Friction stir processing pretreatment method for lead wire
By using the friction stir processing pretreatment method, the problems of high wire breakage rate and performance degradation of low plasticity materials in the manufacture of wires were solved. The method achieved uniform dispersion and efficient plastic deformation of the material, thereby improving the performance and processing efficiency of the wires.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-04-03
AI Technical Summary
In the manufacturing process of wires, low-plasticity materials such as high-strength aluminum alloys and graphene composites have a high wire breakage rate during cold drawing. Traditional pretreatment processes lead to the deterioration of conductivity and mechanical properties, mechanical rolling pretreatment is uneven, and chemical treatment leads to surface contamination and is not suitable for composite materials.
The pretreatment method of friction stirring is adopted to promote grain refinement through strong plastic deformation. The friction stirring process is carried out in one or more passes using a stirring head and stirring pin. Combined with the design of special stirring pin and parameter optimization, the material is ensured to have uniform rheology and dispersion, and the reaction at the enhanced phase/matrix interface is avoided.
It effectively improves the plasticity of the material, avoids interfacial reactions and grain coarsening, ensures high recrystallization structure and uniform dispersion, improves the tensile strength and elongation of the wire, and breaks through the bottleneck of wire breakage rate in the manufacture of fine wires.
Smart Images
Figure CN121776649A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metal plastic processing technology, and specifically to a method for pretreatment of wire materials by friction stirring. Background Technology
[0002] Plastic working of metals is a fundamental metal processing technique that uses external forces to induce plastic deformation in metals, resulting in products with desired shapes, dimensions, structures, and properties. In the field of wire and conductor manufacturing, highly conductive metals such as silver, copper, and aluminum, as well as their composite materials, are widely used in precision electronic devices due to their excellent electrical conductivity.
[0003] However, these materials face significant challenges when drawn into thin filaments (<1 mm in diameter): 1. Processing challenges of low-plasticity materials: Low-plasticity materials such as high-strength aluminum alloys and graphene-reinforced composite materials suffer from wire breakage rates as high as 25-40% during cold drawing due to work hardening. 2. Defects of traditional pretreatment processes: Although annealing can restore plasticity, it can cause coarsening of metal grains or interfacial reactions between the reinforcing phase and matrix of composite materials, which seriously degrades the conductivity and mechanical properties of the final conductor. 3. Limitations of existing technologies: Mechanical rolling pretreatment is difficult to uniformly improve the plasticity of the bar core; chemical treatment leads to surface contamination and is not suitable for composite materials.
[0004] Therefore, the industry urgently needs a pretreatment method that can effectively improve the plasticity of metals while preserving the intrinsic properties of materials, in order to break through the bottleneck of wire breakage rate in the manufacture of fine wires. Summary of the Invention
[0005] To address the shortcomings of the prior art, the present invention aims to provide a pretreatment method for friction stir processing of wire materials. This method utilizes friction stir processing to promote grain refinement through intense plastic deformation, thereby uniformly mixing graphene with high-strength aluminum alloy. This effectively solves the problem of insufficient material plasticity and avoids the problem of interfacial reactions between the reinforcing phase and the matrix.
[0006] Specifically, on the one hand, the present invention provides a method for pretreatment of conductive wires by friction stirring, which includes the following steps: S1: Configuration of stirring head: The stirring head includes a stirring shaft and a stirring pin disposed at the end of the stirring shaft, and the side of the stirring pin is provided with spiral patterns; S2: Material pretreatment: A material groove is opened on the surface of the metal sheet to be processed, and the material groove is filled with composite material; S3: Friction stirring process: The stirring head is driven by a motor to rotate, and the area containing the material tank on the metal sheet to be processed is subjected to single or multiple passes of friction stirring process to form a stirring zone in the metal sheet. In multi-pass processing, each processing path is parallel to the others, and the distance between the center lines of adjacent processing paths is 0.5d, where d is the diameter of the stirring needle. S4: Blank cutting: Taking the direction perpendicular to the processing path in the horizontal plane as the width direction of the mixing area, cut a blank plate with a rectangular cross-section in the horizontal direction within the mixing area for subsequent processing; The centerline of the rectangle along its width coincides with the centerline of the mixing zone along its width, and the width of the rectangle satisfies the following conditions: W = (0.6 - 0.8)S, where W is the width of the rectangle and S is the width of the stirring area; The length of the rectangle is the maximum value that can be achieved within the mixing area.
[0007] Furthermore, the diameter D of the stirring shaft and the length L of the stirring needle satisfy the following ratio: D:L = 3 - 3.5: 1.
[0008] Furthermore, the pitch of the spiral thread is 0.3-0.5mm.
[0009] Furthermore, the stirring needle is cylindrical, frustum-shaped, or cylindrical or frustum-shaped with at least three planes cut off from its sides.
[0010] Furthermore, the composite material is one or more of graphite, graphene, and carbon nanotubes.
[0011] Further: In step S3, during the friction stir processing, the downward pressure of the stirring head causes the metal to be processed to undergo plastic deformation, and the depth of the plastic deformation layer is ≥ 80% of the thickness of the plate.
[0012] Furthermore: When performing multi-pass processing, the number of processing paths shall not be less than 3 passes.
[0013] Further: In step S3, the stirring head is machined at an angle of 0°-5°.
[0014] Furthermore: In step S3, the processing parameters for friction stir machining are as follows: When processing pure aluminum or aluminum alloys, the stirring head speed is 300-1500 rpm and the travel speed is 20-120 mm / min; When processing pure copper or copper alloys, the stirring head speed is 600-1500 rpm and the travel speed is 20-100 mm / min; When processing pure silver or silver alloys, the stirring head speed is 600-1500 rpm and the travel speed is 15-90 mm / min.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention, through plastic deformation by friction stirring and the specially configured stirring pin, enables deep and uniform rheological transformation of metal or alloy materials during processing, effectively avoiding the problem of insufficient material plasticity and the problems of interfacial reaction and grain coarsening between the reinforcing phase and matrix caused by traditional pretreatment methods.
[0016] 2. This invention adopts a single-pass or multi-pass processing strategy and ensures that adjacent processing paths are parallel to each other and the center distance is 0.5d, where d is the diameter of the stirring needle. This effectively eliminates the anisotropy of the structure. In this way, when performing multi-pass stirring friction processing, each position will be processed twice, preventing possible incomplete processing problems, while ensuring the uniform dispersion of the material.
[0017] Meanwhile, this invention provides a scientific method for cutting billets, which maximizes the cutting of billets that meet the standards after the mixing and processing is completed, ensuring processing efficiency and controlling costs while avoiding billets with insufficient metal flow in the edge passes, thus ensuring the uniform dispersion of materials.
[0018] 3. The pretreated metal and composite material blanks of this invention have a high recrystallization structure, in which the proportion of equiaxed crystals is >90% and the average grain size is ≤10μm, which provides a core plasticity guarantee for the subsequent cold drawing process into high-precision wires and breaks through the bottleneck of fine wire manufacturing. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the pretreatment method for friction stirring processing according to the present invention; Figure 2 This is a cross-sectional view of the billet in the mixing zone of the present invention; Figure 3 The stress-strain curves of Example 1 and its control group of the present invention are shown below; Figure 4 The figure shows the EBSD test results of the wire end face of Example 1 of the present invention and its control group. Detailed Implementation
[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0021] Combination Figure 1 and Figure 2 As shown, the present invention provides a pretreatment method for friction stirring processing of wire materials, comprising the following steps: S1: Configuration of stirring head: The stirring head includes a stirring shaft and a stirring pin disposed at the end of the stirring shaft, and the side of the stirring pin is provided with spiral patterns; The ratio of the diameter D of the stirring shaft to the length L of the stirring needle should satisfy: D:L = 3-3.5:1. If this ratio is too low, the needle will be too long, and due to insufficient rigidity, it may break during the movement of the stirring head. If this ratio is too high, the length of the stirring shaft will be much greater than the stirring needle, resulting in a flattened material flow area that cannot penetrate deep into the material, thus reducing the processing effect. Therefore, based on stirring head design experience and experimental verification, a ratio of D:L = 3-3.5:1 is considered optimal.
[0022] The spiral thread pitch is 0.3-0.5mm. The purpose of the threaded stirring pin is to enhance the material flow. If the pitch is too short, it will make the stirring pin difficult to process and reduce the surface quality; if the pitch is too long, it will reduce the material flow. Therefore, based on the design experience of stirring heads and experimental verification, the optimal pitch is controlled at 0.3-0.5mm.
[0023] The stirring pin is cylindrical, frustum-shaped, or cylindrical or frustum-shaped with at least three planes cut off from its sides. Ordinary cylindrical or frustum-shaped pins are easy to manufacture, but during the stirring and friction process, material may stick to the sides of the stirring pin. Experiments have shown that cutting off at least three planes from the sides of the cylindrical or frustum-shaped stirring pin can result in a uniform and fine microstructure after stirring.
[0024] S2: Material pretreatment: A material groove is opened on the surface of the metal sheet to be processed, and the material groove is filled with composite material.
[0025] The composite material is one or more of graphite, graphene, and carbon nanotubes. The purpose of filling the material tank with the composite material is to prevent the composite material from splashing outside the processing area during the processing, which would waste raw materials or even affect the processing effect.
[0026] S3: Friction Stir Processing: The stirring head is driven by a motor to rotate and perform single or multiple passes of friction stirring processing on the area containing the material tank on the metal sheet to be processed, forming a stirring zone within the metal sheet. In the case of multiple passes, the processing path of the first pass starts near the material tank and passes through the material tank, so that the composite material and the metal sheet to be processed are fully mixed.
[0027] In multi-pass processing, the processing paths are parallel to each other, and the distance between the centerlines of adjacent processing paths is 0.5d, where d is the diameter of the stirring needle. The distance between adjacent processing centers in multi-pass processing controls the degree of material mixing and dispersion. If the distance between adjacent centers is too short, the processing areas will overlap excessively, reducing processing efficiency; if the distance between adjacent centers is too long, the overlapping area will decrease, affecting the uniform dispersion of the material. Based on parameter selection experience and experimental verification, controlling the distance between adjacent centers to 0.5 times the diameter d of the stirring needle is optimal.
[0028] In this process, the downward pressure of the stirring head causes plastic deformation in the metal to be processed, with the depth of the plastic deformation layer being ≥ 80% of the plate thickness. This ensures that the pretreatment area of friction stir processing essentially covers the entire thickness of the plate, reducing material loss and waste. When the above parameters are appropriately selected, the friction stir processing pretreatment process will result in a plastic deformation layer depth close to the plate thickness, effectively pretreating the entire plate.
[0029] The stirring head has a machining tilt angle of 0°-5°. This is used to ensure the smooth progress of the friction stir machining pretreatment. A certain tilt angle of the stirring head can effectively improve the material flow during machining. Based on experience in parameter selection and experimental verification, controlling this machining tilt angle within the range of 0°-5° is optimal.
[0030] The processing parameters for friction stir machining are as follows: When processing pure aluminum or aluminum alloys, the stirring head speed is 300-1500 rpm and the travel speed is 20-120 mm / min.
[0031] When processing pure copper or copper alloys, the stirring head speed is 600-1500 rpm and the travel speed is 20-100 mm / min.
[0032] When processing pure silver or silver alloys, the stirring head speed is 600-1500 rpm and the travel speed is 15-90 mm / min.
[0033] S4: Blank cutting: Taking the direction perpendicular to the processing path in the horizontal plane as the width direction of the mixing area, cut a blank plate with a rectangular cross-section in the horizontal direction within the mixing area for subsequent processing.
[0034] The centerline of the rectangle along its width coincides with the centerline of the mixing zone along its width, and the width of the rectangle satisfies the following conditions: W = (0.6 - 0.8)S, where W is the width of the rectangle and S is the width of the stirring area.
[0035] The length of the rectangle is the maximum value that can be achieved within the mixing area.
[0036] At the edge of the stirring zone, due to the increased temperature during friction stirring, some of the metal at the edge softens at high temperature and flows into the stirring zone, making the actual width of the stirring zone slightly wider than the area processed by the stirring head. At the same time, because the edge of the stirring zone in the width direction only undergoes a single friction stirring process during multi-pass processing, the uniformity of this part is low. Therefore, a rectangular blank with a width W=(0.6-0.8)D is cut. This parameter controls the appropriate composite material processing area to be cut from the processing area after the friction stirring pretreatment.
[0037] If the width is too short, the area of material that can be selected after friction stir processing pretreatment will be smaller, resulting in a decrease in processing efficiency. If the width is too long, it will select areas of material that have not flowed sufficiently and have not been completely pretreated by friction stir processing, which may lead to a decrease in the pretreatment effect. Based on experience in parameter selection and experimental verification, the optimal cut-off width is controlled at W = (0.6-0.8)S.
[0038] Along the length of the mixing zone, since it is processed in the same pass, its uniformity is relatively high. Therefore, the maximum value can be taken in the mixing zone along the length to ensure the largest possible billet area and guarantee processing efficiency.
[0039] The technical solution of the present invention will be further illustrated below through embodiments: The conductive composite materials of the present invention are shown in Table 1, which contains the materials and processes used in Examples 1-4 and Comparative Example 1.
[0040] Table 1 Example 1. The graphene-reinforced AA-1060 composite material was pretreated using a friction stir process with the following parameters: rotation speed 1200 rpm, travel speed 20 mm / min, 1 pass; after pretreatment, the material was cold-drawn to a diameter of 0.5 mm and the continuous filament length was ≥15 m.
[0041] Example 2. The graphite-reinforced AA-1060 composite material was pretreated using friction stir processing. The specific process parameters were: rotation speed 900 rpm, travel speed 30 mm / min, 3 passes. After pretreatment, the material was cold-drawn to a diameter of 0.36 mm and the continuous filament length was ≥20 m.
[0042] Example 3. The graphene-reinforced AA-6201 composite material was pretreated using a friction stir process with the following parameters: rotation speed 900 rpm, travel speed 30 mm / min, 6 passes. After pretreatment, the elongation of the material increased by 56.25%.
[0043] Example 4. The graphite-reinforced AA-6201 composite material was pretreated using a friction stir process with the following parameters: rotation speed 600 rpm, travel speed 60 mm / min, and 9 passes. After pretreatment, the elongation of the material increased by 30.37%.
[0044] Comparative Example 1. Mechanical property tests were conducted on AA-1060 composites reinforced with carbon nanotubes that had not undergone friction stir processing pretreatment, and it was found that their elongation decreased by 72.95%. When the filaments were cold-drawn to a diameter of 1.2 mm, a large number of cracks appeared, making continuous filament production impossible.
[0045] Table 2 below shows the performance indicators of Example 1 and its control group. Table 2 Combination Figure 3 and Figure 4 As shown, Figure 3 The stress-strain curves of Example 1 and its control group of the present invention are shown below; Figure 3 The diagram depicts the relationship between stress and strain in the tensile tests conducted on the filaments prepared in Example 1 and its control group. From... Figure 3 As can be seen, as the stretching process proceeds, the control group fractured at an elongation of 1.25%, with a tensile strength of 193 MPa before fracture; Example 1 fractured at an elongation of 1.50%, with a tensile strength of 224 MPa before fracture. Therefore, the tensile strength and elongation performance in Example 1 were improved. Figure 4 The figure shows the EBSD test results of the wire end face of Example 1 of the present invention and its control group. Figure 4 The distribution of high-angle grain boundaries (HAGB) and small-angle grain boundaries (LAGB) at the wire end interfaces was described during EBSD experiments on the wires prepared in Example 1 and its control group. Figure 4 It can be seen that the end interfaces of both Example 1 and the control group exhibit fine equiaxed grain characteristics. The average grain size of Example 1 is 1.51 micrometers, and the average grain size of the control group is 1.66 micrometers. Therefore, the grain refinement in Example 1 is improved.
[0046] As can be seen from the above data, the metal sheet treated by the friction stir processing pretreatment method of the present invention has significantly improved tensile strength, yield strength and elongation, effectively avoiding the problem of insufficient material plasticity and avoiding the problems of interfacial reaction and grain coarsening between the reinforcing phase and matrix caused by traditional pretreatment methods.
[0047] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for pretreatment of conductive wires by friction stirring, characterized in that: It includes the following steps: S1: Configuration of stirring head: The stirring head includes a stirring shaft and a stirring pin disposed at the end of the stirring shaft, and the side of the stirring pin is provided with spiral patterns; S2: Material pretreatment: A material groove is opened on the surface of the metal sheet to be processed, and the material groove is filled with composite material; S3: Friction stirring process: The stirring head is driven by a motor to rotate, and the area containing the material tank on the metal sheet to be processed is subjected to single or multiple passes of friction stirring process to form a stirring zone in the metal sheet. In multi-pass processing, each processing path is parallel to the others, and the distance between the center lines of adjacent processing paths is 0.5d, where d is the diameter of the stirring needle. S4: Blank cutting: Taking the direction perpendicular to the processing path in the horizontal plane as the width direction of the mixing area, cut a blank plate with a rectangular cross-section in the horizontal direction within the mixing area for subsequent processing; The centerline of the rectangle along its width coincides with the centerline of the mixing zone along its width, and the width of the rectangle satisfies the following conditions: W = (0.6 - 0.8)S, where W is the width of the rectangle and S is the width of the stirring area; The length of the rectangle is the maximum value that can be achieved within the mixing area.
2. The pretreatment method for friction stirring processing of wire as described in claim 1, characterized in that: The diameter D of the stirring shaft and the length L of the stirring needle satisfy the following condition: D:L = 3 - 3.5:
1.
3. The pretreatment method for friction stirring processing of wire as described in claim 1, characterized in that: The pitch of the spiral thread is 0.3-0.5mm.
4. The pretreatment method for friction stirring processing of wire as described in claim 1, characterized in that: The stirring needle is cylindrical, frustum-shaped, or cylindrical or frustum-shaped with at least three planes cut off from its sides.
5. The pretreatment method for friction stirring processing of wire as described in claim 1, characterized in that: The composite material is one or more of graphite, graphene, and carbon nanotubes.
6. The pretreatment method for friction stirring processing of wire as described in claim 1, characterized in that: In step S3, during the friction stir processing, the downward pressure of the stirring head causes the metal to be processed to undergo plastic deformation, and the depth of the plastic deformation layer is ≥ 80% of the thickness of the plate.
7. The pretreatment method for friction stirring processing of wire as described in claim 1, characterized in that: When performing multi-pass processing, the number of processing paths shall not be less than 3 passes.
8. The method for pretreatment of wire materials by friction stirring as described in any one of claims 1-7, characterized in that: In step S3, the stirring head is machined at an angle of 0°-5°.
9. The pretreatment method for friction stirring processing of wire as described in claim 8, characterized in that: In step S3, the processing parameters for friction stir machining are as follows: When processing pure aluminum or aluminum alloys, the stirring head speed is 300-1500 rpm and the travel speed is 20-120 mm / min; When processing pure copper or copper alloys, the stirring head speed is 600-1500 rpm and the travel speed is 20-100 mm / min; When processing pure silver or silver alloys, the stirring head speed is 600-1500 rpm and the travel speed is 15-90 mm / min.