Cross-system equivalents
Cross-system grades are nearest counterparts, not drop-in substitutes. Chemistry and mechanical envelopes overlap but are not identical — where a design code names a grade, order that grade. Final selection should be confirmed by your project engineer against the governing code.
| Standard system | Grade designation |
|---|---|
| ASME / ASTM | A815 UNS S31803 / S32205 · S32750 |
| EN / DIN | 1.4462 / 1.4410 |
| JIS | SUS329J3L |
| GOST | — |
| GB | 022Cr23Ni5Mo3N |
Where this grade belongs
- Seawater cooling, desalination and SWRO plant
- Offshore topsides, subsea manifolds and FPSO process piping
- Chemical tankers and cargo systems
- Any line where chloride SCC has taken out austenitic material before
Where it does not
The failures we see most often are not bad material — they are the right material in the wrong service.
- Above ~300 °C — Prolonged exposure risks 475 °C embrittlement and sigma phase formation. Duplex has a real upper temperature ceiling that austenitics do not.
- Uncontrolled fabrication — Duplex is unforgiving of bad welding — heat input and interpass temperature drive the ferrite balance. Insist on qualified procedures and ferrite measurement.
- Treating S31803 and S32750 as interchangeable — They are different alloys at different price points. Super duplex is specified for a reason; substituting standard duplex into a seawater line is a failure waiting to happen.
What we supply in Duplex S31803 / S32205
Forms: Butt-weld elbows, tees, reducers and caps; forged flanges in the matching A182 F51 / F53 / F55 grades
Size range: DN15 – DN900 typical, larger to enquiry
Documentation available
- EN 10204 3.1 material test certificate traceable to the heat number
- NORSOK M-650 qualified manufacturing on request
- Ferrite content measurement reported per heat
- Corrosion testing to ASTM G48 Method A on request
- PMI (positive material identification) on request
- NACE MR0175 / ISO 15156 where sour service is specified
Frequently asked
What is the difference between duplex 2205 and super duplex 2507?
Alloy content and therefore pitting resistance. S31803 / S32205 (2205) sits around PREN 35; S32750 (2507) exceeds PREN 40, which is the usual threshold for continuous full-strength seawater duty.
Why is NORSOK M-650 asked for on duplex?
It qualifies the manufacturer's specific production route — melting, forming and heat treatment — rather than just testing the finished part. For duplex, how the material was made determines whether the phase balance is right, so buyers on offshore projects generally require it.
Can duplex replace 316L one-for-one?
Not dimensionally without checking — the higher strength often allows a thinner wall, which changes the schedule. And duplex has a lower maximum service temperature than 316L. Both need confirming against the design.
Related grades
- ASTM A403 WP316 / WP316L — Austenitic stainless steel — 316 / 316L
- ASTM A403 WP304 / WP304L — Austenitic stainless steel — 304 / 304L
- API 5L & ASTM A106 Gr.B — Line pipe and seamless pressure pipe
Full cross-reference across all families: Technical Guide § 2 — Material Grade Equivalents. Pressure class and schedule conversion: § 3 — Pressure Ratings & Pipe Schedules.