Forging has been one
of the most common methods for the manufacture of car pistons for many years
due to the ability to create a variety of different shapes from a number of
materials. The desired material is first heated up to around 75% of its melting
point which loosens the crystalline structure of the metal to reduce the flow
stress and reduce the amount of energy that will be required to deform the
material. The reason hot forging is used over cold is because temperatures are
required in order avoid strain hardening during deformation. The hot material
is then placed either manually or autonomously into the cavity before the press/hammer
comes down and forces the material into the shape of the cavity. The press is
sometimes heated as well as the material at the same temperature to reduce
temperature loss of the material while the pressing takes place. Some presses depending on the material and
size of the part you are producing are forced with pressures of up to and
higher than 2000 tonnes (made, 2013).
Once the material has been pressed into shape the part is the removed and left
To be able to perform closed die forging there are many
costs involved. The initial tooling cost for this process is huge and is the
most expensive. You must buy/manufacture your two dies in the shape of the
product you want to produce. You Must also consider the cost of the
hammer/press that is used to force the material into shape. This can be huge
depending on the materials used and the size of the part.
You must also consider material costs which will vary
completely depending on the properties you require the part to have as
different grades of metal come at different prices.
The post forging processes that are required can greatly
increase the overall cost o the process as heat treatment is typically required
to achieve the material properties that you require. Also surface treatment and
machining maybe required afterwards which can be costly.