Laser welding method and laser welding apparatus

Abstract

A laser welding method for welding an object by irradiating the object with laser light that includes a main power region, which includes at least one main beam, and an auxiliary power region, which includes at least one auxiliary beam having a smaller power density than the main beam, for example, said laser welding method having a step for forming a molten pool by irradiating the object with laser light, and a step for solidifying the molten pool, and the object being irradiated with the auxiliary beam such that a void formed inside the molten pool reaches the outside of the molten pool before the molten pool solidifies.

Description

[Technical Field]

[0001] This invention relates to a laser welding method and a laser welding apparatus. [Background technology]

[0002] A technique for laser welding multiple metal components, such as flat wires, is known (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 6674588 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In laser welding of metal components, including flat wires, the formation of voids within the weld prevents the acquisition of the required joint strength. Furthermore, it is difficult to detect the presence or absence of voids through visual inspection.

[0005] Therefore, one of the objectives of the present invention is to obtain an improved and novel laser welding method and laser welding apparatus that, for example, can suppress the generation of voids. [Means for solving the problem]

[0006] The laser welding method of the present invention is a laser welding method that welds an object by irradiating the object with laser light including, for example, a main power region including at least one main beam and a sub-power region including at least one sub-beam having a lower power density than the main beam, and comprises the steps of forming a molten pool by irradiating the object with the laser light and solidifying the molten pool, wherein the sub-beam is irradiated onto the object such that voids formed in the molten pool are released from the molten pool before the molten pool solidifies.

[0007] In the laser welding method described above, in the step of forming the molten pool, the laser light may be irradiated such that the number of voids in the lower half of the weld formed by the solidification of the molten pool is less than or equal to the number of voids in the upper half.

[0008] In the laser welding method described above, the main power region may be located inside the outer edge of the sub-power region.

[0009] In the laser welding method described above, the sub-power region may include a plurality of sub-beams as the at least one sub-beam, and the main beam may be surrounded by the plurality of sub-beams.

[0010] In the laser welding method described above, the sub-power region may include one sub-beam surrounding the main power region, as the at least one sub-beam.

[0011] The laser welding method may include a step after the step of forming the molten pool in which the molten pool is irradiated with the laser light to temporarily maintain the molten pool in a molten state.

[0012] In the laser welding method described above, the power of the laser beam may be lower in the step of temporarily maintaining the molten pool in a molten state compared to the step of forming the molten pool.

[0013] In the laser welding method described above, the power of the main beam may be lower in the step of temporarily maintaining the molten pool in a molten state compared to the step of forming the molten pool.

[0014] In the laser welding method described above, the depressions that occur on the surface of the molten pool due to the irradiation of the laser light in the step of temporarily maintaining the molten pool in a molten state may be shallower than the depressions that occur on the surface of the molten pool due to the irradiation of the laser light in the step of forming the molten pool.

[0015] In the laser welding method described above, in the step of temporarily maintaining the molten pool in a molten state, the power density of the laser beam on the surface of the molten pool is 10 7 [W / cm 2 or less.

[0016] In the laser welding method described above, in the step of temporarily maintaining the molten pool in a molten state, the power density of the laser beam on the surface of the molten pool is 10 6 [W / cm 2 or less.

[0017] In the laser welding method described above, in the step of forming the molten pool, the main beam is irradiated, and in the step of temporarily maintaining the molten pool in a molten state, irradiation of the main beam may be stopped.

[0018] In the laser welding method described above, from the step of forming the molten pool to the step of temporarily maintaining the molten pool in a molten state, an irradiation time of the main beam may be shorter than an irradiation time of the sub beam.

[0019] In the laser welding method described above, a wavelength of the main beam and a wavelength of the sub beam may be the same.

[0020] In the laser welding method described above, a wavelength of the main beam and a wavelength of the sub beam may be different.

[0021] In the laser welding method described above, the wavelength of the main beam is not less than 800 [nm] and not more than 1200 [nm], and the wavelength of the sub beam may be not more than 550 [nm].

[0022] In the laser welding method described above, a plurality of beams included in at least one of the main power region and the sub power region may be formed by a beam shaper.

[0023] In the laser welding method described above, the laser beam may be swept while being irradiated onto the object.

[0024] In the laser welding method described above, at least a portion of the sub-power region may be located behind the main power region in the sweeping direction of the laser beam with respect to the object.

[0025] In the laser welding method described above, the laser beam may be swept in a straight line.

[0026] In the laser welding method described above, the laser beam may be irradiated at a fixed point during the step of temporarily maintaining the molten pool in a molten state.

[0027] In the laser welding method described above, in the step of temporarily maintaining the molten pool in a molten state, the laser beam may be swept along a path that curves around the center of the molten pool when viewed in the direction of irradiation of the laser beam.

[0028] In the laser welding method described above, the object to be welded may be made of any one of the following materials: copper-based metal material, aluminum-based metal material, nickel-based metal material, iron-based metal material, and titanium-based metal material.

[0029] In the laser welding method described above, the molten pool may be formed to span between a first end of a first member made of a metal material in a first direction and a second end of a second member made of a metal material adjacent to the first member in a second direction intersecting the first direction, the second end of the second member in the first direction, and the second end of the first member positioned such that the distance of the first end from the second end along the first direction is 0 or more.

[0030] In the laser welding method described above, the members constituting the object may be flat rectangular wire conductors.

[0031] The laser welding apparatus of the present invention comprises, for example, a laser oscillator and an optical head that irradiates a target object with laser light emitted from the laser oscillator, wherein the laser light includes at least one main beam and at least one sub-beam having a lower power density than the main beam, and is irradiated to form a molten pool on the target object, and the sub-beam is irradiated to the target object such that voids formed in the molten pool escape from the molten pool before the molten pool solidifies.

[0032] The laser welding apparatus may include a sensor for detecting the temperature of the molten pool and an output unit for outputting information indicating the welding quality based on the detection result of the sensor.

[0033] The laser welding apparatus may include a sensor for detecting the temperature of the molten pool, a variable mechanism capable of changing the irradiation state of the laser light, and a control unit that controls the operation of the variable mechanism based on the detection result of the sensor. [Effects of the Invention]

[0034] According to the present invention, for example, an improved novel laser welding method and laser welding apparatus can be obtained that can suppress the generation of voids. [Brief explanation of the drawing]

[0035] [Figure 1] Figure 1 is an illustrative schematic diagram of a laser welding apparatus according to the first embodiment. [Figure 2] Figure 2 is an exemplary and schematic side view of an object before welding in the laser welding method of the embodiment. [Figure 3] Figure 3 is an exemplary and schematic side view of an object after welding using the laser welding method of the embodiment. [Figure 4] Figure 4 is an explanatory diagram illustrating the concept of the principle of the diffractive optical element included in the laser welding apparatus of the embodiment. [Figure 5] Figure 5 is a schematic diagram showing an example of a beam (spot) on the surface of an object being welded by a laser welding apparatus according to an embodiment. [Figure 6] Figure 6 is a schematic diagram showing an example of a beam (spot) on the surface of an object being welded by a laser welding apparatus according to an embodiment. [Figure 7] Figure 7 is a schematic diagram showing an example of a beam (spot) on the surface of an object being welded by a laser welding apparatus according to an embodiment. [Figure 8] Figure 8 is a schematic diagram showing an example of a beam (spot) on the surface of an object being welded by a laser welding apparatus according to an embodiment. [Figure 9] Figure 9 is an exemplary and schematic side view of an object in the process of forming a molten pool by the laser welding method of the embodiment. [Figure 10] Figure 10 is an illustrative and schematic plan view of the laser beam sweep path on an object by the laser welding method of the embodiment. [Figure 11] Figure 11 is an illustrative schematic diagram showing the time-dependent changes in the temperature of the molten pool and the output of the laser device in the laser welding method of the first embodiment. [Figure 12] Figure 12 is an exemplary and schematic perspective view of a rectangular wire containing a member as the object to be laser-welded according to the embodiment. [Figure 13] Figure 13 is an exemplary and schematic side view of a weld formed by the laser welding method of the embodiment. [Figure 14] Figure 14 is an illustrative schematic diagram of a laser welding apparatus according to a second embodiment. [Figure 15] Figure 15 is a graph showing the light absorption rate of each metal material as a function of the wavelength of the irradiated laser light. [Figure 16] Figure 16 is an illustrative schematic diagram showing the time-dependent changes in the temperature of the molten pool and the output of the laser device in the laser welding method of the second embodiment. [Figure 17] Figure 17 is an exemplary and schematic side view of an object in the molten pool maintenance process using the laser welding method of the second embodiment. [Figure 18] Figure 18 is a schematic plan view showing an example of the laser beam irradiation position on the molten pool in the laser welding method of the second embodiment. [Figure 19] Figure 19 is a schematic plan view showing an example of the laser beam sweep path over the molten pool in the laser welding method of the second embodiment. [Figure 20] Figure 20 is a schematic plan view showing an example of the laser beam sweep path over the molten pool by the laser welding method of the second embodiment. [Figure 21] Figure 21 is an illustrative block diagram of a laser welding apparatus according to an embodiment. [Figure 22] Figure 22 is an exemplary flowchart showing the processing procedure for outputting inspection results using the laser welding apparatus of the embodiment. [Figure 23] Figure 23 is an exemplary flowchart showing the processing procedure for void suppression control using a laser welding apparatus of an embodiment. [Modes for carrying out the invention]

[0036] Illustrative embodiments of the present invention are disclosed below. The configurations of the embodiments shown below, as well as the actions and results (effects) brought about by such configurations, are examples only. The present invention can also be realized by configurations other than those disclosed in the following embodiments. Furthermore, according to the present invention, it is possible to obtain at least one of the various effects (including derived effects) that can be obtained by the configuration.

[0037] The following embodiments have similar components. In the following, these similar components will be given common reference numerals, and redundant descriptions may be omitted.

[0038] In each figure, direction X is represented by arrow X, direction Y by arrow Y, and direction Z by arrow Z. Directions X, Y, and Z intersect and are perpendicular to each other. The Z direction is the direction in which the multiple members of the object W extend. Note that the Z direction is approximately vertically upward, but it may be inclined with respect to the vertical upward.

[0039] Furthermore, in this specification, ordinal numbers are assigned for convenience to distinguish parts, components, directions, etc., and do not indicate priority or order.

[0040] [First Embodiment] [Configuration of a laser welding system] Figure 1 is a diagram showing the schematic configuration of a laser welding apparatus 100 according to the first embodiment. As shown in Figure 1, the laser welding apparatus 100 comprises a laser device 110, an optical head 120, an optical fiber 130, a drive mechanism 140, a sensor 150, and a controller 200.

[0041] The laser welding apparatus 100 irradiates the surface of the object W to be laser-welded with laser light L. The energy of the laser light L partially melts the object W, and as it cools and solidifies, the object W is welded. The object W has multiple components, and these multiple components are joined together by laser welding.

[0042] The multiple components that make up the object W can each be made of, for example, copper-based metal materials such as copper or copper alloys, aluminum-based metal materials such as aluminum or aluminum alloys, nickel-based metal materials such as nickel or nickel alloys, iron-based metal materials such as iron or iron alloys, or titanium-based metal materials such as titanium or titanium alloys. The multiple components may be made of the same metal material or of different metal materials. The multiple components that make up the object W may or may not be conductors.

[0043] The laser device 110 has a laser oscillator and, for example, is configured to output single-mode laser light with a power of several kW. Alternatively, the laser device 110 may have, for example, multiple semiconductor laser elements internally, and be configured to output multi-mode laser light with a power of several kW as the combined output of these multiple semiconductor laser elements. Furthermore, the laser device 110 may have various laser light sources, such as fiber lasers, YAG lasers, and disk lasers. The laser device 110 also outputs laser light with a wavelength of, for example, 400 nm or more and 1200 nm or less.

[0044] The optical fiber 130 optically connects the laser device 110 and the optical head 120. In other words, the optical fiber 130 guides the laser light output from the laser device 110 to the optical head 120. When the laser device 110 outputs single-mode laser light, the optical fiber 130 is configured to propagate the single-mode laser light. In this case, the M of the single-mode laser light 2 The beam quality is set to 1.3 or lower. 2 Beam quality is M 2 It can also be called a factor.

[0045] The optical head 120 is an optical device for irradiating the laser light input from the laser device 110 toward the object W. The optical head 120 includes a collimating lens 121, a focusing lens 122, a mirror 123, a DOE 125 (diffractive optical element), and a galvanoscanner 126. The collimating lens 121, focusing lens 122, mirror 123, DOE 125, and galvanoscanner 126 may also be referred to as optical components.

[0046] Each collimating lens 121 collimates the laser light input via the optical fiber 130. The collimated laser light becomes parallel light.

[0047] Mirror 123 reflects the laser beam, which has been made parallel by the collimating lens 121, and directs it towards the galvanoscanner 126. A DOE 125 is provided between mirror 123 and the galvanoscanner 126. The DOE 125 will be described later.

[0048] The galvanometer scanner 126 has multiple mirrors 126a and 126b, and by controlling the angles of these mirrors 126a and 126b, the direction of emission of the laser beam L from the optical head 120 can be switched, thereby changing the irradiation position of the laser beam L on the surface of the object W. The angles of the mirrors 126a and 126b are changed by motors (not shown) controlled, for example, by a controller 200. By changing the emission direction of the laser beam L while irradiating it, the laser beam L can be swept over the surface of the object W.

[0049] The focusing lens 122 focuses the laser light, which arrives from the galvanoscanner 126 as parallel light, and irradiates the target object W with the laser light L (output light).

[0050] However, the optical components of the optical head 120 are not limited to these, and the optical head 120 may have other optical components.

[0051] The drive mechanism 140 changes the relative position of the optical head 120 with respect to the object W. The drive mechanism 140 includes, for example, a rotation mechanism such as a motor, a reduction mechanism that reduces the rotational output of the rotation mechanism, and a motion conversion mechanism that converts the rotation reduced by the reduction mechanism into linear motion. The controller 200 can control the drive mechanism 140 so that the relative position of the optical head 120 with respect to the object W in the X, Y, and Z directions changes. The drive mechanism 140 can change (switch) the object W to be laser-welded from among a plurality of objects W supported by a support mechanism (not shown). The drive mechanism 140 can also change the irradiation position of the laser beam L on the object W. Furthermore, the drive mechanism 140 can be used to change the irradiation point in conjunction with changing the irradiation direction of the laser beam on the object W. In addition, the drive mechanism 140 can change the irradiation position while the laser beam L is irradiated onto the surface of the object W. In other words, the drive mechanism 140 can sweep the laser beam L over the surface of the object W.

[0052] Sensor 150 is a sensor that detects the temperature of a molten pool formed on an object W by irradiation with laser light L, and is, for example, a radiation thermometer or an infrared thermography camera.

[0053] The controller 200 controls the operation of the laser device 110, the drive mechanism 140, and the galvanometer scanner 126 based on the detection results of the sensor 150. These devices—the laser device 110, the drive mechanism 140, and the galvanometer scanner 126—can each change the irradiation state of the laser light L irradiated from the optical head 120 onto the object W. In other words, the laser device 110, the drive mechanism 140, and the galvanometer scanner 126 are examples of variable mechanisms and can also be referred to as objects controlled by the controller 200.

[0054] Figure 2 is a side view showing the object W before welding. As shown in Figure 2, the object W has two members 20 (21, 22). Both members 20 are made of metal material.

[0055] Both members 20 extend in the Z direction and have ends 20a (21a, 22a) in the Z direction. The ends 20a spread out intersecting the Z direction. That is, the ends 20a extend in both the X and Y directions. The Z direction is an example of a first direction.

[0056] The two members 20 are adjacent to each other in the X direction, which intersects the Z direction, and are aligned in the X direction. A gap g is formed between the faces 21b, 22b (20b) that face each other in the X direction. The size of the gap g is 0 or greater. That is, the two members 20 may be in at least partial contact. The X direction is an example of a second direction.

[0057] In this embodiment, the Z-direction displacement δ of the end portion 21a of member 21 relative to the end portion 22a of member 22 is set to be 0 or greater. That is, among two members 20 in such a relative positional relationship, an example of the first end portion is an end portion 21a that is in the same position as the end portion 22a in the Z direction or that is shifted in the Z direction relative to the end portion 22a, and an example of the second end portion is an end portion 22a that is shifted in the opposite direction in the Z direction relative to the end portion 21a. Member 21 having end portion 21a is an example of the first member, and member 22 having end portion 22a is an example of the second member. Member 21 (first member) may also be referred to as a member that protrudes relatively in the Z direction, and member 22 (second member) may also be referred to as a member that is recessed relatively in the Z direction.

[0058] When welding the object W, i.e., the two members 20, the optical head 120 irradiates the laser beam L toward the end 20a. The direction of irradiation of the laser beam L is either opposite to the Z direction or inclined with respect to the opposite Z direction.

[0059] Figure 3 is a side view showing the state of the object W after welding. As shown in Figure 3, when laser light L is irradiated onto the end 20a, the two members 20 melt at the end 20a, and a welded joint 23 is formed that spans across the two ends 20a. The welded joint 23 is formed when the molten pool that was formed spanning across the two ends 20a cools and solidifies. The molten pool, which is a fluid metallic material, has a shape that bulges in the Z direction due to surface tension. Consequently, the welded joint 23 formed from the solidified molten pool also has a shape that bulges in the Z direction. The welded joint 23 mechanically connects the two members 21 and 22. Furthermore, if the two members 21 and 22 are made of conductive metals, the welded joint 23 electrically connects the two members 21 and 22.

[0060] Furthermore, as described above, the optical head 120 has a DOE 125. It shapes the shape of the laser beam (hereinafter referred to as the beam shape). Figure 4 is an explanatory diagram illustrating the concept of the principle of the DOE 125. As conceptually illustrated in Figure 4, the DOE 125 has a configuration in which, for example, multiple diffraction gratings 125a with different periods are superimposed. The DOE 125 can shape the beam by bending or superimposing parallel light in the direction influenced by each diffraction grating 125a. The DOE 125 may also be called a beam shaper.

[0061] [Beam (spot) shape] The DOE125 splits collimated laser light into multiple beams. Figures 5-8 show examples of laser beams L formed on the surface Wa of the object W, respectively. In Figures 5-8, for simplicity, beam B1 is shown as a solid line and beam B2 as a dashed line. The optical head 120 can output laser light containing multiple beams in various arrangements by changing the DOE125. The DOE125 is an example of a beam shaper.

[0062] The DOE125 splits a laser beam into multiple beams. These multiple beams include at least one beam B1 and at least one beam B2. Beam B2 has a lower power density than beam B1. Beam B1 is an example of a primary beam, and beam B2 is an example of a secondary beam. Furthermore, beam B1 forms the primary power region, and beam B2 forms the secondary power region.

[0063] In the example shown in Figure 5, a spot of one beam B1 and a spot of a beam B2 that is wider than beam B1 are formed on the surface Wa. Beam B1 and its outer edge B1a are located inside the outer edge B2a of beam B2. Beams B1 and B2 may be arranged concentrically or eccentrically. Furthermore, the outer edge B1a may be inscribed within the outer edge B2a.

[0064] In the example shown in Figure 6, a spot of one beam B1 and multiple spots of beams b2 surrounding beam B1 are formed on the surface Wa. The beams b2 are arranged in a roughly ring shape. Beam b2 is an example of a sub-beam, and a sub-power region is formed by multiple beams b2.

[0065] In the example shown in Figure 7, a spot of one beam B1 and spots of multiple beams b2 surrounding beam B1 are formed on the surface Wa. The beams b2 are arranged in a roughly rectangular shape, that is, along the sides of a virtual rectangle. Beam b2 is an example of a sub-beam, and a sub-power region is formed by multiple beams b2.

[0066] Furthermore, in the example shown in Figure 8, a spot of one beam B1 and a spot of one annular beam B2 surrounding beam B1 are formed on the surface Wa. Beam B1 and its outer edge B1a are located inside the inner edge B2b of beam B2. Although beam B2 has an annular shape, it is not limited to this and may have other shapes, such as a rectangular frame shape. Also, a part of beam B2 may be cut out.

[0067] [Laser welding method] Figure 9 is a side view of the object W during the process of forming the molten pool 23W in the laser welding method (hereinafter referred to as the formation process). For the sake of explanation, in the following, the laser beam L irradiated onto the end 21a of member 21 is referred to as laser beam L1, and the laser beam L irradiated onto the end 22a of member 22 is referred to as laser beam L2. However, both laser beams L1 and L2 are emitted from the same optical head 120.

[0068] First, as shown in Figure 9, at least one of the following is performed: irradiation of the end 21a of member 21 with laser light L1(L) and irradiation of the end 22a of member 22 with laser light L2(L). This forms a molten pool 23W on the ends 21a and 22a, spanning between them. The molten pool 23W is formed by the melting of the metal material of members 21 and 22. In other words, the molten pool 23W contains the metal material of members 21 and 22. Furthermore, the molten pool 23W is in a fluid state.

[0069] In this process, voids V may form inside the molten pool 23W. Since voids V can lead to a decrease in the weld strength of the welded joint 23, it is preferable that voids V do not remain in the solidified state.

[0070] The laser beam L may be swept while irradiated. Figure 10 is an explanatory diagram showing an example of the sweep paths of the laser beams L1 and L2(L) at the ends 21a and 22a. As shown in Figure 10, the laser beam L1 is swept linearly in the Y direction intersecting the X direction in region A1, for example, on the side of end 22a from the center C1 in the X direction of end 21a. Similarly, the laser beam L2 is swept linearly in the Y direction intersecting the X direction in region A2, for example, on the side of end 21a from the center C2 in the X direction of end 22a. In regions A1 and A2, the sweeping of the laser beams L1 and L2 may be performed multiple times.

[0071] Thus, it has been found that when the laser beams L1 and L2 are swept in a linear motion, the number of voids V in the welded area 23 is reduced. This is thought to be because turbulence in the flow of the fluid metal material within the fluid molten pool 23W can be suppressed. Furthermore, by sweeping back and forth in a linear motion, thermal energy can be continuously supplied to a wider area of ​​the molten pool 23W, thereby suppressing localized cooling and solidification of the 23W.

[0072] Figure 11 shows the time-dependent changes in the temperature of the molten pool 23W and the output of the laser beam from the laser device 110 during welding according to this embodiment. In Figure 11, the time-dependent changes in temperature during laser welding in this embodiment are shown by a solid line. For comparison, the time-dependent changes in temperature during laser welding in the conventional technique, where a similar welded joint 23 is obtained on the same object W by irradiation with a single beam of laser light, are shown by a dashed line.

[0073] As shown in Figure 11, in this embodiment, the laser device 110 starts outputting at time t0 and stops outputting at time t1. After time t1, the molten pool 23W cools naturally in a room temperature atmosphere, and consequently the temperature of the molten pool 23W gradually decreases.

[0074] In the conventional technology, the temperature Tr of the molten pool 23W decreases to the melting point Tm at time ter, as shown by the dashed line. In contrast, in this embodiment, the temperature T1 of the molten pool 23W decreases to the melting point Tm at time te1, which is later than time ter, as shown by the solid line. The molten pool 23W is in a molten state at a temperature higher than the melting point Tm. Note that temperature T1 is the temperature during the formation process of the molten pool 23W, and as an example, it is the highest temperature during that formation process.

[0075] As is clear from Figure 11, in this embodiment, the temperature T1 of the molten pool 23W when forming the molten pool 23W, that is, the temperature T1 of the molten pool 23W when the laser device 110 is emitting laser light, is higher than the temperature Tr of the molten pool 23W in the conventional technology. This is because, as described above, the laser light L has multiple beams B1, B2 as illustrated in Figures 5-7. That is, when the laser light L has beams B1, B2, even if the temperature of the molten pool 23W is higher, flow turbulence and sputtering are less likely to occur in the molten state, i.e., the flowing state of the molten pool 23W, and voids V are also less likely to occur. For this reason, the output of the laser light L can be increased to raise the temperature T1 of the molten pool 23W more than in the case of a single beam, and consequently, the temperature difference ΔT (=T1-Tm) between the temperature of the molten pool 23W and the melting point Tm can be increased compared to the case of a single beam. Therefore, according to this embodiment, the temperature T1 of the molten pool 23W can be increased to a level that does not affect the welding quality, thereby making the descent time Δt1 (=te1-t1) until the temperature T1 of the molten pool 23W drops to the melting point Tm longer than in the case of a single beam.

[0076] Furthermore, in this embodiment, the rate of temperature decrease after time t1 is slower (lower) than in the conventional technology. This is because the laser beam L has beams B1 and B2, as illustrated in Figures 5-7. That is, because the laser beam L has beam B2 with a lower power density, a gentler temperature distribution can be formed over a wider area of ​​the object W than in the case of a single beam while the molten pool 23W is formed. This suppresses the rapid cooling of the object W after the irradiation of the laser beam L is stopped. Therefore, in this respect as well, according to this embodiment, the temperature decrease time Δt1 until the temperature T1 of the molten pool 23W drops to the melting point Tm can be made longer than in the case of a single beam.

[0077] Voids V, which are air bubbles in the molten pool 23W, rise within the molten pool 23W and exit it when the molten pool 23W is in a molten state, i.e., a fluid state. Therefore, the longer the molten pool 23W remains in a molten state, the more voids V are discharged from the molten pool 23W, and the less voids V remain in the solidified weld 23. In this regard, as described above, according to this embodiment, because the laser beam L has beams B1 and B2, the descent time Δt1 is longer compared to the case of a single beam, and the molten pool 23W can be maintained in a molten state for a longer period of time. Therefore, according to this embodiment, a weld 23 with fewer voids V can be formed.

[0078] Through diligent research by the inventors, it was confirmed that by setting beams B1 and B2 to the arrangement and power density exemplified in Figures 5-7 and described above, a molten state of the molten pool 23W can be maintained for a longer period of time and void V can be further reduced compared to the case of a single beam.

[0079] According to this embodiment, the arrangement and power density of beams B1 and B2 can be set so as to ensure the temperature T1 of the molten pool 23W required for at least one void V to escape from the molten pool 23W, and the descent time Δt1 (=te1-t1) from temperature T1 to the melting point Tm. Note that the temperature T1 and the descent time Δt1 will be different values ​​depending on the material, the heat dissipation of the environment, the ambient temperature, etc.

[0080] [flat angle line] Figure 12 is a perspective view of a rectangular wire 10 including a member 20. Member 20 is, for example, the core wire (internal conductor) of the rectangular wire 10 as shown in Figure 12. The rectangular wire 10 has member 20 and a covering 30 for member 20. Member 20 is made of a conductive metallic material. The cross-sectional shape of member 20 perpendicular to the extension direction is approximately rectangular. The covering 30 is insulating and is made of, for example, enamel or synthetic resin material. The covering 30 may have an enamel layer and an extruded resin layer surrounding the enamel layer. The laser welding apparatus 100 is applied to welding the ends 20a of member 20 as the core wire of such a rectangular wire 10 together. In this case, the covering 30 is removed near the ends of the two rectangular wires 10 in the extension direction. Then, as shown in Figure 2, the ends 20a of two members 20, which are positioned adjacent to each other in the same direction (extension direction), are welded together by the laser welding device 100.

[0081] The rectangular wire 10 may constitute a coil provided in a rotating electric machine, such as a motor or motor generator. The laser welding method using the laser welding apparatus 100 of this embodiment can be applied to welding the ends of adjacent coils set in a stator core.

[0082] However, the member 20 that constitutes the object W is not limited to the core wire of the rectangular wire 10, but may be any member that extends in the Z direction, is adjacent to another in the X direction, has its end 20a close to another, and has side surfaces 20b facing each other in the X direction, as shown in Figure 2. The member 20 may be a plate-shaped member or a wire.

[0083] [Voids remaining in the weld] Figure 13 is an exemplary side view of the weld 23. In this embodiment, as shown in Figure 13, the irradiation conditions of the laser beam L, particularly the irradiation conditions of beam B2 (sub-beam), are set so that the number of voids V in the lower half Rl of the weld 23 is less than or equal to the number of voids V in the upper half Ru of the weld 23. Here, the virtual plane VP is a plane that passes through the exact midpoint between the upper end 23a and the lower end 23b of the weld 23 in the vertical direction during welding and solidification, and extends horizontally during welding and solidification. The upper half Ru is the part above the virtual plane VP and is the part opposite to the lower half Rl with respect to the virtual plane VP. The lower half Rl is the part of the weld 23 below the virtual plane VP and is the part opposite to the upper half Ru with respect to the virtual plane VP. In the molten pool 23W, the voids V move upward. Therefore, when the molten state of the molten pool 23W is maintained by irradiation with laser light L (beam B2), the voids V formed in the lower half Rl rise and move to the upper half Ru or outside the molten pool 23W, and the voids V that could not escape mainly remain in the upper half Ru. Thus, a state is obtained in the welded joint 23 where the number of voids V in the lower half Rl is less than or equal to the number of voids V in the upper half Ru. In other words, the state in the welded joint 23 where the number of voids V in the lower half Rl is less than or equal to the number of voids V in the upper half Ru can be said to be a state in which the effect of reducing voids V by irradiation with beam B2 has been obtained.

[0084] In this way, by appropriately setting the laser beam L, particularly beam B2, so that the number of voids V in the lower half Rl is less than or equal to the number of voids V in the upper half Ru, it is possible to form a welded joint 23 that has the required bonding strength and conductivity, while having fewer voids V. In the example in Figure 13, the number of voids V in the upper half Ru is 2 and the number of voids V in the lower half Rl is 0, but the number of voids V is not limited to this example.

[0085] As described above, in the laser welding method and laser welding apparatus 100 of this embodiment, the beam B2 (sub-beam) is irradiated onto the object W such that at least one of the voids V formed in the molten pool 23W escapes to the outside of the molten pool 23W before the molten pool 23W solidifies. Furthermore, the beam B1 (main beam) and beam B2 (sub-beam) are set so that the temperature of the molten pool 23W changes over time so that a molten pool 23W is formed in the object W, and at least one of the voids V formed in the molten pool 23W escapes to the outside of the molten pool 23W.

[0086] Therefore, according to this embodiment, the void V in the welded portion 23 can be further reduced, and the decrease in the strength of the welded portion 23 due to the void V can be suppressed.

[0087] [Second Embodiment] [Configuration of a laser welding system] Figure 14 is a diagram showing the schematic configuration of the laser welding apparatus 100A of the second embodiment. As shown in Figure 14, the laser welding apparatus 100A differs from the first embodiment in that it includes a plurality of laser devices 111, 112 (110) and a sensor 150 provided on the optical head 120A. In addition, the optical head 120A also differs from the first embodiment in that, as a result of including these, it has a collimating lens 121-2, filters 124, 127, and a mirror 128.

[0088] Each laser device 111, 112 (110) has a laser oscillator. In this embodiment, the laser devices 111 and 112 output laser light of different wavelengths.

[0089] The laser device 111 outputs a first laser beam with a wavelength of, for example, 800 nm or more and 1200 nm or less. The laser device 111 may also be referred to as the first laser device, and the laser oscillator in the laser device 111 may also be referred to as the first laser oscillator.

[0090] On the other hand, the laser device 112 outputs a second laser beam with a wavelength of 550 nm or less. The laser device 112 may also be called the second laser device, and the laser oscillator of the laser device 112 may also be called the second laser oscillator. As an example, the laser device 112 has a semiconductor laser (element) as a laser light source. The laser device 112 may also output laser beam with a wavelength of 400 nm or more and 500 nm or less.

[0091] With the installation of the laser device 112, a filter 124 is provided on the optical head 120A. The first laser beam reflected by the mirror 123 is X It moves in the opposite direction and heads towards filter 124. Note that the first laser beam is at optical head 120A X In configurations where input is directed in the opposite direction, mirror 123 is unnecessary.

[0092] Filter 124 is, for example, a high-pass filter that transmits the first laser beam but reflects the second laser beam without transmitting it. The first laser beam passes through filter 124 and heads towards the galvanoscanner 126. On the other hand, filter 124 reflects the second laser beam, which has become parallel light by the collimating lens 121-2. The second laser beam reflected by filter 124 also heads towards the galvanoscanner 126.

[0093] Filter 127 is located between mirror 123 and filter 124. Filter 127 transmits the first laser beam from mirror 123 toward filter 124 and reflects the light arriving from the surface Wa of the object W (see Figures 5-7) and passing through filter 124 toward mirror 128. The light reflected by mirror 128 is input to sensor 150. With this configuration, sensor 150 can capture an image of the surface Wa. Sensor 150 is, for example, an infrared thermography camera and can detect the temperature distribution on the surface Wa.

[0094] In this embodiment as well, a DOE 125 is provided. The DOE 125 is positioned between the collimating lens 121-2 and the filter 124 to shape the beam of the second laser beam. However, the optical head 120A may have a DOE that shapes the beam of the first laser beam.

[0095] The laser welding apparatus 100A may be equipped with a sensor 150 as in the first embodiment, instead of the sensor 150 described above. Alternatively, the laser welding apparatus 100 of the first embodiment may be equipped with a sensor 150 attached to the body of the optical head 120, as in this embodiment.

[0096] [Wavelength and light absorption rate] Here, we will explain the light absorption rate of metallic materials. Figure 15 is a graph showing the light absorption rate of various metallic materials as a function of the wavelength of the irradiated laser light L. In the graph of Figure 15, the horizontal axis is wavelength and the vertical axis is absorption rate. Figure 15 shows the relationship between wavelength and absorption rate for aluminum (Al), copper (Cu), gold (Au), nickel (Ni), silver (Ag), tantalum (Ta), and titanium (Ti).

[0097] Although the properties differ depending on the material, it can be seen that for each metal shown in Figure 15, the energy absorption rate is higher when using blue or green laser light (second laser light) than when using general infrared (IR) laser light (first laser light). This characteristic is particularly pronounced for copper (Cu) and gold (Au), among others.

[0098] When laser light is shone onto an object W with a relatively low absorption rate relative to the wavelength used, most of the light energy is reflected and does not affect the object W as heat. Therefore, relatively high power is required to obtain a molten region of sufficient depth. In that case, the rapid energy input to the center of the beam causes sublimation and the formation of a keyhole.

[0099] On the other hand, when laser light is irradiated onto an object W that has a relatively high absorption rate for the wavelength used, much of the input energy is absorbed by the object W and converted into thermal energy. In this process, if a laser beam with a low power density is irradiated, thermal conduction type melting occurs.

[0100] According to the optical head 120A of this embodiment, a laser beam L having a beam B1 from a first laser beam from a laser device 111 and a beam B2 from a second laser beam from a laser device 112 can be irradiated onto the target object W.

[0101] From the above, by outputting a first laser beam with a wavelength of 800 nm or more and 1200 nm or less, and a second laser beam with a wavelength of 500 nm or less, and irradiating the target object W with the second laser beam after melting it with the first laser beam, thermal energy can be efficiently supplied to the molten pool 23 W, thereby more efficiently suppressing localized cooling and solidification of the molten pool 23 W. In addition, in order to irradiate the target object W with the first laser beam and then the second laser beam, the time periods during which the first and second laser beams are emitted may be controlled independently, as will be described later. Furthermore, at least a portion of the second laser beam may be irradiated behind the first laser beam in the sweep direction of the laser beam L. In this case, at least a portion of the area irradiated by the first laser beam and the area irradiated by the second laser beam may overlap.

[0102] The controller 200 can control the operation of the laser devices 111 and 112 independently. Specifically, it can independently control the time period when laser device 111 is emitting the first laser beam, i.e., beam B1, and the time period when laser device 112 is emitting the second laser beam, i.e., beam B2.

[0103] [Laser welding method] Figure 16 shows the time-dependent changes in the temperature of the molten pool 23W and the output of the laser beam from the laser devices 111, 112 (110) during welding according to this embodiment. In Figure 16, the notation for temperature is the same as in Figure 11 of the first embodiment. However, for the laser beam output, the time-dependent changes in the output of the first laser beam (main beam) are shown by a solid line, and the time-dependent changes in the output of the second laser beam (sub-beam) are shown by a dashed line.

[0104] As shown in Figure 16, in this embodiment, the laser device 111 starts outputting at time t0 and stops outputting at time t2. In contrast, the laser device 112 starts outputting at time t0 but stops outputting at time tk, which is after time t2. After time tk, the molten pool 23W is naturally cooled in a room temperature atmosphere, and the temperature of the molten pool 23W gradually decreases accordingly.

[0105] Between time t0 and time t2, the laser beam L contains beams B1 and B2. Irradiation of the object W with the laser beam L during this period forms a molten pool 23W. In other words, in the laser welding method of this embodiment, the process of forming the molten pool 23W is performed between time t0 and time t2.

[0106] Between time t2 and time tk, the laser beam L contains only beam B2 and not beam B1. As a result, the output of the laser beam L is lower than between time t0 and time t2, when beams B1 and B2 are included. During this time, the laser beam L is set so that the molten state of the molten pool 23W is maintained by irradiating the molten pool 23W with the laser beam L. In other words, in the laser welding method of this embodiment, between time t2 and time tk, a process (hereinafter referred to as the maintenance process) is performed to temporarily maintain the molten state of the molten pool 23W while suppressing further formation and expansion of the molten pool 23W and also suppressing solidification of the molten pool 23W, by appropriately setting the specifications related to the irradiation of the laser beam L and beams B1 and B2, such as the shape, arrangement, power density, irradiation position, sweep path, and sweep speed of beams B1 and B2. The maintenance process may also be referred to as the extension process.

[0107] Figure 17 is a side view of the object W during the maintenance process of a laser welding method. As shown in Figure 17, during the maintenance process, laser beams L1 and L2 (L) are irradiated onto the molten pool 23W. In addition, even during the maintenance process, the laser beams L1 and L2 (L) may be swept while being irradiated in a linear manner, as shown in Figure 10. The irradiation position, sweep path, sweep speed, etc., may be the same as or different from those in the forming process. In the maintenance process, the laser beams L1 and L2 (L) may be irradiated over a wider area than in the forming process.

[0108] As is clear from Figure 16, by including such a maintenance step, the time Δt2 for the temperature T2 to drop to the melting point Tm in the formation step of the molten pool 23W can be made even longer than the time Δt1 in the first embodiment. That is, the time Δt2 is longer than the time Δt1 because it includes the time of the maintenance step (Δtk = tk - t2, maintenance time).

[0109] Figures 18-20 are plan views illustrating the irradiation position or sweep path of the laser beam L to the molten pool 23W during the maintenance process, i.e., views from the direction of irradiation of the laser beam L. Figure 18 shows the case where the laser beam L is irradiated to the center C in a plan view of the molten pool 23W, Figure 19 shows the case where the laser beam L is swept in a curved path around the center C, and Figure 20 shows the case where the laser beam L is swept in a bent path around the center C. In the cases of Figures 19 and 20, the number of sweeps may be one, less than one, or two or more. In each of these cases, under the condition that heat from the laser beam L is transferred (reaches) throughout the entire molten pool 23W, the effect is obtained that voids V are removed from the molten pool 23W and the amount of voids V in the weld 23 is reduced. During the maintenance process, the laser beam L may be irradiated continuously or intermittently. For example, in the case of Figure 18, the laser beam L may be intermittently irradiated onto the center C, or the laser beam L may be intermittently irradiated while sweeping along a trajectory as shown in Figures 19 and 20. Furthermore, the laser beam L may not be intermittently irradiated onto a single point as in Figure 18, but rather onto multiple points sequentially. 19,20 In cases like the one described, where the laser beam L is swept along a curved path around the center C, and a less turbulent (laminar) swirling flow is formed in the molten pool 23W, voids V become even easier to escape from the molten pool 23W due to buoyancy and fluid movement.

[0110] Furthermore, when the molten pool 23W is irradiated with laser light L, a depression (a depression in the opposite direction to the Z direction, hereinafter simply referred to as a depression) occurs in the area of ​​the surface of the molten pool 23W that is irradiated with laser light L. Through diligent research by the inventors, it has been found that if the depression caused by the irradiation of laser light L in the maintenance process is shallower than the depression caused by the irradiation of laser light L in the process of forming the molten pool 23W, it is possible to perform higher quality welding with less spatter and voids V. The depression deepens in proportion to the power density. Therefore, it is preferable that the power density of the laser light L on the surface of the molten pool 23W in the maintenance process is lower than the power density on the surface of the molten pool 23W in the process of forming the molten pool 23W.

[0111] The depth of such indentations can be measured by configuring the sensor 150 as an optical coherence tomography (OCT) sensor, as shown in Figure 14. In the laser welding apparatus 100A shown in Figure 14, the controller 200 may control the power of the laser device 110 so that the indentations generated in the maintenance process are shallower than the indentations generated in the process of forming the molten pool 23W, or so that the indentations in the maintenance process are below a predetermined value.

[0112] [Power density] Experimental studies by the inventors have shown that the power density [W / cm²] of the laser beam L irradiated during the maintenance process on the surface of the molten pool 23W is low. 2 It was found that there is a suitable range for ]. [Table 1] Table 1 shows the welding quality determination results based on the number of voids V in the welded portion 23 corresponding to the range of power density, which are obtained from the results of experiments performed on a plurality of samples with different power densities of laser beam L. In measuring the number of voids V, voids having a diameter of 100 [μm] or more in one cross-section viewed from the side direction of the sample after welding are counted. In the determination, ⊚ indicates the case where the number of voids V is 10 or less (excellent), ○ indicates the case where the number of voids V is more than 10 and 20 or less (good), △ indicates the case where the number of voids V is more than 20 and 30 or less (acceptable), and × indicates the case where the number of voids V is more than 30 (poor).

[0113] As shown in Table 1, the power density Pd is 10 7 [W / cm 2 and it is found that the power density Pd is preferably 10 6 [W / cm 2 or less, and more preferably 10[W / cm²] or less. This can be presumed to be because if the power density Pd is too high, a keyhole is formed in the molten pool 23W, which increases spatter and consequently increases the number of voids V.

[0114] Further, it is found that the power density Pd is preferably larger than 10 3 [W / cm 2 , and more preferably larger than 10 4 [W / cm 2 . This can be presumed to be because if the power density Pd is too low, the molten state of the molten pool 23W cannot be sufficiently maintained, and the molten pool 23W solidifies earlier.

[0115] As described above, according to the laser welding method and laser welding apparatus 100A of the present embodiment, after the step of forming the molten pool 23W (forming step), the step of temporarily maintaining the molten pool 23W in a molten state (maintaining step) can be performed by irradiating the molten pool 23W with laser beams L1, L2 (L).

[0116] Therefore, according to this embodiment, the number of voids V in the welded portion 23 can be further reduced, and the decrease in the strength of the welded portion 23 due to the voids V can be further suppressed.

[0117] Furthermore, this embodiment also achieves a condition in which, as an effect of the maintenance process, the number of voids V in the lower half Rl of the welded joint 23 is less than or equal to the number of voids V in the upper half Ru.

[0118] [Third Embodiment] [Block diagram and processing procedure of laser welding equipment] Figure 21 is a block diagram of the laser welding apparatus 100,100A. The laser welding apparatus 100,100A includes, for example, a controller 200, a memory unit 210, a sensor 150, a laser device 110, a galvanometer scanner 126, a drive mechanism 140, and an output unit 220.

[0119] The controller 200 is a computer and has a processor (circuit) such as a CPU (central processing unit), and a main memory unit such as RAM (random access memory) and ROM (read-only memory). The controller 200 is, for example, an MCU (microcontroller unit). The storage unit 210 has a non-volatile storage device such as an SSD (solid state drive) or HDD (hard disk drive). The controller 200 is an example of a control unit. The storage unit 210 may also be called an auxiliary storage device.

[0120] The processor operates as an irradiation control unit 201, a detection control unit 202, a determination unit 203, an output control unit 204, and a parameter modification unit 205 by reading programs stored in ROM or the storage unit 210 and executing each process. The programs can be provided as installable or executable files recorded on a computer-readable recording medium. The recording medium may also be called a program product. Information such as values, tables, and maps used in the calculations performed by the program and the processor may be pre-stored in ROM or the storage unit 210, or they may be stored in the storage unit of a computer connected to a communication network and downloaded to the storage unit 210 via the communication network. The storage unit 210 stores the data written by the processor. Furthermore, the calculations performed by the controller 200 may be executed at least partially by hardware. In this case, the controller 200 may include, for example, an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0121] The output unit 220 is a device capable of outputting information indicating the judgment result in the form of sound or image, and may be, for example, a monitor (display), speaker, buzzer, printer, etc. Alternatively, the output unit 220 may be a communication unit or the like that outputs data indicating the judgment result to other devices outside the controller 200.

[0122] [Procedure for outputting test results] Figure 22 is a flowchart of the processing procedure for outputting inspection results. As shown in Figure 22, first, the controller 200 operates as an irradiation control unit 201 and controls the laser device 110, galvanometer scanner 126, and drive mechanism 140 to irradiate the object W with laser light L in a predetermined procedure to weld the object W (S11). In S11, as described above, the irradiation control unit 201 controls the operation of at least one of the laser device 110, galvanometer scanner 126, and drive mechanism 140 to irradiate the object W with laser light L at the specifications of beams B1 and B2 that produce descent times Δt1 and Δt2 required for at least one void V to be discharged from the molten pool 23W, and at a maintenance time Δtk. The laser device 110, galvanometer scanner 126, and drive mechanism 140 are controlled by the controller 200 in the laser welding apparatus 100 and 100A, and are also examples of variable mechanisms that can change the irradiation state of the laser light L. The irradiation control unit 201 and controller 200 are examples of control units.

[0123] Next, the controller 200 operates as a detection control unit 202 and detects the temperature of the molten pool 23W (S12). In S12, the detection control unit 202 may, for example, detect the highest temperature of the molten pool 23W, or it may detect the temperature of the molten pool 23W at at least one time after a predetermined time has elapsed from the irradiation start time (time t0).

[0124] Next, the controller 200 operates as a determination unit 203 and determines the quality of the welded joint 23 based on the temperature detection result (S13). In S13, the determination unit 203 determines the quality of the welded joint 23 according to predetermined criteria based on the temperature detected in S2. For example, the determination unit 203 determines the quality of the welded joint 23 to be good if the detected temperature at a predetermined time is above a threshold corresponding to that predetermined time, and determines the quality of the welded joint 23 to be poor if the detected temperature is below the threshold. The threshold temperature corresponding to the quality of the determination result, the timing of the inspection, etc., are set in advance based on experimental results.

[0125] Next, the controller 200 operates as an output control unit 204 and controls the output unit 220 to output the determination result in a predetermined output format (S14).

[0126] Next, the controller 200 operates as a parameter change unit 205 and changes the control parameters related to the irradiation of laser light L according to the determination result (S15). The control parameters that can be changed in S15 are, for example, the output of the laser device 110, the output time by the laser device 110, the output period of beam B1, the output period of beam B2, etc. The parameter change unit 205 stores the changed parameter values ​​in the storage unit 210. When performing a similar laser welding operation in the future, the controller 200 reads the control parameters stored in the storage unit 210 and controls the controlled objects such as the laser device 110, galvanometer scanner 126, and drive mechanism 140 to perform laser welding with the stored, i.e., changed, control parameters.

[0127] [Processing procedure for void suppression control] Figure 23 is a flowchart of the control process for suppressing voids. As shown in Figure 23, first, the controller 200 operates as an irradiation control unit 201 and controls the controlled objects such as the laser device 110, galvanometer scanner 126, and drive mechanism 140 to irradiate the object W with laser light L in a predetermined procedure to form a molten pool 23W (S21). S21 is the process of forming the molten pool 23W. In S21, the controller 200 also operates as a detection control unit 202 and detects the temperature of the molten pool 23W at predetermined timings, for example, at regular time intervals.

[0128] Furthermore, in S21, the controller 200 may provide feedback control to the controlled objects (variable mechanisms) such as the laser device 110, the galvanometer scanner 126, and the drive mechanism 140, so that the temperature of the molten pool 23W is maintained at a predetermined temperature or changes over a predetermined period of time.

[0129] Next, the controller 200 operates as a determination unit 203 and determines whether a predetermined condition (first condition) has been met for the molten pool 23W formation process (S22). In S22, the determination unit 203 determines, for example, that the first condition has been met if the temperature of the molten pool 23W has remained above a first threshold temperature for a period of time equal to or longer than the first threshold time, based on the change in temperature of the molten pool 23W over time. This ensures that the molten pool 23W and the member 20 are in a state where sufficient descent times Δt1 and Δt2 are secured for the void V to escape.

[0130] If the first condition is not met (No in S22), the process of forming the molten pool 23W in S21 continues. If the first condition is met (Yes in S22), the processing procedure is completed for the laser welding apparatus 100 of the first embodiment. For the laser welding apparatus 100A of the second embodiment, the process proceeds to S23.

[0131] In S23, the controller 200 operates as an irradiation control unit 201 and controls the controlled objects such as the laser device 110, galvanometer scanner 126, and drive mechanism 140 to irradiate the object W with only laser light L, for example beam B2, in a predetermined procedure to maintain the molten pool 23W in a molten state (S23). This S23 is the molten pool 23W maintenance process. In S23, the controller 200 also operates as a detection control unit 202 and detects the temperature of the molten pool 23W at predetermined timings, for example, at regular time intervals.

[0132] Furthermore, in S23, the controller 200 may provide feedback control to the controlled objects (variable mechanisms) such as the laser device 110, the galvanometer scanner 126, and the drive mechanism 140, so that the temperature of the molten pool 23W is maintained at a predetermined temperature or changes over a predetermined period of time.

[0133] Next, the controller 200 operates as a determination unit 203 and determines whether a predetermined condition (second condition) has been met for the maintenance process of the molten pool 23W (S24). In S24, the determination unit 203 determines, for example, that the second condition has been met if the temperature of the molten pool 23W has remained above the second threshold temperature for a period of time equal to or longer than the second threshold time, based on the change in temperature over time of the molten pool 23W. This ensures a sufficient maintenance time Δtk and, consequently, a descent time Δt2 for the void V to escape.

[0134] If the second condition is not met (No in S24), the maintenance process for the molten pool 23W in S23 continues. If the second condition is met (Yes in S24), the processing procedure ends.

[0135] As described above, the laser welding apparatus 100,100A may also include a sensor 150 for detecting the temperature of the molten pool 23W and an output unit 220 for outputting information indicating the welding quality based on the detection result from the sensor 150.

[0136] With this configuration and control, the presence or absence of voids V in the weld 23 can be inspected non-destructively and relatively easily. Furthermore, by changing the control parameters of the laser welding devices 100 and 100A based on the welding quality determination results, the welding quality in subsequent laser welding operations can be improved.

[0137] Furthermore, as in this embodiment, the controller 200 may control the operation of controlled objects (variable mechanisms) such as the laser device 110, the galvanometer scanner 126, and the drive mechanism 140, based on the detection result of the sensor 150 that detects the temperature of the molten pool 23W.

[0138] This configuration and control allows for more precise formation and maintenance of the molten pool 23W, resulting in advantages such as more reliable suppression of void V and reduced wasted energy consumption while suppressing the generation of void V.

[0139] Although embodiments of the present invention have been illustrated above, these embodiments are merely examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the spirit of the invention. Furthermore, each configuration, shape, and other specifications (structure, type, orientation, model, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be modified as appropriate.

[0140] For example, a laser welding apparatus may be equipped with multiple laser devices (laser light sources) that emit laser light of the same wavelength.

[0141] Furthermore, for example, when irradiating with laser light, known wobbling, weaving, power modulation, etc., may be performed to adjust the surface area of ​​the molten pool. [Industrial applicability]

[0142] This invention can be used in laser welding methods and laser welding apparatus. [Explanation of Symbols]

[0143] 10... Flat rectangular line 20... Components 20a...end 20b…side 21...Component (First component) 21a...End (first end) 21b...side 22...Component (Second component) 22a...End (second end) 22b…side 23... Welded parts 23W…Melting pool 23a…Top end 23b…lower end 30... Covering 100, 100A… Laser welding equipment 110, 111, 112… Laser devices (laser oscillators, variable mechanisms) 120, 120A… Optical head 121, 121-1, 121-2… Collimating lenses 122... Focusing lens 123...Mirror 124... Filter 125...DOE 125a...Diffraction grating 126... Galvanoscanner (Variable Mechanism) 126a, 126b…Mirror 127…Filter 128...Mirror 130… Fiber optic 140…Drive mechanism (variable mechanism) 150...Sensor 200... Controller (control unit) 201... Irradiation control unit (control unit) 202...Detection and Control Unit 203...Judgment section 204…Output Control Unit 205...Parameter change section 210...Storage section 220...Output section A1…area A2…area B1... Beam (main beam, main power area) B1a...outer edge B2... Beam (sub-beam, sub-power region) B2a...outer edge B2b... Common-law marriage b2...beam C…center C1…center C2…center g...gap L, L1, L2... Laser light Pd...Power Density Ru... Upper half Rl... Lower half t0,t1,t2,te1,ter,tk...time T1,T2,Tr…Temperature Tm... Melting point V...Void VP…Virtual Plane W...Object Wa... Surface X…direction (second direction) Y…direction (third direction) Z…direction (first direction) δ...shift Δt1, Δt2… Descent time Δtk… Duration ΔT…Temperature difference

Claims

1. A step of forming a molten pool so as to span between the first end and the second end by irradiating at least one of the first end of a first member made of a metal material in a first direction, and the second end of a second member made of a metal material adjacent to the first member in a second direction intersecting the first direction, and positioned such that the distance of the first end from the second end along the first direction is 0 or more, during the first time period, In the second time period following the end of the first time period, the process of maintaining the molten pool in a molten state by irradiating the molten pool, which is formed to span between the first end and the second end, with the laser beam at a lower power than that used in the process of forming the molten pool, either by fixed-point irradiation or sweeping, so that voids formed in the molten pool escape to the outside of the molten pool before the molten pool solidifies, The process of solidifying the aforementioned molten pool, A laser welding method having, The laser light includes a main power region containing at least one main beam, and a sub-power region containing at least one sub-beam having a lower power density than the main beam. In the process of forming the molten pool, both the main beam and the sub-beam are irradiated, A laser welding method in which, in the step of maintaining the molten pool in a molten state, irradiation of the main beam is stopped and only the sub-beam is irradiated.

2. The laser welding method according to claim 1, wherein the wavelength of the main beam is 800 nm or more and 1200 nm or less, and the wavelength of the sub-beam is 550 nm or less.

3. In the process of forming the molten pool, The main power region is located inside the outer edge of the sub-power region, The sub-power region includes a plurality of sub-beams as the at least one sub-beam, and the main beam is surrounded by the plurality of sub-beams, Alternatively, the laser welding method according to claim 1 or 2, wherein the sub-power region includes, as the at least one sub-beam, one sub-beam surrounding the main power region.

4. The laser welding method according to any one of claims 1 to 3, wherein in the step of maintaining the molten pool in a molten state, the power of the laser beam is lower than in the step of forming the molten pool.

5. A laser welding method according to any one of claims 1 to 4, wherein the depressions that occur on the surface of the molten pool due to the irradiation of the laser light in the step of maintaining the molten pool in a molten state are made shallower than the depressions that occur on the surface of the molten pool due to the irradiation of the laser light in the step of forming the molten pool.

6. In the step of maintaining the molten pool in a molten state, the power density of the laser beam on the surface of the molten pool is set to 10 ７ [W / cm] ２ The laser welding method according to any one of claims 1 to 5, wherein the method is as follows:

7. In the step of maintaining the molten pool in a molten state, the power density of the laser beam on the surface of the molten pool is set to 10 ６ [W / cm] ２ The laser welding method according to claim 6, wherein the following is performed.

8. A laser welding method according to any one of claims 1 to 7, wherein the irradiation time of the main beam is made shorter than the irradiation time of the sub-beam from the step of forming the molten pool to the step of maintaining the molten pool in a molten state.

9. A laser welding method according to any one of claims 1 to 8, wherein a plurality of beams included in at least one of the main power region and the sub-power region are formed by a beam shaper.

10. The laser welding method according to any one of claims 1 to 9, wherein in the step of maintaining the molten pool in a molten state, the laser beam is swept in a straight line or in a curved path around the center of the molten pool when viewed in the direction of irradiation of the laser beam.

11. The laser welding method according to any one of claims 1 to 10, wherein the first member and the second member are each made of one of the following materials: copper-based metal material, aluminum-based metal material, nickel-based metal material, iron-based metal material, and titanium-based metal material.

12. The laser welding method according to claim 11, wherein the first member and the second member are conductors of a rectangular wire.

13. A laser welding apparatus for performing the laser welding method described in any one of claims 1 to 12, A laser oscillator, An optical head that irradiates at least one of the first end and the second end with laser light emitted from the laser oscillator, A laser welding device equipped with this device.

14. A sensor for detecting the temperature of the molten pool, An output unit that outputs information indicating welding quality based on the detection results of the aforementioned sensor, A laser welding apparatus according to claim 13, comprising:

15. A sensor for detecting the temperature of the molten pool, A variable mechanism capable of changing the irradiation state of the laser light, A control unit that controls the operation of the variable mechanism based on the detection result of the sensor, A laser welding apparatus according to claim 13 or 14, comprising:

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