EP3591088B1 - Device for hot dip coating of a metal strip - Google Patents

Description

Technical Field

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

Technical Background (Background Art)

Conventional coil coating systems, such as systems for continuous hot-dip galvanizing of steel strip, have a continuous furnace, a molten bath (zinc bath), a device for adjusting the (zinc) coating thickness and a subsequent cooling device in the direction of travel of the strip. In the continuous furnace, the steel strip is heat-treated in a continuous process, wherein the continuous furnace can 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 setting 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 molten bath. The protective gas is intended to prevent the annealed strip from oxidizing before coating (galvanizing), which means that wetting and thus adhesion of the coating or coating (zinc layer) to the surface of the steel strip would not be possible or only poorly and thus the required quality standards cannot be met. In particular, because of the different treatments, different gas atmospheres are sometimes required in the areas (chambers) in the continuous furnace. Between the continuous furnace and the molten bath, the steel strip is passed through a sluice flooded with protective gas, with the exclusion of the ambient atmosphere, which is also known as a trunk among experts.

In the operation of a continuous strip galvanizing line, zinc vapor is produced which gets into the trunk. It was recognized that the steel strip moving in the direction of the zinc bath entrains protective gas downwards in the trunk, whereby the entrained protective gas on the surface of the zinc bath absorbs zinc vapor, which condenses or resublimates on the colder inner walls of the trunk when the entrained protective gas rises Zinc dust 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 generation of zinc dust within the trunk in continuous strip galvanizing plants or to remove the zinc vapor and / or dust that has arisen, devices are used within the trunk which cause the atmosphere to circulate within the trunk by targeted blowing in at one or more points, combined with suction at one or more points to discharge or remove the dusty atmosphere. For example, from the German patent specification 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 -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 being a plurality of suction openings for suctioning off protective gas laden with zinc vapor and / or zinc dust, wherein a plurality of suction openings are arranged or can be arranged on the first side of the steel strip and a plurality of suction openings on the second side of the steel strip, wherein the blower -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.

The arrangement of the blow-and-suction unit within the trunk, however, leads to a reduction in the cross-section of the steel belt, so that if vibrations and / or fluctuating operating conditions occur in the galvanizing line during operation, the belt does not swing out of the plane of the direction of belt travel, and thus does not prevent it Contact with the blow-suction unit cannot be ruled out, which can damage the belt and the system. There is a need for further optimization in relation to the state of the art.

Summary of Invention

The invention is based on the object of providing a device for hot-dip coating a metal strip, with which an operationally reliable coating process can be ensured under fluctuating operating conditions.

This object is achieved by a device with the features of 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 guiding and heating the metal strip, with a vessel arranged in the running direction of the metal strip behind the continuous furnace and 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 trunk comprising a blow-suction unit with at least one injection unit and at least one suction unit, which are arranged on at least one wall, in particular on two opposing walls of the trunk, the at least one suction unit is arranged in the running direction of the metal strip behind the at least one injection unit, wherein the at least one injection unit has at least one slot opening for blowing gas into the trunk and the at least one suction unit has at least one slot opening for sucking off Ga s from the trunk, wherein the at least one slot opening extends transversely to the direction of travel of the metal strip.

The inventors have found that, due to the arrangement of the at least one slot opening of the injection unit and / or suction unit, the at least one slot opening essentially flush with the wall of the trunk and / or being arranged in line with the wall, compared to the one in State of the art shown complete arrangement of the blow-suction unit within the trunk, the flow cross-section is not disadvantageously reduced, so that a contact between the metal band and trunk or (further) parts / components of the trunk can be excluded and thereby prevents damage and an operationally reliable coating process can be ensured. The blow-suction unit with the at least one blow-in unit and the at least one suction unit are or are mounted on the outside of the wall of the trunk, so that the blow-in and / or suction unit with its or theirs via suitable openings in the wall of the trunk. their slot opening (s) flush with the Complete the wall of the trunk. The blow-suction unit arranged or mounted on the wall of the trunk from the outside also has the advantage of easy accessibility, especially during operation, and thus the possibility of quick and uncomplicated maintenance and / or cleaning. An injection unit with a suction unit adjacent in the running direction of the metal strip are preferably located opposite one another on two opposite walls of the trunk. The two opposing walls run essentially parallel to the surface of the metal strip. Two further (opposite) walls complete or define the trunk, which essentially runs with a longitudinally rectangular cross section, 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 band is preferably a steel band.

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 injection unit has a plurality of slot openings with interruptions in between. If several slot openings are provided in the transverse direction or transversely to the running direction of the metal strip with interruptions, a tight gas curtain can be created, for example, so that the metal vapor rising from the melt is specifically prevented from rising further inside the trunk or into the continuous furnace. The injection unit preferably has at least two rows, with exactly two rows or more than two rows being provided, of 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. As a result of the arrangement in rows and the interruptions in the rows, the slot openings can be used optimally, since in particular the jet expansion that occurs from adjacent slot openings escaping gas flows do not influence each other (negatively) and thus a closed gas curtain can form. Due to the staggered arrangement of the slot openings in an injection unit in relation to the slot openings or interruptions in the injection unit provided on the opposite wall, a tight gas curtain is also formed in the outer areas of the trunk that are not traversed by the metal strip and in which the blown gas streams meet .

According to one embodiment of the device, the slot openings of the injection unit have a width b1 with a distance a1 between the rows in the range of 2 ^∗ b1 ≤ a1 4 ^∗ b1, with a sectional overlap ü1 in the range of a1 ü1 ü 2 ^∗ a1 , with a length l1, which corresponds to 35 ^∗ b1 ≤ l1 ≤ 70 ^∗ b1. In order to set a gas curtain that is as dense 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 injection unit, a minimum distance between the rows twice the width achieves good results, and if the distance is more than four times the width, the gas flow splits 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 several slot openings arranged with interruptions in the transverse direction or transversely to the running direction of the metal strip are provided, effective suction can be promoted so that the metal vapor rising from the melt can be suctioned off in a targeted manner. The suction unit preferably has at least two rows, with exactly two rows or more than two rows being provided, consisting of 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 used optimally 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 distance a2 between the rows in the range of 3 ^∗ b2 ≤ a2 8 ^∗ b2, with a sectional overlap ü2 in the range of a2 ü2 2 ^∗ a2 , with a length l2, which corresponds to 20 ^∗ b1 ≤ l1 ≤ 60 ^∗ b1. The slot opening is preferably the suction unit larger than the slot opening of the injection unit, whereby the widths and the lengths are in the following relationship to one another, with 3 ^∗ b1 ≤ b2 ≤ 10 ^∗ b1 and 2 ^∗ l1 ≤ l2 ≤ 6 ^∗ l1. The smaller dimension of the slot opening of the injection unit is intended to cause a certain impulse in connection with a circulation of the atmosphere within the trunk, whereby the larger dimension of the slot opening of the suction unit is intended to ensure that the metal vapor and / or metal dust can be discharged without clogging or clogging the slot opening (s) avoided and thereby the maintenance intervals can be extended, especially for cleaning purposes.

According to one embodiment of the device, the at least one injection 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. In this way, the flow conditions can be kept largely the same over the width of the injection and extraction unit.

According to one embodiment of the device, the at least one blow-in unit and / or the at least one suction unit are divided into several sections, in particular in their longitudinal extension or transversely to the running direction of the metal strip, the sections being separated from one another in a gastight manner and each section being provided with its own central opening is, in particular, is or can be connected to a line for supplying or removing gas. As a result of this division into sections that are preferably of equal width / length, the flow conditions can be further improved over the width of the trunk and, in particular, the required power per line can be reduced.

According to a preferred embodiment of the device, the injection unit has an essentially nozzle-shaped cross section, the slot opening being provided in the narrowest area of the nozzle-shaped cross section, the slot opening or the slot openings being / are provided in the end area 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 uv-shaped cross section, the slot opening in the narrowest area and the slot openings in the end areas of the legs of the uv-shaped Cross-section is / are provided. 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 sucked off through the at least one suction unit than the volume flow of gas blown in through the at least one adjacent blow-in unit. The extracted volume flow is at least 1.5 times greater than the volume flow blown in through the adjacent injection unit. This creates a negative pressure inside the trunk in the atmosphere located below the suction unit in the direction of travel of the metal belt, which, together with the gas curtain of the injection unit, can largely ensure that there is no backflow into the gas atmosphere above the injection unit in the trunk and thus a decoupling the gas atmosphere within the trunk can be guaranteed.

According to one embodiment of the method, the blown gas 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.

Brief Description of Drawings

Fig. 1)

eine skizzierte Darstellung einer Vorrichtung nach dem Stand der Technik,

Fig. 2)

eine schematische Darstellung einer erfindungsgemäßen Ausführung einer Vorrichtung im Querschnitt eines Rüssels,

Fig. 3)

eine perspektivische Teildarstellung der Ausführung in Figur 2 und

Fig. 4)

einen schematischen Schnitt in der Ebene A-A entlang der Wandung des Rüssels gemäß Figur 3.

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

Fig. 1)

a sketched representation of a device according to the prior art,

Fig. 2)

a schematic representation of an embodiment of a device according to the invention in the cross section of a trunk,

Fig. 3)

a perspective partial representation of the embodiment in Figure 2 and

Fig. 4)

a schematic section in the plane AA along the wall of the trunk according to Figure 3 .

Description of the Preferred Embodiments (Best Mode for Carrying out the Invention)

In Figure 1 a sketched device (10) is 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 strip (1), with a symbolically illustrated continuous furnace (12) for passing through and heating the metal strip (1), with one in the running direction (L) of the metal strip (1) behind the continuous furnace (12) with a melt (11.1) filled vessel (11), with a trunk (13) arranged between the continuous furnace and the first vessel (11) for guiding and introducing the metal strip (1) into the Melt (11.1) in the vessel (11), with a deflection roller (15) arranged in the vessel (11) for deflecting and guiding the metal strip (1) out of the vessel (11). Additional stabilizing rollers (18) can be arranged in the vessel (11), which in particular stabilize the metal strip (1) when it emerges from the melt (11.1) and cause the strip to run smoothly, in particular in connection with above the vessel (11) on both sides wiping nozzles (19) arranged on the exiting metal strip (1) for adjusting the layer thickness on the metal strip (1), preferably for adjusting a constant layer thickness.

The trunk (13) comprises a blow-suction unit (14) with at least one blowing unit (14.1) and at least one suction unit (14.2), which are arranged in particular on two opposing walls (13.1) of the trunk (13). The at least one suction unit (14.2) is arranged in the running direction (L) of the metal strip (1) behind the at least one injection unit (14.1), the at least one injection unit (14.1) having at least one slot opening (14.11) for injecting 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 from the trunk (13). The slot opening (14.11, 14.21) extends essentially transversely to the running direction (L) of the metal strip (1). The arrangement of the blow-and-suction unit (14) inside the trunk (13) leads to a reduction in the flow 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 swinging of the belt out of the plane of the running direction (L) of the metal belt (1) is not prevented and contact with the blow-suction unit (14) cannot be ruled out, so that damage to the metal belt (1) and also in the system (10, 13) can arise.

Figure 2 shows a schematic representation of an embodiment of the device (10) according to the invention in the cross section of a trunk (13). The flow cross-section of the trunk (13) is no longer disadvantageously reduced, so that contact between metal strip (13) and trunk (13) or parts thereof 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) is arranged outside the trunk (13), preferably arranged or mounted from the outside on the wall (13.1) of the trunk (13), the at least one The slot opening (14.11, 14.21) of the at least one injection 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). This also rules out the fact that the parts / components that negatively influence the circulation and / or flow of the gas within the trunk (13) are not present in comparison with the prior art. There are two opposite injection units (14.1) with two opposite suction units (14.2) located behind them in the running direction (L) of the metal strip (1) at a defined distance.

In Figure 3 FIG. 3 is a partial perspective view of the embodiment in FIG Figure 2 shown, which quasi shows the area of the blow-suction unit (14) below the transport plane of the metal belt (1). In the partial illustration it can be seen that the slot openings (14.11) of the injection unit (14.1) are arranged offset from one another, cf. Figure 4 . In the case of the injection unit (14.1), the illustration shows the outermost slot opening (14.11) in the upper one, seen in the width direction of the trunk (13), cf. Figure 4 , or opposite to the running direction (L), row arranged and the bottom row begins with an interruption, viewed from left to right, cf. also Figure 4 . The in Figure 3 opposite injection unit (14), not shown, the outermost slot opening (14.11) is arranged in the lower row and the upper row begins with an interruption. As a result of this arrangement, the gas streams emerging from the slot openings (14.11), in particular in their main extent, reach the respective opposite wall (13.1) unhindered, 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), contact of the gas streams only in the area of the unavoidable areas of the jet expansions. With this configuration, a gas curtain is achieved which is very stable and has a very good sealing effect.

The injection unit (14.1, 14'.1) has an essentially nozzle-shaped cross-section, with the slot opening (s) (14.11) in the narrowest area of the nozzle-shaped cross section and the slot opening (s) (14.11) in the end area of the nozzle-shaped cross section, in particular opposite one another from the central opening (14.12) is / are provided. The suction unit (14.2, 14'.2), on the other hand, has an essentially combined uv-shaped cross section, the slot opening (14.21) being provided in the narrowest area and the slot openings (14.21) being provided in the end areas of the legs of the uv-shaped cross section / are.

Figure 4 shows a schematic section (AA) in the plane of the wall (13.1) of the trunk (13) in a plan view on the side assigned to the surface of the metal strip (1), quasi the wall (13.1) of the trunk (13.1) running below the metal strip (1). 13), having an arrangement of a blow-suction unit according to the invention (14, 14.1, 14.2). The injection 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), each of which has interruptions or spaces between the slot openings (14.11). For the supply or discharge of gas to the injection unit (14.1, 14'.1) or from the suction unit (14.2, 14'.2), lines (not shown) are provided which can be connected to the central openings (14.12, 14.22) or are connected, cf. Figure 3 .

The slot openings (14.11) each have a width b1 and a length l1. The two rows of slot openings (14.11) are spaced a1 apart in the running direction (L). The slot openings (14.11) of adjacent rows are offset from one another so that a slot opening (14.11) of the adjacent row is assigned to an interruption in one row. The slot openings (14.11) are made longer than the intervening interruptions so that, viewed in the running direction (L), an overlap (ü1) of the ends of the slot openings (14.11) is created. The overlap (ü1) is designed uniformly along the injection unit (14.1, 14'.1).

Seen in the running direction (L), a suction unit (14.2) is arranged, which also comprises two sections (14'.2) and are indicated by dashed lines in the drawing, with two rows of slot openings (14.21), each of which has interruptions or spaces between the Have slot openings (14.21). The slot openings (14.21) each have a width b2 and a length l2. The two rows of slot openings (14.21) are spaced apart from one another at a distance a2 in the running direction (L). The slot openings (14.21) of adjacent rows are offset from one another, so that an interruption in one row is assigned a slot opening (14.21) of the adjacent row. The slot openings (14.21) are made longer than the intervening interruptions so that, viewed in the running direction (L), an overlap (ü2) of the ends of the slot openings (14.21) is created. The overlap (ü2) is formed uniformly along the injection unit (14.2, 14'.2). Compared to the slot openings (14.11) of the injection unit (14.1), the slot openings (14.21) of the suction unit (14.2) are larger, with four slot openings (14.21) being provided in the top row as shown and in the row below two.

The slot openings (14.11, 14.21) close flush with the wall (13.1) of the trunk or are arranged in alignment with the wall (13.1).

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 particularly preferably be used 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.

Claims (13)

1. Device (10) for hot dip coating a metal strip (1), having a continuous furnace for directing and heating the metal strip (1); having a vessel (11) which in the running direction (L) of the metal strip (1) is disposed behind the continuous furnace and is filled with a melt (11.1); having a nozzle pipe (13) which for directing and introducing the metal strip (1) into the melt (11.1) in the vessel (11) is disposed between the continuous furnace and the vessel (11), wherein the nozzle pipe (13) comprises a blower/suction unit (14) having at least one injecting unit (14.1) and at least one suctioning unit (14.2) which are disposed on at least one wall (13.1) of the nozzle pipe (13), wherein the at least one suctioning unit (14.2) in the running direction (L) of the metal strip (1) is disposed behind the at least one injecting unit (14.1), wherein the at least one injecting unit (14.1) has at least one slot opening (14.11) for injecting gas into the nozzle pipe (13), and the at least one suctioning unit (14.2) has at least one slot opening (14.21) for suctioning gas from the nozzle pipe (13), wherein the at least one slot opening (14.11, 14.21) extends so as to be transverse to the running direction (L) of the metal strip (1), characterized in that the at least one slot opening (14.11, 14.21) of the injecting unit (14.1) and/or of the suctioning unit (14.2) are/is disposed in such a manner that said slot opening (14.11, 14.21) ends so as to be flush with the wall (13.1) of the nozzle pipe (13) and/or is disposed so as to be aligned with the wall (13.1).
2. Device according to Claim 1, wherein the at least one injecting unit (14.1) has a plurality of slot openings (14.11) having interruptions lying therebetween.
3. Device according to one of the preceding claims, wherein the at least one injecting unit (14.1) has at least two rows from a plurality of slot opening (14.11) having interruptions lying therebetween, wherein the slot openings (14.11) of the rows are disposed so as to be mutually offset and when mutually adjacent so as to overlap at least in portions.
4. Device according to Claim 3, wherein the slot openings (14.11) have a width b1 having a spacing a1 in the range from 2^∗b1 ≤ a1 ≤ 4^∗b1 between the rows, wherein an overlap ü1 in portions is in the range from a1 ≤ ü1 ≤ 2^∗a1, having a length l1 which corresponds to 35^∗b1 ≤ l1 ≤ 70^∗b1.
5. Device according to one of the preceding claims, wherein the at least one suctioning unit (14.2) has a plurality of slot openings (14.21) having interruptions lying therebetween.
6. Device according to one of the preceding claims, wherein the at least one suctioning unit (14.2) has slot openings (14.21) having interruptions lying therebetween in at least two rows, wherein the slot openings (14.21) of the rows are disposed so as to be mutually offset and when mutually adjacent so as to overlap at least in portions.
7. Device according to Claim 6, wherein the slot openings (14.21) have a width b2 having a spacing a2 in the range from 3^∗b2 ≤ a2 ≤ 8^∗b2 between the rows, wherein an overlap ü1 in portions is in the range from a2 ≤ ü2 ≤ 2^∗a2, having a length l2 which corresponds to 20^∗b2 ≤ l2 ≤ 60^∗b2.
8. Device according to one of Claims 5 or 7, wherein the slot opening (14.21) of the suctioning unit (14.2) is larger than the slot opening (14.11) of the injecting unit (14.1), wherein the widths and lengths mutually correlate as follows, where 3^∗b1 ≤ b2 ≤10^∗b1 and 2^∗l1 ≤ l2 ≤ 6^∗l1.
9. Device according to one of the preceding claims, wherein the at least one injecting unit (14.1) and the at least one suctioning unit (14.2) comprise in each case one central opening (14.12, 14.22) which for feeding or discharging gas is disposed opposite the slot opening (14.11, 14.21).
10. Device according to Claim 9, wherein the at least one injecting unit (14.1) and/or the at least one suctioning unit (14.2) are/is subdivided into a plurality of portions (14'.1, 14'.2), wherein the portions (14'.1, 14'.2) are mutually separated in a gas-tight manner and each portion (14'.1, 14'.2) is provided with a dedicated central opening (14.12, 14.22).
11. Device according to one of the preceding claims, wherein the at least one injecting unit (14.1) has a substantially jet-shaped cross section, wherein the slot opening (14.11) is provided in the narrowest region of the jet-shaped cross section.
12. Device according to one of the preceding claims, wherein the at least one suctioning unit (14.1) has a substantially combined u/v-shaped cross section, wherein the slot opening (14.21) is provided in the narrowest region of the combined u/v-shaped cross section.
13. Device according to one of the preceding claims, wherein an injecting unit (14.1) and a suctioning unit (14.2) that is adjacent in the running direction (L) of the metal strip (1) lie in each case so as to be mutually opposite on two walls (13.1) of the nozzle pipe (13).

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