Composite material and method for producing said composite material

1 . A composite material comprising:

a support layer composed of a wrought aluminum alloy, and

an external solder layer provided on one or both flat sides of the support layer, wherein the external solder layer is composed of an aluminum solder alloy containing at least 0.1 wt % bismuth (Bi) and the solder layer has a rolled surface,

wherein the solder layer has partially exposed silicon particles on its surface, which constitute a first area fraction of a total area of the surface of the solder layer, wherein the first area fraction is greater than 2.5%.

2 . The composite material according to claim 1 , wherein the first area fraction is less than 25%.

3 . The composite material according to claim 1 , wherein the first area fraction is in a range from 3 to 10%.

4 . The composite material according to claim 1 , wherein the aluminum solder alloy contains up to 0.40 wt % bismuth (Bi).

5 . The composite material according to claim 1 , wherein the rolled surface of the solder layer has a gloss value according to DIN EN ISO 2813:2014 of at least 50 GU measured at an angle of 60° and transversely to a rolling direction.

6 . The composite material according to claim 1 , wherein the rolled surface has the silicon particles pressed into an aluminum matrix of the solder layer.

7 . The composite material according to claim 6 , wherein the aluminum matrix of the solder layer on the rolled surface forms a reference profile of a roughness profile of the rolled surface, wherein the silicon particles that are partially exposed on the rolled surface do not protrude from the reference profile.

8 . The composite material according to claim 1 , wherein the silicon particles are situated in depressions in the rolled surface.

9 . The composite material according to claim 1 , wherein the aluminum solder alloy contains

from 6.8 to 13

wt % silicon (Si),

from 0.1 to 0.40

wt % bismuth (Bi),

from 0.10 to 0.40

wt % magnesium (Mg),

optionally—individually or in combination:

up to 1.2

wt % zinc (Zn)

up to 0.6

wt % iron (Fe)

up to 0.2

wt % titanium (Ti)

up to 0.2,

wt % manganese (Mn)

up to 0.2

wt % copper (Cu)

up to 0.03%

wt % strontium (Sr)

up to 0.2

wt % tin (Sn)

up to 0.2

wt % antimony (Sb)

as well as residual aluminum and inevitable production-related impurities, each totaling at most 0.05 wt % and together totaling at most 0.15 wt %.

10 . The composite material according to claim 1 , wherein a ratio in wt % of magnesium (Mg) to bismuth (Bi) in the aluminum solder alloy is less than or equal to 4.

11 . The composite material according to claim 1 , wherein the wrought aluminum alloy contains

from 0 to 1.6

wt % manganese (Mn),

from 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)

as well as residual aluminum and inevitable production-related impurities, each totaling at most 0.05 wt % and together totaling at most 0.15 wt %.

12 . The composite material according to claim 1 , wherein the wrought aluminum alloy is of type EN AW-1xxx, EN AW-3xxx, EN AW-5xxx, or EN AW-6xxx.

13 . The composite material according to claim 1 , wherein the composite material is plated sheet metal or a plated strip.

14 . A method for producing the composite material according to claim 1 , comprising:

subjecting the composite material to cold rolling with at least one cold rolling pass, wherein 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.

15 . The method according to claim 14 , wherein the pickling treatment takes place between two cold rolling passes of the cold rolling process and/or immediately before a last cold rolling pass of the cold rolling process.

16 . The method according to claim 14 , wherein the pickling agent has a pH value in a range from 11.0 to 14.0 and/or a duration of the pickling treatment is in a range from 15 to 300 seconds.

17 . The method according to claim 14 , wherein a pickling depth of the pickling treatment is in a range from 1 to 7 μm.

18 . The method according to claim 14 , wherein the pickling agent is an alkaline pickling agent.

19 . A method of using the composite material according to claim 1 , comprising using the composite material in a flux-free thermal joining method by soldering under a protective gas at atmospheric pressure.

20 . The method according to claim 18 , wherein the alkaline pickling agent contains a sodium hydroxide solution with a concentration in a range from 8 to 16 wt %.