By:Yufan Zhu, Date: 02/12/2018

• Forging basically involves two things : metal and external forces that located at a concentrated point. The purpose of forging is to shape the metal into a desired shape. Usually forging will involve the use of hammer or die to deliver the force and the way to classified different types of forging involves their temperature. There are cold forging ( also known as cold working), warm forging and hot forging (hot working). As the names suggest, the latter two also need to apply heat to the metal surface.

The left one is cold forging and the right one is the hot forging, notice the difference in metal temperature.

There are two types of hot forging: The close die and open die forging. Difference between them is while the close die forging 's die contains per cut work piece in it while the open forging simply press a piece of preheated metal into a die 

*The earliest metalworking dates back to about 4500 B.C. Based on my findings it is hard to pinpoint who exactly invented and first use it but a lot of the resources points to the inhabitants of Sumerians.

*Yet some of the most important development of this process comes from Romanians who combined water power and the forging of metals as the hammer was driven by water power rather than human hands.

*Originally forging was used to crate decorative items. Yet the most important applications of it was to craft weapons and hand tools. The blacksmiths in the dark age master the art of forging.
*Nowadays forging can be used in produce metal plate, engine parts and other applications that require lightweight work piece with high strength.

*The forging process if used alone can produce precision products but with CNC machining the tolerance can be even higher.

*But when combined with advanced manufacturing process such as CNC machining. Forging is able to produce parts with incredible tolerance.One of the example being the Formula 1's engine pistons, the tolerance is so tight that the engine block has to be preheat before firing up

Advantages and Disadvantages

It produce products with high strength, lightweight characteristics and when combined with other manufacturing process will also produce very accurate products.

But due to the fact that metal crystals are elongated during the process, the product tends to be brittle. Moreover, the product will be more expensive than casting counterparts. ($279 pistons for small block Chevy vs $133 pistons for the same engine, price from summit racing's website)

The tooling cost is much higher than casting. The close-die hot forging for instance, averages $1500-$4000 for investment in die which may only lasts for 5000-10000 production run.

Casting on the other hand will have longer lifespan for tools and depends on the complexity of the work piece, will cost less in tools than the forging.

Hot forging also consumes a lot of energy as it needs continuous input of heat.