The heat-affected zone (HAZ) of a weld, is the area of base metal, which is not melted during welding but has had its microstructural properties altered by welding. In this study, the application of expert systems such as response surface method to optimize the heat affected zone using tungsten inert gas was pursued. The central composite design matrix was employed to collect data from the sets of experiments. The specimen was made from mild steel plates and welded with the tungsten inert gas process. Thereafter, the response surface methodology was employed to optimize and predict the responses from the process parameters. The result of the response surface method shows that the current has a very strong influence on the heat affected zone. The model for minimizing heat affected zone has a goodness of fit value of 94%. Finally, the numerical solution obtained shows that a current of 130Amp, a voltage of 20.94volts, and a speed of 0.48m/min produced a result with heat affected zone of 3.42mm, with a desirability of 0.76 which is acceptably very good.
