Welding method, laser welding system, metal component, electrical component, and electronic device

Abstract

A welding method is provided in which a laser beam moving relative to an object in a scanning direction is irradiated onto the surface of the object, thereby melting the portion of the object irradiated with the laser beam to perform welding. The laser beam comprises a first laser beam having a wavelength of 800 nm to 1200 nm and a second laser beam having a wavelength of 550 nm or less. The wavelength of the second laser beam is, for example, 400 nm to 500 nm.

Description

Technical Field

[0001] The present invention relates to a welding method, a laser welding system, a metal component, an electrical component and an electronic device. Background Art

[0002] Laser welding is a well-known method for welding metal objects. Laser welding involves irradiating the portion of the object to be welded with a laser beam, melting that portion using the laser's energy. A pool of molten metal material forms in the irradiated area, which then solidifies, achieving welding.

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

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application No. 2010-508149 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] Furthermore, during welding, it is necessary to suppress welding defects such as spatter and pores. Spatter is formed by the scattering of molten metal, so if such spatter is generated, the amount of metal material at the weld site will be reduced. In other words, if the generation of spatter increases, the amount of metal material at the weld site will be insufficient, which will also cause poor strength. In addition, the generated spatter adheres to the periphery of the weld site, but if the spatter is later peeled off and attached to the circuit, etc., it will cause abnormalities in the circuit. Therefore, there are cases where it is difficult to weld components for the circuit. In addition, pores are roughly spherical cavities generated in the weld site, and are one of the reasons for the reduction in weld strength.

[0009] Therefore, one of the objects of the present invention is to provide, for example, a welding method, a laser welding system, a metal member, an electric component, and an electronic device that can further suppress welding defects.

[0010] Solutions to Problems

[0011] In the welding method of the present invention, for example, there is a welding method in which welding is performed by irradiating a surface of a processing object with a laser that moves relative to the processing object in a scanning direction, thereby melting the portion of the processing object irradiated with the laser, wherein the laser includes a first laser with a wavelength of greater than 800 [nm] and less than 1200 [nm] and a second laser with a wavelength of less than 550 [nm].

[0012] In the welding method, the wavelength of the second laser light may be 400 nm or more and 500 nm or less.

[0013] In the welding method, the processing object may be any one of a copper-based metal material, an aluminum-based metal material, a nickel-based metal material, an iron-based metal material, and a titanium-based metal material.

[0014] In the welding method, at least a portion of a second spot formed on the surface by the second laser may be located ahead of a first spot formed on the surface by the first laser in the scanning direction.

[0015] In the welding method, the first light spot and the second light spot may at least partially overlap on the surface.

[0016] In the welding method, on the surface, a second outer edge of the second light spot may surround a first outer edge of the first light spot.

[0017] In the welding method, when the width of the weld portion formed on the surface when only the first laser is irradiated without irradiating the second laser is set to wb, and the outer diameter of the second spot when the first laser and the second laser are irradiated is set to D2, the following formula (1) may be satisfied:

[0018] wb-400<D2<wb+400 (1)

[0019] Set the outer diameter of the second light spot.

[0020] In the welding method, on the surface, an output ratio of the power of the second laser beam to the power of the first laser beam may be 0.1 or more and 2 or less.

[0021] In the welding method, the laser may include a plurality of beams.

[0022] In the welding method, the plurality of light beams may be formed by a beam shaper.

[0023] In the welding method, the arithmetic mean roughness of the surface may be 21 [μm] or less.

[0024] In the welding method, the scanning speed of the laser beam on the surface may be 50 [mm / s] or higher.

[0025] In addition, the laser welding system of the present invention includes, for example: a first laser oscillator that oscillates a first laser with a wavelength of not less than 800 [nm] and not more than 1200 [nm]; a second laser oscillator that oscillates a second laser with a wavelength of not more than 500 [nm]; an optical head that performs welding by irradiating a surface of a processing object with laser light including the first laser and the second laser, thereby melting a portion of the processing object irradiated with the laser light; a control unit that controls the laser oscillation timing and power of the first laser and the second laser; and a cooling mechanism that cools the first laser oscillator, the second laser oscillator and the optical head, wherein the processing object and the laser light are configured to be movable relative to each other in a manner such that the laser light moves relative to the processing object in a scanning direction.

[0026] The laser welding system may include a galvano scanner configured to change an emission direction of the laser light so as to move the laser light along the scanning direction on the surface.

[0027] The laser welding system may include a beam shaper that divides the laser light into a plurality of beams.

[0028] In addition, the metal component of the present invention is, for example, a metal component, which has a first surface, a second surface on the back side of the first surface, and a weld portion extending along the first surface, wherein the weld portion has: a weld metal extending from the first surface toward the second surface; and a heat-affected portion located around the weld metal, the weld metal having: a first portion located at a position separated from the first surface in the thickness direction from the first surface toward the second surface; and a second portion located between the first portion and the first surface, and the average value of the cross-sectional area of ​​the grains in the cross section perpendicular to the extension direction of the weld portion is larger than that of the first portion.

[0029] In the metal member, an average value of the cross-sectional area of ​​the crystal grains included in the second portion may be 1.8 times or more the average value of the cross-sectional area of ​​the crystal grains included in the first portion.

[0030] In addition, the metal component of the present invention is, for example, a metal component having a first surface, a second surface on the back side of the first surface, and a weld portion extending along the first surface, wherein the weld portion has: a weld metal extending from the first surface toward the second surface; and a heat-affected zone located around the weld metal, and when the first grain boundary number ratio is expressed as the following formula (3-1),

[0031] Rb1=N12 / N11 (3-1)

[0032] Here, Rb1 is the first grain boundary number ratio, N11 is the number of grain boundaries intersecting a straight test line of a specified length along the first surface in a test section perpendicular to the first surface and along the extension direction of the weld, N12 is the number of grain boundaries intersecting a straight test line of the specified length extending in a direction perpendicular to the first surface in the test section, and the weld metal has: a third portion located at a position separated from the first surface in a thickness direction from the first surface toward the second surface; and a fourth portion located between the third portion and the first surface, and the first grain boundary number ratio is lower than the first grain boundary number ratio of the third portion.

[0033] In addition, the metal component of the present invention is, for example, a metal component having a first surface, a second surface on the back side of the first surface, and a weld portion extending along the first surface, wherein the weld portion has: a weld metal extending from the first surface toward the second surface; and a heat-affected zone located around the weld metal, and when the second grain boundary number ratio is expressed as the following formula (3-2),

[0034] Rb2=max(N22 / N21, N21 / N22) (3-2)

[0035] Here, Rb2 represents a second grain boundary number ratio, N21 represents the number of grain boundaries intersecting a straight test line extending in a first direction between a direction along the first surface and a direction perpendicular to the first surface in a test cross section perpendicular to the first surface and along the extending direction of the weld, N22 represents the number of grain boundaries intersecting a straight test line extending in a second direction perpendicular to the first direction and having the prescribed length in the test cross section, and max(N22 / N21, N21 / N22) is (N22 / N21) when (N22 / N21) is (N21 / N22) or more, and is (N21 / N22) when (N22 / N21) is less than (N21 / N22). The weld metal includes a third portion located at a position separated from the first surface in a thickness direction from the first surface toward the second surface, and a fourth portion located between the third portion and the first surface, wherein the second grain boundary number ratio is higher than the second grain boundary number ratio of the third portion.

[0036] Furthermore, the metal component of the present invention is, for example, a metal component including a first surface, a second surface on the back side of the first surface, and a weld portion extending along the first surface, wherein the weld portion includes: a weld metal extending from the first surface toward the second surface; and a heat-affected zone located around the weld metal.

[0037] When the first grain boundary number ratio is expressed as the following formula (3-1),

[0038] Rb1=N12 / N11 (3-1)

[0039] Here, Rb1 is the first grain boundary number ratio, N11 is the number of grain boundaries intersecting a straight test line of a predetermined length along the first surface in a test cross section perpendicular to the first surface and along the extending direction of the weld portion, N12 is the number of grain boundaries intersecting a straight test line of the predetermined length extending in a direction perpendicular to the first surface in the test cross section, and the second grain boundary number ratio Rb2 is expressed as the following formula (3-2):

[0040] Rb2=max(N22 / N21, N21 / N22) (3-2)

[0041] Here, Rb2 is a second grain boundary number ratio, N21 is the number of grain boundaries intersecting a straight test line extending in a first direction between a direction along the first surface and a direction perpendicular to the first surface in a test cross section perpendicular to the first surface and along the extending direction of the weld portion, N22 is the number of grain boundaries intersecting a straight test line extending in a second direction perpendicular to the first direction and having the prescribed length in the test cross section, and max(N22 / N21, N21 / N22) is calculated when (N22 / N21) is less than (N21 / N22). In the case of the above, it is set to (N22 / N21); in the case where (N22 / N21) is less than (N21 / N22), it is set to (N21 / N22), and the weld metal has: a third portion, which is located at a position separated from the first surface in the thickness direction from the first surface toward the second surface relative to the first surface; and a fourth portion, which is located between the third portion and the first surface, the first grain boundary number ratio of the fourth portion is lower than the first grain boundary number ratio of the third portion and the second grain boundary number ratio of the fourth portion is higher than the second grain boundary number ratio of the third portion.

[0042] Furthermore, the electrical component of the present invention may include, for example, the aforementioned metal member as a conductor.

[0043] Furthermore, the electronic device of the present invention may include the metal member as a conductor, for example.

[0044] Effects of the Invention

[0045] According to the present invention, for example, a welding method, a laser welding system, a metal member, an electric component, and an electronic device capable of further suppressing welding defects can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is an exemplary schematic configuration diagram of the laser welding device according to the first embodiment.

[0047] Figure 2 1 is an illustrative schematic diagram showing a laser beam (spot) formed on the surface of a workpiece by the laser welding apparatus according to the first embodiment.

[0048] Figure 3 This is a graph showing the absorptivity of each metal material to light of the wavelength of the irradiated laser light.

[0049] Figure 4 It is an illustrative and schematic cross-sectional view of a welding portion according to an embodiment.

[0050] Figure 5 It is an illustrative and schematic cross-sectional view showing a part of a welding portion according to an embodiment.

[0051] Figure 6 This is a graph showing experimental results of welding using a combination of the power density of the first laser beam and the power density of the second laser beam generated by the laser welding device of the first embodiment.

[0052] Figure 7 This is a graph showing experimental results of welding using combinations of the width of the weld portion and the second spot diameter when irradiating with the first laser beam generated by the laser welding device of the first embodiment alone.

[0053] Figure 8 This is a graph showing the correlation between the output ratio, which is the ratio of the power of the second laser beam to the power of the first laser beam generated by the laser welding device according to the embodiment, and the spatter suppression rate.

[0054] Figure 9 1 is an illustrative and schematic cross-sectional view of a weld portion according to an embodiment, and is a cross-sectional view taken along a scanning direction and perpendicular to a surface.

[0055] Figure 10 It is used as a reference example to Figure 9 This is an illustrative and schematic cross-sectional view of a welded portion formed by irradiating a single first laser beam with the same power, and is a cross-sectional view taken along a scanning direction and perpendicular to the surface.

[0056] Figure 11 yes Figure 9 An enlarged view of a portion of .

[0057] Figure 12 This is an explanatory diagram showing a case where a first reference line is applied to one position in a cross section of a weld portion according to an embodiment.

[0058] Figure 13 This is an explanatory diagram showing a case where a second reference line is applied to one position in a cross section of a weld portion according to an embodiment.

[0059] Figure 14 This is an exemplary schematic configuration diagram of a laser welding device according to a second embodiment.

[0060] Figure 15 This is an explanatory diagram showing the concept of the principle of the diffractive optical element included in the laser welding device according to the second embodiment.

[0061] Figure 16 This is an exemplary schematic configuration diagram of a laser welding device according to a third embodiment.

[0062] Figure 17 This is an exemplary schematic configuration diagram of a laser welding device according to a fourth embodiment.

[0063] Figure 18 This is an exemplary schematic configuration diagram of a laser welding system according to a fifth embodiment.

[0064] Figure 19 This is an exemplary schematic configuration diagram of a laser welding system according to a sixth embodiment.

[0065] Figure 20 This is an exemplary schematic configuration diagram of a laser welding device according to a seventh embodiment.

[0066] Figure 21 This is a schematic diagram showing an example of a laser beam (spot) formed on the surface of a workpiece by the laser welding apparatus according to the seventh embodiment.

[0067] Figure 22 This is a schematic diagram showing an example of a laser beam (spot) formed on the surface of a workpiece by the laser welding apparatus according to the seventh embodiment.

[0068] Figure 23 This is a schematic diagram showing an example of a laser beam (spot) formed on the surface of a workpiece by the laser welding apparatus according to the seventh embodiment.

[0069] Figure 24 This is an exemplary schematic configuration diagram of a laser welding device according to an eighth embodiment.

[0070] Figure 25 This is an exemplary schematic configuration diagram of a laser welding device according to a ninth embodiment.

[0071] Figure 26 This is a schematic diagram showing an example of a laser beam (spot) formed on the surface of a workpiece by the laser welding apparatus according to the embodiment.

[0072] Figure 27 It is an illustrative and schematic cross-sectional view of a weld portion according to an embodiment, taken along a scanning direction and perpendicular to a surface, and is a cross-sectional view of a front end portion of the weld portion in the scanning direction.

[0073] Figure 28 It is used as a reference example to Figure 27 This is an illustrative and schematic cross-sectional view of a weld portion formed by irradiating a single first laser with the same power at a cross section along the scanning direction and perpendicular to the surface, and is a cross-sectional view of the front end portion of the weld portion in the scanning direction. DETAILED DESCRIPTION

[0074] The following discloses exemplary embodiments of the present invention. The structures of the embodiments shown below and the functions and results (effects) brought about by the structures are merely examples. The present invention can also be implemented using structures other than those disclosed in the following embodiments. In addition, according to the present invention, at least one of the various effects (including derived effects) obtained by the structures can be obtained.

[0075] The embodiments shown below have the same structure. Therefore, according to the structure of each embodiment, the same function and effect based on the same structure can be obtained. In addition, below, there is a situation where the same reference numerals are marked on these same structures and repeated descriptions are omitted.

[0076] In each figure, the X direction is indicated by arrow X, the Y direction is indicated by arrow Y, and the Z direction is indicated by arrow Z. The X, Y, and Z directions intersect and are orthogonal to each other. The Z direction is the normal direction of the surface Wa (processing surface) of the workpiece W.

[0077] In addition, in this specification, ordinal numbers are used for the purpose of distinguishing parts, components, locations, lasers, directions, etc., and do not indicate priority or order.

[0078] [First embodiment]

[0079] Figure 1 FIG. 1 is a schematic structural diagram of the laser welding device 100 according to the first embodiment. Figure 1 As shown, the laser welding device 100 includes a laser device 111 , a laser device 112 , an optical head 120 , and an optical fiber 130 .

[0080] Laser devices 111 and 112 each include a laser oscillator and, as an example, are configured to output a laser beam with a power of several kW. Alternatively, laser devices 111 and 112 may include, for example, multiple semiconductor laser elements internally and be configured to output a multi-mode laser beam with a power of several kW as the combined output of the multiple semiconductor laser elements. Laser devices 111 and 112 may also include various laser sources such as fiber lasers, YAG lasers, and disk lasers.

[0081] The laser device 111 outputs a first laser beam having a wavelength of 800 nm to 1200 nm. The laser device 111 is an example of a first laser device. The laser oscillator included in the laser device 111 is an example of a first laser oscillator.

[0082] On the other hand, laser device 112 outputs a second laser beam having a wavelength of 500 nm or less. Laser device 112 is an example of a second laser beam. Laser device 112 preferably outputs a second laser beam having a wavelength of 400 nm or more and 500 nm or less. The laser oscillator included in laser device 112 is an example of a second laser beam oscillator.

[0083] The optical fiber 130 guides the laser beams output from the laser devices 111 and 112 to the optical head 120 .

[0084] The optical head 120 is an optical device for irradiating the laser light input from the laser devices 111 and 112 toward the processing object W. The optical head 120 includes a collimating lens 121, a condensing lens 122, a reflecting mirror 123, and an optical filter 124. The collimating lens 121, the condensing lens 122, the reflecting mirror 123, and the optical filter 124 can also be referred to as optical components.

[0085] The optical head 120 is configured to be able to change its relative position to the object W in order to irradiate the surface Wa of the object W with the laser light L while scanning the laser light L. The relative movement of the optical head 120 and the object W can be achieved by moving the optical head 120, moving the object W, or moving both the optical head 120 and the object W.

[0086] Note that the optical head 120 may be configured to include a galvanic scanner (not shown) or the like, thereby being capable of scanning the laser light L on the surface Wa.

[0087] The collimating lenses 121 (121-1, 121-2) collimate the laser beams input via the optical fiber 130. The collimated laser beams become parallel beams.

[0088] The reflector 123 reflects the first laser beam, which has been parallelized by the collimating lens 121-1. The first laser beam reflected by the reflector 123 travels in the opposite direction of the Z direction toward the filter 124. It should be noted that in a configuration in which the first laser beam is input to the optical head 120 so as to travel in the opposite direction of the Z direction, the reflector 123 is unnecessary.

[0089] Filter 124 is a high-pass filter that transmits the first laser beam and reflects the second laser beam, preventing it from transmitting. The first laser beam passes through filter 124 and travels in the opposite direction of the Z direction toward condenser lens 122. Meanwhile, filter 124 reflects the second laser beam, which has been parallelized by collimating lens 121-2. The second laser beam, reflected by filter 124, travels in the opposite direction of the Z direction toward condenser lens 122.

[0090] The condenser lens 122 condenses the first laser beam and the second laser beam, which are parallel light, and irradiates the object W as laser light L (output light). The object W is an example of a metal member.

[0091] Irradiation with the laser light L forms a weld 14 on the workpiece W. The weld 14 extends from the front surface Wa toward the back surface Wb and extends linearly in the scanning direction SD along the front surface Wa. The front surface Wa is an example of a first surface, and the back surface Wb is an example of a second surface.

[0092] Figure 2 Schematic diagram showing the beam (spot) of the laser light L irradiated onto the surface Wa of the object W. Figure 2 As shown, on surface Wa, the beam of laser light L is formed as follows: beam B1 of the first laser beam overlaps beam B2 of the second laser beam, beam B2 is larger (wider) than beam B1, and outer edge B2a of beam B2 surrounds outer edge B1a of beam B1. On surface Wa, beam B1 is an example of a first light spot, and beam B2 is an example of a second light spot.

[0093] Figure 2 The arrow SD shown in FIG. Figure 2 As shown, the beam of laser light L has a point-symmetric shape with respect to the center point C. Therefore, the shape of the beam of laser light L (spot) is the same in any scanning direction SD. Therefore, when a moving mechanism is provided for relatively moving the optical head 120 and the object W to scan the surface Wa with laser light L, the moving mechanism only needs to have a mechanism capable of relative translation, and the mechanism capable of relative rotation may be omitted.

[0094] The workpiece W can be made of a metal material with relatively high thermal conductivity. Examples of such metal materials include copper-based metals, aluminum-based metals, nickel-based metals, iron-based metals, and titanium-based metals. Specifically, they include copper, copper alloys, aluminum, aluminum alloys, tin, nickel, nickel alloys, iron, stainless steel, titanium, and titanium alloys. The workpiece W is an example of a metal component.

[0095] [Wavelength, light absorptivity, and melting state]

[0096] Here, the light absorptivity of metal materials will be described. Figure 3 Graph showing the absorptivity of each metal material to light of the wavelength of the irradiated laser light L. Figure 3 The horizontal axis of the graph is wavelength and the vertical axis is absorbance. Figure 3 , the relationship between wavelength and absorptivity is shown for aluminum (Al), copper (Cu), gold (Au), nickel (Ni), silver (Ag), tantalum (Ta), and titanium (Ti).

[0097] Although the properties vary depending on the material, Figure 3 The metals shown in the figure show that the absorption rate of energy is higher when using blue or green laser light (second laser light) than when using conventional infrared (IR) laser light (first laser light). This characteristic is particularly pronounced in copper (Cu) and gold (Au).

[0098] When laser light is irradiated onto an object W with a relatively low absorption rate at the wavelength being used, most of the light energy is reflected, preventing it from affecting the object W as heat. Therefore, to achieve a sufficiently deep melt zone, a relatively high power must be applied. In this case, the center of the beam is rapidly injected with energy, causing sublimation and forming a keyhole.

[0099] On the other hand, when laser light is irradiated onto an object W having a relatively high absorption rate at the wavelength being used, most of the input energy is absorbed by the object W and converted into heat. This means that excessive power need not be applied, resulting in heat-conductive melting without the formation of pinholes.

[0100] In this embodiment, the wavelength of the first laser beam, the wavelength of the second laser beam, and the material of the object W are selected so that the absorption rate of the object W to the second laser beam is higher than the absorption rate of the first laser beam. Figure 2 In the case of the scanning direction SD1, under the scanning effect of the laser spot L, the second laser beam B2 is first used to scan the Figure 2 The second laser beam is irradiated onto the welded portion of the workpiece W (hereinafter referred to as the welded portion) from an area B2f in front of the scanning direction SD. Thereafter, the welded portion is irradiated with the first laser beam B1, and then the welded portion is irradiated again with the second laser beam from an area B2b located behind the scanning direction SD1 of the second laser beam B2.

[0101] Therefore, in the welded area, a heat-conducting melt zone is first generated by irradiation with the second laser beam, which has a higher absorptivity, in region B2f. Subsequently, a deeper, pinhole-shaped melt zone is generated in the welded area by irradiation with the first laser beam. In this case, since a heat-conducting melt zone is already formed in the welded area, a melt zone of the desired depth can be formed using a lower-power first laser beam than would be possible without this heat-conducting melt zone. Furthermore, the melt state of the welded area is then altered by irradiation with the second laser beam, which has a higher absorptivity, in region B2b. From this perspective, the wavelength of the second laser beam is preferably set to 550nm or less, and more preferably to 500nm or less.

[0102] In addition, the inventors have confirmed through experimental research that Figure 2 Welding performed by irradiation with the laser beam L can reduce welding defects. This is presumably because the workpiece W is preheated by the region B2f of the beam B2 before the beam B1 arrives, thereby further stabilizing the molten pool of the workpiece W formed by the beams B2 and B1.

[0103] [Welding method]

[0104] In welding using the laser welding apparatus 100, the workpiece W is first positioned so that the surface Wa of the workpiece W is irradiated with laser light L. Then, while the laser light L, including the beams B1 and B2, is irradiating the surface Wa, the laser light L and the workpiece W are moved relative to each other. As a result, the laser light L is irradiated onto the surface Wa while moving (scanning) along the scanning direction SD. The portion irradiated with the laser light L melts and then solidifies as the temperature decreases, thereby completing the welding of the workpiece W.

[0105] [Cross-section of welded portion]

[0106] Figure 4 1 is a cross-sectional view of a weld portion 14 formed on a workpiece W. Figure 4 It is a cross-sectional view perpendicular to the scanning direction SD (X direction) and along the thickness direction (Z direction). Figure 4 It extends in a direction perpendicular to the paper surface. Figure 4 The figure shows a cross section of a weld 14 formed on a copper plate W having a thickness of 2 mm. It can be inferred that the shape of the weld 14 formed by a plurality of plate-shaped metal materials stacked in the thickness direction (Z direction) is roughly the same as the shape of the weld formed by a single metal material of the same thickness.

[0107] like Figure 4 As shown, weld 14 includes weld metal 14a extending from surface Wa in the opposite direction to the Z direction, and a heat-affected zone 14b located around weld metal 14a. Weld metal 14a is a portion that is melted and then solidified by irradiation with laser light L. Weld metal 14a can also be referred to as a melted and solidified portion. Heat-affected zone 14b is a portion of the base material of workpiece W that is affected by heat and remains unmelted.

[0108] The width of the weld metal 14a along the Y direction becomes narrower as it moves away from the surface Wa. That is, the cross section of the weld metal 14a has a tapered shape that becomes thinner in the direction opposite to the Z direction.

[0109] Furthermore, the inventors have found, through detailed analysis of this cross section, that the weld metal 14a includes a first portion 14a1 remote from the surface Wa and a second portion 14a2 between the first portion 14a1 and the surface Wa.

[0110] The first portion 14a1 is formed by pinhole-shaped melting caused by irradiation with the first laser beam, while the second portion 14a2 is formed by melting caused by irradiation with the second laser beam B2 in a region B2b located behind the scanning direction SD1. Analysis using the EBSD method (electron back scattered diffraction pattern) revealed that the grain sizes in the first portion 14a1 and the second portion 14a2 differ. Specifically, in a cross section perpendicular to the X direction (scanning direction SD), the average cross-sectional area of ​​the grains in the second portion 14a2 is larger than the average cross-sectional area of ​​the grains in the first portion 14a1.

[0111] The inventors have confirmed that when only the first laser beam B1 is irradiated onto the welded portion, that is, when the region B2b located behind the surface Wa in the scanning direction SD1 is not irradiated with the beam B2, the second portion 14a2 is not formed, and the first portion 14a1 extends deeply from the surface Wa in the direction opposite to the Z direction. In other words, in this embodiment, it can be inferred that the second portion 14a2 is formed near the surface Wa by irradiation with the region B2b located behind the surface Wa in the scanning direction SD1, and therefore the first portion 14a1 is formed on the opposite side of the surface Wa from the second portion 14a2, in other words, at a position separated from the surface Wa in the direction opposite to the Z direction.

[0112] Figure 5 It is a cross-sectional view showing a part of the weld portion 14 . Figure 5 The grain boundaries obtained by EBSD are shown. Figure 5 In the example, grain A with a grain diameter of 13 [μm] or less is painted black. It should be noted that 13 [μm] is not a threshold value of physical properties, but a threshold value set for the analysis of the experimental results. Figure 5 It is clear that the crystal grains A are more abundant in the first portion 14a1 and less abundant in the second portion 14a2. In other words, the average cross-sectional area of ​​the crystal grains in the second portion 14a2 is larger than the average cross-sectional area of ​​the crystal grains in the first portion 14a1. The inventors have confirmed through experimental analysis that the average cross-sectional area of ​​the crystal grains in the second portion 14a2 is at least 1.8 times the average cross-sectional area of ​​the crystal grains in the first portion 14a1.

[0113] like Figure 5As shown in region I in FIG, relatively small grains A are concentrated at locations separated from the surface Wa in the Z direction, extending elongatedly in the Z direction. Furthermore, analysis at multiple locations at different positions in the X direction (scanning direction SD) confirmed that the region where the grains A are concentrated also extends along the scanning direction SD. Since welding is performed while scanning, it can be inferred that the crystals form in the same morphology along the scanning direction SD.

[0114] In the case where it is difficult to distinguish the first portion 14a1 from the second portion 14a2 based on the appearance or hardness distribution in the cross section, the Figure 4 、 5 The first region Z1 and second region Z2, geometrically determined based on the position and width wb of the weld metal 14a on the surface Wa, are defined as the first portion 14a1 and the second portion 14a2, respectively. As an example, the first region Z1 and the second region Z2 are quadrilateral regions extending in the Z direction with a width wm (constant width in the Y direction) in a cross section perpendicular to the scanning direction SD. The second region Z2 can be defined as a region extending from the surface Wa along the Z direction to a depth d. The first region Z1 can be defined as a region deeper than the depth d, in other words, a region on the opposite side of the surface Wa relative to the depth d. The width wm can be, for example, 1 / 3 of the width wb (average bead width) of the weld metal 14a on the surface Wa, and the depth d (height, thickness) of the second region Z2 can be, for example, 1 / 2 of the width wb. Furthermore, the depth of the first region Z1 can be, for example, three times the depth d of the second region Z2. Through experimental analysis of multiple samples, the inventors confirmed that, under these settings for first and second zones Z1 and Z2, the average cross-sectional area of ​​the grains in the second zone Z2 is greater than the average cross-sectional area of ​​the grains in the first zone Z1 by at least 1.8 times. This relationship between the grain sizes of the first and second zones Z1 and Z2 is considered a key factor in achieving strong weld strength in the workpiece W, and this determination can also serve as evidence of the formation of the first portion 14a1 and the second portion 14a2 in the weld metal 14a through welding.

[0115] Furthermore, the inventors have found through experimental studies that the thickness T of the object W to be processed by laser welding according to this embodiment (see Figure 1 ) is 0.05 [mm] or more and 2.0 [mm] or less, the same results can be obtained.

[0116] [Laser power density]

[0117] Figure 6: is a graph showing experimental results of welding using a combination of the power density Pd1 of the first laser beam and the power density Pd2 of the second laser beam on the surface Wa of the workpiece W. Figure 6 In the table, "○" indicates a very low number of spatters and pores (excellent), "◇" indicates a low number of spatters and pores (good), and "△" indicates a low number of spatters and pores but with some other undesirable conditions, such as large energy loss (acceptable). Here, as an example, "excellent" indicates a case where the number of pores per unit length (e.g., 1 [cm]) of a linear weld is 1 or less, while "good" and "acceptable" indicate a case where the number of pores per unit length of the weld is 2 or more and less than 5. In this experiment, the wavelength of the first laser was 1070 [nm], the output of the first laser was 1.5 [kW], and the wavelength of the second laser was 450 [nm], the output of the second laser was 150 [W].

[0118] according to Figure 6 It was found that the power density of the second laser Pd2 was 0.16 [MW / cm 2 ] and above 1.5[MW / cm 2 ] can suppress the number of sputtering and the number of pores. This is considered to be because the power density Pd2 of the second laser is lower than 0.16 [MW / cm 2 ] (lower limit) is too low, because the light energy absorbed by the copper plate surface is insufficient and the preheating effect cannot be fully obtained. 2 ] (upper limit) is high, the second laser also causes pinhole-type melting.

[0119] [Spot diameter]

[0120] The beam B1 and the beam B2 each have a Gaussian power distribution in the radial direction of a cross section perpendicular to the optical axis direction of the beam. However, the power distribution of the beam B1 and the beam B2 is not limited to the Gaussian shape. Figure 2 Thus, in each figure where each light beam B1 or B2 is represented by a circle, the diameter of the circle representing the light beam B1 or B2 is the beam diameter of the light beam B1 or B2. The beam diameter of each light beam B1 or B2 is defined as the diameter of the circle including the peak value of the light beam and 1 / e of the peak intensity. 2 It should be noted that, although not shown in the figure, in the case of a non-circular beam, the beam perpendicular to the scanning direction SD can be made to have a peak intensity of 1 / e 2 The length of the region with the above-mentioned intensity is defined as the beam diameter. In addition, the beam diameter on the surface Wa of the processing object W is referred to as the spot diameter.

[0121] Figure 7The figure shows the width wb (weld bead width) of the welded portion when the light beam B1 is irradiated alone and the spot diameter D2 (outer diameter, see Figure 2 ) combined welding experimental results. Figure 7 The meaning of the symbols (○, ◇, △) and the standards and Figure 6 In this experiment, the wavelength of the first laser light was 1070 [nm], the output of the first laser light was 1 [kW], and the wavelength of the second laser light was 450 [nm], the output of the second laser light was 400 [W].

[0122] The inventors have found through experimental studies that when the width wb of the weld portion and the spot diameter D2 are in a predetermined relationship when the light beam B1 is irradiated alone, that is, when the following formula (1) is satisfied,

[0123] wb-400<D2<wb+400 (1)

[0124] The number of sputterings can be suppressed.

[0125] Furthermore, it was found that, when the following formula (1A) is satisfied,

[0126] wb-50<D2<wb+50 (1A)

[0127] The number of sputtered objects can be suppressed without causing other inconveniences such as an increase in energy loss.

[0128] [Suppression of Sputtering by the Output Ratio of the First Laser and the Second Laser]

[0129] Figure 8 The graph shows the correlation between the output ratio (Rp = Pw2 / Pw1), which is the ratio of the second laser power (Pw2) to the first laser power (Pw1), and the sputtering suppression rate. Here, the sputtering suppression rate Rs is defined by the following formula (2).

[0130] Rs=1-Nh / Nir (2)

[0131] Here, Nh is the number of sputters generated in a predetermined area when both the first laser and the second laser are irradiated, and Nir is the number of sputters generated in a predetermined area when only the first laser is irradiated at the same power as when Nh is measured. Figure 8 The chart shows the results of multiple experiments at each output ratio. The line segment corresponding to the output ratio represents the range of variation in the sputtering suppression rate for multiple samples (at least three samples) at that output ratio, and the mark represents the median of the sputtering suppression rate for each output ratio.

[0132] like Figure 8As shown, through experimental research by the inventors, it was found that the output ratio Rp is preferably 0.1 or more and less than 0.18 (○), more preferably 0.18 or more and less than 0.3 (◎), and even more preferably 0.3 or more and less than 2 (◎◎).

[0133] [Scanning speed]

[0134] Furthermore, the inventors conducted experiments on multiple samples at different scanning speeds and found that the generation of sputtering and pores varies depending on the scanning speed. Specifically, they found that, from the perspective of reducing the number of sputtering and pores, the scanning speed is preferably 50 [mm / s] or higher, and more preferably 100 [mm / s] or higher.

[0135] [Gap suppression effect]

[0136] Furthermore, the inventors' experimental studies have revealed that welding performed by irradiation with both the first laser beam and the second laser beam reduces the occurrence of voids (porosity) in the weld portion 14 compared to welding performed by irradiation with the first laser beam alone.

[0137] Figure 9 This is a cross-sectional view of the weld 14 formed by irradiation with both the first laser and the second laser, taken along the scanning direction and perpendicular to the surface Wa. Figure 10 It is used as a reference example to Figure 9 A cross-sectional view of the weld 14 formed by irradiating the first laser beam with the same power as in the case of FIG. 1 , along the scanning direction and perpendicular to the surface Wa. Figure 10 The conditions other than the single irradiation of the first laser beam in the example are set to Figure 9 The same situation as the example.

[0138] If the Figure 9 and Figure 10 Comparison shows that welding by irradiation of both the first laser and the second laser ( Figure 9 ), compared with welding by irradiation of the first laser alone ( Figure 10 ), the generation of voids V in the weld portion 14 is reduced.

[0139] [Differences in location due to grain orientation]

[0140] Figure 11 yes Figure 9 The inventors have found through their experimental research that if Figure 11As shown, in the weld 14 formed by irradiation with both the first laser and the second laser, the orientation (longitudinal direction, growth direction) of the crystal grains differs depending on the depth from the surface Wa. This is believed to be due to the different growth conditions of the crystal grains during solidification in the third portion 14a3, which is formed by the pinhole-shaped melting caused by irradiation with the first laser, and the fourth portion 14a4, which is formed by the melting caused by irradiation with the area B2b located behind the scanning direction in the second laser beam B2. Here, the third portion 14a3 is located at a position far from the surface Wa and is equivalent to the first portion 14a1 described above. In addition, the fourth portion 14a4 is located between the third portion 14a3 and the surface Wa and is equivalent to the second portion 14a2 described above.

[0141] In order to numerically represent such a structure, the inventors defined an index representing the orientation (longitudinal direction) of crystal grains in each portion within the weld 14 based on A.2: Cutting method of JIS G 0551:2020.

[0142] Specifically, if Figure 11 As shown in FIG, in the cross-sectional image, two first reference lines R1 and a second reference line R2 are used, including two straight test lines that are orthogonal to each other. Figure 11 In the figure, the first reference line R1 is represented by a solid line, and the second reference line R2 is represented by a dotted line. The first reference line R1 has two mutually orthogonal diameters of the reference circle R0 as straight test lines L11 and L12. One straight test line L11 extends in the X direction (scanning direction) along the surface Wa, and the other straight test line L12 extends in the Z direction orthogonal to the surface Wa. In addition, the second reference line R2 has two mutually orthogonal diameters of the same reference circle R0 as the first reference line R1 as straight test lines L21 and L22. One straight test line L21 extends in a direction between the X direction and the Z direction, and the other straight test line L22 extends in a direction between the opposite direction of the X direction and the Z direction, or between the opposite direction of the Z direction and the X direction. The angle difference between the straight test lines L11 and L21 is 45° or 135°, and the angle difference between the straight test lines L12 and L22 is 45° or 135°. The length of the diameter of the reference circle R0, that is, the lengths of the straight test lines L11, L12, L21, and L22 is, for example, a length corresponding to 200 [μm] (an example of a predetermined length), but can be appropriately set according to the size of the crystal grains.

[0143] Then, at each point P in the weld portion 14 , the first reference line R1 and the second reference line R2 are applied to obtain the first grain boundary number ratio Rb1 and the second grain boundary number ratio Rb2 using the following equations (3-1) and (3-2).

[0144] Rb1=N12 / N11 (3-1)

[0145] Rb2=max(N22 / N21, N21 / N22) (3-2)

[0146] Here, N11 is the number of grains that intersect the linear test line L11, and N12 is the number of grains that intersect the linear test line L12. N21 is the number of grains that intersect the linear test line L21, and N22 is the number of grains that intersect the linear test line L22. The number of grains can also be called the number of grain boundaries. In formula (3-2), when (N22 / N21) is greater than (N21 / N22), max(N22 / N21, N21 / N22) is (N22 / N21), and when (N22 / N21) is less than (N21 / N22), max(N22 / N21, N21 / N22) is (N21 / N22). In actual measurement, the above measurement is performed at any predetermined location or locations, for example, at least 10 locations, in a microscope photograph of an XZ cross section taken at 50x magnification, and the average values ​​thereof can be set as Rb1 and Rb2, respectively. It should be noted that if any of N11, N12, N21, and N22 is zero at a certain point P within the weld 14, the grain boundary count at that point P may not be used to calculate Rb1 and Rb2.

[0147] Figure 12 、 13 This shows a case where the first reference line R1 is applied to a point P in the cross section of the weld portion 14 ( Figure 12 ) and the case where the second reference line R2 is applied ( Figure 13 ) is a schematic diagram of the invention. Figure 12 、 13 As shown, the number of intersections between the grains A (grain boundaries) and the straight test lines L11, L12, L21, and L22 is different. Figure 12 、 13 In the example, the angle difference between the straight test line L21 and the grain A is relatively small, so the grain boundary number N21 is smaller than the other grain boundary numbers N11, N12, and N22. Figure 12 、 13 The point P shown in the example is called the point P where the second grain boundary number ratio Rb2 is higher than the first grain boundary number ratio Rb1. Similarly, in the above definition, at a point P within reference circle R0 where the angular difference between the long side of grain A and the X direction is relatively small, the first grain boundary number ratio Rb1 is relatively high and greater than the second grain boundary number ratio Rb2. Furthermore, at a point P where the angular difference between the long side of grain A and the direction between the X and Z directions (the 45° direction) is relatively small, the second grain boundary number ratio Rb2 is relatively high and greater than the first grain boundary number ratio Rb1.

[0148] The inventors' experimental studies have revealed that the first grain boundary ratio Rb1 at each point P within the fourth portion 14a4 is lower than the first grain boundary ratio Rb1 at each point P within the third portion 14a3. Furthermore, the second grain boundary ratio Rb2 at each point P within the fourth portion 14a4 is higher than the second grain boundary ratio Rb2 at each point P within the third portion 14a3. Furthermore, the first grain boundary ratio Rb1 is higher than the second grain boundary ratio Rb2 at each point P within the third portion 14a3, and the second grain boundary ratio Rb2 is higher than the first grain boundary ratio Rb1 at each point P within the fourth portion 14a4. The presence of such locations within the weld 14 with different first grain boundary ratios Rb1 and second grain boundary ratios Rb2 is considered a key factor in achieving strong weld strength in the workpiece W and can serve as evidence that welding was achieved using both the first and second laser beams.

[0149] Furthermore, experimental studies by the inventors have revealed that welding performed using the laser welding apparatus 100 of this embodiment using irradiation with the first and second laser beams yields excellent results (equivalent to the aforementioned "excellent") even when the arithmetic mean roughness Ra of the surface Wa of the workpiece W is 21 μm or less. These experiments were conducted with arithmetic mean roughness Ra of 21 μm, 8 μm, and 6 μm, and excellent results were achieved in all cases. Conventional laser welding apparatuses sometimes reflect laser light on surfaces Wa that are, for example, near-mirror surfaces, making welding difficult or impossible. In this regard, according to this embodiment, laser light is more efficiently absorbed by the surface Wa. Therefore, even for workpieces W with near-mirror surfaces such as those with arithmetic mean roughness Ra of 21 μm or less, or even lower, such as 8 μm or 6 μm, better welding can be achieved using lower-power laser light.

[0150] As described above, in the welding method of this embodiment, for example, laser light L is irradiated onto the surface Wa so as to relatively move the spot along the surface Wa, thereby welding the workpiece W. The laser light L includes a first laser light having a wavelength of 800 nm to 1200 nm and a second laser light having a wavelength of 550 nm or less.

[0151] In addition, the wavelength of the second laser light is preferably 400 nm or more and 500 nm or less.

[0152] According to such a method, for example, higher-quality welding with fewer welding defects can be performed.

[0153] In addition, in this embodiment, for example, on the surface Wa, the beam B2 of the second laser (the second irradiation area) is wider than the beam B1 of the first laser (the first irradiation area), and the outer edge B2a (the second outer edge) of the beam B2 surrounds the outer edge B1a (the first outer edge) of the beam B1.

[0154] This method can provide a workpiece W having a welded portion 14 with fewer weld defects and higher quality. Advantages include lowering the power of the first laser beam and eliminating the need for relative rotation of the optical head 120 and the workpiece W.

[0155] In this embodiment, the object W is made of, for example, copper, aluminum, nickel, iron, or titanium. Note that the metal material may or may not be conductive.

[0156] The effects brought about by the welding method of this embodiment can be obtained when the workpiece W is made of any of the above-mentioned materials.

[0157] In the present embodiment, for example, on the surface Wa, at least a portion of the second laser beam B2 (second spot) is located ahead of the first laser beam B1 (first spot) in the scanning direction SD.

[0158] In addition, in the present embodiment, for example, on the surface Wa, the beam B1 and the beam B2 at least partially overlap.

[0159] In addition, in the present embodiment, for example, on the surface Wa, the light beam B2 is wider than the light beam B1.

[0160] In addition, in the present embodiment, for example, on the surface Wa, the outer edge B2a (second outer edge) of the light beam B2 surrounds the outer edge B1a (first outer edge) of the light beam B1.

[0161] In this embodiment, for example, the width wb of the weld portion and the spot diameter D2 when the light beam B1 is irradiated alone are determined in such a manner as to satisfy the following formula (1):

[0162] wb-400<D2<wb+400 (1)

[0163] Set the spot diameter D2.

[0164] In the present embodiment, for example, on the surface Wa, the output ratio of the power of the second laser beam to the power of the first laser beam is 0.1 or more and 2 or less.

[0165] As described above, the inventors have confirmed that welding performed by irradiating the surface Wa with a laser beam L that forms beams B1 and B2 in this manner can reduce welding defects. This is presumably because, as described above, the workpiece W is preheated by region B2f of beam B2 before the arrival of beam B1, thereby further stabilizing the molten pool of the workpiece W formed by beams B2 and B1. Therefore, using laser L with these beams B1 and B2, for example, it is possible to perform welding with fewer welding defects and higher quality. Furthermore, by configuring these beams B1 and B2, it is possible to achieve, for example, lower the power of the first laser beam. Furthermore, when beams B1 and B2 are irradiated coaxially, the advantage is that relative rotation of the optical head 120 and the workpiece W is eliminated.

[0166] In addition, the welding metal 14a of the processing object W (metal component) of this embodiment has: a first portion 14a1, which is located at a position separated from the surface Wa (first surface) in the thickness direction (opposite direction of the Z direction); and a second portion 14a2, which is located between the first portion 14a1 and the surface Wa and has a larger average value of the cross-sectional area of ​​the grains than the first portion 14a1.

[0167] In addition, in this embodiment, in the cross section of the weld portion 14 perpendicular to the extension direction (X direction, scanning direction SD), the average cross-sectional area of ​​the grains included in the second portion 14a2 is 1.8 times or more the average cross-sectional area of ​​the grains included in the first portion 14a1.

[0168] As described above, such a welded portion 14 is formed by Figure 2 The first laser beam B1 and the second laser beam B2 are irradiated onto the surface Wa while scanning in the scanning direction SD. Figure 2 Welding performed by irradiation with the laser beam L can reduce welding defects. Therefore, according to the above configuration, for example, a workpiece W (metal component) can be obtained that has a welded portion 14 with fewer welding defects and higher weld quality. Furthermore, according to this embodiment, for example, advantages such as lowering the power of the first laser beam or eliminating the need for relative rotation between the optical head 120 and the workpiece W can be achieved.

[0169] The metal member to be processed W can be applied to various electrical components and electronic devices incorporating these components. Examples of these electrical components include conductors such as terminals, busbars, coils, and battery tabs. Furthermore, electronic devices incorporating these conductors include, for example, motors, battery packs, inverters, and computers.

[0170] [Second embodiment]

[0171] Figure 14 This is a schematic diagram of a laser welding apparatus 100A according to the second embodiment. In this embodiment, the optical head 120 includes a DOE 125 between the collimating lens 121-1 and the reflective mirror 123. Other than this, the laser welding apparatus 100A has the same structure as the laser welding apparatus 100 according to the first embodiment.

[0172] The DOE 125 shapes the shape of the first laser beam B1 (hereinafter referred to as beam shape). Figure 15 As a conceptual example, the DOE 125 includes, for example, a structure in which multiple diffraction gratings 125a with different periods are overlapped. The DOE 125 bends parallel light in a direction influenced by each diffraction grating 125a, or overlaps it, thereby shaping the beam. The DOE 125 can also be called a beam shaper.

[0173] It should be noted that the optical head 120 may also include a beam shaper disposed after the collimating lens 121-2 to adjust the beam shape of the second laser beam, and a beam shaper disposed after the optical filter 124 to adjust the beam shapes of the first and second laser beams. By appropriately shaping the beam shape of the laser beam L using the beam shaper, the occurrence of welding defects can be further suppressed during welding.

[0174] [Third embodiment]

[0175] Figure 16 This is a schematic diagram of a laser welding device 100B according to a third embodiment. In this embodiment, the optical head 120 includes a galvano-scanner 126 between the filter 124 and the condenser lens 122. Other than this, the laser welding device 100B has the same structure as the laser welding device 100 according to the first embodiment.

[0176] The galvano-scanner 126 includes two mirrors 126a and 126b. By controlling the angles of the mirrors 126a and 126b, the irradiation position of the laser light L can be moved and the laser light L can be scanned without moving the optical head 120. The angles of the mirrors 126a and 126b are each changed by, for example, a motor (not shown). This configuration eliminates the need for a mechanism to relatively move the optical head 120 and the workpiece W, resulting in a more compact device.

[0177] [Fourth embodiment]

[0178] Figure 17This is a schematic diagram of a laser welding apparatus 100C according to a fourth embodiment. In this embodiment, the optical head 120 includes a DOE 125 (beam shaper) between the collimating lens 121-2 and the optical filter 124. Other than this, the laser welding apparatus 100C has the same configuration as the laser welding apparatus 100B according to the third embodiment. This configuration achieves the same effects as the third embodiment due to the inclusion of the galvano-scanner 126, as well as the same effects as the second embodiment due to the inclusion of the DOE 125 (beam shaper).

[0179] It should be noted that, in this embodiment, the optical head 120 may also include a beam shaper disposed after the collimating lens 121-1 and adjusting the beam shape of the first laser beam, a beam shaper disposed after the filter 124 and adjusting the beam shapes of the first laser beam and the second laser beam, and the like.

[0180] [Fifth embodiment]

[0181] Figure 18 1 is a schematic configuration diagram of a laser welding system 1000 including the laser welding device 100 according to the first embodiment. Note that the laser welding system 1000 may include laser welding devices 100A to 100C according to other embodiments instead of the laser welding device 100 .

[0182] The laser welding system 1000 includes, in addition to the laser welding device 100 , a main power supply 1001 , sub-power supplies 1002 and 1003 , an integrated controller 1004 , and a cooling mechanism 1005 .

[0183] The main power supply 1001 supplies power to the sub-power supplies 1002 and 1003 . The sub-power supply 1002 supplies power to the laser device 111 , and the sub-power supply 1003 supplies power to the laser device 112 .

[0184] Integrated controller 1004 controls the operation of both laser device 111 and laser device 112. Specifically, it can control the power, oscillation timing, and wavelength of the laser light output by laser devices 111 and 112, and can also control scanning-related operations, such as the relative movement mechanism and the operation of galvano-scanner 126. This allows for integrated and more reliable control of laser device 111 (first laser oscillator) and laser device 112 (second laser oscillator). Integrated controller 1004 is an example of a control unit.

[0185] The cooling mechanism 1005 includes, for example, pipes 1006 through which a refrigerant, such as a coolant, flows. The pipes 1006 are arranged to pass through each of the laser devices 111 and 112 and the optical head 120. The cooling mechanism 1005 can switch the supply and stop of the refrigerant flowing through each pipe 1006, change the flow rate, or adjust the temperature of the refrigerant. This allows the laser devices 111 and 112 and the optical head 120 to be cooled, for example, to stabilize the operation of the laser devices 111 and 112 or to suppress excessive temperature increases in the optical head 120. It should be noted that the operation of the cooling mechanism 1005 can also be controlled by the integrated controller 1004.

[0186] [Sixth embodiment]

[0187] Figure 19 This is a schematic diagram of the structure of a laser welding system 1000A including the laser welding device 100 of the first embodiment. It should be noted that the laser welding system 1000A may also include the laser welding devices 100A to 100C of other embodiments instead of the laser welding device 100. In this embodiment, the laser welding system 1000A has the same structure as the laser welding system 1000 of the fifth embodiment, except that it includes a controller 1004-1 for the laser device 111 and a controller 1004-2 for the laser device 112 instead of the integrated controller 1004. This structure also achieves the same effects as the laser welding system 1000 of the fifth embodiment. Controllers 1004-1 and 1004-2 are examples of control units.

[0188] [Seventh embodiment]

[0189] Figure 20 FIG. 1 is a schematic structural diagram of a laser welding device 100D according to a seventh embodiment. The laser welding device 100D is modified based on the laser welding device 100 according to the first embodiment. Figure 20As shown, in this embodiment, the optical head 120 includes a first section 120-1, a second section 120-2, and a third section 120-3. The first section 120-1 includes a collimating lens 121-1 and a reflector 123. The second section 120-2 includes a collimating lens 121-2, a filter 124, and a condenser lens 122. The third section 120-3 is interposed between the first section 120-1 and the second section 120-2. The first laser beam, reflected by the reflector 123 and output from the first section 120-1, passes through the opening of the third section 120-3, enters the second section 120-2, and then enters the filter 124. In addition, the first portion 120-1, the second portion 120-2, and the third portion 120-3 are each configured to be relatively slidable in a manner such that the optical axis of the laser light output from the first portion 120-1 and input to the second portion 120-2 is shifted in a direction orthogonal to the optical axis (orthogonal to the Z direction) while maintaining the optical axis of the laser light output from the first portion 120-1 and input to the second portion 120-2 in a parallel state. Figure 20In the example, the first portion 120-1 and the third portion 120-3 are configured to be able to slide relative to each other in the X direction or the direction opposite to the X direction without changing their posture relative to the Z direction. In addition, the second portion 120-2 and the third portion 120-3 are configured to be able to slide relative to each other in the Y direction and the direction opposite to the Y direction without changing their posture relative to the Z direction. Specifically, an annular and plate-shaped flange 120a extending in a direction perpendicular to the optical axis direction of the first laser is provided at the outlet of the first laser of the first portion 120-1 and the inlet of the first laser of the second portion 120-2. Furthermore, the third portion 120-3 having an annular and plate-shaped shape extending in a direction perpendicular to the optical axis direction of the first laser is sandwiched between the two flanges 120a. The two flanges 120a and the third portion 120-3 can slide relative to each other along their respective abutting surfaces without changing their posture relative to the Z axis. A guide mechanism (not shown) is provided between the first portion 120-1 and the third portion 120-3 to guide relative sliding in the X direction and to enable fixation at any relative position in the X direction. A guide mechanism (not shown) is provided between the second portion 120-2 and the third portion 120-3 to guide relative sliding in the Y direction and to enable fixation at any relative position in the Y direction. In such a structure, by adjusting the sliding positions of the two guide mechanisms, the optical axis of the first laser beam input to and output from the filter 124 and the optical axis of the second laser beam output from the filter 124 can be shifted in a direction orthogonal to these optical axes. It should be noted that the first portion 120-1 and the laser device 111 and the second portion 120-2 and the laser device 112 are connected by flexible optical fibers 130, so that even if the position of the first portion 120-1 or the second portion 120-2 changes, the laser devices 111 and 112 can be fixed in advance.

[0190] Figures 21-23 FIG. 2 shows an example of laser beams B1 and B2 formed on the surface Wa of the workpiece W by the laser welding device 100D. Figures 21-23 As shown, according to the laser welding device 100D, the relative positions of the beams B1 and B2 can be arbitrarily changed. Figures 21-23In this way, when at least a portion of the light beam B2 (second light spot) is located ahead of the light beam B1 (first light spot) in the scanning direction SD, and when the light beams B1 and B2 are in contact with each other or at least partially overlap, the same effect as in the first embodiment can be obtained based on the preheating effect of the light beam B2. In addition, it was also found that when at least a portion of the light beam B2 is located ahead of the light beam B1 in the scanning direction SD, the light beams B1 and B2 can also be separated by a small distance. It should be noted that Figures 21-23 These are merely examples, and the arrangement of the light beams B1 and B2 obtained by the laser welding device 100D and the sizes of the light beams B1 and B2 are not limited to the following. Figures 21-23 It should be noted that the light beam B2 is located ahead of the light beam B1 in the scanning direction SD, as shown in FIG. Figure 23 As shown, on the surface Wa, at least a portion of the light beam B2 exists in a region ahead of an imaginary straight line VL passing through the leading end of the light beam B1 in the scanning direction SD and perpendicular to the scanning direction SD.

[0191] [Eighth Embodiment]

[0192] Figure 24 FIG. 1 is a schematic structural diagram of a laser welding device 100E according to an eighth embodiment. The laser welding device 100E is modified based on the laser welding device 100B according to the third embodiment. Figure 24 As shown, the laser welding apparatus 100E includes a position adjustment mechanism 140 that variably adjusts the position of the collimating lens 121 in the optical axis direction. The position adjustment mechanism 140 allows the sizes (spot diameters D1 and D2) of the light beams B1 and B2 on the surface Wa of the workpiece W to be appropriately changed. In other words, the position adjustment mechanism 140 can also be referred to as a spot size variable mechanism. It should be noted that the same position adjustment mechanism 140 can also be applied to the condenser lens 122, or to both the collimating lens 121 and the condenser lens 122. Furthermore, it can be applied to the collimating lens 121 and the condenser lens 122 of the laser welding apparatuses 100, 100A, 100C, 100D, and 100F of other embodiments.

[0193] [Ninth embodiment]

[0194] Figure 25 This is a schematic diagram of a laser welding device 100F according to a ninth embodiment. In this embodiment, the optical head 120 includes a first portion 120-1 for irradiating the first laser beam L1 and a second portion 120-2 for irradiating the second laser beam L2, each consisting of a separate main body (housing). This structure also achieves the same functions and effects as the above-mentioned embodiments.

[0195] in addition, Figure 26 An example of the spots of the light beams B1 and B2 formed on the surface Wa of the workpiece W by the laser welding apparatus 100, 100A to 100F according to any of the above-mentioned embodiments is shown. Figure 26 As shown, the spot diameter of the light beam B2 may be substantially the same as the spot diameter of the light beam B1. Although not shown, the spot diameter of the light beam B2 may be smaller than the spot diameter of the light beam B1.

[0196] The above examples illustrate embodiments of the present invention, but the above embodiments are merely examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in various other ways, and can be omitted, replaced, combined, or modified in various ways without departing from the main purpose of the invention. In addition, the specifications of various structures, shapes, and the like (structure, type, direction, model, size, length, width, thickness, height, number, configuration, position, material, etc.) can be appropriately modified for implementation.

[0197] For example, when scanning the laser beam on the object to be processed, the surface area of ​​the molten pool may be adjusted by scanning using known wobbling, weaving, output modulation, and the like.

[0198] Furthermore, the object to be processed may have a relatively thin layer of another metal on the surface of the metal, such as a plated metal plate.

[0199] In addition, the center of the first laser beam and the center of the second laser beam do not necessarily need to coincide with each other and may be offset from each other.

[0200] Alternatively, the first laser beam may be partially located outside the second laser beam.

[0201] [Cross-section of welded portion]

[0202] Figure 27 : is a cross-sectional view of the welding portion 14 of the embodiment along the scanning direction SD and at a cross section perpendicular to the surface Wa, and is a cross-sectional view of the front end portion of the welding portion 14 in the scanning direction SD. Figure 28 It is used as a reference example to Figure 27 The present invention is a cross-sectional view of the weld 14 formed by irradiating the first laser beam with the same power alone, taken along the scanning direction SD and perpendicular to the surface Wa, and is a cross-sectional view of the front end portion of the weld 14 in the scanning direction SD.

[0203] exist Figure 27 、 28 In the cross-sectional view shown, the outline of the molten pool (welded portion 14 ) is visualized by image processing. Figure 27 The molten pool formed in the processing by the hybrid laser irradiating the first laser and the second laser in this embodiment is shown. Figure 28 Compared with the molten pool formed by processing using a fiber laser irradiated with only the first laser, as shown in FIG. Figure 27 As shown by the dotted line frame DL, the tail is long in the rear of the scanning direction SD. Figure 27 As shown in FIG. 1 , the front portion 14f of the molten pool (welded portion 14) of this embodiment extends forward in the scanning direction SD. As a result, the length Lw1 of the molten pool formed in the processing using the hybrid laser in the scanning direction SD (see FIG. 1 ) is reduced. Figure 27 ) is greater than the length Lw2 in the scanning direction SD of the molten pool formed in the processing using the fiber laser (refer to Figure 28 ) is long. That is, in processing using a hybrid laser, the molten pool becomes larger than in processing using a fiber laser. It can be inferred that in the hybrid laser processing of irradiating the first laser and the second laser according to this embodiment, the irradiation of the second laser (blue laser) causes the molten pool to expand and the internal heat convection to be more stabilized, and the expansion of the keyhole opening causes the vapor pressure during evaporation to be more easily dissipated outward. Therefore, compared with irradiation with the first laser alone, a molten pool with suppressed sputtering and a stable state can be obtained.

[0204] Industrial Applicability

[0205] The present invention can be utilized in welding methods, laser welding systems, metal components, electrical components, and electronic equipment.

[0206] Description of Reference Numerals

[0207] 14 welding portion, 14a welding metal, 14a1 first portion, 14a2 second portion, 14a3 third portion, 14a4 fourth portion, 14b heat-affected zone, 14f front portion, 100, 100A to 100F laser welding device, 111 laser device (first laser oscillator), 112 laser device (second laser oscillator), 120 optical head, 120-1 first portion, 120-2 second portion, 120-3 third portion, 120a flange, 121, 121- 1. 121-2 collimating lens, 122 focusing lens, 123 reflecting mirror, 124 filter, 125 DOE (diffraction optical element), 125a diffraction grating, 126 galvano-scanner, 126a, 126b reflecting mirrors, 130 optical fiber, 140 position adjustment mechanism, 1000, 1000A laser welding system, 1001 main power supply, 1002, 1003 auxiliary power supplies, 1004 integrated controller (control unit), 1004-1, 1004-2 controllers (control units), 1005 cooling mechanism, 1006 piping, A grain, B1 beam (first spot), B1a outer edge, B2 beam (second spot), B2a outer edge, B2b region, B2f region, C center point, D1 spot diameter (outer diameter), D2 spot diameter (outer diameter), d depth, I region, L laser, L1 first laser, L2 second laser, L11, L12, L21, L22 straight test lines, Lw1, Lw2 length, N11, N12, N21, N22 grain boundary number, P point, Pd1 (first laser) power density, Pd2 (second laser) power density, R0 reference circle, R1 first reference line, R2 second reference line, SD, SD1 scanning direction, T thickness, V gap (pore), W processing object, Wa surface, Wb back side, wb width (on the surface of weld metal), wm width (first area and second area), X direction, Y direction, Z direction (thickness direction), Z1 first area (first part), Z2 second area (second part).

Claims

1. A welding method for welding a surface of a workpiece by irradiating a laser beam that moves relative to the workpiece in a scanning direction, thereby melting the portion of the workpiece irradiated with the laser beam, wherein: The laser light includes a first laser light having a wavelength of 800 nm to 1200 nm and a second laser light having a wavelength of 550 nm or less. When the width of the weld formed on the surface when only the first laser is irradiated without irradiating the second laser is set as wb, and the outer diameter of the second spot formed on the surface by the second laser when irradiating the first laser and the second laser is set as D2, so as to satisfy the following formula (1), wb-400<D2<wb+400 (1) Set the outer diameter of the second light spot.

2. The welding method according to claim 1, wherein: The wavelength of the second laser light is not less than 400 nm and not more than 500 nm.

3. The welding method according to claim 1 or 2, wherein: The processing object is any one of copper-based metal materials, aluminum-based metal materials, nickel-based metal materials, iron-based metal materials and titanium-based metal materials.

4. The welding method according to claim 1 or 2, wherein: On the surface, at least a portion of a second spot formed on the surface by the second laser light is located ahead of a first spot formed on the surface by the first laser light in the scanning direction.

5. The welding method according to claim 4, wherein: On the surface, the first light spot and the second light spot at least partially overlap.

6. The welding method according to claim 4, wherein: On the surface, the second outer edge of the second light spot surrounds the first outer edge of the first light spot.

7. The welding method according to claim 1 or 2, wherein: On the surface, an output ratio of the power of the second laser beam to the power of the first laser beam is 0.1 or more and 2 or less.

8. The welding method according to claim 1 or 2, wherein: The laser includes a plurality of beams.

9. The welding method according to claim 8, wherein: The plurality of light beams are formed by a beam shaper.

10. The welding method according to claim 1 or 2, wherein: The arithmetic mean roughness of the surface is 21 μm or less.

11. The welding method according to claim 1 or 2, wherein: The scanning speed of the laser on the surface is greater than 50 mm / s.

12. A laser welding system, wherein: The laser welding system has: a first laser oscillator for oscillating a first laser beam having a wavelength of not less than 800 nm and not more than 1200 nm; a second laser oscillator for oscillating a second laser beam having a wavelength of 500 nm or less; an optical head configured to perform welding by irradiating a surface of a workpiece with laser light including the first laser light and the second laser light, thereby melting a portion of the workpiece irradiated with the laser light; a control unit that controls the laser oscillation timing and power of the first laser and the second laser; and a cooling mechanism for cooling the first laser oscillator, the second laser oscillator, and the optical head; The processing object and the laser are configured to be movable relative to each other in a manner such that the laser moves relative to the processing object in a scanning direction. When the width of the weld formed on the surface when only the first laser is irradiated without irradiating the second laser is set as wb, and the outer diameter of the second spot formed on the surface by the second laser when irradiating the first laser and the second laser is set as D2, so as to satisfy the following formula (1), wb-400<D2<wb+400 (1) Set the outer diameter of the second light spot.

13. The laser welding system according to claim 12, wherein: The laser welding system includes a galvano scanner configured to change an emission direction of the laser light so as to move the laser light along the scanning direction on the surface.

14. The laser welding system according to claim 13, wherein: The laser welding system includes a beam shaper that divides the laser light into a plurality of beams.

15. A metal member comprising a first surface, a second surface on the back side of the first surface, and a welding portion extending along the first surface, wherein: The welding portion has: weld metal extending from the first surface toward the second surface; as well as The heat-affected zone is located around the weld metal. The weld metal has: a first portion located at a position separated from the first surface in the thickness direction from the first surface toward the second surface; and a second portion located between the first portion and the first surface, and having a larger average value of the cross-sectional area of ​​the grains in a cross section perpendicular to the extension direction of the weld than the first portion.

16. The metal component according to claim 15, wherein An average value of the cross-sectional area of ​​the crystal grains included in the second portion is 1.8 times or more the average value of the cross-sectional area of ​​the crystal grains included in the first portion.

17. A metal member comprising a first surface, a second surface on the back side of the first surface, and a welding portion extending along the first surface, wherein: The welding portion has: weld metal extending from the first surface toward the second surface; as well as The heat-affected zone is located around the weld metal. When the first grain boundary number ratio is expressed as the following formula (3-1), Rb1=N12 / N11(3-1) Here, Rb1 is the first grain boundary ratio, N11 is the number of grain boundaries intersecting a straight test line of a predetermined length along the first surface in a test cross section perpendicular to the first surface and along the extending direction of the weld portion, and N12 is the number of grain boundaries intersecting a straight test line of the predetermined length extending in a direction perpendicular to the first surface in the test cross section. The weld metal has a third portion located at a position spaced apart from the first surface in a thickness direction from the first surface toward the second surface; and a fourth portion located between the third portion and the first surface, wherein the first grain boundary number ratio is lower than the first grain boundary number ratio of the third portion.

18. A metal member comprising a first surface, a second surface on the back side of the first surface, and a welding portion extending along the first surface, wherein: The welding portion has: weld metal extending from the first surface toward the second surface; and The heat-affected zone is located around the weld metal. When the second grain boundary number ratio is expressed as the following formula (3-2), Rb2=max(N22 / N21, N21 / N22) (3-2) Here, Rb2 is a second grain boundary number ratio, N21 is the number of grain boundaries intersecting a straight test line extending in a first direction between a direction along the first surface and a direction perpendicular to the first surface in a test cross section perpendicular to the first surface and along the extending direction of the weld, N22 is the number of grain boundaries intersecting a straight test line extending in a second direction perpendicular to the first direction and having the prescribed length in the test cross section, and max(N22 / N21, N21 / N22) is N22 / N21 when N22 / N21 is N21 / N22 or greater, and is N21 / N22 when N22 / N21 is less than N21 / N22. The weld metal has a third portion located at a position spaced apart from the first surface in a thickness direction from the first surface toward the second surface; and a fourth portion located between the third portion and the first surface, wherein the second grain boundary number ratio is higher than the second grain boundary number ratio of the third portion.

19. A metal member comprising a first surface, a second surface on the back side of the first surface, and a welding portion extending along the first surface, wherein: The welding portion has: weld metal extending from the first surface toward the second surface; and The heat-affected zone is located around the weld metal. When the first grain boundary number ratio is expressed as the following formula (3-1), Rb1=N12 / N11(3-1) Here, Rb1 is the first grain boundary ratio, N11 is the number of grain boundaries intersecting a straight test line of a predetermined length along the first surface in a test cross section perpendicular to the first surface and along the extending direction of the weld portion, and N12 is the number of grain boundaries intersecting a straight test line of the predetermined length extending in a direction perpendicular to the first surface in the test cross section. When the second grain boundary number ratio Rb2 is expressed as the following formula (3-2), Rb2=max(N22 / N21, N21 / N22) (3-2) Here, Rb2 is a second grain boundary number ratio, N21 is the number of grain boundaries intersecting a straight test line extending in a first direction between a direction along the first surface and a direction perpendicular to the first surface in a test cross section perpendicular to the first surface and along the extending direction of the weld, N22 is the number of grain boundaries intersecting a straight test line extending in a second direction perpendicular to the first direction and having the prescribed length in the test cross section, and max(N22 / N21, N21 / N22) is N22 / N21 when N22 / N21 is N21 / N22 or greater, and is N21 / N22 when N22 / N21 is less than N21 / N22. The weld metal has a third portion located at a position spaced apart from the first surface in a thickness direction from the first surface toward the second surface; and a fourth portion located between the third portion and the first surface, wherein the first grain boundary number ratio of the fourth portion is lower than the first grain boundary number ratio of the third portion and the second grain boundary number ratio of the fourth portion is higher than the second grain boundary number ratio of the third portion.

20. An electrical component, wherein: The electrical component includes the metal member according to any one of claims 15 to 19 as a conductor.

21. An electronic device, wherein: The electronic device includes the metal member according to any one of claims 15 to 19 as a conductor.

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