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 - 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 - JOUR A1 - Sproesser, G. A1 - Chang, Y.-J. A1 - Pittner, Andreas A1 - Finkbeiner, M. A1 - Rethmeier, Michael T1 - Environmental energy efficiency of single wire and tandem gas metal arc welding N2 - This paper investigates gas metal arc welding (GMAW) with respect to energy consumption and its associated environmental impacts. Different material transfer modes and power levels for single wire GMAW (SGMAW) and tandem GMAW (TGMAW) are evaluated by means of the indicator electrical deposition efficiency. Furthermore, the wall-plug efficiency of the equipment is measured in order to describe the total energy consumption from the electricity grid. The results show that the energy efficiency is highly affected by the respective process and can be significantly enhanced by a TGMAW process. The wall-plug efficiency of the equipment shows no significant dependency on the power range or the material transfer mode. Moreover, the method of life cycle assessment (LCA) is adopted in order to investigate the influences of energy efficient welding on the environmental impacts. In the comparative LCA study, the demand of electrical energy is reduced up to 24%. In consequence, the indicator values for global warming potential (100), acidification potential, eutrophication potential, and photochemical ozone creation potential are reduced up to 11%. KW - Energy input KW - Tandem welding KW - MAG welding KW - Environment KW - Lifetime PY - 2017 DO - https://doi.org/10.1007/s40194-017-0460-y SN - 0043-2288 SN - 1878-6669 VL - 61 IS - 4 SP - 733 EP - 743 PB - Springer CY - Heidelberg AN - OPUS4-39877 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 - 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 - JOUR A1 - Sproesser, Gunther A1 - Chang, Y.-J. A1 - Pittner, Andreas A1 - Finkbeiner, M. A1 - Rethmeier, Michael T1 - Life cycle assessment of welding technologies for thick metal plate welds N2 - Life Cycle Assessment (LCA) is applied in evaluating environmental impacts of state-of-the-art welding technologies. Manual Metal Arc Welding (MMAW), Laser Arc-Hybrid Welding (LAHW) and two Gas Metal Arc Welding (GMAW) variants are used to join a plate of 20 mm thick structural steel. The LCA results indicate that for 1 m weld seam, MMAW causes the highest environmental impacts in global warming potential (GWP), eutrophication potential (EP), acidification potential (AP), and photochemical ozone creation potential (POCP) among the selected processes, and the LAHW variant performances the least. Filler material and electricity consumptions generally dominate the impacts and reach shares of up to 80% and 61% in the respective impact categories. However, electrode coating consumption in MMAW remarkably contributes impacts on AP and EP, for instance 52% of AP and 76% of EP. Strategies for improvement of the applied welding technologies are discussed. KW - Life Cycle Assessment (LCA) KW - Arc welding KW - Laser arc-hybrid welding KW - Resource efficiency PY - 2015 DO - https://doi.org/10.1016/j.jclepro.2015.06.121 SN - 0959-6526 VL - 108 IS - Part: A SP - 46 EP - 53 PB - Elsevier Science CY - Amsterdam AN - OPUS4-34969 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bachmann, Marcel A1 - Avilov, Vjaceslav A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Numerical 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 - JOUR A1 - Pittner, Andreas A1 - Schwenk, Christopher A1 - Rethmeier, Michael A1 - Weiß, D. T1 - Automated generation of temperature fields for numerical welding simulation KW - Welding simulation KW - Temperature field generation KW - Optimization KW - Neural networks PY - 2009 SN - 0288-4771 VL - 27 IS - 2 SP - 219 EP - 224 CY - Tokyo, Japan AN - OPUS4-19826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grünenwald, S. A1 - Seefeld, T. A1 - Vollertsen, F. A1 - Gook, Sergej A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laserstrahl-MSG-Hybridschweißen dicker Bleche aus Rohrleitungsstahl mit Faserlasern hoher Leistung N2 - In diesem Beitrag werden die Ergebnisse aus einem gemeinschaftlich durchgeführten Forschungsprojekt zur Schweißeignung unlegierter Stähle mit Laserstrahl- und Lichtbogenschweißverfahren vorgestellt. Es wurden Schweißversuche in Ein- sowie Mehrlagentechnik mit Blechdicken von 16, 20 und 28 mm durchgeführt sowie die Prozessgrenzen für die Spaltüberbrückbarkeit, den Kantenversatz und das Schweißen in Zwangspositionen untersucht. Für die Schweißversuche kamen Faserlaser mit Leistungen von 8, 20 und 30 kW in Verbindung mit einem MAG-Schweißprozess als Laserstrahl-MSG-Hybridschweißen zum Einsatz. Mit dem 30-kW-Faserlaser war es möglich, 28 mm dicke Bleche einlagig zu schweißen, jedoch besteht weiterer Forschungsbedarf, um Aussagen über die erreichbare Qualität treffen zu können. Bei 20 kW Laserstrahlleistung wurde zum einlagigen Schweißen von Blechen mit einer Dicke von 20 mm eine entsprechende Nahtvorbereitung benötigt, 16 mm dicke Bleche konnten dagegen ohne Vorbereitung der Naht im Stumpfstoß geschweißt werden. In der Mehrlagentechnik wurden mit dem 8-kW-Faserlaser 16 mm dicke Bleche vorbereitet mit einer Y-Naht geschweißt. Hierbei wurde die Wurzellage hybrid geschweißt, die Füll- und Decklagen mit einem reinen MAG-Prozess. PY - 2010 SN - 0036-7184 VL - 62 IS - 6 SP - 338 EP - 347 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-21810 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gook, Sergej A1 - Gumenyuk, Andrey A1 - Lammers, Marco A1 - Rethmeier, Michael T1 - Peculiarities of the process of orbital laser-arc welding of thick-walled large-diameter pipes KW - Hybrid laser-arc welding KW - Orbital welding KW - High-pressure pipelines KW - Fibre-optic lasers PY - 2010 SN - 0005-111x SN - 0005-2302 VL - 689 IS - 9 SP - 5 EP - 13 CY - Kiev, Ukraine AN - OPUS4-22979 LA - rus AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weber, Gert A1 - Thommes, H. A1 - Gaul, Holger A1 - Hahn, O. A1 - Rethmeier, Michael T1 - Resistance spot welding and weldbonding of advanced high strength steels KW - Resistance spot welding KW - High strength steel KW - Weldbonding KW - Widerstandspunktschweißen KW - Hochfester Stahl KW - Punktschweißkleben PY - 2010 DO - https://doi.org/10.1002/mawe.201000687 SN - 0933-5137 SN - 1521-4052 VL - 41 IS - 11 SP - 931 EP - 939 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-22948 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Distortion optimisation of beam-welded industrial parts by means of numerical welding simulation KW - Distortion KW - Optimisation KW - Weld plan modification KW - Industrial parts KW - Automotive application KW - Numerical welding simulation KW - Laser beam welding KW - Electron beam welding KW - Finite element analysis KW - FEA PY - 2010 SN - 1741-8410 SN - 1741-8429 VL - 5 IS - 4/5 SP - 412 EP - 422 PB - Inderscience Enterprises Ltd CY - Genève, Switzerland AN - OPUS4-22705 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pittner, Andreas A1 - Weiß, D. A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Methodology to improve applicability of welding simulation N2 - The objective of this paper is to demonstrate a new simulation technique which allows fast and automatic generation of temperature fields as input for subsequent thermomechanical welding simulation. The basic idea is to decompose the process model into an empirical part based on neural networks and a phenomenological part that describes the physical phenomena. The strength of this composite modelling approach is the automatic calibration of mathematical models against experimental data without the need for manual interference by an experienced user. As an example for typical applications in laser beam and GMA-laser hybrid welding, it is shown that even 3D heat conduction models of a low complexity can approximate measured temperature fields with a sufficient accuracy. In general, any derivation of model fitting parameters from the real process adds uncertainties to the simulation independent of the complexity of the underlying phenomenological model. The modelling technique presented hybridises empirical and phenomenological models. It reduces the model uncertainties by exploiting additional information which keeps normally hidden in the data measured when the model calibration is performed against few experimental data sets. In contrast, here the optimal model parameter set corresponding to a given process parameter is computed by means of an empirical submodel based on relatively large set of experimental data. The approach allows making a contribution to an efficient compensation of modelling inaccuracies and lack of knowledge about thermophysical material properties or boundary conditions. Two illustrating examples are provided. KW - Welding simulation KW - GMA-laser hybrid welding KW - Laser beam welding KW - Neural networks KW - Global optimisation KW - Stochastic search method KW - Inverse heat conduction problem KW - Model prediction PY - 2008 DO - https://doi.org/10.1179/136217108X329322 SN - 1362-1718 SN - 1743-2936 VL - 13 IS - 6 SP - 496 EP - 508 PB - Maney CY - London AN - OPUS4-18300 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Karkhin, Victor A1 - Pittner, Andreas A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Simulation of inverse heat conduction problems in fusion welding with extended analytical heat source models N2 - The paper presents bounded volume heat sources and the corresponding functional-analytical expressions for the temperature field. The power density distributions considered here are normal, exponential and parabolic. The sources model real heat sources like the welding arc, laser beam, electron beam, etc., the convection in the weld pool as well as the latent heat due to fusion and solidification. The parameters of the heat source models are unknown a priori and have to be evaluated by solving an inverse heat conduction problem. The functional-analytical technique for calculating 3D temperature fields in butt welding is developed. The proposed technique makes it possible to reduce considerably the total time for data input and solution. It is demonstrated with an example of laser beam welding of steel plates. KW - Laser beam welding KW - Volume heat source KW - Functional-analytical solution KW - Inverse modelling PY - 2011 DO - https://doi.org/10.1007/s11706-011-0137-1 SN - 2095-025X SN - 2095-0268 VL - 5 IS - 2 SP - 119 EP - 125 PB - Springer CY - Secaucus, N.J. AN - OPUS4-24164 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gaul, Holger A1 - Weber, Gert A1 - Rethmeier, Michael T1 - Influence of HAZ cracks on fatigue resistance of resistance spot welded joints made of advanced high strength steels N2 - A method is reported with which heat affected zone (HAZ) cracks in a specific region of spot welded joints, made of advanced high strength steels, could be realised. The influence of HAZ cracks on the fatigue behaviour, which is the focus of the contribution, was studied by evaluating the stiffness characteristics as a function of the number of cycles N in comparison with crack-free specimens, i.e. by analysing HAZ and fatigue cracks on the specimen surface and the surface of fatigue fractures containing beach marks. It was found that the fatigue cracks are not initiated at the HAZ cracks. The number of cycles to failure Nf is not significantly reduced for specimens with HAZ cracks. Overall, the examinations did not reveal any influence of HAZ cracks on the fatigue strength of resistance spot welded joints. KW - Discontinuities KW - AHSS KW - HAZ crack KW - Spot welding KW - Advanced high strength steels KW - Fatigue PY - 2011 DO - https://doi.org/10.1179/1362171810Y.0000000031 SN - 1362-1718 SN - 1743-2936 VL - 16 IS - 5 SP - 440 EP - 445 PB - Maney CY - London AN - OPUS4-24214 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pittner, Andreas A1 - Weiß, D. A1 - Schwenk, Christopher A1 - Rethmeier, Michael T1 - Fast temperature field generation for welding simulation and reduction of experimental effort N2 - The quality of welding processes is governed by the occurring induced distortions yielding an increase in production costs due to necessary reworking. Especially for more complex specimens, it is difficult to evaluate the optimal configuration of welding sequences in order to minimize the distortion. Even experienced welding operators can solve this task only by trial and error which is time and cost consuming. In modern engineering the application of welding simulation is already known to be able to analyse the heat effects of welding virtually. However, the welding process is governed by complex physical interactions. Thus, recent weld thermal models are based on many simplifications. The state of the art is to apply numerical methods in order to solve the transient heat conduction equation. Therefore, it is not possible to use the real process parameters as input for the mathematical model. The model parameters which allow calculating a temperature field that is in best agreement with the experiments cannot be defined directly but inversely by multiple simulations runs. In case of numerical simulation software based on finite discretization schemes this approach is very time consuming and requires expert users. The weld thermal model contains an initial weakness which has to be adapted by finding an optimal set of model parameters. This process of calibration is often done against few experiments. The range of model validity is limited. An extension can be obtained by performing a calibration against multiple experiments. The focus of the paper is to show a combined modelling technique which provides an efficient solution of the inverse heat conduction problem mentioned above. On the one hand the inverse problem is solved by application of fast weld thermal models which are closed form solutions of the heat conduction equation. In addition, a global optimization algorithm allows an automated calibration of the weld thermal model. This technique is able to provide a temperature field automatically that fits the experimental one with high accuracy within minutes on ordinary office computers. This fast paradigm permits confirming the application of welding simulation in an industrial environment as automotive industry. On the other hand, the initial model weakness is compensated by calibrating the model against multiple experiments. The unknown relationship between model and process parameters is approximated by a neural network. The validity of the model is increased successively and enables to decrease experimental effort, For a test case, it is shown that this approach yields accurate temperature fields within very short amount of time for unknown process parameters as input data to the model contributing to the requirement to construct a substitute system of the real welding process. KW - Heat flow KW - Neural networks KW - Simulating KW - Temperature KW - Welding PY - 2011 SN - 0043-2288 SN - 1878-6669 VL - 55 IS - 09-10 SP - 83 EP - 90 PB - Springer CY - Oxford AN - OPUS4-24603 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schempp, Philipp A1 - Schwenk, Christopher A1 - Rethmeier, Michael A1 - Cross, C.E. T1 - Weld metal grain refinement of aluminium alloy 5083 through controlled additions of Ti and B N2 - Kornfeinung im Schweißgut kann die mechanischen Eigenschaften der Schweißnaht und die Schweißeignung des Grundwerkstoffs deutlich verbessern. Eine Möglichkeit korngefeintes Schweißgut zu erreichen, ist das Versetzen des Schmelzbades mit kornfeinenden Mitteln. In dieser Studie wird gezeigt wie Titan- und Borzusätze Korngröße und -struktur von WIG-Schweißnähten der Al-Legierung 5083 (Al Mg4,5Mn0,7) beeinflussen. Dazu wurden in einem Gießprozess stäbchenförmige Einlagen hergestellt, die aus Grundwerkstoff und definierten Zusätzen der Kornfeinungslegierung Al Ti5B1 bestanden. Sie wurden als Ersatz für einen Schweißzusatzwerkstoff in einer Nut im Grundwerkstoff untergebracht und im WIG-Verfahren überschweißt. Durch die Steigerung des Titan- und Borgehalts im Schweißgut konnte dessen mittlere Korngröße deutlich verringert werden. Außerdem wurde eine Änderung der Kornstruktur beobachtet. Die Ergebnisse können als Grundlage genutzt werden, um die empfohlene chemische Zusammensetzung von Schweißzusätzen für Lichtbogenschweißen von Aluminium anzupassen. KW - Aluminium-Legierung 5083 KW - Kornfeinung KW - WIG-Schweißen PY - 2011 DO - https://doi.org/10.3139/120.110265 SN - 0025-5300 VL - 53 IS - 10 SP - 604 EP - 609 PB - Hanser CY - München AN - OPUS4-24654 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinze, Christoph A1 - Michael, Thomas A1 - Pittner, Andreas A1 - Rethmeier, Michael T1 - Schwierigkeiten bei der Anwendung der aktuellen Normung in Bezug auf Mikrorisse in Schweißverbindungen hochfester vergüteter Feinkornbaustähle N2 - Die aktuelle Normung bezüglich mikroskopischer Untersuchungen von Schweißverbindungen und die Zulässigkeit von Mikrorissen sowie deren Definition ist nicht eindeutig. Nach der Darstellung derzeit gültiger Normen im Bereich der Bewertung von Schweißnähten, Qualifizierung von Schweißverfahren und Ausführung von Schweißverbindungen, wird auf Grundlage aktueller Schweißversuche an hochfesten vergüteten Feinkornbaustählen die Problematik von Mikrorissen diskutiert. Offene Punkte und Fragen bzw. Verbesserungsmöglichkeiten werden aufgezeigt und zur Diskussion gestellt. Schließlich wird auf die Klärung des Einflusses von Mikrorissen auf die mechanisch- technologischen Werkstoffkennwerte der Schweißverbindung unter statischer sowie zyklischer Beanspruchung hingewiesen. --------------------------------------------------------------------------------------------------------------------------------------------------------------- Neither the latest standardisation with regard to microscopic investigations on welded joints nor the permissibility of microcracks and their definition are unambiguous. According to the representation of currently applicable standards in the fields of the assessment of welds, the qualification of welding processes and the execution of welded joints, the problems associated with microcracks are discussed on the basis of the latest welding tests on high-strength quenched-and-tempered fine-grained structural steels. Not only outstanding points and questions but also improvement possibilities are indicated and opened for discussion. Finally, attention is drawn to the clarification of the influence of microcracks on the mechanical- technological material parameters of the welded joint subjected to both static and cyclic stresses. KW - Festigkeit KW - Hochfester Stahl KW - Normen KW - Rissbildung KW - Schweißnahtfehler KW - Werkstofffragen KW - Strength KW - High-strength steel KW - Standards KW - Crack formation KW - Weld defects KW - Material questions PY - 2012 SN - 0036-7184 VL - 64 IS - 7 SP - 412 EP - 416 PB - Verl. für Schweißen u. Verwandte Verfahren, DVS-Verl. CY - Düsseldorf AN - OPUS4-26338 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinze, Christoph A1 - Pittner, Andreas A1 - Rethmeier, Michael A1 - Babu, S. S. T1 - Dependency of martensite start temperature on prior austenite grain size and its influence on welding-induced residual stresses N2 - Austenite grain growth during welding is a critical factor for controlling weld microstructure in addition to nominal composition and thermal cycles. Recently, experimental data suggesting a decrease in martensite start temperature with a decrease in prior austenite grain size has been published. However, the actual sensitivity of this phenomenon on residual stresses evolution in the heat-affected zone has not been investigated, yet. Therefore, a numerical model was modified to consider this phenomenon. Numerical simulations were performed for welding of a low-alloy structural steel with minimum yield strength of 355 MPa (S355J2+N) and a heat-resistant steel P91 or 9Cr–1Mo, respectively. The results clarify the influence of prior austenite grain size on the residual stress development and show the importance martensite transformation temperatures and final martensite fraction. Consequently, the residual stress evolution of P91, which completely transforms to martensite while cooling, based on the enhanced model leads to maximum stress differences of 200 MPa in the heat-affected zone. KW - Prior austenite grain size KW - Martensite start temperature KW - Welding-induced residual stress KW - Numerical simulation KW - Gas metal arc welding PY - 2013 DO - https://doi.org/10.1016/j.commatsci.2012.11.058 SN - 0927-0256 VL - 69 SP - 251 EP - 260 PB - Elsevier CY - Amsterdam AN - OPUS4-27633 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kolkoori, Sanjeevareddy A1 - Höhne, Christian A1 - Prager, Jens A1 - Rethmeier, Michael A1 - Kreutzbruck, Marc T1 - Quantitative evaluation of ultrasonic C-scan image in acoustically homogeneous and layered anisotropic materials using three dimensional ray tracing method N2 - Quantitative evaluation of ultrasonic C-scan images in homogeneous and layered anisotropic austenitic materials is of general importance for understanding the influence of anisotropy on wave fields during ultrasonic non-destructive testing and evaluation of these materials. In this contribution, a three dimensional ray tracing method is presented for evaluating ultrasonic C-scan images quantitatively in general homogeneous and layered anisotropic austenitic materials. The directivity of the ultrasonic ray source in general homogeneous columnar grained anisotropic austenitic steel material (including layback orientation) is obtained in three dimensions based on Lamb's reciprocity theorem. As a prerequisite for ray tracing model, the problem of ultrasonic ray energy reflection and transmission coefficients at an interface between (a) isotropic base material and anisotropic austenitic weld material (including layback orientation), (b) two adjacent anisotropic weld metals and (c) anisotropic weld metal and isotropic base material is solved in three dimensions. The influence of columnar grain orientation and layback orientation on ultrasonic C-scan image is quantitatively analyzed in the context of ultrasonic testing of homogeneous and layered austenitic steel materials. The presented quantitative results provide valuable information during ultrasonic characterization of homogeneous and layered anisotropic austenitic steel materials. KW - Ultrasonic non-destructive evaluation KW - Ultrasonic C-scan image KW - Anisotropic austenitic steel KW - 3D ray tracing KW - Directivity PY - 2014 DO - https://doi.org/10.1016/j.ultras.2013.08.007 SN - 0041-624x VL - 54 IS - 2 SP - 551 EP - 562 PB - Elsevier CY - Amsterdam AN - OPUS4-29733 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -