JP2020044543A - Laser welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser welding method capable of suppressing the generation of spatter during welding. SOLUTION: A first laser beam 81 and a second laser beam 82 having the same optical axis as the first laser beam 81 and capable of irradiating the peripheral portion of the irradiation region of the first laser beam 81. Is irradiated onto the work 9, and in the irradiation step, the energy density of the second laser light 82 is 1.5% or more and 4.5% or less of the energy density of the first laser light 81. There is a laser welding method. [Selection diagram] Fig. 3

Description

  The present invention relates to a laser welding method.

As a method of welding a work, a method of irradiating the work with laser light is known.
Patent Literature 1 discloses a laser welding method of irradiating a workpiece with laser light including a first laser light and a second laser light capable of irradiating a peripheral portion of an irradiation area of the first laser light. Have been.

JP 2014-073526 A

The inventors have found the following problems with respect to the laser welding method.
In the laser welding method disclosed in Patent Document 1, the energy density of the second laser light is set lower than the energy density of the first laser light. However, in order to suppress the occurrence of spatter during welding, it is necessary to appropriately set the energy density of the second laser light in comparison with the energy density of the first laser light.

  The present invention has been made in view of such a problem, and has as its object to provide a laser welding method capable of suppressing generation of spatter during welding.

  One mode for achieving the above object is a laser welding method, wherein a first laser beam has the same optical axis as the first laser beam, and a peripheral portion of an irradiation region of the first laser beam. And irradiating the workpiece with a second laser beam capable of irradiating the laser beam. In the irradiating step, the energy density of the second laser beam is 1. 5% or more and 4.5% or less.

  In the laser welding method according to the present invention, the energy density of the second laser light is 1.5% or more and 4.5% or less of the energy density of the first laser light. In a molten pool generated by irradiation with only the second laser beam, generation of spatter is suppressed. The molten metal evaporated from the keyhole generated by the irradiation of the first laser light adheres to the molten pool generated by the irradiation of the second laser light alone. Therefore, in the laser welding method according to the present invention, generation of spatter during welding is suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the laser welding method which can suppress generation | occurrence | production of the spatter at the time of welding can be provided.

1 is an overall view of a laser welding device according to a first embodiment. It is sectional drawing of the laser beam cut | disconnected in the surface perpendicular | vertical to an optical axis. It is a perspective view of the work at the time of welding. It is the whole laser welding device concerning a 2nd embodiment. It is the whole laser welding device concerning a 3rd embodiment. It is a flowchart which shows the monitoring method of the amount of spatters. 4 is a graph showing an example of plasma light intensity measured using a camera. 5 is a graph showing measurement results of the amount of spatter in Examples 1 and 2 and Comparative Examples 1 and 2. It is a graph which shows the measurement result of the amount of spatters in Examples 3-8 and Comparative Examples 3-6.

  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, in order to clarify the description, the following description and drawings are simplified as appropriate.

(First embodiment)
First, a configuration of an apparatus (a laser welding apparatus according to the first embodiment) for performing the laser welding method according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall view of the laser welding apparatus according to the first embodiment. FIG. 2 is a cross-sectional view of a laser beam cut along a plane perpendicular to the optical axis. FIG. 3 is a perspective view of the workpiece during welding.

  As shown in FIG. 1, the laser welding apparatus 1 includes a head 4, a control unit 5, an oscillator 6, and a fiber 7. The head 4 includes galvano mirrors 41 and 42 as shown in FIG. The arrow in the head 4 shown in FIG. 1 indicates the traveling direction of the laser light. FIG. 1 shows a work 9 in addition to the laser welding apparatus 1. As shown in FIG. 2, the laser light 8 includes a first laser light 81 and a second laser light 82. As shown in FIG. 3, the work 9 includes work constituent members 91 and 92. FIG. 3 shows the laser beam 8 in addition to the work 9.

  Naturally, the right-handed xyz rectangular coordinates shown in FIG. 1 and other drawings are for convenience in describing the positional relationship of the components. Usually, the positive direction of the z-axis is vertically upward and the xy plane is the horizontal plane, which is common between the drawings.

  As shown in FIG. 1, the head 4 is a member that irradiates a work 9 with a laser beam 8 oscillated from an oscillator 6. The head 4 includes galvanometer mirrors 41 and 42. The galvanometer mirror 41 is connected to, for example, an x-axis motor (not shown). The galvanomirror 42 is connected to, for example, a y-axis motor (not shown). The x-axis motor enables the galvanometer mirror 41 to rotate in the x-axis direction. The y-axis motor enables the galvanometer mirror 42 to rotate in the y-axis direction. The traveling direction of the laser beam 8 incident on the head 4 is adjusted by the rotation of the galvanometer mirrors 41 and 42.

  As shown in FIG. 1, the head 4 is connected to the control unit 5. The control unit 5 controls the direction of the path of the laser light 8 incident on the head 4. The control unit 5 controls the direction of the path of the laser light 8 by controlling the rotation of an x-axis motor and a y-axis motor (not shown), for example. The control unit 5 is connected to the oscillator 6 in addition to the head 4. The oscillator 6 oscillates a laser beam 8. The control unit 5 controls the output of the laser light 8 oscillated from the oscillator 6 and the like. The laser light 8 is, for example, a fiber laser. The wavelength of the laser beam 8 can be, for example, 1030 nm or more and 1120 nm or less.

  The laser light 8 oscillated from the oscillator 6 enters the head 4 through the fiber 7. The laser light 8 oscillated from the oscillator 6 is adjusted to the shape shown in FIG. The fiber 7 includes a core having a circular cross section, a first clad formed to cover the core, and a second clad formed to cover the first clad. The core is doped with a rare earth element such as ytterbium (Yb). The refractive index of the fiber 7 decreases in the order of the core, the first clad, and the second clad.

  Laser light 8 is amplified in fiber 7. As shown in FIG. 1, the laser welding device 1 includes two fibers 7. The laser beam 8 incident on one of the two fibers 7 is oscillated from the fiber 7 as a first laser beam 81 shown in FIG. The laser light 8 incident on the other of the two fibers 7 is oscillated from the fiber 7 as the second laser light 82 shown in FIG. The oscillated first laser light 81 and second laser light 82 are combined, and the laser light 8 is adjusted to the shape shown in FIG.

  FIG. 2 is a cross-sectional view of the laser light 8 cut along a plane perpendicular to the optical axis. As shown in FIG. 2, the laser light 8 includes a first laser light 81 and a second laser light 82. Each of the first laser light 81 and the second laser light 82 has a circular cross section cut along a plane perpendicular to the optical axis. The first laser light 81 and the second laser light 82 have the same optical axis. Therefore, the second laser light 82 can irradiate the peripheral portion of the area where the first laser light 81 can be irradiated.

  D1 shown in FIG. 2 is the radius of the first laser beam 81. D2 shown in FIG. 2 is the radius of the second laser light 82. The radius d1 of the first laser light 81 is smaller than the radius d2 of the second laser light 82. The radius d1 of the first laser light 81 is, for example, 25% or more and 35% or less of the radius of the second laser light 82. The energy density of the second laser light 82 is 1.5% or more and 4.5% or less of the energy density of the first laser light 81.

  The laser welding method according to the first embodiment includes a step of irradiating the work 9 with the first laser light 81 and the second laser light 82. FIG. 3 shows a perspective view of the work 9 when performing the irradiation step.

  The work 9 is a member made of steel. The work 9 is, for example, a butted material of a steel plate and a steel material. The work 9 includes work constituent members 91 and 92. In the example shown in FIG. 3, the work 9 has a rectangular parallelepiped shape. However, the shape of the work 9 is not particularly limited. The work 9 may have, for example, a cylindrical shape. The work components 91 and 92 are joined at the joining surface 9a as shown in FIG.

  In the example shown in FIG. 3, the joining surface 9a is joined while moving the irradiation area of the laser beam 8 from the positive side of the joining surface 9a to the negative side of the y-axis. In the area where the laser beam 8 is irradiated, the work constituent members 91 and 92 are melted to form a molten pool 9c.

  The region irradiated with the first laser light 81 is irradiated with a laser having a higher energy density than the region irradiated with only the second laser light 82. Therefore, in the region irradiated with the first laser beam 81, the melting of the work constituent members 91 and 92 is particularly easy to proceed. Therefore, a keyhole 9d is formed in a region irradiated with the first laser beam 81.

  In the keyhole 9d, when the work constituent members 91 and 92 are melted, the molten metal evaporates. The molten metal evaporated in the keyhole 9d may jump out of the keyhole 9d. The molten metal that has jumped out of the keyhole 9d adheres to a molten pool 9c formed at the periphery of the keyhole 9d.

  When the irradiation area of the laser beam 8 moves, the molten pool 9c cools and generates a bead 9b. When the molten pool 9c cools, the molten metal attached to the molten pool 9c forms a bead 9b together with the molten pool 9c. Therefore, even if the molten metal evaporates in the keyhole 9d, generation of spatter is less likely to occur.

  Further, the region irradiated with only the second laser light 82 is gradually heated, and the molten pool 9c is shallow. Therefore, evaporation of the molten metal is less likely to occur in a region irradiated with only the second laser light 82. Therefore, in a region where only the second laser light 82 is irradiated, spatter hardly occurs. With the above configuration, the laser welding method according to the first embodiment can suppress the generation of spatter during welding.

(Second embodiment)
Next, a configuration of an apparatus (a laser welding apparatus according to the second embodiment) for performing the laser welding method according to the second embodiment of the present invention will be described with reference to FIG. FIG. 4 is an overall view of the laser welding apparatus according to the second embodiment. As shown in FIG. 4, the laser welding apparatus 2 includes a DOE 43 in addition to the configuration shown in FIG. FIG. 4 shows the work 9 in addition to the laser welding device 2. The other configuration is the same as the configuration described in the first embodiment, and a duplicate description will be appropriately omitted.

  The laser welding device 2 includes a DOE (Diffractive Optical Element) 43. The DOE 43 may be arranged at any position on the path of the laser beam 8. The DOE 43 is arranged in the head 4, for example, as shown in FIG. In the laser welding apparatus 2, instead of adjusting the shape of the laser light 8 by the arrangement of the fibers 7 in the laser welding apparatus 1, the shape of the laser light 8 is changed as shown in FIG. Adjust.

  With the above configuration, the laser welding device 2 can perform a step of irradiating the work 9 with the first laser light 81 and the second laser light 82. Therefore, the laser welding method according to the second embodiment can suppress generation of spatter during welding. Further, the laser welding method according to the second embodiment can provide the same effects as those described in the first embodiment.

(Third embodiment)
Next, a configuration of an apparatus (a laser welding apparatus according to the third embodiment) for performing the laser welding method according to the third embodiment of the present invention will be described with reference to FIGS. FIG. 5 is an overall view of the laser welding apparatus according to the third embodiment. A solid line arrow in the head 4 shown in FIG. 5 indicates a traveling direction of the laser beam. The dotted arrow in the head 4 shown in FIG. 5 indicates the traveling direction of the reflected light. FIG. 6 is a flowchart showing a method for monitoring the amount of spatter. FIG. 7 is a graph illustrating an example of plasma light intensity measured using a camera.

  The laser welding device 3 includes a mirror 44 and a camera 45 in addition to the configuration shown in FIG. In the step of irradiating the work 9 with the first laser light 81 and the second laser light 82, the first laser light 81 and the second laser light 82 are reflected, and a part of the reflected light is The light enters the head 4 as indicated by a dotted arrow shown in FIG. The mirror 44 is arranged on the path of the reflected light that has entered the head 4.

  The camera 45 can capture the reflected light reflected by the mirror 44. Specifically, a part of the reflected light incident on the head 4 passes through the galvanometer mirror 41 after being reflected by the galvanometer mirror 42. When the mirror 44 is disposed on the path of the reflected light, the reflected light intensity can be photographed using the camera 45.

  The camera 45 is connected to the control unit 5. When performing the step of irradiating the first laser light 81 and the second laser light 82 to the work 9, the laser welding apparatus 3 monitors the amount of spatter using the reflected light intensity photographed by the camera 45. It can be performed. A specific example of the method of monitoring the amount of sputtering is shown in the flowchart of FIG.

  In the method of monitoring the amount of spatter, monitoring is performed by dividing a portion to be welded into m sections. Here, m is an integer of 2 or more. When the method of monitoring the amount of sputtering is performed, the energy density of the second laser light 82 is set to a predetermined value of 1.5% to 4.5% of the energy density of the first laser light 81. The reflected light intensity is photographed using the camera 45 in advance. Then, the difference between the maximum value and the minimum value of the reflected light intensity within a predetermined time, that is, the amplitude is defined as a constant A.

  In the method of monitoring the amount of sputtering, first, a step of measuring the reflected light intensity in the first section (Step S1) is performed. Specifically, the reflected light is photographed using the camera 45, and the control unit 5 measures the reflected light intensity in the first section.

  Next, a step (Step S2) of determining whether the amplitude of the reflected light intensity is smaller than a constant A is performed. FIG. 7 shows an example of the waveform of the reflected light intensity measured in step S1. When the difference between the maximum value and the minimum value of the reflected light intensity is smaller than the constant A, as in the waveform shown by the dotted line in FIG. 7, it is determined that the amount of spatter generated in the first section is smaller than a predetermined value. . That is, it is determined that the welding in the first section is good. If the welding in the first section is good in step S2, the welding in the second section is performed.

  On the other hand, when the difference between the maximum value and the minimum value of the reflected light intensity is equal to or larger than the constant A, as in the waveform shown by the solid line in FIG. to decide. That is, it is determined that the welding in the first section is defective. If the welding in the first section is defective in step S2, a step (step S3) of determining whether or not the defective percentage of welding is smaller than B% is performed on the entire portion to be welded.

  When the defect rate of the welding is smaller than B% for the entire portion to be welded, the step of adjusting the laser output (Step S4) is performed, and the welding in the second section is performed. Thus, steps S1 to S4 are repeated until the m-th section, and the entire portion to be welded is welded.

  When welding the n-th section, in step S3, if the section with poor welding quality is B% or more for the entire portion to be welded, the welding in the (n + 1) -th section is stopped. I do. The work 9 whose welding has been stopped is disposed of as a defective welding product.

  In the laser welding method according to the third embodiment, when performing the step of irradiating the work 9 with the first laser light 81 and the second laser light 82, the above-described method of monitoring the amount of spatter is performed. In addition, generation of spatter during welding can be suppressed. Further, the laser welding method according to the third embodiment can provide the same effects as those described in the first and second embodiments.

  Hereinafter, the present invention will be described specifically with reference to examples. The description is not intended to limit the invention.

[Examples 1 and 2]
In Example 1, the work 9 was welded with the energy density of the second laser light 82 set to 1.8% of the energy density of the first laser light 81. The radius d1 of the first laser beam 81 in Example 1 was 0.25, where 1 was the radius d2 of the second laser beam 82. The work 9 used in Example 1 was a butted material of a steel plate and a steel material. In Example 2, the work 9 was welded in the same manner as in Example 1 except that the energy density of the second laser light 82 was set to 4.5% of the energy density of the first laser light 81. .

[Comparative Examples 1-2]
In Comparative Example 1, the work 9 was welded in the same manner as in Example 1 except that the energy density of the second laser light 82 was set to 0% of the energy density of the first laser light 81. In Comparative Example 2, the work 9 was welded in the same manner as in Example 1 except that the energy density of the second laser light 82 was set to 100% of the energy density of the first laser light 81.

(Measurement of spatter amount)
The spatter amount in Examples 1 and 2 and Comparative Examples 1 and 2 was measured. FIG. 8 shows the measurement results. As shown in FIG. 8, Examples 1 and 2 had a smaller amount of spatter than Comparative Examples 1 and 2. Thus, when the energy density of the second laser light 82 is set to 1.5% or more and 4.5% or less of the energy density of the first laser light 81, generation of spatter during welding can be suppressed. Was confirmed.

[Examples 3 to 8]
In Example 3, welding was performed such that the welding depth, that is, the depth of the keyhole 9d was 1.2 mm. The energy density of the second laser light 82 in Example 3 was 4.5% of the energy density of the first laser light 81. In Example 4, welding was performed in the same manner as in Example 3 except that the welding depth was 3 mm. In Example 5, welding was performed in the same manner as in Example 3 except that the welding depth was 3.8 mm.

  In Example 6, welding was performed in the same manner as in Example 3 except that the welding depth was 4 mm. In Example 7, welding was performed in the same manner as in Example 3 except that the welding depth was 4.1 mm. In Example 8, welding was performed in the same manner as in Example 3 except that the welding depth was 4.2 mm.

[Comparative Examples 3 to 6]
In Comparative Example 3, welding was performed such that the welding depth was 1.5 mm. The energy density of the second laser light 82 in Comparative Example 3 was 100% of the energy density of the first laser light 81. In Comparative Example 4, welding was performed in the same manner as in Comparative Example 3 except that the welding depth was 3 mm. In Comparative Example 5, welding was performed in the same manner as in Comparative Example 3 except that the welding depth was 3.2 mm. In Comparative Example 6, welding was performed in the same manner as in Comparative Example 3 except that the welding depth was 4 mm.

(Measurement of spatter amount)
The amount of spatter in Examples 3 to 8 and Comparative Examples 3 to 6 was measured. FIG. 9 shows the measurement results. As shown in FIG. 9, Examples 3 to 8 had a smaller amount of spatter than Comparative Examples 3 to 6. Therefore, when the energy density of the second laser light 82 is set to 1.5% or more and 4.5% or less of the energy density of the first laser light 81, generation of spatter during welding can be suppressed. Was confirmed.

  As shown in Comparative Examples 3 to 6, as the welding depth increases, the generation of spatter increases. However, in Examples 3 to 8, it was clarified that even when the welding depth was deep, it was possible to suppress an increase in spatter generation.

  According to the invention according to the present embodiment described above, a laser welding method capable of suppressing generation of spatter during welding can be provided.

  It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist.

1, 2, 3 Laser welding device 4 Head 41, 42 Galvano mirror 44 Mirror 45 Camera 5 Control unit 6 Oscillator 7 Fiber 8 Laser light 81 First laser light 82 Second laser light 9 Work 91, 92 Work constituent member 9a Joining surface 9b Bead 9c Weld pool 9d Keyhole

Claims (1)

A first laser beam;
Irradiating the workpiece with a second laser beam having the same optical axis as the first laser beam and capable of irradiating a peripheral portion of an irradiation region of the first laser beam,
In the irradiating step, the energy density of the second laser light is 1.5% or more and 4.5% or less of the energy density of the first laser light.
Laser welding method.

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