IBR Approved · Alloy Steel (CrMo)
ASTM A234 WP11 Buttweld Pipe Fittings
1.25Cr-0.5Mo-Si chromium-molybdenum alloy steel fittings for boiler headers, superheater and reheater piping to ~580°C. 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 WP11 Is Used
- ✓ Boiler headers and superheater and reheater piping
- ✓ Steam lines in power and process plants
- ✓ Refinery fired-heater and process piping at elevated temperature
WP11 Compared With Related Grades
| Grade | Chemistry | Key difference |
|---|---|---|
| A234 WP12 | 1Cr-½Mo | Lower silicon; often specified alongside WP11 |
| A234 WP11 | 1¼Cr-½Mo-Si | Silicon 0.50–1.00% for better oxidation resistance |
| A234 WP22 | 2¼Cr-1Mo | Higher chromium and molybdenum for higher temperatures |
| A234 WP5 | 5Cr-½Mo | More chromium for hydrogen and sulphur-bearing refinery service |
How to Specify WP11 Fittings on a Purchase Order
A complete order line avoids clarification rounds. Example:
Equal tee, 6" SCH 80, ASTM A234 WP11 Class 1, ASME B16.9, IBR Form IV (Part D), EN 10204 3.1
- ✓ State Class 1 or Class 2 (different strength levels)
- ✓ Ask for the heat treatment record and hardness results
- ✓ Add IBR Form IV (Part D) for Indian boiler piping
Grade Overview
ASTM / ASME A234 WP11 is a 1.25Cr-0.5Mo-Si chromium-molybdenum alloy steel for wrought buttweld fittings in elevated-temperature service. The chromium and molybdenum give significantly better creep strength and oxidation resistance than carbon steel above 450°C, while the silicon addition improves scale resistance. It is the entry grade of the CrMo alloy ladder, used up to approximately 580°C.
For boiler and steam piping under the Indian Boiler Regulations, WP11 fittings are supplied IBR approved with Form IV (Part D). Its EN counterpart is the silicon-bearing grade 10CrMo5-5 (material number 1.7338).
PWHT is mandatory
All WP11 welds require post-weld heat treatment, typically 690–730°C, to temper the hardened heat-affected zone and avoid hydrogen cracking. Post-PWHT hardness and the time-temperature record are reported on the EN 10204 3.1 certificate. Filler metal: ER80S-B2 (GTAW) / E8018-B2 (SMAW). ASME P-No. 4.
Chemical Composition — A234 WP11
| Element | Requirement | Note |
|---|---|---|
| Carbon (C) | 0.05 – 0.15% | Weldability |
| Manganese (Mn) | 0.30 – 0.60% | — |
| Silicon (Si) | 0.50 – 1.00% | Oxidation / scale resistance |
| Chromium (Cr) | 1.00 – 1.50% | Creep & oxidation |
| Molybdenum (Mo) | 0.44 – 0.65% | Creep resistance |
| P / S | ≤ 0.030% each | Impurity limits |
Mechanical Properties — A234 WP11 (Class 1)
| Property | Requirement |
|---|---|
| Tensile Strength | 415 – 585 MPa (60 – 85 ksi) |
| Yield Strength (min) | 205 MPa (30 ksi) |
| Elongation (min) | ≥ 20% (per specification formula) |
| Heat Treatment | Annealed or normalised & tempered; PWHT after welding |
Equivalent Grades
| Product Form | Specification |
|---|---|
| Buttweld fittings | ASTM / ASME A234 WP11 |
| Seamless pipe | ASTM A335 P11 |
| Forgings / flanges | ASTM A182 F11 |
| EN designation | 10CrMo5-5 (W.Nr. 1.7338) |
EN 10253 equivalent: see WP11 pipe fittings on arshyapipefittings.com, and the European grade EN 1.7338 (10CrMo5-5).
Fitting Types Available in WP11
- Elbows — 45° / 90° / 180°, LR & SR
- Tees — equal & reducing
- Reducers — concentric & eccentric
- Caps — buttweld end closures
Related grades: WP22 · WP5 · WP91 · IBR Form IV (Part D) guide · IBR grades list · Carbon vs alloy vs stainless
Testing & Inspection — WP11
- Chemical analysis of each heat, confirming 1.25Cr-0.5Mo with the silicon addition that improves oxidation resistance.
- Tensile and hardness tests to ASTM A234 for the class ordered (Class 1 shown above; Class 2 and 3 on request).
- Positive material identification (PMI) to confirm chromium and molybdenum and prevent mix-ups with carbon steel or WP22.
- Dimensional and visual inspection to ASME B16.9; NDE (MT / UT / RT) as specified in your purchase order.
Dimensions & Size Range — ASME B16.9
WP11 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, in schedules SCH 20 to SCH 160 / XXS. 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 WP11 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.
WP11 Fittings — Frequently Asked Questions
What is the difference between WP11 Class 1, 2 and 3?
The chemistry is the same; the classes differ in strength. Per ASTM A234: Class 1 — 415–585 MPa tensile, 205 MPa min. yield; Class 2 — 485–655 MPa tensile, 275 MPa yield; Class 3 — 520–690 MPa tensile, 310 MPa yield. Specify the class on your enquiry.
How does WP11 compare with WP22?
WP11 (1.25Cr-0.5Mo) suits boiler and steam lines at moderate temperatures. WP22 (2.25Cr-1Mo) has higher creep strength and better resistance to high-temperature hydrogen, so it is preferred in hydroprocessing and hotter steam service. See P11 and P22 in boiler and steam service.
Is post-weld heat treatment required for WP11?
Yes — PWHT at 690–730°C is mandatory after welding to temper the heat-affected zone and relieve stresses.