ASTM A216 WCB: Cast Carbon Steel
ASTM A216 WCB is the most widely used cast carbon steel grade for pressure-containing components in oil and gas, petrochemical, and power generation piping systems. The “W” designates weldable quality, “C” indicates carbon steel, and “B” identifies the specific grade level within the A216 specification.
| Property | Value |
|---|---|
| Specification | ASTM A216 / ASME SA-216 |
| Grade | WCB |
| Material type | Cast carbon steel |
| Carbon content | 0.30% max |
| Manganese | 1.00% max |
| Silicon | 0.60% max |
| Sulfur | 0.045% max |
| Phosphorus | 0.04% max |
| Tensile strength | 485-655 MPa (70-95 ksi) |
| Yield strength | 250 MPa min (36 ksi) |
| Elongation | 22% min (in 2 inches) |
| Temperature range | -29°C to 425°C (-20°F to 800°F) |
| Heat treatment | Normalized, normalized and tempered, or quenched and tempered |
Chemical Composition and Mechanical Properties
ASTM A216 covers three grades: WCA, WCB, and WCC. WCB occupies the middle ground, offering higher strength than WCA while maintaining good weldability. The carbon content is capped at 0.30%, which balances hardness with ductility and keeps the material weldable without mandatory preheat in many applications.
WCB is the cast equivalent of ASTM A105 forged steel. Both serve carbon steel piping systems operating at ambient to moderately elevated temperatures. The key distinction is manufacturing method: WCB components are cast (molten steel poured into molds), while A105 parts are forged from solid billets.
Where ASTM A216 WCB Is Used
WCB dominates cast valve body specifications for standard service conditions:
- Gate, globe, and check valve bodies per API 600, API 602, and BS 1868
- Ball valve bodies per API 6D and API 608
- Valve bonnets and covers for pressure classes 150 through 2500
- Cast fittings and flanges where casting is more economical than forging
The material pairs with ASTM A105 forged components (flanges, small-bore valves) and carbon steel pipes in grades A106 B, A53, and API 5L.
Temperature Limits
WCB is rated for service from -29°C to 425°C. Below -29°C, impact toughness degrades and the specification requires ASTM A352 LCB for low-temperature service. Above 425°C, creep becomes a concern and alloy steel castings per ASTM A217 (WC6, WC9, C5) are required.
Testing and Quality
ASTM A216 requires chemical analysis, mechanical testing (tensile and yield), and visual examination of all castings. Supplementary requirements include radiographic examination (S1), magnetic particle inspection (S5), and hydrostatic testing per the applicable valve standard. All castings must be supplied with mill test certificates per EN 10204 3.1 or 3.2.
For sour service (H2S environments), WCB castings must comply with NACE MR0175 hardness limits (22 HRC max) and may require supplementary NDT.
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