Study of properties of laser welds of Domex 700 MC material using arc preheating

This thesis deals with the study of influence of preheating/reheating by TIG arc method in the laser welding process of Domex 700 MC fine-grained steel through the evaluation of laser-welds properties, respectively properties of welds made by laser-TIG hybrid technology. The main part of this thesis is experiment, in which Domex 700 MC plates 3 mm thick were welded – first using laser itself, then using laser with arc preheating and finally using laser with arc reheating. The variable parameter during the processes preheating or reheating was distance of TIG tungsten electrode and laser beam (DLA = 1 mm, 2 mm and 4 mm). The criterion for the assessment of welds properties thus produced was tensile strength verified by the tensile test. For a more detailed study of the laser-welds properties, a macrostructure / weld microstructure analysis and a Vickers hardness test were performed