Forging

Forging is the oldest known metal working process, dating back to the days when prehistoric peoples learned to heat sponge iron and beat it with a stone to form a useful implement.

Forging is a manufacturing process where metal is plastically deformed under great pressure into high-strength parts known as forgings.

It is important to note that the forging process is entirely different from the casting or foundry processes, in which the metal used is melted, then poured or injected into a die.

The forging process can create parts that are stronger than those manufactured by any other metal process.

Material

Just about any metal can be forged. Some of the more common metals include:

Carbon, alloy and Stainless steels Tool steels Aluminum Titanium Brass and Copper High-temperature alloys which contain cobalt, nickel or molybdenum.

Equipment

Typical equipment used to produced forgings:

• Hammers deform the metal into shape with controlled high-impact blows.
• Presses squeeze the metal into shape with controlled high pressure.
• Upsetters are basically forging presses used horizontally for a forging process known as "upsetting".
• Ring rollers turn a hollow round piece of metal under extreme pressure against a rotating roll, thereby squeezing out a one-piece ring with no welding required.

Process

There are four basic processes used to produce a forged part:

Impression Die Forging Cold Forging Open Die Forging Seamless Rolled Ring Forging

Impression Die Forging

Impression die forging deforms metal between two dies that contain a precut profile of the desired part. Because metal flow is restricted by the die contours, this process can yield more complex shapes and closer tolerances than open-die forming processes. Impression die forging accounts for the bulk of commercial forging production. Parts weighing from ounces to 60,000 lbs. can be produced using this method.

Cold Forging

A chemically lubricated bar slug is forced into a closed die under extreme pressure. The unheated metal then flows into the desired shape. Forward extrusion involves steel flow in the direction of the ram. It is used when the diameter of the bar is to be decreased and the length increased. Backward extrusion, where the metal flows opposite to the ram force, generates hollow parts. In upsetting, the metal flows at right angles to the ram, increasing diameter and reducing length.

Cold forging encompasses many processes:

Bending Cold drawing Cold heading Coining Extrusions

There are times when warm forging practices are selected over cold forging especially for higher carbon grades of steel or where in process anneals can be eliminated.

Open Die Forging

This process progressively works the starting stock into the desired shape, most commonly between flat-faced dies not confined laterally during forging. A forging from a few pounds up to more than 150 tons can be produced. Open die forgings are limited only by the size of the starting stock, namely, the largest ingot that can be cast. These types of forgings require subsequent machining in almost all cases.

Seamless Rolled Ring Forging

Seamless rolled ring forging is typically performed by punching a hole in a round piece of metal (creating a donut shape) and then rolling and squeezing (or in some cases, pounding) the donut into a thin ring. Forged rings can weigh up to 350,000 lbs. with heights up to more than 9 ft. High tangential strength and ductility make forged rings well suited for torque and pressure resistant components.

Among the industries that depend on forgings are:

automotive and truck agricultural machinery equipment valves fittings petrochemical applications hand tools hardware off-highway railroad equipment general industrial equipment marine aerospace and more

Forgings are found in 20% of the products representing the Gross Domestic Product of the United States.