Laser welding of copper using a high power disc laser at green wavelength

Haubold, Martin; Ganser, Andreas; Eder, Tobias; Zäh, Michael F.

doi:10.1016/j.procir.2018.08.161

Cited by 43 publications

(15 citation statements)

References 17 publications

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“…The change from the pioneering CO 2 lasers (λ = 10.6 µm) to solid-state lasers (λ ≈ 1 µm) realized as thin-disk or fiber lasers based on Yb:YAG and Nd:YAG led to strong increases in efficiency, absorptivity and applicability [2,3]. Due to the rapidly expanding market for electric mobility, copper, with its excellent electrical conductivity, and thus also copper joining-ranging from small applications, such as hairpins up to large cross-section applications like high-current conductors-has been gaining importance [4,5]. However, copper welding with near-infrared (IR) laser sources suffers from low absorptivity and low reproducibility, i.e., locally varying welding depths, as well as process instabilities, resulting in excessive spatter formation and porosity [6].…”

Section: Introductionmentioning

confidence: 99%

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Kohl

Kaufmann

Schmidt

2022

Metals

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With its excellent automation capability and localized energy input enabling precise, reproducible welds, laser beam welding represents a preferred industrial joining technology. Electro-mobility drastically increases the need for defect-free and automatable copper joining technologies. However, copper welds that are produced with state-of-the-art infrared lasers often suffer from spattering and porosity. Recent publications show distinct improvements using novel beam sources at visible wavelengths, attributing them to increased absorptivity. Nevertheless, this cannot fully explain the steadier process behavior. This wavelength-dependent process stability has not yet been investigated sufficiently. Therefore, we have developed a predictive material-dependent criterion indicating process stability based on the example of copper heat-conduction spot welding. For this purpose, we combined energy balances with thermo-physical material properties, taking into account the wavelength and temperature dependence of the optical properties. This paper presents the key mechanism that we identified as decisive for process stability. The criterion revealed that X-points (unique, material-specific wavelengths) represent critical stability indicators. Our calculations agree very well with experimental results on copper, steel and aluminum using two different wavelengths and demonstrate the decisive, material-dependent wavelength impact on process stability. This knowledge will help guide manufacturers and users to choose and develop beam sources that are tailored to the material being processed.

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Section: Introductionmentioning

confidence: 99%

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Kohl

Kaufmann

Schmidt

2022

Metals

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“…Changing the laser wavelength from the infrared region (fiber laser λ = 1070 ± 10 nm) to the visible region (green laser λ = 515 nm [14], and blue laser λ = 450 nm [15]) is inspired by the low optical reflectivity of copper for the visible radiation. Although fully dense copper parts could be manufactured using green or blue lasers via other laser-based AM processes [16][17][18], researchers have not yet disclosed the density, mechanical, electrical, or thermal properties of such LPBF fabricated parts. Moreover, the newly developed green or blue laser technology is costly and still in the research phase.…”

Section: Introductionmentioning

confidence: 99%

Highly conductive and strong CuSn0.3 alloy processed via laser powder bed fusion starting from a tin-coated copper powder

Jadhav

Deprez

et al. 2020

Additive Manufacturing

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Despite the high demand, the successful fabrication of fully dense, highly conductive, and strong copper components via laser powder bed fusion (LPBF) is not readily evident. This is mainly due to the low optical absorption of copper, which inhibits the complete melting of copper powders when using commercially available fiber-laser-based LPBF machines. Accordingly, this article proposes a novel approach of using optically absorptive metal-coated copper powders for the fabrication of fully dense, highly conductive, and strong copper components via LPBF. To validate this approach, the surface of the copper powder is modified by applying a very thin (62 ± 14 nm) layer of metallic tin via an immersion plating technique. The application of only a 0.28 wt% of metallic tin coating significantly improved the room temperature powder optical absorption by ~170% at the fiber laser wavelength. Consequently, crack-free and fully dense copper parts combining high thermal conductivity of 334 ± 4 W/(m•K) and electrical conductivity of 80 ± 1% international annealed copper standard (%IACS) with a good tensile strength of 256 ± 14 MPa, yield strength of 203 ± 4 MPa, and ductility of 21 ± 2 % have been fabricated using a fiber laser with an output laser power of 500 W.Furthermore, the article also describes the negative influence of the presence of a high amount of (0.091 wt%) sulfur, which originates from the organic additives during sub-optimal coating conditions, on the LPBF processing behavior of CuSn alloys. As such, high sulfur-containing tin-coated copper powders do not allow the fabrication of fully dense parts due to the occurrence of solidification cracks and the formation of pores. Subsequently, the optimum tin coating methodology, which limits the amount of sulfur below 0.0025 wt%, is described. The use of sulfur-free powder is recommended for the successful LPBF processing of fully dense parts made of copper and copper alloys.

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“…To improve the welding quality, many methods have been studied such as wobbling welding [3] , laser pro-structured surface [4,5] , Cu-based nano-composite absorber [6] , laser power modulation [7] , and welding in vacuum [8,9] . On the other hand, the absorption of Cu also shows a strong wavelength dependence [2] , so the green laser (wavelength 532 nm, absorption coefficient of 40% at room temperature) [10][11][12] and blue semiconductor laser (wavelength 450 nm, absorption coefficient of 67% at room temperature) [13] have been applied to Cu welding, and improved results were obtained. However, the cost of both green and blue lasers is still very high.…”

Section: Introductionmentioning

confidence: 99%

Micro-spot-welding of copper sheets with an IR vortex beam

Wang

Qin

et al. 2022

中国光学快报

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Copper welding with an infrared (IR) Gaussian laser beam usually shows obvious instability, spatters, and worse surface morphology due to the Gaussian distribution, temperature-dependent IR absorption, and high thermal conductivity in copper. In this paper, the IR quasi-continuous-wave Gaussian beam was converted into a vortex ring beam with a phase-plate and then applied to the micro-spot-welding of copper sheets. The welding with the vortex beam demonstrated a significantly improved welding performance, smoother surface morphology, and higher welding stability. Besides, no spatters appeared in the welding process.

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Laser welding of copper using a high power disc laser at green wavelength

Cited by 43 publications

References 17 publications

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Why Color Matters—Proposing a Quantitative Stability Criterion for Laser Beam Processing of Metals Based on Their Fundamental Optical Properties

Highly conductive and strong CuSn0.3 alloy processed via laser powder bed fusion starting from a tin-coated copper powder

Micro-spot-welding of copper sheets with an IR vortex beam

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