TY - JOUR A1 - Czeskleba, Denis A1 - Rhode, Michael A1 - Wandtke, Karsten A1 - Irfan, Muhammad Dary A1 - Kannengiesser, Thomas T1 - Hydrogen diffusion in thick-walled S690 SAW joints: part 2 – predictive modeling of heat input and microstructure influence N2 - High-strength low-alloy (HSLA) steels such as S690 are widely employed in thick-walled welded structures, where hydrogen-assisted cold cracking (HACC) remains a persistent concern. While microstructure-specific hydrogen diffusion coefficients (DH) for weld metal (WM), heat-affected zone (HAZ), and base material (BM) were experimentally established in Part 1 of this study, their quantitative influence on hydrogen accumulation and effusion has not yet been fully clarified. This work presents a transient, spatially resolved numerical model for simulating hydrogen transport in multi-pass submerged arc welds. The model integrates experimentally determined DH values with realistic thermal cycles and temperature-dependent boundary conditions. Developed in Python, the simulation tool is purpose-built for hydrogen diffusion in welded joints. It offers a focused, transparent alternative. It offers a focused, transparent alternative to general-purpose finite element platforms. Parametric analyses demonstrate that, although the diffusion coefficients vary by up to 50%, their impact on overall hydrogen retention is minor. In contrast, plate thickness, bead geometry, cooling time (t₈/₅), and interpass temperature exert a dominant influence on hydrogen distribution. Despite clear microstructural differences between the thermomechanically rolled (S690MC) and quenched and tempered (S690Q) variants, including opposite HAZ hardness responses (softening in S690MC, hardening in S690Q) in the (pen)ultimate weld bead, the simulations confirm that their diffusion behavior and hydrogen solubility are closely aligned. Consequently, differences in DH and solubility exert only a minor influence on hydrogen retention compared to thermal exposure and joint geometry. These findings support the interchangeable use of both steel grades in terms of HACC risk due to hydrogen diffusion kinetics under comparable welding conditions. KW - Hydrogen assisted cracking KW - Numerical simulation KW - Diffusion KW - Submerged arc welding PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655721 DO - https://doi.org/10.1007/s40194-026-02395-1 SN - 0043-2288 SP - 1 EP - 16 PB - Springer Science and Business Media LLC AN - OPUS4-65572 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröder, Nina T1 - Herausforderungen und Potenziale moderner Hochleistungs-Lichtbogenprozesse für effiziente Reparaturmaßnahmen an Altstahlkonstruktionen N2 - Stahltragwerke, die im späten 19. und frühen 20. Jahrhundert errichtet wurden, stellen noch heute einen wesentlichen Bestandteil der technischen Infrastruktur dar. Ein erheblicher Anteil der Brücken- und Ingenieurbauwerke befindet sich seit mehr als 80 oder sogar 100 Jahren in Betrieb und ist kontinuierlich steigenden Verkehrsaufkommen, Achslasten sowie dynamischen Einwirkungen ausgesetzt. Vor dem Hintergrund dieser zunehmenden Beanspruchungen sind beanspruchungsgerechte und konstruktiv angemessene Instandsetzungsstrategien unerlässlich, um die langfristige strukturelle Integrität sicherzustellen und zugleich den vorhandenen Baubestand nachhaltig zu erhalten. Da historische Stahlkonstruktionen überwiegend für genietete oder geschraubte Verbindungen ausgelegt wurden, stellt die nachträgliche Umsetzung geschweißter Reparatur- oder Verstärkungsmaßnahmen eine besondere Herausforderung dar. Neben den spezifischen werkstofflichen Eigenschaften alter Flussstähle sind insbesondere schweißbedingte Eigenspannungen sowie mikrostrukturelle Veränderungen zu berücksichtigen, da diese die Tragfähigkeit und das Gesamttragverhalten maßgeblich beeinflussen können. Infolgedessen müssen Instandsetzungskonzepte nicht nur die geometrische Wiederherstellung gewährleisten, sondern zugleich an den tatsächlichen Spannungszustand und die betrieblichen Beanspruchungen des Tragwerks angepasst werden. Vor diesem Hintergrund untersucht die vorliegende Arbeit MAG-Schweißversuche an Mischverbindungen zwischen historischem und modernem Baustahl. Der Nahtöffnungswinkel wurde systematisch zwischen 50° und 30° variiert, um den Einfluss der Fugengeometrie auf das Schweißgutvolumen, die Wärmeeinbringung sowie den resultierenden Eigenspannungszustand zu analysieren. Darüber hinaus kamen innovative Hochleistungs-Lichtbogenprozesse, wie beispielsweise ein modifizierter Sprühlichtbogen, zum Einsatz, um eine kontrollierte und reduzierte Wärmeeinbringung zu ermöglichen. Ziel ist es, schweißbedingte Eigenspannungen durch eine Optimierung von Prozessführung und Fugengestaltung zu minimieren und damit eine technisch fundierte sowie beanspruchungsgerechte Instandsetzungsstrategie für bestehende historische Stahltragwerke mit langfristiger Gebrauchstauglichkeit bereitzustellen. T2 - Forschungsseminar an der OvGU Magdeburg CY - Magdeburg, Germany DA - 18.02.2026 KW - Flussstahl KW - Reparaturmaßnahmen KW - Schweißeignung KW - Modifizierter Sprühlichtbogen KW - Eigenspannungen PY - 2026 AN - OPUS4-65577 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Czeskleba, Denis A1 - Rhode, Michael A1 - Wandtke, Karsten A1 - Irfan, Muhammad Dary A1 - Kannengiesser, Thomas T1 - Hydrogen diffusion in thick-walled S690 saw joints: part 1—experimental determination of microstructure-dependent diffusion coefficients N2 - High-strength low-alloyed steel S690 is widely used in heavy-duty applications, such as structural components, mobile cranes, and industrial plant construction, owing to their high strength and weldability. However, thick-plate submerged arc welding (SAW) can introduce elevated hydrogen levels and residual stresses that promote time-delayed hydrogen-assisted cold cracking (HACC). Accurate, microstructure-specific diffusion data are scarce, limiting predictive HACC assessments. This study presents an experimental determination of hydrogen diffusion coefficients (DH) in two S690 variants: thermomechanically rolled (S690MC) and quenched and tempered (S690Q). Multi-layer SAW welds were produced from 30 mm thick plate material at three heat input levels, and diffusion membranes were extracted from weld metal (WM), heat-affected zone (HAZ), and base material (BM). Hydrogen permeation tests, conducted in accordance with DIN En ISO 17081, yielded flux curves normalized in time from which DH was derived using the inflection-point method. At room temperature, DH values ranged from 6 × 10−5 mm2/s to 9 × 10−5 mm2/s across all regions and heat inputs, with no significant difference between S690MC and S690Q. Weld metal exhibited marginally lower DH, attributed to enhanced hydrogen trapping, while base material measurements showed greater variability. These microstructure-resolved diffusion coefficients add quantitative data for modern S690 SAW welds and provide internally consistent input parameters for the numerical simulations presented in part 2. The results support improved parameterization for subsequent assessments of HACC risk through the optimization of welding parameters. KW - Hydrogen assisted cracking KW - Submerged arc welding KW - Diffusion KW - Electrochemical permeation KW - Microstructure PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655711 DO - https://doi.org/10.1007/s40194-026-02400-7 SN - 0043-2288 SP - 1 EP - 15 PB - Springer Science and Business Media LLC AN - OPUS4-65571 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kaiser, Sebastian T1 - Bestimmung des Temperaturfeldes beim Schweißen im Betrieb an Wasserstoff-Ferngasleitungen N2 - Grüner Wasserstoff wird als zukünftiger Energieträger eine wichtige Rolle bei der Dekarbonisierung spielen. Sein großtechnischer Transport über große Entfernungen wird über ein Wasserstoff-Pipelinennetz erfolgen. Ein solches Netz erfordert regelmäßig Schweißarbeiten zu Reparatur-, Wartungs- oder Erweiterungszwecken. Im Erdgasnetz ist es gängige Praxis, Schweißarbeiten während des Betriebs auszuführen, da es technisch und wirtschaftlich äußerst schwierig ist, eine Pipeline außer Betrieb zu nehmen. Im Fall von Wasserstoffpipelines ist hierbei jedoch zu beachten, dass Wasserstoff in den Pipelinestahl absorbiert werden kann. Dies kann zu einer Beeinträchtigung der Materialeigenschaften oder sogar zum Versagen der Pipeline führen, da die bekannten Effekte der wasserstoffinduzierten Versprödung und der wasserstoffunterstützten Rissbildung auftreten können. Die Wasserstoffaufnahme ist dabei wesentlich von den beim Schweißen auftretenden erhöhten Temperaturen abhängig. Um genaue Kenntnisse der zu erwartenden Temperaturen zu erlangen, wurden Schweißversuche an Ersatzgeometrien durchgeführt und Temperaturverläufe an diesen gemessen. Basierend auf den Temperaturmessungen sollen im weiteren Verlauf in Zusammenarbeit mit der TU Graz Temperaturfelder sowie die resultierende Wasserstoffaufnahme und -diffusion mittels FEM berechnet werden. T2 - Forschungsseminar OvGU-Magdeburg CY - Magdeburg, Germany DA - 18.02.2026 KW - Pipeline KW - Schweißen KW - Wasserstoff PY - 2026 AN - OPUS4-65565 LA - mul AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bär, J. A1 - Kanna, N.K. A1 - Duarte, Larissa A1 - Madia, Mauro T1 - Determination of the Kitagawa-Takahashi Diagram using DC Potential Drop Measurements N2 - The Kitagawa-Takahashi Diagram is an important tool for describing the fatigue limit of components containing defects. The models used for its description differ, particularly in the transition region corresponding to the short crack regime. Therefore, for a reliable statement about the fatigue limit in this area, an experimental validation of the models is necessary. However, the standardized staircase method requires a large number of samples and has a long test duration. In this work, a method is presented that allows a simpler and faster validation of the Kitagawa-Takahashi Diagram in the region of short cracks. Rectangular notches with a defined width and depth were manufactured in flat samples of a low-alloyed steel with two different heat treatments using an engraving laser. This method allows a rapid production of very sharp notches without plastic deformation and with only a slight thermal influence on the surrounding material. The samples prepared in this way were fatigued with block wise increasing loads until failure. Cracks are detected by means of a Direct Current Potential Drop method. The length of the loading block (number of cycles) is determined by the measured potential drop. This procedure enables a reliable and precise determination of the limit stress for the respective notch size with low experimental effort and time consumption. The tests have shown that in case of the normalized steel none of the models describes the determined values for the fatigue limit. For the hardened steel, the plot of the fatigue limit as a function of the Murakami parameter √area in combination with the El Haddad model allows a satisfactory description of the measured values. T2 - 5th International Symposium on Fatigue Design and Material Defects CY - Trento, Italy DA - 14.05.2025 KW - Kitagawa-Takahashi diagram KW - Damage tolerance KW - Fatigue KW - Potential drop KW - Fracture mechanics PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655519 DO - https://doi.org/10.1016/j.prostr.2025.12.283 VL - 76 SP - 27 EP - 34 PB - Elsevier B.V. AN - OPUS4-65551 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witte, Julien A1 - Treutler, Kai A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Influence of Microstructure on the Machinability and Surface Integrity of Additively Manufactured Iron Aluminides N2 - The increasing global focus on energy and resource efficiency has stimulated a growing interest in additive manufacturing. AM offers economic advantages and enables an efficient use of materials. However, AM components often require subsequent mechanical post-processing, such as machining (e.g. milling), to achieve the final contours or surfaces. This is a particular challenge due to the heterogeneous and anisotropic nature of AM structures, which affect machining and the resulting component properties. High-performance materials such as iron aluminide represent a promising alternative to conventional high-temperature materials with a significant economic advantage. However, the strength and hardness properties, which are advantageous for applications in highly stressed lightweight components, pose a challenge for economical machining in addition to the AM microstructure properties. The difficult-to-cut material causes accelerated tool wear and insufficient surface quality. This study shows that crack-free additive manufacturing of the three-component system of iron-nickel-aluminum is possible, and advantages in terms of machinability compared to FeAl-AM components are achieved. The more homogeneous microstructure leads to a reduction in cutting forces, with positive effects on the machinability and optimized surface integrity. Ultrasonic assisted milling (USAM) offers great potential to address the major challenges posed by difficult-to-cut materials and additively manufactured weld structures. Therefore, this study focuses on assessing the transferability of previous positive results by USAM to the selected iron aluminide alloys. The machinability of the aluminides is analyzed by varying significant influencing variables in finish milling experiments and evaluated in terms of the loads on the tool and the resulting surface integrity. T2 - AA Meeting of Commission IX ‘Behavior of Metals subject to Welding’ CY - Rhodes, Greece DA - 08.07.2024 KW - Iron aluminide KW - Additive manufacturing KW - Machinability KW - Surface integrity KW - Ultrasonic-assisted milling PY - 2026 SP - 1 EP - 16 AN - OPUS4-65530 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dixneit, J. A1 - Gibmeier, J. A1 - Kromm, Arne A1 - Schubnell, J. A1 - Lang, F. A1 - Loebich, F. A1 - Carl, E.-R. A1 - Ya, W. T1 - Residual stress distribution of a large component manufactured by AM-DED-Arc from high-strength weld filler material X90 N2 - Currently, DED-Arc manufactured components are not covered by design guidelines, and design factors such as residual stress factors are not defined for such components. This hinders industrial use, especially for components with a remaining surface waviness required by industry. For the first time the stress state of a high-strength, low-alloy, large-scale DED-Arc component was characterised in the as-built state and after cutting off the component from the substrate plate. Complementary methods of residual stress analyses were applied to gain a holistic insight into the residual stress distributions of a thick-walled part. In the as-built state, direction-dependent and position-dependent tensile residual stresses were found for the component at the level of the yield strength of the part. The additive manufacturing strategy continuous spiral deposition has no significant influence on the residual stresses in bead threshold area compared to the residual stresses of the remaining component. For this case, bead threshold is no structural imperfection. By removing the part from the substrate plate, the residual stresses are significantly redistributed. Tensile residual stresses are then present at a moderate level. Compressive residual stresses were determined in the volume of the deposited material. The general consideration of ‘‘high’’ tensile residual stresses in such thick-walled components is rather conservative. Therefore, design guidelines should take the manufacturing condition into account. KW - AM-DED-Arc KW - Residual stress KW - High strength steel PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655239 DO - https://doi.org/10.1177/03093247251406876 SN - 2041-3130 SP - 1 EP - 18 PB - SAGE AN - OPUS4-65523 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Nina A1 - Uhlig, Marvin A1 - Kromm, Arne A1 - Schröpfer, Dirk A1 - Höfer, Kevin A1 - Hensel, Jonas A1 - Kannengießer, Thomas T1 - Challenges in the evaluation of the weldability of old mild steels for future use N2 - For reasons of sustainability and cost efficiency, there is an increasing trend in the steel-processing industry to retrofit existing structures, avoiding costly shutdowns or dismantling. Although welding is a cost-effective joining method, it is rarely applied to old steels, whereas riveted or bolted connections are often uneconomical. Repair and refurbishment frequently require the replacement of damaged material or the creation of dissimilar old–new steel joints. Due to the varied manufacturing processes of historical steels, not all twentieth-century steels are inherently weldable, making an initial assessment of weldability essential. In this study, a historical non-deoxidized mild steel (produced by Siemens–Martin processing) originating from the construction of the Berlin Radio Tower (erected in 1926) was investigated using dilatometry to analyze its welding behavior. A database of welding CCT diagrams and HAZ simulations was established to support practice-oriented welding experiments, providing key insights into their weld-metallurgical behavior and weldability. Furthermore, initial welding trials were conducted, and the local residual stress states in dissimilar old–new steel joints were determined. These foundational investigations are critical for the development of innovative, load-adapted welding concepts for the repair and refurbishment of existing old-steel infrastructure in Germany. KW - Old mild steels KW - Repair welding KW - Weldability KW - Thermo-physical simulation KW - CCT diagrams PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-654784 DO - https://doi.org/10.1007/s40194-026-02366-6 SN - 1878-6669 SP - 1 EP - 14 PB - Springer nature AN - OPUS4-65478 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübner, Martin A1 - Dittmann, Florian A1 - Kromm, Arne A1 - Varfolomeev, Igor A1 - Kannengiesser, Thomas T1 - Enhancement of the fatigue strength by application of a low transformation temperature (LTT) welding consumable N2 - Low transformation temperature (LTT) welding consumables offer a possibility to enhance fatigue strength in welded components without post-treatment. By lowering the martensite start temperature (MS), the volume expansion during transformation near ambient temperature reduces welding related tensile residual stresses in fatigue-critical areas. To evaluate this effect, longitudinal stiffeners were used, a LTT and conventional filler serve as welding consumable, also high frequency mechanical impact (HFMI) treatment was carried out. Three single-pass and six additional-pass sample series were investigated on residual stress and fatigue strength. The additional welds were applied in fatigue crack critical areas with different weld shapes, achieved by varying welding parameters. Mechanical tests on reference samples evaluated the properties of the diluted LTT welds. Although reduced toughness was observed, no fatigue cracks occurred in LTT single-pass weld roots. The fatigue strength at two million cycles increased from 81 MPa to 121 MPa compared to conventional welds, while HFMI reached 146 MPa. With an additional LTT weld pass the results varied from 138 MPa to 196 MPa, depending to the shape and residual stress state. The results show that LTT fillers effectively enhance fatigue performance, and that weld geometry and parameter selection are as critical as the chemical composition for maximizing the LTT effect. CY - Genua, Italy DA - 22.06.2025 KW - Low transformation temperature (LTT) KW - Martensite start temperature KW - Residual stress KW - Longitudenal stiffener KW - Fatigue strength PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-654520 DO - https://doi.org/10.1007/s40194-026-02356-8 SP - 1 EP - 14 PB - Springer Nature AN - OPUS4-65452 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Engelking, Loenz A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas A1 - Eissel, Antonia A1 - Treutler, Kai A1 - Wesling, Volker T1 - Herstellung beanspruchungsgerechter Oberflächen durch Kombination innovativer additiver und abtragender Fertigungsschritte an hochbelasteten Komponenten N2 - Die additive Fertigung mittels Schweißverfahren bietet große ökonomische Vorteile für eine ressourceneffiziente Bauteilherstellung. Offene Fragen bezüglich Homogenität, Anisotropie der Schweißgefüge und den damit verbundenen Bauteileigenschaften stehen einer wirtschaftlichen Verarbeitung oftmals im Wege. Finale Bauteilgeometrie und Oberflächengüte erfordern meist komplementäre subtraktive Fertigungsschritte. Werkstoffe für hochbelastbare Komponenten sind oftmals schwer span bar. In einem Vorhaben der BAM und des ISAF wurde untersucht, wie die Modifikation der AM-Schweißzusätze und das ultraschallunterstützte Fräsen (US) die Zerspanungssituation verbessern. Der vorliegende Artikel stellt wesentliche Zusammenhänge zwischen Legierung, Gefüge und Zerspanung zweier schwer spanbarer Hochleistungslegierungen (FeNi und CoCr) dar. Großes Potenzial zeigte neben dem US die Modifikation mit Zr und Hf bei Zulegierung in das Schweißgut mittels Beschichtung von Massivdrähten bzw. Herstellung von Fülldrähten. KW - Additive Fertigung (AM) KW - Ultraschallunterstütztes Fräsen (US) KW - Werkstoffmodifikation KW - Oberflächenintegrität KW - Zerspanbarkeit schwer spanbarer Legierungen KW - Ressourceneffizienz in Prozessketten KW - Hochleistungslegierungen KW - Technologietransfer für KMU PY - 2025 SN - 978-3-96144-304-8 VL - 2026 SP - 290 EP - 298 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-65246 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -