Experimental and numerical study of dissimilar fiber laser welding of martensitic AISI 1060 carbon steel with different configuration with austenitic 304 and ferritic 420 stainless steel.

Welding with fiber laser for two distinct stainless steel types was performed to join with the martensitic carbon steel (AISI 1060) in order to assess the effect of laser welding operating parameters for two dissimilar materials on the weld characterization thorough experimental design method and numerical investigation. A full central composite design (CCD) matrix in accordance with the response surface methodology (RSM) was developed to represent the responses variations by equations including quadratic and nonlinear interaction terms. Different laser welding parameters were taken into account, such as laser power, linear speed of welding, focal distance of the beam, and beam deviation. The responses considered were the temperature field next to the melt pool border line, the maximum penetration depth of the fusion zone and the ultimate tensile strength of the dissimilar weld joint. Additionally, the variation of the microstructure fusion zone and adjacent areas and failure mechanism of the weld joint were evaluated. The experimental results indicate that the temperature field measured at the vicinity of the melt pool fusion line with both 304 and 420 stainless steel which primarily influenced by the incident power of the laser and linear velocity of beam, respectively. Additionally, the numerical simulation results are in good agreement with temperature experimental results at vicinity of fusion line where the temperature measured, experimentally. Apart from this, at the center of the fusion zone, the temperature clearly predicts via numerical simulation results which is not possible to assess experimentally. A clear comparison between the temperature distribution with different joint configuration illustrates that distinct relation between the temperature variation rate and different thermal conductivity coefficient of AISI 1060 with different AISI 304 and 420 joint configuration resulted different temperature distribution. The weld joint microstructure for 420 stainless steel-AISI 1060 steel joint at fusion boundary zone consists of columnar dendrites and skeletal columnar ferrite. At the center of fusion zone, a cellular-type structure is seen. For 304 stainless steel joint, the fusion zone has composed of a remarkable part of skeletal delta-ferrite and dendritic microstructure at austenite matrix microstructure. The fracture section of 304 steel has a ductile fracture and the depth of fracture dimples and cavities toward 304 stainless steel are higher than AISI 1060 steel.