Chrome-Moly Alloy Steel Flanges & Fittings — F5 to F91
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.
Teshi Group manufactures chrome-moly flanges to ASTM A182 and fittings to ASTM A234, normalised and tempered with recorded furnace charts, and supplies them with IBR certification for boiler service.
Chrome-moly alloy steel — grades, chemistry and properties
Grades and ASTM / ASME specifications
| Grade | Forged flanges & fittings | Butt weld fittings | Plate | Pipe |
|---|---|---|---|---|
| F5 (5Cr-½Mo)UNS K41545 · W.Nr. 1.7362 | ASTM A182 F5 | ASTM A234 WP5 | ASTM A387 Gr 5 | ASTM A335 P5 |
| F9 (9Cr-1Mo)UNS K90941 · W.Nr. 1.7386 | ASTM A182 F9 | ASTM A234 WP9 | ASTM A387 Gr 9 | ASTM A335 P9 |
| 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 |
Chemical composition (weight %, maximum unless a range is given)
| Grade | C | Mn | Si | Cr | Mo | N | Nb | V |
|---|---|---|---|---|---|---|---|---|
| F5 (5Cr-½Mo) | 0.15 | 0.30–0.60 | 0.50 | 4.0–6.0 | 0.44–0.65 | — | — | — |
| F9 (9Cr-1Mo) | 0.15 | 0.30–0.60 | 0.50–1.00 | 8.0–10.0 | 0.90–1.10 | — | — | — |
| 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 (minimum, room temperature)
| Grade | Tensile strength | Yield strength (0.2 %) | Elongation | Note |
|---|---|---|---|---|
| F5 (5Cr-½Mo) | 485 MPa (70 ksi) | 275 MPa (40 ksi) | 20 % | Refinery heaters |
| F9 (9Cr-1Mo) | 585 MPa (85 ksi) | 380 MPa (55 ksi) | 20 % | Hydrogen service |
| 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 |
Values are minimums and limits from the governing ASTM / ASME specifications, summarised for convenience. The current edition of the specification takes precedence; confirm requirements against your project specification.
Where it 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
Chrome-moly alloy steel products we manufacture
All products
01OEM manufacturerWeld Neck Flanges
ASME B16.5 · ASME B16.47
02OEM manufacturerBlind Flanges
ASME B16.5 · ASME B16.47
03OEM manufacturerSlip-On Flanges
ASME B16.5 · EN 1092-1 Type 12
04OEM manufacturerButt Weld Elbows
ASME B16.9 · ASME B16.25
05OEM manufacturerButt Weld Tees
ASME B16.9 · ASME B16.25
06OEM manufacturerWeldolets & Sockolets
MSS SP-97 · ASME B16.11
Industries and projects
Power Generation
Where Chrome-moly alloy steel is specified
ViewIndustrySteel & Metals
Where Chrome-moly alloy steel is specified
ViewIndustryRefining
Where Chrome-moly alloy steel is specified
ViewProjectsMega-projects & EPC supply
Project BOQs, shutdowns and annual rate contracts
ViewGrade data sheets
Other materials
Chrome-moly alloy steel by product
FAQ
Chrome-moly alloy steel: common questions
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.
Can Teshi Group supply IBR-certified alloy steel flanges?
Yes. Teshi Group is IBR approved and supplies chrome-moly flanges and fittings with IBR certification for boiler and steam service when the order requires it.
Where are chrome-moly fittings used in steel plants?
In blast-furnace hot-blast stoves and mains, waste-heat recovery and captive power plant steam lines, where temperatures exceed the limits of carbon steel.
Chrome-moly alloy steel grade data sheets
Chrome-moly alloy steel overview →Chemical composition, mechanical properties and PDF data sheet for each grade.
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