Method and device for applying a layer to a flat steel product

Abstract

A device (150) for applying a layer (10) to the front side and / or the rear side of a flat steel product (100), - A zinc alloy molten bath (11) having an inlet side (E) and an outlet side (A), - A peeling nozzle device (14) having at least one gas nozzle (15) for blowing off the front side or the rear side of the flat steel product (100) with gas (G), the peeling nozzle device (14) being arranged and configured within the region of the outlet side (A), - A steam device (50) configured to emit gaseous steam and provide a controlled steam atmosphere within the near - distance region (NB) of the front side and / or the rear side of the flat steel product (100), the controlled steam atmosphere having an absolute local humidity greater than 1 g / m 3 and less than 300 g / m 3 is provided, the steam device (50) is provided with a device (150).

Description

Technical Field

[0001] The present invention relates to a device capable of coating flat steel products with a zinc (Zn) or zinc-aluminum-magnesium (ZnAlMg)-based layer, for example as a protective coating. It also relates to the corresponding method.

Background Art

[0002] It is well known that flat steel products 100 such as steel strips or steel plates are coated with zinc (Zn) or ZnAlMg alloys to improve corrosion resistance. In practice, this is usually done by immersing the flat steel product 100 coming out of the furnace into a zinc alloy molten bath 11, as shown in FIG. 1 using an exemplary device 150. To protect the flat steel product 100 from oxidation, this is typically introduced into the bath 11 on the inlet side E through the trunk 12 using an inert atmosphere. In the bath 11, the flat steel product 100 is deflected by the (zinc bath) roller 13 and moved upward from the outlet side A of the bath 11. When the flat steel product 100 comes out of this bath 11, the molten alloy film adhering to the front and rear sides of the flat steel product 100 is stripped to the target thickness (within the micrometer range) or to the target surface coating (unit g / m 2 ) by a gas jet from the gas nozzle 15 of the stripping nozzle device, and then the flat steel product 100 is conveyed to the cooling area 16. This continuous method is generally referred to as hot dip galvanizing.

[0003] Details of suitable methods and particularly suitable alloy compositions are described, for example, in Patent Document 1.

[0004] There is prior art that mentions water or water vapor in relation to the hot dip galvanizing of flat steel products. The corresponding documents are listed below, where the interesting points are briefly described.

[0005] Patent Document 2 deals with the control of zinc vapor in relation to the hot-dip plating of iron-based metal strips. A low-oxygen atmosphere containing a small amount of water vapor is provided in a sealed area (corresponding to the trunk 12 in FIG. 1) on the inlet side of the immersion tank. This small amount of water is intended to prevent the formation of zinc vapor on the surface of the immersion tank. The dew point of the gas used on the inlet side is set so that zinc vapor cannot be formed.

[0006] The object in Patent Document 3 is to produce a galvanized steel strip having a surface with an increased friction coefficient. To increase the friction coefficient, water is sprayed onto the surface of the flat steel product under pressure after gas blowing. The particle size of the water droplets should be at least 0.07 mm, preferably more than 1.5 mm. By spraying the water droplets, unevenness is intentionally formed on the surface of the steel strip. This document pursues a different object, and the corresponding technical teachings proceed in a completely different direction from the present invention.

[0007] There are even more stringent requirements regarding the surface quality of hot-dip galvanized flat steel products, not just for protection against corrosion. Especially in the automotive industry, products that meet the highest surface requirements are expected. However, providing a homogeneous surface is not a trivial matter.

[0008] The main problem is often surface defects in the ZnAlMg layer. For example, defects in the form of marble patterns (marble effect), "toothpick" shapes, or "beach pattern" shapes may form on the ZnAlMg layer, or slag formation may occur. There are also patents (for example, Patent Document 4 and Patent Document 5) that attempt to eliminate similar surface defects (luster effect or detached oxide film) by other means (reduction of the O2 content around the peeling nozzle).

[0009] Similar surface defects can also occur in some situations with Zn coatings containing a low proportion of Al (typically less than 1 wt.%). These coatings can be referred to here as ZnAl coatings.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Document

[0011]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] Therefore, the problem is to provide a device for coating flat steel products with a ZnAlMg layer or a ZnAl layer that is particularly durable with respect to corrosion and has a strong protective effect, and the surface of the protective coating should be particularly homogeneous, without a marble pattern (no “marble effect”) and / or without matchstick defects (no “matchsticks”). The aim is to achieve a surface quality that meets the highest customer requirements.

[0013] Additionally, the device should consume as little energy as possible, be cost-effective in operation, and be robust in use.

Means for Solving the Problems

[0014] According to the present invention, there is provided a corresponding device that uses a continuous (melting) process and enables a flat steel product to be provided with a metal ZnAlMg layer or a ZnAl layer that can act as, for example, a (protective) coating. This layer is intended to protect the steel substrate of the flat steel product from external influences. Hereinafter, the corresponding immersion bath is referred to as a zinc melting bath, and the term zinc alloy melting bath is intended to include both a melting bath containing mainly zinc (Zn) and a small amount of aluminum (Al) mixture (typically less than 1% by weight), and a melting bath containing a ZnAlMg alloy. The layer to be applied is herein also referred to as a Zn-containing (protective) layer.

[0015] A device for applying a ZnAlMg layer or a ZnAl layer to a flat steel product has been proposed. In all embodiments, this device - has a zinc alloy melting bath with an inlet side and an outlet side, - is a peeling nozzle device having at least one gas nozzle for blowing off the front or rear side of the flat steel product with gas, and is arranged and configured within the region of the outlet side, - is a steam device arranged and configured to release gaseous steam and provide a controlled steam atmosphere within the region of the front side and / or the rear side of the flat steel product, and the controlled steam atmosphere has an absolute local humidity greater than 1 g / m 3 and less than 300 g / m 3 and preferably has an absolute local humidity in the range from 2.71 g / m 3 to 50 g / m 3 of the steam device. is provided.

[0016] All embodiments relate to applying a Zn-containing (protective) layer to a flat steel product, and the thickness of this layer is intended to correspond to the target thickness (according to the corresponding specifications). This layer is formed by passing the flat steel product through a zinc alloy melting bath and blowing and removing the gas at the outlet side of the bath using a peeling nozzle device equipped with at least one gas nozzle.

[0017] In all embodiments, the zinc alloy of the zinc alloy molten bath has the following composition, namely, - an aluminum content within the range of 1.0 to 3.0 weight percent, preferably within the range of 1.3 to 2.8 weight percent, and - a magnesium content within the range of 1.0 to 2.5 weight percent, preferably within the range of 1.2 to 2.2 weight percent and - the remainder of the zinc alloy molten bath is zinc and optionally contains one or more additional elements selected from Si, Sb, Pb, Ti, Ca, Mn, Sn, Zr, Sr, La, Ce, or Bi, with the weight-related content of each additional element in the metal coating being less than 0.1% and including unavoidable impurities.

[0018] In all embodiments, the zinc alloy of the zinc alloy molten bath has the following composition, namely, - an aluminum content of less than 1.0 weight percent, preferably within the range of 0.1 to 0.5 weight percent and - the remainder of the zinc alloy molten bath is zinc and unavoidable impurities.

[0019] In all or at least some of the embodiments, the device may be set or prepared to produce and coat flat steel products according to a specification having a ZnAlMg layer or a ZnAl layer and to blow off the layer before coating.

[0020] When setting / preparing the device, the following system parameters and / or method parameters, namely, - the bath temperature of the alloy molten bath, and / or - the thickness of the nozzle lip gap, and / or - the distance between the nozzle lip gap and the front or rear side of the flat steel product, - the strip width of the flat steel product, - the strip speed at which the flat steel product is moved along the peeling nozzle device, - The flow rate of the gas discharged through the nozzle lip gap in the forward or rearward direction One or more of which are determined.

[0021] Preferably, for all system parameters and / or method parameters in all embodiments, the following definitions, namely - The thickness of the nozzle lip gap is in the range of 0.5 to 5 mm, preferably in the range of 0.6 to 2 mm, particularly preferably in the range of 0.8 to 1.5 mm, and / or - The effective flow rate D across the strip width is in the range of 200 to 8000 Nm 3 per hour, and / or - The distance between the nozzle lip gap and the front or rear side of the flat steel product is in the range of 2 to 15 mm, preferably in the range of 3 to 12 mm, and / or - The strip speed is in the range of 50 to 200 m / min, preferably in the range of 70 to 150 m / min apply.

[0022] The system parameters and method parameters define the so-called peeling efficiency AWZ, which is essentially constant when applying the layer (as long as the corresponding parameters do not change). However, a slight variation in the peeling efficiency AWZ is also possible.

[0023] All embodiments may then have the following sensor constellations, namely - At least one sensor for determining the absolute local humidity in the near-field region of the device, or - At least one sensor for determining the absolute local humidity within the periphery of the device, or - At least one sensor for measuring the absolute local humidity in the near-field region of the device and at least one sensor for measuring the absolute local humidity within the periphery of the device One of which may be included.

[0024] In all or at least some of the embodiments, the method involves passing a flat steel product through a zinc alloy molten bath (ZnAl, ZnAlMg) with a ZnAlMg layer or a ZnAl layer according to the target specifications, such that it is applied to at least one side of the flat steel product. On the discharge side thereof, stripping gas exits through the nozzle lip gap of at least one gas nozzle in the direction of the flat steel product, blowing off the coating according to the target specifications, and the stripping efficiency AWZ is the following parameter that is essentially kept constant when applying the coating, namely, d Thickness of the nozzle lip gap of the gas nozzle of the stripping nozzle device, D Nm 3 Effective gas flow rate (quantity) of gas per side of the flat steel product across the strip width in units of / h, w Strip width of the flat steel product in units of mm, 2b Half-width of the pressure distribution of the gas in the flat steel product in units of mm, v Strip speed in units of m / min at which the flat steel product is moved along the stripping nozzle device is defined by, This method includes the following steps, namely, - Before and / or during the execution of the method, the absolute local humidity in the controlled water vapor atmosphere in the near-field region on the front and / or rear side of the flat steel product, and / or the ambient air humidity f UG is determined, - The determined humidity (determined, for example, as absolute humidity) is related to the stripping efficiency AWZ to determine whether the condition f > AWZ or f UG > AWZ is satisfied, - If the condition is satisfied, the method of applying the layer is initialized or continued, or if the condition is not satisfied, the absolute local air humidity in the controlled water vapor atmosphere in the near-field region is increased by using a water vapor device adapted to release gaseous water vapor, such that the condition f > AWZ is satisfied in the near-field region, and then the method of applying the layer is initialized or continued characterized by including.

[0025] In at least some embodiments, the peeling efficiency is

[0026]

Number

[0027] defined as follows.

[0028] In at least some embodiments, the peeling efficiency is

[0029]

Number

[0030] defined as follows.

[0031] In each case, the following, namely, d is the thickness of the nozzle lip gap of the gas nozzle of the peeling nozzle device, D is the effective gas flow rate (quantity) of the gas for each side of the flat steel product across the strip width, k is a proportionality coefficient of a dimensionless quantity, w is the strip width of the flat steel product, 2b is the half-width of the pressure distribution of the gas in the flat steel product, v is the strip speed at which the flat steel tray product is moved along the peeling nozzle device applies.

[0032] When determining the values for the half-width and the proportionality coefficient using the ratio of the distance to the thickness of the lip gap of the nozzle, the following definitions, namely, Case 1.1:

[0033]

Number

[0034] Case 1.2:

[0035]

Number

[0036] Case 1.3:

[0037]

Number

[0038] is applied.

[0039] In order to prevent the formation of marble patterns and / or cotton swab defects in the ZnAlMg layer or ZnAl layer to be formed, in at least some of the embodiments, the absolute local humidity f is determined within the near-field region of the controlled water vapor atmosphere. Preferably, in all embodiments, the absolute local humidity f of the controlled water vapor atmosphere is determined within a predefined virtual cylindrical volume that surrounds or encloses the flat steel product within the region of at least one gas nozzle. In this case, this predefined virtual cylindrical volume defines the near-field region. Since the gas mixing is carried out near the front and rear sides of the flat steel product, when defining the virtual cylindrical volume, the regions parallel to the front and rear sides of the flat steel product are excluded. Preferably, the virtual cylindrical volume is limited for this purpose by two planes each having a distance s / 2 from the flat steel product.

[0040] Determined ambient humidity f UG is greater than the peeling efficiency (i.e., f UG > AWZ), the layer can be formed without marble patterns or without the formation of cotton swab defects. The determined ambient humidity f UG is currently lower than the peeling efficiency (i.e., f UG < AWZ), the absolute local humidity f in the controlled water vapor atmosphere is intentionally increased until the absolute local humidity f in the near-field region is greater than the peeling efficiency (f > f UG and f > AWZ). Only then is a coating formed without marble patterns or without the formation of cotton swab defects.

[0041] In at least some of the embodiments, the absolute local humidity f of the controlled water vapor atmosphere is generated by using a water vapor device. That is, the water vapor device is configured to selectively increase the absolute local humidity f in the controlled water vapor atmosphere, i.e., within the short-distance region.

[0042] In all embodiments, the controlled water vapor atmosphere is defined within the short-distance region of the water vapor device, or the controlled water vapor atmosphere is provided within the short-distance region of the water vapor device. In all embodiments, this short-distance region can be defined by a predefined virtual cylindrical volume that extends to both sides of the flat steel product and surrounds or encloses at least one gas nozzle. However, in all embodiments, this volume can also be optionally defined by a housing or enclosure that surrounds the flat steel product from both sides. When a housing or enclosure is used, the inner region thus defined is referred to as the short-distance region.

[0043] In at least some of the embodiments, the short-distance region of the water vapor device has a volume in the range of 1 m 3 to 10 m 3 and preferably at least 2 m 3 in volume. When determining the absolute local humidity within the short-distance region (by direct or indirect measurement), it must be considered that the flat steel product can be drier directly compared to regions further away from the flat steel product due to the mixing of gaseous water vapor and stripping gas.

[0044] In all embodiments, the absolute local humidity is preferably selectively increased in the short-distance region of the water vapor device (when the ambient humidity f UG should be less than AWZ), and the monitoring or control of the current absolute local humidity is performed using direct or indirect measurements at a distance more than 20 cm from the flat steel product to avoid significantly drier regions.

[0045] In all embodiments, the device or the peeling nozzle system may comprise an automatic coating control configured to automatically adjust the flow rate of the (peeling) gas in order to maintain the target thickness of the coating to be applied essentially constant. The automatic coating control is preferably configured to be able to compensate for variations in one or more system parameters and method parameters.

[0046] In all embodiments using a ZnAlMg alloy molten bath, the aluminum content (in weight percent) may be equal to or greater than the magnesium content (in weight percent).

[0047] In all embodiments or at least some of the embodiments, the unavoidable impurities are in a range significantly less than 1 weight percent (wt.%), preferably the total of all unavoidable impurities is less than 0.5 weight percent.

[0048] The exact defined bath composition, the ambient humidity f in the close vicinity of the water vapor device UG and optionally, the combination of monitoring or observing the current absolute local humidity f and the targeted adjustment of the absolute local air humidity f in the close vicinity of the water vapor device can form a surface showing no or negligible marble pattern and no or negligible brush defects. During the formation of the corresponding coating, the peeling efficiency AWZ is kept essentially constant to obtain a consistent coating (within the range of the given specifications).

[0049] In all embodiments, according to the invention, the value of the absolute local air humidity f to be present within the close vicinity of the flat steel product is in the range from 1 g / Nm 3 to 300 g / Nm 3 preferably in the range from 2.71 g / Nm 3 to 50 g / Nm 3 which means that the device can be reliably operated at an absolute local humidity f within the described range of values.

[0050] In all embodiments, following the peeling nozzle device, optionally, a strip stabilization device may follow which functions to automatically stabilize the movement of the flat steel product.

[0051] In all embodiments, the device preferably - in an alloy melting bath in which the bath temperature TB is in the range of 400 < TB < 480 °C, preferably in the range of 409 < TB < 473 °C, particularly preferably in the range of 420 < TB < 460 °C, - by a nozzle distance from the flat steel product in the range from 2 to 15 mm, preferably in the range from 3 to 12 mm, - using a gas flow in the range from 200 to 8000 Nm per hour per meter of strip width 3 flows through the nozzle lip gap in the direction of the flat steel product, and blows off the flat steel product on the outlet side of the alloy melting bath using (peeling) gas, is operated.

[0052] The specifications of the ZnAl and ZnAlMg alloy concepts defined above are the result of numerous investigations and calculations. Within the specified limits of the alloy concepts defined here, the technical teachings presented here have been found to be particularly successful.

[0053] In at least some of the embodiments, the ambient moisture f UG is measured permanently.

[0054] In at least some of the embodiments, the ambient moisture f UG is measured from time to time.

[0055] In at least some of the embodiments, the absolute local humidity f is measured permanently in the near - distance region.

[0056] In at least some of the embodiments, the absolute local humidity f within the near - distance region is measured from time to time.

[0057] Preferably, in all embodiments, the device comprises: <TB red Bath temperature TB in the range of <460°C red In this range, slag formation may also be reduced.

[0058] In particular tests it has been shown that the method described here gives very good results in practice. It has been shown that excellent results can be obtained through targeted (pre)adjustment of the stripping process (or the corresponding stripping efficiency AWZ) as long as the absolute local air humidity f is set or specified higher than the stripping efficiency AWZ in the near field.

[0059] The development of the new method and the targeted adaptation of the absolute air humidity f in the near-field area to the (method and system) parameters (or the corresponding stripping efficiency AWZ) are based on theoretical considerations, various simulations of the stripping process and numerous tests.

[0060] The process in the area of ​​the stripping nozzle device and on the flat steel product is highly complex and depends on a large number of (method and system) parameters and influencing variables (or the corresponding stripping efficiency). Therefore, the device relies on some simplifying assumptions and specifications to obtain reproducible results.

[0061] By specifically increasing the absolute local humidity f in the controlled water vapor atmosphere (called the near field region), additional freedom is gained for the definition or specification of method and system parameters.

[0062] Further advantageous embodiments of the invention are the subject of the dependent claims.

[0063] Embodiments of the invention are explained in more detail below with reference to the drawings. [Brief description of the drawings]

[0064]

Figure 1

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 3C

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Figure 7

Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0065] This relates to a device 150 (see for example FIG. 2A) for applying a layer 10 to a strip-shaped flat steel product 100 (see FIG. 2B where layer 10 can be vaguely recognized on both sides). This layer 10 is formed by passing the flat steel product 100 from the input side E through a zinc alloy molten bath 11 to the output side A and blowing it off on the output side A with a (stripping) gas G using a stripping nozzle device 14. The purpose of the stripping nozzle device 14 is to strip off the excess (still liquid) ZnAlMg layer or ZnAl layer (layer 10) at the flat steel product 100 after it exits the bath 11.

[0066] In the context of the present invention, care should be taken to ensure that the layer 10 is formed according to (predetermined) specifications (the specifications define, for example, the target thickness) and that no marble pattern and / or matchstick defects occur. More precisely, it is important to avoid these "defects" when the ambient conditions in the production area (for example, the production hall) change. The ambient air humidity f UG Even if it may change around the device 150, the device 150 according to the present invention ensures that no marble pattern and / or matchstick defects occur and that the layer 10 continues to be produced according to the specifications.

[0067] In all embodiments, the specifications can specify, for example, the target thickness of the layer 10 and / or the target (surface) coating of the layer 10. Typically, there is a narrowly specified tolerance range for the target thickness. As long as the layer 10 to be formed is within the tolerance range, the layer 10 essentially meets the requirements of the specifications.

[0068] In at least some of the embodiments, the device 150 is operated and controlled such that each layer 10 on the strip side of the flat steel product 100 has a target thickness within the tolerance range of the specifications. Preferably, in all embodiments, the target thickness of each layer 10 on the side of the strip is in the range of 3 to 30 μm, and particularly preferably in the range of 4.5 to 15 μm.

[0069] Preferably, in at least some of the embodiments, the target surface coating (coating for each side of the strip) is in the range of 20 to 200 g / m 2 and particularly preferably in the range of 30 to 100 g / m 2 .

[0070] The process within the area of the peeling nozzle device 14 and at the flat steel product 100 is very complex and depends on a number of parameters and influencing variables.

[0071] In all embodiments, the peeling nozzle device 14 comprises at least one gas nozzle 15 (if only one side of the strip is to be blown off), or two gas nozzles 15 facing each other (if both sides of the strip are to be blown off). Figures 2A and 5 show an embodiment with two nozzles 15, and Figure 3A shows an embodiment with only one nozzle 15. The flow rate D of the (peeling) gas G discharged in the forward or rearward direction through the nozzle lip gap 17 is here indicated in Nm 3 (Nm 3 represents standard cubic meters). A standard cubic meter is the amount of gas G contained in a volume of 1 cubic meter. This applies at a temperature of 0 °C and a pressure of 1.01325 bar.

[0072] In order to be able to reliably apply the ZnAlMg-based layer 10 which essentially corresponds to the target thickness, the zinc alloy in the zinc alloy melt bath 11 has, in all or at least some of the embodiments, the following composition, namely - an aluminum content in the range of 1.0 weight percent to 3.5 weight percent, preferably in the range of 1.3 weight percent to 2.8 weight percent, and - a magnesium content in the range of 1.0 weight percent to 2.5 weight percent, preferably in the range of 1.2 weight percent to 2.2 weight percent and has a composition of - The remaining part of the zinc alloy molten bath 11 is zinc and, optionally, contains one or more additional elements selected from Si, Sb, Pb, Ti, Ca, Mn, Sn, Zr, Sr, La, Ce, or Bi, and the weight-related content of each additional element in the metal coating (i.e., within layer 10) is less than 0.1% and includes inevitable impurities.

[0073] In at least some of all embodiments or embodiments related to the ZnAlMg-based layer 10, the metal bath, as the alloy molten bath 11, has the following alloying concept, namely, - The aluminum content (in weight percent) is in the range of 2.09 weight percent to 2.66 weight percent, - The magnesium content (in weight percent) is in the range of 1.45 weight percent to 2.24 weight percent, - The remaining part is zinc and, optionally, contains one or more additional elements selected from Si, Sb, Pb, Ti, Ca, Mn, Sn, Zr, Sr, La, Ce, or Bi, and the weight-related content of each additional element in the metal coating (i.e., within layer 10) is less than 0.1% and includes inevitable impurities A particularly preferred ZnAlMg alloy having a composition according to this is supplied.

[0074] To ensure that a ZnAl-based layer 10 essentially corresponding to the target thickness can be implemented, the zinc alloy of the zinc alloy molten bath 11, in all or at least some of the embodiments, has the following composition, namely, - An aluminum content of less than 1.0 weight percent, preferably in the range of 0.1 to 0.5 weight percent and - The remaining part of the zinc alloy molten bath is zinc and inevitable impurities.

[0075] To prevent the formation of marble patterns and / or toothpick defects, or to significantly reduce marble patterns and toothpick defects, the absolute local air humidity f and / or the ambient air humidity f within the near-distance region NB UGis preferably determined continuously or occasionally (e.g., by direct or indirect measurement) in all embodiments.

[0076] In all embodiments, device 150 includes a water vapor device 50 (see FIGS. 2A and 5), which is described in more detail. This water vapor device 50 is preferably arranged in the region of the outlet side A of bath 11 in all embodiments.

[0077] In at least some of the embodiments, the absolute local air humidity f within the short - range region NB (see FIGS. 2A and 5) of the water vapor device 50 is specifically adjusted (increased). In FIGS. 2A and 5, the corresponding device 150 is arranged or configured within the short - range region NB or is provided with a humidity sensor 51 protruding into the short - range region NB so as to be able to continuously or occasionally control the absolute local air humidity f within the short - range region NB. The control of the absolute local air humidity f within the short - range region NB enables a targeted control of the air humidity f within the short - range region NB.

[0078] However, in all embodiments, the humidity sensor 51 for determining the absolute local air humidity f can also be arranged and configured at different locations of the device 150.

[0079] In all embodiments, device 150 may include at least one humidity sensor 56 for determining the ambient air humidity f, as shown in the upper right of FIGS. 2A and 5. UG

[0080] The absolute air humidity f is a physical quantity that can be expressed, for example, in units of g / m 3 . In other words, this is the mass ratio of the gaseous water WG within a standardized volume body having a volume of 1 m 3 . In other words, the absolute air humidity f indicates the content of water vapor that is gaseous within the volume body. f and f UG are here used as symbols in the formula for the absolute air humidity. In all embodiments, the absolute air humidity f and f UG ​can be approximately estimated from the air temperature TL and the relative air humidity r, whereby the formula

[0081] [Number]

[0082] is applied, provided that r is the relative air humidity in % units, TL is the air temperature in °C units.

[0083] In all embodiments, the measurement / monitoring of the absolute local air humidity f can be carried out directly or indirectly (preferably within the short - distance region NB). Indirect measurement is understood to mean, among other things, measuring the air temperature TL and the relative air humidity r and calculating / deriving the absolute local humidity f. Thus, the ambient air humidity f UG can also be determined in all embodiments by measuring the air temperature TL and the relative air humidity r of the ambient air and calculating / deriving the absolute ambient air humidity.

[0084] According to the invention, the value of the absolute local air humidity f, which should be present near the flat steel product 100 within the short - distance region NB between the outlet side A and the cooling region 16 (if present), is in the range of from 1 g / m 3 to less than 300 g / m 3 in all embodiments. Preferably, the absolute local air humidity f is in the range of from 2.71 g / m 3 to 50 g / m 3 in all embodiments.

[0085] The device 150 enables the targeted adaptation / adjustment of the absolute local air humidity f within the short - distance region NB within the value range of from 1 g / m 3 to 300 g / m 3 .

[0086] For this purpose, in all embodiments, the device 150 can comprise at least one vapor generator DG within or near the short - range region NB. In FIG. 2A, an embodiment having two vapor generators DG is shown, which are placed on the upper edge of the short - range region NB near the front and rear sides of the flat steel product 100. FIG. 5 shows an embodiment having four vapor generators DG, which are placed outside the short - range region NB and introduce gaseous steam WG into the short - range region NB via gas pipelines 54 and inlet bridges 53 near the front and rear sides of the flat steel product 100.

[0087] Preferably, in all embodiments, one or more vapor generators DG, adapted as high - purity vapor generators that generate gaseous steam WG from purified water or highly purified water, are used.

[0088] Before the layer 10 is applied to the flat steel product 100 and before the layer 10 is blown off, the device 150 is set or prepared. During the setting / preparation process, in all embodiments, the following system parameters and / or method parameters, namely, - the bath temperature (TB) of the molten bath 11, and / or - the thickness of the nozzle lip gap 17, and / or - the nozzle distance Z between the nozzle lip gap 17 and the front or rear side of the flat steel product, - the strip width w of the flat steel product 100, - the strip speed v at which the flat steel product 100 is moved through the peeling nozzle device 14, - the flow rate of the (peeling) gas G discharged through the nozzle lip gap 17 in the front or rear direction of one or more of these can be set.

[0089] In all embodiments, care is taken such that system parameters and / or method parameters are specified such that layer 10 to be applied essentially corresponds to the specification. This means that, for example, a layer 10 is applied and blown off such that it corresponds to the target thickness (within the tolerance range) and at the same time shows no or only very few marble patterns and no or only very few toothpick defects.

[0090] In all embodiments, the current flow rate D of gas G can be automatically adjusted in a known manner (e.g., for each control by automatic coating control) so as to essentially keep the target thickness of layer 10 to be applied constant when one or more of the system parameters and / or method parameters are to be changed.

[0091] The mathematical relationships that can be used here during setting / preparation are explained below. Also explained is how the so-called peeling efficiency AWZ can be defined by method and system parameters.

[0092] Figure 3A also shows the nozzle distance Z between the nozzle 15 and the corresponding strip side (here the front side) of the flat steel product 100, and further the thickness d of the nozzle lip gap 17. The nozzle lip gap 17 serves as the gas outlet gap of the peeling nozzle device 14.

[0093] Figure 3A additionally, purely schematically, shows the supply of gaseous water vapor WG according to the invention (by means of two block arrows on the right and left sides of the nozzle 15).

[0094] Figure 3A can be used to define adjustable parameters (system parameters and method parameters), or the peeling efficiency AWZ. Important adjustable method and system parameters are - the thickness d of the nozzle lip gap 17, - the flow rate D of gas G, - The distance Z between the nozzle lip gap 17 and the (strip) side of the flat steel product 100, - The strip speed v at which the flat steel product 100 is moved out of the zinc alloy molten bath 11 (advancing parallel to the x-axis) is as follows.

[0095] Figure 3B shows a schematic diagram of the gas pressure curve P generated along the front side of the flat steel product 100. The pressure P depends on the position on the x-axis. Ideally, the pressure curve P has the shape of a Gaussian curve as shown in Figure 3B. This Gaussian curve is often used to determine the half-width at P S / 2, where P S represents the maximum pressure. 2b represents the half-width in millimeters. A narrow gas jet is defined by a small half-width 2b. The larger (wider) the gas jet becomes, the larger the half-width 2b becomes. Further detailed information is described in Non-Patent Document 1.

[0096] The gas jet emerging from the nozzle 14, together with the force of gravity (for example, when the flat steel product 100 is pulled vertically upward from the bath 11 as shown in Figures 2A and 5), applies a shear force τ to the stationary liquid layer 10. Figure 3C shows the shear force τ with respect to the position on the x-axis (the shear force τ is determined by the negative first derivative of the pressure profile in Figure 3B). This is the shear force τ acting on the layer 10 to be peeled off. The course of the shear force curve τ is symmetric with respect to the point x = 0, τ = 0 as a first approximation (when the strip speed v parallel to the x-axis is ignored). The nozzle 15 is arranged directly above the x = 0 position where the distance Z > 0. τ max defines the maximum shear force occurring in the layer 10 to be peeled off.

[0097] Between the time t (see Figure 3C) for the strip-shaped flat steel product 100 to pass through the distance l between the maximum shear forces, the strip speed v, and the half-width 2b, there is Equation (1)

[0098]

Equation

[0099] There is a direct relationship as represented by

[0100] In all embodiments, the strip speed v is preferably in the range of 50 m / min to 200 m / min, and particularly preferably in the range of 70 m / min to 150 m / min.

[0101] The equation describing the dynamic flow behavior of the gas G in the flat steel product 100 is very complex. This is due to the fact that in the gas jet exiting through the nozzle lip gap 17 of the nozzle 15, regions having a laminar flow pattern and a turbulent flow pattern are formed on the layer 10 of the flat steel product 100. Additionally, the gas jet draws in ambient air, and the ambient air swirls together with the gas G. Details are described, for example, in Non-Patent Document 1 already mentioned. In addition to the ambient air, the gas jet also draws in gaseous water vapor WG.

[0102] The statistical evaluation of complex tests and measurement results did not result in directly usable results regarding the correlation with the peeling nozzle parameters, air humidity, and the marble pattern due to the complex interrelationships. Only after a systematic investigation of various internal and external influencing variables did a correlation appear between the degree of the marble pattern of the layer 10 and the ambient conditions of the test facility. Air humidity, in particular, shows an influence on the marble pattern.

[0103] Further targeted investigations and graphical processing of the results of these tests first showed the correlation between (ambient) air humidity and the marble pattern. FIG. 4 shows a summary graphical representation of a number of tests, with the absolute air humidity f (g / m 3 ) on the vertical axis and the peeling efficiency AWZ (as a summary or generic term for method and device parameters) on the horizontal axis.

[0104] By weighting and adding two variables τ max and t (see also FIG. 3C and Equation (1)), the absolute ambient air humidity fUG The peel efficiency AWZ, which can be directly compared, is as follows (inequality (2.1)), that is,

[0105]

Number

[0106] can be determined as follows.

[0107] The right side of inequality (2.1) corresponds to the peel efficiency AWZ, that is, the following relational expression (2.2) f UG > AWZ (2.2) holds.

[0108] In at least some embodiments, the peel efficiency is as follows, that is,

[0109]

Number

[0110] is defined as follows.

[0111] In at least some embodiments, the peel efficiency is

[0112]

Number

[0113] is defined as follows.

[0114] In each case, as follows, that is, d is the thickness of the nozzle lip gap of the gas nozzle of the peel nozzle device 14, D is the effective gas flow rate (quantity) of the gas G per side of the flat steel product 100 over the strip width w, k is a proportionality coefficient of a dimensionless quantity, w is the strip width of the flat steel product 100, 2b is the half-width of the pressure distribution of the gas G in the flat steel product 100, v is the strip speed at which the flat steel product 100 is moved along the peeling nozzle device 14 is applicable.

[0115] When determining the values for the half of the half-width b and the proportionality coefficient k using the ratio of the nozzle distance Z to the thickness d of the nozzle lip gap 17, the following definitions, namely, Case 1.1:

[0116]

Number

[0117] Case 1.2:

[0118]

Number

[0119] Case 1.3:

[0120]

Number

[0121] is applicable (by which, three cases 1.1, 1.2 and 1.3 are distinguished).

[0122] Figure 4 is referred to below. The black-filled circles in Figure 4 represent flat steel products 100 with a marble pattern clearly formed on the surface of layer 10, and the gray-filled circles represent flat steel products 100 with a medium marble pattern formed. On the other hand, the unfilled circles represent that there is no marble pattern or the degree is negligible. All the tests shown were carried out at a nozzle lip gap thickness of d = 1.0 mm.

[0123] In total, five pairs of tests (Examples 1 to 5) are shown in Figure 4. The corresponding methods and system parameters, as well as the peeling efficiency AWZ and the absolute air humidity f measured within the near - distance region NB, are shown in Table 1. Table 1 is shown as Figure 7. The third column from the end in Table 1 indicates whether the water vapor device 50 was switched on to increase the local air humidity. The black, gray, and white circles are used in Table 1 according to Figure 4. The second - last column indicates in text form whether there was a strong marble pattern, a medium marble pattern, or no marble pattern at all, and the last column on the far right in Table 1 indicates whether the condition of the inequality f > AWZ was satisfied.

[0124] The straight line Ge is inserted into the graph of Figure 4 as a boundary line, and as a first approximation, it distinguishes those tests with a marble pattern from those tests that showed no marble pattern or only a negligible degree of marble pattern. In the tests above the straight line Ge, no marble pattern appears or only a negligible degree of marble pattern appears (the corresponding flat steel product 100 with a layer 10 without a marble pattern is shown in Figure 6A). The straight line Ge can be well understood as a function of the peeling efficiency AWZ, f = AWZ is defined as.

[0125] A detailed evaluation of the test results shows that it is possible to ensure that the inequality (2.2) is always satisfied during production by specifically increasing the absolute local air humidity f within the near - distance region NB for a given peeling efficiency AWZ.

[0126] In all embodiments, the bath temperature TB of the alloy melting bath 11 is preferably in the range of 400 < TB < 480 °C, preferably in the range of 409 < TB < 473 °C, and particularly preferably in the range of 420 < TB < 460 °C.

[0127] In all embodiments, the bath temperature TB within the specified temperature range is specified for operating the molten bath 11. It is important to maintain this temperature range (temperature domain) because more undesirable slag can form on the flat steel product 100 when operating beyond the specified range.

[0128] The bath temperature TB can be predetermined in all embodiments, for example, using an induction heating device 30 (see FIGS. 2A and 5) or a resistance heater.

[0129] To avoid slag formation, the alloy molten bath 11 is preferably operated at a reduced bath temperature TB red in all embodiments. The reduced bath temperature TB red is preferably within the range 420 < TB red < 460 °C as already described.

[0130] The bath temperature TB is an important parameter and can preferably be set / pre-set relatively freely within the aforementioned temperature limits in all embodiments when other method and system parameters are adjusted such that the AWZ remains essentially constant, and when the air humidity in the near - distance region NB is adjusted such that the condition f > AWZ is still satisfied.

[0131] When operating the device 150, in all embodiments, preferably the following, namely, - The thickness d of the nozzle lip gap 17 is in the range from 0.5 to 5 mm, preferably in the range from 0.6 to 2 mm, particularly preferably in the range from 0.8 to 1.5 mm, and / or - The flow rate D is in the range from 200 to 8000 Nm 3 per hour, and / or - The distance Z is in the range from 2 to 15 mm, preferably in the range from 3 to 12 mm, and / or - The strip speed v is in the range from 50 to 200 m / min, preferably in the range from 70 to 150 m / min Attention is paid to this.

[0132] The device 150 operates with particularly high reliability within these (value) ranges.

[0133] In all embodiments, the corresponding gas nozzle 15 has a longitudinal extension parallel to the y-axis. Preferably, in all embodiments, the nozzle 15 has an effective length (referred to as the nozzle length DL) corresponding to the strip width w of the strip-shaped flat steel product 100 (see FIGS. 6A to 6C). The thickness d of the gas nozzle 15 is defined parallel to the x-axis (see FIG. 3A).

[0134] In all embodiments, the strip width w of the strip-shaped flat steel product 100 is in the range from 500 mm to 2500 mm, particularly preferably in the range from 1159 mm to 1614 mm.

[0135] In at least some of the embodiments, the absolute local air humidity f in the short-distance region NB is measured permanently or sometimes, and when there is a "risk" that the absolute local humidity f in the short-distance region NB drops below the threshold value defined by the AWZ, the air humidity is increased by using the water vapor device 50. For this purpose, the steam generator DG can increase the release of gaseous water vapor, or the steam generator DG can be turned on to generate gaseous water vapor.

[0136] In at least some of the embodiments, the steam generator DG preferably includes a steam generator and a valve 55 (see FIG. 5) that can control the flow of gas through, for example, the conduit 54. For this purpose, the steam generator and / or the valve 55 can be connected to the control device 250 in all embodiments (not shown).

[0137] The absolute local air humidity f is preferably not directly measurable at the impact line where the gas G impinges on the layer 10 to be peeled off, since the mixed gas is relatively "dry" there (i.e., contains little air humidity). Instead, the local absolute air humidity f is preferably measured directly or indirectly in all embodiments in a region at least s / 2 = 20 cm away from the impact line. In the embodiment shown in FIG. 2A, the humidity sensor 51 is arranged accordingly slightly above the nozzle 15 and the impact line. In the embodiment of FIG. 5, the humidity sensor 51 is arranged slightly below the nozzle 15 and the impact line.

[0138] In FIG. 2B, the virtual cylindrical volume vZV is shown schematically as an example. This pre-defined virtual cylindrical volume vZV surrounds or encloses the flat steel product 100 within the region of at least one gas nozzle 15 (not shown in FIG. 2B). In this case, this pre-defined virtual cylindrical volume vZV defines the near-distance region NB. Since the mixing of the gases WG and G takes place near the front and rear sides of the flat steel product 100, the definition of the virtual cylindrical volume vZV excludes the regions parallel to the front and rear sides of the flat steel product 100, as shown in FIG. 2B. Preferably, the virtual cylindrical volume vZV is delimited for this purpose by two planes each having a distance s / 2 from the flat steel product 100.

[0139] FIGS. 2A and 5 show an approach for directly measuring the absolute local air humidity f and the ambient air humidity f UG The device 150 comprises, for example, two humidity sensors 51 (at least one on each side of the strip) and a humidity sensor 56. In the schematic view, each of these sensors 51, 56 has two contacts, which can be connected, for example, to the controller 250. The corresponding connections or lines V1, V2, V3, V4, V5, V6 are shown in FIGS. 2A and 5 by dashed lines.

[0140] In all embodiments, as humidity sensors 51 and 56, sensors of the following design or operating mode, namely, - Mechanically operating measurement sensors based on the expansion or contraction of a (usually organic) measurement element caused by humidity, - Psychrometric measurement sensors in which two identical very precise thermometers are used and the gas flow to be measured is induced at a defined speed, - Capacitance measurement sensors, for example, equipped with a humidity-sensitive capacitor having two planar electrodes, - Dew point hygrometers that determine the air humidity with a dew point mirror and evaluate the condensation of water vapor when the dew point is exceeded, - Resistance measurement methods, for example, in which the impedance of the alternating current resistance of a moisture-absorbing element is determined, - Spectroscopic measurement methods, for example, that measure the gaseous moisture content in the near or mid-infrared (NIR or MIR) range without contact, can be used.

[0141] When indirectly measuring the absolute local air humidity f or the ambient air humidity f UG the air humidity is not measured directly, but the current air humidity is determined indirectly (for example, optically).

[0142] The indirect determination of the absolute local air humidity f can be carried out in all embodiments by measuring the surface properties of the coated flat steel product 100 (three examples of the coated flat steel product 100 are shown in FIGS. 6A, 6B, and 6C). The corresponding measurement of the surface properties can be carried out optically, for example, before or after an optional cooling zone 16 (for example, by optically measuring the reflectivity of the surface of layer 10). If there is little or no marble pattern, the reflectivity is higher than a predetermined limit value. If the reflectivity decreases (for example, falls below the tolerance limit), the air humidity in the short-distance region NB can be adjusted so that the inequality f > AWZ is satisfied again.

[0143] All embodiments of device 150 may include a controller 250. In all embodiments, this controller 250 is configured as a computer-aided automation and control unit and may include a human-machine interface, a computer, and a database.

[0144] In all embodiments, the controller 250 may be part of the overall system controller of device 150 or may be connected to the overall system controller in all embodiments.

[0145] The setting / preparation of device 150 by adjusting parameters (system parameters or method parameters) may then be performed in these embodiments by the overall system controller and / or by the controller 250.

[0146] In all embodiments, the aforementioned peeling efficiency AWZ may be calculated by the controller 250 and / or the overall system controller. The corresponding formula is described below. However, in all embodiments, the peeling efficiency AWZ may also be determined by external means (e.g., using a workstation computer).

[0147] Preferably, an inert gas is used as the (peeling) gas G in all embodiments. Nitrogen or a gas mixture containing nitrogen has been demonstrated to be particularly effective.

[0148] Note that the system and method parameters, or the peeling efficiency AWZ, remain essentially constant in order to ensure that the target thickness of layer 10, i.e., the coating for each side of the strip, does not change or changes very little. In Examples 1 and 2, AWZ remains constant (see Table 1 in Figure 7). In Examples 3, 4, and 5, AWZ remains essentially constant (see Table 1 in Figure 7).

[0149] However, when particularly increasing the absolute local air humidity f within the short-distance region NB, attention should be paid to ensuring that, in addition to the marble pattern, other defects such as the formation of toothpick-shaped defects and slag are also avoided.

[0150] For example, when the ambient air humidity f UG is very low, the intake of dry ambient air can cause the formation of a marble pattern on the layer 10 (when f UG is smaller than AWZ). Here, the present invention plays its role by automatically increasing the absolute local air humidity f in the controlled water vapor atmosphere within the short-distance region NB of the flat steel product 100 while AWZ is substantially kept constant.

[0151] Preferably, the inequality (2.2) is implemented in the controller 250 by software, or a pair of values for the peeling efficiency AWZ and the corresponding minimum humidity f min to be specified is stored in one or more tables. By using a "look-up" table, the controller 250 can then determine the minimum value f min for the absolute local air humidity value f for the currently effective peeling efficiency AWZ and transfer it to the water vapor device 50. The water vapor device 50 then generates an absolute local humidity value f within the short-distance region NB that is greater than f min In these embodiments, f min corresponds, although with some difference, to the straight line Ge in FIG. 4.

[0152] In all embodiments, parameters (system and / or method parameters) within the following numerical values or value ranges are preferably used. The individual numerical values or value ranges in Table 2 (Table 1) are not correlated with each other or are only correlated in partial ranges because their respective maximum and minimum values are derived from different test cases. Only their respective maximum and minimum values are obtained from Table 1 (FIG. 7) and summarized here.

[0153]

Table 1

[0154] Table 1 (see Figure 7) shows specific numerical values for the test results shown in Figure 4. Table 1 in Figure 7 designates suitable methods and / or system parameters, or the peeling efficiency AWZ, and by increasing the absolute local humidity value f within the short-distance region NB (as shown by way of example in Figure 6A), shows five test examples in which a layer 10 without a visible marble pattern was formed. In the first two columns of Table 1, the coating and strip width w for each side of the flat steel product 100 are given according to the specifications.

[0155] In the test examples shown graphically in Figure 4 and shown in Table 1 (Figure 7), the following principle was applied. When marble pattern defects occurred under a given ambient air humidity f UG under given method and system conditions, the absolute local air humidity f within the short-distance region NB (corresponding to the left side of inequality (2.2)) can be increased according to the present invention until inequality (2.2) is satisfied at least within the short-distance region NB in order to eliminate the marble pattern.

[0156] The method and system conditions, i.e., the parameters of the process and the peeling nozzle, can be left unchanged except for normal variations in production, as can be seen by looking at Table 1 (Figure 7).

[0157] Table 1 uses five examples 1 to 5 to illustrate the use of the water vapor device 50 for increasing the absolute local humidity f within the short-distance region NB.

[0158] In certain embodiments 1 to 5, the nozzle spacing Z, the nozzle lip gap d, and the strip speed v are kept constant, and the coating, strip width w, nozzle pressure, flow rate D, and bath temperature TB are not intentionally changed and only follow normal manufacturing variations. This means that in each of the embodiments, the stripping efficiency AWZ calculated thereby does not essentially change (±10%). Preferably, the device 150 is operated in all embodiments such that when the absolute local air humidity f in the short-distance region NB is increased and the method and system parameters are adjusted, the calculated stripping efficiency AWZ changes by a maximum of ±5%.

[0159] The initial situation for Example 1 is shown below 1.1 in Table 1 (Table 1, row 1.1). With the given method and stripping nozzle parameters, as a result, the currently dominant absolute ambient air humidity f UG is 3.8 g / m 3 and according to inequality (2.2), the stripping efficiency AWZ is 9.6. The condition of inequality (2.2) for production without generating a marble pattern, i.e., f > AWZ, is not satisfied. In fact, strong marble pattern defects also occurred in production under these conditions. Figure 4 shows the corresponding black circles at AWZ = 9.6 and f = 3.8 g / m 3 .

[0160] Based on this, the local absolute air humidity f in the short-distance region NB was increased from 3.8 to 20.6 g / m 3 using the water vapor device 50, and the method and stripping nozzle parameters remained within the range of normal process scatter (Table 1, row 1.2). After the targeted increase in the air humidity f value, the condition of inequality (2.2) for production without generating a marble pattern, i.e., f > AWZ, was not satisfied. In fact, marble pattern defects no longer occurred on layer 10 under these conditions. Figure 4 shows the corresponding white circles at AWZ = 9.6 and f = 20.6 g / m 3 . The block arrow with the designation 1.1 → 1.2 shows this first example.

[0161] Examples 2 to 5 should be understood to be similar to Example 1. The block arrow with the designation 2.1→2.2 identifies the second embodiment, and the block arrow with the designation 3.1→3.2 identifies the third embodiment. Examples 4 and 5 are also shown as best as possible in FIG. 4.

[0162] Pairs of values for the peeling efficiency AWZ and the absolute local air humidity f may be excerpted from Table 1 of FIG. 7 (sorted in ascending order of the peeling efficiency AWZ). All values for the absolute local air humidity f are greater than their respective AWZ (in FIG. 4, the corresponding white-filled circles are above the straight line Ge).

[0163]

Table 2

[0164] From Table 1 of FIG. 7, the following pairs of values may also be excerpted for the peeling efficiency AWZ and the absolute local air humidity f (sorted in ascending order of the peeling efficiency AWZ). All values for the absolute local air humidity f are smaller than their respective AWZ (in FIG. 4, the corresponding black or gray-filled circles are below the straight line Ge).

[0165]

Table 3

[0166] FIG. 5 shows a further embodiment of the device 150, the absolute local air humidity f within the short-distance region NB and the ambient air humidity f near the device 150 UGAn approach for directly measuring is also used here. The equipment of device 150 is similar to the device 150 shown in FIG. 2A, and thus the description of FIG. 2A is also referred to. However, in contrast to FIG. 2A, the device 150 in FIG. 5 has a housing 52. Such a housing 52 is optional because the water vapor device 50 is sufficient for the present invention when generating a sufficiently high absolute local air humidity f within the short-distance region NB.

[0167] The liquid ZnAlMg alloy or ZnAl alloy is placed in bath 11, which is shown here as a rectangular container with an open top. Only a short length section of the flat steel product 100 having a strip shape, after being lifted out of the immersion in bath 11, is shown in FIG. 5. The flat steel product 100 is vertically induced from bath 11 in the x-axis direction at a strip speed v between two opposing gas nozzles 15 of the peeling nozzle device.

[0168] Here, the water vapor device 50 is provided with the aforementioned housing 52, which is defined here, for example, by the shape of an approximate cylinder in three-dimensional space. In FIG. 5, this approximately cylindrical housing 52 of the water vapor device 50 is shown schematically. The housing 52 consists here of two housing halves arranged symmetrically with respect to the x-axis. The short-distance region NB defined in this way appears to be placed between the two halves of the housing.

[0169] The housing 52 of the steam device 50 can be divided into four quadrants in a schematic cross-section. Here, the steam device 50 includes one steam generator DG for each quadrant (i.e., two steam generators DG for each half of the housing). Each steam generator DG is arranged and configured outside the near-distance region NB (or outside the housing 52). As schematically shown, each steam generator DG can introduce gaseous steam WG into the near-distance region NB via a corresponding gas pipeline 54, valve 55, and inlet bridge 53. In the cross-sectional view of FIG. 5, it can be seen that each inlet bridge 53 is fluidly connected to the near-distance region NB via at least one passage opening in the housing 52. In this way, the gas can flow from each steam generator DG through the pipeline 54, valve 55, and inlet bridge 53 into the near-distance region NB. The housing 52 can optionally have a series of such passage openings parallel to the y-axis so that the gas WG can be evenly distributed within the near-distance region NB.

[0170] In this embodiment, the housing 52 of the steam device 50 sits directly on the nozzle 15 of the peeling nozzle device and has a housing height defined parallel to the x-axis. Preferably, the housing length defined parallel to the y-axis corresponds to at least the strip width w of the flat steel product 100 and / or the length DL of the nozzle 15 (which is also defined parallel to the y-axis) in all embodiments.

[0171] The housing 52 of the steam device 50 can also have different shapes in all embodiments.

[0172] As schematically shown, each of the nozzles 15 is supplied with an inert (peeling) gas G using a pump P G Two pumps P G are connected to the controller 250 for control (or regulation), and thus, for example, the controller 250 can control the gas flow rate D for each strip side. The corresponding connection lines or conduits are labeled V7, V8, V9, and V10 in FIG. 5. The pump PG Here, for example, it is referred to as a blower having a control valve.

[0173] Preferably, all embodiments of device 150 include control of the flow rate D of gas G (referred to as automatic coating control), which is configured such that layer 10 having an essentially constant target thickness is always produced even when other method and system parameters change. For this purpose, the control system comprises at least one sensor (not shown) that measures the actual thickness of layer 10 after excess molten zinc has been blown off. If the actual thickness is less than the target thickness, the control decreases the flow rate D and vice versa.

[0174] In all or at least some of the embodiments, the absolute local air humidity f in the near - distance region NB can be measured along a horizontal y - line that extends parallel to the flat steel product 100 and parallel to the y - axis (which is, for example, at least s / 2 = 20 cm away from the flat steel product 100). In the embodiment of FIG. 2A, the horizontal y - line described is placed approximately in the region between nozzle 15 of the peeling nozzle device 14 and the two steam generators DG. In the embodiment of FIG. 5, the y - line described is between the outlet side A of the bath 11 and nozzle 15 (here, slightly below nozzle 15).

[0175] Each of the nozzles 15 can be moved parallel to the z - axis by a motor or actuator (not shown). The motor or actuator can be connected to the controller 250. There is a sensor (not shown) to enable control of the nozzle spacing Z. This allows the nozzle distance Z to be set and / or controlled via the controller 250. The control of the nozzle distance Z can be laser - assisted in all embodiments. If half of the housing in housing 52 is mechanically connected to the nozzle 15, this half of the housing can be moved in conjunction with the nozzle.

[0176] In all embodiments, the controller 250 may also be connected to the induction heater 30 or the electrical resistance heater of the bath 11 to adjust the bath temperature TB. When the coil 30 is the induction heater shown in FIG. 5, the controller 250 can set the operating frequency for driving the coil 30 via the frequency generator FG. Accordingly, the frequency generator FG is connected to the controller 250 for control purposes as shown. The corresponding connection lines or conduits are labeled V11 and V12 in FIG. 5A.

[0177] Preferably, in all or at least some of the embodiments, the water vapor device 50 is configured to specify the absolute local air humidity f within a local area NB in the range from 1 g / m 3 to 300 g / m 3 and preferably in the range from 2.71 g / m 3 to 50 g / m 3 , and the water vapor device 50 is preferably switched on or switched in only when f UG <AWZ.

[0178] In all embodiments, the volume of the near-field region NB of the water vapor device 50 (e.g., defined by the virtual cylindrical volume vZV or the housing 52) can be in the range from 1 m 3 to 10 m 3 .

[0179] FIG. 8 shows exemplary steps of a method that can be carried out in the device 150 described. FIG. 8 shows the steps in the form of a flowchart. Before the method for applying the layer 10 to the flat steel product 100 is carried out, the individual components and elements of the device 150 are set or prepared (step S1). The device 150 can be set or prepared, for example, based on the target specifications of the layer 10 to be applied. The setting or preparation includes the definition and (pre-) setting of method and system parameters.

[0180] Before setting S1, during setting S1, or after setting S1, the corresponding peeling efficiency AWZ is determined (step S2). Then, one of the inequalities or a "look-up" table is used to determine whether the condition f > AWZ is satisfied (step S3). If f is greater than AWZ (YES in the flowchart), a method for applying layer 10 can be started (step S4). If the condition f > AWZ is not satisfied (NO in the flowchart), the method branches to step S5. In step S5, the air humidity f in the short-distance region NB is increased by the water vapor device 50. Then, again in step S3, it is checked whether the condition f > AWZ is currently satisfied.

[0181] Optionally, the method and / or system parameters may be slightly adjusted at an intermediate step, and this adjustment is preferably carried out such that AWZ remains essentially constant in all embodiments.

[0182] Similarly, the check of the condition f > AWZ may be repeated from time to time when applying layer 10, thereby enabling reaction to changing ambient conditions. If f within the surroundings or within the short-distance region NB of the device 150 decreases, it should be checked again (as in step S3) whether the condition f > AWZ is still satisfied. If yes, the application of layer 10 is continued. Otherwise, the air humidity f in the short-distance region NB can be increased (similar to step S5).

[0183] f UG If it drops significantly near the device 150 and no reasonable adjustment within the target specifications is possible, this process can be interrupted.

Explanation of Reference Numerals

[0184] 10 (protective) layer / (protective) coating 11 zinc melting bath / zinc alloy melting bath / (immersion) bath 12 trunk 13 roller 14 Nozzle / Peeling Nozzle Device 15 Gas Nozzle / Peeling Nozzle 16 Cooling Region 17 (Gas) Nozzle Lip Gap 30 Induction Heating Device 50 Additional Device / Steam Device 51 Humidity Sensor (Short - Range Region) 52 Housing 53 Inlet Bridge 54 Gas Pipeline 55 Valve 56 Humidity Sensor (Short - Range Region) 100 Plain Steel Product / Steel Strip / Steel Plate / Strip 100,10 Coated Plain Steel Product / Steel Strip / Steel Plate 150 Device 250 Controller A Outlet Side AWZ Peeling Efficiency 2b Half Width d Thickness of Nozzle Lip Gap D Gas Flow Rate per Band Side DG Steam Generator DL Nozzle Length E Inlet Side f Absolute Air Humidity f UG (Absolute) Ambient Air Humidity f min Minimum Value of Absolute Air Humidity FG Frequency Generator G (Peeling) Gas Ge Straight Line k Proportionality Coefficient NB Short - Range Range P Pressure P g Pump P S Maximum Pressure r Relative Air Humidity in % s / 2 Distance S1,S2,··· Steps T Temperature TL Air Temperature t Time TB Bath Temperature TB red Decrease in bath temperature τ Shearing force τ max Maximum shearing force generated v Strip speed V1, V2, V3, ··· Connection part / conduit vZV Virtual cylinder volume w Strip width WG Gaseous water vapor x-axis y-axis z-axis Z Nozzle interval

Claims

1. A device (150) for applying a layer (10) to the front side and / or the rear side of a flat steel product (100), comprising: - A zinc alloy molten bath (11) (ZnAl, ZnAlMg) having an inlet side (E) and an outlet side (A); - A peeling nozzle device (14) having at least one gas nozzle (15) for blowing off the front side or the rear side of the flat steel product (100) with a gas (G), the peeling nozzle device (14) being arranged and configured within the region of the outlet side (A). - A steam device (50) configured to emit gaseous steam and provide a controlled steam atmosphere within a short-distance region (NB) on the front side and / or the rear side of the flat steel product (100), wherein the controlled steam atmosphere has an absolute local humidity (f) greater than 1 g / m ３ and less than 300 g / m ３ , and the absolute local humidity (f) is preferably in the range of 2.71 g / m ３ to 50 g / m ３ , the steam device (50) and The device (150) according to claim 1.

2. For applying the layer (10), the system parameters and method parameters of the device (150) are set such that the layer (10) can be blown off by the peeling nozzle device (14) according to a predetermined specification, and the system parameters and method parameters define a peeling efficiency (AWZ) that is essentially constant when applying the layer (10). The device (150) according to claim 1.

3. The peeling efficiency (AWZ) is defined as either 【Number 1】 or or 【Number 2】 where d is the thickness (d) of the nozzle lip gap (17) of the at least one gas nozzle (15) of the peeling nozzle device (14) in mm; k is a dimensionless proportionality coefficient; D is Nm ３ / h, which is the effective gas flow rate (quantity) (D) of the gas (G) for each side of the flat steel product (100) over the strip width (w) in units of w is the strip width of the flat steel product (100) in mm; 2b is the half-width of the pressure distribution of the gas (G) in the flat steel product (100) in mm; v is the strip speed in m / min at which the flat steel product (100) is moved through the close proximity region (NB) along the peeling nozzle device (14). The device (150) according to claim 2.

4. Using the ratio of the distance (Z) to the thickness (d) of the nozzle lip gap (17), the following definitions are applied to the half of the half-width (b) and the proportionality coefficient (k), namely: Case 1.1: Case 1.2: 【Number 3】 Case 1.3: 【Number 4】 The device (150) according to any one of claims 1 to 3. 【Number 5】

5. When determining the value of the half of the half-width (b) and the proportionality coefficient (k) using the ratio of the distance (Z) to the thickness (d) of the nozzle lip gap (17), the following simplified definitions are applied: ​ Case 2.1: 【Number 6】 Case 2.2: 【Number 7】 Device (150) according to any one of claims 1 to 3, characterized in that it is applied.

6. - The thickness (d) of the nozzle lip gap (17) is in the range of 0.5 mm to 10 mm, preferably in the range of 0.8 mm to 2.0 mm, and / or - The flow rate (D) is in the range of 200 to 8000 Nm per hour ３ and / or - The distance (Z) between the nozzle lip gap (17) and the front or rear side of the flat steel product (100) is in the range of 2 mm to 15 mm, preferably in the range of 3 mm to 12 mm, and / or - The strip speed (v) is in the range of 50 m / min to 200 m / min, preferably in the range of 70 m / min to 150 m / min, and / or - The short-distance area (NB) is 1 m ３ to 10 m ３ within the volume of, preferably at least 2 m ３ in volume Device (150) according to claim 3, characterized in that.

7. The absolute local air humidity (f) is effective in a virtual cylinder volume defined on the one hand by the virtual cylinder surface and on the other hand by two virtual planes extending parallel to the flat steel product (100) at both side portions of the flat steel product (100), the cylinder volume being a volume in the range from 1 m ３ to 10 m ３ and preferably having a volume of at least 2 m ３ The measurement of the absolute local humidity (f) is carried out directly or indirectly, characterized in that the device (150) according to any one of claims 1 to 5.

8. Device (150) according to any one of claims 2 to 7, characterized in that it comprises a controller (250) adapted to adjust the controlled water vapor atmosphere so that the absolute humidity (f) satisfies the inequality f > AWZ when blowing off the layer (10).

9. Device (150) according to any one of claims 1 to 7, characterized in that the water vapor device (50) at least partially encloses the front and / or rear sides of the flat steel product (100) with a housing (52), whereby the controlled water vapor atmosphere can be defined as a quasi-static ambient condition within a short distance range (NB) inside the housing (52).

10. Device (150) according to claim 9, characterized in that the absolute local air humidity (f) within the short distance region (NB) of the housing (52) is measurable, and the measurement of the absolute local humidity (f) is carried out directly or indirectly.

11. The short-range region (NB) of the housing (52) is within a volume ranging from 1 m ３ to 10 m ３ and preferably has a volume of at least 2 m ３ The device (150) according to claim 9 or 10, characterized in that it has a volume.

12. The predetermined specifications determine the coating of the layer (10) and / or the target thickness of the layer (10), and the layer (10) to be applied has the following specifications, namely, - The coating of the layer (10) for each side of the flat steel product (100) is from 20 g / m ２ to 200 g / m ２ within the range, preferably from 30 g / m ２ to 100 g / m ２ within the range, and / or - The target thickness of the layer (10) for each side of the flat steel product (100) is in the range of 3 μm to 30 μm, preferably in the range of 4.5 μm to 15 μm Device (150) according to any one of claims 2 to 11, characterized in that it satisfies.

13. A sufficiently high absolute local air humidity (f) within the short-distance region (NB) is predetermined by the controlled water vapor atmosphere for a given peeling efficiency (AWZ) in order to prevent the formation of marble patterns and / or toothpick defects in the layer (10), the device (150) according to any one of claims 1 to 12.

14. - At least one humidity sensor (51) is arranged and configured within the short-distance region (NB) of the water vapor device (50) so as to be able to directly measure the absolute local air humidity (f) within the short-distance region (NB); - At least one humidity sensor (56) is provided to be able to directly measure the absolute local air humidity (f ＵＧ ) within the periphery of the device (150). The device (150) according to any one of claims 1 to 12, characterized in that.

15. Comprising at least one steam generator (DG) so that the absolute local air humidity (f) can be automatically adjusted such that the absolute local air humidity (f) is higher than the peeling efficiency (AWZ), the device (150) according to any one of claims 1 to 14.

16. A method of applying a layer (10) according to a target specification to at least one side of a flat steel product (100) by moving the flat steel product (100) through a zinc alloy molten bath (11) (ZnAl, ZnAlMg), wherein a peeling gas (G) exits to the outlet side (A) through a nozzle lip gap (17) of at least one gas nozzle (15) in the direction of the flat steel product (100) to blow off the layer (10) according to the target specification, the peeling efficiency (AWZ) being the following parameters, namely, D is the thickness (d) of the nozzle lip gap (17) of the gas nozzle (15) of the peeling nozzle device (14); D is Nm ３ / h, which is the effective gas flow rate (quantity) (D) of the gas (G) per side of the flat steel product (100) over the strip width (w). w is the strip width of the flat steel product in units of mm; 2b is the half-width of the pressure distribution of the gas (G) in the flat steel product (100) in units of mm; v is the strip speed in units of m / min at which the flat steel product (100) is moved along the peeling nozzle device (14); Defined by The method comprises the following steps, namely, - Before and / or while executing the method, the absolute local air humidity (f) in a controlled water vapor atmosphere in the near-distance region (NB) on the front side and / or rear side of the flat steel product (100), and / or the ambient air humidity (f ＵＧ ) is determined; - Relating the determined humidity (f, f ＵＧ ) to the peeling efficiency (AWZ), and determining whether the condition f > AWZ or f ＵＧ > AWZ is satisfied; - If the condition is met, initialize or continue the method for applying the layer (10), or if the condition is not met, increase the absolute local air humidity (f) in the controlled water vapor atmosphere by using a water vapor device (50) adapted to release gaseous water vapor, so as to satisfy the condition f > AWZ, and then initialize or continue the method for applying the layer A method comprising.

17. The peeling efficiency (AWZ) is 【Number 8】 Defined as, Or, 【Number 9】 Defined as Is either of the above, Where, d is the thickness (d) of the nozzle lip gap (17) in mm of the gas nozzle (15) of the peeling nozzle device (14), D is Nm ３ / h, which is the effective gas flow rate (quantity) (D) of the gas (G) for each side of the flat steel product (100) over the strip width (w) with Nm / h as the unit, k is a dimensionless proportionality coefficient, w is the strip width of the flat steel product (100) in mm, 2b is the half-width of the pressure distribution of the gas (G) in the flat steel product (100) in mm, v is the strip speed in m / min at which the flat steel product (100) is moved through the near-distance region (NB) along the peeling nozzle device (14) The method according to claim 16, characterized in that the above is applied.

18. The method according to claim 16 or 17, characterized in that the absolute local air humidity (f) of the controlled water vapor atmosphere is determined at the front side and / or the rear side of the flat steel product (100) at a distance exceeding 20 cm from the front side and / or the rear side.

19. The method according to any one of claims 16 to 18, characterized in that a controller (250) configured to adjust the absolute local air humidity (f) by adjusting the controlled water vapor atmosphere so that the condition f > AWZ is satisfied when applying and blowing off the layer (10) is used.

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