Composite material and method for producing said composite material

Abstract

The invention relates to a composite material and to a method for producing said composite material, comprising a carrier layer made of an aluminum wrought alloy and an outer solder layer which is provided on one or both faces of the carrier layer and which is made of an aluminum solder alloy, wherein the solder layer has partly exposed silicon particles (1a) on the surface (O) thereof, said silicon particles forming a first proportion of the entire area of the surface (O) of the solder layer. In order to ensure a soldering capability without flux in a stable manner, the solder layer has a rolled surface (O) and the aluminum solder alloy thereof has at least 0.1 wt.% of bismuth (Bi), wherein the first proportion is greater than 2.5%.

Description

[0001] Composite material and process for producing this composite material

[0002] Technical area

[0003] The invention relates to a method for producing a composite material and to this composite material, in particular clad sheet or clad strip, with a carrier layer made of a wrought aluminum alloy and with an outer solder layer made of an aluminum solder alloy provided on one or both flat sides of the carrier layer, wherein the solder layer has partially exposed silicon particles on its surface, which form a first area portion of the total area of ​​the surface of the solder layer.

[0004] State of the art

[0005] For flux-free CAB brazing (controlled atmosphere brazing), EP2844466B1 discloses a composite material with a carrier layer or core layer made of an AA 3003 wrought aluminum alloy and a brazing layer made of an AISi12 aluminum brazing alloy. This brazing layer has partially exposed silicon particles on its surface. To create these silicon particles on the surface, the brazing layer is alkaline-pickled after cold rolling the finished composite. However, this also significantly roughens the rolled surface of the brazing layer.

[0006] The disadvantage is that these comparatively abrasive silicon particles on the surface, in combination with the increased surface roughness, lead to increased tool wear on a sheet metal processing tool, for example a punching tool, with which the composite material is prepared for soldering in the dimensions.

[0007] Description of the invention The invention therefore has the object of modifying a composite material of the type described at the outset in such a way that it can be subjected to mechanical separation processes with low wear despite being flux-free solderable.

[0008] The invention solves the problem with regard to the composite material by the features of claim 1.

[0009] By having a rolled surface for the solder layer, it can be ensured that the silicon particles partially exposed on the surface protrude at most up to the reference plane formed by the surrounding aluminum matrix. The abrasive effect of the silicon particles on a cutting tool is therefore reduced accordingly, particularly because such a rolled surface can also be characterized by correspondingly reduced roughness parameters. However, the composite material according to the invention (for example in the form of a sheet or strip) can not only be characterized by low-wear processing or further processing using mechanical cutting methods, but also retains its flux-free solderability. This is achieved by having a rolled surface for the solder layer and an aluminum solder alloy containing at least 0.1 wt.% bismuth (Bi), with the first area fraction being greater than 2.5%.This results in a flux-free solderable composite material that can be prepared for soldering in the same way as other composite materials that cannot be soldered flux-free.

[0010] For example, a flux-free soldering operation may be sufficient if the initial surface area is less than 25%. Despite exposed silicon particles, tool wear can be kept to a minimum – even more so if the initial surface area is less than 20% or, for example, less than 12%.

[0011] Preferably, the first area percentage is in the range of 3 to 10%. In particular, starting at a lower limit of 3%, the brazing process and thus the brazing result can be significantly improved. Up to the upper limit of 10%, tool wear can remain comparatively low, which minimizes maintenance requirements for the tools that further process the sheet or strip.

[0012] If the aluminum brazing alloy contains up to 0.40 wt.% bismuth (Bi), the wettability between the molten brazing material and the material to be joined can be significantly improved. This, in turn, allows for slightly larger gaps, which can, however, be of considerable importance for the resulting brazing result.

[0013] Low-wear tool processing of the composite material can be recognized, for example, by the fact that the rolled surface (0) of the brazing layer has a gloss value according to DIN EN ISO 2813:2014 of at least 50 GU, measured at an angle of 60° and perpendicular to the rolling direction. Preferably, the gloss value according to DIN EN ISO 2813:2014 is greater than 60 GU. For example, a measuring device called "micro-TRI-gloss S" from BYK-Gardner GmbH can be used for this measurement.

[0014] The rolled surface can contain silicon particles pressed into the aluminum matrix of the solder layer, which are anchored in the aluminum matrix by the rolling process. These pressed silicon particles lead to an enrichment of silicon on the surface of the solder layer, which in turn improves the melting properties during soldering. This ensures that the composite material remains flux-free during soldering, even after forming with comparatively high degrees of deformation, opening up universal applicability for the composite material.

[0015] Tool wear during further processing of the sheet or strip can be further reduced if the aluminum matrix of the solder layer on the rolled surface forms a reference profile on the roughness profile of the rolled surface, whereby the silicon particles partially exposed on the rolled surface do not protrude from this reference profile. The silicon particles are preferably located in depressions on the rolled surface. For example, each depression runs at least partially, in particular completely, around one or more silicon particles. This interrupts the flat course of the oxide layer over the surface of the aluminum matrix and makes it easier to break it up during flux-free soldering. This can further simplify the handling of the composite material during soldering, especially when soldering without flux.

[0016] The aluminum brazing alloy preferably contains from 6.8 to 13 wt.% silicon (Si), from 0.1 to 0.40 wt.% bismuth (Bi), and from 0.10 to 0.40 wt.% magnesium (Mg). The aluminum brazing alloy preferably contains from 8.5 to 12 wt.% silicon (Si). The aluminum brazing alloy preferably contains from 0.1 to 0.3 wt.% bismuth (Bi). The aluminum brazing alloy preferably contains from 0.2 to 0.35 wt.% magnesium (Mg).

[0017] Optionally individually or in combination, the aluminum solder alloy can comprise: up to 1.2%, in particular up to 0.3% by weight of zinc (Zn) up to 0.6%, in particular up to 0.5% by weight of iron (Fe) up to 0.2% by weight of titanium (Ti) up to 0.2%, in particular up to 0.1% by weight of manganese (Mn) up to 0.2%, in particular up to 0.1% by weight of copper (Cu) up to 0.03%, in particular up to 0.02% by weight of strontium (Sr) up to 0.2%, in particular up to 0.1% by weight of tin (Sn) up to 0.2%, in particular up to 0.1% by weight of antimony (Sb)

[0018] The remainder of the aluminum solder alloy consists of aluminum and unavoidable impurities due to manufacturing, each containing a maximum of 0.05 wt.% and a total of a maximum of 0.15 wt.%.

[0019] Preferably, the ratio of magnesium (Mg) to bismuth (Bi) by weight in the aluminum solder alloy is less than or equal to 4. This can, among other things, prevent unwanted deposits in the soldering furnace. A ratio in the range of 0.5 to 2.7 can have a particularly beneficial effect on the breakup of the aluminum oxide layer during soldering. In particular, this range can also ensure that the solder is sufficiently flowable.

[0020] The wrought aluminum alloy preferably contains from 0 to 1.6 wt.% manganese (Mn), from 0 to 0.90 wt.% copper (Cu), and from 0.05 to 1.0 wt.% silicon (Si). The wrought aluminum alloy can preferably contain from 0.8 to 1.4 wt.% manganese (Mn). The wrought aluminum alloy can preferably contain from 0.05 to 0.6 wt.% copper (Cu). The wrought aluminum alloy can preferably contain from 0.05 to 0.6 wt.% silicon (Si).

[0021] Optionally, individually or in combination, the wrought aluminum alloy may comprise: up to 0.60, in particular up to 0.45 wt.% iron (Fe) up to 0.8, in particular up to 0.6, wt.% magnesium (Mg) up to 0.15, in particular up to 0.10, wt.% zinc (Zn) up to 0.20 wt.% titanium (Ti)

[0022] The remainder of the wrought aluminum alloy consists of aluminum and unavoidable impurities due to the manufacturing process, each containing a maximum of 0.05 wt.% and a total of a maximum of 0.15 wt.%.

[0023] For example, the wrought aluminum alloy for achieving the advantages of the invention is an aluminum alloy of the type EN AW-1xxx, EN AW-3xxx, EN AW-5xxx or EN AW-6xxx.

[0024] The invention solves the problem with regard to the method for producing the composite material by the features of claim 13.

[0025] As is known, the composite material can be reduced to its final thickness by cold rolling. This cold rolling of the sheet or strip (also referred to as sheet metal strip or metal strip) can be used to create a rolled surface on the solder layer. According to the invention, an increase in the first surface area of ​​silicon particles exposed on the surface of the solder layer is achieved by subjecting the composite material to cold rolling with at least one cold rolling pass. Before a cold rolling pass of the at least one cold rolling pass, the surface of the solder layer is subjected to a pickling treatment with a pickling agent, in particular an alkaline one. In this way, a surface comprising silicon particles with nevertheless low roughness can be reproducibly created.

[0026] For example, the pickling treatment can be carried out between two cold rolling passes of the cold rolling if the cold rolling comprises several cold rolling passes.

[0027] A comparatively high first area fraction of silicon particles exposed on the surface of the solder layer can be achieved if cold rolling takes place immediately before the last cold rolling pass.

[0028] Preferably, the pickling treatment can be carried out between two cold rolling passes of the cold rolling process and / or immediately before the last cold rolling pass of the cold rolling process in order to make the process more user-friendly.

[0029] Preferably, a stain with a pH value in the range of 11.0 to 14.0 is used. A stain with a pH value in the range of 12 to 13.5 may be sufficient for the desired initial surface area.

[0030] The pickling time should preferably be in the range of 15 to 300 seconds to expose a sufficiently high number of silicon particles on the surface while still maintaining sufficient bonding to the aluminum matrix. A pickling time in the range of 30 to 90 seconds may be considered sufficient.

[0031] For example, if the pickling depth is in the range of 1 to 7 pm, a sufficiently high number of silicon particles can be exposed by removing the aluminum matrix surrounding the silicon particles.

[0032] The alkaline pickling solution preferably contains a sodium hydroxide solution with a concentration in the range of 8 to 16% by weight to ensure sufficient pickling action. The composite material according to the invention produced by the process according to the invention is particularly suitable for flux-free, thermal joining processes, in particular soldering, preferably under a protective gas atmosphere. In particular, the joining process can also take place under atmospheric pressure according to DIN ISO 2533 (1013.25 hPa).

[0033] Short description of the drawings

[0034] The figures show the subject matter of the invention in more detail.

[0035] Fig. 1 a is a plan view of a first composite material A without pickling treatment, Fig. 1 b is a plan view of a second composite material B with a pickling treatment after cold rolling,

[0036] Fig. 1 c is a plan view of a third composite material C with a pickling treatment before the last cold rolling pass,

[0037] Fig. 1 d is a plan view of a fourth composite material D with a pickling treatment before the last cold rolling pass,

[0038] Fig. 1 e is a plan view of a fifth composite material E with a pickling treatment before the last cold rolling pass,

[0039] Fig. 1f is a plan view of a sixth composite material F with a pickling treatment before the last cold rolling pass,

[0040] Figures 2a to 2f show representations of a respective first surface portion of exposed silicon particles of the composite materials A, B, C, D, E and F of Figures 1a to 1f,

[0041] Fig. 3a is an enlarged plan view of a silicon particle of Fig. 1 c and

[0042] Fig. 3b is a sectional view along lines III-III of Fig. 3a.

[0043] Ways to implement the invention

[0044] Figures 1 a to 1 f show secondary electron micrographs of the surface of the respective composite material measured with a Zeiss type EVO 40 scanning electron microscope with an accelerating voltage of 15 kV and a working distance of 10.5 mm.

[0045] Figures 2a to 2f are a silicon mapping with a resolution of 512 x 384 pixels, composed of 25 individual images. From these figures 2a to 2f, the first surface area of ​​the partially exposed silicon particles was evaluated using the Olympus Stream software, phase analysis with a threshold of 160 for figures 2a to 2d and a threshold of 210 for figures 2e and 2f in the inverted view.

[0046] To demonstrate the achieved effects, six AF composite materials were produced in sheet form, although a strip (often referred to as sheet metal strip) is also conceivable. They were produced by roll-bonding the flat sides of a carrier layer (often also called the core layer) with a brazing layer. The AF composite materials represent brazing material. The material thickness after roll-bonding is 1.5 mm (millimeters) for composite material A, 0.5 mm for composite materials B and C, and 1.0 mm for composite materials D to F.

[0047] The carrier layers of the composite materials A to F each comprise an aluminium wrought alloy with and the remainder being aluminum and unavoidable impurities due to manufacturing, each with a maximum of 0.05 wt.% and a total of 0.15 wt.%. The brazing layers of composite materials A to F comprise an aluminum brazing alloy with and the remainder being aluminium and unavoidable impurities due to manufacturing, each with a maximum of 0.05 wt% and a total of no more than 0.15 wt%.

[0048] Composite A:

[0049] Composite A comprises a carrier layer made of an aluminium alloy of type EN AW-3xxx and a brazing layer according to Table 1, which corresponds to type EN AW-4xxx.

[0050] Fig. 1 a shows a secondary electron micrograph of the surface of composite material A measured with a Zeiss type EVO 40 scanning electron microscope with an accelerating voltage of 15 kV and a working distance of 10.5 mm.

[0051] According to Fig. 1a, a small number of silicon particles 1a are exposed on the surface of composite material A, as can be seen as light gray, rounded areas surrounded by a black border in Fig. 1a. The silicon particles 1a are surrounded by the aluminum matrix 2. Some silicon particles 1b shine through the surface but are not exposed on the surface.

[0052] Fig. 2a illustrates the first area fraction of the partially exposed silicon particles 1 a of the composite material A. The first area fraction is 0.4%.

[0053] Composite B: In contrast to composite A, composite B was subjected to an alkaline pickling treatment with a pH of 12.9, containing a sodium hydroxide solution with a concentration of 12 wt%, and a duration of 75 s (seconds) after the last cold rolling pass in the cold rolling of the composite to its final thickness.

[0054] Fig. 1 b shows a micrograph of the surface of composite B. A high number of silicon particles 1 a are exposed on the surface of composite A - as can be seen from the bright areas in Fig. 1 b.

[0055] Fig. 2b illustrates the first area fraction of the exposed silicon particles 1 a of the composite material B. The first area fraction is 24.3%.

[0056] Composite material C (according to the invention):

[0057] In the case of composite material C according to the invention, the alkaline pickling attack on the surface of the solder layer described for composite material B was carried out - in the exemplary embodiment immediately - before the last cold rolling pass in the cold rolling of the composite material to its final thickness.

[0058] Fig. 1 c shows a micrograph of the surface of the composite material C according to the invention. The number of silicon particles 1 a exposed on the surface of the composite material C, as seen as light gray, rounded areas surrounded by a black border in Fig. 1 c, is increased compared to Fig. 1 a of the composite material A. However, in relation to the composite material B, this number is significantly lower.

[0059] Fig. 2c illustrates the first area fraction of the partially exposed silicon particles 1 a of the composite material C. The first area fraction is 7.2%.

[0060] Composite material D (according to the invention):

[0061] The composite material D according to the invention was also subjected to an alkaline pickling attack on the surface of the solder layer—in the exemplary embodiment, immediately before the last cold rolling pass in the cold rolling of the composite material to its final thickness. Fig. 1d shows a micrograph of the surface of the composite material D according to the invention. The number of silicon particles 1a exposed on the surface of the composite material D, as can be seen as light gray, rounded areas surrounded by a black border in Fig. 1d, is increased compared to Fig. 1a of the composite material A. In relation to the composite material C, this number is similar.

[0062] Fig. 2d illustrates the first area fraction of the partially exposed silicon particles 1 a of the composite material C. The first area fraction is 4.2%.

[0063] Composite material E (according to the invention):

[0064] The composite material E according to the invention represents a solder material which has a carrier layer made of an aluminum alloy of type 6xxx and a solder layer of type 4xxx.

[0065] Composite E was also subjected to an alkaline pickling attack on the surface of the solder layer—in the exemplary embodiment, immediately before the last cold rolling pass in the cold rolling of the composite to its final thickness. Fig. 1e shows a micrograph of the surface of the composite E according to the invention. The number of silicon particles 1a exposed on the surface of composite E, as can be seen as light gray, rounded areas surrounded by a black border in Fig. 1e, is increased compared to Fig. 1a of composite A and is similar to composites C and D, but significantly lower than in composite B.

[0066] Fig. 2e illustrates the first area fraction of the partially exposed silicon particles 1 a of the composite material E. The first area fraction is 7%.

[0067] Composite material F (according to the invention):

[0068] The composite material F according to the invention represents a solder material which has a carrier layer made of an aluminum alloy of type 1xxx and a solder layer of type 4xxx.

[0069] Composite F was also subjected to an alkaline pickling attack on the surface of the solder layer—in the exemplary embodiment, immediately before the last cold rolling pass in the cold rolling of the composite to its final thickness. Fig. 1f shows a micrograph of the surface of the composite F according to the invention. The number of silicon particles 1a exposed on the surface of composite F, as can be seen as light gray, rounded areas surrounded by a black border in Fig. 1f, is increased compared to Fig. 1a of composite A and is similar to composites C, D, and E, but significantly lower than in composite B.

[0070] Fig. 2f illustrates the first area fraction of the partially exposed silicon particles 1 a of the composite material F. The first area fraction is 8%.

[0071] Sheet metal parts were separated from the sheet-like composite materials A to F using a mechanical separation process, namely punching. Furthermore, the composite materials A to F were brazed together using a flux-free CAB brazing process, i.e., by flux-free brazing with another aluminum material of type 3003 under atmospheric pressure according to DIN ISO 2533 (1013.25 hPa).

[0072] Composite materials A to F are characterized by the following properties:

[0073] Table 1 : Measurement data

[0074] As can be seen from Table 1, composite material A cannot be joined using a flux-free CAB brazing process. Although flux-free brazing is possible with composite material B, the disadvantage of this composite material B with its pickled surface and protruding silicon particles 1 a is high flank wear on a cutting or forming tool used to cut or shape composite material B before joining. The surface topography has a significant influence on the friction conditions during further processing of the brazing material and subsequently also on the springback during forming. High springback after forming leads to a not insignificantly poor dimensional tolerance, which causes problems with the minimum gap width during brazing. High surface roughness also has a negative effect on the max.The formability of the materials is impaired because the lubricant can no longer distribute evenly in the contact zone of the rough surface. Flank wear is primarily caused by abrasion of the cutting edges on the exposed Si particles of the brazing layer, which protrude significantly from the surface of the aluminum matrix due to pickling.

[0075] In addition, composite B also exhibits a gloss value of 25 GU, which is lower than the other composites, measured at an angle of 60° and perpendicular to the rolling direction. This also demonstrates the negative surface properties of composite B.

[0076] In the composite materials C, D, E, and F according to the invention, a different surface can be seen. Here, Si particles protruding from the surface contour on the aluminum matrix are not visible - as can be seen in Fig. 1c to 1f. The silicon particles 1a are pressed into the aluminum matrix of the solder layer due to the rolling, namely cold rolling, and thus do not protrude from a reference profile OB on the roughness profile of the rolled surface 0 of the solder layer. This reference profile OB is formed by the aluminum matrix 2 of the solder layer on the rolled surface, as can be seen in Fig. 3b. The reference profile OB is formed by the highest peak on the roughness profile of the aluminum matrix 2. For example, the maximum roughness depth Rt and Rmax of the roughness profile are shown for the sake of clarity.This significantly reduces the flank wear of tools and results in better dimensional accuracy of the formed parts, which is required for flux-free soldering.

[0077] Also visible in the silicon particles 1a is a depression 3 on the surface 0 of the solder layer (see Fig. 1c), which at least partially surrounds the indented silicon particles 1a. The depression 3 is elongated in the rolling direction, as can be seen, for example, in the eye-shaped boundary contour in Fig. 1c. The silicon particles 1a are located in this depression 3.

[0078] These silicon particles, which are pressed in as shown in Fig. 1 c to 1 f, have little to no influence on the gloss of the surface. Therefore, in the case of composite materials

[0079] C, D, E and F can be expected to have a nearly equally high gloss value, as is the case with composite A - which can also be seen in Table 1. In direct comparison with composite B, composites C,

[0080] D, E and F, however, have significantly higher gloss values. Table 1 clearly shows this difference in the gloss values ​​between the non-pickling composite A, the composite B pickled without subsequent cold forming, and the composites C, D, E and F pickled before the last cold rolling step. This is also very clearly visible in Figures 1a, 1b and 1c to 1f. It can be seen that the initial area fraction of exposed silicon particles is considerably increased by pickling before the last cold rolling - this is in comparison to a material without pickling treatment, which also shows indented silicon particles on the surface, but in much smaller numbers.

[0081] The pickling process dissolves the aluminum matrix surrounding the silicon particles, leaving the silicon particles on the surface, where they now detach from the matrix.

[0082] The amount of material removed from the aluminum matrix by pickling depends, among other things, on the temperature, duration, and concentration of the pickling solution, and can therefore be easily adjusted with great flexibility. Following the pickling process, the cold rolling deformation of the material presses the silicon particles protruding from the surface into the aluminum matrix due to their greater strength compared to the aluminum matrix. This increases the number of silicon particles on the surface and enriches the surface of the solder material with silicon. This enrichment, which cannot be achieved through a rolling process without additional pickling treatment, improves soldering when used with fluxes and allows application in flux-free soldering with the same deformation behavior of the material.

[0083] The flux-free solderable composite materials C, D, E and F according to the invention can therefore be subjected to low-wear mechanical separation processes, for example punching, and do not require any special measures for geometric preparation before a joining process.

[0084] In general, it is noted that "in particular" can be translated into English as "more particularly." A feature preceded by "in particular" is to be considered an optional feature that can be omitted and thus does not constitute a limitation, for example, of the claims. The same applies to "vorzugsweise," translated into English as "preferably."

Claims

Patent claims:

1. Composite material, in particular clad sheet or clad strip, with a carrier layer of an aluminium wrought alloy and with an external solder layer of an aluminium solder alloy provided on one or both flat sides of the carrier layer, wherein the solder layer has partially exposed silicon particles (1a) on its surface (0) which form a first area fraction of the total area of ​​the surface (0) of the solder layer, characterized in that the solder layer has a rolled surface (0) and its aluminium solder alloy has at least 0.1 wt.% bismuth (Bi), wherein the first area fraction is greater than 2.5%.

2. Composite material according to claim 1, characterized in that the first area fraction is less than 25%, in particular less than 20% or less than 12%.

3. Composite material according to claim 1 or 2, characterized in that the first area fraction is in the range of 3 to 10%.

4. Composite material according to claim 1, 2 or 3, characterized in that the aluminium solder alloy contains up to 0.40 wt.% bismuth (Bi).

5. Composite material according to one of claims 1 to 4, characterized in that the rolled surface (0) of the solder layer has a gloss value according to DIN EN ISO 2813:2014 of at least 50 GU, preferably greater than 60 GU, measured at an angle of 60° and transverse to the rolling direction.

6. Composite material according to one of claims 1 to 5, characterized in that the rolled surface (0) has silicon particles (1 a) pressed into an aluminium matrix of the solder layer.

7. Composite material according to one of claims 1 to 6, characterized in that the aluminium matrix of the solder layer forms a reference profile (OB) on the roughness profile of the rolled surface (0) on the rolled surface (0), wherein the Silicon particles (1a) that are partially exposed on the rolled surface (0) do not protrude beyond this reference profile (OB).

8. Composite material according to one of claims 1 to 7, characterized in that the silicon particles (1 a) are located in depressions (3) on the rolled surface (0).

9. Composite material according to any one of claims 1 to 8, characterized in that the aluminum solder alloy contains 6.8 to 13, in particular 8.5 to 12, wt.% silicon (Si), 0.1 to 0.40, in particular 0.1 to 0.3, wt.% bismuth (Bi), 0.10 to 0.40, in particular 0.2 to 0.35, wt.% magnesium (Mg), optionally individually or in combination: up to 1.2, in particular up to 0.3, wt.% zinc (Zn), up to 0.6, in particular up to 0.5, wt.% iron (Fe), up to 0.2, wt.% titanium (Ti), up to 0.2, in particular up to 0.1, wt.% manganese (Mn), up to 0.2, in particular up to 0.1, wt.% copper (Cu), up to 0.03%, in particular up to 0.02%, wt.% strontium (Sr) 0.2, in particular up to 0.1, wt.% tin (Sn) up to 0.2, in particular up to 0.1, wt.% antimony (Sb) and as a remainder aluminium as well as impurities unavoidable due to the manufacturing process with each a maximum of 0.05 wt.% and a total of no more than 0.15 wt.%.

10. Composite material according to one of claims 1 to 9, characterized in that the ratio of the wt.% of magnesium (Mg) to bismuth (Bi) in the aluminium solder alloy is less than or equal to 4, in particular in the range of 0.5 to 2.

7.

11. Composite material according to one of claims 1 to 10, characterized in that the wrought aluminum alloy contains 0 to 1.6 wt.% manganese (Mn), in particular 0.8 to 1.4 wt.% copper (Cu), and 0 to 0.90 wt.% copper (Cu). from 0.05 to 1.0 wt.% silicon (Si), optionally individually or in combination: up to 0.60 wt.% iron (Fe), up to 0.8 wt.% magnesium (Mg), up to 0.15 wt.% zinc (Zn), up to 0.20 wt.% titanium (Ti), and as a remainder aluminium, as well as impurities unavoidable due to the manufacturing process, each with a maximum of 0.05 wt.% and a total of no more than 0.15 wt.%.

12. Composite material according to one of claims 1 to 11, characterized in that the wrought aluminum alloy is of type EN AW-1xxx, EN AW-3xxx, EN AW-5xxx or EN AW-6xxx.

13. Method for producing the composite material according to one of claims 1 to 12, wherein the composite material is subjected to cold rolling with at least one cold rolling pass, wherein, prior to one cold rolling pass of the at least one cold rolling pass, the surface (O) of the solder layer is subjected to pickling treatment with a pickling agent, in particular an alkaline one.

14. Method according to claim 13, characterized in that the pickling treatment takes place between two cold rolling passes of the cold rolling process and / or immediately before the last cold rolling pass of the cold rolling process.

15. Method according to claim 13 or 14, characterized in that a pickling solution with a pH value in the range of 11.0 to 14.0, in particular in the range of 12 to 13.5, is used and / or that the pickling time is in the range of 15 to 300, in particular from 30 to 90, seconds.

16. Method according to one of claims 13 to 15, characterized in that the pickling depth is in the range of 1 to 7 pm.

17. Method according to one of claims 13 to 16, characterized in that the alkaline pickling solution comprises a sodium hydroxide solution with a concentration in the range of 8 to 16% by weight.

18. Use of a composite material according to one of claims 1 to 12, produced in particular according to the method according to one of claims 13 to 17, for a flux-free thermal joining process, in particular soldering, preferably under protective gas, in particular under atmospheric pressure.

Images