Laser welding methods and laser welding equipment

Abstract

The laser welding method includes the following steps: A welding step involves irradiating the surface of a workpiece with a laser beam by simultaneously scanning the laser in the X-direction to create a predetermined pattern, thereby welding the workpiece. The laser is scanned such that a first pattern located in front of the origin along the X-direction becomes wider in the Y-direction than a second pattern located behind the origin. The laser output is controlled such that the output of the laser drawing the first pattern is lower than the output of the laser drawing the second pattern.

Description

Technical Field

[0001] This disclosure relates to laser welding methods and laser welding apparatus. Background Technology

[0002] Because laser welding utilizes a high power density of laser light irradiating the workpiece, it enables high-speed and high-quality welding. In particular, in scanning welding, where welding is performed while the laser is rapidly scanning the workpiece surface, the laser beam can be moved at high speed to the next welding point during periods when welding is not in progress, thus shortening the overall welding time (see, for example, Patent Document 1). Furthermore, regarding laser scanning methods, methods for scanning the laser to depict Lissajous patterns on the workpiece surface have been proposed previously (see, for example, Patent Documents 2 and 3). Moreover, scanning welding can be applied not only to conventional steel materials but also to the welding of thin sheets of steel materials that have undergone surface treatments such as galvanizing (see, for example, Patent Document 4).

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-095934

[0006] Patent Document 2: Japanese Patent Application Publication No. 60-177983

[0007] Patent Document 3: Japanese Patent Application Publication No. 11-104877

[0008] Patent Document 4: Japanese Patent No. 4915315 Summary of the Invention

[0009] -The technical problem the invention aims to solve-

[0010] However, zinc's boiling point (906°C) is significantly lower than iron's melting point (1535°C). Therefore, in lap welding where two steel plates with galvanized layers on each surface are seamlessly overlapped, the galvanized layer on the overlapping surface of the steel plates reaches its evaporation temperature before the iron melts. The resulting zinc vapor can destabilize pinholes or the molten pool, or form porosity inside the workpiece, or, in extreme cases, cause molten pool spatter, resulting in welding defects.

[0011] However, the existing structures disclosed in Patent Documents 1 to 3 do not disclose any lap welding of steel plates with galvanized layers, nor do they disclose the aforementioned technical problems.

[0012] On the other hand, Patent Document 4 discloses a method in which the laser beam is oscillated back and forth along the welding direction, and the laser output in the forward oscillation is lower than the laser output in the backward oscillation. In this way, steel plates can be welded together after the galvanized layer has been removed.

[0013] However, in the method disclosed in Patent Document 4, the laser trajectory overlaps in both the forward and backward processes. Furthermore, the width of the laser in the direction intersecting the welding direction is the same in both the forward and backward processes. Because of these factors, there is a concern that areas where sufficient removal of the galvanized layer cannot be ensured for the welding area, potentially leading to welding defects.

[0014] This disclosure is made in view of this, and its object is to provide a laser welding method and a laser welding apparatus for suppressing the generation of welding defects and obtaining a weld with a good shape in the lap welding of plates with a covering layer such as a galvanized layer.

[0015] -Methods for solving technical problems-

[0016] To achieve the above objectives, the laser welding method disclosed herein is characterized by comprising: a welding step in which the laser is scanned two-dimensionally to irradiate the surface of a workpiece while traveling in the welding direction, thereby welding the workpiece, wherein the workpiece is constructed of two base materials, each comprising a plate-like portion, wherein the plate-like portions are overlapped and at least a covering layer is formed on the surface of the plate-like portions, and the boiling point of the covering layer is lower than the melting point of the base materials; in the welding step, the laser is scanned to depict a predetermined pattern on the surface of the workpiece, wherein a first depicting pattern located in front of the origin of the predetermined pattern along the welding direction is wider with respect to a direction intersecting the welding direction than a second depicting pattern located behind the origin; the output of the laser is controlled such that the output of the laser depicting the first depicting pattern is lower than the output of the laser depicting the second depicting pattern; the predetermined pattern is a pattern in which two asymmetrical annular patterns meet and continue at the origin.

[0017] The laser welding apparatus disclosed herein is characterized by comprising at least: a laser oscillator for generating laser light; a laser head for receiving the laser light and irradiating a workpiece; and a controller for controlling the operation of the laser head and the output of the laser light. The laser head includes a laser scanner for scanning the laser light in a first direction and a second direction intersecting the first direction. When the workpiece is constructed of two base materials comprising plate-like portions that overlap each other, and a covering layer is formed on at least the surface of the plate-like portions, and the boiling point of the covering layer is lower than the melting point of the base materials, the controller controls the laser scanner. The laser is driven and controlled to draw a predetermined pattern on the surface of the workpiece. A first drawing pattern located in front of the origin of the predetermined pattern along the welding direction is wider than a second drawing pattern located behind the origin in the direction intersecting the welding direction. Furthermore, the controller controls the output of the laser so that the output of the laser drawing the first pattern is lower than the output of the laser drawing the second pattern. The predetermined pattern is a pattern of two asymmetrical ring patterns that meet and continue at the origin.

[0018] -Invention Effects-

[0019] According to this disclosure, the covering layer between two plate-shaped portions can be removed, and the generation of welding defects caused by vapors generated from the evaporation of the covering layer can be suppressed. Furthermore, the weld seam formed on the workpiece can be made to have a good shape. Attached Figure Description

[0020] Figure 1 This is a schematic structural diagram of the laser welding apparatus according to Embodiment 1.

[0021] Figure 2 This is a schematic diagram of the laser scanner.

[0022] Figure 3 This is a schematic diagram of the cross-section of the workpiece.

[0023] Figure 4 It is a diagram representing the scanning pattern of a laser.

[0024] Figure 5 It is a diagram showing the scanning trajectory of the laser along the welding direction.

[0025] Figure 6 It is a graph showing the relationship between the laser's position and its output.

[0026] Figure 7 This is a schematic diagram showing the changes in the state of the workpiece along the welding direction when irradiated by a laser.

[0027] Figure 8 This is a diagram showing the relationship between the laser's position and output in Modified Example 1.

[0028] Figure 9 This is a schematic diagram showing the changes in the state of the workpiece along the welding direction when irradiated by a laser.

[0029] Figure 10 This is a graph showing the relationship between the laser output and the depth of the pinhole.

[0030] Figure 11A This is a diagram showing the first scan pattern of the laser involved in Modification Example 2.

[0031] Figure 11B This is a diagram showing the second scanning pattern of the laser involved in Modification Example 2.

[0032] Figure 11C This is a diagram showing the third scan pattern of the laser involved in Modified Example 2.

[0033] Figure 12 This is a diagram showing the scanning trajectory of the laser along the welding line involved in Embodiment 2.

[0034] Figure 13A This is a graph showing the relationship between the laser's position and output at the start of welding.

[0035] Figure 13B This is a graph showing the relationship between the laser's position and output at the end of the welding process.

[0036] Figure 14A This is a diagram showing the first scan pattern of the laser involved in Modification Example 3.

[0037] Figure 14B This is a diagram showing the second scan pattern of the laser involved in Modified Example 3.

[0038] Figure 14C This is a diagram showing the third scan pattern of the laser involved in Modification Example 3.

[0039] Figure 15 This is a diagram showing a general outline of the scanning trajectory of the laser involved in Embodiment 3.

[0040] Figure 16A This is a diagram showing the pattern of the first solder joint.

[0041] Figure 16B This is a diagram showing the pattern of the second solder joint.

[0042] Figure 16C This is a diagram showing the pattern of the third solder joint.

[0043] Figure 16DThis is a diagram showing the pattern of the 4th solder joint.

[0044] Figure 16E This is a diagram showing the pattern of the 5th solder joint.

[0045] Figure 16F This is a diagram showing the pattern of the 6th solder joint.

[0046] Figure 16G This is a diagram showing the pattern of the 7th solder joint. Detailed Implementation

[0047] The embodiments of this disclosure are described below with reference to the accompanying drawings. Furthermore, the following description of preferred embodiments is merely illustrative and is not intended to limit the scope of this disclosure, its applications, or its uses.

[0048] (Implementation Method 1)

[0049] [Structure of laser welding equipment and laser scanner]

[0050] Figure 1 A schematic diagram showing the structure of the laser welding apparatus according to this embodiment. Figure 2 This is a schematic diagram showing the basic structure of a laser scanner. Figure 3 A schematic diagram showing the cross-section of the workpiece.

[0051] Furthermore, in the following description, the direction parallel to the travel direction of the laser LB from the reflector 33 to the laser scanner 40 may be referred to as the X direction, the direction parallel to the optical axis of the laser LB emitted from the laser head 30 may be referred to as the Z direction, and the directions orthogonal to the X and Z directions may be referred to as the Y direction. When the surface of the workpiece 200 is flat, the XY plane encompassing the X and Y directions can be approximately parallel to the surface or at a certain angle to it.

[0052] like Figure 1 As shown, the laser welding device 100 includes: a laser oscillator 10, an optical fiber 20, a laser head 30, a controller 50, and a robotic arm 60.

[0053] The laser oscillator 10 is a laser source that is powered by a power source not shown and generates laser LB. Alternatively, the laser oscillator 10 may comprise a single laser source or multiple laser modules. In the latter case, lasers emitted separately from the multiple laser modules are coupled and emitted as laser LB. Furthermore, the laser source or laser module used in the laser oscillator 10 can be appropriately selected based on the material of the workpiece 200, the shape of the welding area, etc.

[0054] For example, fiber lasers, disk lasers, or YAG (Yttrium Aluminum Garnet) lasers can also be used as laser sources. In this case, the wavelength of the laser LB is set in the range of 1000 nm to 1100 nm. Alternatively, semiconductor lasers can be used as laser sources or laser modules. In this case, the wavelength of the laser LB is set in the range of 800 nm to 1000 nm. Furthermore, visible light lasers can also be used as laser sources or laser modules. In this case, the wavelength of the laser LB is set in the range of 400 nm to 600 nm.

[0055] The optical fiber 20 is optically coupled to the laser oscillator 10. The laser LB generated in the laser oscillator 10 is incident on the optical fiber 20 and transmitted to the laser head 30 inside it.

[0056] The laser head 30 is mounted at the end of the optical fiber 20 and irradiates the workpiece 200 with the laser LB transmitted from the optical fiber 20.

[0057] In addition, the laser head 30, as an optical component, includes a collimating lens 32, a reflector 33, a condenser lens 34, and a laser scanner 40. These optical components are housed inside the housing 31 in a prescribed configuration.

[0058] The collimating lens 32 receives the laser beam LB emitted from the optical fiber 20, converts it into parallel light, and directs it onto the reflecting mirror 33. Furthermore, the collimating lens 32 is connected to a drive unit (not shown) and is configured to be displaceable in the Z-direction according to a control signal from the controller 50. By displacing the collimating lens 32 in the Z-direction, the focal position of the laser beam LB is changed, allowing the laser beam LB to appropriately illuminate the workpiece 200 according to its shape. In other words, the collimating lens 32, in combination with the drive unit (not shown), also functions as a focal position adjustment mechanism for the laser beam LB. Alternatively, the focal position of the laser beam LB can also be changed by displacing the condenser lens 34 via the drive unit.

[0059] The reflector 33 reflects the laser LB from the transmission collimating lens 32, causing it to be incident on the laser scanner 40. The surface of the reflector 33 is set at approximately 45 degrees to the optical axis of the laser LB from the transmission collimating lens 32.

[0060] The focusing lens 34 is reflected by the reflecting mirror 33, causing the laser LB scanned by the laser scanner 40 to focus onto the surface of the workpiece 200.

[0061] like Figure 2As shown, the laser scanner 40 is a known galvanometer scanner having a first galvanometer lens 41 and a second galvanometer lens 42. The first galvanometer lens 41 has a first reflector 41a, a first rotation axis 41b, and a first drive unit 41c, and the second galvanometer lens 42 has a second reflector 42a, a second rotation axis 42b, and a second drive unit 42c. The laser LB from the transmission focusing lens 34 is reflected by the first reflector 41a and further reflected by the second reflector 42a, irradiating the surface of the workpiece 200.

[0062] For example, the first drive unit 41c and the second drive unit 42c are galvanometer motors, and the first rotating shaft 41b and the second rotating shaft 42b are the output shafts of the motors. Although not shown, the first reflector 41a mounted on the first rotating shaft 41b is rotated by the first drive unit 41c using a driver that operates according to a control signal from the controller 50, thereby rotating the first reflector 41a around the axis of the first rotating shaft 41b. Similarly, the second reflector 42a mounted on the second rotating shaft 42b is rotated by the second drive unit 42c using a driver that operates according to a control signal from the controller 50, thereby rotating the second reflector 42a around the axis of the second rotating shaft 42b.

[0063] The laser LB is scanned in the X direction by rotating the first reflector 41a around the axis of the first rotation axis 41b to a predetermined angle. Similarly, the laser LB is scanned in the Y direction by rotating the second reflector 42a around the axis of the second rotation axis 42b to a predetermined angle. In other words, the laser scanner 40 is configured to scan the laser LB two-dimensionally in the XY plane and irradiate the workpiece 200.

[0064] The controller 50 controls the laser oscillation of the laser oscillator 10. Specifically, it controls the laser oscillation by providing control signals such as output current and on / off time to a power supply (not shown) connected to the laser oscillator 10. Furthermore, the controller 50 controls the output of the laser LB.

[0065] Furthermore, the controller 50 controls the movement of the laser head 30 according to the selected laser welding program. Specifically, it controls the drive of the laser scanner 40 and the collimating lens 32 (not shown) located on the laser head 30. Further, the controller 50 controls the movement of the robot arm 60. Additionally, the laser welding program is stored in a storage unit (not shown) located inside the controller 50 or elsewhere, and can be retrieved by commands from the controller 50.

[0066] The controller 50 has an integrated circuit such as an LSI (not shown) or a microcomputer, and the functions of the controller 50 can be realized by executing a laser welding program as software on the integrated circuit. Alternatively, a separate controller 50 can be provided to control the movement of the laser head 30 and a separate controller 50 to control the output of the laser LB.

[0067] The robotic arm 60 is a multi-jointed robot mounted on the housing 31 of the laser head 30. Furthermore, the robotic arm 60 is interactively connected to the controller 50 to move the laser head 30, thereby tracing a predetermined trajectory according to the laser welding procedure. Alternatively, a separate controller (not shown) may be provided to control the movements of the robotic arm 60.

[0068] Figure 1 The laser welding apparatus 100 shown is capable of laser welding workpieces 200 of various shapes. For example, such as Figure 3 As shown, galvanized layers 211 and 221 are formed on the surfaces of the workpiece 200, which consists of a first sheet 210 and a second sheet 220 containing steel plates, and are irradiated with laser LB to perform lap welding. By forming galvanized layers 211 and 221 on the surfaces of the first sheet 210 and the second sheet 220, rust on the steel plates can be prevented. Furthermore, the structure and material of the workpiece 200 being laser-welded are not limited to... Figure 3 The example shown.

[0069] [The mathematical representation of the Lissajous pattern]

[0070] Figure 4 The laser scanning pattern is represented by the laser LB being scanned to depict a Lissajous pattern (hereinafter also referred to as a Lissajous graphic) on the surface of workpiece 200 in the XY plane.

[0071] Figure 4 The Lissajous pattern shown is obtained by vibrating the laser LB in the X direction at a predetermined frequency as a sine wave, and in the Y direction at a frequency different from that in the X direction (half the frequency in the X direction) as a sine wave. Furthermore, as described, the scanning patterns in the X and Y directions of the laser LB are determined based on the rotational motion of the first reflecting mirror 41a and the second reflecting mirror 42a. When the position coordinates of the Lissajous pattern obtained by driving the first reflecting mirror 41a are defined as X, and the position coordinates of the Lissajous pattern obtained by driving the second reflecting mirror 42a are defined as Y, the position coordinates X and Y are represented by the following equations (1) and (2), respectively.

[0072] X=a1×sin(nt)···(1)

[0073]

[0074] X=a2×sin(nt)···(3)

[0075]

[0076] Here,

[0077] a1: Amplitude in the X direction of the scan pattern LS1 within the Lissajous pattern.

[0078] b1: Amplitude in the Y direction of the scan pattern LS1 within the Lissajous pattern.

[0079] a2: Amplitude in the X direction of the scan pattern LS2 within the Lissajous pattern.

[0080] b2: Amplitude in the Y direction of the scan pattern LS2 within the Lissajous pattern.

[0081] n: Frequency of the first reflecting mirror 41a

[0082] m: Frequency of the second reflecting mirror 42a

[0083] t: time

[0084] The phase difference when the first reflector 41a or the second reflector 42a is driven, specifically, the angular deviation set during the rotational motion of the first reflector 41a and the second reflector 42a.

[0085] Scan pattern LS1 (hereinafter also referred to as the first drawing pattern LS1) is Figure 4 The scan pattern shown in the Lissajous pattern is located on the + side in the X direction, and the scan pattern LS2 (hereinafter also referred to as the second drawing pattern LS2) is located on the - side in the X direction.

[0086] In addition, the position coordinates X and Y shown in equations (1) to (4) are represented by the static coordinate system of the Lissajous pattern with the position of the laser head 30 fixed.

[0087] Furthermore, frequency n and frequency m correspond to the driving frequencies of the first reflector 41a and the second reflector 42a, respectively.

[0088] according to Figure 4 It can be seen that the Lissajous pattern in this embodiment is asymmetrical about the center line that passes through the origin O and extends in the Y direction.

[0089] The first drawing pattern LS1 located in front of the origin O along the X direction corresponds to a1=1, b1=1, n=1, m=2 in equations (1) and (2). On the other hand, the second drawing pattern LS2 located behind the origin O corresponds to the values ​​in equations (3) and (4), where a2 = 0.5, b2 = 0.5, n = 1, m = 2, ... In other words, in both the X and Y directions, the first depiction pattern LS1 becomes a larger pattern than the second depiction pattern LS2. Therefore, the depiction length of the first depiction pattern LS1 is longer than the depiction length of the second depiction pattern LS2. In addition, a1, a2, b1, and b2 are normalized by 1 based on the size of the first depiction pattern LS1. Furthermore, the phase difference of equations (1) to (4) It can be either 0 degrees or 180 degrees.

[0090] Furthermore, the pattern synthesized by combining the first depiction pattern LS1 and the second depiction pattern LS2 is a Lissajous pattern in the shape of an infinity symbol. In addition, the actual size of the Lissajous pattern, in other words, the amplitude in the X and Y directions, is in the range of approximately 1 mm to 10 mm.

[0091] Here, as Figure 4 As shown, when the drawing distance of the Lissajous pattern in the X direction in the specified time variable Δt is set as ΔX, the drawing distance in the Y direction is set as ΔY, and the drawing distance of the Lissajous pattern in the time variable Δt is set as ΔL, ΔX, ΔY, and ΔL are respectively represented by the following equations (5) to (7).

[0092] ΔX=a1×n×cos(nt)×Δt···(5)

[0093]

[0094] ΔL=Δt×{(ΔX) 2 +(ΔY) 2} 1 / 2 ···(7)

[0095] Therefore, the drawing speed V of the Lissajous pattern is expressed by the following equation (8).

[0096] V=ΔL / Δt···(8)

[0097] Formulas (5) to (8) are formulas for LS1 generated based on formulas (1) to (2). Similarly, formulas for LS2 can be generated based on formulas (3) to (4). The details are omitted here.

[0098] [Laser Welding Method]

[0099] Figure 5The figure shows the scanning trajectory of the laser along the welding direction, with the shapes of the multiple Lissajous patterns corresponding to the shape of the weld. Furthermore, the multiple Lissajous patterns shown in the figure represent the positional changes of the laser LB relative to the time it takes to draw the pattern as it travels along the welding direction. Figure 6 This indicates the relationship between the laser's depicted position and its output. Figure 7 This schematically illustrates the changes in the state of the workpiece along the welding direction during laser irradiation.

[0100] in addition, Figure 4 The Lissajous pattern shown moves from the origin O to... during a period of 1 cycle. Figure 4 The direction of the arrows AR1 and AR2 shown is obtained by scanning the laser LB. Specifically, during one cycle, the laser LB is scanned so that it traces the position from the origin O through positions A→B→C→O→D→E→F→O.

[0101] In this embodiment, a robotic arm 60 moves the laser head 30 at a predetermined speed in the + direction of the X direction (hereinafter, sometimes referred to as the welding direction WD), and irradiates the surface of the workpiece 200 with the laser LB. Further, a laser scanner 40 is used to scan the laser LB two-dimensionally, so as to draw a pattern on the surface of the workpiece 200. Figure 4 The Lissajous pattern is shown. Furthermore, in this embodiment, [the pattern is] used to [address the specific details]. Figure 3 The following example illustrates the case of workpiece 200 being lap-welded.

[0102] like Figure 4 As shown, the first pattern LS1, drawn along the welding direction WD towards the origin O in the Lissajous pattern, has a larger scanning amplitude in both the X and Y directions compared to the second pattern LS2, drawn towards the rear of the origin O. Specifically, in equations (1) and (2), assuming a1 = 1, b1 = 1, n = 1, and m = 2, we obtain... Figure 4 The first depiction pattern LS1 is shown. Furthermore, in equations (3) and (4), with a2 = 0.5, b2 = 0.5, n = 1, and m = 2, we obtain... Figure 4 The second depiction pattern LS2 is shown.

[0103] Therefore, it can be seen that the scan width LAC in the Y direction of the first depiction pattern LS1 is twice as wide as the scan width LDF in the Y direction of the second depiction pattern LS2. Furthermore, as... Figure 5As shown, the scan width LAC corresponds to the width in the Y direction of the zinc plating layers 211 and 221 that are removed (hereinafter also referred to as the zinc plating layer removal width LAC), and the scan width LDF corresponds to the weld width of workpiece 200 (hereinafter also referred to as the weld width LDF). Additionally, the weld width LDF corresponds to the width in the Y direction of the weld (not shown), but the two are often not entirely consistent. This is due to the influence of heat conduction during welding, which often results in the actual weld width in the Y direction being slightly wider than the weld width LDF.

[0104] As described above, the zinc plating removal width LAC is set wider than the weld width LDF in the Y direction. Therefore, in the scanning trajectory of the laser LB, zinc plating layers 211 and 221 are removed on both sides of the weld width LDF in the Y direction, while creating unwelded areas on the first sheet 210 and the second sheet 220. Furthermore, in the following description, the width of this area in the Y direction is sometimes referred to as the zinc plating removal width LNZn at the weld periphery.

[0105] On the other hand, such as Figure 6 As shown, the output P1 of the laser LB used to depict the first depiction pattern LS1 is set to be lower than the output P2 of the laser LB used to depict the second depiction pattern LS2.

[0106] against Figure 3 In the prior art, when workpiece 200 is lap-welded seamlessly using laser LB, there is a concern, as described above, that zinc vapor generated before the iron melts may cause welding defects. However, according to this embodiment, the zinc plating layers 211 and 221 present at the interface between the first plate 210 and the second plate 220 can be removed, and the generation of welding defects associated with zinc vapor generation can be suppressed. This will be further explained below.

[0107] By setting the output of laser LB1 to Figure 6 The output P1, as shown, forms a small hole 301 of depth LK1 by laser LB1 along the optical axis at a position B, for example, forward of the origin O of the Bilisar pattern, via laser LB1 (shown as b-b'), further forming a molten pool 311 around it. At this point, the depth LK1 of the small hole 301 does not reach the interface between the first plate 210 and the second plate 220; similarly, the molten pool 311 also does not reach the interface between the first plate 210 and the second plate 220. In other words, the first plate 210 is not completely melted to the bottom by laser LB1.

[0108] On the other hand, through the input heat from the laser LB1 reaching the interior of the aperture 301 and the heat generated in the molten pool 311, the temperature of the interface between the first plate 210 and the second plate 220 rises and reaches the boiling point of zinc, causing the zinc plating layers 211 and 221 present at the interface to evaporate. As a result, the zinc plating layers 211 and 221 are removed from the interface along the X direction from the origin O for a length LZn.

[0109] Furthermore, by setting the output of laser LB2 to Figure 6 The output P2, as shown, creates a small hole 302 of depth LK2 by laser LB2 along the optical axis e-e', located further back from the origin O of the Bilisar pattern, for example, at position E. A molten pool 312 is then formed around this hole. At this point, the small hole 302 penetrates the first plate 210 and reaches the interior of the second plate 220. Similarly, the molten pool 312 is formed from the surface of the first plate 210 into the interior of the second plate 220. In other words, by laser LB2, the interface between the first plate 210 and the second plate 220, after the zinc plating layers 211 and 221 have evaporated and been removed, is melted, and a weld portion 320 is formed behind the molten pool 312, where the first plate 210 and the second plate 220 are welded.

[0110] Furthermore, as described above, in the Y direction, the zinc plating removal width LAC is wider than the weld width LDF. On both sides of the weld width LDF in the Y direction, the zinc plating layers 211 and 221 are removed, and on the other hand, areas where the first plate 210 and the second plate 220 are not welded are formed.

[0111] By performing laser welding on areas where the zinc plating layers 211 and 221 are reliably removed, the instability of the pinholes 302 and the molten pool 312 caused by zinc vapor can be reduced. Similarly, welding defects such as porosity formed inside the workpiece 200 due to zinc vapor, spatter caused by splashing in the molten pool 312, and arc craters can be suppressed.

[0112] [Effects, etc.]

[0113] As described above, the laser welding method according to this embodiment includes a welding step in which the laser LB travels in the X direction (first direction), and the laser LB is scanned in two dimensions and irradiated onto the surface of the workpiece 200, thereby welding the workpiece 200.

[0114] Workpiece 200 is constructed by seamlessly overlapping a first sheet 210 with a galvanized layer 211 on its surface and a second sheet 220 with a galvanized layer 221 on its surface. Both the first sheet 210 and the second sheet 220 are steel sheets.

[0115] During the welding process, the laser LB is vibrated along the X direction as a sinusoidal wave with a first frequency n, and along the Y direction (second direction) as a sinusoidal wave with a second frequency m. Thus, the laser LB is scanned on the surface of the workpiece 200 to depict a Lissajous pattern in the shape of the number ∞.

[0116] Furthermore, the laser LB is scanned so that the first drawing pattern LS1, located in front of the origin O of the Lissajous pattern along the welding direction WD (the + lateral direction of the X direction), becomes a pattern that is wider in the Y direction than the second drawing pattern LS2 located behind the origin O.

[0117] The output P of the laser LB is controlled such that the output P1 of the laser LB in drawing the first drawing pattern LS1 is lower than the output P2 of the laser LB in drawing the second drawing pattern LS2.

[0118] Furthermore, in the depiction of the first pattern LS1, the galvanized layers 211 and 221 present at the interface between the first plate 210 and the second plate 220 are removed. In the depiction of the second pattern LS2, the first plate 210 and the second plate 220, with the galvanized layers 211 and 221 removed, are welded together.

[0119] According to this embodiment, the zinc plating layers 211 and 221 present at the interface between the first plate 210 and the second plate 220 can be removed, and the generation of welding defects associated with the generation of zinc vapor can be suppressed. In addition, the weld formed on the workpiece 200 can be made to have a good shape.

[0120] In the method disclosed in Patent Document 4, the laser is not scanned in the direction intersecting the welding direction, and the laser trajectory overlaps in both the forward and backward processes. Furthermore, the width of the laser in the direction intersecting the welding direction is the same in both the forward and backward processes. Therefore, due to the laser spot size and output, the width of the zinc plating layer removed relative to the weld width cannot be sufficiently ensured regarding the direction intersecting the welding direction, raising concerns about welding defects caused by zinc vapor generation during workpiece welding. Additionally, there is concern about the shape of the weld seam deteriorating.

[0121] On the other hand, according to this embodiment, as described above, the scanning laser LB is used such that, with respect to the Y direction, the zinc plating removal width LAC is wider than the weld width LDF. Therefore, it is possible to sufficiently ensure that the area where the zinc plating is removed relative to the weld area can suppress the generation of weld defects associated with zinc vapor. Furthermore, this results in a well-shaped weld seam formed on the workpiece 200.

[0122] The laser welding apparatus 100 according to this embodiment includes at least: a laser oscillator 10 that generates laser LB, a laser head 30 that receives laser LB and irradiates workpiece 200, and a controller 50 that controls the operation of laser head 30 and the output P of laser LB.

[0123] The workpiece 200 is constructed by seamlessly overlapping a first sheet 210 with a galvanized layer 211 on its surface and a second sheet 220 with a galvanized layer 221 on its surface. Both the first sheet 210 and the second sheet 220 are steel plates.

[0124] The laser head 30 has a laser scanner 40 that scans the laser LB in the X direction (first direction) and the Y direction (second direction) that intersects the X direction.

[0125] The controller 50 causes the laser LB to vibrate in the X direction as a sine wave with a first frequency and in the Y direction as a sine wave with a second frequency. Thus, the controller 50 drives the laser scanner 40 so that the laser LB draws an ∞-shaped Lissajous pattern on the surface of the workpiece 200.

[0126] Furthermore, the controller 50 drives the laser scanner 40 so that the first drawing pattern LS1, which is located further forward than the origin O of the Lissajous pattern along the welding direction (X direction), becomes a pattern that is wider in the Y direction than the second drawing pattern LS2, which is located further back.

[0127] The controller 50 controls the output P of the laser LB so that the output P1 of the laser LB in drawing the first drawing pattern LS1 is lower than the output P2 of the laser LB in drawing the second drawing pattern LS2.

[0128] According to the laser welding apparatus of this embodiment, the zinc plating layers 211 and 221 present at the interface between the first plate 210 and the second plate 220 can be removed, and the generation of welding defects associated with the generation of zinc vapor can be suppressed. In addition, the weld formed on the workpiece 200 can be made to have a good shape.

[0129] The laser welding apparatus 100 also includes a robotic arm 60 equipped with a laser head 30, and a controller 50 controls the movement of the robotic arm 60. The robotic arm 60 moves the laser head 30 relative to the surface of the workpiece 200 in a specified direction.

[0130] By configuring the robotic arm 60 in this way, the welding direction of the laser LB can be changed. Furthermore, it allows for easy laser welding of workpieces 200 with complex shapes, such as three-dimensional shapes.

[0131] The laser oscillator 10 and the laser head 30 are connected by an optical fiber 20, and the laser LB is transmitted from the laser oscillator 10 to the laser head 30 through the optical fiber 20.

[0132] By arranging the optical fiber 20 in this way, laser welding can be performed on the workpiece 200 located separately from the laser oscillator 10. This increases the degree of freedom in configuring the various parts of the laser welding apparatus 100.

[0133] The laser scanner 40 includes: a first galvanometer 41 that scans the laser LB in the X direction and a second galvanometer 42 that scans the laser LB in the Y direction.

[0134] By configuring the laser scanner 40 in this way, the laser LB can be scanned in two dimensions easily. Furthermore, since a known galvanometer scanner is used as the laser scanner 40, the cost increase of the laser welding apparatus 100 can be suppressed.

[0135] The laser head 30 also includes a collimating lens 32, which is configured to change the focal position of the laser LB along the Z direction, which intersects both the X and Y directions. In other words, the collimating lens 32 is configured to change the focal position of the laser LB along the Z direction, which intersects the surface of the workpiece 200. In other words, the collimating lens 32, in combination with a drive unit (not shown), also functions as a focal position adjustment mechanism for the laser LB.

[0136] In this way, the focal position of the laser LB can be easily changed, and the laser LB can be appropriately irradiated according to the shape of the workpiece 200.

[0137] In this embodiment, the laser LB travels in the + direction of the X direction by moving the laser head 30 in the X direction, but it is also possible to move the laser head 30 in the Y direction to make the laser LB travel in the Y direction. In other words, the welding direction can also be set to the Y direction. In this case, the frequency n needs to be set to 2 and the frequency m needs to be set to 1 to change the shape of the Lissajous pattern. In this way, the controller 50 can drive the laser scanner 40 so that the first drawing pattern LS1, which is located in front of the origin O of the Lissajous pattern along the welding direction, i.e., the Y direction, becomes a pattern that is wider in the X direction than the second drawing pattern LS2, which is located behind the origin O. In other words, the laser LB can be scanned so that the first drawing pattern LS1 becomes a pattern that is wider in the X direction than the second drawing pattern LS2. As a result, the width of the zinc plating layers 211 and 221 that are removed can be obtained sufficiently wide relative to the welding width, and the generation of welding defects caused by zinc vapor can be suppressed.

[0138] Furthermore, the direction in which the Lissajous pattern is depicted is not particularly limited to the direction described above. For example, it can also be drawn from the origin O towards [the direction described above] during one cycle. Figure 4 The Lissajous pattern is drawn by scanning the laser LB in the directions of arrows AR3 and AR4. Specifically, the laser LB can also be scanned during one cycle, so that the pattern is drawn from the origin O through the positions C→B→A→O→F→E→D→O.

[0139] <Variation Example 1>

[0140] Figure 8 This illustrates the relationship between the laser's depicted position and its output in this variation. Figure 9 This schematically illustrates the changes in the state of the workpiece along the welding direction during laser irradiation. Figure 10 This indicates the relationship between the laser output and the depth of the pinhole. Additionally, for ease of explanation, in... Figures 8-10 In the accompanying drawings shown thereafter, the same reference numerals are used for the same locations as in Embodiment 1, and detailed descriptions are omitted.

[0141] This modified example differs from the structure shown in Embodiment 1 in the following aspects. Specifically, during the transition from the first drawing pattern LS1 to the second drawing pattern LS2, control is performed to continuously increase the output P of the laser LB. Furthermore, during the transition from the second drawing pattern LS2 to the first drawing pattern LS1, control is performed to continuously decrease the output P of the laser LB.

[0142] Specifically, such as Figure 8 As shown by the dashed line, when the laser LB's drawing position moves from the origin O to D, the output P of the laser LB is continuously increased from P1 to P2 from the moment the laser LB passes through the origin O until a period t1 elapses. In this case, the control curve S1 of the output P can be either a straight line or a curve. Furthermore, when the laser LB's drawing position moves from the origin O to A, the output P of the laser LB is continuously decreased from P2 to P1 from the moment the laser LB passes through the origin O until a period t2 elapses. In this case, the control curve S2 of the output P can also be either a straight line or a curve.

[0143] In this way, the formation of porosity inside the workpiece 200 can be suppressed. Furthermore, the molten pool 312 can be stabilized. This will be explained further.

[0144] like Figure 9As shown, consider the case where the drawing position of the laser LB moves in the X direction from the position O" behind the origin O to the position O' in front of the origin O, that is, when transferring from the second drawing pattern LS2 to the first drawing pattern LS1 in the Lissajous pattern. In this case, if the output P of the laser LB is stepped down from P2 to P1, the small hole 302 with a depth of LK2 will sharply change its shape to the small hole 301 with a depth of LK1 (LK1 < LK2). As a result, the portion with a length of LK12 from the bottom of the small hole 302 to Figure 9 the length LK12 shown is sharply closed due to the surface tension of the molten metal. There is almost no problem when the small hole 302 is closed sequentially from the bottom upwards, but in most cases, in the portion from the bottom to the length LK12, the small hole 302 is closed at one or more positions at almost the same timing. If this occurs, there is a concern that voids may remain below or above the closed portion, forming air holes inside the workpiece 200.

[0145] On the other hand, through this modification example, as Figure 8 shown, the output P of the laser LB is continuously decreased from P2 to P1 along the control curve S2. Therefore, the shape change from the small hole 302 to the small hole 301 becomes slow, and the remaining voids in the middle can be suppressed. As a result, the formation of air holes inside the workpiece 200 can be suppressed.

[0146] In addition, consider the case where the drawing position of the laser LB moves from the position O' to the position O", that is, when transferring from the first drawing pattern LS1 to the second drawing pattern LS1 in the Lissajous pattern. In this case, the output P of the laser LB is stepped up from P1 to P2, and the small hole 301 with a depth of LK1 sharply changes its shape to the small hole 302 with a depth of LK2. As a result, there is a concern that an excessive impact is applied to the molten pool 312. If the molten pool 312 becomes unstable and fluctuates, there is a concern that it will be reflected in the shape of the weld bead, and a weld bead with a good shape cannot be formed.

[0147] On the other hand, through this modification example, as Figure 8 shown, the output P of the laser LB is continuously increased from P1 to P2 along the control curve S1. Therefore, the shape change from the small hole 301 to the small hole 302 becomes slow, and the instability of the molten pool 312 can be suppressed. As a result, the deterioration of the shape of the weld bead can be suppressed, and a weld bead with a good shape can be obtained.

[0148] In addition, by controlling the output P as shown in the control curves S1 and S2, it is easy for the output P to stably reach the target value. In addition, the control of the output P of the laser LB is performed by the controller 50.

[0149] In addition, as Figure 10As shown, when forming a pinhole in workpiece 200, the output P of the laser LB needs to be above a specified value. In the region where the output P is lower than this specified value (heat conduction welding region Rc), pinholes that cause the workpiece 200 to soften or melt due to the input heat of the laser LB will not form. If the output P is increased from this region, it reaches the pinhole welding region Rk via the transfer region Rt. If this region is reached, a pinhole is formed in workpiece 200, and the depth of the pinhole increases with the increase of the output P. The pinhole welding region Rk is included together with the outputs P1 and P2.

[0150] <Variation Example 2>

[0151] Figure 11A This represents the first scan pattern of the laser involved in this variation. Figure 11B This indicates the second scan pattern. Figure 11C This represents the third scan pattern of the laser.

[0152] In actual laser welding, the parameters a1, b1, a2, b2, n, and m shown in equations (1) to (4) can be appropriately changed according to the material of the workpiece 200, the joint shape, and the required weld shape and width. Therefore, the scanning pattern of the laser LB is not particularly limited to Figure 4 The pattern shown.

[0153] For example, such as Figure 11A As shown, in pattern LS1, the ratio of parameters a1 to b1 is set to 2:1, and in pattern LS2, the ratio of parameters a2 to b2 is set to 2:1. Alternatively, a2 and b2 can be set to half of a1 and b2, respectively. Furthermore, as... Figure 11B As shown, only in the pattern LS2, parameters a2 and b2 are changed from... Figure 4 The pattern shown is changed, with a2 = 1 and b2 = 0.5. Furthermore, as... Figure 11C As shown, in drawing pattern LS1, the ratio of parameter a1 to b1 can be set to 2:1, and in drawing pattern LS2, the ratio of parameter a2 to b2 can be set to 4:1.

[0154] Furthermore, the values ​​of parameters a1, b1, a2, and b2 shown in equations (1) to (4) are not particularly limited to [specific values]. Figure 4 as well as Figures 11A-11C The example shown.

[0155] Furthermore, as described above, the ratio of the frequency n of the first reflector 41a to the frequency m of the second reflector 42a, in other words, the ratio of the vibration frequency n:m of the laser LB in the X direction (i.e., the first frequency) to the vibration frequency m of the Y direction (i.e., the second frequency), is set to 1:2. Therefore, regarding the Y direction intersecting the welding direction, the first drawing pattern LS1 located in front of the origin O can be made wider than the second drawing pattern LS2 located behind the origin O. On the other hand, when the welding direction is the Y direction, the ratio n:m of the first frequency to the second frequency is set to 2:1. Therefore, regarding the X direction intersecting the welding direction, the first drawing pattern LS1 located in front of the origin O can be made wider than the second drawing pattern LS2 located behind the origin O. Furthermore, by adhering to this frequency ratio, the driving frequencies of the first reflector 41a and the second reflector 42a can be changed according to the shape of the workpiece 200 or the required weld shape.

[0156] (Implementation Method 2)

[0157] Figure 12 This indicates the scanning trajectory of the laser along the welding line in this embodiment. Figure 13A This indicates the relationship between the laser's position at the start of welding and its output. Figure 13B This indicates the relationship between the laser's position at the end of the welding process and its output.

[0158] like Figure 12 , Figure 13A As shown, in this embodiment, during a predetermined period after the start of laser welding (the first period), the output of the laser LB used for drawing the first drawing pattern LS1 is set to P1, while the output of the laser LB used for drawing the second drawing pattern LS2 is set to zero. This differs from the structure shown in Embodiment 1. During the first period, the rear end of the Lissajous pattern, in other words... Figure 4 The distance that the position E shown in the diagram is moved along the welding direction WD is equivalent to... Figure 12 The length L2 is shown. Furthermore, the length L2 is approximately twice the length of the second depicted pattern LS2 in the X direction.

[0159] In addition, such as Figure 12 , Figure 13B As shown, in this embodiment, during a predetermined period before the end of laser welding (the second period), the output of the laser LB used for drawing the second drawing pattern LS2 is set to P2, while the output of the laser LB used for drawing the first drawing pattern LS1 is set to zero. This differs from the structure shown in Embodiment 1. During the second period, the leading edge of the Lissajous pattern, in other words... Figure 4 The distance that the position corresponding to the depicted position B is moved along the welding direction WD is equivalent to Figure 12 The length L1 shown is approximately equal to the sum of the length of the first depiction pattern LS1 in the X direction and the length of the second depiction pattern LS2 in the Y direction.

[0160] According to this embodiment, when laser LB is irradiated with output P2 and the workpiece 200 is welded in areas where the zinc plating layers 211 and 221 have been reliably removed, the generation of welding defects caused by zinc vapor can be reliably suppressed. Furthermore, a good weld shape can be achieved. This will be further explained below.

[0161] When welding of workpiece 200 begins at the origin O of the Lissajous pattern at the welding start point, a first pattern LS1 is drawn in front of the welding start point along the welding direction WD, and a second pattern LS2 is drawn behind the welding start point. At this time, as... Figure 6 As shown, if the output P of laser LB is controlled, then laser LB with output P2 will be irradiated behind the welding start point, while the zinc plating layers 211 and 221 have not been removed. If this occurs, zinc vapor will be generated in the portion where the zinc plating layer has not been removed, as described above, further causing welding defects.

[0162] To avoid such adverse conditions, in this embodiment, during the first period after the start of laser welding, the output of the laser LB when drawing the second drawing pattern LS2 is set to zero. In this way, the high-output (=P2) laser LB is prevented from irradiating areas where the zinc plating layers 211 and 221 have not been removed, and the generation of welding defects caused by zinc vapor is reliably suppressed.

[0163] Furthermore, in order to suppress the generation of welding defects, it is necessary to remove at least the galvanized layers 211 and 221 from the start point to the end point of welding. However, for example, if the galvanized layers 211 and 221 are unnecessarily removed beyond the end point of welding, there is a concern that this may result in a reduction in the corrosion resistance of the steel plates, namely the first plate 210 and the second plate 220.

[0164] To avoid such adverse conditions, in this embodiment, during the second period before the laser welding ends, the output of the laser LB used to draw the first drawing pattern LS1 is set to zero. This allows the length LW of the welded area to be set to a desired value, and shortens the length LZN of the zinc plating layers 211 and 221 that are removed. This suppresses unnecessary removal of the zinc plating layers 211 and 221, and prevents a decrease in corrosion resistance in the first sheet 210 and the second sheet 220, which are steel plates.

[0165] Furthermore, from the viewpoint of simultaneously suppressing welding defects and reducing the reduction in corrosion resistance of the first plate 210 and the second plate 220, it is of course preferable that, after the welding of the workpiece 200 is completed, the length LZN of the portion of the galvanized layer 211, 221 removed along the welding direction WD is the same as or greater than the length LW of the portion of the workpiece 200 welded along the welding direction WD. Therefore, in the figure, the laser output is zero in the portion LS2S shown by the midpoint line during L2 and the portion LS1E shown by the midpoint line during L1.

[0166] <Variation Example 3>

[0167] Figures 14A-14C These represent the first to third scan patterns of the laser involved in this modified example. Additionally, in Figures 14A-14C In the scan pattern, the arrows depicted indicate the direction of laser LB.

[0168] The scanning pattern of the laser LB disclosed herein is not limited to the Lissajous pattern shown in Embodiment 1 and Modification 2. For example, as Figure 14A As shown, it can also be a composite pattern of two circular patterns with mutually asymmetrical shapes, respectively connected at the origin O and sandwiched by the Y-axis. Furthermore, as... Figure 14B As shown, it can also be a composite pattern of two elliptical patterns with mutually asymmetrical shapes, respectively connected at the origin O and sandwiched between the Y-axis. Figure 14B In the example shown, the major axis is in the Y direction and the minor axis is in the X direction in both elliptical patterns. However, the major axis can also be set to the X direction and the minor axis to the Y direction. Figure 14C As shown, it can also be a composite pattern of two rhomboid patterns with mutually asymmetrical shapes, respectively connected at the origin O and sandwiched between the Y-axis. Furthermore, when the welding direction WD is parallel to the Y-direction, Figures 14A-14C The scanning pattern shown can also be a composite pattern of two annular patterns arranged asymmetrically about the Y-axis. Furthermore, the size of each of the two annular patterns can be appropriately changed.

[0169] In other words, the scanning pattern of the laser LB in this application specification can be any pattern consisting of two ring-shaped patterns that meet at a single point and are continuous, and is not limited to... Figures 14A-14C Examples shown, and variations thereof. Furthermore, these patterns are obtained by driving the first reflector 41a and the second reflector 42a according to predetermined driving patterns, respectively.

[0170] By configuring the laser welding method and laser welding apparatus 100 in this way, the same effect as the structure shown in Embodiments 1 and 2 and Modifications 1 and 2 can be achieved.

[0171] Furthermore, the so-called "prescribed pattern" as the scanning pattern of the laser LB refers to a pattern in which two asymmetrical ring patterns are connected and continuous at a point, in this case, the origin O. This "prescribed pattern" naturally includes the Lissajous pattern disclosed in this application specification.

[0172] (Implementation Method 3)

[0173] Figure 15 This represents a general outline of the laser scanning trajectory involved in Embodiment 3. Figures 16A-16G These represent the patterns of solder joints 1 through 7, respectively.

[0174] In Embodiment 1, a so-called line welding method is used to describe laser welding of workpiece 200 while the laser LB travels on the + side in the X direction. However, the laser welding method disclosed herein can also be applied to spot welding.

[0175] For example, such as Figure 15 As shown, consider the case where the laser LB travels along the circular solder joint pattern SP indicated by the double-dotted line. Additionally, Figure 15 The scanning pattern SP1 of the laser LB shown is consistent with... Figure 4 The scanned patterns shown have similar shapes.

[0176] In this case, to ensure high-speed and reliable removal of the zinc plating layers 211 and 221 from the workpiece 200, it is preferable to design the scanning pattern SP1 of the laser LB as two asymmetrical annular patterns that meet and continue at the origin O, preferably as a Lissajous pattern in the shape of an infinity symbol. Furthermore, for ease of explanation, the scanning pattern SP1 of the laser LB is illustrated as a Lissajous pattern, but the actual waveform of the scanning pattern SP1 varies depending on the travel speed of the laser LB. For example, although not illustrated, the first depiction pattern LS1 and the second depiction pattern LS2 are separated along the welding direction WD, or in this case, clockwise along the weld point pattern SP, with the separation distance varying depending on the travel speed of the laser LB. Moreover, both the first depiction pattern LS1 and the second depiction pattern LS2 are deformed shapes extending along the circumferential direction of the weld point pattern SP.

[0177] In this embodiment, the laser LB is also scanned along the welding direction WD, so that the first drawing pattern LS1, which is in front of the origin O of the scanning pattern SP1, becomes a pattern that is wider in the Y direction than the second drawing pattern LS2, which is behind the origin O.

[0178] In this way, during the drawing of the first drawing pattern LS1, the galvanized layers 211 and 221 present at the interface between the first plate 210 and the second plate 220 are removed. During the drawing of the second drawing pattern LS2, the first plate 210 and the second plate 220, with the galvanized layers 211 and 221 removed, are spot-welded together.

[0179] In addition, in order to clamp the solder joint pattern SP, the irradiation width of the laser LB is the same on the inner and outer sides of the solder joint pattern SP in the radial direction. It is preferable to scan the laser LB so that the center line (not shown) passing through the origin O and dividing the scanned pattern SP1 into the first depiction pattern LS1 and the second depiction pattern LS2 is always orthogonal to the tangent direction at the origin O in the solder joint pattern SP.

[0180] Furthermore, considering the structures shown in Embodiments 1 and 2, and Modifications 1 to 3, and further in this embodiment, the laser welding method of this disclosure can be said to have the following structure. In other words, the laser welding method of this disclosure includes: a welding step in which the laser LB is scanned two-dimensionally and irradiated onto the surface of the workpiece 200 while the laser LB travels in the welding direction WD, thereby welding the workpiece 200.

[0181] The workpiece 200 is constructed by seamlessly overlapping a first sheet 210 with a galvanized layer 211 on its surface and a second sheet 220 with a galvanized layer 221 on its surface. Both the first sheet 210 and the second sheet 220 are steel plates.

[0182] During the welding process, the scanning laser LB is used to draw a specified pattern on the surface of the workpiece 200. The specified pattern refers to a pattern in which two asymmetrical ring-shaped patterns meet and continue at the origin O.

[0183] Furthermore, the laser LB is scanned so that the first drawing pattern LS1, which is located in front of the origin O of the specified pattern along the welding direction WD, becomes a wider pattern in the direction intersecting the welding direction WD compared to the second drawing pattern LS2, which is located behind the origin O.

[0184] The output P of the laser LB is controlled so that the output P1 of the laser LB in drawing the first drawing pattern LS1 is lower than the output P2 of the laser LB in drawing the second drawing pattern LS2.

[0185] Furthermore, in the depiction of the first drawing pattern LS1, the galvanized layers 211 and 221 present at the interface between the first sheet metal 210 and the second sheet metal 220 are removed. In the depiction of the second drawing pattern LS2, the first sheet metal 210 and the second sheet metal 220, with the galvanized layers 211 and 221 removed, are welded together. This case also includes the case where the first sheet metal 210 and the second sheet metal 220 are spot-welded together.

[0186] In this way, even if there is no gap between the first plate 210 and the second plate 220, the zinc plating layers 211 and 221 present at the interface between the first plate 210 and the second plate 220 can be removed, and the generation of welding defects associated with the generation of zinc vapor can be suppressed. In addition, the weld formed on the workpiece 200 can be made to have a good shape.

[0187] The laser welding apparatus 100 disclosed herein includes at least: a laser oscillator 10 that generates a laser LB; a laser head 30 that receives the laser LB and irradiates the workpiece 200; and a controller 50 that controls the operation of the laser head 30 and the output P of the laser LB.

[0188] The workpiece 200 is constructed by seamlessly overlapping a first sheet 210 with a galvanized layer 211 on its surface and a second sheet 220 with a galvanized layer 221 on its surface. Both the first sheet 210 and the second sheet 220 are steel plates.

[0189] The laser head 30 has a laser scanner 40 that scans the laser LB in the X direction (first direction) and the Y direction (second direction) that intersects the X direction.

[0190] The laser scanner 40 is driven and controlled so that the laser LB draws a specified pattern on the surface of the workpiece 200.

[0191] Furthermore, the controller 50 drives the laser scanner 40 so that the first drawing pattern LS1, which is located further forward of the origin O of the Bilisar pattern along the welding direction WD, becomes a wider pattern in the direction intersecting the welding direction WD compared to the second drawing pattern LS2, which is located behind it.

[0192] The controller 50 controls the output P of the laser LB so that the output P1 of the laser LB in drawing the first drawing pattern LS1 is lower than the output P2 of the laser LB in drawing the second drawing pattern LS2.

[0193] By configuring the laser welding apparatus 100 in this way, even without a gap between the first plate 210 and the second plate 220, it is possible to remove the zinc plating layers 211 and 221 present at the interface between the first plate 210 and the second plate 220, and to suppress the generation of welding defects associated with zinc vapor. Furthermore, it is possible to achieve a good weld shape on the workpiece 200. This also includes cases where the first plate 210 and the second plate 220 are spot-welded together.

[0194] Furthermore, when spot welding the first plate 210 and the second plate 220 together, it is not necessary to set the weld pattern SP to... Figure 15 The circular pattern shown. The first plate 210 and the second plate 220 can be spot welded together.

[0195] Based on this viewpoint, the solder joint pattern SP can take various shapes. For example, such as Figure 16A As shown, the solder joint pattern SP can also be set as a partially open loop shape, such as... Figure 16F As shown, the solder joint pattern SP can also be set as a waveform. Furthermore, as... Figure 16G As shown, the solder joint pattern SP can also be set to a roughly U-shape. Additionally, as... Figure 16A , Figures 16C-16E as well as Figure 16G As shown, if a portion of the weld pattern SP is opened, an outlet for air, oil, etc., can be formed between the first plate 210 and the second plate 220, which can result in a good weld shape.

[0196] (Other implementation methods)

[0197] It is also possible to appropriately combine the structural elements shown in Embodiments 1 to 3 and Modifications 1 to 3 to create new embodiments. For example, when drawing the scanning patterns shown in Embodiment 2, the output P of the laser LB can be controlled as shown in Modification 1.

[0198] Furthermore, in embodiments 2 and 3, and variations 1 to 3, for example, the laser LB can be scanned such that during one cycle, it travels from the origin O through the plotting positions C→B→A→O→F→E→D→O. Moreover, the timing of the change in the laser LB's output P can be altered by changing the order of the plotting positions.

[0199] In addition, Figure 1 In the example shown, the focusing lens 34 is positioned at the front of the laser scanner 40, but it can also be positioned at the rear of the laser scanner 40, in other words, between the laser scanner 40 and the light emission port of the laser head 30.

[0200] Furthermore, the scanning pattern of the laser LB can be a Lissajous pattern by vibrating the laser LB in the X direction as a cosine wave with a first frequency and in the Y direction as a cosine wave with a second frequency. In this case, the amplitudes a and b of the first reflector 41a and the second reflector 42a, the frequencies n and m of the first reflector 41a and the second reflector 42a, and consequently the phase... It has also been appropriately changed.

[0201] Furthermore, considering the structure shown in Modified Example 3 and Embodiment 3, when the scanning pattern of the laser LB is a Lissajous pattern in the shape of an ∞, the laser LB is scanned as follows. In other words, the laser LB is made to vibrate in a sine wave or cosine wave with a first frequency along the welding direction WD, and to vibrate in a sine wave or cosine wave with a second frequency along the direction intersecting the welding direction WD.

[0202] Furthermore, in this application specification, to address Figure 3 The example shown is of workpiece 200 subjected to laser welding, but it is not particularly limited to this. For example, workpiece 200 may also be constructed of two base materials each comprising plate-like portions, i.e., the plate-like portions overlap each other, and a zinc-plated layer is formed at least on the surface of the plate-like portions. In this case, the base material can be iron, mild steel, or high-tensile steel. The melting points of these are all higher than the boiling point of zinc. Furthermore, a zinc alloy plating containing zinc and aluminum may be formed on the surfaces of the two base materials. In other words, a plating with zinc as the main component may also be formed on the surfaces of the two base materials. Here, "a plating with zinc as the main component" means a plating containing 60% or more zinc. In addition, a coating layer containing materials other than zinc may be formed on the surfaces of the two base materials respectively. In this case, the materials of the coating layer and the base materials are set separately such that the boiling point of the material constituting the coating layer is lower than the melting point of the material constituting the base material.

[0203] In the case of laser welding of the workpiece 200, in the drawing of the first drawing pattern LS1, the covering layer between the plate-shaped parts is removed. In the drawing of the second drawing pattern LS2, the two plate-shaped parts with the covering layer removed are welded to each other.

[0204] When laser welding is performed on a workpiece 200 with such a structure, by applying the laser welding method and laser welding apparatus disclosed herein, it is possible to suppress the generation of welding defects caused by the vapor generated by the evaporation of the coating layers such as zinc plating 211 and 221, and of course, it is also possible to make the weld shape good.

[0205] Industrial availability

[0206] The laser welding method disclosed herein can suppress the generation of welding defects caused by vapor generated by the evaporation of the coating layer, and is therefore useful for lap welding of two components on which a coating layer such as a galvanized layer is formed on the surface.

[0207] -Symbol Explanation-

[0208] 10 Laser Oscillators

[0209] 20 optical fibers

[0210] 30 laser heads

[0211] 31. Shell

[0212] 32 Collimating Lens

[0213] 33. Reflector

[0214] 34 Condensing Lens

[0215] 40 laser scanners

[0216] 41 First galvanometer mirror

[0217] 41a First reflecting mirror

[0218] 41b First Rotational Axis

[0219] 41c First Drive Unit

[0220] 42 Second galvanometer mirror

[0221] 42a Second reflecting mirror

[0222] 42b Second Rotation Axis

[0223] 42c Second Drive Unit

[0224] 50 controllers

[0225] 60 robotic arms

[0226] 200 workpieces

[0227] 210 First-grade sheet (base material)

[0228] 211 Zinc plating (coating)

[0229] 220 Second sheet material (base material)

[0230] 221 Zinc plating (coating)

[0231] 301, 302 small holes

[0232] 311, 312 Molten Pool

[0233] 320 Welding section.

Claims

1. A laser welding method comprising: a welding step of irradiating a workpiece surface by scanning the laser in two dimensions while the laser travels in the welding direction, thereby welding the workpiece. The workpiece is constructed in which two base materials, each comprising a plate-shaped portion, overlap each other, and at least on the surface of the plate-shaped portions, a covering layer is formed, wherein the boiling point of the covering layer is lower than the melting point of the base materials. In the welding step, the laser is scanned such that: a predetermined pattern is drawn on the surface of the workpiece, and among the predetermined patterns, a first drawn pattern located in front of the origin of the predetermined pattern along the welding direction becomes a wider pattern with respect to the direction intersecting the welding direction compared to a second drawn pattern located behind the origin. During the welding step, the laser output is controlled such that the laser output during the drawing of the first pattern is lower than the laser output during the drawing of the second pattern. The specified pattern is a pattern in which two asymmetrical ring-shaped patterns meet and continue at the origin. In the process of drawing the first drawing pattern, the covering layer between the plate-shaped portions is removed. In the process of depicting the second pattern, the two plate-shaped portions with the cover layer removed are welded together.

2. The laser welding method according to claim 1, wherein, The specified pattern is an ∞-shaped Lissajous pattern extending in the welding direction. In the welding step, the laser is vibrated along the welding direction as a sinusoidal wave with a first frequency, and the laser is vibrated along a direction intersecting the welding direction as a sinusoidal wave with a second frequency, thereby scanning the surface of the workpiece to depict the Lisajous pattern.

3. The laser welding method according to claim 2, wherein, The ratio of the first frequency to the second frequency is 1:

2.

4. The laser welding method according to any one of claims 1 to 3, wherein, Control is performed so that the laser output continuously increases during the transfer from the first drawing pattern to the second drawing pattern. Control is performed so that the laser output continuously decreases during the transition from the second drawing pattern to the first drawing pattern.

5. The laser welding method according to any one of claims 1 to 3, wherein, During the first period after the welding of the workpiece begins, the laser output for drawing the second drawing pattern is set to zero within a specified drawing length. During the second period before the welding of the workpiece is completed, the output of the laser used to draw the first drawing pattern is set to zero within a specified drawing length.

6. The laser welding method according to claim 5, wherein, The prescribed drawing length for setting the laser output to zero during the first period is twice the length of one cycle of the second drawing pattern, and the prescribed drawing length for setting the laser output to zero during the second period is the same as the sum of the lengths of one cycle of the first drawing pattern and the lengths of one cycle of the second drawing pattern.

7. The laser welding method according to any one of claims 1 to 3, wherein, The workpiece is spot-welded by directing the laser in the welding direction.

8. The laser welding method according to any one of claims 1 to 3, wherein, The coating is a zinc-based plating.

9. A laser welding apparatus, comprising at least: A laser oscillator generates laser light. A laser head receives the laser and irradiates the workpiece; and The controller controls the movement of the laser head and the output of the laser. The laser head includes a laser scanner that scans the laser in a first direction and a second direction intersecting the first direction. In the case where the workpiece is constructed in which two base materials, each comprising a plate-shaped portion, overlap each other, and a covering layer is formed at least on the surface of the plate-shaped portions, and the boiling point of the covering layer is lower than the melting point of the base materials, The controller drives the laser scanner such that the laser draws a predetermined pattern on the surface of the workpiece, and among the predetermined patterns, a first drawn pattern located in front of the origin of the predetermined pattern along the welding direction is wider with respect to the direction intersecting the welding direction than a second drawn pattern located behind the origin. The controller controls the output of the laser so that the laser output during the drawing of the first drawing pattern is lower than the laser output during the drawing of the second drawing pattern. The specified pattern is a pattern in which two asymmetrical ring-shaped patterns meet and continue at the origin. In the process of drawing the first drawing pattern, the covering layer between the plate-shaped portions is removed. In the process of depicting the second pattern, the two plate-shaped portions with the cover layer removed are welded together.

10. The laser welding apparatus according to claim 9, wherein, The specified pattern is an ∞-shaped Lissajous pattern extending in the welding direction. The controller drives the laser scanner to depict the Lisajous pattern on the surface of the workpiece by vibrating the laser along the welding direction as a sine wave with a first frequency and vibrating the laser along a direction intersecting the welding direction as a sine wave with a second frequency.

11. The laser welding apparatus according to claim 10, wherein, The ratio of the first frequency to the second frequency is 1:

2.

12. The laser welding apparatus according to any one of claims 9 to 11, wherein, The laser welding device also includes: a robotic arm equipped with the laser head. The controller controls the movements of the robotic arm. The robotic arm moves the laser head relative to the surface of the workpiece in a predetermined direction.

13. The laser welding apparatus according to any one of claims 9 to 11, wherein, The laser oscillator is connected to the laser head via an optical fiber. The laser beam passes through the optical fiber and is transmitted from the laser oscillator to the laser head.

14. The laser welding apparatus according to any one of claims 9 to 11, wherein, The laser scanner includes a first galvanometer lens that scans the laser in the first direction and a second galvanometer lens that scans the laser in a second direction that intersects the first direction.

15. The laser welding apparatus according to any one of claims 9 to 11, wherein, The laser head also has a focus position adjustment mechanism. The focal position adjustment mechanism is configured to change the focal position of the laser along a direction that intersects the surface of the workpiece.

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