Metal Forging

A forged crankshaft. Image ©IPH Hannover

Metal forging is the oldest metal forming process which produces parts by the process of metal deformation.

The forging process is classified into two different types on the basis of the deformation mechanism: impact forging and compression forging.

In impact forging, an impact force is applied to the work piece using a hammer. In compression forging, a constant pressure is applied to the work piece. Forging processes can also be classified into two more types based on the temperature of the work piece; hot forging is done at the recrystallization temperature of the material, and cold forging done at room temperature.

Regardless of which process type is used, the process is quite simple. The work piece is placed on the bottom die and the top part die applies the impact or compression load to deform the work piece into the required shape.

Forged connecting rods


Materials for Metal Forging

A material must be ductile in nature in order to be processed by forging. Materials like low alloy steel, high alloy steel, stainless steel, carbon steel, magnesium alloy, aluminum, nickel alloy, copper and titanium alloy can be forged.

Design Considerations

Process variations

There are six different types of forging operations:

  1. Open Die Forging uses a flat die set to deform the work piece.
  2. Impression Die Forging uses a die with a cavity and applies compression force to give the work piece the shape of the cavity.
  3. Flashless Forging uses a fixed amount of material and compresses it in a closed die.
  4. Hand Forging is used by blacksmiths. The work piece is heated and then shaped using hand tools like hammers.
  5. Upset Forging use two dies to grip the work piece and a third die to shape the head section of work piece.
  6. Roll Forging use rollers to reduce the thickness of a ring or donut shaped work piece.

Economic Considerations

Quality Considerations