Estimation and Optimization of Specific Heat of TIG Weld of Mild Steel (s275) Using Response Surface Methodology

Specific heat, an intrinsic thermal property, represents the amount of heat energy required to raise the temperature of a substance by one degree Celsius. Accurate estimation of specific heat in welded metals is crucial for understanding thermal behavior during and after welding processes, especially in applications where temperature control and energy efficiency are essential. This study focuses on the prediction and optimization of the specific heat of mild steel weldments using Response Surface Methodology (RSM), a statistical technique for modeling and analyzing the effects of multiple variables. A total of 100 welded mild steel specimens, each measuring 60 mm × 40 mm × 10 mm, were prepared through controlled Tungsten Inert Gas (TIG) welding operations. During the experiments, key process parameters - welding current, arc voltage, and shielding gas flow rate - were systematically varied to observe their effect on specific heat. The experimental data collected were analyzed using Design Expert 13 software, enabling statistical modeling, regression analysis, and optimization. A second-order quadratic model was developed to describe the relationship between specific heat and the input parameters. The optimal parameter combination was determined to be 180 A, 19 V, and 13 L/min, resulting in a predicted specific heat value of 445.106 J/kg°C. The developed model provides a useful predictive tool for future thermal analysis of welded structures.