Aluminum alloy for heat exchanger fins

Abstract

An aluminum alloy fin stock material comprising about 0.9-1.2 wt. % Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt. % Cu, 1.0-1.5 wt. % Mn, 0-0.1% Mg and 0.0-3.0% Zn, with remainder Al and impurities at ≦0.15 wt. %. The aluminum alloy fin stock material is produced in a form of a sheet by a process comprising the steps of direct chill casting an ingot, hot rolling the ingot after the direct chill casting, cold rolling the aluminum alloy to an intermediate thickness, inter-annealing the aluminum alloy cold rolled to an intermediate thickness at a temperature between 200 and 400° C., and cold rolling the material after inter-annealing to achieve % cold work (% CW) of 20 to 40%. The aluminum alloy fin stock material possesses an improved combination of one or more of pre- and/or post-brazes strength, conductivity, sag resistance and corrosion potential. It is useful for fabrication of heat exchanger fins.

We claim: 
     
         1 . An aluminum alloy, comprising about 0.9-1.2 wt. % Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt. % Cu, 1.0-1.5 wt. % Mn, 0-0.1% wt. Mg and 0.0-3.0% wt. Zn, with remainder Al and impurities at ≦0.15 wt. %. 
     
     
         2 . The aluminum alloy of  claim 1 , comprising about 0.9-1.2 wt. % Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt. % Cu, 1.0-1.5 wt. % Mn, 0-0.1 wt. % Mg and 0.2-3.0% wt. Zn, with remainder Al and impurities at ≦0.15 wt. %. 
     
     
         3 . The aluminum alloy of  claim 1 , comprising about 0.9-1.2 wt. % Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt. % Cu, 1.2-1.4 wt. % Mn, 0-0.1 wt. % Mg and 0.0-3.0 wt. % Zn, with remainder Al and impurities at ≦0.15 wt. %. 
     
     
         4 . The aluminum alloy of  claim 1 , wherein one or more of Zr, V, Cr or Ni is present at below 0.05 wt. %. 
     
     
         5 . The aluminum alloy of  claim 1 , wherein the alloy is in a form of an aluminum alloy sheet. 
     
     
         6 . The aluminum alloy of  claim 1 , wherein the alloy is in a form of an aluminum alloy sheet produced by a process comprising:
 direct chill casting the aluminum alloy into an ingot;   hot rolling the ingot after the direct chill casting into a hot rolled sheet;   after the hot rolling, cold rolling the hot rolled sheet into an intermediate thickness sheet;   after cold rolling, inter-annealing the the intermediate thickness sheet at 200-400° C.; and, after inter-annealing, cold rolling the intermediate thickness sheet to achieve % cold work (% CW) of 20 to 40%, resulting in the aluminum alloy sheet having a thickness of 70-100 μm.   
     
     
         7 . The aluminum alloy of  claim 5 , wherein the aluminum alloy sheet has ultimate tensile strength of one or both of: at least 200 MPa, measured in pre-brazed condition, or at least 150 MPa, measured post-brazing. 
     
     
         8 . The aluminum alloy of  claim 5 , wherein the aluminum alloy sheet has corrosion potential of −740 mV or less, measured post-brazing. 
     
     
         9 . The aluminum alloy of  claim 5 , wherein the aluminum alloy sheet has electrical conductivity of 43-47 IACS, measured post-brazing. 
     
     
         10 . The aluminum alloy of  claim 6 , wherein the aluminum alloy sheet has ultimate tensile strength of one or both of: at least 200 MPa, measured in pre-brazed condition, or at least 150 MPa, measured post-brazing. 
     
     
         11 . The aluminum alloy of  claim 6 , wherein the aluminum alloy sheet has corrosion potential of -740 mV or less, measured post-brazing. 
     
     
         12 . The aluminum alloy of  claim 6 , wherein the aluminum alloy sheet has electrical conductivity of 43-47 IACS, measured post-brazing. 
     
     
         13 . A heat exchanger comprising the aluminum alloy of  claim 1 . 
     
     
         14 . The heat exchanger of  claim 12 , wherein the heat exchanger is a motor vehicle heat exchanger. 
     
     
         15 . The heat exchanger of  claim 12 , wherein the heat exchanger is a radiator, a condenser or an evaporator. 
     
     
         16 . A process of making a fin stock aluminum alloy sheet, comprising:
 direct chill casting into an ingot an aluminum alloy comprising 0.9-1.2 wt. % Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt. % Cu, 1.0-1.5 wt. % Mn, 0-0.1 wt. % Mg and 0.0-3.0 wt. % Zn, with remainder Al and impurities at ≦0.15 wt. %;   hot rolling the ingot after the direct chill casting into a hot rolled sheet;   after the hot rolling, cold rolling the aluminum alloy into an intermediate thickness sheet;   after cold rolling, inter-annealing the intermediate thickness sheet at 200-400° C.; and, after inter-annealing, cold rolling the intermediate thickness sheet to achieve % cold work (% CW) of 20 to 40%, resulting in the finstock aluminum alloy sheet having a thickness of 70-100 μm.   
     
     
         17 . The process of  claim 16 , wherein the fin stock aluminum alloy sheet has ultimate tensile strength of one or both of: at least 200 MPa, measured in pre-brazed condition, or at least 150 MPa, measured post-brazing. 
     
     
         18 . The process of  claim 16 , wherein the fin stock aluminum alloy sheet has a corrosion potential of −740 mV or less, measured post-brazing. 
     
     
         19 . The process of  claim 16 , wherein the fin stock aluminum alloy sheet has electrical conductivity of 43-47 IACS, measured post-brazing. 
     
     
         20 . A process of making a heat exchanger comprising joining by brazing at least one first aluminum alloy form fabricated from the aluminum alloy of  claim 1  with a second aluminum alloy form, comprising:
 assembling and securing the two or more aluminum forms together; and, heating the two or more aluminum forms to a brazing temperature until joints are created among the two or more aluminum forms by capillary action. 
 
     
     
         21 . A heat exchanger fin fabricated from the aluminum alloy of  claim 1 .