Method for the purification of an aluminium alloy

Abstract

Method for the purification of an aluminium alloy containing an alloying element wherein the aluminium alloy is subjected to a fractional crystallisation process. At least the aluminium alloy is separated into a product stream having a content of the alloying element less than the content of the alloying element in the aluminium alloy and a downgrade stream having a content of the alloying element higher than the content of the alloying element in the aluminium alloy. The downgrade stream is subjected to a process of separation of intermetallics wherein an additive is added to the downgrade stream to form a mixture containing intermetallics formed, and from this mixture a waste stream and a recycle stream is separated which waste stream contains a higher content of the alloying element than the recycle stream, and the recycle stream is fed at least partly into the fractional crystallisation process.

1 . Method for the purification of an aluminium alloy containing an alloying element comprising the steps of: 
 subjecting the aluminium alloy to a fractional crystallisation process comprising: 
 separating at least the aluminium alloy into a product stream having a content of the alloying element less than the content of the alloying element in the aluminium alloy and a downgrade stream having a content of the alloying element higher than the content of the alloying element in the aluminium alloy, and  
   subjecting the downgrade stream is subjected to a process of separation of intermetallics wherein an additive is added to the downgrade stream to form a mixture containing the intermetallics formed and from this mixture a waste stream and a recycle stream is separated which waste stream contains a higher content of the alloying element than the recycle stream, and    feeding the recycle stream at least partly into the fractional crystallisation process.    
     
     
         2 . Method according to  claim 1 , wherein the additive comprises at least one element chosen from Si, Mn, Cu, Co and Ni.  
     
     
         3 . Method according to  claim 1 , wherein the additive comprises mainly Mn.  
     
     
         4 . Method according to  claim 1 , wherein the alloying element is Fe.  
     
     
         5 . Method according to  claim 4 , wherein the Fe content in the aluminium alloy is less than 1.7 weight %.  
     
     
         6 . Method according to  claim 4 , wherein the Fe content in the aluminium alloy is more than 0.4 weight %.  
     
     
         7 . Method according to  claim 1 , wherein the intermetallics comprise aluminium-alloying element-additive intermetallics.  
     
     
         8 . Method according to  claim 4 , wherein the Fe content in the aluminium alloy is less than 1.5 weight %.  
     
     
         9 . Method according to  claim 4 , wherein the Fe content in the aluminium alloy is more than 0.5 weight %.  
     
     
         10 . Method according to  claim 8 , wherein the Fe content in the aluminium alloy is more than 0.5 weight %.