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Extrusion Presses

Double-Action Tube Extrusion Presses

The main extrusion system works together with an independent piercing or mandrel system, allowing the mandrel to pierce, position or remain controlled during forming. The platform is primarily intended for seamless tubes and hollow products that require mandrel-assisted forming.

Products

Platform Overview

Double-action extrusion presses add an independent piercing or mandrel motion system to the main extrusion action. In a typical seamless tube process from a solid billet, the billet is compacted, the mandrel pierces and positions itself relative to the die, and the main extrusion system pushes metal through the gap between the mandrel and the die to form a tubular product. This platform is primarily for products where the mandrel must participate directly in forming the inner surface.

The forming process shown is a typical sequence; actual action order is determined by equipment structure, billet form, mandrel strategy and control policy.

Typical Forming Process

  1. Billet is loaded into the container and compacted by the main extrusion system.
  2. The piercing/mandrel system advances the mandrel into the billet.
  3. The mandrel reaches the process-defined position and remains or moves under control.
  4. The main extrusion system continues to apply pressure.
  5. Metal flows out through the gap between the mandrel and the die to form a tube.
  6. The press decompresses, retracts and prepares for the next cycle.

Typical Products and Application Boundaries

  • Seamless tubes formed from solid billets by piercing and extrusion
  • Tubes produced from hollow billets where mandrel participation is needed for dimensional control
  • Hollow products requiring independent mandrel action after technical evaluation

Two hollow-product categories should be distinguished:

  • Seam-welded hollow extrusions: metal splits in a porthole die and re-welds, leaving longitudinal weld zones. These are normally produced with single-action presses
  • Mandrel-method seamless tubes: metal flows continuously around the mandrel without splitting and re-welding. This is the main application direction for double-action equipment

Main Engineering Characteristics

  • Main extrusion system and piercing/mandrel system act independently and must be coordinated
  • Provides the motion basis for piercing solid billets and extruding seamless tubes
  • Mandrel position directly affects tube wall thickness and forming stability
  • Mandrel-billet friction and the resulting axial load must be considered in equipment and die design
  • Protection and monitoring of the mandrel, piercing stem, die and hydraulic control system are essential