CH720499B1 - Precious metal dial made from at least two gold alloys for a watch component - Google Patents

Abstract

The invention relates to a precious metal dial (10) based on at least two gold alloys, characterized in that it comprises a first part (11), referred to as the structural part, made of a first gold alloy containing at least 375‰ by weight of gold, and a second part (12), referred to as the aesthetic part, partially or totally covering the first part (11), the second part (12) being made of a second gold alloy containing at least 375‰ by weight of gold with a composition different from that of the first gold alloy; the two parts (11, 12) being inseparable. The invention also relates to a method for manufacturing such a precious metal dial based on at least two gold alloys.

Description

technical field

[0001] The present invention relates to a titratable precious metal dial based on at least two gold alloys for a timepiece, in particular for a wristwatch.

[0002] The invention also relates to a method of manufacturing such a precious metal dial based on at least two gold alloys.

State of the art

[0003] In a traditional manner, dials for watch parts are massive, one-piece parts generally manufactured by machining in the base material of the dial, such as stone, precious or non-precious metal, or ceramic, to obtain the desired three-dimensional shape, and finished with a decoration operation to obtain the desired aesthetic effects.

[0004] In the particular case of metal dials, the manufacture of the dials usually requires machining, deformation and/or cutting steps of the base metal material.

[0005] Once shaped, the base material is then decorated during a decoration or finishing operation, which may include engraving, guilloché work, and/or enameling. Therefore, the metal base material of the dial is generally annealed before these decoration and finishing operations are carried out, in order to minimize the hardness of the metal alloy of the dial's base material and thus facilitate these finishing and decoration steps.

[0006] However, these annealing states of certain alloys, and in particular precious metal alloys, generate problems with shock resistance.

[0007] In the specific case of solid gold dials (particularly for dials with a purity of 18K or higher), their significant mass and the low mechanical properties of the gold alloys used exacerbate this shock resistance issue, as these solid gold dials can easily deform upon impact. The low mechanical properties of the gold alloys can also be problematic during the dial assembly process.

[0008] This is accentuated when using solid gold dials with a specific color and little or no copper, the mechanical properties of which may be very low (hardness less than 100Hv in the annealed state).

Summary of the invention

[0009] In this context, the invention aims to provide a titratable precious metal dial based on at least two gold alloys, making it possible to remedy at least one of the drawbacks described above.

[0010] The dial according to the invention makes it possible to have a titratable gold dial having both the required aesthetic properties (specific color) while preserving sufficiently high mechanical characteristics to withstand shocks (hardness greater than 100Hv in the annealed state).

[0011] To this end, the invention proposes a precious metal dial based on at least two gold alloys characterized in that it comprises a first part, called the structural part, made in a first gold alloy having at least 375‰ by weight of gold and a second part, called the aesthetic part, covering in part or in whole the first part, the second part being made in a second gold alloy having at least 375‰ by weight of gold and having a different composition from the first gold alloy; the two parts being inseparable.

[0012] Preferably, the second part completely covers the first part.

[0013] Thus, thanks to the invention, it is possible to obtain a solid dial in titratable gold (having a fineness of at least 9K) having a visible face in a "soft" gold alloy, such as for example in a green gold alloy, while having a dial having improved mechanical characteristics and superior to the hardness of the green gold alloy (in the annealed state) by the use of a structural part in a "hard" gold alloy having a hardness greater than or equal to 100 Hv, configured to resist the various stresses related to the use of a watch part.

[0014] Thus, each part constituting the final solid dial is titled or titled with a minimum title of 9K.

[0015] Preferably, the invention proposes a precious metal dial based on at least two gold alloys characterized in that it comprises a first part, called the structural part, made of a first gold alloy having at least 750‰ by weight of gold and a second part, called the aesthetic part, covering in part or in whole the first part, the second part being made of a second gold alloy having at least 750‰ by weight of gold and having a different composition from the first gold alloy; the two parts being inseparable.

[0016] Thanks to the invention, it is possible to obtain a solid dial in titratable gold having a visible face in "soft" gold alloy, such as for example in green gold alloy, with a fineness greater than or equal to 18K.

[0017] In addition to the characteristics mentioned in the preceding paragraphs, the precious metal dial based on at least two gold alloys according to the invention may have one or more additional characteristics from among the following, considered individually or according to all technically possible combinations:

–

the first gold alloy forming the first part has a higher hardness than the second gold alloy forming the second part;

–

the first gold alloy forming the first part has a hardness greater than or equal to 100Hv, preferably greater than or equal to 120Hv; for example the first gold alloy has a hardness of around 135Hv;

–

the second part covering the first part is made of a second gold alloy having a hardness of less than 100Hv;

–

The first gold alloy comprises, expressed by weight, the following elements:

or: in a proportion equal to or greater than 750‰;

o copper: balance at 1000‰;

or optionally in a proportion between 0 and 50‰, inclusive, at least one of the following elements: silver, indium, palladium, gallium, zinc;

or optionally, at least one grain refiner, in a proportion between 0 and 0.5‰, inclusive;

the respective proportions of all the constituent elements of the gold alloy complementing each other up to 1000 ‰;

–

The first gold alloy comprises, expressed by weight, the following elements:

o or: 750‰ ;

silver: 50‰;

o copper: balance at 1000‰;

or optionally, at least one grain refiner, such as iridium, in a proportion between 0 and 0.5‰, inclusive;

the respective proportions of all the constituent elements of the gold alloy complementing each other up to 1000 ‰;

–

the second gold alloy is green, purple, blue, pink, white, grey or yellow gold;

–

The second gold alloy is a green gold alloy comprising, expressed by weight, the following elements:

or: in a proportion equal to or greater than 750‰;

o silver: balance at 1000‰;

or optionally at least one grain refiner in a proportion between 0 and 0.5‰, inclusive;

or optionally copper in a proportion between 0 and 100‰, inclusive of terminals;

or optionally zinc in a proportion between 0 and 100‰, inclusive;

or optionally indium in a proportion between 0 and 50‰, inclusive;

or optionally palladium in a proportion between 0 and 50‰, inclusive;

the respective proportions of all the constituent elements of the gold alloy complementing each other up to 1000‰;

–

the dial includes a filler element ensuring continuity of material between the first part and the second part; the filler element being made of a third gold alloy comprising, expressed by weight, at least 375‰ of gold; preferably at least 750‰ of gold;

–

the first part, the second part and the filler element are made of respective gold alloys comprising the same proportion by weight of gold;

–

the filler element is a brazing alloy or gold alloy filler metal;

–

the input element comprises, expressed by weight, at least 375‰ of gold and in balance for example at least one of the following elements: silver, copper, zinc, gallium;

–

the input element comprises, expressed by weight, at least 750‰ of gold and in balance for example at least one of the following elements: silver, copper, zinc, gallium;

–

the additive has a melting point below 450°C;

–

the additive has a melting point above 450°C.

[0018] The invention also relates to a timepiece comprising such a dial made of precious metal according to the invention.

[0019] The invention also relates to a method for manufacturing a precious metal dial according to the invention, characterized in that the manufacturing method comprises the following steps:

has)

manufacturing of a first disc in the first gold alloy;

b)

manufacturing a second disc in the second gold alloy; preferably, the diameter of the second disc being smaller than the diameter of the first disc;

c)

welding the second disc to the first disc by a welding process without filler metal to form a monobloc assembly.

[0020] Preferably, the manufacturing process further comprises a step d) of cutting the monobloc assembly obtained in step c) according to a determined geometric contour to obtain the final dimensions of the precious metal dial.

[0021] According to one embodiment, the process for manufacturing a precious metal dial according to the invention comprises the following steps:

has)

manufacturing of a first disc in the first gold alloy;

b)

manufacturing a second disc in the second gold alloy; preferably, the diameter of the second disc being smaller than the diameter of the first disc;

c)

assembly of the two discs, the second disc covering the first disc; the two discs being assembled by the manual or automatic deposition of a gold alloy brazing compound comprising, expressed by weight, at least 375‰ of gold, preferably at least 750‰, in the form of a paste, on the first disc and in contact with the second disc, the brazing being able to be deposited on part of the perimeter or on the entire perimeter of the second disc;

d)

maintaining the assembly of the two disks obtained in step c);

e)

heating of the assembly obtained in step d) to fuse the brazing to the two discs and obtain a monobloc assembly, the brazing migrating by capillary action in the joint plane of the two discs held together; preferably, the heating step is carried out at a temperature between 550°C and 750°C.

[0022] Preferably, the manufacturing process further comprises a step f) of cutting the monobloc assembly obtained in step e) according to a contour of determined geometry to obtain the final dimensions of the precious metal dial.

[0023] According to one embodiment, the process for manufacturing a precious metal dial according to the invention comprises the following steps:

has)

manufacturing of a first disc in the first gold alloy;

b)

manufacturing a second disc in the second gold alloy; preferably, the diameter of the second disc being smaller than the diameter of the first disc;

c)

depositing, manually or automatically, of a paste solder, in gold alloy comprising, expressed by weight, at least 375‰ of gold, preferably at least 750‰ of gold, on at least one surface of one of the two discs, the solder being deposited in part or on the whole of said at least one surface;

d)

assembly of the two discs, the second disc covering the first disc;

e)

maintaining the assembly of the two disks obtained in step d);

f)

heating the assembly obtained in step e) to fuse the brazing to the two discs and obtain a single-piece assembly; preferably, the heating step is carried out at a temperature between 550°C and 750°C.

[0024] Preferably, the manufacturing process further comprises a step g) of cutting the monobloc assembly obtained in step f) according to a contour of determined geometry to obtain the final dimensions of the precious metal dial.

[0025] According to one embodiment, the process for manufacturing a precious metal dial according to the invention comprises the following steps:

has.

manufacturing of a first disc in the first gold alloy;

b.

manufacturing a second disc in the second gold alloy; preferably, the diameter of the second disc being smaller than the diameter of the first disc; step a) or b) comprising the following substeps:

–

a step of depositing, manually or automatically, a gold alloy brazing alloy as a filler element, in the form of a strip on the first alloy, or the second alloy;

–

a heating step, for example in a pass-through furnace, to fuse the brazing to the first alloy, or to the second alloy, in order to obtain a first monobloc assembly; preferably, the heating step is carried out at a temperature between 550°C and 750°C;

–

optionally a rolling step of the first monobloc assembly to obtain a desired thickness;

–

a cutting step of the first single-piece assembly obtained previously to obtain the desired dimensions of the first disc, or the second disc;

c.

assembly of the two discs obtained in steps a) and b), by placing the second disc on the first disc on the brazed side;

d.

maintaining the assembly of the two disks obtained in step c);

e.

heating the assembly obtained in step d) to fuse the brazing to the other disc and obtain a second monobloc assembly; preferably, the heating step is carried out at a temperature between 550°C and 750°C.

[0026] Preferably, the manufacturing process further includes a step f) of cutting the second one-piece assembly according to a determined geometric contour to obtain the final dimensions of the precious metal dial.

[0027] Preferably, the manufacturing process further comprises a heat treatment step and/or a finishing step.

[0028] Other features and advantages of the present invention will become apparent from the following description of preferred embodiments, presented by way of non-limiting example with reference to the accompanying drawings.

Brief description of the figures

[0029] The aims, advantages and features of the present invention will become apparent from reading the detailed description below with reference to the following figures.

Figure 1 represents a first example of the realization of a titratable precious metal dial based on at least two gold alloys according to the invention.

Figure 2 represents a second example of the realization of a titratable precious metal dial based on at least two gold alloys according to the invention.

Figure 3 represents the component parts of a titratable precious metal dial based on at least two gold alloys manufactured according to the manufacturing process of the invention, according to a first embodiment.

Figure 4 represents the component parts of a titratable precious metal dial based on at least two gold alloys manufactured according to the manufacturing process of the invention, according to a second embodiment.

Figure 5 represents the component parts of a titratable precious metal dial based on at least two gold alloys manufactured according to the manufacturing process of the invention, according to a third embodiment.

Detailed description of the invention

[0030] In general, in the present application the hardness values of gold alloys are given in the annealed condition, unless otherwise specified.

[0031] Figure 1 schematically illustrates a first example of the embodiment of a precious metal dial 10 based on at least two gold alloys. Such a dial 10 is a solid piece composed of at least 375‰ by weight of gold, as well as each alloy composing it. Thus, such a dial is a dial presenting, as a whole, at least 9K of gold.

[0032] Preferably, the dial 10 is a solid piece composed of at least 750‰ by weight of gold.

[0033] The dial 10 according to the invention is a solid gold dial having a minimum fineness of 18 carats.

[0034] The dial 10 consists of an inseparable assembly of a first structural part 11, lower part of the dial 10, made of a first gold alloy, chosen for its structural properties, and a second aesthetic part 12, upper part of the dial 10, covering in part or in whole the first structural part 11, the second aesthetic part 12 being made of a second gold alloy chosen mainly for its aesthetic properties, and in particular for its color, without concern for its mechanical characteristics, and in particular the hardness of the alloy in question in the annealed state.

[0035] The upper face 14 of the second aesthetic part 12 forms the upper surface of the dial 10, intended to be the visible part of the dial. The lower face 15 of the first structural part 11 forms the lower surface of the dial 10, intended to be opposite the watch movement.

[0036] Preferably, the upper surface 14 of the second aesthetic part 12 comprises decorations applied or created in the mass by any techniques known in the prior art. By way of example, the decorations may be engraved or guillochéd directly into the mass of the second aesthetic part 12.

[0037] The upper face 14 of the second aesthetic part 12 may also have enamelled, lacquered, varnished, etc. parts.

[0038] In a conventional manner, and according to the needs, the dial 10 can also be covered, at least in part at the level of the upper surface 14 of the second aesthetic part 12, with a protective coating, for example against the tarnishing of the gold alloy used for the realization of this second aesthetic part 12.

[0039] The first structural part 11 is made from a piece, for example a disc, made of a first gold alloy comprising, expressed by weight, at least 375‰ of gold, preferably at least 750‰ of gold. The first structural part 11 forms the structural base of the dial 10 configured to provide the mechanical strength of the dial 10.

[0040] Preferably, the first structural part 11 is made of a "hard" gold alloy having a hardness greater than or equal to 100 Hv, preferably greater than or equal to 120 Hv. For example, the first structural part 11 has a hardness of 135 Hv.

[0041] For example, the first structural part 11 is made of a first gold alloy comprising, expressed by weight, at least 375‰ of gold, and in balance copper, so as to obtain a gold alloy standardized with the best possible mechanical properties by the addition of copper.

[0042] For example, the first structural part 11 is made of a first gold alloy comprising, expressed by weight, at least 750‰ of gold, and in balance copper, so as to obtain a gold alloy with the best possible mechanical properties by the addition of copper.

[0043] For example, the second gold alloy can be 9 carat, 10 carat, 14 carat, 15 carat, 18 carat, 20 carat, 21.6 carat or 22 carat gold.

[0044] Optionally, the first gold alloy of the first structural part 11 may also comprise, in a proportion between 0 and 50‰ (inclusive), expressed by weight of the alloy, at least one of the following elements: silver, indium, palladium, gallium, zinc. The respective proportions of all the constituent elements of the alloy are complementary up to 1000‰.

[0045] Optionally, the first gold alloy of the first structural part 11 may also comprise, in a proportion between 0 and 0.5‰ (inclusive), expressed by weight of the alloy, a grain refiner, such as iridium. The respective proportions of all the constituent elements of the alloy are completed up to 1000‰.

[0046] The first structural part 11 is for example made of a 5N18 gold alloy, which is an 18-carat 5N red gold.

[0047] The first structural part 11 is for example made of a first gold alloy comprising, expressed by weight, the following elements:

–

or: in a proportion of 750‰;

–

silver: in a proportion of 50‰;

–

copper: balance at 1000‰;

–

optionally, at least one grain refiner, such as iridium, in a proportion between 0 and 0.5‰;

the respective proportions of all the elements of the gold alloy complementing each other up to 1000‰. Such a gold alloy has a hardness of 135Hv.

[0048] The second aesthetic part 12 is made from a piece, for example a disc, made from a second gold alloy comprising, expressed by weight, at least 375‰ of gold.

[0049] Preferably, the second aesthetic part 12 is made of a second gold alloy comprising, expressed by weight, at least 750‰ of gold.

[0050] The second gold alloy has a different composition and color than the first gold alloy.

[0051] For example, the second gold alloy may be 9 carat, 10 carat, 14 carat, 15 carat, 18 carat, 20 carat, 21.6 carat, 22 carat, 23 carat, or 24 carat gold.

[0052] Preferably, the second aesthetic part 12 is made of a second "soft" gold alloy having a hardness of less than 100 Hv.

[0053] Thanks to the dial 10 according to the invention, the second aesthetic part 12 can be made of a gold alloy having a hardness of less than 60 Hv without reducing the ability of the gold dial 10 to withstand shocks, thanks to the use of the first structural part 11.

[0054] Preferably, the second aesthetic part 12 is made of a second gold alloy whose composition has a proportion of copper less than 150‰ by weight, preferably less than 50‰ by weight.

[0055] The second gold alloy of this second aesthetic part 12 can be green, purple, blue, pink, white, grey or yellow gold.

[0056] For example, the second aesthetic part 12 is made of a second green gold alloy comprising, expressed by weight, a minimum of 750‰ of gold and silver in balance at 1000‰.

[0057] For example, the second aesthetic part 12 is made of an 18-carat green gold alloy, called electrum gold, comprising, expressed by weight, 750‰ of gold and 250‰ of silver.

[0058] For example, the second aesthetic part 12 is made of a green gold alloy comprising, expressed by weight, the following elements:

–

or: in a proportion at least equal to 750‰;

–

silver: balance at 1000‰;

–

optionally at least one grain refiner, such as iridium, in a proportion between 0 and 0.5‰, inclusive;

–

optionally copper in a proportion between 0 and 100%; copper can be used to improve hardness if needed;

–

optionally zinc in a proportion between 0 and 100‰, inclusive; zinc can be used to tint the green color of the gold alloy as required;

–

optionally indium in a proportion between 0 and 50‰, inclusive; indium can be used to tint the color of the gold alloy according to requirements;

–

optionally palladium in a proportion between 0 and 50‰, inclusive; palladium can be used to improve the oxidation and tarnish resistance of the green gold alloy;

the respective proportions of all the constituent elements of the gold alloy complementing each other up to 1000‰.

[0059] It should be noted that the addition of zinc in the gold alloy, in particular in a proportion greater than 100‰, complicates the casting of the gold alloy and therefore the manufacture of the disc forming the second aesthetic part 12 of the dial 10. Consequently, the proportion of zinc in the second gold alloy will preferably be chosen to be less than 100‰ by weight of the alloy.

[0060] According to the first embodiment illustrated in Figure 1, the second aesthetic part 12 is joined to the first structural part 11 without the addition of a filler element, brazing, filler metal or a fusion piece to form the fusion of the two parts 11, 12.

[0061] This first embodiment can be achieved by a welding process without filler metal, for example by a spot welding process, a laser welding process or an electron beam welding process.

[0062] Thus, a first method for manufacturing a precious metal dial 10 based on at least two gold alloys according to the invention consists of:

–

to manufacture a first disc in the first gold alloy;

–

manufacture a second disc in the second gold alloy; preferably, the diameter of the second disc being smaller than the diameter of the first disc;

–

weld the second disc to the first disc using a filler metal-free welding process to form a single-piece assembly;

–

Optionally, cut the one-piece assembly according to a determined geometric contour to obtain the final dimensions of the precious metal dial 10.

[0063] Figure 2 illustrates a second example of an embodiment of a precious metal dial 20 based on at least two gold alloys according to the invention. The dial 20 is identical to the dial 10 described with reference to Figure 1, except for the characteristics that will be described below.

[0064] In this second embodiment, the second aesthetic part 12 is joined to the first structural part 11 by the use of a filler element 13 made of a third gold alloy comprising, expressed by weight, at least 375‰ of gold, preferably at least 750‰ of gold.

[0065] Preferably, the filler element 13 is a filler metal made from the third gold alloy added during a brazing or welding process. The filler element 13 ensures material continuity between the first structural part 11 and the second aesthetic part 12. The filler element 13 is, for example, a brazing alloy.

[0066] For example, the first gold alloy, the second gold alloy and the third gold alloy of the input element 13 have different grades.

[0067] For example, the first gold alloy, the second gold alloy and the third gold alloy of the feed element 13 each have, expressed by weight, at least 750‰ of gold.

[0068] For example, the first gold alloy, the second gold alloy and the third gold alloy of the filler element 13 have the same fineness, that is to say the same proportion of gold by weight in the respective alloy, for example 750‰ by weight.

[0069] Preferably, the input element 13 comprises at least 750‰ of gold and in balance at least one of the following compounds: silver, copper, zinc, gallium.

[0070] For example, the feed element 13 has a melting point below 450°C.

[0071] For example, the feed element 13 has a melting point above 450°C.

[0072] The melting point of the filler element 13 is determined and modifiable according to the proportions of silver, zinc and gallium used in the third gold alloy.

[0073] The first structural part 11 and the second aesthetic part 12 of the dial 10, 20 are formed from disc-shaped initial pieces. However, the first structural part 11 and the second aesthetic part 12 of the gold dial 10, 20 can be formed from initial pieces of various shapes (round, square, etc.) and with varying dimensions depending on the requirements.

[0074] Preferably, the first structural part 11 and the second aesthetic part 12 of the dial 10, 20 are formed from discs having a thickness between 0.1mm and 1.5mm, preferably between 0.2mm and 0.5mm.

[0075] Preferably, the first structural part 11 has a greater thickness than the second aesthetic part 12.

[0076] The discs used to make the first structural part 11 and the second aesthetic part 12 have a diameter between 10mm and 60mm. The dimensions are adapted according to the needs and the final dimensions of the dial 10, 20.

[0077] The discs used to make the first structural part 11 and the second aesthetic part 12 have a flatness of less than 0.1mm, preferably less than 0.05mm, in particular to ensure the capillary flow of the feed element 13.

[0078] Figure 3 illustrates a first method of manufacturing the dial 20 shown in Figure 2. This first manufacturing method comprises the following steps:

–

manufacturing a first disc 11a in a first structural gold alloy as described above;

–

manufacturing a second disc 12a in a second aesthetic gold alloy as described above; preferably, the diameter of the second disc 12a is smaller than the diameter of the first disc 11a;

–

assembly of the two discs 11a and 12a, the second disc 12a, made in the second aesthetic gold alloy, forms the second aesthetic part 12 of the dial 20 and covers the first disc 11a forming the first structural part 11 of the dial 20; the two discs 11a and 12a being assembled by the manual or automatic deposition of a gold alloy braze 13 as a filler element, in the form of a paste, on the first disc 11a and in contact with the second disc 12a, the gold alloy braze 13 being able to be deposited on part of the perimeter or on the entire perimeter of the second disc 12a;

–

maintaining the assembly of the two disks 11a and 12a, for example by adding a weight of neutral material on the upper surface 14a of the second disk 12a, for example in graphite or in sapphire because they do not react with gold alloys and have sufficient temperature resistance;

–

heating the assembly, for example in a pass-through furnace, allowing the brazing 13 to fuse to the two discs 11a, 12a and obtain a monobloc assembly, the brazing 13 migrating by capillary action in the joint plane of the two discs 11a, 12a; preferably, the heating step is carried out at a temperature between 550°C and 750°C;

–

Optionally, cutting the entire one-piece assembly according to a determined geometric contour to obtain the final dimensions of the precious metal dial.

[0079] Figure 4 illustrates a second method of manufacturing the dial 20 shown in Figure 2. This second manufacturing method comprises the following steps:

–

manufacturing of a first disc 11a in a first structural gold alloy as described above;

–

manufacturing a second disc 12a in a second aesthetic gold alloy as described above; preferably, the diameter of the second disc 12a is smaller than the diameter of the first disc 11a;

–

depositing, manually or automatically, of a gold alloy braze 13' as a filler element, in the form of a paste, on the upper surface 16 of the first disc 11a; the braze 13' can be deposited in part or on the whole of the upper surface 16 of the first disc 11a;

–

assembly of the two discs 11a and 12a, by placing the second disc 12a, made in the second aesthetic gold alloy forming the second aesthetic part 12 of the dial 20, on the gold alloy brazing 13' placed on the first disc 11a forming the first structural part 11 of the dial 20;

–

maintaining the assembly of the two disks 11a and 12a, for example by adding a weight on the upper surface 14a of the second disk 12a, for example in graphite or in sapphire for temperature resistance;

–

heating the assembly, for example in a pass-through oven, to fuse the brazing 13' to the two discs 11a, 12a and obtain a monobloc assembly; preferably, the heating step is carried out at a temperature between 550°C and 750°C;

–

Optionally, cutting the entire one-piece assembly according to a determined geometric contour to obtain the final dimensions of the precious metal dial.

[0080] Figure 5 illustrates a third method of manufacturing the dial 20 shown in Figure 2.

[0081] This third manufacturing method comprises the following steps:

–

manufacturing of a first disc 11a in a first structural gold alloy as described above;

–

manufacturing a second disc 12a in a second aesthetic gold alloy as described above; preferably, the diameter of the second disc 12a is smaller than the diameter of the first disc 11a;

–

In this third method, the manufacturing step of the first disc 11a or the manufacturing step of the second disc 12a comprises:

–

a step of depositing, manually or automatically, a 13'' gold alloy brazing as a filler element, in the form of a strip on the first alloy, or the second alloy;

–

a heating step for example in a pass-through furnace, to fuse the 13'' brazing to the first alloy, or to the second alloy, in order to obtain a first monobloc assembly; preferably, the heating step is carried out at a temperature between 550°C and 750°C;

–

optionally a rolling step of the first monobloc assembly to obtain a desired thickness;

–

a cutting step to obtain the desired dimensions of the first disc 11a, or of the second disc 12a.

[0082] The third manufacturing method further comprises the following steps:

–

assembly of the two discs 11a and 12a obtained previously, by placing the second disc 12a, made in the second aesthetic gold alloy forming the second aesthetic part 12 of the dial 20, on the first disc 11a forming the first structural part 11 of the dial 20 on the side of the brazing strip 13'';

–

maintaining the assembly of the two disks 11a and 12a, for example by adding a weight on the upper surface 14a of the second disk 12a, for example in graphite or in sapphire for temperature resistance;

–

heating the assembly, for example in a pass-through oven, to fuse the brazing 13'' to the other disc, i.e. to the second disc 12a, or to the first disc 11a, and obtain a second monobloc assembly; preferably, the heating step is carried out at a temperature between 550°C and 750°C;

–

Optionally, cutting the second one-piece assembly according to a determined geometric contour to obtain the final dimensions of the precious metal dial.

[0083] Optionally, the manufacturing methods described above may include at least one heat treatment step (annealing, stress relieving, etc.), and/or at least one finishing step (polishing, decorating, etc.).

Claims (20)

1. Precious metal dial (10, 20) based on at least two gold alloys characterized in that it comprises a first part (11), called structural part, made of a first gold alloy having at least 375‰ by weight of gold and a second part (12), called aesthetic part, covering in part or in whole the first part (11), the second part (12) being made of a second gold alloy having at least 375‰ by weight of gold and having a different composition from the first gold alloy; the two parts (11, 12) being inseparable, the first gold alloy forming the first part (11) having a higher hardness than the hardness of the second gold alloy forming the second part (12). 2. Precious metal dial (10, 20) according to the preceding claim, characterized in that the first gold alloy forming the first part (11) has a hardness greater than 100Hv, preferably greater than or equal to 120Hv. 3. Precious metal dial (10, 20) according to any one of the preceding claims, characterized in that the second part (12) covering the first part (11) is made of a second gold alloy having a hardness of less than 100Hv. 4. Precious metal dial (10, 20) according to any one of the preceding claims characterized in that it comprises a first part (11), called structural part, made of a first gold alloy having at least 750‰ by weight of gold and a second part (12), called aesthetic part, covering in part or in whole the first part (11), the second part (12) being made of a second gold alloy having at least 750‰ by weight of gold and having a different composition from the first gold alloy; the two parts (11, 12) being inseparable. 5. A precious metal dial (10, 20) according to any one of the preceding claims, characterized in that the first gold alloy comprises, expressed by weight, the following elements: – gold: in a proportion equal to or greater than 750‰; – copper: in proportions of 1000‰; – optionally, in a proportion between 0 and 50‰, inclusive, at least one of the following elements: silver, indium, palladium, gallium, zinc; – optionally, at least one grain refiner, in a proportion between 0 and 0.5‰, inclusive; the respective proportions of all the constituent elements of the gold alloy being added together up to 1000‰. 6. Precious metal dial (10, 20) according to any one of the preceding claims, characterized in that the first gold alloy comprises, expressed by weight, the following elements: – gold: 750‰; – silver: 50‰; – copper: approximately 1000‰; – optionally, at least one grain refiner, such as iridium, in a proportion between 0 and 0.5‰, inclusive; the respective proportions of all the constituent elements of the gold alloy being completed up to 1000‰. 7. Precious metal dial (10, 20) according to any one of the preceding claims, characterized in that the second gold alloy is green, purple, blue, pink, white, grey or yellow gold. 8. Precious metal dial (10, 20) according to any one of the preceding claims, characterized in that the second gold alloy is a green gold alloy comprising, expressed by weight, the following elements: – gold: in a proportion equal to or greater than 750‰; – silver: balance at 1000‰; – optionally at least one grain refiner in a proportion between 0 and 0.5‰, inclusive; – optionally copper in a proportion between 0 and 100‰, inclusive; – optionally zinc in a proportion between 0 and 100‰, inclusive; – optionally indium in a proportion between 0 and 50‰, inclusive; – optionally palladium in a proportion between 0 and 50‰, inclusive; the respective proportions of all the constituent elements of the gold alloy complementing each other up to 1000‰. 9. Precious metal dial (20) according to any one of the preceding claims, characterized in that it comprises a filler element (13) ensuring the continuity of material between the first part (11) and the second part (12); the filler element (13) being made of a third gold alloy comprising, expressed by weight, at least 375‰ of gold. 10. Precious metal dial (20) according to the preceding claim, characterized in that the filler element (13) is made of a third gold alloy comprising, expressed by weight, at least 750‰ of gold. 11. Precious metal dial (20) according to any one of claims 9 to 10, characterized in that the first part (11), the second part (12) and the filler element (13) are made of respective gold alloys comprising the same proportion by weight of gold. 12. Precious metal dial (20) according to any one of claims 9 to 11, characterized in that the filler element (13) comprises, expressed by weight, at least 375‰ of gold, preferably at least 750‰ of gold, and in balance at least one of the following elements: silver, copper, zinc, gallium. 13. Precious metal dial (20) according to any one of claims 9 to 12, characterized in that the filler element (13) has a melting point below 450°C. 14. Precious metal dial (20) according to any one of claims 9 to 12, characterized in that the filler element (13) has a melting point above 450°C. 15. Timepiece comprising a precious metal dial (10, 20) according to any one of the preceding claims. 16. A method for manufacturing a precious metal dial (10) according to any one of claims 1 to 14, characterized in that the manufacturing process comprises the following steps: a. manufacturing a first disc in the first gold alloy; b. manufacturing a second disc in the second gold alloy; preferably, the diameter of the second disc being smaller than the diameter of the first disc; c. welding the second disc to the first disc by a filler metal-free welding process to form a single piece; d. Optionally, cutting the monobloc assembly obtained in step c) according to a determined geometric contour to obtain the final dimensions of the precious metal dial (10). 17. A method for manufacturing a precious metal dial (20) according to any one of claims 1 to 14, characterized in that the manufacturing process comprises the following steps: a. manufacturing a first disc (11a) in the first gold alloy; b. manufacturing a second disc (12a) in the second gold alloy; preferably, the diameter of the second disc (12a) being smaller than the diameter of the first disc (11a); c. assembling the two discs (11a, 12a), the second disc (12a) overlapping the first disc (11a); the two discs (11a, 12a) being joined by manually or automatically depositing a gold alloy braze (13) comprising, by weight, at least 375‰ gold, preferably at least 750‰ gold, in the form of a paste, onto the first disc (11a) and in contact with the second disc (12a), the braze (13) being able to be deposited on part or all of the perimeter of the second disc (12a); d. maintaining the assembly of the two discs (11a, 12a) obtained in step c); e. heating the assembly obtained in step d) to fuse the braze (13) to the two discs (11a, 12a) and obtain a single-piece assembly, the braze (13) migrating by capillary action in the joint plane of the two discs (11a, 12a) held together; Preferably, the heating step is carried out at a temperature between 550°C and 750°C; f. Optionally, cutting the monobloc assembly obtained in step e) according to a determined geometric contour to obtain the final dimensions of the precious metal dial (20). 18. A method for manufacturing a precious metal dial (20) according to any one of claims 1 to 14, characterized in that the manufacturing process comprises the following steps: a. manufacturing a first disc (11a) in the first gold alloy; b. manufacturing a second disc (12a) in the second gold alloy; preferably, the diameter of the second disc (12a) being smaller than the diameter of the first disc (11a); c. manually or automatically depositing a paste solder (13') of a gold alloy comprising, expressed by weight, at least 375‰ gold, preferably at least 750‰ gold, onto at least one surface of one of the two discs (11a, 12a), the solder (13') being deposited in part or over all of said at least one surface; d. assembly of the two disks (11a, 12a), the second disk (12a) covering the first disk (11a); e. maintenance of the assembly of the two disks (11a, 12a) obtained in step d); f. heating the assembly obtained in step e) to fuse the solder (13') to the two discs (11a, 12a) and obtain a single-piece assembly; preferably, the heating step is carried out at a temperature between 550°C and 750°C; g. optionally, cutting the single-piece assembly obtained in step f) according to a predetermined geometric contour to obtain the final dimensions of the precious metal dial (20). 19. A method for manufacturing a precious metal dial (20) according to any one of claims 1 to 14, characterized in that the manufacturing process comprises the following steps: a. manufacturing a first disc (11a) in the first gold alloy; b. manufacturing a second disc (12a) in the second gold alloy; preferably, the diameter of the second disc (12a) being smaller than the diameter of the first disc (11a); step a) or b) comprising the following substeps: – a step of manually or automatically depositing a gold alloy brazing alloy (13'') as a filler element, in the form of a strip, onto the first or second alloy; – a step of heating, for example in a convection furnace, to fuse the brazing alloy (13'') to the first or second alloy, in order to obtain a first monolithic assembly; Preferably, the temperature-setting step is carried out at a temperature between 550°C and 750°C; – optionally, a rolling step of the first monoblock assembly to obtain the desired thickness; – a cutting step of the first monoblock assembly obtained previously to obtain the desired dimensions of the first disc (11a), or of the second disc (12a); c. assembly of the two discs (11a, 12a) obtained in steps a) and b), by placing the second disc (12a) onto the first disc (11a) on the brazed side (13"); d. holding the assembly of the two discs (11a, 12a) obtained in step c); e. heating the assembly obtained in step d) to fuse the brazed side (13") to the other disc (11a, 12a) and obtain a second monoblock assembly; preferably, the heating step is carried out at a temperature between 550°C and 750°C; f. Optionally, cutting the second one-piece assembly according to a determined geometric contour to obtain the final dimensions of the precious metal dial. 20. Method of manufacturing a precious metal dial (20) according to any one of claims 16 to 19, characterized in that the manufacturing process includes an additional heat treatment step of annealing or stress relieving and/or a finishing step.