TY - CONF A1 - Nietzke, Jonathan A1 - Rhode, Michael A1 - Mente, Tobias A1 - Kannengießer, Thomas T1 - Experimental and numerical characterization of hydrogen diffusion in thick-walled submerged arc welded joint of S420G2+M offshore steel grade N2 - Offshore wind turbines are an important goal in national energy strategies worldwide. Foundation structures are manufactured from submerged arc welded (SAW) plates with thicknesses up to 200 mm. In that connection, high-strength steels like the S420G2+M are more and more applied offering the possibility for increased stability and load-bearing capacity of the foundations. These offshore steel grades can show a susceptibility for delayed hydrogen assisted cold cracking of the weld joints. For that purpose, a minimum waiting time (MWT) of up to 48 h (dependent on applied standards) is recommended before non-destructive testing is allowed and conducted. But this concept is based on older steel grades that have been used for three or more decades. Nowadays, the metallurgical improvements (clean steels, proper rolling, and heat treatment) of base materials and well as welding consumables must be anticipated. Hence, the MWT concept should be critically discussed as it is assumed to be very conservative. For that reason, the focus of this study was to investigate the diffusion behavior in S420G2+M steel and its multi-layer SAW joint. Electrochemical permeation experiments were carried at room temperature. Boundary conditions were anticipated in terms of using different sample thicknesses. From the experimental data, hydrogen diffusion coefficients and absorbed diffusible hydrogen concentrations had been calculated. It was shown that hydrogen diffusion in the base material is increased compared to the weld metal. In addition, the sample thickness had a significant on the calculated diffusion coefficients. The minimum and maximum diffusion coefficients had been used for numerical modelling of the hydrogen diffusion in the welding joint. It became clear that a MWT must be always regarded together with a critical initial diffusible hydrogen concentration for the evaluation of a possible delayed cracking as diffusion times were mostly > 48 h due to the thick plates. T2 - 4th International Conference on Metals and Hydrogen - Steely & Hydrogen 2022 CY - Ghent, Belgium DA - 11.10.2022 KW - Hydrogen KW - Submerged arc welding KW - Diffusion KW - Minimum waiting time KW - Electrochemical permeation PY - 2022 SP - 1 EP - 11 CY - Ghent, Belgium AN - OPUS4-56075 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Nietzke, Jonathan A1 - Czeskleba, Denis A1 - Kannengießer, Thomas T1 - Untersuchung von Spannungsrelaxationsrissmechanismen mittels Simulation einachsiger Spannungszustände in der Grobkornzone von UP-geschweißtem CrMoV-Stahl N2 - Druckbehälter mit großen Wandstärken (250+ mm) aus hochwarmfesten, niedriglegierten Stählen werden hauptsächlich Mehrdraht-Unterpulver-(UP) geschweißt. Der damit verbundene hohe Energieeintrag führt unter anderem zu hohen lokalen Schweißeigenspannungen, welche bei unsachgemäßer Prozessführung der notwendigen Wärmenachbehandlung (PWHT) zu Spannungsrelaxationsrissen (SRR) führen. In den Bewertungskriterien zur Spannungsrelaxationsrissanfälligkeit finden weder die, mit klassischen, freischrumpfenden Schweißversuchen nicht abbildbaren, erhöhten Eigenspannungen aus der Schrumpfbehinderung der Bauteilsteifigkeit Beachtung, noch die damit einhergehenden metallurgischen Effekte wie bspw. das Ausscheidungswachstum während der PWHT und damit einhergehende Härteunterschiede an den Korngrenzen bzw. die vorzeitige Alterung durch Bildung differenter Sonderkarbide. Die Aufheizrate des PWHT als Einflussfaktor für die SRR-Bildung bleibt derzeit ebenfalls unbeachtet. Daher wurde eine Versuchsmethodik entwickelt, die eine mögliche SRR-Anfälligkeit durch die Kopplung von thermischer und mechanischer Beanspruchung untersucht. Dazu wurden Proben mit unterschiedlichen Gefügen thermisch simuliert und während des PHWT repräsentativ mit sehr hohen Lasten/Eigenspannungen mechanisch beansprucht. Dazu wurde an Kleinzugproben für das as-welded UP-Schweißgut und die thermisch simulierte GKZ eines 13CrMoV9-10 die Dehnung des Prüfbereichs bei variablen Querspannungen und Aufheizraten gemessen. Diese aufheizraten- und gefügeabhängige Längenänderung der Probe wurde durch mathematische Prozeduren analysiert. Damit war es möglich, singuläre werkstoffliche Effekte auf μm-Ebene (Ausscheidungswachstum) als summarische Längen- bzw. Volumenänderung per klassischer Kurvendiskussion zu beschreiben. Die erste und zweite Ableitung zeigten eine ausscheidungsabhängige Härtezunahme, welche von der Spannung und Aufheizrate im geringen Maß linear abhängig war. Gleichzeitig sind Volumenänderungen bei Bildung und Wachstum differenter Sonderkarbide bekannt, welche zusammen mit gefügespezifischen Untersuchungen und der neuen Versuchsmethodik zu einer verbesserten Beurteilung der SRR-Anfälligkeit von geschweißten CrMoV-Stählen beitragen sollen. Prinzipiell ist die vorgestellte Methodik jedoch werkstoff- und zustandsoffen, d.h. sowohl für Grundwerkstoff e als auch definierte Wärmebehandlungsbedingungen geeignet. Dies ermöglicht erstmals die Schaffung einer Transfergröße zwischen Labor und realen Schweißungen, unter Beibehaltung der Bauteilsteifigkeit, d.h. vereinfachte, aber realistische Eigenspannungsabbildung als Grundlage für weitergehende gefügespezifische metallurgische Effekte während des PWHT. T2 - DVS Congress 2022 CY - Koblenz, Germany DA - 19.09.2022 KW - UP-Schweißen KW - Spannungsrelaxationsriss KW - Wärmenachbehandlung KW - Ersatzgeometrie KW - Prüfverfahren PY - 2022 SN - 978-3-96144-190-7 VL - 382 SP - 69 EP - 75 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-55946 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Repair welding of pressurized in-service hydrogen pipelines - A review on current challenges and strategies N2 - As energy carrier of the future, green hydrogen can make a decisive contribution to a sustainable energy supply. Particularly important is the decarbonization of heavy industry. Therefore, a reliable supply of hydrogen must be guaranteed. A hydrogen pipeline grid can achieve this purpose. In Europe concrete plans for a hydrogen pipeline grid already exist, as the so called “European Hydrogen backbone”. As building a completely new pipeline grid is economically not justifiable, a dual-way strategy of repurposing natural gas (NG) pipelines and newly built pipelines is intended. Long distance pipeline grids require regular maintenance and repairs. For natural gas (NG) pipelines in-service welding is state of the art. Concepts such as hot-tapping (drilling into pressurized pipelines) and “stoppling” (sealing off pipeline sections after installing bypasses or pressure relieves) allow the repair of damaged pipeline sections or the installation of new branches without shutting the pipeline down, which in most cases isn’t possible from an economic standpoint. The EIGA 121/14 guideline already pointed out in 2014 that “a hydrogen hot-tap shall not be considered a routine procedure”. This shows that the determination of the transferability of these repair concepts to hydrogen pipelines is of utmost importance. Due to the degrading effects of hydrogen on mechanical proper-ties, commonly referred to as “hydrogen embrittlement” it is necessary to understand and investigate the occurring effects. In the special case of repair welding on in-service hydrogen pipelines an increased hydro-gen uptake due to a large heat input and microstructural changes in the material needs to be considered. Therefore, material degradation must be investigated to determine whether modifications of repair procedures are necessary to ensure a reliable and safe hydrogen transportation via pipelines. For this reason, this paper gives an overview on existing weld repair concepts and its risks and limitations in terms of hydrogen absorption and possible embrittlement effects when transferred to hydrogen pipelines. The complexity lies in a large variety of materials (low alloyed steels), pipeline diameters and corresponding welded joints. The material compatibility of materials in used (repurposed NG-pipelines) and new condition must be investigated. Particularly for repurposed/used pipelines the effect of a pre-matured/corroded inner surface and sometimes insufficient documentation of the material “history” needs to be considered. An overview on ongoing and completed R&D-projects with respect to repair concepts for hydrogen pipelines and hydrogen effects on pipeline materials is given. The focus hereby lies on possible methods of material testing and modeling. Its current difficulties, limits and possible solution will be discussed. T2 - IIW Intermediate Meeting, Com. II-A CY - Incheon, Republic of Korea DA - 12.03.2024 KW - Hydrogen KW - Repair welding KW - Pipelines KW - In-service PY - 2024 AN - OPUS4-59674 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Combined effect of heating rate and restraint condition on stress relief cracking susceptibility during PWHT of thick-walled Cr-Mo-V steel submerged arc welded joints N2 - Contemporary steels creep-resistant steels like the 13CrMoV9-10 are used as thick plates e.g., for applications in hydrocrackers. The large plate thickness requires high efficiency welding processes like submerged arc welding (SAW) and a mandatory post weld heat treatment (PWHT). The PWHT-parameters stem from a combination of empirical knowledge and traditional experiments on free shrinking (FS) welds. In that connection, the formation of so-called stress-relief cracking (SRC) must be anticipated. The SRC susceptibility of a welded component is a complex combination and interaction of com-ponent specific, thermal, and metallurgical factors. Many of which have to date not been conclusively researched. For example, it is well known that SRCs develop during PWHT due to formation and growth of carbides on prior austenite grain boundaries, resulting in a significant hardness increase (secondary hardening) and toughness decrease. This leads to a high SRC susceptibility of the coarse grain heat-affected zone (CGHAZ) of the last weld bead during PWHT. This is intensified in case of high residual stresses from the component-specific, structurally induced stiffness. In combination with multi-layer welding this leads to a multiaxial stress distribution. Nonetheless, the combined effect of PWHT and high-residual stresses on the SRC formation is merely unknown. For that reason, this study presents the effect of different heating rates in conjunction with a certain component stiffness. For that reason, SAW joints of 13CrMoV9-10 steel were investigated under FS and defined external restraint condition. T2 - IIW Intermediate Meeting, Com. II-A CY - Incheon, Republic of Korea DA - 12.03.2024 KW - Stress relief cracking KW - Welding KW - Post weld heat treatment KW - Submerged arc welding KW - Cr-Mo-V steel KW - Creep-resisting steel PY - 2024 AN - OPUS4-59673 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Call for interested people to contribute to series of comprehensive papers on welding and joining of components for sustainable energy systems N2 - Joining and welding technologies are of high importance for the manufacturing of components and parts used in sustainable energy generation, conversion, and transport. In that connection, offshore and on-shore installed wind turbines are of high interest for the generation of electrical energy as well as photo-voltaic systems (solar cells). The electricity can be either directly transported or conversed via power-to-gas e.g., to hydrogen. In that scope, electrolyzer up to MW-range are of interest as well as the conver-sion back to electricity via fuel cells. In addition, hydrogen is a key element of the decarburization of in-dustries as well as the mobility sector encompassing sea, air and land transportation driven by hydrogen or its derivates. Well-known examples cover the direct reduction of iron ore to replace the conventional blast furnace process up to gas turbines or fuel cells for home-end use. All mentioned technologies re-quire reliable components, which are to a high extend dependent on joining and especially welding pro-cessing of materials. Especially, the (petro-) chemical industry has many years of experience with both materials used in hydrogen applications. The challenge is e.g., the transition to mass production of sys-tem components of electrolyzers/fuel cells and for distribution grids. At this point, the scalability of cur-rently applied joining processes often limits the economic efficiency, whereas especially laser welding or additive manufacturing will be of high interest. In that connection, it is very important to provide answers by joint research of universities, institutes, and industrial companies. Very often, solutions are already available and “just” have to be investigated and adapted for the new application, like repair welding of NG pipelines. For that reason, we want to set up a series of comprehensive papers with the aforementioned title. The idea is to get an in-depth but manageable overview of the importance of joining technologies in sustaina-ble energy generation, conversion, and transport encompassing current processes, limitations, and fur-ther perspectives. In that connection, the additive manufacturing is gaining more and more attention. If applicable, current challenges in the adaption or creation of new standards/regulations shall be addressed. T2 - IIW Intermediate Meeting, Com. II-A CY - Incheon, Republic of Korea DA - 12.03.2024 KW - Hydrogen KW - Welding KW - Comprehensive study KW - Component manufatcturing KW - Additive manufacturing PY - 2024 AN - OPUS4-59676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Simulation der Wasserstoffverteilung in UP-geschweißten Grobblechen als Bewertungstool für die Kaltrissanfälligkeit von Offshorestrukturen N2 - Gründungsstrukturen für Offshore-Windkraftanlagen bestehen in der Regel aus hochfesten Stahlgrobblechen, die im UP-Verfahren geschweißt werden, durch den u.U. größere Mengen an Wasserstoff eingebracht werden können. Die große Blechdicke führt zudem zu langen Diffusionswegen und einer verlängerten Diffusionszeit für den Wasserstoff. Infolgedessen kann sich der Wasserstoff in Bereichen mit hoher mechanischer Spannung und Dehnung ansammeln und daher zu einer verzögerten Kaltrissbildung führen. Aufgrund der verzögerten Diffusion muss daher eine Mindestwartezeit von bis zu 48 h eingehalten werden, bevor eine zerstörungsfreie Prüfung durchgeführt wird. Darüber hinaus ist die Beurteilung möglicher Kaltrissstellen sehr komplex. Es wurde daher ein numerisches Modell zur Abbildung einer bauteilähnlichen Schweißnahtprüfung entwickelt. Dazu wurde das Temperaturfeld während des Schweißens und der anschließenden Abkühlung experimentell bestimmt und numerisch simuliert. Auf dieser Grundlage wurde Diffusionsmodell zur numerischen Simulation der zeitlich-örtlichen Wasserstoffkonzentration erstellt. Mit diesem Modell wurden zwei Anwendungsfälle simuliert: (1) Veränderung der Wasserstoffverteilung als Funktion des Temperaturzyklus während des Mehrlagenschweißens und (2) für das Wartezeitintervall ≤ 48 h. Ein Vorteil des Diffusionsmodells ist die Simulation einer normierten Konzentration, d.h. zwischen „0“ (kein Wasserstoff) und „1“ (max. Konzentration), die auf experimentell ermittelte Wasserstoffkonzentrationen skaliert werden kann. T2 - 6. Symposium Materialtechnik CY - Clausthal-Zellerfeld, Germany DA - 20.02.2025 KW - Gründungsstrukturen KW - Offshore KW - Kaltrissbildung KW - Wasserstoff KW - Numerische Simulation PY - 2025 AN - OPUS4-62616 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Fügetechnik für Wasserstofftechnologien: Ausgewählte Themen und Herausforderungen N2 - Die Präsentation fasst die Bedeutung der Fügetechnik für Wasserstofftechnologien im Rahmen der Arbeiten für einer Studie (DVS-Berichte Nr. 373) mit besonderer Berücksichtigung der Normung und Regelwerkssetzung zusammen. T2 - Sitzung des DIN-Gemeinschaftsarbeitsausschusses NA 092 00 05 GA, NAS/NMP: Zerstörende Prüfung von Schweißverbindungen CY - Online meeting DA - 10.03.2022 KW - Wasserstoff KW - Fügetechnik KW - Schweißen KW - Wasserstofftechnologien KW - Bedeutung PY - 2022 AN - OPUS4-54447 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Bewertungsmethode zur Interaktion von Metallurgie und Reaktionskräften beim PWHT warmfester Stähle N2 - Die Präsentation fasst die Entwicklung einer Ersatzprüfmethode für sogenannte Stress-Relief-Cracks (SRC) bei dickwandigen und kriechfesten geschweißten Stahlkomponenten zusammen. Über die Kombination von gezielter mechanischer Beanspruchung unter hoher Temperaturbeanspruchung werden die Effekte des Post Weld Heat Treatments auf SRC realistisch erstmal auf Laborskala nachgebildet. T2 - Sitzung des DIN-Gemeinschaftsarbeitsausschusses NA 092 00 05 GA, NAS/NMP: Zerstörende Prüfung von Schweißverbindungen CY - Online meeting DA - 10.03.2022 KW - PWHT KW - Warmfeste Stähle KW - UP Schweißen KW - Metallurgie KW - Stress relief cracking PY - 2022 AN - OPUS4-54448 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Reliable hydrogen determination in metallic materials and their weld joints: Parameters and challenges N2 - In the course of tomorrow's hydrogen-based energy transition, the construction of the corresponding infrastructure will play a central role. The majority of materials used to date are typically welded for component fabrication. In that context, steels are widely applied and can be prone to hydrogen embrittlement. This includes the classical delayed cold cracking during welding processing as well as embrittlement phenomena during operation. For the evaluation of any hydrogen effect on, for example, the mechanical properties of a welded metallic material, the hydrogen content must be precisely determined. In the case of welds, for example, according to ISO 3690, this is the isothermal carrier gas hot extraction (CGHE). CGHE is based on accelerated hydrogen degassing due to thermal activation of hydrogen at elevated temperatures. In addition to the pure quantification of hydrogen, thermal desorption analysis (TDA) with varied heating rates can be used to determine and evaluate the bonding state at microstructural defects in the material. For both techniques, experimental and measurement influences have to be considered, which have a great effect on the result. For CGHE, for example, ISO 3690 suggests different sample geometries as well as minimum extraction times. The present study summarizes results and experiences of numerous investigations with different sample temperatures and geometries (ISO 3690 type B and cylindrical TDA samples) regarding: the influence of the sample surface (polished/welded), measurement accuracies depending on the sample volume as well as the insufficient monitoring of the effect of the PI controller on the extraction temperature. In particular, a deviating extraction temperature to the set temperature, can significantly falsify the measurement results. Based on the results, methods are shown to quickly reach the desired extraction temperature without having to physically interfere with the measurement equipment. This serves to substantially improve the reliability of hydrogen measurement through increased signal stability and accelerated hydrogen desorption. In general, an independent temperature measurement with dummy samples for the selected heating procedure is advisable to exclude possible unwanted temperature influences already before the measurement. In addition (and way more important), the methods described can be transferred directly to industrial applications. T2 - 47th MPA-Seminar CY - Stuttgart, Germany DA - 10.10.2023 KW - Hydrogen assisted cracking KW - Carrier gas hot extraction KW - Welding KW - ISO 3690 KW - Metals PY - 2023 AN - OPUS4-58677 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Fügetechnik in Wasserstofftechnologien - Forschungsbedarf für die Branche (Kurzversion) N2 - Die Studie gibt einen kurzen Überblick über die jetzige Bedeutung der Fügetechnik in Wasserstofftechnologien und über zukünftige Forschungsbedarfe für die Branche in den einzelnen Technologiefeldern Wasserstofferzeugung, -speicherung, -transport und -nutzung. Fügetechnologien haben dabei wesentliche Bedeutung für die erfolgreiche Umsetzung von technischen Komponenten der Wasserstofftechnologien. Die Schwerpunkte bzw. Forschungsbedarfe ergeben sich bspw. durch die Erstellung neuer Infrastruktur für Wasserstoffspeicherung und -transport sowie durch Umnutzung der bestehenden Erdgasinfrastruktur. Bei der Wasserstofferzeugung und -anwendung wird z.B. die Entwicklung effiziente Massenproduktionsmethoden von Elektrolyseuren und Brennstoffzellen einen wichtigen Meilenstein bilden und laserbasierte Fügetechnologien sind hier zum Teil schon etabliert. Die additive Fertigung nimmt dabei eine Querschnittsposition ein und besitzt hohes Anwendungspotential für die Zukunft z.B. für die Fertigung von Komponenten in Gasturbinen. Aus den technischen Fragestellungen und Forschungsbedarfen ergeben sich zudem Herausforderungen für die notwendige Neu- und Weiterentwicklung von technischen Regelwerken und Normen und den Eingang in die Aus- und Weiterbildung von fügetechnischem Fachpersonal. T2 - DVS Congress 2021 CY - Online meeting DA - 14.09.2021 KW - Wasserstoff KW - Fügetechnik KW - Forschung KW - Werkstoff KW - Bedarf PY - 2021 SN - 978-3-96144-146-4 VL - 371 SP - 612 EP - 624 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-53370 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Czeskleba, Denis A1 - Kannengießer, Thomas T1 - Kurzbericht zum Projekt „Entwicklung von Wärmenachbehandlungskonzepten zur Vermeidung von Spannungsrelaxationsrissen an Bauteilen aus hochwarmfesten Stählen“ (DVS-Nr. 01.2261 / IGF-Nr. 20171 N) N2 - Komponenten aus dickwandigen, hochwarmfesten CrMoV-Stählen erfordern eine anspruchsvolle UP-Schweißverarbeitung. Dabei muss die notwendige Wärmenachbehandlung der Schweißnaht (PWHT) sicher beherrscht werden. Hier kann u.U. Bauteilversagen infolge von Spannungsrelaxationsrissbildung (SRR) auftreten. Bislang erfolgt die Beurteilung der SRR-Neigung primär über Ersatzgrößen, wie temperaturbedingte Änderung der Härte und Duktilität. Die Wirkung der konstruktiven Schrumpfbehinderung einer Schweißnaht auf die SRR ist bislang völlig unbekannt. Hier setzt das Forschungsprojekt an, hinsichtlich der Gewinnung und Optimierung der Parameter für die PWHT unter realitätsnahen Bauteilsteif igkeiten (def inierte Einspannbedingung) mit dem Ziel der SRR-Vermeidung. Am Beispiel des niedriglegierten, hochwarmfesten Stahls 13CrMoV9-10 wurden UP- Schweißungen unter industriepraktischen Bedingungen freischrumpfend bzw. unter definierter Schrumpfbehinderung durchgeführt. Diese wurden mit unterschiedlichen PWHT-Szenarien (Variation der Auf heizrate und Endtemperatur) beaufschlagt. Die Ergebnisse des Projektes DVS 01.2261 / IGF 20171 N werden in diesem Beitrag vorgestellt, wie Aussagen zur SRR-Suszeptibilität in Abhängigkeit von Mikrostruktur und vorliegender mehrachsiger mechanischer Beanspruchung der Schweißnaht vor/während des PWHT. Für einen kritischen Zustand sind hohe Kräfte / Spannungen notwendig, die in freischrumpfenden Schweißversuchen u.U. nicht abbildbar sind. Die Berücksichtigung des mikrostrukturspezifischen Ausscheidungsverhaltens (in Schweißgut und Wärmeeinflusszone) unter realitätsnahen Einspannbedingungen ist für die Bewertung einer SRR-Suszeptibilität notwendig. Instrumentierte Schweißversuche unter definierter Schrumpfbehinderung ermöglichen hier das Monitoring der entstehenden Reaktionskräfte, -momente bzw. -spannungen. Ausgehend von diesem Referenzzustand erfolgte die Applikation der PWHT-Szenarien bzw. deren praktische Überprüfung. Zusätzlich wurde eine Ersatzprüfmethodik entwickelt, die die Betrachtung der mikrostrukturspezifischen SRR-Suszeptibilität unter Beibehaltung der äußeren Schrumpfbehinderung der Schweißnaht während des PWHT ermöglicht. Hierdurch wird die Bauteilübertragbarkeit ermöglicht und eine Transfergröße geschaffen, welche die Bauteilbewertung hinsichtlich der SRR-Neigung umfasst. T2 - DVS Congress 2022 CY - Koblenz, Germany DA - 19.09.2022 KW - UP-Schweißen KW - Spannungsrelaxationsriss KW - Forschungsprojekt KW - Dickblech KW - Wärmebehandlung PY - 2022 SN - 978-3-96144-190-7 SP - 76 EP - 82 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-55944 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengiesser, Thomas A1 - Kromm, Arne T1 - In-service and repair welding of pressurized hydrogen pipelines–a review on current challenges and strategies N2 - Hydrogen is the energy carrier for a sustainable future without fossil fuels. As this requires a reliable transportation infrastructure, the conversion of existing natural gas (NG) grids is an essential part of the worldwide individual national hydrogen strategies, in addition to newly erected pipelines. In view of the known effect of hydrogen embrittlement, the compatibility of the materials already in use (typically low-alloy steels in a wide range of strengths and thicknesses) must be investigated. Initial comprehensive studies on the hydrogen compatibility of pipeline materials indicate that these materials can be used to a certain extent. Nevertheless, the material compatibility for hydrogen service is currently of great importance. However, pipelines require frequent maintenance and repair work. In some cases, it is necessary to carry out welding work on pipelines while they are under pressure, e.g., the well-known tapping of NG grids. This in-service welding brings additional challenges for hydrogen operations in terms of additional hydrogen absorption during welding and material compatibility. The challenge can be roughly divided into two parts: (1) the possible austenitization of the inner piping material exposed to hydrogen, which can lead to additional hydrogen absorption, and (2) the welding itself causes an increased temperature range. Both lead to a significantly increased hydrogen solubility in the respective materials compared to room temperature. In that connection, the knowledge on hot tapping on hydrogen pipelines is rare so far due to the missing service experiences. Fundamental experimental investigations are required to investigate the possible transferability of the state-of-the-art concepts from NG to hydrogen pipeline grids. This is necessary to ensure that no critical material degradation occurs due to the potentially increased hydrogen uptake. For this reason, the paper introduces the state of the art in pipeline hot tapping, encompassing current research projects and their individual solution strategies for the problems that may arise for future hydrogen service. Methods of material testing, their limitations, and possible solutions will be presented and discussed. KW - In-service KW - Welding KW - Hydrogen pipeline KW - Review PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-638847 DO - https://doi.org/10.1007/s40194-025-02127-x SN - 0043-2288 SP - 1 EP - 24 PB - Springer Science and Business Media LLC AN - OPUS4-63884 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Czeskleba, Denis A1 - Irfan, Muhammad Dary A1 - Wandtke, Karsten A1 - Kaiser, Sebastian A1 - Kannengießer, Thomas T1 - Wasserstoffdiffusion in hochfesten UP-Schweißverbindungen – einfacher als gedacht N2 - Hochfeste Baustähle werden im modernen Stahlbau aus wirtschaftlichen und konstruktiven Gründen zunehmend eingesetzt, z. B. im Gebäude-, Anlagen- oder Mobilkranbau. Durch den Einsatz von Stählen mit höheren 690 MPa) können durch die Reduzierung der Wanddicke erhebliche Gewichtsreduzierungen und geringere Verarbeitungskosten erreicht werden, insbesondere bei der Verwendung des Unterpulverschweißen (UP) durch seine hohe Abschmelzleistung. Aufgrund ihrer speziellen Mikrostruktur haben hochfeste Stähle eine begrenzte Duktilität und sind anfälliger für wasserstoffunterstützte Kaltrisse (HACC). Darüber hinaus führen große mittels UP geschweißter Blechdicken zu hohen Schweißeigenspannungen und langen Diffusionswegen für z.B. durch den Schweißprozess eingebrachten Wasserstoff. Abgesicherte Diffusionskoeffizienten für UP-Schweißungen dieser Festigkeitsklasse sind als Grundlage für die Abschätzung des Zeitintervalls einer möglichen verzögerten Kaltrissbildung oder für Nachwärmung zur Wasserstoffreduktion nur sehr begrenzt verfügbar. Aus diesem Grund wurden experimentelle Versuche zur mikrostruktur-spezifischen Diffusion in S690-Schweißungen durchgeführt. Dazu wurde ein thermomechanisch (TM) gewalzter bzw. vergüteter (QL) Zustand dieses Werkstoffs betrachtet, sowie das jeweilige charakteristische Schweißgut und WEZ. Dazu wurden den Schweißmikrostrukturen lokal Proben entnommen und über Permeations- bzw. Warmauslagerungsversuche die gefügespezifische Diffusion von Raumtemperatur bis 400°C charakterisiert. Im Gegensatz zu bekannten Effekten des Wärmebehandlungszustandes der Grundwerkstoffe auf die Diffusion in MSGSchweißverbindungen, zeigten die Wasserstoffdiffusionskoeffizienten über alle untersuchten Gefügezustände keine signifikanten Unterschiede, insbesondere nicht für die lokale WEZ diverser, untersuchter Streckenergiebereiche. Aus praktischer Anwendersicht können daher dickwandige UP-Verbindungen hinsichtlich einer verzögerten Wasserstoffdiffusion nur anhand der einfach ermittelbaren Diffusionskoeffizienten für den Grundwerkstoffkoeffizient beurteilt werden. Zudem zeigte sich, dass der unterschiedliche Walz- und Wärmebehandlungszustand (TM vs. QL) in UP-Schweißnähten eine untergeordnete Rolle für die Wasserstoffdiffusion und damit für die mögliche Zeitverzögerung der Kaltrissbildung hat. Ergänzende numerische Simulationen der Wasserstoffverteilung bestätigten das Verhalten. T2 - DVS Congress 2025 CY - Essen, Germany DA - 16.09.2025 KW - Unterpulverschweißen KW - Wasserstoffdiffusion KW - Wasserstoffunterstützte Kaltrissbildung KW - Wasserstoffrisse PY - 2025 SN - 978-3-96144-299-7 DO - https://doi.org/10.53192/DVSC20250330 VL - 401 SP - 330 EP - 340 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-64132 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Numerical simulation of weld heat input effect on microstructure and hydrogen diffusion in thick-walled S690 submerged arc welded joints N2 - High-strength, low-alloy (HLSA) steels such as S690 are an attractive option for heavy industries such as offshore wind turbines and peripheral equipment due to their combination of excellent mechanical properties and weldability. The construction of these thick-walled structures requires highly efficient welding processes such as submerged arc welding (SAW). However, SAW presents challenges related to delayed hydrogen assisted cold cracking (HACC). Despite its importance, the effect of different diffusion coefficients on the cold cracking susceptibility of different microstructures within SAW-welded S690 steels is not fully understood. For this reason, the present study focuses on comparing the cold cracking susceptibility of thermomechanically rolled (TM) or quenched and tempered (QL) variants of S690 steel. SAW was performed on specimens of both steel grades to produce weldments consisting of weld metal, heat-affected zone (HAZ), and base metal. Electrochemical hydrogen permeation tests (ISO 17081) were performed to determine the microstructure specific coefficients. Using the obtained coefficients, a numerical model was developed to identify the time- and microstructure-dependent local hydrogen diffusion and its influence on the distribution within the welds. The results showed that the TM grade exhibited slightly accelerated hydrogen diffusion compared to the QL grade, which is beneficial for hydrogen reduction and increases the HACC resistance. However, the further simulations with different ply sequences showed that the welding heat input (i.e. welding ply sequence) had a significantly higher effect on hydrogen accumulation. Specifically, increased welding heat input and increased thicknesses decrease hydrogen diffusivity. For this reason, microstructure-specific hydrogen diffusion played a minor role in thick-layer SAW joints compared to the need to control the welding parameters (layer sequence, individual layer thickness, welding heat input). T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - Hydrogen assisted cracking KW - Welding KW - High strength steels KW - Numerical simulation KW - Electrochemical permeation PY - 2025 AN - OPUS4-64158 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Hydrogen trap characterization in 200 and 1,000 bar charged CoCrNi medium entropy alloy compared to steel AISI 316L N2 - Multiple principal element alloys (MPEAs) represent a new class of metallic materials. MPEAs, such as the CoCrNi medium entropy alloy (MEA), have attracted considerable research attention as potential materials to replace, for example, austenitic steels in high-pressure hydrogen environments. Due to the relatively new alloy concept, studies on the specific hydrogen diffusion and trapping behavior of high-pressure hydrogen-charged CoCrNi MEAs are rare so far. For this reason, a CoCrNi-MEA was investigated and compared to an austenitic stainless steel, AISI 316L. Both materials were subjected to high pressure hydrogen loading for two different pressures: 200 bar and 1,000 bar. After charging, thermal desorption analysis (TDA) was used with three heating rates from 0.125 K/s to 0.500 K/s to clarify the specific hydrogen desorption and trapping behavior. To the best of our knowledge, this study is the first to characterize hydrogen diffusion and trapping in 1,000 bar high-pressure charged CoCrNi. For this purpose, the underlying TDA spectra were analyzed in terms of peak deconvolution into a metallurgically justifiable number of defined peaks. The individual peak temperatures and activation energies “EA” were calculated. The following conclusions can be drawn from the results obtained: (1) Exposure to 200 bar or 1,000 bar leads to an increase in hydrogen absorption, regardless of the material investigated, expressed by a significantly increased desorption rate at 1,000 bar. However, the effusion peaks typically occur only at high temperatures. The (2) TDA showed that a four-peak deconvolution scenario was sufficient to describe the trapping behavior and the "EA" indicated the dominance of irreversible traps. In addition, the average trapping energy is higher than in the 316L. The (3) charge pressure related hydrogen solubility was in the order of: CoCrNi-MEA < 316L for both pressures and (4) charging at 1000 bar results in an average concentration of 49 wt.ppm (CoCrNi-MEA) and > 75 wt.ppm (316L). In summary, the CoCrNi-MEA was characterized by a reduced solubility, but very deep entrapment compared to the 316L. For this reason, further application potentials of the MEA may arise. T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - Medium entropy alloy KW - Hydrogen KW - Trapping KW - Diffusion KW - High-pressure charging PY - 2025 AN - OPUS4-64160 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Effect of Ti and Nb on hydrogen trapping in welded S690 HSLA steel and effect on delayed cold cracking N2 - Fine-grain, high-strength, low-alloy (HSLA) structural steels with yield strengths > 600 MPa are now the state of the art in construction applications such as mobile cranes and civil engineering. HSLA grades derive their strength from a combination of specific heat treatment and the underlying chemical composition. In this context, Ti or Nb are essential to obtain a fine-grained microstructure as well as the necessary carbides or nitrides for precipitation strengthening. In this context, the specific effect of Ti or Nb-rich compounds on hydrogen trapping and diffusion is well known for special laboratory cast alloys, but unknown for realistic steel compositions. For this reason, a series of S690Q-based alloys were synthesized, close to a real steel composition, but with well controlled Ti or Nb additions in different amounts. Specimens were obtained from these alloys by electrochemical discharge machining (EDM). The specimens were tested using the well-established electrochemical permeation technique. From the experimental results, the hydrogen diffusion coefficients and the analytical subsurface hydrogen concentration were calculated. In addition, the hydrogen trapping behavior at elevated temperatures was interpreted by thermal desorption analysis (TDA) using different heating rates of hydrogen charged samples. The results showed that in contrast to metallurgically "pure" laboratory cast alloys, realistic chemical compositions were similar in their hydrogen trapping behavior, despite some small differences. All investigated steel grades exhibited shallow and reversible hydrogen trapping, regardless of their chemical composition. Of course, the experiments only allowed the calculation of effective diffusion coefficients and trapping energies, which represent an average of the entire microstructure. Nevertheless, HSLA steels are typically joined by arc welding, which includes the risk of delayed hydrogen assisted cracking. From the point of view of welding practice, however, a more or less identical hydrogen diffusion behavior means that no special "metallurgically specific", justifiable measures need to be considered, despite the well-established processes such as "soaking" or dehydrogenation heat treatment. Of course, a closer look at the heat-affected zone (HAZ) or the weld metal of the specific welds is necessary. However, especially in the case of thick-walled welds, it is assumed that the weld metal and HAZ are similar to the base material due to the multi-layer welding, which results in multiple annealing cycles of the weld metal and HAZ. T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - Hydrogen assisted cracking KW - HSLA KW - Diffusion KW - Electrochemical permeation PY - 2025 AN - OPUS4-64156 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Component test for the assessment of in-service welding on/onto pressurized hydrogen pipelines N2 - Hydrogen is the energy carrier of tomorrow and requires a reliable large-scale transport infrastructure. In addition to new pipelines, the conversion of existing natural gas (NG) pipeline grids is an essential part. The transport of hydrogen is fundamentally different from that of NG, as hydrogen can be absorbed into the pipeline material. Given the effects of hydrogen embrittlement, the material compatibility (low alloy steels in a wide range of strengths and thicknesses) must be investigated. However, pipelines e.g. require maintenance or the need for installation of additional outlets with the necessity of welding on/onto the pipelines while they are still in service, i.e. with gas flow under high pressure, such as the well-known "hot tapping". This in-service welding poses challenges for hydrogen operations. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility and diffusivity compared to room temperature. In addition, possible surface reactions of the present iron oxides (e.g. magnetite or hematite) with the hot hydrogen should be considered. In this context, the knowledge of hydrogen pipelines is scarce due to the lack of operational experience. Fundamental experimental investigations are required to investigate the transferability from NG to hydrogen pipeline grids. For this reason, the present study presents a specially designed mock-up / demonstrator concept for the realistic assessment of the welding process conditions. The mock-up was designed to allow in-situ temperature measurement during the welding process as well as ex-post sample extraction for quantification of the absorbed hydrogen concentration. For safety reasons, the required volume of pressurized hydrogen was limited by inserting a solid cylinder to ensure a 1 cm thick layer of hydrogen gas. Welding experiments on the DN60 and DN200 pressurized mock-ups showed the possibility of safe welding on or onto pressurized hydrogen pipelines. Indeed, the austenitizing temperature was reached on the inner surface of the pipeline, especially on thinner-walled pipelines, using current welding parameter recommendations. This corresponded to an increased hydrogen uptake in the welded area of several ppm. From this point of view, the suggested component concept is a viable strategy for the screening of several materials and welding parameter combinations under realistic operational conditions. T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - In-service welding KW - Pipeline KW - Hydrogen KW - Component test PY - 2025 AN - OPUS4-64159 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Component-test for determination of welding residual stresses and their effect on stress relief cracking in thick-walled welds N2 - Controlling the residual stress level during welding of creep-resistant Cr-Mo-V steels is crucial to avoid so called stress relief cracking (SRC) during post weld heat treatment (PWHT) of large-scale components. In the present study, a laboratory scale test specimen (slotted sample with 400 mm width, 400 mm length and 25 mm thickness) was used to simulate thick-walled component welds made of 13CrMoV9-10. The aim was to identify the level and distribution of residual stresses to evaluate the suitability of the specimen for laboratory based SRC testing. High restraint was ensured by the specimen geometry with a narrow welding gap in the center. This gap was filled by multi-layer submerged arc welding. Two specimens were welded with identical parameters and compared in the as-welded state and after PWHT (705 °C for 10 h). Neutron diffraction was used to determine the residual stresses in the weld metal, the heat-affected zone (HAZ) and the base material at different depths longitudinal, transverse, and normal to the welding direction. The experiments were performed on the former instrument E3 of the research reactor BER II of Helmholtz-Zentrum Berlin (HZB), Germany. Complementarily, laboratory X-ray diffraction was applied to characterize the surface residual stresses. In the welded condition, especially in the weld metal and the adjacent HAZ, the longitudinal residual stresses reached values of up to 1,000 MPa to 1,200 MPa due to the increasing strength and hardness of the CrMoV-material during welding. The conducted welding experiments revealed that way higher residual stresses in the welded joint have to anticipated before the PWHT is performed than it was expected in advance. This demonstrated the necessity of suitable component-like welding tests as they must ensure realistic mechanical stiffness (hindered shrinkage of welding joint by slotted self-restraint sample) and heat dissipation conditions (definition of minimum welding joint thickness vs. welding process-specific heat input). T2 - FEMS Euromat 2025 - 18th European Congress and Exhibition on Advanced Materials and Processes CY - Granada, Spain DA - 15.09.2025 KW - Component test KW - Submerged arc welding KW - Post weld heat treatment KW - Residual stresses KW - Neutron diffraction PY - 2025 AN - OPUS4-64161 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 - 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 - Schröder, Nina A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Mikrolegierungseinfluss auf das Ausscheidungsverhalten und die mechanischen Eigenschaften geschweißter hochfester Baustähle N2 - Mikrolegierungselemente, wie Nb und Ti, sind für die signifikante Festigkeitssteigerung von vergüteten, hochfesten Feinkornbaustählen mit einer Nominalstreckgrenze ≥ 690 MPa unerlässlich. Normvorgaben zur chemischen Zusammensetzung geben dabei nur obere Grenzwerte für die Hersteller vor. Weiterhin wirken sich bereits kleine Abweichungen in der Legierungsroute teilweise drastisch auf die mechanischen Eigenschaften aus. Somit wird eine adäquate Vorhersage der Schweißeignung und der Integrität der Schweißverbindung aufgrund der variierenden Mikrogefüge erschwert bis unmöglich. Unerwünschte Nebeneffekte sind die mögliche Erweichung der Wärmeeinflusszone (WEZ) als auch der gegenteilige Effekt der Aufhärtung. Vor diesem Hintergrund werden erstmals systematisch die unterschiedlichen Mikrolegierungsrouten mit variierenden Ti und Nb-Gehalten an Versuchsschmelzen untersucht. Die Stahlgüte S690QL bildet dabei die Grundlage der chemischen Zusammensetzung sowie der entsprechenden Wärmebehandlung. Zur Untersuchung der jeweiligen Schweißeignung wurden Dreilagen-Schweißungen mittels moderner MAG-Hochleistungsschweißprozesse durchgeführt und kritische Gefügebereiche mit hoher Erweichung/Aufhärtung identifiziert. Der Fokus der analytischen Betrachtungen lag hier auf der Identifikation der Phasenumwandlungen beim Abkühlen und auf dem metallurgischen Ausscheidungsverhalten. Zusätzlich wurden isotherme und nicht-isotherme Phasenberechnungen mit der Software Thermo-Calc durchgeführt. Mechanisch-technologische Untersuchungen zur Kerbschlagzähigkeit mittels Kerbschlagbiegeversuchen durchgeführt wurden, bestätigen dabei die Ergebnisse der thermodynamischen Simulation bezüglich des Ausscheidungsverhaltens während der Temperatur-Zeit Schweißzyklen. Daraus lässt sich der Einfluss der Wärmeeinwirkung beim Schweißen auf die Gefügeausbildung in der WEZ und der korrespondierenden mechanischen Eigenschaften qualitativ beschreiben. T2 - DVS Congress 2023 Große Schweißtechnische Tagung CY - Essen, Germany DA - 11.09.2023 KW - WEZ-Erweichung KW - Mikrolegierungseinflüsse KW - Hochfester Feinkornbaustahl KW - Kerbschlagzähigkeit PY - 2023 SN - 978-3-96144-230-0 VL - 389 SP - 218 EP - 225 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-59419 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Combined effect of heating rate and restraint condition on stress relief cracking susceptibility during PWHT of thick walled Cr Mo V steel submerged arc welded joints N2 - Contemporary steels creep-resistant steels like the 13CrMoV9-10 are used as thick plates e.g., for applications in hydrocrackers. The large plate thickness requires high efficiency welding processes like submerged arc welding (SAW) and a mandatory post weld heat treatment (PWHT). The PWHT-parameters stem from a combination of empirical knowledge and traditional experiments on free shrinking (FS) welds. In that connection, the formation of so-called stress-relief cracking (SRC) must be anticipated. The SRC susceptibility of a welded component is a complex combination and interaction of com-ponent specific, thermal, and metallurgical factors. Many of which have to date not been conclusively researched. For example, it is well known that SRCs develop during PWHT due to formation and growth of carbides on prior austenite grain boundaries, resulting in a significant hardness increase (secondary hardening) and toughness decrease. This leads to a high SRC susceptibility of the coarse grain heat-affected zone (CGHAZ) of the last weld bead during PWHT. This is intensified in case of high residual stresses from the component-specific, structurally induced stiffness. In combination with multi-layer welding this leads to a multiaxial stress distribution. Nonetheless, the combined effect of PWHT and high-residual stresses on the SRC formation is merely unknown. For that reason, this study presents the effect of different heating rates in conjunction with a certain component stiffness. For that reason, SAW joints of 13CrMoV9-10 steel were investigated under FS and defined external restraint condition. T2 - 77th IIW Annual Assembly and International Conference, Meeting of Commission II-A CY - Ixia, Rhodes, Greece DA - 07.07.2024 KW - Stress relief cracking KW - Submerged arc welding KW - Post weld heat treatment KW - Cr-Mo-V steel PY - 2024 AN - OPUS4-60675 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Joining technologies for hydrogen components: current need and future perspectives N2 - The study provides an overview of the aspects of joining and its importance in manufacturing of components for the more and more important field of hydrogen as key factor for the energy transition to a decarburized future. To this end, the fundamentals of the technology fields of hydrogen production, storage, transport, and application are presented and the state of the art of manufacturing of components for hydrogen technologies by joining is summarized. Based on representative examples from practice, research and development, the importance of joining technology in hydrogen technologies is clearly highlighted and perspectives for the future are derived. From a macroeconomic perspective, the focal points, or trends of joining technologies here include: the erection of new infrastructure for hydrogen storage and transport, and the safe conversion of existing natural gas infrastructure and its challenges for welded materials. In addition, we show the problems that are anticipated with in-service repair welding of hydrogen pipelines. In hydrogen applications, the efficient mass production of fuel cells and electrolysers is becoming increasingly important. For that reason, the importance of additive manufacturing is highlighted. Finally, the challenges for technical regulations and standardization by using hydrogen are shown. T2 - AJP 2023: 3rd International Conference on Advanced Joining Processes 2023 CY - Braga, Portugal DA - 19.10.2023 KW - Hydrogen KW - Infractstructure KW - Joining KW - Welding KW - Research PY - 2023 AN - OPUS4-58674 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Quantitative Bestimmung von Wasserstoff durch Heißgasextraktion: Erfahrungen und Grenzen N2 - Die Trägergas-Heißextraktion (TGHE) mit Warmauslagerung (d.h. ohne Schmelzen der Proben) ist eine häufig angewandte Technik zur Bestimmung von Wasserstoff, u.a. für Schweißverbindungen aber auch allgemein für Metalle geeignet. Die TGHE basiert auf der beschleunigten Wasserstoffausgasung aufgrund der thermischen Aktivierung bei erhöhten Temperaturen. Die Norm ISO 3690 schlägt hierzu verschiedene Probengeometrien sowie die erforderliche Mindestextraktionszeit in Abhängigkeit der Temperatur vor. Die vorliegende Präsentation fasst die Ergebnisse und Erfahrungen zahlreicher Testläufe an der BAM der letzten 15 Jahre mit unterschiedlichen Probentemperaturen, Geometrien, etc. zusammen, die die Wasserstoffbestimmung beeinflussen können. Dabei handelt es sich insbesondere um die Bewertung des Absorptionskoeffizienten für Infrarotstrahlung der Probenoberfläche, die begrenzte Empfindlichkeit von WLD im Vergleich zum MS, die Temperaturmessung, u.v.m. Zusammenfassend lässt sich sagen, dass die Temperatur die treibende Kraft der TGHE ist. Es werden Vorschläge zur Verbesserung der Zuverlässigkeit der Wasserstoffbestimmung gemacht, die von der Stabilität des Wasserstoffsignals während der Extraktion und der Auswertung der aufgezeichneten Daten abhängt. Im Allgemeinen ist eine unabhängige Temperaturmessung mit Dummy-Proben für die weitere Datenanalyse nützlich, insbesondere wenn diese Daten für die Berechnung der Einfangkinetik verwendet werden. T2 - Herbstsitzung des DGM Arbeitskreises "Materialprüfung unter Wasserstoff" CY - Dortmund, Germany DA - 19.11.2024 KW - Wasserstoff KW - Trägergasheißextraktion KW - Messung KW - Massenspektrometrie KW - Schweißen PY - 2024 AN - OPUS4-61721 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Czeskleba, Denis A1 - Nietzke, Jonathan A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Investigation of stress relief crack susceptibility of CrMoV steels coarse grain HAZ via simulation of uniaxial stress conditions during PWHT N2 - Creep-resistant steels such as the 13CrMoV9-10, used in the construction of thick-walled pressure vessels, are most commonly submerged arc welded (SAW). These steels can develop stress relief cracks (SRC) if the mandatory post weld heat treatment (PWHT) is performed improperly. Current PWHT parameters, such as heating rate and holding time at a specific holding temperature, are based on both empirical experience and conventional free shrinking welding experiments to characterize the SRC-susceptibility of the weld. These cannot adequately depict the higher residual stresses caused by the structurally induced stiffness of the surrounding construction. This study discusses the development of a repeatable, precise, and time-efficient methodology to study the effects of different stress levels and heating rates on the SRC susceptibility of the coarse grain heat-affected zone (CGHAZ). For that purpose, samples were thermically treated to simulate a coarse grain heat-affected zone (CGHAZ) and subsequently exposed to representative levels of stress during the heating phase of a PWHT. The recorded stress and heating rate–dependent strains were mathematically analyzed via curve tracing/calculus to identify interdependent effects. This procedure facilitates the measurement of material characteristics such as carbide growth on grain boundaries at the µm-scale via an integrated value over the entire sample volume. The first and second derivatives show a slight, precipitate-dependent, increase in hardness of the sample, depending on the heating rate and applied stress. This new methodology generates an improved assessment of the SRC susceptibility of SAW microstructures of creep-resistant CrMoV steels. KW - Submerged arc welding KW - Creep-resistant steel KW - Stress relief cracking KW - Component-like test KW - Post weld heat treatment PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-576007 DO - https://doi.org/10.1007/s40194-023-01539-x SN - 0043-2288 SP - 1 EP - 9 PB - Springer Nature CY - Basel (CH) AN - OPUS4-57600 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Kromm, Arne A1 - Mente, Tobias A1 - Brackrock, Daniel A1 - Czeskleba, Denis A1 - Kannengießer, Thomas T1 - Component test for the assessment of delayed hydrogen-assisted cracking in thick-walled SAW joints for offshore applications N2 - Offshore wind turbines continuously increase in size and weight and demand adequate offshore foundations concepts like monopiles, tripods, or jackets. These components are typically constructed using submerged arc welding (SAW) with high-strength thick steel plates like the S420ML. During welding, the occurrence of delayed hydrogen-assisted cracking (HAC) must be anticipated. HAC is a critical combination of the local hydrogen concentration within a susceptible microstructure under certain mechanical load, i.e., the occurring (welding) residual stresses. The welding sequence of the thick-walled plates complicates the residual stress distribution due to the necessary repeated thermal cycling, i.e., welding seam/layer deposition to fill the joint. For that purpose, SAW with two-wire-technique was used to weld a specially designed and prototype-like mock-up of a real component with a thickness of 50 mm, filled with over 20 passes and a seam length of 1000 mm. Additional welded stiffeners simulated the effect of a high restraint, to achieve critical HAC conditions. The necessity of a minimum waiting time (MWT) before the NDT can be conducted (to exclude HAC) was critically verified by the application of ultrasonic testing of the welded joint at different time-steps of the NDT of up to 48 h after the completion welding. The residual stresses were determined by a robot XRD goniometer. Tensile residual stresses up to the yield limit are found both in the weld metal and in the heat-affected zone. Numerical modeling allowed the qualitative estimation of the hydrogen diffusion in the weld. No noticeable HAC occurrence was identified and confirms the high cracking resistance of the investigated material. Finally, the applicability of the MWT concept should be critically discussed. KW - Hydrogen KW - Cold cracking KW - Minimum Waiting Time KW - Offshore steel grade KW - Component test PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-591981 DO - https://doi.org/10.1007/s40194-023-01658-5 SP - 1 EP - 15 PB - Springer Science and Business Media LLC AN - OPUS4-59198 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Nina A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Thermodynamic prediction of precipitations behaviour in HAZ of a gas metal arc welded S690QL with varying Ti and Nb content N2 - For a significant increase in the strength of high-strength fine-grained structural steels with a nominal yield strength ≥690 MPa, the addition of microalloying elements such as Nb and Ti is required. The standard specifications for the chemical composition of these steels (e.g., in EN 10025-6) often only give the manufacturer limit contents to achieve the defined properties. The effect of the alloying elements in the heat affected zone (HAZ) is sometimes completely contrary. This makes it difficult to adequately predict the batch dependency regarding weldability and the load-bearing behaviour of the welded joint. Three different micro-alloyed steels of the grade S690QL were produced on a laboratory scale, focusing on different Nb and Ti contents. To investigate the tempering effect, these were gas metal arc welded in three layers. In addition to metallographic investigations of individual HAZ areas, thermodynamic phase calculations were carried out using Thermo-Calc, following variations in the chemical composition. This provides an understanding of phase transformation, precipitation growth, and dissolution during welding as a function of temperature and cooling conditions. The results show a divergent metallurgical behaviour in the HAZ of the three different micro-alloyed steels. Thereby, the Ti micro-alloyed grade showed a strong softening of the HAZ in contrast to the Nb micro-alloyed grade. This can be attributed to a contrary precipitation behaviour during welding. KW - High-strength structural steel KW - Gas metal arc welding KW - HAZ-softening KW - Microalloying influences KW - Thermodynamic simulation PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-579988 DO - https://doi.org/10.1007/s40194-023-01550-2 SN - 0043-2288 SP - 1 EP - 10 PB - Springer AN - OPUS4-57998 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Nina A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Influence of microalloying on precipitation behavior and notch impact toughness of welded high‑strength structural steels N2 - Microalloying elements such as Nb and Ti are essential to increase the strength of quenched and tempered high-strength low alloy (HSLA) structural steels with nominal yield strength ≥ 690 MPa and their welded joints. Standards such as EN 10025–6 only specify limits or ranges for chemical composition, which leads to variations in specific compositions between steel manufacturers. These standards do not address the mechanical properties of the material, and even small variations in alloy content can significantly affect these properties. This makes it difficult to predict the weldability and integrity of welded joints, with potential problems such as softening or excessive hardening of the heat-affected zone (HAZ). To understand these metallurgical effects, previous studies have investigated different microalloying routes with varying Ti and Nb contents using test alloys. The high-strength quenched and tempered fine-grained structural steel S690QL is the basic grade regarding chemical composition and heat treatment. To evaluate weldability, three-layer welds were made using high-performance MAG welding. HAZ formation was investigated, and critical microstructural areas were identified, focusing on phase transformations during cooling and metallurgical precipitation behavior. Isothermal thermodynamic calculations for different precipitations were also carried out. Mechanical properties, especially Charpy notch impact toughness, were evaluated to understand the influence of different microalloys on the microstructure of the HAZ and mechanical properties. KW - High-strength structural steel KW - Gas metal arc welding KW - HAZ-softening KW - Notch impact toughness KW - Microalloying influences KW - Thermodynamic simulation PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-608548 DO - https://doi.org/10.1007/s40194-024-01827-0 SN - 0043-2288 SP - 1 EP - 13 PB - Springer AN - OPUS4-60854 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Evaluation of local strain behavior of cross-weld tensile specimens of micro-alloyed high-strength steels by digital image correlation N2 - Microalloying elements such as Nb and Ti play a decisive function in achieving the desired mechanical strength of quenched and tempered, high-strength fine-grain structural steels with a nominal yield strength ≥ 690 MPa. The current specifications for the chemical composition only provide manufacturers with upper limits. However, even minor deviations in the alloy concept can have a significant impact on the mechanical properties. Consequently, accurate prediction of weldability and the integrity of welded joints becomes difficult or even impossible due to differences in composition and the resulting microstructures. Undesirable consequences include a possible softening of the heat-affected zone (HAZ) or, conversely, hardening effects. In view of these challenges, various microalloying strategies with different Ti and Nb contents are being systematically investigated for the first time using specially developed laboratory casting alloys. Each alloying route is based on the common S690QL, maintaining both the chemical composition and the heat treatment parameters. To analyse the weldability, three-layer welds were performed using gas metal arc welding (GMAW) and critical microstructures, such as areas of the heat-affected zone (HAZ) that exhibit significant softening or hardening, were identified. The effect of the softened HAZ region on failure was evaluated using transverse tensile specimens. Digital image correlation (DIC) is used to image changes in local strains in different HAZ regions in situ. Using a specially developed mirror system, the local strains of the microstructure zones on the top and bottom of the weld are recorded simultaneously. This makes it possible to analyse how the weld seam geometry (e.g., V-seam) influences the strain gradients. In addition, the analysis of the local deformation helps to understand the effects of the softened HAZ on the global strain, the fracture constriction, the fracture position, and the overall fracture behavior. T2 - IIW Intermediate Meeting, Com. II-A CY - Incheon, Republic of Korea DA - 12.03.2024 KW - Welding KW - High-strength steel KW - Alloy concept KW - Cross-weld tensile sample KW - Mechanical properties PY - 2024 AN - OPUS4-59675 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Welding of in service hydrogen pipelines for repair and maintenance purposes Concepts and Challenges N2 - Hydrogen will make a decisive contribution to a sustainable large-scale energy supply, the transport of which will be based on long-distance pipeline grids. Previous material compatibility studies have shown that the currently used low-alloy pipe steels are generally suitable for hydrogen pipelines. However, this cannot be directly transferred to the case of repair welding. For technical and economic reasons, welding work on hydrogen pipelines in service is usually carried out during operation under continuous pressure and gas flow. In this context, concepts such as hot tapping and stoppling are well established in natural gas (NG) grids and crude oil transportation. In hot tapping, a pressurized pipeline is drilled by flanging a sealed, pressure-tight system consisting of a shut-off valve and drilling equipment. For this purpose, sleeves (made of preformed cylindrical half-shells) must be welded by longitudinal seams and then welded to the product-carrying pipeline by circumferential girth welds. Preheat temperatures of approximately 100 °C must be maintained for most manual metal arc (MMA) / shielded metal arc welding (SMAW) and 250 °C for the interpass temperature in multi-pass welding. This is particularly important for thin-walled pipelines because the austenitizing temperature is exceeded on the inside of the pipeline when the girth welds are welded. As a result, significantly higher hydrogen absorption in the pipeline steel is expected, with possible degradation of mechanical properties or cracking. T2 - MSE 2024: International Materials Science and Engineering Congress CY - Darmstadt, Germany DA - 24.09.2024 KW - Hydrogen KW - Repair welding KW - Pipelines KW - In-service PY - 2024 AN - OPUS4-61155 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Joining technology for the new hydrogen economy: Current need and future perspectives N2 - This presentation gives an overview on the importance of joining processes for component fabrication in hydrogen technologies. For that reason, the current need and future research and developement activites are highlighted for the three technological fields: hydrogen storage, transport and use (in terms of the emerging field of additive manufacturing). Finally, some remarks are given for necessary changes in the standardization. T2 - Laser Colloquium Hydrogen 2024 CY - Aachen, Germany DA - 10.09.2024 KW - Hydrogen technologies KW - Joining KW - Welding KW - Challenges KW - Standardization PY - 2024 AN - OPUS4-61012 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - "H2-SuD" Einfluss des Schweißens auf die Wasserstoffaufnahme und Degradation im Betrieb befindlicher H2-Ferngasleitungen, Statusbericht – März 2024 N2 - Die Umstellung der Wirtschaft auf wasserstoffbasierte Energieversorgung soll in Deutschland vor allem auf Basis der Umstellung des bestehenden Erdgasnetzes erfolgen. ­Dabei sollen ca. 90 % dieser Fernleitungsnetze auf dem bestehenden Erdgasnetz basieren. Die Beimischung von Wasserstoff zum Erdgas als auch der reine Wasserstofftransport werfen jedoch die Frage auf, ob und wie kompatibel die eingesetzten Materialien sind. Die Reparatur- und Erweiterungsfähigkeit von Erdgas-Bestandspipelines ist zu klären, wenn diese auf Wasserstoff umgestellt werden. Denn gerade Gashochdruckleitungen müssen regelmäßig gewartet und erweitert werden, um einen ordnungsgemäßen Betrieb sicherzustellen. Insbesondere das Schweißen unter Betriebsdruck bzw. an in Betrieb befindlichen Gasleitungen ist eine der wichtigsten Instandhaltungstechnologien, unabhängig von der Zusammensetzung des geförderten Mediums. Es ist daher dringend notwendig, eine geeignete Teststrategie zu erarbeiten, welche die nötigen Vorrausetzungen für sicheres Schweißen an in Betrieb befindlichen Druckwasserstoffleitungen schafft und entsprechende Kriterien für die Praxis liefert. Im Projekt H2-SuD - Einfluss des Schweißens auf die Wasserstoffaufnahme und Degradation im Betrieb befindlicher H2-Ferngasleitungen - soll geklärt werden, ob und wie stark mit einer Eigenschaftsdegradation geschweißter Rohrstähle in Gasnetzen in Folge einer Wasserstoffaufnahme zu rechnen ist. Die Präsentation gibt dazu einen kurzen Überblick über den aktuellen Status des Projektes. Die Förderung erfolgt im Rahmen der DVGW-Innovationsprogammes Wasserstoff (Nr. G 202131). T2 - DVGW - Arbeitsgruppentreffen CY - Berlin, Germany DA - 19.03.2024 KW - Wasserstoff KW - Pipeline KW - Reparaturschweißen KW - Betrieb KW - Hochdruck PY - 2024 AN - OPUS4-59758 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Kurzvorstellung des DVGW-geförderten Projektes “H2SuD” - Einfluss des Schweißens auf die Wasserstoffaufnahme und Degradation im Betrieb befindlicher H2-Gasleitungen N2 - Die Wasserstoffinfrastruktur ist eine zentraler Bestandteil der erfolgreichen Umsetzung der wasserstoffbasierten Energiewende. Dabei bilden Ferngasleitungen quasi das "Rückgrat" der Transportinfrastruktur großer Gasmengen. Dabei müssen unter Umständen Reparaturen an den Pipelines durchgeführt werden. Dabei ist in der Erdgasinfrastruktur das Schweißen an in Betrieb befindlichen (d.h. von Gas durchflossenen) Pipelines Stand der Technik. Es ist jedoch vollkommen offen, inwieweit diese Technik auf die reine Wasserstoffpipelines übertragbar sind. Hierzu leistet das Projekt H2SuD wichtige Beiträge zur Aufklärung des Einfluss eines Reparaturschweißprozesses auf die Wasserstoffaufnahme und Degradation im Betrieb befindlicher H2 Gasleitungen. T2 - Sitzung des Unterarbeitskreises / UAK 2.1.1 "Rohrleitungen" im Rahmen der Normungsroadmap Wasserstofftechnologien CY - Online meeting DA - 16.06.2023 KW - Wasserstoff KW - Schweißen KW - Pipeline KW - Reparatur KW - Prüfverfahren PY - 2023 AN - OPUS4-57714 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Mente, Tobias T1 - Zuverlässige Wasserstoff Bestimmung in Metallen und ihren Schweißverbindungen: Parameter, Einflüsse, Grenzen N2 - Im Zuge der wasserstoffbasierten Energiewirtschaft von morgen, kommt der Errichtung der dementsprechenden Infrastruktur die zentrale Rolle zu. Der überwiegende Teil bisher eingesetzter und meist geschweißter Werkstoffe, wie Stähle, kann unter bestimmten Bedingungen zur Wasserstoffversprödung neigen. Dies umfasst die klassische verzögerte Kaltrissbildung während der Schweißverarbeitung als auch Versprödungsphänomene während des Betriebs. Für die Bewertung eines jeden Wasserstoffeffektes auf bspw. die mechanischen Eigenschaften eines geschweißten metallischen Werkstoffes, muss der Wasserstoffgehalt präzise bestimmt werden, Im Fall von Schweißnähten ist die beispielsweise nach der ISO 3690, die klassische isotherme Trägergas-Heißextraktion (TGHE). Die TGHE basiert dabei auf der beschleunigten Wasserstoffentgasung aufgrund der thermischen Aktivierung des Wasserstoffs bei erhöhten Temperaturen. Neben der reinen Quantifizierung des Wasserstoffs, kann über die thermische Desorptionsanalyse (TDA) mit variierten Heizraten, der Bindungszustand an mikrostrukturellen Defekten im Material festgestellt und bewertet werden. Für beide Techniken sind experimentelle und messtechnische Einflüsse zu beachten, die großen Effekt auf das Ergebnis haben. Für die TGHE schlägt die ISO 3690 schlägt beispielswiese verschiedene Probengeometrien sowie Mindestextraktionszeiten vor. Die vorliegende Studie fasst Ergebnisse und Erfahrungen zahlreicher Untersuchungen an der Bundesanstalt für Materialforschung und -prüfung (BAM) mit unterschiedlichen Probentemperaturen und Geometrien (ISO 3690 Typ B und zylindrische TDA-Proben) zusammen hinsichtlich: Einfluss der Probenoberfläche (poliert/geschweißt), Messgenauigkeiten in Abhängigkeit des Probenvolumens sowie die unzureichende Überwachung des Effektes des PI-Reglers auf die Extraktionstemperatur. Insbesondere eine abweichende Extraktionstemperatur zur eingestellten Temperatur, kann die Messergebnisse wesentlich verfälschen. Basierend auf den Ergebnissen werden Methoden aufgezeigt, um schnell die gewünschte Extraktionstemperatur zu erreichen, ohne physisch in das Messequipment eingreifen zu müssen. Dies dient der wesentlichen Verbesserung der Zuverlässigkeit der Wasserstoffmessung durch erhöhte Signalstabilität und beschleunigte Wasserstoffdesorption. Im Allgemeinen ist eine unabhängige Temperaturmessung mit Dummy-Proben für die gewählte Heizprozedur angeraten, um mögliche unerwünschte Temperatureinflüsse bereits vor der Messung auszuschließen. Die beschriebenen Methoden können ohne großen Aufwand direkt in die industrielle Anwendung überführt werden. T2 - DVS Congress 2023 CY - Essen, Germany DA - 11.09.2023 KW - Wasserstoff KW - Schweißen KW - Forschung KW - ISO 3690 PY - 2023 SN - 978-3-96144-230-0 VL - 389 SP - 435 EP - 442 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-58309 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Wasserstoffabhängige mechanische Eigenschaften der Schweißnahtgefüge niedriglegierter Stähle für Ferngasleitungen N2 - Der Vortrag stellt aktuelle Ergebnisse des Fosta-Forschungsprojektes P1668 vor. Ziel ist hier, die Wasserstoffresistenz geschweißter Mikrostrukturen gängiger und neuer Pipeline-Stählen zu untersuchen. Im Fokus stehen hierbei durch physikalische Simulation nachgebildete, schweißnahtähnliche Mikrostrukturen in Form von (1) Wärmeeinflusszonen mit unterschiedlicher Abkühlgeschwindigkeit und (2) angelassene Zonen zur Simulation der typischen Mehrlagenschweißungen. Aus diesen repräsentativen Mikrostrukturen werden Zugproben extrahiert welche elektrochemisch oder mit Druckwasserstoff beladen werden. Aus diesen wird dann eine Datenbasis der spezifischen mechanische Eigenschaften unter Wasserstoff bereitgestellt. Die so entwickelte, praxisorientierte Prüfstrategie ermöglicht die schnelle und zuverlässige Bewertung sowohl in Betrieb befindlicher als auch neuer Rohrleitungswerkstoffe. T2 - Herbstsitzung des DGM Arbeitskreises "Materialprüfung unter Wasserstoff" CY - Dortmund, Germany DA - 19.11.2024 KW - Wasserstoff KW - Pipeline KW - Mechanische Kennwerte KW - Schweißen KW - Prüfung PY - 2024 AN - OPUS4-61750 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Standardization and examples for R & D activities on hydrogen technologies with respect to testing procedures in Germany N2 - This contribution briefly summarizes the standardization activities in accordance with the "Nationale Roadmap Wasserstofftechnologien" and presents selected results on the activities in Germany with scope on hydrogen transport in pipelines. The talk was given during a panel discussion to set-up a steering committee for standardization for hydrogen pipelines and welding , coordinated by the International Institute of Welding. T2 - IIW Annual Assembly, Meeting of Commission XI CY - Singapore DA - 19.07.2023 KW - Hydrogen KW - Welding KW - Pipelines KW - Standardization KW - Research PY - 2023 AN - OPUS4-57976 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Intended weld repair of in service hydrogen pipelines N2 - In the course of tomorrow's hydrogen-based energy transition, the construction of the corresponding infrastructure will play a central role. In that context, large diameter long-distance transmission pipelines for hydrogen will be the backbone in the European Union with service pressures from 70 to 90 bar (e.g., de-pending on national regulations). It is a major goal to repurposing the existing natural gas (NG) infrastructure despite the necessity of new pipelines. From that point of view repair welding or further welding of branch pipe etc. can be necessary during in-service, i.e., permanent flow of pressurized hydrogen. The reason is that a shut-down of large diameter pipelines is not easy or sometimes merely impossible. At the moment, it is entirely open if current repair welding procedures for NG pipe-lines can be transferred to pure hydrogen pipelines. For that reason, a collaborative project between BAM, DVGW (German Association for Gas and Water Professions) and a large number of gas grid operators, pipeline manufacturers and construction companies was initiated in 2023 to answer questions on: (1) How many hydrogen is additionally absorbed during the preheating and maintaining at interpass temperature under remaining operational pressures? (2) Is the hydrogen concentration sufficient to reach a critical condition? (3)Which material and weld microstructure are the most susceptible? (4) Is there a difference in the repair welding behavior of NG pipelines with materials in “used” condition? (5) Which welding parameters and joint dimensions must be ensured for safe repair welding? The final aim of this project is the publication of a recommended practice for repair welding of in-service hydrogen pipelines. For that reason, the present study gives an overview on: (A) current practice in repair welding of in-service pipelines and (b) plans for hydrogen pipelines and first results of international research projects. T2 - IIW Annual Assembly, Meeting of Commission XI CY - Singapore DA - 19.07.2023 KW - Hydrogen KW - Repair Welding KW - Pipelines KW - Research PY - 2023 AN - OPUS4-57975 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Unter Druck gesetzt: Die unterschätzte Bedeutung des In-Service-Schweißen für die Wasserstoffinfrastruktur der Zukunft N2 - Wasserstoff leistet als Energieträger der Zukunft einen entscheidenden Beitrag zur nachhaltigen Energieversorgung. Der Transport wird vorwiegend durch das europäische Ferngasleitungsnetz erfolgen. Bisherige Untersuchungen zeigen, dass bisher verwendete Rohrstähle grundsätzlich für den Wasserstofftransport geeignet sind. Diese Eignung ist nicht direkt auf Reparaturfragestellungen im Betrieb übertragbar, da Schweißungen aus technisch-ökonomischen Gründen oft unter fortwährendem Gasfluss durchgeführt werden. Ein im Erdgasnetz angewandtes Konzept ist das Anbohren druckführender Pipelines („Hot Tapping“). Dazu werden Zylinderhalbschalen zuerst durch Längs- und dann per Rohrrundnähten an die Pipeline geschweißt. Essenziell ist dabei die maßgeschneiderte Wärmeeinbringung, um das „Durchbrennen“ in die Pipeline zu vermeiden. Für zukünftige Wasserstoffpipelines liegt der Fokus u.a. auf dünnwandigen Leitungen. Im Gegensatz zu Erdgas, führen die beim Schweißen erreichten hohen Temperaturen an der Innenseite der Pipeline zu einer zusätzlichen Wasserstoffaufnahme in den Rohrstahl mit möglicher Materialdegradation. Zur praktischen Lösung der Fragestellung, sind internationale Aktivitäten im Gang. Diese umfassen bspw. die Möglichkeiten und Weiterentwicklung von realistischen Prüfkonzepten (u.a. durch maßstäbliche Bauteilversuche). Dazu untersucht die Bundesanstalt für Materialforschung und -prüfung (BAM) in einem DVGW-geförderten Kooperationsprojekt zusammen mit den grossen Gasnetzbetreibern, die Frage der Übertragbarkeit der Schweißkonzepte der Erdgastechnik auf zukünftiger Wasserstoffpipelines. T2 - Herbstsitzung des DGM Arbeitskreises "Materialprüfung unter Wasserstoff" CY - Dortmund, Germany DA - 19.11.2024 KW - Wasserstoff KW - Pipeline KW - Reparaturschweißen KW - Komponententest PY - 2024 AN - OPUS4-61723 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Schaupp, Thomas ED - Brockmann, S. ED - Krupp, U. T1 - Wasserstoffunterstützte Kaltrissbildung in Schweißnähten hochfester Stahlgüten - Anforderungen an die Prüfung N2 - Wasserstoff kann eine Rissbildung u.U. auch noch nach Tagen in der Schweißnaht bewirken. Dabei stellen höherfeste Stähle etablierte Kaltrissprüftests vor Herausforderungen. Generell nimmt die zur Rissvermeidung tolerierbare Wasserstoffkonzentration mit zunehmender Festigkeit der Werkstoffe ab. Zudem verändern weiterentwickelte Schweißverfahren die Nahtgeometrie und Wärmeeinbringung und die Ausbildung risskritischer Mikrostrukturen (z.B. Wärmeeinflusszone). Am Beispiel des Implant- und Tekken-Tests werden die Einsatz- u. Anwendungsgrenzen bewertet. Zu berücksichtigen ist, dass beim Schweißen eine äußere mechan. Beanspruchung durch bauteilspezifische Steifigkeitsverhältnisse wirksam ist. Zusätzlich werden weiterführende Prüfverfahren zur Bestimmung der Wasserstoffkonzentration und -diffusion in Schweißnähten vorgestellt, wie die Trägergasheißextraktion (TGHE) für die Ermittlung der Wasserstoffkonzentration (ISO 3690) oder Hochtemperaturdiffusionskoeffizienten. Diese Werte sind für die schweißtechnische Praxis von großer Bedeutung, um Haltezeiten z.B. für das Wasserstoffarmglühen abzuleiten. T2 - Tagung Werkstoffprüfung 2021 CY - Online meeting DA - 02.12.2021 KW - Wasserstoff KW - Kaltrissprüfung KW - Schweißen KW - Stahl KW - Hochfest PY - 2021 SN - 978-3-941269-98-9 SP - 15 EP - 20 PB - Stahlinstitut VDEh CY - Düsseldorf AN - OPUS4-53900 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Large scale hydrogen assisted cracking test for thick walled SAW joints for offshore applications N2 - Offshore wind turbines continuously increase in size and weight and demand adequate offshore foundations concepts like monopiles, tripods or jackets. These components are typically submerged arc welded (SAW) high-strength thick steel plates like the S420ML. During welding, the occurrence of delayed hydrogen assisted cracking (HAC) must be anticipated. HAC is a critical combination of the local hydrogen concentration within a susceptible microstructure under certain mechanical load, i.e., the occurring (welding) residual stresses. The welding sequence of the thick-walled plates complicate the residual stress distribution due to the necessary repeated thermal cycling, i.e., welding seam / layer deposition to fill the joint. For that purpose, SAW with two-wire-technique was used to weld a specially designed and prototype-like mock-up of a real component with a thickness of 50 mm, filled with 22 passes and a seam length of 1,000 mm. Additional welded stiffeners simu-lated the effect of a high restraint, to stimulate critical HAC conditions. The necessity of a minimum waiting time (MWT) before the NDT can be conducted (to exclude HAC) was critically verified by the application of ultrasonic testing of the welded joint at different time-steps of the NDT of 48 h after welding. The residual stresses were determined by a robot XRD goniometer. Tensile residual stresses up to the yield limit are found both in the weld metal and in the heat-affected zone. Numerical modelling allowed the qualitative estimation of the hydrogen diffusion in the weld. A remarkable HAC occurrence was not identified and proves both, a certain resistance of the weld joint to HAC and the (questionable) duration of the MWT. T2 - IIW Annual Assembly, Meeting of Commission II-C CY - Singapore DA - 19.07.2023 KW - Mock-up KW - Hydrogen assisted cracking KW - Submerged arc welding KW - Offshore KW - Steel PY - 2023 AN - OPUS4-57977 LA - eng 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 - TY - CONF A1 - Schröder, Nina A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Einfluss unterschiedlicher Mikrolegierungsrouten eines S690QL auf das Ausscheidungsverhalten in der Wärmeeinflusszone N2 - Mikrolegierungselementen, wie Nb und Ti sind für eine signifikante Festigkeitssteigerung von vergüteten, hochfesten Feinkornbaustählen mit einer Nominalstreckgrenze ≥ 690 MPa unerlässlich. Normvorgaben zur chemischen Zusammensetzung dieser Stähle geben zur Erzielung der vorgeschriebenen Eigenschaften dabei oft nur Grenzgehalte für die Hersteller vor. Die Wirkung der Mikrolegierungselemente bzw. ihrer Karbide und/oder Nitride ist teilweise komplett konträr, insbesondere bei Auflösung und Wiederausscheidung in der WEZ bei identischem Schweißzusatz. Somit wird eine adäquate Vorhersage der Chargenabhängigkeit hinsichtlich der Schweißeignung und des Tragverhaltens der Schweißverbindung erschwert. Eine unerwünschte Eigenschaft ist dabei die Erweichung der WEZ, wie auch u.U. der gegenteilige Effekt der Aufhärtung. Vor diesem Hintergrund werden im Rahmen eines DFG-Vorhabens systematisch Mikrolegierungs-routen mit variierenden Ti- und Nb-Gehalten des hochfesten und vergüteten Feinkornbaustahls S690QL untersucht. Dazu wird das MAG-Schweißen mit modifizierten Sprühlichtbogen verwendet, welches durch hohe Abschmelzleistung gekennzeichnet ist und schmalere Nahtöffnungswinkel (α = 30°) ermöglicht. An Dreilagen-Schweißungen wird der Effekt der metallurgischen Zusammensetzung in Kombination mit hoher Wärmeeinwirkung auf die Ausbildung einer kritischen WEZ-Gefügezone mit Erweichung und/oder exzessiver Aufhärtung untersucht. Ein besonderes Augenmerk wird auf die Phasenumwandlungen und das Ausscheidungsverhalten im Gefüge der Wärmeeinflusszone gelegt. Neben umfangreichen metallographischen Untersuchungen einzelner WEZ-Bereiche wurden, unter Variation der chemischen Zusammensetzung, thermodynamische Phasenberechnungen mittels Thermo-Calc durchgeführt. Hierdurch wird ein Verständnis zur Phasentransformation und Ausscheidungswachstum und -auflösung während des Schweißens in Abhängigkeit von Temperatur und Abkühlbedingungen geschaffen. Das Ziel ist es, den Einfluss der Wärmeeinwirkung auf die Gefügeausbildung in der WEZ und dessen mechanischer Eigenschaften zu analysieren. Insbesondere wird hier auf die Auswirkung der unterschiedlichen Mikrolegierungskonzepte (Ti oder Nb) geachtet. T2 - 5. Symposium Materialtechnik CY - Clausthal-Zellerfeld, Germany DA - 23.02.2023 KW - WEZ Erweichung KW - Thermodynamische Simulation KW - Mikrolegierungseinfluss KW - Schweißen von hochfesten FKB PY - 2023 SN - 978-3-8440-9105-2 VL - 12 SP - 332 EP - 343 PB - Shaker Verlag AN - OPUS4-58006 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Mente, Tobias A1 - Kannengießer, Thomas A1 - Schaupp, Thomas A1 - Zavdoveev, Anatoly T1 - Challenges for testing hydrogen-assisted cold cracking in weld seams of high-strength steel grades N2 - Hydrogen can cause weld cold cracking even days after fabrication. In this respect, higher strength steels present a challenge to established cold crack testing. In general, the tolerable hydrogen concentration for crack prevention decreases with increasing material strength. In addition, advanced welding processes require changes in weld geometry and heat input. This directly influences the formation of crack-critical microstructures, e.g. in hardened areas of the heat-affected zone. The limits of use and application of modern cold cracking tests are evaluated by (1) the externally loaded Implant-test and (2) the self-restraint Tekken-test. In particular, external mechanical stresses, which cause additional mechanical loads on the components during welding, must be considered due to the component-specific stiffness of high-strength steels. Accompanying test methods for determining hydrogen concentration and diffusion in welds are presented, such as carrier gas hot extraction for determining hydrogen concentration (ISO 3690) or temperature-dependent diffusion coefficients. These values are of great importance for a holistic approach to the evaluation of the cold cracking sensitivity of high strength steels. KW - Hydrogen KW - Welding KW - Cold cracking test KW - High-strength steel PY - 2024 DO - https://doi.org/10.37434/tpwj2024.08.01 SN - 0957-798X VL - 2024 IS - 8 SP - 3 EP - 9 PB - International Association "Welding" CY - Kyiv, Ukraine AN - OPUS4-60946 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Wasserstoffunterstützte Kaltrissbildung in Schweißnähten hochfester Stahlgüten - Anforderungen an die Prüfung N2 - Die Vortrag gibt einen Überblick, warum Kaltrissprüfung von geschweißten Stählen ständig weiterentwickelt werden muss. Am Beispiel des Implant- und Tekken-Tests werden die Einsatz- u. Anwendungsgrenzen bewertet. Zu berücksichtigen ist, dass beim Schweißen eine äußere mechan. Beanspruchung durch bauteilspezifische Steifigkeitsverhältnisse wirksam ist. Zusätzlich werden weiterführende Prüfverfahren zur Bestimmung der Wasserstoffkonzentration und -diffusion in Schweißnähten vorgestellt, wie die Trägergasheißextraktion (TGHE) für die Ermittlung der Wasserstoffkonzentration (ISO 3690) oder Hochtemperaturdiffusionskoeffizienten. Diese Werte sind für die schweißtechnische Praxis von großer Bedeutung, um Haltezeiten z.B. für das Wasserstoffarmglühen abzuleiten. T2 - Tagung Werkstoffprüfung 2021 CY - Online meeting DA - 02.12.2021 KW - Wasserstoff KW - Kaltrissprüfung KW - Schweißen KW - Stahl KW - Hochfest PY - 2021 AN - OPUS4-53902 LA - deu 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 - Repair Welding of In-Service Hydrogen Pipelines - Concepts and Challenges N2 - Hydrogen is set as the energy carrier of tomorrow for a more sustainable fossil fuel free future. As this necessitates a reliable transport infrastructure, repurposing of the existing natural gas grid is planned. With regards to the well-known effect of hydrogen embrittlement, the compatibility of utilized materials must be investigated. First comprehensive studies on pipeline material hydrogen compatibility indicate that these materials can be applied to a certain extent. Nonetheless, the material compatibility is currently of high interest and focus of numerous research projects worldwide. However, pipelines require frequent maintenance and repair work. As part of these, in some cases it is necessary to do weldments onto pipelines while they are pressurized. This in-service welding introduces additional challenges for the material compatibility. Due to the resulting high temperatures, the metallurgical changes in the material and of course the presence of high-pressure hydrogen in the pipeline, additional investigations need to be conducted to ensure that no critical material degradation because of increased hydrogen absorption occurs and an overall material compatibility is given. For this reason, the present paper introduces in-service welding on pipelines. An overview of current research projects that deal with the application of in-service welding specifically on hydrogen pipelines and the emerging problems when applying these techniques on hydrogen pipelines is given. Methods of material testing, their limits and possible solutions are presented and discussed. T2 - 2024 15th International Pipeline Conference CY - Calgary, Alberta, Canada DA - 23.09.2024 KW - Hydrogen KW - Pipeline KW - Welding KW - In-Service PY - 2024 SN - 978-0-7918-8856-8 DO - https://doi.org/10.1115/IPC2024-133052 SP - 1 EP - 6 PB - The American Society of Mechanical Engineers (ASME) CY - New York AN - OPUS4-62262 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Zuverlässige Wasserstoffbestimmung in Metallen und ihren Schweißverbindungen: Parameter, Einflüsse, Grenzen N2 - Im Zuge der wasserstoffbasierten Energiewirtschaft von morgen, kommt der Errichtung der dementsprechenden Infrastruktur die zentrale Rolle zu. Der überwiegende Teil bisher eingesetzter und meist geschweißter Werkstoffe, wie Stähle, kann unter bestimmten Bedingungen zur Wasserstoffversprödung neigen. Dies umfasst die klassische verzögerte Kaltrissbildung während der Schweißverarbeitung als auch Versprödungsphänomene während des Betriebs. Für die Bewertung eines jeden Wasserstoffeffektes auf bspw. die mechanischen Eigenschaften eines geschweißten metallischen Werkstoffes, muss der Wasserstoffgehalt präzise bestimmt werden, Im Fall von Schweißnähten ist die beispielsweise nach der ISO 3690, die klassische isotherme Trägergas-Heißextraktion (TGHE). Die TGHE basiert dabei auf der beschleunigten Wasserstoffentgasung aufgrund der thermischen Aktivierung des Wasserstoffs bei erhöhten Temperaturen. Neben der reinen Quantifizierung des Wasserstoffs, kann über die thermische Desorptionsanalyse (TDA) mit variierten Heizraten, der Bindungszustand an mikrostrukturellen Defekten im Material festgestellt und bewertet werden. Für beide Techniken sind experimentelle und messtechnische Einflüsse zu beachten, die großen Effekt auf das Ergebnis haben. Für die TGHE schlägt die ISO 3690 schlägt beispielswiese verschiedene Probengeometrien sowie Mindestextraktionszeiten vor. Die vorliegende Studie fasst Ergebnisse und Erfahrungen zahlreicher Untersuchungen an der Bundesanstalt für Materialforschung und -prüfung (BAM) mit unterschiedlichen Probentemperaturen und Geometrien (ISO 3690 Typ B und zylindrische TDA-Proben) zusammen hinsichtlich: Einfluss der Probenoberfläche (poliert/geschweißt), Messgenauigkeiten in Abhängigkeit des Probenvolumens sowie die unzureichende Überwachung des Effektes des PI-Reglers auf die Extraktionstemperatur. Insbesondere eine abweichende Extraktionstemperatur zur eingestellten Temperatur, kann die Messergebnisse wesentlich verfälschen. Basierend auf den Ergebnissen werden Methoden aufgezeigt, um schnell die gewünschte Extraktionstemperatur zu erreichen, ohne physisch in das Messequipment eingreifen zu müssen. Dies dient der wesentlichen Verbesserung der Zuverlässigkeit der Wasserstoffmessung durch erhöhte Signalstabilität und beschleunigte Wasserstoffdesorption. Im Allgemeinen ist eine unabhängige Temperaturmessung mit Dummy-Proben für die gewählte Heizprozedur angeraten, um mögliche unerwünschte Temperatureinflüsse bereits vor der Messung auszuschließen. Die beschriebenen Methoden können ohne großen Aufwand direkt in die industrielle Anwendung überführt werden. T2 - DVS Congress 2023 CY - Essen, Germany DA - 11.09.2023 KW - Wasserstoff KW - Messung KW - Trägergasheißextraktion KW - ISO 3690 KW - Schweißverbindung PY - 2023 AN - OPUS4-58307 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Component test for the assessment of hydrogen assisted cracking susceptibility of thick-walled submerged arc welded offshore steels N2 - Offshore wind turbines (OWT) are a key factor of the sustainable energy generation of tomorrow. The continuously increasing installation depths and weight of the OWTs require suitable foundation concepts like monopiles or tripods. Typically, mild steels like the S420ML are used with plate thicknesses up to several hundreds of mm causing high restraints in the weld joints. Due to the large plate thickness, submerged arc welding (SAW) with multiple wires is the state-of-the-art welding procedure. As a result of the very high stiffness of the construction, a certain susceptibility for time-delayed hydrogen-assisted cracking (HAC) may occur. The evaluation of crack susceptibility is very complex due to the component size and stiffness of real offshore structures. For this purpose, a near-component test geometry was developed to transfer the real stiffness conditions to laboratory (i.e., workshop) scale. The investigated mock-up, weighing 350 kg, comprised heavy plates (thickness 50 mm, seam length 1,000 m) joined by a 22-pass submerged arc weld. Additional stiffeners simulated the effect of high restraint or shrinkage restraint of the weld. Extreme scenarios of hydrogen absorption during welding were simulated via the use of welding fluxes in dry (HD < 5 ml/100g Fe) and moisture condition (HD > 15 ml/100g Fe). The residual stresses were determined by a robot X-ray diffractometer. Areas of critical tensile residual stress (at the level of the yield strength) were found in the weld metal and heat affected zone. To identify possible delayed cracking, the welds were tested by phased array ultrasonic testing (PAUT) after 48 h. Summarized, no significant occurrence of HAC was detected, indicating the high crack resistance of the welded joint, i.e., a suitable combination of base material, welding consumable and welding parameters. T2 - AJP 2023: 3rd International Conference on Advanced Joining Processes 2023 CY - Braga, Portugal DA - 19.10.2023 KW - Hydrogen assisted cracking KW - Submerged arc welding KW - Component test KW - NDT KW - Waiting time PY - 2023 AN - OPUS4-58672 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Giese, Marcel A1 - Schröder, Nina A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Kadoke, Daniel A1 - Kruse, Julius T1 - Local strain behaviour in cross weld tensile specimens of microalloyed high strength steels using digital image correlation N2 - This study specifically examines the role of the microalloying element titanium (Ti) in achieving the desired mechanical properties of quenched and tempered high-strength fine-grain structural steels, with a nominal yield strength of ≥ 690 MPa. Current specifications limit chemical composition only by defining upper thresholds, but even minor variations in Ti content can substantially alter mechanical properties. Consequently, accurate prediction of weldability and welded joint integrity becomes challenging, as variations in Ti lead to distinct microstructural characteristics, potentially causing undesirable softening or hardening effects in the heat-affected zone (HAZ). To address these complexities, two distinct titanium concentrations were systematically investigated for the first time using specially developed laboratory-cast alloys. Both alloying configurations were based on the standard S690QL grade, with consistent chemical composition and heat treatment parameters maintained across the samples. For the weldability analysis, three-layer welds were executed using gas metal arc welding (GMAW), allowing for the identification of critical microstructural zones within the HAZ that exhibit significant softening or hardening. The influence of the softened HAZ region on failure mechanisms was assessed through transverse tensile tests. Digital image correlation (DIC) was employed to capture local strain variations across different HAZ regions in situ. With a custom-developed mirror system, local strains in microstructural zones on both the top and bottom surfaces of the weld were recorded simultaneously. This setup enabled a detailed analysis of how weld seam geometry (e.g., V-groove configuration) influences strain gradients. Additionally, the investigation of localized deformation provided insights into how variations in Ti content within the HAZ affect global strain, fracture constriction, fracture location, and overall fracture behavior. T2 - MPA Seminar 2024 Materials Processes Applications CY - Stuttgart, Germany DA - 08.10.2024 KW - HAZ-Softening KW - Digital Image Correlation KW - Cross weld tensile test PY - 2024 AN - OPUS4-61488 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Erxleben, Kjell A1 - Kaiser, Sebastian A1 - Rhode, Michael A1 - Kannengiesser, Thomas A1 - Kromm, Arne T1 - In-service and repair welding of pressurized hydrogen pipelines–a review on current challenges and strategies N2 - Hydrogen is the energy carrier for a sustainable future without fossil fuels. As this requires a reliable transportation infrastructure, the conversion of existing natural gas (NG) grids is an essential part of the worldwide individual national hydrogen strategies, in addition to newly erected pipelines. In view of the known effect of hydrogen embrittlement, the compatibility of the materials already in use (typically low-alloy steels in a wide range of strengths and thicknesses) must be investigated. Initial comprehensive studies on the hydrogen compatibility of pipeline materials indicate that these materials can be used to a certain extent. Nevertheless, the material compatibility for hydrogen service is currently of great importance. However, pipelines require frequent maintenance and repair work. In some cases, it is necessary to carry out welding work on pipelines while they are under pressure, e.g., the well-known tapping of NG grids. This in-service welding brings additional challenges for hydrogen operations in terms of additional hydrogen absorption during welding and material compatibility. The challenge can be roughly divided into two parts: (1) the possible austenitization of the inner piping material exposed to hydrogen, which can lead to additional hydrogen absorption, and (2) the welding itself causes an increased temperature range. Both lead to a significantly increased hydrogen solubility in the respective materials compared to room temperature. In that connection, the knowledge on hot tapping on hydrogen pipelines is rare so far due to the missing service experiences. Fundamental experimental investigations are required to investigate the possible transferability of the state-of-the-art concepts from NG to hydrogen pipeline grids. This is necessary to ensure that no critical material degradation occurs due to the potentially increased hydrogen uptake. For this reason, the paper introduces the state of the art in pipeline hot tapping, encompassing current research projects and their individual solution strategies for the problems that may arise for future hydrogen service. Methods of material testing, their limitations, and possible solutions will be presented and discussed. KW - In-service KW - Hydrogen KW - Repair welding KW - Pipeline PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-638944 DO - https://doi.org/10.1007/s40194-025-02127-x SN - 0043-2288 SP - 1 EP - 24 PB - Springer Science and Business Media LLC AN - OPUS4-63894 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Thermal desorption spectroscopy for identification of diffusion and trapping in CoCrFeMnNi high-entropy alloy at 1,000 bar high-pressure hydrogen N2 - First studies on the mechanical behavior of high-entropy alloys (HEAs) in high-pressure hydrogen environment are available. In contrast, the underlying hydrogen absorption, diffusion and trapping in these HEAs like the Cantor-alloy was less in the scientific scope so far. For that reason, the CoCrFeMnNi-HEA was compared to a conventional AISI 316L austenitic steel, by exposing to high-pressure hydrogen charging at 200 bar and very-high pressure at 1,000 bar. Thermal desorption analysis (TDA) was applied with different heating rates (0.125 K/s to 0.500 K/s). The underlying TDA spectra were analyzed in terms of a reasonable peak deconvolution to into a defined number of peaks and the calculation of the activation energies for the respective and predominant hydrogen trap sites. Both materials show a comparable hydrogen diffusivity. The obtained activation energies suggest that in case of the CoCrFeMnNi-HEAs an interaction of the austenitic phase as well as the direct atomic bonding of hydrogen to the metal atoms are the dominant traps, since “impurities” such as carbides or inclusions are only present in trace amounts. Available literature suggests that the Cr and Mn-content is here of special interest for the direct hydrogen bonding at solute atoms. Despite the activation energy, the trap occupancy rate must be considered in terms of a pressure-related hydrogen absorption. The derived apparent hydrogen solubility was in the order: 316L < CoCrFeMnNi-HEA for both charging pressures. Especially, the 1,000 bar values lead to noteworthy results with > 70 wt.ppm for the AISI 316L and >130 wt.ppm for the CoCrFeMnNi. In fact, both the hydrogen diffusion and trapping data on gaseous high-pressure hydrogen charged HEAs are rare so far. The results of the present study allow a deeper understanding of hydrogen trapping in the regarded CoCrFeMnNi-system. T2 - 1st Conference on Hydrogen in Materials Science and Engineering (H2-MSE) CY - Freiburg, Germany DA - 11.02.2025 KW - High-entropy alloy KW - Hydrogen diffusion KW - High-pressure charging KW - Thermal desorption analysis PY - 2025 AN - OPUS4-62543 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Diffusion and trapping of gaseous hydrogen charged CoCrFeMnNi-HEA vs. austenitic steel AISI 316L at pressure up to 1000 bar N2 - First studies on the mechanical behavior of high-entropy alloys (HEAs) in high-pressure hydrogen environment are available. In contrast, the underlying hydrogen absorption, diffusion and trapping in these HEAs like the Cantor-alloy was less in the scientific scope so far. For that reason, the CoCrFeMnNi-HEA was compared to a conventional AISI 316L austenitic steel, by exposing to high-pressure hydrogen charging at 200 bar and very-high pressure at 1,000 bar. Thermal desorption analysis (TDA) was applied with different heating rates (0.125 K/s to 0.500 K/s). The underlying TDA spectra were analyzed in terms of a reasonable peak deconvolution to into a defined number of peaks and the calculation of the activation energies for the respective and predominant hydrogen trap sites. Both materials show a comparable hydrogen diffusivity. The obtained activation energies suggest that in case of the CoCrFeMnNi-HEAs an interaction of the austenitic phase as well as the direct atomic bonding of hydrogen to the metal atoms are the dominant traps, since “impurities” such as carbides or inclusions are only present in trace amounts. Available literature suggests that the Cr and Mn-content is here of special interest for the direct hydrogen bonding at solute atoms. T2 - MSE 2024: International Materials Science and Engineering Congress CY - Darmstadt, Germany DA - 24.09.2024 KW - High-entropy alloy KW - Hydrogen KW - Trapping KW - Diffusion KW - High-pressure charging PY - 2024 AN - OPUS4-61156 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Dissimilar metal TIG weld joints of multiple principal element alloys (MPEA) to austenitic steel 304 N2 - Multi-element alloys (MPEA - Multiple Principal Element Alloys) represent a new class of materials consisting of at least three alloying elements, each with 5 to 35 atomic %. This material class includes high-entropy alloys (HEA, with n ≥ 4 elements). The underlying alloying concept differs fundamentally from conventional materials such as the Fe-based steel. For this purpose, the alloying elements are specifically selected, and the microstructures are adjusted in a single-phase and, in some cases, multi-phase manner. The aim is to identify highly innovative MPEA with individually adjustable properties for industrial applications. In the last 20 years, however, the focus has been on pure material synthesis. With the increase in available material quantities, the focus is on processing issues such as joining and welding processes. In that connection, the weldability of MPEAs has received very little attention so far. Experience with dissimilar metal welds (DMWs) is completely lacking but is essential for the application of these materials if joint to conventional materials. This study presents selected experimental results on the weldability of MPEA-DMWs and the resulting microstructures. For this purpose, the equiatomic CoCrFeMnNi (HEA) was investigated in cold-rolled (CR) and heat-treated (HT) condition and joined by tungsten inert gas (TIG) welding to an austenitic stainless steel 304. The DMWs showed defect-free conditions (no lack of fusion, cracks and so on), whereas the cold-rolling increases the microhardness. The global mechanical properties were obtained by instrumented tensile tests of cross-weld samples and showed sufficient yield and tensile strength comparable to that of the individual base materials (BM). The local strain conditions were determined by digital image correlation and showed the highest local strains to occur in the intermixed weld metal. Indeed, the preferred fracture location of the cross-weld tensile samples was in the weld metal. Finally, the experiments proofed the weldability of the MPEAs to conventional 304. This enables targeted further considerations for example as structural materials. T2 - FEMS EUROMAT 2023 CY - Frankfurt a. M., Germany DA - 04.09.2023 KW - Multi-principal element alloys KW - TIG welding KW - Dissimilar metal weld (DMW) joint KW - Microstructure KW - Mechanical properties KW - Digital Image Correlation (DIC) PY - 2023 AN - OPUS4-58222 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Erxleben, Kjell A1 - Richter, Tim A1 - Schröpfer, Dirk T1 - Charakterisierung der WIG und FSW-Mischverbindungen neuartiger Multielement-Legierungen mit einem austenitischen Stahl N2 - Multielement-Legierungen (MPEA - Multiple Principal Element Alloys), gemeinhin und partiell fälschlicherweise auch als Hochentropielegierungen bezeichnet) stellen eine neue Klasse von Werkstoffen dar, die aus mindestens drei Legierungselementen mit jeweils 5 bis 35 Atom-% bestehen. Somit unterscheidet sich dieses Legierungskonzept fundamental von konventionellen Werkstoffen wie Stahl oder Nickellegierungen. Hierzu werden die Legierungselemente gezielt ausgewählt und die Mikrostrukturen ein- und zum Teil auch mehrphasig eingestellt. Das Ziel ist dabei, hochinnovative MPEA mit individuell einstellbaren Eigenschaften für die industrielle Anwendung zu identifizieren. Dabei werden insbesondere Zielkonflikte, wie bspw. der Trade-off zwischen Festigkeit und Duktilität bei konventionellen Stählen, überwunden. Insbesondere die hohe mechanische Festigkeit bei höchster Korrosionsbeständigkeit sind bei bestimmten Legierungssystemen von hohem Interesse. Hier kann u.a. die Substitution klassischer hochlegierter Stähle oder Ni-Basislegierungen perspektivisch erfolgen. In den letzten 20 Jahren lag der Fokus jedoch auf der reinen Materialsynthese. Mit der Zunahme verfügbarer Werkstoffquantitäten, stehen Verarbeitungsfragen, wie werkstoff- und beanspruchungsgerechte Füge- bzw. Schweißverfahren jetzt im Mittelpunkt. Der Schweißeignung von MPEA wurde bisher nur äußert wenig Aufmerksamkeit zuteil. Erfahrungen zu Mischverbindungen (DMWs - Dissimilar Metal Welds) fehlen dabei vollständig, sind jedoch essenziell für die Anwendung dieser Werkstoffe in Verbindung mit konventionellen Werkstoffen. Die vorliegende Studie präsentiert erstmals im deutschen Sprachraum, die umfassenden experimentellen Ergebnisse zur Schweißeignung von MPEA-Mischverbindungen und der resultierenden Mikrostruktur. Dazu wurden zwei äquiatomare MPEAs in Form einer Co20Cr20Fe20Mn20Ni20 (Hochentropie-) und Co33.3Cr33.3Ni33.3 (Mediumentropielegierung) mittels WIG und Rührreibschweißen mit einem konventionellen, korrosionsbeständigem Cr-Ni-Stahl AISI 304 (1.4301 bzw. X5CrNi18-10) gefügt. Die erstmals untersuchten DMWs resultierten dabei in sehr interessanten Mikrostrukturen, mechanisch-technologische Eigenschaften wurden durch instrumentierte Zugversuche gewonnen, die gleichzeitig der Ermittlung der lokalen Verformung im Schweißnahtbereich dienten (durch Verwendung der berührungslosen DIC-Digital Image Correlation-Technik). Dabei zeigt sich für beide Schweißverfahren eine Erweichung in der Wärmeeinflusszone (WEZ) der MPEAs sowie eine geringfügig verminderte Zugfestigkeit, bei einer deutlichen Abnahme der Bruchdehnung. Durch die Experimente konnte der prinzipielle Nachweis der Schweißeignung der MPEAs für DMWs mit konventionellen Werkstoffen erbracht werden, die auch eine dementsprechende mechanische Beanspruchbarkeit ermöglichen. Dies ermöglicht weitere Betrachtungen zur Anwendung dieser innovativen Werkstoffe. T2 - DVS Congress 2023 CY - Essen, Germany DA - 11.09.2023 KW - Schweißeignung KW - Mischverbindung KW - Hochentropielegierung KW - Multielement-Legierung KW - FSW KW - WIG PY - 2023 SN - 978-3-96144-230-0 VL - 389 SP - 615 EP - 623 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-58352 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kaiser, Sebastian A1 - Rhode, Michael T1 - Repair welding of pressurized in-service hydrogen pipelines: A review on current challenges and strategies N2 - As energy carrier of the future, green hydrogen can make a decisive contribution to a sustainable energy supply. Particularly important is the decarbonization of heavy industry. Therefore, a reliable supply of hydrogen must be guaranteed. A hydrogen pipeline grid can achieve this purpose. In Europe concrete plans for a hydrogen pipeline grid already exist, as the so called “European Hydrogen backbone”. As building a completely new pipeline grid is economically not justifiable, a dual-way strategy of repurposing natural gas (NG) pipelines and newly built pipelines is intended. Long distance pipeline grids require regular maintenance and repairs. For NG pipelines in-service welding is state of the art. Concepts such as hot-tapping (drilling into pressurized pipelines) and “stoppling” (sealing off pipeline sections after installing bypasses or pressure relieves) allow the repair of damaged pipeline sections or the installation of new branches without shutting the pipeline down, which in most cases isn’t possible from an economic standpoint. The EIGA 121/14 guideline already pointed out in 2014 that “A hydrogen hot-tap shall not be considered a rou-tine procedure, […]”. This shows that the determination of the transferability of these repair concepts to hydrogen pipelines is of utmost importance. Due to the degrading effects of hydrogen on mechanical properties, commonly referred to as “hydrogen embrittlement” it is necessary to understand and investigate the occurring effects. In the special case of repair welding on in-service hydrogen pipelines an increased hydrogen uptake due to a large heat input and microstructural changes in the material needs to be considered. Therefore, material degradation must be investigated to determine whether modifications of repair procedures are necessary to ensure a reliable and safe hydrogen transportation via pipelines. For this reason, this paper gives an overview on existing weld repair concepts and its risks and limitations in terms of hydrogen absorption and possible embrittlement effects when transferred to hydrogen pipelines. The complexity lies in a large variety of materials (low alloyed steels), pipeline diameters and corresponding weld-ed joints. The material compatibility of materials in used (repurposed NG-pipelines) and new condition must be investigated. Particularly for repurposed/used pipelines the effect of a pre-matured/corroded inner surface and sometimes insufficient documentation of the material “history” needs to be considered. An overview on ongoing and completed R&D-projects with respect to repair concepts for hydrogen pipelines and hydrogen effects on pipeline materials is given. T2 - 77th IIW Annual Assembly and International Conference, Meeting of Commission II-A "Metallurgy of Weld Metals" CY - Ixia, Rhodes Island, Greece DA - 07.07.2024 KW - Hydrogen KW - Pipeline KW - In-Service Welding PY - 2024 AN - OPUS4-60757 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -