Aluminium alloy for lithographic sheet

Abstract

The invention discloses an Al alloy suitable for processing into a lithographic sheet, the alloy having a composition in wt %: Mg 0.05 to 0.30, Mn 0.05 to 0.25, Fe 0.11 to 0.40, Si up to 0.25, Ti up to 0.03, B up to 0.01, Cu up to 0.01, Cr up to 0.03, Zn up to 0.15, unavoidable impurities up to 0.05 each, 0.15 total, Al balance. Also disclosed is a method of processing the Al alloy.

1 - 36 . (canceled)  
     
     
         37 . A method of processing an Al alloy having a composition in wt %:  
       
         
           
                 
                 
                 
                 
               
                     
                     
                 
                     
                     
                 
                     
                   Mg 
                   0.05 to 
                   0.30 
                 
                     
                   Mn 
                   0.05 to 
                   0.25 
                 
                     
                   Fe 
                   0.11 to 
                   0.40 
                 
                     
                   Si 
                   up to 
                   0.25 
                 
                     
                   Ti 
                   up to 
                   0.03 
                 
                     
                   B 
                   up to 
                   0.01 
                 
                     
                   Cu 
                   up to 
                   0.01 
                 
                     
                   Cr 
                   up to 
                   0.03 
                 
                     
                   Zn 
                   up to 
                   0.15 
                 
                     
                   Zr 
                   up to 
                   0.005 
                 
                     
                     
                 
                     
                     
                 
             
                
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
         Unavoidable impurities up to 0.05 each, 0.15 total Al balance,  
         which method comprises the steps of: casting, homogenising, optional hot rolling, cold rolling, and optional interannealing, wherein the homogenisation step is carried out by heating the cast alloy to a temperature of 550 to 610° C. for 1 to 10 hours and subsequently cooling to a hot rolling temperature of between 450 and 550° C.  
       
     
     
         38 . A method according to  claim 37 , wherein the casting step is carried out by DC casting.  
     
     
         39 . A method according to  claim 37 , which does not comprise the optional interannealing step.  
     
     
         40 . A method according to  claim 37 , wherein the internnealing is batch interannealing.  
     
     
         41 . A method according to  claim 40 , wherein the interannealing is carried out at 300 to 500° C. for 1 to 5 hours.  
     
     
         42 . A method according to  claim 37 , wherein the interannealing is continuous internnealing.  
     
     
         43 . A method according to  claim 42 , wherein the continuous interannealing is carried out at 450 to 600° C. for less than 10 minutes.  
     
     
         44 . A method according to  claim 37 , further comprising the step of electrograining.  
     
     
         45 . A method according to  claim 44 , wherein the alloy is electrograined in hydrochloric acid.  
     
     
         46 . A method according to  claim 44 , wherein the alloy is electrograined in nitric acid.  
     
     
         47 . A method according to  claim 44 , wherein the alloy is capable of being electrograined in both hydrochloric and nitric acids.  
     
     
         48 . A method of processing an Al alloy having a composition in wt %:  
       
         
           
                 
                 
                 
                 
               
                     
                     
                 
                     
                     
                 
                     
                   Mg 
                   0.05 to 
                   0.30 
                 
                     
                   Mn 
                   0.06 to 
                   0.25 
                 
                     
                   Fe 
                   0.11 to 
                   0.40 
                 
                     
                   Si 
                   up to 
                   0.25 
                 
                     
                   Ti 
                   up to 
                   0.03 
                 
                     
                   B 
                   up to 
                   0.01 
                 
                     
                   Cu 
                   up to 
                   0.01 
                 
                     
                   Cr 
                   up to 
                   0.03 
                 
                     
                   Zn 
                   up to 
                   0.15 
                 
                     
                   Zr 
                   up to 
                   0.005 
                 
                     
                     
                 
                     
                     
                 
             
                
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
         Unavoidable impurities up to 0.05 each, 0.15 total Al balance,  
         which method comprises the steps of: casting, homogenising, optional hot rolling, cold rolling, and optional interannealing, wherein the homogenisation step is carried out by heating the cast alloy to a temperature of 550 to 610° C. for 1 to 10 hours and subsequently cooling to a hot rolling temperature of between 450 and 550° C.