Forged vs Cast Valve: Material Selection

Quick Answer

Forged valves are manufactured by shaping solid steel billets under heat and pressure. Cast valves are manufactured by pouring molten metal into molds. Forged valves have a denser, stronger microstructure and are standard for small-bore, high-pressure, and critical services. Cast valves are used for larger sizes where forging is impractical or uneconomical.

Details

The body manufacturing method is one of the most important factors in valve selection. It determines the valve’s mechanical properties, defect susceptibility, size range, and applicable standards.

Forged valves start from a solid steel billet that is heated and shaped under compressive force (die forging, hammer forging, or press forging). The forging process refines the grain structure, eliminates porosity, and produces a body with superior mechanical strength and fatigue resistance. Forged valves are specified per API 602 (gate, globe, check) and API 608 (ball).

Cast valves start from molten steel poured into a sand mold or investment casting shell. Casting allows complex body geometries and large sizes that cannot be forged. However, casting introduces the risk of porosity, shrinkage cavities, and inclusions that must be detected by radiography (RT) or ultrasonic testing (UT). Cast valves are specified per API 600 (gate), API 623 (globe), BS 1868 (check), and API 6D.

Comparison Table

Parameter	Forged Valve	Cast Valve
Manufacturing	Billet shaped by compressive force	Molten metal poured into mold
Grain structure	Dense, uniform, refined	Dendritic, may have porosity
Mechanical strength	Higher (superior yield and tensile)	Lower (cast structure)
Defect risk	Low (no porosity)	Higher (shrinkage, porosity, inclusions)
NDE requirements	VT, MT/PT (surface only)	RT or UT (volumetric, per ASME B16.34)
Size range	1/4” to 4” (typically up to 2”)	2” to 60”+
Pressure classes	150-2500, plus Class 800	150-2500
End connections	Threaded, socket weld, butt-weld	Flanged, butt-weld, pressure-seal
Standards	API 602, API 608	API 600, API 623, BS 1868, API 6D
Body materials (CS)	ASTM A105	ASTM A216 WCB/WCC
Body materials (SS)	ASTM A182 F304/F316	ASTM A351 CF8/CF8M
Cost (small bore)	Baseline	More expensive (casting mold + NDE)
Cost (large bore)	Not available	Baseline
Lead time	Shorter (standard sizes in stock)	Longer (casting + machining + NDE)
Weight	Compact (thick walls, small bore)	Heavier (larger body)

When to Specify Each

Forged: all small-bore isolation valves (1/2” to 2”), Class 800 socket weld and threaded valves, high-pressure applications, critical services (sour gas, high-temperature hydrogen), and any application where superior body integrity is required.

Cast: all valves above 4” (where forging is impractical), large-diameter pipeline valves, flanged process valves, and moderate-pressure applications where casting defects are controlled by radiographic inspection.

In the 2” to 4” overlap zone, forged valves are preferred for socket weld and threaded connections, while cast valves are standard for flanged connections.

Common Mistake

Accepting a cast valve for a small-bore high-pressure application (e.g., 1” Class 1500 socket weld) to save cost. Cast valves in these sizes are more expensive (due to casting and NDE costs) and less reliable than forged valves. API 602 forged valves are both cheaper and stronger for small-bore service.

For a detailed comparison of cast and forged steel properties, see the guide to cast vs forged steel making.

Read the full guide to valve types