Mechanism of A-TIG and AA-TIG (advanced A-TIG)

Abstract

The A-TIG welding technique involving a 2 to 3-fold deeper penetration shape being obtained when welding is performed with coating of activating fluxes, such as oxides, on the weldpool surface before welding, is now acknowledged as an important way of solving some key drawbacks of TIG welding, such as shallow penetration shape and low productivity, and has in recent years been intensively researched.^1–12 This enhanced TIG welding effect was discovered at the Paton Research Institute, Ukraine in the 1960s¹³, being recognized as extremely useful for TIG welding applications. No unified opinion has yet been formed in respect of its mechanism. When broadly divided into proposed explanatory models, the phenomenon is basically ascribed to arc shrinkage^1–9 and a change in the direction of Marangoni convection.^{3, 10–12} More recently, experiments have been conducted to determine not only the effects of different fluxes, but also the effect of the amount of flux coated on workpieces.^{14, 15} The most viable avenue for clarification of the A-TIG mechanism is through detailed analysis of the weldpool oxygen content. An explanatory theory previously enunciated by Tanaka¹⁶ is validated by experimental results based on model simulations. Based on these data, a novel AA-TIG technique (advanced ATIG)¹⁷ has been developed to obtain a 2 to 3-fold greater penetration depth in much the same way by shielding gas control. This article profiles A-TIG and AA-TIG.