Impact toughness of laser-welded butt joints of the new steel grade Strenx 1100MC

The detailed influence of the energy input of autogenous laser welding by means of a modern solid-state disk laser on the structure of the weld metal, the heat-affected zone and the mechanical properties of 5.0-mm-thick butt joints of STRENX 1100MC was studied.Laser-welding trails were conducted over a wide range of energy inputs, from approximately 100 up to 400 J/mm.The studies showed no tendency for the cracking of butt joints, despite the low energy inputs of the welding.However, a significant decrease in the hardness was revealed in the heat-affected zone.The static tensile strength was found to be slightly lower (by approx.8 %) compared to the tensile strength of the base material.There was also a strong relationship between the impact toughness of the test joints and the energy input of the laser welding.However, the impact toughness of the laser-welded joints was significantly lower than that of the base material.This article attempts to explain the drop in the toughness and the static tensile strength with respect to the structural transformations of the weld metal and the heat-affected zone, depending on the welding parameters, especially the energy input, and thus the heating conditions of the welding.