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 - 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 - 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 - CONF A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Hadick, C. A1 - Schu, K. T1 - Quantification of hydrogen uptake during in-service hydrogen pipeline welding N2 - Hydrogen must be transported on a large scale from producers to consumers to ensure the energy transition. The necessary pipeline grid is achieved by conversion of the natural gas (NG) grid and building new pipelines. Welding during service as part e.g. of “hot-tapping” is unavoidable for maintenance/repair/expansion. Based on existing studies, the basic material compatibility of (low-alloyed) pipeline steels with hydrogen is postulated. However, this cannot be assumed for the case of in-service welding on pipelines in pressurized condition. The reason is the increased temperature e.g. by preheating and (in particular) during welding of the single passes. As a result, the inner pipeline surface undergoes multiple short-term heating but to high temperatures. In particular, the first passes can result in a temperature close to the austenitic transformation of the material for small wall thicknesses. Both increase the hydrogen uptake into the welded joint. If hydrogen embrittlement is likely to occur, depends on the hydrogen uptake, which must be quantified. For this purpose, welding experiments on pressurized demonstrators were conducted. The hydrogen uptake at 100 bar was compared to reference experiments with nitrogen. A new sample extraction routine for the quantification of the weld-zone specific hydrogen uptake was established. Comprehensive experiments with different steels (P235, L360, L485), wall thicknesses (4.1 mm to 7.8 mm) and diameters (DN50 and DN200) were conducted. In addition, the influence of the welding layer sequence on the hydrogen uptake between single- and multi-layer welds was investigated. Analytical approaches were used to approximate the hydrogen uptake in the respective weld zones. The main findings were that the layer sequence and especially the wall thickness have a large influence on the hydrogen uptake. T2 - 20th Pipeline Technology Conference ptc2025 CY - Berlin, Germany DA - 06.05.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding KW - component test PY - 2025 SP - 1 EP - 12 AN - OPUS4-63166 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Czeskleba, Denis A1 - Fleißner-Rieger, H. A1 - Nietzke, Jonathan A1 - Kannengießer, Thomas T1 - Combined heating rate and restraint condition effect on stress relief cracking during PWHT of thick-walled Cr–Mo-V steel SAW joints N2 - Creep-resistant steels such as 13CrMoV9-10 are utilized in the manufacture of thick-walled pressure vessels and are typically joined by submerged arc welding (SAW). However, these materials are susceptible to stress relief cracking (SRC) if the required post weld heat treatment (PWHT) is not applied correctly. Existing PWHT guidelines, encompassing heating rate and dwell (or holding) time at a given temperature, are derived from a synthesis of empirical knowledge and typically free-shrinkage weld experiments to assess the susceptibility to SRC. Therefore, this study discusses the combined effect of the PWHT heating rate under free-shrinkage compared to restrained shrinkage. Welding experiments were conducted (using plates with a thickness of 25 mm) for both shrinkage conditions for a variety of heating rates and maximum temperatures. In-situ acoustic emission analysis was used to locate propagating SRCs during PWHT. Hardness measurements, mechanical property characterization (Charpy impact strength), and microstructure correlation were used to evaluate the SRC susceptibility. The results suggested that the influence of heating rate could not be directly related to SRC formation and that the initial weld microstructure prior to PWHT was more relevant in terms of very high hardness in the coarse grain heat affected zone, especially that of the last beads in the top layer of the welding sequence. This was seen in the form of random, unexpected SRC occurrence in only one specimen at a heating rate commonly used in welding practice (approximately 100 K/h). In this context, the additional effect of an external shrinkage restraint on SRC must be considered in the form of increasing mechanical loads during welding, which are typically not within the scope of welding practice. To mitigate the probability of SRC during PWHT, it is imperative to reduce the welding heat input and to restrict the structural shrinkage restraint of the weld joint. KW - Component test KW - Stress relief cracking KW - PWHT KW - Creep-resistant steel PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-631439 DO - https://doi.org/10.1007/s40194-025-02062-x SN - 1878-6669 SP - 1 EP - 17 PB - Springer Nature AN - OPUS4-63143 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Engelking, Lorenz A1 - Scharf-Wildenhain, R. A1 - Schröpfer, Dirk A1 - Hälsig, A. A1 - Kannengießer, Thomas A1 - Hensel, J. T1 - Influence of heat input on properties and residual stresses in hybrid addi-tive manufacturing of high strength steels using MSG processes N2 - The application of steels with a higher yield strength allows reductions in wall thickness, component weight and production costs. Hybrid additive manufacturing based on Gas Metal Arc Welding (GMAW) processes (DED-Arc) can be used to realise highly effi-cient component modifications and repairs on semi-finished products and additively manufactured structures. There are still a number of key issues preventing widespread implementation, particularly for SMEs. In addition to the manufacturing design, detailed information about assembly strategy and geometric adaptation of the component for modifications or repairs are missing. These include the welding-related stresses associ-ated with the microstructural influences caused by the additive manufacturing steps, particularly in the transition area of the substrate and filler material interface. The pre-sent research focuses the effect of welding heat control during DED-Arc process on the residual stresses, especially in the transition area. Defined specimens were welded fully automatically with a high-strength solid wire (yield strength > 790 MPa) especially adapted for DED-Arc on S690QL substrate. The working temperature and heat input were systematically varied for a statistical effect analysis on the residual stress state of the hybrid manufactured components. Regarding heat control, t8/5 cooling times within the recommended processing range (approx. 5 s to 20 s) were complied. The investiga-tion revealed a significant influence of the working temperature Ti on the compressive residual stresses in the transition area and the tensile residual stresses at the base of the substrate. High working temperatures result in lower compressive residual stresses, heat input E does not significantly affect the tensile stresses. T2 - 6. Symposium Materialtechnik CY - Clausthal-Zellerfeld, Germany DA - 20.02.2025 KW - DED-Arc KW - Residual stress KW - Heat control PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-632188 DO - https://doi.org/10.21268/20250506-3 SP - 110 EP - 122 AN - OPUS4-63218 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kaiser, Sebastian A1 - Erxleben, Kjell A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Herausforderungen beim Schweißen im Betrieb an Wasserstoff-Ferngasleitungen N2 - Als Energieträger der Zukunft kommt grünem Wasserstoff große Bedeutung bei der Energiewende und der zukünftigen, nachhaltigen Energieversorgung zu Teil. Zum effizienten und sicheren Transport des Wasserstoffs ist die Bereitstellung einer Pipeline-Infrastruktur geplant. Die meisten Länder verfolgen hierbei die Strategie der Umwidmung bestehender Erdgastransportleitungen, ergänzt durch Errichtung neuer Pipelines. Die bestehenden Erdgasnetze sind dabei aus unterschiedlichsten Rohrgeometrien und Materialien zusammengesetzt. Bei der Umwidmung von Erdgaspipelines zum Transport von Wasserstoff müssen daher Fragen der Materialverträglichkeit hinsichtlich des als Wasserstoffversprödung bekannten Phänomens der Beeinträchtigung der mechanischen Eigenschaften metallischer Werkstoffe durch Wasserstoff betrachtet werden. Bisherige Forschungsergebnisse und Feldversuche deuten darauf hin, dass die niedriglegierten, ferritischen Stähle, aus denen die Ferngasleitungen des Erdgasnetzes überwiegend bestehen, für den Transport von Wasserstoff unter normalen Betriebsbedingungen geeignet sind. Eine Frage, die bislang weniger Aufmerksamkeit erhielt, ist die, wie sich das Schweißen im Betrieb an Wasserstoffpipelines auf die Materialkompatibilität auswirkt. Im Erdgasnetz sind etablierte Verfahren wie beispielsweise das „Hot-Tapping“ unumgänglich für die Instandhaltung und Erweiterung des Netzes. Hierbei werden an eine im Betrieb befindliche Pipeline geteilte T-Stücke aufgeschweißt, über die die Pipeline dann mit geeigneten Bohrvorrichtungen während eines ununterbrochenen Betriebs angebohrt werden kann. Um zu beurteilen, ob diese Verfahren gefahrlos auf Wasserstoffpipelines übertragen werden können, müssen Problemstellungen betrachtet werden, die sich durch den Wärmeeintrag ins Material beim Schweißen ergeben. Wasserstofflöslichkeit und Diffusionsgeschwindigkeit sind temperaturabhängig. Erhöhte Temperaturen könnten eine Wasserstoffaufnahme ins Material bewirken, die zu einer kritischen Degradation der mechanischen Eigenschaften des Materials führen könnte. Die Temperaturen, die beim Schweißen erreicht werden, führen lokal zur Überschreitung der Austenitisierungstemperatur. Austenit weist eine deutlich höhere Löslichkeit von Wasserstoff auf, während die Diffusionsgeschwindigkeit des Wasserstoffs in dieser Phase deutlich herabgesetzt ist. Es wird vermutet, dass dies zu einer lokal erhöhten Wasserstoffkonzentration führt. Damit geht ein erhöhtes Risiko einer kritischen Materialdegradation einher. Durch die lange Zeitdauer beim Schweißen von mehrlagigen Rundkehlnähten an großen Pipelines, einschließlich einer möglichen Vorwärmprozedur, ist weiterhin zu klären, ob der aus Anwendungsfällen in der Petrochemie bekannte Hochtemperaturwasserstoffangriff auftritt. Der vorliegende Beitrag liefert einen Überblick über das Schweißen im Betrieb an Gaspipelines, hierbei auftretenden Herausforderungen bei der möglichen Anwendung auf Wasserstoffleitungen. Dabei werden auch aktuelle Forschungsprojekte zum Thema Schweißen an Wasserstoffpipelines im Betrieb eingehend diskutiert. In diesem Zusammenhang werden erste Ergebnisse des gemeinschaftlichen Forschungsprojektes „H2-SuD: Einfluss des Schweißens auf die Wasserstoffaufnahme und Degradation im Betrieb befindlicher H2-Ferngasleitungen“ des Deutschen Vereins des Gas- und Wasserfaches (DVGW), der Bundesanstalt für Materialforschung und -prüfung (BAM) und deutscher Gasnetzbetreiber (Open Grid Europe, ONTRAS Gastransport, u.v.m.) präsentiert. T2 - 53. Sondertagung - Schweißen im Anlagen-und Behälterbau 2025 CY - Munich, Germany DA - 18.03.2025 KW - Materialdegradation KW - Pipeline KW - Schweißen KW - Wasserstoff PY - 2025 SN - 978-3-96144-290-4 (Print) SN - 978-3-96144-291-1 (E-Book) VL - 2025 SP - 106 EP - 115 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-62911 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröder, Nina A1 - Kromm, Arne A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Innovatives Instandsetzungsschweißen von Altstahl: Materialverhalten und Herausforderungen N2 - Aus Gründen der Nachhaltigkeit und Wirtschaftlichkeit gibt es in der stahlverarbeiten-den Industrie einen Trend zum Bauen im Bestand, um kostenintensive Sperrungen oder Rückbau zu vermeiden. Schweißen wird dabei als wirtschaftliches Fügeverfahren im Zusammenhang mit Altstählen kaum genutzt, obwohl Nieten- und Schraubenverbindungen oft unwirtschaftlich sind. Für die Instandsetzung ist häufig beschädigtes Bestands-material durch neue Stähle zu ersetzen bzw. Alt-Neu-Stahl-Mischverbindungen herzu-stellen. Aufgrund der verschiedenen Herstellungsprozesse von Altstählen ist nicht jeder Stahl aus dem 20. Jahrhundert schweißgeeignet. Daher ist zunächst eine Schweißeignungsprüfung erforderlich. In den vorliegenden Untersuchungen wurden verschiedene Altstähle hinsichtlich ihres Schweißverhaltens mittels Dilatometrie analysiert. Ziel war es, eine Datenbasis aus Schweiß-Zustands-Zeit-Diagrammen und Simulationen der Wärmeeinflusszone zu erstellen, um praxisrelevante Schweißuntersuchungen ableiten zu können. Diese geben wesentlichen Aufschluss hinsichtlich ihres schweißmetallurgischen Verhaltens und ihrer Schweißeignung. Solche Grundlagen sind zur Entwicklung innovativer schweißtechnischer Konzepte zur beanspruchungsgerechten Instandsetzung bestehender Altstahl-Infrastruktur in Deutschland notwendig. T2 - 6. Symposium Materialtechnik, 20. bis 21. Februar 2025 CY - Clausthal-Zellerfeld, Germany DA - 20.02.2025 KW - Altstahl KW - Schweiß-ZTU Diagramme KW - Instandsetzungsschweißen KW - Schweißeignungsprüfung KW - Dilatometrie PY - 2025 SN - 978-3-8440-9961-4 DO - https://doi.org/10.21268/20250505-1 VL - 15 SP - 370 EP - 380 PB - Shaker Verlag GmbH CY - Düren AN - OPUS4-63377 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Rhode, Michael A1 - Mente, Tobias A1 - Kannengießer, Thomas A1 - Czeskleba, Denis T1 - Simulation of hydrogen distribution in submerged arc welded heavy plates as tool for evaluating cold cracking sensitivity for offshore structures N2 - Foundation structures for offshore wind turbines are typically made of heavy plate struc-tural steels, such as S420ML, welded by submerged arc welding. Due to the welding process conditions, higher amounts of hydrogen can be introduced. In this context, large plate thicknesses result in long diffusion paths and a prolonged diffusion time for hydrogen at ambient temperature and possible delayed hydrogen-assisted cold cracking. As a result, hydrogen can accumulate in areas of high mechanical stress and strain. Due to the delayed diffusion, a minimum waiting time of up to 48 h must be observed before non-destructive testing can be performed. In addition, the assessment of possible cold crack locations is very complex. For this reason, a numerical model of a component-like weld test was developed to simulate the temperature field during welding and subsequent cooling. A hydrogen diffusion model based on the temporal-local temperature distribution was established. It was applied to simulate the change of hydrogen distribution as a function of temperature cycle during multi-layer welding and further for the entire waiting time interval ≤ 48 h. As a result, crack critical areas could be evaluated in terms of accu-mulated hydrogen. An advantage of the diffusion model is the simulation of a normalized concentration, i.e. between "0" (no hydrogen) and "1" (max. concentration), which can be scaled to experimentally determined hydrogen concentrations. Finally, selected results for increased real hydrogen ingress are presented, which confirm the relatively high crack resistance of the S420 submerged arc welded joint. KW - Hydrogen assisted cracking KW - Diffusion KW - Numerical simulation KW - Offshore steel PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-632416 DO - https://doi.org/10.21268/20250507-6 SP - 1 EP - 12 PB - Technische Universität Clausthal CY - Clausthal-Zellerfeld, Deutschland AN - OPUS4-63241 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Hadick, C. A1 - Schu, K. T1 - Component test concept for evaluation of in-service welding on pressurized hydrogen pipelines N2 - Hydrogen is set as the energy carrier of tomorrow and most countries will achieve large-scale hydrogen transport through the conversion of the natural gas (NG) grid and the construction of new pipelines. The interaction between hydrogen and the pipeline materials differs fundamentally from that of NG, as hydrogen is readily absorbed into the material. Considering the possible hydrogen embrittlement (HE), the compatibility of the pipeline materials (low-alloyed steels with a wide strength/thickness range) must be investigated. However, pipelines require intervention for maintenance, repair, or grid expansion with welding on/onto the pipelines while in service, i.e. the well-known "hot tapping" and "plugging" or “stoppling”. The challenges compared to NG can be broadly divided into the possible austenitization of the inner pipe material exposed to hydrogen and the welding itself. Both result in a significant increase in hydrogen solubility and could potentially pose challenges in terms of HE. Emphasis is placed on the word "could" because knowledge of "hot tapping" on hydrogen pipelines is scarce due a lack of service experience. To this end, this study proposes a concept for a component-like demonstrator with the objectives: (1) safe feasibility of "hot tapping" on pressurized model hydrogen pipeline sections, (2) facilitate ex-post sample extraction for the purpose of quantifying the absorbed hydrogen concentrations, and (3) ensure in-situ temperature measurement during welding to monitor the pipeline surface temperature. For safety reasons in the event of an unintentional "burn-through", a solid cylinder was inserted in the demonstrator to restrict the hydrogen gas volume to a small, pressurized layer. Reference pipeline surface temperature measurements were ensured on comparable, unpressurized geometries. The investigated range of welding conditions was investigated for representative material/thickness combinations (DN50 to DN200), suggesting the feasibility of the demonstrator for the determination of reliable in-service welding conditions for both installed and new pipelines for hydrogen service. T2 - 20th Pipeline Technology Conference ptc2025 CY - Berlin, Germany DA - 06.05.2025 KW - In-service KW - Hydrogen KW - Pipeline KW - Repair welding KW - component test PY - 2025 SP - 1 EP - 11 AN - OPUS4-63168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -