EP4121579A1

EP4121579A1 - Method for producing markings on galvanized steel strip or steel plate and galvanized steel strip or steel plate with marking of this kind

Info

Publication number: EP4121579A1
Application number: EP21714105.0A
Authority: EP
Inventors: Johann Gerdentisch; Thomas Steck; Ernst Commenda
Original assignee: Voestalpine Stahl GmbH
Current assignee: Voestalpine Stahl GmbH
Priority date: 2020-03-18
Filing date: 2021-03-17
Publication date: 2023-01-25
Also published as: WO2021185914A1; EP3882374A1

Abstract

The invention relates to a method for producing markings on galvanized steel strip or steel plate, wherein a metal salt solution, more particularly an inorganic metal salt solution, is applied to regions of the steel surface, and the steel surface is then electrolytically galvanized. The invention also relates to galvanized steel strip or steel plate with marking produced in this manner.

Description

Process for creating markings on galvanized steel strips or

Steel sheets and galvanized steel strips or steel sheets with such a marking

The invention relates to a method for producing identifications through areas with different visual appearances on galvanized steel strips or steel plates with the features of claim 1.

The invention further relates to galvanized steel strips or steel sheets produced by the above-mentioned method with areas with different visual appearances according to the preamble of claim 13.

A marking is defined below as a surface change that is visible to the human eye or measurable or detectable for a measuring device, which makes the changed area distinguishable relative to unchanged areas. There are markings that are visible to the human eye without any aids. A simple example is font of a first color on a background of a different color. There are also markings that are only visible to the human eye when they are illuminated with light of a certain wavelength (e.g. UV light). The human eye is widely used for the detection of such markings. If a marking or change can be detected by the human eye, i.e. the relative differences between the changed area (the "marking") and a background can be detected, one speaks of a visible change or, in this case, marking. Such a marking calls you visible effect to the human eye.

It is known to provide steel strips with a wide variety of identifications, which relate to the material, the batch, the brand, the manufacturer and the like. Markings have become increasingly important in recent years. On the one hand, for the traceability of product-relevant information along the production chain within the framework quality assurance; on the other hand, it is about the provision of product-specific information for the user.

A marking on a steel surface can be created by various methods. Markings are often achieved through mechanical and / or chemical processing.

Mechanical processing induces a change in topography, i.e. depressions and / or elevations are created on the surface. Depressions can be created by removing material, for example by laser embossing. Elevations are mostly created by applying structuring elements, e.g. by printing. A change in topography changes the surface through elevations or depressions which either cause an optical effect (e.g. through a shadow cast) and are visible to the human eye or can be measured using a measuring device.

Nowadays, different printing processes are used for printing, such as screen printing, indirect gravure printing or inkjet printing.

Screen printing is a printing process in which the material to be applied is applied with a squeegee through a fine-meshed fabric onto the surface to be printed. The mesh openings of the fabric are made impermeable at those points of the fabric where no material is to be applied in accordance with the printed image.

Indirect gravure printing is a printing process in which the elements to be imaged are present as depressions in the printing matrix. The entire printing matrix is dipped into the material to be applied before printing and the excess material is removed with a doctor blade so that the material to be applied is only located in the depressions. The material transfer takes place through high contact pressure and adhesive forces between the surface to be printed and the material.

Ink-Jet is a matrix printing process in which the material to be applied is in liquid form and is applied by targeted shooting or deflection of small drops of material. The drops of material are generated using a piezoelectric transducer and then electrostatically charged via a charging electrode. Then the Drops of material are accelerated and their trajectory is controlled by means of a deflection electrode. After it hits the surface to be printed, a print image is generated.

In the processes mentioned, structuring elements are applied to the surface to be marked. These are mostly foreign substances that have a different chemical composition and therefore different physical properties than the coated surface. This can possibly make further surface treatment or processing of the workpiece more difficult.

Depressions or embossments on metallic surfaces are now often produced using laser technology.

A change in topography can also be produced by chemical means. It is known to produce depressions on the surface by etching with acids. For this purpose, the metal surface to be treated is brought into contact with, for example, hydrochloric or sulfuric acid. The depth of the marking is directly related to the treatment time.

When the desired depth is reached, the surface is treated with a basic solution, for example caustic soda, in order to prevent possible corrosion from remaining acid residues.

An optical effect or a marking can also be created by means of a coating. It can be an organic or an inorganic coating.

An organic coating can be organic lacquers. Optical effects are often created using organic multilayer systems, such as the colofer®vario process. A steel surface is pretreated free of chromate. A chromate-free primer is then applied. The visual effect is defined by a basecoat and a texture layer on top. Finally, a top coat is applied. Several system runs are required for this. This increases the production costs. In addition, further processing of the workpiece coated in this way is made more difficult. An inorganic coating can be a metallic coating, such as a zinc coating. A zinc coating is usually applied for corrosion protection purposes.

Various galvanizing processes are known. A common galvanizing process is so-called hot-dip galvanizing (also known as hot-dip galvanizing). Steel is immersed continuously (e.g. strip or wire) or piece by piece (e.g. components) at temperatures of around 450 ° C to 600 ° C in a melt of liquid zinc (the melting point of zinc is 419.5 ° C). The zinc melt conventionally has a zinc content of at least 98.0% by weight in accordance with DIN EN ISO 1461. In the case of a continuously galvanized strip, the zinc layer has a thickness of 5 μm to 40 μm. In the case of a piece-wise galvanized component, the zinc layer can have a thickness of 50 μm to 150 μm.

In the case of electrolytic galvanizing (galvanic galvanizing), steel strips or steel plates are not immersed in a zinc melt, but in a zinc electrolyte.

The steel to be galvanized is introduced into the solution as a cathode and a dimensionally stable electrode is used as the anode. Electricity is passed through the electrolyte solution. The zinc present in ionic form (oxidation level +11) is reduced to metallic zinc and deposited on the steel surface. Compared to hot-dip galvanizing, electrolytic galvanizing can apply thinner layers of zinc. The zinc layer thickness is proportional to the strength and duration of the current flow, whereby - depending on the workpiece and anode geometry - a layer thickness distribution arises over the entire workpiece.

Careful surface pretreatment is required to ensure the adhesion and uniformity of the zinc layer. This can be, for example, degreasing, alkaline cleaning, pickling, rinsing and / or pickling. After galvanizing, one or more subsequent treatments can be carried out, such as phosphating, oiling, passivating, applying organic coatings (cathodic dip painting).

It is also known to define the visual appearance of electrolytically deposited zinc layers by changing parameters. This can, for example, be a changed electrolyte composition. The pre-treatment of the steel surface also plays a major role. Optical effects can be achieved, for example, by changing the pickling or cleaning parameters can be varied. The disadvantage here is that the optical effect relates to the entire bandwidth and cannot be controlled locally. This means that no local identification patterns can be generated with this method.

From DE 10 2017 106 672 A1 a marking and / or marking by means of laser of hot-dip galvanized metal components is known. The markings are achieved by printing (e.g. ink printing) or embossing (e.g. laser technology). The laser marking is carried out in such a way that the protective properties of the galvanized layer are retained in full. To generate the permanent marking, the zinc layer is selectively removed in a specified area by means of a laser and then subjected to a chemical reaction with an ambient gas (reaction gas). The chemical conversion of the zinc layer leads, among other things, to oxides that are visually different from the surrounding zinc layer and in this way create an optical effect or a pattern.

A comparable method is known from DE 10 2007 010 932 A1. The markings on the steel surface are also removed by laser.

The zinc layer can be completely removed in order to increase the legibility of the marking. The subsequent oxidation of the base material increases the optical contrast.

DE 40 33 230 A1 describes a combined marking process in which a Me tallband is processed mechanically and chemically in order to create a surface structure. Initially, embossing engravings are made using a laser. The exposed areas are then etched by an acid to a specified depth, so that after the etching process, which can be repeated several times for the purpose of obtaining superimposed structures, a desired engraved profile is created.

A structuring process for electroplated thermoplastics is known from DE 103 20 237 A1. The thermoplastic is removed by a burning laser beam in the area of the desired symbols or structural elements. A galvanic layer is applied to the thermoplastic surface structured in this way. Since there is no thermoplastic layer in the structuring area, no electroplated layer can form there. As a result, the laser-generated structuring is also visible on the top electroplated layer. From DE 10 2011 051 266 A1 a structuring method is known in which structuring elements are applied to the surface to be structured by means of ink printing. The elevations produced by the ink pressure are hardened through. The surface is then coated with an electroplating layer.

In the case of the mentioned labeling methods, it is disadvantageous that the labeling can only be achieved with foreign substances. This can lead to problems with follow-up treatment. In addition, it is not possible to influence the appearance locally. Thus, the design options are limited in the above-mentioned methods. Furthermore, the mentioned labeling procedures are not suitable for in-line use.

The object of the invention is to provide a method for generating markings on galvanized steel strips or steel sheets, which does not affect the zinc layer and can be controlled locally in a targeted manner.

The object is achieved with a method having the features of claim 1.

Advantageous further developments are identified in the dependent claims.

A further object of the invention is to create a steel strip or sheet steel made according to the above-mentioned method with areas with a marking which is easily detectable and in particular visible and allows problem-free processing and further processing.

The object is achieved with a steel strip or sheet steel with the features of claim 13.

Advantageous further developments are identified in the dependent claims.

According to the invention, markings are created on galvanized steel strips which do not negatively affect further processing. In the context of the invention, a marking is understood to mean everything that is suitable for visually representing information or a pattern or design, that is to say for example writing, barcodes, patterns, designs. The identification according to the invention can appear on any surface, for example a partial surface of a tape (for example barcode) or over the entire surface (for example pattern, brand, company name).

This marking can be perceptible to the human eye, i.e. that there are areas of a first type which can be optically distinguished from areas of the second type by the human eye. Areas of the first type (first areas) thus have a visually different effect than areas of the second type (second areas) and thus together form the identification.

According to the invention, the identifiers can be detected by the human eye and thus also by measuring devices or sensors in that a light / dark contrast is generated, with first areas being brighter than second areas, for example. Or the areas of the first type have a different color than the areas of the second type, the color tone distance being so large that it is visible to the human eye or can be detected by a sensor.

In particular, it is provided according to the invention to design the areas of the first type and the areas of the second type with different reflectivities. The reflectivity is referred to, among other things, as gloss. Different gloss is visible to the human eye. In addition, gloss can also be measured. This is used, for example, when assessing paint surfaces, in particular on motor vehicles.

However, the performance of the human eye should not be underestimated here; the trained eye of specialists is often used in the assessment, whereby the human eye is very good at perceiving relative differences in gloss on a surface.

Machine or automated gloss measurements are particularly advantageous when absolute reflection values are to be determined by measuring different surfaces, for example in the course of a series of measurements, for example of manufactured goods. This is especially true when the products are processed inline and are therefore no longer available for a comparison measurement after the measurement. If there are first areas with a different gloss (higher or lower) than the second areas, this can be measured by a sensor as well as detected by the human eye.

Measuring devices such as sensors are used for fully automatic detection of machine-readable identification, for example barcodes.

Identifications that are an advertising message, a brand name, safety instructions or the like are aimed at people and can therefore be perceived with the human eye.

In the following, a difference in gloss which can be detected by the human eye (and thus inevitably can also be detected by machine) is generally also referred to as an optical impression.

In particular, the markings according to the invention can be measured with measuring devices, the measurements being gloss measurements in accordance with ISO 2813: 2014 or color measurements in accordance with EN ISO 11664-3: 2013. Both measurement methods can be used.

With both measurement methods, the rule of thumb also applies that relative gloss differences between the areas of the first type and the areas of the second type, measured in accordance with ISO 2813, of 10% can be seen with the eye (floch gloss more difficult than matt) and that color differences in these areas are measured in accordance with EN ISO 11664 summarized as dE * are distinguishable with the eye from a value of 1.

The method according to the invention generates labels in which the relative gloss differences or the color differences are so far apart that the required differences for recognition with the eye are clearly, and in particular exceeded several times. In other words, the marks are easily perceptible to the human eye.

According to the invention, areas with different optical impressions, in particular with areas with different optical properties (eg gloss) that cause the visual appearance, are produced on galvanized steel strip or galvanized steel plates without changing the topography of the zinc layer. That means that after subsequent Coating steps the marking is no longer visible, because the surface is just moderate.

In addition, a physically and largely chemically homogeneous zinc layer is guaranteed. The visual impression is based on the generation of critical log ra phic different areas.

The invention provides that a salt solution is applied locally in a targeted manner to a steel strip, in particular a continuously rolled cold wide strip (KBB). The solution can be applied using any transfer method. This can be, for example, inkjet printing, stamping or indirect gravure printing. The steel surface is then electrolytically galvanized.

Inorganic and / or organic salt solutions are suitable for this process, in particular metal salt solutions are well suited. The metal salt solutions can contain, for example, metal ions of the 4th, 5th main group and / or 7th, 11th subgroup. It is advantageous if the following metals are included as cations: Mn, Sn, Pb, Bi, Cu, Au, Ag. It is particularly advantageous if the metal salt solution used comprises bismuth ions.

Organic, inorganic ions or complexing agents can be used as anions. Inorganic anions can be monovalent, such as, for example, F ^~ , CI, G, Br, divalent, such as, for example, O ^{2 ~} , S ^{2 ~} , or have a complex structure, such as, for example, NO3 ² , SO ² , OH-. It is advantageous if chloride, nitrate, sulfate ions, hydroxide or oxide ions are present as inorganic anions. It is particularly advantageous if nitrate ions are used.

Anions derived from organic acids can be used as organic anions. It can be, for example, carbonates, alcoholates, organic sulfates, organic nitrates. It is advantageous if acetate, citrate and / or oxalate ions are present in the salt solution used.

Thus, within the scope of the invention, the solution used can be selected from the group of Mn, Sn, Pb, Bi, Cu, Au, Ag and nitrate, chloride, hydroxide, oxide, sulfate, acetate, citrate, oxalate and mixtures and combinations thereof. After the salt solution has been applied, a so-called cementation reaction sets in, especially at low pH values. A metallic intermediate layer is formed on the steel surface. The reaction can be exemplified by the following equation:

2M ^{X +} + xFe -> 2M | + xFe ²⁺ (1)

It can be seen that the metal ions are reduced from the salt solution and deposited on the steel surface. The deposited intermediate layer can have a layer thickness which is in the nanometer range.

According to Paunovic, M; Schlesinger, M (1998) "Fundamentals of electrochemical deposition", Wiley, New York, pages 161-166 understand a deposition of a more noble metal on a less noble metal without the application of electricity (displacement deposition). The driving force for this spontaneously occurring process is the different Nernst ^' see potentials of the two redox systems involved. The process is self-limiting, since the reaction requires exposed surface for progress. A well-known example is the cementation reaction of copper on zinc corresponding to the reaction Cu2 + + Zn = Cu + Zn2 + The technical application is the recovery of precious metals such as copper and gold from electronic scrap using iron and zinc. To assess which is the more precious redox couple, the activities of all parties involved must be taken into account. For example, tin can be used without external power application Deposits copper in the presence of cyanides In addition, the cyanides shift the copper potential to negative values and thereby allow the deposition of tin on copper (an important reaction in printed circuit boards).

The saline solution is applied in-line. It is advantageous that the desired pattern is not impaired by the entire system cycle.

It is also advantageous that further processing steps are not necessary.

After the salt solution has been applied, the steel strip or steel plate is electrolytically galvanized. For this purpose, the steel plate and / or the steel strip is brought into contact with a zinc electrolyte solution. The zinc ions present in the electrolyte solution are reduced by the current passed through and crystallize on the surface to be coated. This Process is called electrocrystallization. The zinc layer produced can have a layer thickness that is in the micrometer range.

The layer thickness ratio of the metallic intermediate layer and the zinc layer can be defined as 1: 1000 to 1: 20000, for example.

The electrocrystallization of the zinc is influenced by the underlying metallic intermediate layer in such a way that the crystallization in this area (hereinafter also "area of the first type") takes place in a different manner and in particular in a significantly more orderly manner. This leads to an increased symmetry of the zinc lattice The appearance of the zinc in the pretreated areas is changed in such a way that the pretreated areas in particular have a higher gloss.

It is advantageous that there is no topography change, such as the layer thickness or the sheet thickness.

It is also advantageous that no foreign substances or foreign elements are applied to the zinc surface. This means that the marked surface is fully compatible with the other typical subsequent processes, such as phosphating, passivating, oiling, cleaning, and applying organic coatings.

The invention thus relates to a method for producing markings on galvanized steel strips or steel sheets, a metal salt solution, in particular an inorganic metal salt solution, being applied to the steel surface in areas and the steel surface then being electrolytically galvanized.

In a further development, a metal salt solution is used, its cations from the group of Mn, Sn, Pb, Bi, Cu, Au, Ag and its anions from the group of nitrate, chloride, Flydroxide, oxide, acetate, citrate, oxalate and mixtures thereof and combinations can be selected.

In a further development, a metal salt solution is used, the solution containing bismuth ions.

In a further development, a metal salt solution is used, the solution comprising bis mut (111) -n itrat- pen ta hydrate and dilute nitric acid. In a further development, the applied metal salt solution enters into a cementation reaction with the steel surface in such a way that the metals are electrochemically deposited from the metal salt solution without the effect of external current, so that a metallic intermediate layer is deposited on the steel surface.

In a further development, the metallic intermediate layer has a layer thickness in the nanometer range.

In a further development, the layer thickness ratio of the metallic intermediate layer and the zinc layer located above it is between 1: 1000 to 1: 20000.

In a further development, the zinc electrocrystallization is influenced by the metallic intermediate layer, so that the crystallization of the zinc above the metallic intermediate layer takes place in a more orderly manner with an axially and radially higher alignment rate.

In a further development, a continuously rolled cold wide strip, in particular a ge annealed continuously rolled cold wide strip, is used as the substrate.

In a further development, the zinc layer is deposited over the areas treated with the salt solution and untreated areas, both areas having a common, indistinguishable topography after galvanizing.

In a further development, the zinc layer over the areas of the first type treated with the salt solution has a different gloss measured in accordance with ISO 2813 and / or a color difference measured in accordance with EN ISO 11664 due to the increased crystallization order compared to the areas of the second type.

In a further development, the relative gloss difference exceeds 10% and / or the color difference exceeds 1 for dE *.

Another aspect of the invention relates to an electrolytically galvanized steel strip or sheet steel with a marking, in particular produced by an aforementioned method, the electrolytically galvanized steel strip or the steel plate having areas of the first type and areas of the second type, both areas having the same topography, in particular Zinc layer thickness, the areas of the first type having a thin metallic intermediate layer between the steel surface and the zinc layer and the identification being formed in that the areas of the first type are optically distinguishable from the areas of the second type for the human eye and / or a sensor.

In a further development, the areas of the first type have a different optical effect than the areas of the second type and thus together form the identification.

In a further development, the zinc layer over the areas of the first type treated with the salt solution has a different gloss measured in accordance with ISO 2813 and / or a color difference measured in accordance with EN ISO 11664 due to the increased crystallization order compared to the areas of the second type, which is a for the human Visual impression that can be detected by the eye and measuring sensors, the relative gloss difference exceeding 10% and / or the color difference exceeding 1 for dE *.

In a further development, the metallic intermediate layer comprises a metal or metals which can be selected from the group of Mn, Sn, Pb, Bi, Cu, Au, Ag.

In a further development, the metallic intermediate layer comprises bismuth.

In a further development, the metallic intermediate layer and the zinc layer have layer thicknesses which are in a ratio of 1: 1000 to 1: 20000 to one another.

The invention is explained by way of example with the aid of a drawing. It shows:

Figure 1: Changed appearance of the zinc over the metallic

Intermediate layer;

FIG. 2: a surface of a sheet metal treated according to the invention;

FIG. 3: A table with the measured values of the degree of gloss measurement; FIG. 4: the CIEIab color space for color measurements;

FIG. 5: a table showing the measurement results of the color measurement;

FIG. 6: a table with the summarized values of the color measurement;

FIG. 7: electron micrographs of the different areas, showing the order structure of the zinc surface;

Figure 8: Light microscope and topographical image of a modified zinc layer.

According to the invention, a salt solution is applied to the steel surface. A KBB (continuously rolled cold wide strip), in particular an annealed KBB (continuously rolled cold wide strip), is used as the starting material. The steel strip provided with the salt solution is then electrolytically galvanized in-line in one pass through the plant. The areas treated according to the invention with the salt solution are still visible after galvanizing. In Figure 1 one recognizes an identification pattern generated by the method according to the invention.

The generated identification pattern shows no topography change in terms of layer thickness or sheet thickness change. This can be seen in FIGS. 7 and 8. The light microscope image of the galvanized steel strip, shown in FIG. 8 in the top right-hand image, shows an optical impression produced according to the invention. The area shown in the dark is the area of the first type, which has a metallic intermediate layer. The zinc atoms are deposited on this metallic intermediate layer in a more ordered crystal structure according to Figure 7, which creates the different visual appearance, in particular areas with different optical properties (e.g. gloss, color difference) that create an optical impression. The brightly shown area was not treated with the salt solution and therefore only has an electrolytically deposited zinc layer.

The right-hand area shown at the top right in FIG. 8 is, as stated, the area with the metallic intermediate layer according to the invention. In this case, this area appears darker. This is also related to the lighting, in this case a ring light, which is hardly reflected by the relatively flat area (evenly arranged "zinc shingles"). In the disordered area on the left, however, there are several surfaces that reflect the light and therefore appear brighter. The gloss effect created depends on the lighting angle.

In the overview image in FIG. 8 on the right, the treated area on the right appears lighter because the lighting was chosen differently in this case.

The image at the bottom right in FIG. 8 is a topographical image of the same sample. It can be seen that both areas have an identical topography. There are no elevations or depressions in the area of the marking.

As already stated, the markings according to the invention can be measured with measuring devices, the measurements being gloss measurements in accordance with ISO 2813: 2014 or color measurements in accordance with EN ISO 11664-3: 2013. Both measuring methods are common and applicable.

For both measurement methods, the rule of thumb applies that relative gloss differences between the areas of the first type and the areas of the second type, measured in accordance with ISO 2813, of 10% can be seen with the eye (floch gloss more difficult than matt) and that color differences in these areas measured in accordance with EN ISO 11664 are summarized as dE * are distinguishable with the eye from a value of 1.

As shown below, the method according to the invention generates characteristics in which the relative gloss differences or the color differences are so far apart that the differences required for recognition with the eye are clearly, and in particular exceeded several times. In other words, the marks are easily perceptible to the human eye.

The invention is explained by way of example on the basis of an exemplary embodiment.

An inorganic aqueous metal salt solution is prepared by adding 50 mL FINO3 (IN) to a spatula tip of Bi (N03) 3'5Fl20. The solution is stirred at room temperature until the salt is completely dissolved. The stock solution prepared in this way is then diluted with deionized water in a ratio of 1: 9. The diluted salt solution is applied in-line to a KBB (continuously rolled cold wide strip) using ink-jet or indirect gravure printing. The steel strip pretreated in this way is then electrolytically galvanized. After the electrolytic galvanizing, a gloss measurement is carried out in accordance with the standard given above and a color measurement in accordance with the standard also given above.

Gladly when measuring gloss. ISO 2813 measures gloss at three different angles. With regard to the exact measuring process, reference is made to the standard.

FIG. 2 shows a sample sheet produced according to the above-mentioned sequence with an area of the first type on the left and an area of the second type on the right.

Three measurements were carried out for each area and each angle. One recognizes very strong differences, especially for 85 °, whereby the standard also suggests 85 ° for surfaces of the type examined.

In Figure 3, the degrees of gloss in the treated and untreated state are compared again. Since relative gloss differences of 10% can be detected by the human eye, it can be seen that the gloss level differences below 85 ° are easily visible to the human eye.

The color measurement according to EN ISO 11664 takes place in the CIELab color space, which is shown in Figure 4, together with the recorded values. With regard to the measurement process, reference is made to the standard.

FIG. 5 shows a table with the recorded values and the resulting color deviations which are also summarized in the table according to FIG.

The color differences are summarized as dE * value. The rule here is that a value of 1 or greater can be distinguished from the human eye.

The values determined are all higher, with the differences being particularly pronounced at 15 ° and 45 °. However, all values show that the differences are clear and easy to perceive with the human eye. The differences are particularly strong when viewed at 45 ° followed by 75 °. Watching is also a so-called "flop effect" which means that depending on trachtungswinkel Be the color differences or Flelligkeitsunterschiede can beat an inversion To ^¬, but what does not change the distinctness.

The influence of the intermediate layer according to the invention on the zinc layer can be seen particularly well in FIG. 7. FIG. 7 shows an electron microscope image in which an area is visible in the middle in which all order states occur.

On the left, an area can be seen and enlarged which has no inventive layer (intermediate layer) between itself and the steel substrate. This area shows no axial or radial order whatsoever with regard to the zinc flakes. The reflection will be very diffuse in this case.

A zinc coating is shown in the picture on the right. The metallic intermediate layer is located under this zinc coating.

One recognizes a significantly increased order, i.e. in particular a stronger linear alignment with larger contiguous flat surfaces. The reflection will be less diffuse here and accordingly this area will also be visually distinguishable from the other area.

In the overall picture, one can also see very well that the metallic intermediate layer underneath clearly has no influence on the topography.

In the case of the invention, it is advantageous that the salt solution is applied locally in a targeted manner. As a result, the visual impression that occurs later or a marking can be defined locally in a targeted manner.

It is advantageous here that the marking produced according to the invention is no longer visible after a further coating, for example a cathodic dip coating.

The marking according to the invention can thus be used for markings of any kind. It can be used, for example, for material description and / or data backup, such as for batch number, coil number, Fiersteller information. In addition, barcodes or 3D codes can be generated with the method according to the invention. In addition, the brand name under which the material is sold, possibly in combination with the name of the manufacturer or design or pattern on the strip or sheet metal.

It is conceivable that the emissivities of such a sheet can also be changed in certain areas by the corresponding coating. This is an important factor when heating sheet metal, as it affects the heat absorption capacity. In processes in which the hardness or tensile strength can be adjusted via heating and austenitization followed by quenching, the degree of heating can be adjusted via different emissivities, so that different degrees of austenitization and thus hardness / tensile strengths can also be set via the surface conditioning according to the invention are.

Claims

1. A method for generating markings on galvanized steel strips or steel sheets, wherein a metal salt solution, in particular an inorganic metal salt solution, is applied in certain areas to the steel surface and the steel surface is then electrolytically galvanized.

2. The method according to any one of the preceding claims, characterized in that a metal salt solution is used whose cations from the group of Mn, Sn, Pb, Bi, Cu, Au, Ag and their anions from the group of nitrate, chloride, hydroxide, Oxide, acetate, citrate, oxalate and mixtures and combinations thereof can be selected.

3. The method according to any one of the preceding claims, characterized in that a metal salt solution is used, the solution containing bismuth ions.

4. The method according to any one of the preceding claims, characterized in that a metal salt solution is used, the solution comprising bismuth (III) nitrate pentahydrate and dilute nitric acid.

5. The method according to any one of the preceding claims, characterized in that the applied metal salt solution enters into a cementation reaction with the steel surface in such a way that the metals are electrochemically deposited from the metal salt solution without the effect of external current, so that a metallic intermediate layer is deposited on the steel surface will.

6. The method according to claim 5, characterized in that the metallic intermediate layer has a layer thickness in the nanometer range.

7. The method according to claim 5 or 6, characterized in that the layer thickness ratio of the metallic intermediate layer and the zinc layer located above it is between 1: 1000 to 1: 20000.

8. The method according to claim 5 to 7, characterized in that the zinc electrocrystallization is influenced by the metallic interlayer, so that the crystallization of the zinc above the metallic interlayer is more orderly with an axially and radially higher alignment rate.

9. The method according to any one of the preceding claims, characterized in that a continuously rolled cold wide strip, in particular an annealed continuously rolled cold wide strip, is used as the substrate.

10. The method according to any one of the preceding claims, characterized in that the zinc layer is deposited over the areas treated with the salt solution and untreated areas, both areas having a common, indistinguishable topography after galvanizing.

11. The method according to any one of the preceding claims, characterized in that the zinc layer over the areas treated with the salt solution has a different gloss measured according to ISO 2813 and / or a color difference measured according to EN ISO 11664 due to the increased crystallization order compared to the untreated areas .

12. The method according to any one of the preceding claims, characterized in that the relative gloss difference exceeds 10% and / or the color difference exceeds the value 1 for dE *.

13. Electrolytically galvanized steel strip or sheet steel with a marking, in particular produced by a method according to one of the preceding claims, characterized in that the electrolytically galvanized steel strip or the steel plate has areas of the first type and areas of the second type, both areas having the same common, indistinguishable topography,, where the areas of the first type have a thin metallic intermediate layer between the steel surface and zinc layer and where the identification is formed in that the areas of the first type are optically for the human eye and / or a sensor from the areas of the second type are distinguishable.

14. Steel strip or steel sheet according to claim 13, characterized in that the zinc layer over the areas of the first type treated with the salt solution has a higher different level due to the increased crystallization order compared to the areas of the second type Gloss measured according to ISO 2813 and / or has a color difference measured according to EN ISO 11664, which creates a visual impression that can be detected by the human eye and measuring sensors, the relative gloss difference exceeding 10% and / or the color difference exceeding 1 for dE *.

15. Steel strip or steel sheet according to one of claims 13 to 14, characterized in that the metallic intermediate layer comprises a metal or metals which can be selected from the group of Mn, Sn, Pb, Bi, Cu, Au, Ag.

16. Steel strip or sheet steel according to one of claims 13 to 15, characterized in that the metallic intermediate layer comprises bismuth.

17. Steel strip or sheet steel according to one of claims 13 to 16, characterized in that the metallic intermediate layer has a layer thickness in the nanometer range.

18. Steel strip or sheet steel according to one of claims 13 to 17, characterized in that the metallic intermediate layer and the zinc layer have layer thicknesses which are in a ratio of 1: 1000 to 1: 20000 to one another.