JP4754426B2 - LASER LASER WELDING METHOD AND DEVICE - Google Patents

Description

  The present invention superimposes a plurality of plate materials, and irradiates laser light from the superposition direction in the vicinity of the end portion of the superposed plate material, while moving the laser light along the end portion, The present invention relates to a lap laser welding method and a laser welding apparatus used therefor.

As a body panel of an automobile, a cross section having a flange portion 2 and a bent portion 3 formed of a thin plate material made of high-strength steel, as shown in FIG. A frame member in which the overlapped portion is joined by spot welding or the like, and the flange portion 2 and the plate member 4 or the plate member 4 interposed between the flange portions as shown in FIGS. A frame member in which they are similarly joined, and a frame member in which a plurality of structural members 1 are stacked in the same direction as shown in FIG. 1d are used.
When laser welding is used for joining the overlapped portion, the joint strength is high by continuous welding, and welding can be performed from one side, so that the joint portion can be compared with spot welding and arc welding that have been used conventionally. There are advantages that the degree of freedom in design is large, the width of the flange portion is narrowed, and the structural member can be reduced in size and weight.

Conventionally, in laser welding of lap weld joints of plate materials, if the gap between the plate materials in the overlapped portion varies, the welding quality deteriorates, and therefore, the focus has been on optimizing the gap between the plate materials.
For example, pressing the roller from the laser irradiation side to the overlapping part, moving the roller together with the laser beam, pressing one plate against the other plate and adjusting the distance between them, or welding the plates together Patent Document 1 discloses that the flange portions are sandwiched from both sides by a pair of rollers and welded in the same manner.

  However, in a structural member made of high-strength steel, the width of the flange portion is shortened to reduce the weight of the member, and the vicinity of the overlapped portion end is welded so as to melt to the lower plate material to increase the joint strength. Then, the present inventors' research has further found that weld solidification cracking becomes a problem.

That is, as shown in FIG. 2a, the laser beam is irradiated from the overlapping direction, that is, the direction intersecting the flange, to the flange portion of the frame member in which the both side flange portions of the structural member having a hat-shaped cross section are overlapped with each other. When welding is started so as to melt to the lower plate material and welding is started from the longitudinal end portion of the flange, as shown in FIG. appear.
Further, as shown in FIG. 3, even when the welding start point is not the longitudinal end portion of the flange 2 and a point separated from the end portion by a predetermined distance is the welding start point, the central portion of the welded portion is expanded after welding. And cracks may occur. In the figure, 8 is a laser welding head.

  This is because when the laser beam is irradiated and welded so as to melt up to the stacked lower plate material, the flange part on the end side from the melted part is solidified until the melted part formed by the laser light irradiation is solidified. It will be in the state separated from the flange body. At this time, if the width of the part is small, it is considered that the part expands due to heat conduction from the welded portion, and the part is deformed, pulling the weld bead in the middle of solidification, and cracking occurs during solidification.

Conventionally, Patent Literature 3 and Patent Literature 4 are known as techniques for preventing cracking and deformation of a welded portion in laser welding.
In Patent Document 3, when laser welding a lap joint of a member made of high carbon steel and a member made of stainless steel or the like, shrinkage cracking occurs due to shrinkage stress generated at the time of melt solidification, and the cracking, It describes that the position of the joint portion is devised to prevent the tensile stress from being applied to the melted portion.

Further, in Patent Document 4, when one plate member is abutted against the other plate member having a narrow width and the butt portion is laser-welded, the narrower plate member is deformed by heat and the butt portion is deformed. Since the interval is widened, it is described that the butt portions of both plate materials are temporarily attached to prevent deformation of the plate materials.
However, these documents do not mention at all the above solidification cracks and solutions for the same.

As described above, in laser welding of a thin plate material, the width of the flange portion is shortened to reduce the weight of the member, and further, the vicinity of the overlapping portion end portion is welded so as to melt to the lower plate material. Conventionally, it has not been known that weld solidification cracks occur when welding is performed so as to increase the joint strength.
JP-A-8-90264 JP 2004-130323 A Japanese Patent Laid-Open No. 11-245065 JP 59-215288 A

  Therefore, in view of the situation as described above, the present invention superimposes a plurality of plate materials and emits laser light from the superposition direction so as to melt up to the laminated lower plate material in the vicinity of the end portion of the superposed plate materials. It is an object of the present invention to provide a laser welding method that does not cause solidification cracks as described above and a laser welding apparatus used therefor when the stacked plate members are welded together by moving the laser beam along the end while irradiating. And

In order to solve the above problems, the present invention is characterized as follows.
The invention of the overlap laser welding method according to claim 1 irradiates a laser beam from the overlapping direction so that a plurality of plate members are overlapped, and the overlapped lower plate member is melted in the vicinity of the end portion of the overlapped plate member. and while, moving along the edge of the plate where the laser beam was continuously said superimposing, in the laser welding method for welding superimposed sheet together, against the end face of the end portion along the welding direction of the plate A bulge restraining member that suppresses bulging outward of a portion located on the end side from the laser irradiation portion of the plate material is disposed, and the bulge restraining member is deformed by bulging of the portion. Thus to support as given reaction force opposed to the force, characterized by welding while suppressing swelling of the site.

According to a second aspect of the invention of the lap laser welding method, as described in the claim, the bulge restraining member that moves together with the laser beam can be restrained with respect to the welding traveling direction. It is characterized by being arranged rearward .
According to a third aspect of the invention of the lap laser welding method, as described in the claim, the bulging suppression member is a bulging suppression plate, and the bulging suppression covers at least a welding range. The bulging suppression plate is arranged in advance along the end surface of the end portion of the stacked plate members.
According to the invention of the lap laser welding method of claim 4, the bulge restraining member is a bulge restraining pin, and the bulge restraining pin is It is characterized in that it is carried out by arranging a plurality at intervals along the end face of the end portion of the plate material that has been overlapped in advance so as to cover at least the welding range.

The invention of the overlap laser welding method according to claim 5 has a laser welding head for irradiating laser light, and is overlapped so as to melt up to the overlapped lower plate member in the vicinity of the end portions of the overlapped plate members. In a laser welding apparatus that welds the overlapped plate members to each other in the welding direction of the plate members by moving the laser welding head continuously along the end portions of the overlapped plate members while irradiating laser light from the alignment direction. a said end along at least the end surface of the end portion in the vicinity of the laser beam is irradiated in contact, suppressing the bulging outward of the site located on the end portion side from the laser irradiation section of the plate The bulge suppressing member is disposed, and the bulge suppressing member is supported so as to be given a reaction force against the deformation force caused by the bulging of the portion .

In the invention of the lap laser welding method according to claim 6, the bulge suppressing member is a member common to the laser welding head, and is rearward with respect to the welding progress direction from the laser welding head. It is attached so that it may be arrange | positioned, It moves with a laser beam, It is characterized by the above-mentioned.

Invention lap laser welding method 請 Motomeko 7 as described in the claim, that the bulging inhibiting member is a roller disposed in contact with an end surface of said end portion of the plate Features.

According to the invention of the lap laser welding method of claim 8 , as described in the claim, the bulge suppressing member is a spatula-like member disposed in contact with the end face of the end portion of the plate member. It is characterized by.
In the invention of the lap laser welding method of claim 9 , as described in the claim, the bulge suppressing member is previously provided along the end surface of the end portion of the plate material so as to cover at least the welding range. It is the bulging suppression plate arrange | positioned, It is characterized by the above-mentioned.
In the invention of the lap laser welding method of claim 10 , as described in the claim, the bulge suppressing member is previously provided along the end surface of the end portion of the plate material so as to cover at least the welding range. A plurality of bulge-inhibiting pins arranged at intervals.

According to the first and fifth aspects of the present invention, for example, even if the lower plate material overlapped with the structural member made of high-strength steel is sufficiently melted, the welded portion is overlapped without causing solidification cracks. Since the combined plate materials can be laser welded to each other, a welded portion having high strength can be formed even if the width of the overlapped portion is narrow, and the structural member can be reduced in size and weight.
According to the invention concerning Claim 2 and Claim 6-Claim 8 , prevention of a crack can be automatically performed with progress of laser welding. Moreover, according to the invention which concerns on Claim 6 , prevention of the solidification crack accompanying the progress of welding can be performed more effectively.
According to the inventions according to claim 3, claim 4, claim 9 and claim 10 , by using a jig fixed in advance, it is possible to more easily and reliably carry out the prevention of solidification cracks, Even when welding is started from the end as shown in FIG. 2 , solidification cracking can be reliably prevented.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS.
When producing a frame member by laminating a plate-like member having a flange at the end such as a hat-shaped structural member shown in FIG. 1 with a similar flange or plate material and laser welding between the two, For example, when using a structural member with a narrower flange width, such as within 8 mm, to reduce the weight of the entire frame member, the distance from the weld bead to the flange end is shorter in the range of 1.5 mm to 3.5 mm. In such a condition, as shown in FIG. 3, even if welding is started at a position away from the longitudinal end portion of the flange, the heat conduction from the welded portion as described above is required. The part deformed by this pulls the weld bead during solidification, and solidification cracking is likely to occur.
For the structural member, a steel plate having a tensile strength of 270 MPa or more is used, but solidification cracking occurs when a steel plate of 440 MPa or more is used as at least one plate material of the stacked plate materials.

  In order to reduce the weight of the structural member, it is more effective to make the flange width within 8 mm. In such a flange width, the distance from the weld bead to the flange end is 1.5 mm to 3.5 mm. If the flange end is less than 1.5 mm, the flange end side melts to the flange end and is easily melted off. If it exceeds 3.5 mm, welding is started at a position away from the flange longitudinal end. This is because solidification cracks as shown in FIG. 3 do not occur.

Therefore, the present inventors investigated the cause of solidification cracking and examined a method for preventing the cracking during solidification by means of welding work.
FIG. 4 shows the relationship between the temperature of the solidification process and the strain generated around the weld in the laser welding of thin plates. In the figure, a steel plate having a thickness of 1.2 mm and a tensile strength of 590 MPa comprising mass%, carbon content of 0.06%, silicon content of 0.5% and manganese content of 1.5% is used. This was obtained by using a sample obtained by performing overlap laser welding under the conditions of an output of 2 kW and a welding speed of 2 m / min.

According to FIG. 4, a tensile force acts on the welded portion immediately below the liquidus temperature, and when the temperature is sufficiently lowered from the liquidus temperature, a compressive force acts on the welded portion. In the region (2) in the solidification process behind the laser light irradiation position, a large strain in the tensile direction is generated, which can be said to lead to solidification cracking.
In order to suppress the bulging, it was found that the bulging can be suppressed by applying a force of about 12 kgf to the member while in the region (2) in the solidification process of the weld bead.

Therefore, in the present invention, welding is performed while forcibly suppressing the bulging of the portion located on the end side from the laser irradiation portion of the plate material.
More specifically, the bulging is suppressed using a bulging suppressing member. As the bulge suppressing member, there are a case where a moving jig that moves with the movement of the irradiation position of the laser beam is used and a case where a fixed jig that is arranged in advance at the end of the plate material is used.

Hereinafter, embodiments in each case will be described.
(1) When using a moving jig FIG.5, 6 shows the embodiment in the case of using the jig which moves with a laser welding head. 5 and 6 show an example in which the bulge suppressing member is attached to the arm tip of the welding robot together with the laser welding head, but the moving device is not limited to the welding robot.

  5A and 5B, reference numeral 5 denotes a roller used as a bulge suppressing member, which is attached to a bracket 6 attached to an arm tip of a welding robot via a roller support member 7 so as to be rotatable. And it contacts with the end surface of the flange 2 of the plate material which is a welding work, and moves together with the movement of the laser welding head 8 similarly attached to the placket 6.

Further, as described above, since a large distortion occurs while the welded portion is in the region (2) in FIG. 4, in order to prevent the roller from bulging out the member while the welded portion is in the region, It arrange | positions so that it may contact | abut to the end surface of the flange 2 2.5 mm-5 mm back from a laser beam irradiation position.
The roller support member 7 is preferably attached to the bracket 6 so that the position of the roller support member 7 can be adjusted so that the welding direction between the laser welding head 8 and the roller 5 and the distance in the direction perpendicular thereto can be adjusted. At this time, the roller support member 7 can be automatically moved by an external command using a driving device.
Further, the number of rollers is not limited to one as shown in the figure, but may be two or more. In this case, the range for suppressing the bulging becomes wider. Is preferable.

  One end of an optical fiber 9 whose other end is connected to a laser oscillator is connected to the laser welding head 8. As a laser oscillator provided at the other end of the optical fiber 9, for example, a YAG laser is used, and welding is performed while the laser welding head 8 is moving under welding conditions of a processing point output of 3 kW and a welding speed of 3 m / min. .

Then, in advance, a structural member having an overlaid flange 2 as shown in FIG. 1 is positioned and fixed on a predetermined work fixture, and the roller 5 is brought into contact with the end face of the flange, and the laser welding head is attached to the flange 2. Position the top and start welding.
As shown in FIG. 3, the welding start point is a position spaced from the longitudinal end of the flange in the longitudinal direction of the flange, and the position where the roller 5 can reliably contact the longitudinal end surface of the flange.
Since the roller 5 is supported by the arm of the welding robot so as to apply a reaction force that opposes the deformation force caused by welding, the irradiated portion of the laser beam is melted, and as the welding progresses, the end portion of the roller 5 extends from the molten portion Even if the flange portion on the side is separated from the flange main body and the portion is about to thermally expand due to heat conduction from the welded portion, it can be suppressed by the roller.

  In Patent Document 2, in a laser welding apparatus provided with a processing head that overlaps flange portions of a plurality of workpieces and moves along the overlapping portion while irradiating the overlapping portion with laser light, the processing head In addition, a laser welding apparatus provided with a position scanning roller that contacts the tip of the flange is disclosed, and the scanning roller is pressed toward the flange end by a spring, but accurately copies the shape of the flange end. For this reason, the spring force is not increased, and the copying roller has no action to prevent bulging.

  FIG. 6 shows a modified example of the moving jig, and shows a preferable example when the lower plate 11 is arranged so as to protrude from the plate 12 arranged above. In the figure, reference numeral 10 denotes a spatula-like suppressing member for suppressing bulging, which is attached to the bracket 6 and arranged so as to be movable together with the laser welding head 8 in the same manner as the roller. The tip of the spatula-like restraining member is formed to have the same or a slight thickness as the plate disposed above, and is formed so that it can be reliably engaged with the plate. Further, it is desirable that the spatula-like suppressing member has a curved portion at the front and rear in order to smoothly move. The spatula-like suppressing member has an advantage that it can be formed in a width corresponding to the member because it can take a wider area in direct contact with the plate material end than the roller.

(2) When using a fixing jig In FIG. 7, the example in the case of suppressing a bulging with the fixing jig which covers the welding range 15 at least is shown. FIG. 7a is an example using a continuous bulge suppressing plate 13 that is arranged in advance along the end face, and FIG. 7b is a bulge suppressing pin 14 that is arranged in advance at intervals along the end face. It is an example using. Reference numeral 16 denotes a welding start point.

The bulge suppressing plate 13 and the pin 14 shown in FIGS. 7a and 7b are preliminarily arranged on the work fixture so as to cover at least the welding range 15, and overlapped flanges as shown in FIG. When the structural member having 2 is positioned and fixed on the work fixture, the flange end face is arranged so as to contact the bulge suppressing plate 13 or the pin 14. Thereby, the bulge of the part located in the flange end surface side from a fusion | melting part is suppressed.
In FIG. 7b, a cylindrical pin is illustrated, but the pin may have a prismatic shape or a width in the longitudinal direction of the flange.

In the case of the bulge suppressing pin shown in FIG. 7b, it is necessary to install it at an interval of 10 mm or less, preferably an interval of 5 mm or less so that the welded portion is always subjected to compressive stress.
When using a fixture, especially a continuous expansion suppression plate, as shown in Fig. 2 , even if welding is started from the end, the expansion of the end is suppressed and solidification cracking is reliably prevented. can do.

  The embodiment described above is an example of the present invention, and the present invention is not limited by the embodiment, and is defined only by matters described in the claims of the claims. Other embodiments can also be implemented.

It is a figure which shows the example of the member which has a lap joint. It is a figure which shows one example of a solidification crack. It is a figure which shows the other example of a solidification crack. It is a figure which shows the relationship between the temperature of the solidification process after welding, and distortion. It is a figure which shows one example of the bulging suppression member which concerns on this invention. It is a figure which shows the other example of the bulging suppression member which concerns on this invention. It is a figure which shows the further another example of the bulging suppression member which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Structural member of hat-shaped cross section 2 Flange part of structural member 3 Bending part of structural member 4 Plate material 5 Roller swelling suppression member 6 Placket 7 Roller support member 8 Laser welding head 9 Optical fiber 10 Spatial swelling restraining member 13 Swelling Suppression plate 14 Swelling suppression pin 15 Welding range 16 Welding start point

Claims (10)

A plurality of plate materials are superposed, and laser light is continuously superposed while irradiating laser light from the superposition direction so as to melt up to the superposed lower plate material in the vicinity of the end of the superposed plate material. In the laser welding method in which the stacked plate materials are welded together, moved along the edges of the plate materials,
In contact with the end surface of the end portion along the welding direction of the plate material, is disposed to suppress swelling suppressing member bulging outward of the portion located at the end side of the laser irradiation section of the plate, and overlaid laser welding, characterized in that depending on the support to be given a reaction force to counteract the bulging inhibiting member the deformation force by the bulging of the site, welding while suppressing swelling of the site Method. 2. The lap laser welding method according to claim 1, wherein the bulge suppression is performed by arranging a bulge suppression member that moves together with the laser beam behind the laser beam in the welding progress direction .   The bulge restraining member is a bulge restraining plate, and the bulge restraining plate is disposed in advance along the end surface of the end portion of the overlapped plate member by covering the bulge restraining plate covering at least the welding range. The lap laser welding method according to claim 1, wherein the lap laser welding method is performed.   The bulge restraining member is a bulge restraining pin, and the bulge is restrained along the end surface of the end portion of the plate member that has been overlapped in advance so that the bulge restraining pin covers at least the welding range. The lap laser welding method according to claim 1, wherein a plurality of laser welding are performed at intervals. A laser welding head that irradiates laser light, and laser welding is performed while irradiating the laser light from the overlapping direction so as to melt up to the stacked lower plate material in the vicinity of the ends of the stacked multiple plate materials. In a laser welding apparatus for continuously moving a head along an end portion of the stacked plate members and welding the stacked plate members to each other,
A the end portion along the welding direction of the plate, the end face of the end portion in the vicinity of at least the laser beam is irradiated in contact with, outside the site located on the end portion side from the laser irradiation section of the plate The bulge suppressing member for suppressing the bulging of the laser beam is disposed, and the bulging suppressing member is supported so as to be applied with a reaction force that opposes the deformation force caused by the bulging of the portion. apparatus. The bulge suppressing member is attached to a member common to the laser welding head so as to be arranged behind the laser welding head in the welding progress direction, and moves together with the laser beam. Item 6. The lap laser welding apparatus according to Item 5. The overlap laser welding apparatus according to claim 6, wherein the bulge suppressing member is a roller disposed in contact with an end face of the end portion of the plate member. The overlap laser welding apparatus according to claim 6, wherein the bulge suppressing member is a spatula-like member disposed in contact with an end face of the end portion of the plate member.   6. The overlapping laser according to claim 5, wherein the bulge restraining member is a bulge restraining plate arranged in advance along the end surface of the end portion of the plate so as to cover at least the welding range. Welding equipment.   The bulge restraining member is a bulge restraining pin that is arranged in advance at intervals along the end face of the end portion of the plate so as to cover at least the welding range. The lap laser welding apparatus described in 1.

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