WO2024147093A1 - Alliage d'or ayant des propriétés de recouvrance après déformation - Google Patents

Alliage d'or ayant des propriétés de recouvrance après déformation Download PDF

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Publication number
WO2024147093A1
WO2024147093A1 PCT/IB2024/050047 IB2024050047W WO2024147093A1 WO 2024147093 A1 WO2024147093 A1 WO 2024147093A1 IB 2024050047 W IB2024050047 W IB 2024050047W WO 2024147093 A1 WO2024147093 A1 WO 2024147093A1
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WO
WIPO (PCT)
Prior art keywords
weight
gold
copper
palladium
gold alloy
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PCT/IB2024/050047
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English (en)
Inventor
Sergio ARNABOLDI
Marta ROSSINI
Federico GALEOTTI
Original Assignee
Argor - Heraeus Sa
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Argor - Heraeus Sa filed Critical Argor - Heraeus Sa
Publication of WO2024147093A1 publication Critical patent/WO2024147093A1/fr

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  • Objects realized in metallic material exhibit deformability characteristics.
  • the deformation of a body can be of an elastic or plastic type. The deformation occurs as a result of the application on the material of a traction, compression or bending force.
  • An elastic type deformation is characterized in that the body, upon cessation of a deformation force, is capable of returning to an original size and/or shape.
  • the plastic type deformation typically occurs with the application of forces greater with respect to the forces necessary to deform in an elastic way a body.
  • the yield strength is that force which, when applied to the above-mentioned body, determines the passage from the elastic behaviour to the plastic behaviour.
  • the Gold alloy is specifically destined to realize jewelry objects with improved mechanical properties, in particular characterized by the increase in yield strength in order to make it comparable to that of 3N and 5N alloys.
  • the Applicant notes that the yield strength is significantly higher with respect to the one of commercial Nickel-free gray Gold alloys.
  • the alloy comprises:
  • the alloy comprises: Gallium and/or at least a grain refining element, preferably at least one between Indium, Rhenium and Ruthenium.
  • said at least a grain refining element is present in pre-alloy, said pre-alloy having the following basis:
  • the amount in weight of Gallium and/or of said at least a grain refining element determines the reaching of 1000 ⁇ in weight.
  • said Gold alloy is characterized in that it is free from Nickel.
  • said Gold alloy is characterized in that it is free from Arsenic.
  • said Gold alloy is characterized in that it is free from Platinum.
  • Gallium is present in the amount substantially comprised between 4 ⁇ in weight and 7 ⁇ in weight. According to a further non-limiting aspect, Gallium is present in the amount comprised between 3,5 ⁇ in weight and 4,5 ⁇ in weight.
  • said alloy comprises at least a grain refining element, preferably at least one among Iridium, Rhenium or Ruthenium.
  • said Iridium is pre-alloyed with Copper.
  • said Rhenium and/or Ruthenium is pre - alloyed with Palladium.
  • the at least a grain refining element in particular the at least one among Indium, Rhenium or Ruthenium, is present in the amount until 1 ⁇ in weight.
  • the Gold alloy comprises:
  • the Gold alloy according to one or more of the preceding aspects comprises:
  • 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*, comprised between 6,2 and 10,5, preferably between 6,6 and 10.
  • the Gold alloy has a color defined, on the CIELAB 1976 color range, and according to the color measurement conditions according to CIE D65, by the following color coordinates:
  • Gold alloys whose color falls within the aforementioned coordinates, and in particular within a square defined on the coordinates a* and b* when placed on orthogonal axes in a color chart, is considered gray.
  • the Gold alloy has a color defined, on the CIELAB 1976 color range, and according to the color measurement conditions according CIE D65, by the following color coordinates:
  • L* comprised between 83 and 84,5, preferably between 83,2 and 84,3; a*, comprised between 2,7 and 3,7, preferably between 2,9 and 3,5; b*, comprised between 8,9 and 9,9, preferably between 8,7 and 9,7.
  • a method of producing a Gold alloy comprising a mixing step at least of Gold, Copper, Palladium and Cobalt in the amounts described in one or more of the above-mentioned aspects.
  • the following table shows some specific compositions studied in detail by the Applicant.
  • the amounts of the Gold alloy elements are shown in the table in ⁇ in weight.
  • the value of yield strength is higher with respect to the yield strength of a corresponding test sample realized in 3N alloy.
  • Test samples realized with the alloys according to the present disclosure, and in particular the test sample realized with the composition LRS 848, show a value of yield strength higher than the one of corresponding test samples realized in the alloys Pd125 and Pd60, commercially known, when subject to traction and after thermal ageing.
  • the 3N and 5N alloys show a good behaviour in terms of elastic return, while the compositions Pd125 and Pd60 show a poor behaviour.
  • the Applicant notes that the Pd125 and Pd60 alloys are used for their thermosetting properties.
  • the regulation ISO 8654:2017 furthermore, tabulates the L*, a* b* nominal values in trichromatic coordinates for the 0N-6N alloys of standard color, including tolerances.
  • the following is an excerpt from the regulation wherein the chromatic limits of the alloys defined by ISO 8654:2017 standard are defined as pink/red.
  • ISO 8654 regulation proposes furthermore recommended chemical compositions for each of the 0N-6N alloys. Specifically for the pink/red alloys, the compositions are as indicated in table:
  • some test samples of Gold alloy are subject to an initially increasing deformation force F, in particular progressively increasing and then progressively decreasing.
  • Ftest the height or position Li of the midpoint assessed at a predetermined deformation force
  • Lt the height or position of the midpoint
  • the deformation force F is progressively reduced until reaching the predetermined deformation force value (Ftest) and in that condition the new height or position L2 of the midpoint is detected.
  • the graph of figure 2 compares the Gold alloy according to the 848, 849 and 850 embodiment with some other alloys: 3N, 5N and Pd125 according to the compositions given in table 5.
  • compositions 848, 849, 850 show better performances if the content of Cobalt is increased.
  • the hardening process for the Gold alloys herein described takes place by exposing the above-mentioned alloys to a specific and predefined hardening temperature for each specific formulation, for a time substantially equal to 1 h, then allowing the alloy to cool until room temperature.
  • the purpose of hardening is to promote the formation of precipitates and/or crystalline phase changes, activated by the high temperature, which allow the alloy to acquire a greater hardness with respect to the hardness after annealing.
  • the cooling of the test samples of the alloys in table 9 has been carried out by immersion in water at room temperature.
  • compositions 848 and 849 due to the high content of Cobalt, show a significantly higher hardness with respect to the other compositions in particular after hardening.
  • the hardnesses according to Table 8 are measured on the Vickers scale with an applied load of 1 kgf.
  • the present disclosure furthermore refers to a process of production of a Gold alloy.
  • the process of production of the Gold alloy according to the invention comprises, starting from the pure elements according to the above, the mixing of at least: - Gold, between 700 ⁇ in weight and 800 ⁇ in weight,
  • the method herein described comprises a step of introduction of the mixture into a melting crucible, and of a subsequent melting by heating until complete melting by introduction into the melting crucible.
  • the starting elements from which the alloys herein described are realized are pure elements; preferably, Gold has a purity of 99.99%, Copper has a purity of 99.99%, Palladium has a purity of 99.95%, Silver has a purity of 99.99%, Cobalt and Iridium have a purity of 99.95% and Gallium has a purity of 99.99%.
  • a particular embodiment comprises a step of realizing a pre-alloy of Culr, and of mixing:
  • graphite die is useful because graphite is a solid lubricant, and typically shows low friction among its surfaces and those of the melted metal typically allowing to obtain an easy extraction of the element contained therein without fractures and with the minimum amount of defects present on its surface.
  • a step of superheating of the mixture takes place, in which the mixture is heated up to a temperature of about 1250°C, and in any case to a temperature above 1200°C, in order to homogenize the chemical composition of the metal bath.
  • the value of pressure in the melting chamber again reaches a vacuum level lower than 1x10 -2 mbar, useful for eliminating part of the slag produced by the melting of pure elements.
  • the bars or castings are extracted from the bracket.
  • Gold alloy bars or castings are obtained from the graphite conduit and are subject to a rapid cooling by a step of water immersion, in order to reduce and possibly avoid phase variations.
  • the bars or castings are subject to a step of rapid cooling, preferably but not limited in water, in order to avoid phase changes at the solid state.
  • the Gold alloys according to the present disclosure can also be processed in a particularly effective manner to result with uniform surfaces, free from visible second phases or carbides. Therefore, the Gold alloys according to the present disclosure can be favorably used for high jewelry applications, and in particular for realizing high jewelry objects.
  • Non-limiting examples of jewelry objects realized at least partially by means of the Gold alloy herein described are: bracelets, watch bracelets, buckles, watch cases, watch hands, watch inner mechanisms, bracelet bezels, earrings, ornaments, rings, gemstone holders, ingots, in particular collector's ingots, collector's coins, necklaces, necklace closing elements, for earrings or for bracelets.
  • the Gold alloys according to the present disclosure can be applicable for objects which enter in direct contact with the human skin, and are at low allergy risk.

Abstract

L'invention concerne un alliage d'or pour des applications de bijouterie ou d'horlogerie, spécifiquement destiné à réaliser des objets de bijouterie ayant au moins des propriétés de recouvrance partielle de forme et/ou de taille après l'application d'une force de déformation, comprenant : - de l'or, entre 700 ‰ en poids et 800 ‰ en poids, - du cuivre, entre 25 ‰ en poids et 170 ‰ en poids, - du palladium, entre 50 ‰ en poids et 165 ‰ en poids, - du cobalt, entre 7 ‰ en poids et 40 ‰ en poids. L'alliage d'or est un alliage de couleur grise.
PCT/IB2024/050047 2023-01-04 2024-01-03 Alliage d'or ayant des propriétés de recouvrance après déformation WO2024147093A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT102023000000051 2023-01-04
CHCH000008/2023 2023-01-04

Publications (1)

Publication Number Publication Date
WO2024147093A1 true WO2024147093A1 (fr) 2024-07-11

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DARKENING et al. The study presents the results of investigation of the resistance to sulfur corrosion and of the mechanical properties of silver alloys without copper, of 925 fineness. As the alloy additions there were used elements which are able to create on the alloy surface an oxide layer as a protection against corrosion and which reduces the SFE of the alloy. The obtained silver alloys without copper, of 925 fineness, are characterized by high resistance to the action of sulfur corrosion and good mechanical properties.