Aluminum alloy heat exchanger and method of producing refrigerant tube used for the heat exchanger
An aluminum alloy heat exchanger is produced by applying a coating material that is prepared by adding a binder to a mixture of an Si powder and a Zn-containing compound flux powder to a surface of an aluminum alloy refrigerant tube, assembling a bare fin that is formed of an Al—Mn—Zn alloy with the refrigerant tube, and brazing the refrigerant tube and the bare fin by heating in an atmosphere-controlled furnace, the refrigerant tube being an extruded product of an aluminum alloy that comprises 0.5 to 1.7% (mass %, hereinafter the same) of Mn, less than 0.10% of Cu, and less than 0.10% of Si, with the balance being Al and unavoidable impurities.
1. A method of producing an aluminum alloy refrigerant tube that is used in the manufacture of an aluminum alloy heat exchanger, comprising the steps of:
providing an ingot of an aluminum alloy comprising 0.5-1.7 mass % of Mn, less than 0.10% of Cu and less than 0.10% of Si, with the balance being Al and unavoidable impurities;
subjecting the ingot of the aluminum alloy to a homogenization heat treatment that holds the ingot at a temperature of from 400-650° C. for 4 hours or more; and
hot-extruding the ingot to produce the aluminum alloy refrigerant tube.
2. The method of claim 1 , wherein the homogenization heat treatment includes a first-stage heat treatment that holds the ingot at 570-650° C. for 2 hours or more, followed by cooling the ingot to 200° C. or less, and a second-stage heat treatment that holds the ingot at 400-550° C. for 3 hours or more.
3. The method of claim 1 , wherein the homogenization heat treatment includes a first-stage heat treatment that holds the ingot at 570-650° C. for 2 hours or more and a second-stage heat treatment that holds the ingot at 400-550° C. for 3 hours or more.
4. The method of claim 3 , wherein the aluminum alloy refrigerant tube has an aluminum alloy bare fin made of an Al—Mn—Zn alloy brazed thereto, the Al—Mn—Zn alloy further comprising at least one of 0.001 to 0.10 mass % of In and 0.001 to 0.10 mass % of Sn.
5. The method of claim 4 , wherein the homogenization heat treatment includes the first-stage heat treatment, followed by cooling the ingot to 200° C. or less, and the second-stage heat treatment.