A method of laser flight welding of a vehicle door inner panel

Abstract

The present application relates to the technical field of welding, and provides a laser flying welding method for a door inner plate, which comprises the following steps: S1: providing a workpiece for the door inner plate, and clamping the workpiece through a tooling fixture, wherein the workpiece comprises a first workpiece, a second workpiece, a third workpiece, a fourth workpiece, a fifth workpiece, a sixth workpiece and a seventh workpiece; S2: welding the first workpiece and the second workpiece by using a point spiral welding point mode; S3: welding the first workpiece and the third workpiece and welding the first workpiece and the fourth workpiece by using a linear welding point mode; S4: welding the first workpiece and the fifth workpiece and welding the first workpiece and the sixth workpiece by using a point spiral welding point mode, a linear welding point mode or a C-shaped welding point mode; S5: welding the seventh workpiece and the second workpiece by using a linear welding point mode; and S6: welding the seventh workpiece and the fifth workpiece by using a linear welding point mode.

Description

Technical Field

[0001] The present invention relates to the technical field of welding, and in particular to a method for laser flying welding of a vehicle door inner panel. Background Art

[0002] With economic development and the implementation and promotion of the "dual carbon" policy, the automotive industry, as a leading sector in global economic development, has entered a period of rapid development and transformation. "Energy conservation, environmental protection, and safety" have become the mainstream trends in the automotive industry. Vehicle lightweighting is a key measure to achieve the "new four modernizations" of the automotive industry. It is one of the key measures to reduce greenhouse gas emissions, improve fuel efficiency, and lower vehicle operating costs. It is also a key technology for achieving intelligent emission reduction in automobiles and can effectively promote the sustainable development of the automotive industry. With the trend of vehicle lightweighting, how to achieve this has become a key issue. The key to a vehicle's fuel consumption lies in the engine's displacement and the vehicle's gross weight. While maintaining the vehicle's overall structure, quality, and overall performance, reducing the vehicle's weight can increase power, reduce noise, enhance maneuverability and stability, and improve safety, while also increasing speed, reducing fuel consumption, and lowering exhaust emissions. Scientific research data shows that a 10% reduction in vehicle weight can increase gasoline and diesel efficiency by 6%-8%; a 10% reduction in rolling friction resistance can increase gasoline and diesel efficiency by 3%; and a 10% increase in the transmission efficiency of trailer axles, gearboxes, and other equipment can increase gasoline and diesel efficiency by 7%. The vehicle body accounts for approximately 30% of the vehicle's total weight. When fully loaded, approximately 70% of fuel consumption is consumed by the vehicle's weight. Therefore, reducing vehicle weight significantly benefits fuel efficiency, handling reliability, and crash safety.

[0003] There are currently two main approaches to lightweighting automobiles: one is to replace the material, replacing steel with aluminum alloy. In this way, with the same material volume, the density of steel is 7.8g / cm3, while the density of aluminum is 2.7g / cm3. In this way, the weight can be reduced to 2 / 3 of the previous one. For example, Tesla introduced aluminum alloy die-casting, which on the one hand improves the strength of aluminum alloy and on the other hand reduces the weight of the whole vehicle. This is basically the future development direction. Another idea is to continue to use steel for the body, but reduce the amount of steel used by reducing the size, thereby reducing the weight. Among them, the most direct way to reduce weight is to optimize the joint structure and reduce the overhang to reduce the weight.

[0004] In automobile manufacturing, the most widely used welding method is resistance spot welding, with the number of resistance spot welds in a whole vehicle reaching 3,000 to 4,000. Resistance spot welding is widely used in the connection of automobile body-in-white due to its advantages of being economical, efficient, and easy to automate. However, different resistance welding guns and electrode caps of different geometric shapes are required for welding of body structures at different locations and thicknesses. The large number of equipment required and the large workload seriously restrict the welding efficiency of automobile bodies. In addition, resistance spot welding has high energy consumption and large overlap margins. Compared with resistance spot welding, laser welding can effectively reduce overhang, such as Figure 1A and Figure 1B At the same time, the resistance spot welding process requires clamping, which limits the design of the welded parts and fixtures. Laser welding, on the other hand, can be performed on one side, which provides greater design freedom and a more efficient and flexible welding process. It can reduce the weight of the vehicle body structure and meet new structural designs while also improving welding efficiency. This has a broader application prospect in the production and manufacturing of automobile bodies.

[0005] At present, domestic laser welding technology is mostly used in the production and manufacturing of passenger cars, while the manufacturing of commercial vehicles is still mainly based on resistance spot welding. Since the commercial vehicle body and the passenger vehicle body have significant differences in structural design and application, there are higher requirements for body strength and welding quality, so the R&D cycle and R&D cost are relatively high.

[0006] Laser spot welding, as a new spot welding method, has its own unique advantages compared to traditional resistance spot welding. Laser spot welding uses laser as a heat source, with advantages such as fast spot welding speed, short welding time, small weld spot size, large weld spot depth-to-width ratio, high welding precision and flexible process parameter adjustment. It can also perform non-contact single-sided spot welding. In addition, the laser has good accessibility, which can reduce the position and structural restrictions during spot welding, and has lower requirements for the spatial distribution of welding structures and fixtures. Resistance spot welding requires extremely high electrode pressure during welding, which can easily cause welding deformation, while laser welding has less deformation and more beautiful welds. Figure 2A and Figure 2B As shown. The adjustment range of parameters such as the distance between welding spots and the overlap amount is large; it does not require a large amount of auxiliary equipment and can quickly adapt to product changes to meet market demand. The high precision and high flexibility of laser spot welding enable it to replace traditional resistance spot welding and riveting processes in actual production, especially in the automotive industry. In addition, laser welding technology is very suitable for automated production. The fiber optic transmission technology developed in recent years has expanded the long-distance welding capability of lasers; and through the three-dimensional laser galvanometer scanning welding technology, the laser beam can continuously weld multiple welding spots within a certain circular scanning range, which can minimize the waste of non-productive time caused by repeated positioning of each welding spot, greatly improve welding efficiency, and reduce production cycle, such as Figure 3As shown in the figure, a single laser welding robot can even replace multiple resistance spot welding robots for simultaneous welding, improving production efficiency while reducing equipment procurement costs. This makes it an ideal automated spot welding technology for automotive body-in-white production and has been widely recognized in industrial manufacturing applications.

[0007] Compared with general laser spot welding technology, laser flying welding technology has the advantages of higher welding efficiency, more flexible weld form, lower production cost, etc. Through extremely short time rapid positioning, it can minimize the waste of non-productive time caused by repeated positioning of each welding point while welding at high speed, greatly improving welding efficiency and reducing production cycle. Figure 4 As shown, compared to traditional spot welding technology, laser on-the-fly welding allows for customized weld form and direction, increasing design and process flexibility. Furthermore, weld distribution can be customized according to process requirements, achieving flexible and variable weld position and form, perfectly optimizing weld stress and making it suitable for rapid multi-spot welding of various large workpieces and complex curved surfaces. Therefore, using laser on-the-fly welding technology instead of traditional spot welding has extremely broad application prospects in improving welding quality and efficiency.

[0008] Laser spot welding technology has the advantages of high energy density, high efficiency, good accessibility, small heat-affected zone, high precision and strong adaptability. It can quickly adapt to the changing needs of products and production lines. Compared with the existing resistance spot welding production lines, it does not require large-scale changes, and the joint quality evaluation can still use the existing resistance spot welding quality evaluation standards. It can replace resistance spot welding according to needs and has great application prospects in improving welding quality and welding efficiency.

[0009] Through the above analysis, the problems existing in the existing resistance spot welding process are:

[0010] (1) The resistance spot welding process has low welding efficiency. Currently, the resistance spot welding production of the door inner panel is mainly done by workers manually. In addition, due to the different material thickness combinations of different parts of the door inner panel, a total of four resistance welding clamps with different parameters are required for spot welding. In actual production, the welding clamps need to be replaced according to different welding parts, which greatly reduces the welding efficiency.

[0011] (2) The weld form is limited by the shape and size of the electrode. In addition, due to the size and shape of the resistance spot welding clamp, it is difficult to insert the welding clamp into certain edges and special-shaped locations of the door for welding, which limits the process flexibility.

[0012] (3) Resistance spot welding requires the use of welding clamps for welding, which limits the design of the workpiece to be welded and the fixture. Therefore, the extension of the welding joint structure must be increased to reserve a clamping position for the welding clamp, which increases the difficulty of designing the shape of the door inner panel stamping part and increases the weight of the door inner panel.

[0013] To sum up, how to replace the existing resistance spot welding process with laser flight welding technology for car door welding; how to use a robot laser flight welding system to study a new laser flight welding process suitable for car doors, improve welding production efficiency, reduce porosity, and increase weld tensile and shear strength, and replace the original resistance spot welding production process, has become the content to be explored in this invention.

[0014] In response to the problems of weld quality control and robot follow-up control scheme in the above-mentioned laser flight welding process of car doors, by analyzing the formation mechanism of the microstructure, the dynamic changes of the molten pool and the metallurgical problems of zinc-aluminum-magnesium welding during the welding process, the present invention designs a robot follow-up control scheme, develops methods of laser flight welding and robot follow-up control, and realizes automatic welding technology of laser flight welding system with coordinated control of the robot and 3D galvanometer laser welding head of the car door, replacing the original resistance spot welding production process, realizing the first application of laser flight welding technology on commercial vehicle doors, and at the same time laying a process foundation for the lightweight improvement design of the car door structure. Summary of the Invention

[0015] In view of this, the purpose of the present invention is to provide a method for laser flight welding of vehicle door inner panels that can solve or at least alleviate the above-mentioned problems, so as to realize the automatic welding technology of the laser flight welding system that coordinates the control of the vehicle door robot and the 3D galvanometer laser welding head, replace the original resistance spot welding production process, realize the application of laser flight welding technology on vehicle doors, and at the same time lay the process foundation for the lightweight improvement design of the vehicle door structure.

[0016] The technical solution provided by the present invention is: a method for laser flying welding of a vehicle door inner panel, comprising the following steps:

[0017] S1: providing workpieces for a vehicle door inner panel and clamping the workpieces by a fixture, wherein the workpieces include a first workpiece, a second workpiece, a third workpiece, a fourth workpiece, a fifth workpiece, a sixth workpiece, and a seventh workpiece;

[0018] S2: welding the first workpiece to the second workpiece by using a point spiral welding method;

[0019] S3: Welding the first workpiece to the third workpiece and the first workpiece to the fourth workpiece using a linear welding method;

[0020] S4: welding the first workpiece to the fifth workpiece, and welding the first workpiece to the sixth workpiece by using a point spiral weld, a linear weld, or a C-shaped weld;

[0021] S5: Welding the seventh workpiece to the second workpiece using a linear welding method;

[0022] S6: Weld the seventh workpiece and the fifth workpiece using a linear welding method.

[0023] In some embodiments, in step S2, the materials used for the first workpiece and the second workpiece are 1.25mmDC05 and 2.7mm HC420 respectively, and the welding position is welded from the inside to the outside. The welding process is performed in a stacked relative position with 2.7mm HC420 on top and 1.25mmDC05 on the bottom.

[0024] In some embodiments, in step S2, the process parameters of the spot spiral welding are:

[0025]

[0026] In some embodiments, in step S3, the material used for the first workpiece is 1.5mmDC01, and the materials used for the third and fourth workpieces are 1.25mmDC05 respectively. The welding position is performed from the outside to the inside, and the welding process is carried out in a stacked relative position of 1.25mmDC05 on top and 1.5mmDC01 on the bottom.

[0027] In some embodiments, in step S3, the straight-line solder joint is a wide straight-line solder joint, and the process parameters of the wide straight-line solder joint are:

[0028]

[0029] In some embodiments, in step S4, the material used for the first workpiece is 1.25mm DC01, and the materials used for the fifth and sixth workpieces are 1.25mm DC05 respectively. The welding position is welded from the inside to the outside, and the welding process is carried out in a stacked relative position of 1.25mm DC01 on top and 1.25mm DC05 on the bottom.

[0030] In some embodiments, in step S4, the process parameters of the spot spiral welding are:

[0031]

[0032] The process parameters of straight solder joints and C-type solder joints are:

[0033]

[0034] In some embodiments, in step S5, the material used for the seventh workpiece is 1.0mmDC01, the material used for the second workpiece is 2.7mmHC420, the welding position is from top to bottom, and the welding process is performed in a stacked relative position of 1.0mmDC01 on top and 2.7mmHC420 on the bottom.

[0035] In some embodiments, in step S5, the straight-line solder joint is a wide straight-line solder joint, and the process parameters of the wide straight-line solder joint are:

[0036]

[0037]

[0038] In some embodiments, in step S6, the materials used for the seventh workpiece and the fifth workpiece are 1.0mmDC01 and 1.25mmDC01 respectively, and the welding position is performed from top to bottom. The welding process is performed in a stacked relative position of 1.0mmDC01 on top and 1.25mmDC01 on the bottom.

[0039] In some embodiments, in step S6, the straight-line solder joint is a wide straight-line solder joint, and the process parameters of the wide straight-line solder joint are:

[0040]

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] 1. The laser flying welding method for the inner panel of a vehicle door provided by the present invention can realize the automatic welding technology of the laser flying welding system in which the robot of the vehicle door and the 3D galvanometer laser welding head are coordinated to control the vehicle door, replacing the original resistance spot welding production process, realizing the application of laser flying welding technology on the vehicle door, and at the same time laying the technological foundation for the lightweight improvement design of the vehicle door structure.

[0043] 2. Compared with the traditional resistance spot welding process, the laser flight welding method of the vehicle door inner panel provided by the present invention can replace four resistance spot welding robots to weld the vehicle door inner panel assembly within the same vehicle door inner panel assembly welding time, which greatly improves the welding efficiency, shortens the production cycle, and reduces the production cost; for a single welding position, the tensile shear strength of the laser flight welding weld is higher than that of the resistance spot welding weld, which improves the overall rigidity of the connection; unlike resistance spot welding, laser flight welding can achieve single-sided penetration of the weld, which provides greater flexibility for the weld position and welding structure design; and the laser flight welding technology can customize the weld form and weld direction, and with a variety of scanning trajectories, the weld form is more flexible, which increases the flexibility of design and process; at the same time, the weld distribution can be customized according to the process requirements, and the weld position and weld form are flexible and changeable, so that the weld force optimization can be perfectly achieved, which is suitable for rapid multi-point welding of various large workpieces and complex surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1A A schematic diagram of resistance spot welding overhang is shown.

[0045] Figure 1B A schematic diagram of laser welding overhang is shown.

[0046] Figure 2A The product obtained by resistance spot welding is shown.

[0047] Figure 2B The product obtained by laser welding is shown.

[0048] Figure 3 A schematic diagram of three-dimensional laser galvanometer scanning welding technology is shown.

[0049] Figure 4 A schematic diagram comparing the laser flying welding process steps with the general spot welding process steps is shown.

[0050] Figure 5 A schematic structural diagram of a door inner panel is shown.

[0051] Figure 6A A schematic diagram showing the first step of the spot welding process for a heavy truck door.

[0052] Figure 6B A schematic diagram showing the second step of the heavy truck door spot welding process.

[0053] Figure 7 A schematic diagram of the spiral scanning trajectory is shown.

[0054] Figure 8 A schematic diagram of a wide straight line scanning trajectory is shown.

[0055] Figure 9A The topography of the solder joint is shown.

[0056] Figure 9B The backside morphology of the solder joint is shown.

[0057] Figure 10 A linear solder joint power waveform is shown.

[0058] Figure 11 The surface morphology of the solder joint is shown.

[0059] Figure 12 The laser spot welding power waveform is shown.

[0060] Figure 13A The topography of the solder joint is shown.

[0061] Figure 13B The backside morphology of the solder joint is shown.

[0062] Figure 14 A linear solder joint power waveform is shown.

[0063] Figure 15AA wide straight line solder joint surface topography is shown.

[0064] Figure 15B The surface morphology of a C-type solder joint is shown.

[0065] Figure 16 A linear solder joint power waveform is shown.

[0066] Figure 17 A wide straight line solder joint surface topography is shown.

[0067] Figure 18 A linear solder joint power waveform is shown.

[0068] Figure 19 A wide straight line solder joint surface topography is shown.

[0069] Figure 20A A schematic diagram of the solder joint distribution of the three parts of the first process is shown.

[0070] Figure 20B A schematic diagram of solder joint distribution of the fourth part of the first process is shown.

[0071] Figure 21 Shows the overall and local welding point diagrams of the heavy truck door inner panel.

[0072] Figure 22 A comparison of the tensile shear strength of single welds of resistance spot welding and laser on-the-fly welding of different material combinations is shown.

[0073] Figure 23 Shows the failure diagram of the resistance spot welding specimen after the test.

[0074] Figure 24A Failure diagram of the laser on-the-fly welded specimen after the test showing interface separation.

[0075] Figure 24B The damage diagram of the laser on-the-fly welding specimen after the test is shown, showing the weld tearing out.

[0076] Figure 24C The failure diagram of the laser flight welding specimen after the test shows that some welds were torn out and the base material was torn.

[0077] Figure 24D The damage diagram of the laser on-the-fly welding specimen after the test shows the heat-affected zone and the tearing of the base material. DETAILED DESCRIPTION

[0078] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0079] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0080] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0081] In the present invention, terms such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "side", "bottom", etc. indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention, and do not specifically refer to any part or element in the present invention, and should not be understood as limiting the present invention.

[0082] In the present invention, terms such as "fixed connection," "connected," and "connection" should be interpreted broadly to mean a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediary. Relevant researchers or technicians in this field may determine the specific meanings of these terms in the present invention based on specific circumstances, and they should not be construed as limitations of the present invention.

[0083] One embodiment of the present invention is used to weld practical workpieces for heavy truck door inner panel assembly. The heavy truck door inner panel assembly contains a total of 7 workpieces, using 3 different materials with different thicknesses. The main chemical compositions of the three materials are shown in Table 1. Material DC01 has 3 different thicknesses. The door inner panel structure and workpiece assembly position diagram are shown in Figure 5 shown.

[0084] Table 1 Chemical composition of test materials (wt.%)

[0085]

[0086] The door inner panel assembly welding process includes two processes and seven welding positions. The first process includes welding workpiece ① with workpieces ②, ③, ④, ⑤, and ⑥. Figure 6A As shown; the second process includes welding workpiece ⑦ and workpieces ② and ⑤, as shown Figure 6B shown.

[0087] There are five different combinations of workpieces with different materials and plate thicknesses at different welding positions. Therefore, five different welding processes need to be designed for the welding of the door inner panel assembly. The combinations of different materials and plate thicknesses and the welding process groupings are shown in Table 2.

[0088] Table 2 Combinations of different materials and thicknesses for door inner panels

[0089]

[0090]

[0091] In the experiment, a robotic laser flight welding platform was used to conduct laser welding process tests. The welding equipment included: intelliWELD II 3D galvanometer laser welding head produced by Blackbird, Raycus RFL-C8000XZ fiber laser, Hanli HL-8000-QG2 / 2 water chiller, KUKA six-axis robot and Jaguar LS-15 air compressor. The 3D galvanometer laser welding head can be controlled by the RobotSyncUnit user software editing program for welding.

[0092] The door inner panel is fixed by a customized fixture, and the door inner panel and other workpieces are clamped by manual or pneumatic fixtures, and measured with a 0.2mm feeler gauge to ensure that the gap between the two workpieces is within 0.2mm to prevent the surface collapse of the weld due to excessive gap between the workpieces, which will affect the quality of the laser flight welding weld.

[0093] The galvanometer laser flying welding process is divided into three types: point spiral welding point, linear welding point and C-shaped welding point. The specific scanning path of the spiral line scanning trajectory of the point spiral welding point is as follows: Figure 7 As shown. Linear solder joints are divided into wide linear solder joints and narrow linear solder joints. In wide linear solder joints, the laser beam moves in a straight line while swinging horizontally along a circular trajectory. The laser beam swing diagram is shown in Figure 8 As shown. Narrow linear welds involve the laser beam moving in a straight line with no lateral oscillation. The C-shaped weld process is identical to the wide linear weld process, with only the laser beam's trajectory modified to a C-shape. For welding the inner panels of heavy truck doors, three welding methods are available: spiral welds, wide linear welds, and C-shaped welds.

[0094] 1.1.25mm DC05 and 2.7mm HC420 flying welding process

[0095] The materials used for the door inner panel ① and workpiece ② are 1.25mm DC05 and 2.7mm HC420, respectively. Due to the relative position of the welding robot and fixture, as well as the robot's range of motion, welding can only be performed from the inside out. Therefore, the welding process test was conducted with the 2.7mm HC420 on top and the 1.25mm DC05 on the bottom.

[0096] The welds of 1.25mm DC05 and 2.7mm HC420 laser on-the-fly welding are in the form of point spirals.

[0097] 1.1 point spiral type

[0098] The specific welding process parameters of spiral welding spots are shown in Table 3. The surface morphology of the welding spots is shown in Table 3. Figure 10 As shown in the figure, it can be seen that the surface of the solder joint is relatively flat with a small amount of spatter, the center of the solder joint is slightly concave, the back of the solder joint is welded through, and the surface quality of the solder joint is good.

[0099] Table 3 Process parameters of spiral welding points

[0100]

[0101]

[0102] 2.1.25mm DC05 and 1.5mm DC01 flying welding process

[0103] The materials used for the door inner panel ① and workpieces ③ and ④ are 1.5mmDC01 and 1.25mmDC05 respectively. Here, workpieces ③ and ④ need to be assembled in the groove on the upper edge of the door inner panel. Due to the position limitation of the fixture, the welding position here needs to be welded from the outside to the inside. Therefore, the welding process test is carried out in a relative position of stacking 1.25mmDC05 on top and 1.5mmDC01 on the bottom.

[0104] The 1.25mm DC05 and 1.5mm DC01 laser on-the-fly welding joints are wide straight lines.

[0105] 2.1 Wide straight line

[0106] The specific welding process parameters of wide straight solder joints are shown in Table 4 and Figure 11 The surface morphology of the solder joint is shown in Figure 12 As shown in the figure, it can be seen that the linear surface has a circular scanning track rotation morphology, the solder joint surface is relatively flat, the back of the solder joint is fully welded, and the solder joint surface quality is good.

[0107] Table 4 Process parameters of wide straight solder joints

[0108]

[0109] 3.1.25mm DC05 and 1.25mm DC01 flying welding process

[0110] The materials used for the door inner panel ① and workpieces ⑤ and ⑥ are 1.25mm DC01 and 1.25mm DC05, respectively. Due to the relative position of the welding robot and the fixture, as well as the robot's range of motion, welding can only be performed from the inside out. Therefore, the welding process test was conducted with the 1.25mm DC01 on top and the 1.25mm DC05 on the bottom stacked.

[0111] The laser flying welding spots of 1.25mm DC01 and 1.25mm DC05 are in three forms: point spiral type, wide straight type and C type.

[0112] 3.1-point spiral

[0113] The specific welding process parameters of spiral welding spots are shown in Table 5 and Figure 12 The surface morphology of the solder joint is shown in Figure 13A and Figure 13B As shown in the figure, it can be seen that there is a spiral track rotation morphology on the surface of the solder joint, the solder joint surface is relatively flat, the back of the solder joint is welded through, and the solder joint surface quality is good.

[0114] Table 5 Process parameters of spiral solder joints

[0115]

[0116] 3.2 Wide Straight Type and C Type

[0117] The specific welding process parameters of wide straight solder joints are shown in Table 6 and Figure 14 The surface morphology of the solder joint is shown in Figure 15A and Figure 15B As shown in the figure, it can be seen that the surfaces of the linear and C-shaped solder joints have circular scanning track rotation morphology, the solder joint surface is relatively flat, the back of the solder joint is welded through, and the solder joint surface quality is good.

[0118] Table 6 Process parameters of wide straight and C-shaped solder joints

[0119]

[0120] 4.1.0mm DC01 and 2.7mm HC420 on-the-fly welding process

[0121] The materials used for workpiece ⑦ and workpiece ② are 1.0mmDC01 and 2.7mmHC420 respectively. At the same time, due to the relative position of the welding robot and the fixture, welding can only be performed from top to bottom. Therefore, the welding process test is carried out in a stacked relative position of 1.0mmDC01 on top and 2.7mmHC420 on the bottom.

[0122] The welds of 1.0mmDC01 and 2.7mmHC420 laser flying welding are wide straight lines.

[0123] 4.1 Wide Straight Line

[0124] The specific welding process parameters of wide straight solder joints are shown in Table 7 and Figure 16 The surface morphology of the solder joint is shown in Figure 17 As shown in the figure, it can be seen that the linear surface has a circular scanning track rotation morphology, the solder joint surface is relatively flat, the back of the solder joint is fully welded, and the solder joint surface quality is good.

[0125] Table 7 Process parameters of wide straight solder joints

[0126]

[0127]

[0128] 5.1.0mm DC01 and 1.25mm DC01 flying welding process

[0129] The materials used for workpiece ⑦ and workpiece ⑤ are 1.0mmDC01 and 1.25mmDC01 respectively. At the same time, due to the relative position of the welding robot and the fixture, welding here can only be performed from top to bottom. Therefore, the welding process test is carried out in a stacked relative position of 1.0mmDC01 on top and 1.25mmDC01 on the bottom.

[0130] The laser flying welding spots of 1.0mmDC01 and 1.25mmDC01 are wide straight lines.

[0131] 5.1 wide straight line

[0132] The specific welding process parameters of wide straight solder joints are shown in Table 8 and Figure 18 The surface morphology of the solder joint is shown in Figure 19 As shown in the figure, it can be seen that the linear surface has a circular scanning track rotation morphology, the solder joint surface is relatively flat, the back of the solder joint is fully welded, and the solder joint surface quality is good.

[0133] Table 8 Process parameters of wide straight solder joints

[0134]

[0135] Robot Programming

[0136] Robotic on-the-fly welding first requires recording the position of each weld point. This step requires robot teaching for each weld point, allowing the robot to reach the corresponding position and maintain defocus. Next, the robot trajectory program is programmed. This step allows the software to record the robot trajectory. When programming, ensure that the robot has an initial acceleration phase, a mid-welding phase, and a deceleration phase, as welding is only possible at a constant speed. This prevents interference. Once the trajectory is complete, import it into the Bubo software. Finally, the robot trajectory is designed to organize the weld points based on the time periods during which welding is possible and the time periods during which welding is not.

[0137] Distribution of welding points on the inner door panel

[0138] Light truck door welding is mainly divided into two processes and four parts. The first process includes four parts and is the process with the most welds. The purpose of this division is to allow the robot to maintain a constant speed during the welding process, to facilitate program modification during adjustment testing, and to prevent a program from containing too many welds, which may cause collisions during the welding test. Figure 20A and Figure 20B shown.

[0139] Processing results

[0140] The actual effect after the door inner panel welding is completed is as follows Figure 21 shown.

[0141] According to the technical requirements of the project, the strength of laser flight welding welds should not be lower than that of resistance spot welding welds. Therefore, the same welding process parameters as the door inner panel are used to weld on the test plate and perform tensile shear tests. In the test, resistance spot welding and laser flight welding are used to perform single-weld point tensile shear test specimens on 5 different material combinations, and the differences in weld point strength between resistance spot welding welds and laser flight welding welds in the single-weld point case are compared and analyzed.

[0142] The tensile and shear performance tests of the specimens were conducted on an MTSMTS Criterion C45 universal testing machine. The resistance spot welding process parameters are shown in Table 9-1. The laser on-the-fly welding process parameters refer to the above content.

[0143] Table 9-1 Resistance spot welding process parameters

[0144]

[0145] In the tensile shear test, the single weld tensile shear specimens were torn along the heat affected zone around the weld and the base material. Figure 22 It can be seen that the strength of laser flying welding welds is higher than that of resistance spot welding welds under different material combinations, and the strength of linear welds is higher than that of spiral welds. This meets the technical requirements of the project.

[0146] Table 9-2 Comparison of tensile shear strength of single weld spot between resistance spot welding and laser flying welding of different material combinations

[0147]

[0148]

[0149] Analysis of fracture behavior of laser on-the-fly welding joints

[0150] The same welding process parameters as the door inner panel were used to weld the test plate and conduct tensile shear test. In the tensile shear test, the resistance spot welding tensile specimens all suffered mixed failure forms of partial weld tearing and parent material tearing. The specimen failure diagram after the test is shown in the figure below. Figure 23 As shown. In the laser flight welding tensile specimen, when the flight welding spot is not fully penetrated and the molten core is small, the damage form of the weld spot is interface separation, as shown in Figure 24A As shown in the figure; when the flying welding spot is fully penetrated and the nugget is small, the damage form of the weld spot changes to the weld spot tearing form, as shown in the figure. Figure 24B As shown in the figure, when the size of the weld nugget in the flying welding spot continues to increase, the damage form of the weld spot changes to a mixed damage form of partial weld spot tearing and base material tearing, as shown in the figure. Figure 24C As shown in the figure, when the size of the weld nugget in the flying welding spot continues to increase and exceeds a certain critical size, the damage form of the weld spot changes to the heat-affected zone and the base material tearing, as shown in the figure. Figure 24D shown.

[0151] When the laser flight welding spot is completely penetrated and the weld core is large, the damage form of the weld is a mixed damage form of partial weld tearing and base material tearing. According to the analysis of the tensile shear test results, the strength of the laser flight welding spot is equivalent to or slightly higher than that of the resistance spot welding spot. When the laser flight welding spot exceeds a certain critical size, the damage form of the weld is tearing of the heat affected zone and the base material. According to the analysis of the tensile shear test results, the strength of the laser flight welding spot will be greater than that of the resistance spot welding spot.

[0152] In summary, the present invention has successfully developed a laser flying welding process for vehicle doors to replace the resistance spot welding process through research on the laser flying welding process and follow-up control scheme for heavy truck door inner panels, and successfully realized the first application of laser flying welding technology on domestic commercial vehicle doors. At the same time, according to the actual process test data in the laboratory, compared with the traditional resistance spot welding process, within the same door inner panel assembly welding time, one laser flight welding robot can replace four resistance spot welding robots to weld the door inner panel assembly, greatly improving the welding efficiency, shortening the production cycle, and reducing production costs; for a single welding position, the tensile shear strength of the laser flight welding weld is higher than that of the resistance spot welding weld, which improves the overall rigidity of the connection; unlike resistance spot welding, laser flight welding can achieve single-sided penetration of the weld, providing greater flexibility for the weld position and welding structure design; and laser flight welding technology can customize the weld form and weld direction, and with a variety of scanning trajectories, the weld form is more flexible, increasing the flexibility of design and process; at the same time, the weld distribution can be customized according to process requirements, and the weld position and weld form are flexible and changeable, so that the weld force optimization can be perfectly achieved, which is suitable for rapid multi-point welding of various large workpieces and complex surfaces. This invention not only successfully realized the first application of laser flying welding technology on domestic commercial vehicle doors, providing a solid technical and theoretical basis for laser flying welding technology of heavy vehicle bodies, but also laid a technological foundation for the lightweight improvement design of vehicle body structures. It has important theoretical significance and application value for the development of the automotive industry.

[0153] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for laser flying welding of a door inner panel, characterized in that: The following steps are involved: S1: providing workpieces for a vehicle door inner panel and clamping the workpieces by a fixture, the workpieces including a first workpiece, a second workpiece, a third workpiece, a fourth workpiece, a fifth workpiece, a sixth workpiece, and a seventh workpiece; S2: welding the first workpiece to the second workpiece by using a point spiral welding method; S3: Welding the first workpiece to the third workpiece and the first workpiece to the fourth workpiece using a linear welding method; S4: welding the first workpiece to the fifth workpiece, and welding the first workpiece to the sixth workpiece by using a point spiral weld, a linear weld, or a C-shaped weld; S5: Welding the seventh workpiece to the second workpiece using a linear welding method; S6: Welding the seventh workpiece to the fifth workpiece using a linear welding method; In step S2, the process parameters of the point spiral welding are: ； In step S4, the process parameters of the point spiral welding are: ； The process parameters of straight solder joints and C-type solder joints are: 。 2. The method for laser on-the-fly welding of a vehicle door inner panel according to claim 1, characterized in that: In step S2, the materials used for the first workpiece and the second workpiece are 1.25mm DC05 and 2.7mm HC420 respectively, and the welding position is welded from the inside to the outside. The welding process adopts the relative position of stacking 2.7mm HC420 on top and 1.25mm DC05 on the bottom.

3. The method for laser on-the-fly welding of a vehicle door inner panel according to claim 1, characterized in that: In step S3, the material used for the first workpiece is 1.5mmDC01, and the materials used for the third and fourth workpieces are 1.25mmDC05 respectively. The welding position is welded from the outside to the inside, and the welding process adopts the relative position of stacking 1.25mmDC05 on the top and 1.5mmDC01 on the bottom. In step S3, the linear weld is a wide linear weld, and the process parameters of the wide linear weld are: 。 4. The method for laser on-the-fly welding of a vehicle door inner panel according to claim 1, characterized in that: In step S4, the material used for the first workpiece is 1.25mm DC01, and the materials used for the fifth and sixth workpieces are 1.25mm DC05 respectively. The welding position is welded from the inside to the outside, and the welding process is carried out in a stacked relative position of 1.25mm DC01 on top and 1.25mm DC05 on the bottom.

5. The method for laser on-the-fly welding of a vehicle door inner panel according to claim 1, characterized in that: In step S5, the material used for the seventh workpiece is 1.0mmDC01, and the material used for the second workpiece is 2.7mmHC420. The welding position is from top to bottom, and the welding process adopts the relative position of stacking 1.0mmDC01 on top and 2.7mmHC420 on the bottom.

6. The method for laser on-the-fly welding of a vehicle door inner panel according to claim 5, characterized in that: In step S5, the straight-line solder joint is a wide straight-line solder joint, and the process parameters of the wide straight-line solder joint are: 。 7. The method for laser on-the-fly welding of a vehicle door inner panel according to claim 1, characterized in that: In step S6, the materials used for the seventh workpiece and the fifth workpiece are 1.0mmDC01 and 1.25mmDC01 respectively, and the welding position is welded from top to bottom. The welding process adopts the relative position of stacking 1.0mmDC01 on top and 1.25mmDC01 on the bottom.

8. The method for laser on-the-fly welding of a vehicle door inner panel according to claim 7, characterized in that: In step S6, the straight-line solder joint is a wide straight-line solder joint, and the process parameters of the wide straight-line solder joint are: 。

Images