EP0380774B1 - Method of and installation for regulating a liquid metal level in the pouring basin of continuous casting plants for strips - Google Patents

Method of and installation for regulating a liquid metal level in the pouring basin of continuous casting plants for strips Download PDF

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Publication number
EP0380774B1
EP0380774B1 EP89121941A EP89121941A EP0380774B1 EP 0380774 B1 EP0380774 B1 EP 0380774B1 EP 89121941 A EP89121941 A EP 89121941A EP 89121941 A EP89121941 A EP 89121941A EP 0380774 B1 EP0380774 B1 EP 0380774B1
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EP
European Patent Office
Prior art keywords
level
electrode
molten metal
casting
eddy current
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EP89121941A
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German (de)
French (fr)
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EP0380774A3 (en
EP0380774A2 (en
Inventor
Tsuneo Sasaki
Hirotaka Tanaka
Kouichi Ohno
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Krupp Stahl AG
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Krupp Stahl AG
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/18—Controlling or regulating processes or operations for pouring
    • B22D11/181—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level
    • B22D11/186—Controlling or regulating processes or operations for pouring responsive to molten metal level or slag level by using electric, magnetic, sonic or ultrasonic means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
    • B22D11/0637—Accessories therefor
    • B22D11/064—Accessories therefor for supplying molten metal

Definitions

  • the invention relates to a method for controlling the level of the casting level in the casting room of a continuous casting machine, in which the level of the bath level is measured continuously and deviations from a predetermined level are converted into control signals for shifting the level to the specified level, whereby in addition to the continuous contactless level measurement by means of an eddy current sensor at least an actual value of the level of the casting level is measured by the contact of an electrode with the level of the level which can be detected with respect to its height, and the actual value of the contact measurement is used to calibrate the eddy current measurement.
  • the melt itself then creates a conductive connection between the two electrodes and thus triggers a signal indicating this actual value of the level of the mold level, which signal is used to calibrate the eddy current sensor.
  • the actual value of the mold level is not measured at any time, but rather it is confirmed that certain actual values are reached when the melt comes into contact with the counter electrodes.
  • liquid steel will attach to the electrodes of the electrode sensor.
  • the approach of the liquid steel forms a bridge between the electrodes and solidifies slightly, which means that there is a fear that the conductive state will be maintained even if the bath level later drops again.
  • This measuring method which is based on the conductive state of the electrode sensor, is indeed suitable for detecting the bath level at the time of the start of the casting process, but can no longer record the level of the molten steel with high accuracy if the casting level is at its predetermined value, i.e. a certain amount has reached steady state.
  • the bath rises depending on the supply of the molten steel, with no bridge forming to keep the electrodes in a conductive state, so that a certain bath level height can be exactly detected.
  • the mold level measurement must therefore show sensitive fluctuations in the height of the mold level.
  • Continuous, non-contact measurement using an eddy current sensor is very suitable for this purpose, but the measurement result also includes eliminable influences from the electromagnetic properties of the environment. These environmental influences are not fundamentally constant due to thermal deformations of the device and can thus lead to more or less significant distortions in the height measurement and to errors in the mold level control in the course of the casting time.
  • the object of the invention is to avoid these disadvantages and the disadvantages inherent in a stationary electrode sensor and to provide a method for regulating the level of the mold level, the reliability of which is maintained over the entire casting time.
  • Another object of the invention is to provide a device which is particularly suitable for solving the process technology.
  • the object is achieved in that the contact measurement is repeated periodically throughout the casting by means of a vertically movable electrode and the eddy current measurement is calibrated after each repetition.
  • the electrode passes through a stationary light barrier on its lowering path in the direction of the bath level before reaching the bath level and the travel of the electrode from the light barrier to contact with the casting level is measured in order to record the actual value of the level of the casting level.
  • a device for regulating the level of the casting level in the casting room of a continuous casting line is proposed with an eddy current sensor above the melting bath, with an electrode which is in contact with the melt when the actual value of a level of the leveling level is detected, with a control device to which the eddy current sensor and the electrode are connected and which contains a program with which the continuous signal sequences of the eddy current sensor can be converted into control signals, taking into account the actual value signal of the electrode, with which at least one of the casting parameters feed quantity of the molten metal into the casting chamber and casting speed for the purpose of shifting the Casting level can be changed to a predetermined level.
  • the electrode can be moved vertically and the path of travel of the electrode can be detected, and that a light barrier or the like is arranged above the weld pool and above the highest intended height of the casting level and in the path of travel of the electrode.
  • a graphite electrode is expediently used to largely rule out melting of the electrode on the electrode.
  • the eddy current sensor 5 is connected to a control unit 7 via a line 6.
  • An electrode 8 is arranged on an electrode suspension 9 above the weld pool 3 and can be moved vertically by activating a reversible stepper motor 10.
  • the respective position of the electrode 8 is entered into the control unit by the stepper motor via a line 11.
  • the dashed electrode 8 ' has contact with the casting mirror 4, whereby a contact is triggered by the contact with the electrode 8', which is also transmitted to the control unit 7 via the electrode suspension 9 and the line 11.
  • a light barrier consisting of transmitter 12, receiver 13 and light beam, here a laser beam 14, is also connected to control unit 7 via a further line 15.
  • a deflection roller 16 and a shielding tube 17 are provided.
  • the travel path 18 of the electrode 8 is indicated by a dash-dotted line which crosses the light beam 14 of the light barrier at point A; contact point B is assigned to the lower position of electrode 8 '.
  • FIG. 2 shows a top view of the casting vessel 1 of a belt casting installation, a shielding plate 19 being provided here between the eddy current sensor 5 and the electrode 8.
  • a carrying device 20 holds the eddy current sensor 5.
  • the casting nozzle 21 which forms the casting slot in a two-roll belt casting machine together with two cooled casting rolls, not shown, arranged one above the other.
  • the mold level H is plotted against the casting time t, where h1, h2, h3, h4 is a height difference between the value indicated by the eddy current sensor 5 and measured by the electrode 8 at the casting times t1, t2, t3 and t4 specify.
  • 1 is a system for direct measurement of the bath level using the touch method, with the aim of obtaining the correction information for the eddy current sensor 5.
  • a touch-type measuring terminal namely an electrode 8 is attached above the bath level 4 and is moved up and down at a constant speed by means of the stepping motor 10 or a similar motor which can measure the rotation exactly.
  • the electrode 8 is made of graphite, so that a current can flow when it contacts the lower end of the bath level 4. It moves up and down in travel path 18. So that you can see whether the electrode 8 is at point A or not, the optical system consisting of transmitter 12 and receiver 13 is installed. If e.g. B.
  • a laser beam 14 is emitted from the transmitter 12, the light path being interrupted by the electrode 8, it is perceived that the electrode 8 is located at point A.
  • another sensor element - such as. B. a limit switch - can also be used.
  • the electrode 8 is lowered from the stepping motor 10 to the contact point B. If this is an electrode 8 made of graphite, this is put under tension via a wire. If the electrode 8 touches the bath level 4, a current flows, the detection of which can be used as evidence of whether the electrode 8 is at the contact point B or not.
  • the movement distance between point A and contact point B can be found out by counting the steps on the stepping motor 10.
  • the mold level 4 of the melting bath 3 can be measured with a high accuracy of less than +/- 0.1 mm.
  • the mold level 4 measured in this way is fed to the control unit 7 in order to be used as information for the correction of the value measured by the eddy current sensor 5. Since point A can be set at a point distant from the bath level 4 using the above-mentioned method, it is to be avoided that the electrode 8 is exposed to a high temperature of the heat radiated from the bath level 4. This means that the bath level 4 can be measured with high accuracy without being influenced by temperatures and thermal expansion, etc.
  • the electrode 8 can be used repeatedly because the measuring principle for detecting the bath level is not based on a conductive state. Furthermore, since the electrode 8 located at the contact point B is detected with the help of the laser beam 14 when starting up again, the liquid steel or the base metal which is being deposited has no influence on the measuring accuracy. When the electrode 8 moves up or down, its position and movement could influence the measurement result of the eddy current sensor 5. It is therefore recommended to attach a shielding tube 17 or a shielding plate 19 around the electrode 8.
  • FIG 2 shows a top view of how the electrode 8 is shielded from the eddy current sensor 5 by the shielding plate 19. Waves form on the bath surface during the supply of the liquid steel or the casting process, which can also influence the measurement result of the electrode 8.
  • electrodes 8 can be arranged at several points in the casting chamber, so that the casting level 4 can be detected based thereon by one or more of the electrodes 8 responding by contact with the bath level 4; thus the influence of wave formation can be suppressed.
  • the invention was tested with a two-roll belt casting machine in the production of stainless steel strips.
  • Liquid stainless steel with SUS 304 composition was fed to the melt pool 3 and tapes cast 2.0 mm thick and 650 mm wide.
  • the behavior of the casting level 4 of the liquid steel supplied to the molten bath 3 after the start of the feed was recorded as a diagram in FIG. 3, which showed an increasing curve.
  • the bath level 4 was measured by means of the electrode 8 at the time t1 during the supply of liquid steel, the value measured by the eddy current sensor 5 was subject to error h1.
  • the error h1 is calculated in the control unit 7 so that the value detected by the eddy current sensor 5 is corrected upwards.
  • the level in the casting room 2 increased even further.
  • the measured value of the eddy current sensor 5 had an error h2.
  • the value detected by the eddy current sensor 5 was corrected upwards in the same way.
  • the bath level was measured periodically by means of the electrode 8.
  • the respective measured value of the eddy current sensor 5 was corrected upwards or downwards accordingly. In this way, the liquid steel was fed while maintaining the casting level 4 at the desired level, so that strips were cast.
  • the example explained above was a continuous casting machine using the duo-roll process with different roll diameters.
  • the present invention is in no way restricted by the example explained here and can be applied to the other continuous casting machines which work with the duo-roll, single drum, single belt, duo belt, roller belt method and others, in which the liquid steel released in the bath is rapidly removed Cooling and solidification tapes are made.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Casting Support Devices, Ladles, And Melt Control Thereby (AREA)

Abstract

The invention relates to the regulation of the liquid metal level in the pouring basin 2 of a continuous casting plant and provides that the liquid metal level 4 should be measured continuously in contactless fashion via an eddy-current sensor 5, that the eddy-current sensor 5 should be calibrated periodically by measurement involving contact, via an electrode 8 which can be raised and lowered, and that the passage of the electrode 8 through a fixed point, the point A, be monitored by means of a laser beam 14.

Description

Die Erfindung betrifft ein Verfahren zur Regelung der Gießspiegelhöhe im Gießraum einer Bandstranggießanlage, bei dem die Badspiegelhohe kontinuierlich gemessen wird und Abweichungen von einer vorgegebenen Höhenlage in Steuersignale zur Verschiebung des Gießspiegels auf die vorgebene Höhenlage umgesetzt werden, wobei neben der kontinuierlichen berührungslosen Höhenmessung mittels eines Wirbelstromsensors wenigstens ein Istwert der Gießspiegelhöhe durch den bezüglich seiner Höhenlage erfaßbaren Kontakt einer Elektrode mit dem Gießspiegel gemessen und der Istwert der Kontaktmessung zur Eichung der Wirbelstrommessung verwendet wird.
Ausgehend von der europäischen Patentanmeldung 83 102 701.1 (Veröffentlichungsnummer 0 194 327), die ein Verfahren zur Regelung der Lage des Gießspiegels im Gießraum einer Bandstranggießanlage betrifft, bei dem die von der Badspiegelhöhe abhängigen Meßsignale von Sensoreinheiten in Steuersignale zur Veränderung des Gießspiegels auf eine vongegebene Gießspiegelhöhe umgesetzt werden, wird in der DE-A-3 934 975 (veröffentlicht nach dem Anmeldetag der vorleigenden Erfindung) vorgeschlagen, für die Höhenmessung einen Wirbelstomsensor einzusetzen und diesen mir einem in das Schmelzbad eingetauchten Elektrodenmeßfühler zu eichen.
Dieser Elektrodenmeßfühler sieht eine ständig eingetauchte längere und eine kürzere Gegenelektrode vor, die erst Kontakt mit der Schmelze bekommt, wenn der Badspiegel entsprechend weit angestiegen ist.The invention relates to a method for controlling the level of the casting level in the casting room of a continuous casting machine, in which the level of the bath level is measured continuously and deviations from a predetermined level are converted into control signals for shifting the level to the specified level, whereby in addition to the continuous contactless level measurement by means of an eddy current sensor at least an actual value of the level of the casting level is measured by the contact of an electrode with the level of the level which can be detected with respect to its height, and the actual value of the contact measurement is used to calibrate the eddy current measurement.
Starting from the European patent application 83 102 701.1 (publication number 0 194 327), which relates to a method for regulating the position of the pouring level in the casting room of a continuous casting machine, in which the measurement signals, which are dependent on the level of the bath level, are sent from sensor units into control signals for changing the level to a given level implemented, it is proposed in DE-A-3 934 975 (published after the filing date of the present invention) to use an eddy current sensor for height measurement and to calibrate it with an electrode sensor immersed in the molten bath.
This electrode sensor provides a constantly immersed longer and a shorter counter electrode, which only comes into contact with the melt when the bath level has risen accordingly.

Die Schmelze selbst stellt dann eine leitende Verbindung zwischen den beiden Elektroden her und löst so ein diesen Istwert der Gießspiegelhöhe anzeigendes Signal aus, das zur Eichung des Wirbelstromsensors verwendet wird. Auch bei einem Elektrodenmeßfühler mit mehreren Gegenelektroden wird nicht der Istwert der Gießspiegelhöhe zu einem beliebigen Zeitpunkt gemessen sondern bestätigt, daß bestimmte Istwerte beim Kontakt der Schmelze mit den Gegenelektroden jeweils erreicht sind.
Bei diesem Verfahren ist es unvermeidbar, daß sich an den Elektroden des Elektrodenmeßfühlers beispielsweise flüssiger Stahl ansetzt. Der Ansatz des flüssigen Stahls bildet eine Brücke zwischen den Elektroden und erstarrt leicht, wodurch zu befürchten ist, daß auch dann der leitende Zustand aufrechterhalten bleibt, wenn später der Badspiegel wieder absinkt.
Dieses Meßverfahren, das auf dem leitenden Zustand des Elektrodenmeßfühlers beruht, ist zwar zur Erfassung des Badspiegels zum Zeitpunkt des Beginns des Gießvorganges geeignet, kann aber den Stand des flüssigen Stahls nicht mehr mit hoher Genauigkeit erfassen, wenn der Gießspiegel seinen vorgegebenen Wert, also einen gewissen stationären Zustand erreicht hat. Beim Beginn des Vergießens steigt das Bad je nach Zufuhr des flüssigen Stahles an, wobei sich keine Brücke, die die Elektroden in leitendem Zustand hält, bildet, so daß eine bestimmte Badspiegelhöhe exakt nachgewiesen werden kann.
Nach dem Angießen kommt es nun darauf an, einen vorgegebenen Gießspiegel so genau wie möglich einzuhalten, um ein dünnes Band konstanter Dicke und hoher Qualität erzeugen zu können. Die Gießspiegelmessung muß also feinfühlig Schwankungen der Gießspiegelhöhe anzeigen. Hierfür ist die kontinuierliche, berührungslose Messung mittels eines Wirbelstromsensors an sich sehr geeignet, doch gehen in das Meßergebnis auch eliminierbare Einflüsse aus den elektromagnetischen Eigenschaften des Umfeldes ein. Diese Umgebungseinflüsse sind aufgrund thermischer Verformungen der Vorrichtung nicht grundsätzlich konstant und können so im Laufe der Gießzeit zu mehr oder weniger bedeutenden Verzerrungen der Höhenmessung und zu Fehlern in der Gießspiegelregelung führen.The melt itself then creates a conductive connection between the two electrodes and thus triggers a signal indicating this actual value of the level of the mold level, which signal is used to calibrate the eddy current sensor. Even in the case of an electrode sensor with several counter electrodes, the actual value of the mold level is not measured at any time, but rather it is confirmed that certain actual values are reached when the melt comes into contact with the counter electrodes.
With this method, it is inevitable that, for example, liquid steel will attach to the electrodes of the electrode sensor. The approach of the liquid steel forms a bridge between the electrodes and solidifies slightly, which means that there is a fear that the conductive state will be maintained even if the bath level later drops again.
This measuring method, which is based on the conductive state of the electrode sensor, is indeed suitable for detecting the bath level at the time of the start of the casting process, but can no longer record the level of the molten steel with high accuracy if the casting level is at its predetermined value, i.e. a certain amount has reached steady state. At the start of casting, the bath rises depending on the supply of the molten steel, with no bridge forming to keep the electrodes in a conductive state, so that a certain bath level height can be exactly detected.
After casting, it is now important to adhere to a given casting level as precisely as possible in order to be able to produce a thin strip of constant thickness and high quality. The mold level measurement must therefore show sensitive fluctuations in the height of the mold level. Continuous, non-contact measurement using an eddy current sensor is very suitable for this purpose, but the measurement result also includes eliminable influences from the electromagnetic properties of the environment. These environmental influences are not fundamentally constant due to thermal deformations of the device and can thus lead to more or less significant distortions in the height measurement and to errors in the mold level control in the course of the casting time.

Aufgabe der Erfindung ist es, diese Nachteile und die einem stationären Elektrodenmeßfühler anhaftenden Nachteile zu vermeiden und ein Verfahren zur Regelung der Gießspiegelhöhe zu schaffen, dessen Zuverlässigkeit über die gesamte Gießzeit erhalten bleibt.
Eine weitere Aufgabe der Erfindung ist es, eine insbesondere für die Lösung der Verfahrenstechnik geeignete Einrichtung bereitzustellen.The object of the invention is to avoid these disadvantages and the disadvantages inherent in a stationary electrode sensor and to provide a method for regulating the level of the mold level, the reliability of which is maintained over the entire casting time.
Another object of the invention is to provide a device which is particularly suitable for solving the process technology.

Verfahrenstechnisch wird die Aufgabe dadurch gelöst, daß die Kontaktmessung mittels einer vertikal verfahrbaren Elektrode während des gesamten Gusses periodisch wiederholt wird und nach jeder Wiederholung eine Eichung der Wirbelstrommessung erfolgt.In terms of process technology, the object is achieved in that the contact measurement is repeated periodically throughout the casting by means of a vertically movable electrode and the eddy current measurement is calibrated after each repetition.

Gemäß einer Weiterentwicklung der Erfindung ist vorgesehen, daß die Elektrode auf ihrem Absenkweg in Richtung auf den Badspiegel vor Erreichen des Badspiegels eine ortsfeste Lichtschranke durchläuft und zur Erfassung des Istwertes der Gießspiegelhöhe der Verfahrweg der Elektrode von der Lichtschranke bis zum Kontakt mit dem Gießspiegel gemessen wird.
Zur Durchführung des erfindungsgemäßen Verfahrens wird eine Einrichtung zur Regelung der Gießspiegelhöhe im Gießraum einer Bandstranggießanlage vorgeschlagen mit einem Wirbelstromsensor über dem Schmelzbad, mit einer Elektrode, die bei Erfassung des Istwertes einer Höhenlage des Gießspiegels in Kontakt mit der Schmelze ist, mit einer Steuervorrichtung, an die der Wirbelstromsensor und die Elektrode angeschlossen sind und die ein Programm enthält, mit dem die kontinuierlichen Signalfolgen des Wirbelstromsensors unter Berücksichtigung des Istwertsignals der Elektrode in Steuersignale umsetzbar sind, mit denen wenigstens einer der Gießparameter Zuführmenge der Metallschmelze in den Gießraum und Gießgeschwindigkeit zum Zwecke der Verschiebung des Gießspiegels auf eine vorgegebene Gießspiegelhöhe veränderbar ist.According to a further development of the invention, it is provided that the electrode passes through a stationary light barrier on its lowering path in the direction of the bath level before reaching the bath level and the travel of the electrode from the light barrier to contact with the casting level is measured in order to record the actual value of the level of the casting level.
In order to carry out the method according to the invention, a device for regulating the level of the casting level in the casting room of a continuous casting line is proposed with an eddy current sensor above the melting bath, with an electrode which is in contact with the melt when the actual value of a level of the leveling level is detected, with a control device to which the eddy current sensor and the electrode are connected and which contains a program with which the continuous signal sequences of the eddy current sensor can be converted into control signals, taking into account the actual value signal of the electrode, with which at least one of the casting parameters feed quantity of the molten metal into the casting chamber and casting speed for the purpose of shifting the Casting level can be changed to a predetermined level.

Sie ist erfindungsgemäß derart gestaltet, daß die Elektrode vertikal verfahrbar und der Verfahrweg der Elektrode erfaßbar ist, und daß über dem Schmelzbad und über der höchsten vorgesehenen Höhenlage des Gießspiegels und im Verfahrweg der Elektrode eine Lichtschranke oder dergleichen angeordnet ist.
Um Anbackungen von Schmelze an der Elektrode weitgehend auszuschließen wird zweckmäßigerweise eine Graphitelektrode verwendet.It is designed according to the invention in such a way that the electrode can be moved vertically and the path of travel of the electrode can be detected, and that a light barrier or the like is arranged above the weld pool and above the highest intended height of the casting level and in the path of travel of the electrode.
A graphite electrode is expediently used to largely rule out melting of the electrode on the electrode.

Die Erfindung wird nachfolgend anhand der Figuren beschrieben.
Es zeigt schematisch:

Fig. 1
eine Gießspiegelregelung einer Bandstranggießanlage
Fig. 2
eine Draufsicht auf das Gießgefäß einer Bandstranggießanlage
Fig. 3
ein Gießdiagramm
Fig. 1 zeigt aus einer Bandstranggießanlage ein Gießgefäß 1 im Schnitt, dessen Gießraum 2 ein Schmelzbad 3 enthält. Die mit überhöhten Wellen anschaulich dargestellte Oberfläche des Schmelzbades 3 ist im Gießbetrieb der Gießspiegel 4, der beim Bandstranggießen auf einer vorgegebenen Höhenlage zu halten ist. Über dem Schmelzbad 3 ist im Gießraum 2 ein Wirbelstromsensor 5 ortsfest angeordnet, mit dessen Hilfe über die Veränderung der Flußdichte in einer Spule die Höhenlage des Gießspiegels 4 kontinuierlich berührungslos gemessen wird.
Unter dem Wirbelstromsensor 5 sei eine stromdurchflossene Spule verstanden, die bekanntlich aufgrund des durchfließenden Stromes ein Magnetfeld erzeugt. Das Magnetfeld wird beeinflußt, wenn sich ihm ein elektrisch leitender Körper, hier der Gießspiegel 4 nähert. Diese Beeinflussung bewirkt eine Veränderung des Stromflusses in der Spule, die erfaßt und in einen Höhenwert des Gießspiegels 4 umgesetzt werden kann.The invention is described below with reference to the figures.
It shows schematically:
Fig. 1
a mold level control of a continuous strip caster
Fig. 2
a plan view of the casting vessel of a continuous strip caster
Fig. 3
a casting diagram
1 shows a casting vessel 1 in section from a continuous strip casting plant, the casting chamber 2 of which contains a molten bath 3. The surface of the melting bath 3, which is clearly illustrated with excessive waves, is the casting level 4 in the casting operation, which is to be kept at a predetermined height during strip casting. Above the melt pool 3, an eddy current sensor 5 is arranged in a fixed manner in the casting chamber 2, with the aid of which the height of the casting level 4 is continuously measured without contact by changing the flux density in a coil.
The eddy current sensor 5 is understood to be a current-carrying coil which, as is known, generates a magnetic field due to the current flowing through it. The magnetic field is influenced when an electrically conductive body, here the mold level 4, approaches it. This influence causes a change in the current flow in the coil, which can be detected and converted into a height value of the casting level 4.

Der Wirbelstromsensor 5 steht über eine Leitung 6 mit einem Steuergerät 7 in Verbindung.
Über dem Schmelzbad 3 ist eine Elektrode 8 an einer Elektrodenaufhängung 9 angeordnet und vertikal verfahrbar, indem ein reversierbarer Schrittmotor 10 aktiviert wird. Die jeweilige Position der Elektrode 8 wird vom Schrittmotor über eine Leitung 11 dem Steuergerät eingegeben.
In ihrer unteren Position hat die gestrichelt gezeichnete Elektrode 8' Kontakt mit dem Gießspiegel 4, wobei dabei durch den Kontakt von der Elektrode 8' ein Signal ausgelöst wird, welches über die Elektrodenaufhängung 9 und die Leitung 11 ebenfalls dem Steuergerät 7 übertragen wird.
Eine aus Sender 12, Empfänger 13 und Lichtstrahl, hier einem Laserstrahl 14 bestehende Lichtschranke steht mit einer weiteren Leitung 15 ebenfalls mit dem Steuergerät 7 in Verbindung.
Weiterhin sind eine Umlenkrolle 16 und ein Abschirmrohr 17 vorgesehen.
Der Verfahrweg 18 der Elektrode 8 ist durch eine strichpunktierte Linie angedeutet, die den Lichtstrahl 14 der Lichtschranke im Punkt A kreuzt; der unteren Position der Elektrode 8' ist der Kontaktpunkt B zugeordnet.The eddy current sensor 5 is connected to a control unit 7 via a line 6.
An electrode 8 is arranged on an electrode suspension 9 above the weld pool 3 and can be moved vertically by activating a reversible stepper motor 10. The respective position of the electrode 8 is entered into the control unit by the stepper motor via a line 11.
In its lower position, the dashed electrode 8 'has contact with the casting mirror 4, whereby a contact is triggered by the contact with the electrode 8', which is also transmitted to the control unit 7 via the electrode suspension 9 and the line 11.
A light barrier consisting of transmitter 12, receiver 13 and light beam, here a laser beam 14, is also connected to control unit 7 via a further line 15.
Furthermore, a deflection roller 16 and a shielding tube 17 are provided.
The travel path 18 of the electrode 8 is indicated by a dash-dotted line which crosses the light beam 14 of the light barrier at point A; contact point B is assigned to the lower position of electrode 8 '.

Fig. 2 zeigt eine Draufsicht auf das Gießgefäß 1 einer Bandgießanlage, wobei hier zwischen dem Wirbelstromsensor 5 und der Elektrode 8 eine Abschirmplatte 19 vorgesehen ist. Eine Tragvorrichtung 20 hält den Wirbelstromsensor 5. Am vorderen Ende des Gießgefäßes 1 liegt die Gießdüse 21, die bei einer Zweirollen-Bandgießmaschine zusammen mit zwei übereinander angeordneten, nicht dargestellten gekühlten Gießwalzen den Gießschlitz bildet.FIG. 2 shows a top view of the casting vessel 1 of a belt casting installation, a shielding plate 19 being provided here between the eddy current sensor 5 and the electrode 8. A carrying device 20 holds the eddy current sensor 5. At the front end of the casting vessel 1 is the casting nozzle 21, which forms the casting slot in a two-roll belt casting machine together with two cooled casting rolls, not shown, arranged one above the other.

In dem Gießdiagramm nach Fig. 3 ist die Gießspiegelhöhe H über der Gießzeit t aufgetragen, wobei h1, h2, h3, h4 eine Höhendifferenz zwischen dem vom Wirbelstromsensor 5 angezeigten und von der Elektrode 8 gemessenen Wert zu den Gießzeiten t1, t2, t3 und t4 angeben.3, the mold level H is plotted against the casting time t, where h1, h2, h3, h4 is a height difference between the value indicated by the eddy current sensor 5 and measured by the electrode 8 at the casting times t1, t2, t3 and t4 specify.

Im Folgenden wird anhand der Figuren das Wesentliche der vorliegenden Erfindung zusammen mit ihrer Wirkung weiter erklärt. Bei Fig. 1 handelt es sich um ein System zur direkten Messung des Badspiegels nach dem Berührungsverfahren, und zwar mit dem Ziel, die Korrekturinformation für den Wirbelstromsensor 5 zu bekommen. Über dem Badspiegel 4 wird ein Meßterminal vom Berührungs-Typ, nämlich eine Elektrode 8 angebracht, welche mittels des Schrittmotors 10 oder eines ähnlichen Motors, der die Drehung exakt messen kann, mit einer konstanten Geschwindigkeit auf- bzw. abwärts bewegt wird. Die Elektrode 8 besteht aus Graphit, so daß bei der Berührung von deren unterem Ende mit dem Badspiegel 4 ein Strom fließen kann. Sie bewegt sich im Verfahrweg 18 auf und ab. Damit man erkennt, ob sich die Elektrode 8 am Punkt A befindet oder nicht, ist das aus Sender 12 und Empfänger 13 bestehende optische System installiert. Wenn z. B. ein Laserstrahl 14 aus dem Sender 12 emittiert wird, wobei der Lichtweg durch die Elektrode 8 unterbrochen wird, wird wahrgenommen, daß sich die Elektrode 8 am Punkt A befindet. Zur Erfassung am Bezugspunkt A kann ein anderes Sensorelement - wie z. B. ein Grenzschalter - ebenfalls verwendet werden. Ausgehend von dem obigen Zustand, wird die Elektrode 8 vom Schrittmotor 10 bis zum Kontaktpunkt B herabgelassen. Wenn es sich dabei um eine Elektrode 8 handelt, die aus Graphit besteht, wird diese über einen Draht unter Spannung gesetzt. Berührt die Elektrode 8 den Badspiegel 4, so fließt ein Strom, dessen Erfassung als Nachweis dafür herangezogen werden kann, ob sich die Elektrode 8 am Berührungspunkt B befindet oder nicht. Umgekehrt kann die Elektrode 8' am Kontaktpunkt B eingestellt und von dort nach oben bewegt werden, damit die Bewegungsstrecke, die die Elektrode 8 vom Kontaktpunkt B bis zum Punkt A zurücklegt, gemessen werden kann.In the following, the essentials of the present invention, together with its effect, are further explained on the basis of the figures. 1 is a system for direct measurement of the bath level using the touch method, with the aim of obtaining the correction information for the eddy current sensor 5. A touch-type measuring terminal, namely an electrode 8, is attached above the bath level 4 and is moved up and down at a constant speed by means of the stepping motor 10 or a similar motor which can measure the rotation exactly. The electrode 8 is made of graphite, so that a current can flow when it contacts the lower end of the bath level 4. It moves up and down in travel path 18. So that you can see whether the electrode 8 is at point A or not, the optical system consisting of transmitter 12 and receiver 13 is installed. If e.g. B. a laser beam 14 is emitted from the transmitter 12, the light path being interrupted by the electrode 8, it is perceived that the electrode 8 is located at point A. For detection at reference point A, another sensor element - such as. B. a limit switch - can also be used. Starting from the above state, the electrode 8 is lowered from the stepping motor 10 to the contact point B. If this is an electrode 8 made of graphite, this is put under tension via a wire. If the electrode 8 touches the bath level 4, a current flows, the detection of which can be used as evidence of whether the electrode 8 is at the contact point B or not. Conversely, the electrode 8 'can be set at the contact point B and moved upwards from there, so that the movement distance which the electrode 8 travels from the contact point B to the point A can be measured.

Der Bewegungsabstand zwischen Punkt A und Kontaktpunkt B kann durch Zählung der Schritte am Schrittmotor 10 in Erfahrung gebracht werden. Nach dem hier beschriebenen Verfahren läßt sich der Gießspiegel 4 des Schmelzbades 3 mit einer unter +/- 0,1 mm liegenden hohen Genauigkeit messen. Der so gemessene Gießspiegel 4 wird dem Steuergerät 7 zugeführt, um als Information zur Korrektur an dem durch den Wirbelstromsensor 5 gemessenen Wert herangezogen zu werden.
Da nach dem o.g. Verfahren der Punkt A an einer vom Badspiegel 4 entfernten Stelle eingestellt werden kann, ist zu vermeiden, daß die Elektrode 8 einer hohen Temperatur der vom Badspiegel 4 ausgestrahlten Wärme ausgesetzt wird. Dies bedeutet, daß ohne Beeinflussung durch Temperaturen und thermische Ausdehnung usw. der Badspiegel 4 mit hoher Genauigkeit gemessen werden kann.
Auch wenn sich an der Spitze der Elektrode 8 beispielsweise flüssiger Stahl einmal angesetzt hat, kann die Elektrode 8 wiederholt benutzt werden, weil das Meßprinzip zur Erfassung des Badspiegels nicht auf leitendem Zustand beruht. Da ferner die am Kontaktpunkt B befindliche Elektrode 8 beim Wiederhochfahren mit Hilfe des Laserstrahles 14 erfaßt wird, bleibt der sich ansetzende flüssige Stahl oder das Grundmetall ohne Einfluß auf die Meßgenauigkeit.
Bei auf- oder abwärtiger Bewegung der Elektrode 8 könnte es vorkommen, daß dessen Position und Bewegung das Meßergebnis des Wirbelstromsensors 5 beeinflußt. Deshalb ist es zu empfehlen, um die Elektrode 8 ein Abschirmrohr 17 oder eine Abschirmplatte 19 anzubringen.The movement distance between point A and contact point B can be found out by counting the steps on the stepping motor 10. According to the method described here, the mold level 4 of the melting bath 3 can be measured with a high accuracy of less than +/- 0.1 mm. The mold level 4 measured in this way is fed to the control unit 7 in order to be used as information for the correction of the value measured by the eddy current sensor 5.
Since point A can be set at a point distant from the bath level 4 using the above-mentioned method, it is to be avoided that the electrode 8 is exposed to a high temperature of the heat radiated from the bath level 4. This means that the bath level 4 can be measured with high accuracy without being influenced by temperatures and thermal expansion, etc.
Even if, for example, liquid steel has once deposited on the tip of the electrode 8, the electrode 8 can be used repeatedly because the measuring principle for detecting the bath level is not based on a conductive state. Furthermore, since the electrode 8 located at the contact point B is detected with the help of the laser beam 14 when starting up again, the liquid steel or the base metal which is being deposited has no influence on the measuring accuracy.
When the electrode 8 moves up or down, its position and movement could influence the measurement result of the eddy current sensor 5. It is therefore recommended to attach a shielding tube 17 or a shielding plate 19 around the electrode 8.

In Fig. 2 ist als Draufsicht dargestellt, wie die Elektrode 8 durch die Abschirmplatte 19 vom Wirbelstromsensor 5 abgeschirmt ist.
An der Badoberfläche bilden sich während der Zufuhr des flüssigen Stahls oder des Gießvorganges Wellen, welche ebenfalls das Meßergebnis der Elektrode 8 beeinflussen können.2 shows a top view of how the electrode 8 is shielded from the eddy current sensor 5 by the shielding plate 19.
Waves form on the bath surface during the supply of the liquid steel or the casting process, which can also influence the measurement result of the electrode 8.

In diesem Fall können an mehreren Stellen im Gießraum 2 Elektroden 8 angeordnet werden, damit man darauf beruhend den Gießspiegel 4 erfaßt, indem eine oder mehrere der Elektroden 8 durch Berührung mit dem Badspiegel 4 angesprochen haben; somit kann der Einfluß von Wellenbildung unterdrückt werden.In this case, electrodes 8 can be arranged at several points in the casting chamber, so that the casting level 4 can be detected based thereon by one or more of the electrodes 8 responding by contact with the bath level 4; thus the influence of wave formation can be suppressed.

Die Erfindung wurde mit einer Zweirollen-Bandgießmaschine bei der Herstellung von Edelstahlbändern erprobt.
Flüssiger nichtrostender Stahl mit SUS 304-Zusammensetzung wurde dem Schmelzbad 3 zugeführt und Bänder mit einer Dicke von 2,0 mm und einer Breite von 650 mm gegossen. Das Verhalten des Gießspiegels 4 des dem Schmelzbad 3 gelieferten flüssigen Stahls nach Beginn der Zufuhr nahm man als Diagramm Fig. 3 auf, das einen ansteigenden Kurvenverlauf verzeichnete. Als jedoch zum Zeitpunkt t1 während der Zufuhr von flüssigem Stahl der Badspiegel 4 mittels der Elektrode 8 gemessen wurde, war der vom Wirbelstromsensor 5 gemessene Wert mit Fehler h1 behaftet. Infolgedessen wird der Fehler h1 im Steuergerät 7 errechnet, damit der vom Wirbelstromsensor 5 erfaßte Wert nach oben korrigiert wird.
Bei fortgesetzter Zufuhr von flüssigem Stahl erhöhte sich der Füllstand im Gießraum 2 noch weiter. Zu dem Zeitpunkt t2, wo der Gießspiegel 4 sein stationäres Niveau erreichte, wurde dieser erneut mittels der Elektrode 8 gemessen. Dabei wurde festgestellt, daß der Meßwert des Wirbelstromsensors 5 mit Fehler h2 behaftet war. Beruhend auf dem Meßfehler h2 wurde auf gleiche Weise der vom Wirbelstromsensor 5 erfaßte Wert nach oben korrigiert.
Im Stadium, in dem der Badspiegel 4 des Schmelzbades 3 seinen stationären Zustand erreichte, wurde das Badniveau mittels der Elektrode 8 periodisch gemessen. Unter Zugrundelegung des jeweils zum Zeitpunkt t3, t4 festgestellten Meßfehlers h3, h4 wurde der jeweilige Meßwert des Wirbelstromsensors 5 nach oben bzw. unten entsprechend korrigiert. Auf diese Weise wurde unter Aufrechterhaltung des Gießspiegels 4 auf dem Soll-Niveau der flüssige Stahl zugeführt, so daß Bänder gegossen wurden.The invention was tested with a two-roll belt casting machine in the production of stainless steel strips.
Liquid stainless steel with SUS 304 composition was fed to the melt pool 3 and tapes cast 2.0 mm thick and 650 mm wide. The behavior of the casting level 4 of the liquid steel supplied to the molten bath 3 after the start of the feed was recorded as a diagram in FIG. 3, which showed an increasing curve. However, when the bath level 4 was measured by means of the electrode 8 at the time t1 during the supply of liquid steel, the value measured by the eddy current sensor 5 was subject to error h1. As a result, the error h1 is calculated in the control unit 7 so that the value detected by the eddy current sensor 5 is corrected upwards.
With continued supply of liquid steel, the level in the casting room 2 increased even further. At the point in time t2 when the casting level 4 reached its stationary level, this was measured again by means of the electrode 8. It was found that the measured value of the eddy current sensor 5 had an error h2. Based on the measurement error h2, the value detected by the eddy current sensor 5 was corrected upwards in the same way.
In the stage in which the bath level 4 of the molten bath 3 reached its steady state, the bath level was measured periodically by means of the electrode 8. On the basis of the measurement error h3, h4 determined at the time t3, t4, the respective measured value of the eddy current sensor 5 was corrected upwards or downwards accordingly. In this way, the liquid steel was fed while maintaining the casting level 4 at the desired level, so that strips were cast.

Die so unter Konstanthaltung des Gießspiegels 4 auf dem Soll-Wert während gesamter Phase des Bandgießens, also unter stabiler Betriebsbedingung hergestellten Bänder wiesen weder fehlerhafte Banddicke noch Gaseinschluß usw. auf und zeichneten sich durch hervorragende Eigenschaft aus.
Bei dem oben erläuterten Beispiel handelte es sich um eine Stranggießmaschine nach dem Duowalzenverfahren mit unterschiedlichen Walzendurchmessern. Doch die vorliegende Erfindung wird keineswegs durch das hier erläuterte Bei spiel eingeschränkt und kann auf die sonstigen nach dem Duowalzen-, Einzeltrommel-, Einzelgürtel-, Duogürtel-, Walzengürtelverfahren u. a. arbeitenden Stranggießmaschinen angewandt werden, bei denen aus dem im Bad abgegebenen flüssigen Stahl durch rasche Abkühlung und Erstarrung Bänder hergestellt werden.The strips produced in this way while keeping the casting level 4 constant at the desired value during the entire phase of the strip casting, that is to say under stable operating conditions, had neither defective strip thickness nor gas inclusion, etc. and were distinguished by excellent properties.
The example explained above was a continuous casting machine using the duo-roll process with different roll diameters. However, the present invention is in no way restricted by the example explained here and can be applied to the other continuous casting machines which work with the duo-roll, single drum, single belt, duo belt, roller belt method and others, in which the liquid steel released in the bath is rapidly removed Cooling and solidification tapes are made.

Claims (4)

  1. A method and apparatus for controlling the level of molten metal in the pouring basin of a continuous strip casting installation, wherein said level is continuously measured and deviations from a required height are converted into control signals to displace said level to the required height, wherein besides the continuous contactless measuring of the height by means of an eddy current sensor, at least one actual value of the height of the level being measured by the contact, whose height can be determined, of an electrode with the level of the molten metal, the actual value of the contact measurement being used for the calibration of the eddy current measurement, wherein the contact measurement is periodically repeated throughout casting by means of a vertically movable electrode, the eddy current measurement being calibrated after each repetition.
  2. A method according to claim 1, characterized in that on its downward path in the direction of the level of the molten metal, before it reaches said level the electrode passes through a fixed light barrier, and the path covered by the electrode from the light barrier to the contact with the level of the molten metal is measured in order to determine the actual value of said level.
  3. An apparatus for controlling the level of the molten metal in the pouring chamber of a continuous strip casting installation, having an eddy current sensor above the bath of molten metal, an electrode which is in contact with the molten metal when the actual value of its height is determined, and a control device, to which the eddy current sensor and the electrode are connected and which contains a programme by which the continuous sequences of signals of the eddy current sensor can be converted, allowing for the actual value signal of the electrode, into control signals by means of which at least one of the casting parameters, namely the quantity of the molten metal supplied to the pouring chamber and the casting speed, can be changed in order to displace the level of the molten metal to a required height, wherein the electrode (8) can travel vertically and the path covered by the electrode (8) can be determined, and a light barrier (14) or the like is disposed above the bath (3) of molten metal and above the highest required height of the level (4) of the molten metal and in the path covered by the electrode (8).
  4. An apparatus according to claim 3, characterized in that the electrode is made of graphite.
EP89121941A 1989-02-02 1989-11-28 Method of and installation for regulating a liquid metal level in the pouring basin of continuous casting plants for strips Expired - Lifetime EP0380774B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP1022530A JPH02205234A (en) 1989-02-02 1989-02-02 Method for detecting molten metal surface level in cast strip continuous casting
JP22530/89 1989-02-28

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EP0380774A2 EP0380774A2 (en) 1990-08-08
EP0380774A3 EP0380774A3 (en) 1992-01-29
EP0380774B1 true EP0380774B1 (en) 1994-11-02

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WO2004090491A2 (en) * 2003-03-31 2004-10-21 Saudi Arabian Oil Company Measurement of molten sulfur level in receptacles
KR20120015453A (en) * 2009-06-15 2012-02-21 가부시키가이샤 아이에이치아이 Strip casting method and twin roll casting machine
CN111628625B (en) * 2020-05-12 2021-12-10 中国科学技术大学 Device for driving liquid metal liquid drops by light-controlled electric field

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DE3146360C2 (en) * 1981-11-23 1983-10-27 Wieland-Werke Ag, 7900 Ulm Device for level control of the bath level in a continuous casting mold
DE3323749A1 (en) * 1983-07-01 1985-01-03 Norddeutsche Affinerie AG, 2000 Hamburg METHOD FOR REGULATING THE BATH MIRROR LEVEL OF A METAL MELT
JPS60187455A (en) * 1984-03-08 1985-09-24 Kobe Steel Ltd Detection of molten metal level in casting mold
EP0194327A1 (en) * 1985-03-09 1986-09-17 Fried. Krupp Gesellschaft mit beschränkter Haftung Apparatus for regulating the position of the liquid metal level within a double belt continuous casting mould
US4728875A (en) * 1986-10-20 1988-03-01 Allegheny Ludlum Corporation Method and apparatus for monitoring a liquid level

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JPH02205234A (en) 1990-08-15
ATE113510T1 (en) 1994-11-15
EP0380774A3 (en) 1992-01-29
JPH0513747B2 (en) 1993-02-23
EP0380774A2 (en) 1990-08-08
DE58908599D1 (en) 1994-12-08

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