Platinum alloy

Abstract

The present disclosure relates to a platinum alloy for jewelry applications, comprising: platinum, from 920% by weight to 980% by weight; tin, 0.5% to 35% by weight; ru, 8% by weight to 45% by weight, or copper, 2% by weight to 45% by weight.

Description

Technical Field

[0001] This disclosure relates to the field of metallurgy, and in particular to the field of platinum alloys. Specifically, the present invention relates to a platinum alloy for jewelry applications.

[0002] This disclosure also relates to jewelry items made of the platinum alloys described herein. Background Technology

[0003] Platinum alloys are metallic alloys that can be used in jewelry making. In particular, due to their mechanical and functional properties, platinum alloys are advantageously used in the manufacture of watchmaking mechanisms.

[0004] These mechanical structures can be concealed within the case back or made visible, thus preserving the aesthetic appeal of the watch itself. In such cases, the case back is typically made of a transparent element (e.g., sapphire crystal or plastic), allowing the user to observe the internal mechanical structure when not wearing the watch.

[0005] Platinum alloys can also be used to make jewelry items, such as watch or bracelet components, which are destined to come into direct contact with human skin.

[0006] In jewelry applications, the brightness or luster of an alloy plays a crucial role: the higher the brightness, the higher the aesthetic quality of the item, and therefore the higher the value of the alloy. In the CIELAB system, this property is represented by the coordinate L... It is defined by [the relevant authority / method].

[0007] Platinum alloys used in jewelry applications should possess optimal machinability, specifically the ability to withstand all machining processes commonly used in the production of jewelry or watch parts. In particular, platinum alloys should not exhibit defects such as cracks or fractures when subjected to plastic deformation (rolling, drawing, etc.) and / or machining.

[0008] Among the applications considered, platinum-ruthenium alloys are renowned for their machinability; particularly as a binary alloy composed of 950‰ platinum and 50‰ ruthenium. These alloys not only possess a high melting temperature exceeding 1700°C, but also exhibit limitations in machinability, especially in cutting processes. For instance, diamond polishing processes, widely used for other precious alloy families (especially gold alloys of different karats), are virtually unusable for manufacturing platinum-ruthenium binary alloy components.

[0009] GB 546 897 A discloses improvements to platinum alloys for jewelry and dental applications, and specifically discloses an alloy comprising at least 82% platinum, 0.35% to 5% tin, and the remainder consisting substantially of one or more other platinum group metals, each in an amount of not less than 0.5%. Similarly, US 2 273 806 A discloses platinum alloys containing a small amount of tin for jewelry and dental applications.

[0010] The purpose of this disclosure is to describe a platinum alloy that can achieve better machinability. Summary of the Invention

[0011] To overcome the aforementioned drawbacks, and particularly to obtain alloys with optimal machinability, the applicant has conceived of platinum alloys according to the aspects described herein. These aspects may be combined with each other or with portions of the specific embodiments or claims.

[0012] According to this disclosure, a platinum alloy for jewelry applications is described, comprising:

[0013] Platinum, 920‰ to 980‰ by weight;

[0014] Tin, 5‰ to 35‰ by weight;

[0015] Ruthenium, 8% to 45% by weight, or copper, 2% to 45% by weight.

[0016] According to another non-limiting aspect, the tin content is from 10 wt% to 30 wt%, preferably from 12 wt% to 28 wt%.

[0017] According to another non-limiting aspect, the copper content is from 4 wt‰ to 41 wt‰, preferably from 8 wt‰ to 39 wt‰, and more preferably from 8 wt‰ to 34 wt‰.

[0018] According to another non-limiting aspect, the ruthenium content is from 10 wt% to 43 wt%, preferably from 15 wt% to 38 wt%, and more preferably from 15 wt% to 35 wt%.

[0019] According to another non-limiting aspect, the platinum content is from 930 wt% to 970 wt%, preferably from 940 wt% to 960 wt%.

[0020] According to another non-limiting aspect, the alloy comprises:

[0021] Tantalum, 2% to 30% by weight, preferably 4% to 25% by weight, more preferably 8% to 20% by weight, and / or

[0022] Niobium, 2 to 20 wt%, preferably 4 to 15 wt%, more preferably 5 to 10 wt%.

[0023] According to another non-limiting aspect, the total weight of platinum, tin, ruthenium, tantalum and / or niobium, or the total weight of platinum, tin, copper, tantalum and / or niobium, makes the alloy reach 1000‰ by weight.

[0024] According to another non-limiting aspect, the total weight of platinum, tin, and ruthenium makes the alloy reach 1000‰ by weight.

[0025] According to another non-limiting aspect, the total weight of platinum, tin, and copper makes the alloy reach 1000‰ by weight.

[0026] According to another non-limiting aspect, the alloy comprises:

[0027] Chromium, 2 wt% to 18 wt%, preferably 5 wt% to 15 wt%; and / or

[0028] Molybdenum, 2% to 18% by weight, preferably 5% to 15% by weight.

[0029] According to another non-limiting aspect, the total weight of platinum, tin, ruthenium, chromium and / or molybdenum, or the total weight of platinum, tin, copper, chromium and / or molybdenum, makes the alloy reach 1000‰ by weight.

[0030] According to another non-limiting aspect, the alloy comprises:

[0031] Gallium, 5 wt% to 23 wt%, preferably 8 wt% to 20 wt%, more preferably 10 wt% and 18 wt%; or

[0032] Gold, 2% to 14% by weight, preferably 4% to 12% by weight, more preferably 6% to 8% by weight; or

[0033] Palladium, 2% to 18% by weight, preferably 4% to 16% by weight, more preferably 6% to 14% by weight.

[0034] According to another non-limiting aspect, the total weight of platinum, tin, copper, gallium, or gold or palladium makes the alloy reach 1000‰ by weight.

[0035] According to another non-limiting aspect, the total weight of platinum, tin, ruthenium, or platinum, tin, and copper reaches 970% by weight of the alloy, preferably 975% by weight, and more preferably 980% by weight.

[0036] According to another non-limiting aspect, the platinum alloy contains at least one of iridium, rhenium, vanadium, indium, and hafnium, in a total amount not exceeding 30‰ by weight, preferably not exceeding 25‰ by weight, and more preferably not exceeding 20‰ by weight.

[0037] According to another non-limiting aspect, the alloys described herein are characterized in that they are ternary or quaternary.

[0038] According to another non-limiting aspect, the alloy described herein is characterized by having a coordinate L that is at least equal to 85 in the CIELAB 1976 color space and according to the color measurement conditions of CIE D65. The color.

[0039] According to another non-limiting aspect, the alloy described herein is characterized in that its hardness is at least equal to 150 Vickers points, optionally, wherein when copper is included, the platinum alloy is characterized in that its hardness is at least equal to 155 Vickers points, or wherein when ruthenium is included, the platinum alloy is characterized in that its hardness is at least equal to 160 Vickers scale, preferably at least equal to 170 Vickers scale.

[0040] According to another non-limiting aspect, the alloy consists of 930 to 970 wt%, preferably 940 to 960 wt%, of platinum and 18 to 35 wt%, preferably 22 to 34 wt%, of ruthenium.

[0041] According to this disclosure, a platinum alloy is also described, which is composed of the following components:

[0042] Platinum, 920 wt% to 980 wt%, preferably 930 wt% to 970 wt%, more preferably 940 wt% to 960 wt%;

[0043] Tin, 5% to 35% by weight, preferably 10% to 30% by weight, more preferably 12% to 28% by weight;

[0044] or:

[0045] Ruthenium, 8‰ to 45‰ by weight,

[0046] Copper, 2‰ to 45‰ by weight,

[0047] At least one of the following:

[0048] Tantalum, 2% to 30% by weight, preferably 4% to 25% by weight, more preferably 8% to 20% by weight, and / or

[0049] Niobium, 2% to 20% by weight, preferably 4% to 15% by weight, more preferably 5% to 10% by weight.

[0050] Alternatively, at least one of the following can be used as a substitute for tantalum and / or niobium:

[0051] Chromium, 2 wt% to 18 wt%, preferably 5 wt% to 15 wt%; and / or

[0052] Molybdenum, 2% to 18% by weight, preferably 5% to 15% by weight.

[0053] Alternatively, in place of tantalum and / or niobium and / or chromium and / or molybdenum, at least one of the following:

[0054] Gallium, 5 wt% to 23 wt%, preferably 8 wt% to 20 wt%, more preferably 10 wt% to 18 wt%; or

[0055] Gold, 2% to 14% by weight, preferably 4% to 12% by weight, more preferably 6% to 8% by weight; or

[0056] Palladium, 2% to 18% by weight, preferably 4% to 16% by weight, more preferably 6% to 14% by weight.

[0057] According to this disclosure, a jewelry article is described that comprises a platinum alloy according to one or more aspects of the present invention.

[0058] According to another non-limiting aspect, jewelry articles include jewelry or watches or watch chains or movements or parts of mechanical watch movements.

[0059] According to another non-limiting aspect, the watchband is configured to be worn on the wrist, and / or the movement or components of a mechanical watch movement are configured to be mounted in the watch. Attached Figure Description

[0060] Some embodiments of the platinum alloy articles of this disclosure will now be described with reference to the accompanying drawings, and a brief description thereof is given below.

[0061] Figure 1 The diagram shows a Cartesian plot, where the horizontal axis represents data related to the grain quality of the platinum alloy; the vertical axis represents data related to the alloy's brightness, represented as the coordinate L according to CIELAB 1976. . Detailed Implementation

[0062] This disclosure describes a platinum alloy for jewelry applications that has high machinability, particularly during cutting and / or diamond polishing operations.

[0063] The applicant has demonstrated that the machinability of platinum alloys is related to the characteristics of their microstructure and has conducted various studies on grain-refining elements, the purpose of which, when introduced into the alloy, is to improve its machinability.

[0064] The applicant has conducted various studies on specific compositions, in which the platinum content is typically between 920‰ and 980‰ by weight. Due to the high platinum content and considering the expensive cost of platinum, it is clear that the primary application of the platinum alloys described herein is in high-end jewelry / watchmaking. This does not preclude other applications for the platinum alloys described herein. Jewelry / watchmaking applications should not be limited thereto.

[0065] The applicant has conducted in-depth research on the platinum alloy that is the target of this invention, and in particular has examined it under an optical microscope, which revealed a microstructure characterized by very fine grains and exhibits particularly high reflectivity.

[0066] The applicant is particularly concerned with the quality of the platinum alloy, especially its average grain size, followed by its grain uniformity. The applicant also notes that known platinum and ruthenium alloys exhibit very high melting temperatures. In fact, the melting temperatures of platinum and ruthenium alloys may cause partial breakage of the melting crucible, thereby contaminating the molten alloy with elements other than the intended composition.

[0067] To this end, the applicant has conceived of a platinum alloy containing 5‰ to 35‰ tin by weight. The inclusion of tin in the platinum alloy lowers the alloy's melting temperature, thereby reducing contaminant content and thus providing greater flexibility in selecting the melting crucible. The applicant notes that the inclusion of tin helps improve the alloy's machinability. The applicant also notes that, in addition to tin, the presence of niobium or partial substitution of niobium can also improve the alloy's machinability.

[0068] To ensure suitable mechanical properties for jewelry processing, the applicant is primarily interested in two types of platinum-tin alloys, including ruthenium or copper in addition to the aforementioned platinum and tin.

[0069] The applicant noted that copper, compared to ruthenium, generally helps to lower the melting temperature. For this reason, certain formulations characterized by the presence of copper instead of ruthenium still exhibit improved machinability and are less affected by contaminants released from the melting crucible compared to known types of platinum alloys.

[0070] The platinum alloys disclosed herein have also been studied in terms of performance, including not only the changes in their chemical composition but also the effects of diverse production processes on their performance.

[0071] The following shows some specific combinations of platinum alloys studied by the applicant.

[0072]

[0073] Table 1

[0074] The combinations shown in Table 1 are specific combinations obtained by the applicant after studying a general family of platinum alloys used in jewelry applications, including:

[0075] Platinum, 920‰ to 980‰ by weight;

[0076] Tin, 5‰ to 35‰ by weight;

[0077] Ruthenium, 8% to 45% by weight, or copper, 2% to 45% by weight.

[0078] Platinum-ruthenium alloys are traditionally used in jewelry applications, while platinum-copper alloys include combinations that use copper instead of ruthenium, and because copper is less expensive than ruthenium, they represent a more economical production option.

[0079] Copper and ruthenium help to provide platinum alloys with sufficient hardness and machinability for jewelry applications.

[0080] From the previous general family, the applicant focused the study on the first general subfamily, in which the tin content is from 10 wt% to 30 wt%, preferably from 12 wt% to 28 wt%.

[0081] The applicant is particularly interested in alloys from the general family of alloys containing copper instead of ruthenium, wherein the copper content is from 4 wt‰ to 41 wt‰, preferably from 8 wt‰ to 39 wt‰, and more preferably from 8 wt‰ to 34 wt‰.

[0082] Alternatively, the applicant may choose from a general family of alloys containing ruthenium instead of copper, with particular interest in Group 3 alloys, wherein the ruthenium content is from 10 wt% to 43 wt%, preferably from 15 wt% to 38 wt%, and more preferably from 15 wt% to 35 wt%.

[0083] The alloy was further studied in detail, with a platinum content of 930 to 970 wt%, preferably 940 to 960 wt%. The amount of platinum introduced in this paper, particularly its correlation with the first, second, and third subgroup combinations, has been investigated.

[0084] The applicant has conceived several embodiments of the alloys according to this disclosure, which exhibit a non-negligible amount of tantalum. According to the applicant's analysis, the presence of tantalum, in some cases partially replacing ruthenium, has determined a further reduction in the alloy grain size, and the resulting alloys are characterized by greater brightness compared to combinations of platinum alloys that do not contain tantalum. The applicant has also conceived of platinum alloy families containing niobium and / or chromium.

[0085] In particular, the platinum alloys that the applicant is interested in contain:

[0086] Tantalum, 2% to 30% by weight, preferably 4% to 25% by weight, more preferably 8% to 20% by weight, and / or

[0087] Niobium, 2 to 20 wt%, preferably 4 to 15 wt%, more preferably 5 to 10 wt%.

[0088] Some subgroup alloys containing the amounts of tantalum and / or niobium described in the preceding paragraph are quaternary alloys, wherein the total weight of platinum, tin, ruthenium, tantalum and / or niobium, or—for alloys containing copper but not ruthenium—the total weight of platinum, tin, copper, tantalum and / or niobium, makes the alloy reach 1000‰ by weight.

[0089] These subsequent families are families that implement the final combination according to Table 1, such as families with codes 318, 319, 322, 531, and 561.

[0090] As previously stated, the applicant has studied other groups of platinum alloys, among which:

[0091] Chromium, 2 wt% to 18 wt%, preferably 5 wt% to 15 wt%; and / or

[0092] Molybdenum, 2% to 18% by weight, preferably 5% to 15% by weight.

[0093] Some subgroup alloys containing the amounts of chromium and / or molybdenum described in the preceding paragraph are quaternary alloys, i.e., in which the total weight of platinum, tin, ruthenium, chromium and / or molybdenum, or—for alloys containing copper but not ruthenium—the total weight of platinum, tin, copper, chromium and / or molybdenum makes the alloy reach 1000‰ by weight.

[0094] These subsequent families are families that implement the final combination according to Table 1, such as families with codes 326 and 327.

[0095] Based on the aforementioned general family of combinations, and within the defined scope of the first, second, and third subfamilies, the applicant, through further analysis of combinations in which the platinum content is 930 wt% to 970 wt%, preferably 940 wt% to 960 wt%, has conceived of several families of platinum alloys, which, in addition to the aforementioned amounts of platinum, copper, or ruthenium, also contain:

[0096] Gallium, 5 wt% to 23 wt%, preferably 8 wt% to 20 wt%, more preferably 10 wt% to 18 wt%; or

[0097] Gold, 2% to 14% by weight, preferably between 4% and 12% by weight, more preferably between 6% and 8% by weight; or

[0098] Palladium, 2% to 18% by weight, preferably 4% to 16% by weight, more preferably 6% to 14% by weight.

[0099] The applicant is particularly interested in quaternary platinum alloys, i.e., alloys in which the total weight of platinum, tin, copper and one of gallium, gold or palladium makes the alloy 1000‰ by weight.

[0100] Other platinum alloy families studied by the applicant are those in which the total weight of platinum, tin, ruthenium or platinum, tin, and copper reaches 970% by weight of the alloy, preferably 975% by weight, and more preferably 980% by weight; these platinum alloy families are characterized by the presence of at least one of iridium, rhenium, vanadium, indium, and hafnium, in a total amount not exceeding 30% by weight, preferably not exceeding 25% by weight, and more preferably not exceeding 20% ​​by weight.

[0101] The applicant has carefully studied a specific subfamily of platinum alloys that is a ternary alloy family from the general family, which is within the defined range of at least one of the first and third subfamilies of platinum alloys, specifically referring to a platinum content of 930 wt‰ to 970 wt‰, preferably 940 wt‰ to 960 wt‰, and a ruthenium content of 18 wt‰ to 35 wt‰, preferably 22 wt‰ to 34 wt‰, containing only ruthenium.

[0102] In view of the above considerations, it is clear that this disclosure discloses a platinum alloy composed of the following components:

[0103] Platinum, 920 wt% to 980 wt%, preferably 930 wt% to 970 wt%, more preferably 940 wt% to 960 wt%;

[0104] Tin, 5% to 35% by weight, preferably 10% to 30% by weight, more preferably 12% to 28% by weight;

[0105] or:

[0106] Ruthenium, 8‰ to 45‰ by weight,

[0107] Copper, 2‰ to 45‰ by weight,

[0108] At least one of the following:

[0109] Tantalum, 2% to 30% by weight, preferably 4% to 25% by weight, more preferably 8% to 20% by weight, and / or

[0110] Niobium, 2% to 20% by weight, preferably 4% to 15% by weight, more preferably 5% to 10% by weight.

[0111] Alternatively, at least one of the following can be used as a substitute for tantalum and / or niobium:

[0112] Chromium, 2 wt% to 18 wt%, preferably 5 wt% to 15 wt%; and / or

[0113] Molybdenum, 2% to 18% by weight, preferably 5% to 15% by weight.

[0114] Alternatively, instead of tantalum and / or niobium and / or chromium and / or molybdenum, a selection from at least one of the following may be used:

[0115] Gallium, 5 wt% to 23 wt%, preferably 8 wt% to 20 wt%, more preferably 10 wt% to 18 wt%; or

[0116] Gold, 2% to 14% by weight, preferably 4% to 12% by weight, more preferably 6% to 8% by weight; or

[0117] Palladium, 2% to 18% by weight, preferably 4% to 16% by weight, more preferably 6% to 14% by weight.

[0118] Based on the above research, the combinations in Table 1 are obtained as specific implementation schemes for certain platinum alloy subfamilies, and preferred combinations for the following subfamilies are obtained.

[0119] Combination 309 belongs to the platinum alloy subgroup and consists of 947 wt‰ to 957 wt‰ platinum, 15 wt‰ to 25 wt‰ tin, and 23 wt‰ to 33 wt‰ ruthenium.

[0120] Combination 318 belongs to the platinum alloy subgroup and consists of 947 wt‰ to 957 wt‰ platinum, 15 wt‰ to 25 wt‰ tin, 13 wt‰ to 23 wt‰ ruthenium, and 5 wt‰ to 15 wt‰ niobium.

[0121] Combination 319 belongs to the platinum alloy subgroup and consists of 947 wt‰ to 957 wt‰ platinum, 15 wt‰ to 25 wt‰ tin, 13 wt‰ to 23 wt‰ ruthenium, and 5 wt‰ to 15 wt‰ tantalum.

[0122] The applicant specifically notes that combinations 309, 318, and 319 can be covered by a specific subfamily of platinum alloys, which consists of the following components:

[0123] Platinum, 942% to 963% by weight, preferably 947% to 957% by weight.

[0124] Tin, 10‰ to 30‰ by weight, preferably 15‰ to 25‰ by weight.

[0125] Ruthenium, 18‰ (or 21‰) to 35‰, preferably 23‰ to 33‰,

[0126] Optionally, at least one, preferably one, of the following components: niobium, 2 wt% to 17 wt%, preferably 5 wt% to 15 wt%, and / or tantalum, 2 wt% to 17 wt%, preferably 5 wt% to 15 wt%.

[0127] The total amount of platinum, tin, and ruthenium, along with optional niobium and / or tantalum, reaches 1000‰ by weight. Therefore, the alloy is a ternary, quaternary, or optionally pentagonal alloy.

[0128] Combination 320 belongs to the platinum alloy subgroup and consists of 947 wt‰ to 957 wt‰ platinum, 10 wt‰ to 20 wt‰ tin, and 26 wt‰ to 40 wt‰ ruthenium.

[0129] Combination 322 belongs to the platinum alloy subgroup and consists of 947 wt‰ to 957 wt‰ platinum, 10 wt‰ to 20 wt‰ tin, 18 wt‰ to 28 wt‰ ruthenium, and 5 wt‰ to 15 wt‰ tantalum.

[0130] Combination 325 belongs to the platinum alloy subgroup and consists of 947 wt‰ to 957 wt‰ platinum, 10 wt‰ to 20 wt‰ tin, 23 wt‰ to 33 wt‰ ruthenium, and 2 wt‰ to 10 wt‰ niobium.

[0131] Combination 326 belongs to the platinum alloy subgroup and consists of 947 wt‰ to 957 wt‰ platinum, 10 wt‰ to 20 wt‰ tin, 18 wt‰ to 28 wt‰ ruthenium, and 5 wt‰ to 15 wt‰ chromium.

[0132] Combination 327 belongs to the platinum alloy subgroup and consists of 947 wt‰ to 957 wt‰ platinum, 10 wt‰ to 20 wt‰ tin, 18 wt‰ to 28 wt‰ ruthenium, and 5 wt‰ to 15 wt‰ molybdenum.

[0133] Combination 528 belongs to the platinum alloy subgroup, which consists of 947 wt‰ to 957 wt‰ platinum, 9 wt‰ to 19 wt‰ tin, 15 wt‰ to 25 wt‰ copper, and 7 wt‰ to 21 wt‰ gallium.

[0134] Combination 530 belongs to the platinum alloy subgroup, which consists of 947 wt‰ to 957 wt‰ platinum, 13 wt‰ to 23 wt‰ tin, and 25 wt‰ to 35 wt‰ copper.

[0135] Combination 531 belongs to the platinum alloy subgroup and consists of 947 wt‰ to 957 wt‰ platinum, 5 wt‰ to 15 wt‰ tin, 25 wt‰ to 35 wt‰ copper, and 2 wt‰ to 13 wt‰ tantalum.

[0136] Combination 561 belongs to the platinum alloy subgroup and consists of 948 to 958 wt% platinum, 5 to 15 wt% tin, 24 to 34 wt% copper, and 2 to 13 wt% niobium.

[0137] The applicant specifically notes that combinations 531 and 561 can be covered by a specific subfamily of platinum alloys, which consists of the following components:

[0138] Platinum, 942 to 963 wt%, preferably 947 to 957 wt% or 948 to 958 wt%.

[0139] Tin, 2% to 17% by weight, preferably 5% to 15% by weight.

[0140] Copper, 21‰ to 39‰ by weight, preferably 25‰ to 35‰ by weight or between 24‰ and 34‰ by weight.

[0141] At least one, preferably one, of the following components: tantalum, 2 to 13 wt%, preferably 3 to 12 wt%, or niobium, 2 to 13 wt%, preferably 3 to 12 wt%.

[0142] The total amount of platinum, tin, copper, and optionally tantalum and / or niobium reaches 1000‰ by weight.

[0143] Combination 567 belongs to the platinum alloy subgroup and consists of 948 to 958 wt% platinum, 20 to 30 wt% tin, 7 to 17 wt% copper, and 5 to 15 wt% palladium.

[0144] Combination 569 belongs to the platinum alloy subgroup, which consists of 948 to 958 wt% platinum, 20 to 30 wt% tin, and 9 to 19 wt% copper.

[0145] Table 2 below shows some physical properties of the specific platinum alloy combinations described in Table 1. For ease of graphical representation, the two tables are separated.

[0146] A column in the table below shows the qualitative characteristics of the grains, particularly those downstream of the alloy annealing step. These qualitative characteristics are defined by an index according to UNI EN ISO 643, which provides an assessment of grain size and / or uniformity using a normalized lattice and optical or electron microscopy.

[0147] The platinum alloy annealing described herein is performed at a temperature below its melting temperature, followed by a slow and / or controlled cooling process.

[0148] The higher the value shown in the column above, the smaller the average grain size, and the higher the quality of the platinum alloy. Another column shows the coordinate L. In CIELAB chromaticity, luminance represents the brightness of the alloy. A higher brightness value corresponds to better alloy quality.

[0149]

[0150] Table 2

[0151] In Table 2, the hardness values ​​are shown according to the Vickers hardness scale. All the specific combinations described in Table 2 show better machinability than known alloys both before and after remelting.

[0152] All the specific combinations described in Table 2 show uniform grains.

[0153] The brightness of an alloy, physically expressed as reflectivity, is partly related to its grain size. Larger grain sizes result in more uneven surfaces on objects made from the alloy. Therefore, reflectivity decreases with increasing grain size and increases with decreasing grain size. However, it can be assumed that higher coordinates L... This does not necessarily correspond to an equivalent grain with a smaller average grain size. In fact, coordinate L It may be affected by other factors.

[0154] In particular, it is noted that platinum alloys containing ruthenium (combinations 309, 318, 319, 320, 322, 325, 326, 327) exhibit, on average, greater brightness than platinum alloys containing copper (combinations 528, 530, 531, 561, 567, 569). However, as previously pointed out, platinum alloys conceived in this manner exhibit higher costs compared to platinum alloys in which ruthenium is replaced by copper.

[0155] By comparison, the applicant noted that, under the same measurement conditions as in Table 2, pure platinum showed coordinates L. =87.5. Therefore, the combination of 309 and 325 exhibits even higher brightness than pure platinum.

[0156] In Table 2, from the columns related to grain size index, it is noted that using ruthenium as a substitute for copper yields better and (especially important) more uniform grains. Therefore, the surface finish of the platinum-tin-ruthenium combination described in this disclosure can be, on average, higher than that of the platinum-tin-copper combination described in this disclosure.

[0157] It is also noted that the presence of tantalum can significantly improve the grain size. In fact, comparing combination 320 and combination 322 (where combination 322 has 10‰ less ruthenium, which is replaced by an equal weight of tantalum), it is noted that combination 322 shows a grain size index of 9, while combination 320 is 7 / 8.

[0158] In terms of hardness in the annealed state, platinum-tin alloys containing ruthenium are on average harder than platinum-tin alloys containing copper as a substitute for ruthenium; the exception is composite 531, whose hardness is comparable to that of platinum-tin-ruthenium alloys due to the presence of tantalum.

[0159] Extracted from Table 2 Figure 1 The graph shows the grain quality (according to UNI EN ISO 643 index) in the second-to-last column of Table 2 on the horizontal axis, and the coordinates L in the last column of Table 2 on the vertical axis. .from Figure 1 As can be seen from the figure, in terms of grain quality / brightness ratio, the best combination to consider overall is 325, 322, 309, 318, and 319. Secondly, in a narrower range, the combination of 325 and 322 can be considered.

[0160] The color of platinum alloys is uniquely measured in the CIELAB 1976 color space, which is based on the first parameter L. The second parameter a and the third parameter b Define the color, where the first parameter L The first parameter represents brightness and uses a value between 0 (black) and 100 (white), while the second parameter a... and the third parameter b This represents the chromaticity parameter. Specifically, in the CIELAB 1976 color range, achromatic grayscale is determined by a... =b The point with a value of 0 is used for identification; the second parameter a A positive value indicates that the higher the value of the second parameter, the more red the color tends to be; the second parameter a The negative value of a indicates that the second parameter a The higher the absolute value (even a negative value), the more green the color tends to be; the third parameter b A positive value indicates that the higher the value of the third parameter, the more yellow the color tends to be; the third parameter b The negative value indicates the third parameter b The higher the absolute value (even a negative value), the more blue the color tends to be. Additionally, the second parameter a... and the third parameter b Convert to polar coordinate parameters as defined below: C ab =

[0161]

[0162] Cab The parameter is defined as "chromaticity", Cab The higher the parameter value, the higher the color saturation; Cab The lower the value of the parameter, the lower the color saturation, and the closer it is to grayscale.

[0163] From Table 2, and particularly from the applicant's study of the various platinum alloy families described herein, it has been noted that particular interest is focused on specific combinations falling within the aforementioned elemental ranges, presented in the CIELAB 1976 color space and, according to the color measurement conditions of CIE D65, at coordinates L... A color value at least equal to 85. Preferably, alloys of particular interest display coordinates L at least equal to 85.5. .

[0164] Furthermore, from the combinations in Table 2, it can be observed that particular attention is paid to alloys characterized by a Vickers hardness of at least 150.

[0165] In particular, when copper is included, the platinum alloy articles disclosed herein are characterized by a hardness of at least 155 Vickers hardness.

[0166] Conversely, when the alloy contains ruthenium, the platinum alloy is characterized by a hardness of at least 160 Vickers hardness, preferably at least 170 Vickers hardness.

[0167] In one embodiment, the melting process of the platinum alloy described herein is a discontinuous melting process. A discontinuous melting process is a process of melting a mixture and casting it into a graphite mold or ingot. In this case, the aforementioned elements are melted and cast in a controlled atmosphere.

[0168] More specifically, the melting operation is preferably performed only after at least three atmosphere conditioning cycles have been completed in the melting chamber. This conditioning first involves reducing the vacuum level to below 1 × 10⁻⁶. -2 The pressure was initially set at millibars (mbar), then partially saturated with argon at 500 mbar. During melting, the argon pressure was maintained at a level between 500 and 800 mbar. Once the pure elements were completely melted, a superheating step was performed on the mixture, where it was heated to temperatures between 1600°C and 1850°C to homogenize the chemical composition of the molten metal pool. During this superheating step, the pressure in the melting chamber again dropped below 1 × 10⁻⁶ mbar. -2 A vacuum of millibars is useful for eliminating some of the slag produced during the melting of pure elements.

[0169] At this point, during the casting process, the molten material is poured into a mold or ingot.

[0170] Once solidified, the ingot or casting is removed from the support. As the alloy solidifies, the platinum alloy ingot or casting is obtained from the graphite conduit and rapidly cooled via a water immersion step to reduce and, as far as possible, avoid phase changes. In other words, the ingot or casting undergoes a rapid cooling step, preferably, but not limited to, water, to avoid phase changes in the solid state.

[0171] The platinum alloys according to this disclosure can also be processed in a particularly efficient manner to produce a uniform surface free of visible second phases or carbides. Therefore, the platinum alloys according to this disclosure can be advantageously used in high-end jewelry applications, particularly for the manufacture of high-end jewelry articles.

[0172] Non-limiting examples of jewelry items made, at least in part, from the platinum alloys described herein include: bracelets, watch chains, watch clasps, watch cases, watch hands, watch internals, bracelet settings, earrings, ornaments, rings, gemstone settings, ingots (especially collectible ingots), collectible coins, necklaces, and clasping elements for necklaces / earrings / bracelets.

[0173] The platinum alloys disclosed herein can be used in articles that come into direct contact with human skin, and there is virtually no risk of allergic reactions.

[0174] The platinum alloy articles disclosed herein possess exceptional luster and superior machinability, making them particularly suitable for jewelry applications.

[0175] Finally, it is clear that the items disclosed herein may be added to, modified or modified in a manner that would be obvious to those skilled in the art without departing from the scope set forth in the appended claims.

Claims

1. Platinum alloys for jewelry applications, comprising: - Platinum, 920‰ to 980‰ by weight; - Tin, 5‰ to 35‰ by weight; - Ruthenium, 8 wt% to 45 wt%, or copper, 2 wt% to 45 wt%.

2. The platinum alloy according to claim 1, wherein the tin content is from 10‰ to 30‰ by weight, preferably from 12‰ to 28‰ by weight.

3. The platinum alloy according to claim 1 or 2, wherein the copper content is from 4 wt‰ to 41 wt‰, preferably from 8 wt‰ to 39 wt‰, more preferably from 8 wt‰ to 34 wt‰.

4. The platinum alloy according to claim 1 or 2, wherein the ruthenium content is from 10 wt% to 43 wt%, preferably from 15 wt% to 38 wt%, more preferably from 15 wt% to 35 wt%.

5. The platinum alloy according to one or more of the preceding claims, wherein the platinum content is from 930 wt% to 970 wt%, preferably from 940 wt% to 960 wt%.

6. The platinum alloy according to one or more of the preceding claims, comprising: - Tantalum, 2 to 30 wt%, preferably 4 to 25 wt%, more preferably 8 to 20 wt%, and / or - Niobium, 2 to 20 wt%, preferably 4 to 15 wt%, more preferably 5 to 10 wt%; The total weight of platinum, tin, ruthenium, tantalum and / or niobium, or the total weight of platinum, tin, copper, tantalum and / or niobium, makes the alloy reach 1000‰ by weight.

7. The platinum alloy according to one or more of the preceding claims, comprising: -Chromium, 2 wt% to 18 wt%, preferably 5 wt% to 15 wt%; and / or -Molybdenum, 2 wt% to 18 wt%, preferably 5 wt% to 15 wt%; The total weight of platinum, tin, ruthenium, chromium and / or molybdenum, or the total weight of platinum, tin, copper, chromium and / or molybdenum, makes the alloy reach 1000‰ by weight.

8. The platinum alloy according to one or more of the preceding claims, comprising: -GaN, 5 wt% to 23 wt%, preferably 8 wt% to 20 wt%, more preferably 10 wt% to 18 wt%; or - Gold, 2% to 14% by weight, preferably 4% to 12% by weight, more preferably 6% to 8% by weight; or -Palladium, 2 wt‰ to 18 wt‰, preferably 4 wt‰ to 16 wt‰, more preferably 6 wt‰ to 14 wt‰; The total weight of platinum, tin, copper, gallium, or gold or palladium makes the alloy reach 1000‰ by weight.

9. The platinum alloy according to one or more of claims 1 to 5, wherein the total weight of platinum, tin, and ruthenium, or the total weight of platinum, tin, and copper, reaches 970% by weight of the alloy, preferably 975% by weight, and more preferably 980% by weight. The platinum alloy contains at least one of iridium, rhenium, vanadium, indium, and hafnium, with a total amount not exceeding 30‰ by weight, preferably not exceeding 25‰ by weight, and more preferably not exceeding 20‰ by weight.

10. A platinum alloy according to one or more of the preceding claims, wherein the platinum alloy is ternary or quaternary, and / or the platinum alloy has coordinates L of at least 85 in the CIELAB 1976 color space and according to CIE D65 color measurement conditions. The color, And / or the platinum alloy has a hardness of at least 150 Vickers points, optionally, wherein when copper is included, the platinum alloy is characterized in that the hardness of the platinum alloy is at least 155 Vickers points, or wherein when ruthenium is included, the platinum alloy is characterized in that the hardness of the platinum alloy is at least 160 Vickers points, preferably at least 170 Vickers points.

11. The platinum alloy according to one or more of the preceding claims, wherein the platinum alloy comprises the following components: - Platinum, 920 wt% to 980 wt%, preferably 930 wt% to 970 wt%, more preferably 940 wt% to 960 wt%; - Tin, 5% to 35% by weight, preferably 10% to 30% by weight, more preferably 12% to 28% by weight; -or: -Ruthenium, 8‰ to 45‰ by weight - Copper, 2‰ to 45‰ by weight -At least one of the following: - Tantalum, 2 to 30 wt%, preferably 4 to 25 wt%, more preferably 8 to 20 wt%, and / or -Niobium, 2 to 20 wt%, preferably 4 to 15 wt%, more preferably 5 to 10 wt%. - Alternatively, in place of tantalum and / or niobium, at least one of the following: -Chromium, 2 wt% to 18 wt%, preferably 5 wt% to 15 wt%; and / or -Mo, 2% to 18% by weight, preferably 5% to 15% by weight. - Alternatively, in place of tantalum and / or niobium and / or chromium and / or molybdenum, at least one of the following: -GaN, 5 wt% to 23 wt%, preferably 8 wt% to 20 wt%, more preferably 10 wt% to 18 wt%; or - Gold, 2% to 14% by weight, preferably 4% to 12% by weight, more preferably 6% to 8% by weight; or -Palladium, 2 to 18 wt%, preferably 4 to 16 wt%, more preferably 6 to 14 wt%.

12. Jewelry articles comprising a platinum alloy according to one or more of the preceding claims.

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