DE102018211182A1 - Device and method for hot dip coating a metal strip - Google Patents

Abstract

The invention relates to a device (10) for the hot dip coating of a metal strip (1), with a continuous furnace for passing and heating the metal strip (1), with a device arranged in the running direction (L) of the metal strip (1) behind the continuous furnace with a melt ( 11.1) filled vessel (11), with a trunk (13) arranged between the continuous furnace and the vessel (11) for passing and introducing the metal strip (1) into the melt (11.1) in the vessel (11), the trunk (13 ) comprises a blow-suction unit (14) with at least one blow-in unit (14.1) and at least one suction unit (14.2), which is arranged on at least one wall (13.1), in particular on two opposite walls (13.1) of the trunk (13) are, wherein the at least one suction unit (14.2) in the running direction (L) of the metal strip (1) is arranged behind the at least one blowing unit (14.1), the at least one blowing unit (14.1) at least one key It opening (14.11) for blowing gas into the trunk (13) and the at least one suction unit (14.2) have at least one slot opening (14.21) for sucking gas out of the trunk (13), the slot opening (14.11, 14.21) being transverse extends to the running direction (L) of the metal strip (1), the at least one slot opening (14.11, 14.21) of the blowing unit (14.1) and / or suction unit (14.2) being arranged such that it is essentially flush with the wall (13.1) of the Closes proboscis (13) or partially protrudes into the proboscis (13).

Description

Technical field

The invention relates to a device for hot-dip coating a metal strip and a method for hot-dip coating a metal strip.

Technical Background (Background Art)

Conventional coil coating systems, such as systems for the continuous hot-dip galvanizing of steel strip, have in particular a continuous furnace, a molten bath (zinc bath), a device for adjusting the (zinc) coating thickness and a subsequent cooling device in the belt running direction. In the continuous furnace, the steel strip is heat-treated in the continuous process, the continuous furnace being able to be divided into several chambers in which different treatments, in particular in connection with different temperatures, can be carried out. These treatments can preferably include the setting of the desired mechanical properties in the steel strip base material by, for example, recrystallization of the steel structure. An area (chamber) in the continuous furnace can define a zone for reducing the iron oxides formed on the surface of the steel strip. Another area (chamber) can define a cooling zone in the continuous furnace, in which the steel strip is cooled, preferably under protective gas (HNX), to a temperature close to the temperature of the melting bath. The protective gas is intended to prevent the annealed strip from oxidizing prior to coating (galvanizing), as a result of which wetting and thus adhesion of the coating or coating (zinc layer) to the surface of the steel strip would not be possible, or would be possible only with difficulty, and thus the required quality requirements cannot be met. Because of the different treatments in particular, different gas atmospheres are therefore sometimes required in the areas (chambers) in the continuous furnace. The steel strip is carried out between the continuous furnace and the melting bath, excluding the ambient atmosphere, in a lock flooded with protective gas, which is also referred to in the trade as a proboscis.

In the operation of a continuous strip galvanizing plant, zinc vapor is generated, which gets into the proboscis. It was recognized that the steel strip moving in the direction of the zinc bath entrains protective gas downwards in the proboscis, the entrained protective gas on the zinc bath surface absorbing zinc vapor, which condenses or resublimates on the colder inner walls of the proboscis as the entrained protective gas rises and becomes zinc dust there settles, which falls on the zinc bath and / or the steel strip during operation and thus causes surface defects (galvanizing defects).

In order to reduce the formation of zinc dust within the proboscis in continuous strip galvanizing plants or to remove the zinc vapor and / or dust that is generated, devices are used within the proboscis which cause circulation of the atmosphere inside the proboscis by targeted blowing in at one or more points. combined with suction at one or more points to remove or remove the dusty atmosphere. For example, from the German patent DE 10 2015 108 334 B3 a device for avoiding surface defects caused by zinc dust on a steel strip to be coated in a continuous hot-dip galvanizing process is known, the steel strip to be coated being conveyable through the device at least in sections along an axial direction, with a blow-suction unit, the blow-suction -Unit has a plurality of injection openings for applying protective gas to the steel strip, wherein a plurality of injection openings are arranged or can be arranged on a first side of the steel strip and a plurality of injection openings on a second side of the steel strip, the blow-suction unit having a plurality of suction openings for suction of protective gas loaded with zinc vapor and / or zinc dust, wherein a plurality of suction openings on the first side of the steel strip and a plurality of suction openings on the second side of the steel strip are arranged or can be arranged, wherein the blow-suction unit has a blow-in area in which the blow-in openings are arranged, and a suction area, seen in the axial direction, behind the blow-in area in which the suction openings are arranged.

However, the arrangement of the blow-suction unit within the trunk leads to a reduction in the through-flow cross section of the steel strip, so that in the event of vibrations and / or fluctuating operating conditions in the strip galvanizing system, the strip does not prevent the strip from vibrating out of the plane of the strip running direction during operation, and thus contact with the blow-suction unit cannot be ruled out, which can result in damage to the belt and also in the system. There is a need for further optimization in relation to the state of the art.

Summary of the Invention

The invention is based on the object of an apparatus and a method for hot-dip coating a metal strip To provide with which or with which fluctuating operating conditions an operationally reliable coating process can be ensured.

This object is achieved by a device with the features of patent claim 1. Further advantageous embodiments of the invention are listed in the subordinate claims.

According to the invention, a device for hot-dip coating a metal strip is provided, with a continuous furnace for passing through and heating the metal strip, with a vessel arranged behind the continuous furnace in the running direction of the metal strip, with a vessel filled with melt, with a trunk arranged between the continuous furnace and the vessel for passing through and Introducing the metal strip into the melt in the vessel, the proboscis comprising a blow-suction unit with at least one blow-in unit and at least one suction unit, which are arranged on at least one wall, in particular on two opposite walls of the proboscis, the at least one suction unit is arranged behind the at least one blowing unit in the running direction of the metal strip, the at least one blowing unit closing at least one slot opening for blowing gas into the trunk and the at least one suction unit closing at least one slot opening m have suction of gas from the trunk, the at least one slot opening extending transversely to the running direction of the metal strip.

The inventors have found that by arranging the at least one slot opening of the blowing unit and / or suction unit, the at least one slot opening being essentially flush with the wall of the trunk and / or being arranged in alignment with the wall or (only) partially protrudes into the trunk, compared to the complete arrangement of the blow-suction unit within the trunk shown in the prior art, the flow cross-section is not disadvantageously reduced, so that contact between the metal band and trunk or (further) parts / components of the Rüssels can be excluded from this, thereby preventing damage and ensuring a reliable coating process. The blowing-suction unit with the at least one blowing unit and the at least one suction unit are or are mounted from the outside on the wall of the trunk, so that the blowing and / or suction unit with its or close their slot opening (s) flush with the wall of the proboscis or only a part of the blowing and / or suction unit with their slot opening (s) or only the section of the blowing and / or suction unit that the slot opening (en) includes, protrudes into the trunk. The blow-suction unit, which is arranged or installed from the outside on the wall of the trunk, also has the advantage of easy access, in particular also during operation, and thus the quick and uncomplicated maintenance and / or cleaning possibility. Preferably, an injection unit with a suction unit adjacent in the running direction of the metal strip is located opposite each other on two opposite walls of the trunk. The two opposite walls run essentially parallel to the surface of the metal strip. Two further (opposite) walls complete or define the trunk, which essentially has a rectangular cross section in the longitudinal direction, and are oriented essentially perpendicular to the edge of the metal strip.

The melt in the vessel is a metallic melt, which preferably consists of zinc or a zinc alloy or alternatively can consist of aluminum or an aluminum alloy.

The metal strip is preferably a steel strip.

A slot opening is defined by a slot-shaped cross section with a width b and a length I, where I is a multiple of b, in particular I> 10 * b, preferably I> 20 * b.

According to a first embodiment of the device, the blowing unit has a plurality of slot openings with interruptions therebetween. If several slit openings are provided, which are arranged in the transverse extension or transversely to the running direction of the metal strip, for example, a dense gas curtain can be generated so that the metal vapor rising from the melt is specifically prevented from further rising within the trunk or into the continuous furnace. The blowing unit preferably has at least two rows, exactly two rows or more than two rows can be provided, from a plurality of slot openings with interruptions therebetween, the slot openings of the rows being arranged offset to one another and in particular overlapping at least in sections adjacent to one another. Due to the arrangement in rows and the interruptions in the rows, the slot openings can be optimally used, since in particular the beam expansion occurring in the gas streams emerging from adjacent slot openings does not influence one another (negatively) and a closed gas curtain can thereby form. Due to the staggered arrangement of the slot openings in a blowing unit A tight gas curtain also forms on the slot openings or interruptions of the blowing unit provided on the opposite wall in the outer regions of the trunk, which are not traversed by the metal strip and in which the blown-in gas flows meet.

According to one embodiment of the device, the slot openings of the blowing unit have a width b1 with a distance a1 between the rows in the range of 2 * b1 a a1 4 4 * b1, with an overlap in sections ü1 lies in the range of a1 ≤ ü1 ≤ 2 * a1, with a length l1, which corresponds to 35 * b1 ≤ l1 ≤ 70 * b1. In order to set a gas curtain that is as tight as possible, the slot openings should not be too far apart from one another. It has been shown that, based on the width b1 of the slot openings of the blowing unit, a minimum distance between the rows of twice the width achieves good results, and at a distance of more than four times the width, the gas flow divides and a tight gas curtain can no longer be guaranteed.

According to one embodiment of the device, the suction unit has a plurality of slot openings with interruptions in between. If a plurality of slot openings arranged in the transverse extension or transverse to the running direction of the metal strip are provided with interruptions, effective suction can be favored so that the metal vapor rising from the melt can be extracted in a targeted manner. The suction unit preferably has at least two rows, in which case exactly two rows or more than two rows can be provided, from a plurality of slot openings with interruptions in between, the slot openings of the rows being offset from one another and in particular overlapping at least in sections adjacent to one another. Due to the arrangement in rows and the interruptions in the rows, the slot openings can be optimally used for suction and thus for the targeted removal of the rising metal vapor and / or dust.

According to one embodiment of the device, the slot openings of the suction unit have a width b2 with a spacing a2 between the rows in the range of 3 * b2 a a2 8 8 * b2, with a section overlap ü2 in the range of a2 ü ü2 2 2 * a2 , with a length l2, which corresponds to 20 * b1 ≤ l1 ≤ 60 * b1. The slot opening of the suction unit is preferably larger than the slot opening of the blowing unit, the widths and the lengths being in the following relationship to one another, with 3 * b1 b b2 10 10 * b1 and 2 * l1 l l2 6 6 * l1. The smaller dimension of the slot opening of the blowing unit is intended to cause a certain impulse in connection with a circulation of the atmosphere inside the trunk, whereby the larger dimension of the slot opening of the suction unit is to ensure that the metal vapor and / or metal dust is removed without clogging or clogging the slot opening (s) can be avoided and the maintenance intervals can be extended, in particular for cleaning.

According to one embodiment of the device, the at least one blowing unit and the at least one suction unit each comprise at least one central opening arranged opposite the slot opening for supplying or removing gas. As a result, the fluidic conditions can be kept largely the same across the width of the blowing and suction unit.

According to one embodiment of the device, the at least one blowing unit and / or the at least one suction unit, in particular in their longitudinal extension or transverse to the running direction of the metal strip, are divided into several sections, the sections being gas-tightly separated from one another and each section being provided with its own central opening is, in particular can be connected to a line for supplying or discharging gas. This division into sections of preferably the same width / length allows the flow conditions over the width of the trunk to be further improved and, in particular, the power required per line to be additionally reduced.

According to a preferred embodiment of the device, the blowing unit has an essentially nozzle-shaped cross section, the slot opening being provided in the narrowest region of the nozzle-shaped cross section, the slot opening or slot openings being / being provided in the end region of the nozzle-shaped cross section. The nozzle-shaped cross section has a geometry that is advantageous in terms of flow technology.

According to a preferred embodiment of the device, the suction unit has an essentially combined u-v-shaped cross-section, the slit opening being provided in the narrowest area or the slit openings in the end regions of the legs of the u-v-shaped cross-section. Such a design has a positive influence on the flow conditions and can improve the suction effect.

Devices according to the invention are preferably operated for hot-dip coating a metal strip in that a larger volume flow of gas is drawn off through the at least one suction unit than that through the at least one adjacent blowing unit injected volume flow of gas. The extracted volume flow is at least 1.5 times greater than the volume flow blown in by the adjacent blowing unit. This creates a negative pressure inside the trunk on the atmosphere located in the direction of travel of the metal strip below the suction unit, which can largely be used together with the gas curtain of the blowing unit to ensure that there is no backflow into the gas atmosphere in the trunk above the blowing unit and thus decoupling the gas atmosphere inside the proboscis can be guaranteed.

According to one embodiment of the method, the gas which is blown in consists of nitrogen or alternatively of a mixed gas. The mixed gas can contain nitrogen and hydrogen in a proportion of up to 10% by volume.

list of figures

• 1) eine skizzierte Darstellung einer Vorrichtung nach dem Stand der Technik,
• 2) eine schematische Darstellung einer erfindungsgemäßen Ausführung einer Vorrichtung im Querschnitt eines Rüssels,
• 3) eine perspektivische Teildarstellung der Ausführung in 2 und
• 4) einen schematischen Schnitt in der Ebene A-A entlang der Wandung des Rüssels gemäß 3.

The invention is explained in more detail below with reference to drawings. The same parts are always provided with the same reference numerals. Show in detail:

• 1 ) a sketched representation of a device according to the prior art,
• 2 ) a schematic representation of an embodiment of a device according to the invention in the cross section of a proboscis,
• 3 ) is a partial perspective view of the execution in 2 and
• 4 ) a schematic section in the plane AA along the wall of the trunk according to 3 ,

Description of the preferred embodiments (Best Mode for Carrying out the Invention)

In 1 is a sketched device ( 10 ) shown as it is known from the prior art. The device ( 10 ) is suitable for hot dip coating a metal strip ( 1 ), preferably a steel band ( 1 ), with a symbolic continuous furnace ( 12 ) for passing through and heating the metal strip ( 1 ), with a running direction ( L ) of the metal band ( 1 ) behind the continuous furnace ( 12 ) arranged with a melt ( 11.1 ) filled vessel ( 11 ), with a between the continuous furnace and the first vessel ( 11 ) arranged trunk ( 13 ) for passing through and introducing the metal strip ( 1 ) into the melt ( 11.1 ) in the vessel ( 11 ), with one in the vessel ( 11 ) arranged pulley ( 15 ) for deflecting and rejecting the metal strip ( 1 ) from the vessel ( 11 ). In the vessel ( 11 ) additional stabilizing rollers ( 18 ) which, in particular, the metal strip ( 1 ) on leaving the melt ( 11.1 ) stabilize and cause a smooth belt run, especially in connection with above the vessel ( 11 ) on both sides of the emerging metal strip ( 1 ) arranged scraping nozzles ( 19 ) to adjust the layer thickness on the metal strip ( 1 ), preferably for setting a constant layer thickness.

The trunk ( 13 ) includes a blow-suction unit ( 14 ) with at least one blowing unit ( 14.1 ) and at least one suction unit ( 14.2 ), which in particular on two opposite walls ( 13.1 ) of the trunk ( 13 ) are arranged. The at least one suction unit ( 14.2 ) is in the running direction ( L ) of the metal band ( 1 ) behind the at least one blowing unit ( 14.1 ) arranged, the at least one blowing unit ( 14.1 ) at least one slot opening ( 14:11 ) for blowing gas into the trunk ( 13 ) and the at least one suction unit ( 14.2 ) at least one slot opening ( 14:21 ) to extract gas from the trunk ( 13 ) exhibit. The slot opening ( 14:11 . 14:21 ) extends essentially transversely to the running direction ( L ) of the metal band ( 1 ). The arrangement of the blow-suction unit ( 14 ) inside the trunk ( 13 ) leads to a reduction in the cross-section of the metal strip ( 1 ), so that in the event of vibrations and / or fluctuating operating conditions in the device ( 10 ) for coating during operation an oscillation of the belt from the plane of the running direction ( L ) of the metal band ( 1 ) not prevented and thus also contact with the blow-suction unit ( 14 ) cannot be excluded, so that damage to the metal band ( 1 ) and also in the facility ( 10 . 13 ) can arise.

2 shows a schematic representation of an embodiment of the device according to the invention ( 10 ) in the cross section of a proboscis ( 13 ). The flow cross-section of the trunk ( 13 ) is no longer disadvantageously reduced, so that contact between the metal strip ( 13 ) and proboscis ( 13 ) or parts of it can be excluded and damage can be prevented and an operationally reliable coating process can be ensured. According to the invention, the blow-suction unit ( 14 ) outside the trunk ( 13 ) arranged, preferably from the outside on the wall ( 13.1 ) of the trunk ( 13 ) arranged or mounted, the at least one slot opening ( 14:11 . 14:21 ) the at least one blowing unit ( 14.1 ) and / or the at least one suction unit ( 14.2 ) is arranged such that it is essentially flush with the wall ( 13.1 ) of the trunk ( 13 ) completes. Alternatively, and not shown here, it can partly be placed in the trunk ( 13 ) protrude. This also prevents the circulation and / or flow of the gas within the proboscis ( 13 ) not negatively influencing parts / components compared to the prior art available. There are two opposite blowing units ( 14.1 ) with in the running direction ( L ) of the metal band ( 1 ) at a defined distance behind, two opposite suction units ( 14.2 ) arranged.

In 3 is a partial perspective view of the embodiment in 2 shown which virtually covers the area of the blow-suction unit ( 14 ) below the transport level of the metal belt ( 1 ) shows. In the partial representation it can be seen that the slot openings ( 14:11 ) of the blowing unit ( 14.1 ) are arranged offset to each other, cf. 4 , The illustration shows for the blowing unit ( 14.1 ) in the width direction of the proboscis ( 13 ) seen outermost slot opening ( 14:11 ) in the top, cf. 4 , or opposite to the running direction ( L ), Row arranged and the lower row begins with an interruption, viewed from left to right, cf. also 4 , The same applies to the in 3 opposite blowing unit (not shown) ( 14 ) the outermost slot opening ( 14:11 ) arranged in the lower row and the upper row begins with an interruption. This arrangement means that the slit openings ( 14:11 ) escaping gas flows, especially in their main extension, unhindered to the respective opposite wall ( 13.1 ), at least in the outer areas not traversed by the metal strip, or respectively meet the slot openings ( 14:11 ) facing surface of the metal strip ( 1 ), whereby the gas flows can only be touched in the area of the unavoidable areas of the beam expansions. This configuration achieves a gas curtain that is very stable and has a very good sealing effect.

The blowing unit ( 14.1 . 14'.1 ) has an essentially nozzle-shaped cross section, the slot opening (s) ( 14:11 ) in the narrowest area of the nozzle-shaped cross section or the slot opening (s) ( 14:11 ) in the end region of the nozzle-shaped cross-section, in particular opposite the central opening ( 14:12 ) arranged, is / are. The suction unit ( 14.2 . 14'.2 ), on the other hand, has an essentially combined u-shaped cross section, the slot opening ( 14:21 ) in the narrowest area or the slot openings ( 14:21 ) is / are provided in the end regions of the legs of the u-shaped cross section.

4 shows a schematic section ( AA ) in the plane of the wall ( 13.1 ) of the trunk ( 13 ) in top view on the surface of the metal strip ( 1 ) assigned side, quasi the one below the metal band ( 1 ) running wall ( 13.1 ) of the trunk ( 13 ), comprising an arrangement of a blow-suction unit according to the invention ( 14 . 14.1 . 14.2 ). The blowing unit ( 14.1 ) comprises two sections ( 14'.1 ), which are indicated by dashed lines in the drawing, with two rows of slot openings ( 14:11 ), the interruptions or spaces between the slot openings ( 14:11 ) exhibit. For the supply or discharge of gas to the blowing unit ( 14.1 . 14'.1 ) or from the suction unit ( 14.2 . 14'.2 ) lines are provided, which are not shown and which connect to the central openings ( 14:12 . 14:22 ) are connectable or are connected, cf. 3 ,

The slot openings ( 14:11 ) each have a width b1 and a length l1 on. The two rows of slot openings ( 14:11 ) are at a distance from each other a1 in the direction of travel ( L ) away. The slot openings ( 14:11 ) adjacent rows are offset from one another, so that an interruption of a row creates a slot opening ( 14:11 ) is assigned to the adjacent row. The slot openings ( 14:11 ) are longer than the interruptions in between, so that in the running direction ( L ) seen an overlap ( ü1 ) the ends of the slot openings ( 14:11 ) arises. The overlap ( ü1 ) is along the blowing unit ( 14.1 . 14'.1 ) trained uniformly.

In the direction of travel ( L ) is a suction unit ( 14.2 ) arranged, which also two sections ( 14'.2 ) and are indicated by dashed lines in the drawing, with two rows of slot openings ( 14:21 ), the interruptions or spaces between the slot openings ( 14:21 ) exhibit. The slot openings ( 14:21 ) each have a width b2 and a length l2 on. The two rows of slot openings ( 14:21 ) are at a distance from each other a2 in the direction of travel ( L ) away. The slot openings ( 14:21 ) adjacent rows are offset from one another, so that an interruption of a row creates a slot opening ( 14:21 ) is assigned to the adjacent row. The slot openings ( 14:21 ) are longer than the interruptions in between, so that in the running direction ( L ) seen an overlap (ü2) of the ends of the slot openings ( 14:21 ) arises. The overlap (ü2) is along the blowing unit ( 14.2 . 14'.2 ) trained uniformly. Compared to the slot openings ( 14:11 ) of the blowing unit ( 14.1 ) are the slot openings ( 14:21 ) of the suction unit ( 14.2 ) larger, with four slot openings in the upper row as shown and two slot openings in the row below ( 14:21 ) are provided.

The slot openings ( 14:11 . 14:21 ) close flush with the wall ( 13.1 ) of the trunk or are aligned with the wall ( 13.1 ) arranged or protruding (only) in part, in particular the part of the one with the blowing unit ( 14.1 ) and / or suction unit ( 14.2 ) related Slot openings ( 14:11 . 14:21 ), in the trunk ( 13 ) into it.

The invention is not limited to the embodiments shown, but the individual features can be combined with one another as desired. Zinc or different zinc alloys can be used particularly preferably as melts, in particular zinc alloys with different contents of magnesium and / or aluminum and / or nickel. Alternatively, aluminum or aluminum alloys can also be used.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102015108334 B3 [0004]

Claims (16)

Device (10) for hot-dip coating a metal strip (1), with a continuous furnace for passing through and heating the metal strip (1), with a vessel arranged in the running direction (L) of the metal strip (1) behind the continuous furnace with a vessel filled with melt (11.1) (11), with a trunk (13) arranged between the continuous furnace and the vessel (11) for passing and introducing the metal strip (1) into the melt (11.1) in the vessel (11), the trunk (13) being a blow Suction unit (14) with at least one blowing unit (14.1) and at least one suction unit (14.2), which are arranged on at least one wall (13.1), in particular on two opposite walls (13.1) of the trunk (13), the at least one suction unit (14.2) in the running direction (L) of the metal strip (1) is arranged behind the at least one blowing unit (14.1), the at least one blowing unit (14.1) having at least one slot opening (14.11) for insertion read gas into the proboscis (13) and the at least one suction unit (14.2) have at least one slot opening (14.21) for aspirating gas from the trunk (13), the at least one slot opening (14.11, 14.21) being transverse to the direction of travel ( L) of the metal strip (1), characterized in that the at least one slot opening (14.11, 14.21) of the blowing unit (14.1) and / or suction unit (14.2) is arranged such that it is essentially flush with the wall (13.1) of the Closes proboscis (13) or partially protrudes into the proboscis (13). Device after Claim 1 The at least one blowing unit (14.1) has a plurality of slot openings (14.11) with interruptions in between. Device according to one of the preceding claims, wherein the at least one blowing unit (14.1) has at least two rows of a plurality of slot openings (14.11) with interruptions therebetween, the slot openings (14.11) of the rows being arranged offset from one another and in particular adjacent to one another at least overlap in sections. Device after Claim 3 , wherein the slot openings (14.11) have a width b1 with a spacing a1 between the rows in the range of 2 * b1 ≤ a1 ≤ 4 * b1, with a section overlap ü1 in the range of a1 ≤ ü1 ≤ 2 * a1, with a Length 11, which corresponds to 35 * b1 ≤ l1 ≤ 70 * b1. Device according to one of the preceding claims, wherein the at least one suction unit (14.2) has a plurality of slot openings (14.21) with interruptions in between Device according to one of the preceding claims, wherein the at least one suction unit (14.2) has slot openings (14.21) with interruptions in between in at least two rows, the slot openings (14.21) of the rows being arranged offset to one another and in particular overlapping at least in sections adjacent to one another. Device after Claim 6 , wherein the slot openings (14.21) have a width b2 with a spacing a2 between the rows in the range from 3 * b2 ≤ a2 ≤ 8 * b2, with a segmental overlap ü1 in the range from a2 ≤ ü2 ≤ 2 * a2, with a Length 12, which corresponds to 20 * b2 ≤ l2 ≤ 60 * b2. Device according to one of the Claims 5 or 7 , wherein the slot opening (14.21) of the suction unit (14.2) is larger than the slot opening (14.11) of the blowing unit (14.1), the widths and the lengths being in the following relationship to one another, with 3 * b1 ≤ b2 ≤ 10 * b1 and 2 * l1 ≤ l2 ≤ 6 * l1. Device according to one of the preceding claims, wherein the at least one injection unit (14.1) and the at least one suction unit (14.2) each comprise at least one central opening (14.12, 14.22) arranged opposite the slot opening (14.11, 14.21) for supplying or discharging gas. Device after Claim 9 , the at least one blowing unit (14.1) and / or the at least one suction unit (14.2) being subdivided into a plurality of sections (14'.1, 14'.2), the sections (14'.1, 14'.2) are separated from each other in a gastight manner and each section (14'.1, 14'.2) is provided with its own central opening (14.12, 14.22). Device according to one of the preceding claims, wherein the at least one injection unit (14.1) has a substantially nozzle-shaped cross section, the slot opening (14.11) being provided in the narrowest region of the nozzle-shaped cross section. Device according to one of the preceding claims, wherein the at least one suction unit (14.1) has a substantially combined u-v-shaped cross section, the slot opening (14.21) being provided in the narrowest region of the u-v-shaped cross section. Device according to one of the preceding claims, wherein an injection unit (14.1) with an adjacent one in the running direction (L) of the metal strip (1) Suction unit (14.2) are located opposite each other on two walls (13.1) of the trunk (13). Method for hot-dip coating a metal strip (1) with a device (10) according to one of the preceding claims, wherein a larger volume flow of gas is sucked out by the at least one suction unit (14.2) than the volume flow blown in by the at least one adjacent blowing unit (14.1) Gas. Procedure according to Claim 14 , wherein the extracted volume flow corresponds to at least 1.5 times the volume flow introduced. Procedure according to Claim 14 or 15 , wherein the injected gas consists of nitrogen or a mixed gas, the mixed gas containing nitrogen and hydrogen, where the hydrogen content can be up to 10% by volume.

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