EP3303650A1

EP3303650A1 - Device and method for improved extraction of metal vapor

Info

Publication number: EP3303650A1
Application number: EP16727969.4A
Authority: EP
Inventors: Sridhar Palepu; Michael Peters; Norbert Schaffrath; Sabine Zeizinger
Original assignee: ThyssenKrupp Steel Europe AG; ThyssenKrupp AG
Current assignee: ThyssenKrupp Steel Europe AG; ThyssenKrupp AG
Priority date: 2015-05-27
Filing date: 2016-05-20
Publication date: 2018-04-11
Anticipated expiration: 2036-05-20
Also published as: JP2018515693A; US10689742B2; EP3303650B1; KR20180012289A; WO2016188922A1; US20180171458A1; CN107683343A; DE102015108334B3; ES2763351T3; CN107683343B

Abstract

The invention relates, among other things, to a device for avoiding surface flaws, caused by metal dust, on a metal strip to be coated in a continuous hot-dip coating process, wherein at least some segments of the metal strip to be coated can be conveyed through the device in an axial direction, comprising a blowing/sucking unit, wherein the blowing/sucking unit has a plurality of blow-in openings for applying protective gas to the metal strip, wherein a plurality of blow-in openings are or can be arranged on a first side of the metal strip and a plurality of blow-in openings are or can be arranged on a second side of the metal strip, wherein the blowing/sucking unit has a plurality of suction openings for extracting protective gas laden with metal vapor and/or metal dust, wherein a plurality of suction openings are or can be arranged on the first side of the metal strip and a plurality of suction openings are or can be arranged on the second side of the metal strip. The aim of improving the extraction of metal vapor by means of the protective gas and of reducing the dispersion of metal vapor is solved in that the blowing/sucking unit has a blow-in region, in which the blow-in openings are arranged, and a suction region, which is arranged after the blow-in region in the axial direction and in which the suction openings are arranged.

Description

Apparatus and method for improved metal vapor extraction

The invention relates, inter alia, to a device for preventing surface defects caused by metal dust on a metal strip to be coated in a continuous hot dip process, wherein the metal strip to be coated can be conveyed through the device at least in sections along an axial direction, with a blow-suction unit the blow-suction unit with a plurality of injection openings for loading the metal strip with

Shielding gas, wherein a plurality of injection openings on a first side of the metal strip and a plurality of injection openings on a second side of the metal strip are arranged or arranged, wherein the blow-suction unit, a plurality of suction openings for sucking with metal vapor and / or

Metal dust loaded inert gas, wherein a plurality of suction openings on the first side of the metal strip and a plurality of suction openings on the second side of the metal strip are arranged or arranged.

The invention also relates to a method for preventing surface defects caused by metal dust on a continuous one

Hot dip process to be coated metal strip, comprising the steps:

Transporting the metal strip to be coated at least in sections along an axial direction by a device, in particular by a device according to the invention, wherein the device comprises a blow-suction unit, applying the metal strip with inert gas through a plurality of injection openings of the blowing-suction unit, wherein a plurality of injection openings are arranged on a first side of the metal strip and a plurality of injection openings are arranged on a second side of the metal strip, and suction with metal vapor and / or

Metal dust loaded inert gas through a plurality of suction openings of the blow-suction unit, wherein a plurality of suction openings on the first side of the metal strip and a plurality of suction openings are arranged on the second side of the metal strip. Generic devices and methods are already known in a similar form from the prior art. For example, devices for continuous hot-dip galvanizing steel strip are used, which consist inter alia of a continuous furnace and a zinc bath (molten bath). In the continuous furnace, the steel strip is continuously annealed. Recrystallization of the steel sets the desired mechanical properties of the base material. In addition, iron oxides formed in a preheating zone are thereby reduced. In a following on the continuous furnace cooling zone, the tape is under inert gas to a

Temperature cooled near the molten bath temperature. The protective gas is intended to prevent the annealed strip from oxidizing before galvanizing, which would considerably impair the adhesion of the zinc layer. As a connector between the continuous furnace and the zinc bath, a so-called furnace trunk is used.

In the furnace bowls of continuous strip galvanizing systems of the prior art, deposits of zinc dust usually occur which, especially in the case of vibrations occurring in the installation, fall on the zinc bath and / or steel strip in larger pieces and thus cause surface defects (galvanizing defects).

To counteract this, from JP 7157853 (A), for example, a

Device for removing zinc vapor in a trunk of a continuous strip galvanizing plant known. To the resulting on the Zinkbadoberfläche

To remove zinc vapor, the furnace trunk is provided on both sides of the band in each case a single injection opening (circulation opening) and vertically below both sides of the band, each with a single suction opening. In one

Embodiment, the suction openings are each formed as a longitudinal slot in a tube which penetrates a side wall of the trunk and on the

The top and bottom of the steel strip extends over the entire steel strip width. Due to the design and arrangement of the injection openings and Suction openings, however, it is to be assumed that this known device can not satisfactorily counteract the spread of zinc vapor in the furnace trunk and, as a result, promotes the spread of zinc vapor in the furnace trunk. This was attributed to the fact that this moved towards the zinc bath

Under certain circumstances, steel strip in the trunk may entrain protective gas downwards, the entrained protective gas absorbing zinc vapor at the zinc bath surface, which condenses or resublimates on the colder interior walls of the trunk when the entrained protective gas ascends and settles there as dust.

To counteract this, it is proposed according to WO 2014/006183 AI to avoid the entrainment of the protective gas. For this purpose, several injection openings and suction openings are provided and the distance between the respective

Injection opening and a suction opening associated therewith are selected and the flow velocity of the protective gas emerging from the respective injection opening is controlled such that an entrainment of protective gas occurring in the direction of the zinc bath during movement of the metal strip is counteracted. This is essentially achieved by having a mixed area with both

Einblasöffnungen is provided as well as with suction. In other words, the area with injection openings and the area with extraction openings completely overlap or mesh with one another like a comb.

However, it has been shown that in this solution may be the

Zinc vapor extraction is not achieved satisfactorily. In particular, it has been shown that the blocking of the rising zinc vapor continues

is in need of improvement, which is attributed in the solutions of the prior art to a direct mixing of zinc vapor and inert gas.

It was also found that in some cases an inhomogeneous

Temperature distribution in the trunk can prevail, causing a deposit of

Metal steam favors. The present invention is therefore an object of the invention to provide a generic device and a generic method with which the extraction of metal vapor by the inert gas improves and the spread of

Metal vapor can be reduced.

The problem is in a generic device and in a

generic method solved in that the blow-suction unit a

Einblasbereich, in which the injection openings are arranged, and seen in the axial direction behind the blowing region arranged suction, in which the suction openings are arranged has.

It has been shown that the fact that the suction region in the axial direction (that is seen in the tape running direction) is arranged behind the injection area, the properties of the device and the method can be significantly improved. The invention thus turns away from the most recent state of the art, which provides a mixed arrangement of injection openings and suction openings, conscious, and follows a contrary approach. Although this also provides a variety of injection openings and suction openings. However, these are provided in separate successively arranged areas. It has been shown that the combination of on the one hand a plurality of openings on each side of the band and on the other just no mixed, but rather a separate arrangement of the injection openings on the one hand and the suction on the other hand in successive areas due to numerous effects is advantageous.

In particular, an improved metal vapor extraction and an effective barrier system for ascending metal vapor, for example, in a furnace trunk can be achieved by the device or the method. This is attributed inter alia to the fact that the direct mixing of metal vapor and protective gas can be reduced by the arrangement and design of the injection area and the suction area. In addition, it has been shown that an improved, that is to say homogeneous, temperature distribution in the trunk is achieved by the device or the method can be achieved, which in turn counteracts a local condensation or resublimation of metal vapor. In addition, a positive guidance laterally ascending metal vapors can be avoided. The remains

comparatively simple construction essentially independent of the width of a used oven trunk. As a result, the device or the method can finally be used for higher metal vapor concentrations.

The continuous hot dipping process may in particular be a continuous hot dip galvanizing. Accordingly, the metal bath or molten bath may in particular be a zinc bath. Accordingly, the metal vapor or

Metal dust in particular zinc vapor or zinc dust. Accordingly, the coating may in particular be a galvanizing.

The metal strip may in particular be a steel strip. For example, the steel strip is conveyed through the device in a coil-to-coil process. The first side of the metal strip is, for example, a top or front side of the

Metal strip. The second side of the metal strip is, for example, a bottom or rear side of the metal strip. The metal strip may, for example, have a width of at least 1000 mm, preferably at least 1300 mm, particularly preferably at least 1500 mm. It has been shown that the device or the method is also suitable for very broad bands.

The metal strip can be conveyed in the axial direction, for example, at a belt speed of at least 80 m / min, preferably at least 100 m / min, particularly preferably at least 120 m / min. For example, is the

Belt speed at most 180 m / min. Even at these high

Speeds can be achieved an effective barrier to the zinc vapor and homogeneous temperatures. In the device or the method, other blow-suction units may be provided. So it is at least one blow-suction unit provided. Under one / the blow-suction unit is therefore at least one / understand the at least one blowing-suction unit.

Characterized in that the suction area seen in the axial direction behind the

Einblasbereich is arranged, moves the conveyed in the axial direction metal strip first through the injection area and then through the suction. In this case, the injection area is in particular free of suction openings and the suction area is free of injection openings. That means the injection openings and the

Suction openings are spatially separated. The injection area and the suction area, for example, adjoin one another directly.

The injection openings and / or the suction openings may for example be at least partially provided as bores, which is the production of the

Device simplified.

The protective gas is, for example, a gas which prevents the oxidation of the metal strip. For example, the shielding gas is a hydrogen-nitrogen mixture (HNX). For example, the shielding gas about 95% N ₂ and about 5% H ₂ .

The protective gas is, for example, at a temperature of at least 430 ° C, preferably at least 440 ° C, more preferably at a temperature of at least 550 ° C, in particular at a temperature of about 600 ° C, blown. As a result, condensation or resublimation of the metal vapor is further counteracted.

According to a preferred embodiment of the device according to the invention, the injection openings and the suction openings are provided in such a way that the protective gas injected through the injection openings of the injection area is initially deliberately entrained with the metal strip conveyed by the apparatus in the axial direction and flows in the axial direction and then counter to axial

Direction to the suction of the suction area flows. The injection openings and the suction openings, for example, can be correspondingly arranged and / or formed for this purpose.

Accordingly, according to a preferred embodiment of

According to the invention, the protective gas injected through the injection openings of the injection area is first deliberately entrained with the metal strip conveyed by the device in the axial direction and flows in the axial direction and then flows counter to the axial direction to the suction openings of the suction area.

It has been shown that by an arrangement of the suction in axial

Direction seen behind the injection a targeted flow of the protective gas can be achieved. In this case, contrary to the objective of the prior art, the entrainment of the protective gas by the metal strip is deliberately provoked instead of counteracting it. This will cause a direct mixing of

Metal vapor and inert gas is reduced and an effective barrier system for rising metal vapor is provided. At the same time a particularly homogeneous temperature distribution is achieved. This makes the device or the

Process also for higher metal vapor concentrations, which were previously unsatisfactory to handle.

For example, the injected inert gas first flows along the surface of the metal strip with the metal strip in the axial direction until the flow hits the surface of the metal bath or molten bath and is deflected there. There, for example, the shielding gas absorbs a large part of the metal vapors of the metal bath. Subsequently, the shielding gas flows at a distance from the surface of the

Metal strip, for example, along a wall, for example one

Ofenrüssels, opposite to the axial direction to the suction of the

Absaugbereichs. This results in a continuous flow of the protective gas, so that an uninterrupted Metalldampfabsaugung is achieved. According to a preferred embodiment of the device according to the invention, the injection area and the suction area are arranged without overlapping. An overlap is understood in particular to mean that one region at least partially coincides with the other region. The injection area formed by the injection openings and the suction area formed by the suction openings therefore do not overlap. For example, in the axial direction, initially only inflation openings and then exclusively suction openings are provided. It has been shown that this further improves the extraction of metal vapor by the protective gas and the propagation of metal vapor can be further reduced.

According to a further embodiment of the device according to the invention, the injection openings of the injection area and / or the suction openings of the

Absaugbereichs arranged at least partially in a regular grid, in particular with a shortest distance of at least 30mm, preferably at least 40mm, more preferably at least 60mm. In this way, in particular a particularly homogeneous temperature distribution can be achieved and, on the other hand, a further optimized flow of the protective gas can be achieved, which counteracts the propagation of metal vapor.

For example, the injection openings of the injection area and the

Suction openings of the suction arranged in the same regular grid. For example, the injection openings and / or the suction openings are arranged in a rectangular grid. In other words, the injection openings and / or the suction openings are located, for example, on the nodes of a (imaginary) two-dimensional rectangular grid. For example, the shortest distance of the injection openings and / or the suction openings in the axial direction is greater than transverse to the axial direction. For example, the shortest distance is the

Injection openings and / or the suction openings in the axial direction between 50mm and 150mm, preferably between 80mm and 120mm, more preferably wipe

90mm and 110mm. For example, the shortest distance is the

Injection openings and / or the suction openings in the axial direction about 100mm. For example, the shortest distance of the injection openings and / or the suction openings transverse to the axial direction between 30 mm and 90mm, preferably between 40mm and 80mm, more preferably between 50mm and 70mm.

For example, the shortest distance of the injection openings and / or the suction openings transverse to the axial direction is about 60mm.

According to a preferred embodiment of the device according to the invention, the suction openings are at least partially larger than the injection openings formed. The size of the injection openings or suction openings is understood in particular to mean the (average) diameter of the opening. The diameter of the

Einblasöffnungen is preferably between 5mm and 10mm, preferably about 8mm. The diameter of the suction openings is preferably between 8mm and 15mm, preferably about 10mm. It has been found that this can be achieved with respect to an efficient metal vapor extraction further improved flow.

It is also advantageous in this regard if the standard volume flow for the suction is greater than the standard volume flow for blowing. For example, the standard volume flow for injection per side of the metal strip is at least 100 Nm ³ / h (standard cubic meter), preferably at least 150 Nm ³ / h. For example, the standard volume flow is 100-300 Nm ³ / h. Of the

However, standard volume flow may also be higher depending on the width of the device. For example, the standard volume flow for the suction per side of the metal strip is at least 150 Nm ³ / h, preferably at least

200Nm ³ / h. For example, the standard volume flow is 150-400 Nm ³ / h. Of the

However, standard volume flow may also be higher depending on the width of the device.

According to a further embodiment of the device according to the invention, the injection openings are at least partially provided such that the protective gas in

Substantially transversely to the axial direction of the injection openings in the direction of respective side of the metal strip flows. These are the injection openings

for example, arranged and / or trained accordingly.

Accordingly, according to a preferred embodiment of the method according to the invention, the protective gas flows essentially transversely to the axial direction

Direction of the respective side of the metal strip from the injection openings.

It has been shown that in this way the flow profile of the protective gas can be further optimized, resulting in particular in a reduction of the propagation of metal vapor.

For example, the protective gas flowing out of the injection openings is directed at an angle of 70 ° to 110 °, preferably 80 ° to 100 °, particularly preferably about 90 ° in the direction of the respective side of the metal strip.

According to a further embodiment of the device according to the invention, the blow-suction unit comprises a first blow-suction box, which is arranged or can be arranged on the first side of the metal strip to be coated, and a second blow-suction box, which on the second side the metal strip to be coated is arranged or can be arranged. In this case, the device may also include other blowing suction boxes.

By providing blow-suction boxes, the loading of the metal strip with protective gas can be realized in a structurally particularly simple manner from both sides. In addition, the blow-suction boxes allow, for example, a simple way

Scalability of the device. In addition, can be achieved by the blow-suction boxes surface contact with the protective gas and suction of the metal vapor. For example, the blow-suction boxes are substantially flat. For example, the blow-suction boxes have at least one connection to

Blowing in the shielding gas and at least one connection for sucking off the

Mixture of inert gas and metal vapor / metal dust on. According to a further embodiment of the device according to the invention, the blow-suction boxes each have at least one blow box for providing the

Einblasbereichs and at least one suction box to provide the suction on. By providing separate blow boxes and suction boxes, a spatially separate arrangement of the injection area and the

Absaugbereichs be achieved in a simple manner. A blow box and a

Suction box, for example, be separated by a partition. Likewise, a blow-suction box can also have a plurality of blow boxes and / or suction boxes. These can, for example, also by a partition

be separated from each other. For example, the blow boxes and / or the suction boxes each have a connection for blowing in the protective gas or for

Extracting the mixture of protective gas and metal vapor / metal dust on.

According to a further embodiment of the device according to the invention, the device comprises a furnace trunk for connecting a continuous furnace with a metal bath, wherein the blow-suction unit is at least partially provided in the furnace trunk.

Accordingly, the method according to a preferred embodiment of the method is at least partially in a furnace trunk for connecting a

Continuous furnace carried out with a metal bath.

The furnace trunk can be heated, for example, at least partially,

for example, to a temperature of at least 400 ° C, preferably at least 450 ° C. The furnace trunk has, for example, an inlet opening for retracting the

Metal strip and an outlet opening for extending the metal strip. The furnace trunk tapers, for example, at least in sections, for example, from the inlet opening in the direction of the outlet opening. According to a preferred embodiment of the method according to the invention is the

Device supplied in the axial direction before the blow-suction unit a sealing gas. For this purpose, the device, for example, a barrier gas introduction exhibit. For example, the shielding gas can also be used for the purging gas and the purging gas corresponds to the composition already described, for example (HNX). For example, the sealing gas with at least 300 Nm ³ / h, for example, blown on one side. By a pressure different gas introduction can advantageously be achieved in some areas different pressure conditions. By feeding the barrier gas, the gas flow in the trunk can be shielded, for example, by an oven, thus preventing entrainment of zinc vapor into other parts of the apparatus, such as the furnace. According to a preferred embodiment of the device according to the invention, the device also has one or more of the following units: a continuous furnace upstream of the blow-suction unit for heating the metal strip to be coated; a metal bath following the blow-suction unit, in particular a zinc bath, for coating the metal strip and optionally a stripping device adjoining the metal bath for adjusting the thickness of the coating of the metal strip; a separator for cleaning the through the

Suction openings extracted and with metal vapor and / or metal dust laden inert gas; a heating device for heating the protective gas supplied via the injection openings, in particular to a temperature of more than 430 ° C.

Accordingly, the method according to a preferred embodiment of the method according to the invention additionally comprises one or more of the steps:

Heating the metal strip to be coated in a continuous furnace upstream of the blow-suction unit; Coating of the metal strip in a metal bath following the blow-suction unit, in particular a zinc bath, and optionally

Adjusting the thickness of the coating of the metal strip by a the

Metal bath subsequent scraper; Clean the by the

Suction holes extracted and laden with metal vapor and / or metal dust inert gas in a separator; Heating the protective gas supplied via the injection openings in a heating device, in particular to a temperature greater than 430 °. The temperature of the metal bath is for example between 400 ° C and 500 ° C, preferably between 440 ° C and 470 ° C.

The stripping device can be realized, for example, by air nozzles, for example air steel flat nozzles.

The zinc deposition apparatus may preferably be provided with a cooling device which effects resublimation of the metal vapor. The resulting metal dust can be separated by means of a separator from the protective gas and passed, for example, in a collecting container.

By the preceding and following description of method steps according to preferred embodiments of the method, corresponding means or devices for carrying out the method steps by preferred embodiments of the device should also be disclosed. Also should by the

Disclosure of means for performing a method step of

corresponding method step be disclosed.

The invention will be explained in more detail with reference to the drawing. In this case, further preferred embodiments and advantages of the invention of the drawing and the description of the embodiment shown in the drawing can be taken. In the drawing shows

Fig. 1 is a longitudinal sectional view of an embodiment of a

Device according to the invention for carrying out a

Embodiment of a method according to the invention; a perspective view of the Ofenrüssels of Fig. 1; a longitudinal sectional view of the Ofenrüssels of Fig. 1; 4 is a plan view of the injection area and the suction area of the blower

Suction box of Fig. 1.

Fig. 1 shows a longitudinal sectional view of an embodiment of a

Device 1 according to the invention in the form of a continuous

Hot-dip galvanizing plant for carrying out an embodiment of a method according to the invention. The device 1 has in particular a

Oven trunk 2 on. A metal strip 4 to be galvanized, for example steel strip, is annealed in a continuous furnace (not shown) and fed to a zinc bath 6 under protective gas (HNX). The band 4 dips obliquely down into the zinc bath 6 and is deflected by a roller 8 arranged in the zinc bath 6 upwards. The bath temperature is typically in the range of about 440 ° C to 470 ° C. Upon exiting the bath 6, the band 4 ruptures a quantity of liquid zinc that is considerably above the desired level

Coating thickness may be. The still liquid excess coating material is stripped off by means of the air jet flat nozzles 10 extending across the band width from the first side and the second side (ie the upper side and the lower side or front side and rear side) of the now coated band 4.

To avoid excessive cooling (in particular below the dew point or Resublimationstemperatur of inert gas-zinc vapor mixture) of the Ofenrüssels 2 in the area near the zinc bath 6 optional insulating 12 (for example, mineral wool and / or ceramic plates) can be provided.

By means of the Ofenrüssels 2 is to be prevented inter alia that the annealed strip 4 oxidized before galvanizing, whereby the adhesion of the zinc layer

would be worsened. Therefore, the band 4 is subjected to inert gas. The

Shielding gas is also intended to serve the propagation of zinc vapor

counteract. For this reason, the furnace trunk 2 is equipped with a special blow-suction unit 14, which acts on the metal strip 4 with inert gas and sucks the loaded with zinc vapor and / or zinc dust shielding gas. FIG. 2 shows a perspective view of the oven bowl 2 from FIG. 1, and FIG. 3 shows a longitudinal sectional view of the oven bowl 2 from FIG. 1.

The metal strip to be coated 4 is in this section along an axial direction 16 through the furnace trunk 2 and by the blow-suction unit 14 of the

Device 1 transported. The blow-suction unit 14 has a plurality of

Einblasöffnungen 18 for acting on the metal strip 4 with inert gas. In this case, a plurality of injection openings 18 are arranged on a first side of the metal strip and a plurality of injection openings 18 on a second side of the metal strip, so that the metal strip 4 can be acted upon on both sides with the protective gas. In this case, the injection openings 18 form an injection area 20. The blowing-suction unit 14 also has a plurality of suction openings 22 for extracting protective gas laden with metal vapor and / or metal dust. In this case, a plurality of suction openings 22 on the first side of the metal strip 4 and a plurality of suction openings 22 on the second side of the metal strip 4th

arranged. The suction openings 22 form a suction area 24.

The injection area 20, in which the injection openings 18 are arranged, is seen in the axial direction 16 behind the suction area 24, in which the

Suction openings 22 are arranged arranged. In this case, the blowing region 20 and the suction region 24 are arranged without overlapping.

The blow-suction unit 14 comprises a first blow-suction box 14a, which is arranged on the first side of the metal strip 4 to be coated, and a second blow-suction box 14b, which on the second side of the to be coated

Metal strip 4 is arranged. The blow-suction boxes 14a, 14b each have two blow boxes 26a and 26b for providing the blow-in area 20 and two suction boxes 28a and 28b respectively for providing the suction area 24. The

Blow boxes 26a (or 26b) are mutually separated by a partition wall 42a (or 42b). Also, the suction boxes 28a (or 28b) are mutually separated by a partition wall 44a (or 44b). Also For example, the blow box 26a (or 26b) and the suction box 28a (or 28b) are separated from each other by a partition wall 46a (or 46b).

The individual blow boxes 26a, 26b each have separate connections 30a, 30b for supplying protective gas. The standard volume flow for blowing through the ports 30a is about 150Nm ³ / h. The standard flow for blowing through the ports 30b is also about 150 Nm ³ / h. The standard volume flow for the suction through the ports 32a is about 200Nm ³ / h. Of the

Standard volume flow for the suction through the ports 32b is also about 200Nm ³ / h.

At the same time by means of the barrier gas inlet 3 (see Fig. 1) sealing gas in the

Device 1 are initiated. The sealing gas is identical here to the protective gas and is blown in at 300 Nm ³ / h through the barrier gas inlet 3, as also illustrated by the arrows 33 in FIG. 3. The sealing gas is advantageously fed between two sealing flaps (see FIG. By the sealing gas, the gas flow in the furnace trunk 2 is shielded by an upstream furnace, so that a

Introducing zinc vapor into the oven is prevented. For example, the pressure decreases from the area of the protective gas inlet 3 over the area of the blow boxes 26a or 26b to the area of the suction boxes 28a or 28b.

As can be seen in particular in FIG. 3, the injection openings 18 are provided such that the protective gas flows essentially transversely to the axial direction 16 out of the injection openings in the direction of the respective side of the metal strip 4. In this case, the protective gas is blown through the injection openings 18 perpendicularly in the direction of the respective side of the metal strip 4. The flow direction of the

Shielding gas is illustrated by arrows 34. The protective gas injected through the injection openings 18 of the injection area 20 is first deliberately entrained with the metal strip 4 conveyed by the device 1 in the axial direction 16 and flows in the axial direction 16. The protective gas flows along the surface of the metal strip 4. Subsequently, the protective gas flows mixed with zinc vapor and Zinc dust along the wall of the furnace trunk 2 against the axial direction 16 to the suction openings 22 of the suction 24th

Points 36 illustrate the distribution and concentration of the

Zinc vapor and zinc dust. The concentration of zinc dust and zinc vapor decreases noticeably against the axial direction 16. The blow-suction unit 14 provides an effective barrier for the zinc vapor and the zinc dust and effective extraction of the zinc vapor and the zinc dust. Assuming, for example from a zinc vapor entry of about 34g / hr through the zinc bath 6 from simulations result in a zinc vapor concentration of about 5 x 10 ^"5 kg / m ³ in the vicinity of the zinc bath 6 in the lower region of the furnace snout. In

Extraction zone 24 results in only a zinc vapor concentration of about 3 x 10 ^" ⁵ kg / m ³ to about 7 x 10 ^{" 6} kg / m ³ . In the injection region 20, the zinc vapor concentration is already lower than 7 x 10 ^"6 kg / m ^3.

At a higher zinc vapor entry 340 g / h resulting in the suction region 24 still zinc vapor concentrations of up to 5 x 10 ^"5 kg / m ^3. However, this fall in the injection region 20 to less than 1 x ^{10" 5} kg / m ^3, partly on below 7 × 10 ^-6 kg / m ^3. Thus, the device or the method is also for such high

Zinc vapor inputs suitable.

Finally, FIG. 4 shows by way of example a plan view of the injection region 20 and the suction region 24 of the blow-suction box 14a from FIG. 1. The injection openings 18 of the injection region 20 and the suction openings 22 of the suction region 24 are arranged in a regular grid. In this case, the shortest distance between adjacent openings 18, 22 in the axial direction 16 is greater than transverse to the axial direction 16. The shortest distance 38 of the injection openings 18 or the suction openings 22 in the axial direction is approximately 100 mm here. The shortest distance 40 of the injection openings 18 or the suction openings 22 transversely to the axial direction 16 is about 60 mm. The

Injection openings 18 are smaller than the suction openings 22 are formed. Of the Diameter of the injection openings 18 is about 8mm. The diameter of the suction openings 22 is about 10mm.

Claims

P a n t a n s p r e c h e

Device for avoiding metal dust

Surface defects on a metal strip (4) to be coated in a continuous hot dip process, wherein the metal strip (4) to be coated is conveyable through the device (1) at least in sections along an axial direction (16),

with a blow-suction unit (14), wherein the blow-suction unit (14) has a plurality of injection openings (18) for acting on the metal strip (4) with inert gas, wherein a plurality of injection openings (18) on a first Side of the metal strip (4) and a plurality of injection openings (18) on a second side of the metal strip (4) are arranged or arranged, wherein the blow-suction unit (14) has a plurality of suction openings (22) for sucking with metal vapor and / or metal dust laden inert gas, wherein a plurality of suction openings (22) on the first side of the metal strip (4) and a plurality of suction openings (22) on the second side of the metal strip (4) are arranged or arranged,

characterized in that

the blow-suction unit (14) has a blowing area (20) in which the

Injection openings (18) are arranged, and arranged in the axial direction (16) behind the blowing region (20) arranged suction region (24) in which the suction openings (22) are arranged comprises.

Device according to claim 1,

the injection openings (18) and the suction openings (22) being provided such that the protective gas injected through the injection openings (18) of the injection area (20) is first mixed with the metal strip (4) conveyed in the axial direction (16) by the device (1) ) is deliberately entrained and flows in the axial direction (16) and then flows against the axial direction (16) to the suction openings (22) of the suction region (24). Apparatus according to claim 1 or 2,

wherein the blowing region (20) and the suction region (24) are arranged without overlapping.

Device according to one of claims 1 to 3,

wherein the injection openings (18) of the injection area (20) and / or the

Suction openings (22) of the suction area (24) are arranged at least partially in a regular grid, in particular with a shortest distance (38, 40) of at least 30mm, preferably at least 40mm, more preferably at least 60mm.

Device according to one of claims 1 to 4,

wherein the suction openings (18) at least partially larger than that

Injection openings (22) are formed.

Device according to one of claims 1 to 5,

wherein the injection openings (18) are at least partially provided such that the protective gas flows substantially transversely to the axial direction (16) from the injection openings (18) in the direction of the respective side of the metal strip (4).

Device according to one of claims 1 to 6,

wherein the blow-suction unit (14) comprises a first blow-suction box (14a) which is arranged or can be arranged on the first side of the metal strip (4) to be coated, and wherein the blow-suction unit (14) a second blow-suction box (14b) which is arranged or can be arranged on the second side of the metal strip (4) to be coated.

Device according to claim 7, wherein the blow-suction boxes (14a, 14b) each have at least one blow box (26a, 26b) for providing the blowing area (20) and at least one suction box (28a, 28b) for providing the suction area (24).

Device according to one of claims 1 to 8,

wherein the device (1) has a furnace trunk (2) for connecting a

Continuous furnace with a metal bath (6), wherein the blow-suction unit (14) is at least partially provided in the furnace trunk (2).

Device according to one of claims 1 to 9,

wherein the device (1) also has one or more of the following units:

one of the blow-suction unit (14) upstream continuous furnace for

Heating the metal strip (4) to be coated;

a metal bath (6) following the blow-suction unit (14), in particular zinc bath, for coating the metal strip (4) and optionally a stripping device (10) adjoining the metal bath (6) for adjusting the thickness of the coating of the metal strip ( 4); a separation device for cleaning the through the suction openings (22) sucked and loaded with metal vapor and / or metal dust protective gas;

a heating device for heating the protective gas supplied via the injection openings (18), in particular to a temperature of more than 430 ° C.

Method for avoiding metal dust

Surface defects on a metal strip to be coated in a continuous hot dip process, comprising the steps:

Conveying the metal strip to be coated at least in sections along an axial direction through a device, in particular according to one of claims 1 to 10, the device having a blow-suction unit, Impinging the metal strip with inert gas over a variety of

Injection openings of the blow-suction unit, wherein a plurality of

Einblasöffnungen are arranged on a first side of the metal strip and a plurality of injection openings on a second side of the metal strip, and suction of metal vapor and / or metal dust laden inert gas through a plurality of suction openings of the blow-suction unit, wherein a plurality of suction openings the first side of the metal strip and a plurality of suction openings are arranged on the second side of the metal strip, characterized in that

the blow-suction unit, a blowing area, in which the injection openings are arranged, and seen in the axial direction behind the

Einblasbereich arranged suction, in which the suction openings are arranged has.

Method according to claim 11,

wherein the blown through the injection openings of the injection

Shielding gas first with the through the device in the axial direction

conveyed metal strip is deliberately entrained and flows in the axial direction and then flows against the axial direction to the suction of the suction.

Method according to claim 11 or 12,

wherein the protective gas substantially transversely to the axial direction of the

Injection openings in the direction of the respective side of the metal strip flows.

Method according to one of claims 11 to 13,

wherein the process is carried out at least partially in a furnace trunk for connection of a continuous furnace with a metal bath.

Method according to one of claims 11 to 14,

wherein the device is supplied in the axial direction in front of the blow-suction unit, a sealing gas. Method according to one of claims 11 to 15,

the method additionally comprising one or more of the steps:

Heating the metal strip to be coated in a continuous furnace upstream of the blow-suction unit;

Coating the metal strip in a metal bath following the blow-suction unit, in particular a zinc bath, and optionally adjusting the thickness of the coating of the metal strip by a metal bath

Metal bath subsequent scraper;

Clean the aspirated through the suction and with

Metal vapor and / or metal dust laden inert gas in one

separator;

Heating the protective gas supplied via the injection openings in a heating device, in particular to a temperature greater than 430 ° C.