JP2006346741A - Laser welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve weld strength through formation of a stable and sound weld bead free from blowholes by performing the laser welding of steel sheets keeping a designated distance of gap each other so as to prevent generation of decomposition gas or releasing of the gas even if a small amount of vaporized gas is generated due to overheat of a metal sheet during laser welding. <P>SOLUTION: The welding method is applied for welding workpieces 11, 12 at least either one of which is a zinc coated steel sheet. Both the steel sheets are temporarily joined through a temporary fixing member 14 with a designated thickness at the positions other than predetermined welding points on the workpieces. Then the laser welding is performed at the predetermined welding points on the workpieces, keeping the open gap equivalent to the designated thickness. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser welding method, and more particularly to a laser welding method capable of maintaining a gap between plate materials at a constant value and increasing a degree of freedom of welding by reducing a pressing jig in welding of metal plates.

  Conventionally, when laser welding a steel plate as a metal plate, as shown in Patent Document 1 below, laser welding is performed in a state where an organic thin insert material is interposed between steel plates to be joined, and the insert material is interposed. It is carried out.

Laser welding is performed by driving a scan head provided at the tip of a welding robot and irradiating a predetermined position of a positioned workpiece with laser light, as shown in Patent Document 2 below.
JP-A-6-7978 JP-A-10-180472

  Conventionally, since it is necessary to keep the gap between galvanized steel sheets below a certain level so that laser welding is appropriately performed, it is necessary to firmly hold the workpiece using a pressing jig. For this reason, there exists a problem that the range of laser welding is restrict | limited because a holding jig becomes obstructive. Therefore, if laser welding is performed with the insert material interposed, the clamp jig can be reduced to increase the degree of freedom of welding, but if laser welding is performed with an insert material of 0.2 mm or more in thickness, There is a problem that the gas generated when the metal plate evaporates and the pyrolysis gas of the insert material are not released but enter the weld bead to form a blow hole and the welding strength is lowered.

  The present invention has been made to solve the conventional problems as described above, and provides a laser welding method capable of ensuring the welding strength by preventing the occurrence of blow holes in the welding of metal plates. Objective.

  In order to achieve the above object, a laser welding method according to the present invention is a laser welding method for welding a workpiece made of a metal plate, and has a predetermined thickness at a site other than a welding point defined for the workpiece. Both steel plates are temporarily fixed by interposing a temporary fixing member, and laser welding is performed in a state where a gap corresponding to the predetermined thickness is opened at a welding point defined on the workpiece.

  According to the laser welding method according to the present invention configured as described above, in the workpiece made of a metal plate, the steel plates are laser-welded with a gap of a predetermined thickness being opened. No decomposition gas is generated during welding, and even if a small amount of evaporative gas is generated by heating the metal plate, the gas is released, so that no blowhole is generated, and a stable and good weld bead can be obtained. Welding strength can be improved.

  Hereinafter, a laser welding method according to the present invention will be described in detail with reference to the drawings.

  1 and 2 are views for explaining a laser welding method according to Embodiment 1 of the present invention. FIG. 1 is a partial external view of a workpiece, FIG. 2A is a plan view of a laser welding portion, and FIG. 2B is a cross-sectional view of the laser welding portion.

  In the present embodiment, at least one of the steel plates is made of a galvanized steel plate. In the present embodiment, the upper steel plate 11 is a galvanized steel plate, and the lower steel plate 12 is an SPC material. An example is given. When the upper steel plate 11 and the lower steel plate 12 are laser-welded, a temporary fixing having a predetermined thickness is provided at a portion of the lower steel plate 12 other than the welding points 13a, 13b, 13c, 13d, and 13e defined on the workpiece 10. Adhesive tapes 14a, 14b, 14c, and 14d as members are attached. Although only five welding points are shown in the drawing, the same number of welding points as the number of welding points located on the near side of the upper steel plate 11 are actually located on the back side of the upper steel plate 11. In the figure, only four adhesive tapes are attached, but in reality, the adhesive tape is attached between all the welding points. In the present embodiment, an acrylic quasi-structured adhesive tape having a thickness of 0.4 mm or more or an epoxy-based structural adhesive tape having a thickness of 0.8 to 1.0 mm is used.

  When the adhesive tape is applied as described above, the upper steel plate 11 and the lower steel plate 12 are attached together, and both the steel plates are temporarily fixed with the applied adhesive tape. In this state, a gap corresponding to the thickness of the adhesive tape is provided between the steel plates at the welding point. In this way, when the steel plates are temporarily fixed together, welding can be performed without using a jig for firmly pressing the steel plates together, and there is no part that becomes an obstacle to laser irradiation, and the degree of freedom and speed of laser welding. Will improve.

  Next, these welding points 13a, 13b, 13c, 13d, and 13e are laser-welded with a gap between the two steel plates. As shown in FIG. 2A, only the welding points 13a, 13b, and 13c are welded linearly in the laser welded portion after laser welding. Further, the cross-sectional view of the laser welded portion is as shown in FIG. 2B, and the upper steel plate 11 and the lower steel plate 12 are joined at the welding points 13a, 13b, 13c, 13d, and 13e. Since laser welding is performed with a gap between the upper steel plate 11 and the lower steel plate 12, zinc vapor that evaporates during laser welding is released from the gaps 15a, 15b, 15c between the welding points 13a, 13b, 13c. As a result, the occurrence of blow holes can be suppressed, a stable and good weld bead can be obtained, and the welding quality can be improved. Further, since the gap is uniform, the state of the weld bead is also good.

  The laser welding as described above is performed by a laser welding apparatus as shown in FIG.

  As shown in FIG. 3, the laser welding apparatus 20 includes a robot 22, a processing head 24, and a control device 26. The robot 22 is designed to be capable of remote welding in which welding is performed by irradiating a laser beam from a location distant from the welding point of the workpiece, and a machining head 24 is attached to the end of the arm. The processing head 24 has a laser irradiation mechanism for scanning the laser beam irradiated to the welding point, and performs the focus adjustment of the laser beam and the adjustment of the irradiation position by this mechanism. The control device 26 controls the operation of the laser irradiation mechanism of the processing head 24, outputs laser light, and controls the operation of the robot 22. The control device 26 and the machining head 24 are connected by an optical fiber 28, and the control device 26 and the robot 22 are connected by a control line 30.

  The machining head 24 is configured as shown in FIG. In the processing head 24, a variable focus mechanism 40 and a scan mirror 50 are provided as laser irradiation mechanisms. The variable focus mechanism 40 is supported so as to be movable forward and backward in the laser light irradiation direction with respect to the irradiation end of the optical fiber 28, and includes a diffusion lens 42, a condenser lens 44, and a condenser lens 46. By adjusting the position of the variable focus mechanism 40 with respect to the irradiation end of the optical fiber 28, the focal length in the irradiation direction changes. A scan mirror 50 is swingably attached to the rear stage of the focus variable mechanism 40 in the laser light output direction. As the scan mirror 50 swings, the laser beam output from the variable focus mechanism 40 is scanned over the workpiece. A laser irradiation port 52 is opened below the processing head 24, and the laser beam reflected by the scan mirror 50 is irradiated to the welding point of the workpiece via the laser irradiation port 52. The position adjustment of the focus changing mechanism 40 and the swing of the scan mirror 50 are controlled by the control device 26.

  FIG. 5 is a block diagram showing the configuration of the control system and the control system of the machining head.

  The processing head 24 includes a variable focus mechanism 40 and a scan mirror 50. The focus variable mechanism 40 is adjusted in position by a lens position adjusting servo motor 60, and the scan mirror 50 is oscillated by a laser scanning motor 62. Position adjustment is performed. The control device 26 includes an optical system control unit 72, and the optical system control unit 72 controls the movement of the lens position adjusting servo motor 60 and the laser scanning motor 62. The optical system control unit 72 includes a laser generator (not shown), and guides laser light from the laser generator to the focus variable mechanism 40 through the optical fiber 28. The control device 26 further includes a robot control unit 74, and the operation of the robot 22 is controlled by the robot control unit 74. Further, the control device 26 includes a laser irradiation position detection unit 76, and the laser irradiation position detection unit 76 acquires position information of each arm of the robot 22 from the robot control unit 74 and grasps the laser irradiation position based on the position information. To do. The acquired position information is used by the optical system control unit and used for swing control of the scan mirror 50.

  The laser welding apparatus configured as described above operates as shown in the operation flowchart of FIG. This operation will be described with reference to FIG.

  First, upon receiving an instruction to start laser welding, the optical system control unit 72 drives the lens position adjustment servo motor 60 to adjust the position of the variable focus mechanism 40 relative to the optical fiber end so that the laser beam is focused at the welding point. Adjust. This adjustment may be performed manually, or may be performed automatically by reading data on the focal position set for each work by the optical system control unit 72 (S1). Next, the robot control unit 74 moves the machining head 24 at a predetermined constant speed (S2). The position of the machining head 24 at this time, in other words, the laser irradiation position is detected by the laser irradiation position detector 76 (S3). The optical system control unit 72 adjusts the position (swing angle) of the scan mirror 50 according to the detected laser irradiation position (S4). Until the welding of all the welding points is completed, the processes of S2 to S4 are repeated (S5: NO), and when the welding of all the welding points is completed (S5: YES), the laser welding is finished. In the above embodiment, the focus of the laser beam is adjusted only before the start of the welding operation, and the adjustment is not performed during the operation. However, the workpiece is not flat and the height differs depending on the position of the welding point. In this case, the focal position is changed according to the detected laser irradiation position.

  The series of processes described above will be described with reference to FIG. 7. Laser welding is performed as follows. First, assuming that the welding points 13a to 13f are set on the workpiece, the machining head 24 moves at a constant speed without resting in the direction of the arrow shown in the drawing. The oscillating angle of the scan mirror 50 is such that the laser beam accurately strikes the welding point 13a while the machining head 24 moves, and that the laser beam is reflected in the direction opposite to the moving direction of the machining head 24. It changes every moment and welding is performed at a speed slower than the moving speed of the machining head 24. When the welding of the welding point 13a is completed, the oscillation angle of the scan mirror 50 is suddenly changed to the moving direction of the machining head 24 in order to irradiate the laser beam instantaneously to the starting position of the next welding point 13b. Then, while moving the machining head 24 at a constant speed, the swing angle of the scan mirror 50 is changed as described above, and laser welding is performed by irradiating the welding point 13b with laser light. The above operation is performed up to the welding point 13f to complete the welding.

  In the above embodiment, the galvanized steel plate is exemplified as the metal plate. However, the present invention can be applied to other types of steel plates. Moreover, in the above embodiment, although the case where adhesive tape 14a, 14b, 14c, 14d was affixed between welding points 13a, 13b, 13c was illustrated, as shown in FIG. Adhesive tapes 14a and 14b may be attached so as to sandwich 13b and 13c.

  Furthermore, as shown in FIG. 9, the adhesive tape 14 which affixes the whole site | parts other than the welding points 13a, 13b, 13c may be sufficient. When the pressure-sensitive adhesive tape having the form as shown in FIG. 9 is used, it is not necessary to perform sealing for airtightness and watertightness between the two steel plates in a subsequent process, so that the production efficiency can be improved. Moreover, since the adhesive tape 14 should just be affixed continuously to a steel plate, while improving the efficiency of the affixing operation | work, the fatigue characteristics, strength, torsional rigidity after welding can be improved, and the reinforcement effect of welding is obtained. be able to.

  Moreover, as shown in FIG. 10, by making the steel plate into a joggle structure, the gap between the portions where the adhesive tape is interposed can be made larger than the gap between the welding points 13a, 13b, 13c, and the thick adhesive tape 14a. , 14b, 14c, and 14d can be used. For this reason, the reinforcing effect of welding is enhanced, the handling property is high, the workability is good, and the manufacturing is easy, so that it is relatively inexpensive and the cost can be reduced.

  Moreover, in the above embodiment, although the adhesive tape was used for the adhesion | attachment means which functions as a temporary fix | stop member, it is also possible to use a paste-form adhesive. In this case, it is preferable to include a mixture for adjusting the gap between the steel plates in the adhesive. As the mixture, for example, inelastic small spheres such as glass and ceramic can be used.

  In order to secure a gap between welding points using an adhesive, as shown in FIGS. 11 (a) and 11 (b), a paste-like shape in which small spheres are mixed between the welding points 13a, 13b, and 13c. The adhesive is dripped and both steel plates are pressed with a predetermined force. As a result, the adhesive is interposed in the gaps at predetermined intervals by the small spheres at portions other than the welding points 13a, 13b, and 13c.

  When using an adhesive, it is necessary to preliminarily harden with a precure device and adjust the gap between the two steel plates before performing the welding operation. When the adhesive is thermosetting, it is necessary to perform main curing in an oven.

  As described above, according to the present embodiment, both the steel plates are temporarily fixed so that a gap is opened in the portion where laser welding is performed, and both the steel plates are welded in a state where the gap is open. Holes do not occur, a stable and good weld bead can be obtained, and the welding strength can be improved. In addition, since both the steel plates are joined at a portion other than the welding point with an adhesive tape or an adhesive, the fatigue characteristics, strength, and torsional rigidity after welding can be increased, and a welding reinforcement effect can be obtained.

  The laser welding method according to the present invention can be used for welding a workpiece that has been galvanized.

It is a partial external view of a workpiece. (A) is a top view of a laser welding part, (b) is sectional drawing of a laser welding part. It is a figure which shows schematic structure of a laser welding apparatus. It is a specific block diagram of a processing head. It is a block diagram which shows the structure of the control system of a control apparatus and a process head. It is an operation | movement flowchart of a laser welding apparatus. It is a figure where it uses for operation | movement description of a laser welding apparatus. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention.

Explanation of symbols

10 works,
11 Upper steel plate,
12 Lower steel plate,
13a, 13b, 13c, 13d, 13e welding points,
14a, 14b, 14c, 14d adhesive tape,
15a, 15b, 15c gap,
20 laser welding equipment,
22 Robot,
24 processing head,
26 control device,
28 optical fiber,
30 control lines,
40 Focus variable mechanism,
42 diffuser lens,
44 condenser lens,
46 condenser lens,
50 scan mirror,
52 Laser irradiation port,
60 Lens position adjustment servo motor,
62 laser scanning motor,
72 Optical system control unit,
74 Robot controller,
76 Laser irradiation position detector.

Claims (8)

A laser welding method for welding a workpiece made of a metal plate,
Temporarily fixing both steel plates by interposing a temporary fixing member of a predetermined thickness at a site other than the welding point defined for the workpiece,
A laser welding method comprising performing laser welding at a welding point defined on the workpiece in a state where a gap corresponding to the predetermined thickness is open.   The laser welding method according to claim 1, wherein the temporary fixing member is an adhesive means provided between the welding points.   The laser welding method according to claim 1, wherein the temporary fixing member is an adhering means provided over the entire region other than the welding point.   The laser welding method according to claim 2 or 3, wherein the adhesive means is an adhesive tape or an adhesive.   The laser welding method according to claim 4, wherein the adhesive contains a mixture for adjusting the thickness.   6. The laser welding method according to claim 5, wherein the mixture is an inelastic small sphere.   In the laser welding, the welding point is welded by moving a scan mirror provided in the machining head while moving a machining head that outputs laser light at a constant speed. The laser welding method according to claim 1.   The laser welding method according to claim 7, wherein the machining head is attached to an arm end of a robot.

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