EP1120797B1 - Manufacturing process for a wire-conductor made of composite material with a copper matrix and wire-conductor obtained by the process - Google Patents

Description

The invention relates to a method for manufacturing a conductive wire made of a copper matrix composite material in which are scattered metal or ceramic particles, the wire conductor obtained from this method, and a shielding braid.

Copper is a widely used material, because of its high electrical conductivity, as the material constituting the conducting wire in electrical and electronic cables.

However, copper has mechanical characteristics mediocre often insufficient to make it the material of the thread cable conductor having to have a high mechanical strength, especially in flexion and torsion.

Traditionally, a copper alloy is used which, by different hardening mechanisms, has a mechanical strength superior to copper, while exhibiting electrical conductivity at less than 85% of the electrical conductivity of copper. Among these alloys include 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 electrical conductivity interesting (90% of that of copper) and a good mechanical resistance better than copper (load at break in tension = 420 MPa).

The present invention aims to provide a method of making it possible to obtain a conductive wire having a better electrical conductivity than the alloys of the prior art, at the same time more mechanical resistance, especially in torsion and in bending, as well as good high temperature stability of these properties mechanical.

• on fournit un fil de base réalisé dans ledit matériau composite,
• on réalise un revêtement du fil de base avec un matériau ductile afin d'obtenir un fil primaire présentant un diamètre nominal,
• on réalise le tréfilage dudit fil primaire pour aboutir à un fil secondaire présentant un diamètre final, et
• on réalise un traitement de recuit dudit fil secondaire afin de relâcher les contraintes induites par le tréfilage.

The manufacturing method according to the present invention is characterized in that it comprises the following steps:

• providing a base wire made of said composite material,
• the base wire is coated with a ductile material to obtain a primary wire having a nominal diameter,
• drawing of said primary wire to obtain 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 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 of the base wire includes the electrolytic deposition of a layer silver having a thickness of between 1 and 10 μm, preferably between 3 and 6 μm.

• dégraissage alcalin du fil de base,
• rinçage à l'eau du fil de base,
• décapage acide du fil de base,
• rinçage à l'eau du fil de base.
• dépôt par voie électrolytique d'une sous-couche d'argent sur le fil de base,
• dépôt par voie électrolytique d'une couche d'argent sur ladite sous-couche afin de former le fil primaire, et
• rinçage à l'eau du fil primaire.

Preferably, said step of coating the base wire comprises the following steps:

• alkaline degreasing of the base wire,
• rinsing with water of the basic thread,
• acid pickling of the base wire,
• rinsing with water of the base wire.
• electrolytic deposition of a silver underlayer on the base wire,
• electrolytically deposition of a silver layer on said underlayer to form the primary wire, and
• rinsing the primary wire with water.

A favorable solution for the manufacturing technique provides that the drawing includes several passes in a machine of multi-cold wire drawing and allows to obtain a final diameter for the wire secondary 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 thread as a result of the aforementioned manufacturing method, this thread being made of a copper matrix composite material in which are dispersed metal or ceramic particles, this wire being characterized by it further comprises a coating of ductile material and in that it has an electrical conductivity of not less than 92% of the Electrical conductivity of copper (International Annealed Copper Standard).

In addition, preferably, the wire according to the present invention is characterized in that when a braid shielding electromagnetic cable is made with said conductive wire, when said cable is subjected to one million (1,000,000) cycles of flexion and torsion combined, each cycle of flexion and torsion corresponding to the passage of a cable section relative to an initial position, on the one hand relative to a main direction of the cable from a 0 ° position, to a position at + 140 °, a position at -140 ° and the return at the 0 ° position (torsion), and secondly with respect to a direction orthogonal to said main direction of the cable from a 0 ° position, to a position at + 140 °, to a position at -140 ° and the return to the 0 ° position (bending), said Braid has a maximum electrical resistance variation of 7%.

In addition, preferably, the conducting wire has a value of tensile breaking load 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 electrolytically obtained silver 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 drawings are given only indicative and not limiting.

• la figure 1 est une section transversale d'un câble utilisé pour effectuer des tests de résistance mécanique du fil conducteur objet de la présente invention,
• la figure 2 est une représentation schématique du test de tenue à la flexion et à la torsion mis en oeuvre, et
• la figure 3 est une courbe comparative de la tenue en flexion et en torsion du câble de la figure 1 selon qu'il utilise ou non le fil conducteur selon la présente invention.

Reference will be made to the accompanying drawings, in which:

• FIG. 1 is a cross section of a cable used to perform mechanical strength tests on the conductor wire of the present invention,
• FIG. 2 is a schematic representation of the bending and torsion strength test used, and
• Figure 3 is a comparative curve of the bending and torsion resistance of the cable of Figure 1 according to whether or not it uses the conductive wire according to the present invention.

According to one of the essential characteristics of this invention, the method of manufacturing the lead wire uses a basic wire made of a copper matrix composite material in which are dispersed metal or ceramic particles. The composite material used is therefore developed by powder metallurgy by dispersing homogeneous way of metallic or ceramic fine particles (eg examples of oxides, carbides, nitrides or silicides) in a copper matrix.

Thus, the effect of these scattered particles on the microstructure copper metallurgy makes it possible, on the one hand, to increase the resistances mechanical properties of the material and, on the other hand, to maintain this mechanical strength up to high temperatures, without much altering the electrical conductivity of the copper matrix.

The manufacturing method according to the present invention allows obtaining a conductive wire having, surprisingly, very high mechanical performance, electrical conductivity and holding high temperature mechanics.

The manufacturing method according to the present invention comprises essentially three basic wire processing steps performed in the said 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 SCM Metal Products Inc. (reference UNS C15 715). This composite material contains 0.25 to 0.35% by weight of aluminum oxide particles dispersed in the copper matrix and 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 common thread according to the present invention.

The next stage of the manufacturing process consists, in particular to avoid breakage of the basic wire during the subsequent passage through the cold wire drawing machine for continuous reduction of the section of the base wire, to deposit a silver coating on the base wire, this coating being preferentially carried out electrolytically and having a thickness of 3 to 6 μm.

More specifically, this step of coating the base wire silver comprises the following steps: alkaline degreasing of the wire of base, baseline water rinse, acid stripping of base wire, rinsing base wire water, electrolytic deposition of silver underlayment on the base wire, electrolytic deposit of a layer of silver on the underlayer to form a primary wire, and rinsing with water of the primary wire.

This primary wire (silver wire) is then, in a second step, drawn continuously using a multipass cold drawing machine, the last channels used to lead to a secondary line having a final diameter of 0.106 mm, or 0.100 mm or 0.079 mm. At During this stage, we note that the silver coating remains continuous and homogeneous and results in a layer of thickness about 1 micron.

The last stage of the manufacturing process consists of a heat treatment. This heat treatment is intended to restore the ductility of the composite material by attenuating the internal stresses of the material created by the drawing step. Advantageously, this treatment thermal will consist of an annealing during which the secondary wire has been brought to a temperature between 450 and 520 ° C for a time between 150 and 210 min.

As can be seen in Table I below, this annealing heat treatment makes it possible to very significantly improve the mechanical and electrical characteristics of the drawn wires. In this table, the value of the load at break and the elongation at break in a tensile test, as well as the electrical conductivity of the wires expressed as a percentage of the electrical conductivity of the copper referred to as IACS, have indeed been reported. (International Annealed Copper Standard corresponding to 1.7241 micro.ohms.cm at 20 ° C).

Surprisingly, it can be seen that after the treatment of annealing, a conductive wire having a conductivity about 95% (94% or 96%) of the electrical conductivity of the copper, that is to say, much higher than that of the base wire. In addition, notes that the conductive wire according to the present invention has a 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, i.e., high temperature stability of these mechanical properties, the following test was implemented.

A Cu-Cd alloy wire and a resulting lead of the process according to the present invention, the two wires having a diameter 0.1 mm, were heated to 400 ° C for one hour. The reduction of the tensile strength of these yarns was measured at the end of this thermal aging.

It can be seen that the Cu-Cd alloy conductor wire has a loss of 20% of its load at break in tension while the wire conductor according to the present invention has only a loss in load at break of 5%. The result is that the common thread from manufacturing method according to the present invention presents a better thermal resistance with respect to a conductor wire Cu-Cd alloy.

To complete the tests to evaluate the resistance of the conductive wire from the process according to the present invention, a Bending and torsion strength test was set up. In this test, the thread resulting from the manufacturing process according to the present invention has been used for the formation of an electromagnetic shielding braid at within an electric cable which is illustrated in Figure 1.

This cable 10 includes one hundred and forty two coaxial conductors distributed in eight groups (reference 12) of sixteen coaxial cables and seven pairs (reference 14) of coaxial cables. The set of cables coaxial cable is twisted around a central anti-wrenching fiber 16, the whole being wrapped in a ribbon 18 surrounded by the armor braid 20, itself protected by an outer sheath 22 made of plastic.

During this bending and torsion strength test shown in FIG. FIG. 2, a sample 24 of the cable 10 described above is subjected to combined bending and torsion cycles.

During each cycle, the flexion aspect includes rotational movements with respect to a horizontal axis (X, X '), these movements being constituted by the passage of the sample 24 since a initial position 0 at position + 140 °, then its transition from position + 140 ° at the -140 ° position and finally its passage from the -140 ° position to the position initial 0.

For this, the sample 24 orthogonally crosses a horizontal beam 26 driven in rotation (non drive mechanism represented) and which imposes the movement previously described back and forth in rotation (arrow A in FIG. 2) around the horizontal axis (X, X ') which is parallel to the longitudinal direction of the beam 26.

During each cycle, the twist aspect includes rotational movements with respect to an axis (Y, Y ') orthogonal to the axis horizontal (X, X '), these movements being constituted by the passage sample 24 from an initial position 0 to the position + 140 °, and then its passage from position + 140 ° to position -140 ° and finally its passage from the position -140 ° at the initial position 0.

For this purpose, a torsion module 28 passes through the beam 26 according to the axis (Y, Y ') forming a pivot connection, a section of the sample 24 being housed integrally inside the torsion module 28 according to the axis (Y, Y ').

More specifically, as can be seen in Figure 2 which substantially represents the position at + 140 °, a first end 24a of sample section protrudes 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 exceeds a second sleeve 28b forming a second part of the module 28.

Thus, the sample 24 is entirely subject to the movements of module 28, including the previously described movement of back and forth in rotation (arrows B in FIG. 2) about the axis (Y, Y ') (mechanism driving in rotation around (Y, Y ') not shown).

We understand that the rotations around the axes (X, X ') and (Y, Y') at the same time, the angular position of the sample 24 having at each moment the same value between -140 ° and + 140 °, on the one hand in flexion 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 completely free of movement, so subject only to the gravity. This test makes it possible to reconstitute the requests to which a cable connected to a portable medical electrical appliance is subjected such as a probe.

• point de départ :position à 0° correspondant à une position verticale du câble, l'étrier 28a' étant en bas,
• flexion :280°/cycle,
• torsion : 280°/cycle,
• fréquence de cycle : 9 cycles/min,
• nombre de cycles : 1 000 000 au moins sans rupture de fil conducteur dans la tresse.

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,
• flexion: 280 ° / cycle,
• twist: 280 ° / cycle,
• cycle frequency: 9 cycles / min,
• number of cycles: 1 000 000 at least without breakage of conductive wire in the braid.

For comparison purposes, this same test was implemented for a cable A as defined above having a braid shielding 20 made of Cu-Cd-Cr alloy and for a cable B having a braid of shielding made with the lead wire resulting from the method of manufacture according to the present invention.

It is apparent from the graph in Figure 3 that cable B has a electrical resistance much more stable, thereby leading to an efficiency more shielding than the A cable.

Indeed, in the case of the test corresponding to FIG. notes a maximum variation of the electrical resistance of the braid of 20.4% for cable A and 4.4% for cable B. During a test campaign, it has been found that the most important value of the maximum variation of the electrical resistance of a braid made with the conductive thread according to the invention, that is to say the largest difference in the electrical resistance during a test, is 7%.

The thread resulting from the manufacturing process according to the The present invention thus appears to have a greater mechanical resistance, combined with better thermal resistance, while having a higher electrical conductivity than the conductor wires of the prior art.

The present invention also relates to a braiding shield electromagnetic device for an electric cable, comprising at least one wire driver as defined above.

Claims (14)

1. Process for manufacture of a conductor wire made from a composite material with a copper matrix in which metallic or ceramic particles are dispersed, characterised by the fact that it includes the following steps:

   a basic wire is provided made from the said composite material,

   the basic wire is coated with a ductile material in order to obtain a primary wire having a nominal diameter,

   wiredrawing of the said primary wire is performed in order to obtain a secondary wire having a final diameter, and

   the said secondary wire is subjected to an annealing treatment in order to relax the stresses caused by the wiredrawing.
2. Process as described in claim 1, characterised by the fact that the said ductile material belongs to the group comprising silver, gold, platinum, palladium and their alloys.
3. Process as described in any one of the preceding claims, characterised by the fact that the said particles include aluminium oxide, preferably at the rate of 0.2 to 0.4% by weight of the composite material.
4. Process as described in any one of the preceding claims, characterised by the fact that the said step of coating the basic wire comprises electrolytic deposition of a layer of silver having a thickness of between 1 and 10 µm, and preferably between 3 and 6 µm.
5. Process as described in claim 4, characterised by the fact that the said step of coating the basic wire comprises the following steps:

   alkaline degreasing of the basic wire,

   rinsing of the basic wire with water,

   acidic cleaning of the basic wire,

   rinsing of the basic wire with water,

   electrolytic deposition of an under-layer of silver on the basic wire,

   electrolytic deposition of a layer of silver on the said under-layer in order to form the primary wire, and

   rinsing of the primary wire with water.
6. Process as described in any one of the preceding claims, characterised by the fact that the wiredrawing comprises a plurality of passes in a cold multipass wiredrawing machine and allows a final diameter to be obtained for the secondary wire at least five times smaller than the nominal diameter of the primary wire, and preferably substantially ten times smaller.
7. Process as described in any one of the preceding claims, characterised by the fact that the said annealing treatment includes the heating of the said secondary wire between 450 and 520°C for 150 to 210 minutes.
8. Conductor wire resulting from the manufacturing process as described in any one of claims 1 to 7, this conductor wire being made from a composite material with a copper matrix in which metallic or ceramic particles are dispersed, this wire being characterised by the fact that it also includes a coating of a ductile material and by the fact that it has an electrical conductivity at least equal to 92% of the electrical conductivity of copper called International Annealed Copper Standard, corresponding to 1.7241 microohm.cm at 20°C.
9. Process for manufacture of an electromagnetic shielding braid (20) for a cable (10) with the said conductor wire as described in claim 8, characterised by the fact that, when the said cable (10) is subjected to a million (1 000 000) cycles of combined flexing and twisting, each cycle corresponding, on passage of a section of cable relative to an initial position, on the one hand, for twisting (B), relative to a main direction (Y, Y') of the cable from a 0° position, to a position at +140°, to a position at -140° and return to the 0° position, and on the other hand, for flexing (A), relative to a direction (X, X') at right-angles to the said main direction (Y, Y') of the cable from a 0° position, to a position at +140°, to a position at -140° and return to the 0° position, the said braid (20) has a maximum variation in electrical resistance of 7%.
10. Conductor wire as described in claim 8, characterised by the fact that it has a breakage load value under traction greater than or equal to 300 MPa.
11. Conductor wire as described in claim 8, characterised by the fact that the said ductile material belongs to the group comprising silver, gold, platinum, palladium and their alloys.
12. Conductor wire as described in claim 11, characterised by the fact that the said ductile material is a layer of silver obtained electrolytically.
13. Conductor wire as described in any one of claims 8 and 10 to 12, characterised by the fact that the said particles include aluminium oxide, preferably at the rate of 0.2 to 0.4% by weight of the composite material.
14. Electromagnetic shielding braid (20) for an electric cable, comprising at least a conductor wire as described in one of claims 8 and 10 to 13.

Images