Numerical Simulation and Experimental Analysis of Thermal Cycles and Phase Transformation Behavior of Laser-Welded Advanced Multiphase Steel

This work presents the results of the comparison between simulations and experiments of the laser welding of advanced multiphase steel. The numerical simulations of welding with different parameters were carried out using the Sysweld software. The geometry of the weld and structural constituents as well as stress distributions were analyzed. The simulated thermal cycles were incorporated in the JMatPro software to determine the phase transformation kinetics during cooling. The experimental tests were performed to compare the simulations with the real results. According to them, the shape of the weld and its width were symmetrical according to the weld axis. The simulated values were higher compared to the real one at heat inputs higher than 0.048 kJ/mm. The microstructure investigations conducted with scanning electron microscopy showed a good agreement in the fusion zone. Some differences in the microstructure of heat-affected zone and transition zone were identified. According to the phase transformation simulations, the weld should be composed of only martensite. The real microstructure was composed of martensite and some fraction of bainite in the heat affected zone. The more complex microstructure consisting of ferrite, bainite and retained austenite was present in the transition zone. The results of measured and simulated hardness indicated the good agreement with the difference of 17 HV0.1.