* Forging is a process in which material is shaped by the application of localized compressive forces exerted manually or with power hammers, presses or special forging machines. * The process may be carried out on materials in either hot or cold state.
FORGING PROCESSES are:
1. Open – die hammer forging
* It is the simplest forging process which is quite flexible but not suitable for large scale production. It is a slow process. The resulting size and shape of the forging are dependent on the skill of the operator. 2. Impression – die drop forging (closed die forging)
* The process uses shaped dies to control the flow of metal. * The heated metal is positioned in the lower cavity and on it one or more blows are struck by the upper die. This hammering makes the metal to flow and fill the die cavity completely. * Excess metal is squeezed out around the periphery of the cavity to form flash. * On completion of forging, the flash is trimmed off with the help of a trimming die. Coining: (Ex of impression die forging)
* It is a closed – die forging process used mainly for minting coins and making of jewelry. * In order to produce fine details on the work material the pressures required are as large as five or six times the strength of the material. * Lubricants are not employed in this process because they can get entrapped in the die cavities and, being incompressible, prevent the full reproduction of fine details of the die.
3. Press Forging
* Press forging, which is mostly used for forging of large sections of metal, uses hydraulic press to obtain slow and squeezing action instead of a series of blows as in drop forging. * The continuous action of the hydraulic press helps to obtain uniform deformation throughout the entire depth of the work piece. Therefore, the impressions obtained in press forging are cleaner. * Press forgings generally need smaller draft than drop forgings and have greater...