Method of making a heat exchanger with an enhanced material system

1. A method of manufacturing an aluminum heat exchanger comprising the steps of:

providing a plurality of refrigerant tubes extruded of an AA3000 series Al alloy having 0.3 percent by weight (wt %) max of Si, 0.20 wt % max of Fe, 0.03 wt % max of Cu, and between 0.90 to 1.10 wt % of Mn;

applying a Zn coating onto the exterior surface of at least one of said plurality of refrigerant tubes;

providing a plurality of fins manufactured from an AA3000 series Al alloy having 0.3 to 1.0 wt % of Si, 0.4 wt % of Fe max, 0.05 wt % max of Cu, from 1.3 to 1.8 wt % of Mn, between 1.2 to 1.8 wt % of Zn, and 0.20 wt % max of Zr;

providing at least one header manifold having a plurality of refrigerant tube slots, wherein said at least one manifold is formed from an AA3000 series Al alloy sheet having a cladding, wherein said Al alloy sheet includes a core having 0.6 wt % max of Si, 0.7 wt % max of Fe, from 0.05 to 0.65 wt % of Cu, from 1.0 to 1.6 wt % of Mn, 0.20 wt % max of Mg, 0.10 wt % max of Zn, and 0.25 wt % max of Ti;

assembling said fins between adjacent pairs of said refrigerant tubes;

inserting the open ends of said plurality of refrigerant tubes into corresponding said refrigerant tube slots of header manifold, thereby forming a heat exchanger assembly; and

heat treating said heat exchanger assembly at a sufficient time and temperature to braze said plurality of refrigerant tubes, fins, and said at least one header manifold into a single unitary structure, and to diffuse said Zn coating into said refrigerant tubes to form a Zn diffusion layer;

wherein said step of said applying a Zn coating onto the exterior surface of at least one of said plurality of refrigerant tubes includes applying a sufficient amount of Zn to obtain said Zn diffusion layer having 1 to 3 wt % of Zn after brazing, and

wherein said heat exchanger assembly is heat treated at a time and temperature to uniformly diffuse said Zn to less than 85 microns beneath said surface of refrigerant tube.

2. The method of manufacturing an aluminum heat exchanger of claim 1 , wherein said cladding of Al alloy sheet of header manifold comprises 6.8 to 8.2 wt % of Si, 0.8 wt % max of Fe, 0.25 wt % max of Cu, 0.10 wt % max of Mn and 0.9 to 1.1 wt % Zn.

3. The method of manufacturing an aluminum heat exchanger of claim 1 , wherein said cladding of Al alloy sheet of header manifold comprises 9.0 to 11.0 wt % of Si, 0.8 wt % max of Fe, 0.30 wt % max of Cu, 0.05 wt % max of Mn, 0.05 wt % max of Mg, and 0.9 to 1.1 wt % of Zn.

4. The method of manufacturing an aluminum heat exchanger of claim 1 , wherein the step of applying a sufficient amount of Zn onto the exterior surface of at least one of said plurality of refrigerant tubes includes applying the exterior surface with a reactive Zn flux compound, wherein said reactive Zn flux compound is delivered by a roll coated organic binder.

5. The method of manufacturing an aluminum heat exchanger of claim 4 , wherein said reactive Zn flux compound is 6KZnF3.

6. The method of manufacturing an aluminum heat exchanger of claim 1 , wherein the step of applying a sufficient amount of Zn onto the exterior surface of at least one of said plurality of refrigerant tubes includes a mixture of elemental zinc powder and a controlled atmosphere brazed (CAB) flux applied by glass plasma or organic binder.

7. The method of manufacturing an aluminum heat exchanger of claim 6 , wherein said CAB flux includes potassium fluoroaluminate (K 1-3 Al F3-6) flux or a mixture of potassium fluoroaluminate flux (K 1-3 Al F3-6) and lithium flux (Li3 AlF6).

8. The method of manufacturing an aluminum heat exchanger of claim 1 , wherein said Zn is applied to greater than 85% of said surface area of refrigerant tube at about 4 to 6 g/m2 before brazing.

9. A method of manufacturing an aluminum heat exchanger comprising the steps of:

providing a plurality of refrigerant tubes formed of a AA3000 series AlMn1 alloy;

applying a zinc flux compound onto the surfaces of said AlMn1 alloy refrigerant tubes;

providing a plurality of fins formed of AA3003 alloy having a 0.05 wt % max of Cu and 1.2 to 1.8 wt % of Zn;

providing a header manifold having an AA4343 or AA4045 cladding formulated with a 0.9 to 1.1 wt % Zn addition;

applying a controlled atmosphere brazed (CAB) flux on said header manifold;

assembling said refrigerant tubes, said fins, and said header manifold, thereby forming a heat exchanger assembly; and

thermal degreasing and brazing said heat exchanger assembly;

wherein said step of applying a zinc flux compound includes applying a sufficient amount of Zn to obtain said Zn diffusion layer having 1 to 3 wt % of Zn after brazing, and

wherein said heat exchanger assembly is heat treated at a time and temperature to uniformly diffuse said Zn to less than 85 microns beneath said surface of refrigerant tube.

10. The method of manufacturing an aluminum heat exchanger of claim 9 , wherein said zinc flux compound includes reactive zinc flux 6KZnF3 delivered by a roll coated organic binder.

11. The method of manufacturing an aluminum heat exchanger of claim 9 , wherein said zinc flux compound includes a mixture of elemental zinc powder and CAB flux delivered by gas plasma or a roll coated organic binder.

12. The method of manufacturing an aluminum heat exchanger of claim 11 , wherein said CAB flux includes a fluoroaluminate (K 1-3 Al F3-6) flux or a mixture of potassium fluoroaluminate flux (K 1-3 Al F3-6) and lithium flux (Li3 AlF6).

13. A method of manufacturing an aluminum heat exchanger comprising the steps of:

providing a plurality of refrigerant tubes extruded of an AA3000 series Al alloy having between 0.9 to 1.1 wt % of Mn;

applying a Zn coating onto the exterior surface of at least one of said plurality of refrigerant tubes;

providing a plurality of fins manufactured from an AA3000 series Al alloy having between 1.2 to 1.8 wt % of Zn and 0.05 wt % max of Cu;

providing at least one header manifold having a plurality of refrigerant tube slots, wherein said at least one manifold is formed from an AA3000 series Al alloy sheet having a cladding, wherein said Al alloy sheet includes a core having from 1.0 to 1.6 wt % of Mn;

assembling said fins between adjacent pairs of said refrigerant tubes;

inserting the open ends of said plurality of refrigerant tubes into corresponding said refrigerant tube slots of header manifold, thereby forming a heat exchanger assembly; and

heat treating said heat exchanger assembly at a sufficient time and temperature to braze said plurality of refrigerant tubes, fins, and said at least one header manifold into a single unitary structure, and to diffuse said Zn coating into said refrigerant tubes to form a Zn diffusion layer;

wherein said step of said applying a Zn coating onto the exterior surface of at least one of said plurality of refrigerant tubes includes applying a sufficient amount of Zn to obtain said Zn diffusion layer having 1 to 3 wt % of Zn and a depth of less than 85 microns after brazing.

14. The method of manufacturing an aluminum heat exchanger of claim 13 , further comprising the step of coating said heat exchanger assembly after brazing with a vanadium, zirconium or chromium conversion coating; a titanium based ceramic coating; or an E-coat epoxy or polyurethane coating with a primer pretreatment.

15. The method of manufacturing an aluminum heat exchanger of claim 14 , further comprising the step applying an organic polymer resin topcoat.