JP2012115909A - Laser welding method and laser welding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser welding method and a laser welding apparatus, wherein butt welding of a plate material can be performed in a short welding time at low cost without the need for a cutting device and a cutting process.SOLUTION: The laser welding method includes: a first irradiation step of irradiating at least one portions to be welded of a pair of opposing plate materials 6 with a laser 12 a plurality of times while changing the irradiation positions of laser 12 from an end surface of the plate material 6, to temporarily melting the portions; a gap-adjusting step of adjusting an interval between the portions of the pair of plate materials 6 so that the interval falls within an allowable gap; and a second irradiation step of irradiating the portions with the laser 12 to weld the plate materials 6.

Description

  The present invention relates to laser welding using laser light, and more particularly to a laser welding method and laser welding apparatus for performing butt welding of a pair of plate members.

  In a steel production line, a steel sheet (thin plate material) is wound as a product coil after being subjected to processing such as rolling, cold rolling, and plating. At this time, in order to perform the said process continuously to a steel plate, the welding of a sheet | seat is required. For example, there are cases where a thin plate material is butt-welded and laser-welded. In such a case, if the end surface of the workpiece, which is a thin plate material cut by a shearing machine, is butted as it is, the butt plate material if the weld length is long A gap is likely to occur between the two. At this time, since the space that is acceptable for normal welding becomes narrow when it is a thin plate, problems arise such that the plate members are not joined to each other or a hole is formed in the welded portion. Therefore, in the conventional laser welding method and its laser welding system, both end faces of the plate to be welded are ground by the grinding means prior to welding with the laser in order to improve the butt accuracy and make the gap between the plates less than the allowable gap. After grinding, the gap between the end faces of the plate to be welded was adjusted and welded with a laser beam (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2004-249305 (page 11, FIG. 3)

  In the conventional laser welding method and the laser welding system, an apparatus for performing a grinding process is required, and installation space, cost, and maintenance are also required. Furthermore, if a thin plate material having a thickness of 0.1 mm is welded, the end face of the welded plate material needs to be butt-accurate, so that processing accuracy in units of several μm is required, and processing time is required.

  The present invention has been made in order to solve the above-described problems. A laser welding method and a laser welding apparatus that do not require a cutting device or a cutting process, are inexpensive, and can reduce welding time. The purpose is to obtain.

  In the laser welding method and the laser welding apparatus according to the present invention, the laser irradiation position is changed a plurality of times from the end surface of the plate material of at least one of the pair of plate materials facing each other, and the laser beam is irradiated to the welding portion a plurality of times. A first irradiation step for temporarily melting the welded portion, a gap adjusting step for adjusting the distance between the welded portions of the pair of plate members to be within an allowable gap, And a second irradiation step for welding the plate material.

  In the laser welding method and the laser welding apparatus according to the present invention, when the welded portion is irradiated with the laser prior to welding and temporarily melted, the laser irradiation position from the end surface of the plate material of the welded portion is changed and the laser is changed. Since butt welding is performed after a plurality of irradiations, no cutting device or grinding process is required, and costs can be reduced and the welding process time can be reduced.

It is a block diagram of the laser welding apparatus which shows Embodiment 1 of this invention. It is the schematic diagram which showed the state at the time of shear cutting | disconnection of the board | plate material which shows Embodiment 1 of this invention. It is the schematic diagram which showed the state after the shear cutting | disconnection of the board | plate material which shows Embodiment 1 of this invention. It is the schematic diagram which showed the gap amount G at the time of matching the board | plate material which shows Embodiment 1 of this invention. It is the schematic diagram which showed the laser irradiation state to the both ends of the board | plate material which shows Embodiment 1 of this invention. It is the schematic diagram which showed the state by which the both-ends surface shape of the board | plate material which shows Embodiment 1 of this invention was processed into the spherical shape. It is the schematic diagram which showed the shield state of the welding part by the argon gas in the butt welding which shows Embodiment 1 of this invention. It is the schematic diagram which showed the model by which the end surface shape of the board | plate material which shows Embodiment 1 of this invention is processed into a spherical shape. It is the schematic diagram which showed the relationship between the tolerance | permissible gap and the melting allowance in the butt-welding of thickness 0.1mm which shows Embodiment 1 of this invention. It is the schematic diagram which showed the relationship between the largest permissible gap and plate | board thickness in the butt welding of the board | plate material which shows Embodiment 1 of this invention. It is the schematic diagram which showed the change of the shape of the board | plate material end surface by the laser irradiation which shows Embodiment 1 of this invention. It is the schematic diagram which showed the shape of the board | plate material end surface after shear cutting | disconnection which shows Embodiment 2 of this invention. It is the schematic diagram which showed the laser irradiation position in the board | plate end surface which shows Embodiment 2 of this invention, and the end surface shape after laser irradiation. It is the schematic diagram which showed the gap G at the time of matching the board | plate material which shows Embodiment 2 of this invention. It is a block diagram of the laser welding apparatus which shows Embodiment 3 of this invention. It is a flowchart of the laser butt-welding method which shows Embodiment 3 of this invention. It is a block diagram of the laser welding apparatus which shows Embodiment 4 of this invention. It is a flowchart of the laser butt welding method which shows Embodiment 4 of this invention.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a laser welding apparatus using a plate material butt laser welding method according to Embodiment 1 for carrying out the present invention. This apparatus includes clamping devices 1a and 1b for holding and fixing a preceding plate material 6a and a subsequent plate material 6b which are welded plate materials. Further, the clamping devices 1a and 1b are provided with adjusting means for adjusting the interval between the welded portions at the opposite ends of the plate material by moving the clamp device holding the plate material. Further, a machining head 2 for machining a plate material with a laser, a laser beam oscillator 3 for supplying a laser beam to the machining head 2, a shear cutting machine 4 for shearing the plate material to be welded before butt welding, and a machining head 2 And a shear cutting machine 4 and a carriage (conveying means) 5 that moves in the plate width direction along the welded portion, and a work supply device 7 that sends out the plate material 6. Although not shown here, there may be an NC (Numerical Control) control device that controls them.

  Next, a welding method using this welding apparatus will be described. As shown in FIG. 2, the preceding plate material 6a and the subsequent plate material 6b sent out by the work supply device 7 are fixed by the clamp devices 1a and 1b. The shear cutting machine 4 includes an upper blade 8 that can move up and down, and a lower blade 9 that supports the plate material 6, and the plate material 6 is cut by lowering the upper blade 8. At this time, the clearance 10 can be adjusted by moving the upper blade 8 left and right depending on the target plate thickness.

Thereafter, the distance between the clamps 1a and 1b is adjusted while holding the plate material 6 cut by the shear cutting machine 4. In the case of performing ordinary butt welding, both end portions 6a _E and 6b _E of the plate members 6a and 6b shown in FIG. However, as shown in FIG. 4, when the cutting accuracy of the sheared plate material 6 is poor, when a portion of the plate material 6 is abutted, a part of the plate abuts, but in a part of the gap G is vacant, and the welding is performed as it is. Doing so will cause poor welding.

  In the present invention, first, the gap between the plate members is adjusted by the adjusting means of the clamps 1a and 1b with the gap G left to some extent as shown in FIG. The gap adjustment at this time may be adjusted by measuring the gap of the welded portion of the plate material so that it will be in a state exceeding the welding allowable gap described later in any place, or a somewhat broader interval. May be set. That is, it is not necessary to weld at any place during laser irradiation. Thereafter, the carriage 5 is caused to travel so that the machining head 2 comes directly above the welding start point of the plate to be welded. A columnar back roll 11b that can be rotated about 11a is provided directly below the plate 6 and is attached to a lower portion of the carriage 5 on which the processing head 2 is mounted.

  Thereafter, as shown in FIG. 5, the carriage 5 is caused to travel while irradiating the laser 12, and the end of the plate material that is the welded portion is temporarily melted. At this time, the spot diameter of the laser 12 irradiated on the plate material surface is preferably larger than the gap G. Therefore, it is desirable that the spot diameter can be changed by moving the processing head 2 up and down to change the focal position of the beam. Even when the spot diameter is small and both end faces of the plate cannot be melted once, the end faces can be temporarily melted once by reciprocating the carriage. During irradiation with the laser beam, it is preferable to prevent oxidation of the molten metal by spraying a shielding gas, here argon gas, from the tip of the nozzle attached to the processing head 2 or the like.

  FIG. 6 shows the state of the plate after the laser beam irradiation. A part of both end surfaces of the plate material 6 is melted to form a spherical shape. At this time, when the end surface of the plate 6 is spherical, the gap G becomes larger than before the laser beam irradiation. Next, the clamps 1a and 1b are moved, the gap G is adjusted, and the plate material 6 is abutted. Thereafter, irradiation with a laser beam along the butt portion enables good welding with no welding failure. In this butt state, the gap does not necessarily have to be zero, and even in a state where the gap is somewhat open, both end faces of the plate member 6 are partially increased in thickness, so that the gap tolerance is widened. Welding is possible. That is, it is only necessary that the interval between the welded portions after the interval between the plate members is within an allowable gap that can be welded, which will be described later, at any location.

  FIG. 7 is a view showing a state at the time of butt welding after the end surface of the plate material is processed into a spherical shape. The spheroidized plate materials are butted together and, for example, welding is performed at a laser output of 2.0 kW, a welding speed of 13 m / min, and a beam spot diameter of 0.6 mm. At that time, if oxygen is dissolved in the molten metal during welding, the surface tension is lowered, the balance between the weight of the molten metal and the surface tension is lost, and the molten bead becomes unstable. As a result, the bead hangs down or melts down at the weld. In order to prevent this, a shield gas (argon gas) 13a may be blown from the nozzle at the tip of the processing head 2 to the welded portion to suppress oxidation of the molten metal. Furthermore, by performing a back shield by applying a shield gas (argon gas) 13b from the back of the plate material with the nozzle 14 at the time of welding, it becomes stronger than the shield only from the nozzle at the tip of the processing head 2 and enables stable welding. It becomes. Further, helium having high thermal conductivity may be used as the shielding gas instead of argon.

  In addition, when there is no back roll 11b directly under the plate material 6 irradiated with the laser beam being welded, the thinner the plate thickness of the plate material 6 in the clamped state, the lower the rigidity and the plate material droops, and butt welding. Is impossible. The back roll 11b serves to prevent misunderstanding of both end faces of the plate material by lifting the plate material of the portion irradiated with the laser beam from below, sandwiching it with the clamp, and fixing. Since the back roll 11b is attached to the carriage 5, the back roll 11b is positioned immediately below the laser beam irradiating portion at any time along the traveling of the carriage 5, so that welding can be stabilized. It is necessary to prevent the back roll 11b from hitting the spherical portions on both end faces of the plate material during the first and second laser beam weldings.

  In the following, the maximum allowable gap in butt welding of plate materials will be described in detail by comparing theoretical values and experimental values using a simple model. The model used is shown in FIG. This is a model in which a hemispherical molten metal having a radius r is formed on the end face when only T is melted from the end face of the sheet material in a state where there is a gap of G in butt welding with a thickness h. Since the radius r and θ (= π−wetting angle) are uniquely determined by determining the value of a certain plate thickness h and the melting allowance T, the molten metal in FIG. 8B forms a bridge (both hemispheres). Assuming that the molten metal is in contact, G is obtained. Next, the maximum allowable gap Gmax is obtained by changing the melting allowance T. The calculation method is shown below. First, the following three relational expressions are derived from FIG.

  In order to express the gap G by the radii r and θ from the above simultaneous equations, first, the equation (4) is derived from the equation (2), and the equation (5) is obtained by substituting the equation (1). Further, when equation (5) is substituted into equation (3), equation (6) is obtained.

  Thus, the allowable gap G can be expressed by the radii r and θ. Next, FIG. 9 shows the allowable gap when the melting thickness is changed from 0.01 mm to 0.10 mm with a plate thickness of 0.1 mm. When the melting allowance is 0.04 mm, the allowable gap is maximum at 0.021 mm. Further, the maximum allowable gap Gmax when the beam spot diameter is 0.6 mm, the plate thickness is 0.4 mm, and 1.6 mm is obtained, and the result compared with the experimental value is shown in FIG. From this figure, it can be seen that as the plate thickness increases, welding is possible even if the gap becomes wider.

From this result, as shown in FIG. 11A, for example, when the plate thickness h is 0.5 mm, even if the gap is 100 μm in the butt state, welding can be performed without defect. However, according to the method of the present invention, for example, the laser output is 1.5 kW, the welding speed is 12 m / min, the beam spot diameter is 1 mm, and the melting allowance T is set to 860 μm from the end face of the plate material. A hemispherical plate material having a radius of 390 μm is obtained on the end face. This can be regarded as an increase in the plate thickness due to the bulge of the end portion. Here, considering a square end surface equivalent to a hemispherical cross-sectional area as shown in FIG. _A can be considered as an end of 0.62 mm, and by applying the same treatment to the other plate material, it is possible to expect an increase in the gap tolerance between the plate materials, and to allow a gap of up to 130 μm in the butt state. Become.

  In this case, when spheroidizing the end surface by the first laser irradiation, the laser is irradiated to the end portions of both the preceding plate material and the following plate material, but when the initial gap amount is small, only one plate material is irradiated. Laser irradiation may be performed.

  According to the laser welding method and the laser welding apparatus configured as described above, the welding portion is irradiated with a laser beam prior to welding to be temporarily melted, and then butt welding is performed. This eliminates the need for a process, thereby reducing costs and shortening the welding process time. Furthermore, since it can be considered that the thickness of the end portion has increased due to the spheroidization of the end surface, an increase in the gap tolerance between the plate materials can be expected, and welding is possible even if the butt accuracy is somewhat poor.

  Further, when the both end surfaces of the plate material are made spherical or welded, if a shield gas is blown from the back surface of the processing head or the plate material to irradiate the laser beam, oxidation of the molten metal can be prevented. As a result, the surface tension of the melted metal can be prevented from being lowered, it can be prevented from sagging due to its own weight, and the spherical shape can be maintained. Even if it is bad, welding is possible. At this time, when helium gas is used as the shielding gas, cooling of the weld bead is promoted, and increase in the weight of the molten metal and deformation thereof can be suppressed, so that more stable welding is possible.

  Furthermore, if the back roll is provided, it is possible to prevent the thin plate material from drooping, and to prevent a mistake in the both end faces of the thin plate material. In addition, since the back roll is attached to the carriage, it is located at any time directly below the laser beam irradiation section along the carriage travel, so that the welding can be stabilized.

Embodiment 2. FIG.
Here, a description will be given of a change in shape of the plate material when an actual thin plate material is used and laser is applied to the end of the plate material before performing butt welding. Examples of plate steel include plain steel, high-tensile steel, high-carbon steel, electromagnetic steel plate, and stainless steel. As an example, FIG. 12 shows the shape of a thin plate material used for welding. The plate thickness h is 0.1 mm, the plate width W is 100 mm, and the unevenness of the plate end surface by shear cutting is about 50 μm. In other words, when the plate materials after cutting the shear are abutted together, a gap of about 100 μm is left at the center of the plate. As shown in FIG. 9, in butt welding with a plate thickness of 0.1 mm, the allowable gap that can be welded is 21 μm, and it is impossible to weld with a shear-cut plate material.

  Next, FIG. 13A shows a laser beam irradiation state for spheroidizing the end face of the plate material after shear cutting. The welding conditions at this time are, for example, laser output: 300 W, welding speed: 5 m / min, beam spot diameter R: 0.6 mm, and beam irradiation position L: 0.1 mm. The spheroidizing treatment of the plate material end face differs in the size of spheroidization depending on how much the plate material is melted. In particular, the beam irradiation position L (related to the melting allowance T) has a great influence. In this case, in the plate material shown in FIG. 12, there is a difference of 16 μm between the concavo-convex amount of the plate end surface at 32 μm near X = 0 mm in the plate width direction (welding direction) and 16 μm near X = 100 mm. In such a case, there is a method of changing the beam irradiation position L in the middle other than the method of performing the spheroidizing process by a single laser irradiation. Further, it is conceivable that the unevenness is further reduced when the laser irradiation is performed twice from X = 0 mm to the X-axis plus direction and X = 100 mm to the X-axis minus direction. At this time, the beam irradiation in the X-axis plus direction is up to the vicinity of X = 40 mm where the plate material is most concave, and thereafter the laser is turned off, the carriage is run, and the beam irradiation position L is changed. The beam irradiation in the negative direction of the axis may be performed as a spheroidizing process by setting a portion where the laser is not irradiated between X = 100 mm and X = 40 mm.

  FIG. 13B shows the result of laser irradiation up to approximately X = 60 mm in the positive direction of the X axis. From this result, the maximum convex portion was +4.0 μm, the maximum concave portion was −5.7 μm, and the unevenness amount was 9.7 μm. Thus, the effect that the unevenness is reduced is seen compared with the unevenness amount of 50 μm before the laser irradiation. It is also possible to repeat the same process, that is, to irradiate the laser a plurality of times.

  As described above, the initial gap G (see FIG. 14A) when the plate members were butted was about 100 μm. However, the laser irradiation (irradiation position may be changed as appropriate) to the hatched portion, FIG. As shown in (b), the gap G between the plate members is 9.7 × 2 = 19.4 μm, which is within the butt allowable gap with a plate thickness of 0.1 mm, so that subsequent butt welding is possible.

  Note that the gap is reduced by irradiating laser on both end faces of the plate to be welded before performing butt welding, so that a part of the end surface is melted to obtain a plate to be welded having a spherical shape due to the influence of surface tension. In this case, it is considered that the corner portion of the plate material has a larger amount of dissolution than the center portion, and the spherical radius becomes relatively larger and the retraction amount increases (the Y-axis value becomes smaller). Note that the use of this method may be found by comparing the thickness of the central and corner welds by looking at the beat shape after the subsequent butt welding.

  Thus, the laser irradiation to the end of the plate material before laser welding has the effect of improving the gap tolerance and reducing the amount of unevenness, so that welding becomes easy, and a grinding device and a grinding process become unnecessary. Cost can be reduced and the welding process time can be shortened.

Embodiment 3 FIG.
Here, an example of a laser welding apparatus using the laser welding method of the first and second embodiments will be described. FIG. 15 is a diagram illustrating a state in which the imaging device 16 is attached to the processing head 2. By setting the half mirror 15 and the imaging device 16 coaxially with the laser beam, it is possible to check the abutting state of the plate material before welding or to easily match the laser irradiation position of the abutting portion. An image processing device 17 and an NC control device 19 are also provided.

  In order to perform butt welding after spheroidizing the end face by laser irradiation, it is necessary to bring the clamp devices 1a and 1b close to each other and adjust the gap G to a butt position where welding is possible. It is difficult to narrow the gap G and make a match without making a difference. Therefore, while moving the carriage 5 in the welding line direction again, as shown in FIG. 15, the image of the imaging device 16 attached to the processing head 2 is imaged using the image processing device 17, and the narrowest gap between both plate materials is used. If the amount is measured and then the clamp is moved by this minimum gap amount in accordance with an instruction from the NC control device 19, it is possible to make a match without causing a mistake.

  The operation instruction of the NC controller 19 of the laser welding apparatus configured as described above will be described with reference to FIG. This figure is a flowchart showing an outline of an operation procedure of laser butt welding using the imaging device 16. Subsequent to the start of step 111, the end portion of the preceding plate material 6a is clamped in step 112, and the subsequent plate material 6b is supplied to the laser welding machine by the work supply device. In step 113, the subsequent plate 6 b is clamped, and the plate clamped in step 114 is cut by the shear cutting machine 4. In step 115, the gap is adjusted so as to exceed the welding allowable gap, and the laser irradiation is positioned by the imaging device 16 attached to the machining head 2. In step 116, laser is irradiated to spheroidize the end face of the plate material. Thereafter, the carriage 5 is moved, the image of the imaging device 16 is processed by the image processing device 17, and the butt gap is measured (step 117). The gap is adjusted by moving the clamp by the minimum gap at that time (step 118), laser irradiation is performed in step 119, welding is performed, and the welding process is terminated in step 120.

  Here, although the clamp is moved by the measured minimum gap, the plate material at the position of the minimum gap is abutted and brought into contact therewith. Therefore, if it is moved further, a mistake will occur. In order to achieve good welding, it is sufficient that the interval between the welded parts after the interval between the plate members is within the allowable gap that can be welded at any location. There is no need to move, and the amount of movement may be slightly smaller than the minimum gap.

  According to the laser welding apparatus configured as described above, the welded portion is irradiated with a laser beam prior to welding according to an instruction from the NC control apparatus to be temporarily melted, and then the gap is adjusted to perform butt welding. This eliminates the need for a cutting device and a grinding process, thereby reducing costs and shortening the welding process time. Further, since the welding position and the gap can be accurately measured, the welding can be performed without causing a mistake, and stable welding can be performed.

Embodiment 4 FIG.
Here, another example of the laser welding apparatus using the laser welding method of the first and second embodiments will be described. Although the imaging apparatus 16 is used in the welding apparatus of the third embodiment, a case where a two-dimensional laser displacement sensor is used will be described here. FIG. 17 is a view showing a state in which the two-dimensional laser displacement sensor 18 is attached to the rear side of the machining head 2 in the laser irradiation direction. Further, an inspection device 20 and an NC control device 19 are also provided.

  Since the two-dimensional laser displacement sensor 18 is attached to the rear side in the laser irradiation direction of the processing head 2 when processing the end portions of both plate materials into a spherical shape with a laser beam, immediately after the end surface spheronization processing of the plate material, The gap G can be measured. The minimum gap amount from the two-dimensional laser displacement sensor 18 may be read by the inspection device 20 and the clamp may be moved by the minimum gap amount according to an instruction from the NC control device 19.

  An operation instruction of the NC controller 19 of the laser welding apparatus configured as described above will be described with reference to FIG. This figure is a flowchart showing an outline of an operation procedure of laser butt welding using the two-dimensional laser displacement sensor 18. Subsequent to the start of step 211, the terminal portion of the preceding plate material 6a is clamped in step 212, and the subsequent plate material 6b is supplied to the laser welding machine by the work supply device. In step 213, the subsequent plate 6 b is clamped, and the plate clamped in step 214 is cut by the shear cutting machine 4. In step 215, the gap is adjusted so as to exceed the welding allowable gap, and the laser irradiation is positioned by the CCD camera attached to the machining head 2 or the two-dimensional laser displacement sensor 18 and the inspection device 20. In step 216, laser is irradiated to spheroidize the end face of the plate material. At that time, the butt gap is measured by the two-dimensional laser displacement sensor 18 attached to the rear side of the machining head 2 in the laser irradiation direction (step 217). At that time, the clamp is moved by the amount corresponding to the minimum gap (step 218), laser is irradiated in step 219, and welding is performed. In step 220, the welding process is completed.

  Here, the two-dimensional laser displacement sensor 18 is attached to the machining head 2, but may be attached directly to the carriage 5 as long as it is located behind the laser irradiation direction.

  According to the laser welding apparatus configured in this way, the gap is measured simultaneously with the spheroidization of the end face, so that the time can be shortened. In addition, since the gap can be measured accurately, it is possible to make a match without causing a mistake and stable welding can be performed.

1a clamping device, 1b clamping device, 2 machining head, 3 laser light oscillator, 4 shear cutting machine, 5 carriage, 6 plate material, 6a preceding plate material, 6b following plate material, 6a _E end, 6b _E end, 7 work supply Device, 8 Upper blade, 9 Lower blade, 10 Clearance, 11a Back roll shaft, 11b Back roll, 12 Laser, 13a Shield gas, 13b Shield gas, 14 Nozzle, 15 Half mirror, 16 Imaging device, 17 Image processing device, 18 Two-dimensional laser displacement sensor, 19 NC control device, 20 inspection device, G gap, Gmax maximum allowable gap, h plate thickness, ha plate thickness, L laser beam irradiation position from end face of plate material, spot diameter of R laser beam, T melting , W plate width, XX axis, Y Y axis, r hemispherical radius generated on the plate end face after laser beam irradiation, θ π-wetting Horn.

Claims (4)

A laser beam is irradiated from the end face of the plate material of at least one of the pair of plate members facing each other, and the laser beam is irradiated to the welded portion a plurality of times to temporarily melt the welded portion. Irradiation process,
A gap adjusting step for adjusting the distance between the welded portions of the pair of plate members to be within the welding allowable gap;
A laser welding method comprising: a second irradiation step of welding the plate member by irradiating the welded portion with a laser. 2. The laser welding according to claim 1, wherein the first irradiation step irradiates the welded portion with a laser from one end side and the other end side of the plate material of the welded portion toward a portion where the interval between the welded portions is the widest. Method. After the irradiation position is changed from the end face of the plate material of at least one of the pair of plate materials held facing the welding portion, laser irradiation is performed a plurality of times, and the welding portion is temporarily melted. A processing head for welding the plate material by irradiating the welded portion of the plate material with a laser;
And a gap adjusting means for adjusting an interval between the welded parts before welding the pair of plate members. 4. The laser welding apparatus according to claim 3, wherein the gap measuring means is an imaging device attached coaxially with the laser of the machining head or a laser displacement sensor attached to the rear side of the machining head in the laser irradiation direction.

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