FR2473025A1 - METHOD AND APPARATUS FOR PREVENTING THE OSCILLATION OF A TAPE DURING TRIPPING - Google Patents

Abstract

IN A CONTINUOUS GALVANIZATION LINE, THE OSCILLATION OF A STEEL STRIP 10 REMOVED FROM A MOLTEN ZINC BATH 12 IS PREVENTED BY ANTI-VIBRATION MAGNETS 34, 36, 38, 40, AVAILABLE IN THE VICINITY OF THE SIDE EDGES OF THE STRIP . THE MAGNETS INDUCE IN THE WIDTH OF THE BAND A CERTAIN TENSION AND THE AMPLITUDE OF THE OSCILLATIONS OF THE BAND PERPENDICULARLY ON ITS SURFACE IS REDUCED. IN ADDITION, BY THE MAGNETIC FORCE OF THE MAGNET, THE DEFLECTION OF THE STRIP IS CORRECTED AND A UNIFORM COATING IS OBTAINED. THE PROVISION BETWEEN THE MAGNET AND THE EDGE OF THE STRIP IS AUTOMATICALLY ADJUSTED BY MEANS THAT CONTINUOUSLY DETECT THIS GAP.

Description

The present invention relates to a method and apparatus for

  to prevent the oscillation of a strip of magnetic material treated continuously while the strip passes in various treatment lines such as continuous galvanizing lines, annealing lines, lines of

  stripping and verification lines.

  In all of these lines, numerous treatments and verifications

  The strip should usually be made when the strip is running at high speed. For example, the thickness of the material to be coated is controlled on a strip, in a continuous galvanizing line, when the strip is running at a speed of 200m / 49 or more * Likewise,

  the detection of the flow rate or the thickness of the material of the ban-

  of must be performed when the latter scrolls.

  Usually these bands are supported at a certain

  short distance by two rollers or drive cylinders with

  tension exerted on the strip in the direction of

  the latter, but many inter-

  come in the strip between the adjacent rollers, namely

  an oscillation in the direction of thickness and width

  tape gor, and also a convex or concave deformation of the surfaces of this tape. These problems become important when the speed of the tape increases and cause deterioration in the quality of this tape due to a lack of precision in the processing. , leading to detection errors in the

  verifications of the flow or in the thickness of the strip.

  The object of the present invention is therefore to propose a method and an apparatus making it possible to prevent the oscillations or the deformations of a strip which occur when the latter

parade.

  According to the invention, the oscillation or the

  deformation of a moving strip by applying a magnetic field

  tick across the width of the strip. The magnetic field acts by attracting the side edge of the strip in the direction of the magnetic field and causes tension in this region, in the sen's of its width, so as to reduce the amplitude of the band oscillations and also correct the deflection of

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  the strip, across its width.

  The tension of a strip across the width of the strip is

  non uniform and weak even if a voltage is applied in the direction

  longitudinal configuration, in particular when the configuration of the strip in the portions of its lateral edges has undulations, which results in an oscillation of the strip.

  strip acts advantageously on these portions of lateral edges and prevents

  che oscillation and deformations.

  As a means of producing a magnetic field, it is possible to apply, for example, a permanent magnet, a linear motor or a solenoid.

  same way, any type of strip or strip made of a material

  magnetic wire can be applied to the present invention.

  According to one of the characteristics of the invention, the means of production

  tion of a magnetic field are placed on the passage of a moving strip, in the vicinity of its lateral edge and without contact with the strip, so as to attract the lateral edge of the strip in the direction of the magnetic field and give this strip a tension in the width direction. The location of said magnetic device is preferably adjusted so as to maintain a given spacing between the device

  magnetic and the lateral edge of the strip.

  According to another characteristic of the invention, the magnetizing device

  that is suitable for preventing band oscillations in a device

  continuous coating of metal, so as to obtain advantageously-

  a uniform thickness of metal coating due to the suppression of the band's oscillations. Similarly, by using such a magnetic device, the bending of the band is eliminated, which makes it possible to improve the coating surfaces of the latter.

  magnetic device can also be applied to prevent oscillations

  tions or deflections of a tape, other than in a

  continuous metal coating, for example in test lines

tion of the tape continuously.

  The other characteristics and advantages of this

  invention will be more evident on reading the following description,

  with reference to the accompanying drawings which represent, as

  Illustrative, several embodiments of the invention.

  Figure 1 is a perspective view of a galvanizing apparatus

  continuous having the magnetic device according to the present invention.

  Figure 2 is an assembly diagram according to a first embodiment of the invention, Figure 3 is an enlarged cross-sectional view of the magnetic device of Figure 1, Figure 4 is a cross-sectional view taken along

line IV-IV of figure 3.

  FIG. 5 is a graph showing an experimental result of the amplitudes of oscillation of the strip with and without the magnetic device of the invention, FIGS. 6 (a) and 6 (b) are schematic graphs

  respectively showing the experimental results of amplitu-

  of oscillation without and with the magnetic device of the invention, FIG. 7 is a graph showing the relationships between the magnetic force and a spacing between strip and magnetic device, FIG. 8 is a schematic side view of a second mode of embodiment of the invention, and Figure 9 is a schematic sectional view of a third embodiment of a magnetic device according to the present invention. Figure 1 shows an embodiment of the invention in

  which the magnetic device, hereinafter called "anti-magnet

  vibration ", is suitable for a continuous galvanizing device with wiping nozzles. The galvanizing device includes a roller

  lower 14, two idler rollers 16 and 18, one upper roller

  laughing 32 which continuously pass a steel strip 10 in a bath of molten zinc 12, two wiping nozzles 20 and 22 disposed above the surface of the bath of molten zinc 12 and adapted to carry out wiping by the coated steel strip gas 10. In this galvanizing apparatus, the thickness of the coating on the surface of the steel strip is controlled by spraying gas from the wiping nozzles 20 and 22 placed above the surface of the bath 12 on both sides of the

  strip when this is removed from the molten zinc bath 12. The thick-

  seur is usually adjusted by varying the distance between the front nozzle 20 and the rear nozzle 22, the jet pressure

  gas and the tape unwinding speed.

  The wiping nozzles 20 and 22 are supported in a sliding manner.

  health by a support 28. The distance between the strip 10 and the

4 2473025.

  wiping nozzles 20 and 22 is regulated by a control motor 30.

  By operating this control motor 30, the wiping nozzles and 22 can move parallel away from or towards the front and rear surfaces of the strip 10. The wiping gas is introduced into the nozzles 20 and 22, respectively,

by pipes 24 and 26.

  The steel strip, after removal of the zinc bath 12, cannot be supported in any direct way until the coating metal is cooled and solidified, so that the position of the upper roller 32 must be sufficient, taking into account the tape unwinding speed. In practice, a range

  free height of 40 m is necessary when the speed of unwinding-

  ment is 20it / [min. The increase in the length of this free span and the increase in the speed of unwinding of the strip act so as to favor the oscillation and the deformation of the strip 10, so that the distance between the wiping nozzles 20 and 22 and the surfaces of the strip must be continuously controlled or kept larger. For example, the strip 10 is the seat of a lateral oscillation of 3 to 10 mm of amplitude at a frequency of 1 to 7 Hz. The dynamic pressure of the gas jet from the nozzles 20 and 22 varies depending on the lateral oscillation of the belt. The thickness of the coating metal on the strip 10 decreases as the distance decreases, and increases as the distance increases, causing

  non-uniformity of the thickness of the coating layers.

  For the reasons stated above, there is an increasing demand for a galvanizing apparatus capable of

  produce a uniform coating layer at high speed.

  Although it has been proposed to reduce the thickness of the coating layer by increasing the pressure of the wiping gas, this pressure can only be brought to about 0.6 kg / cm 2, because the noise level increases due to gas pressure. The present embodiment of the invention provides four magnetic anti-vibration units 34, 36, 38 and 40 in the immediate vicinity of the lateral edges of the strip. Thanks to the magnetic force of the magnet, the lateral edges of the oscillating band are attracted towards a region where the intensity of the magnetic flux is more

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  large, which prevents any oscillation of this band. The magnetic units 38 and 40 are fixed to a side plate 42 and the units 34 and 36 to another side plate, both placed at

  near the corresponding lateral edge of the strip.

  In addition, to maintain the steel strip in a region in which it is held stably, it is necessary to keep a small constant gap between the magnetic units and the side edges of the strip. In practice, warping of the strip or variations in the width of the strip is inevitable. For the reason mentioned above, the side plates 42 are slidably supported by a column 50 by means of a threaded rod

  44 coupled to a control motor 48 via a run-

  line 46. The side plate 42 can move parallel far or near the lateral edge of the strip under the action of the control motor

  48, so as to give a desired spacing between the magnetic units

  ticks 38, 40 and the corresponding lateral edge of the leaf. The units

  magnetic 34 and 36 can also move in the direction of the lar-

  tape feeder so as to keep a given interval between them

  and the corresponding side edge of the strip.

  In the present embodiment of the invention, four units

  magnetic 34, 36, 38 and 40 are used to prevent oscillations

  of the strip, but this number of magnets is not limiting. We can

  use, for example, only the two higher magnetic units

  res 34 and 38. If the case allows, it is also possible to use only one magnetic unit, for example unit 34. In addition, the location of the

  magnetic units is not limited to this embodiment.

  In the case of a ga-wiping type galvanizing apparatus, preventing the strip from oscillating between the wiping nozzles 20 and 22 is most effective in obtaining a uniform thickness of the coating metal. This is why it is preferable to locate the magnetic unit near the lateral edge of the strip, between the two wiping nozzles 20 and 22 o the magnetic force of

the magnet is the largest.

  In the present invention, the idler rollers 16 and 18 are used to ensure stable galvanization, but these rollers can produce oscillations in the strip due to adaptation errors in the support parts or the eccentricity of said rollers. thermal deformation. l1-is therefore desirable to omit these rollers from

  - 5 return to ensure the effect of the magnetic unit.

  Referring now to Figure 2, o the magnetic units 34 and 38 are placed in the vicinity of the respective lateral edges of the strip 10. These magnetic units 34 and 38 are respectively provided with detectors 68 and 66 which detect

  the spacing between the lateral edge of the strip 10 and the uni-

  magnetic detectors. As detectors, we can apply a magnetic

  photoelectric detector or another type of position detector

  The signals from detectors 66 and 68 are applied to comparators 62 and 64 where a pre-established signal produced in a preset circuit 60 is introduced. Comparators 62 and 64 produce signals corresponding to the actual signals detected and the signal The output signals of the comparators 62 and 64 are respectively transmitted by amplifiers and 72 to the control motors 48 and 49.The threaded rods 44 and 45 connected to the magnetic units 38 and 34 are associated with the output shafts of the control motors 48 and 49 and the magnetic units can therefore be moved when the rods

are powered by motors.

  According to this arrangement, if the actual spacing between the magnetic unit

  tick and the lateral edge of the strip is not equal to the pre-determined desired value, the control motor is actuated according to the sign representative of the deviation, so that the magnetic unit is placed at the desired predetermined location In this way, the distance between the magnetic unit and the side edge of the strip is adjusted so that the magnetic force applied

  at this lateral edge is kept practically constant.

  Referring to Figures 3 and 4, we will now explain the details of the magnetic units. In the case of the galvanizing device, it is preferable to place the magnetic unit near the wiping nozzle for the reasons stated above. above, but this magnetic unit must be placed under strong thermal radiation coming from the metal of fusion and gas

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  hot wiping. The permanent magnet is particularly <thermolabile and its magnetic force tends to decrease under the action of heat. To solve this problem, the magnetic unit 34 consists of a hermetic cylindrical container 112 enclosing a plurality of permanent magnets 102, 104, 106

  and 108 through which a coolant flows.

  The permanent magnets 102, 104, 106 and 108 are fixed to a T-shaped partition wall 110 which delimits a passage for

  the coolant in the airtight container 112.

  The magnets are fixed in notches formed on the surface

  from wall 110 and directed towards an interior wall of the recess

  pient 112. At the upper end of the container, tight plugs 114 and 116 are fixed which include an inlet pipe 52

  and an outlet pipe 54 for the coolant.

  This sealed container 112 is placed near the lateral edge of the strip 10 so that the magnets 102, 104, 106 and 108 are located opposite this lateral edge. To improve the efficiency of the magnetic unit 34, it is preferable to use, for the container 112, nonmagnetic materials such as stainless steel. Likewise, it is preferable to use a thin material for this container 112. According to the present embodiment, the reduction of the magnetic force caused by heat can be eliminated. You can also prevent molten metal splashes from sticking

  to magnets or airtight container 112.

  In the present embodiment, it is preferable to place the magnets 102, 104, 106 and 108 on the partition wall so that the direction of the magnetic field of the respective magnets is, in order, SNS or NSN so to get the

  most effective magnetic field. It is better, too, to use

  be a non-magnetic material to improve the performance of.

anti-vibration magnets.

  FIG. 5 is a graph showing the effect, obtained by the anti-vibration magnet, of preventing the band from oscillating, according to which the magnet is distant from the lateral edge of the

  strip so as not to exert a magnetic force thereon.

  between instants 2 and 6 s. As can be seen in this figure, if

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  the magnetic force is applied to the strip, the amplitude of the oscillations of this strip is kept at most between 2 and 3mm, while the amplitude is approximately 10mm if the magnet is

  away from the side edge of the strip. The oscillation prevention effect

  tions will appear better from experiments where continuous galvanizing is carried out by the apparatus of FIG. 1 with a steel strip 1.20 min thick, 1000 mm wide, a running speed of 123 mm / mn and a zinc content of 300 g / m 2. Figures 6 (a) and 6 (b) show the results of experiments, respectively without and with anti-vibration magnets. The results show that, if the magnet is not used, the maximum amplitude of the oscillations of the strip of 7 mm appears at the lateral edge of the strip and the minimum amplitude of 4 mm appears in the middle of the width of the strip. bandaged. In the same way, the strip deforms or folds back and its section

  transverse becomes concave or convex if the magnet is not used.

  The value of this deflection or deformation, usually called "canoeing", is about 8 min. On the other hand, if the anti-vibration magnet is placed near the lateral edges of the strip, as shown in Figure 6 (hJ not only the amplitude of oscillation at the edge becomes

  smaller (2.5mm) but also this "canoeing" disappears!

  The effect of the anti-vibration magnet will be more apparent on reading Table 1 below on which the thicknesses of the coating metal on the surface of the resulting strips are measured according to the present invention with the anti-vibration magnet and according to the classic method of galvanizing without this magnet. The measuring tape is manufactured by the gas wiping method in such a way that a steel strip 1.20 mm thick and 1000 mm wide is coated, at a running speed of 123 m / min. , with a zinc layer of 300 g / m The measurement is carried out by the so-called 3-point method according to the standard

  Japanese industrialist (H0401) "Test method for galvanized tape".

úI-took ten test pieces from resulting strips taken at equal distance from the direction of the tape feeder and the weight of zinc coating of the test pieces was measured by the

process called "antimony chloride".

  As can be seen in Table 1, the thickness of the

  coating is not uniform by the conventional method.

  in particular, due to the deformation or deflection of the strip ("canoeing"), the thickness of the covering is less on the lateral part and more important on the central part

  front of the strip and reverse on the other side.

On the other hand, according to the present invention with the anti-vibration magnet, the thickness of the coating is uniform everywhere

  on both sides of the strip, which proves that the anti-magnet

  vibration is effective to prevent not only lateral oscillation but also deformation or deflection such as

band "canoeing".

Table 1

Weight of zinc (a / m)

  Figure 7 shows the relationships of the applied magnetic force

qué a strip of steel and the spacing between the lateral edge of the strip and the surface of the magnet. The magnet used in this test is formed of several rectangular magnetized parts

  cobalt stacked on top of each other to form the magnetic unit

The tick shown in figure 3 has a useful length of the magnetic unit, located opposite the side edge of the strip, of around 500mm. As shown in figure 7, the

magnetic force decreases if the strip is thinner.

derives the reliability of the mechanism controlling the spacing, it is

Side Test points in the direction of the Mo-

  of the width of the strip _yenne strip 1 2 3 4 5 6 7 8 9 10 Present Before 15 152 151 150 146 14 B 150 154 150 14 1 495 invention Rear 150 154 152 156 155 152 154 i18 151 152 152.4 (with magnet) Total 300 306 303 306 301 300 304 302 301 300 302.3 Method Front 142 147 150 157 163 153 150 158 140 145 15095 classic Rear 154 152 150 143 145 143 150 150 155 152 149s4 (without T magnet) Total 296 299 300 300 308 296 300 308 295 297 299.4

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  better to maintain a spacing of 4 to 6mm approximately for

obtain a magnetic force of 5 to 25 kg.

FIG. 8 shows another embodiment of the invention, according to which the anti-vibration magnet is applied to a continuous strip verification line. One strip 120 passes over two

  rollers 122 and 124.tn detector 126 which detects ---------

the thickness of the strip 120 by laser beam or X-ray is placed on the passage of the strip between the rollers 122 and 124 and anti-vibration magnets 128 are placed in the vicinity of the respective lateral edges of the strip 120 below the detector 126 Thanks to this mounting of the magnets 124, it is possible to prevent detection errors due to oscillation, deformation or deflection of the strip because this oscillation or deformation of the strip is

  effectively removed by the magnet.

  It is efficient and desirable to narrow the two ends 132 and 134 of the magnet as shown in FIG. 9, because this increases the density of the magnetic flux acting on the edge.

lateral of the strip 130.

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Claims (20)

1. Method for preventing the oscillation of a strip made of magnetic material which moves continuously over a predetermined path, characterized in that it comprises a phase of application of a magnetic field to the strip (10) in the width direction so as to give it tension in the   widthwise without contact with the strip.   2. Method for preventing the oscillation of a strip according to claim 1, characterized in that the magnetic field   tick is applied to the strip (10) from the two side edges. 3. Method for preventing the oscillation of a strip   according to claim 1 or 2, characterized in that it comprises takes, moreover, a phase of detection of the position of the edge   lateral of the strip and a phase of regulation of the magnetic force   tick generated by the magnetic field applied to the strip in function of the detection result.   4. Method for preventing the oscillation of a strip according to claim 3, characterized in that the value of the   magnetic force applied to the tape is regulated - essentially evenly constant on the two lateral edges of the strip.   5. Method for preventing the oscillation of a strip according to claim 4, characterized in that the value of the magnetic force applied to the strip is kept identical on both sides of the strip. 6. Apparatus for preventing the oscillation of a strip made of a magnetic material which runs continuously on a predetermined path, characterized in that it comprises: A magnetic device (34, 36, 38, 40) aiming preventing oscillation of the strip, arranged in the vicinity of at least one lateral edge of the strip, and without contact with the strip, said magnetic device being adapted to impart a certain tension to the strip in the width direction by applying a magnetic field at the tape.   7. Apparatus for preventing the oscillation of a strip according to claim 6, characterized in that said magnetic device (34, 36, 38, 40) is arranged in the vicinity of the edges -12   corresponding side of the band. 8. Apparatus for preventing the oscillation of a strip   according to claim 6 or 7, characterized in that the device magnetic tape is arranged along the lateral edge of the strip. 9. Apparatus for preventing the oscillation of a strip according to claim 6 or 7, characterized in that the device   magnetic consists of a permanent like. 10. Apparatus for preventing the oscillation of a strip according to claim 9, characterized in that the magnetic device consists of a plurality of permanent magnets arranged along the edge of the strip.   11. Apparatus for preventing the oscillation of a strip according to claim 8, characterized in that the device ma-   magnetic has magnetic poles arranged along the edge   tape in S and N order alternately. 12. Apparatus for preventing the oscillation of a strip according to claim 8, characterized in that it further comprises a device for detecting the position of the edge side of the strip and a device for controlling the spreading tement between said magnetic device and the corresponding lateral edge of the strip, by shifting the magnetic device:   in response to the detected value so as to maintain a spread   practically constant between the two.   13. Apparatus for preventing the oscillation of a strip according to claim 6 or 7, characterized in that it further comprises a device (112) for cooling the magnetic device. 14. Apparatus for preventing the oscillation of a strip according to claim 13, characterized in that the cooling device (112) comprises a non-magnetic envelope around the magnetic device and comprises an inlet (52) and an outlet ( 54) allowing the passage of the coolant through the envelope.   15. Apparatus for continuously applying a coating   ment of molten metal on the surface of a magnetic strip characterized in that it comprises a bath (12) for storing the molten metal, a device (14, 16, 18, 32) for guiding the strip in immersion in the bath, a device for removing the strip from the bath, a device for regulating the thickness of the coating of molten metal on the surfaces of a strip removed from the bath and a magnetic device preventing oscillation of the strip, arranged at the in the vicinity of the edges of the strip, without making contact with the strip, and making it possible to apply a magnetic field across the width of the strip.   16. Apparatus for continuously applying a coating of molten metal according to claim 15, characterized in that the magnetic device is placed in the vicinity of the device thickness control.   17. Apparatus for continuously applying a coating of molten metal according to claim 15 or 16, characterized in   that the magnetic device consists of a permanent magnet nent.   18. Apparel] for continuously applying a coating of molten metal according to claim 17, characterized in that the device is a continuous galvanizing device. 19. Apparatus for continuously applying a coating of molten metal according to claim 18, characterized in that the thickness control device consists of a pair of wiping nozzles (20, 22) which send a gas on the corresponding surfaces of the strip in order to remove excess coating metal.   20. Apparatus for continuously applying a coating of molten metal according to claim 16, characterized in that it further comprises a device for detecting the position of the lateral edge of the strip and a device for regulating the distance between the magnetic device and the corresponding edge edge of the tape, shifting the magnetic device in response at the value detected in order to maintain an essential distance constant between the two.