TY - CONF A1 - Rhode, Michael T1 - Development of a component test for assessment of delayed hydrogen assisted cracking susceptibility of thick walled submerged arc welded high strength offshore steels N2 - Offshore Wind Turbines (OWT) are a key factor in tomorrow's sustainable energy generation. The ever-increasing installation depth and weight of OWTs require suitable foundation concepts such as monopiles or tripods. Typically, mild steels such as S420ML are used with plate thicknesses of up to several hundred mm, resulting in high restraints in the welded joints. The large plate thickness requires high-efficiency welding processes such as submerged arc welding (SAW) with multiple wires. Due to the very high stiffness and plate thickness of the large-scale offshore structure, a susceptibility to time-delayed hydrogen assisted cracking (HAC) may occur. The evaluation of this 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 350 kg mock-up studied consisted of 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 by using flux in dry (HD < 5 ml/100g Fe) and wet (HD > 15 ml/100g Fe) conditions. Weld residual stresses were determined using a robotic X-ray diffractometer. Areas of critical tensile residual stress (at the level of the yield strength) were found in the weld metal and in the heat affected zone, suggesting that these weld sub-zones are the most critical in the case of hydrogen ingress. To identify possible delayed cracking, the welds were tested by phased array ultrasonic testing (PAUT) after welding, 6 h, 12 h, 24 h, and a maximum of 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 parameters. T2 - MSE 2024: International Materials Science and Engineering Congress CY - Darmstadt, Germany DA - 24.09.2024 KW - Hydrogen KW - Offshore wind turbine KW - Component test KW - Submerged arc welding KW - Minimum waiting time PY - 2024 AN - OPUS4-61154 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Assessment of in-service welding conditions for pressurized hydrogen pipelines via component test N2 - Hydrogen is the energy carrier of tomorrow. This requires a reliable transport infrastructure with the ability to carry large amounts of hydrogen e.g. for steel industry or chemical industry. The conversion of existing natural gas (NG) grids is an essential part of the worldwide hydrogen strategies, in addition to the construction of new pipelines. In this context, the transportation of hydrogen is fundamental different from NG as hydrogen can be absorbed into the pipeline material. Given the well-known effects of hydrogen embrittlement, the compatibility of the materials for the intended pipelines must be investigated (typically low alloy steels in a wide range of strengths and thicknesses). However, pipelines require frequent maintenance, repair or the need for installation for further outlets. In some cases, it is necessary to perform welding on or onto the pipelines while they are still in service, i.e. with active gas flow under high pressure, e.g. such as the well-known “hot tapping”, see Fig. 1a. This in-service welding causes challenges for hydrogen operations in terms of additional hydrogen absorption during welding and the material compatibility. The challenge can be roughly divided into the possible austenitization of the inner pipe material exposed to hydrogen, which can lead to sufficient hydrogen absorption, and the welding itself, which causes an increased temperature range. Both lead to a significant increase in hydrogen solubility and diffusivity of the respective materials compared to room temperature. In this context, knowledge about hot tapping on hydrogen pipelines is scarce due to the lack of operating experience. Fundamental experimental investigations are required to investigate the transferability from NG to hydrogen pipeline grids. For this reason, the present study introduces a specially designed mock-up / demonstrator concept for the realistic assessment of the welding processing conditions, see Fig. 1b. The mock-up was designed to enable in-situ temperature measurement during welding as well as ex-post extraction of samples for the quantification of the absorbed hydrogen concentration, see Fig. 1c. For safety measures, the necessary pressurized hydrogen volume was limited by the insertion of a solid cylinder ensuring a 1 cm hydrogen gas layer. Welding experiments on the pressurized mock-ups with the diameters DN50 and DN200 have shown that the austenitization temperature can be reached on the inner surface of the pipeline, especially on thinner-walled pipelines, using current welding practices. This corresponds to an increased hydrogen uptake in the welded area of several ppm T2 - 1st Conference on Hydrogen in Materials Science and Engineering (H2-MSE) CY - Siegburg, Germany DA - 11.02.2025 KW - Hydrogen KW - Pipeline KW - In-service welding KW - Component test PY - 2025 AN - OPUS4-62544 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Residual Stresses in Multi-Layer Component Welds T2 - 5th International Conference on Trends in Welding Research CY - Chicago, IL, USA DA - 2012-06-04 PY - 2012 AN - OPUS4-26607 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Influence of heat control on hydrogen distribution in high-strength multi-layer welds with narrow groove N2 - High-strength low-alloyed (HSLA) steels with yield strength ≥ 690 MPa are gaining popularity in civil engineering and construction of heavy vehicles. With increasing yield strength, the susceptibility for degradation of the mechanical properties in presence of diffusible hydrogen, i.e. hydrogen-assisted cracking (HAC) generally increases. HAC is a result of the critical interaction of local microstructure, mechanical load and hydrogen concentration. In existing standards for welding of HSLA steels, recommendations (preheating, interpass temperature and hydrogen removal heat treatment) are given to limit the amount of introduced hydrogen during welding. The recommendations are based on investigations with conventional arc welding processes. In the past decade, modern weld technologies were developed to enable welding of narrower weld seams with V-grooves of 30°, e.g. the modified spray arc process. In that connection, a reduced number of weld runs and weld volume are important technical and, hence, economic benefits. In the present study, the hydrogen distribution in S960QL multi-layer welds with thickness of 20 mm was analyzed depending on heat control. The influence of different weld seam opening angles (grooves), heat input, interpass temperature and hydrogen removal procedures was investigated. The results show that weldments with narrow groove contained increased diffusible hydrogen amount. Reasons had been longer diffusion path and higher wire feeding rate compared to conventional welds with wider 60° Vgroove. Hydrogen concentration has been reduced by decreasing both the heat input and interpass temperature. Hydrogen free weldments were achieved via hydrogen removal heat treating at 250 °C for 5 h subsequently after welding. Regarding the strength of the investigated steel, it is recommended to conduct a heat treatment after welding. For the first time, hydrogen concentration gradients were experimentally determined across the weld seam thickness in HSLA multi-layer welds. T2 - Intermediate Meeting of IIW Commission II-A CY - Genoa, Italy DA - 05.03.2018 KW - Hydrogen assisted cracking KW - Welding KW - Heat control KW - High-strength steel PY - 2018 AN - OPUS4-44426 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Specimen temperature during CGHE and influence on hydrogen determination N2 - Hydrogen determination in weld seams is standardized in ISO 3690. In accordance to this standard, a defined time for hydrogen collection has to be anticipated for different extraction temperatures. In other words, the temperature is the most important value that has to be monitored in addition to the aimed hydrogen determination. The specimen geometry has influence on the real sample temperature during CGHE vs. the adjusted furnace temperature. This presentation gives a short summary on possible influences on the "correct" hydrogen determination temperature during carrier gas hot extraction (CGHE) using infrared radiation driven furnace. The main findings are: (1) specimen surface is important in terms of polished or oxidized condition, (2) specimen geometry is important for fast heating, (3) PID-values of control software are a considerable influence to accelerate the heating process depite thick specimens and (4) independent sample temperature determination before CGHE is strongly recommended. T2 - Intermediate Meeting of IIW Subcommission II-E CY - Genoa, Italy DA - 05.03.2018 KW - Hydrogen KW - Welding KW - Carrier gas hot extraction KW - Temperature KW - Measurement PY - 2018 AN - OPUS4-44427 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Microalloying influence on precipitation behavior and mechanical properties of welded high strength structural steels N2 - Microalloying elements, such as Nb and Ti, are essential for the targeted mechanical strength of quenched and tempered, high-strength fine-grained structural steels with a nominal yield strength ≥ 690 MPa. Current specifications for chemical composition only provide upper limits for manufacturers. But even small deviations in the alloying route can have a drastic effect on the mechanical properties. Thus, an adequate prediction of the weldability and the integrity of the welded joint becomes difficult or even impossible due to the varying composition and, hence, the microstructures. Undesirable side effects are the possible softening of the heat-affected zone (HAZ) as well as the opposite effect of hardening. Against this background, different microalloying routes with varying Ti and Nb contents are systematically investigated for the first time on specially designed lab-cast alloys. The basis of each alloy route was the common S690QL in terms of both the chemical composition as well as the heat treatment. To investigate the weldability, three-layer welds were performed using metal active gas welding (MAG) and critical microstructural areas with high softening/hardening were identified. The scope was here on the identification of phase transformations during cooling and on the respective metallurgical precipitation behavior. Isothermal and non-isothermal phase calculations were performed using Thermo-Calc® and showed that the prediction of the non-equilibrium precipitation characteristics during welding is not trivial, especially for this relatively complex chemical composition. The mechanical properties of the welded joints were identified by both Charpy tests (toughness) and tensile tests (strain and strength). During the test, the local straining behavior of the welded joints, was identified using a digital image correlation (DIC) system, see Figure 1. Despite the generally good weldability of the materials, the results show a significant influence of the microalloying route as well as the welding heat input on the different precipitation kinetics. T2 - FEMS EUROMAT 2023 CY - Frankfurt a. M., Germany DA - 04.09.2023 KW - High-strength KW - Steel KW - Mechanical properties KW - Welding KW - Thoughness PY - 2023 AN - OPUS4-58221 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Determination of inner pipe surface temperatures during in-service welding on hydrogen pipelines by means of component-like mock up experiments N2 - Hydrogen is considered as one of the most important energy carriers in the future. The necessary large-scale transport over long distances requires a suitable pipeline infrastructure. Current plannings encompass a dual-way strategy of repurposing existing natural gas (NG) pipelines, supplemented by the construction of new hydrogen pipelines. In some cases, such as necessary grid extensions or installation of bypasses in case of repair work, techniques like “hot tapping” are applied. These techniques include so-called in-service welding on pressurized pipelines and are state-of-the-art for NG grids and oil pipelines. The existing NG pipeline grid consists of a wide range of materials with different strengths, diameters, and wall thicknesses. In this context, the material compatibility is crucial. The main difference between hydrogen and NG is that hydrogen can both penetrate the material and cause hydrogen embrittlement. In that connection, in-service welding encompasses elevated temperatures for a certain time during the typically multi-layer welding process. Locally even austenitization temperature can be reached or surpassed. Austenite has a higher hydrogen solubility at a significantly lower diffusion rate, which could lead to a critical hydrogen accumulation. Especially the inner pipe surface temperature is from utmost interest, as this interface is exposed to the pressurized hydrogen (up to 100 bar). However, direct measurement of the locally occurring temperatures is very challenging. For this reason, a component-like geometry was developed. The geometry consists of a pipeline segment with a metal sheet joined to the pipe segment, representing similar heat dissipation conditions as in the field. In addition, typical welding parameters were applied that are currently used in the NG grid. This allows the welding of realistic multi-layer fillet welds on the outer pipe wall with simultaneous temperature measurement using manifold thermocouples at defined positions: (1) adjacent to the weld seam on the outer pipe surface, (2) on the inner pipe surface and (3) on the welded metal sheet. To ensure realistic conditions, manual shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) was investigated. The effects of different wall thicknesses and welding heat inputs on the temperature distribution and peak temperatures achieved on the inner pipe surface during welding vary depending on the chosen method. Peak temperatures above austenitization temperature up to 1078 °C have been measured on L245 pipes with wall thickness of 3.6 mm. For pipes made from higher strength materials, such as L485, with a wall thickness of 8 mm, peak temperatures between 607 °C and 755 °C were recorded. Temperature and austenitization directly affects hydrogen diffusivity and solubility, showing the importance of the findings. The temperature profile and cooling conditions influence the mechanical properties of the material as well. For this reason, metallurgical investigations are carried out to assess the hardness and microstructure of the welds. Hardening up to 248 HV10 was detected in the heat-affected zone (HAZ) of the top layer, which could lead to a locally increased susceptibility to hydrogen assisted cracking. Meanwhile, the minimum hardness found in the HAZ of the root layer was as low as 144 HV10, indicating a softening. The results of this study provide valuable insights into the suitability of existing materials and geometries for hydrogen transport. Secondly, the data collected will serve as a basis for planned numerical simulations to further improve knowledge and optimize welding processes to ensure the integrity and safety of hydrogen pipelines. T2 - IIW Intermediate Meeting, Com. II-A CY - Trollhättan, Sweden DA - 10.03.2025 KW - Testing KW - In-service welding KW - Hydrogen KW - Pipelines PY - 2025 AN - OPUS4-62690 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Influence of various microalloying strategies on the mechanical properties of weld seams in S690QL steel N2 - Microalloying elements such as niobium (Nb) and titanium (Ti) play a crucial role in achieving the desired mechanical properties of quenched and tempered high-strength fine-grained structural steels with a nominal yield strength of ≥ 690 MPa. Current specifications for the chemical composition only define upper limits for these elements, providing manufacturers with some flexibility. However, even minor deviations in alloying concepts can significantly influence the resulting mechanical properties. Consequently, accurately predicting weldability and the integrity of welded joints becomes challenging or even unfeasible due to variations in composition and the associated microstructural changes. Potential adverse effects include the softening of the heat-affected zone (HAZ) or, conversely, localized hardening phenomena. To address these challenges, various microalloying strategies with different Ti and Nb contents are being systematically investigated for the first time using specially designed laboratory-cast alloys. Each alloying approach is based on the commonly used S690QL steel grade while maintaining consistent chemical composition and heat treatment parameters. To evaluate the weldability, three-layer welds were produced using gas metal arc welding (GMAW), and critical microstructural regions, particularly those within the heat-affected zone (HAZ) exhibiting significant softening or hardening, were identified. The influence of the softened HAZ region on failure behavior was assessed through transverse tensile testing. Digital image correlation (DIC) was employed for in situ analysis of local strain distributions across different HAZ regions. In addition, Charpy tests were carried out on BM, WM and HAZ to determine the Charpy impact toughness. This was supported by metallographic analyses and thermodynamic simulation using ThermoCalc. T2 - IIW Intermediate Meeting, Com. II-A CY - Trollhättan, Sweden DA - 10.03.2025 KW - Welding KW - Microalloy elements KW - High strength steels KW - Mechanical properties PY - 2025 AN - OPUS4-62691 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Microstructure and local mechanical properties of friction stir welded dissimilar joints of CoCrFeMnNi and CoCrNi to austenitic steel AISI 304 N2 - Multiple principal element alloys (MPEA) represent a meanwhile widely investigated material class, which encompass high-entropy (HEA) and medium-entropy alloys (MEA). They are fundamentally different from conventional materials like Fe-Cr-Ni-based austenitic steels. However, the focus has been merely on the material synthesis. With the increase in available material quantities, the focus is now shifting to processing issues such as joining and welding. In this context, the weldability of MPEAs has received very little attention so far. In addition, MPEA/HEA/MEA are and will be expensive due to the alloying concept. From this point of view, also such materials will also have to be joined with other conventional materials like austenitic steels. In particular, there is a lack of experience with dissimilar metal welds (DMWs) and the corresponding mechanical properties. For this reason, the present study summarizes comprehensive experimental results on equiatomic CoCrFeMnNi (HEA) and CoCrNi (MEA), joined by solid-state friction stir welding (FSW) to an austenitic steel AISI 304. The mechanical properties were obtained by cross-weld tensile tests. For the first time (for these welding process and materials), the local strains in the different weld microstructures were measured in-situ by digital image correlation (DIC). A significant influence of the FSW process on both the resulting microstructure and the mechanical performance of the DWMs was identified. For example, the dynamic recrystallization plays a significant role in the performance of the welded joint. In addition, the FSW experiments proofed the weldability of both MPEAs when joined to austenitic steel AISI 304. This allows for further focused consideration of these highly innovative MPEAs. T2 - MSE 2024: International Materials Science and Engineering Congress CY - Darmstadt, Germany DA - 24.09.2024 KW - High-entropy alloy KW - Dissimilar metal weld KW - Microstructure characterization KW - Mechanical properties KW - Friction stir welding PY - 2024 AN - OPUS4-61157 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Update on "Call for interested people to contribute to series of comprehensive papers on welding and joining of components for sustainable energy systems" N2 - Based on the initial call in March 2024, an update time-frame is introduced on the working plan for a comprehensive review paper series on joining and welding technologies for the manufacturing of components and parts used in sustainable energy generation, conversion, and transport with focus on hydrogen and wind energy. T2 - 77th IIW Annual Assembly and International Conference, Meeting of Commission II-A CY - Ixia, Rhodes, Greece DA - 07.07.2024 KW - Review paper KW - Research study KW - Hydrogen KW - Joining KW - Welding PY - 2024 AN - OPUS4-60674 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -