TY - JOUR A1 - Tölle, Florian A1 - Gumenyuk, Andrey A1 - Backhaus, A. A1 - Olschok, S. A1 - Rethmeier, Michael A1 - Reisgen, U. T1 - Welding residual stress reduction by scanning of a defocused beam JF - Journal of materials processing technology N2 - The residual stresses in narrow electron or laser beam welds with high stress gradients are decreased without any contact surfaces or additional equipment by applying the welding beam after welding in a defocused mode for heating the material regions in a certain distance from the weld on both sides. In case of electron beam application, the beam is positioned and focused by the electromagnetic coil with high frequency. In case of laser beam application a laser scanner optics enables fast positioning by an optomechanic beam deflection, while defocusing of the laser beam is obtained by increasing the distance between scanner optics and workpiece. Dependent on the component geometry and on the beam power different process parameters are used. The adjustable process parameters are the radius and the power of the defocused beam and the transversal and longitudinal distances between the welding and the defocused beam. The mechanism and the influence of the process parameters are investigated by FEM-simulation and a number of experiments on a ferritic steel S355J2+N with 5 mm thickness. FEM-simulation is used to reduce the matrix of process parameters for the experiments. The best experimental result shows a stress reduction of about 70%. KW - Residual stresses KW - Stress reduction KW - High energy beam welding KW - Post-weld heat treatment KW - Laser scanner optics PY - 2012 DO - https://doi.org/10.1016/j.jmatprotec.2011.07.019 SN - 0924-0136 SN - 1873-4774 VL - 212 IS - 1 SP - 19 EP - 26 PB - Elsevier CY - Amsterdam AN - OPUS4-24787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Simulation of an inductive weld pool support for deep penetration laser beam welding of metal parts JF - Journal of iron and steel research international N2 - three-dimensional laminar steady state numerical model was used to investigate the influence of an altemating current (ac) magnetic field during single pass high power laser beam keyhole welding of 20 mm thick aluminum. The three-dimensional heat transfer, fluid dynamics and electromagnetic field equations were solved with the commercial finite element package COMSOL Multiphysics. Dominant physical effects of the process were taken into account: Thermo-capillary (Marangoni) convection at the upper and lower weld pool surfaces, natural convection due to the gravity influence and the latent heat of solid-liquid phase transition. Simulations were conducted for several magnetic field strengths and it was found that the gravity drop-out associated with welding of thick plates due to the hydrostatie pressure can be prevented by the application of an ac magnetic field below the weld specimen of around 70 mT (rms) at an oscillation frequency of 450 Hz. The inductive support System allows for single-pass laser beam welding of thick aluminum plates. The flow pattem in the molten zone and the temperature distributions are significantly changed by the application of the electromagnetic forces in the weld pool. KW - Electromagnetic weld pool support KW - Laser beam welding KW - Lorentz force KW - Marangoni stresses KW - Natural convection PY - 2012 SN - 1006-706X SN - 1001-0963 VL - 19 IS - Suppl. 1 SP - 114 EP - 117 PB - Ed. Board CY - Beijing AN - OPUS4-26913 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reisgen, U. A1 - Olschok, S. A1 - Backhaus, A. A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Tölle, Florian T1 - Reduction of weld residual stresses with the electron beam T2 - 2nd International electron beam welding conference (IEBW) T2 - 2nd International electron beam welding conference (IEBW) CY - Aachen, Germany DA - 2012-03-26 PY - 2012 SN - 978-3-87155-299-1 N1 - Serientitel: DVS-Berichte – Series title: DVS-Berichte VL - 285 SP - 128 EP - 132 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-26110 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tölle, Florian A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Reduction of residual stresses in laser beam welds by means of defocused laser beams JF - Science and technology of welding and joining N2 - Longitudinal residual stresses in beam welds ranging at the value of the local yield strength can diminish the lifespan of components. To extend the service life of welds special methods of welding residual stress reduction were developed earlier which are however not effective for beam welds in complex component geometries. Application of beam welding sources for postwelding heat treatment of components has become a flexible tool for reducing longitudinal stresses in beam welds. Such heat treatment in a specific transversal distance to the weld by a defocused beam results in huge stress reductions depending on the used process parameters. Experimental results for ferritic and austenitic steels reveal weld stress reductions to up to compressive stresses. For different materials and diverse material thicknesses special process parameter regions have to be used in this procedure. At a transmission component this procedure shows a stress reduction by >300 MPa. KW - Post-welding heat treatment KW - Stress reduction KW - Residual stress KW - Beam welding PY - 2012 DO - https://doi.org/10.1179/1362171812Y.0000000019 SN - 1362-1718 SN - 1743-2936 VL - 17 IS - 5 SP - 381 EP - 385 PB - Maney CY - London AN - OPUS4-26000 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Graf, Benjamin A1 - Rethmeier, Michael T1 - Potential for repair welding technology based on laser metal deposition for chemical industry T2 - Fitness for Service in Chemical Industries T2 - Fitness for Service in Chemical Industries CY - Aswan, Egypt DA - 2012-11-25 PY - 2012 AN - OPUS4-27359 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Lammers, Marco A1 - Rethmeier, Michael T1 - PA position full penetration high power laser beam welding of up to 30 mm thick AlMg3 plates using electromagnetic weld pool support JF - Science and technology of welding and joining N2 - Full penetration 15 kW Yb fibre laser butt welding of thick AlMg3 (AW 5754) plates was performed in PA position. A contactless inductive electromagnetic weld pool support system was used to prevent gravity dropout of the melt. The welding speed needed to achieve 20 mm penetration was ~0·5 m min-1. An ac power supply of ~244 W at 460 Hz was necessary to completely suppress gravity dropout of the melt and eliminate sagging of the weld pool root side surface. The oscillating magnetic field can suppress the Marangoni convection in the lower part of the weld pool. The system was also successfully used in the full penetration welding of 30 mm thick AlMg3 plates. KW - High power laser beam welding KW - Electromagnetic weld pool support KW - Full penetration PY - 2012 DO - https://doi.org/10.1179/1362171811Y.0000000085 SN - 1362-1718 SN - 1743-2936 VL - 17 IS - 2 SP - 128 EP - 133 PB - Maney CY - London AN - OPUS4-25888 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Numerical simulation of full-penetration laser beam welding of thick aluminium plates with inductive support JF - Journal of Physics D N2 - A three-dimensional laminar steady-state numerical model was developed to investigate the influence of an alternating current (ac) magnetic field during high-power full-penetration laser welding on the weld pool dynamics and weld cross section of a 20 mm thick aluminium plate in flat position. Three-dimensional heat transfer, fluid dynamics including phase transition and electromagnetic field partial differential equations were solved iteratively with the commercial finite element software COMSOL Multiphysics using temperature-dependent material properties up to evaporation temperature. Thermocapillary convection at the weld pool surfaces, natural convection and latent heat of solid–liquid phase transition were taken into account in this model. Solidification was modelled by the Carman–Kozeny equation for porous media morphology. The ac magnet was mounted on the root side of the weld specimen. The magnetic field was aligned perpendicular to the welding direction. The flow pattern in the melt and thus also the temperature distribution were significantly changed by the application of oscillating magnetic fields. It was shown that the application of an ac magnetic field to laser beam welding allows for a prevention of the gravity drop-out. The simulation results are in good qualitative agreement with the experimental observations. KW - Electromagnetic weld pool support KW - Laser beam welding KW - Lorentz force KW - Marangoni stresses KW - Natural convection PY - 2012 DO - https://doi.org/10.1088/0022-3727/45/3/035201 SN - 0022-3727 SN - 1361-6463 VL - 45 IS - 3 SP - 035201-1 - EP - 035201-13 PB - IOP Publ. CY - Bristol AN - OPUS4-25286 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Multi-physics process simulation of static magnetic fields in high power laser beam welding of aluminium T2 - COMSOL Conference 2012 (Proceedings) N2 - A three-dimensional turbulent steady state numerical model was used to investigate the influence of a stationary magnetic field during partial penetration high power laser beam keyhole welding of thick aluminum parts. COMSOL Multiphysics was used to calculate the three-dimensional heat transfer, fluid dynamics and electromagnetic field equations. Thermo-capillary (Marangoni) convection at the upper weld pool surface, natural convection due to gravity and latent heat of solid-liquid phase transition were taken into account. It shows that the application of steady magnetic fields produces a braking Lorentz force in the melt based on the Hartmann effect. The flow pattern in the weld pool and also the temperature distribution and associated weld pool geometry thus change significantly. Convective flows in the melt can effectively be suppressed and the influence of thermo-capillary flow is diminished to a thin surface layer. T2 - COMSOL Conference 2012 CY - Milan, Italy DA - 10.10.2012 KW - Electromagnetic weld pool control KW - Laser beam welding KW - Lorentz force KW - Marangoni convection KW - Buoyancy PY - 2012 SN - 978-0-9839688-7-0 SP - 1 EP - 7 AN - OPUS4-26993 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tölle, Florian A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Backhaus, A. A1 - Olschok, S. A1 - Reisgen, U. T1 - Mechanische Entlastung zur Eigenspannungsreduzierung in Strahlschweißnähten durch Anwendung eines defokussierten Strahls - Teil 2: Qualifizierung für komplexe Nahtgeometrien JF - Schweißen und Schneiden : Fachzeitschrift für Schweißen und verwandte Verfahren N2 - Schweißzugeigenspannungen in Strahlschweißnähten auf Höhe der lokalen Werkstoffstreckgrenze können die Bauteileigenschaften sowie deren Lebensdauer negativ beeinflussen. Die Nutzung der Schweißquelle für eine nachträgliche Behandlung der geschweißten Bauteile bietet eine kostengünstige und flexible Methode zur Reduzierung dieser Spannungen. Dabei wird durch einen oszillierenden defokussierten Elektronen- bzw. Laserstrahl, der Werkstoff beidseitig der Schweißnaht auf mehrere hundert Grad Celsius erwärmt, um dort zusätzliche Zugspannungsbereiche hervorzurufen. Die so erzeugten Längszugspannungszonen führen zu einer mechanischen Entlastung der Schweißnaht. Experimentelle Messungen der Längseigenspannungen an linearen Elektronen- und Laserstrahlschweißnähten im ersten Teil des Beitrags zeigten, dass die Spannungen mit diesem Verfahren um bis zu 70% reduziert werden können. In weiteren experimentellen Untersuchungen wird dieses Verfahren für kompliziertere Schweißnahtgeometrien getestet. An axialen sowie radialen Rundnähten an ferritischen Werkstoffen konnten ebenfalls hohe Spannungsreduktionen von über 50% erzielt werden. Zudem wurde dieses Verfahren mit einer für das Schweißen üblichen Laserstrahlschweißoptik ohne Scan-Funktion geprüft. Hierbei zeigte das Wärmebehandeln in zwei Arbeitsschritten noch größere Spannungsreduktionen im Vergleich zur Anwendung einer Laserstrahlscanneroptik zur quasisimultanen Wärmebehandlung auf beiden Seiten der Schweißnaht. ------------------------------------------------------------------------------------------------------------------------------------------- Residual tensile welding stresses in beam welds at the level of the local yield strength of the material may influence the properties of components as well as their service lives. The utilisation of the welding source for the subsequent treatment of the welded components offers a cost-favourable and flexible method of reducing these stresses. In this respect, an oscillating defocused electron or laser beam serves to heat the material on both sides of the weld up to several hundred degrees Celsius in order to induce additional tensile stress regions there. The longitudinal tensile stress zones produced in this way lead to the mechanical relief of the weld. Experimental measurements of the longitudinal residual stresses on linear electron and laser beam welds in the first part of the article showed that the stresses can be reduced by up to 70% with this process. In further experimental investigations, this process is tested for more complicated weld geometries. It was also possible to achieve great reductions in the stresses (over 50%) on both axial and radial circular welds on ferritic materials. Moreover, this process was tested with laser beam welding optics which are customary for welding and do not perform a scanning function. In this respect, the heat treatment in two work steps showed even greater reductions in the stresses in comparison with the application of laser beam scanner optics for quasi-simultaneous heat treatment on both sides of the weld. KW - Elektronenstrahlschweißen KW - Laserstrahlschweißen KW - Simulation und Berechnung KW - Spannungen KW - Wärmebehandlung KW - Electron beam welding KW - Laser welding KW - Simulation and calculation KW - Stresses KW - Heat treatment PY - 2012 SN - 0036-7184 VL - 64 IS - 7 SP - 406 EP - 411 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-26339 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tölle, Florian A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Backhaus, A. A1 - Olschok, S. A1 - Reisgen, U. T1 - Mechanische Entlastung zur Eigenspannungsreduzierung in Strahlschweißnähten durch Anwendung eines defokussierten Strahls - Teil 1: Spannungsabbaumechanismus an linearen Strahlschweißnähten JF - Schweißen und Schneiden : Fachzeitschrift für Schweißen und verwandte Verfahren N2 - Schweißzugeigenspannungen in Strahlschweißnähten auf Höhe der lokalen Werkstoffstreckgrenze können die Bauteileigenschaften sowie deren Lebensdauer beeinflussen. Die Nutzung der Schweißquelle für eine nachträgliche Behandlung der geschweißten Bauteile bietet eine kostengünstige und flexible Methode zur Reduzierung dieser Spannungen. Dabei wird durch einen oszillierenden defokussierten Elektronen- bzw. Laserstrahl der Werkstoff beidseitig der Schweißnaht auf mehrere hundert Grad Celsius erwärmt, um dort zusätzliche Zugspannungsbereiche hervorzurufen. Die so erzeugten Längszugspannungszonen führen zu einer mechanischen Entlastung der Schweißnaht. Experimentelle Messungen zeigen, dass die Längseigenspannungen in der Schweißnaht mit diesem Verfahren um bis zu 70% reduziert werden können. Hierbei wurde neben der experimentellen Untersuchung dieses Verfahrens an Linearnähten an 5 mm dicken Blechen des Werkstoffs S355J2+N auch eine umfassende Analyse der Einflüsse der Verfahrensparameter auf die Spannungsreduktion mittels FEMSimulation durchgeführt. Anhand der Ergebnisse wird der Entlastungsmechanismus diskutiert. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ Residual tensile welding stresses in beam welds at the level of the local yield strength of the material may influence the properties of components as well as their service lives. The utilisation of the welding source for the subsequent treatment of the welded components offers a cost-favourable and flexible method of reducing these stresses. In this respect, an oscillating defocused electron or laser beam serves to heat the material on both sides of the weld up to several hundred degrees Celsius in order to induce additional tensile stress regions there. The longitudinal tensile stress zones produced in this way lead to the mechanical relief of the weld. Experimental measurements show that the longitudinal residual stresses in the weld can be reduced by up to 70% with this process. In this case, not only was the experimental investigation into this process conducted on linear welds on 5 mm thick sheets made of the S355J2+N material but a comprehensive analysis of the influences of the process parameters on the stress reduction was also made by means of FEM simulation. The relief mechanism is discussed on the basis of the results. KW - Elektronenstrahlschweißen KW - Laserstrahlschweißen KW - Simulation und Berechnung KW - Spannungen KW - Wärmebehandlung KW - Electron beam welding KW - Laser welding KW - Simulation and calculation KW - Stresses KW - Heat treatment PY - 2012 SN - 0036-7184 VL - 64 IS - 6 SP - 332 EP - 340 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-26340 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -