IBR Approved · Stainless Steel
ASTM A403 WP316L Buttweld Pipe Fittings
Low-carbon 316L (17Cr-12Ni-2.5Mo) austenitic stainless steel — the standard grade for welded process piping in chemical, pharmaceutical, food and marine service. Elbows, tees, reducers and caps to ASME B16.9 / B16.28, IBR approved with Form III-C, EN 10204 3.1 / 3.2 traceable.
Grade Overview
ASTM / ASME A403 WP316L is a low-carbon molybdenum-bearing austenitic stainless steel — the default grade for welded stainless process piping. The 2–3% molybdenum gives markedly better resistance to pitting and general corrosion than 304/304L, and the low carbon (≤0.035%) prevents sensitization in the heat-affected zone during welding.
316L fittings are supplied IBR approved with Form III-C for boiler and steam service within the applicable limits. The EN counterpart is 1.4404 (X2CrNiMo17-12-2).
✓ No PWHT required — supplied solution annealed
As an austenitic stainless steel, 316L does not require post-weld heat treatment and does not undergo martensitic transformation during welding. Keep inter-pass temperature ≤ 150°C and use a matching ER316L (GTAW) / E316L-16 (SMAW) filler. ASME P-No. 8, Group 1. Passivation per ASTM A967 is available for pharmaceutical and food-grade service.
Chemical Composition — WP316L / 1.4404
| Standard | C | Cr | Ni | Mo | Mn | Si |
|---|---|---|---|---|---|---|
| ASTM A403 WP316L | ≤0.035 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | ≤2.0 | ≤1.0 |
| EN 1.4404 | ≤0.030 | 16.5–18.5 | 10.0–13.0 | 2.0–2.5 | ≤2.0 | ≤1.0 |
Mechanical Properties — WP316L
| Property | Requirement |
|---|---|
| Tensile Strength (min) | 485 MPa (70 ksi) |
| Yield Strength (min) | 170 MPa (25 ksi) |
| Elongation (min) | ≥ 30% |
| Heat Treatment | Solution annealed |
Equivalent Grades
| Product Form | Specification |
|---|---|
| Buttweld fittings | ASTM / ASME A403 WP316L · EN 1.4404 · UNS S31603 |
| Seamless pipe | ASTM A312 TP316L |
| Forgings / flanges | ASTM A182 F316L |
| Plate | ASTM A240 316L |
Fitting Types Available in 316L
- Elbows — 45° / 90° / 180°, LR & SR
- Tees — equal & reducing
- Reducers — concentric & eccentric
- Caps & Stub Ends — closures & lap joints