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TY  - THES
AU  - Akyel, Fatma Nur
TI  - Reduktion von Eigenspannung und Verzug beim Laserstrahlschweißen von nichtrostendem Stahl und Baustahl durch den LTT-Effekt
VL  - 2026,1
PB  - Rheinisch-Westfälische Technische Hochschule Aachen
VL  - Dissertation
CY  - Düren
M1  - RWTH-2026-00167
SN  - 978-8191-0465-7
T2  - Aachener Berichte Fügetechnik
SP  - 1 Online-Ressource : Illustrationen
PY  - 2026
N1  - Druckausgabe: 2026. - Auch veröffentlicht auf dem Publikationsserver der RWTH Aachen University
N1  - Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2025
AB  - This work investigates the low transformation temperature effect (LTT-effect) in ferritic-pearlitic mild steel and austenitic CrNi steel during laser beam welding. In contrast to what is common in the literature, no special filler materials are used; instead, the chemical composition in the weld seam is generated in situ using dissimilar combinations of conventional materials. The aim is to influence the martensite transformation temperature and strain behaviour by varying the material composition in the weld seam. Chemical analyses, metallographic examinations and hardness measurements are carried out in laboratory tests in order to analyse the changes in microstructure and the dependence of hardness on the martensite transformation temperature. The results are compared with reference welds (similar welds). Residual stress measurements show that residual compressive stresses occur in LTT-welds, while tensile residual stresses dominate in reference welds. The level of residual compressive stresses depends on the chemical composition. These results are supported by diffraction experiments. In order to understand the strain behaviour during the phase transformations, experiments are carried out on selected CrNi steel samples at the Deutsches Elektronen-Synchrotron (DESY). It is shown that martensite formation continuously builds up compressive stresses that compensate for thermal shrinkage. Thermal simulations determine the transformation temperature and the time at which the compressive stress is introduced. By calculating the strains, the compressive strain behaviour due to the LTT effect can be highlighted. Displacement transducer measurements confirm that the LTT effect reduces component distortion. In summary, it is shown that the LTT effect can be successfully used with dissimilar material combinations in mild steel and CrNi steel in order to generate specific compressive stresses and minimise distortion. In particular, depending on the load case, the required compressive strain can be adjusted by varying the chemical composition.
LB  - PUB:(DE-HGF)11 ; PUB:(DE-HGF)3
DO  - DOI:10.18154/RWTH-2026-00167
UR  - https://publications.rwth-aachen.de/record/1024586
ER  -