Dry machinable aluminum castings

Abstract

Additions of small but effective amounts of one or more of bismuth, indium, lead and/or tin to an aluminum casting alloy markedly improved the dry machinability of a casting made from the modified alloy. The added elements, which are softer and lower melting than the matrix alloy form as small globules in the microstructure of the aluminum casting. These globules do not adversely affect the strength or hardness of the casting but enable surfaces of the casting to be machined without the use of a cooling and lubricating machining fluid.

1 . A method of making an aluminum alloy article comprising: 
 making a casting of the article from an aluminum alloy comprising, by weight, 5% to 18% silicon, 1.3% max iron, 0.2% max copper or 2% to 5% copper, 1.3% max magnesium, 0.6% max manganese, about 0.5% to about 2% of one or more machining lubricity imparting elements selected from the group consisting of bismuth, indium, lead and tin, and aluminum; the casting containing a dispersed phase containing the lubricity imparting element; and    machining a surface of the casting with a cutting tool to remove cast material without the use of a machining fluid.    
   
   
       2 . The method of making an aluminum alloy article as recited in  claim 1  comprising making a casting of the article from an aluminum alloy comprising, by weight, 5% to 13% silicon, 1.3% max iron, 0.2% max copper, 1.3% max magnesium, 0.6% max manganese, about 0.5% to about 2% of one or more machining lubricity imparting elements selected from the group consisting of bismuth, indium, lead and tin, and aluminum.  
   
   
       3 . The method of making an aluminum alloy article as recited in  claim 1  comprising making a casting of the article from an aluminum alloy comprising, by weight, 5% to 13% silicon, 1.3% max iron, 2% to 5% copper, 1.3% max magnesium, 0.6% max manganese, about 0.5% to about 2% of one or more machining lubricity imparting elements selected from the group consisting of bismuth, indium, lead and tin, and aluminum.  
   
   
       4 . The method of making an aluminum alloy article as recited in  claim 1  comprising making a casting of the article from an aluminum alloy comprising, by weight, 16% to 18% silicon, 1.3% max iron, 4% to 5% copper, 0.4% to 0.65% magnesium, 0.1% max manganese, about 0.5% to about 2% of one or more machining lubricity imparting elements selected from the group consisting of bismuth, indium, lead and tin, and aluminum.  
   
   
       5 . The method of making an aluminum alloy article as recited in  claim 1  comprising making a casting of the article from an aluminum alloy comprising, by weight, 5% to 7.5% silicon, 1% max iron, 2% to 5% copper, 0.5% max magnesium, 0.6% max manganese, about 0.5% to about 2% of one or more machining lubricity imparting elements selected from the group consisting of bismuth, indium, lead and tin, and aluminum.  
   
   
       6 . The method of making an aluminum alloy article as recited in  claim 1  in which the lubricity imparting element is selected from the group consisting of bismuth and tin.  
   
   
       7 . The method of making an aluminum alloy article as recited in  claim 2  in which the lubricity imparting element is selected from the group consisting of bismuth and tin.  
   
   
       8 . The method of making an aluminum alloy article as recited in  claim 3  in which the lubricity imparting element is selected from the group consisting of bismuth and tin.  
   
   
       9 . The method of making an aluminum alloy article as recited in  claim 4  in which the lubricity imparting element is selected from the group consisting of bismuth and tin.  
   
   
       10 . The method of making an aluminum alloy article as recited in  claim 5  in which the lubricity imparting element is selected from the group consisting of bismuth and tin.  
   
   
       11 . The method of making an aluminum alloy article as recited in  claim 1  in which the machining lubricity imparting element is bismuth.  
   
   
       12 . The method of making an aluminum alloy article as recited in  claim 2  in which the machining lubricity imparting element is bismuth.  
   
   
       13 . The method of making an aluminum alloy article as recited in  claim 3  in which the machining lubricity imparting element is bismuth.  
   
   
       14 . The method of making an aluminum alloy article as recited in  claim 4  in which the machining lubricity imparting element is bismuth.  
   
   
       15 . The method of making an aluminum alloy article as recited in  claim 5  in which the machining lubricity imparting element is bismuth.