Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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Process advantages of laser hybrid welding compared to conventional arc-based welding processes for joining thick steel structures of wind tower

2023-12-22 , Brunner-Schwer, Christian , Üstündag, Ömer , Bakir, Nasim , Gumenyuk, Andrey , Rethmeier, Michael

The most common welding processes when joining thick-walled steels in the industry are arc-based welding processes such as GMAW or SAW. For this purpose, the sheets are joined in multi-layer technique, which can lead to productivity losses due to high welding times. The process-specific challenges in welding thick steels using multi-layer technique relate to the high heat input from the process. Therefore, alternative welding processes are being actively sought. A suitable alternative is provided by beam-based welding processes such as the laser hybrid welding processes, which are characterized by deep penetration welds and lower heat input. With implementation of the laser hybrid welding process in the heavy industry, such as the wind tower industry, economic benefits can be reached such as the increase in productivity by reducing the layer number, and the lower consumption of filler material and energy. When comparing SAW welded 25 mm thick steels in five to six layers and single-pass laser hybrid welding, the welding time can be reduced more than 80 % and the costs of filler material, flux and energy can be saved up to 90 %. However, the industrial use of the laser hybrid welding process is still limited to applications, where the material thickness does not exceed 15 mm due to some process-specific challenges such as the sagging, sensitivity to manufacturing tolerances such as gaps and misalignment, limited filler wire mixing, and deteriorated mechanical properties resulting from high cooling rates. To overcome these challenges, a contactless electromagnetic backing based on an externally applied AC magnetic field was used. Eddy currents are induced due to the oscillating magnetic field, and an upward-oriented Lorentz force is generated to counteract the droplets formed due to gravitational forces. It allows to weld up to 30 mm thick structural steels in a single-pass with a 20-kW fiber laser system. Additionally, the gap bridgeability and the misalignment of edges were increased to 2 mm when welding 20 mm thick steels. With the aid of the AC magnetic field, a vortex was formed in the weld root, which had a positive effect on the filler wire mixing.

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Plasma-Laser-Auftragschweißen als hybrides Beschichtungsverfahren

2023 , Brunner-Schwer, Christian

Bauteile sind in einer Vielzahl von Industriezweigen korrosiven, abrasiven oder thermischen Belastungen ausgesetzt. Um mit diesen Belastungen umzugehen, sind kostenintensive Werkstoffe notwendig. Alternativ besteht durch Beschichtungen die Möglichkeit, Bauteiloberflächen an ausgewählten Stellen vor den Belastungen zu schützen. Zur Exploration möglicher Effizienzsteigerungen und Verbesserung der Umwelteinwirkungen werden kontinuierlich Auftragschweißprozesse für das Panzern, Plattieren oder Puffern von Bauteilen weiterentwickelt. Vor diesem Hintergrund wird in dieser Arbeit eine neuartige Kombination aus Plasmalichtbogen und Laserstrahlung zu einem hybriden Auftragschweißprozess untersucht. Neben der Analyse der technischen Leistungsfähigkeit des hybriden Auftragschweißprozesses erfolgt eine ökologische Betrachtung anhand einer vergleichenden Ökobilanzierung sowie einer Wirtschaftlichkeitsanalyse anhand einer Kostenvergleichsrechnung.

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A life cycle assessment of joining processes in the automotive industry, illustrated by the example of an EV battery case

2023 , Brunner-Schwer, Christian , Lemke, Josefine , Biegler, Max , Schmolke, Tobias , Spohr, Sebastian , Meschut, Gerson , Eckstein, Lutz , Rethmeier, Michael

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.

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Sensor integration in hybrid additive manufactured parts for real-time monitoring in turbine operations

2021 , Uhlmann, Eckart , Polte, Julian , Kersting, Robert , Brunner-Schwer, Christian , Neuwald, Tobias

Real-time monitoring of operation conditions such as tempeatures and vibrations enables efficiency enhancement for maintenance tasks. In energy industry monitoring of critical components such as turbine blades is essential for the operation safety. But the effective recording of critical process data is a challenging task due to the extreme operating conditions. With a hybrid processing approach combining two additive manufacturing technologies new classes of self-monitoring components become possible allowing data acquisition directly inside the component. Using the example of a turbine blade, the hybrid process chain is described. The turbine blade blank is produced via Laser Powder Bed Fusion (L-PBF) with channels for the integration of high temperature sensors. After integration cavities were closed by Laser Directed Energy Deposition (L-DED) followed by classical milling operations for part finishing. The data acquisition is integrated in state-of-the-art product l ifecycle monitoring (PLM) software to create a digital twin. Evaluation shows that temperature could be successfully monitored at conditions of Π= 550°C.

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Laserstrahlhybridschweissen von Türmen für Windkraftanlagen - Ökonomische und ökologische Vorteile

2023-12-19 , Üstündag, Ömer , Bakir, Nasim , Brunner-Schwer, Christian , Knöfel, Frieder , Gook, Sergej , Gumenyuk, Andrey , Rethmeier, Michael

Das Laserstrahlhybridschweißen ist beim Schweißen von Türmen für Windkraftanlagen eine Alternative zum Unterpulver schweißen von Dickblechen in Mehrlagentechnik und bietet hier ökonomische und ökologische Vorteile. Der industrielle Einsatz des Verfahrens ist jedoch durch prozessspezifische Herausforderungen eingeschränkt. Die im Beitrag beschriebene kontaktlose elektromagnetische Badstütze dient zur Erweiterung des Verfahrenspotenzials im Dickblechbereich >15 mm.

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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

2023 , Simón Muzás, Juan , Brunner-Schwer, Christian , Hilgenberg, Kai , Rethmeier, Michael

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.

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Laserstrahlhybridschweißen von Türmen für Windkraftanlagen

2022-08-29 , Üstündag, Ömer , Bakir, Nasim , Brunner-Schwer, Christian , Knöfel, Frieder , Gook, Sergej , Rethmeier, Michael , Gumenyuk, Andrey

Das Laserstrahlhybridschweißen ist beim Schweißen von Türmen für Windkraftanlagen eine Alternative zum Unterpulverschweißen von Dickblechen in Mehrlagentechnik und bietet hier ökonomische und ökologische Vorteile. Der industrielle Einsatz des Verfahrens ist jedoch durch prozessspezifische Herausforderungen eingeschränkt. Die im Beitrag beschriebene kontaktlose elektromagnetische Badstütze dient zur Erweiterung des Verfahrenspotenzials im Dickblechbereich >15 mm.

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Feasibility study of joining of carbon fibre-reinforced polymer composites and aluminium alloys by electron beam welding for use in lightweight construction

2023-05-12 , Yalcinyüz, Behiye Aybike , Brunner-Schwer, Christian , Biegler, Max , Rethmeier, Michael

In recent years, new solutions to reduce the weight of components used in the automotive, railway, and aircraft industries have been researched. Carbon Fibre Composites (CFC) have been used to replace metals in products requiring lightweight construction, such as aircraft or high-performance vehicles due to their exceptional mechanical strength. However, the use of CFCs is limited by the reason of their poor thermal conductivity, particularly on components requiring effective dissipation of power losses. To respond to the requirements, the idea of the material combination of metals and polymer-based composites is proposed. In this study, electron beam welding is used for the joining of aluminium alloys and polymer-based composites. Within the experiments, the relevant process parameters such as beam current, welding speed, and heat input have been optimized to achieve the welding of the aluminium alloys. Then, the joining of aluminium alloys and carbon fibre-reinforced polymer composites has been investigated through the optimized welding process parameters for aluminium alloys. Conclusions are drawn regarding the carbon-fibre reinforced polymer composites (PA6-CF) and aluminium alloys (AlMg3) being joinable through electron beams.

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On Welding of High-Strength Steels Using Laser Beam Welding and Resistance Spot Weld Bonding with Emphasis on Seam Leak Tightness

2023 , Schmolke, Tobias , Brunner-Schwer, Christian , Biegler, Max , Rethmeier, Michael , Meschut, Gerson

The design of most electric vehicles provides for the positioning of the heavy energy storage units in the underbody of the cars. In addition to crash safety, the battery housing has to meet high requirements for gas tightness. In order to test the use of high-strength steels for this sub-assembly, this paper examines welded joints utilizing resistance spot weld bonding and laser remote welding, with special regard to the gas tightness of the welds. For this purpose, the pressure difference test and helium sniffer leak detection are presented and applied. The combination of both leak test methods has proven ideal in experimental investigations. For laser remote welding, gas-tight seams can be achieved with an inter-sheet gap of 0.1 mm, even if occasionally leaking samples cannot be prevented. Resistance spot welding suits gas-tight joining with both one- and two-component adhesives. Against the background of leak tightness, process fluctuations that lead to weld spatter and defects in the adhesive layer must be prevented with high priority.

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Laser Welding of L-PBF AM components out of inconel 718

2022 , Brunner-Schwer, Christian , Simón-Muzás, Juan , Biegler, Max , Hilgenberg, Kai , Rethmeier, Michael

With regard to efficient production, it is desirable to combine the respective advantages of additively and conventionally manufactured components. Particularly in the case of large-volume components that also include filigree or complex structures, it makes sense to divide the overall part into individual elements, which afterwards have to be joined by welding. The following research represents a first step in fundamentally investigating and characterizing the joint welding of Laser Powder Bed Fusion (L-PBF) components made of Inconel 718. For this purpose, bead-on-plate welds were performed on plates manufactured using the L-PBF process and compared with the conventionally manufactured material. Conventional laser beam welding was used as welding process. The weld geometry was investigated as a function of the L-PBF build-up orientation. It was found that the welding depth and weld geometry differ depending on this orientation and in comparison to the conventional material.

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