What Is A182 F22? 2.25Cr-1Mo Forged Steel
When to Specify A182 F22
ASTM A182 Grade F22 is a 2-1/4 chromium, 1 molybdenum (2.25Cr-1Mo) forged alloy steel for flanges, fittings, and valve components operating up to 595°C (1100°F). F22 is the workhorse chrome-moly forging grade for refinery hydroprocessing units and power plant high-temperature steam systems where F11 (1.25Cr-0.5Mo) lacks sufficient creep strength or hydrogen attack resistance.
| Property | A182 F22 Class 3 |
|---|---|
| Specification | ASTM A182 / ASME SA-182 |
| UNS designation | K21590 |
| Alloy system | 2-1/4Cr-1Mo |
| Carbon | 0.05-0.15% |
| Chromium | 2.00-2.50% |
| Molybdenum | 0.87-1.13% |
| Manganese | 0.30-0.60% |
| Silicon | 0.50% max |
| Tensile strength (min) | 515 MPa (75 ksi) |
| Yield strength (min) | 310 MPa (45 ksi) |
| Elongation (min) | 20% |
| Reduction of area (min) | 30% |
| Hardness (max) | 235 HBW (Class 3) |
| Max service temp | 595°C (1100°F) |
| Heat treatment | Normalize + temper, or quench + temper |
| Matching pipe | ASTM A335 P22 |
| Cast equivalent | ASTM A217 WC9 |
F22 Class Designations
| Class | Tensile (min) | Yield (min) | Hardness (max) | Usage |
|---|---|---|---|---|
| Class 1 | 415 MPa (60 ksi) | 205 MPa (30 ksi) | 170 HBW | Rarely specified |
| Class 3 | 515 MPa (75 ksi) | 310 MPa (45 ksi) | 235 HBW | Standard for piping |
Class 3 is the default for virtually all piping applications. It provides higher allowable stress values for pressure design per ASME B31.3 and ASME B16.5.
Hydrogen Attack Resistance
The primary advantage of F22 over F11 in refinery service is resistance to high-temperature hydrogen attack (HTHA). Per API 941 (Nelson curves), 2.25Cr-1Mo operates safely at higher hydrogen partial pressures and temperatures than 1.25Cr-0.5Mo. This makes F22 the standard forging material for:
- Hydrotreater and hydrocracker reactor flanges and nozzle forgings
- Hydrogen recycle compressor piping flanges
- HP separator and hot flash drum nozzle connections
- Reformer outlet piping flanges
Applications
F22 pairs with A335 P22 seamless pipe, A234 WP22 buttweld fittings, and A217 WC9 cast valve bodies. All components in a 2.25Cr-1Mo piping class must match to avoid dissimilar-metal weld complications.
Testing and Welding
All F22 forgings require heat treatment (normalize + temper or quench + temper). Mill test certificates per EN 10204 3.1 document chemistry, mechanical properties, and heat treatment condition. NDT (UT, MT) and hydrostatic testing follow the applicable flange or fitting standard. Welding requires preheat (200-250°C minimum), matching E/ER 9018-B3 filler metals, and mandatory PWHT at 690-750°C. The forging process ensures uniform grain structure and mechanical properties essential for high-temperature cycling service.
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