# US 9,433,996 B2 · Method of making a heat exchanger with an enhanced material system

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- Number: US 9,433,996 B2
- Document ID: US9433996B2
- Status: Granted
- Kind: B2
- Application number: 14/112,129
- Filed: 2012-04-25
- Published: 2014-02-06
- Granted: 2016-09-06
- Earliest claimed: 2011-04-25
- Assignees: Mahle International GmbH
- Applicants: Douglas C. Wintersteen; Kurt R. Mittlefehldt
- Inventors: Douglas C. Wintersteen; Kurt R. Mittlefehldt
- Web page: https://patentgrep.com/patent/US9433996B2

## CPC

- B21D 53/08: of both metal tubes and sheet metal (connecting tubes in openings B21D39/06)
- B23K 1/0012: {Brazing of heat exchangers}
- B23K 1/203: {Fluxing, i.e. applying flux onto surfaces}
- B23K 35/362: Selection of compositions of fluxes (B23K35/365, B23K35/368 take precedence)
- B32B 15/016: {all layers being formed of aluminium or aluminium alloys}
- C22C 21/00: Alloys based on aluminium
- C22C 21/10: with zinc as the next major constituent
- F28D 1/05366: {Assemblies of conduits connected to common headers, e.g. core type radiators}
- F28F 1/126: {consisting of zig-zag shaped fins (F28F1/105 takes precedence)}
- F28F 19/02: by using coatings, e.g. vitreous or enamel coatings
- F28F 19/06: of metal
- F28F 21/084: {from aluminium or aluminium alloys}
- F28F 21/089: {Coatings, claddings or bonding layers made from metals or metal alloys (F28F19/06 takes precedence)}
- B23K 2103/10: Aluminium or alloys thereof
- F28F 2275/04: by brazing
- Y10T 29/4938: Common fin traverses plurality of tubes
- Y10T 29/49885: with coating before or during assembling
- Y10T 29/49968: Metal fusion joining
- B21D: WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL (working or processing of wire B21F)
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- F28D: HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT (fluid heaters having heat generating means and heat transferring means F24H; furnaces F27; details of heat-exchange apparatus of general)
- F28F: DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION (water and air traps, air venting F16)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The disclosure relates to a method of manufacturing a heat exchanger assembly with an enhanced material system. The enhanced material system includes refrigerant tubes extruded from a high purity AA3000 series alloy billet having about 1% by weight (wt %) Mn and pre-braze treated with either a reactive zinc flux or a mixture of elemental zinc powder and a controlled atmosphere brazed (CAB) flux applied by glass plasma or organic binder, such as an organic binder, fins formed from modified a AA3003 alloy having less than 0.05 wt % Cu and from 1.2 to 1.8% wt % Zn, and header manifolds manufactured from a AA3000 series alloy with a AA4000 series cladding having 0.9 to 1.1 wt % Zn. The enhanced material system may also include a post braze coating and a subsequent organic polymer resin topcoat.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 1)

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.

### Claim 5 (depends on 4)

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

### Claim 6 (depends on 1)

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.

### Claim 7 (depends on 6)

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).

### Claim 8 (depends on 1)

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.

### Claim 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.

### Claim 10 (depends on 9)

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.

### Claim 11 (depends on 9)

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.

### Claim 12 (depends on 11)

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).

### Claim 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.

### Claim 14 (depends on 13)

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.

### Claim 15 (depends on 14)

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