EP2768996B1 - Hot dip galvanizing method for coating a steel strip and apparatus therefor - Google Patents

Hot dip galvanizing method for coating a steel strip and apparatus therefor Download PDF

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Publication number
EP2768996B1
EP2768996B1 EP11791018.2A EP11791018A EP2768996B1 EP 2768996 B1 EP2768996 B1 EP 2768996B1 EP 11791018 A EP11791018 A EP 11791018A EP 2768996 B1 EP2768996 B1 EP 2768996B1
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EP
European Patent Office
Prior art keywords
bath
inductors
strip
inductor
pan
Prior art date
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EP11791018.2A
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German (de)
French (fr)
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EP2768996A1 (en
Inventor
Marc Anderhuber
Alain Daubigny
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ArcelorMittal SA
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ArcelorMittal SA
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Priority to HUE11791018A priority Critical patent/HUE036709T2/en
Priority to PL11791018T priority patent/PL2768996T3/en
Publication of EP2768996A1 publication Critical patent/EP2768996A1/en
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    • 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
    • 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
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • 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
    • C23C2/325—Processes or devices for cleaning the bath

Definitions

  • the invention relates to the iron and steel industry, and more particularly to the coating installations by dipping steel strips, whereby said strips are covered with a layer of zinc or zinc alloy (in the case of galvanizing), or another type of metal or metal alloy such as an aluminum-silicon alloy.
  • the moving strip passes into a container containing the metal or the metal coating alloy, maintained in the liquid state.
  • the coating is deposited on the strip that then emerges from the bath, and passes through a device controlling the thickness of the coating and contributing to its solidification, usually consisting of nozzles throwing a gas on the surface of the coating.
  • a device controlling the thickness of the coating and contributing to its solidification usually consisting of nozzles throwing a gas on the surface of the coating.
  • the strip Prior to entering the bath, the strip is heated by an annealing furnace and then cooled to a temperature close to the bath temperature to create optimal adhesion conditions between the strip and the coating.
  • the bath is formed in the formation of oxides and intermetallic precipitates, essentially based on Zn and Fe in the case of a galvanizing bath, containing liquid zinc which will be considered in a preferred manner in the remainder of the description, without it constituting an exclusive application of the invention.
  • These precipitates are called "mattes".
  • Some mattes have a density higher than that of the bath, and decant at the bottom of the tank without hindering the galvanizing process.
  • Others on the other hand, have a density lower than that of the bath and float on its surface. They are likely to be incorporated in the coating of the strip, and thus to create defects therein.
  • the matte towards a container located away from the entry and exit areas of the band, this container is then extracted from the tray and emptied using a robotic system or not.
  • the operator pushes the matte towards an area of the tank where a device such as a robot evacuates to a container outside the tray, in which they are collected.
  • the coating thickness control system deposited on the strip consists of blowing nozzles, and can use inert gases such as nitrogen to limit the oxidation of the coating.
  • inert gases such as nitrogen to limit the oxidation of the coating.
  • the use of these inert gases is also a source of risk for the operator, because of the lack of oxygen in the atmosphere around the tank that it involves.
  • the higher the speed of the web the more the coating thickness control nozzles must project a large amount of gas to maintain the coating thickness constant. This has the effect of increasing the ambient temperature around the bath, because the blowing gas transports the heat of the strip and the bath to the working area of the operators.
  • a solution devised by some steelmakers has been to replace, at least for the most part, the human intervention to bring matts into the robot's action zone by the action of electromagnetic devices.
  • electromagnetic devices Using sliding fields generated by inductors such as linear motors, electromagnetic forces, to which the metal or liquid metal alloy is sensitive (so-called “magnetomotive” forces), move the metal or metal alloy liquid that drives the matte in an area of the tank where the robot is active, creating a recirculation path mattes leading them into said area.
  • electromagnetic devices are described, for example, in the documents JP-A-10-053850 , JP-A-54-33234 , JP-A-2005-068545 , JP 11-006046 .
  • JP-A-54-33234 teaches to dispose of the field-sliding inductors all around the band in its exit zone of the tank, the sliding fields bringing the matts into the corner of the tank where there is a conveyor belt which evacuates the mattes out of the tank in a container that collects them.
  • the entrance to the The strip in the galvanizing bath is, as is often the case, inside a tube immersed in the bath and connected upstream to the annealing furnace, and the matts which have decanted on the surface of the bath can not come into contact with the surface of the band in this area. It is therefore sufficient to place inductors in the environment of the exit zone of the strip.
  • JP-A-10-053850 teaches to have screens parallel to the strip in its area of entry into the tray, and sliding field inductors are arranged in the vicinity of the two ends of each screen.
  • the magnetic fields thus generated make it possible to attract the mattes out of the zone between the screens and including the band.
  • the object of the invention is to provide a method and a device for removing supernatant low density matts at the surface of the galvanizing bath guaranteeing a better efficiency than known devices, by using a minimum of inductors.
  • the subject of the invention is a galvanization process by dipping a strip of steel running in a liquid metal bath, such as zinc, or a metal alloy contained in a tank, according to which away from the surface of the strip matts that are formed during galvanization and float on the surface of the bath, by means of at least one inductor, each inductor producing a sliding electromagnetic field oriented in a given direction and generating a force magnetomotive, all of said magnetomotive forces displacing said matte towards a receptacle responsible for collecting them and / or towards an area of the bath surface from which they are discharged, characterized in that, for at least one of said inductors, it intermittently reverses said direction of its sliding electromagnetic field so as to change the flow of matte inside the tray.
  • a liquid metal bath such as zinc, or a metal alloy contained in a tank
  • At least two of them may be disposed along the exit zone of the bath strip, and the direction of their respective magnetic fields is intermittently reversed.
  • the invention also relates to a coating installation by dipping a steel strip, comprising a tray containing a liquid bath of metal or metal alloy in which the strip travels, and at least one inductor, each inductor creating an electromagnetic field and magnetomotive forces contributing to bring the mattes generated during the coating in the vicinity of a container intended to receive them and / or in the zone of action of a robot or an operator which brings them into said container, characterized in that at least one of said inductors comprises a device for reversing the direction of the electromagnetic field generated by said inductor.
  • It may comprise at least two inductors located on either side of the exit zone of the bath strip, and said inductors each comprise a device for reversing the direction of the electromagnetic field that it generates.
  • Said inductors can be mounted on brackets to adjust their location above the tray and their distance from the surface of the bath.
  • Said installation may comprise automated devices for controlling the distance between each of the inductors and the level of the surface of the bath.
  • two inductors frame the strip in its exit zone of the bath so as to move the matts away from the surfaces of the strip by moving them parallel to it, and two inductors are each arranged along a wall of the tank, substantially in the extension of the other two inductors.
  • the tray containing the bath has a generally rectangular shape
  • the container in which the mattes are collected, and / or the area of action of the robot or the operator from which they are removed, is placed in a corner the tray opposite one of the inductors, and in the corner of the tank opposite the other of the inductors is placed an inductor for directing the matte to said container.
  • the installation may comprise means for controlling the reversal of the direction of the electromagnetic field generated by at least one inductor which are themselves controlled by a device making it possible to evaluate the quantity of mattes accumulated in at least one zone of the tank. and to determine when such an inversion is desirable.
  • At least one of said inductors may be a three-phase linear motor.
  • At least one of said three-phase linear motors is of the type in which the coils surround the magnetic core.
  • the invention is based on the use of sliding field inductors, at least one of which has the possibility of varying intermittently the direction of the sliding field during their use, so the direction of the magnetomotive force that causes the moving of the mattes.
  • the tank containing the liquid coating metal is of small dimensions, the presence of a single inductor can be sufficient, if the direction of its sliding field can, according to the invention, be reversed intermittently.
  • This variation of the direction of the field makes it possible not to have a constant configuration of the privileged paths of circulation of the mattes on the surface of the bath.
  • Inversion (performed at regular intervals or not) of the direction of the field generated by at least one inductor, preferably at least by inductors flanking the two sides of the strip in its area of penetration into the tray, makes it possible to modify the circulation path of the mattes.
  • the dead zones and recirculation loops that could be established when the fields had a given direction are "broken" by the reversal of this direction, and the mattes that had eventually accumulated there are brought back into the circulation circuit that leads them to the robot's action area, or even directly to the container that collects them. Human intervention to perform this recirculation of mattes is no longer necessary.
  • the number of inductors that would be necessary to evacuate the mattes present on the entire surface of the bath can be reduced, knowing that it is not necessarily necessary that a given area of the tank, in particular those located relatively far from the belt, is permanently concerned by the traffic flows.
  • each motor must be such that the engine can find its place in the production line, given the dimensions usual tray, tape and space available to implement the engines above the tray, especially when you want to implement on a pre-existing installation.
  • the length of an engine is from 200 to 2000 mm, its width from 100 to 1000 mm and its height from 50 to 600 mm.
  • the polar pitch of the motor that is to say the distance between two coils fed by the same phase, can vary from 50 to 700 mm. It corresponds to the zone of action of the magnetic field. The lower the polar pitch, the closer the motor should be to the bath surface for a given efficiency in matte training. Placement of the motor 100 mm from the surface of the bath is generally accompanied by the choice of a polar pitch of the order of 300 mm taking into account other preferred characteristics of the engines.
  • the operating frequency of the motors can range from 1 to 500 Hz. It influences the direction of the magnetomotive force in the liquid Zn, as has been seen above.
  • the force is optimally as tangential as possible with respect to the surface of the bath, so as not to create agitation outside the immediate vicinity of the surface (in particular agitation which would tend to return to the heart of the bath matts having decanted at bottom of the tray or those supernatant on the surface) and ensure as efficient a displacement as possible supernatants supernatant on the surface. All things being equal, especially the polar pitch, the electromagnetic force is all the more tangential as the frequency is low.
  • the intensity of the current passing through each notch of the motors must be sufficient to create a magnetomotive force of 1000 to 20 000 ampere-turns, knowing that for a given winding, the higher the intensity of the current, the greater the magnetomotive force generated is .
  • the figure 1 schematically represents a three-phase linear motor of a type known in itself, used as an inductor in the context of the invention. It comprises, conventionally, a magnetic core 1 of length L and width l constituted by an assembly of sheets of soft iron. Soft iron is used to maximize the magnetic flux, and the sheet construction reduces the occurrence of eddy currents, hence Joule losses.
  • the core comprises slots 2 in which are placed electrical conductors forming coils 3-8, these coils 3-8 are themselves connected to each other to form windings.
  • it is a three-phase motor, comprising three windings of two coils arranged alternately.
  • the coil 3 is thus connected to the coil 6, the coil 4 is connected to the coil 7 and the coil 5 is connected to the coil 8.
  • Each coil 3-8 is supplied with a phase shift of 2 ⁇ / 3 to create the magnetic field sliding that will create the magnetomotive force moving the mattes in the same direction as the field.
  • the coils 3-8 can be cooled by an internal circulation of water
  • the figure 2 shows the wiring diagram of the motor, with the star connection showing the alternation of the coil connections.
  • a phase inverter 30 which makes it possible, in a single actuating operation, to modify the connections of the coils connected to the phases 1 and 2 (respectively, in the example represented , the coils 3, 5, 6, 8) so as to be able to instantly reverse the direction of the sliding field, knowing that the connections of the coils 4, 7 connected to the phase 3 remain unchanged. So, in the configuration shown in solid lines on the figure 2 , where the coils 3 and 6 are connected to the phase 1 and the coils 5 and 8 to the phase 2, the field slides from left to right according to the arrow 31. In the configuration shown in dotted line on the figure 2 where the coils 3 and 6 are connected to the phase 2 and the coils 5 and 8 are connected to the phase 1, the field slides from right to left according to the arrow 32.
  • FIGs 3 to 5 schematically the magnetomotive forces and their orientations in the galvanizing bath 9 for frequencies of current running through the motor of 10 Hz ( figure 3 ), 50 Hz ( figure 4 ) and 250 Hz ( figure 5 ).
  • the arrows represent, depending on their orientations and their lengths, the preferred directions of said forces and their intensities. It can be seen that, as has been said, the lower the frequency, the more the magnetomotive force is exerted tangentially to the surface of the bath, and is therefore effective, at the same current intensity, for moving the matts in the desired direction. But a low frequency leads to a low intensity of the magnetomotive forces.
  • the most conventional linear motors comprise a flat winding, with flat coils passing through the core (see for example the document EP-A-0 949 749 ). But for a greater compactness of the engine, particularly in width, it is preferable to give it the configuration shown schematically in the figures, where the coils 3-8 are arranged around the core 1.
  • the document "Fluid flow in a continuous casting [0006] ISIJ International, 2001, vol.41 No. 8, pp851-858) describes in more detail such linear motors.
  • the figure 6 schematically represents a galvanizing installation equipped, in the example shown, four linear motors 11-14 of the type of that of the figure 1 and capable of implementing the invention.
  • this installation comprises a bin 15 of generally rectangular shape, provided with means for maintaining the temperature of the liquid bath 9 of zinc or, more generally, of zinc alloy (or, remember, any other metal or metal alloy that can be used to coat the strip 16), it contains.
  • the scrolling strip 16 to be galvanized penetrates the bath 9 in an oblique direction. Very often, as has been said, this penetration takes place, in fact, inside a protective tube, connected in its upstream part to the annealing line which has made it possible to adjust the temperature of the strip to a value close to that of the bath 9.
  • the strip 16 passes around a roller located inside the tank 15, and leaves the bath 9 in the vertical, coated with its galvanizing layer, towards the other elements of the galvanizing installation known in themselves. same and having no influence on the design of the invention.
  • the galvanized strip 16 passes, at its exit from the bath 9, between two gas blowing devices 17, 18 which adjust the thickness of the coating on each of the surfaces of the strip 16 and cool it, thus contributing to its good solidification.
  • To collect the mattes can be placed in a corner of the tray 15 a container in which the mattes can be collected after being pushed with the 11-14 engines, or, as shown, a robot 20 disposed in the vicinity of the tray 15 can be moved in all directions of space to extract the mattes bath 9 and send them in a container 19 placed next to the tray 15.
  • the bath level 9 tends to drop during the operation, and if the distance between the motor 11-14 and the surface 10 increases, the force magnetomotive decreases.
  • a progressive lowering of the engine 11-14 by its 21-24 stem makes it possible to keep this distance constant, and thus to keep the magnetomotive force constant in direction and in intensity, all other things being equal.
  • Another way of acting on the magnetomotive force is to increase the intensity of the current flowing through the motor 11-14.
  • Means may be provided for automatically controlling the distance between each motor 11-14 and the surface 10 of the bath 9 at the variation of the level of said surface 10.
  • Two motors 11, 12 frame the strip 16 in its outlet area of the bath 9 so as to move the matts away from the surfaces of the strip 16 by moving them parallel to it.
  • Two motors 13, 14 are, in the non-limiting example shown, each disposed along a side wall of the tray 15 and parallel to it, substantially in the extension of the two other motors 11, 12, so as to follow said matte wall which penetrate into their respective areas of action, and send them to the zone of action 25 of the robot 20 which pushes them in the container 19 located in the immediate vicinity of the tank 15.
  • the zone 25 of the robot 20 is opposite to one 14 of the motors arranged along a side wall of the tank 15.
  • the parallelism of the side walls of the tank 15 and the motors 13, 14 represented on the figures 6 , 7 and 8 is, as we have said, only an example of a non-limiting provision.
  • the orientation of these motors 13, 14 is to be optimized according to the precise configuration of the tank 15 and the precise location of the action zone 25 of the robot 20. This optimization can lead to having at least one of these motors 13 14 obliquely with respect to the side wall of the tank 15 from which it is close.
  • the invention solves this problem by providing that at least one of the motors 11-14 has means for reversing the direction of the electromagnetic field it generates, so the direction of the magnetomotive force that causes the matte to move.
  • This inversion can take place systematically at predetermined time intervals and be controlled manually or automatically, previous experiments having made it possible to determine with which optimal frequency this inversion must be carried out. depending on the conditions of the galvanization (including the running speed of the strip 16, the nature of the bath 9 ). It can also take place irregularly, at times determined by the operator of the installation, or by any automated device operating, for example, by being slaved to means for evaluating the amount of mattes accumulated in a system. or specific areas of the bin 15.
  • This evaluation of the amount of mattes accumulated can be provided, for example, by an analysis of the images captured by cameras (infrared or otherwise) aimed at areas of potential accumulation of mattes. It makes it possible for an operator, or an automatic galvanization plant management device, to estimate that the accumulation of mattes in one or more areas of the bath surface 9 is about to become excessive or is already so, and it is therefore desirable to reverse the direction of the field of at least one of the motors 11-14.
  • phase switch 30 which modifies the power supply of the motor coils.
  • This switch 30 is installed in the electrical control cabinet of the installation and can be controlled remotely by an operator and / or by an automatic system. The change of direction of the sliding field is instantaneous.
  • FIG. 7 a first state of operation of the motors 11-14 is shown in which the motors 11, 12 both drive the matts towards the left side wall of the tank 15. They are taken up by the field generated by the motor 14 located along the of this left side wall 26, and sent towards the container 19 if it is integrated with the tray 15, or, as shown, in the zone of action 25 of the robot 20. Simultaneously, the motor 13 located along the right side wall 27 of the tank 15 sends the matte that captures its electromagnetic field along the right side wall 27 to the zone of action 25 of the robot 20. These matts also tend to be deflected by the front wall 28 of the tank 15 towards the zone of action 25 of the robot 20.
  • the various arrows represented on the figure 7 (as well as Figures 8 and 9 ) show the displacements of the mattes induced by the magnetomotive forces generated by the various motors 11-14.
  • the figure 8 represents a second state of operation of the motors 11-14, in which the directions of the fields generated by the motors 11, 12 flanking the strip 16, after a certain time of use of the configuration of the figure 7 have, according to the invention, been inverted with respect to the case of the figure 7 .
  • This time the matts in the vicinity of the strip 6 are oriented towards the motor 13 located along the right side wall 27 of the tank 15.
  • the motors 13, 14 operate as in the case of the figure 7 .
  • This inversion is already sufficient to create movements of the matts on the surface of the bath 9 which are able to "break" the dead zones and the recirculation zones created in the configuration of the figure 7 .
  • the two motors 11, 12 flanking the strip 16 both lead the matte in the same direction. But this configuration is not mandatory, it can be provided, if the location of the matte to move requires, the field directions of said motors 11, 12 are opposed, and permanently or temporarily.
  • the two motors 11, 12 flanking the strip 16 have the same length and are exactly opposite. But this configuration is not mandatory and it can be expected that these motors 11, 12 have different lengths and / or are offset relative to each other, if it turns out that it is beneficial to the good evacuation of the mattes in the particular configuration of the tank 15 used.
  • the figure 9 schematically presents a variant of the case of Figures 6 to 8 , in which a fifth motor 29 arranged obliquely in the right front corner of the tank 15 has been added. It is thus located on the path of the matts pushed by the motor 13 situated along the right side wall 27 of the tank 15, and has in order to reinforce the effect of this motor 13 in the expedition of the mattes towards the action zone 25 of the robot 20. It is thus possible to reduce the size of the action zone 25 of the robot 20 and generally, increase the efficiency of the evacuation of mattes from the vicinity of Band 16 and direction of the zone of action 25 of the robot 20.
  • the motors 11, 12 surrounding the band 16 have, as in the case of Figures 7 and 8 alternating their electromagnetic fields in one direction or the other.
  • the various motors 11-14 or 11-14, 29, or at least some of them are movable during operation in a direction that allows them to accompany the movement of the mattes, and thus to assist the movement of a given group of mattes for a longer duration than if the engine 11-14 or 11-14, 29 gave them only one pulse, when these matts are located below the zone initial action of the motor 11-14 or 11-14, 29.
  • the examples which have been described are not limiting and other provisions of the inductors are conceivable, in particular when the zone where the strip 16 enters the bath 9 must also be free of mattes if the strip 16 is It is found in the open air, or if the container 19 collecting the mattes and / or the zone of action 25 of the robot 20 are placed elsewhere than they are in the examples shown.
  • the skilled person will be able to adapt the number and arrangement of the inductors to the particular geometry of its coating installation, the essential being the existence of the possibility of intermittently reversing the direction of action of at least one of the inductors to avoid perpetuation dead zones and recirculation loops on the surface of the bath 9, which is conducive to the accumulation of the mattes.

Description

L'invention concerne la sidérurgie, et plus particulièrement les installations de revêtement au trempé des bandes d'acier, par lesquelles lesdites bandes sont recouvertes d'une couche de zinc ou d'alliage de zinc (dans le cas d'une galvanisation), ou d'un autre type de métal ou d'alliage métallique tel qu'un alliage aluminium-silicium.The invention relates to the iron and steel industry, and more particularly to the coating installations by dipping steel strips, whereby said strips are covered with a layer of zinc or zinc alloy (in the case of galvanizing), or another type of metal or metal alloy such as an aluminum-silicon alloy.

On rappelle que lors du revêtement au trempé d'une bande d'acier, la bande en défilement passe dans un bac renfermant le métal ou l'alliage métallique de revêtement, maintenu à l'état liquide. Le revêtement se dépose sur la bande qui ressort ensuite du bain, et traverse un dispositif contrôlant l'épaisseur du revêtement et contribuant à sa solidification, constitué généralement par des buses projetant un gaz sur la surface du revêtement. Préalablement à sa pénétration dans le bain, la bande est réchauffée par un four de recuit puis refroidie à une température proche de la température du bain pour créer les conditions d'adhérence optimale entre la bande et le revêtement.It is recalled that during the dip coating of a steel strip, the moving strip passes into a container containing the metal or the metal coating alloy, maintained in the liquid state. The coating is deposited on the strip that then emerges from the bath, and passes through a device controlling the thickness of the coating and contributing to its solidification, usually consisting of nozzles throwing a gas on the surface of the coating. Prior to entering the bath, the strip is heated by an annealing furnace and then cooled to a temperature close to the bath temperature to create optimal adhesion conditions between the strip and the coating.

Au cours de la traversée du bain, on assiste au sein du bain à la formation d'oxydes et de précipités intermétalliques, essentiellement à base de Zn et de Fe dans le cas d'un bain de galvanisation, contenant du zinc liquide qui sera considéré de manière privilégiée dans la suite de la description, sans qu'il constitue une application exclusive de l'invention. Ces précipités sont appelés « mattes ». Certaines mattes ont une densité plus élevée que celle du bain, et décantent au fond du bac sans gêner le processus de galvanisation. D'autres, en revanche, ont une densité inférieure à celle du bain et flottent à sa surface. Elles sont susceptibles d'être incorporées au revêtement de la bande, et donc d'y créer des défauts. Ces mattes de faible densité, qui seront les seules considérées dans la suite du texte, doivent donc être éloignées autant que possible de la zone d'entrée de la bande dans le bain (si cette entrée s'effectue à l'air libre, ce qui n'est pas toujours le cas) et de la zone de sortie de la bande hors du bain, et être évacuées du bac au fur et à mesure de leur formation.During the passage through the bath, the bath is formed in the formation of oxides and intermetallic precipitates, essentially based on Zn and Fe in the case of a galvanizing bath, containing liquid zinc which will be considered in a preferred manner in the remainder of the description, without it constituting an exclusive application of the invention. These precipitates are called "mattes". Some mattes have a density higher than that of the bath, and decant at the bottom of the tank without hindering the galvanizing process. Others, on the other hand, have a density lower than that of the bath and float on its surface. They are likely to be incorporated in the coating of the strip, and thus to create defects therein. These low-density mattes, which will be the only ones considered in the rest of the text, must therefore be as far as possible away from the inlet zone of the strip in the bath (if this entry is made in the open air, this which is not always the case) and the exit zone of the band out of the bath, and be evacuated from the tank as and when they are formed.

A cet effet, le plus classiquement, un opérateur se tenant au voisinage du bac pousse, à l'aide d'un outil, les mattes en direction d'un récipient situé à l'écart des zones d'entrée et de sortie de la bande, ce récipient étant ensuite extrait du bac et vidé à l'aide d'un système robotisé ou non. Dans d'autres cas, l'opérateur pousse les mattes en direction d'une zone du bac où un dispositif tel qu'un robot les évacue vers un récipient extérieur au bac, dans lequel elles sont recueillies.For this purpose, the most conventionally, an operator standing in the vicinity of the tank pushes, with a tool, the matte towards a container located away from the entry and exit areas of the band, this container is then extracted from the tray and emptied using a robotic system or not. In other cases, the operator pushes the matte towards an area of the tank where a device such as a robot evacuates to a container outside the tray, in which they are collected.

Cette opération est inconfortable et potentiellement dangereuse pour l'opérateur, car il doit se tenir à proximité immédiate d'un bain de métal liquide chaud, avec les désagréments et les risques liés à la chaleur et à la possibilité de projections du métal liquide. Par ailleurs, le système de contrôle de l'épaisseur de revêtement déposé sur la bande est constitué de buses de soufflage, et peut utiliser des gaz inertes tels que de l'azote afin de limiter l'oxydation du revêtement. L'utilisation de ces gaz inertes est aussi une source de risques pour l'opérateur, de par le manque d'oxygène dans l'atmosphère autour du bac qu'il implique.This operation is uncomfortable and potentially dangerous for the operator, because it must be in the immediate vicinity of a bath of hot liquid metal, with the inconvenience and the risks related to the heat and the possibility of projections of the metal liquid. Furthermore, the coating thickness control system deposited on the strip consists of blowing nozzles, and can use inert gases such as nitrogen to limit the oxidation of the coating. The use of these inert gases is also a source of risk for the operator, because of the lack of oxygen in the atmosphere around the tank that it involves.

De plus, cette opération de nettoyage des mattes impose une limitation de la vitesse de défilement de la bande, car une vitesse élevée favorise la production des mattes, que l'opérateur et le robot doivent avoir le temps d'évacuer.In addition, this operation of cleaning the mattes imposes a limitation of the running speed of the band, because a high speed favors the production of mattes, that the operator and the robot must have time to evacuate.

Egalement, plus la vitesse de la bande est élevée, plus les buses de contrôle de l'épaisseur de revêtement doivent projeter une quantité de gaz importante pour maintenir l'épaisseur de revêtement constante. Ceci a pour effet d'augmenter la température ambiante autour du bain, car le gaz de soufflage transporte la chaleur de la bande et du bain vers la zone de travail des opérateurs.Also, the higher the speed of the web, the more the coating thickness control nozzles must project a large amount of gas to maintain the coating thickness constant. This has the effect of increasing the ambient temperature around the bath, because the blowing gas transports the heat of the strip and the bath to the working area of the operators.

Enfin, afin de limiter les pertes d'énergie thermique liées au chauffage du bain, il est envisagé que certaines nouvelles installations de revêtement soient entièrement capotées. Il serait donc nécessaire, dans ce cas, de limiter les interventions extérieures, et notamment celle d'un opérateur pour le démattage, afin d'éviter des décapotages trop fréquents de l'installation.Finally, in order to limit the thermal energy losses associated with the heating of the bath, it is envisaged that certain new coating installations are completely covered. It would therefore be necessary, in this case, to limit the external interventions, and in particular that of an operator for the removal, in order to avoid too frequent knockouts of the installation.

Il y a donc un besoin d'accroître la sécurité, la rapidité et l'efficacité de l'évacuation des mattes par rapport à cette technique classique, sans pour autant modifier radicalement le procédé de galvanisation lui-même et la conception générale de l'installation qui le met en oeuvre.There is therefore a need to increase the safety, speed and efficiency of the evacuation of mattes compared to this conventional technique, without radically altering the galvanizing process itself and the overall design of the installation that implements it.

Une solution imaginée par certains sidérurgistes a été de remplacer, au moins pour l'essentiel, l'intervention humaine pour l'amenée des mattes dans la zone d'action du robot par l'action de dispositifs électromagnétiques. A l'aide de champs glissants générés par des inducteurs tels que des moteurs linéaires, des forces électromagnétiques, auxquelles le métal ou l'alliage métallique liquide sont sensibles (forces dites « magnétomotrices »), font se déplacer le métal ou l'alliage métallique liquide qui entraîne les mattes dans une zone du bac où le robot est actif, en créant un chemin de recirculation des mattes les conduisant dans ladite zone. De tels dispositifs sont décrits, par exemple, dans les documents JP-A-10-053850 , JP-A-54-33234 , JP-A-2005-068545 , JP-11-006046 .A solution devised by some steelmakers has been to replace, at least for the most part, the human intervention to bring matts into the robot's action zone by the action of electromagnetic devices. Using sliding fields generated by inductors such as linear motors, electromagnetic forces, to which the metal or liquid metal alloy is sensitive (so-called "magnetomotive" forces), move the metal or metal alloy liquid that drives the matte in an area of the tank where the robot is active, creating a recirculation path mattes leading them into said area. Such devices are described, for example, in the documents JP-A-10-053850 , JP-A-54-33234 , JP-A-2005-068545 , JP 11-006046 .

JP-A-54-33234 , par exemple, enseigne de disposer des inducteurs à champ glissant tout autour de la bande dans sa zone de sortie du bac, les champs glissants amenant les mattes dans le coin du bac où se trouve une bande transporteuse qui évacue les mattes hors du bac dans un récipient qui les recueille. Dans son cas, l'entrée de la bande dans le bain de galvanisation s'effectue, comme c'est souvent le cas, à l'intérieur d'un tube plongeant dans le bain et connecté en amont au four de recuit, et les mattes qui ont décanté à la surface du bain ne peuvent venir en contact avec la surface de la bande dans cette zone. Il est donc suffisant de placer des inducteurs dans l'environnement de la zone de sortie de la bande. JP-A-54-33234 , for example, teaches to dispose of the field-sliding inductors all around the band in its exit zone of the tank, the sliding fields bringing the matts into the corner of the tank where there is a conveyor belt which evacuates the mattes out of the tank in a container that collects them. In his case, the entrance to the The strip in the galvanizing bath is, as is often the case, inside a tube immersed in the bath and connected upstream to the annealing furnace, and the matts which have decanted on the surface of the bath can not come into contact with the surface of the band in this area. It is therefore sufficient to place inductors in the environment of the exit zone of the strip.

JP-A-10-053850 enseigne de disposer des écrans parallèlement à la bande dans sa zone d'entrée dans le bac, et des inducteurs à champ glissant sont disposés au voisinage des deux extrémités de chaque écran. Les champs magnétiques ainsi générés permettent d'attirer les mattes hors de la zone comprise entre les écrans et incluant la bande. JP-A-10-053850 teaches to have screens parallel to the strip in its area of entry into the tray, and sliding field inductors are arranged in the vicinity of the two ends of each screen. The magnetic fields thus generated make it possible to attract the mattes out of the zone between the screens and including the band.

Dans le cas où il n'y a pas de robot, de tels dispositifs permettent de toute façon de faciliter le travail de l'opérateur qui n'a plus à agir que dans une zone du bac dont la surface est relativement limitée.In the case where there is no robot, such devices in any case facilitate the work of the operator who has more to act in a tray area whose surface is relatively limited.

L'expérience montre, cependant, que l'efficacité de ces dispositifs aurait intérêt à être encore améliorée. En particulier, une évacuation aussi complète que possible des mattes sans intervention humaine devrait pouvoir être réalisée, et ce avec un minimum d'inducteurs. Optimalement, un seul inducteur pourrait être suffisant si le bac est de faibles dimensions.Experience shows, however, that the effectiveness of these devices would benefit from further improvement. In particular, an evacuation as complete as possible of the mattes without human intervention should be possible, and with a minimum of inductors. Optimally, a single inductor could be sufficient if the tray is small.

Le but de l'invention est de proposer un procédé et un dispositif d'éloignement des mattes de faible densité surnageant à la surface du bain de galvanisation garantissant une meilleure efficacité que les dispositifs connus, en utilisant un minimum d'inducteurs.The object of the invention is to provide a method and a device for removing supernatant low density matts at the surface of the galvanizing bath guaranteeing a better efficiency than known devices, by using a minimum of inductors.

A cet effet, l'invention a pour objet un procédé de galvanisation au trempé d'une bande d'acier en défilement dans un bain liquide de métal, tel que du zinc, ou d'alliage métallique contenu dans un bac, selon lequel on éloigne de la surface de la bande les mattes qui sont formées au cours de la galvanisation et flottent à la surface du bain, au moyen d'au moins un inducteur, chaque inducteur produisant un champ électromagnétique glissant orienté selon une direction donnée et générant une force magnétomotrice, l'ensemble desdites forces magnétomotrices déplaçant lesdites mattes en direction d'un récipient chargé de les recueillir et/ou en direction d'une zone de la surface du bain d'où elles sont évacuées, caractérisé en ce que, pour au moins un desdits inducteurs, on inverse par intermittence ladite direction de son champ électromagnétique glissant de manière à modifier les écoulements des mattes à l'intérieur du bac.For this purpose, the subject of the invention is a galvanization process by dipping a strip of steel running in a liquid metal bath, such as zinc, or a metal alloy contained in a tank, according to which away from the surface of the strip matts that are formed during galvanization and float on the surface of the bath, by means of at least one inductor, each inductor producing a sliding electromagnetic field oriented in a given direction and generating a force magnetomotive, all of said magnetomotive forces displacing said matte towards a receptacle responsible for collecting them and / or towards an area of the bath surface from which they are discharged, characterized in that, for at least one of said inductors, it intermittently reverses said direction of its sliding electromagnetic field so as to change the flow of matte inside the tray.

Parmi lesdits inducteurs, on peut disposer au moins deux d'entre eux le long de la zone de sortie de la bande du bain, et on inverse par intermittence la direction de leurs champs magnétiques respectifs.Among said inductors, at least two of them may be disposed along the exit zone of the bath strip, and the direction of their respective magnetic fields is intermittently reversed.

L'invention a également pour objet une installation de revêtement au trempé d'une bande d'acier, comportant un bac renfermant un bain liquide de métal ou d'alliage métallique dans lequel défile la bande, et au moins un inducteur, chaque inducteur créant un champ électromagnétique et des forces magnétomotrices contribuant à amener les mattes générées au cours du revêtement au voisinage d'un récipient destiné à les recevoir et/ou dans la zone d'action d'un robot ou d'un opérateur qui les amène dans ledit récipient, caractérisé en ce qu'au moins un desdits inducteurs comporte un dispositif permettant d'inverser la direction du champ électromagnétique généré par ledit inducteur.The invention also relates to a coating installation by dipping a steel strip, comprising a tray containing a liquid bath of metal or metal alloy in which the strip travels, and at least one inductor, each inductor creating an electromagnetic field and magnetomotive forces contributing to bring the mattes generated during the coating in the vicinity of a container intended to receive them and / or in the zone of action of a robot or an operator which brings them into said container, characterized in that at least one of said inductors comprises a device for reversing the direction of the electromagnetic field generated by said inductor.

Elle peut comporter au moins deux inducteurs situés de part et d'autre de la zone de sortie de la bande du bain, et lesdits inducteurs comportent chacun un dispositif permettant d'inverser la direction du champ électromagnétique qu'il génère.It may comprise at least two inductors located on either side of the exit zone of the bath strip, and said inductors each comprise a device for reversing the direction of the electromagnetic field that it generates.

Lesdits inducteurs peuvent être montés sur des potences permettant de régler leur emplacement au-dessus du bac et leur distance avec la surface du bain.Said inductors can be mounted on brackets to adjust their location above the tray and their distance from the surface of the bath.

Ladite installation peut comporter des dispositifs automatisés d'asservissement de la distance entre chacun des inducteurs et le niveau de la surface du bain.Said installation may comprise automated devices for controlling the distance between each of the inductors and the level of the surface of the bath.

Selon un mode de réalisation, deux inducteurs encadrent la bande dans sa zone de sortie du bain de manière à éloigner les mattes des surfaces de la bande en les faisant se déplacer parallèlement à elle, et deux inducteurs sont disposés chacun le long d'une paroi du bac, sensiblement dans le prolongement des deux autres inducteurs.According to one embodiment, two inductors frame the strip in its exit zone of the bath so as to move the matts away from the surfaces of the strip by moving them parallel to it, and two inductors are each arranged along a wall of the tank, substantially in the extension of the other two inductors.

Dans ce cas, le bac contenant le bain a une forme générale rectangulaire, le récipient dans lequel les mattes sont recueillies, et/ou la zone d'action du robot ou de l'opérateur depuis laquelle elles sont évacuées, est placé dans un coin du bac à l'opposé d'un des inducteurs, et dans le coin du bac opposé à l'autre des inducteurs est placé un inducteur destiné à orienter les mattes vers ledit récipient.In this case, the tray containing the bath has a generally rectangular shape, the container in which the mattes are collected, and / or the area of action of the robot or the operator from which they are removed, is placed in a corner the tray opposite one of the inductors, and in the corner of the tank opposite the other of the inductors is placed an inductor for directing the matte to said container.

L'installation peut comporter des moyens de commande de l'inversion de la direction du champ électromagnétique généré par au moins un inducteur qui sont eux-mêmes asservis à un dispositif permettant d'évaluer la quantité de mattes accumulées dans au moins une zone du bac et de déterminer le moment où une telle inversion est souhaitable.The installation may comprise means for controlling the reversal of the direction of the electromagnetic field generated by at least one inductor which are themselves controlled by a device making it possible to evaluate the quantity of mattes accumulated in at least one zone of the tank. and to determine when such an inversion is desirable.

Au moins un desdits inducteurs peut être un moteur linéaire triphasé.At least one of said inductors may be a three-phase linear motor.

De préférence, au moins un des dits moteurs linéaires triphasés est du type dans lequel les bobines entourent le noyau magnétique.Preferably, at least one of said three-phase linear motors is of the type in which the coils surround the magnetic core.

Comme on l'aura compris, l'invention repose sur l'utilisation d'inducteurs à champ glissant dont au moins un d'entre eux présente la possibilité de faire varier par intermittence la direction du champ glissant au cours de leur utilisation, donc la direction de la force magnétomotrice qui provoque le déplacement des mattes. Eventuellement, si le bac renfermant le métal liquide de revêtement est de faibles dimensions, la présence d'un seul inducteur peut être suffisante, si la direction de son champ glissant peut, selon l'invention, être inversée par intermittence.As will be understood, the invention is based on the use of sliding field inductors, at least one of which has the possibility of varying intermittently the direction of the sliding field during their use, so the direction of the magnetomotive force that causes the moving of the mattes. Eventually, if the tank containing the liquid coating metal is of small dimensions, the presence of a single inductor can be sufficient, if the direction of its sliding field can, according to the invention, be reversed intermittently.

Cette variation de direction du champ permet de ne pas avoir une configuration constante des chemins privilégiés de circulation des mattes à la surface du bain.This variation of the direction of the field makes it possible not to have a constant configuration of the privileged paths of circulation of the mattes on the surface of the bath.

En effet, les inventeurs ont constaté qu'une telle constance des chemins de circulation était néfaste pour l'efficacité du dispositif électromagnétique d'entraînement des mattes. Elle conduit à la création de zones mortes et de boucles de recirculation fermées, localisées dans certaines zones du bac. Les mattes ont donc tendance à y demeurer ou à s'y accumuler, et ne peuvent donc être enlevées par le robot si la zone d'action de celui-ci ne concerne pas les zones mortes et les zones où se situent les boucles de recirculation. Et si elles sont, en plus, éloignées du récipient recueillant les mattes, il faut qu'un opérateur les amène dans le récipient ou la zone d'action du robot, avec tous les inconvénients que l'on a précédemment cités en termes de sécurité et de conditions de travail.Indeed, the inventors have found that such constancy of the circulation paths was detrimental to the effectiveness of the electromagnetic device for driving the mattes. It leads to the creation of dead zones and closed recirculation loops, located in certain areas of the tank. Mattes therefore tend to remain or accumulate there, and therefore can not be removed by the robot if the zone of action of this one does not concern the dead zones and the zones where the recirculation loops are located . And if they are, in addition, removed from the container collecting the mattes, it is necessary that an operator brings them into the container or the zone of action of the robot, with all the disadvantages mentioned above in terms of safety and working conditions.

L'inversion (effectuée à intervalles réguliers ou non) de la direction du champ généré par au moins un inducteur, de préférence au moins par des inducteurs encadrant les deux côtés de la bande dans sa zone de pénétration dans le bac, permet de modifier le chemin de circulation des mattes. Ce faisant, les zones mortes et les boucles de recirculation qui ont pu s'instaurer lorsque les champs avaient une direction donnée sont « cassées » par l'inversion de cette direction, et les mattes qui s'y étaient éventuellement accumulées sont ramenées dans le circuit de circulation qui les conduit vers la zone d'action du robot, voire directement vers le récipient qui les recueille. Une intervention humaine pour effectuer cette remise en circulation des mattes n'est donc plus nécessaire. Egalement, le nombre d'inducteurs qui seraient nécessaires pour évacuer les mattes présentes sur l'ensemble de la surface du bain peut être réduit, sachant qu'il n'est pas forcément nécessaire qu'une zone donnée du bac, en particulier celles situées relativement loin de la bande, soit concernée en permanence par les courants de circulation.Inversion (performed at regular intervals or not) of the direction of the field generated by at least one inductor, preferably at least by inductors flanking the two sides of the strip in its area of penetration into the tray, makes it possible to modify the circulation path of the mattes. In doing so, the dead zones and recirculation loops that could be established when the fields had a given direction are "broken" by the reversal of this direction, and the mattes that had eventually accumulated there are brought back into the circulation circuit that leads them to the robot's action area, or even directly to the container that collects them. Human intervention to perform this recirculation of mattes is no longer necessary. Also, the number of inductors that would be necessary to evacuate the mattes present on the entire surface of the bath can be reduced, knowing that it is not necessarily necessary that a given area of the tank, in particular those located relatively far from the belt, is permanently concerned by the traffic flows.

L'invention sera mieux comprise à la lecture de la description qui suit, donnée en référence aux figures annexées suivantes :

  • la figure 1 représente un exemple de moteur linéaire qui est utilisable dans le cadre de l'invention ;
  • la figure 2 représente le schéma électrique du moteur linéaire de la figure 1 ;
  • les figures 3 à 5 représentent schématiquement les variations de l'orientation des forces magnétomotrices générées par le moteur linéaire de la figure 1 en fonction de la fréquence du courant qui le parcourt ;
  • la figure 6 représente schématiquement en perspective un exemple d'installation de galvanisation à laquelle peut s'appliquer l'invention ;
  • les figures 7 et 8 montrent schématiquement en vue de dessus l'installation de la figure 6 pour deux configurations possibles d'écoulement des mattes réalisables selon l'invention ;
  • la figure 9 montre schématiquement en vue de dessus une variante de l'installation de la figure 6 dans laquelle un moteur linéaire supplémentaire est utilisé.
The invention will be better understood on reading the description which follows, given with reference to the following appended figures:
  • the figure 1 represents an example of a linear motor that can be used in the context of the invention;
  • the figure 2 represents the circuit diagram of the linear motor of the figure 1 ;
  • the Figures 3 to 5 schematically represent the variations in the orientation of the magnetomotive forces generated by the linear motor of the figure 1 depending on the frequency of the current flowing through it;
  • the figure 6 schematically represents in perspective an example of galvanizing installation to which the invention can be applied;
  • the Figures 7 and 8 schematically show in top view the installation of the figure 6 for two possible configurations of matte flow achievable according to the invention;
  • the figure 9 schematically shows in top view a variant of the installation of the figure 6 in which an additional linear motor is used.

La conception générale des moteurs linéaires triphasés qui, selon un exemple privilégié de l'invention, assurent la création des champs glissants, est classique, mais leur dimensionnement et leurs caractéristiques doivent convenir aux besoins de l'installation. Une contrainte est, en particulier, d'obtenir une efficacité satisfaisante du champ glissant lorsque le moteur est placé à une distance du bain de galvanisation optimalement comprise entre 20 et 100 mm, distance à laquelle on évite en général que la surface du bain ne vienne en contact avec le moteur, ou que des projections de zinc liquide ne viennent le détériorer.The general design of three-phase linear motors which, according to a preferred example of the invention, ensure the creation of sliding fields, is conventional, but their size and their characteristics must be suitable for the needs of the installation. A constraint is, in particular, to obtain a satisfactory efficiency of the sliding field when the motor is placed at a distance from the galvanizing bath optimally between 20 and 100 mm, distance which is generally avoided that the surface of the bath does not come in contact with the engine, or that projections of liquid zinc do not deteriorate.

Théoriquement, une distance moteur-bain de 1 à 350 mm est possible (elle est à ajuster aussi en fonction du pas polaire et de la puissance du moteur), sachant que plus cette distance est faible, plus l'efficacité du moteur est élevée, toutes choses étant égales par ailleurs. Mais la géométrie et les conditions précises de fonctionnement de l'installation de galvanisation doivent être considérées pour le choix de la distance optimale. Les moteurs sont d'ailleurs optimalement montés chacun sur une potence qui permet de régler leur emplacement exact au-dessus du bain, y compris en hauteur, selon les besoins instantanés de la mise en oeuvre de l'invention qui peuvent varier selon divers paramètres tels que :

  • la vitesse de défilement de la bande et ses variations, qui créent des perturbations plus ou moins importantes à la surface du bain ;
  • la vitesse de formation des mattes, qui dépend d'ailleurs entre autres de la vitesse de défilement de la bande, et qui, lorsqu'elle est importante parce que la bande défile rapidement, peut nécessiter une efficacité maximale des moteurs pour éloigner les mattes de la bande ; on aura alors intérêt à placer les moteurs au plus près de la surface du bain.
Theoretically, a motor-bath distance of 1 to 350 mm is possible (it is to be adjusted also according to the polar pitch and the engine power), knowing that the lower this distance, the higher the efficiency of the engine, all things being equal. But the exact geometry and operating conditions of the galvanizing system must be considered when choosing the optimal distance. The motors are also optimally mounted each on a bracket that allows to adjust their exact location above the bath, including height, according to the instant needs of the implementation of the invention which may vary according to various parameters such than :
  • the running speed of the band and its variations, which create more or less significant disturbances on the surface of the bath;
  • the rate of matte formation, which depends, moreover, on, among other things, the running speed of the strip, and which, when it is important because the strip is running rapidly, may require maximum efficiency of the engines in order to keep the matts away from the band ; it will be advantageous to place the motors as close to the surface of the bath.

L'encombrement en longueur et en volume de chaque moteur doit être tel que le moteur puisse trouver sa place dans la ligne de production, compte tenu des dimensions usuelles du bac, de la bande et de l'espace disponible pour implanter les moteurs au-dessus du bac, surtout lorsqu'on veut les implanter sur une installation préexistante. Pratiquement, la longueur d'un moteur est de 200 à 2000 mm, sa largeur de 100 à 1000 mm et sa hauteur de 50 à 600 mm.The overall length and volume of each motor must be such that the engine can find its place in the production line, given the dimensions usual tray, tape and space available to implement the engines above the tray, especially when you want to implement on a pre-existing installation. In practice, the length of an engine is from 200 to 2000 mm, its width from 100 to 1000 mm and its height from 50 to 600 mm.

La longueur et la largeur du moteur définissent sa surface active : plus la surface active est grande, plus la zone balayée par le moteur est grande, mais aussi plus l'encombrement du moteur est important, ce qui peut rendre sa mise en place difficile. Bien entendu, tous les moteurs d'une même installation ne sont pas forcément identiques. Le choix des dimensions du moteur est adapté à la taille de la zone qu'il doit balayer. Optimalement, les moteurs encadrant la bande ont une longueur de l'ordre de la largeur de la bande pour garantir que les mattes seront écartées de l'ensemble de la zone de pénétration de la bande dans le bain de galvanisation. Mais cette condition n'est pas toujours remplie sur des installations destinées à traiter des bandes de largeurs diverses (de 600 à 2000 mm par exemple). Pour y remédier, on peut envisager :

  • soit de disposer de plusieurs jeux de moteurs, de largeurs différentes, et pouvant être changés rapidement entre deux opérations de galvanisation de bandes de largeurs différentes ;
  • soit, comme on l'envisagera plus loin, d'utiliser plusieurs moteurs placés côte à côte et pouvant être mis en service ou hors service selon la largeur de la bande à revêtir.
The length and width of the motor define its active surface: the larger the active area, the greater the area swept by the engine, but also the larger the size of the engine, which can make its implementation difficult. Of course, all the engines of the same installation are not necessarily identical. The choice of the dimensions of the motor is adapted to the size of the zone which it must sweep. Optimally, the motors flanking the strip have a length of the order of the width of the strip to ensure that the mattes will be spaced from the entire penetration zone of the strip in the galvanizing bath. However, this condition is not always fulfilled on installations intended to treat strips of various widths (from 600 to 2000 mm for example). To remedy this, we can consider:
  • either to have several sets of motors, of different widths, and can be changed quickly between two operations galvanizing bands of different widths;
  • or, as will be discussed later, to use several motors placed side by side and can be put into service or out of service depending on the width of the band to be coated.

Le pas polaire du moteur, c'est-à-dire la distance entre deux bobines alimentées par la même phase, peut varier de 50 à 700 mm. Il correspond à la zone d'action du champ magnétique. Plus le pas polaire est réduit, plus il faut placer le moteur près de la surface du bain pour obtenir une efficacité donnée de l'entraînement des mattes. Un placement du moteur à 100 mm de la surface du bain s'accompagne généralement du choix d'un pas polaire de l'ordre de 300 mm compte tenu des autres caractéristiques préférées des moteurs.The polar pitch of the motor, that is to say the distance between two coils fed by the same phase, can vary from 50 to 700 mm. It corresponds to the zone of action of the magnetic field. The lower the polar pitch, the closer the motor should be to the bath surface for a given efficiency in matte training. Placement of the motor 100 mm from the surface of the bath is generally accompanied by the choice of a polar pitch of the order of 300 mm taking into account other preferred characteristics of the engines.

La fréquence de fonctionnement des moteurs peut aller de 1 à 500 Hz. Elle influe sur la direction de la force magnétomotrice dans le Zn liquide, comme on l'a vu plus haut. La force est optimalement aussi tangentielle que possible par rapport à la surface du bain, de manière à ne pas créer d'agitation hors du voisinage immédiat de la surface (en particulier une agitation qui tendrait à remettre au coeur du bain les mattes ayant décanté au fond du bac ou celles surnageant à la surface) et assurer un déplacement aussi efficace que possible des mattes surnageant à la surface. Toutes choses étant égales par ailleurs, notamment le pas polaire, la force électromagnétique est d'autant plus tangentielle que la fréquence est faible.The operating frequency of the motors can range from 1 to 500 Hz. It influences the direction of the magnetomotive force in the liquid Zn, as has been seen above. The force is optimally as tangential as possible with respect to the surface of the bath, so as not to create agitation outside the immediate vicinity of the surface (in particular agitation which would tend to return to the heart of the bath matts having decanted at bottom of the tray or those supernatant on the surface) and ensure as efficient a displacement as possible supernatants supernatant on the surface. All things being equal, especially the polar pitch, the electromagnetic force is all the more tangential as the frequency is low.

L'intensité du courant traversant chaque encoche des moteurs doit être suffisante pour créer une force magnétomotrice de 1000 à 20 000 Ampère-tours, sachant que pour un enroulement donné, plus l'intensité du courant est élevée, plus la force magnétomotrice générée est grande.The intensity of the current passing through each notch of the motors must be sufficient to create a magnetomotive force of 1000 to 20 000 ampere-turns, knowing that for a given winding, the higher the intensity of the current, the greater the magnetomotive force generated is .

La figure 1 représente schématiquement un moteur linéaire triphasé d'un type connu en lui-même, utilisable comme inducteur dans le cadre de l'invention. Il comporte, classiquement, un noyau magnétique 1 de longueur L et de largeur l constitué par un assemblage de feuillets en fer doux. Le fer doux est utilisé pour maximiser le flux magnétique, et la construction en feuillets permet de réduire l'apparition de courants de Foucault, donc les pertes par effet Joule. Le noyau comporte des fentes 2 dans lesquelles sont placés des conducteurs électriques formant des bobines 3-8, ces bobines 3-8 étant elles-mêmes connectées les unes aux autres pour former des enroulements. Dans l'exemple représenté, il s'agit d'un moteur triphasé, comportant trois enroulements de deux bobines disposées en alternance. La bobine 3 est donc reliée à la bobine 6, la bobine 4 est reliée à la bobine 7 et la bobine 5 est reliée à la bobine 8. Chaque bobine 3-8 est alimentée avec un déphasage de 2π/3 pour créer le champ magnétique glissant qui va créer la force magnétomotrice déplaçant les mattes selon la même direction que le champ. Les bobines 3-8 peuvent être refroidies par une circulation interne d'eau.The figure 1 schematically represents a three-phase linear motor of a type known in itself, used as an inductor in the context of the invention. It comprises, conventionally, a magnetic core 1 of length L and width l constituted by an assembly of sheets of soft iron. Soft iron is used to maximize the magnetic flux, and the sheet construction reduces the occurrence of eddy currents, hence Joule losses. The core comprises slots 2 in which are placed electrical conductors forming coils 3-8, these coils 3-8 are themselves connected to each other to form windings. In the example shown, it is a three-phase motor, comprising three windings of two coils arranged alternately. The coil 3 is thus connected to the coil 6, the coil 4 is connected to the coil 7 and the coil 5 is connected to the coil 8. Each coil 3-8 is supplied with a phase shift of 2π / 3 to create the magnetic field sliding that will create the magnetomotive force moving the mattes in the same direction as the field. The coils 3-8 can be cooled by an internal circulation of water.

La figure 2 montre le schéma électrique du moteur, avec la connexion en étoile montrant l'alternance des connexions des bobines.The figure 2 shows the wiring diagram of the motor, with the star connection showing the alternation of the coil connections.

Pour la mise en oeuvre aisée de l'invention, il est prévu un inverseur de phase 30 qui permet, en une seule opération d'actionnement, de modifier les connexions des bobines reliées aux phases 1 et 2 (respectivement, dans l'exemple représenté, les bobines 3, 5, 6, 8) de façon à pouvoir inverser instantanément la direction du champ glissant, sachant que les branchements des bobines 4, 7 reliées à la phase 3 restent inchangés. Ainsi, dans la configuration représentée en traits pleins sur la figure 2, où les bobines 3 et 6 sont reliées à la phase 1 et les bobines 5 et 8 à la phase 2, le champ glisse de gauche à droite selon la flèche 31. Dans la configuration représentée en pointillés sur la figure 2 où les bobines 3 et 6 sont reliées à la phase 2 et les bobines 5 et 8 sont reliées à la phase 1, le champ glisse de droite à gauche selon la flèche 32.For the easy implementation of the invention, a phase inverter 30 is provided which makes it possible, in a single actuating operation, to modify the connections of the coils connected to the phases 1 and 2 (respectively, in the example represented , the coils 3, 5, 6, 8) so as to be able to instantly reverse the direction of the sliding field, knowing that the connections of the coils 4, 7 connected to the phase 3 remain unchanged. So, in the configuration shown in solid lines on the figure 2 , where the coils 3 and 6 are connected to the phase 1 and the coils 5 and 8 to the phase 2, the field slides from left to right according to the arrow 31. In the configuration shown in dotted line on the figure 2 where the coils 3 and 6 are connected to the phase 2 and the coils 5 and 8 are connected to the phase 1, the field slides from right to left according to the arrow 32.

Le pas polaire du moteur, c'est-à-dire la distance « p » entre deux bobines alimentées par la même phase, par exemple les bobines 3 et 6 dans l'exemple représenté, est, comme on l'a dit, de 50 à 700 mm. Un pas polaire de 300 mm pour un moteur de longueur de 600 à 700 mm s'avère être un bon compromis entre les différents impératifs à concilier :

  • un pas polaire suffisamment long pour qu'il ne soit pas nécessaire de placer le moteur à une distance trop réduite du bain de galvanisation, ce qui pourrait l'endommager ;
  • un pas polaire suffisamment réduit pour ne pas conduire à un moteur dont la longueur serait exagérément grande.
The polar pitch of the motor, that is to say the distance "p" between two coils fed by the same phase, for example coils 3 and 6 in the example shown, is, as has been said, 50 to 700 mm. A polar pitch of 300 mm for a motor length of 600 to 700 mm proves to be a good compromise between the various imperatives to reconcile:
  • a polar pitch long enough that it is not necessary to place the motor at a too small distance from the galvanizing bath, which could damage it;
  • a polar pitch small enough not to lead to a motor whose length would be exaggeratedly large.

Les figures 3 à 5 schématisent les forces magnétomotrices et leurs orientations dans le bain de galvanisation 9 pour des fréquences du courant parcourant le moteur de 10 Hz (figure 3), 50 Hz (figure 4) et 250 Hz (figure 5). Les flèches représentent, en fonction de leurs orientations et de leurs longueurs, les directions privilégiées desdites forces et leurs intensités. On voit que, comme on l'a dit, plus la fréquence est basse, plus la force magnétomotrice s'exerce tangentiellement à la surface 10 du bain, et est donc efficace, à intensité du courant égale, pour faire se déplacer les mattes dans la direction souhaitée. Mais une fréquence faible conduit à une intensité faible des forces magnétomotrices. Le choix de la fréquence du courant doit aussi être effectué en combinaison avec celui du pas polaire pour obtenir la géométrie de l'installation la plus favorable à son bon fonctionnement. On juge finalement préférable d'avoir une fréquence relativement basse et un pas polaire relativement élevé pour ne pas être obligé de placer le moteur à une distance trop faible du bain, afin d'obtenir une force magnétomotrice d'intensité néanmoins convenable, et qui s'exerce principalement selon une direction efficace pour la bonne circulation des mattes. Un courant de fréquence 10Hz, un pas polaire de 300 mm, un moteur de longueur totale de 600 à 700 mm comportant six bobines de 96 spires, chacune parcourues par un courant d'intensité 150 A, et procurant donc une force magnétomotrice de 15 000 Ampère-tours représente un bon compromis s'il est placé à une distance de 50 à 100 mm de la surface 10 du bain 9.The Figures 3 to 5 schematically the magnetomotive forces and their orientations in the galvanizing bath 9 for frequencies of current running through the motor of 10 Hz ( figure 3 ), 50 Hz ( figure 4 ) and 250 Hz ( figure 5 ). The arrows represent, depending on their orientations and their lengths, the preferred directions of said forces and their intensities. It can be seen that, as has been said, the lower the frequency, the more the magnetomotive force is exerted tangentially to the surface of the bath, and is therefore effective, at the same current intensity, for moving the matts in the desired direction. But a low frequency leads to a low intensity of the magnetomotive forces. The choice of the current frequency must also be made in combination with that of the polar pitch to obtain the geometry of the installation most favorable to its proper operation. Finally, it is judged preferable to have a relatively low frequency and a relatively high polar pitch so as not to be obliged to place the motor at a too small distance from the bath, in order to obtain a magnetomotive force of nevertheless suitable intensity, and which exercises mainly in an effective direction for the good circulation of the mattes. A current of frequency 10Hz, a polar pitch of 300 mm, a motor of total length of 600 to 700 mm comprising six coils of 96 turns, each traversed by a current of intensity 150 A, and thus providing a magnetomotive force of 15,000 Ampere-turns represents a good compromise if placed at a distance of 50 to 100 mm from the surface 10 of the bath 9.

Les moteurs linéaires les plus classiques comportent un enroulement plat, avec des bobines plates traversant le noyau (voir par exemple le document EP-A- 0 949 749 ). Mais pour une plus grande compacité du moteur, en particulier en largeur, il est préférable de lui conférer la configuration représentée schématiquement sur les figures, où les bobines 3-8 sont disposées autour du noyau 1. Le document « Fluid flow in a continuous casting mold driven by linear induction motors » (ISIJ International, 2001, vol.41 N°8, pp851-858) décrit plus en detail de tels moteurs linéaires.The most conventional linear motors comprise a flat winding, with flat coils passing through the core (see for example the document EP-A-0 949 749 ). But for a greater compactness of the engine, particularly in width, it is preferable to give it the configuration shown schematically in the figures, where the coils 3-8 are arranged around the core 1. The document "Fluid flow in a continuous casting [0006] ISIJ International, 2001, vol.41 No. 8, pp851-858) describes in more detail such linear motors.

La figure 6 représente schématiquement une installation de galvanisation équipée, dans l'exemple représenté, de quatre moteurs linéaires 11-14 du type de celui de la figure 1, et aptes à la mise en oeuvre de l'invention. De façon classique, cette installation comporte un bac 15 de forme générale rectangulaire, pourvu de moyens de maintien en température du bain liquide 9 de zinc ou, plus généralement, d'alliage de zinc (ou, rappelons-le, de tout autre métal ou alliage métallique susceptible d'être utilisé pour le revêtement de la bande 16), qu'il contient. La bande en défilement 16 à galvaniser pénètre dans le bain 9 selon une direction oblique. Très souvent, comme on l'a dit, cette pénétration s'effectue, en fait, à l'intérieur d'un tube de protection, relié dans sa partie amont à la ligne de recuit qui a permis de régler la température de la bande à une valeur proche de celle du bain 9. Par souci de clarté, ce tube n'a pas été représenté sur la figure 6, de même que sur les figures 7, 8 et 9. La bande 16 passe autour d'un rouleau situé à l'intérieur de la cuve 15, et ressort du bain 9 à la verticale, revêtue de sa couche de galvanisation, en direction des autres éléments de l'installation de galvanisation connus en eux-mêmes et n'ayant pas d'influence sur la conception de l'invention. Comme il est connu, la bande 16 galvanisée passe, à sa sortie du bain 9, entre deux dispositifs de soufflage de gaz 17, 18 qui ajustent l'épaisseur du revêtement sur chacune des surfaces de la bande 16 et le refroidissent, contribuant donc à sa bonne solidification. Pour recueillir les mattes, on peut placer dans un coin du bac 15 un récipient dans lequel les mattes peuvent être recueillies après y avoir été poussées à l'aide des moteurs 11-14, Ou alors, comme représenté, un robot 20 disposé au voisinage du bac 15 peut être déplacé dans toutes les directions de l'espace afin d'extraire les mattes du bain 9 et les envoyer dans un récipient 19 placé à côté du bac 15.The figure 6 schematically represents a galvanizing installation equipped, in the example shown, four linear motors 11-14 of the type of that of the figure 1 and capable of implementing the invention. In a conventional manner, this installation comprises a bin 15 of generally rectangular shape, provided with means for maintaining the temperature of the liquid bath 9 of zinc or, more generally, of zinc alloy (or, remember, any other metal or metal alloy that can be used to coat the strip 16), it contains. The scrolling strip 16 to be galvanized penetrates the bath 9 in an oblique direction. Very often, as has been said, this penetration takes place, in fact, inside a protective tube, connected in its upstream part to the annealing line which has made it possible to adjust the temperature of the strip to a value close to that of the bath 9. For the sake of clarity, this tube has not been shown on the figure 6 , as well as Figures 7, 8 and 9 . The strip 16 passes around a roller located inside the tank 15, and leaves the bath 9 in the vertical, coated with its galvanizing layer, towards the other elements of the galvanizing installation known in themselves. same and having no influence on the design of the invention. As is known, the galvanized strip 16 passes, at its exit from the bath 9, between two gas blowing devices 17, 18 which adjust the thickness of the coating on each of the surfaces of the strip 16 and cool it, thus contributing to its good solidification. To collect the mattes, can be placed in a corner of the tray 15 a container in which the mattes can be collected after being pushed with the 11-14 engines, or, as shown, a robot 20 disposed in the vicinity of the tray 15 can be moved in all directions of space to extract the mattes bath 9 and send them in a container 19 placed next to the tray 15.

Les moteurs linéaires 11-14 sont disposés sur des potences 21-24 qui permettent de modifier leurs positions respectives au-dessus du bain 9 pour optimiser :

  • la situation de la zone d'action de chaque moteur 11-14 ;
  • et la distance verticale entre la surface 10 du bain 9 et chacun des moteurs 11-14.
The linear motors 11-14 are arranged on brackets 21-24 which make it possible to modify their respective positions above the bath 9 to optimize:
  • the situation of the action zone of each engine 11-14;
  • and the vertical distance between the bath surface 9 and each of the motors 11-14.

En effet, du fait de la consommation progressive du zinc au cours de la galvanisation, le niveau du bain 9 tend à baisser au cours de l'opération, et si la distance entre le moteur 11-14 et la surface 10 augmente, la force magnétomotrice diminue. Un abaissement progressif du moteur 11-14 par sa potence 21-24 permet de conserver constante cette distance, donc de conserver constante la force magnétomotrice en direction et en intensité, toutes choses étant égales par ailleurs. Un autre moyen d'agir sur la force magnétomotrice est d'augmenter l'intensité du courant traversant le moteur 11-14. Bien entendu, on peut combiner un réglage de la distance entre le moteur 11-14 et la surface 10 du bain 9 et un réglage de l'intensité du courant pour maîtriser la force magnétomotrice. Des moyens peuvent être prévus pour asservir automatiquement la distance entre chaque moteur 11-14 et la surface 10 du bain 9 à la variation du niveau de ladite surface 10.Indeed, due to the progressive consumption of zinc during galvanizing, the bath level 9 tends to drop during the operation, and if the distance between the motor 11-14 and the surface 10 increases, the force magnetomotive decreases. A progressive lowering of the engine 11-14 by its 21-24 stem makes it possible to keep this distance constant, and thus to keep the magnetomotive force constant in direction and in intensity, all other things being equal. Another way of acting on the magnetomotive force is to increase the intensity of the current flowing through the motor 11-14. Of course, it is possible to combine an adjustment of the distance between the motor 11-14 and the surface 10 of the bath 9 and a setting of the intensity of the current to control the magnetomotive force. Means may be provided for automatically controlling the distance between each motor 11-14 and the surface 10 of the bath 9 at the variation of the level of said surface 10.

La disposition des différents éléments principaux de l'installation telle que représentée sur la figure 6 apparaît aussi sur les figures 7 et 8. Deux moteurs 11, 12 encadrent la bande 16 dans sa zone de sortie du bain 9 de manière à éloigner les mattes des surfaces de la bande 16 en les faisant se déplacer parallèlement à elle. Deux moteurs 13, 14 sont, dans l'exemple non limitatif représenté, disposés chacun le long d'une paroi latérale du bac 15 et parallèlement à elle, sensiblement dans le prolongement des deux autres moteurs 11, 12, de façon à faire longer ladite paroi aux mattes qui pénètrent dans leurs zones d'action respectives, et à les envoyer vers la zone d'action 25 du robot 20 qui les pousse dans le récipient 19 situé à proximité immédiate du bac 15. Dans l'exemple représenté, la zone d'action 25 du robot 20 se situe à l'opposé de l'un 14 des moteurs disposés le long d'une paroi latérale du bac 15.The arrangement of the different main elements of the installation as shown on the figure 6 also appears on Figures 7 and 8 . Two motors 11, 12 frame the strip 16 in its outlet area of the bath 9 so as to move the matts away from the surfaces of the strip 16 by moving them parallel to it. Two motors 13, 14 are, in the non-limiting example shown, each disposed along a side wall of the tray 15 and parallel to it, substantially in the extension of the two other motors 11, 12, so as to follow said matte wall which penetrate into their respective areas of action, and send them to the zone of action 25 of the robot 20 which pushes them in the container 19 located in the immediate vicinity of the tank 15. In the example shown, the zone 25 of the robot 20 is opposite to one 14 of the motors arranged along a side wall of the tank 15.

Le parallélisme des parois latérales du bac 15 et des moteurs 13,14 représenté sur les figures 6, 7 et 8 n'est, comme on l'a dit, qu'un exemple de disposition non limitatif. L'orientation de ces moteurs 13, 14 est à optimiser selon la configuration précise du bac 15 et l'emplacement précis de la zone d'action 25 du robot 20. Cette optimisation peut conduire à disposer au moins l'un de ces moteurs 13, 14 obliquement par rapport à la paroi latérale du bac 15 dont il est proche.The parallelism of the side walls of the tank 15 and the motors 13, 14 represented on the figures 6 , 7 and 8 is, as we have said, only an example of a non-limiting provision. The orientation of these motors 13, 14 is to be optimized according to the precise configuration of the tank 15 and the precise location of the action zone 25 of the robot 20. This optimization can lead to having at least one of these motors 13 14 obliquely with respect to the side wall of the tank 15 from which it is close.

Les inventeurs ont constaté que l'efficacité d'un tel système, fonctionnant en régime permanent avec des forces magnétomotrices sensiblement constantes au moins en direction, ne permettait pas de parvenir à une efficacité maximale de l'évacuation des mattes.The inventors have found that the effectiveness of such a system, operating in steady state with magnetometric forces substantially constant at least in direction, did not allow to achieve maximum efficiency of the evacuation of mattes.

En effet, on assiste à terme, du fait de la stabilité des écoulements à la surface du bain 9, à la création de zones mortes où les mattes viennent s'accumuler et restent immobiles sans être captables par un des moteurs 11-14, et aussi de zones dans lesquelles les mattes circulent en boucles, en ayant peu de possibilités de s'échapper pour rejoindre le flux normal de circulation qui doit les conduire dans la zone d'action 25 du robot 20 (ou directement dans le récipient 19 si celui-ci est placé dans le bac 15 lui-même). On observe donc une accumulation des mattes dans certaines zones, qui peut finir par constituer une source de pollution pour l'ensemble du bain 9 et détériorer la qualité de la galvanisation.Indeed, due to the stability of the flows on the surface of the bath 9, the creation of dead zones where the mattes accumulate and remain motionless without being captured by one of the motors 11-14, and also areas in which the matte circulate in loops, having little opportunity to escape to join the normal flow of circulation which must lead them in the zone of action 25 of the robot 20 (or directly in the container 19 if the one it is placed in the tray 15 itself). There is therefore an accumulation of mattes in certain areas, which may end up as a source of pollution for the entire bath 9 and deteriorate the quality of the galvanization.

L'invention résout ce problème en prévoyant qu'au moins un des moteurs 11-14 dispose de moyens permettant d'inverser la direction du champ électromagnétique qu'il génère, donc la direction de la force magnétomotrice qui fait se déplacer les mattes. Cette inversion peut avoir lieu systématiquement à des intervalles de temps prédéterminés et être commandée manuellement ou automatiquement, des expériences préalables ayant permis de déterminer avec quelle fréquence optimale cette inversion doit être effectuée en fonction des conditions de la galvanisation (notamment la vitesse de défilement de la bande 16, la nature du bain 9...). Elle peut aussi avoir lieu de façon irrégulière, à des moments déterminés par l'opérateur de l'installation, ou par un dispositif automatisé quelconque fonctionnant, par exemple, en étant asservi à des moyens d'évaluation de la quantité de mattes accumulées dans une ou des zones déterminées du bac 15.The invention solves this problem by providing that at least one of the motors 11-14 has means for reversing the direction of the electromagnetic field it generates, so the direction of the magnetomotive force that causes the matte to move. This inversion can take place systematically at predetermined time intervals and be controlled manually or automatically, previous experiments having made it possible to determine with which optimal frequency this inversion must be carried out. depending on the conditions of the galvanization (including the running speed of the strip 16, the nature of the bath 9 ...). It can also take place irregularly, at times determined by the operator of the installation, or by any automated device operating, for example, by being slaved to means for evaluating the amount of mattes accumulated in a system. or specific areas of the bin 15.

Cette évaluation de la quantité de mattes accumulées peut être fournie, par exemple, par une analyse des images captées par des caméras (infrarouges ou autres) visant les zones d'accumulation potentielle des mattes. Elle rend possible à un opérateur, ou à un dispositif automatique de gestion de l'installation de galvanisation, d'estimer que l'accumulation des mattes dans un ou plusieurs endroits de la surface 10 du bain 9 est sur le point de devenir excessive ou l'est déjà, et qu'il est donc souhaitable de procéder à ladite inversion de la direction du champ d'au moins un des moteurs 11-14.This evaluation of the amount of mattes accumulated can be provided, for example, by an analysis of the images captured by cameras (infrared or otherwise) aimed at areas of potential accumulation of mattes. It makes it possible for an operator, or an automatic galvanization plant management device, to estimate that the accumulation of mattes in one or more areas of the bath surface 9 is about to become excessive or is already so, and it is therefore desirable to reverse the direction of the field of at least one of the motors 11-14.

L'inversion de la direction de la force magnétomotrice associée au(x) moteur(s) 11-14 concerné(s) provoque une perturbation transitoire de la circulation des mattes, qui permet ainsi d'agiter des zones auparavant stables (zones mortes ou boucles de recirculation). Cette agitation ramène les mattes qui se trouvent dans ces zones au sein du nouveau chemin privilégié de circulation des mattes qui est ainsi créé, et lesdites mattes peuvent être évacuées. Ce nouveau chemin de recirculation va, à son tour, créer de nouvelles zones mortes et boucles de recirculation, mais elles pourront être « cassées » de la même façon par une inversion ultérieure de la direction du champ créé par au moins un des inducteurs 11-14.The inversion of the direction of the magnetomotive force associated with the 11-14 engine (s) concerned causes a transient disturbance of the flow of the mattes, which thus makes it possible to shake previously stable zones (dead zones or recirculation loops). This agitation brings the matts that are in these areas within the new privileged path of circulation of the mattes which is thus created, and said mattes can be evacuated. This new recirculation path will, in turn, create new dead zones and recirculation loops, but they can be "broken" in the same way by a subsequent inversion of the direction of the field created by at least one of the inductors 11. 14.

Ces moyens d'inversion du champ de l'inducteur 11-14 peuvent être constitués, de manière très simple, par un commutateur qui modifie l'alimentation des différentes bobines 3-8. Pour cela, comme on l'a vu et représenté sur la figure 2, il suffit de prévoir un commutateur de phase 30 qui modifie l'alimentation des bobines du moteur. Ce commutateur 30 est installé dans l'armoire électrique de pilotage de l'installation et peut être commandé à distance par un opérateur et/ou par un système automatique. Le changement de direction du champ glissant est instantané.These means of inverting the field of the inductor 11-14 can be constituted, very simply, by a switch that changes the power of the various coils 3-8. For that, as we have seen and represented on the figure 2 it is sufficient to provide a phase switch 30 which modifies the power supply of the motor coils. This switch 30 is installed in the electrical control cabinet of the installation and can be controlled remotely by an operator and / or by an automatic system. The change of direction of the sliding field is instantaneous.

Dans le cas représenté sur les figures 7 et 8, ce sont les moteurs 11, 12 qui entourent la bande 16 dans sa zone de sortie du bain 9 qui sont équipés de moyens d'inversion du sens du champ électromagnétique qu'ils génèrent.In the case represented on the Figures 7 and 8 it is the motors 11, 12 which surround the strip 16 in its outlet zone of the bath 9 which are equipped with means for reversing the direction of the electromagnetic field they generate.

Dans le cas de la figure 7, on a représenté un premier état de fonctionnement des moteurs 11-14 dans lequel les moteurs 11, 12 entraînent tous deux les mattes vers la paroi latérale gauche du bac 15. Elles y sont reprises par le champ généré par le moteur 14 situé le long de cette paroi latérale gauche 26, et envoyés en direction du récipient 19 si celui-ci est intégré au bac 15, ou, comme représenté, dans la zone d'action 25 du robot 20. Simultanément, le moteur 13 situé le long de la paroi latérale droite 27 du bac 15 envoie les mattes que capte son champ électromagnétique le long de la paroi latérale droite 27 vers la zone d'action 25 du robot 20. Ces mattes tendent également à être déviées par la paroi frontale 28 du bac 15 en direction de la zone d'action 25 du robot 20. Les différentes flèches représentées sur la figure 7 (de même que sur les figures 8 et 9) montrent les déplacements des mattes induits par les forces magnétomotrices générées par les différents moteurs 11-14.In the case of figure 7 a first state of operation of the motors 11-14 is shown in which the motors 11, 12 both drive the matts towards the left side wall of the tank 15. They are taken up by the field generated by the motor 14 located along the of this left side wall 26, and sent towards the container 19 if it is integrated with the tray 15, or, as shown, in the zone of action 25 of the robot 20. Simultaneously, the motor 13 located along the right side wall 27 of the tank 15 sends the matte that captures its electromagnetic field along the right side wall 27 to the zone of action 25 of the robot 20. These matts also tend to be deflected by the front wall 28 of the tank 15 towards the zone of action 25 of the robot 20. The various arrows represented on the figure 7 (as well as Figures 8 and 9 ) show the displacements of the mattes induced by the magnetomotive forces generated by the various motors 11-14.

La figure 8 représente un second état de fonctionnement des moteurs 11-14, dans lequel les directions des champs générés par les moteurs 11, 12 encadrant la bande 16, au bout d'un certain temps d'utilisation de la configuration de la figure 7, ont été, selon l'invention, inversées par rapport au cas de la figure 7. Cette fois, les mattes se trouvant au voisinage de la bande 6 sont orientées vers le moteur 13 situé le long de la paroi latérale droite 27 du bac 15. Les moteurs 13, 14 fonctionnent comme dans le cas de la figure 7. Cette inversion est déjà suffisante pour créer des mouvements des mattes à la surface 10 du bain 9 qui sont capables de « casser » les zones mortes et les zones de recirculation crées dans la configuration de la figure 7.The figure 8 represents a second state of operation of the motors 11-14, in which the directions of the fields generated by the motors 11, 12 flanking the strip 16, after a certain time of use of the configuration of the figure 7 have, according to the invention, been inverted with respect to the case of the figure 7 . This time, the matts in the vicinity of the strip 6 are oriented towards the motor 13 located along the right side wall 27 of the tank 15. The motors 13, 14 operate as in the case of the figure 7 . This inversion is already sufficient to create movements of the matts on the surface of the bath 9 which are able to "break" the dead zones and the recirculation zones created in the configuration of the figure 7 .

On repassera de façon manuelle ou automatique dans la configuration de la figure 7 lorsque l'accumulation des mattes dans les nouvelles zones mortes et boucles de recirculation créées sera sur le point de devenir excessive, comme précédemment décrit.It will be passed manually or automatically in the configuration of the figure 7 when the accumulation of mattes in the new dead zones and recirculation loops created will be on the verge of becoming excessive, as previously described.

Dans l'exemple représenté, les deux moteurs 11, 12 encadrant la bande 16 entraînent tous deux les mattes dans la même direction. Mais cette configuration n'est pas obligatoire, on peut prévoir, si la localisation des mattes à déplacer le nécessite, que les directions des champs desdits moteurs 11, 12 soient opposées, et ce de façon permanente ou temporaire.In the example shown, the two motors 11, 12 flanking the strip 16 both lead the matte in the same direction. But this configuration is not mandatory, it can be provided, if the location of the matte to move requires, the field directions of said motors 11, 12 are opposed, and permanently or temporarily.

Egalement, dans l'exemple représenté, les deux moteurs 11, 12 encadrant la bande 16 ont la même longueur et se font exactement face. Mais cette configuration n'est pas obligatoire et on peut prévoir que ces moteurs 11, 12 aient des longueurs différentes et/ou soient décalés l'un par rapport à l'autre, s'il s'avère que cela est profitable à la bonne évacuation des mattes dans la configuration particulière du bac 15 utilisé.Also, in the example shown, the two motors 11, 12 flanking the strip 16 have the same length and are exactly opposite. But this configuration is not mandatory and it can be expected that these motors 11, 12 have different lengths and / or are offset relative to each other, if it turns out that it is beneficial to the good evacuation of the mattes in the particular configuration of the tank 15 used.

La figure 9 présente schématiquement une variante du cas des figures 6 à 8, dans laquelle on a ajouté un cinquième moteur 29 disposé obliquement dans le coin avant droit du bac 15. Il est donc situé sur le trajet des mattes poussées par le moteur 13 situé le long de la paroi latérale droite 27 du bac 15, et a pour fonction de renforcer l'effet de ce moteur 13 dans l'expédition des mattes en direction de la zone d'action 25 du robot 20.. On peut ainsi réduire la taille de la zone d'action 25 du robot 20 et, de manière générale, augmenter l'efficacité de l'évacuation des mattes hors du voisinage de la bande 16 et en direction de la zone d'action 25 du robot 20. Les moteurs 11, 12 encadrant la bande 16 ont, comme dans le cas des figures 7 et 8, leurs champs électromagnétiques en alternance dans l'une ou l'autre direction.The figure 9 schematically presents a variant of the case of Figures 6 to 8 , in which a fifth motor 29 arranged obliquely in the right front corner of the tank 15 has been added. It is thus located on the path of the matts pushed by the motor 13 situated along the right side wall 27 of the tank 15, and has in order to reinforce the effect of this motor 13 in the expedition of the mattes towards the action zone 25 of the robot 20. It is thus possible to reduce the size of the action zone 25 of the robot 20 and generally, increase the efficiency of the evacuation of mattes from the vicinity of Band 16 and direction of the zone of action 25 of the robot 20. The motors 11, 12 surrounding the band 16 have, as in the case of Figures 7 and 8 alternating their electromagnetic fields in one direction or the other.

On peut aussi envisager que les différents moteurs 11-14 ou 11-14, 29, ou au moins certains d'entre eux, soient déplaçables en cours d'opération dans une direction qui leur permette d'accompagner le déplacement des mattes, et ainsi d'assister le déplacement d'un groupe de mattes donné pendant une durée plus longue que si le moteur 11-14 ou 11-14, 29 ne leur donnait qu'une seule impulsion, lorsque ces mattes sont situées en-dessous de la zone d'action initiale du moteur 11-14 ou 11-14, 29.It can also be envisaged that the various motors 11-14 or 11-14, 29, or at least some of them, are movable during operation in a direction that allows them to accompany the movement of the mattes, and thus to assist the movement of a given group of mattes for a longer duration than if the engine 11-14 or 11-14, 29 gave them only one pulse, when these matts are located below the zone initial action of the motor 11-14 or 11-14, 29.

Bien entendu, les exemples des figures 6-9 ne sont pas limitatifs, tant du point de vue du nombre de moteurs que de leur disposition. On peut aussi prévoir que d'autres moteurs que des moteurs 11, 12 encadrant la bande 16 (en plus d'eux ou à leur place) puissent avoir leurs directions d'action inversables. Mais les environs de la zone de sortie de la bande 16 étant les plus sensibles en termes de risques de pollution du dépôt de zinc, ou d'alliage métallique de revêtement en général, par les mattes (si la zone d'entrée de la bande est protégée par un tube connecté au four de recuit comme c'est souvent le cas), il est clair que, de préférence, des moteurs d'une grande efficacité doivent y être disposés. Et surtout si ces moteurs 11, 12 sont les plus puissants du dispositif, c'est de préférence ceux dont il sera le plus profitable d'inverser les directions d'action. On peut aussi prévoir de remplacer l'un et/ou l'autre de ces deux moteurs 11, 12, dont la longueur est, si possible, du même ordre que la largeur de la bande, par plusieurs moteurs de plus petite taille disposés les uns à côté des autres et dont les champs magnétiques auraient la même direction. Ce peut être une façon de résoudre un problème d'encombrement que pourrait poser l'implantation d'un moteur unique de grande taille dans le bain, particulièrement dans le cas du moteur 12 situé entre la zone d'entrée de la bande 16 dans le bain 9 et la zone de sortie de la bande 16. Ce peut aussi être une façon de faire facilement varier la taille de la zone d'action des moteurs encadrant la bande 16 en fonction de la largeur de la bande 16 si celle-ci peut prendre plusieurs valeurs différentes sur une même installation de revêtement. Pour cela, il suffit de mettre électriquement hors service les moteurs qui débordent au-delà de la largeur de la bande 16, voire également de les déplacer à l'écart du bac 15.Of course, the examples of Figures 6-9 are not limiting, both in terms of the number of engines and their disposition. It is also possible that other motors than motors 11, 12 flanking the strip 16 (in addition to them or in their place) can have their directions of action reversible. But the vicinity of the exit zone of the strip 16 being the most sensitive in terms of risks of pollution of the deposit of zinc, or coating metal alloy in general, by the mattes (if the zone of entry of the strip is protected by a tube connected to the annealing furnace as is often the case), it is clear that, preferably, motors of high efficiency must be arranged there. And especially if these motors 11, 12 are the most powerful device, it is preferably those which it will be most profitable to reverse the directions of action. It is also possible to replace one and / or the other of these two motors 11, 12, whose length is, if possible, of the same order as the width of the strip, by several smaller engines arranged next to each other and whose magnetic fields would have the same direction. This may be a way to solve a problem of size that could pose the implementation of a single large engine in the bath, particularly in the case of the motor 12 located between the input zone of the strip 16 in the bath 9 and the exit zone of the strip 16. This may also be a way to easily vary the size of the action zone of the motors flanking the strip 16 as a function of the width of the strip 16 if it can take several different values on the same coating plant. For this, it is enough to electrically out of order engines that overflow beyond the width of the band 16, or even to move them away from the tray 15.

Bien entendu, les exemples qui ont été décrits ne sont pas limitatifs et d'autres dispositions des inducteurs sont envisageables, en particulier lorsque la zone où la bande 16 pénètre dans le bain 9 doit elle aussi être exempte de mattes si la bande 16 s'y trouve à l'air libre, ou si le récipient 19 recueillant les mattes et/ou la zone d'action 25 du robot 20 sont placés ailleurs qu'il ne le sont dans les exemples représentés. L'homme du métier saura adapter le nombre et la disposition des inducteurs à la géométrie particulière de son installation de revêtement, l'essentiel étant l'existence de la possibilité d'inverser par intermittence la direction d'action d'au moins un des inducteurs pour éviter la pérennisation des zones mortes et des boucles de recirculation à la surface 10 du bain 9, qui est propice à l'accumulation des mattes.Of course, the examples which have been described are not limiting and other provisions of the inductors are conceivable, in particular when the zone where the strip 16 enters the bath 9 must also be free of mattes if the strip 16 is It is found in the open air, or if the container 19 collecting the mattes and / or the zone of action 25 of the robot 20 are placed elsewhere than they are in the examples shown. The skilled person will be able to adapt the number and arrangement of the inductors to the particular geometry of its coating installation, the essential being the existence of the possibility of intermittently reversing the direction of action of at least one of the inductors to avoid perpetuation dead zones and recirculation loops on the surface of the bath 9, which is conducive to the accumulation of the mattes.

Pour des bacs 15 de faibles dimensions, il est envisageable de n'utiliser qu'un moteur unique dont on fait varier par intermittence la direction du champ glissant qu'il génère. Dans ce cas il peut être judicieux de prévoir deux récipients 19 situés chacun dans le prolongement dudit moteur mais à l'opposé l'un de l'autre, pour recueillir les mattes déplacées lors des périodes pendant lesquelles le champ du moteur glisse selon l'une ou l'autre direction.For containers 15 of small dimensions, it is possible to use only a single motor which is varied intermittently the direction of the sliding field it generates. In this case it may be wise to provide two containers 19 each located in the extension of said engine but opposite each other, to collect the matte displaced during the periods during which the engine field slides according to the one or the other direction.

A titre d'exemple non limitatif, pour une mise en oeuvre de l'invention sur une installation de galvanisation de bandes d'acier de 650 à 1350 mm de largeur défilant normalement à 60-120 m/min mais étant susceptibles de défiler à une vitesse supérieure à 200 m/min grâce à l'utilisation de l'invention, on peut utiliser un bac 15 rectangulaire de 4 x 3,20 m et quatre moteurs 11-14 disposés comme sur les figures 6 à 8, Ces moteurs sont alimentés par un courant de fréquence 10Hz. Ils ont chacun un pas polaire de 300 mm, une longueur totale de 600 à 700 mm, et comportent chacun six bobines de 96 spires, chacune parcourue par un courant d'intensité 150 A, et procurant donc une force magnétomotrice de 15 000 Ampère-tours.By way of nonlimiting example, for an implementation of the invention on a galvanizing installation of steel strips 650 to 1350 mm in width normally moving at 60-120 m / min but being able to scroll to a greater than 200 m / min thanks to the use of the invention, it is possible to use a rectangular tank 4 x 3.20 m and four motors 11-14 arranged as on the Figures 6 to 8 These motors are powered by a 10Hz frequency current. They each have a pitch of 300 mm, a total length of 600 to 700 mm, and each comprise six coils of 96 turns, each traversed by a current of intensity 150 A, and thus providing a magnetomotive force of 15,000 amps. towers.

Claims (11)

  1. A method for hot-dip coating of a steel strip (16) running in a bath (9) of liquid metal or of a metal alloy contained in a pan (15), according to which the dross which are formed during the coating and float at the surface (10) of the bath (9), are moved away from the surface of the strip (16), by means of at least one inductor (11-14, 29), each inductor (11-14, 29) producing a sliding electromagnetic field oriented along a given direction and generating a magnetomotive force, the whole of said magnetomotive forces displacing said dross towards a container (19) intended to collect them and/or towards an area (25) of the surface (10) of the bath (9) from which they are discharged, characterized in that, for at least one of said inductors (11-14, 29), said direction of its sliding electromagnetic field is reversed intermittently so as to modify the flows of the dross inside the pan (15).
  2. The method according to claim 1, characterized in that among said inductors (11-14, 29), at least two (11, 12) of them are positioned along the area where the strip (16) exits the bath, and in that the direction of their respective magnetic fields are reversed intermittently.
  3. A hot dip coating facility for a steel strip (16), including a pan (15) containing in the liquid state, a bath (9) of liquid metal or metal alloy, in which the strip runs (16), and at least one inductor (11-14, 29), each inductor (11-14, 29) generating an electromagnetic field and magnetomotive forces contributing to bringing the dross generated during the galvanization to the vicinity of a container (19) intended to receive them and/or into the action area (25) of a robot (20) or of an operator who brings them into said container (19), characterized in that at least one of said inductors (11-14, 29) includes a device allowing reversal of the direction of the electromagnetic field generated by said inductor (11-14).
  4. The facility according to claim 3, characterized in that it at least includes two inductors (11, 12) located on either side of the exit area of the strip (16) from the bath (9), and in that said inductors (11, 12) each include a device allowing reversal of the direction of the electromagnetic field which it generates.
  5. The facility according to one of claims 3 or 4, characterized in that said inductors (11-14, 29) are mounted on brackets (21-24) allowing adjustment of their location above the pan (15) and their distance to the surface (10) of the bath (9).
  6. The facility according to one of claims 3 to 5, characterized in that it includes automated devices for servo-controlling the distance between each of the inductors (11-14, 29) and the level of the surface (10) of the bath (9).
  7. The facility according to one of claims 3 to 6, characterized in that two inductors (11, 12) frame the strip (16) in the area where it exits the bath (9) so as to move the dross away from the surfaces of the strip (16) by having them move parallel therewith, and in that two inductors (13, 14) are each positioned along a wall (26, 27) of the pan (15), substantially in the extension of the two other inductors (11, 12).
  8. The facility according to claim 7, characterized in that the pan (15) containing the bath (9) has a generally rectangular shape, in that the container (19) in which the dross are collected or the action area (25) of the robot (20) or of the operator is located in a corner of the pan (15) opposite to one of the inductors (13, 14), and in that in the corner of the pan (15) opposite to the other one of the inductors (13, 14), an inductor (29) is placed intended to orient the dross towards said container (19).
  9. The facility according to one of claims 3 to 8, characterized in that it includes means for controlling the reversal of the direction of the electromagnetic field generated by at least one inductor (11-15) which are themselves subordinate to a device allowing to evaluate the amount of accumulated dross in at least one area of the pans (15).
  10. The facility according to one of claims 3 to 9, characterized in that at least one of said inductors (11-14, 29) is a three-phase linear motor.
  11. The facility according to claim 10, characterized in that at least one of said three-phase linear motors (11-14, 29) is of the type in which the coils (3-8) surround the core (1).
EP11791018.2A 2011-10-20 2011-10-20 Hot dip galvanizing method for coating a steel strip and apparatus therefor Active EP2768996B1 (en)

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CA2852363A1 (en) 2013-04-25
RU2566115C1 (en) 2015-10-20
CN104040013A (en) 2014-09-10
US9719162B2 (en) 2017-08-01
BR112014009495B1 (en) 2020-11-10
US11072846B2 (en) 2021-07-27
US20140329033A1 (en) 2014-11-06
EP2768996A1 (en) 2014-08-27
PL2768996T3 (en) 2017-12-29
BR112014009495A2 (en) 2017-04-18
MX2014004695A (en) 2014-10-17
JP2014530960A (en) 2014-11-20
KR20140092354A (en) 2014-07-23

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