EP3414365A1

EP3414365A1 - Aluminium alloy sheet optimised for forming

Info

Publication number: EP3414365A1
Application number: EP17702054.2A
Authority: EP
Inventors: Frank Hirschmann; Kathrin Eckhard; Bernhard Kernig; Gernot NITZSCHE; Henk-Jan Brinkman
Original assignee: Hydro Aluminium Rolled Products GmbH
Current assignee: Speira GmbH
Priority date: 2016-01-27
Filing date: 2017-01-25
Publication date: 2018-12-19
Anticipated expiration: 2037-01-25
Also published as: CN108603304A; JP2019508585A; US20180340268A1; CN108603304B; JP7080817B2; EP3414365B1; US11131037B2; WO2017129605A1; KR20180095095A; KR101986330B1

Abstract

The invention relates to a strip or sheet consisting of an aluminium alloy with a surface structure prepared for a forming process on one side or on both sides, particularly a strip or sheet for formed motor vehicle components. The aim of the invention is to provide an aluminium alloy strip or sheet with a surface structure prepared for a forming process, which is easy to produce and has improved tribological properties with regard to a subsequent forming process. To this end, the strip or sheet consisting of an aluminium alloy has a surface, on one or both sides, comprising recesses produced using an electrochemical graining method, as lubricant pockets.

Description

Forming optimized aluminum alloy sheet

The invention relates to a band or sheet of an aluminum alloy with an at least partially provided, one or both sides, for a

Forming process prepared surface structure, in particular a band or sheet for formed vehicle components. Moreover, the invention relates to a method for producing a strip or sheet with one for a

Forming process prepared one or two-sided surface structure of an aluminum alloy and a corresponding use of a formed band or sheet.

In the automotive industry, sheets of aluminum alloys are increasingly being used to realize weight-saving potential in motor vehicle construction. Tapes and sheets for the manufacture of automotive components are usually made of AA7xxx, AA6xxx, AA5xxx or AA3xxx aluminum alloys. They are characterized by medium to very high strengths and a very good

Forming behavior off. The strengths are essentially material properties, whereas the formability by u. a. the material properties, the

Surface topography, the amount of lubricant, the type of lubricant and the tool surface in combination. Here is the material itself with its forming properties, such as the elongation at break, in

Foreground. In addition, but also plays the surface topography or the

Surface structure of the strip or sheet is a major role and the proportion of lubricants on the surface of the sheet. At the same time, the tool material, the tool surface, the contact pressure during forming, the temperature and the forming speed have a great influence. To at the band or

Sheet metal production already provide maximum forming properties, tapes and sheets of aluminum alloy are usually provided in the last rolling pass with a surface structure in order to be on the belt or sheet metal surface or to introduce depressions on both sides, which serve as lubricant pockets. These lubricant pockets leave an applied lubricant up to

Forming process on the sheet surface and allows greater degrees of deformation of the sheet or strip. During forming, the lubricant can also be transported out of the lubricant pockets to other areas of the sheet to provide local lubrication. For this purpose, the rollers used are provided with a texture which, depending on the chosen process for structuring the roller leads to a different texture on the belt. For example, a surface texture produced by an electrical discharge texturing (EDT) process provides a high number of peaks in the surface profile, and an electron beam texturing (EBT) process can be used to provide controlled distribution of wells in the surface. Through a "shot blasting texturing" (SBT) method, the

Embossing rollers are also textured. Also, a textured chrome layer or laser textured surfaces were used. all

It is common for production steps that the surface structure is replaced by a

Rolling step is transferred from the roller to the surface of the aluminum strip. Typically, the thickness of the band is reduced again in order to be able to transfer the texture.

High demands on the forming properties are also required in other technical areas, for example in the production of

Beverage cans, in particular of the can body and the can lid, of AA3xxx or AA5xxx aluminum alloys.

From the German translation of the European patent DE 602 13 567 T2 a method for embossing a surface structure of aluminum strips is known in which over a plurality of stitches imprinting the texture without reducing the thickness of the band. In addition, it is described that for the application of lithographic printing plate supports a corresponding roll-embossed sheet can also be subjected to an electro-chemical graining. lithographic However, printing plate supports are neither suitable for motor vehicles nor intended for further forming steps. It is rather a completely different field of application of aluminum sheets, because the sheets are electrochemically roughened to be provided with a coating and used in printing. With regard to the improvement of the forming behavior of

In any case, aluminum alloy strips or sheets in forming processes contain no mention of the above-mentioned European patent specification for the person skilled in the art.

From the US patent application US 2008/0102404 AI is an electro-chemical graining of an aluminum surface for the production of lithographic

Pressure plate carriers known for roughening the surfaces. Electrochemical graining, in contrast to electrochemical etching, which uses direct current, takes place using alternating current or pulsed direct current. This ensures that the etching process is interrupted again and again and the surface is not deep, for example, deep channels are etched, but only superficial troughs are generated, so a graining or roughening of the surface is achieved. However, lithographic printing plate supports are not intended for further forming. Japanese Patent Application JP S63 141722 discloses a method for

Production of a hard aluminum sheet for forming processes in which deep microchannels are etched by electrolytic etching, which serve to anchor a polyamide layer on the sheet. About the polyamide layer, the deformation of the sheet is to be facilitated. However, the present invention is not concerned with the provision of sheets and tapes with

Polyamide coating. Rather, tapes and sheets are to be provided, which are used, for example, in the vehicle and painted after forming. The improvement of the forming properties of the bands or sheets should therefore be achieved without a polyamide coating.

Japanese Patent Application JP H06 287722 discloses a method for

Coating an aluminum strip described with fluoroplastic, wherein the Surface of the tape also first electrolytically using

DC is etched. The German patent application DE 103 45 934 discloses a Umformvorbereitetes aluminum strip for automotive components, wherein the

Surface conventionally, for example, roll embossed using EDT textured rolls.

On this basis, the present invention is based on the object, an aluminum alloy strip or sheet with a for a forming process

prepared surface structure to provide, which is easy to produce and has improved tribological properties with respect to a subsequent forming process. In addition, it is an object of the invention to propose a manufacturing method for a corresponding aluminum alloy strip or sheet and its use. According to a first teaching of the present invention, the object for an aluminum alloy strip or sheet is achieved in that the strip or sheet has on one or both sides a surface with recesses made using electrochemical graining as lubricant pockets. The inventors have recognized that by means of an electrochemical graining process, lubricant pockets can be introduced into the surface of an aluminum alloy strip, which can significantly improve the forming behavior of the sheet, i. significantly influence the tribological properties of the sheet. This is particularly interesting for sheet metal with a minimum thickness of 0.8 mm, since in sheets or strips with these thicknesses next to the

Material properties in particular the surface properties due to the higher forming forces than thinner sheets or strips in the

Forming become more important. In comparison to the conventional, mechanically embossed surface structures, it was found that the electrochemically grained surfaces have a significantly different structure. The surface of the aluminum alloy strip further has the rolled, plateau-like texture which is interspersed with wells introduced into the surface using electrochemical graining. This is a clear difference to the previously used rolled-in surface textures or depressions. The indentations introduced into the aluminum alloy strips or sheets during electrochemical graining have, in comparison to the mechanical ones

Embossing a higher trapped volume and thus a significantly larger reduced bowl depth. The surface has, in addition to the previously introduced by the rolling surface structure, for example, a "mill-finish" surface structure, depressions, some of which very abruptly from the

Fall off surface and partially undercuts or negative opening angle. This embodiment of the recesses is specific to the

Manufacturing process due to electro-chemical graining. Due to the specific nature of the recesses by the electro-chemical graining, the aluminum alloy strip or sheet according to the invention has a

Improved absorption behavior with respect to the used during forming

Lubricants. The wells formed as lubricant pockets, which are introduced by the electro-chemical graining in the sheet, show a significantly greater reduced bowl depth and a significantly higher closed void volume. It can therefore a higher amount of lubricant for the forming process

to be provided. This is also reflected in the improved

Forming properties of the strips or sheets thus produced again. In addition, electro-chemical graining is a process that is on a large scale

is economically applicable and thus suitable for mass production. Preferably, the band or sheet of an aluminum alloy has a

Minimum thickness of 0.8 mm. Aluminum alloy tapes or sheets having a thickness of at least 0.8 mm are often subjected to a forming process, such as deep-drawing, for example, to bring a flat sheet into a specific shape required for the application. Preferred thicknesses in

Automotive sector are also 1.0 to 1.5 mm or up to 2.0 mm. But also

Aluminum sheets with thicknesses of up to 3 mm or up to 4 mm undergo forming processes transformed and used in the automotive sector, for example in suspension applications or as a structural part. The larger the thickness, the higher the required forming forces. But this increases the demands on the forming properties of the sheets, their surface and the materials. The inventive

Surface design thus contributes to achieving improved forming results in all thickness ranges, but especially in the larger thickness ranges from 0.8 mm.

According to a further embodiment, the band or the sheet at least partially made of an aluminum alloy of the type AA7xxx, type AA6xxx, type

AA5xxx or type AA3xxx, in particular, of an aluminum alloy of the type AA7020, AA7021, AA7108, AA6111, AA6060, AA6016, AA6014, AA6005C, AA6451, AA5454, AA5754, AA5251, AA5182, AA3103 or AA3104. In addition, an AlMgö alloy for the strip or sheet may also be used with preference. Finally, the use of plated composites with the abovementioned alloys, for example as a core alloy, is also conceivable. For example, a AA8016 or AA6060 core alloy clad with an AA8079 aluminum alloy has very good forming properties even without surface treatment by electrochemical graining. It is assumed that this

Properties can be additionally improved via the surface texture according to the invention. The said aluminum alloys have in common that they are usually preferred for use in motor vehicles. They are characterized by high formability and the provision of medium to very high strengths. For example, after curing, the AA6xxx or AA7xxx aluminum alloys can achieve very high strengths and are used in structural applications. The above-mentioned high magnesium aluminum alloys of the type AA5xxx and AlMgö are not hardenable, but in addition to a very good forming behavior they have directly high strength values. The alloys of the AA3xxx type provide medium-high strength in motor vehicle construction and are preferably used for components in which the rigidity is of primary importance and a high degree of stability Formability is required. It has been shown that in the abovementioned materials, a particular increase in the forming behavior of strips and sheets according to the invention can be achieved. AA3xxx alloys, for example the AA3104 or the AA3103 and some AA5xxx, such as the mentioned AA5182 but also the alloys AA5027 or AA5042 are also used for the production of beverage cans and must therefore also very good forming properties at the same time good

Have surface properties after forming. It is therefore assumed that the aluminum alloys of the type AA3xxx and AA5xxx, in particular the said AA3104, AA3103, AA5182, AA5027 or AA5042 in the beverage can production of the specific, electro-chemically grained

Benefit from the surface during forming with large degrees of deformation. As already stated, the electrochemical graining process results in a very specific surface topography, i. to specific pronounced depressions, which serve as lubricant pockets. To describe the specifically designed surface topography, according to EN ISO 25178, the areal surface is described

Roughness measurement the reduced peak height S _P k, the kernel depth Sk and the reduced bowl depth (also called reduced groove depth) S _V k available.

All three parameters can be read from a so-called Abbott curve according to EN ISO 25178. To get the Abbott curve, a

Surface usually optically measured three-dimensionally. In the measured three-dimensional height profile of the surface flat surfaces which extend parallel to the measured surface, introduced at a height c, wherein c is preferably determined as the distance to the zero position of the measured surface. The surface area of the cut surface of the introduced flat surfaces with the measured surface in the height c is determined and divided with the entire measuring surface in order to obtain the surface portion of the cut surface on the total measuring surface. This area fraction is determined for different heights c. The Cut surface height is then represented as a function of the area fraction, resulting in the Abbott curve, Fig. 1.

With the help of the Abbott curve, the reduced peak height (S _P k), kernel depth (Sk) and the reduced beaker depth (S _V k) can be determined. All three parameters refer to different surface properties. It was determined that the reduced bowl depth (S _V k) in particular correlates with improved forming behavior.

The Abbott curve usually has an S-shaped course for rolled surfaces. In this S-shaped curve of the Abbott curve, a secant with a length of 40% of the material fraction is shifted in the Abbott curve until it has a minimum slope amount. This is usually in

Turning point of the Abbott curve of the case. The extension of this straight line up to 0% material or 100% material content in turn gives two values for the height c at 0% or 100% material content. The vertical distance of the two points gives the kernel depth Sk of the profile. The reduced well depth S _V k results from a triangle A ₂ with a base length of 100% - Smr 2, which is coextensive with the valley surfaces of the Abbott curve, with Smr 2 being from the intersection of the Abbott curve with a parallel to the X axis, which extends through the intersection of the extension of the secant with the 100% abscissa is. The height of this surface-identical triangle corresponds to an area measurement of the reduced bowl depth S _V k, FIG. 1.

The reduced peak height _P S k is the height of the same area with the tip surfaces of the Abbott curve triangle with the base length SMRL. Smrl results from the intersection of the Abbott curve with a parallel to the X-axis, which passes through the intersection of the extension of the above-mentioned secant with the 0% -axis.

The parameters Sk, S _P k and S _V k in a surface measurement allow separate consideration of the profile with respect to the core region, tip region and

Ridge area or trough area. The surface density of the texture n _C ] _m can also be used as a further parameter of the surface. The bowl density indicates the maximum number of closed empty volumes, ie the depressions or depressions, depending on the measuring height c per mm ² . The measuring height c corresponds to the value c, which is also shown in the Abbott curve. The measuring height c thus corresponds to 100% of the highest elevation of the surface and 0% of the lowest point of the surface profile.

The following applies: n _c i (c) = number of closed empty surfaces per unit area (1 / mm ² ) for a given measurement height c (%) and ricim = MAX (n _c i (Ci)), where n _c i _{m is} the maximum number corresponds to the closed empty areas per unit area (1 / mm ² ) with Ci = 0 to 100%.

Finally, the closed void volume V _vc i serves the surface of the

Characterization of the surface. It determines the absorption capacity of the surface, for example for lubricants. The closed void volume is through

Determination of the closed empty space A _V d (c) determined as a function of the measuring height c. The closed void volume V _vc i then results from: Also with the help of the obliquity of the topography of the surface S _Sk , the surface can be described. This indicates whether the measured surface is one

plateau-like structure with recesses or has a embossed by peaks or peaks surface. The S _sk is, according to DIN EN ISO 25178-2, the quotient of the mean cube of the ordinate values and the cube of the mean square height S _q . The following applies: where A is the limited surface part of the measurement and z is the height of the measurement

Measuring point. For S _q applies:

If Ssk is less than zero, then there is a plateau-like, indented surface. At a value for S _S k greater than zero, the surface is embossed by peaks and has no or only a very small plateau-like surface portion.

According to a preferred embodiment, at least one band or sheet surface has a reduced depression depth Svk of 1.0 μm-6.0 μm, preferably 1.5 μm-4.0 μm, particularly preferably 2.2 μm to 4 μm. With a reduced bowl depth of Ι, Ομιτι - 6.0 μηι can be provided by at least a factor of 4 larger reduced cavity depth Svk than conventionally roll-embossed surface structures on the strip or sheet of aluminum alloy according to the invention. The preferred values selected for the reduced tray depth

allow an improved forming behavior, without the later

Surface properties, for example, the surface appearance after painting to influence.

Preferably, according to a further embodiment of the tape according to the invention, the closed void volume V _vc i is at least 450 mm ³ / m ² , preferably at least 500 mm ³ / m ² . As a practical upper limit may be 1000 mm ³ / m ² or

800 mm ³ / m ^{2 are} considered. However, values are also above

1000 mm ³ / m ² conceivable. The strip surface according to the invention can thus be clear provide more lubricant for the forming process than the conventional surfaces previously used.

The aluminum alloy strip according to the invention has, according to a further embodiment, an at least 25% increased blister density n _c i _{m of} the surface compared to conventionally produced surface textures, for example EDT textures. The well density of the surface is preferably more than 80 to 180 wells per mm ² , preferably 100 to 150 wells per mm ² . A further embodiment of the aluminum alloy strip has a skewness of the topography of the surface S _S k of 0 to -8, preferably -1 to -8. This ensures that the surface has a plateau-like structure, which with

Wells is provided so that lubricant pockets are provided. This surface topography, in particular with a skewness of -1 to -8 becomes

For example, achieved by electro-chemical graining a "mill-finish" rolling surface and has a preferred forming behavior.

According to a further embodiment of the strip or sheet according to the invention, this has the state annealed ("0"), solution annealed and quenched ("T4") or the state H19 or H48. Both states have a maximum

Forming on and allow together with the novel

Surface structure of the strip or sheet an enlargement of the

Formability. While the state "0" is provided by each material, hardenable materials, for example AA6xxx alloys, are solution-annealed and then quenched This condition is referred to as T4 However, both states are generally preferred for forming processes, since in this state the metal sheet or metal sheet is used In the condition T4 an additional increase of the strength by hardening is made possible The alloys for the can production are preferably in the condition H19 or H48, since thereby the necessary strength can be provided after the forming and further processing to the beverage can.

According to a further embodiment, the band or sheet has a passivation layer applied after electrochemical graining. These

Passivation layer usually consists of chromate-free

Conversion materials that protect the surface of the aluminum strip or sheet from corrosion. A specific passivation layer therefore represents the conversion layer. The passivation applied after electrochemical graining affects the provision of lubricant pockets for the catalyst

Forming process of the strip or sheet not, so that even passivated strips and sheets can be provided with a surface optimized for Umformoperationen surface. As an alternative to passivation, the aluminum sheet or strip may be provided, at least in some areas, with a protective oil in order to protect the aluminum strip or aluminum alloy sheet from corrosion.

According to a further embodiment, the band or sheet on the surface at least partially on a forming aid, in particular a dry lubricant, which as a protective layer and as a lubricant in subsequent

Can serve forming processes. This makes it possible to provide a particularly storable product available, which is also easy to handle due to the protective layer.

According to a second teaching of the present invention, the above-described object of a method for producing an aluminum alloy strip or sheet is achieved in that a hot and / or cold-rolled strip or sheet consisting of an aluminum alloy after rolling is subjected to a single- or double-sided electrical subjected to chemical graining, wherein by the electrochemical graining homogeneously distributed wells as lubricant pockets in the Band or sheet are introduced from an aluminum alloy. The way

produced aluminum alloy tapes or sheets have specific

Surfaces on. The rolled-in texture of the strip or sheet is retained except for the additional indentations introduced by electrochemical graining. The roll texture forms, for example, in the case of a "mill finish" surface, a plateau-like surface in which homogeneously distributed depressions are present as lubricant pockets Thus, the aluminum alloy strip or sheet produced according to the invention differs markedly from conventionally produced aluminum alloy strips and sheets whose texture is due to the textured roller embossing is not formed plateau-like.

The strip or sheet is preferably subjected to a forming process, for example deep-drawing. Thermoforming in practice usually includes deep drawing and stretch drawing parts. In this case, the aluminum alloy strip or sheet previously with a forming aid, for example with a lubricant or

Dry lubricant, so that the existing lubricant in the lubricant pockets even better forming behavior is achieved due to the optimized surface structure and better lubricant occupancy. According to a further embodiment of the aluminum alloy strip or sheet, the mean roughness S _{a of} the surface of the strip or sheet 0.5 μηι to 2.0 μ ^η ι, preferably 0.7 μιτι to 1.5 μιτι, more preferably 0.7 μηι is up to 1.3 μηι or preferably 0.8 μιη to 1.2 μπι. Sheets or strips for internal parts of a motor vehicle preferably have a mean roughness Sa of 0.7 μιη - 1.3 μη and outer skin parts of a motor vehicle average roughness Sa of 0.8 μιιι to 1.2 μηι on. Exterior and interior parts of a motor vehicle then receive a very good surface appearance.

Preferably, the hot and / or cold rolled strip or sheet further has a minimum thickness of 0.8 mm. Aluminum alloy strips or sheets with a thickness of at least 0.8 mm are often a forming process, for example Deep drawing, for example, to bring a flat sheet in a specific, required for the application, form. Preferred thicknesses in

In addition, automotive sector are also 1.0 to 1.5 mm, for example, for attachments such as doors, hoods and flaps, but also 2 mm to 3 mm or 4 mm for example, structural components, such as parts of the frame structure or the chassis. Corresponding sheets are subjected to forming processes and in the automotive sector, for example in suspension applications or as

Structural part, used. The greater the thickness of the sheets, the higher the required forming forces. This also increases the surface friction in the tool during

Forming. With increasing thickness, the demands on the

Forming properties of the sheets or strips. The surface design therefore contributes to achieving maximum forming results. Height

Forming requirements are required in particular for attachments with sheet thicknesses of 1.0 mm to 1.5 mm, since the possibility of individual shaping of the often visible sheets plays a very important role here.

But also bands or sheets with a smaller thickness, such as ribbons for the production of beverage cans with a thickness of less than 0.8 mm, for example, 0.1 mm to 0.5 mm, can benefit from the present invention introduced surface structure, such as in the production of

Beverage cans the limits of the forming properties of the

Aluminum alloy strips and sheets are usually almost exhausted. It is assumed that the aluminum alloy strips produced according to the invention with a reforming-optimized surface also have another

Improvement of the deformation of these thin sheets allows.

As already stated above, in contrast to the known prior art, the surface structure of the aluminum strip by an electro-chemical

Graining method performed with an electrolyte. On the

Charge carrier entry and the current density, the surface structure and the proportion of the roughened surface can be adjusted without additional rolling step. The process is not only easy to handle, but also scales well for large throughput volumes.

According to a first embodiment of the method according to the invention depressions are preferably in the band or sheet surface with a reduced

Dump depth SVK of Ι, Ομηι - 6.0 μιη, preferably 1.5 μηι - 4,0μηι, more preferably 2.2 μηι to 4.0 μπι introduced by the electro-chemical graining. It has been found that tapes with corresponding surface topography achieve improved properties in the drawing test with a cross tool. The tribological properties of the aluminum sheet or strip can thus be improved. With the limited depression depths S _v k of 1.5 μπι to 4.0 μη and 2.2 μπι to 4.0 μιτι an improved deformation behavior can be achieved without the later

According to a further embodiment, the strip or sheet is preferably subjected to a cleaning step before the electrochemical graining, in which by alkaline or acid pickling and optionally by using further

Degreasing media cleaned the surface and a homogeneous material removal is carried out. The removal of material is intended essentially to remove surface impurities introduced by rolling, so that a very suitable surface is available for electrochemical graining.

The electrochemical graining with HNO 3 is preferably carried out in a concentration of 2 to 20 g / l, preferably 2.5 to 15 g / l and with a charge carrier input of at least 200 C / dm ² , preferably at least 500 C / dm ² . The current densities may vary from at least 1 A / dm ² , preferably to 60 A / dm ² or 100 A / dm ² . This is the indication of peak AC densities or peak current densities of pulsed DC. With the mentioned parameters it is possible while maintaining economical

Process times and electrolyte temperatures of less than 75 ° C, preferably in Range between room temperature and 50 ° C or 40 ° C, a sufficient

To achieve surface coverage of the grained areas. As an alternative to

Nitric acid can also be used hydrochloric acid as an electrolyte. The method according to the invention can be further developed in that, after the electrochemical graining, a passivation of the strip surface, preferably by applying a conversion layer, is carried out and / or a forming aid is applied. Under a forming aid, for example, lubricants and dry lubricants, which may optionally be melted understood. The conversion layer and the forming aid may be formed as a protective layer and individually or simultaneously improve the corrosion resistance and thus the shelf life of the strip or sheet. The forming aid additionally improves the forming properties. In addition, as an alternative to the conversion layer and at least partially a protective oil to protect against corrosion

Aluminum alloy strip surface or the sheet surface are applied. Preferably, the application of the conversion layer with the application of a preferably meltable forming aid, in particular a meltable

If the said process steps are carried out at least partly in a common production line, a particularly economical production of a corresponding strip surface or a corresponding strip surface can be achieved

Aluminum alloy strip or sheet.

Correspondingly produced strips and sheets are both storable and can be handled in a simple manner, since they are protected against corrosion and mechanical damage.

Preferably, the strip or sheet is electrochemically grained after soft annealing or solution heat treatment and quenching. This has the advantage that the heat treatment can not adversely affect the surface properties of the sheet after the electrochemical graining and in relation to the Forming requirements optimized tape or sheet metal can be provided. Optionally, the surface texturing can be carried out by electrochemical graining but also before the final annealing, ie the soft annealing or the solution annealing and quenching.

According to a further embodiment of the method according to the invention, the method steps are preferably carried out in a production line:

Unwinding the tape from a reel,

- cleaning and pickling of the tape,

- electro-chemical graining of the tape and

- at least in a sectoral order of a forming aid and / or a

Conversion layer or alternatively a protective oil.

By these manufacturing steps, storable aluminum alloy tapes can be provided in an economical manner. The on the

Forming process prepared surface of the aluminum alloy strips or - sheets remains substantially unchanged during storage in their properties. As forming aids are lubricants, in particular

Dry lubricants, for example hotmelts used. These form at

Room temperature (20-22 ° C) a non-running, pasty, almost grip-proof thin film on the belt or sheet surface based on mineral oil, synthetic oil and / or renewable raw materials. In comparison with protective oils, hotmelts have improved lubricating properties, in particular during deep drawing.

Finally, according to a third teaching, the object is achieved by a formed sheet metal of a motor vehicle made of an inventive band or sheet made of an aluminum alloy.

Formed sheets, in particular parts of a motor vehicle, sometimes require very high degrees of deformation, which can provide the band or sheet according to the invention. The degrees of deformation are achieved by the specific surface structure of the sheets or strips, which also on the finished end product of the formed sheet metal still at least partially preserved. This depends on the specific forming process. Due to the better forming properties can more

Weight saving potential for motor vehicles can be achieved by the greater versatility of aluminum alloy sheets. In particular, the

Shaping requirements on the sheet metal, that is mold requirements due to the design, are better met with aluminum alloy sheets.

In addition, the invention will be explained in more detail with reference to embodiments in conjunction with the drawings. In the drawing shows

FIG. 1 schematically shows the determination of the parameters S _k , Sp _k and S _Vk on the basis of a

Abbott curve,

Fig. 2 is a micrograph of a non-inventive

Embodiment,

3 is a microscopic enlarged view of an embodiment of a strip surface according to the invention, Fig. 4 is a schematic representation of an embodiment of a

Production line for carrying out the method according to the invention,

Fig. 5 is a schematic sectional view of an embodiment

strip or sheet according to the invention,

Fig. 6a), 6b) schematically shows the experimental design of the drawing test with a

Cross tool for determining the forming behavior in a perspective sectional view,

Fig. 7 is a diagram of the maximum plate holding force in kN at

Pulling test with a cross tool depends on Diameter of the sheet,

Fig. 8 shows the maximum plate holding force for different diameter tube with normal and very high lubricant use and

9 shows a diagram of the maximum plate holding force in kN as a function of the application quantity in g / m ^{2 of} a lubricant.

FIG. 1 first shows how the parameter values for the kernel depth Sk, the reduced bowl depth S k and the reduced peak height S _p k can be determined from an Abbott curve. The determination is carried out in accordance with DIN-EN-ISO 25178 for a standard-compliant measuring surface. Typically, optical essess procedures, such as confocal microscopy are applied to a height profile of a

To determine the measuring surface. From the height profile of the measuring surface, the surface portion of the profile can be determined, which cuts a surface parallel to the measuring surface in the height c or runs above the surface. If the height c of the cut surface is represented as a function of the area ratio of the cut surface to the total area, the Abbott curve is obtained, which shows the typical S-shaped course for rolled surfaces.

In order to determine the kernel depth Sk, the reduced pit depth Svk or the reduced peak height Spke, a secant D with a length of 40% is shifted in the determined Abbott curve on the Abbott curve such that the absolute value of the slope of the secant D is minimal. From the difference of the abscissa values of the intersecting points of the secant D with the abscissa at 0% area proportion as well as at 100% area proportion, the kernel depth Sk of the surface results. The reduced peak height S _P k and the reduced bowl depth S _v k corresponds to the height of a triangle which is coextensive with the tip surface AI or the groove surface A2 of the Abbott curve. The triangle of the top surface AI has as base the value Smrl, which is derived from the

Intersection of parallels to the X-axis with the Abbott curve results, the

Parallel to the X-axis through the intersection of the secant D with the abscissa at 0% - Area share runs. The triangle of the Riefenfläche or well surface A2 has the base area of the value 100% - Smr2, where Smr2 is the intersection of a parallel to the X-axis with the Abbott curve and the parallel to the X-axis through the intersection of the secant D with the Abscissa at 100% area share proceeds.

These characteristics can be used to characterize the measurement profile. It can be determined whether it is a plateau-like height profile with depressions or, for example, outweigh the peaks in the height profile of the measuring surface. In the former, the value for S _v k increases, in the latter case the value for S _P k.

As a further parameter of the surface, the surface density of the texture n _c i _m can also be determined from the optical measurement of the surfaces via the maximum number of closed void volumes n _c i _m , ie the depressions or troughs as a function of the measurement height c in percent per mm ² be determined. This gives the number of closed empty spaces per unit area (1 / mm ² ) for a given measuring height c (%). From n _c i (c) the maximum n _c i _{m is} determined. The larger n _c the finer the surface structure. Furthermore, the optical measurement can also be used to determine the closed void volume Vvcl by integrating the closed void spaces A _vc i (c) over the measured height c. The closed void volume is also a characteristic surface feature of the tapes and sheets of the invention. As already stated, the measurement of the roughness of the surface takes place optically, since in comparison to a tactile measurement it is possible to scan much faster. The optical detection takes place, for example, via interferometry or confocal microscopy, as was done in the present measurement data. According to EN ISO 25178-2, the measuring surfaces are also determined in size. The measured data were determined using square measuring surfaces with a side length of 2 mm each In order to show the differences between the conventional ribbons roughened, for example with EDT-structured rolls, and the ribbons structured according to the invention, FIG. 2 first shows a 250-fold enlarged view of a conventional strip surface. Fig. 3, however, shows a

Embodiment of a strip surface according to the invention, which was produced by an electro-chemical graining method, also in 250-fold magnification. It can be clearly seen that on the one hand the structures are finer in electrochemical graining and on the other in depressions in a plateau-like manner

Surface exist. Unlike the conventional one shown in FIG

Walzprägen be introduced into the material in the electro-chemical graining invention no peaks, but the rolled surface, here a mill-finish surface, changed or modulated only by introducing wells. It is currently believed that due to the larger closed void volumes, the cavities created during electrochemical graining can provide more lubricants for the forming process and therefore improved forming properties. It was also recognized that the higher bowl depth S _V k can obviously provide lubricants even during high surface loads during forming and thus the

Improved forming behavior.

4, a first embodiment of a method is now based on a

Schaubildes a production line for producing a strip B according to the invention shown. In the illustrated embodiment, via a reel 1, the band B, which is preferably at least partially made of an aluminum alloy type AA7xxx, type AA6xxx or, type AA5xxx or type AA3xxx, in particular AA7020, AA7021, AA7108, AA6111, AA6060, AA6014, AA6016, AA6106, AA6005C, AA6451, AA5454, AA5754, AA5182, AA5251, AA3104, AA3103 or AlMg6,

settled. The thickness of the band is preferably at least 0.8 mm, but at most 3 mm and preferably between 1.0 mm and 1.5 mm, for example when used in the automotive sector. Basically, the thickness, for example, in bands for the beverage can production also be 0.1 mm to 0.5 mm. Also With these thin tapes, the improved forming behavior becomes noticeable in the case of the beverage can production which requires maximum degrees of deformation.

The unwound with the reel 1 tape has according to the present

Embodiment preferably the state annealed "0", if it is an aluminum alloy of the type AA5xxx, AlMg6 or A3xxx or the state solution annealed and quenched "T4" in the case of an aluminum alloy of type AA6xxx or type AA7xxx. Thus, the tape is already in a particularly good formable state. However, it is also conceivable to carry out the heat treatment after the surface treatment or the introduction of the depressions and thereby to machine the surface of hard rolls. Bands and sheets for the beverage can production of the type AA5xxx or AA3xxx are also available in the condition H19 or painted in the condition H48, before they are formed. According to the embodiment, the unwound aluminum alloy strip B is fed to an optional trimming operation for trimming the side edges 2. Thereafter, as an option, the belt passes through a straightening device to remove deformations from the belt. In the device 4, the belt is subjected to a cleaning and a pickling step. As a stain come here

Mineral acids but also bases, for example based on caustic soda. As a result, the response of the belt to the electrochemical grain can be improved. Step 4 of pickling is also optional. After rinsing, the aluminum strip is subjected in step 5 to an electro-chemical graining process in which recesses are introduced into the surface. In electrochemical graining, depressions are introduced into the strip by the reaction of the electrolyte with the aluminum alloy strip, and aluminum is dissolved out at the respective sites. Preferably, the electrochemical graining is set such that a depression depth S _V k of Ι, Ομιτι - 6.0 μπι, preferably 1.5μιτι - 4.0 μπι, more preferably 2.2 μιη to 4.0 μηι is achieved. It has been shown that with these characteristics the forming behavior of the

Aluminum alloy strip is very good in a subsequent forming process. Preferably, the electrochemical graining with HNO3 (nitric acid) in a concentration of 2.5 to 20 g / l, preferably at 2.5 to 15 g / 1 with alternating current at a frequency of 50 Hz is performed. The load carrier entry is

preferably at least 200 C / dm ² , preferably at least 500 C / dm ² , in order to achieve a sufficient surface coverage with electro-chemically introduced depressions. For this purpose, at least 1 A / dm ² , preferably up to 100 A / dm ² and more are used as peak current densities. The choice of the current density and the concentration of the electrolyte depends on the production speed and can be adjusted accordingly. In particular, the reactivity and thus the production rate can also be influenced by the temperature of the electrolyte. Preferably, the electrolyte may have a temperature of at most 75 ° C. With nitric acid as the electrolyte, a preferred operating range is between room temperature and about 40 ° C, at most 50 ° C. As the electrolyte in addition to nitric acid and hydrochloric acid is suitable.

The electrochemical graining of the surface of the strip B preferably takes place on both sides in step 6. But it is also conceivable that only one side a corresponding surface structure is introduced. Subsequently, according to the exemplary embodiment shown in FIG. 5, in step 6 either a protective oil can be applied or the aluminum alloy strip surface can be passivated, for example by applying a conversion layer. These too

Processing steps are optional. Drying is preferably carried out in step 7 before, in step 8 according to the illustrated embodiment, an optional layer comprising a forming aid is applied to the strip, preferably on both sides. The forming aid is preferably a lubricant, in particular a meltable dry lubricant, for example a hotmelt. A meltable dry lubricant can as

Protective layer and lubricant handling the inventive

Aluminum alloy tapes or sheets simplify and at the same time Further improve forming properties. For example, wool wax can also be used as a dry lubricant from renewable raw materials.

As an alternative to winding the band B with the reel 11, a blank can also be cut to length over the band shears 10. In step 9, optical inspection of the tape for errors is provided so that surface defects are detected early.

As already stated, the exemplary embodiment from FIG. 4 shows a plurality of optional work steps which are carried out inline in the same production line directly one after the other. The embodiment of FIG. 4 is therefore a particularly economical variant of the method according to the invention. But it is also conceivable, only the unwinding of a tape according to step 1 and the electro-chemical graining according to step 5 with a coiling or cutting in

To combine sheet metal blanks. Basically, an electro-chemical graining of sheet metal blanks is conceivable.

FIG. 5 now shows, in a schematic sectional view, an exemplary embodiment of a strip B according to the invention, which has depressions 12 introduced into the surface on both sides and additionally an applied layer of a meltable dry lubricant 13. A corresponding band B has maximum forming properties and can also be easily stored because the surface is protected. Corresponding bands B, even with a unilaterally grained surface can also be used as outer skin parts of a motor vehicle, since the surface is maximally protected before the forming process and / or significantly supports the deformation. Made from a strip B sheets have due to the surface protection a very good handling in

Forming process on.

To the forming properties of electro-chemically grained surfaces

In order to check the plates in the forming process, drawing tests were carried out with a cross tool. Fig. 6a shows the configuration of Cross tool in a perspective sectional view. The cross tool comprises a punch 21, a hold-down 22 and a die 23. The sheet 24 to be tested has been produced either by a conventional method,

for example, roughened only by EDT rolling or only with the electro-chemical graining invention, but also in addition to EDT rolling.

During the drawing attempt in the cross tool, the plate 24 designed as a blank is deep-drawn by the punching force FST, wherein with the force FN the hold-down 22 and the die 23 are pressed onto the sheet metal blank. The cruciform punch 21 has a width of 126 mm along the axes of the cross, whereas the die has an opening width of 129.4 mm. The circular blanks 24 were made of different aluminum alloys and had different

Diameter up. The circular blanks were also with different

Surface topographies equipped to investigate the forming behavior.

The surface topographies of the comparative examples were produced by conventional methods by roll milling with an EDT textured roll or by rolling with a roll having a "finish" finish. Both the surfaces embossed with EDT rolls and the "Mill-Finish" -prepared surfaces were additionally electrochemically roughened with the method according to the invention in order to show the technical effect of roughening.

In the experiments, the punch 21 was lowered at a speed of 1.5 mm / s in the direction of sheet metal and the sheet 4 deep-drawn according to the shape of the punch. The punch force and punch travel were measured and recorded until the sample ruptured. The larger the diameter of the blank, which could be reshaped without tearing, the better the forming properties of the sheet.

Finally, both AA5xxx and AA6xxx-type aluminum alloy sheets were produced with the various surface topographies and their surface parameters using a confocal Measure microscope. The tapes of the AA5xxx aluminum alloy were in the "0" state, the aluminum alloy tapes of the AA6xxx type in the "T4" state. As AA5xxx an aluminum alloy of the type AA 5182 was used. The aluminum alloy of the AA6xxx alloy corresponded to an AA6005C aluminum alloy. Experiments VI to V4 were performed with an identical

Aluminum alloy of type AA6005C and the experiments V5 to V8 made with an identical aluminum alloy of type AA5182 to influences

different compositions within the types of alloys

excluded.

Both the roughened an EDT textured roll sheets as well as equipped with a "mill finish" surface panels were additionally subjected to an electrochemical graining and designated Runs V3 and V4. In the electrochemical graining was carried out at an HN0 ₃ concentration of 2, 5 g / 1 to 15 g / 1 a charge carrier input of 500 C / dm ² made so that homogeneously distributed wells were produced for the tests V3 and V4 .. The trough depth S _V k of the surface of the electro-chemically grained sheets was between 1.0 μπι to 6.0 μιτι All surfaces were coated with a lubricant type AVILUB Metapress.The layer thickness was 1 g / m ^2. The following table shows the four different surface variants and the associated sheet thicknesses:

Table 1

The samples were then tested in the cross tool for their forming behavior. All experiments were carried out in the state T4, that is solution-annealed and quenched. During the drawing test with a cross tool, the sheet holding force is determined at which the sheet breaks during the drawing process. It was found that with the sheet metal blanks with a "Mill Finish" surface according to VI

Holding forces of 45 kN could be achieved with a diameter of 185 mm. The roll stamped sheet metal blanks achieved 55 kN holding forces with the same diameter. It was found that an additional roughening of the EDT roll embossed surface according to experiment V4 led to identical results. The combination of "Mill-Finish" surface and subsequent electro-chemical graining according to V3 showed tearers only at plate holding forces of more than 65 kN, which is a significant improvement in forming behavior compared to EDT variants V2 and V4.

The four test variants VI to V4 were also subjected to further drawing tests with a cross tool, in which a draw film was additionally used on both sides. The drawing film was a conventional deep-drawing film made of PTFE with a thickness of 45 μηι used. In a third variant, the sheets were coated with a lot of lubricant [8 g / m ² ] before the drawing test and the drawing tests were carried out in the cross tool with a drawing film. This should suppress the effect of the different surfaces.

FIG. 8 shows the test results. It was found that when using a drawing film in the additionally roughened by electrochemical graining surfaces of the plates V3 and V4 sheet holding forces compared to the non-roughened surfaces of the sheets VI and V3 could be significantly increased. Here it was shown that the variant V4 with 520 kN at 185 mm diameter reached the highest values, followed by the variant V3 with 490 kN. Significantly lower values were achieved with 410 kN for variant V2 and 385 kN for variant VI. Without drawing film, the sheet holding forces are almost identical for all four

Experimental variants.

In the experiments with 195 mm diameter tube with double-sided drawing film using a high lubricant coating of 8 g / m ² was found

as expected, the sheets of greater wall thickness according to VI and V3 achieve higher values than the roll-formed sheets of tests V2 and V4, which are equipped with a lower wall thickness. As expected, hang

Neglecting the effects of the different surface topographies of Experiments VI to V4 due to the use of a high level of lubricant

[8 g / m ² ] the forming properties of the sheets in the drawing test with a

Cross tool only on the wall thickness of the sheets.

In Fig. 9 has now been examined how the addition of lubricant

Reformability of the different surface topographies improved. It was found that the electro-chemically grained variants show a significantly stronger effect when added to lubricants, so that it can be assumed that a larger amount of lubricants can be applied and a larger

Lubricant effect can be achieved. The sheet holding force could in Kreuzwerkzeugversuch The electrochemically grained "Mill Finish" surface according to V3 can be increased to about 85 kN The electrochemically grained EDT textured surface according to V4 allowed 80 kN and the conventional EDT textured surface according to V2 70 kN Conventional "mill-finish" surface according to VI, however, achieved in this experiment only about 55kN maximum.

Finally, both AA5xxx and AAoxxx type aluminum alloy sheets were produced with the various surface topographies and measured for their surface parameters using a confocal microscope. The tapes of the AA5xxx aluminum alloy were in the "O" state and the aluminum alloy tapes of the AA6xxx type were in the "T4" state. As AA5xxx an aluminum alloy of the type AA 5182 was used. The aluminum alloy of the AAöxxx alloy corresponded to an aluminum alloy of the AA6005C type.

Runs V2, V6 were conventionally textured using EDT rollers. Experiments VI and V5 had conventional "mill finish" surfaces As shown in Table 2, the EDT textured surfaces were electrochemically grained and evaluated as Runs V4 and V8, and the same was done for the "Mill -Finish "surfaces of both aluminum alloys performed. The electrochemically grained sheets were evaluated as Runs V3 and V7. In electrochemical graining, an HNO ₃ concentration of 4 g / 1 at a charge carrier input of 500 C / dm ² in the experiments V3 and V4 and a HN0 ₃ concentration of 5 g / 1 at a charge carrier entry of 900 C / dm ² at V7 and V8 used. The electrolyte temperature was at all

Variants between 30 ° C and 40 ° C.

In the optical measurement of the surfaces of the test sheets falls

as expected to that the sheets conventionally produced by means of EDT textured rolls V2, V6 have significantly higher values with respect to the roughness average S _a and the reduced peak height _P S k as the "Mill- The electrochemically grained embodiments V3, V4, V7 and V8, on the other hand, showed average roughness S _{a at} about the level of the EDT surface texture of Runs V2 and V6 The measured values are shown in Table 2 indicated.

In contrast to the conventional texture, however, the value for the reduced well depth S _V k in electrochemical graining increases by more than a factor of 4, here at least a factor of 5. This clearly indicates the differences in the textures.

The closed void volume V _vc i, which represents the volume for the provision of lubricant in lubricant pockets, is larger in the conventionally with EDT rollers textured strips V2, V6 with 362 and 477 mm ³ / m ² compared to 151 mm ³ / m ² or 87mm ³ / m ^{2 of} the "Mill Finish" variants VI and V5.

By contrast, the electrochemically grained embodiments V3, V4 and V7 and V8 according to the invention show a closed void volume V _vc of at least 500 mm ³ / m ² . The important for the intake of lubricant closed

Void volume can be increased significantly more than 10% in the bands according to the invention, which have undergone an electrochemical graining step.

The bulk density of the structure with values of the inventive variants V3, V4, V7 and V8 of more than 80 per mm ² , preferably between 100 per mm ² and 150 per mm ² , by significantly more than 25% greater than conventional EDT-textured Belt surfaces of Comparative Experiments V2 and V6.

The different topography of the embodiments of the invention, which on the basis of the different values of the reduced bowl depth S _V k, the closed void volume Vvci and the surface density of the surface is made responsible for the improvement of Umformverhaltens.

As a result, it can also be a formed sheet, such as a

Door inner panel or a skin part of a motor vehicle are provided, which undergoes high degrees of deformation until it is made to the final shape. With the method according to the invention and with the strip or sheet according to the invention, an even wider field of application for aluminum alloys in the field of motor vehicles can thus be opened, since the larger degrees of deformation allow further possible applications.

Table 2

Since electrochemical graining is also used in the production of printing plate supports, several EC-grained litho sheets of the Alxxx alloy were measured and the measurement results summarized as experiment V13. Although litho sheets are roughened electrochemically, the roughening serves a different purpose. Litho tapes and sheets are also fed to any forming, but coated after electrochemical thawing with a photosensitive layer. The roughening should be as uniform as possible enable. Litho sheets and tapes are therefore within the meaning of the present

Invention not prepared for forming.

Therefore, the surfaces optimized according to the invention for forming show marked differences to lithoplates, such as those in the topography

summarized measurement results of various measured litho sheets, shown in Comparative Example V13 show. Litho sheets generally have not only significantly lower average roughness values S _a , but also have a significantly lower reduced bowl depth S _V k. The mean bowl density n _c i _m , however, is slightly higher than the electrochemically grained, form-optimized surfaces of the sheets V4 according to the invention , V3, V7 and V8.

In addition, electro-chemically grained surfaces of an embodiment according to the invention were investigated in the case of different degrees of deformation in the cross tool in comparison to surfaces of conventional EDT rolls of textured sheets of an AA6xxx alloy. It was found that the surfaces differ markedly in the area of slightly reshaped areas, as shown in FIGS. 2 and 3. However, after the forming process, for example in the hold-down area and in the die radius of the crusher tool, ie in heavily deformed areas, the surfaces showed almost identical characteristics. Thus, despite providing improved forming behavior, it is expected that the different initial topography will not affect the surface appearance. Aluminum alloy ribbons and sheets according to the invention are therefore

for example, very well suited for the provision of body parts of a body of a motor vehicle.

Claims

claims

1. strip or sheet of an aluminum alloy with an at least

partially provided on one or both sides, prepared for a forming process surface structure,

characterized in that

the belt or sheet has on one or both sides a surface with recesses produced using an electrochemical graining method as lubricant pockets, wherein the at least one belt or

Sheet surface has a reduced bowl depth S _V k of 1.0 μη to 6.0 μιτι.

2. strip or sheet according to claim 1,

characterized in that

the band or sheet at least partially of an aluminum alloy of the type AA7xxx, AA6xxx, AA5xxx or AA3xxx, in particular AA7020, AA7021, AA7108, AA6111, AA6060, AA6014, AA6016, AA6005C, AA6451, AA5454, AA5754, AA5182, AA5251, AlMg6, AA3104 and AA3103 exists.

3. strip or sheet according to claim 1 or 2,

characterized in that

at least one band or sheet surface has a reduced bowl depth S _V k of preferably 1.5 μηι to 4.0 μηα, more preferably 2.2 μπι to 4.0 μπι.

4. strip or sheet according to one of claims 1 to 3,

characterized in that

the sheet or strip is annealed ("0"), solution annealed and quenched ("T4") or H19 or H48. Band or sheet according to one of claims 1 to 4,

characterized in that

the strip or sheet has a passivation layer applied after electrochemical graining.

Tape or sheet according to any one of claims 1 to 5,

characterized in that

on the surface of the band or sheet at least partially a lubricant or a dry lubricant is provided.

Tape or sheet according to any one of claims 1 to 6,

characterized in that

the average roughness of the surface S _a 0.7 μιη to 1.5 μιτι, preferably 0.7 μηι to 1.3 μη or preferably 0.8 μιη to 1.2 μπι.

Process for producing a strip or sheet with one for one

Forming process prepared one- or two-sided surface structure, in particular a strip or sheet according to claim 1 to 7,

characterized in that

a hot-rolled and / or cold-rolled strip or sheet after electro-chemical graining (5) is subjected, wherein at least partially homogeneously distributed depressions are introduced as lubricant pockets in the band or sheet by the electrochemical graining, wherein in the band or Sheet surface depressions are introduced with a reduced bowl depth S _v k of 1.0 μπι to 6.0 μιη by the electro-chemical graining.

Method for producing a tape according to claim 8,

characterized in that

in the strip or sheet surface depressions with a reduced

Dump depth Sk of 1.5 μπι to 4.0 μιη or preferably 2.2 μπι to 4.0 μιη be introduced by the electro-chemical graining. A method of manufacturing a tape according to claim 8 or 9,

characterized in that

the strip is subjected to a cleaning step (4) prior to the electrochemical graining, in which by alkaline or acid pickling the

Surface cleaned and a homogeneous material removal is made.

Method for producing a strip according to one of Claims 8 to 10, characterized in that

the electro-chemical graining (5) using HN0 ₃ in one

Concentration of 2.5 to 20 g / 1 with a charge carrier entry of

at least 200 C / dm ² , preferably at least 500 C / dm ^{2 is} performed.

Method for producing a strip according to one of Claims 8 to 11, characterized in that

after the electrochemical graining a passivation of the surface, preferably by applying a conversion layer (6) is performed and / or a protective layer comprising a meltable forming aid is applied to the strip surface.

Method for producing a strip according to one of Claims 8 to 12, characterized in that

a strip (B) is electrochemically grained after soft annealing ("O" state), after solution heat treatment and quenching ("T4" state) or hard as rolled in the H19 state.

Method for producing a strip according to one of Claims 8 to 13, characterized in that

the process steps are carried out inline in a production line:

Unwinding the tape from a reel (1),

Cleaning and pickling of the band (4), - Electro-chemical graining of the band (5) and

- at least in a sectoral order of a forming aid and / or a

Conversion layer (6) or alternatively a protective oil.

Method for producing a strip according to one of Claims 8 to 14, characterized in that

Subsequently, after the application of the conversion layer, a protective layer comprising a meltable forming aid (8) is applied.

Formed sheet metal of a motor vehicle made of a sheet metal according to one of claims 1 to 7.