Forging is a process of shaping iron and other malleable metals by hammering or pressing. Forging is carried out above or below the re-crystallization temperature of the metal. A primary purpose of forging is to shape a metal, but it also redefines the grain size and arrangements. The forged metal becomes more ductile. Forging improves the structure of a metal like better resistance to fatigue and impact, compared to other shaping processes such as casting or machining.
Forging is mainly a shaping process where the metal is Drawn-out, Upset or Squeezed or compressed. Forging is also used to join metal pieces.
1 Drawing-out: The length is increased by decreasing the cross-section, such as wires, rolled sections, etc.
2 Upsetting: The length decreases but cross-section increases, such as for forming nails, rivets, bolts and coin stamping.
3 Bending: It is done by hammering the work around a form, such as for pipes, plates or dished ends (top-bottom of vessels).
4 Joining: Two pieces of metal form a joint, by hammering them together at high temperature (such as for copper and brass items).
5 Punching: Forming small openings or slits in the metal by a punch of the proper shape, often over a hollowed section. Punching is also accompanied by forming of the edge profiles.
6 Cutting Forming or cutting large holes or shapes by punching, shearing, etc.
7 Die Forming: Forging is also squeezing metals by producing multi-directional flow to fill in a shaped die through compression. Shaping dies are, open, closed or impression dies. It is usually done hot to increase the plasticity of metal and so reduce the required force. Open-die forging is used to form parts that are too big for a closed die, or where only a few pieces are required. Closed-die forging is used for items to be made to close tolerances and where no machining is required. Coins are formed with impressions on two sides and also with side-edge patterns. Scooter and other carburetors are formed by pressure die casting, a process of forging.
Forging is also called a smithy. The chief activities of iron workshops, since ancient times, have been to heat the metal and beat it to a shape, or Forging. Hand-held Hammer has been chief tool for forging, but in the last two centuries powered hammers and presses are used.