Method for producing aluminum alloy heat exchanger

1. A method for producing an aluminum alloy heat exchanger comprising applying a coating material prepared by mixing an Si powder, a flux powder, and a binder to a surface of a multiport flat refrigerant tube, assembling an aluminum alloy bare fin with the multiport flat refrigerant tube, and brazing the multiport flat refrigerant tube and the aluminum alloy bare fin to obtain an aluminum alloy heat exchanger, the multiport flat refrigerant tube being formed of an aluminum alloy extruded material that comprises 0.6 to 1.7 mass % of Mn, less than 0.10 mass % of Si, and less than 0.05 mass % of Cu, with the balance being Al and unavoidable impurities, the aluminum alloy bare fin being a corrugated fin that is obtained by forming an Al—Mn—Zn alloy material, the coating material being prepared by mixing an Si powder, a Zn-containing compound flux powder, a Zn-free compound flux powder, and a binder, the Si powder being applied in an amount of 1 to 4 g/m 2 , the Zn-containing compound flux powder being applied in an amount of 1 to 9 g/m 2 , the Zn-free compound flux powder being applied in an amount of 1 to 9 g/m 2 , the Si powder, the Zn-containing compound flux powder, and the Zn-free compound flux powder being applied in an amount of 5 to 20 g/m 2 in total, a content of the binder in the coating material being 5 to 40%, and the aluminum alloy heat exchanger obtained by brazing having a configuration in which a deep area of the refrigerant tube has the highest potential, and the potential decreases in order from a surface area of the refrigerant tube, a fin joint fillet, and the fin.

2. The method for producing an aluminum alloy heat exchanger according to claim 1 , wherein the aluminum alloy extruded material that forms the refrigerant tube further comprises one or more elements among 0.30 mass % or less of Ti, 0.10 mass % or less of Sr, and 0.30 mass % or less of Zr.

3. The method for producing an aluminum alloy heat exchanger according to claim 1 , wherein the Si powder has a maximum particle size of 35 μm or less.

4. The method for producing an aluminum alloy heat exchanger according to claim 1 , wherein the Zn-containing compound flux powder is KZnF 3 .

5. The method for producing an aluminum alloy heat exchanger according to claim 1 , wherein the Zn-free compound flux powder is a potassium fluoroaluminate.

6. The method for producing an aluminum alloy heat exchanger according to claim 1 , wherein the aluminum alloy bare fin is formed of an aluminum alloy that comprises 0.1 to 1.8 mass % of Mn and 0.8 to 3.0 mass % of Zn, with the balance being Al and unavoidable impurities.

7. The method for producing an aluminum alloy heat exchanger according to claim 6 , wherein the aluminum alloy that forms the aluminum alloy bare fin further comprises one or more elements among 0.001 to 0.10 mass % of In and 0.001 to 0.10 mass % of Sn.

8. The method for producing an aluminum alloy heat exchanger according to claim 1 , wherein the aluminum alloy bare fin is formed of an aluminum alloy that comprises 0.1 to 1.8 mass % of Mn, 0.8 to 3.0 mass % of Zn, and one or more elements among 0.1 to 1.2 mass % of Si, 0.01 to 0.8 mass % of Fe, 0.05 to 0.5 mass % of Mg, 0.3 mass % or less of Cu, 0.3 mass % or less of Cr, 0.3 mass % or less of Zr, and 0.3 mass % or less of Ti, with the balance being Al and unavoidable impurities.

9. The method for producing an aluminum alloy heat exchanger according to claim 8 , wherein the aluminum alloy that forms the aluminum alloy bare fin further comprises one or more elements among 0.001 to 0.10 mass % of In and 0.001 to 0.10 mass % of Sn.

10. The method for producing an aluminum alloy heat exchanger according to claim 1 , wherein the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment that holds the ingot at 400 to 650° C. for 4 hours or more, and hot-extruding the ingot.

11. The method for producing an aluminum alloy heat exchanger according to claim 1 , wherein the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment, and hot-extruding the ingot, the homogenization heat treatment including a first-stage heat treatment that holds the ingot at 550 to 650° C. for 2 hours or more, and a second-stage heat treatment that cools the ingot subjected to the first-stage heat treatment to 400 to 550° C., and holds the ingot at 400 to 550° C. for 3 hours or more.

12. The method for producing an aluminum alloy heat exchanger according to claim 1 , wherein the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment, and hot-extruding the ingot, the homogenization heat treatment including a first-stage heat treatment that holds the ingot at 550 to 650° C. for 2 hours or more, and a second-stage heat treatment that cools the ingot subjected to the first-stage heat treatment to 200° C. or less, and holds the ingot at 400 to 550° C. for 3 hours or more.

13. The method for producing an aluminum alloy heat exchanger according to claim 1 , wherein the Si powder has a maximum particle size of 35 μm or less, the Zn-containing compound flux powder is KZnF 3 , and the Zn-free compound flux powder is a potassium fluoroaluminate.

14. The method for producing an aluminum alloy heat exchanger according to claim 13 , wherein the aluminum alloy bare fin is formed of an aluminum alloy that comprises 0.1 to 1.8 mass % of Mn and 0.8 to 3.0 mass % of Zn, with the balance being Al and unavoidable impurities.

15. The method for producing an aluminum alloy heat exchanger according to claim 14 , wherein the Si powder has a maximum particle size of 35 μm or less, the Zn-containing compound flux powder is KZnF 3 , the Zn-free compound flux powder is a potassium fluoroaluminate, and the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment that holds the ingot at 400 to 650° C. for 4 hours or more, and hot-extruding the ingot.

16. The method for producing an aluminum alloy heat exchanger according to claim 14 , wherein the Si powder has a maximum particle size of 35 μm or less, the Zn-containing compound flux powder is KZnF 3 , the Zn-free compound flux powder is a potassium fluoroaluminate, and the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment, and hot-extruding the ingot, the homogenization heat treatment including a first-stage heat treatment that holds the ingot at 550 to 650° C. for 2 hours or more, and a second-stage heat treatment that cools the ingot subjected to the first-stage heat treatment to 400 to 550° C., and holds the ingot at 400 to 550° C. for 3 hours or more.

17. The method for producing an aluminum alloy heat exchanger according to claim 14 , wherein the Si powder has a maximum particle size of 35 μm or less, the Zn-containing compound flux powder is KZnF 3 , the Zn-free compound flux powder is a potassium fluoroaluminate, and the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment, and hot-extruding the ingot, the homogenization heat treatment including a first-stage heat treatment that holds the ingot at 550 to 650° C. for 2 hours or more, and a second-stage heat treatment that cools the ingot subjected to the first-stage heat treatment to 200° C. or less, and holds the ingot at 400 to 550° C. for 3 hours or more.

18. The method for producing an aluminum alloy heat exchanger according to claim 13 , wherein the aluminum alloy bare fin is formed of an aluminum alloy that comprises 0.1 to 1.8 mass % of Mn, 0.8 to 3.0 mass % of Zn, and one or more elements among 0.1 to 1.2 mass % of Si, 0.01 to 0.8 mass % of Fe, 0.05 to 0.5 mass % of Mg, 0.3 mass % or less of Cu, 0.3 mass % or less of Cr, 0.3 mass % or less of Zr, and 0.3 mass % or less of Ti, with the balance being Al and unavoidable impurities.

19. The method for producing an aluminum alloy heat exchanger according to claim 18 , wherein the Si powder has a maximum particle size of 35 μm or less, the Zn-containing compound flux powder is KZnF 3 , the Zn-free compound flux powder is a potassium fluoroaluminate, and the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment that holds the ingot at 400 to 650° C. for 4 hours or more, and hot-extruding the ingot.

20. The method for producing an aluminum alloy heat exchanger according to claim 18 , wherein the Si powder has a maximum particle size of 35 μm or less, the Zn-containing compound flux powder is KZnF 3 , the Zn-free compound flux powder is a potassium fluoroaluminate, and the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment, and hot-extruding the ingot, the homogenization heat treatment including a first-stage heat treatment that holds the ingot at 550 to 650° C. for 2 hours or more, and a second-stage heat treatment that cools the ingot subjected to the first-stage heat treatment to 400 to 550° C., and holds the ingot at 400 to 550° C. for 3 hours or more.

21. The method for producing an aluminum alloy heat exchanger according to claim 18 , wherein the Si powder has a maximum particle size of 35 μm or less, the Zn-containing compound flux powder is KZnF 3 , the Zn-free compound flux powder is a potassium fluoroaluminate, and the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment, and hot-extruding the ingot, the homogenization heat treatment including a first-stage heat treatment that holds the ingot at 550 to 650° C. for 2 hours or more, and a second-stage heat treatment that cools the ingot subjected to the first-stage heat treatment to 200° C. or less, and holds the ingot at 400 to 550° C. for 3 hours or more.

22. The method for producing an aluminum alloy heat exchanger according to claim 13 , wherein the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment that holds the ingot at 400 to 650° C. for 4 hours or more, and hot-extruding the ingot.

23. The method for producing an aluminum alloy heat exchanger according to claim 13 , wherein the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment, and hot-extruding the ingot, the homogenization heat treatment including a first-stage heat treatment that holds the ingot at 550 to 650° C. for 2 hours or more, and a second-stage heat treatment that cools the ingot subjected to the first-stage heat treatment to 400 to 550° C., and holds the ingot at 400 to 550° C. for 3 hours or more.

24. The method for producing an aluminum alloy heat exchanger according to claim 13 , wherein the aluminum alloy extruded material that forms the refrigerant tube is obtained by casting an ingot, subjecting the ingot to a homogenization heat treatment, and hot-extruding the ingot, the homogenization heat treatment including a first-stage heat treatment that holds the ingot at 550 to 650° C. for 2 hours or more, and a second-stage heat treatment that cools the ingot subjected to the first-stage heat treatment to 200° C. or less, and holds the ingot at 400 to 550° C. for 3 hours or more.