PLATINUM ALLOY AND METHOD OF PRODUCTION THEREOF

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a platinum alloy and a method of production thereof. In particular, the present invention relates to platinum alloys that are suitable for the fabrication of ornamental articles such as rings, necklaces, bracelets, earrings, watch bands, watch bodies and other jewelry. Furthermore, the present invention relates to an ornamental article made from the platinum alloy and a method of production thereof.

BACKGROUND OF THE INVENTION

[0002] Platinum is a precious metal and is relatively expensive. In recent years platinum has come into increasing prominence as a metal used for jewelry fabrication. Platinum for fine jewelry is commonly sold in high concentrations of over 85 percent by weight.

[0003] Pure platinum metal (Pt1000) is soft and does not have the mechanical strength for most jewelry applications. For this reason, in most jewelry applications various kinds of platinum alloys are employed. Platinum alloys are desirable for their neutral color when combined with gems, they are hypoallergenic, they have high tensile strength, and a pleasurable heft due to their high-density.

[0004] The jewelry industry uses three main classes of platinum alloys. These classes are Pt950, Pt900 and Pt850. These alloys have a platinum content of 95, 90 and 85 wt.%, respectively. Commercially available alloys frequently used in the fabrication of jewelry include Pt/Ir 900/100 (90 wt.% platinum and 10 wt.% iridium), PtCu950 (95 wt.% of platinum and 5 wt.% of copper) and PtCo950 (95 wt.% of platinum and 5 wt.% of cobalt).

[0005] Various high platinum content jewelry materials are known in the art. The term "high platinum content" as used herein refers to platinum alloys having a platinum content equal or greater than 85 wt.%.

[0006] For example, U.S. Patent. 4,165,983 describes an alloy for fabricating jewelry containing at least 95 wt.% platinum, 1.5 to 3.5 wt.% gallium, and a balance of at least one of indium, gold, palladium, silver, copper, cobalt, nickel, ruthenium, iridium and rhodium. U.S. Patent 5,846,352 describes a heat-treated platinum-gallium alloy for fabricating jewelry containing 1 to 9 wt.% gallium and a small amount of palladium. Japanese published patent application JP 61-133340 describes an alloy for fabricating jewelry consisting of 84 to 96 wt.% platinum, 1 to 10 wt.% gallium, 0.5 to 10 wt.% copper, and 0.01 to 5 wt.% cobalt. Japanese published patent application JP 61-034133 describes an alloy for fabricating jewelry containing 84 to 96 wt.% platinum, 0.5 to 10 wt.% cobalt, 0.5 to 10 wt.% copper and 0.01 to 0.5 Y, B, CaB mischmetal.

[0007] Although such alloys have satisfactory mechanical and optical properties that make them suitable for jewelry fabrication, these alloys are expensive to produce due to their high platinum content.

[0008] There are also a number of low platinum content jewelry materials known in the art. The term "low platinum content" as used herein refers to platinum alloys having a platinum content smaller than 85 wt.%.

[0009] U.S. Patent No. 6,048,492 describes a platinum alloy composition for use in jewelry products containing about 58.5 wt.% of platinum, 26.5 to 36.5 wt.% of palladium and 5 to 15 wt.% of either iridium, copper or ruthenium. U.S. Patent 2,279,763 describes a ductile platinum alloy containing 10 to 80 wt.% of platinum, 12 to 90 wt.% of palladium, and 1 to 15 wt.% of ruthenium.
WO2004/059019 Al describes PT-base bulk solidifying amorphous alloys utilizing platinum and other ingredients and requiring the presence of phosphorous. The amorphous alloys described in this document are prepared by quenching the molten alloy from above the melt temperature to ambient temperatures and thus achieving a substantially (i.e. non-crystalline) structure of the alloy and requiring more than 50% to be in the amorphous state.

[0010] A disadvantage of known low platinum content jewelry materials is that they often have inferior mechanical and physical properties compared to the high platinum content jewelry materials. In particular, the castability of known low platinum content jewelry materials is not as good as that of high platinum content alloys. Also, the color of known low platinum content jewelry materials differs from the typical "platinum color" of Pt950 alloys that is desired by most customers of fine jewelry. Hence, low platinum content jewelry materials are often rejected by customers for aesthetical reasons. In fact, it is very difficult to produce a low platinum content jewelry material that combines both the mechanical strength and workability as well as the optical properties of high platinum content materials.

[0011] Due to the potential improvements in properties and performance of such alloys, there is a need for additional alloys suitable for use in jewelry and art applications.

[0012] Accordingly, it would be desirable to provide a platinum alloy composition suitable for jewelry that is less expensive than the platinum that is presently available, yet still provides a platinum jewelry item with desirable technological and optical properties.

SUMMARY OF THE INVENTION

[0013] According to the present invention there is provided an improved low platinum content alloy composition that consists of a platinum alloy comprising 63.01 to 69.99 wt,% of platinum, 1.5 to 10 wt.% of cobalt, 20.01 to 35.49 wt.% of copper, and optionally 0.001 to 2 wt.% of at least one first metal selected from the group consisting of iridium and ruthenium, 0.001 to 2 wt.% of at least one second metal selected from the group consisting of indium and gallium, 0.001 to 5 wt.% of palladium, 0.001 to 0.5 wt.% of silicon, 0.001 to 0.5 wt.% of zirconium, phosphorous in an amount of less than 4.2 wt.%, the balance being copper and unavoidable impurities. The alloys according to the present invention are particularly well suited for the fabrication of ornamental articles, such as rings, necklaces, earrings, watch bands, watch bodies and other jewelry.

[0014] Surprisingly, it was found that despite of their relatively low platinum content the alloys of the present invention exhibit excellent mechanical and optical properties that make them extremely suitable for the manufacturing of ornamental products such as jewelry of any kind. Due to the lower density of the alloys of the present invention it is possible to manufacture thinner, lighter constructions and castings at considerable less cost than with high platinum content alloys (e.g. Pt850, Pt900, Pt950).

[0015] The platinum alloys of the present invention have a lower melting range compared to known low platinum content alloys as described in, for example, U.S. Patent 6,048,492. Due to their relatively low melting temperature they cast easier than previously known platinum alloys and are more energy efficient. This lower temperature alloy also allows a lower mold temperature, decreasing defect rate due to shrinkage porosity, investment cracking, inclusions, and contaminations that occur more readily at highly-elevated temperatures.

[0016] The alloys according to the present invention are particularly well suited for the fabrication of jewelry due to their improved hardness, workability, castability, deformability, wear and abrasion properties, and resistance to corrosion. The platinum alloy composition of the invention appears and looks no different than 95 percent platinum, but is substantially lighter, less dense, and thus, less expensive to produce. In fact, the platinum alloy composition of the present invention has essentially the same color and appearance as PtCu950 alloy.

[0017] The invention further relates to a method of preparing the alloys of the present invention by formulating and mixing the components of the alloy in the specified amounts and melting them together.

[0018] The alloy may be formed into a desired shape. Such operations are many and include casting or fabricating. Some examples of fabrication can be by rolling of the alloy into a sheet, drawing a wire, molding, casting, forging, stamping or constructing the object or shape useful as a jewelry component.

[0019] Accordingly, the invention also relates to a method of manufacturing an ornamental article, which comprises formulating one of the platinum alloys described above and then utilizing the alloy as a component of jewelry.

[0020] Further, the invention also relates to the use of such alloys in the production of ornamental articles such as jewelry. Still further, the invention relates to ornamental articles comprising such alloys.

[0021] Accordingly, it is an object of the invention to provide an improved low platinum content platinum alloy composition.

[0022] Still another object of the invention is to provide an improved platinum alloy composition that is suitable for use in jewelry for the mass commercial market.

[0023] A further object of the invention is to provide an improved platinum alloy composition which is substantially lighter and less dense than conventional platinum alloy compositions.

[0024] Still further it is an object of the invention to provide platinum alloys which may be cast more readily than known platinum alloys.

[0025] Still other objects and advantages of the invention will in part be obvious, and will in part be apparent from the following description.

DETAILED DESCRIPTION

[0026] The platinum alloy compositions of the invention include platinum in an amount of 63.01 to 69.99 wt.%. The platinum content of the alloy compositions of the invention is significantly lower than that of conventional Pt850, Pt900 and Pt950 platinum alloys commonly used in the jewelry industry.

[0027] According to the invention the platinum alloy consists of a platinum alloy consisting of: 63.01 to 69.99 wt,% of platinum,
1.5 to 10 wt.% of cobalt; and
22.01 to 35.49 wt.% of copper.

[0028] Preferably, the platinum content of this alloy is from 63.5 to 66.5 wt.% , in particular from 64 to 66 wt.%, based on the total alloy composition. If the platinum content of the alloy is smaller than about 63 wt.% the workability and stampability of the alloy decrease significantly and the alloy loses its platinum-like color. If the platinum content of the alloy is greater than about 70 wt.%, the costs for the production of the alloy increase significantly while, at the same time, the mechanical and chemical properties of the alloy do not improve significantly.

[0029] Preferably, the cobalt content of the alloys of the present invention is from 1.5 to 10 wt.%, in particular 2.0 to 8.0 wt.% or 2.0 to 6.0 wt.%, based on the total alloy composition. If the cobalt content of the alloy is smaller than about 1.5 wt.%, the mechanical properties and the workability of the alloy decrease significantly and the alloy loses its platinum-like color. If the cobalt content of the alloy is greater than about 8 wt.% the alloy becomes too hard.

[0030] Preferably, any balance in the alloys of the present invention is made up by copper.

[0031] The platinum alloys of the present invention may further comprise 0.001 to 2 wt.% of at least one first metal selected from the group consisting of iridium and ruthenium. A combination of these elements may also be added, so long as the total amount does not exceed 2 wt.% of the alloy composition. Iridium and/or ruthenium can be added as metal hardeners in order to improve the hardness of the alloy, with iridium being the preferred hardener since it offers gradual hardness improvements over a wide range of concentrations, with no deterioration of alloy properties.

[0032] The platinum alloys of the present invention may further comprise 0.001 to 2 wt.% of at least one second metal selected from the group consisting of indium and gallium. A combination of these elements may also be added, so long as the total amount does not exceed 2 wt.% of the alloy composition. Indium and gallium may be added to improve the precipitation hardening of the alloy. The platinum alloys of the present invention may further comprise palladium in an amount of 0.001 to 5 wt.%, preferably 0.25 to 2.5 wt.%. An addition of palladium is useful in order to vary the color of the alloy.

[0033] The platinum alloys of the present invention may further comprise silicon in an amount of 0.001 to 0.5 wt.%, preferably in an amount of 0.1 to 0.3 wt.%. It was found that an addition of silicon in the specified amount improves the casting properties of the alloy and results in a smoother surface of the casted article. This effect is particularly desirable when the alloy of the present invention is used for the manufacture of an ornamental article where excellent casting properties are required. It was found that silicon in the amounts specified is soluble in the Pt-Co-Cu alloys of the present invention and results in the aforementioned effect. In contrast thereto, addition of silicon to high content platinum alloys generally results in inhomogeneous low melting phases and is thus undesirable.

[0034] The platinum alloys of the present invention may further comprise zirconium in an amount of 0.001 to 0.5 wt.%, preferably in an amount of 0.1 to 0.3 wt.%. It was found that an addition of zirconium in the specified amount improves the workability of the alloys.

[0035] According to a preferred embodiment of the present invention, the total amount of other elements present in the platinum alloy besides Pt, Cu, and Co does not exceed about 10 wt.%, preferably about 7.5 wt.%, even more preferably about 5 wt.%, and most preferably about 4 wt.%, based on the total weight of the platinum alloy.

[0036] The platinum alloy of the present invention may be present in a crystalline state or in an amorphous state. Preferably, the platinum alloy of the present invention is present in a substantially crystalline state. The term "substantially crystalline state" as used herein means that the platinum alloy is greater than fifty percent crystalline by volume. Preferably, the platinum alloy is at least about ninety percent crystalline by volume, more preferably at least ninety five percent crystalline by volume and most preferably about one hundred percent crystalline by volume.

[0037] While phosphorous can be used as an additive in some platinum alloys to make the alloy more brittle and/or amorphous, the addition of phosphorous to the alloy of the present invention is not particularly preferred since it is not desired to produce an amorphous alloy. Therefore, if phosphorous is added to the platinum alloy of the present invention, such an addition should be done in moderate amounts. Preferably, the amount of phosphorous contained in the platinum alloy of the present invention is less than 4.2 wt.%, more preferably less than 3.4 wt.%, even more preferably less than 2.3 wt.% and most preferably less than about 1.5 wt.% of phosphorous, based on the total alloy composition. According to another preferred embodiment the platinum alloy of the present invention contains less than about 2.0 wt.% and more preferably less than about 1 wt.% of phosphorous, based on the total alloy composition.

[0038] According to another embodiment of the invention, the platinum alloy consists of 63.5 to 67.5 wt.% of platinum, 1.5 to 8 wt.% of cobalt, and 24.5 to 35 wt.% of copper, wherein copper may be substituted by one or more of the following elements in the amounts specified:

[0039] 0.001 to 2 wt.% of at least one of said first metals; 0.001 to 2 wt.% of at least one of said second metals; 0.001 to 5 wt.% of palladium; 0.001 to 0.5 wt.% of silicon; and/or 0.001 to 0.5 wt.% of zirconium.

[0040] The alloys of the present invention exhibit excellent mechanical and physical properties such as tensile, strength, Vickers hardness and elongation at break. The tensile strength of the platinum alloys of the present invention is in the range of 450 to 800 N/mm2. The Vickers hardness of the platinum alloys of the present invention, measured at softened state, is in the range of 130 to 210 HV10. The elongation at break of the platinum alloys of the present invention is at least about 20 %.

[0041] A further advantage of the present invention is that the color tone of the platinum alloy corresponds essentially to the platinum white color tone of a PtCu950 alloy, which is aesthetically very appealing.

[0042] The alloys of the present invention may be prepared by conventional alloying methods that are well known in the art. The preparation of the alloy generally includes the step of melting platinum, cobalt and copper and any other component in the specified amounts. The method may further include the step of hardening the alloy by cold working or heat treatment.

[0043] The method may include the steps of annealing and then quenching the alloy, before hardening the alloy.

[0044] The alloys are usually cast from melts under a shielding gas and then shaped. After shaping, they may be subjected to heat treatment, possibly under a shielding gas, to improve their mechanical properties.

[0045] In order to prepare the platinum alloy composition of the invention, a high temperature melting process is carried out. This can achieved using induction melting equipment, as is well known in the art. At all times, extreme care should be exercised in order to limit metal contamination, as platinum is easily contaminated by many elements routinely present in the environment. Such care
can be achieved by melting the metals in either a vacuum or an inert gas atmosphere, by preventing contact with other metals, and by preventing mixing with silica-based products.

[0046] The platinum alloy is preferably melted and blended together by induction heating in appropriate crucibles for platinum alloys. After melting, the alloy can be poured through water to create grain-shot and can then be dried, weighed and used for casting.

[0047] For the preparation of the alloy of the present invention, the components of the inventive composition are preferably melted in a silica crucible (for small, fast melts) or a zirconium oxide (for large, slow melts) crucible in an induction oven. It is preferred to use a vacuum or inert gas in the melting process and to place all components of the alloy composition in the crucible at the same time. In the melting of the alloy, the molten metals should preferably be "turned" (utilizing medium to low frequency induction fields) in order to obtain an appropriate mixing of the metals.

[0048] Following the melting step, the resulting alloy nugget elements can be subjected to cold rolling and/or annealing in order to improve mechanical qualities of the mix. Thereafter, the mixed metal composition can optionally be re-melted as before, and a shot or plate be produced.

[0049] The preparation of the platinum alloys of the present invention can further comprise an annealing step. Annealing can be carried out either in a furnace or with a torch, as is well known in the art. The annealing temperature depends on the platinum content and the melting point of the alloy and will readily be determined by a person of ordinary skill by routine experiments. Preferably, the annealing is done in a furnace that is atmosphere controlled with shielding gas.

[0050] The shielding gas can be any of the non-oxidizing inert gasses, such as argon, nitrogen, or mixtures thereof; anti-oxidizing gasses such as hydrogen, carbon monoxide, or "forming" or "cracked ammonia" gas (nitrogen with a few percent of hydrogen). The piece can also be protected from oxidation by enveloping them with commercially available heat-treating wraps.

[0051] The alloys can be used for a wide variety of jewelry components, such as rings, clasps, spring parts; even compression-spring settings for gemstones, and the like:

[0052] Furthermore, the alloys can be repeatedly annealed and heat-treated/age-hardened, if desired.

[0053] As used herein, the term "age-hardening" is essentially synonymous with the term "precipitation hardening" which results from the formation of tiny particles of a new constituent (phase) within a solid solution. The presence of these particles create stress within the alloy and increase its yield strength and hardness. See, B. A. Rogers, "The Nature of Metals", p.320 (Iowa State University Press, 1964); H. W. Polock, "Materials Science and Metallurgy", p. 266 (Reston Pub. Inc. 1981) and "The Metals Handbook", pp.1-2 (Am. Soc'y Metals, 1986).

[0054] In their annealed/softened state the alloys can be worked by standard jewelry-making techniques: they can be rolled, drawn, soldered to, shaped, bent, stamped, etc. These alloys can be applied to a variety of designs for springs, gemstone mountings in rings, pendants, bracelets, chains, precious metal art objects, and the like.

[0055] It should be noted that in designing for structure of the jewelry or art object, the smallest cross-sectional area and shape of a component is taken into account. It is possible to adapt the design of the alloy to almost any configuration. The basic forms of these designs can vary, from simple sheet, to ring-shapes and more complex helixes, v-shapes, and the like. Objects can be wire, sheet, springs of all types, pendants, chain-links, brooches, and a multitude of others. Standard jewelry soldering techniques can be applied and repairs requiring heat can be carried out. The alloys can be shaped, bent, built onto, annealed, and when the piece is done, the spring power and hardness can be regained by heat-treatment.

[0056] The ornamental product can be made by casting. The hardness of the alloys may also be further increased by heat treatment. The heat treatment may be carried out in a range of from 300 to 950 °C with a suitable value being in the range of from 600 to 950 °C, and typically of the order of 800 °C. The alloys can be softened by standard annealing procedures, typically at about 1000 °C to 1030 °C, or higher.

[0057] The alloys may be used in the form of wire, sheet or other manufactured article and may be given intricate shapes and forms due to their great hardness combined with great ductility.

[0058] The alloys according to the present invention can be used, for example, in the fabrication of wedding bands. Such weddings bands are generally produced by sawing blanks from tubes and then further working the blanks by suitable measures, such as milling, drawing, forging, and polishing.

[0059] Other jewelry articles that can be manufactured from the alloys according to the present invention include, for example, rings, necklaces, bracelets, earrings, bangles, stickpins, watch bands, watch bodies, wristwatches, tooth picks as well as other decorative articles such as ballpoint pens, letter openers, pocket knife handles, and the like.

[0060] The following Examples are provided to illustrate certain aspects of the invention and it is understood that such an Example does not limit the scope of the invention as defined in the appended claims.

EXAMPLE

[0061] An alloy of the composition as specified in the following table was weighted and molten under vacuum in a zirconia crucible in a vacuum induction furnace at a temperature of 1480 to 1500 °C to obtain a homogeneous melt. The alloy was cast into a steel mold to form blocks having a dimension of 20 x 140 mm.

[0062] In the following table, the physical properties of the alloy specimens thus formed are specified. The melting range was determined by measuring the cooling curve of the alloy with a Degussa resistance furnace HR1/Pt/PtRH10 equipped with a Linseis thermo element and a temperature-time-plotter L250. The Vickers hardness was determined according to DIN 50133 using a Wolpert V-Testor 4521 instrument. The tensile strength, elongation at break and yield stress were determined according to DIN 50145 using a Zwick Z010 instrument. The color was determined visually.

COMPARISON EXAMPLE

[0063] A commercially available Pt/Cu 950/50 alloy was weighted and molten under vacuum in a zirconia crucible in a vacuum induction furnace to obtain a homogeneous melt. The alloy was cast into a steel mold to form blocks having a dimension of 20 x 140 mm.

[0064] The physical properties of the alloy specimens thus formed were tested as described above and are specified in the following table.

TABLE

	EXAMPLE 1	EXAMPLE 2	COMPARATIVE
			EXAMPLE
Composition	Pt 65 wt.%	Pt 65 wt.%	Pt 95 wt.%
	Cu 31.5 wt.%	Cu 31.25 wt.%	Cu 5 wt.%
	Co 3.5 wt.%	Co 3.5 wt.%
		Si 0.25 wt.%
Density	14.4	14.4	20.3
Color	platinum white	platinum white	platinum white
Melting Range	1390-1450	1390 -1450	1730-1745
Castability	very good	excellent	fair
Workability	good	good	good
Hardness [HV]
softened state	120	120	110
20 % cold rolled	190	190	185
40 % cold rolled	230	230	210
60 % cold rolled	260	260	235
Tensile Strength
[N/mm2]
softened state	600	600	320
60 % cold rolled	∼ 1000	∼ 1000	∼ 800
Yield Stress	350	350	130
[N/mm2]
Elongation at	>35	>35	> 30
Break [%]

[0065] The experimental results indicate that the alloy according to the present invention exhibits superior casting, wear and abrasion properties when compared to a conventional Pt/Cu 950/50 alloy. The results of Example 1 further indicate that the castability of the alloy of the present invention is enhanced by addition of small amounts of silicon. Furthermore, the experimental results indicate that the forming properties and the color tone of the alloy according to the present invention are comparable to those of a conventional Pt/Cu 950/50 alloy. The alloy according to the present invention was found to be an excellent material for the manufacture of jewelry articles such as rings, bracelets or necklaces

[0066] The principle of the invention and the best mode contemplated for applying that principle have been described. It is to be understood that the foregoing is illustrative only and that other means and techniques can be employed without departing from the true scope of the invention defined in the following claims.

Claims

1. A platinum alloy comprising:

- 63.01 to 69.99 wt,% of platinum,

- 1.5 to 10 wt.% of cobalt,

- 20.01 to 35.49 wt.% of copper,
and optionally

- 0.001 to 2 wt.% of at least one first metal selected from the group consisting of iridium and ruthenium,

- 0.001 to 2 wt.% of at least one second metal selected from the group consisting of indium and gallium,

- 0.001 to 5 wt.% of palladium,

- 0.001 to 0.5 wt.% of silicon,

- 0.001 to 0.5 wt.% of zirconium,

- phosphorous in an amount of less than 4.2 wt.%,
the balance being copper and unavoidable impurities.

2. The platinum alloy of claim 1, wherein said alloy has a substantially crystalline structure.

3. The platinum alloy of claim 1, wherein said alloy comprises 63.5 to 66.5 wt.% of platinum.

4. The platinum alloy of claim 1, wherein said alloy comprises 64 to 66 wt.% of platinum.

5. The platinum alloy of claim 1, wherein said alloy comprises about 65 wt.% of platinum.

6. The platinum alloy of any one of claims 1 to 5, wherein said alloy comprises 2.0 to 6.0 wt.% of cobalt.

7. The platinum alloy of any one of claims 1 to 6, wherein said alloy comprises 2.5 to 5.5 wt.% of cobalt.

8. The platinum alloy of any one of claims 1 to 7, wherein said alloy comprises 0.1 to 0.3 wt.% of silicon.

9. The platinum alloy of any one of claims 1 to 8, wherein said alloy comprises 0.1 to 0.3 wt.% of zirconium.

10. The platinum alloy of any one of claims 1 to 9, wherein the total amount of other elements present in said platinum alloy besides Pt, Cu, and Co does not exceed 10 wt.%, based on the total weight of said platinum alloy.

11. The platinum alloy of any one of claims 1 to 10, wherein the total amount of other elements present in said platinum alloy besides Pt, Cu, and Co does not exceed 7.5 wt.%, based on the total weight of said platinum alloy.

12. The platinum alloy of any one of claims 1 to 11, wherein the total amount of phosphorous present in said platinum alloy is less than about 2.0 wt.% based on the total weight of said platinum alloy.

13. The platinum alloy of any one of claims 1 to 12, consisting of:

63.5 to 67.5 wt.% of platinum,

1.5 to 8 wt.% of cobalt, and

24.5 to 35 wt.% of copper,
wherein copper may be substituted by one or more of the following elements in the amounts specified:

0.001 to 2 wt.% of at least one of said first metals; 0.001 to 2 wt.% of at least one of said second metals; 0.001 to 5 wt.% of palladium;

0.001 to 0.5 wt.% of silicon, and/or

0.001 to 0.5 wt.% of zirconium.

14. The platinum alloy of any one of claims 1 to 13, wherein the tensile strength of said alloy is in the range of 450 to 800 N/mm².

15. The platinum alloy of any one of claims 1 to 14, wherein the Vickers hardness of said alloy, measured at soft state, is in the range of 130 to 210 HV10.

16. The platinum alloy of any one of the claims 1 to 15,
wherein the elongation at break of said alloy is at least 20 %.

17. The platinum alloy of any one of claims 1 to 16, wherein the color tone of said alloy corresponds essentially to the platinum white color tone of a PtCu950 alloy.

18. A method of preparing an alloy according to any one of claims 1 to 17, which comprises (a) blending the components of the alloy; and (b) melting the alloy.

19. A platinum-colored material for ornamental purposes comprising a platinum alloy according to any one of claims 1 to 17.

20. An ornamental article comprising the platinum alloy of any one of claims 1 to 17.

21. The ornamental article of claim 20, wherein said ornamental article is a ring, a necklace, an earring, a watch band, a watch body or other jewelry.

22. A method of fabricating the ornamental article of claim 20 or 21, which comprises forming the ornamental article from an alloy according to any one of claims 1 to 17.

23. The method of claim 22, wherein the alloy is casted into the shape of the ornamental article.

24. The use of a platinum alloy according to any one of claims 1 to 17 for the manufacture of an ornamental article such as a ring, a necklace, an earring, a watch band, a watch body or other jewelry.

Ansprüche

1. Platinlegierung, enthaltend:

- 63,01 bis 69,99 Gew.-% Platin,

- 1,5 bis 10 Gew.-% Cobalt,

- 20,01 bis 35,49 Gew.-% Kupfer,
und wahlweise

- 0,001 bis 2 Gew.-% mindestens eines ersten Metalls, das aus der Gruppe ausgewählt ist, die aus Iridium und Ruthenium besteht,

- 0,001 bis 2 Gew.-% mindestens eines zweiten Metalls, das aus der Gruppe ausgewählt ist, die aus Indium und Gallium besteht,

- 0,001 bis 5 Gew.-% Palladium,

- 0,001 bis 0,5 Gew.-% Silicium,

- 0,001 bis 0,5 Gew.-% Zirconium und

- Phosphor mit einem Anteil von unter 4,2 Gew.-%,

wobei der Rest aus Kupfer und unvermeidlichen Verunreinigungen besteht.

2. Platinlegierung nach Anspruch 1, wobei diese Legierung ein im Wesentlichen kristallines Gefüge besitzt.

3. Platinlegierung nach Anspruch 1, wobei dieses Legierung 63,5 bis 66,5 Gew.-% Platin enthält.

4. Platinlegierung nach Anspruch 1, wobei diese Legierung 64 bis 66 Gew.-% Platin enthält.

5. Platinlegierung nach Anspruch 1, wobei diese Legierung etwa 65 Gew.-% Platin enthält.

6. Platinlegierung nach einem der Ansprüche 1 bis 5, wobei diese Legierung 2,0 bis 6,0 Gew.-% Cobalt enthält.

7. Platinlegierung nach einem der Ansprüche 1 bis 6, wobei diese Legierung 2,5 bis 5,5 Gew.-% Cobalt enthält.

8. Platinlegierung nach einem der Ansprüche 1 bis 7, wobei diese Legierung 0,1 bis 0,3 Gew.-% Silicium enthält.

9. Platinlegierung nach einem der Ansprüche 1 bis 8, wobei diese Legierung 0,1 bis 0,3 Gew.-% Zirconium enthält.

10. Platinlegierung nach einem der Ansprüche 1 bis 9, wobei der Gesamtanteil an anderen Elementen, die in dieser Platinlegierung außer Pt, Cu und Co vorhanden sind, 10 Gew.-%, bezogen auf das Gesamtgewicht der Platinlegierung, nicht übersteigt.

11. Platinlegierung nach einem der Ansprüche 1 bis 10, wobei der Gesamtanteil an anderen Elementen, die in dieser Platinlegierung außer Pt, Cu und Co vorhanden sind, 7,5 Gew.-%, bezogen auf das Gesamtgewicht der Platinlegierung, nicht übersteigt.

12. Platinlegierung nach einem der Ansprüche 1 bis 11, wobei der Gesamtanteil an Phosphor, der in dieser Platinlegierung vorhanden ist, weniger als etwa 2,0 Gew.-%, bezogen auf das Gesamtgewicht der Platinlegierung, beträgt.

13. Platinlegierung nach einem der Ansprüche 1 bis 12, die aus:

- 63,5 bis 67,5 Gew.-% Platin,

- 1,5 bis 8 Gew.-% Cobalt und

- 24,5 bis 35 Gew.-% Kupfer
besteht, wobei Kupfer durch eines oder mehrere der folgenden Elemente mit nachstehenden Anteilen substituiert sein kann:

- 0,001 bis 2 Gew.-% mindestens eines der ersten Metalle,

- 0,001 bis 2 Gew.-% mindestens eines der zweiten Metalle,

- 0,001 bis 5 Gew.-% Palladium,

- 0,001 bis 0,5 Gew.-% Silicium und/oder

- 0,001 bis 0,5 Gew.-% Zirconium.

14. Platinlegierung nach einem der Ansprüche 1 bis 13, wobei die Zugfestigkeit dieser Legierung im Bereich von 450 bis 800 N/mm² liegt.

15. Platinlegierung nach einem der Ansprüche 1 bis 14, wobei die Vickers-Härte dieser Legierung, gemessen im ungehärteten Zustand, im Bereich von 130 bis 210 HV10 liegt.

16. Platinlegierung nach einem der Ansprüche 1 bis 15, wobei die Bruchdehnung dieser Legierung mindestens 20 % beträgt.

17. Platinlegierung nach einem der Ansprüche 1 bis 16, wobei der Farbton dieser Legierung im Wesentlichen dem platinweißen Farbton einer PtCu950-Legierung entspricht.

18. Verfahren zur Herstellung einer Legierung nach einem der Ansprüche 1 bis 17, welches (a) Vermischen der Komponenten der Legierung und (b) Erschmelzen der Legierung umfasst.

19. Platinfarbenes Material für Schmuckzwecke, das eine Platinlegierung nach einem der Ansprüche 1 bis 17 umfasst.

20. Schmuckerzeugnis, das die Platinlegierung nach einem der Ansprüche 1 bis 17 umfasst.

21. Schmuckerzeugnis nach Anspruch 20, das ein Ring, eine Halskette, ein Ohrring, ein Uhrarmband, ein Uhrgehäuse oder eine andere Goldschmiedearbeit ist.

22. Verfahren zur Herstellung des Schmuckerzeugnisses nach Anspruch 20 oder 21, welches das Formen des Schmuckerzeugnisses aus einer Legierung nach einem der Ansprüche 1 bis 17 umfasst.

23. Verfahren nach Anspruch 22, wobei die Legierung zu der Form des Schmuckerzeugnisses gegossen wird.

24. Verwendung einer Platinlegierung nach einem der Ansprüche 1 bis 17 zur Herstellung eines Schmuckerzeugnisses wie eines Rings, einer Halskette, eines Ohrrings, eines Uhrarmbandes, eines Uhrgehäuses oder einer anderen Goldschmiedearbeit.

Revendications

1. Alliage de platine comprenant :

- 63,01 à 69,99% en masse de platine,

- 1,5 à 10% en masse de cobalt,

- 20,01 à 35,49% en masse de cuivre, et le cas échéant

- 0,001 à 2% en masse d'au moins un premier métal choisi dans le groupe formé de l'indium et du ruthénium.

- 0,001 à 2% en masse d'au moins un second métal choisi dans le groupe de l'indium et du gallium.

- 0,001 à 5% en masse de palladium.

- 0,001 à 0,5% en masse de silicium

- 0,001 à 0,5% en masse de zirconium.

- du phosphore en quantité inférieure à 4,2% en masse, le solde étant cuivre et impuretés inévitables.

2. Alliage de platine selon la revendication 1, dans lequel ledit alliage possède une structure sensiblement cristalline

3. Alliage de platine selon la revendication 1, dans lequel ledit alliage comprend 63,5 à 66,5% en masse de platine.

4. Alliage de platine selon la revendication 1, dans lequel ledit alliage comprend 64 à 66% en masse de platine.

5. Alliage de platine selon la revendication 1, dans lequel ledit alliage comprend environ 65% en masse de platine.

6. Alliage de platine selon l'une quelconque des revendications 1 à 5, dans lequel ledit alliage comprend 2,0 à 6,0% en masse de cobalt.

7. Alliage de platine selon l'une quelconque des revendications 1 à 6, dans lequel ledit alliage comprend 2,5 à 5,5% en masse de cobalt.

8. Alliage de platine selon l'une quelconque des revendications 1 à 7, dans lequel ledit alliage comprend 0,1 à 0,3% en masse de silicium.

9. Alliage de platine selon l'une quelconque des revendications 1 à 8, dans lequel ledit alliage comprend 0,1 à 0,3% en masse de zirconium.

10. Alliage de platine selon l'une quelconque des revendications 1 à 9, dans lequel la quantité totale d'autres éléments présents dans ledit alliage de platine, en plus de Pt, Cu et Co, ne dépasse pas 10% en masse, sur base de la masse totale dudit alliage de platine.

11. Alliage de platine selon l'une quelconque des revendications 1 à 10, dans lequel la quantité totale d'autres éléments présents dans ledit alliage de platine, en plus de Pt, Cu et Co, ne dépasse pas 7,5% en masse, sur base de la masse totale dudit alliage de platine.

12. Alliage de platine selon l'une quelconque des revendications 1 à 11, dans lequel la quantité totale de phosphore présent dans ledit alliage de platine est inférieure à environ 2,0% en masse, sur base de la masse totale dudit alliage de platine.

13. Alliage de platine selon l'une quelconque des revendications 1 à 12, composé de :

- 63,5 à 67,5% en masse de platine,

- 1,5 à 8% en masse de cobalt, et

- 24,5 à 35% en masse de cuivre,

dans lequel le cuivre peut être remplacé par l'un ou plusieurs de éléments suivants, dans les quantités spécifiées :

- 0,001 à 2% en masse de l'un au moins desdits premiers métaux;

- 0,001 à 2% en masse de l'un au moins desdits seconds métaux;

- 0,001 à 5% en masse de palladium;

- 0,001 à 0,5% en masse de silicium; et/ou

- 0,001 à 0,5% en masse de zirconium.

14. Alliage de platine selon l'une quelconque des revendications 1 à 13, dans lequel la résistance à la traction dudit alliage se situe dans l'intervalle de 450 à 800 N/mm².

15. Alliage de platine selon l'une quelconque des revendications 1 à 14, dans lequel la dureté Vickers dudit alliage, mesurée à l'état doux, se situe dans l'intervalle de 130 à 210 HVlO.

16. Alliage de platine selon l'une quelconque des revendications 1 à 15, dans lequel l'allongement à la rupture dudit alliage est d'au moins 20%.

17. Alliage de platine selon l'une quelconque des revendications 1 à 16, dans lequel le ton dudit alliage correspond sensiblement au ton blanc platine d'un alliage PtCu950.

18. Procédé de préparation d'un alliage selon l'une quelconque des revendications 1 à 17, qui comprend les étapes consistant à (a) mélanger les composants de l'alliage et (b) faire fondre l'alliage.

19. Matériau de couleur platine à but d'ornement, comprenant un alliage de platine selon l'une quelconque des revendications 1 à 17.

20. Article d'ornement comprenant l'alliage de platine selon l'une quelconque des revendications 1 à 17.

21. Article d'ornement selon la revendication 20,
dans lequel ledit article d'ornement est une bague, un collier, une boucle d'oreille, un bracelet de montre, un boîtier de montre ou un autre article de bijouterie.

22. Procédé de fabrication de l'article d'ornement de la revendication 20 ou 21, qui comprend l'étape consistant à former l'article d'ornement à partir d'un alliage selon l'une quelconque des revendications 1 à 17.

23. Procédé selon la revendication 22, dans lequel l'alliage est coulé à la forme de l'article d'ornement.

24. Utilisation de l'alliage de platine selon l'une quelconque des revendications 1 à 22, pour la fabrication d'un article d'ornement tel qu'une bague, un collier, une boucle d'oreille, un bracelet de montre, un boîtier de montre ou un autre article de bijouterie.