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 - 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 - Sohail, M. A1 - Han, S.-W. A1 - Na, S.-J. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Characteristics of weld pool behavior in laser welding with various power inputs JF - Welding in the world N2 - This paper investigates the numerical simulations of multi-kilowatt disk laser and fiber laser welding, ranging from 6 to 18 kW to study the behavior of molten pool in 20-mm-thick steel plate by using Volume-Of-Fluid (VOF) method and several mathematical models like Gaussian heat source, recoil pressure, Marangoni flow, buoyancy force, and additional shear stress and heat source due to the metallic vapor. Vortex flow pattern is observed for higher laser power except for 6-kW case, and the higher the laser power, the bigger the vortex flow pattern. Welding speed has an influence on molten pool in terms of depth of penetration and size of molten pool, but overall shape of molten pool remains the same. The reasons for the vortex flow pattern in high-power laser welding are the absorption of more energy at the bottom of keyhole, which promotes more liquid metal at the bottom, while for lower power with lower speed, the melt formation is more uniform in the thickness direction and most of the molten metal in the lower part of keyhole reaches the top of molten pool, and consequently, no vortex flow pattern is observed in the keyhole bottom. KW - Laser welding KW - Mathematical models KW - Simulating KW - Molten pool KW - Flow PY - 2014 DO - https://doi.org/10.1007/s40194-014-0112-4 SN - 0043-2288 SN - 1878-6669 VL - 58 IS - 3 SP - 269 EP - 277 PB - Springer CY - Oxford AN - OPUS4-30644 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Simón Muzás, Juan A1 - Brunner-Schwer, Christian A1 - Hilgenberg, Kai A1 - Rethmeier, Michael T1 - Mechanical properties of laser welded joints of wrought and heat treated PBF LB/M Inconel 718 parts depending on build direction T2 - Joining (Welding and Brazing) - Lasers in Manufacturing Conference 2023 N2 - Laser-based Powder Bed Fusion of Metal (PBF-LB/M) is a broadly used metal additive manufacturing (AM) method for fabricating complex metallic parts, whose sizes are however limited by the build envelope of PBF-LB/M machines. Laser welding arises as a valid joining method for effectively integrating these AM parts into larger assemblies. PBF-LB/M components must usually be stress-relieved before they can be separated from the build plate. An additional heat treatment can be beneficial for obtaining homogeneous mechanical properties across the seam or for the formation of desired precipitations in nickel-based-alloys. Therefore, the tensile performance of laser welded hybrid (AM/wrought) and AM-AM tensile samples of Inconel 718 is examined after undergoing three different heat treatments and considering three relevant build directions. It can be shown that the build orientation is an influencing factor on weld properties even after two applied heat treatments. T2 - Lasers in Manufacturing LiM 2023 CY - Munich, Germany DA - 26.09.2023 KW - Inconel 718 KW - Laser welding KW - PBF/LB-M KW - Hybrid components KW - Heat treatments KW - Build direction KW - Tensile performance PY - 2023 SP - 1 EP - 10 PB - Proceedings Lasers in Manufacturing 2023 CY - München AN - OPUS4-58394 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shcheglov, Pavel A1 - Uspenskii, S.A. A1 - Gumenyuk, Andrey A1 - Petrovskii, V.N. A1 - Rethmeier, Michael A1 - Yermachenko, V. M. T1 - Plume attenuation of laser radiation during high power fiber laser welding JF - Laser physics letters N2 - The results of an in-situ plume-laser interaction measurement during welding of mild steel with a 5 kW ytterbium fiber laser are reported. A measurement of the attenuation of probe laser beam passing through the plume has allowed to estimate the plume characteristics like the size of the extinction area and the spatial distribution of the extinction coefficient. The power loss of the fiber laser radiation propagating through the whole plume length was calculated. Together with a measured temporal characteristics of extinction the result indicates a significant decreasing of the laser radiation stability, which can lead to the formation of the macroscopic welding defects. KW - Laser welding KW - Plume KW - Beam attenuation KW - Particles PY - 2011 DO - https://doi.org/10.1002/lapl.201110010 SN - 1612-2011 VL - 8 IS - 6 SP - 475 EP - 480 PB - Wiley-VCH CY - Berlin AN - OPUS4-24812 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quiroz, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Saldabilita di lamiere in acciaio inossidabile austenico ed austeno-ferritico ad alto contenuto di manganese con processo laser JF - Rivista Italiana della Saldatura N2 - Manganese alloyed stainless steels represent a cost-effective alternative to conventional CrNi- stainless steels due to strong fl uctuations of the market prices for nickel seen during the last years. In CrMnNi steels, nickel is partially replaced by lower-cost manganese and small amounts of nitrogen for stabilization of the austenitic phase. This also brings benefi ts regarding the mechanical properties, as it results in an increased material strength. Laser beam welding of such materials was investigated for direct comparison with Standard CrNi steels. Main emphasis was laid on fi nding adequate process parameters to achieve a stable welding process and obtain a good weld quality. Two different laser sources, a 4.4 kW Nd:YAG and a 5 kW CO2 laser, were used to weld 1.5 mm stainless steel sheets in continuous wave mode. A high-Mn austenitic (1.4376) and a lean duplex (1.4162) steel, as well as the standard austenitic (1.4301) and duplex (1.4362) grades were selected as test materials. Both butt and lap joint confi gurations were studied. Experiments were carried out systematically, varying the welding speed, laser power and focal point position in order to determine adequate process windows. The infl uence of the shielding gas type and fl ow rate on the process stability and the weld quality were investigated. The effects of weld edge preparation on the weld appearance and quality levels attained were also examined. The obtained welded joints were subjected to radiographic tests for detection of internal imperfections. Also a metallurgical characterization of the samples regarding the resulting phase composition or balance and hardness depending on the welding process parameters was conducted. Furthermore, tensile and potentiodynamic tests were performed to evaluate the mechanical and corrosion properties, respectively. The results provide an insight into the advantages and limitations of the laser beam welding process for joining high-manganese alloyed stainless steels. Conditions for the production of defect-free and corrosion-resistant welds having good mechanical properties could be determined. KW - Weldability KW - Austenitic stainless steels KW - Corrosion KW - CO2 lasers KW - Duplex stainless steels KW - Laser welding KW - Manganese KW - Mechanical properties KW - Shielding gases KW - YAG lasers PY - 2016 SN - 0035-6794 VL - 68 IS - 1 SP - 33 EP - 43 AN - OPUS4-38100 LA - ita AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quiroz Penaranda, Vanessa A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigations on laser beam welding of high-manganese austenitic and austenitic-ferritic stainless steels JF - The Paton welding journal KW - Laser welding KW - CO2- and Nd:YAG laser KW - Stainless austenitic and duplex steels KW - Higher manganese content KW - Process stability KW - Shielding atmosphere KW - Weld metal KW - Microstructure KW - Mechanical properties KW - Corrosion resistance PY - 2012 SN - 0957-798X VL - 1 SP - 10 EP - 14 PB - E. O. Paton Electric Welding Institute of the National Acad. of Sciences of Ukraine CY - Kyïv AN - OPUS4-27062 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Quiroz Penaranda, Vanessa A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laser beam weldability of high-manganese austenitic and duplex stainless steel sheets JF - Welding in the world N2 - Manganese alloyed stainless steels represent a cost-effective alternative to conventional CrNi- stainless steels due to strong fluctuations of the market prices for nickel seen during the last years. In CrMnNi steels, nickel is partially replaced by lower-cost manganese and small amounts of nitrogen for stabilization of the austenitic phase. This also brings benefits regarding the mechanical properties, as it results in an increased material strength. Laser beam welding of such materials was investigated for direct comparison with standard CrNi steels. Main emphasis was laid on finding adequate process parameters to achieve a stable welding process and obtain a good weld quality. Two different laser sources, a 4.4 kW Nd:YAG and a 5 kW CO2 laser, were used to weld 1.5 mm stainless steel sheets in continuous wave mode. A high-Mn austenitic (1.4376) and a lean duplex (1.4162) steel, as well as the standard austenitic (1.4301) and duplex (1.4362) grades were selected as test materials. Both butt and lap joint configurations were studied. Experiments were carried out systematically, varying the welding speed, laser power and focal point position in order to determine adequate process windows. The influence of the shielding gas type and flow rate on the process stability and the weld quality were investigated. The effects of weld edge preparation on the weld appearance and quality levels attained were also examined. The obtained welded joints were subjected to radiographic tests for detection of internal imperfections. Also a metallurgical characterization of the samples regarding the resulting phase composition or balance and hardness depending on the welding process parameters was conducted. Furthermore, tensile and potentiodynamic tests were performed to evaluate the mechanical and corrosion properties, respectively. The results provide an insight into the advantages and limitations of the laser beam welding process for joining high-manganese alloyed stainless steels. Conditions for the production of defect-free and corrosion-resistant welds having good mechanical properties could be determined. KW - Austenitic stainless steels KW - Corrosion KW - CO2 lasers KW - Duplex stainless steels KW - Laser welding KW - Manganese KW - Mechanical properties KW - Shielding gases KW - YAG lasers KW - Weldability PY - 2012 SN - 0043-2288 SN - 1878-6669 VL - 56 IS - 1/2 SP - 9 EP - 20 PB - Springer CY - Oxford AN - OPUS4-25404 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Petrovskii, V.N. A1 - Uspenskii, S.A. A1 - Shcheglov, Pavel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of a vapor-plasma welding torch induced by a high-power ytterbium fiber laser JF - Nuclear physics and engineering KW - Laser welding KW - Condensation KW - Diagnostic of the torch PY - 2011 SN - 2079-5629 VL - 2 IS - 2 SP - 159 EP - 165 PB - MAIK Nauka AN - OPUS4-24811 LA - rus AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Petrat, T. A1 - Winterkorn, René A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Build-up strategies for temperature control using laser metal deposition for additive manufacturing JF - Welding in the World N2 - The track geometry created with laser metal deposition (LMD) is influenced by various parameters. In this case, the laser power has an influence on the width of the track because of an increasing energy input. A larger melt pool is caused by a rising temperature. In the case of a longer welding process, there is also a rise in temperature, resulting in a change of the track geometry. This paper deals with the temperature profiles of different zigzag strategies and spiral strategies for additive manufacturing. A two-color pyrometer is used for temperature measurement on the component surface near the melt pool. Thermocouples measure the temperatures in deeper regions of a component. The welds are located in the center and in the edge area on a test part to investigate the temperature evolution under different boundary conditions. The experiments are carried out on substrates made from mild steel 1.0038 and with the filler material 316L. The investigations show an influence on the temperature evolution by the travel path strategy as well as the position on the part. This shows the necessity for the development and selection of build-up strategies for different part geometries in additive manufacturing by LMD. KW - Laser welding KW - Clad steels KW - Temperature distribution KW - Heat flow KW - Laser surfacing PY - 2018 DO - https://doi.org/10.1007/s40194-018-0604-8 SN - 0043-2288 SN - 1878-6669 VL - 62 IS - 5 SP - 1073 EP - 1081 PB - Springer AN - OPUS4-45773 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -