Development of Mathematical Model for Prediction and Control of Weld Dilution in MIG Welded Stainless Steel 202 Plates

The attributes of the weld joint are determined by its microstructural composition. Therefore, it is imperative to have an appropriate combination of welding input process variables which result in the desired weld composition that governs mechanical and chemical attributes of the weld joint during its service life. The degree of mixing of base metal and deposited metal is expressed by dilution, which is defined as the fraction of the weight of base metal melted in the weld bead to the total weld bead weight represented in percentage. Sometimes special filler material is used to achieve desirable properties in the weld for which the composition of the filler and base metal can differ significantly. In such cases, it becomes very important to evaluate the dilution caused by the base metal in the resulting weld. The extent of dilution is governed by input welding variables such as welding speed, wire feed rate, torch angle, standoff distance and voltage. In order to control the extent of dilution, it calls for wisely selecting the input parameters and to analyze the possibility of relating these variables with resulting dilution. Such a model was developed to relate the above-mentioned input parameters with the resulting dilution using statistical technique. The experiment under investigation was conducted on the Stainless Steel 202 plate on which AISI 308L filler wire was deposited by metal inert gas welding, and graphical results of direct and combined effects of two input process variables were scrutinized using response surface methodology (RSM). Parametric optimization of weld dilution was also done using RSM, and the appropriacy of the established mathematical model was verified by analysis of variance (ANOVA) technique.