High-strength, high-conductivity and low-dislocation-density copper alloy micro-fine wire for signal transmission and preparation method thereof

Abstract

The invention relates to a high-strength, high-conductivity and low-dislocation-density copper alloy wire for signal transmission and connection and a preparation method of the high-strength, high-conductivity and low-dislocation-density copper alloy wire. The fine control problems of uneven components and structures during casting, grain orientation / microdefects in the forming process and the like are solved, the wire has good machining performance, and the wire still has good mechanical and electrical properties after subsequent machining.

Description

Technical Field

[0001] This invention relates to the technical field of metal processing, specifically to a high-strength, high-conductivity, low-dislocation-density copper alloy microwire and its preparation method. Background Technology

[0002] Copper alloy wires are crucial conductors for transmitting electricity and electrical signals in key systems such as signal transmission, electric drives, and intelligent sensing. Copper-tin alloys, possessing good strength, conductivity, corrosion resistance, weldability, thermal conductivity, and low cost, are widely used in automotive wiring harnesses, medical equipment cables, ABS cables, microphone coils, and industrial robots. These fields are continuously developing towards higher intelligence, higher performance, and lower cost, requiring key conductor materials to possess both high strength and high conductivity. However, current copper alloys commonly used in wires and cables face challenges in simultaneously improving their mechanical and electrical properties. The solute elements in the casting and forming processes lack sufficient precision in controlling the grain orientation and microscopic defects of the material, resulting in poor product consistency and significantly limiting their application.

[0003] Patent CN119663045A discloses a special copper-tin alloy material, its preparation method, and its applications. This method prepares high-tin-content special copper-tin alloy parts through extrusion, rolling, and cryogenic treatment. However, the high-temperature hot extrusion and rolling processes of this method suffer from uneven deformation, high residual stress, and are unfavorable for processing ultra-long, fine wires. Patent CN114480894A discloses an industrial production process for high-strength copper-tin alloy contact wires. This method improves processing performance by adding zinc to the copper-tin alloy. The copper-tin alloy contact wires obtained using continuous casting, extrusion, rolling, and cold drawing achieve a tensile strength of over 527.8–531.5 MPa and a conductivity of over 70.9–71.2% IACS. However, this method requires the addition of Zn, increasing costs, and the uniformity of trace elements and microstructure are difficult to control precisely during preparation, leaving room for improvement in both mechanical and electrical properties. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-strength, high-conductivity, low-dislocation-density copper alloy wire for signal transmission and its preparation method. This method produces copper alloy micro-wires with excellent mechanical and electrical properties, low cost, high tensile strength, and high conductivity. It solves the problems of fine control during casting, such as uneven composition and microstructure, and grain orientation / microscopic defects during forming. This results in wires with good processing performance and good mechanical and electrical properties even after subsequent processing.

[0005] The technical solution of the present invention is, A high-strength, high-conductivity, low-dislocation-density copper alloy microfilament for signal transmission is disclosed. This microfilament is composed of tin, copper, and other unavoidable impurities, with the mass percentage of tin being 0.03-0.3%, and the remainder being copper and impurities. The diameter of the microfilament is 0.03-0.157 mm, and its fine grains... <111> The crystal orientation is preferentially aligned, and the 2*10 of the microfilaments 14 / m 2 <Average dislocation density<15*10 14 / m 2 .

[0006] The preparation method of the above-mentioned copper alloy micro-wires includes the following steps: 1) Weigh copper and tin according to the proportions described in claim 1, and smelt them into ingots; 2) Continuous casting of ingots yields copper-tin alloy continuous casting rods; 3) The continuous casting rod is continuously extruded to 12-16mm, through multiple passes of equal diameter angular extrusion. After each pass of extrusion, it is rotated 90° around the axis to obtain a copper-tin alloy extrusion rod. During extrusion, the angle between the outer ends of the deformation die is 20° to 90°, and the angle between the two straight sections is 90° to 120°. 4) Heat-treat the copper-tin alloy extrusion bar in a protective atmosphere, cool it to room temperature and draw it to 8-10 mm, with a deformation of 25% per pass and a drawing speed of 15 m / min; heat-treat it again, cool it to room temperature, and draw it in multiple passes to obtain copper-tin alloy micro wires with a diameter of 0.03-0.157 mm.

[0007] Step 1) describes a melting method performed in a vacuum furnace with a vacuum degree ≤ 2.0 × 10⁻⁶. -2 Pa, heating temperature is 1200℃-1300℃, holding time is 2-3h, and cooling is carried out with the furnace.

[0008] Step 2) The continuous casting is a vertical downward drawing continuous casting, and the method is that the vacuum degree is ≤2.0×10 -2 Pa, filled with argon gas, heated to 1150℃-1250℃, held for 30-45 min, continuous casting derrick speed 100-150 mm / min, traction and pause time 200 ms, cooling water temperature for lower continuous casting 20-35℃, cooling water flow rate 25-40 L / min.

[0009] Step 2) The diameter of the copper-tin alloy continuous casting rod is 16-20mm.

[0010] Step 3) The continuous extrusion is carried out using an extruder with a main extruder speed of 2.0-5.0 rpm, a wheel surface gap of 0.3-0.4 mm, and a die cavity preheating temperature of 550±10℃.

[0011] Step 3) The number of times the multi-pass equal diameter angular extrusion is 2 to 6; the extrusion speed of the equal diameter angular extrusion is 1-10 mm / s.

[0012] Step 4) The protective atmosphere is nitrogen or argon.

[0013] Step 4) The heat treatment temperature is 200-300℃, and the holding time is 45-90 min. The second heat treatment temperature is 500-600℃, and the holding time is 15-20 min.

[0014] Step 4) The multi-pass drawing process is as follows: when the diameter of the copper-tin alloy wire rod is ≥8mm, the deformation per pass is 20%-30%, and the drawing speed is 10-20m / min; when the diameter of the copper-tin alloy wire rod is 3mm≤ and <8mm, the deformation per pass is 15%-20%, and the drawing speed is 20-80m / min; when the diameter of the copper-tin alloy wire rod is 0.8mm≤ and <3mm, the deformation per pass is 10%-15%, and the drawing speed is 80-500m / min; when the diameter of the copper-tin alloy wire is <0.8mm, the deformation per pass is 5%-10%, and the drawing speed is 500-1000m / min.

[0015] The beneficial effects of this invention include the following: (1) The present invention uses a vacuum vertical casting method to obtain copper-tin alloy billet before deformation processing. By controlling the continuous casting process, axial columnar crystals are obtained, which increases the uniformity of composition and structure, avoids tin segregation and defects such as porosity and inclusions, improves the surface quality of the rod, and lays the foundation for subsequent large deformation processing and micro drawing. It avoids cracking and wire breakage during processing, and can achieve 500,000 meters of continuous wire during subsequent processing. (2) Fine equiaxed crystals are obtained through continuous extrusion, achieving the goal of strengthening the mechanical properties (such as tensile strength and hardness) of the material through fine grain reinforcement. During the extrusion process, the diffusion of tin is accelerated under a temperature rise environment, and solid solution treatment is achieved during the extrusion process. Furthermore, the continuous extrusion method can prepare ultra-long materials, with high production efficiency and good surface finish of the rod, which is beneficial for subsequent processing and improving the consistency of the products, with batch fluctuations in wire diameter less than 2%.

[0016] (3) By combining two heat treatments with a drawing process, dislocations are recovered to a certain extent while ensuring that the tensile strength is not reduced, thus reducing the dislocation density and achieving a fine-grained and uniform microstructure with a density of 2*10. 14 / m 2 <Average dislocation density<15*10 14 / m 2 This further improves conductivity, ensuring conductivity >87% IACS.

[0017] (4) By using a low-speed, multi-pass equal-diameter angular extrusion method, large deformation of pure shear is introduced, resulting in refined and uniform grains. This causes equiaxed grains to undergo single or multiple slip, transforming them into elongated shapes with parallel shear strain directions. When the slip reaches a certain level, it evolves into a shape along the shear strain direction. <111> Fine grains with a preferred crystal orientation achieve improved strength and electrical conductivity without the addition of other elements. By designing process parameters such as angle and speed, friction and localized heating are reduced, preventing material softening and uneven deformation, thus improving overall performance.

[0018] Based on the above results, multiple experiments have shown that the filaments produced by the above method with refined microstructure control have excellent mechanical and electrical properties. Specifically, the tensile strength of the 0.155~0.157mm filaments is >750MPa, the conductivity is >87%IACS, and the filaments have good processing performance. When the filaments are processed to 0.03mm, the tensile strength is >1150MPa, and the conductivity is still >87%IACS. Attached Figure Description

[0019] Figure 1 Metallographic image of the cross-section of the continuous casting rod showing longitudinal columnar crystal structure; Figure 2 The images and EBSD inverse pole figures of the copper-tin alloy wire drawn to φ0.9mm in Example 2 show a uniform and fine microstructure. <111> Directional texture; Figure 3 The image shows the statistical distribution of grain size in the cross-section of Example 2, with an average grain size of 0.9 μm. Figure 4 This is a dislocation density statistics chart for Example 2, with an average dislocation density of 7.6*10. 14 / m 2 ; Figure 5 Metallographic profile of the copper-tin alloy cross section in Example 2; Figure 6 Photograph of a copper-tin alloy microwire sample; Figure 7 Metallographic profile of a copper-tin alloy cross section, Comparative Example 1; Figure 8 Metallographic profile of a copper-tin alloy cross section for comparative example 2. Detailed Implementation

[0020] The following description, in conjunction with the accompanying drawings and specific embodiments, provides further details.

[0021] This invention uses Cu with a purity of ≥99.999% and Sn with a purity of ≥99.95% as raw materials. Example 1:

[0022] The preparation of high-strength, high-conductivity, low-dislocation-density copper alloy microwires includes the following steps: 1) Weigh 99.91 wt.% copper blocks and 0.09 wt.% tin particles into a graphite crucible, and evacuate the furnace to a vacuum level ≤2.0 × 10⁻⁶. -2 Pa, heated to 1250℃, held for 2 hours, cooled in the furnace, and smelted into ingots; 2) Add the ingot to the lower-draw continuous casting furnace and evacuate to a vacuum level of ≤2.0×10⁻⁶. -2 Pa, filled with argon gas for protection, heated to 1200℃, held for 35min, the speed of the guide rod for the downward continuous casting is 150mm / min, using intermittent working mode, the traction and pause time are both 200ms, the cooling water temperature for the downward continuous casting is 25℃, the cooling water flow rate is 30L / min, and a copper-tin alloy rod with a diameter of 18mm is continuously cast.

[0023] 3) The copper-tin alloy continuous casting rod is placed in an extrusion press for extrusion. The main machine speed is 3.0 rpm, the wheel surface clearance is 0.4 mm, and the die cavity preheating temperature is 550℃. After continuous extrusion to 14 mm, the sample surface is wiped with anhydrous ethanol and lubricant is applied. It is then placed in the hydraulic press die channel for multi-pass equal-diameter angular extrusion. The outer end angle of the customized deformation die is 60°, the angle between the two straight sections is 120°, the extrusion speed is 5 mm / s, and after each extrusion pass, the die is rotated 90° around the axis, and extrusion is repeated 4 times.

[0024] 4) Heat-treat the extrusion rod under nitrogen protection, heating it to 200℃ and holding it for 60 minutes, then cooling it to room temperature for drawing. The deformation amount per drawing pass is 25%, the drawing speed is 15m / min, and the wire is drawn to a diameter of 10mm. Then, heat-treat it in nitrogen, heating it to 550℃ and holding it for 20 minutes, then cooling it to room temperature for drawing. When the diameter of the copper-tin alloy wire rod is ≥8mm, the deformation per pass during drawing is 20%, and the drawing speed is 20m / min; when the diameter of the copper-tin alloy wire rod is 3mm≤ and <8mm, the deformation per pass during drawing is 15%, and the drawing speed is 50m / min; when the diameter of the copper-tin alloy wire rod is 0.8mm≤ and <3mm, the deformation per pass during drawing is 10%, and the drawing speed is 400m / min; when the diameter of the copper-tin alloy wire is <0.8mm, the deformation per pass during drawing is 5%, and the drawing speed is 800m / min, resulting in a micro-wire with a diameter of 0.155mm.

[0025] 5) A Niehof machine was used to strand 7 wires at a speed of 60m / min, a rotation speed of 5000rpm, and a single wire tension of 1.0 N, to obtain a wire harness core material with a stranded outer diameter of approximately 0.466mm.

[0026] The copper-tin alloy microwires obtained in Example 1 tested had a tensile strength of 763 MPa, a conductivity of 87.8% IACS, an elongation of 3.5%, and an average dislocation density of 5.1 × 10⁻⁶. 14 / m 2 The tensile strength of the stranded wire harness core is 757 MPa, the resistance at 20℃ is 145 mΩ / m, and no wire breakage occurred during 550,000 meters of continuous pulling and stranding. Example 2:

[0027] The preparation of high-strength, high-conductivity, low-dislocation-density copper alloy microwires includes the following steps: 1) Weigh 99.83 wt.% copper ingots and 0.17 wt.% tin particles into a graphite crucible, and evacuate the furnace to a vacuum level ≤2.0 × 10⁻⁶. -2 Pa, heated to 1250℃, held for 2 hours, cooled in the furnace, and smelted into ingots; 2) Add the ingot to the lower-draw continuous casting furnace and evacuate to a vacuum level of ≤2.0×10⁻⁶. -2 Pa, argon gas protection, heated to 1200℃, held for 35 min, the derrick speed of the downward continuous casting was 120 mm / min, using intermittent working mode, with traction and pause times both 200 ms, the cooling water temperature of the downward continuous casting was 25℃, and the cooling water flow rate was 30 L / min, continuously casting a copper-tin alloy rod with a diameter of 16 mm. See [link / reference]. Figure 1 .

[0028] 3) The copper-tin alloy continuous casting rod is placed in an extrusion press for extrusion. The main machine speed is 3.0 rpm, the wheel surface clearance is 0.4 mm, and the die cavity preheating temperature is 550℃. After continuous extrusion to 12 mm, the sample surface is wiped with anhydrous ethanol and lubricant is applied. It is then placed in the hydraulic press die channel for multi-pass equal-diameter angular extrusion. The outer end angle of the customized deformation die is 60°, the angle between the two straight sections is 120°, the extrusion speed is 5 mm / s, and after each extrusion pass, the die is rotated 90° around the axis and extruded twice.

[0029] 4) The extrusion rod is heat-treated under nitrogen protection, heated to 200℃, held for 60 minutes, and then cooled to room temperature for drawing. The deformation per drawing pass is 25%, the drawing speed is 15 m / min, and the wire is drawn to a diameter of 8 mm. It is then heat-treated in nitrogen again, heated to 550℃, held for 20 minutes, and cooled to room temperature for further drawing. When the diameter of the copper-tin alloy wire rod is 3 mm ≤ 8 mm, the deformation per drawing pass is 15%, and the drawing speed is 50 m / min; when the diameter of the copper-tin alloy wire rod is 0.8 mm ≤ 3 mm, the deformation per drawing pass is 10%, and the drawing speed is 400 m / min; when the diameter of the copper-tin alloy wire is < 0.8 mm, the deformation per drawing pass is 5%, and the drawing speed is 800 m / min, resulting in a micro-wire with a diameter of 0.155 mm. See [link to relevant documentation]. Figures 2-6 .

[0030] 5) A Niehof machine was used to strand 7 wires at a speed of 60m / min, a rotation speed of 5000rpm, and a single wire tension of 1.0 N, to obtain a wire harness core material with a stranded outer diameter of approximately 0.466mm.

[0031] The copper-tin alloy microfilaments obtained in Example 2 tested had a tensile strength of 772 MPa, a conductivity of 87.3% IACS, an elongation of 2.5%, and an average dislocation density of 7.6 × 10⁻⁶. 14 / m 2 The tensile strength of the stranded wire harness core is 765 MPa, the resistance at 20℃ is 148 mΩ / m, and no wire breakage occurred during continuous pulling and stranding of 520,000 meters. Example 3:

[0032] The preparation of high-strength, high-conductivity, low-dislocation-density copper alloy microwires includes the following steps: 1) Weigh out 99.93 wt.% copper blocks and 0.07 wt.% tin particles and place them in a graphite crucible. In a vacuum furnace, evacuate the vacuum to ≤2.0 × 10⁻⁶. -2 Pa, heated to 1250℃, held for 2 hours, cooled in the furnace, and smelted into ingots; 2) Add the ingot to the lower-draw continuous casting furnace and evacuate to a vacuum level of ≤2.0×10⁻⁶. -2 Pa, filled with argon gas for protection, heated to 1200℃, held for 35min, the speed of the guide rod for the downward continuous casting is 150mm / min, the intermittent working mode is adopted, the traction and pause time are both 200ms, the cooling water temperature for the downward continuous casting is 25℃, the cooling water flow rate is 30L / min, and a copper-tin alloy rod with a diameter of 20mm is continuously cast.

[0033] 3) The copper-tin alloy continuous casting rod is placed in an extrusion press for extrusion. The main machine speed is 3.0 rpm, the wheel surface clearance is 0.4 mm, and the die cavity preheating temperature is 550℃. After continuous extrusion to 14 mm, the sample surface is wiped with anhydrous ethanol and lubricant is applied. It is then placed in the hydraulic press die channel for multi-pass equal-diameter angular extrusion. The outer end angle of the customized deformation die is 60°, the angle between the two straight sections is 120°, the extrusion speed is 5 mm / s, and after each extrusion pass, the die is rotated 90° around the axis, for a total of 6 extrusion passes.

[0034] 4) Heat-treat the extrusion rod under nitrogen protection, heating to 200℃ and holding for 80 minutes, then cooling to room temperature for drawing. The deformation per drawing pass is 25%, and the drawing speed is 15 m / min. Draw to a diameter of 10 mm, then heat-treat in nitrogen to 600℃ and hold for 20 minutes, then cool to room temperature for drawing. When the diameter of the copper-tin alloy wire rod is ≥8 mm, the deformation per drawing pass is 20%, and the drawing speed is 20 m / min; when the diameter of the copper-tin alloy wire rod is 3 mm ≤ and <8 mm, the deformation per drawing pass is 15%, and the drawing speed is 50 m / min; when the diameter of the copper-tin alloy wire rod is 0.8 mm ≤ and <3 mm, the deformation per drawing pass is 10%, and the drawing speed is 400 m / min; when the diameter of the copper-tin alloy wire rod is <0.8 mm, the deformation per drawing pass is 5%, and the drawing speed is 800 m / min. A microfilament with a diameter of 0.155 mm was obtained. Half of the filament was taken and drawn to 0.03 mm. The deformation per drawing pass was 5%, and the drawing speed was 1000 m / min, resulting in microfilaments with diameters of 0.155 mm and 0.03 mm.

[0035] 5) A Niehof machine was used to strand 7 wires of 0.155mm diameter at a speed of 60m / min, a rotation speed of 5000rpm, and a single wire tension of 1.0N to obtain a stranded core material with an outer diameter of approximately 0.466mm.

[0036] The 0.155 mm copper-tin alloy microwire prepared in Example 3 had a tensile strength of 759 MPa, a conductivity of 88.1% IACS, an elongation of 3.5%, and an average dislocation density of 3.9 × 10⁻⁶. 14 / m 2 The stranded wire harness core has a tensile strength of 754 MPa and a resistivity of 142 mΩ / m at 20℃. The copper-tin alloy microwire with a diameter of 0.03 mm has a tensile strength of 1167 MPa and a conductivity of 88.8% IACS. Example 4:

[0037] The preparation of high-strength, high-conductivity, low-dislocation-density copper alloy microwires includes the following steps: 1) Weigh out 99.87 wt.% copper ingots and 0.13 wt.% tin particles and place them in a graphite crucible. In a vacuum furnace, evacuate the vacuum to ≤2.0 × 10⁻⁶. -2 Pa, heated to 1250℃, held for 2 hours, cooled in the furnace, and smelted into ingots; 2) Add the ingot to the lower-draw continuous casting furnace and evacuate to a vacuum level of ≤2.0×10⁻⁶. -2Pa, filled with argon gas for protection, heated to 1200℃, held for 35min, the speed of the traction rod for the downward continuous casting is 120mm / min, the intermittent working mode is adopted, the traction and pause time are both 200ms, the cooling water temperature for the downward continuous casting is 25℃, the cooling water flow rate is 30L / min, and a copper-tin alloy rod with a diameter of 18mm is continuously cast.

[0038] 3) The copper-tin alloy continuous casting rod is placed in an extrusion press for extrusion. The main machine speed is 3.0 rpm, the wheel surface clearance is 0.4 mm, and the die cavity preheating temperature is 550℃. After continuous extrusion to 14 mm, the sample surface is wiped with anhydrous ethanol and lubricant is applied. It is then placed in the hydraulic press die channel for multi-pass equal-diameter angular extrusion. The outer end angle of the customized deformation die is 60°, the angle between the two straight sections is 120°, the extrusion speed is 5 mm / s, and after each extrusion pass, the die is rotated 90° around the axis, and extrusion is repeated 4 times.

[0039] 4) Heat-treat the extrusion rod under nitrogen protection, heating to 200℃ and holding for 80 minutes, then cooling to room temperature for drawing. The deformation per drawing pass is 25%, and the drawing speed is 15 m / min. Draw to a diameter of 10 mm, then heat-treat in nitrogen to 550℃ and hold for 20 minutes, then cool to room temperature for drawing. When the diameter of the copper-tin alloy wire rod is ≥8 mm, the deformation per drawing pass is 20%, and the drawing speed is 40 m / min; when the diameter of the copper-tin alloy wire rod is 3 mm ≤ and <8 mm, the deformation per drawing pass is 15%, and the drawing speed is 50 m / min; when the diameter of the copper-tin alloy wire rod is 0.8 mm ≤ and <3 mm, the deformation per drawing pass is 10%, and the drawing speed is 400 m / min; when the diameter of the copper-tin alloy wire rod is <0.8 mm, the deformation per drawing pass is 5%, and the drawing speed is 800 m / min. A microfilament with a diameter of 0.155 mm was obtained.

[0040] 5) A Niehof machine was used to perform 7-wire stranding at a speed of 60m / min, a rotation speed of 5000rpm, and a single-wire tension of 1.0 N, resulting in a wire harness core material with a stranded outer diameter of approximately 0.468mm.

[0041] The copper-tin alloy microwires obtained in Example 4 tested had a tensile strength of 768 MPa, a conductivity of 87.5% IACS, an elongation of 3%, and an average dislocation density of 6.4 × 10⁻⁶. 14 / m 2 The tensile strength of the stranded wire harness core is 761 MPa, the resistance at 20℃ is 146 mΩ / m, and no wire breakage occurred during 550,000 meters of continuous pulling and stranding. Example 5:

[0042] The preparation of high-strength, high-conductivity, low-dislocation-density copper alloy microwires includes the following steps: 1) Weigh out 99.76 wt.% copper ingots and 0.24 wt.% tin particles and place them in a graphite crucible. In a vacuum furnace, evacuate the vacuum to ≤2.0 × 10⁻⁶. -2 Pa, heated to 1300℃, held for 2 hours, cooled in the furnace, and smelted into ingots; 2) Add the ingot to the lower-draw continuous casting furnace and evacuate to a vacuum level of ≤2.0×10⁻⁶. -2 Pa, filled with argon gas for protection, heated to 1250℃, held for 35min, the speed of the traction rod for the downward continuous casting is 150mm / min, using intermittent working mode, the traction and pause time are both 200ms, the cooling water temperature for the downward continuous casting is 25℃, the cooling water flow rate is 30L / min, and a copper-tin alloy rod with a diameter of 16mm is continuously cast.

[0043] 3) The copper-tin alloy continuous casting rod is placed in an extrusion press for extrusion. The main machine speed is 3.0 rpm, the wheel surface clearance is 0.4 mm, and the die cavity preheating temperature is 550℃. After continuous extrusion to 14 mm, the sample surface is wiped with anhydrous ethanol and lubricant is applied. It is then placed in the hydraulic press die channel for multi-pass equal-diameter angular extrusion. The outer end angle of the customized deformation die is 60°, the angle between the two straight sections is 120°, the extrusion speed is 5 mm / s, and after each extrusion pass, the rod is rotated 90° around the axis and extruded twice.

[0044] 4) Heat-treat the extrusion rod under nitrogen protection, heating to 200℃ and holding for 80 minutes, then cooling to room temperature for drawing. The deformation per drawing pass is 25%, and the drawing speed is 15 m / min. Draw to a diameter of 10 mm, then heat-treat in nitrogen to 600℃ and hold for 20 minutes, then cool to room temperature for drawing. When the diameter of the copper-tin alloy wire rod is ≥8 mm, the deformation per drawing pass is 20%, and the drawing speed is 20 m / min; when the diameter of the copper-tin alloy wire rod is 3 mm ≤ and <8 mm, the deformation per drawing pass is 15%, and the drawing speed is 50 m / min; when the diameter of the copper-tin alloy wire rod is 0.8 mm ≤ and <3 mm, the deformation per drawing pass is 10%, and the drawing speed is 400 m / min; when the diameter of the copper-tin alloy wire rod is <0.8 mm, the deformation per drawing pass is 5%, and the drawing speed is 800 m / min. A microfilament with a diameter of 0.155 mm was obtained. Half of the filament was taken and drawn to 0.03 mm. The deformation per drawing pass was 5%, and the drawing speed was 1000 m / min, resulting in microfilaments with diameters of 0.155 mm and 0.03 mm.

[0045] 5) A Niehof machine was used to strand 7 wires of 0.155 mm diameter at a speed of 60 m / min, a rotation speed of 5000 rpm, and a single wire tension of 1.0 N to obtain a stranded core material with an outer diameter of approximately 0.468 mm.

[0046] The 0.155 mm copper-tin alloy microwire prepared in Example 5 tested showed a tensile strength of 781 MPa, a conductivity of 87.1% IACS, an elongation of 2%, and an average dislocation density of 11.4 × 10⁻⁶. 14 / m 2 The stranded wire harness core has a tensile strength of 770 MPa and a resistivity of 150 mΩ / m at 20℃. The copper-tin alloy microwire with a diameter of 0.03 mm has a tensile strength of 1181 MPa and a conductivity of 88.2% IACS. Comparative Example 1:

[0047] Steps 1) and 2) are the same as in Example 2.

[0048] 3) The copper-tin alloy rod is continuously drawn. When the diameter of the copper-tin alloy wire rod is ≥8mm, the deformation per pass is 25% and the drawing speed is 15m / min; when the diameter of the copper-tin alloy wire rod is 3mm≤ and <8mm, the deformation per pass is 15% and the drawing speed is 50m / min; when the diameter of the copper-tin alloy wire rod is 0.8mm≤ and <3mm, the deformation per pass is 10% and the drawing speed is 400m / min; when the diameter of the copper-tin alloy wire is <0.8mm, the deformation per pass is 5% and the drawing speed is 800m / min, to obtain a micro wire with a diameter of 0.155mm.

[0049] The 0.155 mm copper-tin alloy microwire prepared in Comparative Example 1 was tested and found to have a tensile strength of 683 MPa, a conductivity of 85.2% IACS, an elongation of 1.5%, and an average dislocation density of 27.71 × 10⁻⁶. 14 / m 2 During the process of continuing to draw the wire to 0.03mm at a rate of 5% per pass and a drawing speed of 800m / min, the wire broke 4 times in a length of 18,000 meters.

[0050] Compared with Example 2, Comparative Example 1, despite having the same composition, exhibits relatively poor uniformity due to the absence of the multi-pass equal diameter angular extrusion, heat treatment, and drawing steps described in this invention. Figure 7 and Figure 5 In subsequent microfilament processing, the breakage rate is relatively high because simple drawing applies force to the surface of the filament, and the uniformity near the surface is higher than that of the core, failing to achieve the solution treatment and microstructure refinement effects of Example 2. Furthermore, it can be seen that the strength improvement effect achieved by drawing for the same continuous casting rod diameter is limited, and the conductivity also decreases to some extent due to dislocation accumulation. Comparative Example 2:

[0051] 1) Weigh 99.83 wt.% copper ingots and 0.17 wt.% tin particles into a graphite crucible, and evacuate the furnace to a vacuum level ≤2.0 × 10⁻⁶.-2 Pa, heat to 1250℃, hold for 2 hours, and pour into a φ40mm water-cooled copper mold; 2) The ingot is placed in an extrusion press for extrusion. The main machine speed is 3.0 rpm, the wheel surface clearance is 0.4 mm, and the die cavity preheating temperature is 550℃. After continuous extrusion to 14 mm, the sample surface is wiped with anhydrous ethanol and lubricant is applied. It is then placed in the hydraulic press die channel for multiple passes of equal diameter angular extrusion. The outer end angle of the customized deformation die is 60°, the angle between the two straight sections is 120°, the extrusion speed is 5 mm / s, and after each extrusion pass, the die is rotated 90° around the axis, and extrusion is performed 4 times.

[0052] 4) The extrusion rod is drawn. When the diameter of the copper-tin alloy wire rod is ≥8mm, the deformation per pass is 25% and the drawing speed is 15m / min; when the diameter of the copper-tin alloy wire rod is 3mm≤ and <8mm, the deformation per pass is 15% and the drawing speed is 50m / min; when the diameter of the copper-tin alloy wire rod is 0.8mm≤ and <3mm, the deformation per pass is 10% and the drawing speed is 400m / min; when the diameter of the copper-tin alloy wire is <0.8mm, the deformation per pass is 5% and the drawing speed is 800m / min, to obtain a micro wire with a diameter of 0.155mm.

[0053] Tests showed that the 0.155mm copper-tin alloy microwire prepared in Comparative Example 2 had a tensile strength of 740MPa, a conductivity of 83.7% IACS, and an elongation of 1.0%. During the subsequent drawing process to 0.03mm at a rate of 5% deformation per pass and a drawing speed of 800m / min, the wire broke three times within a 3500-meter stretch.

[0054] Compared with Example 2, Comparative Example 2, due to the absence of continuous casting, heat treatment, and drawing steps, resulted in significantly poorer uniformity of the microstructure of the wire formed from the cast ingot after extrusion and drawing, despite having the same composition. Figure 8 and Figure 5 Furthermore, the micro-machining process has an extremely high breakage rate, making mass production impossible. During the cooling and solidification process, Sn segregation occurs as crystallization progresses from the outer edge of the large ingot towards the core. Additionally, surface defects and porosity introduce into the ingot, affecting subsequent processing performance. Moreover, although continuous extrusion and equal-diameter angular extrusion significantly improved tensile strength (compared to Comparative Example 1), the electrical conductivity was significantly lower due to casting defects and the lack of subsequent multi-stage heat treatment to regulate the microstructure.

[0055] Conclusion: The high-strength, high-conductivity copper-tin alloy wire prepared by the method described in this invention, through the design of a process route including vertical continuous casting, continuous extrusion, equal-diameter angular extrusion, drawing, and multi-pass heat treatment, and precise control of the microstructure, results in a fine, uniform microstructure. <111> With a preferred crystal orientation and low dislocation density, the copper alloy wire possesses high tensile strength, high conductivity, and excellent micro-processing performance.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A high-strength, high-conductivity, low-dislocation-density copper alloy microwire for signal transmission, characterized in that, The microfilament is composed of tin, copper, and other unavoidable impurities, with tin comprising 0.03-0.3% by mass, and the remainder being copper and impurities. The microfilament has a diameter of 0.03-0.157 mm, and its fine grains are... <111> The crystal orientation is preferentially aligned, and the 2*10 of the microfilaments 14 / m 2 <Average dislocation density<15*10 14 / m 2 .

2. The method for preparing the copper alloy micro-wires according to claim 1, characterized in that, Includes the following steps: 1) Weigh copper and tin according to the proportions described in claim 1, and smelt them into ingots; 2) Continuous casting of ingots yields copper-tin alloy continuous casting rods; 3) The continuous casting rod is continuously extruded to 12-16mm, through multiple passes of equal diameter angular extrusion. After each pass of extrusion, it is rotated 90° around the axis to obtain a copper-tin alloy extrusion rod. During extrusion, the angle between the outer ends of the deformation die is 20° to 90°, and the angle between the two straight sections is 90° to 120°. 4) Heat-treat the copper-tin alloy extrusion bar in a protective atmosphere, cool it to room temperature and draw it to 8-10 mm, with a deformation of 25% per pass and a drawing speed of 15 m / min; heat-treat it again, cool it to room temperature, and draw it in multiple passes to obtain copper-tin alloy micro wires with a diameter of 0.03-0.157 mm.

3. The preparation method according to claim 2, characterized in that: Step 1) describes a melting method performed in a vacuum furnace with a vacuum degree ≤ 2.0 × 10⁻⁶. -2 Pa, heating temperature is 1200℃-1300℃, holding time is 2-3h, and cooling is carried out with the furnace.

4. The preparation method according to claim 2, characterized in that: Step 2) The continuous casting is a vertical downward drawing continuous casting, and the method is that the vacuum degree is ≤2.0×10 -2 Pa, filled with argon gas, heated to 1150℃-1250℃, held for 30-45 min, continuous casting derrick speed 100-150 mm / min, traction and pause time 200 ms, cooling water temperature for lower continuous casting 20-35℃, cooling water flow rate 25-40 L / min.

5. The preparation method according to claim 2, characterized in that: Step 2) The diameter of the copper-tin alloy continuous casting rod is 16-20mm.

6. The preparation method according to claim 1, characterized in that: Step 3) The continuous extrusion is carried out using an extruder with a main extruder speed of 2.0-5.0 rpm, a wheel surface gap of 0.3-0.4 mm, and a die cavity preheating temperature of 550±10℃.

7. The preparation method according to claim 2, characterized in that: Step 3) The number of times the multi-pass equal diameter angular extrusion is 2 to 6; the extrusion speed of the equal diameter angular extrusion is 1-10 mm / s.

8. The preparation method according to claim 2, characterized in that: Step 4) The protective atmosphere is nitrogen.

9. The preparation method according to claim 1, characterized in that: Step 4) The heat treatment temperature is 200-300℃, and the holding time is 45-90 min. The second heat treatment temperature is 500-600℃, and the holding time is 15-20 min.

10. The preparation method according to claim 2, characterized in that: Step 4) The multi-pass drawing process is as follows: when the diameter of the copper-tin alloy wire rod is ≥8mm, the deformation per pass is 20%-30%, and the drawing speed is 10-20m / min; when the diameter of the copper-tin alloy wire rod is 3mm≤ and <8mm, the deformation per pass is 15%-20%, and the drawing speed is 20-80m / min; when the diameter of the copper-tin alloy wire rod is 0.8mm≤ and <3mm, the deformation per pass is 10%-15%, and the drawing speed is 80-500m / min; when the diameter of the copper-tin alloy wire is <0.8mm, the deformation per pass is 5%-10%, and the drawing speed is 500-1000m / min.

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