Welding method for improving mechanical and conductive performance of flat copper wire joint

Abstract

A welding method for improving mechanical and conductive performance of a flat copper wire joint relates to the technical field of welding, and comprises the following steps: firstly, pretreating the surface of a flat copper wire to be welded: controlling a tool head to perform multi-pass variable-amplitude variable-pressure high-frequency micro-forging on the surface of the flat copper wire; in the high-frequency micro-forging process, in each pass, the tool head outputs constant amplitude and constant pressure, meanwhile, the tool head generates a tangential extrusion effect on the flat copper wire in the process of moving along the surface of the flat copper wire, and under the combined action of high-frequency micro-forging and tangential extrusion, {111} lt is generated on the surface of the flat copper wire; 110gt, 110gt; crystal orientation; the surface has {111} lt; 110gt, 110gt; the crystal-oriented flat copper wires are in lap joint with one another and are subjected to ultrasonic welding, and the ultrasonic welding vibration direction is parallel to the lt; 110gt, 110gt; direction. By improving the welding density of the welding interface and the thickness of the welded material, the purpose of improving the mechanical and conductive performance of the ultrasonic welding copper sheet joint is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of welding, in particular to a welding method for improving the mechanical and conductive properties of a flat copper wire joint. Background Art

[0002] It is known that pure copper has excellent electrical and thermal conductivity, and has become the preferred material for the flat copper wire armature winding conductor coil in the flat copper wire motor in the field of new energy vehicles; ultrasonic welding has the advantages of low welding temperature, no spatter, large solder joint area, low energy consumption, and insensitivity to the electrical and thermal conductivity of the parent material, and is increasingly widely used in the field of new energy vehicles. Ultrasonic welded flat copper wire joints are the main joints in the flat copper wire armature winding. Their mechanical and electrical conductivity directly affect the efficiency and safety and reliability of the flat copper wire motor, and thus are related to whether the key technologies of driving motors in the field of new energy vehicles can achieve major breakthroughs.

[0003] The thickness of flat copper wire is generally greater than 1 mm, and the hardness is relatively high. When ultrasonically welding flat copper wire, the thick and hard flat copper wire is not conducive to the transmission of ultrasonic vibration at the welding interface, which will reduce the welding density and the thickness of the material after welding at the welding interface, and have an adverse effect on the mechanical and conductive properties of the welded joint. Therefore, it is urgent to invent a welding method that improves the mechanical and conductive properties of flat copper wire joints. Summary of the invention

[0004] The invention aims to provide a welding method for improving the mechanical and electrical conductivity of a flat copper wire joint.

[0005] The technical solution adopted by the present invention is: a welding method for improving the mechanical and conductive properties of flat copper wire joints, pre-treating the surface of the flat copper wire to be welded so that {111} <110> The crystal orientation then places the surface with {111} <110> Crystalline oriented flat copper wires are overlapped and ultrasonically welded. The vibration direction of ultrasonic welding is parallel to <110> direction.

[0006] As a preferred solution, a method for pretreating the surface of a flat copper wire to be welded comprises the following steps: controlling a tool head to perform multiple passes of variable amplitude and variable pressure high-frequency micro-forging on the surface of the flat copper wire; in the above-mentioned high-frequency micro-forging process, in each pass, the tool head outputs a constant amplitude and a constant pressure, and at the same time, the tool head produces a tangential extrusion effect on the flat copper wire during its movement along the surface of the flat copper wire, and under the combined action of high-frequency micro-forging and tangential extrusion, the surface of the flat copper wire produces {111} <110> Crystal orientation.

[0007] As a preferred solution, the variable amplitude means that the amplitude applied by the tool head to the flat copper wire in different passes is adjusted and changed in real time, and presents a trend of gradually increasing, the amplitude is 10 to 65 μm, and the vibration direction of the amplitude is perpendicular to the surface of the flat copper wire.

[0008] As a preferred solution, the variable pressure means that the pressure applied by the tool head to the flat copper wire in different passes is adjusted and changed in real time, and presents a trend of gradually increasing, and the pressure is 0.2-0.8 MPa.

[0009] As a preferred solution, the high-frequency micro-forging refers to the high-frequency micro-impact of the tool head on the surface of the flat copper wire under the action of the applied amplitude and pressure, and the frequency of the high frequency is 20 to 40 kHz.

[0010] As a preferred solution, the moving speed of the tool head along the surface of the flat copper wire is 2 to 7 mm / s. During the high-frequency micro-forging process, a certain friction force is generated between the moving tool head and the surface of the flat copper wire, and the friction force will generate a certain tangential extrusion force on the flat copper wire.

[0011] As a preferred solution, after the surface of the flat copper wire is pretreated, the surface is cleaned with 5% to 6% dilute hydrochloric acid for 10-20 seconds, and then cleaned with alcohol and dried.

[0012] As a preferred solution, the rectangular copper wire is made of pure copper or copper alloy and has a thickness of 1.0 to 3.0 mm.

[0013] As a preferred embodiment, the surface of the flat copper wire is {111} <110> The thickness of the crystal orientation is 40 to 50 μm.

[0014] As a preferred solution, the ultrasonic welding process parameters are as follows: welding time is 0.8 to 1.3 s, welding pressure is 40 to 60 psi, and welding amplitude is 45 to 70 μm.

[0015] The beneficial effects of the present invention are: Based on the shortcomings of the prior art, the present invention provides a welding method for improving the mechanical and conductive properties of flat copper wire joints. By optimizing the welding process, the surface of the flat copper wire to be welded is pretreated to produce {111} <110> The crystal orientation then places the surface with {111} <110> Crystalline oriented flat copper wires are overlapped and ultrasonically welded. The vibration direction of ultrasonic welding is parallel to <110> direction, due to {111} <110> The crystal orientation is the close-packed plane and close-packed direction of face-centered cubic structure copper and its alloys, where the spacing between atoms is the largest and the resistance is the smallest under shear force; therefore, during ultrasonic welding, {111} <110> Crystal orientation can reduce the friction of the welding interface, increase the time of ultrasonic vibration on the welding interface, and significantly increase the temperature of the welding surface, which will increase the density of vacancies, thereby increasing the degree of plastic deformation and recrystallization process of the welding interface, thereby achieving the purpose of improving the welding density of the welding interface. At the same time, due to the enhanced recrystallization effect, the {111} <110> The crystal orientation disappears and the crystal orientation is randomly distributed. In addition, due to the small friction force at the welding interface, the time of mutual extrusion and friction between the welding head / base and the flat copper wire surface is reduced, which will help to increase the thickness of the material after welding. The increase in welding density and the thickness of the material after welding is conducive to improving the mechanical properties and conductivity of the welded joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 The inverse pole figure of the flat copper wire surface after pretreatment in Example 1 of the present invention; Figure 2 This is a metallographic image of the joint interface of the pre-treated flat copper wire after welding in Example 1 of the present invention; Figure 3 This is a fracture morphology diagram of a pre-treated flat copper wire welded joint after a tensile test in Example 1 of the present invention; Figure 4 The inverse pole figure of the flat copper wire surface in Comparative Example 1 without pretreatment; Figure 5 This is a metallographic image of the joint interface of the flat copper wire after welding without pretreatment in Comparative Example 1; Figure 6 This is a fracture morphology of the flat copper wire welded joint that has not been pretreated in Comparative Example 1 after a tensile test. DETAILED DESCRIPTION

[0018] The following specific examples are given to further clearly, completely and in detail illustrate the technical solution of the present invention. This example is the best example based on the technical solution of the present invention, but the protection scope of the present invention is not limited to the following examples.

[0019] A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint, the steps are as follows: First, the surface of the flat copper wire to be welded is pretreated. The pretreatment process is: control the tool head to perform multiple passes of variable amplitude and variable pressure high-frequency micro-forging on the surface of the flat copper wire; in the above high-frequency micro-forging process, in each pass, the tool head outputs a constant amplitude and a constant pressure, and at the same time, the tool head produces a tangential extrusion effect on the flat copper wire during the movement of the tool head along the surface of the flat copper wire. Under the combined action of high-frequency micro-forging and tangential extrusion, the surface of the flat copper wire produces {111} <110> Crystal orientation; Then the surface has {111} <110> Crystalline oriented flat copper wires are overlapped and ultrasonically welded. The vibration direction of ultrasonic welding is parallel to <110> direction.

[0020] It should be noted that: the tool head moves from an initial position on one side of the flat copper wire surface to a set position on the other side to complete one pass of processing, and then the tool head returns to the initial position, adjusts the output amplitude and pressure of the tool head, and performs the next pass of processing.

[0021] In this scheme, the variable amplitude means that the amplitude applied by the tool head to the flat copper wire in different passes is adjusted and changed in real time, and shows a trend of gradually increasing, the amplitude is 10 to 65 μm, and the vibration direction of the amplitude is perpendicular to the surface of the flat copper wire; the variable pressure means that the pressure applied by the tool head to the flat copper wire in different passes is adjusted and changed in real time, and shows a trend of gradually increasing, and the pressure is 0.2 to 0.8 MPa.

[0022] In this solution, the high-frequency micro-forging refers to the high-frequency micro-impact of the tool head on the surface of the flat copper wire under the applied amplitude and pressure, the high frequency is 20 to 40 kHz, and the number of multiple passes described in this article is generally less than 20 times.

[0023] In this solution, the moving speed of the tool head along the surface of the flat copper wire is 2-7 mm / s. During the high-frequency micro-forging process, a certain friction force is generated between the moving tool head and the surface of the flat copper wire, and this friction force will produce a certain tangential extrusion force on the flat copper wire.

[0024] In this scheme, after the surface of the flat copper wire is pretreated, the surface is cleaned with 5% to 6% dilute hydrochloric acid for 10-20 seconds, and then cleaned with alcohol and dried.

[0025] In this solution, the flat copper wire is made of pure copper or copper alloy and has a thickness of 1.0 to 3.0 mm.

[0026] In this embodiment, the surface of the flat copper wire is {111} <110> The thickness of the crystal orientation is 40 to 50 μm.

[0027] In this scheme, the ultrasonic welding process parameters are as follows: welding time is 0.8-1.3 s, welding pressure is 40-60 psi, and welding amplitude is 45-70 μm.

[0028] Embodiment 1, A method for improving the mechanical and electrical properties of ultrasonically welded flat copper wire joints is provided. Two flat copper wire samples with a thickness of 1 mm and a length of 100 mm are taken, and the surfaces of the flat copper wires to be welded are pretreated to produce {111} <110> The crystal orientation then places the surface with {111} <110> Crystalline oriented flat copper wires were overlapped and ultrasonically welded. After the flat copper wire surface was pretreated, the treated surface was cleaned with 5% dilute hydrochloric acid for 10 s, then cleaned with alcohol and dried.

[0029] In this embodiment, the composition of the flat copper wire is pure copper; the pretreatment process of the flat copper wire surface is as follows: the tool head is controlled to perform multiple passes of variable amplitude and variable pressure high-frequency micro-forging on the flat copper wire surface; in the above high-frequency micro-forging process, in each pass, the tool head outputs a constant amplitude and a constant pressure, and at the same time, the tool head produces a tangential extrusion effect on the flat copper wire during the movement of the tool head along the surface of the flat copper wire. Under the combined action of high-frequency micro-forging and tangential extrusion, the surface of the flat copper wire produces {111} <110> Crystal orientation; the technical parameters of the tool head are as follows: the amplitude applied in the 1st to 3rd passes is 10-20 μm, and the amplitude gradually increases to 65 μm with the increase of the passes; the pressure applied in the 1st to 3rd passes is 0.2-0.25 MPa, and the pressure gradually increases to 0.8 MPa with the increase of the passes; the frequency of the tool head is 20-40 kHz.

[0030] The welding process parameters are as follows: welding time is 0.8 s, welding pressure is 40 psi, and welding amplitude is 45 μm. The weld density of the welded joint is 75.5%, the thickness of the welded material is 1.93 mm, the resistance is 63.8 μΩ, and the tensile strength is 3885.6 N.

[0031] After implementation, the inverse pole figure of the cross section along the thickness direction of the flat copper wire after surface pretreatment is as follows Figure 1 As shown, it can be seen that the crystal orientation is {111} <110> , thickness is 40μm. The metallographic image of the joint interface after welding is as follows Figure 2 As shown in the figure, it can be seen that the welding interface is well welded and there are few unwelded areas. After the tensile test, the fracture morphology of the joint is as follows Figure 3 As shown, it can be seen that there are many dimples on the surface, indicating that the welding interface has a good metallurgical bond and high welding strength.

[0032] Embodiment 2, A method for improving the mechanical and electrical properties of ultrasonically welded flat copper wire joints is provided. Two flat copper wire samples with a thickness of 1.5 mm and a length of 100 mm are taken, and the surfaces of the flat copper wires to be welded are pretreated to produce {111} <110> crystal orientation, with a thickness of 45 μm, and then the surface has {111} <110> Crystalline oriented flat copper wires are overlapped and ultrasonically welded. After the flat copper wire surface is pretreated, the treated surface is cleaned with 5.5% dilute hydrochloric acid for 15 s, then cleaned with alcohol and dried. The composition of the flat copper wire is pure copper. After surface treatment, the surface is {111} <110> The thickness of the crystal orientation is 30 to 50 μm. The welding process parameters are as follows: welding time is 1.1 s, welding pressure is 48 psi, and welding amplitude is 53 μm.

[0033] The test verified that the welding density of the welded joint was 73.4%, the thickness of the welded material was 2.92 mm, the resistance was 49.5 μΩ, and the tensile strength was 3358.2 N.

[0034] Embodiment 3, A method for improving the mechanical and electrical properties of ultrasonically welded flat copper wire joints is provided. Two flat copper wire samples with a thickness of 3 mm and a length of 100 mm are taken, and the surfaces of the flat copper wires to be welded are pretreated to produce {111} <110> The crystal orientation then places the surface with {111} <110> Crystalline oriented flat copper wires are overlapped and ultrasonically welded. After the flat copper wire surface is pretreated, the treated surface is cleaned with 6% dilute hydrochloric acid for 20 s, then cleaned with alcohol and dried. The composition of the flat copper wire is pure copper. After surface treatment, the surface is {111} <110> The thickness of the crystal orientation is 50 μm. The welding process parameters are as follows: welding time is 1.3 s, welding pressure is 60 psi, and welding amplitude is 70 μm.

[0035] The test verified that the welding density of the welded joint was 68.4%, the thickness of the welded material was 5.89 mm, the resistance was 38.3 μΩ, and the tensile strength was 3089.6 N.

[0036] Comparative Example 1 The difference between the welding method of the flat copper wire of this comparative example and that of Example 1 is that the pretreatment step of the surface of the flat copper wire is removed, and the remaining parameters of the flat copper wire sample and the welding process parameters are exactly the same as those of Example 1; The specific steps are as follows: Take two flat copper wire samples with a thickness of 1 mm and a length of 100 mm, clean the surface with 5% dilute hydrochloric acid for 10-20 s, then clean and dry with alcohol, and then perform ultrasonic welding. The composition of the flat copper wire is pure copper. The welding process parameters are as follows: welding time is 0.8 s, welding pressure is 40 psi, and welding amplitude is 45 μm. The welding interface temperature is 253.6 ℃, the welding density of the joint after welding is 38.6%, the thickness of the material after welding is 1.86 mm, the resistance is 79.6 μΩ, and the tensile strength is 1550.7 N.

[0037] After implementation, the inverse pole figure of the cross section of the flat copper wire base material along the thickness direction is as follows Figure 4 As shown in Figure 1, it can be seen that the crystal orientation is randomly distributed. The metallographic image of the joint interface after welding is shown in Figure 1. Figure 5 As shown in the figure, it can be seen that there are many unwelded areas on the welding interface. After the tensile test, the fracture morphology of the joint is as follows Figure 6 As shown, it can be seen that there are fewer dimples on the surface, indicating that the metallurgical bonding at the welding interface is poor.

[0038] The parts not described in detail in the above embodiments are prior art.

[0039] It should be noted that although the present invention is described by the above embodiments, the present invention may also have other various embodiments. Without departing from the spirit and scope of the present invention, it is obvious that those skilled in the art may make various corresponding changes and deformations to the present invention, but these changes and deformations should all fall within the scope of protection of the appended claims of the present invention and their equivalents.

Claims

1. A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint, characterized in that: The surface of the flat copper wire to be welded is pretreated to produce {111} <110> The crystal orientation then places the surface with {111} <110> Crystalline oriented flat copper wires are overlapped and ultrasonically welded. The vibration direction of ultrasonic welding is parallel to <110> direction.

2. A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint according to claim 1, characterized in that: The method for pretreating the surface of a flat copper wire to be welded comprises the following steps: controlling a tool head to perform multiple passes of variable amplitude and variable pressure high-frequency micro-forging on the surface of the flat copper wire; in the above-mentioned high-frequency micro-forging process, in each pass, the tool head outputs a constant amplitude and a constant pressure, and at the same time, the tool head produces a tangential extrusion effect on the flat copper wire during the movement of the tool head along the surface of the flat copper wire, and under the combined action of high-frequency micro-forging and tangential extrusion, the surface of the flat copper wire produces {111} <110> Crystal orientation.

3. A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint according to claim 2, characterized in that: The variable amplitude means that the amplitude applied by the tool head to the flat copper wire in different passes is adjusted and changed in real time, and presents a trend of gradual increase, the amplitude is 10-65 μm, and the vibration direction of the amplitude is perpendicular to the surface of the flat copper wire.

4. A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint according to claim 2, characterized in that: The variable pressure means that the pressure applied by the tool head to the flat copper wire in different passes is adjusted and changed in real time, and presents a trend of gradually increasing, and the pressure is 0.2-0.8 MPa.

5. A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint according to claim 2, characterized in that: The high-frequency micro-forging refers to the high-frequency micro-impact of the tool head on the surface of the flat copper wire under the action of the applied amplitude and pressure, and the frequency of the high frequency is 20 to 40 kHz.

6. A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint according to claim 2, characterized in that: The moving speed of the tool head along the surface of the flat copper wire is 2-7 mm / s. During the high-frequency micro-forging process, a certain friction force is generated between the moving tool head and the surface of the flat copper wire, and the friction force will generate a certain tangential extrusion force on the flat copper wire.

7. A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint according to claim 2, characterized in that: After the surface of the flat copper wire is pretreated, the surface is cleaned with 5% to 6% dilute hydrochloric acid for 10-20 seconds, and then cleaned with alcohol and dried.

8. A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint according to claim 2, characterized in that: The flat copper wire is made of pure copper or copper alloy and has a thickness of 1.0 to 3.0 mm.

9. A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint according to claim 2, characterized in that: The surface of the flat copper wire is {111} <110> The thickness of the crystal orientation is 40 to 50 μm.

10. A welding method for improving the mechanical and electrical conductivity of a flat copper wire joint according to claim 2, characterized in that: The ultrasonic welding process parameters are as follows: welding time is 0.8-1.3 s, welding pressure is 40-60 psi, and welding amplitude is 45-70 μm.

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