HK1237379B - Method for fabrication of a gold alloy wire - Google Patents
Method for fabrication of a gold alloy wire Download PDFInfo
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- HK1237379B HK1237379B HK17111377.1A HK17111377A HK1237379B HK 1237379 B HK1237379 B HK 1237379B HK 17111377 A HK17111377 A HK 17111377A HK 1237379 B HK1237379 B HK 1237379B
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Description
Field of the Invention
The present invention relates to a method for producing cast 8 to 11 carat gold alloy wire having an initial diameter less than or equal to 20 mm to obtain a wire with a final diameter between the initial cast diameter and 0.1 mm.
The present invention relates to the field of metallurgy of alloys for use in the watchmaking and jewellery industries.
Background of the Invention
There are two main types of gray gold alloys on the market: alloys where the whitening metal of gold is nickel, and alloys where this metal is palladium.
Although less commonly used in jewelry due to their allergenic properties, nickel alloys are still used in watchmaking for parts that never come into contact with the skin. Furthermore, the low material cost of nickel compared to palladium makes such alloys advantageous for these watchmaking applications.
However, each of these gold alloys has disadvantages.
Indeed, despite the fact that these gold-nickel alloys exhibit extremely low chroma (which makes them very attractive due to their relative whiteness), they are suitable for only one forming mode—lost wax casting—because in the annealed state, they possess a high hardness, typically exceeding 260 HV for an 18-karat gold alloy containing 21% nickel by mass. This hardness means that they are difficult to cold-work and are therefore unsuitable for the working conditions of jewelers and manufacturers of external watch parts such as watch cases, hands, dial appliques, etc., who are the main users of these alloys. In particular, during the testing of these gold-nickel alloys, it was noted that they are prone to cracking during the cold drawing operation and during the heat/hardening treatment, as well as during the recrystallization annealing after deformation, especially when the nickel content exceeds 5% by mass.
It is also noted that alloys with a relatively low gold content, typically 9-karat gold alloys, are susceptible to cracking corrosion under stress, as described, for example, by B. Neumeyer in the publication entitled "A facile chemical screening method for the detection of stress corrosion cracking in 9-carat gold alloys", Gold Bulletin, Vol. 42, No. 3, 2009. This document discloses, in particular, in Table 1 on page 75, a 10-karat gold alloy, which can be used in the form of wire or sheet, containing 10.3 to 20% Ni, 25.2 to 41.6% Cu and 4.3 to 13.1% Zn, and having a production process comprising several rolling steps and annealing at 800° C. in an N 2 and H 2 atmosphere.
Palladium-gold alloys are expensive due to the price of palladium and the fact that considerable amounts must be added to the alloy to obtain the whitening effect. Furthermore, although the hardness of palladium-gold alloys (typically 120 HV) does allow satisfactory cold working, it is insufficient to meet the requirements necessary for the manufacture of external watch parts.
Nickel-gold alloys are difficult to manufacture by rolling: multiple rolling passes create undesirable metallurgical defects, so the alloy's forgeability decreases as the rolling process progresses. Unfortunately, recrystallization annealing, performed to restore properties, homogenizes the alloy with accompanying hardening through solution treatment of nickel, which is detrimental to subsequent deformation.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will become apparent upon reading the following detailed description with reference to the accompanying drawings, wherein the sole FIGURE 1 is a block diagram illustrating the steps of the method of the present invention.
SUMMARY OF THE INVENTION
In an attempt to overcome the disadvantages of nickel and palladium and to contribute to the whitening effect of the gold alloy, other elements such as cobalt, iron and silver may be added. However, it has been found that the amounts required in the alloy to achieve the color and ductility properties required in the watchmaking and jewelry sectors bring other disadvantages.
Typically, cobalt, which has properties close to those of nickel, can at least partially replace nickel, but this substitution greatly increases most mechanical characteristics to the detriment of the alloy's ductility.
The addition of iron in excess of a few percentage points results in a ferromagnetic effect. This effect occurs in both palladium-gold and nickel-gold alloys. This effect can be detrimental to some applications, particularly in the watchmaking industry, where the effects of external magnetic fields can interfere with the timekeeping performance of a timepiece.
Low silver content does not contribute to the whitening effect, but since it is relatively neutral in the metallurgical properties of gold alloys, it can act as a balance to complete the fineness composition. The disadvantage is that when it exceeds a few percentage points, it causes the alloy to lose its luster and promotes separation from the iron-based elements nickel, cobalt and iron, thereby causing a ferromagnetic effect.
The market has attempted to address this problem by proposing a white or grey nickel-gold alloy comprising 37.5 to 37.7% gold, approximately 9% nickel, approximately 2% palladium, approximately 9% silver, approximately 32% copper, and approximately 10% zinc by mass, with the remainder consisting of various elements intended to improve the alloy's properties. This grey gold alloy has good resistance to cracking under various mechanical stress conditions, particularly fatigue and cold working, but its relatively low nickel content means it has a yellowish tint, meaning it does not meet the whiteness standards required for use in the jewellery or watchmaking industries.
The applicant has also tested another white or gray gold alloy that includes nickel but lacks palladium and silver. This white or gray nickel-gold alloy contains 37.5 to 37.7% gold, approximately 19% nickel, approximately 31% copper, approximately 12% zinc, and approximately 0.5% manganese by mass, with the remainder consisting of various elements intended to improve the alloy's properties. The brightness and color of this gray gold alloy meet the standards required for use in jewelry or watchmaking, but it exhibits poor cracking resistance under various stress conditions, particularly during recrystallization heat treatment.
One object of the present invention is therefore to identify conditions for obtaining gold alloy wires which allow to substantially improve white or grey gold alloys by providing a grey gold alloy which is cobalt-free, iron-free, silver-free and palladium-free and has a high nickel content, making it possible to exclude palladium without reducing the deformability or the metallurgical properties of the alloy, and by developing a conversion process for obtaining small-diameter wires of good metallurgical quality which are homogeneous and free of microcracks.
To this end, the present invention relates to a method for producing cast 8 to 11 karat gold alloy wire having an initial diameter less than or equal to 20 mm, according to claim 1, to obtain a wire having a final diameter between the initial cast diameter and 0.1 mm.
The development of the present invention allows the selection of a cobalt-free, iron-free, silver-free and palladium-free grey gold alloy with a high nickel content, whose deformability allows deformation by cold drawing techniques without risk of cracking and which is economical and easy to manufacture.
One advantage of the present invention is that a gold alloy wire is obtained that offers a favourable compromise between colour and brightness, sufficient whiteness to meet the aesthetic requirements of the field of external timepiece components, and resistance to cracking during forming by cold working.
Another advantage is the ease of polishing and the high whiteness achieved after polishing.
Detailed description of preferred embodiments
To this end, the present invention relates to a method for producing cast 8 to 11 karat gold alloy wire having an initial diameter less than or equal to 20 mm to obtain a wire with a final diameter between the initial cast diameter and 0.1 mm.
This method utilizes the so-called wire rolling technique, which is actually a drawing technique in which the material is forced successively through a channel of decreasing cross-section in the form of a die.
This method includes the following steps:
-(10) preparing an alloy composition comprising, by mass %,
Au: 33.33% to 45.84%,
Zn: 3.64% to 12.44%,
Cu: 18.46% to 45.02%,
Ni: 9.88% to 33.78%,
and 0.0 to 5.0% of at least one element selected from Ir, In, Ti, Si, Ga, Re,
The total element content of the alloy is limited to 100% by adjusting the Cu content.
(11) the production of cast bars by continuous casting, the cross-section of which is inscribed within a diameter of 8.0 to 20.0 mm,
(12) rolling said as-cast bar, preferably in a substantially rectangular cross-section, preferably by rotating the intermediate product obtained through a quarter-turn before each rolling pass and limiting the cross-sectional deformation to a value less than or equal to 20% per pass,
- (13) measuring the cumulative deformation of the intermediate product compared to the initial cross-section of the rod in the as-cast state,
- (14) stopping the wire rolling when the cumulative cross-sectional deformation is 60% to 75% to anneal the intermediate product with an intermediate cross-section between 600 and 650° C. for 30 minutes in a reducing gas atmosphere, preferably N 2 +H 2 ,
(15) restarting the wire rolling with the same parameters, measuring the cumulative deformation of the intermediate product compared to the intermediate cross section, and stopping the rolling when the cumulative cross-sectional deformation between the cross section of the intermediate product and the intermediate cross section is 60% to 75% for annealing, and repeating the wire rolling, measuring and annealing process until the desired intermediate product cross section is reached,
- (16) Drawing the intermediate product so that the cross section returns to a substantially circular profile and section wire is obtained.
More particularly, during the wire rod rolling process, the cross-sectional deformation is limited to a value less than or equal to 13% per pass.
The number of annealing steps is preferably limited to three.
In one particular embodiment, the number of draw passes is limited to three.
In a particular embodiment, the filaments obtained by said drawing passes are reshaped.
In a particular embodiment, the profiled wire is cut to length upon completion of manufacture.
In a particular embodiment, within the alloy composition, the mass percentage content is limited to:
Au: 33.33% to 45.84%,
Zn: 4.48% to 12.44%,
Cu: 22.72% to 45.02%,
Ni: 12.16% to 33.78%,
In another specific embodiment, within the alloy composition, the mass percentage content is limited to:
-Au: 37.50% to 37.70%,
-Zn: 4.20% to 11.67%,
-Cu: 21.23% to 42.21%
-Ni: 11.36% to 31.67%.
In yet another specific embodiment, within the alloy composition, the mass percentage content is limited to:
-Au: 41.67% to 42.50%,
-Zn: 3.86% to 10.89%,
-Cu: 19.59% to 39.39%,
-Ni: 10.49% to 29.55%.
In yet another specific embodiment, within the alloy composition, the mass percentage content is limited to:
Au: 33.33% to 45.84%,
Zn: 3.64% to 10.11%,
Cu: 18.46% to 36.58%,
Ni: 9.88% to 27.44%.
More particularly, 0.002 to 1.000 mass % of at least one element Ir, Ti, Si is incorporated into the alloy composition.
More specifically, 0.30 to 1.00 mass % of Si is incorporated into the alloy composition.
More particularly, 20 to 500 ppm of Ti is incorporated into the alloy composition.
More specifically, 0.000 to 0.002 mass % Re is incorporated into the alloy composition.
More specifically, 1.00 to 4.00 mass% of In is incorporated into the alloy composition.
More particularly, the filaments are produced with a diameter greater than or equal to 0.1 mm.
More particularly, the wire is manufactured with a diameter less than or equal to 20.0 mm.
In a preferred embodiment, this wire is deformed by stamping to form a dial or dial appliqué or hands.
By using an alloy that meets the above definition, a grey gold alloy is obtained that meets all the criteria required for an alloy intended for use in the watchmaking and jewellery sectors (particularly in terms of colour and brightness and the ability to be cold worked without risk of cracking). This is combined with satisfactory corrosion resistance. 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-karat alloy and comprises, in mass%, 29 to 30% gold, 4.8 to 13% Zn, 24.2 to 47% Cu and 13 to 35% nickel and possibly up to 5% of at least one element chosen from Ir, In, Ti, Si, Ga, Re.
According to a particular embodiment, the gold alloy is a 9-karat alloy and comprises 37.5 to 38.5% gold, 4.2 to 11.5% Zn, 21.5 to 41.5% Cu and 11.5 to 31.2% nickel and possibly up to 5% of at least one element chosen from Ir, In, Ti, Si, Ga, Re.
According to another embodiment, the gold alloy is a 10 karat alloy and comprises, in mass %, 41.5 to 42.5% gold, 3.9 to 10.7% Zn, 19.9 to 38.8% Cu and 10.7 to 29.1% nickel and possibly up to 5% of at least one element chosen from Ir, In, Ti, Si, Ga, Re.
According to yet another embodiment, the gold alloy is a 13-karat alloy and comprises, in mass %, 54 to 55% Au, 3.1 to 8.4% Zn, 15.7 to 30.4% Cu and 8.4 to 22.8% nickel and possibly up to 5% of at least one element chosen from Ir, In, Ti, Si, Ga, Re.
According to a variant of the above embodiment, the gold alloy includes at least one element Ir, Ti, Si, the proportion of each element being 0.002 to 1 mass%, and when the alloy includes Si, the proportion of Si is preferably 0.3 to 1 mass%, and when it includes Ti, the proportion of Ti is preferably 20 to 500 ppm, and when it includes Re, the proportion of Re is preferably 0.002 mass%, and when it includes indium, the proportion of indium is preferably 1 to 4 mass%.
The gold alloy of the present invention is particularly useful for making parts for watches or jewellery, and in particular for making dials, dial appliques and hands for watches. In this application, the alloy avoids the need for rhodium plating, which is commonly used in the watchmaking field, to provide a satisfactory white colour and brightness to the treated parts.
To prepare the gray gold alloy composition of the present invention, the procedure is as follows:
The major elements involved in the alloy composition have a purity of 999.9 parts per thousand and are deoxidized.
The elements of the alloy composition are placed in a crucible and heated until the elements are melted.
Heating was performed in a sealed induction furnace under nitrogen partial pressure.
The molten alloy is then poured into an ingot mould.
After solidification, the ingot is water hardened.
The hardened ingot is then cold rolled and then annealed. The work harden rate between anneals is 66 to 80%, preferably 60 to 75%.
Each annealing lasted 20 to 30 minutes and was performed at 650°C in a reducing atmosphere containing N2 and H2 .
Cooling after annealing can be achieved by water quenching.
The following examples were made according to the conditions listed in Table 1 below and all relate to 7 to 13 karat grey gold alloys. The proportions indicated are expressed in mass %. Table 1 is divided into two parts: alloys strictly according to the invention, and other variants.
Table 1: Alloys of the present invention
| No. | Au. | Pd. | Ag. | Cu. | Ni. | Zn. | Ti. | Mn. |
| 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 |
Table 1: Other variants
| No. | Au. | Pd. | Ag. | Cu. | Ni. | Zn. | Ti. | Mn. |
| 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 a prior art alloy which is not white enough due to the absence of nickel, and alloys Nos. 1 and 2 made and tested by the applicant cracked during the recrystallization heat treatment.
The different compositions of the present invention, namely alloys No. 3 to 8, were developed and subjected to deformation tests to meet the requirements of brightness, whiteness and deformability required for alloys intended for use in the watchmaking and jewellery sectors and were found to be satisfactory.
Table 2 below lists various properties of the alloys in Examples No. 0 to No. 8 of Table 1. Table 2 specifically provides information on the hardness of the alloys in the cast, annealed, and drawn states, and on the color measured in a three-axis coordinate system. This three-dimensional measurement system is called CIELab, where CIE is the acronym for the International Commission on Illumination and LAB is the axis 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 value +a; green = negative value -a), and the b axis measures the yellow-blue component (yellow = positive value +b; blue = negative value -b). (See ISO 7724, an international standard established by the International Commission on Illumination.)
Table 2
As is clear from Table 2, prior art alloy No. 0 has a strong b* component, which gives it a yellowish appearance that is unacceptable for watchmaking applications, while alloys Nos. 3 to 5 according to the invention have a significantly lower b* component, so that the yellow component of the color of the alloys is not noticeable to the human eye. Alloys Nos. 1 and 2 meet the aesthetic criteria with regard to color, but cannot be cold-mechanically deformed without cracking.
Field of the Invention
The present invention relates to a method for producing cast 8 to 11 carat gold alloy wire having an initial diameter less than or equal to 20 mm to obtain a wire with a final diameter between the initial cast diameter and 0.1 mm.
The present invention relates to the field of metallurgy of alloys for use in the watchmaking and jewellery industries.
Background of the Invention
There are two main types of gray gold alloys on the market: alloys where the whitening metal of gold is nickel, and alloys where this metal is palladium.
Although less commonly used in jewelry due to their allergenic properties, nickel alloys are still used in watchmaking for parts that never come into contact with the skin. Furthermore, the low material cost of nickel compared to palladium makes such alloys advantageous for these watchmaking applications.
However, each of these gold alloys has disadvantages.
Indeed, despite the fact that these gold-nickel alloys exhibit extremely low chroma (which makes them very attractive due to their relative whiteness), they are suitable for only one forming mode—lost wax casting—because in the annealed state, they possess a high hardness, typically exceeding 260 HV for an 18-karat gold alloy containing 21% nickel by mass. This hardness means that they are difficult to cold-work and are therefore unsuitable for the working conditions of jewelers and manufacturers of external watch parts such as watch cases, hands, dial appliques, etc., who are the main users of these alloys. In particular, during the testing of these gold-nickel alloys, it was noted that they are prone to cracking during the cold drawing operation and during the heat/hardening treatment, as well as during the recrystallization annealing after deformation, especially when the nickel content exceeds 5% by mass.
It is also noted that alloys with a relatively low gold content, typically 9-karat gold alloys, are susceptible to cracking corrosion under stress, as described, for example, by B. Neumeyer in the publication entitled "A facile chemical screening method for the detection of stress corrosion cracking in 9-carat gold alloys", Gold Bulletin, Vol. 42, No. 3, 2009. This document discloses, in particular, in Table 1 on page 75, a 10-karat gold alloy, which can be used in the form of wire or sheet, containing 10.3 to 20% Ni, 25.2 to 41.6% Cu and 4.3 to 13.1% Zn, and having a production process comprising several rolling steps and annealing at 800° C. in an N 2 and H 2 atmosphere.
Palladium-gold alloys are expensive due to the price of palladium and the fact that considerable amounts must be added to the alloy to obtain the whitening effect. Furthermore, although the hardness of palladium-gold alloys (typically 120 HV) does allow satisfactory cold working, it is insufficient to meet the requirements necessary for the manufacture of external watch parts.
Nickel-gold alloys are difficult to manufacture by rolling: multiple rolling passes create undesirable metallurgical defects, so the alloy's forgeability decreases as the rolling process progresses. Unfortunately, recrystallization annealing, performed to restore properties, homogenizes the alloy with accompanying hardening through solution treatment of nickel, which is detrimental to subsequent deformation.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will become apparent upon reading the following detailed description with reference to the accompanying drawings, wherein the sole FIGURE 1 is a block diagram illustrating the steps of the method of the present invention.
SUMMARY OF THE INVENTION
In an attempt to overcome the disadvantages of nickel and palladium and to contribute to the whitening effect of the gold alloy, other elements such as cobalt, iron and silver may be added. However, it has been found that the amounts required in the alloy to achieve the color and ductility properties required in the watchmaking and jewelry sectors bring other disadvantages.
Typically, cobalt, which has properties close to those of nickel, can at least partially replace nickel, but this substitution greatly increases most mechanical characteristics to the detriment of the alloy's ductility.
The addition of iron in excess of a few percentage points results in a ferromagnetic effect. This effect occurs in both palladium-gold and nickel-gold alloys. This effect can be detrimental to some applications, particularly in the watchmaking industry, where the effects of external magnetic fields can interfere with the timekeeping performance of a timepiece.
Low silver content does not contribute to the whitening effect, but since it is relatively neutral in the metallurgical properties of gold alloys, it can act as a balance to complete the fineness composition. The disadvantage is that when it exceeds a few percentage points, it causes the alloy to lose its luster and promotes separation from the iron-based elements nickel, cobalt and iron, thereby causing a ferromagnetic effect.
The market has attempted to address this problem by proposing a white or grey nickel-gold alloy comprising 37.5 to 37.7% gold, approximately 9% nickel, approximately 2% palladium, approximately 9% silver, approximately 32% copper, and approximately 10% zinc by mass, with the remainder consisting of various elements intended to improve the alloy's properties. This grey gold alloy has good resistance to cracking under various mechanical stress conditions, particularly fatigue and cold working, but its relatively low nickel content means it has a yellowish tint, meaning it does not meet the whiteness standards required for use in the jewellery or watchmaking industries.
The applicant has also tested another white or gray gold alloy that includes nickel but lacks palladium and silver. This white or gray nickel-gold alloy contains 37.5 to 37.7% gold, approximately 19% nickel, approximately 31% copper, approximately 12% zinc, and approximately 0.5% manganese by mass, with the remainder consisting of various elements intended to improve the alloy's properties. The brightness and color of this gray gold alloy meet the standards required for use in jewelry or watchmaking, but it exhibits poor cracking resistance under various stress conditions, particularly during recrystallization heat treatment.
One object of the present invention is therefore to identify conditions for obtaining gold alloy wires which allow to substantially improve white or grey gold alloys by providing a grey gold alloy which is cobalt-free, iron-free, silver-free and palladium-free and has a high nickel content, making it possible to exclude palladium without reducing the deformability or the metallurgical properties of the alloy, and by developing a conversion process for obtaining small-diameter wires of good metallurgical quality which are homogeneous and free of microcracks.
To this end, the present invention relates to a method for producing cast 8 to 11 karat gold alloy wire having an initial diameter less than or equal to 20 mm, according to claim 1, to obtain a wire having a final diameter between the initial cast diameter and 0.1 mm.
The development of the present invention allows the selection of a cobalt-free, iron-free, silver-free and palladium-free grey gold alloy with a high nickel content, whose deformability allows deformation by cold drawing techniques without risk of cracking and which is economical and easy to manufacture.
One advantage of the present invention is that a gold alloy wire is obtained that offers a favourable compromise between colour and brightness, sufficient whiteness to meet the aesthetic requirements of the field of external timepiece components, and resistance to cracking during forming by cold working.
Another advantage is the ease of polishing and the high whiteness achieved after polishing.
Detailed description of preferred embodiments
To this end, the present invention relates to a method for producing cast 8 to 11 karat gold alloy wire having an initial diameter less than or equal to 20 mm to obtain a wire with a final diameter between the initial cast diameter and 0.1 mm.
This method utilizes the so-called wire rolling technique, which is actually a drawing technique in which the material is forced successively through a channel of decreasing cross-section in the form of a die.
This method includes the following steps:
-(10) preparing an alloy composition comprising, by mass %,
Au: 33.33% to 45.84%,
Zn: 3.64% to 12.44%,
Cu: 18.46% to 45.02%,
Ni: 9.88% to 33.78%,
and 0.0 to 5.0% of at least one element selected from Ir, In, Ti, Si, Ga, Re,
The total element content of the alloy is limited to 100% by adjusting the Cu content.
(11) the production of cast bars by continuous casting, the cross-section of which is inscribed within a diameter of 8.0 to 20.0 mm,
(12) rolling said as-cast bar, preferably in a substantially rectangular cross-section, preferably by rotating the intermediate product obtained through a quarter-turn before each rolling pass and limiting the cross-sectional deformation to a value less than or equal to 20% per pass,
- (13) measuring the cumulative deformation of the intermediate product compared to the initial cross-section of the rod in the as-cast state,
- (14) stopping the wire rolling when the cumulative cross-sectional deformation is 60% to 75% to anneal the intermediate product with an intermediate cross-section between 600 and 650° C. for 30 minutes in a reducing gas atmosphere, preferably N 2 +H 2 ,
(15) restarting the wire rolling with the same parameters, measuring the cumulative deformation of the intermediate product compared to the intermediate cross section, and stopping the rolling when the cumulative cross-sectional deformation between the cross section of the intermediate product and the intermediate cross section is 60% to 75% for annealing, and repeating the wire rolling, measuring and annealing process until the desired intermediate product cross section is reached,
- (16) Drawing the intermediate product so that the cross section returns to a substantially circular profile and section wire is obtained.
More particularly, during the wire rod rolling process, the cross-sectional deformation is limited to a value less than or equal to 13% per pass.
The number of annealing steps is preferably limited to three.
In one particular embodiment, the number of draw passes is limited to three.
In a particular embodiment, the filaments obtained by said drawing passes are reshaped.
In a particular embodiment, the profiled wire is cut to length upon completion of manufacture.
In a particular embodiment, within the alloy composition, the mass percentage content is limited to:
Au: 33.33% to 45.84%,
Zn: 4.48% to 12.44%,
Cu: 22.72% to 45.02%,
Ni: 12.16% to 33.78%,
In another specific embodiment, within the alloy composition, the mass percentage content is limited to:
-Au: 37.50% to 37.70%,
-Zn: 4.20% to 11.67%,
-Cu: 21.23% to 42.21%
-Ni: 11.36% to 31.67%.
In yet another specific embodiment, within the alloy composition, the mass percentage content is limited to:
-Au: 41.67% to 42.50%,
-Zn: 3.86% to 10.89%,
-Cu: 19.59% to 39.39%,
-Ni: 10.49% to 29.55%.
In yet another specific embodiment, within the alloy composition, the mass percentage content is limited to:
Au: 33.33% to 45.84%,
Zn: 3.64% to 10.11%,
Cu: 18.46% to 36.58%,
Ni: 9.88% to 27.44%.
More particularly, 0.002 to 1.000 mass % of at least one element Ir, Ti, Si is incorporated into the alloy composition.
More specifically, 0.30 to 1.00 mass % of Si is incorporated into the alloy composition.
More particularly, 20 to 500 ppm of Ti is incorporated into the alloy composition.
More specifically, 0.000 to 0.002 mass % Re is incorporated into the alloy composition.
More specifically, 1.00 to 4.00 mass% of In is incorporated into the alloy composition.
More particularly, the filaments are produced with a diameter greater than or equal to 0.1 mm.
More particularly, the wire is manufactured with a diameter less than or equal to 20.0 mm.
In a preferred embodiment, this wire is deformed by stamping to form a dial or dial appliqué or hands.
By using an alloy that meets the above definition, a grey gold alloy is obtained that meets all the criteria required for an alloy intended for use in the watchmaking and jewellery sectors (particularly in terms of colour and brightness and the ability to be cold worked without risk of cracking). This is combined with satisfactory corrosion resistance. 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-karat alloy and comprises, in mass%, 29 to 30% gold, 4.8 to 13% Zn, 24.2 to 47% Cu and 13 to 35% nickel and possibly up to 5% of at least one element chosen from Ir, In, Ti, Si, Ga, Re.
According to a particular embodiment, the gold alloy is a 9-karat alloy and comprises 37.5 to 38.5% gold, 4.2 to 11.5% Zn, 21.5 to 41.5% Cu and 11.5 to 31.2% nickel and possibly up to 5% of at least one element chosen from Ir, In, Ti, Si, Ga, Re.
According to another embodiment, the gold alloy is a 10 karat alloy and comprises, in mass %, 41.5 to 42.5% gold, 3.9 to 10.7% Zn, 19.9 to 38.8% Cu and 10.7 to 29.1% nickel and possibly up to 5% of at least one element chosen from Ir, In, Ti, Si, Ga, Re.
According to yet another embodiment, the gold alloy is a 13-karat alloy and comprises, in mass %, 54 to 55% Au, 3.1 to 8.4% Zn, 15.7 to 30.4% Cu and 8.4 to 22.8% nickel and possibly up to 5% of at least one element chosen from Ir, In, Ti, Si, Ga, Re.
According to a variant of the above embodiment, the gold alloy includes at least one element Ir, Ti, Si, the proportion of each element being 0.002 to 1 mass%, and when the alloy includes Si, the proportion of Si is preferably 0.3 to 1 mass%, and when it includes Ti, the proportion of Ti is preferably 20 to 500 ppm, and when it includes Re, the proportion of Re is preferably 0.002 mass%, and when it includes indium, the proportion of indium is preferably 1 to 4 mass%.
The gold alloy of the present invention is particularly useful for making parts for watches or jewellery, and in particular for making dials, dial appliques and hands for watches. In this application, the alloy avoids the need for rhodium plating, which is commonly used in the watchmaking field, to provide a satisfactory white colour and brightness to the treated parts.
To prepare the gray gold alloy composition of the present invention, the procedure is as follows:
The major elements involved in the alloy composition have a purity of 999.9 parts per thousand and are deoxidized.
The elements of the alloy composition are placed in a crucible and heated until the elements are melted.
Heating was performed in a sealed induction furnace under nitrogen partial pressure.
The molten alloy is then poured into an ingot mould.
After solidification, the ingot is water hardened.
The hardened ingot is then cold rolled and then annealed. The work harden rate between anneals is 66 to 80%, preferably 60 to 75%.
Each annealing lasted 20 to 30 minutes and was performed at 650°C in a reducing atmosphere containing N2 and H2 .
Cooling after annealing can be achieved by water quenching.
The following examples were made according to the conditions listed in Table 1 below and all relate to 7 to 13 karat grey gold alloys. The proportions indicated are expressed in mass %. Table 1 is divided into two parts: alloys strictly according to the invention, and other variants.
Table 1: Alloys of the present invention
| No. | Au. | Pd. | Ag. | Cu. | Ni. | Zn. | Ti. | Mn. |
| 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 |
Table 1: Other variants
| No. | Au. | Pd. | Ag. | Cu. | Ni. | Zn. | Ti. | Mn. |
| 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 a prior art alloy which is not white enough due to the absence of nickel, and alloys Nos. 1 and 2 made and tested by the applicant cracked during the recrystallization heat treatment.
The different compositions of the present invention, namely alloys No. 3 to 8, were developed and subjected to deformation tests to meet the requirements of brightness, whiteness and deformability required for alloys intended for use in the watchmaking and jewellery sectors and were found to be satisfactory.
Table 2 below lists various properties of the alloys in Examples No. 0 to No. 8 of Table 1. Table 2 specifically provides information on the hardness of the alloys in the cast, annealed, and drawn states, and on the color measured in a three-axis coordinate system. This three-dimensional measurement system is called CIELab, where CIE is the acronym for the International Commission on Illumination and LAB is the axis 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 value +a; green = negative value -a), and the b axis measures the yellow-blue component (yellow = positive value +b; blue = negative value -b). (See ISO 7724, an international standard established by the International Commission on Illumination.)
Table 2
As is clear from Table 2, prior art alloy No. 0 has a strong b* component, which gives it a yellowish appearance that is unacceptable for watchmaking applications, while alloys Nos. 3 to 5 according to the invention have a significantly lower b* component, so that the yellow component of the color of the alloys is not noticeable to the human eye. Alloys Nos. 1 and 2 meet the aesthetic criteria with regard to color, but cannot be cold-mechanically deformed without cracking.
Claims (17)
1. A method for manufacturing cast 8 to 11 carbide alloy wires with an initial diameter less than or equal to 20 mm to obtain a wire with a final diameter between the initial cast diameter and 0.1 mm, characterized in that:
-(10) Prepare an alloy composition comprising, by mass %:
Au: 33.33% to 45.84%,
Zn: 3.64% to 12.44%,
Cu: 18.46% to 45.02%,
Ni: 9.88% to 33.78%,
And 0.0% to 5.0% of at least one element selected from Ir, In, Ti, Si, Ga, and Re.
The total elemental content of the alloy is limited to 100% by adjusting the Cu content.
-(11) A casting rod is manufactured by continuous casting, the cross section of which is inscribed in a circle with a diameter of 8.0 to 20.0 mm;
-(12) Rolling the cast bar with a basic rectangular cross-section wire rod—by rotating the intermediate product before each wire rolling pass through a right-angle stroke, and limiting the cross-sectional deformation to a value of less than or equal to 20% per pass.
-(13) Measure the cumulative deformation of the intermediate product compared with the initial cross-section of the bar in the casting state.
-(14) When the cumulative cross-sectional deformation is 60% to 75% , stop the wire rolling and anneal the intermediate product with the intermediate cross-section at 600°C to 650°C for 20 to 30 minutes in a reducing gas atmosphere consisting of N2 and H2, followed by gas or water cooling.
-(15) Start wire rolling again with the same parameters, measure the cumulative deformation of the intermediate product compared with the intermediate cross section, and stop rolling when the cumulative cross-sectional deformation between the intermediate product cross section and the intermediate cross section is 60% to 75% for annealing, and repeat the wire rolling, measurement and annealing process until the desired intermediate product cross section is achieved.
-(16) Draw the intermediate product to restore the cross section to the basic circular profile and obtain the cross section wire.
2. The method according to claim 1, characterized in that, during the wire rolling process, the cross-sectional deformation is limited to a value of less than or equal to 13% per pass.
3. The method according to claim 1, wherein the number of annealing processes is limited to 3.
4. The method according to claim 1, characterized in that the number of drawing passes is limited to 3.
5. The method according to claim 1, characterized in that the filament obtained by the drawing is reshaped.
6. The method according to claim 1, characterized in that the cross-sectional wire is cut to a certain length upon completion of manufacturing.
7. The method according to claim 1, characterized in that, within the alloy composition, the mass percentage content is limited to:
Au: 33.33% to 45.84%,
Zn: 4.48% to 12.44%,
Cu: 22.72% to 45.02%,
Ni: 12.16% to 33.78%.
8. The method according to claim 1, characterized in that, within the alloy composition, the mass percentage content is limited to:
-Au: 37.50% to 37.70%,
-Zn: 4.20% to 11.67%,
-Cu: 21.23% to 42.21%,
-Ni: 11.36% to 31.67%.
9. The method according to claim 1, characterized in that, within the alloy composition, the mass percentage content is limited to:
-Au: 37.5% to 38.5%,
-Zn: 4.20% to 11.5%,
-Cu: 21.5% to 41.5%,
-Ni: 11.5 to 31.2%.
10. The method according to claim 1, characterized in that, within the alloy composition, the mass percentage content is limited to:
-Au: 41.67% to 42.50%,
-Zn: 3.86% to 10.89%,
-Cu: 19.59% to 39.39%,
-Ni: 10.49% to 29.55%.
11. The method according to claim 1, characterized in that, within the alloy composition, the mass percentage content is limited to:
Au: 33.33% to 45.84%,
Zn: 3.64% to 10.11%,
Cu: 18.46% to 36.58%,
Ni: 9.88% to 27.44%.
12. The method according to claim 1, characterized in that at least one element, Ir, Ti, or Si, is incorporated into the alloy composition at a mass percentage of 0.002 to 1.000%.
13. The method according to claim 1, characterized in that 0.30 to 1.00% by mass of Si is incorporated into the alloy composition.
14. The method according to claim 1, characterized in that 20 to 500 ppm of Ti is incorporated into the alloy composition.
15. The method according to claim 1, characterized in that 0.000 to 0.002% by mass of Re is incorporated into the alloy composition.
16. The method according to claim 1, characterized in that 1.00 to 4.00% by mass of In is incorporated into the alloy composition.
17. The method according to claim 1, characterized in that the wire is deformed by stamping to form a dial or dial inlay or hands.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP15193182.1 | 2015-11-05 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| HK1237379A1 HK1237379A1 (en) | 2018-04-13 |
| HK1237379B true HK1237379B (en) | 2019-11-01 |
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