WO2001011101A1 - Method and device for continuously producing a metal surface coating on a moving sheet metal - Google Patents

Method and device for continuously producing a metal surface coating on a moving sheet metal Download PDF

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Publication number
WO2001011101A1
WO2001011101A1 PCT/FR2000/002066 FR0002066W WO0111101A1 WO 2001011101 A1 WO2001011101 A1 WO 2001011101A1 FR 0002066 W FR0002066 W FR 0002066W WO 0111101 A1 WO0111101 A1 WO 0111101A1
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WO
WIPO (PCT)
Prior art keywords
strip
crucible
coating
coating metal
magnetic
Prior art date
Application number
PCT/FR2000/002066
Other languages
French (fr)
Inventor
Marc Anderhuber
Alain Daubigny
François NONNE
Pascal Gardin
René Pierret
Original Assignee
Usinor
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Usinor filed Critical Usinor
Priority to AU65773/00A priority Critical patent/AU6577300A/en
Publication of WO2001011101A1 publication Critical patent/WO2001011101A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
    • C23C2/24—Removing excess of molten coatings; Controlling or regulating the coating thickness using magnetic or electric fields
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips

Definitions

  • the present invention relates to a method and a device for continuously producing a metal surface coating on a moving sheet, in particular a carbon steel sheet.
  • the invention is particularly intended for the galvanization of sheet metal strips, typically with a thickness of the order of a few tenths of a millimeter to a few millimeters.
  • the coating metal deposited is zinc; it could also be other conventional coating metals, or alloys of these metals.
  • the current process of galvanizing is known by the designation of hot-dip galvanizing.
  • the strip to be coated is driven in scrolling and circulates from the top to the bottom then from the bottom to the top while passing in the low position around a roller of horizontal axis immersed in a bath of molten zinc.
  • the strip on which the zinc is deposited comes out of the galvanizing bath upwards, substantially vertically.
  • Various means known in themselves, can be used to solidify the zinc and regulate the deposited layer.
  • Another technique known in particular from WO-94/13850 and O-93/18198, consists in passing the strip only from the bottom up through the coating metal bath. The strip then passes through a slot, formed in the bottom of the container, or crucible, containing the coating metal. To contain the molten metal and prevent it from flowing through the space existing between the strip and the edges of the slot, one or more sliding field inductors are used, placed under the crucible, around a vertical channel opening into the bottom of crucible, the walls of the channel being tightly connected to the bottom of the crucible.
  • This channel extends over a certain height, typically of the order of a meter, and its section is determined so as to provide a space of the order of 1 to 2 cm from each side of the strip, sufficient to prevent the band rub against the walls of the channel.
  • the strip is conventionally guided by deflection rollers, respectively arranged one at the bottom, under the crucible, and the other at the top of the installation, at a distance of the order of 10 to 20 meters above the lower roll.
  • the large distance between the two holding rollers is necessary to allow the coating metal to solidify before the strip passes over the upper roller. For the same reason, no guide roller can be used near the crucible, since it would strongly risk marking the still insufficiently solidified coating.
  • the strip therefore passes from the bottom upwards in this channel before passing through the crucible containing the bath of molten coating metal, from a height of the order of 50 cm for example.
  • wiping nozzles are arranged on each side of the strip, to regulate by the breath of an air gap the thickness of the coating and simultaneously participate in its cooling and its solidification.
  • the molten metal is held in lift in the slot of the channel, substantially at mid-height thereof, on the one hand by the upward driving effect caused by the high speed travel of the strip, typically on the order of several m / s, and on the other hand, predominantly, by the electromagnetic forces developed in the conductive metal in fusion by the sliding field inductors, also called linear motors, placed around the channel.
  • the magnetic field generating these forces is therefore a relatively low frequency field, greater than 30 Hz, typically of the order of 50 to 200 Hz. It follows that the field generates by each of the inductors placed on either side of the strip also exerts magnetic forces on the said steel strip, the temperature of which is much lower than the Curie point. These forces are forces of attraction which destabilize the moving web. In fact, when the strip is perfectly centered in the channel, in the plane of symmetry of the inductors, theoretically the forces of attraction of the strip exerted on each side are balanced.
  • this is a very unstable equilibrium position which is broken as soon as a disturbance moves the strip towards one or the other of the inductors.
  • a disturbance for example a vibration of the strip due to the mechanical scrolling members, or a displacement generated by a movement of the molten metal in the crucible, the strip is attracted towards the inductor to which it is closest. , which increases the imbalance.
  • the strip is found applied against one of the walls of the channel, and the coating operation cannot continue, not only because of the friction generated and the degradation of the surface of the strip which could result therefrom, but also because the coating regulator can of course no longer be ensured under these conditions.
  • It aims in particular to propose a method and an installation of the type defined above, for producing a metallic coating on a moving strip, which make it possible to produce a coating as regular as possible, ensuring the centering of the strip in the household slot and channel under the crucible, and without risking damaging the coating by direct contact with guide elements.
  • the invention relates to a process for producing a metallic coating on a moving strip, according to which the strip is passed substantially vertically through a bath of the coating metal contained in a crucible, by passing through a slot in the bottom of said crucible, this process being characterized in that the transverse position of the strip is adjusted by means of magnetic forces exerted on said strip, on each side thereof, the intensity of the magnetic forces applied respectively to each face of the strip being determined so as to maintain the strip in a predetermined transverse position.
  • the strip can be maintained in said predetermined position, in principle a position as much as possible centered in the crucible slot and in the channel of the inductors of lift of the coating metal, as well as between the nozzles. spinning, thus ensuring the required quality of the coating.
  • the positioning of the strip is ensured without contact, which is necessary so as not to damage the barely solidified coating of the strip.
  • the magnetic forces which must act on the strip can be generated by any means capable of essentially causing magnetic forces of attraction, and not repulsive forces, and therefore continuous or low frequency magnetic fields produced will preferably be used for this purpose, even preferentially. , by electromagnets supplied with low frequency current or even better with direct or rectified current.
  • Magnetic forces are applied to the strip at the outlet of the crucible, ie above the coating metal bath. It is in fact at this location that the trajectory of the strip is most likely to be deviated from its ideal rectilinear trajectory, because it is then distant from the guide rollers of the strip, and moreover it is at this point. place where the strip is most affected by the possible disturbing effects of the inductors used to contain the coating metal bath. It is also at this location that a deviation from the trajectory of the strip risks leading to defects in the coating, such as insufficient thickness or, on the contrary, too great, or irregularity in this thickness.
  • magnetic forces can also be applied under the crucible, for example at the level of the strip passage channel, and generated by the inductors placed around this channel to maintain in lift the liquid coating metal in said channel.
  • inductors intended to ensure tightness to also act on the position of the sheet is possible because the field generated by these inductors is a field at a frequency low enough to exert on the ferromagnetic band essentially forces of attraction , while playing the role of linear motor on the non-magnetic metal of the coating to maintain the latter in lift.
  • the use of electromagnets above the coating bath makes it possible to dissociate the levitation function for supporting the liquid metal bath, from the function of centering the strip, and thus to have a greater latitude of action to regulate the position of the band without acting on the level of the lower meniscus of the bath.
  • the position of the strip is measured above the coating metal bath, and the intensity of the magnetic forces of each side of the strip is regulated as a function of the measured position of the strip.
  • the centering effect of the strip is however felt at the level of the channel located under the crucible, thanks to the tension, even slight, applied to the strip between the two rollers lower and upper, more than 10 m apart, which support it mechanically.
  • This tension is sufficient to give a certain longitudinal rigidity to the strip, sufficient for the centering to ensure above the crucible repercute about 1 to 2 m below, at the level of the channel.
  • the application of magnetic forces on the strip above the crucible therefore means that they are applied in a place where the longitudinal bomb of the strip would tend to be greater , which is of course favorable for the precision of the regulation.
  • each electromagnet is associated with a specific position sensor, and the intensity of the field produced by each electromagnet is regulated as a function of the measurement made by the associated sensor.
  • This arrangement makes it possible, in addition, to regulate the flatness of the strip, in the transverse direction, in particular upstream of the spinning nozzles, and perfect parallelism with respect to said spinning nozzles, and thus provide even better regulation of the coating, by guaranteeing a homogeneous effect of the wiping over the entire width of the strip and on each of its faces.
  • the subject of the invention is also a device for producing a metallic coating on a moving ferromagnetic strip, comprising a crucible intended to contain a liquid bath of coating metal, the bottom of the crucible comprising a slot for passage of the strip, the said slot extending downwards by a passage channel around which electromagnetic sealing means are placed to contain the coating metal, characterized in that it comprises magnetic means for adjusting the transverse position of the strip, places above the crucible on either side of the trajectory of said strip, and agencies so as to produce at the level of said trajectory continuous or low frequency magnetic fields, of adjustable intensity.
  • the intensity of the magnetic fields produced by the magnetic means for adjusting the position of the strip is independently adjustable for the adjusting means situated respectively on one side and on the other of the strip.
  • the magnetic means for adjusting the position of the strip comprise electromagnets situated above the crucible, several electromagnets are distributed on each side of the strip, transverse to the trajectory of the strip,
  • the device includes position sensors of the strip, located above the crucible, and preferably, each electromagnet is associated with a sensor and means for regulating the intensity of the supply current of the electro- magnet according to the signal provided by the sensor.
  • the magnetic means for adjusting the transverse position of the strip can also be constituted by the sealing means. electromagnetic used to contain the coating metal.
  • FIG. 1 is a partial schematic perspective view of such an installation
  • FIG. 2 is a plan view of the installation
  • FIG. 3 is a sectional view along line III-III of Figure 2.
  • the continuous galvanizing installation illustrated in the figures comprises a crucible 10 containing a bath of molten zinc 1, crossed from bottom to top by the steel strip 2 to be galvanized.
  • the strip 2 is driven in scrolling, in a manner known per se, in the direction of the arrow F, and is guided by a lower deflection roller 11 and an upper deflection roller 12. It is kept in slight tension between these rollers.
  • the crucible 1 is located between the two rollers 11, 12, closer to the lower roller, so that a sufficient distance exists between the zinc bath 1 and the upper roller 12, so that the zinc is solidified before the strip does goes on the upper roller.
  • a slot 13 for the passage of the strip is formed in the bottom of the crucible which is extended downwards by a channel 14, of section corresponding to the slot in the bottom of the crucible.
  • Electromagnetic sealing means such as inductors 15 are placed on either side of the channel to generate on the molten zinc which tends to flow in said channel electromagnetic forces directed upwards, opposing this flow.
  • These inductors shown schematically on the The drawings are stators of linear motors supplied by a current of fairly low frequency, from 15 to 100 Hz for example, producing a rising sliding field.
  • the thickness of the strip 2 is of the order of a few tenths of a millimeter, and its width of the order of several tens of centimeters, or of the meter,
  • the width of the slot 13 and of the channel 14 for passing the strip is of the order of a few centimeters, typically about 3 cm,
  • the height of the channel 14 is of the order of a meter and the height of the coating metal 1 in the crucible 10 of approximately 50 cm, while the distance between the lower 11 and upper 12 rollers for guiding the strip is of the order of 10 to 20 m, all these dimensions being given only by way of example.
  • wiping nozzles 16 in the form of ramps extending transversely on either side of the path of the strip, to blow towards the strip a jet of air ensuring cooling zinc deposits and contributes to the regularity of its thickness.
  • electromagnets 20 are arranged on each side of the trajectory of the strip, to exert on this latter magnetic forces of attraction.
  • Each electromagnet 20 is associated with a tape position sensor 21, for example a transducer of the type known per se, both connected to a regulation box 22, of the PID regulator type, adapted to adjust the intensity. of the supply current of the electromagnet 20 as a function of the position of the strip determined by the sensor 21.
  • the invention is not limited to the device described above only by way of example.
  • the location of the magnetic means for adjusting the position of the strip and of the sensors is preferably between the crucible and the wiping nozzles, this location is in no way limiting.
  • the sensors will preferably be kept close to the spinning nozzles, since this is generally at this level, above the crucible and at distance from the two guide rollers, that the amplitude of the deviations of the strip is likely to be the greatest, and therefore at this level that the measurement will have the best sensitivity.

Abstract

The invention concerns a method for producing a metal coating on a moving ferromagnetic strip (2) which consists in causing the strip (2) to pass substantially vertically in a metal coating bath (1) contained in a crucible (10), causing it to pass through a slot (13) provided in the base of the crucible, and in adjusting the transverse position of the strip using magnetic forces generated for example by electromagnets (20) placed above the crucible and produced on said strip, on either side thereof, the intensity of the magnetic forces respectively applied on each face of the strip being determined so as to maintain the strip in a predetermined transverse position.

Description

Procédé et dispositif de réalisation en continu d'un revêtement de surface métallique sur une tôle en défilement. Method and device for continuously producing a metal surface coating on a moving sheet.
La présente invention concerne un procède et un dispositif de réalisation en continu d'un revêtement de surface métallique sur une tôle en défilement, notamment une tôle en acier au carbone. L'invention s'adresse particulièrement a la galvanisation des bandes de tôle, typiquement d'une épaisseur de l'ordre de quelques dixièmes de millimètres a quelques millimètres. Typiquement pour une opération de galvanisation, le métal de revêtement dépose est du zinc ; il pourrait également s'agir d'autres métaux de revêtement classiques, ou d'alliages de ces métaux.The present invention relates to a method and a device for continuously producing a metal surface coating on a moving sheet, in particular a carbon steel sheet. The invention is particularly intended for the galvanization of sheet metal strips, typically with a thickness of the order of a few tenths of a millimeter to a few millimeters. Typically for a galvanizing operation, the coating metal deposited is zinc; it could also be other conventional coating metals, or alloys of these metals.
Le procède courant de galvanisation est connu sous la désignation de galvanisation au trempe. La bande a revêtir est entraînée en défilement et circule du haut vers le bas puis du bas vers le haut en passant en position basse autour d'un rouleau d'axe horizontal immerge dans un bain de zinc fondu. La bande sur laquelle le zinc s'est dépose ressort du bain de galvanisation vers le haut, sensiblement a la verticale. Divers moyens, connus en eux-mêmes, peuvent être utilises pour assurer la solidification du zinc et la régulante de la couche déposée .The current process of galvanizing is known by the designation of hot-dip galvanizing. The strip to be coated is driven in scrolling and circulates from the top to the bottom then from the bottom to the top while passing in the low position around a roller of horizontal axis immersed in a bath of molten zinc. The strip on which the zinc is deposited comes out of the galvanizing bath upwards, substantially vertically. Various means, known in themselves, can be used to solidify the zinc and regulate the deposited layer.
Une autre technique, connue notamment par WO- 94/13850 et O-93/18198, consiste a faire passer la bande uniquement de bas en haut a travers le bain de métal de revêtement. La bande passe alors a travers une fente, ménagée dans le fond du récipient, ou creuset, contenant le métal de revêtement. Pour contenir le métal en fusion et éviter son écoulement par l'espace existant entre la bande et les bords de la fente, on utilise un ou des inducteurs a champ glissant, places sous le creuset, autour d'un chenal vertical débouchant dans le fond du creuset, les parois du chenal étant raccordées de manière etanche au fond du creuset. Ce chenal s'étend sur une certaine hauteur, typiquement de l'ordre du mètre, et sa section est déterminée de manière a ménager un espace de l'ordre de 1 a 2 cm de chaque côte de la bande, suffisant pour éviter que la bande vienne frotter contre les parois du chenal. On notera que la bande est classiquement guidée par des rouleaux de renvoi, disposes respectivement l'un en partie basse, sous le creuset, et l'autre en partie haute de l'installation, a une distance de l'ordre de 10 a 20 mètres au-dessus du rouleau inférieur. La distance importante séparant les deux rouleaux de maintien est nécessaire pour permettre au métal de revêtement de se solidifier avant que la bande passe sur le rouleau supérieur. Pour la même raison, aucun rouleau de guidage ne peut être utilise a proximité du creuset, puisqu'il risquerait fortement de marquer le revêtement encore insuffisamment solidifie.Another technique, known in particular from WO-94/13850 and O-93/18198, consists in passing the strip only from the bottom up through the coating metal bath. The strip then passes through a slot, formed in the bottom of the container, or crucible, containing the coating metal. To contain the molten metal and prevent it from flowing through the space existing between the strip and the edges of the slot, one or more sliding field inductors are used, placed under the crucible, around a vertical channel opening into the bottom of crucible, the walls of the channel being tightly connected to the bottom of the crucible. This channel extends over a certain height, typically of the order of a meter, and its section is determined so as to provide a space of the order of 1 to 2 cm from each side of the strip, sufficient to prevent the band rub against the walls of the channel. It will be noted that the strip is conventionally guided by deflection rollers, respectively arranged one at the bottom, under the crucible, and the other at the top of the installation, at a distance of the order of 10 to 20 meters above the lower roll. The large distance between the two holding rollers is necessary to allow the coating metal to solidify before the strip passes over the upper roller. For the same reason, no guide roller can be used near the crucible, since it would strongly risk marking the still insufficiently solidified coating.
La bande passe donc du bas vers le haut dans ce chenal avant de traverser le creuset contenant le bain de métal de revêtement en fusion, d'une hauteur de l'ordre de 50 cm par exemple. Au-dessus du bain, des buses d'essorages sont disposées de chaque côte de la bande, pour régulariser par le souffle d'une lame d'air l'épaisseur du revêtement et participer simultanément a son refroidissement et a sa solidification. Le métal en fusion est maintenu en sustentation dans la fente du chenal, sensiblement a mi-hauteur de celui-ci, d'une part par l'effet d'entraînement vers le haut provoque par le défilement a grande vitesse de la bande, typiquement de l'ordre de plusieurs m/s, et d'autre part, de manière prépondérante, par les forces électromagnétiques développées dans le métal conducteur en fusion par les inducteurs a champ glissant, encore appelés moteurs linéaires, places autour du chenal.The strip therefore passes from the bottom upwards in this channel before passing through the crucible containing the bath of molten coating metal, from a height of the order of 50 cm for example. Above the bath, wiping nozzles are arranged on each side of the strip, to regulate by the breath of an air gap the thickness of the coating and simultaneously participate in its cooling and its solidification. The molten metal is held in lift in the slot of the channel, substantially at mid-height thereof, on the one hand by the upward driving effect caused by the high speed travel of the strip, typically on the order of several m / s, and on the other hand, predominantly, by the electromagnetic forces developed in the conductive metal in fusion by the sliding field inductors, also called linear motors, placed around the channel.
Des forces électromagnétiques relativement importantes sont nécessaires pour maintenir le métal de revêtement en lévitation, en s' opposant a la pression hydrostatique de ce métal liquide. Le champ magnétique générateur de ces forces est donc un champ a relativement basse fréquence, supérieur a 30 Hz, typiquement de l'ordre de 50 a 200 Hz. Il en resuite que le champ génère par chacun des inducteurs places de part et d' autre de la bande exerce également des forces magnétiques sur la dite bande en acier, dont la température est bien inférieure au point de Curie. Ces forces sont des forces d'attraction qui déstabilisent la bande en défilement. En effet, lorsque la bande est parfaitement centrée dans le chenal, dans le plan de symétrie des inducteurs, théoriquement les forces d'attraction de la bande exercées de chaque côte s'équilibrent. Mais il s'agit la d'une position d'équilibre très instable qui est rompu des qu'une perturbation déplace la bande vers l'un ou l'autre des inducteurs. Suite a une telle perturbation, par exemple une vibration de la bande due aux organes mécaniques de défilement , ou un déplacement génère par un mouvement du métal en fusion dans le creuset, la bande se trouve attirée vers l'inducteur dont elle est le plus proche, ce qui accroît le déséquilibre. In fine, la bande se retrouve appliquée contre une des parois du chenal, et l'opération de revêtement ne peut se poursuivre, non seulement a cause du frottement génère et de la dégradation de la surface de la bande qui pourrait en résulter, mais aussi parce que la régulante du revêtement ne peut bien sûr plus être assurée dans ces conditions.Relatively electromagnetic forces Important are necessary to keep the coating metal in levitation, opposing the hydrostatic pressure of this liquid metal. The magnetic field generating these forces is therefore a relatively low frequency field, greater than 30 Hz, typically of the order of 50 to 200 Hz. It follows that the field generates by each of the inductors placed on either side of the strip also exerts magnetic forces on the said steel strip, the temperature of which is much lower than the Curie point. These forces are forces of attraction which destabilize the moving web. In fact, when the strip is perfectly centered in the channel, in the plane of symmetry of the inductors, theoretically the forces of attraction of the strip exerted on each side are balanced. However, this is a very unstable equilibrium position which is broken as soon as a disturbance moves the strip towards one or the other of the inductors. Following such a disturbance, for example a vibration of the strip due to the mechanical scrolling members, or a displacement generated by a movement of the molten metal in the crucible, the strip is attracted towards the inductor to which it is closest. , which increases the imbalance. Ultimately, the strip is found applied against one of the walls of the channel, and the coating operation cannot continue, not only because of the friction generated and the degradation of the surface of the strip which could result therefrom, but also because the coating regulator can of course no longer be ensured under these conditions.
Il n' existe pas actuellement de moyens de réglage de la position de la bande en sortie du creuset, c'est a dire suffisamment près au-dessus de celui-ci, permettant de maintenir la position centrée requise de la bande dans le chenal, ou de moyens de régulation permettant de s'opposer a toute dérive de cette position. Comme de^a indique ci-dessus, il n'est pas possible d'utiliser a cet endroit un quelconque moyen de maintien mécanique, puisque la bande est alors trop fraîchement revêtue pour accepter un contact sans détériorer le revêtement. La présente invention a pour but de résoudre les problèmes indiques ci-dessus. Elle vise en particulier a proposer un procède et une installation du type défini ci-dessus, pour la réalisation d'un revêtement métallique sur une bande en défilement, qui permettent de réaliser un revêtement le plus régulier possible, en assurant le centrage de la bande dans la fente et le chenal ménages sous le creuset, et sans risquer d'abîmer le revêtement par un contact direct avec des éléments de guidage.There are currently no means for adjusting the position of the strip at the outlet of the crucible, that is to say sufficiently close above the latter, making it possible to maintain the required centered position of the strip in the channel, or regulation means making it possible to oppose any drift from this position. As of ^ a indicated above, it is not possible to use any mechanical means at this location, since the strip is then too freshly coated to accept contact without damaging the coating. The object of the present invention is to solve the problems indicated above. It aims in particular to propose a method and an installation of the type defined above, for producing a metallic coating on a moving strip, which make it possible to produce a coating as regular as possible, ensuring the centering of the strip in the household slot and channel under the crucible, and without risking damaging the coating by direct contact with guide elements.
Avec ces objectifs en vue, l'invention a pour objet un procédé de réalisation d'un revêtement métallique sur une bande en défilement, selon lequel on fait passer la bande sensiblement verticalement dans un bain du métal de revêtement contenu dans un creuset, en la faisant passer par une fente ménagée dans le fond du dit creuset, ce procédé étant caractérisé en ce qu' on règle la position transversale de la bande au moyen de forces magnétiques exercées sur la dite bande, de chaque côte de celle-ci, l'intensité des forces magnétiques appliquées respectivement sur chaque face de la bande étant déterminée de manière à maintenir la bande dans une position transversale prédéterminée.With these objectives in view, the invention relates to a process for producing a metallic coating on a moving strip, according to which the strip is passed substantially vertically through a bath of the coating metal contained in a crucible, by passing through a slot in the bottom of said crucible, this process being characterized in that the transverse position of the strip is adjusted by means of magnetic forces exerted on said strip, on each side thereof, the intensity of the magnetic forces applied respectively to each face of the strip being determined so as to maintain the strip in a predetermined transverse position.
Grâce à l'invention, la bande peut être maintenue dans la dite position prédéterminée, en principe une position autant que possible centrée dans la fente du creuset et dans le chenal des inducteurs de sustentation du métal de revêtement, ainsi que entre les buses d'essorage, assurant ainsi la qualité requise du revêtement. Le positionnement de la bande est assure sans contact, ce qui est nécessaire pour ne pas détériorer le revêtement à peine solidifié de la bande. Les forces magnétiques devant agir sur la bande peuvent être générées par tous moyens susceptibles de provoquer essentiellement des forces magnétiques d'attraction, et non des forces répulsives, et on utilisera donc preferentiellement a cet effet des champs magnétiques continus ou basse fréquence produits, encore preferentiellement , par des electroaimants alimentes en courant basse fréquence ou encore mieux en courant continu ou redresse. Des forces répulsives ne seraient pas en elles- mêmes gênantes pour ce qui est du positionnement de la bande, car la combinaison de telles forces appliquées de chaque côte de la bande serait par nature auto-centrante, donc favorable. Mais de telles forces répulsives agiraient également sur la couche de métal de revêtement dépose, avec comme conséquence un effet de décollement perturbateur ou même destructeur de la dite couche, déposée sur la surface de la bande mais encore non totalement solidifiée en sortie du creuset. II est incidemment rappelé ici que, de manière générale, un champ magnétique est susceptible de générer deux types de forces :Thanks to the invention, the strip can be maintained in said predetermined position, in principle a position as much as possible centered in the crucible slot and in the channel of the inductors of lift of the coating metal, as well as between the nozzles. spinning, thus ensuring the required quality of the coating. The positioning of the strip is ensured without contact, which is necessary so as not to damage the barely solidified coating of the strip. The magnetic forces which must act on the strip can be generated by any means capable of essentially causing magnetic forces of attraction, and not repulsive forces, and therefore continuous or low frequency magnetic fields produced will preferably be used for this purpose, even preferentially. , by electromagnets supplied with low frequency current or even better with direct or rectified current. Repulsive forces would not in themselves be troublesome with regard to the positioning of the strip, since the combination of such forces applied to each side of the strip would be self-centering in nature, therefore favorable. But such repulsive forces would also act on the coating metal layer deposited, with the consequence of a disruptive or even destructive detachment effect of said layer, deposited on the surface of the strip but still not completely solidified at the outlet of the crucible. It is incidentally recalled here that, in general, a magnetic field is capable of generating two types of force:
- des forces dites purement magnétiques, ou forces d'aimantation, qui sont des forces d'attraction n'agissant, dans le domaine ici concerne, que sur la bande en acier ferromagnétique et pas sur le métal de revêtement, notamment du zinc ou alliage de zinc, non magnétique, et des forces électromagnétiques, répulsives, générées par des champs variables avec une fréquence suffisamment élevée, qui agissent sur les métaux conducteurs, et qui sont notamment utilisées, dans le domaine de la présente invention, pour maintenir le métal de revêtement liquide dans le creuset. Avec une alimentation en courant a basse ou très basse fréquence, c'est a dire a moins de 200 Hz, ou en courant continu, seules des forces d' aimantation, attractives, sont générées. On utilisera preferentiellement un courant de fréquence inférieure ou égale a 50 Hz, ou un courant continu ou redresse. Ainsi, l'utilisation d' électro-aimants dans ces conditions permet une action sur la bande a distance, donc sans risque d'un contact destructeur du revêtement, tout en limitant très fortement l'action du cnamp sur le revêtement de zinc ou autre métal ou alliage électriquement conducteur.- so-called purely magnetic forces, or magnetization forces, which are attractive forces acting, in the field here concerned, only on the ferromagnetic steel strip and not on the coating metal, in particular zinc or alloy zinc, non-magnetic, and electromagnetic forces, repulsive, generated by variable fields with a sufficiently high frequency, which act on the conductive metals, and which are in particular used, in the field of the present invention, to maintain the metal of liquid coating in the crucible. With a power supply at low or very low frequency, that is to say at less than 200 Hz, or direct current, only attractive magnetization forces are generated. Preferably a current of frequency less than or equal to 50 Hz, or a direct or rectified current will be used. Thus, the use of electromagnets under these conditions allows an action on the strip at a distance, therefore without risk of a destructive contact of the coating, while very strongly limiting the action of the cnamp on the zinc coating or other electrically conductive metal or alloy.
Les forces magnétiques sont appliquées sur la bande en sortie du creuset, c'est à dire au-dessus du bain de métal de revêtement. C'est en effet à cet endroit que la trajectoire de la bande risque le plus d'être déviée par rapport à sa trajectoire rectiligne idéale, car on est alors éloigné des rouleaux de guidage de la bande, et de plus c'est à cet endroit que la bande subit le plus les éventuels effets perturbateurs des inducteurs utilises pour contenir le bain de métal de revêtement. C'est également à cet endroit qu' une déviation de la trajectoire de la bande risque de conduire à des défauts du revêtement, tels que épaisseur insuffisante ou au contraire trop importante, ou irrégularité de cette épaisseur. En effet, la régularité du revêtement est notamment obtenue grâce a l'action de buses d'essorage disposées de chaque côté de la bande, au-dessus du creuset, et des variations de distance de la bande par rapport à ces buses ont comme conséquence des variations sur l'épaisseur de revêtement. Au pire, on risquerait même d'obtenir un frottement, tout à fait rédhibitoire, de la bande sur les dites buses. On comprendra donc qu'il est particulièrement avantageux de réguler la position de la bande, en appliquant sur celle-ci les dites forces magnétiques, au-dessus du creuset, avant les buses d'essorage, c'est à dire entre le creuset et les dites buses . Toutefois, en complément a la disposition qui vient d'être mentionnée, des forces magnétiques peuvent aussi être appliquées sous le creuset, par exemple au niveau du chenal de passage de la bande, et générées par les inducteurs places autour de ce chenal pour maintenir en sustentation le métal de revêtement liquide dans le dit chenal. L'utilisation des inducteurs destines a assurer l'etancheite pour également agir sur la position de la tôle est possible du fait que le champ génère par ces inducteurs est un champ a fréquence suffisamment basse pour exercer sur la bande ferromagnétique essentiellement des forces d'attractions, tout en jouant le rôle de moteur linéaire sur le métal non magnétique du revêtement pour maintenir ce dernier en sustentation. Une telle disposition est cependant difficilement exploitable a elle seule du fait qu' il serait alors très difficile d' assurer a la fois la régulation du maintien du niveau du ménisque inférieur a l'intérieur du chenal de passage de la bande, et la régulation de la position transversale de la bande, conformément a l'invention. On pourrait cependant envisager d' agir sur les inducteurs de manière a ce que l'effet de sustentation globalement assure par les inducteurs places des deux côtes de la bande soit maintenu constant, ou ajuste pour maintenir le ménisque inférieur a bon niveau, et que le rapport des intensités des champs générées par les inducteurs situes respectivement d'un côte et de l'autre de la bande soit ajuste pour exercer sur la bande les forces d'attractions dirigées dans le sens requis pour la maintenir centrée. II apparaîtra cependant clairement que l'utilisation d' electroaimants au-dessus du bain de revêtement permet de dissocier la fonction de lévitation pour soutenir le bain de métal liquide, de la fonction de centrage de la bande, et ainsi d'avoir une plus grande latitude d' action pour réguler la position de la bande sans agir sur le niveau du ménisque inférieur du bain. Selon une disposition préférentielle, on mesure la position de la bande au-dessus du bain de métal de revêtement, et on régule l' intensité des forces magnétiques de chaque côte de la bande en fonction de la position mesurée de la bande.Magnetic forces are applied to the strip at the outlet of the crucible, ie above the coating metal bath. It is in fact at this location that the trajectory of the strip is most likely to be deviated from its ideal rectilinear trajectory, because it is then distant from the guide rollers of the strip, and moreover it is at this point. place where the strip is most affected by the possible disturbing effects of the inductors used to contain the coating metal bath. It is also at this location that a deviation from the trajectory of the strip risks leading to defects in the coating, such as insufficient thickness or, on the contrary, too great, or irregularity in this thickness. Indeed, the regularity of the coating is notably obtained thanks to the action of wiping nozzles arranged on each side of the strip, above the crucible, and variations in the distance of the strip relative to these nozzles have the consequence variations in coating thickness. At worst, there is even a risk of obtaining a completely unacceptable rubbing of the strip on said nozzles. It will therefore be understood that it is particularly advantageous to regulate the position of the strip, by applying to it the said magnetic forces, above the crucible, before the wiping nozzles, that is to say between the crucible and the said nozzles. However, in addition to the arrangement which has just been mentioned, magnetic forces can also be applied under the crucible, for example at the level of the strip passage channel, and generated by the inductors placed around this channel to maintain in lift the liquid coating metal in said channel. The use of inductors intended to ensure tightness to also act on the position of the sheet is possible because the field generated by these inductors is a field at a frequency low enough to exert on the ferromagnetic band essentially forces of attraction , while playing the role of linear motor on the non-magnetic metal of the coating to maintain the latter in lift. However, such an arrangement is difficult to exploit on its own because it would then be very difficult to ensure both the regulation of maintaining the level of the lower meniscus inside the channel for passage of the strip, and the regulation of the transverse position of the strip, in accordance with the invention. One could however consider acting on the inductors so that the overall lift effect provided by the inductors placed on the two sides of the strip is kept constant, or adjusted to keep the lower meniscus at a good level, and that the ratio of the field intensities generated by the inductors located respectively on one side and the other of the strip is adjusted to exert on the strip the attraction forces directed in the direction required to keep it centered. It will however be clear that the use of electromagnets above the coating bath makes it possible to dissociate the levitation function for supporting the liquid metal bath, from the function of centering the strip, and thus to have a greater latitude of action to regulate the position of the band without acting on the level of the lower meniscus of the bath. According to a preferred arrangement, the position of the strip is measured above the coating metal bath, and the intensity of the magnetic forces of each side of the strip is regulated as a function of the measured position of the strip.
L'effet de centrage de la bande, bien que les forces soient preferentiellement appliquées au-dessus du creuset, se repercute cependant au niveau du chenal situe sous le creuset, grâce a la tension, même légère, appliquée sur la bande entre les deux rouleaux inférieur et supérieur, distants de plus de 10 m, qui la soutiennent mécaniquement. Cette tension est suffisante pour conférer une certaine rigidité longitudinale a la bande, suffisante pour que le centrage assure au-dessus du creuset se repercute environ 1 a 2 m plus bas, au niveau du chenal. Comme l'ensemble du creuset est situe plus près du rouleau inférieur, l'application des forces magnétiques sur la bande au-dessus du creuset fait donc qu' elles sont appliquées en un lieu ou le bombe longitudinal de la bande tendrait a être plus important, ce qui est bien sûr favorable pour la précision de la régulation .The centering effect of the strip, although the forces are preferably applied above the crucible, is however felt at the level of the channel located under the crucible, thanks to the tension, even slight, applied to the strip between the two rollers lower and upper, more than 10 m apart, which support it mechanically. This tension is sufficient to give a certain longitudinal rigidity to the strip, sufficient for the centering to ensure above the crucible repercute about 1 to 2 m below, at the level of the channel. As the whole crucible is located closer to the lower roller, the application of magnetic forces on the strip above the crucible therefore means that they are applied in a place where the longitudinal bomb of the strip would tend to be greater , which is of course favorable for the precision of the regulation.
Selon encore une autre disposition préférée, on utilise pour générer les forces magnétiques plusieurs electroaimants de chaque côte de la bande, chaque electroaimant étant associe a un capteur de position spécifique, et on régule l' intensité du champ produit par chaque electro-aimant en fonction de la mesure effectuée par le capteur associe. Cette disposition permet d'assurer, en complément, une régulation αe la planeite de la bande, dans le sens transversal, notamment en amont des buses d'essorage, et un parfait parallélisme par rapport aux dites buses d'essorage, et ainsi d'assurer encore mieux la régulante du revêtement, en garantissant un effet homogène de l'essorage sur toute la largeur de la bande et sur chacune de ses faces. L'invention a aussi pour objet un dispositif de réalisation d'un revêtement métallique sur une bande ferromagnétique en défilement, comportant un creuset destine a contenir un bain liquide de métal de revêtement, le fond du creuset comportant une fente de passage de la bande, la dite fente se prolongeant vers le bas par un chenal de passage autour duquel sont places des moyens d' etancheite électromagnétiques pour contenir le métal de revêtement, caractérise en ce qu'il comporte des moyens magnétiques de réglage de la position transversale de la bande, places au dessus du creuset de part et d'autre de la trajectoire de la dite bande, et agences de manière a produire au niveau de la dite trajectoire des champs magnétiques continus ou a basse fréquence, d' intensité réglable.According to yet another preferred arrangement, several electromagnets are used on each side of the strip to generate the magnetic forces, each electromagnet being associated with a specific position sensor, and the intensity of the field produced by each electromagnet is regulated as a function of the measurement made by the associated sensor. This arrangement makes it possible, in addition, to regulate the flatness of the strip, in the transverse direction, in particular upstream of the spinning nozzles, and perfect parallelism with respect to said spinning nozzles, and thus provide even better regulation of the coating, by guaranteeing a homogeneous effect of the wiping over the entire width of the strip and on each of its faces. The subject of the invention is also a device for producing a metallic coating on a moving ferromagnetic strip, comprising a crucible intended to contain a liquid bath of coating metal, the bottom of the crucible comprising a slot for passage of the strip, the said slot extending downwards by a passage channel around which electromagnetic sealing means are placed to contain the coating metal, characterized in that it comprises magnetic means for adjusting the transverse position of the strip, places above the crucible on either side of the trajectory of said strip, and agencies so as to produce at the level of said trajectory continuous or low frequency magnetic fields, of adjustable intensity.
Selon d'autres caractéristiques particulières :According to other particular characteristics:
- l' intensité des champs magnétiques produits par les moyens magnétiques de réglage de la position de la bande est réglable indépendamment pour les moyens de réglage situes respectivement d'un côte et de l'autre de la bande.the intensity of the magnetic fields produced by the magnetic means for adjusting the position of the strip is independently adjustable for the adjusting means situated respectively on one side and on the other of the strip.
- les moyens magnétiques de réglage de la position de la bande comportent des electroaimants, situes au- dessus du creuset, - plusieurs electroaimants sont repartis de chaque côte de la bande, transversalement a la trajectoire de la bande,the magnetic means for adjusting the position of the strip comprise electromagnets situated above the crucible, several electromagnets are distributed on each side of the strip, transverse to the trajectory of the strip,
- le dispositif comporte des capteurs de position de la bande, situes au-dessus du creuset, et preferentiellement , a chaque electro-aimant est associe un capteur et des moyens de régulation de l' intensité du courant d'alimentation de l' electro-aimant en fonction du signal fourni par le capteur.- The device includes position sensors of the strip, located above the crucible, and preferably, each electromagnet is associated with a sensor and means for regulating the intensity of the supply current of the electro- magnet according to the signal provided by the sensor.
Selon une autre disposition, les moyens magnétiques de réglage de la position transversale de la bande peuvent être aussi constitues par les moyens d' etancheite électromagnétiques utilisés pour contenir le métal de revêtement .According to another arrangement, the magnetic means for adjusting the transverse position of the strip can also be constituted by the sealing means. electromagnetic used to contain the coating metal.
D'autres caractéristiques et avantages apparaîtront dans la description qui va être faite d'une installation de galvanisation de bandes en acier conforme à 1' invention .Other characteristics and advantages will appear in the description which will be given of an installation for galvanizing steel strips according to the invention.
On se reportera aux dessins annexés dans lesquels :Reference is made to the appended drawings in which:
- la figure 1 est une vue schématique partielle en perspective d'une telle installation, la figure 2 est une vue en plan de 1' installation,FIG. 1 is a partial schematic perspective view of such an installation, FIG. 2 is a plan view of the installation,
- la figure 3 est une vue en coupe selon la ligne III-III de la figure 2. L' installation de galvanisation en continu illustrée sur les figures comporte un creuset 10 contenant un bain de zinc fondu 1, traversé de bas en haut par la bande d'acier 2 à galvaniser. La bande 2 est entraînée en défilement, de manière connue en soi, dans le sens de la flèche F, et est guidée par un rouleau de renvoi inférieur 11 et un rouleau de renvoi supérieur 12. Elle est maintenue en légère tension entre ces rouleaux. Le creuset 1 est situé entre les deux rouleaux 11, 12, plus près du rouleau inférieur, de sorte qu'une distance suffisante existe entre le bain de zinc 1 et le rouleau supérieur 12, pour que le zinc soit solidifié avant que la bande ne passe sur le rouleau supérieur.- Figure 3 is a sectional view along line III-III of Figure 2. The continuous galvanizing installation illustrated in the figures comprises a crucible 10 containing a bath of molten zinc 1, crossed from bottom to top by the steel strip 2 to be galvanized. The strip 2 is driven in scrolling, in a manner known per se, in the direction of the arrow F, and is guided by a lower deflection roller 11 and an upper deflection roller 12. It is kept in slight tension between these rollers. The crucible 1 is located between the two rollers 11, 12, closer to the lower roller, so that a sufficient distance exists between the zinc bath 1 and the upper roller 12, so that the zinc is solidified before the strip does goes on the upper roller.
Une fente 13 de passage de la bande est ménagée dans le fond du creuset qui se prolonge vers le bas par un chenal 14, de section correspondant à la fente du fond du creuset. Des moyens d' étanchéité électromagnétiques tels que des inducteurs 15 sont placés de part et d'autre du chenal pour générer sur le zinc en fusion qui tend à s'écouler dans le dit chenal des forces électromagnétiques dirigées vers le haut, s' opposant à cet écoulement. Ces inducteurs, schématisés sur les dessins, sont des stators de moteurs linéaires alimentes par un courant de fréquence assez basse, de 15 a 100 Hz par exemple, produisant un champ glissant remontant.A slot 13 for the passage of the strip is formed in the bottom of the crucible which is extended downwards by a channel 14, of section corresponding to the slot in the bottom of the crucible. Electromagnetic sealing means such as inductors 15 are placed on either side of the channel to generate on the molten zinc which tends to flow in said channel electromagnetic forces directed upwards, opposing this flow. These inductors, shown schematically on the The drawings are stators of linear motors supplied by a current of fairly low frequency, from 15 to 100 Hz for example, producing a rising sliding field.
Il est signale que sur les dessins le rapport réel entre les différentes dimensions n' a volontairement pas été respecté, par souci de clarté, pour mieux illustrer les problèmes auxquels l'invention remédie et les solutions qu'elle y apporte. Il est rappelé que dans la pratique : - l'épaisseur de la bande 2 est de l'ordre de quelques dixièmes de millimètre, et sa largeur de l'ordre de plusieurs dizaines de centimètres, ou du mètre,It should be noted that, in the drawings, the real relationship between the different dimensions has been deliberately not respected, for the sake of clarity, to better illustrate the problems which the invention remedies and the solutions which it provides. It is recalled that in practice: the thickness of the strip 2 is of the order of a few tenths of a millimeter, and its width of the order of several tens of centimeters, or of the meter,
- la largeur de la fente 13 et du chenal 14 de passage de la bande est de l'ordre de quelques centimètres, typiquement environ 3 cm,the width of the slot 13 and of the channel 14 for passing the strip is of the order of a few centimeters, typically about 3 cm,
- la hauteur du chenal 14 est de l'ordre du mètre et la hauteur de métal de revêtement 1 dans le creuset 10 d'environ 50 cm, alors que la distance entre les rouleaux inférieur 11 et supérieur 12 de guidage de la bande est de l'ordre de 10 à 20 m, toutes ces dimensions étant données uniquement a titre d'exemple.the height of the channel 14 is of the order of a meter and the height of the coating metal 1 in the crucible 10 of approximately 50 cm, while the distance between the lower 11 and upper 12 rollers for guiding the strip is of the order of 10 to 20 m, all these dimensions being given only by way of example.
Au-dessus du creuset 10 sont disposés des buses d'essorage 16 sous forme de rampes s' étendant transversalement de part et d'autre de la trajectoire de la bande, pour souffler en direction de la bande un jet d' air assurant le refroidissement du zinc dépose et participant à la régularité de son épaisseur. Comme cela a déjà été indiqué, l est donc important que non seulement la bande reste centrée dans le chenal 14, mais aussi qu'elle reste bien centrée entre les buses 16 et parallèle a celles-ci, pour assurer la régulante du revêtement. Il faut donc éviter que la bande ne vienne dans une position décalée latéralement comme illustre en pointillé par le tracé 2' de la figure 3.Above crucible 10 are arranged wiping nozzles 16 in the form of ramps extending transversely on either side of the path of the strip, to blow towards the strip a jet of air ensuring cooling zinc deposits and contributes to the regularity of its thickness. As already indicated, it is therefore important that not only the strip remains centered in the channel 14, but also that it remains well centered between the nozzles 16 and parallel to them, to ensure the regulation of the coating. It is therefore necessary to prevent the strip from coming in a laterally offset position as illustrated in dotted lines by the line 2 ′ in FIG. 3.
A cet effet, conformément a l'invention, des électro-aimants 20 sont disposes de chaque côte de la trajectoire de la bande, pour exercer sur celle ci des forces magnétiques d'attraction. Preferentiellement , pour pouvoir agir de manière différenciée sur des zones longitudinales différentes, on disposera plusieurs electroaimants 20, par exemple trois de chaque côte, repartis sur la largeur de la bande. A chaque électro- aimant 20 est associe un capteur 21 de position de la bande, par exemple un capteur mductif de type connu en soi, tous deux connectes a un boîtier de régulation 22, de type régulateur dit PID, adapte pour ajuster 1' intensité du courant d'alimentation de l' electroaimant 20 en fonction de la position de la bande déterminée par le capteur 21. L'invention n'est pas limitée au dispositif décrit ci-dessus uniquement a titre d'exemple. En particulier, si la localisation des moyens magnétiques de réglage de la position de la bande et des capteurs est preferentiellement entre le creuset et les buses d'essorage, cette localisation n'est nullement limitative. Dans le cas ou les dits moyens magnétiques seraient places ailleurs, ou constitues par les inducteurs 15, on maintiendra cependant preferentiellement les capteurs a proximité des buses d'essorage, puisque c'est en gênerai a ce niveau, au- dessus du creuset et a distance des deux rouleaux de guidage, que l'amplitude des déviations de la bande risque d'être la plus grande, et donc a ce niveau que la mesure aura la meilleure sensibilité. To this end, in accordance with the invention, electromagnets 20 are arranged on each side of the trajectory of the strip, to exert on this latter magnetic forces of attraction. Preferably, to be able to act in a differentiated manner on different longitudinal zones, there will be several electromagnets 20, for example three on each side, distributed over the width of the strip. Each electromagnet 20 is associated with a tape position sensor 21, for example a transducer of the type known per se, both connected to a regulation box 22, of the PID regulator type, adapted to adjust the intensity. of the supply current of the electromagnet 20 as a function of the position of the strip determined by the sensor 21. The invention is not limited to the device described above only by way of example. In particular, if the location of the magnetic means for adjusting the position of the strip and of the sensors is preferably between the crucible and the wiping nozzles, this location is in no way limiting. In the case where the said magnetic means would be placed elsewhere, or constituted by the inductors 15, however, the sensors will preferably be kept close to the spinning nozzles, since this is generally at this level, above the crucible and at distance from the two guide rollers, that the amplitude of the deviations of the strip is likely to be the greatest, and therefore at this level that the measurement will have the best sensitivity.

Claims

REVENDICATIONS
1. Procède de réalisation d'un revêtement métallique sur une bande ferromagnétique (2) en défilement, selon lequel on fait passer la bande (2) sensiblement verticalement dans un bain du métal de revêtement (1) contenu dans un creuset (10), en la faisant passer par une fente (13) ménagée dans le fond du dit creuset, caractérise en ce qu'on règle la position transversale de la bande au moyen de forces magnétiques exercées sur la dite bande en sortie du creuset (10), c'est a dire au-dessus du bain de métal de revêtement (1), de chaque côte de la bande, l' intensité des forces magnétiques appliquées respectivement sur chaque face de la bande étant déterminée de manière a maintenir la bande dans une position transversale prédéterminée.1. Method for producing a metallic coating on a moving ferromagnetic strip (2), according to which the strip (2) is passed substantially vertically through a bath of the coating metal (1) contained in a crucible (10), by passing it through a slot (13) formed in the bottom of said crucible, characterized in that the transverse position of the strip is adjusted by means of magnetic forces exerted on said strip at the outlet of the crucible (10), c is to say above the coating metal bath (1), on each side of the strip, the intensity of the magnetic forces applied respectively on each side of the strip being determined so as to maintain the strip in a transverse position predetermined.
2. Procède selon la revendication 1, caractérise en ce que les forces magnétiques sont générées par des champs magnétiques continus ou basse fréquence produits par des electroaimants (20) .2. Method according to claim 1, characterized in that the magnetic forces are generated by continuous or low frequency magnetic fields produced by electromagnets (20).
3. Procède selon la revendication 1, caractérise en ce qu'on mesure la position de la bande (2) au-dessus du bain de métal de revêtement (1), et on régule l'intensité des forces magnétiques de chaque côte de la bande en fonction de la position mesurée de la bande.3. Method according to claim 1, characterized in that the position of the strip (2) is measured above the coating metal bath (1), and the intensity of the magnetic forces of each side of the strip as a function of the measured position of the strip.
4. Procède selon la revendication 2, caractérise en ce que pour générer les forces magnétiques, on utilise plusieurs electroaimants (20) situes de chaque côte de la bande, au dessus du bain de métal de revêtement, 1' intensité du champ produit par chaque electroaimant étant régulée en fonction de la mesure de position de la bande effectuée par un capteur associe (21) . 4. Method according to claim 2, characterized in that to generate the magnetic forces, using several electromagnets (20) located on each side of the strip, above the coating metal bath, the field strength produced by each electromagnet being regulated as a function of the tape position measurement carried out by an associated sensor (21).
5. Procède selon la revendication 2, caractérise en ce que des champs magnétiques sont produits en complément par des inducteurs (15) placés sous le creuset (10) autour d'un chenal (14) de passage de la bande (2), ces inducteurs étant par ailleurs utilises pour maintenir en sustentation le métal de revêtement liquide dans le dit chenal .5. Method according to claim 2, characterized in that magnetic fields are produced in addition by inductors (15) placed under the crucible (10) around a channel (14) for passing the strip (2), these inductors also being used to maintain the liquid coating metal in the said channel.
6. Dispositif de réalisation d'un revêtement métallique sur une bande ferromagnétique (2) en défilement, comportant un creuset (10) destine a contenir un bain liquide de métal de revêtement (1) , le fond du creuset comportant une fente (13) de passage de la bande, la dite fente se prolongeant vers le bas par un chenal (14) de passage autour duquel sont places des moyens d' etancheite électromagnétiques (15) pour contenir le métal de revêtement, caractérisé en ce qu'il comporte des moyens magnétiques (20) de réglage de la position transversale de la bande, placés au-dessus du creuset (10) de part et d'autre de la trajectoire de la dite bande, et agences de manière à produire au niveau de la dite trajectoire des champs magnétiques continus ou a basse fréquence, d'intensité réglable.6. Device for producing a metallic coating on a moving ferromagnetic strip (2), comprising a crucible (10) intended to contain a liquid bath of coating metal (1), the bottom of the crucible comprising a slot (13) strip passage, said slot extending downwards by a passage channel (14) around which are placed electromagnetic sealing means (15) to contain the coating metal, characterized in that it comprises magnetic means (20) for adjusting the transverse position of the strip, placed above the crucible (10) on either side of the trajectory of said strip, and arranged so as to produce at the level of said trajectory continuous or low frequency magnetic fields of adjustable intensity.
7. Dispositif selon la revendication 6, caractérise en ce que les moyens magnétiques de réglage de la position de la bande comportent des electroaimants (20) .7. Device according to claim 6, characterized in that the magnetic means for adjusting the position of the strip comprise electromagnets (20).
8. Dispositif selon la revendication 7, caractérise en ce qu'il comporte des capteurs (21) de position de la bande, situes au-dessus du creuset (10).8. Device according to claim 7, characterized in that it comprises sensors (21) of position of the strip, located above the crucible (10).
9. Dispositif selon la revendication 8, caractérise en ce qu'a chaque electro-aimant (20) est associe un capteur (21) et des moyens (22) de régulation de l'intensité du courant d'alimentation de l' electro-aimant en fonction du signal fourni par le capteur. 9. Device according to claim 8, characterized in that each electromagnet (20) is associated with a sensor (21) and means (22) for regulating the intensity of the supply current of the electro- magnet according to the signal provided by the sensor.
PCT/FR2000/002066 1999-08-05 2000-07-19 Method and device for continuously producing a metal surface coating on a moving sheet metal WO2001011101A1 (en)

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FR99/10297 1999-08-05
FR9910297A FR2797277A1 (en) 1999-08-05 1999-08-05 METHOD AND DEVICE FOR THE CONTINUOUS PRODUCTION OF A METAL SURFACE COATING ON A SLIP

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