Alloy Steel WP11 / WP22 / WP91 Pipe Fittings
Teshi Group manufactures Alloy Steel WP11 / WP22 / WP91 pipe fittings (ASTM A234 WP11, WP22, WP91, chrome-moly fittings) as an OEM in India — butt weld fittings to ASME B16.9 and forged socket weld and threaded fittings to ASME B16.11, with heat-number traceability on every piece.
Chromium–molybdenum steels keep their strength and resist creep and hydrogen attack at high temperature, which makes them standard for steam, boiler, refinery heater and hot-blast service.
Alloy Steel WP11 / WP22 / WP91 pipe fittings at a glance
| Material | Alloy Steel WP11 / WP22 / WP91 |
|---|---|
| Specification | Butt weld: ASTM A234 WP11 Cl.1 / ASTM A234 WP22 Cl.1 / ASTM A234 WP91 · Forged: ASTM A182 F11 Cl.2 / ASTM A182 F22 Cl.3 / ASTM A182 F91 |
| UNS / W.Nr. | K11572 / 1.7335 · K21590 / 1.7380 · K90901 / 1.4903 |
| Sizes | Butt weld NPS ½"–48", Sch 5S–XXS · Forged NPS ⅛"–4" |
| Pressure class | Wall to pipe schedule (B16.9) · Class 2000, 3000, 6000, 9000 (B16.11) |
| Facing / ends | Bevelled ends to ASME B16.25; socket weld and NPT threaded ends |
| Certification | EN 10204 3.1 standard · 3.2 with third-party inspection · IBR on request |
| Testing | PMI, hardness, dimensional; UT, IGC, impact and ferrite as specified |
Alloy Steel WP11 / WP22 / WP91 chemistry and mechanical properties
Chemical composition of Alloy Steel WP11 / WP22 / WP91 (weight %, maximum unless a range)
| Grade | C | Mn | Si | Cr | Mo | N | Nb | V |
|---|---|---|---|---|---|---|---|---|
| F11 Cl.2 (1¼Cr-½Mo) | 0.10–0.20 | 0.30–0.80 | 0.50–1.00 | 1.00–1.50 | 0.44–0.65 | — | — | — |
| F22 Cl.3 (2¼Cr-1Mo) | 0.05–0.15 | 0.30–0.60 | 0.50 | 2.00–2.50 | 0.87–1.13 | — | — | — |
| F91 (9Cr-1Mo-V) | 0.08–0.12 | — | — | 8.0–9.5 | 0.85–1.05 | 0.03–0.07 | 0.06–0.10 | 0.18–0.25 |
Mechanical properties of Alloy Steel WP11 / WP22 / WP91 (minimum, room temperature)
| Grade | Tensile strength | Yield strength (0.2 %) | Elongation | Note |
|---|---|---|---|---|
| F11 Cl.2 (1¼Cr-½Mo) | 485 MPa (70 ksi) | 275 MPa (40 ksi) | 20 % | Steam lines |
| F22 Cl.3 (2¼Cr-1Mo) | 515 MPa (75 ksi) | 310 MPa (45 ksi) | 20 % | Boiler headers |
| F91 (9Cr-1Mo-V) | 585 MPa (85 ksi) | 415 MPa (60 ksi) | 20 % | Supercritical boilers |
Matching specifications by product form
| Grade | Forged flanges & fittings | Butt weld fittings | Plate | Pipe |
|---|---|---|---|---|
| F11 Cl.2 (1¼Cr-½Mo)UNS K11572 · W.Nr. 1.7335 | ASTM A182 F11 Cl.2 | ASTM A234 WP11 Cl.1 | ASTM A387 Gr 11 | ASTM A335 P11 |
| F22 Cl.3 (2¼Cr-1Mo)UNS K21590 · W.Nr. 1.7380 | ASTM A182 F22 Cl.3 | ASTM A234 WP22 Cl.1 | ASTM A387 Gr 22 | ASTM A335 P22 |
| F91 (9Cr-1Mo-V)UNS K90901 · W.Nr. 1.4903 | ASTM A182 F91 | ASTM A234 WP91 | ASTM A387 Gr 91 | ASTM A335 P91 |
Limits and minimums from the governing ASTM / ASME specifications, summarised for convenience; the current edition takes precedence.
Pressure rating
Butt weld fittings carry the same pressure rating as straight seamless pipe of the same material and wall thickness, so the fitting schedule is matched to the line pipe (ASME B16.9). Forged socket weld and threaded fittings are rated by class — 3000 and 6000 for socket weld, 2000, 3000 and 6000 for threaded — per ASME B16.11.
Types we manufacture
Dimension charts
Where Alloy Steel WP11 / WP22 / WP91 is used
- Boiler, superheater and steam headers (IBR)
- Supercritical and ultra-supercritical power plants (F91)
- Blast-furnace hot-blast stoves and mains
- Refinery heaters and hydrogen service
- Petrochemical high-temperature lines
Testing & certification
- Normalised and tempered with recorded furnace charts
- Hardness testing of every heat treatment lot
- UT and MPI as specified; PMI on every piece
- IBR Form III-C certification when specified
Related materials
FAQ
Alloy Steel WP11 / WP22 / WP91 pipe fittings: common questions
What specification covers Alloy Steel WP11 / WP22 / WP91 pipe fittings?
Alloy Steel WP11 / WP22 / WP91 butt weld fittings are made to ASTM A234 WP11 Cl.1 / ASTM A234 WP22 Cl.1 / ASTM A234 WP91 with dimensions to ASME B16.9; forged socket weld and threaded fittings are made to ASTM A182 F11 Cl.2 / ASTM A182 F22 Cl.3 / ASTM A182 F91 with dimensions to ASME B16.11.
What is the chemical composition of F11 Cl.2 (1¼Cr-½Mo)?
F11 Cl.2 (1¼Cr-½Mo) (UNS K11572): C 0.10–0.20, Mn 0.30–0.80, Si 0.50–1.00, Cr 1.00–1.50, Mo 0.44–0.65 (weight %; single values are maximums).
What are the minimum mechanical properties of F11 Cl.2 (1¼Cr-½Mo)?
Tensile strength 485 MPa (70 ksi), yield strength 275 MPa (40 ksi), elongation 20 %.
Is Teshi Group a manufacturer of Alloy Steel WP11 / WP22 / WP91 pipe fittings in India?
Yes. Teshi Group has manufactured flanges and fittings in India since 1971 and is ISO 9001:2015 certified and IBR approved. Every Alloy Steel WP11 / WP22 / WP91 piece is hard-stamped with its heat number and supplied with an EN 10204 3.1 certificate; 3.2 with third-party inspection on request.
Which chrome-moly grade is used for steam lines?
F11 (1¼Cr-½Mo) and F22 (2¼Cr-1Mo) are the common grades for steam and boiler lines; F91 (9Cr-1Mo-V) is used in supercritical and ultra-supercritical power plants for its creep strength.
How are F91 flanges heat treated?
F91 is normalised and tempered, typically normalised around 1040–1080 °C and tempered at 730–800 °C, with recorded furnace charts and hardness checks on every lot.
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