Estimation of Solidus and Liquidus Temperature of TIG Mild Steel (S275) Using Response Surface Methodology

The solidus and liquidus temperatures are critical parameters in materials science, particularly for alloys, defining the boundaries between solid and liquid phases during melting and solidification. The solidus is the highest temperature at which an alloy is excellent, and the liquidus is the lowest temperature at which an alloy is completely liquid. Understanding these temperatures is crucial for processes like casting, brazing, and materials' behavior under high temperatures. This research aims to estimate the solidus and liquidus temperatures of mild steel (S275) weld metal by applying Response Surface Methodology (RSM) to the Tungsten Inert Gas (TIG) welding process. The input parameters considered in the study include welding current, welding voltage, and gas flow rate, while the output responses are the solidus and liquidus temperatures. The methodology helps identify the optimal combination of these input parameters that yields the most accurate values for the solidus and liquidus temperatures of the mild steel weld metal. The suggested model for solidus temperature has an R<sup>2</sup>of 0.9984, an Adjusted R<sup>2</sup> of 0.9970, and a Predicted R<sup>2</sup> of 0.9306. In contrast, Liquidus temperature has an R<sup>2</sup> of 0.9997, an Adjusted R<sup>2</sup> of 0.9994, and a Predicted R<sup>2</sup> of 0.9994, showing a significant model and indicating a desirability value of 91.5%.