FR2804539A1 - METHOD FOR MANUFACTURING A CONDUCTIVE WIRE MADE OF A COMPOSITE MATERIAL WITH COPPER MATRIX AND CONDUCTIVE WIRE OBTAINED BY SAID METHOD - Google Patents

Abstract

The invention relates to a method of manufacturing a conductive wire made of a composite material having a copper matrix in which metallic or ceramic particles are dispersed, and the conductive wire obtained by this method. According to the invention, the method comprises the following steps: - providing a base wire made of said composite material, - coating the base wire with a ductile material in order to obtain a primary wire having a nominal diameter, the drawing of said primary wire is carried out in order to end up with a secondary wire having a final diameter, and an annealing treatment of said secondary wire is carried out in order to release the stresses induced by the drawing. Application to the manufacture of an electromagnetic shielding braid of an electric cable.

Description

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  The invention relates to a method for manufacturing a conductive wire.

  tor made of a composite material with a copper matrix in which are dispersed metallic or ceramic particles, and the wire

  conductor obtained from this process.

  Copper is a widely used material, due to its high electrical conductivity, as the material constituting the conductive wire.

  in electrical and electronic cables.

  However, copper has mediocre mechanical characteristics which are often insufficient for it to constitute the material of the cable conductor wire which must have high mechanical resistance,

especially in bending and torsion.

  Traditionally, a copper alloy is then used which, by different hardening mechanisms, has a mechanical strength superior to copper, while having an electrical conductivity at least equal to 85% of the electrical conductivity of copper. Among these

  alloys, there may be mentioned Cu-Cd, Cu-Zr, Cu-Fe and Cu-Cd-Cr.

  Among these alloys, the last aforementioned alloy (copper-cadmium-

  chromium) is widely used because it has an interesting electrical conductivity (90% of that of copper) and good mechanical resistance

  better than copper (tensile strength = 420 MPa).

  The object of the present invention is to provide a manufacturing process which makes it possible to obtain a conductive wire having better electrical conductivity than the alloys of the prior art, at the same time as increased mechanical resistance, in particular in torsion and in bending, as well as good stability at high temperature of these mechanical properties. The manufacturing process according to the present invention is characterized in that it comprises the following steps: - a base wire produced from said composite material is provided, - the base wire is coated with a ductile material in order to obtain a primary wire having a nominal diameter, - the primary wire is drawn by a wire to result in a secondary wire having a final diameter, and

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  an annealing treatment of said secondary wire is carried out in order to release the

  stresses induced by wire drawing.

  Advantageously, said ductile material belongs to the group

  including silver, gold, platinum, palladium and their alloys.

  In a particularly advantageous manner, said particles comprise aluminum oxide, preferably from 0.2 to 0.4% by weight

composite material.

  According to another advantageous arrangement, said coating step-

  The basic wire comprises the electrolytic deposition of a silver layer having a thickness of between 1 and 10 μm, preferably

between 3 and 6 pm.

  Preferably, said step of coating the base wire comprises the following steps: - alkaline degreasing of the base wire, rinsing with water of the base wire, - acid pickling of the base wire, - rinsing with water of the base wire, - electrolytic deposition of a silver undercoat on the base wire, - electrolytic deposition of a silver layer on said undercoat in order to form the primary wire, and

  - rinsing with water of the primary wire.

  A favorable solution as regards the manufacturing technique provides that the wire drawing comprises several passages in a cold multi-pass wire drawing machine and makes it possible to obtain a final diameter for the secondary wire at least five times smaller than the nominal diameter of the wire.

  primary, preferably substantially ten times smaller.

  The present invention also relates to a conductive wire as it results from the aforementioned manufacturing process, this conductive wire being produced from a composite material with a copper matrix in which the metallic or ceramic particles are dispersed, this wire being characterized in that that it further comprises a coating of ductile material and in that it has an electrical conductivity at least equal to 92% of the

  electrical conductivity of copper (International Annealed Copper Standard).

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  Furthermore, preferably, the conducting wire according to the present invention is characterized in that when an electromagnetic cable shielding braid is produced with said conducting wire, when said cable is subjected to a million (1,000,000) cycles of combined bending and twisting, each bending and twisting cycle corresponding to the passage of a section of cable relative to an initial position, on the one hand relative to a main direction of the cable from a position 0, to a position at +140, towards a position at -140 and the return to position 0 (torsion), and on the other hand with respect to a direction orthogonal to said main direction of the cable from a position 0, towards a position at +140, towards a position at -140 and the return to position 0 (bending), said

  braid has a maximum electrical resistance variation of 7%.

  In addition, preferably, the conductive wire has a value of

  tensile strength greater than or equal to 300 Mpa.

  Advantageously, said ductile material belongs to the group

  including silver, gold, platinum, palladium and their alloys.

  Preferably, the ductile material is a layer of silver obtained by electrolytic means and said particles comprise aluminum oxide, preferably from 0.2 to 0.4% by weight of the material.

composite.

  An exemplary embodiment will now be described and illustrated.

  below. It is understood that the description and the drawings are given only

indicative and not limiting.

  Reference will be made to the appended drawings, in which: - Figure 1 is a cross section of a cable used to carry out mechanical resistance tests of the conductive wire which is the subject of the present invention, - Figure 2 is a schematic representation of the test of flexural and torsional resistance used, and - Figure 3 is a comparative curve of the flexural and torsional resistance of the cable of Figure 1 depending on whether or not it uses the conductive wire

according to the present invention.

  According to one of the essential characteristics of the present invention, the method of manufacturing the conductive wire uses a basic wire

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  made of a composite material with a copper matrix in which are dispersed metallic or ceramic particles. The composite material used is therefore produced by powder metallurgy by uniformly dispersing fine metallic or ceramic particles (for example oxides, carbides, nitrides or silicides) in a

copper matrix.

  Thus, the effect of these dispersed particles on the metallurgical copper microstructure makes it possible, on the one hand, to increase the mechanical strengths of the material and, on the other hand, to maintain this mechanical strength up to high temperatures, without alter electrical conductivity too much

of the copper matrix.

  The manufacturing method according to the present invention makes it possible to obtain a conductive wire having, surprisingly, very high mechanical performance, electrical conductivity and resistance

mechanical at high temperature.

  The manufacturing method according to the present invention essentially comprises three stages of treatment of the basic wire produced in the aforementioned composite material, namely successively silvering, wire drawing

  and annealing heat treatment.

  The tests carried out used as composite material the "GLIDCOP" (registered trademark) sold by the company SCM Metal Products Inc. (reference UNS C15 715). This composite material contains from 0.25 to 0.35% by weight of aluminum oxide particles dispersed in the copper matrix and it has a maximum electrical conductivity equal to 92% of that of copper. The size of these particles is between 3 and 12 nanometers. A 0.8 mm diameter base wire made of this material was used as a starting point to develop a conductive wire according to the

present invention.

  The next step in the manufacturing process consists, in particular in order to avoid breaking the base wire during the subsequent passage through the cold drawing machine allowing the continuous reduction of the section of the base wire, to deposit a coating in money on the core wire this

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  coating preferably being produced electrolytically and

  having a thickness of 3 to 6 μm.

  More specifically, this step of coating the base wire with silver comprises the following steps: alkaline degreasing of the base wire, rinsing with water of the base wire, acid pickling of the base wire, rinsing with water. water from the base wire, electrolytic deposition of a silver undercoat on the base wire, electrolytic deposition of a silver layer on the

  undercoat to form a primary wire, and rinse the primary wire with water.

  This primary wire (silver wire) is then, in a second step, drawn continuously using a cold multi-pass wire drawing machine, the last dies used making it possible to end up with a secondary wire having a final diameter of 0.106 mm, or 0.100 mm or 0.079 mm. During this step, we see that the silver coating remains continuous and

  homogeneous and results in a layer of thickness approximately 1 pim.

  The last step of the manufacturing process consists of a heat treatment. The purpose of this heat treatment is to restore the ductility of the composite material by reducing the internal stresses of the material created by the wire drawing step. Advantageously, this heat treatment will consist of an annealing during which the secondary wire has been brought to a temperature of between 450 and 520 ° C. for a time of between 150 and 210 min. As can be seen in Table I below, this treatment

  thermal annealing significantly improves the characteristics

  mechanical and electrical characteristics of drawn wires. In this table, the value of the breaking load and the elongation during the rupture is reported in a tensile test, as well as the electrical conductivity of the wires expressed as a percentage of the electrical conductivity of copper called IACS. (International Annealed Copper Standard corresponding to

1.7241 micro.ohms.cm at 20 C).

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Table I

  Evolution of the characteristics of the wires before and after the heat treatment. Breaking load Elongation Conductivity MPa% _% IACS Basic wire 645 1.0 88 Wire 0 untreated 631 0.8 87 0.079 mm treated 357 5.5 94 Wire 0 untreated 694 1.2 88 0.106 mm treated 352 8.3 96 Surprisingly, we can therefore see that after the above annealing treatment, a conductive wire is obtained having an electrical conductivity of the order of 94 to 95% of the electrical conductivity of copper, that is to say much greater than that of the base wire. In addition, it is found that the conductive wire according to the present invention has better

  electrical conductivity than the alloys used in the prior art.

  In order to illustrate the thermal behavior of the conductive wire obtained according to

  the process of the present invention, that is to say the stability at high temperature

  eradication of these mechanical properties, the following test was carried out.

  A conductive wire of Cu-Cd alloy and a conductive wire resulting from the method according to the present invention, the two wires having a diameter of 0.1 mm, were brought to 400 C for one hour. The reduction in tensile strength of these wires was measured after this

thermal aging.

  It is found that the conductive wire of Cu-Cd alloy has a loss of 20% of its tensile strength at break while the conductive wire according to the present invention has only a loss of tensile load of 5%. It therefore follows that the conductive wire from the manufacturing process according to the present invention has better

  thermal resistance compared to a conductive wire of Cu-Cd alloy.

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  In order to complete the tests making it possible to evaluate the mechanical resistance of the conductive wire resulting from the process according to the present invention, a test of resistance to bending and to torsion was set up. In this test, the conductive wire resulting from the manufacturing process according to the present invention was used for the formation of an electromagnetic shielding braid at

  within an electric cable which is illustrated in figure 1.

  This cable 10 comprises one hundred and forty two coaxial conductors distributed within eight groups (reference 12) of sixteen coaxial cables and seven pairs (reference 14 of coaxial cables). All the coaxial io cables are twisted around a central anti-tearing fiber 16, all

  being wrapped in a ribbon 18 surrounded by the shielding braid 20, it

  even protected by an outer sheath 22 of plastic material.

  During this flexural and torsional resistance test illustrated in FIG. 2, a sample 24 of the cable 10 described above is subjected to

  combined bending and twisting cycles.

  During each cycle, the flexion aspect comprises rotational movements relative to a horizontal axis (X, X '), these movements being constituted by the passage of the sample 24 from an initial position 0 to the position +140 , then its passage from position +140 to position -140 and finally its passage from position -140 to position

initial 0.

  For this, the sample 24 crosses orthogonally a horizontal beam 26 driven in rotation (drive mechanism not shown) and which imposes the movement described above back and forth in rotation (arrow A in FIG. 2) around of the horizontal axis (X, X ') which

  is parallel to the longitudinal direction of the beam 26.

  During each cycle, the torsion aspect comprises rotational movements relative to an axis (Y, Y ') orthogonal to the horizontal axis (X, X') mentioned above, these movements being constituted by the passage of the sample 24 from an initial position 0 to position +140, then its passage from position +140 to position -140 and finally its passage from

  position -140 to initial position 0.

  To this end, a torsion module 28 crosses the beam 26 along the axis (Y, Y ') by forming a pivot connection, a section of the sample 24

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  being integrally housed inside the torsion module 28 according to

the axis (Y, Y ').

  More precisely, as can be seen in FIG. 2 which represents substantially the position at +140, a first end 24a of the section of the sample projects from a first sleeve 28a surrounded by a stirrup 28a ', these two elements forming a first part of the module 28, and a second end 24b of the section of the sample protrudes by one

  second sleeve 28b forming a second part of module 28.

  Thus, the sample 24 is entirely subjected to the movements i0 of the module 28, including the previously described movement back and forth in rotation (arrows B in FIG. 2) around the axis (Y, Y ') (mechanism

  drive in rotation around (Y, Y ') not shown).

  It is understood that the rotations around the axes (X, X ') and (Y, Y') take place at the same time, the angular position of the sample 24 having at all times the same value between -140 and +140, d '' a part in bending

  around the axis (X, X '), and on the other hand in torsion around the axis (Y, Y').

  Apart from the section retained by the module 28, the sample 24 of the cable is entirely free to move, therefore subject only to gravity. This test makes it possible in particular to reconstruct the stresses to which a cable connected to a portable medical electrical device is subjected.

such as a probe.

  This test is carried out under the following conditions: - starting point: position at 0 corresponding to a vertical position of the cable, the stirrup 28a 'being at the bottom, - bending: 280 / cycle, - torsion: 280 / cycle, cycle frequency: 9 cycles / min, - number of cycles at least 1,000,000 without wire breakage

conductor in the braid.

  For comparison purposes, this same test was carried out for a cable A as defined above having a shielding braid made of Cu-Cd-Cr alloy and for a cable B having a shielding braid 20 made with the wire conductor resulting from the

  manufacturing according to the present invention.

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  It can be seen from the graph in FIG. 3 that the cable B has a much more stable electrical resistance, thereby resulting in greater shielding efficiency, than the cable A. In fact, in the case of the test corresponding to the figure 3, there is a maximum variation in the electrical resistance of the braid of 20.4% for cable A and 4.4% for cable B. During a test campaign, it was found that the most important value of the maximum variation of the electrical resistance of a braid produced with the conductive wire according to the invention, that is to say the greatest deviation of the

  electrical resistance during a test is 7%.

  The conductive wire resulting from the manufacturing process according to the present invention therefore appears to have greater mechanical resistance, combined with better thermal resistance, while having an electrical conductivity greater than the conductive wires of

prior art.

  The present invention also relates to an electromagnetic shielding braid for an electric cable, comprising at least one wire

  conductor as defined above.

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Claims (14)

  1. A method of manufacturing a conductive wire made of a composite material with a copper matrix in which metallic or ceramic particles are dispersed, characterized in that it comprises the following steps: - a basic wire produced in said is provided composite material, - a coating of the base wire is carried out with a ductile material in order to obtain a primary wire having a nominal diameter, one draws said primary wire to result in a secondary wire having a final diameter, and - one realizes an annealing treatment of said secondary wire in order to loosen the   stresses induced by wire drawing.   2. Method according to claim 1, characterized in that said ductile material belongs to the group comprising silver, gold, platinum, palladium and their alloys.   3. Method according to any one of the preceding claims,   characterized in that said particles comprise aluminum oxide,   preferably from 0.2 to 0.4% by weight of the composite material.   4. Method according to any one of the preceding claims,   characterized in that said step of coating the base wire comprises the electrolytic deposition of a silver layer having a   thickness between 1 and 10 gm, preferably between 3 and 6 gm.   5. Method according to claim 4, characterized in that said step of coating the base wire comprises the following steps: - alkaline degreasing of the base wire, - rinsing with water of the base wire, - acid pickling of the wire base, - rinsing of the base wire with water, - electrolytic deposition of a silver undercoat on the base wire, - electrolytic deposition of a silver layer on said undercoat in order to form the primary wire, and   - rinsing with water of the primary wire. 1 2804539   6. Method according to any one of the preceding claims,   characterized in that the wire drawing comprises several passages in a cold multi-pass wire drawing machine and makes it possible to obtain a final diameter for the secondary wire at least five times smaller than the nominal diameter of the primary wire, preferably substantially ten times smaller.   7. Method according to any one of the preceding claims,   characterized in that said annealing treatment includes heating said   secondary wire between 450 and 520 C for 150 to 210 minutes.   8. Conductive wire made of a composite material with a copper matrix in which are dispersed metallic or ceramic particles, characterized in that it also comprises a coating of ductile material and in that it has an electrical conductivity at least equal at 92% of the electrical conductivity of copper (International Annealed Copper Standard).   9. Conductive wire according to claim 8, characterized in that when an electromagnetic cable shielding braid is produced with said conductive wire, when said cable is subjected to a million (1,000,000) of combined bending and twisting cycles , each corresponding cycle, the passage of a cable section relative to an initial position, on the one hand, for the twist (B), relative to a main direction (Y, Y ') of the cable from a position 0 , towards a position at +140, towards a position at -140 and the return to position 0, and on the other hand, for bending (A), with respect to a direction (X, X ') orthogonal to said direction main of the cable (Y, Y ') from a position 0, towards a position at +140, towards a position at -140 and the return to position 0, said braid has a   maximum electrical resistance variation of 7%.   10. A conducting wire according to claim 8 or 9 characterized in that it has a tensile load value greater than or equal to 300 MPa.   11. A conducting wire according to claim 8, characterized in that said ductile material belongs to the group comprising silver, gold, platinum, palladium and their alloys.   12. Lead wire according to claim 11, characterized in that said   ductile material is a layer of silver obtained by electrolytic means. 12 2804539   13. Lead wire according to any one of claims 8 to 12,   characterized in that said particles comprise aluminum oxide,   preferably from 0.2 to 0.4% by weight of the composite material.   14. Electromagnetic shielding braid for an electric cable, comprising at least one conductive wire according to one of the claims. 8 to 13.