High Strength Aluminum Fin Stock for Heat Exchanger

Abstract

The present invention provides an aluminum alloy fin stock material with higher strength, and improved sag resistance for use in heat exchangers, such as automotive heat exchangers. The aluminum alloy fin stock material is produced from an aluminum alloy comprising about 0.8-1.4 wt % Si, 0.4-0.8 wt % Fe, 0.05-0.4 wt % Cu, 1.2-1.7 wt % Mn and 1.20-2.3 wt % Zn, with the remainder as Al. The aluminum alloy fin stock material is made by a process comprising direct chill casting the aluminum alloy into an ingot, preheating the ingot, hot rolling the preheated ingot, cold rolling the ingot and inter-annealing at a temperature of 275-400° C. After inter-annealing, the aluminum alloy fin stock material is a cold rolled in a final cold rolling step to achieve % cold work (% CW) of 20-35%.

1 . An aluminum alloy comprising about 0.8-1.4 wt % Si, 0.4-0.8 wt % Fe, 0.05-0.4 wt % Cu, 1.2-1.7 wt % Mn and 1.20-2.3 wt % Zn, with the remainder as Al. 
     
     
         2 . The aluminum alloy of  claim 1 , comprising about 0.9-1.3 wt % Si, 0.45-0.75 wt % Fe, 0.10-0.3 wt % Cu, 1.3-1.7 wt % Mn and 1.30-2.2 wt % Zn, with the remainder as Al. 
     
     
         3 . The aluminum alloy of  claim 1 , comprising about 0.9-1.2 wt % Si, 0.5-0.75 wt % Fe, 0.15-0.3 wt % Cu, 1.4-1.6 wt % Mn and 1.4-2.1 wt % Zn, with the remainder as Al. 
     
     
         4 . The aluminum alloy of  claim 1 , comprising about 0.9-1.1 wt % Si, 0.5-0.6 wt % Fe, 0.15-0.25 wt % Cu, 1.5-1.6 wt % Mn and 1.5-1.6 wt % Zn, with the remainder as Al. 
     
     
         5 . The aluminum alloy of  claim 1 , comprising about 0.90-1.0 wt % Si, 0.55 wt % Fe, 0.15-0.20 wt % Cu, 1.5 wt % Mn and 1.5 wt % Zn, and with the remainder as Al. 
     
     
         6 . The aluminum alloy of  claim 5 , comprising about 0.95 wt % Si and 0.15 wt % Cu. 
     
     
         7 . The aluminum alloy of  claim 1 , comprising about 1.0-1.2 wt % Si, 0.5-0.6 wt % Fe, 0.2-0.3 wt % Cu, 1.4-1.55 wt % Mn and 1.9-2.1 wt % Zn, with the remainder as Al. 
     
     
         8 . The aluminum alloy of  claim 1 , comprising about 0.95% Si, 0.2% Cu, 0.6% Fe, 1.45% Mn, and 1.55% Zn, remainder Al. 
     
     
         9 . The aluminum alloy of  claim 1 , comprising about 1.15 wt % Si, 0.25 wt % Cu, 0.6 wt % Fe, 1.5 wt % Mn, and 2.0 wt % Zn, remainder Al. 
     
     
         10 . The aluminum alloy of  claim 1 , further comprising up to 0.2% each of one or both of Cr or Zr. 
     
     
         11 . An aluminum alloy fin stock material produced from the aluminum alloy of  claim 1  by a process, comprising:
 direct chill casting the aluminum alloy into an ingot; 
 preheating the ingot to 450 to 500° C. for 2 to 16 hours; 
 hot rolling the preheated ingot; 
 cold rolling the ingot; 
 inter-annealing at a temperature of 275-400° C.; 
 after inter-annealing, performing a final cold rolling step to achieve % cold work (% CW) of 20 to 35%. 
 
     
     
         12 . The aluminum alloy fin stock material of  claim 11 , wherein the ingot is preheated at 480° C. for 2-16 hours. 
     
     
         13 . The aluminum alloy fin stock material of  claim 11 , wherein the ingot is preheated for 2-12 hours. 
     
     
         14 . The aluminum alloy fin stock material of  claim 11 , wherein the interannealing temperature is 325 to 375° C. 
     
     
         15 . The aluminum alloy fin stock material of  claim 11 , wherein the interannealing temperature is 300, 350 or 400° C. 
     
     
         16 . The aluminum alloy fin stock material of  claim 11 , wherein the interannealing temperature is 300° C. and % CW is about 25%. 
     
     
         17 . The aluminum alloy fin stock material of  claim 11 , wherein the interannealing temperature is 350° C. or 400° C. and % CW is about 29%. 
     
     
         18 . The aluminum alloy fin stock material of  claim 11 , wherein the gauge achieved in the final cold rolling step is between 45 μm and 80 μm. 
     
     
         19 . The aluminum alloy fin stock material of  claim 18 , having a minimum ultimate tensile strength of about 130 MPa, measured post-brazing. 
     
     
         20 . The aluminum alloy fin stock material of  claim 18 , having an ultimate tensile strength of about 137 MPa, measured post-brazing. 
     
     
         21 . The aluminum alloy fin stock material of  claim 18 , having a corrosion potential of −680 mV or lower vs. standard calomel electrode (SCE). 
     
     
         22 . The aluminum alloy fin stock material of  claim 18 , having an electrical conductivity of about 41.5% or 43.3% International Annealed Copper Standard (IACS). 
     
     
         23 . A heat exchanger comprising the aluminum alloy fin stock material of  claim 11 . 
     
     
         24 . The heat exchanger of  claim 23 , wherein the heat exchanger is an automotive heat exchanger. 
     
     
         25 . The heat exchanger of  claim 23 , wherein the heat exchanger is a radiator, a condenser or an evaporator 
     
     
         26 . A process for making an aluminum alloy fin stock material, comprising direct chill casting the aluminum alloy of  claim 1  into an ingot;
 preheating the ingot to 450-500 ° C. for 2 to 16 hours; 
 hot rolling the preheated ingot; 
 cold rolling the ingot; 
 inter-annealing at a temperature of 275 to 400° C.; and, 
 after inter-annealing, performing a final cold rolling step to achieve % cold work (% CW) of 20-35%.