TY - CONF A1 - Schröpfer, Dirk T1 - Fachvortrag: Innovative Probenherstellungim Lichte der Proben-Bauteil-Beziehungen N2 - Der Vortrag erörtert die aktuellen fachlichen Herausforderungen und Ziele in der Zentralwerkstatt/FB9.2 der BAM für den Helmholtz-AK "Bau wissenschaftlicher Geräte" T2 - Helmholtz-Arbeitskreis "Bau wissenschaftlicher Geräte", 18. Jahrestagung CY - Berlin, Germany DA - 10.05.2023 KW - Probenfertigung KW - Erneuerbare Energien KW - Additive Fertigung KW - Wasserstoff-Sicherheit PY - 2023 AN - OPUS4-59263 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Beanspruchungen bei der Fertigung hochfester Komponenten N2 - Hochfeste und -warmfeste Legierungen nehmen in vielen Bereichen des Maschinen- und Anlagenbaus eine immer größere Rolle ein, deren Wirtschaftlichkeit und Effizienz durch eine kostensparende und präzise fügetechnische und abtragende Fertigung bestimmt wird. Komponenten aus modernen hochfesten Werkstoffen erfordern aufgrund ihres spezifischen Legierungskonzeptes und Gefüges und der oft hohen thermo-mechanischen Belastungen speziell adaptierte Fertigungsabläufe. Der Beitrag stellt einige Themenschwerpunkte vor, bei denen fertigungsbedingte Beanspruchungen und Eigenschaftsdegradationen an hochinnovativen Werkstoffen optimiert und wirtschaftliche Fertigungsbedingungen untersucht werden. T2 - Forschungsseminar OVGU CY - Magdeburg, Germany DA - 15.11.2018 KW - Eigenspannungen KW - MAG-Schweißen KW - Hochfeste Feinkornbaustähle KW - Bauteilprüfung KW - Zerspanung KW - HEA KW - Hochtemperaturwerkstoffe PY - 2018 AN - OPUS4-46608 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Beanspruchungen bei der Fertigung hochfester Komponenten N2 - Hochfeste und -warmfeste Legierungen nehmen in vielen Bereichen des Maschinen- und Anlagenbaus eine immer größere Rolle ein, deren Wirtschaftlichkeit und Effizienz durch eine kostensparende und präzise fügetechnische und abtragende Fertigung bestimmt wird. Komponenten aus modernen hochfesten Werkstoffen erfordern aufgrund ihres spezifischen Legierungskonzeptes und Gefüges und der oft hohen thermo-mechanischen Belastungen speziell adaptierte Fertigungsabläufe. Der Beitrag stellt einige Themenschwerpunkte vor, bei denen fertigungsbedingte Beanspruchungen und Eigenschaftsdegradationen an hochinnovativen Werkstoffen optimiert und wirtschaftliche Fertigungsbedingungen untersucht werden. T2 - Forschungsseminar, Access, Aachen CY - Aachen, Germany DA - 19.11.2018 KW - Bauteilprüfung KW - Eigenspannungen KW - Hochfeste Feinkornbaustähle KW - HEA KW - Hochtemperaturwerkstoffe KW - MAG-Schweißen KW - Zerspanung PY - 2018 AN - OPUS4-47723 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Beanspruchungsgerechtes ultraschallunterstütztes Fräsen Generativ gefertigter Turbinenbauteile N2 - Die Beschaffung und Verarbeitung von Werkstoffen für hochbelastete Komponenten sind meist kostenintensiv. Bestrebungen zur Kosten- und Ressourceneffizienz führen zu komplexeren Strukturen bzw. Konturen, sodass generative Fertigungsschritte zur Bauteilreparatur und -fertigung deutliche ökonomische Vorteile bieten. Hierfür sind generative und abtragende Fertigungsschritte komplementär und gezielt aufeinander abzustimmen, um beanspruchungsgerechte Funktionsflächen herzustellen. T2 - Forschungsseminar, TU Clausthal (ISAF) CY - Clausthal-Zellerfeld, Germany DA - 31.01.2018 KW - Eigenspannungen KW - Auftragschweißen KW - Zerspanung KW - Ultraschallunterstütztes Fräsen KW - Generative Fertigung PY - 2018 AN - OPUS4-47724 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Neues aus der BAM / Fachbereich 9.2 N2 - In dieser Präsentation werden die neuesten Herausforderungen und der Stand des Fachbereiches 9.2 für die Mitarbeit im AK des HGF "Bau wissenschaftlicher Geräte" dargestellt. Hierfür werden Neuigkeiten aus dem Bereich Materialprüfung in der BAM präsentiert und mit den Arbeiten der Zentralwerkstatt, die hierfür notwendig sind, in Zusammenhang gebracht. T2 - Helmholtz-Arbeitskreis "Bau wissenschaftlicher Geräte" CY - Berlin, Germany DA - 12.06.2024 KW - Fertigungsverfahren KW - Fertigungskompetenz PY - 2024 AN - OPUS4-62293 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Helmholtz-AK "Bau wissenschaftlicher Geräte" - Neues aus der BAM / Fachbereich 9.2 N2 - In dieser Präsentation werden die neuesten Herausforderungen und der Stand des Fachbereiches 9.2 für die Mitarbeit im AK des HGF "Bau wissenschaftlicher Geräte" dargestellt. T2 - Helmholtz-Arbeitskreis "Bau wissenschaftlicher Geräte", 18. Jahrestagung CY - Berlin, Germany DA - 10.05.2023 KW - Werkstatt KW - Erneuerbare Energien PY - 2023 AN - OPUS4-59262 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Studies on the pore formation in super duplex stainless steel welds N2 - When welding super duplex stainless steels a non-admissible pore formation can occur even if recommended processing guidelines are followed strictly. To investigate this phenomenon and to determine the influencing factors different claddings were produced using gas metal arc welding and submerged arc welding. The welding consumables, the shielding gas and the welding flux were varied. As shielding gases several mixtures, based on argon and 30 % helium, with various amounts of nitrogen, nitric oxide, carbondioxid and oxygen were applied. As welding flux agglomerated fluoride basic fluxes and aluminate fluoride basic fluxes were used. Different batches of the similar solid filler wire G 25 9 4 N L were used to produce the claddings on the base material UNS32750. To determine the pore formation X-ray examinations and microsections were used, to analyze the chemical composition of the claddings melt extractions and spectrometric examinations were applied. Additionally, the microhardness and the ferrite number were detected. The studies have shown the shielding gas, the welding flux and the filler metal possess a great influence on the pore formation. Even small variations in the chemical composition of the welding consumables lead to totally different results. In addition, the ferrite number and the chemical composition of the claddings depend strongly on the used gases and filler metals. T2 - IIW Intermediate Meeting, C-IIA CY - Madrid, Spain DA - 29.02.2016 KW - Cladding KW - Welding KW - Duplex stainless steels KW - Pore formation PY - 2016 AN - OPUS4-38786 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Influence of the weld thermal cycle on residual stress evolution and cold cracking ressistance in welded high-strength steel constructions N2 - The application of high-strength fine-grained structural steels with yield stress ≥ 690 MPa permits significant weight reductions and cost savings. Since welding is the major joining technology, e.g. in mobile crane industry, the sustainable and economical application of these grades depends on the load-bearing capacity and safety of the welds. An economical processing of high-strength steels is determined above all by the avoidance of cold cracking, apart from achieving demand-oriented mechanical properlies in the weid area. High tensile residual stresses are disadvantageaus regarding the cold cracking resistance and strength of welded components. Furthermore, high restraints commonly appearing in component welds increase residual stresses. Hence, in this research the influences of heat control on residual stresses and the overall structural Ioad of welded structures were quantified. The relationship between the weid thermal cycle and the resulting residual stress under additional shrinkage restraint was analysed by a successive augmentation of the restraint intensity. This was achieved by systematic low Ioad and component weid tests. lt was observed that the heat control significantly affects the local residual stresses and the overall structural Ioad of welded structures. A high interpass temperature increases the global and local welding stresses in particular. Moreover, the transferability of experimental welding results obtained from small specimens according to applicable codes to real component geometries was investigated. With the help of these findings it is possible to improve existing heat control concepts for high-strength steel welding. T2 - 2nd METEC & ESTAD 2015 - European steel technology and application days conference CY - Düsseldorf, Germany DA - 15.06.2015 KW - Residual stresses KW - Welding KW - HEat control KW - GMAW KW - Restraint KW - High-strength steels KW - Cold cracking KW - MAG welding KW - Process parameters PY - 2015 SP - P668, 1 EP - 7 AN - OPUS4-34988 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Hamm, C. A1 - Röser, T. A1 - Michels, H. T1 - Vom Kokillenguss bis zur Fräsbearbeitung - Bauteile aus innovativen Eisen- und Titanaluminiden wirtschaftlich herstellen N2 - Der Beitrag gibt einen kurzen Einblick in das gerade bewilligte ZIM-Vorhaben „Technologie und Werkzeuge für ultraschallunterstütztes Fräsen von Eisen- und Titan-Aluminid-Bauteilen (TeWuFeAl)“. In dem Vorhaben wird durch 2 KMU aus dem Bereichen der Werkzeugentwicklung (Wolf GmbH) und der Anwendung (AWB GmbH) sowie durch 2 Forschungsinstitute, Access e. V. und Bundesanstalt für Materialforschung und -prüfung (BAM), die Herstellbarkeit sicherheitsrelevanter Leichtbauteile aus FeAl und TiAl durch das besonders wirtschaftliche Kokillengussverfahren und die anschließende ultraschallunterstützte Zerspanung untersucht. KW - Eisenaluminid KW - Titanaluminid KW - Kokillenguss KW - Fräsbearbeitung KW - Ultraschallunterstütztes Fräsen KW - Oberflächenintegrität PY - 2020 SP - 12 PB - Manufacturing Innovation Network e. V. CY - Varel, Germany AN - OPUS4-51593 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Reichel, Levin A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Modern welding processes for optimising repair welds on high strength offshore steels N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future. To achieve these high outputs, turbines far from coast are required with large subsea jacket structures (30 m up to 50 m) and tall towers (up to 200 m). High-strength steels with a yield strength up to 500 MPa and wall thicknesses up to 150 mm are increasingly being used for these structures. This plac-es high demands on welding manufacturing, especially for high-strength offshore steels. During the manu-facturing process detected defects by NDT require localized repair of welds by gouging and rewelding. Due to a lack of investigations, there are no repair concepts and information in standards and guidelines, par-ticularly for high-strength thick plate joints made of high-strength offshore steels. However, these are ur-gently needed to enable manufacturers, especially SMEs, to carry out safe and economical repairs. There-fore, BAM started the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal with controlled high-performance GMAW pro-cesses and optimized narrow gouging grooves. The experimental analyses take into account the complex interaction of process, material, and design-related influences on the formation of weld induced stresses and the special microstructure of high-strength fine-grain structural steels. Welding-related material degra-dation and crack-critical residual tensile stresses need to be avoided to ensure high component safety and performance. A reduction in residual stress in the presence of high restraint conditions can be achieved by adapted heat control (if no disassembly measures are possible). The repair process involves manual thermal gouging, which allows the groove configuration to be modi-fied. Modern welding processes using high frequency arc control provide deep root penetration and focused energy input capable of welding narrow seams. A comparison was made between the traditional weld con-figuration with a wide 45° groove and transition arc welding and a narrow 30° groove with modern welding process. Even in the case of free shrinkage specimens, the narrow groove weld exhibits a significant reduc-tion of residual stresses, cf. Figure 1, especially in the HAZ and toward the adjacent base material. This can be attributed to the lower weld metal volume needed and the reduction of heat input per layer due to the controlled arc process. For the purposes of this comparison, the same weld seam build-up (but different number of layers) has been applied to both seam configurations. Note that in industrial application (manu-al welding), the wider groove would be welded with several off-center weld beads with conventional weld-ing process. In this analysis this would cause asymmetric effects regarding the residual stress state, diffi-cult to compare to each other. Component-related welding experiments on special testing equipment, adapted process and heat control concepts along with variable groove configurations will be developed and recommendations for guidelines elaborated. This is the prerequisite for fully utilizing the strength potential of high-strength steels and making a valuable contribution to the energy transition in Germany, especially for steel-processing SMEs. T2 - IIW Intermediate Meeting CII CY - Trollhättan, Sweden DA - 10.03.2025 KW - Repair welding KW - Gouging KW - Residual stress KW - Offshore wind turbines KW - High-strength steels PY - 2025 AN - OPUS4-62743 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Findeisen, Dietmar A1 - Schröpfer, Dirk T1 - Energy efficiency in materials testing by reactive power part 2: resonance method in fatigue testing N2 - Reactive power is related to the type of power that does not consume energy but stores it. In the design of test machines, the utilization of this physical phenomenon would be very beneficial. Reactive power allows for the combination of power amplification with energy savings, making it an ideal principle for conducting long-term tests that involve high loads and prolonged energy consumption. This work focuses on testing machines operating in resonance, which allows for higher test frequencies and reduced test durations. Various types of fatigue testing machines, including those with rotating-unbalance actuators, servo-hydraulic actuators, and piezoelectric actuators, are examined through vibration analysis, methodical design, and mechatronics. Resonant testing machines provide significant advantages in energy efficiency and test accuracy for a wide range of applications in materials testing. These methods are crucial for future applications in industries where energy efficiency and precise fatigue testing are critical, such as aerospace, automotive, and civil engineering. KW - Reactive power KW - Amplitude magnification KW - Power amplification KW - Fatigue testing KW - Resonant test machines PY - 2024 DO - https://doi.org/10.1515/mt-2024-0350 SP - 1 EP - 11 PB - Walter de Gruyter GmbH AN - OPUS4-62356 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Findeisen, Dietmar A1 - Schröpfer, Dirk T1 - Energy efficiency in materials testing by reactive power – part 1: power recirculating method in wear testing N2 - Reactive power is related to the type of power that does not consume energy but stores it. In the design of test machines, the utilization of this physical phenomenon would be very beneficial. Reactive power allows for the combination of power amplification with energy savings, making it an ideal principle for conducting long-term tests that involve high loads and prolonged energy consumption. This concept is illustrated in this work focusing test machines used in rotary testing procedures. Drive element pairs, which serve as component test objects, are primarily exposed to wear stress. These stressed element pairs are consequently integral parts of a tribological system. The underlying principles of power amplification and power feedback are explained from the perspectives of drive technology, systematic design, methodical design, and mechatronics. KW - Reactive power KW - Power amplification KW - Power feedback KW - Wear testing KW - Strained element pairs PY - 2024 DO - https://doi.org/10.1515/mt-2023-0136 VL - 67 IS - 1 SP - 189 EP - 197 PB - Walter de Gruyter GmbH AN - OPUS4-62355 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Richter, Tim A1 - Delgado Arroyo, Diego A1 - Börner, Andreas A1 - Schröpfer, Dirk A1 - Rhode, Michael A1 - Lindner, T. A1 - Löbel, M. A1 - Preuß, B. A1 - Lampke, T. T1 - Ultrasonic assisted milling of a CoCrFeNi medium entropy alloy N2 - Medium and High Entropy Alloys (MEA/HEA) are recently developed material classes, providing manifold applications, e.g., due to extraordinary structural properties. In that connection, the machinability as important issue for the processing of these materials was not in the scientific focus. This study focusses on experimental analysis of milling process conditions including ultrasonic assisted milling (USAM) and their effects on the resulting surface integrity of equiatomic CoCrFeNi-MEA specimens. For that reason, milling parameters (cutting speed, feed per cutting edge) were systematically varied for both conventional milling and USAM. The surface integrity was analyzed in terms of topography, defects, and residual stresses. Especially USAM leads to a decrease of occurring cutting forces and, hence, to an improvement of the surface integrity. Beneficial effects were observed in terms of lower tensile residual stresses at high cutting speed and feed per cutting edge. KW - Medium entropy alloy KW - Ultrasonic Assisted Machining KW - Surface Integrity PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-554458 DO - https://doi.org/10.1016/j.procir.2022.05.203 VL - 108 SP - 879 EP - 884 PB - Elsevier B.V. AN - OPUS4-55445 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Rhode, Michael A1 - Wetzel, Annica A1 - Oczan, Ozlem A1 - Nietzke, Jonathan A1 - Richter, Tim A1 - Schröpfer, Dirk T1 - Corrigendum: Hydrogen diffusion and local Volta potential in high- and medium-entropy alloys (2020 IOP Conf. Ser.: Mater. Sci. Eng. 882 012015) N2 - In the sub-section “2.1 Investigated materials” the chemical composition of Co, Cr and Mn was in wrong order for both HEA and MEA. The content of table 1 is here included in the correct version. PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-527050 DO - https://doi.org/10.1088/1757-899X/882/1/012027 VL - 882 SP - 1 EP - 2 PB - IOP Publishing CY - Bristol AN - OPUS4-52705 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Erxleben, Kjell A1 - Richter, Tim A1 - Schröpfer, Dirk A1 - Mente, Tobias A1 - Michael, Thomas T1 - Local mechanical properties of dissimilar metal TIG welded joints of CoCrFeMnNi high entropy alloy and AISI 304 austenitic steel N2 - Multiple principal element alloys encompass the well-known high entropy alloys (HEA). The alloy system represents a new class of materials consisting of at least three alloying elements, each containing 5 to 35 at.%. Thus, this alloying concept differs fundamentally from conventional materials such as steel or nickel alloys. For this purpose, the alloying elements are specifically selected, the microstructures are adjusted in a single-phase and, in some cases, multi-phase manner. In particular, conflicting goals, such as the trade-off between strength and ductility in conventional steels, are overcome. However, in the last 20 years, the focus has been on material synthesis. With the increase in available material quantities, the focus is now on processing issues such as joining and welding processes. The weldability of HEAs has received very little attention so far. The experience with dissimilar metal welds is completely lacking but is essential for the application of these materials in combination with conventional materials. The present study presents comprehensive experimental results on the weldability of an equimolar CoCrFeMnNi-HEA in cold-rolled and heat-treated condition, which was joined by tungsten inert gas welding to an austenitic steel AISI 304. The mechanical properties of the dissimilar metal welds were characterized by cross-weld tensile samples, whereas the local deformation in the weld of the different welding zones was measured by digital image correlation. In accordance with the respective initial HEA condition (cold-rolled vs. heat-treated), the local strain behavior was divergent and influenced the global mechanical properties of both DMW types. Nonetheless, the experiments provided proof in principle of the weldability for dissimilar joints of the CoCrFeMnNi-HEA welded to conventional materials like austenitic stainless steels ensuring a corresponding capability for mechanical loading. This allows further considerations on the application of these innovative materials. KW - TIG welding KW - High-entropy alloys KW - Mechanical properties KW - Dissimilar metal weld PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-595775 DO - https://doi.org/10.1007/s40194-024-01718-4 SN - 0043-2288 SP - 1 EP - 11 PB - Springer Science and Business Media LLC AN - OPUS4-59577 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Richter, Tim A1 - Giese, Marcel A1 - Rhode, Michael A1 - Schröpfer, Dirk A1 - Michael, Thomas A1 - Fritsch, Tobias T1 - Influence of Surface Preparation on Cracking Phenomena in TIG-Welded High and Medium Entropy Alloys N2 - Multi-element systems with defined entropy (HEA—high entropy alloy or MEA—medium entropy alloy) are rather new material concepts that are becoming increasingly important in materials research and development. Some HEA systems show significantly improved properties or combinations of properties, e.g., the overcoming of the trade-off between high strength and ductility. Thus, the synthesis, the resulting microstructures, and properties of HEA have been primarily investigated so far. In addition, processing is crucial to achieve a transfer of potential HEA/MEA materials to real applications, e.g., highly stressed components. Since fusion welding is the most important joining process for metals, it is of vital importance to investigate the weldability of these materials. However, this has rarely been the subject of research to date. For that reason, in this work, the weldability depending on the surface preparation of a CoCrFeMnNi HEA and a CoCrNi MEA for TIG welding is investigated. The fusion welding of longer plates is described here for the first time for the CoCrNi alloy. The welds of both materials showed distinct formation of cracks in the heat affected Zone (HAZ). Optical and scanning electron microscopy analysis clearly confirmed an intergranular fracture topography. However, based on the results, the crack mechanism cannot be conclusively identified as either a liquid metal embrittlement (LME) or hot cracking-like liquid film separation. T2 - 2nd International Conference on Advanced Joining Processes CY - Sintra, Portugal DA - 21.10.2021 KW - TIG welding KW - Cracking KW - High entropy alloy KW - Medium entropy alloy KW - Surface preparation PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-541697 DO - https://doi.org/10.3390/jmmp6010005 SN - 2504-4494 VL - 6 IS - 5 SP - 1 EP - 13 PB - MDPI CY - Basel (CH) AN - OPUS4-54169 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Delgado Arroyo, Diego A1 - Richter, Tim A1 - Schröpfer, Dirk A1 - Boerner, Andreas A1 - Rhode, Michael A1 - Lindner, T. A1 - Preuß, B. A1 - Lampke, T. T1 - Influence of Milling Conditions on AlxCoCrFeNiMoy Multi-Principal-Element Alloys N2 - Multi-Principal-Element or High-Entropy Alloys (MPEAs/HEAs) have gained increasing interest in the past two decades largely due to their outstanding properties such as superior mechanical strength and corrosion resistance. However, research studies on their processability are still scarce. This work assesses the effect of different machining conditions on the machinability of these novel alloys, with the objective of advancing the introduction of MPEA systems into industrial applications. The present study focuses on the experimental analysis of finish-milling conditions and their effects on the milling process and resulting surface finish of CoCrFeNi, Al0.3CoCrFeNi and Al0.3CoCrFeNiMo0.2 alloys fabricated via Spark Plasma Sintering. Ball-nose-end milling experiments have been carried out various milling parameters such as cutting speed, feed per cutting edge, and ultrasonic assistance. In situ measurements of cutting forces and temperature on the tool edge were performed during the experiments, and surface finish and tool wear were analyzed afterwards. The results exhibited decreasing cutting forces by means of low feed per cutting edge and reduced process temperatures at low cutting speed, with the use of ultrasonic-assisted milling. It was shown that the machinability of these modern alloys through conventional, as well as modern machining methods such as ultrasonic-assisted milling, is viable, and common theories in machining can be transferred to these novel MPEAs. KW - Multi-principal element alloys KW - Finish milling KW - Spark plasma sintering KW - Ultrasonic-assisted milling KW - Microstructure characterization PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-572990 DO - https://doi.org/10.3390/coatings13030662 VL - 13 IS - 3 SP - 1 EP - 18 PB - MDPI (Multidisciplinary Digital Publishing Institute) CY - Basel (CH) AN - OPUS4-57299 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Buzolin, R.H. A1 - Richter, Tim A1 - Pixner, F. A1 - Rhode, Michael A1 - Schröpfer, Dirk A1 - Enzinger, N. T1 - Microstructure and texture characterisation of friction stir welded CoCrNi and CoCrFeMnNi multi-principle element alloys N2 - This work investigates the microstructure formed in friction stir welds of FCC alloys, focused on two multiprincipal alloys: a CoCrFeMnNi high-entropy alloy (HEA) and a CoCrNi medium-entropy alloy (MEA). A commercial stainless steel AISI 304 is used for comparison. The largest nugget was formed in the MEA, while the smallest was formed in the HEA. Grain refinement occurs in the stirred zone in all welds. Discontinuous dynamic recrystallisation is the predominant restoration mechanism during friction stir welding of the three investigated alloys. A sharp decrement in the Σ3 boundary fraction occurs in the stirred zone of the AISI 304 and HEA welds, while comparable values with the base metal are found for the MEA weld. The peak in the maximum index of crystallographic texture is observed on the advancing side of the stirred zone of the AISI 304 weld. A strong <001> θ-fibre texture is formed in the advancing side of the nugget in the AISI 304 from a well-established {123} <634> S-type texture in the base metal. Multiple crystallographic texture components without specific fibres are identified in most regions of the welds, indicating the complex shear path history during friction stir welding. KW - Microstructure KW - Multiple principal element alloy KW - Friction stir welding KW - Electron backscattered diffraction KW - Crystallographic texture PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-572987 DO - https://doi.org/10.1016/j.mtcomm.2023.105870 VL - 35 SP - 1 EP - 14 PB - Elsevier Ltd. CY - Amsterdam (NL) AN - OPUS4-57298 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Richter, Tim A1 - Diese, Marcel A1 - Rhode, Michael A1 - Schröpfer, Dirk T1 - Characterization of cracking phenomena in TIG welds of high and medium entropy alloy N2 - Multi-element systems with defined entropy (HEA - High Entropy Alloy or MEA - Medium Entropy Alloy) are rather new material concepts that are becoming increasingly important in materials research and development. Some HEA systems show significantly improved properties or combinations of properties, e.g., the overcome of the trade-off between high strength and ductility. Thus, the synthesis, the resulting microstructures, and properties of HEA have been primarily investigated so far. In addition, processing is crucial to achieve a transfer of potential HEA/MEA materials to real applications, e.g. highly stressed components. Since fusion welding is the most important joining process for metals, it is of vital importance to investigate the weldability of these materials. However, this has rarely been the subject of research up to date. For that reason, in this work the weldability depending on the surface preparation of a CoCrFeMnNi-HEA and a CoCrNi-MEA for TIG welding is investigated. The fusion welding of longer plates is described here for the first time for the CoCrNi alloy. The welds of both materials showed distinct formation of cracks in the heat affected zone (HAZ). Optical and scanning electron microscopy analysis clearly confirmed an intergranular fracture topography. But based on the results, the crack mechanism cannot be conclusively clarified as either a liquid metal embrittlement (LME) or hot cracking like liquid film separation occurred. T2 - 2nd International Conference on Advanced Joining Processes CY - Online meeting DA - 21.10.2021 KW - High Entropy Alloy KW - TIG welding KW - Cracking PY - 2021 AN - OPUS4-53607 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Formation of multi-axial welding stresses due to material behaviour during fabrication of high-strength steel components N2 - Today an expanding application of high-strength steels in modern welded constructions can be observed. The economical use of these steel grades largely depends on the strength and reliability of the weldments. Therefore the special microstructure and mechanical properties of these grades have to be taken into account by keener working ranges regarding the welding parameters. However, performance and safety of welded components are strongly affected by the stresses occurring during and after welding fabrication locally in the weld seam and globally in the whole component, especially if the shrinkage and distortion due to welding are restrained. Some extensive studies describe the optimization of the welding stresses and the metallurgical effects regarding an adapted welding heat control. In particular lower working temperatures revealed to be effective to significantly reduce the local and global welding induced residual stresses of the completed weld. However, decreased interpass temperatures cause concurrently higher stresses during welding fabrication. This work shows some strategies to reduce these in-process stresses. With help of multi-axial welding stress analyses in component-related weld tests using a special 2-MN-testing facility differences in stress build-up are described in detail for root welds, filler layers and subsequent cooling to ambient temperature. T2 - IIW Intermediate Meeting, C-II-A CY - Trollhättan, Sweden DA - 06.03.2017 KW - Residual stresses KW - GMA Welding KW - High-strength steels KW - Process parameters KW - Restraint PY - 2017 AN - OPUS4-41066 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Hensel, J. A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Einfluss von Wärmeführung und Bauteildesign auf die Eigenschaften und fertigungsbedingten Beanspruchungen additiv geschweißter hochfester Feinkornbaustähle N2 - Hochfeste Feinkornbaustähle verfügen über großes Potenzial für gewichtsoptimierte, effiziente Strukturen in vielen modernen Stahlkonstruktion. Weitere Effizienzsteigerungen können durch additives Fertigen sowie bionische Bauweisen erreicht werden. Hochfeste Zusatzwerkstoffe für additives MSG-Schweißen (engl.: Wire Arc Additive Manufacturing, WAAM) sind bereits von den Schweißzusatzherstellern lieferbar. Eine breite industrielle Anwendung insbesondere für KMU ist aufgrund fehlender quantitativer Erkenntnisse und Richtlinien bezüglich schweißbedingter Beanspruchungen und Bauteilsicherheit während der Herstellung und des Betriebs derzeit stark limitiert. In einem gemeinsamen Forschungsprojekt (FOSTA-P1380/IGF21162BG) der BAM und der TU Chemnitz werden daher die mit Eigenspannungsausbildung und der Gefahr einer Kaltrissbildung verbundenen prozess- und werkstoffbedingten sowie konstruktiven Einflüsse beim WAAM hochfester Stähle untersucht. Der vorliegende Beitrag fokussiert die Analyse der Auswirkungen von Schweißwärmeführung und Design der WAAM-Bauteile auf die Abkühlbedingungen, Gefüge, mechanisch-technologischen Eigenschaften und Eigenspannungen. Hierfür werden geometrisch definierte Probenkörper (Hohlquader) vollautomatisiert mit einem speziellen, hochfesten WAAM-Massivdraht (Streckgrenze >790 MPa) geschweißt. Die Wärmeführung und Probenabmessungen werden innerhalb eines statistischen Versuchsplans variiert. Die Schweißwärmeführung wird dabei so eingestellt, dass die t8/5-Abkühlzeiten im empfohlenen Verarbeitungsbereich (ca. 5 s bis 20 s) sichergestellt sind. Hierzu ließen sich über zusätzliche thermo-physikalische Umformsimulationen mittels Dilatometer die komplexen Wärmezyklen abbilden und die resultierende Zugfestigkeit des Schweißgutes bestimmen. Das WAAM-Schweißen komplexer Geometrien mit variierenden Schweißwärmeführungen und geometrischen Verhältnissen bzw. Wanddicken bedingt neben den Auswirkungen auf die Abkühlbedingungen, Abkühlzeiten und Gefüge deutliche Einflüsse auf die konstruktiven Steifigkeitsverhältnisse beim Schweißen. Es zeigen sich anhand der Schweißexperimente signifikante Auswirkungen durch Probenskalierung und Wärmeeinbringung auf die resultierenden lokalen Eigenspannungen. Die Folge können ungünstige Bauteileigenschaften und risskritische Zugeigenspannungen sein. T2 - DVS Congress 2022 CY - Koblenz, Germany DA - 19.09.2022 KW - MAG-Schweißen KW - Additive Fertigung KW - Eigenspannungen KW - Hochfester Stahl KW - Kaltrisssicherheit KW - Wärmeführung KW - Windenergie PY - 2022 SN - 978-3-96144-189-1 VL - 382 SP - 737 EP - 745 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-56719 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Load analyses of welded high-strength steel structures using image correlation and diffraction techniques N2 - In an increasing number of modern steel applications, high-strength structural steel grades are demanded to meet specifications regarding a high load-bearing capacity and a low operating weight. Lightweight design rules enhance the safety requirements, especially for welded joints. Besides a higher cracking risk for high-strength steel welds, the formation of tensile residual stresses might lead to fracture due to overloading or premature failure if not adequately considered. In this study, a stress-strain analysis was conducted at component-related structures from S960QL using digital image correlation while preheating, welding and cooling adjacent to the weld seam. X-ray diffraction analysis of the local residual stresses in the weld seam showed a good comparability with global analyses using either a DIC system or a special testing facility, which allowed in situ measurements of welding loads. By analysing two different seam geometries, it could be shown that lower multi-axial stresses arise if a narrower weld groove is used. Comparative analyses revealed a direct correlation of the local residual stresses in the weld with transverse shrinkage restraint, whereas the residual stress level in the HAZ is significantly affected by the bending restraint of the weld construction and the occurring bending stresses, respectively. KW - Process parameters KW - Residual stresses KW - Restraint KW - GMAwelding KW - High-strength steels PY - 2018 DO - https://doi.org/10.1007/s40194-018-0566-x SN - 0043-2288 SN - 1878-6669 VL - 62 IS - 3 SP - 459 EP - 469 PB - Springer CY - Berlin, Heidelberg AN - OPUS4-44270 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Eissel, A. A1 - Engelking, Lorenz A1 - Treutler, K. A1 - Schröpfer, Dirk A1 - Wesling, V. A1 - Kannengießer, Thomas ED - da Silva, L. F. M. ED - Martins, P. A. F. ED - Reisgen, U. T1 - Nickel-Iron-Alloy Modification to Enhance Additively Welded Microstructure for Subsequent Milling N2 - The aerospace industry uses nickel–iron alloys, e.g., FeNi36, to create moulding tools for composite materials, since these alloys have a low coefficient of thermal expansion. Nickel–iron alloys are hard-to-cut materials. The moulding tools are large in size and involve complex structures, making them cost-intensive and difficult to manufacture. Thus, the focus is set on additive manufacturing, which can additionally enable the repair of components in order to eliminate local defects. However, the process usually results in a heterogeneous microstructure and anisotropic mechanical properties. As there is a high demand for a precise and exact fit of the precision moulds and the surface quality, the welded components must be subsequently machined. Additionally, inhomogeneous microstructure may lead to unstable cutting forces and conditions. Consequently, a modification of the microstructure morphology is achieved through specific alloy modifications in order to stabilise and improve the subsequent machining process. Therefore, titanium and zirconium are chosen as modification elements with a maximum 1% weight percent and are added to nickel–iron alloy powder. The elements are alloyed, and build-up welded by plasma-transferred-arcwelding. The resulting microstructure morphology of the welded wall structure and the machining properties are then determined. It can be shown that titanium has a significant effect on the structural morphology of the welded layers, as well as on the machining. KW - Alloy modification KW - Alloy 36 KW - Plasma-transferred arc welding KW - Ultrasonic-assisted milling KW - Surface integrity PY - 2022 SN - 978-3-030-95463-5 DO - https://doi.org/10.1007/978-3-030-95463-5_6 SP - 85 EP - 99 PB - Springer CY - Cham AN - OPUS4-55484 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Formation of multi-axial welding stresses due to material behaviour during fabrication of high-strength steel components N2 - Today an expanding application of high-strength steels in modern welded constructions can be observed. The economical use of these steel grades largely depends on the strength and reliability of the weldments. Therefore the special microstructure and mechanical properties of these grades have to be taken into account by keener working ranges regarding the welding parameters. However, performance and safety of welded components are strongly affected by the stresses occurring during and after welding fabrication locally in the weld seam and globally in the whole component, especially if the shrinkage and distortion due to welding are restrained. Some extensive studies describe the optimization of the welding stresses and the metallurgical effects regarding an adapted welding heat control. In particular lower working temperatures revealed to be effective to significantly reduce the local and global welding induced residual stresses of the completed weld. However, decreased interpass temperatures cause concurrently higher stresses during welding fabrication. This work shows some strategies to reduce these in-process stresses. With help of multi-axial welding stress analyses in component-related weld tests using a special 2-MN-testing facility differences in stress build-up are described in detail for root welds, filler layers and subsequent cooling to ambient temperature. T2 - IIW Annual Assembly 2017 CY - Shanghai, China DA - 25.06.2017 KW - Residual stresses KW - GMA Welding KW - Restraint KW - High-strength steels KW - Process parameters PY - 2017 AN - OPUS4-41075 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Residual stress formation in DED-arc manufactured high strength steel components N2 - Additive manufacturing (AM) processes enable the efficient production of advanced constructions. New developments in topology optimization are leading to weight-optimized designs of increasing complexity. Direct energy deposition processes (DED) such as wire and arc-based additive manufacturing are an important method of additive manufacturing. The wire filler metals enable a wide range of materials, while the arc process provides a high deposition rate compared to laser and powder-based processes. Combined with the use of high-strength steels, the thickness of walls or components can be significantly reduced in the context of lightweight construction, which results in significant savings in energy, costs, time and resources. Suitable high-strength steel filler metals are commercially available for DED-arc AM processes. However, guidelines and quantitative knowledge about welding stresses and cold cracking issues during component production and service are lacking. This limits the industrial application considerably. In a joint project of BAM and Chemnitz University of Technology, the main influences and complex interactions of material, production process, design and processing steps on the residual stress level are investigated. The aim is to develop processing recommendations and a cold cracking test for economical processing and stress-related design of high-strength steels with DED-arc. This study focuses on residual stress analysis by neutron diffraction (ND) and X-ray diffraction (XRD) on defined test specimens. The ND analysis were performed at the Paul Scherrer Institute- Villigen, Switzerland (PSI) and the XRD analysis at BAM. The study shows a quantitative and qualitative comparison of the residual stress magnitudes and distribution between the component bulk (ND) and surface (XRD) analyses. The ND analysis reveals that in DED-arc AM walls the residual stresses dominate in the direction of welding and are negligibly small in each case transverse to the direction of welding. The topology of the analyzed residual stresses shows almost identical residual stress maps compared to XRD. In addition, the residual stresses are significantly influenced by the solid phase transformation of the material due to low cooling times and less post heat treatment cycles of following AM layers in the area of the top layer. T2 - IIW Intermediate Meeting C-II/CIX CY - Munich, Germany DA - 06.03.2023 KW - Additive manufacturing KW - High strength steel KW - Residual stress PY - 2023 AN - OPUS4-59307 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Projektvorstellung FOSTA P1311: Beanspruchungsgerechte Reparatur von Schweiß-verbindungen bei der Fertigung von Bauteilen aushochfesten Feinkornbaustählen N2 - Bei der Montage von Stahlkonstruktionen kommt es trotz anforderungsgerechter schweißtechnischer Fertigung vereinzelt zur Detektion von unzulässigen Unregelmäßigkeiten im Schweißbereich. Die Verarbeitungsregelwerke empfehlen das lokale thermische Ausfugen betroffener Bereiche und erneutes Schweißen, geben aber aufgrund fehlender wissenschaftlich fundierter Untersuchungen kaum Informationen zu adäquaten Reparaturkonzepten. Dies betrifft insbesondere die Berücksichtigung und Optimierung resultierender schweißbedingter Beanspruchungen durch hohe Schrumpfbehinderungen der Ausfugenuten sowie der Gefügedegradation angrenzender Bereiche durch das Ausfugen und erneute Schweißen. Gerade bei hochfesten Stahlgüten ergeben sich dadurch häufig reduzierte mechanische Eigenschaften und zusätzliche schweißbedingte Beanspruchungen sowie erneut auftretende Nahtdefekte. Deshalb sind für das Forschungsvorhaben systematische bauteilrelevante Untersuchungen der schweißbedingten Beanspruchungen und Gefügeveränderungen reparierter Schweißnähte in Abhängigkeit von der Schrumpfbehinderung und Wärmeführung beim Schweißen und Ausfugen sowie von der Reparaturzyklenanzahl geplant, mit dem Ziel Empfehlungen für beanspruchungs- und werkstoffgerechte Reparaturkonzepte abzuleiten. Hierfür sind gerade Analysen an hochfesten Stahlgüten S500 für den Offshore-Bereich und S960QL für den Mobilkranbau interessant, die zur Errichtung und Fertigung hocheffizienter Konstruktionen wie Windenergieanlagen notwendig sind. Die Erkenntnisse bieten eine Grundlage für entsprechende Normen und Regelwerke. Damit können letztlich Schäden und zumeist teure Nacharbeiten verhindert und eine verbesserte Ausnutzung des hohen Festigkeitspotentials hochfester Stähle erreicht werden. Gerade auch KMU können mit Blick auf die Kosten für Fertigung, Schweißarbeit und Material von den Erkenntnissen beim Einsatz hochfester Stähle, die für eine effiziente Realisierung der Energiewende in Deutschland notwendig sind, profitieren T2 - NA 092-00-05 GA (DVS AG Q 4/Q 4.1) CY - Hamm, Germany DA - 04.03.2020 KW - Reparatur KW - Eigenspannungen KW - Schweißen KW - Wärmeführung KW - Hochfester Feinkornbaustahl KW - Gefügedegradation PY - 2020 AN - OPUS4-51584 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Hensel, J. A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Heat control and design‑related effects on the properties and welding stresses in WAAM components of high‑strength structural steels N2 - Commercial high-strength fller metals for wire arc additive manufacturing (WAAM) are already available. However, widespread industrial use is currently limited due to a lack of quantitative knowledge and guidelines regarding welding stresses and component safety during manufacture and operation for WAAM structures. In a joint research project, the process- and material-related as well as design infuences associated with residual stress formation and the risk of cold cracking are being investigated. For this purpose, reference specimens are welded fully automated with defned dimensions and systematic variation of heat control using a special, high-strength WAAM fller metal (yield strength>790 MPa). Heat control is varied by means of heat input (200–650 kJ/m) and interlayer temperature (100–300 °C). The ∆t8/5 cooling times correspond with the recommendations of fller metal producers (approx. 5–20 s). For this purpose, additional thermo-physical forming simulations using a dilatometer allowed the complex heat cycles to be reproduced and the resulting ultimate tensile strength of the weld metal to be determined. Welding parameters and AM geometry are correlated with the resulting microstructure, hardness, and residual stress state. High heat input leads to a lower tensile stress in the component and may cause unfavorable microstructure and mechanical properties. However, a sufciently low interlayer temperature is likely to be suitable for obtaining adequate properties at a reduced tensile stress level when welding with high heat input. The component design afects heat dissipation conditions and the intensity of restraint during welding and has a signifcant infuence on the residual stress. These complex interactions are analyzed within this investigation. The aim is to provide easily applicable processing recommendations and standard specifcations for an economical, appropriate, and crack-safe WAAM of high-strength steels. KW - GMA welding KW - Additive manufacturing KW - Residual stresses KW - High-strength steel KW - Cold cracking safety KW - Heat control KW - Wind energy PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-567397 DO - https://doi.org/10.1007/s40194-022-01450-x SN - 1878-6669 VL - 2022 SP - 1 EP - 11 PB - Springer CY - Berlin AN - OPUS4-56739 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Eissel, A. A1 - Engelking, Lorenz A1 - Gustus, R. A1 - Treutler, K. A1 - Wesling, V. A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Alloy modification for additive manufactured Ni alloy components—part I: effect on microstructure and hardness of Invar alloy N2 - Alloy 36 (1.3912), also known as “Invar,” is an alloy with 36% nickel. The alloy has a remarkably low thermal expansion coefficient in certain temperature ranges. This peculiarity is called the invar effect, which was discovered in 1896 by the Swiss physicist Charles Édouard Guillaume. Therefore, it is used in applications in which dimensional stability is critical, such as molding tools for composite materials in aerospace, automotive applications, or liquified natural gas (LNG) cargo tanks. Moreover, increasingly complex structures and the optimization of resource efficiency also require additive manufacturing steps for the production or repair of components. Additively manufactured components have a heterogeneous microstructure and anisotropic mechanical properties. In addition, the manufactured components require subsequent machining surface finishing, like finish milling, to achieve their final contour. Nickel iron alloys are difficult to machine. Additionally, inhomogeneous microstructure may lead to unstable cutting forces and conditions. In part I of this investigation, the initial alloy 36 is modified with the elements Ti, Zr, and Hf up to a maximum of 0.33 wt.-%. The influence of the modification elements on the microstructure as well as on the hardness of the AM components is examined. Furthermore, one modification is applied to metal arc welding process and investigated. Part II focuses on the effect of the alloy modifications on machinability as well as on the surface integrity of plasma-transferred-arc-welded (PTA) and finish milled invar components. T2 - 75th IIW Annual Assembly CY - Tokyo, Japan DA - 17.07.2022 KW - Alloy modification KW - Alloy 36 KW - Plasma-transferred arc welding PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-571777 DO - https://doi.org/10.1007/s40194-023-01510-w SN - 0043-2288 SP - 1 EP - 9 PB - Springer CY - Heidelberg AN - OPUS4-57177 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Engelking, Lorenz A1 - Eissel, A. A1 - Schröpfer, Dirk A1 - Treutler, K. A1 - Kannengießer, Thomas A1 - Wesling, V. T1 - Optimisation of surface residual stresses using ultrasonic‑assisted milling for wire‑arc additive manufactured Ni alloy components N2 - Nickel alloys are cost intensive materials and generally classified as difficult-to-cut material. However, machining of these materials is needed especially in case of alloy 36 (1.3912), which is commonly used in mould construction for the production of fibre-reinforced composites. With regard to repair, modification and manufacturing of such components, additive manufacturing offers significant economic advantages. Nevertheless, subsequent machining steps are needed to achieve the final component contour and defined surface conditions. Dependent on the material and machining process conditions, detrimental tensile residual stresses may be the result on the machined surface, having negative impact on the component performance and safety. In this investigation, machining experiments were carried out on wire arc additive manufactured components made of alloy 36, varying the cutting speed and the feed rate. In addition, the conventional milling process (CM) was compared with a modern, hybrid machining process, the ultrasonic-assisted milling (US). The cutting forces and the surface-near residual stresses were analysed using X-ray diffraction. A significant improvement of the machinability as well as the surface integrity by using the ultrasonic assistance was observed, especially at low cutting speeds. The CM induced mainly tensile residual stresses, the US mainly compressive residual stresses. KW - Surface integrity KW - Ultrasonic-assisted milling KW - Additive manufacturing KW - Ni alloy KW - Alloy 36 PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-575246 DO - https://doi.org/10.1007/s00170-023-11326-z SN - 1433-3015 VL - 126 IS - 9 SP - 4191 EP - 4198 PB - Springer Nature AN - OPUS4-57524 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Witte, Julien A1 - Schröpfer, Dirk A1 - Hamacher, M. A1 - Michels, H. A1 - Hamm, C. A1 - Appelt, M. A1 - Börner, Andreas A1 - Kannengießer, Thomas T1 - Tool development for hybrid finishing milling of iron aluminides N2 - The importance of high-temperature materials made of iron aluminides (FeAl) has been increasing in light weight applications, e.g., airplane turbines, due to the high material’s specific strength. However, the highly economic production by means of permanent mold casting involves special microstructures for Fe26Al4Mo0.5Ti1B alloy components leading to difficult machinability for subsequent finishing milling and low surface qualities. Major effects of tool and machining parameter variation incorporating ultrasonic assistance on the milling process and surface integrity are shown. Loads for tool and component surface are significantly adjustable to enable an economic process chain regarding the surface integrity of safety-relevant components. KW - Ultrasonic-assisted milling KW - Iron aluminide KW - Surface integrity KW - Tool wear PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-566294 DO - https://doi.org/10.1016/j.procir.2022.03.123 SN - 2212-8271 VL - 108 SP - 793 EP - 798 PB - Elsevier B.V. AN - OPUS4-56629 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schröpfer, Dirk A1 - Becker, Amadeus A1 - Kannengießer, Thomas T1 - Kurzdarstellung der Projektergebnisse: Beanspruchungsgerechte Reparatur von Schweißverbindungen bei der Fertigung von Bauteilen aus hochfesten Feinkornbaustählen N2 - Bei der Montage von Stahlkonstruktionen kommt es trotz anforderungsgerechter schweißtechnischer Fertigung vereinzelt zur Detektion von unzulässigen Unregelmäßigkeiten im Schweißbereich. In einem Forschungsprojekt (FOSTA P1311) wurden Untersuchungen durchgeführt und Kenntnisse erarbeitet, um mittelfristig vor allem KMU beanspruchungsgerechte Reparaturkonzepte zur Verfügung zu stellen. Damit können letztlich Schäden und zumeist teure Nacharbeiten verhindert und eine verbesserte Ausnutzung des hohen Festigkeitspotentials hochfester Stähle erreicht werden. Gerade KMU können mit Blick auf die Kosten für Fertigung, Schweißarbeit und Material von den Erkenntnissen beim Einsatz hochfester Stähle, die für eine effiziente Realisierung der Energiewende in Deutschland notwendig sind, profitieren. KW - MAG-Schweißen KW - Hochfester Stahl KW - Eigenspannungen KW - Thermisches Ausfugen KW - Reparaturschweißen KW - Gefügedegradation PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-555822 SP - 1 EP - 2 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-55582 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Hensel, J. T1 - Fertigungsbedingte Beanspruchungen und Kaltrisssicherheit in generativ gefertigten Bauteilen aus hochfesten Feinkornbaustählen - Kurzdarstellung der Projektergebnisse, FOSTA P1380 N2 - Die Verwendung hochfester Feinkornbaustähle hat für viele Anwendungen des Stahlbaus ein großes Potenzial für gewichtsoptimierte, effiziente Strukturen mit ho-her mechanischer Beanspruchbarkeit. Weitere Zugewinne an Effizienz sind durch generative Fertigungsschritte sowie bionische Bauweisen erzielbar. Hierzu stehen bereits kommerzielle hochfeste drahtförmige Zusatzwerkstoffe für formgebendes MSG-Schweißen zur Verfügung. Dem Einsatz stehen noch fehlende quantitative Aussagen zu den fertigungsbedingten Beanspruchungen und der Bauteilsicherheit während Herstellung und Betrieb im Wege. Dies betrifft insbesondere prozess- sowie materialbedingte Einflüsse und die konstruktive Schrumpfbehinderung verbunden mit der Ausbildung hoher Zugeigenspannungen und damit zusammenhängenden Kaltrissbildung. Hierfür wurden im Projekt detaillierte und anwenderbezogene Kenntnisse zu den komplexen Wechselwirkungen zwischen Schweißprozess und Wärmeführung während der Fertigung, der metallurgischen Vorgänge und insbesondere der vorliegenden konstruktiven Einflüsse auf die entstehenden Eigenspannungen erarbeitet, um ein frühzeitiges Bauteilversagen aufgrund eines hohen fertigungsbedingten Beanspruchungsniveaus bis hin zu einer Rissbildung während der Fertigung sicher zu vermeiden. Gleichzeitig wurden die Einflüsse auf die mechanisch-technologischen Gütewerte systematisch analysiert. Zudem wurden die Auswirkungen trennender Verfahren durch Entfernen der Substratplatte sowie durch die spanende Bearbeitung der Vorformlinge zu Endbauteilgeometrien geklärt, da diese unmittelbar den Eigenspannungszustand beeinflussen und deutlichen Verzug der Bauteile auslösen. Für das generative Schweißen konnten Verarbeitungsempfehlungen sowie Normenvorgaben erarbeitet werden. Dies hilft insbesondere KMU eine wirtschaftliche, beanspruchungsgerechte und risssichere generative Fertigung von Bauteilen aus hochfesten Feinkornbaustählen zu ermöglichen. KW - MAG-Schweißen KW - Additive Fertigung KW - Eigenspannungen KW - Kaltrisssicherheit KW - Hochfester Stahl PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-582198 N1 - Das IGF-Vorhaben IGF-Nr. 21162 BG (P 1380) "Fertigungsbedingte Beanspruchungen und Kaltrisssicherheit in generativ gefertigten Bauteilen aus hochfesten Feinkornbaustählen" der Forschungsvereinigung Stahlanwendung e. V. wurde über die AiF im Rahmen des Programms zur Förderung der Industriellen Gemeinschaftsforschung (IGF) vom Bundesministerium für Wirtschaft und Klimaschutz aufgrund eines Beschlusses des Deutschen Bundestages gefördert. SP - 1 EP - 2 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-58219 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Witte, Julien A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Stresses in repair welding of high-strength steels—part 1: restraint and cold cracking risk N2 - AbstractThe sustainable and resource-efficient production of wind energy plants requires the use of modern high-strength fine-grain structural steels. This applies to both foundation and erection structures, like mobile or ship cranes. During the assembly of steel structures, unacceptable defects can occasionally be found in the weld area. In most cases, the economical solution would be local thermal gouging of the affected areas and re-welding. Due to the high shrinkage restraint of the joint groove in the overall structure, the superposition of global and local welding-induced stresses may lead to crack formation and component failure, particularly in interaction with the degradation of the microstructure and mechanical properties of high-strength steels during the repair process. However, manufacturers hardly have any information about these issues and there is a lack of recommendations and guidelines to take these safety-relevant aspects into account in adequate repair concepts. The aim of this research is to derive recommendations for repair concepts appropriate to the stresses and materials involved providing a basis for standards and guidelines to avoid cold cracking, damage and expensive reworking especially for high-strength steels. Part 1 of this study involves systematic investigations of influences of shrinkage restraint during repair welding of two high-strength steels S500MLO for offshore application and S960QL for mobile crane structures. The quantification of the shrinkage restraint of repair weld joints was achieved by means of experimental and numerical restraint intensity analysis. In welding experiments with self-restrained slot specimens, restraint intensity and introduction of hydrogen via the welding arc using anti spatter spray were varied systematically to analyse the effect on welding result, residual stresses and cold cracking. It could be shown that increasing restraint intensities result in significantly higher transverse residual stress levels. In the case of hydrogen introduction S500MLO showed no cold cracking independent of the restraint conditions. However, S960QL was found to be considerably cold cracking sensitive if hydrogen is introduced. With increasing restraint intensity length and number of cold cracks increases significantly. Part 2 [1] of this study is focussed on microstructure and residual stresses due to gouging and stress optimization via adequate heat control parameters in repair welding. KW - Metals and Alloys KW - Mechanical Engineering KW - Mechanics of Materials PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-595212 DO - https://doi.org/10.1007/s40194-024-01691-y SN - 0043-2288 SP - 1 EP - 13 PB - Springer Science and Business Media LLC AN - OPUS4-59521 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Witte, Julien A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Stresses in repair welding of high-strength steels—part 2: heat control and stress optimization N2 - In welding of high-strength steels, e.g. for foundations and erection structures of wind energy plants, unacceptable defects can occasionally be found in the weld area, which should be removed by thermal gouging and subsequent re-welding. High shrinkage restraint of repair welds may lead to crack formation and component failure, predominantly in interaction with degraded microstructures and mechanical properties due to repair cycles. This study aims for elaboration of recommendations for repair concepts appropriate to the stresses and materials involved to avoid cold cracking, damage and expensive reworking. In part 1 [1] of this study, systematic investigations of influences of shrinkage restraint on residual stresses and cold cracking risk during repair welding of two high-strength steels S500MLO for offshore application and S960QL for mobile crane structures were focussed. In this part 2, the microstructure, particularly hardness, and residual stresses due to gouging and influences of heat control parameters in repair welding are analysed. A clear reduction in residual stress after gouging can be observed, especially for the specimens with restrained transverse shrinkage. Gouging to a depth of approx. 2/3 of the seam height does not lead to a complete relaxation of the observed reaction forces. Particularly for the higher strength steel S960QL, there are pronounced areas influenced by the gouging process in which a degradation of the microstructure and properties should be assumed. Overall, the repair welds show a significant increase in the width of the weld and HAZ compared to the original weld, especially in the case of S960QL/G89. The repair welds show higher welding-induced stresses than the original welds, especially in the areas of the HAZ and the base metal close to the weld seam. This behaviour can be attributed overall to increased restraint conditions due to the remaining root weld or shorter gouge grooves. In good agreement with earlier investigations, the residual stresses transverse to the weld can be significantly reduced by upwardly limited working or interpass temperatures, and the reaction stresses resulting from high restraint conditions can be effectively counteracted. The influence of the heat input on the stress formation is low compared to the interpass temperature for both test materials. KW - Repair-welding KW - Wind Energy KW - High-strength steels KW - Cold cracking KW - Residual stresses KW - Offshore steels PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-600259 DO - https://doi.org/10.1007/s40194-024-01731-7 SN - 0043-2288 SP - 1 EP - 15 PB - Springer Nature AN - OPUS4-60025 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Willeke, Maraike A1 - Giese, Marcel A1 - Lorenz, Swenja A1 - Treutler, Kai A1 - Schröpfer, Dirk A1 - Wesling, Volker A1 - Kannengießer, Thomas T1 - Effect of alloy modification on the wear protection coatings made of Ni- and Co-based materials and surface machinability via ultrasonic milling process N2 - AbstractWear-resistant coatings are required for highly efficient and economical steel components in equipment, process, and power plant engineering to withstand high corrosive, tribological, thermal, and mechanical stresses. Co-alloys are used as wear-resistant coatings for steel components, tailored to the specific application. The substitutability of Co alloys with Ni-based wear protection systems, in addition to price and supply uncertainties, is facilitated by the combination of innovative welding and machining processes such as ultrasonic-assisted milling. The aim of the study is to improve the machinability of two different hard-facing alloys while maintaining the same wear protection potential. Therefore, the wear-resistant alloys NiMoCrSi (Colmonoy C56) and CoMnCrSi (Tribaloy T400) were modified by the alloying additions Nb, Hf, and Ti and then applied to a carbon-manganese steel S355 using the plasma transfer arc (PTA) welding process. The influence of the alloying additions on the microstructure as KW - Wear resistance KW - Co-based alloy KW - Ni-based alloy KW - PTA welding process KW - Ultrasonic assisted milling process PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-623931 DO - https://doi.org/10.1007/s00170-024-14955-0 SN - 0268-3768 SP - 1 EP - 17 PB - Springer Science and Business Media LLC AN - OPUS4-62393 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Giese, Marcel A1 - Gräbner, Maraike A1 - Schröpfer, Dirk A1 - Treutler, Kai A1 - Lorenz, Svenja A1 - Kannengießer, Thomas A1 - Wesling, Volker T1 - Alloy modification and ultrasonic-assisted milling of wear-resistant alloys with defined surfaces N2 - The reduction of CO2 emissions is closely linked to the development of highly efficient and economical steel components in plant and process engineering. To withstand the high combined corrosive, tribological, thermal, and mechanical stresses, wear-resistant coatings tailored to the application and steel grade are used. In addition to the increasing demand to substitute conventional cobalt alloys with nickel alloys, there is also a growing need for defined or functional surfaces of high integrity. Due to high tool wear, milling operations required to produce the complex geometries of the components are often not economically feasible for SMEs. By means of alloy modification of the filler metals for nickel-based plasma build-up welded wear-resistant coatings and by the use of innovative ultrasonic-assisted milling processes more favourable machinability shall be achieved without reducing the wear protection potential. In this paper, the influence of the microstructure and precipitation morphology adjusted by means of alloy modification on the machinability is investigated. This is done based on a wear protection alloy NiCrMoSiFeB (trade name: Colmonoy 56 PTA) typically used for screw machines, which substitutes conventional CoCr alloys (Stellite). Metallurgical investigations and in-situ measurements of occurring process forces and temperatures at the tool cutting edge during milling as well as subsequent investigations of tool wear and surface integrity allow a detailed analysis and correlation between microstructural properties and machinability. For the cast samples, a clear change in the microstructure and hardness can be seen through the addition of Al, Ti, or Nb. These differences lead to an improvement in the machining process for Nb. Al and Ti cause long-needled or star-shaped precipitations and hardness increases, which lead to higher cutting forces and increased tool wear. KW - Cladding KW - Wear resistant alloys KW - Alloy modification KW - Post-processing KW - Ultrasonic assisted milling KW - Renewable energy PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-622918 DO - https://doi.org/10.1007/s40194-024-01786-6 SN - 1878-6669 VL - 68 SP - 2567 EP - 2575 PB - Springer Science and Business Media LLC CY - Berlin ; Heidelberg AN - OPUS4-62291 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Optimization of welding loads with narrow groove and application of modified spray arc process N2 - Current efforts for lightweight design result in a growing application of high-strength fine-grained structural steel in modern constructions, e.g. mobile cranes, with yield strength from 960 MPa. The design of welded structures and welding processes becomes more challenging with increasing material strength and elastic ratios. High residual stresses are able to diminish lifetime, load capacity and component safety and should be avoided. Recent analyses have shown strong influences of heat control and restraint of the weld due to arising reaction stresses, superimposing with local residual welding stresses. Modern inverter technologies allowed the development of numerous modified spray arc processes driven by power source manufacturers, which provide virtually similar features and several benefits, enabling welding of narrower seams with reduced weld volumes and total heat inputs. This research focuses on welding loads due to modified weld seams. The global reaction forces and moments and their superposition with local residual stresses in welded components due to external shrinkage restraints were investigated using a special testing facility and XRD. The restraint intensity, weld seam geometry and welding process were varied for statistical evaluations of resulting welding loads. When welding under restraint, a reduction of the weld seam volume causes significantly lower reaction stress levels. KW - Residual stresses KW - MAG welding KW - Restraint KW - High-strength steels KW - Process parameters PY - 2017 DO - https://doi.org/10.1007/s40194-017-0484-3 SN - 1878-6669 SN - 0043-2288 VL - 61 IS - 6 SP - 1077 EP - 1087 PB - Springer CY - Berlin Heidelberg AN - OPUS4-41071 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Becker, Amadeus A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas A1 - Michael, Thomas T1 - Konstruktive Einflüsse bei der beanspruchungsgerechten Reparatur geschweißter Bauteile aus hochfesten Feinkornbaustählen N2 - Für eine nachhaltige und ressourceneffiziente Fertigung von Windkraftanlagen ist der Einsatz moderner hochfester Feinkornbaustähle vielfach notwendig. Bei der Montage hochfester Stahlkonstruktionen kommt es trotz anforderungsgerechter schweißtechnischer Fertigung vereinzelt zur Detektion von unzulässigen Unregelmäßigkeiten im Schweißbereich. Derzeitige Normen und Verarbeitungsrichtlinien geben hierbei kaum Informationen zu adäquaten Reparaturkonzepten, insbesondere für hochfeste Stähle. Vor diesem Hintergrund werden an der Bundesanstalt für Materialforschung und -prüfung (BAM) bauteilrelevante Untersuchungen zu den schweißbedingten Beanspruchungen und Gefügeveränderungen bei der schweißtechnischen Reparatur durch lokales thermisches Ausfugen und erneutes Schweißen durchgeführt. Hierzu werden einige wesentliche Ergebnisse an Beispielen des Ingenieurbaus, mit Blick auf die mechanisch-technologischen Eigenschaften und Eigenspannungen erörtert. In einem aktuellen Vorhaben (FOSTA P1311, IGF 20162N) sind darauf aufbauend die Einflüsse durch die Schrumpfbehinderung und Wärmeführung beim Reparaturschweißen hochfester Feinkornbaustähle (S500MLO, S960QL) sowie die Reparaturzyklenanzahl Fokus systematischer Untersuchungen. Mittels strukturmechanischer Berechnungen ließen sich hierzu selbstbeanspruchende Probenformen identifizieren, die unterschiedliche definierte Steifigkeitsverhältnisse von Reparaturschweißnähten realer Bauteile abbilden. Schweißnähte an diesen bauteilähnlichen Proben weisen signifikant erhöhte schweißbedingte Beanspruchungen mit zunehmenden (Biege-)Einspanngraden auf. Im Vergleich mit bisherigen Erkenntnissen wird gezeigt, dass eine sichere Reparatur solcher Schweißnähte nur mittels optimaler Reparaturkonzepte und Wärmeführung gelingt, um diesen hohen Beanspruchungen und auch den speziellen Gefügen hochfester Stähle Rechnung zu tragen. Ziel der Untersuchungen ist es letztlich, Empfehlungen für beanspruchungs- und werkstoffgerechte Reparaturkonzepte gerade für KMU abzuleiten, um Schäden und zumeist teure Nacharbeiten zu vermeiden. T2 - 4. Niedersächsisches Symposium Materialtechnik CY - Online meeting DA - 25.02.2021 KW - Eigenspannungen KW - Gefügedegradation KW - Hochfester Feinkornbaustahl KW - Reparatur KW - Schweißen PY - 2021 SN - 978-3-8440-8021-6 SN - 2364-0804 VL - 10 SP - 488 EP - 501 PB - Shaker Verlag CY - Düren AN - OPUS4-53315 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Eissel, A. A1 - Treutler, K. A1 - Wesling, V. A1 - Engelking, Lorenz A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Modifikation von CoCr-Legierungen für die additive lichtbogenbasierte Fertigung N2 - Für Komponenten im Turbinen- oder Anlagenbau werden aufgrund ihrer Eigenschaften häufig Kobalt-Chrom-Legierungen verwendet. Diese weisen eine hohe Korrosionsbeständigkeit und hohen Verschleißwiederstand auf. Aufgrund der komplexen Strukturen und dem Bestreben nach Ressourceneffizienz wird zur Herstellung der Komponenten die additive Fertigung verwendet. Hierbei sind hinsichtlich der Inhomogenität und Anisotropie der Gefüge und deren Eigenschaften weitere Kenntnisse notwendig. Bei den vorliegenden Belastungen liegt ein erhöhter Anspruch an die Oberflächenintegrität vor, welcher durch komplementären Einsatz von additiven und abtragenden Fertigungsschritten sichergestellt wird. Dabei sind gerade Co-Cr-Legierungen wegen der niedrigen Wärmeleitfähigkeit verbunden mit hoher Festigkeit und Zähigkeit äußerst herausfordernd mit Blick auf eine wirtschaftliche Zerspanung mit geometrisch bestimmter Schneide. Ausgehend von dieser Problemstellung erfolgt im Zuge eines Gemeinschaftsvorhabens des ISAF in Kooperation mit der BAM eine gezielte Beeinflussung des Gefüges. Ziel des Projektes ist die Zusammenhänge zwischen verschiedenen Legierungsmodifikationen, der entstehenden Gefügemorphologie und den Zerspanungseigenschaften von Co- Cr-Legierungen für die additive Fertigung mittels PTA darzustellen. Der Fokus liegt auf dem Beheben der bestehenden Nachteile bei gleichzeitigem Aufrechthalten der besonderen Eigenschaften der Legierung. Durch das Hinzulegieren von variierenden Gehalten von Zirkonium und Hafnium wird die Gefügeveränderung eingestellt. Es hat sich gezeigt, dass Hafnium als zusätzliches Legierungselement einen deutlichen Einfluss auf die Gefügemorphologie hat. Darüber hinaus wird die Auswirkung der Legierungsmodifikation auf die Härte und die Zerspanbarkeit dargestellt. T2 - 42. Assistentenseminar der Wissenschaftlichen Gesellschaft Fügetechnik e.V. CY - Blankenau, Germany DA - 06.10.2021 KW - Legierungsmodifikation KW - ultraschallunterstütztes Fräsen KW - Additive Fertigung PY - 2022 SN - 978-3-96144-210-2 VL - 385 SP - 103 EP - 113 PB - DVS Media GmbH AN - OPUS4-56658 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin A1 - Kromm, Arne A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Moderne Schweißverfahren zur Optimierung von Reparaturschweißungen an hochfesten Offshore-Stählen N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future, for which high-strength steels with a yield strength of up to 500 MPa and wall thicknesses up to 150 mm are increasingly being used. The repair of weld seams when detecting defects during NDT requires local-ized gouging and rewelding. This involves high demands on welding manufacturing, especially for high-strength steels. Due to a lack of investigations, there are no re-pair concepts and information in standards and guidelines, particularly for high-strength thick plate joints made of high-strength offshore steels. However, these are urgently needed to enable processors, especially SMEs, to carry out safe and eco-nomical repairs. Therefore, BAM started the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal with controlled high-performance GMAW processes and optimized narrower gouging grooves. The experimental analyses consider the complex interaction of material, process, and design-related influences on the formation of weld-related stresses and the special microstructure of high-strength fine-grain structural steels. Welding-related material degradation and crack-critical residual tensile stresses need to be avoided to ensure high component safety and performance. With component-related welding experiments on special testing equipment, adapted process and heat control concepts along with variable groove configurations will be developed and recommendations for guidelines elabo-rated. This is the prerequisite for fully utilizing the strength potential of high-strength steels and making a valuable contribution to the energy transition in Germany, espe-cially for steel-processing SMEs. T2 - Symposium Materialtechnik TU Clausthal CY - Clausthal-Zellerfeld, Germany DA - 19.02.2025 KW - Reparaturschweißen KW - Thermisches Ausfugen KW - Offshore KW - Sprühlichtbogen KW - Eigenspannungen PY - 2025 AN - OPUS4-62630 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Correlation of process, design and welding residual stresses in WAAM of high-strength steel components N2 - High-strength fine-grained structural steels have great potential for modern weight optimized steel construc-tions. Efficient manufacturing and further weight savings are achievable due to Wire Arc Additive Manu-facturing (WAAM). First commercial high-strength welding consumables for WAAM are already available. However, the application is still severely limited due to a lack of knowledge and guidelines for the industry regarding welding residual stresses and component safety in manufacturing and operation. Residual stresses may be critical regarding the special microstructure of high-strength steels in context with the risk of cold cracking and component performance in service. Therefore, process- and material-related influences, as well as the design effects on residual stress formation and cold cracking, are being investi-gated in a research project (IGF 21162 BG) focusing a high-strength WAAM welding consumable with yield strength of over 800 MPa. Objectives are the establish-ment of special WAAM cold cracking tests and pro-cessing recommendations allowing economical, suita-ble, and crack-safe WAAM of high-strength steels. First studies on process-related influences showed transfor-mation residual stresses arising during cooling, which significantly influence stress evolution of the compo-nent during layer-wise build-up. This has not yet been investigated for WAAM of high-strength steels. Focus of this study is on the systematic investigation of interactions of the WAAM welding process and design with cooling time, hardness, and residual stresses. Defined open hollow cuboids were welded and investi-gated under systematic variation (design of experi-ments, DoE) of the scale/dimensions (cf. Fig. 1a) and heat control (interlayer temperature Ti: 100–300 °C), heat input E: 200–650 kJ/m. The welding parameters were kept constant as possible to avoid any influence by the arc and the material transfer mode. The heat input adjusted primarily via the welding speed. The resulting different weald bead widths were considered by different build-up strategies (weld beads per layer) to ensure defined wall thicknesses. The hardness was determined on cross-sections taken from the manufac-tured hollow cuboids (Fig. 1c) and the analysis of the residual stress state was carried out by means of X-ray diffraction (XRD) at defined positions on the lateral wall (Fig. 1b). The hardness is higher at the top compared to the lower weld beads, as shown in Fig. 1c exemplarily for central test parameters of the DoE = 425 kJ/mm, Ti = 200 °C). This may be attributed to the specific heat control of the top weld beads, i.e., quenching effects, which are not tempered by weld beads above as is the case for lower weld beads implying a higher hardness. It was observed that the hardness level decreases with increasing energy per unit length, while the in-terpass temperature has a rather low influence on the hardness Residual stress analysis was performed on the lat-eral wall in the welding direction, cf. Fig. 1b, to deter-mine the influence of heat control and design. In the top area of the wall, maximum longitudinal residual stress-es of up to over 500 MPa exhibit, which corresponds to approx. 65% of the nominal yield strength of the mate-rial. The statistic evaluation of stress levels in welding direction of all test specimens show that adaption of heat input may reduce welding stresses up to 50%. In-terpass temperature has less pronounced effect on cool-ing times, microstructure, and on the residual level within parameter matrix. Overall, the results show a significant influence of heat input and component di-mensions on the residual stresses and minor effect of the interpass temperature. Hence, the properties of the specimens may be effectively adjusted via heat input. The working temperatures should be considered for global shrinkage behavior or restraints. Such investiga-tions of residual stress are necessary to further deter-mine local and global welding stresses regarding the consequences on the component safety during manu-facturing and service. T2 - 6th International Symposium on Visualization in Joining & Welding Science through Advanced Measurements and Simulation CY - Osaka, Japan DA - 25.10.2022 KW - MAG-Schweißen KW - Additive Fertigung KW - Eigenspannungen KW - Hochfester Stahl KW - Kaltrisssicherheit KW - Wärmeführung KW - Windenergie PY - 2022 AN - OPUS4-56725 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Engelking, Lorenz A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas A1 - Eissel, A. A1 - Treutler, K. A1 - Wesling, V. T1 - Herstellung beanspruchungsgerechter Oberflächen durch Kombination innovativer additiver und abtragender Fertigungsschritte an hochbelasteten Komponenten N2 - Die additive Fertigung (AM) durch schweißtechnische Verfahren eröffnet vielfach ökonomische Vorteile für eine ressour-ceneffiziente Bauteilherstellung. Gerade hinsichtlich der Homogenität und Anisotropie der resultierenden Schweißgefüge und den damit verbundenen Eigenschaften gibt es noch offene Fragestellungen. Die Einstellung der finalen Bauteilgeo-metrie und Oberflächengüte erfordert den komplementären Einsatz abtragender Fertigungsschritte. Hochleistungslegie-rungen auf der Basis von Nickel oder Kobalt sind aufgrund ihrer niedrigen Wärmeleitfähigkeit verbunden mit hoher Festigkeit und Zähigkeit schwer spanbar. Eine gezielte Gefügebeeinflussung mittels Modifikation der AM-Schweißzusatz-werkstoffe und der Einsatz des ultraschallunterstützten Fräsens (US) bietet das Potential insgesamt die Zerspanungssi-tuation zu verbessern. Dieser Lösungsansatz unter Gewährleistung des Erhalts der geforderten Werkstoff- bzw. Bauteileigenschaften ist Untersuchungsgegenstand eines Gemeinschaftsvorhabens (IGF-Nr. 20.979 N/DVS-Nr. 1.3211) der BAM und TU Clausthal/ISAF. Der vorliegende Beitrag stellt Ergebnisse für die beiden untersuchten FeNi- und CoCr-Legierungen sowie wesentliche Zusammenhänge zwischen Legierungsmodifikation, entstehender Gefügemorphologie und Zerspanungseigenschaften der mittels MAG additiv gefertigter Proben vor. Das größte Potential für die Modifikation zeigten Zr und Hf. Die Zulegierung in das Schweißgut erfolgte durch Beschichtung von Massivdrähten sowie durch Her-stellung von Fülldrähten. T2 - DVS Congress - GST CY - Essen, Germany DA - 11.09.2023 KW - Legierungsmodifikation KW - Ultraschallunterstütztes Fräsen KW - Additive Fertigung KW - Oberflächenintegrität PY - 2023 SN - 978-3-96144-230-0 VL - 389 SP - 697 EP - 703 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-58380 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schaupp, Thomas A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Kaltrissbildung in Mehrlagenschweißungen - Einflussanalyse von Nahtgeometrie und Wärmeführung beim Einsatz modifizierter Sprühlichtbögen N2 - Ausgehend vom derzeit vorrangigen Einsatz in Mobilkranen, kommen höherfeste Feinkornbaustähle mit Streckgrenzen ab 960 MPa zunehmend auch in anderen modernen Stahlkonstruktionen zur Anwendung. Dies ist aufgrund aktueller Forderungen nach Energie- und Ressourceneffizienz im Sinne des konstruktiven Leichtbaus vielfach notwendig. Die Verwendung höherfester Stähle sowie deren schweißtechnische Verarbeitung, insbesondere in sicherheitsrelevanten Tragstrukturen, erfordert ein tiefgreifendes Verständnis der Zusammenhänge zwischen Schweißverfahren, Wärmeeinbringung, Abkühlbedingungen sowie den daraus resultierenden metallurgischen Vorgängen in der Schweißnaht und den nahtnahen Bereichen. Vorwiegend werden höherfeste Güten mittels MAG-Prozess geschweißt. Bedeutende Fortschritte in der Regelungstechnik führten unter den Herstellern von Schweißstromquellen in den letzten Jahren zur Entwicklung zahlreicher modifizierter Sprühlichtbogenprozesse (mod. SLB). Diese Prozesse ähneln sich in ihren Eigenschaften und ermöglichen die bekannten positiven Aspekte, wie Einsparung an Schweißzusatz sowie Schweiß- und Rüstzeit aufgrund der Möglichkeit reduzierter Nahtöffnungswinkel. Der mod. SLB bedingt zusammen mit einer anderen Nahtgeometrie veränderte Naht- und Schweißraupenquerschnitte sowie einen abweichenden Lagenaufbau. Diese wirtschaftlich-technisch attraktive Möglichkeit reduzierter Nahtöffnungswinkel findet in den Regelwerken zur schweißtechnischen Verarbeitung höherfester Feinkornbaustähle unter Vermeidung von Kaltrissbildung bisher keine Berücksichtigung. Dabei gilt es, gerade die Interaktion der Haupteinflussgrößen auf die Kaltrissbildung unter reduziertem Nahtöffnungswinkel zu betrachten. Im Rahmen zweier AiF-Forschungsvorhaben (IGF-Nr. 17.978 N, 18.596 BR) wurde daher der Einfluss der Wärmeführung anhand vergleichender Mehrlagenschweißungen mittels konventionellem Übergangslichtbogen und mod. SLB mit angepasster Nahtkonfiguration auf schweißbedingte Beanspruchungen sowie auf die Wasserstoffkonzentration im Schweißgut untersucht. T2 - DVS Congress 2018 - Große Schweißtechnische Tagung CY - Friedrichshafen, Germany DA - 17.09.2018 KW - Kaltriss KW - Hochfester Feinkornbaustahl KW - MAG-Schweißen PY - 2018 SN - 978-3-96144-036-8 VL - 344 SP - 73 EP - 78 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-45977 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Optimization of welding loads using modified spray arc process N2 - Current efforts for lightweight design result in a growing application of high-strength fine-grained structural steel in modern steel constructions, e.g. mobile cranes, with yield strength from 960 MPa. The design of welded structures and the welding process become more challenging with increasing material strength due to higher elastic ratios. The formation of high residual stresses, which are able to diminish lifetime, load capacity and component safety, has to be avoided. Recent numerical and experimental analyses have shown a strong influence of the heat control and the rigidity of the weld on the welding stresses. Global reaction stresses due to an external shrinkage restraint superimpose with local residual stresses in the weld seam. Modern inverter technologies allowed the development of numerous modified spray arc processes driven by the power source manufactures with almost equal characteristics. They provide several well-known technical and economic benefits, like the possibility of welding narrower seam configurations. As a result a smaller weld volume, total heat input and, therefore, reduced welding stresses are achievable. This research focuses on the welding loads due to modified weld seams. The global reaction forces in welded components due to an external shrinkage restraint were investigated in a special in-house developed testing facility. Additionally, the superposition of the local residual stresses, global stresses and bending moments were analysed with the help of X-ray diffraction. The intensity of the restraint, the weld seam configuration and the weld process (transitional arc and modified spray arc) were varied for a statistical evaluation of the resulting welding loads. It was observed that under restraint a smaller weld seam volume affects reduced reaction stresses. T2 - IIW Intermediate Meeting, C-IIA CY - Madrid, Spain DA - 29.02.2016 KW - Process parameters KW - Residual stresses KW - MAG Welding KW - Restraint KW - High-strength steels PY - 2016 AN - OPUS4-38785 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Optimization of welding loads using modified spray arc process N2 - Current efforts for lightweight design result in a growing application of high-strength fine-grained structural steel in modern steel constructions, e.g. mobile cranes, with yield strength from 960 MPa. The design of welded structures and the welding process become more challenging with increasing material strength due to higher elastic ratios. The formation of high residual stresses, which are able to diminish lifetime, load capacity and component safety, has to be avoided. Recent numerical and experimental analyses have shown a strong influence of the heat control and the rigidity of the weld on the welding stresses. Global reaction stresses due to an external shrinkage restraint superimpose with local residual stresses in the weld seam. Modern inverter technologies allowed the development of numerous modified spray arc processes driven by the power source manufactures with almost equal characteristics. They provide several well-known technical and economic benefits, like the possibility of welding narrower seam configurations. As a result a smaller weld volume, total heat input and, therefore, reduced welding stresses are achievable. This research focuses on the welding loads due to modified weld seams. The global reaction forces in welded components due to an external shrinkage restraint were investigated in a special in-house developed testing facility. Additionally, the superposition of the local residual stresses, global stresses and bending moments were analysed with the help of X-ray diffraction. The intensity of the restraint, the weld seam configuration and the weld process (transitional arc and modified spray arc) were varied for a statistical evaluation of the resulting welding loads. It was observed that under restraint a smaller weld seam volume affects reduced reaction stresses. T2 - IIW Annual Assembly 2016 CY - Melbourne, Australia DA - 10.07.2016 KW - Process parameters KW - Residual stresses KW - MAG Welding KW - Restraint KW - High-strength steels PY - 2016 AN - OPUS4-38787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Einfluss der Wärmeführung auf die Eigenspannungsausbildung und Kaltrisssicherheit in geschweißten Konstruktionen aus hochfesten Feinkornbaustähleneinfluss der Wärmeführung auf die Eigenspannungsausbildung und Kaltrisssicherheit in geschweißten Konstruktionen aus hochfesten Feinkornbaustählen N2 - Im Vortrag wurden die wesentlichen Ziele und Erkenntnisse des IGF-Vorhabens 17267 N "Wärmeführung und Kaltrisssicherheit" vorgestellt. Der Einfluss der Wärmeführung auf die schweißbedingte Eigenspannungsausbildung in geschweißten Konstruktionen konnte in Abhängigkeit der konstruktiven Steifigkeit und der Bauteildimensionen quantifiziert werden. Ferner wurden Aussagen zur Beeinflussung und Absenkung der Eigenspannungen und der Gesamteigenbeanspruchung von Schweißkonstruktionen erarbeitet. Es zeigte sich, dass eine Reduktion der lokalen Eigenspannungen und der Eigenbeanspruchung von geschweißten Konstruktionen durch eine geringere Wärmeeinbringung möglich ist. Eine Absenkung der Zwischenlagentemperatur erwies sich dabei unter anderem als besonders günstig. Damit ist es möglich vorhandene Wärmeführungskonzepte für hochfeste Stähle zu optimieren und dadurch die Kaltrissbildung zu vermeiden. Weiterführend ist durch die Quantifizierung der im realen Bauteil auftretenden Eigenspannungen bzw. mithilfe gezielter Beeinflussung des Eigenspannungsniveaus eine bessere Ausnutzung der Materialeigenschaften bei der Auslegung von Schweißkonstruktionen aus hochfesten Stählen möglich. Dadurch können ressourceneffizientere Stahlkonstruktionen durch Reduktion von Material- und Fertigungskosten erzielt werden. T2 - FOSTA Praktikergespräche CY - Darmstadt, Germany DA - 21.06.2016 KW - Schweißprozessparameter KW - Eigenspannungen KW - MAG-Schweißen KW - Hochfeste Feinkornbaustähle KW - Einspannung KW - Röntgendiffraktometrie PY - 2016 AN - OPUS4-38789 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Multi-axial analyses of welding stresses in high-strength steel welds N2 - Today’s efforts for lightweight design result in a growing application of high-strength structural steels from 960 MPa. In welded structures of these steels increased demands regarding component safety and a high elastic ratio should be considered. Hence, the prevention of an evolution of high welding induced tensile residual stresses is required. Recent studies showed that component related restraint conditions of welds are able to elevate welding induced stresses to critical values, depending on material characteristics, the welding process and parameters. This work involves multi-axial welding loads as a consequence of the superposition of local residual stresses, global reaction stresses and moments, varying the welding parameters under different restraint conditions. The global welding loads are measured via GMA-weld tests in a special testing facility and via a DIC(Digital Image Correlation)-system in a slot weld. Local transverse residual stresses were analysed by means of X-ray diffraction. The application of a less amount of weld runs due to a modified welding parameters and welds seam configurations revealed as a beneficial approach to reduce welding loads in high-strength steels. T2 - 10th International Conference on Residual Stresses CY - Sydney, Australia DA - 04.07.2016 KW - X-ray diffraction KW - High-strength Steel KW - Welding KW - Reaction Stress PY - 2016 AN - OPUS4-38788 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Einsatz modifizierter Sprühlichtbogenprozesse zur Optimierung schweißbedingter Beanspruchungen an Bauteilen aus hochfesten Feinkornbaustählen N2 - In dem IGF-Vorhaben IGF-Nr. 17978 N (P 1011) wurden unter gezielter definierter Schrumpfbehinderung Schweißexperimente an hochfesten Feinkornbaustählen durchgeführt, um den Einfluss der Wärmeführung sowie den Einsatz modifizierter Sprühlichtbogenprozesse verbunden mit schmaleren Nahtfugen auf die lokalen Eigenspannungen und die Gesamteigenbeanspruchungen an geschweißten Bauteilen zu analysieren. Diese Kurzdarstellung fasst die wesentlichen Zusammenhänge zu schweißbedingten Beanspruchungen an hochfesten Schweißverbindungen sowie einige der erarbeiteten Erkenntnisse und erreichten Ziele des Forschungsprojektes zusammen. KW - Schweißverbindung KW - Eigenspannungen KW - Hochfester Feinkornbaustahl KW - Schweißprozess PY - 2016 SP - 1 EP - 2 AN - OPUS4-38653 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Einsatz modifizierter Sprühlichtbogenprozesse zur Optimierung schweißbedingter Beanspruchungen an Bauteilen aus hochfesten Feinkornbaustählen (FOSTA P1011 / IGF-Nr. 17978 N) N2 - In dem Vortrag wurden die wesentlichen Ziele und Ergebnisse zu dem IGF-Vorhaben 17978 N "Bauteilbeanspruchung modifizierter Sprühlichtbögen" vorgestellt. Mit dem modifizierten Sprühlichtbogen ist das Schweißen einer schmaleren Nahtkonfiguration realisierbar. Die Effekte, die sich aufgrund der angepassten Nahtkonfiguration und reduzierten Wärmeinbringung auf die Eigenspannungen und Gesamteigenbeanspruchung einer Schweißkonstruktion ergeben, konnten im Vergleich zu konventionellen Schweißprozessen und Nahtkonfigurationen analysiert werden. Ferner ließen sich realitätsnahe Untersuchungen unter Variation von Bauteildimension und -steifigkeit durchführen, um Aussagen zur Beeinflussung schweißbedingter Beanspruchungen in hochfesten Bauteilen zu erarbeiten. Es zeigte sich, dass bei optimaler Wärmeführung eine Absenkung des Nahtöffnungswinkels und damit Nahtvolumens signifikant geringere Reaktionsspannungen und -momente bewirkt. Dies führt gerade bei Hemmung des Winkelverzugs zu deutlich reduzierten Quereigenspannungen in der Wärmeeinflusszone aufgrund geringerer Biegespannungen. Die Erkenntnisse erlauben eine gezielte Reduzierung der Eigenspannungen sowie einer erhöhte Risssicherheit bei der Montage und dem Betrieb von Bauteilen aus hochfesten Stählen. Weiterführend ist durch die Quantifizierung der am realen Bauteil auftretenden Eigenspannungen bzw. mithilfe einer planmäßigen Beeinflussung des Eigenspannungsniveaus eine verbesserte Ausnutzung der Materialeigenschaften bei der Auslegung hochfester Schweißkonstruktionen möglich. Dadurch sind ressourceneffiziente Stahlkonstruktionen mittels Reduktion von Material- und Fertigungskosten erzielbar. Mit der gegenwärtig bereits verfügbaren Anlagentechnik ist die Anwendung der gewonnen Forschungsergebnisse kurzfristig realisierbar und angesichts der ökonomischen Vorteile rentieren sich gegebenenfalls notwendige Neuanschaffungen schnell. T2 - FOSTA Praktikergespräche CY - Darmstadt, Germany DA - 21.06.2016 KW - Modifizierter Sprühlichtbogen KW - Eigenspannungen KW - MAG-Schweißen KW - Hochfeste Feinkornbaustähle KW - Einspannung KW - Röntgendiffraktometrie KW - Schweißprozessparameter PY - 2016 AN - OPUS4-38790 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Engineering approach to assess residual stresses in welded components N2 - Present trends to lightweight design lead to an expanding relevance of high-strength fine-grained structural steels especially in mobile crane constructions. With growing material strength, the challenge for welding fabrication increases, since high loading capacities and safety requirements have to be accomplished. The utilisation of the high strength potential often requires complex constructions associated with high restraint conditions while welding. Increased residual stresses may occur due to superimposing reaction and restraint stresses, which have to be quantified and evaluated to ensure the safety and integrity of high-strength steel constructions. Particularly, the scope of residual stresses has to be taken into account for different effects in the HAZ, notches, weld and base metal. Commonly, conservative assumptions of residual stresses lead to distinct underestimations of the load bearing capacity particularly for welded high-strength steel constructions. This study concludes results of recent works of the researchers regarding the complex interaction among heat control, material and restraint intensity on the residual stress state in welded components. These analyses are extended by further experiments. Based on the obtained major effects, an approach for a welding residual stress assessment regarding component design according to prevailing standards for crane construction, an important application for high-strength steels, is presented. KW - Process parameters KW - Residual stresses KW - MAG welding KW - Restraint KW - High-strength steels PY - 2017 DO - https://doi.org/10.1007/s40194-016-0394-9 SN - 0043-2288 SN - 1878-6669 VL - 91 IS - 1 SP - 91 EP - 106 PB - Springer CY - Berlin, Heidelberg AN - OPUS4-39044 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Kannengießer, Thomas A1 - Schröpfer, Dirk T1 - Einsatz modifizierter Sprühlichtbogenprozesse zur Optimierung schweißbedingter Beanspruchungen an Bauteilen aus hochfesten Feinkornbaustählen N2 - Aufgrund aktueller Leichtbaubestrebungen sowie Forderungen nach Energie- und Ressourceneffizienz werden zunehmend hochfeste Feinkornbaustähle mit Streckgrenzen ≥ 690 MPa in modernen Stahlkonstruktionen eingesetzt. Vorrangig werden diese mit Streckgrenzen bis 960 MPa verarbeitet und mittels MAG-Schweißprozessen gefügt. Moderne Invertertechnik ermöglichte jüngst zahlreiche Firmenentwicklungen (bspw. „DeepARC“, „forceArc“), die zu modifizierten Sprühlichtbögen (mod. SLB) mit ähnlichen Eigenschaften führten. Neben den bekannten wirtschaftlichen Vorteilen dieser mod. SLB, lassen gerade die reduzierten möglichen Nahtöffnungswinkel und die geringere Wärmeeinbringung eine positive Wirkung auf schweißbedingte Beanspruchungen erwarten. Erste Eigenspannungsanalysen bei vorangegangenen Schweißeignungsuntersuchen mit mod. SLB zeigten bereits bei freischrumpfenden Laborproben geringere Zugeigenspannungen in der Schweißnaht im Vergleich zu konventionell geschweißten Proben. Die betriebsfeste Auslegung von hochfesten Schweißkonstruktionen und die Ausnutzung hoher Streckgrenzen erfordern jedoch eine ausreichende Quantifizierung schweißbedingter Beanspruchungen der mod. SLB unter definierter, bauteilrelevanter Schrumpfbehinderung. Dies betrifft sowohl die Kräfte und Spannungen im lokalen Schweißnahtbereich als auch die Gesamtbeanspruchung sowie den Einfluss von Wärmeführung, Bauteilgeometrie, Einspanngrad und Nahtöffnungswinkel. Hierzu lagen in der Industrie, besonders bei den KMU, kaum Kenntnisse vor und sollten deshalb als Ziel dieses Forschungsprojektes erarbeitet werden. Die vergleichenden Untersuchungen mit konventionellen Lichtbogen und mod. SLB mit angepasster Nahtkonfiguration erfolgten mithilfe von speziellen Prüfanlagen, mit der reale Bauteilsteifigkeiten abgebildet werden können. Bei beiden Prozessvarianten waren mit den gewählten Parametern Schweißnähte unter Erfüllung der Anforderungen an die mechanisch-technologischen Eigenschaften realisierbar. Bei den Analysen konnte eine signifikante Reduzierung der Eigenbeanspruchungen durch eine verminderte Wärmeeinbringung bei dem Einsatz einer Nahtkonfiguration mit abgesenktem Nahtöffnungswinkel beobachtet werden. Insbesondere erwiesen sich zur Absenkung mehrachsiger Beanspruchungszustände aufgrund von Biegemomenten in den bauteilnahen Schweißungen die engeren Nahtspalte als zielführend. Eine Vorstellung der erarbeiteten Kenntnisse und Empfehlungen in entsprechenden Gremien zur Normung erfolgten, um mittelfristig vor allem den KMU eine einfachere Konstruktionsauslegung und sichere Verarbeitung hochfester Feinkornbaustähle zu ermöglichen. Mit einer normativen Absicherung kann Qualifizierungs- und Zulassungsaufwand eingespart werden, der aktuell beim Einsatz hochfester Stähle vielfach notwendig ist. Ferner werden die Betriebe durch die Ergebnisse in die Lage versetzt, die technischen und wirtschaftlichen Vorteile der mod. SLB-Prozesse auszunutzen und signifikante Einsparungen bei Schweißzusatz, Schweiß- und Rüstzeit sowie unter Berücksichtigung der Eigenbeanspruchung optimierte Ergebnisse hinsichtlich der Tragfähigkeit von Bauteilen zu erreichen und die Produktivität zu erhöhen. KW - MAG-Schweißen KW - Hochfester Stahl KW - Eigenspannungen KW - Kaltrisssicherheit PY - 2017 UR - https://matplus.shop/produkt/p-1011-einsatz-modifizierter-spruehlichtbogenprozesse-zur-optimierung-schweissbedingter-beanspruchungen-an-bauteilen-aus-hochfesten-feinkornbaustaehlen-2 SN - 978-3-946885-12-2 N1 - Das IGF-Vorhaben 17978 N wurde über die Arbeitsgemeinschaft industrieller Forschungsvereinigungen "Otto von Guericke" (AiF) im Rahmen des Programms zur Förderung der Industriellen Gemeinschaftsforschung (IGF) vom Bundesministerium für Wirtschaft und Energie (BMWi) aufgrund eines Beschlusses des Deutschen Bundestages gefördert VL - P 1011 SP - 1 EP - 136 PB - Verlag und Vertriebsgesellschaft CY - Düsseldorf AN - OPUS4-59257 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Richter, Tim A1 - Erxleben, Kjell A1 - Rhode, Michael A1 - Schröpfer, Dirk A1 - Michael, Thomas A1 - Börner, Andreas T1 - Microstructure characterization of dissimilar metal welds of innovative high- and medium-entropy alloys to austenitic stainless steels joint by tungsten inert gas and friction stir welding N2 - The new multi-element alloying concept of systems with defined entropy (HEA — high-entropy alloy or MEA — medium-entropy alloy) is increasing in material research interest. Improved properties or combinations of properties are shown by several systems. Thus, the resulting microstructures and production of HEA/MEA as well as properties have been primarily investigated so far. Furthermore, processing is a key issue to transfer HEA/MEA systems to real components. Since welding is the most important joining process for metals, it is crucial to investigate the influence of welding to guarantee component integrity. Since most HEA are made of expensive alloying elements such as Co or Ni, they will not be used entirely as structural materials. Thus, it can be advantageous to weld conventional alloys such as austenitic stainless steels with the HEA and MEA to produce components that are both application-oriented and economically viable. Therefore, in this paper, first results of dissimilar metal welding, by tungsten inert gas (TIG) and friction stir welding (FSW), of a CoCrFeMnNi HEA as well as a CoCrNi MEA with a conventional AISI 304 austenitic stainless steel are presented. The focus is on the microstructure formation due to the two welding processes. The results of TIG welding show a dendritic microstructure, whereas in FSW both materials are stirred but still coexist. KW - Metals and Alloys KW - Mechanical Engineering KW - Mechanics of Materials PY - 2023 DO - https://doi.org/10.1007/s40194-023-01618-z SN - 1878-6669 SP - 1 EP - 9 PB - Springer AN - OPUS4-59252 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -