Aluminum alloy extruded product exhibiting excellent surface properties, method of manufacturing the same, heat exchanger multi-port tube, and method of manufacturing heat exchanger including the multi-port tube

Abstract

An aluminum alloy extruded product exhibiting excellent surface properties, comprising 0.8 to 1.6% of Mn and 0.4 to 0.8% of Si at a ratio of Mn content to Si content (Mn %/Si %) of 0.7 to 2.4, with the balance being Al and inevitable impurities, the number of intermetallic compounds with a diameter (circle equivalent diameter) of 0.1 to 0.9 μm dispersed in a matrix being 2×10 5 or more per square millimeter. The aluminum alloy extruded product allows extrusion of a thin multi-port tube at a high limiting extrusion rate, prevents deposits from adhering to the surface of the extruded tube, and may be suitably used as a constituent member for an aluminum alloy automotive heat exchanger.

1 . An aluminum alloy extruded product exhibiting excellent surface properties, comprising 0.8 to 1.6% (mass %; hereinafter the same) of Mn and 0.4 to 0.8% of Si at a ratio of Mn content to Si content (Mn %/Si %) of 0.7 to 2.4, with the balance being Al and inevitable impurities, the number of intermetallic compounds with a diameter (circle equivalent diameter; hereinafter the same) of 0.1 to 0.9 μm dispersed in a matrix being 2×10 5  or more per square millimeter.  
   
   
       2 . The aluminum alloy extruded product according to  claim 1 , further comprising 0.05% or less of Cu.  
   
   
       3 . The aluminum alloy extruded product according to  claim 1 , further comprising 0.2% or less of Mg.  
   
   
       4 . The aluminum alloy extruded product according to  claim 1 , further comprising 0.30% or less of Ti.  
   
   
       5 . A heat exchanger multi-port tube comprising the aluminum alloy extruded product according to  claim 1 .  
   
   
       6 . A method of manufacturing an aluminum alloy extruded product exhibiting excellent surface properties, the method comprising: melting and casting an aluminum alloy having the composition according to  claim 1  to obtain an ingot; subjecting the ingot to homogenization which includes a first-stage heat treatment in which the ingot is maintained at 550 to 650° C. for two hours or more and a second-stage heat treatment in which the ingot is cooled to 400 to 500° C. at an average temperature decrease rate of 20 to 60° C./h and maintained at that temperature for three hours or more; heating the ingot at 480 to 560° C.; and extruding the ingot.  
   
   
       7 . A method of manufacturing an aluminum alloy extruded product exhibiting excellent surface properties, the method comprising: melting and casting an aluminum alloy having the composition according to  claim 1  to obtain an ingot; subjecting the ingot to homogenization which includes a first-stage heat treatment in which the ingot is maintained at 550 to 650° C. for two hours or more and a second-stage heat treatment in which the ingot is cooled to room temperature, heated to 400 to 500° C. at an average temperature increase rate of 20 to 60° C./h, and maintained at that temperature for three hours or more; heating the ingot at 480 to 560° C.; and extruding the ingot.  
   
   
       8 . A method of manufacturing a heat exchanger comprising extruding a heat exchanger multi-port tube using the method according to  claim 6 , and joining the multi-port tube to a heat exchanger by brazing.