Platinum alloy

Abstract

A nickel-free and cobalt-free platinum alloy including, expressed by weight, from 95.0% to 96.0% of Pt, from 0.5% to 4.5% of Ir, from 0.01% to 2% of Au, from 0 to 2% of Ge, and from 0 to 1% of at least one of the alloying elements Ru, Rh, Pd, Sn, Ga, Re, the respective percentages of all of the elements of the alloy adding up to 100%.

Claims

1. A nickel-free and cobalt-free platinum alloy, comprising, expressed by weight, the following elements: 95.0% to 96.0% of Pt, 2.2% to 4.4% of Ir 0.01% to 0.8% of Au 0.01% to 1.5% of Ge 0 to 1% of at least one of the alloying elements Ru, Rh, Pd, Sn, Ga, Re, the respective percentages of all of the elements of the alloy adding up to 100%.

2. The platinum alloy according to claim 1, comprising, expressed by weight, from 95.0% to 96.0% of Pt, from 2.9% to 4.3% of Ir, from 0.05% to 0.6% of Au, from 0.01% to 1% of Ge, and from 0 to 1% of at least one of the alloying elements Ru, Rh, Pd, Sn, Ga, Re, the respective percentages of all of the elements of the alloy adding up to 100%.

3. The platinum alloy according to claim 1, comprising, expressed by weight, from 95.0% to 96.0% of Pt, from 3.5% to 4.2% of Ir, from 0.05% to 0.6% of Au, from 0.06% to 0.5% of Ge, and from 0 to 1% of at least one of the alloying elements Ru, Rh, Pd, Sn, Ga, Re, the respective percentages of all of the elements of the alloy adding up to 100%.

4. A timepiece or piece of jewellery comprising at least one component made from Nickel-free and cobalt-free platinum alloy, comprising, expressed by weight, the following elements: 95.0% to 96.0% of Pt, 0.5% to 4.5% of Ir 0.01% to 0.8% of Au 0.01 to 2% of Ge 0 to 1% of at least one of the alloying elements Ru, Rh, Pd, Sn, Ga, Re, the respective percentages of all of the elements of the alloy adding up to 100%.

5. The timepiece or piece of jewellery according to claim 4, wherein the at least one component is selected from the group consisting of a watch case, a dial, a bracelet or watch strap, a bracelet or watch strap clasp or buckle, a crown, an index, an applique, a hand, a jewel and an accessory.

6. A method of making a timepiece or piece of jewellery comprising applying the platinum alloy of claim 1 in the timepiece or piece of jewellery.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(1) The alloy of the present invention is a nickel-free and cobalt-free platinum alloy at the grade of 95%.

(2) According to the invention, the platinum alloy comprises, expressed by weight, from 95.0% to 96.0% of Pt, from 0.5% to 4.5% of Ir, from 0.01% to 2% of Au, from 0 to 2% of Ge, and from 0 to 1% of at least one of the alloying elements Ru, Rh, Pd, Sn, Ga, Re, the respective percentages of all of the elements of the alloy adding up to 100%.

(3) According to a first variant, the platinum alloy comprises, expressed by weight, from 95.0% to 96.0% of Pt, from 2.2% to 4.4% of Ir, from 0.01% to 0.8% of Au, from 0.01% to 1.5% of Ge, and from 0 to 1% of at least one of the alloying elements Ru, Rh, Pd, Sn, Ga, Re, the respective percentages of all of the elements of the alloy adding up to 100%.

(4) According to a second variant, the platinum alloy comprises, expressed by weight, from 95.0% to 96.0% of Pt, from 2.9% to 4.3% of Ir, from 0.05% to 0.6% of Au, from 0.01% to 1% of Ge, and from 0 to 1% of at least one of the alloying elements Ru, Rh, Pd, Sn, Ga, Re, the respective percentages of all of the elements of the alloy adding up to 100%.

(5) According to a third variant, the platinum alloy comprises, expressed by weight, from 95.0% to 96.0% of Pt, from 3.5% to 4.2% of Ir, from 0.05% to 0.6% of Au, from 0.06% to 0.5% of Ge, and from 0 to 1% of at least one of the alloying elements Ru, Rh, Pd, Sn, Ga, Re, the respective percentages of all of the elements of the alloy adding up to 100%.

(6) The alloying elements, such as Ru, Rh and Ga may be used for improving the hardness, Sn makes it possible to lower the melting temperature, Re and Pd have the same behaviour as the platinum elements.

(7) The platinum alloys according to the invention find a particular application for the production of a timepiece or piece of jewellery. In this application, this alloy makes it possible in particular to have a brilliant colour and also sufficient hardness for being machined, cast, crimped and polished.

(8) In order to prepare the platinum alloy according to the invention, the following processes are carried out:

(9) The main elements incorporated into the composition of the alloy have a purity of between 999 and 999.9 per thousand and are deoxidized.

(10) The elements of the composition of the alloy are placed in a crucible that is heated until the elements melt.

(11) The heating is carried out in an airtight induction furnace under partial pressure of nitrogen.

(12) The molten alloy is cast in an ingot mould.

(13) After solidification, the ingot is subjected to water quenching.

(14) Next the quenched ingot is cold-rolled and then annealed. The degree of work hardening between each annealing is from 66% to 80%.

(15) Each annealing lasts 20 to 30 minutes and is carried out between 900 C. and 1100 C. under a reducing atmosphere composed of N.sub.2 and H.sub.2.

(16) The cooling after the annealing operations is carried out by water quenching.

(17) The examples which follow were carried out in accordance with the conditions disclosed in Table 2 below and all relate to 95% platinum alloys or to commercial platinum alloy references. The proportions indicated are expressed as percentages by weight.

(18) TABLE-US-00002 TABLE 2 Table of the compositions of the alloys tested. Pt Ir Au Ge 1 (comp) 80 20 2 (comp) 85 15 3 (comp) 90 10 4 (comp) 95 5 5 (inv) 95.3 3.5 1 0.2 6 (inv) 95.3 4 0.5 0.2 7 (inv) 95.3 4.5 0.01 0.19 8 (inv) 95.3 4.2 0.01 0.49 9 (inv) 95.3 3.7 0.01 0.99

(19) The various properties of the alloys obtained according to Examples no. 1 to no. 9 from Table 2 will be found in Table 3 below.

(20) Table 3 in particular gives information relating to the Vickers hardness of the alloy in the annealed condition, and also to the colour measured in a three-axis coordinate system.

(21) This three-dimensional measurement system referred to as CIELab, CIE being the acronym of the International Commission on Illumination in French and Lab being the three coordinate axes, the L axis measuring the white-black component (black=0; white=100), the a axis measuring the red-green component (red=positive values +a; green=negative values a) and the b axis measuring the yellow-blue component (yellow=positive values +b; blue=negative values b). (cf. standard ISO 7724 established by the International Commission on Illumination).

(22) The colorimetric values are measured with a MINOLTA CM 3610 d machine under the following conditions:

(23) Illuminant: D65

(24) Tilt: 10

(25) Measurement: SCI+SCE (specular component included+excluded)

(26) UV: 100%

(27) Measurement focal length: 4 mm

(28) Calibration: black body and white body

(29) TABLE-US-00003 TABLE 3 Table of the colours and hardness of the alloys tested. L a* b* HV 1 (comp) 88.4 0.6 3.4 242 2 (comp) 88.4 0.6 3.7 172 3 (comp) 87.6 0.6 4.0 130 4 (comp) 88.1 0.7 4.0 76 5 (inv) 87.6 0.7 4.2 145 6 (inv) 87.8 0.7 4.1 149 7 (inv) 87.5 0.7 4.3 145 8 (inv) 87.9 0.7 4 200 9 (inv) 87.7 0.7 4.1 210

(30) Alloys no. 1 to no. 3 are commercial PtIr binary alloys which have the drawback of having no internationally recognised legal grade.

(31) Alloy no. 4 is the Pt950Ir50 alloy which has the drawback of having too low a hardness to be used in the watchmaking field.

(32) Alloys no. 5 to no. 9 of the invention were produced and tested in deformation in order to meet the double constraint of brilliance/whiteness and of deformability required for alloys intended to be used in the watchmaking and jewellery field, i.e. for having chromatic values such that L87, a*0.7 and b*4.3, and also a hardness of between 140 Hv and 220 Hv, and preferably between 140 Hv and 160 Hv.

(33) The alloys of the comparative examples do not make it possible to meet this double constraint.