WO2003029501A1

WO2003029501A1 - High percentage zinc alloy for use with silver or gold

Info

Publication number: WO2003029501A1
Application number: PCT/US2001/030819
Authority: WO
Inventors: Daniel Davitz
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-03
Filing date: 2001-10-03
Publication date: 2003-04-10
Anticipated expiration: 2004-04-03
Also published as: TW570985B

Abstract

The present invention provides an additive alloy consisting essentially of (7) percent to (45) percent by weight copper, (40) percent to (84.50) percent by weight zinc, and 0.1 percent to (4) percent by weight silicon, the alloy being free of gold or silver. The invention includes a method of manufacturing a tarnish-resistant, corrosion-resistant and substantially less brittle alloy for suitable use in jewellery such as rings, earrings, and bangles. The method includes admixing the additive alloy with a precious metal to obtain an admixed alloy, which is substantially brittleness free and highly tarnish resistant. The process of making the admixed alloy into a shot form is illustrated in Figure 4, wherein the molten metal (14) is poured through a graphite strainer (20) having a multiplicity of holes (22) and into a container (24) having water (26) therein, and the mixture then forms shots or grains (28).

Description

Application for United States Letters Patent

TO ALL WHOM IT MAY CONCERN:

Be it known that I, Daniel Davitz, a citizen of the United States, residing at 4103 Florence Way, Glenview, Illinois 60025, have invented a new and useful "HIGH PERCENTAGE ZINC ALLOY FOR USE WITH SILVER OR GOLD" of which the following is a specification. HIGH PERCENTAGE ZINC ALLOY FOR USE WITH SILVER OR GOLD BACKGROUND OF THE INVENTION

The invention relates generally to an alloy that is used in combination with silver or gold, and specifically to an alloy that when combined with silver or gold provides these precious metals with improved tarnish resistance and improved casting qualities.

Sterling silver jewelry and other sterling silver utensils derive their value from the intrinsic value of the precious metal and also from the aesthetic color of the metal. However, manufacturing products with sterling silver is fraught with problems since the base alloy is usually brittle after casting. Moreover, sterling silver tarnishes over time. Several attempts have been made to improve the tarnish resistance and corrosion resistance of sterling silver, and also to improve the casting qualities of sterling silver. However, many of these attempts have still resulted in alloys that are too expensive for substantial commercial use. By way of example, an alloy called Astro White, an alloy called "precium" and the alloy in U.S. Patent No. 5,037,708, developed by the present inventor, have been found to be too costly for substantial commercial use.¹

With respect to gold alloys, various gold alloys have different shades. Some gold alloys are greenish yellow, some are white, and some are red. The alloys currently added to gold are problematic since they do not have low enough surface tension so that they can (once added to the gold) provide material that conforms to intricate molds. Moreover, the addition of these alloys to gold results in materials that still have the problem of tarnishing too rapidly. There exists a need for an inexpensive, tarnish resistant, corrosion resistant gold and silver alloy, and alloy additive that when combined with gold and silver has desirable properties.

The present invention fulfills these and other related needs. SUMMARY OF THE INVENTION

In accordance with the present invention, a metal alloy is disclosed which when silver is added is more tarnish resistant, corrosion resistant and with better working properties and consisting of the following ingredients: about .1 percent to 4 percent by weight silicon, about 40 percent to 84.50 percent by weight zinc, about 7 percent to 45 percent by weight copper and/or indium. The alloy is free of gold or silver. It is an object of the invention to provide a precursor alloy when mixed with silver or gold that is more corrosion resistant and more tarnish resistant than conventional alloys.

It is yet a further object of the invention to provide the above referenced alloy which is cast into jewelry. The jewelry is selected from the group consisting of a ring, an earring, and a bangle. The alloy has a melting temperature in the range of about 500 degrees F to about 600 degrees F.

It is yet another object of the invention to provide a jewelry alloy suitable for rings, ear rings and bangles containing about 90 to 95 percent by weight silver, from 0 percent to about 3.5 percent by weight copper, from 0 percent to about 7.5 percent by weight zinc and from 0 percent to about 0.25 percent by weight silicon. Optionally, the jewelry alloy further includes in the range of about 0.25 percent by weight boron and in the range of about V_ percent to about 1 percent indium.

In yet another aspect of the invention, the invention includes a method of manufacturing a tarnish-resistant, corrosion-resistant and substantially brittleness-free alloy suitable for use in jewelry. The additive alloy consists essentially of about 7 to 45 percent by weight copper, about 40 percent to about 84.5 percent by weight zinc, and about .1 percent to

¹ U.S. Patent Nos. 5,882,441 and 5,817,195 also developed by the present inventor describe improvements of these alloys. about 4 percent by weight silicon, the alloy being free of gold or silver. The additive alloy is heated at 560° F for about 15 minutes either in an argon environment or in a vacuum. Usually, it is made in 500 oz. quantities. The method further includes admixing the additive alloy with a precious metal to obtain an admixed alloy.

In another variant of the invention, the precious metal comprises 90 to 95 percent by weight silver. In another variant, the precious metal includes gold. The precious metal is added to the additive alloy in portions in a crucible under an argon environment. The admixed alloy can then be melted at a temperature in the range of about 1700 degrees F to about 1800 degrees F.

The method includes casting the admixed alloy using a temperature in the range of about 1810 degrees F to about 1910 degrees F.

The objects and features of the present invention, other than those specifically set forth above, will become apparent in the detailed description of the invention set forth below. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front vertical section view of a crucible containing the alloy of the present invention and a precious metal for mixture therefor.

FIG. 2 is a front cutaway view of a container having a plurality of apertures on its base portion used to manufacture shot from the alloy of the present invention.

FIG. 3 is a front perspective view of a graphite board having a plurality of apertures there through used for forming shot from the alloys of the present invention. FIG. 4 is a front perspective view of the alloy of the present invention being poured from a heated crucible into a graphite shot maker, and shot passing through apertures in the shot maker to a tub having water therein

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an additive alloy consisting essentially of about 7 percent to about 45 percent by weight copper², about 40 percent to about 84.5 percent by weight zinc, and about .1 percent to about 4 percent by weight silicon, said alloy being free of gold or silver. The additive alloy can be cast into jewelry when used in combination with another precious metal.

To be considered in the sterling family, we must use a minimum of 92.5 percent by weight silver and usually to make up the balance to 100 percent is copper. But in this invention, the copper is reduced to enhance the tarnish resistance and the corrosion resistance by the replacement of most of the copper with zinc. We found that this gives us a more stable color alloy than sterling silver, and eliminates the brittleness of sterling silver after casting. The ratio of silver due to cost and to be considered like sterling silver is 92.5 percent by weight silver, 4.4 percent by weight zinc, 3 percent by weight copper, .1 percent by weight silicon. Zinc enhances color and helps in the tarnish and corrosion resistance, silicon makes smoother castings by being a deoxidizer and making the molten metal more fluid.

The specific gravity of the alloy is 8.85 GR/Cc plus or minus GMS/CC. Other physical proprieties are:

Low hardness 85 Brinell Heat treated in furnace 850° F and quenched.

High hardness 130 Brinell Heat treated in furnace 850° F and bench cooled.

² All percentages referred to herein are percent by weight of the total weight of the material or mixture. Elongation 15% to 28%

Specifically, the preferred alloy formula in accordance with the invention is:

Silver 90 to 95% by weight

Zinc 4 to 6% by weight

Copper 1 to 4% by weight

Silicon .1 to .25% by weight

The combined alloy has better working properties than conventional sterling silver or conventional gold alloys and results in a harder sterling silver combination alloy that is very tarnish resistant, and can be manufactured at lower cost than conventional alloys while still retaining the working and color properties of silver or gold that are most aesthetically pleasing and desirable.

The additive alloy contains zinc, and a low percentage of silicon and may optionally contain a small amount of indium. When silver is added, the combined alloy polishes, looks like and works like sterling silver. Yet in a 5 percent chlorine atmosphere, the combination alloy is superior to conventional sterling silver containing 92.5 percent by weight silver and 7.5 percent by weight copper. The combination alloy showed no discoloration while the conventional sterling silver/copper alloy turned black. A comparison of the combination alloy and the conventional alloy in a sulfur gas atmosphere yielded the same results: the combination alloy was still bright and the conventional alloy tarnished.

Another improvement of the invention over the prior art involves the addition of zinc instead of only copper in the additive alloy. The zinc in combination with a small amount of copper and silicon provides increased hardness and increased corrosion resistance (while providing better working properties and reduced brittleness) of the additive alloy and combination alloy. These increased working properties include, by way of example, a casting temperature in the range of about 1810 degrees F to about 1910 degrees F, and a melting temperature in the range of about 1700 degrees F to about 1800 degrees F.

The various formulations of the present invention having the above described properties include a jewelry alloy suitable for rings, ear rings and bangles containing about 92.5 percent by weight silver, from 0 percent about 6.0 percent by weight zinc, from 0 percent to about 7.5 percent by weight copper and from 0 percent to about 2.5 percent by weight silicon. In a variant of the invention, the jewelry alloy further comprises (or consists essentially of in one variant) in the range of about 0 to 0.25 percent by weight boron and in the range of about Y_ percent to about 5 percent indium.

The invention also provides a method of manufacturing a tarnish-resistant, corrosion- resistant and substantially brittleness-free alloy suitable for use in jewelry. The method includes initially preparing an additive alloy consisting essentially of about 7 percent to about 45 percent by weight copper, about 40 percent to about 84.5 percent by weight zinc, and about .1 percent to about 4 percent by weight silicon. The additive alloy is free of gold or silver. In a Preferred Embodiment, Vz teaspoon of Calcium Boride is added to the admixed alloy before putting the alloy in the furnace.

As shown in FIGS. 1-4, the additive alloy (10) is admixed with a precious metal (12) to obtain an admixed alloy (14). In a preferred embodiment approximately one half of the total precious metal (12) is poured into a crucible (16). The alloy (10) is then poured into the crucible (16). The remaining precious metal (12) is then added to the crucible (16). The mixture (14) is heated between 1850 and 1950 degrees F in crucible (16), with inert gas (18) covering the admixed alloy (14). When the mixture is cherry red, it is poured through a graphite strainer (20, FIG. 4) having a multiplicity of holes (22) and into a container (24) having water (26) therein. The mixture forms shots or grains (28). The grains (28) are subsequently scrubbed in soapy water, then washed with clear water and dried. In an alternative embodiment, the graphite strainer may take the form of a graphite board (30) having a plurality of holes (32) extending therethrough (as shown in FIG. 3).

The furnace used may comprise a gas furnace or induction coils. With induction coils, the crucible (16) melts the metal (12). With a gas furnace, the heat from the gas flame melts the metal (12). The crucible (16) with metal (12) therein is placed into the gas furnace after it turns cherry red, or place the crucible (16) into the induction coils until the crucible (16) is cherry red. At the same time, the shot crucible (20) is put into the furnace.

The admixture alloy (10) is prepared by mixing zinc, copper, and silicon, heating the mixture to between 1700 and 1800 degrees F in the furnace, (not shown), and tumbling in a closed container or crucible (16) having an inert gas (18) filling the container (16).

After the metal (14) is molten completely, the heat source is immediately removed either by turning the induction coils off or by removing from gas furnace. Continuing to heat the metal will ruin the quality and looks of the shot. The metal (14) is then stirred with a carbon rod (not shown). The shot crucible (20) is placed in the adapter or rack (20A) over cold water - with ice cubes when necessary and the molten metal (14) is poured slowly into the shot crucible (20).

Manufacturing Notes

A #3 Crucible is used for small orders, a #10 for large orders of 1000 oz. or more but not more than 200 oz.

A #1 or #2 Crucible is used for the shot maker crucible (20). 1/32 holes are placed in the #1 crucible so that the metal can flow evenly from the crucible (20).

Steps for manufacturing:

A. Start furnace so that it is at it's maximum heat. B. Fill a 30-gallon tank with cold water until it reaches four inches from top of tank. In the tank, a catch is placed for the metal as it drops into the water.

C. A crucible holder or adapter is placed above tank of water so that the crucible (20) will be about 18" above the water line.

D. The metals are placed in the crucible (16) in order of their melting point. Zinc is never placed on top; always place zinc in crucible (16) first. If you are manufacturing Astrolite Gold, place zinc 1^st, copper 2^nd, silver 3^rd, indium 4^th, until all the metals are melted. Use calcium boride as the flux and use it sparingly. To place the indium in, then melt it, you must remove the crucible (16) from the furnace and slowly lower the indium into the melt and then stir with a graphite rod. Metals are tested by placing a graphite (carbon) rod in a flame from the furnace and then placing the rod in the crucible to make sure the metals are melted. When the melted melts show a clear surface then it is ready to pour.

E. Flux for these alloys will always be a half teaspoon or less of calcium boride or .01% silicon and calcium boride.

Heat Treatment:

A suitable heat treatment will either harden or soften a metal, as desired.

1. To age harden the alloy, the optimum temperature for age hardening is 300-500 degrees F. Maintain the alloy at this temperature for 1 hour. Allow to cool at room temperature. Of course, it depends on the thickness of the product used. You increase time for thicker products.

2. To harden the alloy without age hardening, heat product to 850- 1100 degrees F for 2 hours and bench cool; at room temperature till product is room temperature.

3. To soften the alloy, bring the temperature to 850 degrees F and quench as soon as you withdraw from the furnace. EXAMPLE ONE (MANUFACTURE OF A STERLING ALLOY OR GOLD ALLOY)

Using a graphite crucible or ceramic crucible, there was placed about one half of the gold or silver of a predetermined amount into the bottom of the crucible. The additive alloy described above was added to the gold or silver substrate. Thereafter, more gold and silver are added on top of the additive alloy/combined alloy. If a vacuum is not used in combination with the mixing process, argon is utilized in a manner known in the art. The use of the argon keeps oxygen from the additive alloy and permits proper integration of the zinc into the alloy. Alternatively, the mixing process can occur under a vacuum. The resulting alloy is heated to either 1850 degrees F for silver, +_ 50, or 1950, + 50, for gold until melted.

In another variant of the invention, the additive alloy consists essentially of .1 percent to 4 percent by weight silicon, 40 percent to 84.5 percent by weight zinc, and 7 percent to 45 percent by weight copper and/or indium.

To be considered in the sterling family, one must use at least 92.5 percent by weight silver and, in the conventional sterling silver alloy, include copper in the remainder. However, use of zinc in this invention instead of copper enhances the tarnish resistance and the corrosion resistance of the combination alloy. Use of the zinc and the other formulations described herein also provides for a more stable color for the alloy and conventional sterling silver, and eliminates the brittleness of conventional sterling silver after casting. A particularly preferred ratio is 92.5 percent by weight silver, 4.4 percent by weight zinc, and 3 percent by weight copper, and 0.1 percent by weight silicon. The zinc enhances the color and provides increased tarnish and corrosion resistance and the silicon acts as a deoxidizer and makes the additive and combination alloy in its molten state more fluid and more easily workable.

In another variant of the invention, the method includes the addition of a precious metal including 90 percent to 95 percent by weight silver. In another embodiment, the precious metal includes gold of between 40 percent to 90 percent, depending on the carat sought. Obviously, silver is not present in this embodiment.

The method also includes optionally adding to the additive alloy in the range of about 0.25 percent to about 1 percent by weight boron, and in the range of about V_ percent to about 1 percent indium to the precious metal, casting the admixed alloy using a temperature in the range of about 1810 degrees F to about 1910 degrees F, and/or melting the admixed alloy at a temperature in the range of about 1700 degrees F to about 1800 degrees F.

While only a few, preferred embodiments of the invention have been described hereinabove, those of ordinary skill in the art will recognize that the embodiment may be modified and altered without departing from the central spirit and scope of the invention. Thus, the preferred embodiment described hereinabove is to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced herein.

EXAMPLES 2, 3 AND 4

Additional formulations are as follows:

All figures are percent by weight.

Claims

CLAIMS I CLAIM:

1. A method of manufacturing a tarnish resistant, corrosion resistant and substantially brittleness free alloy suitable for use in jewelry comprising; mixing an additive alloy consisting essentially of about 7 percent to about 45 percent by weight copper, about 40 percent to about 84.50 percent by weight zinc, and about 0.1 percent to about 4 percent by weight silicon; providing 90 to 95 percent by weight silver relative to said additive alloy; placing half of said silver in a crucible; placing said admixture in said crucible over said silver; placing the remaining half of said silver in said crucible; maintaining said crucible in an inert gas; heating the resulting alloy in an inert gas environment until said alloy and silver are melted.

2. The method of claim 1 and further comprising: pouring said resulting alloy through a graphite strainer having a plurality of uniform holes there through and into a container of water, so as to form shots; cooling said shots; removing said shots from said water and tumbling said alloy in a mixer in the presence of soap and water; and washing said shots in water and drying said shots.

3. The method of claim 2 wherein said graphite strainer comprises: a graphite board having a plurality of holes formed therein to allow said melted alloy to pour therethrough and form shots.

4. The method of claim 2 wherein said graphite strainer comprises a graphite crucible having a plurality of holes formed on the bottom thereof.

5. The method of claim 2 and further comprising: heating said shot members to between 1810 and 1910 degrees F; until melted to a liquid and; casting said melted liquid into desired jewelry shapes.

6. The method of claim 2 wherein said holes are 1/32 in diameter.

7. The method of claim 5 wherein said jewelry shapes comprise one of the group consisting of bangles, rings and ear rings.

8. The jewelry alloy of claim 1 and further mixing about 0 to about 0.25 percent by weight copper and about Y. percent to about 1 percent indium with said additive alloy.

9. A master metal composition adapted to be alloyed with silver, consisting essentially of the following parts by weight: about .1 to 4 percent silicon; 40 to 84.50 percent zinc; and 7 to 45 percent copper.

10. The master metal composition of claim 9, and further comprising 0 to 1 percent indium.

11. The master metal composition of claim 9, and further comprising .05 to 1 percent nickel.

12. An alloy for use as an additive to a precious metal, said alloy comprising about 5.75 percent to about 45 percent by weight copper, about 3 percent to about 80 percent by weight zinc, and about 0.1 percent to about 4 percent by weight silicon, said alloy being free of gold or silver.

13. The alloy of claim 12 combined with a precious metal, and cast into jewelry, said jewelry selected from the group consisting of a ring, an earring, and a bangle.

14. The alloy of claim 13 having a casting temperature in the range of about 1810 degrees F to about 1910 degrees F.

15. The alloy of claim 13 having a melting temperature in the range of about 1700 degrees F to about 1800 degrees F.

16. A jewelry alloy suitable for rings, ear rings and bangles containing about 90 to 95 percent by weight silver, from 3.5 percent about 7.35 percent by weight zinc, from 1 percent to about 3 percent by weight copper and from .1 percent to about .25 percent by weight silicon.

17. The jewelry alloy of claim 16 and further comprising about 0 to about 0.25 percent by weight copper and about Vz percent to about 1 percent indium.

18. A method of manufacturing a tarnish-resistant, corrosion-resistant and substantially brittleness-free alloy suitable for use in jewelry comprising; mixing an additive alloy consisting essentially of about 7 percent to about 45 percent by weight copper, about 40 percent to about 84.50 percent by weight zinc, and about 0.1 percent to about 0.4 percent by weight silicon, said alloy being free of gold or silver; admixing said additive alloy with a precious metal to obtain an admixed alloy.

19. The method of claim 18 in which said precious metal comprises 90 percent to 95 percent by weight silver.

20. The method of claim 18 in which said precious metal comprises gold.

21. The method of claim 18 further comprising adding to said additive alloy in the range of about 0.25 percent to about 1 percent by weight boron, and in the range of about Vi percent to about 1 percent indium.

22. The method of claim 18 further comprising casting said admixed alloy using a temperature in the range of about 1810 degrees F to about 1910 degrees F.

23. The method of claim 18 further comprising melting said admixed alloy at a temperature in the range of about 1700 degrees F to about 1800 degrees F.