Optimization of CO2 Laser Beam Welding Process Parameters to Attain Maximum Weld Strength in Dissimilar Metals

Abstract

In this study, influence of CO2 laser beam welding (LBW) process parameters such as laser power (P), welding speed (S), focal distance (F) on dissimilar metals of low carbon steel (AISI 1018) and austenitic stainless steel (AISI 316) was examined by using central composite design (CCD) based response surface methodology (RSM). Experimental investigations were performed on 4 kW CO2 laser (TRUMPF TLC1005) with the laser beam spot diameter of 0.15mm and a focal length of 15-25mm. Analysis of variance (ANOVA) was used to analyze the interaction effect of different parameters on the maximum weld strength. A ratification experiment was also carried out in order to validate the optimal process parameters values. Based on the investigation, the maximum weld strength of 458.21 N/mm2 was observed for dissimilar metal butt joint with the optimized laser power of 2600W, the focal distance of 25 mm and a welding speed of 1.5 m/min. Microstructure studies revealed cellular austenite in the form of dendrite and columnar type features accredited to the higher cooling rates concerned with laser welding process. Energy dispersive X-ray analysis (EDX) is carried out to measure the nature of the chemical element distribution in the weld interface. Microhardness tests showed that the maximum hardness was produced in weldment 151-458 Hv and fusion boundary of austenitic stainless steel 193-434 Hv, fusion boundary of low carbon steel 156-468 Hv.