Welding method and welding apparatus

Abstract

To suppress the occurrence of sputtering.SOLUTION: A welding method includes the step of irradiating a workpiece including a member made of tough pitch copper with laser light, thereby melting and welding the workpiece. The laser light is formed of a main beam and an auxiliary beam, at least part of which disposed anteriorly in a sweep direction. The power density of the main beam has an intensity of generating at least a keyhole. The power density of the auxiliary beam has an intensity that is lower than the power density of the main beam and melts the workpiece without generating the keyhole generated by at least the pressure of a metal vapor. The laser light forms a shallow region being a molten pool that is shallower than a molten pool formed in a region irradiated with the main beam in a region irradiated with the auxiliary beam and is filled with the workpiece that has been melted and liquefied. Before the shallow region formed in the region irradiated with the auxiliary beam is solidified, a melting intensity region of the main beam reaches the shallow region, and the depth of the shallow region is deeper than 10 μm.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

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

[0002] Laser welding is a well-known method for welding metal materials such as iron and copper. Laser welding is a welding method in which a laser beam is irradiated onto the welding area of ​​the workpiece, and the energy of the laser beam melts the area to be welded. A pool of molten metal material called a molten pool is formed in the welding area irradiated with the laser beam, and welding is performed when the metal material in the molten pool solidifies.

[0003] Furthermore, when irradiating a workpiece with laser light, the laser beam profile may be shaped according to the purpose. For example, when using laser light to cut a workpiece, a technique for shaping the laser beam profile is known (see, for example, Patent Document 1).

[0004] Previously, due to the low output of laser beam generators, laser welding was primarily used for metal materials with low reflectivity (high absorptivity). However, in recent years, the focusing capabilities of laser beam generators have improved, and laser welding of metal materials with high reflectivity, such as copper and aluminum, is also becoming practical (see, for example, Patent Documents 2-4). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 2010-508149 [Patent Document 2] Japanese Patent Application Publication No. 7-214369 [Patent Document 3] Japanese Patent Publication No. 2004-192948 [Patent Document 4] International Publication No. 2010 / 131298 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Incidentally, it is known that spatter, or flying debris, is generated from the molten pool during welding. This spatter is scattered molten metal, and reducing its generation is important in preventing processing defects. The generated spatter adheres to the area around the weld, and if it later peels off and adheres to electrical circuits, it can cause malfunctions in the electrical circuits. Therefore, welding components for electrical circuits is difficult. Furthermore, since spatter is scattered molten metal, its generation also means that the amount of metal material at the weld is reduced. In other words, if a lot of spatter is generated, the amount of metal material at the weld becomes insufficient, which can lead to strength defects and other problems.

[0007] Furthermore, even if the output of the laser beam generator is improved, the reflectivity of the metal material does not change, and it is necessary to irradiate it with laser light of sufficient intensity to compensate for the high reflectivity. In particular, when the workpiece begins to melt, it is necessary to irradiate it with high-intensity laser light to compensate for the high reflectivity, but once melting begins, the high reflectivity decreases, and the intensity of the laser light becomes excessive. This excess laser energy causes an increase in evaporated metal and unwanted disturbances in the molten metal, increasing the possibility of welding defects such as spatter and voids.

[0008] The present invention has been made in view of the above, and its object is to provide a welding method and welding apparatus that suppress the generation of spatter. [Means for solving the problem]

[0009] To solve the above-mentioned problems and achieve the objective, a welding method according to one aspect of the present invention includes the steps of: placing a workpiece in a region irradiated with laser light from a laser device; moving the laser light and the workpiece relative to each other while irradiating the workpiece with the laser light from the laser device; and performing welding by melting the irradiated portion of the workpiece while sweeping the laser light over the workpiece, wherein the laser light is composed of a main beam and a sub-beam, at least a part of which is located forward in the sweeping direction, and the power density of the main beam is equal to or greater than the power density of the sub-beam.

[0010] In one aspect of the present invention, the welding method is such that the power density of the main beam is at least strong enough to generate a keyhole.

[0011] A welding method according to one aspect of the present invention further comprises a sub-beam with a lower power density than the main beam, located behind the main beam in the sweeping direction.

[0012] A welding method according to one aspect of the present invention further comprises a sub-beam having a lower power density than the main beam, positioned transversely to the sweep direction of the main beam.

[0013] A welding method according to one aspect of the present invention comprises a laser beam further dispersed around the main beam, with a sub-beam having a lower power density than the main beam.

[0014] In one aspect of the present invention, the welding method is such that the sub-beam has a ring shape surrounding the main beam or an arc shape that is part of the ring shape surrounding the main beam.

[0015] In one embodiment of the present invention, the main beam and the sub-beam of the laser light are configured such that at least a portion of the molten pool formed by the main beam and the molten pool formed by the sub-beam overlap.

[0016] In the welding method according to one aspect of the present invention, the wavelength of the laser beam forming at least the secondary beam among the main beam and the secondary beam has a reflectance lower than the reflectance in the infrared region of the processing target.

[0017] In the welding method according to one aspect of the present invention, the wavelength of the laser beam forming the main beam is the same as the wavelength of the laser beam forming the secondary beam.

[0018] In the welding method according to one aspect of the present invention, the main beam and the secondary beam are laser beams emitted from the same oscillator.

[0019] In the welding method according to one aspect of the present invention, the main beam and the secondary beam are laser beams emitted from different oscillators.

[0020] In the welding method according to one aspect of the present invention, the main beam and the secondary beam are formed by a beam shaper disposed between the oscillator and the processing target.

[0021] In the welding method according to one aspect of the present invention, the beam shaper is a diffractive optical element.

[0022] In the welding method according to one aspect of the present invention, the processing target is at least two members to be welded, and the step of arranging the processing target in the region irradiated with the laser beam is a step of arranging the at least two members so as to overlap, contact, or be adjacent to each other.

[0023] In the welding method according to one aspect of the present invention, the beam diameter of the secondary beam is substantially equal to or larger than the beam diameter of the main beam.

[0024] A laser welding apparatus according to one aspect of the present invention comprises a laser oscillator and an optical head that receives light emitted from the laser oscillator to generate laser light, and irradiates the generated laser light toward a workpiece to melt the irradiated portion of the workpiece and perform welding. The optical head is configured such that the laser light and the workpiece can move relative to each other, and welding is performed by sweeping the laser light over the workpiece while melting. The laser light consists of a main beam and a sub-beam, at least a part of which is located forward in the sweeping direction, and the power density of the main beam is greater than or equal to the power density of the sub-beam.

[0025] In one aspect of the present invention, the laser welding apparatus has a power density of the sub-beam that is at least strong enough to melt the workpiece.

[0026] A laser welding apparatus according to one aspect of the present invention further comprises a sub-beam with a lower power density than the main beam, located behind the main beam in the sweeping direction.

[0027] A laser welding apparatus according to one aspect of the present invention further comprises a sub-beam having a lower power density than the main beam, positioned transversely to the sweep direction of the main beam.

[0028] A laser welding apparatus according to one aspect of the present invention further comprises a sub-beam with a lower power density than the main beam, dispersed around the main beam.

[0029] In one aspect of the present invention, the laser welding apparatus has a sub-beam that is ring-shaped surrounding the main beam or arc-shaped which is part of the ring shape surrounding the main beam.

[0030] In one aspect of the present invention, the laser welding apparatus is configured such that the main beam and the sub-beam of the laser light overlap at least a portion of the molten pool formed by the main beam and the molten pool formed by the sub-beam.

[0031] In one aspect of the present invention, the laser welding apparatus has a wavelength such that at least the wavelength of the laser light forming the sub-beam has a lower reflectance than the reflectance of the infrared region of the workpiece.

[0032] In one aspect of the present invention, the laser welding apparatus has a wavelength of laser light that forms the main beam that is the same as the wavelength of laser light that forms the sub-beam.

[0033] In one aspect of the present invention, the laser welding apparatus is configured such that the optical head generates the laser light consisting of a main beam and a sub-beam from light emitted from a single laser oscillator.

[0034] A laser welding apparatus according to one aspect of the present invention includes a beam shaper positioned between the laser oscillator and the workpiece in the optical head, and the diffractive optical element forms the main beam and the sub-beam from light emitted from the single laser oscillator.

[0035] In one aspect of the present invention, the laser welding apparatus is configured such that the beam shaper is a diffractive optical element.

[0036] In one aspect of the present invention, the laser welding apparatus comprises a laser oscillator composed of two different laser emitters, and the main beam and the sub-beam are laser light emitted from the two different oscillators, respectively.

[0037] In one aspect of the present invention, the laser welding apparatus is configured such that the workpiece is at least two members to be welded.

[0038] In one aspect of the present invention, the laser welding apparatus has a beam diameter of the sub-beam that is approximately equal to or greater than the beam diameter of the main beam.

[0039] In one aspect of the present invention, the laser welding apparatus is configured such that the beam shaper is rotatably mounted.

[0040] A laser welding apparatus according to one aspect of the present invention has a plurality of laser oscillators, and the optical head generates the laser light by combining the light emitted from the plurality of oscillators.

[0041] A laser welding apparatus according to one aspect of the present invention further comprises a plurality of laser oscillators and a multicore fiber that combines the light emitted from the plurality of laser oscillators internally and guides it to the optical head.

[0042] In one aspect of the present invention, the laser welding apparatus is configured such that the optical head can sweep the laser beam over the fixed workpiece.

[0043] In one aspect of the present invention, the laser welding apparatus has a fixed irradiation position of the laser beam from the optical head, and the workpiece is held so as to be movable relative to the fixed laser beam. [Effects of the Invention]

[0044] The welding method and welding apparatus according to the present invention have the effect of suppressing the generation of spatter. [Brief explanation of the drawing]

[0045] [Figure 1] Figure 1 is a diagram showing the schematic configuration of a welding apparatus according to the first embodiment. [Figure 2A] Figure 2A shows a comparison of the situations in which laser light melts the workpiece. [Figure 2B] Figure 2B shows a comparison of the situations in which laser light melts the workpiece. [Figure 3A] Figure 3A shows an example of the cross-sectional shape of a laser beam. [Figure 3B] Figure 3B shows an example of the cross-sectional shape of a laser beam. [Figure 3C] Figure 3C shows an example of the cross-sectional shape of a laser beam. [Figure 3D] Figure 3D shows an example of the cross-sectional shape of a laser beam. [Figure 3E]Figure 3E shows an example of the cross-sectional shape of a laser beam. [Figure 3F] Figure 3F shows an example of the cross-sectional shape of a laser beam. [Figure 4] Figure 4 shows a schematic configuration of a welding apparatus according to the second embodiment. [Figure 5] Figure 5 shows a schematic configuration of a welding apparatus according to the third embodiment. [Figure 6] Figure 6 shows a schematic configuration of a welding apparatus according to the fourth embodiment. [Figure 7] Figure 7 shows a schematic configuration of a welding apparatus according to the fifth embodiment. [Figure 8] Figure 8 shows a schematic configuration of a welding apparatus according to the sixth embodiment. [Figure 9A] Figure 9A shows an example of an optical fiber configuration. [Figure 9B] Figure 9B shows an example of an optical fiber configuration. [Figure 10] Figure 10 shows the cross-sectional shape of the laser beam used in the experiment. [Figure 11] Figure 11 shows an example of the cross-sectional shape of a laser beam. [Figure 12] Figure 12 shows an example of the cross-sectional shape of a laser beam. [Figure 13] Figure 13 is a graph showing the reflectance of typical metallic materials with respect to the wavelength of light. [Figure 14A] Figure 14A shows a comparison of the situations in which laser light melts the workpiece. [Figure 14B] Figure 14B shows a comparison of the situations in which laser light melts the workpiece. [Figure 15] Figure 15 is a diagram illustrating the concept of a diffractive optical element. [Modes for carrying out the invention]

[0046] The welding method and welding apparatus according to the embodiments of the present invention will be described in detail below with reference to the attached drawings. However, the present invention is not limited to the embodiments described below. Furthermore, it should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from reality. Even between drawings, there may be parts where the dimensional relationships and ratios differ.

[0047] (First Embodiment) Figure 1 is a diagram showing the schematic configuration of a welding apparatus according to the first embodiment. As shown in Figure 1, the welding apparatus 100 according to the first embodiment is an example of a configuration of an apparatus that melts a workpiece W by irradiating it with laser light L. As shown in Figure 1, the welding apparatus 100 includes an oscillator 110 that emits laser light, an optical head 120 that irradiates the workpiece W with laser light, and an optical fiber 130 that guides the laser light emitted by the oscillator 110 to the optical head 120. The workpiece W is at least two members to be welded.

[0048] The oscillator 110 is configured to oscillate, for example, a multimode laser beam with an output of several kW. For example, the oscillator 110 may be configured to include a plurality of semiconductor laser elements internally, and to oscillate a multimode laser beam with an output of several kW as the total output of the plurality of semiconductor laser elements, or various lasers such as fiber lasers, YAG lasers, and disk lasers may be used.

[0049] The optical head 120 is an optical device for focusing the laser light L, guided from the oscillator 110, to a power density strong enough to melt the workpiece W, and irradiating the workpiece W with it. To this end, the optical head 120 is equipped with a collimating lens 121 and a focusing lens 122 inside. The collimating lens 121 is an optical system for first aligning the laser light guided by the optical fiber 130, and the focusing lens 122 is an optical system for focusing the aligned laser light onto the workpiece W.

[0050] The optical head 120 is provided so as to be able to change its relative position to the workpiece W in order to move (sweep) the irradiation position of the laser beam L on the workpiece W. Methods for changing the relative position to the workpiece W include moving the optical head 120 itself or moving the workpiece W. That is, the optical head 120 may be configured to sweep the laser beam L with respect to a fixed workpiece W, or the irradiation position of the laser beam L from the optical head 120 may be fixed, and the workpiece W may be held so as to be movable relative to the fixed laser beam L. In the step of positioning the workpiece W in the area irradiated by the laser beam L, at least two members to be welded are positioned so as to overlap, be in contact with, or be adjacent to each other.

[0051] The optical head 120 according to the first embodiment includes a diffractive optical element 123 as a beam shaper between the collimating lens 121 and the focusing lens 122. The diffractive optical element referred to here is an optical element 1502 which is an assembly of multiple diffraction gratings 1501 with different periods, as conceptually shown in Figure 15. Laser light passing through this is bent in the direction influenced by each diffraction grating, overlaps, and can form laser light in any shape. In this embodiment, the diffractive optical element 123 is for shaping the laser light L such that the profile of the power density of the laser light L on the workpiece W has a sub-beam with a lower power density than the main beam, which is located in front of the main beam with a higher power density in the direction of movement. The diffractive optical element 123 can be configured to be rotatable. It can also be configured to be replaceable.

[0052] Here, the power density of the main beam or sub-beam includes the peak, and the peak intensity is 1 / e 2 This is the power density in the intensity range above a certain value. Also, the beam diameter of the main beam or sub-beam includes the peak, and the peak intensity is 1 / e 2 This is the diameter of the region with an intensity of 1 / e. For non-circular beams, in this specification, it is 1 / e of the peak intensity in the direction perpendicular to the direction of movement. 2The length of the region where the above intensity is achieved is defined as the beam diameter. The beam diameter of the secondary beam may be approximately equal to or greater than that of the primary beam.

[0053] The effect of having a secondary beam with a lower power density than the main beam, located ahead of the main beam with a higher power density, on the power density profile of the laser beam L on the workpiece W, is as follows. Figures 2A and 2B show a comparison of the situations in which the laser beam melts the workpiece.

[0054] As shown in Figure 2A, in conventional laser welding, the laser beam has one beam B, so a molten pool WP is formed as a molten region in the opposite direction of movement (arrow v) from the position where the laser beam is irradiated, where the workpiece W is molten. On the other hand, as shown in Figure 2B, in the welding apparatus and welding method using the first embodiment, the profile of the power density of the laser beam on the workpiece W with respect to the direction of movement has a main beam B1 and a sub-beam B2. The power density of the main beam B1 is, for example, at least strong enough to generate a keyhole. Keyholes will be described in detail later. The sub-beam B2 has a lower power density than the main beam B1 and is located ahead of the main beam B1 in the direction of movement (arrow v). The power density of the sub-beam B2 is strong enough to melt the workpiece W in the presence of the main beam B1 or on its own. Therefore, a molten pool WP1 is formed as a molten region, located ahead of the position where the main beam B1 is irradiated, and shallower than the depth to which the main beam B1 melts. For convenience, this will be called the shallow region R.

[0055] As shown in Figure 2B, the melting intensity regions of the laser beams of the main beam B1 and the sub-beam B2 may overlap, but do not necessarily need to overlap; it is sufficient that the molten pools overlap. It is sufficient that the melting intensity region formed by the main beam B1 reaches the molten pool formed by the sub-beam B2 before the molten pool formed by the sub-beam B2 solidifies. As described above, the power densities of the main beam B1 and the sub-beam B2 are strong enough to melt the workpiece W, and the melting intensity region refers to the range of the laser beam around the main beam B1 or sub-beam B2 that has a power density sufficient to melt the workpiece W.

[0056] In the welding apparatus and welding method according to the first embodiment, the presence of a shallow region R ahead of the position to which the main beam B1 is irradiated stabilizes the molten pool WP1 near the irradiation position of the main beam B1. As mentioned above, spatter is the scattering of molten metal, so stabilizing the molten pool WP1 near the irradiation position of the main beam B1 leads to the suppression of spatter generation. In fact, this effect of suppressing spatter generation was confirmed in the experiments described later.

[0057] The welding method according to the first embodiment includes the steps of: placing the workpiece W in the area irradiated by laser light L from an oscillator 110, which is a laser device; moving the laser light L and the workpiece W relative to each other while irradiating the workpiece W with the laser light L from the oscillator 110; and performing welding by melting the irradiated portion of the workpiece W while sweeping the laser light L over the workpiece W. At this time, the laser light L is composed of a main beam B1 and a sub-beam B2, at least a part of which is located forward in the sweeping direction, and the power density of the main beam B1 is equal to or greater than the power density of the sub-beam B2. The workpiece W is at least two members to be welded. The step of placing the workpiece W in the area irradiated by laser light L is the step of placing at least two members so that they overlap, are in contact with, or are adjacent to each other.

[0058] Furthermore, it is preferable that the power density of the sub-beam B2 be such that the shallow region R is deeper than the diameter of the allowable porosity (welding defects such as voids, pits with holes from the inside to the surface, and blowholes). This makes it less likely for porosity to occur because impurities adhering to the surface of the workpiece W, which is one of the causes of porosity, flow through the shallow region R and into the molten pool WP1 formed by the main beam B1. The allowable diameter of porosity is determined, for example, according to the intended use of the workpiece W. Generally, 200 μm or less is acceptable, 100 μm is preferred, 50 μm or less is more preferred, 30 μm or less is even more preferred, 20 μm or less is even more preferred, 10 μm or less is even more preferred, and it is most preferable that there be no porosity at all.

[0059] Next, referring to Figures 3A to 3F, we will explain examples of laser beam cross-sectional shapes such that the profile of the laser beam's power density on the workpiece has a sub-beam with a lower power density than the main beam, located ahead of the main beam in the direction of movement, and with reference to Figures 3A to 3F. The examples of laser beam cross-sectional shapes shown in Figures 3A to 3F are not essential configurations, but by designing the diffractive optical element 123 so that the laser beam cross-sectional shapes exemplified in Figures 3A to 3F are realized on the surface of the workpiece W, a laser beam profile suitable for implementing the present invention can be realized. Note that in all cases, the laser beam cross-sectional shapes exemplified in Figures 3A to 3F have the upward direction of movement (arrow v in the figure) as the direction of movement.

[0060] Figure 3A shows an example in which a sub-beam B2, having a peak P2 and a lower power density than the main beam B1, is located ahead of the main beam B1, which has a peak P1 and a high power density. As shown in Figure 3A, it is preferable that the region around the sub-beam B2 with a power density capable of melting the workpiece is wider in the direction perpendicular to the direction of movement than the region around the main beam B1 with a power density capable of melting the workpiece. Therefore, as shown in Figure 3A, the sub-beam B2 may be extended into a continuous region rather than being a point shape.

[0061] Figure 3B shows an example where a secondary beam B2 with a lower power density is located not only in front of the main beam B1, which has a higher power density, but also behind the main beam B1 in the direction of movement. Welding is not always performed only in the forward direction, but also in the reverse direction. Therefore, as shown in the example in Figure 3B, by providing a secondary beam B2 with a lower power density than the main beam B1 behind the main beam B1 in the direction of movement, the effects of the present invention can be obtained without changing the orientation of the optical head.

[0062] Figure 3C shows an example where a secondary beam B2 with a lower power density is located forward of the main beam B1 in the direction of movement, and also located laterally to the main beam B1 in the direction of movement, with a lower power density than the main beam B1. Welding is not always performed along a straight line. Therefore, as shown in the example in Figure 3C, by providing a secondary beam B2 with a lower power density than the main beam B1 in the laterally to the direction of movement of the main beam B1, the effects of the present invention can be obtained even when welding corners.

[0063] Figure 3D shows an example where a secondary beam B2 with a lower power density is located ahead of the main beam B1 in the direction of movement, and also behind and laterally to the main beam B1 in the direction of movement, with a secondary beam B2 having a lower power density than the main beam B1. In other words, the example shown in Figure 3D combines the advantages of both the examples shown in Figures 3B and 3C.

[0064] Figure 3E shows an example where a secondary beam B2, with a lower power density than the main beam B1, is dispersed around the main beam B1. In the examples shown in Figures 3A to 3D, the secondary beam B2 was configured linearly, but it is not necessary for the secondary beam B2 to be continuous as long as they are placed at relatively close intervals. This is because placing the secondary beam B2 at relatively close intervals connects the shallow region R, thus providing an effective result. Figure 3F shows an example where a secondary beam B2, with a lower power density than the main beam B1, is arranged in a ring shape around the main beam B1. Conversely to Figure 3E, it is also possible to provide the secondary beam B2 in a continuous ring around the beam.

[0065] The distance d between the main beam B1 and the sub-beam B2 (for example, shown in Figure 3A) is the shortest distance between the outer edge of the beam diameter of the main beam B1 and the outer edge of the beam diameter of the sub-beam B2. The distance d should be such that the molten region formed by the main beam B1 can reach the molten pool formed by the sub-beam B2 before the molten pool solidifies. Preferably, the distance d is less than twice the beam diameter of the sub-beam B2, more preferably less than 1, and even more preferably less than 0.5.

[0066] Furthermore, the power densities of the main beam B1 and the secondary beam B2 may be equal.

[0067] (Second Embodiment) Figure 4 is a diagram showing the schematic configuration of a welding apparatus according to the second embodiment. As shown in Figure 4, the welding apparatus 200 according to the second embodiment is an example of a configuration of an apparatus that irradiates the workpiece W with laser light L to melt the workpiece W. The welding apparatus 200 according to the second embodiment realizes the welding method by the same operating principle as the welding apparatus according to the first embodiment. Therefore, only the configuration of the welding apparatus 200 will be described below.

[0068] As shown in Figure 4, the welding apparatus 200 includes an oscillator 210 that emits laser light, an optical head 220 that irradiates the workpiece W with the laser light, and an optical fiber 230 that guides the laser light emitted by the oscillator 210 to the optical head 220.

[0069] The oscillator 210 is configured to oscillate, for example, a multimode laser beam with an output of several kW. For example, the oscillator 210 may be configured to include a plurality of semiconductor laser elements internally, and to oscillate a multimode laser beam with an output of several kW as the total output of the plurality of semiconductor laser elements, or various lasers such as fiber lasers, YAG lasers, and disk lasers may be used.

[0070] The optical head 220 is an optical device for focusing the laser light L, guided from the oscillator 210, to a power density strong enough to melt the workpiece W, and irradiating the workpiece W with it. To this end, the optical head 220 is equipped with a collimating lens 221 and a focusing lens 222 inside. The collimating lens 221 is an optical system for first aligning the laser light guided by the optical fiber 230, and the focusing lens 222 is an optical system for focusing the aligned laser light onto the workpiece W.

[0071] The optical head 220 has a galvanoscanner between the focusing lens 222 and the workpiece W. The galvanoscanner is a device that can move the irradiation position of the laser beam L without moving the optical head 220 by controlling the angles of two mirrors 224a and 224b. In the example shown in Figure 4, a mirror 226 is provided to guide the laser beam L emitted from the focusing lens 222 to the galvanoscanner. The angles of the mirrors 224a and 224b of the galvanoscanner are changed by motors 225a and 225b, respectively.

[0072] The optical head 220 according to the second embodiment includes a diffractive optical element 223 between the collimating lens 221 and the focusing lens 222. The diffractive optical element 223 is for shaping the laser beam L such that the profile of the power density of the laser beam L on the workpiece W in the direction of movement has a sub-beam with a lower power density than the main beam located ahead of the main beam in the direction of movement, and its function is the same as in the first embodiment. In other words, the diffractive optical element 223 is designed to realize a laser beam profile suitable for carrying out the present invention, such as the cross-sectional shape of the laser beam illustrated in Figures 3A to F.

[0073] (Third embodiment) Figure 5 is a diagram showing the schematic configuration of a welding apparatus according to the third embodiment. As shown in Figure 5, the welding apparatus 300 according to the third embodiment is an example of a configuration of an apparatus that irradiates a workpiece W with laser light L to melt the workpiece W. The welding apparatus 300 according to the third embodiment realizes the welding method by the same operating principle as the welding apparatus according to the first embodiment, and the configuration other than the optical head 320 (oscillator 310 and optical fiber 330) is the same as in the second embodiment. Therefore, only the configuration of the optical head 320 will be described below.

[0074] The optical head 320 is an optical device for focusing the laser light L, guided from the oscillator 310, to a power density strong enough to melt the workpiece W, and irradiating the workpiece W with it. To this end, the optical head 320 is equipped with a collimating lens 321 and a focusing lens 322 inside. The collimating lens 321 is an optical system for first aligning the laser light guided by the optical fiber 330, and the focusing lens 322 is an optical system for focusing the aligned laser light onto the workpiece W.

[0075] The optical head 320 has a galvanoscanner between the collimating lens 321 and the focusing lens 322. The mirrors 324a and 324b of the galvanoscanner have their angles changed by motors 325a and 325b, respectively. In the optical head 320, the galvanoscanner is positioned differently from that in the second embodiment, but similarly, by controlling the angles of the two mirrors 324a and 324b, the irradiation position of the laser beam L can be moved without moving the optical head 320.

[0076] The optical head 320 according to the third embodiment includes a diffractive optical element 323 between the collimating lens 321 and the focusing lens 322. The diffractive optical element 323 is for shaping the laser beam L such that the profile of the power density of the laser beam L on the workpiece W has a sub-beam with a lower power density than the main beam located ahead of the main beam in the direction of movement, and its function is the same as in the first embodiment. In other words, the diffractive optical element 323 is designed to realize a laser beam profile suitable for carrying out the present invention, such as the cross-sectional shape of the laser beam illustrated in Figure 3.

[0077] (Fourth Embodiment) Figure 6 is a diagram showing the schematic configuration of a welding apparatus according to the fourth embodiment. As shown in Figure 6, the welding apparatus 400 according to the fourth embodiment is an example of a device configuration that melts the workpiece W by irradiating it with laser beams L1 and L2. The welding apparatus 400 according to the fourth embodiment realizes the welding method by the same operating principle as the welding apparatus according to the first embodiment. Therefore, only the device configuration of the welding apparatus 400 will be described below.

[0078] As shown in Figure 6, the welding apparatus 400 includes a plurality of oscillators 411, 412 that emit laser light, an optical head 420 that irradiates the workpiece W with the laser light, and optical fibers 431, 432 that guide the laser light emitted by the oscillators 411, 412 to the optical head 420.

[0079] The oscillators 411 and 412 are configured to oscillate, for example, multimode laser light with an output of several kW. For example, each oscillator 411 and 412 may be equipped with multiple semiconductor laser elements and configured to oscillate multimode laser light with an output of several kW as the total output of these multiple semiconductor laser elements, or various lasers such as fiber lasers, YAG lasers, and disk lasers may be used.

[0080] The optical head 420 is an optical device for focusing the laser beams L1 and L2, respectively, guided from oscillators 411 and 412, to a power density strong enough to melt the workpiece W, and irradiating the workpiece W with it. To this end, the optical head 420 is equipped with a collimating lens 421a and a focusing lens 422a for the laser beam L1, and a collimating lens 421b and a focusing lens 422b for the laser beam L2. The collimating lenses 421a and 421b are optical systems for first aligning the laser beams guided by optical fibers 431 and 432, respectively, while the focusing lenses 422a and 422b are optical systems for focusing the aligned laser beams onto the workpiece W.

[0081] The optical head 420 according to the fourth embodiment is also configured such that the power density profile of the laser beams L1 and L2 on the workpiece W has a sub-beam with a lower power density than the main beam, located ahead of the main beam in the direction of movement, and with a lower power density than the main beam. That is, of the laser beams L1 and L2 that the optical head 420 irradiates onto the workpiece W, laser beam L1 can be used to form the main beam and laser beam L2 can be used to form the sub-beam. Although the example shown in the figure uses only laser beams L1 and L2, by appropriately increasing the number of beams, it is possible to configure the system to realize a laser beam profile suitable for carrying out the present invention, such as the cross-sectional shape of the laser beam illustrated in Figure 3.

[0082] (Fifth embodiment) Figure 7 is a diagram showing the schematic configuration of a welding apparatus according to the fifth embodiment. As shown in Figure 7, the welding apparatus 500 according to the fifth embodiment is an example of a device configuration that melts the workpiece W by irradiating it with laser beams L1 and L2. The welding apparatus 500 according to the fifth embodiment realizes the welding method by the same operating principle as the welding apparatus according to the first embodiment. Therefore, only the device configuration of the welding apparatus 500 will be described below.

[0083] As shown in Figure 7, the welding apparatus 500 includes an oscillator 510 that emits laser light, an optical head 520 that irradiates the workpiece W with the laser light, and optical fibers 531, 533, and 534 that guide the laser light emitted by the oscillator 510 to the optical head 520.

[0084] In the fifth embodiment, the oscillator 510 is, for example, a fiber laser, a YAG laser, a disk laser, etc., and is used to generate both laser beams L1 and L2 to irradiate the workpiece W. For this purpose, a branching unit 532 is provided between the optical fibers 531, 533, and 534 that guide the laser beams emitted by the oscillator 510 to the optical head 520, and is configured to branch the laser beams emitted by the oscillator 510 before guiding them to the optical head 520.

[0085] The optical head 520 is an optical device for focusing the laser beams L1 and L2, which are branched by the branching unit 532, to a power density strong enough to melt the workpiece W, and irradiating the workpiece W with it. To this end, the optical head 520 is equipped with a collimating lens 521a and a focusing lens 522a for the laser beam L1, and a collimating lens 521b and a focusing lens 522b for the laser beam L2. The collimating lenses 521a and 521b are optical systems for first aligning the laser beams guided by the optical fibers 533 and 534, respectively, while the focusing lenses 522a and 522b are optical systems for focusing the aligned laser beams onto the workpiece W.

[0086] The optical head 520 according to the fifth embodiment is also configured such that the power density profile of the laser beams L1 and L2 on the workpiece W has a sub-beam with a lower power density than the main beam, located in front of the main beam in the direction of movement, and with a lower power density than the main beam. In other words, of the laser beams L1 and L2 that the optical head 520 irradiates onto the workpiece W, laser beam L1 can be used to form the main beam and laser beam L2 can be used to form the sub-beam. Although the example shown in the figure uses only laser beams L1 and L2, by appropriately increasing the number of beams, it is possible to configure the system to realize a laser beam profile suitable for carrying out the present invention, such as the cross-sectional shape of the laser beam illustrated in Figure 3.

[0087] (Sixth Embodiment) Figure 8 is a diagram showing the schematic configuration of a welding apparatus according to the sixth embodiment. As shown in Figure 8, the welding apparatus 600 according to the sixth embodiment is an example of a device configuration that melts a workpiece W by irradiating it with laser light L. The welding apparatus 600 according to the sixth embodiment realizes the welding method by the same operating principle as the welding apparatus according to the first embodiment. Therefore, only the device configuration of the welding apparatus 600 will be described below.

[0088] As shown in Figure 8, the welding apparatus 600 includes a plurality of oscillators 611, 612 that emit laser light, such as a fiber laser, YAG laser, or disk laser; an optical head 620 that irradiates the workpiece W with the laser light; and optical fibers 631, 632, 635 that guide the laser light emitted by the oscillators 611, 612 to the optical head 620.

[0089] In the sixth embodiment, the laser light emitted by oscillators 611 and 612 is coupled before being guided to the optical head 620. To this end, coupling sections 634 are provided between the optical fibers 631, 632, and 635 that guide the laser light emitted by oscillators 611 and 612 to the optical head 620, and the laser light emitted by oscillators 611 and 612 is guided in parallel through the optical fiber 635.

[0090] Here, with reference to Figures 9A and 9B, we will describe the configuration examples of optical fibers 631 (and 632) and optical fiber 635. As shown in Figure 9A, optical fibers 631 (and 632) are ordinary optical fibers. That is, optical fibers 631 (and 632) are optical fibers in which a cladding Cl with a lower refractive index than the core Co is formed around a single core Co. On the other hand, as shown in Figure 9B, optical fiber 635 is a so-called multicore optical fiber. That is, optical fiber 635 has two cores Co1 and Co2, and a cladding Cl with a lower refractive index than the cores Co1 and Co2 is formed around these two cores Co1 and Co2. At the coupling section 634, the core Co of optical fiber 631 and the core Co1 of optical fiber 635 are coupled, and the core Co of optical fiber 632 and the core Co2 of optical fiber 635 are coupled.

[0091] Returning to Figure 8, the optical head 620 is an optical device for focusing the laser beam L, coupled by the coupling portion 634, to a power density strong enough to melt the workpiece W, and irradiating the workpiece W with it. To this end, the optical head 620 is equipped with a collimating lens 621 and a focusing lens 622 inside.

[0092] In this embodiment, the optical head 620 does not have a diffractive optical element, nor does it have separate optical systems for multiple laser beams. However, since the laser beams emitted by oscillators 611 and 612 are coupled before being guided to the optical head 620, the profile of the power density of the laser beam L on the workpiece W with respect to the direction of movement is configured such that a sub-beam with a lower power density than the main beam is located ahead of the main peak with a higher power density in the direction of movement.

[0093] In all embodiments of this specification, the welding mode of the main beam may be either keyhole welding or heat conduction welding. Keyhole welding, as used herein, is a welding method that utilizes a high power density and the indentation or hole (keyhole) created by the pressure of metal vapor generated when the workpiece W is melted. On the other hand, heat conduction welding is a welding method that melts the workpiece W by utilizing the heat generated when laser light is absorbed on the surface of the base material.

[0094] (Verification Experiment 1) Here, we will explain the results of Verification Experiment 1 of the effects of the present invention. The apparatus configuration used in Verification Experiment 1 is the configuration of the welding apparatus 100 according to the first embodiment, and as a conventional apparatus configuration, a configuration was used in which the diffractive optical element 123 was omitted from the welding apparatus 100. As common experimental conditions, the output of the oscillator 110 was set to 3 kW, the relative movement speed between the optical head 120 and the workpiece W was set to 5 m / min, and nitrogen gas was used as the shielding gas.

[0095] The diffractive optical element 123 is formed by a main beam B1 having a peak P1 and a sub-beam B2 having a peak P2, as shown in Figure 10. The sub-beam B2 is designed so that the arc-shaped cross-section of the laser beam, which is part of the ring shape surrounding the main beam B1, is irradiated onto the workpiece W. The occurrence of sputtering was observed in two directions of movement of the laser beam formed by this diffractive optical element 123: in the direction of arrow A and in the direction of arrow B in the figure. In the conventional apparatus configuration, the laser beam irradiated onto the workpiece W has the arc portion of the cross-sectional shape of the laser beam shown in Figure 10 removed.

[0096] In other words, in this verification experiment 1, moving in the direction of arrow A in the figure corresponds to a situation where the secondary beam B2, which has a lower power density than the main beam B1, is located in front of the main beam B1 in the direction of movement, and moving in the direction of arrow B in the figure corresponds to a situation where the secondary beam B2, which has a lower power density than the main beam B1, is located behind the main beam B1 in the direction of movement, and the conventional configuration corresponds to a situation where only the main beam B1 is irradiated.

[0097] In situations where only the main beam B1 is irradiated, and in situations where the secondary beam B2, which has a lower power density than the main beam B1, is located behind the main beam B1 in the direction of movement and has a higher power density, a large amount of sputtering occurs. In contrast, in situations where the secondary beam B2, which has a lower power density than the main beam B1, is located in front of the main beam B1 in the direction of movement and has a lower power density than the main beam B1, sputtering is significantly reduced to about 20% or less.

[0098] This verification experiment 1 also showed that a welding apparatus and a welding method using it, in which the profile of the power density of the laser beam L on the workpiece W has a secondary peak with a lower power density than the main peak, is located ahead of the main peak with a higher power density in the direction of movement, has the effect of suppressing spatter generation.

[0099] Furthermore, we confirmed that the effect was also present under conditions without the use of nitrogen gas, as shown in Table 1. Table 1 shows four experiments. The material to be processed was SUS304 with a thickness of 10 mm. DOE is a diffractive optical element. Focal position is the focal position of the main beam and sub-beam, and is just focused on the surface. Set output is the power of the laser light output from the oscillator. Speed ​​is the sweep speed. In terms of appearance, experiments No. 3 and 4 yielded the most favorable results. [Table 1]

[0100] Figures 11 and 12 show examples of the cross-sectional shape of laser beams, where a V-shaped sub-beam B2 with a lower power density than the main beam B1 is located ahead of the main beam B1 in the direction of movement. Figure 11 shows an example where the main beam B1 and sub-beam B2 overlap, while Figure 12 shows an example where the main beam B1 and sub-beam B2 do not overlap.

[0101] (Reflectance of metallic materials) Here, we will explain the reflectance of metallic materials. The graph shown in Figure 13 shows the reflectance of representative metallic materials in relation to the wavelength of light. In the graph shown in Figure 13, the horizontal axis is wavelength and the vertical axis is reflectance, and examples of metallic materials listed are aluminum, copper, gold, nickel, platinum, silver, stainless steel, titanium, and tin. Note that the graph shown in Figure 13 is a graph of data described in NASA TECHNICAL NOTE (D-5353).

[0102] As can be seen from the graph in Figure 13, copper and aluminum have higher reflectivity compared to stainless steel. This difference is particularly pronounced in the wavelength range of infrared laser light commonly used in laser welding. For example, around 1070 nm, the reflectivity of copper and aluminum is about 95%, meaning that only about 5% of the energy of the irradiated laser light is absorbed by the workpiece. This means that the efficiency of the irradiated energy is about one-sixth that of stainless steel.

[0103] On the other hand, even though materials like copper and aluminum have high reflectivity, this doesn't mean they have high reflectivity for all wavelengths of light. The change in reflectivity is particularly pronounced for copper. As mentioned above, while copper's reflectivity is around 95% at approximately 1070 nm, at yellow wavelengths (e.g., 600 nm), it drops to about 75%, and then decreases sharply, reaching about 20% at ultraviolet wavelengths (e.g., 300 nm). Therefore, laser welding using blue or green laser light is more energy-efficient than using typical infrared laser light. Specifically, it is preferable to use laser light with wavelengths between 300 nm and 600 nm.

[0104] The wavelength range mentioned above is merely an example; by using laser light with a wavelength lower than the infrared reflectance of the target material, laser welding can be performed with higher energy efficiency in terms of reflectance. In this case, the infrared region is preferably defined as 1070 nm, which is the wavelength of infrared laser light commonly used in laser welding.

[0105] The welding method and welding apparatus according to the embodiments of the present invention described below utilize the above-mentioned characteristics.

[0106] (Seventh Embodiment) The welding apparatus according to the seventh embodiment can be realized by the welding apparatus 100 according to the first embodiment shown in Figure 1.

[0107] The laser oscillator 110 is configured to oscillate, for example, a multimode laser beam with an output of several kW. For example, the laser oscillator 110 may be configured to include a plurality of semiconductor laser elements internally, and to oscillate a multimode laser beam with an output of several kW as the total output of the plurality of semiconductor laser elements. In the seventh embodiment, from the above viewpoint, it is preferable that the laser oscillator 110 is configured to oscillate laser beam with a wavelength between 300 nm and 600 nm. Furthermore, it is even more preferable to select a laser oscillator 110 that oscillates at a wavelength that lowers the reflectivity of the workpiece W, depending on the workpiece W.

[0108] The optical head 120 according to the seventh embodiment includes a diffractive optical element 123 as a beam shaper between a collimating lens 121 and a focusing lens 122. The diffractive optical element 123 is for shaping the laser beam L such that the profile of the power density of the laser beam L on the workpiece W in the sweep direction has a sub-beam located ahead of the main beam in the sweep direction. Therefore, the welding apparatus 100 according to the seventh embodiment is configured to separate laser beams emitted from the same laser oscillator 110 using the diffractive optical element 123, and as a result, the wavelengths of the laser beams forming both the main beam and the sub-beam are the same. The diffractive optical element 123 can be configured to be rotatable. It can also be configured to be replaceable.

[0109] The effect of having a main beam and a sub-beam located ahead of the main beam in the sweep direction of the power density profile of the laser beam L on the workpiece W is as follows. Figures 14A and 14B show a comparison of the situation in which the laser beam melts the workpiece.

[0110] As shown in Figure 14A, in conventional laser welding, the laser beam has one beam B, so the unmelted metal W1 ahead of the position where the laser beam is irradiated in the sweep direction (arrow v) is melted by the energy of the laser beam, and a molten pool WP of the workpiece W is formed in the opposite direction from the position where the laser beam was irradiated in the sweep direction (arrow v). Subsequently, the molten pool WP resolidifies into resolidified metal W2, and the workpiece W is welded.

[0111] On the other hand, as shown in Figure 14B, in the welding apparatus and welding method using the 11th embodiment, the profile of the power density of the laser beam on the workpiece W with respect to the sweep direction has a main beam B1 and a sub-beam B2. The sub-beam B2 has a lower power density than the main beam B1 and is located ahead of the main beam B1 in the sweep direction (arrow v). Furthermore, the power density of the sub-beam B2 is strong enough to melt the workpiece W in the presence of the main beam B1 or on its own. Therefore, a molten pool is formed ahead of the position where the main beam B1 is irradiated, and shallower than the depth to which the main beam B1 melts. For convenience, this will be called the forward molten pool WPf.

[0112] As shown in Figure 14B, the melting intensity regions of the laser beams of the main beam B1 and the sub-beam B2 do not necessarily need to overlap; it is sufficient that the molten pools overlap. In other words, it is sufficient that the melting intensity region formed by the main beam B1 reaches the forward molten pool WPf before the molten pool formed by the sub-beam B2 solidifies. As described above, the power densities of the main beam B1 and the sub-beam B2 are strong enough to melt the workpiece W, and the melting intensity region refers to the range of the laser beam around the main beam B1 or sub-beam B2 that has a power density sufficient to melt the workpiece W.

[0113] In the welding apparatus and welding method using the 11th embodiment, the presence of a forward molten pool WPf in front of the position where the main beam B1 is irradiated stabilizes the state of the molten pool WP near the irradiation position of the main beam B1. As mentioned above, spatter is the scattering of molten metal, so stabilizing the state of the molten pool WP near the irradiation position of the main beam B1 leads to the suppression of spatter generation.

[0114] Furthermore, in the welding apparatus and welding method according to the seventh embodiment, the wavelength of the laser light forming at least the sub-beam B2 (both in this example) of the main beam B1 and sub-beam B2 is a wavelength with a reflectivity lower than the reflectivity in the infrared region of the workpiece. Therefore, even with metallic materials such as copper and aluminum, which have high reflectivity in the infrared wavelength, a forward molten pool WPf can be efficiently formed.

[0115] In the welding apparatus and welding method using the seventh embodiment, it is preferable that the power density in the sub-beam B2 is lower than that in the main beam B1. More specifically, the power density in the sub-beam B2 is 1 × 10⁻¹⁰. 7 W / cm 2 The following is preferable. The purpose of the sub-beam B2 is to form a forward molten pool WPf in front of the position irradiated by the main beam B1, and the function of the forward molten pool WPf is to stabilize the state of the molten pool WP near the irradiation position of the main beam B1. The depth of the forward molten pool WPf can be shallow enough to stabilize the molten pool WP, and as mentioned above, by setting the laser light forming the sub-beam B2 to a wavelength with a reflectivity lower than the reflectivity in the infrared region of the workpiece, the reflectivity to the workpiece is reduced, so an excessively high power density is not required. If the power density of the sub-beam is excessively high, the sub-beam itself will become a cause of sputter generation. On the other hand, the purpose of the main beam is to sufficiently melt the workpiece W and to reliably weld the workpiece. Considering these factors, it is preferable that the power density of the sub-beam B2 is lower than that of the main beam B1.

[0116] Examples of laser beam cross-sectional shapes that result in a profile of the laser beam's power density on the workpiece in the sweep direction having a sub-beam located ahead of the main beam in the sweep direction are shown in Figures 3A-3F, 11, and 12.

[0117] The laser beam directed to the secondary beam B2 has a lower power density than the main beam B1, which is intended for welding. Therefore, even if the secondary beam B2 is directed in a direction other than the intended forward direction, it will not interfere with the original welding operation. For example, let's assume the intensity of the laser beam forming the main beam B1 is 1 kW and the intensity of the laser beam forming the secondary beam B2 is 300 W.

[0118] As is clear from the example described above, the sub-beam P2 does not necessarily have to be a profile where the peak value is at a single point. Profiles with peak values ​​over a certain area (including linear areas), or profiles where points with peak values ​​are located at relatively close intervals, do not have a substantial effect on the formed molten pool. Therefore, we will refer to these as sub-beam P2 without distinction.

[0119] (Eighth embodiment) The welding apparatus according to the eighth embodiment can be realized by the welding apparatus 200 according to the second embodiment shown in Figure 4.

[0120] The laser oscillator 210 is configured to oscillate multimode laser light with an output of several kW, for example. For example, the laser oscillator 210 includes a plurality of semiconductor laser elements and is configured to oscillate multimode laser light with an output of several kW as the total output of the plurality of semiconductor laser elements. The laser oscillator 210 is preferably configured to oscillate laser light with a wavelength between 300 nm and 600 nm, similar to the eighth embodiment. Furthermore, it is more preferable to select a laser oscillator 210 that oscillates at a wavelength that lowers the reflectivity of the workpiece W, depending on the workpiece W.

[0121] In the welding apparatus and welding method according to the eighth embodiment, the wavelength of the laser light forming at least the sub-beam (both in this example) of the main beam and sub-beam has a lower reflectivity than the reflectivity in the infrared region of the workpiece. Therefore, even with metallic materials such as copper and aluminum, which have high reflectivity in the infrared wavelength, a forward molten pool can be efficiently formed.

[0122] (Ninth Embodiment) The welding apparatus according to the ninth embodiment can be realized by the welding apparatus 300 according to the third embodiment shown in Figure 5.

[0123] The optical head 320 includes a diffractive optical element 323 as a beam shaper between the collimating lens 321 and the focusing lens 322. The diffractive optical element 323 is for shaping the laser beam L such that the profile of the power density of the laser beam L on the workpiece W in the sweep direction has a sub-beam located ahead of the main beam in the sweep direction. In other words, the diffractive optical element 323 is designed to realize a laser beam profile suitable for carrying out the present invention, such as the cross-sectional shape of the laser beam illustrated in Figures 3A to 3F, 11 and 12.

[0124] In the welding apparatus and welding method according to the ninth embodiment, the wavelength of the laser light forming at least the sub-beam (both in this example) of the main beam and sub-beam has a lower reflectivity than the reflectivity in the infrared region of the workpiece. Therefore, even with metallic materials such as copper and aluminum, which have high reflectivity in the infrared wavelength, a forward molten pool can be efficiently formed.

[0125] (Tenth embodiment) The welding apparatus according to the tenth embodiment can be realized by the welding apparatus 400 according to the fourth embodiment shown in Figure 6.

[0126] In the tenth embodiment, laser oscillators 411 and 412 are different laser oscillators and may oscillate laser light of the same wavelength, or they may be configured to oscillate different laser light. In that case, laser oscillator 412 is configured such that the wavelength of the laser light L2 forming the sub-beam of the main beam is between 300 nm and 600 nm.

[0127] The optical head 420 is configured such that the profile of the power density of the laser beams L1 and L2 on the workpiece W has a sub-beam located ahead of the main beam in the sweep direction. That is, of the laser beams L1 and L2 that the optical head 420 irradiates onto the workpiece W, laser beam L1 is used for main beam formation and laser beam L2 is used for sub-beam formation. Although the example shown in the figure uses only laser beams L1 and L2, by appropriately increasing the number of beams, it is possible to configure the system to realize a laser beam profile suitable for carrying out the present invention, such as the cross-sectional shape of the laser beam exemplified in Figures 3A to 3F, 11 and 12.

[0128] In the welding apparatus and welding method using the 10th embodiment, the wavelength of the laser light forming at least the sub-beam among the main beam and sub-beam is a wavelength with a reflectivity lower than the reflectivity in the infrared region of the workpiece. Therefore, even with metal materials that have high reflectivity in the infrared wavelength, such as copper and aluminum, a forward molten pool can be efficiently formed. On the other hand, the wavelength of the laser light L1 forming the main beam does not necessarily have to be a wavelength with a reflectivity lower than the reflectivity in the infrared region of the workpiece. Therefore, the laser oscillator 411 can be a high-power infrared laser oscillator, similar to conventional products. In other words, in this embodiment, the wavelength of the laser light forming the sub-beam is a wavelength with a reflectivity lower than the reflectivity of the workpiece at the wavelength of the laser light forming the main beam. Even with metal materials that have high reflectivity in the infrared wavelength, the reflectivity becomes low in the molten state. Therefore, even if the laser oscillator 411 is a high-power infrared laser oscillator such as a fiber laser, YAG laser, or disk laser, the workpiece can be sufficiently melted.

[0129] (11th embodiment) The welding apparatus according to the 11th embodiment can be realized by the welding apparatus 500 according to the 5th embodiment shown in Figure 7.

[0130] The optical head 520 is configured such that the profile of the power density of the laser beams L1 and L2 on the workpiece W has a sub-beam located ahead of the main beam in the sweep direction. That is, of the laser beams L1 and L2 that the optical head 520 irradiates onto the workpiece W, laser beam L1 is used for main beam formation and laser beam L2 is used for sub-beam formation. Although the example shown in the figure uses only laser beams L1 and L2, by appropriately increasing the number of beams, it is possible to configure the system to realize a laser beam profile suitable for carrying out the present invention, such as the cross-sectional shape of the laser beam exemplified in Figures 3A to 3F, 11 and 12.

[0131] In the welding apparatus and welding method according to the 11th embodiment, the wavelength of the laser light forming at least the sub-beam (both in this example) of the main beam and sub-beam has a lower reflectivity than the reflectivity in the infrared region of the workpiece. Therefore, even with metallic materials such as copper and aluminum, which have high reflectivity in the infrared wavelength, a forward molten pool can be efficiently formed.

[0132] (12th embodiment) The welding apparatus according to the 12th embodiment can be realized by the welding apparatus 600 according to the 6th embodiment shown in Figure 8.

[0133] In the twelfth embodiment, laser oscillators 611 and 612 are different laser oscillators and may oscillate laser light of the same wavelength, or they may be configured to oscillate different laser light. In that case, laser oscillator 612 is configured such that the wavelength of the laser light forming the sub-beam of the main beam is between 300 nm and 600 nm.

[0134] In the twelfth embodiment, the laser light emitted by the laser oscillators 611 and 612 is coupled before being guided to the optical head 620. To this end, coupling sections 634 are provided between the optical fibers 631, 632, and 635 that guide the laser light emitted by the laser oscillators 611 and 612 to the optical head 620, and the laser light emitted by the laser oscillators 611 and 612 is guided in parallel through the optical fiber 635.

[0135] The optical head 620 is an optical device for focusing the laser beam L, coupled by the coupling portion 634, to a power density strong enough to melt the workpiece W, and irradiating the workpiece W with it. To this end, the optical head 620 is equipped with a collimating lens 621 and a focusing lens 622 inside.

[0136] In this embodiment, the optical head 620 does not have a beam shaper, nor does it have separate optical systems for multiple laser beams. However, since the laser beams emitted by the laser oscillators 611 and 612 are coupled before being guided to the optical head 620, the profile of the power density of the laser beam L on the workpiece W with respect to the sweep direction is configured to have a sub-beam located ahead of the main beam in the sweep direction.

[0137] In the welding apparatus and welding method using the 12th embodiment, the wavelength of the laser light forming at least the sub-beam among the main beam and sub-beam is a wavelength with a reflectivity lower than the reflectivity in the infrared region of the workpiece. Therefore, even with metal materials that have high reflectivity in the infrared wavelength, such as copper and aluminum, a forward molten pool can be efficiently formed. On the other hand, the wavelength of the laser light L1 forming the main beam does not necessarily have to be a wavelength with a reflectivity lower than the reflectivity in the infrared region of the workpiece. Therefore, the laser oscillator 611 can be a high-power infrared laser oscillator, similar to conventional products. In other words, in this embodiment, the wavelength of the laser light forming the sub-beam is a wavelength with a reflectivity lower than the reflectivity of the workpiece at the wavelength of the laser light forming the main beam. Even with metal materials that have high reflectivity in the infrared wavelength, the reflectivity becomes low in the molten state. Therefore, even if the laser oscillator 611 is a high-power infrared laser oscillator such as a fiber laser, YAG laser, or disk laser, the workpiece can be sufficiently melted.

[0138] In all the embodiments mentioned above, the welding method for the main beam may be not only heat conduction welding but also keyhole welding.

[0139] (Verification Experiment 2) Here, the results of Verification Experiment 2 of the effects of the present invention will be described. The apparatus configuration used in Verification Experiment 2 is the same as that of the welding apparatus according to the 7th embodiment, and is the same as that of welding apparatus 100. The first experimental condition as a comparative example uses a configuration in which the diffractive optical element 123 is omitted from welding apparatus 100, and the second experimental condition corresponding to the present invention is equipped with a diffractive optical element 123 designed so that the laser light is irradiated onto the workpiece W with the irradiation surface shape shown in Figure 10, but the wavelength of the laser light used is in the blue region. As common experimental conditions, the sweep speed between the optical head 120 and the workpiece W is set to 5 m / min, and nitrogen gas is used as the shielding gas. The workpiece W is made of tough pitch copper with a thickness of 2 mm.

[0140] More specifically, under the first experimental condition, as the laser oscillator 110, a multimode fiber laser device with an oscillation wavelength of 1070 nm is used, and this is used with an output of 3 kW. Then, by irradiating the processing target with a single spot without passing through the diffractive optical element 123, the spot diameter at the focus point is 100 μm, and its average power density is 3.8×10 7 W / cm 2 is set.

[0141] Under the second experimental condition, as the laser oscillator 110, a semiconductor laser device with an oscillation wavelength of 450 nm is used, and this is used with an output of 1 kW. The diffractive optical element 123 to be used is designed such that laser light with an irradiation surface shape as shown in FIG. 10 is irradiated onto the processing target W. The distribution of the output is such that 300 W out of the 1 kW output is almost evenly distributed to the semicircular sub-beams. At this time, the average power density of the main beam is 2.2×10 6 W / cm 2 and the average power density of the sub-beam is 8.0×10 4 W / cm 2 is.

[0142] Under the above experimental conditions, a verification experiment was conducted, and the following results were obtained.

[0143] Under the first experimental condition, the power density at the focus point exceeded the melting threshold of pure copper, a keyhole was formed, and welding was possible, but at the same time, sputtering and welding defects frequently occurred.

[0144] On the other hand, under the second experimental condition, although the output of the laser oscillator was 1 kW, since the copper material has a high absorption rate at a wavelength of 450 nm, welding could be performed to the desired depth, and moreover, it was also possible to form a front melting pool by the 300 W semicircular sub-beam arranged in front of the scanning direction. As a result, due to the effect of the front melting pool formed by the sub-beam, sputtering and welding defects were significantly reduced, and it was confirmed from high-speed camera observations that they became 20% or less.

[0145] [[ID=3l]] This verification experiment also showed that a welding apparatus and welding method using it, in which the power density profile of the laser beam L on the workpiece W has a sub-beam located ahead of the main beam in the direction of movement, and the wavelength of the laser beam forming at least the sub-beam has a lower reflectivity than the infrared reflectivity of the workpiece, is effective in suppressing spatter generation.

[0146] Although the present invention has been described above based on embodiments, the present invention is not limited to the above embodiments. Combinations of the components of each of the above embodiments are also included within the scope of the present invention. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the above embodiments, and various modifications are possible. [Explanation of Symbols]

[0147] 100, 200, 300, 400, 500, 600 welding equipment 110, 210, 310, 411, 412, 510, 611, 612 Oscillators 120, 220, 320, 420, 520, 620 Optical Heads 121,221,321,421a,421b,521a,521b,621 Collimating Lens 122,222,322,422a,422b,522a,522b,622 Focusing lens 123,223,323 diffractive optical elements 224a,224b,226,324a,324b Mirror 225a, 225b, 325a, 325b motors 130,230,330,431,432,531,533,534,631,632,635 Optical fiber 532 Branch Unit 634 Joint

Claims

1. A laser beam from a laser device is irradiated onto a workpiece, which includes a component made of copper or aluminum, and the workpiece is melted and welded. Including the process, The laser beam consists of a single main beam and a sub-beam that is at least a portion of the main beam located forward in the sweep direction, the power density of the main beam is at least strong enough to generate a keyhole, and the power density of the sub-beam is lower than that of the main beam and strong enough to melt the workpiece without generating a keyhole caused by the pressure of the metal vapor. The wavelength of the laser light forming the main beam is in the infrared region. The wavelength of the laser light forming the sub-beam is between 300 nm and 600 nm. The laser light forms a shallow region in the area irradiated by the sub-beam, which is a molten pool that is shallower than the molten pool formed in the area irradiated by the main beam, and is filled with the molten and liquid workpiece. Before the shallow region formed in the area irradiated by the sub-beam solidifies, the melting intensity region of the main beam reaches the shallow region. The depth of the aforementioned shallow area is greater than 10 μm. A welding method in which the workpiece is welded using a laser.

2. The welding method according to claim 1, wherein the laser beam further comprises a sub-beam having a lower power density than the main beam, located behind the main beam in the sweeping direction.

3. The welding method according to claim 1, wherein the laser light further comprises a sub-beam having a lower power density than the main beam, in a direction laterally to the sweep direction of the main beam.

4. The welding method according to claim 1, wherein the laser light further comprises a sub-beam having a lower power density than the main beam, dispersed around the main beam.

5. The welding method according to claim 1, wherein the sub-beam has a ring shape surrounding the main beam or an arc shape that is part of the ring shape surrounding the main beam.

6. The welding method according to any one of claims 1 to 5, wherein the main beam and the sub-beam of the laser light are configured such that at least a portion of the molten pool formed by the main beam and the molten pool formed by the sub-beam overlap.

7. The welding method according to claim 6, wherein the distance between the main beam and the sub-beam is less than twice the beam diameter of the sub-beam.

8. The power density in the aforementioned sub-beam is 1 × 10⁻⁶ ７ W / cm ２ The welding method according to claim 1, which is as follows:

9. The welding method according to claim 1, wherein the main beam and the sub-beam are laser beams emitted from different oscillators.

10. The welding method according to claim 9, wherein at least one of the main beam and the sub-beam is formed by a beam shaper positioned between the oscillator and the workpiece.

11. The welding method according to claim 10, characterized in that the beam shaper is a diffractive optical element.

12. The welding method according to claim 10, characterized in that the distance between the main beam and the sub-beam is less than one times the beam diameter of the sub-beam.

13. The welding method according to claim 1, wherein the object to be processed is at least two members to be welded, and the step of arranging the object to be processed in a region irradiated with laser light is a step of arranging the at least two members to overlap, be in contact with, or be adjacent to each other.

14. The welding method according to claim 1, wherein the beam diameter of the sub-beam is approximately equal to or greater than the beam diameter of the main beam.

15. A laser beam from a laser device is irradiated onto a workpiece, which includes a component made of copper or aluminum, and the workpiece is melted and welded. Including the process, The laser beam consists of a single main beam and a sub-beam that is at least a portion of the main beam located forward in the sweep direction, wherein the main beam has an intensity that generates at least a keyhole, and the sub-beam has a power density lower than that of the main beam and an intensity that melts the workpiece without generating a keyhole caused by the pressure of the metal vapor. The wavelength of the laser light forming the main beam is in the infrared region. The wavelength of the laser light forming the sub-beam is between 300 nm and 600 nm. The laser light forms a shallow region in the area irradiated by the sub-beam, which is a molten pool that is shallower than the molten pool formed in the area irradiated by the main beam, and is filled with the molten and liquid workpiece. Before the shallow region formed in the area irradiated by the sub-beam solidifies, the melting intensity region of the main beam reaches the shallow region. The depth of the aforementioned shallow area is greater than 10 μm. A welding method in which the workpiece is welded using a laser.

16. The welding method according to claim 1 or 15, wherein the laser beam is irradiated toward the workpiece while a shielding gas is supplied.

17. A laser oscillator, An optical head that receives light emitted from a laser oscillator to generate laser light, and irradiates the generated laser light onto a workpiece including a component made of copper or aluminum to melt and weld the irradiated portion of the workpiece, It is composed of, The optical head is configured such that the laser beam and the workpiece can move relative to each other, and welding is performed by sweeping the laser beam over the workpiece while melting, The laser beam consists of a single main beam and a sub-beam that is at least a portion of the main beam located forward in the sweep direction, the power density of the main beam is at least strong enough to generate a keyhole, and the power density of the sub-beam is lower than that of the main beam and strong enough to melt the workpiece without generating a keyhole caused by the pressure of the metal vapor. The wavelength of the laser light forming the main beam is in the infrared region. The wavelength of the laser light forming the sub-beam is between 300 nm and 600 nm. The laser light forms a shallow region in the area irradiated by the sub-beam, which is a molten pool that is shallower than the molten pool formed in the area irradiated by the main beam, and is filled with the molten and liquid workpiece. Before the shallow region formed in the area irradiated by the sub-beam solidifies, the melting intensity region of the main beam reaches the shallow region. The depth of the aforementioned shallow area is greater than 10 μm. A welding device that uses a laser to weld the workpiece.

18. The welding apparatus according to claim 17, wherein the laser beam further comprises a sub-beam having a lower power density than the main beam, located behind the main beam in the sweeping direction.

19. The welding apparatus according to claim 17, wherein the laser light further comprises a sub-beam having a lower power density than the main beam, in a direction later than the sweep direction of the main beam.

20. The welding apparatus according to claim 17, wherein the laser light further comprises a sub-beam having a lower power density than the main beam, dispersed around the main beam.

21. The welding apparatus according to claim 17, wherein the sub-beam has a ring shape surrounding the main beam or an arc shape that is part of the ring shape surrounding the main beam.

22. The welding apparatus according to any one of claims 17 to 21, wherein the main beam and the sub-beam of the laser light are configured such that at least a portion of the molten pool formed by the main beam and the molten pool formed by the sub-beam overlap.

23. The welding apparatus according to claim 17, wherein the wavelength of the laser light forming at least the sub-beam among the main beam and the sub-beam has a wavelength that has a lower reflectance than the reflectance in the infrared region of the workpiece.

24. The power density in the aforementioned sub-beam is 1 × 10⁻⁶ ７ W / cm ２ The welding apparatus according to claim 23, which is as follows:

25. The welding apparatus according to claim 23 or 24, wherein the wavelength of the laser light forming the main beam is the same as the wavelength of the laser light forming the sub-beam.

26. The welding apparatus according to claim 17, wherein the optical head generates the laser light consisting of the main beam and the sub-beam from light emitted from a single laser oscillator.

27. The welding apparatus according to claim 26, wherein the optical head includes a beam shaper positioned between the laser oscillator and the workpiece, and the beam shaper forms the main beam and the sub-beam from light emitted from the single laser oscillator.

28. The welding apparatus according to claim 27, characterized in that the beam shaper is a diffractive optical element.

29. The welding apparatus according to claim 27 or 28, characterized in that the distance between the main beam and the sub-beam is less than one times the beam diameter of the sub-beam.

30. The welding apparatus according to claim 17, wherein the laser oscillator is composed of two different laser oscillators, and the main beam and the sub-beam are laser light emitted from the two different laser oscillators, respectively.

31. The welding apparatus according to claim 17, wherein the object to be processed is at least two members to be welded.

32. The welding apparatus according to claim 17, wherein the beam diameter of the sub-beam is approximately equal to or greater than the beam diameter of the main beam.

33. The welding apparatus according to claim 27 or 28, wherein the beam shaper is rotatably mounted.

34. There are multiple laser oscillators, The welding apparatus according to claim 17, wherein the optical head generates the laser light by combining the light emitted from the plurality of laser oscillators.

35. There are multiple laser oscillators, The welding apparatus according to claim 17, further comprising a multicore fiber that combines the light emitted from the plurality of laser oscillators and guides it to the optical head.

36. The welding apparatus according to claim 17, wherein the optical head is configured to sweep the laser beam over the fixed workpiece.

37. The welding apparatus according to claim 17, wherein the irradiation position of the laser beam from the optical head is fixed, and the workpiece is held so as to be movable relative to the fixed laser beam.

38. A laser oscillator, An optical head that receives light emitted from a laser oscillator to generate laser light, and irradiates the generated laser light onto a workpiece including a component made of copper or aluminum to melt and weld the irradiated portion of the workpiece, It is composed of, The laser beam consists of a single main beam and a sub-beam that is at least a portion of the main beam located forward in the sweep direction, wherein the main beam has an intensity that generates at least a keyhole, and the sub-beam has a power density lower than that of the main beam and an intensity that melts the workpiece without generating a keyhole caused by the pressure of the metal vapor. The wavelength of the laser light forming the main beam is in the infrared region. The wavelength of the laser light forming the sub-beam is between 300 nm and 600 nm. The laser light forms a shallow region in the area irradiated by the sub-beam, which is a molten pool that is shallower than the molten pool formed in the area irradiated by the main beam, and is filled with the molten and liquid workpiece. Before the shallow region formed in the area irradiated by the sub-beam solidifies, the melting intensity region of the main beam reaches the shallow region. The depth of the aforementioned shallow area is greater than 10 μm. A welding device that uses a laser to weld the workpiece.

39. The welding apparatus according to claim 17 or 38, wherein the laser beam is irradiated toward the workpiece while a shielding gas is supplied.

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