Welding DSS

[firstmech]

What are the major challenges in welding DSS to itself? \nPlease share the practical difficulties for welder, and inspectors.

[neo]

I would say the heat input stands out.
Maintain the interpass temperature at 100-150 C to make sure those harmful intermetallic phases do not form.

[ben]

API 582 mentions oxygen content of the back purging gas at the weld that shall be reduced to maximum of 0.5%. And to have an oxygen concentration monitoring system is mandatory. That stands critical to DSS welding.
For compliance to interpass temperature, base metal correponding maximum value shall be applied as mentioned in Table 5.

[firstmech]

Yes, I saw that in API 582. Do you know about any other specified precautions from other guides on welding DSS?

[octane]

One of the most common real-world failures occurs when pipe fit-up takes longer than expected and the root purge is stopped too early. The weld may pass radiography because it has no volumetric defects, but the oxidized root can later become the initiation point for pitting corrosion and premature failure in chloride-containing service.
Successful duplex welding therefore depends not only on producing a sound weld, but also on tightly controlling welding parameters, shielding, and inspection throughout fabrication. This is why fabrication standards such as ASME Section IX, along with guidance from organizations like the International Institute of Welding, place strong emphasis on qualified procedures and disciplined execution when welding duplex stainless steels.

[irish]

ASME Section IX Nonmandatory Appendix M provides specialized guidelines for qualifying welding procedures and performance for Duplex Stainless Steels (DSS), focusing on phase balance control, alloy classification, and precise thermal cycles.
I would recommend you to just go through that to pick up the right things when considering welding dSS.

[Dlew]

In addition to what has already been mentioned, shielding gas composition is important as well as that is directly connected to the weld quality. Argon is the one used for GTAW, although the addition of approximately 2–3% nitrogen is recommended as nitrogen promotes austenite reformation during weld solidification and improves pitting corrosion resistance.