Laser welding method, laser welding apparatus, and laser welding program

Abstract

To provide a laser welding method that can suppress a weld defect from being formed.SOLUTION: In the laser welding method, in which a laser beam is irradiated toward an irradiation target surface of a welding target formed of a plurality of overlaid metal plates to weld the plurality of metal plates, the plurality of metal plates include: a first metal plate that forms the irradiation target surface; and a second metal plate that forms a surface opposite to the irradiation target surface in the welding target. The laser welding method includes: a first step of irradiating the irradiation target surface with the laser beam, thereby, welding the plurality of metal plates so as to form a welded part; and a second step of irradiating, with the laser beam, a target range of the irradiation target surface including at least part of the welded part, thereby, remelting at least the first metal plate without remelting the second metal plate among the plurality of metal plates after the first step.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a laser welding method, a laser welding apparatus, and a laser welding program.

Background Art

[0002] Conventionally, when welding metal plates, a technique for reducing welding defects is known (for example, Patent Document 1). In the conventional method, at a location with a gap, a first laser irradiation for melting the upper plate to reduce the gap and a second laser irradiation for performing laser irradiation through to the back side of the lower plate are performed.

Prior Art Documents

Patent Documents

[0003] [[ID=2H

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when laser irradiation is performed through to the back side of the lower plate in the second laser irradiation, the back side of the lower plate is melted, so the shrinkage force during solidification increases, and there is a risk of solidification cracking.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms. According to one embodiment of the present disclosure, a laser welding method is provided for welding a plurality of metal plates by irradiating a laser beam toward a surface to be irradiated with a welding object formed by a plurality of stacked metal plates. The plurality of metal plates include a first metal plate that forms the surface to be irradiated and a second metal plate that forms the surface of the welding object opposite to the surface to be irradiated. The laser welding method comprises a first step of welding the plurality of metal plates to form a weld by irradiating the surface to be irradiated with the laser beam; a second step after the first step of irradiating a target area of ​​the surface to be irradiated that includes at least a part of the weld, thereby remelting at least the first metal plate without remelting the second metal plate; and an inspection step performed between the first step and the second step for checking whether a welding defect has been formed in the first step, wherein if it is determined in the inspection step that there is a welding defect, the second step is executed, and if it is determined in the inspection step that there is no welding defect, the second step is not executed.

[0006] (1) According to one embodiment of the present disclosure, a laser welding method is provided for welding a plurality of metal plates by irradiating a laser beam toward the irradiated surface of a workpiece to be welded, which is made up of a plurality of stacked metal plates. The plurality of metal plates include a first metal plate that forms the irradiated surface and a second metal plate that forms the surface of the workpiece to be welded opposite to the irradiated surface. The laser welding method comprises a first step of welding the plurality of metal plates to form a weld by irradiating the irradiated surface with the laser beam, and a second step after the first step of irradiating a target area of ​​the irradiated surface that includes at least a part of the weld, thereby remelting at least the first metal plate among the plurality of metal plates without remelting the second metal plate. According to this embodiment, even if a welding defect is formed in the first step, the welding defect, such as solidification cracks, can be repaired by remelting in the second step. In the second step, since the second metal plate is not remelted among the plurality of metal plates, the volume of molten metal can be reduced compared to the case in which the second metal plate is also remelted. Therefore, the shrinkage force during solidification is reduced, and the occurrence of new solidification cracks caused by laser irradiation in the second step can be suppressed. (2) A laser welding method according to the above embodiment, wherein the irradiation diameter of the laser beam in the second step may be larger than the irradiation diameter of the laser beam in the first step. According to this embodiment, welding defects can be repaired regardless of the location of the welding defect by remelting the entire area of ​​the weld. (3) A laser welding method according to the above embodiment, wherein the state of the laser light irradiated in the second step may be a defocused state. According to this embodiment, the laser light can be irradiated in a defocused state, which is a state in which the laser light is attenuated compared to the in-focus state. (4) A laser welding method according to the above embodiment, further comprising an inspection step performed between the first step and the second step, for inspecting whether or not a welding defect has been formed in the first step, wherein the second step is performed if it is determined in the inspection step that a welding defect exists, and does not need to be performed if it is determined in the inspection step that there is no welding defect. According to this embodiment, the second step can be performed only when a welding defect has been formed, so welding can be performed efficiently by omitting the unnecessary second step. (5) A laser welding method according to the above embodiment, wherein in the inspection step, if it is determined that there is a welding defect, the location of the welding defect is identified, the target range in the second step includes the location of the identified welding defect, and the irradiation diameter of the laser beam in the second step may be smaller than the irradiation diameter of the laser beam in the first step. According to this embodiment, by using a laser beam with a small irradiation diameter, the metal portion of the welding defect in the uppermost metal plate can be locally remelted. As a result, the volume of molten metal can be reduced, the shrinkage force during solidification is reduced, and the occurrence of new solidification cracks caused by laser irradiation in the second step can be further suppressed. (6) In the above-described embodiment of the laser welding method, the plurality of metal plates may be composed of two metal plates, the first metal plate and the second metal plate. According to this embodiment, the laser welding method can be applied to weld the two metal plates. This disclosure can also be implemented in various forms other than laser welding methods. For example, it can be implemented in the form of a laser welding apparatus, a method for manufacturing a laser welding apparatus, a method for controlling a laser welding apparatus, a laser welding program that implements the control method, a non-temporary recording medium that stores the computer program, etc. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic diagram showing the configuration of a laser welding apparatus. [Figure 2] A flowchart illustrating the steps of the laser welding process. [Figure 3] A schematic diagram illustrating each step of the laser welding process. [Figure 4] A flowchart showing the procedure of the laser welding process according to the second embodiment. [Figure 5] A schematic diagram illustrating each step of the laser welding process according to the second embodiment. [Modes for carrying out the invention]

[0008] A. First Embodiment: A1. Laser welding equipment: Figure 1 is a schematic diagram showing the configuration of a laser welding apparatus 100 used to irradiate a laser beam LB in a laser welding process. As shown in Figure 1, the laser welding apparatus 100 irradiates a laser beam LB towards the irradiated surface WS of a workpiece W formed by stacked metal plates. Specifically, in this embodiment, the multiple metal plates consist of two metal plates, including a first metal plate Wa and a second metal plate Wb. The first metal plate Wa forms the irradiated surface WS. The second metal plate Wb forms the back surface WSb of the workpiece W, which is the surface opposite to the irradiated surface WS. In this embodiment, the material of the first metal plate Wa and the second metal plate Wb is aluminum. When the laser beam LB is irradiated onto the workpiece W, the first metal plate Wa and the second metal plate Wb are welded together. Note that the material of the metal plates to which this laser welding method is applied is not limited to aluminum, but may also be light metals such as magnesium, or iron or steel.

[0009] The laser welding apparatus 100 comprises a laser oscillator 10, a laser scanner 20 as a laser irradiation unit, and a control unit 60.

[0010] The laser oscillator 10 emits laser light LB. The laser oscillator 10 and the laser scanner 20 are connected via an optical fiber cable 11. The laser scanner 20 includes a collimating lens 30, a dichroic mirror 40, a first reflective mirror 21, a diffractive optical element (DOE) 22, a Z lens drive unit 23, a second reflective mirror 25, a focusing lens 26, a galvanometer scanner unit 27, and protective glass 28.

[0011] The laser beam LB emitted from the laser oscillator 10 enters the inside of the laser scanner 20 via the optical fiber cable 11. The laser beam LB is then adjusted to a parallel state by the collimating lens 30. Subsequently, the laser beam LB is reflected by the dichroic mirror 40 and the first reflective mirror 21, reaching the DOE 22.

[0012] DOE22 adjusts the irradiation pattern of the laser beam LB. Specifically, DOE22 emits the incident laser beam LB as a laser beam LB with a different power density distribution shape than when it was incident.

[0013] The laser beam LB, adjusted by the DOE22, reaches the Z lens 24, which is built into the Z lens drive unit 23. The Z lens drive unit 23 has a movement mechanism for moving the position of the Z lens 24 in the optical axis direction, and a driver for driving the movement mechanism. As the position of the Z lens 24 in the optical axis direction moves, the focal position of the laser beam LB emitted from the laser scanner 20 is changed.

[0014] Thereafter, the laser beam LB is reflected by the second reflection mirror 25 and enters the galvanometer scanner unit 27 through the condenser lens 26. The galvanometer scanner unit 27 includes a mirror that reflects the laser beam LB, a change mechanism that changes the angle of the mirror, and a driver that drives the change mechanism. Then, the galvanometer scanner unit 27 changes the irradiation position of the laser beam LB on the irradiated surface WS of the welding object W by changing the angle of the built-in mirror. The laser beam LB emitted from the galvanometer scanner unit 27 is irradiated onto the irradiated surface WS of the welding object W through the protective glass 28.

[0015] The control unit 60 is configured as a computer having a CPU and a memory. A laser welding program for executing the laser welding process is stored in the memory. The control unit 60 controls the laser oscillator 10 and the laser scanner 20 by executing the laser welding program stored in the memory. Specifically, the control unit 60 commands the laser oscillator 10 with the output value of the laser beam LB. Also, the control unit 60 commands the Z-lens drive unit 23 with a distance such that the focal position is plus in the direction approaching the laser scanner 20 and minus in the direction moving away from the laser scanner 20 based on a predetermined reference focal position F0. When the welding object W is arranged such that the position of the irradiated surface WS coincides with the reference focal position F0, the irradiation diameter, which is the diameter of the substantially circular irradiation range of the laser beam LB on the irradiated surface WS, increases due to the deviation of the focal position from the reference focal position F0.

[0016] The state where the focal position of the laser beam LB coincides with the irradiated surface WS is called the just focus state. The state where the focal position of the laser beam LB is between the laser scanner 20 and the irradiated surface WS is called the defocus state. The state where the focal position of the laser beam LB is at a position farther from the laser scanner 20 than the irradiated surface WS is called the in-focus state. The laser beam LB in the defocus state is more attenuated than the laser beam LB in the in-focus state.

[0017] A2. Laser Welding Process: FIG. 2 is a flowchart showing the procedure of a laser welding process for realizing the laser welding method according to the present embodiment. FIG. 3 is an explanatory diagram schematically depicting the cross-section of the welding object W in each step of the laser welding process. In the first step P10 of FIG. 2, the first metal plate Wa and the second metal plate Wb are welded by irradiating the irradiated surface WS with the laser beam LB. In the first step P10, the welded portion 80 shown in FIG. 3, which is the portion where the metal melted by the irradiation of the laser beam LB solidifies, is formed. The first step P10 is also referred to as the main welding step of this welding process.

[0018] The first step P10 is executed by the control unit 60 performing a first process of irradiating the laser scanner 20 with the laser beam LB for welding the first metal plate Wa and the second metal plate Wb to form the welded portion 80. Also, the function exerted by the control unit 60 when performing the first process is referred to as the first function.

[0019] As shown in "P10 Irradiation" of FIG. 3, in the first step P10 of the present embodiment, non-penetrating welding is performed such that the metal is melted to an extent that does not reach the back surface WSb of the second metal plate Wb. In the first step P10, the laser beam LB in a defocused state is irradiated. In "P10 Irradiation" of FIG. 3, the melted metal portion is indicated by cross-hatching. As shown in "After P10 Irradiation" of FIG. 3, in the first step P10, the portion where the metal melted by the irradiation of the laser beam LB solidifies is the welded portion 80 indicated by single hatching.

[0020] By the way, in welding, welding defects 81 may be formed in the welded portion 80. In "After P10 Irradiation" of FIG. 3, as an example of the welding defect 81, solidification cracking where the solidified portion cracks and blowholes which are cavities formed in the welded portion 80 are depicted. The next second step P20 is performed to repair the welding defect 81.

[0021] In the second step P20 shown in Figure 2, the laser beam LB is irradiated onto the target area including at least a portion of the welded area 80, so that the second metal plate Wb is not remelted, and the first metal plate Wa is remelted. In other words, in the second step P20, only the first metal plate Wa, which is the uppermost metal plate including the irradiated surface WS, is remelted. The second step P20 is also called the remelting step.

[0022] The second step P20 is performed by the control unit 60 after the first process by irradiating a target area of ​​the irradiated surface WS, including at least a part of the welded area 80, with laser light LB to remelt at least the first metal plate Wa, without remelting the second metal plate Wb, of the two metal plates Wb. The function exhibited by the control unit 60 as a result of the second process is called the second function.

[0023] As shown in Figure 3, in the second step P20 of this embodiment, a laser beam LB with an irradiation diameter D2 that is larger than the irradiation diameter D1 of the laser beam in the first step P10 is irradiated onto the welded portion 80. The irradiation position of the laser beam in the first step P10 and the irradiation position of the laser beam in the second step P20 are the same. As a result, the entire area of ​​the welded portion 80 that is exposed to the irradiated surface WS formed in the first step P10 can be remelted. Therefore, regardless of the location of the welding defect 81, the metal portion in which the welding defect 81 is formed can be remelted.

[0024] In the second step P20, a defocused laser beam LB is irradiated. The amount of heat input to the workpiece W by the laser beam LB in the second step P20 is smaller than the amount of heat input by the laser beam LB in the first step P10. The irradiation diameter D2 of the laser beam LB in the second step P20 is larger than the irradiation diameter D1 of the laser beam LB in the first step P10. Therefore, by making the amount of heat input in the second step P20 smaller than the amount of heat input by the laser beam LB in the first step P10, only the first metal plate Wa can be remelted. The amount of heat input is adjusted by irradiation conditions such as the laser output of the laser beam LB, the irradiation time of the laser beam LB, and the irradiation diameter of the laser beam LB. In this embodiment, a laser beam LB with laser conditions that allow only the first metal plate Wa to be remelted, as determined in advance by experiments, is irradiated.

[0025] In the second step P20, only the first metal plate Wa, which is the uppermost metal plate of the object to be welded W, is remelted. This suppresses the formation of new welding defects 81 caused by laser irradiation in the second step P20. Unlike this embodiment, if the second metal plate Wb were also remelted in addition to the first metal plate Wa, the volume of molten metal would increase, and the shrinkage stress of the metal during solidification would increase, potentially leading to solidification cracks. In this respect, according to this embodiment, by remelting only the first metal plate Wa, the volume of molten metal can be made smaller compared to the case where the second metal plate Wb is also remelted, thus suppressing the formation of new welding defects 81, which are solidification cracks.

[0026] Furthermore, if the second metal plate Wb is also remelted in addition to the first metal plate Wa, a larger amount of heat needs to be applied to the workpiece W by laser irradiation in order to melt a large volume of metal. When a large amount of heat is applied, spatter may be generated, potentially leading to the formation of holes such as blowholes. In this respect, according to this embodiment, compared to the case in which the second metal plate Wb is also remelted, the amount of heat applied can be reduced, thereby suppressing the generation of spatter and preventing the formation of new welding defects 81, namely blowholes.

[0027] As shown in Figure 3, "After P20 irradiation," the metal molten by laser irradiation solidifies in a state where the metal portion where solidification cracks have occurred is sealed so that it is not exposed. This improves the reduction in strength caused by the solidification cracks formed in the first step P10. Furthermore, when the object to be welded W is used in a manner in which water flows between the first metal plate Wa and the second metal plate Wb, water leakage can be suppressed. In detail, there is an embodiment in which the first metal plate Wa and the second metal plate Wb each have a shape that forms a space for water (not shown) to flow between the first metal plate Wa and the second metal plate Wb. In this embodiment, the metal molten and solidified in the second step P20 seals the portion of the metal portion where solidification cracks have occurred that is exposed to the irradiated surface WS, thereby suppressing water leakage from between the first metal plate Wa and the second metal plate Wb through the solidification cracks to the irradiated surface WS of the first metal plate Wa.

[0028] The dashed line in Figure 3 shows an example of a welding defect 81, namely a blowhole, where a blowhole is formed in the first step P10. Even when a blowhole is formed, similar to solidification cracking, the molten metal in the second step P20 solidifies to fill the blowhole cavity. Therefore, by executing the second step P20, the strength reduction caused by the blowhole formed in the first step P10 can be improved.

[0029] Furthermore, the inventors have confirmed that even if a blowhole is formed in the first step P10, if the volume of the blowhole is less than or equal to half the volume of the metal molten in the first step P10, the welding defect 81 can be repaired to meet the target strength by performing the second step P20.

[0030] According to the first embodiment described above, the laser welding method comprises a first step P10 and a second step P20. In the second step P20, of the two metal plates, the first metal plate Wa and the second metal plate Wb, the second metal plate Wb is not remelted. Therefore, compared to the case in which both the first metal plate Wa and the second metal plate Wb are remelted, the volume of molten metal can be reduced, the shrinkage force during solidification is reduced, and the occurrence of new solidification cracks caused by irradiation with laser light LB in the second step P20 can be suppressed.

[0031] Furthermore, the irradiation diameter D2 of the laser beam LB in the second step P20 is larger than the irradiation diameter D1 of the laser beam LB in the first step P10. Therefore, regardless of the location of the welding defect 81, the welding defect 81 can be repaired by remelting the metal portion in which the welding defect 81 is formed.

[0032] Furthermore, the laser beam LB irradiated in the second step P20 is in a defocused state. This allows the laser beam LB to be irradiated in a defocused state, which is attenuated compared to the in-focus state of the laser beam LB. In addition, the multiple metal plates are composed of two plates: a first metal plate Wa and a second metal plate Wb. The laser welding method according to this application is suitable for welding two metal plates.

[0033] B. Second Embodiment: Figure 4 is a flowchart showing the procedure of the laser welding process according to the second embodiment. Figure 5 is a schematic explanatory diagram showing each step of the laser welding process according to the second embodiment. In this embodiment, the inspection process is performed between the first step P10 and the second step P20, and the irradiation conditions of the laser beam LB in the second step P20 differ from the first embodiment. Components identical to those in the first embodiment are denoted by the same reference numerals, and detailed reference numerals are omitted as appropriate.

[0034] As shown in Figure 4, after the first step P10 is performed, image acquisition for defect inspection is performed in step P12. Specifically, the laser welding apparatus 100 according to this embodiment further includes a camera (not shown) that images the irradiated surface WS. The image captured by the camera is transmitted to the control unit 60. Using the image captured by the camera, it is possible to confirm welding defects 81, such as holes and cracks, formed on the surface of the welded part 80.

[0035] In step P14 of Figure 4, it is determined whether or not there is a welding defect 81. Specifically, the control unit 60 determines whether or not there is a welding defect 81 by performing image processing on the captured image. If it is determined that there is a welding defect 81, the location of the welding defect 81 is identified in step P16. Steps P12, P14, and P16 are also called inspection steps.

[0036] In another embodiment of the inspection process, the presence or absence of welding defects 81 may be determined by visually inspecting images captured by a camera. Alternatively, instead of a camera, a laser beam may be shone onto the welded area 80, and the presence or absence of welding defects 81 may be determined using the reflected light.

[0037] If a welding defect 81 is determined to exist in step P14, steps P16 and the second step P20 are performed. In the second step P20 of this embodiment, unlike the first embodiment, the laser beam LB is irradiated not over the entire area of ​​the welded portion 80 exposed to the irradiated surface WS, but only to the portion of the welding defect 81 exposed to the irradiated surface WS.

[0038] Specifically, the area irradiated by the laser beam LB in the second step P20 includes the location of the welding defect 81 identified in step P16. Furthermore, as shown in Figure 5, the irradiation diameter D3 of the laser beam in the second step is smaller than the irradiation diameter D1 of the laser beam in the first step P10. This allows for the localized remelting of the metal portion of the first metal plate Wa in which the welding defect 81 is formed.

[0039] Furthermore, the laser output of the laser beam LB in the second step P20 is smaller than the laser output of the laser beam LB in the first step P10. In this embodiment, the irradiation diameter D3 in the second step P20 is smaller than the irradiation diameter D1 in the first step P10. Therefore, by making the laser output of the laser beam LB in the second step P20 smaller than the laser output of the laser beam LB in the first step P10, the energy density in the irradiation range of the laser beam LB is reduced, and only the first metal plate Wa can be remelted. As in the first embodiment, in the second step P20, the laser beam LB is irradiated with laser conditions determined in advance by experiments or other means that only the first metal plate Wa can be remelted.

[0040] As shown in Figure 4, the laser welding process ends after the execution of the second step P20. Furthermore, if it is determined in step P14 that there are no welding defects 81, steps P16 and the second step P20 are skipped, and the laser welding process ends. Note that in Figure 5, a hole formed in the irradiated surface WS is depicted as an example of a welding defect 81; however, this embodiment can also be applied, for example, when solidification cracks are formed in a limited area of ​​the weld 80.

[0041] According to the second embodiment described above, the second step P20 is performed when it is determined that there is a welding defect in step P14, and is not performed when it is determined that there is no welding defect in step P14. Therefore, the second step P20 can be performed only when a welding defect 81 is formed, and welding can be performed efficiently by omitting the unnecessary second step P20.

[0042] Furthermore, the irradiation diameter D3 of the laser beam LB in the second step P20 is smaller than the irradiation diameter D1 of the laser beam LB in the first step P10. Therefore, the metal portion of the welding defect 81 can be locally remelted. As a result, the volume of molten metal can be reduced, which reduces the shrinkage force during solidification and further suppresses the occurrence of new solidification cracks caused by laser irradiation in the second step.

[0043] C. Other embodiments: (C1) In the first embodiment described above, non-penetrating welding is performed. This laser welding method can also be applied to penetrating welding, in which the metal is melted and welded to the back surface WSb of the second metal plate Wb. Furthermore, in the first embodiment described above, the laser beam LB is not scanned during the welding process. This laser welding method can also be applied to welding methods in which the irradiated laser beam LB is scanned along a line. Regardless of the welding method of this welding, when irradiating with laser beam LB to repair welding defects 81, the formation of new welding defects 81 can be suppressed by not melting the second metal plate Wb that forms the back surface WSb.

[0044] (C2) In the first embodiment described above, the plurality of metal plates are composed of two metal plates, a first metal plate Wa and a second metal plate Wb. The number of plurality of metal plates is not limited to two. Even when welding three or more metal plates, by not remelting the bottommost metal plate, the second metal plate Wb, in the second step P20, the volume of molten metal can be reduced compared to when the second metal plate Wb is also remelted, thereby suppressing the formation of solidification cracks. It is preferable to remelt fewer metal plates in the second step P20, as this reduces the volume of molten metal and the amount of heat input. Therefore, for example, when welding three metal plates, it is preferable to remelt only the first metal plate Wa in the second step P20. When welding defects 81 are formed in the first step P10, welding defects 81 such as blowholes are more likely to be formed on the topmost metal plate, the first metal plate Wa. Therefore, even when only the first metal plate Wa is melted in the second step P20, the welding defect 81 can be repaired by filling the blowhole cavity with metal.

[0045] (C3) In the second embodiment described above, if a welding defect is determined to exist in step P14, the metal portion in which the welding defect 81 is formed is locally remelted in the second step P20. In another embodiment, if a welding defect is determined to exist, in the second step P20, a laser beam LB with an irradiation diameter D2 that is larger than the irradiation diameter D1 in the first step P10 may be irradiated, similar to the first embodiment. In this case as well, laser welding can be efficiently performed by executing the second step P20 when a welding defect is determined to exist and not executing the second step P20 when no welding defect is determined to exist.

[0046] (C4) In the first embodiment described above, a defocused laser beam LB is irradiated in the first step P10 and the second step P20. The laser beam LB irradiated in the first step P10 and the second step P20 may be an in-focus laser beam LB instead of a defocused laser beam LB. Furthermore, the in-focus state and the defocused state of the laser beam LB irradiated in the first step P10 may be different from the in-focus state and the defocused state of the laser beam LB irradiated in the second step P20.

[0047] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features of the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0048] 10…Laser oscillator, 11…Optical fiber cable, 20…Laser scanner, 21…First reflective mirror, 23…Z lens drive unit, 24…Z lens, 25…Second reflective mirror, 26…Focusing lens, 27…Galvanometer scanner unit, 28…Protective glass, 30…Collimating lens, 40…Dichroic mirror, 60…Control unit, 80…Welded area, 81…Welding defect, 100…Laser welding apparatus, D1, D2, D3…Irradiation diameter, F0…Reference focal position, LB…Laser beam, P10…First process, P12, P14, P16…Process, P20…Second process, W…Workpiece to be welded, WS…Irradiated surface, Wa…First metal plate, Wb…Second metal plate

Claims

1. A laser welding method for welding multiple metal plates, wherein a laser beam is irradiated onto the surface of a welding target object formed by stacking multiple metal plates to weld the multiple metal plates, The plurality of metal plates include a first metal plate that forms the surface to be irradiated and a second metal plate that forms the surface of the object to be welded opposite to the surface to be irradiated. The aforementioned laser welding method is A first step involves welding the plurality of metal plates together to form a welded portion by irradiating the surface to be irradiated with the laser light, A second step is performed in which, after the first step, the laser light is irradiated onto a target area of ​​the surface to be irradiated, including at least a part of the welded portion, to remelt at least the first metal plate among the plurality of metal plates, without remelting the second metal plate. An inspection step performed between the first step and the second step, comprising an inspection step for checking whether or not a welding defect was formed in the first step, If it is determined in the inspection process that there is a welding defect, the second step is executed. A laser welding method wherein, if it is determined in the inspection step that there are no welding defects, the second step is not performed.

2. A laser welding method according to claim 1, A laser welding method wherein the irradiation diameter of the laser beam in the second step is larger than the irradiation diameter of the laser beam in the first step.

3. A laser welding method according to claim 1 or 2, A laser welding method wherein the state of the laser light irradiated in the second step is a defocused state.

4. A laser welding method according to claim 1, In the inspection process described above, if it is determined that there is a welding defect, the location of the welding defect is identified. The scope of the second step includes the location of the identified welding defect, A laser welding method wherein the irradiation diameter of the laser beam in the second step is smaller than the irradiation diameter of the laser beam in the first step.

5. A laser welding method according to claim 1, A laser welding method in which the plurality of metal plates are composed of two metal plates, the first metal plate and the second metal plate.

6. A laser welding apparatus for welding multiple metal plates by irradiating a laser beam onto the surface of a welding target object formed by stacking multiple metal plates, A laser irradiation unit that irradiates the surface to be irradiated with the laser light, The system includes a control unit for controlling the laser irradiation unit, The plurality of metal plates include a first metal plate that forms the surface to be irradiated and a second metal plate that forms the surface of the object to be welded opposite to the surface to be irradiated. The control unit, A first process involves irradiating the laser irradiation unit with the laser beam used to weld the plurality of metal plates and form a welded portion, A second process is performed, in which, after the first process, the laser light is irradiated to a target area of ​​the irradiated surface, including at least a portion of the welded area, so as to remelt at least the first metal plate, without remelting the second metal plate among the plurality of metal plates. An inspection process performed between the first process and the second process, the inspection process for checking whether or not a welding defect was formed in the first process, If the inspection process determines that there is a welding defect, the second process is executed. A laser welding apparatus that, in the inspection process, determines that there are no welding defects and does not perform the second process.

7. A laser welding program for welding multiple metal plates by irradiating a laser beam onto the surface of a welding target object formed by stacking multiple metal plates, The plurality of metal plates include a first metal plate that forms the surface to be irradiated and a second metal plate that forms the surface of the object to be welded opposite to the surface to be irradiated. A first function that performs a first process of irradiating the surface to be irradiated with the laser light for welding the plurality of metal plates to form a welded part, A second function is performed, after the first process, in which the laser light is irradiated onto a target area of ​​the irradiated surface, including at least a part of the welded portion, to remelt at least the first metal plate, without remelting the second metal plate among the plurality of metal plates. An inspection function is implemented in a computer, which performs an inspection process between the first process and the second process, to check whether or not a welding defect was formed in the first process. The second process in the second function is This is performed if the aforementioned inspection process determines that there is a welding defect. A laser welding program that is executed when it is determined in the inspection process that there are no welding defects.

Images