EP0192043B1 - Apparatus for measuring the level of the molten metal in a vessel, especially in a continuous-casting mould - Google Patents

Apparatus for measuring the level of the molten metal in a vessel, especially in a continuous-casting mould Download PDF

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Publication number
EP0192043B1
EP0192043B1 EP86100498A EP86100498A EP0192043B1 EP 0192043 B1 EP0192043 B1 EP 0192043B1 EP 86100498 A EP86100498 A EP 86100498A EP 86100498 A EP86100498 A EP 86100498A EP 0192043 B1 EP0192043 B1 EP 0192043B1
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EP
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Prior art keywords
coils
coil
primary coil
measurement
level
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EP86100498A
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German (de)
French (fr)
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EP0192043A1 (en
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Jean Liesch
Jo Simon
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Arcelor Luxembourg SA
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Arbed SA
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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

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  • the invention relates to a device for measuring the filling level of liquid metals in receptacles, in particular continuous casting molds, which device comprises a primary coil, which creates an electromagnetic field, and two secondary measurement coils according to the preambles of the claims. 1 and 7.
  • a measuring device for determining the level of liquid metal in an ingot mold, comprising a primary coil supplied with alternating current and two secondary measurement coils connected in opposition.
  • the density of the coils of the secondary coils is increased around the usual working levels.
  • the object of the invention is to remedy the drawbacks of the measurement devices of the state of the art and to propose a device of reduced size, giving rise to signals whose interpretation is simple, having a measurement range. extended and allowing easy calibration.
  • a first secondary measurement winding S runs along the primary winding over its entire height and inside it.
  • a second secondary compensation winding S ' is arranged outside the primary winding.
  • Fig.2 shows an alternative embodiment of the device according to the invention. It is a coil of cylindrical shape, with a length of 20 to 30cm and a diameter of 20 to 30mm, which is introduced into a suitable housing, drilled in the copper plate of the mold, thick of 40 to 50 mm.
  • This sensor which must withstand fairly high temperatures, has no active component, but only winding wires which can withstand this temperature. It essentially consists of a triple coil 20 for level measurement, with a length of 10 to 15cm, and possibly a triple coil 21 for level detection and calibration of the measurement system, with a length of 2 at 5cm.
  • the measuring device 20 just like the detection and calibration device 21 comprises a primary winding P 2 resp. P 3 , a secondary measurement winding S 2 resp.
  • the two secondary windings are arranged on either side of the primary winding and this over its entire height.
  • a linear monotonic signal (V 2n , V 3n ) results as a function of the distance (height H of the metal bath).
  • the lower winding 21 allows easy detection of the steel during startup.
  • the coil S 2 can also be produced in at least two parts as explained above with reference to FIG. 1. This rod-shaped sensor of circular section is particularly compact and easily fits in one of the copper plates of the ingot mold. To increase the surface of the turns facing the bath, the stick can be given a rectangular section.
  • fig. 4 is shown a particularly advantageous embodiment of primary and secondary coils according to the invention, based on the observation that the difference in voltages between secondary coil and reference coil as a function of the height of the bath is far from having linearity required, such as fig. 1 or fig. 2 suggests.
  • the different coils are subdivided into several stages, each stage possibly containing a different number of turns. Inside a stage, the turns are arranged in one or more superimposed lots, a lot being constituted by a monolayer of adjacent turns; to simplify manufacture, a batch may possibly extend over several floors.
  • the transverse dimension does not change from one stage to another one can in the case of a reduced number of lots in certain stages, fill the remaining space with cardboard or else pour it a plastic material; you can also choose the diameter of the turns so as to fill all the space available inside a floor. This latter possibility cannot obviously be chosen when a batch of turns crosses several stages.
  • the number of batches to be assembled in a stage is determined experimentally so that the difference of the signals picked up by the coils S and S 'varies as monotonously as possible according to the height of the bath and comprises a minimum of parasitic signals .
  • the reference coil S ' contains few or no turns in the two extreme stages and an identical number of lots as the secondary coil S in the other stages.
  • the secondary coil S contains a maximum of lots (eg 9) in the extreme stages and a minimum of lots (eg 5) in the stage (s) located in the center. In the floor located at the bath level the number of lots is high (eg 7).
  • the number of batches included in the different stages of the primary coil P is usually slightly lower than that in the stages of the secondary coil S; the turns of the primary coil, on the other hand, generally have a larger diameter than that of the turns of the secondary coils.
  • Certain lower stages of the primary coil (with the exception of the stage situated at the lower end, which has a primary function when starting the casting) can be devoid of turns and then only contain a connection between the two adjacent floors.
  • at least one stage of the secondary coil S has a sample.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
  • Continuous Casting (AREA)

Abstract

1. Apparatus for measuring the level of molten metal (M) in a vessel, especially a continous casting mould (K), by sensing the secondary electromagnetic fields emanating from the liquid metal, the apparatus comprising a primary coil (P, P2 , P4 ) creating a time varying electromagnetic field, two secondary measurement coils (S, S2 , S'2 ; S4 , S'4 ) extending along substantially the entire height of the primary coil and positioned on the opposed sides of the primary coil and means for delivering the difference of the signals sensed by the secondary measurement coils, characterized in that at least one of the coils (P; P2 ; P4 ; S, S'; S2 , S'2 ; S4 , S'4 ) is subdivided into at least two superimposed stages (40, 41, 42, 43, 44) having different magnetic properties and in that at least on stage of the secondary measurement coils (S, S2 , S4 ) includes at its ends connections for relaying the calibrating signals.

Description

L'invention concerne un dispositif pour mesurer le niveau de remplissage de métaux liquides dans des récipients, notamment des lingotières de coulée continue, lequel dispositif comporte und bobine primaire, qui crée un champ électromagnétique, et deux bobines secondaires de mesure suivant les préambules des revendications 1 et 7.The invention relates to a device for measuring the filling level of liquid metals in receptacles, in particular continuous casting molds, which device comprises a primary coil, which creates an electromagnetic field, and two secondary measurement coils according to the preambles of the claims. 1 and 7.

En vue de la régulation de la vitesse d'alimentation en métal liquide ainsi que de la vitesse d'extraction du brin, il est extrêmement important de pouvoir déterminer en permanence la hauteur du bain dans une lingotière de coulée continue. Ceci explique qu'on connaît quantité de procédés de mesure utilisant des caméras de télévision, des éléments radioactifs ou faisant emploi des propriétés electromagnétiques de la matière. Des méthodes de mesure basées sur des phénomènes électromagnétiques, notamment le repérage de courants de Foucault induits dans le métal liquide d'une lingotière, ont à résoudre deux sortes de problèmes:

  • - la lingotière en cuivre absorbe les champs électromagnétiques de façon telle qu'il devient difficile de séparer le signal du bruit,
  • - en vue du brassage du métal liquide, les lingotières sont souvent munies d'électro-aimants puissants, créateurs de champs magnétiques qui sont des centaines de fois plus importants que les champs propres et qui peuvent perturber les mesures.
In order to regulate the speed of supply of liquid metal as well as the speed of extraction of the strand, it is extremely important to be able to permanently determine the height of the bath in a continuous casting mold. This explains why a large number of measurement methods are known using television cameras, radioactive elements or making use of the electromagnetic properties of matter. Measurement methods based on electromagnetic phenomena, in particular the identification of eddy currents induced in the liquid metal of an ingot mold, have to solve two kinds of problems:
  • - the copper ingot mold absorbs electromagnetic fields in such a way that it becomes difficult to separate the signal from the noise,
  • - in view of the mixing of the liquid metal, the ingot molds are often provided with powerful electromagnets, creators of magnetic fields which are hundreds of times more important than the clean fields and which can disturb the measurements.

Dans son brevet EP 10.539 la demanderesse a décrit un procédé de mesure du niveau de remplissage de métaux liquides dans des lingotières de coulée continue, dans lequel on prévoit une bobine primaire et deux bobines secondaires identiques entre elles, branchées en opposition et montées coaxialement et symétriquement par rapport au plan median de la bobine. On dispose les bobines primaires et secondaires autour de la lingotière sans qu'il y ait contact physique. On mesure, en plus de la tension induite dans les bobines secondaires, la conductivité du métal liquide et on détermine la hauteur du niveau suivant la valeur de la tension mesurée, corrigée en fonction de la valeur de la conductivité. Lorsque la lingotière est vide, la tension secondaire totale est nulle. Lorsque le niveau du liquide monte, des tensions prépondérantes sont induites dans la bobine inférieure, de sorte que la tension globale monte. Au point d'asymétrie maximale, lorsque le niveau se trouve entre les bobines secondaires, on obtient également un maximum de la tension secondaire totale. Lorsque le niveau du liquide continue de monter, le degré d'asymétrie ainsi que la tension secondaire totale diminuent de nouveau. On observe par conséquent une courbe de mesure en forme de cloche avec deux pentes pratiquement linéaires sur 35% de la hauteur.In its patent EP 10.539, the applicant has described a method for measuring the filling level of liquid metals in continuous casting molds, in which a primary coil and two identical secondary coils are provided, connected in opposition and mounted coaxially and symmetrically with respect to the median plane of the coil. The primary and secondary coils are placed around the ingot mold without physical contact. In addition to the voltage induced in the secondary coils, the conductivity of the liquid metal is measured and the height of the level is determined according to the value of the measured voltage, corrected as a function of the value of the conductivity. When the ingot mold is empty, the total secondary voltage is zero. When the liquid level rises, preponderant voltages are induced in the lower coil, so that the overall tension rises. At the point of maximum asymmetry, when the level is between the secondary coils, a maximum of the total secondary voltage is also obtained. As the fluid level continues to rise, the degree of asymmetry and the total secondary voltage decrease again. A bell-shaped measurement curve is therefore observed with two practically linear slopes over 35% of the height.

Etant donné la disposition perpendiculaire des enroulements au vecteur inducteur du champ électromagnétique de brassage, qui agit en plus de façon différente sur les enroulements, on est confronté à des problèmes complexes d'extraction du signal utile des signaux parasitaires. La mise au point des équipements tout comme le recalibrage du système de mesure, exigés par l'usure des plaques et les variations de température, sont délicats. D'un autre côté, par suite de la courbe de mesure en forme de cloche, un repérage non équivoque du niveau du métal à l'intérieur du champ de mesure n'est pas toujours donné; une identification non équivoque du niveau du métal à l'extérieur du champ de mesure, signalant ou bien un débordement imminent du métal ou alors une percée du brin, n'est pas possible.Given the perpendicular arrangement of the windings to the inductor vector of the electromagnetic stirring field, which also acts differently on the windings, we are faced with complex problems of extracting the useful signal from the parasitic signals. The equipment development as well as the recalibration of the measurement system, required by the wear of the plates and temperature variations, are delicate. On the other hand, due to the bell-shaped measurement curve, an unequivocal identification of the level of the metal inside the measurement field is not always given; an unequivocal identification of the level of the metal outside the measurement field, signaling either an imminent overflow of the metal or a breakthrough of the strand, is not possible.

Dans le document GB-A-834.783, il est décrit un dispositif de mesure pour déterminer le niveau du métal liquide dans une lingotière, comprenant une bobine primaire alimentée en courant alternatif et deux bobines secondaires de mesure branchées en opposition. Pour améliorer localement la sensibilité du dispositif de mesure, la densité des spires des bobines secondaires est augmentée aux abords des niveaux de travail habituels.In document GB-A-834,783, a measuring device is described for determining the level of liquid metal in an ingot mold, comprising a primary coil supplied with alternating current and two secondary measurement coils connected in opposition. To locally improve the sensitivity of the measuring device, the density of the coils of the secondary coils is increased around the usual working levels.

D'après le document US-A-3.366.873, on connaît un dispositif pour mesurer le niveau de métal liquide dans un récipient et comprenant trois bobines rectangulaires disposées sur un des côtés du récipient. Les deux bobines de mesure longent la bobine alimentée en courant alternatif sur pratiquement toute sa hauteur et sont disposées de part et d'autre de celle-ci. Ce document a servi de base pour la formulation des préambules des revendications 1 et 7.From document US-A-3,366,873, a device is known for measuring the level of liquid metal in a container and comprising three rectangular coils arranged on one side of the container. The two measuring coils run along the coil supplied with alternating current over almost its entire height and are arranged on either side thereof. This document served as the basis for the formulation of the preambles of claims 1 and 7.

L'invention a pour but de remédier aux inconvénients dont sont entachés les dispositifs de mesure de l'état de la technique et de proposer en dispositif de dimension réduite, donnant lieu à des signaux dont l'interprétation est simple, ayant une plage de mesure étendue et permettant un calibrage aisé.The object of the invention is to remedy the drawbacks of the measurement devices of the state of the art and to propose a device of reduced size, giving rise to signals whose interpretation is simple, having a measurement range. extended and allowing easy calibration.

Ce but est atteint par le dispositif selon l'invention tel qu'il est caractérisé dans les revendications 1 et 7. Des variantes d'exécution sont décrites dans les revendications dépendantes.This object is achieved by the device according to the invention as characterized in claims 1 and 7. Variant embodiments are described in the dependent claims.

Parmi les avantages relevons la réduction des dimensions des différentes bobines, ce qui est particulièrement intéressant lorsque la place disponible est réduite par la présence d'un inducteur de brassage; celui-ci agit alors de manière comparable sur les bobines de mesure et crée des signaux qui, lors d'un branchement en opposition des bobines, se compensent dans de larges proportions. Par suite de la disposition symétrique et adjacente des différentes bobines ainsi que des dimensions restreintes de l'ensemble, les influences des variations de température sont négligeables; ceci permet par ailleurs de faire. lors de la mise en service, des contrôles et des calibrages à froid. L'ensemble électronique de traitement des signaux est d'une extrême simplicité.Among the advantages note the reduction in the dimensions of the different coils, which is particularly advantageous when the available space is reduced by the presence of a stirring inductor; this then acts in a comparable manner on the measurement coils and creates signals which, when connected in opposition to the coils, compensate each other in large proportions. Owing to the symmetrical and adjacent arrangement of the different coils as well as the restricted dimensions of the assembly, the influences of temperature variations are negligible; this also makes it possible to do. during commissioning, checks and cold calibrations. The electronic signal processing system is extremely simple.

L'invention est exposée ci-après plus en détail à l'aide de dessins représentant seulement un mode d'exécution.

  • - La figure 1 représente de façon schématique et partielle une coupe à travers des bobines conformes à l'invention, ainsi que les différentes tensions mesurées en fonction de la hauteur du métal dans la lingotière.
  • - La figure 2 représente de manière schématique une coupe à travers un capteur cylindrique conforme à l'invention ainsi que differentes tensions mesurées en fonction de la hauteur du métal dans la lingotière.
  • - La figure 3 représente, à une échelle plus grande, une coupe selon la ligne III-III à travers le dispositif représenté en figure 2.
  • - La figure 4 représente de manière schématique une coupe partielle à travers un ensemble de bobines réalisées conformément à l'invention.
The invention is set out below in more detail with the aid of drawings representing only one embodiment.
  • - Figure 1 shows schematically and partially a section through coils according to the invention, as well as the different tensions measured as a function of the height of the metal in the mold.
  • - Figure 2 shows schematically a section through a cylindrical sensor according to the invention as well as different tensions measured as a function of the height of the metal in the mold.
  • - Figure 3 shows, on a larger scale, a section along line III-III through the device shown in Figure 2.
  • - Figure 4 schematically shows a partial section through a set of coils produced in accordance with the invention.

Sur la fig. 1 on distingue la section rectangulaire d'un bobinage primaire P qui entoure le bain de métal en fusion M. Un premier bobinage secondaire de mesure S longe le bobinage primaire sur toute sa hauteur et à l'intérieur de celui-ci. Un deuxième bobinage secondaire de compensation S' est disposé à l'extérieur du bobinage primaire. Lorsqu'on prend la différence entre les signaux captés par les bobines S et S' en fonction de la hauteur du bain H, on observe dans le cas idéal, tel qu'indiqué sur la partie droite de la fig. 1, une tension Vn qui croît de manière monotone en fonction du niveau du bain. Cette méthode, qui semble a priori élégante, n'aboutit pas dans ce cas d'application à une précision satisfaisante. En effet, la tension Vn mesurée ne dépend pas uniquement du niveau du bain, mais également d'autres grandeurs. Pour être à même d'attribuer un niveau précis du métal à une tension mesurée, il faudrait par conséquent pour les conditions de coulée en présence (nuance d'acier, température de coulée etc.) déterminer chaque fois expérimentalement la valeur de la tension maximum Vnm en remplissant la lingotière pratiquement à ras bord. Or, une telle méthode de calibrage est entachée de risques de débordement et de surchauffe de pièces qui ne sont pas prévues pour fonctionner à une température si élevée. Pour pallier cet inconvénient, le déposant propose de subdiviser la bobine secondaire de mesure en au moins deux parties, par exemple en deux parties égales Sa et Sb, tel que représenté sur la fig. 1.In fig. 1 a distinction is made between the rectangular section of a primary winding P which surrounds the bath of molten metal M. A first secondary measurement winding S runs along the primary winding over its entire height and inside it. A second secondary compensation winding S 'is arranged outside the primary winding. When we take the difference between the signals picked up by the coils S and S 'as a function of the height of the bath H, we observe in the ideal case, as indicated on the right side of FIG. 1, a voltage V n which increases monotonically as a function of the level of the bath. This method, which seems a priori elegant, does not lead in this case of application to a satisfactory precision. Indeed, the voltage V n measured does not depend only on the level of the bath, but also on other quantities. To be able to assign a precise level of the metal to a measured tension, it would therefore be necessary for the casting conditions present (steel grade, casting temperature etc.) to determine each time experimentally the value of the maximum tension V nm by filling the mold almost to the brim. However, such a calibration method is marred by risks of overflow and overheating of parts which are not intended to operate at such a high temperature. To overcome this drawback, the applicant proposes to subdivide the secondary measurement coil into at least two parts, for example into two equal parts Sa and S b , as shown in FIG. 1.

Notons qu'il est conseillé de disposer la partie inférieure Sa du bobinage S légèrement en dessous du niveau normal du bain. En effet, la différence des signaux captés par la partie de bobine Sa et la bobine S'en fonction de la hauteur du bain métallique H passe par un maximum (voir courbe Ve, partie de droite de la fig. 1). Lors du démarrage de coulée, on observe la variation des courbes V, et Vn. Lorsque la courbe V. passe par son maximum Vem, conditionné principalement par la nuance et la température de l'acier et la disposition de la bobine Sa, on peut attribuer la différence de tension apparaissant à ce moment aux extrémités des bobines S et S' à un niveau du bain déterminé et on peut extrapoler la valeur Vnm qu'aurait le maximum de la courbe Vn si le niveau du métal montait si haut.Note that it is advisable to place the lower part Sa of the coil S slightly below the normal level of the bath. Indeed, the difference of the signals picked up by the coil part Sa and the coil S'as a function of the height of the metal bath H passes through a maximum (see curve V e , right part of fig. 1). During the start of casting, the variation of the curves V, and V n is observed. When the curve V. passes through its maximum V em , conditioned mainly by the grade and temperature of the steel and the arrangement of the coil Sa, the difference in voltage appearing at this moment can be attributed to the ends of the coils S and S 'at a determined bath level and we can extrapolate the value V nm that the maximum of the curve V n would have if the level of the metal rose so high.

Pareillement, il est possible de faire un étalonnage à tout moment de la coulée en diminuant le niveau du bain jusqu'en dessous de l'extrémité supérieure de la partie de bobine Sa. Il est évident qu'une subdivision de la bobine S en un plus grand nombre de parties (p. ex. 3 ou 4) rend cet étalonnage encore plus précis, sinon pratiquement permanent.Similarly, it is possible to make a calibration at any time of the casting by reducing the bath level to below the upper end of the coil part Sa. It is obvious that a subdivision of the coil S into a more parts (eg 3 or 4) make this calibration even more precise, if not almost permanent.

La fig.2 montre une variante d'exécution du dispositif selon l'invention. Il s'agit d'une bobine de forme cylindrique, d'une longueur de 20 à 30cm et d'un diamètre de 20 à 30mm, qui est introduite dans un logement approprié, foré dans la plaque de cuivre de la lingotière, épaisse de 40 à 50 mm. Ce capteur, qui doit supporter des températures assez élevées, ne comporte aucun composant actif, mais seulement des fils de bobinage pouvant supporter cette température. Il se compose essentiellement d'un triple bobinage 20 de mesure de niveau, d'une longueur de 10 à 15cm, et éventuellement d'un triple bobinage 21 de détection de niveau et de calibration du système de mesure, d'une longueur de 2 à 5cm. Le dispositif de mesure 20 tout comme le dispositif de détection et de calibration 21 comporte un enroulement primaire P2 resp. P3, un enroulement secondaire de mesure S2 resp. S3 et un enroulement secondaire de référence S2' resp. S3'. Les deux enroulements secondaires sont disposés de part et d'autre de l'enroulement primaire et cela sur toute sa hauteur. Par un montage approprié en opposition il en résulte, comme indiqué sur la droite de chaque système de bobines, un signal monotone linéaire (V2n, V3n) en fonction de la distance (hauteur H du bain métallique). Le bobinage inférieur 21 permet une détection aisée de l'acier lors du démarrage. La bobine S2 peut en outre être réalisée en au moins deux parties comme expliqué plus haut en rapport avec la fig. 1. Ce capteur en forme de bâtonnet de section circulaire est particulièrement compact et se loge facilement dans une des plaques en cuivre de la lingotière. Pour augmenter la surface des spires en regard du bain, on peut donner au bâtonnet une section rectangulaire.Fig.2 shows an alternative embodiment of the device according to the invention. It is a coil of cylindrical shape, with a length of 20 to 30cm and a diameter of 20 to 30mm, which is introduced into a suitable housing, drilled in the copper plate of the mold, thick of 40 to 50 mm. This sensor, which must withstand fairly high temperatures, has no active component, but only winding wires which can withstand this temperature. It essentially consists of a triple coil 20 for level measurement, with a length of 10 to 15cm, and possibly a triple coil 21 for level detection and calibration of the measurement system, with a length of 2 at 5cm. The measuring device 20 just like the detection and calibration device 21 comprises a primary winding P 2 resp. P 3 , a secondary measurement winding S 2 resp. S 3 and a secondary reference winding S 2 'resp. S 3 '. The two secondary windings are arranged on either side of the primary winding and this over its entire height. As a result of suitable mounting in opposition, as shown on the right of each coil system, a linear monotonic signal (V 2n , V 3n ) results as a function of the distance (height H of the metal bath). The lower winding 21 allows easy detection of the steel during startup. The coil S 2 can also be produced in at least two parts as explained above with reference to FIG. 1. This rod-shaped sensor of circular section is particularly compact and easily fits in one of the copper plates of the ingot mold. To increase the surface of the turns facing the bath, the stick can be given a rectangular section.

En fig.4 est représentée une exécution particulièrement avantageuse de bobines primaires et secondaires selon l'invention, basée sur l'observation que la différence des tensions entre bobine secondaire et bobine de référence en fonction de la hauteur du bain est loin de présenter la linéarité exigée, tel que la fig. 1 ou la fig. 2 le laisse supposer. Pour linéariser la tension Vn, les différentes bobines sont subdivisées en plusieurs étages, chaque étage pouvant contenir un nombre de spires différent. A l'intérieur d'un étage les spires sont disposées en un ou plusieurs lots superposés, un lot étant constitué par une mono- couche de spires adjacentes; pour simplifier la fabrication, un lot peut s'étendre éventuellement sur plusieurs étages. Etant donné que pour une bobine donnée, la dimension transversale ne change pas d'un étage à l'autre on peut dans le cas d'un nombre réduit de lots dans certains étages, remplir l'espace restant par du carton ou bien y couler une matière plastique; on peut également choisir le diamètre des spires de manière à remplir tout l'espace disponible à l'intérieur d'un étage. Cette dernière possibilité ne peut évidemment pas être choisie lorsqu'un lot de spires traverse plusieurs étages.In fig. 4 is shown a particularly advantageous embodiment of primary and secondary coils according to the invention, based on the observation that the difference in voltages between secondary coil and reference coil as a function of the height of the bath is far from having linearity required, such as fig. 1 or fig. 2 suggests. To linearize the voltage V n , the different coils are subdivided into several stages, each stage possibly containing a different number of turns. Inside a stage, the turns are arranged in one or more superimposed lots, a lot being constituted by a monolayer of adjacent turns; to simplify manufacture, a batch may possibly extend over several floors. Given that for a given reel, the transverse dimension does not change from one stage to another one can in the case of a reduced number of lots in certain stages, fill the remaining space with cardboard or else pour it a plastic material; you can also choose the diameter of the turns so as to fill all the space available inside a floor. This latter possibility cannot obviously be chosen when a batch of turns crosses several stages.

Le nombre de lots à monter dans un étage est déterminé expérimentalement de manière à ce que la différence des signaux captés par les bobines S et S' varie de manière aussi monotone que possible en fonction de la hauteur du bain et comporte un minimum de signaux parasitaires. En général on peut dire que la bobine de référence S' contient peu ou pas de spires dans les deux étages extrêmes et un nombre identique de lots que la bobine secondaire S dans les autres étages. La bobine secondaire S contient par contre un maximum de lots (p. ex. 9) dans les étages extrêmes et un minimum de lots (p. ex. 5) dans le ou les étages situés au centre. Dans l'étage situé au niveau du bain le nombre de lots est élevé (p. ex. 7). Le nombre de lots compris dans les différents étages de la bobine primaire P est habituellement légèrement plus faible que celui dans les étages de la bobine secondaire S; les spires de la bobine primaire par contre ont en général un diamètre plus élevé que celui des spires des bobines secondaires. Certains étages inférieurs de la bobine primaire (à l'exception de l'étage situé à l'extrémité inférieure, qui a une fonction primordiale lors du démarrage de la coulée) peuvent être démunis de spires et ne contiennent alors qu'une connexion entre les deux étages adjacents. Dans le but de procéder à un calibrage du signal relevé sur les extrémités des bobines secondaires S et S', branchées en opposition, au moins un étage de la bobine secondaire S possède un prélèvement.The number of batches to be assembled in a stage is determined experimentally so that the difference of the signals picked up by the coils S and S 'varies as monotonously as possible according to the height of the bath and comprises a minimum of parasitic signals . In general it can be said that the reference coil S 'contains few or no turns in the two extreme stages and an identical number of lots as the secondary coil S in the other stages. On the other hand, the secondary coil S contains a maximum of lots (eg 9) in the extreme stages and a minimum of lots (eg 5) in the stage (s) located in the center. In the floor located at the bath level the number of lots is high (eg 7). The number of batches included in the different stages of the primary coil P is usually slightly lower than that in the stages of the secondary coil S; the turns of the primary coil, on the other hand, generally have a larger diameter than that of the turns of the secondary coils. Certain lower stages of the primary coil (with the exception of the stage situated at the lower end, which has a primary function when starting the casting) can be devoid of turns and then only contain a connection between the two adjacent floors. In order to calibrate the signal detected on the ends of the secondary coils S and S ', connected in opposition, at least one stage of the secondary coil S has a sample.

En ce qui concerne le remplissage des cinq étages 40, 41, 42, 43, 44 des trois bobines P4, S4 et S'4, montées autour de la lingotière K, on peut relever ce qui suit:

  • - le nombre de lots de spires par étage est proportionnel à l'épaisseur (dessinée) de la bobine dans cet étage; l'espace restant est rempli par du papier isolant.
  • - la bobine primaire P4 possède 7 lots de spires à son extrémité inférieure (étage 40) et son maximum de lots (10 lots) à son étage supérieur.
  • - la bobine secondaire S4 possède un maximum de lots (13) aux étages extrêmes 40 et 44.
  • - la bobine de référence S'4 ne possède pas de spire dans ses étages extrêmes 40 et 44.
  • - dans cette variante d'exécution, les différents lots de spires traversent à chaque fois un maximum d'étages: la bobine de référence S'4 possède par exemple cinq lots qui s'étendent sur les étages 41, 42, 43 et deux lots supplémentaires aux étages 41 et 43.
As regards the filling of the five stages 40, 41, 42, 43, 44 of the three coils P 4, S 4 and S ' 4 , mounted around the ingot mold K, the following can be noted:
  • - the number of batches of turns per stage is proportional to the thickness (drawn) of the coil in this stage; the remaining space is filled with insulation paper.
  • - the primary coil P 4 has 7 lots of turns at its lower end (stage 40) and its maximum number of lots (10 lots) on its upper stage.
  • - the secondary coil S 4 has a maximum of lots (13) on the extreme stages 40 and 44.
  • - the reference coil S ' 4 does not have a turn in its extreme stages 40 and 44.
  • - in this variant, the different batches of turns each pass through a maximum of stages: the reference coil S ' 4 has for example five batches which extend over stages 41, 42, 43 and two batches additional floors 41 and 43.

Il est bien évident que la subdivision d'une bobine en cinq étages n'est pas limitative; selon les applications on peut la subdiviser en un nombre plus grand ou plus faible d'étages. Pareillement, en modifiant le nombre de lots de spires par étage ou le nombre de bobines secondaires, on reste dans le cadre de la présente invention.It is obvious that the subdivision of a coil into five stages is not limiting; depending on the applications, it can be subdivided into a greater or lesser number of stages. Similarly, by modifying the number of batches of turns per stage or the number of secondary coils, it remains within the scope of the present invention.

Notons que dans des cas particuliers, il est possible de supprimer le ou les enroulements secondaires de référence S' et de retrancher des signaux captés par la bobine de mesure S un signal dérivé directement de la tension appliquée à la bobine primaire P ou même un signal en provenance d'une source constante.Note that in special cases, it is possible to suppress the secondary reference winding (s) S 'and to subtract from the signals picked up by the measurement coil S a signal derived directly from the voltage applied to the primary coil P or even a signal from a constant source.

Claims (8)

1. Apparatus for measuring the level of molten metal (M) in a vessel, especially a continous casting mould (K), by sensing the secondary electromagnetic fields emanating from the liquid metal, the apparatus comprising a primary coil (P, P2, P4) creating a time varying electromagnetic field, two secondary measurement coils (S, 52, S'2; S4, 5'4) extending along substantially the entire height of the primary coil and positioned on the opposed sides of the primary coil and means for delivering the difference of the signals sensed by the secondary measurement coils, characterized in that at least one of the coils (P; P2; P4; S, S'; 52, S'2; S4, S'4) is subdivided into at least two superimposed stages (40, 41, 42, 43, 44) having different magnetic properties and in that at least on stage of the secondary measurement coils (S, S2, S4) includes at its ends connections for relaying the calibrating signals.
2. Apparatus according to claim 1, characterized in that at least two of the stages (40, 41, 42, 43, 44) of at least one coil comprise mutually distinct numbers of windings.
3. Apparatus according to one of the claims 1 or 2, characterized in that the coils surround the bath of liquid metal (M).
4. Apparatus according to one of the claims 1 or 2, characterized in that the coils have a substantially cylindrical shape, the coils being positioned alongside and adjacent to the liquid metal.
5. Apparatus according to claim 4, characterized in that two sets of cylindrical coils (P2, S2, S'z; P3, S3, S'3) are positioned one above the other, the lower set (P3, S3, S'3) having substantially the same transverse dimension, but a lesser height than the upper set and being used at start-up.
6. Apparatus according to one of the claims 1 to 5, characterized in that there are two secondary coils, wherein the first (S, 52, S4) subdivided into at least two parts (Sa, Sb), is used for measurement and the second (S', S'2, S'4) for reference, with the reference coil connected in opposition to the measurement coil and possibly to at least one of said parts of the measurement coil located below the liquid bath level.
7. Apparatus for measuring the level of molten metal (M) in a vessel, especially a continuous casting mould (K), by sensing the secondary electromagnetic fields emanating from the liquid metal, the apparatus comprising a primary coil (P, P2, P4) creating a time varying electromagnetic field, characterized in that there is a single secondary measurement coil (S, 52, S4) positioned between the liquid metal (M) and the primary coil (P, P2, P4), in that the secondary coil extends along substantially the entire height of the primary coil and in that the secondary coil is connected in opposition to a signal derived directly from the voltage applied to the primary coil or a signal derived from a constant voltage source.
8. Apparatus according to claim 7, characterized in that at least one of the coils is subdivided into at least two superimposed stages (40, 41, 42, 43, 44) having mutually distinct magnetic properties.
EP86100498A 1985-02-01 1986-01-16 Apparatus for measuring the level of the molten metal in a vessel, especially in a continuous-casting mould Expired EP0192043B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT86100498T ATE41617T1 (en) 1985-02-01 1986-01-16 DEVICE FOR LEVEL MEASUREMENT IN CONTAINERS, ESPECIALLY CONTINUOUS CASTING MOLDS.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
LU85754A LU85754A1 (en) 1985-02-01 1985-02-01 DEVICE FOR MEASURING THE FILLING LEVEL OF LIQUID METALS IN CONTAINERS
LU85754 1985-02-01

Publications (2)

Publication Number Publication Date
EP0192043A1 EP0192043A1 (en) 1986-08-27
EP0192043B1 true EP0192043B1 (en) 1989-03-22

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EP86100498A Expired EP0192043B1 (en) 1985-02-01 1986-01-16 Apparatus for measuring the level of the molten metal in a vessel, especially in a continuous-casting mould

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EP (1) EP0192043B1 (en)
JP (1) JPS61178616A (en)
AT (1) ATE41617T1 (en)
DE (1) DE3662496D1 (en)
LU (1) LU85754A1 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3908199A1 (en) * 1989-03-14 1990-09-27 Leybold Ag DEVICE FOR IDENTIFYING THE MELTING FRONT OF A MELT
US5232043A (en) * 1989-03-14 1993-08-03 Leybold Aktiengesellschaft Device for identifying the solid-liquid interface of a melt
DE69025445T2 (en) * 1989-09-19 1996-09-05 Nippon Steel Corp Method and device for determining a melt level
ITPN20060005A1 (en) 2006-01-27 2007-07-28 Ergoline S Lab S R L PROCEDURE AND DEVICE FOR THE MEASUREMENT AND CONTROL OF THE HEIGHT OF LIQUID METAL IN A CRYSTALLIZER.

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB834783A (en) * 1955-05-26 1960-05-11 United Steel Companies Ltd Improvements relating to apparatus for controlling the continuous casting of metals
US3366873A (en) * 1966-09-15 1968-01-30 Atomic Energy Commission Usa Linear responsive molten metal level detector
LU80410A1 (en) * 1978-10-25 1980-05-07 Arbed METHOD FOR MEASURING THE LEVEL OF METALS IN CONTAINERS, ESPECIALLY IN CONTINUOUS CASTING CHILLERS
LU83699A1 (en) * 1981-10-16 1983-06-08 Arbed METHOD FOR MONITORING A CONTINUOUS CHOCOLATE IN OPERATION
LU83969A1 (en) * 1982-02-23 1983-09-02 Arbed METHOD FOR MEASURING THE LEVEL OF LIQUID METALS IN CONTINUOUS CASTING PLANTS
DE3427563C2 (en) * 1984-07-26 1986-12-11 Stopinc Ag, Baar Device for electromagnetic level measurement for metallurgical vessels

Also Published As

Publication number Publication date
JPS61178616A (en) 1986-08-11
EP0192043A1 (en) 1986-08-27
LU85754A1 (en) 1986-09-02
ATE41617T1 (en) 1989-04-15
DE3662496D1 (en) 1989-04-27

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