EP3165622A1 - Method 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% Zn, from 18.46% to 45.02% Cu, from 9.88% % and 33.78% of Ni, and 0.0 to 5.0% of elements among Ir, In, Ti, Si, Ga, Re,
a bar is continuously cast, with a diameter of 8.0 to 20.0 mm,
the said bar is rolled by limiting the deformation of the section to less than 20% per pass, preferably 13%,
the accumulated deformation is measured with respect to the initial section,
the yarn rolling is stopped when the cumulative deformation reaches 60% to 75%, an annealing is carried out,
the yarn rolling is resumed and the yarn rolling, measuring and annealing process is repeated until the desired section is reached,
the intermediate product is stretched to obtain a profiled wire of circular section.

Description

Field of the invention

The present invention relates to a process for producing 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 a final diameter which is between the diameter initial cast and 0.1 mm.

The invention relates to the field of alloy metallurgy for watchmaking and jewelery.

Background of the invention

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

Although still less used, in jewelry, because of allergenic properties, nickel alloys can still 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.

Each of these gold alloys, however, 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, lost wax casting, 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.

It should also be noted that alloys with a relatively low gold content, typically 9-carat alloys, are susceptible to stress cracking and corrosion as described, for example, by B. Neumeyer in the publication entitled "A easy chemical screening method for the detection of stress corrosion cracking in 9 carat gold alloys", Gold Bulletin, volume 42 No. 3 2009 . This document discloses in particular, page 75, Table 1, a 10 carat gold alloy, comprising 10.3 to 20% of Ni, 25.2 to 41.6% of Cu, and 4.3 to 13.1% of Zn, which is usable as a yarn or as a sheet, and a production process of which comprises several rolling steps, and annealing under an atmosphere of N ₂ and H ₂ at 800 ° C,

Palladium gold alloys are expensive given the price of palladium, and because it must be added to the alloy in substantial amounts to achieve 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 elaboration by rolling of nickel alloy gold wire is difficult: the multiplication of the rolling passes produces undesirable metallurgical defects, thus the malleability of the alloy decreases as the rolling progresses. 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.

Brief description of the drawings

Other features and advantages of the invention will appear on reading the detailed description which follows, with reference to the accompanying drawings, wherein the single figure shows, in logic diagram form, the steps of the method according to the invention.

Summary of the invention

Other elements such as cobalt, iron and silver can be added to try to overcome the disadvantages of nickel and palladium, while participating in the whitening effect of gold alloys. 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 close to those of nickel, may be substituted at least partially for nickel, but this substitution greatly increases 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 of bringing beyond a few percent the tarnishing 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 nickel-white 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% silver, of the order of 32% of Cu and of the order of 10% of zinc, the rest being formed of different elements intended for improve 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 or gray nickel gold 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 color that meets the criteria required for use in jewelery or watchmaking, but it has a poor resistance to cracking under various conditions. 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, without iron, without silver and palladium-free and high-nickel-free to remove palladium without reducing its deformability properties and metallurgical properties, and developing a transformation process to obtain small diameter wire of good metallurgical quality, homogeneous and without micro-cracks.

For this purpose, the invention relates to a process for producing 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 initial diameter cast and 0.1 mm, according to claim 1.

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

An advantage of the present invention is the obtaining 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 and the 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

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

This process uses the so-called wire-rolling technology, which is in fact a stretching, where the material is forced to pass successively through passages of increasingly smaller sections, in the form of notches or more conventionally in the form of dies.

• (10) on effectue une composition d'alliage comportant, en pourcentage en masse du total:
  • Au entre 33,33% à 45,84%,
  • Zn entre 3,64% et 12,44%,
  • Cu entre 18,46% et 45,02%,
  • Ni entre 9,88% et 33,78 %,
  • et de 0,0 à 5,0% d'au moins un des éléments choisi parmi Ir, In, Ti, Si, Ga, Re,
  • et le total des teneurs des éléments dudit alliage étant limité à 100% par adaptation de la teneur en Cu,
• (11) on effectue la coulée d'une barre en coulée continue, dont la section est inscrite dans un diamètre de 8,0 à 20,0 mm,
• (12) on lamine au fil la barre obtenue brute de coulée, de préférence sous une section sensiblement rectangulaire, de préférence en tournant le produit intermédiaire obtenu d'un quart de tour avant chaque passe de laminage, et on limite la déformation de la section à une valeur inférieure ou égale à 20% par passe,
• (13) on mesure la déformation cumulée sur le produit intermédiaire par rapport à la section initiale de la barre brute de coulée,
• (14) on cesse le laminage au fil quand la déformation cumulée de la section est comprise entre 60% et 75%, pour effectuer un recuit sur un produit intermédiaire de section intermédiaire entre 600 et 650 °C durant 30 minutes sous protection de gaz réducteur, de préférence N2+H2,
• (15) on reprend le laminage au fil avec les mêmes paramètres, on mesure la déformation cumulée sur le produit intermédiaire par rapport à cette section intermédiaire, et on cesse le laminage quand la déformation cumulée de la section, entre la section du produit intermédiaire et la section intermédiaire, est comprise entre 60% et 75%, pour effectuer un recuit, et on réitère le processus de laminage au fil, de mesure, et de recuit jusqu'à l'atteinte de la section de produit intermédiaire souhaitée,
• (16) on étire le produit intermédiaire pour ramener la section à un profil sensiblement circulaire et obtenir un fil profilé.

This process comprises the following steps:

• (10) an alloy composition comprising, as a 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 0.0 to 5.0% of at least one of Ir, In, Ti, Si, Ga, Re,
  • and the total contents of the elements of said alloy being limited to 100% by adaptation of the Cu content,
• (11) casting of a bar in continuous casting, whose section is inscribed in a diameter of 8.0 to 20.0 mm,
• (12) the obtained raw bar of casting is rolled over, preferably under a substantially rectangular section, preferably by rotating the intermediate product obtained a quarter of a turn before each rolling pass, and the deformation of the section is limited at a value less than or equal to 20% per pass,
• (13) measuring the cumulative deformation on the intermediate product with respect to the initial section of the raw bar,
• (14) the yarn rolling is stopped when the cumulative deformation of the section is between 60% and 75%, to anneal an intermediate product of intermediate section between 600 and 650 ° C for 30 minutes under protection of reducing gas preferably N2 + H2,
• (15) the yarn rolling is repeated with the same parameters, the accumulated deformation on the intermediate product is measured with respect to this intermediate section, and the rolling is stopped when the cumulative deformation of the section, between the section of the intermediate product and the intermediate section is between 60% and 75% for annealing, and the yarn rolling, measuring, and annealing process is repeated until the desired intermediate product section is reached,
• (16) stretching the intermediate product to bring the section to a substantially circular profile and obtain a profiled wire.

More particularly, during wire rolling, 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, the wire obtained by these stretching passes is straightened.

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

• Au entre 33,33% à 45,84%,
• Zn entre 4.48% et 12,44%,
• Cu entre 22.72% et 45,02%,
• Ni entre 12,16% et 33,78 %.

In a particular embodiment, it is limited, within the alloy composition, in 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%,
• Neither between 12.16% and 33.78%.

• Au entre 37,50% et 37,70%,
• Zn entre 4,20% et 11,67%
• Cu entre 21,23% et 42,21%
• Ni entre 11,36% et 31,67%.

In another particular embodiment, it is limited, within the alloy composition, in 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 42.21%
• Neither between 11.36% and 31.67%.

• Au entre 41,67% et 42,50%,
• Zn entre 3,86% et 10,89%
• Cu entre 19,59% et 39,39%,
• Ni entre 10,49% et 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 41.67% and 42.50%,
• Zn between 3.86% and 10.89%
• Cu between 19.59% and 39.39%,
• Neither between 10.49% and 29.55%.

• Au entre 33,33% à 45,84%,
• Zn entre 3,64% et 10,11%,
• Cu entre 18,46% et 36,58%,
• Ni entre 9,88% et 27,44 %,

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

More particularly, within the alloy composition, there is incorporated into the If, between 0.30% and 1.00% as a percentage by mass of the total.

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

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

More particularly, within the alloy composition, In is incorporated between 1.00% and 4.00% by weight percent 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 embodiment, this wire is converted by stamping to form a dial, or a dial applique, or a needle.

With an alloy as defined above, a gray gold alloy is obtained which satisfies all the criteria required for alloys intended to be used in the watch and jewelery fields, in particular with regard to its color and its brilliance. that 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, 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 % Cu and between 13 and 35% nickel, and optionally 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 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 possibly at most 5% of at least one of the elements selected from Ir, In, Ti, If, Ga, Re.

According to yet another variant, the gold alloy is a 13 carat alloy and comprises in mass, between Au 54 and 55%, between 3.1 and 8.4% of Zn, between 15.7 and 30.4% of Cu and between 8.4 and 22.8% of 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 If, 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 Re, the proportion Re is preferably 0.002% by weight, and when it comprises indium, the proportion of indium is preferably 1 to 4% by weight.

The gold alloys according to the invention find particular application for the production of timepieces, jewelery or jewelery and in particular for the production of dials, dial appliques and indicator needles for coin watchmaking. 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.

• Les principaux éléments entrant dans la composition de l'alliage ont une pureté de 999.9 pour mille et sont désoxydés.

In order to prepare the gray gold alloy composition according to the invention, the procedure is as follows:

• The main elements in the composition of the alloy have a purity of 999.9 per thousand and are deoxidized.

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 cast in an ingot mold.

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

The hardened ingot is then cold rolled and 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 N ₂ and H ₂ .

Cooling after annealing can be done by quenching with water.

The following examples have been made in accordance with the conditions set forth in Table 1 below and all relate to gray gold alloys. from 7 to 13 carats. The proportions indicated are expressed as a percentage by mass. This table 1 is separated into two parts: alloys strictly according to the invention, and variants. Table 1: Alloys according to the invention No. At. Pd. Ag. Cu. Or. Zn. Ti. Min. 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 7.00 0.00 0.00 8 41.70 0.00 0.00 34.00 17.75 6.55 0.00 0.00 No. At. 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 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 2 37.70 0.00 0.00 31.27 19.00 12.00 0.03 0.00

Alloy No. 0 is an alloy of the prior art which is not white enough for lack of nickel and No. 1 and 2 alloys made and tested by the plaintiff crack during thermal recrystallization treatments.

Various 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, annealed and hardened state. 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 (positive values = red + a; green = -a negative values) and the axis b measuring the yellow-blue component (yellow = positive values + b, blue = negative values -b). (see ISO7724 standard issued by the International Commission on Illumination). Table 2 No. L. at*. * b. Hv poured Hv annealing Hv hardened Esq.% 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

It can be seen from Table 2 that alloy No. 0 of the prior art has a strong component b * which gives it an unacceptable yellowish appearance for a watchmaking application while the alloys of the invention No. 3 to No. 5 have a component b * significantly lower making 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 (17)

A process for producing 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 a final diameter, between the initial cast diameter and 0.1 mm, characterized in what : - (10) 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 0.0 to 5.0% of at least one of Ir, In, Ti, Si, Ga, Re, and the total contents of the elements of said alloy being limited to 100% by adaptation of the Cu content, - (11) the casting of a bar in continuous casting, whose section is inscribed in a diameter of 8.0 to 20.0 mm; - (12) said yarn bar is rolled under a substantially rectangular section, rotating the intermediate product obtained a quarter turn before each rolling pass to the wire, and the deformation of the section is limited to a value less than or equal to 20% per pass, (13) measuring the cumulative deformation on the intermediate product with respect to the initial section of said raw bar, - (14) the yarn rolling is stopped when the cumulative deformation of the section is between 60% and 75%, to anneal an intermediate intermediate product at a temperature between 600 ° C and 650 ° C for a period of 20 to 30 minutes, under a reducing atmosphere composed of N ₂ and H ₂ , said annealing being followed by cooling under gas or with water; - (15) the yarn rolling is repeated with the same parameters, the accumulated deformation on the intermediate product is measured with respect to said intermediate section, and the yarn rolling is stopped when the cumulative deformation of the section, between the section of the intermediate product and said intermediate section, is between 60% and 75%, to anneal, and the yarn rolling, measuring, and annealing process is repeated until the desired intermediate product section is reached , - (16) the intermediate product is stretched to bring the section back to a profile substantially circular and obtain a profiled wire. Method according to claim 1, characterized in that , during wire rolling, the deformation of the section is limited to a value of less than or equal to 13% per pass. Process according to Claim 1 or 2, characterized in that the number of said anneals is limited to three. Method according to one of Claims 1 to 3, characterized in that the number of stretching passes is limited to three. Process according to one of Claims 1 to 4, characterized in that said wire obtained by said drawing passes is straightened. Method according to one of claims 1 to 5, characterized in that said profiled wire is cut to length after its complete elaboration. Process according to one of claims 1 to 6, characterized in that , within said alloy composition, the percentage content by weight 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%, Neither between 12.16% and 33.78%, Process according to one of claims 1 to 6, characterized in that , within said alloy composition, the percentage content by weight of the total, the contents: - between 37.50% and 37.70%, - Zn between 4.20% and 11.67% - Cu between 21.23% and 42.21% - Neither between 11.36% and 31.67%. Process according to one of claims 1 to 6, characterized in that , within said alloy composition, the percentage content by weight of the total, the contents: - between 37.5 and 38.5% of gold, Zn between 4.2 and 11.5%, - Cu between 21.5 and 41.5%, - Ni between 11.5 and 31.2% of nickel. Process according to one of Claims 1 to 6, characterized in that in said alloy composition, as a percentage by mass of the total, the contents: - between 41.67% and 42.50%, Zn between 3.86% and 10.89% Cu between 19.59% and 39.39%, - Neither between 10.49% and 29.55%. Process according to one of claims 1 to 6, characterized in that , within said alloy composition, the percentage content by weight 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%, Process according to one of Claims 1 to 11, characterized in that at least one of the elements Ir, Ti and Si is incorporated in said alloy composition between 0.002% and 1.000% by weight percentage of the total. Process according to one of Claims 1 to 11, characterized in that within the said alloy composition, Si is incorporated between 0.30% and 1.00% by weight percentage of the total. Process according to one of Claims 1 to 11, characterized in that Ti, between 20 and 500 ppm, is incorporated into said alloy composition. Process according to one of Claims 1 to 11, characterized in that within the said alloy composition Re is included between 0.000% and 0.002% by weight percentage of the total. Process according to one of claims 1 to 11, characterized in that within the said alloy composition, In is incorporated between 1.00% and 4.00% by weight percentage of the total. Method according to one of claims 1 to 16, characterized in that said wire is converted by stamping to form a dial, or a dial applique, or a needle.

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