What Is ASTM A217? Cast Alloy Steel
ASTM A217 covers cast alloy steel grades for valve bodies, flanges, and fittings designed for high-temperature and high-pressure service. These chrome-moly and chrome-moly-vanadium castings operate where standard carbon steel (ASTM A216 WCB) loses strength due to creep.
| Grade | Alloy System | Cr | Mo | Max Service Temp | Forged Equivalent |
|---|---|---|---|---|---|
| WC1 | C-1/2Mo | - | 0.45-0.65% | 455°C (850°F) | A182 F1 |
| WC6 | 1-1/4Cr-1/2Mo | 1.0-1.5% | 0.45-0.65% | 565°C (1050°F) | A182 F11 |
| WC9 | 2-1/4Cr-1Mo | 2.0-2.75% | 0.9-1.2% | 595°C (1100°F) | A182 F22 |
| C5 | 5Cr-1/2Mo | 4.0-6.5% | 0.45-0.65% | 650°C (1200°F) | A182 F5 |
| C12 | 9Cr-1Mo | 8.0-10.0% | 0.9-1.2% | 650°C (1200°F) | A182 F9 |
| C12A | 9Cr-1Mo-V | 8.0-9.5% | 0.85-1.05% | 650°C (1200°F) | A182 F91 |
Grade Selection by Service Temperature
The chromium content determines oxidation and sulfidation resistance at elevated temperatures. Molybdenum provides creep strength. Higher chrome grades resist high-temperature corrosion better but cost more.
WC6 (1-1/4Cr-1/2Mo) is the workhorse for steam service and hydrocarbon processing between 425°C and 565°C. It pairs with ASTM A335 P11 pipes and A182 F11 forged fittings and flanges.
WC9 (2-1/4Cr-1Mo) handles higher temperatures up to 595°C and provides better resistance to hydrogen attack in refinery hydroprocessing units. It matches A335 P22 pipe and A182 F22 forgings.
C5 (5Cr-1/2Mo) and C12 (9Cr-1Mo) serve the highest-temperature applications in power generation and refinery heater circuits, where superior sulfidation resistance is critical.
Mechanical Properties
| Grade | Tensile (min) | Yield (min) | Elongation (min) | Heat Treatment |
|---|---|---|---|---|
| WC6 | 485 MPa (70 ksi) | 275 MPa (40 ksi) | 20% | Normalize + temper, or Q&T |
| WC9 | 485 MPa (70 ksi) | 275 MPa (40 ksi) | 20% | Normalize + temper, or Q&T |
| C5 | 485 MPa (70 ksi) | 275 MPa (40 ksi) | 20% | Normalize + temper, or Q&T |
| C12 | 620 MPa (90 ksi) | 415 MPa (60 ksi) | 18% | Normalize + temper, or Q&T |
All grades require heat treatment. The normalize-and-temper cycle refines grain structure and relieves residual casting stresses. Quench-and-temper may be used for thicker sections where through-hardening is needed.
Typical Applications
- Refinery units: FCC, hydrocracker, reformer, and coker valve bodies operating above 425°C
- Power plants: main steam and hot reheat valve bodies in fossil and combined-cycle plants
- Petrochemical: ethylene cracker transfer line valves, high-temperature reactor outlet piping
Quality and Testing
ASTM A217 mandates chemical analysis, tensile testing, and heat treatment documentation. Supplementary requirements cover radiographic examination, magnetic particle inspection, and Charpy impact testing when specified. Valve castings must be hydrostatically tested per ASME B16.34 or the applicable API standard. Mill test certificates per EN 10204 3.1 are standard; 3.2 certificates with third-party witness are common for critical services.
The casting process for alloy grades requires tighter foundry controls than carbon steel to manage segregation of chromium and molybdenum during solidification.
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