TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser‑arc welding of laser‑ and plasma‑cut 20‑mm‑thick structural steels N2 - It is already known that the laser beam welding (LBW) or hybrid laser-arc welding (HLAW) processes are sensitive to manufacturing tolerances such as gaps and misalignment of the edges, especially at welding of thick-walled steels due to its narrow beam diameter. Therefore, the joining parts preferably have to be milled. The study deals with the influence of the edge quality, the gap and the misalignment of edges on the weld seam quality of hybrid laser-arc welded 20-mm-thick structural steel plates which were prepared by laser and plasma cutting. Single-pass welds were conducted in butt joint configuration. An AC magnet was used as a contactless backing. It was positioned under the workpiece during the welding process to prevent sagging. The profile of the edges and the gap between the workpieces were measured before welding by a profile scanner or a digital camera, respectively. With a laser beam power of just 13.7 kW, the single-pass welds could be performed. A gap bridgeability up to 1 mm at laser-cut and 2 mm at plasma-cut samples could be reached respectively. Furthermore, a misalignment of the edges up to 2 mm could be welded in a single pass. The new findings may eliminate the need for cost and time-consuming preparation of the edges. KW - Hybrid laser-arc welding KW - Thick-walled steel KW - Edge quality KW - Gap bridgeability KW - Laser cutting KW - Plasma cutting PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-552013 SN - 0043-2288 VL - 66 SP - 507 EP - 514 PB - Springer AN - OPUS4-55201 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meng, Xiangmeng A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - The detrimental molten pool narrowing phenomenon in wire feed laser beam welding and its suppression by magnetohydrodynamic technique N2 - Element transport in the wire feed laser beam welding (WFLBW) is directly determined by the molten pool shape and thermo-fluid flow therein. In this paper, an untypical molten pool profile, i.e., elongated at its top and bottom but narrowed at the middle, is found experimentally by real-time metal/glass observa- tion and numerically by multi-physical modeling. Ex-situ X-ray fluorescence element mapping is used to characterize the element dilution status in the fusion zone. For the first time, the detrimental influence of the molten pool narrowing on the element transport is identified and discussed, combining the exper- imental and numerical results. A magnetohydrodynamic technique is utilized to suppress the narrowing, aiming at a more homogenous element distribution. It is found that due to the interaction of the two dominant circulations from the top and bottom regions of the molten pool, a low-temperature region is formed. It leads to an untypical growth of the mushy zone, narrowing the molten pool in the middle re- gion. Its detrimental effect on material mixing is non-negligible considering the direct blocking effect on the downward flow and the premature solidification at the middle region. The Lorentz force from a trans- verse oscillating magnetic field can change the flow pattern into a single-circulation type. The downward transfer channel is widened, and its premature solidification is prevented because the low-temperature- gradient region is mitigated. This paper provides a supplementary reason regarding the common issue of insufficient material mixing during LBW, and a promising technique to optimize the process. KW - Thermo-fluid flow KW - Element transport KW - Laser beam welding KW - Magnetohydrodynamics KW - Multi-physical modeling PY - 2022 U6 - https://doi.org/10.1016/j.ijheatmasstransfer.2022.122913 VL - 193 SP - 122913 PB - Elsevier B.V. AN - OPUS4-55006 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Pittner, Andreas A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Einlagiges MSG-Hochleistungsschweißen von dickwandigen Baustählen mit kontaktloser elektromagnetischer Schmelzbadsicherung N2 - Diese Arbeit zeigt erstmals die Anwendung einer elektromagnetischen Schmelzbadstütze beim einlagigen MSG-Schweißen von dickwandigen Stählen. Die innovativen Entwicklungen im Bereich des Lichtbogenschweißverfahrens ermöglichen eine Erhöhung der Abschmelzleistung, um die Einschweißtiefe zu steigern. Somit kann die Lagenanzahl reduziert und die Produktivität gesteigert werden. Allerdings besteht insbesondere beim einlagigen Schweißen von dickwandigen Bauteilen in PA-Position ein erhöhtes Risiko für das gravitationsbedingte Austropfen der Schmelze an der Wurzel. Zur Verhinderung werden Badstützen eingesetzt, die mechanisch angebracht und nach dem Schweißen entfernt werden müssen, was zeit- und kostenintensiv ist. Die im Rahmen dieser Studie eingesetzte elektromagnetische Schmelzbadstütze wirkt dem gravitationsbedingten Austropfen der Schmelze entgegen und kompensiert den hydrostatischen Druck. Sie wirkt kontaktlos, was im Gegensatz zu herkömmlichen Badstützen vorteilhaft ist, so dass auf eine zeit- und kostenintensive Nachbearbeitung der Schweißnahtwurzel verzichtet werden kann. Das auf extern angelegten oszillierenden Magnetfeldern beruhende Verfahren wird dabei unterhalb des zu schweißenden Bauteils positioniert. Die Magnetfeldlinien sind quer zur Schweißrichtung ausgerichtet, sodass längs zur Schweißrichtung Wirbelströme im Werkstück und eine stets nach oben gerichtete Lorentzkraft generiert werden. Mit Hilfe der elektromagnetischen Badstütze konnten beim einlagigen MSG-Schweißen von 8 mm bis 12 mm die Tropfenbildung vermieden werden. Die innovative Technologie ermöglicht es dickwandige Bauteile einlagig zu schweißen und reduziert die Nachbearbeitungszeit deutlich. T2 - DVS Congress 2022 - Große Schweißtechnische Tagung CY - Koblenz, Germany DA - 19.09.2022 KW - Hochleistungsschweißen KW - MSG-Schweißen KW - Elektromagnetische Schmelzbadsicherung PY - 2022 AN - OPUS4-56368 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Improvement of Charpy impact toughness by using an AC magnet backing system at laser hybrid welding of thick S690QL steels N2 - The study deals with the influence of the heat input and the resulting cooling times on the microstructure and Charpy impact toughness of single-pass laser hybrid welded 20-mm thick high-strength steel S690QL. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured in-situ using a pyrometer and an optical fibre in three different depths of the seam where Charpy impact test specimens were also later taken. Thereby, three different heat inputs from 1.3 kJ/mm to 2 kJ/mm were investigated. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required impact toughness of 38 J/cm2 could be reached in dependance on applied heat input, especially at the heat input of 1.6 kJ/mm. T2 - LANE 2022: 12th CIRP Conference on Photonic Technologies CY - Fürth, Germany DA - 04.09.2022 KW - Laser hybrid welding KW - Electromagnetic backing KW - Charpy impact toughness KW - Thick-plate welding KW - Thermal cycles PY - 2022 AN - OPUS4-56369 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Pittner, Andreas A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Einlagiges MSG-Hochleistungsschweißen von dickwandigen Baustählen mit kontaktloser elektromagnetischer Schmelzbadsicherung N2 - Diese Arbeit zeigt erstmals die Anwendung einer elektromagnetischen Schmelzbadsicherung beim einlagigen MSG-Schweißen von dickwandigen Stählen. Die innovativen Entwicklungen im Bereich des Lichtbogenschweißverfahrens ermöglichen eine Erhöhung der Abschmelzleistung, um die Einschweißtiefe zu steigern. Somit kann die Lagenanzahl reduziert und die Produktivität gesteigert werden. Allerdings besteht insbesondere beim einlagigen Schweißen von dickwandigen Bauteilen in PA-Position ein erhöhtes Risiko für das gravitationsbedingte Austropfen der Schmelze an der Wurzel. Zur Verhinderung werden Badsicherungen eingesetzt, die mechanisch angebracht und nach dem Schweißen entfernt werden müssen, was zeit- und kostenintensiv ist. Die im Rahmen dieser Studie eingesetzte elektromagnetische Schmelzbadsicherung wirkt dem gravitationsbedingten Austropfen der Schmelze entgegen und kompensiert den hydrostatischen Druck. Sie wirkt kontaktlos, was im Gegensatz zu herkömmlichen Badsicherungen vorteilhaft ist, so dass auf eine zeit- und kostenintensive Nachbearbeitung der Schweißnahtwurzel verzichtet werden kann. Das auf extern angelegten oszillierenden Magnetfeldern beruhende Verfahren wird dabei unterhalb des zu schweißenden Bauteils positioniert. Die Magnetfeldlinien sind quer zur Schweißrichtung ausgerichtet, sodass längs zur Schweißrichtung Wirbelströme im Werkstück und eine stets nach oben gerichtete Lorentzkraft generiert werden. Mit Hilfe der elektromagnetischen Badsicherung konnten beim einlagigen MSG-Schweißen von bis zu 10 mm dicken Blechen die Tropfenbildung vermieden werden. Die innovative Technologie ermöglicht es, dickwandige Bauteile einlagig zu schweißen und reduziert die Nachbearbeitungszeiten und -kosten deutlich. T2 - DVS Congress 2022 - Große Schweißtechnische Tagung CY - Koblenz, Germany DA - 19.09.2022 KW - Elektromagnetische Schmelzbadsicherung KW - Hochleistungsschweißen KW - MSG-Schweißen PY - 2022 SN - 978-3-96144-189-1 VL - 382 SP - 640 EP - 645 PB - DVS Media GmbH AN - OPUS4-56371 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Brunner-Schwer, C. A1 - Knöfel, F. A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laserstrahlhybridschweissen von Türmen für Windkraftanlagen Ökonomische und ökologische Vorteile N2 - 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. KW - Elektromagnetische Badstütze KW - Laserhybridschweißen KW - Windkraftanlagen KW - Ökonomische und ökologische Vorteile PY - 2022 VL - 7 SP - 340 EP - 347 PB - DVS Media GmbH AN - OPUS4-56372 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Improvement of Charpy impact toughness by using an AC magnet backing system for laser hybrid welding of thick S690QL steels N2 - The study deals with the influence of the heat input and the resulting cooling times on the microstructure and Charpy impact toughness of single-pass laser hybrid welded 20-mm thick high-strength steel S690QL. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured in-situ using a pyrometer and an optical fibre in three different depths of the seam where Charpy impact test specimens were also later taken. Thereby, three different heat inputs from 1.3 kJ/mm to 2 kJ/mm were investigated. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required impact toughness of 38 J/cm2 could be reached in dependance on applied heat input, especially at the heat input of 1.6 kJ/mm. T2 - 12th CIRP conference on photonic technologies [lane 2022] CY - Fürth, Germany DA - 04.09.2022 KW - Thick-plate welding KW - Laser hybrid welding KW - Electromagnetic backing KW - Charpy impact toughness KW - Thermal cycles PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-563731 VL - 111 SP - 462 EP - 465 PB - Elsevier B.V. AN - OPUS4-56373 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jokisch, T. A1 - Gook, S. A1 - Marko, A. A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laser beam welding of additive manufactured components: Applicability of existing valuation regulations N2 - With additive manufacturing in the powder bed, the component size is limited by the installation space. Joint welding of additively manufactured parts offers a possibility to remove this size limitation. However, due to the specific stress and microstructure state in the additively built material, it is unclear to what extent existing evaluation rules of joint welding are also suitable for welds on additive components. This is investigated using laser beam welding of additively manufactured pipe joints. The welds are evaluated by means of visual inspection, metallographic examinations as well as computed tomography. The types of defects found are comparable to conventional components. This is an indicator that existing evaluation regulations also map the possible defects occurring for weld seams on additive components. KW - Weld imperfections KW - Additive manufacturing KW - Weldability KW - Laser welding PY - 2022 VL - 2 SP - 109 EP - 113 PB - DVS Media GmbH AN - OPUS4-56374 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Elektromagnetische Schmelzbadbeeinflussung beim Laserhybridschweißen von Dickblechen N2 - Die technischen Entwicklungen in der Lasertechnologie in den letzten Jahrzehnten haben eine neue Generation von Hochleistungslasersystemen im Leistungsbereich bis zu 100 kW auf den Markt gebracht. Dennoch ist die industrielle Anwendung des Hochleistungslaserstrahlschweißens auf bis zu 15 mm dicke Bleche beschränkt. Mögliche Ursachen der Einschränkungen des Verfahrens sind z.B. die Sensibilität des Verfahrens auf Fertigungstoleranzen wie Spalt und Kantenversatz, die erhöhte Tropfenbildung bei höheren Blechdicken und eine inhomogene Verteilung des Zusatzwerkstoffes beim Laserhybridschweißen. In dieser Studie wird ein auf extern angelegte Magnetfelder basierte elektromagnetische Schmelzbadstütze eingesetzt, um die Grenzen des Verfahrens zu erweitern und die Herausforderungen zu minimieren. Der wesentliche Vorteil der elektromagnetischen Schmelzbadstütze ist, dass sie berührungslos arbeitet. Mit Hilfe der elektromagnetischen Schmelzbadstütze konnten bei 20 mm dicken Proben aus S355J2 die Tropfenbildung an der Wurzel vermieden werden. Zudem wurde der Einfluss der Kantenqualität auf die Schweißnahtqualität untersucht, wobei verschiedene Schneidverfahren zur Kantenvorbereitung eingesetzt wurden, wie z.B. Plasma-, Brenn- oder Laserschneiden. Es konnte gezeigt werden, dass auch bei schlechteren Kantenvorbereitung im Gegensatz zu gefrästen Bauteilen die Werkstoffe einlagig mittels Laserhybridschweißen bei einer hohen Schweißnahtqualität gefügt werden konnten. Bei plasmageschnittenen Proben wurden zudem eine Spaltüberbrückbarkeit bzw. Kantenversatz von bis zu 2 mm sicher überbrückt. Des Weiteren war es mit Hilfe der externen Magnetfelder möglich, die Durchmischung des Zusatzwerkstoffes über die gesamte Schweißnahttiefe deutlich zu homogenisieren. T2 - 42. Assistentenseminar der Wissenschaftlichen Gesellschaft Fügetechnik e.V. CY - Blankenau, Germany DA - 06.10.2021 KW - Elektromagnetische Schmelzbadstütze KW - Laserhybridschweißen KW - Dickblech PY - 2022 VL - 385 SP - 1 EP - 7 PB - DVS Media GmbH AN - OPUS4-56375 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of the weld pool geometry on solidification cracking in partial penetration high power laser beam welding N2 - Solidification cracking is still a serious problem in laser beam welding, especially in the welding of thick-walled plates. The influence of weld pool geometry on solidification cracking in partial penetration welding of thick plates is investigated within scope of this study. Therefore, a specific experimental setup of steel and quartz glass in butt configuration and on the side with high-speed camera were used to record the weld pool shape. In addition, the influence of laser inclination angle on the weld pool geometry and on solidification crack formation was investigated. The results show a bulge in the weld pool root, which is separated from an upper region by a necking region. This leads to a case where there are three different longitudinal region lengths with different solidification zones. This temporal sequence of solidification strongly promotes the formation of solidification cracks in the weld root. T2 - 12th CIRP Conference on photonic technologies (LANE 2022) CY - Fürth, Germany DA - 04.09.2022 KW - Laser beam welding KW - Partial penetration KW - Weld pool shape PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-563940 VL - 111 SP - 397 EP - 400 PB - Elsevier B.V. AN - OPUS4-56394 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, Sergej A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Method for defect-free hybrid laser-arc welding of closed circumferential welds N2 - This paper presents investigation results of a process for defect-free hybrid laser arc welding (HLAW) of closed circumferential welds. The process aims to avoid weld imperfections in the overlap area of a HLAW circumferential weld. A process control strategy for closing the circumferential weld was developed to achieve a defect-free overlap region by controlling the solidification conditions at the end of the weld. The controlled heat flow is achieved by adjusting the parameters of both welding processes involved, the laser beam as well as gas metal arc welding (GMAW) process. Experimental investigations were carried out on 12 mm to 15 mm thick tube sections. The influence of process parameters such as the laser ramp time, the change in magnification scale and the defocusing of the laser beam on the solidifi-cation conditions at the end of the circumferential weld was investigated to find an optimum strategy for ramping out the process energy. Within the framework of the experimental studies, it was demonstrated that defocusing the laser beam in the range between 60 mm and 100 mm over a short run-out area of the weld of approximately 15 mm led to a significantly better weld formation in the overlap area. A favourable cup-shaped weld shape could be achieved without a tendency to crack. The laser optics with a motor-driven lens system made it possible to increase the laser beam diameter without changing the position of the GMAW arc relative to the component surface. KW - Weld defects KW - Hybrid welding KW - Laser beam welding KW - Pipe manufacturing KW - Gas shielded arc welding PY - 2021 VL - 20 IS - 4 SP - 334 EP - 339 PB - DVS Media AN - OPUS4-54665 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Thermal Cycles and Charpy Impact Toughness of Single-Pass Hybrid Laser-Arc Welded Thick-Walled Structures N2 - The study deals with the influence of the heat input on the thermal cycles and Charpy impact toughness for hybrid laser-arc welding of 25 mm thick structural steel S355J2 using a 20-kW high-power laser in combination with an electromagnetic weld pool support. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured using a pyrometer in combination with an optical fibre in three different locations near to fusion lines corresponding to different heights of the seam. Also, Charpy impact specimens were taken from different parts of the weld joint corresponding to the different heights. The influence of the heat input was investigated for 1.8 kJ mm-1 and 3.2 kJ mm-1. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required values could be reached in dependance on applied heat input. T2 - Lasers in Manufacturing Conference 2021 CY - Online meeting DA - 21.06.2021 KW - laser hybrid welding KW - Charpy impact toughness KW - thick plate welding KW - thermal cycles PY - 2021 SP - 1 EP - 8 AN - OPUS4-53926 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Artinov, Antoni A1 - Meng, Xiangmeng A1 - Bakir, Nasim A1 - Üstündag, Ömer A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - The bulging effect and its relevance in high power laser beam welding N2 - The present work deals with the recently confirmed widening of the weld pool interface, known as a bulging effect, and its relevance in high power laser beam welding. A combined experimental and numerical approach is utilized to study the influence of the bulge on the hot cracking formation and the transport of alloying elements in the molten pool. A technique using a quartz glass, a direct-diode laser illumination, a high-speed camera, and an infrared camera is applied to visualize the weld pool geometry in the longitudinal section. The study examines the relevance of the bulging effect on both, partial and complete penetration, as well as for different sheet thicknesses ranging from 8 mm to 25 mm. The numerical analysis shows that the formation of a bulge region is highly dependent on the penetration depth and occurs more frequently during partial penetration above 6 mm and complete penetration above 8 mm penetration depth, respectively. The location of the bulge correlates strongly with the cracking location. The obtained experimental and numerical results reveal that the bulging effect increases the hot cracking susceptibility and limits the transfer of alloying elements from the top of the weld pool to the weld root. T2 - 18th Nordic Laser Materials Processing Conference (18th NOLAMP) KW - High-power laser beam welding KW - Bulge effect KW - Solidification cracking KW - Multi-physical modelling KW - Metal mixing PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-539149 VL - 1135 IS - 012003 SP - 1 EP - 11 PB - IOP Publishing AN - OPUS4-53914 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of an external applied AC magnetic field on the melt pool dynamics at high-power laser beam welding N2 - The study deals with the determination of the influence of an externally applied oscillating magnetic field on the melt pool dynamics in high power laser beam and hybrid laser arc welding processes. An AC magnet was positioned under the workpiece which is generating an upward directed electromagnetic force to counteract the formation of the droplets. To visualise the melt flow characteristics, several experiments were carried out using a special technique with mild steel from S355J2 with a plate thickness of up to 20 mm and a quartz glass in butt configuration. The profile of the keyhole and the melt flow were recorded with a highspeed camera from the glass side. Additionally, the influence of the magnetic field orientation to the welding direction on the filler material dilution on laser hybrid welding was studied with variating oscillation frequency. The element distribution over the whole seam thickness was measured with X-ray fluorescence (XRF). The oscillation frequency demonstrated a great influence on the melt pool dynamics and the mixing of the elements of the filler wire. The highspeed recordings showed, under the influence of the magnetic field, that the melt is affected under strong vortex at the weld root, which also avoids the formation of droplets. T2 - 18th Nordic Laser Materials Processing Conference (18th NOLAMP) KW - Laser beam welding KW - AC magnetic field KW - Melt pool dynamics KW - Filler wire mixing PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-539231 VL - 1135 IS - 012017 SP - 1 EP - 10 PB - IOP Publishing AN - OPUS4-53923 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of the gap bridgeability at high-power laser hybrid welding of plasma-cut thick mild steels with AC magnetic support N2 - One of the challenges of the high-power hybrid laser welding of thick steels is the sensitivity of the process of the process to manufacturing tolerances. This usually leads to a time-consuming preparation of the welding edges, such as milling. The study deals with the influence of the edge quality of milled and plasma-cut steel made of S355J2 with a wall thickness of 20 mm on the laser hybrid welded seam quality. Furthermore, the gap bridgeability and the tolerances towards edge misalignment was investigated. An AC magnet was used as backing support to prevent sagging and positioned under the workpiece, to generate an upwards directed electromagnetic pressure. The profiles of the edges and the gap on the top and root side were measured using a digital camera. Single-pass laser hybrid welds of plasma-cut edges could be welded using a laser beam power of just 13.7 kW. A gap bridgeability up to 2 mm and misalignment of edges up to 2 mm could be achieved successful. Additionally, the independence of the cutting side and the welding side was shown, so that samples were welded to the opposite side to their cutting. For evaluation of internal defects or irregularities, X-ray images were carried out. Charpy impact strength tests were performed to determine the toughness of the welds. T2 - X International Conference «Beam Technologies & Laser Application» KW - Laser hybrid welding KW - Magnetic bath support KW - Plasma-cut samples KW - Thick plate welding PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-539248 VL - 2077 IS - 012007 SP - 1 EP - 8 PB - IOP Publishing AN - OPUS4-53924 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Observation of the weld pool shape in partial penetration welding and its influence on solidification crack formation for high-power laser beam welding N2 - In this study, steel-glass experiments were conducted to observe the melt pool geometry using a high-speed camera. The high-speed recordings and optical flow analysis show that two main flows take place in form of vortices. The lower vortex drives the melt backwards from the front keyhole wall and thus causes an extension of the melt pool, which is called bulging. This bulging promotes solidification cracking by forming a closed area filled with melt and the accumulation of impurities in the final solidification phase, resulting in low-melting phases which are under tensile stress at the end of solidification. T2 - Lasers in Manufacturing Conference 2021 CY - Online meeting DA - 21.06.2021 KW - Laser beam welding KW - Weld pool shape KW - Solidification craking KW - Partial penetration PY - 2021 SP - 1 EP - 5 AN - OPUS4-53587 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jokisch, T. A1 - Gook, S. A1 - Marko, A. A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laserstrahlschweißen additiv gefertigter Bauteile: Einsetzbarkeit bestehender Bewertungsvorschriften N2 - Bei der additiven Fertigung im Pulverbett ist die Bauteilgröße durch den Bauraum begrenzt. Das Verbindungsschweißen additiv gefertigter Teile bietet eine Möglichkeit diese Größenbegrenzung aufzuheben. Aufgrund des spezifischen Spannungs- und Gefügezustands im additiv aufgebauten Teil ist jedoch unklar, inwiefern bestehende Bewertungsvorschriften des Verbindungsschweißens auch für Schweißnähte an additiv gefertigten Bauteilen geeignet sind. Dies wird anhand des Laserstrahlschweißens additiv gefertigter Rohrverbindungen untersucht. Die Schweißnähte werden mittels visueller Prüfung, metallografischer Untersuchungen sowie Computertomografie ausgewertet. Die festgestellten Fehlerarten sind vergleichbar zu konventionellen Bauteilen. Dies ist ein Indikator dafür, dass bestehende Bewertungsvorschriften die möglichen auftretenden Defekte auch für Schweißnähte an additiven Bauteilen abbilden. KW - Schweißunregelmäßigkeiten KW - Additive Fertigung KW - Laserstrahlschweißen KW - Schweißeignung PY - 2021 VL - 73 IS - 3 SP - 132 EP - 137 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-53575 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Thermal Cycles and Charpy Impact Toughness of Single-Pass Hybrid Laser-Arc Welded Thick-Walled Structures N2 - The study deals with the influence of the heat input on the thermal cycles and Charpy impact toughness for hybrid laser-arc welding of 25 mm thick structural steel S355J2 using a 20-kW high-power laser in combination with an electromagnetic weld pool support. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured using a pyrometer in combination with an optical fibre in three different locations near to fusion lines corresponding to different heights of the seam. Also, Charpy impact specimens were taken from different parts of the weld joint corresponding to the different heights. The influence of the heat input was investigated for 1.8 kJ mm-1 and 3.2 kJ mm-1. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required values could be reached in dependance on applied heat input. T2 - Lasers in Manufacturing Conference 2021 CY - Online meeting DA - 21.06.2021 KW - Hybrid laser-arc welding KW - Thick-walled structures KW - Charpy impact toughness KW - Thermal cycles PY - 2021 AN - OPUS4-53576 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser-arc welding of laser and plasma-cut 20 mm thick structural steels N2 - It is already known that the laser beam welding (LBW) or hybrid laser-arc welding (HLAW) processes are sensitive to manufacturing tolerances such as gaps and misalignment of the edges, especially at welding of thick-walled steels due to its narrow beam diameter. Therefore, the joining parts preferably have to be milled. The study deals with the influence of the edge quality, the gap and the misalignment of edges on the weld seam quality of hybrid laser-arc welded 20 mm thick structural steel plates which were prepared by laser and plasma-cutting. Single-pass welds were conducted in butt-joint configuration. An AC magnet was used as a contactless backing. It was positioned under the workpiece during the welding process to prevent sagging. The profile of the edges and the gap between the workpieces were measured before welding by a profile scanner or a digital camera, respectively. With a laser beam power of just 13.7 kW, the single-pass welds could be performed. A gap bridgeability up to 1 mm at laser-cut and 2 mm at plasma-cut samples could be reached respectively. Furthermore, a misalignment of the edges up to 2 mm could be welded in a single-pass. The new findings may eliminate the need for cost and time-consuming preparation of the edges. T2 - 74th IIW Annual Assembly and International Conference 2021 CY - Online meeting DA - 07.07.2021 KW - Hybrid laser-arc welding KW - Thick-walled steel KW - Edge quality KW - Gap bridgeability KW - Misalignment of the edges KW - Plasma-cutting KW - Laser-cutting PY - 2021 AN - OPUS4-53577 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Elektromagnetische Schmelzbadbeeinflussung beim Laserhybridschweißen von Dickblechen N2 - -Elektromagnetische Schmelzbadstütze wurde beim Laserhybridschweißen von Dickblechen erfolgreich zur Unterdrückung der Tropfenbildung eingesetzt -Auch bei „schlechteren“ Kantenqualitäten konnten einlagige Schweißnähte mit hoher Qualität erzielt werden -Spaltüberbrückbarkeit bis zu 2 mm (bei plasmageschnittenen Proben) konnte gewährleistet werden -Homogenere Verteilung des Zusatzwerkstoffes wurde erzielt T2 - 42. Assistentenseminar der Wissenschaftlichen Gesellschaft Fügetechnik e.V. CY - Blankenau (Beverungen), Germany DA - 06.10.2021 KW - Laserhybridschweißen KW - Elektromagnetische Schmelzbadbeeinflussung KW - Dickblech PY - 2021 AN - OPUS4-53578 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Churiaque, C. A1 - Sanchez-Amaya, J.M. A1 - Üstündag, Ömer A1 - Porrua-Lara, M. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Improvements of hybrid laser arc welding for shipbuilding T-joints with 2F position of 8 mm thick steel N2 - the joints throughout the structure. The flat units are constituted by butt welded flat plates, on which longitudinal T-welded reinforcements are placed to rigidize the structure. Among the different welding technologies, Hybrid Laser Arc Welding (HLAW) is becoming a mature process, profitable and highly productive. In addition, more innovative welding equipment are being developed nowadays, offering greater work flexibility, and raising expectations of achieving better quality, and economic viability. Another key point of HLAW to keep in mind is that structural distortions are reduced, resulting in decreasing the cost and time of straightening work. In the present contribution, the influence of HLAW parameters on the quality of fillet joints of naval steel has been analysed. Experimental HLAW tests were performed with a high power disk laser to join EH36 naval steel plates, with a T configuration. The influence of different processing parameters has been analysed, as the laser power, welding speed, wire feed rate and the configuration of the HLAW processes (including head angle and laser/arc leading process). In addition, FEM simulations were carried out in order to estimate residual stresses and distortion of welded part. The distortion values provided by FEM presented excellent agreement with the measured experimental results. To evaluate the welds, non destructive tests including X-ray tests, metallographic analysis of cross sections, and microhardness mapping tests were performed. Full penetration 8 mm T welds were obtained for the first time at an industrially applicable 2F position with a reasonable HLAW head angle, in one single step without sealing root, and using zero gap square groove Edge preparation. The present contribution presents welding rates up to 2.2 m/min for 2F T-joints of this steel thickness, a much higher processing velocity than previously reported for industrial applications. KW - Hybrid laser arc welding PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-528410 VL - 143 SP - 1 EP - 20 PB - Elsevier Ltd. AN - OPUS4-52841 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid Laser-Arc Welding of Thick-Walled, Closed, Circumferential Pipe Welds N2 - The application of hybrid laser-arc welding (HLAW) for joining closed circumferential welds is a challenge due to the high risk of forming a defective overlap area with a shrinkage void or solidification cracks in the material thickness. A series of HLAW experiments were performed to understand the development of a faulty overlap area when closing the circumferential weld. Welding trials on flat specimens and pipe segments were supported by numerical analyses in which the thermomechanical behavior of the welds in the overlap area was investigated. Different process control strategies were tested, including variations in defocusing levels and the overlap length. The newly developed HLAW head, including laser optics with a motor-driven collimation system, made it possible to defocus the laser beam during welding without disturbing the stability of the welding process. High-level defocusing of the laser beam of more than 40 mm relative to the specimen surface with a resulting beam diameter of > 2.9 mm, and in combination with a short overlap length of 15 mm, was promising with respect to the formation of a desired cup-shaped weld profile that is resistant to solidification cracks. KW - Hybrid Laser-Arc Welding KW - Thick-Walled Steel KW - High-Power Welding KW - Crater KW - Pipe Welding PY - 2022 U6 - https://doi.org/10.29391/2022.101.002 SN - 0043-2296 VL - 101 IS - 1 SP - 15 EP - 26 PB - American Welding Society CY - New York, NY AN - OPUS4-55508 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser-arc welding of thick-walled pipe segments with optimization of the end crater N2 - The study deals with the application of the high-power hybrid-laser arc welding process on up to 15 mm thick pipe segments with the intention to avoid end crater imperfections during closing of the circumferential welds, where the pipes were turned during welding in 1G- and 2Gpositions. Different techniques such as laser power ramp-down, abrupt switch-off of the laser power and change of the magnification of the laser spot diameter and defocusing of the laser beam relative to the workpiece were tested to remove the laser energy from the process. It could be shown that a high defocusing of the optic system above 40 mm with a resulting beam diameter > 2.9 mm in a short overlap length of approx. 20 mm leads to the formation of a cup-shaped weld seam, which is preferred for avoidance of cracks and pores in the end crater. A laser optics with motor-driven lens system was used for the welding experiments to defocuse the laser beam without changing the position of the arc. KW - Hybrid laser-arc welding KW - Circumferential weld KW - Thick-walled steel KW - Single-pass welding KW - End crater PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-513260 VL - 94 SP - 676 EP - 679 PB - Elsevier B.V. AN - OPUS4-51326 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Straße, Anne A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Schmidt, M. ED - Vollertsen, F. ED - Govekar, E. T1 - LMD coatings as filler material for laser beam welded 30 mm thick plates N2 - The development of high energy laser sources enables single-pass welds of thick plates up to 30 mm, but often additional materials are needed to influence the properties of the weld seams. However, the homogenous distribution of filler materials in form of e.g. electrodes is only possible up to 7 mm while the elements are only traceable up to a depth of 14 mm. To overcome this problem a two-step process is used where first the edges of the weld partners are coated with the filler material by laser metal deposition (LMD) and afterwards are welded by laser beam. Single-pass welds with electromagnetic weld pool support of 30 mm thick S355 J2+N-plates with austenitic AISI 316L-coatings were investigated as well as the influence of the coatings to the penetration depth of the laser beam without electromagnetic weld pool support in double-sided joints. The weld seams were tested by X-ray inspection and cross sections. T2 - 11th CIRP Conference on Photonic Technologies [LANE 2020] CY - Online meeting DA - 07.09.2020 KW - Penetration depth KW - Laser metal deposition (LMD) KW - Laser beam welding KW - Filler material distribution PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-512790 SN - 2212-8271 VL - 94 SP - 293 EP - 297 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-51279 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gook, S. A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Verfahren zum fehlerfreien Laserstrahl-Hybridschweißen von gechlossenen Rundnähten N2 - In diesem Beitrag werden Ergebnisse der Untersuchungen eines Verfahrens zum fehlerfreien Laserstrahl Hybridschweißen von geschlossenen Rundnähten vorgestellt. Das Verfahren zielt auf die Vermeidung von Schweißimperfektionen im Überlappbereich einer laserstrahlhybridgeschweißten Rundnaht. Eine Strategie der Prozessführung beim Schließen der Rundnaht wurde entwickelt, mit der ein fehlerfreier Überlappbereich durch die Kontrolle der Erstarrungsbedingungen am Schweißnahtende erreicht wird. Die kontrollierte Wärmeführung wird durch eine Anpassung der Parameter von beiden beteiligten Schweißprozessen, dem Laserstrahl- sowie MSG­ Schweißprozess realisiert. Experimentelle Untersuchungen wurden an 12 mm bis 15 mm dicken Rohrabschnitten durchgeführt. Der Einfluss von Prozessparametern wie der Laserleistungsrampe und Rampenzeit, der Veränderung des Abbildungsmaßstabes und der Defokussierung des Laserstrahls auf die Erstarrungsbedingungen am Ende der Rundnaht wurde untersucht, um eine optimale Strategie zum Herausführen der Prozessenergie zu finden. Im Rahmen der experimentellen Untersuchungen konnte gezeigt werden, dass eine Defokussierung des Laserstrahls im Bereich zwischen 60 mm und 100 mm über einen kurzen Auslaufbereich der Naht von ca. 15 mm zu einer deutlich besseren Nahtausbildung im Überlappbereich führte. Es konnte eine günstige kelchförmige Schweißnahtform ohne eine Tendenz zur Rissbildung erzielt werden. Die Laseroptik mit motorisch angesteuertem Linsensystem ermöglichte dabei eine Vergrößerung des Laserstrahldurchmessers ohne eine Veränderung der Position des MSG-Lichtbogens relativ zur Bauteiloberfläche. T2 - DVS Congress 2020 CY - Online meeting DA - 14.09.2020 KW - Defokussierung KW - Endkrater KW - Laser-Hybridschweißen KW - Rundnaht KW - Überlappbereich PY - 2020 SN - 978-3-96144-098-6 VL - 365 SP - 855 EP - 860 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-51324 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Experimental and numerical study on the influence of the laser hybrid parameters in partial penetration welding on the solidification cracking in the weld root N2 - In this study, the influence of the welding speed, the arc power, and the laser focal position on the solidification crack formation for partial penetration laser hybrid–welded thick-walled plates was investigated. The solidification cracking in the weld root is a result of interaction between metallurgical and geometrical and thermomechanical factors. Experimentally, a direct correlation between the welding speed and the crack number was observed. That is by reducing the welding velocity, the crack number was decreased. The focal position shows also a significant influence on the crack number. By focusing the laser on the specimen surface, the crack number has been significantly diminished. The wire feed speed showed a very slight influence on the crack formation. That is due to the large distance between the critical region for cracking and the arc region. The numerical model shows a high stress concentration in the weld root for both components (vertical and transversal). Numerically, the reduced welding speed showed a strong impact on stress, as the model demonstrated a lower stress amount by decreasing the welding speed. The metallurgical factors, such as the assumed accumulation of the low-melting eutectics in the weld root, should be a contribution for solidification cracking, where the tensile stress is acting. KW - Laser hybrid welding KW - Solidification cracking KW - Partial penetration welding KW - Weld root KW - Numerical simulation PY - 2020 U6 - https://doi.org/10.1007/s40194-020-00847-w VL - 64 SP - 501 EP - 511 PB - Springer AN - OPUS4-50625 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gook, Sergej A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Vermeidung von Schweißimperfektionen im Überlappbereich bei laserstrahlhybridgeschweißten Rundnähten N2 - Die Laserstrahl-Hybrid-Schweißtechnologie erweist sich in der schweißtechnischen Fertigung immer mehr als innovative Alternative gegenüber anderen Schweißverfahren. Obwohl das Laserstrahl-Hybridschweißverfahren viele wirtschaftliche Vorteile gegenüber herkömmlichen Schweißverfahren aufweist, wie z.B. große Einschweißtiefe und dadurch eine reduzierte Anzahl von Schweißlagen, geringe thermische Belastung des Grundwerkstoffes aufgrund reduziertem Wärmeeintrag, konnte das Schweißverfahren überwiegend für das Schweißen von Längsnähten demonstriert werden. Eine Vielzahl von Schweißaufgaben, z.B. beim Schweißen von Segmenten von Windkraftanlagen oder dem Orbitalschweißen beim Verlegen von Großrohrleitungen sieht vor, dass die zu schweißenden Bauteile mit einer Rundnaht zusammengefügt werden. Die schweißtechnische Herausforderung ist hier, dass beim Schließen einer Rundnaht mit der Entstehung eines fehlerbehafteten Überlappbereiches zu rechnen ist. Ein zentrales Problem im Überlappbereich einer laserstrahl- sowie laserhybridgeschweißten Rundnaht ist die Bildung von Imperfektionen wie Poren, Rissen sowie die Bildung eines Endkraters, welcher als geometrische Kerbe wirkt. Bisher liegen keine universellen Lösungen zur fehlerfreien Ausführung von geschlossenen Rundnähten beim Laserstrahl-Hybridschweißen vor. Diese Studie befasst sich mit der Entwicklung eines Verfahrens, mit dem die Entstehung von o.g. Schweißimperfektionen vermieden wird. Die Strategie der Prozessführung beim Schließen der Rundnaht sieht hervor, dass ein fehlerfreier Überlappbereich durch die Kontrolle der Erstarrungsbedingungen am Schweißnahtende erreicht werden kann. Die kontrollierte Wärmeführung wird durch eine Anpassung der Parameter von beiden beteiligten Schweißprozessen, dem Laserstrahl- sowie MSG-Schweißprozess realisiert. Im Rahmen dieser Arbeit wurde eine Serie von Schweißversuchen an 9,5 mm dicken Rohabschnitten aus hochfestem Pipelinestahl X100Q mit Variation der Prozessparameter wie der Laserleistung, der Defokussierung des Laserstrahls sowie der Endkraterfüllzeit im Überlappbereich der Rundnaht durchgeführt. Nachfolgend werden die erzielten Ergebnisse dargestellt und diskutiert. T2 - DVS-Studentenkongress 2019 CY - Dusseldorf, Germany DA - 16.09.2019 KW - Laserstrahlschweißen KW - Laserhybridschweißen KW - Rundnaht KW - Endkrater KW - Überlappbereich KW - Defokussierung PY - 2019 SP - 370 EP - 378 AN - OPUS4-49242 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Neueste Entwicklungen im Bereich des Hochleistungslaserstrahl- und Hybridschweißens von hohen Blechdicken N2 - Bislang kommt das Laserstrahlschweißen bzw. Laserhybridschweißen hauptsächlich bei Dickblechen mit einer Wandstärke von bis zu 15 mm zum Einsatz. Für Anwendungen über 20 mm war dieses Verfahren aufgrund einiger Herausforderungen bisher nur bedingt realisierbar. Eine von der Bundesanstalt für Materialforschung und -prüfung (BAM) entwickelte elektromagnetische Schmelzbadunterstützung ermöglicht nun ein einlagiges Schweißen von bis zu 30 mm Wandstärke. KW - Laserstrahlschweißen KW - Laserhybridschweißen KW - Modellierung KW - Elektromagnetische Schmelzbadunterstützung KW - Kaltzähe Stähle PY - 2020 VL - 2 SP - 26 EP - 30 PB - DVV Media Group GmbH CY - Hamburg AN - OPUS4-51632 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser-arc welding of thick-walled pipe segments with optimization of the end crater N2 - The study deals with the application of the high-power hybrid-laser arc welding process on up to 15 mm thick pipe segments with the intention to avoid end crater imperfections during closing of the circumferential welds, where the pipes were turned during welding in 1G- and 2G-positions. Different techniques such as laser power ramp-down, abrupt switch-off of the laser power and change of the magnification of the laser spot diameter and defocusing of the laser beam relative to the workpiece were tested to remove the laser energy from the process. It could be shown that a high defocusing of the optic system above 40 mm with a resulting beam diameter > 2.9 mm in a short overlap length of approx. 20 mm leads to the formation of a cup-shaped weld seam, which is preferred for avoidance of cracks and pores in the end crater. A laser optics with motor-driven lens system was used for the welding experiments to defocuse the laser beam without changing the position of the arc. T2 - 11th CIRP Conference on Photonic Technologies LANE 2020 CY - Online Meeting DA - 07.09.2020 KW - End crater KW - Hybrid laser-arc welding KW - Circumferential weld PY - 2020 AN - OPUS4-51634 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Gook, S. A1 - Rethmeier, Michael T1 - Investigation of the mechanical properties of single-pass hybrid laser-arc welded thick X120 pipeline steel plates N2 - High heat input leads to grain coarsening and softening in WM and HAZ; the tensile strength is reduced. Low heat input leads to inadmissible hardening in the WM; the impact strength is reduced. The proposed t8/5-time of 3 s to 15 s could be achieved through the reduced welding velocity. The concept of electromagnetic weld pool support system allowed single-pass welds in flat position without gravity drop-outs even for reduced welding speeds; in this way the heat input can be controlled. The adaptation of the electromagnetic weld pool support system to laser and laser hybrid welding process can dramatically increase the potential field of application of these technologies for real industrial implementation. T2 - 14th Pipeline Technology Conference 2019 CY - Berlin, Germany DA - 18.03.2019 KW - Toughness KW - Hybrid laser-arc welding KW - Pipeline steel X120 KW - Electromagnetic weld pool support KW - Mechanical properties PY - 2019 AN - OPUS4-49894 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Avoidance of end crater imperfections at high-power laser beam welding of closed circumferential welds N2 - The present work deals with the development of a strategy for the prevention of end crater defects in high-power laser welding of thick-walled circumferential welds. A series of experiments were performed to understand the influence of the welding Parameters on the formation of end crater defects such as pores, cracks, root excess weld metal and shrinkage cavities in the overlap area. An abrupt switch-off of the laser power while closing the circumferential weld leads to a formation of a hole which passes through the whole welded material thickness. A laser power ramp-down causes solidification cracks which are initiated on the transition from full-penetration mode to partial penetration. Defocusing the laser beam led to promising results in terms of avoiding end crater defects. Cracks and pores in the overlap area could be effectively avoided by using defocusing techniques. A strategy for avoiding of end crater imperfections was tested on flat specimens of steel grade S355J2 with a wall thickness of between 8 mm and 10 mm and then transferred on the 10 mm thick pipe sections made of high-strength pipeline steel API5L-X100Q. KW - Laser beam welding KW - Circumferential weld KW - End crater PY - 2019 U6 - https://doi.org/10.1007/s40194-019-00841-x SP - 1 PB - Springer AN - OPUS4-50270 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of oscillating magnetic field on the keyhole stability in deep penetration laser beam welding N2 - The stability of the keyhole decreases for deep penetrated high-power laser beam welding. The keyhole tends to collapse with increasing laser power and e.g. keyhole induced porosity can occur. This study deals with the observation of the keyhole during high-power laser beam welding in partial penetration mode by means of a high-speed camera. A butt configuration of 25 mm thick structural steel and transparent quartz glass was used for the experiments. An oscillating magnetic field was applied perpendicular to the welding direction on the root side of the steel plate. The keyhole was highlighted with a coaxial diode laser. It was ascertained that the stability of the keyhole and the weld penetration depth were increased by applying an oscillating magnetic field with an oscillating frequency of 1.2 kHz and a magnetic flux density of 50 mT. KW - Magnetic field KW - Laser beam welding KW - Keyhole stability PY - 2021 U6 - https://doi.org/10.1016/j.optlastec.2020.106715 SN - 0030-3992 VL - 135 SP - 106715 PB - Elsevier Ltd. AN - OPUS4-52007 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Verfahren zum fehlerfreien Laserstrahl-MSG-Hybridschweißen geschlossener Rundnähte N2 - In diesem Beitrag werden Ergebnisse der Untersuchungen eines Verfahrens zum fehlerfreien Laserstrahl-MSG-Hybridschweißen von geschlossenen Rundnähten vorgestellt. Das Verfahren zielt auf die Vermeidung von Schweißnahtunregelmäßigkeiten im Überlappbereich einer hybridgeschweißten Rundnaht. Eine Strategie der Prozessführung beim Schließen der Rundnaht wurde entwickelt, mit der ein fehlerfreier Überlappbereich durch die Kontrolle der Erstarrungsbedingungen am Schweißnahtende erreicht wird. Die kontrollierte Wärmeführung wird durch eine Anpassung der Parameter von beiden beteiligten Schweißprozessen, dem Laserstrahl sowie dem Metallschutzgas (MSG)-Schweißprozess, realisiert. Experimentelle Untersuchungen wurden an 12 bis 15 mm dicken Rohrabschnitten durchgeführt. Der Einfluss von Prozessparametern wie der Veränderung des Abbildungsmaßstabs und der Defokussierung des Laserstrahls auf die Erstarrungsbedingungen am Ende der Rundnaht wurde untersucht, um eine optimale Strategie zum Herausführen der Prozessenergie zu finden. Im Rahmen der experimentellen Untersuchungen konnte gezeigt werden, dass eine Defokussierung des Laserstrahls im Bereich zwischen 60 mm und 100 mm über einen kurzen Auslaufbereich der Naht von etwa 15 mm zu einer deutlich besseren Nahtausbildung im Überlappbereich führt. Es konnte eine günstige kelchförmige Schweißnaht ohne eine Tendenz zur Rissbildung erzielt werden. Die Laseroptik mit motorisch angesteuertem Linsensystem ermöglichte dabei eine Vergrößerung des Laserstrahldurchmessers ohne eine Veränderung der Position des MSG-Lichtbogens relativ zur Bauteiloberfläche. KW - Hybrid welding KW - Laser beam welding KW - Pipe manufacturing KW - As-shielded arc welding KW - Weld defects PY - 2021 VL - 73 IS - 3 SP - 116 EP - 121 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-52365 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Meng, Xiangmeng A1 - Artinov, Antoni A1 - Bachmann, Marcel A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - A numerical study on the suppression of a detrimental weld pool profile in wire feed laser beam welding by magnetohydrodynamic technique N2 - The weld quality and the possible defect formation are directly determined by the weld pool shape and the thermo-fluid dynamics therein. In this paper, an untypical weld pool profile, i.e., elongated at its top and bottom but narrowed at the middle, is found experimentally and numerically in the wire feed laser beam welding. The detrimental influence of the weld pool narrowing on the element transport is analyzed and discussed. A magnetohydrodynamic technique is utilized to suppress the narrowing, aiming at a more homogenous element distribution. It is found that a low-temperature region is formed in the middle of the weld pool due to the interaction of the two dominant circulations from the top and bottom regions. The weld pool is significantly narrowed due to the untypical growth of the mushy zone in the low-temperature region, which results in a direct blocking effect on the downward flow and the premature solidification in the middle region. The Lorentz force produced by a transverse oscillating magnetic field shows the potential to change the flow pattern into a single-circulation type and the low-temperature-gradient region is mitigated. Therefore, the downward transfer channel is widened, and its premature solidification is prevented. The numerical results are well validated by experimental measurements of metal/glass observation and X-ray fluorescence element mapping. T2 - 13th International Seminar Numerical Analysis of Weldability CY - Seggau, Austria DA - 04.09.2022 KW - Thermo-fluid flow KW - Element transport KW - Laser beam welding KW - Magnetohydrodynamics KW - Multi - physical modeling PY - 2023 SN - 2410-0544 VL - 13 SP - 143 EP - 160 PB - Verlag der Technischen Universität Graz AN - OPUS4-58806 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Churiaque, C. A1 - Sanchez-Amaya, J.M. T1 - High-power hybrid laser arc welding of thick materials with electromagnetic weld pool support N2 - In addition to the many advantages of deep penetration, increased welding speed and a low sensitivity to manufacturing tolerances such as gap and edge offset, the hybrid laser arc welding (HLAW) process is used increasingly in industrial applications such as shipbuilding or pipeline manufacturing. Nonetheless, thick-walled sheets with a wall thickness of 20 mm or more are still multi-pass welded using the arc welding process, due to increased process instability by increasing laser power. Welding at reduced speed, especially in a flat position, leads to an irregular formation of the root part such as dropping. The hydrostatic pressure exceeds the surface tension, which decreases with increasing seam width. In order to prevent gravity drop-outs, the use of a melt pool support is necessary. Usual weld pool supports such as ceramic or powder supports require time-consuming mechanical detachment. The electromagnetic weld pool support system, which is described in this study, operates without contact and based on generating Lorentz forces in the weld pool. An externally applied oscillating magnetic field induces eddy currents and generates an upward directed Lorentz force, which counteracts the hydrostatic pressure. This allows single-pass welds up to 30 mm by hybrid laser arc welding process with a 20-kW fibre laser. Moreover, it is favoured by the diminished welding speed the cooling rate which leads to an improvement of the mechanical-technological properties of the seams – the lower formation of martensite in the microstructure enables better Charpy impact toughness. The electromagnetic weld pool support extends the limitation of the laser hybrid welding process in the thick sheet area. By adapting the electromagnetic weld pool support to the laser and laser hybrid welding process, the application potential of these technologies for industrial implementation can be drastically increased. T2 - 23rd Technical Conference on Welding and Joining Technologies CY - Irun, Spain DA - 07.03.2023 KW - Laser hybrid welding KW - Thick-walled steel KW - Electromagnetic backing KW - High-power laser PY - 2023 AN - OPUS4-58613 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Analysis of microstructure and mechanical properties of single-pass laser hybrid welded thick-walled steels up to 30 mm with contactless electromagnetic backing N2 - The study deals with the influence of the heat input on the thermal cycles, the microstructure and the mechanical properties for laser-hybrid welded steels of S355J2 with thicknesses up to 30 mm using a 20-kW high-power laser with contactless electromagnetic backing. The focus is on the change of the mechanical properties over the seam thickness. Therefore, the impact toughness and tensile strength were tested in different depths. Based on the experiments, a heat input of 1.3 kJ/mm - 1.6 kJ/mm, 2 kJ/mm - 2.4 kJ/mm and 3.7 kJ/mm were recommended when single-pass welding of 20 mm, 25 mm and 30 mm with a 20-kW laser in regard to the minimum requirements of the mechanical properties, respectively. Lower heat inputs led to undesired microstructure consisting of martensite, hardening and deteriorated impact toughness, where higher heat inputs led to grain-coarsening and even loss of impact strength due to the formation of retained-austenite on the grain boundaries. T2 - EMPOrIA 2023 - International Joint Conference CY - Aachen, Germany DA - 16.05.2023 KW - Laser hybrid welding KW - Electromagnetic backing KW - Thermal cycles KW - Charpy impact toughness KW - Thick-plate welding PY - 2023 AN - OPUS4-58614 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Kampffmeyer, D. A1 - Wolters, M. A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of shielding gas on filler wire mixing at laser hybrid welding of thick high strength steels N2 - The laser hybrid welding process offers many advantages during welding oft hick-walled steels, such as the increased penetration depth and, thus, reduced number of layers, reduced heat input and decreased distortion compared to arc-based welding processes. Especially, when welding high-strength steels (HSS), the reduced heat input plays an essential role. However, a major challenge when laser hybrid welding of thick-walled steels is the limited filler wire mixing over the entire seam thickness, which can lead to changed mechanical properties over the depth. To overcome this issue, the add of oxygen into the shielding gas and its influence on the filler wire mixing and finally to the mechanical properties were investigated within this work. Therefore, 20 mm thick S690QL steels were laser hybrid welded in a single-pass. A contactless electromagnetic backing was used to avoid sagging. The admixture of oxygen was performed by a gas mixer, where the oxygen content was varied between 0 % and 7.2 %. The experiments were also accompanied by laser beam welding tests in steel/glass configuration, where the melt pool geometry as well as the melt flow characteristics were captured by a high-speed camera. It can be concluded, that adding of 2 % to 4 % oxygen into the shielding gas had a positive effect on the filler wire mixing, were up to a depth of 18 mm elements of the filler wire could be observed. T2 - 19th Nordic Laser Material Processing Conference CY - Turku, Finland DA - 22.08.2023 KW - Laser hybrid welding KW - Electromagnetic backing KW - Shielding gas KW - Charpy impact toughness KW - Thick-plate welding KW - Filler wire mixing PY - 2023 AN - OPUS4-58615 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Brunner-Schwer, C. A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Process advantages of laser hybrid welding compared to conventional arc-based welding processes for joining thick steel structures of wind tower N2 - 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 beam or 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, an electromagnetic backing was used within the framework of this work, which works contactless and is based on an externally applied AC magnetic field. 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. A further significant advantage of the EM backing was the possibility to expand the process parameter window to maintain desired cooling times and mechanical properties, without suffering adverse effects concerning the root quality of the weld. T2 - 19th Nordic Laser Material Processing Conference CY - Turku, Finland DA - 22.08.2023 KW - Laser hybrid welding KW - Wind energy PY - 2023 AN - OPUS4-58616 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rethmeier, Michael A1 - Artinov, Antoni A1 - Meng, Xiangmeng A1 - Bakir, Nasim A1 - Üstündag, Ömer A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey T1 - The bulging effect and its relevance in high power laser beam welding N2 - The present work deals with the recently confirmed widening of the weld pool interface, known as a bulging effect, and its relevance in high power laser beam welding. A combined experimental and numerical approach is utilized to study the influence of the bulge on the hot cracking formation and the transport of alloying elements in the molten pool. A technique using a quartz glass, a direct-diode laser illumination, a high-speed camera, and two thermal imaging cameras is applied to visualize the weld pool geometry in the longitudinal section. The study examines the relevance of the bulging effect on both, partial and complete penetration, as well as for different sheet thicknesses ranging from 8 mm to 25 mm. The numerical analysis shows that the formation of a bulge region is highly dependent on the penetration depth and occurs above 10 mm penetration depth. The location of the bulge correlates strongly with the cracking location. The obtained experimental and numerical results reveal that the bulging effect increases the hot cracking susceptibility and limits the transfer of alloying elements from the top of the weld pool to the weld root. T2 - 1st Annual Assembly and Conference of The Welding Federation of Africa (TWF-Africa) CY - Cairo, Egypt DA - 14.03.2023 KW - Laser beam welding KW - Melt pool dinamics PY - 2023 AN - OPUS4-58695 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of heat input on cooling rates and mechanical properties of laser hybrid welded thick structural steels N2 - The laser hybrid welding process offers many advantages such as the high penetration depth and high welding speed, and it is characterized by its low heat input compared to the arc-based welding processes, which makes the laser hybrid welding process as a suitable alternative process when welding thick-walled steels. However, there are some challenges when using laser hybrid welding process for thick steels. Due to the uneven cooling conditions and the inhomogeneous filler wire mixing, a typical laser hybrid weld can be divided into two different zones over the depth: the arc-dominated zone on the upper part and the laser-dominated zone in the root part. This leads to different mechanical properties in a laser hybrid welded joint. Due to the high cooling rates and the lack of filler wire in the laser-dominated zone, this area is more critical regarding the mechanical properties, especially the Charpy impact toughness. A low heat input can lead to undesired microstructure consisting of martensite, hardening and deteriorated impact toughness due to the high cooling rate, where higher heat inputs can lead to grain-coarsening and even loss of impact strength. This study deals with the influence of the welding speed and resulting heat input on the cooling rates, the microstructure and the mechanical properties of single-pass laser hybrid welded steels of S355J2 with thickness up to 30 mm. The experiments were performed with a 20-kW fibre laser system and a contactless electromagnetic weld backing on up to 30 mm thick steels in butt-joint configuration in 1G welding position. The cooling time was measured in three different locations near to fusion lines corresponding to different heights of the seam using a special configuration with pyrometers, collimators, and optical fibres. The test specimens for the Charpy impact testing and tensile testing were extracted in up to three different depths. Based on the experiments, a heat input of 1.3 kJ/mm - 1.6 kJ/mm, 2 kJ/mm - 2.4 kJ/mm and 3.7 kJ/mm were recommended when single-pass laser hybrid welding of 20 mm, 25 mm and 30 mm thick structural steels in regard to the minimum requirements of the mechanical properties, respectively. The optical measurement of the cooling times in different depths could be carried out reproducibly. T2 - Advances in Welding and Metal Additive Manufacturing Technologies 2023 CY - Istanbul, Türkiye DA - 30.10.2023 KW - Laser hybrid welding KW - Electromagnetic backing KW - Charpy impact toughness KW - Thick-plate welding KW - Thermal cycles PY - 2023 AN - OPUS4-58942 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -