TY - JOUR A1 - Bachmann, Marcel A1 - Kunze, R. A1 - Avilov, Vjaceslav A1 - Rethmeier, Michael T1 - Finite element modeling of an alternating current electromagnetic weld pool support in full penetration laser beam welding of thick duplex stainless steel plates N2 - An electromagnetic weld pool support system for 20 mm thick duplex stainless steel AISI 2205 was investigated numerically and compared to experiments. In our former publications, it was shown how an alternating current (AC) magnetic field below the process zone directed perpendicular to the welding direction can induce vertically directed Lorentz forces. These can counteract the gravitational forces and allow for a suppression of material drop-out for austenitic stainless steels and aluminum alloys. In this investigation, we additionally adopted a steady-state complex magnetic permeability model for the consideration of the magnetic hysteresis behavior due to the ferritic characteristics of the material. The model was calibrated against the Jiles–Atherton model. The material model was also successfully tested against an experimental configuration before welding with a 30 mm diameter cylinder of austenitic stainless steel sur-rounded by duplex stainless steel. Thereby, the effects of the Curie temperature on the magnetic characteristics in the vicinity of the later welding zone were simulated. The welding process was modeled with a three-dimensional turbulent steady-state model including heat transfer and fluid dy-namics as well as the electromagnetic field equations. Main physical effects, the thermo-capillary (Marangoni) convection at the weld pool boundaries, the natural convection due to gravity as well as latent heat of solid–liquid phase transitions at the phase boundaries were accounted for in the model. The feedback of the electromagnetic forces on the weld pool was described in terms of the electromagnetic-induced pressure. The finite element software COMSOL Multiphysics 4.2 was used in this investigation. It is shown that the gravity drop-out associated with the welding of 20 mm thick duplex stainless steel plates due to the hydrostatic pressure can be prevented by the application of AC magnetic fields between around 70 and 90 mT. The corresponding oscillation frequencies were between 1 and 10 kHz and the electromagnetic AC powers were between 1 and 2.3 kW. In the experiments, values of the electromagnetic AC power between 1.6 and 2.4 kW at os-cillation frequencies between 1.2 and 2.5 kHz were found to be optimal to avoid melt sagging or drop-out of melt in single pass full-penetration laser beam welding of 15 and 20 mm thick AISI 2205. KW - Laser KW - Numerical simulation KW - Laser beam welding KW - Electromagnetic weld pool support KW - Duplex stainless steel PY - 2016 DO - https://doi.org/10.2351/1.4943906 VL - 28 IS - 2 SP - 022404-1 EP - 022404-9 PB - AIP Publishing AN - OPUS4-35676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Bakir, Nasim T1 - Numerical simulation of solidification crack formation during laser beam welding of austenitic stainless steels under external load N2 - Solidification cracking phenomena taking place under Controlled Tensile Weldability (CTW) test conditions have already been investigated both experimentally and numerically via FEA in order to get a better understanding of the mechanisms of hot crack formation during laser beam welding of austenitic steel grades. This paper develops a three dimensional finite element model employing the contact elements technique to simulate the formation and propagation of solidification cracks during laser full penetration welding of fully austenitic stainless steel 1.4376. During the experimental procedure the resulting strain and displacement directed to the laser beam in the Close vicinity of the weld pool was measured at the surface of the workpiece using a Digital Image Correlation (DIC) technique with an external diode laser as an illuminating source. Local strain fields, global loads and crack lengths predicted by the model are in good Agreement with those observed in experiments. T2 - The 3rd IIW South‐East European Welding Congress CY - Timisoara, Romania DA - 03.06.2015 KW - Solidification cracking KW - DIC technique KW - Laser beam welding KW - Contact element KW - FEA PY - 2015 SN - 978-606-554-955-5 SP - 1 EP - 6 CY - Timisoara, Romania AN - OPUS4-36519 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 - JOUR A1 - Yang, Chunliang A1 - Yan, Fan A1 - Meng, Xiangmeng A1 - Putra, Stephen Nugraha A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Phase-field simulation of the dendrite growth in aluminum alloy AA5754 during alternating current electromagnetic stirring laser beam welding N2 - Electromagnetic stirring is known to promote material flow, reduce porosity, uniform elements distribution, and refine grain in laser beam welding (LBW), which enhances the applicability of LBW in various industries. In this study, a phase-field model of dendrite growth in AA5754 Al alloy electromagnetic stirring laser beam welding was established. The model considered the thermal electromagnetic Lorentz force resulting from the interaction between the electric field generated by the Seebeck effect and the magnetic field, as well as the temperature gradient and solidification rate of the solidification interface obtained from the computational fluid dynamics electromagnetic stirring LBW model. The variation rules of dendrite growth with different magnetic parameters and effects are analyzed. Comprehensively, the magnetic field promotes the solidification rate, thus promoting interfacial instability and a large magnetic flux density leads to a faster interface instability. The solidification rate as well as the temperature gradient affect the growth rate, and the accelerated growth caused by the so lidification rate with a high frequency and a large magnetic flux density effectively inhibits the slow growth caused by the temperature gradient. The thermal electromagnetic Lorentz force is the main factor for the branch increment at low frequencies, while both thermal electromagnetic Lorentz force and temperature gradient in crease the number of branches at high frequencies. The calculated average branch numbers considering various factors in the stable stage under different magnetic parameters were consistent with the results of the scanning electron microscope tests. KW - Laser beam welding KW - Electromagnetic KW - Aluminum alloys KW - Phase field method KW - Dendrite growth PY - 2024 DO - https://doi.org/10.1016/j.ijheatmasstransfer.2023.124754 SN - 0017-9310 VL - 218 SP - 1 EP - 16 PB - Elsevier Ltd. AN - OPUS4-58489 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bachmann, Marcel A1 - Meng, Xiangmeng A1 - Artinov, Antoni A1 - Rethmeier, Michael T1 - Evaluation of narrowed weld pool shapes and their effect on resulting potential defects during deep penetration laser beam welding N2 - This study presents mechanisms of the evolution of a narrowed region in the weld pool center during deep penetration laser beam welding. In numerous numerical studies presented in this study, it was also found that the local reduction of the weld pool size can cause detrimental effects on the melt flow behavior and the resulting properties of the welds. A particularly large influence of this effect was identified in three aspects. Firstly, the local variation of the solidification sequence of the weld pool causes an increase in the hot-cracking susceptibility due to a locally delayed solidification. Secondly, it was proven that a change in the local length and width of the weld pool is associated with an adverse impact on the potential flow routes of the molten material that induces stronger local variations of its solidification. Thus, the element mixing, e.g. during the welding with filler materials, is blocked. This leads to a non-homogeneous chemical composition of the final weld and can cause undesired effects on the final material properties. Finally, another observed effect is related to the reduced ability of process pores to reach the top surface. As this type of porosity is usually produced around the keyhole tip, the change of the fluid flow regime above this area plays a significant role in determining the final path of the pores until the premature solidification in the middle of the weld pool captures them. This study summarizes mainly numerical results which were supported by selected experimental validation results. T2 - International Congress of Applications of Lasers & Electro-Optics 2022 CY - Orlando, FL, USA DA - 17.10.2022 KW - Weld pool shape KW - Laser beam welding KW - Solidification KW - Porosity KW - Numerical process simulation PY - 2022 SP - 1 AN - OPUS4-56532 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bachmann, Marcel A1 - Kunze, R. A1 - Avilov, Vjaceslav A1 - Rethmeier, Michael T1 - Finite element modelling of an AC electromagnetic weld pool support in full penetration laser beam welding of thick duplex stainless steel plates N2 - An electromagnetic weld pool support system for 20 mm thick duplex stainless steel AISI 2205 was investigated numerically and compared to experiments. In our former publications, it was shown how an AC magnetic field below the process zone directed perpendicular to the welding direction can induce vertically directed Lorentz forces. These can counteract the gravitational forces and allow for a suppression of material drop-out for austenitic stainless steels and aluminum alloys. In this investigation, we additionally adopted a steady-state complex magnetic permeability model for the consideration of the magnetic hysteresis behavior due to the ferritic characteristics of the material. The model was calibrated against the Jiles-Atherton model. The material model was also successfully tested against an experimental configuration before welding with a 30 mm diameter cylinder of austenitic stainless steel surrounded by duplex stainless steel. Thereby, the effects of the Curie temperature on the magnetic characteristics in the vicinity of the later welding zone were simulated. The welding process was modelled with a 3D turbulent steady-state model including heat transfer and fluid dynamics as well as the electromagnetic field equations. Main physical effects, the thermo-capillary (Marangoni) convection at the weld pool boundaries, the natural convection due to gravity as well as latent heat of solid–liquid phase transitions at the phase boundaries were accounted for in the model. The feedback of the electromagnetic forces on the weld pool was described in terms of the electromagneticinduced pressure. The FE software COMSOL Multiphysics 4.2 was used in this investigation. It is shown that the gravity drop-out associated with the welding of 20 mm thick duplex stainless steel plates due to the hydrostatic pressure can be prevented by the application of AC magnetic fields between around 70 mT and 90 mT. The corresponding oscillation frequencies were between 1 kHz and 10 kHz and the electromagnetic AC powers were between 1 kW and 2.3 kW. In the experiments, values of the electromagnetic AC power between 1.6 kW and 2.4 kW at oscillation frequencies between 1.2 kHz and 2.5 kHz were found to be optimal to avoid melt sagging or drop-out of melt in single pass fullpenetration laser beam welding of 15 mm and 20 mm thick AISI 2205. T2 - ICALEO 2015 - 34th International congress on applications of lasers & electro-optics CY - Atlanta, GA, USA DA - 2015-10-18 KW - Electromagnetic weld pool support KW - Laser beam welding KW - FE simulation KW - Duplex stainless steel PY - 2015 SN - 978-1-940168-05-0 SP - 650 EP - 659 AN - OPUS4-35036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yang, Fan A1 - Meng, Xiangmeng A1 - Putra, Stephen Nugraha A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical studies of process porosity suppression by magnetohydrodynamic technology during the laser beam welding of aluminum alloy N2 - Magnetohydrodynamic (MHD) technology is acknowledged as a promising method for mitigating the porosity defects in laser-welded joints of aluminum alloys. A transient 3D multi-physical numerical model of laser beam welding (LBW), coupled with the MHD and oscillating metal vapor plume model, is developed to study the suppression mechanisms of process porosity by an external magnetic field. The experimental results demonstrate that the porosity ratio is reduced by 93.5 % as the oscillating magnetic field is applied. This significant reduction confirms the effectiveness of the MHD technology in suppressing porosity defects. A downward time-averaged Lorentz force is induced in the weld pool, which affects the fluid flow pattern and the weld pool profile. The change of the flowing pattern in the weld pool by the magnetic field does not always have a positive effect on the porosity suppression. In addition, an analytical model shows that the bubble escape window is expanded by 62 % under the effect of the oscillating magnetic field. The additional upward velocity provided by the electromagnetic expulsive force on the bubbles and the change of weld pool profile are considered favorable factors in eliminating the porosity defects. The numerical and analytical model developed for analyzing the bubble escape window have been validated by experimental results. KW - Laser beam welding KW - Aluminum alloy KW - Process porosity defects KW - Magnetohydrodynamic technology KW - Bubble escape KW - Numerical simulation PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-637642 DO - https://doi.org/10.1016/j.ijheatmasstransfer.2025.127525 SN - 0017-9310 VL - 253 SP - 1 EP - 13 PB - Elsevier Ltd. AN - OPUS4-63764 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Artinov, Antoni A1 - Karkhin, V. A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Mathematical modeling of the geometrical differences between the weld end crater and the steady-state weld pool N2 - The geometrical characteristics of the weld end crater are commonly used as a means of validating numerical results in welding simulations. In this paper, an analytical model is developed for calculating the cooling stage of the welding process after the moving energy source is turned off. Solutions for various combinations of heat sources and heated bodies are found. It is shown that after turning off the Energy source, additional melting of the base material in the longitudinal direction may occur due to the overheated liquid metal. The developed technique is applied to complete-penetration keyhole laser beam welding of 2 mm thick austenitic stainless-steel plate 316L at a Welding speed of 20 mm/s and a laser power of 2.3 kW. The results show a theoretical increase in the weld end crater length of up to 19% compared to the length of the steady-state weld pool. It is found that at the moment of switch off, the weld end crater center, where solidification of the liquid metal ends, is shifted from the heat source axis toward the weld pool tail. The solidification rate and the direction of crystallization of the molten material during the welding process and those in the weld end crater differ significantly. A good agreement between the computational results and the welding experiments is achieved. KW - Weld end crater KW - Steady-state weld pool KW - Mathematical modeling KW - Solidification KW - Laser beam welding PY - 2020 DO - https://doi.org/10.2351/7.0000068 VL - 32 IS - 2 SP - 022024-1 EP - 022024-6 PB - AIP Publishing AN - OPUS4-50767 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritzsche, André A1 - Hilgenberg, Kai A1 - Teichmann, F. A1 - Pries, H. A1 - Dilger, K. A1 - Rethmeier, Michael T1 - Improved degassing in laser beam welding of aluminum die casting by an electromagnetic field N2 - The paper describes an experimental investigation of the electromagnetic porosity reduction in partial penetration laser beam welding of 6 mm thick aluminum die casting AlSi9MnMg. The Investigation reveals that the usage of an electromagnetic field leads to a significant reduction of the porosity as well as to a surface smoothing of aluminum die casting. Based on the reference case without an electromagnetic influence, the porosity area was reduced gradually up to 76%. Metallurgical pores as well as process pores were removed from the weld pool. Also the weld reinforcement was improved up to 78%. Best results were reached with a frequency of 4325 Hz and a magnetic flux density of 348 mT. Although a complete prevention of porosity was not achieved, the best weld seam reached a high quality and can be ranked in valuation group B of DIN EN ISO 13919-2:2001–12. KW - Laser beam welding KW - Die-cast aluminum KW - Porosity reduction KW - Electromagnetic influence PY - 2018 DO - https://doi.org/10.1016/j.jmatprotec.2017.10.021 SN - 0924-0136 VL - 253 SP - 51 EP - 56 PB - Elsevier CY - Amsterdam AN - OPUS4-42767 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fritzsche, André A1 - Hilgenberg, Kai A1 - Teichmann, F. A1 - Pries, H. A1 - Rethmeier, Michael T1 - Electromagnetic porosity Reduction in Laser Beam Welding of Die-Cast Aluminum Alloy N2 - The present paper investigates the electromagnetic porosity reduction in partial penetration laser beam welding of 6 mm aluminum die casting AlSi9MnMg. Applying an electromagnetic field, a significant reduction of the porosity as well as smoothing of the surface of aluminum die casting can be observed. Starting from the reference case without an electromagnetic support, the porosity was reduced by 76 %. Especially big pores can be removed from the weld pool effectively due to their beneficial volume-to-area ratio whereas very small metallurgical pores tend to remain within the weld pool even when higher magnetic flux densities are applied. T2 - Lasers in Manufacturing Conference 2017 CY - Munich, Germany DA - 26.06.2017 KW - Laser beam welding KW - Die-cast aluminum KW - Porosity reduction KW - Electromagnetic influence PY - 2017 SP - 1 EP - 10 AN - OPUS4-41244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -