EP1536900B2 - Method for commencing a casting process - Google Patents

Method for commencing a casting process Download PDF

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Publication number
EP1536900B2
EP1536900B2 EP03798105A EP03798105A EP1536900B2 EP 1536900 B2 EP1536900 B2 EP 1536900B2 EP 03798105 A EP03798105 A EP 03798105A EP 03798105 A EP03798105 A EP 03798105A EP 1536900 B2 EP1536900 B2 EP 1536900B2
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EP
European Patent Office
Prior art keywords
casting
strip
velocity
speed
starting
Prior art date
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EP03798105A
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German (de)
French (fr)
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EP1536900B1 (en
EP1536900A1 (en
Inventor
Gerald Hohenbichler
Gerald Eckerstorfer
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SIEMENS VAI METALS Technologies GmbH
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Siemens VAI Metals Technologies GmbH Austria
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Application filed by Siemens VAI Metals Technologies GmbH Austria filed Critical Siemens VAI Metals Technologies GmbH Austria
Priority to SI200330195T priority Critical patent/SI1536900T1/en
Priority to AT03798105T priority patent/ATE312676T1/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0622Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars formed by two casting wheels
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16Controlling or regulating processes or operations
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22DCASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16Controlling or regulating processes or operations
    • B22D11/161Controlling or regulating processes or operations for automatic starting the casting process

Definitions

  • the invention relates to a method for starting a casting process in a Zweiwalzeng screen thanks without the application of a Anfahrstranges.
  • essentially cooled molds with a continuous mold cavity are used, in which the molten metal introduced on the input side solidifies, at least in the area of contact with the mold cavity walls.
  • a substantially solidified metal strand is withdrawn from the mold.
  • a first filling of the mold cavity is carried out with molten metal, in particular a predominantly vertical orientation of the mold cavity a completely solidified initial piece must be achieved so that the molten metal does not flow through the mold uncontrollably and exits from it.
  • the casting thickness of the metal strand to be produced, the solidification conditions and the amount of heat which can be dissipated through the Ferm cavity walls during the short residence time in the mold are of considerable importance.
  • a starting strand is usually introduced into the mold before the start of casting, which largely but not necessarily completely closes the outlet cross section of the mold cavity and only after the formation of a solid compound of the introduced melt with the Anfahrstrangkopf and a pronounced strand shell with sufficient thickness along the mold cavity walls with a pair of driving rollers from the mold is discharged.
  • This start-up requires at least a new Anfahrstrangkopf coupled to the Anfahrstrang at each restart of the caster.
  • Such a Anfahrstrang as it is used in formed by Breitseitanofficen and narrow side walls strip steel casting molds, for example, from US-A 4,719,960 known.
  • a starter line for the special application in a two-roll lapping plant is in EP-A 208 642 described.
  • This Anfahrstrang contains a dummy head with two flanges formed by thin metal strips, which abut the lateral surfaces of the casting rolls and thus form a space for receiving the inflowing molten metal.
  • the Aus disciplinen the Anfahrstranges and the cast strip from the casting gap formed by the casting rolls takes place.
  • a dummy bar is not absolutely necessary because the open casting gap is bridged within a very short time due to the rapid solidification of the molten metal at the mold walls. Start-up procedures in which no start-up train is required are also already known several times.
  • a starting method is known, in which the two cooperating casting rolls are brought to a start position before pouring, in which no casting gap is present and the casting rolls stand still. Immediately after the start of the melt supply and a first strand shell formation on the two lateral surfaces of the casting rolls they are moved apart on the Railg fauxspalt (strip thickness) and brought the Gleß Ober along a start-up curve on operating casting speed.
  • a starting process with stationary casting rolls is very unreliable because the is-pouring in the melt space can not be measured with the necessary accuracy to the narrowest cross section between the casting rolls. Therefore, neither an increase in force between the two casting rolls nor the degree of filling of the mold is reasonably controllable.
  • a different degree of solidification of the melt along the bandwidth and in particular near the side plate can cause significant Kell Struktur by solidified metal above the narrowest cross-section and subsequently lead to side plate damage. Furthermore, in such a starting method with standing casting rolls, there is an increased risk for sectional strand-shell adhesives in sections on the lateral surface of the casting rolls.
  • a casting method for a two-roll caster is known in which, before the start of the supply of melt, the casting gap between the two casting rolls is set to a value reduced with respect to the operating casting nip.
  • the supply of melt occurs in rotating casting rolls, wherein the casting speed is adjusted so that the thickness of the produced strip is greater than the previously set casting gap.
  • the tendency to drip metal melt is reduced by a reduced casting gap.
  • the ones described above with regard to the JP-A 61-266159 described disadvantages to an increasing extent, in particular the tendency to side plate damage.
  • Object of the present invention is therefore, To avoid the disadvantages of the prior art described above and to propose a method for starting a casting in a two-roll casting device and a device for carrying out the method, wherein the passage of molten metal through the casting gap can be kept low and at the same time the tendency to form wedge and Thickening at the beginning of the cast strip is avoided as possible. At the same time a separation of a first piece of the cast strip, which does not meet the quality requirements of a continuous production to be achieved by the subsequently produced under largely stationary operating conditions band without the need for mechanical separation devices are required.
  • the casting speed is always determined by the casting roll peripheral speed since the strand shells formed and adhered to the casting roll shells are transported at this velocity through the narrowest cross section between the casting rolls and bonded together.
  • the start casting speed is a low casting speed at which, due to the extended residence time of the forming strand shells in the melt space, an increased strand shell growth occurs and therefore the downwardly open casting gap can be bridged particularly quickly.
  • the banding casting speed is a casting speed which depends in particular on the current liquid metal casting level and also on the solidification conditions and the casting roll separation force required due to the steel analysis, in which strip formation and removal of the formed strip take place downwards and are maintained at the largely constant strip forming conditions can be.
  • the molten metal is continuously filled up to the level of the operating casting level, with the belt forming speed continuously increasing with increasing casting level.
  • the casting gap is kept in the claimed process during the entire starting process on the value of the operating casting thickness, there are additional benefits: By a reduced start-casting speed, a low band throughput is achieved until complete achievement of the target Radiog informLites and kept such a small amount of rejects , Furthermore, the operating casting thickness, which is not reduced in the starting phase, causes less interference, which, as a result of solidification on the narrow side walls, leads to widening of the casting gap when passing through the casting cross section and possibly uncontrolled tearing of the cast strand.
  • the starting casting speed is chosen smaller than half the operating casting speed, the casting rolls usually rotate.
  • the starting phase can also be initiated with standing casting rolls, so that the start casting speed at the beginning of the feeding of molten metal is still 0 m / min and the casting rolls are then rapidly accelerated.
  • a start casting speed in this range allows a good timing between the melt feed to the attainment of the operating pouring level and the ramp-up of the start casting speed to a belting casting speed that approximates the operating casting speed. This is accomplished by a moderate, steady increase in casting roll peripheral speed to a belting casting speed that matches a measurable target casting level To ensure reliable banding (strand shell formation on the casting roll surfaces in the molten pool). Accordingly, the belt-forming casting speed is adjusted or regulated in accordance with a measurable target casting level.
  • Another way of optimally adjusting the banding casting speed is to control the banding casting speed in response to the release force occurring between the casting rolls.
  • the separating force acting between the two casting rolls is, for a given casting gap, a measure of the strand shell thickness and the current solidification state in the narrowest cross section between the casting rolls. It is higher as the solidification process in this area progresses.
  • the predominantly rising metal bath level in the start phase which has a significant influence on strand shell formation, is also taken into account here.
  • the measured values of a bath level measurement and a separation force measurement can also be used in combination.
  • the band-separating casting speed is to be understood as the casting speed at which the first part of the cast metal strip, which was produced under unsteady casting conditions in the starting phase of the casting process and is thus to be regarded as scrap material, is separated from the continuously following metal strip produced under largely stationary casting conditions.
  • This separation takes place according to a possible embodiment exclusively under the action of the dead weight of the narrowest cross section between the casting rollers leaving down hanging starting piece of the cast metal strip by tearing it in the casting gap by increasing the casting speed on the belt separation casting speed, the solidification conditions and thus the mechanical properties of the cast strip in G confusequerites, especially by reducing the tensile strength, so changed that the strip in this cross-section tears off without additional mechanical measures.
  • the separation of the cast metal strip at tape release casting speed can be accomplished by the action of a gravitational action increased tape tension applied by a driver assembly located downstream of the casting nip of the two-roll caster.
  • An improvement in the separation conditions can be achieved by superposing a short-term increase in casting thickness by 5 to 40% on the increase in casting speed to the strip-separation casting speed.
  • the belt separation casting speed is higher than the operation casting speed, preferably 5% to 40% higher than the operation casting speed.
  • This belt separation casting speed is set briefly as soon as approximately stationary casting conditions are reached. It is preferred that even a consistent strip quality is ensured.
  • the strip separation casting speed is expediently set in the starting phase when the molten metal in the melting chamber has essentially reached the desired operating casting level.
  • the casting speed is increased to approximately the operating casting speed before reaching the desired operating pouring mirror in the melting chamber.
  • the proposed method allows the steady state casting operation to be achieved within 5 to 60 seconds after the start of metal melt feed into the melt space.
  • At least reference data of the instantaneous casting speed and the current G foolador let the molten metal in the melting space and / or the instantaneous separation force between the casting rolls and / or the gap width between the casting rolls and / or the strip thickness of the cast metal strip determined continuously during the casting start and fed to a computing unit and generated from these reference data including a mathematical model for the starting process manipulated variables for the casting speed, for the position of a Bandleit stimulate and for the transport speed of the cast metal strip in a belt conveyor and transmitted to the drive units of these devices become.
  • the separation conditions for the separation of the first piece of the cast metal strip in the casting cross-section are improved when using the mathematical model based on current input data such as steel grade, operating casting thickness, temperature ratios, quality related Solidification conditions, etc., in addition a manipulated variable for the distance positioning of the two casting rolls to each other, in particular an increased starting casting thickness, is generated.
  • the quality of the metal strip produced can be continually optimized and adapted to changing operating conditions in general and during the casting process if the mathematical model comprises a metallurgical model for forming a specific microstructure in the cast metal strip and / or for influencing the geometry of the cast metal strip.
  • a two-roll caster equipped in this way enables the acquisition of current production data from the steelmaking process and their joint processing with measurement data at the caster in a computer model for optimizing the starting process.
  • a separating force measuring device for determining the instantaneous, caused essentially by the banding separating force between the two casting rolls or a position-measuring device for determining the instantaneous gap width between the casting rolls or a measuring device for determining the instantaneous strip thickness is used.
  • Each of these measurements provides reference data which at least indirectly produce a mathematically describable relationship with the strand shell formation in the melt pool and thus with the metal strand formation in the narrowest cross section between the casting rolls and which can therefore be used in a mathematical model to calculate manipulated variables in order to minimize or minimize the starting process Optimized in terms of shape and trackability of the strip breaking edge.
  • a further improvement of the starting method can be achieved by combining at least two of these measuring methods, wherein the measurements are carried out simultaneously and processed in a correspondingly expanded mathematical model.
  • a further optimization of the method results when at least one of the two casting rolls is coupled to a casting roll adjusting device and the computing unit is additionally connected by a signal line to a casting roll adjusting device for setting a starting casting thickness.
  • the casting format preferably the operating casting thickness
  • the steel production taken characteristic data such as the superheating temperature of the melt, and measured data on the system in the process model
  • the present method and the associated two-roll caster is suitable for casting molten metals, preferably Fe-containing metal alloys, in particular for steels.
  • a two-roll caster with the necessary for carrying out the method according to the invention Facilities is in Fig.1 shown schematically. It consists of two in a horizontal plane at a distance from each other and equipped with an internal cooling, not shown, casting rolls 1, 2. These are rotatably supported in shaft bearings 3, 4 and coupled with rotary actuators 5, 6, the opposing rotation of the casting rolls 1, 2 to G confusewalzenachsen 1 ', 2' with a controllable peripheral speed, which corresponds to the casting speed allow. To determine the instantaneous casting speed, at least one of the casting rolls 1, 2 or the associated rotary drives 5, 6 or the cast metal strip itself is assigned a speed measuring device 34.
  • One of the two casting rolls 2 is slidably supported in the horizontal plane transversely to the casting roll axis 2 'and coupled to a casting roll adjusting device 7, whereby the distance between the two casting rolls 1, 2 is adjustable adjustable to each other.
  • side plates 8 are pressed against the front side, which together with a portion of the lateral surfaces 9, 10 of the rotating casting rolls form a melting chamber 11 for receiving molten metal 12.
  • the molten metal 12 is continuously and regulated introduced from an intermediate vessel 13 through a dip tube 14 in the melt space 11, so that during the stationary casting operation, the melt supply through the Tauchrohrauslässe in submerged form, ie always below a held at a constant level casting mirror 15.
  • a level measuring device 16 arranged above the melting space 11, a continuous monitoring of the level of the casting mirror takes place.
  • the solid shell shells 19, 20 formed on the lateral surfaces 9, 10 of the casting rolls in the melting chamber 11 are connected in the casting gap 18 to a substantially solidified metal strip 21, which is conveyed downwardly from the casting gap 18 by the rotational movement of the casting rolls 1, 2, by a downstream one pivotable Bandleit recognized 22 and tape guide rollers 23 is deflected in a substantially horizontal transport direction and one of a pair of drive rollers belt conveyor 24 is discharged from the Zweiwalzengit listening.
  • the arc-shaped Bandleit Vietnamese 22 is connected to a drive unit 25, which makes it possible to pivot the Bandleit Vietnamese 22 from a retreat position A to an operating position B and back.
  • the tape guide is in the retraction position A and is pivoted after the separation of a first piece of the cast metal strip in the operating position B and can remain there during the entire stationary production process.
  • a scrap receiving carriage 26 is arranged, in which at most initially dripping metal melt and the first portion of the cast strip can be collected and transported away if necessary.
  • the scrap receiving trolley can also be designed without wheels. It may be positioned within a chamber wall enclosing the path of the cast metal strip from the casting rolls to the first driver. Also, this first portion of the cast strip does not necessarily fall directly into the scrap receiving trolley, but can also be fed indirectly thereto.
  • the cast metal strip After the cast metal strip emerges from the belt transport device 24 equipped with a drive unit 27, it is finished in further processing devices 28 (not illustrated in detail) and finally wound into bundles 29 and / or cut into sheets.
  • the further treatment devices 28 may be formed, for example, by rolling stands, trimming devices, surface treatment devices, thermal treatment devices of various kinds, such as heating devices, holding ovens, temperature compensation furnaces, and cooling sections.
  • the Zweiwalzengitinnate is equipped with a computing unit 36, which makes it possible to automatically perform the starting process in response to predetermined input variables and determined on the device current metrics.
  • a computing unit 36 which makes it possible to automatically perform the starting process in response to predetermined input variables and determined on the device current metrics.
  • optimal manipulated variables such as the start casting speed v gSt , the position of the belt guide , the drive speed of the belt conveyor and possibly the starting casting thickness D St and other control variables are generated in the arithmetic unit and the starting process continuously controlled and supervised.
  • Manipulated variables which are generated from the arithmetic unit 36 for carrying out the starting process, are based on measurement data from the casting plant that are currently collected and that directly or indirectly have a connection with the strand shell growth.
  • Predestined for this purpose are the instantaneous level of the casting mirror 15, ie the level of the casting mirror in the melting space 11, which can be determined continuously by means of a level-measuring device 16.
  • the release force F Tr between the two casting rolls 1, 2 represents a reaction force on the passed strand shells and also provides a reference value for the degree of solidification in the narrowest cross section between the casting rolls. It is to be determined with a separating force measuring device 30, which is associated with the casting roll bearings 3, 4 or incorporated in the G confusewalzenverstell issued 7.
  • Another way to determine a reference size provides the instantaneous gap width G between the casting rolls, which is closely related to the release force F Tr , since a higher separation force increased radial deflection of the casting rolls 1, 2 causes each other or their deformation.
  • This can be measured directly by a position measuring device 31 on the casting rolls or indirectly via a strip thickness measuring device 32.
  • the simultaneous measurement and processing of the measurement data of several of the measuring systems described minimizes the time required for the start of the system and in particular increases the quality of the strip breaking edge of the subsequent metal strip with regard to their geometry and their ability to be guided through the plant, as well as the quality of the product produced from the start of production.
  • the solidification conditions on the lateral surfaces 9, 10 of the two casting rolls and in the casting gap 18 at steady-state casting speed and at belt separation casting speed are in the FIGS. 2a and 2b compared.
  • the two casting rolls 1, 2 are set to a casting gap 18, which corresponds in particular to the stationary casting level and the operating casting thickness D of the desired cast metal strip.
  • the two strand shells 19, 20 are joined together and it forms at stationary casting conditions a solidified metal strip.
  • the V-shaped lines 37 illustrate the transition from 100% melt to a mixing area with an increasing solids content and the V-shaped line 38 illustrates the transition to 100% solids, thus the solidified strand part.
  • Fig. 2b Figure 12 shows the changed solidification conditions at a belt-separation casting speed which is increased over the operation-casting speed. This means that the peripheral speed of the casting rolls is increased. The cooling conditions were not changed. As a result, the available strand shell formation time in the melt space and thus the strand shell growth is reduced, so that the fürerstarrungspraxis 39 shifts in the casting direction and in G confusequerites either an increased proportion of liquid content is present and / or the average strip temperature is at least higher than at operating casting speed. In both cases, the tensile strength of the hanging down metal strip piece at the strip separation casting speed is reduced so far that the metal strip breaks off under the action of its weight in G confusequerites.
  • the casting speed is increased to such a high belt separation casting speed and then immediately lowered again so that no separation force is temporarily measured.
  • molten metal flows because of the lack of connection between the two strand shells and under the effect of ferrostatic pressure in the space below the narrowest cross section between the casting rolls after. This leads to a bulging of the metal strip and a considerable rewarming of the near-surface strip layers and to the demolition under the influence of the downside band weight.
  • the G confusetikpractic h Gsp can be measured only after reaching a certain degree of filling, since the melt space is constricted due to the casting roll arrangement to G confusequerites toward funnel-shaped and in this very narrow range a level measurement is not technically feasible. After a period of about 5 to 15 seconds, which can be variably selected, the operating pouring level h Betr is reached and maintained at this level.

Abstract

The invention relates to a method for improving the conditions at the commencement of a casting process in a twin-roll casting device, which does not use a dummy bar, said method comprising the following steps: an operating casting thickness is set and the casting rolls are rotated at a casting-roll peripheral speed, which corresponds to a reduced commencing casting speed in relation to the casting speed for stationary operation; molten metal is fed into one of the rotating casting rolls and into the molten metal chamber that is configured from lateral plates lying against the rolls and a cast metal bar with an essentially constant, predetermined cross-sectional size is formed, whilst the casting speed is simultaneously increased to a strip forming casting speed; the casting speed is subsequently increased to a strip separating speed, which is significantly higher than the speed sufficient to cause solidification and the metal strip that has been cast up to this point is separated; the stationary operation casting speed is set; the following cast metal strip is deviated onto a strip transport unit and the stationary casting operation commences. The invention also relates to a twin-roll casting device for carrying out said method.

Description

Die Erfindung betrifft ein Verfahren zum Starten eines Gießvorganges in einer Zweiwalzengießeinrichtung ohne Anwendung eines Anfahrstranges.The invention relates to a method for starting a casting process in a Zweiwalzengießeinrichtung without the application of a Anfahrstranges.

Zur Herstellung eines kontinuierlich gegossenen Metallstranges unbestimmter Länge werden im Wesentlichen gekühlte Kokillen mit einem durchgehenden Formhohlraum eingesetzt, in welchem die eingangsseitig eingebrachte Metallschmelze zumindest im Kontaktbereich mit den Formhohlraumwänden erstarrt. Ausgangsseitig wird ein im Wesentlichen durcherstarrter Metallstrang aus der Kokille abgezogen. Beim Start des Gleßvorganges ist eine Erstfüllung des Formhohlraumes mit Metallschmelze durchzuführen, wobei Insbesondere bei vorwiegend vertikaler Ausrichtung des Formhohlraumes ein zur Gänze durcherstarrtes Anfangsstück erzielt werden muss, damit die Metallschmelze nicht unkontrolliert die Kokille durchströmt und aus ihr austritt. Hierbei kommt vor allem der Gießdicke des zu erzeugenden Metallstranges, den Erstarrungsbedingungen und der in der kurzen Aufenthaltszeit in der Kokille durch die Fermhohlraumwände abführbaren Wärmemenge wesentliche Bedeutung zu.To produce a continuously cast metal strand of indeterminate length, essentially cooled molds with a continuous mold cavity are used, in which the molten metal introduced on the input side solidifies, at least in the area of contact with the mold cavity walls. On the output side, a substantially solidified metal strand is withdrawn from the mold. At the start of the Gleßvorganges a first filling of the mold cavity is carried out with molten metal, in particular a predominantly vertical orientation of the mold cavity a completely solidified initial piece must be achieved so that the molten metal does not flow through the mold uncontrollably and exits from it. Here, above all, the casting thickness of the metal strand to be produced, the solidification conditions and the amount of heat which can be dissipated through the Ferm cavity walls during the short residence time in the mold are of considerable importance.

Um den unkontrollierten Austritt von Metallschmelze aus der Kokille in der Startphase des Gießprozesses sicher zu vermeiden, wird üblicherweise vor Gießbeginn ein Anfahrstrang in die Kokille eingebracht, der den Austrittsquerschnitt des Formhohlraumes weitgehend aber nicht zwangsläufig vollständig verschließt und erst nach Ausbildung einer festen Verbindung der eingebrachten Schmelze mit dem Anfahrstrangkopf und einer ausgeprägten Strangschale mit ausreichender Dicke entlang der Formhohlraumwände mit einem Treibrollenpaar aus der Kokille ausgefördert wird. Dieses Anfahrverfahren erfordert bei jedem Neustart der Gießanlage zumindest einen neuen an den Anfahrstrang ankoppelbaren Anfahrstrangkopf. Ein derartiger Anfahrstrang, wie er bei von Breitseitanwänden und Schmalseitenwänden gebildeten Bandstahl-Gleßkokillen verwendet wird, ist beispielsweise aus der US-A 4,719,960 bekannt.In order to reliably avoid the uncontrolled discharge of molten metal from the mold in the startup phase of the casting process, a starting strand is usually introduced into the mold before the start of casting, which largely but not necessarily completely closes the outlet cross section of the mold cavity and only after the formation of a solid compound of the introduced melt with the Anfahrstrangkopf and a pronounced strand shell with sufficient thickness along the mold cavity walls with a pair of driving rollers from the mold is discharged. This start-up requires at least a new Anfahrstrangkopf coupled to the Anfahrstrang at each restart of the caster. Such a Anfahrstrang as it is used in formed by Breitseitanwänden and narrow side walls strip steel casting molds, for example, from US-A 4,719,960 known.

Ein Anfahrstrang für die spezielle Anwendung in einer Zweiwalzen-Gleßanlage ist in der EP-A 208 642 beschrieben. Dieser Anfahrstrang enthält einen Anfahrkopf mit zwei von dünnen Blechstreifen gebildeten Flanschen, die an den Mantelflächen der Gießwalzen anliegen und so einen Raum für die Aufnahme der einströmenden Metallschmelze bilden. Unmittelbar nach der ersten Strangschafenbildung erfolgt das Ausfördern des Anfahrstranges und des angegossenen Bandes aus dem von den GießwalZen gebildeten Gießspalt.A starter line for the special application in a two-roll lapping plant is in EP-A 208 642 described. This Anfahrstrang contains a dummy head with two flanges formed by thin metal strips, which abut the lateral surfaces of the casting rolls and thus form a space for receiving the inflowing molten metal. Immediately after the first strand sheep formation the Ausfördern the Anfahrstranges and the cast strip from the casting gap formed by the casting rolls takes place.

Bei sehr geringen Gießdicken, vorzugsweise unterhalb von 5,0 mm Gießdicke, ist ein Anfahrstrang nicht zwingend notwendig, da durch die schnelle Erstarrung der Metallschmelze an den Kokillenwänden deroffene Gießspalt innerhalb sehr kurzer Zeit Überbrückt wird. Anfahrverfahren, bei denen kein Anfahrstrang benötigt wird, sind ebenfalls bereits mehrfach bekannt.At very low casting thicknesses, preferably below 5.0 mm casting thickness, a dummy bar is not absolutely necessary because the open casting gap is bridged within a very short time due to the rapid solidification of the molten metal at the mold walls. Start-up procedures in which no start-up train is required are also already known several times.

Beispielsweise ist aus der JP-A 61 -266 159 ein Startverfahren bekannt, bei welchem die beiden zusammenwirkenden Gießwalzen vor Gießbeginn in eine Start-Position gebracht werden, bei der kein Gießspalt vorhanden ist und die Gießwalzen stillstehen. Unmittelbar nach Beginn derSchmelzenzufuhr und einer ersten Strangschalenbildung an den beiden Mantelflächen der Gießwalzen werden diese auf den Betriebsgießspalt (Banddicke) auseinandergefahren und die Gleßgeschwindigkeit entlang einer Hochfahrkurve auf Betriebs-Gießgeschwindigkeit gebracht. Ein Startvorgang mit stillstehenden Gießwalzen ist jedoch sehr unzuverlässig, weil der ist-Gießspiegel im Schmelzenraum nicht bis an den engsten Querschnitt zwischen den Gießwalzen mit notwendiger Genauigkeit gemessen werden kann. Es ist daher weder ein Kraftanstieg zwischen den beiden Gießwalzen noch der Füllgrad der Kokille vernünftig regelbar. Eine unterschiedlich starke Erstarrung der Schmelze entlang der Bandbreite und insbesondere in Seitenplattennähe kann eine erhebliche Kellbildung durch erstarrtes Metall oberhalb des engsten Querschnittes hervorrufen und nachfolgend zu Seitenplattenbeschädigungen führen. Weiters besteht bei einem derartigen Startverfahren mit stehenden Gießwalzen ein erhöhtes Risiko zu abschnittsweisen Strangschalenklebern auf der Mantelfläche der Gießwalzen.For example, is from the JP-A 61-26159 a starting method is known, in which the two cooperating casting rolls are brought to a start position before pouring, in which no casting gap is present and the casting rolls stand still. Immediately after the start of the melt supply and a first strand shell formation on the two lateral surfaces of the casting rolls they are moved apart on the Betriebsgießspalt (strip thickness) and brought the Gleßgeschwindigkeit along a start-up curve on operating casting speed. However, a starting process with stationary casting rolls is very unreliable because the is-pouring in the melt space can not be measured with the necessary accuracy to the narrowest cross section between the casting rolls. Therefore, neither an increase in force between the two casting rolls nor the degree of filling of the mold is reasonably controllable. A different degree of solidification of the melt along the bandwidth and in particular near the side plate can cause significant Kellbildung by solidified metal above the narrowest cross-section and subsequently lead to side plate damage. Furthermore, in such a starting method with standing casting rolls, there is an increased risk for sectional strand-shell adhesives in sections on the lateral surface of the casting rolls.

Aus der WO 01/21342 ist ein Angießverfahren für eine Zweiwalzengießeinrichtung bekannt, bei dem vor Beginn der Schmelzenzufuhr der Gießspalt zwischen den beiden Gießwalzen auf einen gegenüber dem Betriebsgießspalt reduzierten Wert eingestellt wird. Die Schmelzenzufuhr erfolgt bei rotierenden Gießwalzen, wobei die Gießgeschwindigkeit so eingestellt wird, dass die Dicke des erzeugten Bandes größer ist, als der zuvor eingestellte Gießspalt. Grundsätzlich wird durch einen verringerten Gießspalt die Neigung zum Durchtropfen von Metallschmelze reduziert. Andererseits treten bei kleinen Gleßspalten die zuvor bezüglich der JP-A 61-266 159 beschriebenen Nachteile in zunehmenden Maße auf, insbesondere die Neigung zu Seitenplattenbeschädigungen.From the WO 01/21342 For example, a casting method for a two-roll caster is known in which, before the start of the supply of melt, the casting gap between the two casting rolls is set to a value reduced with respect to the operating casting nip. The supply of melt occurs in rotating casting rolls, wherein the casting speed is adjusted so that the thickness of the produced strip is greater than the previously set casting gap. Basically, the tendency to drip metal melt is reduced by a reduced casting gap. On the other hand, in the case of small splits, the ones described above with regard to the JP-A 61-266159 described disadvantages to an increasing extent, in particular the tendency to side plate damage.

Weitere Angleßverfahren für übliche Zweiwalzengießeinrichtungen mit speziellen Verfahrensvorschritten für den Verlauf der Gießgeschwindigkeit in der Startphase oder die Wahl einer günstigen Startgießdikke in Relation zur Betriebsgießdicke sind aus der JP-A 63-290654 , der JP-A 1-133644 oder der JP-A 6-114504 bereits bekannt. Die EP-A 867 244 beschreibt eine Regelung, mit der in der Startphase des Gießprozesses in aufeinander folgenden Zeitperioden zuerst die Momentangeschwindigkeit der Gießwalzen in Abhängigkeit von einer Badhöhenmessung im Schmelzenpool zwischen den Gießwalzen und danach die Metallschmelzenzufuhr In Abhängigkeit von einer Walzengeschwindigkeitsmessung geregelt wird.Other Angleßverfahren for conventional Zweiwalzengießeinrichtungen with special process steps for the course of the casting speed in the starting phase or the choice of a favorable starting casting thickness in relation to Betriebsgießdicke are from the JP-A 63-290654 , of the JP-A 1-133644 or the JP-A 6-114504 already known. The EP-A 867 244 describes a scheme with which in the start phase of the casting process in successive periods of time, first the instantaneous speed of the casting rolls in response to a Badhöhenmessung in the melt pool between the casting rolls and then the molten metal supply is controlled in response to a roller speed measurement.

Aufgabe der vorliegenden Erfindung ist es da-her, die eingangs beschriebenen Nachteile des Standes der Technik zu vermeiden und ein Verfahren zum Starten eines Gießvorganges in einer Zweiwalzen-Gießeinrichtung sowie eine Einrichtung zur Durchführung des Verfahrens vorzuschlagen, wobei der Durchtritt von Metallschmelze durch den Gießspalt gering gehalten werden kann und gleichzeitig die Neigung zu Keilbildungen und Verdickungen am Anfang des gegossenen Bandes möglichst vermieden wird. Gleichzeitig soll eine Trennung eines ersten Stückes des gegossenen Bandes, welches den Qualitätsansprüchen einer kontinuierlichen Produktion nicht entspricht, von dem nachfolgend unter weitgehend stationären Betriebsbedingungen erzeugten Bandes erreicht werden, ohne dass hierfür mechanische Trenneinrichtungen benötigt werden.Object of the present invention is therefore, To avoid the disadvantages of the prior art described above and to propose a method for starting a casting in a two-roll casting device and a device for carrying out the method, wherein the passage of molten metal through the casting gap can be kept low and at the same time the tendency to form wedge and Thickening at the beginning of the cast strip is avoided as possible. At the same time a separation of a first piece of the cast strip, which does not meet the quality requirements of a continuous production to be achieved by the subsequently produced under largely stationary operating conditions band without the need for mechanical separation devices are required.

Diese Aufgabe wird durch das erfindungsgemäße Verfahren mit folgenden Schritten gelöst:

  • Einstellen einer Betriebs-Gießdicke und Rotieren der Gießwalzen mit einer Gießwalzen-Umfangsgeschwindigkeit, die einer gegenüber einer stationären Betriebs-Gießgeschwindigkeit verringerten Start-Gießgeschwindigkeit entspricht,
  • Zuführen von Metallschmelze in einen von den rotierenden Gießwalzen und den an ihnen anliegenden Seitenplatten gebildeten Schmelzenraum und Ausbilden eines gegossenen Metallbandes mit im Wesentlichen gleichbleibendem, vorbestimmtem Querschnittsformat bei gleichzeitiger Erhöhung der Gießgeschwindigkeit auf eine Bandbildungs-Gießgeschwindigkeit,
  • nachfolgendes Erhöhen der Gießgeschwindigkeit auf eine Bandtrenn-Gießgeschwindigkeit, die signifikant höher ist, als eine den aktuellen Durcherstarrungsbedingungen genügende Gießgeschwindigkeit und Abtrennen des bisher gegossenen Metallbandes,
  • Einstellen der stationären Betriebs-Gießgeschwindigkeit,
  • Umlenken des nachfolgenden gegossenen Metallbandes zu einer Bandtransporteinrichtung und Beginn eines stationären Gießbetriebes.
This object is achieved by the method according to the invention with the following steps:
  • Adjusting an operating casting thickness and rotating the casting rolls at a casting roll peripheral speed that corresponds to a reduced starting casting speed from a steady state casting speed;
  • Feeding molten metal into a melt space formed by the rotating casting rolls and the side plates adjacent thereto and forming a cast metal strip of substantially uniform, predetermined cross-sectional size while increasing the casting speed to a ribbon casting speed;
  • subsequently increasing the casting speed to a belt separation casting speed that is significantly higher than a casting speed sufficient for the current through-solidification conditions and separating the metal strip cast to date;
  • Adjusting the steady state casting speed,
  • Redirecting the subsequent cast metal strip to a belt conveyor and beginning of a stationary casting operation.

Die Gießgeschwindigkeit wird stets von der Gießwalzen-Umfangsgeschwindigkeit bestimmt, da die an den Gießwalzenmäntel gebildeten und anhaftenden Strangschalen mit dieser Geschwindigkeit durch den engsten Querschnitt zwischen den Gießwalzen transportiert und miteinander verbunden werden.The casting speed is always determined by the casting roll peripheral speed since the strand shells formed and adhered to the casting roll shells are transported at this velocity through the narrowest cross section between the casting rolls and bonded together.

Die Start-Gießgeschwindigkeit ist eine niedrige Gießgeschwindigkeit, bei welcher wegen der verlängerten Verweilzeit der sich bildenden Strangschalen im Schmelzenraum ein verstärktes Strangschalenwachstum eintritt und daher der nach unten offenen Gießspalt besonders schnell überbrückt werden kann.The start casting speed is a low casting speed at which, due to the extended residence time of the forming strand shells in the melt space, an increased strand shell growth occurs and therefore the downwardly open casting gap can be bridged particularly quickly.

Die Bandbildungs-Gießgeschwindigkeit ist eine insbesondere vom jeweils aktuellen Flüssigmetall-Gießspiegel und auch von den Erstarrungsbedingungen sowie der aufgrund der Stahlanalyse erforderlichen Gießrollen-Trennkraft abhängige Gießgeschwindigkeit, bei der eine Bandbildung und der Abtransport des gebildeten Bandes nach unten erfolgt und bei der weitgehend gleichbleibende Bandformungsbedingungen eingehalten werden können. Während des Überganges von der Start-Gießgeschwindigkeit zur Bandbildungs-Gießgeschwindigkeit erfolgt dje kontinuierliche Füllung des Schmelzenraumes mit Metallschmelze bis auf das Niveau des Betriebs-Gießspiegels, wobei die Bandbildungs-Gießgeschwindigkeit mit steigendem Gießspiegel kontinuierlich zunimmt.The banding casting speed is a casting speed which depends in particular on the current liquid metal casting level and also on the solidification conditions and the casting roll separation force required due to the steel analysis, in which strip formation and removal of the formed strip take place downwards and are maintained at the largely constant strip forming conditions can be. During the transition from the start casting speed to the belt casting speed, the molten metal is continuously filled up to the level of the operating casting level, with the belt forming speed continuously increasing with increasing casting level.

Da der Gießspalt beim beanspruchten Verfahren während des ganzen Startvorganges auf dem Wert der Betriebs-Gießdicke gehalten wird, ergeben sich zusätzliche Vorteile: Durch eine verringerte Start-Gießgeschwindigkeit wird ein geringer Banddurchsatz bis zum vollständigen Erreichen des Soll-Betriebsgießspiegels erzielt und solcherart der Ausschussanteil gering gehalten. Weiters bewirkt die in der Startphase nicht verringerte Betriebs-Gießdicke weniger Störungen, die infolge von Erstarrungen an den Schmalseitenwänden zu Gießspaltaufweitungen beim Durchgang durch den Gießquerschnitt und gegebenenfalls unkontrollierten Abrissen des gegossenen Stranges führen. Der Verzicht auf eine radiale Verschiebung der Gießwalzen, die zwangsweise eintritt, wenn der Startvorgang mit einer gegenüber der Betriebs-Gießdicke verkleinerten Start-Gießdicke begonnen wird, bewirkt weiters eine Verringerung der parasitären Erstarrungen, die sich an den relativ kalten, freigegebenen Zonen an den Seitenplatten bilden würden.Since the casting gap is kept in the claimed process during the entire starting process on the value of the operating casting thickness, there are additional benefits: By a reduced start-casting speed, a low band throughput is achieved until complete achievement of the target Betriebsgießspiegels and kept such a small amount of rejects , Furthermore, the operating casting thickness, which is not reduced in the starting phase, causes less interference, which, as a result of solidification on the narrow side walls, leads to widening of the casting gap when passing through the casting cross section and possibly uncontrolled tearing of the cast strand. The elimination of a radial displacement of the casting rolls, which occurs forcibly when the starting operation is commenced with a reduced compared with the operating casting thickness starting casting thickness, further causes a reduction of the parasitic solidification, which at the relatively cold, released zones on the side plates would form.

Zur Erzielung eines ausreichend schnellen Strangschalenwachstums an den Mantelflächen der Gießwalzen und damit einer schnellen Überbrückung des Gießspaltes durch erstarrte Metallschmelze wird die Start-Gießgeschwindigkeit kleiner gewählt als die halbe Betriebs-Gießgeschwindigkeit, wobei die Gießwalzen üblicherweise rotieren. Bei Gießdicken über 3 mm kann die Startphase auch mit stehenden Gießwalzen eingeleitet werden, sodass die Start-Gießgeschwindigkeit bei Beginn des Zuführens von Metallschmelze noch 0 m/min beträgt und die Gießwalzen anschließend rasch beschleunigt werden.To achieve a sufficiently rapid strand shell growth on the lateral surfaces of the casting rolls and thus a fast bridging of the casting gap by solidified molten metal, the starting casting speed is chosen smaller than half the operating casting speed, the casting rolls usually rotate. For casting thicknesses greater than 3 mm, the starting phase can also be initiated with standing casting rolls, so that the start casting speed at the beginning of the feeding of molten metal is still 0 m / min and the casting rolls are then rapidly accelerated.

Besonders günstige Bedingungen für die schnelle Überbrückung des Gießspaltes durch erstarrte Metallschmelze in der Startphase ergeben sich, wenn die Start-Gießgeschwindigkeit weniger als 12 m/min beträgt. Eine Start-Gießgeschwindigkeit in diesem Bereich ermöglicht eine gute zeitliche Abstimmung zwischen der Schmelzenzuführung bis zur Erreichung des Betriebs-Gießspiegels und dem Hochfahren der Start-Gießgeschwindigkeit auf eine Bandbildungs-Gießgeschwindigkeit, die etwa der Betriebs-Gießgeschwindigkeit entspricht. Dies wird durch eine moderate, stetige Erhöhung der Gießwalzenumfangsgeschwindigkeit auf eine Bandbildungs-Gießgeschwindigkeit erreicht, die zu einem messbaren Soll-Gießspiegel passt, um eine zuverlässige Bandbildung (Strangschalenbildung auf den Gießwalzenoberflächen im Schmeizenpool) zu gewährleisten. Dementsprechend wird die Bandbildungs-Gießgeschwindigkeit entsprechend einem messbaren Soll-Gießspiegel eingestellt oder geregelt.Particularly favorable conditions for the rapid bridging of the casting gap by solidified molten metal in the starting phase arise when the starting casting speed is less than 12 m / min. A start casting speed in this range allows a good timing between the melt feed to the attainment of the operating pouring level and the ramp-up of the start casting speed to a belting casting speed that approximates the operating casting speed. This is accomplished by a moderate, steady increase in casting roll peripheral speed to a belting casting speed that matches a measurable target casting level To ensure reliable banding (strand shell formation on the casting roll surfaces in the molten pool). Accordingly, the belt-forming casting speed is adjusted or regulated in accordance with a measurable target casting level.

Eine weitere Möglichkeit die Bandbildungs-Gießgeschwindigkeit bestmöglich einzustellen besteht darin, dass die Bandbildungs-Gießgeschwindigkeit in Abhängigkeit von der zwischen den Gießwalzen auftretenden Trennkraft geregelt wird. Die zwischen den beiden Gießwalzen wirkende Trennkraft ist bei einem vorgegebenen Gießspalt ein Maß für die Strangschalendicke und den aktuellen Erstarrungszustand im engsten Querschnitt zwischen den Gießwalzen. Sie ist höher, je weiter der Erstarrungsvorgang in diesem Bereich fortgeschritten ist. Der in der Startphase überwiegend stets steigende Metallbadspiegel, der auf die Strangschalenbildung maßgeblichen Einfluss nimmt, wird hier mitberücksichtigt.Another way of optimally adjusting the banding casting speed is to control the banding casting speed in response to the release force occurring between the casting rolls. The separating force acting between the two casting rolls is, for a given casting gap, a measure of the strand shell thickness and the current solidification state in the narrowest cross section between the casting rolls. It is higher as the solidification process in this area progresses. The predominantly rising metal bath level in the start phase, which has a significant influence on strand shell formation, is also taken into account here.

Zur Regelung der Bandbildungs-Gießgeschwindigkeit können auch die Messwerte einer Badspiegelmessung und einer Trennkraftmessung in Kombination herangezogen werden.To regulate the banding casting speed, the measured values of a bath level measurement and a separation force measurement can also be used in combination.

Als Bandtrenn-Gießgeschwindigkeit ist diejenige Gießgeschwindigkeit zu verstehen, bei der der erste Teil des gegossenen Metallbandes, welcher unter instationären Gießbedingungen in der Startphase des Gießprozesses erzeugt wurde und somit als Ausschussmaterial anzusehen ist, vom kontinuierlich nachfolgenden unter weitgehend stationären Gießbedingungen erzeugten Metallband abgetrennt wird. Diese Trennung erfolgt nach einer möglichen Ausführungsform ausschließlich unter Einwirkung des Eigengewichtes des den engsten Querschnitt zwischen den Gießwalzen verlassenden nach unten hängenden Anfangsstückes des gegossenen Metallbandes durch Abreißen desselben im Gießspalt Durch die Erhöhung der Gießgeschwindigkeit auf die Bandtrenn-Gießgeschwindigkeit werden die Erstarrungsbedingungen und damit die mechanischen Eigenschaften des gegossenen Bandes im Gießquerschnitt, speziell durch Verringerung der Zugfestigkeit, so verändert, dass das Band in diesem Querschnitt ohne zusätzliche mechanische Maßnahmen abreißt.The band-separating casting speed is to be understood as the casting speed at which the first part of the cast metal strip, which was produced under unsteady casting conditions in the starting phase of the casting process and is thus to be regarded as scrap material, is separated from the continuously following metal strip produced under largely stationary casting conditions. This separation takes place according to a possible embodiment exclusively under the action of the dead weight of the narrowest cross section between the casting rollers leaving down hanging starting piece of the cast metal strip by tearing it in the casting gap by increasing the casting speed on the belt separation casting speed, the solidification conditions and thus the mechanical properties of the cast strip in Gießquerschnitt, especially by reducing the tensile strength, so changed that the strip in this cross-section tears off without additional mechanical measures.

Alternativ kann das Abtrennen des gegossenen Metallbandes bei Bandtrenn-Gießgeschwindigkeit unter Einwirkung eines gegenüber der Schwerkraftwirkung erhöhten Bandzuges erfolgen, der durch eine Treiberanordnung aufgebracht wird, die austrittsseitig unterhalb des Gießspaltes der Zweiwalzengießeinrichtung angeordnet ist.Alternatively, the separation of the cast metal strip at tape release casting speed can be accomplished by the action of a gravitational action increased tape tension applied by a driver assembly located downstream of the casting nip of the two-roll caster.

Eine Verbesserung der Abtrennbedingungen kann erreicht werden, wenn der Erhöhung der Gießgeschwindigkeit auf die Bandtrenn-Gießgeschwindigkeit eine kurzzeitige Vergrößerung der Gießdicke um 5 bis 40 % überlagert wird.An improvement in the separation conditions can be achieved by superposing a short-term increase in casting thickness by 5 to 40% on the increase in casting speed to the strip-separation casting speed.

Die Bandtrenn-Gießgeschwindigkeit ist höher als die Betriebs-Gießgeschwindigkeit, vorzugsweise ist sie um 5% bis 40% höher als die Betriebs-Gießgeschwindigkeit.The belt separation casting speed is higher than the operation casting speed, preferably 5% to 40% higher than the operation casting speed.

Diese Bandtrenn-Gießgeschwindigkeit wird kurzzeitig eingestellt, sobald annähernd stationäre Gießbedingungen erreicht sind. Bevorzugt wird, dass auch bereits eine gleichbleibende Bandqualität sichergestellt ist. Die Bandtrenn-Gießgeschwindigkeit wird in der Startphase zweckmäßig dann eingestellt, wenn die Metallschmelze im Schmelzenraum im Wesentlichen den Soll-Betriebsgießspiegel erreicht hat.This belt separation casting speed is set briefly as soon as approximately stationary casting conditions are reached. It is preferred that even a consistent strip quality is ensured. The strip separation casting speed is expediently set in the starting phase when the molten metal in the melting chamber has essentially reached the desired operating casting level.

Um einen kontinuierlichen Übergang zu stationären Gießbedingungen und damit zu stationären Erstarrungsbedingungen an den Gießwalzen und im Gießspalt zu gewährleisten ist es zweckmäßig, wenn vor dem Erreichen des Soll-Betriebsgießspiegels im Schmelzenraum die Gießgeschwindigkeit auf etwa die Betriebs-Gießgeschwindigkeit gesteigert wird.In order to ensure a continuous transition to stationary casting conditions and thus stationary solidification conditions on the casting rolls and in the casting gap, it is expedient if the casting speed is increased to approximately the operating casting speed before reaching the desired operating pouring mirror in the melting chamber.

Das vorgeschlagene Verfahren ermöglicht, dass der stationäre Gießbetrieb innerhalb von 5 bis 60 sec nach Beginn der Zufuhr von Metallschmelze in den Schmelzenraum erreicht wird.The proposed method allows the steady state casting operation to be achieved within 5 to 60 seconds after the start of metal melt feed into the melt space.

Insbesondere bei sehr dünnen Bändern ist es vorteilhaft, dass bei Starten eines Gießvorganges eine gegenüber der Betriebs-Gießdicke vergrößerte Start-Gießdicke eingestellt wird und diese Start-Gießdicke frühestens nach Ausbilden eines gegossenen Metallbandes mit gleichbleibenden Querschnittsformat auf die Betriebs-Gießdicke zurückgeführt wird. Dieses Verfahren wird vorzugsweise angewendet bei Gießdicken unter 2,5 mm, da speziell in diesem Dickenbereich die eingangs beschriebenen Schwierigkeiten mit Seitenplattenerstarrungen und Keilbildung und nachfolgenden unkontrollierten Bandrissen auftreten können und das der Bandtrennung nachfolgende Band dadurch eine bessere Eigensteifigkeit zur Führung durch die Anlage besitzt.Especially with very thin bands, it is advantageous that when starting a casting process compared to the operating casting thickness increased start casting thickness is set and this start casting thickness is returned to the operating casting thickness at the earliest after forming a cast metal strip with constant cross-sectional format. This method is preferably used with casting thicknesses of less than 2.5 mm, since especially in this thickness range, the difficulties described above with Seitenplattenerstarrungen and wedge formation and subsequent uncontrolled tape cracks can occur and the band separation subsequent band thus has a better inherent rigidity for guidance through the system.

Zur Gewährleistung eines automatisierten Ablaufes des Startverfahrens ist es zweckmäßig, dass zumindest Referenzdaten der momentanen Gießgeschwindigkeit und der momentanen Gießspiegelhöhe der Metallschmelze im Schmelzenraum und/oder der momentanen Trennkraft zwischen den Gießwalzen und/oder der Spaltweite zwischen den Gießwalzen und/oder der Banddicke des gegossenen Metallbandes während des Gießstartes kontinuierlich ermittelt und einer Recheneinheit zugeführt werden und aus diesen Referenzdaten unter Einbeziehung eines mathematischen Modelles für den Startvorgang Stellgrößen für die Gießgeschwindigkeit, für die Position einer Bandleiteinrichtung und für die Transportgeschwindigkeit des gegossenen Metallbandes in einer Bandtransporteinrichtung generiert und an die Antriebseinheiten dieser Einrichtungen übermittelt werden.To ensure an automated sequence of the starting process, it is expedient that at least reference data of the instantaneous casting speed and the current Gießspiegelhöhe the molten metal in the melting space and / or the instantaneous separation force between the casting rolls and / or the gap width between the casting rolls and / or the strip thickness of the cast metal strip determined continuously during the casting start and fed to a computing unit and generated from these reference data including a mathematical model for the starting process manipulated variables for the casting speed, for the position of a Bandleiteinrichtung and for the transport speed of the cast metal strip in a belt conveyor and transmitted to the drive units of these devices become.

Zusätzlich werden die Abtrennbedingungen für die Abtrennung des ersten Stückes des gegossenen Metallbandes im Gießquerschnitt verbessert, wenn aus dem mathematischen Modell auf der Grundlage von aktuellen Eingangsdaten, wie Stahlqualität, Betriebs-Gießdicke, Temperaturverhältnisse, qualitätsbezogene Erstarrungsbedingungen etc., zusätzlich eine Stellgröße für die Abstandspositionierung der beiden Gießwalzen zueinander, insbesondere eine erhöhte Start-Gießdicke, generiert wird.In addition, the separation conditions for the separation of the first piece of the cast metal strip in the casting cross-section are improved when using the mathematical model based on current input data such as steel grade, operating casting thickness, temperature ratios, quality related Solidification conditions, etc., in addition a manipulated variable for the distance positioning of the two casting rolls to each other, in particular an increased starting casting thickness, is generated.

Die Qualität des erzeugten Metallbandes kann generell und während des Gießprozesses laufend optimiert und an wechselnde Betriebsbedingungen angepasst werden, wenn das mathematische Modell ein metallurgisches Modell zur Ausbildung eines bestimmten Gefüges im gegossenen Metallband und/oder zur Beeinflussung der Geometrie des gegossenen Metallbandes umfasst.The quality of the metal strip produced can be continually optimized and adapted to changing operating conditions in general and during the casting process if the mathematical model comprises a metallurgical model for forming a specific microstructure in the cast metal strip and / or for influencing the geometry of the cast metal strip.

Eine Zweiwalzengießeinrichtung zur Durchführung des beschriebenen Verfahrens zum Starten eines Gießvorganges ohne Anfahrstrang besteht aus zwei mit Drehantrieben gekoppelten, gegensinnig rotierenden Gießwalzen und an den Gießwalzen anliegende Seitenplatten, die gemeinsam einen Schmelzenraum zur Aufnahme der Metallschmelze formen, sowie mindestens einer verlagerbaren Bandleiteinrichtung und mindestens einer Bandtransporteinrichtung. Sie ist dadurch gekennzeichnet,

  • dass den Gießwalzen eine Geschwindigkeitsmesseinrichtung zur Ermittlung der momentanen Gießgeschwindigkeit zugeordnet ist,
  • dass dem Schmelzenraum eine Niveaumesseinrichtung zur Ermittlung der momentanen Gießspiegelhöhe der Metallschmelze zugeordnet ist,
  • dass die Geschwindigkeitsmesseinrichtung und die Niveaumesseinrichtung durch Signalleitungen mit einer Recheneinheit verbunden sind und
  • die Recheneinheit durch Signalleitungen mit dem Drehantrieb der Gießwalzen, mit einer Positionsstelleinrichtung der Bandleiteinrichtung und dem Antrieb einer Bandtransporteinrichtung verbunden ist. Die beiden Gießwalzen können auch mit einem gemeinsamen Drehantrieb unter Zwischenschaltung eines Verteilergetriebes gekoppelt sein.
A Zweiwalzengießeinrichtung for carrying out the described method for starting a casting without start-up strand consists of two coupled with rotary actuators, counter-rotating casting rolls and adjacent to the casting rolls side plates, which together form a melting space for receiving the molten metal, and at least one displaceable strip guide and at least one belt transport device. It is characterized
  • that the casting rolls are assigned a speed measuring device for determining the instantaneous casting speed,
  • in that a level measuring device for determining the instantaneous casting level height of the molten metal is assigned to the melting space,
  • that the speed measuring device and the level measuring device are connected by signal lines to a computing unit, and
  • the arithmetic unit is connected by signal lines to the rotary drive of the casting rolls, to a position adjusting device of the strip guiding device and to the drive of a belt transporting device. The two casting rolls can also be coupled with a common rotary drive with the interposition of a transfer case.

Eine solcherart ausgestattete Zweiwalzengießeinrichtung ermöglicht die Übernahme von aktuellen Erzeugungsdaten aus dem Stahlerzeugungsprozess und deren gemeinsame Verarbeitung mit Messdaten an der Gießeinrichtung in einem Rechenmodell zur Optimierung des Startverfahrens.A two-roll caster equipped in this way enables the acquisition of current production data from the steelmaking process and their joint processing with measurement data at the caster in a computer model for optimizing the starting process.

Ein zweckentsprechender Ablauf des erfindungsgemäßen Verfahrens ist auch möglich, wenn statt der kontinuierlichen Messung der Gießspiegelhöhe im Schmelzenraum mit einer Niveaumesseinrichtung alternativ eine Trennkraft-Messeinrichtung zur Ermittlung der momentanen, im wesentlichen durch die Bandbildung hervorgerufenen Trennkraft zwischen den beiden Gießwalzen oder eine Positions-Messeinrichtung zur Ermittlung der momentanen Spaltweite zwischen den Gießwalzen oder eine Messeinrichtung zur Ermittlung der momentanen Banddicke eingesetzt wird. Jede dieser Messungen liefert Referenzdaten, die zumindest indirekt einen mathematisch beschreibbaren Zusammenhang mit der Strangschalenausbildung im Schmelzenpool und damit mit der Metallstrangbildung im engsten Querschnitt zwischen den Gießwalzen herstellen und die daher in einem mathematischen Modell zur Errechnung von Stellgrößen herangezogen werden können, um den Startvorgang zeitminimiert bzw. optimiert hinsichtlich Form und Führbarkeit der Bandabrisskante durchzuführen. Eine weitere Verbesserung des Startverfahren kann durch Kombination von mindestens zwei dieser Messmethoden erzielt werden, wobei die Messungen zeitgleich durchgeführt und in einem dementsprechend erweiterten mathematischen Modell verarbeitet werden.An appropriate sequence of the method according to the invention is also possible if, instead of the continuous measurement of Gießspiegelhöhe in the melting chamber with a level measuring device alternatively a separating force measuring device for determining the instantaneous, caused essentially by the banding separating force between the two casting rolls or a position-measuring device for determining the instantaneous gap width between the casting rolls or a measuring device for determining the instantaneous strip thickness is used. Each of these measurements provides reference data which at least indirectly produce a mathematically describable relationship with the strand shell formation in the melt pool and thus with the metal strand formation in the narrowest cross section between the casting rolls and which can therefore be used in a mathematical model to calculate manipulated variables in order to minimize or minimize the starting process Optimized in terms of shape and trackability of the strip breaking edge. A further improvement of the starting method can be achieved by combining at least two of these measuring methods, wherein the measurements are carried out simultaneously and processed in a correspondingly expanded mathematical model.

Eine weitere Optimierung des Verfahrens ergibt sich, wenn zumindest eine der beiden Gießwalzen mit einer Gießwalzen-Verstelleinrichtung gekoppelt und die Recheneinheit zusätzlich durch eine Signalleitung mit einer Gießwalzen-Verstelleinrichtung zur Einstellung einer Start- Gießdicke verbunden ist. Dadurch kann für vorgegebene Produktionskenngrößen, wie insbesondere die Stahlqualität, das Gießformat, vorzugsweise die Betriebs-Gießdicke, sowie aus der Stahlproduktion übemommene Kenndaten, wie beispielsweise die Überhitzungstemperatur der Schmelze, und aus Messdaten an der Anlage im Prozessmodell eine spezifische höhere Start-Gießdicke ermittelt und an der Gießanlage eingestellt werden.A further optimization of the method results when at least one of the two casting rolls is coupled to a casting roll adjusting device and the computing unit is additionally connected by a signal line to a casting roll adjusting device for setting a starting casting thickness. As a result, for specific production parameters, in particular the steel quality, the casting format, preferably the operating casting thickness, as well as the steel production taken characteristic data, such as the superheating temperature of the melt, and measured data on the system in the process model, a specific higher starting casting thickness determined be adjusted at the casting plant.

Das vorliegende Verfahren und die zugehörige Zweiwalzengießanlage ist für das Vergießen von Metallschmelzen, vorzugsweise Fe-hältige Metalllegierungen, insbesondere für Stähle, geeignet.The present method and the associated two-roll caster is suitable for casting molten metals, preferably Fe-containing metal alloys, in particular for steels.

Weitere Vorteile und Merkmale der Erfindung ergeben sich aus der nachfolgenden Beschreibung nicht einschränkender Ausführungsbeispiele, wobei auf die beiliegenden Figuren Bezug genommen wird, die folgendes zeigen:

Fig. 1
eine schematische Darstellung einer Zweiwalzengießeinrichtung zur Durchführung des erfindungsgemäßen Verfahrens,
Fig.2a
eine schematische Darstellung der Erstarrungsbedingungen im Gießspalt bei Betriebs-Gießgeschwindigkeit,
Fig.2b
eine schematische Darstellung der Erstarrungsbedingungen im Gießspalt bei Bandtrenn-Gießgeschwindigkeit,
Fig. 3
den Verlauf der Gießgeschwindigkeit, der Gießspaltweite, des Gießspiegelsignals und der Gießwalzen-Trennkraft während des Startens eines Gießvorganges für einen Stahl der Qualität AISI 304.
Further advantages and features of the invention will become apparent from the following description of non-limiting embodiments, reference being made to the attached figures, which show the following:
Fig. 1
a schematic representation of a Zweiwalzengießeinrichtung for performing the method according to the invention,
2a
a schematic representation of the solidification conditions in the casting gap at operating casting speed,
2b
a schematic representation of the solidification conditions in the casting gap at belt separation casting speed,
Fig. 3
the course of the casting speed, the casting gap width, the casting level signal and the casting roll separation force during the start of a casting process for an AISI 304 grade steel.

Eine Zweiwalzengießanlage mit den für die Durchführung des erfindungsgemäßen Verfahrens notwendigen Einrichtungen ist in Fig.1 schematisch dargestellt. Sie besteht aus zwei in einer Horizontalebene im Abstand voneinander angeordneten und mit einer nicht dargestellten Innenkühlung ausgestatteten Gießwalzen 1, 2. Diese sind in Wellenlagern 3, 4 drehbar abgestützt und mit Drehantrieben 5, 6 gekoppelt, die ein gegensinniges Rotieren der Gießwalzen 1, 2 um Gießwalzenachsen 1', 2' mit einer regelbaren Umfangsgeschwindigkeit, die der Gießgeschwindigkeit entspricht, ermöglichen. Zur Bestimmung der momentanen Gießgeschwindigkeit ist zumindest einer der Gießwalzen 1, 2 oder den zugeordneten Drehantrieben 5, 6 oder auch dem gegossenen Metallband selbst eine Geschwindigkeitsmesseinrichtung 34 zugeordnet. Eine der beiden Gießwalzen 2 ist in der Horizontalebene quer zur Gießwalzenachse 2' verschiebbar abgestützt und mit einer Gießwalzen-Verstelleinrichtung 7 gekoppelt, wodurch der Abstand der beiden Gießwalzen 1, 2 zueinander regelbar einstellbar ist. An die Gießwalzen 1, 2 sind stirnseitig Seitenplatten 8 anpressbar angestellt, die gemeinsam mit einem Abschnitt der Mantelflächen 9, 10 der rotierenden Gießwalzen einen Schmelzenraum 11 für die Aufnahme von Metallschmelze 12 bilden. Die Metallschmelze 12 wird aus einem Zwischengefäß 13 durch ein Tauchrohr 14 in den Schmelzenraum 11 kontinuierlich und geregelt eingebracht, sodass während des stationären Gießbetriebes die Schmelzenzufuhr durch die Tauchrohrauslässe in untergetauchter Form, d.h. stets unterhalb eines auf konstantem Niveau gehaltenen Gießspiegels 15 erfolgt. Durch eine oberhalb des Schmelzenraumes 11 angeordnete Niveaumesseinrichtung 16 erfolgt eine kontinuierliche Überwachung der Gießspiegelhöhe.A two-roll caster with the necessary for carrying out the method according to the invention Facilities is in Fig.1 shown schematically. It consists of two in a horizontal plane at a distance from each other and equipped with an internal cooling, not shown, casting rolls 1, 2. These are rotatably supported in shaft bearings 3, 4 and coupled with rotary actuators 5, 6, the opposing rotation of the casting rolls 1, 2 to Gießwalzenachsen 1 ', 2' with a controllable peripheral speed, which corresponds to the casting speed allow. To determine the instantaneous casting speed, at least one of the casting rolls 1, 2 or the associated rotary drives 5, 6 or the cast metal strip itself is assigned a speed measuring device 34. One of the two casting rolls 2 is slidably supported in the horizontal plane transversely to the casting roll axis 2 'and coupled to a casting roll adjusting device 7, whereby the distance between the two casting rolls 1, 2 is adjustable adjustable to each other. On the casting rolls 1, 2 side plates 8 are pressed against the front side, which together with a portion of the lateral surfaces 9, 10 of the rotating casting rolls form a melting chamber 11 for receiving molten metal 12. The molten metal 12 is continuously and regulated introduced from an intermediate vessel 13 through a dip tube 14 in the melt space 11, so that during the stationary casting operation, the melt supply through the Tauchrohrauslässe in submerged form, ie always below a held at a constant level casting mirror 15. By means of a level measuring device 16 arranged above the melting space 11, a continuous monitoring of the level of the casting mirror takes place.

Ausgangsseitig ist der Schmelzenraum 11 durch den Gießspalt 18 begrenzt, der durch den Abstand der beiden Gießwalzen 1, 2 voneinander festgelegt ist und die Gießdicke D des gegossenen Metallbandes bestimmt. Die an den Mantelflächen 9, 10 der Gießwalzen im Schmelzenraum 11 gebildeten erstarrten Strangschalen 19, 20 werden im Gießspalt 18 zu einem weitgehend durcherstarrten Metallband 21 verbunden, welches durch die Rotationsbewegung der Gießwalzen 1, 2 aus dem Gießspalt 18 nach unten ausgefördert, durch eine nachgeordnete verschwenkbare Bandleiteinrichtung 22 und Bandführungsrollen 23 in eine weitgehend horizontale Transportrichtung umgelenkt und einer von einem Treibrollenpaar gebildeten Bandtransporteinrichtung 24 aus der Zweiwalzengießeinrichtung ausgefördert wird. Die bogenförmig ausgebildete Bandleiteinrichtung 22 ist mit einer Antriebseinheit 25 verbunden, die es ermöglicht, die Bandleiteinrichtung 22 von einer Rückzugsposition A in eine Betriebsposition B und zurück zu verschwenken. Während des Startvorganges des Gießprozesses befindet sich die Bandleiteinrichtung in der Rückzugsposition A und wird nach dem Abtrennen eines ersten Stückes des gegossenen Metallbandes in die Betriebsposition B verschwenkt und kann dort während des gesamten stationären Produktionsprozesses verbleiben. Vertikal unterhalb des Gießspaltes 18 ist ein Schrottaufnahmewagen 26 angeordnet, in welchem allenfalls anfangs durchtropfende Metallschmelze und der erste Abschnitt des gegossenen Bandes aufgefangen und bei Bedarf abtransportiert werden kann.On the output side of the melting chamber 11 is limited by the casting gap 18, which is determined by the distance between the two casting rolls 1, 2 from each other and determines the casting thickness D of the cast metal strip. The solid shell shells 19, 20 formed on the lateral surfaces 9, 10 of the casting rolls in the melting chamber 11 are connected in the casting gap 18 to a substantially solidified metal strip 21, which is conveyed downwardly from the casting gap 18 by the rotational movement of the casting rolls 1, 2, by a downstream one pivotable Bandleiteinrichtung 22 and tape guide rollers 23 is deflected in a substantially horizontal transport direction and one of a pair of drive rollers belt conveyor 24 is discharged from the Zweiwalzengießeinrichtung. The arc-shaped Bandleiteinrichtung 22 is connected to a drive unit 25, which makes it possible to pivot the Bandleiteinrichtung 22 from a retreat position A to an operating position B and back. During the starting process of the casting process, the tape guide is in the retraction position A and is pivoted after the separation of a first piece of the cast metal strip in the operating position B and can remain there during the entire stationary production process. Vertically below the casting gap 18, a scrap receiving carriage 26 is arranged, in which at most initially dripping metal melt and the first portion of the cast strip can be collected and transported away if necessary.

Der Schrottaufnahmewagen kann auch ohne Räder ausgeführt sein. Er kann innerhalb einer Kammerumwandung, die den Weg des gegossenen Metallbandes von den Gießwalzen bis zum ersten Treiber umschließt, positioniert sein. Auch muss dieser erste Abschnitt des gegossenen Bandes nicht notwendigerweise direkt in den Schrottaufnahmewagen fallen, sondern kann auch indirekt diesem zugeführt werden.The scrap receiving trolley can also be designed without wheels. It may be positioned within a chamber wall enclosing the path of the cast metal strip from the casting rolls to the first driver. Also, this first portion of the cast strip does not necessarily fall directly into the scrap receiving trolley, but can also be fed indirectly thereto.

Nachdem das gegossene Metallband aus der mit einer Antriebseinheit 27 ausgestattete Bandtransporteinrichtung 24 austritt, wird es in nicht näher dargestellten Weiterbehandlungseinrichtungen 28 veredelt und abschließend zu Bunden 29 gewickelt und/oder zu Tafeln zerteilt. Die Weiterbehandlungseinrichtungen 28 können beispielsweise von Walzgerüsten, Besäumeinrichtungen, Oberflächenbehandlungseinrichtungen, thermischen Behandlungseinrichtung verschiedenster Art, wie Heizeinrichtungen, Halteöfen, Temperaturausgleichsöfen, und Kühlstrecken gebildet sein.After the cast metal strip emerges from the belt transport device 24 equipped with a drive unit 27, it is finished in further processing devices 28 (not illustrated in detail) and finally wound into bundles 29 and / or cut into sheets. The further treatment devices 28 may be formed, for example, by rolling stands, trimming devices, surface treatment devices, thermal treatment devices of various kinds, such as heating devices, holding ovens, temperature compensation furnaces, and cooling sections.

Die Zweiwalzengießeinrichtung ist mit einer Recheneinheit 36 ausgestattet, die es ermöglicht, den Startvorgang in Abhängigkeit von vorgegebenen Eingangsgrößen und an der Einrichtung ermittelten aktuellen Messgrößen automatisiert durchzuführen. Mit Kenndatenfeldem und/oder einem mathematischen Modell werden in der Recheneinheit optimale Stellgrößen, wie die Start-Gießgeschwindigkeit vgSt, die Position der Bandleiteinrichtung, die Antriebsgeschwindigkeit der Bandtransporteinrichtung und gegebenenfalls die Start-Gießdicke DSt und weitere Stellgrößen generiert und der Startvorgang fortlaufend geregelt und überwacht.The Zweiwalzengießeinrichtung is equipped with a computing unit 36, which makes it possible to automatically perform the starting process in response to predetermined input variables and determined on the device current metrics. With Kenndatenfeldem and / or a mathematical model optimal manipulated variables, such as the start casting speed v gSt , the position of the belt guide , the drive speed of the belt conveyor and possibly the starting casting thickness D St and other control variables are generated in the arithmetic unit and the starting process continuously controlled and supervised.

Stellgrößen, die zur Durchführung des Startverfahrens aus der Recheneinheit 36 generiert werden, beruhen auf aktuell erhobene Messdaten aus der Gießanlage, die direkt oder indirekt einen Zusammenhang mit dem Strangschalenwachstum aufweisen. Hierfür prädestiniert sind das momentane Niveau des Gießspiegels 15, d.h. die Gießspiegelhöhe im Schmelzenraum 11, welche mit einer Niveaumesseinrichtung 16 kontinuierlich ermittelt werden kann. Die Trennkraft FTr zwischen den beiden Gießwalzen 1, 2, stellt eine Reaktionskraft auf die durchgeleiteten Strangschalen dar und liefert ebenfalls einen Referenzwert für den Grad der Durcherstarrung im engsten Querschnitt zwischen den Gießwalzen. Sie ist mit einer Trennkraft-Messeinrichtung 30 zu ermittelt, die den Gießwalzenlagerungen 3, 4 zugeordnet oder in der Gießwalzenverstelleinrichtung 7 eingebaut ist. Eine weitere Möglichkeit, eine Referenzgröße zu ermitteln, bietet die momentane Spaltweite G zwischen den Gießwalzen, die eng mit der Trennkraft FTr zusammenhängt, da eine höhere Trennkraft ein erhöhtes radiales Ausweichen der Gießwalzen 1, 2 voneinander bzw. deren Verformung bewirkt. Dies kann auf direktem Weg durch eine Positionsmesseinrichtung 31 an den Gießwalzen oder auf indirektem Weg über eine Banddicken-Messeinrichtung 32 gemessen werden. Die zeitgleiche Messung und Verarbeitung der Messdaten von mehreren der beschriebenen Messsysteme minimiert den Zeitaufwand für den Anlagenstart und erhöht insbesondere die Qualität der Bandabrisskante des nachfolgenden Metallbandes hinsichtlich deren Geometrie und deren Führbarkeit durch die Anlage, sowie auch die Qualität des erzeugten Produktes vom Produktionsbeginn an.Manipulated variables, which are generated from the arithmetic unit 36 for carrying out the starting process, are based on measurement data from the casting plant that are currently collected and that directly or indirectly have a connection with the strand shell growth. Predestined for this purpose are the instantaneous level of the casting mirror 15, ie the level of the casting mirror in the melting space 11, which can be determined continuously by means of a level-measuring device 16. The release force F Tr between the two casting rolls 1, 2, represents a reaction force on the passed strand shells and also provides a reference value for the degree of solidification in the narrowest cross section between the casting rolls. It is to be determined with a separating force measuring device 30, which is associated with the casting roll bearings 3, 4 or incorporated in the Gießwalzenverstelleinrichtung 7. Another way to determine a reference size, provides the instantaneous gap width G between the casting rolls, which is closely related to the release force F Tr , since a higher separation force increased radial deflection of the casting rolls 1, 2 causes each other or their deformation. This can be measured directly by a position measuring device 31 on the casting rolls or indirectly via a strip thickness measuring device 32. The simultaneous measurement and processing of the measurement data of several of the measuring systems described minimizes the time required for the start of the system and in particular increases the quality of the strip breaking edge of the subsequent metal strip with regard to their geometry and their ability to be guided through the plant, as well as the quality of the product produced from the start of production.

Die Erstarrungsbedingungen an den Mantelflächen 9, 10 der beiden Gießwalzen und im Gießspalt 18 bei stationärer Betriebs-Gießgeschwindigkeit und bei Bandtrenn-Gießgeschwindigkeit sind in den Figuren 2a und 2b gegenübergestellt. Bei stationärer Betriebs-Gießgeschwindigkeit (Fig. 2a) befinden sich die beiden Gießwalzen 1, 2 auf einen Gießspalt 18 eingestellt, der insbesondere dem stationären Gießspiegel und der Betriebs-Gießdicke D des gewünschten gegossenen Metallbandes entspricht. Hierbei bildet sich an jeder der Mantelflächen 9, 10 der Gießwalzen je eine in Drehrichtung der Gießwalzen, somit zum Gießspalt 18 orientiert, zunehmend dicker werdende Strangschale 19, 20 aus. Im Gießquerschnitt 18 werden die beiden Strangschalen 19, 20 zusammengefügt und es bildet sich bei stationären Gießbedingungen ein durcherstarrtes Metallband. Die V-förmigen Linien 37 veranschaulichen hierbei den Übergang von 100 % Schmelze zu einem Mischbereich mit einem zunehmenden Festkörperanteil und die V-förmige Linie 38 veranschaulicht den Übergang zu 100 % Festkörperanteil, somit den durcherstarrten Strangteil. Fig. 2b zeigt die geänderten Erstarrungsbedingungen bei einer Bandtrenn-Gießgeschwindigkeit, die gegenüber der Betriebs-Gießgeschwindigkeit erhöht ist. Das bedeutet, dass die Umfangsgeschwindigkeit der Gießwalzen vergrößert ist. Die Kühlbedingungen wurden hierbei nicht verändert. Dadurch wird die verfügbare Strangschalen-Bildungszeit im Schmelzenraum und damit das Strangschalenwachstum verringert, sodass sich der Durcherstarrungspunkt 39 in Gießrichtung verschiebt und im Gießquerschnitt entweder noch ein erhöhter Anteil von Flüssigkörperanteil vorhanden ist und/oder die durchschnittliche Bandtemperatur zumindest höher liegt als bei Betriebs-Gießgeschwindigkeit. In beiden Fällen ist die Zugfestigkeit des nach unten hängenden Metallbandstückes bei der Bandtrenn-Gießgeschwindigkeit soweit herabgesetzt, dass das Metallband unter der Einwirkung seines Gewichtes im Gießquerschnitt abreißt.The solidification conditions on the lateral surfaces 9, 10 of the two casting rolls and in the casting gap 18 at steady-state casting speed and at belt separation casting speed are in the FIGS. 2a and 2b compared. At stationary operating casting speed ( Fig. 2a ), the two casting rolls 1, 2 are set to a casting gap 18, which corresponds in particular to the stationary casting level and the operating casting thickness D of the desired cast metal strip. Here, on each of the lateral surfaces 9, 10 of the casting rolls, one each in the direction of rotation of the casting rolls, thus oriented to the casting gap 18, increasingly thicker strand shell 19, 20 forms. In the casting cross section 18, the two strand shells 19, 20 are joined together and it forms at stationary casting conditions a solidified metal strip. In this case, the V-shaped lines 37 illustrate the transition from 100% melt to a mixing area with an increasing solids content and the V-shaped line 38 illustrates the transition to 100% solids, thus the solidified strand part. Fig. 2b Figure 12 shows the changed solidification conditions at a belt-separation casting speed which is increased over the operation-casting speed. This means that the peripheral speed of the casting rolls is increased. The cooling conditions were not changed. As a result, the available strand shell formation time in the melt space and thus the strand shell growth is reduced, so that the Durcherstarrungspunkt 39 shifts in the casting direction and in Gießquerschnitt either an increased proportion of liquid content is present and / or the average strip temperature is at least higher than at operating casting speed. In both cases, the tensile strength of the hanging down metal strip piece at the strip separation casting speed is reduced so far that the metal strip breaks off under the action of its weight in Gießquerschnitt.

In einer bevorzugten Ausführungsform wird die Gießgeschwindigkeit auf eine so hohe Bandtrenn-Gießgeschwindigkeit erhöht und anschließend gleich wieder abgesenkt, dass vorübergehend keine Trennkraft gemessen wird. In dieser kurzen Phase fließt Metallschmelze wegen der mangelnden Verbindung zwischen den beiden Strangschalen und unter der Wirkung des ferrostatischen Druckes in den Raum unterhalb des engsten Querschnittes zwischen den Gießwalzen nach. Dadurch kommt es lokal zu einem Ausbauchen des Metallbandes und einer erheblichen Wiedererwärmung der oberflächennahen Bandschichten und unter dem Einfluss des nach unten hängenden Bandeigengewichtes zum Abriss.In a preferred embodiment, the casting speed is increased to such a high belt separation casting speed and then immediately lowered again so that no separation force is temporarily measured. In this short phase molten metal flows because of the lack of connection between the two strand shells and under the effect of ferrostatic pressure in the space below the narrowest cross section between the casting rolls after. This leads to a bulging of the metal strip and a considerable rewarming of the near-surface strip layers and to the demolition under the influence of the downside band weight.

Fig. 3 zeigt den Ablauf des beschriebenen Verfahrens zum Starten eines Gießvorganges in einer Zweiwalzengießanlage für einen rostfreien Cr-Ni-Stahl der Qualität AISI 304 mit einer stationären Betriebs-Gießdicke D = 2,5 mm und einer Betriebs-Gießgeschwindigkeit VgBetr = 60 m/min. Vor der Schmelzenzuführung wird der Betriebsgießspalt von 2,5 mm eingestellt und die Gießwalzen mit einer Umfangsgeschwindigkeit angetrieben, die einer Start-Gießgeschwindigkeit vgSt = 10 m/min entspricht. Mit Beginn der Schmelzenzuführung wird die Gießgeschwindigkeit vg kontinuierlich bis auf die Bandbildungs-Gießgeschwindigkeit vgBb erhöht, die etwa der Betriebs-Gießgeschwindigkeit vgBetr = 60 m/min entspricht. Bereits kurz nach Beginn der Schmelzenzufuhr kommt es zur Überbrückung des nach unten offenen Gießspaltes durch die sich bildenden Strangschalen bei noch sehr geringer Gießgeschwindigkeit. Dies zeigt sich am kurzfristig stark ansteigenden Kurvenverlauf für die Gießspaltposition G und die Gießwalzen-Trennkraft FTr, die direkt korrelieren. Die Gießspaltposition G wird am Hydraulikkolben eines AGC-Systems gemessen. Mit zunehmender Gießgeschwindigkeit Vg kehrt sich die Tendenz einer ansteigenden Trennkraft wieder um, da auch die Strangschalenbildung wegen der geringeren Verweildauer der Strangschale im Schmelzenraum abnimmt. Das Gießspiegelniveau hGsp ist erst nach Erreichen eines bestimmten Füllgrades messbar, da der Schmelzenraum bedingt durch die Gießwalzenanordnung zum Gießquerschnitt hin trichterförmig verengt ist und in diesem sehr engen Bereich eine Niveaumessung technisch nicht realisierbar ist. Nach einer Zeitspanne von etwa 5 bis 15 sec, die variabel gewählt werden kann, wird der Betriebs-Gießspiegel hBetr erreicht und auf diesem Niveau gehalten. Damit sind annähernd konstante Gießbedingungen erreicht und es wird die Gießgeschwindigkeit für eine kurze Zeitspanne von 0,2 sec auf die Bandtrenn-Gießgeschwindigkeit vgTr = 80 m/min erhöht, die 20 m/min höher liegt, als die stationäre Betriebs-Gießgeschwindigkeit vgBetr. Bei dieser Bandtrenn-Gießgeschwindigkeit reisst das gegossene Metallband unter dem Einfluss des Eigengewichtes im engsten Querschnitt zwischen den Gießwalzen ab. Hierbei fällt die Gießwalzen-Trennkraft FTr kurzzeitig auf Null zurück. Mit Rückführung der Gießgeschwindigkeit auf den Wert der Betriebs-Gießgeschwindigkeit vgBetr = 60 m/min steigt die Gießwalzen-Trennkraft FTr unmittelbar auf den Wert vor der Anhebung der Gießgeschwindigkeit auf die Bandtrenn-Gießgeschwindigkeit an. Damit sind die Bedingungen für einen stationären Gießbetrieb erreicht und die Herstellung eines Stahlbandes gleichbleibender Qualität gewährleistet. Fig. 3 shows the sequence of the described method for starting a casting process in a two-roll caster for a stainless steel Cr-Ni AISI 304 grade steel with a stationary operating casting thickness D = 2.5 mm and an operating casting speed V gBetr = 60 m / min. Prior to the melt feed, the operating nip is set at 2.5 mm and the casting rolls are driven at a peripheral speed corresponding to a starting casting speed v gSt = 10 m / min. With the start of the melt supply, the casting speed v g is continuously increased to the banding casting speed v gBb , which corresponds approximately to the operation casting speed v gBetr = 60 m / min. Shortly after the start of the supply of melt, bridging of the downwardly open casting gap through the forming strand shells occurs at a very low casting speed. This can be seen in the short-term strongly rising curve for the Gießspaltposition G and the casting roll separation force F Tr , which correlate directly. The Gießspaltposition G is measured on the hydraulic piston of an AGC system. With increasing casting speed V g , the tendency of an increasing separation force reverses again, since the strand shell formation decreases because of the shorter residence time of the strand shell in the melt space. The Gießspiegelniveau h Gsp can be measured only after reaching a certain degree of filling, since the melt space is constricted due to the casting roll arrangement to Gießquerschnitt toward funnel-shaped and in this very narrow range a level measurement is not technically feasible. After a period of about 5 to 15 seconds, which can be variably selected, the operating pouring level h Betr is reached and maintained at this level. Thus, approximately constant casting conditions are achieved and the casting speed is increased for a short period of 0.2 sec to the belt separation casting speed v gTr = 80 m / min, which is 20 m / min higher than the stationary operating casting speed v gBetr , At this belt separation casting speed, the cast metal strip tears under the influence of its own weight in the narrowest cross section between the casting rolls. In this case, the casting-roll separation force F Tr falls back to zero for a short time. Returning the casting speed to the value of the operating casting speed v gBetr = 60 m / min., The casting roll separation force F Tr immediately increases to the value before raising the casting speed to the belt separation casting speed. Thus, the conditions for a stationary casting operation are reached and the production of a steel strip consistent quality guaranteed.

Claims (19)

  1. A method for starting a casting operation in a two-roll casting device without start-up strand, characterized by the following steps:
    • setting an operating casting thickness (D) and rotating the casting rolls (1, 2) at a casting-roll circumferential velocity which corresponds to a starting casting velocity (VgSt), which is lower than a steady-state operating casting velocity (VgBetr),
    • feeding metal melt (12) into a melt space (11), which is formed by the rotating casting rolls (1, 2) and the side plates (8) bearing against them, and forming a cast metal strip (21) with a substantially constant, predetermined cross-sectional format while at the same time increasing the casting velocity (Vg) to a strip-forming casting velocity (VgBb),
    • then increasing the casting velocity (Vg) to a strip-separating casting velocity (VgTr), which is significantly higher than a casting velocity (Vg) which is sufficient for the prevailing full solidification conditions, and separating off the metal strip (21) which has been cast thus far,
    • setting a steady-state operating casting velocity (VgBetr),
    • diverting the subsequent cast metal strip (21) to a strip-conveying device (24) and commencing steady-state casting operation.
  2. The method as claimed in claim 1, characterized in that the starting casting velocity (VgSt) is lower than half the operating casting velocity (VgBetr).
  3. The method as claimed in claim 1 or 2, characterized in that the starting casting velocity (VgSt) is less than approximately 12 m/min.
  4. The method as claimed in one of claims 1 to 3, characterized in that the starting casting velocity (VgSt) is still 0 m/min when metal melt starts to be supplied and is then accelerated.
  5. The method as claimed in one of the preceding claims, characterized in that the strip-forming casting velocity (VgBb) is set so as to correspond to a measurably desired mold level (hGsp).
  6. The method as claimed in one of the preceding claims, characterized in that the strip-forming casting velocity (VgBb) substantially corresponds to the steady-state operating casting velocity (VgBetr).
  7. The method as claimed in one of the preceding claims, characterized in that the strip-forming casting velocity (VgBb) is regulated as a function of the separating force (FTr) which occurs between the casting rolls.
  8. The method as claimed in one of the preceding claims, characterized in that the strip-separating casting velocity (VgTr) is higher than the strip-forming casting velocity (VgBb) and/or the operating casting velocity (VgBetr).
  9. The method as claimed in one of claims 1 to 7, characterized in that the strip-separating casting velocity (VgTr) is 5% to 40% higher than the strip-forming casting velocity (VgBb) and/or the operating casting velocity (VgBetr).
  10. The method as claimed in one of the preceding claims, characterized in that a brief increase in the casting thickness (D) by 5 to 40% is superimposed on the increase in the casting velocity to the strip-separating casting velocity (VgTr).
  11. The method as claimed in one of the preceding claims, characterized in that the strip-separating casting velocity (VgTr) is set as soon as the metal melt in the melt space (11) has substantially reached the desired operating mold level (hGsp).
  12. The method as claimed in one of the preceding claims, characterized in that the cast metal strip is separated off at the strip-separating casting velocity (VgTr) by the cast strip being torn off under the action of the metal strip's own weight in the casting nip (18) between the casting rolls (1, 2).
  13. The method as claimed in one of the preceding claims, characterized in that the cast metal strip is separated off at the strip-separating casting velocity (VgTr) under the action of increased strip tension.
  14. The method as claimed in one of the preceding claims, characterized in that the casting velocity (Vg) is increased to approximately the operating casting velocity (VgBetr) at least during a period before the desired operating mold level (hgsp) is reached in the melt space (11).
  15. The method as claimed in one of the preceding claims, characterized in that the steady-state casting operation is reached within 5 to 60 sec of the metal melt first being fed into the melt space (11).
  16. The method as claimed in one of the preceding claims, characterized in that when starting a casting operation for the production of a very thin metal strip, a starting casting thickness (DSt) which is greater than the operating casting thickness (D) is set, and this starting casting thickness is reduced to the operating casting thickness (D) at the earliest after a cast metal strip with a substantially constant, predetermined cross-sectional format has been formed.
  17. The method as claimed in one of the preceding claims, characterized in that at least reference data relating to the instantaneous casting velocity (Vg) and the instantaneous mold level of the metal melt and/or the instantaneous separating force (FTr) between the casting rolls and/or the nip width (G) between the casting rolls and/or the strip thickness of the cast metal strip are determined continuously while casting is starting up and are fed to a calculation unit (36), and on the basis of a mathematical model for the starting operation, these reference data are used to generate control variables for the casting velocity, for the position of a strip-guiding device (22), and for the conveying velocity of the cast metal strip in a strip-conveying device (24) and to transmit these control variables to the drive units (5, 6, 25, 27) of these devices.
  18. The method as claimed in claim 15, characterized in that a control variable for the spacing positioning of the casting rolls (1, 2) with respect to one another, in particular a starting casting thickness (DSt), is additionally generated from the mathematical model.
  19. The method as claimed in claim 15 or 16, characterized in that the mathematical model comprises a metallurgical model relating to the formation of a defined microstructure in the cast metal strip and/or to the influencing of the geometry of the cast metal strip.
EP03798105A 2002-09-12 2003-08-18 Method for commencing a casting process Expired - Lifetime EP1536900B2 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
SI200330195T SI1536900T1 (en) 2002-09-12 2003-08-18 Method and device for commencing a casting process
AT03798105T ATE312676T1 (en) 2002-09-12 2003-08-18 METHOD AND DEVICE FOR STARTING A CASTING PROCESS

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AT13672002 2002-09-12
AT0136702A AT411822B (en) 2002-09-12 2002-09-12 METHOD AND DEVICE FOR STARTING A CASTING PROCESS
PCT/EP2003/009110 WO2004028725A1 (en) 2002-09-12 2003-08-18 Method and device for commencing a casting process

Publications (3)

Publication Number Publication Date
EP1536900A1 EP1536900A1 (en) 2005-06-08
EP1536900B1 EP1536900B1 (en) 2005-12-14
EP1536900B2 true EP1536900B2 (en) 2012-08-15

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US (1) US7156153B2 (en)
EP (1) EP1536900B2 (en)
KR (1) KR101143384B1 (en)
CN (1) CN100577326C (en)
AT (1) AT411822B (en)
AU (1) AU2003258624B2 (en)
DE (1) DE50301955D1 (en)
MX (1) MXPA05002697A (en)
WO (1) WO2004028725A1 (en)

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CN101300092B (en) * 2005-10-28 2011-08-31 诺韦利斯公司 Method for casting metal ingot, metal ingot and method for manufacturing metal sheet product using same
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JP6511968B2 (en) * 2015-06-03 2019-05-15 日産自動車株式会社 Twin-roll vertical casting apparatus and twin-roll vertical casting method
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Also Published As

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CN100577326C (en) 2010-01-06
MXPA05002697A (en) 2005-05-27
CN1681613A (en) 2005-10-12
US20050224210A1 (en) 2005-10-13
WO2004028725A1 (en) 2004-04-08
AU2003258624A1 (en) 2004-04-19
EP1536900B1 (en) 2005-12-14
AU2003258624B2 (en) 2008-11-20
KR101143384B1 (en) 2012-05-23
EP1536900A1 (en) 2005-06-08
US7156153B2 (en) 2007-01-02
KR20050057316A (en) 2005-06-16
ATA13672002A (en) 2003-11-15
AT411822B (en) 2004-06-25
DE50301955D1 (en) 2006-01-19

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