1. Open-Die Forging

Open-die forging is a forming method in which the metal billet is deformed under impact or compressive force between upper and lower dies. The billet is allowed to flow freely in the horizontal direction.

Process Characteristics

• Simple equipment: Forging hammers, hydraulic presses and other equipment are adopted with low investment cost.
• High flexibility: Parts of various shapes such as shafts, rings and cylinders can be forged.
• Low precision: The shape and dimension are controlled mainly by manual operation. It is suitable for small-batch production or large forgings (e.g. large generator rotors).

Typical Applications

Large shaft components (such as crankshafts), gear blanks, flanges, etc.

2. Closed-Die Forging

In closed-die forging, the metal billet is deformed under compressive or impact force inside the die cavity, and finally forms a forging consistent with the cavity profile.

Classification and Characteristics

Hammer Forging

• Equipment: Steam-air hammers, electro-hydraulic hammers, etc.
• Features: High production efficiency and relatively good forging precision for medium and small batch production; high vibration and noise.
• Applications: Automobile engine connecting rods, gears, etc.

Hot Forging Press Forging

• Equipment: Mechanical presses (e.g. crank presses), hydraulic presses.
• Features: High dimensional accuracy and good surface finish of forgings for mass production; high die cost and not suitable for complex-shaped forgings.
• Applications: Automobile wheel hubs, bearing rings, etc.

Screw Press Forging

• Equipment: Screw press, which combines the features of hammer forging and press forging.
• Features: Simple structure and easy operation for small and medium-sized forgings; relatively low production efficiency.
• Applications: Valve components, small gears, etc.

3. Upsetting

Upsetting is a forging process where compressive force is applied axially to the metal billet to reduce its height and enlarge its cross-sectional area.

Process Characteristics

• Uniform deformation: It can refine the metal microstructure and improve mechanical properties.
• Application scenarios: Widely used to manufacture disk-type parts (e.g. gear blanks) and flange components; also used as a preforming operation before closed-die forging.
• Notes: The billet tends to buckle if the ratio of height to diameter is excessive, so the deformation amount must be controlled.