Sterling silver alloy and articles made from same

Abstract

An improved sterling silver alloy. Like all sterlings, the improved alloy is at least 92.5 percent silver by weight. It has less copper than traditional sterlings: 3.0 percent versus the traditional 7.5 percent. Additionally, the improved alloy includes about 2.75 percent palladium, about 1.0 percent tin, and about 0.75 percent zinc, all by weight. A grain refiner, such as ruthenium, may also be provided. The components of the preferred alloy are melted, degassed, remelted, and then formed into casting grains, wire, and etc. The resulting alloy is significantly harder, as cast, than traditional sterlings: 95-120 Vickers versus 65 Vickers for traditional sterlings. The improved alloy also exhibits improved corrosion resistance. Other than a slightly higher (<200° F.) liquidus temperature, the improved alloy may be worked in substantially the same manner as traditional sterlings. Pieces cast from the improved alloy may be age hardened to about 160 Vickers, if desired.

I claim: 
     
         1 . A sterling silver comprising:
 at least about 92.5 percent, by weight, silver, and wherein said silver is alloyed with between about 2.0 percent and about 3.7 percent copper by weight, and between about 2.5 percent and about 3.3 percent palladium by weight, and tin and wherein said sterling silver is free of germanium.   
     
     
         2 . A sterling silver according to  claim 1  wherein said silver is further alloyed with zinc. 
     
     
         3 . A sterling silver according to  claim 2  wherein said copper comprises about 2.8 percent by weight of said sterling silver. 
     
     
         4 . A sterling silver according to  claim 2  wherein said palladium comprises about 2.75 percent by weight of said sterling silver. 
     
     
         5 . A sterling silver according to  claim 2  wherein said tin comprises between about 0.5 and about 1.25 percent by weight of said sterling silver. 
     
     
         6 . A sterling silver according to  claim 5  wherein said tin comprises about 1.0 percent by weight of said sterling silver. 
     
     
         7 . A sterling silver according to  claim 2  wherein said zinc comprises between about 0.50 and about 1.25 percent by weight of said sterling silver. 
     
     
         8 . A sterling silver according to  claim 7  wherein said zinc comprises about 0.75 percent by weight of said sterling silver. 
     
     
         9 . A sterling silver according to  claim 2  further comprising a grain refiner. 
     
     
         10 . A sterling silver according to  claim 9  wherein said grain refiner is ruthenium. 
     
     
         11 . A sterling silver according to  claim 10  wherein said ruthenium comprises about 0.005 percent by weight of said sterling silver. 
     
     
         12 . A sterling silver according to  claim 9  wherein said sterling silver has an as cast hardness of a least about 95 on the Vickers scale. 
     
     
         13 . A sterling silver according to  claim 12  wherein said sterling silver has an as cast hardness between about 95 and about 120 on the Vickers scale. 
     
     
         14 . A sterling silver according to  claim 12  wherein said alloy is susceptible to age hardening. 
     
     
         15 . A sterling silver alloy according to  claim 14  wherein said alloy is age hardenable to about 160 on the Vickers scale. 
     
     
         16 . A method of making one or more jewelry articles comprising:
 placing a casting grains of an alloy in a crucible, wherein said alloy comprises
 at least 92.5 percent, by weight, silver; 
 about 3.0 percent, by weight, copper; 
 about 2.75 percent, by weight, palladium; 
 about 1.0 percent, by weight, tin; and 
   completely melting said casting grains by heating said crucible to a temperature of at least about 1790 degrees F.;   pouring said molten alloy into an investment mold containing one or more jewelry article shaped cavities;   allowing said molten alloy to cool and solidify within said investment mold to form said one or more jewelry articles, wherein said jewelry article has an as cast hardness of at least about 95 on the Vickers scale;   removing said investment mold from said solidified one or more jewelry articles; and   polishing said one or more jewelry articles.   
     
     
         17 . A method of making one or more jewelry articles according to  claim 16  wherein said jewelry article has an as cast hardness of between about 95 and about 120 on the Vickers scale.