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 | A403 WP321 / WP347 |
| EN / DIN | 1.4541 / 1.4550 |
| JIS | SUS321 / SUS347 |
| GOST | 12Х18Н10Т |
| GB | 06Cr18Ni11Ti |
Where this grade belongs
- Refinery and petrochemical high-temperature process lines
- Exhaust, flue and heat-recovery systems
- Expansion joints and bellows where repeated thermal cycling occurs
- Service sustained in the 425 – 815 °C sensitisation range
Where it does not
The failures we see most often are not bad material — they are the right material in the wrong service.
- Ambient-temperature chloride service — Stabilisation buys high-temperature stability, not chloride resistance. If the problem is chlorides rather than temperature, 316L or duplex is the better answer.
- General-purpose substitution for 304L — 321 and 347 cost more and are harder to source in odd sizes. Specify them where the temperature genuinely calls for it.
What we supply in ASTM A403 WP321 / WP347
Forms: Butt-weld elbows, tees, reducers and caps; forged flanges in the matching A182 F321 / F347 grades
Size range: DN15 – DN900 typical, larger to enquiry
Documentation available
- EN 10204 3.1 material test certificate traceable to the heat number
- PMI (positive material identification) on request
- Intergranular corrosion testing to ASTM A262 on request
- PED 2014/68/EU with 4.3 material appraisal
Frequently asked
When should I use 321 instead of 304L?
When the line sits for extended periods in the roughly 425 – 815 °C range. 304L resists sensitisation during welding; 321 and 347 resist it during sustained high-temperature service, which is a different problem.
What is the difference between 321 and 347?
The stabilising element — titanium in 321, niobium in 347. 347 is often preferred where the material will be welded, since niobium carbides are more stable through the weld thermal cycle.
What is the EN equivalent of WP321?
1.4541 is the counterpart usually referenced; WP347 corresponds to 1.4550.
Related grades
- ASTM A403 WP316 / WP316L — Austenitic stainless steel — 316 / 316L
- ASTM A403 WP304 / WP304L — Austenitic stainless steel — 304 / 304L
- ASTM A234 WP11 / WP22 / WP91 — Chrome-moly alloy steel
Full cross-reference across all families: Technical Guide § 2 — Material Grade Equivalents. Pressure class and schedule conversion: § 3 — Pressure Ratings & Pipe Schedules.