Reduction of distortion during laser beam welding by applying an in situ alloyed LTT effect and considering influencing factors

In rail vehicle construction, austenitic stainless steels are used to achieve lightweight design concepts, as the higher specific strength of the material allows the thickness of parts to be reduced. However, when these are welded to create complex structures, increased welding distortion occurs even with low-heat joining processes such as laser beam welding.

In order to reduce distortion, an in situ low transformation temperature (LTT) effect has been achieved using commercially available materials rather than specially manufactured LTT alloys. The LTT effect introduces compressive stresses into the weld seam, which counteract the formation of welding distortion due to tensile stresses. However, in the case of complex structures, several other factors influence the formation of distortion. The influence of the LTT effect and other factors such as tack welding, clamping and cooling conditions were analysed by distortion measurements and a maximum distortion reduction was determined.