Upset forging is used to produce head in a bolt, screw, bar, etc. Only a certain portion of the material is deformed and rest is unaffected from the deformation. Upset forging generally employs split dies that contain multiple positions or cavities and may be opened and closed type. The heated bar or rod is positioned in the die and clamped. A hydraulic ram moves longitudinally against the bar, upsetting it into the die cavity.
In open upset forging, the unsupported length (l) of the rod does not exceed 3d to prevent its buckling, ‘d’ being rod diameter. If l > 3d, then closed upset forging is preferred with die diameter, D ≤ 1.5d.
Advantages of Upset Forging
- It has better forging quality than obtained by drop forging.
- There is very little flash.
- It has cheaper maintenance and higher productivity.
- The upsetting process can be automated.
Disadvantages of Upset Forging
- It is not suitable for forging of heavier job.
- The maximum diameter of the stock which can be upsetting is limited (about 25 cm).
- Intricate non-symmetrical and heavy jobs are difficult to be forged by this process.
- It has high tooling cost.
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