EP4097267A1 - Sheet metal packaging product with a structured surface and method for producing a sheet metal packaging product of this type - Google Patents

Abstract

The invention relates to sheet metal packaging products, in particular tinplate or electrolytically chrome-plated sheet steel (ECCS), consisting of a sheet steel substrate (S) with a thickness in the region of 0.1 mm to 0.6 mm and a coating (B), in particular made of tin and/or chromium or chromium and chromium oxide, that is electrolytically deposited on at least one side of the sheet metal substrate. In addition, at least one surface of the sheet metal packaging product provided with the coating (B) has a surface profile with periodically repeating structure elements in at least one direction, wherein an autocorrelation function resulting from the surface profile has a plurality of side lobes with a height of at least 20%, preferably at least 30% of the height of the main lobe. These sheet metal packaging products have improved and novel surface properties.

Description

Sheet metal packaging product with a structured surface and method for producing such a sheet metal packaging product

The invention relates to a sheet-metal packaging product according to the preamble of claim 1, as well as a method for producing a sheet-metal packaging product.

Cold-rolled sheet metal packaging products in the form of electrolytically tinned and specially chrome-plated steel are standardized in DIN EN 10 202 (European standard EN 10 202: 2001). Sheet-metal packaging products according to this standard are simply cold-rolled or double-reduced soft steels that are either electrolytically tinned (tinplate) or electrolytically special chromium-plated (Electrolytic Chromium Coated Steel, ECCS). Single cold-rolled sheet packaging products are available in nominal thicknesses from 0.1 mm to approx. 0.6 mm, in particular from 0.17 mm to 0.49 mm, and double-reduced sheet packaging products are supplied in nominal thicknesses from 0.13 mm to 0.29 mm . The sheet-metal packaging products can be in the form of strips (which are wound into rolls) or in the form of panels. The strips have nominal widths of at least 600 mm, with slit strips also being able to have a smaller gap width.

Electrolytically tinned tinplate is understood according to the standard to be a cold-rolled sheet or strip made of unalloyed steel with a low carbon content, which is coated on both sides with tin applied in a continuous, electrolytic process. Electrolytically differentially tinned tinplate is also available, where one side (e.g. the top) has a larger tin layer than the other side (e.g. the underside).

In order to achieve high corrosion resistance and a glossy surface, it is customary with tinplate to heat the electrodeposited tin layer to a temperature above the melting point of tin after tinning the steel sheet substrate and then to cool it. As a result of this temperature treatment, a coating is produced on the sheet steel substrate, which is composed of an iron-tin alloy on the surface of the sheet steel substrate and a layer of free tin close to the surface. This top layer of free tin gives the melted tinplate a high Gloss value. In order to increase the gloss of the tinplate surface, skin-pass rolls that are ground and polished according to the standard can be used, with which the tin surface of the tinplate is re-rolled or skin-pass in a secondary rolling process (skin-passing), the degree of reduction of the secondary rolling process during skin-passing preferably being less than or equal 5% (gloss dressing).

Furthermore, so-called “stone-fmish / fine-stone-fmish” surfaces are known from the standard, which are characterized by a directional surface structure that results from the use of ground skin-pass rollers, which have a pronounced grinding structure and a higher roughness than that for skin pass rollers used have a shiny surface. Furthermore, when using blasted skin pass rollers, a “blasted surface” can be achieved. When using blasted skin pass rollers, tinplate can either have a matt silver surface if the tin layer is melted, or a matt surface if the tin layer is not melted. In addition, skin pass rollers are used, which are textured by means of EDT (“electro discharge texturing”).

The standard defines electrolytically chromium-plated steel (ECCS) as cold-rolled, electrolytically treated sheet or strip made of soft steel with a low carbon content, which has a layer of metallic chrome directly on the sheet steel substrate and a cover layer of hydrated chrome oxide or chrome hydroxide on the metallic chrome layer.

For the surface finish of sheet metal packaging products, the standard specifies the nominal surface roughness of the sheet steel substrate by means of defined arithmetic mean roughness (Ra) which, for example, for tinplate with a glossy surface at Ra <0.35 pm and for a silver-matt tinplate surface at Ra> 0.90 pm lie. In the case of special electrolytically chromed sheet steel (ECCS), the surface roughness required by the standard is in the range of 0.25 pm to 0.45 pm for a "fine stone" surface and in the range of 0.35 pm for a "stone" surface until 0.60 pm.

In terms of the optical properties of the surfaces of sheet metal packaging products, such as their gloss, Reflection and brightness, as well as with regard to the corrosion resistance and mechanical properties, such as, for example, the resistance to abrasion, are increasingly demanding requirements that cannot be met by the sheet-metal packaging products available in accordance with the standards and known from the prior art. The surface properties of known sheet metal packaging products are conventionally influenced by the surface topography, which is set in tinplate production, for example, during re-rolling (skin passing). Due to the manufacturing steps that are common for this, in which, for example, ground, blasted or eroded skin-pass rolls are used during re-rolling (secondary cold rolling or skin-passing), the required surface properties cannot be achieved, or only to a limited extent, since the structures of the work rolls used in re-rolling (skin-pass rolls ) are partly too inhomogeneous and partly too strongly directed. Due to the inhomogeneous surface structure of the work rolls, for example, it is not possible to set a homogeneous surface with a directed gloss effect.

With regard to the corrosion resistance and the processability of the sheet metal packaging products in the production of packaging containers, such as food and beverage cans, increasingly higher demands are placed on the material. To improve the corrosion resistance of sheet metal packaging products, higher weight requirements for the tin layer or the chromium / chromium oxide layer could be created. However, this is ruled out from the point of view of resource efficiency, because it requires higher amounts of coating materials (such as tin and chromium). To this extent, there is a need to improve the corrosion resistance of sheet metal packaging products without increasing the weight of the electrodeposited coating.

Increasingly higher requirements are also being placed on the processability of sheet metal packaging products in forming processes, such as deep-drawing and ironing processes, in which packaging containers or parts thereof are formed from the sheet metal packaging product. A major problem in the processing of sheet metal packaging products in the form of tinplate tapes wound on coils is based on the abrasion of particles from the electrodeposited tin coating. After the electrolytic coating of the sheet steel substrate, which takes place regularly in coil coating systems, the Sheet metal packaging products wound onto a roll and transported to Elmforming systems for further processing for the production of packaging, where they are unwound from the roll and cut into sheets. During this processing step, rollers are used to guide and guide the belt, which come into contact with the surface of the coated belt. In this case, and also in the further processing steps when forming the packaging sheet metal by means of forming tools, particles of the

Loosen coating materials (such as tin) from the coating. This creates harmful abrasion, which can arise in particular when winding and unwinding the tape into a roll, as well as when dividing the roll into panels and also when forming the Elm in drawing and Elmforming tools. The abrasion material, which consists at least essentially of the material of the metallic coating (i.e., for example, tin in the case of tinplate), can lead to re-contamination of the belt as well as the guide and steering rollers and / or the forming tools. Furthermore, the abrasion of particles can

Coating materials adhere to the surface of the packaging containers made from sheet metal packaging products using the Elmforming process and contaminate the filled goods when the packaging containers are filled with a filling material. In order to avoid this, the guide and elbow pulleys used for winding and unwinding the strips, as well as the drawing and elbow shaping tools used for the elm shaping process, are cleaned regularly. This is time-consuming and costly and reduces the efficiency of the manufacturing processes for the sheet-metal packaging products and the packaging containers made therefrom.

Proceeding from this, the invention is based on the following objects: On the one hand, the higher requirements placed on the surface properties of the sheet metal packaging products, such as optimized and specifically adjustable gloss, reflection and brightness properties, are to be met. On the other hand, the corrosion resistance of the sheet-metal packaging products should also be improved while the weight of the electrodeposited coating remains the same, as well as the processability of the sheet-metal packaging products during transport and in the production of packaging by means of the Elmforming process.

These objects are achieved according to the invention by a sheet metal packaging product having the features of claim 1. Preferred embodiments and aspects as well as advantageous properties and features of the invention Sheet metal packaging products result from the dependent claims. The method for producing sheet-metal packaging products with the features of claim 11 also contributes to achieving the object. The sheet metal packaging product according to the invention is in particular in the form of an electrolytically tinned steel sheet (tinplate) or in the form of an electrolytically chromium-plated steel sheet (ECCS) and consists of a steel sheet substrate with a thickness in the range from 0.1 mm to 0.6 mm and an electrolytic one Coating of tin (in the case of tinplate) or of chromium / chromium oxide (in the case of ECCS) deposited on at least one surface, preferably on both surfaces of the sheet steel substrate, and according to the invention has a surface structure with a plurality of uniform, ie homogeneous periodically recurring structural elements distributed over the surface of the sheet metal packaging product. The coating of the sheet metal packaging product, which is deposited electrolytically on at least one side of the sheet steel substrate, consists of tin and / or chromium or chromium and chromium oxide, the coating being a tin layer with a weight of 1 to 15 g / m ² tin and / or a layer of chromium and / or chromium oxide with a total weight of the chromium in the chromium / chromium oxide layer in the range from 5 to 200 mg / m ² . The sheet metal packaging product according to the invention is characterized in that at least one surface of the sheet metal packaging product provided with the coating has a surface profile with periodically recurring structural elements in at least one direction and has an autocorrelation function resulting from the surface profile with an absolute maximum and a plurality of secondary maxima, the height of which is at least 20%, preferably at least 30% of the height of the absolute maximum.

Further coatings or layers can optionally be present on the electrolytic coating. In the case of tinplate, for example, a passivation layer made of chrome and / or chrome oxide or made of a chrome-free material can be applied, and polymer layers made of thermoplastics can be applied to the chrome / chrome oxide coating of ECCS, for example. A tin coating can be melted by heating the tin-plated sheet steel substrate to temperatures above the melting point of tin. The periodically recurring structural elements on the surface of the sheet metal packaging product according to the invention can have different shapes and in particular be shaped as concave or plateau-shaped, flattened elevations. Periodically recurring depressions can also be provided which are surrounded by elevations.

The periodically recurring structures are first made in a manufacturing process by secondary cold rolling of an already primarily cold-rolled sheet steel substrate, in particular in a re-rolling step with a re-rolling degree in the range of 5% to 50% or a skin-pass with a re-rolling degree of less than 5%, in particular in the range of 1 % to 4%, introduced into the surface of the sheet steel substrate by means of at least one surface-structured roller, and the sheet steel substrate which is surface-structured in this way is then refined by electrolytically depositing the coating.

The method according to the invention for producing a sheet metal packaging product with a structured surface comprises the following steps:

- providing a primarily cold-rolled sheet steel substrate (S) with a thickness in the range from 0.1 mm to 0.6 mm;

Recrystallizing annealing of the primarily cold-rolled sheet steel substrate

(S);

- Rerolling or skin pass of the recrystallizing annealed sheet steel substrate (S) in a double-stand rerolling mill, wherein a first stand of the rerolling mill has at least one work roll with an unstructured, in particular with a blasted or polished roll surface, and a second stand of the rerolling mill has at least one work roll with a having surface-structured roller surface;

- Electrolytic coating of the re-rolled or tempered sheet steel substrate (S) on at least one side with a coating (B) of tin and / or of chromium or chromium and chromium oxide, the coating (B) being a tin layer with a weight in the range of 1 up to 15 g / m ^{2 of} tin and / or a layer of chromium or chromium oxide with a Total weight of the chromium in the chromium or chromium oxide layer in the range from 5 to 200 mg / m ² ;

- wherein on the surface of the steel sheet electrolytically coated with the coating (B) results in a surface profile with structural elements recurring periodically in at least one direction and the

Surface structure has an autocorrelation function which has an absolute maximum and a plurality of secondary maxima, the height of which is at least 20% and preferably at least 30% of the height of the absolute maximum.

The re-rolling or skin pass of the recrystallizing annealed sheet steel substrate takes place in the method according to the invention in a double-stand re-rolling mill, which has a first stand with at least one work roll with an unstructured, in particular with a blasted or polished roll surface, and a second stand with at least one work roll with a Includes (deterministic) surface-structured roll surface. The roll surface of the or each work roll of the first stand is unstructured in the sense that the roll surface has a statistically uncorrelated structure without periodically recurring patterns. This applies, for example, to smooth, polished or blasted surfaces of work rolls or to roll surfaces that are produced with a shot-blast texturing process (SBT) or an electrical discharge (EDT) process or an electron beam process (“electro beam texturing “, EDT) have been treated. In contrast, the roll surface of the or each work roll of the second stand is structured in the sense that the roll surface has a correlated, deterministic structure with periodically recurring structural elements. This applies, for example, to surfaces of work rolls that have been specifically structured with a pulsed laser, in particular with an ultrashort pulse laser, in order to generate a deterministic surface structure with periodically recurring structural elements. The autocorrelation function of the surface profile of such work rolls with a (deterministic) surface-structured roll surface has an absolute maximum and a plurality of secondary maxima in at least one direction, in particular in the circumferential direction and / or perpendicular thereto, the height of which is at least 60%, preferably at least 70% of the Height of the absolute maximum. The re-rolling of the recrystallizing annealed sheet steel substrate is expediently carried out wet using coolants and lubricants, whereas skin-passing is usually carried out dry or using special wet dressing agents. Preferably, two quattro stands arranged one behind the other in the strip running direction of the sheet steel substrate are used for re-rolling or skin pass, each frame preferably having an upper and a lower work roll between which the recrystallizing annealed sheet steel substrate is passed. The two work rolls are arranged perpendicular to the strip running direction between two larger back-up rolls (an upper and a lower back-up roll), the surface of a back-up roll being in contact with the roll surface of the associated work roll in order to stabilize the work roll. However, other roll stands, for example with six rolls, can also be used. The roll surface of the two work rolls of the first and the second stand is expediently designed to be the same. However, it is also possible, in particular in the second stand, to use two work rolls with differently structured roll surfaces. As a result, a different surface structure can be embossed on the underside of the sheet steel substrate than on the upper side.

The or each surface-structured roller of the second stand can in particular be a work roller (skin-pass roller) which is surface-structured by a pulse laser, in particular a short pulse laser or an ultra-short pulse laser, in a texturing process, with which the sheet steel substrate is in one secondary cold rolling step or skin pass is carried out in a skin pass step. When re-rolling or skin-passing, the surface structure of the work roll is embossed into the surface of the sheet steel substrate. The sequence of the two roll stands (i.e. the first and second stand) in the direction of travel of the sheet steel substrate is arbitrary, that is, the first stand with the unstructured roll surface and then the second stand with the structured roll surface can be re-rolled or dressed or vice versa. A more even and cleaner surface structure is achieved if the first stand with the unstructured roll surface and then with the second stand with the structured roll surface is subsequently rolled or passaged, which is why this variant is preferred. With the first stand, the thickness of the sheet steel substrate passed through the opposite work rolls is reduced (this is up to 5% during skin pass and between 5 and 50% during re-rolling).

During skin pass treatment (with re-rolling degrees of less than 5%, in particular from 1 to 4%), the steel sheet substrate, which was already cold-rolled in the first cold rolling step (primary cold rolling) and is considerably (regularly more than 85%) reduced in thickness, is pre-structured in the first stand with the unstructured Work rolls. This pre-structuring of the surface, which is strongly and unevenly influenced during the primary cold rolling, enables the introduction of a better structured, deterministic surface structure in the subsequent second stand with the work rolls arranged therein with a structured, uniform surface with periodically arranged structural elements.

During re-rolling (with re-rolling degrees of more than 5%, in particular from 10 to 50%), there is on the one hand a further reduction in thickness to achieve the desired final thickness of preferably less than 0.5 mm, together with the associated work hardening. In addition, a pre-structuring of the sheet steel substrate, which was already cold-rolled in the first cold-rolling step (primary cold-rolling) and thereby considerably (regularly more than 80%) reduced in thickness, takes place in the first stand with the unstructured work rolls. This pre-structuring of the surface of the primarily cold-rolled steel sheet in the first stand is necessary during re-rolling in order to be able to introduce a structured, deterministic surface structure at all. For this purpose, after re-rolling in the first stand, the steel sheet re-rolled to the desired final thickness is provided in the subsequent second stand with the work rolls arranged therein with a structured, uniform surface structure with periodically arranged structural elements.

With the described post-rolling or skin-pass passages, sheet steel substrates can be produced which have a surface profile with structures that recur periodically along selected directions (in particular in the rolling direction or perpendicular to the rolling direction), the periodicity as well as the uniformity and uniformity of the Surface structures can be quantified by means of an autocorrelation function and the height of a plurality of secondary maxima of the autocorrelation function of a surface profile along at least one preferred direction is at least 40% and preferably at least 60% of the height of the main maximum (or the absolute maximum).

Deviations in the regularity of surface structures are determined by means of the autocorrelation function with z (x) = 0; xg [0, quantifiable. The autocorrelation function is used here to assess the periodicity of the surface profile z (x) and especially the surface roughness along specified directions (x) in the plane of the surface.

It has been shown that the desired properties of the structured surface of the coated sheet metal packaging products, which can be characterized by an autorrelation function, whose secondary maxima are at least 30% of the height of the absolute maximum, at least in the case of the twice cold-rolled (DR) sheet steel substrates only with a two-stand operation can be achieved during skin pass or re-rolling. In order to be able to produce coated packaging sheets (i.e. tinplate or ECCS) with an autorrelation function, the secondary maxima of which are at least 30% of the height of the absolute maximum, it is necessary to create a surface structure with an autorrelation function in the sheet steel substrate, the secondary maxima of which are at least 40% of the Have the height of the absolute maximum, since during the electrolytic coating of the structured surface of the substrate a certain leveling of the periodically recurring structural elements takes place.

The invention therefore also provides, as an intermediate product of the method according to the invention, a cold-rolled steel sheet with a thickness in the range from 0.05 mm to 0.6 mm, the surface of which has a surface profile with periodically recurring structural elements in at least one direction, one being derived from the surface profile The resulting autocorrelation function has a plurality of secondary maxima, the height of which is at least 40% of the height of the main maximum. The secondary maxima of the autocorrelation function preferably have a height of at least 50% of the height of the main maximum and particularly preferably at least 60% of the height of the main maximum along a preferred direction.

During the electrolytic deposition of the coating on the surface-structured steel sheet substrate, the coated steel sheet at least essentially retains the previously introduced surface structure, since during the electrolytic deposition of the coating, the coating material (tin for tinplate or chromium / chromium oxide for ECCS) is uniform, ie with an at least largely homogeneous support, deposited on the structured surface of the sheet steel substrate contumah. Corresponding to the surface structuring of the sheet steel substrate, the sheet metal packaging product produced in this way, like the substrate, has a surface profile with a plurality of structures that are uniformly distributed over the surface and recur periodically at least in one direction. This gives the sheet metal packaging product according to the invention a deterministic surface structure with a surface which has a defined and reproducible topography which differs in particular from a topography with a statistical distribution of surface structures such as elevations, depressions and sharp points.

The sheet metal packaging products according to the invention consequently have a surface profile with periodically recurring structures on their surface in at least one (selected) direction, the surface profile resulting in an autocorrelation function with a plurality of secondary maxima and the height of the secondary maxima according to the invention at least 20%, preferably at least 30 % of the height of the main maximum. A tin coating applied electrolytically to the re-rolled or tempered sheet steel substrate can optionally also be melted, with the melting of the coating further leveling the surface structures and thereby reducing the height of the secondary maxima of the autorrelation function. Preferably, the tin plates with a melted tin layer still have a white color Autorrelation function whose secondary maxima are at least 20% of the height of the absolute maximum. It was found that the surface structure of the sheet steel substrate can at least largely be retained if the steel substrate is electrolytically coated with a metallic coating, in particular a tin coating or a coating of chromium and chromium oxide. It is true that the regular surface profile of the sheet steel substrate is slightly smoothed by the electrolytic coating. Nevertheless, even after the electrolytic coating, the surface profile of the coated sheet metal packaging product with the periodically recurring structures remains surprisingly and clearly recognizable from the minimum heights of a plurality of secondary maxima in the autorrelation function of more than 20% (with melted tin coatings), preferably of more than 30%.

Through a targeted selection and setting of the surface topology, the sheet metal packaging products according to the invention can be used to set the surface-sensitive properties such as corrosion resistance, gloss and abrasion in a targeted manner and to adapt them to different applications. For example, the optical

Surface properties of the sheet metal packaging product, such as gloss, reflection and brightness, can be influenced by the selection and setting of the surface structure and adapted to the desired properties and applications. Furthermore, by selecting and setting a suitable surface structure, the corrosion resistance of the sheet metal packaging product can be improved and the abrasion during transport and the

Further processing of the packaging sheet product can be minimized.

The invention enables, for example, an improvement in the corrosion resistance of the sheet metal packaging product without having to increase the weight of the coating by a deterministic structuring of the surface of the sheet metal packaging product with convex or plateau-shaped elevations that recur periodically on the surface. As a result of this design of the surface structure, the surface of the sheet metal packaging product in this embodiment of the invention, in contrast to conventional ones Sheet metal packaging products with a statistically distributed surface structure, do not have any sharp points that could break off when the sheet metal packaging is subjected to mechanical stress or that could damage the coating. The sheet metal packaging products according to the invention can therefore also be processed better without impairing the corrosion resistance, since they are more resistant to mechanical stresses.

The surface roughness (in particular the arithmetic mean roughness Ra) is in the range from 0.01 to 2.0 μm, preferably in the range from 0.1 to 1.0 μm, and in particular in the range from 0.1 to 0, depending on the application and optimization case , 3 pm. The low surface roughness is adapted to the low thickness of the sheet steel substrate, which is in the range for fine sheet metal between 0.1 mm and 0.6 mm. Due to the low surface roughness, homogeneous surface properties can be achieved, which improve the corrosion resistance of the sheet metal packaging product even under (mechanical) stress during transport and when forming in forming tools. Due to the low surface roughness, fewer particles and / or dust of the material of the coating are detached from the surface of the coated packaging sheet product during transport and reshaping of the sheet metal packaging product, which means that less corrosion-prone areas with a damaged or completely detached coating layer can form.

In preferred exemplary embodiments of the invention, the (deterministic) surface structures are distinguished, for example, by a regularly arranged pattern with periodically recurring elevations. When raised in this context, points are meant on the surface of the sheet metal packaging product which protrude by an average height (h) above a surface level averaged over the entire surface. The elevations can be convex or flattened on their upper side in the shape of a plateau and are surrounded by depressions which are preferably flat or concave. The Ra value measured in the depressions is preferably less than or equal to 0.1 μm.

The elevations expediently have an (average) height (h) of 0.1 to 8.0 μm, in particular 0.2 to 4.0 μm and preferably less than 3.0 μm. Correspondingly, the (mean) depth (t) of the depressions is in the range from 0.1 to 8.0 μm, in particular from 0.2 to 4.0 μm and preferably less than 3.0 μm. Preferably they show periodically Recurring structural elements, in particular the elevations or depressions, have a width at half the height (“full width at half maximum”, FWHM) of at least 10 gm and in particular in the range from 60 gm to 250 gm. The elevations can assume different geometric shapes and in particular be rectangular, strip-shaped or web-shaped, square, cylindrical, leaf-shaped, sickle-shaped, ring-shaped, etc. The elevations can each have the same shape or different shapes. Such a surface structure with convex or plateau-shaped elevations proves to be advantageous with regard to the corrosion resistance of the sheet metal packaging product, because in comparison to a stochastic surface structure with sharp points (with a radius of curvature <0.2 mm) on the convex or plateau-shaped flattened upper side of the elevations mechanical stress there is a lower risk of damage to the coating. In the case of the surface structures of sheet metal packaging products with sharp points known from the prior art, there is a risk of the sharp points breaking off or the coating at the sharp points being peeled off under mechanical stress, which results in uncoated areas in which the steel of the sheet steel underneath The exposed substrate is exposed to environmental influences or the sometimes aggressive contents of the packaging and thus tends to oxidize or corrode.

One parameter for the quantitative description of the corrosion properties of tinplate is the so-called IET value, which is measured in the standardized “iron exposure test” and describes the tin porosity of the tin coating. With constant conditions of the manufacturing process, such as pretreatment (cleaning), total tin plating and constant process parameters, the tin porosity (IET value) depends essentially on the surface roughness (arithmetic mean roughness Ra) and (quadratically) on the tin plating Sn (in g / m ² ) . In the case of tinplate with a specified weight Sn of the tin (m / A, mass per area in g / m ² ) and a specified average roughness Ra, the following current densities j _IET = I ZA (electrical current per area in mA / cm ² ) multiplied by the square of the weight application Sn (in g / m ² ):

• with mean roughness of Ra <1.0 pm: j _IET · Sn ² <1.9 (mA / cm ² ) - (g / m ² ) ² • for average roughness (Ra) in the range of 1.0 mih <Ra <2.0 mih: j _IET · Sn ² <3.3 (m A / cm ² ) · (g / m ² ) ² .

A maximum tolerable tin porosity for packaging applications is preferably IET values of <0.5 mA / cm ² .

A deterministic surface structure with plateau-shaped or convex elevations also proves to be advantageous with regard to a lower tendency to wear. Compared to a stochastic surface structure with sharp points that can break off under mechanical stress, there is a lower risk of damage to the coating and thereby abrasion on the plateau-shaped flattened areas of the elevations.

To reduce abrasion, it is also advantageous if the surface structure has a plurality of web-shaped or strip-shaped elevations and / or depressions that run parallel to one another. If the sheet steel substrate is in the form of a strip extending in a longitudinal direction of the strip, it is useful if the web-shaped or strip-shaped elevations or depressions extend in the longitudinal direction of the strip. The resulting depressions form a reservoir, distributed evenly over the surface of the sheet metal packaging product, for receiving particles of the coating which are detached from the coating due to abrasion. The particles detached from the coating can collect in the reservoir of the depressions and are thereby bound to the surface of the sheet metal packaging product and can therefore not adhere to guide or deflection rollers or forming tools and contaminate them. The depressions evenly distributed over the surface of the sheet metal packaging product expediently form open or closed chambers which can accommodate the particles loosened from the coating by abrasion. The chambers formed by the depressions are surrounded by elevations that completely enclose the chambers. However, it is also possible for adjacent chambers to be connected to one another via connecting channels. This enables particles of the coating material to be pushed out of one chamber into an adjacent chamber, for example when the belt is being transported over guide or deflection rollers. This ensures a uniform distribution of the abrasion over the surface of the sheet metal packaging product and thereby a complete absorption of the abrasion in the Reservoir formed by the depressions made possible. It is useful if the height of the elevations or the depth of the depressions is at least substantially homogeneous for all elevations / depressions. As a result, a reservoir is formed that is distributed uniformly over the surface of the sheet metal packaging product for the absorption of abrasion. A sufficient receiving volume of the reservoir can be achieved if the area proportion of the elevations in the total area of the sheet metal packaging product is between 20% and 50% and preferably between 24% and 45%. Correspondingly, the proportion of the area of the depressions in the total area of the sheet metal packaging product is between 50% and 80% and preferably between 55% and 76%.

The setting of defined gloss properties and in particular the achievement of high and largely direction-independent gloss values can be achieved if the surface structure has convex or plateau-shaped elevations and groove-shaped depressions. The elevations are expediently convex or have a largely flat plateau on their upper side. The groove-shaped depressions have an at least largely flat groove base. The flank walls between the groove bottom of the depressions and the top of the elevations can stand vertically or be inclined to the vertical (for example in the form of a cone or a truncated cone). In cross-section, the elevations have, for example, a rectangular shape or a trapezoidal shape. For reasons of manufacturing technology, the cross-sectional shape of an isosceles trapezoid is usually established, which tapers towards the surface.

A regularly arranged pattern with elevations and / or depressions leads to an optically homogeneous surface and thus to an improvement in the gloss properties. An optically homogeneous surface can be achieved if the elevations and the depressions are at least essentially the same size. In particular if the structural elements have depressions with an at least substantially planar

In order to achieve high gloss values, it is advantageous if the areas of the indentation base of the individual structural elements are at least essentially the same size.

In this way, with sheet metal packaging products according to the invention, gloss values of more than 50 gloss units (GE) and preferably more than 100 gloss units (GE), in particular between 100 and 800 gloss units (GE) with a surface roughness (Ra) of less than 0.5 gm and more than 0.1 gm can be achieved. The gloss properties are characterized by high isotropy in the plane of the surface. The surface of the sheet metal packaging products can have an at least essentially direction-independent gloss value, the difference between the gloss value (A gloss) in the rolling direction and a transverse direction perpendicular thereto preferably being less than 100 gloss units (GE) and particularly preferably 70 gloss units (GE) or less is, in particular with a surface roughness (Ra) of 0.01 to 2.0 gm.

The sheet metal packaging products according to the invention can, if necessary, be provided with further coatings or layers. For example, the tinplate according to the invention can be passivated with a chromium / chromium oxide coating or by wet-chemical application of a chromium-free passivation layer in order to avoid unhindered oxidation of the tin surface. Furthermore, organic coatings, such as organic lacquers or polymer coatings made of thermoplastic polymers such as PET, PP or PE or mixtures thereof, can be applied to the surfaces of the sheet metal packaging products according to the invention in order to increase the corrosion resistance and the resistance to acids and sulfur-containing materials and the deformability of the material .

These and other advantages and properties of the invention emerge from the exemplary embodiments described in more detail below with reference to the accompanying drawings. The drawings show:

FIG. 1: a schematic representation of sheet metal packaging products according to the invention in a sectional view, FIG. 1 a showing a sheet metal packaging product consisting of a sheet steel substrate and a coating and FIG.

FIG. 2: enlarged, schematic sectional illustration in the area of the surface of FIG

Coating a packaging sheet product according to the invention;

Figure 3: Schematic sectional representation in the surface area of a

Sheet metal packaging product according to the prior art (Fig. 3a) and according to the invention (FIG. 3b), in each case before (left side) and after (right side) the application of the coating on the steel sheet substrate;

FIG. 4a: Microscopic representation of the surface of a conventional one

Sheet metal packaging product according to the prior art with an associated surface profile (height profile), the surface of the sheet steel substrate having been dressed by a blasted or ground skin pass roller prior to the application of the coating;

Figure 4b to 4g: Height profiles of the surface of surface-structured

Skin pass rollers (left side in each case) and the surfaces of sheet metal packaging products according to the invention which have been dressed with this skin pass roller before (FIGS. 4b, 4c and 4d) or after (FIGS. 4e, 4f and 4g) the electrolytic application of the coating (right side in each case);

Figure 5a to 5g: three-dimensional microscopic representations of

Surface profiles of the steel sheets according to Figures 4a and 4b to 4g (in each case above), together with a roughness profile of the surface (each below) and the autocorrelation function resulting from the roughness profile (each in the middle of the figure), the microscopic representation the surface, the roughness profile and the associated autocorrelation functions in each case before the electrolytic deposition of a tin coating (Figures 5b, 5c and 5d, left), after the electrolytic deposition of a tin coating (Figure 5a, left or Figures 5b, 5c and 5d in the middle) and is shown after (in each case right side) a melting of the tin coating;

FIG. 6: Representation of the IET values measured in the “Iron Exposure Test” (IET) on inventive and non-inventive tinplate multiplied by the square of the tin plating as a function of the surface roughness (arithmetic mean roughness Ra in pm) of the tinplate samples; FIG. 7: Representation of the dependency on the gloss values measured on inventive and non-inventive tinplate sheets (in gloss units GE) on the surface roughness (arithmetic mean roughness Ra in pm);

FIG. 8: Representation of the dependence of the isotropy of the gloss values measured on tinplate according to the invention and not according to the invention (as A gloss values in gloss units GE) on the surface roughness (arithmetic mean roughness Ra in pm);

In Fig. La a packaging sheet metal product is shown schematically in section. The sheet metal product consists of a sheet steel substrate S with a thickness in the sheet metal range (0.1 mm to 0.6 mm) and a coating B deposited electrolytically on the sheet steel substrate S. The sheet steel substrate is a cold-rolled sheet steel made of a steel with low carbon content. Suitable compositions of the steel of the steel sheet substrate S are defined in the European standard DIN EN 10 202. The steel sheet substrate S preferably has the following composition in relation to the weight proportions of the alloy components of the steel:

- C: 0.01-0.1%,

- Si: <0.03%,

- Mn: 0.1-0.6%

- P: <0.03%,

- S: 0.001-0.03%,

- Al: 0.002-0.1%,

- N: 0.001-0.12%, preferably less than 0.07%

- optional Cr: <0.1%, preferably 0.01-0.05%,

- optional Ni: <0.1%, preferably 0.01-0.05%,

- optional Cu: <0.1%, preferably 0.002-0.05%,

- optional Ti: <0.09%,

- optional B: <0.005%,

- optional Nb: <0.02%,

- optional Mo: <0.02%,

- optional Sn: <0.03%, Remainder iron and unavoidable impurities.

The coating B can be a tin coating or a coating of chromium and chromium oxide (and possibly chromium hydroxides). In case of a

Tin coating is referred to as tinplate. In the case of a chromium / chromium oxide coating that has been deposited electrolytically on the sheet steel substrate, one speaks of electrolytically specially chromium-plated steel sheet (Electrolytic Chromium Coated Steel, ECCS). In the case of tinplate, the weight requirements of the coating B are typically in the range from 1 to 15 g / m ² and in particular between 2 and 6 g / m ^{2 of} tin. In the case of ECCS, the weight of the chromium in the chromium-chromium oxide layer is typically in the range from 50 to 200 mg / m ² and in particular between 70 and 150 mg / m ² .

On the coating B, further coatings or layers, for example in the form of passivation layers or organic layers such as lacquers or

Polymer coatings. This is shown schematically in FIG. 1b in that an overlay P is shown on the coating B. FIG. The overlay P can, for example, be a passivation layer in the case of tinplate. As is customary with tinplate, the passivation layer can be composed of metallic chromium and / or chromium oxide. The passivation layer can, however, also be a chromium-free passivation layer applied wet-chemically to the tin surface. In the case of tinplate, the passivation layer is intended to prevent unhindered oxide growth on the tin surface and thereby ensure that the tinplate is stable over long periods of time without oxidation of the tin surface. In the case of tinplate, the surface of the coating or the entire tin coating can also be melted after its electrolytic deposition on the steel sheet substrate by heating the tinplate to temperatures above the melting temperature of tin.

The overlay P can also be formed by an organic overlay, such as, for example, by an organic lacquer or by a polymer coating made of a thermoplastic polymer, in particular PET or PP. In the case of ECCS in particular, it is customary to coat the chromium oxide surface of the ECCS with a polymer coating made of a thermoplastic polymer, for example by laminating on a PET or PP film, in order to achieve the To improve corrosion resistance and the resistance of the material to acids and also the formability of the material.

2 shows a schematic representation of a sheet metal packaging product according to the invention in the area of the surface of the coating B. As can be seen from FIG. 2, the surface of the sheet metal packaging product has a plurality of elevations E arranged next to one another (in the sectional illustration shown) and depressions V lying in between. The elevations E have a (mean) height h above an average surface level 0. Compared to the average surface level 0, the depressions V have a depth t. The depressions V are groove-shaped with an at least largely flat groove base cl, c2, c3. The elevations E are plateau-shaped with an essentially flat plateau surface bl, b2, b3, b4. The flanks a1, a2, a3, a4 of the depressions V and the elevations E are, as can be seen from FIG. 2, slightly inclined with respect to the vertical plane. In the sectional illustration shown in FIG. 2, this results in isosceles trapezoids or truncated cones for the shape of the elevations E, which taper conically towards the surface (Gaussian or tophat profile).

To achieve homogeneous surface properties, it is useful if the shape and arrangement of the elevations E and the depressions V are as uniform or regular as possible.

In particular, the areas of the groove base cl, c2, c3 of the groove-shaped depressions V are as equally large as possible. Deviations are preferably less than or equal to 10%. In a corresponding manner, the plateau areas (b1 to b4) of the plateau-shaped elevations are preferably approximately the same size and the flanks al-a4, which extend between the recesses V and the elevations E adjacent thereto, preferably also show no differences in FIG Tilt. The heights h of the elevations can vary by a maximum of 25% and the depths t of the depressions likewise preferably fluctuate only slightly by approximately 10% or less.

The uniformity and regularity of the surface structures of the sheet metal packaging products according to the invention can be described mathematically with the aid of autocorrelation. The autocorrelation (also cross autocorrelation) describes in general the correlation of a signal or profile z (x) with itself at an earlier point in time or at a different location x.

Without shifting, Y _zz (0) gives the variance of the height values z (x) of the profile with x in the interval from 0 to l: (variance) or = R _q ²

For the calculation of roughness parameters according to DIN EN ISO 4288: 1998-04 in the roughness range Ra = 0.1 pm to 1 pm, preferably a scanning length l _t of 4.8 mm should be used. After Gaussian high-pass filtering with cutoff wavelength L _c = 0.8 mm and separation of the edge areas, an evaluation length of l = 4 mm remains for calculating the characteristic values.

In Figures 5a and 5b to 5g are (each in the figure below) surface profiles (roughness profiles) of a conventional packaging sheet product (Figure 5a) and of packaging sheet products according to the invention (Figures 5b to 5g) and associated autocorrelation functions of the surface profile (each in the middle of Figure). FIG. 5a shows the surface structure of tinplate with a conventional steel substrate with a statistically uncorrelated surface structure. Figures 5b to 5d show the surface structure of steel sheets according to the invention before coating with tin (left side) and after a double-sided electrolytic coating with a tin layer of 2.8 g / m ² (middle and right side of the figure), the middle picture each shows the tin surface in the melted state and the right picture shows the tin surface before melting. Figures 5e to 5g show further examples of the surface structure of tinplate according to the invention (before and after melting the tin coating).

The amplitudes of the autocorrelation with respect to the main maximum H (at x = 0) are

Y (x) normalized (normalized autorrelation function - ^ -). The height of the secondary maxima N of the normalized autorrelation function, which can be a maximum of 1 or 100% due to the normalization, represent a measure of the regularity and uniformity of the periodic along the selected direction (x) in the surface plane Symmetry property (Y _zz (- x) = Y _zz (c)) the autocorrelation function is shown in the figures only for positive x values; for negative values it is a mirror image of the ordinate. To determine the highest (secondary) maxima of the autocorrelation of the surface profile, the measuring section should be placed in one of the preferred directions of the sample, in particular in the longitudinal direction of the strip (or the rolling direction of the cold-rolled packaging sheet) or perpendicular to it.

A comparison of the non-inventive comparison sample according to FIG. 5a with the sheet metal packaging products according to the invention (FIGS of 20% of the main maximum, whereas the level of the secondary maxima in the comparison sample not according to the invention is (significantly) less than 20%. The sheet metal packaging products according to the invention with a deterministic surface structure accordingly have a significantly more uniform surface profile with periodically recurring structural elements.

The shape of the periodically recurring structural elements, in particular the elevations E and the depressions V, can be adapted in each case to the application of the sheet metal packaging products according to the invention or the specifications for the production of packaging therefrom. Suitable cross-sectional shapes for the elevations E and the depressions V can be essentially trapezoidal and dome-shaped.

The elevations E and the depressions V can also be circular or ring-shaped in the area. For special applications, in particular to achieve homogeneous optical properties such as reflectivity and gloss, strip-shaped or web-shaped elevations E or depressions V have proven to be advantageous. The elevations E can be convex or, in a preferred manner, have a plateau-shaped, flattened upper side which is as flat as possible. The recesses V expediently have a largely flat recess surface.

Examples of surface structures with periodically recurring structural elements are shown in FIGS. 4b to 4g, the surface of the work roll with which the The sheet steel substrate has been cold-rolled (passaged) before the electrolytic application of the coating B, and the surface structure of the passivated surface of the sheet steel substrate resulting therefrom is shown on the right-hand side. The data of the rolls (pairs) used in the secondary cold rolling (skin pass) of the steel sheet substrate can be found in Table 1.

In the examples of FIGS. 4b to 4d, a re-rolling mill was used for re-rolling (secondary cold rolling) of the sheet steel substrate, which was equipped in a first stand with a first work roll with a blasted roller surface and in a second stand with a second work roll with a structured roller surface. The surface structure of the structured roll surface of the second work roll is shown in FIGS. 4b to 4d in each case on the left in the figure. In the examples of FIGS. 4e to 4g, a roller mill was used for secondary cold rolling of the sheet steel substrate, which was equipped in a first stand with a first work roll with a structured roller surface and in a second stand with a second work roll with a polished roller surface. The surface structure of the structured roll surface of the first work roll is shown in FIGS. 4e to 4g on the left in the figure.

The surface topographies of the sheet metal packaging products according to the invention shown in FIGS Range from 0.1 to 1.0 pm and in particular in the range from 0.1 to 0.3 pm. The surface roughness, in particular the value for the arithmetic mean roughness Ra, can be adapted to the respective application in the sheet metal packaging products according to the invention and set in a targeted manner by selecting the geometry and size of the periodically recurring surface structures (elevations E and depressions V).

To produce the sheet metal packaging products according to the invention, the sheet steel substrate S is surface-structured after or during (primary) cold rolling Roll re-rolled (secondary cold rolling with a re-rolling degree in the range from 5% to 45%) or skin-pass with a re-rolling degree of less than 5%. The surface-structured work rolls used for this can be, for example, rolls structured with a short pulse laser (KPL) or with an ultra-short pulse laser (UKPL). In Table 1, the rollers structured with an ultra-short pulse laser are identified with the abbreviation “UKPL”. It is pointed out that, despite this designation, the invention is not limited to the production of the deterministic surface structure by means of a roller structured with an ultrashort pulse laser (UKPL). The surface structures of the sheet metal packaging products according to the invention can also be embossed by rollers structured in another way. However, the rollers used for this always have a deterministically structured roller surface which is impressed into the surface of the substrate when the sheet steel substrate S is rolled. The surface structure of the roll is embossed in a secondary cold rolling step with a degree of reduction (re-rolling degree) of more than 5% to a maximum of 50% or in a skin pass step in which the cold-rolled steel sheet with a low degree of reduction of a maximum of 5% after a primary cold rolling is passaged.

After the deterministic surface structure of the work roll (skin pass roll) has been introduced into the surface of the sheet steel substrate S, the coating B is applied according to the invention by electrolytic deposition of the coating material (e.g. tin for tinplate and chrome / chrome oxide for ECCS) on the structured surface of the Sheet steel substrate S. During the electrolytic deposition of coating B on sheet steel substrate S, the deterministic surface structure of the sheet steel substrate is essentially retained, so that the coated sheet metal packaging product also has a deterministic surface structure with a uniform topography, as shown schematically in FIG. 2 . The deterministic surface structure is also retained when an additional pad P is applied to the coating B, as shown in FIG to which coating B is applied. The application of the coating B reduces the (relative) height of the secondary maxima of the autorrelation function compared to the uncoated sheet steel substrate by an average of 10 to 20%. However, with the method according to the invention, surface structures of the coated Achieve packaging sheet metal product whose autocorrelation function has a plurality of secondary maxima with a (relative) height of at least 20% of the main maximum.

Due to the deterministic surface structure of the accordingly manufactured sheet metal packaging products according to the invention, many problems can be eliminated which can arise in the conventional manufacture of sheet metal packaging products (in particular in the case of tinplate and ECCS). Typical problems that arise in the conventional production of sheet metal packaging products are explained below with reference to FIG Surface of sheet metal packaging products according to the invention is shown, by means of which the problems of the prior art can be eliminated. FIG. 3 shows a schematic sectional illustration of a sheet steel substrate S before (left side) and after (right side) the application of a coating B, FIG FIG. 3b shows a substrate treated according to the invention or a sheet metal packaging product according to the invention with a deterministic surface structure. As can be seen from Fig. 3a, the surface of the steel sheet substrate S and the packaging sheet product coated with the coating B has a statistical (i.e. a non-deterministically predetermined) surface topology with peaks Sp and valleys Ta. The height of the peaks Sp and the depth and / or the geometry of the valleys Ta are inconsistent, ie inhomogeneous over the entire surface of the sheet steel substrate S (Fig. 3a, left) or of the coated sheet metal packaging product (Fig. 3a, right) distributed. This surface structure of conventional packaging sheet products leads to a number of problems:

The sharp points Sp can easily break off or be flattened when the sheet metal packaging product is subjected to mechanical stress, for example during transport or when it is formed into packaging. When the tips Sp are broken off or flattened, the coating B is damaged or completely removed in places. This creates free, uncoated areas where the sheet steel substrate S, which is susceptible to corrosion, is exposed to environmental influences and the contents Packaging made of sheet metal packaging is exposed and can corrode as a result. Furthermore, this creates abrasion of the coating material, which is harmful during further processing of the sheet metal packaging products. Furthermore, dirt particles and residues of oils and fats can accumulate in the pocket-shaped valleys Ta of the surface structure of conventional packaging sheet products, which can no longer be completely removed even when cleaning the coating surface of the packaging sheet products, due to irregularly shaped valleys with undercuts. In particular, fats, cleaning agents, rolling oils or other residues from the manufacturing process of the sheet metal packaging product can accumulate in the deep and / or geometrically undefined valleys Ta, which make cleaning of the surface of the sheet metal packaging product difficult and the coating quality, such as the porosity of the tin coating on tinplate, negative can influence. Soiling of the surface as well as the formation of condensate, which is deposited in the deep valleys, also have a negative effect on the corrosion resistance.

In FIG. 4a, an image of a surface structure of a conventional tinplate according to the prior art with a tin coating of 2.8 g / m ² on both sides is shown by way of example with the confocal topography measuring device pSurf mobile from NanoFocus AG. A 20-fold objective with a resolution of approx. 1.56 pm was used for the measurement.

Before the electrolytic application of the tin coating, the surface of the sheet steel substrate of this tinplate was first dressed in a first stand of the tempering mill with a work roll with a blasted surface and then in a second stand with a work roll with a ground roller surface. As a result of the skin passing, the surface of the conventional tinplate has a statistically uncorrelated structure and thus an inhomogeneous surface topography, as can be seen from the associated height profile in FIG. 4a and from the 3D representation of the surface structure, the associated roughness profile and the autocrrelation function in FIG. 5a. The surface structure of the conventional tinplate shows, in particular, a pronounced structure of grooves which extend in the rolling direction (longitudinal direction of the strip-shaped tinplate). Dirt particles and residues from rolling oils can accumulate in the grooves, which cannot be removed by normal cleaning steps. Furthermore, as can be seen in particular from the 2D height profile in FIGS. 4a and 5a and the associated roughness profile in FIG. 5a, the surface structure has pronounced peaks at which the coating can be damaged when subjected to mechanical stress.

These problems of the prior art can be eliminated with the sheet metal packaging products according to the invention. Due to the deterministic and homogeneous surface structure of the sheet metal packaging products according to the invention, they are free from sharp points Sp with radii of curvature greater than 0.2 mm, which could damage the coating and lead to increased abrasion of the coating material and, as a result, greater susceptibility to corrosion of the sheet metal packaging product . In this way, both the susceptibility to corrosion and the disadvantageous effects of abrasion can be avoided. Furthermore, the surfaces of the sheet metal packaging products according to the invention are also free of deep and / or geometrically undefined valleys Ta, in which dirt particles and residues, such as residual fats and rolling oils, could accumulate. This facilitates the cleaning of the surface of the sheet metal packaging products according to the invention and thereby improves the corrosion resistance, because both before and after the coating of the substrate S, the surface of the uncoated or coated steel sheet can be largely completely freed from oil residues, dirt and deposits.

In FIGS. 4b to 4g and 5b to 5g, exemplary embodiments of sheet metal packaging products according to the invention with specific surface structures are shown. The parameters of the roughness profile are listed in FIGS. 5a to 5g below the roughness profile, the abbreviations used in the table of FIGS. 5a to 5g representing the following parameters:

• Ra: mean roughness or arithmetic mean roughness (arithmetic mean of the amounts of all profile values of the roughness profile) · Rq: root mean square of all profile values of the roughness profile

• Rsk: is a measure of the asymmetry of the amplitude density curve In FIG. 4d, a hexagonal surface structure with cylindrical elevations is shown by way of example in a plan view of the surface, which elevations are arranged in a hexagonal structure, each elevation E being shaped cylindrically with an at least substantially flat or convex upper side (as from the surface profile of the figure 5d). The cylindrical elevations have a mean height h and halfway up a mean diameter (FWHM o) and are (on average) apart by a distance d.

The mean height h of elevations is generally (regardless of the geometric shape) preferably in the range from 0.1 to 8 pm, in particular between 0.5 and 4.0 pm. The diameter o preferably has average values in the range of at least 10 μm and preferably from 60 to 250 μm and in particular between 30 and 80 μm. The distance d between adjacent elevations can be, for example, between 30 and 300 μm and in particular in the range from 60 to 250 μm.

The hexagonal basic structure shown in FIG. 4d with a plurality of elevations E can be arranged uniformly over the entire surface of a packaging sheet product according to the invention, so that a uniform, deterministic surface structure with hexagonal arrangements of elevations E results.

The area proportion Mrl of the plateau area of the elevations in relation to the total area of the surface of the sheet metal packaging product (which can be referred to as the “supporting proportion”) is preferably between 5% and 50%. The number of elevations E with radii of curvature greater than 0.2 mm is preferably less than 50 per cm ² and is in particular ^{less than 20 per cm 2} .

Further examples of such surface structures with a hexagonal structure of elevations E are shown in Figures 5e and 5g, each showing the surface of embodiments of a packaging sheet product according to the invention in a plan view with an associated roughness profile (height profile) and the resulting autocorrelation .

The exemplary embodiments of sheet metal packaging products according to the invention shown in FIGS. 5d, 5f and 5g are also suitable due to the selected surface structure a hexagonal arrangement of elevations E in particular for increasing the corrosion resistance of the sheet metal packaging products. This results in particular from the fact that the deterministic surface structure of these examples has no sharp peaks and no deep or geometrically undefined valleys, but instead has a uniform arrangement of elevations with an at least substantially flat plateau on the top of the elevations, as well as with largely flat valleys between the elevations E. The elevations E also withstand severe mechanical stresses due to the plateau-shaped design of the upper side, whereby abrasion and damage to the coating B can be avoided. Furthermore, no dirt or residues can settle in the valleys formed between adjacent elevations. To increase the corrosion resistance, it is advantageous if the mean distance between neighboring structural elements (“peak to peak distance”) is between 60 and 250 pm.

One parameter for the quantitative description of the corrosion properties of tinplate is the so-called IET value, which is measured in the standardized “iron exposure test” and describes the tin porosity of the tin coating. With constant conditions of the manufacturing process, such as pretreatment (cleaning), total tin application and constant process parameters, the tin porosity (IET value) essentially depends on the surface roughness (arithmetic mean roughness Ra) and the tin application (in g / m ² ).

In order to take into account the (quadratic) dependence of the tin porosity (IET value) on the tin coating Sn (weight of the tin in g / m ² ) for tinplate, it makes sense to use the IET value measured on a tinplate sample (in mA / cm ² ) to be multiplied by the square of the tin coating Sn (in g / m ^2). FIG. 6 shows the product of the measured IET value and the square tin plating (Sn ² ) for various tinplate samples, including conventional tinplate and tinplate according to the invention, and plotted against the average roughness Ra of the samples. From the diagram in FIG. 6 it can be calculated that the current density measured in the iron exposure test (IET) j _IET = I ZA (electrical current per area in mA / cm ² ) in the samples according to the invention is at most 1.4 times that arithmetic mean roughness Ra (in pm) plus a constant of 0.5 divided by the tin layer Sn (weight of the tin, m / A, mass per area in g / m ² ) squared is: jiET (in ^) <(1, 4 R _a (in pm) + 0.5) / (Sn) ² . Examples 1, 2 and 3 located below the straight line (y = 1.4 x + 0.5) in the diagram of FIG. 6 meet this condition. Examples 1, 2 and 3 of FIG. 6 are samples with a surface structure according to FIGS. 5d, 5f and 5g.

The IET value can be used to quantitatively demonstrate a positive influence of the deterministic surface structures of the tinplate samples according to the invention on their corrosion resistance of the tinplate. The sheet metal packaging products according to the invention can also be used to optimize the gloss properties. Figures 7 and 8 show diagrams which show the relationship between the gloss values measured on packaging sheets according to the invention (tinplate with a weight of 2.8 g / m ² ) and the isotropy of the gloss values (measured as delta gloss values (A gloss), which represent the difference between the gloss values in the rolling direction and perpendicular to it) from the surface roughness (arithmetic surface roughness Ra). As can be seen from FIG. 7, the gloss value (in gloss units GE) decreases (inversely proportional) with increasing roughness (Ra). With roughness Ra in the range of less than 0.4 μm, gloss values of more than 200 and with Ra <0.1 μm up to approx. 1400 gloss units (GE) can be achieved with the packaging sheets according to the invention.

With a surface roughness of, for example, Ra = 0.1 pm, gloss values of more than 670 and with surface roughness of Ra <0.05 pm of more than 1000 can be achieved.

It can be seen from FIG. 8 that homogeneous gloss properties with delta gloss values of A gloss <100 can be achieved with the packaging sheets according to the invention, whereas conventional packaging sheets (which are referred to as “standard material” in FIG same weight, same process parameters in the electrolytic coating process and same pretreatment) have significantly more inhomogeneous gloss values with A gloss> 100. The value for A gloss in the sheet metal packaging products according to the invention is preferably 70 gloss units (GE) or less.

With the same surface roughness, the A-gloss value for the packaging sheets according to the invention with a deterministic surface structure is at least by a factor of 4 smaller than conventional packaging sheets with a statistically uncorrelated surface structure. This improvement in the homogeneity of the gloss can be explained by the uniform surface structures of the packaging sheets according to the invention with the same height or depth of the surface structures (elevations or depressions) both longitudinally and transversely to the rolling direction (longitudinal direction of the strip).

Furthermore, it can be seen from the diagram in FIG. 8 that the “double I structures” with a surface structure according to FIGS. 4b and 4e have the best results with regard to isotropic or homogeneous gloss effects with regard to the A-gloss value.

Table 1

Claims

Expectations 1. Sheet metal packaging product, in particular tinplate or electrolytically chromium-plated steel sheet (ECCS), consisting of a sheet steel substrate (S) with a thickness in the range from 0.1 mm to 0.6 mm and an electrolytically deposited on at least one side of the sheet steel substrate Coating (B) of tin and / or of chromium or chromium and chromium oxide, the coating (B) having a layer of tin with a weight application in the range from 1 to 15 g / m ^{2 of} tin and / or a layer of chromium and / or chromium oxide a total weight of the chromium in the chromium / chromium oxide layer in the range of 5 to 200 mg / m ² , characterized in that at least one surface of the sheet metal packaging product provided with the coating (B) has a surface profile with periodically recurring structural elements in at least one direction and an autocorrelation function resulting from the surface profile with an absolute maximum and a plurality of secondary max ima, the height of which is at least 20%, preferably at least 30% of the height of the absolute maximum. 2. Sheet metal packaging product according to claim 1, characterized in that the height of a plurality of secondary maxima of the autocorrelation function along a preferred direction on the sheet steel substrate (S) is at least 40% of the height of the main maximum and preferably at least 60%. 3. Sheet metal packaging product according to claim 1, characterized in that the coating (B) is a non-melted tin coating and that the height of a plurality of secondary maxima of the autocorrelation function along a preferred direction of the tin-coated steel substrate is at least 30% of the height of the absolute maximum and preferably at least 50%. 4. Sheet metal packaging product according to one of the preceding claims, characterized in that the sheet metal packaging product has a surface roughness (R _a ) in the range from 0.01 to 2.0 pm, preferably in the range from 0.1 to 1.0 pm and in particular an arithmetic mean roughness in the range from 0.10 to 0.30 pm. 5. Sheet metal packaging product according to one of the preceding claims, characterized in that the topographical shape of the periodically recurring structural elements is convex or plateau-shaped. 6. Sheet metal packaging product according to one of the preceding claims, characterized in that the periodically recurring structural elements have a width at half height (FWHM) of at least 10 pm and preferably between 60 and 250 pm. 7. Sheet metal packaging product according to one of the preceding claims, characterized in that the coating (B) is a tin coating with a predetermined weight (Sn) and that the tin coating in the Iron Exposure Test (IET) has a current density j _IET = I ZA (electrical current per area) in mA / cm ² , which is at most 1.4 times the arithmetic mean roughness Ra in pm of the coated substrate plus a constant of 0.5 divided by the weight application (Sn) in g / m ² squared: ji _ET (in ^) <(1.4 R _a (in pm) + 0.5) / (Sn) ² . 8. Sheet metal packaging product according to one of the preceding claims, characterized in that the coating (B) is a tin coating with a predetermined weight (Sn) of the tin (m / A, mass per area in g / m ² ) and that the iron exposure Test (IET) measured current density j _IET = HA (electrical current per area) in mA / cm ² multiplied by the square of the weight applied (Sn) of the tin with an arithmetic mean roughness of Ra <1.0 pm less than 1.9 (mA / cm ² ) - (g / m ² ) ² and with an arithmetic mean roughness (Ra) of 1.0 pm <Ra <2.0 pm less than 3.3 (mA / cm ² ) - (g / m ² ) is ² . 9. Sheet metal packaging product according to one of the preceding claims, characterized in that the surface structure has a regularly arranged pattern with elevations (E) and / or depressions (V), the elevations preferably by an average height (h) of 0.5 to 3 .0 pm, in particular from 1.0 to 2.0 pm and particularly preferably from less than 2.0 pm above a level averaged over the entire surface of the sheet metal packaging product, and the depressions (V) preferably have an average depth of 0.5 to 3.0 pm, in particular from 1.0 to 2.0 pm, compared to the mean level. 10. Sheet metal packaging product according to one of the preceding claims, characterized in that the surface has convex and / or concave structural elements in a periodically recurring arrangement. 11. Sheet metal packaging product according to one of claims 4 to 10, characterized in that more than 50% of the recurring structural elements form a uniform height level which varies in height by a maximum of ± 100% of the surface roughness Ra. 12. Sheet metal packaging product according to one of the preceding claims, characterized in that the recurring structural elements are at least substantially web-shaped and in particular trapezoidal in cross-section. 13. Sheet metal packaging product according to one of the preceding claims, characterized in that the recurring structural elements are each plateau-shaped with an at least substantially flat plateau surface, the plateau surfaces of individual convex structural elements being preferred and at least substantially the same size. 14. Sheet metal packaging product according to one of the preceding claims, characterized in that the recurring structural elements are each designed as groove-shaped depressions with an at least substantially flat groove base, the areas of the groove base of the individual structural elements being at least substantially the same. 15. Sheet metal packaging product according to one of the preceding claims, characterized in that the recurring structural elements are each designed as groove-shaped depressions and plateau-shaped elevations adjacent thereto, the plateau areas of the plateau-shaped elevations preferably being at least essentially the same size as the areas of the bottom of the depressions. 16. Sheet metal packaging product according to one of the preceding claims, wherein the recurring structural elements comprise convex elevations which are an average height (h) of 0.1 to 8.0 μm, preferably 0.2 to 4.0 gm above the surface of the steel sheet -Substrate (S) protrude. 17. Sheet metal packaging product according to one of the preceding claims, wherein the recurring structural elements comprise depressions which have an average depth (t) of 0.1 to 8.0 μm, preferably 0.2 to 4.0 μm. 18. Sheet metal packaging product according to one of the preceding claims, wherein the periodically recurring structural elements are rectangular or square, strip-shaped, web-shaped, cylindrical, leaf-shaped, sickle-shaped, ring-shaped or hemispherical in plan view. 19. Sheet metal packaging product according to one of the preceding claims, characterized in that it is in the form of a sheet extending in a longitudinal direction (L) Bands are present, the periodically recurring structural elements being web-shaped elevations (E) and / or the groove-shaped depressions (V). 20. Sheet metal packaging product according to claim 20, wherein the average width of the web-shaped elevations (E) and / or the groove-shaped depressions (V) is between 10 pm and 200 pm and preferably in the range from 15 pm to 100 pm. 21. Sheet metal packaging product according to claim 20, wherein the average width (b) of the web-shaped elevations (E) is in the range from 30 pm to 200 pm and the average width (b) of the groove-shaped depressions (V) is in the range from 10 pm to 100 pm . 22. Sheet metal packaging product according to one of the preceding claims, characterized in that the surface structure has depressions in the form of multiple grooves, in particular double grooves, which are arranged in a regular pattern, in particular in the form of a matrix. 23. Sheet metal packaging product according to claim 23, wherein adjacent multiple grooves, in particular adjacent double grooves, are each arranged rotated by 90 ° with respect to one another. 24. Sheet metal packaging product according to one of the preceding claims, characterized in that the surface of the sheet metal packaging product has a gloss value of more than 50 gloss units (GE) and preferably more than 100 gloss units (GE), in particular between 100 and 800 gloss units (GE) with a surface roughness ( Ra) of less than 0.5 pm and more than 0.1 pm. 25. Sheet metal packaging product according to one of the preceding claims, characterized in that the surface of the sheet metal packaging product has an at least substantially direction-independent gloss value, the difference in gloss value (A gloss) in the rolling direction and one perpendicular thereto standing transverse direction is preferably less than 100 gloss units (GE) and particularly preferably 70 gloss units (GE) or less, in particular with a surface roughness (Ra) of 0.01 to 2.0 μm. 26. Sheet metal packaging product according to one of the preceding claims, wherein the plurality of structural elements forms a periodically recurring reservoir for receiving particles which are detached from the coating (B) due to abrasion. 27. Sheet metal packaging product according to claim 26, wherein the reservoir for receiving particles is formed by periodically recurring depressions which receive abrasion particles which are detached from the coating (B) by abrasion. 28. Sheet metal packaging product according to one of the preceding claims, wherein the periodically recurring structural elements comprise elevations (E) and / or depressions (V), the area proportion of the elevations (E) in the total area of the sheet metal packaging product between 20% and 50% and preferably between 24 % and 45% and / or the area share of the Depressions (V) on the total surface of the sheet metal packaging product is between 50% and 80% and preferably between 55% and 76%. 29. Sheet metal packaging product according to one of the preceding claims, characterized in that the periodically recurring structural elements are web-shaped Elevations (E) and / or groove-shaped depressions (V), the average width of the web-shaped elevations (E) and / or the groove-shaped depressions (V) between 10 pm and 120 pm and preferably in the range from 15 pm to 95 pm lies. 30. Sheet metal packaging product according to claim 29, wherein the average width (b) of the web-shaped elevations (E) is in the range from 45 μm to 120 μm and the average width (Ab) of the groove-shaped depressions (V) is in the range from 10 μm to 85 μm . 31. Sheet metal packaging product according to one of the preceding claims, wherein the sheet steel substrate (S) has the following composition in relation to the proportions by weight: - C: 0.01-0.1%, - Si: <0.03%, - Mn: 0.1-0.6% - P: <0.03%, - S: 0.001-0.03%, - Al: 0.002-0.1%, - N: 0.001-0.12%, preferably less than 0.07% - optional Cr: <0.1%, preferably 0.01-0.05%, - optional Ni: <0.1%, preferably 0.01-0.05%, - optional Cu: <0.1%, preferably 0.002-0.05%, - optional Ti: <0.09%, - optional B: <0.005%, - optional Nb: <0.02%, - optional Mo: <0.02%, - optional Sn: <0.03%, - remainder iron and unavoidable impurities. 32. A method for producing a sheet-metal packaging product with a structured surface, the method comprising the following steps: - providing a primarily cold-rolled sheet steel substrate (S) with a thickness in the range from 0.1 mm to 0.6 mm; - Recrystallizing annealing of the primarily cold-rolled sheet steel Substrate (S); - Rerolling or skin-pass treatment of the recrystallizing annealed Sheet steel substrate (S) in a double-stand re-rolling mill, with a first stand of the re-rolling mill at least one Work roll with an unstructured, in particular with a blasted or polished roll surface, and a second stand of the tempering mill has at least one work roll with a surface-structured roll surface; - Electrolytic coating of the re-rolled or skin-pass Sheet steel substrate (S) on at least one side with a coating (B) of tin and / or of chromium or chromium and chromium oxide, the coating (B) being a tin layer with a weight in the range from 1 to 15 g / m ^{2 of} tin and / or comprises a layer of chromium or chromium oxide with a total weight of the chromium in the chromium or chromium oxide layer in the range from 5 to 200 mg / m ^2; - whereby on the surface of the steel sheet electrolytically coated with the coating (B) there is a surface profile with structural elements recurring periodically in at least one direction and the surface structure has an autocorrelation function which has an absolute maximum and a plurality of secondary maxima, the height of which is at least 20% and is preferably at least 30% of the height of the absolute maximum 33. The method according to claim 32, characterized in that the surface of the at least one work roll of the second stand has been structured by a pulsed laser, in particular by a short pulse laser or an ultrashort pulse laser. 34. The method according to claim 32 or 33, characterized in that the coating (B) is a tin coating and that the surface of the coating (B) melted after the electrolytic deposition or with a passivation layer, in particular a chromium / chromium oxide passivation layer or a chromium-free passivation layer is provided. 35. The method according to any one of claims 32 to 34, characterized in that during re-rolling or skin-passing, the thickness of the cold-rolled and electrolytically coated sheet steel substrate (S) is reduced to a final thickness in the range from 0.1 mm to 0.5 mm, with the relative thickness reduction at Rerolling in the range of more than 5% and up to 50% and, during skin passaging, in the range of 0% to 5%, preferably in the range of 1% to 4%. 36. Steel sheet with a thickness in the range from 0.05 mm to 0.6 mm, characterized in that the surface of the steel sheet has a surface profile with periodically recurring structural elements in at least one direction and that an autocorrelation function resulting from the surface profile has a plurality of Has secondary maxima, the height of which is at least 40% of the height of the absolute maximum. 37. Steel sheet according to claim 36, characterized in that the height of the secondary maxima of the autocorrelation function along a preferred direction on the surface of the steel sheet is at least 50% and preferably at least 60% of the height of the absolute maximum.