Thermally induced residual stresses in SS321 welded joints using CO2 laser beam: FEA and experimental study

Abstract

This study investigates the thermal behavior and residual stress development in CO2 laser beam welding of SS321 stainless steel using finite element analysis and experimental validation. A transient thermal simulation with a Gaussian heat source was conducted in ANSYS APDL, and welding experiments were designed with an L4 orthogonal array, varying the laser power, welding speed, and shielding gas flow. The simulation predicted narrow fusion zones and minimal heat-affected zones. Peak temperatures reached 2731 and 1855 K, corresponding to residual stresses of 179 and 108 MPa. Full penetration and defect-free joints were observed, with significant epitaxial grain formation. An increased heat input led to larger bead widths and higher residual stresses, remaining within the material yield strength. Trial-2 (3.0 kW, 1.5 mm/min) was the optimal condition, balancing quality and stress control. The average safety factor was 1.58 for all joints, and all identified residual stresses were observed to be compressive.