Method of making a heat exchanger with an enhanced material system

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.

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.