What is forging?
Forging is manufacturing process where metal is pressed, pounded or squeezed under great pressure into high strength parts known as forgings. The process is normally (but not always) performed hot by preheating the metal to a desired temperature before it is worked. It is important to note that the forging process is entirely different from the casting (or foundry) process, as metal used to make forged parts is never melted and poured (as in the casting process).
Why use forgings and where are they used?
The forging process can create parts that are stronger than those manufactured by any other metalworking process. This is why forgings are almost always used where reliability and human safety are critical. But you'll rarely see forgings, as they are normally component parts contained inside assembled items such airplanes, automobiles, tractors, ships, oil drilling equipment, engines, missiles and all kinds of capital equipment - to name a few.
Types of Forging Processes
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Impression Die Forging
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Open Die Forging (link to Open Die Forging)
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Rolled Ring Forging
How Forgings CompareTo Castings
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Forgings are stronger.
Casting cannot obtain the strengthening effects of hot and cold working. Forging surpasses casting in predictable strength properties - producing superior strength that is assured, part to part.
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Forging refines defects from cast ingots or continuous cast bar.
A casting has neither grain flow nor directional strength and the process cannot prevent formation of certain metallurgical defects. Preworking forge stock produces a grain flow oriented in directions requiring maximum strength. Dendritic structures, alloy segregation's and like imperfections are refined in forging.
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Forgings are more reliable, less costly.
Casting defects occur in a variety of forms. Because hot working refines grain pattern and imparts high strength, ductility and resistance properties, forged products are more reliable. And they are manufactured without the added costs for tighter process controls and inspection that are required for casting.
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Forgings offer better response to heat treatment.
Castings require close control of melting and cooling processes because alloy segregation may occur. This results in non-uniform heat treatment response that can affect straightness of finished parts. Forgings respond more predictably to heat treatment and offer better dimensional stability.
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Forgings' flexible, cost-effective production adapts to demand.
Some castings, such as special performance castings, require expensive materials and process controls, and longer lead times. Open-die and ring rolling are examples of forging processes that adapt to various production run lengths and enable shortened lead times.
