JP2839741B2 - Laser processing apparatus and laser processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding apparatus for welding a metal sheet.

[0002]

2. Description of the Related Art As a conventional laser welding apparatus for a large output, there has been a laser welding apparatus in which laser rods are connected in a cascade type as described in Japanese Patent Application Laid-Open No. 2-67783. However, in the cascade type laser oscillator, since there is a limit on the laser output on the low output side, for example, in a metal steel sheet having a wide thickness of about 0.1 mm to 1.0 mm, which is to be handled in one line, It was difficult to carry out welding of these metal steel plates with one laser welding device. This is because, in order to stably extract the laser output, it is necessary to output an output higher than a certain minimum output. For example, in a cascade type laser oscillator in which laser rods are arranged in N stages in series, the minimum output of the entire device is Is N times the minimum output of one rod. In addition, the cascade type laser oscillator requires a great deal of trouble in adjusting and maintaining the optical axis of the laser oscillation system, and has a problem when used in a line.

[0003] Further, as a device for increasing the output by arranging laser oscillators in parallel and connecting them by an optical fiber, there is a device in which semiconductor lasers are connected by an optical fiber as described in Japanese Patent Application Laid-Open No. 2-142695. According to such a method, although the output can be increased by the coupling, it is limited, and the range in which the processing can be performed is limited to the one that does not require much heat. It is necessary to couple more than one hundred semiconductor lasers, and the optical system becomes very complicated. further,
When welding extremely thin metal steel plates, if continuous or continuous oscillation (CW oscillation) or pulse oscillation is used for welding, burn-through or humping occurs, and stable welding can be performed. And it is difficult with conventional laser welding machines. The reason is briefly described below.

When a metal material is irradiated with laser light, the laser light absorption on a normal metal surface is about 40% in the case of a YAG laser. However, when the metal surface is in a molten state, the laser beam absorptivity rapidly increases to almost 100%. Therefore, when welding is performed with a continuous wave (CW oscillation) YAG laser, the laser beam absorptivity changes in accordance with the melting or unmelting state of the metal surface. Will cause welding defects. In addition, when welding is performed using a pulsed YAG laser, the occurrence of welding defects such as burn-through and humping on a steel sheet can be suppressed as compared with the case of using a continuous oscillation YAG laser. Or rapid cooling, the bending properties of the welded portion are reduced, making it difficult to perform rolling or bending after welding. For the reasons described above, the conventional laser welding apparatus is insufficient for welding metal steel sheets in a wide range of thicknesses, from a very thin one to a thickness of about 1 mm.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a laser welding machine for welding a metal steel sheet over a wide range of sheet thicknesses (for example, in the range of about 0.1 mm to 1.0 mm thickness) which is usually handled by one line. The task is to weld without welding defects.

The present invention relates to a laser processing apparatus having a YAG laser oscillator and a processing light condensing system for condensing and processing a laser beam. A laser oscillator, an incident optical system for injecting the laser light into one or more optical fiber bundles, one or more optical fiber bundles, and condensing and processing light emitted from the optical fiber bundles in machining current Chi lifting the optical system, working with a laser beam modulated to perform
A laser processing apparatus characterized in that it can be used . Further, in a laser processing apparatus having a YAG laser oscillator and a processing condensing system for condensing and processing a laser beam, a plurality of CAG oscillation type YAG laser oscillators and a part of the plurality of YAG laser oscillators are provided. A modulator for periodically attenuating light by a mechanical or electrical method, an input optical system for inputting laser light from the modulator or the YAG laser oscillator to one or more optical fiber bundles, A laser processing apparatus comprising: a plurality of optical fiber bundles; and a processing condensing system for condensing and processing light emitted from the optical fiber bundle, and capable of processing with modulated laser light. It is. Further, each laser light of a Q-switch oscillation type YAG laser oscillator and / or a pulse oscillation type YAG laser oscillator and a CW oscillation type YAG laser oscillator is inputted by an incident optical system.
A laser processing method characterized in that the laser beam is made incident on one or a plurality of optical fiber bundles, and the light emitted from the optical fiber bundle is collected and processed.

[0007]

According to the present invention, as shown in FIG.
Oscillation) Three types of laser oscillators, a YAG laser oscillator 1, a Q-switch oscillation YAG laser oscillator 2, and a pulse oscillation YAG laser oscillator 3, and an incident optical system 6 for condensing the laser output on an optical fiber bundle 7 and It is constituted by a processing light condensing system 8 for condensing light emitted from the optical fiber bundle 7. The effects provided by the three types of laser oscillators will be described below.

Generally, when butt welding thin metal plates, unlike the case of welding thick plates, the edges of the metal steel plates to be welded are melted widely when viewed relative to the thickness of the thin metal plates and welded. There is a need. This is because welding can be performed even if there is a certain butting gap or offset when butting metal sheets. It becomes possible. As described above, in butt welding of thin metal plates, it is of great significance that a wide molten bead can be formed. However, in the case of a very thin metal steel plate (for example, a plate thickness of about 0.1 mm), welding defects such as burn-through and humping occur as described above, and a wide molten bead cannot be formed. Therefore, a butt welding of a very thin metal steel plate requires a high-precision mounting jig, and the welding is very difficult.

However, by providing three types of laser oscillators having different oscillation systems, it is possible to prevent the occurrence of welding defects in a very thin metal steel sheet as described below.
First, a very small portion of the metal surface is instantaneously melted by a Q-switch oscillation YAG laser having a high peak output, and the melting portion is expanded by a pulse oscillation YAG laser. By repeatedly irradiating the Q-switched laser and the pulsed laser in this manner, the surface of the metal steel plate is always in a molten state, and the laser beam absorptivity is maintained at almost 100%. By irradiating the continuous oscillation (CW oscillation) laser to the metal steel sheet having a stable laser beam absorption rate in this manner, the heat quantity necessary for bringing the entire thickness of the metal steel sheet into a molten state is supplied. Since the laser light absorption rate of the metal steel sheet is stable,
Welding without welding defects such as burn-through and humping is possible, and the amount of heat required for melting is supplied by a continuous wave (CW oscillation) laser. No deterioration of the characteristics occurs. As described above, according to the present invention, a very thin metal steel plate can be welded without welding defects.

Furthermore, by providing a plurality of laser oscillators, the value of the minimum output can be made equal to the minimum output of one rod, so that a controllable laser output can be obtained from a low output which cannot be obtained with a conventional laser welding apparatus. be able to. Although FIG. 1 shows two continuous wave (CW) lasers and one Q-switched laser and one pulsed laser, the maximum laser output can be obtained by preparing a plurality of lasers. Can be increased. As described above, the present invention can greatly increase the variable range of laser output, and can weld metal steel sheets having a wide range of thicknesses to be handled by one line by using a single laser welding apparatus. Becomes

In the present invention, as shown in FIG. 2, an optical fiber 7 is used instead of the bending mirror 5 to guide the output of each laser oscillator to the optical fiber 7 in front of the processing and focusing system 8. Is also possible. Further, as shown in FIG. 5, instead of using a pulse laser oscillator, YAG
A method of mechanically chopping a YAG laser beam by rotating or reciprocating at high speed a part having a different laser beam transmittance, an AO, EO modulator, a bending mirror with a PZT element on the back, etc. By periodically interrupting the output of the continuous wave laser using the electrical method described above, a pulse output can be simulated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a laser processing apparatus according to the present invention will be described below.

(1) FIG. 1 is a configuration diagram of an embodiment of the present invention. Two 300W continuous wave YAG laser oscillators 1;
300W Q-switched YAG laser oscillator 2, 300
The laser emitted from the W-pulse YAG laser oscillator 3 is converted by a bending mirror 5 into a fiber incident optical system 6.
And is incident on the fiber 7. The fiber 7 is coupled to a processing condensing system 8 and irradiates the processing target with a laser beam 10. In this embodiment, as shown in FIG. 3, the fiber incident optical system 6 includes a prism-type bending mirror 11 that reflects 45 degrees of total reflection and a lens 1 having an effective diameter of 40 mm and a focal length of 50 mm.
2. The optical fiber 7 used had a numerical aperture of 0.5 and a core diameter of 0.6 mm. When the laser output from the machining condensing system 8 was measured, a wide output range from 50 W to 1.2 kW was obtained by driving only two of the four laser oscillators 1 or driving all the laser oscillators. For a long time, a controlled and stable output could be obtained. This makes the plate thickness from 0.1mm to 1.0mm
Of SUS304 steel sheets over a wide range could be welded without welding defects.

(2) As shown in FIG. 1, the four laser oscillators 1 use lasers that perform different oscillations of CW oscillation, Q switch oscillation, and pulse oscillation, respectively.
The laser beam 7 emitted from the processing light condensing system 8 could be modulated. P _CW = 1/2 Pp and frequency f = 1 kHz in FIG. 8 at a total output of 95 W (constant) using laser beams output modulated by four laser oscillators.
A modulation output is created by superimposing the z, Q switch peak output P _Q = 50 kW, and a SU with a plate thickness of 100 μm is produced.
By performing the bead-on-plate in S304, by changing the duty B / A at the time of modulation, a wider bead can be formed in the laser output by only one of the above three oscillation methods. (FIG. 9). This indicates, as described above, that the present invention has a great advantage in welding metal steel sheets as compared with using a conventional laser welding machine.

(3) In the above embodiment (2), butt welding of SUS304 having a thickness of 100 μm was performed at a duty of 50% at which the widest bead could be formed.
Total laser output 100W, welding speed 2.5m / mi
n, Butt gap width 30 μm, offset 20 μm
In the butt precision, welding without burn-through defects was obtained. The bead thickness was 120% or less of the base material thickness. A welded portion was cut out as a sample and subjected to a repetitive bending test to find that the number of breaks was 50%.
More than once. Although this is inferior to the number of fractures of the base material portion used for reference of 70 times, it is much more than the number of fractures of 35 times when welding is performed only by pulse oscillation, indicating good weldability.

[0016]

According to the present invention, a laser output from 30 W to 1.2 kW can be stably obtained. This allows a wide range of plate thickness (for example, a plate thickness of about 0.1 mm to 1.0 mm)
It is possible to weld metal steel sheets by one laser processing device. Further, the present invention can modulate the laser output irradiated from the machining condensing system by using laser oscillators that oscillate differently in CW output, Q switch output, and pulse output, respectively. In the welding method, welding could be performed without causing any burn-out or humping even under welding conditions.
In addition, laser beams having different CW output, Q switch output, and pulse output of the present invention were superimposed using an optical fiber, and welding was performed with a modulated output, whereby a wide bead could be formed on a metal steel plate. As a result, severe offset conditions (in the past, 10% or less of the plate thickness), which are a problem when welding metal foil, can be reduced, and the restriction on the holder of the metal plate of the welding device can be relaxed. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an embodiment in which output from a laser oscillator is coupled using an optical fiber.

FIG. 3 is a block diagram illustrating a configuration of an incident optical system according to an embodiment in which a plurality of laser outputs are incident on an optical fiber.

FIG. 4 is a block diagram showing a configuration of an embodiment for modulating a laser output.

FIG. 5 is a perspective view showing one embodiment of a laser output modulation device.

FIG. 6 is a front view showing another embodiment of the laser output modulation device.

FIG. 7 is a block diagram showing another embodiment of the laser output modulation device.

FIG. 8 is a waveform diagram conceptually showing a modulated laser output level.

FIG. 9 is a graph showing the relationship between the duty of laser output modulation and the bead formation width.

[Explanation of symbols]

1: CW oscillation laser oscillator 2: Q-switch oscillation laser oscillator 3: Pulse oscillation laser oscillator 4: Laser beam 5: Bending mirror 6: Incident optical system 7: Optical fiber 8: Processing light collecting system 9: Object to be processed 10: Collection Illuminated laser beam 11: Prism type bending mirror 12: Condensing lens 13: Modulator 14: Chopper 15: High laser transmittance portion 16: Low laser transmittance portion 17: Slit plate, small hole 18: PZT element With mirror, galvanometer mirror 19: AO, EO modulator P _CW : CW oscillation laser output value Pp: Pulse oscillation peak output P _Q : Q switch peak output A: Length of one cycle B: Pulse width

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-134259 (JP, A) JP-A-58-147689 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23K 26/00-26/18

Claims (3)

(57) [Claims] 1. A laser processing apparatus having a YAG laser oscillator and a processing light condensing system for condensing and processing a laser beam, wherein a plurality of YAG laser oscillators having different oscillation systems of CW oscillation, Q switch oscillation, and pulse oscillation are provided. And an incident optical system for injecting the laser light into one or more optical fiber bundles, one or more optical fiber bundles, and condensing the light emitted from the optical fiber bundle for processing. machining current Chi lifting an optical system for, as can be processed by a laser beam modulated
Laser processing apparatus characterized by the. 2. A YAG laser oscillator for condensing and processing laser light.
Laser processing equipment with a processing condensing system for performing machining
A plurality of CW oscillation type YAG laser oscillators;
A part of the laser light of several YAG laser oscillators is mechanically
Or a modulator which is periodically attenuated by an electrical method, and
A single laser beam from the controller or the YAG laser oscillator.
Or an incident optical system that enters multiple optical fiber bundles
And one or more optical fiber bundles,
A collection of processing to condense and process the light emitted from the Iver bundle
It has an optical system so that it can be processed with modulated laser light.
A laser processing apparatus. 3. One or a plurality of optical fibers each of which is made of a laser light of a Q-switch oscillation type YAG laser oscillator and / or a pulse oscillation type YAG laser oscillator and a CW oscillation type YAG laser oscillator by an incident optical system. A laser processing method, wherein the laser beam is made incident on a bundle, and the light emitted from the optical fiber bundle is collected and processed.