CH711727A2 - Process for manufacturing a gold alloy wire - Google Patents

Abstract

Process for manufacturing a gold-alloy wire: an alloy comprising from 33.33% to 45.83% Au, from 3.64% to 12.44% by Zn and 18.46% at 45.02% Cu, 9.88% and 33.78% Ni, and from 0.0 to 5.0% of elements among Ir, In, Ti, Si, Ga, Re, continuously a bar diameter of 8.0 to 20.0 mm, said bar is laminated by limiting the deformation of the section to less than 20% per pass, preferably 13%, the cumulative deformation is measured with respect to the initial section, the rolling is stopped when the cumulative deformation reaches 60% to 75%, the annealing is carried out, the rolling is resumed and the rolling, measuring and annealing process is repeated until the desired section is reached; stretches the laminate to obtain a profiled wire of circular section.

Description

Description

Field of the Invention [0001] The present invention relates to a method of manufacturing an 8 to 11 carat gold alloy wire cast to an initial diameter of less than or equal to 20 mm to obtain a wire of one final diameter which is between the initial diameter cast and 0.1 mm.

The invention relates to the field of metallurgy alloys for watches and jewelery.

BACKGROUND OF THE INVENTION There are mainly two kinds of gray gold alloys on the market: alloys in which the gold bleaching metal is nickel, and those in which this metal is palladium. .

Although still used less, in jewelry, because of allergenic properties, nickel alloys can be used in watchmaking for parts that are never in contact with the skin. In addition, the low material cost of nickel compared to palladium makes them interesting alloys for these horological applications.

However, each of these gold alloys has disadvantages.

Indeed, although these alloys of nickel gold, have a very low chromaticity, which makes them very attractive for their relative whiteness, they can have only one mode of shaping, casting by lost wax, because in the annealed state they have a high hardness, typically greater than 260 Hv for an 18K gold alloy with 21% by weight of nickel. However, this hardness makes them little cold deformable and therefore not suitable for the working conditions of jewelers and manufacturers of watchmaking pieces, such as watch cases for hands, dial appliques, etc., the main users of these alloys. . In particular, it has been noted during tests with these nickel-gold alloys that they were sensitive to cracking during cold drawing operations and during heat treatment / quenching, during recrystallization annealing after deformation, especially as soon as the nickel content exceeded 5% by weight.

[0007] It will also be noted that alloys with a relatively low gold content, typically 9-carat alloys, are sensitive to cracking and stress corrosion, as described, for example, by B. Neumeyer in the publication entitled "A facile "Gold Screening," Gold Bulletin, Vol. 42 No. 32009, "Chemical screening method for the detection of stress corrosion cracking in 9 carat gold alloys".

Palladium gold alloys are expensive given the price of palladium, and the fact that it must be added in the alloy in substantial amount to obtain a whitening effect. Furthermore the hardness of palladium gold alloys typically 120 HV certainly allows satisfactory cold deformation but is however not sufficient to meet the requirements for the realization of watchmaking parts.

The rolling-milling of gold alloy son nickel is difficult: the multiplication of rolling passes produces undesirable metallurgical defects, and the malleability of the alloy decreases as the progress of the rolling. Unfortunately the recrystallization anneals carried out for the restoration of the properties homogenize the alloy, with hardening, by dissolving the nickel, unfavorable to the subsequent deformations. SUMMARY OF THE INVENTION [0010] Other elements such as cobalt, iron and silver can be added in an attempt to overcome the disadvantages of nickel and palladium, while participating in the whitening effect of alloys. gold. However, it was found that their amount in the alloy to achieve the color and ductility properties required in the field of watchmaking and jewelery, brought other disadvantages.

Typically, cobalt, which has properties similar to those of nickel, may be substituted at least partially for nickel, but this substitution increases very strongly most of the mechanical characteristics to the detriment of the ductility of the alloy.

The addition of iron after a few percent causes a ferromagnetic effect. This effect is apparent for palladium gold alloys such as nickel alloys. This effect may be detrimental for certain applications, particularly for use in the horological field in which the influence of an external magnetic field can disturb the chronometric performance of a watch movement.

The low-grade silver does not participate in a whitening effect, but since it is relatively neutral in the metallurgical properties of gold alloys, it can be used to make the balance to complete the composition of the title, with the disadvantage to bring beyond a few percent dulling of the alloy, and also to promote a demixtion with the ferrous elements: nickel, cobalt and iron, thus causing the ferromagnetic effect.

The market has already attempted to remedy the aforementioned problems by proposing a white gold or gray nickel alloy comprising, expressed by mass, between 37.5 and 37.7% of gold, of the order of 9% nickel, of the order of 2% of palladium, of the order of 9% of silver, of the order of 32% of Cu and of the order of 10% of zinc, the rest being formed of different elements for improving the properties of the alloy. This gray gold alloy has a good resistance to cracking under various conditions of mechanical stress, including fatigue and cold deformation, but its relative low nickel content makes it on the other hand a color with yellow reflections that does not allow him to meet the whiteness criteria required for use in jewelery or watchmaking.

Another alloy of white gold or nickel gray but free of palladium and silver has also been tested by the applicant. This alloy of white or gray nickel gold comprises, expressed by mass, between 37.5 and 37.7% of gold, of the order of 19% of nickel, of the order of 31% of Cu, of about 12% of zinc and about 0.5% of manganese, the rest being formed of different elements to improve the properties of the alloy. This gray gold alloy has a luster and a color meeting the criteria required for use in jewelery or watchmaking, but it however has a poor resistance to cracking under various stress conditions, especially during recrystallization heat treatments .

The present invention therefore aims to determine the conditions for obtaining gold alloy wire to substantially improve white or gray gold alloys by providing a gray gold alloy without cobalt, iron free , palladium-free, nickel-free, silver-free, palladium free without reducing its deformability properties and metallurgical properties, and developing a processing method for obtaining good quality small diameter wire metallurgical, homogeneous and without micro-cracks.

For this purpose, the invention relates to a method of manufacturing a gold alloy wire of 8 to 11 carats cast to an initial diameter less than or equal to 20 mm to obtain a wire of a final diameter, between the initial diameter cast and 0.1 mm, according to claim 1.

The development of the invention allows the selection of a cobalt-free gray gold alloy, without iron, without silver and without palladium and high nickel content, whose deformability allows its transformation by the technique of cold drawing without risk of cracking, and which is economical to achieve and easy to implement.

An advantage of the present invention is the production of a gold alloy wire having an interesting compromise between a color and a brightness of a whiteness sufficient to meet the aesthetic requirements of the field of watchmaking clothing and resistance to cracking during its forming by cold deformation.

Another advantage is the ease of polishing, and obtaining a great whiteness after polishing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0021] For this purpose, the present invention relates to a process for manufacturing an 8-11 carat gold alloy wire cast to an initial diameter of less than or equal to 20 mm to obtain a wire of a final diameter, between the initial diameter cast and 0.1 mm. This process comprises the following steps: an alloy composition comprising, in percentage by mass of the total:

Au between 33.33% to 45.84%,

Zn between 3.64% and 12.44%,

Cu between 18.46% and 45.02%,

Neither between 9.88% and 33.78%, and from 0.0 to 5.0% of at least one of Ir, In, Ti, Si, Ga, Re, and total element levels said alloy being limited to 100% by adaptation of the Cu content, casting of a bar in continuous casting, the section of which is inscribed in a diameter of 8.0 to 20.0 mm, is carried out; the notch obtained the raw bar of casting, preferably under a substantially rectangular section, preferably by turning the laminate obtained a quarter turn before each rolling pass, and limit the deformation of the section to a value less than or equal to at 20% per pass, the cumulative deformation on the laminate is measured with respect to the initial section of the raw bar, the rolling is stopped when the cumulative deformation of the section is between 60% and 75%, for anneal on a laminate of intermediate section between 600 and 650 ° C for 30 minutes under protectio n of reducing gas, preferably N2 + H2, - the rolling is resumed with the same parameters, the cumulative deformation on the laminate is measured with respect to this intermediate section, and the rolling is stopped when the cumulative deformation of the section, between the laminate section and the intermediate section, is between 60% and 75%, to anneal, and the rolling, measuring, and annealing process is repeated until the desired laminate section is reached, - Stretching the laminate to bring the section to a substantially circular profile and obtain a profiled wire.

More particularly, during rolling on the check mark, the deformation of the section is limited to a value of less than or equal to 13% per pass.

Preferably, the number of anneals is limited to three.

In a particular implementation, the number of stretching passes is limited to three.

In a particular implementation, it straighten the wire obtained by these stretching passes.

In a particular implementation, the profiled wire is cut to length after its complete elaboration.

In a particular implementation, it limits, within the alloy composition, as a percentage by mass of the total, the contents: Au between 33.33% to 45.84%, Zn between 4.48% and 12%. , 44%, Cu between 22.72% and 45.02%, Ni between 12.16% and 33.78%.

In another particular embodiment, it is limited, within the alloy composition, as a percentage by mass of the total, the contents:

Au between 37.50% and 37.70%,

Zn between 4.20% and 11.67%

Cu between 21.23% and 2.21%,

Neither between 11.36% and 31.67%.

In another still particular implementation, it limits, within the alloy composition, in percentage by mass of the total, the contents: - Au between 41.67% and 42.50%, - Zn between 3.86% and 10.89% - Cu between 19.59% and 39.39%, - Ni between 10.49% and 29.55%.

In another still particular implementation, it is limited, within the alloy composition, as a percentage by mass of the total, the contents:

Au between 33.33% to 45.84%,

Zn between 3.64% and 10.11%,

Cu between 18.46% and 36.58%,

Neither between 9.88% and 27.44%.

More particularly, is incorporated in the alloy composition, at least one of the elements Ir, Ti, Si, between 0.002% and 1,000% by mass percentage of the total.

More particularly, is incorporated in the alloy composition, Si, between 0.30% and 1.00% by weight percentage of the total.

More particularly, is incorporated within the alloy composition, Ti, between 20 and 500 ppm.

More particularly, it incorporates, within the alloy composition, Re, between 0.000% and 0.002% by weight percent of the total.

More particularly, it incorporates within the alloy composition, In between 1.00% and 4.00% by weight percentage of the total.

More particularly, said wire is made with a diameter greater than or equal to 0.1 mm.

More particularly, said wire is made with a diameter less than or equal to 20.0 mm.

In a preferred implementation, this wire is stamped to form a dial, or a dial applique, or a needle.

With an alloy meeting the above definition, a gray gold alloy is obtained which satisfies all the criteria required for alloys intended to be used in the watchmaking and jewelery fields, in particular with regard to its color and its brightness as well as its ability to be deformed cold without risk of cracking. To this is added a satisfactory resistance to corrosion. It should also be noted that the absence of palladium and silver makes it possible to obtain an economical alloy.

According to a particular embodiment, a neighbor of the invention, the gold alloy is a 7-carat alloy and comprises, expressed by mass, between 29 and 30% of gold, between 4.8 and 13%. of Zn, between 24.2 and 47% of Cu and between 13 and 35% of nickel, and possibly at most 5% of at least one of the elements selected from Ir, In, Ti, Si, Ga, Re.

According to one embodiment of the invention, the gold alloy is a 9-carat alloy and comprises between 37.5 and 38.5% of gold, between 4.2 and 11.5% of gold. Zn, between 21.5 and 41.5% Cu and between 11.5 and 31.2% nickel, and optionally at most 5% of at least one of the elements selected from Ir, In, Ti, Si, Ga , Re.

According to another embodiment of the invention, the gold alloy is a 10-carat alloy and comprises, expressed by mass, between 41.5 and 42.5% of gold, between 3.9. and 10.7% of Zn, between 19.9 and 38.8% of Cu and between 10.7 and 29.1% of nickel, and optionally at most 5% of at least one of the elements selected from Ir, In , Ti, Si, Ga, Re.

According to yet another embodiment of the invention, the alloy of gold is a 13-carat alloy and has a mass expression of between 54 and 55% between 3.1 and 8.4%. of Zn, between 15.7 and 30.4% Cu and between 8.4 and 22.8% nickel, and optionally at most 5% of at least one of the elements selected from Ir, In, Ti, Si, Ga, Re.

According to a variant of the embodiments above, the gold alloy comprises at least one of the elements Ir, Ti, Si, in a proportion for each element of between 0.002 and 1% by weight, and, when it comprises Si, the proportion of Si is preferably 0.3 to 1% by weight, and when it comprises Ti, the proportion of Ti is preferably 20 to 500 ppm, and when it comprises the proportion of Re is preferably 0.002% by weight, and when it comprises indium, the proportion of indium is preferably between 1 and 4% by weight.

The gold alloys according to the invention find a particular application for the realization of timepieces, jewelery or jewelry and in particular for the realization of dials, dial appliques and indicator hands for timepiece. In this application, this alloy makes it possible in particular to avoid the galvanic deposition of rhodium which is commonly used in the horological field to give the treated parts a brightness and a color of satisfactory whiteness.

To prepare the composition of gray gold alloy according to the invention is carried out as follows: The main elements used in the composition of the alloy have a purity of 999.9 per thousand and are deoxygenated. dice.

The elements of the composition of the alloy are placed in a crucible which is heated until the elements are melted.

The heating is carried out in a sealed induction furnace under partial pressure of nitrogen.

The molten alloy is poured into an ingot mold.

After solidification, the ingot is subjected to quenching with water.

The hardened ingot is then cold rolled and then annealed. The degree of hardening between each annealing is 66 to 80%, and preferably between 60 and 75%.

Each anneal lasts 20 to 30 minutes and is between 600 and 650 ° C under a reducing atmosphere composed of N2 and H2.

Cooling after annealing can be done by quenching with water.

The following examples were made in accordance with the conditions set forth in Table 1 below and all relate to gray gold alloys of 7 to 13 carats. The proportions indicated are expressed as a percentage by mass.

Table 1 [0056] _ No. Au. Pd. Ag. Cu. Or. Zn. Ti. Min. 0 37.57 2.00 9.00 31.83 9.30 10.30 0.00 0.00 1 37.70 0.00 0.00 30.80 19.00 12.00 0.00 0.50 2 37.70 0.00 0.00 31.27 19.00 12.00 0.03 0.00 3 37.70 0.00 0.00 40.30 15.00 7.00 0.00 0.00 4 37.60 0.00 0.00 38.40 17.00 7.00 0.00 0.00 5 37.60 0.00 0.00 36.40 19.00 0.00 0.00 6 29.15 0.00 0.00 41.33 21.57 7.95 0.00 0.00 7 54.20 0.00 0.00 26.70 14.00 5.10 0.00 0.00 8 41.70 0.00 0.00 34.00 17.75 6.55 0.00 0.00 [0057] The alloy No 0 is an alloy of the prior art which does not is not enough white for lack of nickel and alloys No 1 and 2 made and tested by the plaintiff crack during heat treatments recrystallization.

Different compositions of the invention, namely alloys Nos. 3 to 8, have been developed and tested in deformation to meet the triple stress of brightness, whiteness and deformation capacity required for alloys intended to be used in watchmaking and jewelery and have responded satisfactorily.

Different properties of the alloys according to Examples No 0 to No 8 of Table 1 are given in Table 2 below. Table 2 gives in particular the indications relating to the hardness of the alloy in the cast state. annealed and hardened

Claims (17)

as well as the color measured in a three-axis coordinate system. This three-dimensional measuring system called CIELab, CIE being the acronym of the International Commission for Lighting and Lab the three coordinate axes, the L axis measuring the white-black component (black = 0, white = 100), the 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 ), (see IS07724 standard issued by the International Commission on Illumination). Table 2 [0060] _ No. L. a *. * b. Hv poured Hv annealed Hv harden Enclosure% 0 87.66 0.72 9.16 165 180 300 75 1 85.14 -0.04 5.27 150 180 290 70 2 85.34 0.04 5.84 140 180 290 70 3 86.05 1.05 7.01 130 170 280 70 4 85.66 0.58 6.05 135 170 295 70 5 86.08 0.54 5.64 180 195 295 70 [0061] It can be seen from Table 2 that the alloy No 0 of the prior art has a strong component b * which gives it a yellowish appearance which is not acceptable for a watch application whereas the alloys of Invention No. 3 to No. 5 have a substantially lower b * component rendering the yellowish component of the color of the alloy imperceptible to the naked eye. Alloys No. 1 and 2 meet the aesthetic criteria in terms of color but are not allowed to deform mechanically cold without cracking. claims 1. A process for producing an 8-11 carat gold alloy wire cast to an initial diameter less than or equal to 20 mm to obtain a wire of a final diameter, between the initial cast diameter and 0.1 mm, characterized in that: - an alloy composition comprising, in percentage by mass of the total: Au between 33.33% to 45.84%, Zn between 3.64% and 12.44%, Cu between 18, 46% and 45.02%, Ni between 9.88% and 33.78%, and 0.0 to 5.0% of at least one of the elements selected from Ir, In, Ti, Si, Ga, Re , and the total content of the elements of said alloy being limited to 100% by adaptation of the Cu content, the casting of a bar is carried out in continuous casting, the section of which is inscribed in a diameter of 8.0 to 20 μm. 0 mm; said cast bar is rolled under a substantially rectangular section by rotating the laminate obtained by a quarter of a turn before each rolling pass, and the deformation of the section is limited to a value less than or equal to 20 % per pass, - the cumulative deformation on the laminate is measured with respect to the initial section of said raw bar casting, - the rolling is stopped when the cumulative deformation of the section is between 60% and 75%, to perform a annealing on a laminate of intermediate section, at a temperature between 600 ° C and 650 ° C, for a period of 20 to 30 minutes, under a reducing atmosphere composed of N2 and H2, said annealing being followed by cooling under gas or at the water; - The rolling is taken again with the same parameters, the cumulative deformation is measured on the laminate with respect to said intermediate section, and the rolling is stopped when the cumulative deformation of the section, between the section of the laminate and said intermediate section, is included between 60% and 75%, for annealing, and the rolling, measuring, and annealing process is repeated until the desired laminate section is reached, - stretches the laminate to bring the section back to a profile substantially circular and obtain a profiled wire. 2. Method according to claim 1, characterized in that, during the rolling on the check mark, the deformation of the section is limited to a value less than or equal to 13% per pass. 3. Method according to claim 1 or 2, characterized in that limit to three the number of said annealed. 4. Method according to one of claims 1 to 3, characterized in that limits to three the number of stretching passes. 5. Method according to one of claims 1 to 4, characterized in that straightening said wire obtained by said stretching passes. 6. Method according to one of claims 1 to 5, characterized in that cutting said profiled wire to length after its complete elaboration. 7. Method according to one of claims 1 to 6, characterized in that limit, within said alloy composition, as a percentage by mass of the total, the contents: Au between 33.33% to 45.84 %, Zn between 4.48% and 12.44%, Cu between 22.72% and 45.02%, Ni between 12.16% and 33.78%, 8. Method according to one of claims 1 to 6, characterized in that limit, within said alloy composition, as a percentage by mass of the total, the contents: - Au between 37.50% and 37, 70%, - Zn between 4.20% and 11.67% -Cu between 21.23% and 2.21%, - Ni between 11.36% and 31.67%. 9. Process according to one of claims 1 to 6, characterized in that, within said alloy composition, in percentage by mass of the total, the contents: - Au between 41.67% and 42, 50%, - Zn between 3.86% and 10.89% - Cu between 19.59% and 39.39%, - Ni between 10.49% and 29.55%. 10. Method according to one of claims 1 to 6, characterized in that limit, within said alloy composition, as a percentage by mass of the total, the contents: Au between 33.33% to 45.84 %, Zn between 3.64% and 10.11%, Cu between 18.46% and 36.58%, Ni between 9.88% and 27.44%. 11. Method according to one of claims 1 to 10, characterized in that incorporates, within said alloy composition, at least one of the elements Ir, Ti, Si, between 0.002% and 1.000% in percentage. mass of the total. 12. Method according to one of claims 1 to 10, characterized in that incorporates, within said alloy composition, Si between 0.30% and 1.00% by weight percentage of the total. 13. Method according to one of claims 1 to 10, characterized in that incorporates, within said alloy composition, Ti, between 20 and 500 ppm. 14. Method according to one of claims 1 to 10, characterized in that incorporates, within said alloy composition, Re, between 0.000% and 0.002% by weight percentage of the total. 15. Method according to one of claims 1 to 10, characterized in that incorporates within said alloy composition, In between 1.00% and 4.00% by weight percentage of the total. 16. Method according to one of claims 1 to 15, characterized in that said wire is made with a diameter greater than or equal to 0.1 mm. 17. Method according to one of claims 1 to 16, characterized in that said wire is transformed by stamping to form a dial, or a dial applique, or a needle.