Device and method for assisting laser welding of circumferential weld through welding-following ultrasonic vibration

Abstract

The invention discloses a device and a method for assisting laser welding of a circumferential weld by ultrasonic vibration along with welding, which can realize laser welding of the circumferential weld, effectively refine weld grains, reduce residual stress of the weld and improve the mechanical property of the circumferential weld. The device comprises a laser water cooling box, a welding platform, a laser generator, a three-dimensional moving module, a tip, a laser welding torch, an ultrasonic vibration device, a positioning tool, a positioning tool moving module, a four-claw self-centering chuck, a moving module controller and an ultrasonic generator. The laser welding torch and the ultrasonic vibration device are connected with the three-dimensional moving module. The ultrasonic vibration device is connected with the ultrasonic generator through a wire. The laser water cooling box is connected with the laser welding torch through a water pipe; the laser generator is connected with the laser welding torch through a wire. And the positioning tool is fixedly connected with the positioning tool moving module.

Description

Technical Field

[0001] The present invention belongs to the field of laser welding, and in particular, relates to a device and method for laser welding annular welds assisted by ultrasonic vibration during welding. Background Art

[0002] At present, laser welding is one of the most commonly used welding methods, with the advantages of fast welding speed, deep weld penetration, and small welding deformation. During the laser welding process, the metal material in the weld area is heated and melted by the laser and quickly cooled after the laser energy leaves. During the cooling period, the weld material undergoes complex changes such as nucleation, growth, crystallization and phase change, and the whole process is accompanied by energy conversion. Ultrasound refers to mechanical vibration with a frequency higher than 20kHz. Cavitation and acoustic streaming effects will occur in ultrasonic assisted welding. The ultrasonic cavitation process will produce strong shock waves, which can break up the primary coarse crystals and growing dendrites, thereby increasing the nucleation points and improving the nucleation rate. Acoustic streaming plays a key role in destroying the boundary layer, accelerating mass transfer and heat transfer, promoting the dispersion of fine particles, and cleaning surface impurities. It has a good application value in improving the metal solidification process and refining grains. Ultrasonic vibration cross-state treatment of laser welding is to add ultrasonic vibration field in the welding area during laser welding, and use the frequency tracking function of the ultrasonic generator to realize the resonance of the test piece, which affects the formation and movement of the welding molten pool, crystallization solidification and phase change, so as to improve the weld structure, reduce welding defects, control welding stress and deformation, and improve mechanical properties.

[0003] At present, ultrasonic impact assisted welding is mainly aimed at flat plate welding, and the position of ultrasonic vibration is mostly fixed. As the welding heat source moves, the influence of ultrasonic vibration on the weld gradually decreases, and the weld area structure is uneven. Annular weld refers to the weld produced during the welding process on the annular structure, and its shape is annular. For example, when assembling a spacecraft, there is an annular seam on the outer surface of the rocket engine. This requires the welding of annular welds. Therefore, it is very important to develop a device and method for ultrasonic vibration-assisted annular welds. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention proposes a device and method for laser welding annular welds with ultrasonic vibration during welding, which can realize laser welding of annular welds, effectively refine the weld grains, reduce the residual stress of the weld, and improve the mechanical properties of the annular weld.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: In the first aspect, an embodiment of the present invention provides a device for laser welding annular welds assisted by ultrasonic vibration during welding, comprising a laser water cooling box, a welding platform, a laser generator, a three-dimensional mobile module, a top, a laser welding torch, an ultrasonic vibration device, a positioning tool, a positioning tool mobile module, a four-jaw self-centering chuck, a mobile module controller and an ultrasonic generator, wherein the three-dimensional mobile module, the top, the positioning tool mobile module and the four-jaw self-centering chuck are respectively connected to the welding platform, and the top and the four-jaw self-centering chuck are coaxially arranged relative to each other; the three-dimensional mobile module and the positioning tool mobile module are respectively connected to the mobile module controller through wires; the laser welding torch and the ultrasonic vibration device are respectively connected to the three-dimensional mobile module; the ultrasonic vibration device is connected to the ultrasonic generator through a wire; the laser water cooling box is connected to the laser welding torch through a water pipe; the laser generator is connected to the laser welding torch through a wire; the positioning tool is fixedly connected to the positioning tool mobile module.

[0006] As a preferred example, during operation, a workpiece is positioned between the center and the four-jaw self-centering chuck, and the weld to be welded on the workpiece is an annular weld.

[0007] As a preferred example, the three-dimensional mobile module adopts a first ball screw pair, which is driven by a first servo motor to move, with a repeat positioning accuracy of 0.01 mm, an adjustable movement speed range of 0 to 100 mm / s, and an adjustment accuracy of 0.01 mm / s; wherein, the effective stroke of the horizontal X-direction guide rail is 800 mm, the effective stroke of the horizontal Y-direction guide rail is 500 mm, the effective stroke of the vertical Z-direction guide rail is 600 mm, and the vertical Z-direction guide rail has a load-bearing capacity of 50 kg.

[0008] As a preferred example, the positioning tooling moving module adopts a second ball screw pair, which is driven by a second servo motor to move. The repeatability accuracy is 0.01 mm, the adjustable movement speed range is 0-100 mm / s, the adjustment accuracy is 0.01 mm / s, the effective stroke is 800 mm, and the maximum load-bearing capacity in the vertical direction is 30 kg.

[0009] As a preferred example, the ultrasonic vibration device includes an ultrasonic transducer, an ultrasonic amplitude transformer, an ultrasonic transmitting end and an ultrasonic impact needle. The ultrasonic transducer is connected to the ultrasonic generator through a wire, the ultrasonic amplitude transformer is connected to the ultrasonic transducer through a thread, the bottom of the ultrasonic amplitude transformer is the ultrasonic transmitting end; the connecting end of the ultrasonic impact needle is connected to the ultrasonic transmitting end; the needle tip of the ultrasonic impact needle faces the workpiece.

[0010] As a preferred example, the ultrasonic transmitting end is a concave surface; there are at least three ultrasonic impact needles, the needle heads of all ultrasonic impact needles form a concave shape, and the needle heads of the ultrasonic impact needles are in contact with the surface of the workpiece.

[0011] As a preferred example, the needle tip diameter of the ultrasonic impact needle is 3 mm.

[0012] In a second aspect, an embodiment of the present invention further provides a method for laser welding annular welds by ultrasonic vibration-assisted welding, the method comprising: Step 1: Fix the workpiece on the positioning fixture, and adjust the position of the workpiece by adjusting the positioning fixture moving module so that the workpiece is in a position for spot welding; The position of the laser welding torch is adjusted through a three-dimensional moving module, and the laser welding torch is used to perform spot welding positioning on the workpiece to be welded; Step 2: Fix one end of the workpiece after spot welding in a four-jaw self-centering chuck, and place the top against the other end of the workpiece; adjust the laser welding torch spot to align with the weld center of the workpiece through the three-dimensional moving module; adjust the position of the ultrasonic vibration device to make the ultrasonic impact needle contact with the weld center and apply a clamping force; Step 3, start the four-jaw self-centering chuck, the ultrasonic generator and the laser generator, use the four-jaw self-centering chuck 10 to drive the workpiece to rotate, and perform ultrasonic vibration-assisted annular weld laser welding; Step 4: After welding, turn off the laser generator, ultrasonic generator and four-jaw self-centering chuck in sequence.

[0013] As a preferred example, the step 3 specifically includes: first turning on the four-jaw self-centering chuck and the ultrasonic vibration device, then turning on the laser generator, and first welding and then vibrating the same position of the annular weld to be welded on the workpiece.

[0014] As a preferred example, in step 2, adjusting the position of the ultrasonic vibration device includes: adjusting the arrangement arc of the ultrasonic impact needle according to the diameter of the workpiece, so that the needle tip of the ultrasonic impact needle is close to the weld and applies a clamping force to the weld.

[0015] Compared with the prior art, the device and method for laser welding annular welds assisted by ultrasonic vibration during welding of the embodiment of the present invention can realize laser welding of annular welds, effectively refine the weld grains, reduce the residual stress of the weld, and improve the mechanical properties of the annular welds. The device includes a laser water cooling box, a welding platform, a laser generator, a three-dimensional mobile module, a top, a laser welding torch, an ultrasonic vibration device, a positioning tool, a positioning tool mobile module, a four-jaw self-centering chuck, a mobile module controller and an ultrasonic generator. In the process of laser welding annular welds, as the weld moves, ultrasonic vibration is applied, and the ultrasonic sound flow and cavitation effect are uniformly introduced into the molten pool during welding, which can effectively refine the weld grains, suppress welding defects, reduce residual stress after welding, and improve the mechanical properties of the weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the structure of the device according to an embodiment of the present invention; Figure 2 Schematic diagram of the structure of the ultrasonic vibration device in an embodiment of the present invention.

[0017] The figure includes: laser water cooling box 1, welding platform 2, laser generator 3, three-dimensional mobile module 4, top 5, laser welding torch 6, ultrasonic vibration device 7, positioning tool 8, positioning tool mobile module 9, four-jaw self-centering chuck 10, workpiece 11, mobile module controller 12, ultrasonic generator 13, ultrasonic transducer 7-1, ultrasonic amplitude transformer 7-2, ultrasonic transmitting end 7-3, ultrasonic impact needle 7-4. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0019] like Figure 1 As shown, a device for laser welding annular welds with ultrasonic vibration assistance according to an embodiment of the present invention comprises a laser water cooling box 1, a welding platform 2, a laser generator 3, a three-dimensional mobile module 4, a top 5, a laser welding torch 6, an ultrasonic vibration device 7, a positioning tool 8, a positioning tool mobile module 9, a four-claw self-centering chuck 10, a mobile module controller 12 and an ultrasonic generator 13. The three-dimensional mobile module 4, the top 5, the positioning tool mobile module 9 and the four-claw self-centering chuck 10 are respectively connected to the welding platform 2, and the top 5 and the four-claw self-centering chuck 10 are coaxially arranged relative to each other. The three-dimensional mobile module 4 and the positioning tool mobile module 9 are respectively connected to the mobile module controller 12 through wires. The laser welding torch 6 and the ultrasonic vibration device 7 are respectively connected to the three-dimensional mobile module 4. The ultrasonic vibration device 7 is connected to the ultrasonic generator 13 through a wire. The laser water cooling box 1 is connected to the laser welding torch 6 through a water pipe. The laser generator 3 is connected to the laser welding torch 6 through a wire. The positioning fixture 8 is fixedly connected to the positioning fixture moving module 9 .

[0020] In the above embodiment, the tip 5 and the four-jaw self-centering chuck 10 are coaxially arranged relative to each other, and the tip 5 and the four-jaw self-centering chuck 10 are used to fix the workpiece 11 and drive the workpiece 11 to rotate. The workpiece 11 is located between the tip 5 and the four-jaw self-centering chuck 10. The workpiece 11 is driven to rotate by the four-jaw self-centering chuck 10. This can achieve the welding of an annular weld on the surface of the workpiece 11. During the welding process, the pre-positioned laser welding torch 6 and the ultrasonic vibration device 7 remain fixed, and only the workpiece 11 rotates. The workpiece 11 is rotated for welding, the weld is heated evenly, the operation is simple, the size of the workpiece 11 is less affected, and the equipment accuracy requirement is low.

[0021] The laser welding torch 6 and the ultrasonic vibration device 7 are connected to the three-dimensional movable module 4. The positioning fixture 8 is connected to the positioning fixture movable module 9, and the workpiece 11 is installed on the positioning fixture 8. The positioning fixture 8 and the positioning fixture movable module 9 are provided to realize spot welding of the workpiece 11. That is, two separated workpieces are connected into one workpiece by spot welding. Spot welding is also for fixing the position of the weld. The mobile module controller 12 controls the movement of the three-dimensional movable module 4 and the positioning fixture movable module 9 to adjust the position of the laser welding torch 6, the ultrasonic vibration device 7 and the workpiece 11, so as to facilitate spot welding and annular welds. The ultrasonic generator 13 is connected to the ultrasonic vibration device 7, and the ultrasonic generator 13 is used to output ultrasonic electrical signals. After power is turned on, the ultrasonic generator 13 transmits the generated electrical signal to the ultrasonic transducer 7-1 of the ultrasonic vibration device 7, and the ultrasonic transducer 7-1 converts the electrical signal into mechanical vibration and transmits it downward to the ultrasonic horn 7-2, which amplifies the mechanical vibration and applies the ultrasonic vibration to the ultrasonic impact needle 7-4 through the ultrasonic transmitting end 7-3 at the bottom, and acts on the weld through the ultrasonic impact needle 7-4. The laser water cooling box 1 is connected to the laser welding torch 6 through a water pipe. The laser water cooling box 1 is used to store circulating water cooling liquid, and the heat of the laser welding torch 6 during operation is reduced by circulating water cooling liquid to ensure the normal operation of the laser welding torch 6. The laser generator 3 is connected to the laser welding torch 6. The laser generator 3 is used to amplify the light source and transmit the amplified high-density energy beam to the laser welding torch 6 to achieve welding. Preferably, the temperature control range of the laser water cooling box 1 is -19°C to +50°C, and the temperature control accuracy is ±0.1°C. Preferably, the power of the laser generator 3 is 2000 W, the central wavelength is 1080 nm, the welding process is in an argon (99.99% Ar) atmosphere, and the flow rate is 15 L / min. Preferably, the ultrasonic vibration frequency of the ultrasonic generator 13 is 20 kHz, the amplitude is 20 μm, the rated power is 3000 W, the actual adjustable power is 900-2100 W, and the adjustment accuracy is 30 W.

[0022] Preferably, during operation, a workpiece 11 is positioned between the tip 5 and the four-jaw self-centering chuck 10, and the weld to be welded on the workpiece 11 is an annular weld. Preferably, the workpiece 11 is a cylinder or an annular body. When welding an annular weld on the workpiece 11, the workpiece 11 is driven by the four-jaw self-centering chuck 10, while the positions of the laser welding torch 6 and the ultrasonic vibration device 7 remain unchanged, so as to achieve welding of an annular weld on the workpiece 11.

[0023] Preferably, Figure 1As shown, the three-dimensional moving module 4 adopts the first ball screw pair, and the first servo motor drives the first ball screw pair to move, with a repeat positioning accuracy of 0.01 mm, an adjustable motion speed range of 0 to 100 mm / s, and an adjustment accuracy of 0.01 mm / s; wherein, the effective stroke of the horizontal X-direction guide rail is 800 mm, the effective stroke of the horizontal Y-direction guide rail is 500 mm, the effective stroke of the vertical Z-direction guide rail is 600 mm, and the vertical Z-direction guide rail has a load-bearing capacity of 50 kg. The horizontal X direction and the horizontal Y direction are perpendicular to each other, forming a horizontal plane; the vertical Z direction is perpendicular to the horizontal plane. Through the three-dimensional moving module 4, the position of the laser welding torch 6 and the ultrasonic vibration device 7 is adjusted to facilitate welding. The three-dimensional moving module 4 can realize X, Y, and Z three-dimensional movement, and the speed adjustment range is 0 to 500 mm / s, and the adjustment accuracy is 0.01 mm / s. The three-dimensional moving module 4 includes a longitudinal guide rail, a longitudinal slider, a longitudinal motor, a transverse guide rail, a transverse slider, a transverse motor, a vertical guide rail, a vertical slider, and a vertical motor. The longitudinal slider is mounted on the longitudinal guide rail, and the longitudinal motor drives the longitudinal slider to move longitudinally, that is, to move in the Y direction. The transverse guide rail is mounted on the longitudinal slider, the transverse slider is mounted on the transverse guide rail, and the transverse motor drives the transverse slider to move transversely, that is, to move in the X direction. The vertical guide rail is mounted on the transverse slider, the vertical slider is mounted on the vertical guide rail, and the vertical motor drives the vertical slider to move vertically, that is, to move in the Z direction. The laser welding torch 6 and the ultrasonic vibration device 7 are connected to the vertical slider through a connecting rod, and the laser welding torch 6 and the ultrasonic vibration device 7 are respectively connected to the connecting rod through a rotating component. As a preferred example, the rotating component includes a first motor and a second motor, the first motor and the second motor are mounted on the connecting rod, the power output shaft of the first motor is connected to the laser welding torch 6, and the power output shaft of the first motor is connected to the ultrasonic vibration device 7. The laser welding torch 6 and the ultrasonic vibration device 7 can realize three-dimensional movement of X, Y, and Z on the three-dimensional moving module 4, and can be rotated to adjust the angle between 0 and 360 degrees.

[0024] Preferably, the positioning tool moving module 9 adopts a second ball screw pair, and the second ball screw pair is driven to move by a second servo motor, with a repeat positioning accuracy of 0.01 mm, an adjustable motion speed range of 0 to 100 mm / s, an adjustment accuracy of 0.01 mm / s, an effective stroke of 800 mm, and a maximum load-bearing capacity of 30 kg in the vertical direction. By adjusting the position of the positioning tool 8 through the positioning tool moving module 9, the position of the workpiece on the positioning tool 8 is adjusted to facilitate spot welding before the annular weld operation. The positioning tool moving module 9 can realize the up and down movement of the workpiece along the Y direction and 0 to 360° rotation. The positioning tool moving module 9 includes a Y-direction guide rail, a Y-direction slider, a Y-direction motor, a base, and a rotating component. The Y-direction slider is installed on the Y-direction guide rail, the Y-direction motor is connected to the Y-direction slider, drives the Y-direction slider to move up and down along the Y direction, the base is installed on the Y-direction slider, the rotating component is installed on the base, and the rotating component drives the positioning tool 8 to rotate. As a preferred example, the rotating component includes a motor, the motor is mounted on the base through a bearing, and the power output shaft of the motor is connected to the positioning fixture 8. The motor drives the positioning fixture 8 to rotate.

[0025] Preferably, Figure 2 As shown, the ultrasonic vibration device 7 includes an ultrasonic transducer 7-1, an ultrasonic horn 7-2, an ultrasonic transmitting end 7-3 and an ultrasonic impact needle 7-4. The ultrasonic transducer 7-1 is connected to the ultrasonic generator 13 through a wire, the ultrasonic horn 7-2 is connected to the ultrasonic transducer 7-1 through a thread, and the bottom of the ultrasonic horn 7-2 is the ultrasonic transmitting end 7-3; the connecting end of the ultrasonic impact needle 7-4 is connected to the ultrasonic transmitting end 7-3; the needle head of the ultrasonic impact needle 7-4 faces the workpiece 11. The ultrasonic transducer 7-1 is connected to the ultrasonic generator 13 to convert the supersonic frequency electrical signal generated by the ultrasonic generator 13 into mechanical vibration; the ultrasonic horn 7-2 is connected to the ultrasonic transducer 7-1 through a thread to amplify the amplitude of the mechanical vibration generated by the ultrasonic transducer 7-1; the ultrasonic transmitting end 7-3 is connected to the ultrasonic impact needle 7-4 to apply the generated ultrasonic vibration to the weld area through the ultrasonic impact needle 7-4.

[0026] Preferably, the ultrasonic transmitting end 7-3 is concave; there are at least three ultrasonic impact needles 7-4, and the needles of all ultrasonic impact needles 7-4 form a concave shape, and the needles of the ultrasonic impact needles 7-4 are in contact with the surface of the workpiece 11. The surface of the workpiece 11 is an arc surface. The needles of all ultrasonic impact needles 7-4 form a concave shape and are arc-shaped, so that the needles of the ultrasonic impact needles 7-4 are in contact with the surface of the workpiece 11. In this way, the vibration generated by the ultrasonic vibration device 7 when it is working is transmitted to the weld area on the surface of the workpiece 11 through the needle. The arrangement arc of the needles is close to the weld, so that the generated ultrasonic vibration can be evenly applied to the weld, and the ultrasonic sound flow and cavitation effect can evenly promote the heat and mass transfer of the molten pool and the increase of nucleation points to achieve uniform treatment of the annular weld.

[0027] Preferably, ultrasonic impact needles 7-4 of different lengths are selected according to annular welds of different sizes. Specifically, the ultrasonic transmitting end 7-3 is provided with a mounting hole, the upper part of the ultrasonic impact needle 7-4 is a mounting part, and the depth of the mounting hole is greater than the height of the mounting part. A compression spring is provided in the mounting hole, and the compression spring is located above the ultrasonic impact needle 7-4. The mounting part and the mounting hole are threadedly connected. The threaded connection can adjust the height of the ultrasonic impact needle 7-4 outside the mounting hole. When it is necessary to reduce the height of the ultrasonic impact needle 7-4 outside the mounting hole, more mounting parts can be rotated into the mounting hole. When it is necessary to increase the height of the ultrasonic impact needle 7-4 outside the mounting hole, part of the mounting part can be rotated out of the mounting hole. This can accurately adjust the height of the ultrasonic impact needle 7-4 outside the mounting hole, so as to form an arc between the needles of the ultrasonic impact needle 7-4 that is adapted to the annular weld. The compression spring is used to apply pressure to the ultrasonic impact needle 7-4 to reduce the displacement of the ultrasonic impact needle 7-4 in the mounting hole during operation. At the same time, according to the process requirements, when only part of the ultrasonic impact needles 7-4 are required to work, the mounting parts of the ultrasonic impact needles 7-4 that do not need to work are screwed more into the mounting holes, so that the needles of the ultrasonic impact needles 7-4 that do not need to work are separated from the surface of the workpiece. In this process, the ultrasonic impact needles 7-4 that do not need to work do not need to be removed from the ultrasonic transmitting end 7-3, and all ultrasonic impact needles 7-4 are still installed on the ultrasonic transmitting end 7-3. This is useful for improving work efficiency.

[0028] An ultrasonic impact needle 7-4 is installed in each mounting hole. The distance between the edges of adjacent mounting holes is less than 1 mm. In this way, the ultrasonic impact needles 7-4 installed on the ultrasonic transmitting end 7-3 are closely spaced, thereby improving the ultrasonic vibration effect.

[0029] By selecting ultrasonic impact needles 7-4 of appropriate length, they are arranged to form a concave arc to adapt to welds of different diameters, close to the annular weld, and achieve uniform impact on the annular weld. Preferably, the needle tip diameter of the ultrasonic impact needle 7-4 is 3mm. The smaller the diameter of the ultrasonic impact needle 7-4, the greater the possibility that the weld toe will be impacted, and the weld toe will eventually disappear. If the diameter of the ultrasonic impact needle 7-4 is too large, for example, greater than 6mm, the needle tip of the ultrasonic impact needle 7-4 will usually not act on the weld toe, but on the metal material on one side of the weld toe. The weld width of laser welding is relatively small, so an ultrasonic impact needle 7-4 with a smaller diameter is selected.

[0030] When the workpiece 11 is replaced, the ultrasonic impact needle 7-4 is selected according to the diameter of the replaced workpiece 11 and the process requirements. If the number of ultrasonic impact needles 7-4 needs to be increased, the mounting portion of the ultrasonic impact needle 7-4 that has not yet been involved in the work installed on the ultrasonic transmitting end 7-3 is screwed out of the mounting hole, and for all ultrasonic impact needles 7-4 that need to be involved in the work, the mounting portion and the mounting hole adaptation height are readjusted so that the needle heads of all ultrasonic impact needles 7-4 that need to be involved in the work form a concave shape and apply a pressing force to the workpiece 11. If the number of ultrasonic impact needles 7-4 needs to be reduced, the excess ultrasonic impact needles 7-4 are selected from the working ultrasonic impact needles 7-4 located at the ultrasonic transmitting end 7-3, and the mounting portion of the excess ultrasonic impact needles 7-4 is screwed into the mounting hole so that it does not contact the surface of the workpiece 11; for all ultrasonic impact needles 7-4 that need to be involved in the work, the mounting portion and the mounting hole adaptation height are readjusted so that the needle heads of all ultrasonic impact needles 7-4 that need to be involved in the work form a concave shape and apply a pressing force to the workpiece 11.

[0031] The method for performing ultrasonic vibration-assisted laser welding of annular welds using the device of the above embodiment or preferred example includes: Step 1, fix the workpiece 11 on the positioning fixture 8, adjust the position of the workpiece 11 by adjusting the positioning fixture moving module 9, so that the workpiece 11 is in the position for spot welding; adjust the position of the laser welding torch 6 by the three-dimensional moving module 4, and use the laser welding torch 6 to spot weld the position of the workpiece 11 to be welded. Preferably, a laser power of 1000W is used to spot weld the workpiece 11. The workpiece 11 to be welded is divided into two sections, and the two sections of the workpiece are connected as a whole by spot welding in step 1. The connection between the two sections of the workpiece forms a circular weld to be welded in the subsequent steps.

[0032] Step 2: Fix one end of the workpiece 11 after spot welding in the four-jaw self-centering chuck 10, and place the tip 5 against the other end of the workpiece 11; adjust the laser welding torch 6 spot to align with the weld center of the workpiece 11 through the three-dimensional moving module 4; adjust the position of the ultrasonic vibration device 7 so that the ultrasonic impact needle 7-4 contacts the weld center and applies a clamping force. Preferably, a laser power of 1200W is used to weld the annular weld of the workpiece 11.

[0033] The two sections of the workpiece are spot welded together through step 1. Then the spot-welded workpiece 11 is taken out from the positioning fixture 8 and installed between the four-jaw self-centering chuck 10 and the top 5. The position of the laser welding torch 6 is adjusted by the three-dimensional moving module 4 so that the light spot of the laser welding torch 6 is aligned with the center of the weld of the workpiece 11. The position of the ultrasonic vibration device 7 is adjusted by the three-dimensional moving module 4 so that the ultrasonic impact needle 7-4 contacts the center of the weld and applies a clamping force. If the ultrasonic impact needle 7-4 does not apply a clamping force to the weld, and only the surface of the needle contacts the workpiece, the ultrasonic vibration generated cannot effectively act on the weld. After the needle tip of the ultrasonic impact needle 7-4 contacts the workpiece 11, the three-dimensional moving module presses downward in the Z direction by 0.04 to 0.05 mm, so that the ultrasonic impact needle 7-4 applies a clamping force to the weld.

[0034] Step 3, start the four-jaw self-centering chuck 10, the ultrasonic generator 13 and the laser generator 3, use the four-jaw self-centering chuck 10 to drive the workpiece 11 to rotate, and perform ultrasonic vibration-assisted annular weld laser welding.

[0035] In step 3, the four-jaw self-centering chuck 10 is used to drive the workpiece 11 to rotate, and the laser generator 3 performs laser welding on the to-be-welded area of ​​the workpiece 11. The ultrasonic generator 13 performs ultrasonic vibration on the weld.

[0036] Preferably, step 3 specifically includes: first turning on the four-jaw self-centering chuck 10 and the ultrasonic vibration device 7, then turning on the laser generator 3, and first welding and then vibrating the same position of the annular weld to be welded on the workpiece 11.

[0037] In step 3, preferably, the ultrasonic vibration frequency of the ultrasonic generator 13 is 20 kHz, the amplitude is 20 μm, the rated power is 3000W, the actual adjustable power is 900-2100W, and the adjustment accuracy is 30W. The acoustic flow and cavitation effects generated by high-frequency ultrasonic impact produce strong shock waves on the molten pool during the welding process, generate local high temperature and high pressure, break up the primary coarse crystals and growing dendrites, thereby increasing the nucleation points, improving the nucleation rate, and refining the grains. At the same time, high-frequency ultrasonic impact promotes the flow of liquid in the molten pool, makes the elements and temperature distribution of the molten pool more uniform, and suppresses welding defects.

[0038] When ultrasonic vibration is applied during welding, after a plurality of ultrasonic impact needles 7-4 are installed on the ultrasonic transmitting end 7-3, the needle heads of the ultrasonic impact needles 7-4 are closely attached to the weld and apply a pressing force to the weld, so that the acoustic flow and cavitation effects generated by the ultrasound can be evenly applied to the weld, thereby homogenizing the microstructure of the weld, improving the mechanical properties of the annular weld, and reducing the residual stress of the annular weld.

[0039] For the same position of the annular weld to be welded on the workpiece 11, welding is performed first and then vibration is performed. That is to say, for the same position of the annular weld, the laser welding torch 6 is first used to weld to form a weld. As the workpiece 11 rotates, the same position of the annular weld rotates to the bottom of the ultrasonic vibration device 7, and the ultrasonic vibration device 7 generates a strong shock wave to the molten pool that has not yet completely solidified inside the weld. When the molten pool has not yet completely solidified, the acoustic flow and cavitation effect generated by the high-frequency ultrasonic shock generated by the ultrasonic vibration device 7 are used to generate a strong shock wave to the molten pool during the welding process, which promotes heat and mass transfer and the increase of nucleation points, refines the grains, reduces residual stress, and improves the mechanical properties of the weld.

[0040] The distance between the laser emission head of the laser welding torch 6 and the needle head of the ultrasonic impact needle 7-4 is 10-20 mm, ensuring that the ultrasonic impact needle 7-4 acts on the thermoplastic area that has not yet completely solidified after welding.

[0041] Step 4: After welding is completed, turn off the laser generator 3, the ultrasonic generator 13 and the four-jaw self-centering chuck 10 in sequence.

[0042] In the above method, after the positions of the laser welding torch 6 and the ultrasonic vibration device 7 are adjusted by the three-dimensional moving module 4 in step 2, in step 3, the positions of the laser welding torch 6 and the ultrasonic vibration device 7 remain unchanged, and the four-jaw self-centering chuck 10 drives the workpiece 11 to rotate. In this way, the workpiece is rotated at a constant speed, the weld is heated evenly, and the operation is simple.

[0043] Preferably, in step 2, the angle between the laser welding torch 6 and the workpiece 11 is 15°. This is to prevent the workpiece surface from reflecting the light source and damaging the laser welding torch 6. Preferably, the angle between the ultrasonic impact needle 7-4 and the workpiece 11 is 20-40°. This is to maximize the intensity of the reflected longitudinal and transverse waves of the ultrasound in the weld.

[0044] Preferably, in step 2, adjusting the position of the ultrasonic vibration device 7 includes: adjusting the arrangement arc of the ultrasonic impact needle 7-4 according to the diameter of the workpiece 11, so that the needle tip of the ultrasonic impact needle 7-4 is close to the weld and applies a clamping force to the weld.

[0045] Preferably, in step 3, the welding speed is 4 mm / s. Selecting 4 mm / s results in better forming effect and fewer welding defects.

[0046] In the above method, during the welding process, the workpiece 11 is driven to rotate by the rotation of the four-jaw self-centering chuck 10, and the positions of the laser welding torch 6 and the ultrasonic vibration device 7 remain fixed, so as to realize the ultrasonic vibration during the annular weld laser welding process. The ultrasonic vibration is applied as the welding position moves, and is not affected by the size of the welded workpiece.

[0047] The basic principles, main features and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above specific embodiments, and the descriptions in the above specific embodiments and the specification are only for further illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed for protection.

Claims

1. A device for laser welding annular welds assisted by ultrasonic vibration during welding, characterized in that: It comprises a laser water cooling box (1), a welding platform (2), a laser generator (3), a three-dimensional mobile module (4), a top (5), a laser welding torch (6), an ultrasonic vibration device (7), a positioning tool (8), a positioning tool mobile module (9), a four-jaw self-centering chuck (10), a mobile module controller (12) and an ultrasonic generator (13), wherein: The three-dimensional movable module (4), the center (5), the positioning tool movable module (9) and the four-jaw self-centering chuck (10) are respectively connected to the welding platform (2), and the center (5) and the four-jaw self-centering chuck (10) are coaxially arranged relative to each other; the three-dimensional movable module (4) and the positioning tool movable module (9) are respectively connected to the movable module controller (12) through wires; the laser welding torch (6) and the ultrasonic vibration device (7) are respectively connected to the three-dimensional movable module (4); the ultrasonic vibration device (7) is connected to the ultrasonic generator (13) through a wire; the laser water cooling box (1) is connected to the laser welding torch (6) through a water pipe; the laser generator (3) is connected to the laser welding torch (6) through a wire; and the positioning tool (8) is fixedly connected to the positioning tool movable module (9).

2. The device according to claim 1, characterized in that During operation, a workpiece (11) is positioned between the center (5) and the four-jaw self-centering chuck (10), and the weld to be welded on the workpiece (11) is an annular weld.

3. The device according to claim 1, characterized in that The three-dimensional moving module (4) adopts a first ball screw pair, which is driven by a first servo motor to move, with a repeat positioning accuracy of 0.01 mm, an adjustable movement speed range of 0 to 100 mm / s, and an adjustment accuracy of 0.01 mm / s; wherein the effective stroke of the horizontal X-direction guide rail is 800 mm, the effective stroke of the horizontal Y-direction guide rail is 500 mm, the effective stroke of the vertical Z-direction guide rail is 600 mm, and the vertical Z-direction guide rail has a load-bearing capacity of 50 kg.

4. The device according to claim 1, characterized in that The positioning tool moving module (9) adopts a second ball screw pair, which is driven by a second servo motor to move. The repeat positioning accuracy is 0.01 mm, the adjustable movement speed range is 0-100 mm / s, the adjustment accuracy is 0.01 mm / s, the effective stroke is 800 mm, and the maximum load-bearing capacity in the vertical direction is 30 kg.

5. The device according to claim 2, characterized in that The ultrasonic vibration device (7) comprises an ultrasonic transducer (7-1), an ultrasonic horn (7-2), an ultrasonic transmitting end (7-3) and an ultrasonic impact needle (7-4); the ultrasonic transducer (7-1) is connected to an ultrasonic generator (13) via a wire; the ultrasonic horn (7-2) is connected to the ultrasonic transducer (7-1) via a thread; the bottom of the ultrasonic horn (7-2) is the ultrasonic transmitting end (7-3); the connecting end of the ultrasonic impact needle (7-4) is connected to the ultrasonic transmitting end (7-3); and the needle head of the ultrasonic impact needle (7-4) faces the workpiece (11).

6. The device according to claim 5, characterized in that The ultrasonic transmitting end (7-3) is a concave surface; there are at least three ultrasonic impact needles (7-4), the needle heads of all the ultrasonic impact needles (7-4) form a concave shape, and the needle heads of the ultrasonic impact needles (7-4) are in contact with the surface of the workpiece (11).

7. The device according to claim 5, characterized in that The needle tip diameter of the ultrasonic impact needle (7-4) is 3 mm.

8. A method for laser welding annular welds with ultrasonic vibration during welding, characterized in that: The method comprises: Step 1, fix the workpiece (11) on the positioning fixture (8), and adjust the position of the workpiece (11) by adjusting the positioning fixture moving module (9) so that the workpiece (11) is in a position for spot welding; The position of the laser welding torch (6) is adjusted by means of a three-dimensional movable module (4), and the laser welding torch (6) is used to perform spot welding positioning on a position of a workpiece (11) to be welded; Step 2, fix one end of the workpiece (11) after spot welding in a four-jaw self-centering chuck (10), and at the same time, place the tip (5) against the other end of the workpiece (11); adjust the laser welding torch (6) spot to align with the center of the weld of the workpiece (11) through the three-dimensional moving module (4); adjust the position of the ultrasonic vibration device (7) so that the ultrasonic impact needle (7-4) contacts the center of the weld, and apply a pressing force; Step 3, starting the four-jaw self-centering chuck (10), the ultrasonic generator (13) and the laser generator (3), using the four-jaw self-centering chuck 10 to drive the workpiece (11) to rotate, and performing ultrasonic vibration-assisted annular weld laser welding; Step 4: After welding is completed, the laser generator (3), the ultrasonic generator (13) and the four-jaw self-centering chuck (10) are turned off in sequence.

9. The method according to claim 8, characterized in that The step 3 specifically comprises: firstly turning on the four-jaw self-centering chuck (10) and the ultrasonic vibration device (7), then turning on the laser generator (3), and first welding and then vibrating the same position of the annular weld to be welded on the workpiece (11).

10. The method according to claim 8, characterized in that In the step 2, adjusting the position of the ultrasonic vibration device (7) includes: adjusting the arrangement arc of the ultrasonic impact needle (7-4) according to the diameter of the workpiece (11), so that the needle head of the ultrasonic impact needle 7-4 is closely attached to the weld and a pressing force is applied to the weld.

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