2205 Duplex Steel Welding: Heat Input and Phase Ratio Control
The core of duplex steel welding is not "welding it solid," but maintaining the balance between ferrite and austenite.
The performance of 2205 duplex steel comes from a two-phase microstructure of approximately 50:50. The welding thermal cycle will change the phase ratio: excessive heat input or too-slow cooling will precipitate the σ phase, reducing toughness and corrosion resistance; too-low heat input and too-fast cooling will result in an excessively high ferrite ratio.
Practical control: use multi-layer, multi-pass welding, control interpass temperature (generally not exceeding 150°C), avoid wide weaving, generally select ER2209 as the filler material, and a small amount of nitrogen may be added to the shielding gas to promote austenite recovery.
For important components, it is recommended to conduct metallographic sampling inspection to verify the phase ratio, and to retain welding procedure qualification records.
