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

Abstract

The invention belongs to the technical field of welding, and particularly relates to a laser arc hybrid welding method based on light beam scanning pattern optimization design. A laser-arc hybrid welding method based on light beam scanning pattern optimization design comprises the following steps that S1, the welding faces of two dissimilar material metal plates are pretreated, the two dissimilar material metal plates are placed on a welding operation table, the plane position of a welding focus is set, and parameters of a welding gun and a workpiece to be welded are set; s2, setting scanning laser-electric arc welding process parameters; and welding of the two metal plates made of the dissimilar materials is completed according to the set technological parameters. By means of the composite welding method, a melt-brazed joint with good weld forming and mechanical properties can be obtained, energy distribution in the whole welding track can be more uniform, and welding defects are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a laser arc hybrid welding method based on light beam scanning pattern optimization design. Background Art

[0002] With the increasing demand for lightweight components and the need to reduce energy consumption in industries such as aerospace and transportation, the importance of dissimilar metal joining is becoming increasingly apparent. For example, in aerospace, the honeycomb sandwich structure used in aircraft wings requires the connection of titanium alloy skins and aluminum alloy honeycomb sandwiches in wing boxes. However, due to the large differences in thermophysical properties between dissimilar metals, the mechanical properties of welded dissimilar joints are often related to the characteristics of the brittle intermetallic compounds formed at the interface, such as the morphology, thickness and type of the brittle intermetallic compounds.

[0003] There are many studies on dissimilar metal welding, including solid phase welding and fusion welding. Friction stir welding is one of the commonly used solid-state welding techniques. The advantage of friction stir welding is that the formation of thick intermetallic compounds is avoided by precisely controlling the heat input during the joining process. However, the process window for obtaining acceptable joints in friction stir welding is quite narrow, and the welding efficiency is lower than that of fusion welding, which limits its widespread industrial application. Laser-arc hybrid welding (LAHW) is one of the most promising fusion welding technologies because it has the advantages of high welding efficiency, good joint quality, strong bridging ability and high flexibility. Moreover, this welding method can more accurately control the laser energy distribution in the form of laser beam oscillation.

[0004] In order to effectively suppress the formation of thick intermetallic compound layers during the welding of dissimilar metals, a scanning laser arc hybrid welding method based on the optimized design of laser beam scanning patterns was used. The optimized laser beam scanning pattern is an inscribed double circle. This optimized pattern is not only conducive to improving the laser energy distribution around the laser oscillation path, but also can enhance the stirring effect of the laser keyhole on the liquid metal in the molten pool, ultimately enabling the weld joint to obtain better weld formation and better mechanical properties. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a laser arc hybrid welding method based on the optimized design of beam scanning patterns, comprising the following steps:

[0006] S1: pre-treat the welding surfaces of two dissimilar metal plates, place the two dissimilar metal plates on a welding operation table, set the welding focal plane position, and set the parameters of the welding gun and the workpiece to be welded;

[0007] S2: Setting scanning laser-arc welding process parameters; completing the welding of two dissimilar metal plates according to the set process parameters.

[0008] Furthermore, the welding described in S1 is any one of butt welding and lap welding, and the lap welding requires setting a focal position.

[0009] Furthermore, in the butt welding in S1, the two butted dissimilar metal plates are 6061 aluminum alloy and TC4 titanium alloy, the thickness of the metal plates is 2 mm, and a layer of brazing filler metal is applied on the welding surface of the high melting point metal plates, and the brazing filler metal is KAlF 4 When overlapping, the lower part of the overlapping metal plate is 6061 aluminum alloy and the upper part is AZ31B magnesium alloy. The thickness of the metal plate is 2 mm, and a pure titanium foil with a thickness of 0.1 mm is added between the two plates as an intermediate layer.

[0010] Furthermore, the parameters between the welding gun and the workpiece to be welded during butt welding in S1 include an angle and a wire spacing, the angle is 50° to 60°, and the wire spacing is 2-3mm; during lap welding, the laser head is deflected 5° along the welding direction, and the laser focal plane is located 4mm from the upper surface of the magnesium alloy to be welded.

[0011] Furthermore, the scanning laser and arc welding process parameters described in S2 include the angle between the laser beam and the arc welding gun, the laser beam defocus amount, the laser power, the wire feeding speed, the welding speed, the oscillation mode of the laser beam, and the scanning pattern and scanning pattern parameters.

[0012] Furthermore, during butt welding, the angle between the laser beam and the arc welding gun is 65°, the laser beam defocus is 0 mm, the laser power is 2000 W, the wire feeding speed is 4.5 m / min, the welding speed is 1.5 m / min, and the oscillation mode of the laser beam is an inscribed double circle scanning laser; the scanning pattern is an inscribed double circle, the inner circle radius is 0.25 mm, the outer circle radius is 0.5 mm, and the scanning frequency is 300 Hz.

[0013] Furthermore, during lap welding, the laser beam deviates by 5° along the welding direction, the laser beam defocus is +4mm, the laser power is 3100W, the welding speed is 1.8m / min, and the shielding gas flow rate is 20L / min; the oscillation mode of the laser beam is an 8-shaped scanning laser; the scanning pattern is an 8-shaped shape, the radius of the arc part is 0.2mm, the length of the straight line segment is 2mm, and the scanning frequency is 50Hz.

[0014] Furthermore, the pretreatment process described in S1 includes grinding the welding surface with sandpaper to remove the surface oxide film, and then wiping the welding surface with acetone to remove surface oil and dust.

[0015] Furthermore, in the welding process of butt welding of dissimilar metal materials in S2, the action center of the laser and the arc is located on the side of the low-melting-point metal material, 0.8 mm away from the high-melting-point metal material.

[0016] Beneficial Effects

[0017] The laser welding method based on the optimized design of the beam scanning pattern provided by the present invention can significantly reduce the thickness of the intermetallic compound layer formed at the interface of the brazing joint by using the present invention to weld dissimilar metal materials, and obtain good weld appearance and excellent mechanical properties. Laser-arc composite welding is carried out under the laser scanning-free and optimized inscribed double-circle laser scanning mode of the present invention. The welded joint obtained by the inscribed double-circle scanning mode is beautiful and full, and the thickness of the intermetallic compound layer formed at the joint interface is reduced from 5.56μm to 1.18μm, which is 79% thinner; the ultimate tensile strength of the joint is increased from 182MPa to 215MPa, which is nearly 20%. In lap welding, the problems of uneven heating and uneven reaction in circular oscillation laser lap welding are solved. When the oscillation pattern changes from a circle to an 8-shape, the uniformity of the laser energy distribution increases by 60%; under the optimized parameters of a circle radius of 0.2mm and a line length of 2mm, the 8-shaped oscillation increases the effective connection width of the interface to 2.4mm, which is nearly 4 times higher than that of circular oscillation; the intermetallic compounds at the interface are more evenly distributed, and the corresponding shear tension is as high as 4.4kN, which is 3.8 times higher than that of circular oscillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0019] Figure 1 It is a schematic diagram of the scanning laser-arc hybrid welding experimental platform of the present invention;

[0020] Figure 2 A schematic diagram of the relationship between the inscribed double-circle scanning laser trajectory and the positions of the components of the present invention;

[0021] Figure 3 It is a schematic diagram of the cross section of the weld of dissimilar metal welding when the inscribed double-circle scanning laser of the present invention is not regulated and when it is regulated;

[0022] Figure 4 The morphology of the intermetallic compound generated at the interface of the dissimilar metal welding joint when the inscribed double-circle scanning laser of the present invention is not regulated and when it is regulated;

[0023] Figure 5 A schematic diagram of the relationship between the figure-8 scanning laser trajectory and the positions of the components of the present invention;

[0024] Figure 6 A schematic diagram of the design principle of the figure-8 scanning pattern of the present invention;

[0025] Figure 7 Schematic diagram of weld path and laser energy distribution obtained under the figure-eight scanning pattern of the present invention;

[0026] Figure 8 The influence of the figure-8 scanning pattern of the present invention on the surface morphology of the weld and the uniformity of the intermetallic compound (IMC) at the joint interface.

[0027] Markings in the figure:

[0028] 1. Fiber laser; 2. Welding machine; 3. Scanning galvanometer; 4. Welding robot; 5. Welding gun; 6. Welding wire; 7. Laser beam; 8. Electric arc; 9. Keyhole; 10. Molten pool; 11. Parent material; DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments 1-5 and the attached Figures 1 to 8 , clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The present invention provides a laser arc hybrid welding method based on the optimized design of beam scanning patterns, comprising the following steps:

[0031] S1: First, the welding surfaces of the two dissimilar metal plates are polished with sandpaper to remove the oxide film on the surface of the plates, and the polished surfaces are wiped with acetone to remove surface oil and dust. When welding dissimilar metal materials with large differences in melting points, a layer of brazing material is applied on the welding surface of the high-melting-point metal plate to promote the wetting and spreading of the low-melting-point material during welding; then the two dissimilar metal plates are placed on the welding operating table in a butt-jointed manner and clamped with a clamp to ensure that the relative position of the two butt-jointed plates is fixed during welding; the welding focal plane position is adjusted so that the laser focus is located on the upper surface of the workpiece to be welded, and the laser head is tilted by 5° to prevent the laser from reflecting in the original direction and burning the laser head; then the angle between the welding gun and the workpiece to be welded is adjusted so that the angle is between 50° and 60°, and the filament spacing is ensured to be 2-3mm; the laser spot and the tip of the welding wire are in the same straight line to ensure that the straight The line direction is parallel to the welding direction; the welding gun and the laser head with adjusted position relationship are moved perpendicularly to the welding direction to the side of the low-melting-point metal plate 0.8mm away from the butt gap between the two plates. When laser welding is performed in the form of overlap for dissimilar materials with similar melting points, when overlapping, the lower part of the overlapping metal plate is 6061 aluminum alloy and the upper part is AZ31B magnesium alloy, the plate thickness is 2mm, and a pure titanium foil with a thickness of 0.1mm is added between the two plates as an intermediate layer; the focus position is set, and during overlap welding, the laser beam deviates by 5° along the welding direction, the laser beam defocus amount is +4mm, the laser power is 3100W, the welding speed is 1.8m / min, and the shielding gas flow rate is 20L / min; the oscillation mode of the laser beam is an 8-shaped scanning laser; the scanning pattern is an 8-shaped shape, the radius of the arc part is 0.2mm, the length of the straight line part is 2mm, and the scanning frequency is 50Hz;

[0032] S2: Set scanning laser-arc welding process parameters, which include scanning pattern, scanning frequency, scanning amplitude, laser power, welding speed and wire feeding speed. The scanning pattern is an inscribed double circle, and the scanning pattern is the trajectory of the laser beam formed by the galvanometer scanning; the scanning frequency is the number of cycles of the laser beam on the scanning pattern per unit time, and the unit is Hertz (Hz); the scanning amplitude is the maximum distance of the scanning pattern perpendicular to the welding direction. For the inscribed double circle scanning pattern, the scanning amplitude includes the inner circle diameter and the outer circle diameter, and the butt welding of two dissimilar metal plates is completed according to the inscribed double circle scanning path parameters; in the welding process of dissimilar material lap welding, it is necessary to ensure that the laser energy fully overlaps without intersection, and at the same time, uniformly distributed laser energy can be obtained, and it is necessary to ensure that the laser scanning path area is located within the overlapping range of AZ31B magnesium alloy, 6061-T6 aluminum alloy and pure titanium foil.

[0033] Example 1

[0034] S1: The welding surface of the 2mm thick 6061 aluminum alloy and TC4 titanium alloy metal plates was polished with sandpaper to remove the oxide film on the surface of the plates, and the polished surface was wiped with acetone to remove the surface oil and dust, and then a layer of KAlF was applied on the welding surface of the high melting point metal plate. 4 , to promote the wetting and spreading of low-melting-point materials during welding; place the two metal plates on the welding operating table in a butt-jointed form and clamp them with a clamp to ensure that the relative position of the two butt-jointed plates is fixed during welding; then adjust the welding focal plane position so that the laser focus is located on the upper surface of the workpiece to be welded, and tilt the laser head by 5° to prevent the laser from reflecting along the original direction and burning the laser head; then adjust the angle between the welding gun and the workpiece to be welded to 55°, and ensure that the light wire spacing is 2mm; the laser spot and the tip of the welding wire are in the same straight line, and the direction of the straight line is parallel to the welding direction; move the welding gun and the laser head with adjusted position relationship perpendicular to the welding direction to the side of the low-melting-point metal plate 0.8mm away from the butt gap between the two plates, and the action position of each welding component on the upper surface of the welding parent material is as follows Figure 2 As shown in the right figure;

[0035] S2: Set the angle between the laser beam and the arc welding gun to 65°, the filament spacing to 2 mm, the laser beam defocus to 0 mm, the laser power to 2000 W, the wire feeding speed to 4.5 m / min, and the welding speed to 1.5 m / min; set the oscillation mode to inscribed double-circle scanning laser, with an inner circle radius of 0.25 mm, an outer circle radius of 0.5 mm, and a scanning frequency of 300 Hz (the scanning path is as follows Figure 2 (as shown in the left figure in the figure), to complete the butt welding of two dissimilar metal plates.

[0036] from Figure 1 It can be seen that the operating platform includes a fiber laser 1, a welding machine 2, a scanning galvanometer 3, a welding robot 4, a welding gun 5, a welding wire 6, and a laser beam 7 and an arc 8. It also includes a keyhole 9, a molten pool 10, and a base material 11. The specifications include: a six-axis robot system, an IPG laser, Fronius welding, and an IPG D50 oscillating laser head.

[0037] from Figure 3 and Figure 4 It can be seen that after the welding is completed using the above process parameters (using ER4047 aluminum-silicon welding wire with a diameter of 1.2 mm), the weld morphology with a slightly collapsed upper surface obtained without scanning laser ( Figure 3 a) and a thicker brittle intermetallic compound layer is formed at the joint interface ( Figure 4 a), weld obtained by using inscribed double circle scanning laser ( Figure 3 b) The forming is beautiful and full, and the brittle metal compound formed at the joint interface ( Figure 4b) The thickness is significantly thinner, only 1.18 μm. The tensile strength of the weld obtained by the inscribed double-circle scanning laser is 215 MPa, which is nearly 20% higher than that of the non-scanning laser.

[0038] Example 2

[0039] S1: The welding surface of the 2mm thick 6061 aluminum alloy and TC4 titanium alloy metal plates was polished with sandpaper to remove the oxide film on the surface of the plates, and the polished surface was wiped with acetone to remove the surface oil and dust, and then a layer of KAlF was applied on the welding surface of the high melting point metal plate. 4 , to promote the wetting and spreading of low-melting-point materials during welding; place two metal plates on the welding operating table in a butt-jointed form and clamp them with a clamp to ensure that the relative position of the two butt-jointed plates is fixed during welding; then adjust the welding focal plane position so that the laser focus is located on the upper surface of the workpiece to be welded, and tilt the laser head by 5° to prevent the laser from reflecting in the original direction and burning the laser head; then adjust the angle between the welding gun and the workpiece to be welded to 60°, and ensure that the light wire spacing is 3mm; the laser spot and the tip of the welding wire are in the same straight line, and the direction of the straight line is parallel to the welding direction; move the welding gun and the laser head with adjusted position relationship as a whole perpendicular to the welding direction to the side of the low-melting-point metal plate 0.8mm away from the butt gap between the two plates;

[0040] S2: Set the angle between the laser beam and the arc welding gun to 65°, the filament spacing to 2mm, the laser beam defocus to 0mm, the laser power to 2000W, the wire feeding speed to 4.5m / min, and the welding speed to 1.5m / min; set the oscillation mode to inscribed double-circle scanning laser with an inner circle radius of 0.25mm, an outer circle radius of 0.5mm, and a scanning frequency of 300Hz to complete the butt welding of two dissimilar metal plates.

[0041] Example 3

[0042] S1: The welding surface of the 2mm thick 6061 aluminum alloy and TC4 titanium alloy metal plates was polished with sandpaper to remove the oxide film on the surface of the plates, and the polished surface was wiped with acetone to remove the surface oil and dust, and then a layer of KAlF was applied on the welding surface of the high melting point metal plate. 4, to promote the wetting and spreading of low-melting-point materials during welding; place two metal plates on the welding operating table in a butt-jointed form and clamp them with a clamp to ensure that the relative position of the two butt-jointed plates is fixed during welding; then adjust the welding focal plane position so that the laser focus is located on the upper surface of the workpiece to be welded, and at the same time tilt the laser head by 5° to prevent the laser from reflecting in the original direction and burning the laser head; then adjust the angle between the welding gun and the workpiece to be welded to 50°, and ensure that the light wire spacing is 2.5mm; the laser spot and the tip of the welding wire are in the same straight line, and the direction of the straight line is parallel to the welding direction; move the welding gun and the laser head with adjusted position relationship as a whole perpendicular to the welding direction to the side of the low-melting-point metal plate 0.8mm away from the butt gap between the two plates;

[0043] S2: Set the angle between the laser beam and the arc welding gun to 65°, the filament spacing to 2mm, the laser beam defocus to 0mm, the laser power to 2000W, the wire feeding speed to 4.5m / min, and the welding speed to 1.5m / min; set the oscillation mode to inscribed double-circle scanning laser with an inner circle radius of 0.25mm, an outer circle radius of 0.5mm, and a scanning frequency of 300Hz to complete the butt welding of two dissimilar metal plates.

[0044] Example 4

[0045] S1: AZ31B magnesium alloy and 6061-T6 aluminum alloy with specifications of 100×50×2mm were laser welded in the form of overlap, where the AZ31B magnesium alloy was located above the joint and the 6061-T6 aluminum alloy was located below the joint; 0.1mm thick pure titanium foil was added to the overlapping part of the two dissimilar materials to prevent the direct combination of magnesium and aluminum elements in the welding pool to produce brittle intermetallic compounds and reduce the performance of the welded joint; before welding, the plate was polished with sandpaper to remove the oxide film on the surface of the plate, and the polished surface was wiped with acetone to remove surface oil and dust; then the laser head was tilted 5° along the welding direction to prevent the laser from reflecting in the original direction and burning the laser head, and at the same time, the laser focus was adjusted to be 2mm away from the upper surface of the AZ31B magnesium alloy (the defocus amount was +4mm) and the scanning pattern was ensured to be located at the overlapping part of the AZ31B magnesium alloy, 6061-T6 aluminum alloy and pure titanium foil (such as Figure 5 shown);

[0046] S2: Set other laser welding parameters including welding speed of 1.8 m / min, shielding gas flow rate of 20 L / min and laser scanning pattern (circular scanning and figure-8 scanning); when circular scanning is used, the laser power is 2.75 kW, the scanning diameter is 4 mm, and the scanning frequency is 50 Hz; when figure-8 scanning is used, the laser power is 3.1 kW, the radius of the circular part is 0.2 mm, and the length of the straight part is 2 mm to complete the lap welding of dissimilar metal materials.

[0047] After welding, the lap joints obtained under two different scanning patterns were compared and it was found that when the beam oscillation mode changed from circular to figure-8, the uniformity of laser energy distribution increased by 60%. Figure 7 As shown. And after welding with the optimized 8-shaped scanning pattern, the interface layer formed by the lap joint is more evenly distributed (see Figure 8 ), and the shear tensile force of the entire joint also reached 4.4kN, which is 3.8 times that of the joint welded using a circular scanning pattern.

[0048] Laser welding has the advantages of high energy density, small heat-affected zone, and deep penetration, but it has high requirements for welding gap; arc welding has strong adaptability to grooves, but has disadvantages such as low energy density, low welding speed, large post-weld deformation and residual stress. Within this range of light wire spacing, the synergistic effect of the laser heat source and the arc heat source in the laser arc hybrid welding process can be achieved. This synergistic effect refers to giving full play to the advantages of the above two heat sources - compared with laser welding, laser-arc hybrid welding improves the bridging ability between workpieces; compared with arc welding, laser-arc hybrid welding can obtain deeper welds at faster welding speeds.

[0049] Embodiment 5:

[0050] S1: 2mm thick 6061 aluminum alloy and TC4 titanium alloy were pretreated. The pretreatment was to polish the welding surface with sandpaper to remove the surface oxide film, and then wipe the welding surface with acetone to remove the surface oil and dust. When welding dissimilar metal materials with different melting points, a layer of brazing filler metal was applied on the welding surface of the high melting point metal plate. The brazing filler metal was KAlF. 4 The lower part of the overlapping metal plate is 6061 aluminum alloy and the upper part is AZ31B magnesium alloy, the plate thickness is 2mm, and a pure titanium foil with a thickness of 0.1mm is added between the two plates as an intermediate layer; the two dissimilar metal plates are placed on the welding operating table in a butt-jointed form, the welding focus plane position is set, and the parameters of the welding gun and the workpiece to be welded are set; for dissimilar materials with similar melting points, when laser welding is performed in an overlapping form, the focus position is set, and the parameters between the welding gun and the workpiece to be welded during butt welding include the angle between the two and the light wire spacing, the angle is 50°-60°, and the light wire spacing is 2-3mm;

[0051] S2: Set the scanning laser-arc welding process parameters for butt welding. During the butt welding process, the action center of the laser and the arc is located on one side of the low-melting-point metal material, 0.8 mm away from the high-melting-point metal material; during overlap, the laser is located in the middle position above the overlapping area of ​​the two dissimilar metals including the titanium interlayer, and the distance between the laser focus and the upper surface of the parent material above the joint is 2 mm; the angle between the laser beam and the arc welding gun is 65°, the laser beam defocus is 0 mm, the laser power is 2000 W, the wire feeding speed is 4.5 m / min, the welding speed is 1.5 m / min, the oscillation mode of the laser beam is any one of a non-scanning laser and an inscribed double-circle scanning laser, the scanning pattern is an inscribed double circle, the inner circle radius is 0.25 mm, the outer circle radius is 0.5 mm, and the scanning frequency is 300 Hz.

[0052] During lap welding, a comparative test was conducted between a figure-8 scanning laser and a conventional circular scanning laser. In order to avoid any intersections in the figure-8 scanning pattern during the scanning process, the scanning parameters need to be optimized to ensure that the laser energy fully overlaps without intersections while obtaining uniformly distributed laser energy. The optimized laser parameters include a laser power of 3100W, a figure-8 scanning arc segment radius of 0.2mm, and a straight line segment length of 2mm.

[0053] Among them, based on the purpose of eliminating the intersection points along the circular oscillation path, the following is designed: Figure 5 The oscillation path diagram shown in the figure contains two parallel straight lines and an arc connecting the two ends of the line. Then, based on the assumed oscillation path, the oscillation mode is inferred in reverse. The difficulty that needs to be solved is how to realize the straight line L 1 and L 2 Along Figure 6 a and 6b. Since the actual moving speed of the laser spot along the oscillation path (V S ) is the robot welding speed (V 1 ) and the galvanometer scanning speed (V 2 ) of the combined speed, the path portion of the oscillation mode can be based on Figure 6 c and 6d, and solve the target oscillation path in reverse. Assume that V 1 The value and direction of V S The direction of V (i.e. the direction of the target line) is known, then 2 The value and direction of can be obtained. The path of the oscillation pattern obtained by reverse design remains symmetrical after crossing and is connected by arcs of small radius. Finally, the formation Figure 6 The reverse design oscillation mode shown in e is named the 8-shaped oscillation mode because its shape is similar to the number 8. Figure 6 f, obtain the V of the target 8-shaped oscillation without any intersection along the oscillation path. 2 and V 1The parameter settings should satisfy the formula:

[0054]

[0055] Where V 1 is the robot welding speed, V 2 is the scanning speed of the galvanometer, L is the length of the straight line segment in the figure-8 scanning path, and r is the radius of the arc part in the scanning path.

[0056] The present invention provides a laser arc hybrid welding method based on the optimized design of beam scanning graphics, which is suitable for welding of dissimilar metal materials and can significantly improve the quality and mechanical properties of welded joints. By adopting the optimized inscribed double-circle laser scanning method of the present invention, the thickness of the intermetallic compound layer at the interface of the brazing joint of the butt joint is significantly thinned, from 5.56μm under the traditional welding method to 1.18μm, and the thinning rate reaches 79%; at the same time, the ultimate tensile strength of the joint is increased from 182MPa to 215MPa, and the increase is close to 20%. Specifically, compared with non-scanning laser arc hybrid welding, the use of inscribed double-circle scanning laser can significantly improve the fluidity of the welding molten pool, enhance the heat / mass transfer in the molten pool, help the overflow of bubbles, and reduce the thickness of the brittle intermetallic compound layer at the welding interface, thereby achieving good weld formation and excellent mechanical properties. In addition, compared with the traditional circular trajectory, the inscribed double-circle trajectory welding can increase the peak energy inside the trajectory, make the energy distribution in the welding trajectory more uniform, and reduce the generation of welding defects. By using the figure-8 laser scanning method optimized by the present invention, compared with circular scanning, the uniformity of the intermetallic compound layer at the lap joint interface is improved by nearly 1 times, the uniformity of laser energy distribution is improved by 60%, and the shear tension of the joint reaches 4.4 kN, which is 3.8 times that of the welded joint under the circular scanning mode.

Claims

1. A laser arc hybrid welding method based on beam scanning pattern optimization design, characterized in that: The following steps are involved: S1: pre-treat the welding surfaces of two dissimilar metal plates, place the two dissimilar metal plates on a welding operation table, set the welding focal plane position, and set the parameters of the welding gun and the workpiece to be welded; S2: Setting scanning laser-arc welding process parameters; completing the welding of two dissimilar metal plates according to the set process parameters.

2. The laser arc hybrid welding method based on the optimized design of beam scanning pattern according to claim 1 is characterized in that: The welding described in S1 is any one of butt welding and lap welding, and the lap welding requires setting a focal position.

3. The laser arc hybrid welding method based on the optimized design of beam scanning pattern according to claim 1 is characterized in that: During butt welding in S1, the two butted dissimilar metal plates are 6061 aluminum alloy and TC4 titanium alloy, the thickness of the metal plates is 2 mm, and a layer of brazing filler metal is applied on the welding surface of the high melting point metal plate, the brazing filler metal is KAlF4; during overlap welding, the lower part of the overlapped metal plate is 6061 aluminum alloy and the upper part is AZ31B magnesium alloy, the thickness of the metal plate is 2 mm, and a pure titanium foil with a thickness of 0.1 mm is added between the two plates as an intermediate layer.

4. The laser arc hybrid welding method based on the optimized design of beam scanning pattern according to claim 1 is characterized in that: The parameters between the welding gun and the workpiece to be welded during butt welding in S1 include the angle and the wire spacing, the angle is 50° to 60°, and the wire spacing is 2-3mm; during lap welding, the laser head is deflected 5° along the welding direction, and the laser focal plane is located 4mm from the upper surface of the magnesium alloy to be welded.

5. The laser arc hybrid welding method based on the optimized design of beam scanning pattern according to claim 1 is characterized in that: The scanning laser and arc welding process parameters described in S2 include the angle between the laser beam and the arc welding gun, the laser beam defocus amount, the laser power, the wire feeding speed, the welding speed, the oscillation mode of the laser beam, and the scanning pattern and scanning pattern parameters.

6. The laser arc hybrid welding method based on the optimized design of beam scanning pattern according to claim 5 is characterized in that: During butt welding, the angle between the laser beam and the arc welding gun is 65°, the laser beam defocus is 0 mm, the laser power is 2000 W, the wire feeding speed is 4.5 m / min, the welding speed is 1.5 m / min, and the oscillation mode of the laser beam is an inscribed double circle scanning laser; the scanning pattern is an inscribed double circle, the inner circle radius is 0.25 mm, the outer circle radius is 0.5 mm, and the scanning frequency is 300 Hz.

7. According to the laser arc hybrid welding method based on the optimized design of the beam scanning pattern as described in claim 5, during lap welding, the laser beam deviates by 5° along the welding direction, the laser beam defocus is 4 mm, the laser power is 3100 W, the welding speed is 1.8 m / min, and the shielding gas flow rate is 20 L / min; the oscillation mode of the laser beam is an 8-shaped scanning laser; the scanning pattern is an 8-shaped shape, the radius of the arc part is 0.2 mm, the length of the straight line part is 2 mm, and the scanning frequency is 50 Hz.

8. The laser arc hybrid welding method based on the optimized design of beam scanning pattern according to claim 1 is characterized in that: The pretreatment process described in S1 includes grinding the welding surface with sandpaper to remove the surface oxide film, and then wiping the welding surface with acetone to remove surface oil and dust.

9. The laser arc hybrid welding method based on the optimized design of beam scanning pattern according to claim 1 is characterized in that: During the butt welding of dissimilar materials in S2, the action center of the laser and the arc is located on the side of the low-melting-point metal material, 0.8 mm away from the high-melting-point metal material.

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