JP2018187659A - Laser welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser welding method capable of restraining a change in mechanical strength corresponding to a part of a welding part.SOLUTION: An orbit (LP10) of a continuously emitted laser beam (L1) includes a plurality of loop-like wires (LP1) disposed along a boundary (W3) between mutually butted plate-like bodies (W1 and W2), and a wire connection (LP2) for connecting neighboring loop-like wires (LP1). The loop-like wires (LP1) extends so as to pass from the loop starting point (LP0) of one plate-like body (W1)through the other plate-like body (W2) and return to the loop starting point (LP0) of the plate-like body (W1). The wire connection (LP2) connects neighboring loop-like wires (LP1) by connecting the loop starting points (LP0) of the one plate-like body (W1). The laser beam (L1) is emitted toward the boundary (W3) of the mutually butted plate-like bodies (W1 and W2) from above the one plate-like body (W1).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser welding method.

  There is a welding method in which a pair of plate-like bodies that are abutted with each other are welded by irradiation with laser. In the welding method disclosed in Patent Document 1, a laser is irradiated along a trajectory having a spiral shape that goes around a rotation center moving in the welding direction so as to move back and forth between one plate-like body and the other plate-like body. And weld.

International Publication No. 2016/194322

The present inventors have found the following problems.
When welding is performed using such a welding method, the welding depth of the other plate-like body may be shallower than the welding depth of one plate-like body. Therefore, the mechanical strength at the site on the other plate-like body side of the welded portion may be smaller than the mechanical strength at the site on the one plate-like body side of the welded portion.

  This will be described using a specific example. As shown in FIG. 11, while the foil W93 is sandwiched between the plate-like body W91 and the plate-like body W92, the plate-like body W91 and the plate-like body W92 are brought into contact with each other, and the laser beam L91 is vertically applied from above the foil W93. Irradiate in the direction. Subsequently, the laser beam L91 is irradiated along a trajectory having a spiral shape that goes around the rotation center moving in the paper depth direction (here, the Y axis minus side) which is the welding direction. By this irradiation, a part of the foil W93, the plate-like body W91, and the plate-like body W92 is melted and a welded portion W94 is formed. The weld depth D92 on the plate-like body W92 side of the welded portion W94 may be shallower than the weld depth D91 on the plate-like body W91 side of the welded portion W94. As one reason for this, since the locus of the laser beam L91 in the plate-like body W91 is longer than the locus of the laser beam L91 in the plate-like body W92, the irradiation heat given to the plate-like body W91 side by the laser beam L91 is large. It may be larger than that given to the plate-like body W92.

  The present invention suppresses a change in mechanical strength according to the site of the weld.

The laser welding method according to the present invention includes:
A laser welding method for welding by continuously irradiating a laser beam along a track,
The track includes a plurality of loop-like lines arranged side by side along a boundary portion between the plate-like bodies that are abutted (for example, the plate-like bodies W1 and W2) and a connection that connects the adjacent loop-like lines. ,
The loop-like line starts from the loop start point of one plate-like body (for example, plate-like body W1) through the other plate-like body (for example, plate-like body W2) and starts the loop of the one plate-like body. Extending back to the point,
The connection is made by connecting adjacent loop-shaped lines by connecting the loop start points of the one plate-shaped body,
The laser beam is emitted from a laser oscillator disposed above the one plate-like body toward a boundary portion between the plate-like bodies that are butted together.
According to such a configuration, the laser beam can be irradiated so as to travel from one plate-like body side toward the other plate-like body side. As a result, the amount of heat input to the other plate-like body by laser irradiation per unit length of the laser trajectory can be made higher than the amount of heat input to one plate-like body. Therefore, the welding depth of the other plate-like body is less likely to be shallower than the welding depth of one plate-like body, so that the welding strength of the other plate-like body is compared with the welding strength of one plate-like body. Can be suppressed. That is, it is possible to suppress a change in mechanical strength according to the site of the weld.

  The laser welding method according to the present invention can suppress a change in mechanical strength according to the site of the weld.

1 is a schematic diagram showing a configuration of a welding apparatus according to Embodiment 1. FIG. 3 is a schematic diagram showing a welding method according to Embodiment 1. FIG. 3 is a schematic diagram showing a welding method according to Embodiment 1. FIG. 3 is a schematic diagram showing a welding method according to Embodiment 1. FIG. 3 is a flowchart showing a specific example of a welding method according to the first embodiment. It is a graph which shows the plasma light intensity with respect to elapsed time. It is a photograph which shows one specific example of a welding part cross section. It is a graph which shows the maximum welding depth with respect to an irradiation angle. It is the schematic which shows the welding method for calculating | requiring the irradiation angle after correction | amendment. It is the schematic which shows the welding method which irradiates a laser beam with the irradiation angle after correction. It is the schematic which shows the welding method which irradiates a laser beam.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, for clarity of explanation, the following description and drawings are simplified as appropriate.

(Embodiment 1)
The welding method according to the first embodiment will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the configuration of the welding apparatus according to the first embodiment. 2 to 4 are schematic diagrams illustrating a welding method according to the first embodiment. 1-4, 7, and 9-11, the left-handed system XYZ three-dimensional coordinate is prescribed | regulated. In FIGS. 4 and 9 to 11, hatching is appropriately omitted. FIG. 4 shows a cross section of a portion of the work piece W10 shown in the drawing.

(One specific example of laser welding equipment)
The laser welding method 1 according to Embodiment 1 can be performed using the laser welding apparatus 100 shown in FIG. As shown in FIG. 1, the laser welding apparatus 100 includes a control system 10, an articulated robot 20, an NC machine 30, and a welding head 40.

  The control system 10 includes a laser / head control unit 11, a laser oscillator 12, a plasma / thermal radiation recording operation unit 13, a quality recording unit 14, an articulated robot control unit 15, and an NC machine control unit. 16 and the like.

  The laser head controller 11 receives a signal from the welding head 40, and sends a signal to the laser oscillator 12 to instruct the start or stop of laser oscillation and the intensity of laser light to be oscillated. The laser oscillator 12 receives a signal from the laser head controller 11, oscillates a laser beam, and supplies the laser beam to the welding head 40 via the optical fiber 12 a. The plasma light / thermal radiation light recording calculation unit 13 receives a signal about the plasma light / thermal radiation light from the welding head 40 and calculates based on a predetermined program. The quality recording unit 14 receives a signal indicating the result calculated by the plasma light / thermal radiation light recording calculation unit 13 and records the calculation result. As the calculation result, the waveform of the light intensity of the plasma light and the heat radiation light, the quality of the welded portion, and the like can be mentioned. At least one of the control unit 15 of the multi-joint robot and the control unit 16 of the NC machine receives a signal indicating the calculation result of the plasma light / thermal radiation light recording calculation unit 13, and based on the received calculation result, At least one of the joint robot 20 and the NC machine 30 is controlled.

  The articulated robot 20 includes a main body 21 and arms 22 and 23. The main body 21 supports the arm 22 so as to be rotatable around a vertical line (Z axis in FIG. 1) via a drive unit (not shown) such as a servo motor. The arm 22 is pivotally connected to the arm 23 via a drive unit (not shown) such as a servo motor, and the arm 23 supports the welding head 40 at the tip thereof. The articulated robot 20 can rotate the main body 21 and the arms 22 and 23 to cause the welding head 40 to take a predetermined posture while moving the welding head 40 in a predetermined three-dimensional space. .

  The NC machine 30 includes a support surface 31 that supports the workpiece W10, and the support surface 31 is rotated around an axis Y30 (corresponding to the Y axis in FIG. 1) and fixed in a predetermined posture. Can do. The NC machine 30 can move the support surface 31 in the direction of the axis Y30.

  The welding head 40 includes a laser emission port 41, a half mirror 42, a reflection mirror 43, a transmission plate 44, a reflection mirror 45, and a light receiving sensor 46. The laser emission port 41, the half mirror 42, the reflection mirror 43, the transmission plate 44, the reflection mirror 45, and the light receiving sensor 46 are fixed at predetermined positions inside the welding head 40, for example. The light receiving sensor 46 is, for example, a photodiode sensor. The welding head 40 can rotate the transmission plate 44 around a predetermined axis while taking a predetermined posture. For example, the welding head 40 irradiates the laser beam L1 from the transmission plate 44 toward the axis Y30. The irradiation angle θ1 formed by the optical axis of the laser beam L1 and the vertical line Z1 (see FIG. 4) is, for example, in the range of 0 to 90 °. When the laser beam L1 is extended as it is, it intersects the axis Y30. The irradiation angle θ2 formed by the optical axis of the laser beam L1 and the X axis is, for example, in the range of 0 to 90 °. Here, the axis Y30 corresponds to a weld line.

  Here, the paths of the laser light L1 and the reflected light L2 emitted from the melting portion W4 (see FIG. 4) or the vicinity thereof will be described.

  First, the laser oscillator 12 is supplied with electric power from a power source (not shown), oscillates laser light, and emits the laser light from the laser emission port 41 to the half mirror 42 via the optical fiber 12a. The half mirror 42 reflects at least part of the emitted laser light and makes it incident on the reflection mirror 43. The reflection mirror 43 reflects the incident laser beam, passes through the transmission plate 44, and from above the plate-like body W1, the boundary portion between the plate-like bodies W1 and W2 of the workpiece W10 butted together, Alternatively, the light is incident on the foil W3. The workpiece W10 receives the laser light L1, and the reflected light L2 is emitted from the melted part W4 or the vicinity thereof. The reflected light L2 includes at least one of plasma light and heat radiation light.

  At least a part of the reflected light L <b> 2 passes through the transmission plate 44 and enters the reflection mirror 43. The reflection mirror 43 reflects at least a part of the incident reflected light L 2, passes through the half mirror 42, and further enters the reflection mirror 45. The reflection mirror 45 reflects at least a part of the incident reflected light L <b> 2 and makes it incident on the light receiving sensor 46. The light receiving sensor 46 receives the reflected light L2, and converts the intensity of the reflected light L2 into a voltage signal. The plasma light / thermal radiation light recording calculation unit 13 receives the signal converted by the light receiving sensor 46 via a communication cable or the like.

(Laser welding method 1)
As shown in FIG. 2, in the laser welding method 1 according to the first embodiment, first, the workpiece W10 is fixed at a predetermined position. The work piece W10 includes plate-like bodies W1 and W2 and a foil W3. The workpiece W10 is formed by abutting the plate bodies W1 and W2 with the foil W3 sandwiched between the plate body W1 and the plate body W2. In the example shown in FIG. 2, the foil W3 is located at the boundary between the plate-like bodies W1 and W2. The main surfaces of the plate-like bodies W1 and W2 are substantially parallel to a horizontal plane (XY plane in FIG. 2). The laser beam L1 is irradiated from the laser oscillator 12 disposed above the plate-like body W1 toward the boundary between the plate-like bodies W1 and W2 that are abutted. The irradiation angle θ formed by the laser beam L1 and the vertical line Z1 is in the range of more than 0 ° and less than 90 °.

  As shown in FIG. 3, the laser beam L1 is continuously irradiated and welded along the track LP10. Such welding performed along the track LP10 is also referred to as wobbling welding. The track LP10 has a spiral shape that goes around a rotation center that moves in the welding direction. Specifically, the track LP10 includes a plurality of loop-like lines LP1 arranged side by side along the boundary between the butted plate-like bodies W1 and W2, and a connection LP2 connecting the adjacent loop-like lines LP1. Including. In other words, the track LP10 is a single line having a spiral shape that goes around a rotation center that moves in the welding direction. In FIG. 3, the connection line LP2 is shown as a broken line for easy understanding. The loop line LP1 extends so as to return from the loop start point LP0 of the plate-like body W1 to the loop start point LP0 of the plate-like body W1 through the plate-like body W2. The connection LP2 connects adjacent loop lines LP1 by connecting the loop start points LP0 of the plate-like body W1. In the example shown in FIG. 3, the portions of the plate-like bodies W1 and W2 irradiated with the laser light L1 are at least four loop-like lines LP1 adjacent to each other from the Y-axis minus side to the Y-axis plus side. It moves following the connection line LP2 connecting the four loop lines LP1.

  According to such a laser welding method, the laser beam L1 can be irradiated so as to travel from one plate-like body W1 side toward the other plate-like body W2. Thereby, the amount of heat input to the other plate-like body W2 by the laser irradiation per unit length of the track LP10 of the laser light L1 can be made higher than the amount of heat input to the one plate-like body W1. Therefore, the welding depth of the other plate-like body W2 in the welded portion formed by solidifying the melted portion W4 is less likely to be shallower than the welding depth of the one plate-like body W1. Therefore, it can suppress that the welding strength by the side of the other plate-shaped body W2 in a welding part becomes small compared with the welding strength of one plate-shaped body W1 in a welding part. That is, it is possible to suppress a change in mechanical strength according to the site of the weld.

(Laser welding method 2)
By monitoring the reflected light L2 reflected from the portion irradiated with the laser beam L1 during welding, the laser welding method 1 described above is used except that the state of the melted portion W4 is detected and fed back to control the irradiation angle. There is a laser welding method 2 having the same configuration as the above. Such a laser welding method 2 will be described with reference to FIGS. FIG. 5 is a flowchart showing a specific example of the welding method according to the first embodiment. FIG. 6 is a graph showing the plasma light intensity with respect to the elapsed time. FIG. 7 is a photograph showing a specific example of a cross section of the weld.

  Similarly to the laser welding method 1, laser welding is performed. During welding, a welding bead to be welded is divided into m sections in the longitudinal direction, and the welding quality from the first section to the m-th section is determined for each section. Here, m and n are natural numbers. Specifically, it is determined that the determination is performed for the nth section (determination section determination step ST1). In step ST1, it is determined that the determination is performed for the first section at the start.

  Subsequently, it is determined whether or not the entire weld bead has been inspected (weld bead overall inspection completion confirmation step ST2). Specifically, it is confirmed whether or not the n section scheduled to be determined in the determination section determination step ST1 is less than the m section. If the confirmed n section is less than the m section, it is determined that the entire weld bead is not inspected, and if it is equal to or greater than the m section, it is determined that the entire weld bead is inspected.

  Subsequently, the light intensity of the reflected light in the n-th section is calculated (n-section light intensity calculation step ST3). An example of the plasma light intensity of the reflected light with respect to time in the n-th section is shown in FIG. Here, the reflected light may include heat radiation light in addition to plasma light.

  Subsequently, it is determined whether or not the amplitude A1 of the light intensity of the reflected light is smaller than a constant A0 (amplitude determination step ST4). An example of the waveform of the plasma light intensity at the elapsed time is shown in FIG. This elapsed time corresponds to the nth section.

  When it is determined that the amplitude of the plasma light intensity waveform is smaller than the constant A0 as in the waveform OK1 shown in FIG. 6 (amplitude determination step ST4: YES), the nth section, which is the section, has good welding quality. And is determined to be acceptable (quality acceptance confirmation step ST51). Returning to the determination section determination step ST1 (step ST61), the next n + 1 section after the nth section is determined.

  On the other hand, when it is determined that the waveform of the plasma light intensity is not smaller than the constant A0 (amplitude determination step ST4: NO) as in the waveform NG1 shown in FIG. 6, the welding quality is high in the nth section, which is the section. It is defective and is determined to be rejected (quality reject confirmation step ST52). Subsequently, the failure rate from the determined first interval to the n-th interval is calculated, and it is determined whether or not the calculated failure rate is smaller than B1% (quality pass rate confirmation step ST62). B1 is a predetermined numerical value of 0 or more and 100 or less.

  When the rejection rate is smaller than B1% (quality acceptance rate confirmation step ST62: YES), the irradiation angle is adjusted (irradiation angle adjustment step ST71). A specific example of the irradiation angle adjustment step ST71 will be described later. In order to determine the n + 1th section next to the nth section, the process returns to the determination section determination step ST1 (step ST61).

  On the other hand, if the rejection rate is smaller than B1%, that is, B1% or more (quality acceptance rate confirmation step ST62: NO), the entire weld bead is determined to be unacceptable (entire weld bead failure confirmation step). ST72), welding is terminated.

  Now, after returning from step ST61 to determination section determination step ST1, the n + 1th section is determined in the same manner as the determination of the nth section described above. As described above, the steps such as the welding bead overall inspection completion confirmation step ST2, the n-section light intensity calculation step ST3, the amplitude determination step ST4, and the step ST61 are repeated. When this is repeated, it is determined that the entire weld bead has been inspected since the n section scheduled to be determined in the determination section determination step ST1 reaches the m section (weld bead overall inspection completion confirmation step ST2: NO). . And it determines with the whole weld bead having passed (welding bead whole pass confirmation step ST31), and welding is complete | finished.

(Specific example of irradiation angle adjustment step ST71)
Next, a specific example of the irradiation angle adjustment step ST71 (see FIG. 5) will be described with reference to FIGS.

  In a specific example of the irradiation angle adjustment step ST71, the amplitude A1 of the waveform plasma light intensity is equal to or greater than a constant A0, as in the waveform NG1 shown in FIG. As shown in FIG. 7, the relationship between the amplitude A1 in a predetermined range and the difference ΔD12 between the maximum welding depths D1 and D2 of the plate-like bodies W1 and W2 is shown in advance as the cross-section of the welded portions of the plate-like bodies W1 and W2. Find it based on the observed photos. It is preferable to obtain a relationship between the amplitude A1 within a predetermined range and the difference ΔD12 between the maximum welding depths D1 and D2 of the plate-like bodies W1 and W2 while fixing welding conditions such as laser output, operation speed, and frequency. When the amplitude A1 increases, the maximum welding depths D1 and D2 of the plate-like bodies W1 and W2 tend to increase. In the example shown in FIG. 7, if the amplitude is A1, the maximum welding depth D1 of the plate 1 that is a specific example of the plate-like body W1 is 0.296 mm, and the maximum welding of the plate 2 that is a specific example of the plate-like body W2. The depth D2 is 0.240 mm, and the difference ΔD1 is 0.056 mm. In the example shown in FIG. 7, the welding conditions were a laser output of 750 W, an operation speed of 40 mm / sec, and a frequency of 500 Hz.

Here, based on the following relational expression 1, the difference ΔD1 is substituted into Dy [mm] to obtain the corrected irradiation angle θx [°].
Dy = 0.0252 × θx (... Relational expression 1)
C1 = 0.0252 [mm / °]
The coefficient C1 of the relational expression 1 is 0.0252, but may be changed according to welding conditions.
When the difference ΔD1 is 0.056 mm, using the relational expression 1, the corrected irradiation angle θx can be obtained as 2.22 °.

A method for obtaining the above relational expression 1 will be described.
As shown in FIG. 9, a laser welding method except that welding is performed by continuously irradiating laser light along a track extending substantially linearly (in FIG. 9, the Y-axis minus side, in other words, the back side of the paper). 1 and 2 with the irradiation angle θ of the welding conditions in a predetermined range and four levels of 0 ° or more and 5 ° or less, respectively, corresponding to one specific example of the plate-like bodies W1 and W2. (Not shown) is welded. After welding, the cross-sectional structure photograph of the welded portion was observed, and the maximum weld depth D21 of the plate 1 and the maximum weld depth D22 of the plate 2 were measured. Further, the difference ΔD2 between the maximum welding depths D21 and D22 is calculated, and the obtained maximum welding depths D21 and D22 and the difference ΔD2 are shown in FIG. The relational expression 1 described above can be obtained using a least square method or the like.

  As shown in FIG. 8, since the difference ΔD1 is 0.056 mm, it can be determined that the irradiation angle θ is 2.22 ° based on the relational expression 1.

  Here, welding was performed using the laser welding method 2 described above with the irradiation angle θ of the welding conditions set to 2.22 °. Then, as shown in FIG. 10, the maximum welding depth D31 of the plate-like body W1 and the maximum welding depth D32 of the plate-like body W2 were almost the same.

  As described above, in one specific example of the laser welding method 2 described above, the melted portion W34 is solidified to form a welded portion (not shown). It can suppress that the welding strength by the side of the plate-shaped body W1 in the said welding part becomes small compared with the welding strength by the side of the plate-shaped body W2 in the said welding part. That is, it is possible to suppress a change in mechanical strength according to the site of the weld.

  Furthermore, since the irradiation angle θ is controlled based on the reflected light L2 reflected from the melting portion W34 during welding, the laser beam L1 can be irradiated to the melting portion W34 at an appropriate irradiation angle θ for each section. The change of the maximum welding depths D31 and D32 between the plate-like bodies W1 and W2 can be suppressed for each section.

  The lid of the case and the box can be joined using the laser welding methods 1 and 2 described above. The joined case can be mounted on the vehicle while holding the vehicle battery. The part of the case near the joint between the lid and the box is specifically made of a metal material, more specifically pure Al or an Al alloy.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, in the laser welding method 1 described above, the foil 3 is sandwiched between the plate-like bodies W1 and W2, but the plate-like bodies W1 and W2 are in direct contact with each other without sandwiching the foil 3 therebetween. , Welding may be performed.

L1 laser light
LP10 Orbit LP0 Loop start point LP1 Loop line LP2 Connection W10 Workpiece W1 Plate body W2 Plate body W3 Foil

Claims (1)

A laser welding method for welding by continuously irradiating a laser beam along a track,
The trajectory includes a plurality of loop-like lines arranged side by side along the boundary between the butted plate-like bodies, and a connection line connecting adjacent loop-like lines,
The loop-like line extends from the loop start point of one plate-like body to the loop start point of the one plate-like body through the other plate-like body,
The connection is made by connecting adjacent loop-shaped lines by connecting the loop start points of the one plate-shaped body,
Irradiating the laser beam from above the one plate-like body toward the boundary between the plate-like bodies that have been butted together,
Laser welding method.