JPH07132387A - Method and device for laser beam welding - Google Patents

Abstract

PURPOSE:To provide a laser beam welding method where the allowable butt clearance during the welding can be increased, and the stable and higly qualified welding can be executed in the butt welding of a preceding sheet-shaped member to be welded with a succeeding member to be welded. CONSTITUTION:In the laser beam welding method where the laser beam is converged along the butt part having a small gap G between the rear end of a preceding sheet-shaped member 12 to be welded and the forward end of the succeeding member 13 to be welded to weld the but part, either of the members to be welded is melted by the laser beam at the weld starting end 17 of the butt part, and after the small gap G is reduced, the butt part is welded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to laser beam welding in which both ends of a material to be welded ahead and a material to be welded behind are butt-welded, and more particularly to improvement of a welding method thereof.

[0002]

2. Description of the Related Art FIG. 10 and FIG.
It is a perspective view which shows the structure of the conventional laser beam welding apparatus shown by -200986 publication. In the figure, 1 is a common base, 2 and 3 are front and rear clamp devices which are provided on the common base 1 at predetermined intervals in the front and rear, and 4 is between the front clamp device 2 and the rear clamp device 3. Shear device 5 that can be moved back and forth from the left and right direction, and 5 is a back bar device that can be moved back and forth between the front clamp device 2 and the rear clamp device 3 from the left and right direction, like the shear device 4.
Is an upper head mounted on the upper part of the rear clamp device 3, and 7 and 8 move the machining head 9 on the upper head 6 in the left-right direction, that is, in the direction of both strip end faces and in the front-back direction and in the vertical direction between both strip end faces. A welding carriage device, 10 is a transmission pipe for transmitting a laser beam generated by a laser oscillator 11, 12 is a preceding material to be welded (not shown), here, a leading strip, and 13 is a material to be trailing, which is a trailing strip here. , Arrow A indicates the traveling direction of the leading and trailing strips. Further, FIG. 12 shows an optical system of the above-mentioned conventional laser beam welding device, 14 is a mirror for changing the optical path of the laser beam, and 15 is a condenser lens (or a condenser lens attached inside the processing head 9). Mirror), and 16 indicates a laser beam.

Next, the operation will be described. In the steel process line, when the strip is subjected to continuous treatment such as pickling, plating, heat treatment, etc., the strip travels in the direction indicated by arrow A in FIG. And
When the strip is fed to reach the end, the leading strip 12 is moved to the blade width 4a of the shearing device 4 as shown in FIG.
It is guided inside and stops. In this state, the trailing strip 13 has its leading end fed into the blade width 4a of the shearing device 4 and stops. Then, as shown in FIGS. 10 and 13, the back bar device 5 is retracted and the shear device 4 is advanced to be positioned between the front clamp device 2 and the rear clamp device 3. Next, after holding the strips 12 and 13 with both clamp devices 2 and 3, the upper shear blade of the shear device 4 descends to cut the opposite ends of both strips 12 and 13. Subsequently, as shown in FIGS. 11 and 14, the shear device 4 is retracted, and the back bar device 5 is moved.
Moves forward and is positioned between the front clamping device 2 and the rear clamping device 3, and then the front clamping device 2 is moved to the rear clamping device 3 side by the blade width 4a of the shear device 4 to move the leading strip 12 Cutting surface and trailing strip 13
Butt against the cut surface of. Next, the welding carriage device 8 is moved in the front-back direction, that is, so that the processing head 9 is located on the joint between the strips 12 and 13 that are butted.
The processing head 9 is moved in the direction perpendicular to the end faces of the strips 12 and 13, and the processing head 9 is moved in the vertical direction so that the focus of the laser beam is at a predetermined height. When the preparation for welding is completed in this way, the laser beam 16 generated by the laser oscillator 11 is redirected by the mirror 14 and the condenser lens 15 is passed through the transmission tube 10 as shown in FIG. Thus, the welding is started by converging light on both strip joints, and the welding carriage device 7 is moved in the left-right direction, that is, in the end face direction of both strips, so that both strips 12 and 13 are continuously welded.

[0004]

The laser welding by the conventional laser beam welding apparatus is performed as described above. In this laser beam welding apparatus, the cutting shapes of both strips 12 and 13 cut by the shearing device 4 are perfect. 15- (A) without being a straight line, and the feed when the front clamp device 2 after cutting is moved by the blade width 4a of the rear clamp device 3 side shear device 4 Due to the deviation of the set position caused by the precision, there is a gap between the cut surface of the leading strip 12 and the cut surface of the trailing strip 13 as shown in FIG.
A minute gap (hereinafter referred to as a gap) G is generated as shown in (B). Therefore, in the case of a thick plate, it is generally disclosed in JP-A-61-1.
As shown in Japanese Patent No. 76490, if the gap G is small to some extent, a filler wire is inserted and welding is performed. However, when the plate thickness is thin, that is, the strips 12, 13
If the thickness is about 1 mm or less, inserting the filler wire makes it impossible to insert the filler wire because the finished thickness of the welded portion becomes very large. For this reason,
As shown in Japanese Patent No. 272, the cutting surface is ground by a grinding device after cutting. Alternatively, in order to improve the feed accuracy, it is necessary to improve the straightness of the cutting line and the feed accuracy by increasing the mechanical rigidity or the like to make the gap G extremely small. According to experiments, for example, when the plate thickness is 0.2 mm, the butt gap at the welding start end is within about 30 μm, and the butt gap other than the welding start end is allowed up to about 60 μm. In order to keep the gap at the time of welding within an allowable value, in order to improve the straightness of the cutting line and the feed accuracy, there is a problem in that an end surface grinding device is added and the device becomes large in size to increase mechanical rigidity. On the other hand, in order to widen the allowable value of the butt gap, a method of welding by laser beam defocusing (shifting the focus) disclosed in JP-A-3-234388 or a method of welding by scanning a laser beam is also considered. However, in this case, there is a problem in that the welding speed becomes very slow compared to the usual welding method.

The present invention has been made to solve the above problems, and a laser beam welding method capable of performing high-quality and reliable butt welding without increasing the size of the apparatus and reducing the welding speed. The purpose is to obtain a laser beam welding device.

[0006]

[Means for Solving the Problems] Claim 1 according to the present invention
In the laser beam welding method, the laser beam is focused along the abutting portion having a minute gap between the trailing end of the plate-shaped preceding material to be welded and the leading end of the following welding material to weld the abutting portion, Laser welding is applied to one of the materials to be welded at the welding start end of the abutting portion to weld the materials to be welded together, and then the welding of the abutting portion is performed.

In the laser beam welding method according to the second aspect of the present invention, one of the materials to be welded is melted by laser light at the welding start end of the butted portion to narrow the minute gap, and then the butted portion is welded. is there.

Further, in the laser beam welding method according to the third aspect of the present invention, the laser beam is scanned between both materials to be welded only at the welding start end of the abutting portion, and the materials to be welded are welded at the abutting portion after welding. .

Further, in the laser beam welding method according to the fourth aspect of the present invention, the butted portions are welded after the laser beam is defocused on both materials to be welded only at the welding start end of the butted portions to narrow the minute gap. .

According to the fifth aspect of the laser beam welding method, a wire is inserted only at the welding start end of the abutting portion to weld the materials to be welded together, and then the abutting portion is welded.

A laser beam welding method according to a sixth aspect is the laser beam welding method according to the second or fourth aspect, in which the welded portion near the welding start end is cut off after the completion of welding.

According to a seventh aspect of the present invention, there is provided a laser beam welding apparatus in which a laser beam is focused on a butting portion having a minute gap between a rear end of a plate-shaped preceding welding material and a leading end of a succeeding welding material. In the laser beam welding apparatus having the above-mentioned, and traveling the processing head along the abutting portion for welding, a pressurizing means for pressurizing the abutting portion in the plate thickness direction is provided in front of the processing head in the welding direction.

A laser beam welding apparatus according to an eighth aspect is the laser beam welding apparatus according to the seventh aspect, further comprising a heating processing head for defocusing a part of the laser beam to the abutting portion in front of the pressing means in the welding direction. is there.

According to a ninth aspect of the present invention, there is provided the laser beam welding apparatus according to the seventh aspect, wherein means for measuring a minute gap at the butted portion is provided so that the pressing force of the pressurizing means can be adjusted according to the amount of the minute gap. Is.

According to a tenth aspect of the present invention, there is provided a laser beam welding apparatus in which a laser beam is focused on a butting portion having a minute gap between a trailing end of a plate-shaped preceding welding material and a leading end of a following welding material. With a laser beam welding device equipped with a welding head that runs the processing head along the abutting part and welds the abutting part, a heating processing head that slightly irradiates the abutting part with a part of the laser beam in the welding direction and a minute It is provided with a gap measuring means for measuring the gap so that the defocus can be adjusted according to the minute gap amount.

[0016]

The laser beam welding method according to the present invention enables high quality welding by narrowing the gap at the welding start end by melting or expanding by heating at the welding start end. That is, the allowable gap value at the welding start end can be widened.

Further, in the laser beam apparatus according to the present invention, the pressurizing means and the heating head narrow the gap before laser beam welding to enable high quality welding. That is, the allowable gap value can be widened.

[0018]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. 1 is an operation explanatory view of a laser beam welding method according to a first embodiment of the present invention, and FIG. 2 is a sectional view of a laser beam welding apparatus at a welding start end of the first embodiment. In the figure, the components 1 to 14 are the same as the conventional ones, and the description thereof is omitted. Reference numeral 17 is a welding start end, 17G is a gap at the welding start end, 17a is a center shift position of the processing head 9, 18 is a welding end end, C is a gap center, and 19 is a laser beam scanning line.

Next, the operation will be described. As a welding method of this kind, the machining head 9 is usually arranged along the gap center C.
Is moved from the welding start end 17 to the welding end end 18 side to perform laser beam welding of the abutting portion. Here, the center shift position 17a at the welding start end 17 is processed on the trailing strip 13 near the welding start end 17 here. Head 9
To set the laser beam and focus the laser beam to the trailing strip 13
The center shift position 17a of the welding start point is heated and melted, and both strips 12 and 13 at the welding start end are welded.
After that, the processing head 9 is moved to the gap center C in the direction of the arrow B along the laser beam scanning line 19a while irradiating the laser beam, and the laser beam scanning line 19 and the gap center C are aligned in the direction of the welding end 18 while the laser beam is being emitted. Weld. This makes it possible to widen the allowable value of the butt gap at the welding start end in the substantially set state in laser beam welding of the butt portion where the gap at the welding start end is particularly important. According to this welding method, for example, when the welding start end gap exceeds the allowable value of 30 μm (the other abutting portion gap value is 60 μm or less) at the plate thickness of 0.2 mm described above, reliable welding cannot be performed. Even if the welding start end gap is 40 μm, high quality and reliable laser beam welding becomes possible.

The reason why the allowable value of the welding start end gap can be widened in this way is as follows. (1) Since the spot diameter of the laser beam at the focal position is very small, when the gap at the welding start end is large, most of the laser beam passes through the gap (there is no strip), and the strip is It does not melt because the heat input is small. However, as described in the first embodiment, the center shift position 17a is located at the welding start end.
By heating and melting the trailing strip 13 in advance, the molten trailing strip 13 is
2 outflow movement to the two strips 12 at the welding start end,
It acts to fill 13 gaps. As a result, the gap between the strips 12 and 13 at the welding start end is bridged by the melt and welded. (2) Once the welding start ends are welded, the heat of fusion heats both strips 12 and 13,
The end faces of both strips extend in the direction of decreasing the gap and are continuously welded to the end of welding while forming a melt. (3) At the same time, since the absorption rate of the laser beam with respect to the strip increases as the temperature of the strip increases, the laser beam with which the melting portion is irradiated is efficiently absorbed by the strip and further promotes melting to narrow the gap.

In the above embodiment, the processing head is moved from the center shift position 17a along the laser beam scanning line 19b, but the laser beam is irradiated as shown by the laser beam scanning line 19b (dotted line) in FIG. While moving the processing head to a position away from the welding start end 17 by a distance d,
The welding time can be shortened as compared with the above embodiment. In this case, welding cannot be performed from the welding start end 17 to a position separated by a distance d, but if the unwelded portion (shaded portion N) is cut off by a notcher device or the like not shown, it will be a problem in a later process. There is no such thing.

Example 2. Embodiment 2 of the present invention will be described below with reference to the drawings. FIG. 3 is an operation explanatory view of the laser beam welding method according to the second embodiment of the present invention, and FIG. 4 is a sectional view of the laser beam welding apparatus at the welding start end of the second embodiment. In the figure, except for the position of the processing head 9 at the welding start end and the laser beam state, the description is omitted because it is the same as in the first embodiment. Reference numeral 19c indicates a scan scanning line of the laser beam.

Next, the operation will be described. Welding start end 1
At 7, the laser beam is scanned 19c in a direction perpendicular to both strip end faces centering on the butt gap center C to melt the welding start ends 17 of the preceding strip 12 and the following strip 13, and then the scanning is stopped to change the laser beam. Processing head 9 with irradiation
Is moved in the direction of the welding end end 18 along the gap center C and laser beam welding of the abutting portion is performed. As a result, similarly to the first embodiment, the allowable value of the butt gap at the welding start end in the substantially set state is widened. According to this method, the welding time can be shortened as compared with the case where the welding is performed while scanning the entire welding line.

Example 3. The third embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is an operation explanatory view of the laser beam welding method in the third embodiment of the present invention, and FIG. 6 is a sectional view of the laser beam welding apparatus at the welding start end of the third embodiment. In the figure, except for the vertical position of the processing head 9 at the welding start end and the laser beam state, the description is omitted because it is the same as that of the first embodiment. Reference numeral 20 denotes a defocused laser beam.

Next, the operation will be described. Welding start end 1
In 7, the processing head 9 is raised or lowered from a predetermined set height during normal welding to defocus the laser beam and heat the welding start end 17. After that, the processing head 9 is moved to a predetermined height during normal welding while irradiating the laser beam, and is moved in the direction of the welding end point 18 along the gap center C to perform laser beam welding of the abutting portion. This makes it possible to narrow the gap at the welding start end and substantially widen the allowable value of the butt gap at the welding start end in the set state.
According to this method, the welding time can be shortened as compared with the case where the entire welding line is defocused and the welding is performed.

Example 4. In the first and second embodiments, the welding start end 17 is heated and melted at the strip end by the laser beam to weld both strips at the welding start end, and the butt gap of the welding start end in a substantially set state is obtained. However, as shown in FIG. 7, the filler wire 21 is inserted into the gap portion only at the welding start end 17 at the abutting portion of the leading strip 12 and the trailing strip 13 so that the laser The same effects as those in Examples 1 and 2 can be obtained as a welding method in which beam welding is performed and then laser beam welding is performed while the insertion of the filler wire is stopped. Note that if the welding start end where the finished thickness of the weld is increased by this method poses a problem for the convenience of the post-process (for example, variation in plate thickness in the rolling process), it is not described. It is only necessary to cut out the hatched portion N with a notcher device or the like.

Example 5. Further, in each of the above Examples 1 to 4, it is possible to widen the allowable value of the butt gap at the welding start end in a substantially set state by considering the laser beam welding method at the welding start end. However, an embodiment of the apparatus will be described below. FIG. 8 is a schematic diagram showing a partial schematic configuration of a laser beam welding apparatus in a fifth embodiment of the present invention and showing an operating state. In the figure, 5,
Reference numerals 9, 12, 13, 15, and 16 are the same as those in the conventional apparatus, and the description thereof is omitted. 22 is a roller which presses and runs the abutting portion of the strips 12 and 13 at a position preceding the processing head 9, 23 is a pressing mechanism which presses the roller 22 in the strips 12 and 13 direction, and these 22 and 23 form pressing means. ing. Reference numeral 24 is a half mirror that partially divides the laser beam 16 to change the direction, 25 is a mirror that changes the direction of the laser beam from the half mirror 24, and 26 is a heating lens that focuses the laser beam from the mirror 25.
A heating processing head 27 is formed by 5, 26, and heating run of the abutting portion of the strips 12, 13 precedes the roller 22. Reference numeral 28 is a gap sensor that measures the gap G between the strips 12 and 13. Note that arrow D
Indicates the direction of welding progress.

Next, the operation will be described. First, similarly to the conventional example, both ends of the leading strip 12 and the trailing strip 13 are set in a predetermined position with a gap in abutting state. Next, the laser beam 16 is emitted. First, the abutting portion of the strip is heated and expanded by the laser beam from the preceding heating head 27, and the gap is narrowed. Further, the trailing roller 22 passes over this surface and pressurizes it toward the back bar 5 to press and deform the strip end, further narrowing the gap and very narrow when the working head 9 for welding passes. Since welding is performed in the gap state, high-quality welding is possible, and the allowable value of the entire gap can be set to be larger than that of Examples 1 to 4. For example, in this embodiment, the allowable value of the gap at the welding start end for the plate thickness of 0.2 mm is about 50.
μm.

Further, the heating head 2 for gap measurement is used.
As shown in FIG. 9, the operation flow of the roller 7 and the roller 22 is adjusted by adjusting the pressure mechanism 23 according to the gap amount measured by the gap measurement sensor 28 so that the pressing force of the roller 22 is an appropriate value (for example, when the gap is small, To reduce the amount of deformation), the heating processing head 27 also moves the heating lens 26 in the vertical direction (for example, when the gap is small, the defocus is increased to reduce the amount of heating) to adjust the amount of heating. By controlling the optimum gap, more stable and high quality welding becomes possible. It should be noted that the size of the measurement gap is set to a predetermined value in advance, and the size is determined for that value.

Example 6. In the above embodiment, the pressing means (22, 23) and the heating processing head 27 are set at the same time, but only one of them may be installed.

[0031]

As described above, according to the first aspect of the present invention, the laser light is guided along the abutting portion having a minute gap between the rear end of the plate-shaped preceding material to be welded and the leading end of the following material to be welded. In the case of converging and welding the butt joints, one of the materials to be welded is irradiated with laser light at the welding start end of the butt joints to weld the materials to be welded together, and then the butt joints are welded. According to claim 2, after welding one of the materials to be welded with a laser beam at the welding start end of the butt portion to narrow the minute gap, the butt portion is welded, and according to claim 3, The laser beam is scanned between both materials to be welded only at the welding start end of the butted portion, and the materials to be welded are welded at the butted portion after welding, and according to claim 4, at the welding start end of the butted portion. Only the laser light is diff After welding, the welding of the abutting portions is performed after narrowing the minute gap, and according to claim 5, a wire is inserted only at the welding start end of the abutting portions to weld the materials to be welded together before welding the abutting portions. Therefore, there is an effect that it is possible to obtain a laser beam welding method capable of widening the allowable gap value at the welding start end, increasing the size of the apparatus, and performing high-quality and reliable welding without lowering the welding speed.

According to the sixth aspect of the present invention, since the vicinity of the welding start point is cut off after the completion of the laser beam welding method according to the second or fourth aspect, the defective portion at the welding start end is removed. There is no problem in the subsequent process.

Further, according to claim 7 of the present invention, the processing head for converging the laser beam on the abutting portion having a minute gap between the rear end of the plate-shaped preceding material to be welded and the leading end of the following material to be welded. In a laser beam welding device that has a welding head that travels along the abutting portion along with the abutting portion, pressurizing means for pressurizing the abutting portion in the plate thickness direction is provided in front of the processing head in the welding direction. Since the value can be widened, there is an effect that a laser beam welding device capable of performing high-quality and reliable welding can be obtained without increasing the size of the device.

Further, according to claim 8 of the present invention, in claim 7, the heating processing head for irradiating a part of the laser beam to the abutting portion is provided in front of the pressing means in the welding direction. The pressure applied by the pressure means can be lowered, and the gap can be easily narrowed.

According to a ninth aspect of the present invention, in the seventh aspect, means for measuring the minute gap of the butted portion is provided so that the pressing force of the pressurizing means can be adjusted in accordance with the amount of the minute gap, and The laser beam welding device according to claim 10 is provided with a processing head for converging a laser beam at a butting portion having a minute gap between a trailing end of a plate-shaped preceding welding material and a leading end of a following welding material, In a laser beam welding device that runs a processing head along the welded portion of a butt, a heating processing head that defocuses a portion of laser light to the front of the processing head in the welding direction and a gap that measures a minute gap Since the measuring means is provided so that the defocus can be adjusted according to the minute gap amount, it is easy to set the allowable gap value and high quality is achieved. The effect of laser beam welding device is obtained which can reliably welded.

[Brief description of drawings]

FIG. 1 is an operation explanatory diagram of a laser beam welding method according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the laser beam welding apparatus at the welding start end according to the first embodiment.

FIG. 3 is an operation explanatory diagram of a laser beam welding method according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a laser beam welding device at a welding start end according to a second embodiment.

FIG. 5 is an operation explanatory diagram of a laser beam welding method according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a laser beam welding device at a welding start end according to a third embodiment.

FIG. 7 is an operation explanatory diagram of a laser beam welding method according to a fourth embodiment of the present invention.

FIG. 8 is a schematic diagram showing a partial schematic configuration of a laser beam welding apparatus according to a fifth embodiment of the present invention.

FIG. 9 is an explanatory diagram showing an operation flow according to the fifth embodiment.

FIG. 10 is a perspective view showing a configuration of a conventional laser beam welding apparatus.

FIG. 11 is a perspective view showing a configuration of a conventional laser beam welding apparatus.

FIG. 12 is an optical path diagram of a conventional laser beam welding apparatus.

FIG. 13 is a side sectional view of an essential part for explaining an operating state of a conventional laser beam welding apparatus.

FIG. 14 is a side sectional view of an essential part for explaining an operating state of a conventional laser beam welding apparatus.

FIG. 15 is a strip state diagram for explaining a cut state and a butted state of the strip.

[Explanation of symbols]

 9 Processing Head 12 Leading Strip (Preceding Welding Material) 13 Trailing Strip (Tailing Welding Material) 16 Laser Beam 17 Welding Start End 17a Welding Start End Shift Position 17G Welding Start End Gap 19 Laser Light Scanning Line 19a Scan Scanning Line 20 Defocus 21 Filler wire 22 Roller 23 Pressurizing mechanism 27 Processing head for heating 28 Gap sensor G Gap

Claims (10)

[Claims] 1. A laser beam is converged along a butting portion having a minute gap between a trailing end of a plate-shaped preceding material to be welded and a leading end of a following welding material to weld the butting portion. A laser beam welding method, comprising irradiating one of the materials to be welded at the welding start end of the abutting portion to weld the materials to be welded together, and then welding the abutting portion. 2. A laser beam is focused along a butting portion having a minute gap between a trailing end of a plate-shaped preceding material to be welded and a leading end of a following welding material to weld the butting portion. A laser beam welding method, characterized in that one of the materials to be welded is melted by the laser beam at the welding start end of the butt portion to narrow the minute gap, and then the butt portion is welded. 3. A laser beam is focused along a butting portion having a minute gap between a rear end of a plate-shaped preceding welding material and a leading end of a trailing welding material to weld the butting portion. A laser beam welding method, characterized in that the laser beam is scanned between the materials to be welded only at the welding start end of the abutting portion to weld the materials to be welded together, and then the welding of the abutting portion is performed. 4. A laser beam is converged along a butting portion having a minute gap between a trailing end of a plate-shaped preceding material to be welded and a leading end of a following welding material to weld the butting portion. A laser beam welding method, characterized in that the laser beam is defocused to both the materials to be welded only at the welding start end of the abutting portion to narrow the minute gap and then the abutting portion is welded. 5. A laser beam is focused along a butting portion having a minute gap between a trailing end of a plate-shaped preceding welding material and a leading end of a trailing welding material to weld the butting portion. A laser beam welding method, wherein a wire is inserted only into a welding start end of a butt portion to weld the materials to be welded together, and then the butt portion is welded. 6. The laser beam welding method according to claim 2, wherein the vicinity of the welding start end is cut off after the welding is completed. 7. A processing head for converging a laser beam at a butting portion having a minute gap between a trailing end of a plate-shaped preceding material to be welded and a tip of a trailing welding material to be machined is provided, and the machining is performed along the butting portion. A laser beam welding apparatus for moving a head to weld the abutting portion, wherein a laser beam welding device is provided in front of the processing head in a welding direction, a pressurizing means for pressing the abutting portion in a plate thickness direction. . 8. The laser beam welding apparatus according to claim 7, wherein a heating processing head for irradiating a part of the laser beam to the abutting portion in a defocused manner is provided in front of the pressing means in the welding direction. 9. The device according to claim 7, further comprising means for measuring a minute gap at the abutting portion so that the pressing force of the pressure means can be adjusted in accordance with the amount of the minute gap.
The laser beam welding apparatus according to. 10. A machining head for converging laser light at a butting portion having a minute gap between a trailing end of a plate-shaped preceding welding material and a leading end of a following welding material is provided with the machining head along the butting portion. In a laser beam welding device that travels a head and welds the abutting portion, a heating processing head that defocuses a portion of the laser light forward to the processing head in the welding direction and the minute gap are measured. The laser beam welding apparatus is characterized in that the defocus can be adjusted in accordance with the minute gap amount by providing a gap measuring means.