JPH04322892A - Laser beam machine and laser beam machining method - Google Patents

Abstract

PURPOSE:To weld a metallic steel plate whose plate thickness extends over a wide range of about 0.1mm to 1.0mm plate thickness by one set of laser welding machine without generating a welding defect. CONSTITUTION:The machine is constituted of three kinds of laser oscillators of a continuous oscillation (CM oscillation) YAG laser oscillator 1, a Q switch oscillation YAG laser oscillator 2, and a pulse oscillation YAG laser oscillator 3, an incident optical system 6 for condensing their laser outputs to an optical fiber 7 and allowing them to be made incident thereon, and a working condensing system 8 for condensing an emitted light from the optical fiber 7.

Description

[Detailed description of the invention]

0001

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

0002

2. Description of the Related Art As a conventional laser welding device for high output, there is a laser welding device in which laser rods are connected in a cascade type, as described in Japanese Patent Laid-Open No. 2-67783. However, in a cascade type laser oscillator, there is a limit to the laser output on the low output side, so for example, for metal steel sheets with a wide range of thickness from 0.1 mm to 1.0 mm, which are handled on one line, It has been difficult to weld these metal steel plates using a single laser welding device. This means that in order to obtain stable output from the laser, it is necessary to output a certain minimum output.For example, in a cascade type laser oscillator in which N stages of laser rods are arranged in series, the minimum output of the entire device is This is because the output power becomes N times the minimum output of one rod. Furthermore, the cascade type laser oscillator requires a lot of effort to adjust the optical axis of the laser oscillation system and maintain it, which poses a problem when used on a line.

[0003] Furthermore, as a system which aims at increasing the output by arranging laser oscillators in parallel and coupling them through optical fibers, there is a system in which semiconductor lasers are coupled through optical fibers, as described in Japanese Patent Laid-Open No. 2-142695. Although this type of method can increase output through bonding, it is limited, and the range of processing that can be done is limited to those that do not require a large amount of heat, so it is difficult to weld metal steel plates. , it is necessary to combine more than 100 semiconductor lasers, and the optical system becomes extremely complex. moreover,
When welding very thin metal steel plates, if welding is performed using either continuous oscillation (CW oscillation) or pulse oscillation alone, burn-through and humping will occur, making it difficult to perform stable welding. This is difficult to do with conventional laser welding machines. The reason for this will be briefly explained below.

[0004] When a metal material is irradiated with laser light, the laser light absorption rate on the 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 light absorption rate increases rapidly to almost 100%. Therefore, when welding is performed using a continuous wave (CW oscillation) YAG laser, the laser light absorption rate changes depending on whether the metal surface is molten or not, and as a result, the amount of heat input by the laser changes, resulting in burn-through, humping, etc. This will cause welding defects. Furthermore, when welding is performed using a pulsed YAG laser, welding defects such as burn-through and humping on the steel plate can be suppressed compared to when using a continuous wave YAG laser, but the laser irradiation time is short and rapid heating occurs. As a result, the bending properties of the welded part deteriorate and it becomes difficult to perform rolling or bending after welding. For the above-mentioned reasons, conventional laser welding apparatuses have been insufficient for welding metal steel plates over a wide range of thickness, from very thin plates to plate thicknesses of about 1 mm.

[0005]

[Problems to be Solved by the Invention] The present invention aims to weld metal steel plates with a wide range of thicknesses (for example, in the range of about 0.1 mm to 1.0 mm) that are normally handled on one line using a single laser welding machine. The challenge is to weld without welding defects.

[0006]

[Means for Solving the Problems] The present invention provides CW oscillation, Q
Multiple Ys with different oscillation methods for switch oscillation and pulse oscillation
An AG laser oscillator, an input optical system that inputs the laser beams into one or more optical fiber bundles, one or more optical fiber bundles, and condenses the output light from the optical fiber bundles. This is a laser processing device characterized by having a processing light focusing system for performing processing. Also, CW oscillation,
This is a laser welding method in which welding is performed by driving two or more laser oscillators of a plurality of YAG laser oscillators with different oscillation methods of Q-switch oscillation and pulse oscillation.

[0007]

[Operation] 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; It is constituted by a processing condensing system 8 that condenses the light emitted from the optical fiber bundle 7. The effects of having three types of laser oscillators will be explained below.

Generally, when butt welding thin metal plates, unlike when welding thick plates, the edges of the metal steel plates to be welded are melted and welded over a wide area relative to the thickness of the metal plate. There is a need. This is to enable welding even if there is a certain amount of butt gap or offset when butting thin metal sheets.This eases the precision of mounting the thin metal sheets to the welding jig, and allows welding even with rough installation. It becomes possible. As mentioned above, in butt welding of thin metal plates, it is of great significance to be able to form a wide molten bead. However, in the case of a very thin metal steel plate (eg, about 0.1 mm thick), welding defects such as burn-through and humping occur as described above, making it impossible to form a wide molten bead. Therefore, butt welding of very thin metal steel plates requires a high-precision mounting jig, and welding is extremely difficult.

However, by providing three types of laser oscillators with different oscillation methods, it is possible to prevent welding defects from occurring in very thin metal steel sheets, as described below. First, a Q-switch oscillation YAG laser with a high peak output is used to instantaneously melt a small portion of the metal surface, and then a pulse oscillation YAG laser is used to enlarge the molten portion. By repeatedly irradiating with the Q-switched laser and the pulsed laser in this manner, the surface of the metal steel plate is constantly in a molten state, and the laser light absorption rate is kept stable at approximately 100%. By irradiating a continuous wave (CW oscillation) laser onto a metal steel plate whose laser light absorption rate has been stabilized in this manner, the amount of heat necessary to bring the entire thickness of the metal steel plate into a molten state is supplied. Because the laser light absorption rate of metal steel sheets is stable, it is possible to weld without welding defects such as burn-through or humping, and the amount of heat required for melting is reduced by continuous wave (CW oscillation).
Since it is supplied using a laser, the bending properties of the welded part do not deteriorate as would occur when welding is performed using a pulsed laser. As described above, according to the present invention, very thin metal steel plates can be welded without welding defects.

Furthermore, by providing multiple laser oscillators, the minimum output value can be made the same as the minimum output of one rod, so it is possible to obtain controllable laser output from a low output that cannot be obtained with conventional laser welding equipment. be able to. In addition, in Figure 1, the configuration consists of two continuous wave (CW oscillation) lasers, one each of a Q-switch oscillation laser and a pulse oscillation laser, but by preparing multiple units of each laser, the maximum laser output can be achieved. can be made larger. As described above, the present invention allows the variable range of the laser output to be extremely wide, making it possible to weld metal steel plates having a wide range of thickness that are handled on one line using a single laser welding device. becomes.

Furthermore, 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 condensing system 8. is also possible. Furthermore, as shown in Figure 5, instead of using a pulsed laser oscillator, YAG
A method of mechanically chopping YAG laser light by rotating or reciprocating parts with different laser light transmittances at high speed, an AO/EO modulator, or a bending mirror with a PZT element on the back, etc. It is also possible to extract pulsed output in a pseudo manner by periodically cutting off the output of the continuous wave laser using the electrical method described above.

0012

Embodiments Hereinafter, embodiments of the laser processing apparatus according to the present invention will be described.

(1) FIG. 1 is a block diagram of an embodiment of the present invention. Two 300W continuous wave YAG laser oscillators 1,
300W Q-switch YAG laser oscillator 2 and 300W
A laser beam emitted from the W-pulse YAG laser oscillator 3 is guided by a bending mirror 5 to a fiber input optical system 6, and is input into a fiber 7. The fiber 7 is coupled to a processing condensing system 8, and irradiates the workpiece with a laser beam 10. In this embodiment, the fiber input optical system 6 includes a prism-type bending mirror 1 with total reflection of 45 degrees, as shown in FIG.
1 and a lens 12 with an effective diameter of 40 mm and a focal length of 50 mm.
It was constructed by The optical fiber 7 used had a numerical aperture of 0.5 and a core diameter of 0.6 mm. When we measured the laser output from the processing focusing system 8, we found that by driving only two of the four laser oscillators 1 or by driving all laser oscillators, a wide output range from 50 W to 1.2 kW could be achieved. We were able to obtain controlled and stable output over a period of time. As a result, a wide range of SUS304 steel plates with a thickness of 0.1 mm to 1.0 mm could be welded without any welding defects.

(2) As shown in FIG. 1, by using four laser oscillators 1 that perform different oscillations such as CW oscillation, Q-switch oscillation, and pulse oscillation,
It was possible to modulate the laser beam 7 emitted from the processing condensing system 8. Using laser light whose output is modulated by four laser oscillators, the total output is 95W (constant), PCW in Figure 8 is 1/2Pp, frequency f is 1kHz.
By superimposing the z, Q switch peak output PQ = 50kW, a modulated output is created and
When S304 bead-on-plate was performed, by changing the duty B/A during modulation, it was possible to form a wider bead in the laser output by only one type of oscillation among the three oscillation methods mentioned above. (Figure 9). As mentioned above, this shows that the present invention has a great advantage over using a conventional laser welding machine in welding metal steel plates.

(3) In Example (2) above, butt welding of SUS304 plates having a thickness of 100 μm was carried out at a duty of 50%, where the widest bead could be formed. Total laser output 100W, welding speed 2.5m/mi
n, butt gap width 30μm, offset 20μm
Welding without burn-through defects was obtained with a butt accuracy of . In addition, the thickness of the bead is 120% or less of the base metal thickness, and when a welded part was cut out as a sample and subjected to a stress fracture test by repeated bending, the number of fractures was 50%.
It was more than once. Although this is inferior to the 70 times of failure of the base material used as a reference, it is much greater than the 35 times of failure when welding using only pulse oscillation, indicating good weldability.

[0016]

[Effect] According to the present invention, laser output from 30 W to 1.2 kW could be stably obtained. This allows for a wide range of plate thicknesses (for example, plate thicknesses from 0.1 mm to 1.0 mm).
It becomes possible to weld metal steel plates with one laser processing device. Furthermore, by using laser oscillators that oscillate with different CW output, Q-switch output, and pulse output, the present invention can modulate the laser output irradiated from the processing focusing system. The welding method was able to perform welding without causing burn-through or humping, even under welding conditions that would cause such problems. In addition, by superimposing different laser outputs of the present invention, including CW output, Q-switch output, and pulse output, using an optical fiber and performing welding with the modulated output, a wide bead could be formed on the metal steel plate. This makes it possible to alleviate the severe offset conditions (conventionally 10% or less of the plate thickness) that are a problem when welding metal foil, and to ease the constraints on the holder of the metal steel plate in the welding equipment. .

[Brief explanation of drawings]

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

FIG. 2 is a block diagram showing the configuration of an embodiment in which outputs from laser oscillators are coupled using optical fibers.

FIG. 3 is a block diagram showing the configuration of an input optical system in an embodiment that inputs a plurality of laser outputs into an optical fiber.

FIG. 4 is a block diagram showing the configuration of an embodiment in which laser output is modulated.

FIG. 5 is a perspective view showing an 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: Input optical system 7: Optical fiber
8: Processing light focusing system 9: Processing object 1
0: Focused laser beam 11: Prism-type bending mirror 12: Condensing lens 13: Modulator
14: Chopper 15: Part with high laser transmittance 16
: Part with low laser transmittance 17: Slit plate, small hole 18: Mirror with PZT element, galvano mirror 19: A
O, EO modulation element PCW:C
W oscillation laser output value Pp: Pulse oscillation peak output PQ
:Q switch peak output

Claims (3)

[Claims] Claim 1: A laser processing device having a YAG laser oscillator and a processing focusing system for focusing laser light and performing processing, including a plurality of YAG laser oscillators with different oscillation methods of CW oscillation, Q-switch oscillation, and pulse oscillation. , an input optical system that inputs the laser beams into one or more optical fiber bundles, one or more optical fiber bundles,
A laser processing apparatus characterized by having a processing condensing system for condensing the light emitted from the optical fiber bundle and performing processing. 2. The modulator according to claim 1, which periodically attenuates all or part of the plurality of laser beams by a mechanical or electrical method before the laser beams enter the optical fiber from the plurality of laser oscillators. A laser processing device characterized by: [Claim 3] A YAG laser oscillator and a processing focusing system for focusing laser light and processing, and a plurality of YAG lasers with different oscillation methods such as CW oscillation, Q-switch oscillation, and pulse oscillation.
A G laser oscillator, an input optical system that inputs the laser beams into one or more optical fiber bundles, one or more optical fiber bundles, and condenses the output light from the optical fiber bundles. A laser processing method in which processing is performed by driving two or more laser oscillators of the plurality of YAG laser oscillators using a laser processing device having a processing light focusing system for processing.