White gold alloy

Abstract

By including zinc, nickel, copper and cobalt in a 22 kt gold alloy, it is possible to obtain the desired white gold color in an alloy with satisfactory metallurgical properties and with reasonable raw material costs. More specifically, these elements are present in the following ranges: Gold≈91.67%; Zinc 0.4 to 1.5%; Nickel 6.0 to 7.5%; Copper 0.4 to 1.5%; Cobalt 0.02 to 0.50%. Master alloys and methods of making jewelry are also disclosed.

1 . A gold alloy comprising by weight about 90.9-93.0% gold and: 
 0.4 to 1.5% zinc;    6.0 to 7.5% nickel;    0.4 to 1.5% copper; and    0.02 to 0.50% cobalt.    
     
     
         2 . The gold alloy of  claim 1  comprising by weight: 
 0.5 to 1.0% zinc;    6.0 to 7.5% nickel;    0.4 to 0.8% copper; and    0.02 to 0.10% cobalt.    
     
     
         3 . The gold alloy of  claim 2  in which the cobalt is present in about 0.03 to 0.10% by weight.  
     
     
         4 . The gold alloy of  claim 1  in which the alloy comprises by weight about: 
 0.66% zinc;    7.00% nickel;    0.60% copper; and    0.07% cobalt.    
     
     
         5 . The gold alloy of any one of  claim 1  in which the alloy consists essentially of the listed elements.  
     
     
         6 . The gold alloy of any one of  claim 1  in which the gold is present in about 91.67%.  
     
     
         7 . A master alloy for making a gold alloy composition, the master alloy comprising by weight: 
 4.8 to 18.0% zinc;    72.0 to 90.0% nickel;    4.8 to 18.0% copper; and    0.24-6.0% cobalt.    
     
     
         8 . The master alloy of  claim 7  comprising by weight: 
 6.0-12.0% zinc;    72.0 to 90.0% nickel;    4.8 to 9.6% copper; and    0.24-1.2% cobalt.    
     
     
         9 . The master alloy of  claim 8  in which the cobalt comprises 0.4 to 1.2% by weight.  
     
     
         10 . The master alloy of  claim 7  in which the alloy comprises about: 
 7.92% zinc;    84.03% nickel;    7.21% copper; and    0.84% cobalt.    
     
     
         11 . The master alloy of  claim 7  in which the alloy consists essentially of the listed elements.  
     
     
         12 . A method of making a gold alloy composition comprising providing the master alloy of any of claims  7 - 10  and mixing the master alloy with gold in a ratio of about 90.9-93.0% by weight gold with the remainder being master alloy.  
     
     
         13 . The method of  claim 12  in which the gold is present in about 91.67% by weight  
     
     
         14 . A method of making jewelry comprising manufacturing a gold alloy according to any of claims  1 - 4  in the form of a rod or a bar and rolling the bar or rod to a sheet having a substantially reduced thickness.  
     
     
         15 . The method of  claim 14  in which the sheet is stamped into a two or a three-dimensional part.  
     
     
         16 . The method of  claim 14  in which the sheet is manufactured into a threaded part.  
     
     
         17 . The method of  claim 14  in which the sheet is manufactured into a spring or a spring-containing part.  
     
     
         18 . Jewelry comprising the alloy of any of claims  1 - 4 .  
     
     
         19 . Jewelry made by the method of  claim 14.