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 III-C, EN 10204 3.1 / 3.2 traceable.
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 III-C. Its EN counterpart is the silicon-bearing grade 13CrMoSi5-5 (material number 1.7337).
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 | 13CrMoSi5-5 (W.Nr. 1.7337) |
Fitting Types Available in WP11
- Elbows — 45° / 90° / 180°, LR & SR
- Tees — equal & reducing
- Reducers — concentric & eccentric
- Caps — buttweld end closures