Press forging shapes metal by squeezing it in a high-power press, rather than striking it with hammer blows. The action is closer to kneading bread than hitting an anvil, and it deforms the workpiece through its full section thickness.
It is most commonly used as the first shaping process for large cast ingots, closing up internal voids and making a bar more suitable for further forging. After press forging, the workpiece is normally returned to a reheat furnace to bring it back up to temperature ready for hammer or die forging.
Advantages of press forging
The biggest advantage is depth of effect. Hammer forging affects mainly the surface, whereas press forging changes the shape and the interior of the workpiece. It is also more controlled, delivering a more uniform strain rate; as a slower process, a greater degree of control is possible.
- Greater accuracy, with tolerances within 0.01 to 0.02 inch and higher productivity than drop forging
- Dies have less draft, so more complicated shapes can be forged with increased dimensional accuracy
- The speed, pressure and travel of the die are automatically controlled
- Blank feeding and forging removal allow process automation
- The operation is completed in a single squeezing action, which saves time
- Press capacity ranges from 500 to 9000 tonnes, with up to 40 or 50 working strokes per minute, so 40-50 parts can be produced per minute
- The fast delivery time suits mass production of nuts, bolts, rivets, screws, brake levers, bearing races and valves