Welding method and welding equipment

Abstract

The welding method comprises overlapping plated sheet materials having a plating layer formed on the surface of a base material to form a workpiece, placing the workpiece in an area to be irradiated with laser light, irradiating the surface of the workpiece with the multiple beams at positions dispersed so that the centers of the multiple beams do not overlap within a predetermined area on the surface, moving the multiple beams relative to the workpiece while irradiating, sweeping the multiple beams over the workpiece to melt the irradiated portions of the workpiece and weld it, and setting the irradiation distance of the multiple beams so that the molten pools formed on the workpiece by the irradiation of each of the multiple beams overlap each other.

Description

[Technical field]

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

[0002] Laser welding is known as one of the techniques for welding workpieces made of metal materials such as iron and copper. Laser welding is a welding method in which a laser beam is irradiated onto the welded portion of the workpiece, and the welded portion is melted by the energy of the laser beam. A pool of molten metal material called a molten pool is formed at the welded portion irradiated with the laser beam, and the weld is then completed by solidifying the molten pool.

[0003] In some cases, lap welding is performed in which two sheets of metal are overlapped to form a workpiece, and the sheets are joined together by welding. In this case, if the sheet is a plated sheet having a plating layer formed on the surface of the base material, such as a zinc-plated steel sheet, the plating layer evaporates and becomes gas when the steel melts. This occurs when the boiling point of the plating layer is lower than the melting point of the base material. The gas thus generated may disturb the molten pool and deteriorate the flatness of the surface of the molten pool. Such deterioration of the flatness of the surface of the molten pool can cause welding defects.

[0004] In order to solve the problem of poor melting as described above, a technique has been disclosed in which a protrusion is formed on a first plated steel sheet, and when the first and second plated steel sheets are overlapped, the top of the protrusion is abutted against the surface of the second plated steel sheet and a laser beam is irradiated onto the first plated steel sheet from the opposite side to the top of the protrusion, thereby welding the first and second plated steel sheets together (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 07-155974 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned technique has a problem in that an additional process for forming a protrusion on one of the plated steel sheets is required.

[0007] The present invention has been made in consideration of the above, and an object of the present invention is to provide a welding method and welding apparatus that can suppress the occurrence of welding defects during lap welding of plated sheet materials. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, a welding method according to one embodiment of the present invention comprises overlapping plated sheet materials having a plating layer formed on the surface of a base material to form a workpiece, placing the workpiece in an area to be irradiated with laser light, irradiating the surface of the workpiece with the multiple beams by dispersing their positions so that the centers of the multiple beams do not overlap within a predetermined area on the surface, moving the multiple beams relative to the workpiece while irradiating, and melting and welding the irradiated portions of the workpiece while sweeping the multiple beams over the workpiece, and setting the irradiation distance of the multiple beams so that molten pools formed on the workpiece by the irradiation of each of the multiple beams overlap each other.

[0009] In a welding method according to one aspect of the present invention, the multiple beams are irradiated at dispersed irradiation positions so that gas produced by evaporation of the plating layer located inside the object to be processed is discharged from the surface of a molten pool formed by melting the object to be processed.

[0010] In a welding method according to one aspect of the present invention, the irradiation positions of the multiple beams are dispersed and irradiated so that welding defects caused by the gas are kept below an acceptable level.

[0011] In a welding method according to one aspect of the present invention, the multiple beams are arranged so that the shape of a predetermined area to which the multiple beams are irradiated gradually increases in width in a direction perpendicular to the sweep direction.

[0012] In a welding method according to one aspect of the present invention, the plurality of beams have approximately equal peak powers.

[0013] In a welding method according to one aspect of the present invention, the multiple beams are irradiated so that molten pools formed on the workpiece by irradiation of each of the multiple beams overlap each other.

[0014] In a welding method according to one aspect of the present invention, the plurality of beams are spaced apart from one another by a distance equal to or less than six times the beam diameter.

[0015] In a welding method according to one aspect of the present invention, the beam diameter of each of the plurality of beams is 600 μm or less.

[0016] In a welding method according to one aspect of the present invention, the plurality of beams are spaced apart from one another by a distance of 3600 μm or less.

[0017] A welding apparatus according to one embodiment of the present invention includes a laser device, a beam shaper that divides laser light output from the laser device into multiple beams, and an optical head that irradiates the multiple beams toward a workpiece and melts and welds the irradiated portions of the workpiece, the workpiece being composed of overlapping plated sheet material having a plating layer formed on the surface of a base material, the optical head is configured so that the multiple beams and the workpiece are movable relative to each other, and melts and welds the workpiece while sweeping the multiple beams over the workpiece, and the beam shaper divides the laser light so that the optical head can irradiate the multiple beams by dispersing their positions relative to the surface of the workpiece so that the centers of the multiple beams do not overlap within a predetermined area on the surface.

[0018] A welding device according to one aspect of the present invention arranges the multiple beams so that the shape of a predetermined area onto which the multiple beams are irradiated gradually increases in width in a direction perpendicular to the sweep direction.

[0019] In the welding device according to one aspect of the present invention, the plurality of beams have approximately equal peak powers.

[0020] A welding device according to one aspect of the present invention irradiates the multiple beams so that molten pools formed on the workpiece by irradiation of each of the multiple beams overlap each other.

[0021] In a welding device according to one aspect of the present invention, the distance between the plurality of beams is equal to or less than six times the beam diameter.

[0022] In a welding device according to one aspect of the present invention, the beam diameter of each of the plurality of beams is 600 μm or less.

[0023] In a welding device according to one aspect of the present invention, the plurality of beams are spaced apart from one another by a distance of 3600 μm or less. Effect of the Invention

[0024] According to the present invention, it is possible to suppress the occurrence of welding defects during lap welding of plated sheet materials. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a laser welding device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram illustrating a diffractive optical element. [Diagram 3] FIG. 3 is a schematic diagram illustrating a plurality of beams. [Figure 4] FIG. 4 is a schematic diagram illustrating laser light consisting of a single Gaussian beam. [Diagram 5] FIG. 5 is a schematic diagram illustrating a state in which the laser beam in FIG. 4 melts the processing object. [Figure 6] FIG. 6 is a schematic diagram illustrating a state in which the laser beam in FIG. 3 melts the processing object. [Figure 7] FIG. 7 is a schematic diagram illustrating a molten pool formed by a laser beam. [Figure 8] FIG. 8 is a schematic diagram illustrating a molten pool formed by a laser beam. [Figure 9A] FIG. 9A is a schematic diagram illustrating an example in which a diffractive optical element splits a laser beam into a plurality of beams. [Figure 9B] FIG. 9B is a schematic diagram illustrating an example in which a diffractive optical element splits a laser beam into a plurality of beams. [Figure 9C] FIG. 9C is a schematic diagram illustrating an example in which a diffractive optical element splits a laser beam into a plurality of beams. [Figure 9D] FIG. 9D is a schematic diagram illustrating an example in which a diffractive optical element splits a laser beam into a plurality of beams. [Figure 9E] FIG. 9E is a schematic diagram illustrating an example in which a diffractive optical element splits a laser beam into a plurality of beams. [Figure 9F] FIG. 9F is a schematic diagram illustrating an example in which a diffractive optical element splits a laser beam into a plurality of beams. [Figure 9G] FIG. 9G is a schematic diagram illustrating an example in which a diffractive optical element splits a laser beam into a plurality of beams. [Figure 9H] FIG. 9H is a schematic diagram illustrating an example in which a diffractive optical element splits a laser beam into a plurality of beams. [Figure 10] FIG. 10 is a schematic diagram illustrating an example of beam overlap. [Figure 11A] FIG. 11A is a photograph of the surface of a galvanized steel sheet according to a comparative example. [Figure 11B] FIG. 11B is a photograph of the rear surface of a galvanized steel sheet welded by a welding method of a comparative example. [Figure 11C] FIG. 11C is a photograph showing a cross section of a welded galvanized steel sheet of a comparative example. [Figure 12A]FIG. 12A is a photograph of the surface of the galvanized steel sheet by welding in Example 1. [Figure 12B] FIG. 12B is a photograph of the rear surface of the welded galvanized steel sheet of Example 1. [Figure 13A] FIG. 13A is a photograph of the surface of the galvanized steel sheet by welding in Example 2. [Figure 13B] FIG. 13B is a photograph showing a cross section of the welded galvanized steel sheet of Example 2. [Figure 14A] FIG. 14A is a photograph of the surface of the galvanized steel sheet by welding in Example 3. [Figure 14B] FIG. 14B is a photograph showing a cross section of the welded galvanized steel sheet of Example 3. [Figure 15A] FIG. 15A is a photograph of the surface of the galvanized steel sheet by welding in Example 4. [Figure 15B] FIG. 15B is a photograph showing a cross section of the welded galvanized steel sheet of Example 4. [Figure 16] FIG. 16 is a schematic diagram showing a schematic configuration of a laser welding device according to the second embodiment. [Figure 17] FIG. 17 is a schematic diagram showing a schematic configuration of a laser welding device according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiment described below. In addition, in the description of the drawings, the same or corresponding elements are appropriately designated by the same reference numerals.

[0027] (Embodiment 1) 1 is a schematic diagram showing a schematic configuration of a laser welding apparatus according to embodiment 1. The laser welding apparatus 100 includes a laser device 110, an optical head 120, and an optical fiber 130 that connects the laser device 110 and the optical head 120. The workpiece W is formed by overlapping two galvanized steel sheets W1 and W2, which are plated sheet materials.

[0028] The laser device 110 is configured to be able to output laser light with a power of, for example, several kW. For example, the laser device 110 may be configured to include a plurality of semiconductor laser elements therein, and to be able to output multi-mode laser light with a power of several kW as the total output of the plurality of semiconductor laser elements. The laser device 110 may also include various laser light sources such as a fiber laser, a YAG laser, and a disk laser. The optical fiber 130 guides the laser light output from the laser device 110 and inputs it to the optical head 120.

[0029] The optical head 120 is an optical device for irradiating the laser light input from the laser device 110 toward the workpiece W. The optical head 120 includes a collimator lens 121 and a condenser lens 122. The collimator lens 121 is an optical system for collimating the input laser light. The condenser lens 122 is an optical system for condensing the collimated laser light and irradiating the workpiece W as the laser light L.

[0030] The optical head 120 is configured to be able to change its relative position with respect to the workpiece W in order to sweep the laser light L while irradiating the laser light L on the workpiece W. Methods for changing the relative position with respect to the workpiece W include moving the optical head 120 itself and moving the workpiece W. That is, the optical head 120 may be configured to be able to sweep the laser light L with respect to a fixed workpiece W. Alternatively, the irradiation position of the laser light L from the optical head 120 may be fixed, and the workpiece W may be held movably with respect to the fixed laser light L.

[0031] The optical head 120 includes a diffractive optical element 123 as a beam shaper disposed between a collimator lens 121 and a condenser lens 122. The diffractive optical element 123 here is an integral configuration of a plurality of diffraction gratings 123a with different periods, as conceptually shown in Fig. 2. The diffractive optical element 123 can shape the beam by bending the input laser light in a direction influenced by each diffraction grating or by overlapping the light.

[0032] The diffractive optical element 123 splits the laser light input from the collimator lens 121 into multiple beams. Specifically, the diffractive optical element 123 splits the laser light so that the optical head 120 can irradiate the surface of the workpiece W with multiple beams by dispersing the positions of the multiple beams so that the centers of the multiple beams do not overlap within a predetermined area on the surface. Note that, here, a case will be described in which the diffractive optical element 123 is configured to split the laser light input from the collimator lens 121 into multiple beams with equal peak power, but the powers of the beams may be different from each other.

[0033] FIG. 3 is a schematic diagram for explaining a plurality of beams. The laser light L includes a plurality of beams B split by the diffractive optical element 123. The diameter of the circle representing the beam B is the beam diameter. A circular area A is a predetermined area on the surface of the processing object W, and a plurality of (13 in this embodiment) beams B are irradiated to the processing object W in a state where the positions are distributed so that the centers do not overlap within the area A. The area A has a shape corresponding to the shape of the outer contour of the arrangement of the beams B. In addition, two adjacent beams B partially overlap each other. As shown by the dashed line, each beam B has a power distribution of, for example, a Gaussian shape in the radial direction of the beam cross section. However, when the power distributions of all the beams B are superimposed, as shown in FIG. 3, a flat-top power distribution without a protruding sharp peak is obtained.

[0034] The power distribution of the beam B is not limited to a Gaussian shape. The beam diameter of the beam B includes the peak and is 1 / e 2For non-circular beams, this is defined as the diameter of the region with an intensity equal to or greater than the peak intensity in the direction perpendicular to the sweep direction. 2 The length of the region where the intensity is equal to or greater than this is defined as the beam diameter.

[0035] When welding is performed using the laser welding device 100, first, the workpiece W is placed in an area to be irradiated with the laser light L. Next, while the laser light L including the multiple beams B split by the diffractive optical element 123 is irradiated onto the workpiece W, the laser light L and the workpiece W are moved relative to each other to sweep the laser light L, and the workpiece W at the portion irradiated with the laser light L is melted and welded.

[0036] Here, a state in which the laser light irradiated to the surface of the workpiece W melts the workpiece W during welding will be described. First, for comparison, a case will be described in which the laser light irradiated to the surface of the workpiece W is laser light L10 consisting of a single beam B. As described above, the single beam B is, for example, a Gaussian beam having a power distribution of a Gaussian shape in the radial direction of the beam cross section.

[0037] FIG. 5 is a schematic diagram illustrating a state in which the laser beam L10 in FIG. 4 melts the workpiece W, and is a cross-sectional view seen from a direction perpendicular to the sweep direction SD of the laser beam L10.

[0038] The processing object W is composed of two galvanized steel sheets W1 and W2 stacked on top of each other. The galvanized steel sheet W1 is a base material steel sheet W11 on which galvanized layers W12 and W13 are formed on both surfaces. The galvanized steel sheet W2 is a base material steel sheet W21 on which galvanized layers W22 and W23 are formed on both surfaces. The galvanized layers W13 and W22 are located inside the processing object W.

[0039] When the surface of the workpiece W is irradiated with the laser beam L10 and swept in the sweep direction SD, the laser beam L10 melts the workpiece W, forming a molten pool WP10. Here, the laser beam L10 is composed of a single beam B, which is a Gaussian beam, and its power distribution has a relatively sharp peak. Therefore, immediately after the laser beam L10 is irradiated, the temperature rises rapidly in a relatively narrow region of the surface of the workpiece W, melting occurs, and the molten pool WP10 is formed so as to become suddenly deeper. Therefore, the zinc plating layers W13 and W22, which are sandwiched between the steel plates W11 and W21 and have a boiling point lower than the melting point of the steel plates W11 and W21, evaporate and gasify rapidly, sometimes explosively, in a short time. The generated gas G This may disturb the molten pool WP10 and deteriorate the flatness of the surface of the molten pool WP10. Such deterioration of the flatness of the surface of the molten pool WP10 may cause welding defects such as abnormal shapes of weld beads. In addition, since melting occurs suddenly in a relatively narrow area, the gas generated suddenly G The surface area of ​​the molten pool WP10 is relatively small compared to the amount of gas. G In some cases, the metal may not be sufficiently discharged from the surface of the molten pool WP10 to the outside, which may result in poor welding, such as air bubbles remaining after the molten pool WP10 solidifies.

[0040] 6 is a schematic diagram for explaining a state in which the laser beam L in FIG. 3 melts the workpiece W, and is a cross-sectional view seen from a direction perpendicular to the sweep direction SD of the laser beam L. In FIG.

[0041] When the surface of the workpiece W is irradiated with the laser light L and swept in the sweep direction SD, the laser light L melts the workpiece W and a molten pool WP is formed. Here, the laser light L is composed of multiple beams B, and each beam B is irradiated to the area A of the workpiece W with its position dispersed within a relatively wide area A. Therefore, the diameter D of the laser light L is relatively large, reflecting the dispersion of the irradiation position of the beam B. As described above, when the power distributions of all the beams B are superimposed, as shown in Figure 3, it becomes a flat-top power distribution without a sharp peak. Therefore, when the laser light L is irradiated, the temperature rises and melting occurs in the relatively wide area A of the surface of the workpiece W, and the molten pool WP is formed to become deeper relatively slowly. Therefore, the zinc plating layers W13 and W22 evaporate and gasify gradually, not suddenly. As a result, the generated gas G The melting of the molten pool WP is reduced, and the deterioration of the flatness of the surface of the molten pool WP is also reduced. Also, melting occurs slowly over a relatively wide area. Therefore, the gas generated gradually G The gas is sufficiently discharged from the surface of the molten pool WP, which has a relatively large surface area. G This ensures that the exhaust path of the bubbles is secured, and bubbles are less likely to remain after the molten pool WP solidifies. As a result, the occurrence of welding defects can be suppressed.

[0042] How to more effectively prevent welding defects , Ga It is preferable to distribute the irradiation positions of the multiple beams B so that the gas is gradually and sufficiently discharged from the surface of the molten pool WP. In particular, it is preferable to distribute the irradiation positions of the multiple beams B so that welding defects caused by gas are kept below an allowable level. Here, the allowable level means, for example, a level allowed by the required specifications for welding.

[0043] To suppress welding defects more effectively, it is preferable to set the number of beams B, the peak power, and the arrangement of the irradiation positions, and to set the shape of the region A, depending on the characteristics (material, thickness of the base material, thickness of the plating layer, etc.) of the workpiece W. By setting at least one of these items, welding defects can be suppressed more effectively, but by setting two or more of them in appropriate combination, welding defects can be suppressed even more effectively.

[0044] The molten pool formed in the workpiece W will be further described. Figures 7 and 8 are schematic diagrams for explaining the molten pool formed by the laser beam L. Figure 7 shows the case where the laser beam L10, each consisting of one beam B as shown in Figure 4, is irradiated. In this case, when each laser beam L10 is swept, a molten pool WP10 of width WD is formed. However, because the separation distance between the two laser beams L10 (the separation distance between the centers of the beams B) is greater than the width WD, the molten pools WP10 formed in the workpiece W by the irradiation of each beam B do not overlap each other.

[0045] On the other hand, FIG. 8 shows a case where laser light L11 including two beams B is irradiated. In this case, since the separation distance D between the two beams B is smaller than the width WD, the molten pools formed on the workpiece W by the irradiation of each beam B overlap each other, forming a molten pool WP11 wider than the width WD. In FIG. 8, the dashed lines virtually show the contours of the molten pools formed on the workpiece W by the irradiation of each beam B. In this way, when multiple beams B are irradiated so that the molten pools formed on the workpiece W by the irradiation of each of the multiple beams B overlap each other, a molten pool with a wide area is formed as a whole, which is favorable for gas discharge and can suppress or prevent bumping. Therefore, the distance at which multiple beams B are irradiated so that the molten pools formed on the workpiece W by the irradiation of each of the multiple beams B overlap each other is of Set it up.

[0046] In addition, it is preferable that the power distribution of the beam B has a relatively sharp shape. If the power distribution of the beam B has a relatively sharp shape, the penetration depth when melting the workpiece W can be made deep, and the occurrence of welding defects can be suppressed. Furthermore, by making each beam B sharp and allowing the molten pools to overlap each other, a deep and wide molten pool is formed, thereby achieving suitable welding. Using the beam diameter as an index of the sharpness of the beam B, it is preferable that the beam diameter of each beam B is 600 μm or less. In addition, the width W of the molten pool D is, for example, about six times the diameter of each beam, so the distance between the beams B is preferably six times the beam diameter or less. Therefore, the distance between the beams B is preferably, for example, 3600 μm or less. If the beam B has a sharp shape, the power required to achieve the same penetration depth can be reduced and the processing speed can be increased. This makes it possible to reduce the power consumption of the laser welding device 100 and improve the processing efficiency.

[0047] The beam diameter can be designed by appropriately setting the characteristics of the laser device 110, the optical head 120, and the optical fiber 130 used. For example, the beam diameter of the laser light input from the optical fiber 130 to the optical head 120, the diffractive optical element 123, the collimator lens 121, Condenser lens By setting the optical system such as 122, design It is possible.

[0048] 9A to 9H are schematic diagrams for explaining an example in which the diffractive optical element 123 splits the laser light into a plurality of beams. The sweep direction is assumed to be directed upward on the paper. In the example shown in FIG. 9A, the laser light L1 irradiated to the workpiece W includes eight beams B1, each of which is, for example, Gaussian in shape, and is arranged in a ring shape in a circular area A1, which is a predetermined area on the surface of the workpiece W, and is irradiated to the area A1. In the example shown in FIG. 9B, the laser light L2 irradiated to the workpiece W includes eight beams B2, each of which is, for example, Gaussian in shape, and is arranged in a square shape in a square area A2, which is a predetermined area on the surface of the workpiece W, and is irradiated to the area A2. In the example shown in FIG. 9C, the laser light L3 irradiated to the workpiece W includes six beams B3, each of which is, for example, Gaussian in shape, and is arranged in a triangular shape in a triangular area A3, which is a predetermined area on the surface of the workpiece W, and is irradiated to the area A3.

[0049] In the example shown in Fig. 9D, the laser light L4 irradiated to the workpiece W includes 21 beams B4, each of which has, for example, a Gaussian shape, and is arranged so that the outer contour is circular within a circular area A4, which is a predetermined area on the surface of the workpiece W, and is irradiated to the area A4. In the example shown in Fig. 9E, the laser light L5 irradiated to the workpiece W includes 13 beams B5, each of which has, for example, a Gaussian shape, and is arranged so that 12 beams are arranged in a ring shape within a circular area A5, which is a predetermined area on the surface of the workpiece W, and one beam is arranged at the center of the ring and is irradiated to the area A5.

[0050] In the example shown in Fig. 9F, the laser light L6 irradiated to the workpiece W includes 20 beams B6, each of which has a Gaussian shape. Each beam B6 is included in either beam group G1 or beam group G2. Beam group G1 has a mountain shape with its apex facing the sweep direction SD, and beam group G2 is located behind beam group G1 and forms a straight line. Beam groups G1 and G2 are arranged in a triangular area A6, which is a predetermined area on the surface of the workpiece W, and are irradiated to area A6.

[0051] In the example shown in Fig. 9G, the laser light L7 irradiated to the workpiece W includes 13 beams B7, each of which has, for example, a Gaussian shape. The beam B7 has a mountain shape similar to the beam group G1 in Fig. 7(g). The beam B7 is disposed within a triangular area A7, which is a predetermined area on the surface of the workpiece W, and is irradiated to the area A7.

[0052] In the example shown in Fig. 9H, the laser light L8 irradiated to the workpiece W includes a beam B8 having, for example, a Gaussian shape, and a beam group G3. The beam group G3 includes seven beams, each having, for example, a Gaussian shape, which are arranged at equal intervals to form a semicircular arc. The beam B8 is located near the center of the semicircular arc of the beam group G3, and is disposed within an area A8, which is a predetermined area on the surface of the workpiece W, and is irradiated to the area A8.

[0053] In all of FIGS. 9A to 9H, the predetermined area has a shape that corresponds to the outer contour of the shape formed by the multiple beams that are distributed.

[0054] FIG. 10 shows the beam group G of the laser light L6 shown in FIG. 2 10 is a schematic diagram illustrating an example of overlapping of beams B6 in beam group G. 2 In the case of the beam B6, the power is uneven in the arrangement direction of the beam B6. The arrangement, beam shape, etc. may be set so that such unevenness is within an allowable amplitude depending on the desired welding quality, etc.

[0055] In any of FIG. 3 and FIGS. 9A to 9H, it is important to set the peak power of each beam so that the processing target does not suddenly melt immediately after irradiation, as in FIG.

[0056] Also, in Fig. 3, Fig. 9A, 9C to 9H, the multiple beams are arranged so that the shape of the regions A, A1, A3 to A8 gradually expands in width in the direction perpendicular to the sweep direction. With such beam arrangement, the surface area and depth of the molten pool WP of the workpiece W gradually increase during irradiation with the laser light, which is effective in suppressing the occurrence of welding defects. In particular, in Fig. 9F, 9G, and 9H, the beams are arranged with high directivity in the sweep direction, and more beams are arranged on the forward side of the sweep direction. This allows efficient welding. On the other hand, in Fig. 3, Fig. 9A, 9D, and 9E, the multiple beams are arranged isotropically, so that there is an effect that the melting characteristics for the workpiece W do not change even if the sweep direction is arbitrarily changed.

[0057] 9A to 9H can be realized by appropriately designing the characteristics of the diffraction grating that constitutes the diffractive optical element 123. Note that the power of each of the multiple beams contained in each of the laser beams L1 to L8 shown in Figures 9A to 9H may or may not be equal.

[0058] (Comparative Example) As a comparative example, two galvanized steel sheets were welded together using a single laser beam as shown in Fig. 4. The galvanized steel sheets were 1 mm thick steel sheets that had been treated with galvannealed hot-dip plating (GA). The weight of the galvanized coating was 45 g / m on both sides. 2 The laser light used had a wavelength of 1070 nm, a power of 3000 W, and a beam diameter of 300 μm. The sweep speed of the laser light was 20 m / s.

[0059] FIG. 11A is a diagram showing a photograph of the front surface of a galvanized steel sheet by a welding method of a comparative example. FIG. 11B is a diagram showing a photograph of the back surface of a galvanized steel sheet by a welding method of a comparative example. FIG. 11C is a diagram showing a photograph of a cross section of a galvanized steel sheet by a welding method of a comparative example. In FIG. 11A, the bead width indicated by the double arrow was about 1800 μm. It is considered that this bead width is approximately equal to the width of the molten pool. In FIG. 11A, a hole was opened in the part indicated by the arrow. It is considered that this hole was opened by a part of the steel material being scattered. In addition, in FIG. 11B, the bead width indicated by the double arrow was about 1100 μm. In addition, as shown in FIG. 11C, a void was formed in the cross section crossing the bead. It is considered that this void was formed because the width of the molten pool was narrow and gas was not discharged because the bead width was narrow at about 1800 μm.

[0060] Example 1 In Example 1, two galvanized steel sheets were welded together using a laser beam consisting of multiple beams as shown in FIG. For example: The laser beam has the same characteristics as the one used in the experiment. The laser beam has a wavelength of 1070 nm, a power of 3000 W, and a single beam with a beam diameter of 300 μm. The laser beam is shaped as shown in FIG. 9H by using a diffractive optical element. Therefore, the beam diameters of beam B8 and each of the beams constituting beam group G3 are both 300 μm. The diameter of the semicircular arc formed by beam group G3 is about 700 μm. The power ratio of beam B8 to beam group G3 is set to 1:2. The distance between the seven beams constituting beam group G3 is about 180 μm. The sweep speed of the laser beam is set to 20 m / s.

[0061] FIG. 12A is a diagram showing a photograph of the front surface of a galvanized steel sheet by the welding method of Example 1. FIG. 12B is a diagram showing a photograph of the back surface of a galvanized steel sheet by the welding method of Example 1. In FIG. 12A, the bead width indicated by the double arrows was about 4200 μm. This bead width is considered to be approximately equal to the width of the molten pool. The bead width was also about six times the diameter of the semicircular arc formed by the beam group G3, which was about 700 μm. In FIG. 12A, unlike FIG. 11A, no hole was formed. In FIG. 12B, the bead width indicated by the double arrows was about 4000 μm.

[0062] Example 2 In Example 2, two galvanized steel sheets having the same characteristics as those used in Example 1 were welded using a laser beam different from that used in Example 1. The laser beam had a wavelength of 1070 nm, a power of 5500 W, and a single beam having a beam diameter of 300 μm, and was formed into a shape as shown in FIG. 9E by using a diffractive optical element. Therefore, the beam diameter of each beam B5 was 300 μm. The diameter of the circle formed by the twelve beams B5 arranged around the central beam B5 was set to 600 μm. The power ratio between the power of the central beam B5 and the sum of the powers of the twelve beams B5 forming the circle was set to 8:2. The distance between the twelve beams B5 forming the circle was set to about 157 μm. The sweep speed of the laser beam was set to 170 m / s.

[0063] Fig. 13A is a photograph of the surface of a galvanized steel sheet by the welding method of Example 2. Fig. 13B is a photograph of the surface of a galvanized steel sheet by the welding method of Example 2. 2 13A shows a photograph of the cross section of a galvanized steel sheet welded by the welding method. In Fig. 13A, some surface roughness was observed, but no holes were formed. In Fig. 13B, voids were formed in the cross section crossing the bead, but the comparative For example: The results were good, with the size of the voids being significantly smaller than those of the voids that were formed, which may be unacceptable welding defects depending on the application.

[0064] Example 3 In Example 3, two galvanized steel sheets were welded together using the same laser beam as in Example 1. The galvanized steel sheets were 1 mm thick steel sheets that had been electrolytically galvanized (SECC). The weight of the galvanized steel sheets was 20 g / m on both sides. 2 The sweep speed of the laser beam was set to 20 m / s.

[0065] Fig. 14A is a photograph of the surface of a galvanized steel sheet by the welding method of Example 3. Fig. 14B is a photograph of the cross section of a galvanized steel sheet by the welding method of Example 3. In Fig. 14A, no holes were formed, as in Fig. 13A. Moreover, as shown in Fig. 14B, no voids were formed in the cross section crossing the bead, and the bead surface had a smooth shape, indicating an extremely good welding condition.

[0066] Example 4 In Example 4, two galvanized steel sheets were welded together using the same laser beam as in Examples 1 and 3. The galvanized steel sheets were 1 mm thick steel sheets that had been subjected to hot-dip galvanizing (SGCC). The weight of the galvanized coating was 60 g / m on both sides. 2 The sweep speed of the laser beam was set to 20 m / s.

[0067] Fig. 15A is a photograph of the surface of a galvanized steel sheet by the welding method of Example 4. Fig. 15B is a photograph of the cross section of a galvanized steel sheet by the welding method of Example 4. In Fig. 15A, no holes were formed, as in Fig. 14A. In addition, as shown in Fig. 15B, no voids were formed in the cross section crossing the bead, and the weld condition was good.

[0068] As shown in Figs. 13B, 14B, and 15B, gaps are formed between the two zinc-plated steel sheets at locations other than the welded portions, but this does not pose any particular problems in practical use.

[0069] (Embodiment 2) 16 is a diagram showing a schematic configuration of a laser welding apparatus according to embodiment 2. The laser welding apparatus 200 irradiates a processing object W with a laser beam L to weld the processing object W. The laser welding apparatus 200 realizes welding by the same action principle as the laser welding apparatus 100. Therefore, only the device configuration of the laser welding apparatus 200 will be described below.

[0070] The laser welding device 200 includes a laser device 210 , an optical head 220 , and an optical fiber 230 .

[0071] The laser device 210 is configured similarly to the laser device 110, and is configured to be able to output laser light with a power of, for example, several kW. The optical fiber 230 guides the laser light output from the laser device 210 and inputs it to the optical head 220.

[0072] Similar to the optical head 120, the optical head 220 is an optical device for irradiating the laser light input from the laser device 210 towards the workpiece W. The optical head 220 includes a collimator lens 221 and a condenser lens 222.

[0073] Furthermore, the optical head 220 has a galvano scanner disposed between the condenser lens 222 and the workpiece W. The galvano scanner is a device that can move the irradiation position of the laser light L and sweep the laser light L without moving the optical head 220 by controlling the angles of two mirrors 224a and 224b. The laser welding device 200 is provided with a mirror 226 for guiding the laser light L emitted from the condenser lens 222 to the galvano scanner. Moreover, the angles of the mirrors 224a and 224b of the galvano scanner are changed by motors 225a and 225b, respectively.

[0074] The optical head 220 includes a diffractive optical element 223 as a beam shaper disposed between the collimator lens 221 and the condenser lens 222. The diffractive optical element 223 divides the laser light input from the collimator lens 221 into multiple beams with equal peak power, similar to the diffractive optical element 123. Specifically, the diffractive optical element 223 divides the laser light so that the optical head 220 can irradiate the surface of the workpiece W with multiple beams by dispersing the positions of the multiple beams so that the centers of the multiple beams do not overlap each other within a predetermined area on the surface. The diffractive optical element 223 is designed to divide the laser light into multiple beams, for example, as shown in FIG. 3 and FIG. 9A to FIG. 9H. At this time, the distance at which the multiple beams are irradiated is set so that the molten pools formed on the workpiece W by the irradiation of each of the multiple beams overlap each other. This allows the laser welding device 200 to suppress the occurrence of welding defects when welding the workpiece W.

[0075] (Embodiment 3) 17 is a schematic diagram showing a schematic configuration of a laser welding apparatus according to embodiment 3. The laser welding apparatus 300 irradiates a workpiece W with a laser beam L to weld the workpiece W. The laser welding apparatus 300 realizes welding by the same action principle as the laser welding apparatuses 100 and 200. The configurations of the elements other than the optical head 320 (the laser device 310 and the optical fiber 330) are the same as the corresponding elements of the laser welding apparatuses 100 and 200. Therefore, only the device configuration of the optical head 320 will be described below.

[0076] The optical head 320, like the optical heads 120 and 220, is an optical device for irradiating the laser light input from the laser device 310 towards the workpiece W. The optical head 320 includes a collimator lens 321 and a condenser lens 322.

[0077] Furthermore, the optical head 320 has a galvano scanner disposed between the collimator lens 321 and the condenser lens 322. The angles of mirrors 324a and 324b of the galvano scanner are changed by motors 325a and 325b, respectively. In the optical head 320, the galvano scanner is provided at a position different from that of the optical head 220. However, similar to the optical head 220, by controlling the angles of the two mirrors 324a and 324b, it is possible to move the irradiation position of the laser light L and sweep the laser light L without moving the optical head 320.

[0078] The optical head 320 includes a diffractive optical element 323 as a beam shaper disposed between the collimator lens 321 and the condenser lens 322. The diffractive optical element 323 splits the laser light input from the collimator lens 321 into multiple beams with equal peak power, similar to the diffractive optical elements 123 and 223. Specifically, the diffractive optical element 323 splits the laser light so that the optical head 320 can irradiate the surface of the workpiece W with multiple beams by dispersing the positions of the multiple beams so that the centers of the multiple beams do not overlap each other within a predetermined area on the surface. The diffractive optical element 323 is designed to split the laser light into multiple beams, for example, as shown in FIG. 3 and FIGS. 9A to 9H. At this time, the distance at which the multiple beams are irradiated so that the molten pools formed on the workpiece W by the irradiation of each of the multiple beams overlap each other is determined. of This enables the laser welding apparatus 300 to suppress the occurrence of welding defects when welding the workpiece W.

[0079] In the above embodiment, the diffractive optical element splits the laser light into multiple beams with equal peak power. However, the peak powers of the multiple beams do not have to be completely equal. If no beam has a peak that protrudes to the extent that it causes welding defects, the peak powers of those beams can be considered to be approximately equal. In addition, the power distribution of each beam is not limited to a Gaussian shape, and may be another single-peak shape. Furthermore, even if the peak powers of each beam are not equal, the laser light may be split and arranged so that when the power distributions of all the beams are superimposed, they have a flat-top shape without a protruding sharp peak as shown in FIG. 3.

[0080] In addition, when adjacent beams among the divided beams do not overlap, the center distance between the beams is, for example, 20 times or less of the beam diameter. In addition, when the beams do not overlap, it is preferable that the melting regions of each beam overlap. Here, the melting region of the beam is a region where the processing object becomes hotter than the melting point due to the energy given by the beam and melts, and the area may be larger than the beam diameter depending on the thermal conductivity of the processing object. In this case, the peak power of each beam may be equal, approximately equal, or different. In addition, instead of dividing the laser light into multiple beams by a diffractive optical element, multiple laser light sources may be provided, and the beams of laser light output from each of the multiple laser light sources may be used as multiple beams.

[0081] In addition, although the workpiece W is formed by overlapping zinc-plated steel sheets W1 and W2 with no gap between them, the present invention can be applied to a workpiece formed by overlapping zinc-plated steel sheets W1 and W2 with a gap between them. In addition, the plated sheet material constituting the workpiece W is not limited to a zinc-plated steel sheet, and the present invention can be applied to a plated sheet material that is the subject of lap welding.

[0082] Furthermore, when the laser light L is swept over the workpiece W, the sweep may be performed by known wobbling or weaving to increase the surface area of ​​the molten pool.

[0083] Furthermore, the present invention is not limited to the above-mentioned embodiments. The present invention also includes configurations in which the components of the above-mentioned embodiments are appropriately combined. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-mentioned embodiments, and various modifications are possible. [Industrial Applicability]

[0084] As described above, the present invention Welding method and welding equipment teeth, welding It is suitable for application to the above. [Explanation of symbols]

[0085] 100, 200, 300 Laser welding equipment 110, 210, 310 Laser device 120, 220, 320 Optical Head 121, 221, 321 Collimating Lenses 122, 222, 322 Condenser Lens 123, 223, 323 Diffractive optical elements 123a Diffraction Grating 130, 230, 330 Optical Fiber 224a, 224b, 226, 324a, 324b mirror 225a, 225b, 325a, 325b motor A, A1, A2, A3, A4, A5, A6, A7 area B, B1, B2, B3, B4, B5, B6, B7 Beam G1, G2 beam group L, L1, L2, L3, L4, L5, L6, L7 Laser light W Processing target W1, W2 Zinc-plated steel sheet W11, W21 steel plate W12, W13, W22, W23 zinc plating layer

Claims

1. A plated sheet material having a plating layer formed on the surface of a base material is stacked to form a processing object, The object to be processed is placed in a region to be irradiated with laser light; irradiating the surface of the object to be processed with the plurality of beams constituting the laser light in a predetermined area on the surface while dispersing the positions of the plurality of beams so that the centers of the beams do not overlap with each other; While performing the irradiation, the plurality of beams and the processing object are moved relatively to each other, and the plurality of beams are swept over the processing object to melt and weld the processing object in the irradiated portion; setting distances at which the plurality of beams are irradiated such that molten pools formed on the workpiece by the irradiation of each of the plurality of beams overlap each other; Among the plurality of beams, all or a part of two adjacent beams partially overlap each other in a direction perpendicular to a sweep direction of the plurality of beams, The beam diameter of each of the plurality of beams is 600 μm or less. Welding method.

2. The plurality of beams are arranged so that a shape of a predetermined region to be irradiated with the plurality of beams gradually increases in width in a direction perpendicular to the sweep direction. The welding method according to claim 1.

3. The plurality of beams have approximately equal peak powers. The welding method according to claim 1 or 2.

4. The distance between the plurality of beams is 6 times or less than the beam diameter. The welding method according to any one of claims 1 to 3.

5. The distance between the beams is 3600 μm or less. The welding method according to any one of claims 1 to 4.

6. A laser device; a beam shaper that splits the laser light output from the laser device into a plurality of beams; an optical head that irradiates the plurality of beams toward a processing object and melts and welds the processing object at the irradiated portions; Equipped with The processing target is configured by stacking plated sheet materials each having a base material and a plating layer formed on a surface thereof, the optical head is configured so that the plurality of beams and the workpiece are relatively movable, and performs the melting and welding while sweeping the plurality of beams over the workpiece; the beam shaper divides the laser light so that the optical head can irradiate the plurality of beams by dispersing positions of the plurality of beams so that centers of the plurality of beams do not overlap with each other within a predetermined area on the surface of the processing object; Among the plurality of beams, all or a part of two adjacent beams partially overlap each other in a direction perpendicular to a sweep direction of the plurality of beams, The beam diameter of each of the plurality of beams is 600 μm or less. Welding equipment.

7. The plurality of beams are arranged so that a shape of a predetermined region to be irradiated with the plurality of beams gradually increases in width in a direction perpendicular to the sweep direction.

7. The welding apparatus of claim 6.

8. The plurality of beams have approximately equal peak powers.

8. A welding device according to claim 6 or 7.

9. irradiating the plurality of beams such that molten pools formed on the workpiece by each of the irradiation of the plurality of beams overlap each other; The welding device according to any one of claims 6 to 8.

10. The distance between the plurality of beams is 6 times or less than the beam diameter. The welding device according to any one of claims 6 to 9.

11. The distance between the beams is 3600 μm or less. The welding device according to any one of claims 6 to 10.

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