The key to welding 2205 is maintaining a ferrite-to-austenite balance of approximately 50:50, avoiding excessive ferrite that reduces toughness or causes sigma phase precipitation.

Key points: - Heat input is generally controlled at 0.5-2.5 kJ/mm; too high causes sigma phase precipitation, too low results in excessive ferrite. - Select 2209 (ER2209) as filler metal; do not use 316L welding consumables. - Interpass temperature ≤150°C; forced cooling if necessary. - Backing shielding gas (argon or argon-hydrogen mixture) must be properly applied to prevent root oxidation. - Generally no post-weld heat treatment; if required, it must be strictly controlled and the phase ratio verified.

Post-weld metallographic sampling is recommended to confirm the phase ratio.