WO2009024683A2

WO2009024683A2 - Cooling device for use following the galvanisation of a strip material

Info

Publication number: WO2009024683A2
Application number: PCT/FR2008/000969
Authority: WO
Inventors: Pierre-Jérôme BORREL
Original assignee: Siemens Vai Metals Technologies Sas
Priority date: 2007-08-10
Filing date: 2008-07-03
Publication date: 2009-02-26
Also published as: ATE495276T1; WO2009024683A3; EP2176437A2; FR2919877B1; EP2176437B1; DE602008004543D1; FR2919877A1

Abstract

The invention relates to a cooling device for use following the galvanisation of a strip material (M) passing through a metal galvanising bath, the device comprising a cooling cell in the shape of a hollow chamber (5) and two side regions extending between two porous surfaces, on either side of a central region along which the strip passes, a cooling gas being introduced under pressure into the porous surfaces and circulated via said surfaces along both sides of the strip and then discharged via the central region of the cooling cell (5). According to the invention, each cooling cell (5) comprises means (7) for extracting at least most of the discharged gases at the outlet of the central region of the cooling chamber (5), said extraction means being connected to pressurised means (60) in the side regions of the chamber (5) via at least one recirculation system (6), which is provided with a means (8) for cooling the extracted gases before they are introduced under pressure into the side regions of the cooling cell (5).

Description

Cooling device after galvanizing a strip product

The subject of the invention is a cooling device, after galvanizing, of a strip-like product passing through a galvanizing metal bath for the deposition of a coating layer on two opposite faces of the strip. In order to improve the corrosion resistance of the metal sheets used, in particular, in certain applications such as the building, automobile or household appliances, it is common to deposit on the surface of these sheets, a layer of zinc coating or a zinc-based alloy. The sheet being made, normally, by rolling a metal strip, it can be subjected to a galvanizing treatment performed during the running of the strip in a galvanizing line.

By way of example, FIG. 1 schematically shows the usual constitution of a continuous galvanization line comprising successively, in the direction of travel of the strip, that is to say from left to right on FIG. an input section 1 with one or two tape unrollers 10,

10 ', a shear 11, for example a guillotine, a splicing welder 12 for connecting the tail of a first strip from one of the unrollers 10 to the head of the next strip from the other unroller 10', to ensure a continuous operation of the line, and a tape accumulator 13 which allows to reserve a certain length of tape so as to restore it to the line, when the flow is stopped upstream of the accumulator, for make the splice in the welder 12; a section 14 for degreasing the cold-rolled strips or acid pickling of the hot-rolled strips; an annealing furnace 2 comprising a heating section 21, a temperature holding section 22, a cooling section 23 and a section 24 for holding the strip at a controlled temperature before entering the molten zinc bath; a galvanizing section 3 itself, comprising a zinc bath 31 in which is immersed the strip at the outlet of the temperature holding section 24, a device 32 for spinning the liquid zinc to control the thickness of the layer coated on both sides of the strip, optionally an induction furnace 33 whose role will be indicated later, a cooling device 34 and a quenching tank 35 for the final cooling of the strip; an outlet section with, for example, a skin-pass mill 15, a passivation section 16, an outlet accumulator 17, a shear 18 and one or two winders 19.

Such an arrangement is quite conventional but, of course, may be subject to variants, depending on the processing carried out upstream or downstream of the galvanizing section itself.

As schematically shown in FIG. 1, in the galvanizing section 3, the strip M continuously travels between a liquid zinc bath 31 and a final cooling bath 35 along a path defined by a plurality of deflection rollers. and generally comprising a first inlet portion T1 of the strip M in the metal bath 31, in a downward direction, to a first deflector roll immersed in the bath 31, a second outlet portion T2 of the bath 31, in an upward direction, to a pair of baffle rollers 42, 42 'placed at a higher level above the bath 31 and a third portion T3 extending in a downward direction between an upper baffle roll 42 and a lower baffle roll 43 immersed in the final cooling bath 35, the band M then being evacuated, passing over a baffle roll 44, towards the rest of the installation, for example a skin-pass rolling mill 15.

Leaving the bath 31, the strip is covered on both sides with a zinc layer driven upwardly with the strip. The covered strip then passes into a wiper device 32 of known type which makes it possible to control the thicknesses of these two coating layers.

For example, French Patent No. 2,726,288 of the same company discloses such an air knife dewatering device.

In known manner, the installation may comprise, on the upstream part T2 of the path of the strip, at the outlet of the metal bath 31, a heating furnace 33 making it possible to perform a so-called alloy heat treatment which ensures the diffusion of iron from the band, to the zinc coating, to create a real iron / zinc alloy. Such an alliance is interesting, in particular, for the automobile industry because it allows to improve certain surface qualities of the coated sheets such as the adhesion of the paints or the stamping capacity.

The strip must, however, be cooled before plunging into the quenching tank 35. This cooling is usually done by blowing air on both sides of the strip and the installation therefore comprises one or more cooling cells placed. in the path of the strip between the galvanizing tank 31 and the quenching tank 35.

In the case of FIG. 1, where an alloying furnace is placed on the upstream strand T2 of the strip, the installation usually comprises at least one cooling cell 34 placed on the downward path T3, above quenching tank 35 and consisting of a hollow box having two side portions surrounding a central scroll portion of the strip and separated therefrom by a porous wall. A supply duct 36, connected to blowing means (not shown), of the variable speed motor-blower type, makes it possible to introduce pressurized air into the two lateral parts of the box 34 which are separated from the central part. by porous walls 34a, 34b. The air thus introduced into the lateral parts of the box 34 is diffused by the porous walls on both sides of the strip and can be evacuated through the orifices provided at the two ends of the central part of the box, for the passage of the strip M Preferably, the sheath 36 opens at the downstream end of the box 34 in order to provide a circulation of the air blown against the current of the scrolling of the strip.

When no alloying treatment is carried out, the oven 33 can be removed and replaced by a cooling box placed on the upward path T2 of the strip.

In such an installation, the cooling air blown on the strip is ambient air collected outside the building and this air is subject to temperature and humidity variations that may have an influence on the quality of the deposit. . This depends, in fact, cooling conditions, particularly the kinetic energy of the air jet blown on the still liquid zinc and whose effect may vary with the air temperature.

It is therefore necessary, in order to obtain a constant coating quality, to have the possibility of reproducing the cooling parameters such as the flow rate, the hygrometry and the air temperature. blown, which may vary depending on the width and thickness of the product, the outlet temperature of the bath and the chemical composition thereof.

In addition, ambient air that is collected externally to be blown onto the belt may contain dust that can be incorporated into the coating or accumulate in the building.

Similarly, the galvanizing process can generate zinc dust which is then dispersed in the air escaping from the cooling cell through the inlet and outlet ports of the strip at both ends of the cooling box. 34.

Finally, the capture of the outside air, the circulation in ducts and its blowing under pressure by fans determines a significant noise and, consequently, a nuisance for the environment.

The object of the invention is to remedy all of these disadvantages by means of a new arrangement of the cooling means.

This arrangement has, in addition, many advantages for the realization of the galvanizing line, which will be described in detail later. The invention therefore relates, in a general manner, to a cooling device after galvanizing a strip-like product in a galvanizing metal bath for the deposition of a coating layer on two opposite faces of the strip, the device comprising a hollow box-shaped cooling cell having two lateral portions extending on either side of a central strip-running part, between two parallel porous faces, respectively, on both sides of the strip, and pressurized feed means of said side portions in a cooling gas diffused by said porous faces along both sides of the strip and discharged through the central portion of the cooling box.

According to the invention, the device comprises suction means for at least the largest part of the cooling gases discharged at the outlet of the central part of the cooling box, connected to the means for supplying pressure to the lateral parts of the box, by at least one recycling circuit on which is placed a means of 008/000969

cooling of the aspirated gases before their introduction under pressure into the lateral parts of the cooling box.

In a preferred embodiment, the pressurized gas supply means comprise at least one fan having a gas inlet connected to the suction means by the recycling circuit and a pressurized gas outlet connected to the two lateral parts of the cooling box.

Advantageously, the recycling circuit comprises means for filtering the sucked gases placed upstream of the fan, in the direction of circulation of the gases.

Preferably, the recycling circuit comprises a cooling chamber having an inlet connected to the suction means and an outlet connected to the pressurized supply means and in which is placed a heat exchanger for cooling the recycled gases. In a first embodiment of the invention, the two lateral parts of the cooling cell form two elongated hollow box-shaped arms extending respectively along the two sides of the strip, on either side of a central portion extending between two rectangular orifices respectively inlet and outlet of the strip, and the cooling gas suction means comprise at least one hollow box-shaped cell placed at least upstream, in the direction of travel, of the cooling cell and having two arms respectively extending along the two lateral parts of the cooling cell, on either side of a central portion having two rectangular openings for passage of the strip, respectively an inlet and an outlet opening opening near the inlet of the strip in the central portion of the cooling cell for the passage of cooling gases in the suction cell, against the flow of the band. In another embodiment, the cooling cell extends over a certain running length of the strip between an inlet end of the strip at which the central portion of the cell is provided with at least one orifice gas suction connected to the recycling circuit, and an exit end of the strip at which placed at least one pressurized gas supply port of the two side portions of the cooling cell.

Advantageously, the device comprises two gas recirculation circuits arranged on either side of the cooling cell and each comprising a pressurized gas supply means having a gas inlet connected to a suction means placed at a pressure end of the central portion of the cooling cell and a pressurized gas outlet connected to a supply port of the side portions of said cell, and a cooling means of the recycled gas. Particularly advantageously, the cooling cell and the recycling circuit (s) each comprising suction, cooling and pressurized cooling gas supply means form a compact autonomous unit extending over a length limited scrolling band. In particular, the strip moving, at the exit of the galvanizing bath, according to an ascending strand then a downward strand passing over at least one deflector roll, the device comprises at least two compact assemblies placed respectively on the ascending strand and on the strand. downstream and each comprising a cooling cell and at least one recycling circuit with means for suction, cooling and pressurized supply of cooled gas, said assemblies being offset in height so as to be staggered in order to reduce their overall size.

Thanks to these arrangements, the entire installation comprising means for controlling the movement of the strip between a galvanizing bath and a quenching bath and at least one cooling unit comprising a cooling cell and a recycling circuit, is disposed inside a closed building, provided with means for recovering gases and dust and means of sound insulation. The invention is particularly applicable to a galvanic coating installation of a strip product, comprising means for controlling the running of the strip between a liquid metal bath and a quenching bath, along a continuous line. scrolling member defined by a plurality of baffle rollers and having at least one ascending strand output of the metal bath and a descending strand. 69

Thanks to the invention, such an installation can be equipped with several autonomous cooling units, placed respectively on the upstream strand and on the descending strand and each comprising a cooling cell and at least one recycling circuit with suction means. , cooling and pressurized supply of cooled gas.

Advantageously, these self-cooling units with gas recirculation, arranged respectively along a rising strand and a descending strand of the strip, are offset in height relative to each other so as to be placed in position. staggered in order to reduce their overall footprint and the footprint of the installation.

In a preferred embodiment of such an installation, the quenching bath is placed above the metal bath, so that the entire line of travel, between the metal bath and the quench bath, remains in a footprint of the same order as that of the metal bath.

With this arrangement, the strip is supported by a first face on a first baffle roll immersed in the metal bath, coming from a first side thereof and is supported by the same first face on a second baffle roller placed at a higher level, so that the descending part of the strip is placed on the same first side of the metal bath relative to the upward portion of the output of the metal bath.

Thus, the second face of the strip comes into contact with a baffle roller after sufficient cooling and its surface quality is retained.

Moreover, this arrangement makes it possible to place on a second side of the metal bath, opposite to the first input side of the strip, a quality control station of the coating, in front of which passes said second face of the strip, of first in the ascending part of the outlet of the metal bath, then in the last descending part of the output of the installation, after final cooling.

Other features and advantages of the invention will appear in the following description of some particular embodiments, given by way of example and shown in the accompanying drawings. 69

Figure 1 is a general diagram of the assembly of a galvanizing installation of known type.

Figure 2 is an elevational view of a first embodiment of the invention. Figure 3 is a horizontal sectional view along the line I, I of Figure 2.

Figure 4 is a vertical sectional view of a second embodiment of the invention.

Figure 5 shows schematically the adaptation of the invention to a galvanization section of conventional type.

Figure 6 schematically shows a new arrangement of a galvanizing section.

Figure 7 shows a staggered arrangement of the cooling cells. Figure 8 schematically shows another arrangement of a galvanizing installation after annealing.

FIG. 2 diagrammatically shows, in elevation, a cooling device comprising a rectangular section box 5 having, as indicated in FIG. 3, two lateral parts 51, 51 'which extend from both sides another of a central portion 50 having, at its ends, an inlet port 52 and an outlet port 52 'for the passage of the band M which runs inside the box 5 in a substantially vertical scroll plane.

Each lateral portion 51, 51 'is separated from the central portion 50 by a porous face 53, 53' for diffusing, on both sides of the strip M, air introduced under pressure into the box 5 which can therefore be of the same type as the cooling cell 34 described above with reference to FIG.

However, in the case of FIG. 1, the cooling cell 34 is placed on the downstream strand T3 of the strip and the air under pressure is thus introduced through the sheath 36, preferably at its lower part, in order to circulate at against current of the running direction of the band. In the case shown in FIG. 3, the cooling cell 5 is placed on the ascending strand of the band M, the inlet orifice 52 thereof being thus placed at the lower part of the box 5 and the orifice 52 'exit to its part higher. Consequently, the air under pressure is introduced by a sheath 54 opening to the upper part of the box 5, between the two arms 51, 51 'thereof. This air is blown by a variable speed motor-blower unit 60 having an inlet 61 and an outlet 62 on which is connected the sheath 54 for supplying the box 5.

According to an essential characteristic of the invention, whereas, in the usual case, the cooling cell is supplied with ambient air, in the case of the invention, the cooling cell 5 is associated with a recycling circuit 6 for supplying the fan 60 with air sucked at the outlet of the central portion 50 of the box 5.

For this purpose, the cooling cell 5 is associated with a recovery cell 7 in the form of a hollow box, placed upstream of the box 5, in the running direction of the strip, that is to say below the box 5 in the case of Figure 3 where the box is placed on an ascending strand. The recovery cell 7 is therefore also constituted by a hollow box having two rectangular openings for the passage of the strip, respectively a lower inlet orifice 71 and an upper outlet orifice 72 which opens close to the orifice 52. In addition, the recovery box 7 comprises a gas outlet orifice 73 which is connected to the inlet 61 of the fan 60 via a recycling circuit 6 on which is placed a means 8 for cooling the aspirated gases.

In the preferred embodiment shown in Figure 2, the cooling means 8 is a closed chamber comprising a central chamber 81 into which opens a sheath 74 for evacuation of gases, connected to the outlet orifice 73 of the recovery box 7 and an upper portion 82 in the form of converging on which is connected the inlet 61 of the fan 60.

Inside the central chamber 81 is placed a circuit 83 for circulating a coolant for cooling the gases flowing in the chamber 81 and are filtered by a porous wall 84 placed upstream of the convergent 82 to retain the driven dust. At its lower part, the enclosure 8 is closed by a bottom 85 separated from the central chamber 81 by a grid 86, and forming a filtered dust collection pot. FR2008 / 000969

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The inlet 71 of the entrance of the band M in the recovery box 7 has a limited width so as to simply allow the passage of the band without risk of deterioration, taking into account the vibrations thereof. It is the same for the orifice 52 'of exit of the band, formed at the upper end of the cooling box 5.

In contrast, the upper orifice 72 of the box 7 and the lower orifice 52 of the cooling box 5 are a little more open and the two boxes 5 and 7 can, moreover, be connected by a deformable seal. In this way, at least the majority of the gases introduced under pressure by the sheath 54 to the upper part of the cooling box 5 are discharged through the lower orifice 52 and sucked by the recovery box 7 in order to be returned to the inlet 61 of the fan 60 through the recycling circuit 6, after cooling in the chamber 8.

It is thus possible, by adjusting the intensity of cooling by circulation of the heat transfer fluid in the circuit 83, to establish a steady state of the cooling conditions by blowing the air on the band M to ensure a better consistency of the the quality of the deposit. It is thus possible to easily reproduce cooling parameters, in particular the flow rate and the temperature of the supply air, which have been determined in advance according to the product format and the outlet temperature of the metal bath 31 which may vary with the composition. of it. Parameters recognized as correct can thus be directly returned without having to correct them according to the characteristics of the ambient air. It is thus easier to control the so-called "blooming" effect of the zinc deposit which, in conventional installations, results from variations in temperature and hygrometry of the ambient air blown onto the strip.

On the other hand, this circulation in a closed circuit of the cooling air makes it possible to filter it as soon as it leaves the recovery box 7 by eliminating the zinc dust that can be generated by the galvanizing process and which, usually, are dispersed in the ambient air.

Similarly, it is not likely to cause with the cooling air blown on the tape, dust that, in the long run, have accumulated in some parts of buildings. The process according to the invention therefore makes it possible, on the one hand, to improve the quality of the coating and, on the other hand, to protect the environment.

In this respect, in conventional installations, the capture of the outside air by suction ducts promotes the transmission to the outside of the noise of the fans.

Thanks to the invention, on the contrary, the cooling cell 5 forms, with the recovery cell 7 and the fan 60 placed on the recycling circuit 6, a compact assembly which can be more easily isolated to prevent the diffusion of dust and the transmission of noises. FIG. 4 shows, in vertical section, another embodiment of such a compact cooling assembly with gas recirculation.

This cooling device comprises, as in the case of FIGS. 2 and 3, an elongate box 5 having two lateral parts 51, 51 'extending on either side of a central part 50 and separated therefrom. , each by a porous wall 53, 53 'parallel to a vertical plane of travel of the strip which passes through the central portion 50, between a lower inlet orifice 52 and an upper outlet orifice 52'.

In the example shown in FIG. 4, the two lateral parts 51, 51 'are not interconnected and each comprise a gas inlet port 55, 55' connected by a supply duct 54, 54 '. at the outlet 62, 62 'of a variable speed motor-fan unit 60, 60'. These two fans 60, 60 'have a vertical axis and are preferably arranged symmetrically on either side of the vertical plane of travel of the strip M. At the lower part of the box 5, that is to say towards its upstream end in the running direction of the strip, the central portion 50 is provided with two gas suction orifices 73, each connected by a recovery sheath 74, 74 ', to a recycling and cooling circuit 6, 6 '. Each recycling circuit 6, 6 'comprises a cooling chamber 81 connected by a convergent 82 to the inlet 61 of the fan 60. In the cooling chamber 81 passes a circuit 83 for circulating a coolant.

As before, the cooling chamber 81 is separated from the convergent 82 by a filter wall 84 and is extended downwards by a pot 85 for collecting the filtered dusts. The whole of The fan 60 and the cooling chamber 81 thus form a circuit 6 for recycling and cooling the air which is introduced under pressure into the lateral part 51 of the box 5 via the supply orifice 55, which diffuses on the face corresponding M band through the porous wall 53, and is recovered by the suction port 73 and returned to the cooling chamber 81 before returning to the inlet of the fan 60.

The second lateral part 51 'of the box 5 is likewise associated with a recycling and cooling circuit 6' similar to the circuit 6.

As before, the cooling box 5 forms, with the recycling and cooling circuits 6, 6 ', a compact assembly which can be placed in different places in the path of the strip.

Indeed, this compact arrangement makes it possible to distribute a plurality of cooling assemblies with recycling in the path of the strip, between the galvanizing tank 31 and the quenching tank 35. FIG. 5 shows, for example, how several cooling devices according to FIG. The invention can be adapted to a galvanizing section of conventional type, as shown in Figure 1, wherein the strip plunges into the galvanizing tank 31 by passing on a submerged roll 41, spring thereof following a path ascending T2 to upper deflector rollers 42, 42 'and then a downward path T3 to a deflector roll 43 immersed in the quench tank 35.

As indicated above, the galvanizing section may comprise an alloying oven 33 placed at the outlet of the galvanizing tank 31 above the wiper device 32 and extending over a certain length of the upward path T2.

The compact arrangement of the cooling device according to the invention makes it possible to place above the alloying oven 33 a first cooling box 5a associated with one or two recycling circuits with cooling 6a. Similarly, it is possible to place on the downward path T3, one or more cooling boxes 5b, 5c each associated with a recirculation circuit with cooling 6b, 6c. In this case, the arrangement shown in Figure 4 is reversed since, in the path T3, the band flows from top to bottom. FR2008 / 000969

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But the compactness of the cooling device with recycling according to the invention also allows a more advantageous arrangement shown schematically in FIG.

As previously, after being brought to the desired temperature for galvanizing, the strip M plunges into the metal bath 31 along a downward path T1 between the baffle roll 40 of the annealing furnace and the immersed roll 41, and then comes out of the bath 31 along an upward path T2 and then down to the quench bath 35 in a downward path T3. However, instead of being directed outwardly from the upper deflector roll 42, as in the case of Figure 5 which corresponds to the usual arrangement, the band M returns to the side through which it had entered the tray 30 containing the metal bath 31, that is to say to the left side in the figures. The quenching bath 35 is then placed above the galvanizing metal bath 31 and not next to it, towards the exit of the strip.

As a result, the entire galvanizing installation can be arranged in a kind of tower whose footprint does not substantially exceed that of the galvanizing tank 30. This constricted arrangement is facilitated by the fact that, according to the the invention, all the usual sheaths of suction and discharge of the ambient air to the cooling cells are suppressed, each cell forming, with its circuit for recycling and cooling air, a particularly compact autonomous assembly with filtering and cooling of the supply air.

Therefore, such a tower containing the entire galvanizing section can be isolated globally with respect to the environment, both to avoid air pollution by capturing the dust generated by the galvanizing, and to reduce the noises. As before, if it is desired to carry out an alloying treatment, an oven 33 is placed above the wiper device 32 and can be followed by cooling cells 5 placed, not only on the upstream path T2, upstream of the upper roller 42, but also on the downward path T3, above the lower roller 43, each cell 5 8 000969

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being associated with a recycling circuit 6 with cooling of the blown air.

But such a provision has other advantages.

It is known, in fact, that the upper face A of the strip M which bears on the roller 41 immersed in the galvanizing metal bath 31 may be degraded by the defects of this roll. In the conventional arrangement of FIG. 5, in which the quenching bath 35 is placed outwards, next to the galvanizing bath 31, the opposite face A 'of the strip passes over the upper deflector rollers 42, 42' and is Therefore, it is particularly important to be able to place above the alloying oven 33, a cooling device 5a making it possible to ensure sufficient cooling of the metal coating before contact with the roll 42.

However, in the new arrangement of Figure 6, because the band M returns to the left, the side of the inlet in the bath 31, it is the same upper face A which is supported on the upper deflector roller 42 .

In this way, it is only at the lower end of the downward path T3 that the second face A 'of the strip M, turned downwards in the galvanizing bath 31, makes contact with a deflector roll 43. This face A 'can therefore cool successively, along the upward path T2 and, optionally, along the downward path T3, to a temperature enabling it to rest on the lower roller 43 without risk of degradation of the coating.

Thus, it is possible to avoid any alteration of the second face A 'of the band M, turned outwards when passing over the immersed roll 41. This face A' will therefore be reserved for the visible parts of the finished products, for example for a car body and we can tell the user which of the two faces called "exposed face" has the best surface quality. Admittedly, this arrangement requires the construction, above the metal bath 31, of a floor to support the quench tank 35, but this increase in height of the installation does not constitute a real disadvantage, especially for the transformation of an existing installation. On the contrary, the transfer of the quench bath above the metal bath makes it possible to release, next to it, a space which, as will be seen more 8 000969

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far, can be used, for example, to place a station 37 for checking the quality of the tape.

Similarly, the upper roller 42 may be placed at a height sufficient to provide the number of cooling cells 5a, 5b necessary to obtain sufficient cooling of the strip before the contact of its side A 'with the lower roll 43. In this case, this roll

43 can be immersed in the quench bath 35.

However, to more easily accommodate the quench tank 35 above the galvanizing tank 30, it may be necessary to move the quench tank 35 away from the alloying furnace 33 at the same level. For this, the band M can go up an upward path T31 to a second upper roller 44, then descend, in a downward path T32, to a baffle roll 45 immersed in the final cooling bath 35. At the exit of this quench bath 35, the band M follows a rising path

T4 to a pair of upper deflector rollers 46, 46 '' spaced apart from each other so as to pass the strip over the whole of the galvanizing section, then down again, by a T5 downward path, up to a lower roller 47 to be directed towards the rest of the installation, for example a skin-pass 15.

As indicated above, on the side of the galvanizing tray opposite the entrance side of the strip, ie to the right of the tray 30 in FIG. 3, can be placed a verification station 37, by example a control cabin for an operator. This station 37 can thus be placed between the first ascending section T2 of the outlet of the metal bath 31 and the last outlet T5 downstream section of the installation, deflector rollers 48 allowing, possibly, to provide the necessary location for the station 37 The operator placed in the control cabin thus passes, in the ascending section T2, the outer face A 'of the strip which, because of the arrangement according to the invention, comes into contact with the roll 43 only after cooling along the ascending section T2 and the descending section T3. This external face A 'therefore undergoes no degradation and thus constitutes the so-called "exposed" face which will subsequently be the visible face of the sheet, for example for an automobile body.

Thanks to the particular path of the strip, shown schematically in FIG. 6, it is the same exposed face A 'which passes in front of the operator in the last descending section T5, on the other side of the cabin 37.

Thus, the operator sees passing in front of him, successively, twice the same face A '. Knowing the total length of the path and the running speed of the belt which can be measured at any moment, the operator can therefore locate on the exposed face A 'of the belt, immediately above the wiper device 32, a doubtful zone and, after having allowed the time necessary for scrolling, to identify the passage of the same zone on the descending path T5 in order to check the possible presence of a defect after the final cooling and hardening of the coating.

The arrangement according to FIG. 6 thus makes it possible to guarantee the best possible integrity of the exposed face of the coated strip.

Of course, the invention is not limited to the details of the embodiment which has just been described but covers all the variants using equivalent means and remaining in the same protective frame. In particular, the particularly compact arrangement of each cooling assembly comprising an air blast cell 5, a suction box 7 and a recycling circuit 6 with cooling 8 makes it possible to dispose of such assemblies 5, 6, 7, 8 not only along the upward path T2 but also along the downward path T3, so as to achieve sufficient cooling of the coating until the passage of the exposed face A 'on the lower roller 43. Indeed, as shown in FIG. Figure 7, these cooling cells 5a, 5b, 5c each associated with a circuit (not shown) for recycling and cooling, can advantageously be staggered on the ascending strand T2 and the descending strand T3. In this way, the two strands T2, T3 can be separated by a single upper roller 42, which further reduces the footprint of the assembly. Moreover, such an arrangement makes it possible to distribute the cells 5 over a greater length of band and thus to have a less violent blow, which reduces the risks of vibration of the band. R2008 / 000,969

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may have an impact on the quality of the coating, in particular, the regulation of its thickness.

On the other hand, as already indicated with reference to FIG. 5, the arrangement of the recirculation and cooling circuit shown in FIGS. 3 and 4 is reversed when the band is flowing from top to bottom. blow port 54 being then placed at the bottom of the cooling cell 5 and the suction port 73 at the upper part thereof.

Similarly, in the arrangement shown in Figures 2 and 3, the suction box 7 must be disposed above the cooling box 5 if the band flows downwards, so that the circulation of the blown air is always go against the flow of the tape.

Moreover, two embodiments of the device according to the invention have been described and shown in the drawings, but other arrangements would be possible to ensure recycling, cooling and filtering of the air blown into the cooling cell. .

In addition, insofar as, precisely, this cooling air is recovered and recycled, it would be possible to use, for cooling, not the ambient air but another heat transfer fluid, for example a neutral gas. Furthermore, the invention is not limited to the case where, to reduce the length of the annealing line, the strip follows a zig-zag path by passing over two sets of rollers spaced apart in height. Indeed, the invention can also be applied to the case of a continuous annealing furnace in which the band scrolls horizontally over a large length. In this case, shown diagrammatically in FIG. 8, the quenching bath 35 which, according to the invention, is offset backwards with respect to the galvanizing bath 31, can be placed above the outlet end of the enclosure annealing 8 'whose height is, then, relatively reduced. The third part T3 of the path of the strip then extends horizontally by returning upstream to the quench tank 35 which is shifted back a distance sufficient to dispose along said strand T3, at least one compact assembly 5, 6, 7, 8. The fourth portion T4 output quench bath 35 then returns horizontally downstream passing over said cooling assembly. As before, the footprint of the coating plant 3 does not substantially exceed that of the galvanizing bath 31.

Furthermore, the invention has been described in the usual case of a coating by passing on a roll immersed in a bath of liquid metal but it could also be applied to other coating devices, for example of the type in which the galvanizing metal bath is maintained magnetic levitation by means of induction coils arranged along the upward path of the strip after passing on the lower roller 41 which, in this case, is not immersed.

Claims

1. Cooling device after galvanizing a strip product (M) running in a galvanizing metal bath (31) for depositing a coating layer on two opposite faces of the strip (M), device comprising a cell cooler (5) in the form of a hollow box having two lateral portions extending on either side of a central part of the band (M) running between two parallel porous faces, respectively, on both sides of the band (M), and pressurized feed means of said side portions in a cooling gas diffused by said porous faces along both sides of the strip (M) and discharged through the central portion of the cooling box (5) , characterized in that it comprises suction means (7, 73) of at least the largest part of the cooling gases discharged at the outlet of the central portion (50) of the cooling box (5), connected to the means (60) of pressurized imentation of the lateral parts (51, 51 ') of the box (5), by at least one recycling circuit (6) on which is placed a means (8) for cooling the aspirated gases before they are introduced under pressure into the parts sides (51, 51 ') of the cooling box

(5).

2. Cooling device according to claim 1, characterized in that the pressurized gas supply means comprise at least one fan (60) having a gas inlet (61) connected to the suction means (7, 73). ) by the recycling circuit (6) and an outlet (54) of pressurized gas connected to the two lateral parts (51, 51 ') of the cooling box (5).

3. Cooling device according to claim 2, characterized in that the recycling circuit (6) comprises means (84) for filtering the sucked gases, placed upstream of the fan (60), in the direction of circulation of the gases. .

Cooling device according to one of the preceding claims, characterized in that the recirculation circuit (6) comprises a cooling chamber (8) having an inlet (74) connected to the suction means (J, 73). and an output (82) connected to the power supply means (60) under pressure and in which is placed a heat exchanger (83) for cooling the recycled gases.

5. Cooling device according to claim 4, characterized in that the cooling chamber (8) is connected to the means (60) of supply under pressure by a conduit (82) on which is placed a porous wall (84) filtering the recycled gases and comprises a bottom portion (85) for recovering the particles entrained by the gases sucked up and retained by the filtering wall (84).

Cooling device according to one of the preceding claims, characterized in that the two side parts (51, 51 ') of the cooling cell (5) form two hollow elongate box-shaped arms respectively extending along both sides of the strip (M), on either side of a central portion (50) extending between two rectangular inlets, respectively inlet (52) and outlet (52 ') of the strip (M), and that the cooling gas suction means comprise at least one recovery cell (7) placed near the cooling cell (5), at least on the side of the inlet (52) of the band (M) ₁ said recovery cell (7) forming a hollow box having two arms extending respectively along the two side portions (51, 51 ') of the cooling cell (5), on both sides a central part having two rectangular openings for the passage of the strip, respectively one inlet port (71) and an outlet port (72) opening adjacent to the inlet (52) of the strip (M) in the central portion (50) of the cooling cell (5). ) for the passage of cooling gases in the recovery cell (7), against the current of the tape (M).

7. Cooling device according to one of claims 1 to 5, characterized in that the cooling cell (5) extends over a certain length of travel of the strip (M) between an inlet end of the band (M), at which the central portion (50) of the cell is provided with at least one gas suction port (73) connected to the recycling circuit (6), and an outlet end of the strip at which at least one orifice (55) for supplying pressurized gas to the two lateral parts (51, 51 ') of the cooling cell (5) is placed.

8. Cooling device according to one of claims 6 and 7, characterized in that it comprises two circuits (6, 6 ') of recycling gases disposed on either side of the cooling cell (5) and each having a pressurized gas supply means (60, 60 ') having a gas inlet (61) connected to a suction means (7, 73) placed at one end of the central portion (50) of the cooling cell (5) and an outlet (62) of pressurized gas connected to a port (55) for supplying the side portions (51, 51 ') of said cell (5), and means (8) for cooling the recycled gas.

9. Cooling device according to one of the preceding claims, characterized in that the cooling cell (5) and the recycling circuit (6) comprising suction means (7, 73), cooling (8) and supplying pressurized (60) cooled gas, form a compact self-contained unit extending over a limited run length of the web (M).

10. Cooling device according to one of the preceding claims, in a galvanizing installation comprising strip travel control means, between a galvanizing bath (31) and a quench bath (35), along an ascending strand (T2) and at least one descending strand (T3) passing over at least one baffle roll (42), characterized in that the installation comprises at least one self-contained cooling unit which can be placed either on the ascending strand (T2) or on the descending strand (T3) and having a cooling cell (5a, 5b) and at least one recirculation circuit (6a, 6b) with suction means (7, 73) , cooling (8) and pressurized supply (60) in cooled gas.

11. Cooling device according to one of the preceding claims, characterized in that the entire system comprising means for controlling the movement of the strip between a galvanizing bath (31) and a quench bath (35). ) and at least one self-contained assembly comprising a cooling cell (5) and a recirculating circuit with gas cooling (6), is disposed inside a closed chamber provided with means for collecting dust and means for collecting 'soundproofing.

12. Apparatus for coating a strip product (M), comprising means for controlling the movement of the strip (M) between a liquid metal bath (31) and a quenching bath (35), along a continuous line of scroll defined by a plurality of baffle rollers and comprising, an upstream strand (T2) of output of the metal bath (31) and at least one descending strand (T3), characterized in that it comprises at least one autonomous cooling assembly according to one of claims 1 to 9, which can be placed on one or the other of said strands of the line, respectively on the ascending strand (T2) output of the metal bath (31), or on another strand, ascending or descending (T3), each assembly (5) having a cooling cell (5a, 5b) and at least one recycling circuit

(6a, 6b) with suction means (7, 73), cooling (8) and pressurized supply (60) in cooled gas.

13. Apparatus for coating according to claim 11, characterized in that it comprises at least two autonomous assemblies (5) for cooling with gas recirculation, arranged respectively along an ascending strand (T2) and a strand. descending (T3), and said assemblies (5a, 5b) are offset in height relative to each other so as to be staggered in order to reduce their overall size and the footprint of the installation .

14. Installation coating according to one of claims 12 and 13, characterized in that the quench bath (35) is placed above the metal bath (31), so that the entire line of scrolling , between the metal bath (31) and the quench bath (35), remains in a footprint of the same order as that of the metal bath (31).

15. Installation coating according to claim 14, characterized in that the strip (M) is supported by a first face (A) on a first baffle roller (41) immersed in the metal bath (31), coming from a first side thereof and is supported by the same first face (A) on a second baffle roll (42) placed at a higher level, so that the descending portion (T3) is placed on the same first side of the bath metal (31) relative to the upward portion (T2) of the metal bath outlet (31).

16. Installation coating according to claim 15, characterized in that it comprises a station (7) for checking the quality of the coating, placed on a second side of the metal bath (31), opposite the first side of entry of the band (M) and in front of which passes, in the ascending part (T2) of exit of the metallic bath, a second face (A ') of the strip opposite the first support face (A) on the first and second deflection rollers (41, 42), and that the web passes over a submerged deflector roll (45) in the quench bath (35) taking bearing on said submerged roll (45) by said second face (A '), then passes over the whole of the installation by being supported by the same second face (A') on two upper rollers (46, 46). ') separated from each other and down by a final descending part of the output of the installation

(T5), so as to pass in front of the verification station (7) the same second face (A ') of the strip (M), in order to check the state of the coating on this second face (A'), d firstly at the outlet of the metal bath (31) and, secondly, at the outlet of the installation, after final cooling.

17. Installation coating according to one of claims 12 to 16, characterized in that it comprises a heating means (33) of the strip (M) disposed in the upward portion (T2) of the output of the metal bath ( 31), immediately above it, and a compact recirculating cooling assembly (5a, 6a), placed above said heating means (33).

18. Apparatus for coating a strip product (M), comprising means for controlling the movement of the strip (M) between a liquid metal bath (31) and a quenching bath (35), along a continuous running line defined by a plurality of deflection rollers and having at least four parts, respectively a first portion (T1) of entry into the metal bath (31), a second portion (T2) of the outlet of the bath (31) , a third portion (T3) for cooling and a fourth portion (T4) for leaving the quench bath (35), characterized in that it comprises at least one autonomous cooling unit (5) according to one of claims 1 to 11 and that the coating plant is disposed downstream, in the running direction of an annealing line placed inside a closed chamber (8 ') for maintaining a non-oxidizing atmosphere, said enclosure (8 ') extending horizontally between an inlet end and an end outlet region provided with a connecting chute opening into the galvanizing metal bath (31), that the quenching bath (35) is placed above the closed chamber (8 ¹ ), at a certain distance upstream of the outlet end, and that the third part (T3) of the path of the strip, along which is placed at least one cooling means (5) extends horizontally above the closed enclosure (8 ') back upstream to the quench bath (35) from which the fourth bath outlet portion (T4) extends horizontally downstream, passing above said cooling means (5).