Laser flight welding method for vehicle door inner plate

Abstract

The invention relates to the technical field of welding, and provides a vehicle door inner plate laser flight welding method which comprises the following steps that S1, workpieces for a vehicle door inner plate are provided and clamped through a tool clamp, and the workpieces comprise a first workpiece, a second workpiece, a third male workpiece, a fourth workpiece, a fifth workpiece, a sixth workpiece and a seventh workpiece; s2, the first workpiece and the second workpiece are welded in a spot spiral welding spot mode; s3, the first workpiece and the third workpiece are welded in a linear welding spot mode, and the first workpiece and the fourth workpiece are welded; s4, welding the first workpiece and the fifth workpiece and welding the first workpiece and the sixth workpiece in a manner of welding a spiral welding spot, a linear welding spot or a C-shaped welding spot; s5, the seventh workpiece and the second workpiece are welded in a linear welding spot mode; and S6, the seventh workpiece and the fifth workpiece are welded in a linear welding spot mode.

Description

Technical Field

[0001] The 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 the implementation and promotion of economic development and the "dual carbon" policy, the automobile industry, as the leading industry in the development of the world economy, has also entered a stage of rapid development and change. "Energy saving, environmental protection, and safety" have become the mainstream trend of the development of the automobile industry. Lightweighting of automobiles is an important measure to achieve the "new four modernizations" of automobiles. It is one of the important measures to reduce greenhouse gas emissions, improve fuel efficiency, and reduce automobile operating costs. It is also an important technology to achieve intelligent emission reduction of automobiles, which can effectively promote the sustainable development of the automobile industry. With the trend of lightweighting of automobiles, how to achieve lightweighting of automobiles has become an important issue. The key to the fuel consumption of automobiles lies in the displacement of the engine and the total weight of the automobile. Under the condition of keeping the overall structure, quality and overall performance of the automobile unchanged, reducing the net weight of the automobile itself can increase power, reduce noise, improve maneuverability and stability, and improve safety factor, while increasing speed, reducing fuel consumption, and reducing exhaust emissions. Scientific research data show that if the net weight of the entire vehicle is reduced by 10%, the high efficiency of gasoline and diesel can be increased by 6%-8%; if the rolling friction resistance is reduced by 10%, the high efficiency of gasoline and diesel can be increased by 3%; if the transmission efficiency of trailer axles, gearboxes and other equipment is increased by 10%, the high efficiency of gasoline and diesel can be increased by 7%. The car body accounts for about 30% of the total weight of the car. When fully loaded, about 70% of the fuel consumption is used for the weight of the car body. Therefore, the lightweight of the car is of great benefit to the fuel efficiency, vehicle handling reliability and collision safety of the whole vehicle.

[0003] At present, there are two main ideas for the commonly used solutions to lightweight automobiles: one is to replace the material, replacing steel with aluminum alloy. In this way, under the same material volume, the density of steel is 7.8g / cm3, while the density of aluminum is 2.7g / cm3, so the weight can be reduced to 2 / 3 of the previous one. For example, Tesla launched aluminum alloy die-casting aluminum, which on the one hand improves the strength of aluminum alloy and on the other hand can reduce 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, and the number of resistance spot welds in a whole vehicle can reach 3,000 to 4,000. Resistance spot welding is widely used in the connection of automobile body-in-white due to its advantages such as economy, high efficiency, and easy automation. However, different resistance welding guns and electrode caps of different geometric shapes are required for welding of body structures in different positions 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 the overhang, such as Figure 1A and Figure 1B At the same time, the resistance spot welding process requires clamping construction, which limits the design of the welded parts and fixtures, while laser welding can be constructed on one side, with higher design freedom and more efficient and flexible welding process. It can reduce the weight of the body structure and meet new structural designs while also improving welding efficiency, and 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, and the manufacturing of commercial vehicles is still mainly based on resistance spot welding. Since there are significant differences in structural design and application between commercial vehicle bodies and passenger vehicle bodies, there are higher requirements for body strength and welding quality, so the R&D cycle and R&D cost are relatively high.

[0006] As a new spot welding method, laser spot welding has its own unique advantages compared with 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 spot size, large spot depth-to-width ratio, high welding accuracy and flexible process parameter adjustment, and can 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 is easy to cause welding deformation, while laser welding has less deformation and more beautiful welds, such as 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 capabilities of lasers; and through 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 cycles. Figure 3As shown. It is even possible to use one laser welding robot to replace multiple resistance spot welding robots for welding at the same time, which improves production efficiency and reduces equipment procurement costs. Therefore, it is an ideal automated production spot welding technology for automobile body-in-white, and has been widely recognized in the field of 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 with the spot welding technology of traditional processes, laser flying welding can customize the weld form and welding direction, increase the flexibility of design and process, and customize the weld distribution according to process requirements, realize the flexibility and diversity of weld position and weld form, and perfectly realize the optimization of weld force, which is suitable for fast multi-point welding of various large workpieces and complex curved surfaces. Therefore, the use of laser flying welding technology instead of traditional spot welding has extremely broad application prospects in improving welding quality and welding 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. At present, the resistance spot welding production of door inner panels is mainly done by workers manually. In addition, due to the different material thickness combinations of different parts of the door inner panels, a total of 4 resistance welding tongs with different parameters are required for spot welding. In actual production, the welding tongs 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 tongs, it is difficult to insert the tongs 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 tongs for welding, which limits the design of the workpiece to be welded and the fixture. Therefore, the overhang of the welding joint structure must be increased to reserve a clamping position for the welding tongs, which increases the difficulty of designing the shape of the door inner panel stamping and increases the weight of the door inner panel.

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

[0014] In view of the problems of weld quality control and robot follow-up control scheme in the above laser flight welding process of car doors, by analyzing the forming mechanism of microstructure, dynamic changes of molten pool and metallurgical problems of zinc-aluminum-magnesium welding during welding, 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 robot and 3D galvanometer laser welding head of car doors, replacing the original resistance spot welding production process, realizing the first application of laser flight welding technology on commercial vehicle doors, and laying a technological foundation for the lightweight improvement design of 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 inner door 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 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 a technological foundation for the lightweight improvement design of the door structure.

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

[0017] S1: providing workpieces for a 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;

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

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

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

[0023] In some embodiments, in step S2, the materials used for the first workpiece and the second workpiece are 1.25mm DC05 and 2.7mm HC420 respectively, the welding position is welded from the inside to the outside, and the welding process is performed in a relative position of stacking 2.7mm HC420 on top and 1.25mm DC05 on the bottom.

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

[0025]

[0026] In some embodiments, in step S3, the material used for the first workpiece is 1.5mmDC01, the materials used for the third workpiece and the fourth workpiece are 1.25mmDC05 respectively, the welding position is welded 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, the materials used for the fifth workpiece and the sixth workpiece are respectively 1.25mm DC05, 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 point are:

[0031]

[0032] The process parameters of linear 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 welded from top to bottom, and the welding process is performed in a relative position of stacking 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 welded from top to bottom. The welding process is carried out 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 cooperatively controlled, replace the original resistance spot welding production process, realize the application of laser flying welding technology on the vehicle door, and at the same time lay a technological foundation for the lightweight improvement design of the vehicle door structure.

[0043] 2. Compared with the traditional resistance spot welding process, in the laser flight welding method of the door inner panel provided by the present invention, 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, 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-spot 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 step and the general spot welding process step is shown.

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

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

[0052] Figure 6B A schematic diagram showing the second process 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] Fig. 9A The topography of the solder joint is shown.

[0056] Fig. 9B The back side morphology of the solder joint is shown.

[0057] Fig.10 A straight-line solder joint power waveform is shown.

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

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

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

[0061] Fig. 13B The back side morphology of the solder joint is shown.

[0062] Fig.14 A straight-line solder joint power waveform is shown.

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

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

[0065] Fig.16 A straight-line solder joint power waveform is shown.

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

[0067] Fig.18 A straight-line solder joint power waveform is shown.

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

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

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

[0071] Fig.21 The overall and local welding point diagram of the heavy truck door inner panel is shown.

[0072] Fig. 22 A comparison chart of the tensile shear strength of single welds of resistance spot welding and laser flying welding of different material combinations is shown.

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

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

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

[0076] Fig.24C The failure diagram of the laser flying welding specimen after the test is shown, with some welds torn out and the parent material torn.

[0077] Fig.24D The failure diagram of the laser flying welding specimen after the test shows the heat affected zone and the tearing of the base material. DETAILED DESCRIPTION

[0078] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0079] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those 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 exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates 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. indicate directions or positional relationships 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 limitations on the present invention.

[0082] In the present invention, terms such as "fixed connection", "connected", "connection", etc. should be understood in a broad sense, indicating that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. Relevant scientific research or technical personnel in this field can determine the specific meanings of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0083] One embodiment of the present invention is used to weld a heavy truck door inner panel assembly. The heavy truck door inner panel assembly includes 7 workpieces, using 3 different materials with different thicknesses. The main chemical compositions of the three materials are shown in Table 1, where material DC01 has 3 different thicknesses. The door inner panel structure and workpiece assembly position diagram are shown in Table 1. 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 of workpiece ① with workpiece ②, ③, ④, ⑤, ⑥. Fig. 6A As shown; the second process includes welding of workpiece ⑦ and workpieces ② and ⑤, as shown Figure 6B shown.

[0087] There are 5 different combinations of workpieces with different materials and different plate thicknesses at different welding positions. Therefore, 5 different welding processes need to be designed for the welding of the door inner panel assembly. The combination of different materials and plate thicknesses and the welding process grouping 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 robot laser flying welding platform was used to carry out 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 cooler, 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 inner door panel is fixed by a customized fixture, and the inner door 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 affects 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-type welding point. The specific scanning path of the spiral line scanning trajectory of the point spiral welding point is as follows: Figure 7 The linear solder joints are divided into wide linear solder joints and narrow linear solder joints. The wide linear solder joints are when the laser beam moves forward in a straight line and swings horizontally along a circular trajectory. The schematic diagram of the laser beam swing is shown in Figure 8 As shown. Narrow straight welds are welds where the laser beam moves only in a straight line without lateral swing. The C-type weld process is the same as the wide straight weld, except that the laser beam travels in a C-type trajectory. For the welding of the inner panel of a heavy truck door, three types of welding are selected: spiral welds, wide straight welds, and C-type welds.

[0094] 1.1.25mmDC05 and 2.7mmHC420 flying welding process

[0095] The materials used for the door inner panel ① and the workpiece ② are 1.25mm DC05 and 2.7mm HC420 respectively. At the same time, due to the relative position of the welding robot and the fixture and the limitation of the robot's motion range, the welding position here can only be welded from the inside to the outside. Therefore, the welding process test is carried out in a relative position of stacking 2.7mm HC420 on top and 1.25mm DC05 on the bottom.

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

[0097] 1.1 point spiral type

[0098] The specific welding process parameters of the spiral weld are shown in Table 3. The surface morphology of the weld is shown in Table 3. Fig.10 As shown in the figure, it can be seen that the surface of the solder joint is relatively flat and there is 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, and 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 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 Fig.11 The surface morphology of the solder joint is shown in Fig.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 welded through, and the solder joint surface quality is good.

[0107] Table 4 Wide straight solder joint process parameters

[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. At the same time, due to the relative position of the welding robot and the fixture and the limitation of the robot's motion range, the welding position here can only be welded from the inside to the outside. Therefore, the welding process test is carried out in a relative position of stacking 1.25mm DC01 on top and 1.25mm DC05 on the bottom.

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

[0112] 3.1 point spiral type

[0113] The specific welding process parameters of spiral welding spots are shown in Table 5 and Fig.12 The surface morphology of the solder joint is shown in Fig.13A and Fig. 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 surface of the solder joint is relatively flat, the back of the solder joint is welded through, and the surface quality of the solder joint is good.

[0114] Table 5 Spiral solder joint process parameters

[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 Fig.14 The surface morphology of the solder joint is shown in Fig.15A and Fig. 15B As shown in the figure, it can be seen that the surface of the linear and C-shaped solder joints has a 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 line and C-type 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, the welding position here can only be welded 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 1.0mmDC01 and 2.7mmHC420 laser flying welding joints 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 Fig.16 The surface morphology of the solder joint is shown in Fig.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 welded through, and the solder joint surface quality is good.

[0125] Table 7 Wide straight solder joint process parameters

[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, the welding position here can only be welded 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 Fig.18 The surface morphology of the solder joint is shown in Fig.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 welded through, and the solder joint surface quality is good.

[0133] Table 8 Wide straight solder joint process parameters

[0134]

[0135] Robot Programming

[0136] Robot flight welding first needs to record the position of each welding point. This step requires robot teaching for each welding point, so that the robot can reach the corresponding position and ensure the defocus. Secondly, it is necessary to teach and write the robot trajectory program. This step is to let the software record the robot trajectory. When writing, pay attention to let the robot have an initial acceleration section, a middle welding section, because welding can only be done at a constant speed, and a deceleration section to prevent interference. After writing, import the trajectory into the Bubo software. Finally, the robot trajectory can be integrated with the welding time period and the welding time period to arrange the welding points.

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

[0138] The welding points of light truck doors are mainly divided into two processes and four parts. The first process includes four parts and is the process with the most welding points. The purpose of this division is to allow the robot to maintain a uniform speed during the welding process, to facilitate program modification during adjustment and testing, and to prevent a program from containing too many welding points, resulting in collisions during the welding test. The four parts are grouped as follows: Fig. 20A and Fig. 20B shown.

[0139] Processing results

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

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

[0142] The tensile shear performance tests of the samples were all carried out on the MTSMTS Criterion C45 universal testing machine. The resistance spot welding process parameters are shown in Table 9-1. The laser flying 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 are torn along the heat affected zone around the weld and the parent material. Fig. 22 It can be seen that the strength of laser flying welding spots under different material combinations is higher than that of resistance spot welding spots, and the strength of linear welding spots is higher than that of spiral welding spots. 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 on the test plate and conduct tensile shear test. In the tensile shear test, the resistance spot welding tensile specimens were all in a mixed failure form of partial weld tearing and parent material tearing. The specimen failure diagram after the test is as follows Fig.23 As shown. In the laser flying welding tensile specimen, when the flying welding spot is not completely penetrated and the molten core is small, the damage form of the weld spot is the interface separation form, such as Fig.24A As shown in the figure; when the flying welding spot is fully penetrated and the molten core is small, the damage form of the weld spot changes to the weld spot tearing form, such as Fig. 24B As shown in the figure, when the size of the weld nugget of the flying welding spot continues to increase, the damage form of the weld spot changes to a mixed damage form of partial weld tearing and parent material tearing, such as Fig.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 tearing of the heat-affected zone and the parent material, such as Fig.24D shown.

[0151] When the laser flight welding spot is completely penetrated and the molten 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 the resistance spot welding spot strength; and 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 the strength 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 the research on the laser flying welding process and follow-up control scheme for the inner panel of heavy truck doors, 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, 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 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 realized, which is suitable for rapid multi-spot 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 body structures. It has important theoretical significance and application value for the development of the automobile industry.

[0153] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope 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 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 and the second workpiece by using a point spiral welding method; S3: welding the first workpiece to the third workpiece and welding the first workpiece to the fourth workpiece by using a linear welding point 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 and the second workpiece by using a linear welding point method; S6: Welding the seventh workpiece and the fifth workpiece by using a linear welding point method.

2. The method for laser flying welding of a 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 is performed in a relative position of stacking 2.7mm HC420 on top and 1.25mm DC05 on the bottom.

3. The method for laser flying welding of a door inner panel according to claim 2, characterized in that: In step S2, the process parameters of the spot spiral welding point are:

4. The method for laser flying welding of a 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 is performed in a 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:

5. The method for laser on-the-fly welding of a 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 relative position of stacking 1.25mm DC01 on top and 1.25mm DC05 on the bottom.

6. The method for laser flying welding of a door inner panel according to claim 5, characterized in that: In step S4, the process parameters of the spot spiral welding point are: The process parameters of linear solder joints and C-type solder joints are:

7. The method for laser on-the-fly welding of a door inner panel according to claim 1, characterized in that: 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 welded 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.

8. The method for laser flying welding of a door inner panel according to claim 7, 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:

9. The method for laser on-the-fly welding of a 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.

10. The method for laser on-the-fly welding of a door inner panel according to claim 9, 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:

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