Gas tungsten arc process optimization and assessment for robotized position welding of austenitic stainless steel edge joints

Abstract

Gas tungsten arc welding (GTAW) is a common joining method for austenitic stainless steel sheets. Edge joint is frequently used configuration when the aim is to produce weldments e.g., between the tube sheets and the tubes and to other hollow structures needing tight sealing welds and sound joints. In those applications all positions for welding is usually needed. Robotized welding is utilized, when manual welding is not possible, e.g., in maintenance for nuclear power applications. In automatic welding a strict control of location of arc and welding parameters are extremely important.

In this work the aim was to find suitable welding parameters, as pulse parameters, welding speed and shielding gas composition and study their effects on weld joint penetration and weld quality in different welding positions. In addition, the inaccuracy in the alignment of the arc and its effects was tested in different cases. It was found that it was possible to find the optimal parameters in different positions, flat (PA), overhead (PE), and vertical-up position (PF). However, the vertical-down position (PG) was giving a lower joint penetration in the cases which allow sound welds. Therefore, it was considered that the fabrication of the circumferential joint was best done in two steps to avoid the PG position, which ensures that a sound weld with the set 2.6 mm penetration requirement is achieved over the entire circumference. The use of a shielding gas mixture containing argon and 2% hydrogen showed significant advantages over the other three shielding gas compositions tested, which was observed as deeper penetration of the welds.