Influence of laser beam welding in vacuum on the residual stress of non-grain oriented electrical steel sheets
Thomas Krichel, Simon Olschok, Uwe Reisgen

Major components of electrical motors are iron cores made of stacked electrical steel sheets to reduce eddy current loss. All common joining methods cause a degradation of the magnetic properties of the iron cores. Using fusion welding methods thermally induced residual stress degrade the magnetic properties. In this paper, pulsed laser beam welding in vacuum is used to join the individual electrical steel sheets. It is shown, that the intensity of residual stress can be influenced by variation of process parameters like beam power and working pressure.

Keywords: electrical steel sheets; laser beam welding in vacuum; residual stress

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Prevention of porosity in steel/Al laser welded joint with cold-sprayed steel interlayer by means of beam oscillation
Kyohei Maeda, Yuji Sato, Keisuke takenaka, Yoshiaki Kurita, Tesuo Suga, Masahiro Tsukamoto

Nowadays, in the automotive industry, multi-material body designs are widespread for weight reduction. It is well known that in this type of bodies, dissimilar metal joining is one of the main problems. For this reason, we have developed a dissimilar joining method with a cold-sprayed steel interlayer. In this procedure, a steel coating was sprayed onto an aluminium surface, and then, was laser welded to a steel sheet. In our previous research, it was found that porosity in the weld metal occurred in this process probably due to gases in the coating. It has been reported that oscillation welding is effective in preventing porosity in the weld metal of aluminium laser welds. In this study, therefore, the influence of beam oscillation on preventing the porosity formation in the laser welds with the coating was investigated.

Keywords: Laser welding; Cold-spray process; Dissimilar joining; Beam oscillation; Porosity

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Mechanical properties of laser welded joints of wrought and heat-treated PBF-LB/M Inconel 718 parts depending on build direction
Juan Simón-Muzás, Christian Brunner-Schwer, Kai Hilgenberg, Michael Rethmeier

Laser-based Powder Bed Fusion of Metal (PBF-LB/M) is a broadly used metal additive manufacturing (AM) method for fabricating complex metallic parts, whose sizes are however limited by the build envelope of PBF-LB/M machines. Laser welding arises as a valid joining method for effectively integrating these AM parts into larger assemblies. PBF-LB/M components must usually be stress-relieved before they can be separated from the build plate. An additional heat treatment can be beneficial for obtaining homogeneous mechanical properties across the seam or for the formation of desired precipitations in nickel-based-alloys. Therefore, the tensile performance of laser welded hybrid (AM/wrought) and AM-AM tensile samples of Inconel 718 is examined after undergoing three different heat treatments and considering three relevant build directions. It can be shown that the build orientation is an influencing factor on weld properties even after two applied heat treatments.

Keywords: Laser welding; PBF/LB-M; Hybrid components; Heat treatments; Build direction; Tensile performance; Inconel 718

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Innovative welding conception for thin-walled sheet metal components
Axel Jahn, Benjamin Kessler, Andrea Berger, Marko Seifert, Teja Roch

Welding of thin-walled sheet metal structures is a challenging task in various applications. For bipolar plate manufacturing, complex requirements regarding effective welding speed, reliable welding process, high surface quality and minimal distortion have to be fulfilled.
A new welding conception for 100 μm stainless steel strip material was fundamentally developed, using a continuous processing in roll-to-roll principle with laser welding in the roll gap. Weld seams can be produced along and transverse to the strip running direction by using a fast scanner system, achieving very high welding speed of 30 m/min and more. High seam quality, virtually no damage of coated outer skin and minimal welding distortion demonstrate the technological potential.
The set-up including roller system, strip guiding and laser optics will be presented as well as results of process development. Potential application in fusion cell bipolar plate manufacturing will be shown referring complex process chain of strip coating, forming and welding.

Keywords: Laser welding; Hydrogen; Bipolar plate; Stainless steel;

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Parameters optimization of Ti6Al4V alloy welding by pulsed Nd:YAG laser
Hana Chmelíčková, Martina Havelková, Aneta Hrubantová Písaříková, Vlastimil Jíleka,b, Lukáš Václavek

The butt welds of thin Ti6Al4V alloy sheets using a pulsed Nd:YAG laser were investigated to determine the optimal value of peak power and pulse length for creating sound welds. The width of the weld face and the depth of penetration were found to be proportional to increasing peak power and decreasing pulse length. The weld surfaces were measured using a contact profilometer. The influence of laser pulse overlap on the thermal cycle in representative point and cross-section planes was demonstrated by a numerical model. Repeated melting and heating above the transformation temperature by previous and following pulses probably caused the occurrence of a mixed microstructure of α´martensite and massive α in the fusion zone and near the heat-affected zone. Nanohardness tests on the transverse cross-sections showed that the fusion zone was approximately 50% harder than the base material. X-ray diffraction analysis of the central parts of the welds confirmed the presence of coincidence peaks of α´martensite and α phase.

Keywords: Laser welding; Ti6Al4V; FEM model; Nanoindentation; XRD analysis

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Enhancement of weld depth analysis in laser welding by extension of the oct data scope
Ronald Pordzik, Timon Ahlers, Thorsten Mattulat

Due to the challenging environment inside the keyhole during laser welding the evaluation of the penetration depth from measurements via Optical Coherence Tomography (OCT) demands for statistical filtering of the raw OCT-signal. Hereby, most commonly only the highest peak of the OCT-spectrogram is considered while maxima of higher orders and their intensities are neglected. However, due to the high keyhole dynamics the highest peak does not always correspond to the keyhole bottom, but it is possibly still represented in the OCT-spectrogram by higher order maxima. In this study the influence of maxima up to the 5th order and their corresponding intensities on the temporal resolution of the statistical weld depth analysis are investigated based on the frequency distribution of data points. The results show that considering the extended set of information increases the significance of the features in the frequency distribution that are associated with the keyhole depth.

Keywords: keyhole welding; process monitoring; optical coherence tomography

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Prediction of penetration depth in Al/Cu overlap laser welding with a combination of various sensors and deep learning
Sanghoon Kang, Minjung Kang, Yong Hoon Jang, Cheolhee Kim

Al/Cu laser-welded overlap joints, in which weld-penetration depth significantly influences both joint strength and electrical conductivity, are widely applied in automotive battery cells. In this study, the penetration depth was predicted using coaxially photographed weld pool image data (high-speed, CCD camera), photodiode, and spectrometer as input data. Penetration depth was measured by the optical coherence tomography (OCT) system and treated as output data.
Input data were preprocessed using various methods such as average, fast Fourier transform (FFT), and short-time Fourier transform (STFT). Two types of convolution neural network (CNN) models were tested. One is based on a unisensor CNN using only weld pool image data, and the other is a multi-sensor CNN using an additional photodiode or spectrometer signal. A total of 10 combinations were constructed and evaluated for comparison. The highest accuracy was obtained with an average absolute error of 0.02035 mm and a coefficient of determination of 0.98985.

Keywords: Al/Cu overlap welding; optical coherence tomography system; convolution neural network

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Advanced oscillation modes in laser welding
Hana Šebestová, Petr Horník, Zdeněk Chlup, Michal Jambor, Zdeněk Joska, Libor Mrňa

Modern wobble laser welding heads allow a great degree of freedom in the choice of oscillation modes resulting from a superposition of two orthogonal sinusoidal functions. Yet the basic oscillation modes like circular or transversal linear mode are still the most popular in practice. Therefore, unusual oscillation modes with more complex laser spot trajectories were suggested and experimentally achieved. In this way, wavy welds were created into martensitic 22MnB5 steel. The intention was to achieve welds with variable cross-sections, yet with a continuous root. The microstructure and properties of welds were analyzed with emphasis on changes in the heat-affected zone. We aim to provide a deeper understanding of advanced oscillation modes and their impact on the resulting weld quality and mechanical properties.

Keywords: Laser welding; beam oscillation; advanced oscillation mode; weld macrostructure; ultimate tensile strength

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Investigation on laser welding of copper and aluminum by irradiation from copper-side
Yasuhiro Okamotoa,*, Yuki Yamadab, Akihiro Ochib, Akira Okada, Takeshi Yamamurac, Katsutoshi Nagasakic, Kazunobu Mamemo, Norio Nishi

Laser welding of copper and aluminum is an important method to realize the low carbon society, and reliable and strong weld joint is required. In the laser welding of copper and aluminum, the generation of intermetallic compound (IMC) deteriorates the strength and the reliability of weld joint especially in the case of laser irradiation from copper side. High speed scanning and appropriately high intensity of laser beam could contribute the improvement in the stability of copper welding. The laser incident angle of 30 degrees resulted in the reduction of aluminum rich intermetallic compound and porosity, since the excessive spouting of molten aluminum into copper could be reduced. Moreover, uniform and thin IMC could be obtained by combining the angled irradiation and the superposition of near-infrared and blue lasers, which could increase the breaking strength in cross tension test by 80 %, compared with a normal irradiation method.

Keywords: Welding; Copper; Aluminum; IMC; Fiber laser, Blue laser

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A life cycle assessment of joining processes in the automotive industry, illustrated by the example of an EV battery case
Christian Brunner-Schwer, Josefine Lemke, Max Biegler, Tobias Schmolke, Sebastian Spohr, Gerson Meschut, Lutz Eckstein, Michael Rethmeier

Current ecological, economic and social changes are leading to a change in development, design and production of future vehicles. In this context, it is the stated goal of many manufacturers to advance the development of an environmentally friendly vehicle and climate-neutral production throughout the entire supply chain.
This study presents a comparative life cycle assessment of the joining processes laser beam welding, laser brazing and resistance spot welding. For this purpose, an approach tailored to welding processes is presented and applied to the example of a battery case for electric vehicles. For the welding process under consideration, the main influences on the resulting environmental impact categories are evaluated and compared. The requirements for ecologically efficient welding processes are discussed and outlined. The results show that particularly the materials involved, such as the consumption of the filler material, have the greatest environmental impact and thus offer the greatest potential for savings.

Keywords: life cycle assessment; laser beam welding; laser brazing; battery case;

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Enhanced process understanding for laser welding of copper and aluminum alloys with dynamic beam oscillation
Stephan Börner, Dirk Dittrich, Joseph Barrios Larrañaga, Andreas Wetzig, Michael Sawannia, Eveline N. Reinheimer, Andreas Heider, Reiner Ramsayer

The increasing electrification of automotive application require high quality and efficient joining processes for copper and aluminum alloys. Dynamic beam oscillation is suitable to cover the wide range of joining application for copper (thin to thick sheets) through the possibility of adapted energy distribution by one optical setup. However, amount of welding parameters increases strongly, which results in higher complexity of influencing factors.
Deeper process understanding and the identification of crucial process factors is necessary to overcome existing limitations in joint quality such as formation of blowouts, spatters and pores. Therefore, comprehensive insights in the welding process by X-ray imaging, high-speed video-recordings are combined with metallographic analysis. In this paper, the impact of the beam path speed on the process regime and the weld seam quality will be presented. Moreover, the transferability to applications and other difficult to weld materials like aluminum die-cast will be illustrated.

Keywords: laser beam welding; copper; beam oscillation; beam path speed; expanded keyhole; X-ray

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The change of the capillary shape during pore formation and its effect on process emissions
Michael Haas, Felix Zaiß, Jonas Wagner, Marc Hummel, Alexander Olowinsky, Felix Beckmann, Julian Moosmann, Christian Hagenlocher, Andreas Michalowski, Thomas Graf

Detecting the formation of pores during laser beam welding is challenging as pores are not visible from the outside of the weld seam. However, during formation, pores inherently change the capillary shape, leading to a change in its emissions as well as a change in the back reflection of the laser beam. Monitoring of these emissions has already proven to be a suitable tool in order to determine the formation of defects in welds based on statistical methods and empirical evaluations. To clarify the effect of shape fluctuations of the capillary on its emissions during laser beam welding the capillary shape was recorded by means of synchrotron X-ray imaging and the process emissions were simultaneously measured in different spectroscopic ranges. The analysis of the data proves the connection between capillary fluctuations and characteristic changes of the signals and therefore enables the detection of pore formation.

Keywords: laser welding; pore formation; X-ray imaging; process monitoring

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Advanced laser in-situ joining for continuous co-consolidation of carbon fiber-reinforced thermoplastic laminates
Eric Pohl, Maurice Langer, Peter Rauscher, Niklas Bleil, Axel Jahna Andrés F. Lasagni

Advanced laser in-situ joining (CONTIjoin) is a newly developed process for continuous co-consolidation of multidirectional carbon fiber-reinforced thermoplastic laminates onto a substrate material. In contrast to traditional lay-up techniques, like automated fiber placement (AFP) or automated tape laying (ATL), the CONTIjoin process is capable of continuous in-situ co-consolidation of laminates with up to six plies instead of single-layer unidirectional tapes. In the process, a carbon dioxide (CO2) laser in combination with highly dynamic beam deflection is used to heat up the joining partners in the mating area, while a pyrometer feeds temperature information into a control circuit to maintain a high set temperature accuracy. Without further autoclave post-processing, over 90 % of the mechanical performance of a static heat press co-consolidation was shown in interlaminar shear strength (ILSS) tests. The results are part of the Clean Sky 2 campaign for joining two thermoplastic half-shells of the full-scale multifunctional fuselage demonstrator (MFFD).

Keywords: continuous in-situ co-consolidation; thermoplastic composite; laser welding; multifunctional fuselage demonstrator; automated tape laying

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Al/Cu Interfacial gap prediction using multi-sensor signals and deep learning
Hyeonhee Kim, Sanghoon Kang, Yong Hoon Jang ,Minjung Kang

In secondary batteries and fuel cells for electric vehicles, connection between electrodes is inevitable. Achieving consistent weld quality and weld joint properties is critical for reliable battery assembly and electric vehicle performance. Laser welding is sensitive to joint preparation, which secures the electrodes with a jig system, but can create unexpected gaps between the layers. The spacing between the layers provides a path for laser beam dispersion and creates a loose interface. Typically, these electrodes are connected by full-overlap joints, making it difficult to find interfacial gaps during the process. In this study, laser welding was performed the on specimen with overlap joint for Al (top, 0.4 mm)/Cu (bottom, 1.0 mm) with an artificial gap. We proposed two types of convolution neural network (CNN) models to detect gap presence using single-sensor and multi-sensor data. To develop the deep learning model (a fully connected neural network model and a convolutional neural network model), CCD camera, OCT, and photodiode sensor were selected to monitor the weld pool feature, keyhole depth and plasma wavelength, respectively. Test results showed quite good classification performance with over 98% accuracy using a multiple sensor. Multi-sensor CNNs by consolidated image data have improved accuracy compared to those using only image data.

Keywords: convolution neural network; classification; interfacial gap

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Green laser welding process and system technologies for manufacturing parts of electric vehicles
Heeshin Kang, Hyunjong Yoo, Junsoo Park, Myungjin Kim, Jongsik Kim, Eunjoon Chun

Electric vehicles generally use lithium ion batteries with high energy density, and types include prismatic, pouch-type, and cylindrical batteries. In the electric vehicle industry, stable quality is important for electric vehicle battery welding. In addition, in the case of dissimilar materials, in copper-steel welding, the two materials do not form an intermetallic compound due to low solubility with each other, and segregation inside the welded part causes brittleness, which can lead to deterioration of welding quality. Therefore, it is important to set the laser parameters. Therefore, in this study, nickel-coated copper-mild steel materials used in battery tabs and bus bars were welded using a green laser through various process conditions and scan patterns in order to have more stable welding quality. Optimal process parameters that minimize spatter, internal defects, and internal segregation of welds were suggested through excellent mechanical properties and surface and cross-section analysis.

Keywords: greem; laser; welding; electrical vehicle; battery

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Quality and safety monitoring of the laser beam welding process for battery module contacting using a multi-sensor concept
Michael Riesener, Maximilian Kuhn, Christian Höltgen, Florian Kaufmann, Günther Schuh

One of the most relevant joining technologies for electromobility components is laser welding. High precision, contactless welding joints and flexible process design options enable high quality requirements to be met. In the field of battery systems, the weld seam quality of the cell connectors has a direct influence on the performance of the entire system. In addition, there is a risk of cell fire, which can be caused by faulty process conditions. The aspects of quality and safety monitoring therefore play a decisive role in the economic production of high-quality battery systems. Therefore, the aim of this work is to investigate a multi-sensor concept that monitors the quality-critical process parameters temperature and electrical resistance before, during, and after the welding process. Besides recording the sensor values, several test procedures were used to analyse the quality of the welding seams to compare them with the process parameters.

Keywords: Electromobility; Quality Monitoring; Safty Monitoring; Sensor; Welding

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Laser welding of e-mobility materials with variable beam profile lasers and pulse shaping
Mohammed Naeem, Imtiaz Majid, Jason Zhou, Jia Li, Shuming Zhang, Chih-Hao Wang, Lee Chen, Vic Li and Peter Xie

Most of the big automakers around the world are focused on electric vehicles. The battery technology used in these vehicles is lithium-ion batteries because they are smaller and lighter than existing automobile batteries. Batteries used in electric cars are built from a variety of materials, and one of the primary materials is copper.
The use of Variable Beam Profile (VBP) lasers for welding e-mobility materials is demonstrated. The VBP laser uses a dual beam outlet to produce a central point surrounded by another concentric ring of laser light. The use of VBP lasers results in more stable and consistent welding during welding.
This paper highlights welding results achieved with a VBP fibre laser, and power ranging from 6kW to 12kW (different beam qualities) on e-mobility materials and weld joints including dissimilar joints between copper and aluminium-based alloys. The VBP laser results are compared to those obtained via, for instance: pulse shaping of traditional single-beam lasers.

Keywords: Variable beam profile laser; welding; copper; aluminium-based alloy; dissimilar material joints and pulse shaping

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Laser direct joining of metal-polymer hybrid connections using a single beam source and processing station
Andreas Schkutow, René Geiger, Wolfgang Burgmayr, Thomas Frick

Laser direct joining of metals and plastics is a promising process for producing strong and reliable joints for lightweight hybrid structures without the need for adhesives, primers or mechanical fasteners. Commonly this process consists of two separate steps using at least two processing stations: the surface of the metal part is textured to achieve an increased surface roughness and improved mechanical interlock between the components. In another step, the thermoplastic components or the matrix of thermoplastic fiber reinforced composites are selectively heated to allow the melt to flow into the prepared metal structures. In this work, a new method is presented that combines highly efficient laser surface texturing of metallic parts and the selective laser heating of the joining zone in a transmission joining process using a single laser beam source running in different operation modes. This enables a very compact and cost-efficient processing station.

Keywords: Laser direct joining; metal-polymer connections; surface texturing; transmission joining;

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Reduction of transverse hot cracks by means of compressive stresses during laser welding of high strength aluminum alloys with high feed rates
Johannes Michel, Frauke Holder, Jonas Wagner, Felix Zaiß, Christian Hagenlocher, Rudolf Weber, Thomas Graf

Laser welding of high-strength aluminum alloys at high feed rates leads to transverse hot cracks. These cracks present a major challenge for electromobility applications, especially in the manufacturing of battery cases, as transverse hot cracks can lead to a leaky weld seam and potential component failure. To determine suitable strategies for the avoidance of transverse cracks, their formation was experimentally investigated and theoretically analyzed. A simulation of the temperature field and the fluid flow in the melt pool showed a decrease of the static pressure at the liquidus isotherm at high feed rates. The decrease of the static pressure in the melt pool impairs the liquid feeding between the solidifying grains and increases the risk of transverse hot cracking. To balance this pressure drop in the melt, a mechanic compressive stress was applied on the sample during welding. Such stresses are present in case of welding e.g., rollforming profiles. The resulting welds show a significant reduction of transverse cracks which highlights the potential of applying external mechanical compressive stress to reduce the formation of transverse hot cracks.

Keywords: Laser Beam Welding; Aluminum Alloys; Electromobility Applications; Transverse Hot Cracking; Compressive Stress

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Gap management of stainless-steel Laser Beam Welding with dynamic tailored beam shaping based on Multi-Plane Light Conversion
Mathieu Meunier, Avinash Kumar, Rosa Arrias, Jorge Luis Arias Otero, Adrien Douard, Gwenn Pallier*, Guillaume Labroille

The increasing automation of the automotive industry has resulted in the widespread use of laser technology, particularly in Laser Beam Welding (LBW) of complex materials like ferritic and austenitic steels used for exhaust systems. However, this may be challenging, and the use of the right beam shape can enhance the process performance and robustness to meet the high-quality standards. This paper focuses on LBW of 1mm steel, and how the Custodian project has developed a methodology to tailor the beam shape to the process. The appropriate shape for this study includes an inner intense spot and a background top-hat shape. A unique dynamic beam shaper based on Multi-Plane Light Conversion (MPLC) has been developed to adapt the shape to the welding bead in real-time. The optical performance of the beam shaper is described, as well as its impact on the quality of LBW with an 8kW 1.07μm laser.

Keywords: Laser; steel; welding; automative industry; beam shaping; dynamic tailored beam shaping

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An extended process window for copper welding with a tailored beam-shaping based on Multi-Plane Light Conversion
Avinash Kumar, Nicolas Gaillard, Eveline Reinheimer, Adeline Orieux, Adrien Douard, Gwenn Pallier, David Lemaitre, Christian Hagenlocher, Guillaume Labroille

Copper is a popular material in electric engines due to its high electrical and thermal conductivity. However, welding copper can be difficult because of its low absorptivity of the laser energy at 1μm and high thermal conductivity. In this study, we introduce a new approach of copper laser welding using a Multi-Plane Light Conversion (MPLC) beam shaper which stabilizes the melt pool.
A high-speed x-ray imaging was used to evaluate the geometry of capillary and the occurrence of pores during the process showing that no pores are present for a wider set of parameters compared to a single-fiber process. According to X-rays and macrographics the developed system allows for deep penetration welding of depths of up to 2.8mm at 8kW and 3m/min, as well as welding up to 25m/min at 8kW. The system allows for defect-free welding at lower and higher speeds compared to dual-core fiber and single-fiber systems.

Keywords: Laser; Welding; Copper; E-mobility; MPLC; beam shaping; Busbars; X-Ray; pores; spatters; laser head

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X-ray imaging of the influence of static and dynamic beam shaping on pore formation during laser welding of copper hairpins
Eveline N. Reinheimer, Christian Hagenlocher, Rudolf Weber, Thomas Graf

Laser beam welding provides a very efficient process for joining copper pins in electric drives, which are referred to as hairpins. The occurrence of pores in such joints reduces the conducting cross-section area and increases the electric resistance. The present work is an investigation of the process pore and spatter formation during welding hairpins with different welding contours. The welds are observed by radiographing the capillary in the processing zone. With the observation it was possible to determine the influence of different contours on the formation of pores and spatters The results show an influence of the welding contour on the formation of process pores and spatters. The occurrence of pores therefore influences the tensile strength of the welded hairpins.

Keywords: X-Ray Imaging; Copper; Hairpin Welding; Beam Shaping

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LTT effect simulation by varying the Cr-Ni compositions in the weld zone during laser beam welding for high alloy steel and studying its influence on Ms temperature and residual stresses
Karthik Ravi, Krishna Murthy, Akyel, Fatma, Olschok, Simon, Reisgen, Uwe

The main objective of this work is to study and reduce the formation of residual stresses generated during laser beam welding. The reduction of residual stresses is achieved by introducing the effect of Low Transformation Temperature (LTT) in the weld. Commonly this effect is used in unalloyed steel, but in this study the effect is introduced in stainless steel by introducing an unalloyed filler wire. By varying the filler wire deposition and laser power, the Cr-Ni content can be varied (Cr varied between 13-15%). The thermo-metallurgical-mechanical simulation model is created by defining the initial phase fractions, mechanical constraints, and thermal-mechanical properties for different Cr-Ni compositions in the weld and the base metal. The computed Ms. temperature and strain rate variations for different Cr-Ni compositions are validated by dilatometer, and the residual stresses are validated by drill hole method, and optimum Cr-Ni composition is selected to achieve lower reduced residual stress.

Keywords: Numerical simulation; Residual stresses; LTT effect; Laser beam welding

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In-situ laser heat treatment during laser beam welding of dual-phase steels
Martin Dahmen, Rebar Hama-Saleh Abdullah, Dora Maischner, Patrick Meyer, Alexander Olowinsky

During laser beam welding of dual-phase steels with tensile strengths above 780 MPa premature weld failure has been detected. Local embrittlement and the formation of micro-cracks are assumed to be possible reasons for the failure. Local in-situ heat treatment has been applied using laser radiation with the aim to soften fused zone and the fusion line area and, simultaneously to rise hardness in the tempering zone. Trials were undertaken to test the feasibility of laser heat treatment at feed rates typical for laser beam welding of thin sheet metal of DP980 in two gauges and from two manufacturing routes. The power density as well as the stand-off were varied to reveal the effects of utilising the weld heat for the heat treatment. The results indicate the possibility to reduce the hardness in fused zone and coarse-grain zone whereas the tempering zone tends to broaden depending on the power applied for laser heat treatment.

Keywords: Laser beam welding; laser heat treatment; heat-affected zone; dual-phase steel softening

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Suppression of spatter in deep penetration welding of pure copper plate using blue-IR superimposed laser
Shumpei Fujio, Mao Sudo, Keisuke Takenaka, Yuji Sato, Timotius Pasang, Masahiro Tsukamoto

In this research, a bead-on-plate welding of pure copper was conducted with a hybrid laser which superimposed an infrared (IR) laser and a high-intensity blue laser to achieve a deep-penetration and spatter-less welding of pure copper. In the hybrid laser welding, the blue laser was used for preheating to increase the absorptivity of pure copper for IR laser. To investigate an effect of the blue laser preheating, a welding with the hybrid laser was conducted varying the blue laser intensity. During welding, melt pool, keyhole, and spatter were observed. As the results, it was found that the IR laser was irradiated onto melted copper which has high absorptivity during the welding with the high-intensity blue laser preheating. This effect caused to ease a fluctuation of the absorptivity of copper and led to stabilize the melt pool and keyhole formation. Stabilization of them led to a reduction of spatters.

Keywords: Fiber laser; Blue diode laser; Welding, Copper; Spatter

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Ring transformation with a new axicon lens and its laser welding of copper
Kazunori Komori, Masaki Takemoto, Takashi Sakamoto, Kyohei Maeda, Keiichiro Tomari, Toshifumi Ogawa

We developed a 'New Axicon Lens' to convert from Gaussian beam profile to ring beam profile. This new axicon lens
integrates a condenser lens and an axicon lens and does not have cone-point in center. New Axicon lens uses
characteristics formulas which have a very small conic constant and a quadratic term that is not usually used in aspherical
lens. At the same time, we also developed a tilt mechanism and the profiler to correct the deflection of the laser from the
delivery fiber. In addition, we confirmed that the ring bias can be adjusted. Finally, we customized to a ring to a ring with
center. By using them, we tried pure copper welding and studied welding characteristics, such as amount of sputtering.

Keywords: NIR Laser; Axicon Lens; Cupper welding; Profiler; Tilt correction mechanism

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High-speed welding in EV industry with next-gen laser sources delivering superimposed beams
Oliver Bocksrocker, Alessia Riccio, Nicolai Speker, Mark Richmond, Tim Hesse

Over the last years laser welding with superimposed beams has lifted the welding performance in terms of speed and quality on a new level. However, the use of a superimposing ring beam increases the overall spot size on the surface of the material to be welded, which can be critical in some welding tasks, such as welding of thin metal foils. Therefore, a new laser source with increased brilliance and very small ring spots, covering the main spot, has been developed and applied for welding tasks from electric vehicle industries. It is shown that the welding speed and process stability can be increased with this new approach and a big scanning field at the same time can be achieved.

Keywords: Welding, battery, busbar, hairpin, bipolar plates, E-Mobility