EP3606682B1 - Descaling device and method for chemically descaling a metal strip - Google Patents

Description

The invention relates to a descaling device for chemically descaling a metal strip according to the preamble of claim 1 and a method for chemically descaling a metal strip according to the preamble of claim 9, as from JP S51 147449 A is known.

When a metal strip is hot rolled, a layer of scale forms on its surface. Before any subsequent cold rolling of the metal strip, the layer of scale must be removed. For this reason in particular, a metal strip is usually subjected to descaling after hot rolling, during which the scale layer is removed.

In the field of chemical descaling of a metal strip, in which a mostly acidic pickling agent is used, a distinction is made between so-called dip pickling and so-called spray pickling. In dip pickling, the metal strip to be treated is immersed in a dip tank filled with the pickling agent, whereas in spray pickling, the pickling agent is sprayed onto the metal strip to be treated. Spray pickling technology is characterized by a short treatment time compared to dip pickling. The invention is based on the object of making it possible to achieve high pickling effectiveness in a spray pickling treatment of a metal strip.

This object is achieved according to the invention by a descaling device according to claim 1 and by a method according to claim 9.

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

The descaling device according to the invention for chemically descaling 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 further spraying device have a first outer spraying unit for spraying the pickling agent onto a first edge area of the upper/lower side of the metal strip and a second outer spraying unit for spraying the pickling agent onto a second edge area of the upper/lower side of the metal strip opposite the first edge area on. In addition, the first spraying device also has a central spraying unit for spraying the pickling agent onto a central region of the upper/lower side of the metal strip located between the edge regions.

At least one of the two outer or the middle spraying unit of the first spraying device has several rows of full jet nozzles and each of the spraying units of the first spraying device has its own dressing agent distribution chamber.

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

The nozzles of the respective injection unit are advantageously connected to their dressing agent distribution chamber. Such an embodiment of the spray device enables the spray device to be manufactured in a structurally simple manner and requires little control effort for the spray device.

Due to their simple geometry, solid jet nozzles are comparatively robust and inexpensive to manufacture.

While previously used in descaling nozzles such. B. flat jet nozzles, tongue nozzles or cone jet nozzles, each generate a jet that widens and thus has an inhomogeneous impulse distribution, a closed, stable and high-energy full jet can be generated with the help of a full jet nozzle, which has a homogeneous impulse distribution across its jet diameter and spreads over a great length not or hardly widens. With such a high-energy full jet, a laminar boundary layer of the pickling agent that forms or has been 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 effectiveness. In addition, such a high-energy full jet enables adhering scale to be "sprayed away" mechanically.

Due to the higher pickling effectiveness, the treatment time required for complete descaling of the metal strip can be shortened. This enables a shorter treatment section (shorter structural length) or - with the same treatment section - a higher conveying speed of the metal strip.

Furthermore, when using one or more full-jet nozzles - since the jet of a full-jet nozzle does not widen or hardly widens over a long distance and thus makes a high impact on the metal strip surface possible - a lower pickling agent supply pressure is required for the spraying device than when using Flat jet nozzles, tongue nozzles or cone jet nozzles to achieve the same pickling effect. This in turn enables lower operating costs, e.g. B. because cheaper pumps can be used. For example, the spraying device can be operated with a dressing supply pressure of 4 bar.

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

The full-jet nozzles of the spraying device preferably each have a dressing-agent outlet hole with a non-constant cross-section. For example, the cross-sectional area of the dressing agent outlet hole of the respective full-jet nozzle can decrease toward the outlet-side nozzle end of the full-jet nozzle. The end of the nozzle facing the metal strip is to be understood as the outlet-side nozzle end of a nozzle. Correspondingly, the end of the nozzle facing away from the metal strip is to be understood as the inlet-side nozzle end of a nozzle.

The narrowest point of the dressing agent outlet hole of the respective solid jet nozzle is preferably located at the nozzle end on the outlet side. The dressing agent outlet hole of the respective full jet nozzle can in particular be designed in the shape of a funnel.

Furthermore, it is preferred if the dressing agent outlet bore of the respective full jet nozzle has an inside diameter of at least 2 mm and at most 6 mm at its narrowest point. It is particularly preferred if the dressing agent outlet hole of the respective full jet nozzle has an inner diameter of 4 mm at its narrowest point.

A further development of the descaling device according to the invention provides that the additional spraying device also has a central spraying unit with one or more slot nozzles for spraying the pickling agent onto a central area of the upper/lower side of the metal strip located between the edge areas, as well as its own pickling agent distribution chamber.

While a pickling agent jet generated by a solid jet nozzle typically results in a point-like pickling agent being applied to the metal strip surface, a pickling agent jet generated by a slot nozzle, usually in a linear application of pickling agent to the metal strip surface. With the help of a slot nozzle, a closed, stable and high-energy jet can be generated, which has a homogeneous impulse distribution and does not widen or hardly widens over a long distance. By using one or more slit nozzles, similar advantages can be achieved as with the use of one or more solid jet nozzles.

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

The two outer injection units are preferably equipped with nozzles of the same type. If the first outer βere injection unit z. B. has one or more full jet nozzles, the second outer injection unit advantageously also has one or more full jet nozzles. If the first outer injection unit has one or more slit nozzles, the second outer injection unit advantageously also has one or more slit nozzles.

It is also advantageous if the spraying device has a central spraying unit for spraying the pickling agent onto a central area of the upper/lower side of the metal strip located between the edge areas. It is particularly preferred if the middle injection unit has one or more full jet nozzles, in particular several rows of full jet nozzles, and/or one or more slotted nozzles, in particular for the reasons mentioned above.

Each of the aforesaid spraying units advantageously comprises a set of nozzles for spraying the pickling agent on the upper/lower side of the metal strip.

Advantageously, the spray device is designed as a spray bar. In this case, the dressing agent distribution chambers mentioned above can be formed, for example, with the aid of partition walls, in particular partition plates, arranged inside the spray boom. In other words, if the spraying device is designed as a spray bar, the individual dressing agent distribution chambers can be separated from one another by a plurality of partitions, in particular metal partitions. The partition walls preferably bring about only a small reduction in the internal volume of the spray boom, so that friction losses inside the spray boom can be kept low.

In another variant of the invention, the spraying device can, for example, comprise separate spray bars, which form the above-mentioned spraying units. In such a case, it is expedient if these separate spray bars are offset from one another perpendicularly to the conveying direction. They can also be arranged offset from one another in the conveying direction. Alternatively, the separate spray bars can be arranged in the same position in relation to the conveying direction.

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

The spray device preferably has an internal height of at least 10 cm. This makes it possible to avoid high pressure gradients inside the spraying device. The inner height of the spraying device is to be understood as meaning its inner dimension perpendicular to the upper/lower side of the metal strip.

The descaling device can have its own pickling agent supply line for each of the three injection units. Preferably, the descaling device comprises a first dressing agent supply line, which is connected to the first outer injection unit on the outlet side, a second dressing agent supply line, which is connected to the second outer injection unit on the outlet side, and a third dressing agent supply line, which is connected to the middle injection unit on the outlet side is.

Advantageously, each of the three treatment agent supply lines opens into the respective injection unit perpendicular to its injection direction. This means that the first treatment agent supply line advantageously opens into the first outer injection unit perpendicular to the spraying direction of the first outer injection unit, while the second treatment agent supply line opens into the second outer injection unit perpendicular to the spraying direction of the second outer injection unit and the third treatment agent supply line opens perpendicular to the Injection direction of the middle injection unit opens into the middle injection unit. In this way, a uniform pressure distribution in the individual injection units and thus a uniform pressure distribution at their nozzles can be achieved.

Each of the spraying units is advantageously set up to spray the pickling agent perpendicularly or essentially perpendicularly onto the upper/lower side of the metal strip. This will e.g. This is achieved, for example, when the nozzles of the injection units are aligned in such a way that the injection units each have an injection direction that is perpendicular or essentially perpendicular to the top/bottom side of the metal strip, i.e. vertically or essentially vertically upwards or vertically or essentially vertically downwards.

The direction in which the injection unit applies the dressing is to be understood as the injection direction of the respective injection unit squirts. The phrase "substantially perpendicular to the top/bottom of the metal strip" can be understood as deviating from the right angle to the top/bottom of the metal strip by up to +/-20°, preferably up to +/-10°.

Furthermore, at least one of the injection units of the injection device can be mounted such that it can be tilted/pivoted, 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 discharge rate of the respective spray unit of the spray device can be adjusted, in particular continuously or in a number of discrete steps.

The discharge rate of the dressing agent from the respective injection unit is to be understood as the amount of dressing agent exiting from the respective injection unit per unit of time, ie the volume flow of the dressing agent exiting from the respective injection unit.

Within the meaning of the invention, controlling a variable can be a regulation of this variable, i. H. Controlling with a measured value feedback, include. The previously mentioned control device can therefore in particular be a regulating device.

In addition, according to the invention, a variable can be "adjusted in several discrete steps" if this variable can also be set to a further value between these two values in addition to the value zero and a maximum value of the variable (achievable in the descaling device). In other words, within the meaning of the invention, a variable can be “adjusted in a number of discrete steps” if this variable can be set to at least two other values in addition to the value zero.

The control device can be used to set the dressing agent discharge rate of the middle injection unit, preferably independently of the dressing agent discharge rate of the first outer injection unit and independently of the dressing agent discharge rate of the second outer injection unit. This makes it possible to set the pickling agent treatment of the metal strip in the width direction on the upper/lower side of the metal strip depending on the width profile of the scale layer thickness on the upper/lower side of the metal strip.

Typically, the thickness of the scale layer is greater at the strip edges than in the middle of the strip. If the metal strip is uniformly exposed to the pickling agent across its width, the result is that, in the case of heavy exposure to the pickling agent, the middle area of the strip is "overpickled", i.e. not only the layer of scale but also the underlying base material is removed by the pickling agent, whereas in the case of a weak application of pickling agent, the layer of scale is not completely removed, especially at the strip edges.

If the metal strip has a thicker layer of scale at the edge areas of its top/bottom than in the middle area between the top/bottom, the pickling agent discharge rate of the middle injection unit can be set to a lower value than the pickling agent discharge rate of the outer injection units. In this way it is possible to achieve a homogeneous descaling result. In addition, since overpickling of the metal strip can be avoided, it is possible to reduce the need for the pickling agent, which in turn makes it possible to reduce the amount of regeneration of the pickling solution.

In a preferred manner, the control device can be used to set the rate of discharge of the dressing agent from the first outer injection unit independently of the rate of discharge of the dressing agent from the second outer injection unit. This makes it possible to be the first Edge area of the top/bottom of the metal strip to be applied with a different amount of pickling agent than the second edge area of the top/bottom of the metal strip.

Furthermore, the control device can include several dressing agent delivery pumps, which are connected to the spray device on the output side. The dressing agent can be conveyed to the spraying device with the aid of the dressing agent feed pumps. The dressing feed pumps can be used to adjust the dressing dispensing rates of the injection units. The pickling agent delivery pumps can in particular be frequency-controlled pumps.

One of the dressing supply pumps can be connected to the two outer spray units while another of the dressing supply pumps can be connected to the middle spray unit. Alternatively, a first dressing agent feed pump can be connected to the first outer injection unit, a second dressing agent feed pump to the second outer injection unit, and a third dressing agent feed pump to the middle injection unit.

The pickling agent feed pumps are preferably connected to a control unit of the control device. The control unit is advantageously set up to set the delivery rate of the respective dressing agent delivery pump, in particular continuously or in a number of discrete steps. It is also advantageous if the delivery rate of the respective pump can be adjusted independently of the delivery rates of the other pickling agent delivery pumps. By changing the respective delivery rate, the discharge rate of the dressing agent of the respective injection unit can be changed.

Furthermore, the control device can include a plurality of valves. These can be used as an alternative or in addition to the dressing feed pumps for adjusting the dressing discharge rates of the injection units. Advantageously, the spray device is on the inlet side with the valves connected, in particular via the aforementioned mordant supply lines.

A common valve or a separate valve can be provided for the two outer injection units. A separate valve is preferably provided for the central injection unit. It is also advantageous if the valves are connected to the control unit of the control device.

The control unit is preferably set up to set the valve position of the respective valve, in particular continuously or in a number of discrete steps. By changing the respective valve position, the discharge rate of the dressing agent of the respective injection unit can be changed.

Furthermore, the aforementioned dressing agent supply lines can each be equipped with a pressure and/or flow sensor for monitoring the dressing agent pressure or dressing agent flow rate in the respective dressing agent supply line. These sensors are preferably connected to the control unit of the control device. The control device, in particular its control unit, can be set up to control the aforementioned dressing agent delivery pumps and/or the valves as a function of the sensor signals from these sensors.

In addition to the above-mentioned spraying units, the spraying device can have further spraying units for spraying the pickling agent onto the upper/lower side of the metal strip. For example, the injection device can have a first further injection unit between the middle and the first outer injection unit and have a second further injection unit between the middle and the second outer injection unit. The discharge rate of the dressing agent from the respective further injection unit is preferably independent of the discharge rate of the dressing agent by means of the control device of the other injection units of the injection device.

In addition, the control device can have a sensor unit with one or more sensors for detecting a surface parameter of the metal strip, in particular a surface parameter dependent on a scale layer thickness of the metal strip.

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

Furthermore, the sensor unit can be set up in particular to measure said surface parameter in a spatially resolved manner over the width of the metal strip, ie a width profile of the surface parameter. In relation to the conveying direction, the sensor unit can be arranged in front of or behind the spraying device.

In addition, it is advantageous if the sensor unit is connected to the control unit of the control device. The control device, in particular its control unit, is preferably set up to adjust the discharge rate of the dressing agent from the respective injection unit as a function of an output signal from the sensor unit.

Furthermore, the pickling agent discharge rate of the respective injection unit can depend on one or more known production parameters, such as e.g. B. the so-called coiling temperature of the metal strip and / or its material quality can be controlled. Such a parameter is advantageously transmitted to the control device, in particular to its control unit. The control unit is preferably set up to determine the discharge rate of the dressing agent that is to be set for the respective injection unit based on the data sent to the control unit to calculate transmitted sensor signals and/or production parameters.

Furthermore, the descaling device has at least one additional spraying device, in particular at least one additional spray bar, for spraying the pickling agent onto the same side of the metal strip as the first-mentioned spraying device. The first-mentioned and the other spraying device(s) are preferably arranged one behind the other in the conveying direction.

Just like the first-mentioned spraying device, such a further spraying device can have a first outer spraying unit for spraying the pickling agent onto the first edge area of the upper/lower side of the metal strip and a second spraying unit for spraying the pickling agent onto the second edge area of the upper/lower side of the metal strip. If necessary, such a further spraying device can have a central spraying unit for spraying the pickling agent onto the central area of the upper/lower side of the metal strip. In such a further spraying device, the discharge rates of the dressing agent from its spraying units can preferably be controlled by means of the control device in the same way as the discharge rates of the dressing agent from the spraying units of the first-mentioned spraying device.

Furthermore, the first-mentioned and the further spraying device(s) can have different types of nozzles. One of the spray devices can, for. B. (exclusively) have jet nozzles, another of the spray devices in turn can, for. B. (exclusively) slot nozzles.

In addition, the descaling device can have at least one additional spraying device for spraying the pickling agent onto the other side of the metal strip. The wording "other side" of the metal strip is to be understood as follows: If the spraying device mentioned first sprays the pickling agent onto the upper side of the metal strip, the other side is the bottom of the metal band. Conversely, if the former spraying device sprays the pickling agent on the underside of the metal strip, the other side is the top side of the metal strip. The features mentioned in connection with the first-mentioned spraying device can relate in an analogous manner to such an additional spraying device.

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

Furthermore, the descaling device can have a dip tank for a dip pickling treatment of the metal strip. In relation to the conveying direction, this is preferably arranged behind the spray device. The dip pickling treatment in the dip tank can serve to even out the pickling effect and/or to remove scale residues that have not been removed during the spray treatment.

In addition, the descaling device can have a further dip tank for a dip pickling treatment of the metal strip, with the spraying device being able to be arranged, for example, between the two dip tanks in relation to the conveying direction.

In the method according to the invention for chemically descaling a metal strip, a pickling agent is sprayed onto an upper or lower side of the metal strip with the aid of at least one first spray device and at least one further spray device. In this case, the pickling agent is applied by a first outer spraying unit of the first and the further spraying device to a first edge area of the upper/lower side of the metal strip and from a second outer Injection unit of the first and the further injection device sprayed onto a second edge region of the upper/lower side of the metal strip opposite the first edge region. In addition, a pickling agent is sprayed from a middle spraying unit of the first spraying device onto a middle area of the top/bottom side of the metal strip located between the edge areas. In the method according to the invention, it is provided that the dressing is sprayed from at least one of the two outer spraying units or from the middle spraying unit of the first spraying device through several rows of solid jet nozzles and from at least one of the two outer spraying units of the further spraying device through one or more slotted nozzles onto the upper -/underside 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 spraying unit of the at least one further spraying device onto a central 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 to carry out the method according to the invention. This means that the devices mentioned in connection with the method can in particular be elements of the descaling device.

The spraying of the pickling agent onto the metal strip preferably causes not only a chemical descaling of the metal strip, but also a mechanical removal of the layer of scale.

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, the pickling agent that is sprayed onto the metal strip is or contains an acid, such as e.g. e.g. hydrochloric acid. The metal strip can 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 dressing agent discharge rate of the first outer spray unit and a dressing agent discharge rate of the second outer spray unit of the at least one first spray device and/or the at least one additional spray device are each set to a value with the aid of a control device that depends on a dressing agent -Exit rate of the respective middle injection unit of the first injection device and the further injection device is different. In this way, a homogeneous descaling result can be achieved, particularly in the event that the scale has a different thickness in the edge regions than in the middle region.

For example, the pickling agent exit rate of the first outer injection unit and the pickling agent exit rate of the second outer injection unit can be set using the control device to a value that is greater than the pickling agent exit rate of the middle injection unit, especially in the case of a larger scale layer thickness on the two edge areas .

In principle, it is possible for the dressing agent exit rate of the first outer injection unit and the dressing agent exit rate of the second outer injection unit to be set to different values using the control device. It is e.g. B. possible that only the discharge rate of dressing of the two outer injection units is adjusted using the control device to a value that is different from the discharge rate of dressing of the middle injection unit.

Preferably, the pickling agent discharge rate of the respective injection unit of the at least one first spraying device and/or the at least one further spraying device is set with the aid of the control device in such a way that the metal strip is subjected to a predetermined pickling agent spraying profile in its width direction by the first and/or the further spraying device becomes. The spray profile of the pickling agent is to be understood as the profile of the quantity of pickling agent applied to the metal strip by the spraying device along a predetermined direction (here: the direction of the width of the metal strip).

In the first and/or in the second edge region, the spray profile of the dressing agent can increase or decrease outwards, in particular increase or decrease linearly. Furthermore, the spray profile can be symmetrical with respect to the center plane of the strip. In the present case, a strip center plane is to be understood as a vertical plane with respect to which the metal strip has mirror symmetry.

Furthermore, the pickling spray profile that is applied to the metal strip can have no plateau. Alternatively, the mordant spray profile can have a plateau, in particular between the two said edge areas.

A mordant spray profile of the type mentioned above can, for. B. be realized in that the nozzles of the first outer injection unit are arranged next to each other in a triangle, the nozzles of the second outer injection unit are arranged next to each other in a triangle and the nozzles of the middle injection unit are arranged in a trapezoidal shape, in particular in the form of an isosceles trapezoid, or also in a triangular shape next to each other.

The description given so far of advantageous configurations of the invention contains numerous features, some of which are summarized in the individual dependent patent claims. However, these features can can also be considered individually and combined to form other meaningful 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, method features can also be seen as a property of the corresponding device unit.

Although some terms in the specification and claims are used in the singular or in conjunction with a numeral, the scope of the invention should not be limited to the singular or the respective numeral.

The properties, features and advantages of the invention described above and 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 exemplary embodiments serve to explain the invention and do not limit the invention to the combinations of features specified therein, not even in relation to functional features. In addition, suitable features of each exemplary embodiment can also be explicitly considered in isolation, removed from one exemplary embodiment, introduced into another exemplary embodiment to supplement it and combined with any of the claims.

If the same reference symbols are used in different figures, then these designate essentially the same or corresponding elements. For reasons of expediency, however, elements which are essentially the same or correspond to one another can also be denoted by different reference symbols.

FIG 1

ein Ausführungsbeispiel einer erfindungsgemäßen Entzunderungsvorrichtung zum chemischen Entzundern eines Metallbandes;

FIG 2

einen Schnitt durch die Entzunderungsvorrichtung aus FIG 1;

FIG 3

eine Darstellung von zwei Spritzvorrichtungen der Entzunderungsvorrichtung;

FIG 4

ein Beizmittel-Spritzprofil, mit dem das Metallband in der Entzunderungsvorrichtung beaufschlagt wird;

FIG 5

eine Darstellung von zwei anderen Spritzvorrichtungen für eine Entzunderungsvorrichtung;

FIG 6

ein Beizmittel-Spritzprofil, mit welchem ein Metallband bei Verwendung einer der Spritzvorrichtungen aus FIG 5 beaufschlagt wird.

Show it:

FIG 1

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

FIG 2

cut out a section through the descaling device FIG 1 ;

3

a representation of two spray devices of the descaling device;

FIG 4

a pickling spray profile applied to the metal strip in the descaling device;

5

a representation of two other spray devices for a descaling device;

6

a mordant spray profile with which a metal strip when using one of the spray devices 5 is applied.

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

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

In addition, the descaling device 2 comprises a plurality of upper spraying devices 12 for spraying a pickling agent 14 containing hydrochloric acid onto an upper side 16 of the metal strip 4 and a plurality of lower spraying devices 12 for spraying the pickling agent 14 onto a lower side 18 of the metal strip 4. In FIG 1 four upper spray devices 12 and four lower spray devices 12 are shown as an example. In principle, the descaling device 2 a 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 device 6 . Likewise, the lower spray devices 12 are arranged one behind the other in the conveying direction 8 of the belt conveyor device 6 . Furthermore, the spray devices 12 are each designed as a spray bar.

In the present exemplary embodiment, all of the upper spray devices 12 of the descaling device 2 are arranged at the same height. This means that all of the upper spray devices 12 of the descaling device 2 are at the same distance from the upper side 16 of the metal strip 4 . In addition, all the lower sprayers 12 of the descaling device 2 are arranged at the same height. This means that all of the lower spray devices 12 of the descaling device 2 are at the same distance from the underside 18 of the metal strip 4 .

The distance between the upper spray devices 12 and the upper side 16 of the metal strip 4 can be smaller or larger than the distance between the lower spray devices 12 and the underside 18 of the metal strip 4 . Alternatively, these two distances can be the same. It is particularly preferred if the distance between the lower spray devices 12 and the underside 18 of the metal strip 4 is smaller than the distance between the upper spray devices 12 and the upper side 16 of the metal strip 4 .

Some of the upper and lower squirts 12 are squirts 12a of a first type. Others of the upper squirts 12 are squirts 12b of a second type. The spray devices 12a of the first type have a plurality of solid jet nozzles 20, whereas the spray devices 12b of the second type have a plurality of slot nozzles 22 (cf. 3 ).

In the present exemplary embodiment, the spray devices 12a of the first type and the spray devices 12b of the second type are arranged alternately in the conveying direction 8 of the belt conveyor device 6 . This means that a spray device 12a of the first type is followed in the conveying direction 6 by a spray device 12b of the second type, which in turn is followed in the conveying direction 8 by a spray device 12a of the first type and so on.

The sprayers 12b of the second type - i. 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 spray devices 12 does not necessarily have to be such an alternating arrangement. Furthermore, the same number of spraying device 12a of the first type and spraying device 12b of the second type does not necessarily have to be present. In addition, it is fundamentally possible to use only spray 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 pickling chamber 24 comprises a lower chamber part 26 for receiving the pickling agent 14 flowing off the metal strip 4 and an upper chamber part 28 arranged above the lower chamber part 26.

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

Furthermore, the descaling device 2 comprises a control device 38, of which FIG 1 whose control unit 40, whose first sensor unit 42a and whose second sensor unit 42b are shown.

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

The metal strip 4 is transported by the strip conveyor device 6 parallel to its longitudinal direction 48 through the descaling device 2 . In the pickling chamber 24 , the spraying devices 12 apply the pickling agent 14 to the metal strip 4 in order to chemically descale the metal strip 4 , ie to remove a layer of scale on the metal strip 4 .

The upper row of sensors 44 of the first sensor unit 42a detects a surface parameter of the metal strip 4 in front of the spray devices 12 spatially resolved over the width of the metal strip 4 , which parameter depends on the scale layer thickness on the upper side 16 of the metal strip 4 . Correspondingly, the lower row of sensors 46 of the first sensor unit 42a in front of the spray devices 12 spatially resolved over the width of the metal strip 4 detects a surface parameter of the metal strip 4, which is the scale layer thickness on the underside 18 of the metal strip 4 is dependent.

The upper row of sensors 44 of the second sensor unit 42b behind the spray devices 12 also detects a surface parameter of the metal strip 4 spatially resolved over the width of the metal strip 4, which is dependent on the scale layer thickness on the upper side 16 of the metal strip 4. Correspondingly, the lower row of sensors 46 of the second sensor unit 42b behind the spray devices 12 spatially resolved over the width of the metal strip 4 detects a surface parameter of the metal strip 4 which is dependent on the scale layer thickness on the underside 18 of the metal strip 4 . The rows of sensors 44, 46 of the second sensor unit 42b can in particular each detect the same surface parameter as the rows of sensors 44, 46 of the first sensor unit 42a.

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

The application of the pickling agent to the metal strip 4 is controlled with the aid of the control unit 40 as a function of the aforementioned sensor signals in such a way that the most homogeneous possible descaling result is achieved, preferably with complete removal of the scale layer.

In principle, it is possible for the descaling device 2 to have only one of the two sensor units 42a, 42b instead of both sensor units 42a, 42b and for the treatment of the metal strip 4 with the pickling agent to be controlled as a function of the sensor signals on only one of the sensor units 42a, 42b.

The descaling device 2 can also have one or more immersion tanks (not shown in the figures) for an immersion pickling treatment of the metal strip 4 . For example, the descaling device 2 can have an immersion tank of the pickling chamber 24 and another immersion tank behind the pickling chamber 24 . In the respective immersion tank, the same pickling agent that is sprayed onto the metal strip 4 by the spraying devices 12, or a different pickling agent can be used.

FIG 2 shows a section through the descaling device 2 along the section plane II-II FIG 1 .

With reference to FIG 2 the design of the spray devices 12 is described in more detail below.

As already mentioned above, the spray devices 12 are each designed as a spray bar.

The upper spraying devices 12 each comprise a first outer spraying unit 50 for spraying the pickling agent 14 onto a first edge area 52 of the upper side 16 of the metal strip 4, a second outer spraying unit 54 for spraying the pickling agent 14 onto a second edge area 56 of the upper side opposite the first edge area 52 16 of the metal strip 4 and a central spraying unit 58 arranged between the two outer spraying units 50, 54 for spraying the pickling agent 14 onto a central region 60 of the upper side 16 of the metal strip 4 located between the edge regions 52, 56.

Correspondingly, the lower spraying devices 12 each comprise a first outer spraying unit 50 for spraying the pickling agent 14 onto a first edge area 52 of the underside 18 of the metal strip 4, a second outer spraying unit 54 for spraying the pickling agent 14 onto a second edge area 56 opposite the first edge area 52 Underside 18 of the metal strip 4 and a central spraying unit 58 arranged between the two outer spraying units 50, 54 for spraying the pickling agent 14 onto a central region 60 of the underside 18 of the metal strip 4 located between the edge regions 52, 56.

Said injection units 50, 54, 58 of the respective injection 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 (cf. 3 ).

In addition, the spraying units 50 , 54 , 58 are set up to spray the pickling agent 14 perpendicularly onto 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 such that the injection units 50, 54, 58 each have an injection direction 64 which is perpendicular to the top 16 or bottom 18 of the metal strip 4, i.e. vertically upwards or vertically down.

The distance between the spray devices 12 and the strip surface, more precisely the distance between their nozzles 20, 22 and 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 dressing agent distribution chamber 66, to which the nozzles 20, 22 of the respective injection unit 50, 54, 58 are each 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 treatment agent supply line 68 opens into the respective injection unit 50, 54, 58 perpendicularly to its injection direction 64, as a result of which an even pressure distribution in the individual injection units 50, 54, 58 is achieved.

Furthermore, the previously mentioned control device 38 comprises a plurality of dressing agent feed pumps 70, with a separate dressing agent feed pump 70 being provided for each of the injection units 50, 54, 58 in the present exemplary embodiment (cf. 3 ). Each of the injection units 50, 54, 58 is on the they connected dressing agent supply line 68 connected on the input side with the associated dressing agent feed pump 70. In principle, it is possible for spraying units 50 , 54 , 58 of different spraying devices 12 to be supplied with the dressing agent 14 via a common dressing agent feed pump 70 . In the latter case, the descaling device can have a total of three pickling agent feed pumps 70 for all the spray devices 12 together, for example.

Said dressing agent feed pumps 70 are also each connected to the previously mentioned control unit 40 of the control device 38, which is set up to control the dressing agent volume flows of the dressing agent feed pumps 70 using a predetermined control algorithm.

The control device 38 is set up to set the dressing agent discharge rate of the respective injection unit 50, 54, 58, independently of the dressing agent discharge rates of the other injection units 50, 54, 58. By changing the dressing agent volume flow of one of the dressing agent feed pumps 70, the control unit 40 can change the dressing agent discharge rate of the associated injection unit 50, 54, 58.

The sum of the pickling agent exit rates of the three spray units 50, 54, 58 of the respective spray device 12 is preferably in the range from 100 to 150 m ³ /h.

As previously mentioned, depending on the previously mentioned sensor signals from the sensor units 42a, 42b, the application of the pickling agent to the metal strip 4 is controlled in such a way that the most homogeneous possible descaling result is achieved.

If the scale layer thickness in the central region 60 of the metal strip 4 is less than at the edge regions 52, 56 of the metal strip 4, the pickling agent exit rate of its first outer spraying unit 50 and the pickling agent exit rate of its second outer Injection unit 54 is set by the control device 38 to a value that is greater than the pickling agent discharge rate of its central injection unit 58. If, on the other hand, the scale layer thickness in the central region 60 of the metal strip 4 is greater than at the edge regions 52, 56 of the metal strip 4 in the respective spraying device 12, the dressing agent discharge rate of its first outer spraying unit 50 and the dressing agent discharge rate of its second outer spraying unit 54 are each set by the control device 38 to a value that is smaller than the dressing agent discharge rate of its middle spraying unit 58.

If the scale layer thickness is symmetrical with respect to a vertical strip center plane, the respective spraying device 12 has its first outer spraying unit 50 and its second outer spraying unit 54 set its pickling exit rate to the same value by the controller 38 .

In the event of a production-related reduction in the conveying speed of the metal strip 4, one or more injection units 50, 54, 58 of the injection devices 12 can be switched off in order to prevent the metal strip 4 from being overpickled.

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

In 3 the previously mentioned solid jet nozzles 20 of the spray device 12a of the first type as well as the previously mentioned slot nozzles 22 of the spray device 12b of the second type are visible.

In addition, 3 the dressing supply pumps 70 already mentioned and the dressing supply lines 68 connected to the injection units 50, 54, 58 are shown.

In the spray device 12a of the first type, the full-jet nozzles 20 are arranged in a plurality of rows of nozzles aligned perpendicular to the conveying direction 8, with these rows of nozzles being arranged equidistantly from one another. In the respective row of nozzles, the full-jet nozzles 20 are also arranged equidistantly from one another.

The distance between adjacent solid jet nozzles 20 from the same row of nozzles can in particular correspond to the distance between adjacent rows of nozzles. This distance can B. be 25 mm. At their outlet opening, the solid jet nozzles 20 preferably have an inside diameter of 4 mm.

Furthermore, the full jet nozzles 20 of one row of nozzles are offset relative to the full jet nozzles 20 of the adjacent nozzle row with respect to the longitudinal direction of the row, in order to avoid the formation of a strip-shaped spray pattern on the metal strip 4 .

In the spraying device 12b of the second type, each of its spraying units 50, 54, 58 has slotted nozzles 22 of different widths, which are arranged equidistantly one behind the other in the conveying direction 8 of the belt conveyor device 6, with the slotted nozzles 22 each being aligned perpendicularly to the conveying direction 8.

Both in the spraying device 12a of the first type and in the spraying device 12b of the second type, the dressing agent distribution chambers 66 of the two outer spraying units 50, 54 have a triangular cross-sectional shape, while the middle spraying unit 58 has a cross-sectional shape that corresponds to an isosceles trapezium. The arrangement of the solid jet nozzles 20 and the width of the slotted nozzles 22 is adapted to the cross-sectional shape of the respective injection unit 50, 54, 58.

Both in the spraying device 12a of the first type and in the spraying device 12b of the second type, the pickling agent distribution chambers 66 are separated by partitions, which in 3 are indicated by dashed lines separated from each other.

Alternatively or in addition to one or more of the spray devices 12a, 12b of the first or second type, the descaling device 2 can have a spray device that is not divided into three spray units whose pickling agent exit rates can be adjusted independently of one another, but has only a single spray unit. Such a spray device can, for example, have slit nozzles which essentially extend over the entire width of the spray device.

FIG 4 FIG. 12 shows, in the form of a diagram, a pickling spray profile applied to the metal strip 4 by one of the spraying devices 12a of the first type or one of the spraying devices 12b of the second type.

In the diagram, the amount of pickling agent V sprayed onto the metal strip 4 by the spraying 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 spray units 50, 54 to the mordant spray profile is represented in the diagram by a dashed line, respectively, while the contribution of the middle spray unit 58 is represented by a dotted line.

The mordant spray profile shown has mirror symmetry. In the central area 60 of the metal strip 4, the spray profile of the pickling agent has a plateau 72. This means that the spray profile of the pickling agent changes in the middle area 60 not with the longitude coordinate x. In contrast, in the first and in the second edge region 52, 56 of the metal strip 4, the pickling spray profile (starting from the plateau 72) increases towards the outside.

5 12 shows an injection device 12c of a third type and an injection device 12d of a fourth type.

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

The spray device 12c of the third type, like the spray device 12a of the first type, has a plurality of solid jet nozzles 20, whereas the spray device 12d of the fourth type, like the spray device 12b of the second type, has a plurality of slot nozzles 22.

The spraying devices 12c, 12d of the third and fourth type differ from the two spraying devices 12a, 12b of the first and second type in that in the spraying device 12c of the third type and the spraying device 12d of the fourth type, the dressing agent distribution chambers 66 of the two outer spraying units 50, 54 and the dressing agent distribution chamber 66 of the central injection unit 58 have a triangular cross-sectional shape.

Also, in the embodiment are off 5 Valves 74 are provided for controlling the discharge rate of the dressing agent from the respective injection unit 50, 54, 58 instead of dressing agent feed pumps. In the present example, the valves 74 are each arranged in one of the dressing supply lines 68 . The valves 74 can be controlled by a control unit such as the control unit 40 of the descaling device 2 FIG 1 being controlled. In principle, it is possible to use valves and pickling feed pumps in combination to control the Dressing agent exit rate of the respective injection unit 50, 54, 58 to use.

6 shows a pickling spray profile with which a metal strip 4 is applied when one of the two spraying devices 12c, 12d is switched off to apply the pickling substance to the metal strip 4 5 is used.

This mordant spray profile differs from the mordant spray profile FIG 4 in that it has no plateau in the middle area 60 of the metal strip 4 . Instead, the mordant splash profile takes off 6 from the center of the band outwards.

Those in the diagrams of FIG 4 and 6 The mordant spray profiles shown are exemplary mordant spray profiles. In each of these two diagrams, the area enclosed by the two broken lines and the dotted line in each case with the abscissa represents an example of a control range of the associated injection unit 50, 54, 58 the amount of pickling agent V sprayed onto the metal strip 4 in the first edge area 52, in the central area 60 and/or in the second edge area 56 assume other values.

Although the invention has been 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.

Reference List

2

descaling device

4

metal strap

6

belt conveyor device

8th

conveying direction

10

role

12

spray device

12a

Spraying device of the first type

12b

Spraying device of the second type

12c

Sprayer of the third type

12d

Fourth type sprayer

14

mordants

16

top

18

bottom

20

full jet nozzle

22

slot nozzle

24

pickling chamber

26

chamber part

28

chamber part

30

pair of squeezing rollers

32

pair of squeezing rollers

34

squeeze roller

36

squeeze roller

38

control device

40

control unit

42a

sensor unit

42b

sensor unit

44

sensor array

46

sensor array

48

longitudinal direction

50

injection unit

52

edge area

54

injection unit

56

edge area

58

injection unit

60

middle area

62

latitude direction

64

spray direction

66

Treatment agent distribution chamber

68

Dressing supply line

70

Dressing agent feed pump

72

plateau

74

Valve

Claims (14)

1. Descaling device (2) for the chemical descaling of a metal strip (4), comprising at least one first spraying device (12, 12a, 12c) and at least one further spraying device (12, 12b, 12d) for spraying a pickling agent (14) onto the same top side or bottom side (16, 18) of the metal strip (4),

   - wherein the first spraying device (12, 12a, 12c) and the further spraying device (12, 12b, 12d) each comprise a first outer spraying unit (50) for spraying the pickling agent (14) onto a first edge region (52) of the top side/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 side/bottom side (16, 18) of the metal strip (4) situated opposite the first edge region (52),

   - wherein the first spraying device (12, 12a, 12c) comprises a middle spraying unit (58) for spraying the pickling agent (14) onto a middle region (60) of the top side/bottom side (16, 18) of the metal strip (4) situated between the edge regions (52, 56) and

   - wherein each of the spraying units (50, 54, 58) of the first spraying device (12, 12a, 12c) comprises its own pickling agent distribution chamber (66),
   characterized in that

   - at least one of the spraying units (50, 54, 58) of the first spraying device (12, 12a, 12c) comprises multiple rows of full jet nozzles (20),

   - at least one of the two outer spraying units (50, 54) of the further spraying device (12, 12b, 12d) comprises one or more slit nozzles (22) and in that

   - each of the two outer spraying units (50, 54) of the further spraying device (12, 12b, 12d) comprises its own pickling agent distribution chamber (66).
2. Descaling device (2) according to Claim 1,
   characterized in that the at least one further spraying device (12, 12b, 12d) comprises a middle spraying unit (58) for spraying the pickling agent (14) onto a middle region (60) of the top side/bottom side (16, 18) of the metal strip (4) situated between the edge regions (52, 56), wherein the middle spraying unit (58) of the further spraying device (12, 12b, 12d) comprises one or more slit nozzles (22) as well as its own pickling agent distribution chamber (66).
3. Descaling device (2) according to one of the preceding claims,
   characterized in that the spraying 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 dispersing rate of the respective spraying unit (50, 54, 58) of the spraying device (12, 12a-12d) is adjustable.
5. Descaling device (2) according to Claim 4,
   characterized in that by means of the control device (38) the pickling agent dispersing rate of the middle spraying unit (58) is adjustable independently of the pickling agent dispersing rate of the first outer spraying unit (50) and independently of the pickling agent dispersing rate of the second outer spraying unit (54).
6. Descaling device (2) according to Claim 4 or 5,
   characterized in that the control device (38) comprises multiple pickling agent delivery pumps (70) for adjusting the pickling agent dispersing rates of the spraying units (50, 54, 58), wherein the pickling agent delivery pumps (70) are connected at the exit side to the spraying device (12, 12a-12d).
7. Descaling device (2) according to one of Claims 4 to 5,
   characterized in that the control device (38) comprises multiple valves (74) for adjusting the pickling agent dispersing rates of the spraying units (50, 54, 58), wherein the spraying device (12, 12a-12d) is connected at the entry side to the valves (74).
8. Descaling device (2) according to one of Claims 4 to 7,
   characterized in that the control device (38) comprises a sensor unit (42a, 42b) having one or more sensors for detecting a surface parameter of the metal strip (4), especially a surface parameter dependent on the thickness of the scale layer of the metal strip (4), and the control device (38) is designed to adjust the pickling agent dispersing rate of the respective spraying unit (50, 54, 58) in dependence on an output signal of the sensor unit (42a, 42b).
9. Method for the chemical descaling of a metal strip (4), in which in each case a pickling agent (14) is sprayed onto the same top side or bottom side (16, 18) of the metal strip (4) by means of at least one first spraying device (12, 12a, 12c) and at least one further spraying device (12, 12b, 12d), wherein the pickling agent (14) is sprayed

   - by a first outer spraying unit (50) of the first spraying device (12, 12a, 12c) and by a first outer spraying unit (50) of the further spraying device (12, 12b, 12d) onto a first edge region (52) of the top side/bottom side (16, 18) of the metal strip (4) and

   - by a second outer spraying unit (54) of the first spraying device (12, 12a, 12c) and by a second outer spraying unit (54) of the further spraying device (12, 12b, 12d) onto a second edge region (56) of the top side/bottom side (16, 18) of the metal strip (4) situated opposite the first edge region (52) and

   - by a middle spraying unit (58) of the first spraying device (12, 12a, 12c) onto a middle region (60) of the top side/bottom side (16, 18) of the metal strip (4) situated between the edge regions (52, 56),
   characterized in that

   - the pickling agent (14) is sprayed onto the top side/bottom side (16, 18) of the metal strip (4) by at least one of the spraying units (50, 54, 58) of the first spraying device (12, 12a, 12c) through multiple rows of full jet nozzles (20) and

   - by at least one of the two outer spraying units (50, 54) of the further spraying device (12, 12b, 12d) through one or more slit nozzles (22).
10. Method according to Claim 9,
    characterized in that the pickling agent (14) is sprayed onto a middle region (60) of the top side/bottom side (16, 18) of the metal strip (4) situated between the two edge regions (52, 56) through one or more slit nozzles (22) of a middle spraying unit (58) of the at least one further spraying device (12, 12b, 12d) .
11. Method according to Claim 10,
    characterized in that a pickling agent dispersing rate of the first outer spraying unit (50) and a pickling agent dispersing rate of the second outer spraying 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) are set by means of a control device (38) to a respective value which is different from a pickling agent dispersing rate of the respective middle spraying unit (58) of the first spraying device and the further spraying device.
12. Method according to Claim 11,
    characterized in that the pickling agent dispersing rate of the respective spraying unit (50, 54, 58) of the at least one first spraying device (12, 12a, 12c) and/or the at least one further spraying device (12, 12b, 12d) is set with the aid of the control device (38) such that the metal strip (4) is acted upon in its width direction (62) by the first spraying device (12, 12a, 12c) and/or by the further spraying device (12, 12b, 12d) with a given pickling agent spray profile, wherein the pickling agent spray profile increases or decreases to the periphery in the first and/or in the second edge region (52, 56).
13. Method according to Claim 12,
    characterized in that the pickling agent spray profile has no plateau.
14. Method according to Claim 12,
    characterized in that the pickling agent spray profile has a plateau (72) between the two edge regions (52, 56).

Images