Multiobjective optimization of welding process variables in RMD and FCAW techniques using a heat transfer search algorithm for 316LN stainless steel

This study aims to identify the optimal parameters for regulated metal deposition (RMD) and flux-cored arc welding (FCAW) processes when joining 316LN stainless steel. The objective was to determine the optimal settings for current (A), voltage (V), and gas flow rate (GFR, L/min) to achieve the desired weld bead characteristics, including bead width (BW), bead height (BH), depth of penetration (DOP), and heat-affected zone (HAZ). A Box–Behnken design based on response surface methodology was employed for the bead-on-plate trials. Mathematical models were developed from the experimental data and validated through analysis of variance and residual analysis, with R-squared values confirming model accuracy. The heat transfer search (HTS) algorithm was used for both single objective and multiobjective optimization. For RMD, optimal results were achieved with a BW of 9.95 mm, BH of 4.39 mm, DOP of 2.26 mm, and HAZ of 0.29 mm, at 130 A, 18 V, and 20 L/min GFR. For FCAW, optimal values were a BW of 11.45 mm, BH of 3.59 mm, DOP of 2.15 mm, and HAZ of 0.40 mm, at 210 A, 24 V, and 10 L/min GFR. The Pareto solutions offered a most suitable choice of the optimal configuration, balancing the desired BW, BH, DOP, and HAZ values. The effectiveness of the HTS algorithm is demonstrated by the minimal differences between predicted and measured values, highlighting its high accuracy in optimizing 316LN stainless steel welding parameters.