X2CrNiMo17-12-2 · ASTM A403 WP316L · S31603 · PRE ~24
The most widely specified stainless steel for chemical process, pharmaceutical, food & beverage, and general industrial piping worldwide. Low carbon (C ≤ 0.030%) prevents intergranular sensitisation in the weld HAZ. 2–2.5% Mo provides chloride resistance beyond 304L. The default SS grade for UK, Netherlands, Scandinavia, and USA projects.
| System | Designation |
|---|---|
| EN Werkstoffnummer (W.Nr.) | 1.4404 |
| EN Grade Name | X2CrNiMo17-12-2 |
| ASTM UNS | S31603 |
| ASTM Fittings | A403 WP316L (dual-cert: 316/316L) |
| AWS Filler (GTAW) | ER316L |
| AWS Filler (SMAW) | E316L-15 / E316L-17 |
| European Market Use | UK, NL, Scandinavia, USA — dominant 316L specification |
| CE Europe / Germany | Specify 1.4571 (316Ti) instead — different convention |
| Element | 1.4404 (316L) | 1.4401 (316) | Role |
|---|---|---|---|
| C | ≤0.030% | ≤0.070% | Low C prevents Cr₂₃C₆ precipitation (sensitisation) |
| Cr | 16.5–18.5% | 16.5–18.5% | Passive film, pitting resistance |
| Ni | 10.0–13.0% | 10.0–13.0% | Austenite stability, corrosion resistance |
| Mo | 2.0–2.5% | 2.0–2.5% | PRE contribution: 3.3×%Mo — chloride pitting resistance |
| N | ≤0.10% | ≤0.10% | PRE contribution: 16×%N — strengthening |
| PRE (calculated) | ~24 | ~24 | Cr + 3.3Mo + 16N |
| W.Nr. | Grade | PRE | Key Feature | Specify When |
|---|---|---|---|---|
| 1.4401 | 316 | ~24 | Standard 316 | Non-welded service only; prefer 316L |
| 1.4404 ★ | 316L | ~24 | Low C (≤0.030%) | UK/NL/USA — standard welded SS piping |
| 1.4571 ★ | 316Ti | ~24 | Ti stabilised | Germany/Italy/CE Europe — DIN/AD 2000 convention |
| 1.4432 | 316L Hi-Mo | ~26 | Mo 2.5–3.0% | Moderate chloride uplift; specify explicitly |
| 1.4435 | 316L Nuclear | ~26 | Ni 12.5–15%; FN≤1 | Nuclear, pharma WFI, fatigue-critical |
