Grey gold alloy

Abstract

A grey gold alloy which is nickel-free, cobalt-free, iron-free, silver-free, copper-free, zirconium-free, niobium-free, chromium-free and manganese-free, including, expressed in weight percent, from 75.0 to 76.5% of Au, from 15 to 23% of Pd, from 0.5 to 5% of Rh, from 0 to 7% of Pt, and from 0 to 5% of at least one of the alloying elements Ir, Ru, Ti, In, Ga, B and Re, the respective percentages of all the alloying elements adding up to 100%.

Claims

1. A grey gold alloy, consisting of, expressed in weight percent: 75.0 to 76.5% of Au; 15 to 23% of Pd: 0.5 to 5% of Rh: 0 to 7% of Pt; and 0 to 5% of Ir, 0 to 5% of Ru, less than 0.05% Ti, less than 4% in, less than 2% Ga, less than 0.03% B, and less than 0.002% Re, the respective percentages of all the elements of the alloy adding up to 100%, wherein the grey gold alloy is cold rolled and then annealed, and wherein the grey gold alloy has a hardness from 140 HV to 225 HV.

2. The alloy of claim 1, wherein the Pt is present in at least 0.5%.

3. The alloy of claim 1, wherein the Pd is in a range of from 17 to 22.5%, wherein the Rh is in a range of from 0.5 to 4%, and wherein the Pt, if present, is no more than 6%.

4. The alloy of claim 3, wherein the Pt is present in at least 0.5%.

5. The alloy of claim 1, wherein the Pd is in a range of from 18 to 22.5%, wherein the Rh is in a range of from 1.5 to 3%, wherein the Pt, if present, is no more than 4%, wherein the Ir, if present, is no more than 4%, and wherein the Ru, if present, is no more than 4%.

6. The alloy of claim 5, wherein the Pt is present in at least 1%.

7. The alloy of claim 1, wherein the Pd is in a range of from 19 to 22%, the Rh is in a range of from 1.5 to 3%, the Pt, if present, is no more than 4.5%, the Ir, if present, is no more than 4.5%, and the Ru, if present, is no more than 4.5%.

8. The alloy of claim 7, wherein the Pt is present in at least 1%.

9. The alloy of claim 1, wherein the Pd is in a range of from 19 to 21.5%, the Rh is in a range of from 1.5 to 3%, the Pt, if present, is no more than 4%, the Ir, if present, is no more than 4%, and the Ru, if present, is no more than 4%.

10. The alloy of claim 1, wherein the Ir is present in a range of from 0.002 to 1%, and/or the Ti is present in a range of from 0.002 to 1%.

11. The alloy of claim 1, wherein the Ti is present in a range of from 20 to 500 ppm.

12. The alloy of claim 1, wherein theft is present in a range of from 0.01 to 1%.

13. The alloy of claim 1, wherein the In is present in a range of from 1 to 4%.

14. A timepiece or piece of jewelry, comprising a component made of the alloy of claim 1.

15. The timepiece or piece of jewelry of claim 14, wherein the component is a watch case, a dial, a wristband, a bracelet, a bracelet clasp, a jewel, or an accessory.

16. The alloy of claim 1, having a hardness from 140 HV to 180 HV, and having color values L≥80, a* <1.5, and b*<5.

17. The alloy of claim 1, having color values L≥0.5, a*<1.2, and b*<5.

18. A grey gold alloy, comprising, expressed in weight percent; 75.0 to 76.5% of Au; 15 to 23% of Pd: 0.5 to 5% of Rh: 0 to 7% of Pt; and no more than 1% of Ir, no more than 1% of Ru, no more than 0.05% of Ti, no more than 4% of In, no more than 2% of Ga, no more than 1% of B, no more than 1% of Re, the respective percentages of all the elements of the alloy adding up to 100%, wherein the alloy has color values L≥80.5, a*<1.2, and b*<5, and wherein the alloy has an annealed Vickers hardness in a range of from 140 to 211.

19. The alloy of claim 18, comprising at least 1.99% of the Pt, wherein the annealed Vickers hardness is no more than 175, and wherein the alloy is free of Ni, Co, Fe, Ag, Cu, Zr, Nb, Cr, and Mn.

20. A grey gold alloy, consisting of, expressed in weight percent: 75.0 to 76.5% of Au; 15 to 23% of Pd; 0.5 to 5% of Rh; 0 to 7% of Pt; and no more than 1% of Ir, no more than 1% of Ru, no more than 0.05% of Ti, no more than 4% of In, no more than 2% of Ga, no more than 1% of B, no more than 1% of Re, the respective percentages of all the elements of the alloy adding up to 100%, wherein the alloy has color values 80.5≤L≤81.1, 1.1≤a*≤1.2, and 4.6≤b*≤5.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(1) The alloy of the present invention is a grey gold alloy which is nickel-free, cobalt-free, iron-free, silver-free, copper-free, manganese-free, zirconium-free, chromium-free and niobium-free.

(2) According to a first embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 15 to 23% of Pd, from 0.5 to 5% of Rh, from 0 to 7% of Pt, and from 0 to 5% of at least one of the alloying elements Ir, Ru, Ti, In, Ga, B and Re, the respective percentages of all the alloying elements adding up to 100%. If present, the percentage of platinum is comprised between 0.5 and 7%.

(3) According to a second embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 17 to 22.5% of Pd, from 0.5 to 4% of Rh, from 0 to 6% of Pt, and from 0 to 5% of at least one of the alloying elements Ir, Ru, Ti, In, Ga, B and Re, the respective percentages of all the alloying elements adding up to 100%. If present, the percentage of platinum is comprised between 0.5 and 6%.

(4) According to a third embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 18 to 22.5% of Pd, from 1.5 to 3% of Rh, from 0 to 4% of Pt, and from 0 to 4% of at least one of the alloying elements Ir, Ru, Ti, In, Ga, B and Re, the respective percentages of all the alloying elements adding up to 100%. If present, the percentage of platinum is comprised between 1 and 4%.

(5) According to a fourth embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 19 to 22% of Pd, from 1.5 to 3% of Rh, from 0 to 4.5% of Pt, and from 0 to 4.5% of at least one of the alloying elements Ir, Ru, Ti, In, Ga, B and Re, the respective percentages of all the alloying elements adding up to 100%. If present, the percentage of platinum is comprised between 1 and 4.5%.

(6) According to a fifth embodiment, the gold alloy is an 18 carat alloy and comprises, expressed in weight percent, from 75.0 to 76.5% of Au, from 19 to 21.5% of Pd, from 1.5 to 3% of Rh, from 0 to 4% of Pt, and from 0 to 4% of at least one of the alloying elements Ir, Ru, Ti, In, Ga, B and Re, the respective percentages of all the alloying elements adding up to 100%. If present, the percentage of platinum is comprised between 1 and 4%.

(7) According to a variant of the above embodiments, the gold alloy comprises at least one of the elements Ir, Ti, in a proportion of each element comprised between 0.002 and 1% by weight.

(8) In a variant where the alloy comprises Ir, the proportion of Ir is preferably comprised between 0.01 and 1% by weight.

(9) In a variant where the alloy comprises Ti, the proportion of Ti is preferably comprised between 20 and 500 ppm.

(10) In a variant wherein the alloy comprises Re, the proportion of Re is preferably comprised between 0.002 and 1% by weight, and preferably close to 0.002% by weight.

(11) In a variant where the alloy comprises In, the proportion of indium is preferably comprised between 1 and 4% by weight.

(12) In a variant where the alloy comprises Ga, the proportion of Ga is preferably comprised between 0.2 and 2% by weight.

(13) In a variant where the alloy comprises B, the proportion of B is preferably comprised between 0.002 and 1% by weight, and more preferably comprised between 0.005 and 0.03% by weight.

(14) In a variant where the alloy comprises Ru, the proportion of Ru is preferably comprised between 0.002 and 1% by weight, and more preferably comprised between 0.008 and 0.015% by weight.

(15) The gold alloys of the invention find particular application in the production of timepieces or pieces of jewelry. In this application, the alloy avoids the need for rhodium plating which is commonly used in the fields of watchmaking and jewelry to give sufficiently white colour and brightness to the parts treated.

(16) To prepare the grey gold alloy according to the invention, the procedure is as follows:

(17) The main elements involved in the composition of the alloy have a purity of between 999 and 999.9 per thousand and are deoxidised.

(18) The elements of the alloy composition are placed in a crucible and heated until the elements melt.

(19) The heating is performed in a sealed induction furnace under a nitrogen partial pressure.

(20) The melted alloy is then poured into an ingot mould.

(21) After solidifying, the ingot is water hardened.

(22) The hardened ingot is then cold rolled and then annealed. The rate of strain hardening between each annealing is from 66 to 80%.

(23) Each annealing operation lasts between 20 to 30 minutes and occurs at 900° C. in a reducing atmosphere comprising N.sub.2 and H.sub.2.

(24) Cooling between each annealing is accomplished by water quenching.

(25) The following examples have been produced in accordance with the conditions set out in Table 1 above and all relate to 18 carat grey gold alloys or to colour references of alloys available on the market. The proportions indicated are expressed in percentage by weight.

(26) TABLE-US-00001 TABLE 1 N.sup.o Au. Pd. Pt. Rh. Ag. Ga. Fe. B. Cu. Ru. Ir. Cr. Mn. Zr. Nb. In. Ti.  1 (comp.) 75.1 24.9  2 (comp.) 75.1 7 3 14.9  3 (comp.) 75.1 19 1.9 2 2  4 (comp.) 75.1 15 6 3.9  5 (comp.) 75.1 21 0.5 3.4  6 (comp.) 75.5 15 9 0.5  7 (comp.) 75.5 14 5 0.5 5  8 (inv.) 76 16 7 1  9 (comp.) 75 24 1 0.01 10 (inv.) 75 23 2 0.01 11 (comp.) 75 23 2 0.01 12 (comp.) 76.5 7.5 15 1 0.01 13 (inv.) 75.1 20.9 2 2 0.01 14 (inv.) 75.1 22.9 2 0.01 15 (comp.) 75.1 20.9 4 16 (inv.) 75.1 17.9 5 2 0.01 17 (inv.) 75.1 21.9 3 0.01 18 (inv.) 75.1 18.9 3 3 0.01 19 (inv.) 75.1 18.3 5 1.6 0.01 20 (inv.) 75.1 21.3 2 1.6 0.01 21 (inv.) 75.5 20.5 1.99 2 0.01 0.01 22 (comp.) 100

(27) Table 2 below sets out various properties of alloys obtained in examples No 1 to No 22 of Table 1.

(28) Table 2 provides, in particular, indications relating to the Vickers hardness of the alloy in the annealed state, and to the colour measured in a three-axis coordinate system.

(29) This three-dimensional measuring system known as CIELab, CIE being the acronym for the International Commission on Illumination and Lab the axes of the three coordinates; the L axis measures the white-black component (black=0; white=100), the a axis measures the red-green component (red=positive values+a; green=negative values −a), and the b axis measures the yellow-blue component (yellow=positive values+b; blue=negative values −b). (cf. ISO 7724 standard established by the International Commission on Illumination).

(30) The colorimetric values are measured with a MINOLTA CM 3610 d apparatus in the following conditions: Illuminant: D65 Tilt: 10° Measurement: SCI+SCE (specular component included+excluded) UV: 100% Focal length: 4 mm Calibration: black body and white body

(31) TABLE-US-00002 TABLE 2 No L a* b* HV  1 (comp.) 80.4 1.2 4.4 117  2 (comp.) 80.9 0.3 2.6 370  3 (comp.) 81.2 1.0 3.9 276  4 (comp.) 82.6 1.5 6.6 122  5 (comp.) 80.3 1.4 5.3 114  6 (comp.) 80.6 1.2 5.0 122  7 (comp.) 80.7 1.4 5.7 128  8 (inv.) 80.7 1.2 5.0 169  9 (comp.) 80.0 1.3 5.1 129 10 (inv.) 80.6 1.2 4.8 147 11 (comp.) 79.9 1.2 5.1 75 12 (comp.) 80.6 1.4 6.2 130 13 (inv.) 80.6 1.2 4.6 149 14 (inv.) 80.3 1.2 4.7 174 15 (comp.) 79.8 1.2 4.6 103 16 (inv.) 81.0 1.1 4.6 175 17 (inv.) 80.8 1.2 4.6 211 18 (inv.) 80.9 1.2 4.6 202 19 (inv.) 81.1 1.2 4.6 147 20 (inv.) 80.7 1.2 4.7 162 21 (inv.) 80.5 1.2 4.6 147 22 (comp.) 90.2 1.0 2.1 —

(32) Alloy No 1 is the binary 18 carat Au—Pd alloy.

(33) Alloys No 2 and No 3 are prior art alloys and have the drawback of excessive hardness.

(34) Alloy No 4 (18 carat gold with 15% Pd) and No 5 (18 carat gold with 21% Pd) are market benchmarks.

(35) Alloy No 22 is the colorimetric reference of rhodium plating.

(36) The 18 carat grey gold alloys of the invention were developed and tested in deformation to meet the dual constraint of brightness/whiteness and capacity for deformation required for alloys intended to be used in the fields of watchmaking and jewelry, namely to have colour values such that L≥80, a*<1.5 et b*<5, and a Vickers hardness comprised between 140 HV and 225 HV, and preferably comprised between 140 HV and 180 HV.

(37) The alloys of the comparative examples do not meet this dual constraint.