EP3606682A1

EP3606682A1 - Descaling device and method for chemically descaling a metal strip

Info

Publication number: EP3606682A1
Application number: EP18714262.5A
Authority: EP
Inventors: Klaus Kofler; Alois Stadlbauer
Original assignee: Primetals Technologies Austria GmbH
Current assignee: Primetals Technologies Austria GmbH
Priority date: 2017-04-04
Filing date: 2018-03-30
Publication date: 2020-02-12
Anticipated expiration: 2038-03-30
Also published as: CN110446566A; MX2019011859A; EP3606682B1; JP6903766B2; JP2020515417A; RU2019134817A; US20200047231A1; RU2753355C2; KR20190133712A; CN110446566B; EP3606682C0; RU2019134817A3; EP3385008A1; WO2018185028A1

Abstract

The invention relates to a descaling device (2) for chemically descaling a metal strip (4), comprising a spraying device (12, 12a-12d) for spraying a pickling agent (14) onto a top or bottom side (16, 18) of the metal strip (4). The spraying device (12, 12a-12d) has a first outer spraying unit (50) for spraying the pickling agent (14) onto a first edge region (52) of the top/bottom side (16, 18) of the metal strip (4) and a second outer spraying unit (54) for spraying the pickling agent (14) onto a second edge region (56) of the top/bottom side (16, 18) of the metal strip (4), which second edge region lies opposite the first edge region (52). At least one of the two outer spraying units (50, 54) has one or more solid stream nozzles (20), in particular a plurality of rows of solid stream nozzles (20), and/or one or more slotted nozzles (22).

Description

description

Descaling apparatus and method for descaling a metal strip chemically

The invention relates to a descaling device for the chemical descaling of a metal strip according to the preamble of claim 1 and to a method for the chemical descaling of a metal strip according to the preamble of claim 10.

When hot rolling a metal strip is formed on the surface of a scale layer. Prior to the possible nachfol ^¬ constricting cold rolling of the metal strip, the scale layer must be removed. In particular, for this reason, a metal strip after hot rolling is usually subjected to descaling, in which the scale layer is removed.

In the field of chemical descaling of a metal strip, in which a most acidic pickling agent is used, a distinction is made between the so-called Tauchbeizen and the so-called Spritzbeizen. In immersion pickling, the metal strip to be treated is immersed in a dip tank filled with the pickling agent, whereas in the case of spray pickling, the pickling agent is sprayed onto the metal strip to be treated. The technology of spray pickling is characterized in Ver ^¬ equal to immersion pickling by a short treatment time from.

The invention is based, to allow the achievement of a high pickling efficiency at a spray ^¬ treatment of a metal strip the task.

This object is achieved by a Entzun ^¬ derungsvorrichtung according to claim 1 and by a method according to claim 10th

Advantageous embodiments of the invention are the subject of the dependent claims and the following description, wherein the features of advantageous embodiments may relate both to the descaling device and to the method.

The descaling device according to the invention for the chemical descaling of a metal strip comprises at least one first spraying device and at least one further spraying device for spraying a pickling agent onto an upper or lower side of the metal strip. The first and the other

Spraying devices have a first outer injection unit for spraying the pickling agent on a first edge region of the top / bottom of the metal strip and a second outer injection unit for spraying the pickling on a second edge region opposite the first edge region of the top / bottom of the metal strip. Moreover, the first injection device also has a central injection unit for spraying the etching agent onto a middle region of the top / bottom side of the metal strip located between the edge ^regions .

At least one of the two outer and the central injection unit of the first injection device has a plurality of rows of full-jet nozzles and each of the injection units of the first injection device has its own Beizmittel- distribution chamber.

In the further spraying device, at least one of the two outer injection units has one or more slot nozzles, and each of the two outer injection units has its own pickling agent distribution chamber.

The nozzles of the respective injection unit are advantageously connected to their pickling agent distribution chamber. Such an embodiment of the spray device allows a structurally simple manufacturability of the spray device and a low control effort for the spray device.

Full jet nozzles are comparatively robust and inexpensive to produce due to their simple geometry. While previously used in Entzunderungsvorrichtungen nozzles such. As flat jet nozzles, Tongue nozzles or cone jet nozzles, each generating a beam that expands and thus has an inhomogeneous momentum distribution, can be using a Vollstrahldüse produce a closed, stable and energy-rich full jet, which has a homogeneous Impulsvertei ^{¬ treatment} over its beam diameter away and itself does not expand or hardly expand over a great length. With such a high-energy full jet, a laminar boundary layer of the mordanting agent formed or formed on the metal strip can be kept as thin as possible, which has a positive effect on the mass transfer and thus increases the pickling efficiency. In addition, such an energetic full jet allows a mechanical "spraying away" adhering Zunders.

Due to the higher pickling efficiency, the treatment time necessary for complete descaling of the metal strip can be shortened. This allows a shorter treatment path (shorter structural length) or - at a constant treatment ^¬ ment distance - a higher conveying speed of the metal ^¬ band.

Furthermore, when using one or more full-jet nozzles - since the jet of a full-jet nozzle does not expand or barely expand over a large length and thus makes a high impact on the metal strip surface possible - a lower etching agent supply pressure is required for the injection device than with the use of Flat jet nozzles, tongue nozzles or cone jet nozzles to achieve the same pickling effect. This in turn allows lower operating costs, eg. B. because cheaper pumps can be ^¬ sets. For example, the spray device can be operated with a pickling agent supply pressure of 4 bar.

In addition, the jet produced by a full-jet nozzle advantageously contains no admixture of ambient air. With In other words, the jet generated by a full jet nozzle advantageously does not mix with the surrounding air.

The full jet nozzles of the spray device preferably each have a pickling agent outlet bore with a non-constant cross section. For example, the cross-sectional area of the ^¬ Beizmittelauslassbohrung the respective full jet nozzle to the output-side end of the full jet toward decrease. The output side nozzle end of a nozzle is to be understood as the end facing the metal band. Entspre ^¬ is accordingly to be understood as input-side nozzle end of a nozzle which faces away from the metal strip end.

Preferably, the narrowest point of the Beizmittelauslassbohrung the respective jet nozzle is at the output side nozzle end. The Beizmittelauslassbohrung the respective full jet nozzle may be formed in particular funnel-shaped.

Further, it is preferred if the Beizmittelauslassbohrung the respective full jet nozzles at its narrowest point an inner diameter of at least 2 mm and at most 6 mm on ^¬ has. It is particularly preferred if the Beizmittelaus ^¬ fitting hole of the respective jet nozzle has at its narrowest point has an internal diameter of 4 mm.

An inventive development of the Entzunderungsvorrich- device provides that the further spray device additionally a central injection unit with one or more slit ^¬ nozzles for spraying the pickling on a located between the edge regions middle region of the top / bottom of the metal strip and a separate pickling agent distribution chamber having.

While a full jet generated by a mordant ^¬ beam typically results in a punctiform Beizmittelbeauf ^¬ deposition of the metal strip surface, resulting in a The pickling agent jet produced by a slot nozzle usually results in a linear pickling agent loading of the metal strip surface. Using a slot nozzle, a closed, stable and high-energy beam can be generated, which has a homogeneous impulse distribution and does not expand or hardly expand over a large length. By using one or more slot dies, similar advantages can be achieved as when using one or more full jet nozzles.

Advantageously, the descaling device comprises a belt conveyor for transporting the metal belt along a horizontal conveying direction. The belt conveyor may, for. B. be designed as a roller conveyor. Preferably, the conveying direction corresponds to the longitudinal direction of the metal strip to be treated. In other words, by means of the belt conveyor, the metal strip is preferably transported ent ^¬ long its longitudinal direction.

Preferably, the two outer injection units are equipped with nozzles of the same type. If the first externa ^¬ ßere injection unit z. B. one or more jet nozzles which, so also has the second outer injection unit ^¬ advantageous way legally to one or more jet nozzles. If the first outer injection unit has one or more

Slit nozzles, so the second outer Spritzein ^¬ unit advantageously also has one or more slot ^¬ nozzles.

Further, it is advantageous if the spraying device has a central injection unit for spraying the etching agent on a middle region of the upper / lower side of the metal strip situated between the edge regions. Particularly be ^¬ vorzugt it when the average injection unit, one or more jet nozzles, in particular more rows of jet nozzles, and / or has one or more slot nozzles, in particular from the above-mentioned reasons. Is Each of the aforementioned injection units advantageously has a group of nozzles for spraying the pickling agent on the top / bottom of the metal strip.

Advantageously, the spray device is designed as a spray bar ^¬ . In this case, the aforementioned etching agent distribution chambers may be formed, for example, by means of partitions arranged in the interior of the spray bar, in particular separating plates. In other words, in the case of an embodiment of the spray device as a spray bar, the individual seed dressing can distribution chambers from ^¬ be separated by a plurality of partitions, in particular separating plates. The partitions preferably cause only a small reduction of the internal volume of the spray bar so ^¬ that frictional losses within the spray bar can be kept low ge ^¬.

In another variant of the invention, the spray device may for example comprise separate spray bars, which form the aforementioned injection units. In such a case, it is expedient if these separate spray bars are arranged offset from one another perpendicular to the conveying direction. In the conveying direction, they can also be arranged offset zuei ^¬ each other. Alternatively, the separate spray bars, with respect to the conveying direction, may be arranged in the same position.

Furthermore, the spray device in each of its pickling agent distribution chambers can have a device which ensures that the nozzles of the respective injection unit are homogeneously charged with the pickling agent.

Preferably, the spray device has an internal height of at least 10 cm. This makes it possible to avoid high pressure gradients in the interior of the spray device. The inner height of the spray device is to be understood as the inner dimension perpendicular to the upper / lower surface of the metal strip. The descaling device may have its own pickling agent supply line for each of the three injection units. Preferably, the descaling device comprises a first mordant-supply line which has its output connected to the first external injection unit, a second seed-supply line which has its output connected to the second outer injection unit, and a drit ^¬ te mordant-supply line, the output side of the middle with the Injection unit is connected.

Advantageously, each of the three leads mordant versor ^¬ supply lines in the respective injection unit perpendicular to the spray direction. That is, advantageously opens the first mordant supply line perpendicular to the spraying direction of the first outer injection unit in the first outer injection unit, while the second seed dressing supply ^¬ conduit opens perpendicularly to the direction of injection of the second outer injection unit in the second outer injection unit and the third mordant Supply line perpendicular to

Spray direction of the center injection unit in the middle

Injection unit opens. In this way, a uniform pressure distribution in the individual injection units and thus a uniform pressure distribution can be achieved at the nozzle.

Each of the injection units is advantageously to be oriented ^¬, the mordant perpendicular or substantially perpendicular ^¬ right to the upper / lower side of the metal strip aufzusprit ^¬ zen. This is z. B. then reached when the nozzles of the

Injection units are aligned so that the Spritzeinhei ^¬ th each have a spray direction that is perpendicular or substantially perpendicular to the top / bottom of the Metallban ^¬ the so vertically or substantially vertically upward or vertically or substantially vertically downwards from - is directed.

The direction of injection of the respective injection unit is to be understood as the direction in which the injection unit controls the pickling unit. medium sprayed. The phrase "substantially at the top / bottom side of the metal strip at right angles" can be used as with egg ^¬ ner deviation of up to +/- 20 °, preferably up to +/- 10 °, understood from the right angle to the upper / lower side of the metal strip become.

Furthermore, at least one of the injection units of

Spray device tilting / pivoting be stored, preferably about a horizontal axis parallel to the conveying direction.

In an advantageous embodiment of the invention, the descaling device has a control device by means of which a pickling agent outlet rate of the respective spray ^¬ unit of the spray device is adjustable, in particular continuously or in several discrete steps.

As a mordant discharge rate of the respective spray unit per unit time from the respective injection unit austre ^¬ tends amount of seed dressing, ie the volumetric flow of the exiting from the respective injection unit mordant to understand.

For the purposes of the invention, controlling a quantity may be a regulation of that size, i. H. Control with a measured value feedback, include. The aforementioned control device can therefore in particular be a regulating device.

Moreover, for the purposes of the invention, a variable is "adjustable in several discrete steps" if, apart from the value zero and a maximum value (which can be reached in the descaling device), this variable can also be set to a further value between these two values. In other words, for the purposes of the invention, a variable is then "adjustable in a plurality of discrete steps" if this variable can be set to at least two further values except for the value zero. By means of the control device is the seed dressing exit of the central injection unit ^¬ rate preferably independent of the seed dressing discharge rate of the first outer injection unit and independent of the seed dressing discharge rate of the second outer injection unit adjustable. Thereby, it is possible to use the top / bottom side of the metal strip depending on how the width profile of the scale layer thickness is arranged on the top / bottom side of the metal strip to adjust the Beizmittelbe ^¬ aufschlagung of the metal strip in the width direction accordingly.

Typically, the scale layer thickness is greater at the strip edges than in the strip center region. If the metal strip is applied across its width homogeneously with the dressing, this means that in the event of a strong Beizmittelbe ^¬ aufschlagung the strip center area "überbeizt" is not only the scale layer, but also already underlying base material is removed from the mordant, whereas in the case of a weak Beizmittelbeaufschlagung the scale layer is not completely worn off ^¬ especially at the band edges.

Has the metal strip at the edge regions of its upper / lower a larger scale layer thickness than in between ^¬ lying middle region of the Top / Bottom, the mordant-discharge rate of the average spray-unit ei ^¬ NEN lower value may be set as the seed-dressing Exit rates of the outer injection units. In this way it is possible a homogeneous Entzunderungsergebnis to erzie ^¬ len. In this case, since over-pickling of the metal strip can be avoided, it is also possible to reduce the need for mordant, which in turn enables a reduction in the regeneration cost of the pickling solution.

Preferably, the mordant discharge rate of the first outer injection unit is connected by means of the control device un ^¬ adjustable according to the mordant-discharge rate of the second outer injection unit. This makes it possible for the first one To apply to the edge region of the top / bottom of the metal strip with a different seed amount than the second edge region of the top / bottom of the metal strip.

Further, the control device may comprise a plurality of pickling agent feed pumps, which are connected on the output side with the injection device. The pickling agent can be conveyed to the spraying device with the help of the pickling feed pumps. The mordant feed pumps may be used to adjust the pickle exit rates of the injection units. The pickling-conveying pumps may in particular be frequency-controlled pumps.

One of the seed-dressing feed pumps may be connected to the two outer injection units, while another of the seed-dressing feed pumps may be integrally joined to the central ^¬ injection unit. Alternatively it can be connected to a first seed-dressing feed pump to the first outer injection unit, a second seed-feed pump to the second outer injection unit and a third seed-feed pump to the middle Spritzein ^¬ unit.

The mordant feed pumps are preferably connected to a control unit of the control device. The control unit is advantageously set up to adjust the ^conveying power of the respective pickling agent feed pump, in particular continuously or in a plurality of discrete

Steps. Further, it is advantageous if the delivery rate of the respective pump is adjustable independently of the delivery rates of the other pickling agent delivery pumps. By varying the respective delivery rate, the pickling agent discharge rate of the respective injection unit can be changed.

Furthermore, the control device can comprise a plurality of valves. These can be used as an alternative or in addition to the pickling feed pumps for adjusting the pickling outlet rates of the injection units. Advantageously, the injection device is on the input side with the Venti- len, in particular via the aforementioned pickling agent supply lines.

For the two outer injection units, a common valve or in each case a separate valve can be provided. For the average injection unit preferably own Ven ^¬ til provided. Further, it is advantageous if the valves are connected to the control unit of the control device. The control unit is preferably configured to

Adjust valve position of the respective valve, in particular continuously or in several discrete steps. By varying the respective valve position, the pickling agent outlet rate of the respective injection unit can be changed.

Further, the aforementioned mordant ^¬ supply lines can in each case with a pressure and / or flow sensor for monitoring the pressure or seed dressing seed dressing throughput flow be provided in the respective seed dressing supply line. These sensors are preferably connected to the con troll ^¬ unit of the control device. The control device, in particular its control unit, can be turned to ^¬ directed to control the above-mentioned seed-dressing feed pumps and / or valves in dependence on the sensor signals from these sensors.

The spray device in addition to the aforementioned injection units further injection units for spraying the etchant onto the top / bottom of the metal strip aufwei ^¬ sen. For example, the spraying device may have a first further injection unit between the middle and the first outer injection unit and a second further injection unit between the middle and the second outer injection unit. The mordant discharge rate of each ^¬ weiligen further injection unit is preferably independent of the seed dressing exit means of the control device rates of the other injection units of the sprayer adjustable.

Moreover, the control device may include a sensor unit having one or more sensors for sensing a surface parameter of the metal strip, in particular a layer of scale is dependent on a thickness of the metal strip Oberflächenpa ^¬ rameters having.

The surface parameter may, for example, be the scale layer thickness itself or another surface ^parameter dependent on the scale layer. In particular, the sensor unit may comprise one or more non-contact sensors for detecting the surface parameter.

Further, the sensor unit may in particular be adapted to said surface parameters spatially resolved manner across the width of the metal strip, that is to measure a width profile of the upper surface ^¬ parameters. The sensor unit may be arranged in front of or behind the injection device, with respect to the conveying direction.

Moreover, it is advantageous if the sensor unit is connected to the control unit of the control device. Said control device, in particular the control unit is preferably adapted to adjust the mordant discharge rate of the respective spray unit in response to an off ^¬ output signal of the sensor unit.

Furthermore, the pickling agent outlet rate of the respective injection unit in dependence of one or more known production parameters, such as. As the so-called reel temperature of the metal strip and / or its material ^quality , ge ^¬ controls. Such a parameter is advantageously transmitted to the control device, in particular to its control unit. The control unit is preferably set up to adjust the pickling agent outlet rate of the respective injection unit to be set on the basis of the control unit to calculate transmitted sensor signals and / or production parameters.

Furthermore, the descaling device may comprise at least one further spray device, in particular at least one further spray bar for spraying the etchant onto the same side of the metal strip as the first-mentioned injection ^¬ device. The former and the further injection device (s) are preferably arranged one behind the other in the conveying direction.

Like the first-mentioned spray device comprises a sol ^¬ che other injection device may include a first outer injection unit for injecting the mordant to the first edge region of the top / bottom side of the metal strip and a second spray ^¬ unit for spraying of the mordant to the second edge ^¬ area of the top / Have underside of the metal strip. Ge ^¬ optionally such a further spray device can have a mean injection unit for injecting the mordant to the central region of the top / bottom of the metal strip. Preferably, in such a further injection device, the pickling agent discharge rates of their injection units are controllable in the same way by means of the control device as the etching agent discharge rates of the injection units of the first-mentioned injection device.

Further, the former and further injection apparatuses may have different types of nozzles. One of the spray devices can, for. B. (only) have full jet nozzles, another of the spray devices in turn may, for. B. (exclusively) have slot nozzles.

In addition, the descaling device may have at least one additional spraying device for spraying the pickling agent onto the other side of the metal strip. The phrase "the other side" of the metal strip is to be understood as follows: If the former Spritzvorrich ^¬ tung up the mordant on top of the metal strip injected, the other side is the bottom of the Metallban ^¬. Conversely, the other hand, if the first-mentioned spraying device splashes the mordant to the underside of Me ^¬ tallbandes, the upper surface of the metal strip. The features mentioned in connection with the first-mentioned spraying device can relate analogously to such an additional spraying device.

Those elements of the descaling device which come into contact with the mordant advantageously consist of an acid-resistant material, in particular of a plastic and / or a ceramic. The aforementioned nozzles may for example consist of polyvinylidene fluoride (PVDF) and / or polypropylene (PP) or contain these materials.

Furthermore, the descaling device may have a Tauchbehäl ter for a dip pickling treatment of the metal strip. This is, with respect to the conveying direction, preferably arranged behind ter the spray device. The Tauchbeizbehandlun in the dip tank can serve to remove the pickling effect to uniform and / or scale residues that have not been removed during the spray treatment.

In addition, the descaling device may have a further dip tank for a dip pickling treatment of the metal strip, wherein the spray device, based on the conveying direction, for example, between the two dip tanks may be arranged.

In the method according to the invention for the chemical descaling of a metal strip, a pickling agent is sprayed onto an upper or lower side of the metal strip by means of at least one first injection device and at least one further injection device. Here, the mordant from a first outer injection unit of the first and the further injection device to a first edge region of the top / bottom of the metal strip and from a second outer Injection unit of the first and the further spray device on a first edge region opposite the second edge region of the top / bottom of the metal strip injected ^¬ . In addition, a pickling agent is sprayed from a central injection unit of the first injection device onto a middle region of the upper / lower side of the metal strip situated between the edge regions. In the OF INVENTION ^¬ to the invention method it is provided that the mordant of at least one of the two outer injection units and from the central injection unit of the first injection apparatus by a plurality of rows of jet nozzles and of at least one of the two outer injection units of the further spray device by one or more slot nozzles the top / bottom of the metal strip is sprayed on.

It is particularly preferred if the pickling agent is sprayed through one or more slot nozzles from a central injection unit of the at least one further injection device onto a middle region of the upper / lower side of the metal strip located between the two edge regions.

The descaling device according to the invention can be used for carrying out the method according to the invention. That is, the devices mentioned in connection with the method may in particular be elements of the descaling device.

The spraying of the pickling agent on the metal strip preferably causes not only a chemical descaling of Me ^¬ tallbandes, but also a mechanical removal of the scale layer.

In the method, the metal strip is preferably transported parallel to its longitudinal direction by a belt conveyor device, in particular by the aforementioned belt conveyor device of the descaling device. Preferably is or contains the mordant, which is sprayed onto the Me ^¬ tallband, an acid, such as. Hydrochloric acid. The metal strip may in particular be a steel strip. Furthermore, the metal strip is preferably a hot-rolled metal strip.

In an advantageous embodiment of the invention, a seed dressing discharge rate of the first outer injection unit so ^¬ as a seed dressing discharge rate of the second outer injection unit of the at least one first spraying device and / or at least set to a further spray device using a control device in each case to a value which is different from a pickling agent outlet rate of the respective central injection unit of the first injection device or of the further injection device. Thereby, in particular in the case where the scale at the edge regions having a different thickness than in the central area, a seamless front ho ^¬ Entzunderungsergebnis be achieved. For example, the seed exit rate of the first outer injection unit and the seed exit rate of the second outer injection unit can be set by the control device to a value that is greater than the etchant exit rate of the center injection unit, especially in the case of a larger scale layer thickness on the both border areas.

Basically, it is possible that the mordant egress ^¬ rate of the first outer injection unit and the mordant-off occurs rate of the second outer injection unit by using the

Control device set to different values ^¬ who. So it is z. B. possible that only the mordant-off ^¬ takes rate of one of the two outer injection units using the control device is set to a value that is different from the seed-dressing product exit rate of the central injection unit. Preferably, the mordant discharge rate of each injection unit is the at least one first injection device and / or the at least one further spray device with- help of the control device is set such that the Me ^¬ tallband defined in its width direction from the first and / or the further spray device with a Beizmittel-spray profile is applied. The profile of the amount of seed applied to the metal strip by the spray device along a predetermined direction (here: the width direction of the metal strip) is to be understood as the pickling agent spray profile.

The mordant spray profile can outwardly to-the first and / or two ^¬ th edge region or decrease, in particular linearly increase or decrease. Furthermore, the spray profile may be symmetrical with respect to the belt center plane. As a band center plane a vertical plane is herein to be understood with respect to which the metal strip has a mirror symmetry ^¬.

Furthermore, the mordanting spray profile applied to the metal strip may be plateauless. Alternatively, the seed-dressing spray profile may include a plateau, the special ^¬ between said two edge portions.

A pickling spray profile of the type mentioned above can, for. B be realized in that the nozzles of the first outer injection unit are arranged triangular side by side, the nozzles of the second outer injection unit are arranged triangular side by side and the nozzles of the central injection unit trapezoidal, in particular in the form of an isosceles trapezium, or also triangular shaped side by side.

The previously given description of advantageous embodiments of the invention includes numerous features that are partially reproduced in the individual dependent claims to several zusammenzusch st. These features may but also considered individually and combined into meaningful further combinations. In particular, these features can each be combined individually and in any suitable combination with the descaling device according to the invention and the method according to the invention. Furthermore, process features can also be seen as a property of the corresponding device unit.

Although some terms are used singularly or in conjunction with a number word in the description or in the claims, the scope of the invention for these terms should not be limited to the singular or the respective number word.

The above-described characteristics, features and advantages of the invention as well as the manner in which they are achieved will become clearer and more clearly understood in connection with the following description of the exemplary embodiments of the invention, which are explained in more detail in connection with the figures. The examples serve to He ^¬ explanation of the invention and not to limit the invention to the details given herein, combinations of features, not even in terms of functional features. In addition, to appropriate features of each embodiment considered in isolation ex ^¬ plicitly from an off exemplary implementation removed in another operation example to from its comple ^¬ wetting introduced and bined with any of claims kom ^¬.

If the same reference characters are used in different figures, these designate essentially the same or corresponding elements. For the sake of Suitably ^¬ ness substantially equal or mutually corresponding elements but can also be referred to by different reference numerals.

Show it: an embodiment of a descaling device according to the invention for the chemical descaling of a metal strip;

2 shows a section through the descaling device of FIG. 1;

3 shows a representation of two spray devices of

descaling;

4 shows a pickling spray profile, with which the metal strip is applied in the descaling device;

5 shows an illustration of two other spraying devices for a descaling device; a mordanting-spray profile, with which a Me ^¬ tallband when using one of the Spritzvorrichtun conditions of FIG 5 is applied.

1 shows an embodiment of a descaling device 2 according to the invention for the chemical descaling of a metal strip 4 in a schematic representation.

The descaler 2 is equipped with a belt conveyor 6 for conveying the metal belt 4 along a conveying direction 8. In the present embodiment, the belt conveyor 6 is designed as a roller conveyor with a plurality of rollers 10.

Moreover, the descaling device 2 includes a plurality of upper spray means 12 containing for spraying a hydrochloric acid etchant 14 to an upper surface 16 of the Metallban ^¬ of 4, and a plurality of lower spray means 12 for on ^¬ splashing of the etchant 14 to a bottom 18 of the Me ^¬ tallbandes 4. In FIG 1 By way of example, four upper spray devices 12 and four lower spray devices 12 are shown. In principle, the descaling device 2 can ne higher or lower number of such spray devices 12 have.

The upper spray devices 12 are arranged one behind the other in the conveying direction 8 of the belt conveyor 6. Likewise, the lower spray devices 12 are arranged one behind the other in the conveying direction 8 of the belt conveyor 6. Furthermore, the spray devices 12 are each formed as a spray bar.

In the present embodiment, all upper spray ^¬ devices 12 of the descaling 2 are arranged at the same height. That is, all of the upper Spritzvorrich ^¬ obligations 12 of the descaling device 2 have the same distance to the top side 16 of the metal strip 4 on. In addition, all lower spray devices 12 of the descaling device 2 are arranged at the same height. That is, al ^¬ le lower spray devices 12 of the descaling 2 have the same distance from the bottom 18 of Me ^¬ tallbandes 4 on.

The distance that the upper spray means 12 comprise the top side 16 of the metal strip 4 can be less than or RESIZE ^¬ SSER than the distance that the lower spray means 12 comprise the bottom 18 of the metal strip. 4 Alternatively, these two distances may be the same. It is particularly preferred if the distance that the lower spray devices 12 have to the lower side 18 of the metal strip 4 is smaller than the distance that the upper spray devices 12 have to the upper side 16 of the metal strip 4.

Some of the upper and lower spray devices 12 are spray devices 12a of a first type. Others of the upper spray devices 12 are spray devices 12b of a second type. The spraying devices 12a of the first type have a plurality of full-jet nozzles 20, whereas the spraying devices 12b of the second type have a plurality of slot nozzles 22 (see FIG. In the present exemplary embodiment, the spraying devices 12a of the first type and the spraying devices 12b of the second type are arranged alternately in the conveying direction 8 of the belt conveyor device 6. That is, to a spray ^¬ device 12a of the first type follows in the conveying direction 6, a spraying device 12b of the second type, on which in turn follows in the conveying direction 8, a spray device 12a of the first type and so on.

The injection devices 12b of the second type - d. H. the spray devices 12b with slot nozzles 22 - are used in this arrangement, in particular, to homogenize the descaling result.

However, the arrangement of the sprayers 12 need not necessarily be such an alternate arrangement. Furthermore, there need not necessarily be the same number of first type injector 12a and second type injector 12b. In addition, it is basically possible to use only spraying devices 12 of the same type in the descaling device 2.

Furthermore, the descaling device 2 has a pickling chamber 24, in which said spraying devices 12 are arranged. The Beizkammer 24 includes a lower chamber portion 26 for receiving the effluent from the metal strip 4 mordant 14 so ^¬ as a which is arranged above the lower chamber member 26 obe ^¬ res chamber part 28th

Furthermore, the descaling device 2 has a first pair of pinch rollers 30 and a second pair of pinch rollers 32, each with an upper pinch roller 34 and a lower pinch roller 36. The first pair of squeezing rollers 30 is arranged in front of the pickling chamber 24, relative to the conveying direction 8, whereas the second squeezing roller pair 32 is arranged in the pickling chamber 24. The squeezing rollers 34, 36 support and guide the metal strip 4. When passing through Squeezing roller pair 30, 32 is displaced by the squeezing rollers 34, 36 a liquid located on the metal strip surface. Furthermore, the Ent scaling device 2 comprises a

Control device 38, of which in FIG 1, the control unit 40, the first sensor unit 42a and the second Sen ^¬ sensor unit 42b are shown. Said sensor units 42a, 42b are connected to the control unit 40 and each comprise an upper sensor row 44 and a lower sensor row 46. The rows of sensors 44, 46 of the first sensor unit 42a are arranged in front of the spray devices 12, relative to the conveying direction 8 of the belt conveyor 6. The rows of sensors 44, 46 of the second sensor unit 42b are, with respect to the conveying direction 8 of the belt conveyor 6, arranged behind the spray devices 12. The sensor rows 44, 46 of the respective sensor unit 42a, 42b are preferably arranged outside the pickling chamber 24, as shown in FIG.

From the belt conveyor 6, the metal strip 4 is transported parallel to its longitudinal direction 48 through the descaling device 2. In the pickling chamber 24, the metal strip 4 is acted upon by the spraying devices 12 with the etching agent 14 in order to deminish the metal strip 4 chemically, that is to say to remove a scale layer located on the metal strip 4. The upper sensor row 44 of the first sensor unit 42a detected before the spray devices 12 spatially resolved over the width of the metal strip 4, a surface parameter of the metal strip 4, which is dependent on the scale layer thickness on the top 16 of the metal strip 4. Accordingly, the lower sensor array 46 of the first sensor unit detects 42a in front of the spray devices 12 ^¬ a spatially resolved manner across the width of the metal strip 4 is a surface parameter of the metal strip 4, which by the scale layer thickness on the underside 18 of the metal strip 4 is dependent.

The upper sensor array 44 of the second sensor unit 42b ER- summarizes behind the spray means 12 is also spatially resolved manner across the width of the metal strip 4 is a Oberflächenpa ^¬ parameters of the metal strip 4, which is dependent on the scale thickness on the top side 16 of the metal strip. 4 Entspre ^¬ accordingly the lower sensor array 46 of the second transmitter detects soreinheit 42b behind the spray means 12 in a spatially resolved over the width of the metal strip 4 is a Oberflächenpa ^¬ parameters of the metal strip 4, which is dependent on the scale thickness on the underside 18 of the metal strip. 4 The Sen ^¬ sorreihen 44, 46 of the second sensor unit 42b can detect the same surface parameters such as the sensor arrays 44, 46 of the first sensor unit 42 and in particular in each case.

The sensor signals generated by the sensor rows 44, 46 of the sensor units 42a, 42b are transmitted to the control unit 40.

Using the control unit 40, the ^¬ Beizmittelbeauf suppression of the metal belt 4 in response to the aforementioned sensor signals is controlled such that a homogeneous as possible is preferably achieved with Entzunderungsergebnis vollständi ger ^¬ remove the scale layer.

In principle, it is possible that the descaling, 42b 2, instead of both sensor units 42a only one of the two sensor units 42a, 42b and that entspre ^¬ accordingly the Beizmittelbeaufschlagung of the metal strip 4 as a function of the sensor signals of only one of the sensor units 42a, is controlled 42b. The descaling device 2 may further comprise one or more (not shown figuratively) immersion tank for a dip pickling treatment of the metal strip 4. For example, the descaler 2 may be a dip tank the pickling chamber 24 and a further dip tank behind the pickling chamber 24 have. In the respective dip tank, the same pickling agent that is sprayed onto the metal strip 4 by the spray devices 12 or another pickling agent can be used.

2 shows a section through the descaling device 2 along the sectional plane II-II of FIG 1. Referring to FIG 2, the embodiment of the spray devices 12 will be described in more detail below.

As previously mentioned, the spray devices 12 are each formed as a spray bar.

The upper injection devices 12 each comprise a first outer injection unit 50 for spraying the etching agent 14 onto a first edge region 52 of the upper side 16 of the metal strip 4, a second outer injection unit 54 for spraying the etching agent 14 onto a second edge region 56 of the upper side opposite the first edge region 52 16 of the metal strip 4 and an intermediate injection unit 58 arranged between the two outer injection units 50, 54 for spraying the etching agent 14 on a middle region 60 of the upper side 16 of the metal strip 4 situated between the edge regions 52, 56.

Correspondingly, the lower injection devices 12 each comprise a first outer injection unit 50 for spraying the etching agent 14 onto a first edge region 52 of the underside 18 of the metal strip 4, a second outer injection unit 54 for spraying the etching agent 14 onto a second edge region 56 opposite the first edge region 52 Bottom 18 of the metal strip 4 and arranged between the two outer injection units 50, 54 central injection unit 58 for spraying the pickling agent 14 to a zwi ^¬ 's the edge regions 52, 56 located central region 60 of the underside 18 of the metal strip 4th The said injection units 50, 54, 58 of the respective

Spray device 12 are arranged one behind the other in the width direction 62 of the metal strip 4. In addition, each of the injection units 50, 54, 58 has a plurality of nozzles 20, 22 (see FIG.

In addition, the injection units 50, 54, 58 are adapted to spray the pickling agent 14 perpendicular to the upper side 16 or lower side 18 of the metal strip 4. The nozzles 20, 22 of the injection units 50, 54, 58 are aligned so that the injection units 50, 54, 58 each have an injection direction 64 which is perpendicular to the top 16 and bottom 18 of the metal strip 4, ie vertically upwards or vertically down, is aligned.

The spacing of the spray devices 12 to the strip surface, more precisely the distance of their nozzles 20, 22 to the strip surface, can be up to 500 mm in the present example.

Furthermore, each of the injection units 50, 54, 58 has its own pickling agent distribution chamber 66, to which the nozzles 20, 22 of the respective injection unit 50, 54, 58 are respectively connected with their inlet-side nozzle end.

Furthermore, the descaling device 2 has its own pickling agent supply line 68 for each of the injection units 50, 54, 58. The respective seed dressing ^¬ supply line 68 opens into the respective injection unit 50, 54, 58 perpendicular to the spray direction 64, whereby a uniform pressure distribution in the individual injection units 50, 54, is achieved 58th

Furthermore, the aforementioned control device 38 includes a plurality of pickling agent feed pumps 70, wherein in the present

Embodiment for each of the injection units 50, 54, 58 a separate pickling agent feed pump 70 is provided (see FIG 3). Each of the injection units 50, 54, 58 is above the they connected Beizmittel supply line 68 on the input side verbun ^{¬ ¬} with the associated Beizmittel-feed pump. In principle, it is possible that the injection units 50, 54, 58 of different spray means 12 via a same overall my seed-feed pump 70 with the dressing 14 are ver ^¬ provides. In the latter case, for example, the descaling device may have a total of three pickling agent feed pumps 70 for all sprayers 12. Said seed-feed pump 70 are also connected respectively to the aforementioned control unit 40 of the control device 38 which is adapted to control the volumetric flows of the seed dressing seed-dressing feed pumps 70 using egg ^¬ nes predetermined control algorithm.

The control device 38 is adapted to adjust the Beizmit ^¬ tel-discharge rate of the respective injection unit 50, 54, 58, regardless of the mordant discharge rates of the other injection units 50, 54, 58. By egg ne change in the mordant-volume stream of a the pickling ^¬ medium-feed pump 70 can change the control unit 40, the mordant discharge rate of the associated injection unit 50, 54, 58th Preferably, the sum of the pickling agent outlet rates of the three injection units 50, 54, 58 of the respective spray device 12 is in the range of 100 to 150 m ³ / h.

As previously mentioned, depending on the aforementioned sensor signals of the sensor units 42a, 42b, the Beizmittelbe ^¬ aufschlagung of the metal strip 4 is controlled such that a homogeneous as possible Ent is zunderungsergebnis achieved.

If the scale layer thickness in the central region 60 of the metal strip 4 is lower than at the edge regions 52, 56 of the metal strip 4, the seed rate of its first outer injection unit 50 as well as the etchant exit rate of its second outer layer are determined in the respective spray device 12. The injection unit 54 is set by the control device 38 in each case to a value which is greater than the Beizmit ^¬ tel-exit rate of their central injection unit 58. If the scale layer thickness in the central region 60 of the metal strip 4, however, is greater than at the edge regions 52, 56 of the metal strip 4, the mordant discharge rate of their first outer injection unit 50 and the seed-dressing product exit rate of their second externa ^¬ ßeren injection unit 54 are adjusted by the control device 38 respectively to a value at the respective spray device 12 which is smaller than the Beizmit ^¬ tel-discharge rate of their middle injection unit 58.

If the scale layer thickness is symmetrical with respect to a vertical band center plane, at the respective

Spray device 12, the pickling agent outlet rate of ers ^¬ th outer injection unit 50 and the pickling agent outlet rate of its second outer injection unit 54 by the controller 38 set to the same value. In the case of a production-related reduction in the conveying speed of the metal strip 4, one or more injection units 50, 54, 58 of the spray devices 12 can be switched off in order to avoid over-pickling of the metal strip 4.

FIG. 3 shows a spraying device 12a of the first type and a spraying device 12b of the second type of the descaling device 2, in each case from their side facing the metal strip 4.

In FIG. 3, the aforementioned full jet nozzles 20 of the first type of spray device 12a and the aforementioned slot nozzles 22 of the second type of spray device 12b are visible.

In addition, the already mentioned pickling agent feed pumps 70 and the pickling agent supply lines 68 connected to the injection units 50, 54, 58 are shown in FIG. In the case of the injection device 12a of the first type, the full-jet nozzles 20 are arranged in a plurality of rows of nozzles oriented perpendicular to the conveying direction 8, wherein these nozzle rows are arranged equidistant from each other. In the respective row of nozzles, the full-jet nozzles 20 are also arranged equidistant from each other.

The distance between adjacent jet nozzles 20 in the same due-senreihe may in particular correspond to the distance between adjacent Düsenrei ^¬ hen. This distance can z. B. 25 mm. At their outlet opening, the full-jet nozzles 20 preferably have an inner diameter of 4 mm. Furthermore, the jet nozzles 20 of a nozzle row with respect to the row longitudinal direction offset relative to the jet nozzles 20 of the adjacent nozzle row arranged to prevent the emergence ei ^¬ nes strip-shaped spray pattern on the metal strip. 4

In the case of the injection device 12b of the second type, each of its injection units 50, 54, 58 has slot nozzles 22 of different width, which are disposed equidistantly one behind the other in the conveying direction 8 of the belt conveyor 6, the slot nozzles 22 being aligned perpendicular to the conveying direction 8.

In both the first-type spray device 12a and the second-type spray device 12b, the mordant distribution chambers 66 of the two outer injection units 50, 54 have a triangular cross-sectional shape, while the middle injection unit 58 has a cross-sectional shape corresponding to an isosceles trapezoid. The arrangement of the jet nozzles 20 and the width of the slot nozzles 22 is adapted to the respective injection unit 50, 54, 58 at the cross-sectional shape. Both in the sprayer 12a of the first type and in the sprayer 12b of the second type, the mordant distribution chambers 66 are separated from one another by partition walls, which are indicated by dashed lines in FIG.

Alternatively, or in addition to one or more of the spray device 12a, 12b of the first or second type, the descaling device 2 may have a spray device that is not divided into three injection units, the pickling ^¬ medium-withdrawal rates are adjustable independently of one another, but the only one injection unit having. Such a spray device may, for example, have slot nozzles which extend substantially the entire width of the spray device.

4 shows a mordant spray profile with which the metal ribbon ^¬ 4 of one of the spray devices 12a of the first type or of the injection devices of the second type 12b is aufschlagt loading, in the form of a diagram.

In the diagram, the seed quantity V sprayed onto the metal strip 4 by the spray device 12a, 12b is shown in the form of a solid line as a function of a length coordinate x in the width direction 62 of the metal strip 4. The value b of the abscissa length coordinate x corresponds to the width of the metal strip 4.

The contribution of the two outer injection units 50, 54 to the mordanting spray profile is shown in the diagram in each case by means of a dashed line, whereas the contribution of the central injection unit 58 is shown by means of a dotted line. The illustrated mordant spray profile has a mirror symmetry ^¬. In the central region 60 of the metal strip 4, the mordanting spray profile has a plateau 72. That is, in the central region 60, the mordanting spray profile changes not with the length coordinate x. In contrast, in the first and in the second edge region 52, 56 of the metal strip 4, the mordanting spray profile (starting from the plateau 72) increases toward the outside.

5 shows a spraying device 12c of a third type so as ^¬ a spraying device 12d of a fourth type.

These two spray devices 12c, 12d can be used in the descaling device 2 of FIG. 1 alternatively or additionally to one or more of the spray devices 12a, 12b described above.

The sprayer 12c of the third type, like the sprayer 12a of the first type, has a plurality of full jet nozzles 20, whereas the spray gun 12d of the fourth type, like the sprayer 12b of the second type, has a plurality of slot nozzles 22. The third and fourth type of sprayers 12c, 12d are different from the two first and second type of sprayers 12a, 12b in that the third type of sprayer 12c and the fourth type of sprayer 12d have the mordant distribution chambers 66 of the two outer injection units, respectively 50, 54 and the seed-dressing distribution chamber 66 of the central injection unit 58 have a three ^¬ polygonal cross-sectional shape.

In addition, in the embodiment of FIG. 5, for controlling the pickling agent discharge rate of the respective injection unit 50, 54, 58, valves 74 are provided instead of pickling agent feed pumps. In the present example, the valves 74 are each disposed in one of the mordant supply lines 68. The valves 74 can be controlled by a control unit such as the control unit 40 of the descaling device 2 from FIG. Basically, it is possible to use valves and pickling feed pumps in combination to control the Pickling agent exit rate of the respective injection unit 50, 54, 58 to use.

6 shows a mordanting-spray profile, with which a metal band 4 is acted upon when the Beizmittelbeaufschla ^¬ tion of the metal strip 4 one of the two spray devices 12c, 12d of FIG 5 is used.

This seed-dressing spray pattern is different from the seed-dressing spray profile of Figure 4 in that it has no Pla ^¬ teau in the central region 60 of the metal strip. 4 Instead, the pickling spray profile from FIG. 6 increases from the middle of the strip toward the outside. The mordant spray ^profiles shown in the diagrams of FIG. 4 and FIG. 6 are exemplary mordant spray ^profiles . In each of these two diagrams, the area enclosed by the two dashed lines and the dotted line with the abscissa represents by way of example a control range of the associated injection unit 50, 54, 58. Depending on the set pickling agent exit rate of the respective injection unit 50, 54, 58 can the sprayed on the metal ribbon 4 ^¬ Beizmittelmenge V in the first edge region 52, take other values in the middle region 60 and / or in the second edge region of the 56th

Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom without departing from the scope of the invention. LIST OF REFERENCE NUMBERS

2 descaling device

4 metal band

6 belt conveyor

8 conveying direction

10 roll

12 spray device

12a sprayer of the first type 12b sprayer of the second type

12c sprayer of the third type

12d sprayer fourth type

14 pickling agent

16 top

18 bottom

20 full jet nozzle

22 slot nozzle

24 pickpockets

26 chamber part

28 chamber part

30 pair of squeezing rollers

32 pair of squeezing rollers

34 squeezing roller

36 squeezing roller

38 control device

40 control unit

42a sensor unit

42b sensor unit

44 sensor array

46 sensor series

48 longitudinal direction

50 injection unit

52 edge area

54 injection unit 56 border area

58 injection unit

60 middle range

62 width direction

64 spray direction

66 Mordant distribution chamber

68 Pickling supply line

70 Pickling pump

72 plateau

74 valve

Claims

claims

A descaling device (2) for chemically descaling a metal strip (4) comprising at least one first injection device (12, 12a, 12c) and at least one other

Spray device (12, 12b, 12d) for spraying a mordant (14) to a top or bottom (16, 18) of Me ^¬ tallbandes (4),

- Wherein the first injection device (12, 12a, 12c) and the further injection device (12, 12b, 12d) each have a first outer injection unit (50) for spraying the etching agent (14) on a first edge region (52) of the top / bottom (16, 18) of the metal strip (4) and a second outer spray ^¬ unit (54) for spraying of the etchant (14) to a first edge region (52) opposed second edge region (56) of the top / bottom faces (16, 18 ) of the metal strip (4) and

- wherein said first spray device (12, 12a, 12c) is a mitt ^¬ sized injection unit (58) for spraying of the etchant (14) to a between the edge regions (52, 56) lying middle region (60) of the top / bottom (16 , 18) of the metal ^band (4),

characterized in that

- at least one of the injection units (50, 54, 58) of the first injection device (12, 12a, 12c) has a plurality of rows of full jet nozzles (20),

each of the injection units (50, 54, 58) of the first spray device (12, 12a, 12c) has its own pickling agent distribution chamber (66),

- At least one of the two outer injection units (50, 54) of the further injection device (12, 12 b, 12 d) one or more slot nozzles (22) and that

- Each of the two outer injection units (50, 54) of the further injection device (12, 12 b, 12 d) has its own pickling agent distribution chamber (66).

2. descaling device (2) according to claim 1, characterized in that the at least one further injection device (12, 12b, 12d) comprises a central injection unit (58) for spraying the etching agent (14) on a between the edge regions (52, 56) located central region (60) of the top / bottom (16, 18) of the metal strip (4), said central injection unit (58) of the further Spritzvorrich ^¬ device (12, 12b, 12d) has one or more slot nozzles (22) and a separate mordant-distribution chamber (66).

3. descaling device (2) according to one of the preceding claims,

characterized in that the spray device (12, 12a-12d) is designed as a spray bar.

4. descaling device (2) according to one of the preceding claims,

characterized by a control device (38) by means of which a pickling agent outlet rate of the respective spray ^¬ unit (50, 54, 58) of the injection device (12, 12a-12d) can be adjusted.

5. descaling device (2) according to one of the preceding claims,

characterized in that by means of the control device (38), the pickling agent outlet rate of the central injection unit (58) independently of the pickling agent outlet rate of the first outer injection unit (50) and independently of the pickling agent outlet rate of the second outer injection unit (54) ^ein¬ adjustable is.

A descaling device (2) according to claim 4 or 5, characterized in that the control device (38) comprises a plurality of seed-conveying pumps (70) for adjusting the pickling-discharge rates of the injection units (50, 54, 58), the pickling-conveying pumps (70) on the output side with the spray device (12, 12a-12d) are connected.

A descaling device (2) according to any one of claims 4 to 5,

characterized in that the control device (38) comprises a plurality of valves (74) for adjusting the pickling agent outlet rates of the injection units (50, 54, 58), the

Spraying device (12, 12a-12d) on the input side with the Venti ^¬ sources (74) is connected.

8. descaling device (2) according to one of claims 4 to 7,

characterized in that the control device (38) has a sensor unit (42a, 42b) with one or more sensors for detecting a surface parameter of the metal strip (4), in particular a surface parameter dependent on a scale layer thickness of the metal strip (4), and the control device (38) is adapted to adjust the pickling agent discharge rate of the respective injection unit (50, 54, 58) in response to an output signal of the sensor unit (42a, 42b).

9. A process for the chemical descaling of a metal strip (4), in which by means of at least one first spray device (12, 12a, 12c) and at least one further spray device (12, 12b, 12d) a pickling agent (14) on an upper or lower side ( 16, 18) of the metal strip (4) is sprayed, wherein the mordant (14)

from a first outer injection unit (50) of the first injection device (12, 12a, 12c) and from a first outer injection unit (50) of the further injection device (12, 12b, 12d) to a first edge region (52) of the upper / lower side (16, 18) of the metal strip (4) and

from a second outer injection unit (54) of the first injection device (12, 12a, 12c) and from a second outer injection unit (54) of the further injection device (12, 12b, 12d) to a second edge region opposite the first edge region (52) ( 56) of the top / bottom (16, 18) of the metal strip (4) and from a central injection unit (58) of the first injection device (12, 12a, 12c) to a middle region (60) of the upper / lower side (16, 18) of the metal strip (4) located between the edge regions (52, 56)

is sprayed on,

characterized in that

the etching agent (14) of at least one of the injection ^units (50, 54, 58) of the first injection device (12, 12a,

12c) through a plurality of rows of full jet nozzles (20) and

- Of at least one of the two outer injection units

(50, 54) of the further spray device (12, 12b, 12d) through one or more slot nozzles (22)

on the top / bottom (16, 18) of the metal strip (4) is injected ^¬ .

10. The method according to claim 9,

characterized in that the pickling means (14) through one or more slot nozzles (22) of a central injection unit (58) of the at least one further spray device (12, 12b, 12d) on a middle region between the two edge regions (52, 56) ( 60) of the top / bottom (16, 18) of the metal strip (4) is sprayed.

11. The method according to claim 10,

characterized in that a pickling agent discharge rate of the first outer injection unit (50) and a pickling agent discharge rate of the second outer injection unit (54) of the at least one first spraying device (12, 12a, 12c) and / or the at least one further spraying device (12, 12b, 12d) by means of a control device (38) are each set to a value which is different from a pickling agent outlet rate of the respective central injection unit (58) of the first injection device and the other injection device.

12. The method according to claim 11,

characterized in that the pickling agent discharge rate of the respective injection unit (50, 54, 58) of the at least one first injection device (12, 12a, 12c) and / or the at least one further injection device (12, 12b, 12d) is adjusted by means of the control device (38) such that the metal strip (4) in its width direction (62) from the first injection device (12, 12a, 12c) and / or from the others

Spraying device (12, 12b, 12d) is acted upon with a predetermined etching agent spray profile, wherein the etching agent spray profile in the first and / or in the second edge region (52, 56) increases towards the outside or decreases.

13. The method according to claim 12,

characterized in that the mordanting spray profile is pla ^¬ teaulos.

14. The method according to claim 12,

characterized in that the mordanting-Spritzprofil zwi ^¬ tween the two edge regions (52, 56) has a plateau (72).