EP0447387B1 - Process for continuous casting, especially non ferrous metals and mould for carrying out said process - Google Patents
Process for continuous casting, especially non ferrous metals and mould for carrying out said process Download PDFInfo
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- EP0447387B1 EP0447387B1 EP91890025A EP91890025A EP0447387B1 EP 0447387 B1 EP0447387 B1 EP 0447387B1 EP 91890025 A EP91890025 A EP 91890025A EP 91890025 A EP91890025 A EP 91890025A EP 0447387 B1 EP0447387 B1 EP 0447387B1
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- mould
- casting
- graphite mould
- protective gas
- graphite
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
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- the invention relates to a process for the continuous casting of non-ferrous metals in particular by means of a mold unit which has a cooled, in particular water-cooled, outer metal jacket and an inner, one or more part gas-permeable graphite mold which forms the strand cross section, the graphite mold having a protective gas from the outside is applied, which penetrates them across.
- the invention further relates to a mold assembly for performing this method.
- Mold aggregates consist of an outer, cooled metal jacket and an inner graphite mold that forms the strand cross-section. Depending on the strand format, single or multi-part graphite molds are used. Such mold aggregates, which are generally known, are described in detail in the "Manual of Continuous Casting" by Dr. E. Herrmann, 1980, pages 102 to 107. They are mainly used for casting non-ferrous metals (non-ferrous metals) and cast iron. Only electrographite is used as the material for the molds, which is characterized by high thermal conductivity, low wettability by liquid metals, good sliding properties and high self-lubricity.
- the graphite mold can be pressed as a cylindrical shaped body into an outer casing pipe, for example made of copper, or the casing pipe can be shrunk onto the graphite mold.
- the graphite mold can also consist of individual plates which enclose a cavity with a rectangular, for example square, cross section.
- the formation of the cooling system and its connection with the graphite mold are of a high quality end product and high production output special meaning. For a perfect heat transfer between the graphite mold and the cooling medium, a positive connection between the graphite mold and the cooling jacket is therefore absolutely necessary.
- the present invention is based on the knowledge that the cooling effect sought by the cooling unit is not only badly deteriorated due to deformations, but also because metal vapors formed during the casting process penetrate into the pores of the graphite mold and cause metallic deposits in the pores as a result of their sublimation , whereby the thermal conductivity of the graphite mold is significantly deteriorated
- the invention is therefore based on the object of avoiding this disadvantageous effect.
- a mold of the type mentioned at the outset that the application of protective gas to the graphite mold begins before the start of the casting process and is maintained during this, thereby forming an effective diffusion barrier in the graphite mold transverse to the casting direction. Since the graphite mold is already exposed to protective gas at the beginning of the casting process, no metal vapors can penetrate into it, which means that those caused by the penetration of metal vapors adverse effects can be avoided.
- the protective gas is preferably also fed through the graphite mold to the shrink gap.
- a mold assembly according to the invention is preferably provided with channels, grooves or the like extending in the longitudinal direction thereof and / or with channels extending transversely thereto. formed, through which the protective gas is supplied to the graphite mold and diffuses through it.
- the consequence of the diffusion barrier is that the metal vapors released during the continuous casting are kept at a temperature level in the strand shell-mold contact area which prevents sublimation of the alloy elements.
- the metal vapors are conveyed into the shrink gap with the aid of the protective gas and the extrudate movement, in which they cool and, after reaching the sublimation temperature, settle as a deposit on the cast strand. As a result, they have no disruptive influence on the graphite mold.
- the diffusion barrier not only prevents the penetration of vaporous alloy elements into the graphite mold, but also prevents oxygen from entering the graphite mold, so that no reaction between oxygen and carbon and therefore no graphite oxidation can occur. Not only is a constant heat flow achieved for high-quality production, but at the same time the service life of the graphite mold is significantly extended by preventing graphite oxidation.
- the simultaneously created oxygen barrier also means that the metal vapors are not subject to oxidation and that the first strand shell formation, which is in direct contact with the graphite mold, also takes place without oxidation.
- the diffusion barrier effected according to the invention is optimally effective if the longitudinal channels for the protective gas supply cover not only the liquid and shell-forming area, but also part of the shrink gap, so that sufficient protective gas flows into it, thereby preventing possible oxidation when the cast strand is cooled further .
- the gas permeability of the graphite mold, based on nitrogen, is given by the graphite manufacturers in Milli Darcy. If the oxygen barrier remains intact until the oxidation temperature of the casting material is undershot, a casting product with an optimal surface quality can be produced, which enables immediate further shaping of a large number of non-ferrous metals without the previously required machining surface treatment.
- an inert gas such as helium can also be used as the protective gas.
- helium has an approximately 10% higher dynamic viscosity than nitrogen, so that the flow rate through the graphite mold per unit time decreases by about 10% at the same pressure conditions.
- it has five times the thermal conductivity, which causes an improved heat flow in the graphite mold, which is of great importance for the heat flow in the shrink gap. The increased heat flow causes an increased cooling capacity and thus an increased production in the time unit.
- This mold assembly has a graphite mold 1, which is in one piece in the case of round formats. Rectangular formats are preferably made in several parts as so-called plate elements.
- the graphite mold 1 is positively surrounded by a metal jacket 2, in particular cooled by water. Both parts form the mold assembly, which is connected to a mold attachment and furnace closing unit 3 by means of screws 4.
- the mold attachment and furnace closing unit 3 consists of a section steel structure, which is lined with a part 6 made of refractory material after the attachment of the mold assembly 1, 2 and after the insertion of a cooling panel 5.
- the cooling panel 5 prevents an undesirable lowering of the temperature of the liquid metal located in front of the mold inlet.
- the part 6 is joined in a metal-tight manner by interposing an insulating mat 7 with a further part 8 made of refractory material of the metal receptacle by means of screws, not shown.
- the metal feed to the mold assembly 1, 2 takes place via a trumpet-shaped opening 9 in the metal receptacle.
- the water-cooled metal jacket 2 has an annular channel 10 at the point of contact with the graphite mold 1, which is followed by longitudinal channels 11 distributed over the circumference.
- the annular channel 10 or the longitudinal channels 11 are fed with a protective gas, for example nitrogen or helium, before the start of the casting process and during the same via supply channels 12 to 15, which gas is supplied to the graphite mold 1 at a pressure adapted to the system and passes through it.
- the channel system can also be provided in the graphite mold 1.
- the protective gas penetrates on the one hand to the liquid or already partially solidified metal, thereby preventing the penetration of evaporating alloy elements.
- the gas penetrates into the part 6 made of refractory material and into the shrink gap 1a and prevents the entry of oxygen there, thereby preventing oxidation of the graphite mold, the metal vapors and the surface of the cast strand 1b.
- the protective gas entering the shrink gap 1a protects the surface of the cast strand 1b from possible oxidation even as it cools further.
- the diffusion or oxygen barrier makes it possible to cast copper with an oxygen content of more than 150 ppm without a reaction between the oxygen and the carbon.
- the interface temperature of the graphite mold with the casting material experiences an additional reduction due to the constant flooding of protective gas, so that a higher cooling capacity and thus a higher production per unit of time is made possible.
- helium an additional increase in cooling intensity and thus an increase in production is possible due to its five-fold thermal conductivity compared to nitrogen.
- the method according to the invention is of great advantage in particular when casting non-ferrous metals (non-ferrous metals), since penetration of vaporous alloy components into the graphite mold is prevented.
- the fact that the protective gas prevents oxidation of the graphite mold and the surface of the metal strand is also important when casting metals which do not contain easily evaporating alloy components, e.g. Cast iron, of importance.
Abstract
Description
Die Erfindung betrifft ein Verfahren zum Stranggießen von insbesondere NE-Metallen mittels eines Kokillenaggregates, welches einen gekühlten, insbesondere wassergekühlten, äußeren Metallmantel und eine innere, den Strangquerschnitt formende, ein- oder mehrteilige gasdurchlässige Graphitkokille aufweist, wobei die Graphitkokille von außen her mit einem Schutzgas beaufschlagt wird, welches diese quer durchsetzt. Die Erfindung betrifft weiters ein Kokillenaggregat zur Durchführung dieses Verfahrens.The invention relates to a process for the continuous casting of non-ferrous metals in particular by means of a mold unit which has a cooled, in particular water-cooled, outer metal jacket and an inner, one or more part gas-permeable graphite mold which forms the strand cross section, the graphite mold having a protective gas from the outside is applied, which penetrates them across. The invention further relates to a mold assembly for performing this method.
Kokillenaggregate bestehen aus einem äußeren, gekühlten Metallmantel und einer inneren, den Strangquerschnitt formenden Graphitkokille. Dabei kommen je nach dem Strangformat ein- oder mehrteilige Graphitkokillen zum Einsatz. Derartige Kokillenaggregate, welche allgemein bekannt sind, sind im "Handbuch des Stranggießens" von Dr.E.Herrmann, 1980, Seiten 102 bis 107 ausführlich beschrieben. Sie werden vorallem zum Gießen von Nichteisen-Metallen (NE-Metallen) und von Gußeisen verwendet. als Werkstoff für die Kokillen wird ausschließlich Elektrographit verwendet, welcher sich durch hohe Wärmeleitfähigkeit, geringe Benetzbarkeit durch flüssige Metalle, gute Gleiteigenschaften und hohe Selbstschmierfähigkeit auszeichnet.Mold aggregates consist of an outer, cooled metal jacket and an inner graphite mold that forms the strand cross-section. Depending on the strand format, single or multi-part graphite molds are used. Such mold aggregates, which are generally known, are described in detail in the "Manual of Continuous Casting" by Dr. E. Herrmann, 1980, pages 102 to 107. They are mainly used for casting non-ferrous metals (non-ferrous metals) and cast iron. Only electrographite is used as the material for the molds, which is characterized by high thermal conductivity, low wettability by liquid metals, good sliding properties and high self-lubricity.
Die Graphitkokille kann als zylindrischer Formkörper in ein äußeres, z.B. aus Kupfer bestehendes Mantelrohr eingepreßt sein oder das Mantelrohr kann auf die Graphitkokille aufgeschrumpft sein. Die Graphitkokille kann aber auch aus einzelnen Platten bestehen, welche einen Hohlraum mit einem rechteckigen, z.B. quadratischen Querschnitt umschließen. Unabhängig von der jeweiligen Ausführungsform sind für ein qualitativ hochwertiges Endprodukt und eine hohe Produktionsleistung die Ausbildung des Kühlsystems und dessen Verbindung mit der Graphitkokille von besonderer Bedeutung. Für einen einwandfreien Wärmetransport zwischen der Graphitkokille und dem Kühlmedium ist daher eine formschlüssige Verbindung zwischen der Graphitkokille und dem Kühlmantel unbedingt erforderlich.The graphite mold can be pressed as a cylindrical shaped body into an outer casing pipe, for example made of copper, or the casing pipe can be shrunk onto the graphite mold. However, the graphite mold can also consist of individual plates which enclose a cavity with a rectangular, for example square, cross section. Regardless of the particular embodiment, the formation of the cooling system and its connection with the graphite mold are of a high quality end product and high production output special meaning. For a perfect heat transfer between the graphite mold and the cooling medium, a positive connection between the graphite mold and the cooling jacket is therefore absolutely necessary.
Der praktische Betrieb hat jedoch gezeigt, daß auch bei optimaler Verbindung nach relativ kurzer Gießzeit ein Abfall des Wärmetransportes aus der Graphitkokille verursacht wird. Dies gilt insbesondere bei jenen Kupferlegierungen, die niedrig schmelzende und verdampfende Legierungselemente als Beimengungen aufweisen. Hierzu gehört z.B. Zink, das in Kupferlegierungen, wie Messing, Neusilber und ähnlichen Legierungen, enthalten ist. Der Grund hierfür liegt darin, daß die bei den Gießtemperaturen verdampfenden Legierungselemente in die Wandung der Graphitkokille bzw. durch diese Wandung hindurch diffundieren und in dieser bzw. am angrenzenden metallischen Kühlmantel sublimieren, also vom gasförmigen bzw. dampfförmigen Zustand unmittelbar in den festen Zustand übergehen. Diese Diffusionen führen mit zunehmender Gießdauer zu einer wachsenden Verschlechterung des Wärmeflusses und vor allem zu örtlich sehr unterschiedlichen Wärmeflüssen, wodurch in verstärktem Maße Gußfehler auftreten. Diese unterschiedlichen Wärmeflüsse stellen zudem auch eine Gefahr für die formschlüssige Verbindung der Graphitkokille mit dem Kühlmantel dar, sodaß mechanische Verformungen der Graphitkokille, vor allem bei Plattenelementen, nicht ausgeschlossen werden können.Practical operation has shown, however, that even with an optimal connection, a decrease in the heat transport from the graphite mold is caused after a relatively short casting time. This applies in particular to those copper alloys which have low-melting and evaporating alloy elements as admixtures. This includes e.g. Zinc, which is contained in copper alloys such as brass, nickel silver and similar alloys. The reason for this is that the alloy elements evaporating at the casting temperatures diffuse into the wall of the graphite mold or through this wall and sublimate in this or on the adjacent metallic cooling jacket, i.e. they change directly from the gaseous or vaporous state to the solid state. With increasing casting time, these diffusions lead to an increasing deterioration in the heat flow and, above all, to locally very different heat flows, as a result of which casting defects occur to an increased extent. These different heat flows also pose a risk for the positive connection of the graphite mold with the cooling jacket, so that mechanical deformations of the graphite mold, especially with plate elements, cannot be excluded.
Die vorstehend dargelegten Schwierigkeiten sind bekannt und wurden zu vermeiden gesucht. So ist es aus der DE-PS 26 57 207 bekannt, in den sich zwischen der Graphitkokille und dem erstarrenden Strang ausbildenden Schrumpfspalt ein Schutzgas, insbesondere Stickstoff, einzuleiten. Durch diese Maßnahme kann jedoch im Entstehungsbereich der Zinkverdampfung, d.h. im Liquidus-Solidusbereich, die störende Diffusion der dampfförmigen Ausscheidungen in die bzw. durch die Wandung der Graphitkokille hindurch nicht verhindert werden.The difficulties outlined above are known and attempts have been made to avoid them. It is known from DE-PS 26 57 207 to introduce a protective gas, in particular nitrogen, into the shrink gap which forms between the graphite mold and the solidifying strand. By this measure, however, zinc evaporation, i.e. in the liquidus solidus area, the disruptive diffusion of the vaporous precipitates into or through the wall of the graphite mold cannot be prevented.
Aus der DE-OS 37 18 372 ist es weiters bekannt, die Graphitkokille mindestens zweischichtig auszubilden und zwischen den Schichten eine Metallfolie als Diffusionssperre anzuordnen. Diese Maßnahme ist zwar wirkungsvoller, jedoch verhindert sie nicht eine Diffusion in jenem Bereich der Graphitkokille, welcher mit dem Gießprodukt unmittelbar in Berührung steht.From DE-OS 37 18 372 it is also known to form the graphite mold at least two layers and between the Arrange layers of a metal foil as a diffusion barrier. Although this measure is more effective, it does not prevent diffusion in that area of the graphite mold which is in direct contact with the cast product.
Aus der GB-A-2 109 722 und aus der US-A-3 502 135 ist es bekannt, der Außenseite von Graphitkokillen zum Gießen von Metallen, insbesondere von NE-Metallen, ein Schutzgas zuzuführen, welches die Graphitkokille quer durchsetzt. Dieser Maßnahme liegt die Erkenntnis zugrunde, daß aufgrund der thermischen Belastungen der Graphitkokille und des Kühlaggregates Verformungen bedingt werden, welche den zwischen dem Kühlaggregat und der Graphitkokille erforderlichen Wärmeübergang verschlechtern, weswegen die durch das Kühlaggregat angestrebte Kühlwirkung nicht mehr erzielt wird. Um diesen Nachteil zu vermeiden, ist es aus dem Stand der Technik gemäß den zitierten beiden Literaturstellen bekannt, durch die Graphitkokille während des Gießvorganges ein Gas hindurchzuleiten, welches die erforderliche Kühlung der Graphitkokille gewährleistet.From GB-A-2 109 722 and from US-A-3 502 135 it is known to supply a protective gas to the outside of graphite molds for casting metals, in particular non-ferrous metals, which passes through the graphite mold transversely. This measure is based on the knowledge that, due to the thermal loads on the graphite mold and the cooling unit, deformations are caused which deteriorate the heat transfer required between the cooling unit and the graphite mold, which is why the cooling effect sought by the cooling unit is no longer achieved. In order to avoid this disadvantage, it is known from the prior art according to the two references cited to pass a gas through the graphite mold during the casting process, which ensures the necessary cooling of the graphite mold.
Der gegenständlichen Erfindung liegt demgegenüber die Erkenntnis zugrunde, daß die durch das Kühlaggregat angestrebte Kühlwirkung nicht nur aufgrund von Verformungen, sondern auch deshalb stark verschlechtert wird, daß während des Gießvorganges entstehende Metalldämpfe in die Poren der Graphitkokille eindringen und in diesen infolge deren Sublimation metallische Ablagerungen bedingen, wodurch die Wärmeleitfähigkeit der Graphitkokille maßgeblich verschlechtert wirdIn contrast, the present invention is based on the knowledge that the cooling effect sought by the cooling unit is not only badly deteriorated due to deformations, but also because metal vapors formed during the casting process penetrate into the pores of the graphite mold and cause metallic deposits in the pores as a result of their sublimation , whereby the thermal conductivity of the graphite mold is significantly deteriorated
Der Erfindung liegt demnach die Aufgabe zugrunde, diesen nachteiligen Effekt zu vermeiden. Dies erfolgt bei einer Kokille der eingangs genannten Gattung dadurch, daß die Beaufschlagung der Graphitkokille mit Schutzgas vor dem Beginn des Gießvorganges einsetzt und während dieses aufrechterhalten wird, wodurch in der Graphitkokille quer zur Gießrichtung eine gegenüber in diese eindringende Metalldämpfe wirksame Diffusionssperre gebildet wird. Da dabei die Graphitkokille schon am Beginn des Gießvorganges mit Schutzgas beaufschlagt ist, können in diese keine Metalldämpfe eindringen, wodurch die durch das Eindringen von Metalldämpfen bedingten nachteiligen Effekte vermieden werden. Vorzugsweise wird das Schutzgas durch die Graphitkokille hindurch auch dem Schrumpfspalt zugeführt.The invention is therefore based on the object of avoiding this disadvantageous effect. In the case of a mold of the type mentioned at the outset, that the application of protective gas to the graphite mold begins before the start of the casting process and is maintained during this, thereby forming an effective diffusion barrier in the graphite mold transverse to the casting direction. Since the graphite mold is already exposed to protective gas at the beginning of the casting process, no metal vapors can penetrate into it, which means that those caused by the penetration of metal vapors adverse effects can be avoided. The protective gas is preferably also fed through the graphite mold to the shrink gap.
Ein erfindungsgemäßes Kokillenaggregat ist vorzugsweise mit sich in dessen Längsrichtung und bzw. oder mit sich dazu quer erstreckenden Kanälen, Nuten od.dgl. ausgebildet, durch welche hindurch der Graphitkokille das Schutzgas zugeleitet wird und durch diese diffundiert. Dadurch, daß die Graphitkokille im Bereich der höchsten Temperaturen, d.h. vom flüssigen Metalleinlauf bis nach der schrumpfspaltbildung, über ein Kanalsystem mit einem Schutzgas durchflutet wird, wodurch eine Diffusionssperre bewirkt wird, wird verhindert, daß niedrig schmelzende und verdampfende Legierungselemente in die Graphitkokille eindringen. Die Diffusionssperre hat zur Folge, daß die beim Stranggießen frei werdenden Metalldämpfe im Kontaktbereich Strangschale - Kokille auf einem Temperaturniveau gehalten werden, das eine Sublimation der Legierungselemente verhindert. Die Metalldämpfe werden vielmehr unter Mithilfe des Schutzgases und der Strangabzugsbewegung in den Schrumpfspalt gefördert, in welchem sie abkühlen und sich nach dem Erreichen der Sublimationstemperatur als Niederschlag am Gußstrang absetzen. Hierdurch nehmen sie auf die Graphitkokille keinen störenden Einfluß.A mold assembly according to the invention is preferably provided with channels, grooves or the like extending in the longitudinal direction thereof and / or with channels extending transversely thereto. formed, through which the protective gas is supplied to the graphite mold and diffuses through it. The fact that the graphite mold is flooded with a protective gas in a channel system in the area of the highest temperatures, i.e. from the liquid metal inlet to after the shrinkage gap formation, which causes a diffusion barrier, prevents low-melting and evaporating alloy elements from penetrating into the graphite mold. The consequence of the diffusion barrier is that the metal vapors released during the continuous casting are kept at a temperature level in the strand shell-mold contact area which prevents sublimation of the alloy elements. Rather, the metal vapors are conveyed into the shrink gap with the aid of the protective gas and the extrudate movement, in which they cool and, after reaching the sublimation temperature, settle as a deposit on the cast strand. As a result, they have no disruptive influence on the graphite mold.
Die Diffusionssperre unterbindet nicht nur das Eindringen dampfförmiger Legierungselemente in die Grafitkokille, sondern sie unterbindet auch den Zutritt von Sauerstoff zur Grafitkokille, sodaß keine Reaktion zwischen Sauerstoff und dem Kohlenstoff und damit keine Grafitoxydation eintreten kann. Es wird damit nicht nur ein konstanter Wärmefluß für eine qualitativ hochwertige Produktion erzielt, sondern es wird gleichzeitig auch durch Verhinderung einer Grafitoxydation die Standzeit der Grafitkokille wesentlich verlängert. Die gleichzeitig entstehende Sauerstoffsperre bewirkt außerdem, daß die Metalldämpfe keiner Oxydation unterliegen und auch die erste Strangschalenbildung, welche im direkten Kontakt mit der Grafitkokille steht, ohne Oxydation erfolgt.The diffusion barrier not only prevents the penetration of vaporous alloy elements into the graphite mold, but also prevents oxygen from entering the graphite mold, so that no reaction between oxygen and carbon and therefore no graphite oxidation can occur. Not only is a constant heat flow achieved for high-quality production, but at the same time the service life of the graphite mold is significantly extended by preventing graphite oxidation. The simultaneously created oxygen barrier also means that the metal vapors are not subject to oxidation and that the first strand shell formation, which is in direct contact with the graphite mold, also takes place without oxidation.
Die erfindungsgemäß bewirkte Diffusionssperre ist dann optimal wirksam, wenn die Längskanäle für die Schutzgaszuführung nicht nur den flüssigen und schalenbildenden Bereich, sondern auch einen Teil des Schrumpfspaltes überdecken, damit in diesen ausreichend Schutzgas einströmt, wodurch bei der weiteren Abkühlung des Gußstranges eine mögliche Oxydation unterbunden wird. Die Gasdurchlässigkeit der Grafitkokille, bezogen auf Stickstoff, wird von den Grafitherstellern in Milli Darcy angegeben. Bleibt die Sauerstoffsperre bis zum Unterschreiten der Oxydationstemperatur des Gießwerkstoffes aufrecht, so kann ein Gießprodukt mit optimaler Oberflächengüte hergestellt werden, wodurch bei einer Mehrzahl von NE-Metallen eine sofortige Weiterverformung ohne die bisher notwendige spanabhebende Oberflächenbearbeitung ermöglicht ist.The diffusion barrier effected according to the invention is optimally effective if the longitudinal channels for the protective gas supply cover not only the liquid and shell-forming area, but also part of the shrink gap, so that sufficient protective gas flows into it, thereby preventing possible oxidation when the cast strand is cooled further . The gas permeability of the graphite mold, based on nitrogen, is given by the graphite manufacturers in Milli Darcy. If the oxygen barrier remains intact until the oxidation temperature of the casting material is undershot, a casting product with an optimal surface quality can be produced, which enables immediate further shaping of a large number of non-ferrous metals without the previously required machining surface treatment.
Anstelle von Stickstoff kann als Schutzgas auch ein Edelgas, wie Helium, verwendet werden. Helium weist zwar einerseits eine um etwa 10% höhere dynamische Viskosität gegenüber Stickstoff auf, sodaß bei gleichen Druckverhältnissen die Durchflußmenge durch die Grafitkokille je Zeiteinheit um etwa 10% abnimmt. Es hat jedoch andererseits die fünffache Wärmeleitfähigkeit, wodurch in der Grafitkokille ein verbesserter Wärmefluß bewirkt wird, was für den Wärmefluß im Schrumpfspalt von großer Bedeutung ist. Der erhöhte Wärmefluß bewirkt eine verstärkte Kühlleistung und damit eine erhöhte Produktion in der Zeiteinheit.Instead of nitrogen, an inert gas such as helium can also be used as the protective gas. On the one hand, helium has an approximately 10% higher dynamic viscosity than nitrogen, so that the flow rate through the graphite mold per unit time decreases by about 10% at the same pressure conditions. On the other hand, however, it has five times the thermal conductivity, which causes an improved heat flow in the graphite mold, which is of great importance for the heat flow in the shrink gap. The increased heat flow causes an increased cooling capacity and thus an increased production in the time unit.
Das erfindungsgemäße Verfahren ist nachstehend anhand der Zeichnung näher erläutert. Diese zeigt ein Kokillenaggregat zur Durchführung des erfindungsgemäßen Verfahrens, im Längsschnitt und teilweise abgebrochen.The method according to the invention is explained in more detail below with reference to the drawing. This shows a mold assembly for carrying out the method according to the invention, in longitudinal section and partially broken off.
Dieses Kokillenaggregat weist eine Grafitkokille 1 auf, welche bei Rundformaten einteilig ist. Rechteckige Formate sind vorzugsweise mehrteilig als sogenannte Plattenelemente ausgeführt. Die Grafitkokille 1 ist von einem insbesondere durch Wasser gekühlten Metallmantel 2 formschlüssig umgeben. Beide Teile bilden das Kokillenaggregat, welches mit einer Kokillenanbau- und Ofenverschließeinheit 3 mittels Schrauben 4 verbunden ist.This mold assembly has a
Die Kokillenanbau- und Ofenverschließeinheit 3 besteht aus einer Profilstahlkonstruktion, welche nach dem Anbau des Kokillenaggregates 1, 2 sowie nach dem Einsetzen einer Rückkühlblende 5 mit einem Teil 6 aus Feuerfestmaterial ausgekleidet wird. Die Rückkühlblende 5 verhindert eine unerwünschte Temperaturabsenkung des vor dem Kokilleneinlauf befindlichen flüssigen Metalls. Der Teil 6 ist durch Zwischenschalten einer Isoliermatte 7 mit einem weiteren Teil 8 aus Feuerfestmaterial des Metallaufnahmegefäßes mittels nicht dargestellter Schrauben metalldicht zusammengefügt. Der Metallzulauf zum Kokillenaggregat 1,2 erfolgt über eine trompetenförmige Öffnung 9 im Metallaufnahmegefäß.The mold attachment and
Der wassergekühlte Metallmantel 2 weist an der Kontaktstelle mit der Grafitkokille 1 einen Ringkanal 10 auf, an den sich über den Umfang verteilte Längskanäle 11 anschließen. Der Ringkanal 10 bzw. die Längskanäle 11 werden vor Beginn des Gießvorganges und während desselben über Zufuhrkanäle 12 bis 15 mit einem Schutzgas, z.B. Stickstoff oder Helium, gespeist, welches mit einem dem System angepaßten Druck der Grafitkokille 1 zugeführt wird und diese durchsetzt. Das Kanalsystem kann auch in der Grafitkokille 1 vorgesehen sein.The water-cooled metal jacket 2 has an
Aufgrund der Gasdurchlässigkeit der Grafitkokille 1 dringt das Schutzgas einerseits bis zum flüssigen bzw. bereits teilweise erstarrten Metall vor, wodurch das Eindringen verdampfen-der Legierungselemente verhindert wird. Andererseits dringt das Gas in den Teil 6 aus Feuerfestmaterial sowie in den Schrumpfspalt 1a ein und verhindert dort den Zutritt von Sauerstoff, wodurch eine Oxydation der Grafitkokille, der Metalldämpfe sowie der Oberfläche des Gußstranges 1b verhindert wird. Weiters schützt das in den Schrumpfspalt 1a gelangende Schutzgas die Oberfläche des Gußstranges 1b auch während ihrer weiteren Abkühlung vor einer möglichen Oxydation.Due to the gas permeability of the
Zudem wird durch die Diffusions- bzw. Sauerstoffsperre das Gießen von Kupfer mit über 150 ppm Sauerstoffgehalt ermöglicht, ohne daß eine Reaktion zwischen dem Sauerstoff und dem Kohlenstoff eintritt. Weiters erfährt die Grenzflächentemperatur der Grafitkokille zum Gießwerkstoff durch die ständige Durchflutung von Schutzgas eine zusätzliche Absenkung, sodaß eine höhere Kühlleistung und damit eine höhere Produktion je Zeiteinheit ermöglicht wird. Bei Verwendung von Helium wird aufgrund dessen fünffacher Wärmeleitfähigkeit gegenüber Stickstoff eine zusätzliche Steigerung der Kühlintensität und damit eine Produktionserhöhung ermöglicht.In addition, the diffusion or oxygen barrier makes it possible to cast copper with an oxygen content of more than 150 ppm without a reaction between the oxygen and the carbon. Furthermore, the interface temperature of the graphite mold with the casting material experiences an additional reduction due to the constant flooding of protective gas, so that a higher cooling capacity and thus a higher production per unit of time is made possible. When using helium, an additional increase in cooling intensity and thus an increase in production is possible due to its five-fold thermal conductivity compared to nitrogen.
Das erfindungsgemäße Verfahren ist insbesondere beim Gießen von Nichteisenmetallen (NE-Metallen) von großem Vorteil, da ein Eindringen von dampfförmigen Legierungsbestandteilen in die Grafitkokille verhindert wird. Die Tatsache, daß durch das Schutzgas Oxydationen der Grafitkokille und der Oberfläche des Metallstranges verhindert werden, ist jedoch auch beim Gießen von solchen Metallen, welche keine leicht verdampfenden Legierungsbestandteile enthalten, wie z.B. Gußeisen, von Bedeutung.The method according to the invention is of great advantage in particular when casting non-ferrous metals (non-ferrous metals), since penetration of vaporous alloy components into the graphite mold is prevented. However, the fact that the protective gas prevents oxidation of the graphite mold and the surface of the metal strand is also important when casting metals which do not contain easily evaporating alloy components, e.g. Cast iron, of importance.
Claims (6)
- A method for the continuous casting of in particular non-ferrous metals by means of a chill mould unit, which has a cooled, in particular water-cooled, outer metal shell (2) and an inner, gas-permeable graphite mould (1), which shapes the casting cross section and consists of one or more parts, wherein a protective gas is applied to the graphite mould (1) from the outside, and passes through the latter in a transverse direction, characterised in that the application of protective gas to the graphite mould (1) starts before the commencement of the casting process and is maintained throughout said process, whereby in the graphite mould (1), transversely to the direction of casting, there is formed a diffusion barrier, which is effective in respect of metal vapours which may seep into the graphite mould.
- A method according to claim 1, wherein the protective gas is also supplied to the contraction gap (1a) through the graphite mould (1), characterized in that by means of the protective gas, which flows off into the contraction gap (1a), the surface of the casting (1b) is protected from oxidation, even while it is cooling down further.
- A method according to one of claims 1 and 2, characterised in that when the inert gas helium is used, as known per se, on the basis of its fivefold thermal-conductivity in comparison with nitrogen, an additional rise in the cooling intensity, and consequently an increase in production are rendered possible.
- A method according to one of claims 1 to 3, characterised in that the diffusion barrier also permits the casting of oxygenous copper having an oxygen content of over 150 ppm, without a reaction being caused between the oxygen and the cooling material.
- A method according to one of claims 1 to 4, characterized in that the interfacial temperature of the graphite mould (1) relative to the casting material is additionally decreased because of a constant flooding with protective gas, whereby a higher cooling capacity, and consequently a higher level of production per unit of time are achieved.
- A chill mould unit having a gas-permeable graphite mould surrounded with a cooling shell for carrying out the method according to one of claims 1 to 5, which chill mould unit is formed with ducts (10, 11), grooves, or suchlike extending in a longitudinal direction and/or with ducts (10, 11), grooves, or suchlike extending transversely thereto, by way of which a protective gas can be supplied to the graphite mould (1), and can diffuse through said mould, characterised in that the ducts (10, 11), grooves, or suchlike are provided in the graphite mould (1).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT482/90 | 1990-03-01 | ||
| AT0048290A AT395390B (en) | 1990-03-01 | 1990-03-01 | METHOD FOR THE CONTINUOUS CASTING OF PARTICULARLY NON-METALS AND CHILLET UNIT FOR CARRYING OUT THIS METHOD |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0447387A1 EP0447387A1 (en) | 1991-09-18 |
| EP0447387B1 true EP0447387B1 (en) | 1995-09-20 |
Family
ID=3491777
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP91890025A Expired - Lifetime EP0447387B1 (en) | 1990-03-01 | 1991-02-14 | Process for continuous casting, especially non ferrous metals and mould for carrying out said process |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0447387B1 (en) |
| AT (2) | AT395390B (en) |
| DE (1) | DE59106503D1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0470608B1 (en) * | 1990-08-09 | 1999-11-24 | Nippon Steel Corporation | Method and apparatus for continuous casting |
| DE4311031C2 (en) * | 1993-03-30 | 1996-07-11 | Mannesmann Ag | Device for the continuous continuous casting of metals |
| CN110117729A (en) * | 2019-04-26 | 2019-08-13 | 厦门百路达高新材料有限公司 | A method of producing graphene metal |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT171448B (en) * | 1950-02-09 | 1952-05-26 | Mannesmann Ag | Process for the continuous casting of steel and iron alloys in water-cooled molds |
| CH431826A (en) * | 1966-03-31 | 1967-03-15 | Wertli Alfred | Process for the continuous casting of metals and device for carrying out the process |
| DE2657207C2 (en) * | 1976-12-17 | 1978-10-05 | Kreidler Werke Gmbh, 7000 Stuttgart | Process for the continuous casting of metal alloys, in particular brass alloys and continuous casting mold for carrying out the process |
| GB2034215B (en) * | 1978-11-13 | 1982-08-11 | Timex Corp | Mould for continuous casting |
| FR2515545A1 (en) * | 1981-10-30 | 1983-05-06 | Griset Ets | CONTINUOUS CASTING CHAIN OF METALS, IN PARTICULAR COPPER ALLOYS |
| GB8401976D0 (en) * | 1984-01-25 | 1984-02-29 | Imi Refiners Ltd | Casting apparatus |
| FR2599650B2 (en) * | 1985-07-30 | 1988-08-26 | Pechiney Aluminium | METAL LOADING DEVICE |
-
1990
- 1990-03-01 AT AT0048290A patent/AT395390B/en not_active IP Right Cessation
-
1991
- 1991-02-14 EP EP91890025A patent/EP0447387B1/en not_active Expired - Lifetime
- 1991-02-14 AT AT91890025T patent/ATE128049T1/en not_active IP Right Cessation
- 1991-02-14 DE DE59106503T patent/DE59106503D1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DE59106503D1 (en) | 1995-10-26 |
| ATE128049T1 (en) | 1995-10-15 |
| ATA48290A (en) | 1992-05-15 |
| EP0447387A1 (en) | 1991-09-18 |
| AT395390B (en) | 1992-12-10 |
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