Method for producing a coated perforated steel strip

Abstract

The invention relates to a method for producing a metal-coated and perforated metal strip, wherein the metal strip, and in particular sheet steel strip with a periodic hole pattern, is continuously electrolytically coated with one or more metals in an electrolytic coating device, characterised in that the current density in the coating of the sheet steel strip fulfils the following equation to prevent dendrite formation: current density < 58 + 110 / exp (1.3 * x) in A / dm2 where: x = D / a where: largest in-circle diameter of the perforation D in mm, anode distance a in mm and applicable in the range for x > 0.2.

Description

[0001] Process for producing coated perforated steel strip

[0002] The invention relates to a method for producing coated perforated steel strip and the steel strip thus produced.

[0003] It is known to perforate steel strip before further processing, particularly with a hole pattern. The holes can be circular or take on any other shape, creating a hole pattern on the one hand or a grid on the other.

[0004] One application for such perforated steel strips is, for example, the cladding of noise barriers and the like. Since such noise barriers, as well as other outdoor applications, typically require protection from corrosion, steel sheets with an appropriate corrosion protection layer are often used for this purpose. The most commonly used corrosion protection layer is a zinc coating. Such zinc coatings are well-known and are applied either by electrolytic processes (ELO galvanizing) or via hot-dip galvanizing processes. ELO coatings are usually pure zinc coatings. In the hot-dip galvanizing process, alloys are typically used whose main element is zinc and which contain admixtures of aluminum, magnesium, or other elements.

[0005] When producing perforated sheets, strip-galvanized material is usually used, which is either electrolytically or hot-dip galvanized and then given the intended hole pattern by punching.

[0006] The disadvantage here is that, depending on the sheet thickness, little or no corrosion protection is provided on the punching surfaces. Furthermore, it is known to punch ungalvanized strip material, process it into blanks, and then galvanize the individual pieces. However, this has the disadvantage that small holes can become clogged. Furthermore, the sequence of punching, blank production, and piece galvanizing is expensive and complex.

[0007] Furthermore, it is conceivable to continuously coat such ungalvanized sheets with a hole pattern using the Sendzimir process, but such hot-dip galvanizing is fraught with major problems, since during hot-dip galvanizing, after passing through the zinc bath, stripping nozzles are usually used which use compressed air to strip off the adhering zinc to the desired thickness, which leads to turbulence in the area of ​​the holes and thus to uneven layer densities.

[0008] In the well-known Gravitel process, differences in layer thickness and dendrites at the edges of the holes are also to be expected because the current density becomes uneven due to the holes in the strip.

[0009] From DE19834759 Al a method is known for removing zinc dendrites, which form on the edges of a sheet metal strip during electrolytic galvanizing.

[0010] In “Dendritic zinc growth on the edges of flat steel strip during electro galvanizing,” LN Bengoa, S Bruno, HA Lazzarino, PR Serea, WA Eglia; International Congress of Science and Technology of Metallurgy and Materials, SAM CONAMET 2013; dendrite growth at the edges is also treated.

[0011] GB 1325933 Al describes a PVD coating process for metal meshes. In this process, a strip is guided horizontally through a PVD coating chamber. The walls of the coating chamber are positioned close to the strip to minimize losses.

[0012] The coating material is only evaporated on the underside, but the strip should be homogeneous and evenly coated on both the top and bottom sides. This is only achievable, however, if the hole area / total area ratio is^1 (in the projection perpendicular to the strip), i.e. the holes make up the majority. For this, a hole area / total area ratio of > 0.8 is required. It is also stated that electrochemical pre-cleaning before evaporation is sufficient. The coating layer thickness should be regulated by the strip speed or the strip temperature. Both methods have significant weaknesses. For higher layer thicknesses, the strip speed must be reduced, which also reduces productivity. If the strip temperature is changed, the layer formation (morphology) changes, and a higher strip temperature leads to higher vapor densities and leaks.

[0013] US Pat. No. 5,059,455 B discloses a process for hot-dip galvanizing perforated steel strip. In this process, a steel strip with a low perforation area, namely less than 23%, is subjected to a post-coating process. With this comparatively low perforation area, the strip can be coated under similar conditions to an unperforated steel strip. In a post-treatment step, the cut burr is re-rolled.

[0014] EP 1479 474 B1 discloses a method for galvanizing a metallic flat material. First, holes are punched into the flat material, then the material is hot-dip galvanized and cut to length. Finally, after galvanizing, serrations are rolled onto the flat material.

[0015] The object of the invention is to provide a method for producing perforated steel strips, which in particular enables corrosion protection even in the area of ​​the hole edges and can be carried out economically, ie with a comparatively high deposition rate.

[0016] The problem is solved by a method having the features of claim 1.

[0017] Advantageous further developments are identified in the dependent subclaims.

[0018] The inventors recognized that a uniform distribution of the coating of zinc and, if necessary, other metals, especially the coating of the punched edges, is necessary. This should combine minimal deviations and a good surface finish with excellent coating quality.

[0019] According to the invention, a method is proposed in which a perforated steel strip, including expanded metal or long blanks, is coated in a continuous electrolytic galvanizing process, wherein the setting of the maximum current density depends on the geometry of the hole pattern.

[0020] Typically, perforated sheets are not electrolytically galvanized because of a number of disadvantages.

[0021] On the one hand, in electrolytic galvanizing processes, the strip is pulled through a system with numerous deflection rollers and / or squeezing rollers, which requires a certain minimum strip tension. However, due to the reduced strip cross-section of perforated sheets, this is problematic, as the sheet can tear.

[0022] Furthermore, it is known that the edge effect on sheet metal causes dendrites to grow on the edges during coating, which must be removed from the longitudinal edges of the strip after ELO coating. The effort required to do this at the hole edges has so far prevented coating using the ELO process.

[0023] According to the invention, it was discovered that a conventional electrolytic coating process cannot be readily transferred to sheets with perforated areas. It was found that coating a conventional perforated sheet with conventional system parameters either leads to the sheet tearing and / or damage to parts of the system, such as current rollers.

[0024] According to the invention, the operation of the system is adapted to a perforated sheet in such a way that, on the one hand, the load-bearing capacity (= residual tensile strength) of the strip is taken into account and, on the other hand, the speed of the coating is throttled to a previously determined level in order to prevent damage to the system.

[0025] It has been found that speeds between 5 m / min and 120 m / min, especially between 10 m / min and 50 m / min, are well suited for this purpose.

[0026] Another aspect plays a role here. In electrolytic processes, the strip must also be dried after contact with the liquids. As expected, drying perforated strips is technically more complicated because a lot of liquid remains along the edges due to surface tension, and the edge length per square meter is much higher for a perforated strip. If a perforated strip is to be dried and a conventional system is used for this, good drying of the strip, and in particular the edges, is also possible on conventional systems at such belt speeds if non-opposing air knife nozzles and convection dryers are used, blowing perpendicularly or obliquely onto the strip. The air knife nozzles can preferably have an angle of 20° to 70° to the normal to the strip.

[0027] The volume fraction of the hole pattern is preferably at least 30%, therefore the volume fraction of the remaining sheet is less than 70%. This can be particularly advantageous for applications of components for thermal regulation, for example heat management for agricultural machinery, which must still offer protection against external damage, as well as applications in the field of noise insulation. Here, the hole pattern can advantageously amount to more than 50% or even more than 70% by volume. According to the invention, it was recognized that the geometry of the hole pattern plays a key role in setting the current density, which must be selected to avoid dendrite formation. Surprisingly, the inventors discovered that the maximum current density that can be applied during coating depends essentially on the largest perforation (i.e. the largest inner diameter of the perforation) and less on the total punching volume.This means that, for example, a strip with a high volume fraction of the hole pattern with comparatively small perforations can be coated with a higher current density than a strip with a single comparatively large perforation.

[0028] To avoid dendrite formation, the following relationship must be fulfilled depending on the hole pattern:

[0029] Current density < 58 + 110 / exp (1.3 * x) in A / dm 2 where: x = D / a where: largest inscribed diameter of the perforation D in mm,

[0030] Anode distance a in mm and valid in the range for x > 0.2.

[0031] As mentioned, this means that the largest inner diameter is the relevant influencing factor for the maximum average current density. Maximum average current density, as defined by the invention, is the current intensity per cathode area that is set to electrolytically apply a coating to the steel strip.

[0032] The validity range arises from the fact that x cannot be chosen to be arbitrarily small. Theoretically, a value for x of, for example, 0.1 is possible if D is very small and a is very large, for example with a largest inner diameter of 1 mm and an anode spacing of 10 mm. However, such a small hole pattern would be very difficult to coat and could possibly cause other problems. Therefore, according to the invention, the validity range is set to x > 0.2. Preferably, the validity range is set to x >= 0.5. The anode spacing a is the distance which is set on the system from the anode to the sheet. If the anodes are not parallel to the sheet, this is the distance which is closest to the strip. The anode spacing is between 1 mm and 50 mm, preferably between 7 mm and 12 mm.

[0033] In order to make the coating more efficient and increase the speed of galvanizing, it may be advantageous to choose the current density using the following relationship:

[0034] Current density > 35 + 110 / exp (1.3 * x) in A / dm 2

[0035] This can be advantageous for the deposition rate and thus the possible strip speed through the galvanizing plant.

[0036] Particularly advantageous for accommodating the coating of the perforated walls is perforation with an inscribed circle diameter of 0.4 to 50 mm, in particular 1 to 20 mm. This inscribed circle diameter can, in particular, correspond at least to the sheet thickness. For perforations that are not circular but, for example, elliptical or rectangular, the inscribed circle diameter within the meaning of the invention corresponds to the notional circle diameter of the largest possible inscribed circle that could be drawn into the perforation.

[0037] A hole pattern within the meaning of the invention can comprise a wide variety of patterns, which can be repeating similarly to a pattern repeat, as well as having unperforated areas along and / or across the tape direction, which are provided, for example, for mechanical requirements (stability, rigidity) or for subsequent processing operations (e.g., bending). Furthermore, it should be noted here that the terms "hole" and "perforation" are used interchangeably within the meaning of the invention.

[0038] The volume fraction of the hole pattern can in particular also be less than 70%, in particular less than 60% and in particular less than 50%, so that in the case of a hole pattern with round holes with a hole spacing of 7 mm and a hole radius of 2.5 mm in a hexagonal arrangement with a sheet thickness of 2 mm, for example, the volume fraction of the hole pattern is approximately 46%.

[0039] A correspondingly perforated metal strip can be produced in a separate facility and then delivered to the coating plant. However, it is also advantageous to provide an inline process, particularly in the steelworks, whereby the metal strip is first continuously punched or perforated to create the desired hole pattern. The strip can then be fed to a pretreatment station for cleaning and / or pickling. In particular, the perforated edges can also be treated, for example, by sandblasting. The strip can then enter the coating line, where it is subsequently continuously electroplated inline.

[0040] The inline process offers several advantages. First, the punching waste is generated before coating. The uncoated punching waste can be directly reused as steel scrap in the steel mill. Furthermore, transport routes are short. Another advantage of the inline process is that the resulting surfaces are less aged. This eliminates the need to remove corrosion products from the uncoated metal sheet during storage and / or transport. Furthermore, the pretreatment of slightly oxidized or non-corroded surfaces can be carried out comparatively more efficiently.

[0041] With the invention, a layer thickness ratio of 0.9, i.e., the minimum layer thickness in the area of ​​the hole wall to the average layer thickness outside the holes, can be achieved. This is achieved by setting the ratio of the inscribed circle diameter D to the sheet thickness s to greater than 6.

[0042] This is advantageous in cases of increased corrosion requirements or a comparatively low layer thickness, since 90% of the layer thickness can also be ensured in the area of ​​the perforated wall.

[0043] However, it has also been shown that even with a thinner layer thickness in the center of the hole wall, corrosion does not occur earlier, since the corrosive attack begins at the edges and does not occur first in the center of the wall. In thin sheets and relatively large holes, the minimum layer thickness at the hole walls can even be greater than the average layer thickness in the area outside the holes due to the peak effect of the edges.

[0044] The layer thickness of the metallic coating can be easily adjusted to thicknesses of 2.5 μm to 50 μm, and in particular to 4 μm to 20 μm per strip side surface, allowing even comparatively thick coatings to be deposited. This is particularly advantageous in construction applications, where high corrosion protection is often required. With the invention, with an adapted operating mode and, in particular, with a tensile force limitation on the one hand or with a corresponding throttling of the strip speed on the other, an ideal coating of the hole edges is achieved, thus achieving comprehensive corrosion protection of a perforated sheet, which is also made possible in an economical process.

[0045] Surprisingly, dendrite formation does not occur despite the comparatively high current density.

[0046] It has been found advantageous to limit the tensile force on the strip according to the residual cross-section in such a way that, where the strip is flat, the maximum tensile stress does not exceed 70%, preferably 50%, of the yield strength of the strip.

[0047] Advantageously, the strip is coated using a galvanic system consisting of 2 to 50 coating cells. This means that a system with just two coating cells is already sufficiently capable of ensuring the coating of perforated sheets according to the invention. However, by increasing the number of coating cells, the current density can be reduced at the same strip speed. This advantageously allows for thicker coatings, as already mentioned above, or higher strip speeds to be realized without defects.

[0048] The invention thus relates in particular to a method for producing metallically coated and perforated metal strip, wherein the metal strip and in particular the steel sheet strip with a perforation or with a hole pattern is continuously electrolytically coated with one or more metals in an electrolytic coating device, wherein the current density during the coating of the steel sheet strip satisfies the following relationship to avoid dendrite formation:

[0049] Current density < 58 + 110 / exp (1.3 * x) in A / dm 2 where: x = D / a where: largest inscribed diameter of the perforation D in mm,

[0050] Anode spacing a in mm and valid for x > 0.2. A further development provides for the metal strip to have a sheet thickness s of 0.4 mm to 2.5 mm.

[0051] The advantage here is that, on the one hand, sufficient mechanical rigidity and stability can be ensured, and, on the other hand, a reliably uniform coating can be achieved at such thicknesses. From 2.5 mm, there is an increased risk of uneven coating in the walls and undesirable edge effects.

[0052] A further development provides that the speed of the strip is set by the coating device to improve corrosion protection between 5 m / min and 120 m / min, in particular between 10 m / min and 50 m / min.

[0053] The advantage here is that such belt speeds allow good drying of the belt and especially of the edges even on conventional systems, whereby offset arranged stripping nozzles and convection dryers are used.

[0054] A further development provides for the anode spacing a to be between 1 mm and 50 mm, preferably between 7 mm and 12 mm. It is advantageous that the anode spacing is at a certain distance from the strip; at a spacing of less than 1 mm, there is a risk of the strip touching the anode, which can cause damage. At a spacing of more than 50 mm, the energy loss due to the electrolyte resistance becomes too high.

[0055] A further development involves coating the strip with one, several, or all of the following materials: zinc, tin, manganese, chromium, copper, nickel, iron, or an alloy thereof. Zinc is particularly advantageous in this regard, as it can provide comparatively high corrosion protection at a low cost.

[0056] A further development provides that the layer thickness of the metallic coating is 2.5 pm to 50 pm, preferably 4 pm to 20 pm, per strip side surface.

[0057] The advantage here is that even thick coatings can be deposited that meet the high corrosion protection requirements in the construction sector.

[0058] A further development provides that in order to achieve a layer thickness ratio of the metallic coating from the minimum value in the walls of the perforations to the average value in the area outside the holes of greater than 0.9, the ratio of inscribed circle diameter D / sheet thickness s is > 6. The advantage here is that a high deposition rate in the wall can be ensured by appropriately selecting the inscribed circle diameter of the perforation in relation to the sheet thickness, i.e. with a ratio of D / s > 6. This means that, for example, with a layer thickness of 10 pm on average outside the holes, at least 9 pm can be ensured as the minimum value in the hole wall. This can ensure particularly high corrosion protection and high uniformity across the entire strip.

[0059] A further development provides for the strip to be coated with a galvanic system consisting of 2 to 50 coating cells.

[0060] The advantage here is that by increasing the number of coating cells, the current density can be reduced, which means that thicker layers or higher belt speeds can be achieved without errors.

[0061] A further development stipulates that the remaining volume fraction of the steel sheet strip be less than 70%. This has the advantage that even comparatively high punching volumes can be processed and still be reliably coated. This can also be advantageous for applications in thermal management or noise protection, as the greatest possible permeability of the steel sheet can be advantageous in these cases.

[0062] A further development stipulates that the remaining volume fraction of the steel sheet strip be greater than 20%. This is advantageous because it ensures mechanical stability.

[0063] A further development stipulates that the current density satisfies the following relationship:

[0064] Current density > 35 + 110 / exp(l,3 * x) in A / dm 2

[0065] This can be advantageous for the deposition rate and thus the possible maximum strip speed through the galvanizing plant.

[0066] A further development provides that the largest inscribed circle diameter of the perforation D is between 0.4 mm and 50 mm, in particular 1 mm and 20 mm.

[0067] The advantage here is that, even if the minimum hole size is exceeded, a sufficient amount of coating can be present in the hole walls without dendrite formation occurring at the edges. Choosing an excessively large hole size can negatively impact mechanical stability. A further development requires the metal strip to be either cold-rolled, annealed, or pickled hot-rolled, and to be pretreated before coating.

[0068] A further development provides for the metal strip to be post-treated after coating. In particular, the post-treatment can include the steps of operating, passivation, and / or phosphating in any combination.

[0069] The advantage here is that the perforation allows for a relatively larger amount of oil, such as prelube, to be applied to the non-perforated areas during a lubrication step, for example, by spraying. This means that these areas, which will later be beveled, can retain more oil, which can facilitate post-processing.

[0070] The phosphating step is particularly advantageous because it takes place up to a certain layer thickness and the process stops automatically when this height is reached, so this step can be particularly advantageous for perforated belts.

[0071] According to the invention, it is also possible to combine the post-treatment steps, for example, the combination of phosphating and passivation or phosphating and oiling is particularly advantageous with regard to paint adhesion and corrosion protection.

[0072] A further development provides that the metal strip is continuously punched or perforated to produce the desired hole pattern and is then continuously electrolytically coated inline.

[0073] The advantage here is that the punching waste is generated before coating and can be recycled directly in the steelworks.

[0074] A further aspect of the invention relates to a device for carrying out the method described above, wherein the device comprises a punching system and an electrolytic coating unit.

[0075] The invention is explained by way of example with reference to a drawing. It shows:

[0076] Figure 1: A schematic hole pattern;

[0077] Figure 2: Micrographs of a hole edge including the surrounding material in the coated state; Figure 3: The representation according to Figure 2 in an enlarged form;

[0078] Figure 4: A table with test results;

[0079] Figure 5: A metal strip coated according to the invention wound into a coil;

[0080] Figure 6: A close-up view of an exemplary coated according to the invention

[0081] Loch bi Ids;

[0082] Figure 7: A representation of the hole pattern from Figure 6 in the production line;

[0083] Figure 8: A close-up view of an exemplary hole pattern coated according to the invention;

[0084] Figure 9: Four exemplary hole patterns with and without dendrites;

[0085] Figure 10: A diagram showing the maximum current density;

[0086] Figure 11: An example representation for determining the inscribed circle diameter;

[0087] Figure 1 shows a highly schematic representation of an exemplary hole pattern, in this case a hexagonal hole structure with hole spacing a=7 mm, hole radius r=2.5 mm; the sheet thickness s is 0.9 mm. The total coated area F including the hole walls is approximately 70% compared to the area Fo of a sample without holes, because: 0.704

[0088] The smallest cross-section of the punched sheet in relation to the cross-section of the unpunched sheet is (a-2r) / a, i.e. 2 / 7.

[0089] In Figures 2 and 3, the micrographs shown show the coating of the surface and the hole edges of the above-mentioned band with the hole pattern mentioned.

[0090] As you can see, the coating is very even with no defects and no strong differences in thickness.

[0091] Figure 4 shows a table with nine tests with different hole patterns, as well as different maximum inscribed diameters D ranging from 4 to 90 mm, and various anode-to-sheet distances a. The ratio x was calculated in each case, and the maximum current density was determined. The actual current density used is shown next to it. The zinc coating was then qualitatively assessed and examined for dendrite formation.

[0092] It can be seen that no dendrite formation occurred at a current density below the current density limit. However, at a current density that was too high (as in experiments 3, 4, and 6), strong dendrite growth was clearly visible. This can also be clearly seen in Figure 9, bottom left and bottom right.

[0093] The table clearly shows that the absolute value of the current density is not the only decisive factor, but rather depends on the ratio D / a. For example, the current density used in Experiment 3 was 79 A / dm 2 and led to dendrites, in experiment 5 it was 80 A / dm 2 i.e. a higher value, which in itself is more likely to lead to dendrites, but this was not a problem due to the selected hole pattern and anode spacing.

[0094] Figures 5 to 7 show example hole patterns from or in production. Figure 6 shows a hole pattern Qg 10-15; this means a square row with a side length of 10 mm for the square holes and a distance of 15 mm from hole center to hole center, resulting in a web width of 5 mm between the holes. "Row" means that in this example, these holes are arranged in a line and not offset. The sheet thickness s was 2 mm. The inscribed circle diameter D is therefore also 10 mm.

[0095] Figure 6 shows another example hole pattern. A 1.5 mm thick sheet was used here. It shows circular holes with a 5 mm diameter, arranged offset. The hole pattern is an Rv 5-8, i.e., 5 mm hole diameter with 8 mm hole spacing. The web width is therefore 3 mm. In this example, the holes are round and arranged offset in a hexagonal pattern. For this example, this means D = 5 mm, s = 1.5 mm.

[0096] The strip is galvanized and post-treated, in this case phosphated.

[0097] Figure 7 shows an image of the perforated strip in the electrolytic coating line with the same patterns as in Figure 6.

[0098] This makes it possible to effectively coat even perforated strips. Figure 8 shows an edge coated according to the invention in a perforation directly at the punched edge of the perforation. It shows the steel sheet (1), an electrolytically deposited zinc layer (2) on top of it, and on top of that, a paint layer (3), which was optionally applied after the galvanizing step.

[0099] The punch burr on the steel strip is clearly visible; this is almost unavoidable during production. The invention advantageously demonstrates that the zinc layer adheres particularly well to the punch burr, meaning that this particularly exposed area is galvanized with a comparatively thick layer of zinc. This is even more evident if the steel strip is subsequently painted in an optional process step, since this layer adheres comparatively thinly to this edge, which would therefore represent a weak point.

[0100] Figure 10 shows the formula for determining the maximum average current density across the selected hole pattern. Applying a current density below the curve can prevent dendrite formation.

[0101] Figure 11 shows an example of how the inscribed circle diameter is determined. It is the diameter of the largest circle that lies entirely within the punched area. For the example perforation pattern shown in Figure 11, which in this case represents a type of offset double hole, the largest inscribed circle diameter is determined by inscribing the largest possible circle into the pattern. In Figure 11, this corresponds to one of the two hole diameters of the double hole, thus resulting in D for the entire perforation.

Claims

Claims 1. A method for producing metallically coated and perforated metal strip, wherein the metal strip, and in particular sheet steel strip with a periodic hole pattern, is continuously electrolytically coated with one or more metals in an electrolytic coating device, characterized in that the current density during the coating of the sheet steel strip satisfies the following relationship to avoid dendrite formation: Current density < 58 + 110 / exp (1.3 * x) in A / dm 2 where: x = D / a where: largest inscribed diameter of the perforation D in mm, Anode distance a in mm and valid in the range for x > 0.

2.

2. Method according to claim 1, characterized in that the metal strip has a metal sheet thickness s of 0.4 mm to 2.5 mm.

3. Method according to claim 1 or 2, characterized in that the speed of the belt through the coating device is set between 5 m / min and 120 m / min, in particular between 10 m / min and 50 m / min.

4. Method according to one of the preceding claims, characterized in that the anode distance a is between 1 mm and 50 mm, preferably between 7 mm and 12 mm.

5. Method according to one of the preceding claims, characterized in that the strip is coated with one element, several or all elements from the group zinc, coated with tin, manganese, chromium, copper, nickel, iron or an alloy thereof.

6. Method according to one of the preceding claims, characterized in that the layer thickness of the metallic coating is 2.5 pm to 50 pm, preferably 4 pm to 20 pm, per strip side surface.

7. Method according to one of the preceding claims, characterized in that in order to achieve a layer thickness ratio of the metallic coating from the minimum value in the walls of the perforations to the average value in the area outside the holes of greater than 0.9, the ratio of D / s is > 6.

8. Method according to one of the preceding claims, characterized in that the strip is coated with a galvanic system consisting of 2 to 50 coating cells.

9. Method according to one of the preceding claims, characterized in that the remaining volume fraction of the steel sheet strip is less than 70%.

10. Method according to one of the preceding claims, characterized in that the remaining volume fraction of the steel sheet strip is greater than 20%.

11. Method according to one of the preceding claims, characterized in that the current density satisfies the following relationship: Current density > 35 + 110 / exp(l,3 * x) in A / dm 2 12. Method according to one of the preceding claims, characterized in that the largest inscribed circle diameter of the perforation D is between 0.4 mm and 50 mm, in particular 1 mm to 20 mm.

13. Method according to one of the preceding claims, characterized in that the metal strip is either a hard-rolled cold-rolled strip or an annealed cold-rolled strip or a pickled hot-rolled strip and is pretreated before coating.

14. Method according to one of the preceding claims, characterized in that during the pretreatment the metal strip is pretreated with alkali and / or blasted.

15. Method according to one of the preceding claims, characterized in that the metal strip is post-treated after coating.

16. The method according to any one of the preceding claims, characterized in that the post-treatment comprises the steps of operating and / or passivating and / or phosphating in any combination.

17. The method according to any one of the preceding claims, characterized in that the metal strip is continuously punched or perforated to produce the desired hole pattern and is then continuously electrolytically coated inline.

18. Device, in particular for carrying out a method according to claims 1 to 17, characterized in that the device comprises a punching system and an electrolytic coating unit.

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