Quick Answer
WCB is the workhorse cast carbon steel grade of ASTM A216, used for valve bodies, pump casings, flanges and general pressure-containing parts at moderate temperatures. It offers 485–655 MPa tensile strength, good weldability, and low cost. If a drawing says “cast steel” with no grade, WCB is almost always what the designer meant — but a proper RFQ should state ASTM A216 Grade WCB explicitly.
Chemical Composition (ASTM A216 WCB)
| Element | Limit |
|---|---|
| Carbon | ≤ 0.30% |
| Manganese | ≤ 1.00% |
| Silicon | ≤ 0.60% |
| Phosphorus | ≤ 0.035% |
| Sulfur | ≤ 0.035% |
| Residuals (Cu, Ni, Cr, Mo, V) | Individually limited; total ≤ 1.00% |
The standard also ties carbon and manganese together: for each 0.01% carbon below the maximum, an increase of 0.04% manganese above the limit is allowed, up to 1.28%. Foundries use this flexibility to balance strength and weldability heat by heat.
Mechanical Properties
| Property | Requirement |
|---|---|
| Tensile strength | 485–655 MPa (70–95 ksi) |
| Yield strength, min | 250 MPa (36 ksi) |
| Elongation in 50 mm, min | 22% |
| Reduction of area, min | 35% |
WCA vs WCB vs WCC: Picking Within A216
| Grade | Tensile (MPa) | Yield min (MPa) | When to use |
|---|---|---|---|
| WCA | 415–585 | 205 | Maximum weldability, lower-stress parts |
| WCB | 485–655 | 250 | Default general-purpose grade |
| WCC | 485–655 | 275 | Higher yield at same tensile; heavier-duty valves |
WCC gets its extra yield strength from a higher allowed manganese content at lower carbon — which also makes it slightly more weld-friendly than WCB at equal strength. Many valve OEMs have quietly standardized on WCC for exactly that reason.
Heat Treatment and Condition of Supply
A216 castings are supplied heat treated — normalized, or normalized and tempered, or annealed. Normalizing refines the as-cast grain structure and brings mechanical properties into specification. If your application involves post-weld heat treatment or specific hardness windows for machining, state that in the purchase order rather than assuming the foundry default.
What It Costs and How It’s Cast
WCB is among the least expensive cast steels. For small and medium parts with good surface finish requirements, it is commonly poured through investment casting; larger or simpler geometry runs through sand casting at lower tooling cost. Typical applications we cast at YCUMETAL include valve bodies and bonnets, pump casings, pipeline components and structural machinery parts.
Specifying WCB in an RFQ: Checklist
- Call out ASTM A216 Grade WCB (or WCC if you need the higher yield)
- State service temperature; A216 covers moderate temperatures — for low-temperature toughness requirements look at ASTM A352 grades instead
- Require chemical and mechanical certificates per heat
- Specify NDT level if pressure-containing: visual only, or MPI, or radiography on critical sections
- Note welding plans so carbon equivalent can be managed
FAQ
Is WCB the same as mild steel?
Close in chemistry, but WCB is a casting grade with its own certification requirements. Calling it “mild steel casting” on a drawing invites ambiguity.
Can WCB be welded?
Yes, readily — that is one reason it dominates valve manufacturing. Repair welding at the foundry is also permitted by the standard under qualified procedures.
What is the WCB service temperature range?
Commonly applied from about −29°C up to roughly 425°C in pressure service. Outside that window, low-temperature (A352) or elevated-temperature grades are the correct choice.
WCB vs LCB — what’s the difference?
LCB is the low-temperature counterpart from ASTM A352, impact tested at −46°C. Same general chemistry family, different toughness guarantee.