Timepiece or piece of jewellery or gemstone jewellery made of gold

Abstract

A zinc-free gold alloy containing by weight between 37% and 38.5% of gold, between 4 and 32% of palladium and/or silver, between 25% and 54% of copper and between 0% and 10% of gallium. A timepiece or piece of jewellery or gemstone jewellery made of this alloy.

Claims

1. A zinc-free gold alloy containing by weight between 37.5% and 38.5% of gold; palladium and/or silver in a total percentage comprised between 4% and 32%, between 39% and 54% of copper and between 0% and 10% of gallium.

2. The gold alloy according to claim 1, wherein said alloy contains by weight between 37.5% and 38.5% of gold; palladium and/or silver in a total percentage comprised between 5% and 26%, between 39% and 53% of copper and between 0% and 8.5% of gallium.

3. The gold alloy according to claim 1, wherein said alloy contains by weight between 37.5% and 38.5% of gold; palladium and/or silver in a total percentage comprised between 6% and 19.5%, between 39% and 52% of copper and between 2% and 7% of gallium.

4. The gold alloy according to claim 1, wherein said alloy contains by weight between 37.5% and 38.5% of gold; palladium and/or silver in a total percentage comprised between 7% and 17%, between 41% and 52% of copper and between 7% and 6% of gallium.

5. The gold alloy according to claim 1, wherein said alloy contains by weight between 37.5% and 38.5% of gold; palladium and/or silver in a total percentage comprised between 7% and 14.5%, between 44% and 51% of copper and between 2% and 6% of gallium.

6. The gold alloy according to claim 1, wherein said alloy contains by weight between 37.5% and 38.5% of gold, between 0 and 5% of palladium, between 4 and 27% of silver, between 39% and 54% of copper and between 0% and 10% of gallium.

7. The gold alloy according to claim 1, wherein said alloy contains by weight between 37.5% and 38.5% of gold, between 0% and 5% of palladium, between 4% and 12% of silver, between 45% and 51% of copper and between 3% and 5% of gallium.

8. The gold alloy according to claim 7, wherein said alloy contains 2 wt. % of palladium.

9. The gold alloy according to claim 1, wherein said alloy contains by weight a maximum of 0.05% of an element selected from among iridium, rhenium and ruthenium.

10. The gold alloy according to claim 1, wherein said alloy is free of nickel, cobalt, iron and manganese.

11. The gold alloy according to claim 1, wherein in the CIELAB colour lab space said alloy has an a* value comprised between 1 and 8 and a b* value comprised between 12 and 18.

12. The gold alloy according to claim 1, wherein in the CIELAB colour lab space said alloy has an a* value comprised between 5.5 and 7.5 and a b* value comprised between 14 and 16.

13. The gold alloy according to claim 1, wherein said alloy has a hardness HV1 comprised between 125 and 180.

14. A timepiece or piece of jewellery or gemstone jewellery made of a Zinc-free gold alloy containing by weight between 37.5% and 38.5% of gold; palladium and/or silver in a total percentage comprised between 4% and 32%, between 39% and 54% of copper and between 0% and 10% of gallium.

Description

DESCRIPTION OF THE INVENTION

(1) The present invention relates to a zinc-free gold alloy more particularly intended for application in the field of horology or jewellery or gemstone jewellery. It thus also concerns the timepieces or pieces of jewellery or gemstone jewellery made of this alloy. ‘Timepieces’ is used to mean both external components, such as a case, a dial, a dial applique, a bracelet, etc. and movement components, such as a plate, a bar or a balance.

(2) The gold alloy according to the invention contains by weight between 37.5% and 38.5% of gold, silver and/or of palladium with a total of these two elements comprised between 4 and 32%, between 25.0% and 54.0% of copper and between 0 and 10% of gallium. It has the peculiarity of being zinc-free. It is also nickel-free, cobalt-free, iron-free and manganese-free.

(3) Advantageously, the gold alloy contains between 5 and 26 wt. % of silver and/or palladium.

(4) Preferably, the gold alloy contains between 6 wt. % and 19.5 wt. % of silver and/or palladium.

(5) More preferably, the gold alloy contains between 7 wt. % and 17 wt. % of silver and/or palladium.

(6) In a particularly preferred manner, the gold alloy contains between 7 wt. % and 14.5 wt. % of silver and/or palladium.

(7) Further, the gold alloy contains between 0 and 0.05 wt. % (inclusive) of an element selected from among iridium, rhenium and ruthenium and advantageously the alloy contains 0.0025 wt. % of iridium.

(8) To prepare the gold alloy, the various elements of the composition are melted before being cast. The casting ingot is then deformed with a work hardening rate higher than or equal to 75% in several passes with intermediate annealing treatments performed at a temperature of 650° C. for 30 minutes. After cooling, the blanks are dimensioned, for example by machining.

(9) The alloys obtained after deformation and annealing have in the CIELAB colour space (in accordance with the following standards: CIE No. 15, ISO 7724/1, DIN 5033-7, ASTM E-1164) an a* value comprised between 1 and 8, preferably between 5.5 and 7.5, and a b* value comprised between 12 and 18, preferably between 14 and 16.

(10) They have a hardness comprised between 125 and 180 HV1, preferably between 130 and 180 HV1. They have an electrochemical potential greater than or equal to 0.52 volts, the latter being obtained by adding together the electrochemical potential of each element of the alloy multiplied by its atomic concentration.

(11) Table 1 shows the composition by ‰ weight of the following alloys available on the market: No. 843, No. 844 and No. 859 containing zinc, and two laboratory alloys No. 846 and No. 848 containing zinc, these five alloys being comparative examples. Zinc-free alloys Nos. 849-852, 854-858 and 860 are 9 carat gold alloys according to the invention. The measured colorimetric values, the measured hardnesses (HV1) and the calculated electrochemical potentials are also set out in Table 1. The colorimetric L*a*b* values were measured with a KONICA MINOLTA CM-2600d spectrophotometer with a D65 illuminant and an angle of observation of 10°.

(12) TABLE-US-00001 TABLE 1 Compositions [‰.sub.weight] Hardness E.sub.0 Colorimetry (D65, 10°) Cu. Zn. Ga. Pd. Ag. Au. [HV1] [Volts] L* a* b* 843 Comparison 423.5 109.0 92.0 375.5 113 0.407 91.5 0.7 20.3 844 376.0 114.0 134.0 376.0 133 0.418 91.9 −0.2   20.0 846 293.0 40.0 291.0 376.0 170 0.621 92.1 2.2 15.8 848 346.8 77.2 200.0 376.0 179 0.508 92.0 0.9 17.8 859 573.0 24.0 27.0 376.0 * 0.504 * * * 849 Invention 311.0 22.0 291.0 376.0 153 0.661 91.9 2.4 14.3 851 384.0 40.0 200.0 376.0 162 0.584 90.8 2.6 16.1 852 311.0 22.0 20.0 271.0 376.0 170 0.665 90.5 3.0 13.0 854 384.0 40.0 20.0 180.0 376.0 171 0.588 89.8 3.3 14.7 855 450.0 40.0 20.0 114.0 376.0 152 0.552 88.6 4.9 15.2 856 500.0 40.0 20.0 64.0 376.0 131 0.526 87.1 6.7 15.0 857 425.0 40.0 20.0 139.0 376.0 164 0.565 87.1 5.7 16.6 858 400.0 40.0 20.0 164.0 376.0 163 0.579 87.3 5.2 16.4 860 500.0 40.0 84.0 376.0 * 0.523 * * * * not measured

(13) These calculations and tests clearly show that the alloys according to the invention have good corrosion resistance (electrochemical potential above 0.52 volts), as well as hardness in the annealed state that easily allows the deformation thereof (between 130 and 175 HV). They all have an a* value within the range of 2-7 and a b* value in the range of 13-18. In particular, alloy 856 has a 4N shade according to standard ISO 8654: 2019.