Carbon Steel Valve Material
General / GeneralDefinition
Carbon steel is the most widely used valve body and component material, covering roughly 70% of all industrial valve applications. It offers a combination of adequate strength, moderate corrosion resistance, good weldability, and low cost that makes it the default choice for oil, gas, water, steam, and general chemical services from -20F to 800F. The principal grades — cast WCB/WCC and forged A105/LF2 — are specified in virtually every valve standard and available from every manufacturer worldwide.
Working Principle
Carbon steel is an iron-carbon alloy with carbon content between 0.05% and 0.35%. The carbon provides strength and hardenability, while the iron matrix gives ductility and toughness. For valve bodies, the steel is cast (WCB, WCC per ASTM A216) or forged (A105 per ASTM A105) into the required shape. Heat treatment (normalizing, quenching and tempering) adjusts mechanical properties for specific service requirements. The 0.3% carbon limit in WCB and A105 ensures adequate weldability without preheat for most applications. For low-temperature service, the chemistry is controlled (LF2 per ASTM A350) and the material is normalized and tempered to maintain Charpy impact toughness at -50F.
Types & Variants
| Grade | Form | Min Temp | Tensile (ksi) | Use |
|---|---|---|---|---|
| A216 WCB | Cast | -20F | 70-95 | General purpose valve bodies |
| A216 WCC | Cast | -20F | 70-95 | Higher-pressure cast bodies |
| A105 | Forged | -20F | 70-95 | Small forged bodies, flanges, fittings |
| A350 LF2 | Forged | -50F | 70-95 | Low-temperature forged components |
| A352 LCC | Cast | -50F | 70-95 | Low-temperature cast bodies |
| A333 Gr 6 | Pipe | -50F | 60 | Low-temperature piping (welded to valve) |
Materials
WCB (A216): 0.30% C max, 1.00% Mn max, 0.60% Si max. Tensile 70-95 ksi, yield 36 ksi min. WCC: higher carbon and manganese for slightly higher strength. A105 (forged): 0.35% C max, 0.60-1.05% Mn, 0.10-0.35% Si. Tensile 70-95 ksi, yield 36 ksi min. LF2 (A350): controlled chemistry for low-temp; Charpy impact tested at -50F. LCC (A352): cast equivalent of LF2 for low-temperature valve bodies. All grades accept weld overlay for seat and stem facing (Stellite, 13Cr).
Applicable Standards
ASTM A216 (cast carbon steel for high-temperature service), ASTM A105 (forged carbon steel fittings and flanges), ASTM A350 (forged carbon steel for low-temperature), ASTM A352 (cast carbon steel for low-temperature). ASME B16.34 defines pressure-temperature ratings for all grades. ASME B31.3 and B31.1 specify allowable stresses for piping design. NACE MR0175/ISO 15156 imposes hardness limits (22 HRC max) for sour service.
Applications
Oil and gas production: WCB gate and ball valves on gathering and transmission lines. Refining: WCB gate, globe, and check valves on crude, naphtha, and product services from ambient to 650F. Power generation: WCB and WC6 valves on boiler feedwater and low-pressure steam. Water treatment: WCB butterfly and gate valves on raw and treated water. HVAC: WCC and A105 valves on chilled and hot water. Any application where the temperature stays below 800F and the corrosion rate of carbon steel is acceptable (typically <5 mpy with appropriate corrosion allowance).
Advantages
- Lowest cost of all metallic valve materials
- Widely available from every valve manufacturer worldwide
- Good mechanical properties for most industrial pressure classes
- Excellent weldability for fabrication and repair
- Well-understood with decades of service history and design data
Disadvantages
- Corrodes in water, acids, and many chemicals without protection
- Not suitable for temperatures above 800F (creep and graphitization)
- Standard grades lose toughness below -20F (use LF2/LCC for low-temp)
- Hardness-limited for sour service (22 HRC per NACE MR0175)
- No inherent corrosion resistance — relies on coatings, inhibitors, or allowan