EP2192596B1 - Brand with limited spring effect - Google Patents

Abstract

The strand has electrical wires made of copper and tin alloy, where transversal cross sectional area of the strand is 0.35 square mm. The copper and tin alloy comprises tin content of 17000 parts per million, oxygen content of 400 parts per million and unavoidable impurities content of 100 parts per million, where the rest of content of the alloy is copper. The electrical wires are free-from thermal treatment during fabrication of the strand.

Description

The present invention relates to a strand comprising one or more electrical conductors, to an electric cable and to a wiring harness.

It typically, but not exclusively, applies to electrical control cables or power cables used to transmit currents. Such cables are conventionally formed by a plurality of electrical conductors (or strands) of copper. This plurality of wires is twisted to form a strand with a cross section of at most 0.5 mm ² , and the strand is surrounded by an insulating sheath, obtained for example by extrusion.

These cables are used in various fields of the industry, such as for example the automotive industry, where they are assembled into bundles for the power supply of various equipment. These cables must thus be the lightest possible, and have a small footprint while maintaining good mechanical strength.

By trying to replace the annealed copper strands with hard copper alloy strands to improve the mechanical strength of the strand formed of these strands, it has been found that said copper alloy strands were difficult to manipulate during the manufacture of the strands. because of an effect called "spring" of these electrical conductors son.

• une teneur en étain d'au moins 1500 ppm (0,15 % en poids) et d'au plus 2500 ppm (0,25 % en poids),
• une teneur en oxygène d'au plus 400 ppm (0,04 % en poids),
• une teneur en impuretés inévitables d'au plus 100 ppm (0,01 % en poids), et
• le reste de la teneur dudit alliage étant du cuivre, le(s) fil(s) conducteur(s) électrique(s) étant exempt(s) de traitement thermique lors de la fabrication du toron.

The object of the present invention is to overcome the drawbacks of the prior art techniques by proposing a strand of (cross) section of at most 0.35 mm ² comprising one or more electrical conductor wires (A), characterized in that each electrical conductor wire is made of a copper-tin alloy comprising:

• a tin content of at least 1500 ppm (0.15% by weight) and at most 2500 ppm (0.25% by weight),
• an oxygen content of not more than 400 ppm (0.04% by weight),
• an unavoidable impurity content of not more than 100 ppm (0.01% by weight), and
• the remainder of the content of said alloy being copper, the (s) wire (s) conductor (s) electrical (s) being free (s) of heat treatment during the manufacture of the strand.

• une teneur en étain d'au moins 700 ppm (0,07 % en poids) et d'au plus 1200 ppm (0,12 % en poids),
• une teneur en oxygène d'au plus 50 ppm (0,005 % en poids), de préférence d'au plus 5 ppm (0,0005 % en poids),
• une teneur en impuretés inévitables d'au plus 100 ppm (0,01 % en poids), et
• le reste de la teneur dudit alliage étant du cuivre,
  le(s) fil(s) conducteur(s) électrique(s) étant exempt(s) de traitement thermique lors de la fabrication du toron.

Another object according to the invention is a strand of (cross) section of at most 0.35 mm ² comprising one or more electrical conductor wires (B), characterized in that each electrical conductor wire is made of an alloy of copper and tin comprising:

• a tin content of at least 700 ppm (0.07% by weight) and at most 1200 ppm (0.12% by weight),
• an oxygen content of at most 50 ppm (0.005% by weight), preferably at most 5 ppm (0.0005% by weight),
• an unavoidable impurity content of not more than 100 ppm (0.01% by weight), and
• the remainder of the content of said alloy being copper,
  the electric conductor wire (s) being free from heat treatment during the manufacture of the strand.

The copper used to make the alloy of electrical conductors B is commonly called CuOF for "Oxygen Free" Copper.

It has been found that the two types of yarn A and B according to the invention, and therefore the respective strands resulting therefrom, have a significantly limited spring effect while guaranteeing satisfactory mechanical strength.

Above a tin content of 2500 ppm (0.25% by weight) for the electrical conductor wire A or above a tin content of 1200 ppm (0.12% by weight) for the electrical conductor wire B the spring effect of the electrical conductor wire becomes important and it is very difficult and compelling to handle it.

Below a tin content of 1500 ppm (0.15% by weight) for the electrical conductor wire A or below a tin content of 700 ppm (0.07% by weight) for the electrical conductor wire B, the mechanical strength such as the tensile strength decreases significantly and thus the electrical conductor tends to break much more easily.

In addition, the electrical conductor wire A or B according to the invention, and therefore the respective strands resulting therefrom, advantageously has an improved 180 ° bending strength and thus limits the risk of breakage of the wire in handling operations. assemblies, transport, installations or uses.

Finally, the electrical conductor wire A or B according to the invention, and therefore the respective strands resulting therefrom, have a very good electrical conductivity (IACS) at ambient temperature, this electrical conductivity being able to be of the order of 90%.

The abbreviation "ppm" in the present description means "parts per million by weight". In other words, the quantity x (or the content) in ppm of a z element is expressed relative to the total weight of the alloy.

The term "unavoidable impurities" means the sum of the metallic or non-metallic elements included in the alloy, excluding copper, tin and oxygen, during the manufacture of said alloy. These impurities may be for example the following elements: Ag, As, Bi, Fe, Pb, S, Sb, Se, Te, Cd, Cr, Mn, P, Ni, Co, S, Fe and / or Zn.

The term "heat treatment during the manufacture of the strand" is understood to mean any conventional heat treatment that makes it possible to obtain an annealed state of the electrical conductor wire or wires. This treatment is to be differentiated from structural modifications related in particular to thermal aging when using the strands after their manufacture.

Typically, an annealing heat treatment causes a rearrangement of the microstructure of the alloy that makes up the electrical conductor wire (s), in particular the copper grains that make up the alloy have a size that increases after annealing. Therefore, the heat treatment during the manufacture of a strand inevitably induces a decrease in the mechanical strength of the alloy that makes up the electrical conductor wire (s).

When the strand comprises several electrical conductors, these conductive son are twisted together. When the strand comprises only one electrical conductor wire, this single wire is not twisted.

The electrical conductor son or wires that make up the strand preferably have a diameter ranging from 0.10 to 0.67 mm.

According to a preferred embodiment, the strand according to the invention is advantageously not compressed circularly.

The unavoidable impurities content, or sum of unavoidable impurities, in the alloy according to the invention, whether the electrical conductive wire A or the electrical conductor wire B, may be at most 65 ppm.

According to the embodiment of the electrical conductor wire A, the tin content may be strictly greater than 1500 ppm (0.15% by weight), and preferably at least 1700 ppm (0.17% by weight). The tin content may be furthermore at most 2200 ppm (0.22% by weight).

As for the oxygen content, it can be at most 300 ppm (0.03% by weight). Preferably, the oxygen content may be at least 100 ppm, and more preferably at least 150 ppm (0.015% by weight).

According to the embodiment of the electrical conductor wire B, the tin content may be at most 1000 ppm (0.1% by weight). Preferably, the tin content may be at least 800 ppm (0.08% by weight).

In a particularly preferred embodiment, each electrical conductor wire is tinned, that is to say that it is covered with a thin metal layer of tin on its surface. In particular, tinning improves the weldability of the electrical conductors.

Another object according to the invention is an electrical cable comprising a strand of one or more electrical conductor wires A or B, extending in the longitudinal direction of the cable, said strand being surrounded along the cable by an insulating sheath.

Another object according to the invention is a wiring harness comprising a plurality of electrical cables as defined above.

Other features and advantages of the present invention will appear in the light of the examples which follow with reference to the single figure, said examples and figure being given for illustrative and not limiting.

The figure 1 represents the tensile strength (MPa) as a function of the tin concentration (% by weight) of an alloy of Cu / Sn and a CuOF / Sn alloy respectively in the form of an electrical conductor wire and in the form of 'a strand of 7 electrical conductors.

Examples Method of manufacturing electrical conductor wires A and B

The electrical conductor son according to the invention are conventionally manufactured from a casting of copper and tin, this casting being then rolled on the same production line.

Unlike the manufacture of electrical conductors son A, the casting step for the manufacture of electrical conductors son B is carried out under vacuum.

The bar of copper / tin alloy thus obtained is drawn by a cold drawing operation for the purpose of transforming the metal bar into electrical conductor wires in successive passes through dies of smaller and smaller diameters. As the diameter of the bar at the rolling exit is important, in particular of the order of 6 to 10 mm, the section reduction is generally done in two successive drawing operations. The first drawing machine reduces the diameter of the wire to a value of 2.5 to 1.6 mm. The second drawing machine reduces the wire to the final diameter, that is to say from 0.10 to 0.67 mm. Before passing on the second drawing machine, it may be possible to tin the electrical conductor, that is to say to deposit a thin layer of tin electrodeposition on the surface of said wire.

At the output of drawing, no annealing operation is performed, and the resulting alloy thus remains in a hardened state.

After this drawing step, the electrical conductors son obtained are twisted to obtain a strand.

In a further step, said strand may be surrounded by an insulating sheath of the electrically insulating polymeric layer type.

The alloys obtained are detailed in Table 1 below. <b><u> Table 1 </ u></b> Electrical conductor Cu / Sn alloy CuOF / Sn alloy A1 A2 B1 B2 Tin content 1700 4500 1000 2500 Oxygen content 250 250 <5 <5 Impurity content <65 <65 <65 <65

The contents of metallic elements in copper / tin alloys (Cu / Sn or CuOF / Sn) are conventionally determined using a spectrograph marketed by ARL under the reference Thermo Optec 3460.

The oxygen content of the alloys is conventionally determined using an oxygen analyzer marketed by LECO under the reference R0116.

Flexibility test

This is a test to appreciate the mechanical memory of a driver, ie its rigidity.

• réaliser un ressort à spires jointives sur un mandrin d'un diamètre de 20 mm et sous une contrainte axiale (masse) de l'ordre de 400 g,
• relaxer le ressort en supprimant la contrainte axiale,
• couper le ressort longitudinalement, et
• sur les spires coupées, mesurer le diamètre relaxé et le plé, le plé étant le déport d'une spire exprimé en mm.

The procedure consists, from a strand of seven wires drawn electrical conductors with a unit diameter of 0.202 mm, to:

• producing a spring with contiguous turns on a mandrel with a diameter of 20 mm and under an axial stress (mass) of the order of 400 g,
• relax the spring by removing the axial stress,
• cut the spring longitudinally, and
• on the cut turns, measure the relaxed diameter and the ply, the ply being the offset of a turn expressed in mm.

The results of this test are collated in Tables 2 and 3 below.

dans laquelle le Diamètre enroulement est le diamètre du mandrin, à savoir 20 mm. Tableau 2 Torons de 7 fils conducteurs électriques Alliage Cu/Sn A1 Alliage Cu/Sn A2 Relaxation (%) Plé (mm) Relaxation (%) Plé (mm) Test 1 1,4 15 2,0 8 Test 2 1,3 6 2,1 28 Test 3 1,3 11 2,0 32 Test 4 1,3 4 2,4 34 Test 5 1,4 17 2,2 15 Test 6 1,3 12 2,0 25 Test 7 1,4 5 2,1 10 Test 8 1,3 14 2,0 12 Test 9 1,2 22 2,0 24 Test 10 1,4 15 2,0 22 Moyenne en nombre sur les 10 tests 1,3 12 2,1 21 Tableau 3 Torons de 7 fils conducteurs électriques Alliage CuOF/Sn B1 Alliage CuOF/Sn 82 Relaxation Plé Relaxation Plé (%) (mm) (%) (mm) Test 1 1,4 14 1,9 16 Test 2 1,2 9 2,1 19 Test 3 1,2 13 2,0 22 Test 4 1,3 15 2,0 17 Test 5 1,2 17 2,1 26 Test 6 1,3 11 1,8 24 Test 7 1,2 7 1,9 19 Test 8 1,3 10 2,0 22 Test 9 1,3 7 2,0 17 Test 10 1,4 8 1,9 17 Moyenne en nombre sur les 10 tests 1,3 11 2,0 20 In Tables 2 and 3, the percent relaxation (%) is defined by the following formula: $$\frac{\mathrm{Relaxed\; diameter}-\mathrm{Coiling\; diameter}}{\mathrm{Coiling\; diameter}}x100$$

wherein the winding diameter is the diameter of the mandrel, namely 20 mm. <b><u> Table 2 </ u></b> Strands of 7 electric conductors Cu / Sn alloy A1 Cu / Sn A2 alloy Relaxation (%) Plé (mm) Relaxation (%) Plé (mm) Test 1 1.4 15 2.0 8 Test 2 1.3 6 2.1 28 Test 3 1.3 11 2.0 32 Test 4 1.3 4 2.4 34 Test 5 1.4 17 2.2 15 Test 6 1.3 12 2.0 25 Test 7 1.4 5 2.1 10 Test 8 1.3 14 2.0 12 Test 9 1.2 22 2.0 24 Test 10 1.4 15 2.0 22 Average in number of the 10 tests 1.3 12 2.1 21 Strands of 7 electric conductors CuOF / Sn B1 alloy CuOF / Sn 82 alloy Relaxation Plé Relaxation Plé (%) (Mm) (%) (Mm) Test 1 1.4 14 1.9 16 Test 2 1.2 9 2.1 19 Test 3 1.2 13 2.0 22 Test 4 1.3 15 2.0 17 Test 5 1.2 17 2.1 26 Test 6 1.3 11 1.8 24 Test 7 1.2 7 1.9 19 Test 8 1.3 10 2.0 22 Test 9 1.3 7 2.0 17 Test 10 1.4 8 1.9 17 Average in number of the 10 tests 1.3 11 2.0 20

The results of Tables 2 and 3 clearly show that the strands made of electrical conductor son according to the invention (alloy Cu / Sn A1 or alloy CuOF / Sn B1) has a relaxation and a plé means much lower than those formed strands lead wires according to the prior art (Cu / Sn A2 alloy or CuOF / Sn B2 alloy). Thus, the spring effect of the strands according to the present invention is much less marked than those of the prior art.

Holding at 180 ° bend

This is a quick test of repeated bends on a bending radius substantially equal to zero. Folding consists of bending a 180 degree electrical conductor wire and returning it to its initial position.

The test is applicable over a range of electrical conductor wires with diameters from about 0.15 mm to about 0.51 mm. For the test, drawn wire leads with a diameter of 0.202 mm were used.

To do this, the first end of a portion of electrical conductor wire is attached to a rigid rod having two longitudinal parallel faces and two longitudinal edges. This rod is secured to a crank for rotating said rod on its longitudinal axis.

The second end of said portion is fixed to an axial stress (mass) of 85 g making it possible to maintain permanent contact the electrical conductor wire and the strip during the test.

The operating procedure of the 180 ° bend test is to rotate the crank 180 ° so that the electrical conductor wire wraps around the ruler by remaining in contact with both sides as well as with one of the two edges. longitudinal lines of the rod. The stop of the rod makes it possible to bend the electrical conductor wire by 180 ° thanks to the mass suspended at the second end of said wire. The electrical conductor thus folded is unfolded. This protocol is repeated on the same portion of folded wire until the wire breaks.

The results of this test are summarized in Tables 4 and 5 below. <b><u> Table 4 </ u></b> Electrical conductor Cu / Sn alloy A1 Cu / Sn A2 alloy Number of folds of 180 ° round-trip before wire break Test 1 10 6 Test 2 8 6 Test 3 10 6 Test 4 8 7 Test 5 9 6 Test 6 9 6 Test 7 8 7 Test 8 7 6 Test 9 7 6 Test 10 7 7 Test 11 10 6 Test 12 8 6 Average in number of the 12 tests 8 6 Electrical conductor Alloy CuOF / Sn Alloy B1 CuOF / Sn B2 Number of folds of 180 ° round-trip before wire break Test 1 10 7 Test 2 8 7 Test 3 9 6 Test 4 10 7 Test 5 7 7 Test 6 9 6 Test 7 9 6 Test 8 8 6 Test 9 10 7 Test 10 10 6 Test 11 9 6 Test 12 9 6 Average in number of the 12 tests 9 6

The average number obtained on the 12 electrical conductor wires (12 tests) according to the invention (Cu / Sn A1 alloy and CuOF / Sn B1 alloy) is greater than that obtained on the 12 electrical conductor wires according to the prior art (alloy Cu / Sn A2 and CuOF / Sn B2 alloy). Thus, the electrical conductor wire according to the invention, and the resulting strand, is much more resistant to mechanical stresses experienced by the son during handling, assembly, transportation, installation or use.

Tensile strength test

• d'un fil conducteur électrique d'un diamètre de 0,202 mm constitué d'un alliage de Cu / Sn comprenant la teneur en oxygène et en impuretés de l'alliage A1 (courbe intitulée « single wire Cu+Sn »), et d'un toron comprenant un assemblage de 7 de ces fils (courbe intitulée « strand Cu+Sn »), d'une part, et
• d'un fil conducteur électrique d'un diamètre de 0,202 mm constitué d'un alliage de CuOF / Sn comprenant la teneur en oxygène et en impuretés de l'alliage B1 (courbe intitulée « single wire CuOF+Sn »), et d'un toron comprenant un assemblage de 7 de ces fils (courbe intitulée « strand CuOF+Sn »), d'autre part.

The figure 1 represents the tensile strength (MPa), or mechanical strength, as a function of the tin content (% by weight):

• an electrical conductor wire with a diameter of 0.202 mm made of a Cu / Sn alloy comprising the content of oxygen and impurities of the alloy A1 (curve called "single wire Cu + Sn"), and of a strand comprising an assembly of 7 of these threads (curve entitled "Strand Cu + Sn"), on the one hand, and
• an electrical conductor wire with a diameter of 0.202 mm made of a CuOF / Sn alloy comprising the oxygen content and impurities of the alloy B1 (curve called "single wire CuOF + Sn"), and of a strand comprising an assembly of 7 of these son (curve entitled "Strand CuOF + Sn"), on the other hand.

Whether it is the curves of the electrical conductor wires or the strands, it is found that the mechanical strength decreases significantly from 0.15% by weight (1500 ppm) of tin in the Cu / Sn alloys and for of tin less than 0.15% by weight, and from 0.07-0.08% by weight (700-800 ppm) of tin in CuOF / Sn alloys and tin contents of less than 0.07% by weight.

Claims (8)

1. A strand with a section of at most 0.35 mm² comprising one or more electrically conducting wires (A), characterized in that each electrically conducting wire consists of an alloy of copper and tin comprising:

   - a tin content of at least 1,500 ppm and of at most 2,500 ppm,

   - an oxygen content of at most 400 ppm,

   - a content of inevitable impurities of at most 100 ppm, and

   - the remainder of the contents of said alloy being copper,
   the electrically conducting wire(s) being without any heat treatment during the manufacturing of the strand.
2. The strand according to claim 1, characterized in that the tin content is strictly greater than 1,500 ppm.
3. The strand according to claim 1 or 2, characterized in that the tin content is at least 1,700 ppm.
4. The strand according to any of the preceding claims, characterized in that the tin content is at most 2,200 ppm.
5. A strand with a section of at most 0.35 mm² comprising one or more electrically conducting wires (B), characterized in that each electrically conducting wire consists of an alloy of copper and tin comprising:

   - a tin content of at least 700 ppm and of at most 1,200 ppm,

   - an oxygen content of at most 50 ppm, preferably at most 5 ppm,

   - a content of inevitable impurities of at most 100 ppm,
   and

   - the remainder of the contents of said alloy being copper,
   the electrically conducting wire(s) being without any heat treatment during the manufacturing of the strand.
6. The strand according to any of the preceding claims, characterized in that the strand is not circularly compressed.
7. An electric cable including a strand as defined in claims 1 to 6, extending in the longitudinal direction of the cable, said strand being surrounded along the cable by an insulating sheath.
8. A wiring bundle comprising a plurality of electric cables according to claim 7.

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