Gold alloy with deformation recovery properties

Abstract

A gold alloy for jewelry or watchmaking applications, particularly intended to achieve jewelry objects with at least partial shape and / or size recovery properties after the application of a deforming force, comprising 700‰ to 800‰ by weight of gold, 25‰ to 170‰ by weight of copper, 50‰ to 165‰ by weight of palladium, 7‰ to 40‰ by weight of cobalt. This gold alloy is a grey alloy.

Description

[Technical Field]

[0001] This disclosure relates to the field of metallurgy, and in particular to the field of gold alloys. In particular, this disclosure relates to gold alloys for jewelry and watchmaking applications.

[0002] The present disclosure also relates to jewelry and watchmaking objects realized at least in part by the gold alloys described herein. [Background technology]

[0003] Objects realized with metallic materials exhibit deformable properties. The deformation of the object can be of the elastic or plastic type. The deformation occurs as a result of the application of a traction, compression or bending force to the material.

[0004] Elastic-type deformation is characterized by the ability of the object to return to its original size and / or shape upon cessation of the deforming force.

[0005] Plastic type deformation is characterized by the fact that the object can no longer return to its original size and / or shape upon cessation of the deforming force, in other words, its size and / or shape is changed irreversibly relative to its original size and / or shape.

[0006] Plastic deformation typically occurs when a force greater than that required to deform an object elastically is applied. Yield strength is the force that, when applied to such an object, determines the transition from elastic to plastic behavior.

[0007] The maximum deformation limit that an object can withstand is called the breaking load.

[0008] In particular, objects realized in gold alloys can also undergo deformations of elastic or plastic type.

[0009] During its operational life, a definite object realized with gold alloys will be subjected to various static or cyclic deformation forces. When the object realized with gold alloys is connected to other similar or different objects or integrated into a more complex object, any plastic deformations may be formed, play may occur, friction may occur, and misalignment may occur.

[0010] As a result, an object realized with a gold alloy may, over time, acquire an altered size and / or shape relative to its original size and / or shape.

[0011] Changing the shape of an object realized with gold alloys is disadvantageous because differences in size or shape due to the effect of applying a greater force than the yield strength can impair the functionality of the object.

[0012] Usually, yellow (according to 3N ISO 8654) and red (according to 5N ISO 8654) gold alloys are known to typically exhibit good mechanical properties, in particular high yield strength, hardness and elasticity, and are therefore generally observed to be used without problems when their use is intended for jewellery or watchmaking objects which are subject to particularly high stresses in the course of their working life.

[0013] Gray gold alloys that have the ability to recover from deformation are also known to exhibit important mechanical properties, particularly high yield strength, hardness, and elasticity. Typically, such alloys utilize the properties of nickel to achieve higher mechanical recovery performance than nickel-free gold alloys.

[0014] Document US Patent No. 5,173,132 shows a gold alloy 14k in which there is cobalt in the range of 1‰ to 7‰ and nickel in the range of 10‰ to 50‰, the cobalt and nickel being used for grain refinement to further improve the workability of the alloy.

[0015] However, the use of nickel is strongly discouraged when the alloy is used in objects intended for direct contact with human skin, especially when the gold alloy is intended for jewelry applications intended for objects in direct contact with human skin. Indeed, nickel is known to cause allergic reactions. Summary of the Invention [Problem to be solved by the invention]

[0016] The object of the present disclosure is to describe a gold alloy that makes it possible to overcome the above-mentioned drawbacks, and also to describe a jewelry or watchmaking object that comprises a gold alloy that makes it possible to overcome the above-mentioned drawbacks.

[0017] The object of the present disclosure is finally to describe a method for producing gold alloys that makes it possible to overcome the above-mentioned drawbacks. [Means for solving the problem]

[0018] Applicant has devised several gold alloys with improved mechanical characteristics, which are described herein in some of their main aspects, which may be combined with each other or with parts of the detailed description or claims.

[0019] According to aspects of the present disclosure, described herein is a gold alloy for jewelry applications, the gold alloy comprising: 700‰ to 800‰ by weight of gold, 25% to 170% by weight of copper, 50% by weight to 165% by weight of palladium, 7 wt‰ to 40 wt‰ cobalt Includes.

[0020] The applicant notes that this gold alloy is particularly aimed at achieving jewelry objects with improved mechanical properties, characterized in particular by an increase in yield strength to make it comparable to the 3N and 5N alloys.

[0021] Applicant notes that the yield strength is significantly higher relative to the yield strength of commercially available nickel-free grey gold alloys.

[0022] According to a further non-limiting aspect, the alloy comprises: 700‰ to 800‰ by weight of gold, 25% to 95% by weight of copper, 85% by weight to 165% by weight of palladium, 7 wt‰ to 40 wt‰ of cobalt, 7% to 60% silver by weight Includes.

[0023] According to a further non-limiting embodiment, the alloy includes gallium and / or at least one grain refining element, preferably at least one of iridium, rhenium, and ruthenium.

[0024] According to a further non-limiting embodiment, the at least grain refining element is present in a pre-alloy, the pre-alloy being based on: copper when the grain refining element is iridium, or Palladium when the grain refining element is rhenium or ruthenium.

[0025] According to a further non-limiting embodiment, the amount by weight of gallium and / or at least one of said at least grain refining elements, preferably iridium, rhenium or ruthenium, determines the attainment of 1000% by weight.

[0026] According to a further non-limiting aspect, the gold alloy is characterized in that it is nickel-free.

[0027] According to a further non-limiting aspect, the gold alloy is characterized in that it is arsenic-free.

[0028] According to a further non-limiting aspect, the gold alloy is characterized in that it does not contain platinum.

[0029] According to a further non-limiting embodiment, the gold alloy comprises 1 wt% to 10 wt%, preferably 2 wt% to 9 wt%, and more preferably 3 wt% to 8 wt% gallium.

[0030] According to a further non-limiting embodiment, gallium is present in an amount substantially comprised between 4% and 7% by weight.

[0031] According to a further non-limiting embodiment, gallium is present in an amount comprised between 3.5% and 4.5% by weight.

[0032] According to a further non-limiting embodiment, the alloy includes at least a grain refining element, preferably at least one of iridium, rhenium, or ruthenium.

[0033] According to a further non-limiting embodiment, the iridium is pre-alloyed with copper.

[0034] According to a further non-limiting embodiment, the rhenium and / or ruthenium is pre-alloyed with palladium.

[0035] According to a further non-limiting embodiment, at least one grain-refining element, particularly at least one of iridium, rhenium, or ruthenium, is present in an amount up to 1% by weight.

[0036] According to a further non-limiting aspect, the gold alloy comprises: 730‰ to 770‰ by weight of gold, 40% to 90% by weight of copper, 100% by weight to 150% by weight of palladium, 8 wt‰ to 30 wt‰ of cobalt, 8% to 55% by weight of silver Includes.

[0037] According to a further non-limiting aspect, the gold alloy comprises: 740‰ to 760‰ by weight of gold, 50% to 90% by weight of copper, 100% by weight to 150% by weight of palladium, 8 wt‰ to 30 wt‰ of cobalt, 8% to 55% by weight of silver Includes.

[0038] According to a further non-limiting aspect, the gold alloy comprises: 740‰ to 760‰ by weight of gold, 50% to 90% by weight of copper, 110% by weight to 140% by weight, preferably 115% by weight to 135% by weight, of palladium, 10% by weight to 25% by weight of cobalt, 8% to 50% silver by weight Includes.

[0039] According to a further non-limiting aspect, the gold alloy comprises: 120% to 130% palladium by weight Includes.

[0040] According to a further non-limiting embodiment, the gold alloy according to one or more of the preceding embodiments comprises: 45% by weight to 65% by weight, preferably 50% by weight to 60% by weight, copper and 35% by weight to 52% by weight, silver, or 75‰ to 95‰ by weight, preferably 80‰ to 90‰ by weight of copper and 7‰ to 13‰ by weight, preferably 8‰ to 12‰ by weight of silver Includes.

[0041] According to a further non-limiting embodiment, the gold alloy has the following color coordinates in the CIELAB 1976 color range and according to the CIE D65 color measurement conditions: L* comprised between 80 and 84.5, preferably between 81 and 84; a* is comprised between 1.2 and 3.7, preferably between 1.5 and 3.5; b* included in 6.2 to 10.5, preferably 6.6 to 10 The color has a value defined by:

[0042] According to a further non-limiting embodiment, the color is gray and / or the gold alloy is a gray gold alloy.

[0043] According to a further non-limiting embodiment, the gold alloy has the following color coordinates in the CIELAB 1976 color range and according to the CIE D65 color measurement conditions: L* comprised between 80 and 84.5, preferably between 81 and 84; a* included in 1.2 to 2.4, preferably 1.5 to 2.1; b* in the range of 6.7 to 8.5, preferably 7 to 8.3 The color has a value defined by:

[0044] For the purposes of this disclosure, gold alloys whose color is contained within the aforementioned coordinates, particularly within the square defined by the coordinates a* and b* when placed on orthogonal axes on a color chart, are considered gray.

[0045] According to a further non-limiting embodiment, the gold alloy is a gray gold alloy.

[0046] According to a further non-limiting embodiment, the gold alloy has the following color coordinates in the CIELAB 1976 color range and according to the CIE D65 color measurement conditions: L* included in 83 to 84.5, preferably 83.2 to 84.3; a* comprised between 2.7 and 3.7, preferably between 2.9 and 3.5; b* in the range of 8.9 to 9.9, preferably 8.7 to 9.7 The color has a value defined by:

[0047] According to a further non-limiting aspect, the gold alloy comprises: 730‰ to 770‰ by weight, preferably 740‰ to 760‰ by weight, of gold; 150% by weight to 170% by weight, preferably 155% by weight to 165% by weight, copper; 50% by weight to 70% by weight, preferably 55% by weight to 65% by weight, of palladium, 7 wt‰ to 13 wt‰ of cobalt, 10% wt. to 30% wt. of iron, Optionally, at least one grain refining element, preferably at least one of iridium, rhenium or ruthenium, in an amount of up to 1% by weight. Includes.

[0048] According to a further non-limiting embodiment, the sum of gold, copper, palladium, cobalt, iron and optionally at least a grain-refining element amounts to 1000% by weight.

[0049] According to a further non-limiting aspect, the gold alloy comprises: 700‰ to 800‰ by weight of gold, 25% to 75% by weight of copper, 85% by weight to 165% by weight of palladium, 7 wt‰ to 40 wt‰ of cobalt, 7‰ to 60‰ by weight of silver, 1‰ to 10‰‰ by weight, preferably 2‰ to 9‰ by weight, more preferably 3‰ to 8‰ by weight of gallium, at least one grain-refining element, preferably iridium, rhenium or ruthenium, in an amount of up to 1% by weight It consists of:

[0050] According to a further aspect, a jewelry object is also described that includes a gold alloy according to one or more of the aspects described herein.

[0051] According to a further non-limiting embodiment, the jewelry object has a yield strength equivalent to the yield strength of a corresponding jewelry object realized with a 3N or 5N alloy.

[0052] In particular, said yield strength is greater than that of a corresponding jewelry object that does not contain nickel and is realized with commercially known grey gold alloys.

[0053] According to a further non-limiting embodiment, the gold alloy is a gray gold alloy.

[0054] According to a further non-limiting aspect, the jewelry object comprises a jewel, or a watch, or a watch bracelet, or a movement, or a part of a mechanical watch movement.

[0055] According to a further non-limiting aspect, the timepiece or mechanical timepiece movement is configured to be worn or attached to a wristwatch, respectively.

[0056] According to the present disclosure, there is further described a method for producing a gold alloy, comprising mixing at least gold, copper, palladium, and cobalt in the amounts set forth in one or more of the above aspects.

[0057] According to a further non-limiting aspect, the method comprises: 700‰ to 800‰ by weight of gold, 9 wt‰ to 79 wt‰ copper, 85% by weight to 165% by weight of palladium, 7 wt‰ to 40 wt‰ of cobalt, 7% to 60% silver by weight with 16% by weight of a CuIr pre-alloy.

[0058] The alloy articles of the present disclosure will now be described with reference to certain preferred embodiments and with reference to the accompanying drawings, a brief description of which is provided below. [Brief explanation of the drawings]

[0059] [Figure 1] 1 shows a Cartesian diagram illustrating a monotonic traction test, where the abscissa indicates the relative deformation (in percentage) undergone by the specimen and the ordinate indicates the stress undergone by the specimen. [Figure 2] 1 shows a Cartesian diagram in which the abscissa indicates the distance corresponding to the displacement corresponding to the midpoint of a gold alloy test piece when subjected to a bending force at three points, and the ordinate indicates the bending force. [Figure 3]2 shows a Cartesian diagram representing a color chart according to the a* and b* coordinates of the CIELAB 1976 color gamut, with particular compositions specifically studied by the applicant indicated. The colors detected in the graph of FIG. 2 are obtained according to measurements according to CIE D65. DETAILED DESCRIPTION OF THE INVENTION

[0060] The present disclosure presents gold alloys with improved deformation recovery properties. The gold alloys described herein are advantageously applicable to objects that are preferably subjected to various deformation forces (which must be kept below the yield strength) during their operational life. These objects may be high jewelry or watchmaking objects, and may be connected to other identical or similar objects or integrated into more complex objects. In non-limiting embodiments, these objects may be part of a bracelet, a bracelet, or a watch movement.

[0061] As will become more apparent from the following description, applicant has focused on embodiments of gold alloys that exhibit observably different colors relative to the colors coded by the 0N-6N standard according to ISO 8654. In particular, a group of alloys contemplated by applicant is the group of gray gold alloys.

[0062] Applicant has devised a family of grey gold alloys containing an amount of gold substantially equal to 18k gold, which have the following characteristics: 700‰ to 800‰ by weight of gold, 25% to 170% by weight of copper, 50% by weight to 165% by weight of palladium, 7 wt‰ to 40 wt‰ cobalt It has.

[0063] This alloy family optionally includes 7% to 60% by weight of silver.

[0064] Depending on whether silver is present, in non-limiting embodiments, the sum of the amounts by weight of gold, copper, palladium, cobalt, or the sum of the amounts by weight of gold, copper, palladium, cobalt, and silver is equal to 1000‰ by weight. For this reason, the present disclosure expressly refers to a group of specific gold alloys consisting of 700‰ to 800‰ by weight gold, 25‰ to 170‰ by weight copper, 50‰ to 165‰ by weight palladium, 7‰ to 40‰ by weight cobalt, or consisting of 700‰ to 800‰ by weight gold, 25‰ to 170‰ by weight copper, 50‰ to 165‰ by weight palladium, 7‰ to 40‰ by weight cobalt, and 7‰ to 60‰ by weight silver.

[0065] From this general group of gold alloys, the applicant has selected the following elements in the following composition: 700‰ to 800‰ by weight of gold, 25% to 95% by weight of copper, 85% by weight to 165% by weight of palladium, 7 wt‰ to 40 wt‰ of cobalt, 7% to 60% silver by weight He emphasized a more limited group, including

[0066] Preferably, but not exclusively, the gold alloy according to the above composition can be realized using the above-mentioned materials exclusively, i.e., gold, copper, palladium, cobalt, silver in amounts up to 1000% by weight.

[0067] The group of alloys described herein is nickel-free to ensure compatibility with all applications in which objects realized with gold alloys must come into direct contact with human skin.

[0068] The family of gold alloys described herein further includes no arsenic.

[0069] Some embodiments of the alloys of the present disclosure have improved performance with respect to mechanical performance and further comprise 1% to 10% by weight, preferably 2% to 9% by weight, and more preferably 3% to 8% by weight, of gallium.

[0070] Some embodiments have gallium present in an amount substantially between 4% and 7% by weight. Applicant has specifically studied two main groups of gold alloys, those having gallium in an amount equal to 4% by weight or those having gallium in an amount equal to 7% by weight.

[0071] In particular, cobalt and gallium act as thermal hardeners through a solubilization and precipitation process.

[0072] Among the alloys studied by the applicant, some preferred embodiments include iridium as a grain refiner. Other embodiments of the gold alloys disclosed herein include a grain refiner selected between rhenium and / or ruthenium. More grain refiners may be present simultaneously.

[0073] In an embodiment, the amount by weight of gallium and / or at least one of the grain refiners, preferably iridium, rhenium or ruthenium, determines the amount of 1000% by weight. The grain refiner may be present in an amount up to 1% by weight.

[0074] Indeed, applicants have devised specific embodiments of gold alloys in which the amounts of gold, copper, silver, cobalt, palladium and gallium reach 1000% by weight, and these alloys are alloys composed exclusively of six elements.

[0075] Additionally, applicant has devised a specific embodiment of a gold alloy containing gold, copper, silver, cobalt, palladium, gallium and at least one grain-refining element (iridium and / or rhenium and / or ruthenium) in an amount up to 1000 wt.%.

[0076] However, it is noted that the use of at least one grain refining element, particularly at least one of iridium, rhenium or ruthenium, may be subject to inclusion in the pre-alloy.

[0077] In particular, the alloy that is the subject of this disclosure is a platinum-free alloy.

[0078] From the general groupings above, the Applicant has identified: 730‰ to 770‰ by weight of gold, 40% to 90% by weight of copper, 100% by weight to 150% by weight of palladium, 8 wt‰ to 30 wt‰ of cobalt, 8% to 55% by weight of silver The authors investigated the behavior of a group of gold alloys containing 740 wt‰ to 760 wt‰ gold, 50 wt‰ to 90 wt‰ copper, and palladium, cobalt and silver within the above ranges, optionally in the presence of gallium and the above-mentioned grain-refining elements.

[0079] Further research is needed. 730‰ to 770‰ by weight of gold, 40% to 90% by weight of copper, 110% by weight to 140% by weight, preferably 115% by weight to 135% by weight, of palladium, 10% by weight to 25% by weight of cobalt, 8% to 50% silver by weight This was realized in a group of gold alloys including

[0080] The Applicant has carried out studies on two subgroups of gold alloys, focusing on a copper content equal to 55% by weight and a silver content comprised between 40% and 50% by weight, or on a higher copper content substantially equal to 85% by weight and a reduced silver content of about 10% by weight.

[0081] In particular, two alloy subgroups have been identified: 45‰ to 65‰, preferably 50‰ to 60‰, copper and 35‰ to 52‰, silver; or 75‰ to 95‰, preferably 80‰ to 90‰, copper and 7‰ to 13‰, preferably 8‰ to 12‰, silver. These subgroups have been studied in combination with 700‰ to 800‰, gold, 85‰ to 165‰, palladium, and 7‰ to 40‰, cobalt, as well as with gallium and / or iridium, as mentioned above. Some specific embodiments of gold alloys are derived from these two subgroups and are designated by the reference numbers 848, 849, and 850.

[0082] The following table shows some specific compositions that have been studied in detail by the applicant. The amounts of gold alloying elements are given in the table in % by weight.

[0083] [Table 1]

[0084] In compositions according to Table 1, the attainment of 1000% by weight of the alloy is preferably determined by the addition of 1% of grain refining elements including at least one of iridium, rhenium or ruthenium and / or at least one of copper, silver, palladium, cobalt or gallium in a pre-alloy with copper or palladium.

[0085] Further variations of gold alloys according to compositions 848, 849 and 850 are, for example, the following subgroups: 740‰ to 760‰ by weight of gold, 50‰ to 60‰ by weight of copper, 100‰ to 150‰ by weight, preferably 115‰ to 135‰ by weight of palladium, 20‰ to 30‰ by weight of cobalt, 35‰ to 55‰ by weight of silver, 3‰ to 8‰ by weight, preferably 3‰ to 5‰ or 6‰ to 8‰ by weight of gallium and optionally at least one grain-refining element comprising at least one of iridium, rhenium or ruthenium and / or at least one of copper, silver, palladium, cobalt or gallium, preferably in a pre-alloy with copper or palladium, in an amount of up to 1‰ by weight so as to determine the reaching of 1000‰ by weight of the gold alloy. It is in accordance with the following.

[0086] Further variations of gold alloys according to compositions 848, 849 and 850 are, for example, of the following subgroups: 740‰ to 760‰ by weight gold, 50‰ to 60‰ by weight copper, 100‰ to 150‰ by weight, preferably 115‰ to 135‰ by weight palladium, 20‰ to 30‰ by weight cobalt, 35‰ to 55‰ by weight silver, 3‰ to 8‰ by weight, preferably 3‰ to 5‰ or 6‰ to 8‰ by weight gallium and at least grain refining elements optionally comprising at least one of iridium, rhenium or ruthenium, preferably in a pre-alloy with copper or palladium. and the amounts of gold, copper, silver, palladium, cobalt, gallium and optionally at least grain refining elements are such that 1000% by weight is reached.

[0087] Further variations of gold alloys according to compositions 848, 849 and 850 are, for example, of the following subgroups: 740‰ to 760‰ by weight of gold, 70‰ to 95‰ by weight of copper, 100‰ to 150‰ by weight, preferably 115‰ to 135‰ by weight of palladium, 20‰ to 30‰ by weight of cobalt, 7‰ to 13‰ by weight of silver, 3‰ to 8‰ by weight of gallium and optionally at least one grain-refining element comprising at least one of iridium, rhenium or ruthenium and / or at least one of copper, silver, palladium, cobalt or gallium in an amount of up to 1‰ by weight, preferably in a pre-alloy with copper or palladium, so as to determine the attainment of 1000‰ by weight of the gold alloy. It is in accordance with the following.

[0088] Further variations of gold alloys according to compositions 848, 849 and 850 are, for example, of the following subgroups: 740‰ to 760‰ by weight of gold, 70‰ to 95‰ by weight of copper, 100‰ to 150‰ by weight, preferably 115‰ to 135‰ by weight of palladium, 20‰ to 30‰ by weight of cobalt, 7‰ to 13‰ by weight of silver, 3‰ to 8‰ by weight of gallium and optionally at least grain refining elements including iridium, rhenium or ruthenium. and the amounts of gold, copper, silver, palladium, cobalt, gallium and optionally at least grain refining elements are such that 1000% by weight is reached.

[0089] A further group of gold alloys investigated by the applicant are: 730‰ to 770‰ by weight, preferably 740‰ to 760‰ by weight, of gold; 150% by weight to 170% by weight, preferably 155% by weight to 165% by weight, copper; 50% by weight to 70% by weight, preferably 55% by weight to 65% by weight, of palladium, 7 wt‰ to 13 wt‰ cobalt It includes:

[0090] In particular, gold alloys containing 10 wt% to 30 wt% iron in addition to the elements in the amounts described in the previous paragraph were studied.

[0091] The applicant's research has focused in particular on a group of alloys in which, in addition to iron, iridium may also be present as a grain refiner, and from this particular group, composition 844 was extracted, as shown in the table below.

[0092] [Table 2]

[0093] In composition 844, the missing 1 wt% to complete 1000 wt% can be at least one grain refining element, preferably at least one of iridium, rhenium, or ruthenium, and / or one of copper, silver, palladium, cobalt, gallium, or iron.

[0094] Further variations of gold alloys according to composition 844 are, for example, as follows: - 740‰ to 760‰ by weight gold, 150‰ to 170‰ by weight copper, 40‰ to 80‰ by weight, preferably 50‰ to 70‰ by weight palladium, 5‰ to 15‰ by weight cobalt, 10‰ to 30‰ by weight iron and optionally at least grain refining elements preferably comprising at least one of iridium, rhenium or ruthenium, wherein the amounts of gold, copper, palladium, cobalt, iron and optionally at least grain refining elements preferably comprising at least one of iridium, rhenium or ruthenium are such that reaching 1000‰ by weight is determined.

[0095] The performance of the above gold alloys was compared to that of two benchmark gold alloys presented herein below.

[0096] [Table 3]

[0097] As shown in Figure 1, the alloys of the above group, when tested in the heat-aged (hardened) condition, exhibit tensile yield strengths comparable to those exhibited by the 5N alloy tested in the hardened condition. Furthermore, the yield strengths achieved by the alloys of the present subject matter are higher than those exhibited by the 3N alloy and the commercial nickel-free grey alloy, which are then subjected to tensile stresses in the heat-aged (hardened) condition.

[0098] In particular, the graph in FIG. 1 shows stress-strain curves for monotonic traction tests performed on various alloys, including those of the presently disclosed subject matter.

[0099] The yield strength value (Rp0.2), measured in MPa and specified according to the ISO 6892 rules for traction testing of metallic materials, as the point determined by the intersection of the flow stress curve with a line having a slope equal to the elastic modulus of the material and intercepting the abscissa axis corresponding to the value 0.002, was considered an indicator of improved mechanical properties.

[0100] From the results obtained, it was observed that the yield strength values ​​obtained for the compositions of the presently disclosed subject matter were substantially at least equivalent to the yield strength values ​​of the 5N alloy tested in the hardened state.

[0101] In particular, for composition LRS848 shown in FIG. 3, the yield strength values ​​are higher with respect to the yield strength of the corresponding test sample achieved with the 3N alloy.

[0102] Test samples realized with alloys according to the present disclosure, in particular test samples realized with composition LRS848, exhibit higher yield strength values ​​when subjected to traction and after heat aging than corresponding test samples realized with commercially known alloys Pd125 and Pd60.

[0103] From an application point of view, the improved mechanical properties obtained with the alloys of the subject of the present invention with respect to those exhibited by commercial grey gold alloys make it possible to guarantee a material with increased elastic recovery after undergoing deformation.

[0104] The 3N and 5N alloys exhibit good behavior in terms of elastic return, whereas the compositions Pd125 and Pd60 exhibit poor behavior. The Applicant notes that the Pd125 and Pd60 alloys are used for their thermosetting properties.

[0105] Applicant has observed that composition 844 exhibits limited effectiveness with respect to elastic recovery compared to the other compositions previously described in Table 1. Alloy 5N is a red gold alloy, and it is observed that alloys close to the 5N standard, by composition, usually exhibit optimal behavior with respect to recovery after deformation. Alloy 3N is a yellow gold alloy.

[0106] The above embodiment exhibits the colors shown in Table 5.

[0107] [Table 4]

[0108] FIG. 3 shows the colours of the alloys of Table 4 in a Cartesian graph in colour coordinates a* and b*.

[0109] The color of the alloys was measured according to CIE D65 with a light source used as the light source having a color temperature of approximately 6500 K. In particular, the applicant carried out color measurements with a spectrophotometer mod. Konica-Minolta CM3610d with an observation angle of 2° and a measurement area of ​​6 mm, using a light source according to the D65 standard with a color temperature equal to 6504 K.

[0110] Table 5 includes color coordinates expressed according to a specific color scale and according to specific color measurements described below.

[0111] Within the above general alloy group, the following color coordinates are obtained in the CIELAB 1976 color range and according to the color measurement conditions according to CIE D65: L* comprised between 80 and 84.5, preferably between 81 and 84; a* is comprised between 1.2 and 3.7, preferably between 1.5 and 3.5; b* included in 6.2 to 10.5, preferably 6.6 to 10 The focus was on alloys that exhibit a substantially gray color defined by

[0112] Applicant notes that the color measurement standard used to obtain the above values ​​is ISO 8654.

[0113] In particular, the alloys of the subgroup to which compositions 848, 849 and 850 belong have the following color coordinates in the CIELAB 1976 color range and according to the color measurement conditions according to CIE D65: L* comprised between 80 and 84.5, preferably between 81 and 84; a* included in 1.2 to 2.4, preferably 1.5 to 2.1; b* in the range of 6.7 to 8.5, preferably 7 to 8.3 The color is essentially gray as defined by

[0114] In particular, the alloys of the subgroup to which composition 844 belongs have the following color coordinates in the color range of CIELAB 1976 and according to the color measurement conditions according to CIE D65: L* included in 83 to 84.5, preferably 83.2 to 84.3; a* comprised between 2.7 and 3.7, preferably between 2.9 and 3.5; b* in the range of 8.9 to 9.9, preferably 8.7 to 9.7 The color is essentially gray as defined by

[0115] The color of gold alloys is uniquely measured in the CIELAB 1976 color range, which defines colors based on a first parameter L*, a second parameter a*, and a third parameter b*. The first parameter L* specifies lightness and ranges from 0 (black) to 100 (white). The second and third parameters a* and b* represent chromaticity parameters. In particular, in the CIELAB 1976 color range, the achromatic grayscale is specified by the point where a* = b* = 0. A positive value of the second parameter a* indicates a color with a tendency toward red, and a negative value of the second parameter a* indicates a color with a tendency toward green, even if the second parameter a* is negative, and a positive value of the third parameter b* indicates a color with a tendency toward yellow, and a negative value of the third parameter b* indicates a color with a tendency toward blue, even if the third parameter b* is negative, and a negative value of the third parameter b* indicates a color with a tendency toward blue, even if the third parameter b* is negative, and a negative value of the third parameter b* indicates a color with a tendency toward blue, even if the third parameter b* is negative, and a negative value of the third parameter b* indicates a color with a tendency toward yellow, even if the third parameter b* is negative, and a negative value of the third parameter b* indicates a color with a tendency toward blue, even if the third parameter b* is negative, and a negative value of the third parameter b* indicates a color with a tendency toward blue. Furthermore, the second parameter a* and the third parameter b* can be converted into polar parameters defined as follows:

number

[0116] C ab *The parameter is defined as "saturation", C ab *The higher the value of the parameter, the more saturated the color will be, and ab *The lower the parameter value, the less saturated the color and the more grayscale it tends to be. To the best of the applicant's knowledge, alloys with a gold content higher than 750‰ that can be used as white or gray gold alloys and do not require rhodium plating surface treatment can be optionally used as C ab *Indicates a value <8. ab* The parameters specify the color tone.

[0117] In particular, the ISO 8654:2017 regulation defines seven color designations for gold alloys for jewelry. Specifically, these alloys are defined according to the following table, where the colors are defined by standard criteria, designated 0N to 6N:

[0118] [Table 5]

[0119] With regard to the measurement of the color of gold alloys, regulation ISO 8654 specifically stipulates that the measuring device must comply with publication CIE N°15.

[0120] Regulation ISO 8654:2017 further tabulates the nominal values ​​of L*, a*, and b* in the trichromatic coordinates for 0N to 6N alloys of standard colors, including tolerances. Below is an excerpt from the regulation that defines the color limits of alloys defined by the ISO 8654:2017 standard as pink / red:

[0121] [Table 6]

[0122] In relation to the preceding table, it is therefore possible to obtain, within the CIELAB 1976 color range, multiple regions each representing a color range within which an alloy can be claimed to exhibit a 0N...6N color. The gray alloys disclosed herein exhibit significantly different color coordinates relative to the color coordinates of alloys according to compositions 0N-6N.

[0123] The ISO 8654 rule further suggests recommended chemical compositions for each of the 0N to 6N alloys. Specifically, for pink / red alloys, the compositions are as shown in the table below:

[0124] [Table 7]

[0125] It has been previously noted that gold alloys exhibit improved mechanical properties.

[0126] The graph in Figure 2 shows a Cartesian diagram in which the abscissa represents the distance corresponding to the displacement of a gold alloy test sample when subjected to a bending force, and the ordinate represents the bending force. The displacement of the test sample is measured in μm. The bending force is measured in N.

[0127] The graph in Figure 2 was obtained using a three-point bending test, in which each test sample was subjected to a bending force that increased along its centerline until it reached a linear displacement along the direction of force application equal to 4000 μm. Once this linear displacement along the direction of force application equal to 4000 μm was reached, the bending force of the test sample was gradually reduced, and the residual deformation value when the test sample was subjected to a bending force of 10 N was determined.

[0128] Generally, to evaluate the goodness of a gold alloy with respect to deformation recovery, several test samples of the gold alloy are first subjected to an increasing deformation force F (specifically, a gradual increase followed by a gradual decrease). In a three-point bending test, a given deformation force (F test The height or position L1 of the intermediate point is measured, which is evaluated by the maximum displacement value (L t ) is reached. When the predetermined maximum displacement value is reached, the deformation force F increases to the predetermined deformation force value (F test ), at which point a new height or position L2 of the midpoint is detected.

[0129] For the applicant, the performance of an alloy in terms of deformation recovery is better the smaller the difference ΔL, which is defined as follows: ΔL=L 2,Ftest,crescente -L 1,Ftest,decrescente

[0130] According to the measurement process carried out to obtain the graph of Figure 2, the smaller the difference, the more optimal the properties of the gold alloy under consideration in terms of recovery after deformation. This is because the smaller the residual displacement of the test sample, the lower the deformation of the object achieved by the alloy itself.

[0131] In the example graph in Figure 2, F test= 10N, Dt = 4000 μm.

[0132] The graph in FIG. 2 compares gold alloys according to the embodiments 848, 849 and 850 with several other alloys according to the compositions shown in Table 5: 3N, 5N and Pd125.

[0133] The following values ​​were obtained: ΔL 848 =470μm ΔL 849 = 600 μm ΔL 850 =950μm ΔL 844 =1250μm ΔL 5N = 400 μm ΔL 3N = 600 μm ΔL Pd125 =1700μm

[0134] Furthermore, it is observed that with the same palladium content (compositions 848, 849, 850), the gold alloys perform better when the cobalt content is increased.

[0135] The following table shows hardness values ​​for certain embodiments of gold alloys devised by the applicant.

[0136] [Table 8]

[0137] The hardening process for the gold alloys described herein is carried out by exposing the alloys to the specific and prescribed hardening temperature of each particular formulation for a time period substantially equal to one hour, and then allowing the alloy to cool to room temperature. The purpose of hardening is to promote high temperature activated precipitate formation and / or crystalline phase changes, which allows the alloy to attain higher hardness relative to its post-annealing hardness.

[0138] The cure temperatures described for the formulations of this invention are shown in the table below.

[0139] [Table 9]

[0140] Quenching of the test samples of the alloys in Table 9 was carried out by immersion in water at room temperature.

[0141] In particular, it is observed that compositions 848 and 849, due to their high cobalt content, exhibit significantly higher hardness relative to the other compositions, especially after curing. The hardness according to Table 8 is measured on the Vickers scale under a load of 1 kgf.

[0142] The present disclosure further refers to a manufacturing process for the gold alloy.

[0143] In one of its more general embodiments, the process for producing a gold alloy according to the invention comprises, starting from the pure elements according to the above, the steps of: 700‰ to 800‰ by weight of gold, 25% to 170% by weight of copper, 50% by weight to 165% by weight of palladium, 7 wt‰ to 40 wt‰ cobalt This includes mixing the

[0144] Further ranges for blend weights are set forth above and will not be repeated below.

[0145] The method described herein includes the steps of introducing the mixture into a melting crucible and then melting it by heating it in the melting crucible until it is completely melted.

[0146] The starting elements from which the alloys described herein are realized are pure elements, preferably gold having a purity of 99.99%, copper having a purity of 99.99%, palladium having a purity of 99.95%, silver having a purity of 99.99%, cobalt and iridium having a purity of 99.95%, and gallium having a purity of 99.99%.

[0147] The method may include mixing a pre-alloy of CuIr in a collection of the aforementioned elements.

[0148] Accordingly, certain embodiments may include the steps of providing a CuIr pre-alloy; 700‰ to 800‰ by weight of gold, 9 wt‰ to 79 wt‰ copper, 85% by weight to 165% by weight of palladium, 7 wt‰ to 40 wt‰ of cobalt, 7% to 60% silver by weight with 16% by weight of a CuIr pre-alloy.

[0149] The melting process is preferably a continuous casting melting process, i.e. a process in which starting from the free end of the gold bar or melt, solidification and removal of the solidified gold is carried out continuously, in particular in continuous melting processes in which a graphite die is used.

[0150] The use of graphite dies is useful because graphite is a solid lubricant and typically exhibits low friction between its surface and the surface of the molten metal, typically allowing for easy removal of the elements contained therein without spalling and with minimal defects present on its surface.

[0151] The pure element melting process for forming the gold alloy according to the present invention may in particular be a discontinuous gold melting process or a continuous gold melting process.

[0152] The discontinuous gold melting process is a process in which a mixture is melted and cast into molds or ingots realized with graphite. In this case, the elements are melted and cast in a controlled atmosphere. More specifically, the melting operation is preferably carried out only after at least three cycles of adjusting the atmosphere in the melting chamber. This adjustment is carried out by first reducing the vacuum level to 1×10 -2 The process involves reducing the pressure to less than 100 mbar, followed by partial saturation with argon at 500 mbar. During melting, the argon pressure is maintained at a pressure level between 500 mbar and 800 mbar. Once complete melting of the pure elements is reached, a step of superheating the mixture is carried out, in which the mixture is heated to a temperature of up to about 1250 °C, and in any case to a temperature above 1200 °C, in order to homogenize the chemical composition of the metal bath. During the superheating step, the pressure in the melting chamber is adjusted to a value of 1 × 10, which is again useful for removing some of the slag generated by the melting of the pure elements. -2 A vacuum level of less than mbar is reached.

[0153] At this point, in a casting step, the molten material is poured into molds or ingots made of graphite, and the melting chamber is repressurized with an inert gas, preferably argon, injected at a pressure higher than 700 mbar, in particular higher than 800 mbar.

[0154] Upon solidification, the bar or casting is removed from the bracket. Once the alloy has solidified, the gold alloy bar or casting is obtained from the graphite conduit and subjected to a rapid cooling step by a water immersion step to reduce and possibly avoid phase transformation. In other words, the bar or casting is subjected to a rapid cooling step, preferably, but not limited to, in water, to avoid phase changes in the solid state.

[0155] The advantages of the gold alloys according to the present disclosure are clear in light of the above description. In particular, due to their improved mechanical properties, the gold alloys according to the present disclosure make it possible to realize objects (even for high jewelry) that change very little in size even when subjected to relevant and / or repeated deformation forces, thereby providing a longer operational life for both themselves and any object to which they are connected or contained. The deformation recovery properties are comparable to those of 3N and 5N alloys and significantly better than those of commercially available gray alloys that do not contain Ni.

[0156] Furthermore, gold alloys according to the present disclosure can also be processed in a particularly effective manner to provide a uniform surface free of visible second phases or carbides, and therefore can be advantageously used to realize high jewelry applications, and in particular high jewelry objects.

[0157] Non-limiting examples of jewelry objects at least partially realized with the gold alloys described herein are bracelets, watch bracelets, buckles, watch cases, watch hands, watch inner mechanisms, bracelet bezels, earrings, ornaments, rings, gem holders, ingots, in particular collector's ingots, collector's coins, necklaces, necklace closure elements, for earrings or for bracelets.

[0158] Gold alloys according to the present disclosure may be applicable to objects that come into direct contact with human skin and pose a low allergy risk.

[0159] Finally, it is clear that additions, modifications or variations that are obvious to those skilled in the art may be applied to what forms the subject matter of the present invention without thereby departing from the scope provided by the appended claims.

Claims

1. 1. A gold alloy for jewelry applications, particularly intended to achieve jewelry objects having at least partial shape and / or size recovery properties after the application of a deformation force, comprising: 700%wt to 800%wt gold, 25% by weight to 170% by weight of copper, 50% by weight to 165% by weight of palladium, 7% to 40% by weight of cobalt Gold alloy containing

2. 700%wt to 800%wt gold, 25% by weight to 95% by weight of copper, 85% by weight to 165% by weight of palladium, 7% by weight to 40% by weight of cobalt, 7% to 60% by weight silver 10. The gold alloy of claim 1, comprising:

3. further comprising gallium and / or at least one of the grain refining elements, preferably iridium, rhenium or ruthenium, wherein the amount by weight of gallium and / or said at least one of the grain refining elements, preferably iridium, rhenium or ruthenium, determines the amount of gallium and / or said at least one of the grain refining elements, preferably iridium, rhenium or ruthenium, to reach 1000% by weight, said gold alloy being characterized in that it is nickel-free, that it is arsenic-free, and that it is platinum-free; the alloy is a gray alloy; Said grey has the following colour coordinates in the colour gamut of CIELAB 1976 and according to the colour measurement conditions according to CIE D65: L* comprised between 80 and 84.5, preferably between 81 and 84; a* comprised between 1.2 and 3.7, preferably between 1.5 and 3.5, b* included in 6.2 to 10.5, preferably 6.6 to 10 3. The gold alloy of claim 1 or 2, defined by:

4. A gold alloy according to claim 2 or 3, containing from 1 to 10% by weight, preferably from 2 to 9% by weight, more preferably from 3 to 8% by weight, of gallium.

5. said at least one grain refining element being present in an amount of up to 1% by weight; 4. The gold alloy of claim 3, wherein optionally the iridium is pre-alloyed with copper and / or the rhenium and / or ruthenium is pre-alloyed with palladium.

6. 730% by weight to 770% by weight of gold, 40% by weight to 90% by weight of copper, 100% by weight to 150% by weight of palladium, 8% by weight to 30% by weight of cobalt, 8% to 55% by weight silver The gold alloy of any one of claims 2 to 5, comprising:

7. 740‰ to 760‰ by weight of gold, 50% by weight to 90% by weight of copper, 100% by weight to 150% by weight of palladium, 8% by weight to 30% by weight of cobalt, 8% to 55% by weight silver 7. The gold alloy of claim 6, comprising:

8. 740‰ to 760‰ by weight of gold, 50% by weight to 90% by weight of copper, 110% by weight to 140% by weight, preferably 115% by weight to 135% by weight, of palladium, 10% by weight to 25% by weight of cobalt, 8% to 50% by weight silver 8. The gold alloy of claim 7, comprising:

9. Copper is present at 45% by weight to 65% by weight, preferably 50% by weight to 60% by weight, and silver is present at 35% by weight to 52% by weight, or 6. A gold alloy according to any one of claims 1 to 5, wherein copper is present at from 75 wt% to 95 wt% and preferably from 80 wt% to 90 wt% and silver is present at from 7 wt% to 13 wt% and preferably from 8 wt% to 12 wt%.

10. A gold alloy according to any one of claims 1 to 9, characterized in that it is nickel-free.

11. 730% by weight to 770% by weight, preferably 740% by weight to 760% by weight, of gold, 150% by weight to 170% by weight, preferably 155% by weight to 165% by weight, of copper, 50% to 70% by weight, preferably 55% to 65% by weight, of palladium, 7% by weight to 13% by weight of cobalt, 10% by weight to 30% by weight of iron, Optionally, at least one grain refining element, preferably at least one of iridium, rhenium, or ruthenium 2. The gold alloy of claim 1, comprising: gold, copper, palladium, cobalt, iron and optionally at least one of said at least grain refining elements, preferably iridium, rhenium or ruthenium, totalling 1000% by weight.

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