JP2008213005A - Laser welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain stable welding quality while securing sufficient welding strength and sealability, and also to suppress the bending of the object to be machined after welding. <P>SOLUTION: Workpieces 10A, 10B are moved in such a manner that the machining point is located in one end side of a welding schedule region R, and the workpieces 10A, 10B are irradiated with laser beams, so as to form a first spot weld zone W1. Successively, the irradiation of the laser beams is temporarily stopped, the workpieces 10A, 10B are moved in such a manner that the machining point is located in the other end side of the welding schedule region R, and the workpieces 10A, 10B are irradiated with laser beams, so as to form a second spot weld zone W2 which is not superimposed on the first spot weld zone W1 immediately close to the same. Then, by repeating the laser beam irradiation, a continuous weld zone W in which the spot weld zones are mutually connected along the welding schedule region R is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser welding method for sequentially forming a plurality of spot welds along a planned welding region of a workpiece by irradiating a laser beam.

Conventionally, a laser welding method is known in which a plurality of workpieces are overlapped and these workpieces are welded by continuous irradiation while moving a laser beam (for example, Patent Document 1). reference).
JP 2005-329412 A

  However, the laser welding method as described above has the following problems because the laser beam is sequentially and continuously irradiated along the planned welding region. That is, due to livestock heat generated by the laser beam, the penetration of the workpiece differs at the welding start position and the welding end position, and the welding quality becomes unstable. Further, thermal distortion due to the laser beam is likely to accumulate, and the workpiece is greatly bent at the welding start position and the welding end position.

  Further, in recent years, in the laser welding method as described above, sufficient welding strength and sealing performance of a workpiece are strongly desired.

  Therefore, the present invention provides a laser welding method and a laser welding apparatus capable of obtaining stable welding quality while ensuring sufficient welding strength and sealing performance, and capable of suppressing bending of a workpiece after welding. It is an issue to provide.

  In order to solve the above-described problem, a laser welding method according to the present invention welds workpieces by bringing the scheduled welding regions of a plurality of workpieces into contact with each other and irradiating a laser beam along the welding scheduled regions. A laser welding method for forming a welded portion along a planned region, comprising: sequentially forming a plurality of spot welded portions in the planned welded region, and forming a continuous welded portion formed by connecting the spot welded portions to each other. The step of forming the continuous welded portion includes the step of forming the next spot welded portion so as not to overlap the spot welded portion formed most recently.

  Since this laser welding method includes a step of forming the next spot welded portion so as not to overlap the spot welded portion formed most recently, the heat generated by the laser beam when forming the most recently formed spot welded portion is next. Thus, it is possible to suppress the influence on the spot welded portion, to suppress the penetration of the workpieces in these spot welded portions, and to obtain a stable weld quality. In addition, since it includes the step of forming the next spot welded portion so as not to overlap the spot welded portion that has been formed most recently, thermal distortion due to the laser beam when the spot welded portion that has been formed most recently is accumulated. That can be suppressed, and bending of the workpiece after welding can be suppressed. In addition, since a continuous weld portion formed by connecting the spot weld portions to each other is formed, it is possible to ensure a sufficient weld strength and sealability of the workpiece.

  Here, in the step of forming the continuous welded portion, the next spot is formed so as not to overlap both the spot welded portion formed most recently and the spot welded portion formed before the spot welded portion formed nearest. It is preferable to include the process of forming a welding part. In this case, the effect of livestock heat by the laser beam on the next spot weld is suppressed when forming both the spot weld formed in the immediate vicinity and the spot weld formed in front of the spot weld formed in the immediate vicinity. In addition, it is possible to suppress accumulation of thermal distortion due to the laser beam when forming both of them. Therefore, it is possible to obtain a more stable welding quality while ensuring sufficient welding strength and hermeticity, and to further suppress bending of the workpiece after welding.

  In addition, the step of forming the continuous welded portion preferably includes a step of forming the next spot welded portion at the midpoint between the plurality of already formed spot welded portions.

  Further, in the step of forming the continuous welded portion, the connecting spot is alternately connected so as to connect to the step of forming the first and second spot welded portions that are separated from each other and to each of the first and second spot welded portions. And forming a welded portion.

  Further, in the step of forming the continuous welded portion, it is preferable to repeat a pattern for forming a plurality of spot welded portions sequentially from the start point side to the end point side where the laser beam is irradiated in the planned welding region. In this case, the number and distance of scanning with the laser beam along the planned welding area can be reduced.

  The spot welded portion is preferably a non-penetrating spot welded portion that is not exposed at the other end opposite to the one end irradiated with the laser beam on the workpiece. Thereby, compared with the case where a spot weld part is a penetration spot weld part exposed to the other end of a workpiece, the heat input to a workpiece can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, while ensuring sufficient welding strength and airtightness, stable welding quality can be obtained, and it becomes possible to suppress the bending of the workpiece after welding.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted. In the present embodiment, terms such as “upper” and “lower” are based on the state shown in the drawings and are for convenience.

  FIG. 1 is a schematic view showing a laser welding apparatus according to an embodiment of the present invention. As shown in FIG. 1, the laser welding apparatus 1 is used for, for example, laminating and welding an outer panel and a bone member (hereinafter referred to as “workpieces (workpieces) 10A and 10B”) used in a railway vehicle structure. Here, a continuous weld W for welding the workpieces 10A and 10B to each other is formed by irradiating the workpieces 10A and 10B stacked on each other with a laser beam from the workpiece 10A side. In addition, in the following description, the case where the linear continuous welding part W is formed in the approximate center part seen from the irradiation direction in workpiece | work 10A, 10B is illustrated.

  The laser welding apparatus 1 includes a feeding device 21, a workpiece fixing device 22, a laser irradiation device 23, and a gas supply device 24. Each of these devices 21 to 24 is connected to a higher-level control unit (not shown), and automatically executes each operation according to operation instruction information output from this control unit.

  The feeding device 21 is a device that scans the irradiation position of the laser beam onto the workpieces 10A and 10B, and has a movable stage (driving means) 25 on which the workpieces 10A and 10B can be placed. When the feeding device 21 receives operation instruction information for instructing the start of scanning from the control unit, the feeding device 21 scans (moves) the movable stage 25 along the scheduled welding region R. Thereby, the workpieces 10A and 10B placed on the movable stage 25 move relative to the irradiation position of the laser beam by the laser irradiation device 23 along the planned welding region R. That is, the feeder 21 moves the laser beam relative to the workpieces 10A and 10B. A control device (control means) 14 is connected to the movable stage 25 of the feeding device 21.

  The workpiece fixing device 22 is a device that fixes the workpieces 10A and 10B to the movable stage 25, and includes a plurality (two in this case) of pressure jigs 26 each having a long pressing plate 26a. When receiving the operation instruction information for instructing the operation start from the control unit, the workpiece fixing device 22 lowers the long pressurizing jig 26 from above the workpieces 10A and 10B placed on the movable stage 25. And the adhesiveness of the workpiece | work 10A, 10B of the welding scheduled area | region R vicinity is improved by pressing the both ends of the workpiece | work 10A, 10B which pinched | interposed the welding planned area | region R against the movable stage 25 with the elongate pressing plate 26a.

  The laser irradiation device 23 is a device that irradiates a laser beam intermittently on the welding regions R of the workpieces 10A and 10B, and has a laser head (laser light source) 27 disposed above the workpieces 10A and 10B. ing. When receiving the operation instruction information for instructing the start of irradiation from the control unit, the laser irradiation device 23 emits a YAG laser from the tip of the laser head 27. The control device 14 is connected to the laser head 27 of the laser irradiation device 23.

  The control device 14 includes a CPU, a ROM, a RAM, and the like, and controls the driving of the laser head 27 and the movable stage 25 by executing software held in the ROM by the CPU.

  Returning to FIG. 1, the gas supply device 24 is a device that supplies assist gas to the planned welding region R of the workpieces 10 </ b> A and 10 </ b> B, and is arranged so as to be inclined at about 45 degrees with respect to the workpieces 10 </ b> A and 10 </ b> B. A nozzle 28 is provided. When the gas supply device 24 receives operation instruction information for instructing start of supply from the control unit during the operation of the laser irradiation device 23, the gas supply device 24 supplies assist gas to the irradiation position of the laser beam with a predetermined supply amount. As the assist gas, helium gas, argon gas, or the like is used for the purpose of preventing oxidation and sputtering of the workpieces 10A and 10B.

  Next, the operation of the described laser welding apparatus 1 will be described. First, the workpieces 10 </ b> A and 10 </ b> B are placed on the movable stage 25, and the pressing jig 26 is lowered from above to fix the workpieces 10 </ b> A and 10 </ b> B to the movable stage 25. Subsequently, the control unit outputs operation instruction information to each of the workpiece fixing device 22, the laser irradiation device 23, the feeding device 21, and the gas supply device 24, and starts laser irradiation, workpiece feeding, and supply of assist gas. . Then, the laser beam is intermittently irradiated along the planned welding region R from the upper surface 11 side of the workpiece 10A, and simultaneously, the workpieces 10A and 10B are scanned a plurality of times along the planned welding region R (laser beam irradiation). ). As a result, a continuous weld W formed by connecting substantially circular spot welds along the planned welding region R in a top view is formed.

  Here, the laser beam irradiation described above will be described in detail. First, the control unit 14 scans the movable stage 25 and moves the workpieces 10A and 10B so that the irradiation position (processing point) of the laser beam is positioned at the welding start position on one end side of the planned welding region R. Then, the laser beam is applied to the workpieces 10A and 10B from the laser head 27, and the workpieces 10A and 10B are melted and evaporated at the processing points, thereby forming a first spot weld W1 having a substantially circular planar shape (see FIG. 2 (a)). At this time, laser characteristics such as laser output and irradiation time are controlled by the control device 14, and the first spot welded portion W1 is non-penetrating (hereinafter simply referred to as “non-penetrating”) that is not exposed on the lower surface 12 of the workpiece 10B. It has become.

  Subsequently, after the irradiation of the laser beam is temporarily stopped and the workpiece 10A, 10B is moved by scanning the movable stage 25 by the control device 14 so that the processing point is located on the other end side of the planned welding region R, A laser beam is applied to the workpieces 10A and 10B from the laser head 27 to form a second spot welded portion W2 that is separated from the first spot welded portion W1 and is non-penetrating (see FIG. 2B). In other words, the second spot weld W2 is formed so as not to overlap the first spot weld W1 formed most recently.

  Subsequently, the irradiation of the laser beam is once again stopped, and the control unit 14 scans the movable stage 25 to move the workpieces 10A and 10B so that the processing point is located at the center of the planned welding region R, and then the laser is moved. A laser beam is applied to the workpieces 10A and 10B from the head 27 to form a third spot weld W3 that is separated from the first and second spot welds W1 and W2 and is not penetrated (see FIG. 3A). ). That is, the spot welded portion W3 is formed so as not to overlap both the second spot welded portion W2 formed in the nearest place and the first spot welded portion W1 formed in front of the second spot welded portion W2 formed in the nearest place. To do.

  Subsequently, the laser beam irradiation is once again stopped, and the movable stage 25 is scanned by the control device 14 so that the processing point is located between the first welded portion W1 and the third welded portion W3 in the planned welding region R. Then, after moving the workpieces 10A and 10B, the laser beam is irradiated from the laser head 27 to the workpieces 10A and 10B, and the non-penetrating fourth spot welded portion W4 is formed in the first welded portion W1 and the third welded portion W3. (See FIG. 3B). Thereafter, the irradiation of the laser beam is once again stopped, and the movable stage 25 is scanned by the control device 14 so that the processing point is located between the second welded portion W2 and the third welded portion W3 in the planned welding region R. After moving the workpieces 10A and 10B, the laser beam is irradiated from the laser head 27 to the workpieces 10A and 10B, and the non-penetrating fifth spot weld W5 is formed with the second weld W2 and the third weld W3. (See FIG. 4A).

  Then, by repeating such laser beam irradiation (that is, laser beam irradiation that forms the next spot welded portion at the midpoint between the plurality of spot welded portions that have already been formed), the spot welded portion is welded to the region R to be welded. The continuous welding part W formed by connecting along is formed (see FIG. 4B). That is, the continuous welded portion W is continuously formed by overlapping spot-shaped spot welds formed with a time difference in the planned welding region R by intermittent (discrete) irradiation of the laser beam along the planned welding region R. Will be formed. As shown in FIG. 5, the welded portion W has a wave shape (pulse train shape) in which the circular shape is continuous on the upper surface 11 of the workpiece 10A.

  Alternatively, as another example of the laser beam irradiation described above, first, the first spot welded portion W1 is formed on one end side of the planned welding region R (see FIG. 6A), and the second spot weld is formed on the other end side. A portion W2 is formed (see FIG. 6B). Subsequently, a third spot weld W3 is formed on the inner side (right side in the figure) of the first spot weld W1 so as to overlap only the first spot weld W1 (see FIG. 7A). Subsequently, a fourth spot weld W4 is formed on the inner side (left side in the figure) of the second spot weld W2 so as to overlap only the second spot weld W2 (see FIG. 7B). And by repeating such laser beam irradiation, a continuous weld W formed by connecting spot welds along a planned welding region R may be formed. That is, specifically, the first and second spot welds W1 and W2 that are spaced apart from each other are formed so that the spot welds are sequentially formed from the outside to the inside of the planned welding region R. In some cases, the connected spot welds are alternately formed so as to be connected to each of the spot welds W1, W2, and the continuous weld W is formed.

  Alternatively, as yet another example of the laser beam irradiation described above, first, a plurality of spot welds are sequentially formed from one end side to the other end side of the planned welding region R so as not to overlap each other. Subsequently, a plurality of spot welds are sequentially formed again from one end side to the other end side of the planned welding region R so as to overlap each other end side of the sequentially formed spot weld portions. . And by repeating such laser beam irradiation, a continuous weld W formed by connecting spot welds along a planned welding region R may be formed. That is, a pattern in which a plurality of spot welds are sequentially formed from the start point side (one end side) to which the laser beam is irradiated in the planned welding region R may be repeated a plurality of times. In this case, as described above, a plurality of spot welds are sequentially formed from the start point side toward the end point side, so that the number of scans and the scan distance of the movable stage 25 can be reduced and the tact time can be reduced.

  Alternatively, as still another example of the laser beam irradiation described above, first, the first spot weld W1 positioned at the center of the planned welding region R is formed, and the first spot is positioned on one end side of the planned welding region R and the first spot. The second spot welded portion W2 is formed so as not to overlap the welded portion W1, and the third spot welded portion W3 is formed so as to be positioned on the other end side of the planned welding region R and not overlapped with the first spot welded portion W1. . Subsequently, a fourth spot weld W4 is formed between the first and second spot welds W1, W2, and a fifth spot weld W5 is formed between the first and third spot welds W1, W3. . And by repeating such laser beam irradiation, a continuous weld W formed by connecting spot welds along a planned welding region R may be formed. That is, the continuous weld W may be formed by sequentially forming spot welds from the inside to the outside of the planned welding region R.

  As mentioned above, according to this embodiment, in order to form the next 2nd spot welding part W2 so that it may not overlap with the 1st spot welding part W1 formed most recently, the 1st spot welding part W1 formed most recently is formed. The influence of livestock heat generated by the laser beam on the next second spot weld W2 can be suppressed, and the penetration of the workpieces 10A and 10B in these spot welds W1 and W2 can be suppressed from each other, and stable welding quality can be achieved. Can be obtained.

  Furthermore, since the next spot welded portion W2 is formed so as not to overlap the spot welded portion W1 formed in this manner, thermal distortion due to the laser beam when forming the spot welded portion W1 formed most recently is accumulated. This can suppress the bending of the workpieces 10A and 10B after welding. In addition, since the continuous welded portion W formed by connecting the spot welded portions to each other is formed, it is possible to ensure sufficient welding strength and sealing performance of the workpieces 10A and 10B.

  Here, the third spot welded portion W3 is formed so as not to overlap both the second spot welded portion W2 formed most recently and the spot welded portion W1 formed before the second spot welded portion W2. Therefore, the influence of livestock heat generated by the laser beam when forming both the first and second spot welds W1 and W2 on the spot weld W3 can be suppressed, and both the first and second spot welds W1 and W2 can be suppressed. It is possible to suppress accumulation of thermal distortion due to the laser beam when forming the film. Accordingly, it is possible to obtain a more stable welding quality while ensuring sufficient welding strength and sealing performance, and it is possible to further suppress the bending of the workpieces 10A and 10B after welding.

  In the present embodiment, as described above, since the spot welded portion is a non-penetrating spot welded portion that is not exposed on the lower surface 12 of the workpiece 10B, the spot welded portion is a through spot welded portion that is exposed on the lower surface 12. In comparison, heat input to the workpieces 10A and 10B can be reduced.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  For example, in the above embodiment, the movable stage 25 is scanned to move the laser beam relative to the workpieces 10A and 10B. However, the laser irradiation apparatus may be moved to move the laser beam relative to the workpiece. . Moreover, in the said embodiment, although the lap welding which superimposes and welds workpiece | work 10A, 10B was performed, you may perform the butt welding which butt | matches and welds workpiece | work 10A, 10B.

  Moreover, in the said embodiment, although the linear welding part W was formed in the irradiation direction view, it may be a curved welding part, and of course may be a rectangle or a round thing.

It is the schematic which shows the laser welding apparatus which concerns on one Embodiment of this invention. FIG. 6 is a schematic side sectional view along a planned processing region for explaining laser beam irradiation. It is a figure which shows the continuation of FIG. 2 for demonstrating laser beam irradiation. It is a figure which shows the continuation of FIG. 3 for demonstrating laser beam irradiation. It is a top view of the workpiece | work after welding. FIG. 6 is a schematic side sectional view along a planned processing region for explaining another example of laser beam irradiation. It is a figure which shows the continuation of FIG. 6 for demonstrating the other example of laser beam irradiation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laser welding apparatus, 10A, 10B ... Workpiece | work (workpiece), 14 ... Control apparatus (control means), 25 ... Movable stage (drive means), 27 ... Laser head (laser light source), R ... Plane welding area, W ... continuous weld, W1 ... first spot weld (weld), W2 ... second spot weld (weld), W3 ... third spot weld (weld), W4 ... fourth spot weld ( Welded portion), W5... Fifth spot welded portion (welded portion).

Claims (6)

A laser welding method for forming a welded portion along the planned welding region of the workpiece by contacting a planned welding region of a plurality of workpieces with each other and irradiating a laser beam along the planned welding region. There,
Forming a plurality of spot welds sequentially in the planned welding region, and forming a continuous weld formed by connecting the spot welds to each other;
In the step of forming the continuous weld,
A laser welding method comprising a step of forming a next spot welded portion so as not to overlap a spot welded portion formed most recently. In the step of forming the continuous weld,
A step of forming the next spot welded portion so as not to overlap both the spot welded portion formed most recently and the spot welded portion formed before the spot welded portion formed most recently is included. Item 2. The laser welding method according to item 1. In the step of forming the continuous weld,
3. The laser welding method according to claim 1, further comprising a step of forming a next spot weld at the midpoint of the plurality of spot welds that have already been formed. In the step of forming the continuous weld,
Forming first and second spot welds spaced apart from each other;
3. The laser welding method according to claim 1, further comprising a step of alternately forming connection spot welds so as to be connected to each of the first and second spot welds. In the step of forming the continuous weld,
5. The laser welding method according to claim 1, wherein a pattern for forming a plurality of spot welds is sequentially repeated a plurality of times from the start point side to the end point side where the laser beam is irradiated in the welding scheduled region.   The said spot welding part is a non-penetrating spot welding part which is not exposed to the other end on the opposite side to the one end irradiated with a laser beam in a workpiece. Laser welding method.

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