This is my first blog since Duplex World Seminar & Summit took place earlier this month, the culmination of 18 months of planning and hard work by all those involved. I’m always impressed by the dedication of the speakers, moderators and Steering Committee to furthering knowledge and sharing their experience with the duplex community. Almost forty experts gave freely of their time and knowledge to present papers and host workshops.
As always some topics generate more discussions than others. Among this years ‘greatest hits’ in terms of questions it generated was the plenary by Lars Haldorsen, the Leading Advisor for Metallic Materials & Welding at Statoil, Norway. Lars discussed the challenges of welding duplexes, illustrated with experiences from the field.
It’s no secret that welding duplex and super duplex is challenging. Lars explained: “The challenges are associated with the practical welding itself, defect types and rates, the dual microstructures
and the tendency of precipitation of various intermetallic phases, secondary microstructural
constituents (e.g. secondary austenite, chromium nitrides). These effects result in reduced mechanical and corrosion properties of the weld and Heat Affected Zone (HAZ)."
Drawing on experience from the field – Statoil operates over 800 platforms, 33 subsea facilities and 7 onshore refineries/processing plants – Lars went on to explain that the failure modes of duplex are mainly associated with operational conditions and manufacturing defects.
Fatigue and corrosion, including HISC, are the most frequently experienced failure modes both for AISI 300-series and duplex steels, Lars explained. While the effect of poor piping support design is most probably the reason for the high frequency of fatigue failures, he focused on the root causes from welding and fabrication which contribute with 17% of the failure rate.
In the December issue of Stainless Steel World we will feature an extensive article based on Lars much acclaimed plenary presentation. If you’d like to learn about his experience and the challenges of welding duplex, contact me at email@example.com