In open-die forging, two dies having simple geometric shapes are employed, normally on large workpieces.

• A. It uses two dies with simple geometric shapes and is used for large workpieces
• B. It uses a wax pattern and investment mold
• C. It uses a two-piece permanent mold
• D. It uses dies with complex curved shapes

Answer: (B)

Open-die forging relies on two dies with simple, flat or basic shapes, letting the metal flow and deform while the dies stay apart, which makes it suitable for forming large workpieces. The description that mentions a wax pattern and investment mold, however, is characteristic of investment casting, where a wax replica is coated with ceramic material to form a mold, the wax is melted away, and metal is poured into the mold. That process is different from forging and does not involve two simple dies shaping the workpiece. The other options point to related but distinct processes: a two-piece permanent mold corresponds to permanent-mold (die-casting-like) processes, and dies with complex curved shapes are typical of closed-die or impression forging, not open-die. The concept being tested is distinguishing forging from casting methods and recognizing that open-die forging uses simple dies for large parts, while investment casting uses wax patterns and investment molds.