Hybrid welding method

Abstract

The hybrid welding method of the present disclosure includes a first step in which a laser beam (LB) is irradiated on a surface of a workpiece (40) along a predetermined welding line, and a second step in which, after the first step, a portion irradiated by the laser beam (LB) is further arc-welded. In a first step, a laser beam (LB) is irradiated on a workpiece (40) while performing two-dimensional scanning, thereby forming a weld pool (41) having a predetermined width in directions intersecting the thickness direction of the workpiece (40) and the direction along a weld line. In the second step, the arc welding is performed while the forward feed and the reverse feed of the welding wire (22) are repeated at a predetermined cycle.

Description

Technical Field

[0001] The present invention relates to a hybrid welding method of laser welding and arc welding. Background Art

[0002] In recent years, the electrification of automobiles has been developing rapidly. In the process of achieving electrification, it is very necessary to reduce the weight of the vehicle body, especially the battery, which is a heavier component, because it is directly related to the driving range. In this case, for the battery housing, 6000 series aluminum alloy is used as a material that is lightweight and has excellent strength and durability.

[0003] Generally, in welding of aluminum or aluminum alloy, pores are easily generated inside the welded part, and the pores may cause a decrease in welding quality. A method for suppressing the generation of such pores has been proposed (for example, Patent Document 1).

[0004] In the method disclosed in Patent Document 1, in laser-arc hybrid welding in which arc welding and laser welding are performed on the same welding line, after arc welding is performed along a predetermined welding line, laser welding is performed while periodically changing the focal position of the laser beam in a direction intersecting the welding line with respect to the arc welding portion. In this way, it is possible to suppress the periodic variation of the width of the molten pool formed on the workpiece, and to make the molten pool width constant. Thus, the formation of pores can be suppressed.

[0005] It should be noted that the term "pores" refers to a general term for pores generated in the weld metal portion due to gas generated in the molten metal and pits that open in a caterpillar-like manner to the surface of the workpiece.

[0006] Patent Document 1: Japanese Patent Publication No. 2016-059936 Summary of the invention

[0007] -Technical problem to be solved by the invention-

[0008] In order to shorten the manufacturing cycle, when welding materials such as aluminum or aluminum alloys, which have fast heat conduction and heat dissipation, and solidify before the generated bubbles escape, resulting in residual pores, it is necessary to further increase the welding speed. However, if the welding speed is set too high in laser welding, a defect called undercut will occur. Undercut is a defect in which a concave depression is formed on the side of the weld due to the solidification of molten metal before covering the concave part in the molten pool when the welding speed is too high. In addition, in welding such as a full penetration weld, a defect called underfill will occur. Underfill is a defect in which the molten metal droops to the back side, resulting in a depression on the weld surface. Therefore, in the method disclosed in Patent Document 1, in which arc welding is used as the first welding and laser welding is used as the second welding, defects will occur in the laser welding performed later, so it is impossible to simultaneously increase the welding speed, reduce welding defects, and ensure the penetration depth.

[0009] The present disclosure is completed to solve the above-mentioned technical problems, and its purpose is to provide a hybrid welding method of laser welding and arc welding, which can reduce welding defects such as porosity and welding defects related to depressions on the weld surface such as undercut and incomplete welding while ensuring the depth of penetration, and can also increase the welding speed.

[0010] -Technical solutions for solving technical problems-

[0011] In order to achieve the above-mentioned purpose, the hybrid welding method involved in the present disclosure is characterized in that it includes a first step and a second step, in which a laser beam is irradiated onto the surface of a workpiece along a specified welding line, and in the second step, after the first step, arc welding is further performed on the irradiated portion of the laser beam, and the material of the workpiece is any one of aluminum, aluminum alloy, magnesium, magnesium alloy, copper and copper alloy. In the first step, the laser beam is irradiated onto the workpiece while performing two-dimensional scanning, so as to form a molten pool with a specified width in directions respectively intersecting the thickness direction of the workpiece and the direction along the welding line, and in the second step, the arc welding is performed while repeatedly feeding the welding wire forward and backward at a specified cycle.

[0012] -Effects of the Invention-

[0013] According to the present disclosure, it is possible to reduce welding defects such as pores and welding defects related to depressions on the weld surface such as undercut and underfill while ensuring the penetration depth, and it is also possible to increase the welding speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a simplified structural diagram of a composite welding device according to an embodiment;

[0015] Figure 2 is a schematic diagram showing the tilt state of the welding head relative to the welding direction;

[0016] Figure 3 is a graph showing the relationship between the laser output and the recess depth according to the comparative example;

[0017] Figure 4 is a diagram showing a Z-direction profile of a weld according to an example of a comparative example;

[0018] Figure 5 is a diagram showing a Z-direction profile of a weld of another example involved in a comparative example;

[0019] Figure 6 is a graph showing the relationship between the laser output, the penetration depth, and the number of pores according to the comparative example;

[0020] Figure 7 An X-ray diffraction image and a cross-sectional shape image of a weld according to a comparative example are shown;

[0021] Fig. 8A is a schematic diagram showing a scanning trajectory when a laser beam is made to perform simple harmonic oscillation in a direction intersecting a welding line;

[0022] Figure 8B It is shown that the laser beam is directed in accordance with Fig. 8A A schematic diagram of the scanning trajectory of the laser beam when the laser head is moved along the welding line at a specified speed in the welding direction while scanning along the trajectory shown;

[0023] Fig. 9A is a schematic diagram showing a scanning trajectory when a laser beam is scanned in a circular shape;

[0024] Fig. 9B It is shown that the laser beam is directed in accordance with Fig. 9A A schematic diagram of the scanning trajectory of the laser beam when the laser head is moved along the welding line at a specified speed in the welding direction while scanning along the trajectory shown;

[0025] Fig.10 is a diagram showing the relationship between the scanning form of the laser beam and the depth of the depression;

[0026] Fig.11 1 is a diagram showing an example of a Z-direction profile of a weld when a laser beam is scanned in a sinusoidal wave shape;

[0027] Fig.12 is a diagram showing another example of the Z-direction profile of a weld when the laser beam is scanned in a spiral shape;

[0028] Fig.13is a diagram showing the relationship between the scanning form of the laser beam and the melting depth and the number of pores;

[0029] Fig.14 is a graph showing the relationship between the scanning frequency, the penetration depth, and the number of pores when the laser beam is scanned in a sinusoidal wave shape with a scanning amplitude of 1.5 mm;

[0030] Fig.15 is a graph showing the relationship between the scanning frequency, the penetration depth, and the number of pores when the laser beam is scanned in a spiral shape with a scanning amplitude of 1.0 mm;

[0031] Fig.16 is a graph showing the relationship between the scanning frequency, the penetration depth, and the number of pores when the laser beam is scanned in a spiral shape with a scanning amplitude of 1.5 mm;

[0032] Fig.17 is a graph showing the relationship between the penetration depth and the number of pores during laser welding;

[0033] Fig.18A This is an image of the weld surface shape when the laser beam is scanned in a sinusoidal shape with a scanning amplitude of 1.5 mm and a scanning frequency of 440 Hz, and the laser output is 5 kW.

[0034] Fig.18B yes Fig.18A X-ray diffraction image of the weld shown;

[0035] Fig.18C yes Fig.18A An image of the cross-sectional shape of the weld shown;

[0036] Fig.19A This is an image of the weld surface shape when the laser beam is scanned in a spiral shape with a scanning amplitude of 1.5 mm and a scanning frequency of 100 Hz, and the laser output is 5 kW.

[0037] Fig.19B yes Fig.19A X-ray diffraction image of the weld shown;

[0038] Fig.19C yes Fig.19A An image of the cross-sectional shape of the weld shown;

[0039] Fig. 20A is a surface shape image of a weld during hybrid welding according to a comparative example;

[0040] Fig. 20B yes Fig. 20A X-ray diffraction image of the weld shown;

[0041] Fig. 20C yes Fig. 20AAn image of the cross-sectional shape of the weld shown;

[0042] Fig.21A is a surface shape image of a weld during hybrid welding according to the embodiment;

[0043] Fig.21B yes Fig.21A X-ray diffraction image of the weld shown;

[0044] Fig. 21C yes Fig.21A An image of the cross-sectional shape of the weld shown;

[0045] Fig. 22 It is a schematic diagram of the plane shape of the weld;

[0046] Fig.23A The laser welding in the comparative example Fig. 22 Schematic diagram of the cross section at line AA;

[0047] Fig. 23B The laser welding in the comparative example Fig. 22 A schematic cross-sectional view of the BB line;

[0048] Fig.24A The laser welding method according to the embodiment Fig. 22 Schematic diagram of the cross section at line AA;

[0049] Fig. 24B The laser welding method according to the embodiment Fig. 22 Schematic diagram of the cross section at line BB. DETAILED DESCRIPTION

[0050] The following is a description of the embodiments of the present disclosure based on the accompanying drawings. It should be noted that the following description of the preferred embodiments is essentially only an example and is not intended to limit the present disclosure, its application objects or its use.

[0051] (Implementation Method)

[0052] [1: Structure of hybrid welding device]

[0053] Figure 1 A schematic diagram of the structure of a hybrid welding device according to an embodiment is shown. Figure 2 The figure schematically shows the tilt state of the welding head relative to the welding direction.

[0054] It should be noted that, in the following description, the surface of the workpiece 40 irradiated with the laser beam LB and the arc is referred to as the "surface", and the surface of the workpiece 40 opposite to the surface in the thickness direction is referred to as the "back surface". In addition, the thickness direction of the workpiece 40 is referred to as the Z direction, the direction along the welding line on the surface of the workpiece 40 is referred to as the X direction, and the direction on the surface of the workpiece 40 orthogonal to the X direction is referred to as the Y direction. The X direction is also referred to as the welding direction.

[0055] It should be noted that in the present application specification, "orthogonal", "parallel" or "identical" refers to orthogonal, parallel or identical including the assembly tolerance and processing tolerance of the composite welding device 30 and its components, and does not mean that the comparison objects are orthogonal, parallel or identical in a strict sense.

[0056] like Figure 1 As shown, the hybrid welding device 30 includes a laser welding device 10 and an arc welding device 20 .

[0057] The laser welding device 10 includes a robot arm 13, a laser head 11, and an optical fiber 12 (see Figure 2 ) and a laser light source (not shown), the laser head 11 is installed at the front end of the robot arm 13 and irradiates the laser beam LB, one end of the optical fiber 12 is connected to the laser head 11, and the laser light source is optically coupled to the other end of the optical fiber. In addition, the laser welding device 10 also has a robot arm control unit 14 and a laser output control unit (not shown), the robot arm control unit 14 is connected to the robot arm 13, and the laser output control unit controls a power supply (not shown) connected to the laser light source and the operation of the power supply.

[0058] An optical scanner (not shown) for two-dimensionally scanning the surface of the workpiece 40 with the laser beam LB is provided inside the laser head 11. The optical scanner is, for example, a well-known galvanometer scanner.

[0059] The arc welding device 20 includes a robot arm 24, a welding torch 21, and a welding wire feeding device 23. The welding torch 21 is mounted on the front end of the robot arm 24, and the welding wire feeding device 23 is mounted on the robot arm 24. The welding wire 22 (see FIG. 2 ) is fed to the welding wire feeding device 23. Figure 2 ) is fed in the direction toward the surface of the workpiece 40 (forward feeding), and the welding wire 22 is also fed in the direction away from the surface of the workpiece 40 (reverse feeding). The welding torch 21 holds the welding wire 22 in a manner that enables the welding wire 22 to be fed. In addition, the arc welding device 20 further includes a robot arm control unit 25 and an arc control unit (not shown), wherein the robot arm control unit 25 is connected to the robot arm 24, and the arc control unit controls a welding power source (not shown) electrically connected to the welding wire 22 and the operation of the welding power source.

[0060] The robot control units 14 and 25 , the laser control unit and the arc control unit are respectively composed of one or more CPUs (Central Processing Units) or one or more MCUs (Micro Controller Units).

[0061] It should be noted that, in the following description, the laser head 11 for performing laser welding and the welding torch 21 for performing arc welding are collectively referred to as a welding head.

[0062] In this embodiment, laser welding is first performed on the workpiece 40, and then arc welding is further performed on the welded portion formed by laser welding to finally form a weld (for example, see Fig.21A ).

[0063] At this time, laser welding is performed while the laser head 11 is retracted relative to the welding direction. On the other hand, in arc welding, the welding torch 21 is advanced relative to the welding direction.

[0064] Here, advancing the welding torch 21 means: Figure 2 As shown, the front end of the welding torch 21 is positioned ahead of the rear end in the welding direction of the workpiece 40. Retracting the laser head 11 means that the front end of the laser head 11 is positioned behind the rear end in the welding direction of the workpiece 40.

[0065] The state in which the line connecting the front end and the rear end of the welding head is perpendicular to the surface of the workpiece 40 is called a surface vertical state. In laser welding and arc welding, welding can also be performed with the welding head in the surface vertical state.

[0066] In addition, in both laser welding and arc welding, shielding gas is blown toward the welding part during the welding process. Alternatively, shielding gas may be blown only from the arc side. Shielding gas is blown toward the welding part from the nozzle at the front end through a gas pipeline (not shown) provided in the welding torch 21.

[0067] It should be noted that, in the present embodiment, the arc welding robot arm and the laser welding robot arm are respectively independent structures, and two robots are used for composite welding, but it can also be configured as follows: an arc welding torch for arc welding and a laser welding head for laser welding are integrated to form a welding head, and one robot arm is used to perform arc welding and laser welding.

[0068] [2: Preliminary study on laser welding conditions]

[0069] As described above, it is difficult to increase the welding speed while obtaining a predetermined penetration depth in arc welding. On the other hand, in laser welding, since the power density of the laser beam LB is high, it is possible to increase the welding speed while obtaining a predetermined penetration depth. However, whether these can be achieved while reducing welding defects varies depending on the material of the workpiece 40, etc., and therefore it is necessary to set the welding conditions appropriately.

[0070] In particular, when the material of the workpiece 40 is aluminum or an aluminum alloy, porosity 43 as a welding defect is easily generated (see, for example, Figure 7 ), the pores 43 are bubbles 43a generated during the welding process (for example, see Fig.23A ) remains inside the workpiece 40. In this regard, the following is revealed in the paper by Li et al.: By moving the laser head along the welding line while scanning the laser beam in a direction intersecting the welding line, the pores 43 can be reduced, especially when the laser beam is scanned in a spiral shape, the effect of reducing pores is best (Liqun Li, Jianfeng Gong, Hongbo Xia, Genchen Peng, Yu Hao, Shenghao Mengand Jiming Wang, "Influence of scan paths on flow dynamics and weld formations during oscillating laser welding of 5A06 alumihum alloy", Journal of Materials Research and Technology (US), 2021, Vol. 11, p. 19-32).

[0071] The paper points out that the reason why the pores 43 can be reduced is that by performing welding while scanning the laser beam as described above, the speed of the molten flow in the molten pool can be reduced, the temperature gradient can be reduced, and also because the shape of the vortex generated by the flow of liquid metal inside the molten pool is very complex.

[0072] However, this paper only discusses welding speeds equivalent to those of arc welding, that is, only cases where the welding speed is extremely low for laser welding (1.0 m / min), without revealing the operation at high welding speeds required for practical applications, such as welding speeds of more than 3 m / min.

[0073] Therefore, the inventors of the present application conducted preliminary studies on the conditions of laser welding in hybrid welding and investigated the relationship between the penetration depth and the occurrence of welding defects.

[0074] When laser welding or hybrid welding of laser welding and arc welding is used to perform welding with a high welding speed of more than 3 m / min and deep penetration, i.e., high-speed deep penetration welding, if the material of the workpiece 40 is a material such as aluminum or aluminum alloy that has fast heat conduction, fast heat dissipation, and solidifies before the generated pores escape, then pores 43 will be significantly generated inside the welding part during welding.

[0075] Table 1 shows the shapes of the workpieces and the laser welding conditions in the preliminary study.

[0076]

Table 1

[0077]

[0078] It should be noted that in this preliminary study, laser welding was performed to form a linear weld 50 on a plate material having a shape shown in Table 1, that is, a workpiece 40. That is, a weld line is a straight line extending in a predetermined direction. It should be noted that in the following description, the direction along the weld line is referred to as the X direction, the direction orthogonal to the weld line on the surface of the workpiece 40 is referred to as the Y direction, and the direction orthogonal to the X direction and the Y direction is referred to as the Z direction. The Z direction corresponds to the thickness direction of the workpiece 40.

[0079] In addition, although these are not described in Table 1, the wavelength of the laser beam LB is 975 nm, and the beam diameter of the laser beam LB is approximately several hundred μm (500 μm to 700 μm).

[0080] It should be noted that the surface shape and cross-sectional shape were observed using a microscope as a shape evaluation of the weld 50. In addition, an X-ray diffraction image of the workpiece including the weld 50 was obtained mainly to evaluate the presence and number of pores 43. It should be noted that the weld 50 was formed on the surface of the workpiece 40, and the length of the weld 50 was 130 mm.

[0081] [2-1: Preliminary study on laser welding (comparative example)]

[0082] In addition, a preliminary study was conducted using a comparative example in which the laser beam LB was not scanned in a direction intersecting the weld line but laser welding was performed in a linear manner in the direction along the weld line. In the comparative example, the laser output was specified so that it was changed in units of 50 W within the range of 2000 W to 4000 W, and the study was conducted. First, the results of the comparative example are described.

[0083] Figure 3 The relationship between the laser output and the depth of the recess on the weld surface according to the comparative example is shown. Figure 4FIG. 1 shows a Z-direction profile of a weld according to an example of a comparative example. Figure 5 The Z-direction profiles of other example welds are shown.

[0084] like Figure 3 As shown in FIG. 1 , until the laser output reaches 2500W, almost no depression is formed on the workpiece 40. On the other hand, when the laser output exceeds 2500W, the depth of the depression based on the surface of the workpiece 40 becomes deeper as the laser output increases. This is because, until the laser output reaches 2500W, the workpiece 40 is in a heat conduction welding mode in which welding is performed by heat conduction, and almost all of the laser light is reflected, so the penetration depth of the workpiece 40 is shallow. On the other hand, when the laser output exceeds 2500W, the workpiece 40 is formed by forming a small hole 42 (for example, see FIG. Fig.23A ) is used for keyhole welding. In the keyhole 42, the laser beam is repeatedly reflected, i.e., multiple reflections occur, so that the penetration depth of the workpiece 40 becomes deeper. In addition, as the penetration depth becomes deeper, the molten metal will be scattered (sputtering) or the undercut 51 will be generated, thereby generating a depression on the weld surface. In addition, when the laser output is 3500W or more, due to the excessive heat input, the molten pool will droop toward the back plate side, and a depression caused by underfill 52 will be generated on the weld surface.

[0085] Figure 4 Shown in Figure 3 The Z-direction profile of the weld 50 formed under the laser output condition (about 3250W) at the circle marked with symbol IV in FIG. Figure 4 As shown, a depression is formed on both sides of the weld 50. The depression is called an undercut 51.

[0086] Figure 5 Shown in Figure 3 FIG. 5 is a diagram showing the Z-direction profile of the weld 50 formed under the laser output condition (about 3800 W) at the circle marked with the symbol V in FIG. 5 . Under this condition, Figure 5 As shown, a depression is formed in the entire portion where the weld 50 is formed. This depression is referred to as an underfill 52.

[0087] and Figure 4 , Figure 5 The corresponding laser output conditions are equivalent to keyhole welding. Figure 4 Under the conditions shown, the molten pool 41 formed during laser welding (for example, see Fig.23A ) does not reach the back of the workpiece 40, which is the so-called partial penetration state. Figure 5Under the conditions shown, the molten pool 41 formed during laser welding reaches the back side of the workpiece 40, which is a so-called complete penetration state. In this case, a full penetration weld is formed on the back side of the workpiece 40. Since a portion of the molten pool 41 droops from the back side of the workpiece 40, the above-mentioned under-welded portion 52 is formed.

[0088] It can be seen that when laser welding becomes a keyhole welding mode and the penetration depth becomes deeper than a certain level, a depression will be formed, and the depth of the depression will also become deeper as the laser output increases.

[0089] On the other hand, in the preliminary study related to the comparative example, an interesting correlation was found between the laser output (Laser Output) and the number of porosity 43 (Number of porosity).

[0090] Figure 6 The relationship between the laser output, the penetration depth, and the number of pores in the comparative example is shown. Figure 7 A surface shape image, an X-ray diffraction image, and a cross-sectional shape image of a weld according to a comparative example are shown.

[0091] It should be noted that Figure 7 The images shown are in Figure 6 2 and 3. The images of the weld seam 50 formed under the laser output conditions at the circles marked with symbols I to III in FIG.

[0092] like Figure 6 As shown in FIG. 1 , when the laser welding is in the heat conduction welding mode, the penetration depth is almost independent of the laser output (the penetration depth is about 0.3 mm to 0.4 mm). In addition, the number of pores 43 is independent of the laser output and is zero. In this case, the workpiece 40 is almost not melted, and the small hole 42 is not formed, so it can be considered that the pores 43 are not generated.

[0093] In contrast, when laser welding is performed in keyhole welding mode, Figure 6 As shown, the melting depth increases with the increase of laser output and reaches saturation at 3 mm. This is because the thickness of the workpiece 40 is 3 mm, so it reaches a complete melting state.

[0094] On the other hand, the number of pores 43 increases monotonically with the increase of laser output, then turns to decrease when the laser output is about 3200W, and then decreases monotonically after the laser output exceeds 3200W.

[0095] Considering the change in penetration depth due to the laser output, it is considered that when the penetration is completely achieved and the penetration weld begins to be formed, the number of pores 43 begins to decrease.

[0096] In addition, if Figure 7 As shown in the middle section of FIG. 1 , in the partially melted state, multiple pores 43 are observed inside the X-ray diffraction image. It should be noted that in the X-ray diffraction image, the color of the low-density portion is light. In the X-ray diffraction image, the white portion is considered to be the pore 43, and the number of the pores 43 is counted.

[0097] On the other hand, Figure 7 As shown in the lower part of , in the fully melted state, the number of pores 43 is reduced as compared with the partially melted state as shown in the X-ray diffraction image.

[0098] However, in the case of partial penetration state and complete penetration state, the number of pores 43 is not zero, and is not reduced to less than a dozen. Figure 7 From the cross-sectional shape images of the middle and lower sections, it can be observed that the air hole 43 is formed on the side close to the back side of the workpiece 40.

[0099] Based on these, it is inferred that the generation of the pores 43 is related to the formation of the keyhole 42. The bottom of the keyhole 42 is a portion directly irradiated by the laser beam LB, and the state of the molten pool 41 around it is also more likely to become unstable than other areas.

[0100] In addition, in this study, the material of the workpiece 40 is A6061, which is one of the aluminum alloys. Compared with iron, aluminum or aluminum alloys have a lower melting point and higher thermal conductivity, so they will melt quickly under the irradiation of the laser beam LB, and when they are no longer irradiated by the laser beam LB, the molten part will solidify quickly. It can be considered that: coupled with this factor, the bubbles 43a are easily trapped at the bottom of the unstable small hole 42, thereby generating pores 43. In addition, it can be inferred that: when it becomes a completely melted state, since the bottom of the small hole 42 is close to the back of the workpiece 40, the bubbles 43a are easy to escape from the bottom of the thinned small hole 42 to the back of the workpiece 40, thereby reducing the number of pores 43.

[0101] However, in a preliminary study involving a comparative example in which laser welding was performed linearly along the weld line instead of scanning the laser beam LB in a direction intersecting the weld line, the number of pores 43 could not be reduced to zero even when laser welding was performed to achieve complete penetration.

[0102] [2-2: Preliminary research on laser welding]

[0103] Based on the results of the preliminary study related to the comparative example, laser welding was performed while scanning the laser beam LB in a direction intersecting the weld line as attempted by Lee et al. Here, two types of scanning modes of the laser beam LB were studied.

[0104] Fig. 8A This is a schematic diagram showing a scanning trajectory when a laser beam is made to perform simple harmonic vibration in a direction intersecting with a weld line. Figure 8B It is shown that the laser beam is directed in accordance with Fig. 8A Schematic diagram of the scanning trajectory of the laser beam when the laser head is moved along the welding line at a predetermined speed while scanning along the trajectory shown. Fig. 9A This is a schematic diagram showing a scanning trajectory when a laser beam is scanned in a circular shape. Fig. 9B It is shown that the laser beam is directed in accordance with Fig. 9A Schematic diagram of the scanning trajectory of the laser beam when the laser head is moved along the welding line at a predetermined speed while scanning along the trajectory shown.

[0105] It should be noted that Fig. 8A , Fig. 9A The trajectories shown in FIG. 1 and FIG. 2 are trajectories of the laser beam LB when the optical scanner such as a galvanometer scanner in the laser head 11 is operated while the robot arm 13 is kept stationary without moving in the welding direction.

[0106] The first scanning mode is to scan the laser beam LB on the surface of the workpiece 40 in a sinusoidal shape. Specifically, the laser beam LB is scanned as follows: Fig. 8A , Figure 8B Scan as shown.

[0107] First, if Fig. 8A As shown in FIG. 1 , the laser beam LB is made to perform simple harmonic oscillation in the Y direction with a scanning amplitude A. In this case, the scanning amplitude A is set to 1.5 mm and the scanning frequency is set to 100 Hz. The laser beam LB is made to scan as follows: Fig. 8A The scanning speed is fastest at the midpoint of the trajectory shown, and the scanning speed is slower as it moves away from the midpoint. In addition, the scanning of the laser beam LB is temporarily stopped at both ends of the scanning trajectory.

[0108] While making the laser beam LB follow Fig. 8A The robot 13 is scanned along the trajectory shown in FIG. 1 while the front end of the robot arm 13 is moved along the X direction as the welding direction at a constant speed (in this case, the welding speed (3.0 m / min)). Figure 8B As shown, the laser beam LB is scanned so as to draw a sinusoidal wave shape on the surface of the workpiece 40 .

[0109] The second scanning mode is to scan the laser beam LB in a spiral shape on the surface of the workpiece 40. Specifically, the laser beam LB is scanned in a spiral shape. Fig. 9A , Fig. 9B It should be noted that the spiral shape is also called a cycloid shape.

[0110] First, the laser beam LB is made Fig. 9A The scanning is performed so as to draw a circle as shown. The diameter Φ of the circle corresponds to the scanning amplitude. In this case, the scanning amplitude Φ is set to 1.5 mm and the scanning frequency is set to 100 Hz.

[0111] While making the laser beam LB follow Fig. 9A The robot 13 is scanned along the trajectory shown in FIG. 1 while the front end of the robot 13 is moved along the X direction at a constant speed (= 3.0 m / min). Fig. 9B As shown, the laser beam LB is scanned in a spiral shape on the surface of the workpiece 40 .

[0112] When the laser beam LB is scanned in a sinusoidal shape or when the laser beam LB is scanned in a spiral shape, a molten pool 41 having a Y-direction width corresponding to the scanning amplitude is formed on the workpiece 40 , and a weld 50 is formed after the molten pool 41 solidifies.

[0113] Fig.10 It is a graph showing the relationship between the scanning form of the laser beam and the depth of the concavity on the weld surface. Fig.10 The figure shows the depth of the depression when the workpiece 40 is laser welded in the above two scanning shapes. It should be noted that on the horizontal axis, "sine" represents the scanning shape of a sine wave, and "spiral" represents the scanning shape of a spiral. The number next to "sine" or "spiral" represents the scanning amplitude (mm). In addition, Fig.10 The example shown shows the average value of the results when the laser beam LB is scanned at a plurality of scanning frequencies shown in Table 1.

[0114] Depend on Fig.10 It can be seen that the weld depression depth is the largest when the scanning amplitude is 0.5 mm in both the sine wave scanning form and the spiral scanning form. In these cases, a penetration weld is formed on the back side of the workpiece 40, which is not shown.

[0115] On the other hand, when the scanning amplitude is 1.5 mm, the depth of the depression becomes shallower than when the scanning amplitude is 0.5 mm, but the type of depression formed differs depending on the scanning form.

[0116] Fig.11 This is a diagram showing an example of the Z-direction profile of a weld when a laser beam is scanned in a sinusoidal wave shape. Fig.12 This is a diagram showing another example of the Z-direction profile of the weld when the laser beam is scanned in a spiral shape. Fig.11 , Fig.12 All of them represent the profile when the scanning amplitude is 1.5 mm. Fig.11In the example shown, the scanning frequency is 160 Hz. Fig.12 In the example shown, the scanning frequency is 200 Hz.

[0117] exist Fig.11 In the example shown in FIG. 1 , when the laser beam is scanned in a sinusoidal wave shape, undercuts 51 are formed on both sides of the weld 50. Fig.12 In the example shown when the laser beam is scanned in a spiral shape, a depression 53 is formed in parallel with the weld bead 50. In the latter case, reflecting the formation state of the molten pool 41, it is considered that the depression 53 is formed at a position offset to one side in the Y direction.

[0118] As described above, the type and depth of the recess formed may differ depending on the scanning form of the laser beam LB. In addition, the depth of penetration and the number of pores 43 also differ depending on the scanning form of the laser beam LB.

[0119] Fig.13 is a graph showing the relationship between the scanning form of the laser beam and the depth of melting and the number of pores. Fig.10 The horizontal axis shown is the same. In addition, the scanning form of the laser beam, the penetration depth, and the number of pores 43 are also shown as average values ​​of the results obtained when the laser beam LB is scanned at a plurality of scanning frequencies shown in Table 1.

[0120] Depend on Fig.13 It can be seen that the depth of melt becomes shallower as the scanning amplitude increases in both the sinusoidal scanning form and the spiral scanning form. On the other hand, in terms of the change in the depth of melt relative to the scanning amplitude, when the laser beam LB is scanned in a spiral shape, the depth of melt becomes shallower as the scanning amplitude increases.

[0121] In addition, when the scanning amplitude is 1.5 mm, the number of pores 43 is reduced in both the sine wave scanning form and the spiral scanning form, compared with the case where the scanning amplitude is 0.5 mm. In addition, when the laser beam LB is scanned in a spiral form, the number of pores 43 decreases as the scanning amplitude becomes larger. Here, it can be considered that the reason why the number of pores 43 is smaller when the sine wave scanning amplitude is 0.5 mm compared with the case where the sine wave scanning amplitude is 1.0 mm is that the state of penetration welding has been achieved and the small hole 42 has reached the back side.

[0122] In addition, regarding the condition that the number of pores 43 is small, specifically, Fig.13 The scanning conditions enclosed by the box in the figure are used to study the changes in the penetration depth and the number of pores 43 with respect to the scanning frequency.

[0123] Fig.14This is a diagram showing the relationship between the scanning frequency, the penetration depth, and the number of pores when the laser beam is scanned in a sinusoidal wave shape with a scanning amplitude of 1.5 mm. Fig.15 This is a graph showing the relationship between the scanning frequency, the penetration depth, and the number of pores when the laser beam is scanned in a spiral shape with a scanning amplitude of 1.0 mm. Fig.16 This is a graph showing the relationship between the scanning frequency, the penetration depth, and the number of pores when the laser beam is scanned in a spiral shape with a scanning amplitude of 1.5 mm.

[0124] Depend on Figure 14 to Figure 16 It can be seen that in all these cases, the penetration depth tends to become shallower as the scanning frequency increases. Fig.14 In the example shown, there is a tendency that the reduction in penetration reaches saturation when the scanning frequency is above 440 Hz; Fig.16 In the example shown, there is a tendency that the reduction in penetration reaches saturation when the scanning frequency is 450 Hz or more. Fig.15 In the example shown, although the rate of change of the penetration depth is different before the scanning frequency reaches 300 Hz and after the scanning frequency reaches 300 Hz, the penetration depth decreases monotonically within the scanning frequency range of 100 Hz to 800 Hz.

[0125] In addition, by Figure 14 to Figure 16 It can be seen that in these cases, when the scanning frequency reaches a certain value or more, the number of pores 43 becomes zero. Fig.14 In the example shown, this value is 440 Hz; Fig.15 In the example shown, this value is 240Hz; Fig.16 In the example shown, this value is 100 Hz.

[0126] Based on these, it can be inferred that there may be some correlation between the penetration depth and the number of pores 43. Therefore, the relationship between the penetration depth and the number of pores 43 was studied according to the scanning form of the laser beam LB.

[0127] Fig.17 This is a graph showing the relationship between the penetration depth and the number of pores during laser welding.

[0128] As inferred above, when the penetration depth reaches a certain value or more, there is a tendency that the number of pores 43 increases as the penetration depth increases, and this tendency itself is the same regardless of the scanning form of the laser beam LB.

[0129] However, the degree to which the number of pores 43 increases with increasing penetration depth varies depending on the scanning form of the laser beam LB. Fig.17It can be seen that the number of pores 43 tends to decrease when the laser beam LB is scanned in a spiral shape compared to when the laser beam LB is scanned in a sinusoidal shape. It is believed that this is related to the width of the molten pool 41 formed during the laser welding process in the Y direction, which is a direction intersecting the weld line. This will be described later.

[0130] As a result of the preliminary study conducted as described above, conditions were found under which the number of pores 43 is zero when laser welding is performed while the laser beam LB is two-dimensionally scanned on the surface of the workpiece 40. In this preliminary study, it was confirmed that the number of pores 43 is zero under the following three conditions.

[0131] First, it was confirmed that when the laser beam LB was scanned in a sinusoidal shape, the number of pores 43 was zero by setting the scanning amplitude A to 1.5 mm and the scanning frequency to 440 Hz or more. The penetration depth under this condition was about 1.3 mm.

[0132] Furthermore, it was confirmed that when the laser beam LB was spirally scanned, the number of pores 43 was zero by setting the scanning amplitude Φ to 1.0 mm and the scanning frequency to 240 Hz or more. The penetration depth was about 1.8 mm when the scanning frequency was 240 Hz.

[0133] Furthermore, it was confirmed that when the laser beam LB was spirally scanned, the number of pores 43 was zero by setting the scanning amplitude Φ to 1.5 mm and the scanning frequency to 100 Hz or more. The penetration depth was about 1.8 mm when the scanning frequency was 100 Hz.

[0134] However, in these cases, partial penetration was achieved, but sufficient penetration was not achieved. Therefore, as a further study, laser welding was performed by increasing the laser output from 4 kW to 5 kW, and the shape of the weld was evaluated.

[0135] Fig.18A This is an image of the weld surface shape when the laser beam is scanned in a sinusoidal wave shape with a scanning amplitude of 1.5 mm and a scanning frequency of 440 Hz, and the laser output is 5 kW. Fig.18B yes Fig.18A X-ray diffraction image of the weld shown. Fig.18C yes Fig.18A Image of the cross-sectional shape of the weld shown.

[0136] Fig.19A This is an image of the weld surface shape when the laser beam is scanned in a spiral shape at a scanning amplitude of 1.5 mm and a scanning frequency of 100 Hz, and the laser output is 5 kW. Fig.19B yes Fig.19A X-ray diffraction image of the weld shown. Fig.19C yes Fig.19A Image of the cross-sectional shape of the weld shown.

[0137] Depend on Fig.18C , Fig.19C It can be seen that in these cases, the weld 50 almost reaches the back surface of the workpiece 40. In particular, in the example shown in FIG. 19 , a full penetration weld is formed on the back surface of the workpiece 40.

[0138] On the other hand, Fig.18B , Fig.18C As shown in FIG. 1 , when the laser beam was scanned in a sinusoidal shape at a scanning amplitude of 1.5 mm and a scanning frequency of 440 Hz, the generation of the pores 43 was observed when the laser output was 5 kW. However, when the laser beam was scanned in a spiral shape at a scanning amplitude of 1.5 mm and a scanning frequency of 100 Hz, the generation of the pores 43 was hardly observed even when the laser output was 5 kW.

[0139] In other words, when the laser output was set to 5 kW, pores 43 were seen when the laser beam was scanned in a sinusoidal shape with a scanning amplitude of 1.5 mm and a scanning frequency of 440 Hz, and almost no pores 43 were seen when the laser beam was scanned in a spiral shape with a scanning amplitude of 1.5 mm and a scanning frequency of 100 Hz.

[0140] The case where the laser beam is scanned in a sinusoidal shape with a scanning amplitude of 1.5 mm and a scanning frequency of 440 Hz and the case where the laser beam is scanned in a spiral shape with a scanning amplitude of 1.5 mm and a scanning frequency of 100 Hz are both boundary conditions related to the scanning frequency and the number of pores 43 is zero.

[0141] However, if Fig.17 As shown, when the laser beam LB is scanned in a sinusoidal shape, the number of pores 43 increases more with increasing penetration than when the laser beam LB is scanned in a spiral shape.

[0142] It can be inferred that it is precisely because of this factor that when the laser beam LB is scanned in a sinusoidal shape, the number of pores 43 increases from zero due to the increase in laser output and the deepening of the melting depth. It should be noted that it can be considered that when the laser beam LB is scanned in a sinusoidal shape, the number of pores 43 can also be zero by appropriately setting the relationship between the laser output, the scanning amplitude, and the scanning frequency.

[0143] It should be noted that, at a high welding speed of 3.0 m / min, and a penetration depth of 3.0 mm in a fully penetrated state corresponding to a thickness of 3 mm of the workpiece 40, a laser output of 5 kW, and a laser beam scanning in a spiral shape at a scanning amplitude of 1.5 mm and a scanning frequency of 100 Hz, hybrid welding is performed in which the laser welding described later is performed first, and then the arc welding is performed, and in the arc welding, short-circuit welding of repeatedly feeding the welding wire 22 forward and backward is performed, so that even if welding is performed at a high welding speed of more than 3 m / min, the heat input of the arc welding performed later can be used to suppress the heat dissipation of the molten pool 41, and the discharge of the bubbles 43a in the molten pool 41 can be promoted more stably, and the number of pores 43 inside the welded part can be achieved to be zero. The details will be described later.

[0144] As studied above, it is known that in order to make the number of pores 43 in the weld 50 zero while targeting a welding speed and penetration depth that are above the prescribed level, in this case, in order to make the number of pores 43 in the weld 50 zero while targeting a high welding speed of 3.0 m / min that is sufficiently faster than the welding speed during arc welding and a penetration depth of 3.0 mm that is equivalent to the thickness of the workpiece 40 of 3 mm in a completely penetrated state, it is effective to perform laser welding while scanning the laser beam LB in a direction that intersects the direction along the weld line. In addition, preliminary studies have shown that the scanning form of the laser beam LB can be either a sine wave scanning or a spiral scanning. It should be noted that in each case, the scanning amplitude and scanning frequency need to be appropriately set.

[0145] However, by Figures 18A to 18C , Figures 19A to 19C It is found that the surface roughening of the weld bead 50 and the generation of the depressions 53 cannot be suppressed.

[0146] Based on this, hybrid welding in which arc welding is performed after laser welding is performed in an attempt to improve the shape of the weld bead 50 .

[0147] [2-3: Research on hybrid welding]

[0148] Fig. 20A This is an image of the surface shape of a weld during hybrid welding according to a comparative example. Fig. 20B yes Fig. 20A X-ray diffraction image of the weld shown. Fig. 20C yes Fig. 20A Image of the cross-sectional shape of the weld shown.

[0149] Fig.21A This is a surface shape image of a weld during hybrid welding according to the embodiment. Fig.21B yes Fig.21AX-ray diffraction image of the weld shown. Fig. 21C yes Fig.21A Image of the cross-sectional shape of the weld shown.

[0150] As a comparative example, laser welding was performed under the conditions shown in [2-1]. That is, the laser beam LB was not scanned in a direction intersecting the weld line, but the laser beam LB was laser welded in a linear shape in the direction along the weld line. That is, the welding speed was 3.0 m / min and the laser output was 4 kW. The shape of the weld 50 formed in this case is shown in FIG. Figure 20A to Figure 20C middle.

[0151] On the other hand, in this embodiment, laser welding is performed while the laser beam LB is scanned in a spiral shape in a direction intersecting the welding line. The scanning amplitude Φ is 1.5 mm, and the scanning frequency is 100 Hz. In addition, the welding speed is 3.0 m / min, and the laser output is 5 kW. The shape of the weld 50 formed in this case is shown in FIG. Figures 21A to 21C middle.

[0152] It should be noted that in Figure 20A to Figure 20C The comparative examples shown are examples and Figures 21A to 21C In the examples according to the illustrated embodiments, laser welding is performed by retracting the laser head 11 so that the front end of the laser head 11 is positioned behind the rear end in the welding direction of the workpiece 40 .

[0153] In addition, Figure 20A to Figure 20C The examples shown and Figures 21A to 21C In the examples shown, arc welding was performed under the following conditions.

[0154] The arc current, which is the set current as the moving average, is 100 A, and the arc voltage, which is the set voltage as the moving average, is 11.1 V. In addition, as described above, arc welding is performed by advancing the welding torch 21. The wire diameter of the welding wire 22 is φ1.6 mm. In addition, the arc welding in this case is short-circuit welding in which the welding wire 22 is repeatedly fed forward and reversely at a predetermined frequency (100 to 150 Hz) toward the surface of the workpiece 40.

[0155] Here, the reason why the arc welding is made into short-circuit welding in which forward feeding and reverse feeding are repeated is that: when the molten metal of the welding part of the workpiece 40 becomes liquid, that is, when a molten pool is formed, by repeatedly performing short-circuit welding in which forward feeding and reverse feeding are performed, a humping bead will not be generated even if the welding speed is fast, but a normal weld will be formed. For example, it has the advantage that welding can be performed without any problem even in high-speed welding with a welding speed of 10.0 m / min. Therefore, it is very suitable for hybrid welding in which laser welding is performed first and arc welding is performed later. By such a configuration, it can cope with high-speed welding with a welding speed of more than 3 m / min. Here, a humping bead refers to a weld formed when the amount of molten metal is small and the molten metal is pushed to the rear of the molten pool under the action of strong arc pressure and solidified before it is completely returned in the arc direction when the welding speed is fast.

[0156] The comparative examples Fig. 20C 、Implementation methods involved Fig. 21C It can be seen that in both the comparative example and the present embodiment, a penetration weld is formed on the back surface of the workpiece 40, and a complete penetration state is achieved. In other words, the target penetration depth (=3.0 mm) is achieved.

[0157] On the other hand, from Fig. 20B , Fig. 20C As can be seen from the comparative example, a large number of pores 43 were observed to be generated inside the weld 50. That is, it can be seen that even if arc welding is performed after laser welding, the number of pores 43 cannot be reduced.

[0158] It can be considered that this is because, generally speaking, the heat input per unit area of ​​arc welding is smaller than that of laser welding. Therefore, after laser welding, the molten pool 41 at the arc welding site has a shallower penetration depth, and the pores 43 remaining inside the weld 50 cannot be completely discharged to the outside of the workpiece 40.

[0159] On the other hand, from Fig.21B , Fig. 21C It can be seen from this embodiment that no pores 43 are observed inside the weld 50. Fig. 21C As shown in FIG. 5 , no depression is formed on the surface of the weld 50. Fig.21A , Fig.21B It can be seen that no welding defects such as pits or cracks are generated on the surface of the workpiece 40. In other words, it has been confirmed that in hybrid welding in which laser welding is first performed along the welding direction and then arc welding, by repeatedly performing short-circuit welding in which the welding wire is fed forward and reversely during arc welding at a high welding speed, the surface of the weld after laser welding can be trimmed, and welding can be performed like surfacing, which can suppress the occurrence of welding defects and improve the shape of the weld 50.

[0160] [3: Effects, etc.]

[0161] As described above, the composite welding method involved in this embodiment includes a first step and a second step. In the first step, the laser beam LB is irradiated onto the surface of the workpiece 40 along a specified welding line. In the second step, after the first step, arc welding is further performed on the irradiated part of the laser beam LB.

[0162] In the first step, the laser beam LB is irradiated onto the workpiece 40 while performing two-dimensional scanning, thereby forming a molten pool 41 having a specified width in a direction (Y direction) intersecting the thickness direction (Z direction) of the workpiece 40 and the direction along the welding line (X direction).

[0163] In the second step, arc welding is performed while forward feeding and reverse feeding of welding wire 22 are repeated in a predetermined cycle.

[0164] According to the present embodiment, by performing laser welding before arc welding, it is possible to weld the workpiece 40 at a faster welding speed and obtain a deeper penetration than when arc welding is performed alone. In addition, by performing arc welding after laser welding, short-circuit welding in which forward feeding and reverse feeding are repeated is performed in the arc welding, so that welding can be performed without generating weld humping even in high-speed welding of 3 m / min or more. In addition, by performing arc welding using the welding wire 22, the shape of the weld 50 can be made good without generating depressions such as undercut 51 or under-welded portion 52, and the generation of welding defects such as cracks can be suppressed. It should be noted that weld humping refers to a situation in which the weld 50 is discontinuous when the weld 50 is observed from above, i.e., a so-called hump weld.

[0165] Furthermore, by performing laser welding while two-dimensionally scanning the laser beam LB under predetermined conditions, the generation of the pores 43 can be suppressed.

[0166] In particular, it is considered that the following mechanism works to suppress the occurrence of the pores 43 .

[0167] Fig. 22 It is a schematic diagram of the plane shape of the weld. Fig.23A The laser welding in the comparative example Fig. 22 Schematic diagram of the cross section at line AA. Fig. 23B The laser welding in the comparative example Fig. 22 Schematic diagram of the cross section at line BB. Fig.24A The laser welding method according to the embodiment Fig. 22 Schematic diagram of the cross section at line AA. Fig. 24B The laser welding method according to the embodiment Fig. 22 Schematic diagram of the cross section at line BB.

[0168] First, consider Fig.23A , Fig. 23B These figures are schematic cross-sectional views of the weld 50 when the laser beam LB is not scanned in a direction intersecting the weld line but laser welding is performed in a linear manner along the weld line, that is, schematic cross-sectional views of the weld 50 in the case shown in [2-1].

[0169] like Fig.23A As shown, a molten pool 41 is formed at the irradiation site of the laser beam LB. In addition, inside the molten pool 41, a small hole 42 with an opening on the surface is formed at the irradiation point of the laser beam LB and its vicinity. When the laser beam LB travels along the X direction, the heat input to the workpiece 40 is sharply reduced, so the molten pool 41 solidifies to form a solidified portion 44, which eventually becomes a weld 50. Here, the laser beam LB is directly irradiated on the bottom of the small hole 42. That is, at the bottom of the small hole 42, melting and solidification of the workpiece 40 occur continuously. In addition, it can be considered that: in this part, bubbles 43a are easily generated in the molten pool 41.

[0170] like Fig.23A , Fig. 23B As shown, the width of the small hole 42 becomes narrower as going from the surface to the back side of the workpiece 40, and accordingly, the width of the molten pool 41 also becomes narrower in both the X direction and the Y direction.

[0171] In particular, at the bottom of the small hole 42, when the width of the molten pool 41 becomes narrow, the molten pool 41 solidifies before the bubbles 43a generated inside the molten pool 41 fully escape from the molten pool 41. It is considered that due to this situation, the bubbles 43a generated in the molten pool 41 remain inside the workpiece and become pores 43. In the case of complete penetration, although the bubbles 43a will escape from the bottom of the molten pool 41 to the back of the workpiece 40, if the width of the molten pool 41 is very narrow, the probability that the bubbles 43a remain inside the workpiece and become pores 43 becomes high.

[0172] On the other hand, Fig.24A , Fig. 24B As shown in FIG. 1 , when laser welding is performed while the laser beam LB is scanned in a spiral shape, the irradiation area of ​​the laser beam LB irradiated on the surface of the workpiece 40 per unit time is smaller than that of the laser beam LB. Fig.23A , Fig. 23B Therefore, it can be considered that the width of the molten pool 41 formed on the workpiece 40 is larger in both the X direction and the Y direction. Fig.23A , Fig. 23BFrom this, it can be inferred that: when viewed per unit area, the time until the molten pool 41 solidifies is greater than Fig.23A , Fig. 23B The comparative example shown is long.

[0173] That is, according to the present embodiment, during the laser welding previously performed, the width of the molten pool 41 at the bottom of the small hole 42 can be expanded, and accordingly, the time until the molten pool 41 cools and solidifies at the bottom of the small hole 42 can be extended. In other words, the molten pool 41 can be kept in a liquid state for a long time. It is inferred that as a result, the proportion of bubbles 43a remaining in the molten pool 41 at the bottom of the small hole 42 can be reduced, and the generation of pores 43 can be suppressed.

[0174] It should be noted that, in addition, hybrid welding is performed, in which arc welding and laser welding are performed on the same welding line, wherein laser welding is performed first and then arc welding, in which laser welding is performed while scanning the laser beam LB in a spiral shape, and in which short-circuit welding of repeatedly feeding the welding wire 22 forward and reversely feeding the welding wire 22 is performed, so that even if welding is performed at a high welding speed of more than 3m / min, the heat input of the subsequent arc welding can be used to suppress the heat dissipation of the molten pool 41, and the discharge of bubbles 43a in the molten pool 41 can be more stably promoted. The proportion of bubbles 43a remaining in the molten pool 41 at the bottom of the small hole 42 can be reduced, and the generation of pores 43 can be further suppressed.

[0175] In addition, when laser welding is performed while scanning the laser beam LB in a direction intersecting the weld line, that is, in [2-2], when the scanning amplitude is set to 0.5 mm, the penetration depth becomes deeper, while the number of pores 43 increases compared to the case where the scanning amplitude is 1.0 mm or 1.5 mm.

[0176] In this manner, a large number of pores 43 are likely to remain in welding in which the welding speed is high and the penetration depth is deep.

[0177] On the other hand, according to the present embodiment, by appropriately setting the scanning amplitude and the scanning frequency, the generation of the pores 43 can be significantly reduced compared to the case shown in the comparative example.

[0178] It should be noted that, regardless of whether the scanning form of the laser beam LB is a sine wave shape or a spiral shape, the number of pores 43 can be reduced. However, in the latter case, the effect of being able to deepen the penetration while reducing the number of pores 43 is better. It can be inferred that this is because, in the latter case (scanning in a spiral shape), the width of the molten pool 41 formed on the workpiece 40 is wider.

[0179] In addition, from the above, it is preferable that the width of the molten pool 41 formed on the workpiece 40 when irradiated with the laser beam LB is sufficiently larger than the beam diameter of the laser beam LB.

[0180] According to current studies by the inventors of the present application, it is known that the width of the molten pool 41 at the bottom of the keyhole 42 is preferably not less than three times and not more than nine times the beam diameter of the laser beam LB.

[0181] In addition, the hybrid welding method according to the present embodiment is particularly effective when the material of the workpiece 40 to be welded is a material that conducts heat to the molten pool 41 quickly, dissipates heat quickly, and solidifies before the bubbles 43a generated in the molten pool 41 escape, thereby easily leaving pores 43. Examples of such materials include aluminum and aluminum alloys. In addition, the hybrid welding method according to the present embodiment is also useful when the material of the workpiece 40 is magnesium, a magnesium alloy, copper, or a copper alloy.

[0182] In addition, in the hybrid welding method of the present disclosure, it is preferred to achieve a complete penetration state in laser welding (first step). As described above, the penetration depth is determined by laser welding. Therefore, if the laser welding is in a partial penetration state, sufficient penetration depth may not be ensured. In addition, if a complete penetration state is achieved on the basis of sufficiently expanding the width of the molten pool 41 to form a penetration weld, the bubbles 43a will escape from the bottom of the molten pool 41 to the back of the workpiece 40, and the effect of reducing the number of pores 43 can be expected.

[0183] It should be noted that in laser welding, even in a partial penetration state, the same effect can be expected as long as the bottom of the molten pool 41 reaches the vicinity of the back surface of the workpiece 40 .

[0184] That is, it is preferred that the bottom of the molten pool 41 formed during laser welding reaches the back side of the workpiece 40 , or the bottom extends to the vicinity of the back side of the workpiece 40 .

[0185] (Preferred embodiment)

[0186] In the hybrid welding of the present disclosure, the possible ranges of each welding parameter are as follows.

[0187] First, in the present embodiment, the welding speed is fixed at 3.0 m / min, but the present invention is not limited thereto. From the viewpoint of increasing the welding speed compared to arc welding and improving production efficiency, the welding speed may be 2.0 m / min or more.

[0188] In addition, the scanning frequency of the laser beam LB can be changed within the range of 80 Hz to 1000 Hz. It should be noted that when the welding speed is increased, the laser output and the scanning frequency also need to be increased in accordance with the welding speed. In this way, the depth and width of the molten pool 41 formed on the workpiece 40 can be maintained. It should be noted that if the scanning frequency is low relative to the welding speed, the width of the molten pool 41 will become narrower at the bottom of the keyhole 42, and pores 43 are likely to be generated. On the other hand, if the scanning frequency is too high, the amount of reflection of the laser beam LB on the surface of the workpiece 40 increases. In this case, insufficient penetration may result.

[0189] It should be noted that, from the viewpoint of ensuring the welding speed and the penetration depth and thus reducing the number of pores 43, the scanning frequency when the laser beam LB is scanned in a sinusoidal shape is preferably 80 Hz or more and 600 Hz or less. In addition, the scanning frequency when the laser beam LB is scanned in a spiral shape is preferably 80 Hz or more and 200 Hz or less. In addition, considering that the actual plate thickness of the workpiece 40 is about several mm, the laser output is preferably 2 kW or more.

[0190] The beam diameter of the laser beam LB may be changed within a range of 50 μm to 1000 μm, although it depends on the thickness of the workpiece 40. It should be noted that since the actual thickness of the workpiece 40 is several mm, the beam diameter of the laser beam LB is preferably 200 μm to 800 μm.

[0191] In addition, the hybrid welding method of the present disclosure can also be applied to a workpiece 40 having a thickness of 1.0 mm or more.

[0192] In laser welding, it is preferred to perform welding while retracting the laser head 11, but as described above, laser welding may also be performed in a vertical state. Figure 2 ) is preferably above 0 degrees and below 30 degrees.

[0193] In addition, in the arc welding in the hybrid welding of the present disclosure, the difference between the wire diameter of the welding wire 22 and the scanning amplitude of the laser beam LB in the first step is preferably within a predetermined range.

[0194] The width of the molten pool 41 corresponds to the scanning amplitude of the laser beam LB. If the wire diameter is too thin relative to the width of the molten pool 41, the arc will not expand, and it will be difficult to reliably perform arc welding on the irradiated portion of the laser beam LB. On the other hand, if the wire diameter is too thick, both forward and reverse feeding of the welding wire 22 will become difficult.

[0195] In view of the scanning amplitude (1 mm to 1.5 mm) of the laser beam LB described above, the line diameter is preferably 1.2 mm or more and 1.6 mm or less.

[0196] The wavelength of the laser beam LB is selected from a wavelength range having high absorption efficiency for the workpiece 40. When laser welding the workpiece 40 of the above-mentioned material, the wavelength of the laser beam LB is preferably 400 nm to 1200 nm.

[0197] Specifically, when laser welding is performed on the workpiece 40 made of aluminum, aluminum alloy, magnesium, and magnesium alloy among the above materials, the wavelength of the laser beam LB is preferably not less than 800 nm and not more than 1200 nm.

[0198] In addition, when laser welding is performed on the workpiece 40 made of copper or copper alloy among the above materials, the wavelength of the laser beam LB is preferably not less than 400 nm and not more than 550 nm.

[0199] In arc welding, the feeding frequency of the welding wire 22 can be changed within 50 to 300 Hz, where the feeding frequency is the repetition frequency when forward feeding and subsequent reverse feeding are regarded as one cycle. It should be noted that when the welding speed is increased, the feeding frequency also needs to be increased. From a practical point of view, the feeding frequency is preferably greater than 60 Hz and less than 200 Hz.

[0200] In addition, in order to reliably generate and maintain the arc, it is necessary to Figure 2 As shown, welding wire 22 is made to protrude a predetermined length from the front end of welding torch 21. The protrusion amount can be changed within a range of 5 mm to 30 mm. The protrusion amount is more preferably 10 mm or more and 20 mm or less.

[0201] In addition, the arc current can be changed within a range of 50 A to 700 A. From a practical point of view, the arc current is more preferably 60 A or more and 200 A or less.

[0202] In addition, the distance between the irradiation position of the laser beam LB and the position of the welding wire 22 during arc welding is preferably such that the laser beam LB does not irradiate the welding wire. In addition, the distance should not be too far. Therefore, the distance is preferably about 0 to 5 mm, and more preferably about 2 to 3 mm.

[0203] In addition, the distance between the surface of the workpiece 40 and the front end of the welding wire 22 can be changed within the range of 0 mm to 10 mm. In the present disclosure, since arc welding is short-circuit welding, the range of this distance includes 0 mm. From a practical point of view, the distance between the surface of the workpiece 40 and the front end of the welding wire 22 is more preferably 0 mm or more and 5 mm or less.

[0204] In arc welding, it is preferable to perform welding while advancing the welding torch 21, but as described above, arc welding may also be performed in a vertical state. Figure 2 ) is preferably above 0 degrees and below 30 degrees.

[0205] In addition, the shielding gas blown toward the welding part during hybrid welding is preferably a gas with low reactivity with the workpiece 40, such as an inert gas, and argon (Ar) is more preferred in view of cooling efficiency and cost.

[0206] The flow rate of the shielding gas can be changed within a range of 5 L / min to 50 L / min. From a practical point of view, the flow rate of the shielding gas is more preferably 10 L / min or more and 30 L / min or less.

[0207] It should be noted that the shielding gas is stored in a gas cylinder (not shown) or the like before being blown to the welding part of the workpiece 40. The dew point temperature of the shielding gas during storage is preferably maintained below -40°C. It should be noted that, as is well known, the dew point temperature is the temperature at which the water vapor contained in the gas begins to condense into a liquid phase and causes condensation when the gas is cooled. In fact, the dew point temperature is determined by the temperature and relative humidity of the gas. The temperature when the relative humidity is 100% RH is the dew point temperature.

[0208] In the molten pool 41 , not only the gas remaining in the workpiece 40 but also the gas introduced into the molten pool 41 from the outside of the molten pool 41 may be the cause of the bubbles 43 a and thus the pores 43 .

[0209] If the dew point temperature of the shielding gas is high, the amount of water vapor contained in the shielding gas increases. The water vapor is thermally decomposed during welding to generate hydrogen gas, which may be drawn into the molten pool 41 and cause the formation of pores 43.

[0210] Therefore, by maintaining the dew point temperature of the shielding gas within the above range, the amount of hydrogen gas generated during welding can be reduced, and the generation of pores 43 can be suppressed.

[0211] -Industrial Applicability-

[0212] According to the hybrid welding method disclosed in the present invention, it is possible to reduce welding defects such as pores while ensuring the penetration depth, and it is also possible to increase the welding speed, and therefore it is very useful in welding light metals such as aluminum.

[0213] -Explanation of symbols-

[0214] 10 Laser welding device

[0215] 11 Laser Head

[0216] 12 Fiber Optic

[0217] 13 Robotic Arm

[0218] 14 Robotic arm control unit

[0219] 20 Arc welding equipment

[0220] 21 Welding torch

[0221] 22 welding wire

[0222] 23 Wire feeding device

[0223] 24 Robotic Arm

[0224] 25 Robotic arm control unit

[0225] 30. Composite welding device

[0226] 40 Workpieces

[0227] 41 Molten Pool

[0228] 42 Small holes

[0229] 43 pores

[0230] 44 Solidification section

[0231] 50 Weld

[0232] 51 Undercut

[0233] 52 Incomplete welding

[0234] 53 depression

[0235] LB laser beam

Claims

1. A composite welding method, characterized in that: The hybrid welding method comprises a first step and a second step. In the first step, a laser beam is irradiated onto the surface of the workpiece along a predetermined welding line. In the second step, after the first step, arc welding is further performed on the laser beam irradiated portion. The material of the workpiece is any one of aluminum, aluminum alloy, magnesium, magnesium alloy, copper and copper alloy. In the first step, the laser beam is irradiated onto the workpiece while performing two-dimensional scanning, thereby forming a molten pool having a predetermined width in directions respectively intersecting the thickness direction of the workpiece and the direction along the welding line. In the second step, the arc welding is performed while forward feeding and reverse feeding of the welding wire are repeated in a predetermined cycle.

2. The hybrid welding method according to claim 1, characterized in that: In the first step, small holes opening on the surface of the molten pool are formed inside the molten pool. The width of the molten pool at the bottom of the small hole is not less than three times and not more than nine times the beam diameter of the laser beam.

3. The hybrid welding method according to claim 1, characterized in that: In the first step, the laser beam is irradiated onto the workpiece while scanning in a sinusoidal wave shape or a spiral shape.

4. The hybrid welding method according to claim 3, characterized in that: The scanning frequency when the laser beam is scanned in a sinusoidal wave shape is 80 Hz or more and 600 Hz or less, The scanning frequency when the laser beam is scanned in a spiral shape is 80 Hz or more and 200 Hz or less.

5. The hybrid welding method according to claim 1, characterized in that: The wire diameter of the welding wire is not less than 1.2 mm and not more than 1.6 mm.

6. The hybrid welding method according to claim 1, characterized in that: Blowing a shielding gas toward the welding part of the workpiece, The dew point temperature of the protective gas before blowing was maintained below -40°C.

7. The hybrid welding method according to claim 1, characterized in that: The wavelength of the laser beam is greater than or equal to 400 nm and less than or equal to 1200 nm.

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