Keyhole GTAW with Dynamic Wire Feeding Applied to Orbital Welding of 304L SS Pipes

Abstract

Currently, in the Brazilian Oil and Gas scenario the execution of welding processes for stainless steel consists mostly of manual applications, rendering hard any increase in productivity and repeatability. Therefore, the automation of this step allows several advances such as more reliable results, lower costs and healthier condition for welders. With the aim of developing automation for GTAW welding of these applications, experimental tests were carried out in a 304L stainless steel pipe laid out at 5G position. The samples were orbitally welded by GTAW with dynamic wire feeding process, using a robotic manipulator in two steps of 180º in vertical down progression. The welding parameters and the stable condition obtained are discussed and the weld pool behavior during the root pass was online monitored by HDR (High Dynamic Range) videography. It was possible to reach high welding speed in the root pass, 50 cm/min in a keyhole mode. The wire dynamic movement contributed to reach great process stability and robustness for all joint passes, from root to finishing. The macrographs and x-ray analysis did not indicate discontinuities as porosity nor lack of fusion.

A Review of Orbital Friction Stir Welding

“…The capability of full penetration in a single pass, i.e., being able to perform single-pass welds without stopping, results in a shorter processing time as well as a lower susceptibility to welding failures. Although higher welding speeds (up to 8 mm/s) [16] have been reported in orbital GTAW when compared to FSW, the need for several filling passes makes the overall process slower. In this study, despite the reported defect-free welds of AISI 304 L stainless steel in pipes for the abovementioned travel speeds, no mechanical characterization was conducted.…”

Parameter Optimization in Orbital TIG Welding of SUS 304 Stainless Steel Pipe

“…Moreover, increasing the welding speed to more than 6 mm/s gives rise to the formation of slag. In addition, Riffel et al [17] welded an SUS 304 L stainless steel pipe automatically at a speed of 500 mm/min under the monitor of high-dynamic-range videography. The welded joint was successfully formed without any porosity, discontinuities, or lack of fusion.…”