Abstract
The paper presents results of microstructure and mechanical properties investigation of laser beam welded high-strength steel. Material for test was non-alloyed steel with yield strength of 690 MPa after quenching and tempering in delivery condition. Research carried out on the butt-welded joints shows fine-grain martensitic-bainitic structure of base metal and in the weld. Investigations of mechanical properties revealed the softened zone in HAZ where the hardness decrease without microstructural changes was observed. Moreover, an influence of softened zone and HAZ width on impact strength was observed where the occurrence of lower hardness led to fracture path deviation phenomenon.