Which are the two main forging classifications?

• A. Closed die and open die
• B. Rolling and drawing
• C. Casting and forging
• D. Investment and lost foam

Answer: (A)

Forging is classified by how the dies interact with the workpiece during deformation: one method uses dies that do not fully enclose the metal, and the other uses dies that do. In open-die forging, the dies do not completely enclose the workpiece, so the metal is shaped by successive presses or hammers as it is guided between the dies. This is ideal for large parts and simple geometries where customization and control of grain flow along the length are important, such as shafts or rings. In closed-die forging, also called impression-die forging, the workpiece is enclosed by the cavity of two matching dies. As the dies compress, the material fills the cavity and a near-net shape is produced, often with tighter tolerances and the ability to form more complex geometries, though some flash is created and trimmed. This approach is favored for higher-volume production and parts that benefit from strengthened, directionally solidified grain structures.

Other options refer to different manufacturing processes: rolling and drawing are forming operations, while casting methods like investment or lost-foam involve pouring liquid metal into molds.