TY - CONF A1 - Hübner, Martin A1 - Reichel, Levin A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Modern welding processes for optimising repair welds on high strength offshore steels N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future. To achieve these high outputs, turbines far from coast are required with large subsea jacket structures (30 m up to 50 m) and tall towers (up to 200 m). High-strength steels with a yield strength up to 500 MPa and wall thicknesses up to 150 mm are increasingly being used for these structures. This plac-es high demands on welding manufacturing, especially for high-strength offshore steels. During the manu-facturing process detected defects by NDT require localized repair of welds by gouging and rewelding. Due to a lack of investigations, there are no repair concepts and information in standards and guidelines, par-ticularly for high-strength thick plate joints made of high-strength offshore steels. However, these are ur-gently needed to enable manufacturers, especially SMEs, to carry out safe and economical repairs. There-fore, BAM started the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal with controlled high-performance GMAW pro-cesses and optimized narrow gouging grooves. The experimental analyses take into account the complex interaction of process, material, and design-related influences on the formation of weld induced stresses and the special microstructure of high-strength fine-grain structural steels. Welding-related material degra-dation and crack-critical residual tensile stresses need to be avoided to ensure high component safety and performance. A reduction in residual stress in the presence of high restraint conditions can be achieved by adapted heat control (if no disassembly measures are possible). The repair process involves manual thermal gouging, which allows the groove configuration to be modi-fied. Modern welding processes using high frequency arc control provide deep root penetration and focused energy input capable of welding narrow seams. A comparison was made between the traditional weld con-figuration with a wide 45° groove and transition arc welding and a narrow 30° groove with modern welding process. Even in the case of free shrinkage specimens, the narrow groove weld exhibits a significant reduc-tion of residual stresses, cf. Figure 1, especially in the HAZ and toward the adjacent base material. This can be attributed to the lower weld metal volume needed and the reduction of heat input per layer due to the controlled arc process. For the purposes of this comparison, the same weld seam build-up (but different number of layers) has been applied to both seam configurations. Note that in industrial application (manu-al welding), the wider groove would be welded with several off-center weld beads with conventional weld-ing process. In this analysis this would cause asymmetric effects regarding the residual stress state, diffi-cult to compare to each other. Component-related welding experiments on special testing equipment, adapted process and heat control concepts along with variable groove configurations will be developed and recommendations for guidelines elaborated. This is the prerequisite for fully utilizing the strength potential of high-strength steels and making a valuable contribution to the energy transition in Germany, especially for steel-processing SMEs. T2 - IIW Intermediate Meeting CII CY - Trollhättan, Sweden DA - 10.03.2025 KW - Repair welding KW - Gouging KW - Residual stress KW - Offshore wind turbines KW - High-strength steels PY - 2025 AN - OPUS4-62743 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Dittmann, Florian A1 - Varfolomeev, Igor T1 - Untersuchung der Ermüdungsfestigkeit von LTT-geschweißten Längssteifen mit variierender Nahtausführungen N2 - Low Transformation Temperature (LTT) Schweißzusätze erzeugen während der Abkühlung Druckeigenspannungen in die Schweißnaht und Wärmeeinflusszone durch eine Volumenexpansion, wodurch die Ermüdungsfestigkeit erhöht werden kann. Um das Potential dieser neuartigen Schweißzusätze besser zu quantifizieren, wurden konventionelle Längssteifen als Probenkörper verwendet, welche an den Stirnseiten mit einer LTT-Zusatznaht geschweißt wurden. Durch Variation der Schweißparameter konnten unterschiedliche Nahtformen realisiert werden. Es konnte, je nach Nahtausführung, eine Erhöhung der Ermüdungsfestigkeit bei 2 Millionen Lastwechsel von 64 MPa bis 100 MPa in Gegensatz zu konventionellen Proben festgestellt werden. Somit sind LTT-Zusätze grundsätzlich geeignet, um die Ermüdungsfestigkeit zu erhöhen. T2 - Frühjahrssitzung 2025 des Fachausschusses Eigenspannungen der AWT CY - Karlsruhe, Germany DA - 07.04.2025 KW - LTT (Low Transformation Temperature) KW - Eigenspannungen KW - Ermüdungsfestigkeit KW - Aufmischung PY - 2025 AN - OPUS4-62930 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Dittmann, Florian A1 - Varfolomeev, Igor T1 - Wechselwirkung zwischen Nahtgestaltung und Ermüdungsfestigkeit in LTT-geschweißten Längssteifen N2 - Schweißzusätze mit niedriger Martensitstarttemperatur (Low Transformation Temperature, LTT) induzieren während der Abkühlphase infolge einer volumeninduzierten Martensitumwandlung Druckeigenspannungen in der Schweißnaht sowie in der angrenzenden Wärmeeinflusszone (WEZ). Diese Spannungen können zu einer signifikanten Erhöhung der Ermüdungsfestigkeit führen. Zur quantitativen Bewertung des Potenzials dieser innovativen Werkstoffe wurden konventionelle Längssteifen als Versuchsproben herangezogen, bei denen an den Stirnseiten Schweißnähte unter Verwendung von LTT-Zusatzwerkstoffen appliziert wurden. Durch gezielte Variation der Schweißparameter konnten unterschiedliche Nahtgeometrien realisiert werden. In Abhängigkeit von der Nahtausführung zeigte sich bei einer Belastungszahl von 2 Millionen Zyklen eine Steigerung der Ermüdungsfestigkeit im Bereich von 64 MPa bis 100 MPa im Vergleich zu Referenzproben mit herkömmlichen Schweißzusätzen. Die Ergebnisse belegen, dass der Einsatz von LTT-Schweißzusätzen grundsätzlich geeignet ist, die Ermüdungsfestigkeit geschweißter Strukturen zu verbessern. T2 - Din Sitzung: Gemeinschaftsarbeitsausschuss NAS/NMP, Zerstörende Prüfung von Schweißverbindungen CY - Online meeting DA - 20.03.2025 KW - LTT (Low Transformation Temperature) KW - Eigenspannungen KW - Ermüdungsfestigkeit KW - high-strength steels PY - 2025 AN - OPUS4-62929 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 - JOUR A1 - Liepold, Philipp A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - A Force Based Determination of Hot Cracking Susceptibility N2 - Two high-strength, low-alloy Gas Metal Arc Welding (GMAW) wires were evaluated for their susceptibility to Solidification Cracking (SC) using a modified version of the Transverse Motion Weldability (TMW) test. In theoriginal TMW test, the Transverse Displacement Speed (TDS) is varied iteratively, and crack lengths are measured in each iteration. The modified version eliminates the need for multiple runs by continuously reducing the TDS over a single run. Rather than emphasizing crack lengths, this method assesses the reaction force to the TDS, thereby determining a Critical TDS (CTDS). This critical point directly correlates with the cessation of SC growth. CTDS values were measured under a range of welding parameters, thereby demonstrating the influence of Welding speed and arc energy (U × I/welding speed) on SC susceptibility for the tested filler metals. The CTDS data obtained from this testing method have the potential to provide valuable insights for practical applications in the field. KW - Force based KW - Neural Network KW - TRS PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-640140 DO - https://doi.org/10.5781/JWJ.2025.43.4.10 SN - 2466-2100 VL - 43 IS - 4 SP - 447 EP - 457 AN - OPUS4-64014 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liepold, Philipp A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Transvarestraint testing of high-strength steel filler metal N2 - High-strength steel welds are typically not known to be susceptible to Solidification Cracking (SC). However, modern light-weight constructions may force welding in highly restrained conditions, which are known to increase the probability of Solidification Crack (SC) emergence. In this article, the Modified Varestraint-Transvarestraint (MVT) test was used to evaluate the hot cracking susceptibility of welds made from high-strength, low-alloyed filler material. The materials tested include solid wires and a metal-cored wire. All wires are typically used in the Gas Metal Arc Welding (GMAW) process. Susceptibility to SC was measured over a wide range of welding parameters and bending speeds. Results show little affinity of the tested materials to SC. However, crack length increases in most cases with arc energy ( U ∙ I∕welding speed ) and welding speed. The length of the longest crack in one test specimen follows a similar trend until high welding speeds, where stagnation of crack length with changing arc energy was observed. KW - MVT KW - Varestraint KW - Transvarestraint KW - Solidification cracking KW - High-strength steel PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-630084 DO - https://doi.org/10.1007/s40194-025-02042-1 SN - 1878-6669 VL - 2025 SP - 1 EP - 12 PB - Springer CY - Berlin ; Heidelberg AN - OPUS4-63008 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Influence of residual stresses and heat control on stress relief cracking in a CrMoV steel mockup N2 - Preventing failures in the manufacture or operation of petrochemical reactors made from creep-resistant, low-alloy steels such as 13CrMoV9-10 still requires research, despite over 60 years of investigation into the field of stress relief cracking. Welding this steel grade requires care. This is due to its low toughness and high strength in the welded condition if not heat treated after welding, combined with an increased susceptibility to cracking during stress relaxation. Previous research on cracking in creep resistant steels has focused on thermal and metallurgical factors; however, little knowledge has been gained on cracking under real-life restraint conditions. In this work, the influence of welding heat control on cracking was investigated by simulating the manufacturing conditions prevailing in the construction of petrochemical reactors using a special weld mockup. The application of acoustic emission analysis showed that cracks formed during post-weld heat treatment in a temperature range between 300 °C and 500 °C. Compared to small scale samples, the toughness of the restrained welds was significantly lower. SEM and TEM analyses of all samples revealed early ageing due to early precipitation of special carbides during post-weld heat treatment under restraint. Neutron diffraction experiments showed that the residual stresses in the weld seam reach the yield point of the material. The presentation provides an overview of how a comprehensive assessment of the integrity of submerged arc welded CrMoV steels can be achieved in the laboratory. T2 - Cracking Phenomena in Welding and Additive Manufacturing 2025 CY - Trollhättan, Sweden DA - 12.03.2025 KW - CrMoV KW - Stress Relief Cracking KW - Sub-merged arc welding PY - 2025 AN - OPUS4-62783 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin A1 - Kromm, Arne A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Moderne Schweißverfahren zur Optimierung von Reparaturschweißungen an hochfesten Offshore-Stählen N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future, for which high-strength steels with a yield strength of up to 500 MPa and wall thicknesses up to 150 mm are increasingly being used. The repair of weld seams when detecting defects during NDT requires local-ized gouging and rewelding. This involves high demands on welding manufacturing, especially for high-strength steels. Due to a lack of investigations, there are no re-pair concepts and information in standards and guidelines, particularly for high-strength thick plate joints made of high-strength offshore steels. However, these are urgently needed to enable processors, especially SMEs, to carry out safe and eco-nomical repairs. Therefore, BAM started the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal with controlled high-performance GMAW processes and optimized narrower gouging grooves. The experimental analyses consider the complex interaction of material, process, and design-related influences on the formation of weld-related stresses and the special microstructure of high-strength fine-grain structural steels. Welding-related material degradation and crack-critical residual tensile stresses need to be avoided to ensure high component safety and performance. With component-related welding experiments on special testing equipment, adapted process and heat control concepts along with variable groove configurations will be developed and recommendations for guidelines elabo-rated. This is the prerequisite for fully utilizing the strength potential of high-strength steels and making a valuable contribution to the energy transition in Germany, espe-cially for steel-processing SMEs. T2 - Symposium Materialtechnik TU Clausthal CY - Clausthal-Zellerfeld, Germany DA - 19.02.2025 KW - Reparaturschweißen KW - Thermisches Ausfugen KW - Offshore KW - Sprühlichtbogen KW - Eigenspannungen PY - 2025 AN - OPUS4-62630 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Dittmann, Florian A1 - Varfolomeev, Igor T1 - Effect of weld design on fatigue strength of welded components using LTT filler materials N2 - Low transformation temperature (LTT) filler metals are an innovative approach to reduce tensile residual stress in weld seams and the surrounding heat affected zone (HAZ). The reduced tensile stress leads to an improvement in the fatigue strength of welded components. LTT filler metals are characterized by a reduced martensite start temperature (Ms), which is close to room temperature because of their chemical composition. This paper focuses on the hybrid use of LTT filler metals, where the LTT filler is applied as an additional layer to conventional welds on fatigue-critical spots. Conventional gas metal arc welded longitudinal stiffeners are used as specimens and at the face ends of the stiffeners, a second LTT layer was added with various weld modifications. These modifications were achieved by changing the welding parameters such as welding speed and offset to the first layer. These samples were used to analyze shape, dilution and resulting Ms, residual stress and fatigue strength. The dilution and dilatometer verified Ms did not change significant, although the surface of the 2nd LTT weld seam was varying clear with each modification. However, the weld modification had a significant effect on the residual stress state and the fatigue strength. The X-ray determined residual stress in the HAZ became lower when the weld toe of the LTT layer was further away from the stiffener. The Fatigue strength is clearly dependent on the residual stress state. The lower the residual stress at weld toe, the higher the fatigue strength. All samples with LTT weld exhibit significantly higher fatigue strength values than conventionally single and double-layer welded samples. The results show that on the one hand LTT filler metals increase the fatigue strength, and on the other hand the impact of LTT fillers materials is not restricted to the dilution and Ms, the shape of the weld seam must also be considered. T2 - IIW Intermediate Meeting CII CY - Trollhättan, Sweden DA - 10.03.2025 KW - LTT (Low Transformation Temperature) KW - Residual stress reduction KW - Fatigue strength KW - High-strength steels KW - Welding PY - 2025 AN - OPUS4-62708 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin A1 - Kromm, Arne A1 - Michael, Thomas A1 - Schroepfer, Dirk A1 - Kannengiesser, Thomas T1 - Modern welding processes for optimizing repair welding on high-strength offshore steels N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future, for which high-strength steels with a yield strength of up to 500 MPa and wall thicknesses up to 150 mm are increasingly being used. The repair of weld seams when detecting defects during NDT requires localized gouging and rewelding. This involves high demands on welding manufacturing, especially for highstrength steels. Due to a lack of investigations, there are no repair concepts and information in standards and guidelines, particularly for high-strength thick plate joints made of high-strength offshore steels. However, these are urgently needed to enable processors, especially SMEs, to carry out safe and economical repairs. Therefore, BAM startedthe FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair(local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal with controlled high-performance GMAW processes and optimized narrower gouging grooves. The experimental analyses consider the complex interaction of material, process, and designrelated influences on the formation of weld-related stresses and the special microstructure of high-strength fine-grain structural steels. Welding-related material Degradation and crack-critical residual tensile stresses need to be avoided to ensure high component safety and performance. With component-related welding experiments on special testing equipment, adapted process and heat control concepts along with variable groove configurations will be developed and recommendations for guidelines elaborated. This is the prerequisite for fully utilizing the strength potential of high-strength steels and making a valuable contribution to the energy transition in Germany, especially for steelprocessing SMEs. T2 - 6. Symposium Materialtechnik CY - Clausthal-Zellerfeld, Germany DA - 20.02.2025 KW - Narrow groove KW - Optimized repair welding KW - Modern welding processes KW - High-strength steel PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-636520 DO - https://doi.org/10.21268/20250507-5 SP - 3 EP - 15 AN - OPUS4-63652 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Liepold, Philipp A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Semantic Segmentation for Hot Cracking N2 - The images in this dataset are light microscope images of the surfaces of modified Varestraint-Transvarestraint test samples. The training images show the surface of a tungsten inert gas weld with possible hot cracks. The dataset is intended for use in training crack segmentation networks. This database consists of images in .png format. The training images were taken in 24-bit, 3-color channels with an optical light microscope (Keyence). The corresponding mask images are 8-bit grayscale images, where 255-valued pixels (white) denote crack areas and 0-valued pixels (black) denote non-cracked areas. This dataset was created manually with the help of a self-written segmentation program based on OpenCV. I used it to train networks based on ViT, ConvNeXt, U-Net, and EfficientNet architectures. The images were taken at magnifications of 50x and 100x. The dataset is structured as follows: Wire → Magnification (50, 100) → Data (train, mask = label) → Numbered images (1, 2, 3, …) (There may be missing numbers. The reasons are: 1) I did not take images of all surfaces if they were not cracked, and 2) the 100x magnification images were taken at a later point, by which time some samples had already been prepared for further evaluation, so no images could be taken.) For every image number in train, there is an equivalent number in mask with the same image size (but a different channel size, since train is 3-channel color and mask is single-channel). There is no fixed image size (h × w). If you want to train a network, I recommend either rescaling or taking sub-images for both the training and mask sets, or using architectures that can handle varying input sizes. The research project " Evaluation of design-induced solidification cracks during welding of high-strength fine-grained structural steels" is funded by the Federal Ministry of Economics and Climate Protection as part of the "Industrial Collective Research" programme on the basis of a resolution of the German Bundestag. This project IGF 01IF21837N FE 1 / P 1516 from the Research Association for steel Application (FOSTA), Düsseldorf, is carried out at Bundesanstalt für Materialforschung und -prüfung. KW - CNN KW - Segmentation KW - Hot cracking KW - AI PY - 2025 DO - https://doi.org/10.5281/zenodo.16919144 PB - Zenodo CY - Geneva AN - OPUS4-64031 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 - JOUR A1 - Liepold, Philipp A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Investigation of restraint intensity influence on solidification cracking of high-strength filler materials in fillet welds via CTS testing N2 - In addition to chemical composition, metallurgy, and welding parameters, the intensity of restraint is one of the key variables influencing solidification cracking (SC). Due to their high strength-to-density ratio, many modern lightweight steel constructions increasingly rely on high-strength steel. Given the theoretical framework of solidification cracking theory, tests tend to focus on the effects of strain rate. Externally restrained tests have provided valuable insights into solidification crack susceptibility. In practice, most welded structures are self-restrained; therefore, self-restraint tests more accurately reflect real-world applications. By varying the plate thickness in controlled thermal severity (CTS) tests conducted on S1100 QL, it was possible to adjust the intensity of restraint on fillet welds at a high level. Testing was performed using four different filler wires for gas metal arc welding (GMAW), including three solid wires and one metal-cored wire. Additionally, two sets of welding parameters were evaluated. High arc energy (U × I/welding speed) and increased welding speed were found to be more prone to solidification cracking compared to the parameter set with lower arc energy and welding speed. The results indicate a correlation between increasing restraint severity and a higher incidence of solidification cracking. KW - CTS KW - Controlled thermal severity KW - High-strength steel KW - GMAW KW - Restraint PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-631315 UR - 1878-6669 DO - https://doi.org/10.1007/s40194-025-02046-x SP - 1 EP - 13 PB - Springer AN - OPUS4-63131 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Dittmann, Florian A1 - Kromm, Arne A1 - Varfolomeev, Igor A1 - Kannengießer, Thomas T1 - Residual stress reduction using a low transformation temperature welding consumable with focus on the weld geometry N2 - Low transformation temperature (LTT) welding consumables represent an innovative approach to realize compressive residual stress in the weld seam and HAZ. LTT welding consumables use the volume-expanding martensitic phase transformation near room temperature to generate compressive residual stress during cooling. This article focuses on the weld geometry and its influence on residual stress reduction using an LTT welding consumable. For this purpose, layers with an LTT welding consumable were additionally applied to the front sides of conventionally welded longitudinal stiffeners. Different weld geometries of the second weld seam could be realized by varying the welding parameters. These samples were analyzed for geometric parameters, chemical composition, and residual stress. While the chemical composition and martensite start temperature (MS) were only slightly influenced by parameter changes, a clear influence with regard to residual stress and weld geometry was observed. Depending on the shape of the second LTT weld seam, residual stress reductions of 200 to 500 MPa were achieved using the same LTT welding consumable. T2 - IIW Annual Assembly and International Conference CY - Rhodes Island, Dodecanisa, Greece DA - 07.07.2024 KW - Low transformation temperature (LTT) KW - Martensite start temperature KW - Dilution KW - Weld geometry KW - Residual stress PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-633707 DO - https://doi.org/10.1007/s40194-025-02094-3 SN - 1878-6669 SP - 1 EP - 11 PB - Springer Nature CY - Berlin ; Heidelberg AN - OPUS4-63370 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröder, Nina A1 - Kromm, Arne A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Innovatives Instandsetzungsschweißen von Altstahl: Materialverhalten und Herausforderungen N2 - Aus Gründen der Nachhaltigkeit und Wirtschaftlichkeit gibt es in der stahlverarbeiten-den Industrie einen Trend zum Bauen im Bestand, um kostenintensive Sperrungen oder Rückbau zu vermeiden. Schweißen wird dabei als wirtschaftliches Fügeverfahren im Zusammenhang mit Altstählen kaum genutzt, obwohl Nieten- und Schraubenverbindungen oft unwirtschaftlich sind. Für die Instandsetzung ist häufig beschädigtes Bestands-material durch neue Stähle zu ersetzen bzw. Alt-Neu-Stahl-Mischverbindungen herzu-stellen. Aufgrund der verschiedenen Herstellungsprozesse von Altstählen ist nicht jeder Stahl aus dem 20. Jahrhundert schweißgeeignet. Daher ist zunächst eine Schweißeignungsprüfung erforderlich. In den vorliegenden Untersuchungen wurden verschiedene Altstähle hinsichtlich ihres Schweißverhaltens mittels Dilatometrie analysiert. Ziel war es, eine Datenbasis aus Schweiß-Zustands-Zeit-Diagrammen und Simulationen der Wärmeeinflusszone zu erstellen, um praxisrelevante Schweißuntersuchungen ableiten zu können. Diese geben wesentlichen Aufschluss hinsichtlich ihres schweißmetallurgischen Verhaltens und ihrer Schweißeignung. Solche Grundlagen sind zur Entwicklung innovativer schweißtechnischer Konzepte zur beanspruchungsgerechten Instandsetzung bestehender Altstahl-Infrastruktur in Deutschland notwendig. T2 - 6. Symposium Materialtechnik, 20. bis 21. Februar 2025 CY - Clausthal-Zellerfeld, Germany DA - 20.02.2025 KW - Altstahl KW - Schweiß-ZTU Diagramme KW - Instandsetzungsschweißen KW - Schweißeignungsprüfung KW - Dilatometrie PY - 2025 SN - 978-3-8440-9961-4 DO - https://doi.org/10.21268/20250505-1 VL - 15 SP - 370 EP - 380 PB - Shaker Verlag GmbH CY - Düren AN - OPUS4-63377 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin A1 - Kromm, Arne A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Moderne Schweißverfahren zur Optimierung der Reparatur von hochfesten Offshore-Stählen N2 - Der Ausbau der Offshore-Windenergie mit Anlagenleistungen von über 10 MW er-fordert zunehmend den Einsatz hochfester Stähle mit Streckgrenzen ab 460 MPa bei Wanddicken von bis zu 150 mm. Inakzeptable Defekte, die während bzw. nach der schweißtechnischen Montage solcher dickwandigen Verbindungen im Nahtbereich detektiert werden, können wirtschaftlich durch lokales Ausfugen und anschließendes Schweißen noch in der Fertigung repariert werden. Insbesondere bei hochfesten Baustählen stellt dies hohe Anforderungen an die schweißtechnische Fertigung, da bislang keine standardisierten Reparaturkonzepte oder normativen Vorgaben existie-ren. Praxisnahe Empfehlungen sind hier vor allem für kleine und mittlere Unterneh-men (KMU) notwendig, damit diese Reparaturschweißungen sicher und wirtschaft-lich durchführen können. Die laufende Untersuchung (FOSTA P1629/IGF 01IF22746N) legt daher den Schwerpunkt auf die Optimierung der Reparaturverfahren mit dem Ziel, schweißbe-dingte Beanspruchungen zu reduzieren, weil diese häufig zu erneuten Bildung Fehl-stellen führen. Hierfür werden hochfeste, dickwandige Verbindungen aus Offshore-Stahlgüten im Streckgrenzenbereich von 355 MPa bis 460 MPa untersucht. Die ex-perimentellen Analysen berücksichtigen dabei die komplexen Wechselwirkungen zwischen werkstoff- und prozess- sowie konstruktionsbedingten Einflüssen auf den Beanspruchungszustand nach dem Schweißzyklus (Verbindungsschweißen, Ausfu-gen, Reparaturschweißen). Diese Faktoren, wie z. B. die Steifigkeitsverhältnisse der Schweißnaht, sind von entscheidender Bedeutung für die resultierenden Eigenspan-nungen, die sich infolge der schweißtechnischen Reparatur ausbildet. Um die Bau-teilsicherheit und Leistungsfähigkeit zu gewährleisten, sind insbesondere risskriti-sche, mehrachsige Eigenspannungszustände zu vermeiden. So lassen sich moderne Hochleistungs-MAG-Schweißprozesse mit hierfür optimierten, schmaleren Fugen-geometrien in bauteilbezogenen Schweißversuchen auf Großprüfanlagen untersu-chen, um hierfür angepasste Prozess- und Wärmeführungsparameter zu identifizie-ren und angepasste Reparaturkonzepte abzuleiten. Ziel ist es, Handlungsempfehlun-gen für Richtlinien und Normen zu erarbeiten, die das Potenzial hochfester Stähle voll ausschöpfen und die Anwendbarkeit im Offshore-Stahlbau, insbesondere für KMU, substanziell stärken. Auf diese Weise leistet das Projekt einen entscheiden-den Beitrag zur erfolgreichen Umsetzung der Energiewende in Deutschland. T2 - NA 092-00-05 GA "Gemeinschaftsarbeitsausschuss NAS/NMP, Zerstörende Prüfung von Schweißverbindungen (DVS AG Q 4/Q 4.1)" CY - Online meeting DA - 20.03.2025 KW - Reparaturschweißen KW - Thermisches Ausfugen KW - Offshore KW - Moderne Schweißprozesse PY - 2025 AN - OPUS4-62749 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin A1 - Schroepfer, Dirk A1 - Kromm, Arne A1 - Kannengiesser, Thomas T1 - Stress-Optimised Welding Repair for High-Strength Offshore Steel Joints N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future. To achieve these high outputs, turbines far from the coast are required, featuring large subsea jacket structures (30 m up to 50 m) and tall towers (up to 200 m). High-strength steels with a yield strengths up to 500 MPa and wall thicknesses of up to 120 mm are increasingly being used for these structures. During manufacture, weld defects detected by non-destructive testing (NDT) require localized repair (gouging and rewelding). To date, there is a lack of repair concepts and information in standards and guidelines. Therefore, BAM initiated the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal. This research aims to develop a stress-optimized repair concept for thick plate joints, using controlled high-performance GMAW processes and optimized, narrow gouging grooves. Thermal and mechanical gouging are performed, allowing the groove configuration to be modified. Modern welding processes provide deep root penetration and focused energy input capable of welding narrow seams. The aimed residual stress reduction can be attributed to the lower input of weld metal due to the changes in groove configuration and to the reduction in heat input per layer due to the controlled arc process. The experimental analyses take into account the interaction of process, material, and design-related influences on the formation of weld induced stresses. Concluding with recommendations for guidelines elaborated for steel-processing SMEs. T2 - MPA Stuttgart 2025 CY - Stuttgart, Germany DA - 06.10.2025 KW - Repair welding KW - Residual stress KW - High-strength steels KW - Gouging KW - Modern welding processes PY - 2025 AN - OPUS4-64347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Nina A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Kadoke, Daniel A1 - Kruse, Julius T1 - Effect of Ti microalloying on the local strain behavior of cross-weld tensile samples determined by digital image correlation N2 - High-strength low-alloyed (HSLA) steels with yield strength / proof stress ≥ 600 MPa are the basis of modern light-weight steel constructions. Indeed, the economic and ecological benefits strongly depend on their processability in terms of welding. In this context, the use of highly productive welding processes and suitable welding consumables is of vital interest and requires a fundamental understanding of the microstructural changes in the HSLA steel and especially the heat-affected zone (HAZ) of the welded joint. Microalloying elements, such as Ti or Nb, are essential to achieve the desired mechanical properties. To analyse the weldability, three-layer welds were performed using gas metal arc welding (GMAW) and critical microstructures, such as areas of the HAZ that exhibit significant softening or hardening, were identified. The effect of the softened HAZ region on failure was evaluated using cross-weld tensile specimens. Digital image correlation (DIC) was used for in-situ monitoring of the development and accumulation of the local strains in different HAZ regions during tensile testing. Using a specially designed mirror system, the local strains of the microstructure zones on the top and bottom of the weld were recorded simultaneously. In addition, the analysis of the local deformation helps to understand the effects of the softened HAZ on the global strain, the reduction in area, the fracture position, and the overall fracture behavior. KW - High-strength structural steel KW - Microalloying influences KW - HAZ-softening KW - Digital Image Correlation KW - Constraint effect KW - Thermodynamic simulation PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-643558 DO - https://doi.org/10.1007/s40194-025-02185-1 SP - 1 EP - 17 PB - Springer Nature AN - OPUS4-64355 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Uhlig, Marvin A1 - Schröder, Nina A1 - Höfer, Kevin A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Hensel, Jonas T1 - Schweißverfahrensqualifikation an Stumpfnahtverbindungen aus Altstahl- und Feinkornbaustahl N2 - Der Erhalt und die Ertüchtigung bestehender Stahltragwerke gewinnen im Bauwesen zunehmend an Bedeutung. Besonders betroffen sind Konstruktionen aus sogenannten Flussstählen, die im Zeitraum zwischen etwa 1880 und 1940, noch vor Einführung der ersten Stahlnorm DIN 488-1, in großem Umfang im Brücken-, Wasserbau- und Hochspannungsanlagenbau verwendet wurden. Diese Stähle wurden in historischen erstellungsverfahren wie dem Thomas-, Bessemer- oder Siemens-Martin-Verfahren erzeugt und weisen im Vergleich zu heutigen Baustählen eine deutlich größere Streuung in ihren chemischen und mechanischen Eigenschaften auf. Trotz ihres hohen Alters sind viele dieser Tragwerke nach wie vor im Betrieb und befinden sich am Rande ihrer statischen und funktionalen Anforderungen. Ihr Rückbau und Ersatz durch Neubauten sind jedoch oftmals mit erheblichem wirtschaftlichem, logistischem und ökologischem Aufwand verbunden. Daher rückt die Instandhaltung und Weiterverwendung solcher Altbauwerke verstärkt in den Fokus von Infrastrukturprogrammen, Sanierungsstrategien und besitzt eine große kulturelle Bedeutung. Im Rahmen der vorliegenden Untersuchung soll das Potenzial des MAG-Schweißens mit G 18 8 Mn Zusatzwerkstoff für Stumpfnahtverbindungen aus Flussstahl und Feinkornbaustahl qualifiziert werden. Ziel ist es, durch experimentelle und werkstofftechnische Analysen weitere Erkenntnisse über die Schweißbarkeit historischer Stähle zu gewinnen, Anwendungsempfehlungen für die Praxis abzuleiten und damit einen Beitrag zur sicheren und wirtschaftlichen Sanierung historischer Infrastrukturbauwerke zu leisten. T2 - DVS Congress 2025 CY - Essen, Germany DA - 16.09.2025 KW - Altstahl KW - MAG-Schweißen KW - Seigerungen KW - Instandsetzung KW - Feinkornbaustahl PY - 2025 SN - 978-3-96144-298-0 VL - 401 SP - 1 EP - 17 AN - OPUS4-64278 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - From the field to the lab and back: Evaluating the integrity of welded components using scaled experiments N2 - This contribution addresses the question of how the behaviour of complex parts or components in industrial practice can be simulated using simple welding experiments in the laboratory. It is demonstrated how so-called mock-ups can be utilised for this purpose. In particular, a test rig specially designed for scaled welding experiments is shown. It allows mechanical restraints and stiffnesses to be simulated, as well as typical welding process parameters and post weld heat treatments. Selected examples show how solidification crack growth during welding of high-strength steels can be quantified, under which conditions stress relaxation cracks occur during the heat treatment of heat-resistant steels, and how the integrity of pressurised hydrogen pipelines can be assessed during repair welding. T2 - 4th International Conference on Advanced Joining Processes 2025 CY - Coimbra, Portugal DA - 16.10.2025 KW - High strength steel KW - Stress relief cracking KW - Hydrogen PY - 2025 AN - OPUS4-64505 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin A1 - Schroepfer, Dirk A1 - Kromm, Arne A1 - Kannengiesser, Thomas T1 - Reduction of residual stress by narrowing the repair groove: Optimising repair welding with modern welding processes for high strength offshore steels N2 - The ongoing German energy transition will require offshore wind turbines with outputs of >10 MW in the future. Turbines with these high outputs must be located far from the coast, with up to 50 m large subsea jacket structures and tall towers. These structures are increasingly fabricated of high-strength steels with a yield strength up to 500 MPa and wall thicknesses of up to 120 mm. During production, weld defects identified through non-destructive testing (NDT) must be locally repaired by gouging and rewelding. Standards and guidelines lack sufficient concepts and information regarding such repair procedures. To address this gap, BAM launched the FOSTA project P1629 (IGF 01IF22746N) to explore stress-optimised repair concepts, specifically local gouging and welding, for high-strength thick plate joints made from offshore-grade steels with yield strengths between 355 MPa and 460 MPa, including matching weld metals. This research aims to develop a stress-optimised repair concept for thick plate joints, utilising controlled high-performance GMAW techniques and narrow gouging grooves. Both thermal and mechanical gouging methods are applied, enabling adjustments to the groove geometry. Modern welding processes offer deep root penetration and concentrated energy input, making them suitable for narrow seams. The intended reduction in residual stress results from the decreased weld metal volume, due to modified groove shapes and the lower heat input per layer achieved through controlled arc processes. Experimental investigations examine how process parameters, material properties, and design factors interact to influence the development of welding-induced stresses. The project concludes with practical recommendations for guidelines tailored to steel-processing SMEs. T2 - 4th International Conference on Advanced Joining Processes (AJP 2025) CY - Coimbra, Portugal DA - 16.10.2025 KW - Repair welding KW - Residual stress KW - Modern welding processes KW - High-strength offshore steel KW - Narrow groove PY - 2025 AN - OPUS4-64887 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Dittmann, Florian A1 - Kromm, Arne A1 - Varfolomeev, Igor A1 - Kannengiesser, Thomas T1 - Improvement of Fatigue Resistance through the Application of a Low-Transformation-Temperature Welding Consumable N2 - Low transformation temperature (LTT) welding consumables are an innovative approach to reduce tensile residual stress in weld seams and the surrounding heat affected zone (HAZ). The reduced tensile stress can lead to an improvement in fatigue strength of welded components. LTT alloys are characterized by a chemical composition which reduce the martensite start temperature (Ms) close to room temperature. This article focuses on a hybrid use of LTT filler metals, where the LTT filler is applied as an additional layer to conventional welds on fatigue-critical spots. Conventional gas metal arc welded longitudinal stiffeners are used as specimens. At the face ends of the stiffeners, a second LTT layer was added with various modifications in weld shapes. These different shapes were achieved by changing the welding parameters such as welding speed and offset to the first layer. These samples were used to analyze shape, dilution, resulting Ms, residual stress and fatigue strength. The dilatometer verified Ms and dilution did not change significant, although the area of the 2nd LTT weld seam was varying clear with each modification. However, the weld modification had a significant effect on the residual stress state and the fatigue strength. The X-ray determined residual stress in the HAZ became lower when the weld toe of the LTT layer was further away from the stiffener. All samples with LTT weld exhibit significantly higher fatigue strength values than conventionally single and double-layer welded samples. The lower the residual stress at weld toe, the higher the fatigue strength. The results show that on the one hand LTT filler metals increase the fatigue strength, and on the other hand the impact of LTT fillers materials is not restricted to the dilution and Ms, the shape of the weld seam must also be considered. T2 - 4th international Conference on Advanced Joining Processes AJP CY - Combria, Portugal DA - 16.10.2025 KW - Low transformation temperature (LTT) KW - Residual stress reduction KW - Fatigue strength KW - Longitudenal stiffener PY - 2025 AN - OPUS4-65090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Werkstoffsichere Dickblechschweißung und KI N2 - Der Vortrag zeigt, welche Herausforderungen beim Schweißen sogenannter Dickblechverbindungen bestehen und welche Strategien zur Lösung genutzt werden können. Ansätze zur Fehlerprävention werden vorgestellt. Es wird dargestellt, wie KI-basierte Methoden die Fehlererkennung erleichtern. Letztlich werden Potentiale zur effizienten Fehlerbeseitigung aufgezeigt und der Anwendernutzen herausgestellt. T2 - Mitgliederversammlung der Forschungsvereinigung Stahlanwendung e. V. CY - Essen, Germany DA - 17.12.2025 KW - UP-Schweißen KW - Eigenspannungen KW - Künstliche Intelligenz KW - Reparatur PY - 2025 AN - OPUS4-65210 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -