Method for producing aluminum alloy having improved semi-solid molding capability and billet thereof

Abstract

A method for producing a billet of an aluminum alloy having an improved semi-solid molding capability, in which the aluminum alloy comprises, in wt %, 0.005 to 0.5 Ti, 0.0001 to 0.1 B, and the balance substantially aluminum, comprises pouring the aluminum alloy in a molten state into a cooling mold to perform the semi-continuous casting of the aluminum alloy; providing a billet having a solidified layer on its surface by primary cooling-down of the molten aluminum alloy using the mold; pulling the billet out of the mold; and feeding a refrigerant onto the surface of the billet to effect secondary cooling-down of the billet. The primary cooling-down is separated from the secondary cooling-down by the distance of 150 mm or less. The refrigerant for the secondary cooling-down is in contact with the billet at an angle between 20° or greater and less than 80° in the casting direction.

1 . An aluminum alloy having an improved semi-solid molding capability, comprising, in wt %, 0.005 to 0.5 Ti, 0.0001 to 0.1 B, and balance substantially aluminum.  
   
   
       2 . An aluminum alloy having an improved semi-solid molding capability, as defined in  claim 1 , wherein Ti to be added to provide fine grain structure of said aluminum alloy is added in a form of an Al—Ti master alloy before being further added in a form of an Al—Ti—B master alloy.  
   
   
       3 . An aluminum alloy having an improved semi-solid molding capability, as defined in  claim 1 , wherein amounts of Ti and B to be added to provide fine grain structure of said aluminum alloy are in a Ti-to-B-ratio of 3 to 40, (Al x .Ti y ) B 2 (x= 1 to 7, y=1 to 9) is a particle having a size of 10 μm or less, and an atomic weight ratio of Al x  to Ti y  is 0.2 to 2.5.  
   
   
       4 . A method for producing a billet of an aluminum alloy having an improved semi-solid molding capability, said aluminum alloy comprising, in wt %, 0.005 to 0.5 Ti, 0.0001 to 0.1 B, and balance substantially aluminum, said method comprising: pouring said aluminum alloy in a molten state into a cylindrical, forced cooling mold from top of said mold in order to perform semi-continuous casting of said aluminum alloy; providing a billet having a solidified layer formed on a surface of said billet by executing primary cooling-down of said molten aluminum alloy using said mold; pulling said billet out of said mold by lowering a bottom block which supports a bottom end of said billet;. and feeding a refrigerant onto the surface of said billet to effect secondary cooling-down of said billet, wherein said primary cooling-down is separated from said secondary cooling-down by a distance of 150 mm or less, and wherein said refrigerant for use in said secondary cooling-down is brought into contact with said billet at an angle between 20° or greater and less than 80° in a casting direction.  
   
   
       5 . A method for producing a billet of an aluminum alloy having an improved semi-solid molding capability, as defined in  claim 4 , wherein Ti in said molten aluminum alloy is added in a form of an Al—Ti master alloy before being further added in a form of an Al—Ti—B master alloy.  
   
   
       6 . A method for producing a billet of an aluminum alloy having an improved semi-solid molding capability, as defined in  claim 4 , wherein amounts of Ti and B in said aluminum alloy are in a Ti-to-B-ratio of 3 to 40, (Al x .Ti y ) B 2 (x= 1 to 7, y=1 to 9) is a particle having a size of 10 μm or less, and an atomic weight ratio of Al x  to Ti y  is 0.2 to 2.5.  
   
   
       7 . A method for producing a billet of an aluminum alloy having an improved semi-solid molding capability, as defined in  claim 4 , wherein after said secondary cooling-down to enhance said semi-continuous casting of said aluminum alloy, a tertiary cooling-down refrigerant is brought into contact with said billet at an angle between 20° or greater and less than 80° in the casting direction to further increase cooling-down of said billet.  
   
   
       8 . A method for producing a billet of an aluminum alloy having an improved semi-solid molding capability, as defined in  claim 4 , wherein said providing said billet having said solidified layer formed on the surface of said billet comprises expelling said molten aluminum alloy from a float at an angle between 20° or greater and less than 80° in the casting direction to feed said molten aluminum alloy out of said mold in order to control a level of said molten aluminum alloy, said float being positioned in said mold on a surface of said molten aluminum alloy.