Hyperbaric Gas Metal Arc Welding of API X65 Pipeline Steel at 12, 25 and 35 Bar

Remotely controlled subsea welding is often required for pipeline repair and hot tapping where pipelines are installed in water depths beyond acceptable diving depths. The present investigation concerns the development of hyperbaric gas metal arc welding of X65 steel. Welding was carried out at 12-35 bar with low alloyed steel and Inconel 625 wires. All welds gave overmatch situation with respect to strength. Toughness requirements at -30 degrees C were also satisfactory met, although the Charpy values tend to be close to the minimum required individual values of 40J due to high oxygen and fairly high nitrogen contents. The Inconel 625 weld metal toughness was very high. This was also the case for the fusion line toughness for both wires.