Laser welding method for curved thin plates

Abstract

The present application discloses a method for laser welding curved thin plates, comprising positioning and docking a first welding section and a second welding section, wherein the connecting surfaces of the first welding section and the second welding section are both identically curved, the curved surfaces comprising a plurality of first and second arc surfaces connected end to end, and a welding gun disposed on one side of the connecting surfaces; and simulating a welding path based on the first and second arc surfaces, and controlling the welding gun to laser weld the connecting surfaces of the first and second welding sections along the welding path. The present application achieves the setting of the welding path by employing an automated welding machine, and can maintain slow welding at a low speed for a long time, thereby ensuring that the first and second welding sections of the "plum blossom" cross-section structure made of forged rods of high-temperature resistant stainless steel are welded to each other, saving labor and enabling mass production of products.

Description

Technical Field

[0001] The present application relates to the field of nuclear power equipment manufacturing technology, and in particular to a laser welding method for curved thin plates. Background Art

[0002] Take a plum blossom-shaped structural component in the main equipment of the nuclear island as an example. Figure 1 As shown, Figure 1 Schematic diagram of the structure of an existing plum blossom-shaped structural member, which is composed of an upper grid plate 910 and a lower grid plate 920 welded by a laser 930. The upper grid plate 910 and the lower grid plate 920 are both processed from forged rods, and six convex and concave surfaces are formed after processing. The cross-sectional shape of the upper grid plate 910 and the lower grid plate 920 is similar to a "plum blossom".

[0003] However, currently, the welding of plum blossom-shaped curved products mainly uses tungsten inert gas welding (TIG welding). During welding, it is necessary to use a tool to rotate the product while manually tracking the weld seam along the curved surface trajectory with the welding torch. The welding torch must always be equidistant from the product at any position to finally complete the welding of the plum blossom-shaped structural component. However, when using TIG welding, it is difficult for the welder to distinguish the position and shape of the weld seam through the mask, making it more prone to defects such as lack of fusion, porosity, and tungsten inclusions, requiring a high level of welder skill. Furthermore, because plum blossom-shaped structural components must be made of forged rods made of high-temperature resistant stainless steel, the welding speed is slow and the welding efficiency is low, making rapid mass production of the product impossible. Summary of the Invention

[0004] The purpose of this application is to provide a laser welding method for curved thin plates to solve the technical problem that when the upper and lower grid plates of the "plum blossom" cross-section structure made of forged rods of high-temperature resistant stainless steel are welded to each other, the welding speed is slow, the welding efficiency is low, and the product cannot be quickly mass-produced.

[0005] To achieve the above objectives, one embodiment of the present application provides a laser welding method for a curved thin plate, comprising the following steps:

[0006] Positioning and docking the first welding section and the second welding section, wherein the connecting surfaces of the first welding section and the second welding section are both identically curved, and the curved surfaces include a plurality of first arc surfaces and second arc surfaces connected end to end, and a welding gun is provided on one side of the connecting surfaces for welding the connecting surfaces of the first welding section and the second welding section; and

[0007] A welding path is simulated according to the first arc surface and the second arc surface, and the welding gun is controlled to perform laser welding on the interface between the first welding section and the second welding section along the welding path.

[0008] In the laser welding method for a curved thin plate described in one embodiment of the present application, the first arc surface is a convex surface, the second arc surface is a concave surface, and the first arc surface and the second arc surface are arranged at an interval.

[0009] In the laser welding method for curved thin plates described in one embodiment of the present application, in the welding path setting step and the welding step, laser welding path simulation is completed in the motion simulation software RobotStudio to form the welding path; three-dimensional modeling is performed in the motion simulation software RobotStudio to complete the modeling of the first welding segment and the second welding segment, the welding gun is imported into the motion simulation software RobotStudio and the relative speed and distance between the welding gun and the first welding segment and the second welding segment are adjusted to remain unchanged; the rotation speed of the welding gun and the rotation angular velocity of the first welding segment and the second welding segment are set so that the relative speed between the welding gun and the first welding segment and the second welding segment remains unchanged during the welding process; the welding gun is set perpendicular to the outer surfaces of the first welding segment and the second welding segment and the distance remains unchanged.

[0010] In an embodiment of the present application, a laser welding method for a curved thin plate is described, wherein, in simulating a welding path based on a first arc surface and a second arc surface, the method includes the following steps:

[0011] The welding gun is arranged to move relative to the interface, the distance between the welding gun and the outer edge of the interface between the first welding section and the second welding section is maintained constant, and the movement speed, rotation speed, and rotation angle of the welding gun, the first welding section, and the second welding section are adjusted so that the relative speed of the welding gun along the outer edge of the interface remains constant;

[0012] a step of generating a welding path and motion parameters, wherein, according to the step of setting the movement of the welding gun relative to the interface, the movement path of the welding gun along the interface is used as the welding path, and the movement speed, rotation speed, and rotation angle of the welding gun, the first welding section, and the second welding section are used as motion parameters; and

[0013] The welding step is to place the welding gun at the position corresponding to the interface between the first welding section and the second welding section in an inert protective gas environment, turn on the welding gun, and use laser positioning welding or laser deep penetration welding to weld the interface between the first welding section and the second welding section to form a weld.

[0014] In the laser welding method for curved thin plates described in one embodiment of the present application, in the step of setting the movement of the welding gun relative to the connecting surface, a plane coordinate system is established on the plane where the connecting surface is located with the center point of the connecting surface as the origin, and the plane coordinate system has a horizontal axis and a vertical axis, and the horizontal axis and the vertical axis are both located on the symmetry axis of the connecting surface; an intersection point of the edge of the connecting surface and the horizontal axis or the vertical axis is set as the arc starting point, and the welding gun forms a first arc surface or a second arc surface from the arc starting point in a clockwise or counterclockwise direction to reach the welding end point; the welding gun uses the welding end point as the arc starting point of the next second arc surface or the first arc surface and circulates in the same direction until the outer edge of the connecting surface is formed, and the path of the welding gun surrounding the outer edge of the connecting surface is used as the welding path.

[0015] In the laser welding method for curved thin plates described in one embodiment of the present application, in the welding step, the laser positioning welding is carried out in a full-length or segmented manner, with each segment being 50 to 60 mm long and each segment being spaced 90 to 100 mm apart.

[0016] In the laser welding method for curved thin plates described in one embodiment of the present application, in the welding step, the welding parameters of the laser positioning welding are: laser power 3 to 4 kW, welding speed 5 to 8 mm / s, defocus amount +17 to +20 mm, and shielding gas flow rate 40 to 50 L / min.

[0017] In the laser welding method for curved thin plates described in one embodiment of the present application, in the welding step, the welding parameters of the laser deep penetration welding are: laser power 4 to 6 kW, welding speed 5 to 8 mm / s, defocus amount +17 to +20 mm, and shielding gas flow rate 40 to 50 L / min.

[0018] In the laser welding method for curved thin plates described in one embodiment of the present application, in the welding step, the laser power begins to be reduced 1-3 seconds before the welding gun returns to the first arc starting point after welding one circle; the laser power is reduced by 150-200W per second for 4 seconds; the laser power is reduced by 300-350W per second for 5 seconds; the laser power is reduced by 500-600W per second until it is reduced to 0W.

[0019] In the laser welding method for curved thin plates described in one embodiment of the present application, in the welding preparation step, the welding material used for the first welding section and the second welding section is austenitic stainless steel 316H.

[0020] The laser welding method for curved thin plates described in one embodiment of the present application further includes, after the welding step: a weld polishing step, in which the weld is polished after all welding is completed to make the outer surface position of the interface between the first welding section and the second welding section smoothly transition; and a chromium nitriding heat treatment step, in which the weld at the interface between the first welding section and the second welding section is subjected to chromium nitriding heat treatment.

[0021] The beneficial effect of the present application is that it provides a laser welding method for curved thin plates, which realizes the setting of the welding path by adopting an automated welding machine, and can maintain slow welding at a low speed for a long time, thereby ensuring that the first welding section and the second welding section of the "plum blossom" cross-section structure made of high-temperature resistant stainless steel forging rods are welded to each other, saving labor and enabling mass production of products. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The following describes the specific implementation methods of the present application in detail in conjunction with the accompanying drawings to present the technical solutions and other beneficial effects of the present application.

[0023] Figure 1 This is a structural diagram of a plum blossom-shaped structural component of the existing nuclear island main equipment.

[0024] Figure 2 This is a structural diagram of the positioning machine in an embodiment of the present application.

[0025] Figure 3 This is a schematic diagram of the relative positions during welding in an embodiment of the present application.

[0026] Figure 4 This is a partial structural diagram of a welding machine in an embodiment of the present application.

[0027] Figure 5 This is the front view of the arc-shaped protective gas module described in the embodiment of the present application.

[0028] Figure 6 This is a top view of the arc-shaped protective gas module described in the embodiment of the present application.

[0029] Figure 7 This is a right side view of the arc-shaped protective gas module described in the embodiment of the present application.

[0030] Figure 8 This is a top view of the fixing block described in the embodiment of the present application.

[0031] Figure 9 This is a bottom view of the fixing block described in the embodiment of the present application.

[0032] Figure 10 This is a side view of the fixing block described in the embodiment of the present application.

[0033] Figure 11 Schematic diagram of the structure of the trachea joint described in the embodiment of this application.

[0034] Figure 12 Schematic diagram of the structure of the main protective gas device described in the embodiment of this application.

[0035] Figure 13 This is a flow chart of the laser welding method for curved thin plates in an embodiment of the present application.

[0036] Figure 14 This is a structural diagram for decomposing the movement speed of the laser welding gun in an embodiment of the present application.

[0037] Figure 15 This is a schematic diagram of the specific operation steps during welding in the embodiment of this application.

[0038] Figure 16 This is a schematic diagram of the non-destructive testing position during the welding process in an embodiment of the present application. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0040] In the description of the present application, it should be understood that the terms "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0041] like Figure 2 、 Figure 3 As shown, a welding machine is provided in an embodiment of the present application, including a positioning machine 2 for fixing a workpiece 1 to be welded.

[0042] like Figure 3 、 Figure 4As shown, the welding machine also includes a guide rail platform 3, a robot 4 movably arranged on the guide rail platform 3, and a laser 5 located at the end of the robotic arm of the robot 4. The laser 5 is used to generate laser as a welding gun. The welding gun hereinafter refers to the laser 5. The emission port of the laser 5 corresponds to the weld seam setting of the workpiece 1 to be welded.

[0043] like Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 As shown, the welding machine further includes a protective nozzle device, which is used in conjunction with the welding gun during welding. The protective nozzle device is used to provide an inert protective gas so that the welding position of the workpiece 1 to be welded is in an inert protective gas environment.

[0044] The protection nozzle device includes a weld tail protection device and a main protection gas device. Figure 5-Figure 11 As shown, the weld tail protection device includes an arc-shaped shielding gas module 6, a fixing block 7 and a gas pipe joint 8. Figure 5 This is a front view of the arc-shaped protective gas module 6; Figure 6 is a top view of the arc-shaped shielding gas module 6; Figure 7 It is a right side view of the arc-shaped shielding gas module 6; Figure 8 is a top view of the fixing block 7; Figure 9 is a bottom view of the fixing block 7; Figure 10 is a side view of the fixing block 7; Figure 11 Schematic diagram of the structure of the trachea connector 8.

[0045] The arc-shaped shielding gas module 6 is installed at the end of the robot arm 4 and is on the same horizontal plane as the laser 5. Its position during welding is just Figure 3 The laser 5 is shown obscured. The arc-shaped shielding gas module 6 is approximately 83 mm long, 6 mm wide at the head, and 1 mm thick. The fixing block 7 is 25 mm thick, 72 mm long, and 32 mm wide. A recess 71 is provided in the center of the fixing block 7. Within this recess 71 are multiple airway holes 72 located in a straight line. The airway connector 8 is threaded into the airway holes 72 from the side facing away from the recess 71. First fixing holes 73 are provided on the edge of the fixing block 7, surrounding the recess 71. These first fixing holes 73 are preferably eight threaded holes that connect to the arc-shaped shielding gas module 6. Four airway holes 72 are located in the center, and the airway connector 8 is threaded to connect the air pipes. During welding, the fixing block 7 is used to secure the arc-shaped shielding gas module 6 to the side of the welding gun. Shielding gas enters through the four airway holes 72 and is ultimately discharged from the arc-shaped tail, providing protection for the weld tail.

[0046] The arc-shaped shielding gas module 6 includes a mounting base 61 and an air guide wall 62 located on one side of the mounting base 61. The side of the mounting base 61 facing away from the air guide wall 62 is mounted to the fixing block 7. A through hole 63 is provided in the middle of the mounting base 61. The through hole 63 corresponds to the groove 71 and has the same shape and size as the groove 71. The air guide wall 62 surrounds the through hole 63 and is provided with an air outlet 64 on the side facing away from the mounting base 61. The air outlet 64 is located on the same side as the emission port of the laser 5. The cross-section of the air outlet 64 is smaller than that of the through hole 63, and the width of the air outlet 64 is 4 mm. The air guide wall 62 includes a vertical sidewall 621 and an arc-shaped sidewall 622. The vertical sidewall 621 and the arc-shaped sidewall 622 are integrally formed, with the vertical sidewall 621 facing the laser 5. The arc radius of the arc-shaped sidewall 622 is the same as the concave radius of the workpiece 1 being welded, approximately 63 mm, to prevent the module from colliding with the concave surface of the plum blossom-shaped component during the protection process. A second fixing hole 65 is provided on the edge of the mounting base 61. The second fixing hole 65 corresponds to the first fixing hole 73 and is threaded together with fasteners to ensure a sealed connection between the arc-shaped shielding gas module 6 and the fixing block 7.

[0047] like Figure 12 As shown, Figure 12It is a schematic structural diagram of the main protective gas device 9. The main protective gas device 9 includes a fixing seat 91, a clamping device 92 and a nozzle 93. The fixing seat 91 is provided with a plurality of first threaded holes 911, and a fastener passes through the first threaded holes 911 to be fixed to a support frame. The fixing seat 91 is L-shaped, the first threaded holes 911 are provided on the bottom surface of the fixing seat 91, and the side surface of the fixing seat 91 is provided with a second threaded hole 912. The clamping device 92 includes an adjusting block 921 and a clamp 922. The adjusting block 921 is provided with a third threaded hole 9211 corresponding to the second threaded hole 912. The fixing seat 91 and the clamping device 92 are fixed by a fastener passing through the two threaded holes 912 and the third threaded hole 9211 at the same time. The positioning block 921 is in an elongated strip shape, with a fixing through-hole 9212 defined along its length. One end of the clamp 922 is fixed to the nozzle 93, while the other end of the clamp 922 is fixed to the fixing through-hole 9212. The nozzle 93 comprises a tube body 931 and a nozzle head 932. The nozzle head 932 forms an angle with the axial axis of symmetry of the tube body 931, facilitating the upward spraying of inert gas by the primary shielding gas device 9 when positioned below the weld seam of the workpiece 1 being welded. The clamp 922 is provided with a fixing plate 9221 and a fixing rod 9222. The fixing plate 9221 is fixedly connected to the tube body 931. The fixing rod 9222 is screwed into the threaded hole on the fixing plate 9221, and the end of the fixing rod 9222 is inserted into the fixing through hole 9212 and screwed into the fixing through hole 9212, thereby realizing that the fixing rod 9222 presses the fixing plate 9221 and fixes it to the fixing through hole 9212.

[0048] The main shielding gas device 9 uses a separate gas pipe to blow plasma and smoke upward from the bottom. The workpiece 1 is sealed to form a closed environment, and a separate gas pipe is used to inject back shielding gas from the back of the workpiece 1 to protect the back weld from oxidation. This shielding nozzle arrangement forms a shielding system, blowing simultaneously during welding to protect the weld. The arc-shaped shielding gas module 6 is specifically designed for curved weld protection, a function that cannot be achieved by shielding gas modules in the prior art.

[0049] The welding machine further includes a memory and a processor; the memory stores a computer program, and the processor is configured to run the computer program in the memory to perform operations in the laser welding method. The memory stores a plurality of instructions suitable for loading by the processor.

[0050] Please refer to Figure 3As shown, the welded workpiece 1 of this application is divided into a first welding section 11 and a second welding section 12. The interface between the first welding section 11 and the second welding section 12 is both plum blossom-shaped, and this interface is the weld seam. The first welding section 11 and the second welding section 12 are positioned and docked with each other. The interface between the first welding section 11 and the second welding section 12 is both the same curved surface, which includes a plurality of first and second curved surfaces connected end to end. A laser 5 is positioned on one side of each of the connecting surfaces as a welding gun; the first curved surface is convex, the second curved surface is concave, and the first and second curved surfaces are spaced apart. This patent designs a robot motion method capable of performing plum blossom-shaped curved surface welding path trajectories, realizing laser welding of plum blossom-shaped and special-shaped curved products. The method is characterized by using programming to realize the curved trajectory of the laser welding gun, controlling the rotation of the laser welder and the rotation of the welded workpiece 1, and achieving reciprocating motion of the laser welding gun within a certain area to complete the welding of the entire plum blossom-shaped curved surface.

[0051] Based on the above structure, Figure 13 As shown, the present application provides a laser welding method for curved thin plates, which is used for welding high-temperature resistant austenitic stainless steel 316H with a thickness of 8 to 10 mm. The weld surface and back surfaces are well-formed, and the metallographic structure is free of any defects (including pores, cracks, inclusions, and lack of fusion). The weld is resistant to high temperatures and intergranular corrosion, and has good tensile properties at high temperatures (350°C, 400°C, 450°C, 550°C, and 650°C). The laser welding method for curved thin plates includes the following steps S1-S5.

[0052] S1. Welding preparation step: Position and dock the first welding segment 11 and the second welding segment 12. The connecting surfaces of the first welding segment 11 and the second welding segment 12 are identically curved, comprising a plurality of first and second arcuate surfaces connected end-to-end. Preferably, the first and second arcuate surfaces connected end-to-end form a plum blossom shape having six petal-shaped arcs connected end-to-end. A welding gun is positioned on one side of the connecting surface for welding the connecting surfaces of the first welding segment 11 and the second welding segment 12. The welding material used for the first welding segment 11 and the second welding segment 12 is austenitic stainless steel 316H.

[0053] The first welding section 11 and the second welding section 12 are composed of an upper grid plate and a lower grid plate. The upper grid plate and the lower grid plate are both processed from forged rods. After processing, 6 convex and concave surfaces are formed, which are shaped like a "plum blossom". The maximum diameter of the welding part is 355-360mm, the minimum diameter is 291-295mm, and the thickness is 8 to 10mm. Laser welding adopts a horizontal welding method to butt weld the upper grid plate and the lower grid plate. During welding, the welding gun reciprocates within an angle range, and the rotating shaft rotates in one direction with the workpiece 1 to be welded, thereby ensuring that the welding gun always remains perpendicular to the surface of the workpiece 1 to be welded and equidistant from the workpiece 1 to be welded during the welding process. Adjust the rotation speed of the welding gun and the rotation speed of the workpiece 1 to be welded, and weld the 6 convex and concave surfaces separately under the premise that the relative speed remains unchanged, and finally complete the laser welding of the plum blossom-shaped curved surface trajectory of the plum blossom-shaped structural part.

[0054] After the welding preparation step S1, a welding path is simulated based on the first and second arc surfaces, and the welding gun is controlled to perform laser welding along the welding path on the interface between the first welding segment 11 and the second welding segment 12. Simulating the welding path based on the first and second arc surfaces specifically includes steps S2-S5.

[0055] S2. The welding gun is configured to move relative to the interface. The distance between the welding gun and the outer edge of the interface between the first welding section 11 and the second welding section 12 is maintained constant. The movement speed, rotation speed, and rotation angle of the welding gun, the first welding section 11, and the second welding section 12 are adjusted to maintain a constant relative speed of the welding gun along the outer edge of the interface. The first welding section 11 and the second welding section 12 can be set to be stationary, while the welding gun is independently configured to rotate around the interface between the first welding section 11 and the second welding section 12. Alternatively, the welding gun, the first welding section 11, and the second welding section 12 can all rotate, thereby reducing the amount of movement of the welding gun.

[0056] Specifically, a plane coordinate system is established on the plane where the connecting surface is located with the center point of the connecting surface as the origin, and the plane coordinate system has a horizontal axis and a vertical axis, and the horizontal axis and the vertical axis are both located on the symmetry axis of the connecting surface; an intersection of the edge of the connecting surface and the horizontal axis or the vertical axis is set as an arc starting point, and the welding gun forms a petal-shaped first arc surface or a second arc surface from the arc starting point in a clockwise or counterclockwise direction to reach the welding end point; the welding gun uses the welding end point as the arc starting point of the next petal-shaped second arc surface or the first arc surface and circulates in the same direction until the outer edge of the connecting surface is formed, that is, six petal-shaped arcs are formed to form the outer edge curve of the plum blossom-shaped connecting surface, and the path of the welding gun to form the outer edge curve of the connecting surface is used as the welding path.

[0057] Specifically, the plum blossom-shaped edge is decomposed into six "petals," each of which is divided into eight arc segments. The starting and ending points of the first arc segment are determined, and the welding torch's rotation radius and axis angle are set according to the arc radius of the workpiece being welded, simulating the motion trajectory of that segment. The above operations are applied to the remaining seven arc segments to form the motion trajectory of a "petal." This motion model is then applied to the remaining "petals" to complete the plum blossom-shaped trajectory.

[0058] S3, a step of generating a welding path and motion parameters, according to the step of setting the movement of the welding gun relative to the interface, the movement path of the welding gun along the interface is used as the welding path, and the movement speed, rotation speed, and rotation angle of the welding gun, the first welding segment 11, and the second welding segment 12 are used as motion parameters.

[0059] S4, welding step, setting the rotation speed of the welding gun and the rotation angular velocity of the first welding section 11 and the second welding section 12, so that the relative speed between the welding gun and the first welding section 11 and the second welding section 12 remains unchanged during the welding process; setting the welding gun to be perpendicular to the outer surfaces of the first welding section 11 and the second welding section 12 and the distance therebetween remains unchanged; placing the position of the welding gun corresponding to the interface of the first welding section 11 and the second welding section 12 in an inert protective gas environment, turning on the welding gun and using laser positioning welding or laser deep penetration welding to weld the interface of the first welding section 11 and the second welding section 12 to form a weld.

[0060] like Figure 14As shown, specifically, the movement speed of the laser welding gun is decomposed, and the movement speed of the welding gun V1 is decomposed into the welding gun rotation angular velocity Va and the TCP linear motion Vb. During the movement, the TCP trajectory and the center of the welded workpiece 1 are always on the same straight line; the movement of the welded workpiece 1 is the rotation angular velocity V2 of the welded workpiece 1; the welding time t is determined by the segmented arc length of the welded workpiece 1 and the required welding speed, and the rotation angular velocity V2 of the welded workpiece 1 is determined according to the rotation angle of the welded workpiece 1 and the welding time t, so as to realize the linkage between the positioner and the robot; according to the welding surface The TCP speed Vb is determined based on the distance from the center of the workpiece 1 being welded and the welding time t, ensuring that the welding gun always maintains an equidistant distance from the workpiece 1. The welding gun's angular rotational velocity Va is determined based on the offset angle of the segmented arc centered on the welding gun's center and the welding time, ensuring that the welding gun always remains perpendicular to the surface of the workpiece 1 being welded. The six "petals" and 48 arc segments in the plum blossom curve are decomposed into several points. The position, TCP speed, welding gun rotational speed, and angular rotational velocity of the workpiece 1 being welded are controlled at each point and input into the programming software. The program for each point is run to form the entire motion process. The TCP speed, welding gun rotational speed, and angular rotational velocity of the workpiece 1 being welded are corrected at each point to ensure that the relative speed between the welding gun and the workpiece 1 remains unchanged throughout the "plum blossom" motion. The program in RobotStudio is transferred to the welding machine's teach pendant to achieve laser welding of plum blossom-shaped surface trajectories in reality.

[0061] The protective nozzle device is an arc-shaped laser welding protective gas module, which protects the weld when the welding gun performs plum blossom welding to ensure that it does not interfere with the welded workpiece 1. At the same time, it blows away the plasma and metal smoke that affect the propagation of the laser beam and provides gas protection for the weld to prevent oxidation and reduce welding spatter.

[0062] S5, a step of grinding the weld seam. After all welding is completed, the weld seam is ground to make the outer surface position of the interface between the first welding section 11 and the second welding section 12 smoothly transition.

[0063] S6, solution heat treatment and chromization and nitriding heat treatment step, performing solution heat treatment and chromization and nitriding heat treatment on the weld at the interface between the first welding section 11 and the second welding section 12.

[0064] In an embodiment of the present application, in the welding path setting step and the welding step, the laser welding path simulation is completed in the motion simulation software RobotStudio to form the welding path; three-dimensional modeling is performed in the motion simulation software RobotStudio to complete the modeling of the first welding segment 11 and the second welding segment 12, the welding gun is imported into the motion simulation software RobotStudio and the relative speed and distance between the welding gun and the first welding segment 11 and the second welding segment 12 are adjusted to remain unchanged.

[0065] In the embodiment of the present application, in the welding step, the laser positioning welding is performed in a full-length or segmented manner, with each segment being 50 to 60 mm long and each segment being spaced 90 to 100 mm apart.

[0066] In an embodiment of the present application, in the welding step, the welding parameters of the laser positioning welding are: laser power 3 to 4 kW, welding speed 5 to 8 mm / s, defocus amount +17 to +20 mm, and shielding gas flow rate 40 to 50 L / min.

[0067] In an embodiment of the present application, in the welding step, the welding parameters of the laser deep penetration welding are: laser power 4 to 6 kW, welding speed 5 to 8 mm / s, defocus amount +17 to +20 mm, and shielding gas flow rate 40 to 50 L / min.

[0068] When welding, Figure 15 As shown, the welding process sequentially executes the steps of program initialization, signal waiting, laser activation, path program execution, torch shutdown, and program termination. The path program execution step is the aforementioned step S2 of setting the torch's motion relative to the contact surface. The first arc starting point is preferably the middle of the concave surface closest to the center point. From the middle of the concave surface, the path is traced clockwise along the first concave surface, along the first convex surface, and along the second concave surface. The path is then traced through six concave surfaces and six convex surfaces, ultimately arriving at the starting point for the first arc starting point.

[0069] In the process of achieving plum blossom-shaped curved surface welding of high-temperature resistant stainless steel plum blossom-shaped structural parts, since it involves nuclear power products, its non-destructive testing is implemented in the welding process, such as Figure 16 As shown, after machining the welded workpiece 1 , DT and PT are involved; after welding, VT, PT and RT are involved; after solution heat treatment, VT, PT and RT are involved; and after chromizing and nitriding, VT, PT and RT are involved.

[0070] When welding a circular pipe, a linear defect can easily appear at the center of the back of the weld due to the overlap between the arc start and end sections. To prevent these weld defects, the following method is used: During the welding process, the laser power is reduced 1-3 seconds before the welding gun returns to the initial arc start point after welding one circle; the laser power is reduced by 150-200W per second for 4 seconds; the laser power is reduced by 300-350W per second for 5 seconds; and the laser power is reduced by 500-600W per second until it reaches 0W.

[0071] In this example, the weld material used was austenitic stainless steel 316H. After welding using the aforementioned welding parameters, the mechanical properties and impact toughness achieved were shown in the table below. Intergranular corrosion resistance was also acceptable, and no microcracks or deposits that could affect joint performance were observed in the metallographic structure. Tests have shown that these excellent results can be achieved with austenitic stainless steel using the aforementioned welding parameters.

[0072]

[0073] The beneficial effect of the present application is that it provides a laser welding method for curved thin plates, which realizes the setting of the welding path by adopting an automated welding machine, and can maintain slow welding at a low speed for a long time, thereby ensuring that the first welding section and the second welding section of the "plum blossom" cross-section structure made of high-temperature resistant stainless steel forging rods are welded to each other, saving labor and enabling mass production of products.

[0074] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0075] The above is a detailed introduction to a curved surface laser welding method provided in an embodiment of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and core idea of ​​the present application; ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not cause the essence of the corresponding technical solution to deviate from the scope of the technical solution of the embodiments of the present application.

Claims

1. A laser welding method for curved thin plates, characterized in that: Including steps: Positioning and docking the first welding section and the second welding section, wherein the connecting surfaces of the first welding section and the second welding section are both identically curved, the curved surfaces comprising a plurality of first and second arc surfaces connected end to end, the first and second arc surfaces forming a plum blossom shape having six petal-shaped arcs connected end to end, and a welding gun being provided on one side of the connecting surfaces; and Simulating a welding path according to the first arc surface and the second arc surface, and controlling the welding gun to laser weld the interface between the first welding section and the second welding section along the welding path; In simulating a welding path according to the first arc surface and the second arc surface, the steps include: The welding gun is arranged to move relative to the interface, the distance between the welding gun and the outer edge of the interface between the first welding section and the second welding section is maintained constant, and the movement speed, rotation speed, and rotation angle of the welding gun, the first welding section, and the second welding section are adjusted so that the relative speed of the welding gun along the outer edge of the interface remains constant; a step of generating a welding path and motion parameters, wherein, according to the step of setting the movement of the welding gun relative to the interface, the movement path of the welding gun along the interface is used as the welding path, and the movement speed, rotation speed, and rotation angle of the welding gun, the first welding section, and the second welding section are used as motion parameters; as well as The welding step is to place the welding gun at the position corresponding to the interface between the first welding section and the second welding section in an inert protective gas environment, turn on the welding gun, and use laser positioning welding or laser deep penetration welding to laser weld the interface between the first welding section and the second welding section to form a weld.

2. The laser welding method for curved thin plates according to claim 1, characterized in that: The first arc surface is a convex surface, the second arc surface is a concave surface, and the first arc surface and the second arc surface are spaced apart.

3. The laser welding method for curved thin plates according to claim 1, characterized in that: In the relative joint surface movement setting of the welding gun, the laser welding path simulation is completed in the motion simulation software RobotStudio to form the welding path; three-dimensional modeling is performed in the motion simulation software RobotStudio to complete the modeling of the first welding segment and the second welding segment, the welding gun is imported into the motion simulation software RobotStudio and the relative speed and distance between the welding gun and the first welding segment and the second welding segment are adjusted to remain unchanged; the rotation speed of the welding gun and the rotation angular velocity of the first welding segment and the second welding segment are set so that the relative speed between the welding gun and the first welding segment and the second welding segment remains unchanged during the welding process; the welding gun is set perpendicular to the outer surfaces of the first welding segment and the second welding segment and the distance remains unchanged.

4. The laser welding method for curved thin plates according to claim 1, characterized in that: In the step of setting the movement of the welding gun relative to the connecting surface, a plane coordinate system is established on the plane where the connecting surface is located with the center point of the connecting surface as the origin, and the plane coordinate system has a horizontal axis and a vertical axis, and the horizontal axis and the vertical axis are both located on the symmetry axis of the connecting surface; an intersection point of the edge of the connecting surface and the horizontal axis or the vertical axis is set as the arc starting point, and the welding gun forms a first arc surface or a second arc surface from the arc starting point in a clockwise or counterclockwise direction to reach the welding end point; the welding gun uses the welding end point as the arc starting point of the next second arc surface or the first arc surface and circulates in the same direction until the outer edge of the connecting surface is formed, and the path of the welding gun surrounding the outer edge of the connecting surface is used as the welding path.

5. The laser welding method for curved thin plates according to claim 1, characterized in that: In the welding step, the laser positioning welding is performed in a full-length or segmented manner, with each segment being 50 to 60 mm long and each segment being spaced 90 to 100 mm apart.

6. The laser welding method for curved thin plates according to claim 1, characterized in that: In the welding step, the welding parameters of the laser positioning welding are: laser power 3 to 4 kW, welding speed 5 to 8 mm / s, defocusing amount +17 to +20 mm, and shielding gas flow rate 40 to 50 L / min.

7. The laser welding method for curved thin plates according to claim 1, characterized in that: In the welding step, the welding parameters of the laser deep penetration welding are: laser power 4 to 6 kW, welding speed 5 to 8 mm / s, defocusing amount +17 to +20 mm, and shielding gas flow rate 40 to 50 L / min.

8. The laser welding method for curved thin plates according to claim 6 or 7, characterized in that: In the welding step, the laser power begins to decrease 1-3 seconds before the welding gun returns to the first arc starting point after welding one circle; the laser power decreases by 150-200W per second for 4 seconds; the laser power decreases by 300-350W per second for 5 seconds; the laser power decreases by 500-600W per second until it is reduced to 0W.

9. The laser welding method for curved thin plates according to claim 1, characterized in that: After the welding step, the method further comprises: a weld grinding step, after all welding is completed, grinding the weld to make the outer surface position of the interface between the first welding section and the second welding section smoothly transition; and The chromizing and nitriding heat treatment step is to perform chromizing and nitriding heat treatment on the weld at the interface between the first welding section and the second welding section.

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