Sterling silver alloy compositions of exceptional and reversible hardness, and enhanced tarnish resistance
View Patent ↗A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, consists essentially of the following parts by weight: at least about 92.5% silver; about 4.4% to about 5.25% copper; about 0% to about 1.0% zinc; about 0.85% tin; about 0.05% to about 0.3% lithium; about 0.05% to about 0.5% silicon; about 0% to about 1.2% germanium; and about 0% to about 0.02% boron.
1. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, consisting of the following parts by weight:
at least about 92.5% silver;
about 5.0% to about 5.25% copper;
about 0% to about 1.0% zinc;
about 0.85% tin;
about 0.05% lithium;
about 0.05% to about 0.5% silicon;
about 0% to about 1.2% germanium; and
about 0% to about 0.01% boron.
2. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 1 wherein said composition exhibits a tarnish rate of not more than about 3.5 on a scale of from 0 to 5, where 0 is no tarnish and 5 is the tarnish rate of a sterling silver alloy having about 92.5% silver and about 7.5% copper when subjected for about six minutes to vapor of an aqueous solution containing about 650 parts per million of ammonium sulfide heated to a temperature of about 150° F.
3. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 1 wherein said composition has a hardness of about 60 VHN to about 70 VHN when soft annealed by heating to a temperature of about 1200° F. in a non-oxidizing atmosphere, held at a temperature of about 1200° F. for about one hour, and then quenched in water.
4. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 1 wherein said composition has a hardness of at least about 125 VHN when age hardened by heating to a temperature of about 400° F., held at a temperature of about 400° F. for about four hours, and then allowed to cool to room temperature.
5. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 1 consisting of the following parts by weight:
about 92.60% silver;
about 5.25% copper;
about 0.65% zinc;
about 0.85% tin;
about 0.05% lithium;
about 0.10% silicon; and
about 0.50% germanium.
6. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 5 wherein said composition exhibits a tarnish rate of about 3.0 on a scale of from 0 to 5, where 0 is no tarnish and 5 is the tarnish rate of a sterling silver alloy having about 92.5% silver and about 7.5% copper when subjected for about six minutes to vapor of an aqueous solution containing about 650 parts per million of ammonium sulfide heated to a temperature of about 150° F., and wherein said composition has a hardness of about 135 VHN when age hardened by heating to a temperature of about 400° F., held at a temperature of about 400° F. for about four hours, and then allowed to cool to room temperature.
7. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 1 consisting of the following parts by weight:
about 92.60% silver;
about 5.25% copper;
about 0.70% zinc;
about 0.85% tin;
about 0.05% lithium;
about 0.05% silicon; and
about 0.50% germanium.
8. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 7 wherein said composition exhibits a tarnish rate of about 3.0 on a scale of from 0 to 5, where 0 is no tarnish and 5 is the tarnish rate of a sterling silver alloy having about 92.5% silver and about 7.5% copper when subjected for about six minutes to vapor of an aqueous solution containing about 650 parts per million of ammonium sulfide heated to a temperature of about 150° F., and wherein said composition has a hardness of about 140 VHN when age hardened by heating to a temperature of about 400° F., held at a temperature of about 400° F. for about four hours, and then allowed to cool to room temperature.
9. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 1 consisting of the following parts by weight:
about 92.70% silver;
about 5.00% copper;
about 0.70% zinc;
about 0.85% tin;
about 0.05% lithium;
about 0.20% silicon; and
about 0.50% germanium.
10. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 9 wherein said composition exhibits a tarnish rate of about 3.0 on a scale of from 0 to 5, where 0 is no tarnish and 5 is the tarnish rate of a sterling silver alloy having about 92.5% silver and about 7.5% copper when subjected for about six minutes to vapor of an aqueous solution containing about 650 parts per million of ammonium sulfide heated to a temperature of about 150° F., and wherein said composition has a hardness of about 125 VHN when age hardened by heating to a temperature of about 400° F., held at a temperature of about 400° F. for about four hours, and then allowed to cool to room temperature.
11. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 1 consisting of the following parts by weight:
about 92.70% silver;
about 5.00% copper;
about 0.90% zinc;
about 0.85% tin;
about 0.05% lithium; and
about 0.50% silicon.
12. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 11 wherein said composition exhibits a tarnish rate of about 3.5 on a scale of from 0 to 5, where 0 is no tarnish and 5 is the tarnish rate of a sterling silver alloy having about 92.5% silver and about 7.5% copper when subjected for about six minutes to vapor of an aqueous solution containing about 650 parts per million of ammonium sulfide heated to a temperature of about 150° F., and wherein said composition has a hardness of about 130 VHN when age hardened by heating to a temperature of about 400° F., held at a temperature of about 400° F. for about four hours, and then allowed to cool to room temperature.
13. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 1 consisting of the following parts by weight:
about 92.70% silver;
about 5.00% copper;
about 0% zinc;
about 0.85% tin;
about 0.05% lithium;
about 0.20% silicon; and
about 1.20% germanium.
14. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 13 wherein said composition exhibits a tarnish rate of about 3.0 on a scale of from 0 to 5, where 0 is no tarnish and 5 is the tarnish rate of a sterling silver alloy having about 92.5% silver and about 7.5% copper when subjected for about six minutes to vapor of an aqueous solution containing about 650 parts per million of ammonium sulfide heated to a temperature of about 150° F., and wherein said composition has a hardness of about 130 VHN when age hardened by heating to a temperature of about 400° F., held at a temperature of about 400° F. for about four hours, and then allowed to cool to room temperature.
15. A sterling silver alloy composition of exceptional and reversible hardness and enhanced as set forth in claim 1 consisting of the following parts by weight:
about 92.60% silver;
about 5.24% copper;
about 0.65% zinc;
about 0.85% tin;
about 0.05% lithium;
about 0.10% silicon;
about 0.50% germanium; and
about 0.01% boron.
16. A sterling silver alloy composition of exceptional and reversible hardness and enhanced tarnish resistance, as set forth in claim 15 wherein said composition exhibits a tarnish rate of about 3.0 on a scale of from 0 to 5, where 0 is no tarnish and 5 is the tarnish rate of a sterling silver alloy having about 92.5% silver and about 7.5% copper when subjected for about six minutes to vapor of an aqueous solution containing about 650 parts per million of ammonium sulfide heated to a temperature of about 150° F., and wherein said composition has a hardness of about 135 VHN when age hardened by heating to a temperature of about 400° F., held at a temperature of about 400° F. for about four hours, and then allowed to cool to room temperature.