Aluminium alloy sheet product or extruded product for fluxless brazing

1. An aluminium alloy brazing sheet product or extruded product for fluxless brazing, comprising:

an aluminium alloy core having on at least one face an aluminium filler clad layer containing 4% to 15% by weight of Si, the aluminium filler clad layer having an inner-surface and an outer-surface,

wherein the inner-surface of the aluminium filler clad layer is facing the aluminium alloy core and the outer-surface of the aluminium filler clad layer is facing a coating layer of 2 to 45 mg/sq·m of Bi or of a Bi-based alloy, and

wherein the coating layer of Bi or of Bi-based alloy is not covered or overlaid by any further layer comprising one or more metals selected from the group of nickel, cobalt, and iron.

2. The aluminium alloy sheet product or extruded product according to claim 1 , wherein the coating layer is at most 30 mg/sq·m.

3. The aluminium alloy sheet product or extruded product according to claim 1 , wherein the coating layer is at least 4 mg/sq·m.

4. The aluminium alloy sheet product or extruded product according to claim 1 , wherein the coating layer of Bi or of a Bi-based alloy is a plated layer.

5. The aluminium alloy sheet product or extruded product according to claim 1 , wherein the coating layer of Bi or of a Bi-based alloy is not covered or overlaid by any further layer comprising each of nickel, cobalt, palladium, and iron,

wherein the coating layer of Bi or of a Bi-based alloy is not covered or overlaid by any further layer comprising nickel,

wherein the coating layer of Bi or of a Bi-based alloy is not covered or overlaid by any further layer comprising cobalt,

wherein the coating layer of Bi or of a Bi-based alloy is not covered or overlaid by any further layer comprising palladium,

wherein the coating layer of Bi or of a Bi-based alloy is not covered or overlaid by any further layer comprising iron.

6. The aluminium sheet product or extruded product according to claim 1 , wherein the filler clad layer has a composition, in wt. %, of:

Si 4% to 15%,

Mg 0 to 1%,

Fe 0 to 1%,

Cu 0 to 2%,

Mn 0 to 1.5%,

Zn 0 to 1.5%,

Ti 0 to 0.2%,

Sr 0 to 0.05%,

the balance aluminium and incidental impurities.

7. A method of manufacturing an article joined by brazing or an assembly of brazed components, comprising the steps of:

(a) providing components of which at least one is made from a brazing sheet material and/or extruded material according to claim 1 ,

(b) assembling the components into an assembly,

(c) brazing the assembly without applying brazing flux on the assembly of components and brazing the whole assembly in an inert controlled gas atmosphere at a brazing temperature to form a brazed assembly, and

(d) cooling of the brazed assembly.

8. The aluminium alloy sheet product or extruded product according to claim 1 , wherein the filler clad layer has a composition, in wt. %, of:

Si 6% to 13%,

Mg 0 to 0.4%,

Fe 0 to 0.6%,

Cu 0 to 2%,

Mn 0.3 to 1.0%,

Zn 0 to 0.2%,

Ti 0 to 0.15%,

Sr 0 to 0.05%,

free of each of elements Na, Li, K, and Ca; and

free of each of elements Bi, Pb, Y, and Sb;

the balance aluminium and incidental impurities.

9. The aluminium alloy sheet product or extruded product according to claim 1 , wherein the coating layer of Bi or of a Bi-based alloy is applied by a technique selected from the group of thermal spraying, chemical vapour deposition, physical vapour deposition, and kinetic energy metallization.

10. The aluminium alloy sheet product or extruded product according to claim 9 , wherein the physical vapour deposition includes a technique selected from the group of sputtering, electron beam evaporation and cathodic arc deposition.

11. The aluminium alloy sheet product or extruded product according to claim 1 , wherein the coating layer of Bi or of a Bi-based alloy is applied using plating or electroplating.

12. The method according to claim 7 , wherein the coating layer is at most 30 mg/sq·m.

13. The method according to claim 7 , wherein the coating layer is at least 4 mg/sq·m.

14. The method according to claim 7 , wherein the coating layer of Bi or of a Bi-based alloy is a plated layer.

15. The method according to claim 7 , wherein the coating layer of Bi or of a Bi-based alloy is not covered or overlaid by any further layer comprising each of nickel, cobalt, palladium, and iron.

16. The method according to claim 7 , wherein the filler clad layer has a composition, in wt. %, of:

Si 4% to 15%,

Mg 0 to 1%,

Fe 0 to 1%,

Cu 0 to 2%,

Mn 0 to 1.5%,

Zn 0 to 1.5%,

Ti 0 to 0.2%,

Sr 0 to 0.05%,

the balance aluminium and incidental impurities.

17. The method according to claim 7 , wherein the filler clad layer has a composition, in wt. %, of:

Si 6% to 13%,

Mg 0 to 0.4%,

Fe 0 to 0.6%,

Cu 0 to 2%,

Mn 0.3 to 1.0%,

Zn 0 to 0.2%,

Ti 0 to 0.15%,

Sr 0 to 0.05%,

free of each of elements Na, Li, K, and Ca; and

free of each of elements Bi, Pb, Y, and Sb;

the balance aluminium and incidental impurities.

18. The aluminium alloy sheet product or extruded product of claim 5 :

wherein the aluminium alloy core having on at least one face an aluminium filler clad layer containing 4% to 15% by weight of Si, the aluminium filler clad layer having the inner-surface and the outer-surface,

wherein the inner-surface of the aluminium filler clad layer is facing the aluminium alloy core and the outer-surface of the aluminium filler clad layer is facing the coating layer of 4 to 30 mg/sq·m of Bi or of the Bi-based alloy,

wherein the Bi-based alloy is at least 70% by weight Bi.

19. The aluminium alloy sheet product or extruded product of claim 18 , consisting of:

the aluminium alloy core having on at least one face the aluminium filler clad layer,

the aluminium filler clad layer having the inner-surface and the outer-surface,

wherein the filler clad layer containing, in wt. %, Si 6% to 13%, Mg 0 to 0.4%, Fe 0 to 0.6%, Cu 0 to 2%, Mn 0.3 to 1.0%, Zn 0 to 0.2%, Ti 0 to 0.15%, Sr 0 to 0.05%, free of each of elements Na, Li, K, and Ca; and free of each of elements Bi, Pb, Y, and Sb; the balance aluminium and incidental impurities,

wherein the inner-surface of the aluminium filler clad layer is facing the aluminium alloy core and the outer-surface of the aluminium filler clad layer is facing the coating layer of 4 to 30 mg/sq·m of the Bi or of the Bi-based alloy,

wherein the Bi-based alloy is at least 90% by weight Bi.

20. The aluminium alloy sheet product or extruded product of claim 18 , wherein the filler clad layer contains, in wt. %, Si 10% to 15%.