Forged or Cast? The Difference in Flanges and Valve Bodies

"Would a cast one do?" comes up from time to time on flange orders. The answer depends on the item and where it will work.

What the production route changes

• Forging shapes heated material under pressure. The grain structure follows the geometry and there is almost no internal porosity, which gives high strength and toughness.

• Casting pours molten metal into a mould. Complex shapes can be produced in one piece, which is decisive for valve bodies. However, micro voids and segregation can form during solidification, so the inspection scope widens.

What is standard where

Flanges are standardly forged. Specifications for pressure service normally require A105 or A182. If a cast flange is offered, the production route must be confirmed on the certificate.

On the valve side, forged bodies (A105, F316L) are standard at 2" and below, with cast bodies (WCB, CF8M) above. In small bore high pressure valves, a forged body is safer against fatigue and thermal cycling.

Inspection differences

Radiography and pressure testing matter more on cast bodies, and critical service specifies a casting quality level. On forged parts, ultrasonic inspection and hardness testing come to the fore.

See our forged steel fittings and forged valves pages.

FAQ

Can a cast flange be used?
Specifications for pressure service usually require forged material; if cast is offered, the route must be confirmed on the certificate.

Why are valve bodies mostly cast?
The geometry is complex and casting produces it in one piece, which is economical in larger sizes.

Is forged always better?
It has advantages in strength and internal soundness, but complex shapes need casting. The choice is made item by item.