was applied in the Range of 0.5 to 3 mm Hg applied and held as long as up to 10 to 30% of the moisture could be removed from the binder.
  • the only non-organic binder material mentioned in the article by Cole is a sodium silicate binder, which, however, is either mixed with complex ester hardeners or is subjected to a "chemical drying process" using "conventional” CO 2 gassing systems.
  • ester compounds are not recommended because of the environmental problems mentioned above.
  • WO-A-86/00033 describes a process for the production of Core moldings known in the form of sand with water glass as Binder is mixed. The mixture is placed in the core box Exposure to microwave water. There is the Core box made of a material permeable to microwaves, e.g. Plastic, rubber or a multi-layer non-metallic Material.
  • the object of the present invention is now a method develop for the production of core moldings for foundry purposes, that does not have the disadvantages described above. This object is achieved by the in claim 1 specified features solved.
  • the new process is intended to produce complex shaped large series parts in an environmentally friendly, energy-efficient production method are produced in particular as large-volume core moldings can have a sufficient bending strength for handling and a "smooth" compared to previous core sand surfaces Surface and the complete waiver of decay promoting Additives allowed.
  • reprocessing of the "old sand" is intended for any separation or splitting off from Z.
  • organic substances and wet chemical treatment the old sand can be dispensed with and still a circulating core sand can be produced with such physical properties, those with those of the natural raw material originally used are identical.
  • Figure 1 includes a representation comparison of different Molding binder systems under constantly defined conditions.
  • the mold storage time is designated 0 minutes, d. H. the molding material becomes molded articles immediately after mixing processed.
  • the core storage time is 60 minutes, d. H. the molded part is shaped according to the given shape Time stored and then broken.
  • the product according to the invention was produced in a rocking mixer with a mixing time of 50 seconds from 5 kg of molding sand H32 with 2.5% binder and processed on a core shooter of the H 2.5 type, the molding sand in a temperature-controlled core box being exposed to a negative pressure during the filling .
  • the tool temperature was 150 ° C.
  • the compression took place at 2.5 bar overpressure.
  • the resulting gases were extracted with a flow rate of 4 m 3 / h (corresponding to a vacuum of 0.6 bar) before the mold was opened.
  • the core molding was dried in the microwave (600 watts) for 120 seconds.
  • FIG. 1 shows the associated bending strengths with a thinly hatched column with a molding material storage time of 0 min and a core storage time of 60 min.
  • a comparative product was produced using the resol-CO 2 process and with 2.7% binder type.
  • the mixing time was 70 seconds, the compression was carried out under negative pressure at -0.8 bar.
  • the comparison product was then cured in a CO 2 atmosphere at 1 bar for 8.5 seconds.
  • the results are compared in FIG. 1 as a "CO 2 " column with the same molding material storage times of 0 and core storage times of 60 minutes compared to the data according to the invention.
  • CB1, CB2, CB3 Cold Box
  • 0.8 / 0.8% DMEA 0.8 / 0.8% DMEA
  • SO 2 -gassed sand system with 1% EPOXY / 0.25% resin and oxidizer has been manufactured and tested.
  • the bending strengths of the core moldings according to the invention have significantly better values than the SO 2 and CO 2 hardened moldings if the cores are removed from the mold immediately without storage.
  • Figure 5 is the representation of Figure 4 by different Mold storage times added. No figure shows the comparison of regenerates at different core storage times because the Comparative method a stability of the moldings only after removal allow the organic components.
  • the gas volume is displayed system-adjusted, ie the dead volume is taken into account by calculation.
  • Test duration 7.5 minutes under thermal stress.
  • the sand systems were manufactured on the basis of H 32 new sand. For a separate comparison, a sample of unpolluted H 32 new sand was inserted for comparison.

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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)

Abstract

The invention relates to a method for the production of core preforms for foundry in which a) a mixture of inorganic, refractory foundry sand and a water glass-based inorganic binder is produced, b) the mixture is poured into a tempered core box c) the water contained in the mixture is withdrawn by a physical method and d) the core preform is taken out of the core box. The process is characterized by the fact that e) the tempered core box is subjected to a depression during filling f) the temperature/dwell time is adjusted after the closing of the core box so that a dimensionally stable and good bearing shell is formed on the edge of the preform g) the preform is immediately removed after opening of the core box and, under the effect of microwaves, is subjected to a complete drying.

Description

Die Erfindung betrifft ein Verfahren zur Herstellung von Kernformlingen für die Gießereitechnik, wobei eine Mischung aus einem anorganischen, feuerfesten Formsand und einem anorganischen Bindemittel auf Wasserglasbasis hergestellt wird, die Mischung in einen temperierten Kernkasten eingefüllt, das in der Mischung enthaltene Wasser auf physikalischem Wege entzogen und der Kernvorformling dem Kernkasten entnommen wird sowie ein Verfahren zur Herstellung von Umlaufkernsand.The invention relates to a method for producing core moldings for foundry technology, whereby a mixture of an inorganic, fireproof molding sand and an inorganic Binder made of water glass, which The mixture is poured into a tempered core box, which is in the Water contained in the mixture is physically extracted and the core preform is removed from the core box and a Process for the production of circulating core sand.

In einem 1962 veröffentlichten Artikel in der Zeitschrift "Foundry Trade Journal" wurde die Dehydratation-Härtung von Natriumsilikat-gebundenen Kernsanden beschrieben (siehe Foundry Trade Journal, 03. Mai 1962, Seiten 537 - 544).In an article published in the magazine in 1962 "Foundry Trade Journal" was the dehydration curing of Sodium silicate-bound core sands are described (see Foundry Trade Journal, May 3, 1962, pages 537-544).

Die Testproben bestanden aus einem verdichteten Sand-Natriumsilikat-Gemisch. Zur Trocknung der Testproben wurde ein Vakuum im Bereich von 0,5 bis 3 mm Hg aufgebracht und solange gehalten, bis 10 bis 30 % der Feuchte aus dem Binder entfernt werden konnte.The test samples consisted of a compressed sand-sodium silicate mixture. A vacuum was applied in the Range of 0.5 to 3 mm Hg applied and held as long as up to 10 to 30% of the moisture could be removed from the binder.

Weitere Versuche zur Trocknung wurden bei unterschiedlichen Temperaturen zwischen 100 bis 500 °C durchgeführt. Ferner wurde untersucht, wie die Dehydratation durch Zugabe von CO2-Gas beschleunigt werden konnte.Further drying tests were carried out at different temperatures between 100 and 500 ° C. It was also investigated how the dehydration could be accelerated by adding CO 2 gas.

Als Ergebnis wurde am Ende des Artikels festgestellt, daß die Zugabe von CO2-Gas nicht unbedingt erforderlich ist um eine Härtung der Kernformlinge herbeizuführen. Für die praktische Durchführung wird vorgeschlagen, eine Vakuumpumpe mit ausreichender Kapazität zu benutzen, um Kernformlinge in einem "kalten" Verfahren herzustellen. Damit könne man auf eine Erwärmung des Kernkastens verzichten, die bisher wegen der Verwendung von warmaushärtenden Harzen als erforderlich angesehen wurde.As a result, it was found at the end of the article that the addition of CO 2 gas is not absolutely necessary to cause the core moldings to harden. For practical implementation, it is proposed to use a vacuum pump with sufficient capacity to produce core moldings in a "cold" process. This means that one can do without heating the core box, which was previously considered necessary due to the use of thermosetting resins.

Als problematisch wurde jedoch erkannt, daß für die Herstellung von großvolumigen Kernen sehr große und schnell-laufende Pumpen verwendet werden müssen, damit ein ausreichendes Vakuum erzeugt werden kann. Andererseits wird die für die Trocknung durch Evakuierung benötigte Zeit von 8 bis 16 Minuten als hinderlich angesehen, da die lange Behandlungszeit für eine Massenproduktion von Kernformlingen ungeeignet sei.It was recognized as problematic, however, that for the manufacture of large-volume cores very large and fast-running pumps must be used to create a sufficient vacuum can be. On the other hand, it is used for drying by evacuation required time from 8 to 16 minutes as a hindrance viewed because of the long treatment time for mass production of core moldings is unsuitable.

Etwa 10 Jahre später - man benutzte überwiegend harzgebundene Kernformsande - erschienen in der Zeitschrift AFS-Transactions, Band 86, Seiten 227 - 236 ein Aufsatz über "Effekte der Mikrowellen-Erwärmung von Kernformprozessen" von G.S. Cole. Cole beschreibt die Mikrowellenbehandlung von organischen Bindersystemen und stellt im Ergebnis fest, daß bei Verwendung von Mikrowellen der Binderanteil deutlich herabgesetzt werden kann. Dieses hat entscheidende Vorteile für den Umweltschutz, da organische Materialien beim Gießen, beim Lagern und auch beim Entsorgen einer besonderen Behandlung bedürfen. Grundsätzlich ist aber auch bei der Trocknung durch Mikrowellen eine entsprechende Vorsorge gegen den Übertritt der im Binder enthaltenen organischen Materialien in die Abluft zu treffen.About 10 years later - mainly resin-bound ones were used Kernformsande - published in the journal AFS-Transactions, Volume 86, pages 227-236 an essay on "Effects of microwave heating von Kernform Processes "by G.S. Cole. Cole describes the microwave treatment of organic binder systems and as a result finds that when using Microwave the proportion of binder can be significantly reduced. This has decisive advantages for environmental protection because it is organic Materials when pouring, storing and also when disposing require special treatment. Basically is but also a corresponding one when drying with microwaves Prevention of the transfer of the organic contained in the binder To meet materials in the exhaust air.

Als einziges nicht-organisches Bindermaterial wird in dem Aufsatz von Cole ein Natriumsilikat-Binder erwähnt, der allerdings entweder mit komplexen Esterhärtern vermischt wird oder durch "übliche" CO2-Begasungssysteme einem "chemischen-Trocknungsverfahren" unterworfen wird. Hierdurch sind verschlechterte Zerfallseigenschaften des Kerns nach dem Abguß zu erwarten, da der Kernaltsand aufgrund von Verklumpungen der gebildeten Glasphasen nur bedingt regenerierbar ist. Die Verwendung von Ester-Verbindungen ist wegen der oben erwähnten Umweltproblematik nicht empfehlenswert.The only non-organic binder material mentioned in the article by Cole is a sodium silicate binder, which, however, is either mixed with complex ester hardeners or is subjected to a "chemical drying process" using "conventional" CO 2 gassing systems. As a result, deteriorated decay properties of the core are to be expected after the casting, since the core waste sand can only be regenerated to a limited extent on account of clumping of the glass phases formed. The use of ester compounds is not recommended because of the environmental problems mentioned above.

In einem 1993 erschienenen Handbuch über "Formstoffe und Formverfahren" des Deutschen Verlages für Grundstoffindustrie ist auf die Problematik der Regenerierung bei auftretenden Glasphasen hingewiesen (Seite 80/81). In Abb. 3.28 ist auf Seite 83 der Verlauf der Sekundärfestigkeit für CO2-gehärtete Wasserglas-Formstoffe in Abhängigkeit von der Gießtemperatur dargestellt. Dieses Verfahren, das sich in den zurückliegenden 30 Jahren zum Standardverfahren für konventionelle und modifizierte Binderlösungen entwickelt hat, führt zu wasserglasgebundener Formstoffen mit dem in Abb. 3.28 dargestellten Hochtemperaturverhalten , das gekennzeichnet ist durch eine erhöhte Sinterneigung und durch eine unzureichende Zerfallsfähigkeit des Formstoffes nach dem Gießen. Außerdem treten Schmelzphasen auf, die bei der nachfolgenden Abkühlung neue Bindungen mit dem Formgrundstoff ausbilden. Eine Verminderung der dabei erzielten Sekundärfestigkeit läßt sich durch folgende Maßnahmen gemäß "Handbuch" Seite 84 erzielen:

  • 1. Optimierung der Formstoffrezeptur zur Verminderung der Alkalität;
  • 2. Verwendung von Wasserglas-Lösungen mit abgesenktem Binderanteil;
  • 3. Zugabe von zerfallsfördernden Zusätzen.
    • A manual published in 1993 on "Molding Materials and Molding Processes" by the German publishing house for the basic materials industry refers to the problem of regeneration when glass phases occur (page 80/81). Fig. 3.28 shows on page 83 the course of the secondary strength for CO 2 hardened water glass molding materials depending on the casting temperature. This process, which has developed into the standard process for conventional and modified binder solutions in the past 30 years, leads to water glass-bonded molded materials with the high-temperature behavior shown in Fig.3.28, which is characterized by an increased tendency to sinter and by an insufficient disintegration ability of the molded material after casting . In addition, melting phases occur, which form new bonds with the basic molding material during the subsequent cooling. A reduction in the secondary strength achieved can be achieved by the following measures according to "Manual" on page 84:
  • 1. Optimization of the molding material formulation to reduce the alkalinity;
  • 2. Use of water glass solutions with reduced binder content;
  • 3. Addition of decay-promoting additives.

    • Dieses Optimierungsproblem ist bis heute nicht zufriedenstellend gelöst. Das Ablösen der Binderhüllen, bestehend aus dehydratisiertem Natriumsilikat oder aus über chemische Umsetzung gebildete Gelphasen sowie aus den kristallisierten Schmelzphasen und Reaktionsprodukten, erfordert eine intensive Behandlung des Altformstoffes auf naß-chemischen Wege. Bei Estergehärteten Formstoffen liegen teilweise elastische Binderhüllen vor, die den Einsatz kombinierter thermisch-mechanischer Trennverfahren erforderlich machen. This optimization problem is still unsatisfactory solved. Detaching the binder casings, consisting of dehydrated Sodium silicate or from chemical reaction Gel phases as well as from the crystallized melting phases and reaction products, requires intensive treatment of the Waste molding material by wet chemical methods. For ester hardened Molded materials are partially elastic binder covers that the use of combined thermal-mechanical separation processes make necessary.

    Aus der WO-A-86/00033 ist ein Verfahren zur Herstellung von Kernformlingen bekannt, bei dem Formsand mit Wasserglas als Bindemittel gemischt wird. Der Mischung wird im Kernkasten unter Einwirkung von Mikrowellen Wasser entzogen. Hierzu besteht der Kernkasten aus einem für Mikrowellen durchlässigen Material, z.B. Kunststoff, Gummi oder einem mehrschichtigen nicht metallischen Werkstoff. WO-A-86/00033 describes a process for the production of Core moldings known in the form of sand with water glass as Binder is mixed. The mixture is placed in the core box Exposure to microwave water. There is the Core box made of a material permeable to microwaves, e.g. Plastic, rubber or a multi-layer non-metallic Material.

    Aufgabe der vorliegenden Erfindung ist es nunmehr, ein Verfahren zur Herstellung von Kernformlingen für Gießereizwecke zu entwikkeln, das die vorstehend beschriebenen Nachteile nicht aufweist. Diese Aufgabe wird durch die im Patentanspruch 1 angegebenen Merkmale gelöst. Mit dem neuen Verfahren sollen komplex geformte Großserienteile in einer umweltschonenden, energiegünstigen Herstellungsweise insbesondere als großvolumige Kernformlinge erzeugt werden können, die eine für die Handhabung ausreichende Biegefestigkeit und eine im Vergleich zu bisherigen Kernsandoberflächen "glatte" Oberfläche aufweist und die den vollständigen Verzicht auf zerfallsfördernde Zusätze ermöglicht. Bei der Wiederaufbereitung des "Altsandes" soll auf jegliche Auftrennung bzw. Abspaltung von z. B. organischen Stoffen und auf die naß-chemische Behandlung des Altsandes verzichtet werden und dennoch ein Umlaufkernsand mit solchen physikalischen Eigenschaften herstellbar sein, die mit denen des natürlichen ursprünglich eingesetzten Ausgangsproduktes identisch sind.The object of the present invention is now a method develop for the production of core moldings for foundry purposes, that does not have the disadvantages described above. This object is achieved by the in claim 1 specified features solved. The new process is intended to produce complex shaped large series parts in an environmentally friendly, energy-efficient production method are produced in particular as large-volume core moldings can have a sufficient bending strength for handling and a "smooth" compared to previous core sand surfaces Surface and the complete waiver of decay promoting Additives allowed. When reprocessing of the "old sand" is intended for any separation or splitting off from Z. B. organic substances and wet chemical treatment the old sand can be dispensed with and still a circulating core sand can be produced with such physical properties, those with those of the natural raw material originally used are identical.

    Im folgenden wird die Erfindung anhand mehrerer Ausführungsbeispiele näher erläutert. Es zeigen:

    Fig. 1 und Tabelle 1
    Gegenüberstellung der Biegefestigkeiten von AWB- und anderen Kernsystemen in Abhängigkeit von der Kernlagerzeit (KLZ);
    Fig. 2 und Tabelle 2
    Gegenüberstellung der Biegefestigkeiten von AWB- und anderen Kernsystemen in Abhängigkeit bei unterschiedlicher Formstofflagerzeit (FLZ);
    Fig. 3 und Tabelle 3
    Darstellung der Biegefestigkeiten bei veränderter Formstofflagerzeit und veränderter Kernlagerzeit des erfindungsgemäßen Produktes;
    Fig. 4 und Tabelle 4
    Vergleich der Biegefestigkeit des erfindungsgemäßen Produktes mit den Werten von drei anderen Systemen CB1, CB2, CB3 bei wechselnder Kernlagerzeit;
    Fig. 5 und Tabelle 5
    Gegenüberstellung der Biegefestig-kei tswerte des erfindungsgemäßen Produktes mit drei anderen Systemen bei konstanter Formstofflagerzeit aber unterschiedlicher Kernlagerzeit;
    Fig. 6 und Tabelle 6
    Vergleich des erfindungsgemäßen Produktes mit drei anderen Produkten hinsichtlich ihrer Biegefestigkeiten;
    Fig. 7
    Vergleich der Gasmengenbildung bei Sand, AWB- und CB-Produkten.
    The invention is explained in more detail below on the basis of several exemplary embodiments. Show it:
    1 and Table 1
    Comparison of the bending strengths of AWB and other core systems depending on the core storage time (KLZ);
    2 and Table 2
    Comparison of the bending strengths of AWB and other core systems depending on different molding material storage times (FLZ);
    3 and Table 3
    Representation of the bending strengths when the molding material storage time and the core storage time of the product according to the invention change;
    4 and Table 4
    Comparison of the bending strength of the product according to the invention with the values of three other systems CB1, CB2, CB3 with changing core storage times;
    5 and Table 5
    Comparison of the flexural strength values of the product according to the invention with three other systems with constant molding material storage time but different core storage times;
    6 and Table 6
    Comparison of the product according to the invention with three other products with regard to their bending strengths;
    Fig. 7
    Comparison of gas volume formation with sand, AWB and CB products.

    Figur 1 beinhaltet einen Darstellungsvergleich von unterschiedlichen Formstoffbindersystemen bei konstant definierten Bedingungen. Die Formstofflagerzeit ist mit 0 Minuten bezeichnet, d. h. der Formstoff wird sofort nach dem Mischen zu Formlingen verarbeitet. Die Kernlagerzeit ist mit 60 Minuten bezeichnet, d. h. der Formling wird nach der Gestaltgebung mit der vorgegebenen Zeit gelagert und anschließend gebrochen.Figure 1 includes a representation comparison of different Molding binder systems under constantly defined conditions. The mold storage time is designated 0 minutes, d. H. the molding material becomes molded articles immediately after mixing processed. The core storage time is 60 minutes, d. H. the molded part is shaped according to the given shape Time stored and then broken.

    Das erfindungsgemäße Produkt wurde im Schwingmischer mit einer Mischdauer von 50 Sekunden aus 5 kg Formsand H32 mit 2,5 % Bindemittel hergestellt und auf einer Kernschießmaschine vom Typ H 2,5 verarbeitet, wobei der Formsand in einem temperierten Kernkasten während der Befüllung einem Unterdruck ausgesetzt wurde. Die Werkzeugtemperatur betrug 150 °C. Die Verdichtung erfolgte bei 2,5 bar Überdruck. Während einer Verweildauer im Werkzeug von 8 Sekunden wurden die entstandenen Gase vor dem Öffnen des Werkzeuges mit einer Durchflußmenge von 4 m3/h (entsprechend einem Unterdruck von 0,6 bar) abgesaugt. Nach der Entnahme wurde der Kernformling in der Mikrowelle (600 Watt) 120 Sekunden getrocknet. In Figur 1 sind die zugehörigen Biegefestigkeiten mit dünn schraffierter Säule bei einer Formstofflagerzeit von 0 min und eine Kernlagerzeit von 60 min dargestellt.The product according to the invention was produced in a rocking mixer with a mixing time of 50 seconds from 5 kg of molding sand H32 with 2.5% binder and processed on a core shooter of the H 2.5 type, the molding sand in a temperature-controlled core box being exposed to a negative pressure during the filling . The tool temperature was 150 ° C. The compression took place at 2.5 bar overpressure. During a dwell time of 8 seconds in the mold, the resulting gases were extracted with a flow rate of 4 m 3 / h (corresponding to a vacuum of 0.6 bar) before the mold was opened. After removal, the core molding was dried in the microwave (600 watts) for 120 seconds. FIG. 1 shows the associated bending strengths with a thinly hatched column with a molding material storage time of 0 min and a core storage time of 60 min.

    Ein Vergleichsprodukt wurde mit dem Resol-CO2-Verfahren und mit 2,7 % Bindergattierung hergestellt. Die Mischzeit betrug 70 Sekunden, die Verdichtung erfolgte im Unterdruck bei -0,8 bar. Anschließend wurde das Vergleichsprodukt in CO2-Atmosphäre bei 1 bar für 8,5 Sekunden ausgehärtet. Die Ergebnisse sind in Figur 1 als "CO2"-Säule bei gleichen Formstofflagerzeiten von 0 und Kernlagerzeiten von 60 Minuten den erfindungsgemäßen Daten gegenübergestellt.A comparative product was produced using the resol-CO 2 process and with 2.7% binder type. The mixing time was 70 seconds, the compression was carried out under negative pressure at -0.8 bar. The comparison product was then cured in a CO 2 atmosphere at 1 bar for 8.5 seconds. The results are compared in FIG. 1 as a "CO 2 " column with the same molding material storage times of 0 and core storage times of 60 minutes compared to the data according to the invention.

    Weitere Vergleichsprodukte sind als CB1, CB2, CB3 (Cold Box) bezeichnet und mit 0,8/0,8 % DMEA durchgeführt worden. Ferner ist ein SO2-begastes Sandsystem mit 1 % EPOXY/0,25 % Harz und Oxydator hergestellt und getestet worden.Other comparative products are referred to as CB1, CB2, CB3 (Cold Box) and were carried out with 0.8 / 0.8% DMEA. Furthermore, a SO 2 -gassed sand system with 1% EPOXY / 0.25% resin and oxidizer has been manufactured and tested.

    Es zeigt sich, daß die Biegefestigkeiten der erfindungsgemäßen Kernformlinge im Vergleich zu den SO2 und CO2-gehärteten Formlingen deutlich bessere Werte aufweisen, wenn man die Kerne sofort ohne Lagerung aus der Form entnimmt.It can be seen that the bending strengths of the core moldings according to the invention have significantly better values than the SO 2 and CO 2 hardened moldings if the cores are removed from the mold immediately without storage.

    Der in Figur 4 angestellte Vergleich bekannter Cold-Box-Systeme bei unterschiedlichen Kernlagerzeiten und einer Formstofflagerzeit von 0 min mit dem erfindungsgemäßen Kernformling zeigt, daß die erfindungsgemäßen Produkte deutlich bessere Werte als die Vergleichsprodukte aufweisen, wenn FLZ = 0 und KLZ = 0 ist. In Figur 5 ist die Darstellung nach Figur 4 durch unterschiedliche Formstofflagerzeiten ergänzt. Keine Figur zeigt den Vergleich von Regeneraten bei unterschiedlichen Kernlagerzeiten, weil die Vergleichsverfahren eine Stabilität der Formlinge nur nach Entfernung der organischen Bestandteile gestatten. The comparison made in FIG. 4 of known cold box systems with different core storage times and one molding material storage time of 0 min with the core molding according to the invention shows that the products according to the invention have significantly better values than that Show comparison products if FLZ = 0 and KLZ = 0. In Figure 5 is the representation of Figure 4 by different Mold storage times added. No figure shows the comparison of regenerates at different core storage times because the Comparative method a stability of the moldings only after removal allow the organic components.

    Der in Figur 5 gezeigte Vergleich der Biegefestigkeit des erfindungsgemäßen Kernformlings bei unterschiedlichen Kernlagerzeiten läßt erkennen, daß die Festigkeitssteigerung beim erfindungsgemäßen Produkt weniger deutlich ist als bei den Vergleichsprodukten.The comparison shown in Figure 5 of the bending strength of the invention Core moldings with different core storage times shows that the increase in strength in the invention Product is less clear than the comparison products.

    Figur 2 zeigt den Verlauf der Biegefestigkeit in Abhängigkeit der Formstofflagerzeit (FLZ) und der Kernlagerzeit (KLZ). Es wird das AWB-Verfahren mit dem Resol-CO2-Verfahren gegenübergestellt (das Resol-CO2-Verfahren kommt dem klassischen Wasserglas-Verfahren sehr nah, da hierbei die Verfestigung durch eine Gelbildung in den Binderbrücken erfolgt).

  • FLZ 0 : Angaben in Minuten
  • FLZ 30: Angaben in Minuten
    • bei KLZ 0.FIG. 2 shows the curve of the bending strength as a function of the molding material storage time (FLZ) and the core storage time (KLZ). The AWB process is compared with the resol-CO 2 process (the resol-CO 2 process comes very close to the classic water glass process, since it solidifies through gel formation in the binder bridges).
  • FLZ 0: information in minutes
  • FLZ 30: information in minutes
    • at KLZ 0.

    Der Vergleich beider Systeme beruht auf dem Basisneusand H32. Die Versuchsparameter für das AWB-Verfahren sind dem Blatt 3/1 zu entnehmen. Resol-CO2-Verfahren mit 2,7 % Bindergattierung, Mischzeit 70 sec., Verdichtung im Unterdruck -0,8 bar, Aushärtung über CO2/lbar/8,5 sec.The comparison of both systems is based on the basic new sand H32. The test parameters for the AWB method can be found on sheet 3/1. Resol CO 2 process with 2.7% binder, mixing time 70 sec., Compression in negative pressure -0.8 bar, curing over CO 2 / lbar / 8.5 sec.

    Figur 3 enthält eine Darstelllung der Biegefestigkeit in Abhängigkeit der Formstofflagerzeit (FLZ) und der Kernlagerzeit (KLZ) des AWB-Verfahrens.
    2,5 % Bindemittel

  • FLZ 0 : Zeitangaben in Minuten
  • FLZ 15 : Zeitangaben in Minuten
  • FLZ 30 : Zeitangaben in Minuten
  • KLZ 0 : Zeitangaben in Minuten
  • KLZ 60 : Zeitangaben in Minuten
  • KLZ 180: Zeitangaben in Minuten
    • FLZ = Formstofflagerzeit; KLZ = Kernlagerzeit FIG. 3 contains a representation of the bending strength as a function of the molding material storage time (FLZ) and the core storage time (KLZ) of the AWB process.
    2.5% binder
  • FLZ 0: Times in minutes
  • FLZ 15: Times in minutes
  • FLZ 30: Times in minutes
  • KLZ 0: Times in minutes
  • KLZ 60: Times in minutes
  • KLZ 180: Times in minutes
    • FLZ = molding material storage time; KLZ = core storage time

    Verarbeitung eines Materials aus 5 Kg H 32 im Schwingmischer, Mischdauer 50 sec., Verarbeitung auf einer Kernschießmaschine H 2,5
    Werkzeugtemperatur 150°C
    Verdichtung kombiniert 2,5 bar Überdruck und -0,6 bar Unterdruck Verweildauer im Werkzeug 8 sec, mit Absaugung des Werkzeuges 4 m3/h
    Mikrowellentrocknung 120 sec, 600 W
    (Hinweis: der Feststoffanteil des Bindemittels beträgt 35 %).    Processing of a 5 Kg H 32 material in a vibrating mixer, mixing time 50 sec., Processing on a H 2.5 core shooter
    Tool temperature 150 ° C
    Compression combined 2.5 bar overpressure and -0.6 bar negative pressure dwell time in the tool 8 sec, with suction of the tool 4 m 3 / h
    Microwave drying 120 sec, 600 W
    (Note: the solids content of the binder is 35%).

    Die in Figur 4 dargestellten Formstofffestigkeiten wurden mit folgenden Sandsystemen erzeugt: alle Sandsysteme wurden auf der Basis von H 32 Neusand hergestellt.

  • CB 1 0,8/0,8 % DMEA/HA Cold-Box
  • CB 2 0,8/0,8 % DMEA/HA Cold-Box
  • CB 3 0,8/0,8 % DMEA/HA Cold-Box
  • SO2 1%/0,25 % H/Oxyd. Epoxy.
    • The molding material strengths shown in FIG. 4 were generated with the following sand systems: all sand systems were produced on the basis of H 32 new sand.
  • CB 1 0.8 / 0.8% DMEA / HA cold box
  • CB 2 0.8 / 0.8% DMEA / HA cold box
  • CB 3 0.8 / 0.8% DMEA / HA cold box
  • SO2 1% / 0.25% H / oxide. Epoxy.

    • Dies ergibt die Darstellung der Biegefestigkeit gemäß Figur 4 in Abhängigkeit der Kernlagerzeit (KLZ) im Vergleich zu anderen Formstoffsystemen.
    2,5 % Bindemittel AWB-Verfahren

  • KLZ 0 : Zeitangaben in Minuten
  • KLZ 60 : Zeitangaben in Minuten
  • FLZ 0 : Zeitangaben in Minuten
    • FLZ = Formstofflagerzeit; KLZ = KernlagerzeitThis results in the representation of the bending strength according to FIG. 4 as a function of the core storage time (KLZ) in comparison to other molding material systems.
    2.5% binder AWB process
  • KLZ 0: Times in minutes
  • KLZ 60: Times in minutes
  • FLZ 0: Times in minutes
    • FLZ = molding material storage time; KLZ = core storage time

    Wie in Figur 4 wurden die Sandsysteme aus der Basis von H 32 Neusand hergestellt.

  • CB 1 0,8/0,8 % DMEA/HA Cold-Box
  • CB 2 0,8/0,8 % DMEA/HA Cold-Box
  • CB 3 0,8/0,8 % DMEA/HA Cold-Box
  • S02 1%/0,25 % H/Oxyd. Epoxy.
    • As in Figure 4, the sand systems were made from H 32 new sand.
  • CB 1 0.8 / 0.8% DMEA / HA cold box
  • CB 2 0.8 / 0.8% DMEA / HA cold box
  • CB 3 0.8 / 0.8% DMEA / HA cold box
  • S02 1% / 0.25% H / oxide. Epoxy.

    • In Figur 5 ergab sich eine Darstellung der Biegefestigkeit in Abhängigkeit der Kernlagerzeit (KLZ) im Vergleich zu anderen Formstoffsystemen.
    2,5 % Bindemittel AWB-Verfahren

  • KLZ 0 : Zeitangaben in Minuten
  • KLZ 60 : Zeitangaben in Minuten
  • FLZ 30 : Zeitangaben in Minuten
    • FLZ = Formstofflagerzeit; KLZ = KernlagerzeitFIG. 5 shows the bending strength as a function of the core storage time (KLZ) in comparison to other molding material systems.
    2.5% binder AWB process
  • KLZ 0: Times in minutes
  • KLZ 60: Times in minutes
  • FLZ 30: Times in minutes
    • FLZ = molding material storage time; KLZ = core storage time

    Im Darstellungsvergleich gemäß Figur 6 wurden unterschiedliche Formstoffbindersysteme bei konstant definierten Bedingungen gezeigt. Die Formstofflagerzeit ist mit 0 Minuten bezeichnet, d. h. der Formstoff wird sofort nach dem Mischen zu Formlingen verarbeitet. Die Kernlagerzeit ist mit 0 Minuten bezeichnet, d. h. der Formling wird sofort nach der Gestaltgebung gebrochen.

  • FLZ = 0 Minuten
  • KLZ = 0 Minuten
    • In the representation comparison according to FIG. 6, different molding material binder systems were shown under constantly defined conditions. The molding material storage time is designated 0 minutes, ie the molding material is processed into moldings immediately after mixing. The core storage time is designated 0 minutes, ie the molding is broken immediately after shaping.
  • FLZ = 0 minutes
  • KLZ = 0 minutes

    • Alle Sandsysteme wurden auf der Basis von H 32 Neusand im Schwingmischer mit einer Chargengröße von 5 Kg, wie in den vorhergehenden Beispielen, hergestellt.All sand systems were based on H 32 new sand in Vibratory mixers with a batch size of 5 kg, as in the previous ones Examples.

    In Figur 7 wird der Vergleich der Gasmengenbildung von Cold Box und AWB-Formlingen bei thermischer Beanspruchung dargestellt. Systemparameter:

  • Ofentemperatur 770°C
  • Formstoffeinwaage 2g
    • FIG. 7 shows the comparison of the gas volume formation of cold box and AWB moldings under thermal stress. System parameters:
  • Oven temperature 770 ° C
  • Molding weight 2g

    • Die Gasmenge wird systembereinigt dargestellt, d. h. das Totvolumen ist rechnerisch berücksichtigt.
    Versuchsdauer: 7,5 Minuten unter thermischer Beanspruchung.    The gas volume is displayed system-adjusted, ie the dead volume is taken into account by calculation.
    Test duration: 7.5 minutes under thermal stress.

    Die Sandsysteme wurden auf der Basis von H 32 Neusand hergestellt. Zum gesonderten Vergleich wurde eine Probe aus unbelastetem H 32 Neusand zum Vergleich mit eingefügt.
    AWB 2,5 % (Steinhäuser/wasserentzug-härtender Wasserglasbinder) CB Cold Box 0,8/0,8 %.
    Die Proben wurden unter gemeinsamen Raumbedingungen vor dem Versuch 24 Stunden gelagert.    The sand systems were manufactured on the basis of H 32 new sand. For a separate comparison, a sample of unpolluted H 32 new sand was inserted for comparison.
    AWB 2.5% (stone houses / water extraction-hardening water glass binder) CB Cold Box 0.8 / 0.8%.
    The samples were stored under common room conditions for 24 hours before the experiment.

    Claims (12)

    1. Method for the production of core preforms for foundries, wherein
      a) there is produced a mixture of inorganic, fire-resistant moulding sand and an inorganic bonding agent based on water glass,
      b) the mixture is filled into a core box heated to a moderate temperature,
      c) the water contained in the mixture is extracted by a physical method,
      d) the core preform is removed from the core box,
      characterised in
      e) that, while being filled, the core box heated to a moderate temperature is subjected to a vacuum,
      f) that, after the core box has been closed, the temperature/holding time is set in such a way that a dimensionally stable surface shell suitable for carrying is formed at the core preform,
      g) that, immediately after the core box has been opened, the core preform is removed and dried completely by the effect of microwaves.
    2. A method according to claim 1,
      characterised in
      that the vacuum is held between 100 - 400 mbar.
    3. A method according to any one of the preceding claims,
      characterised in
      that the temperature of the core box is held between 150 and 200 °C.
    4. A method according to any one of the preceding claims,
      characterised in
      that the surface shell in the core box heated to a moderate temperature is formed within a time span of 10 to 30 seconds.
    5. A method according to any one of the preceding claims,
      characterised in
      that the processes of complete drying out and through-hardening of the core preform under the effect of microwaves take place within a time span of 30 and 180 seconds.
    6. A method according to any one of the preceding claims,
      characterised in
      that the core box is filled with a mixture of recycled sand consisting of 1.5 to 3.0 % by weight of bonding agent, with reference to the percentage of sand, with the bonding agent containing 20 - 50 % by weight of water glass, the remainder being water.
    7. A Method according to any one of the preceding claims,
      characterised in
      that the percentage of melting phases in the recycled core sand amounts to ≤ 0.1 % by weight.
    8. A method according to any one of the preceding claims,
      characterised in
      that, directly prior to filling the core box, the water content of the bonding agent is increased by 20 - 40 %.
    9. A method according to any one of the preceding claims,
      characterised in
      that the vacuum is sufficient for removing at least the main part of the water contained in the moulding material.
    10. A method of producing a recycled core sand consisting of residual materials of old cores from core preforms according to claim 1, i.e. quartz sand and a bonding agent based on water glass,
      characterised in
      that the residual materials with a bonding agent content of 1.5 to 3% are deaglomerated to the starting primary grain size, that said primary grain comprises a dehydrated water glass/bonding agent sleeve which is free from organic residue and free soda,
      that the percentage of melting phases in the recycled core sand amounts to ≤ 0.1 % by weight and that the quantity of water glass ranges between 1.5 and 3.0 % by weight with reference to the quantity of quartz sand with a maximum percentage of solids of 50 % by weight with reference to the bonding agent.
    11. A method according to any one of the preceding claims,
      characterised in
      that the percentage of primary grain in the recycled core sand mixture amounts to ≥ 99 % by weight.
    12. A method according to any one of the preceding claims,
      characterised in
      that deaglomeration takes place in a jaw crusher of a cross pane mill and that mixing witn the bonding agent takes place in a vibration mixer without classification.
    EP97934549A 1996-08-09 1997-07-26 Method for the production of core preforms and recycling core sand for foundry Expired - Lifetime EP0917499B1 (en)

    Applications Claiming Priority (3)

    Application Number Priority Date Filing Date Title
    DE19632293A DE19632293C2 (en) 1996-08-09 1996-08-09 Process for the production of core moldings for foundry technology
    DE19632293 1996-08-09
    PCT/EP1997/004072 WO1998006522A2 (en) 1996-08-09 1997-07-26 Method for the production of core preforms and recycling core sand for foundry

    Publications (2)

    Publication Number Publication Date
    EP0917499A2 EP0917499A2 (en) 1999-05-26
    EP0917499B1 true EP0917499B1 (en) 2000-11-22

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    EP (1) EP0917499B1 (en)
    AT (1) ATE197683T1 (en)
    DE (2) DE19632293C2 (en)
    DK (1) DK0917499T3 (en)
    ES (1) ES2153677T3 (en)
    HU (1) HU222658B1 (en)
    WO (1) WO1998006522A2 (en)

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    DE10144391C1 (en) * 2001-09-10 2002-10-17 Vaw Mandl & Berger Gmbh Linz Production of molded parts comprises pouring a molding material into a molding tool, adding heat to solidify the molding material by removing moisture, and temporarily passing hot gas
    DE10144193C1 (en) * 2001-09-08 2002-10-31 Vaw Mandl & Berger Gmbh Linz Production of molded parts involves pouring a molding material into a molding tool in an injection molding machine
    DE10209183A1 (en) * 2002-03-04 2003-10-02 Vaw Mandl & Berger Gmbh Linz 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
    DE10209224A1 (en) * 2002-03-04 2003-10-09 Vaw Mandl & Berger Gmbh Linz 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
    WO2010025861A1 (en) * 2008-09-05 2010-03-11 Minelco Gmbh Core or foundry sand coated and/or mixed with water glass, having a water content in the range of ≥ approximately 0.25 wt.% to approximately 0.9 wt.%
    US10232430B2 (en) 2007-10-30 2019-03-19 Ask Chemicals Gmbh Mould material mixture having improved flowability

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    DE19951622A1 (en) * 1999-10-26 2001-05-23 Vaw Ver Aluminium Werke Ag Binder system based on water glass
    WO2003013761A1 (en) * 2001-08-10 2003-02-20 Dipl.-Ing. Laempe Gmbh Method and device for the production of molds or cores for foundry purposes
    DE10200927A1 (en) * 2001-08-10 2003-03-06 Laempe Joachim Method and device for producing molds or cores for foundry purposes
    MXPA04002424A (en) * 2001-09-14 2005-04-11 Hydro Aluminium Deutschland Method for producing castings, molding sand and its use for carrying out said method.
    DE10216464B4 (en) * 2002-04-12 2004-04-15 Deutsches Zentrum für Luft- und Raumfahrt e.V. Silica-bonded core materials, processes for their production and their use
    DE102004042535B4 (en) 2004-09-02 2019-05-29 Ask Chemicals Gmbh Molding material mixture for the production of casting molds for metal processing, process and use
    DE102006003198A1 (en) * 2006-01-24 2007-07-26 Deutsches Zentrum für Luft- und Raumfahrt e.V. Mechanically and thermally stable core, used for light metal- and/or investment casting, comprises hydrophilic aerogel granulates, sand and binding agent
    BRPI0718281B1 (en) 2006-10-19 2015-09-15 Ashland Südchemie Kernfest Gmbh carbohydrate-containing molded semi-product mixture
    DE102006061876A1 (en) 2006-12-28 2008-07-03 Ashland-Südchemie-Kernfest GmbH Molding material mixture, useful for producing casting molds for metal processing, comprises a fireproof molding base material, a binder based on water glass, a particulate metal oxide, e.g. silicon dioxide and further a carbohydrate
    DE102006049379A1 (en) 2006-10-19 2008-04-24 Ashland-Südchemie-Kernfest GmbH Phosphorus-containing molding material mixture for the production of casting molds for metal processing
    DE102008041217A1 (en) * 2008-08-13 2010-02-18 Volkswagen Ag Molding material binder, useful for pourable molding material, preferably molding core inserts for casting mold, where the molding material binder is present in inorganic form
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    Publication number Priority date Publication date Assignee Title
    DE10144193C1 (en) * 2001-09-08 2002-10-31 Vaw Mandl & Berger Gmbh Linz Production of molded parts involves pouring a molding material into a molding tool in an injection molding machine
    DE10144391C1 (en) * 2001-09-10 2002-10-17 Vaw Mandl & Berger Gmbh Linz Production of molded parts comprises pouring a molding material into a molding tool, adding heat to solidify the molding material by removing moisture, and temporarily passing hot gas
    DE10209183A1 (en) * 2002-03-04 2003-10-02 Vaw Mandl & Berger Gmbh Linz 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
    DE10209224A1 (en) * 2002-03-04 2003-10-09 Vaw Mandl & Berger Gmbh Linz 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
    US10232430B2 (en) 2007-10-30 2019-03-19 Ask Chemicals Gmbh Mould material mixture having improved flowability
    WO2010025861A1 (en) * 2008-09-05 2010-03-11 Minelco Gmbh Core or foundry sand coated and/or mixed with water glass, having a water content in the range of ≥ approximately 0.25 wt.% to approximately 0.9 wt.%
    EP2163328A1 (en) * 2008-09-05 2010-03-17 Minelco GmbH Core or foundry sand coated and/or mixed with soluble glass with a water content in the area of >= approx. 0.25 weight % to approx 0.9 weight %

    Also Published As

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    EP0917499A2 (en) 1999-05-26
    DK0917499T3 (en) 2001-02-12
    DE59702665D1 (en) 2000-12-28
    HUP0001766A3 (en) 2000-11-28
    DE19632293C2 (en) 1999-06-10
    ES2153677T3 (en) 2001-03-01
    HU222658B1 (en) 2003-09-29
    DE19632293A1 (en) 1998-02-19
    WO1998006522A3 (en) 1998-06-04
    HUP0001766A2 (en) 2000-09-28
    ATE197683T1 (en) 2000-12-15
    WO1998006522A2 (en) 1998-02-19

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