Modeling of heat transfer, fluid flow, and weld pool dynamics during keyhole laser welding of 316 LN stainless steel using hybrid conical-cylindrical heat source

This study ascertains a three-dimensional (3D) numerical modeling employing hybrid conical-cylindrical heat source concerning the heat transfer, molten fluid flow weld pool dynamics, and cooling rate phenomena associated with the laser weld pool of 316 LN stainless steel (SS) by computational fluid dynamics. The heat source interprets the transmission of laser energy to the substrate by accounting for recoil pressure and surface tension effect using the multiphase flow modeling. The impact of laser power for a constant welding speed on the penetration depth is predicted to select an optimized laser energy input to carry out full penetration laser welding experiment. The model pictures the depth of penetration, temperature distribution, velocity field, and weld pool flow pattern and keyhole behavior for the optimized welding condition. Non-dimensional heat transfer entities such as Peclet and Marangoni numbers are also assessed that provide insight related to the thermal-fluid flow mechanism and final weld fusion zone attributes of the 316 LN SS laser weld. The simulated model agrees well with the experimentally achieved full penetration laser weld giving fair concordance with the weld bead dimensions and thermocouple measurements. The model has been used to calculate the secondary dendritic arm spacing in the fusion zone. Calculated values were in agreement with the measured values. The numerical outcomes recognize that the hybrid conical-cylindrical heat source model is well suited for predicting weld peak temperature, weld pool velocity, weld pool dynamics, weld pool shape, and cooling rate for the laser welding of 316 LN SS.