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

GTAW Keyhole com Alimentação Dinâmica de Arame Aplicado à Soldagem Orbital de Tubos de Aço Inoxidável 304 L

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.

Key-words:
Spools welding; TIP TIG; Stainless steel pipe welding; Root pass; Filling and finishing passes