Magnesium reduction in molten aluminum

Abstract

A salt flux and method for use of the same in cleaning and purifying molten aluminum is disclosed. The salt flux includes an equal proportion of sodium chloride and potassium chloride in a range of ninety percent or more, by weight, of the salt flux. The salt flux further includes aluminum fluoride in a range of less than ten percent by weight. The salt flux is introduced into a furnace using a submergence system such as a side well with an impeller to submerge the salt flux under the surface of the metal bath. Oxides may be collected and removed to reduce inclusions, oxide, and magnesium levels within the metal bath.

What is claimed is: 
     
         1 . A salt flux for molten aluminum treatment, comprising:
 an alkali salt mixture comprising sodium chloride and potassium chloride in an amount of at least 90 weight percent; and   aluminum fluoride in an amount of less than 10 weight percent.   
     
     
         2 . The salt flux of  claim 1 , wherein the alkali salt mixture comprises sodium chloride in an amount of at least 40 weight percent or more and potassium chloride in an amount of at least 40 weight percent or more. 
     
     
         3 . The salt flux of  claim 1 , wherein the alkali salt mixture comprises approximately equal portions by weight of sodium chloride and potassium chloride. 
     
     
         4 . The salt flux of  claim 1 , wherein:
 the aluminum fluoride is in a range of 2.5 to 5 percent by weight; and   the alkali salt mixture is in a range of 95 to 97.5 percent by weight.   
     
     
         5 . The salt flux of  claim 1 , wherein the salt flux comprises a granular homogenous mixture of the alkali salt mixture and the aluminum fluoride. 
     
     
         6 . The flux of  claim 1 , wherein the salt flux has a melting temperature of less than 700 Celsius. 
     
     
         7 . A method for the purification of aluminum and aluminum alloys comprising:
 heating a mass of aluminum and aluminum alloys in a furnace to a liquid phase to produce a metal bath; and   contacting the metal bath with a salt flux beneath a surface of the metal bath, the salt flux comprising:
 an alkali salt mixture comprising sodium chloride and potassium chloride in an amount of at least 90 weight percent; and 
 aluminum fluoride in an amount of less than 10 weight percent. 
   
     
     
         8 . The method of  claim 7 , wherein contacting the metal bath with the salt flux comprises introducing the salt flux with at least one of a lance or a stirring device. 
     
     
         9 . The method of  claim 7 , wherein contacting the metal bath with the salt flux comprises introducing the salt flux to the metal bath with a submergence system of the furnace. 
     
     
         10 . The method of  claim 9 , wherein the submergence system comprises a submergence impeller at a side well of the furnace. 
     
     
         11 . The method of  claim 7 , wherein heating the mass of aluminum and aluminum alloys comprises heating to greater than 680 degrees Celsius and less than 950 degrees Celsius. 
     
     
         12 . The method of  claim 7 , wherein the metal bath comprises magnesium at a concentration of greater than 20 parts per million. 
     
     
         13 . The method of  claim 7 , wherein contacting the metal bath with the salt flux further comprises adding a second flux configured to reduce a concentration of a second element of the metal bath. 
     
     
         14 . The method of  claim 7 , wherein the salt flux comprises a solid fused compound inserted under a surface of the metal bath with a lance. 
     
     
         15 . A method for reduction of magnesium in aluminum comprising:
 heating a mass of aluminum and aluminum alloys in a furnace to a liquid phase to produce a metal bath;   contacting the metal bath with a salt flux comprising:
 an alkali salt mixture comprising sodium chloride and potassium chloride in an amount of at least 90 weight percent; and 
 aluminum fluoride in an amount of less than 10 weight percent; and 
   removing oxides from a surface of the metal bath.   
     
     
         16 . The method of  claim 15 , wherein:
 the alkali salt mixture comprises equal portions by weight of sodium chloride and potassium chloride;   the aluminum fluoride is in a range of 2.5 to 5 percent by weight; and   the alkali salt mixture is in a range of 95 to 97.5 percent by weight.   
     
     
         17 . The method of  claim 15 , wherein contacting the metal bath with the salt flux comprises introducing the salt flux to the metal bath with a submergence system at a side well of the furnace. 
     
     
         18 . The method of  claim 15 , wherein the salt flux is fused from the alkali salt mixture and aluminum fluoride, crushed, and sieved to form granules. 
     
     
         19 . The method of  claim 15 , wherein the aluminum fluoride is less than five percent by weight of the salt flux. 
     
     
         20 . The method of  claim 15 , wherein the aluminum fluoride is less than 2.5 percent by weight of the salt flux.