Strontium for melt oxidation reduction of magnesium and a method for adding stronium to magnesium

Abstract

A method for suppressing oxidation and burning in a molten magnesium alloy which my contain beryllium, comprising covering the exposed surface of the molten alloy in a protective atmosphere and dissolving strontium into the molten alloy is disclosed. This has the benefit of reducing magnesium losses due to oxidation thereby improving efficiency of the process. There is also disclosed a magnesium casting alloy comprising from about 1% to 10% by weight of aluminum, from about 1% to 30% by weight of zinc, from about 0.004% to 0.05 % by weight of strontium and unavoidable impurities, the balance being magnesium. Finally, there is disclosed a beryllium free magnesium die casting which is essentially free of flux inclusions.

What is claimed is:  
     
         1 . A method for suppressing oxidation and burning in a molten magnesium alloy, comprising: 
 covering the exposed surface of the molten alloy in a protective atmosphere; and    dissolving strontium into the molten alloy.    
     
     
         2 . A method for suppressing oxidation and burning in a molten magnesium alloy containing only traces of beryllium, comprising: 
 covering the exposed surface of the molten alloy in a protective atmosphere; and    dissolving strontium into the molten alloy.    
     
     
         3 . A method for suppressing oxidation and burning in a molten magnesium alloy as in claims  1  and  2  wherein the protective gas includes between about 0.04% and 0.35% sulphur hexafluoride and dry-air.  
     
     
         4 . A method for suppressing oxidation and burning in a molten magnesium alloy as in  claim 3  wherein the protective gas further includes carbon dioxide.  
     
     
         5 . A method for suppressing oxidation and burning in a molten magnesium alloy as in claims  1 ,  2 ,  3  and  4  wherein about 0.004% to.0.05% by weight of strontium is dissolved into the molten alloy.  
     
     
         6 . A method for suppressing oxidation and burning in a molten magnesium alloy as in claims  1 ,  2 ,  3 ,  4  and  5  wherein the strontium is in the form of a strontium-aluminum master alloy comprised of about 70 to 95% by weight strontium which is dissolved in the molten alloy at a temperature of about 670° C. to 700° C.  
     
     
         7 . A method for suppressing oxidation and burning in a molten magnesium alloy as in claims  1 ,  2 ,  3 ,  4  and  5  wherein pure strontium is dissolved in the molten alloy at a temperature of about 650° C. to 680° C.  
     
     
         8 . A magnesium casting alloy comprising: 
 from about 1% to 10% by weight of aluminum;    from about 1.5% to 30% by weight of zinc;    from about 0.004% to 0.05% by weight of strontium; and    unavoidable impurities;    the balance being magnesium.    
     
     
         9 . A magnesium casting alloy comprising: 
 from about 9% to 10% by weight of aluminum;    from about 1% to 2% by weight of zinc;    from about 0.004% to 0.05% by weight of strontium; and    unavoidable impurities;    the balance being magnesium.    
     
     
         10 . A magnesium casting alloy comprising: 
 from about 9% to 10% by weight of aluminum;    from about 1% to 2% by weight of zinc;    about 0.007% to 0.0250% by weight of strontium; and    unavoidable impurities;    the balance being magnesium.    
     
     
         11 . A magnesium casting alloy comprising: 
 from about 0.007% by weight of strontium; and    the balance being the alloy designated AZ91E.    
     
     
         12 . A magnesium die casting being essentially free of flux inclusions comprising: 
 from about 1% to 10% by weight of aluminum;    from about 1% to 30% by weight of zinc;    from about 0.01% to 0.05% by weight of strontium; and    unavoidable impurities;    the balance magnesium.