Silver Alloy Compositions
a technology of silver alloys and compositions, applied in the field of silver alloy compositions, can solve the problems of poor reflectivity, poor mechanical properties of prior art alloys, and lack of required appearance of prior art alloys, and achieve the effects of reducing susceptibility to sulphidation, improving tarnish resistance, and reducing susceptibility to fire stain
Inactive Publication Date: 2008-07-10
CARRS OF SHEFFIELD MFG +2
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Benefits of technology
The present invention relates to a new sterling silver alloy composition that has reduced susceptibility to tarnishing and fire stain, while maintaining good mechanical properties. The alloy comprises at least 92.5% silver, 3.0%- 4.0% tin, 1.7%- 2.6% zinc, 0.5%-1.5% indium, and optionally grain refiners such as copper, manganese, iron, nickel, silicon, boron, titanium, iridium, cobalt, and magnesium. The alloy has improved properties such as workability, reflectivity, and flowability.
Problems solved by technology
It is possible to achieve these properties with prior art alloys, but the prior art alloys do not give the required mechanical properties such as workability that can be obtained with 92.5% silver 7.5% copper alloy.
Alternatively, the prior art alloys do not have the required appearance for silverware, but are dull and exhibit a poor reflectivity.
Method used
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[0133]A series of alloys were prepared and cast. Each alloy was cast into a bar test sample. Referring to FIG. 3 herein, there are illustrated the processing steps of test samples. The bar was milled 301 on its upper and lower surfaces to a thickness of approximately 15.24 mm. The bar was then rolled 302 to a thickness of 7.62 mm on the first run (approximately a 50% reduction). The bar was then annealed 303 in a retort furnace after the first rolling at 550° C. for 20 hours in a 95% nitrogen 5% hydrogen atmosphere. A light abrasive clean 304 was then applied to the bar. A second rolling 305 to approximately 3.81 mm (a further 50% reduction) was then applied to each bar, followed by a second annealing 306 under the same conditions as the first annealing. A third rolling 307 to approximately 1.91 mm (a further 50% reduction) was applied to each bar followed by a third annealing 308. The third annealing 308 was performed in a belt furnace to 550° C. under a 75% hydrogen, 25% nitrogen ...
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Abstract
Silver alloy compositions having reduced susceptibility to sulphidation and reduced susceptibility to fire stain relative to 92.5% silver 7.5% copper alloy, and having mechanical properties for casting and forming comparable to or better than 92.5% silver 7.5% copper alloy, and having an appearance similar to 92.5% silver 7.5% copper alloy. The silver alloy compositions include at least 92.5% silver 2.0%-4.0% tin; 1.7%-2.6% zinc and 0.50%-1.5% indium.
Description
FIELD OF THE INVENTION[0001]The field of the invention relates to silver alloy compositions, and in particular to sterling silver alloy compositions that have an improved resistance to sulphidation and formation of fire stain.BACKGROUND TO THE INVENTION[0002]Sterling silver alloys are widely used in jewellery and silverware because of their sparkling reflectivity, their artistic heritage, as well as their bactericidal properties. Jewellery includes items such as rings, earrings, necklaces, bracelets and so on. In the European Union, there are strict regulations governing the amount of nickel that can be present in jewellery and fine jewellery. Silverware includes items such as tableware (cutlery, trays, tea and coffee sets and so on), candlesticks, cigarette lighters, photograph frames, mirrors, coins, musical instruments and the like.[0003]A requirement of sterling silver is that it must contain at least 92.5% silver in order to be entitled to be termed “sterling silver”. Conventio...
Claims
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IPC IPC(8): C22C5/08C22C5/06
CPCC22C1/03C22C5/08C22C5/06C22C1/06
Inventor FAVERJON, FREDERICHOPKINSON, ALAN G.STOREY, JAMES
Owner CARRS OF SHEFFIELD MFG