EP0544931B1 - Method for continuous casting of metal ingots - Google Patents
Method for continuous casting of metal ingots Download PDFInfo
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- EP0544931B1 EP0544931B1 EP91120532A EP91120532A EP0544931B1 EP 0544931 B1 EP0544931 B1 EP 0544931B1 EP 91120532 A EP91120532 A EP 91120532A EP 91120532 A EP91120532 A EP 91120532A EP 0544931 B1 EP0544931 B1 EP 0544931B1
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- European Patent Office
- Prior art keywords
- continuous casting
- lining plate
- metal strips
- strips according
- chill
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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
- B22D11/059—Mould materials or platings
Definitions
- the invention relates to a method for the continuous casting of metallic strands, in particular wide rectangular slabs made of copper or a copper alloy, with a cooling mold lined with highly heat-resistant material for pouring the metal melt.
- molds consisting of cooled copper plates are usually used, which form the mold cavity.
- a highly heat-resistant material for example graphite, can be arranged as a separating or lubricating agent, especially when continuously casting copper and copper alloys between the melt and mold plates (cf. EP-A-52947, SU-A- 806 237).
- the present invention has for its object to provide a method of the type mentioned in such a way that the lining material for the cooling mold has a low thermal resistance and still has sufficient abrasion resistance. Furthermore, the assembly and maintenance effort for the lining should be kept as low as possible.
- the method according to the invention surprisingly achieves a significantly longer lifespan for the lining. Due to the good heat dissipation of the cooling mold, the cast strands also have a very smooth strand shell, so that the surface finishing that has been customary up to now can be omitted.
- the mold has no fastening elements that could additionally hinder the formation of a smooth strand shell. Rather, the problem of fastening the lining plates was solved in that they are sucked onto the mold base plates by negative pressure.
- negative pressure there are numerous holes within the mold base plates, which are connected to a suction or vacuum pump via a pipe system. In this way, a negative pressure can be generated in these holes relative to the ambient atmosphere if the holes on the melt-side surface of the mold base plates are covered and the suction pump is in operation.
- a thin lining plate for example an approximately 3 mm thick graphite plate, is placed on the surface of a mold base plate facing the melt, it is sucked in uniformly by the negative pressure in the bores. With this method it is possible to attach thin-walled lining panels to mold base panels without the need for disruptive connecting elements within these panels.
- a lining plate made of graphite is usually slightly porous, it is necessary that the suction pump is also in operation during the casting process, in order to constantly ensure the negative pressure within the suction hole and thus the adhesion of the graphite plates to the mold base plates.
- the negative pressure in the suction bores and channels can be within a wide range of values.
- a vacuum of significantly less than 10% of the ambient pressure, for example 0.1% of the ambient pressure, is expediently and technically feasible without too much effort.
- a further reduction in the negative pressure is possible without further ado, but does not bring any significant technological advantages.
- the preferred range for the negative pressure to be maintained in the intake system is within the limits of 0.1 to 10% of the ambient pressure (10,000 to 100 Pa).
- the compressive force with which the lining plate is pressed onto the base plate essentially depends on the area of the bore cross sections.
- a rectangular mold suitable for the continuous casting of a copper alloy consisted of two mold base plates for the long sides, which had a length of 400 mm and a width of 300 mm. In each of these two base plates, suction holes with a diameter of 4 mm were made at a distance of about 20 mm, which were arranged horizontally and vertically next to each other in rows.
- the total cross-sectional area of the suction bores is approximately 4200 mm2 and assumes a pressure difference of 50,000 Pa between ambient pressure and internal pressure in the bores, then the total pressure or contact pressure that was exerted on the lining plate is calculated from this information , to about 210 N.
- This pressure force can be increased with the same pressure difference if the number of bores and / or their diameter is increased, since the cross-sectional area effective for the negative pressure is increased in this way.
- the same effect can also be achieved in that the melt-side surface of the mold base plate is covered with fine grooves or suction channels into which the suction holes open. It is particularly advantageous if the intake ducts have a depth of more than 0.05 mm and the width is in the range from 0.05 mm to 3 ⁇ d, d being the thickness of the lining plate.
- the cooling capacity of a mold with a thin-walled lining plate depends to a large extent on the conditions of heat transfer from the lining plate to the cooled mold base plate. Good heat transfer requires intensive contact between the lining plate and the mold base plate. This is guaranteed by a high contact pressure.
- a prerequisite for the suction of usually slightly porous lining plates made of graphite-containing material is that the suction pump has a sufficiently high output. Under unfavorable circumstances, however, these lining plates can corrode, in particular if air is sucked in from the surroundings and reacts with the lining material (e.g. graphite, boron nitride) in the pores of the lining plate.
- the lining material e.g. graphite, boron nitride
- lining plates in which the porosity has been reduced or eliminated, for example, before installation by metal infiltration.
- the lining plate can also be provided on the suction side with a coating that reduces the gas permeability. Lining plates of this type then also have the advantage that the negative pressure in the suction channels can be better maintained, as a result of which both the suction behavior and the contact intensity are improved.
- the contact surfaces of the mold base plate are coated with a mixture of liquid gallium and fine copper dust.
- a thin-walled lining plate made of graphite-containing material is then arranged on the mold base plate.
- the contact mixture penetrates into the microscopic cavities and thus improves the contact. This mixture solidifies as a result of alloying through heat treatment or during the first casting process.
- the contact surfaces of the mold base plates made of copper or a hardenable copper alloy are first roughened and then before application of the lining plates coated with liquid gallium. The gallium fills the small cavities and later solidifies with the material of the mold base plate through the formation of alloys.
- pasty contact media with higher thermal conductivity, which essentially retain their pasty properties even during the casting process.
- These pastes consist of small solid particles, preferably those that have a high thermal conductivity.
- These solid particles for example copper powder particles, are in a liquid carrier medium, which also preferably has a higher thermal conductivity than the material of the lining plate.
- Such a pasty contact medium is applied to the contact surfaces of the mold base plate before the mold base and lining plate are pressed firmly together.
- a paste has proven to be particularly favorable which consists of a mixture of graphite particles or graphite-coated copper powder particles and a carrier material consisting of indium and / or gallium.
- the thickness of the lining plate can range from about 0.2 to 15 mm. A plate thickness of 1 to 5 mm is particularly preferred.
- the lining plate can consist both of graphite-containing material and of a composite material which contains, for example, graphite or boron nitride as a lubricant.
- a sealing tape can also be used, which has a slight flexibility and thus adjusts to possible unevenness when the lining plate is pressed on.
- Frictional forces exerted on the lining plate by the strand shell of the moving cast strand Despite sufficient adhesion of the lining plate to the mold base plate, frictional forces can cause the lining plate to shift somewhat in the pulling direction during operation. This would lead to the fact that the residual gas pressure in the intake duct system can rise due to the penetrating ambient air and the adhesion of the lining plate is deteriorated. If necessary, the casting process would then have to be interrupted in order to reposition the lining plate. In order to avoid this disadvantage, it is expedient to provide brackets on the mold base plate that reliably prevent the lining plate from slipping. In the simplest case, the mold base plate has a small projection at the lower end on which the lining plate is seated.
- a holder can also be provided in the upper part of the mold.
- the brackets must be installed in such a way that the thermal expansion of the lining plate can in no way be impeded.
- the heat transfer resistance between two parallel interfaces can be changed by changing the contact pressure with which the two interfaces are pressed against each other. Accordingly, the local heat flow density within a cooling mold equipped with lining plates can be locally reduced, for example, by locally reducing the contact pressure or the suction pressure. Under certain conditions, this can be desirable for the use of a mold with lining plates.
- the areas on the narrow sides of a mold and especially the corner areas are cooled more than the middle of the long sides, since the ratio of slab surface to slab volume is particularly large here. This finds expression in the fact that the solidification proceeds correspondingly faster in these more cooled areas.
- An uneven or unfavorable solidification behavior can lead to stresses in the solidified material with certain alloys and to cracks or deformations if these stresses become too great.
- the cooling conditions are adapted locally to the desired conditions and that certain partial areas of the lining plate are sucked onto the surface of the mold base plate with a greater contact force than the other areas.
- Locally different contact pressures on the mold base plate can be achieved, for example, by separate suction systems with different negative pressures or by changing the area density of the suction bores or suction channels in some areas.
Abstract
Description
Die Erfindung betrifft ein Verfahren zum kontinuierlichen Gießen von metallischen Strängen, insbesondere breiter Rechteckbrammen aus Kupfer oder einer Kupferlegierung, mit einer mit hochwärmebeständigem Material ausgekleideten Kühlkokille zum Eingießen der Metalischmelze.The invention relates to a method for the continuous casting of metallic strands, in particular wide rectangular slabs made of copper or a copper alloy, with a cooling mold lined with highly heat-resistant material for pouring the metal melt.
Beim kontinuierlichen Stranggießen einer ganzen Reihe von Metallen oder Metallegierungen werden üblicherweise aus gekühlten Kupferplatten bestehende Kokillen verwendet, die den Formhohlraum bilden. Um ein Verschweißen der Kokillenplatten mit der Schmelze zu vermeiden, kann insbesondere beim Stranggießen von Kupfer und Kupferlegierungen zwischen Schmelze und Kokillenplatten ein hochwärmebeständiges Material, beispielsweise Graphit, als Trenn- oder Gleitmittel angeordnet werden (vgl. EP-A-52947, SU-A-806 237).In the continuous casting of a whole series of metals or metal alloys, molds consisting of cooled copper plates are usually used, which form the mold cavity. In order to avoid welding the mold plates to the melt, a highly heat-resistant material, for example graphite, can be arranged as a separating or lubricating agent, especially when continuously casting copper and copper alloys between the melt and mold plates (cf. EP-A-52947, SU-A- 806 237).
So ist es bereits bekannt, die Kokillenwände auf der der Schmelze zugewandten Oberfläche vor dem Gießen mit einer graphithaltigen Aufschlämmung zu beschichten, wobei sich eine relativ lockere Graphitschicht mit einer im Bereich von etwa 0,5 bis 1 mm liegenden Dicke bildet. Diese Beschichtung wird jedoch wegen ihrer geringen Abriebfestigkeit im Laufe des Gießprozesses mechanisch abgetragen. Schon nach einer relativ kurzen Zeit muß der Gießprozeß angehalten und die Kokillenoberfläche mit einer neuen Beschichtung versehen werden.Thus, it is already known to coat the mold walls on the surface facing the melt with a graphite-containing slurry before casting, a relatively loose graphite layer having a thickness in the range from about 0.5 to 1 mm being formed. However, due to its low abrasion resistance, this coating is removed mechanically in the course of the casting process. After a relatively short time, the casting process must be stopped and the mold surface must be given a new coating.
Man hat auch schon versucht, auf der der Schmelze zugewandten Oberfläche der Kokille dicke Graphitplatten auf die gekühlte Kokillengrundplatte festzuschrauben. Hierzu sind jedoch Graphitplatten mit einer Dicke von mindestens 20 mm erforderlich, um die Verschraubungselemente aufnehmen zu können, die innerhalb der Graphitplatte verankert sind. Nachteiligerweise sind derartige Graphitplatten sehr kostspielig und weisen einen relativ hohen thermischen Widerstand auf, der die Kühlung der Kokille erheblich verringert. Hinzu kommt, daß sich die Graphitplatten unter dem Einfluß von thermischen Spannungen wölben können, wodurch sich der Wärmeübergang zwischen den Graphitplatten und der Kühlkokille weiter verschlechtert. Dieser Effekt macht sich insbesondere für den Fall nachteilig bemerkbar, wenn Stränge mit größeren Breiten gegossen werden sollen.Attempts have also already been made to screw thick graphite plates onto the cooled mold base plate on the surface of the mold facing the melt. For this, however, graphite plates with a thickness of at least 20 mm are required in order to be able to accommodate the screwing elements that are within the Graphite plate are anchored. Disadvantageously, such graphite plates are very expensive and have a relatively high thermal resistance, which considerably reduces the cooling of the mold. In addition, the graphite plates can bulge under the influence of thermal stresses, which further deteriorates the heat transfer between the graphite plates and the cooling mold. This effect is particularly noticeable in the case when strands with larger widths are to be cast.
Der vorliegenden Erfindung liegt die Aufgabe zugrunde, ein Verfahren der eingangs genannten Art derart auszubilden, daß das Auskleidungsmaterial für die Kühlkokille einen geringen thermischen Widerstand aufweist und trotzdem über eine ausreichende Abriebfestigkeit verfügt. Ferner sollen der Montage- und Wartungsaufwand für die Auskleidung möglichst gering gehalten werden.The present invention has for its object to provide a method of the type mentioned in such a way that the lining material for the cooling mold has a low thermal resistance and still has sufficient abrasion resistance. Furthermore, the assembly and maintenance effort for the lining should be kept as low as possible.
Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß auf der der Metallschmelze zugewandten Oberfläche der Kühlkokille eine dünnwandige Auskleidungsplatte angeordnet ist, die mit Hilfe von Unterdruck auf der Oberfläche der Kühlkokille gehalten wird. Vorteilhafte Weiterbildungen ergeben sich aus den Unteransprüchen.This object is achieved in that a thin-walled lining plate is arranged on the surface of the cooling mold facing the molten metal, which is held on the surface of the cooling mold by means of negative pressure. Advantageous further developments result from the subclaims.
Mit dem erfindungsgemäßen Verfahren wird überraschend eine wesentlich längere Lebensdauer der Auskleidung erreicht. Durch die gute Wärmeableitung der Kühlkokille weisen die gegossenen Stränge darüber hinaus eine sehr glatte Strangschale auf, so daß die bisher übliche Nachbearbeitung der Oberfläche entfallen kann.The method according to the invention surprisingly achieves a significantly longer lifespan for the lining. Due to the good heat dissipation of the cooling mold, the cast strands also have a very smooth strand shell, so that the surface finishing that has been customary up to now can be omitted.
Innerhalb des Formhohlraums weist die Kokille keine Befestigungselemente auf, die die Ausbildung einer glatten Strangschale zusätzlich behindern könnten. Vielmehr wurde das Problem der Befestigung der Auskleidungsplatten dadurch gelöst, daß diese durch Unterdruck auf die Kokillengrundplatten angesaugt werden. Hierzu befinden sich innerhalb der Kokillengrundplatten zahlreiche Bohrungen, die über ein Leitungssystem mit einer Saug- oder Vakuumpumpe in Verbindung stehen. Auf diese Weise kann in diesen Bohrungen ein Unterdruck gegenüber der Umgebungsatmosphäre erzeugt werden, wenn die Bohrungen auf der schmelzseitigen Oberfläche der Kokillengrundplatten abgedeckt werden und die Saugpumpe in Betrieb ist. Wird eine dünne Auskleidungsplatte, beispielsweise eine etwa 3 mm dicke Graphitplatte, auf die der Schmelze zugewandten Oberfläche einer Kokillengrundplatte gelegt, so wird sie durch den Unterdruck in den Bohrungen gleichmäßig angesaugt. Mit dieser Methode gelingt es, dünnwandige Auskleidungsplatten auf Kokillengrundplatten zu befestigen, ohne daß störende Verbindungselemente innerhalb dieser Platten benötigt werden.Within the mold cavity, the mold has no fastening elements that could additionally hinder the formation of a smooth strand shell. Rather, the problem of fastening the lining plates was solved in that they are sucked onto the mold base plates by negative pressure. For this there are numerous holes within the mold base plates, which are connected to a suction or vacuum pump via a pipe system. In this way, a negative pressure can be generated in these holes relative to the ambient atmosphere if the holes on the melt-side surface of the mold base plates are covered and the suction pump is in operation. If a thin lining plate, for example an approximately 3 mm thick graphite plate, is placed on the surface of a mold base plate facing the melt, it is sucked in uniformly by the negative pressure in the bores. With this method it is possible to attach thin-walled lining panels to mold base panels without the need for disruptive connecting elements within these panels.
Da beispielsweise eine Auskleidungsplatte aus Graphit in der Regel leicht porös ist, ist es notwendig, daß die Saugpumpe auch während des Gießprozesses in Betrieb ist, um so ständig den Unterdruck innerhalb der Ansaugbohrung und damit die Haftung der Graphitplatten auf den Kokillengrundplatten zu gewährleisten.For example, since a lining plate made of graphite is usually slightly porous, it is necessary that the suction pump is also in operation during the casting process, in order to constantly ensure the negative pressure within the suction hole and thus the adhesion of the graphite plates to the mold base plates.
Unter der Voraussetzung, daß der Unterdruck geringer ist als der Umgebungsdruck kann der Unterdruck in den Ansaugbohrungen und -kanälen innerhalb eines weiten Wertebereichs liegen. Zweckmäßig und ohne allzu großen Aufwand technisch realisierbar ist ein Unterdruck von deutlich weniger als 10 % des Umgebungsdrucks, beispielsweise 0,1 % des Umgebungsdrucks. Eine weitere Absenkung des Unterdrucks ist zwar ohne weiteres möglich, bringt jedoch keine nennenswerten technologischen Vorteile. Der bevorzugte Bereich für den in dem Ansaugsystem aufrechtzuerhaltenden Unterdruck, liegt innerhalb der Grenzen von 0,1 bis 10 % des Umgebungsdrucks (10 000 bis 100 Pa). Die Druckkraft, mit der die Auskleidungsplatte auf die Grundplatte gepreßt wird, hängt im wesentlichen von der Fläche der Bohrungsquerschnitte ab.Provided that the negative pressure is lower than the ambient pressure, the negative pressure in the suction bores and channels can be within a wide range of values. A vacuum of significantly less than 10% of the ambient pressure, for example 0.1% of the ambient pressure, is expediently and technically feasible without too much effort. A further reduction in the negative pressure is possible without further ado, but does not bring any significant technological advantages. The preferred range for the negative pressure to be maintained in the intake system is within the limits of 0.1 to 10% of the ambient pressure (10,000 to 100 Pa). The compressive force with which the lining plate is pressed onto the base plate essentially depends on the area of the bore cross sections.
Anhand eines Ausführungsbeispiels wird die Erfindung im folgenden noch näher erläutert.The invention is explained in more detail below using an exemplary embodiment.
Eine zum Stranggießen einer Kupferlegierung geeignete Rechteckkokille bestand aus zwei Kokillengrundplatten für die Längsseiten, die eine Länge von 400 mm und eine Breite von 300 mm besaßen. In jede dieser beiden Grundplatten waren im Abstand von etwa 20 mm Ansaugbohrungen mit einem Durchmesser von 4 mm eingebracht worden, die in Reihen horizontal und vertikal nebeneinander angeordnet waren.A rectangular mold suitable for the continuous casting of a copper alloy consisted of two mold base plates for the long sides, which had a length of 400 mm and a width of 300 mm. In each of these two base plates, suction holes with a diameter of 4 mm were made at a distance of about 20 mm, which were arranged horizontally and vertically next to each other in rows.
Geht man davon aus, daß die gesammte Querschnittsfläche der Ansaugbohrungen etwa 4200 mm² beträgt und nimmt eine Druckdifferenz von 50000 Pa zwischen Umgebungsdruck und Innendruck in den Bohrungen an, so errechnet sich aus diesen Angaben die gesamte Druck- oder Anpreßkraft, die auf die Auskleidungsplatte ausgeübt wurde, auf etwa 210 N.If one assumes that the total cross-sectional area of the suction bores is approximately 4200 mm² and assumes a pressure difference of 50,000 Pa between ambient pressure and internal pressure in the bores, then the total pressure or contact pressure that was exerted on the lining plate is calculated from this information , to about 210 N.
Diese Druckkraft kann bei gleicher Druckdifferenz gesteigert werden, wenn die Anzahl der Bohrungen und/oder ihr Durchmesser vergrößert werden, da so die für den Unterdruck wirksame Querschnittsfläche erhöht wird. Der gleiche Effekt kann auch dadurch erreicht werden, daß die schmelzseitige Oberfläche der Kokillengrundplatte mit feinen Nuten oder Ansaugkanälen überzogen wird, in die die Ansaugbohrungen münden. Besonders vorteilhaft ist es, wenn die Ansaugkanäle eine Tiefe von mehr als 0,05 mm besitzen und die Breite im Bereich von 0,05 mm bis 3 x d liegt, wobei mit d die Dicke der Auskleidungsplatte bezeichnet ist.This pressure force can be increased with the same pressure difference if the number of bores and / or their diameter is increased, since the cross-sectional area effective for the negative pressure is increased in this way. The same effect can also be achieved in that the melt-side surface of the mold base plate is covered with fine grooves or suction channels into which the suction holes open. It is particularly advantageous if the intake ducts have a depth of more than 0.05 mm and the width is in the range from 0.05 mm to 3 × d, d being the thickness of the lining plate.
Die Kühlleistung einer Kokille mit einer dünnwandigen Auskleidungsplatte hängt in hohem Maß von den Bedingungen des Wärmeübergangs von der Auskleidungsplatte zur gekühlten Kokillengrundplatte ab. Ein guter Wärmeübergang erfordert einen intensiven Kontakt zwischen Auskleidungsplatte und Kokillengrundplatte. Dieser wird durch eine hohe Anpreßkraft gewährleistet.The cooling capacity of a mold with a thin-walled lining plate depends to a large extent on the conditions of heat transfer from the lining plate to the cooled mold base plate. Good heat transfer requires intensive contact between the lining plate and the mold base plate. This is guaranteed by a high contact pressure.
Voraussetzung für das Ansaugen üblicherweise leicht poröser Auskleidungsplatten aus graphithaltigem Material ist, daß die Saugpumpe eine ausreichend hohe Leistung besitzt. Unter ungünstigen Umständen kann es jedoch zu einer Korrosion dieser Auskleidungsplatten kommen, insbesondere dann, wenn Luft aus der Umgebung angesaugt wird und in den Poren der Auskleidungsplatte mit dem Auskleidungsmaterial (z. B. Graphit, Bornitrid) reagiert.A prerequisite for the suction of usually slightly porous lining plates made of graphite-containing material is that the suction pump has a sufficiently high output. Under unfavorable circumstances, however, these lining plates can corrode, in particular if air is sucked in from the surroundings and reacts with the lining material (e.g. graphite, boron nitride) in the pores of the lining plate.
Vorteilhaft ist in diesem Fall die Verwendung von Auskleidungsplatten, bei denen die Porosität beispielsweise vor dem Einbau durch Metallinfiltration reduziert bzw. beseitigt wurde. Die Auskleidungsplatte kann aber auch auf der Ansaugseite mit einer Beschichtung versehen werden, die die Gasdurchlässigkeit vermindert. Derartige Auskleidungsplatten haben dann außerdem den Vorteil, daß der Unterdruck in den Ansaugkanälen besser aufrechterhalten werden kann, wodurch sowohl das Ansaugverhalten als auch die Kontaktintensität verbessert wird.In this case it is advantageous to use lining plates in which the porosity has been reduced or eliminated, for example, before installation by metal infiltration. The lining plate can also be provided on the suction side with a coating that reduces the gas permeability. Lining plates of this type then also have the advantage that the negative pressure in the suction channels can be better maintained, as a result of which both the suction behavior and the contact intensity are improved.
Bei der mechanischen Bearbeitung der Kontaktflächen läßt es sich vielfach auch bei größtem technischen Aufwand nicht vermeiden, daß mikroskopisch kleine Unebenheiten vorhanden bleiben. Um insbesondere den Wärmeübergang noch weiter zu verbessern, können in vorteilhaften Ausgestaltungen des erfindungsgemäßen Verfahrens ergänzende Maßnahmen erforderlich sein.During mechanical processing of the contact surfaces, it is often impossible to avoid microscopic unevenness remaining even with the greatest technical effort. In order to improve the heat transfer even further, additional measures may be required in advantageous embodiments of the method according to the invention.
Zur Erhöhung des Wärmeübergangs werden die Kontaktflächen der Kokillengrundplatte mit einer Mischung aus flüssigem Gallium und feinem Kupferstaub bestrichen. Danach wird eine dünnwandige aus graphithaltigem Material bestehende Auskleidungsplatte auf der Kokillengrundplatte angeordnet. Die Kontaktmischung dringt dabei in die mikroskopischen Hohlräume ein und verbessert so den Kontakt. Durch eine Wärmebehandlung oder beim ersten Gießprozeß verfestigt sich diese Mischung durch Legierungsbildung. Bei einer weiteren Verfahrensvariante werden die Kontaktflächen der aus Kupfer oder einer aushärtbaren Kupferlegierung hergestellten Kokillengrundplatten zunächst aufgerauht und dann vor dem Aufbringen der Auskleidungsplatten mit flüssigem Gallium bestrichen. Das Gallium füllt die kleinen Hohlräume aus und verfestigt sich später durch Legierungsbildung mit dem Material der Kokillengrundplatte.To increase the heat transfer, the contact surfaces of the mold base plate are coated with a mixture of liquid gallium and fine copper dust. A thin-walled lining plate made of graphite-containing material is then arranged on the mold base plate. The contact mixture penetrates into the microscopic cavities and thus improves the contact. This mixture solidifies as a result of alloying through heat treatment or during the first casting process. In a further process variant, the contact surfaces of the mold base plates made of copper or a hardenable copper alloy are first roughened and then before application of the lining plates coated with liquid gallium. The gallium fills the small cavities and later solidifies with the material of the mold base plate through the formation of alloys.
Mit besonderem Vorteil können aber auch pastöse Kontakmedien mit höherer Wärmeleitfähigkeit verwendet werden, die auch während des Gießprozesses ihre pastösen Eigenschaften im wesentlichen beibehalten. Diese Pasten bestehen aus kleinen festen Partikeln, vorzugsweise solchen, die eine hohe Wärmeleitfähigkeit besitzen. Diese Feststoffpartikel, beispielsweise Kupferpulverteilchen, befinden sich in einem flüssigen Trägermedium, das ebenfalls vorzugsweise eine höhere Wärmeleitfähigkeit als das Material der Auskleidungsplatte besitzt. Ein derartiges pastöses Kontaktmedium wird auf die Kontaktflächen der Kokillengrundplatte aufgetragen, bevor die Kokillengrund- und Auskleidungsplatte fest zusammengepreßt werden.However, it is also particularly advantageous to use pasty contact media with higher thermal conductivity, which essentially retain their pasty properties even during the casting process. These pastes consist of small solid particles, preferably those that have a high thermal conductivity. These solid particles, for example copper powder particles, are in a liquid carrier medium, which also preferably has a higher thermal conductivity than the material of the lining plate. Such a pasty contact medium is applied to the contact surfaces of the mold base plate before the mold base and lining plate are pressed firmly together.
Als besonders günstig hat sich eine Paste erwiesen, die aus einer Mischung aus Graphitpartikeln oder graphitumhüllten Kupferpulverteilchen und einem aus Indium und/oder Gallium bestehendem Trägermaterial besteht.A paste has proven to be particularly favorable which consists of a mixture of graphite particles or graphite-coated copper powder particles and a carrier material consisting of indium and / or gallium.
Die Dicke der Auskleidungsplatte kann im Bereich von etwa 0,2 bis 15 mm liegen. Besonders bevorzugt ist eine Plattendicke von 1 bis 5 mm. Die Auskleidungsplatte kann sowohl aus graphithaltigem Material aber auch aus einem Verbundwerkstoff bestehen, der beispielsweise Graphit oder Bornitrid als Schmierstoff enthält.The thickness of the lining plate can range from about 0.2 to 15 mm. A plate thickness of 1 to 5 mm is particularly preferred. The lining plate can consist both of graphite-containing material and of a composite material which contains, for example, graphite or boron nitride as a lubricant.
Zur Erhöhung der Sicherheit gegenüber Druckverlusten in den Ansaugkanälen kann es zweckmäßig sein, eine zusätzliche Abdichtung im Randbereich der Ansaugplatte vorzusehen, die einen möglichst gasdichten Abschluß garantiert. Als Dichtungsmaterial kann entweder ein dünner Film aus einem Metall-Lot oder einer solchen pastösen Mischung verwendet werden, die sich auch für die Verbesserung des Wärmeübergangs als besonders günstig erwiesen hat.To increase the security against pressure losses in the intake ducts, it may be appropriate to provide an additional seal in the edge area of the intake plate, which guarantees a gas-tight seal. Either a thin film of a metal solder or such a pasty mixture can be used as the sealing material, which has also proven to be particularly favorable for improving the heat transfer.
Alternativ kann auch ein Dichtungsband verwendet werden, das eine leichte Flexibilität besitzt und sich so beim Anpressen der Auskleidungsplatte möglichen Unebenheiten anpaßt.Alternatively, a sealing tape can also be used, which has a slight flexibility and thus adjusts to possible unevenness when the lining plate is pressed on.
Auf die Auskleidungsplatte wirken Reibungskräfte, die die Strangschale des sich bewegenden Gußstrangs ausübt. Trotz ausreichender Haftung der Auskleidungsplatte auf der Kokillengrundplatte können Reibungskräfte bewirken, daß sich die Auskleidungsplatte während des Betriebs etwas in Abziehrichtung verschieben kann. Dies würde dazu führen, daß der Restgasdruck in dem Ansaugkanalsystem durch die eindringende Umgebungsluft ansteigen kann und die Haftung der Auskleidungsplatte verschlechtert wird. Gegebenenfalls müßte der Gießprozeß dann unterbrochen werden, um die Auskleidungsplatte neu zu positionieren. Um diesen Nachteil zu vermeiden, ist es zweckmäßig, an der Kokillengrundplatte Halterungen vorzusehen, die ein Verrutschen der Auskleidungsplatte mit Sicherheit ausschließen. Im einfachsten Fall besitzt die Kokillengrundplatte am unteren Ende einen kleinen Vorsprung, auf dem die Auskleidungsplatte aufsitzt. Bei Kokillen, die während des Gießprozesses in Abzugsrichtung oszillierend bewegt werden, kann außerdem noch eine Halterung im oberen Teil der Kokille vorgesehen werden. Die Halterungen müssen jedoch so angebracht werden, daß die thermische Ausdehung der Auskleidungsplatte keinesfalls behindert werden kann.Frictional forces exerted on the lining plate by the strand shell of the moving cast strand. Despite sufficient adhesion of the lining plate to the mold base plate, frictional forces can cause the lining plate to shift somewhat in the pulling direction during operation. This would lead to the fact that the residual gas pressure in the intake duct system can rise due to the penetrating ambient air and the adhesion of the lining plate is deteriorated. If necessary, the casting process would then have to be interrupted in order to reposition the lining plate. In order to avoid this disadvantage, it is expedient to provide brackets on the mold base plate that reliably prevent the lining plate from slipping. In the simplest case, the mold base plate has a small projection at the lower end on which the lining plate is seated. In the case of molds which are moved oscillatingly in the withdrawal direction during the casting process, a holder can also be provided in the upper part of the mold. However, the brackets must be installed in such a way that the thermal expansion of the lining plate can in no way be impeded.
Im allgemeinen läßt sich der Wärmeübergangswiderstand zwischen zwei parallel angeordneten Grenzflächen verändern, indem der Anpreßdruck verändert wird, mit dem die beiden Grenzflächen gegeneinander gepreßt werden. Entsprechend läßt sich die lokale Wärmestromdichte innerhalb einer mit Auskleidungsplatten ausgerüsteten Kühlkokille beispielsweise lokal reduzieren, indem die Anpreßkraft bzw. der Ansaugdruck lokal reduziert wird. Für den Einsatz einer Kokille mit Auskleidungsplatten kann dieses unter bestimmten Bedingungen wünschenswert sein.In general, the heat transfer resistance between two parallel interfaces can be changed by changing the contact pressure with which the two interfaces are pressed against each other. Accordingly, the local heat flow density within a cooling mold equipped with lining plates can be locally reduced, for example, by locally reducing the contact pressure or the suction pressure. Under certain conditions, this can be desirable for the use of a mold with lining plates.
Bekanntlich sind die Bereiche an den Schmalseiten einer Kokille sowie besonders die Eckbereiche stärker gekühlt als die Mitten der Längsseiten, da hier das Verhältnis von Brammenoberfläche zu Brammenvolumen besonders groß ist. Dieses findet seinen Ausdruck darin, daß die Erstarrung in diesen stärker gekühlten Bereichen entsprechend schneller vorausschreitet.As is known, the areas on the narrow sides of a mold and especially the corner areas are cooled more than the middle of the long sides, since the ratio of slab surface to slab volume is particularly large here. This finds expression in the fact that the solidification proceeds correspondingly faster in these more cooled areas.
Ein ungleichmäßiges oder ungünstiges Erstarrungsverhalten kann bei bestimmten Legierungen zu Spannungen im erstarrten Material und zu Rissen oder Deformationen führen, wenn diese Spannungen zu groß werden.An uneven or unfavorable solidification behavior can lead to stresses in the solidified material with certain alloys and to cracks or deformations if these stresses become too great.
In derartigen Fällen kann es von Bedeutung sein, daß die Abkühlbedingungen lokal den gewünschten Bedingungen angepaßt werden und gewisse Teilbereiche der Auskleidungsplatte mit einer größeren Anpreßkraft auf die Oberfläche der Kokillengrundplatte anzusaugen als die übrigen Bereiche. Erreicht werden können lokal unterschiedliche Anpreßdrücke auf der Kokillengrundplatte beispielsweise durch getrennte Ansaugsysteme mit verschiedenen Unterdrücken oder durch bereichsweise Änderung der Flächendichte der Ansaugbohrungen oder Ansaugkanäle.In such cases, it may be important that the cooling conditions are adapted locally to the desired conditions and that certain partial areas of the lining plate are sucked onto the surface of the mold base plate with a greater contact force than the other areas. Locally different contact pressures on the mold base plate can be achieved, for example, by separate suction systems with different negative pressures or by changing the area density of the suction bores or suction channels in some areas.
Claims (13)
- Process for continuous casting of metal strips, in particular broad rectangular slabs of copper or copper alloys, with a chill lined with a material resistant to high temperatures into which the metal melt is poured, characterised in that on the surface of the chill facing the metal melt is disposed a thin-walled lining plate which is held on the surface of the chill with the aid of vacuum.
- Process for continuous casting of metal strips according to claim 1, characterised in that the lining plate exhibits a thickness lying in the range from 0.2 to 15 mm, preferably in the range from 1 to 5 mm.
- Process for continuous casting of metal strips according to one of claims 1 or 2, characterised in that the lining plate essentially consists of graphite or boron nitride.
- Process for continuous casting of metal strips according to one of claims 1 or 2, characterised in that the lining plate consists of a composite material which contains graphite or boron nitride as lubricant.
- Process for continuous casting of metal strips according to one of claims 1 to 4, characterised in that a vacuum lying in the range from approximately 10,000 to 100 Pa is maintained to hold the lining plate on the chill.
- Process for continuous casting of metal strips according to one of claims 1 to 5, characterised in that the lining plate is pressed on to the surface of the chill with the aid of suction holes and/or suction grooves disposed in the chill.
- Process for continuous casting of metal strips according to one of claims 1 to 6, characterised in that on the suction side the lining plate is provided with a coating which reduces the gas permeability.
- Process for continuous casting of metal strips according to one of claims 1 to 7, characterised in that a thin layer of a heat-conducting contact medium is disposed between the chill and the lining plate, the contact medium being solid at operating temperature.
- Process for continuous casting of metal strips according to claim 8, characterised in that the contact medium consists of a copper alloy containing gallium.
- Process for continuous casting of metal strips according to one of claims 1 to 7, characterised in that a thin layer of a heat-conducting contact medium is disposed between the chill and the lining plate, the contact medium being pasty at operating temperature.
- Process for continuous casting of metal strips according to claim 10, characterised in that the contact medium consists of a mixture containing graphite particles and having gallium and/or indium as carrier material.
- Process for continuous casting of metal strips according to claim 10, characterised in that the contact medium consists of a mixture which is composed of graphite-coated metal powder particles, preferably copper powder particles, and gallium and/or indium as carrier material.
- Process for continuous casting of metal strips according to one of claims 1 to 7, characterised in that a least one part area of the lining plate is sucked onto the surface of the chill with a greater force than the remaining areas.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4036893A DE4036893C2 (en) | 1990-11-20 | 1990-11-20 | Process for the continuous casting of metallic strands |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0544931A1 EP0544931A1 (en) | 1993-06-09 |
| EP0544931B1 true EP0544931B1 (en) | 1996-05-22 |
Family
ID=6418583
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP91120532A Expired - Lifetime EP0544931B1 (en) | 1990-11-20 | 1991-11-29 | Method for continuous casting of metal ingots |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0544931B1 (en) |
| AT (1) | ATE138301T1 (en) |
| DE (1) | DE4036893C2 (en) |
| DK (1) | DK0544931T3 (en) |
| ES (1) | ES2087216T3 (en) |
| GR (1) | GR3020284T3 (en) |
| LU (1) | LU88041A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102006015282A1 (en) * | 2006-04-01 | 2007-10-04 | Honeywell Technologies Sarl Ecc | Bronze casting mold with thermal insulation lining and casting process for manufacture of drinking water valve housing and fittings |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060070716A1 (en) * | 2004-10-04 | 2006-04-06 | Russel Nippert | Method and system for continuously casting copper alloys |
| CN103357826A (en) * | 2012-04-03 | 2013-10-23 | 中色奥博特铜铝业有限公司 | Method of improving cooling effect of crystallizer |
| DE102014218449A1 (en) * | 2014-09-15 | 2016-03-17 | Schunk Kohlenstofftechnik Gmbh | Mold and method of manufacture |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1313397A (en) * | 1962-01-09 | 1962-12-28 | Yorkshire Imp Metals Ltd | Mold for continuous casting |
| FR2123108A1 (en) * | 1971-01-05 | 1972-09-08 | Mitsubishi Metal Mining Co Ltd | Graphite wall continuous casting mould - with a metal skin |
| GB2087769B (en) * | 1980-11-22 | 1984-08-01 | Mapplebeck John E Ltd | Casting mould |
| BR8605835A (en) * | 1986-11-28 | 1987-09-01 | Mannesmann Sa | METHOD AND DEVICE FOR THE EXTRACTION OF COPPER MOLDS, ENGINES, IN CONTINUOUS LANGUAGE |
-
1990
- 1990-11-20 DE DE4036893A patent/DE4036893C2/en not_active Expired - Fee Related
-
1991
- 1991-11-29 DK DK91120532.6T patent/DK0544931T3/en active
- 1991-11-29 ES ES91120532T patent/ES2087216T3/en not_active Expired - Lifetime
- 1991-11-29 EP EP91120532A patent/EP0544931B1/en not_active Expired - Lifetime
- 1991-11-29 AT AT91120532T patent/ATE138301T1/en not_active IP Right Cessation
- 1991-12-18 LU LU88041A patent/LU88041A1/en unknown
-
1996
- 1996-06-19 GR GR960401665T patent/GR3020284T3/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102006015282A1 (en) * | 2006-04-01 | 2007-10-04 | Honeywell Technologies Sarl Ecc | Bronze casting mold with thermal insulation lining and casting process for manufacture of drinking water valve housing and fittings |
Also Published As
| Publication number | Publication date |
|---|---|
| DK0544931T3 (en) | 1996-10-14 |
| ATE138301T1 (en) | 1996-06-15 |
| LU88041A1 (en) | 1992-07-07 |
| GR3020284T3 (en) | 1996-09-30 |
| ES2087216T3 (en) | 1996-07-16 |
| DE4036893C2 (en) | 1999-05-20 |
| EP0544931A1 (en) | 1993-06-09 |
| DE4036893A1 (en) | 1992-05-21 |
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