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Hydrostatic extrusion

Extrusion process in which an ingot surrounded by a liquid is pushed through a die.

Beskrivning
Illustration of Hydrostatic extrusion

The process

The working material consists of a preheated ingot [1] placed in a pressure chamber [2] with a die [3] in the bottom. The remaining void in the chamber is then filled with a liquid [4]. A tightly fitting piston [5] is pressed against the liquid with an applied pressing force which forces the ingot out of the die in the bottom of the pressure chamber. The ingot then assumes the shape of the die cross-section and is pushed out as a solid axially symmetric rod [6].

The force required to press the ingot through the container is low as the liquid makes the friction against the chamber walls negligible.

As the ingot is cut down and becomes thinner, the force, ate the rear end of the ingot cannot push it through the die with desired results. Because of this, the rear end cannot usually be used.

Synonyms

Hydrostatisk extrudering
Hydrostatic extrusion
Process films
Advantages and disadvantages
In comparison with alternative methods
No friction between the container and the ingot
Low power consumption
Usually increases the material's ductility as high pressure is applied
Large ingots can be extruded
Large cross sections can be extruded, smooth material flow
No residue of ingots left on the container walls
Possible leakage of fluid and pressurized oil
Uncontrolled rate of extrusion at the end
Ingots must be processed to remove surface defects