316L Buttweld Pipe Fittings
ASTM A403 WP316L / EN 1.4404 (X2CrNiMo17-12-2) — 17Cr-12Ni-2.2Mo low-carbon austenitic stainless steel for chemical, pharmaceutical, food and marine applications. No sensitization in HAZ. EN 10253-2 Type B and ASME B16.9. EN 10204 3.1 standard; 3.2 TPI on request.
½″–48″
Size Range
PRE ~24
Pitting Index
480 MPa
Min UTS (EN)
EN 10204
3.1 Std / 3.2 On Req.
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316L Grade Equivalents
| ASTM | EN W.Nr. | EN Name | UNS | ASME P-No. |
|---|---|---|---|---|
| A403 WP316L (fittings) | 1.4404 | X2CrNiMo17-12-2 | S31603 | 8, Gr 1 |
| A182 F316L (flanges) | 1.4404 | X2CrNiMo17-12-2 | S31603 | 8 |
| A312 TP316L (pipe) | 1.4404 | X2CrNiMo17-12-2 | S31603 | 8 |
| A276 316L (bar) | 1.4404 | X2CrNiMo17-12-2 | S31603 | 8 |
Chemical Composition — 316L / 1.4404
| Standard | C | Cr | Ni | Mo | Mn | Si | N |
|---|---|---|---|---|---|---|---|
| ASTM A403 WP316L | ≤0.035 | 16.0–18.0 | 11.0–14.0 | 2.0–3.0 | ≤2.0 | ≤1.0 | — |
| EN 1.4404 (X2CrNiMo17-12-2) | ≤0.030 | 16.5–18.5 | 11.0–14.0 | 2.0–2.5 | ≤2.0 | ≤1.0 | ≤0.11 |
Low carbon (C ≤0.030%) prevents the formation of chromium carbides at grain boundaries (sensitization) during welding — the key advantage of 316L over standard 316 (WP316, EN 1.4401, C ≤0.070%).
Mechanical Properties — 316L / 1.4404
| Standard | Min. UTS (MPa) | Min. YS (MPa) | Elongation (%) | Max. Hardness | HT Condition |
|---|---|---|---|---|---|
| ASTM A403 WP316L | 485 | 170 | ≥35% | 217 HBW | Solution annealed |
| EN 1.4404 (EN 10253-2) | 480–680 | ≥175 | ≥40% | 215 HBW | Solution annealed |
Heat Treatment & Corrosion Considerations
✓ No PWHT Required — 316L supplied and used in the solution annealed condition.
Unlike CrMo alloy steels such as P91 or P22, 316L (ASTM A403 WP316L / EN 1.4404) does not require post-weld heat treatment. Austenitic stainless steels do not undergo martensitic transformation during welding and are not susceptible to hydrogen cracking. The fitting is delivered in the solution annealed condition and no further heat treatment is needed for code-compliant welded joints.
Welding Guidance
- Heat input control: Keep inter-pass temperature ≤150°C to minimise HAZ sensitization (though the low carbon of 316L already significantly mitigates this risk).
- Filler metal: ER316L (GTAW / TIG) or E316L-16 (SMAW / MMA). Match filler to base metal grade.
- Flux: Avoid chloride-containing flux — chloride residues promote pitting and crevice corrosion.
- ASME P-No.: 8, Group 1. Weld procedure qualification per ASME IX or ISO 15614-1.
Passivation (Pharma & Food Applications)
Passivation with nitric acid per ASTM A380 or ASTM A967 is recommended after fabrication for pharmaceutical and food-grade applications. Passivation restores and enhances the native chromium oxide passive layer, removing free iron contamination from machining, grinding, or welding operations.
⚠ Chloride SCC Warning
316L is susceptible to chloride stress corrosion cracking (SCC) above approximately 60°C in chloride-containing environments. For seawater service, high-chloride brines, or elevated-temperature chloride environments, specify duplex stainless steel 2205 (EN 1.4462) or super duplex 2507 (EN 1.4410), which offer significantly higher resistance to chloride SCC. Contact our technical team to discuss material selection for your specific service conditions.
316L Fitting Types Available
90° Elbow (LR & SR)
Long Radius & Short Radius
ASME B16.9
45° Elbow
Long Radius
ASME B16.9
Equal Tee
Straight tee, equal branch
ASME B16.9
Reducing Tee
Reduced branch outlet
ASME B16.9
Concentric Reducer
Inline bore reduction
ASME B16.9
Eccentric Reducer
Flat bottom / top configurations
ASME B16.9
End Cap
Pipe end closure
ASME B16.9
Stub End (Lap Joint)
For use with lap joint flanges
ASME B16.9
Cross / Lateral
Four-way and angled branch
ASME B16.9
316 vs 316L — Key Differences
| Property | 316 (WP316 / EN 1.4401) | 316L (WP316L / EN 1.4404) |
|---|---|---|
| Carbon max | ≤0.070% | ≤0.030% |
| Sensitization risk | Yes (in HAZ if welded) | No (low C prevents carbide precipitation) |
| Preferred for welded | No | Yes |
| Min YS | ≥205 MPa | ≥170 MPa |
| Applications | Non-welded or solid bar | All welded constructions, default choice |
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