321 Buttweld Pipe Fittings
ASTM A403 WP321 / EN 1.4541 (X6CrNiTi18-10) — titanium-stabilised austenitic stainless steel designed for service in the carbide sensitization range (425–850°C). Ti binds carbon as TiC, preventing chromium depletion at grain boundaries. Heat exchangers, furnace components, aircraft exhausts, high-temperature reactors. ASME B16.9 and EN 10253-2 Type B.
½″–48″
Size Range
425–850°C
Stabilised Range
500 MPa
Min UTS (EN)
Ti ≥5×C
Stabilised
Request 321 Quote
Response within 1 business day
321 Grade Equivalents
| ASTM | EN W.Nr. | EN Name | UNS | ASME P-No. |
|---|---|---|---|---|
| A403 WP321 | 1.4541 | X6CrNiTi18-10 | S32100 | 8, Gr 1 |
| A182 F321 | 1.4541 | X6CrNiTi18-10 | S32100 | 8 |
| A312 TP321 | 1.4541 | X6CrNiTi18-10 | S32100 | 8 |
Chemical Composition — 321 / 1.4541
| Standard | C | Cr | Ni | Ti | Mn | Si |
|---|---|---|---|---|---|---|
| ASTM A403 WP321 | ≤0.080 | 17.0–19.0 | 9.0–12.0 | ≥5×C (0.10–0.70) | ≤2.0 | ≤1.0 |
| EN 1.4541 (X6CrNiTi18-10) | ≤0.080 | 17.0–19.0 | 9.0–12.0 | ≥5×C (0.10–0.60) | ≤2.0 | ≤1.0 |
Ti/C ratio on MTR must be verified. Minimum Ti ≥5×C ensures full carbon stabilisation. Note the slightly tighter Ti maximum in the EN specification (0.60% vs 0.70% ASTM).
Mechanical Properties — 321 / 1.4541
| Standard | Min. UTS (MPa) | Min. YS (MPa) | Elongation | Max Hardness | HT Condition |
|---|---|---|---|---|---|
| ASTM A403 WP321 | 515 | 205 | ≥35% | 217 HBW | Solution annealed |
| EN 1.4541 (EN 10253-2) | 500–730 | ≥195 | ≥40% | 215 HBW | Solution annealed |
Heat Treatment & Welding — 321 / 1.4541
✓ No PWHT Required — 321 used in solution annealed condition. Stabilising anneal at 845–900°C optional to maximise TiC precipitation before service.
ASTM A403 WP321 / EN 1.4541 fittings are supplied in the solution annealed condition. Unlike CrMo alloy steels, no post-weld heat treatment is required for code-compliant joints. For applications where maximum sensitization resistance is critical (e.g., prolonged service above 650°C), a post-weld stabilising anneal at 845–900°C may be specified — this promotes TiC precipitation and is distinct from PWHT.
Welding Guidance — Use ER347, Not ER321
- Preferred filler (GTAW/TIG): ER347 (Nb-stabilised). Titanium in ER321 burns off in the arc; ER347's niobium is more arc-stable and provides equivalent anti-sensitization protection.
- SMAW filler: E347-16. Do not use E321-16 where full stabilisation of the weld deposit is required.
- No preheat required for standard wall thicknesses.
- Inter-pass temperature: ≤150°C to minimise HAZ sensitization.
- ASME P-No.: 8, Group 1. Weld procedure qualification per ASME IX or ISO 15614-1.
Stabilising Anneal (Optional, Not PWHT)
For maximum sensitization resistance in service, a post-weld stabilising anneal at 845–900°C can be specified — this drives TiC precipitation throughout the weld and HAZ and is not post-weld heat treatment in the conventional sense. It should be noted in the WPS and approved by the client's inspection authority where applicable.
304L vs 321 — Which to Specify?
| Property | 304L (1.4307) | 321 (1.4541) |
|---|---|---|
| Sensitization prevention | Low C (≤0.030%) | Ti stabilisation |
| Protection at 425–850°C | Limited under prolonged exposure | Yes |
| Max service temp | ~870°C | ~850°C |
| Filler | ER308L | ER347 (not ER321) |
| Cost | Lower | Slightly higher |
For single-pass welding at ambient temperature and short-term elevated-temperature exposure, 304L is typically adequate and more economical. Specify 321 when piping will experience repeated thermal cycles or long-term residence in the 425–850°C sensitization range.
321 Fitting Types Available
90° Elbow (LR & SR)
Long Radius & Short Radius
ASME B16.9 / EN 10253-2
45° Elbow
Long Radius
ASME B16.9 / EN 10253-2
Equal Tee
Straight tee, equal branch
ASME B16.9 / EN 10253-2
Reducing Tee
Reduced branch outlet
ASME B16.9 / EN 10253-2
Concentric Reducer
Inline bore reduction
ASME B16.9 / EN 10253-2
Eccentric Reducer
Flat bottom / top configurations
ASME B16.9 / EN 10253-2
End Cap
Pipe end closure
ASME B16.9 / EN 10253-2
Stub End (Lap Joint)
For use with lap joint flanges
ASME B16.9
180° Return Bend
Long & short radius
ASME B16.9
Ready to order 321 stainless steel fittings?
Specify size, schedule, fitting type, standard (ASME B16.9 or EN 10253-2 Type B), and required MTR (EN 10204 3.1 or 3.2). We respond within 1 business day.
Request a Quote →