TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of the gap bridgeability at high-power laser hybrid welding of plasma-cut thick mild steels with AC magnetic support N2 - One of the challenges of the high-power hybrid laser welding of thick steels is the sensitivity of the process of the process to manufacturing tolerances. This usually leads to a time-consuming preparation of the welding edges, such as milling. The study deals with the influence of the edge quality of milled and plasma-cut steel made of S355J2 with a wall thickness of 20 mm on the laser hybrid welded seam quality. Furthermore, the gap bridgeability and the tolerances towards edge misalignment was investigated. An AC magnet was used as backing support to prevent sagging and positioned under the workpiece, to generate an upwards directed electromagnetic pressure. The profiles of the edges and the gap on the top and root side were measured using a digital camera. Single-pass laser hybrid welds of plasma-cut edges could be welded using a laser beam power of just 13.7 kW. A gap bridgeability up to 2 mm and misalignment of edges up to 2 mm could be achieved successful. Additionally, the independence of the cutting side and the welding side was shown, so that samples were welded to the opposite side to their cutting. For evaluation of internal defects or irregularities, X-ray images were carried out. Charpy impact strength tests were performed to determine the toughness of the welds. T2 - X International Conference «Beam Technologies & Laser Application» KW - Laser hybrid welding KW - Magnetic bath support KW - Plasma-cut samples KW - Thick plate welding PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-539248 DO - https://doi.org/10.1088/1742-6596/2077/1/012007 VL - 2077 IS - 012007 SP - 1 EP - 8 PB - IOP Publishing AN - OPUS4-53924 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - El-Batahgy, A. A1 - Elkousy, M. A1 - Al-Rahman, A. A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael A1 - Gook, S. T1 - Retaining Mechanical Properties of GMA-Welded Joints of 9%Ni Steel Using Experimentally Produced Matching Ferritic Filler Metal N2 - Motivated by the loss of tensile strength in 9%Ni steel arc-welded joints performed using commercially available Ni-based austenitic filler metals, the viability of retaining tensile strength using an experimentally produced matching ferritic filler metal was confirmed. Compared to the austenitic Ni-based filler metal (685 MPa), higher tensile strength in gas metal arc (GMA) welded joints was achieved using a ferritic filler metal (749 MPa) due to its microstructure being similar to the base metal (645 MPa). The microstructure of hard martensite resulted in an impact energy of 71 J (-196 °C), which was two times higher than the specified minimum value of _>34 J. The tensile and impact strength of the welded joint is affected not only by its microstructure, but also by the degree of its mechanical mismatch depending on the type of filler metal. Welds with a harder microstructure and less mechanical mismatch are important for achieving an adequate combination of tensile strength and notched impact strength. This is achievable with the cost-effective ferritic filler metal. A more desirable combination of mechanical properties is guaranteed by applying low preheating temperature (200 °C), which is a more practicable and economical solution compared to the high post-weld heat treatment (PWHT) temperature (580 °C) suggested by other research. KW - 9%Ni steel KW - Ni-based austenitic filler metal KW - Mechanical mismatching KW - Microstructure KW - Post-weld heat treatment KW - Preheating KW - Matching ferritic filler metal PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-564610 DO - https://doi.org/10.3390/ma15238538 SN - 1996-1944 VL - 15 IS - 23 SP - 1 EP - 14 PB - MDPI AN - OPUS4-56461 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Üstündag, Ömer A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Influence of the weld pool geometry on solidification cracking in partial penetration high power laser beam welding N2 - Solidification cracking is still a serious problem in laser beam welding, especially in the welding of thick-walled plates. The influence of weld pool geometry on solidification cracking in partial penetration welding of thick plates is investigated within scope of this study. Therefore, a specific experimental setup of steel and quartz glass in butt configuration and on the side with high-speed camera were used to record the weld pool shape. In addition, the influence of laser inclination angle on the weld pool geometry and on solidification crack formation was investigated. The results show a bulge in the weld pool root, which is separated from an upper region by a necking region. This leads to a case where there are three different longitudinal region lengths with different solidification zones. This temporal sequence of solidification strongly promotes the formation of solidification cracks in the weld root. T2 - 12th CIRP Conference on photonic technologies (LANE 2022) CY - Fürth, Germany DA - 04.09.2022 KW - Laser beam welding KW - Partial penetration KW - Weld pool shape PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563940 DO - https://doi.org/10.1016/j.procir.2022.08.174 VL - 111 SP - 397 EP - 400 PB - Elsevier B.V. AN - OPUS4-56394 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Üstündag, Ömer A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Improvement of Charpy impact toughness by using an AC magnet backing system for laser hybrid welding of thick S690QL steels N2 - The study deals with the influence of the heat input and the resulting cooling times on the microstructure and Charpy impact toughness of single-pass laser hybrid welded 20-mm thick high-strength steel S690QL. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured in-situ using a pyrometer and an optical fibre in three different depths of the seam where Charpy impact test specimens were also later taken. Thereby, three different heat inputs from 1.3 kJ/mm to 2 kJ/mm were investigated. Despite the observed decreased values of both t8/5-cooling time and the Charpy impact toughness in the root part of the seam, the required impact toughness of 38 J/cm2 could be reached in dependance on applied heat input, especially at the heat input of 1.6 kJ/mm. T2 - 12th CIRP conference on photonic technologies [lane 2022] CY - Fürth, Germany DA - 04.09.2022 KW - Thick-plate welding KW - Laser hybrid welding KW - Electromagnetic backing KW - Charpy impact toughness KW - Thermal cycles PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563731 DO - https://doi.org/10.1016/j.procir.2022.08.067 VL - 111 SP - 462 EP - 465 PB - Elsevier B.V. AN - OPUS4-56373 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Raute, J. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Process Setup and Boundaries of Wire Electron Beam Additive Manufacturing of High-Strength Aluminum Bronze N2 - In recent years, in addition to the commonly known wire-based processes of Directed Energy Deposition using lasers, a process variant using the electron beam has also developed to industrial market maturity. The process variant offers particular potential for processing highly conductive, reflective or oxidation-prone materials. However, for industrial usage, there is a lack of comprehensive data on performance, limitations and possible applications. The present study bridges the gap using the example of the high-strength aluminum bronze CuAl8Ni6. Multi-stage test welds are used to determine the limitations of the process and to draw conclusions about the suitability of the parameters for additive manufacturing. For this purpose, optimal ranges for energy input, possible welding speeds and the scalability of the process were investigated. Finally, additive test specimens in the form of cylinders and walls are produced, and the hardness profile, microstructure and mechanical properties are investigated. It is found that the material CuAl8Ni6 can be well processed using wire electron beam additive manufacturing. The microstructure is similar to a cast structure, the hardness profile over the height of the specimens is constant, and the tensile strength and elongation at fracture values achieved the specification of the raw material. KW - Wire electron beam additive manufacturing KW - Aluminum bronze KW - Wire-based additive manufacturing KW - EBAM KW - DED-EB PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-580890 DO - https://doi.org/10.3390/met13081416 VL - 13 IS - 8 SP - 1 EP - 16 PB - MDPI AN - OPUS4-58089 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - El-Sari, B. A1 - Biegler, M. A1 - Rethmeier, Michael T1 - Investigation of the LME Susceptibility of Dual Phase Steel with Different Zinc Coatings N2 - The application of anti-corrosion coated, high-strength steels in the automotive industry has increased in recent years. In combination with various zinc-based surface coatings, liquid metal embrittlement cracking can be observed in some of these materials. A high-quality, crack-free spot-welded joint is essential to realize the lightweight potential of the materials. In this work, the LME susceptibility of different coatings, which will be determined by the crack length and the occurrence rate, will be investigated using a welding under external load setup. The uncoated specimens did not show any LME. EG, GI and GA showed significantly less LME than ZM coatings. The latter coatings showed much larger crack lengths than the EG, GI and GA coatings. Furthermore, two mechanisms regarding the LME occurrence rate were observed: the occurrence of LME in zinc–magnesium coatings was theorized to be driven by the material properties of the coatings, whereas the occurrence of LME at EG, GI and GA samples was forced mainly by the application of the external tensile load. In the experimental setup of this work, the materials were exposed to unusually high mechanical loads (up to 80% of their yield strength) to evoke LME cracks. KW - Widerstandspunktschweißen KW - Hochfester Stahl KW - Liquid Metal Embrittlement KW - Flüssigmetallinduzierte Rissbildung KW - Zink KW - AHSS PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-580428 DO - https://doi.org/10.3390/met13050890 VL - 13 IS - 5 SP - 1 EP - 11 PB - MDPI AN - OPUS4-58042 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Artinov, Antoni A1 - Karkhin, V. A1 - Meng, Xiangmeng A1 - Bachmann, Marcel A1 - Rethmeier, Michael T1 - A General Analytical Solution for Two-Dimensional Columnar Crystal Growth during Laser Beam Welding of Thin Steel Sheets N2 - A technique for calculating the main solidification parameters for a two-dimensional columnar crystal growth during complete penetration laser beam welding of thin steel sheets was developed. Given that the weld pool interface is described by Lamé curves (superellipses) within the horizontal plane of growth, general analytical solutions were derived for the geometry of the crystal axis and the corresponding growth rate and cross-sectional area of the crystal. A dimensionless analysis was performed to provide insights on the dependence of the solidification parameters on the shape and dimensions of the rear part of the weld pool boundary. The derived solutions were applied for the case of complete penetration laser beam keyhole welding of 2 mm thick 316L austenitic chromium-nickel steel sheets. It was shown that the reconstruction of the weld pool boundary with Lamé curves provides higher accuracy and flexibility compared to results obtained with elliptical functions. The validity of the proposed technique and the derived analytical solutions was backed up by a comparison of the obtained solutions to known analytical solutions and experimentally determined shapes and sizes of the crystals on the top surface of the sheet. The dimensions of the calculated crystal axis correlated well with the experimentally obtained results. KW - General analytical solutions KW - Two-dimensional solidification KW - Columnar crystal growth KW - Lamé curves KW - Laser beam welding PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-576788 DO - https://doi.org/10.3390/app13106249 IS - 10 SP - 1 EP - 10 ET - 13 AN - OPUS4-57678 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Prabitz, Konstantin Manuel A1 - Antretter, Thomas A1 - Rethmeier, Michael A1 - El-Sari, Bassel A1 - Schubert, Holger A1 - Hilpert, Benjamin A1 - Gruber, Martin A1 - Sierlinger, Robert A1 - Ecker, Werner T1 - Numerical and experimental assessment of liquid metal embrittlement in externally loaded spot welds N2 - Zinc-based surface coatings are widely applied with high-strength steels in automotive industry. Some of these base materials show an increased brittle cracking risk during loading. It is necessary to examine electrogalvanized and uncoated samples of a high strength steel susceptible to liquid metal embrittlement during spot welding with applied external load. Therefore, a newly developed tensile test method with a simultaneously applied spot weld is conducted. A fully coupled 3D electrical, thermal, metallurgical and mechanical finite element model depicting the resistant spot welding process combined with the tensile test conducted is mandatory to correct geometric influences of the sample geometry and provides insights into the sample’s time dependent local loading. With increasing external loads, the morphology of the brittle cracks formed is affected more than the crack depth. The validated finite element model applies newly developed damage indicators to predict and explain the liquid metal embrittlement cracking onset and development as well as even ductile failure. KW - Resistance spot welding KW - Finite element simulation KW - Advanced high-strength steel KW - Liquid metal embrittlement KW - Damage prediction KW - Tensile resistance spot welding experiment PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-594848 DO - https://doi.org/10.1007/s40194-024-01696-7 SN - 0043-2288 SP - 1 EP - 10 PB - Springer Science and Business Media LLC AN - OPUS4-59484 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strobl, Dominic A1 - Unger, Jörg F. A1 - Ghnatios, C. A1 - Klawoon, Alexander A1 - Pittner, Andreas A1 - Rethmeier, Michael A1 - Robens-Radermacher, Annika T1 - Efficient bead-on-plate weld model for parameter estimation towards effective wire arc additive manufacturing simulation N2 - Despite the advances in hardware and software techniques, standard numerical methods fail in providing real-time simulations, especially for complex processes such as additive manufacturing applications. A real-time simulation enables process control through the combination of process monitoring and automated feedback, which increases the flexibility and quality of a process. Typically, before producing a whole additive manufacturing structure, a simplified experiment in the form of a beadon-plate experiment is performed to get a first insight into the process and to set parameters suitably. In this work, a reduced order model for the transient thermal problem of the bead-on-plate weld simulation is developed, allowing an efficient model calibration and control of the process. The proposed approach applies the proper generalized decomposition (PGD) method, a popular model order reduction technique, to decrease the computational effort of each model evaluation required multiple times in parameter estimation, control, and optimization. The welding torch is modeled by a moving heat source, which leads to difficulties separating space and time, a key ingredient in PGD simulations. A novel approach for separating space and time is applied and extended to 3D problems allowing the derivation of an efficient separated representation of the temperature. The results are verified against a standard finite element model showing excellent agreement. The reduced order model is also leveraged in a Bayesian model parameter estimation setup, speeding up calibrations and ultimately leading to an optimized real-time simulation approach for welding experiment using synthetic as well as real measurement data. KW - Proper generalized decomposition KW - Model order reduction KW - Hardly separable problem KW - Additive manufacturing KW - Model calibration KW - Wire arc additive manufacturing PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-596502 DO - https://doi.org/10.1007/s40194-024-01700-0 SN - 0043-2288 SP - 1 EP - 18 PB - Springer AN - OPUS4-59650 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Vinzenz A1 - Fasselt, Janek Maria A1 - Kruse, Tobias A1 - Klötzer, Christian A1 - Kleba-Ehrhardt, Rafael A1 - Choma, Tomasz A1 - Biegler, Max A1 - Rethmeier, Michael T1 - Using ultrasonic atomization to recycle aluminium bronze chips for additive laser directed energy deposition N2 - Abstract In the post-processing of large maritime components, a considerable amount of waste in the form of milling and grinding chips is produced. At the same time, additive manufacturing technologies have shown great potential in producing high-volume parts for maritime applications, allowing novel design approaches and short lead times. In this context, this study presents a sustainable approach to recycle and use aluminium bronze waste material, generated during post-processing of large cast ship propellers, as feedstock for laser-powder directed energy deposition. The recycling technology used to produce powder batches is inductive re-melting in combination with ultrasonic atomization. The derived metal powders are characterized using digital image analysis, powder flowability tests, scanning electron microscopy as well as energy dispersive X-ray spectroscopy. Compared to conventional metal powders produced by gas atomization, the recycled material shows excellent sphericity and a powder size distribution with a higher content of finer and coarser particles. Metallographic sections of deposited additively produced specimens show an increased hardness and reduced ductility, but also competitive densities and higher yield and ultimate tensile strength compared to cast material. The process chain shows high potential for the maritime sector to enable circular and sustainable manufacturing. KW - Industrial and Manufacturing Engineering PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-594444 DO - https://doi.org/10.1088/1757-899X/1296/1/012036 VL - 1296 IS - 1 SP - 1 EP - 11 PB - IOP Publishing AN - OPUS4-59444 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -