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 - JOUR A1 - Rhode, Michael A1 - Steppan, Enrico A1 - Kannengießer, Thomas A1 - Steger, Jörg ED - Lippold, J. T1 - Effect of hydrogen on mechanical properties of heat affected zone of a reactor pressure vessel steel grade N2 - The steel grade 20MnMoNi5-5 (according to German DIN standard or 16MND5 according to French AFNOR standard) is widely applied in (weld) fabrication of reactor pressure vessel components. Thus, a wide range of welding technologies (like submerged arc welding (SAW) or tungsten inert gas (TIG)) is used resulting in different heat affected zone (HAZ) microstructures. During weld fabrication, the weld joints may take up hydrogen. Especially, the HAZ shows an increased susceptibility for a degradation of the mechanical properties in presence of hydrogen. In addition, the hydrogen-assisted degradation of mechanical properties is influenced by three main local factors: hydrogen concentration, microstructure, and load condition. Hence, the base material (BM) and two different simulated non-tempered as-quenched HAZ microstructures were examined using hydrogen-free and hydrogen-charged tensile specimens. The results indicate that the effect of hydrogen on the degradation is significantly increased in case of the HAZ compared to the BM. In addition, hydrogen has remarkable effect in terms of reduction of ductility. It was ascertained that the degradation of the mechanical properties increases in the order of BM, bainitic HAZ, and the martensitic HAZ. Scanning electron microscope (SEM) investigation showed a distinct change of the fracture topography depended on the microstructure with increasing hydrogen concentration in case of the as-quenched HAZ microstructures. KW - Mechanical properties KW - Pressure vessel steels KW - Heat affected zone KW - Hydrogen KW - Hydrogen embrittlement KW - Low alloy steels PY - 2016 UR - http://link.springer.com/article/10.1007/s40194-016-0325-9 U6 - https://doi.org/10.1007/s40194-016-0325-9 VL - 60 IS - 4 SP - 623 EP - 638 PB - Springer-Verlag GmbH CY - Heidelberg, Germany AN - OPUS4-36454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schaupp, Thomas A1 - Rhode, Michael A1 - Kannengießer, Thomas ED - Lippold, J. ED - Boellinghaus, Thomas ED - Richardson, I. T1 - Influence of welding parameters on diffusible hydrogen content in high-strength steel welds using modified spray arc process N2 - In order to satisfy the growing requirements towards lightweight design and resource efficiency in modern steel constructions, e.g., mobile cranes and bridges, high-strength steels with typical yield strength ≥ 690 MPa are coming into use to an increasing extent. However, these steels require special treatment in welding. The susceptibility for degradation of the mechanical properties in the presence of hydrogen increases significantly with increasing yield strength. In case of missing knowledge about how and the amount of hydrogen that is uptaken during welding, hydrogen-assisted cracking (HAC) can be a negative consequence. Moreover, modern weld technology like the modified spray arc process enables welding of narrower weld seams. In this context, a reduced number of weld beads, volume, and total heat input are technical and economical benefits. This work presents the influence of welding parameters on the diffusible hydrogen content in both (1) single-pass and (2) multi-layer welds. Different hydrogen concentrations were detected by varied contact tube distance, wire feed speed, arc length, and varied arc type (transitional arc and modified spray arc). The results show that all welding parameters have significant influence on the diffusible hydrogen concentration in the single-pass welds. By increasing the number of weld beads in case of multi-layer welding, the hydrogen concentration has been reduced. Whereby, differences in hydrogen concentrations between both arc types are present. KW - Hydrogen KW - MAG welding KW - High-strength steels KW - Process parameters PY - 2018 U6 - https://doi.org/10.1007/s40194-017-0535-9 SN - 0043-2288 SN - 1878-6669 VL - 62 IS - 1 SP - 9 EP - 18 PB - Springer CY - Berlin Heidelberg AN - OPUS4-43864 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Schaupp, Thomas A1 - Münster, C. A1 - Mente, Tobias A1 - Kannengießer, Thomas A1 - Böllinghaus, Thomas T1 - Hydrogen determination in welded specimens by carrier gas hot extraction - a review on the main parameters and their effects on hydrogen measurement N2 - Carrier gas hot extraction (CGHE) is a commonly applied technique for determination of hydrogen in weld joints using a thermal conductivity detector (TCD) for hydrogen measurement. The CGHE is based on the accelerated hydrogen effusion due to thermal activation at elevated temperatures. The ISO 3690 standard suggests different specimen geometries as well as necessary minimum extraction time vs. temperature. They have the biggest influence on precise hydrogen determination. The present study summarizes the results and experience of numerous test runs with different specimen temperatures, geometries (ISO 3690 type B and small cylindrical samples), and factors that additionally influence hydrogen determination. They are namely specimen surface (polished/as-welded), limited TCD sensitivity vs. specimen volume, temperature measurement vs. effects of PI-furnace controller, as well as errors due to insufficient data assessment. Summarized, the temperature is the driving force of the CGHE. Two different methods are suggested to increase the heating rate up to the desired extraction temperature without changing the experimental equipment. Suggestions are made to improve the reliability of hydrogen determination depended on the hydrogen signal stability during extraction accompanied by Evaluation of the recorded data. Generally, independent temperature measurement with dummy specimens is useful for further data analysis, especially if this data is used for calculation of trapping kinetics by thermal desorption analysis (TDA). KW - Hydrogen KW - Carrier gas hot extraction KW - Experimental design KW - Thermal conductivity device PY - 2019 U6 - https://doi.org/10.1007/s40194-018-0664-9 SN - 0043-2288 VL - 63 IS - 2 SP - 511 EP - 526 PB - Springer CY - Berlin, Heidelberg AN - OPUS4-47603 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schaupp, Thomas A1 - Rhode, Michael A1 - Yahyaoui, Hamza A1 - Kannengießer, Thomas ED - Lippold, J. ED - Boellinghaus, Thomas ED - Richardson, I. 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 the presence of diffusible hydrogen, i.e., hydrogen-assisted cracking (HAC), generally increases. HAC is a result of the critical interaction between local microstructure, mechanical load, and hydrogen concentration. In existing standards for welding of HSLA-steels, recommendations including working temperatures and dehydrogenation heat treatment (DHT) are given to Limit the amount of introduced hydrogen during welding. These recommendations are based on investigations into 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, economic benefits. In the present study, the hydrogen distribution in S960QL multi-layer welds with thickness of 20 mm was analyzed. The influence of different weld seam opening angles, heat input, working temperature and DHT were investigated. The results show that weldments with narrow grooves contained an increased amount of diffusible hydrogen. Hydrogen concentration has been reduced by decreasing both the heat input and working temperature. Hydrogen-free weldments were only achieved via subsequent DHT after welding. Furthermore, hydrogen distribution was experimentally determined across the weld seam thickness in HSLA gas metal arc welded multi-layer welds for the first time. KW - Hydrogen KW - GMAW KW - High-strength steels KW - Heat control KW - Heat treatment PY - 2019 U6 - https://doi.org/10.1007/s40194-018-00682-0 SN - 0043-2288 SN - 1878-6669 VL - 63 IS - 3 SP - 607 EP - 616 PB - Springer CY - Berlin Heidelberg AN - OPUS4-47878 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 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-591981 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 -