Abstract:
Gas Tungsten Arc Welding (GTAW) is an arc welding process which is being used in industries for fabrication of tanks, pressure vessels, heat exchangers etc. It involves many parameters which the operator can control and these parameters have a direct influence on weld bead geometry and an indirect influence on mechanical properties of joints. In this study, five parameters i.e. arc current, arc length, torch speed, torch angle and shielding gas flow rate in GTAW have been varied up to five levels and their influence on bead width (BW), depth of penetration (DOP), depth to width (D/W) ratio and weld bead hardness (WBH) is studied. Experiments were designed according to Taguchi L25 orthogonal array (OA) and were conducted on a 3 mm thick plate of stainless steel 304L using automatic GTAW machine. Input parameters were first optimized for each single response separately and optimum parameters were found. Then, using Grey Relational Analysis (GRA), a method to convert a multi response problem into single response, simultaneous optimization of multi responses was carried out. Results were also analyzed using signal to noise (S/N) ratio and Analysis of Variance (ANOVA). It was found that, for simultaneous and individual optimization of each response, arc current is the most influential factor. BW decreases with increase in speed and with decrease in arc current and arc length. DOP increases with increase in current, increase in torch angle and with decrease in speed. D/W ratio increases with increase in arc current and torch angle and decreases with increase in arc length and torch speed. WBH increases with increase in arc current, arc length, torch speed and shielding gas flow rate and decreases with increase in torch angle. The results were also verified with confirmation tests and a good agreement was found between the predicted and measured results.
