A method for manufacturing an HSHCCA conductive wire, intended in particular for obtaining a thin HSHCCA coated wire

Abstract

Method for manufacturing an HSHCCA conductive wire, particularly for obtaining a thin coated HSHCCA wire. The invention relates to a method for manufacturing an HSHCCA conductive wire from an alloy consisting of chromium (0.2 to 0.6%), zirconium (0.02 to 0.06%), phosphorus (less than 0.02%), and impurities to be avoided (less than 0.1%). After melting the various components, continuous casting through a die to obtain a bar, followed by solidification and cooling of the bar, the following steps are carried out: d) a first cold reduction operation of said bar to obtain the shape and cross-section of the wire; e) heat treatment of said wire; f) a second cold reduction operation of said wire to obtain the final shape and cross-section of the conductive wire. Figure for the abstract: Fig. 3

Description

Title of the invention: Method for manufacturing an HSHCCA conductive wire, intended in particular for obtaining a thin HSHCCA coated wire

[0001] The present invention relates to the field of conductive wires made of a copper-based alloy.

[0002] The present invention relates more specifically to a method for manufacturing a HSHCCA conductive wire having a diameter between approximately 1 and approximately 2 mm and which has high mechanical characteristics (HS for "High Strength", i.e., high resistance), high conductivity (HC for "High Conductivity") and obtained from a copper-based alloy (CA for "Copper Alloy").

[0003] From this 1 to 2 mm wire, a fine HSHCCA coated wire with a diameter between 0.03 mm and 0.3 mm can then be manufactured, which can be used for the manufacture of very high performance electrical cables.

[0004] In the remainder of the text, the expression "thin wire" or "thin conducting wire" refers to a wire between 0.03 and 0.3 mm, preferably between 0.05 and 0.3 mm.

[0005] Consequently, the HSHCCA conductive wire with a diameter between 1 and 2 mm, obtained by implementing the present process, can be described as an “intermediate” conductive wire since it can undergo further transformations.

[0006] However, the HSHCCA conductor wire can also constitute a finished product as such.

[0007] The present invention also relates to a method of obtaining a fine HSHCCA coated wire, with a diameter between 0.03 and 0.3 mm, from an intermediate HSHCCA conductive wire with a diameter between 1 and 2 mm.

[0008] In the prior art, patent documents disclosing methods for manufacturing fine conductive wires that can be described as HSHCCA wires are known.

[0009] This is notably the case of the French patent published and issued under number FR 3 078 078, belonging to the same company filing the present application, which relates to a process for manufacturing a fine conductive wire, or a catenary contact wire.

[0010] This French patent describes, more particularly, a process for manufacturing a conductive wire from an alloy consisting of chromium in a proportion of between 0.1 and 0.6% by mass, zirconium in a proportion of between 0.02 and 0.06% by mass, phosphorus in a proportion of less than 0.02% by mass, the remainder of the alloy being copper and unavoidable impurities in a proportion of less than 0.1% by mass.

[0011] The process covered by French patent FR 3 078 078 comprises the following steps:

[0012] a) melting of the different components of the alloy, namely copper, chromium, zirconium and phosphorus, at a temperature above 1200°C, preferably between 1200°C and 1300°C;

[0013] b) continuous casting through a cylindrical die having a diameter D less than 30 mm, allowing to obtain a bar of a diameter close to the diameter D of the die with the maintenance of the liquid metal in the casting furnace at a temperature between 1100 and 1300°C;

[0014] c) solidification of said bar and cooling to a temperature below 100°C, the cooling rate being at least 10°C / s until a temperature of the bar of 1060°C is reached, then at least 15°C / s between 1060 and 1040°C, then at least 20°C / s between 1040 and 1030°C, then at least 25°C / s between 1030 and 1000°C, then at least 30°C between 1000 and 900°C, then at least 20°C / s for temperatures below 900°C, until the bar is cooled to a temperature of at most 100°C;

[0015] d) at least one drawing operation is carried out on said bar to obtain the final shape and cross-section of the wire, in particular wire drawing to obtain a fine wire of a diameter dl between 30 pm and 3 mm, preferably between 0.08 mm and 0.3 mm;

[0016] Note here that, possibly, following this step d) of wire drawing, a step may be implemented in which a surface treatment operation is carried out by depositing a thin layer of a nickel or silver coating, preferably after surface preparation by cleaning, so as to prevent the formation of oxides during the subsequent use of the cable which would generate risks of corrosion, welding difficulties or high frequency conductivity.

[0017] e) final heat treatment, or final tempering treatment, at a temperature between 450 and 500°C for a duration between 1h and 4h.

[0018] The conducting wire thus obtained, following the implementation of these steps, has, on the one hand, a load resistance at break Rm greater than or equal to 414 MPa, on the other hand an electrical conductivity greater than or equal to 85% IACS (International Annealed Copper Standard), and a minimum elongation of 6 to 9% depending on the diameter of the wire.

[0019] It is further indicated that two wire drawing operations can be implemented during the process of manufacturing a conductive wire.

[0020] Thus, in this case, a first wire drawing is carried out following step c) of solidification of said bar and rapid cooling.

[0021] The second wire drawing can be carried out after the surface coating step with silver or nickel.

[0022] However, it is also conceivable that this second wire drawing is carried out directly after the first wire drawing step d).

[0023] Typically, good practice is to separate the wire drawing deformation into two phases, a first phase before the surface preparation and silvering operation, which allows going from the initial diameter of the bar, DO less than 30 mm, at the exit of the solution treatment of step c), to a wire of diameter noted DA, between 30 pm and 3 mm.

[0024] On this wire with diameter DA the silvering (or nickel plating) treatment is carried out, then a second phase by drawing the silver or nickel-plated wire allows obtaining the final diameter DF, less than DA and greater than 30 pm, preferably between 80 and 300 pm.

[0025] Thus, the invention which is described in French patent FR 3 078 078 consists of a process which integrates the solution treatment (step c)) directly during the casting process, after complete solidification.

[0026] The process described here imposes a particular cooling kinetics (or cooling rate), which starts at 1060°C.

[0027] Such cooling kinetics allows for maximum dissolution of the chromium and zirconium present in the starting alloy. Consequently, using the process described here, the proportion of Cr and Zr atoms outside of solution is considerably reduced. However, it is these atoms outside of solution, which are a few micrometers in size, that cause wire breakage during drawing, especially when the desired wire diameter is small, particularly less than 0.1 mm.

[0028] In an earlier, more traditional wire manufacturing method described in European patent EP 0 902 096, the solution treatment is carried out on a diameter of 6.35 mm or less, at a temperature between 870 and 982 °C.

[0029] Such a temperature, much lower than in the previously described French patent, does not allow the advantages highlighted in said patent, in particular limiting wire breakage during wire drawing.

[0030] The method of European patent EP 0 902 096 has the advantage, however, of allowing the use of traditional means to carry out the dissolving and quenching of the wire.

[0031] In the case of European patent EP 0 902 096, the process begins with a solution treatment between 870 and 982 °C, as mentioned above, followed by a first drawing stage to bring the wire to an intermediate diameter, between 0.762 and 3.175 mm, followed by an intermediate tempering heat treatment at a temperature between 316 and 538 °C, for a duration of between 15 min and 10 h.

[0032] After this heat treatment, a second wire drawing step is carried out to bring the wire to its final diameter, less than or equal to 0.254 mm.

[0033] A final tempering treatment is then carried out, the conditions of which are defined identically to those implemented during the intermediate heat treatment, from 15 min to 100, at a temperature between 316 and 538 °C.

[0034] Thus, we usually go through a wire of intermediate diameter, between the solution treatment and the final diameter of the product, before the realization, for example, of a stranded cable by means of a plurality of wires obtained by one or the other of these processes.

[0035] In prior art patents, the characteristics of the finished HSHCCA fine wire, after the final tempering heat treatment, are defined by ASTM B624 with a tensile strength Rm greater than or equal to 414 MPa, an electrical conductivity greater than or equal to 85% IACS, and a minimum elongation of 6 to 9%, depending on the wire diameter.

[0036] In the present invention, it was sought to use the intermediate step, during which the wire is brought to an intermediate diameter, before the final diameter, this step being generally necessary, in order to design an innovative HSHCCA conductive wire.

[0037] Such an HSHCCA conductive wire will, on the one hand, facilitate the implementation of subsequent complementary steps, in particular to avoid breakage during subsequent wire drawing and to facilitate the coating of said innovative conductive wire, which can then be described as "intermediate", with silver or nickel, and, on the other hand, improve the mechanical characteristics of the coated fine conductive wire, or HSHCCA coated fine wire, obtained from this intermediate HSHCCA conductive wire, and also, finally, improve the characteristics of a conductive cable made from a plurality of such HSHCCA coated fine wires.

[0038] In an inventive approach, the inventors conceived of implementing, firstly, the first steps of the manufacturing process of a conductive wire as described in the previous patent FR 3 078 078, then of defining a particular diameter Di of wire, between the diameter Dc of the bar as cast, and the diameter DF of the finished fine conductive wire, on which wire of diameter Di will be implemented, in combination, an intermediate and original heat treatment process, corresponding to an under-tempering treatment and different from the final heat treatment, then an additional operation of reducing the cross-section, particularly limited, of the wire down to a wire diameter noted, in the rest of the application, DA.

[0039] Next, to produce the HSHCCA coated fine conductive wire, it will be necessary to start from this innovative HSHCCA conductive wire and implement the following steps:

[0040] - silver and nickel plating treatment;

[0041] - section reduction or final wire drawing;

[0042] - final heat treatment.

[0043] By combining, in the end, a plurality of HSHCCA coated fine conductive wires, in particular between 2 and 400 wires, in stranding or braiding operations, the conductive cable intended for commercialization is finally obtained.

[0044] To this end, the invention relates to a method for manufacturing an HSHCCA (High Strength High Conductivity Copper Alloy) conductive wire, intended for the subsequent manufacture of a thin HSHCCA-coated conductive wire, from an alloy consisting of chromium in a proportion of between 0.2 and 0.6% by mass, zirconium in a proportion of between 0.02 and 0.06% by mass, phosphorus in a proportion of less than 0.02% by mass, the remainder of the alloy being copper and impurities to be avoided, the sum of whose proportions does not exceed 0.1% by mass, said method comprising at least the following steps:

[0045] - fusion of the different components of the alloy, namely copper, chromium, the zirconium and phosphorus, at a temperature above 1200 °C, preferably between 1200 °C and 1300 °C;

[0046] - continuous casting through a cylindrical die having a diameter D less at 30 mm, allowing to obtain a bar of a diameter DC close to the diameter D of the die with the maintenance of the liquid metal in the casting furnace at a temperature between 1100 and 1300 °C;

[0047] - solidification of said bar and cooling to a lower temperature at 100 °C, the cooling rate being at least equal to 10 °C / s until a bar temperature of 1060 °C is reached, then at least equal to 15 °C / s between 1060 and 1040 °C, then at least equal to 20 °C / s between 1040 and 1030 °C, then at least equal to 25 °C / s between 1030 and 1000 °C, then at least equal to 30 °C between 1000 and 900 °C, then at least equal to 20 °C / s for temperatures below 900 °C, until the bar is cooled to a temperature of no more than 100 °C;

[0048] - said process being characterized in that it comprises, following this step of solidification, the following steps, taken in order:

[0049] - first cold operation of reducing the cross-section by more than 99% of said bar to obtain the shape and section of the wire before heat treatment, with a diameter DI between DI min equal to 1mm and Dlmax equal to 2 mm;

[0050] - heat treatment of under-tempered wire with a diameter DI at a temperature between a minimum temperature (Tmin) of 440°C and a maximum temperature (Tmax) of 460°C, for a holding time of between 3 and 9 hours at Tmin and between 1 and 3 hours at Tmax, or for a maintenance period proportionate to an intermediate temperature between Tmin and Tmax;

[0051] - performing at least one second cold operation to reduce the cross-section by 5 at 20% on said wire with a diameter DI to obtain the final shape and section of the conducting wire, with a diameter noted DA;

[0052] said HSHCCA conductor wire having a breaking load resistance Rm greater than or equal to 500 MPa, and an electrical conductivity between 83 and 90% IACS (International Annealed Copper Standard) and an elongation less than 6%.

[0053] According to particular embodiments of the process:

[0054] - the heat treatment of the under-temperature of step e) is carried out at a temperature equal to 460 °C, for a period of between 1 h and 3 h, more preferably for a period of 2 h;

[0055] - the heat treatment of the under-temperature of step e) is carried out at a temperature equal to 440 °C, for a period of between 3 h and 9 h, more preferably for a period of 6 h;

[0056] - said HSHCCA conducting wire has a diameter DA between DAmin and at 0.89 mm and DAmax equal to 1.95 mm, depending on the starting diameter DI and the applied section reduction rate;

[0057] - the implementation of step f) on a wire of diameter Dl, obtained following step e), in combination with step e), is capable of reducing the electrical conductivity by at least 2% IACS, and of reducing the elongation of said wire by at least 40% of its initial value at the end of step e), and of increasing the value of the load resistance at break Rm by at least 8%;

[0058] step f) of cold section reduction of 5 to 20% is followed by a step fl) of conditioning the HSHCCA conductor wire by bending into a drum or by winding onto a reel or drum;

[0059] The present invention also relates to a method for manufacturing a thin HSHCCA coated conductive wire from the HSHCCA conductive wire obtained according to the detailed process above, in which, after step f) of cross-section reduction, the following steps are carried out: • Silver plating or nickel plating treatment on the HSHCCA conductor wire with a diameter noted DA; • Third cold cross-section reduction operation on said coated HSHCCA conductor wire to obtain the final shape and cross-section of the coated HSHCCA fine conductor wire, with a diameter noted DF; • Final heat treatment to obtain the HSHCCA coated fine conductor wire.

[0060] Preferably, in this process:

[0061] - the third cold section reduction operation consists of wire drawing for switch from DA to DF, with DF between 0.05 mm and 0.3 mm;

[0062] - the final heat treatment is carried out at a temperature between 450 °C and 550 °C, with a holding time of between 1 h and 3 h;

[0063] - said HSHCCA coated fine conductor wire exhibits a load resistance at the rupture Rm greater than 450 MPa, electrical conductivity greater than 90% IACS and elongation A greater than 6%.

[0064] The present invention also relates to a method of manufacturing a conductive cable from a plurality of identical HSHCCA coated fine conductive wires, obtained according to the method, assembled by a stranding operation to obtain said conductive cable.

[0065] Other objects and advantages of the present invention will become apparent during the following description relating to embodiments which are given only by way of indicative and non-limiting examples.

[0066] Understanding this description will be facilitated by referring to the drawings attached in the appendix, in which:

[0067] [Fig.1A] and [Fig.1B] correspond to two graphs; the first, in Figure [Fig.1A] showing the effect of work hardening, by a reduction of section, for different reductions of section from 10 to 75% on copper, and of the annealing temperature (on the x-axis, in degrees Celsius °C), on the Vickers hardness (HV, on the y-axis) of copper Cu-al, for an annealing of one hour; the second graph in Figure [Fig.1B] shows the variation of the tensile strength (*1000 psi) as a function of temperature for different concentrations of Zr in the alloy;

[0068] [Fig.2A] and [Fig.2B] correspond to two graphs, from chapter 3 "structural hardening" publication CICLA (Centre d'Information du Cuivre, Laitons et Alliages), the first, in figure [Fig.2A], illustrates the variation of the hardness (Brinell hardness on the ordinate) of a copper with 0.6% chromium quenched (at 1030°C / 10 min / water), as a function of the duration (min then hours, on the abscissa) and of different tempering temperatures between 350 and 550 °C; on figure [Fig.2B] is illustrated the variation of the electrical conductivity (IACS %) of a copper with 0.6% chromium quenched (at 1030°C / 10 min / water), as a function of the duration (min then hours, on the abscissa) and of different tempering temperatures between 350 and 550 °C;

[0069] [Fig.3] corresponds to a scatter plot illustrating, for an imposed section reduction of 7%, followed by an intermediate heat treatment, under different time and temperature conditions, namely 480°C for 2h, or 500°C for 3h, or 460°C for 2h, the elastic limit values ​​(Rp, in MPa, on the ordinate), and IACS conductivity (on the abscissa, in % IACS) of the HSHCCA conducting wire obtained, in order to demonstrate the interest and effect of the process of the invention;

[0070] [Fig.4] corresponds to a graph in the form of two histograms illustrating the dispersion of the elongation values ​​(A in %) according to the conditions implemented during the intermediate heat treatment step, namely at 460°C for 2h for the histogram in grey, located on the left of the figure, and at 440°C for a holding time of 2h also, for the histogram represented in black, on the right.

[0071] [Fig.5] corresponds to a graph with two curves representing the evolution of the IACS conductivity (in %) on the one hand, and of the elongation (in %) on the other hand, as a function of the section reduction rate imposed during the section reduction step f), after a heat treatment at 460 °C for a duration of 2h.

[0072] The present invention relates to a method for manufacturing a HSHCCA conductive wire, that is to say having a diameter, noted DA, preferably between about 1 mm and about 2 mm.

[0073] Such a conducting wire can, in the present invention, be described as an “intermediate” wire because it is capable of being used for the subsequent manufacture of a thin HSHCCA coated conducting wire.

[0074] In other words, the HSHCCA conductor wire, at the end of the process according to the present invention, can be intended to undergo a plurality of further steps, which will be detailed later in this description, before resulting in the HSHCCA coated fine conductor wire.

[0075] The combination of a multitude of HSHCCA coated fine conductive wires, in particular between 2 and 400 coated fine conductive wires, by braiding or stranding, allows the manufacture of a conductive cable which can finally be marketed.

[0076] That being said, the HSHCCA conductor wire from the process of the invention can also constitute a finished product.

[0077] Returning to the HSHCCA conductor wire according to the present invention, this wire is, more particularly, manufactured from an alloy initially composed of, as a percentage by mass relative to the total mass of the alloy:

[0078] - of chromium (Cr) in a proportion of between 0.2 and 0.6% by mass,

[0079] - of zirconium (Zr) in a proportion of between 0.02 and 0.06% by mass,

[0080] - of phosphorus (P) in a proportion of less than 0.02% by mass,

[0081] the remainder of the alloy being copper (Cu) and inevitable impurities in a proportion less than 0.1% by mass, in other words impurities to be avoided whose sum of proportions cannot exceed 0.1%.

[0082] The method for manufacturing an HSHCCA conductive wire according to the present invention comprises a succession of steps, namely at least the steps which will be described in detail, and in order, in the continuation of the description.

[0083] In a first step of the process, step a), the different components of the alloy, which have been detailed previously, namely Cu, Cr, Zr and P, are melted at a temperature greater than or equal to 1200 °C.

[0084] Preferably, the melting of the alloy constituents is carried out at a temperature between 1200 °C and 1300 °C.

[0085] Following the melting of the different constituent elements of the alloy, a step b) of continuous casting is implemented, through a cylindrical die having a diameter D less than or equal to 30 mm.

[0086] During this step, the liquid metal is maintained in the casting furnace at a temperature between 1100 and 1300 °C.

[0087] Step b) of the process of the invention makes it possible to obtain a bar of a diameter denoted Dc, close to the diameter D of the die, and less than 30 mm.

[0088] Step c) of the process consists of solidifying said bar of diameter Dc and cooling it down to a temperature below 100 °C.

[0089] During this step, the cooling rate is at least equal to 10 °C / s until the bar reaches a temperature of 1060 °C, then at least equal to 15 °C / s for a bar temperature between 1060 and 1040 °C, then at least equal to 20 °C / s between 1040 and 1030 °C, then at least equal to 25 °C / s between 1030 and 1000 °C, then at least equal to 30 °C / s between 1000 and 900 °C, then at least equal to 20 °C / s for temperatures below 900 °C, until the bar is cooled to a temperature of at most 100 °C.

[0090] It should be noted here that steps a), b) and c) of the present process are similar to the steps implemented in the known prior art process described in French patent FR 3 078 078.

[0091] Following the implementation of step c) of solidification and cooling, we therefore have a bar, having a diameter denoted Dc, less than or equal to 30 mm, having undergone a particular solution treatment.

[0092] Said bar of diameter Dc has a particularly large length, so that it can be wound into a coil by bending before the implementation of the following steps of the manufacturing process of the HSHCCA conductive wire according to the invention.

[0093] Step d) of the present process consists of a first cold operation, in particular a drawing or wire drawing of the bar, this operation being more specifically defined by a reduction in cross-section of more than 99% of said bar to obtain the shape and cross-section of the wire before the implementation of a heat treatment step of under-tempering.

[0094] In a manner that is entirely preferable to the process of the present invention, step d) of the process makes it possible to go from the initial diameter Dc of the bar (less than 30 mm), to a diameter Di between Dimin, which is equal to 1mm, and Dimax equal to 2 mm.

[0095] The section reduction rate which is applied during a cold operation allowing a reduction in the diameter of a bar or wire, and to go, in the present case, from an initial casting diameter Dc to a diameter smaller than the initial diameter, in this case Db, is calculated using the following mathematical formula: (Dc2 - Di2) / Dc2, the section reduction rate being expressed in %.

[0096] It was determined by the inventors that, following this first step d) of section reduction, the characteristics of the wire obtained, in terms of electrical conductivity, tensile strength Rm and elongation, are as follows: % IACS > 45; Rm > 430 MPa and A% > 0.5%.

[0097] However, such characteristics may not be optimal, and their dispersion may be detrimental, to the conduct of the subsequent steps usually implemented following the first phase of section reduction, namely surface preparation and silvering or nickel plating, followed by the second phase of wire drawing.

[0098] In particular, the flexibility of the wire following this first phase of section reduction is likely to be insufficient, and may therefore lead to risks of breakage at the final wire drawing stages, as well as brittleness and adhesion defects of the coating (Ag or Ni), also during the final wire drawing.

[0099] On the contrary, in the process of the invention, following the first phase of section reduction, during the subsequent heat treatment e) and section reduction conditioning f) steps which are implemented, and which are specific to the present process of manufacturing a conductive wire of the invention, these three characteristics (% IACS, Rm and A%) will evolve, in particular as a function of the heat treatment adjustment parameters and the applied section reduction rate, so as to reach particularly optimal values ​​for obtaining an HSHCCA conductive wire with improved performance.

[0100] On this HSHCCA wire, it will then be particularly easy to implement further treatments, for obtaining a fine conductive wire coated with HSHCCA, compared with existing processes in the prior art, not implementing these steps e) and f) combined.

[0101] Thus, step e) of the present process consists of a sub-tempered heat treatment performed on said wire having the diameter Db

[0102] This heat treatment, which can be described as intermediate because it is carried out between two cross-section reduction steps, is preferably performed between a minimum temperature Tmin equal to 440°C and a maximum temperature Tmax equal to 460°C, knowing that the time spent at temperature Tmax must be between 1 h and 3 h maximum while the time spent at Tmin must be increased and between 3 h and 9 h.

[0103] In a particularly preferred manner, such an intermediate heat treatment is carried out either at a temperature equal to or about equal to 460 °C for a holding time equal to, or about equal to, 2h.

[0104] Indeed, such conditions make it possible to obtain, in the end, after the implementation of step f) which will be described below, an HSHCCA conductor wire having characteristics, in terms of Rm, A% and %IACS, which are particularly high and interesting for the following operations and the realization of a thin coated HSHCCA conductor wire, and then of a conductor cable with improved performance.

[0105] The results and methods of conducting comparative tests, illustrating this improvement in characteristics, will be given below, by way of non-limiting examples.

[0106] However, it is also conceivable that the intermediate heat treatment of step e) of the present process may be carried out at a temperature below 460°C, in particular at a temperature of 440°C, by increasing the holding time, in particular for a period of between 3 h and 9 h and, more particularly, for a period of 6 h.

[0107] It was thus determined that the under-revenue treatment of step e) is optimized between a minimum temperature Tmin of 440°C and a maximum temperature Tmax of 460°C. The minimum holding time is 1 h at 460°C and 3 h at 440°C, and the holding time can be adjusted proportionally for an intermediate temperature between Tmin and Tmax.

[0108] The maximum holding time is 3 h at 460° and 9 h at 440°C and it can, again, be defined proportionally for an intermediate temperature between Tmin and Tmax.

[0109] Thus, for example, at an intermediate temperature of 450 °C, the holding time can advantageously be between 2 h and 6 h.

[0110] It is recalled here that a revenue treatment usually applied, following a section reduction, will have two effects:

[0111] - The release of mechanical stresses accumulated by work hardening of the material during the first cold deformation;

[0112] - The diffusion of chromium and zirconium atoms put into solution during the step a) through the crystal lattice.

[0113] Regarding the first effect of stress release, the greater the reduction in cross-section during cold deformation, the lower the annealing temperature.

[0114] The attached [Fig. 1 A] shows the effect of work hardening by reducing the cross-section from 10% to 75% on copper, and the influence of the annealing temperature and the work hardening rate on the hardness of copper for an anneal of one hour.

[0115] It can be deduced that, for a section reduction rate greater than 99%, the first effect will be complete for tempering temperatures greater than 200°C.

[0116] As shown in [Fig.1B], zirconium acts inversely to the cold reduction rate on the work hardening retention of the material.

[0117] In the case of a cold reduction greater than 70%, softening starts at a temperature of 300 to 400 °C.

[0118] From a concentration of 0.019% of Zr, a hardening “bump” appears due to the effect of precipitation (effect 2 above), clearly visible for a concentration of Zr of 0.07%, which corresponds to a value slightly higher than the maximum concentration of 0.06% of Zr possible in the alloy on which the process of the present invention is implemented.

[0119] Alloy addition elements can delay the release of stresses introduced during cold wire drawing, such as Zr which acts on work hardening retention up to temperatures of 300 to 400 °C.

[0120] In summary, the first effect will be complete at a temperature level lower than the temperature of step e) of the process of the invention.

[0121] With reference now to Figures 2A and 2B of the accompanying drawings, concerning the second diffusion effect of Cr and Zr atoms through the crystal lattice, during temperature rise, the Cr and Zr atoms accumulate in GP zones (or Guinier-Preston zones, < 10 nm) and form a semi-coherent structure with the matrix. These constitute a very significant perturbation of the lattice, which manifests itself as substantial hardening, and consequently an increase in the tensile strength Rm.

[0122] Over time, and especially under the effect of temperature, the Cr and Zr atoms gradually organize themselves inside the GP zones until the atoms are transformed into precipitates, with a structure of their own inconsistent with the structure of the copper matrix.

[0123] By continuing to increase the time and temperature of tempering, the precipitates coalesce together, the treatment is then described as "over-tempering", and the softening of the material accelerates.

[0124] The tempering time to reach maximum resistance ([Fig.2A]) is lower the higher the temperature, and the tempering time to reach maximum conductivity is lower the higher the temperature.

[0125] Thus, for the conditions of a final income, a maximum of mechanical resistance and electrical conductivity will be sought here, which leads to starting the transformation of GP zones into precipitates, with an incoherent own structure, without however reaching over-tempering, which would lead to the very rapid coalescence of the precipitates to dimensions of several microns, resulting, on the one hand, in a decrease in mechanical resistance, difficulties in carrying out the subsequent wire drawing, and, on the other hand, the prevention of sufficient hardening during the final tempering heat treatment.

[0126] Note that the transformation of GP zones into incoherent precipitates is irreversible, except by carrying out a new solution treatment, which should be avoided for a wire diameter like that of the wire which constitutes the present invention.

[0127] It is understood that the implementation of a heat treatment step at this stage of the manufacturing process of a fine wire is particularly delicate, and it could be envisaged not to carry out such a heat treatment, after the first wire drawing stage, just as in the usual processes of the prior art, before carrying out the silver or nickel coating stage.

[0128] In particular, the process covered by patent FR 3 078 078 does not include a heat treatment step for the production of the wire on which the silvering or nickel plating treatment is then carried out.

[0129] However, it should be noted here that such an option presents the following difficulties:

[0130] - risk of wire breakage during the final wire drawing stages;

[0131] - fragility and poor adhesion of the silver or nickel plating, depending on the in this case, during the second phase of wire drawing;

[0132] - mechanical characteristics conforming to, but very close to, the requirements of the ASTM B624 standard mentioned above, in other words without significant improvement in characteristics.

[0133] The present invention therefore consists of carrying out an under-tempering treatment, with a determined duration and temperature, as already defined above, and combining this under-tempering treatment with a wire drawing step with a low cross-section reduction ratio, so as to allow the characterization of an intermediate wire state, which will facilitate the subsequent manufacturing steps for obtaining the coated fine conductive wire, and will improve the performance of said wire, as well as that of a cable made from a plurality of such wires.

[0134] Thus, during step f) subsequent to the under-income treatment e), implemented in the present process, a second cold operation is carried out.

[0135] During this step f), a limited section reduction, with a rate between 5 and 20%, is implemented on said wire with an initial diameter Di, to obtain the final shape and section of the HSHCCA conducting wire, with a diameter denoted DA.

[0136] Thus, considering a wire, obtained following the first drawing step d), and having a diameter Dimin equal to 1 mm, on which is applied during step f) with a section reduction rate of 5% to 20%, a HSHCCA conductor wire with a diameter Da between 0.97 mm and 0.89 mm (DAmin) is finally obtained.

[0137] If we now consider a wire having a diameter Dimax equal to 2 mm, on which is applied during step f) a reduction rate of cross-section of 5% to 20%, a conducting wire HSHCCA of diameter DA between 1.95 mm (DAmax) and 1.79 mm is finally obtained.

[0138] Consequently, at the end of the process of the invention, a conductive wire HSHCCA is obtained having a diameter between approximately 1 mm (minimum diameter DAmin of 0.89 mm) and approximately 2 mm (maximum diameter DAmax of 1.95 mm).

[0139] It has been demonstrated by the inventors that the implementation of step f) on a wire of diameter Db obtained following step e), in combination with step e), is capable of reducing the electrical conductivity by at least 2% IACS, and of reducing the elongation of said wire by at least 40% of its initial value at the end of step e).

[0140] In addition, the limited section reduction of step f) results in an increase in the value of the load resistance at break Rm of at least 8%.

[0141] Consequently, after implementation of the process of the invention, said HSHCCA conducting wire has the following characteristics:

[0142] - a breaking load resistance Rm greater than or equal to 500 MPa,

[0143] - an electrical conductivity between 83 and 90% IACS (International Annealed Copper Standard) and

[0144] - an elongation of less than 6%, resulting from the reduction of cross-section at low temperatures, between 5 and 20% of step f), applied after the under-income processing of step e).

[0145] It should be noted that, in an alternative embodiment, the cold drawing step f) could possibly have a cross-section reduction ratio greater than 20%; however, in this event, this drawing necessarily requires passing through an intermediate state which corresponds to a cross-section reduction ratio between 5 and 20%, so that, in this intermediate state, the wire obtained has the same characteristics as those mentioned above.

[0146] Similarly, it could be envisaged to implement a cold wire drawing step with a section reduction rate of less than 5%, but which would in this case necessarily be followed by wire drawing with a section reduction rate between 5 and 20% to obtain the desired characteristics.

[0147] Advantageously, for the implementation of steps e) and f), coils of wire, with a mass of 500 to 1000 kg, can be arranged in a static tempering furnace, under atmosphere.

[0148] From each coil, the HSHCCA conductor wire is produced by applying the limited section reduction between 5 and 20%, then it can be conditioned, in a step fl), by bending into a drum or by winding onto a reel or drum, with a quantity of wire from 110 to 260 kg, on average 200 kg.

[0149] Note that, in the case of drum packaging, the HSHCCA conductor wire coils are positioned flat and said wire must not turn around in the drum, in order to ensure subsequent correct unwinding of said wire.

[0150] The limited section reduction, with a rate between 5 and 20%, greatly facilitates the proper conditioning of the wire, while the quality of its surface is very favorable for carrying out a subsequent silver or nickel coating treatment, while maintaining optimal wire flexibility.

[0151] Indeed, from the HSHCCA conductive wire obtained by implementing the steps of the process of the present invention, detailed above, it is then possible to obtain a thin HSHCCA coated conductive wire, by implementing the following steps, following step f) of limited cross-section reduction between 5 and 20% and allowing to obtain said HSHCCA wire of diameter DA substantially between about 1 and about 2 mm (more precisely between DAmin of 0.89 mm and DAmax of 1.95 mm):

[0152] g) silver plating or nickel plating treatment on the HSHCCA conductor wire with a diameter denoted DA, which can then be described as intermediate;

[0153] h) third cold cross-section reduction operation on said HSHCCA intermediate conductor wire to obtain the final shape and cross-section of the HSHCCA coated fine conductor wire, with a diameter denoted DF, between 0.03 and 0.3 mm;

[0154] i) final heat treatment to obtain the HSHCCA coated fine conductive wire.

[0155] Most preferably, the third cold section reduction operation of the aforementioned step h) consists of a wire drawing to go from a diameter DA (between, for the record, DAmin equal to 0.89 mm and DAmax equal to 1.95 mm) to a final diameter noted DF, with DF between DFmin equal to 0.05 mm and DFmax equal to 0.3 mm.

[0156] Thus, it is understood that the final section reduction of step h) is carried out according to a section reduction rate of between 88.6 and 99.9%, following a section reduction of 5% to 20% during step f) carried out on a wire with a diameter of between 1 and 2 mm.

[0157] Advantageously, the final heat treatment is carried out at a temperature between 450 °C and 550 °C, with a holding time at this temperature of between 1 h and 3 h.

[0158] The implementation of these final steps makes it possible to obtain a thin HSHCCA coated conductor wire which has particularly interesting characteristics, namely a load resistance at break Rm greater than 450 MPa, an electrical conductivity greater than 90% IACS and an elongation A greater than 6%.

[0159] Consequently, the finished cable, obtained by assembling a plurality of such fine conducting wires, will perform better than state-of-the-art cables.

[0160] If we now summarize the entire process for manufacturing a thin HSHCCA coated conductive wire, it therefore presents the following steps, taken in order:

[0161] a) melting of the different components of the alloy, namely copper (remaining), chromium (between 0.2 and 0.6%), zirconium (between 0.02 and 0.06%), phosphorus (less than 0.02%), at a temperature above 1200 °C, preferably between 1200 °C and 1300 °C;

[0162] b) continuous casting through a cylindrical die having a diameter D less than 30 mm, allowing to obtain a bar of a diameter Dc close to the diameter D of the die with the maintenance of the liquid metal in the casting furnace at a temperature between 1100 and 1300 °C;

[0163] c) solidification of said bar and cooling to a temperature below 100 °C, the cooling rate being at least 10 °C / s until a temperature of the bar of 1060 °C is reached, then at least 15 °C / s between 1060 and 1040 °C, then at least 20 °C / s between 1040 and 1030 °C, then at least 25 °C / s between 1030 and 1000 °C, then at least 30 °C between 1000 and 900 °C, then at least 20 °C / s for temperatures below 900 °C, until the bar is cooled to a temperature of at most 100 °C;

[0164] d) first cold operation of reducing the cross-section of said bar by more than 99% to obtain the shape and cross-section of the wire before heat treatment, with a diameter Di between Dimin equal to 1mm and Dimax equal to 2 mm;

[0165] e) heat treatment of under-tempered on said wire with a diameter Di either at a temperature less than or equal to 460 °C for a holding time between 1 and 3 h, or at a temperature less than 460 °C and greater than or equal to 440 °C by increasing the holding time between 3 and 9 hours, preferably at 460 °C for 2 h or 460 °C for 6 h;

[0166] f) carrying out at least one second cold operation of reducing the cross-section by 5 to 20% on said wire with a diameter Di to obtain the final shape and cross-section of the HSHCCA conductor wire, with a diameter noted DA between DAmin equal to 0.89 mm and DAmax equal to 1.95 mm, depending on the starting diameter Di and the cross-section reduction rate applied;

[0167] g) silver plating or nickel plating treatment on the HSHCCA conductor wire with a diameter noted DA between DAmin equal to 0.89 mm and DAmax equal to 1.95 mm;

[0168] h) third cold cross-section reduction operation on said HSHCCA coated conductor wire to obtain the final shape and cross-section of the HSHCCA coated fine conductor wire, with a diameter denoted DF, preferably between DFmin equal to 0.05 mm and DFmax equal to 0.3 mm.

[0169] i) final heat treatment to obtain the finished HSHCCA coated fine conductor wire, or HSHCCA coated wire, advantageously carried out at a temperature between 450 and 550 °C for 1 to 3 h.

[0170] The interest and effects of implementing the combined steps e) and f) in the process of the present invention for manufacturing an HSHCCA conductive wire, on the mechanical and electrical conductivity characteristics of a fine conductive wire will now be illustrated through the example below, given by way of non-limiting example.

[0171] Example: Measurement of the mechanical and electrical conductivity characteristics of thin wires after application of different heat treatments

[0172] During the tests carried out, the following steps were implemented for the manufacture of wires:

[0173] a) melting of the different components of the alloy, namely copper (remaining), chromium (0.2 to 0.6%), zirconium (0.02 to 0.06%) and phosphorus (< 0.02%), possibly with impurities to be avoided, the sum of whose proportions must not exceed 0.1%, the melting being carried out at a temperature of 1350 °C;

[0174] b) continuous casting through a cylindrical die having a diameter D allowing to obtain a bar of a diameter Dc equal to 28 mm with the maintenance of the liquid metal in the casting furnace at a temperature of 1250 to 1300 °C;

[0175] c) solidification of said bar and cooling to a temperature below 100 °C, the cooling rate being at least 10 °C / s until a temperature of the bar of 1060 °C is reached, then at least 15 °C / s between 1060 and 1040 °C, then at least 20 °C / s between 1040 and 1030 °C, then at least 25 °C / s between 1030 and 1000 °C, then at least 30 °C between 1000 and 900 °C, then at least 20 °C / s for temperatures below 900 °C, until the bar is cooled to a temperature of at most 100 °C;

[0176] d) first cold reduction operation of greater than 99% of said bar to obtain the shape and cross-section of the wire before heat treatment, with a diameter Di between 1 and 2 mm, more particularly equal to 1.5 mm; and

[0177] Following this cold drawing operation, various tempering heat treatments were implemented, namely:

[0178] - application of a temperature of 460 °C for a holding time of 2 h (conditions of the manufacturing process according to the present invention);

[0179] - application of a temperature of 480 °C for a holding time of 2 h;

[0180] - application of a temperature of 500 °C for a holding time of 3 h.

[0181] For each of these three different heat treatments, at each conditioning, three samples are taken, and the measurements of mechanical resistance (Rp expressed in MPa) and electrical conductivity (% IACS) are carried out.

[0182] It should be noted here that the quantity Rp corresponds to the proportionality limit, which is considered equivalent to the elastic limit. The elastic limit is calculated over a specimen length of 100 mm, and for an elongation of 0.2%.

[0183] As regards the resistance Rm, this corresponds to the maximum load before rupture.

[0184] Therefore, Rm is greater than Rp, statistically based on the transmitted results, and the relationship between the two quantities can be established as follows:

[0185] - If Rp = 450 MPa then Rm = 485 MPa;

[0186] - If Rp = 500 MPa then Rm = 525 MPa;

[0187] - If Rp = 550 MPa then Rm = 565 MPa.

[0188] The results in terms of mechanical resistance (Rp in MPa) and conductivity electrical (% IACS) are illustrated on the attached [Fig.3] graph, for an imposed section reduction of 7% at step f) of the process, following the heat treatment.

[0189] On this graph, a point is defined on the abscissa by the average conductivity and on the ordinate by the average mechanical resistance.

[0190] We observe:

[0191] - The dispersion of mechanical resistance of the points is low for the treatment of 460 °C for 2 hours;

[0192] - The dispersion of mechanical resistance increases with increasing temperature from 480 °C (2 h) to 500 °C (3 h);

[0193] - Maximum mechanical resistance is obtained after a treatment at 460 °C;

[0194] - The higher the heat treatment temperature above 460 °C, the more The extreme positions correspond to high conductivity and low mechanical resistance.

[0195] Thus, the under-tempering treatment of step f) according to the process of the present invention is particularly optimized, because it allows a reduction in the dispersion of mechanical characteristics, avoiding high electrical conductivity values, which are characteristic of an over-tempering treatment.

[0196] The diagram in [Fig.4] illustrates that lowering the under-tempering temperature to 440 °C, maintained for a period of 2 h, shows a lowering and greater dispersion of the elongation value after tempering, compared with under-tempering at a temperature of 460 °C for a period of 2 h.

[0197] Indeed, for an under-temperature treatment of 440 °C for 2 h, the elongation values ​​are between 2.5 and 5% while, for the same duration and an under-temperature of 460 °C, the elongation values ​​obtained are grouped between 4 and 5%.

[0198] However, such a reduction, as well as a greater dispersion, of the elongation value after tempering leads to a reduction in the flexibility of the wire, whereas optimal flexibility is required for carrying out the subsequent conditioning and silvering or nickel plating operations of the wire.

[0199] That being said, with regard to the other characteristics for applying a tempering treatment in step f) at a temperature of 440 °C for 2 h, it has been determined by the inventors that:

[0200] - the electrical conductivity values ​​in % IACS are lower than those obtained for treatment at a temperature of 460 °C for a duration of 2 h, but they remain close;

[0201] - the values ​​obtained in terms of mechanical resistance are particularly high, and systematically above 510 MPa, or even above 520 MPa.

[0202] The results obtained are not included in this description.

[0203] These results, and in particular the fact that the electrical conductivity is lower, demonstrate that, for an intermediate heat treatment temperature of 440 °C, for a holding time of 2 h, the precipitation treatment of the GP zones, accumulating Cr and Zr atoms, is not completed.

[0204] Thus, it can be deduced that, at a temperature of 440 °C, an adjustment, by increasing the tempering time, as indicated previously, to a duration between 3 h and 9 h, will allow an increase in the value of the electrical conductivity, while recovering optimal elongation characteristics, similar to those obtained for treatment at a temperature of 460 °C for 2 h, and sufficiently grouped, to allow good conduct of subsequent treatment operations on the fine conductive wire, when the process is intended for the production of an intermediate wire.

[0205] Furthermore, in all cases, when the temperature is increased beyond 460 °C, in particular to a temperature of 480 °C or 500 °C, whether for 2 h or 3 h, the value of the mechanical resistance Rp decreases, and the dispersion of the results increases, so that the temperature of 460 °C, associated with a duration of 2 h or 3 h, is a maximum.

[0206] The table below compares the results in terms of mechanical characteristics, namely the tensile strength Rm (in MPa) and elongation (A%), and in terms of electrical conductivity, under the following conditions:

[0207] - after a heat treatment of under-tempered material in accordance with step e) of the present invention, at a temperature of 460 °C for a holding period of 2 h;

[0208] - after a heat treatment of over-tempered at a temperature of 500 °C for a maintenance period of 3 hours.

[0209] This table also gives the mechanical and electrical conductivity characteristics after the conditioning step, i.e. after the application of the limited section reduction between 5 and 20% of step f) of the process of the present invention.

[0210] In this case, a 7% reduction in cross-section on the wire diameter was imposed.

[0211] The measurements of the characteristics (IACS %, Rm and A%) are therefore carried out after income and after conditioning.

[0212] __________________________________________________ 460 =C 26 500 °C 3h Rm MPA 497.4 A% 11.0 IACS% 87.0 Rm MPA JA% [_____IACS % 448.0 9.1 j 96.9 After tempering -- step e) Average After conditioning - step f} Average 535.7 4.6 85.2 469.4 | 8.6 j 95.9

[0213] The under-tempering implemented in the present process, compared with the over-tempering at 500 °C, is characterized by:

[0214] - a lower average conductivity value after tempering, namely 87% per ratio to almost 97%, and after conditioning, namely 85% versus almost 96%;

[0215] - a greater increase in the average value of the mechanical characteristics after conditioning; indeed, Rm increases by 8% after conditioning with under-income conditions, from an average of 497.4 MPa to 535.7 MPa, while Rm only increases by 4% after conditioning, with over-income conditions, from 448.0 MPa to 469.4 MPa.

[0216] - a lower average residual elongation value after conditioning, at namely 4.6% against 8.6%, which corresponds to a decrease in the lengthening value between after income and after final conditioning of more than 6% (from an lengthening of 11 to 4.6) i.e. a decrease of more than 40% of its initial value, more precisely a decrease equal to 58% of the initial value ((11-4.6) / 11).

[0217] On the contrary, for a heating at 500 °C for a period of 3 h, the decrease in elongation is only on the order of 5%, going from 9.1% after heating to 8.6% after conditioning ((9.1-8.6) / 9.1).

[0218] The essential result that can be achieved by combining the steps e) of under-tempering and f) of limited section reduction, specific to the process of the invention, is the guarantee of obtaining reproducible and homogeneous characteristics on different batches of wire, and regardless of the position of the wire coil in the furnace at the time of step e).

[0219] The cause of the dispersion of the characteristic values ​​is the transition to over-tempering during heat treatment, which manifests itself by an increase in IACS conductivity values ​​beyond 90%; it is necessary to avoid complete precipitation of chromium and maintain a post-conditioning conductivity between 83 and 90% IACS.

[0220] The inventors believe that step e) of under-tempering in the process of the present invention promotes the resuspension of the finest chromium precipitates by cold working, which is a highly original effect. Resuspension is characterized by a decrease in conductivity (compared to the over-tempering treatment), and it can be observed, from the results presented above, in a novel and previously undocumented manner, that the decrease in conductivity is accompanied by a substantial loss of elongation, reflecting, according to a hypothesis formulated by the inventors, the retention of very fine (nanometric) chromium precipitates.

[0221] A shift in equilibrium therefore occurs between precipitated chromium and chromium in solution, which is only possible in the presence of chromium nanoprecipitates from steps b) and c) of the process of the invention. This concomitant decrease in conductivity and elongation for a relatively small reduction in cross-section during step f) is the way to characterize the chromium precipitates of the material of the invention associated with a sub-temperature within the limits of step e).

[0222] Such conditions implemented in the process of the invention thus also make it possible to achieve values ​​of breaking load of the fine conducting wire after step f) of the present process substantially greater than 500 MPa.

[0223] Such results were obtained for the application of a section reduction during step f) equal to 7%. It can be deduced that the characteristics will evolve by increasing the section reduction up to a maximum of 20%.

[0224] Indeed, the values ​​of electrical conductivity and elongation will decrease, increasing the reduction in cross-section, as illustrated in the attached [Fig.5], while the tensile strength will increase.

[0225] However, the evolution is dampened with increasing section reduction (see [Fig.5]), and, beyond 20% section reduction, the values ​​of electrical conductivity and elongation decrease too significantly.

Claims

1. Demands A process for manufacturing an HSHCCA (High Strength High Conductivity Copper Alloy) conductive wire, intended in particular for the subsequent manufacture of a thin HSHCCA-coated conductive wire, from an alloy consisting of chromium in a proportion of between 0.2 and 0.6% by mass, zirconium in a proportion of between 0.02 and 0.06% by mass, phosphorus in a proportion of less than 0.02% by mass, the remainder of the alloy being copper and impurities to be avoided, the sum of whose proportions does not exceed 0.1% by mass, said process comprising at least the following steps: a) melting of the different components of the alloy, namely copper, chromium, zirconium and phosphorus, at a temperature above 1200 °C, preferably between 1200 °C and 1300 °C; b) continuous casting through a cylindrical die having a diameter D less than 30 mm, allowing to obtain a bar of a diameter Dc close to the diameter D of the die with the maintenance of the liquid metal in the casting furnace at a temperature between 1100 and 1300 °C; (c) solidification of said bar and cooling to a temperature below 100 °C, the rate of cooling being at least 10 °C / s until a temperature of the bar of 1060 °C is reached, then at least 15 °C / s between 1060 and 1040 °C, then at least 20 °C / s between 1040 and 1030 °C, then at least 25 °C / s between 1030 and 1000 °C, then at least 30 °C between 1000 and 900 °C, then at least 20 °C / s for temperatures below 900 °C, until the bar is cooled to a temperature of not more than 100 °C; said process being characterized in that it comprises, following this solidification step, the following steps, taken in order: d) first cold operation of reducing the cross-section of said bar to more than 99% to obtain the shape and cross-section of the wire before heat treatment, with a diameter Di between Dimin equal to 1mm and Dimax equal to 2 mm; e) heat treatment of under-tempered wire with a diameter Di at a temperature between a temperature Tmin equal to 440°C and a temperature Tmax equal to 460°C, for a holding time between 3 and 9 hours at Tmin and between 1 and 3 hours at Tmax, or for a holding time proportionate to an intermediate temperature between Tmin and Tmax; f) carrying out at least one second cold operation of reducing the cross-section by 5 to 20% on said wire with a diameter Di to obtain the final shape and cross-section of the conductor wire, with a diameter noted Da; said HSHCCA conductor wire having a tensile strength Rm greater than or equal to 500 MPa, and an electrical conductivity between 83 and 90% IACS (International Annealed Copper Standard) and an elongation of less than 6%.

2. A method for manufacturing an HSHCCA conductive wire according to claim 1 characterized in that the heat treatment of the under-tempered wire of step e) is carried out at a temperature of 460 °C, for a period of between 1 h and 3 h, more preferably for a period of 2 h.

3. A method for manufacturing an HSHCCA conductive wire according to claim 1 characterized in that the heat treatment of the under-tempered wire of step e) is carried out at a temperature of 440 °C, for a period of between 3 h and 9 h, more preferably for a period of 6 h.

4. A method for manufacturing an HSHCCA conductive wire according to any one of the preceding claims characterized in that said HSHCCA conductive wire has a diameter DA between DAmin equal to 0.89 mm and Da™ equal to 1.95 mm, depending on the starting diameter Di and the applied section reduction rate.

5. A method for manufacturing an HSHCCA conductive wire according to any one of the preceding claims characterized in that the implementation of step f) on a wire of diameter Dl, obtained following step e), in combination with step e), is capable of reducing the electrical conductivity by at least 2% IACS, and of reducing the elongation of said wire by at least 40% of its initial value at the end of step e), and of increasing the value of the load resistance at break Rm by at least 8%.

6. A method for manufacturing an HSHCCA conductive wire according to any one of the preceding claims, characterized in that Step f) of cold section reduction of 5 to 20% is followed by a step fl) of conditioning the HSHCCA conductor wire by bending into a drum or by winding onto a reel or drum.

7. A method for manufacturing a coated HSHCCA fine conductive wire from the HSHCCA conductive wire obtained according to any one of the preceding claims, characterized in that, after step f) of reducing cross-section, the following steps are carried out: g) Silver plating or nickel plating treatment on the HSHCCA conductive wire with a diameter denoted DA; h) Third cold operation of reducing cross-section on said coated HSHCCA conductive wire to obtain the final shape and cross-section of the coated HSHCCA fine conductive wire, with a diameter denoted DF; i) Final heat treatment to obtain the coated HSHCCA fine conductive wire.

8. A method for manufacturing a fine HSHCCA coated conductive wire according to the preceding claim, characterized in that the third cold cross-section reduction operation consists of drawing to go from DA to DF, with DF between 0.05 mm and 0.3 mm.

9. A method for manufacturing a fine HSHCCA coated conductive wire according to any one of claims 7 or 8 characterized in that the final heat treatment is carried out at a temperature between 450 °C and 550 °C, with a holding time between 1 h and 3 h.

10. A method for manufacturing a HSHCCA coated fine conductive wire according to any one of claims 7 to 9 characterized in that said HSHCCA coated fine conductive wire has a breaking load resistance Rm greater than 450 MPa, an electrical conductivity greater than 90% IACS and an elongation A greater than 6%.

11. Method of manufacturing a conductive cable from a plurality of identical HSHCCA coated fine conductive wires, obtained according to any one of claims 7 to 10, assembled by a stranding operation to obtain said conductive cable.

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