TY - JOUR A1 - Gebhardt, M.O. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Numerical analysis of hot cracking in laser-hybrid welded tubes N2 - In welding experiments conducted on heavy wall pipes, the penetration mode (full or partial penetration) occurred to be a significant factor influencing appearance of solidification cracks. To explain the observed phenomena and support further optimization of manufacturing processes, a computational model was developed, which used a sophisticated strategy to model the material. High stresses emerged in the models in regions which showed cracking during experiments. In partial penetration welding, they were caused by the prevention of weld shrinkage due to the cold and strong material below the joint. Another identified factor having an influence on high stress localization is bulging of the weld. PY - 2013 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-302961 DO - https://doi.org/10.1155/2013/520786 SN - 1687-8442 SN - 1687-8434 IS - Article ID 520786 SP - 1 EP - 8 PB - Hindawi Publishing Corporation CY - New York, NY, USA AN - OPUS4-30296 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 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of solidification cracking susceptibility of laser welded joints of austenitic stainless steels N2 - Laser welding is a widely established manufacturing process in many industry sectors. Solidification cracking represents one of the most inadequately solved problems in welding and has major economic implications. The avoidance of hot crack forms for most fusion welding processes poses a key challenge for an important range of metallic construction materials and affects not only the manufacturers of welding equipment and material manufacturers, but also a large number of customers using welding technologies, as well as welding technical standardization and research. Solidification cracking susceptibility was examined with the help of the Controlled Tensile Weldability Test (CTW) developed by Federal Institute for Materials Research and Testing (BAM), Berlin. The test is based on the fact that hot crack formation depends on a critical strain that emerges within a critical temperature range, the so called brittle temperature range (BTR). Using this test and defined investigation programme a centreline solidification crack was generated. By controlling the applied strain during the laser beam welding process, it was possible to determine the critical strain and strain rate that led to solidification cracking formation. The hot cracking susceptibility of the tested stainless steels was qualified and quantified. The results demonstrate that the crack length increases with increasing applied strain. Furthermore, the strain rate has a significant influence on the formation of the solidification crack. T2 - 3rd International conference in Africa and Asia CY - Luxor, Egypt DA - 02.11.2015 KW - Laser beam welding KW - Hot cracking KW - Solidification cracking KW - Hot cracking test PY - 2015 SP - A-29, 1 EP - A-29, 9 AN - OPUS4-36522 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of hot crack susceptibility of laser welded joints of four austenitic steels N2 - Laser welding is a widely established manufacturing process in many industry sectors. Solidification cracking represents one of the most inadequately solved problems in welding and has major economic implications. The avoidance of hot crack is for most fusion welding processes a key challenge for an important range of metallic construction materials and affects not only the manufacturers of welding equipment and material manufacturers, but also a large number of customers using welding technologies, as well as welding standardization and research. In this study a new investigation programme has been developed to qualify the hot cracking susceptibility of a variety of austenitic stainless steels. The results show the possibility of using this technique to determinate the critical values that occur with initiation of solidification cracking during laser beam welding T2 - The METEC and 2nd European Steel Technology and Application Days CY - Düsseldorf, Germany DA - 15.06.2015 KW - Laser beam welding KW - Hot cracking KW - Solidification cracking KW - Hot cracking test PY - 2015 SP - 1 EP - 5 AN - OPUS4-36525 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Na, S.-J. A1 - Han, S.-W. A1 - Muhammad, S. A1 - Zhang, L. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Karhu, M. A1 - Kujanpa, V. T1 - Flow and Bead Formation Characteristics in High Power Laser Welding at Different Welding Positions (Invited Talk) N2 - The numerical simulations of high power laser keyhole welding at different welding positions are performed by using Volume-Of-Fluid (VOF) method. The main material is SS400. The multi-physics phenomenon is considered using several models, such as the heat flux of Gaussian heat source, the recoil pressure with Clausisus-Clapeyron equation, the Marangoni flow considering temperature gradient, the buoyancy force with Boussinesq approximation, the additional shear stress and heat source due to metallic vapor ejected through keyhole entrance, the bubble formation assumed as adiabatic bubble, and the multiple-reflection by solving proper discriminant, are used. To analyze the fluid flow pattern, the concept of streamline formed by reconstructing the value of the velocity vector is applied. Partial and full penetration cases at different welding positions are considered. The welding position seems to have only a minor influence on bead formation characteristics in both cases. This is probably due to the fact that the recoil pressure has a major influence when compared to other driving forces. The flow characteristics and fluid velocity in weld pool are analyzed to compare the gravity direction effect at different welding positions. It is observed that the clockwise flow pattern is mainly formed by the recoil pressure on the keyhole surface in the case of partial penetration. The laser energy can't maintain the whole weld pool when the weld pool size becomes too large. And then the solidification starts from the middle part of weld pool and a necked weld pool shape is formed. In the full penetration welding, the weld pool flow patterns are affected by the leakage of laser power through the full penetration keyhole and also by surface tension. Furthermore, the numerical simulation of full penetration welding with AISI316L is also performed to analyze the effect of material properties. The weld bead shapes obtained by simulations were compared with the corresponding experimental results to confirm the validity of the process models adopted and the CFD simulation tool. T2 - Lasers in Manufacturing Conference 2015 CY - München, Germany DA - 22.06.2015 KW - Macro Processing (Joining, Welding) KW - Weld pool KW - Flow pattern KW - Different welding position KW - Numerical simulation KW - High power laser keyhole welding PY - 2015 SP - 1 EP - 6 AN - OPUS4-37163 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Petrat, Torsten A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Build-up strategies for generating components of cylindrical shape with laser metal deposition N2 - Laser Metal Deposition LMD) as additive manufacturing process offers the potential to produce near net shape components. This reduces the amount of material and post-processing. The components are composed of individual layers. Already mall irregularities within a layer can add up over multiple layers and lead to error propagation. This paper deals with the issue of build-up strategies to minimize irregularities and prevent error propagation. Different travel paths and the influence of a changing starting point regarding to error propagation are discussed. Different deposition rates between core and peripheral area are detected and successfully compensated by adjusting the build-up sequence. Stainless steel and titanium alloy Ti-6Al-4V are used in the experiments. The results are intended to illustrate the potential of an adjusted build-up strategy and provide basic information on the way to an automated deposition process. This paper is of interest for engineers in industry or science using LMD as additive manufacturing process. T2 - Lasers in Manufacturing Conference 2015 CY - Munich, Germany DA - 22.06.2015 KW - Ti - 6Al - 4V KW - Additive Manufacturing KW - Build - up Strategy KW - Laser Metal Deposition KW - Stainless Steel PY - 2015 UR - http://www.wlt.de/lim/Proceedings/Stick/sessions.html SP - 1 EP - 6 AN - OPUS4-37829 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Experimental study and numerical simulation of hot crack formation for novel laser weldability test. N2 - Laser beam welding is a widely established manufacturing process in several industries. The solidification cracking seriously effecting the safety of welded joints could arise during the beam welding of stainless steels caused by high solidification rates. In this study the controlled tensile weldability test (CTW) was used to investigate the solidification cracking susceptibility the fully austenitic stainless steels CrMnNi (1.4376), CrNi (1.4301), CrNiMo (1.4404) and CrNiSi (1.4828) during laser beam welding. The test facility allows welding of specimens with simultaneous application of tensile load along or cross to the welding direction while the speed of tensile force application is either constant or increases linearly. The tensile force increment and/or the displacement are set by means of a CNC controller. Trials were conducted by varying the ultimate tensile strain and cross-head speed while keeping the welding parameters constant. By observing the crack-no crack behaviour and estimating the generated crack length for each trail using a new optimized experimental procedure the influence of the two important conditions (the strain and the strain rate) for the formation of solidification cracks can be investigated, the critical values of strain and strain rate that are responsible for solidification cracking formation have been determined. In the present study a three-dimensional FEM using the contact element technique was developed to simulate the solidification cracking during laser full penetration welding under external load conditions for the steel 1.4376 in order to get a better understanding of the mechanisms of hot crack initiation and the theoretical results were compared to the experimental ones. By comparing the resulting solidification crack with simulated crack, it is possible to determine the critical condition of solidification crack formation in the region where the strains and the strain rates cannot be measured due to the high temperature. The results show a good agreement between numerical calculation and experiment. It is proposed that the solidification cracking susceptibility may be predicted by FEM analysis by using the correct mechanical and thermo-physical constants of the materials. T2 - BEAM TECHNOLOGIES & LASER APPLICATION CY - St. Petersburg, Russia DA - 21.09.2015 KW - Solidification cracking KW - Hot cracking test KW - FEM KW - Laser beam welding PY - 2015 SN - 978-5-7422-5150-7 SP - 55 EP - 68 AN - OPUS4-36615 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Schneider, G. ED - Zschech, E. ED - Petzow, G. T1 - Laserstrahl-MSG-Hybridschweißen von Rohren aus Hochfestem Stahl API-X80/ -X100 N2 - Das Laser-MSG-Hybridschweißverfahren führt bei untersuchten hochfesten Pipelinestählen API X80 und X120 reproduzierbar zu Schweißverbindungen mit anforderungsgerechten Zähigkeitseigenschaften. Eine metallurgische Beeinflussung der Schweißnahtzähigkeit ist durch eine gezielte Auswahl des Zusatzwerkstoffes möglich, wobei die maximale Eindringtiefe des Zusatzwerkstoffes in die Tiefe der Laserhybridnaht zu beachten ist. Die maximal erzielbare Eindringtiefe des Zusatzwerkstoffes ist auf ca. 14 mm begrenzt. Die eingesetzte Art des MSG-Lichtbogens hatte keinen erkennbaren Einfluss auf die Aufmischung im Laseranteil der Laserhybridnaht. Die besseren Ergebnisse der Kerbschlagzähigkeit konnten mit Metallpulverdrähten erreicht werden. Mit den erzielten gemittelten Werten der Schlagarbeit: ca. 200 J bei -60°C für X80 und ca. 53 J bei -40°C für X120 werden Anforderungen der Norm API 5L und DIN EN 10208-2 für die beiden untersuchten Grundwerkstoffe erfüllt. T2 - 49. Metallographie-Tagung CY - Dresden, Germany DA - 16.09.2015 KW - Hochfester Stahl KW - Laserstrahl-MSG-Hybridschweißen PY - 2015 SN - 978-3-88355-410-5 VL - 47 SP - 139 EP - 144 PB - Inventum CY - Sankt Augstin AN - OPUS4-44419 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Avilov, Vjaceslav A1 - Fritzsche, André A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Full penetration laser beam welding of thick duplex steel plates with electromagnetic weld pool support N2 - Full penetration high power bead-on-plate laser beam welding tests of up to 20 mm thick 2205 duplex steel plates were performed in PA position. A contactless inductive electromagnetic (EM) weld pool support system was used to prevent gravity drop-out of the melt. Welding experiments with 15 mm thick plates were carried out using IPG fiber laser YLR 20000 and Yb:YAG thin disk laser TruDisk 16002. The laser power needed to achieve a full penetration was found to be 10.9 and 8.56kW for welding velocity of 1.0 and 0.5 m min(-1), respectively. Reference welds without weld pool support demonstrate excessive root sag. The optimal value of the alternating current (AC) power needed to completely compensate the sagging on the root side was found to be approximate to 1.6 kW for both values of the welding velocity. The same EM weld pool support system was used in welding tests with 20 mm thick plates. The laser beam power (TRUMPF Yb:YAG thin disk laser TruDisk 16002) needed to reach a full penetration for 0.5 m min(-1) was found to be 13.9 kW. Full penetration welding without EM weld pool support is not possible-the surface tension cannot stop the gravity drop-out of the melt. The AC power needed to completely compensate the gravity was found to be 2 kW. (C) 2016 Laser Institute of America 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 - Duplex stainless steel PY - 2015 SN - 978-1-940168-05-0 SP - 571 EP - 579 PB - Amer inst physics CY - Melville, NY, USA AN - OPUS4-35035 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - El-Batahgy, A.M. T1 - Laser and hybrid laser-arc welding of cryogenic 9 % NI Steel N2 - Heat treated 9%Ni steel is considered the most suitable and economic material for construction of large-size liquefied natural gas (LNG) storage tanks which operate at cryogenic temperatures (-196°C). Strength above 700 MPa as well as a minimum impact value of 60 J are required to ensure reliable operation of the LNG tanks at operating temperature. Conventional arc welding processes, including shielded metal arc welding, gas metal arc welding, gas tungsten arc welding and submerged arc welding, are currently used in construction of LNG tanks. Ni based filler wire is the preferred filler metal of choice in LNG tank construction. The main problem with this choice is the lower mechanical properties, particularly tensile strength of the weld metal. To compensate, the wall thickness needs to be excessively thick to ensure the strength of the welded structures. Ni based filler material is expensive and a large quantity is needed to fill the multi-pass weld grooves. These factors significantly add to the cost in the fabrication of LNG storage tanks. For these reasons, exploration of new welding technologies is a priority. A big potential can be seen in laser based welding techniques. Laser beam welding results in much smaller fusion zone with chemical composition and mechanical properties similar to that of the base material. Laser welding is a much faster process and allows for a joint geometry which requires less filler material and fewer welding passes. The advantages of laser welding can help to overcome the problems pointed out above. Trials of autogenous laser welding, laser cold-wire welding and hybrid laser-arc welding conducted on the 9%Ni steel are presented in this paper. Chemical composition of the weld metal as well as effects of welding parameters on the weld formation, microstructure and tensile strength is discussed. Filler wire penetration depth as well as character of its distribution in the narrow laser welds was examined using EPMA - electron probe microanalysis. KW - hardness KW - cryogenic steel KW - laser welding KW - microstructure KW - tensile strength PY - 2016 UR - http://gns.mephi.ru/sites/default/files/journal/file/en.2016.1-4.pdf SN - 2499-9733 VL - 1 IS - 18 SP - 34 EP - 45 PB - Research Nuclear University MEPHl CY - Moskau, Russia AN - OPUS4-36553 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frei, J. A1 - Suwala, H. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Bestimmung der Rissanfälligkeit von hochfesten Stählen beim Widerstandspunktschweißen N2 - Die stetig zunehmenden Anforderungen an Kraftstoffverbrauch, Schadstoffemission, sowie passive Sicherheit haben die Automobilindustrie vor Herausforderungen gestellt, die nur durch einen konsequenten Einsatz moderner hochfester Stahlwerkstoffe zu bewältigen sind. Obgleich eine generelle Eignung dieser Stähle für das Widerstandspunktschweißen (WPS) gegeben ist, kann es durch verschiedene externe Einflüsse im betrieblichen Umfeld zur Rissbildung in der Schweißverbindung kommen. Der Einfluss dieser Risse auf die mechanischen Eigenschaften ist derzeit nicht hinreichend genau erfasst, so dass häufig die Vorgabe einer rissfreien Schweißverbindung besteht. Die Kenntnis der Rissanfälligkeit der verarbeiteten Materialkombinationen sowie von ungünstigen Schweißparametern ist daher für viele Unternehmen von erheblicher wirtschaftlicher Bedeutung. Im Rahmen des FOSTA Projekts P921 „Entwicklung eines Verfahrens zur Bestimmung der Rissanfälligkeit von hochfesten Stählen beim Widerstandspunktschweißen“ wurde ein Ansatz zur Bestimmung der Rissanfälligkeit von WPS-Verbindungen hochfester Stähle entwickelt. Mittels einer hydraulischen Vorrichtung unter Zugbelastung wurden geschweißte, rissbehaftete Proben optisch ausgewertet. Das Verfahren ist geeignet, um ein Werkstoffranking bezüglich der Rissanfälligkeit beim Widerstandspunktschweißen für Werkstoffe aufzustellen. KW - Widerstandspunktschweißen KW - Werkstoffranking KW - Rissanfälligkeit KW - hochfeste Stähle KW - Liquid Metal Embrittlement KW - Lötrissigkeit PY - 2016 DO - https://doi.org/10.3139/120.110904 VL - 58 IS - 7-8 SP - 612 EP - 616 PB - Carl Hanser Verlag CY - München AN - OPUS4-37161 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael 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 threedimensional finite element model employing the contact element 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. KW - Solidification cracking KW - Finite element analysis KW - Imaging KW - Laser welding KW - Austenitic stainless steels PY - 2016 DO - https://doi.org/10.1007/s40194-016-0357-1 SN - 0043-2288 SN - 1878-6669 VL - 60 IS - 5 SP - 1001 EP - 1008 PB - Springer CY - Berlin, Heidelberg AN - OPUS4-37287 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Petrat, T. A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Schmidt, M. ED - Vollertsen, F. ED - Arnold, C. B. T1 - Laser metal deposition as repair technology for a gas turbine burner made of Inconel 718 N2 - Maintenance, repair and overhaul of components are of increasing interest for parts of high complexity and expensive manufacturing costs. In this paper a production process for laser metal deposition is presented, and used to repair a gas turbine burner of Inconel 718. Different parameters for defined track geometries were determined to attain a near net shape deposition with consistent build-up rate for changing wall thicknesses over the manufacturing process. Spot diameter, powder feed rate, welding velocity and laser power were changed as main parameters for a different track size. An optimal overlap rate for a constant layer height was used to calculate the best track size for a fitting layer width similar to the part dimension. Deviations in width and height over the whole build-up process were detected and customized build-up strategies for the 3D sequences were designed. The results show the possibility of a near net shape repair by using different track geometries with laser metal deposition. T2 - LANE - 9 International Conference on Photonic Technologies CY - Fürth, Germany DA - 19.09.2016 KW - Laser metal deposition KW - Inconel 718 KW - Additive manufacturing KW - Maintenance KW - Repair and overhaul PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-376723 UR - http://ac.els-cdn.com/S1875389216301857/1-s2.0-S1875389216301857-main.pdf?_tid=ed1d75de-84a2-11e6-af94-00000aab0f6c&acdnat=1474974777_4917d753cb3d316c4b000ba0760778b5 DO - https://doi.org/10.1016/j.phpro.2016.08.078 SN - 1875-3892 VL - 83 SP - 761 EP - 768 PB - Elservier AN - OPUS4-37672 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Welding with high-power lasers: trends and developments N2 - High-power laser beam welding became new stimuli within the last 10 years due to the availability of a new generation of high brightness multi kilowatt solid state lasers. In the welding research new approaches have been developed to establish reliable and praxis oriented welding processes meeting the demands of modern industrial applications during this time. The paper focuses on some of the current scientific and technological aspects in this research field like hybrid laser arc welding, simulation techniques, utilization of electromagnetic fields or reduced pressure environment for laser beam welding processes, which contributed to the further development of this technology or will play a crucial role in its further industrial implementation. T2 - 9th International Conference on Photonic Technologies - LANE 2016 CY - Fürth, Germany DA - 19.09.2016 KW - High-power Laserbeam Welding KW - Electromagnetic Force KW - Vacuum KW - Simulation PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-377280 DO - https://doi.org/10.1016/j.phpro.2016.08.003 VL - 83 SP - 15 EP - 25 PB - Elsevier B.V. CY - Berlin, Germany AN - OPUS4-37728 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 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 - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Anwendung der digitalen Bildkorrelationstechnik zur Untersuchung der Heißrissanfälligkeit laserstrahlgeschweißter Verbindungen mit dem CTW-Test N2 - In dieser Studie wurde die Heißrissanfälligkeit beim Laserstrahlschweißen für die Werkstoffe 1.4376, 1.4301 und 1.4828 mit Hilfe des CTW­ Test quantifiziert. Bei den Versuchen konnten Erstarrungsrisse in den Proben generiert werden. Zusätzlich können mit der Bildkorrelations-Technik die lokalen Dehnungen und Dehnungs­raten während des Heißrisstests gemessen wer­ den. In Verbindung mit einem externen Dioden­laser zum Beleuchten der zu messende Oberflä­che und lnterferenzfiltern an den Kameras konn­ten die DIC Messungen ohne optische Störungen durchgeführt werden. Die Ergebnisse zeigen, dass die Heißrissbildung bei einer externen Belastung von 3 % für die Stahlsorte 1.4376 zu erwarten ist. Für die Stahls­ orte 1.4301 beträgt dieser Grenzwert 2 % und 1,5 % für die Stahlgüte 1.4828. Außerdem ist zu beobachten, dass die Gesamtrisslänge mit zu­ nehmender äußerer Zugbeanspruchung steigt T2 - 35. Assistentenseminar Füge- und Schweißtechnik CY - Institut für Werkstoff- und Fügetechnik der Otto-von­ Guericke-Universität Magdeburg DA - 01.12.2014 KW - Digitale Bildkorrelationstechnik KW - Heißrissanfälligkeit KW - Untersuchung laserstrahlgeschweißter Verbindungen KW - CTW-Test PY - 2016 SN - 978-3-945023-55-6 VL - 2016/34 SP - 50 EP - 54 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-38065 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Graf, B. A1 - Schuch, M. A1 - Petrat, T. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Combined laser additive manufacturing with powderbed and powder nozzle for turbine parts N2 - Metal additive manufacturing is often based on laser beam processes like Laser Metal Fusion (LMF) or Laser Metal Deposition (LMD). The LMF process is in particular suitable for very complex geometries. However build rate, part volume and material flexibility are limited in LMF. In contrast, LMD achieves higher deposition rates, less restricted part sizes and the possibility to change the material composition during the build-up process. On the other hand, due to the lower spatial precision of the material deposition process, the complexity of geometries is limited. Therefore, combined manufacturing with both LMF and LMD has the potential to utilize the respective advantages of both technologies. In this paper, combined additive manufacturing with LMF and LMD is described for Ti-6Al-4V and Inconel 718. First, lattice structures with different wall thickness and void sizes are built with LMF. The influence of LMD material deposition on these LMF-structures is examined regarding metallurgical impact and distortion. Cross-sections, x-ray computer tomography and 3D-scanning results are shown. For the titanium alloy specimen, oxygen and Nitrogen content in the deposited material are analysed to evaluate the LMD shielding gas atmosphere. The results are used to develop guidelines for a LMD build-up strategy on LMF substrates. With these findings, a gas turbine burner is manufactured as reality test for the combined approach. T2 - 6th International Conference on Additive Technologies iCAT 2016 CY - Nürnberg, Germany DA - 29.11.2016 KW - Ti-6Al-4V KW - Inconel 718 KW - Combined laser manufacturing PY - 2016 SN - 978-691-285-537-6 SP - 317 EP - 323 AN - OPUS4-38702 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Graf, B. A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Combined laser additive manufacturing for complex turbine blades N2 - Laser beam processes are increasingly used in the field of additive manufacturing. Prominent methods are either powderbed-based like Laser Metal Fusion (LMF), or utilizing a powder nozzle like Laser Metal Deposition (LMD). While LMF allows the manufacturing of complex structures, build rate, part volumes and material flexibility are limited. In contrast, LMD is able to operate with high deposition rates on existing parts, and materials can be changed easily during the process. However LMD shape complexity is limited. Utilizing their respective strengths, a combination of these two additive technologies has the potential to produce complex parts with high deposition rates and increased material flexibility. In this paper, combined manufacturing with additive technologies LMF and LMD is described. Its benefit for industry with emphasis on turbomachinery is shown. As reality test for the innovation, an industrial turbine blade is manufactured. KW - Turbine blade KW - Additive manufacturing KW - Laser metal fusion KW - Laser metal deposition PY - 2016 SN - 2499-9733 VL - 3 IS - 20 SP - 34 EP - 42 AN - OPUS4-38709 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Petrat, T. A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Witt, G. ED - Eichmann, M. ED - Kniffka, W. T1 - Strategien zur Erreichung eines konstanten Volumenaufbaus bei der additiven Fertigung mittels Laser-Pulver-Auftragschweißen T1 - Strategies to achieve constant build-up with laser metal deposition N2 - Der Einsatz von Hochleistungswerkstoffen verlangt nach einer hohen Endformnähe der zu fertigenden Bauteile, um den Aufwand und somit die Kosten für Materialeinsatz und Nachbearbeitung möglichst gering zu halten. Der additive Einsatz in Form des Laser-Pulver-Auftragschweißens bietet hierfür durch den gezielten Materialauftrag ein hohes Potential. Herausforderungen bestehen in Bereichen der Vorhersagbarkeit und der Reproduzierbarkeit des Materialauftrages, sowie der Fertigungszeit. Unterschiedliche Einflüsse bei der Schichterzeugung führen dabei zu Abweichungen von der Soll-Geometrie. Die vorliegenden Untersuchungen behandeln den Einfluss von Spurgeometrie, Spurüberlappung, Verfahrweg und Aufbaureihenfolge auf die entstehende Bauteilform. Die Teilung einer Lage in Rand- und Kernbereich ermöglicht einen konturangepassten Verfahrweg und eine Erhöhung der Endformnähe innerhalb einer Ebene. Die Verwendung unterschiedlicher Spurgrößen bei der Bauteilerzeugung verdeutlicht die Möglichkeiten einer hohen Auftragsrate bei gleichzeitig hoher Formgenauigkeit. Bereits kleine Unterschiede beim Materialauftrag zwischen Kern- und Randbereichen, Start- und Endpunkten sowie in Bereichen des Richtungswechsels führen aufgrund von Fehlerfortpflanzung nachmehreren Lagen zu Abweichungen in der Aufbaurichtung. Kompensierungen mittels angepasster Baustrategien werden aufgezeigt und diskutiert. Die Nickelbasislegierung Inconel 718, die Titanlegierung Ti-6Al-4V sowie der austenitische Stahl 316L sind Bestandteil der vorliegenden Untersuchungen. Die gewonnenen Erkenntnisse verdeutlichen das Potenzial einer angepassten Aufbaustrategie zur reproduzierbaren Erzeugung von Bauteilen am Beispiel unterschiedlicher Körpergeometrien. T2 - Rapid.Tech International Trade Show & Conference for Additive Manufacturing CY - Erfurt, Germany DA - 14.06.2016 KW - Laser-Pulver-Auftragschweißen KW - Additive Fertigung KW - Aufbaustrategie KW - 3DDruck KW - Ti-6Al-4V KW - Inconel 718 KW - 316L PY - 2016 SN - 978-3-446-45017-2 SP - 49 EP - 60 PB - Carl Hanser Verlag CY - München, Germany AN - OPUS4-36571 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Avilov, Vjaceslav A1 - Fritzsche, André A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Full penetration laser beam welding of thick duplex steel plates with electromagnetic weld pool support N2 - Full penetration high power bead-on-plate laser beam welding tests of up to 20 mm thick 2205 duplex steel plates were performed in PA position. A contactless inductive electromagnetic (EM) weld pool support system was used to prevent gravity drop-out of the melt. Welding experiments with 15 mm thick plates were carried out using IPG fiber laser YLR 20000 and Yb:YAG thin disk laser TruDisk 16002. The laser power needed to achieve a full penetration was found to be 10.9 and 8.56 kW for welding velocity of 1.0 and 0.5 m min−1, respectively. Reference welds without weld pool support demonstrate excessive root sag. The optimal value of the alternating current(AC) power needed to completely compensate the sagging on the root side was found to be ≈1.6 kW for both values of the welding velocity. The same EM weld pool support system was used in welding tests with 20 mm thick plates. The laser beam power (TRUMPF Yb:YAG thin disk laser TruDisk 16002) needed to reach a full penetration for 0.5 m min−1 was found to be 13.9 kW. Full penetration welding without EM weld pool support is not possible—the surface tension cannot stop the gravity drop-out of the melt. The AC power needed to completely compensate the gravity was found to be 2 kW. KW - Electromagnetic weld pool control KW - Duplex stainless steel KW - Laser beam welding KW - Full penetration welding PY - 2016 DO - https://doi.org/10.2351/1.4944103 SN - 1042-346X SN - 1938-1387 VL - 28 IS - 2 SP - 022420-1 EP - 022420-7 PB - American institute of physics CY - Woodbury, NY, USA AN - OPUS4-35668 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schneider, André A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Impiego di un dispositivo per il vuoto locale di tipo mobile nell'applicazione del processo laser. T1 - Deployment of mobile vacuum device in the application of laser beam welding N2 - Lo sviluppo del pennacchio di vapore durante la saldatura laser di metalli con direzioni di propagazione lungo l'asse del fascio laser comporta una riduzione della potenza del laser assorbita nel keyhole. Questi effetti negativi possono essere notevolmente attenuati mediante l'applicazione di una ridotta pressione ambientale, diminuendo così l'interazione tra il fascio laser ed i prodotti dell'evaporazione, condizione che favorisce la stabilità del processo di saldatura e si traduce in una maggiore profondità di penetrazione. Una tecnica convenzionale utilizza il principio della camera a vuoto, simile a quello utilizzato per la saldatura a fascio elettronico. L'applicazione di questa tecnica è limitata dalle dimensioni della camera e riduce quindi i vantaggi di questo approccio, particolarmente per componenti di grandi dimensioni. Abbiamo dimostrato la possibilità di applicazione del vuoto in forma localizzata con apparecchiature mobili, che consentono di generare una pressione ridotta solo in una piccola zona attorno al keyhole. Utilizzando un dispositivo di chiusura appositamente progettato per la pressione, di tipo mobile, che può essere spostato lungo l'asse del giunto è possibile ottenere una pressione assoluta di circa 200 mbar. Questo è sufficiente per aumentare la profondità di penetrazione di circa il 50%. I campioni di acciaio grado S355 sono stati saldati con una potenza laser incrementale da 5 kW a 12 kW a pressione atmosferica e confrontati con quelli saldati a pressione ambiente di 200 mbar. La valutazione della sezione longitudinale ha rivelato un aumento della profondità di penetrazione dei giunti di circa il 35%. Inoltre, sono stati eseguiti test di saldatura in configurazione di giunti testa a testa con lamiere di 15 mm di spessore con diverse potenze associate al fascio laser eseguiti a pressione atmosferica ed a pressione ambiente ridotta di circa 200 mbar. L'aumento nella profondità di penetrazione fino al 40% è relativo alla pressione ridotta. In particolare, basse velocità di saldatura con pressione ridotta si sono rivelate particolarmente vantaggiose in termini di aumento della penetrazione. N2 - The development of the vapour plume during the laser beam welding of metals with propagation directions along the laser beam axis leads to a reduction of the absorbed laser power in the keyhole. These unfavourable effects can be significantly mitigated by the application of a reduced ambient pressure thus decreasing the interaction between the laser beam and evaporation products, which leads to more stable welding process and results in increased penetration depth. A conventional technique use a vacuum chamber principle, similar to that, used for electron beam welding. Application of this technique is restricted by the chamber size and reduces thus the advantages of this approach especially for large components. We demonstrate a possibility of mobile local vacuum application, which allows to generate a reduced pressure only in small region around the keyhole. By using of specially designed mobile pressure lock which can be moved along the welding direction absolute pressure of around 200 mbar could be obtained. This is sufficient to increase the welding depth by around 50%. Samples from S355 were welded with an incremental laser power from 5 kW to 12 kW at atmospheric pressure and compared to those welded at ambient pressure of 200 mbar. The evaluation of the longitudinal section revealed an increase of the welding depth by about 35%. Furthermore, the welding trials in butt joint configuration on 15 mm thick plates at various laser beam power performed for atmospheric and reduced ambient pressure of around 200 mbar. The increase in welding depth up to 40% was established for reduced pressure. Particularly, low welding speeds under reduced pressure were especially advantageous in terms of increasing the welding depth. KW - laser welding KW - Laserstrahlschweißen KW - vacuum KW - local effects KW - Vakuum KW - Lokale Effekte PY - 2016 SN - 0035-6794 VL - 04 IS - 04 SP - 1 EP - 8 AN - OPUS4-35619 LA - mul 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 assessment and experimental verification of the influence of the Hartmann effect in laser beam welding processes by steady magnetic fields N2 - Controlling the dynamics in the weld pool is a highly demanding challenge in deep-penetration laser beam welding with modern high power laser systems in the multi kilowatt range. An approach to insert braking forces in the melt which is successfully used in large-scaled industrial applications like casting is the so-called Hartmann effect due to externally applied magnetic fields. Therefore, this study deals with its adaptation to a laser beam welding process of much smaller geometric and time scale. In this paper, the contactless mitigation of fluid dynamic processes in the melt by steady magnetic fields was investigated by numerical simulation for partial penetration welding of aluminium. Three-dimensional heat transfer, fluid dynamics including phase transition and electromagnetic field partial differential equations were solved based on temperature-dependent material properties up to evaporation temperature for two different penetration depths of the laser beam. The Marangoni convection in the surface region of the weld pool and the natural convection due to the gravitational forces were identified as main driving forces in the weld pool. Furthermore, the latent heat of solide-liquid phase transition was taken into account and the solidification was modelled by the Carman-Kozeny equation for porous medium morphology. The results show that a characteristic change of the flow pattern in the melt can be achieved by the applied steady magnetic fields depending on the ratio of magnetic induced and viscous drag. Consequently, the weld bead geometry was significantly influenced by the developing Lorentz forces. Welding experiments with a 16 kW disc laser with an applied magnetic flux density of around 500 mT support the numerical results by showing a dissipating effect on the weld pool dynamics. KW - Electromagnetic weld pool control KW - Hartmann effect KW - Laser beam weliding KW - Lorentz force KW - Marangoni flow KW - Natural convection KW - Aluminium PY - 2016 DO - https://doi.org/10.1016/j.ijthermalsci.2015.10.030 SN - 1290-0729 VL - 101 SP - 24 EP - 34 PB - Elsevier CY - Paris AN - OPUS4-35034 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Bakir, Nasim T1 - Entwicklung eines Verfahrens zur Untersuchung der Heißrissresistenz lasergeschweißter Verbindungen N2 - In den letzten Jahrzehnten hat sich die Strahlschweißtechnik signifikant weiterentwickelt und als effizientes und wirtschaftliches Werkzeug in der Industrie etabliert. Für die Untersuchung der Heißrissresistenz verschiedener Werkstoffe existieren zahlreiche eigen- und fremdbeanspruchende Tests. Diese wurden aber speziell für andere Schweißverfahren, insbesondere das Lichtbogenschweißen, konzipiert. Daher besteht die Notwendigkeit eines geeigneten Heißrisstests, bei dem Werkstoffe realen Strahlschweißbedingungen ausgesetzt werden können. Die Entwicklung sowie die Standardisierung einer aussagekräftigen experimentellen Methode stellen einen wichtigen Schritt auf dem Weg zur Vermeidung von Heißrissen und damit für die Gewährleistung der Sicherheit von gefügten Bauteilen dar. Ziel der Forschungsarbeiten ist es, einen geeigneten Test zur effektiven Untersuchung der Heißrissanfälligkeit von lasergeschweißten Verbindungen zu konzipieren und zu entwickeln. KW - Heißrissresistenz PY - 2016 SN - 978-3-942541-94-7 SP - 1 EP - 110 PB - Verlag und Vertriebsgesellschaft mbH CY - Düsseldorf AN - OPUS4-41846 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritzsche, André A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Hilgenberg, Kai A1 - Rethmeier, Michael T1 - High power laser beam welding of thick-walled ferromagnetic steels with electromagnetic weld pool support N2 - The paper describes an experimental investigation of high power laser beam welding with an electromagnetic weld pool support for up to 20 mm thick plates made of duplex steel (AISI 2205) and mild steel (S235JR). The results of the welding tests show a successful application of this technology at ferromagnetic metals. Irregular sagging was suppressed successfully. An ac-power of less than 2 kW at oscillation frequencies between 800 Hz and 1.7 kHz is necessary for a full compasation of the hydrostatic pressure. Thus, it was demonstrated that the electromagnetic weld pool support is not only limited to non-ferromagnetic metals like austenitic steels. For future studies with duplex steel, the use of filler material has to take into account with regard to the balance of the mixed austenitic and ferritic phases. KW - Laser beam welding KW - Thick-walled steel KW - Ferromagnetic steel KW - Weld pool support PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-377593 DO - https://doi.org/10.1016/j.phpro.2016.08.038 SN - 1875-3892 VL - 83 SP - 362 EP - 372 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-37759 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser arc welding of high grade X80 and X120 pipeline steels N2 - The aim of the present work was to investigate the possibilities of hybrid laser arc welding regarding reliable production of longitudinal welds of high strength pipe steels X80 and X120 and to evaluate achievable mechanical properties of laser hybrid welds. The study focused on weld toughness examination in low temperature range up to -60 °C. SЮТЭКЛХО ПТХХОЫ ЦКЭОЫТКХЬ were identified in the context of this task. It could be shown that metal cored electrodes guaranteed sufficient Charpy impact toughness at low temperature for both investigated materials. Modern arc welding technologies such as modified pulsed spray arc were used to promote deeper Penetration of the filler material into the narrow laser welding gap. Edge preparation with a 14 mm deep root face was considered as optimum, because no penetration of the filler material could be detected beyond this depth limit and therefore any metallurgical influences on the weld metal properties through the welding wire could be excluded. KW - High strength steel KW - Longitudinal weld KW - Modified spray arc KW - Pipeline KW - Hybrid laser arc welding PY - 2017 SN - 2499-9733 SN - 2305-414Х VL - 1 IS - 22 SP - 21 EP - 35 AN - OPUS4-44343 LA - rus AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meschut, G. A1 - Janzen, V. A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Frei, J. T1 - Charakterisierung des Bruch- und Festigkeits verhaltens von widerstandspunktgeschweißten Aluminiumverbindungen N2 - Die Reduktion des Fahrzeuggewichts ist ein wesentlicher Ansatz zur Ver-ringerung des Energie- und Ressourcenverbrauchs und damit zur Senkung der CO2-Emissionen im Automobilbau. In der Karosserieentwicklung kann der vermehrte Einsatz von Aluminiumwerkstoffen einen bedeutenden Beitrag dazu leisten. Im preissensitiven Umfeld des Karosseriebaus etabliert sich das bei Stahlanwendungen genutzte Widerstandspunktschweißen zunehmend auch für Aluminiumverbindungen. Verfahrensbedingte Herausforderungen, wie verkürzte Elektrodenstandzeiten und mangelnde Kenntnis über den Einfluss von Imperfektionen auf die Festigkeit, begrenzen dennoch die Weiterverbreitung des Verfahrens und stellen die Prozessrobustheit insgesamt in Frage. Im Rahmen des hier vorgestellten Forschungsvorhabens wurden das Auftreten verschiedener Brucharten experimentell untersucht und Prognosefunktionen zur Abschätzung der Tragfähigkeit von Widerstandspunktschweißverbindungen unter verschiedenen Belastungsfällen erstellt. Anschließend wurde der Einfluss von Oberflächenrissen und Rissen in der Schweißlinse auf die Scherzugfestigkeit sowohl experimentell als auch simulativ analysiert. KW - Aluminium KW - Widerstandspressschweißen KW - Rissbildung KW - Festigkeit KW - Werkstofffragen PY - 2017 UR - http://www.schweissenundschneiden.de/article/charakterisierung-des-bruch-und-festigkeitsverhaltens-von-widerstandspunktgeschweissten-aluminiumverbindungen/ VL - 69 IS - 3 SP - 126 EP - 133 PB - DVS Media GmbH AN - OPUS4-39577 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Petrat, T. A1 - Marko, A. A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael ED - Mayr, P. ED - Berger, M. T1 - Baustrategien zur Beeinflussung von Materialauftrag und Temperaturentwicklung bei der additiven Fertigung mittels Laser-Pulver-Auftragschweißen N2 - Die Weiterentwicklung des Laser-Pulver-Auftragschweißens im Bereich der additiven Fertigung stellt dieses Verfahren vor neue Herausforderungen. Bauteile können schnell und endformnah hergestellt werden, was diese Technik für den Prototypenbau sowie Kleinserienfertigung interessant macht. Die Vielzahl an Varianten, um ein Volumen aus einzelnen Schichten aufzubauen, erhöhen die Möglichkeiten die Eigenschaften des entstehenden Bauteils zu beeinflussen. Hierfür müssen Strategien entwickelt werden, welche einen gleiclunäßigen Materialauftrag bei gleichzeitig optimalen Materialeigenschaften gewährleisten. Die durchgeführten Untersuchungen behandeln den Einfluss von Pendelstrategien sowie Spiralstrategien auf die Temperaturentwicklung und stellen diese vergleichend gegenüber. Um den unterschiedlichen Bedingungen bei der Bauteilfertigung Rechnung zu tragen, wurden Versuche in Randbereichen sowie im zentralen Bereich des Testobjekts untersucht. Die Ergebnisse verdeutlichen die Notwendigkeit angepasste Baustrategien zu entwickeln, um durch einen stabilen Fertigungsprozess Qualität und Eigenschaften eines Bauteils gewährleisten zu können. T2 - FüMoTec 2017 CY - Chemnitz, Germany DA - 14.11.2017 KW - Laser-Pulver-Auftragschweißen KW - Additiv KW - Pendelstrategie KW - Spiralstrategie KW - Temperaturentwicklung PY - 2017 SN - 978-3-96100-034-0 SN - 2365-8096 SN - 2365-810X VL - 2017/2 SP - 27 EP - 36 PB - readbox unipress CY - Münster AN - OPUS4-43104 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of solidification cracking susceptibility during laser beam welding using an in-situ observation technique N2 - Using the novel optical measurement technique together with the optical flow algorithm, a twodimensional deformation analysis during welding has been conducted. This technique provides for the first time a measurement of the strain field locally in the immediate vicinity of the assumed solidification front. The described procedure of the opticalmeasurement allows to determine the real martial-dependent values of critical strain and strain rate characterising transition to the hot cracking during laser welding processes. The local critical strain that obtained in the assumed solidification showed that the local critical strain decreases as the strain rate increases. Moreover, this phenomenon has also been shown with results from the CTW-test, since the global strain decreases with an increase in the external strain rate. KW - Novel optical measurement KW - Local critical strain KW - Solidification cracking KW - Laser beam Welding PY - 2017 DO - https://doi.org/10.1080/13621718.2017.1367550 SN - 1362-1718 SP - 1 EP - 7 PB - Taylor & Francis AN - OPUS4-42918 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Winterkorn, R. A1 - Petrat, T. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Temperature generation of different travel path strategies to build layers using laser metal deposition N2 - Laser Metal Deposition offers the chance to build near net shape parts. The temperature evolution within the process has an influence on track and layer geometries. There are special travel path strategies required to produce near net shape components and reduce shape deviation resulting of error propagation. This paper deals with the temperature progression of individual layers and the maximum heating of deeper substrate regions. Spiral and zig-zag strategies are examined. The investigations are carried out using S235JR as substrate and 316L as powder material. The influence of different strategies on temperature evolution is discussed. The results from the experiments show that various production strategies are associated with different temperature fields. Furthermore, the extent of the temperature variations of layer strategies and layer position are strongly dependent on the production direction. These results demonstrate the importance of developing suitable build-up strategies for parts of complex shape to ensure a stable process with constant temperature as well as even layers. T2 - Lasers in Manufacturing Conference 2017 CY - Munich, Germany DA - 26.06.2017 KW - 316L KW - Additive Manufacturing KW - Temperature behavior KW - Laser Metal Deposition KW - Stainless Steel KW - Edge effects PY - 2017 SP - 1 EP - 5 AN - OPUS4-42878 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - 3D laser metal deposition in an additive manufacturing process chain N2 - Laser metal deposition is described with its applications for additive manufacturing. The necessary process chain is discussed, with regard to weld bead dimensions and 3D build-up strategy. Metallurgical cross sections, x-ray and tensile tests are conducted. As demonstrative components, a gas turbine burner and a turbine blade are shown. T2 - 1st International Congress on Welding, Additive Manufacturing and Associated Non- CY - Metz, France DA - 17.05.2017 KW - Laser metal deposition KW - Additive manufacturing KW - Ti-6Al-4V KW - Turbine industry KW - Process chain PY - 2017 UR - https://icwam.com/sites/default/files/Abstract%20book.pdf SP - AM 34-2 EP - 3 AN - OPUS4-43190 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Üstündag, Ö. A1 - Avilov, Vjaceslav A1 - Fritzsche, André A1 - Rethmeier, Michael T1 - Hybrid laser arc welding of thick-walled ferromagnetic steels with electromagnetic weld pool support N2 - Electromagnetic weld pool support system is illustrated successfully for hybrid laser arc welding of 20 mm ferromagnetic steels. Welding of thick-walled steels in flat position and reduced welding velocities is possible. Skin depth must be smaller than the plate thickness for protect the electric arc against external oscillating magnetic field. Residual magnetic field has a low influence, the deflection of the arc can be neglected. At high AC frequency more AC power is needed for ideal compensation (Hysteresis losses). T2 - The 70th IIW Annual Assembly and International Conference CY - Shanghai, People's Republic of China DA - 25.06.2017 KW - Electromagnetic weld pool support KW - Hybrid laser arc welding PY - 2017 AN - OPUS4-41259 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Untersuchungen der Heißrissanfälligkeit laserstrahlgeschweißter Verbindungen austenitischer Stähle N2 - Die lokalen Dehnungen bzw. Dehngeschwindigkeiten im heißrisskritischen Temperaturintervall sind Funktionen des Temperaturfeldes im Nahbereich des Schmelzbades (Schweißverfahren, Werkstoff), der thermo-mechanischen Kennwerte des Versuchswerkstoffes sowie von außen aufgebrachten Verfor-mungen. Da die lokal vorherrschenden Dehnungen im Nahbereich des Schmelzbades nicht bzw. nur mit sehr aufwendigen Methoden ermittelt werden können, dienen bespielweise die im CTW-Test (Controlled Tensile Weldability) von außen aufgebrachten Dehnungen oder Dehnraten als Kriterium für die Heißriss-empfindlichkeit. In dieser Studie wurde CTW-Test zur Untersuchung der Heißrissresistenz verschiedenen austenitischen Stählen eingesetzt. T2 - 36. Assistentenseminar Füge- und Schweißtechnik CY - Brunswick, Germany DA - 05.10.2015 KW - Heißriss KW - Heißrissresistenz KW - Austenitische Stähle KW - CTW-Test PY - 2017 SN - 978-3-945023-57-0 SP - 106 EP - 111 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-41246 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Bakir, Nasim A1 - Rethmeier, Michael A1 - Pavlov, V. A1 - Zavjalov, S. A1 - Volvenko, S. T1 - Use of optical measurement technique to investigate the hot cracking sensitivity of 316L during laser beam welding N2 - This technique is the first to provide a measurement of the full strain field locally in the immediate vicinity of the solidification front. Dependency between the external strain rate and the critical local strain has been observed. The local critical strain in vicinity of the solidification front has observed between 3.6 and 4.2%. T2 - The 70th IIW Annual Assembly and International Conference CY - Shanghai, People's Republic of China DA - 25.06.2017 KW - Optical measurment technique KW - Hot crack PY - 2017 AN - OPUS4-41258 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Bakir, Nasim T1 - Comparative study of hot cracking susceptibility for laser welded joints by means of a self- restraint and an externally loaded hot cracking tests N2 - Over the past decade, laser beam welding has significantly evolved and established itself as an efficient tool in the industry. Solidification cracking and the weldability of materials have been highly contentious issues for many years. Today, there are many self and externally loaded tests to investigate the hot cracking resistance of steels. The purpose of this paper is to compare the susceptibility of three stainless steel grades to hot cracking by using an externally loaded hot cracking test (CTW) and a self-restraint test in accordance with SEP-220-3. The repeatability and effectiveness of the results are discussed. The experimental results are widely dispersed, implying a low predictive value for the self-restraint test. On the other hand, the results from the externally loaded test exhibit excellent repeatability and provide a quantitative characterization of the susceptibility of steels to hot cracking. T2 - The 5th International Conference on Steels in Cars and Trucks CY - Amsterdam-Schiphol, Netherlands DA - 19.06.2017 KW - Externally loaded test KW - Hot cracking test KW - SEP-1220-3 KW - CTW test KW - Self-restraint test PY - 2017 SP - 1 EP - 8 AN - OPUS4-41174 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pavlov, V. A1 - Gumenyuk, Andrey A1 - Volvenko, S. A1 - Rethmeier, Michael A1 - Bakir, Nasim T1 - Investigation of solidification cracking susceptibility of type 316L stainless steel during laser beam welding using an in-situ observation technique N2 - Laser welding is a widely established manufacturing process in many industry sectors. Solidification cracking as well as the weldability of materials is still since many years a highly contentious issue, particularly regarding the causes of the hot crack formation. Many of studies have been conducted to determine the critical conditions of occurrence of the solidification cracking. In this study a 2D in-situ observation technique in conjunction with laser diodes as the illuminating source has been employed to measure the arising strain field during the laser beam welding process. For the first time the employed technique enabled the in-situ measurement of the transient strain field at the surface of the workpiece directed to the laser beam in the critical range, where the solidification cracking normally occurs. Thus the critical threshold strain values at high temperatures characterizing transition from crack free to crack concomitant welding process could be deduced. T2 - Lasers in Manufacturing Conference 2017 CY - Munich, Germany DA - 26.06.2017 KW - Laser beam Welding KW - Optical measurement technique KW - Critical strain KW - Solidification cracking PY - 2017 SP - 1 EP - 7 AN - OPUS4-41175 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fritzsche, André A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Hilgenberg, Kai T1 - Einsatz einer elektromagnetischen Schmelzbadstütze beim Laserstrahl-(Hybrid)schweißen dickwandiger Stahlbauteile N2 - Die experimentellen Untersuchungen innerhalb dieses Berichtes zeigen die erfolgreiche Anwendung einer elektromagnetischen Schmelzbadstütze beim Laser-strahl(hybrid)schweißen von ferromagnetischen Stäh-len mit einer Werkstückdicke von bis zu 20 mm. Bis-lang wurde dieses System zur Kompensation des hydrostatischen Druckes von Aluminiumlegierungen und austenitischen Stählen eingesetzt. Zunächst wur-den die Versuche an Duplexstählen vorgenommen, die jeweils zur Hälfte aus Austenit und Ferrit bestehen. Im Anschluss daran wurden die Versuche auf bis zu 20 mm dicke Werkstücke aus Baustahl erweitert. In-nerhalb der Versuchsreihen wurden die AC-Leistung sowie die Oszillationsfrequenz variiert. Für Werk-stückdicken von 15 mm war eine AC-Leistung von ca. 1 kW notwendig, um die Wurzelüberhöhung in die Bewertungsgruppe B der für laserstrahlgeschweißten Stähle gültigen DIN EN ISO 13919-1:1996-09 einord-nen zu können. Mit zunehmender AC-Leistung wird die Wurzelüberhöhung sukzessive reduziert. Nach erfolg-reicher Erweiterung auf ferromagnetische Werkstoffe wurde die Anwendung der Technologie für das Laser-strahlhybridschweißen demonstriert, indem praxisrele-vante Y-Nähte an 20 mm dicken Baustählen ohne Wurzelüberhöhung einlagig in Wannenlage geschweißt wurden. Trotz der Beeinflussung des Lichtbogens durch das oszillierende Magnetfeld sowie des zusätz-lich zum hydrostatischen Druck zu berücksichtigenden Lichtbogendruckes wurde eine ideale Kompensation auf der Wurzelseite erzielt. Die Erweiterung des Anwendungsspektrums der elekt-romagnetischen Schmelzbadstütze auf ferromagneti-sche Werkstoffe sowie auf das Laserstrahlhybrid-schweißen eröffnet für zukünftige industrielle Anwen-dungen ein großes Potenzial. Das einlagige Schwei-ßen dickwandiger Bauteile mittels Hochleistungslasern wird in Kombination mit der elektromagnetischen Schmelzbadstütze attraktiver. In nachfolgenden Un-tersuchungen wird der Einsatz der elektromagneti-schen Schmelzbadstütze beim Laserstrahlhybrid-schweißen von Pipelinestählen angestrebt, v. a. im Hinblick auf die Spaltüberbrückbarkeit und der me-chanisch-technologischen Eigenschaften der Schweißverbindungen. Zudem ist beim Schweißen von Duplexstählen der Einsatz von Zusatzwerkstoffen zu berücksichtigen, um das Gleichgewicht zwischen austenitischer und ferritischer Phasen zu stabilisieren. T2 - DVS Congress 2017 CY - Düsseldorf, Germany DA - 26.09.2017 KW - Elektromagnetische Schmelzbadunterstützung KW - Ferromagnetischer Stahl KW - Laserstrahl-(Hybrid)schweißen PY - 2017 SN - 978-3-96144-008-5 VL - 337 SP - 331 EP - 336 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-42312 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Muhammad, S. A1 - Han, S.W. A1 - Na, S.J. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Study on the role of recondensation flux in high power laser welding by computational fluid dynamics simulations N2 - Partial penetration welding with fiber laser on 20mm thick plates was carried out in horizontal position to study the role of secondary heating in modeling of high power fiber laser welding. Experiments were carried out using 18.8kW laser with 1.5 m/min welding speed at Ar assist gas flow rates of 0, 17, 29, and 40 l/min, all four cases show similar bead shape with bright emission of vapor plume. Numerical simulations were performed using volume of fluid method by considering three different models as models A–C. Model A considers only Fresnel reflection inside the keyhole using real time tracking of free surface. Model B considers vapor recondensation flux inside keyhole along with model A. Finally, model C is used, which considers vapor plume heating at 4100K temperature along with models A B. Secondary heating by recondensation and vapor plume is vital in modeling of high power fiber laser welding; especially, the upper part of the bead is more influenced due to secondary heating. Tungsten particles are also used to visualize the flow pattern of melt pool. KW - Laser keyhole welding KW - Fresnel reflection KW - Secondary heat source KW - Plume heating KW - Vapor recondensation KW - High brightness KW - High power KW - Partial penetration KW - Fiber laser PY - 2018 DO - https://doi.org/10.2351/1.4994246 SN - 1042-346X SN - 1938-1387 VL - 30 IS - 1 SP - 012013-1 EP - 012013-12 PB - Laser Institute of America CY - Orlando, Fla. AN - OPUS4-44345 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Üstündağ, Ö. A1 - Fritzsche, A. A1 - Avilov, Vjaceslav A1 - Rethmeier, Michael T1 - Anwendung der Magnettechnik zum Laserstrahlschweißen von dickwandigen Konstruktionen N2 - Elektromagnetische Schmelzbadkontrolle wurde erfolgreich für Laser-MSG-Hybridprozess an einem (ferromagnetischen) 20 mm Baustahl und einem Pipelinestahl eingesetzt. Einlagiges Laserstrahlschweißen von dickwandigen(>20 mm) in PA-Position bei geringeren Schweißgeschwindigkeiten prinzipiell möglich. Reduzierung der Schweißgeschwindigkeit beim Laserstrahlschweißen hat eine Verringerung der notwendigen Laserleistung und eine Verbesserung der mechanisch-technologischen Eigenschaften von Schweißverbindungen zur Folge. T2 - Anwendertreffen Laserverbund Berlin-Brandenburg e.V. CY - Berlin, Germany DA - 17.10.2018 KW - Magnettechnik PY - 2018 AN - OPUS4-43943 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, S. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Orbital hybrid laser-arc welding using a high-power fibre laser for pipeline construction N2 - Recently developed fibre lasers provide multi-kilowatt beam power with high quality at impressive energy efficiency. Combined with gas metal arc welding (GMAW) equipment these lasers can be used in a hybrid process to weld thick-walled constructions single-pass, that are currently welded using multi-pass techniques. The main benefits are a reduction of heat induced distortions, due to the low heat input, as well as savings in filler material and process time. Probable applications can be found in power generation, ship building and pipeline constructions. An orbital (girth) laser-hybrid process using a 20 kW fibre laser and a GMAW torch is currently examined at the BAM, Berlin. The aim of this research is to obtain a stable and crack free girth welding process and to demonstrate its application in pipeline construction. The experiments are carried out on 16 mm thick plates as well pipe rings with 36" (914 mm) pipe diameter of X65. Particular welding parameters, such as welding speed, GMAW power, arc length are varied and their influence on the appearance of the weld in the different welding positions is analyzed. Even though issues remain that demand further research it could already be shown that the rings can be welded using a girth hybrid process that is divided into two half girth processes in downward direction. KW - High-power fibre laser KW - Thick plates KW - Laser-hybrid welding KW - Pipeline PY - 2018 UR - http://gns.mephi.ru/en/issues/2018-126?art=418 SN - 2499-9733 SN - 2305-414X VL - 1 IS - 26 SP - 47 EP - 57 PB - National Research Nuclear University "MEPhI" CY - Volgodonsk AN - OPUS4-45046 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Artinov, Antoni A1 - Gumenyuk, Andrey A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - Numerical simulation on the origin of solidification cracking in laser welded thick-walled structures N2 - One of the main factors affecting the use of lasers in the industry for welding thick structures is the process accompanying solidification cracks. These cracks mostly occurring along the welding direction in the welding center, and strongly affect the safety of the welded components. In the present study, to obtain a better understanding of the relation between the weld pool geometry, the stress distribution and the solidification cracking, a three-dimensional computational fluid dynamic (CFD) model was combined with a thermo-mechanical model. The CFD model was employed to analyze the flow of the molten metal in the weld pool during the laser beam welding process. The weld pool geometry estimated from the CFD model was used as a heat source in the thermal model to calculate the temperature field and the stress development and distributions. The CFD results showed a bulging region in the middle depth of the weld and two narrowing areas separating the bulging region from the top and bottom surface. The thermo-mechanical simulations showed a concentration of tension stresses, transversally and vertically, directly after the solidification during cooling in the region of the solidification cracking. T2 - 27TH INTERNATIONAL CONFERENCE ON METALLURGY AND MATERIALS - METAL 2018 CY - Brno, Czech Republic DA - 23.05.2018 KW - Laser beam welding KW - Weld pool KW - Full penetration KW - Finite element method (FEM) KW - CFD model KW - Numerical simulation KW - Solidification cracking PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-450595 DO - https://doi.org/10.3390/met8060406 SN - 2075-4701 VL - 8 IS - 6 SP - 406, 1 EP - 15 PB - MDPI CY - Basel, Switzerland AN - OPUS4-45059 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gumenyuk, Andrey A1 - Üstündag, Ö. A1 - Fritzsche, André A1 - Avilov, V. A1 - Rethmeier, Michael T1 - High power laser beam welding of thick materials using EM melt pool control N2 - Electromagnetic weld pool support system is illustrated successfully for hybrid laser arc welding of 20 -30 mm ferromagnetic Steels Welding of thick-walled steels in flat position and reduced welding velocities is possible Gap and misalignment between welded plates can be tolerated by use of this Technology Opportunity to reduce the laser beam power because of reduced welding velocity respectively increase of weldable material thickness with a 20 kW- fibre laser Mechanical properties of welds are in correspondence with requirements of Standards. T2 - SLT 2018 10. Stuttgarter Lasertage CY - Suttgart, Germany DA - 05.06.2018 KW - Hydrostatic and arc pressure exceed the Laplace pressure PY - 2018 AN - OPUS4-45229 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of solidification cracking susceptibility during laser beam welding using an in-situ observation technique N2 - In recent years, laser beam welding has found wide applications in many industrial fields. Solidification cracks are one of the most frequently encountered welding defects that hinder obtaining a safe weld joint. Decades of research have shown that one of the main causes of such cracks are the strain and the strain rate. Obtaining meaningful measurements of these strains has always been a major challenge for scientists, because of the specific environment of the measurement range and the many obstacles, as well as the high temperature and the plasma plume. In this study, a special experimental setup with a high-speed camera was employed to measure the strain during the welding process. The hot cracking susceptibility was investigated for 1.4301 stainless steel, and the critical strain required for solidification crack formation was locally and globally determined. KW - Solidification cracking KW - Laser welding KW - Optical measurement KW - In situ strain KW - Critical strain KW - Strain rate PY - 2018 DO - https://doi.org/10.1080/13621718.2017.1367550 SN - 1362-1718 SN - 1743-2936 VL - 23 IS - 3 SP - 234 EP - 240 PB - Taylor and Francis AN - OPUS4-43992 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Petrat, T. A1 - Graf, B. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Build-up Strategies for Laser Metal Deposition in Additive Manufacturing N2 - Laser Metal Deposition (LMD) as a technology for additive manufacturing allows the production of large components outside of closed working chambers. Industrial applications require a stable process as well as a constant deposition of the filler material in order to ensure uniform volume growth and reproducible mechanical properties. This paper deals with the influence of travel path strategies on temperature profile and material deposition. Meandering and spiral hatching strategies are used in the center as well as in the edge of a specimen. The temperature is measured with thermocouples attatched to the backside of the specimen. The tests are carried out on the materials S235JR and 316L. The results show a strong dependence of the maximum temperatures on the travel path strategy and the welding position on the component. T2 - Fraunhofer Direct Digital Manufacturing Conference (DDMC) CY - Berlin, Germany DA - 14.03.2018 KW - Additive Manufacturing KW - Temperature behavior KW - Laser Metal Deposition KW - Stainless Steel KW - 316L KW - Edge effects PY - 2018 SN - 978-3-8396-1320-7 VL - 1 SP - 1 EP - 6 PB - Fraunhofer-Gesellschaft CY - München AN - OPUS4-44719 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Graf, B. A1 - Marko, A. A1 - Petrat, T. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - 3D laser metal deposition: process steps for additive manufacturing N2 - Laser metal deposition (LMD) is an established technology for two-dimensional surface coatings. It offers high deposition rates, high material flexibility, and the possibility to deposit material on existing components. Due to these features, LMD has been increasingly applied for additive manufacturing of 3D structures in recent years. Compared to previous coating applications, additive manufacturing of 3D structures leads to new challenges regarding LMD process knowledge. In this paper, the process steps for LMD as additive manufacturing technology are described. The experiments are conducted using titanium alloy Ti-6Al-4Vand Inconel 718. Only the LMD nozzle is used to create a shielding gas atmosphere. This ensures the high geometric flexibility needed for additive manufacturing, although issues with the restricted size and quality of the shielding gas atmosphere arise. In the first step, the influence of process parameters on the geometric dimensions of single weld beads is analyzed based on design of experiments. In the second step, a 3D build-up strategy for cylindrical specimen with high dimensional accuracy is described. Process parameters, travel paths, and cooling periods between layers are adjusted. Tensile tests show that mechanical properties in the as-deposited condition are close to wrought material. As practical example, the fir-tree root profile of a turbine blade is manufactured. The feasibility of LMD as additive technology is evaluated based on this component. KW - Laser metal deposition KW - Build-up strategy KW - Deposition rate KW - Additive manufacturing PY - 2018 DO - https://doi.org/10.1007/s40194-018-0590-x SN - 0043-2288 SN - 1878-6669 VL - 62 IS - 4 SP - 877 EP - 883 PB - Springer Berlin Heidelberg CY - Heidelberg AN - OPUS4-44868 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Pavlov, V.A. A1 - Zavialov, S.V. A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Development of a measuring technology of strain field in welds N2 - In the article considered the problem of hot cracks occurrence during laser welding process. The main reason of their appearance is strain. The optical method for measuring full field strain locally near the solidification front during laser welding process is proposed. The proposed method of optical measurement allows to determine the real values of the critical strain for various materials characterizing the occurrence of hot cracks in laser welding process. T2 - 20th international conference "Digital signal processing and applications DSPA-2018" CY - Moskau, Russia DA - 28.03.2018 KW - Solidification cracking KW - Critical strain KW - Strain rate KW - Optical measurement KW - Laser welding KW - In situ strain PY - 2018 SN - 978-5-905278-33-4 SP - 749 EP - 754 AN - OPUS4-44910 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 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 - TY - JOUR A1 - Artinov, Antoni A1 - Bakir, Nasim A1 - Bachmann, Marcel A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Weld pool shape observation in high power laser beam welding N2 - The geometry of the melt pool in laser beam welding plays a major role to understand the dynamics of the melt and its solidification behavior. In this study, a butt configuration of 15 mm thick structural steel and transparent quartz glass was used to observe the weld pool geometry by means of high-speed camera and an infrared camera recording. The observations show that the dimensions of the weld pool vary depending on the depth. The areas close to the weld pool surface take a teardrop-shape. A bulge-region and its temporal evolution were observed approximately in the middle of the depth of the weld pool. Additionally, a 3D transient thermal-fluid numerical simulation was performed to obtain the weld pool shape and to understand the formation mechanism of the observed bulging effect. The model takes into account the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature. The numerical results showed good accordance and were furthermore used to improve the understanding of the experimentally observed bulging effect. T2 - LANE Conference 2018 CY - Fürth, Germany DA - 03.09.2018 KW - High power laser beam welding KW - Weld pool shape KW - Bulging KW - Numerical process simulation PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-458759 DO - https://doi.org/10.1016/j.procir.2018.08.043 SN - 2212-8271 VL - 74 SP - 683 EP - 686 PB - Elsevier Ltd. CY - Amsterdam [u.a.] AN - OPUS4-45875 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündağ, Ö. A1 - Fritzsche, André A1 - Avilov, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Hybrid laser-arc welding of thick-walled ferromagnetic steels with electromagnetic weld pool support N2 - The hybrid laser-arc welding (HLAW) process provides many advantages over laser welding and arc welding alone, such as high welding speed, gap bridgeability, and deep penetration. The developments in hybrid laser-arc welding technology using modern high-power lasers allow single-pass welding of thick materials. This technology can be used for the heavy metal industries such as shipbuilding, power plant fabrication, and line-pipe manufacturing. The obvious problem for single-pass welding is the growth of the hydrostatic pressure with increasing thickness of materials leading to drop-out of molten metal. This phenomenon is aggravated at slow welding velocities because of increasing weld seam width followed by a decrease of Laplace pressure compensating the hydrostatic pressure. Therefore, weld pool support is necessary by welding of thick materials with slow welding velocities. The innovative electromagnetic weld pool support system is contactless and has been used successfully for laser beam welding of aluminum alloys and austenitic and ferromagnetic steels. The support system is based on generating Lorentz forces within the weld pool. These are produced by an oscillating magnetic field orientated perpendicular to the welding direction. The electromagnetic weld pool support facilitates a decrease in the welding speed without a sagging and drop-out of the melt thus eliminating the limitations of weldable material thickness. KW - Hybrid laser-arc welding KW - Thick-walled steel KW - Electromagnetic weld pool support KW - Ferromagnetic steels KW - High-power laser beam PY - 2018 DO - https://doi.org/10.1007/s40194-018-0597-3 SN - 1878-6669 VL - 62 IS - 4 SP - 767 EP - 774 PB - Springer AN - OPUS4-46825 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ö. A1 - Fritzsche, André A1 - Avilov, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Study of gap and misalignment tolerances at hybrid laser arc welding of thick-walled steel with electromagnetic weld pool support system N2 - The hybrid laser arc welding (HLAW) process provides many advantages such as improved gap bridgeability, deep penetration and misalignment of edges, that is why the process is used increasingly in industrial applications e.g. shipbuilding, power plant industry and line-pipe manufacturing. The obvious encountered problem for single pass welding in flat position is the gravity drop-out at low welding velocities. With the usage of an electromagnetic weld pool support system, which is based on generating Lorentz forces within the weld pool, wide seams followed by reduced welding velocities could be achieved in this study leading to the realization of a gap bridgeability up to 1 mm, misalignment of edges up to 2 mm and a single pass weld up to 28 mm thickness with a 20-kW fibre laser. These developments expand the boundaries of the HLAW process for different industrial applications. As a result, less accurate preparation of the edges would be sufficient, which saves time for manufacturing. KW - Hybrid laser-arc welding KW - Electromagnetic weld pool support system KW - Thick-walled steel KW - Gap bridgeability KW - Single pass welding KW - Misalignment of edges PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-468263 DO - https://doi.org/10.1016/j.procir.2018.08.016 SN - 2212-8271 VL - 74 SP - 757 EP - 760 PB - Elsevier AN - OPUS4-46826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ö. A1 - Avilov, V. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Full penetration hybrid laser arc welding of up to 28 mm thick S355 plates using electromagnetic weld pool support N2 - The laser hybrid welding process offers many advantages regarding deep penetration, increased welding velocity and with the help of the supplied filler wire an improved bridgeability to gap and misalignment tolerances. High power laser systems with a power of approx. 30 kW are already available on the market. Nevertheless, multi-layer technology with an arc process is still used for welding of plates from a thickness from 20 mm. A potential cause is the process instability with increasing laser power. It is inevitable that gravity drop-out due to the high hydrostatic pressure at increasing wall thickness especially at welding in flat position and with a low welding speed. The surface tension decreases with increasing root width resulting from low welding velocities. To prevent such inadmissible defects of the seam a use of weld pool support is required. Usual weld pool support systems such as ceramic or powder supports require a mechanical detachment which is time-consuming. The electromagnetic weld pool support system described in this work shows an alternative weld pool support which works contactless. It is based on generating Lorentz forces in the weld pool due to oscillating magnetic field and induced eddy currents. This innovative technology offers single pass welds up to 28 mm in flat position and reduced welding velocity with a laser power of just 19 kW. It also leads to improved mechanical-technological properties of the seams because of the slow cooling rate. With usage of an electromagnetic weld pool support the limitation of the hybrid laser arc welding process in the thick sheet metal will be extend. KW - Electromagnetic weld pool support KW - Hybrid laser arc welding KW - Thick-walled steel KW - Single pass welding PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-468276 DO - https://doi.org/10.1088/1742-6596/1109/1/012015 SN - 1742-6596 VL - 1109 SP - 1 EP - 7 PB - IOP Publ. AN - OPUS4-46827 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -