Electrode and spot welding device for dissimilar metal resistance spot welding

Abstract

The application provides a resistance spot welding electrode and a spot welding device for welding dissimilar metals. A plurality of gas holes are arranged on the electrode at the same angle interval around the central axis of the electrode, and the gas holes are connected to a vacuum pumping system of the spot welding device, so that the gas holes in the electrode form a negative pressure, and the electrode can adsorb the welding elements to be welded. A connecting unit is arranged around the electrode connecting rod of the spot welding device, and the gas holes on the electrode are engaged with the connecting unit after the electrode is installed on the electrode connecting rod, so that the gas holes on the electrode are communicated with the vacuum pumping system. The electrode and the spot welding device provided by the application can realize efficient conveying, stable adsorption and high-quality welding of dissimilar metals.

Description

Technical Field

[0001] This invention belongs to the field of dissimilar metal welding, specifically relating to electrodes and spot welding devices for resistance spot welding of dissimilar metals. Background Technology

[0002] Against the backdrop of lightweighting development in the automotive industry, high-strength steel, ultra-high-strength steel, aluminum alloys, and magnesium alloys are increasingly being used in car body manufacturing to replace traditional ordinary steel, thereby achieving weight reduction while ensuring safety performance. In car bodies manufactured using a combination of materials, there is an urgent need for a welding process and equipment to achieve efficient and high-quality welding of dissimilar metals. However, due to the significant differences in thermophysical properties and metallurgical compatibility between dissimilar metals, traditional welding methods are prone to problems such as cracking, brittle intermetallic compounds, and severe deformation, making it difficult for the joints to meet the strength requirements of the application.

[0003] To achieve efficient joining of dissimilar metals, patent document CN114226943B proposes a welding sheet structure and welding device. This device uses welding sheets (referred to as welding elements in this invention) to weld two dissimilar metals, a first metal plate and a second metal plate. The welding sheet is made of the same material as the second metal plate. This avoids the influence of brittle intermetallic compounds on the joint after welding, achieving a high-quality joining of dissimilar metals. During welding, the welding sheet is continuously fed to the electrode through a welding sheet conveying system, thus achieving continuous welding. The welding sheet conveying system disclosed in patent document CN114226943B includes a gripping mechanism arranged around the welding electrode. This gripping mechanism enables continuous gripping of the welding sheet without interfering with the subsequent welding process. However, considering the actual welding conditions and needs in the automotive industry, this gripping mechanism has several disadvantages: (1) After welding a certain number of weld points, the welding surface of the electrode needs to be re-grinded and refurbished. The gripping mechanism, located around the electrode, will interfere with the electrode re-grinding process; (2) The welding electrode has a service life. When the service life is reached, the electrode needs to be replaced. The gripping mechanism will interfere with or reduce the electrode replacement efficiency; (3) After the electrode has been re-grinded several times, the electrode length will be shortened. It is necessary to adjust the distance between the gripping mechanism and the welding surface of the electrode in a timely manner, which increases the complexity of the equipment; (4) In practical applications, the diameter of the welding electrode body is usually larger than the maximum diameter of the outer contour of the material sheet. For example, the electrode body diameter is 19 mm, while the maximum diameter of the outer contour of the material sheet is only 15 mm. This makes it difficult for the gripping mechanism surrounding the electrode to grip small-sized material sheets. To solve the above disadvantages 1-4, the gripping mechanism will become more complex in terms of structure, mechanism movement, and control system, increasing the manufacturing cost of the equipment. In addition, the more complex the gripping structure, the higher the error rate will be in the welding process, which is not conducive to the fast production rhythm in automobile manufacturing. Therefore, there is an urgent need in the field for a welding electrode and apparatus to achieve efficient transfer, gripping, and continuous and robust welding of sheet metal to dissimilar metals. Summary of the Invention

[0004] The purpose of this invention is to provide electrodes and a spot welding device for resistance spot welding of dissimilar metals, so as to solve the problems of continuous material supply and continuous high-quality welding of welding elements during resistance spot welding of dissimilar metals.

[0005] An electrode for resistance spot welding of dissimilar metals is characterized in that at least two gas channels are arranged along the axial direction of the electrode and distributed at equal angular intervals around the central axis of the electrode. The gas channels are connected to a vacuum system to form a negative pressure in the gas channels, thereby enabling the electrode to adsorb the welding element to be welded.

[0006] Furthermore, the electrode sidewall is provided with an annular quick-connect portion, and the gas channel extends from the quick-connect portion to the annular surface surrounding the welding surface of the electrode head. The quick-connect portion is used to connect to the vacuum system.

[0007] Furthermore, the shape of the gas channel in cross-section includes circular, elliptical, or arc-shaped.

[0008] Furthermore, the quick-connect portion is a ring structure with shape features such as a beveled surface or a groove manufactured on the electrode body.

[0009] Furthermore, when the gas channel extends from the quick-connect portion into the annular surface, it includes a straight through-type channel and a curved through-type channel.

[0010] Furthermore, there is a height difference between the annular surface and the welding surface, and its cross-sectional profile is similar to the local outer contour of the welding element to be welded.

[0011] According to another aspect of this disclosure, a dissimilar metal resistance spot welding apparatus is used for continuously conveying welding elements and welding dissimilar metals during welding. The apparatus includes a welding element conveying system, a vacuum system, and a welding system. The vacuum system includes a connecting unit connected to any electrode provided by this invention. The connecting unit is mounted on the outer peripheral surface of an electrode connecting rod near the electrode. After the connecting unit contacts a quick-connect portion on the electrode, the gas channel of the electrode is connected to the vacuum system. The vacuum system creates a negative pressure in the gas channel of the electrode, enabling the electrode to adsorb the welding element to be welded.

[0012] Furthermore, the connecting unit includes: a bracket for mounting an annular component on the electrode connecting rod; a connecting member including a quick-connect port and an internal gas channel, wherein the quick-connect port and the quick-connect portion of the electrode are at least partially complementary structures to achieve a contact connection between the quick-connect port and the quick-connect portion of the electrode, and to connect the gas channel in the connecting member with the gas channel on the electrode; a sliding component for connecting the connecting member to the bracket, allowing the connecting member to slide up and down relative to the bracket; and an elastic component for connecting the connecting member to the bracket, providing resistance when the connecting member slides up and down relative to the bracket.

[0013] Furthermore, the quick-connect port on the connecting member is provided with an annular groove, and the gas channel in the connecting member is connected to the annular groove. After the quick-connect port contacts the electrode quick-connect part, the annular groove at least partially covers all the gas channels on the electrode quick-connect part, so that after the electrode is installed by rotating at any angle along the central axis, the gas channels in the connecting member and the electrode remain connected.

[0014] Furthermore, the quick-connect port of the connecting member is made of a high-temperature resistant material, and the quick-connect port is provided with an annular sealing strip to maintain the airtightness of the connection between the quick-connect port and the electrode.

[0015] Technical effects of the invention:

[0016] (1) The welding electrode structure of the present invention is simple and easy to manufacture. It can simultaneously realize the functions of gripping and welding welding elements, reducing the complexity of the structure of the welding element gripping equipment and its control system.

[0017] (2) Because gas channels are set circumferentially and at equal angular intervals on the annular surface around the electrode welding surface, the electrode can stably and firmly adsorb the welding element.

[0018] (3) The resistance spot welding device of the present invention has a simple structure and low manufacturing cost. While realizing the efficient transmission of welding elements and the rapid grasping of welding elements by electrodes, it also ensures the same replacement efficiency of electrodes as traditional spot welding equipment.

[0019] (4) The electrode of the resistance spot welding device of the present invention is easy to install and can be ground by traditional automated grinding process. There is no interference from other mechanisms during the electrode grinding process, which effectively ensures the high efficiency of electrode grinding.

[0020] (5) Since gas channels are provided on the electrode, the heat dissipation effect of the electrode is increased, which helps to avoid overheating of the electrode during welding and improves the service life of the electrode. Attached Figure Description

[0021] Figure 1 This is a three-dimensional electrode diagram of one embodiment of the present disclosure.

[0022] Figure 2 This is a bottom view of the electrodes, representing one embodiment of this disclosure.

[0023] Figure 3 This is a cross-sectional view of an electrode according to one embodiment of the present disclosure.

[0024] Figure 4 This is a schematic cross-sectional view of the electrode, representing yet another embodiment of the present disclosure.

[0025] Figure 5 This is a schematic diagram of a dissimilar metal resistance spot welding apparatus according to one embodiment of the present disclosure.

[0026] Figure 6 This is a schematic diagram of the electrodes, connecting members, and electrode rods before installation, representing one embodiment of this disclosure.

[0027] Figure 7 This is a three-dimensional schematic diagram of a connecting member according to one embodiment of the present disclosure.

[0028] Figure 8 This is a cross-sectional schematic diagram of a connecting member according to one embodiment of the present disclosure.

[0029] Figure 9 This is a schematic diagram of the electrode and connecting member and electrode rod after installation, according to one embodiment of this disclosure.

[0030] Figure 10 This is a schematic diagram of an electrode gripping and welding component process according to one embodiment of the present disclosure.

[0031] Figure 11 This is a schematic diagram illustrating the relationship between welding current, electrode pressure, and time in resistance spot welding of dissimilar metals as disclosed in this publication.

[0032] Figure 12 This is a schematic diagram of the spot welding process of dissimilar metals in one embodiment of the present disclosure. Detailed Implementation

[0033] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0034] According to one aspect of the present invention, an electrode 100 for resistance spot welding of dissimilar metals is provided, such as... Figures 1 to 3 As shown, a water-cooling hole 108 is provided at the tail 101 of the electrode 100. Cooling water is introduced through the water-cooling hole 108 to dissipate heat from the electrode. The side of the water-cooling hole 108 is typically designed as a tapered surface, which is used to match the electrode connecting rod for installation. At least two gas channels 107 are provided along the axial direction of the electrode 100, distributed at equal angular intervals around the electrode's central axis. Preferably, the number of gas channels 107 is 4 to 8. The gas channels 107 are used to connect to a vacuum system, creating a negative pressure within the gas channels to allow the electrode 100 to adsorb the welding element to be welded. An annular quick-connect portion 102 is provided on the side wall 103 of the electrode. The gas channels 107 extend from the quick-connect portion to the annular surface 104 outside the welding surface sidewall 106 of the electrode head. The quick-connect portion 102 allows the gas channels 107 of the electrode to be quickly connected to the vacuum system. Figure 2 As shown, the gas channels 107 are annularly distributed around the center of the annular surface 104 at equal angular intervals. This facilitates the stable adsorption of the welding element by the electrode 100, preventing the welding element from tilting or falling off during the adsorption process. Figure 3 As shown, from the electrode cross-section, the gas channels 107 are distributed around the water cooling holes 108. In order to avoid the gas channels 107 weakening the strength of the electrode 100, the minimum distance between the gas channels 107 and the sidewall of the water cooling holes 108 is set to be greater than 1.2 mm.

[0035] Depending on the different electrode processing techniques and the process requirements for adsorbing different welding element structures, the shape of the gas channel 107 in cross-section includes circular, elliptical, or arc-shaped.

[0036] In yet another embodiment, such as Figure 4 As shown, the quick-connect portion 102 is an annular structure with beveled surfaces and grooves manufactured on the electrode body. This is beneficial for improving the connection efficiency between the gas channel 107 and the vacuum system while ensuring airtightness. After the electrode 100 wears down due to the preparation of a certain number of solder joints, the welding surface 105 of the electrode head and the outer annular surface 104 of the electrode 100 need to be ground and refurbished. After several grinding cycles, the electrode head gradually shortens in the axial direction. In order to maintain the position of the gas channel 107 on the annular surface 104 after grinding and to ensure the same adsorption effect on the welding element before and after grinding, the gas channel 107 is set as a curved through-type channel, specifically including a gas channel 1072 parallel to the electrode axis and a curved gas channel 1071 connected to the quick-connect portion 102.

[0037] According to another aspect of the present invention, the annular surface 104 is used to assist the welding element in being quickly positioned and firmly adsorbed. Its cross-sectional profile is similar to the profile of the local periphery of the welding element to be adsorbed, and there is a height difference between the annular surface 104 and the central welding surface 105 (e.g., Figure 4 As shown), during welding, the annular surface 104 does not contact the metal workpiece to be welded, but it plays a role in assisting the deformation of the welding element to be welded and limiting the height of the welding element from the workpiece surface after welding.

[0038] According to another aspect of this disclosure, a dissimilar metal resistance spot welding apparatus is provided for continuously feeding welding components and welding dissimilar metals during welding, the structure of which is as follows: Figure 5As shown. The resistance spot welding device includes a welding element conveying system, a vacuum system, and a welding system. The vacuum system includes a connecting unit that connects to any of the electrodes 100 provided by this invention. The connecting unit is mounted on the outer peripheral surface of the electrode connecting rod 300 near the electrode. The connecting unit is connected to a vacuum pump 208 via a gas pipe 207, and the vacuum pump draws a vacuum to allow the electrode 100 to adsorb the welding element 700 to be welded. The welding element conveying system includes a transmission device 601, a material gripping arm 602, a material feeding head 603, a material dropping sensor 604, a material feeding pipe 607, and a material distributor 608. In one feeding process, the transmission device 601 drives the gripping arm 602 to retract to a position below the feeding head 603. The distributor 608 sorts the front and back sides of the welding elements 700, and then, driven by high-pressure gas, conveys them to the feeding head 603 through the feeding pipe 607. The feeding head 603 releases the welding elements 700 one by one onto the gripping arm 602. The drop sensor 604 is used to detect whether the release process of the welding elements 700 is successful. After the gripping arm 602 grabs the welding element 700, it extends to below the electrode 100 for release. Due to the negative pressure at the end of the electrode 100, the welding element 700 is adsorbed. The gripping sensor 605 detects the process of the electrode 100 grabbing the welding element. When the electrode 100 successfully grabs the welding element, the gripping sensor 605 sends a signal to the welding system to execute the welding process.

[0039] Furthermore, in one embodiment, as Figure 6 As shown, the connection unit includes a connecting member 200, an elastic component 204, a sliding component 205, and a bracket 206. The bracket 206 is mounted on the electrode connecting rod 300, and the connecting member 200 is connected to the bracket 206 via the sliding component 205, allowing the connecting member 200 to slide up and down. An elastic component 204 is also provided between the connecting member 200 and the bracket 206. When the connecting member 200 slides up and down, the elastic component 204 applies resistance, ensuring that the quick-connect port 203 and the quick-connect part 102 of the electrode make tight contact when the connecting member 200 is connected to the electrode 100, guaranteeing the airtightness of the connection.

[0040] Figure 7 and Figure 8 The figures shown are a three-dimensional schematic diagram and a cross-sectional schematic diagram of the connecting member 200 in one embodiment. The connecting member 200 is provided with an annular groove 201, a gas channel 202, and a quick-connect port 203. The gas channel 202 inside the connecting member is connected to the annular groove 201; the quick-connect port 203 is a chamfered surface, which is a complementary structure to the quick-connect part of the electrode, so as to realize the connection between the gas channel inside the connecting member 200 and the gas channel on the electrode 100.

[0041] Figure 9This is a schematic diagram showing the electrode 100 and electrode connecting rod 300 after installation. When the electrode 100 is installed onto the electrode connecting rod 300, the connecting member 200 slides upwards under the push of the electrode 100. Under the pressure applied by the elastic component 204, the quick-connect portion 102 on the electrode comes into close contact with the quick-connect port 203 on the connecting member. After the quick-connect port 203 contacts the electrode quick-connect portion 102, the annular groove 201 covers the gas channels 107 on the electrode quick-connect portion 102. Because the annular groove 201 can cover all gas channels 107 360°, the electrode 100 does not need to be installed at a specific angle when installed onto the electrode connecting rod 300. After the electrode 100 rotates at any angle along its central axis, the connecting member 200 and the gas channels in the electrode 100 remain connected, ensuring the efficiency of electrode installation.

[0042] In other embodiments, the quick-connect port 203 of the connecting member is made of a high-temperature resistant material or coated with a high-temperature resistant heat-insulating coating to prevent the high temperature generated by the electrode 100 during welding from affecting the airtightness of the connection between the quick-connect port 203 and the electrode. In addition, to further improve the airtightness of the connection between the quick-connect port 203 and the electrode, an annular sealing strip is also provided on the quick-connect port 203.

[0043] like Figure 10 The diagram shows the process of the electrode gripping and welding element 700. Because the gas channels of electrode 100 are connected to the vacuum adsorption system, a negative pressure is formed, creating a ring-shaped low-pressure zone around the welding surface 105 of the electrode. Figure 10 In stage A1, after the welding element 700, gripped by the gripping arm 602, is conveyed to the underside of the electrode, it is released. Because the annular surface 104 of the electrode is similar to the local contour of the outer periphery of the welding element 700, the outer periphery of the welding element 700 is tightly adhered to the annular surface 104 of the electrode, while the central axial region of the welding element 700 is in contact with the electrode welding surface 105. Figure 10 In the B1 stage, the electrode 100, which then adsorbs the welding element 700, moves to the welding area to weld dissimilar metals.

[0044] In a welding embodiment employing the electrode and spot welding device of the present invention, a schematic diagram of the welding process is shown below. Figure 11 and Figure 12 As shown in the diagram. The first metal, 800, is an aluminum alloy, and the second metal, 900, is advanced high-strength steel. A schematic diagram of the welding process is shown below. Figure 11As shown, the process includes a preheating process, a first metal removal stage, and a welding stage. In the preheating stage, a small current pulse, such as 5 kA, is applied and maintained for 50 ms, ensuring good contact between the welding element 700, the first metal 800, and the second metal 900. In the first metal removal stage, multiple pulsed currents are applied, such as four pulsed currents: the first pulse is 16 kA, the second is 18 kA, the third is 19 kA, and the fourth is 17 kA. Each pulse is maintained for 55 ms, causing the first metal 800 in the weld joint to melt and expand rapidly, generating a jetting (spatter) process that quickly removes the metal from the area covered by the shaft of the welding element, thereby allowing the central shaft of the welding element to quickly penetrate the first metal. In the welding stage, a single current pulse is applied to connect the welding element 700 and the second metal 900. This current pulse has a lower intensity than the current pulse in the first metal removal stage, for example, 13 kA, and is maintained for 450 ms. The specific welding process is as follows: Figure 12 As shown, the upper electrode 100 attracts the welding element 700 above the welding area of ​​the first metal 800, while the lower electrode 500 is located below the welding area of ​​the second metal. During the preheating stage (e.g. Figure 12 In stage A2 of the process, pressure and preheating current are applied to the spot weld between the upper electrode 100 and the lower electrode 500, causing the welded components to adhere tightly to the surface of the first metal 800. Then, a current is applied to the weld joint to remove the first metal 800 (e.g., a current that removes heat from the first metal 800). Figure 12 In stage B2, the first metal rapidly melts and undergoes a jetting process. A large amount of jetted metal 801 is forced into the annular cap structure surrounding the welding element 700. The central axis of the welding element 700, under the pressure of the welding surface 105 of the upper electrode 100, rapidly penetrates the first metal 800 and makes contact with the second metal 900. During stage B2, the gas channels 107 of the upper electrode 100 are always maintained in a vacuum state, increasing the heat dissipation efficiency of the upper electrode. Additionally, the annular surface 104 of the upper electrode 100 presses against the cap structure surrounding the welding element 700, assisting in the deformation of the cap structure and limiting its post-weld height. Finally, in the welding stage (e.g.... Figure 12 In the C2 stage, welding current is applied to the weld joint so that the welding element 700 and the second metal 900 form a common weld nugget 901, thereby obtaining a dissimilar metal joint.

[0045] It should be understood that the above embodiments are only intended to illustrate the technical concept of the present invention to facilitate understanding by those skilled in the art, and are not intended to limit the scope of protection of the present invention. Within the scope of the claims of the present invention, any improvements and equivalent substitutions to the parts, structures, or method steps involved in the above embodiments, especially combinations of different embodiments without causing structural or principle conflicts, fall within the scope of protection of the present invention.

Claims

1. A dissimilar metal resistance spot welding apparatus for continuously conveying welding elements and welding dissimilar metals during welding, the apparatus comprising a welding element conveying system, a vacuum system, and a welding system, characterized in that: The vacuum system includes a connection unit, which is connected to an electrode. The connecting unit is installed on the outer peripheral surface of the electrode connecting rod near the electrode. After the connecting unit contacts the quick-connect part on the electrode, the gas channel of the electrode is connected to the vacuum system. The vacuum system creates a negative pressure in the gas channel of the electrode, so that the electrode can adsorb the welding element to be welded. The connection unit includes: A bracket, a ring-shaped component used for mounting on an electrode connecting rod; The connecting component includes a quick-connect port and an internal gas channel. The quick-connect port and the quick-connect portion of the electrode have at least a complementary structure to achieve a contact connection between the quick-connect port and the quick-connect portion of the electrode, so that the gas channel inside the connecting component is connected to the gas channel on the electrode. A sliding component is used to connect the connecting member to the bracket, allowing the connecting member to slide up and down relative to the bracket. Elastic components are used to connect the connecting member and the support, so that there is resistance when the connecting member slides up and down relative to the support.

2. The dissimilar metal resistance spot welding device according to claim 1, characterized in that, The quick-connect port on the connecting member is provided with an annular groove. The gas channels in the connecting member are connected to the annular groove. After the quick-connect port contacts the electrode quick-connect part, the annular groove at least partially covers all the gas channels on the electrode quick-connect part, so that after the electrode is installed by rotating it at any angle along the central axis, the gas channels in the connecting member and the electrode remain connected.

3. The dissimilar metal resistance spot welding device according to claim 1, characterized in that, The quick-connect port of the connecting component is made of high-temperature resistant material, and the quick-connect port is provided with an annular sealing strip to maintain the airtightness of the connection between the quick-connect port and the electrode.

4. The dissimilar metal resistance spot welding device according to claim 1, characterized in that, The electrode is provided with at least two gas channels distributed around the central axis of the electrode at equal angular intervals. The gas channels are connected to a vacuum system to form a negative pressure in the gas channels, thereby enabling the electrode to adsorb the welding components to be welded. The electrode sidewall is provided with an annular quick-connect portion, and the gas channel extends from the quick-connect portion to the annular surface surrounding the welding surface of the electrode head. The annular surface has a height difference with the welding surface, and its cross-sectional profile is similar to the local outer contour of the welding element to be welded. The quick-connect part is used to connect with the vacuum system to create a negative pressure in the gas channel, so as to enable the electrode to adsorb the welding element to be welded.

5. The dissimilar metal resistance spot welding device according to claim 4, characterized in that, The shape of the gas channel in cross-section includes circular, elliptical, or arc-shaped.

6. The dissimilar metal resistance spot welding device according to claim 4, characterized in that, The quick-connect part is a ring structure with beveled or grooved features manufactured on the electrode body.

7. The dissimilar metal resistance spot welding device according to claim 4, characterized in that, When the gas channel penetrates from the quick-connect portion into the annular surface, it includes a straight through-hole and a curved through-hole.

Images