| About this Abstract |
| Meeting |
2024 AWS Professional Program
|
| Symposium
|
2024 AWS Professional Program
|
| Presentation Title |
Elemental Segregation in the Bondline and the Heat Affected Zone for the High Frequency Electric Resistance Welded X70 Grade Pipeline Steel |
| Author(s) |
Ravikiran Kopparthi, Leijun Li |
| On-Site Speaker (Planned) |
Ravikiran Kopparthi |
| Abstract Scope |
High-frequency electric-resistance welded (HF-ERW) linepipes are widely used to transport oil and natural gas across large distances. Due to the HF-ERW welding process, the microstructural constituents are complex at the weld joint. The as-welded HF-ERW X70 grade pipeline steel consists of a thin bondline (weld zone) and a typical hourglass-shaped heat-affected zone (HAZ). The bondline itself comprises solute-depleted ferrite and solute-enriched martensite-austenite (M/A). On the other hand, the heat-affected zone comprises of bainitic ferrite (BF) and a minor fraction of retained austenite (RA). To understand the formation mechanism of these microstructural constituents, atomic scale characterization was performed using atom probe tomography (APT). A significant carbon partitioning from martensite to austenite without any partitioning of substitutional alloying elements was observed in the bondline. On the other hand, in the heat-affected zone, across the ferrite-retained austenite interface, it was shown to follow the negligible partitioning local equilibrium (NPLE) kinetics for bainite transformation, resulting in a spike of manganese concentration at the interface boundary. The APT experimental results were compared to DICTRA simulations, and the partitioning behavior of alloying elements during the phase transformations was confirmed kinetically. |
| Proceedings Inclusion? |
Undecided |