Method and equipment for treatment of molten aluminium metal

Abstract

A method and an equipment for the treatment of molten aluminium metal, in particular Na removal in a tapping/transport crucible (1) provided with a lid (6). The atmosphere above the molten metal is sub-pressurized to a sub pressure between 300-10 mbar and subsequently exposed to a stirring action generated by an electromagnetic coil (EMS) arranged towards one side of the tapping/transport crucible (1), whereby Na can be removed from the molten aluminium metal without any addition of active or passive agents.

1 - 12 . (canceled) 
     
     
         13 . A method for the treatment of molten aluminium metal for Na removal in a tapping/transport crucible ( 1 ) by generating a stirring action of the molten aluminium metal, the tapping/transport crucible ( 1 ) has a mantle wall of a material that allows an electromagnetic field generated by an electromagnetic coil (EMS) brought in vicinity of said material to generate a stirring action of the molten aluminium metal inside the tapping/transport crucible ( 1 ) when energizing the electromagnetic coil (EMS),
 wherein   the tapping/transport crucible ( 1 ) is adapted to fit a lid ( 6 ) or cover in a substantial air tight manner where the lid is provided with means for continuously evacuating the atmosphere below the lid to a sub pressure between 300-10 mbar during stirring of the aluminium metal, where Na is removed from said space without application of fluxing agents.   
     
     
         14 . The method according to  claim 13 ,
 wherein   the atmosphere is evacuated to a sub pressure between 200-10 mbar.   
     
     
         15 . The method according to  claim 13 ,
 wherein   the atmosphere is evacuated to a sub pressure between 100-10 mbar.   
     
     
         16 . The method according to  claim 13 ,
 wherein   EMS coil is operated to generate forced convection in the upper part of the melt in the tapping/transport crucible ( 1 ) to maximize the exposure of volatile components to the sub pressurized space.   
     
     
         17 . The method according to  claim 13 ,
 wherein   the EMS coil is operated to create highest metal velocity in the bottom part of the crucible to lift metal to the surface region.   
     
     
         18 . The method according to  claim 13 ,
 wherein   the temperature in the metal during treatment is approximately 900° C.   
     
     
         19 . Equipment for the treatment of molten aluminium metal for Na removal in a tapping/transport crucible ( 1 ) and generating a stirring action, the crucible comprises an outer mantle wall ( 4 ), arranged adjacent an electromagnetic coil (EMS) in the metal treatment equipment and that a stirring action of the molten aluminium metal takes place by energizing the electromagnetic coil,
 wherein   the tapping/transport crucible ( 1 ) is provided with a lid ( 6 ) or cover having means for tightly adapt to it and further having means for continuously evacuating the atmosphere below the lid to a sub pressure between 300-10 mbar during the stirring of the aluminium metal for removal of Na without application of fluxing agents.   
     
     
         20 . The equipment according to  claim 19 ,
 wherein   the tapping/transport crucible is made by a mantle wall ( 4 ) made out of a non-ferromagnetic material, such as austenitic stainless steel.   
     
     
         21 . The equipment according to  claim 19 ,
 wherein   the lid ( 6 ) of the tapping/transport crucible is provided with a seal and locking mechanism that secures gas tight connection to the crucible.   
     
     
         22 . The equipment according to  claim 19 ,
 wherein   the lid ( 6 ) of the tapping/transport crucible is provided with a gas connection for connecting to a vacuum pump controlled by a control station.   
     
     
         23 . The equipment according to  claim 19 ,
 wherein   the lid ( 6 ) is provided with an ejector that allows the continuous removal of the atmosphere in the crucible.   
     
     
         24 . The equipment according to  claim 19 ,
 wherein   the lid ( 6 ) is provided with a controllable inlet ( 10 ) for ambient air to enter the inside of the crucible.