LASER WELDING OF THE NEW GRADE OF ADVANCED HIGH-STRENGTH STEEL DOMEX 960

The article presents the results of investigations on autogenous laser welding of the new-generation advanced high-strength steels (AHSS) Domex 960, classified as thermomechanically rolled steel by the manufacturer. There is little information about welding this steel grade, relating only to arc-welding methods. Therefore, a modern disk laser was used for the butt-joint welding of 5.0 mm steel sheets. The results of a microstructure study, tensile tests, technological bending tests, impact-toughness tests and also microhardness measurements showed that a low heat input during the laser welding of the new Domex 960 grade steel is advantageous. A low heat input and thus a high cooling rate of the weld metal and the heat-affected zone (HAZ) led to the formation of a favourable fine-grained microstructure, providing also high mechanical properties of butt joints, comparable to the properties of the base metal. Despite the high cooling rates, there was no significant increase in the microhardness measured across the butt joints. Moreover, a slight decrease in the microhardness was observed in the HAZ.