Rotary piercing

Source: Wikipedia, the free encyclopedia.

Rotary piercing is a hot working metalworking process for forming thick-walled seamless tubing. There are two types: the Mannesmann process, invented in the 1880s, and the Stiefel process, developed two decades later.[1]

Mannesmann process

A schematic of rotary piercing. Key:
  1. Roller configuration
  2. The process starts with the blank fed in from the left.
  3. The stresses induced by the rolls causes the center of the blank to fracture.
  4. Finally, the rolls push the blank over the mandrel to form a uniform inner diameter.

A heated cylindrical billet workpiece is fed between two convex-tapered rollers, which are rotating in the same direction.

yield strength of the billet and causes circumferential fissures to propagate at various radii near the outer surface, and a central longitudinal void to form at the axis. A tapered mandrel is set inside and a short distance from the start of the central void. This mandrel forces the material outward and compresses the material against the back side of the tapered rollers. This compressive loading fuses the circumferential fissures and sets the initial internal and external diameter values. The formed tube is then cooled and can be cold worked to refine the diameters and to achieve the desired yield strengths.[3]

Mannesmann mills can produce tubes as large as 300 mm (12 in) in diameter.[3]

Stiefel process

The Stiefel process is very similar to the Mannesmann process, except that the convex rollers are replaced with large conical disks. This allows for larger tubes to be formed.[3]

References

  1. ^ "The Development History of Seamless Steel Pipe | CSCMP's Supply Chain Quarterly".
  2. ^ Erik Oberg and Franklin Jones, ed.s, Machinery's Encyclopedia … , vol. 6 (New York, New York: The Industrial Press, 1917), pages 333-334.
  3. ^
    ISBN 0-471-65653-4
    .
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