阅读说明：本技术 一种高功率激光焊接镁合金厚板的方法与系统 (Method and system for welding magnesium alloy thick plate by high-power laser ) 是由 李康为 张明军 李河清 张焱 毛聪 于 2020-12-30 设计创作，主要内容包括：本发明公开一种高功率激光焊接镁合金厚板的方法,包括如下步骤：步骤1、提供需要焊接的第一工件与第二工件；步骤2、将工件对接并夹紧；步骤3、提供三光束激光焊接系统,激光头固定于机械手末端；步骤4、启动激光焊接系统,第一激光头的激光束垂直辐照工件对接面,第二、第三激光头倾斜辐照于焊缝两侧。步骤5、开启等离子体检测仪,检测等离子体的尺寸,反馈至功率调节器。步骤6、机械手夹持三个激光头,和等离子体检测仪同步向前运动。步骤7、当机械手运动到焊缝末端时,完成焊接过程。本发明还公开一种高功率激光焊接镁合金厚板的系统。相对于现有技术,本发明可以有效解决因高功率深熔焊接产生的等离子体对入射激光造成的屏蔽问题。(The invention discloses a method for welding a magnesium alloy thick plate by high-power laser, which comprises the following steps: step 1, providing a first workpiece and a second workpiece which need to be welded; step 2, butting and clamping the workpieces; step 3, providing a three-beam laser welding system, wherein a laser head is fixed at the tail end of a manipulator; and 4, starting the laser welding system, wherein the laser beam of the first laser head vertically irradiates the butt joint surface of the workpiece, and the second laser head and the third laser head obliquely irradiate the two sides of the welding seam. And 5, starting a plasma detector, detecting the size of the plasma, and feeding the size back to the power regulator. And 6, clamping the three laser heads by the manipulator, and synchronously moving the three laser heads forwards with the plasma detector. And 7, finishing the welding process when the manipulator moves to the tail end of the welding line. The invention also discloses a system for welding the magnesium alloy thick plate by the high-power laser. Compared with the prior art, the invention can effectively solve the problem of shielding incident laser by plasma generated by high-power deep melting welding.)

1. A method for welding a magnesium alloy thick plate by high-power laser is characterized by comprising the following steps:

step 1, providing a first workpiece and a second workpiece which need to be in butt joint welding.

And 2, butting and clamping the first workpiece and the second workpiece, and ensuring that the two workpieces are on the same horizontal plane.

Step 3, providing a laser welding system, wherein the laser welding system is provided with a laser, a transmission optical fiber, an optical gate, a first operation optical fiber, a second operation optical fiber, a third operation optical fiber, a first laser welding head, a second laser welding head, a third laser welding head, a protective gas nozzle, a plasma/metal steam plume detector, a laser power regulator and a mechanical arm; the first laser welding head is vertically arranged downwards, and the second laser welding head and the third laser welding head are symmetrically distributed on two sides of the first laser welding head in parallel, are transversely distributed in the same plane and are fixed at the tail end of the manipulator through the flange plate.

And 4, starting the laser welding system, starting the protective gas, enabling the first laser welding head to be positioned right above the butt joint, emitting a first laser beam, vertically irradiating the surface of the workpiece, respectively emitting a second laser beam and a third laser beam to be obliquely irradiated on the surface of the workpiece by the second laser welding head and the third laser welding head, synchronously moving forward with the three laser heads, and cooperatively finishing welding.

And 5, starting the plasma/metal steam plume detector, and acquiring the size of the plasma/metal steam plume at the small hole of the first laser beam action area in real time. And monitoring the size of the plasma in real time through a plasma/metal steam plume detector, and when the size of the plasma/metal steam plume exceeds a set value, feeding back the size to the laser power regulator to regulate the output power of the first laser beam, the second laser beam and the third laser beam.

And 6, clamping the first laser welding head, the second laser welding head, the third laser welding head and the plasma/metal steam plume detector by the manipulator to synchronously move along the butt joint so as to implement welding work.

And 7, when the manipulator moves to the tail end of the welding path, closing the laser, closing the protective gas and closing the plasma/metal steam plume detector to finish the welding process.

2. The method for laser welding the magnesium alloy thick plate with high power according to claim 1, wherein the first workpiece and the second workpiece are both magnesium alloy plates with the thickness of 12-20 mm.

3. The method for laser welding magnesium alloy slabs with high power according to claim 1, wherein the power of the first laser beam emitted by the first laser welding head is 5-15 kW, and the power of the second laser beam and the third laser beam emitted by the second laser welding head and the third laser welding head is 0-5 kW.

4. The method for laser welding magnesium alloy thick plates with high power according to claim 1, wherein the included angle formed by the second laser welding head, the third laser welding head and the first laser welding head can be adjusted according to the thickness of a workpiece to be welded, and the adjustment range is 15-45 degrees.

5. The method for high power laser welding of thick magnesium alloy plates according to claim 1, wherein the first laser welding head, the second laser welding head and the third laser welding head are fixed by a robot end square flange and are located in the same plane.

6. The method for laser welding thick magnesium alloy plates with high power according to claim 1, wherein the plasma/metal vapor plume detector comprises an optical filter, a CCD high-speed camera, an image acquisition card, an image processor and the like.

7. The method for high power laser welding of magnesium alloy slabs according to claim 1, wherein the laser power regulator regulates the power of the three laser beams such that the first laser beam and the plasma have a size P₁＝-0.16A²A quadratic relation of +0.44A +14.5, the second laser beam, the third laser beam and the plasma size satisfying P₂＝0.05A²A quadratic relation of +0.09A + 0.3.

Technical Field

The invention relates to the field of laser welding, in particular to a method and a system for high-power laser welding of a magnesium alloy thick plate.

Background

Laser welding has the advantages of non-contact, high efficiency, small thermal deformation and the like, and is widely applied to industries such as automobiles, molds, electronics and the like. With the continuous development of laser technology, the maximum power which can be improved by laser equipment applied in the field of laser welding is continuously improved, and the maximum power reaches the ten-thousand watt level in recent years; in ultra high power laser welding, the extreme energy density due to the extremely high power causes severe evaporation of the material being welded, yielding different characteristics than conventional laser welding at powers below ten thousand watts. Such as the extremely large volume of the photo-plasma/metal vapor plume that occurs during welding, the extremely deep keyhole that exists in the weld pool.

Compared with the common welding method, the biggest difference of laser deep melting welding is that the pinhole effect exists, and laser energy is directly absorbed by the interior of a workpiece material mainly through the pinhole effect; after the pore is formed, there are complex energy balances (i.e., the laser energy absorbed by the pore wall balances the energy lost by thermal conduction through the pore wall and the energy lost by vaporization through the pore wall) and pressure balances (the vaporization pressure balances surface tension, hydrostatic pressure, and hydrodynamic pressure) inside the pore. It is this balance that maintains the stability of the keyhole during laser deep fusion welding. During high-power laser deep fusion welding, molten metal is gasified and ionized to generate plasma/metal steam plumes, the plasma/metal steam plumes have absorption and scattering effects on incident laser, and even shield the laser from being incident to a welding area, so that the energy of the laser which is incident to a small hole is not enough to maintain energy balance and pressure balance, and the small hole is extremely unstable and easy to close.

Because the magnesium alloy has large crystallization temperature area, low melting point, large chemical activity, high heat conductivity coefficient and linear expansion coefficient, welding defects such as air holes, hot cracks, inclusion, coarse grains and the like are easy to appear in the welding process. The welding of magnesium alloy becomes a technical problem restricting the application of magnesium alloy, and especially the welding of high-strength magnesium alloy thick plates (plates or sections with thickness larger than 15 mm) becomes a technical bottleneck of the wide application of magnesium alloy.

In view of the above-mentioned problems occurring during high-power laser deep fusion welding, the following solutions exist in the field of laser welding:

the utility model discloses a 12 months 7 days in 2018, utility model patent with publication number CN 208195928U "binary channels protection air cock and be applicable to the protection gas of ultrahigh power laser welding blow the device", this patent blows off the density of protection gas in order to reduce light-induced plasma through a binary channels protection air cock, has reduced plasma's shielding effect to a certain extent, but improves the stability that the protection air current that blows can reduce the molten bath, influences welding effect, consequently has certain defect.

The invention discloses a high-power laser welding plasma restraining method which is published in 8, 4 and 2020 and has the publication number of CN 111482699A, and the invention adopts the matching of a group of air injection devices and air suction devices to synchronously absorb plasma in the welding process.

The invention discloses an invention patent with publication number CN 109483053A of 'a laser hybrid welding process method of a high-strength magnesium alloy thick plate' published in 3.19.2019.A double-Y-shaped groove form with a truncated edge is adopted for a welding joint groove, the method improves the quality and the performance of the welding joint to a certain extent, but the complicated pretreatment process greatly prolongs the working time and the cost, and is not beneficial to large-scale production.

It can be seen that in the prior art, the plasma/metal steam plume existing outside the small hole is removed strongly, and the method not only can interfere the welding pool, but also has the defects of poor effect, poor adaptability and the like; therefore, a method and a system for high power laser welding of magnesium alloy thick plates with good adaptability, easy control and good welding effect are needed.

Disclosure of Invention

The invention provides a method and a system for welding a magnesium alloy thick plate by high-power laser, aiming at the problem that plasma/metal steam plume generated when the magnesium alloy thick plate is welded by high-power laser deep melting shields incident laser to cause instability in the welding process, and the method and the system have good welding effect.

The invention provides a method for welding a magnesium alloy thick plate by high-power laser, which comprises the following steps:

step 1, providing a first workpiece and a second workpiece which need to be in butt joint welding.

And 2, butting and clamping the first workpiece and the second workpiece, and ensuring that the two workpieces are on the same horizontal plane.

Step 3, providing a laser welding system, wherein the laser welding system is provided with a laser, a transmission optical fiber, an optical shutter, a first operation optical fiber, a second operation optical fiber, a third operation optical fiber, a first laser welding head, a second laser welding head, a third laser welding head, a protective gas nozzle, a plasma/metal steam plume detector, a laser power regulator and a mechanical arm; the first laser welding head is vertically arranged downwards, and the second laser welding head and the third laser welding head are symmetrically distributed on two sides of the plasma/metal steam plume in parallel, are transversely distributed in the same plane and are fixed at the tail end of the manipulator through a flange plate.

And 4, starting the laser welding system, starting the protective gas, enabling the first laser welding head to be positioned right above the butt joint, emitting a first laser beam, vertically irradiating the surface of the workpiece, and respectively emitting a second laser beam and a third laser beam to be obliquely irradiated on the surface of the workpiece by the second laser welding head and the third laser welding head.

And 5, starting the plasma/metal steam plume detector, and acquiring the size of the plasma/metal steam plume at the small hole of the first laser beam action area in real time.

And 6, clamping the first laser welding head, the second laser welding head, the third laser welding head and the plasma body/metal steam plume detector by the manipulator to synchronously move along the butt joint so as to implement welding work.

And 7, when the manipulator moves to the tail end of the welding path, closing the laser, closing the protective gas and closing the plasma/metal steam plume detector to finish the welding process.

In one embodiment, in step 1, the material of the first workpiece and the second workpiece is magnesium alloy.

Further, the thickness of the first workpiece and the second workpiece is 12-20 mm.

In one embodiment, in step 3, the laser power of the laser welding system is 10 to 20 kW.

In one embodiment, in step 3, in the laser welding system, the included angle α formed by the second laser beam and the third laser beam with the center line of the first laser beam can be adjusted according to the thickness of the plate.

Furthermore, the adjusting range of the included angle alpha is 15-45 degrees.

In one embodiment, in step 3, the plasma/metal vapor plume detector includes an optical filter, a CCD high-speed camera, a pattern acquisition card, and a pattern processor.

In one embodiment, in step 4, the power of the first laser beam is 5 to 15kW, and the power of the second laser beam and the power of the third laser beam are 0 to 5 kW.

In one embodiment, in step 4, during laser welding, the second laser beam and the third laser beam form the second small hole, and the end of the third small hole is located in the middle of the first small hole formed by the first laser beam.

In one embodiment, in step 5, during laser welding, the high-speed camera takes a picture in real time, sends the picture to the image processor, judges the size, and when the size of the plasma/metal vapor plume is detected to be larger than a set value, the power of the second laser beam and the third laser beam is increased and the power of the first laser beam is reduced by feeding back the power regulator.

Further, the first laser beam power P₁The change rule along with the plasma/metal steam plume size A follows the following relation:

P₁＝-0.16A²+0.44A+14.5 (1)

further, the power P of the second laser beam₂Power P of third laser beam₃According to plasma/metal vapour plume size AThe change law follows the following relation:

P₂＝0.05A²+0.09A+0.3 (2)

P₃＝0.05A²+0.09A+0.3 (3)

the invention also provides a welding system for high-power laser welding of the magnesium alloy thick plate, which comprises a laser, a transmission optical fiber, an optical gate, a first operation optical fiber, a second operation optical fiber, a third operation optical fiber, a first laser welding head, a second laser welding head, a third laser welding head, a protective gas nozzle, a plasma/metal steam plume detector, a laser power regulator and a manipulator, wherein the transmission optical fiber is arranged on the laser; the first laser welding head, the second laser welding head and the third laser welding head are fixed at the tail end of the manipulator through the flange plate.

In one embodiment, the laser emitted by the laser is split by the optical shutter and transmitted to the first laser welding head, the second laser welding head and the third laser welding head through the first operating optical fiber, the second operating optical fiber and the third operating optical fiber respectively.

In one embodiment, the angles between the second laser welding head, the third laser welding head and the first laser welding head which are fixed on the flange plate at the tail end of the manipulator can be adjusted in real time according to the thickness of a workpiece to be welded, and the adjustment range of the angles is between 10 and 45 degrees.

In one embodiment, the plasma/metal vapor plume detector comprises an optical filter, a CCD high-speed camera lens and an image processor, the laser welding head synchronously moves forwards, the high-speed camera shoots pictures in real time through the optical filter, the pictures are sent to the image processor to judge the size, when the size of the plasma cloud is detected to be larger than a set value, the pictures are fed back to the power regulator, and the output power of the first laser beam, the second laser beam and the third laser beam is regulated.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention adds a second laser beam and a third laser beam which are parallel on the basis of welding a first laser beam, reduces the output power of the first laser beam in real time according to the size of plasma/metal steam plume above the action area of the first laser beam in the laser welding process, simultaneously increasing the output power of the second laser beam and the third laser beam, so that the energy of the second laser beam and the third laser beam effectively compensates the power drop of the first laser beam, the energy balance and the pressure balance in the welding small hole are maintained, the laser welding process is stably carried out, and the energy transmission attenuation and even interruption of the laser beam caused by the shielding effect of the ultra-large plasma/metal steam plume on the first laser beam in the high-power welding process are avoided, so that the energy and the pressure distribution in the laser welding small hole are unbalanced to cause the collapse of the small hole.

2. According to the invention, on the basis of welding by the first laser beam, the second laser beam and the third laser beam which are arranged in parallel are additionally arranged, so that the assembly gap of the butt joint of the thick plate is greatly improved, and the engineering adaptability of the welding process is better.

Drawings

FIG. 1 is a schematic view of a laser welding process for a magnesium alloy slab according to the present invention;

FIG. 2 is a schematic cross-sectional view of a conventional laser welded magnesium alloy slab;

FIG. 3 is a schematic cross-sectional view of a welding process of the method of the present invention;

FIG. 4 is a graph of the output power of the first, second and third laser beams versus the size of the plasma/metal vapor plume during the welding process of the present invention;

in the figure 1: 1. the device comprises a first workpiece 2, a second workpiece 3, a laser 4, a transmission optical fiber 5, a shutter 6, a first operating optical fiber 7, a second operating optical fiber 8, a third operating optical fiber 9, a first laser welding head 10, a second laser welding head 11, a third laser welding head 12, a first laser beam 13, a second laser beam 14, a third laser beam 15, a protective gas nozzle 16, a protective gas cylinder 17, an optical filter 18, a CCD high-speed camera 19, a laser power regulator 20, a mechanical hand

FIG. 2: 1. first workpiece 2, second workpiece 3, molten pool 4, orifice 5, plasma cloud 6, laser beam

FIG. 3: 1. a first workpiece 2, a second workpiece 3, a melt pool 4, a first aperture 5, a second aperture 6, a third aperture 7, a plasma cloud 8, a first laser beam 9, a second laser beam 10, a third laser beam

Detailed Description

The technical solution of the present invention will be described in detail with reference to the accompanying drawings 1-4 and the specific embodiments.

In the embodiment of the present invention, as shown in fig. 1 to 4, a high power laser thick plate welding method includes the following steps.

Step 1, providing a first workpiece 1 and a second workpiece 2 which need to be subjected to deep fusion welding, wherein the first workpiece 1 and the second workpiece 2 are both magnesium alloy plates and can be prepared and formed by a machining method. In this embodiment, the thickness of the first workpiece 1 and the second workpiece 2 is 12 to 20 mm.

And 2, removing impurities on the upper and lower surfaces of the first workpiece 1 and the second workpiece 2, and accurately butting and clamping the first workpiece 1 and the second workpiece 1 to ensure that the first workpiece 1 and the second workpiece 2 are tightly attached, namely the gap between the butting plates is zero.

And 3, providing a laser welding system, wherein the laser welding system is provided with a laser 3, a transmission optical fiber 4, an optical shutter 5, a first operating optical fiber 6, a second operating optical fiber 7, a third operating optical fiber 8, a first laser welding head 9, a second laser welding head 10, a third laser welding head 11 and a protective gas nozzle 15.

Step 4, providing a plasma cloud detector which comprises an optical filter 17, a CCD high-speed camera 18, an image acquisition card and an image processor; the light emitted by the plasma firstly passes through a neutral attenuation filter to linearly attenuate the light intensity, then passes through an interference filter attached to the surface of the CCD to obtain a light intensity signal value under a single wavelength, and finally the light signal is transmitted to a CCD image sensor through a lens.

And 5, providing a laser power regulator 19, and when the plasma detection device detects that the size of the plasma/metal steam plume reaches a set value, transmitting a signal to a feedback device, reducing the energy output of the first laser welding head 9, and increasing the energy output of the second laser welding head 10 and the third laser welding head 11.

And 6, clamping the first laser welding head 9, the second laser welding head 10 and the third laser welding head 11 by the manipulator 20, and synchronously moving the plasma/metal steam plume detectors 17-18 along the butt joints to implement welding work.

And 7, when the manipulator moves to the tail end of the butt joint, turning off the laser, turning off the protective gas and turning off the plasma/metal steam plume detector to finish the welding process.

The first laser welding head 9 outputs a first laser beam 12 which vertically radiates at the center of the butt joint to form a molten pool; the second laser head 10 and the third laser welding head 11 are arranged side by side and symmetrically distributed to respectively output a second laser beam 13 and a third laser beam 14 to simultaneously act on a welding area. The protective gas nozzle 15 is positioned in front of the molten pool, and 99.995% purity argon is blown out at a flow rate of 15-30L/min to act on a welding central area.

The first laser welding head 9, the second laser welding head 10 and the third laser welding head 11 are fixed by a flange 20 at the end of the robot so as to be in the same plane. The included angles between the second laser welding head 10 and the first laser welding head 9 and between the third laser welding head 11 and the first laser welding head 9 are alpha, and the included angles alpha can be adjusted within the range of 10-45 degrees according to the thickness of a workpiece to be welded, so that the tail ends of the second small hole and the third small hole formed by the second laser beam 13 and the third laser beam 14 are just positioned in the middle of the first small hole formed by the first laser beam 12, and the energy is injected for maintaining the energy balance and the pressure balance of the first small hole.

The CCD lens 6 and the optical filter 7 in front of the CCD lens in the plasma detection device focus on the plasma generated by ionization above the molten pool due to drastic temperature change, the camera takes a picture in real time, the picture is sent to the image processor, the size of the plasma cloud is judged, if the size exceeds a set value, the plasma cloud shielding is considered to appear, and at the moment, the information laser power regulator 19 increases the power of the second laser beam 13 and the third laser beam 14, and reduces the power of the first laser beam 12.

The embodiment of the invention also provides a high-power laser thick plate welding system which comprises a laser 3, a transmission optical fiber 4, an optical shutter 5, a first operating optical fiber 6, a second operating optical fiber 7, a third operating optical fiber 8, a first laser welding head 9, a second laser welding head 10 and a third laser welding head 11.

The laser beams focused and emitted by the first laser welding head 9 vertically radiate to the center of the butt joint, the power of the laser beams is 10-15 kW, and the laser beams focused and emitted by the second laser welding head 10 and the third laser welding head 10 are arranged side by side along the welding direction and are symmetrically distributed, and the laser beams are auxiliary laser beams and have the power of 0-5 kW.

Optionally, the laser welding system further includes a second laser welding head 10, a third laser welding head 11 and the first laser welding head 9, which can be adjusted to have an included angle α according to the thickness of the welded workpiece, and the adjustment range of the included angle α is 10 ° to 45 °.

Optionally, the laser welding system further comprises a shielding gas nozzle 15, 99.995% argon can be blown out to act on the welding center area, and the flow range of the argon is 15-30L/min.

Optionally, the laser welding system further includes a plasma detection device, which includes an optical filter 17, a CCD high-speed camera 18, and a corresponding image acquisition card and an image processor; the CCD high-speed camera 18 shoots a picture in real time through the optical filter 17, the picture is transmitted to the image acquisition card, the size of the plasma is judged by the image processor, if the size exceeds an initial set value, the plasma cloud shielding is considered to be generated, and the information is fed back to the laser power adjusting system.

Optionally, the laser welding system further comprises a laser power regulator 19 that can regulate the power output of the first laser welding head 9, the second laser welding head 10, and the third laser welding head 11 in real time, minimizing unnecessary energy consumption.

The embodiment of the invention adds the second laser beam and the third laser beam which are parallel on the basis of the welding of the first laser beam, reduces the output power of the first laser beam in real time according to the size of the plasma/metal steam plume above the action area of the first laser beam in the laser welding process, simultaneously increasing the output power of the second laser beam and the third laser beam, so that the energy of the second laser beam and the third laser beam effectively compensates the power drop of the first laser beam, the energy balance and the pressure balance in the welding small hole are maintained, the laser welding process is stably carried out, and the energy transmission attenuation and even interruption of the laser beam caused by the shielding effect of the ultra-large plasma/metal steam plume on the first laser beam in the high-power welding process are avoided, so that the energy and the pressure distribution in the laser welding small hole are unbalanced to cause the collapse of the small hole.