Mild steel is in the classes of materials with high thermal conductive property, increasing the temperature unduly during welding would be detrimental to the microstructure of the weldment. In this research, we aim to minimize the thermal conductivity of mild steel during welding operation to get a quality weld. To achieve that, Response Surface Methodology (RSM) was employed, where twenty sets of experiments were carried out, adopting the central composite experimental design. Tungsten inert gas welding equipment was used to produce the welded joints; Argon gas was supplied to the weld to shield it from atmospheric interference. Mild steel plates of 60x40x10mm were cut and used as specimen for the work. The k-type thermocouple was used to determine the ambient, solidus and liquidus temperatures. The Response Surface Methodology was employed to analyze the data collected from the experiments. The RSM was employed to optimize and predict the thermal properties of mild steel weldments. The model produced a numerical optimal solution of: current 120.00 Amp, voltage of 23.79 volt and a gas flow rate of 15.71 L/min resulting in a welded material having a thermal conductivity of 51.602 W/m 0C
