Brazing sheet and manufacturing method thereof

1. A brazing sheet usable in brazing performed in an inert-gas atmosphere or in a vacuum without using a flux, comprising:

a core material having a chemical composition containing Mg: 1.3 mass % or less, the remainder being Al and unavoidable impurities;

an intermediate material having a chemical composition containing Mg: 0.40 mass % or more and 6.0 mass % or less, the remainder being Al and unavoidable impurities, and being layered on the core material; and

a filler material having a chemical composition containing Si: 6.0 mass % or more and 13.0 mass % or less, Bi: 0.0040 mass % or more and 0.070 mass % or less, and Mg: 0.050 mass % or more and less than 0.10 mass %, the remainder being Al and unavoidable impurities, and being layered on the intermediate material.

2. The brazing sheet according to claim 1 , wherein the intermediate material further contains Si: 1.0 mass % or more and 13.0 mass % or less.

3. The brazing sheet according to claim 1 , wherein the core material further contains one or two or more elements selected from the group consisting of: Mn: 0.30 mass % or more and 2.0 mass % or less, Si: 0.10 mass % or more and 1.0 mass % or less, Fe: less than 1.0 mass %, Cu: 1.0 mass % or less, Ti: less than 0.10 mass %, Zr: less than 0.30 mass %, and Cr: less than 0.30 mass %.

4. The brazing sheet according to claim 1 , wherein the Mg content in the core material is less than 1.0 mass %.

5. The brazing sheet according to claim 4 , wherein the Bi content in the filler material is less than 0.030 mass %.

6. The brazing sheet according to claim 3 , wherein the Mg content in the core material is less than 1.0 mass %.

7. The brazing sheet according to claim 6 , wherein the Bi content in the filler material is less than 0.030 mass %.

8. The brazing sheet according to claim 7 , wherein the intermediate material further contains Si: 1.0-13.0 mass %.

9. The brazing sheet according to claim 7 , wherein the intermediate material further contains Zn: 0.9-6.0 mass %.

10. The brazing sheet according to claim 9 , wherein the intermediate material further contains Cu: 0.20-2.0 mass %.

11. The brazing sheet according to claim 7 , wherein the intermediate material directly contacts the core material and the filler material directly contacts the intermediate material.

12. The brazing sheet according to claim 1 , wherein:

the Mg content in the intermediate material is 0.20-1.0 mass %, and

the Bi content in the filler material is 0.0040-0.030 mass %.

13. The brazing sheet according to claim 1 , wherein the intermediate material directly contacts the core material and the filler material directly contacts the intermediate material.

14. A method of manufacturing the brazing sheet according to claim 1 , comprising:

preparing a cladding mass by superposing a core-material mass having the chemical composition of the core material according to claim 1 , an intermediate-material mass having the chemical composition of the intermediate material according to claim 1 , and a filler-material mass having the chemical composition of the filler material according to claim 1 ;

preparing a clad sheet by rolling the cladding mass; and

etching the clad sheet using an acid or an alkali.

15. The method of manufacturing the brazing sheet according to claim 14 , comprising:

after the etching has been performed, applying 500 mg/cm′ or more of a protective oil, which has a decomposition temperature that is 200-380° C. in an inert gas atmosphere, to a surface of the brazing sheet.

16. A brazing sheet, comprising:

a core composed of an aluminum alloy comprising 0-1.3 mass % Mg;

an intermediate material layered on the core and being composed of an aluminum alloy comprising 0.4-6.0 mass % Mg; and

a filler layered on the intermediate material and being composed of an aluminum alloy comprising 6.0-13.0 mass % Si, 0.0040-0.070 mass % Bi, and 0.050-0.10 mass % Mg.

17. The brazing sheet according to claim 16 , wherein:

the Mg content in the core material is less than 1.0 mass %;

the Bi content in the filler material is less than 0.030 mass %; and

the filler further contains Fe: 0.18-0.50 mass %.

18. The brazing sheet according to claim 17 , wherein the core material further contains: Mn: 0.30-2.0 mass %, Si: 0.10-1.0 mass %, Fe: 0.6-1.0 mass %, and Cu: 0.15-1.0 mass %.

19. The brazing sheet according to claim 18 , wherein:

a first surface of the intermediate material directly contacts the core;

the filler directly contacts a second surface of the intermediate material that is opposite of the first surface of the intermediate material such that the intermediate material is sandwiched between the core and the filler; and

the filler is an outermost layer of the brazing sheet.

20. A brazing sheet usable in brazing performed in an inert-gas atmosphere or in a vacuum without using a flux, comprising:

a core material having a chemical composition containing Mg: 1.0 mass % or less and one or more elements selected from the group consisting of: Mn: 0.30-2.0 mass %, Si: 0.10-1.0 mass %, Fe: less than 1.0 mass %, Cu: 1.0 mass % or less, Ti: less than 0.10 mass %, Zr: less than 0.30 mass %, and Cr: less than 0.30 mass %, the remainder being Al and unavoidable impurities;

an intermediate material layered on the core material and having a chemical composition containing Mg: 0.40-6.0 mass % and Be: 0.050-0.20 mass %, the remainder being Al and unavoidable impurities; and

a filler material layered on the intermediate material and having a chemical composition containing Si: 6.0-13.0 mass %, Bi: 0.0040-0.030 mass %, and Mg: 0.050-0.10 mass %, the remainder being Al and unavoidable impurities.