Wire material made of copper-silver alloy and method for producing same
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SHOWA ELECTRIC WIRE & CABLE CO LTD
- Filing Date
- 2026-01-21
- Publication Date
- 2026-07-30
Smart Images
Figure JP2026001860_30072026_PF_FP_ABST
Abstract
Description
Wire made of copper-silver alloy and method for manufacturing the same
[0001] The present invention relates to a wire made of a copper-silver alloy and a method for manufacturing the same.
[0002] In recent years, miniaturization of electronic devices has advanced, and various components used have also been miniaturized. Along with this, wiring is also required to have a smaller diameter, and the same strength and operating current as before the diameter reduction are required as characteristics. In order to meet such requirements, alloying is necessary, but there is a trade-off relationship between strength and conductivity, and it is very difficult to simultaneously achieve high strength and high conductivity, which has become a major issue.
[0003] Fig. 5 shows the characteristics of main commercial alloy wires. In most alloys, high strength and high conductivity are not simultaneously satisfied, but for copper-silver alloys, there is a possibility of simultaneously satisfying high strength and high conductivity. Therefore, the applicant has started developing copper-silver alloy wires and is working on the development of flat wires for high magnetic field magnets to which a very large stress is applied during operation, and ultra-fine stranded wires for in-vehicle seat heaters to which a large bending stress is always applied. In addition, copper-silver alloys also have excellent workability and can be made into ultra-fine wires with a diameter of about 0.010 mm. On the other hand, improvement in mechanical properties, particularly wire strength, is also required for ultra-fine wires, and it is considered that by satisfying these requirements, it will contribute to improvement in wiring, routing, and durability, and the applications of copper-silver alloy wires will expand.
[0004] Patent Document 1 below discloses a method for manufacturing an ultra-fine copper alloy wire having strength, high conductivity, and excellent heat resistance in that the tensile strength hardly decreases even under a thermal load, but the tensile strength remained at about 850 MPa.
[0005] Japanese Patent No. 4143086
[0006] An object of the present invention is to obtain an ultra-fine wire made of a copper-silver alloy having at least excellent tensile strength.
[0007] The present invention, made to solve the above problems, is a method for manufacturing a copper-silver alloy wire, comprising at least the steps of: (a) obtaining a base material by continuous casting of a copper-silver alloy having a silver content of 10 wt% or more and 25 wt% or less, with the remainder being copper and unavoidable impurities; and (b) obtaining a wire by performing at least one wire drawing process and heat treatment on the base material, wherein the heat treatment in (b) is as follows: (Degree of processing (η) = LN(A) ０ / A), A ０ The present invention is characterized by including an intermediate heat treatment that is performed only when the cross-sectional area of the original material (A: cross-sectional area of the wire) is 1.5 or more and 3.5 or less, and the wire that has undergone (b) above can be made to have a wire diameter of 0.050 mm or less, a degree of processing of 10 or more, a tensile strength of 1500 MPa or more, and an electrical conductivity of 40% IACS or more. Furthermore, the present invention can be made to have a wire diameter of 0.020 mm or less, a degree of processing of 13 or more, and a tensile strength of 1700 MPa or more, more preferably a wire diameter of 0.010 mm or less, a degree of processing of 14 or more, and a tensile strength of 2000 MPa or more.
[0008] According to the present invention, an ultra-fine wire made of a copper-silver alloy with excellent tensile strength can be obtained.
[0009] Figure 1 showing the relationship between the degree of processing and tensile strength of Ag15wt% wire. Figure 2 showing the relationship between the degree of processing and tensile strength of Ag24wt% wire. Figure 3 showing the relationship between the degree of processing and conductivity of Ag24wt% wire. Figure 4 showing the relationship between the degree of processing and tensile strength of Ag24wt% wire. Figure 5 showing the properties of commercial alloy wire.
[0010] Embodiments of the present invention will be described below with reference to the drawings. In this specification, unless otherwise specified, the "~" indicating a numerical range includes both an upper and lower limit.
[0011] <1> Overview The copper-silver alloy wire according to the present invention (hereinafter also simply referred to as "copper-silver alloy wire") is manufactured by taking a raw material obtained by continuous casting and appropriately combining at least one wire drawing process and heat treatment to thin it to a predetermined wire diameter (diameter of 0.050 mm or less, preferably 0.020 mm or less, more preferably 0.010 mm or less). In this invention, the raw material after the initial wire drawing process is defined as "wire".
[0012] <2> Copper-Silver Alloy The copper-silver alloy composition used as the base material in the method for manufacturing copper-silver alloy wire according to the present invention is assumed to be in the range of 10 wt% to 25 wt% of silver (Ag) relative to copper (Cu). In the present invention, as the copper-silver alloy, oxygen-free copper is used as the base, and silver is mixed in predetermined mass fractions (10 wt%, 15 wt%, 24 wt%) as specified in the tests described later. After uniform melting, a round rod with a diameter of 8 to 15 mm can be used by continuous casting. This base material is then subjected to wire drawing and heat treatment as appropriate to produce a fine wire.
[0013] <3> Heat Treatment The heat treatment performed in the method for manufacturing ultrafine wires made of copper-silver alloy according to the present invention is a process for achieving homogenization to prevent segregation of silver after casting, and precipitation to precipitate the silver phase from the copper-based solid solution phase (β phase) in order to improve the wire strength and conductivity. Therefore, heat treatment can be an important condition for determining the final wire characteristics. Regarding these conditions, we considered equilibrium phase diagrams described in known literature (for example, Metal Data Book Revised 2nd Edition, Maruzen, p417 (1984)) and examined silver concentration, degree of processing to apply heat treatment, and processing conditions to improve the processing limit.
[0014] <4> Wire drawing process In this invention, the degree of wire drawing is defined by the degree of processing defined by the following equation 1. [Equation 1] Degree of processing (η) = LN(A ０ / A) A ０ : Cross-sectional area of the original material A: Cross-sectional area of the wire
[0015] <5> Test Methods for Various Characteristics Tensile strength was measured using an Instron-type tensile testing machine with a gauge length of 100 mm and a test speed of 10 mm / min. Conductivity was measured using the double-bridge method at a voltage terminal distance of 300 to 500 mm at room temperature of 20°C, and converted to conductivity (%IACS).
[0016] <6> Test (1) First, copper and silver were mixed so that the silver content was 15 wt%, and after melting, a round bar-shaped base material with a diameter of 12 mm was produced by continuous casting and then subjected to homogenization treatment. In this test, each test specimen will be compared based on the degree of processing. The degree of processing at this point is set to 0, and wire drawing is performed as appropriate with a reduction ratio of 10-20%, and when the degree of processing reaches 3, heat treatment (intermediate heat treatment) is performed. The aforementioned heat treatment (intermediate heat treatment) was performed at 370°C for 40 hours under reduced pressure nitrogen to achieve the same tensile strength as the degree of processing 0. After that, wire drawing was performed to the predetermined diameter to thin the wire. In this test, heat treatment (intermediate heat treatment) was not performed after wire drawing from the degree of processing 3 onwards.
[0017] <6.1> Relationship between Degree of Processing and Tensile Strength Figure 1 shows the relationship between the degree of processing and tensile strength of Ag15wt% wire. As shown in Figure 1, the tensile strength increases linearly with increasing degree of processing, both before and after heat treatment (intermediate heat treatment). However, the processing limit was reached at a total degree of processing of 11, and it was not possible to increase the degree of processing any further. At this point, the tensile strength was 1600 MPa (Figure 1), and the conductivity was 50% IACS or higher (Figure 3). Therefore, in order to further improve the tensile strength, additional experiments were conducted by adjusting the silver concentration, heat treatment conditions, degree of processing, etc.
[0018] <7> Test (2) Three test specimens (No. 1 to No. 3) were prepared by increasing the silver content to 24 wt%, and while the casting and wire drawing processes of the raw material were carried out under the same conditions as in Test (1), the timing of the intermediate heat treatment was changed as shown in Table 1 below. Tensile tests were then performed on these specimens in the same manner as in Test (1).
[0019] [Table 1]
[0020] <7.1> Relationship between Degree of Processing and Tensile Strength Figure 2 shows the relationship between the degree of processing and tensile strength of Ag24 wt% wire. As shown in Figure 2, all test specimens (No. 1 to No. 3) could be processed to a total degree of processing of 11, the same as the test specimen (Ref.) for test (1). However, the wire No. 2 that underwent intermediate heat treatment at 450°C at a processing degree of 3 showed a lower tensile strength than the Ag15 wt% wire. This phenomenon is thought to be due to annealing progressing because of the large amount of heat applied to the wire.
[0021] <7.2> Degree of Processing and Conductivity Figure 3 shows the relationship between the degree of processing and conductivity of Ag24wt% wire. As shown in Figure 3, all test specimens (Ref., NO. 1 to NO. 3) were able to obtain conductivity exceeding 50% IACS at a total processing degree of 11. Furthermore, at processing degree 3 of No. 2, the wire that underwent intermediate heat treatment at 450°C showed higher conductivity than the other wires. This is thought to be due to annealing progressing during the intermediate heat treatment.
[0022] <7.3> Further Processing Levels Figure 4 shows the relationship between the processing level and tensile strength of Ag24wt% wire when the processing level is further increased from the processing level shown in Figure 2. As shown in Figure 4, for test specimens No. 1 and No. 3, which had high tensile strength at processing level 11 (wire diameter 0.049 mm), the tensile strength did not improve beyond processing level 12, and it is considered that the processing limit was reached. On the other hand, for test specimen No. 2, an improvement in tensile strength was observed even beyond processing level 12. In this test, all test specimens were confirmed to be processable to processing level 14 or higher (wire diameter 0.01 mm), and the tensile strength at that time exceeded 1600 MPa, and for test specimen No. 2, the tensile strength exceeded 2000 MPa. Although not shown in the figure, at processing level 12, the conductivity of all test specimens was 51% IACS or higher, and at processing level 14, No. The conductivity of test specimen 2 was 43% IACS or higher.
[0023] <8> Test (3) Next, copper and silver were mixed so that the silver content was 10 wt%, 15 wt%, and 24 wt%, and after melting, a round bar shape with a diameter of 12 mm was produced by continuous casting and homogenization treatment was performed. In this test as well, each test specimen will be compared based on the degree of processing. The degree of processing at this point is set to 0, and wire drawing is performed as appropriate with a reduction ratio of 10-20%, and heat treatment (intermediate heat treatment) is performed on the wire when the degree of processing reaches approximately 2-3. The aforementioned heat treatment (intermediate heat treatment) was performed at 370°C or 450°C for 40 hours under reduced pressure nitrogen to achieve a tensile strength almost the same as that of the degree of processing 0. After that, wire drawing was performed to the predetermined diameter to make it thinner. In this test as well, no heat treatment (intermediate heat treatment) was performed after the wire drawing process after the intermediate heat treatment. An overview of each test specimen (No. 4 to No. 8) is shown in Table 2 below.
[0024] [Table 2]
[0025] <8.1> Test Results For each test specimen (No. 4 to No. 8), the tensile strength and conductivity at each stage of wire drawing and heat treatment were performed using the same method as in Test (1), as shown in Tables 3 to 7 below.
[0026] [Table 3]
[0027] [Table 4]
[0028] [Table 5]
[0029] [Table 6]
[0030] [Table 7]
[0031] <8.2> Discussion The trends in tensile strength and conductivity of the wires that can be inferred from the results in Tables 3 to 7 are shown below.
[0032] (1) Trend 1: When the silver content of the raw material is set to 10 wt% or more and 25 wt% or less, and heat treatment (intermediate heat treatment) is performed at a processing degree of 1.5 to 3.5, a wire with a diameter of 0.050 mm or less and a processing degree of 10 or more can have a tensile strength of 1500 MPa or more and an electrical conductivity of 40% IACS or more.
[0033] (2) Trend 2 When the silver content of the raw material is set to 10 wt% or more and 25 wt% or less, and heat treatment (intermediate heat treatment) is performed at a processing degree of 1.5 to 3.5, a wire with a diameter of 0.020 mm or less and a processing degree of 13 or more can have a tensile strength of 1700 MPa or more and an electrical conductivity of 40% IACS or more. In particular, for test specimens (No. 5 to No. 7) with a silver content of 15 wt% to 25 wt% in the raw material, the tensile strength was 1800 MPa or more.
[0034] (3) Trend 3 When the silver content of the raw material is set to 10 wt% or more and 25 wt% or less, and heat treatment (intermediate heat treatment) is performed at a processing degree of 1.5 to 3.5, a wire with a diameter of 0.010 mm or less and a processing degree of 14 or more can have a tensile strength of 1800 MPa or more and an electrical conductivity of 40% IACS or more. In particular, among the test specimens (NO. 5 to NO. 7) with a silver content of 15 wt% to 25 wt% in the raw material, the tensile strength of test specimens NO. 5 and NO. 7 was 2000 MPa or more.
[0035] <9> Summary From the results of the tests (1) to (3) described above, it was confirmed that increasing the silver concentration improves tensile strength, and further optimizing the heat treatment conditions contributes to further improvements in tensile strength and workability. In particular, it was found that by using a copper-silver alloy with a silver content of 15 wt% to 25 wt% in the base material and performing the intermediate heat treatment when the degree of processing is 1.5 or more and 3.5 or less, there is a high probability of obtaining a wire with a diameter of 0.010 mm or less and a tensile strength of 2000 MPa or more.
Claims
1. A method for manufacturing a copper-silver alloy wire, comprising at least the steps of: (a) obtaining a base material by continuous casting of a copper-silver alloy having a silver content of 10 wt% or more and 25 wt% or less, with the remainder being copper and unavoidable impurities; and (b) obtaining a wire by performing at least one wire drawing process and heat treatment on the base material, wherein the heat treatment in (b) includes an intermediate heat treatment that is performed only when the degree of processing according to the following formula 1 is 1.5 or more and 3.5 or less: [Formula 1] Degree of processing (η) = LN(A ０ / A) A ０ A: Cross-sectional area of the original material A: Cross-sectional area of the wire A method for manufacturing a copper-silver alloy wire, characterized in that the wire obtained through (b) above has a wire diameter of 0.050 mm or less, a degree of processing of 10 or more, a tensile strength of 1500 MPa or more, and an electrical conductivity of 40% IACS or more.
2. The method for manufacturing a copper-silver alloy wire according to claim 1, characterized in that the wire having undergone (b) has a wire diameter of 0.020 mm or less, a degree of processing of 13 or more, and a tensile strength of 1700 MPa or more.
3. The method for manufacturing a copper-silver alloy wire according to claim 2, characterized in that the wire having undergone (b) has a wire diameter of 0.010 mm or less, a degree of processing of 14 or more, and a tensile strength of 2000 MPa or more.
4. A copper-silver alloy wire characterized in that the silver content is 10 wt% or more and 25 wt% or less, the remainder being copper and unavoidable impurities, the wire diameter is 0.050 mm or less, the tensile strength is 1500 MPa or more, and the conductivity is 40% IACS or more.
5. A copper-silver alloy wire according to claim 4, characterized in that the wire diameter is 0.020 mm or less, the degree of processing is 13 or more, and the tensile strength is 1700 MPa or more.
6. A copper-silver alloy wire according to claim 5, characterized in that the wire diameter is 0.010 mm or less, the degree of processing is 14 or more, and the tensile strength is 2000 MPa or more.