Influence of Welding Parameters on the Mechanical Properties of a Laser-Welded Joint

Laser welding is a well-known and relatively widely-used joining process in the engineering industry. Laser welding is also a proven suitable welding method for the joining of modern, high-strength structural steels. Welding of these steels can be challenging when using traditional manual fusion welding, since limits are set for the minimum and maximum welding energy and the cooling time, to retain the original properties of the base material. In the laser welding process, constant welding parameters are used and the movement is performed mechanically, to achieve a high and even processing speed, so that the welding values set can be fulfilled. In the study, the mechanical properties of laser-welded joints were researched in respect of the welding energy used and the cooling time resulting from different combinations of laser power and travelling speed. Several welds with a variable laser power and travelling speed were joined. The thicknesses of the test materials were 3, 4 and 6 mm and the welding energies used for each thickness were 0.05, 0.07 and 0.15 kJ/mm, respectively. The test material was thermo-mechanically rolled structural steel with 500 MPa of yield strength. The joint configuration used was bead-on-plate. Various destructive testing was performed for welded joints. For example, the transversal tensile strength results only showed just minor differences between the values, whereas the hardness values showed clearer differences between the joints.