JP4580065B2 - Laser welding method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser welding method and apparatus for welding metal members using laser light.
[0002]
[Prior art]
The laser welding method is a technique for irradiating a welded portion of a metal member with a laser beam and melting the welded portion instantaneously by laser energy to perform metallurgical joining. Conventionally, many YAG lasers have been used as solid-state lasers for laser welding. The YAG laser can continuously oscillate and can perform high-speed repetitive oscillation of a giant pulse by a Q switch, and can easily control the waveform of the laser output.
[0003]
[Problems to be solved by the invention]
By the way, in the laser welding method, a metal having high reflectance and thermal diffusion (conductivity) is difficult to melt because of low absorption of laser light, and it is difficult to obtain a good weld joint.
[0004]
Conventionally, a pulsed laser method of irradiating a continuous wave pulsed laser beam has been effective for aluminum alloys, and the inventors of the present application disclosed in Japanese Patent No. 2984962 such as welding peeling in a pulsed laser welding method for aluminum alloys. Disclosed is a waveform control technique that guarantees high-quality weld joints without weld defects. Recently, as a technique for improving the melting characteristics of aluminum alloys, continuous oscillation YAG pulsed laser light (wavelength 1064 nm) and high-speed repetitive pulsed YAG laser light (wavelength 1064 nm) using a Q switch are different directions (two directions). There is also known a technique in which multiple irradiation is performed toward the same welded part.
[0005]
However, in today's industry, a laser welding method effective for metals such as pure aluminum and pure copper, which have a higher reflectance and thermal diffusivity than aluminum alloys, is urgently required.
[0006]
The present invention has been made in view of the above-described conventional situations or problems, and realizes a sufficient penetration cross-sectional area and penetration depth even with a metal member having a high reflectance and a high thermal diffusivity, and is favorable. An object of the present invention is to provide a laser welding method and apparatus capable of obtaining a weld joint.
[0007]
Another object of the present invention is to provide a laser welding method and apparatus effective for improving the melting characteristics of various metal materials.
[0008]
[Means for Solving the Problems]
  In order to achieve the above object, a laser welding method of the present invention is a laser welding method for welding a metal member using laser light, and has a predetermined fundamental wavelength andDesired duration1 / N of the fundamental wavelength (N is 2 or more) so as to be temporally superimposed on the fundamental laser beam at a predetermined timing. A second step of generating a harmonic Q-switched laser beam having an integer) multiple wavelength and a desired high-speed repetitive Q-switching frequency separately from the fundamental laser beam, and the fundamental laser beam and the harmonic Q A third step of causing the switch laser light to enter the same dichroic mirror so that the optical axes thereof intersect at almost right angles, and superimposing both laser lights on the same axis; The superimposed fundamental wave laser beam and the harmonic Q-switched laser beam are condensed and irradiated to a welded portion of the metal member through a common condenser lens, and the welded portion is irradiated with the fundamental wave laser beam and the welded portion. Harmonics And a fourth step of metallurgically bonded both energy-switched laser light.
[0009]
  According to the laser welding method of the present invention,Desired durationThe fundamental wave laser beam having the above and the harmonic Q switch laser beam having the desired high-speed repetition Q-switch frequency are superimposed on the same axis and irradiated onto the welded portion of the metal member, so that both laser beams having different wavelengths can be obtained. The absorption efficiency of the laser energy that maximizes the synergistic effect is enhanced, and a large penetration cross-sectional area and penetration depth can be obtained even with a metal member having a high reflectance and a high thermal diffusivity.
[0010]
In the present invention, preferably, the beam diameter of the harmonic laser beam may be made smaller than the beam diameter of the fundamental laser beam. Thereby, a deep keyhole can be formed in the to-be-welded part of a metal member with a harmonic laser beam.
[0012]
  The laser welding apparatus of the present invention is a laser welding apparatus for welding metal members using laser light, and has a predetermined fundamental wavelength andDesired durationA first lasing unit that generates a continuous wave fundamental wave laser beam having a wavelength of 1 / N (N is an integer of 2 or more) times the fundamental wavelength and a desired high-speed repetitive Q-switch frequency. The first and second laser oscillators that generate the harmonic Q-switched laser light, the first and second harmonics so that the fundamental laser light and the harmonic Q-switched laser light are temporally superimposed at a predetermined timing. A control unit that controls the laser oscillation operation of the laser oscillation unit, the fundamental laser beam from the first laser oscillation unit, and the harmonic Q-switched laser beam from the second laser oscillation unit, respectively. The light beams are incident on both sides of the mirror so that the axes substantially intersect at right angles, and one of the fundamental laser light and the harmonic Q-switched laser light is transmitted straight and the other is reflected at right angles. Dichroic mirror for superimposing both laser beams on the same axis, and condensing the fundamental laser beam and the harmonic Q-switched laser beam superimposed on the same axis from the dichroic mirror And a condensing lens for irradiating the welded portion of the metal member.
[0013]
According to the laser welding apparatus of the present invention, the above-described laser welding method of the present invention can be effectively carried out by such a configuration.
[0014]
As a preferable aspect, the first laser oscillation unit includes a first solid-state laser medium, a first excitation light source, and a first optical resonator, and the first excitation light source is turned on. The optical energy may be supplied to the first solid-state laser medium, and the fundamental laser light may be output in continuous oscillation by the first solid-state laser medium and the first optical resonator.
[0015]
  As a preferred aspect, the second laser oscillation unit includes a second solid-state laser medium, a second excitation light source, a Q switch, a second optical resonator, and a wavelength converter. The second excitation light source is turned on, and the optical energy is supplied to the second solid-state laser medium, and the second solid-state laser medium, the Q switch, and the second optical resonator repeat the high-speed repetition. The fundamental Q-switched laser light having the fundamental wavelength at the Q-switch frequency is output, and the harmonic Q-switched laser having a wavelength that is 1 / N times the fundamental wavelength by the wavelength converter. Convert to lightThe
[0016]
  Moreover, as a preferable aspect, the control unit converts the fundamental laser light into theDesired durationAnd controlling the first laser oscillation unit to continuously oscillate and output the harmonic Q-switched laser light.Desired durationThe second laser oscillation unit is controlled so as to oscillate and output at a desired high-speed repetitive Q-switch frequency during this period.
[0017]
  In the laser welding apparatus of the present invention, preferably, the fundamental laser beam generated from the first laser oscillation unit or the harmonic generated from the second laser oscillation unit.Q switchLet the laser light enter one end surface,From the other end surface, the fundamental laser beam or the harmonic Q-switched laser beam incident on the one end surfaceThe outgoing optical fiber and the other end surface of the optical fiberMore outgoingThe fundamental laser beam or the harmonicsQ switchIt is good also as a structure which comprises the collimator lens which makes a laser beam parallel light and lets it pass to the said dichroic mirror side. Further, the fundamental laser beam generated from the first laser oscillation unit or the harmonic generated from the second laser oscillation unit.Q switchIt is good also as a structure which comprises the beam expander which expands the beam diameter of a laser beam by predetermined magnification, and lets it pass to the said dichroic mirror side.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0019]
In FIG. 1, the structure of the YAG laser welding apparatus in one Embodiment of this invention is shown. This YAG laser welding apparatus includes two YAG lasers 10 and 12, a control unit 14 that controls both lasers 10 and 12, and one emission unit 16.
[0020]
In the first YAG laser 10, the laser oscillator 18 is opposed to the YAG rod 20, the excitation light supply unit 22 that supplies excitation light to the YAG rod 20, and both end faces of the YAG rod 20, and A pair of optical resonator mirrors, that is, a total reflection mirror 24 and a partial reflection mirror (output mirror) 26, which are arranged at a predetermined interval, are provided.
[0021]
The excitation light supply unit 22 includes an excitation light source made of a discharge lamp or a semiconductor laser. The excitation light source generates excitation light EB in accordance with the power supplied from the laser power supply unit 28, and the excitation light EB is supplied to or irradiated on the YAG rod 20, so that the YAG rod 20 is driven by the energy of the excitation light EB. When excited, light is emitted in the axial direction from the end face of the rod by stimulated emission. Of the light emitted from both end faces of the YAG rod 20, the light having the resonance frequency is confined and amplified between the total reflection mirror 24 and the output mirror 26, and a part of the fundamental wave YAG continuously oscillated from the output mirror 26. Laser light (wavelength 1064nm) LB_cwIs output as.
[0022]
Fundamental YAG laser beam LB generated from the first YAG laser 10_cwIs transmitted to the first laser beam inlet 16a of the emission unit 16 through the reflection mirror 30, the incident unit 32, and the optical fiber 34. A cylindrical optical path cover 36 may be provided around the laser transmission path from the laser emission port of the laser oscillator 18 to the incident unit 32. A condensing lens 38 is disposed in the incident unit 32, and a fundamental wave YAG laser LB that has propagated in the air with substantially parallel light._cwIs condensed by a condensing lens 38 and incident on one end face of the optical fiber 34.
[0023]
In the second YAG laser 12, the laser oscillator 40 is opposed to the YAG rod 42, the excitation light supply unit 44 that supplies excitation light to the YAG rod 42, and both end faces of the YAG rod 42. It has a pair of optical resonator mirrors (total reflection mirror 46 and output mirror 48), a Q switch 50, and a wavelength converter 52 arranged at a predetermined interval.
[0024]
The YAG rod 42, the pumping light supply unit 44, and the optical resonator mirrors 46 and 48 are respectively the same as the YAG rod 20, the pumping light supply unit 22 and the optical resonator mirrors 24 and 26 in the laser oscillator 18 of the first YAG laser 10. It may have the same configuration and function.
[0025]
The Q switch 50 is composed of an acousto-optic Q switch, for example. A Q switch control circuit (not shown) in the laser power supply unit 54 drives the Q switch 50 by a high frequency electrical signal that is temporarily interrupted at a predetermined cycle via a Q switch driver 56. As a result, every time the high-frequency electrical signal is interrupted, the Q-switched YAG laser beam LB of a giant pulse having a very high peak power is obtained._Q(Wavelength 1064 nm) is generated from the output mirror 48. This Q switch YAG laser beam LB_QThe repetition frequency corresponds to the Q switch frequency for temporarily interrupting the high-frequency electrical signal.
[0026]
The wavelength converter 52 has an anisotropic crystal. By utilizing the nonlinear effect of the anisotropic crystal, the fundamental wave (wavelength 1064 nm) of the Q-switched YAG laser beam LB from the output mirror 48 is obtained._QQ-switched YAG laser beam LB of the second harmonic (wavelength 532 nm)_SHGConvert to
[0027]
Second harmonic Q-switched YAG laser light LB generated from the laser oscillator 40 of the second YAG laser 12_SHGIs transmitted through the air without passing through the optical fiber and transmitted to the second laser light inlet 16b of the emission unit 16. A cylindrical optical path cover 58 may be provided around the laser transmission path from the laser emission port of the laser oscillator 40 to the second laser light intake port 16b of the emission unit 16.
[0028]
The control unit 14 may be composed of, for example, a microcomputer and necessary peripheral devices, and the first and second lasers 10 are selected according to programs stored in a built-in memory, various condition data set and input by the user, and the like. , 12 are individually and comprehensively controlled through the laser power supply units 28, 54.
[0029]
The emission unit 16 has a cylindrical unit main body 60 having a laser emission port 16 c at the lower end, and necessary optical components are arranged at predetermined positions in the unit main body 60. More specifically, a connector 62 for detachably attaching the end of the optical fiber 34 is provided at the upper end of the unit main body 60, and on a straight axis connecting the connector 62 and the laser emission port 16c at the lower end. A collimator lens 64, a dichroic mirror 66, and a condensing lens 68 are arranged in order from the top at a predetermined interval.
[0030]
Further, a horizontal cylindrical portion 60a that constitutes the second laser light inlet 16b is provided on one side surface of the intermediate portion of the unit body 60, and the second laser 12 from the second laser 12 is provided in the horizontal cylindrical portion 60a. Harmonic Q switch YAG laser beam LB_SHGA beam expander 70 for expanding the beam diameter at a desired magnification is disposed. Here, the beam expander 70 may be set (aligned) so that the optical axis of the collimator lens 64 and the dichroic mirror 66 intersect at substantially right angles.
[0031]
In addition, it is preferable to shield (block) the welded portion WP of the workpiece W from ambient air during laser welding in order to prevent oxidation. When this shielding inert gas such as argon gas (Ar) or nitrogen gas (N2) is blown from the emission unit 16 side to the welded part WP, a shield gas injection part is provided near the laser emission port 16c of the emission unit 16. (Not shown) may be provided.
[0032]
FIG. 2 shows the detailed configuration and operation of the optical system in the emission unit 16. The beam expander 70 may be, for example, a Galileo type composed of a concave lens 72 and a convex lens 74. , F1 and f2, respectively, the magnification N is given by N = φ2 / φ1 = f2 / f1. Second harmonic Q-switched YAG laser beam LB whose beam diameter has been expanded by the beam expander 70_SHGIs incident on the lower surface 66a of the dichroic mirror 66 disposed at an inclination of about 45 ° toward the second laser light inlet 16b toward the center of the unit main body 60 at an incident angle of 45 °.
[0033]
On the other hand, the fundamental wave YAG laser beam LB transmitted from the first YAG laser 10 through the optical fiber 34._cwIs emitted radially from the end face of the optical fiber 34 and is passed through the collimator lens 64, whereby parallel light having a desired beam diameter φ0 is obtained. This beam diameter φ 0 can be adjusted to an arbitrary value by adjusting the distance between the end face of the optical fiber 34 and the collimator lens 64. Preferably, the fundamental wave YAG laser beam LB_cwOf the second harmonic Q-switched YAG laser beam LB from the beam expander 70._SHGThe beam diameter may be set larger than (for example, several times larger) than the beam diameter φ2. A fundamental wave YAG laser beam LB of parallel light having a predetermined beam diameter φ0 by the collimator lens 64_cwIs incident on the upper surface 66b of the dichroic mirror 66 at an incident angle of 45 °.
[0034]
The dichroic mirror 66 is a mirror having a very small absorption and scattering in which a dielectric multilayer film is coated on a glass substrate, and has a high (90% or higher) reflectivity for the second harmonic (wavelength 532 nm) YAG laser light. It shows a high transmittance (90% or more) for the YAG laser light of the fundamental wave (wavelength 1064 nm). Therefore, the fundamental wave YAG laser beam LB that has traveled straight in the vertical direction from the collimator lens 64._cwPasses through the dichroic mirror 66 and proceeds vertically downward. On the other hand, the second harmonic Q-switched YAG laser beam LB that has traveled straight from the beam expander 70 in the horizontal direction._SHGIs reflected by the dichroic mirror 66 vertically downward at a reflection angle of 45 ° (bending path), and the fundamental wave YAG laser beam LB from above is reflected._cwAre superimposed (joined) on almost the same axis.
[0035]
The fundamental wave YAG laser beam LB transmitted or reflected by the dichroic mirror 66 as described above._cwAnd second harmonic Q-switched YAG laser beam LB_SHGAre linearly moved vertically downward on the same axis and are incident on a common condensing lens 68, and are condensed by the condensing lens 68 in the vicinity of the welded portion WP of the workpiece W of the metal member. The condenser lens 68 is a so-called achromatic lens and has a fundamental wave YAG laser beam LB having a different wavelength._cw(Wavelength 1064 nm) and second harmonic Q-switched YAG laser light LB_SHGIt is configured not to produce chromatic aberration with respect to (wavelength 532 nm).
[0036]
Next, the operation of the YAG laser device according to this embodiment will be described. FIG. 3 shows a basic pattern of a laser output waveform suitable for a metal having high reflectivity and high thermal diffusivity, such as pure copper and pure aluminum, in this YAG laser apparatus.
[0037]
In this embodiment, the first laser 10 has a fundamental wave YAG pulsed laser beam having a desired pulse width (duration) Ts as shown in FIG. LB_cwIs generated. Here, this fundamental wave YAG pulse laser beam LB_cwThe power (laser output) Pcw can be set to an arbitrary value within a predetermined range by adjusting the power supplied from the laser power supply unit 28 to the excitation light source of the excitation light supply unit 22.
[0038]
On the other hand, the second laser 12 has a desired high-speed repetition frequency (Q switch frequency) f as shown in FIG._QSecond harmonic Q-switched YAG laser beam LB having_SHGIs generated. Here, the Q switch YAG laser beam LB_SHGPeak power Pp and repetition frequency f_QCan be arbitrarily variably adjusted by controlling the modulation of the high-frequency electrical signal to the Q switch 50. This Q switch YAG laser beam LB_SHGThe average power Pa of the peak power Pp and the duty cycle η (η = f_Q(Τp × 100) and the product (η · Pp). In ordinary laser welding, the fundamental wave YAG pulsed laser beam LB_cwIt may be set to a value lower than the power Pcw.
[0039]
The control unit 14 performs overall control of the laser oscillation operations of the first and second lasers 10 and 12, thereby allowing a continuous wave fundamental wave YAG pulsed laser beam LB as shown in FIG._cwAnd a Q-switched YAG laser beam LB having a high-speed repetition oscillation as shown in FIG._SHGCan be temporally superimposed at an arbitrary timing.
[0040]
Preferably, as shown in FIG. 3C, a continuous wave fundamental wave YAG pulsed laser beam LB is used._cwThe second harmonic Q-switched YAG laser light LB throughout the pulse time (Ts) during which_SHGIs the fast repetition frequency f_QIt may be set to a temporal superposition relationship such that oscillation is output at.
[0041]
FIG. 4 shows a continuous wave fundamental wave YAG pulse laser beam LB in a temporal superposition relationship as shown in FIG._cwAnd second harmonic Q-switched YAG laser beam LB_SHGAre generated by the first and second lasers 10 and 12, respectively, and both laser beams LB are generated._cw, LB_SHGIs schematically shown as a cross-sectional structure of the melted part in the welded part WP when the metal unit (work W) with high reflectivity and high thermal diffusivity is irradiated with the output unit 16 on the same axis as described above. Shown in
[0042]
As a reference (comparative) example, FIGS. 5 and 6 show a continuous wave fundamental wave YAG pulsed laser beam LB._cwAnd second harmonic Q-switched YAG laser beam LB_SHGThe cross-sectional structure of the fusion | melting part at the time of each irradiating to the workpiece | work W independently is shown.
[0043]
  As shown in FIG. 4, according to this embodiment, the continuous wave fundamental wave YAGpulseLaser beam LB_cwAnd second harmonic Q-switched YAG laser beam LB_SHGWith the synergistic effect of coaxial superimposing irradiation, a large penetration cross-sectional area and penetration depth can be obtained even if the workpiece W is a metal member having a high reflectance and a high thermal diffusivity. The mechanism by which such excellent melting characteristics can be obtained by the present invention has not yet been clearly clarified, but the following two factors can be considered.
[0044]
One factor is the second harmonic Q-switched YAG laser beam LB_SHGIn the keyhole KH formed by the fundamental wave YAG pulse laser beam LB_cwIt is conceivable that the absorption efficiency of laser energy can be dramatically improved by proceeding in the axial direction (vertically downward) with multiple reflection. Alternatively, the second harmonic Q-switched YAG laser light LB having a high absorption rate due to a short wavelength._SHGAs a result, the temperature in the vicinity of the welded part WP rises, and there is a high-power fundamental wave YAG pulse laser beam LB._cwIt is conceivable that the absorption efficiency of laser energy increases dramatically by irradiation. In any case, both laser beams LB_cw, LB_SHGAre superimposed on the same axis and incident on the welded part WP, the above synergistic effect is maximized, and the melted part greatly extends both in the horizontal and vertical directions.
[0045]
On the other hand, as shown in FIG. 5, a continuous wave fundamental wave YAG pulse laser beam LB is obtained._cwIs irradiated to a metal member (work W) having a high reflectance and a high thermal diffusivity alone, the laser energy cannot penetrate deep into the welded part WP, so that the penetration depth d 'is very short (shallow).
[0046]
Further, as shown in FIG. 6, the second harmonic Q-switched YAG laser beam LB_SHGIs irradiated to a metal member (work W) having high reflectivity and high thermal diffusivity alone, it can be melted to a certain depth, but it is still a continuous wave fundamental wave YAG pulsed laser beam LB._cwWhen compared with the case of being irradiated on the same axis (D '<D), the penetration cross-sectional area is too small.
[0047]
7 to 9 show data on melting characteristics obtained by applying the present invention to seam welding in comparison with a conventional example.
[0048]
  In the embodiment of FIG. 7, the pulse width Ts of the fundamental wave YAG pulse laser beam LBcw is set toAs shown in the range of 1ms-10msThe penetration depth D (d) of the melted part obtained in the welded part WP when changed is shown. The material of the workpiece W is pure copper (A1050). The main processing conditions are a feed rate v of 0.6 mm / s, a flow rate of shield gas (N2) of 30 l / min, and a second harmonic Q-switched YAG laser beam LB._SHGAverage power Pa is 40W, Q switch frequency f_QIs selected to be 10 kHz. The fundamental wave YAG pulse laser beam LB_cwThe repetition frequency (pulse frequency) may be set to 5 Hz, for example.
[0049]
As is apparent from the graph of FIG. 7, according to the present invention, a maximum penetration depth d of 2 mm or more can be achieved with respect to pure copper (A1050). On the other hand, as shown in FIG. 7 as a comparative example, the fundamental wave YAG pulse laser beam LB_cwWith a single laser welding, it is difficult to achieve a penetration depth of 0.5 mm or more.
[0050]
The embodiment of FIG. 8 shows a fundamental wave YAG pulse laser beam LB._cwWelding cross section S (mm) of the melted part obtained in the welded part WP when the power Pcw and the seam feed speed v are changed²). The material of the workpiece W is stainless steel (Type 304), and the main processing conditions are a flow rate of shield gas (Ar) of 30 liters / min, and a second harmonic Q-switched YAG laser beam LB._SHGAverage power Pa is 43.2 W, Q switch frequency f_QIs selected to be 10 kHz. The fundamental wave YAG pulse laser beam LB_cwThe repetition frequency (pulse frequency) may be set to 5 Hz, for example.
[0051]
From the graph of FIG. 8, the fundamental wave YAG pulse laser beam LB_cwIt can be seen that, regardless of the values of the power Pcw and the seam feed speed v, the melt cross-sectional area of the welded portion is greatly increased according to the present invention. In particular, at 400 to 600 W that is normally used as a laser output value, the fundamental wave YAG pulsed laser beam LB_cwIt can be seen that a melting cross-sectional area of twice or more is obtained as compared with the case of the single case (prior art).
[0052]
In the embodiment of FIG. 9, the melted portion melted by pure copper (A1050), pure aluminum (A5083) and stainless steel (Type 304), which are metal members having high reflectivity and high thermal diffusivity by laser welding under the same conditions. Cross-sectional area S (mm²) For comparison. As main processing conditions, the seam feed speed v is 0.6 mm / s, the flow rate of the shield gas (N2) is 30 liters / min, and the fundamental wave YAG pulse laser beam LB._cwPower Pcw of 275 W, second harmonic Q-switched YAG laser beam LB_SHGAverage power Pa is 40W, Q switch frequency f_QIs selected to be 10 kHz. Fundamental wave YAG pulse laser beam LB_cwThe repetition frequency (pulse frequency) may be set to 5 Hz, for example.
[0053]
From the graph of FIG. 9, according to the present invention, the melt cross-sectional area of the welded portion can be greatly increased with any metal member. By material, pure copper (A1050) <pure aluminum (A5083) <stainless steel (Type 304), and the largest melting cross section is obtained with stainless steel (Type 304).
[0054]
In the above-described embodiment, the fundamental wave YAG laser beam LB generated from the first laser 10._cwIs taken into the first laser light inlet 16a of the emission unit 16 through the optical fiber 34, and the second harmonic Q-switched YAG laser light LB generated by the second laser 12 is used._SHGWas taken into the second laser light inlet 16b of the emission unit 16 without passing through an optical fiber. Such a configuration is an example, and various modifications are possible. For example, fundamental wave YAG laser beam LB_cwIs taken into the second laser beam inlet 16b, and the second harmonic Q-switched YAG laser beam LB_SHGIt is also possible to adopt a configuration in which the light is taken into the first laser light inlet 16a.
[0055]
In the above-described embodiment, the continuous wave fundamental wave YAG laser beam LB is used._cwAnd high-speed repetitive pulse oscillation second harmonic Q-switched YAG laser beam LB_SHGWere superimposed on the same axis and irradiated onto the workpiece W. However, in addition to the second harmonic, other harmonic YAG laser beams such as a third harmonic (wavelength 355 nm) and a fourth harmonic (wavelength 266 nm) can be used. Furthermore, a continuous wave fundamental wave YAG laser beam LB_cwFor example, the second harmonic Q-switched YAG laser beam LB_SHGAnd third harmonic Q-switched YAG laser beam LB_THGA laser welding method in which the two are coaxially superimposed is also possible. In this case, another dichroic mirror may be provided inside or outside the emission unit 16.
[0056]
Moreover, although the above-described embodiment uses a YAG laser, the present invention can also use other lasers (particularly solid lasers).
[0057]
As in the above-described embodiment, the laser welding method of the present invention has a particularly remarkable effect on a metal member having a high reflectivity and a high thermal diffusivity, but it can be applied to other metal members such as an aluminum alloy and iron. It is effective even when applied.
[0058]
【The invention's effect】
As described above, according to the present invention, the melting characteristics of various metal materials can be greatly improved, and a sufficient penetration cross-sectional area and penetration depth can be realized even for metal members having high reflectivity and high thermal diffusivity. And good weld joints can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a YAG laser welding apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration and an operation of an optical system in an emission unit in the YAG laser welding apparatus of the embodiment.
FIG. 3 is a view showing a basic pattern of a laser output waveform of each part in the YAG laser welding apparatus of the embodiment.
FIG. 4 is a diagram schematically showing a cross-sectional structure of a melted portion obtained by laser welding according to an embodiment.
FIG. 5 is a diagram schematically showing a cross-sectional structure of a melted portion obtained by laser welding of a comparative example.
FIG. 6 is a diagram schematically showing a cross-sectional structure of a fusion zone obtained by laser welding of another comparative example.
FIG. 7 is a diagram showing one melting characteristic data obtained by applying the present invention to seam welding in comparison with a conventional example.
FIG. 8 is a diagram showing one melting characteristic data obtained by applying the present invention to seam welding in comparison with a conventional example.
FIG. 9 is a diagram showing one melting characteristic data obtained by applying the present invention to seam welding in comparison with a conventional example.
[Explanation of symbols]
10 First YAG laser
12 Second YAG laser
14 Control unit
16 Output unit
16a First laser beam inlet
16b Second laser beam inlet
64 collimator lens
66 Dichroic Mirror
68 condenser lens
70 beam expander

Claims (9)

A laser welding method for welding metal members using laser light,
A first step of generating a continuous wave fundamental laser beam having a predetermined fundamental wavelength and a desired duration ;
A harmonic Q having a wavelength 1 / N (N is an integer of 2 or more) times the fundamental wavelength and a desired high-speed repetitive Q switch frequency so as to be temporally superimposed on the fundamental laser beam at a predetermined timing. A second step of generating switch laser light separately from the fundamental laser light;
The fundamental laser beam and the harmonic Q-switched laser beam are incident on the same dichroic mirror so that the optical axes thereof intersect at almost right angles, and the third laser beam is superimposed on the same axis. And the process of
The fundamental wave laser beam and the harmonic Q-switched laser beam superimposed on the same axis are condensed and irradiated to a welded portion of the metal member through a common condenser lens, and the welded portion is And a fourth step of metallurgically joining the energy of both the fundamental laser beam and the harmonic Q-switched laser beam.   The laser welding method according to claim 1, wherein a beam diameter of the harmonic Q-switched laser light is made smaller than a beam diameter of the fundamental laser light.   3. The laser welding method according to claim 1, wherein the harmonic Q-switched laser beam is a second harmonic Q-switched laser beam having a wavelength that is ½ times the fundamental wavelength. 4. A laser welding apparatus for welding metal members using laser light,
A first laser oscillation unit that generates a continuous wave fundamental laser beam having a predetermined fundamental wavelength and a desired duration ;
A second laser oscillation unit that generates a harmonic Q-switched laser beam having a wavelength that is 1 / N (N is an integer of 2 or more) times the fundamental wavelength and a desired high-speed repetition Q-switch frequency;
A control unit that controls the laser oscillation operations of the first and second laser oscillation units so that the fundamental laser beam and the harmonic Q-switched laser beam are temporally superimposed at a predetermined timing;
The fundamental laser beam from the first laser oscillation unit and the harmonic Q-switched laser beam from the second laser oscillation unit are incident on both sides of the mirror so that their optical axes intersect at almost right angles. A dichroic mirror that transmits one of the fundamental wave laser beam and the harmonic Q-switched laser beam straight and reflects the other at a right angle to superimpose both laser beams on the same axis;
A condensing lens that condenses the fundamental laser beam and the harmonic Q-switched laser beam superimposed on the same axis from the dichroic mirror and irradiates the welded portion of the metal member. A laser welding apparatus characterized by the above.   The first laser oscillation unit includes a first solid-state laser medium, a first excitation light source, and a first optical resonator, and the first excitation light source is turned on, and the light energy is changed. The laser welding apparatus according to claim 4, wherein the laser beam is supplied to the first solid-state laser medium and the fundamental wave laser light is output in continuous oscillation by the first solid-state laser medium and the first optical resonator.   The second laser oscillation unit includes a second solid-state laser medium, a second excitation light source, a Q switch, a second optical resonator, and a wavelength converter, and the second excitation light source And the optical energy is supplied to the second solid-state laser medium, and the fundamental wavelength at the fast repetition Q-switch frequency by the second solid-state laser medium, the Q switch, and the second optical resonator. The fundamental Q-switched laser light having a wavelength of 1 is output, and the fundamental Q-switched laser light is converted into the harmonic Q-switched laser light having a wavelength 1 / N times the fundamental wavelength by the wavelength converter. The laser welding apparatus according to claim 4 or 5. The control unit controls the first laser oscillation unit that continuously oscillates and outputs the fundamental laser beam for the desired duration, and outputs the harmonic Q-switched laser beam for the duration of the desired duration. The laser welding apparatus according to any one of claims 4 to 6, wherein the second laser oscillation unit is controlled to oscillate and output at a desired high-speed repetition Q switch frequency. The fundamental laser beam generated from the first laser oscillation unit or the harmonic Q-switched laser beam generated from the second laser oscillation unit is incident on one end surface, and is incident on the one end surface. An optical fiber for emitting a fundamental laser beam or the harmonic Q-switched laser beam from the other end surface;
The collimating lens which comprises the said fundamental wave laser beam or the said harmonic Q switch laser beam radiate | emitted from the other end surface of the said optical fiber as parallel light, and passes along the said dichroic mirror side. The laser welding apparatus according to item.   A beam diameter of the fundamental laser beam generated from the first laser oscillation unit or the harmonic Q-switched laser beam generated from the second laser oscillation unit is enlarged by a predetermined magnification to the dichroic mirror side The laser welding apparatus as described in any one of Claims 4-8 which comprises the beam expander which lets it pass to.

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