US-12617042-B2 - Laser apparatus using optical fibers for stable laser welding, and laser welding method using same

US12617042B2US 12617042 B2US12617042 B2US 12617042B2US-12617042-B2

Abstract

The present invention relates to a laser apparatus using optical fibers for stable laser welding and a laser welding method using same. Hybrid ring mode-shaped laser beams, in which a central beam using fiber laser is positioned at the center of outer beams using diode laser, are used to perform welding by irradiating a to-be-welded portion of an object with the outer beams, the central beam, and the outer beams in this order. Thus, since the welding is performed using the central beam as a heat source in a state in which the to-be-welded portion of the object has been heated with a sufficient amount of heat input, the temperature gradient of the to-be-welded portion is low and solidification cracking does not occur. Also, problems such as spatter and voids can be minimized, and the laser welding is stable, and thus a quality of welding that is uniform and stable overall can be obtained.

Inventors

Swook Hann

Assignees

KOREA PHOTONICS TECHNOLOGY INSTITUTE

Dates

Publication Date: 20260505
Application Date: 20210618
Priority Date: 20200904

Claims (8)

1 . A laser device for stable laser welding, the laser device comprising: a first laser light source for irradiating a first laser beam with a first wavelength band of 1030 to 1090 nm in a direction in which an object is located; a second laser light source for irradiating a second laser beam with a second wavelength band of 400 to 480 nm or 800 to 980 nm in a direction in which the object is located; a combiner comprising a plurality of beam coupling optical fibers, the combiner for combining the first laser light source and the second laser light source so that the first laser beam is formed as a central beam, and the second laser beam is formed as an outer beam in an outer area within a preset radius based on the center beam so as to be combined into a hybrid ring mode laser beam; and a delivery optical fiber for delivering the hybrid ring mode laser beam output from the combiner in a direction in which the object is located, wherein the delivery optical fiber comprises a core part, a first clad, a second clad, a third clad, an interlayer formed between the core part and the first clad, and acrylic coating layer; wherein a diameter of the core part is 50 μm or less, a diameter of the interlayer is 50 to 70 μm, a diameter of the first clad is 70 to 400 μm, a diameter of the second clad is 440 μm, a diameter of the third clad is 500 μm, and a diameter of the acrylic coating layer is 550 μm; wherein a difference in refractive index between the core part and the first clad of the delivery optical fiber is 0.00145 or less, a difference in refractive index between the first clad and the second clad is 0.0167 or less, a difference in refractive index between the second clad and the third clad is 0.0578 or less, a difference in refractive index between the core and the interlayer is 0.0167 or more, and a difference in refractive index between the interlayer and the first clad is 0.0167 or less; and wherein numerical aperture (NA) between the first clad and the second clad is 0.22, and NA between the first clad and the third clad is 0.46.
2 . The laser device of claim 1 , further comprising a lens being positioned between the delivery optical fiber and the object to focus the laser beam output from the delivery optical fiber to the object.
3 . The laser device of claim 1 , wherein the delivery optical fiber comprises the core part consisting of a single core and a cladding part consisting of at least one clad, and wherein the combiner comprises a first beam combining optical fiber for combining the first laser beam to the core part, and at least one second beam combining optical fiber for combining the second laser beam to the cladding part.
4 . The laser device of claim 3 , wherein the refractive index of the cladding part is progressively lowered as the cladding part moves away from the core part based on the core part.
5 . The laser device of claim 3 , wherein the delivery optical fiber comprises the core part and the cladding part and further comprises an interlayer having a lower refractive index than the refractive index of the core part, and wherein the interlayer serves as a deep between the center beam and the outer beam so that the hybrid ring mode laser beam is separated into the center beam and the outer beam to be output.
6 . The laser device of claim 1 , wherein the object is a metal material including aluminum so that the first laser light source outputs the first laser beam with the wavelength band of 1030 to 1090 nm, and the second laser light source outputs the second laser with the wavelength band of 800 to 980 nm.
7 . The laser device of claim 1 , wherein the object is a metal material including copper so that the first laser light source outputs the first laser beam with the wavelength band of 1030 to 1090 nm, and the second laser light source outputs the second laser with the wavelength band of 400 to 480 nm.
8 . The laser device of claim 1 , wherein the first laser light source is composed of a fiber laser, and the second laser light source is composed of a direct diode laser (DDL).

Description

TECHNICAL FIELD The present invention relates to a laser device for enabling stable laser welding using a laser beam having a plurality of wavelengths and a laser welding technology using the same. BACKGROUND ART The description in this section merely provides background information on an embodiment of the present invention and does not constitute the prior art. Laser welding is a welding method that uses a laser beam to couple different materials. Laser welding has a high concentration of laser beam energy to cause a small heat-affected zone so that it does not change the chemical, physical, or mechanical settings of the base material. Laser vacuum welding is performed for materials susceptible to oxidation, and setting changes can be minimized. It is widely used because it has advantages in that the quality of the welding surface by laser welding is superior to that of conventional heat resistance or gas welding, and welding is performed while the laser is irradiated from a long distance, thereby enabling safe welding. A laser processing device for processing an object using a laser is disclosed in various ways, such as Korean Patent Laid-Open No. 10-2004-0015996. Such a laser processing device includes an optical system for focusing a laser beam emitted from a laser to an object. In conventional laser welding, a laser beam for welding is irradiated from a laser light source, and the irradiated laser beam is focused on an object to perform laser welding. Currently, the most widely used solid-state laser for laser welding is a YAG laser that generates a light beam having a wavelength of about 1 μm, and a representative Nd: YAG laser has a fundamental wavelength of 1064 nm. In the laser welding method, the optical coupling between the object to be welded and the laser beam is important. If the optical coupling property is not good, the reflectance is high, and the absorption efficiency of laser energy is low, so it is difficult to obtain a good weld joint. A YAG laser beam with a fundamental wavelength (for example, 1064 nm) has poor optical coupling to copper or gold. Since the 532 nm YAG laser beam has high optical coupling to metals such as copper and gold, a laser welding method in which the YAG laser beam of the second harmonic (532 nm) is superimposed on the same optical axis as the pulsed laser beam of the YAG fundamental wave to irradiate the object may be applied. However, in the welding method of superimposing lasers of different wavelengths as described above, the keyhole or penetration depth is still insufficient because the optical coupling time of the second harmonic laser beam, which is an intermittent repetitive pulse, and the object is short. Further, the overlap rate of laser beams of different wavelengths significantly affects welding, such as the penetration depth and the uniformity of the appearance quality, thus the overlap rate for obtaining uniform heat input must be carefully selected. Meanwhile, when the object is a metal material including an aluminum material, heat escapes to the outside because the metal material has a high thermal conductivity in laser welding under general conditions; that is, the reflection amount of heat input is increased, so the energy of the laser beam is not absorbed into the center of the welding object and escapes to the outside. Thus, the absorption rate of the laser beam is significantly reduced. Further, the metal material has a high coefficient of thermal expansion, so cracks or pores are generated due to volume change during welding, so welding cannot be performed stably. In order to solve this problem, when the output of the laser is increased, there is a problem in that the welding quality deteriorates because fragments such as spatters are generated at the welding site of a metal material or the like. As described above, due to the properties of lasers having a short wavelength, highly reflective materials such as aluminum or copper have no choice but to have unsatisfactory welding quality due to limitations on the inherent laser beam absorptivity of the material. Therefore, there is a need for research on laser welding technology using laser beams having different characteristics to obtain high-quality joints for highly reflective materials. DISCLOSURE Technical Problem In order to address the above issues, the present invention provides a laser device using an optical fiber for stable laser welding and a laser welding method using the same in which the laser beams of different wavelength bands are combined into a hybrid ring mode laser beam composed of a central beam and an outer beam to be output in the direction in which the object is positioned through the optical fiber, a hybrid ring mode laser beam is used, and the welding is performed using the central beam as a heat source while lowering the temperature gradient due to pre-heating and post-heating effects on the welding part of the object. However, the technical issue to be achieved by