A welding method for electromagnetic pulse waveform interface connection of copper tube and steel bar

Abstract

This invention discloses a welding method for connecting a copper tube and a steel rod via an electromagnetic pulse waveform interface. The method includes: first, machining an annular groove on the surface of the steel rod to be welded; along the axial direction of the steel rod, the depth of the annular groove gradually increases from the center to both sides, with the center of the groove flush with the axial surface of the steel rod, thus forming an annular tapered groove; then, fitting the copper tube onto the steel rod, aligning it with the surface to be welded; and finally, welding the copper tube and steel rod using electromagnetic pulse welding. This welding method effectively promotes the ejection of metal debris from the copper tube and steel rod at the material interface during the welding process, reducing the retention of high-speed moving metal debris at the interface, thereby avoiding cracks caused by metal debris accumulation and energy concentration at the interface, and thus effectively achieving electromagnetic pulse welding for copper-steel waveform interface connections.

Description

Technical Field

[0001] This invention belongs to the field of applied welding technology, specifically relating to a welding method for connecting copper tubes and steel bars via electromagnetic pulse waveform interfaces. Background Technology

[0002] Copper possesses excellent ductility and electrical and thermal conductivity; however, it has low strength, is easily deformed, and is expensive. Meanwhile, steel is inexpensive and high-strength. Combining copper and steel allows for the full utilization of copper's characteristics, while significantly increasing its strength. Copper / steel composites exhibit excellent comprehensive mechanical properties and offer significant economic benefits. Previously, mechanical interlocking methods were used in the design of copper-steel structures for missile belts / body components in military equipment manufacturing. Currently, the main welding methods for copper / steel rods are diffusion welding and friction welding.

[0003] While diffusion welding is a method for welding copper and steel, it involves heating the copper to temperatures exceeding 1000 ℃ for over 1 minute, which significantly impacts the metal structure on the steel side of the weld, potentially leading to a decrease in strength and hardness. Friction welding, on the other hand, cannot address the issue of uniform pressure application around the copper tube during the upsetting stage, resulting in an unsatisfactory bond strength between the copper tube and the steel bar.

[0004] The electromagnetic pulse welding process for copper tubes / steel bars involves the high-speed impact of the copper tube onto the steel bar. This impact generates a large amount of high-speed copper and steel shavings, pressing the copper metal into the steel metal to complete the welding. When the copper is pressed into the steel with a large and uniform waveform, an interlocking waveform interface is formed, resulting in optimal performance. Chinese Patent 03114647.3 discloses a copper tube welding method, specifically using electromagnetic pulse welding to weld the copper tube onto a steel bar. While this method achieves copper-steel welding, the high-speed impact of the copper tube generates metal shavings that remain at the interface, resulting in a small or indistinct waveform, poor interlocking performance, and difficulty in improving joint strength. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a welding method for connecting copper tubes and steel rods via electromagnetic pulse waveform interfaces. This welding method effectively promotes the ejection of metal debris from the copper tube and steel rod at the material connection interface during the welding process, reduces the retention of high-speed moving metal debris at the material connection interface, thereby avoiding cracks caused by metal debris accumulation and energy concentration at the interface, and thus effectively realizing electromagnetic pulse welding of copper-steel waveform interface connections.

[0006] The technical solution of this invention is implemented as follows:

[0007] A welding method for connecting copper tubes and steel bars via electromagnetic pulse waveforms involves first machining an annular groove on the surface of the steel bar to be welded. Along the axial direction of the steel bar, the depth of the annular groove gradually increases from the center to both sides, with the center of the annular groove flush with the axial surface of the steel bar, thus forming an annular tapered groove. Then, the copper tube is fitted onto the steel bar, facing the surface of the steel bar to be welded. Finally, the copper tube and steel bar are welded using electromagnetic pulse welding.

[0008] Furthermore, the depth of the annular groove increases linearly from the center of the annular groove towards both sides.

[0009] Furthermore, the specific steps include:

[0010] (1) Determine the center line of the inner wall of the copper tube as the initial collision point of the copper tube, determine the center line of the steel bar to be welded as the initial collision point of the steel bar, and process inclined grooves at 2~5° on both sides of the outer circumference of the steel bar where the initial collision point of the steel bar is located, thereby forming an annular groove;

[0011] (2) A copper pipe and a steel rod are overlapped on a welding fixture. The copper pipe is sleeved on the steel rod, the surfaces of the copper pipe and the steel rod to be welded are facing each other, the initial collision point of the steel rod is facing the initial collision point of the copper pipe, and there is a certain welding gap between the copper pipe and the steel rod.

[0012] (3) The capacitor is turned on to discharge the coil, and a time-varying current is passed through the coil. The magnetic field strength is concentrated at the welding part of the workpiece by the magnet collector. By controlling the position of the welding fixture, the central magnetic field of the magnet collector is aligned with the collision start point of the copper tube and the steel rod, so that the copper tube can quickly impact the steel rod under electromagnetic force to achieve electromagnetic pulse welding of the copper tube and the steel rod.

[0013] Furthermore, the surface roughness of the annular groove is 3.2–6.4 μm.

[0014] Furthermore, along the axial direction of the copper tube, the length of the annular groove of the steel rod is greater than the length of the copper tube to be welded.

[0015] Furthermore, the difference between the length of the annular groove of the steel bar and the length of the copper tube to be welded is 1~2 mm.

[0016] Furthermore, the welding gap between the copper tube and the steel rod is 1.5~2 mm.

[0017] Furthermore, along the axial direction of the copper tube, the lengths of the magnets extending from both ends of the copper tube to be welded are 2~3 mm.

[0018] Furthermore, in step (3), the electromagnetic pulse welding discharge voltage is 12-16 KV and the capacitance is 120-240 uF.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention involves creating an annular groove on the surface of a steel rod to be welded, using a copper tube as the moving pipe and the steel rod as the target material. During the welding process, the annular groove causes the slope to gradually increase from the initial point of impact to both sides, thus gradually increasing the collision angle between the copper tube and the steel rod. This, in turn, gradually increases the collision gap from the initial point of impact to both sides. This effectively promotes the ejection of metal debris generated during the welding process from the material connection interface, reduces the retention of high-speed metal debris at the material connection interface, and avoids cracks caused by the accumulation and energy concentration of metal debris at the welding interface. This ensures that the copper is smoothly pressed into the steel, thereby facilitating the electromagnetic pulse welding of the waveform interface connection between the copper tube and the steel rod. Attached Figure Description

[0021] Figure 1 - A schematic diagram of the welding of the copper tube and steel rod of this invention.

[0022] Figure 2-Figure 1 Enlarged view of part I.

[0023] Figure 3 - Schematic diagram of the annular inclined groove for steel bars.

[0024] Figure 4 - Example 1: SEM image of the welding interface.

[0025] Figure 5 - Comparative Example 1: SEM image of the weld interface.

[0026] Figure 6 - SEM image of the weld interface in Comparative Example 2.

[0027] Wherein: 1-coil; 2-insulating tube; 3-magnet collector; 4-first positioning tube; 5-copper tube; 6-steel rod; 7-second positioning tube; 8-double-ended screw; 9-nut; 10-first pressure plate; 11-second pressure plate; 12-third pressure plate; 13-fourth pressure plate; 14-third positioning tube; A-initial collision point of steel rod; α-collision angle; β-inclination angle of annular groove. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] A welding method for connecting a copper tube and a steel rod via electromagnetic pulse waveform involves first machining an annular groove on the surface of the steel rod to be welded. Along the axial direction of the steel rod, the depth of the annular groove gradually increases from the center towards both sides, with the center of the groove flush with the axial surface of the steel rod, thus forming an annular tapered groove. Then, the copper tube is fitted onto the steel rod, directly opposite the surface to be welded. Finally, electromagnetic pulse welding is used to connect the copper tube and the steel rod. The depth of the annular groove increases linearly from the center towards both sides.

[0030] In practical applications, the annular groove is formed by mechanically turning two linear inclined grooves from the middle of the steel bar to be welded outwards. Here, the middle of the annular groove, that is, the position of the collision starting point, should be flush with the outer surface of the steel bar. This indicates that the groove depth in the middle of the annular groove is 0, or that there is no groove in the middle of the annular groove, but only grooves with gradually increasing depth are opened on both sides of the middle of the annular groove.

[0031] As welding progresses, the annular groove on the steel bar gradually increases the collision angle, thereby gradually increasing the collision gap from the initial point of collision to both sides. This effectively promotes the ejection of metal debris from the material connection interface during welding, reduces the retention of high-energy metal debris at the welding interface, and avoids cracks caused by metal debris accumulation and energy concentration at the welding interface. This ensures that the copper is smoothly pressed into the steel, which in turn facilitates electromagnetic pulse welding for the waveform interface connection between the copper tube and the steel bar.

[0032] In specific implementation, a welding method for connecting copper pipes and steel bars via electromagnetic pulse waveform interfaces includes the following steps:

[0033] (1) Determine the center line of the inner wall of the copper tube as the initial collision point of the copper tube, determine the center line of the steel bar to be welded as the initial collision point of the steel bar, and process inclined grooves at 2~5° on both sides of the outer circumference of the steel bar where the initial collision point of the steel bar is located, thereby forming an annular groove;

[0034] (2) A copper pipe and a steel rod are overlapped on a welding fixture. The copper pipe is sleeved on the steel rod, the surfaces of the copper pipe and the steel rod to be welded are facing each other, the initial collision point of the steel rod is facing the initial collision point of the copper pipe, and there is a certain welding gap between the copper pipe and the steel rod.

[0035] (3) The capacitor is turned on to discharge the coil. A time-varying high-intensity current with a very short period is passed through the coil. The magnetic field intensity is concentrated at the welding part of the workpiece by the magnet collector. By controlling the position of the welding fixture, the central magnetic field of the magnet collector is aligned with the collision start point of the copper tube and the steel rod, so that the copper tube can quickly impact the steel rod under electromagnetic force to achieve electromagnetic pulse welding of the copper tube and the steel rod.

[0036] In this way, the annular groove on the steel bar increases the collision gap between copper and steel, allowing copper and steel metal fragments generated during the collision process to fly out quickly from the copper-steel welding interface. This effectively avoids the retention of metal fragments at the welding interface, promotes the formation of a waveform interface during the copper-steel connection process, and thus improves the electromagnetic pulse welding quality of copper pipes and steel bars.

[0037] In practice, the surface roughness of the annular groove is 3.2–6.4 μm.

[0038] Roughness determines the magnitude of the frictional force generated during the collision of copper and steel. This frictional force, in turn, generates frictional heat during the welding process, which affects the temperature during the collision. Studies have shown that if the roughness is too high, the frictional heat is large, and some metals may melt into a liquid state, making it impossible for the copper to be pressed into the steel and difficult to form a local wavy interface. If the roughness is too low, the frictional force is too small, and copper may slide during the collision with steel. This also reduces the ability to remove oxide debris from the metal surface and makes it difficult to form a wavy connection interface, resulting in poor weld quality. Therefore, the roughness must be controlled within a certain range.

[0039] In practice, along the axial direction of the copper tube, the length of the annular groove of the steel rod is greater than the length of the copper tube to be welded. Specifically, the difference between the length of the annular groove of the steel rod and the length of the copper tube to be welded is equal to 1~2 mm.

[0040] Electromagnetic pulse welding is a cold pressure welding process. During the welding process, the workpiece will be squeezed and elongated. Here, the width of the annular groove is 1-2 mm greater than the length of the copper tube to be welded. This ensures that under the action of electromagnetic force, the copper tube is pressed into the steel rod along the length direction and fills the annular groove on the steel rod, while also ensuring that metal chips fly out smoothly from the space of the material interface.

[0041] In practice, the point of impact between the copper tube and the steel bar is located on the outer surface of the mid-section of the magnet collector.

[0042] In practice, along the axial direction of the copper tube, the length of the section to be welded on the copper tube is greater than the length of the magnetizer, ensuring that the copper tube is in the strongest magnetic field within the magnetizer. Specifically, along the axial direction of the copper tube, the length of each end of the section to be welded extending beyond the magnetizer is 2-3 mm. This facilitates obtaining two complete circumferential welds.

[0043] In practice, the welding gap between the copper tube and the steel rod is 1.5~2 mm.

[0044] In specific implementation, in step (3), the electromagnetic pulse welding discharge voltage is 12-16 KV and the capacitance is 120-240 uF. This ensures that the copper and steel metal fragments generated instantaneously by the high-speed impact of the copper tube with the steel rod can be completely pressed into the steel rod, ensuring the welding of the waveform connection interface of the copper tube metallurgical bond.

[0045] This invention employs electromagnetic pulse welding of copper tubes and steel rods. First, the steel rod surface to be welded is machined with an annular groove. Then, the inner wall of the copper tube and the welding surface of the steel rod are cleaned with acetone and quickly dried with cold air. Finally, the copper tube and steel rod are assembled on a coil magnetizer using a welding fixture. A welding diagram is shown below. Figure 1 and Figure 2 As shown, Figure 1The coil magnetizer consists of a coil coil 1, an insulating tube 2, and a magnet collector 3. A steel rod 6 and a copper tube 5 are then assembled inside the magnetizer. During assembly, the copper tube 5 is first fitted onto the steel rod 6, ensuring the initial contact point of the steel rod aligns with the initial contact point of the copper tube. Next, a first positioning tube 4 is assembled outside the copper tube 5. The length of the first positioning tube 4 is slightly less than the length of the steel rod 6. The inner side of the first positioning tube 4 has an annular groove to accommodate the copper tube, and the thickness of the annular groove is equal to the thickness of the copper tube plus the welding gap between the copper tube and the steel rod. Finally, a second positioning tube 7 is installed between the first positioning tube 4 and the steel rod 6, with the upper ends of the second positioning tube 7, the first positioning tube 4, and the steel rod 6 flush. The thickness of the second positioning tube 7 is equal to the thickness of the annular groove. Then, a first pressure plate 10 is installed on the upper end of the first positioning tube 4 and the second positioning tube 7. The first pressure plate 10 has through holes on opposite sides. One end of the double-ended screw 8 extends out of the through hole, and a nut 9 is installed on the double-ended screw outside the through hole. Finally, a fourth pressure plate 13 is installed at the lower end of the steel rod. At the same time, a third positioning tube 14 is sleeved on the steel rod between the first positioning tube 4 and the fourth pressure plate 13, so that the sum of the lengths of the first positioning tube and the third positioning tube is equal to the length of the steel rod. This facilitates the selection of a suitable length of the third positioning tube for length adjustment according to the length of the steel rod. The fourth pressure plate also has through holes on opposite sides. The other end of the double-ended screw passes through the through hole on the fourth pressure plate, and a nut is installed on the double-ended screw outside the fourth pressure plate. In order to further improve the fixing effect on the copper tube and the steel rod, a second pressure plate 11 and a third pressure plate 12 are also provided on the first positioning tube for positioning the side of the first positioning tube. Figure 2 In this context, α is the collision angle, and A is the initial collision point of the steel bar.

[0046] Example 1

[0047] (1) Machining is performed on the surface of the steel bar to be welded. Along the axial direction of the steel bar, two linear inclined grooves are machined from the middle of the part to be welded to both sides. An annular groove with an inclination angle β of 3° is machined, such as... Figure 3 As shown, Figure 3 Point A is the initial collision point of the steel bar;

[0048] (2) Then clean the inner wall of the copper tube and the surface of the steel bar to be welded with acetone, and then dry them quickly with cold air;

[0049] (3) Adopt Figure 1 The method involves assembling a copper tube and a steel rod on a welding fixture, with the surfaces of the copper tube and the steel rod facing each other, the initial collision point of the steel rod facing the initial collision point of the copper tube, and maintaining a 1 mm welding gap between the copper tube and the steel rod.

[0050] (4) Set the electromagnetic pulse charging voltage to 15KV and the capacitor to 240uF. Charge and discharge in the above equipment to pass a time-varying high-intensity current with a very short cycle into the coil and release the electromagnetic force through the magnetizer. Under the action of the electromagnetic force, the copper tube quickly impacts the steel rod to achieve welding.

[0051] The SEM image of the welding waveform interface obtained in this embodiment is as follows: Figure 4 As shown. By Figure 4 It can be seen that when the steel bar is machined with an annular groove with a taper of 3° at the welding point, the metal chips generated by the high-speed impact of the copper tube on the steel bar have flown out of the material connection interface and have not remained at the interface. The connection interface formed after the copper is pressed into the steel is smooth and free from defects such as cracks, pores and large areas of molten metal. A copper-steel waveform connection interface with an amplitude of 18 μm and a wavelength of 170 μm was obtained.

[0052] Comparative Example 1

[0053] The specific steps are the same as in Example 1, except that the inclination angle of the annular groove is 0°. The copper-steel material interface obtained in this example is as follows: Figure 5 As shown, when the angle of the inclined groove in the steel bar is 0, meaning the metal at the welding position of the steel bar has not been machined with an inclined groove, during the direct lap welding of the copper tube and steel bar, the high-speed impact of the copper tube against the steel plate generates high-speed metal debris. Because the copper-steel lap gap is fixed, the amount of metal debris gradually increases as the collision process progresses. Some larger metal debris does not fly out of the copper-steel material interface and remains at the interface. When the high-speed moving metal debris is trapped at the interface, the speed of the metal debris instantly drops to 0, kinetic energy is converted into internal energy, and heat is generated, causing the material at the location where the metal debris is trapped to instantly rise in temperature, leading to melting. Therefore, during the copper-pressing process into the steel, due to the soft sliding of the molten metal, a wavy interface cannot be formed, such as... Figure 5 As shown, it is difficult to obtain a welded joint for the interface connection of copper and steel electromagnetic pulse waveforms.

[0054] Comparative Example 2

[0055] The specific steps are the same as in Example 1, except that the inclination angle of the annular tapered groove is 7°. The copper-steel material connection interface obtained in this example is as follows: Figure 6 As shown, a large number of bonding cracks can be clearly seen at the copper-steel connection interface, and the interface waveform of the material connection is not obvious. This indicates that when the angle of the inclined groove of the steel bar is too large, the gap between the copper tube and the steel bar is too large, resulting in insufficient energy when the copper tube collides with the steel bar to form a metallurgical bond between the interface materials, and thus the welded joint with the waveform interface connection cannot be obtained.

[0056] Finally, it should be noted that the above embodiments of the present invention are merely examples for illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A welding method for connecting copper tubes and steel bars via electromagnetic pulse waveform interfaces, characterized in that, First, an annular groove is machined on the surface of the steel bar to be welded. Along the axial direction of the steel bar, the depth of the annular groove gradually increases from the middle of the annular groove to both sides. The middle of the annular groove is flush with the axial surface of the steel bar, thus forming an annular tapered groove. Then, the copper tube is sleeved on the steel bar and faces the surface of the steel bar to be welded. Finally, the copper tube and the steel bar are welded by electromagnetic pulse. The depth of the annular groove increases linearly from the middle of the annular groove to both sides. The center line of the inner wall of the copper tube is determined as the initial collision point of the copper tube, and the center line of the steel bar to be welded is determined as the initial collision point of the steel bar. Inclined grooves with a 2-5° inclination are machined on both sides of the outer circumference of the steel bar where the initial collision point is located, thereby forming the annular groove.

2. The welding method for connecting copper tubes and steel bars via electromagnetic pulse waveforms according to claim 1, characterized in that, Specifically, the following steps are included: (1) Determine the center line of the inner wall of the copper tube as the initial collision point of the copper tube, determine the center line of the steel bar to be welded as the initial collision point of the steel bar, and process inclined grooves at 2~5° on both sides of the outer circumference of the steel bar where the initial collision point of the steel bar is located, thereby forming an annular groove; (2) A copper pipe and a steel rod are overlapped on a welding fixture. The copper pipe is sleeved on the steel rod, the surfaces of the copper pipe and the steel rod to be welded are facing each other, the initial collision point of the steel rod is facing the initial collision point of the copper pipe, and there is a certain welding gap between the copper pipe and the steel rod. (3) The capacitor is turned on to discharge the coil, and a time-varying current is passed through the coil. The magnetic field strength is concentrated at the welding part of the workpiece by the magnet collector. By controlling the position of the welding fixture, the central magnetic field of the magnet collector is aligned with the collision start point of the copper tube and the steel rod, so that the copper tube can quickly impact the steel rod under electromagnetic force to achieve electromagnetic pulse welding of the copper tube and the steel rod.

3. The welding method for connecting the interface of copper tube and steel rod using electromagnetic pulse waveforms according to claim 2, characterized in that, The surface roughness of the annular groove is 3.2–6.4 μm.

4. The welding method for connecting the interface of copper tube and steel rod using electromagnetic pulse waveforms according to claim 2, characterized in that, Along the axial direction of the copper tube, the length of the annular groove of the steel rod is greater than the length of the copper tube to be welded.

5. The welding method for connecting the interface of copper tube and steel rod using electromagnetic pulse waveforms according to claim 4, characterized in that, The difference between the length of the annular groove of the steel bar and the length of the copper tube to be welded is 1~2 mm.

6. The welding method for connecting the interface of copper tube and steel rod using electromagnetic pulse waveforms according to claim 2, characterized in that, The welding gap between the copper tube and the steel bar is 1.5~2 mm.

7. The welding method for connecting the interface of copper tube and steel rod using electromagnetic pulse waveforms according to claim 2, characterized in that, Along the axial direction of the copper tube, the length of the magnet extending from both ends of the copper tube to be welded is 2~3 mm.

8. The welding method for connecting the interface of copper tube and steel rod using electromagnetic pulse waveforms according to claim 2, characterized in that, In step (3), the electromagnetic pulse welding discharge voltage is 12-16 KV and the capacitance is 120-240 uF.

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