CN119187889A - A laser arc hybrid welding method based on beam scanning pattern optimization design - Google Patents

Abstract

The invention belongs to the technical field of welding, and particularly relates to a laser arc composite welding method based on an optimal design of a light beam scanning pattern. A laser-arc composite welding method based on an optimal design of a light beam scanning pattern comprises the following steps of S1, preprocessing the welding surfaces of two dissimilar metal plates, placing the two dissimilar metal plates on a welding operation table, setting the positions of welding focal planes, setting parameters of a welding gun and a workpiece to be welded, S2, setting scanning laser-arc welding technological parameters, and finishing welding of the two dissimilar metal plates according to the set technological parameters. The composite welding method can obtain the welding and soldering joint with good weld joint forming and mechanical properties, can ensure that the energy distribution in the whole welding track is more uniform, and reduces welding defects.

Description

Laser arc hybrid welding method based on optical beam scanning pattern optimization design

Technical Field

The invention belongs to the technical field of welding, and particularly relates to a laser arc composite welding method based on an optimal design of a light beam scanning pattern.

Background

With the increasing demand of people for lightweight components and the need to reduce energy consumption in the industries of aerospace, transportation and the like, the importance of dissimilar metal connection is increasingly revealed. For example, in aerospace applications, honeycomb sandwich structures used in aircraft wings require the titanium alloy skin to be joined to an aluminum alloy honeycomb sandwich in the wing box. However, due to the large difference in thermophysical properties between dissimilar metals, the mechanical properties of welded dissimilar joints tend to be related to the characteristics of the brittle intermetallic compound formed at the interface, such as morphology, thickness, and type of brittle intermetallic compound.

There is a lot of research on dissimilar metal welding, including solid phase welding and fusion welding. Friction stir welding is one of the common solid state welding techniques. Friction stir welding has the advantage of avoiding the formation of thick intermetallic compounds by precisely controlling the heat input during the joining process. However, friction stir welding has a relatively narrow process window for obtaining an acceptable joint, and the welding efficiency is lower than fusion welding, which limits its wide industrial application. Laser-arc hybrid welding (LAHW) is one of the most promising fusion welding techniques because it has the advantages of high welding efficiency, good joint quality, strong bridging capability, high flexibility, etc. Moreover, the welding mode can control the laser energy distribution more precisely in a laser beam oscillation mode.

In order to effectively inhibit the formation of a thick intermetallic compound layer during dissimilar metal welding, a scanning laser arc composite welding method based on laser beam scanning pattern optimization design is used, and the laser beam scanning pattern after optimization design is inscribed in a double circle. The optimized graph is not only beneficial to improving the laser energy distribution around the laser oscillation path, but also can enhance the stirring effect of the laser lockhole on the liquid metal in the molten pool, and finally, the welding joint obtains better weld joint forming and better mechanical property

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a laser arc composite welding method based on the optimization design of a light beam scanning pattern, which comprises the following steps of;

S1, preprocessing the welding surfaces of two dissimilar metal plates, placing the two dissimilar metal plates on a welding operation table, setting the position of a welding focal plane, and setting parameters of a welding gun and a workpiece to be welded;

S2, setting scanning laser-arc welding process parameters, and finishing welding of two dissimilar metal plates according to the set process parameters.

Further, the welding in S1 is any one of butt welding and lap welding, and the lap welding needs to set a focal position.

In addition, in the butt welding in the step S1, the two butt-jointed dissimilar metal plates are 6061 aluminum alloy and TC4 titanium alloy, the thickness of the metal plates is 2mm, a layer of brazing filler metal is coated on the welding surface of the high-melting-point metal plates, the brazing filler metal is KAlF ₄, in the lap joint process, the lower part of the lap joint metal plates is 6061 aluminum alloy and the upper part of the lap joint metal plates is AZ31B magnesium alloy, the thickness of the metal plates is 2mm, and pure titanium foil with the thickness of 0.1mm is added between the two plates to serve as an intermediate layer.

Further, in the step S1, parameters between the welding gun and the workpiece to be welded in butt welding comprise an included angle and a light wire distance, wherein the included angle is 50-60 degrees, the light wire distance is 2-3mm, in lap welding, the laser head deflects 5 degrees along the welding direction, and a laser focal plane is positioned at the 4mm position of the upper surface of the magnesium alloy to be welded.

Further, the welding process parameters of the scanning laser and the electric arc in S2 include an included angle between the laser beam and the electric arc welding gun, a defocusing amount of the laser beam, a laser power, a wire feeding speed, a welding speed, an oscillation mode of the laser beam, and parameters of a scanning pattern and a scanning pattern.

Further, during butt welding, the included angle between the laser beam and the arc welding gun is 65 degrees, the defocusing amount of the laser beam is 0mm, the laser power is 2000W, the wire feeding speed is 4.5m/min, the welding speed is 1.5m/min, the oscillation mode of the laser beam is inscribed double-circle scanning laser, the scanning pattern is inscribed double-circle, the radius of the inner circle is 0.25mm, the radius of the outer circle is 0.5mm, and the scanning frequency is 300Hz.

Further, during lap welding, the laser beam deviates from 5 degrees along the welding direction, the defocusing amount of the laser beam is +4mm, the laser power is 3100W, the welding speed is 1.8m/min, the protection air flow is 20L/min, the oscillation mode of the laser beam is 8-shaped scanning laser, the scanning pattern is 8-shaped, the radius of an arc part is 0.2mm, the length of a straight line part is 2mm, and the scanning frequency is 50Hz.

Further, the pretreatment process described in S1 includes sanding the welded surface with sandpaper to remove surface oxide films, followed by wiping the welded surface with acetone to remove surface oil stains and dust.

Further, in the welding process of butt welding of the dissimilar metal materials in S2, the action center of the laser and the electric arc is positioned at one side of the low-melting-point metal material and is 0.8mm away from the high-melting-point metal material.

Advantageous effects

According to the laser welding method based on the optical beam scanning pattern optimization design, the thickness of an intermetallic compound layer formed at the interface of the welded joint can be remarkably reduced by adopting the method for welding the dissimilar metal material, and good weld appearance and excellent mechanical properties are obtained. The laser-arc composite welding is carried out in the laser scanning mode without scanning and after the optimization in the invention, the welding joint obtained by using the internal cutting double-circle scanning mode is beautiful and full in shape, the thickness of an intermetallic compound layer formed at the joint interface is thinned from 5.56 mu m to 1.18 mu m, the thickness is thinned by 79%, the ultimate tensile strength of the joint is improved from 182MPa to 215MPa, and the ultimate tensile strength of the joint is improved by nearly 20%. In lap welding, the problems of uneven heating and uneven reaction in circumferential oscillation laser lap welding are solved. When the oscillation pattern is changed into 8 shapes from round, the uniformity of laser energy distribution is improved by 60%, under the optimized parameters of round radius of 0.2mm and line length of 2mm, the 8-shaped oscillation increases the effective connection width of the interface to 2.4mm, which is approximately 4 times higher than the circumferential oscillation, the intermetallic compound at the interface is more uniformly distributed, the corresponding shearing tension is up to 4.4kN, and the effective connection width is improved by 3.8 times compared with the circumferential oscillation.

Drawings

In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following description will briefly explain the drawings required to be used in the examples, it being understood that the following drawings illustrate only some examples of the present invention and are therefore not to be considered limiting of the scope, and that other related drawings may be obtained from these drawings by those skilled in the art without the inventive effort. In the drawings:

FIG. 1 is a schematic diagram of a scanning laser-arc hybrid welding experimental platform of the present invention;

FIG. 2 is a schematic diagram of the relationship between the laser track and each component of the inscribed double-circle scanning system;

FIG. 3 is a schematic diagram of a cross section of a weld seam welded by dissimilar metals when the inscribed double-circle scanning laser of the invention is not regulated;

FIG. 4 is a graph of intermetallic compound morphology generated at the interface of a dissimilar metal welded joint when the inscribed dual-circle scanning laser of the invention is not modulated;

FIG. 5 is a schematic diagram of the relationship between the 8-shaped scanning laser track and each component of the present invention;

FIG. 6 is a schematic diagram of the design principle of the 8-shaped scanning pattern of the present invention;

FIG. 7 is a schematic diagram of a weld path and laser energy distribution obtained under the figure 8 scan pattern of the present invention;

FIG. 8 effect of the 8-shaped scan pattern of the present invention on weld surface topography and uniformity of intermetallic compounds (IMCs) at the joint interface.

The marks in the figure:

1. 2, a welding machine, 3, a scanning vibrating mirror, 4, a welding robot, 5, a welding gun, 6, a welding wire, 7, a laser beam, 8, an electric arc, 9, a keyhole, 10, a molten pool, 11 and a base metal;

Detailed Description

The technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments 1 to 5 of the present invention and fig. 1 to 8, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The invention provides a laser arc composite welding method based on an optimal design of a light beam scanning pattern, which comprises the following steps of:

Firstly, polishing the welding surfaces of two dissimilar metal plates by using sand paper to remove an oxide film on the surfaces of the plates, wiping the polished surfaces by using acetone to remove oil stains and dust on the surfaces, and coating a layer of brazing filler metal on the welding surfaces of the high-melting-point metal plates when the dissimilar metal materials with larger melting point difference are butt-welded so as to promote wetting and spreading of the low-melting-point materials in the welding process; placing two dissimilar metal plates on a welding operation table in a butt joint mode, and clamping by using a clamp to ensure that the relative positions of the two butt-jointed plates are fixed in the welding process; the method comprises the steps of adjusting the plane position of a welding focus so that the laser focus is positioned on the upper surface of a workpiece to be welded, tilting the laser head by 5 degrees to prevent laser from being burnt by reflection along the original direction, adjusting the included angle between the welding gun and the workpiece to be welded, enabling the included angle to be between 50 degrees and 60 degrees, ensuring that the distance between optical wires is 2-3mm, enabling a laser spot and the tip of a welding wire to be positioned on the same straight line, ensuring that the straight line direction is parallel to the welding direction, moving the whole welding gun and the laser head which are well adjusted to the position perpendicular to the welding direction to one side of a low-melting-point metal plate which is 0.8mm away from a butt joint gap of two plates, when the dissimilar materials with similar melting points are subjected to laser welding in a lap joint mode, enabling the lower part of the lap metal plate to be 6061 aluminum alloy and the upper part to be AZ31B magnesium alloy, enabling the plate thickness to be 2mm, adding pure titanium foil with the thickness of 0.1mm between the two plates to be used as an intermediate layer, setting the focus position, enabling the laser beam to deviate by 5 degrees along the welding direction, enabling the defocusing quantity of the laser beam to be 4mm, enabling the laser power to be 3100, enabling the welding speed to be 1.8m/min, protecting the welding speed to be 20L/min, enabling the gas flow to be 8, enabling the laser beam to be 8 to be in a scanning mode, the radius of the arc part is 0.2mm, the length of the straight line part is 2mm, and the scanning frequency is 50Hz;

S2, setting scanning laser-arc welding process parameters, wherein the process parameters comprise a scanning pattern, a scanning frequency, a scanning amplitude, laser power, a welding speed and a wire feeding speed, the scanning pattern is internally tangent double circles, the scanning pattern is a track formed by scanning laser beams by a vibrating mirror, the scanning frequency is the cycle number of the laser beams to the scanning pattern in unit time, the unit is hertz (Hz), the scanning amplitude is the maximum distance of the scanning pattern in a direction perpendicular to the welding direction, for internally tangent double-circle scanning patterns, the scanning amplitude comprises an inner circle diameter and an outer circle diameter, butt welding of two dissimilar metal plates is completed according to the internally tangent double-circle scanning path parameters, the welding process of dissimilar metal lap welding needs to ensure that laser energy is fully overlapped without an intersection point, laser energy can be uniformly distributed, and the laser scanning path area needs to be ensured to be positioned in the overlapping range of AZ31B magnesium alloy, 6061-T6 aluminum alloy and pure titanium foil.

Example 1

The method comprises the steps of S1, polishing a metal plate welding surface with the thickness of 2mm of 6061 aluminum alloy and TC4 titanium alloy by sand paper to remove an oxidation film on the plate surface, wiping the polished surface by acetone to remove oil stains and dust on the surface, coating a layer of KAlF ₄ on the welding surface of a high-melting-point metal plate to promote wetting and spreading of a low-melting-point material in the welding process, placing the two metal plates in a butt joint mode on a welding operation table, clamping by a clamp to ensure that the two plates are in butt joint in the welding process are fixed in relative positions, adjusting the plane position of a welding focus so that a laser focus is positioned on the upper surface of a workpiece to be welded, tilting the laser head by 5 degrees to prevent laser from being burnt down in the original direction, adjusting an included angle between a welding gun and the workpiece to be welded to be 55 degrees and ensuring that the distance between the laser spots and tips of the welding wires are positioned on the same straight line, moving the welding gun and the whole with the straight line direction parallel to the welding direction, and moving the welding head with the adjusted position relationship to the whole perpendicular to the welding direction to the side of the low-melting-point metal plate butt joint gap by 0.8mm, wherein the positions of the base metal plate are welded on the right side of the welding surface of the workpiece as shown in a figure 2;

s2, setting an included angle between a laser beam and an arc welding gun as 65 degrees, setting the distance between optical wires as 2mm, setting the defocusing amount of the laser beam as 0mm, setting the laser power as 2000W, setting the wire feeding speed as 4.5m/min and the welding speed as 1.5m/min, setting the oscillation mode as inscribed double-circle scanning laser, setting the inner circle radius as 0.25mm, the outer circle radius as 0.5mm and the scanning frequency as 300Hz (the scanning path is shown in the left diagram in FIG. 2), and finishing the butt welding of two dissimilar material metal plates.

As can be seen from fig. 1, the operation platform comprises a fiber laser 1, a welding machine 2, a scanning galvanometer 3, a welding robot 4, a welding gun 5, a welding wire 6, a laser beam 7, an electric arc 8, a keyhole 9, a molten pool 10 and a base metal 11, wherein the specifications are a six-axis robot system, an IPG laser, fronius welding and an IPG D50 swinging laser head.

As can be seen from fig. 3 and 4, after the welding is completed by the above process parameters (ER 4047 aluminum silicon welding wire with a diameter of 1.2mm is used), compared with the weld morphology (fig. 3 a) that the upper surface is slightly collapsed down and the joint interface is obtained without scanning laser, a thicker brittle intermetallic compound layer (fig. 4 a) is generated, the weld (fig. 3 b) obtained by using the inscribed double-circle scanning laser is formed to be beautiful and full, and the thickness of the brittle intermetallic compound (fig. 4 b) formed at the joint interface is obviously thinner by only 1.18 μm. The tensile strength of the welding seam obtained by adopting the inscribed double-circle scanning laser is 215MPa, which is improved by approximately 20 percent compared with that of the welding seam obtained by adopting no scanning laser.

Example 2

The method comprises the steps of S1, polishing a metal plate welding surface with the thickness of 2mm of 6061 aluminum alloy and TC4 titanium alloy by sand paper to remove an oxide film on the surface of a plate, wiping the polished surface by acetone to remove oil stains and dust on the surface, coating a layer of KAlF ₄ on the welding surface of a high-melting-point metal plate to promote wetting and spreading of a low-melting-point material in the welding process, placing the two metal plates in a butt joint mode on a welding operation table, clamping by a clamp to ensure that the two plates are in butt joint, fixing the relative positions of the two plates in the welding process, adjusting the plane position of a welding focus so that a laser focus is positioned on the upper surface of a workpiece to be welded, tilting the laser head by 5 degrees to prevent the laser from being burnt down in the original direction, adjusting an included angle between a welding gun and the workpiece to be welded to be 60 degrees, ensuring that the distance between the laser spots and the tip of the welding wire are positioned on the same straight line, and the straight line direction is parallel to the welding direction, and moving the whole welding gun and the laser head with the adjusted position relation to the side of the low-melting-point metal plate 0.8mm away from the butt joint gap of the two plates;

S2, setting an included angle between a laser beam and an arc welding gun as 65 degrees, setting the distance between optical wires as 2mm, setting the defocusing amount of the laser beam as 0mm, setting the laser power as 2000W, setting the wire feeding speed as 4.5m/min and the welding speed as 1.5m/min, setting the oscillation mode as inscribed double-circle scanning laser, setting the inner circle radius as 0.25mm, the outer circle radius as 0.5mm and the scanning frequency as 300Hz, and finishing butt welding of two dissimilar material metal plates.

Example 3

The method comprises the steps of S1, polishing a metal plate welding surface with the thickness of 2mm of 6061 aluminum alloy and TC4 titanium alloy by sand paper to remove an oxide film on the surface of a plate, wiping the polished surface by acetone to remove oil stains and dust on the surface, coating a layer of KAlF ₄ on the welding surface of a high-melting-point metal plate to promote wetting and spreading of a low-melting-point material in the welding process, placing the two metal plates in a butt joint mode on a welding operation table, clamping by a clamp to ensure that the two plates are in butt joint, fixing the relative positions of the two plates in the welding process, adjusting the plane position of a welding focus so that a laser focus is positioned on the upper surface of a workpiece to be welded, tilting the laser head by 5 degrees to prevent laser from being burnt down in the original direction, adjusting the included angle between a welding gun and the workpiece to be welded to be 50 degrees, ensuring that the distance between the laser spots and the tip of the welding wire to be 2.5mm, and moving the whole welding gun and the laser spot and the welding wire to be on the same straight line, wherein the straight line direction is parallel to the welding direction and the welding direction is perpendicular to the welding direction to the side of the low-melting-point metal plate which is 0.8mm away from the butt joint gap of the two plates;

S2, setting an included angle between a laser beam and an arc welding gun as 65 degrees, setting the distance between optical wires as 2mm, setting the defocusing amount of the laser beam as 0mm, setting the laser power as 2000W, setting the wire feeding speed as 4.5m/min and the welding speed as 1.5m/min, setting the oscillation mode as inscribed double-circle scanning laser, setting the inner circle radius as 0.25mm, the outer circle radius as 0.5mm and the scanning frequency as 300Hz, and finishing butt welding of two dissimilar material metal plates.

Example 4

The method comprises the steps of S1, carrying out laser welding on AZ31B magnesium alloy and 6061-T6 aluminum alloy with the specification of 100X 50X 2mm in a lap joint mode, wherein the AZ31B magnesium alloy is positioned above a joint, the 6061-T6 aluminum alloy is positioned below the joint, adding pure titanium foil with the thickness of 0.1mm at the overlapped part of two dissimilar materials to prevent the magnesium element and the aluminum element from being directly combined in a welding pool to generate brittle intermetallic compounds so as to reduce the performance of the welded joint, polishing the surface of a plate by sand paper before welding to remove an oxide film, wiping the polished surface by acetone to remove oil stains and dust on the surface, then, tilting a laser head by 5 degrees along the welding direction to prevent the laser head from being burnt by reflection in the original direction, and simultaneously adjusting the laser focus to be positioned at a position 2mm away from the upper surface of the AZ31B magnesium alloy (the defocusing amount is +4mm) and ensuring that a scanning pattern is positioned at the overlapped part of the AZ31B magnesium alloy, the 6061-T6 aluminum alloy and the pure titanium foil (shown in figure 5);

S2, setting other laser welding parameters including a welding speed of 1.8m/min, a protective gas flow of 20L/min and a laser scanning pattern (circular scanning and 8-shaped scanning), wherein the laser power is 2.75kW when the circular scanning is adopted, the scanning diameter is 4mm, the scanning frequency is 50Hz, the laser power is 3.1kW when the 8-shaped scanning is adopted, the radius of a circular part is 0.2mm, and the length of a straight line part is 2mm, so that the lap welding of the dissimilar metal materials is completed.

Comparing the lap joints obtained under two different scan patterns after welding was completed, it was found that the uniformity of laser energy distribution was improved by 60% when the beam oscillation mode was changed from circular to 8-shaped, as shown in fig. 7. After the welding is performed by using the 8-shaped scanning pattern after the optimal design, the overlapping joint forms an interface layer with more uniform distribution (see figure 8), and meanwhile, the shearing tension of the whole joint also reaches 4.4kN, which is 3.8 times that of the welding joint by using the circular scanning pattern.

The laser welding has the advantages of high energy density, small heat affected zone, large penetration depth and the like, but has high requirement on welding gap, while the arc welding has strong adaptability to grooves, but has the defects of low energy density, small welding speed, large post-welding deformation and residual stress and the like. And in the range of the distance between the optical wires, the laser heat source and the arc heat source can produce synergistic effect in the laser-arc hybrid welding process. The synergistic effect is to fully exert the advantages of the two heat sources, namely, the bridging capability between workpieces is improved by the laser-electric arc combined welding compared with the laser welding, and the deeper welding seam can be obtained by the laser-electric arc combined welding at a faster welding speed compared with the electric arc welding.

Example 5:

The method comprises the steps of S1, pre-treating 2mm 6061 aluminum alloy and TC4 titanium alloy, wherein the pre-treatment comprises the steps of polishing a welding surface by sand paper to remove surface oxide films, then wiping the welding surface by acetone to remove oil stains and dust on the surface, coating a layer of brazing filler metal on the welding surface of a high-melting-point metal plate when different-melting-point metal materials are welded, wherein the brazing filler metal is KAlF ₄, the lower part of the lap joint metal plate is 6061 aluminum alloy and the upper part of the lap joint metal plate is AZ31B magnesium alloy, the plate thickness is 2mm, pure titanium foil with the thickness of 0.1mm is added between the two plates to serve as an intermediate layer, the two different-material metal plates are placed on a welding operation table in a butt joint mode, the welding focal plane position is set, parameters of a welding gun and a workpiece to be welded are set, when the dissimilar materials with the melting points are welded in a lap joint mode, the focal position is set, the parameters between the welding gun and the workpiece to be welded in a lap joint mode comprise an included angle and a light wire spacing of 50 DEG, and the light wire spacing is 2-3mm;

S2, setting scanning laser-arc welding process parameters in butt welding, wherein the action center of laser and electric arc is positioned at one side of a low-melting-point metal material and is 0.8mm away from a high-melting-point metal material in the butt welding process, the laser is positioned at the middle position above a titanium interlayer in an overlapping area of two dissimilar metals, the distance between the laser focus and the upper surface of a base metal positioned above a joint is 2mm, the included angle between the laser beam and an arc welding gun is 65 degrees, the defocusing amount of the laser beam is 0mm, the laser power is 2000W, the wire feeding speed is 4.5m/min, the welding speed is 1.5m/min, the oscillation mode of the laser beam is any one of scanning laser without scanning and scanning laser with double internal circles, the scanning pattern is double internal circles with the radius of 0.25mm, the external circle radius of 0.5mm, and the scanning frequency is 300Hz.

In lap welding, a contrast test is carried out by adopting 8-shaped scanning laser and conventional circular scanning laser, in order to avoid any intersection point of the 8-shaped scanning pattern in the scanning process, the scanning parameters of the 8-shaped scanning pattern are required to be optimally designed so as to ensure that laser energy is fully overlapped and has no intersection point, and meanwhile, uniformly distributed laser energy can be obtained, wherein the optimized laser parameters comprise laser power 3100W, the radius of an 8-shaped scanning arc section is 0.2mm, and the length of a straight line section is 2mm.

The schematic diagram of the oscillation path shown in fig. 5 is designed for the purpose of eliminating the intersection along the circular oscillation path, and includes two parallel straight lines and an arc at both ends of a connecting line. Then, the oscillation mode is inferred reversely from the assumed oscillation path. The difficulty to be solved is how to achieve the oscillation path of the straight lines L ₁ and L ₂ along the one shown in fig. 6a and 6 b. Since the actual moving speed (V _S) of the laser spot along the oscillation path is the combined speed of the robot welding speed (V ₁) and the galvanometer scanning speed (V ₂), the path portion of the oscillation mode can be solved in reverse according to the target oscillation path shown in fig. 6c and 6 d. Assuming that the value and direction of V ₁ and the direction of V _S (i.e., the direction of the target line) are known, the value and direction of V ₂ can be obtained. The paths of the oscillating pattern obtained by reverse design remain symmetrical after crossing and are connected by a small radius arc. Finally, the reverse design oscillation mode shown in fig. 6e is formed, and is named as an 8-shaped oscillation mode because the shape is similar to the number 8. As shown in fig. 6f, the V ₂ and V ₁ parameter settings to obtain a target 8-shaped oscillation without any intersection along the oscillation path should satisfy the formula:

Wherein V ₁ is the welding speed of the robot, V ₂ is the scanning speed of the vibrating mirror, L is the length of a straight line segment in the 8-shaped scanning path, and r is the radius of an arc part in the scanning path.

The invention provides a laser arc composite welding method based on an optimal design of a light beam scanning pattern, which is suitable for welding dissimilar metal materials and can remarkably improve the quality and mechanical properties of a welded joint. By adopting the optimized inscribed double-circle laser scanning mode, the thickness of the intermetallic compound layer at the interface of the welded joint of the butt joint is obviously reduced from 5.56 mu m to 1.18 mu m in the traditional welding method, the reduction rate reaches 79 percent, and meanwhile, the ultimate tensile strength of the joint is improved from 182MPa to 215MPa, and the improvement amplitude is close to 20 percent. Specifically, compared with scanning-free laser arc hybrid welding, the method has the advantages that the mobility of a welding pool can be remarkably improved by adopting inscribed double-circle scanning laser, heat/mass transfer in the pool is enhanced, overflow of bubbles is facilitated, and the thickness of a brittle intermetallic compound layer of a welding interface is reduced, so that good weld joint forming and excellent mechanical properties are realized. In addition, compared with the traditional circular track, the internal tangent double-circular track welding can improve the peak energy in the track, so that the energy distribution in the welding track is more uniform, and the generation of welding defects is reduced. Compared with circular scanning, the 8-shaped laser scanning mode optimally designed by the invention improves the uniformity of the intermetallic compound layer at the lap joint interface by nearly 1 time, improves the uniformity of laser energy distribution by 60 percent, and ensures that the shearing tension of the joint reaches 4.4kN which is 3.8 times that of a welded joint in a circular scanning mode.

Claims (9)

1. The laser arc hybrid welding method based on the optical beam scanning pattern optimization design is characterized by comprising the following steps of:

S1, preprocessing the welding surfaces of two dissimilar metal plates, placing the two dissimilar metal plates on a welding operation table, setting the position of a welding focal plane, and setting parameters of a welding gun and a workpiece to be welded;

S2, setting scanning laser-arc welding process parameters, and finishing welding of two dissimilar metal plates according to the set process parameters.

2. The laser arc hybrid welding method based on the optimal design of the light beam scanning pattern according to claim 1, wherein the welding in the step S1 is either butt welding or lap welding, and the lap welding is required to be provided with a focus position.

3. The laser arc hybrid welding method based on the optimal design of the light beam scanning patterns is characterized in that in the butt welding in the step S1, two butt-jointed dissimilar metal plates are 6061 aluminum alloy and TC4 titanium alloy, the thickness of each metal plate is 2mm, a layer of brazing filler metal is required to be coated on the welding surface of a high-melting-point metal plate, the brazing filler metal is KAlF ₄, in the lap joint process, the lower part of the lap joint metal plate is 6061 aluminum alloy and the upper part of the lap joint metal plate is AZ31B magnesium alloy, the thickness of each metal plate is 2mm, and pure titanium foil with the thickness of 0.1mm is added between the two plates to serve as an intermediate layer.

4. The laser arc composite welding method based on the optimal design of the light beam scanning pattern according to claim 1 is characterized in that parameters between a welding gun and a workpiece to be welded in the butt welding in the step S1 comprise an included angle and a light wire distance, wherein the included angle is 50-60 degrees, the light wire distance is 2-3mm, and a laser head deflects 5 degrees along the welding direction during overlap welding, and a laser focal plane is positioned at the 4mm position of the upper surface of the magnesium alloy to be welded.

5. The laser arc hybrid welding method based on the optimal design of the light beam scanning pattern according to claim 1, wherein the welding process parameters of the scanning laser and the electric arc in the step S2 include an included angle between the laser beam and the electric arc welding gun, a defocusing amount of the laser beam, laser power, wire feeding speed, welding speed, an oscillation mode of the laser beam, and scanning pattern parameters.

6. The laser arc composite welding method based on the optimal design of the light beam scanning pattern is characterized in that in butt welding, an included angle between a laser beam and an arc welding gun is 65 degrees, the defocusing amount of the laser beam is 0mm, the laser power is 2000W, the wire feeding speed is 4.5m/min, the welding speed is 1.5m/min, the oscillation mode of the laser beam is inscribed double-circle scanning laser, the scanning pattern is inscribed double-circle, the radius of an inner circle is 0.25mm, the radius of an outer circle is 0.5mm, and the scanning frequency is 300Hz.

7. The laser arc composite welding method based on the optimal design of the light beam scanning pattern, which is disclosed by claim 5, is characterized in that during lap welding, a laser beam deviates 5 degrees along the welding direction, the defocusing amount of the laser beam is 4mm, the laser power is 3100W, the welding speed is 1.8m/min, the protection gas flow is 20L/min, the oscillation mode of the laser beam is 8-shaped scanning laser, the scanning pattern is 8-shaped, the radius of an arc part is 0.2mm, the length of a straight line part is 2mm, and the scanning frequency is 50Hz.

8. The laser arc hybrid welding method based on the optimal design of the beam scanning pattern according to claim 1, wherein the pretreatment process in S1 comprises polishing the welding surface with sand paper to remove surface oxide film, and then wiping the welding surface with acetone to remove surface oil stains and dust.

9. The laser arc hybrid welding method based on the optimal design of the light beam scanning pattern according to claim 1, wherein the action center of the laser and the electric arc in the welding process of the dissimilar material butt welding in the S2 is positioned at one side of the low-melting-point metal material and is 0.8mm away from the high-melting-point metal material.