Vacuum laser welding system and method

Abstract

This invention provides a vacuum laser welding system and method. By placing the workpiece to be welded completely in a vacuum environment, plasma generation during the laser welding process is suppressed. A reflective device is used to reflect a portion of the laser light penetrating the workpiece to the back of the workpiece, promoting the formation of the back of the weld and further suppressing plasma, increasing the weld penetration depth, and achieving a good weld formation effect. This method ensures the quality of laser welding while also improving welding efficiency and the service life of the welding equipment.

Description

Technical Field

[0001] This invention relates to the field of laser welding technology, and more specifically to a vacuum laser welding system and method. Background Technology

[0002] Aluminum alloys, widely used in aerospace, automotive, and defense industries, possess excellent electrical and thermal conductivity, high specific strength and stiffness, as well as good corrosion resistance and machinability. However, during high-power laser deep penetration welding, the high-energy-density laser beam causes the metal material to rapidly vaporize, forming a keyhole in the laser-affected area of ​​the base material. A large amount of metal vapor is ejected outward from the keyhole, and some of the metal gas atoms and protective gas molecules ionize after absorbing laser energy, forming photo-induced plasma.

[0003] Plasma contains a large number of charged particles and unionized metal vapor particles. When a laser, as an electromagnetic wave, propagates within plasma, it interacts with these particles, resulting in macroscopic loss effects such as absorption, scattering, and refraction, which in turn affect weld formation. This phenomenon, where plasma alters the quality of the welding laser beam, reduces the energy of the laser reaching the workpiece surface, and even interrupts the welding process, preventing the achievement of deeper penetration welds, is called the "plasma shielding effect" in laser welding.

[0004] Currently, there are many methods for controlling photo-induced plasma during laser welding, such as laser oscillation, pulsed laser welding, and side-blown auxiliary gas methods. However, these methods are all limited and cannot significantly increase weld penetration or achieve good weld formation. Therefore, a method for stably suppressing plasma is urgently needed.

[0005] Chinese Patent Publication No. CN103658984A discloses a laser welding plasma side-suction negative pressure device and a laser welding system, including a lens module and a negative pressure module connected together. The lens module is used to fix a lens; the negative pressure module is used to create a negative pressure environment above the weld seam. The negative pressure module includes a negative pressure chamber and an extraction pipe communicating with the negative pressure chamber. The lens module is located in the upper part of the negative pressure chamber, and the lower part of the negative pressure chamber can contact the component to be welded. The extraction pipe is located on the side wall of the negative pressure chamber. A negative pressure environment can be created within the negative pressure chamber by connecting an extraction device to the extraction pipe, thereby suppressing the plasma. However, this system has the following drawbacks:

[0006] 1. Because the device creates a negative pressure environment above the weld, it does not provide good protection for the back of the base material, especially for welding highly fluid metals such as aluminum alloys and copper alloys.

[0007] 2. Because the device is fixed above the weld, there are limitations on the size of the workpiece to be welded, and large structural parts cannot be welded; at the same time, when welding other workpieces, the negative pressure device needs to be reinstalled, and multiple workpieces cannot be welded at the same time, resulting in low work efficiency. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a vacuum laser welding system and method. This system performs laser welding in a vacuum environment, suppresses plasma generation during the laser welding process, and uses a reflective device to ensure that the front and back sides of the workpiece to be welded are formed simultaneously, thereby increasing the weld penetration and achieving a good weld formation effect. This method not only ensures the quality of laser welding but also improves welding efficiency and the service life of welding equipment.

[0009] According to a first aspect of the present invention, a vacuum laser welding system is provided, comprising:

[0010] A vacuum chamber, wherein a laser processing head is provided for laser welding of the workpiece to be welded;

[0011] The working platform includes a welding substrate, on which a plurality of welding bosses are provided, and a reflective device is provided between the welding bosses. The workpiece to be welded is placed on the welding bosses, with the first side of the workpiece to be welded facing the laser processing head and the second side of the workpiece to be welded facing the reflective device.

[0012] The reflective device includes a first reflector and a second reflector, which are connected by a rotating shaft. The first reflector and the second reflector rotate around the rotating shaft, and an arbitrary angle between the first reflector and the second reflector is formed between 0 and 180°.

[0013] The welding substrate is transported from the outside into the vacuum chamber via a track, and the workpiece to be welded is placed under the laser processing head;

[0014] Pump unit, used to reduce the pressure inside the vacuum chamber, so as to maintain the required vacuum state inside the vacuum chamber;

[0015] A water-cooling system is used to cool the laser processing head;

[0016] The vacuum measurement and control system monitors the negative pressure value inside the vacuum chamber in real time through a negative pressure sensor and transmits it to the monitoring system.

[0017] The control system is used to control the operation of the welding substrate and pump group, the opening and closing of the vacuum chamber doors and valves, and the real-time monitoring and adjustment of various parameters.

[0018] Preferably, the angle between the first reflector and the second reflector is 30~60°.

[0019] Preferably, both the first reflector and the second reflector are made of copper.

[0020] Preferably, the negative pressure value inside the vacuum chamber is ≤100Pa.

[0021] Preferably, a protective baffle is provided directly below the laser processing head to prevent laser reflection from burning the laser protective lens.

[0022] Preferably, the tilt angle of the laser processing head is 13°.

[0023] Preferably, the working platform is further provided with a base, and a first track is provided on the base. The welding substrate travels along the first track to a second track inside the vacuum chamber.

[0024] Preferably, the vacuum laser welding system is also equipped with a PLC control system for controlling the start and stop of the vacuum laser welding system.

[0025] According to a second aspect of the present invention, a vacuum welding method using the aforementioned vacuum laser welding system is provided, comprising the following steps:

[0026] Check and confirm that all components of the vacuum laser welding system are working properly. After confirming that they are working properly, adjust the reflector so that the first reflector and the second reflector are at the required angle.

[0027] Place the workpiece to be welded on the welding boss, position the workpiece above the reflector, and align the welding area of ​​the workpiece with the rotating shaft. Use the control system to move the welding substrate along the track into the vacuum chamber, so that the workpiece to be welded is under the laser processing head.

[0028] Adjust the laser spot path and defocusing amount according to the size of the workpiece to be welded, so that the laser processing head is aligned with the part of the workpiece to be welded, thereby determining the initial coordinates of the laser spot and the welding parameters. After inputting the initial coordinates and welding parameters into the control system, close the door of the vacuum chamber, close the air supply valve and argon supply valve, turn on the pump group, adjust the negative pressure in the vacuum chamber to a negative pressure value ≤100Pa, and then start laser welding.

[0029] By using a negative pressure mode ≤100Pa and combining it with a reflective device, the plasma generated by laser welding is suppressed, and the back side of the workpiece to be welded is formed simultaneously.

[0030] Preferably, the welding parameters are as follows:

[0031] Laser power 20-25kW, welding speed 3.0-4.0m / min, defocusing amount -10mm, laser tilt angle 13°.

[0032] Compared with the prior art, the significant advantages of the present invention are as follows:

[0033] The vacuum laser welding system of this invention places the laser processing head in a vacuum chamber and reduces the negative pressure inside the chamber to a vacuum, thereby suppressing plasma and increasing the weld penetration depth, achieving stable and good welding. Simultaneously, a reflector is used to reflect a portion of the laser light penetrating the workpiece to the back of the workpiece. The vast majority of the reflected laser light is reflected to the back of the weld seam, which promotes similar heat input on both sides of the molten pool, reducing the heat input difference and further suppressing plasma, thus promoting weld formation. In this way, welding quality is guaranteed and welding efficiency is improved.

[0034] The vacuum laser welding system of this invention effectively solves the problems of high-temperature plasma seriously affecting welding quality, equipment lifespan, and low efficiency in vacuum welding during high-power laser welding. It can also realize the welding of large components and multiple different parts, thus improving work efficiency. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the vacuum laser welding system of the present invention.

[0036] Figure 2 This is a schematic diagram of the structure of the welding substrate of the present invention.

[0037] Figure 3 This is a schematic diagram of the reflective device of the present invention.

[0038] Figure 4 This is a front view of the weld obtained in Embodiment 1 of the present invention.

[0039] Figure 5 This is a back-side profile of the weld obtained in Embodiment 1 of the present invention.

[0040] Figure 6 This is a front view of the weld seam obtained in Comparative Example 1 of the present invention.

[0041] Figure 7 This is a back-side forming diagram of the weld obtained in Comparative Example 1 of the present invention. Detailed Implementation

[0042] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0043] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described below in more detail, can be implemented in any of a number of ways.

[0044] In the laser welding process of aluminum alloys, in addition to considering the problems caused by the plasma shielding effect, the following issues also need to be considered:

[0045] 1. Because aluminum alloys with the surface oxide film removed have a brighter surface and a higher reflectivity to lasers, the actual laser power applied to the workpiece may be less than the theoretical experimental value, which will cause experimental-theoretical errors.

[0046] 2. In addition, due to the good fluidity of aluminum alloys, back-side forming is often impossible in laser welding, which affects the formation of the weld.

[0047] Therefore, the present invention provides a vacuum laser welding system and method, which suppresses plasma generation during the laser welding process by placing the workpiece to be welded completely in a vacuum environment, and further suppresses plasma and promotes weld formation by reflecting a portion of the laser that penetrates the workpiece to the back of the workpiece through a reflective device.

[0048] To achieve this goal, combined with Figures 1 to 3 In an exemplary embodiment of the present invention, a vacuum laser welding system is provided, which includes a vacuum chamber 100 and a working platform 200.

[0049] like Figure 1 As shown, a laser processing head 110 is provided in the vacuum chamber for laser welding of the workpiece to be welded. One or more laser processing heads 110 can be set as needed, and the tilt angle of the laser processing head is preferably 13°.

[0050] In an optional implementation, the laser processing head is cooled by a water cooling system 300, which is a cooling water device with constant temperature, constant flow and constant pressure. It is connected to the laser head through water pipes and uses coolant to cool the circulating water, thereby reducing the temperature of the laser processing head 110.

[0051] The working platform 200 includes a base 210, on which a first track 211 is provided. The welding substrate 220 travels along the first track 211 to the second track 120 inside the vacuum chamber.

[0052] like Figure 2As shown, the welding substrate 220 is provided with a plurality of welding bosses 221, and a reflective device 222 is provided between the welding bosses 221. At least two welding bosses 221 are provided to support the workpiece 400 to be welded and to suspend the workpiece to be welded. The cavity formed by the welding bosses 221 is used to place the reflective device 222, so that the first surface of the workpiece to be welded faces the laser processing head 110 and the second surface of the workpiece to be welded faces the reflective device 222.

[0053] Combination Figure 2 and Figure 3 As shown, the reflector 222 includes a first reflector 222A and a second reflector 222B. The first reflector 222A and the second reflector 222B are connected by a rotating shaft 222C. The first reflector 222A and the second reflector 222B rotate around the rotating shaft 222C, and an arbitrary angle between the first reflector 222A and the second reflector 222B is formed between 0° and 180°.

[0054] The angle between the first reflector and the second reflector is preferably 30 to 60°. Both the first reflector and the second reflector are preferably made of copper, which makes it easier to reflect the laser.

[0055] After the welder 400 enters the vacuum chamber 100, the area to be welded is placed under the laser processing head 110, so that the area to be welded 410 is aligned with the laser 111 emitted by the laser processing head.

[0056] Thus, during laser welding, while welding the front side of the workpiece, the laser penetrates the workpiece and is reflected to the back side of the workpiece by a reflector, ensuring the formation of the weld pool on the back side and reducing the error between the actual and theoretical laser power.

[0057] In a preferred embodiment, when placing the workpiece 400 to be welded, the part of the workpiece to be welded can be aligned with the rotating shaft 222C, so that the laser, the part to be welded, and the rotating shaft are aligned in pairs, thereby causing most of the reflected laser to be reflected to the back area of ​​the weld, so that the front and back sides of the molten pool obtain similar heat input, reducing the heat input difference, and further suppressing the plasma, thus promoting the formation of the weld.

[0058] The vacuum chamber 100 reduces the pressure inside the vacuum chamber through an external pump set 500, and the negative pressure value inside the vacuum chamber is monitored in real time by a negative pressure sensor set in the vacuum measurement and control system 600. The negative pressure value is ≤100Pa, preferably 30Pa, and the negative pressure value is transmitted to the monitoring system for unified monitoring.

[0059] In an optional embodiment, the vacuum chamber 100 is further provided with an air replenishment valve and an argon replenishment valve, which are used to replenish the required gas through the gas system to adjust the negative pressure inside the vacuum chamber.

[0060] The control system 700 controls the operation of the welding substrate 220 and the pump group 500, the opening and closing of the vacuum chamber door and valves, and monitors and adjusts the real-time changes of various parameters.

[0061] In an optional embodiment, a protective baffle is provided directly below the laser processing head, preferably three in number, and preferably made of copper. Each protective baffle has a through hole in the center for laser penetration. The protective baffles are arranged vertically in sequence, with a gap between each baffle to prevent laser reflection from burning the laser protective lens.

[0062] In an optional implementation, the vacuum laser welding system is further provided with a PLC control system 800 for controlling the start and stop of the vacuum laser welding system.

[0063] In an optional implementation, the vacuum laser welding system also includes a closed-circuit monitoring system for real-time observation of the welding process within the vacuum chamber.

[0064] Preferably, the closed-circuit monitoring system comprises a lighting lamp, three adjustable-focus cameras, a display, and an observation window. Under the illumination of the lighting lamp, images are observed through the cameras and the display, and the welding process is directly observed through the observation window. The observation window is preferably made of high-strength glass.

[0065] In another exemplary embodiment of the present invention, a vacuum welding method employing the aforementioned vacuum laser welding system is provided, comprising the following steps:

[0066] Before the experiment begins, priority should be given to checking whether the vacuum chamber, control system, PLC control system, vacuum measurement and control system, water cooling system, first and second tracks, closed-circuit monitoring system, and pump set are working properly.

[0067] Check and confirm that all components of the vacuum laser welding system are working properly. After confirming that they are working properly, adjust the reflector so that the first reflector 222A and the second reflector 222B are at an angle of 30 to 60 degrees.

[0068] The workpiece 400 to be welded is placed on the welding boss 221, so that the workpiece to be welded is above the reflective device. The welding substrate 220 is driven by the control system 700 to travel through the first track 211 to the second track 120 in the vacuum chamber, so that the workpiece to be welded is under the laser processing head.

[0069] Adjust the laser spot path and defocusing amount according to the size of the workpiece to be welded, so that the laser processing head is aligned with the part of the workpiece to be welded, thereby determining the initial coordinates of the laser spot, that is, the X, Y, and Z axis parameters of the welding starting point, and determining the welding parameters. After inputting the initial coordinates and welding parameters into the control system, close the door of the vacuum chamber, close the air supply valve and argon supply valve, turn on the pump group, adjust the negative pressure in the vacuum chamber to a negative pressure value ≤100Pa, and then start laser welding.

[0070] By using a negative pressure mode ≤100Pa and combining it with a reflective device, the plasma generated by laser welding is suppressed, and the back side of the workpiece to be welded is formed simultaneously.

[0071] In an optional implementation, the welding parameters are as follows:

[0072] Laser power 20-25kW, welding speed 3.0-4.0m / min, defocusing amount -10mm, laser tilt angle 13°.

[0073] The initial coordinates of the laser spot are determined by the laser spot on the workpiece illuminated by the "laser guide beam" of the laser head. The laser head is moved by controlling the handwheel so that the laser spot of the "laser guide beam" reaches the welding start point at the workpiece joint. This start point is the initial coordinate of the laser spot.

[0074] The vacuum laser welding system of the present invention can also be used for vacuum cladding, simply by replacing the welding substrate with a cladding substrate. The vacuum laser welding system and method of the present invention are applicable to, but are not limited to, aluminum alloys.

[0075] To facilitate better understanding, the present invention will be further described below with reference to specific examples, but the process is not limited thereto, and the content of the present invention is not limited thereto.

[0076] Example 1

[0077] Before the experiment begins, priority should be given to checking whether the vacuum chamber, control system, PLC control system, vacuum measurement and control system, water cooling system, first and second tracks, closed-circuit monitoring system, and pump set are working properly.

[0078] After confirming that everything is normal, adjust the reflector so that the first reflector and the second reflector are at a 45° angle.

[0079] A piece of 2A12 aluminum alloy steel, whose oxide film has been removed by an angle grinder, is placed on the welding boss, so that the workpiece to be welded is above the reflector. The control system moves the welding substrate along the first track to the second track in the vacuum chamber, so that the workpiece to be welded is under the laser processing head.

[0080] The workpiece dimensions (200mm×80mm×14mm) were measured using JOG mode, and the laser power was adjusted to 20kW, welding speed to 3.6m / min, defocusing amount to -10mm, welding torch angle to 13°, and spot diameter to 2-3mm according to welding requirements. Then, the initial coordinates of the spot were determined and the initial coordinates and welding parameters were input into the control system.

[0081] Once it is confirmed that there is no one in the vacuum chamber and no foreign objects on the safety door track, the safety door is closed and the closed-circuit monitoring system is turned on via the control panel. The air supply valve and argon supply valve are closed, the chamber is adjusted to vacuum mode, and the large rotary vane pump is turned on. Welding begins when the negative pressure in the chamber reaches 30Pa, and continues until the welding is completed, by observing the negative pressure chamber display screen.

[0082] Formed weld seam, such as Figure 4 and Figure 5 As shown, due to the vacuum state inside the chamber and the low gas content, the laser welding plasma is almost completely suppressed. Furthermore, the reflector reflects a portion of the laser that penetrates the workpiece to be welded back onto the workpiece, ensuring the formation of the back side of the weld pool. The vast majority of the reflected laser light is reflected to the back area of ​​the weld, which will cause the front and back sides of the weld pool to receive similar heat input, reducing the heat input difference and further suppressing the plasma. This results in a weld with a very high aspect ratio, similar to electron beam welding, and significantly increases the welding quality.

[0083] Comparative Example 1

[0084] Welding in an atmospheric environment

[0085] Before the experiment, check that the laser and water chiller are working properly. After confirming that everything is correct, place a piece of 2A12 aluminum alloy of the same size (200mm×80mm×14mm) with the surface oxide film removed directly on the welding platform (without a back reflector). Operate the KUKA robot and adjust the defocus of the laser head to -10mm. Similarly, adjust the laser power to 20kW, welding speed to 3.6m / min, welding torch angle to 13°, and spot diameter to 2-3mm. After adjustment, input the welding parameters into the control system, and then start welding directly until the welding is completed.

[0086] Formed weld seam, such as Figure 6 and Figure 7 As shown, the weld in atmospheric environment has a large amount of spatter, and the weld front and back are unevenly formed with uneven reinforcement. A small number of pores can also be observed.

[0087] As can be seen from the foregoing results, compared with aluminum alloy welding in an atmospheric environment, the welding process using the method of this invention, conducted in a vacuum environment and combined with the reflective device used, results in suppressed plasma and good back-side formation. Therefore, the aluminum alloy weld obtained by this method has excellent shape, a narrower weld, and thus a larger aspect ratio. Due to proper protection of the sheet metal and the near absence of gas, the weld obtained by this method is free of defects such as porosity. Furthermore, it can be seen that welding aluminum alloys in a vacuum environment achieves zero spatter, which is highly beneficial for controlling weld quality.

[0088] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A vacuum welding method for aluminum alloy simultaneous forming of front and back surfaces, characterized by, The method comprises the following steps: A vacuum laser welding system is adopted, which comprises: A vacuum chamber is provided with a laser processing head inside, which is used for laser welding of the workpiece to be welded; A workbench is provided with a welding base plate, and a plurality of welding bosses are arranged on the welding base plate, and a reflecting device is arranged between the welding bosses, the workpiece to be welded is placed on the welding boss, and the first surface of the workpiece to be welded faces the laser processing head, and the second surface of the workpiece to be welded faces the reflecting device; The reflecting device comprises a first reflecting plate and a second reflecting plate, and the first reflecting plate and the second reflecting plate are connected through a rotating shaft, and the first reflecting plate and the second reflecting plate rotate around the rotating shaft; The welding base plate is sent into the vacuum chamber through a track from the outside, and the welding position of the workpiece to be welded is arranged under the laser processing head, and the welding position of the workpiece to be welded is aligned with the rotating shaft, so that the laser, the welding position and the rotating shaft are aligned two by two, and at the same time, an angle of 30-60° is formed between the first reflecting plate and the second reflecting plate, thereby reducing the difference in heat input of the molten pool on the front and back surfaces, further suppressing the plasma, ensuring the welding quality and improving the welding efficiency; A pump group is used to reduce the pressure in the vacuum chamber, so that the required vacuum state is maintained in the vacuum chamber; A water cooling system is used to cool the laser processing head; A vacuum measurement and control system is used to monitor the negative pressure value in the vacuum chamber in real time through a negative pressure sensor, and transmit it to a monitoring system; A control system is used to control the operation of the welding base plate and the pump group, the opening and closing of the vacuum chamber door and the valve, the real-time monitoring and adjustment of various parameters; Check and confirm whether each component of the vacuum laser welding system is working normally, and after confirming that it can work normally, adjust the reflecting device so that the first reflecting plate and the second reflecting plate form the required angle; Place the workpiece to be welded on the welding boss, so that the workpiece to be welded is located above the reflecting device, and the welding position of the workpiece to be welded is aligned with the rotating shaft, and the welding base plate is driven into the vacuum chamber through the track by the control system, so that the workpiece to be welded is located under the laser processing head; According to the size of the workpiece to be welded, adjust the spot path and the defocusing amount, so that the laser processing head is aligned with the welding position of the workpiece, thereby determining the initial coordinates of the laser spot and determining the welding parameters, after inputting the initial coordinates and the welding parameters into the control system, close the door of the vacuum chamber, close the air supplement valve and the argon supplement valve, open the pump group, adjust the negative pressure in the vacuum chamber to be less than or equal to 100 Pa, and then start laser welding; By combining the reflecting device in the mode of negative pressure less than or equal to 100 Pa, the plasma formed by laser welding is suppressed, and the back surface of the workpiece to be welded is formed at the same time.

2. The aluminum alloy face and back simultaneous forming vacuum welding method of claim 1 wherein, The first reflecting plate and the second reflecting plate are both copper reflecting plates.

3. The aluminum alloy face and back simultaneous forming vacuum welding method of claim 1 wherein, A protective baffle is arranged directly below the laser processing head, which is used to prevent the laser reflection from burning the laser protection lens.

4. The aluminum alloy face and back simultaneous forming vacuum welding method of claim 1 wherein, The inclination angle of the laser processing head is 13°.

5. The aluminum alloy face and back simultaneous forming vacuum welding method of claim 1 wherein, The workbench is also provided with a base, and the base is provided with a first track, and the welding base plate is driven onto the second track in the vacuum chamber through the first track.

6. The aluminum alloy face and back simultaneous forming vacuum welding method of claim 1 wherein, The vacuum laser welding system is also provided with a PLC control system, which is used to control the start and stop of the vacuum laser welding system.

7. The aluminum alloy face and back simultaneous forming vacuum welding method of claim 1 wherein, The welding parameters are as follows: Laser power 20-25 kW, welding speed 3.0-4.0 m / min, defocusing amount -10 mm, laser inclination angle 13°. Laser power 20-25 kW, welding speed 3.0-4.0 m / min, defocusing amount -10 mm, laser inclination angle 13°.

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