Method for producing a surface-treated flat steel product provided with a protective coating, strip processing system, and use of a raman spectrometer

Abstract

A method for producing a surface-treated flat steel product provided with a protective coating is disclosed. The method comprises the following steps: (A) providing a flat steel product; (B) skin-passing the flat steel product; (C) post-treating the flat steel product. Raman spectroscopy is carried out on the skin-passed surface and the post-treatment in step (C) is controlled on the basis of the evaluation of the Raman spectrum. The method can be carried out, for example, in a strip processing system (1) for continuously processing a metal strip (2). The strip processing system (1) has a skin-pass stand (3) and a chemical treatment station (4) arranged downstream of the skin-pass stand (3) as viewed in the strip movement direction (P). Raman spectrometers (5, 6) and an evaluation station (7) are also provided.

Description

[0001] T00598

[0002] CK

[0003] Method for producing a surface-treated, protective-coated, steel flat product, strip processing plant and use

[0004] The invention relates to a method for producing a surface-treated steel flat product provided with a protective coating. The invention also relates to a strip processing plant. A further aspect of the invention relates to a use.

[0005] In the production of flat steel products for modern applications, it is of paramount importance that the flat steel product, whether ready for delivery or intended for further processing, meets high standards for its surface quality. Particularly in demanding applications where flat steel products are manufactured with a protective and / or decorative coating, such as an anti-corrosion coating, it is essential to ensure the expected uniformity of the coating and, where applicable, the homogeneity of any subsequent chemical treatment. Furthermore, it is crucial to ensure a consistently good bond between the coating and the substrate to largely prevent any impairment of the coating's functionality and / or visual appearance.

[0006] The term steel flat product usually refers to all rolled steel products in hot- or cold-rolled condition, whether in the form of strip, sheet, blank or plate.

[0007] Providing a large quantity of steel flat products with guaranteed high surface quality presents a significant challenge. For example, steel flat products manufactured as steel strips are produced at high speeds and in considerable lengths, and the finished strip is then wound into a coil. To reliably assess the surface quality of such a steel flat product, it is essential to acquire and analyze surface data efficiently and cost-effectively.

[0008] It is known from practical experience that automated and non-destructive quality control can be provided via methods in which images of the product's surface are taken with a camera and these images are evaluated in digital form using an image processing device. Such methods are suitable for identifying immediately recognizable optical defects, which are generally also visible to the human eye, and for deriving appropriate consequences, which may include, for example, marking a strip as reject.

[0009] However, such methods have the disadvantage that they are limited in the type of surface properties that can be detected.

[0010] The present invention is based on the objective of increasing the reliability of the production of a surface-treated, protective-coated, steel flat product and improving the quality of the produced steel flat products.

[0011] The problem is solved by a method having the features of claim 1. The problem is further solved by a strip processing plant having the features of claim 14. Finally, the problem is solved by a use having the feature of claim 15. A method for producing a surface-treated, protective-coated, flat steel product is proposed.

[0012] The procedure consists of the following steps:

[0013] (A) Providing a steel flat product coated with a protective coating;

[0014] (B) Dressing the coated steel flat product in at least one dressing stand;

[0015] (C) Post-treatment of the dressed coated steel flat product to provide a dischargeable steel flat product or a further processable intermediate product.

[0016] First, a flat steel product is provided, which is coated with a protective layer. In particular, this can be a steel strip coated with a protective layer. The protective layer can, for example, be a corrosion protection layer. In particular, a zinc-based protective layer can be applied to the steel strip, preferably with a thickness between 10 micrometers and 60 micrometers on one side or between 10 micrometers and 60 micrometers on each side. The protective layer can be produced, for example, by hot-dip coating or by vacuum evaporation, for example, a jet vapor deposition process or a variation thereof.

[0017] The steel flat product can, for example, be a steel flat product, in particular a cold-rolled steel flat product, which consists of a steel with the following alloy specification:

[0018] The steel flat product can, for example, be a cold-rolled steel flat product consisting of a steel with the following composition, where all values ​​are in weight percent, abbreviated: wt.%:

[0019] C: 0.001 - 1.0;

[0020] Si: 0.05 - 0.8;

[0021] Mn : 0.05 - 3.0;

[0022] P: maximum 0.15;

[0023] S: maximum 0.05;

[0024] N: maximum 0.10; optional alloying elements: up to 8.0, preferred

[0025] 5, 355; wherein the optional alloying elements may include several of the following elements from the group “Al, Gr, Cu, Nb, Mo, Ni, Ti, V, B, Mg, Ca, Co, W, SEM”:

[0026] Al : 0.05 - 1.65;

[0027] Size: 0.01 - 1.0;

[0028] Cu : 0.01 - 0.80;

[0029] Note: 0.0005 - 0.20;

[0030] Mo : 0.001 - 0.2;

[0031] Ni: 0.01 - 0.2;

[0032] Ti: 0.001 - 0.2;

[0033] V: 0.0001 - 0.1;

[0034] B: 0.0002 - 0.005;

[0035] Mg : 0.0003 -0.5;

[0036] Ca: 0.0001 - 0.1;

[0037] Co: 0.001 - 0.1;

[0038] W : 0.01 - 0.3;

[0039] Sn up to 0.10; and optionally one or more elements from the rare earth metals (SEM) group, provided that the sum of all SEM does not exceed 0.5 wt.%;

[0040] Remaining components: iron and unavoidable impurities. Protective coatings, particularly zinc-based ones, can be used, for example, from one of the following systems: Zn-Mg, Zn-Al, Zn-Al-Mg, Zn-Al-Si, or Zn-Mg-Al-Si.

[0041] Particularly preferred are protective coatings, provided as Z or ZM coatings, applied in a hot-dip coating process, in which the flat steel product is hot-dip coated in a molten bath, the molten bath consisting of:

[0042] Al: 0.1-8.0, preferably 0.8-7.0, particularly preferably 1.0-5.0; in particular 1.1-4.0; optionally Mg: up to 8.0, preferably up to 7.0, particularly preferably up to 5.0, in particular up to 4.0;

[0043] The remainder, apart from unavoidable impurities, is zinc (Zn), where all figures are given in wt%. Impurities in the melt bath may include elements from the group consisting of Si, Sb, Bi, Zr, Ni, Gr, Pb, Ti, Ca, Mn, Sn, La, Ce, Fe, and Gr, in concentrations individually or cumulatively up to 0.5 wt%, in particular up to 0.4 wt%, preferably up to 0.3 wt%. Impurities in the coating may include elements from the group consisting of Si, Sb, Bi, Zr, Ni, Gr, Pb, Ti, Ca, Mn, Sn, La, Ce, Fe, and Cr, in concentrations individually or cumulatively up to 0.5 wt%, in particular up to 0.4 wt%, preferably up to 0.3 wt%, whereby, alternatively, the concentration of Fe may be higher due to diffusion. The remainder is zinc. Steel sheets, cut from steel strips or steel sheet components manufactured from them with a zinc-based corrosion protection coating, have very good cathodic corrosion protection and have been used in automotive engineering for years.If improved corrosion protection is required, the coating contains aluminum with a content of at least 0.8 wt.%, in particular at least 1.0 wt.%, preferably at least 1.1 wt.%, and optionally magnesium with a content of at least 0.8 wt.%, in particular at least 1.0 wt.%. Alternatively, the coating may contain aluminum with a content of up to 8.0 wt.%, preferably up to 7.0 wt.%, particularly preferably up to 5.0 wt.%, and in particular up to 4.0 wt.%, and optionally magnesium with a content of up to 8.0 wt.%, preferably up to 7.0 wt.%, particularly preferably up to 5.0 wt.%, and in particular up to 4.0 wt.%. These concentrations may also be determined by wet chemical assay according to or in accordance with DIN EN ISO 10111:2019 and / or DIN EN ISO 11885:2009.

[0044] In particular, to achieve a predetermined thickness of the Z or ZM coating, which in the solid state can range from 1 pm to 60 pm per side, the molten metal applied to the steel strip while still liquid is stripped off. This is done by passing the coated steel strip through a stripping device after it has left the melt bath. The stripping device includes means, such as nozzles, especially slot nozzles, which apply a gaseous stripping medium to both sides of the steel strip to remove the liquid molten metal. This allows for an asymmetrical coating, i.e., different thicknesses on each side. The thickness of the Z or ZM coating can be adjusted independently on each side, specifically between at least 4 pm, preferably at least 5 pm, and a maximum of 58 pm, preferably between 5 pm and a maximum of 55 pm.In a particular embodiment, the coating thickness is at least 1 pm, preferably at least 2 pm, particularly preferably at least 3 pm, particularly at least 5 pm and at most 25 pm, preferably at most 20 pm and particularly preferably at most 15 pm, particularly at most 10 pm, independently of one another on each side. Alternatively, the coating thickness is determined gravimetrically by peeling according to DIN EN ISO 10111 and converting from mass to thickness based on density, or metallographically in the cross-section.

[0045] Below the minimum limits, sufficient cathodic corrosion protection cannot be guaranteed, and above the maximum limit, joining problems may occur when connecting the steel sheet according to the invention or a component made therefrom with another component.

[0046] Alternatively, the Z or ZM coating has a coating weight of 1 to 650 g / m², i.e., 0.5 to 320 g / m² per side, particularly preferably 10 to 500 g / m², i.e., 5 to 250 g / m² per side. Another alternative is an asymmetric coating.

[0047] Alternatively, the protective coating is designed as a zinc-plated coating (ZF coating), which is applied by hot-dip molten steel in a molten bath and, after application, treated by annealing the coated steel above the zinc melting point. The molten bath consists of:

[0048] Al: 0, 1-1,0;

[0049] The remainder, besides unavoidable impurities, is 100: Zn, where all figures are given in weight percent, abbreviated: wt.%. The coating treated in this way consists of iron-zinc compounds; it is a flat steel product with a so-called ZF coating.

[0050] The metallic coating ZE, which contains unavoidable impurities in addition to zinc and optionally 0.001 wt.% to 1 wt.%, preferably 0.01 wt.% to 1 wt.% aluminum, was electrolytically applied to the dressed substrate, a flat steel product in the form of a sheet or strip (electrolytically applied zinc coating (ZE)). Such sheets are defined, for example, in DIN EN 10152:2017-06; however, the use of hot-rolled strip as

[0051] Sheet metal substrate possible.

[0052] Hot-dip coating processes are known to those skilled in the art. Hot-dip coating can additionally include one or more of the following steps: cleaning the substrate before the hot-dip bath, heating the substrate; after the hot-dip bath, removing the melt using nozzles to achieve the desired coating thickness, cooling the coated substrate to cure the melt, optionally applying a curing agent; optionally, further functional coatings are applied, such as an adhesion promoter, a forming aid, a passivation layer, or a combination thereof.

[0053] The composition of the protective coating corresponds in particular to the composition of the melt bath, optionally with a deviation of a maximum of 0.5 wt%, preferably 0.3 wt%, particularly preferably 0.2 wt%, in particular 0.1 wt%.

[0054] The coated steel flat product undergoes a tempering process in step (B) described above. Tempering serves to impart specific properties to the steel through a slight reduction in thickness and, if necessary, by using textured rollers. A significant purpose of tempering is to achieve advantageous surface properties in the steel flat product, in particular to establish a desired surface texture, for example, to optimize surface wettability and / or to adjust the visual appearance, feel, or other properties. Another purpose is to modify the chemical surface properties, which is achieved by breaking down any oxide layer that may be present on the surface.The dressing of the coated steel flat products is carried out mechanically in at least one dressing stand, and in further development also in a number of several dressing stands arranged one behind the other.

[0055] The process of skin forming is familiar to experts and is described, for example, in the handbook "Forming" by Günter Spur, ISBN: 978-3-446-43004-4, page 155. The surface of the steel sheet after skin forming can exhibit a stochastic surface structure. This is produced using skin forming rollers whose surfaces are textured using an EDT (Effective Laser Technique) process. Alternatively, the surface of the steel sheet after skin forming can exhibit a deterministic surface structure. This is produced using skin forming rollers whose surfaces are textured with a laser. A surface exhibiting a pseudo-stochastic surface structure after skin forming is also conceivable. These surface structures have a (quasi-)stochastic appearance, composed of stochastic elements with a recurring pattern.

[0056] Step (C) provides for a post-treatment of the dressed coated steel flat product to provide a shippable steel flat product or a further processable intermediate product. Post-treatment is a collective term for one or more measures that must be carried out between the dressing process and the delivery of the steel flat product as a ready-to-use steel flat product or as a further processable intermediate product. The post-treatment may, for example, consist of quality control, chemical post-treatment, or a combination of the aforementioned measures, or it may be one or more of the aforementioned steps combined with one or more other steps. In addition to the steps mentioned above, the invention provides for Raman spectroscopy to be performed on the dressed coated surface.

[0057] Raman spectroscopy is an analytical method based on the so-called Raman effect, in which light is scattered inelastically by molecules. In the Raman effect, the energy of the scattered light changes due to interactions with the vibrational or rotational states of the molecules. This method uses a laser to irradiate a sample with light of a defined wavelength; the properties of the scattered light are then measured to obtain information about the molecular composition and structure. A key source of results obtained from Raman spectroscopy is the analysis of the scattered wavelengths, which have changed as a result of inelastic scattering. This change in wavelength provides information, particularly about chemical bonds in the scattering materials.Raman spectroscopy is used, for example, in chemistry and materials science to identify chemical bonds, molecular structures, and crystalline forms. The resulting spectra provide information about the specific vibrational modes of the molecules, allowing conclusions to be drawn about the chemical identity, physical properties, and / or manufacturing history of the substance under investigation. Because Raman spectroscopy is non-destructive and requires no special sample preparation, it is particularly useful for analyzing sensitive or valuable samples.

[0058] The present invention is based on the surprising finding, previously unknown in empirical experiments, that Raman spectroscopic recordings can be used advantageously in addition to the previously known fields of application in a process of manufacturing a surface-treated and protective-coated steel flat product.

[0059] The developers who have worked on this development have found that the surface quality of the surface-treated and protective-coated steel flat products is highly dependent on the process of dressing the coated steel flat product and / or the post-treatment of the dressed steel flat product.

[0060] Empirical experiments have shown this relationship to be particularly evident from the fact that intensity maxima (peaks) occurred at widely separated locations on an intensity-wavenumber diagram. The developers attribute this phenomenon to the fact that a conventional protective coating exhibits both metal oxide bonds (depending on the specific coating used, for example, Zn-O, Mg-O, Al-O, Si-O, or an oxide of two, three, or four of the metals Zn, Mg, Al, and Si, such as MgZn2-O, or several of the aforementioned), and that treating this coated strip with organic substances, such as corrosion protection oils, makes the bonds of these organic substances visible.Without needing to identify the exact type of bond or perform quantitative analyses, the fundamental finding that metal oxide bonds with relatively low wavenumbers (up to about 600 / cm) and bonds of organic substances with relatively high wavenumbers (between 600 and 3500 / cm) are located far apart in recorded Raman spectra offers the possibility of evaluating the obtained spectra, particularly based on empirically derived experience. A key finding of the developers is that generating a Raman spectrum using Raman spectroscopy of a hardened surface of a steel flat product coated prior to hardening yields results that are highly sensitive to surface quality and differ significantly depending on the quality.

[0061] The developers utilize this finding to implement, as a further component of the inventive method, the control of the post-treatment of step (0) based on the evaluation of a Raman spectrum obtained by means of Raman spectroscopy. This means that, according to the invention, at least one measure is carried out on the dressed coated steel flat product before the provision of a deliverable steel flat product or a further processable intermediate product, the method of implementation being determined as a result of the evaluation of the obtained Raman spectrum.

[0062] A particularly preferred method is one in which the evaluation of the obtained Raman spectrum includes a comparison of the obtained Raman spectrum with a reference spectrum. For example, a reference spectrum can be used to represent a target sample, and a comparison of the obtained Raman spectrum should provide the basis for an assessment of whether the provided and tempered steel flat product, possibly after a post-treatment step, meets the requirements represented by the reference spectrum, or whether an unacceptable deviation from the reference spectrum can be identified.

[0063] In an advantageous further development, the post-treatment of step (0) includes a step in which a quality control check of the skinned surface is performed. In a specific embodiment, the post-treatment of step (C) consists of the step in which a quality control check of the skinned surface is performed. The quality control check includes, for example, a comparison of the evaluation of the Raman spectrum obtained on the skinned steel flat product with a reference spectrum. The reference spectrum can, for example, be an empirically determined spectrum previously obtained on an exemplary reference sample.The control of post-treatment, and thus quality control, includes, or in a further development: consists of marking the steel flat product as scrap if the comparison of the obtained Raman spectrum with the reference spectrum shows a deviation that exceeds a tolerated maximum deviation. The deviation can, for example, be the difference between the intensity maximum of the obtained Raman spectrum and the intensity maximum of the reference spectrum at a given wavenumber, and the steel flat product is marked as scrap if the magnitude of the difference exceeds a permissible, i.e., tolerated, maximum value.Alternatively, the deviation could be, for example, the difference between the intensity maximum of the obtained Raman spectrum and the intensity maximum of the reference spectrum within a range of a predetermined wavenumber, and the steel flat product could be marked as rejected if the magnitude of the difference exceeds a permissible, i.e., tolerated, maximum value. This could be implemented, for example, by first normalizing the intensity values ​​of the obtained Raman spectrum and the intensity values ​​of the reference spectrum to each other via a reference peak present in both spectra, so that the respective intensity values, which are represented as "arbitrary units," are normalized to the same y-axis, and then, in a second step, comparing the highest value of the obtained spectrum and the highest value of the reference spectrum within a range around a predetermined wavenumber.The comparison can, for example, consist of identifying or demonstrating a difference, and the steel flat product can be marked as rejected if the difference exceeds a permissible, i.e., tolerated, maximum value. It is particularly preferred that the quality control of the tempered steel flat product be carried out immediately after tempering, that is, before any further post-treatment step, in particular before handling and before cleaning the steel flat product. For this purpose, Raman spectroscopy is performed on the surface of the strip immediately after tempering, that is, before any further post-treatment step, in particular before handling and before cleaning the steel flat product.In this case, controlling the post-treatment of step (C) based on the evaluation of a Raman spectrum obtained by Raman spectroscopy involves initially omitting the post-treatment of step (C) and first performing a second dressing of the strip. Alternatively, and preferably, the quality control of the dressing-treated steel flat product is carried out after an intermediate post-treatment step, that is, before carrying out a further post-treatment step. For this purpose, Raman spectroscopy is performed on the surface of the strip immediately after the intermediate step, that is, before carrying out a further post-treatment step. Alternatively, and preferably, the quality control of the dressing-treated steel flat product is carried out after the last post-treatment step.For this purpose, Raman spectroscopy is performed on the surface of the strip immediately after the last step; preferably, the production of the steel flat product is completed when the steel flat product is not marked as scrap in quality control.

[0064] Alternatively, the deviation can be determined based on the difference between the integral of the obtained spectrum between two given wavenumbers and the integral of the reference spectrum between two given wavenumbers. The steel flat products can then be marked as rejects if the magnitude of this difference exceeds a permissible, i.e., still tolerated, maximum value. Given the importance of empirically determined reference spectra and the required properties of the steel flat products depending on their intended use, it is clear that these examples of evaluation are only two of a large number of conceivable evaluation possibilities.It is essential that the obtained Raman spectrum is used, via comparison with a reference spectrum, to ensure the quality of the treated surface and, in particular, to provide the possibility of immediately detecting if the treated surface deviates from the desired quality, which would then be noticeable, for example, as an increased deviation of the Raman spectrum from a reference spectrum. Since Raman spectroscopy is generally a very fast procedure, it is particularly possible to perform the Raman spectroscopy for quality control inline and / or by-side immediately after the treatment or after further processing steps, such as servicing or alkaline cleaning.The term "inline" refers to a process carried out without time delay during the production of the steel flat product. For example, inline Raman spectroscopy refers to Raman spectroscopy that is performed during the production of the steel flat product, preferably also evaluated during the production of the steel flat product, for example immediately after the tempering and before the post-treatment on the still moving strip in the strip processing plant.

[0065] The term "by-side" refers to a process carried out at a later time, either after the production of the steel flat product or after an intermediate step in its production. For example, by-side Raman spectroscopy refers to Raman spectroscopy that is performed and evaluated at a later time, either after the production of the steel flat product or after an intermediate step in its production. For this purpose, a representative sample is taken from a strip in a traceable manner, for example, by means of optical markers on the strip and the sample, and the process, such as Raman spectroscopy, is then carried out.The representative sample represents a steel flat product, for example strip, or a section of a steel flat product, for example strip, so that it can be traced afterwards which of the manufactured steel flat products or which section of the manufactured steel flat products correspond to the information obtained from the representative sample about their properties and can be assigned to them.

[0066] In particular, it can also be stipulated that the production of steel flat products is interrupted if the quality control of the dressed surface detects a defect; this measure ensures that any defects in strip processing can be rectified immediately after they occur and that further production of defective strip is limited. This has the advantage of limiting manufacturing costs in the long term.

[0067] It is particularly preferred that the post-treatment of step (C) comprises a step or, in a special embodiment, consists of a step in which the treated surface is coated with a corrosion protection oil. Preferably, Raman spectroscopy is performed on the oiled surface immediately after treatment, i.e., before carrying out further post-treatment steps such as cleaning. Coating flat steel products, especially steel strips, with a corrosion protection oil for temporary storage is common practice. Typically, a corrosion protection oil is available that is applied over a large area of ​​the flat steel product.

[0068] Preferably, a number of corrosion protection oils are provided. The control of the post-treatment includes, or in a specific embodiment, consists of selecting a corrosion protection oil from among the available options based on the evaluation of a Raman spectrum generated immediately after operation. This means that several corrosion protection oils are available, for example, two, three, or four different types, and one of these is selected depending on the information that can be extracted from the Raman spectrum. The dependence of the corrosion protection oil selection on the information that can be obtained from the Raman spectrum can, in particular, be derived empirically.The control of the post-treatment includes, in particular, that the coating of the treated surface with a corrosion protection oil is repeated if the comparison of the obtained Raman spectrum with the reference spectrum results in a deviation above a tolerated maximum deviation.

[0069] Alternatively or additionally, the post-treatment of step (C) may include a step, in a specific embodiment consisting of a step in which alkaline cleaning of the surface is carried out, and / or the post-treatment of step (C) may include a step, or consist of a step, in which alkaline oxidation of the surface is carried out, preferably with Raman spectroscopy performed on the surface immediately after the alkaline cleaning or oxidation. The control of the post-treatment preferably includes repeating the alkaline cleaning or alkaline oxidation of the treated surface if the comparison of the obtained Raman spectrum with the reference spectrum yields a deviation above a tolerated maximum deviation.

[0070] Alternatively or additionally, it can be provided that, after initial cleaning with an alkaline cleaner, the Raman spectrum is evaluated to determine whether a repeat cleaning is necessary or whether the cleaning process is complete. In particular, for example, an evaluation of Raman intensity at a wavenumber characteristic of the organic bonds in the oil can be used to determine whether 0.1 is still present on the surface or whether there are still quantities of oil on the surface above a marginal threshold. For example, characteristic intensities in the wavenumber range between 2800 / cm and 3600 / cm can be evaluated, and then, if these intensities are in the noise range or 0, the cleaning is considered complete; if these intensities are above a defined marginal value, a further cleaning step is initiated.This can be repeated iteratively until no more Raman intensities characteristic of oil are detected.

[0071] In particular, it may also be provided that a final sub-step of the post-treatment of step (C) is a concluding quality control step, which includes the preparation of a final Raman spectrum, whereby the steel flat product is marked as non-deliverable if the final quality control step detects a defect; this measure ensures that any defects in strip processing do not lead to the delivery of a defective strip. This has the advantage of increasing product quality.

[0072] Raman spectroscopy is preferably performed as an area scan covering a surface region of the steel flat product. This method not only acquires a single Raman spectrum, but also a number of Raman spectra representing different, preferably homogeneously distributed, locations on the surface of the steel flat product. This allows for the evaluation of the spatially distributed properties of the surface. Furthermore, it avoids the risk of false positives or false negatives resulting from random sampling when only a single Raman spectrum is acquired.

[0073] Particularly preferred is a further training method according to which the evaluation of many or each of the Raman spectra obtained from the area scan provides a comparison of the obtained

[0074] Raman spectrum with a reference spectrum includes .

[0075] If area scans have been performed, quality control can be carried out in a variation of the above explanation by marking the steel flat product as scrap if the comparison of the obtained Raman spectrum with the reference spectrum reveals a deviation above a tolerated maximum deviation for at least a predetermined number of the Raman spectra obtained. For example, it can be stipulated that the product is marked as scrap if the deviation exceeds a tolerated maximum deviation in at least 20 percent of the recorded Raman spectra.

[0076] If surface scans have been performed, the post-treatment can be controlled, for example, by repeating the coating of the treated surface with a corrosion protection oil if the comparison of the obtained Raman spectrum—preferably obtained by Raman spectroscopy performed immediately after coating—with the reference spectrum reveals a deviation above a tolerated maximum deviation for at least a predetermined number of Raman spectra. For example, the coating process can be repeated if the deviation exceeds a tolerated maximum deviation in at least 20 percent of the recorded Raman spectra.

[0077] If surface scans have been performed, the post-treatment can be controlled, for example, by repeating the alkaline cleaning of the treated surface if the comparison of the Raman spectrum obtained, preferably by Raman spectroscopy performed immediately after the alkaline cleaning, with the reference spectrum shows a deviation above a tolerated maximum deviation for at least a predetermined number of Raman spectra obtained, and / or by repeating the alkaline oxidation of the treated surface if the comparison of the Raman spectrum obtained, preferably by Raman spectroscopy performed immediately after the alkaline oxidation, shows a deviation above a tolerated maximum deviation.with the reference spectrum, at least for a given number of the Raman spectra obtained, a deviation above a tolerated maximum deviation results, for example, the deviation above a tolerated maximum deviation is present in at least 20 percent of the recorded Raman spectra.

[0078] According to a beneficial further training, the follow-up treatment of step (0) has a number of two or more steps.

[0079] It is provided that at least two of the steps, preferably all of the steps, are preceded by a characterization of the dressed surface by Raman spectroscopy after the post-treatment of step (C), and / or that at least two of the steps, preferably all of the steps, are followed by a characterization of the dressed surface by Raman spectroscopy after the post-treatment of step (C).

[0080] It is particularly preferred that each post-treatment step is both preceded and followed by Raman spectroscopy. Once this is the case, all the previously described beneficial effects can be achieved, and it can also be ensured that the steel flat product manufacturing process concludes with quality control, thus guaranteeing the provision of the steel flat product of the highest possible quality. A further advantage of this approach is that, should deviations occur, it is possible to identify at which process step the deviations first appeared and thus determine when maintenance work should be scheduled.

[0081] It is particularly preferred that the Raman spectroscopy be performed as confocal Raman spectroscopy. The use of a confocal measurement setup offers the advantage of high contrast and very good spatial resolution. As a result of this high contrast and excellent spatial resolution, it can be ensured, among other things, that the Raman spectroscopy performed for post-treatment and its evaluations yield results that are valid for the entire selected area. This is particularly important for a final quality control step, as confocal Raman spectroscopy is especially advantageous for obtaining comprehensive, high-resolution results.

[0082] Raman spectroscopy is particularly preferably performed with an excitation wavelength between 360 nm and 2128 nm, and preferably between 360 nm and 1064 nm, inclusive. A wavelength between 480 nm and 790 nm is particularly preferred, as experiments have shown that this wavelength allows for a good evaluation of the relevant materials and coatings in the steps described above for all relevant wavenumbers.

[0083] The post-treatment steps are particularly favored when performed using by-side evaluation, by taking representative samples and subjecting them to Raman spectroscopy measurements. The results obtained can then be evaluated as described.

[0084] According to an alternative training method, at least steps (B) and (C) are carried out as a continuous process in a multi-station conveyor system. Raman spectroscopy is performed as an inline measurement and / or by-side, meaning that Raman spectroscopy of the steel flat product takes place during the conveying of the steel flat product within the measuring stations before the first station and / or between the stations and / or after the last station.Particularly preferably, Raman spectroscopy is carried out with a Raman spectrometer coupled to an evaluation unit, which forwards the determined Raman spectra directly to the evaluation unit in real time, so that the evaluation unit can perform the evaluation of the Raman spectra and can directly control the multi-station belt conveying system to control the post-treatment of step (C) based on the evaluation of a Raman spectrum obtained by means of Raman spectroscopy.

[0085] Raman spectroscopy is preferably performed with a stationary Raman probe head, past which the flat steel product is passed. The Raman probe head is preferably arranged on the strip processing machine such that a surface of the flat steel product is passed through a measuring area of ​​the Raman probe head.

[0086] It is particularly preferred that the protective coating be a zinc-based protective coating. In particular, the protective coating can be a Zn-Mg coating.

[0087] In a particularly preferred embodiment, the Zn-Mg coating has been applied in a melt bath with the following melt composition:

[0088] Al: 1-3, preferably 1, 2-1, 6; Mg: 0, 5-3, preferably 1, 0-1, 4;

[0089] Remainder to 100: Zn, where all numerical values ​​are in weight percent, abbreviated: wt. -%. According to a preferred embodiment, the evaluation of the Raman spectrum comprises producing a first set of false-color images, each with a filter for a number of wavenumbers between 200 / cm and 600 / cm, wherein each wavenumber with a local intensity maximum, in particular with a local intensity maximum above a minimum intensity, is assigned a color from a first color spectrum, and wherein a second set of false-color images is produced, each with a filter for a number of wavenumbers between 600 / cm and 3500 / cm, wherein each wavenumber with a local intensity maximum, in particular with a local intensity maximum above a minimum intensity, is assigned a color from a second color spectrum.

[0090] In other words, false-color images are generated, specifically false-color images in the wavenumber range between 200 and 600 cm⁻¹ and false-color images in the wavenumber range between 600 and 3500 cm⁻¹. This approach is based on the understanding that oxide bonds to metals predominate in the wavenumber range between 200 and 600 cm⁻¹, while bonds to organic substances predominate in the wavenumber range between 600 and 3500 cm⁻¹. False-color images filtered at different wavelengths in the wavenumber range between 200 and 600 cm⁻¹ can therefore be attributed to the presence of different metallic phases.False-color images filtered at different wavelengths in the wavenumber range between 600 / cm and 3500 / cm, when compared with false-color images generated in the wavenumber range between 200 / cm and 600 / cm, allow conclusions to be drawn as to which areas, and in connection with which metallic phases, quality control and / or coating with corrosion protection oil and / or alkaline cleaning and / or alkaline oxidation lie within the expected range represented by the reference spectrum.

[0091] Creating a false-color image has the particular advantage that the comparison of the created false-color image with the reference image can be carried out easily using simple image editing software. If the image shows large areas with high intensity, information can be obtained, for example, that a coating of corrosion protection oil is not completely opaque.

[0092] For example, an organic oil component is depicted using a false-color image filtered with a wavenumber between 2850 / cm and 2950 / cm. The presence of high-intensity areas in this wavenumber region can be interpreted as indicating that the surface is not yet completely clean. Therefore, it may be stipulated that the alkaline cleaning process is considered unsuccessful and the process for manufacturing a surface-treated steel flat product is not yet complete if areas with an intensity above an empirically determined and defined intensity threshold are present in this wavenumber range. Consequently, a further alkaline cleaning step is performed. This can be repeated iteratively until complete cleaning is achieved.For example, metal oxide compounds are depicted using a false-color image with a wavenumber between 200 / cm and 600 / cm. The presence of high-intensity areas in this wavenumber region can be interpreted as indicating that the surface is not yet sufficiently deoxidized. Therefore, it may be stipulated that alkaline deoxidation is considered successful and the process for producing a surface-treated steel flat product is complete if no areas with an intensity above an empirically determined and defined intensity threshold are present in this wavenumber range. Otherwise, a further alkaline cleaning step is performed. This can be repeated iteratively until sufficient deoxidation is achieved.

[0093] In the range between 200 / cm and 600 / cm, for example, the following can be concluded:

[0094] Zn-O at 1. Peak maximum = 148 cm⁻¹; peak width = 120–280 cm⁻¹ (weak; narrow = crystalline); 2. Peak maximum = 200 cm⁻¹; 3. Peak maximum = 432 cm⁻¹; peak width = 410–450 cm⁻¹ (strong; narrow = crystalline); 4. Peak maximum = 560 cm⁻¹; on MgZn₂ phases and formation of zinc-magnesium mixed oxides with increased magnesium content at peak maximum = 205 cm⁻¹; peak width = 180–220 cm⁻¹, on zinc-magnesium-aluminum mixed oxides at 1. Peak maximum = 148 cm⁻¹; peak width = 120–280 cm⁻¹ (strong; narrow = crystalline); 2. Peak maximum = 560 cm⁻¹; peak width = 500–600 cm⁻¹. These exemplary data demonstrate that the presence of oxides on certain metallic phases can be inferred from the representation of a location-dependent Raman intensity for selected wavenumbers. By comparing the representation of a location-dependent

[0095] Raman intensity for selected individual wavenumbers in the first wavenumber range 200 / cm and 600 / cm with a location-dependent Raman intensity for selected individual wavenumbers in the second wavenumber range 600 / cm to 3500 / cm allows regions of the second wavenumber range to be identified that can be assigned to regions in the first wavenumber range if the intensity regions of the false-color image from the second set of false-color images and the intensity regions of the false-color image from the first set of false-color images are congruent within tolerated deviations.

[0096] In particular, it can be provided that, using the set of all Raman spectra of an area scan of the scanned surface, a false-color image of the scanned surface is generated for each wavenumber with an intensity maximum identified in at least one Raman spectrum. The false-color images of the first wavenumber range are then compared with the false-color images of the second wavenumber range to obtain an assignment of one of the post-treatment results to different metallic phases in the manner described above.

[0097] According to further training, the control of the post-processing of step (C) is then carried out using the second set of false color images and / or the control of the post-processing of step (C) is carried out using the assignment of the false color image from the second set of false color images to the false color image from the first set of false color images.

[0098] Another aspect of the invention relates to a strip processing plant for the continuous processing of a metallic strip, in particular a steel strip. The strip processing plant comprises at least one tempering stand and a chemical treatment station arranged behind the tempering stand in the direction of strip movement.

[0099] At least one Raman spectrometer is arranged at the strip processing plant for carrying out Raman spectroscopy of a surface of the strip which is passed by the Raman spectrometer, and for forwarding a Raman spectrum obtained by means of Raman spectroscopy to an evaluation station coupled with the Raman spectrum.

[0100] The evaluation station is set up to perform an evaluation of the Raman spectrum.

[0101] It is particularly preferred that the evaluation station has a control unit or is coupled to a control unit which is configured to perform control of a post-treatment of a step (C) in one of the methods according to the invention or one of its further developments.

[0102] Finally, one aspect of the invention provides for the use of a Raman spectrometer, for example, the use of a strip processing plant of the manner described above with a Raman spectrometer, preferably a confocal Raman spectrometer, preferably with a Raman excitation wavelength between 360 nm and 2128 nm inclusive, more preferably between 360 nm and 1064 nm inclusive, for the spectroscopic evaluation of a steel flat product coated with a protective coating. The steel flat product is preferably a steel flat product coated with a zinc-based protective coating.It has surprisingly been shown that metal oxide bonds of zinc-based coatings with Raman peaks at wavenumbers below 600 / cm⁻¹ occupy a distinct range compared to the wavenumbers of relevant organic coatings, between 600 / cm⁻¹ and 3500 / cm⁻¹, particularly corrosion protection oils. This means that the position of the peaks directly indicates whether a coating with an organic layer or a metal oxide bond without an organic layer has been detected by Raman spectroscopy. The inventors recognized this fact and utilize it in the aforementioned further development of the inventive method, since the knowledge of the separated peak wavenumber ranges is used to assign intensity maxima, particularly in false-color representation, to a quality condition of the flat steel product.

[0103] Furthermore, the steel flat product is preferably a steel flat product that has been tempered after coating. The Raman spectrometer is used to record a Raman spectrum after tempering the coated steel flat product and before oiling it as part of a quality control procedure or as part of an oil selection step from a number of available oils, and / or after oiling and before alkaline cleaning as part of a quality control procedure, and / or after alkaline cleaning as part of a quality control procedure.

[0104] The Raman spectrum is analyzed. In particular, the steel flat product is assessed based on this analysis, and this assessment is carried out as part of quality control before delivery.

[0105] The development is explained below using figures that represent an example.

[0106] They show:

[0107] Fig. 1: Results of Raman spectroscopy performed on steel sheets with a protective coating; Fig. 2: a schematic representation of a

[0108] Strip processing system for processing a metallic strip.

[0109] Figure 1 shows the results of Raman spectroscopy performed on steel sheets with a protective coating. Raman spectroscopy was carried out with an excitation wavelength of 488 nm. A Witec Raman probe with a Zeiss lens was used to obtain the Raman spectra, with the following settings:

[0110] Working distance: 1mm,

[0111] 50x (0.7) ,

[0112] Mapping: 10x10; 5x5; 3x3 images;

[0113] Photo of the scan area: 20 pm;

[0114] Method: Area scan; 60x60 pmxpm with 80 points per line and 80 lines per image;

[0115] Integration time: 1 second.

[0116] A flat steel product was provided which was coated in a melt bath with the following composition:

[0117] Al : 1.4;

[0118] Mg : 1.2;

[0119] Remainder to 100: Zn, where all figures are in weight percent, abbreviated: wt.%.

[0120] The circuit board underwent the following steps:

[0121] In step (B) the coated steel flat product was dressed in at least one dressing frame (S100) .

[0122] Following this, in step (C), the dressed coated steel flat product underwent post-treatment to provide a ready-to-run steel flat product or a further processable intermediate product. The post-treatment consisted of steps (CI) to (C3), namely in the following order:

[0123] (CI) Operation (S200) , (C2) Alkaline cleaning (S300) , (C3) Quality control (S400) .

[0124] After performing step S200 as a sub-step of a post-treatment of step (C) with a corrosion inhibitor zdl, a false-color image was produced for an intensity associated with an organic coating (see Fig. 1b). Based on the finding that for a predetermined number of Raman spectra obtained, recognizable by the light spot from which the arrow originates, a deviation of the Raman spectrum from the reference spectrum exceeding a tolerated maximum deviation was observed. Insufficient oil is present in the dark areas, necessitating a repeat lubrication process, preferably after adjusting the lubrication unit to achieve lubrication with an increased amount of applied oil.

[0125] After cleaning step 300 as a sub-step of a post-treatment of step (C), a false-color image was produced for an intensity associated with an organic cleaning fluid (see Fig. 1c). Based on the finding that for a predetermined number of Raman spectra obtained, recognizable by the light spot from which the arrow originates, a deviation of the Raman spectrum from the reference spectrum exceeding a tolerated maximum deviation was observed. Cleaner residues are present in the light areas, necessitating a repeat cleaning process, preferably after adjusting the cleaning unit to achieve cleaning with a reduced amount of cleaner applied.

[0126] Finally, in step 400, a quality control check is performed as a sub-step of a post-treatment of step (C). For this purpose, a false-color image was produced for an intensity corresponding to an organic pretreatment band (see Fig. Id). Based on the finding that for a predetermined number of Raman spectra obtained, recognizable in the dark spot from which the arrow originates, a deviation of the Raman spectrum from the reference spectrum exceeding a tolerated maximum deviation was observed. Insufficient pretreatment is present in the dark areas, so the pretreatment is repeated, preferably after adjusting the pretreatment unit to achieve a pretreatment with an increased amount of pretreatment applied.

[0127] Fig. 2 shows a strip processing plant 1. The strip processing plant 1 is used for the continuous processing of a metallic strip 2, which is fed through the plant. The metallic strip can be, for example, a steel strip. The strip processing plant has a tempering stand 3, with which the texturing of the strip's surface is adjusted for advantageous properties, particularly in mechanical and tribological terms. A chemical treatment station 4 is arranged downstream of the tempering stand 3, viewed in the direction of strip movement P. In the embodiment shown in Fig. 1, this is an application station 4 for applying a corrosion protection oil, which remains temporarily on the strip until it is further processed after transport and / or storage.Prior to further processing, alkaline cleaning and / or alkaline oxidation can be carried out in a plant specifically designed for this purpose, which is not shown here.

[0128] A Raman spectrometer 5 and a Raman spectrometer 6 are arranged at the strip processing system. In the configuration shown, these are stationary Raman probes designed for confocal Raman spectroscopy. Raman spectroscopy is performed on the surface 2' of the strip using the Raman spectrometers 5 and 6 as soon as the strip passes by the respective spectrometer. The Raman spectrum obtained by the Raman spectroscopy is transmitted to an evaluation station 7, which is coupled to the Raman spectrometers 5 and 6. The evaluation station serves to enable the evaluation of the spectra and is equipped with appropriate programming for this purpose.By directly coupling the Raman spectrometers 5, 6, it is possible to evaluate Raman spectra obtained during the inline processing of the tape 2 and thereby control the post-treatment of the tape during or immediately afterwards depending on the evaluation of the Raman spectra.

[0129] Because the strip processing plant 1 shown in Fig. 2 is designed as a multi-station strip conveying plant, and Raman spectroscopy is carried out as an inline measurement, the dressing steps and the post-treatment steps, depending on which sub-steps it comprises, can be carried out completely or partially in the strip processing plant 1.

Claims

CK Patent claims 1. Method for producing a surface-treated, protective-coated, steel flat product, comprising the steps of: (A) Providing a steel flat product coated with a protective coating; (B) Dressing the coated steel flat product in at least one dressing stand; (C) Post-treatment of the dressed coated steel flat product to provide a deliverable steel flat product or a further processable intermediate product; wherein Raman spectroscopy is performed on the dressed surface, wherein the post-treatment of step (C) is controlled by evaluation of a Raman spectrum obtained by Raman spectroscopy.

2. Method according to claim 1, wherein the evaluation of the obtained Raman spectrum comprises a comparison of the obtained Raman spectrum with a reference spectrum.

3. A method according to claim 1 or claim 2, wherein the post-treatment of step (C) comprises a step in which a quality control of the dressed surface is carried out, wherein the control of the post-treatment comprises that the quality control is carried out by marking the steel flat product as rejecting it if the comparison of the obtained Raman spectrum with the reference spectrum shows a Deviation above a tolerated maximum deviation from the result has .

4. Method according to one of the preceding claims, wherein the post-treatment of step (C) comprises a step in which the dressed surface is coated with a corrosion protection oil, wherein the control of the post-treatment comprises repeating the coating of the dressed surface with a corrosion protection oil if the comparison of the obtained Raman spectrum with the reference spectrum results in a deviation above a tolerated maximum deviation.

5. A method according to any of the preceding claims, wherein the post-treatment of step (0) comprises a step in which an alkaline cleaning of the surface is carried out, wherein the control of the post-treatment comprises that the alkaline cleaning of the treated surface is repeated if the comparison of the obtained Raman spectrum with the reference spectrum results in a deviation above a tolerated maximum deviation, and / or the post-treatment of step (0) comprises a step in which an alkaline oxidation of the surface is carried out, wherein the control of the post-treatment comprises that the alkaline oxidation of the treated surface is repeated if the comparison of the obtained Raman spectrum with the reference spectrum results in a deviation above a tolerated maximum deviation.

6. Method according to one of the preceding claims, wherein the Raman spectroscopy is performed as an area scan covering a surface area of ​​the steel flat product to acquire a number of Raman spectra, wherein preferably the evaluation of many of or each of the Raman spectra obtained from the area scan comprises a comparison of the Raman spectrum obtained with a reference spectrum.

7. Method according to one of the preceding claims, wherein the post-treatment of step (C) comprises a step in which a quality control of the dressed surface is carried out, wherein the control of the post-treatment comprises that the quality control is carried out by marking the steel flat product as reject if the comparison of the obtained Raman spectrum with the reference spectrum results in a deviation above a tolerated maximum deviation for at least a predetermined number of the obtained Raman spectra;and / or wherein the post-treatment of step (0) comprises a step in which the dressed surface is coated with a corrosion protection oil, wherein the control of the post-treatment comprises that the coating of the dressed surface with a corrosion protection oil is repeated if the comparison of the obtained Raman spectrum with the reference spectrum yields a result at least for a predetermined number of the obtained Raman spectra; Deviation above a tolerated maximum deviation results in a certain outcome;and / or wherein the post-treatment of step (C) comprises a step in which an alkaline cleaning of the surface is carried out, wherein the control of the post-treatment comprises that the alkaline cleaning of the treated surface is repeated if the comparison of the obtained Raman spectrum with the reference spectrum results in a deviation above a tolerated maximum deviation for at least a predetermined number of the Raman spectra obtained, and / or the post-treatment of step (0) comprises a step in which an alkaline oxidation of the surface is carried out, wherein the control of the post-treatment comprises that the alkaline oxidation of the treated surface is repeated if the comparison of the obtained Raman spectrum with the reference spectrum results in a deviation above a tolerated maximum deviation for at least a predetermined number of the Raman spectra obtained;and / or wherein the post-treatment of step (0) comprises two or more steps, wherein at least two of the steps, preferably all of the steps, of the post-treatment of step (0) are each preceded by a characterization of the dressed surface by Raman spectroscopy, and / or at least two of the steps, preferably all of the steps, of the post-treatment of step (0) are each followed by a characterization of the dressed surface by Raman spectroscopy.

8. Method according to any of the preceding claims, wherein the Raman spectroscopy is performed as confocal Raman spectroscopy, and / or the Raman spectroscopy is performed with an excitation wavelength of 360 nm to 2128 nm, preferably from 360 nm to 1064 nm.

9. Method according to any of the preceding claims, wherein steps (B) and (C) are carried out as a continuous process in a multi-station conveyor system, or step (B) and substeps of step (C) are carried out as a continuous process in a multi-station conveyor system, wherein the Raman spectroscopy is carried out as an inline measurement and / or as a by-side measurement; and / or wherein the Raman spectroscopy is carried out with a stationary Raman probe head past which the steel flat product is passed.

10. A method according to any one of the preceding claims, wherein the protective coating is a zinc-based protective coating; wherein preferably the protective coating is a Zn-Mg coating, or the protective coating is a Zn-Al coating, or the protective coating is a Zn-Al-Mg coating, or the protective coating is a Zn-Al-Si coating, or the protective coating is another coating from the (Zn, Mg, Al, Si) system is ; where The protective coating is particularly preferred if it is made by means of The protective coating is applied by hot-dip immersion in a melt bath, the melt bath consisting of: Al: 0.1-8.0, preferably 0.8-7.0, particularly preferably 1.0-5.0; in particular 1.1-4.0; optionally Mg: up to 8.0, preferably up to 7.0, particularly preferably up to 5.0, in particular up to 4.0; The remainder, besides unavoidable impurities, is Zn to 100%, where all figures are in weight percent, abbreviated: wt.%; or the protective coating is an electrolytically applied protective coating on the shaped steel flat product, wherein the protective coating contains: Al: 0.001-1, preferably 0.01-1; The remainder, besides unavoidable impurities, is 100: Zn, where all figures are in weight percent, abbreviated: wt.%; or the protective coating is a protective coating of iron-zinc compounds applied by hot-dip immersion in a melt bath and treated after application by annealing the coated steel flat product above the Zn melting point, wherein the melt bath consists of: Al: 0, 1-1,0; Remainder, apart from unavoidable impurities, to 100: Zn, where all figures are in weight percent, abbreviated: wt.%.

11. A method according to any of the preceding claims, wherein the evaluation of the Raman spectrum obtained by means of Raman spectroscopy comprises producing a first set of false-color images, each with a filter for a number of wavenumbers between 200 / cm and 600 / cm, wherein each wavenumber is assigned the number of wavenumbers with a local intensity maximum, in particular with a local intensity maximum above a minimum intensity, a color from a first color spectrum is assigned, and a second set of false-color images is produced each with a filter for a number of wavenumbers between 600 / cm and 3500 / cm, wherein each wavenumber of the number of wavenumbers with a local intensity maximum, in particular with a local intensity maximum above a minimum intensity, is assigned a color from a second color spectrum.

12. Method according to claim 11, wherein an assignment of a false-color image from the second set of false-color images to a false-color image from the first set of false-color images is carried out if the intensity regions of the false-color image from the second set of false-color images and the intensity regions of the false-color image from the first set of false-color images are congruent within tolerated deviations.

13. Method according to claim 11 or according to claim 12, wherein the control of the post-treatment of step (C) is carried out based on the second set of false-color images, and / or wherein the control of the post-treatment of step (C) is carried out based on the assignment of the false-color image from the second The set of false-color images is compared to the false-color image from the first set of false-color images.

14. Strip processing plant ( 1 ) for continuous Machining of a metallic strip ( 2 ) , in particular steel strips, wherein the strip processing plant ( 1 ) includes at least one dressing stand ( 3 ) and a ( P ) in the direction of strip movement. The chemical treatment station (4) is arranged behind the dressing frame (3), wherein at least one Raman spectrometer (5, 6) is arranged on the strip processing system (1) for performing Raman spectroscopy of a surface (2') of the strip (2) which is guided past the Raman spectrometer (5, 6), and for forwarding a Raman spectrum obtained by means of Raman spectroscopy to an evaluation station (7) coupled to the Raman spectrum, wherein the evaluation station (7) is configured to perform an evaluation of the Raman spectrum; wherein preferably the evaluation station (7) has a control unit or is coupled to a control unit, wherein the control unit is configured to perform a control of a post-treatment of a step (C) in one of the methods of claims 1 to 13.

15. Use of a Raman spectrometer, preferably a confocal Raman spectrometer, preferably with a Raman excitation wavelength of 360 nm to 2128 nm, more preferably 360 nm to 1064 nm, for the spectroscopic evaluation of a steel flat product coated with a protective coating, preferably a steel flat product coated with a zinc-based protective coating, after dressing the coated steel flat product and before oiling as part of a quality control procedure or as part of an oil selection step from a number of available oils and / or after oiling and before alkaline cleaning as part of a quality control procedure and / or after alkaline cleaning as part of a Quality control, and / or especially before delivery as part of a quality control process.

Images