WCB vs WCC Valve Body: Carbon Steel Casting Grades Explained

The Short Answer

WCB and WCC are both carbon steel casting grades covered by ASTM A216, widely used for valve bodies in general industrial service. They share the same nominal chemical limits in most respects, but WCC has slightly higher strength requirements at low temperatures. The practical difference is usually seen in minimum service temperature: WCC is commonly specified when better low-temperature toughness is required, while WCB covers the majority of standard carbon steel valve body applications.

What Each Designation Means

WCB

WCB (Weldable Cast Carbon, Grade B) is the standard carbon steel casting grade for valve bodies, flanges, and fittings in non-corrosive and mildly corrosive services. It offers good weldability and moderate strength, and it is the default body material for many gate, globe, and check valves in water, steam, oil, and gas service. The maximum service temperature is generally limited by carbon steel behavior, and the minimum temperature is often set around -20°F for standard WCB, although exact limits depend on the design code and impact test requirements.

WCC

WCC is the higher-strength companion grade in ASTM A216. Its tensile and yield requirements are slightly higher than WCB, and it is frequently specified for low-temperature service, typically down to about -50°F in common practice, subject to Charpy impact testing. WCC is a common choice for valve bodies in cold-climate plants, liquefied gas systems, and offshore facilities where the design temperature falls below the WCB limit.

Key Differences

Property	WCB	WCC
Standard	ASTM A216	ASTM A216
Type	Cast carbon steel	Cast carbon steel
Minimum tensile strength	~70 ksi (data needs further verification per edition)	~70 ksi (data needs further verification per edition)
Yield strength requirement	Base level	Slightly higher
Common low-temperature limit	Often around -20°F with impact testing	Often around -50°F with impact testing
Typical service	Water, steam, oil, gas general service	Cold climate, liquefied gas, offshore
Weldability	Good	Good

Which to Choose

For standard plant service at ambient and moderate temperatures, WCB is the economical default and covers most applications. When the design minimum temperature drops below the WCB limit, or when the project specification requires improved low-temperature toughness, WCC is generally specified. The selection is often written directly into the valve specification by the engineering contractor, based on the minimum design metal temperature and the applicable pressure vessel or piping code.

Common Misconceptions

A frequent misconception is that WCC is “stronger” in a practical sense and therefore always better. In reality the strength difference is modest, and the main reason to choose WCC is low-temperature toughness, not higher pressure capability. Another misconception is that WCB cannot be used below freezing at all; many codes allow WCB to specific low temperatures provided Charpy impact testing is performed. The governing factor is the design code and the impact test requirement, not a universal temperature number.

Practical Recommendation

Confirm the minimum design metal temperature (MDMT) from the process data, then match the casting grade to the code requirement. If the MDMT is near or below the WCB limit, specify WCC with impact testing. For most other services, WCB keeps cost down without sacrificing reliability. Verify the material designation, heat treatment, and test reports on the valve nameplate and documentation. For related material comparisons, see our article on CF8M vs CF3M valve bodies and the materials guidance in the valve selection guides.

Conclusion

WCB and WCC are closely related carbon steel casting grades that differ mainly in strength requirements and low-temperature toughness. Select WCB for standard service and WCC when the design temperature demands better impact properties. The designation on the casting tells only part of the story; heat treatment and impact test reports complete it.

This article provides general educational knowledge only and is not professional engineering advice.

Sources & Further Reading

ASTM A216 (Standard Specification for Steel Castings, Carbon, Suitable for Fusion Welding for High-Temperature Service); ASME B16.34 (valve pressure-temperature ratings).

Tags: Valve Materials