Numerical study of the effect of the oscillation frequency in buttonhole welding

Cho, Won Ik; Schultz, Villads; Woizeschke, Peer

doi:10.1016/j.jmatprotec.2018.05.024

Cited by 33 publications

(8 citation statements)

References 12 publications

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“…The buttonhole collapses again due to unfavorable surface tensional pressure conditions, see [31]. It has to be noted here that CFD simulations show a similar effect for a similar welding process [28].…”

Section: Instabilities During Laser Welding With Beam Oscillationsupporting

confidence: 52%

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Process Stability during Laser Beam Welding with Beam Oscillation and Wire Feed

Schultz

2019

JMMP

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Beam oscillation in laser material processing makes it possible to influence process behavior in terms of energy distribution, stability, melt pool dynamics and solidification. Within the setup presented here, the beam is oscillated transverse to the welding direction, and the filler wire is fed to the melt pool of a butt joint with an air gap. One advantage of this setup is the large gap bridging ability. Certain parameter sets lead to the so-called buttonhole welding method, which allows laser welding of smooth and nearly ripple-free seams. Observations showed a transition area between conventional keyhole and buttonhole welding in which the process is destabilized. Welds made with parameter sets from this area contain critical seam defects. Welding experiments with high-speed video recording and a simplified analytical model about the wire-beam interaction have helped to elucidate the mechanisms behind this. EN AW-6082 sheet material in 1.5 mm thickness and ML 4043 filler wire with 1.2 mm diameter were used. The investigations lead to the conclusion that partially melted wire segments result at certain parameter relations which hinder the formation of a buttonhole. If these segments are prevented, buttonhole welding occurs. In the transition area, these segments are very small and can lead to the detachment of a buttonhole, resulting in the named seam defects.

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Section: Instabilities During Laser Welding With Beam Oscillationsupporting

confidence: 52%

“…A different way to learn about the process is by using numerical simulation, see e.g., [28]. This brings additional information e.g., about melt pool flow and temperature.…”

Section: Model Validity and Sensitivitymentioning

confidence: 99%

Process Stability during Laser Beam Welding with Beam Oscillation and Wire Feed

Schultz

2019

JMMP

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“…The amount of molten metal in the weld pool determines mass momentum in combination with forces acting on it. As an example, in welding of thin plates, mass momentum is much lower, thus the toroid-shaped keyhole is created where the surface tension is dominating [36,37].…”

Section: Testing and Characterizationmentioning

confidence: 99%

Laser-arc hybrid welding of 12- and 15-mm thick structural steel

Bunaziv

Dørum

Nielsen

et al. 2020

Int J Adv Manuf Technol

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High-power lasers are very effective in welding of plates thicker than 10 mm due to the keyhole mode. High-power intensity generates a vapor-filled cavity which provides substantial penetration depth. Due to the narrow and deep weld geometry, there is susceptibility to high hardness and weld defects. Imperfections occur due to keyhole instability. A 16-kW disk laser was used for single-pass welding of 12-to 15-mm thick plates in a butt joint configuration. Root humping was the main imperfection and persisted within a wide range of process parameters. Added arc source to the laser beam process may cause increased root humping and sagging due to accelerated melt flow. Humping was mitigated by balancing certain arc and other process parameters. It was also found that lower welding speeds (< 1.2 m/min) combined with lower laser beam power (< 13 kW) can be more positive for suppression of humping. Machined edges provided more consistent root quality and integrity compared with plasma cut welded specimens. Higher heat input (> 0.80 kJ/mm) welds provided hardness level below 325 HV. The welded joints had good Charpy toughness at − 50°C (> 50 J) and high tensile strength.

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“…It enabled the prediction of rel-atively precise results even in a high power laser welding 12) . Recently, a numerical study considering the oscillation of the laser beam was also conducted, and the effect of oscillation frequency on the molten pool was analyzed 13) . In addition, the buttonhole phenomenon arising from the effect of surface tension pressure in laser welding of thin plates was also simulated 14) .…”

Section: Impact Of Wavelengths Of Co 2 Disk and Green Lasers On Fumentioning

confidence: 99%

Impact of Wavelengths of CO<sub>2</sub>, Disk, and Green Lasers on Fusion Zone Shape in Laser Welding of Steel

Cho

2020

Journal of Welding and Joining

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Numerical simulations of the multi-kW laser welding of structural carbon steel were conducted to analyze the effects of laser wavelength on fusion zone shape. For the heat and mass transfer analysis, the basic governing equations were utilized in addition to the volume-of-fluid (VOF) conservation equation to calculate the free surface boundary. Laser welding models that considered phenomena such as multiple reflections of the laser beam at the keyhole, absorption, recoil pressure, and shear stress and heat source by metal vapor generated were used as well. Two models: a general and a simplified model, which were both based on the Fresnel equations, were considered with the wavelengths of CO 2 , disk, and green lasers for calculating of the laser absorptivity of the material. The difference found in the results of the general model and the simplified model in the range of the wavelengths considered, was negligible. In addition, the results obtained for disk laser welding and green laser welding did not exhibit any considerable difference in terms of their impact on the fusion zone shape.

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Numerical study of the effect of the oscillation frequency in buttonhole welding

Cited by 33 publications

References 12 publications

Process Stability during Laser Beam Welding with Beam Oscillation and Wire Feed

Process Stability during Laser Beam Welding with Beam Oscillation and Wire Feed

Laser-arc hybrid welding of 12- and 15-mm thick structural steel

Impact of Wavelengths of CO<sub>2</sub>, Disk, and Green Lasers on Fusion Zone Shape in Laser Welding of Steel

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