Soldagem A-TIG em aços inoxidáveis ferríticos UNS S41003

Abstract

The A-TIG welding is a simple variant of the conventional TIG process which allows increased weld penetration that makes it possible the full penetration welding of 10 mm thick joints with no preparation. Different mechanisms have been proposed to explain the penetration enhancement which include constriction of the electric arc by negative ions formation and changes in liquid metal flow direction in the weld pool driven by surface tension gradient inversion. This study aimed to characterize the effect of TIG welding in an UNS S41003 ferritic stainless steel with different welding parameters and flux types and quantities. Chromium, silicon and titanium oxides were used as fluxes. Mechanized bead-on-plate welding trials were performed on 6 mm thick ferritic stainless steel plates. Welding current and voltage were measured during all trials and stored in computer. Cross sections of both TIG and A-TIG welds were prepared for macrograph examination and weld bead geometry was characterized. The results indicate a small increment in welding voltage (less than 1.0 V) during the passage from TIG to A-TIG welding. Variations of flux type and density and, as expected, of the welding parameters affected the weld bead geometry. No full penetration was achieved in any weld. Comparing these results with those from literature for austenitic stainless steel suggests a lower effect of the flux in A-TIG welding of ferritic stainless steel. The results are discussed considering the proposed mechanisms for the effect of A-TIG.