EP2350333A1

EP2350333A1 - Method and device for draining liquid coating metal at the output of a tempering metal coating tank

Info

Publication number: EP2350333A1
Application number: EP08875613A
Authority: EP
Inventors: Benjamin Grenier; Jean-Jacques Hardy; Roland Ernst; Yves Fautrelle
Original assignee: Centre National de la Recherche Scientifique CNRS; Institut Polytechnique de Grenoble; Siemens VAI Metals Technologies SAS
Current assignee: Centre National de la Recherche Scientifique CNRS; Institut Polytechnique de Grenoble; Clecim SAS
Priority date: 2008-09-23
Filing date: 2008-09-23
Publication date: 2011-08-03
Also published as: AU2008362112A1; AU2008362112B2; JP2012503101A; RU2011116219A; RU2482213C2; CA2737923A1; WO2010034892A1; CN102159745A; BRPI0823127A2; US20110177258A1; KR20110133466A

Abstract

The present invention relates to a method and to a device for draining liquid coating metal, at the outlet of a tempering metal coating tank, from the two sides of a longitudinally continuously running steel strip. The method of the invention particularly comprises transferring the strip coated with liquid coating metal, as it runs at the tank outlet, from a region not subjected to a magnetic field to another region subjected to a static magnetic field generated between the poles of magnetic members arranged opposite each other on either side of the strip and having field lines, or at least a main shell of said field lines, intersecting with said strip over at least one minimum longitudinal extent so that the liquid coating metal is correlatively subjected to a magnetic field variation generating on said liquid metal a force opposite to the running direction thereof with the strip. Due to the low field variation, this magnetic braking effect generates little Foucault current in the strip. The power radiated in order to reach an efficient draining effect of the liquid film is thus very low and the heating of the strip is very advantageously negligible, amongst other advantages.

Description

Method and device for spinning liquid metal coating at the outlet of a metal coating tank by dipping

The present invention relates to a method and a device for spinning liquid metal coating at the outlet of a quilting metal coating tank according to the preamble of claims 1 and 12.

The invention relates to spinning a liquid metal film as a coating liquid metal applied to dipping onto a steel strip in a continuous coating line. "Liquid metal film" means any type of coating applicable to steel strips, for example alloys based on zinc and aluminum.

In order to improve their resistance to corrosion in certain applications such as the building, the automobile or household appliances, a metal coating is deposited on the surface of steel strips, for example zinc or zinc-based alloys. . This coating is made on continuous lines that typically include: • An inlet section with one or two belt unrollers, a guillotine shear, a splicing welder to connect the tail of a strip from one of the unwinders to the head of the next band from the other unroller and thus ensuring continuous operation of the line, a tape accumulator, which restores to the line of the previously accumulated tape when a flow is interrupted upstream of the accumulator for implement the splicing weld.

• A section for degreasing cold rolled strip or acid pickling of hot rolled strip. • An annealing furnace that also maintains temperature controlled strip before entering the bath of liquid metal.

• A coating section itself with the bath of liquid metal in which the strip is immersed, a device for wiping the liquid metal, optionally an induction induction furnace, a cooling and a quenching tank.

• An exit section with a Skin-Pass rolling mill, a passivation device, an output accumulator, a shear and one or two winders.

In a first variant of the process, when it leaves the furnace, the steel strip is immersed obliquely in a bath of liquid metal alloy, it is deflected vertically by a roll immersed in the bath, then passes on a roller called " anti tile 'intended to correct its lateral curvature from its passage on the bottom roller, then on a roll called "pass line" to adjust its vertical trajectory. In a second variant of the process, at its outlet from the furnace, the steel strip is deflected vertically by a roller and then vertically passes through a bath of magnetized metal alloy magnetically lifted. In both cases, at its exit from the coating bath, the strip is covered on both sides with a liquid metal film whose thickness is the result of a balance which is established between the driving forces. of the liquid by the band and forces of gravity. It is necessary to equalize transversely and longitudinally the thickness of the liquid metal coating to a value as close as possible to the objective that combines performance research in the field of protection against corrosion and optimization of the amount of metal consumed. For this, devices are arranged on either side of the strip to ensure the spinning of the liquid film on both sides. Such spin-drying systems have been extensively described, for example in document EP 0 566 497. The principle of spinning consists in blowing a jet of gas in order to produce on the liquid film a necking effect intended to reduce its thickness. , the surplus of wrung film returning by gravity to the coating bath. The distance between the strip and such wipers as well as the gas pressure and the distance between the wipers and the surface of the coating bath and the running speed of the strip are among the essential variables governing the spinning operation. . These variables are controlled from measurements made by measuring devices of the thickness of the coating deposited on each of the two faces of the strip, for example X-ray gauges. For a long time, it has been noted for the limits of the method of gas jet spinning that, at high tape speeds, occurs a phenomenon known as "splashing". This phenomenon, related to the thickness of the driven liquid film which increases with the speed of movement, results from a break in equilibrium between the forces of entrainment by the band, the gravity and a surface tension in a zone of the film where shear stresses develop due to the jet of gas. This results in an ejection of droplets that disrupt the jet of gas, affect the quality of the coating and are most often followed by an explosion of the desired film. The speed of travel of the strip, and therefore the productivity of the coating line, is also limited by the spinning capacity of the liquid film. Many attempts have been made to combat this phenomenon and to allow higher tape speeds. Among these, magnetic systems have been developed that drain the strip of a portion of the liquid coating film, and completed, downstream, by a final spin jet gas.

Several families of processes using magnetic induction are thus known, all these families remaining based on a creation of forces (of Lorentz) within the liquid conducting medium under the combined effect of a current and a magnetic field:

• The so-called "longitudinal flow" processes which implement an induction coil which surrounds the strip and which is supplied with alternating current. This type of device generates field lines substantially parallel to the so-called longitudinal scrolling movement of said alternating current-inducing strip in the metal coating film and the strip. The interaction between the current thus induced and the magnetic field generates the development of radial and axial electromagnetic forces ensuring the spinning of the film. By way of example, JP 5051719 describes such a longitudinal field system supplied with high frequency alternating current.

• "Cross flow" processes that use two separate AC powered induction coils, each placed on one side of the strip. This type of device generates magnetic field lines substantially perpendicular to the longitudinal scrolling of said band inducing eddy currents in the plane of the strip. The interaction between these currents and the magnetic field generates a development of electromagnetic shear forces ensuring the spinning of the liquid metal film. By way of examples, documents DE 2023900 and JP 08-134617 describe such transverse field systems supplied with alternating current of appropriate frequency.

• "Sliding field" processes that implement, on each side of the strip, multipole inductors powered by polyphase alternating current. This type of device generates a magnetic field sliding in the opposite direction to a displacement of the strip scrolling upwards, thereby ensuring a pumping action of the liquid film downwards. By way of example, the documents US 3,518,109 and JP 08-053742 describe such a sliding field system supplied with polyphase alternating current. • The "pressure on a meniscus" process which uses an inductor at the level of a connecting meniscus of the liquid film entrained by the band with the liquid bath. A magnetic field acts on the curvature of the meniscus and thus on the thickness of the driven film. By way of example, document EP 1 138 799 describes such a meniscus control system. This process is very difficult to implement and is limited to the metal coating of small objects such as son. As an alternative to certain processes already described above, permanent magnets have also been used which need to be associated with devices for supplying the strip with electric current by applying friction or pebbles on the strip. leaving these processes therefore not very suitable for spinning. Examples of such methods are described in JP 61-227158 or JP 02-254147. Finally, still in the field of permanent magnets, it has been proposed by JP 2000-212714 to mount a plurality of magnets on a rotating drum to create a variable magnetic field for the purpose of creating useful induction effects. to spin.

These methods each have a number of disadvantages which considerably impede their implementation. These disadvantages can be classified as follows:

• Heating of the band: All longitudinal and transverse flow systems generated by induction coils fed by alternating current produce a considerable heating of the band up to more than 100 ⁰ C. In particular the longitudinal flows which, effect of identical spin, require higher power, can lead, in certain configurations, to temperature rises of up to 150 to 200 ^° C. This heating is likely to disturb a layer of steel / coating combination by promoting undesirable phenomena of diffusion of iron towards the coating. On the other hand, this additional heat supply must then be discharged into a cooling tower, which leads to an increase in its height and / or an increase in the power of air blowing installations.

• Saturation of the band: The magnetic saturation of the band is quite quickly reached in a space generated by magnetic field lines and, as soon as the band is saturated, it itself constitutes a limit to the spinning capacity and therefore to the the speed of the tape. This risk is particularly noticeable in the context of longitudinal flow processes, or even transverse flow processes.

• Tape Marking: Processes powered by electrically powered tape or rollers can not be retained for quality galvanized tape because of mechanical scratches on the tape.

An object of the present invention is in particular to ensure an effective spinning of liquid metal coating at the outlet of a metal coating tank by dipping a steel strip in longitudinal scrolling, for which binding effects of magnetic saturation band are minimized.

A fortiori, the invention also aims to: - minimize band heating;

- avoid mechanical tape / film marking;

- use a magnetic spin avoiding any "splashing" effect;

- allow precise control of the targeted coating thickness.

The invention thus presents a method and a device adapted to solve these problems according to the content of claims 1 and 12. From a spinning method of coating liquid metal at the outlet of a metal coating tank by dipping the two faces of a continuous longitudinal strip of steel, the invention therefore provides that during When the tray is moved out of the tray, the covered strip of the liquid coating metal passes from a region not subject to a magnetic field to another region subject to a static magnetic field created between magnetic pole members placed opposite the - screws on each side of the strip and whose field lines, or at least one main envelope of said field lines, intersect at least a minimum longitudinal extent with said strip, so that the coating liquid metal undergoes correlatively a magnetic field variation generating on said liquid metal a force opposing its movement with the band. Indeed, said longitudinal extent of intersection is chosen minimal and sufficient so as to generate in the liquid metal film eddy currents at a minimum intensity but whose circulation in the static magnetic field is sufficient to generate Lorentz forces necessary for suitably oppose the movement of said liquid metal relative to the web.

The movement of the band in this static magnetic field can thus induce a current in the band, but also and especially in the liquid film where develops, in a known manner, a magnetic brake effect opposite to the band scrolling. .

Due to the small field variation this magnetic brake effect generates few eddy currents in the band. The continuous nature of the magnetic field, due to the absence of a skin effect, limits the power dissipated to achieve an effective wiping effect of the liquid film and thus the heating of the strip is very advantageously insignificant. No contact with the tape is necessary, so marking problems are advantageously avoided. By the use of a magnetic field, in particular for the purpose of spinning in several successive stages by a succession of wiping devices, the disadvantage of the effects of "splashing" is also discarded.

In order to implement the method described according to the invention, an embodiment of a device is possible from a device for wiping liquid metal at the outlet of a metal coating tank by dipping the two faces of a steel strip (1) in continuous longitudinal movement. When leaving the ferry, the device provides that:

at least one first magnetic member is disposed transversely to a first of the two faces of the strip at a given distance from the strip, and a second magnetic member is arranged transversely to a second of the two faces of the strip, substantially at the same distance from said band,

poles of said magnetic members (A1, A2) are distributed opposite each side of the strip in such a way as to generate between the said poles lines of static magnetic field (included in a main envelope) presenting a intersection over at least a minimum longitudinal extent with the band.

A set of subclaims also has advantages of the invention.

Examples of implementation and application are provided using the figures described:

Figure 1 "Longitudinal flow" dewatering device, Figure 2 "Cross flow" wringing device,

Figure 3 "Press on a meisque" spinning device,

Figures 4a, 4b spinning device with magnetic members according to a first embodiment of the invention,

FIGS. 5a, 5b, 5c, 5d electromagnetic body dewatering device according to a second embodiment of the invention,

Figure 6 Spinning principle according to the first embodiment of the invention,

Figure 7 Wringing principle with distance stabilization control according to the second embodiment of the invention.

FIG. 1 shows a device for wiping a metal film for coating the faces of a steel strip (1) in continuous longitudinal longitudinal flow by "longitudinal flow" such as that described previously in the state of the technical. The strip (1) is thus covered on both sides with a liquid film (not shown) and is animated with a vertical movement of speed (V). An induction coil (2) consisting of one or more turns of an electrical conductor and surrounding the strip in the direction of its width is traversed by an alternating current of frequency adapted to an induction leading to the effect of spinning . Figure 1 shows the passage of the current according to one of its alternations. This current generates an alternating magnetic field which manifests on each side of the band by two lobes (L1) and (L2) res- respectively associated with two strands (21, 22) of the coil, shown in section. In the immediate vicinity of the band, the field lines are generated and have a path parallel to the direction of the scrolling thereof, hence the name "longitudinal flow". They do not cross the band, but extend over it over a large longitudinal portion.

FIG. 2 shows a device for wiping a metal film for coating the faces of a steel strip (1) in continuous vertical longitudinal deflection by "transverse flow" such as that previously described in the state of the technical. The strip (1) is thus covered on both sides with a liquid film (not shown) and is animated with a longitudinal vertical movement of speed (V). Two induction coils (2a, 2b), each disposed symmetrically opposite one side of the strip in the direction of its width, are traversed by an alternating current of frequency adapted to an induction leading to the spinning effect. Figure 2 shows the passage of the current in one of its alternans. This current generates an alternating magnetic field which is manifested, on each side of the band, by four lobes (L1, L2, L3, L4) respectively associated with portions of coils (21a, 22a, 21b, 22b). In the immediate vicinity of the strip, field lines are generated and have a path generally perpendicular to the direction of the scrolling thereof and extending at least on sections of width of the strip, hence the name " transverse flow ". These field lines are looped over the coil portion that generates them in a direction perpendicular to the scroll. They do not cross the band but run at least transversely.

Figure 3 shows a spin device "pressure on a meniscus" adapted to a liquid film coating. A strip (1) is thus covered with a liquid film (3) and is animated with a longitudinal vertical movement of speed (V). An induction coil (2) consisting of one or more turns of an electrical conductor surrounding the strip in the direction of its width is traversed by an alternating current of frequency adapted to the effect of spinning. Figure 3 shows the passage of the current according to one of its alternations. The magnetic field acts on the curvature (R; R ') of the meniscus and thus on the thickness of the driven film.

FIGS. 4a, 4b show a spinning device with magnetic organs according to a first embodiment of the invention, and more particularly a device adapted for spinning liquid metal at the outlet of a metal coating tank at quenched on both sides of a steel strip (1) in continuous longitudinal movement. At the outlet of such a tank, the device comprises:

at least one first magnetic member (Al), such as here at least one permanent magnet, is disposed transversely to a first of the two faces of the strip at a given distance from the strip, and a second magnetic member (A2 ) is arranged transversely to a second of the two faces of the strip, substantially at the same distance from said strip,

poles (N, S), here magnets of north / south type, said magnetic members (A1, A2) are distributed opposite each side of the band so as to generate between said poles of the static magnetic field lines (B) included in a main envelope having an intersection over at least a minimum longitudinal extent with the band as provided by the invention.

In other words, the devices according to FIGS. 4a and 4b thus provide that each magnetic member comprises at least one bipolar permanent magnet element (A1, A2) whose magnetic capacitance is fixed so as to induce at least one electromotor field sufficient to generate counter-interaction when the tape is forced to move in the manual field. static gnetic (B) a wiper braking adapted to the layers of metal coating initially deposited on the strip.

The poles of each magnetic member (Al, A2) being the closest together here are of opposite magnetic polarity (N, S). Thus, it is possible to configure the field lines between these poles through the band. The longitudinal extent is therefore reduced to about one height of the magnets used.

It would also be possible to provide that the poles of each magnetic member (Al, A2) being the closest to the band are of the same magnetic polarity.

According to FIG. 4a, poles (S, N) of each magnetic member (A1, A2) being furthest from the strip (transverse external faces of the permanent magnets) are also connected by an external magnetic field guide (C), such as a ferromagnetic yoke frame forming a magnetic guide loop around a strip section.

Thus, according to FIG. 4a, the magnetic poles (N, S) closest to the two magnetic members that face each other on either side of the strip are arranged in such a way that they generate a static magnetic field (B) which forms a magnetic circuit between the north pole (N) of the first magnetic member and the south pole (S) of the second through the band, the magnetic loop being completed between the outer poles, that is to say the north pole (N) of the second magnetic member and the south pole (S) of the first member through a ferromagnetic yoke (C) surrounding the strip.

Alternatively according to FIG. 4b, the dewatering device provides that each magnetic member (Al, A2) comprises two distinct poles successively arranged in the running direction of the strip and connected to at least one magnet by a magnetic field guide (Cl , C2) such that at least one ferromagnetic head portion forming a half loop of magnetic guide so that, between each of the two poles at the ends of the two half-loops are arranged vis-à-vis on both sides of the band, thus completely closing the lines of magnetic field. In other words, two permanent magnets in the shape of a "U" are arranged symmetrically with respect to the band by placing in opposite relation the bases of the two "U" with opposite polarities on either side of the bandaged.

Thus, a first ferromagnetic yoke portion (C1) extends the south pole (S) of the first magnetic member (A1) and a second ferromagnetic yoke portion (C2) extends the north pole (N) of the second magnetic member (A2). The magnetic field (B) traverses for the first time the band between the north pole (N) of the first magnetic member and the south pole (S) of the second magnetic member, and is then channeled on the second ferromagnetic yoke portion (C2), then crosses the strip a second time, the loop being completed in the first part of the ferromagnetic yoke (Cl).

It is here recommended that at the ends of the half-loops, the poles have opposite magnetic polarities so that the two half-loops induce a closed-loop magnetic guidance of the magnetic field (B) through the band.

As described above, it would also be possible that at the ends of the half-loops, the poles have identical magnetic polarities. Spinning will be possible, but less effective than in the configuration with opposite magnetic polarities as above.

Not restrictively to Figures 4a, 4b and therefore also applicable to the following figures, each magnetic member is linearly extended in one or more blocks over a length at least equal to a bandwidth. Also, several magnetic members extended linearly over a length of less than one bandwidth may be distributed one above the other in the running direction of the band and on each side thereof. By thus forming successive areas of intersection field / band minimum extent to avoid magnetic saturations band, this configuration advantageously increases the efficiency of the spinning. For the same purpose, at least one of the magnetic members may be associated with a complementary dewatering device such as by gas jets, or a complementary device for stabilizing tape.

Figures 5a, 5b show two configurations of electro-magnetic wiper device (as magnetic members) according to a second embodiment of the invention in relation respectively to the configurations of Figures 4a, 4b.

In particular in FIG. 5a, the two electromagnetic members (B1, B2) are arranged transversely to the strip travel on either side of the two faces of the strip and are joined by a ferromagnetic yoke (C) surrounding said strip.

Figures 5c, 5d show two other configurations of electro-magnetic wiper device (as magnetic members) according to this second embodiment of the invention.

In particular, FIGS. 5b, 5c and 5d show, according to a configuration of the ferromagnetic yoke in two half-loops (C1, C2) arranged transversely to the strip running on either side of the two faces of the strip, several provisions possible of said electromagnetic organs (B1, B2, B3, B4). In these examples, a magnetic field looping is carried out by two web ties by the magnetic field (B) and by complementary pipe of the magnetic field by means of ferromagnetic half-heads, as in Figure 4b.

The electromagnetic members (B1, B2, B3, B4) are here induction coils associated with the cylinder head (s) (C, Cl, C2) in order to generate the said static magnetic field and to channel field lines around the band and in particular on a minimum extent of intersection with the band. By regulating the supply current of at least one of said induction coils, the intensity of the static magnetic field is controllable according to parameters chosen for a type of spin.

In FIG. 5b, each of the two induction coils (B1, B2) is placed centrally on each "U" shaped half-yoke (C1, C2). In FIG. 5c, each of two induction coils (B1, B2) is placed in the vicinity of one of the magnetic pole ends (N, S) on each U-shaped half-yoke (C1, C2). , each end facing each other on both sides of the band. In FIG. 5d, each of four induction coils (B1, B2, B3, B4) is disposed at one of the four ends of the two half-yokes according to the model of FIG. 5b.

The poles of each electromagnetic element (B1, B2) being the closest together are of opposite magnetic polarity (N, S). Thus, it is possible to configure the field lines between these poles through a strip, (Fig. 5a - 5d with "adequate polarity")

It would also be possible to provide that the poles of each electromagnetic member (B1, B2) being the closest to the band are of identical magnetic polarity. However, it is more difficult in this configuration to minimize the extent of the intersection between the field lines and the band. However, such a configuration makes it possible to it is easier to control the position of the strip between the poles by acting on the direct current of supply of at least one of the two electromagnetic components. Thus, it may be advantageous to have successively in the running direction each of these two configurations (opposite and identical magnetic polarities) for spinning and band stabilizing purposes. Spinning will be possible, but less effective than in the configuration with opposite magnetic polarities as above.

FIG. 6 shows the principle of dewatering a magnetic liquid coating metal film according to the first embodiment of the invention (FIG. 4b). The band

(1) is covered on both sides with the liquid film (not shown) and is driven by a vertical movement of speed

(V) longitudinal scrolling. Two magnetic members (Al,

A2) and their yokes (C1, C2), the shape of which is purely indicative, are each arranged on one side of the strip in the direction of its width and at a distance (e) thereof. They are arranged so that the North Pole

(N) of one of the magnetic members (A1, A2) is located opposite the south pole (S) of the other magnetic member so that the magnetic field (B) is looped in both organs through twice the band (1). The movement of the strip in this static magnetic field (B) induces an electromotor field (E) between the poles with opposite polarity and therefore a current in the strip and the liquid film where a magnetic braking force (F) develops. opposed to scrolling the tape.

Figure 7 shows a principle of spinning by magnetic brake with distance stabilization control (or centering band) according to a second embodiment of the invention (Figure 5b).

At least one of the magnetic members here comprises at least one electromagnetic element (B1, B2) (coil electromagnet of induction) whose magnetic capacitance is adjustable by a control module (MC) via a control signal (Cc) which ideally controls at least one induction coil (B2) encapsulating here the electromagnetic field-guiding element (C2) ), to :

to induce at least one electro-motor field (E) sufficient to generate a counter-interaction during the forced displacement of the strip in the static magnetic field (B), a braking of a wiper character adapted to the metallic coating layers initially deposited. on the band,

advantageously regulating an equidistance between each magnetic member and the band.

The control module (MC) is governed by a processing unit adapted to receive at least one of the following two signals in order to regulate a current setpoint in the induction coil:

a distance measuring signal (Si) originating from a non-contact measurement system (ME) of the distance (e) between the band and one of the electromagnetic elements (B1, B2),

- A magnetic field measurement signal from a field measuring member (MB) to at least one pole of electromagnetic organs, the said field measurement signal being correlated with distance values (e). According to this correlation, a control unit generates a current setpoint in the induction coil of at least one of the electromagnetic members so as to keep the steel strip in a position defined between the poles, capable of providing the better distribution of the coating on both sides of the belt.

Besides the fact that the use of electromagnets makes it possible to ensure magnetic fields that are more intense than permanent magnets, it also makes it possible to ensure precise control. In particular, it makes it possible to maintain Namely the band in a determined position between the two electromagnetic organs.

All the devices proposed in FIGS. 4, 5, 6 and 7 are therefore able to implement the spinning method according to the invention, namely a spinning method of coating liquid metal at the outlet of a coating tank. metal dipping on both sides of a strip of steel (1) in continuous longitudinal movement, for which during the course of travel at the outlet of the tank, the covered band of the liquid metal coating passes from a region not subject to a field magnetic field to another region subjected to a static magnetic field (B) created between poles (N, S) of magnetic members (A1, A2, B1, B2) placed opposite each side of the strip and whose field lines have an intersection over at least a minimum longitudinal extent with said band, so that the liquid coating metal correlatively undergoes a magnetic field variation generating on said liquid metal a force opposing its movement with the ba ndia. The interaction of the static magnetic field and the moving strip generates eddy currents in the strip and the liquid coating film, the circulation of which in the static magnetic field generates Loenterz forces that oppose the scrolling movement. said liquid metal with respect to the strip, hence the magnetic brake effect with respect to the strip (forced).

This magnetic brake effect generates few eddy currents in the strip and the continuous character of the magnetic field, due to the absence of a skin effect, limits the dissipated power to achieve an effective wiping effect of the liquid film and thus the heating of the band is very advantageously negligible.

As previously described, the method ideally provides that the poles arranged in the nearest other of the band are ideally chosen of opposite polarity. This aspect favors the minimization of the extent of intersection between the field lines and the band and therefore advantageously makes it possible to avoid magnetic band saturation effects and high spin efficiency due to the large magnetic field variations in the passage under the poles. A configuration having close poles with identical polarities is also possible, but less effective for a spin of the desired type, however has the advantage of allowing better control of position of the strip between the poles by action on the DC power supply. induction coils.

An intensity of the magnetic field (B) associated with a desired spinning effect is simply controlled by varying a distance (e) between the poles and the strip, the poles being ideally those of permanent magnets in the context of simple autonomous magnetic organs. The method may also advantageously provide that: in at least one point included in the field lines, a distance (e) is evaluated, ideally by direct measurement without contact, between the moving strip and at least one of the two electromagnetic members ( B1, B2) (eg electromagnets) provided with induction coils as magnetically controllable magnetic members, - a direct supply current of at least one of the induction coils is controlled to maintain the centered band between the two electromagnetic organs. A total magnetic flux passing through the strip (see the examples according to FIGS. 4 to 7) can thus be kept static and finely adjusted around its static value.

The DC supply current of at least one of the induction coils (B1, B2) is controlled in order to adapt the intensity of the magnetic field (B) associated with a desired spinning effect. This is appreciable for adapting the method to various types of tape and / or coating and also allows to enslave the spin system to the thickness measurement of the coating by a measuring member such as an X-ray thickness gauge.

The method also provides that:

A) at least at a point included in the field lines, a distance (e) is evaluated between the moving strip and at least one of the two electromagnetic members (B1, B2) by measuring magnetic field variations due to a variation initiated by an air gap effect existing between the band and at least one of the two electromagnetic members. A direct measurement of the distance (e) is also possible, alternatively or complementary to the previous indirect method of magnetic field measurement.

B)

at least two sets of magnetic members are distributed transversely over a width of at least one side of the strip,

and in the case where the magnetic members are electromagnetic members provided with an induction coil, each supply current of the induction coils is controlled separately. The tape position control between the magnetic members is thus efficiently facilitated.

VS)

at least two sets of magnetic members are distributed one above the other in the direction of travel of the strip and on each side thereof,

and in the case where the magnetic members are electromagnetic members provided with an induction coil, each supply current of induction coils is controlled separately. This succession of sets of magnetic or electromagnetic members makes it possible to effectively distribute the effects of spin and tape position control.

The spinning method according to the invention may, if necessary, also be implemented and controlled in combination with a complementary spinning method, such as by gas jets on the strip faces. Likewise, it can be implemented and controlled in association with a complementary band scroll stabilization method.

Claims

claims

1. Method of wringing liquid metal coating at the outlet of a metal coating tank by dipping the two sides of a steel strip (1) in continuous longitudinal scrolling characterized in that during scrolling at the outlet of the tray, the covered strip of the liquid coating metal passes from a region not subject to a magnetic field to another region subjected to a static magnetic field (B) created between poles (N, S) of magnetic members (A1, A2, B1, B2) placed opposite each side of the strip and having field lines intersecting at least a minimum longitudinal extent with said strip, so that the coating liquid metal undergoes correlatively a magnetic field variation generating on said liquid metal a force opposing its movement with the band.

2. Method according to claim 1, wherein the poles arranged most closely on either side of the band are ideally chosen polarity opposite.

3. Method according to claim 1, wherein the poles arranged most closely on either side of the band are ideally chosen of identical polarity.

4. Method according to one of claims 1 to 3, wherein an intensity of the magnetic field (B) associated with a desired spin effect is controlled by varying a distance (e) between the poles and the strip, the poles being ideal - those of permanent magnets.

5. Method according to one of claims 1 to 3, for which:

in at least one point included in the field lines, a distance (e) is evaluated, ideally by direct measurement without contact, between the moving strip and at least one of the two electromagnetic members (B1, B2) provided with induction coils as magnetic members,

- A DC supply of at least one of the induction coils is controlled to control the position of the strip between the two electromagnetic bodies.

6. Method according to claim 5, wherein the direct current supply of at least one of the induction coils (B1, B2) is controlled in order to adapt the intensity of the magnetic field (B) associated with a desired spinning effect.

7. Method according to claim 5 or 6, for which at least one point included in the field lines, a distance

(e) is evaluated between the moving web and at least one of the two electromagnetic members (B1, B2) by measuring magnetic field variations due to variation initiated by an air gap effect existing between the web and at least one of two electromagnetic organs.

8. Method according to one of the preceding claims, for which:

at least two sets of magnetic members are distributed transversely over a width of at least one side of the strip, and in the case where the magnetic members are electromagnetic members provided with an induction coil, each supply current Induction coils are controlled separately.

9. Method according to one of the preceding claims, for which:

at least two sets of magnetic members are distributed one above the other in the running direction of the strip and on each side thereof, and in the case where the magnetic members are members electromagnetic with induction coil, each induction coil supply current is controlled separately.

10. Method according to one of the preceding claims, which being implemented and controlled in combination with a complementary spinning method, such as by throwing gas on the strip faces.

11. Method according to one of the preceding claims, which being implemented and controlled in combination with a complementary band scroll stabilization method.

12. Spinning device of liquid metal at the outlet of a metal coating tank by dipping both sides of a strip of steel (1) in continuous longitudinal movement, characterized in that at the outlet of the tank: - at least one first magnetic member (A1) is disposed transversely to a first of the two faces of the strip at a given distance (e) of the strip, and a second magnetic member (A2) is disposed transversely to a second of the two faces of the strip; strip, substantially at the same distance from said strip, - poles (N, S) of said magnetic members (A1, A2) are distributed vis-à-vis each side of the strip so as to generate between said poles of the static magnetic field lines (B) included in a main envelope intersecting at least a minimum longitudinal extent with the band.

13. Device according to claim 12, wherein the poles of each magnetic member (Al, A2) being the closest together are of opposite magnetic polarity (N, S).

14. Device according to claim 13, wherein the poles of each magnetic member (Al, A2) being the closest to the band are of the same magnetic polarity.

15. Device according to claim 13 or 14, wherein the poles of each magnetic member (Al, A2) being furthest from the strip are connected by an external magnetic field guide (C), such as a ferromagnetic bolt frame forming a magnetic guide loop around a band section.

16. Apparatus according to claim 13 or 14, wherein each magnetic member (A1, A2, B1, B2) comprises two distinct poles successively arranged in the direction of travel of the strip and connected to at least one magnet by a guide. magnetic field (C1, C2) such that at least one ferromagnetic yoke portion forming a half loop of magnetic guide so that, between each of the two poles at the ends of the two half-loops are arranged vis-à-vis -vis on both sides of the band.

17. Device according to claim 13 and 16, for which at the ends of the half-loops, the poles have opposite magnetic polarities so that the two half-loops induce a closed-loop magnetic guidance of the magnetic field (B) through the band. .

18. Apparatus according to claim 14 and 16, wherein at the ends of the half-loops, the poles have identical grating polarities so that the two half-loops induce a semi-closed loop magnetic transverse guidance of the magnetic field (B). transversely to the band.

19. Device according to one of the preceding claims 12-18, wherein each magnetic member is linearly extended in one or more blocks over a length at least equal to a bandwidth.

20. Device according to one of the preceding claims 12-

19, for which a plurality of magnetically extending members linearly over a length at least equal to one bandwidth are distributed one above the other in the running direction of the strip and on each side thereof.

21. Device according to one of the preceding claims 12-

20, for which the magnetic member is associated with a complementary device such as a gas jet dewatering device.

22. Device according to one of the preceding claims 12-21, for which the magnetic member is associated with a complementary device for stabilizing the band.

23. Device according to one of the preceding claims 12-

22, for which each magnetic member comprises at least one bipolar permanent magnet element (A1, A2) whose magnetic capacitance is fixed in order to:

to induce at least one electro-motor field (E) sufficient to generate a counter-interaction during the forced displacement of the strip in the static magnetic field (B), a braking of a wiper character adapted to the metallic coating layers initially deposited. on the tape.

24. Device according to one of the preceding claims 12-

23, for which at least one of the magnetic members comprises at least one electromagnetic element (B1, B2) whose magnetic capacitance is adjustable by a control module (MC) ideally controlling an induction coil encapsulating the electromagnetic element, to :

to induce at least one electro-motor field (E) sufficient to generate a counter-interaction during the forced movement of the band in the static magnetic field (B); wiper character adapted to the metal coating layers initially deposited on the strip,

to regulate an equidistance between each magnetic member and the band.

25. Device according to claim 24, wherein the control module (MC) is governed by a processing unit adapted to receive at least one of the following two signals to regulate a current setpoint in the induction coil: a signal measuring distance (Si) from a non-contact measuring system (ME) of the distance (e) between the band and one of the electromagnetic elements (B1, B2), - a measurement signal of the magnetic field coming from a field measuring member (MB) with at least one pole of electromagnetic members, said field measuring signal being correlable with measured values of distance (e).