Metal forging is a process that uses force to create a metal part of a specific shape and size. It can be done with heat through hot forging or without heat through cold forging. In both cases, the metal is placed into a die and then pounded into shape using a hammer or the other side of the die. The resulting part is trimmed and washed in the finishing process.
Metal is forged with heat because it does not require as much force as cold forging and reduces the stress on the metal. In the hot forging process, the metal is heated to above the re-crystallization point of the metal. For steel this is up to 2,100 degrees Fahrenheit, for aluminum alloys this is between 680 and 970 degrees Fahrenheit and for copper alloys this is between 1,290 and 1,400 degrees Fahrenheit.
Metal that is cold forged is generally at or just under room temperature. This process works best on softer metals. The metal is placed in a die and then struck with a hammer, sometimes multiple times, so that the metal is forced into the die. Cold forged metal does not require as much finishing work as hot forged metal, but may need to be tempered with heat to increase the strength of the par made.
One advantage of forged metal over cast or machined metal is the increased strength of the part. The forging process allows the metal to retain its directional strength by altering the grain of the metal, rather than cutting it off during machining or removing it completely through casting. Forged parts have no internal gas pockets as can occur during casting. Because forging alters the grain of the metal, it is easy to forge a part that meets certain impact strength requirements. A machined part that cuts off the grain of the metal is weaker at the point where the grain meets the edge of the part.
Forging allows metal to be altered into nearly any shape and size. Metal forged parts can weigh up to 400,000 pounds and the process of forging can be combined with other methods to create a part of any shape. Forging can be done in single lots for prototypes or in large lots for mass production.
Forging metal can reduce costs to the manufacturers. Less material is squandering because the metal is selected to fit the desired shape with as little waste as possible. Because of this, less finish work is needed to bring the part to the correct size and surface quality. This saves time and wear on tools.
- Photo Credit forge business image by Sergey Goruppa from Fotolia.com
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