Optimization of A-TIG process parameters using response surface methodology

ABSTRACT

In the present work, the influence of process parameters such as welding current (I), welding speed (S), and flux coating density (F) on different aspects of weld bead geometry for example depth of penetration (DOP), bead width (BW), depth to width ratio (D/W), and weld fusion zone area (WA) were investigated by using the central composite design (CCD). 9–12% Cr ferritic stainless steel (FSS) plates were welded using A-TIG welding. It was observed that all input variables have a direct influence on the DOP, BW, and D/W. However, flux coating density has no significant effect on WA. Mathematical models were generated from the obtained responses to predict the weld bead geometry. An optimized DOP, BW, D/W, and WA of 6.95 mm, 8.76 mm, 0.80, and 41.99 mm², respectively, were predicted at the welding current of 213.78 A, the welding speed of 96.22 mm/min, and the flux coating density of 1.99 mg/cm². Conformity test was done to check the practicability of the developed models. The conformity test results were in good agreement with the predicted values. Arc constriction and reversal in Marangoni convection were considered as major mechanisms for the deep and narrow weld bead during A-TIG welding.

KEYWORDS:

• A-TIG
• flux
• geometry
• macrostructure
• microstructure
• optimization
• steels
• welding