High conductivity bare aluminum finstock and related process

Abstract

A process for making aluminum alloy finstock having improved combinations of post-braze tensile strength, electrical conductivity and self-corrosion resistance. The process includes continuously casting into sheet an alloy composition. The composition includes about 0.35-0.50 wt. % Si, about 1.8-2.6 wt. % Fe, about 0.02-0.30 wt. % Cu, about 0.40-0.70 wt. % Mn, up to about 3.0 wt. % Zn, up to about 0.05 wt. % In; up to about 0.05 wt. % Ti and up to about 0.2 wt. % Zr, the balance aluminum, incidental elements and impurities. The casting including a solidification rate of greater than about 200° C./sec. The sheet is then rolled to an intermediate anneal gauge and then annealed. The sheet is then cold rolled to a desired final gauge.

1 . A process for making aluminum alloy finstock having improved combinations of post-braze tensile strength, electrical conductivity and self-corrosion resistance, said process comprising the steps of: 
 (a) continuously casting into sheet an alloy composition comprising: about 0.35-0.50 wt. % Si, about 1.8-2.6 wt. % Fe, about 0.02-0.30 wt. % Cu, about 0.40-0.70 wt. % Mn, up to about 3.0 wt. % Zn, up to about 0.05 wt. % In; up to about 0.05 wt. % Ti and up to about 0.2 wt. % Zr, the balance aluminum, incidental elements and impurities, said casting including a solidification rate of greater than about 200° C./sec. to substantially avoid formation of primary intermetallic solidification compound;    (b) rolling said sheet to an intermediate anneal gauge;    (c) annealing the rolled sheet; and    (d) cold rolling to final gauge.    
     
     
         2 . The process of  claim 1 , wherein the alloy contains about about 1.8-2.4 wt. % Fe.  
     
     
         3 . The process of  claim 1 , wherein the alloy contains about 0.35-0.45 wt. % Si.  
     
     
         4 . The process of  claim 1 , wherein the alloy contains about 0.10-0.25 wt. % Cu.  
     
     
         5 . The aluminum alloy of  claim 1 , wherein the alloy contains about 0.35-0.45 wt. % Si, about 1.8-2.4 wt. % Fe, about 0.4-0.7 wt. % Mn, about 0.15-0.25 wt. % Cu, up to about 1.5 wt. % Zn and about up to 0.03 wt. % In.  
     
     
         6 . The process of  claim 1 , wherein step (a) is performed with a twin roll caster under rapidly cooling casting conditions that substantially avoid the formation of primary intermetallic solidification compounds and produces a sheet of thickness of about 2.0-10.0 mm.  
     
     
         7 . The process of  claim 1 , wherein step (b) includes an initial intermediate thermal operation either at cast gauge or after some initial cold reduction.  
     
     
         8 . The process of  claim 7 , wherein said intermediate thermal operation includes a 1-8 hour soak in a temperature range of about 320-450° C.  
     
     
         9 . The process of  claim 1 , wherein step (b) comprises cold rolling.  
     
     
         10 . The process of  claim 1 , wherein step (a) is performed with a high speed sheet or belt caster that freezes from at least one surface.  
     
     
         11 . The process of  claim 10 , wherein step (b) includes both hot or warm rolling and cold rolling.  
     
     
         12 . The process of  claim 1 , wherein said finstock has a post-braze ultimate tensile strength of about 125 Mpa or higher and an electrical conductivity value of about 48% IACS or greater.  
     
     
         13 . The process of  claim 1 , wherein step (c) is performed at one or more temperatures below about 450° C.  
     
     
         14 . The process of  claim 1 , wherein step (d) produces less than or equal to about a 50% reduction in sheet thickness.