Age hardenable clad metal having gold fineness and a surface layer with enhanced resistance to tarnish, scratching, and wear

Abstract

The present invention is directed to a jewelry element which includes two layersa cladding layer and a substrate layer, each layer being its own alloy. The cladding layer and the substrate layer each include a base metal such as silver or gold at the same percentages so that the resulting jewelry element can be labeled in accordance with one or more industry-wide requirements. The cladding layer is further enhanced by introduction of a metal providing additional hardness when included in the alloy. By limiting the hardness metal or metals to being deposed only in the cladding layer, less of the hardness metal need be used, thereby reducing cost yet retaining the requisite hardness characteristic. Each of the alloys may further contain other metals for any of a number of reasons, including but not limited to, tarnish resistance.

Claims

1. A cladded jewelry element comprising: a composite substrate layer formed of a first alloy; and a composite cladding layer formed of an age hardenable second alloy comprising from 1-15 weight percent (wt. %) palladium; wherein said substrate layer and said cladding layer are bonded to one another and the most prevalent metal in said first alloy and said second alloy is gold and comprises at least 58 wt. % of each, and said percentage of gold in said cladding layer is within 2 wt. % of the percentage of gold in said substrate layer.

2. The cladded jewelry element of claim 1, wherein gold is at a percentage so that said jewelry element is characterizable as at least 14K.

3. The cladded jewelry element of claim 1, wherein gold is at a percentage so that said jewelry element is characterizable as at least 18K.

4. The cladded jewelry element of claim 1, wherein said percentage of gold in said cladding layer is within 1 wt. % of the percentage of gold in said substrate layer.

5. The cladded jewelry element of claim 1, wherein any additional metals in said substrate layer consist of Ag, Zn, Sn, Ge, Li, Si, and Cu.

6. The cladded jewelry element of claim 1, wherein said bonding is consequential to cold roll bonding.

7. The cladded jewelry element of claim 1, wherein the thickness of the cladding layer is less than the thickness of the substrate layer.

8. The cladded jewelry element of claim 1, wherein the thickness of said cladding layer is less than 25% of the overall thickness.

9. The cladded jewelry element of claim 1, wherein the thickness of said cladding layer is 5-10% of the overall thickness.

10. The cladded jewelry element of claim 1, wherein said substrate layer is absent palladium.

11. The cladded jewelry element of claim 1, wherein said substrate layer is comprised of an age hardenable alloy.

12. A combination metal alloy for jewelry use comprising a cladding layer comprising an age hardenable first alloy with 1-15 wt. % palladium; and a substrate layer comprising a second alloy absent palladium; wherein said cladding layer and said substrate layer are bonded together, each of said first alloy and said second alloy are comprised of at least 58 wt. % gold, and the percentage of gold in said cladding layer is within 2 wt. % of the percentage of gold in said substrate layer.

13. The combination metal alloy for jewelry use of claim 12, wherein any additional metals in said substrate layer consist of Ag, Zn, Sn, Ge, Li, Si, and Cu.

14. The combination metal alloy for jewelry use of claim 12, wherein the thickness of said cladding layer is less than 25% of the overall thickness.

15. The combination metal alloy for jewelry use of claim 12, wherein said substrate layer is cold roll bonded to said cladding layer.

16. The combination metal alloy for jewelry use of claim 12, wherein the thickness of the cladding layer is less than the thickness of the substrate layer.

17. The combination metal alloy for jewelry use of claim 12, wherein the thickness of said cladding layer is 5-10% of the overall thickness.

18. The combination metal alloy for jewelry use of claim 12, wherein gold is at a percentage so that said combination metal alloy when used as a jewelry element is characterizable as at least 18K gold.

19. The combination metal alloy for jewelry use of claim 12, wherein gold is at a percentage so that said combination metal alloy when used as a jewelry element is characterizable as at least 14K gold.

20. The combination metal alloy for jewelry use of claim 12, wherein said substrate layer is comprised of an age hardenable alloy.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 depicts the bonding of two alloys under rolling pressure.

(2) FIG. 2 depicts two alloys which are braze bonded using a solder sheet between them.

(3) FIG. 3 depicts a clad cross section.

DETAILED DESCRIPTION OF THE INVENTION

(4) The present invention is directed to a jewelry element that implements a cladding alloy and a differing substrate alloy such that the overall jewelry element meets the requirements of being called sterling silver, has homogeneity of silver content, and is formed using any of a variety of cladding techniques.

(5) In a second embodiment, the present invention is directed to a jewelry element that implements a cladding alloy and a differing substrate alloy such that the overall jewelry element meets the requirements of being called a particular karat gold, has homogeneity of gold content, and is formed using any of a variety of cladding techniques.

(6) In short, a goal of the present invention is a jewelry element which includes two layersa cladding layer and a substrate layer, each layer being its own alloy. The cladding layer and the substrate layer each include a base metal such as silver or gold at the same percentages so that the resulting jewelry element can be labeled in accordance with one or more industry-wide requirements.

(7) The cladding layer, the substrate layer, or both is further enhanced by introduction of a metal providing additional hardness when included in the alloy or a process for hardening. By limiting the hardness metal or metals to being deposed only in the cladding layer, less of the hardness metal need be used, thereby reducing cost yet retaining the requisite hardness characteristic.

(8) Hardenable Alloys and Hardness.

(9) For regular karat gold alloys (not hardenable) regardless of color, the typical Vickers hardness values in the annealed condition are within the 130-150 range.

(10) For hardenable karat gold alloys regardless of color, the typical Vickers hardness values are: Annealed conditionwithin the 140-160 range; Age hardened conditionwithin the 230-260 range. For traditional sterling silver alloy (92.5% silver and 7.5% copper) the Vickers hardness in the annealed condition is within 60-80 range. This alloy may be age hardened to about 100-110 Vickers.

(11) For hardenable sterling silver alloys the typical Vickers hardness in the annealed condition is within the 60-90 range. The age hardening usually brings the hardness up to 120-140 Vickers. Some special palladium containing sterling silver alloys may be hardened up to 140-170 Vickers.

(12) Each of the alloys may further contain other metals for any of a number of reasons, including but not limited to, tarnish resistance.

(13) Resistance to tarnish is a critical property for sterling silver alloys. On the scale 1 to 5, one may grade the tarnish rate for commercially available sterling silver alloy as follows: Traditional sterling silver5. Not tarnish resistant alloy. Some tarnish resistant and hardenable sterling silver alloysbetween 4 and 3. These are tarnish resistant alloys. Some special palladium containing sterling silver alloys2. Exceptionally tarnish resistant alloys. For a comparison, the tarnish rate for a typical 14K yellow alloy is about 1.

(14) The present invention allows for a variety of combinations of metals in the alloys so that, in one example, tarnish resistance can be improved.

(15) FIG. 3 shows a cross section of such a clad with two distinct alloys: thin layer of Alloy 1 on top of the substrate Alloy 2. The chemistry of Alloy 1 in combination with Alloy 2 and the resulting cladding such as is shown in Table 2 below.

(16) Both cold and hot roll bonding does not utilize solder, and therefore, in the clad of Table 2 below, any portion of the clad (regardless of where it is sampled) is 92.5% minimum silver. In this respect, this clad is a homogeneous 92.5% silver material (other elements in this material are not homogeneous).

(17) The present invention therefore is directed to a formed alloy, such as for jewelry, whereby the substrate and top (or cladding) layers are bonded together, each of the substrate and the top layer has the same percentage makeup of a base metal (for example, silver), each has other metals, elements, and/or compounds, and the bonding is such that the end product has homogeneity of the base metal (in this example, silver) and positive attributes of the other metals, elements, and/or compounds.

(18) The present invention is further directed to a composition for cladding, preferably represented by the distribution by weight shown in Table 2. Cladding two different sterling silver metals changes the overall composition of all the elements except silversilver content stays at, for example, 92.5%.

(19) TABLE-US-00002 TABLE 2 Alloy 1 (top 10% by Alloy 2 (substrate Element thickness 90% by thickness) Clad Ag 92.5 minimum 92.5 minimum 92.5 minimum Pd 2.5 0.25 Zn 0.5 0.7 0.68 Sn 0.85 0.765 Ge 0.5 0.45 Li 0.05 0.045 Si 0.035 0.05 0.0485 Cu Balance Balance Balance

(20) Using Pd by example, by introducing but limiting the overall amount of Pd, such as limited to the clad metal of Table 2, the overall cost for materials is reduced, yet the solution herein results in beneficial tarnish and wear resistance.

(21) Importantly, for purposes of cladding, the thickness of overall Alloy 1 can be from 5-50% and the thickness of Alloy 2 can be from 50-95%.

Example 1

(22) In particular, a known substrate metal (Ag) is preferably used. Such a substrate metal is described in U.S. Pat. No. 7,198,683 to Agarwal and Raykhtsaum (Agarwal). In that patent, Agarwal describes sterling silver alloys that can be age hardened by heat treatment. Similar age hardenable alloys are described in U.S. Patent Publication Nos. 2013/0112322 and 2014/0127075. The alloys described in the latter publications exhibit enhanced tarnish resistance due to the presence of palladium in alloy compositions. Making the clad of thin layer of such alloys on a bulk of former alloy described by U.S. Pat. No. 7,198,683 results in less expensive sterling silver material that is age hardenable with the surface showing enhanced resistance to tarnish. FIG. 3 shows a cross section of such a clad with two distinct metals: thin layer of Metal 1 on top of the substrate Metal 2. The chemistry of Metal 1, Metal 2 and the resulting Clad is shown in the Table 1. Cladding two different sterling silver alloys changes the overall composition of all the elements except silversilver content stays 92.5%.

(23) Introducing a cladding, such as the alloys described in the latter publications, together with a base metal of Agrawal results in less expensive sterling silver material that is age hardenable with the surface showing enhanced resistance to tarnish.

Example 2

(24) Example 2 illustrates the clad of two sterling silver alloys where alloy 1 is hardenable with the exceptionally high resistance to tarnish, and alloy 2 is tarnish resistant but not hardenable, so that the resultant clad is tarnish resistant with the hardenable top. This results in tarnish resistant sterling silver material with the surface layer that shows enhanced hardness and resistance to scratching and wear. In this example, hot roll bonding is used. In general, the temperature used for hot roll bonding can be anywhere from 500 F to 1200 F, depending on alloys, material size, and rolling mill type.

Example 3

(25) Example 3 illustrates the clad of two sterling silver alloys where alloy 1 is hardenable with exceptionally high resistance to tarnish, and alloy 2 is traditional sterling (92.5% silver and 7.5% copper), so that the resultant clad provides the surface with enhanced hardness and tarnish resistance in comparison with traditional sterling silver. This results in sterling silver clad material with the surface layer that shows enhanced resistance to tarnish, higher hardness and resistance to scratching and wear. In this example, hot roll bonding is used.

(26) Traditionally, clad metal is a composite of two or more dissimilar metals bonded together. The bond is usually achieved by applying pressure and heat. Typical methods are cold roll hot roll bonding, as well as braze bonding. In jewelry clad metal of gold and silver alloys on brass is mainly manufactured to make gold-filled and silver-filled products. Respective gold and silver content is reduced in such materials down to 1/10- 1/40 by weight range. This is done specifically to reduce the precious metal cost. The proposed invention deals with the similar metal clad such as sterling silver on sterling silver and karat gold on karat gold with the objective to reduce total palladium content in white color gold and silver in the composites whereas to maintain karat gold and sterling silver requirement.

(27) Examples 4-6 illustrate reduced palladium 14K gold clad options using commercial karat gold alloys. Examples 7 and 8 illustrate similar options for 18K gold. Examples 9 and 10 illustrate sterling silver on sterling silver options. In all these examples the clad layer thickness is set to 10% of the total size for illustration purposes. Although shown in these examples as the clad layer representing 10% of the total size, in general, the clad thickness fraction may vary depending on, for example, manufacturing and cost considerations. Nominally, the clad thickness can vary from 5% to 25%. All the alloys in these examples are nickel-free to be in line with the European nickel-related regulations.

(28) In the examples that follow, unless otherwise stated, the metal percentages are weight percentage.

Example 4

(29) Alloy 1 is a nickel-free 14K white that contains 9.4% palladium. Such high palladium content significantly increases the cost of this 14K alloy. It is evident that the composite of 10% by thickness clad of alloy 1 on 90% by thickness of common 14K yellow substrate alloy 2 preserves 14K requirement (58.5% gold), whereas the overall palladium content (and therefore the cost) in such composite is significantly reduced down to 1%. Such clad can be made by cold and hot roll bonding technique. It also can be made using braze bonding when 14K solder is used. The jewelry article made with such clad sheet, wire or tubing has an appearance of 14K white gold, and it can be called white gold jewelry. However, both alloys 1 and 2 are not hardenable, and may be too soft for some applications where the surface durability such as scratch resistance is critical.

(30) TABLE-US-00003 TABLE 3 Alloy 2. Alloy 1. 90% 10% Clad layer Substrate Composite Au 58.5 58.5 58.5 Ag 30.9 4 6.7 Pd 9.4 1.0 Cu 1.2 32.5 29.0 Zn 5 4.4

Example 5

(31) This example (Table 4) illustrates the clad 10% by thickness of hardenable 14K white alloy 3 on 90% by thickness common 14K yellow substrate alloy 2. Palladium content (and therefore the cost) in such 14K clad is reduced from 12% to 1.3%. As the surface layer is hardenable, the overall composite shows improved surface durability. Alloy 2 is not hardenable, and may not be suitable for some applications when the increased strength is required for the whole clad material.

(32) TABLE-US-00004 TABLE 4 Alloy 2. Alloy 3. 90% 10% Clad layer Substrate Composite Au 58.5 58.5 58.5 Ag 18.9 4 5.5 Pd 12 1.3 Cu 10 32.5 30.0 Zn 0.6 5 4.5

Example 6

(33) This example (Table 5) shows the clad option where both alloys of the clad layer (alloy 3) and of the substrate (alloy 4) are hardenable. Again, the overall composite is 14K and palladium is reduced from 12% down to 1.3%.

(34) TABLE-US-00005 TABLE 5 Alloy 4. Alloy 3. 90% 10% Clad layer Substrate Composite Au 58.5 58.5 58.5 Ag 18.9 12 12.7 Pd 12 1.3 Cu 10 25.5 223.8 Zn 0.6 4 3.6

Example 7

(35) This example (Table 6) illustrates the 18K option where the clad layer alloy 5 has an exceptionally good white color due to fairly high palladium content of 14.9%. Alloy 5 is not hardenable. The alloy 6 of the substrate is hardenable 18K yellow. The overall clad is 18K with the significantly reduced palladium down to 2.7%. Such clad can be made by cold and hot roll bonding technique. It also can be made using braze bonding when 18K solder is used.

(36) TABLE-US-00006 TABLE 6 Alloy 6. Alloy 5. 90% 10% Clad layer Substrate Composite Au 75 75 75.0 Ag 5 12.5 10.9 Pd 14.9 2.7 Cu 5.1 12.5 11.5 Zn 0.0

Example 8

(37) This example (Table 7) illustrates the option where the hardenability of both alloys of the clad and of the substrate is required. Alloy 7 is hardenable 18K white containing 7% palladium. Overall composite is 18K with reduced palladium down to 0.7%.

(38) TABLE-US-00007 TABLE 7 Alloy 6. Alloy 7. 90% 10% Clad layer Substrate Composite Au 75 75 75.0 Ag 5.5 12.5 11.7 Pd 7 0.7 Cu 10 12.5 12.2 Zn 2.5 0.3

Example 9

(39) In this example (Table 8) sterling silver alloy 8 is hardenable with the enhanced resistance to tarnish as it contains 2.5% palladium. Cladding this alloy with another palladium-free exceptionally hardenable sterling silver alloy 9 reduces palladium (and therefore the cost) in overall composite down to 0.25%. The surface layer of such clad shows exceptional resistance to tarnish. The overall composite is hardenable and can be called sterling silver as it maintains 92.5% silver total.

(40) TABLE-US-00008 TABLE 8 Alloy 8. Alloy 9. 10% Clad layer 90% Substrate Composite Ag 92.5 92.5 92.5 Pd 2.5 0.25 Zn 0.5 0.7 0.68 Sn 0.85 0.765 Ge 0.5 0.45 Li 0.05 0.045 Si 0.035 0.05 0.0485 Cu 4.465 5.35 5.2615

Example 10

(41) This example (Table 9) illustrates the clad option of alloy 8 on traditional sterling silver alloy 10 (92.5% silver and 7.5% copper). This option is suitable when there is no need for the substrate alloy to be exceptionally hardenable.

(42) TABLE-US-00009 TABLE 9 Alloy 8. Alloy 10. 10% Clad layer 90% Substrate Composite Ag 92.5 92.5 92.5 Pd 2.5 0.25 Zn 0.5 0.05 Si 0.035 Cu 4.465 7.5 7.2