JP5195019B2 - Cu-Ag alloy wire, winding, and coil - Google Patents

Description

  The present invention relates to an ultrafine Cu-Ag alloy wire and a method for producing the alloy wire. In particular, it relates to a Cu-Ag alloy wire having high strength, high toughness, and high conductivity.

  In a coil used for a speaker such as a portable electric device, a so-called voice coil, a coil turn and a power feeding portion to the turn are usually formed from a series of windings. Since this winding needs to have toughness (elongation) that allows the formation of a turn, conventionally, pure copper having excellent toughness has been used.

  Pure copper has high conductivity but low fatigue resistance (fatigue strength). In order to improve fatigue resistance, alloying is effective. For example, Patent Documents 1 and 2 disclose Cu-Ag alloys that have been strengthened by adding Ag (silver) or Tl (thallium).

Japanese Patent Publication No.49-041014 JP 2001-040439 A

  Since the winding made of pure copper is inferior in fatigue resistance as described above, disconnection may occur at this portion due to excessive vibration applied to the power feeding portion. In particular, depending on the electrical equipment, an extremely fine winding having a wire diameter (diameter) of φ0.1 mm or less is used. Such an extra fine wire is likely to cause the disconnection. Therefore, it is conceivable to improve fatigue resistance by alloying as described above. However, when the additive element is increased, the strength is increased, but the conductivity is lowered. Therefore, in order to obtain a desired conductivity, it is necessary to increase the cross-sectional area of the winding. Then, when an ultrathin wire is desired due to demands for weight reduction and miniaturization, there is a limit to increasing the strength by increasing the amount of additive elements.

  Conventionally, although an alloy wire has been developed focusing on increasing the strength of the ultrafine wire, sufficient examination has not been made on the toughness of the alloy wire.

  Therefore, one of the objects of the present invention is to provide a Cu—Ag alloy wire that is ultrafine but has high strength, high toughness, and high conductivity. Another object of the present invention is to provide a method for producing this alloy wire.

  The present inventors examined improvement of toughness for a Cu-Ag alloy that has higher strength than pure copper and can maintain high electrical conductivity. In order to obtain the desired toughness (elongation of 10% or more), it was considered to soften the wire. However, the conventional alloy wire is improved in elongation by softening, but the strength (fatigue strength) is lowered. Therefore, when the object to be subjected to the softening treatment was examined again, when the cold working before the softening treatment was performed at a specific degree of processing, a decrease in fatigue strength due to softening could be reduced, and as a result, high strength and high toughness, We have obtained knowledge that ultrafine wires with high electrical conductivity can be obtained. Based on this knowledge, the production method of the present invention defines the degree of (final) cold working before softening treatment.

  In addition, the Cu-Ag alloy is subjected to cold working such as wire drawing after casting, thereby causing two-phase separation, and the Ag phase is stretched into a fiber shape (fibrous shape). The strength of the wire drawing material is greatly improved by this Ag phase having a fiber reinforcing function. The two-phase separation is promoted by performing an intermediate heat treatment during the production, and the strength of the heat-treated material is further improved, and it is considered that the strength is easily maintained even after final softening. The alloy wire having a specific elongation in such a fiber reinforced state is considered to significantly improve the fatigue strength. Based on this knowledge, the manufacturing method of the present invention includes an intermediate heat treatment step and a final heat treatment step.

Specifically, the method for producing a Cu-Ag alloy wire of the present invention comprises an ultrafine wire composed of a Cu-Ag alloy containing 2.0 mass% or more and 15.0 mass% or less of Ag, with the balance being Cu and inevitable impurities. A manufacturing method comprising the following steps.
(1) A step of performing an intermediate heat treatment on a material obtained by cold-working a cast material of the Cu-Ag alloy having the above composition. This heat treatment is performed under the condition that the elongation of the wire after the heat treatment is 10% or more.
(2) The heat treatment material that has been subjected to the above intermediate heat treatment is subjected to final cold working under a condition of workability ln (A / A ₀ ): 1 to 10 to form a thin wire material having a wire diameter of 0.1 mm or less Process. Where A is the cross-sectional area of the fine wire material, and A ₀ is the cross-sectional area of the intermediate heat treatment material.
(3) A step of subjecting the fine wire to a final heat treatment. This heat treatment is performed under the condition that the elongation of the wire after the heat treatment is 10% or more.

  According to the production method of the present invention, the Cu-Ag alloy wire of the present invention having ultrafine, high strength, high toughness and high conductivity can be obtained. Specifically, the Cu-Ag alloy wire of the present invention contains 2.0% by mass or more and 15.0% by mass or less of Ag, the balance is made of Cu and inevitable impurities, the wire diameter: 0.1 mm or less, the tensile strength: 290 MPa or more, Elongation: 10% or more, conductivity: 80% IACS or more.

  Since the Cu-Ag alloy wire of the present invention has both high toughness and electrical conductivity as described above, it can be suitably used for those that require high toughness and high electrical conductivity such as coil winding. In particular, since the Cu-Ag alloy wire of the present invention has high strength and high toughness, it is difficult to break even when excessive vibration is applied, and has excellent fatigue characteristics. The production method of the present invention can produce the Cu-Ag alloy wire of the present invention having such high strength, high toughness and high conductivity with high productivity. Hereinafter, the present invention will be described in more detail.

[Cu-Ag alloy wire]
"composition"
The Cu-Ag alloy wire of the present invention is composed of a Cu-Ag alloy containing 2.0 to 15.0 mass% of Ag. If Ag is less than 2.0% by mass, the electrical conductivity is high, but the strength is not sufficiently improved. Although the strength is improved as the amount of Ag increases, the effect is saturated at about 15.0% by mass, and the inclusion of more Ag causes an increase in cost. On the other hand, if it exceeds 15.0% by mass, the electrical conductivity decreases. A more preferable content of Ag is 3% by mass or more and 6% by mass or less. The alloy wire of the present invention does not contain any element other than Ag, and the balance consists of Cu and inevitable impurities. The alloy wire of the present invention realizes high strength by work hardening and fibrous organization by cold working or heat treatment, and does not need to contain an element such as Tl.

"shape"
The Cu-Ag alloy wire of the present invention has a wire diameter (diameter) of 0.1 mm or less. If it exceeds 0.1 mm, it is difficult to obtain a desired elongation (10% or more) even if softening is performed. For example, the wire diameter can be changed by adjusting the degree of processing. The alloy wire obtained by the production method of the present invention is excellent in strength, toughness and electrical conductivity even if it is very fine, such as 0.05 mm or less.

"Tensile strength"
The Cu-Ag alloy wire of the present invention has a high tensile strength of 290 MPa or more. Further, the alloy wire of the present invention is excellent in fatigue resistance even if it has a small diameter, and can prevent disconnection due to vibration during use. The tensile strength can be changed, for example, by adjusting the Ag amount and the processing degree. The alloy wire obtained by the production method of the present invention further provides a high-strength wire of 340 MPa or more.

《Elongation》
The Cu-Ag alloy wire of the present invention is greatly different from the conventional Cu-Ag alloy wire in that it has a high elongation of 10% or more. Thus, when it uses for the coil | winding of a coil, this invention alloy wire is excellent in the moldability of a coil by being excellent in toughness. The elongation can be changed, for example, by adjusting the degree of processing and heat treatment conditions. As the elongation increases, the tensile strength and conductivity tend to decrease, so the upper limit of elongation is preferably 30%. The upper limit of elongation varies depending on the wire diameter, and is considered to be about 20% for an alloy wire having a wire diameter of φ20 μm, for example. A more preferable range of elongation is 15% or more and 20% or less, and a further preferable range is 15% or more and 18% or less.

"conductivity"
The Cu—Ag alloy wire of the present invention has a high conductivity of 80% IACS or more. The conductivity can be changed, for example, by adjusting the composition (Ag amount). Preferably, it is 90% IACS or more.

<Application>
The Cu-Ag alloy wire of the present invention has a small diameter, high strength, high toughness, and high electrical conductivity. Therefore, for applications where such characteristics are desired, such as windings of coils in electrical equipment, more specifically, Can be suitably used for voice coils. When used for the winding, it is preferable to provide an insulating coating layer such as enamel coating on the outer periphery of the alloy wire of the present invention.

[Production method]
《Preparing the material》
In the production method of the present invention, first, a material made of a Cu—Ag alloy having the above composition is prepared. This material is formed by subjecting a cast material (rod) made of a Cu—Ag alloy having the above composition to cold working (hereinafter referred to as first cold working). In particular, the first cold working preferably has a reduction in area of 70% or more. If it is less than 70%, it is difficult to perform the final cold working described later at a predetermined working degree, and the strength cannot be sufficiently improved. A more preferable area reduction ratio is a value at which the wire diameter becomes half or less, that is, 75% or more. Typical examples of the first cold working and the second cold working and final cold working described below include wire drawing using a wire drawing die. The cast material (rod) preferably has a cross-sectional area of 750 mm ² or less. If it is too large, more than 750 mm ^2, it is necessary to increase the area reduction ratio of the first cold working and the strength increases due to work hardening, but the toughness tends to decrease. A more preferable cross-sectional area is 50 mm ² or more and 500 mm ² or less, and a cast material having a diameter of 8 to 25 mm can be suitably used.

《First intermediate heat treatment》
The material is subjected to an intermediate heat treatment (hereinafter referred to as a first intermediate heat treatment). This heat treatment removes distortion caused by cold working before the heat treatment and enhances toughness, and enables final cold working of a specific degree of work performed after the heat treatment. In the manufacturing method of the present invention, an ultrathin wire material having a wire diameter of 0.1 mm or less is formed by the final cold working. Therefore, if this intermediate heat treatment is not performed, disconnections are likely to occur frequently during the final cold working. The intermediate heat treatment is performed so that the elongation of the wire after the intermediate heat treatment is 10% or more. A specific processing method will be described later. For the intermediate heat treatment and the final heat treatment described later, any of continuous processing and batch processing described later can be used.

《Second cold working and second intermediate heat treatment》
The heat treatment material subjected to the (first) intermediate heat treatment may be further subjected to a second cold work and a second intermediate heat treatment in order under the same conditions as the first cold work and the first intermediate heat treatment. By further performing the second cold working and the second intermediate heat treatment, an alloy wire that is further excellent in properties such as strength, toughness, and electrical conductivity can be obtained.

《Final cold working》
The heat treatment material that has been subjected to the intermediate heat treatment is subjected to final cold working to form a fine wire material having a wire diameter of 0.1 mm or less. The condition for this cold working is that the working degree ln (A / A ₀ ) is 1 or more and 10 or less. If the degree of work ln (A / A ₀ ) is less than 1 or more than 10, the tensile strength is small and sufficient fatigue strength cannot be obtained. By such cold working, the alloy structure is made into a very fine fiber shape, and the strength can be increased without impairing the electrical conductivity of the wire. Further, the strength of the wire can be increased by work hardening.

《Final heat treatment (softening treatment)》
A final heat treatment is applied to the fine wire that has undergone the final cold working. The final heat treatment is performed under the condition that the elongation of the wire after the heat treatment is 10% or more. This final heat treatment softens the wire, which has been increased by making the structure finer fibers and work hardened, without significantly reducing the strength, thereby increasing the toughness of the wire.

<Batch processing>
Batch processing is a processing method of heating in a heating container (atmosphere furnace, for example, a box-type furnace) with a heating target in advance, although the amount of processing at one time is limited, the heating state of the entire heating target This is a processing method that makes it easy to obtain a highly elongated wire. In the case where the intermediate heat treatment or the final heat treatment is performed by batch processing, the condition that the elongation of the wire after the heat treatment is 10% or more is that the heating temperature (atmosphere temperature in the container) is 350 ° C. or more and 600 ° C. or less. The holding time is preferably 30 minutes or longer. When the heating temperature is less than 350 ° C. or the holding time is less than 30 minutes, distortion cannot be sufficiently removed in the case of intermediate heat treatment, disconnection is likely to occur, and in the case of final heat treatment, a sufficient toughness improving effect cannot be obtained. Above 600 ° C., the intermediate heat treatment is too soft and the final cold working cannot be performed. In the case of the final heat treatment, not only the strength but also the conductivity is lowered. More preferable conditions are heating temperature: 400 ° C. or higher and 500 ° C. or lower, holding time: 1 hour or longer and 30 hours or shorter.

<Continuous processing>
The continuous treatment is a treatment method in which a heating object is continuously supplied into a heating container and the heating object is continuously heated, and is a treatment method that is excellent in workability in that it can be continuously heated. For continuous treatment, direct energization is performed by directly energizing the object to be heated (continuous energization softening treatment, hereinafter referred to as continuous energization), electromagnetic induction is used to indirectly energize and heat the object to be heated. Indirect energization method (induction heating continuous softening treatment), furnace type (hereinafter referred to as pipe continuous softening) in which a heating object is introduced into a heating container (pipe softening furnace) that is heated and heated by heat conduction. . In the case of continuous processing, control parameters that can be related to desired characteristics (here, elongation) are changed as appropriate, the characteristics (elongation) at that time are measured, and such measurement data is created in advance. Then, based on this data, the parameters may be adjusted so that a desired characteristic value (elongation: 10% or more) is obtained. In the case of the energization method, the control parameters include the supply speed (linear speed) into the container, the size of the heating target (wire diameter), the current value, and the like. In the case of the furnace type, the control parameters are the feed rate (wire speed) into the vessel, the size of the object to be heated (wire diameter), the size of the furnace (diameter of the pipe type furnace), the temperature of the heating atmosphere (400 to 600) ° C is preferred). When, for example, an energization type softening device is arranged on the wire drawing material discharge side of the wire drawing machine, the heating temperature is 350 to 600 by setting the wire speed to several hundred m / min or more, particularly 400 m / min or more. A heat treatment corresponding to a batch treatment at 0 ° C. can be performed, and a wire having an elongation of 10% or more can be obtained after this continuous treatment.

<Characteristics of alloy wire>
The alloy wire obtained by the production method of the present invention has a fine fibrous structure. A Cu—Ag alloy wire having such a structure has high elongation while maintaining a high tensile strength, and can improve fatigue strength. In general, when a softening treatment is applied to copper or a copper alloy, the strength rapidly decreases. On the other hand, in the manufacturing method of the present invention, as described above, by setting the degree of cold working immediately before the softening treatment within a specific range, an alloy wire with reduced strength reduction and excellent toughness can be obtained. The reason for this is not clear, but it is considered that the fiber structure is maintained by the cold working of the above specific working degree and that work hardening by making the diameter 0.1 mm or less is one of the factors.

  The Cu-Ag alloy wire of the present invention is extremely thin but has high strength and high toughness, excellent fatigue resistance, and high electrical conductivity. The production method of the present invention can produce such an alloy wire of the present invention with high productivity.

[Test Example 1]
Cu-Ag alloy wires were prepared under various processing conditions shown in Table 1, and the tensile strength, elongation, and conductivity were measured. The sample was prepared in the order of production of cast material → first cold work → first intermediate heat treatment → (second cold work → second intermediate heat treatment) → final cold work → final heat treatment.

The cast material was made of a Cu—Ag alloy containing 2 to 5 mass% of Ag and the balance being Cu and inevitable impurities (wire diameter φ8 mm or 22 mm, cross-sectional area: 50 mm ² or 380 mm ² ≦ 750 mm ² ). The cast material was subjected to cold working (cold drawing) and heat treatment shown in Table 1 to produce a drawn material having a final wire diameter of φ0.05 to 0.1 mm. For comparison, a drawn wire was prepared by subjecting a cast material of pure copper (tough pitch copper having a known composition) to cold drawing and final heat treatment. In Table 1, the numerical value of cold working indicates the wire diameter (mm) after cold working. Also, in Table 1, the final cold work degree indicates the cross-sectional area of the drawn wire (fine wire) having the final wire diameter A, the cross-sectional area of the heat-treated material subjected to the first intermediate heat treatment, and the second intermediate heat-treated. The obtained sample is assumed to be ln (A / A ₀ ), where A ₀ is the cross-sectional area of the heat-treated material subjected to the second intermediate heat treatment. Further, unless otherwise specified in Table 1, the heat treatment indicates batch processing using an atmospheric furnace. `` (Elongation) '' described in the column of processing conditions indicates the elongation after the first intermediate heat treatment before the final heat treatment for each sample except for the sample No. 2, and the sample No. 2 indicates the elongation after the first intermediate heat treatment. 2 shows the elongation before cold working and the elongation after the second intermediate heat treatment and before the final heat treatment.

  The tensile strength (MPa), elongation (%), and conductivity (% IACS) of the Cu-Ag alloy wire or copper wire obtained by the final heat treatment were measured. The results are shown in Table 2.

As shown in Table 2, by performing intermediate heat treatment and performing cold working at a specific degree of processing (ln (A / A ₀ ) = 1 to 10) and then performing the final heat treatment, the wire diameter φ is reduced. It can be seen that an alloy wire having a high strength (tensile strength: 290 MPa or more), high toughness (elongation: 10% or more), and high conductivity (80% IACS or more) can be obtained even though it is extremely fine of 0.1 mm or less. Moreover, since the obtained alloy wire is high strength and high toughness, it is thought that it is excellent also in fatigue resistance.

  Furthermore, it can be seen from the above test results that the characteristics can be further improved by performing the second cold working and the second intermediate heat treatment. However, since the number of heat treatments is increased, it is considered that only the first cold working and the first intermediate heat treatment may be required in consideration of economy. The second cold working and the second intermediate heat treatment may be performed according to desired characteristics. Further, when the wire diameter is large in the range of 0.1 mm or less, the elongation tends to increase.

[Test Example 2]
The fatigue life of the thin wires of Sample Nos. 5, 7, and 13 produced in Test Example 1 was examined. Here, the fatigue life was evaluated by a bending test using a bending test apparatus as shown in FIG.

  In the bending test, as shown in FIG. 1, a sample S (diameter: φ0.1 mm, length: 600 mm) is placed between a pair of mandrels m arranged opposite to each other, and a weight w (load load: 25g) is attached, and the other end is held by the lever 1 of the testing machine, and the sample S is bent along the outer periphery of the mandrel m with a bending radius R (= 100 mm). The fatigue life is evaluated by the number of bendings until the specimen breaks. The number of bends is counted as one 90 ° reciprocation. For example, when it is bent as shown by the arrow in FIG. 1, the number of bendings is two. The results of the bending test are shown in Table 3.

  As shown in Table 3, Samples Nos. 5 and 7 have a high fatigue strength compared to tough pitch copper, which has high tensile strength, elongation, and electrical conductivity, and generally has high electrical conductivity and high elongation. I understand.

  The above-described embodiment can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration. For example, the content of Ag may be changed.

  The Cu-Ag alloy wire of the present invention can be suitably used for applications where a small diameter, high strength, high toughness, and high conductivity are desired, for example, a winding for a speaker coil of a portable electric device. The production method of the present invention can be suitably used for the production of the alloy wire of the present invention.

It is explanatory drawing which shows the state of a bending test.

Explanation of symbols

  l Lever S Specimen w Weight m Mandrel R Bending radius

Claims (3)

Containing 2.0% by mass or more and 15.0% by mass or less of Ag, the balance being made of Cu and inevitable impurities,
The wire diameter is 0.1mm or less,
A tensile strength of more than 290 MPa, elongation of 10% or more, C u-Ag alloy wire conductivity of Ru der 80% IACS or more guide.   2. A winding comprising the Cu—Ag alloy wire according to claim 1 and an insulating coating layer provided on an outer periphery of the Cu—Ag alloy wire.   A coil comprising the winding according to claim 2.

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