Pores in laser beam welding: generation mechanism and impact on the melt flow

Fetzer, Florian; Berger, Peter; Hu, Haoyue; Weber, Rudolf; Graf, Thomas

doi:10.1117/12.2295798

Cited by 6 publications

(2 citation statements)

References 7 publications

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“…For copper, the lower eddy in the region of the capillary tip is observed to be less pronounced, while the melt pool region close to the sample surface indicates a strong material movement from the deeper melt pool area towards the back rim end of the capillary and above. The observations for steel are in good accordance with investigations in [45] and experimental results from [66].…”

Section: Analysis Of the Characteristic Melt Flow During Laser Beam W...supporting

confidence: 90%

Towards an Understanding of the Challenges in Laser Beam Welding of Copper – Observation of the Laser-Matter Interaction Zone in Laser Beam Welding of Copper and Steel Using in Situ Synchrotron X-Ray Imaging

Kaufmann,

Schrauder,

Hummel

et al. 2023

Lasers Manuf. Mater. Process.

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The increasing demand for contacting applications in electric components such as batteries, power electronics and electric drives is boosting the use of laser-based copper processing. Laser beam welding is a key for an efficient and high-quality electric vehicle production due to its local, non-contact energy input and high automation capability enabling reproducible weld quality. Nevertheless, a major challenge in process design is the combination of energy-efficiency and precise process guidance with regard to weld seam depth and defect prevention (i.e. spatter, melt ejections), partly caused by the high thermal conductivity of copper. High power lasers in the near infrared range and emerging visible laser beam sources with excellent beam quality can provide a suitable joining solution for this purpose. However, the underlying physical phenomena are currently only partly understood and a reflection on the challenges of laser beam welding of copper compared to well researched steel processing has not yet been carried out. In order to improve the understanding of the effect of the different material properties and the influence of process parameters on the vapor capillary and melt pool geometry in laser beam welding, in situ synchrotron investigations on Cu-ETP and S235 using 515 and 1030 nm laser sources were conducted. The material phase contrast analysis was successfully used to distinguish vapor capillary and melt pool phase boundaries during the welding process with high spatial and temporal resolution up to 5 kHz. A significantly different vapor capillary geometry and sensitivity to parameter variation were found between the steel and copper material. In addition, the visualization of characteristic melt flows revealed different melt pool dynamics and a pronounced eddy close to the melt pool surface for copper, which is assumed to be causal for the observation of pronounced spatter formation during copper welding in a certain process window.

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Section: Analysis Of the Characteristic Melt Flow During Laser Beam W...supporting

confidence: 90%

Towards an Understanding of the Challenges in Laser Beam Welding of Copper – Observation of the Laser-Matter Interaction Zone in Laser Beam Welding of Copper and Steel Using in Situ Synchrotron X-Ray Imaging

Kaufmann,

Schrauder,

Hummel

et al. 2023

Lasers Manuf. Mater. Process.

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show abstract

“…a circular geometry 5 . This allows an increase of process stability, a reduction of pore formation and an adaption of the weld geometry and consequently increased weld strength [5][6][7] . Besides the spatial power modulation, the laser power can be modulated over time.…”

Section: Introductionmentioning

confidence: 99%

Influence of ring-shaped laser beam during welding of AW-5083 and AW-6082

Hollatz

Hummel

Lach

et al. 2023

High-Power Laser Materials Processing: Applications, Diagnostics, and Systems XII

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The ongoing development of lasers with integrated beam-shaping features offers new opportunities for research in the field of laser beam welding. Main challenges for laser welding of aluminum alloys, such as AW-5083 or AW-6082, are pore formation and cracking. The locally adapted power distribution has a major influence on the keyhole required for deep penetration welding and therefore on occurring weld defects. To determine the reasons, the use of synchrotron radiation during the welding process enables the visibility of the keyhole shape. This investigation contains an analysis of the keyhole and melt pool shape based on the high-speed video images of the synchrotron radiation. The variation of the power ratio of center beam to ring allows a comparison of the influence of the beam shaping method. To stabilize the keyhole, a temporal power modulation is used for the ring. The results show an influence of the ring mode on the keyhole depth and the melt pool shape. The videos allow an analysis of different mechanisms for pore formation, such as the collapse of the keyhole.

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Tailored laser beam shapes for welding of copper using green laser radiation

Kaufmann,

Roth,

Schmidt

2024

Int J Adv Manuf Technol

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The rapid development of laser beam sources and adapted welding technologies in recent years lead to an increased use of laser welding techniques in automated production nowadays. Especially its precision and local energy input are key features for joining applications in electric vehicle components, where joints have to meet both mechanical and electrical requirements as current-carrying connections. However, the copper materials used are difficult to weld due to their physical properties, making a stable process with fewest seam imperfections only feasible within a limited process window. Recently available beam sources emitting visible laser radiation have proven to overcome the low absorptivity at process start, but spattering is still a prone defect significantly affecting process efficiency and quality. Literature approaches for modifying the energy input point to laser beam shaping as a method for reducing process imperfections, which, however, has not been extensively researched in copper processing using green laser radiation.Thus, this study investigates the influence of a shaped intensity profile for visible laser radiation created with a reflective diffractive optical element in laser beam welding with laser powers up to 3 kW. A characterization of the process dynamics is performed by use of high-speed imaging, and metallographic analysis is used to elaborate benefits of the applied beam shapes. With beam shaping, an enlarged heat conduction welding regime and an advantageous seam shape are found. Furthermore, a decrease in spatter formation during deep penetration welding is detected for the elliptical beam profile, which correlates with an oscillation movement of the capillary.

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Pores in laser beam welding: generation mechanism and impact on the melt flow

Cited by 6 publications

References 7 publications

Towards an Understanding of the Challenges in Laser Beam Welding of Copper – Observation of the Laser-Matter Interaction Zone in Laser Beam Welding of Copper and Steel Using in Situ Synchrotron X-Ray Imaging

Towards an Understanding of the Challenges in Laser Beam Welding of Copper – Observation of the Laser-Matter Interaction Zone in Laser Beam Welding of Copper and Steel Using in Situ Synchrotron X-Ray Imaging

Influence of ring-shaped laser beam during welding of AW-5083 and AW-6082

Tailored laser beam shapes for welding of copper using green laser radiation

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