METHOD FOR COATING A SURFACE OF A METAL STRIP AND A METAL STRIP-COATING DEVICE

Abstract

A method for coating a surface of a substrate may involve coating the surface of the substrate with a wet coating by way of a coating station, conveying the substrate by way of a conveying device, and detecting the surface coated with the wet coating by producing a thermal image of a detection region that comprises part of the surface. The thermal image may be recorded in a spectral range that includes a wavelength between 1 micrometer and 20 micrometers. Further, the detection region may be located directly downstream of the coating station, or the detection region may at least partially include the coating station.

Claims

1.-17. (canceled)

18. A method for coating a surface of a metal strip, the method comprising: coating the surface of the metal strip with a wet coating by way of a coating station; conveying the metal strip by way of a metal strip-conveying device; and detecting the surface coated with the wet coating by producing a thermal image of a detection region that includes at least a part of the surface.

19. The method of claim 18 wherein the thermal image is recorded in a spectral range that includes a wavelength between 1 micrometer and 20 micrometers.

20. The method of claim 18 wherein the detection region is located directly downstream of the coating station or wherein the detection region at least partially comprises the coating station.

21. The method of claim 18 wherein the detection region is at least as large as a widthwise extent of the metal strip.

22. The method of claim 18 wherein the thermal image is produced as a continuous thermal imaging film.

23. The method of claim 22 wherein a portion of the continuous thermal imaging film is produced such that the portion of the continuous thermal imaging film is assignable to at least one of the metal strip or a portion of the metal strip.

24. The method of claim 23 further comprising: continuously scanning the thermal image for differences in temperature; and upon finding a temperature difference that is greater than a reference temperature difference, outputting a marking value that is assigned to at least one of a portion of the metal strip or a roll of the metal strip.

25. The method of claim 24 wherein the reference temperature difference is less than 5.0 K.

26. The method of claim 24 wherein the continuous scanning is performed in situ.

27. The method of claim 18 further comprising irradiating with a heat source at least a portion of the at least the part of the surface of the metal strip with the wet coating that is located in the detection region.

28. The method of claim 27 wherein the heat source includes a thermal radiation output that in the detection region corresponds to a temperature in a range of 35-100 degrees Celsius.

29. The method of claim 18 further comprising: recording a thermal image of a position of the metal strip; ascertaining a change of a measured temperature along a profile of the metal strip; and comparing the change of the measured temperature with respect to a reference value, as a comparative value, with an adjustment table for ascertaining a thickness of the wet coating.

30. The method of claim 18 further comprising recording the thermal image of the at least the part of the surface in the detection region while the surface of the metal strip with the wet coating is still wet or still moist.

31. A metal strip-coating device comprising: a wet coating station for coating a surface of a metal strip that passes through the wet coating station with a wet coating; and a thermal imaging camera that is directed at a detection region, wherein the detection region comprises at least a part of the surface of the metal strip.

32. The metal strip-coating device of claim 31 further comprising a heat source for emitting thermal radiation to the detection region.

33. The metal strip-coating device of claim 31 wherein the detection region is located directly downstream of the wet coating station or wherein the detection region at least partially comprises the wet coating station.

34. The method of claim 31 wherein the detection region is at least as large as a widthwise extent of the metal strip.

35. A computer program product with computer program instructions that cause the method of claim 18 to be performed when the computer program instructions are read by a computing unit, wherein the computing unit is configured to control a thermal imaging camera and has read access to the thermal image produced.

36. A method for detecting defects comprising: thermally imaging with a thermal imaging camera a coating of a first material with a first emissivity on a substrate of a material with a second emissivity, wherein the first emissivity and the second emissivity differ by at least 5%; and detecting based on reflected thermal radiation positions where properties of the coating deviate from desired properties.

Description

[0073] Specific refinements of the invention are more specifically explained in detail below with reference to the figures. The figures and accompanying description of the resultant features should not be interpreted as being restrictive, as applying only to the respective refinements, but serve for illustrating forms of the invention that are given by way of example. Furthermore, the respective features may be used in combination with one another and with features of the above description for possible further development and improvement of the invention, especially in the case of additional refinements that are not represented.

[0074] In the figures:

[0075] FIGS. 1a and 1b: show a schematic representation of a metal strip-coating device;

[0076] FIG. 2: shows various representations of thermal images produced in the course of a method for coating a surface of a metal strip by means of detecting a heat emission of the surface coated with the wet coating:

a) first thermal image,
b) second thermal image,
c) third thermal image,
d) fourth thermal image.

[0077] FIG. 1a illustrates a metal strip-coating device 1. The metal strip-coating device 1 comprises a coating station 2, formed as a wet coating station. A metal strip 3 is passed through the coating station 2 and coated in the coating station 2 with a wet coating. In a region through which the metal strip runs after the coating there is a detection region 5, which is detected by a thermal imaging camera 4. Thereafter, the metal strip is also dried (not shown). The thermal imaging camera 4 ascertains the two-dimensional temperature distribution of the metal strip running through directly after the wetting of the surface of the strip by the application rollers. Arranged on the thermal imaging camera 4 is a computing unit 6, which by means of a computer program product causes the heat emission of the coated surface to be detected and the detected thermal image to be evaluated.

[0078] The arrangement shown in FIG. 1b differs from the arrangement shown in FIG. 1a merely in that a heat source (7) is additionally arranged for emitting thermal radiation to the detection region.

[0079] In the figures of FIG. 2, a sequence of thermal images recorded by means of the thermal imaging camera is represented by way of example, the metal strips being at a temperature of 50 degrees Celsius for production-related reasons. Successively coated metal strips are connected to one another by means of a tack weld. In order that the application rollers are not damaged, they are lifted off or retracted from the strip just before the tack weld arrives and are replaced onto the strip after the tack weld has run through. The strip is consequently uncoated directly upstream and downstream of the tack weld. This coated/uncoated transition has been seen and recorded by the thermal imaging camera.

[0080] In the figures:

[0081] FIG. 2a shows a partially wet running-through tack weld with remains of moisture of the previous cleaning and rinsing operation. After replacement of the wetting roller, uniform coating is resumed. As FIG. 2b shows, however, in an edge region on the left side there is shown or there can be seen a region (A) that is unwetted by the wet coating. In the thermal image represented, as a consequence of the different emissivities, the unwetted region is represented as a colder region on account of the same scale being used both for the wet coating and in the dry region. This is nevertheless just a matter of representation, since the actual temperature is identical. However, here the actual temperature is neither clearly determinable nor required; instead, the detection takes place by means of thermal imaging, as explained, for the identification of unwetted regions. In a further representation, representation c), a temperature spot that is represented as a region of greater thickness can be seen in a circled region. This spot that is represented shows qualitatively an irregularity in the thickness of the coating. The representation of Figure d) shows moist residues, which are represented as regions of lower temperature.