IBR Approved · Stainless Steel
ASTM A403 WP304L Buttweld Pipe Fittings
Low-carbon 304L (18Cr-8Ni) austenitic stainless steel — the general-purpose grade for food, water, cryogenic and process piping where chlorides are low. Elbows, tees, reducers and caps to ASME B16.9 / B16.28, IBR approved with Form IV (Part D) (formerly Form III-C), EN 10204 3.1 / 3.2 traceable.
Where WP304L Is Used
- ✓ General corrosion-resistant process and utility piping
- ✓ Cryogenic and LNG lines
- ✓ Chemical, water and food-grade piping where low carbon prevents weld sensitisation
WP304L Compared With Related Grades
| Grade | Chemistry | Key difference |
|---|---|---|
| A403 WP304 | 18Cr-8Ni | Higher carbon; can sensitise when welded |
| A403 WP304L | 18Cr-8Ni, low carbon | Resists weld sensitisation; standard for welded systems |
| A403 WP316L | +2–2.5% Mo | Better resistance to chlorides |
| A403 WP321 | Ti-stabilised | For sustained high temperatures |
How to Specify WP304L Fittings on a Purchase Order
A complete order line avoids clarification rounds. Example:
Elbow 90° LR, 3" SCH 10S, ASTM A403 WP304L-S, ASME B16.9, EN 10204 3.1
- ✓ State the class: WP-S (seamless), WP-W or WP-WX (welded)
- ✓ Add an intergranular corrosion test (ASTM A262) if your specification requires it
- ✓ State if you need dual-certified 304/304L material
Grade Overview
ASTM / ASME A403 WP304L is the low-carbon version of 304 — the most widely used austenitic stainless steel. With 18% chromium and 8% nickel and no molybdenum, it offers good general corrosion resistance at an economical cost. The low carbon (≤0.035%) prevents sensitization in the heat-affected zone during welding, making it the standard choice for welded 304-type piping.
304L fittings are supplied IBR approved with Form IV (Part D) for boiler and steam service within the applicable limits. The EN counterpart is 1.4307 (X2CrNi18-9). For chloride-bearing or marine service, specify the molybdenum-bearing grade 316L instead.
✓ No PWHT required — supplied solution annealed
As an austenitic stainless steel, 304L 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 ER308L (GTAW) / E308L-16 (SMAW) filler. ASME P-No. 8, Group 1.
Chemical Composition — WP304L / 1.4307
| Standard | C | Cr | Ni | Mn | Si |
|---|---|---|---|---|---|
| ASTM A403 WP304L | ≤0.035 | 18.0–20.0 | 8.0–12.0 | ≤2.0 | ≤1.0 |
| EN 1.4307 | ≤0.030 | 18.0–20.0 | 8.0–10.5 | ≤2.0 | ≤1.0 |
Mechanical Properties — WP304L
| Property | Requirement |
|---|---|
| Tensile Strength (min) | 485 MPa (70 ksi) |
| Yield Strength (min) | 170 MPa (25 ksi) |
| Elongation (min) | ≥ 35% |
| Heat Treatment | Solution annealed |
Equivalent Grades
| Product Form | Specification |
|---|---|
| Buttweld fittings | ASTM / ASME A403 WP304L · EN 1.4307 · UNS S30403 |
| Seamless pipe | ASTM A312 TP304L |
| Forgings / flanges | ASTM A182 F304L |
| Plate | ASTM A240 304L |
EN 10253 equivalent: see 304L pipe fittings on arshyapipefittings.com, and the European grade EN 1.4307 (X2CrNi18-9).
Fitting Types Available in 304L
- Elbows — 45° / 90° / 180°, LR & SR
- Tees — equal & reducing
- Reducers — concentric & eccentric
- Caps & Stub Ends — closures & lap joints
Related grades: 316L · 321 · Duplex 2205 · Stub ends · IBR grades list · Carbon vs alloy vs stainless
Testing & Inspection — 304L
- Chemical analysis of each heat, confirming low carbon (≤0.030%) for resistance to sensitisation after welding.
- Tensile test to ASTM A403 (485 MPa min. tensile, 170 MPa min. yield) after solution annealing.
- Intergranular corrosion test (ASTM A262) available on request.
- Positive material identification (PMI), and pickling & passivation of the surface.
- Dimensional and visual inspection to ASME B16.9; weld radiography or ultrasonic testing for welded classes as below.
Dimensions & Size Range — ASME B16.9
304L fittings are made to ASME B16.9 (long-radius) and ASME B16.28 (short-radius elbows) dimensions, from 1/2" to 48" NB and above. Wall thickness matches the connecting pipe schedule. Centre-to-end dimensions for the most-ordered sizes:
| NPS | Outside diameter (mm) | 90° LR elbow “A” (mm) | 45° LR elbow “B” (mm) | Equal tee “C” (mm) |
|---|---|---|---|---|
| 1/2" | 21.3 | 38 | 16 | 25 |
| 1" | 33.4 | 38 | 22 | 38 |
| 2" | 60.3 | 76 | 35 | 64 |
| 3" | 88.9 | 114 | 51 | 86 |
| 4" | 114.3 | 152 | 64 | 105 |
| 6" | 168.3 | 229 | 95 | 143 |
| 8" | 219.1 | 305 | 127 | 178 |
| 10" | 273.1 | 381 | 159 | 216 |
| 12" | 323.9 | 457 | 190 | 254 |
| 16" | 406.4 | 610 | 254 | 305 |
| 20" | 508.0 | 762 | 318 | 381 |
| 24" | 610.0 | 914 | 381 | 432 |
Long-radius elbows have a centre-line radius of 1.5 × NPS; short-radius (ASME B16.28) 1.0 × NPS. Full tables to NPS 48, reducing tees, reducers and caps are available with every quotation. For EN 10253 dimensions see arshyapipefittings.com.
Export Documentation & Packing
We ship 304L fittings to projects outside India with the documents EPC contractors and inspection agencies expect:
- Mill test certificate — EN 10204 3.1 as standard; 3.2 with third-party witness
- Third-party inspection — Bureau Veritas, TÜV, Lloyd’s Register, SGS, DNV or the client’s own inspector
- IBR Form IV (Part D) — for boiler piping on Indian Boiler Regulations projects
- Traceability — every fitting marked with grade, size, schedule and heat number, matching the certificate
- Packing — seaworthy wooden cases or pallets, bevel ends protected with end caps
- Shipping documents — commercial invoice, packing list and certificate of origin; FOB, CFR or CIF terms
Send your BOQ through the RFQ form (Excel or PDF attachments accepted) or on WhatsApp — quotations are usually issued within 24 hours.
304L Fittings — Frequently Asked Questions
What is the difference between 304 and 304L?
304L has lower carbon (≤0.030%), which avoids chromium-carbide precipitation in the weld heat-affected zone and the intergranular corrosion that follows. Fittings are often dual-certified 304/304L, meeting the chemistry of 304L and the strength of 304.
What do WP-S, WP-W, WP-WX and CR mean?
They are ASTM A403 classes. WP-S is seamless; WP-W, WP-WX and WP-WU are welded, the suffix showing how the welds are examined (radiography or ultrasonic); CR fittings are made to MSS SP-43 dimensions. State the class you need on your enquiry.
When should I choose 316L instead?
When chlorides are present. 304L has no molybdenum, so its pitting and stress-corrosion resistance in chloride service is lower — see chloride limits by grade and WP316L fittings.