Experimental investigation of the effect of laser parameters on the weld bead shape and temperature distribution during dissimilar laser welding of stainless steel 308 and carbon steel St 37

Fiber laser fusion welding of two applicable alloys including 308 stainless steel and low carbon steel (St 37) was performed to assess the formation mechanism of the weld bead and temperature field near the fusion zone. In this research, some parameters including welding speed, laser power, nozzle distance, and beam deviation of the laser beam were determined as the main parameters. The results showed that the effect of the nozzle distance on the temperature field was higher than that of the welding speed and laser power. It was also observed that increasing the nozzle distance caused more absorption of the beam in the parts and there was an almost two-fold increase in the dimensions and volume of the weld bead. The measured temperature near melt pool was decreased about 120 degrees C for st37 while a reduction about 30 degrees C for stainless steel according to increasing nozzle distance from 3 to 7 mm. Unlike carbon steel, the temperature of the stainless steel was clearly decreased at the nozzle distance to the highest point. By increasing the welding speed, the temperature around the molten area was decreased. The beam deflection parameter showed the effect of the temperature gradient index on changes and a temperature decrease was observed by creating a distance from the location of thermocouples. Increasing laser power from 300 to 400 W created wider weld bead about 40% and higher temperature about 40 degrees C for stainless steel in comparison to st37.