Current-guiding magnetic resistance spot welding device and method

Abstract

This invention provides a current-guiding magnetic resistance spot welding device and method, comprising: a current-guiding device for generating and guiding welding current, an iron core or iron cooling water pipe for magnetic conduction, an electrode rod, and an electrode cap. The upper and lower ends of the current-guiding device are fixed to the electrode rod by an interference fit with screws or external clamps. The iron core or iron cooling water pipe serving as the core is located inside the electrode rod and passes through the current-guiding device, with one end extending close to the electrode cap. The electrode cap is tapered to the end of the electrode rod, and the bottom of the electrode cap is the weld nugget formation area. This invention provides similar performance improvement to traditional magnetic control devices. It completely avoids the limitation problems caused by geometric constraints such as the welding profile and clamping, greatly expanding the application range. Furthermore, the device is easy to install and disassemble, saving equipment modification costs. It also saves magnet materials and energy, simplifies the device, and meets the requirements of energy conservation and emission reduction.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic welding technology, specifically to a current-guiding magneto-controlled resistance spot welding device and method. Background Technology

[0002] Resistance spot welding is widely used in the automotive, aerospace, and rail transportation industries. In recent years, magnetically controlled resistance spot welding technology has been proven to improve the weld quality of various metal materials, including high-strength steel, stainless steel, aluminum alloys, aluminum-based composites, and aluminum / steel dissimilar metals. However, traditional magnetically controlled spot welding devices often generate an external magnetic field using a ring-shaped permanent magnet mounted on the outside of the electrode rod. During welding, the magnet needs to be very close to the material, but the raised structure around the weld point limits the working distance of the magnetically controlled device and can even prevent the electrode rod from reaching the correct position, which greatly limits the application range of traditional magnetically controlled devices.

[0003] Chinese patent document CN108788419 discloses a split-type magnetic resistance spot welding device. This device uses a two-lobed magnet instead of a traditional ring magnet, which can handle scenarios with linear obstacles near the weld point, but it still cannot completely solve the limitation problem. Existing magnetic resistance spot welding devices that rely on electromagnetic principles to generate an external magnetic field mainly consist of electromagnets that require additional power supply. For example, Chinese patent document CN101628358 discloses a magnetic resistance spot welding system in the field of electromagnetic welding technology, including an upper excitation coil and a lower excitation coil with opposite polarities mounted on upper and lower electrode rods. However, the coils required in this application are relatively large, still failing to solve the limitation problem, and require additional power supply, increasing energy consumption and making the device more complex. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a current-guiding magnetically controlled resistance spot welding device and method.

[0005] A current-guiding magnetostrictive resistance spot welding apparatus according to the present invention includes: a current-guiding device for generating an external magnetic field, a magnetic guiding device for conducting magnetism inside an electrode rod, an electrode rod, and a detachable electrode cap, wherein: Both ends of the drainage device are fastened to the electrode rod; The electrode cap is located at the end of the electrode rod; The magnetic guiding device is located inside the electrode rod, passes through the installation area inside the electrode rod, and extends to the upper part of the electrode cap. The bottom of the electrode cap is the melting nugget formation area.

[0006] Preferably, the mounting end of the drainage device is in close contact with the electrode rod.

[0007] Preferably, the drainage device is spirally mounted on the electrode rod.

[0008] Preferably, the drainage device is made of a low resistivity material.

[0009] Preferably, one end of the magnetic guiding device is close to the electrode cap to guide the magnetic field generated by the drainage device to act on the molten core below the electrode cap.

[0010] Preferably, the magnetic guiding device uses a soft magnetic material with high magnetic permeability.

[0011] Preferably, the magnetic guiding device includes an iron core or an iron core cooling water pipe.

[0012] Preferably, the magnetic guiding device includes an iron core water pipe, a head spring, and a head magnetic focusing sheet. One end of the iron core water pipe is connected to a cooling water pipe, and the other end is connected to the head magnetic focusing sheet through the head spring.

[0013] Preferably, the upper and lower ends of the drainage device are fixed ends that are in contact with the electrode rod, and the inner wall of the fixed end is interference-fitted with the outer wall of the electrode rod; the area between the two fixed ends is a non-contact end, and its inner wall is clearance-fitted with the outer wall of the electrode rod.

[0014] A current-guiding magnetoresistive spot welding method based on the above-described current-guiding magnetoresistive spot welding device, according to the present invention, includes the following steps: Pre-pressing step: After the lower electrode rod moves to the welding station, the lower electrode rod flow guiding device, iron core and electrode cap fixed to it move downward, the upper electrode rod moves downward, and moves the upper electrode rod flow guiding device, iron core cooling water pipe and electrode cap fixed to it close to the workpiece to be welded. The upper and lower electrode caps first contact the workpiece to be welded, and then clamp the workpiece under the action of the set electrode force. After the set electrode pressure is reached, it is maintained for a certain period of time to provide a reliable conductive path. Welding steps: During welding, the set welding current passes through the electrode rod. When the current flows through the junction of the electrode rod and the current guiding device, part of the current is diverted to the current guiding device and flows spirally along the device structure, generating a magnetic field. This part of the magnetic field is concentrated on the high-permeability iron core and thus guided to the near end of the workpiece. At the same time, the welding current flows through the electrode cap and heats the workpiece to be welded. The joint surface of the workpiece melts to form a weld nugget. The axial welding current interacts with the radial magnetic field generated by the current guiding device to generate a circumferential Lorentz force, which electromagnetically stirs the weld nugget metal. Pressure holding step: After the welding stage, the molten nucleus enters the solidification and cooling stage. The welding pressure is maintained for a period of time to promote cooling and nucleation. At the beginning of this stage, the molten nucleus metal continues to move under inertia. In order to make the Lorentz force continue to act, 5-20% of the welding current can be applied in this stage to further affect the cooling and nucleation process, refine the grains, and eliminate solidification defects. After the pressure holding stage, the upper and lower electrode rods return to their original positions, the electrode caps leave the workpiece, and the welding is completed.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention creatively proposes to guide the welding current to generate an external magnetic field that affects the flow of the weld nugget, eliminating the need to rely on permanent magnets, electromagnetic coils of external power sources, etc., to generate an external energy field. This represents a major breakthrough in the form and working mechanism of magnetic auxiliary devices for resistance spot welding.

[0016] 2. Compared with traditional permanent magnet devices, this invention solves the limitation interference problem caused by fixing permanent magnets around the electrode cap, greatly expanding the application range; at the same time, it avoids the problem of permanent magnet demagnetization caused by high operating temperature in traditional devices, and the working performance is stable.

[0017] 3. This invention saves on rare earth materials used in the manufacture of permanent magnets, thus achieving resource conservation.

[0018] 4. Compared with traditional electromagnet magnetic auxiliary devices, the device of the present invention has a small diameter and small size and does not require an additional power supply or a complex synchronization control program. Therefore, the device is simple, reliable, and applicable to existing production lines, saving equipment modification costs and making it more versatile.

[0019] 5. This invention uses an iron core inside the electrode rod to guide the magnetic field, making the external magnetic field closer to the weld nugget. The external magnetic field generated by this device works together with the welding current to generate a Lorentz force to stir the molten pool and accelerate the flow of molten metal, thereby increasing the diameter of the weld nugget, eliminating defects, and improving the microstructure. Attached Figure Description

[0020] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the drainage magnetic control device in Example 1.

[0021] Figure 2 This is a schematic diagram of a magnetic conductive device.

[0022] Figure 3 This is a schematic diagram of the drainage device structure in Example 1.

[0023] Figure 4 This is a schematic diagram of the magnetic field generated by the magnetic field source in Example 1.

[0024] Figure 5 This is a partial structural diagram of the permanent magnet-assisted magnetic control device for flow diversion in Example 2.

[0025] Figure 6 This is a schematic diagram of the operation of the flexible drainage magnetic auxiliary device in Example 3.

[0026] Figure 7 This is a schematic diagram of the flexible magnetic auxiliary device in Example 3.

[0027] Figure 8 This is a schematic diagram of the structure of a single winding of the flexible magnetic auxiliary device in Example 3.

[0028] Figure 9 This is a schematic diagram of the magnetic field generated by the flexible magnetic auxiliary device in Example 3.

[0029] Figure 10 This is a comparison diagram of the metallographic experimental results of the solder joints in Example 1.

[0030] Figure 11 This is a comparison chart of the experimental results of the tensile and shear mechanical properties of the weld joint in Example 1.

[0031] In the diagram: 1 Cooling water pipe, 2 Upper electrode rod, 3 Iron core cooling water pipe, 4 Upper electrode rod drainage device, 5 Electrode cap, 6 Workpiece to be welded, 7 Lower electrode rod, 8 Lower electrode rod drainage device, 301 Mating thread, 302 Iron core water pipe, 303 Head spring, 304 Head magnetic plate, 401 Threaded hole, 402 Countersunk screw, 403 Right-hand spiral drainage device body, 9 Auxiliary magnet, 10 Bending electrode rod, 11 Flexible drainage device, 12 Bending iron core, 1101 Fixing ring, 1102 Flexible wire, 1103 Threaded hole, 1104 Countersunk screw. Detailed Implementation

[0032] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0033] According to the present invention, a current-guiding magnetic resistance spot welding device and method are provided, comprising a current-guiding device for generating and guiding welding current, an iron core or iron cooling water pipe for magnetic conduction, an electrode rod, and an electrode cap, wherein: the upper end and lower end of the current-guiding device are fixed to the electrode rod by means of screw tightening or external pipe clamp, etc., forming an interference fit; the iron core for magnetic conduction or the iron cooling water pipe acting as the iron core is located inside the electrode rod and passes through the current-guiding device, with one end extending close to the electrode cap; the electrode cap is taperedly fitted to the end of the electrode rod; and the bottom of the electrode cap is the weld nugget formation area.

[0034] The inner diameters of the upper and lower ends of the current-guiding device must fit tightly with the outer diameter of the electrode rod to ensure good contact. The current-guiding device is preferably made of low-resistivity materials such as pure silver or pure copper. The current-guiding device must guide the current in a helical flow, such as a right-hand or left-hand helix, to generate the magnetic field required for magnetically assisted spot welding. If the current-guiding device is installed on both sides of the electrode rod, the current must be guided in opposite directions; that is, if the upper electrode rod guides the current in a right-hand helix, the lower electrode rod guides the current in a left-hand helix; and vice versa.

[0035] The iron core or cooling water pipe is installed inside the cooling water pipe, or is made of a special material. Its length must extend through the magnetron control device, and one end must be close enough to the electrode cap to guide the magnetic field generated by the current-draining device to act on the molten nucleus below the electrode cap. The iron core or cooling water pipe is preferably made of electrical pure iron, silicon steel, or other high-permeability soft magnetic materials. Before installing the current-draining device, the contact point between the electrode rod and the fixed end of the current-draining device must be clean and smooth to reduce contact resistance.

[0036] This invention relates to a current-guiding magnetron resistance spot welding process based on the above-mentioned device, specifically: Step 1, Pre-pressure stage: After the lower electrode rod moves to the welding station, the lower electrode rod drainage device, the iron core, and the electrode cap, which are fixedly connected to it, move the upper electrode rod downward, bringing the upper electrode rod drainage device, the iron core cooling water pipe, and the electrode cap closer to the workpiece to be welded. The upper and lower electrode caps first contact the workpiece, and then clamp the workpiece under the set electrode force. At this time, the distance between the iron core and the workpiece to be welded is also minimized. After reaching the set electrode pressure, it is maintained for a certain period of time to provide a reliable conductive path.

[0037] Step 2, Welding Stage: During welding, the set welding current passes through the electrode rod. When the current flows through the junction of the electrode rod and the current guiding device, a portion of the current is diverted to the current guiding device and flows spirally along the device structure, generating a magnetic field. This magnetic field is concentrated on the high-permeability iron core and guided to the near end of the workpiece. Simultaneously, the welding current flows through the electrode cap and heats the workpiece, melting the workpiece joint surface to form a weld nugget. The axial welding current interacts with the radial magnetic field generated by the current guiding device to produce a circumferential Lorentz force, which electromagnetically stirs the weld nugget metal to increase its size, eliminate defects, and refine the grain size.

[0038] Step 3, Pressure Holding Stage: After the welding stage, the molten metal enters the solidification and cooling stage. Welding pressure must be maintained for a period to promote cooling and nucleation. At the beginning of this stage, the molten metal continues to move under inertia. To ensure the Lorentz force continues to act, 0-20% of the welding current can be applied during this stage to further influence the cooling and nucleation process, refine the grains, and eliminate solidification defects. After the pressure holding stage, the upper and lower electrode rods return to their original positions, the electrode caps leave the workpiece, and the welding is complete.

[0039] The following is a more detailed explanation: Example 1 Figure 1 shows a schematic diagram of a flow-guiding magnetic control device involved in this embodiment. In the figure: a is a schematic diagram of the operation of the double-sided flow-guiding magnetic control device, and b is an assembly structure diagram of the flow-guiding magnetic control device. It includes: a cooling water pipe 1, an upper electrode rod 2, an iron core cooling water pipe 3, an upper electrode rod flow-guiding device 4, an electrode cap 5, a workpiece to be welded 6, a lower electrode rod 7, and a lower electrode rod flow-guiding device 8. The upper electrode rod flow-guiding device 4 and the lower electrode rod flow-guiding device 8 are respectively tightened with screws to achieve an interference fit with the upper electrode rod 2 and the lower electrode rod 7. The cooling water pipe 1 is located in the internal cavity of the electrode rods 2 and 7 and is connected to the iron core cooling water pipe 3 by a thread or pipe thread. The other end of the iron core cooling water pipe 3 is held against the electrode cap 5 by a spring. The electrode cap 5 is respectively set at the free end of the electrode rods 2 and 7.

[0040] In this embodiment, the workpiece 6 to be welded is high-strength steel DP590, with a thickness matching 1.6mm + 1.6mm. As shown in Figure 2, the iron core cooling water pipe 3 consists of a mating thread 301 with the cooling water pipe 1, an iron core water pipe 302, a head spring 303, and a head magnetic focusing plate 304. All parts are preferably made of high-permeability soft magnetic materials such as electrical pure iron or silicon steel. The total length L of the iron core cooling water pipe 3 must be determined based on the length H of the drainage device and the installation distance, and is 30~120mm. The length L1 of the mating thread 301 is 5~10mm, the length L2 of the head spring 303 is 3~15mm, the thickness h1 of the head magnetic focusing plate is 0.5~5mm, the outer diameter D1 of the iron core is the same as or slightly larger than the outer diameter of the cooling water pipe 1, the diameter D2 of the head magnetic focusing plate is 3~16mm, the inner diameter d1 of the iron core cooling water pipe is the same as the inner diameter of the cooling water pipe 1, and the inner diameter d2 of the magnetic focusing plate is 1~10mm. The iron core cooling water pipe 3 serves to guide the magnetic field. The smaller the distance between the head magnetic focusing plate 304 and the workpiece, the better. Figure 4 shows the effect of the presence or absence of an iron core on the magnetic field of the device. Only after the iron core cooling water pipe 3 is applied can the external magnetic field be concentrated around the molten core.

[0041] Figure 3This is a schematic diagram of the drainage device structure in Example 1. In the figure: a is a front view of the drainage device, b is a left view of the drainage device, c is a top view of the drainage device, and d is a triaxial view of the drainage device. As shown in Figure 3, the upper and lower ends of the upper electrode rod drainage device 4 in this embodiment are fixed ends that contact the electrode rod. The fixed ends are drilled with threaded holes 401, allowing for a tight interference fit between the inner wall of the fixed end and the outer wall of the electrode rod via screws 402, reducing contact resistance and guiding more current through the device body 403. The body 403 guides the current spiral flow to generate a magnetic field through grooves and other methods. The spiral directions of the upper and lower drainage devices should be opposite; for example, in this embodiment, the upper electrode rod drainage device 4 is a right-handed spiral, and the lower electrode rod drainage device 8 is a left-handed spiral. The generated magnetic field is shown in Figure 4. Figure 4 In the diagram: a represents the magnetic field generated without an iron core, and b represents the magnetic field generated with an iron core. The inner diameter Da of the fixed end of the device is the same as the outer diameter of the electrode rod; the inner diameter Db of the spiral section of the device is 0-2mm larger than the outer diameter of the electrode rod, but can be the same; the outer diameter Dc of the device is 25-50mm; the device height H is 20-100mm, and the fixed end height h is 3-15mm, while not exceeding 20% ​​of the device height H. The diameter Dd of the countersunk thread head does not exceed the fixed end height h; the thread connection distance a is 1-5mm; the groove width t is as small as possible, limited by the processing technology, and is 1-5mm. Grooves are only cut in the main body 403 section; there are no grooves within the fixed end h range. In this embodiment, the spiral groove starts below the threaded connection of the fixed end and cuts to the threaded connection of the other fixed end, with a pitch P of 30%-200% of the device height H. In this embodiment, the number of grooves is 2, but preferably 1-6.

[0042] This embodiment uses a welding current of 8.5 kA, a welding pressure of 4.2 kN, a pre-pressure time of 200 ms, a welding time of 200 ms, and a holding pressure time of 250 ms. After the lower electrode rod 2 moves to the welding position, its fixedly connected lower electrode rod current-guiding device 8, iron core 3, and electrode cap 5 move downwards, bringing its fixedly connected upper electrode rod current-guiding device 4, iron core cooling water pipe 3, and electrode cap 5 close to the workpiece 6 to be welded. The upper and lower electrode caps 5 first contact the workpiece, and then clamp the workpiece under the set electrode force. At this time, the distance between the iron core 3 and the workpiece 6 is also minimized. After reaching the set electrode pressure, it is maintained for a certain time to provide a reliable conductive path. Current is applied, and during welding, part of the current flows through the current-guiding devices 4 and 8 to generate an external magnetic field. After the power is stopped, the pressure is maintained constant, and after a holding pressure time of 250 ms, the upper and lower electrode rods leave the workpiece 6 and return to their original positions.

[0043] Compared with existing technologies, this embodiment uses welding current to generate the external magnetic field required for electromagnetic stirring, without relying on permanent magnet materials, external power supply, or affecting the grinding and cap-changing process, thus reducing interference. It is also simple to install and highly adaptable. Figure 10 , Figure 11 As shown, stirring the molten nugget with an external magnetic field generated by electromagnetic induction can increase the diameter of the molten nugget by 9.47%, improve the tensile and shear mechanical properties of the welded joint by 5.81%, increase the fracture energy absorption by 30.58%, and significantly refine the microstructure grains. The improvement effect can reach the level of existing technology, completely subverting the traditional magnetic-assisted spot welding process device and achieving resource conservation and energy saving.

[0044] Example 2 Figure 5 This is a partial structural diagram of the flow-guiding permanent magnet auxiliary magnetic control device in Example 2. In the figure: a is the head of the flow-guiding permanent magnet auxiliary magnetic control device, and b is a schematic diagram of the permanent magnet dimensions. As shown in Figure 5, this is one of the embodiments involved in this example, which differs from Example 1 in that an auxiliary magnet 9 is adsorbed and fixed at the magnetic focusing sheet 304 at the head of the iron core cooling water pipe 3.

[0045] The auxiliary magnet 9 is a cylindrical magnet with a central through hole. Its total height h2 is 1~10mm, its maximum diameter D3 is 3~15mm, and the diameter d3 of the central through hole is 1~6mm. The permanent magnet is axially magnetized, with the lower side (near the plate) being N and the upper side (near the electrode rod) being S. The lower electrode device has the same slotted electrode cap and permanent magnet unit, with the upper side (near the plate) being N and the lower side (near the electrode rod) being S.

[0046] Example 3 Figure 6 This is a schematic diagram of the operation of the flexible drainage magnetic auxiliary device in Example 3. Figure 6 In Figure 6, a is a triaxial view of the flexible magnetic auxiliary device in operation, and b is a cross-sectional view of the flexible magnetic auxiliary device in operation. As shown in Figure 6, this embodiment is a flexible drainage magnetic auxiliary device, which differs from Embodiments 1 and 2 in that it is suitable for bending electrode rods and includes: a bending electrode rod 10, a flexible drainage device 11, and a bending iron core 12.

[0047] In this embodiment, the workpiece 6 to be welded is high-strength steel DP590, with a thickness matching 1.6mm + 1.6mm. As shown in Figure 6, the flexible drainage device can be installed on the curved part of the electrode rod. A curved iron core 12 is placed in the cavity. The curved iron core can be composed of multiple small iron rings fixed to the outside of the rubber cooling water pipe, which is convenient for installation. Figure 7This is a schematic diagram of the flexible magnetic auxiliary device in Example 3. In the figure: a is a triaxial view of the flexible magnetic auxiliary device, and b is a cross-sectional view of the flexible magnetic auxiliary device. As shown in Figure 7, the flexible drainage device 11 mainly consists of a fixing ring 1101 and a flexible wire 1102. The fixing ring 1101 has a threaded hole 1103, and the fixing ring 1101 is connected to the curved electrode rod 10 by a countersunk screw 1104.

[0048] The height h3 of the fixing ring 1101 is 3~10mm, and its inner diameter d4 must be the same as the outer diameter of the electrode rod mounting part, fitting tightly. The outer diameter D4 is about 8~20mm larger than the inner diameter d4, which is slightly larger than twice the diameter d5 of the flexible wire 1102. The fixing ring 1101 and the flexible wire 1102 are connected by solid-state welding or other methods.

[0049] The flexible conductor 1102 can be made of soft copper or silver wire, with a thin plastic protective layer. The material of the fixing ring 1101 is consistent with that of the flexible conductor 1102. The conductor should be as thick as possible while meeting the limiting requirements to reduce resistance and increase current conduction. In this embodiment, the diameter d5 of the flexible conductor 1102 is 3~10mm. Resistance can be further reduced by setting multiple turns of winding. In this embodiment, a total of 4 turns of conductor are set, and the single-turn winding and current flow direction are shown in Figure 8. The magnetic field generated by this flexible current-draining device is shown in Figure 9. The magnetic field can still be guided to the vicinity of the molten core by relying on the bent iron core 12.

[0050] Compared with Embodiments 1 and 2, this embodiment is applicable to bent electrode rods or electrode rods with continuously varying radii, further expanding the applicability of the device.

[0051] This invention employs an external current-guiding device on the electrode rod to guide the welding current and generate the radial magnetic field required for magnetically assisted welding. The magnetic field is then guided close to the weld nugget by an iron core built into the electrode rod. Under the influence of this magnetic field, the molten metal undergoes high-speed three-dimensional flow, scouring the weld nugget boundary, while simultaneously altering the solidification and crystallization mode, refining the grain size in the weld nugget area, and reducing or even completely eliminating welding defects. This achieves the effects of increasing the weld nugget diameter and improving the microstructure, with results comparable to traditional magnetic control devices. Because the external current-guiding device can be installed on various electrode rods, away from the weld nugget area, it completely avoids the limiting problems caused by geometric constraints such as the welded profile and clamping, greatly expanding its application range compared to traditional devices. Furthermore, the device is easy to install and disassemble, saving on equipment modification costs. Simultaneously, this innovative device utilizes the welding current to generate the magnetic field, saving magnetic material compared to traditional permanent magnet devices and energy compared to traditional electromagnet devices, simplifying the device and meeting energy conservation and emission reduction requirements. Therefore, this device represents a significant breakthrough in the form and mechanism of magnetically assisted resistance spot welding devices.

[0052] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0053] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A current-guiding magnetic resistance spot welding device, characterized in that, include: A current-guiding device for guiding the spiral flow of welding current to generate an external magnetic field, a magnetic guiding device inside the electrode rod for magnetic conduction, the electrode rod, and a detachable electrode cap, wherein: Both ends of the drainage device are fastened to the electrode rod; The electrode cap is located at the end of the electrode rod; The magnetic guiding device is located inside the electrode rod, passes through the installation area inside the electrode rod, and extends to the upper part of the electrode cap. The bottom of the electrode cap is the melting nugget formation area. One end of the magnetic guiding device is close to the electrode cap to guide the magnetic field generated by the drainage device to act on the molten nucleus below the electrode cap; The magnetic guiding device is made of a soft magnetic material with high magnetic permeability; The magnetic conductive device includes an iron core cooling water pipe.

2. The current-guiding magnetic resistance spot welding device according to claim 1, characterized in that, The drainage device is installed at a point that is in close contact with the electrode rod.

3. The current-guiding magnetic resistance spot welding device according to claim 1, characterized in that, The drainage device is spirally mounted on the electrode rod.

4. The current-guiding magnetic resistance spot welding device according to claim 1, characterized in that, The drainage device is made of a low resistivity material.

5. The current-guiding magnetic resistance spot welding device according to claim 1, characterized in that, The iron core cooling water pipe includes an iron core water pipe, a head spring, and a head magnetic plate. One end of the iron core water pipe is connected to the cooling water pipe, and the other end is connected to the head magnetic plate through the head spring.

6. The current-guiding magnetic resistance spot welding device according to claim 1, characterized in that, The upper and lower ends of the drainage device are fixed ends that are in contact with the electrode rod, and the inner wall of the fixed end is interference-fitted with the outer wall of the electrode rod; the area between the two fixed ends is a non-contact end, and its inner wall is clearance-fitted with the outer wall of the electrode rod.

7. A current-guiding magnetic resistance spot welding method based on the current-guiding magnetic resistance spot welding device according to any one of claims 1-6, characterized in that, Includes the following steps: Pre-pressing step: After the lower electrode rod moves to the welding station, the lower electrode rod drainage device, the iron core cooling water pipe and the electrode cap that are fixed to it move down, the upper electrode rod moves down, and moves the upper electrode rod drainage device, the iron core cooling water pipe and the electrode cap that are fixed to it close to the workpiece to be welded. The upper and lower electrode caps first contact the workpiece to be welded, and then clamp the workpiece under the action of the set electrode force. After the set electrode pressure is reached, it is maintained for a certain period of time to provide a reliable conductive path. Welding steps: When welding with electricity, the set welding current passes through the electrode rod. When the current flows through the junction of the electrode rod and the current guiding device, part of the current is diverted to the current guiding device and flows spirally along the structure of the current guiding device, generating a magnetic field. This part of the magnetic field is concentrated in the high permeability iron core cooling water pipe and thus guided to the near end of the workpiece. The welding current flows through the electrode cap and heats the workpiece to be welded, and the joint surface of the workpiece melts to form a weld nugget; the axial welding current interacts with the radial magnetic field generated by the current guiding device to generate a circumferential Lorentz force, which electromagnetically stirs the weld nugget metal. Pressure holding step: After the welding stage, the molten nucleus enters the solidification and cooling stage. The welding pressure is maintained for a period of time to promote cooling and nucleation. At the beginning of this stage, the molten nucleus metal continues to move under inertia. In order to make the Lorentz force continue to act, 5% to 20% of the welding current is applied in this stage to further affect the cooling and nucleation process, refine the grains, and eliminate solidification defects. After the pressure holding stage, the upper and lower electrode rods return to their original positions, the electrode caps leave the workpiece, and the welding is completed.

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