Rotary piercing

Last updated

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]

Contents

Mannesmann process

A schematic of rotary piercing. Key:
Roller configuration
The process starts with the blank fed in from the left.
The stresses induced by the rolls causes the center of the blank to fracture.
Finally, the rolls push the blank over the mandrel to form a uniform inner diameter. Schraegwalzen.png
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. [2] The rollers are usually 6° askew from parallel with the billet's axis. The rollers are on opposite sides of the billet, and the surface of their largest cross sections are separated by a distance slightly smaller than the outside diameter (OD) of the original billet. The load imparted by the rollers compresses the material and the 6° skew provides both rotation and translation to the billet. The friction between the rollers and the billet is intentionally high, and is sometimes increased by using knurled rollers. This friction establishes stresses varying radially through the billet, with the highest stresses at the outer surface and the central axis. The stress exceeds the 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]

Related Research Articles

<span class="mw-page-title-main">Rivet</span> Permanent mechanical fastener

A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the tail. On installation, the rivet is placed in a punched or drilled hole, and the tail is upset or bucked, so that it expands to about 1.5 times the original shaft diameter, holding the rivet in place. In other words, the pounding or pulling creates a new "head" on the tail end by smashing the "tail" material flatter, resulting in a rivet that is roughly a dumbbell shape. To distinguish between the two ends of the rivet, the original head is called the factory head and the deformed end is called the shop head or buck-tail.

<span class="mw-page-title-main">Rolling-element bearing</span> Bearing which carries a load with rolling elements placed between two grooved rings

In mechanical engineering, a rolling-element bearing, also known as a rolling bearing, is a bearing which carries a load by placing rolling elements between two concentric, grooved rings called races. The relative motion of the races causes the rolling elements to roll with very little rolling resistance and with little sliding.

<span class="mw-page-title-main">Pressure vessel</span> Vessel for pressurised gases or liquids

A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.

<span class="mw-page-title-main">Extrusion</span> Process of pushing material through a die to create long symmetrical-shaped objects

Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex cross-sections; and to work materials that are brittle, because the material encounters only compressive and shear stresses. It also creates excellent surface finish and gives considerable freedom of form in the design process.

Glass tubes are mainly cylindrical hollow-wares. Their special shape combined with the huge variety of glass types, allows the use of glass tubing in many applications. For example, laboratory glassware, lighting applications, solar thermal systems and pharmaceutical packaging to name the largest.

<span class="mw-page-title-main">Residual stress</span> Stresses which remain in a solid material after the original cause is removed

In materials science and solid mechanics, residual stresses are stresses that remain in a solid material after the original cause of the stresses has been removed. Residual stress may be desirable or undesirable. For example, laser peening imparts deep beneficial compressive residual stresses into metal components such as turbine engine fan blades, and it is used in toughened glass to allow for large, thin, crack- and scratch-resistant glass displays on smartphones. However, unintended residual stress in a designed structure may cause it to fail prematurely.

<span class="mw-page-title-main">Rolling (metalworking)</span> Metal forming process

In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is similar to the rolling of dough. Rolling is classified according to the temperature of the metal rolled. If the temperature of the metal is above its recrystallization temperature, then the process is known as hot rolling. If the temperature of the metal is below its recrystallization temperature, the process is known as cold rolling. In terms of usage, hot rolling processes more tonnage than any other manufacturing process, and cold rolling processes the most tonnage out of all cold working processes. Roll stands holding pairs of rolls are grouped together into rolling mills that can quickly process metal, typically steel, into products such as structural steel, bar stock, and rails. Most steel mills have rolling mill divisions that convert the semi-finished casting products into finished products.

Filament winding is a fabrication technique mainly used for manufacturing open (cylinders) or closed end structures. This process involves winding filaments under tension over a rotating mandrel. The mandrel rotates around the spindle while a delivery eye on a carriage traverses horizontally in line with the axis of the rotating mandrel, laying down fibers in the desired pattern or angle to the rotational axis. The most common filaments are glass or carbon and are impregnated with resin by passing through a bath as they are wound onto the mandrel. Once the mandrel is completely covered to the desired thickness, the resin is cured. Depending on the resin system and its cure characteristics, often the mandrel is autoclaved or heated in an oven or rotated under radiant heaters until the part is cured. Once the resin has cured, the mandrel is removed or extracted, leaving the hollow final product. For some products such as gas bottles, the 'mandrel' is a permanent part of the finished product forming a liner to prevent gas leakage or as a barrier to protect the composite from the fluid to be stored.

<span class="mw-page-title-main">Tapered roller bearing</span> Type of roller bearing which can support axial loads

Tapered roller bearings are rolling element bearings that can support axial forces as well as radial forces.

<span class="mw-page-title-main">Flexural strength</span> Material property

Flexural strength, also known as modulus of rupture, or bend strength, or transverse rupture strength is a material property, defined as the stress in a material just before it yields in a flexure test. The transverse bending test is most frequently employed, in which a specimen having either a circular or rectangular cross-section is bent until fracture or yielding using a three-point flexural test technique. The flexural strength represents the highest stress experienced within the material at its moment of yield. It is measured in terms of stress, here given the symbol .

<span class="mw-page-title-main">Fracture (geology)</span> Geologic discontinuity feature, often a joint or fault

A fracture is any separation in a geologic formation, such as a joint or a fault that divides the rock into two or more pieces. A fracture will sometimes form a deep fissure or crevice in the rock. Fractures are commonly caused by stress exceeding the rock strength, causing the rock to lose cohesion along its weakest plane. Fractures can provide permeability for fluid movement, such as water or hydrocarbons. Highly fractured rocks can make good aquifers or hydrocarbon reservoirs, since they may possess both significant permeability and fracture porosity.

<span class="mw-page-title-main">Shear forming</span>

Shear forming, also referred as shear spinning, is similar to metal spinning. In shear spinning the area of the final piece is approximately equal to that of the flat sheet metal blank. The wall thickness is maintained by controlling the gap between the roller and the mandrel. In shear forming a reduction of the wall thickness occurs.

Tube drawing is a process to size a tube by shrinking a large diameter tube into a smaller one, by drawing the tube through a die. This process produces high-quality tubing with precise dimensions, good surface finish, and the added strength of cold working. For this reason this process is established for many materials, mainly metalworking but also glass. Because it is so versatile, tube drawing is suitable for both large- and small-scale production. The large-scale production of glass typically uses a one step process where glass is directly drawn into a tube from a melting tank.

<span class="mw-page-title-main">Burnishing (metal)</span> Deformation of a metal surface due to friction

Burnishing is the plastic deformation of a surface due to sliding contact with another object. It smooths the surface and makes it shinier. Burnishing may occur on any sliding surface if the contact stress locally exceeds the yield strength of the material. The phenomenon can occur both unintentionally as a failure mode, and intentionally as part of a metalworking or manufacturing process. It is a squeezing operation under cold working.

Material failure theory is an interdisciplinary field of materials science and solid mechanics which attempts to predict the conditions under which solid materials fail under the action of external loads. The failure of a material is usually classified into brittle failure (fracture) or ductile failure (yield). Depending on the conditions most materials can fail in a brittle or ductile manner or both. However, for most practical situations, a material may be classified as either brittle or ductile.

<span class="mw-page-title-main">Race (bearing)</span> Track in a bearing along which the rolling elements ride

The rolling-elements of a rolling-element bearing ride on races. The large race that goes into a bore is called the outer race, and the small race that the shaft rides in is called the inner race.

<span class="mw-page-title-main">Tube bending</span>

Tube bending is any metal forming processes used to permanently form pipes or tubing. Tube bending may be form-bound or use freeform-bending procedures, and it may use heat supported or cold forming procedures.

In mechanical engineering, a cam follower, also known as a track follower, is a specialized type of roller or needle bearing designed to follow cam lobe profiles. Cam followers come in a vast array of different configurations, however the most defining characteristic is how the cam follower mounts to its mating part; stud style cam followers use a stud while the yoke style has a hole through the middle.

<span class="mw-page-title-main">Metal spinning</span>

Metal spinning, also known as spin forming or spinning or metal turning most commonly, is a metalworking process by which a disc or tube of metal is rotated at high speed and formed into an axially symmetric part. Spinning can be performed by hand or by a CNC lathe.

A die in polymer processing is a metal restrictor or channel capable of providing a constant cross sectional profile to a stream of liquid polymer. This allows for continuous processing of shapes such as sheets, films, pipes, rods, and other more complex profiles. This is a continuous process, allowing for constant production, as opposed to a sequential (non-constant) process such as injection molding.

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. 1 2 3 Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, p. 404, ISBN   0-471-65653-4.