@misc{WasilewskiDoynovOssenbrinketal., author = {Wasilewski, Eric and Doynov, Nikolay and Ossenbrink, Ralf and Michailov, Vesselin}, title = {Investigations on the thermal conditions during laser beam welding of high-strength steel 100Cr6}, series = {Advances in Industrial and Manufacturing Engineering}, volume = {6}, journal = {Advances in Industrial and Manufacturing Engineering}, issn = {2666-9129}, doi = {10.1016/j.aime.2023.100118}, abstract = {This study examines the thermal conditions during laser beam welding of 100Cr6 high-strength steel using a TruDisk5000 disc laser with a continuous adjustable power range of 100-5000 W. Two parameter sets, characterized by laser power and welding speeds, were analyzed by thermal-metallurgical FE simulations to determine their impact on the thermal conditions during welding. The results show a significant shift in heat coupling, with conduction transitioning to deep penetration welding. As a result of the high welding speeds and reduced energy input, extremely high heating rates up to 2∙104 K s-1 (set A) respectively 4∙105 K s-1 (set B) occur. Both welds thus concern a range of temperature state values for which conventional Time-Temperature-Austenitization (TTA) diagrams are currently not defined, requiring calibration of the material models through general assumptions. Also, the change in energy input and welding speed causes significantly steep temperature gradients with a slope of approximately 5∙103 K mm-1 and strong drops in the temperature rates, particularly in the heat affected zone. The temperature cycles also show very different cooling rates for the respective parameter sets, although in both cases they are well below a cooling time t8/5 of 1 s, so that the phase transformation always leads to the formation of martensite. Since the investigated parameters are known to cause a loss of technological strength and conditionally result in cold cracks, these results will be used for further detailed experimental and numerical investigation of microstructure, hydrogen distribution, and stress-strain development at different restraint conditions.}, language = {en} } @misc{Wasilewski, author = {Wasilewski, Eric}, title = {Force Control Strategies to reduce Weld Distortion and Cold Cracking in Laser Beam Welding}, series = {International Conference of Students and Young Scientists: "Modern Materials and Their Processing Technologies"}, journal = {International Conference of Students and Young Scientists: "Modern Materials and Their Processing Technologies"}, editor = {Gluschkowa, Diana Borysiwna and Dosschetschkina, Iryna Wasyliwna and Lalasarowa, Natalija Oleksijiwna}, address = {Charkow, Ukraine}, pages = {6 -- 16}, abstract = {In recent years, lightweight construction and the demand for resource and energy efficiency have increasingly supported the use of high-strength steels. Laser beam welding (LBW) of these materials is used in industrial mass production to efficiently manufacture high-precise components and parts with the highest quality requirements. Avoiding welding-related defects such as weld distortion and cold cracking is critical. Conventional applications currently meet this requirement to a limited extent due to very restricted process tolerances and the use of non-critical materials, which limits the potential of the joining process. Based on FE welding process simulations, concepts have been developed to reduce distortion and cracking through active control of the LBW process. The underlying models consider the weld induced temperature field, microstructure transformations, and residual stresses to calculate distortion. In addition, the local hydrogen concentration is calculated, and the results of the welding process simulation are evaluated using a cold cracking tool that includes material-specific cracking criteria. The ability to simulate distortion and cold cracking behavior opens up the possibility of parameter variation. From the data collected, concepts of active force introduction with dynamic workpiece clamping have been derived that lead to distortion and cold cracking reduction and promote the weldability of high-strength materials.}, language = {en} }