Aluminium brazing sheet material

1. A brazing sheet material comprising of an aluminium core alloy layer provided with a first brazing clad layer material on one or both sides of said aluminium core layer and at least one second brazing clad layer material positioned between the aluminium core alloy layer and the first braze clad layer material,

wherein the second brazing clad layer material is an Al—Si alloy brazing material having 5% to 20% Si and 0.01% to 3% Mg, and

wherein the first brazing clad layer material is an Al—Si alloy brazing material having 6% to 14% Si and less than 0.4% Mg.

2. Brazing sheet material according to claim 1 , wherein the first Al—Si alloy brazing clad layer material has a Mg content of less than 0.15%.

3. Brazing sheet material according to claim 1 , wherein the first Al—Si alloy brazing clad layer material is Mg-free.

4. Brazing sheet material according to claim 1 , wherein the second Al—Si alloy brazing clad layer material has a Mg content in a range of 0.01% to 1%.

5. Brazing sheet material according to claim 1 , wherein the sum of the Mg content in the first and second Al—Si alloy brazing clad layer material does not exceed 0.25%.

6. Brazing sheet material according to claim 1 , wherein the first and the second Al—Si alloy brazing clad layers may have substantially equivalent solidus and liquidus temperatures.

7. Brazing sheet material according to claim 1 , wherein the first Al—Si alloy brazing clad layer has a composition within the range of AA4045 or AA4343-series aluminium alloy.

8. Brazing sheet material according to claim 1 , wherein the second Al—Si alloy brazing clad layer material further contains one or more wetting elements, and wherein the total amount of the wetting elements is in a range of 0.01% to 0.5%.

9. Brazing sheet material according to claim 1 , wherein the second Al—Si alloy brazing clad layer material furthers contains Bi as wetting element in a range of 0.01% to 0.5%.

10. Brazing sheet material according to claim 9 , wherein the excess Mg with respect to the stoichiometric composition of Bi 2 Mg 3 is 0.07% or less.

11. Brazing sheet material according to claim 1 , wherein the first Al—Si alloy brazing clad layer material further contains one or more wetting elements, and wherein the total amount of the wetting elements is in a range of 0.01% to 0.5%.

12. Brazing sheet material according to claim 1 , wherein each of the first and second Al—Si alloy brazing clad material layers may further contain up to 0.8% Fe, and up to 0.2% Ti, and balance unavoidable impurities and aluminium.

13. Brazing sheet material according to claim 1 , wherein at least one of the first and second Al—Si alloy brazing clad material layers further contain one or more elements selected from the group consisting of 0.1% to 8% of Zn, 0.01% to 1% of In, 0.01% to 1% of Sn, and 0.01% to 1% of Ge.

14. Brazing sheet material according to claim 1 , wherein the first Al—Si alloy brazing clad material layer has a thickness which is 3% to 15% of the entire thickness of said aluminium alloy brazing sheet product, and the second Al—Si alloy brazing clad material layer has a thickness of 3% to 20% of the entire thickness of said aluminium alloy brazing sheet product.

15. A method of manufacturing an assembly of brazed components, comprising the steps of:

a.) forming the components of which at least one is made from an aluminium brazing sheet material according to claim 1 ;

b.) assembling the components into an assembly;

c.) brazing the assembly without applying flux in an inert gas atmosphere at a brazing temperature for a period long enough for melting and spreading of the filler material;

d.) cooling the brazed assembly.

16. A method of manufacturing an assembly of brazed components, comprising the steps of:

a.) forming the components of which at least one is made from an aluminium brazing sheet material according to claim 1 ;

b.) assembling the components into an assembly;

c.) brazing the assembly without applying flux in a vacuum atmosphere at a brazing temperature for a period long enough for melting and spreading of the filler material;

d.) cooling the brazed assembly.

17. A brazed assembly of components incorporating an aluminium alloy brazing sheet according to claim 1 .

18. A brazed assembly according to claim 17 , wherein the brazed assembly is an oil cooler or a B-tube.

19. Brazing sheet material according to claim 1 , wherein the second Al—Si alloy brazing clad layer material has a Mg content in a range of 0.01% 0.50%.

20. Brazing sheet material according to claim 1 , wherein the sum of the Mg content in the first and second Al—Si alloy brazing clad layer material does not exceed 0.10%.

21. Brazing sheet material according to claim 1 , wherein the first Al—Si alloy brazing clad layer material has a Si content in the range of 6% to 12%.

22. Brazing sheet material according to claim 1 , wherein the second Al—Si alloy brazing clad layer material further contains one or more wetting elements selected from the group consisting of Bi, Pb, Li, Sb, Se, Y, and Th, and wherein the total amount of the wetting elements in the second Al—Si alloy brazing clad layer material is in a range of 0.01% to 0.5%.

23. Brazing sheet material according to claim 1 , wherein the second Al—Si alloy brazing clad layer material furthers contains Bi as wetting element in a range of b 0 . 01 % to 0.25%.

24. Brazing sheet material according to claim 23 , wherein the excess Mg with respect to the stoichiometric composition of Bi 2 Mg 3 is 0.05% or less.

25. Brazing sheet material according to claim 1 , wherein the first Al—Si alloy brazing clad layer material further contains one or more wetting elements selected from the group consisting of Bi, Pb, Li, Sb, Se, Y, and Th, and wherein the total amount of the wetting elements the first Al—Si alloy brazing clad layer material is in a range of 0.01% to 0.5%.