Pilgrimage method

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The pilgrim step process refers to manufacturing processes that are associated with the pilgrim step . In general, these are processes in which you work with forward and backward movements, for example when heating a workpiece in order to achieve a certain heat distribution (warm - hot - warm).

Manufacture of pipes

The pilgrimage method, also known as pilgrimage, is a method for the further processing of seamless tubes , in particular steel tubes . The aim of the pilgrimage is to reduce the wall thickness of the seamless pipe manufactured using the Mannesmann process . This enabled the mass production of pipes and thus also z. B. of inexpensive and light bicycles.

Here, the primary material, the so-called tube blank , is passed through a pair of rollers , which has an eccentric surface and performs a back and forth movement on the tube blank. The two rollers rotate in opposite directions. A mandrel is placed inside the tube blank. When the rollers are positioned so that there is the greatest distance between them, the billet with the mandrel is advanced one working step length and rotated. The rollers rotate against the feed direction and narrow the free space until they grip the shell on the mandrel and roll thinner and longer. The mandrel and the shell are carried along with the rotation of the rollers so that just enough material is available for the rolling process. When the rollers have rolled so far that the gap between the hollow and mandrel is released again, the hollow and mandrel are pushed forward again and the process begins again. The change from feed and backward rolling gives the process its name.

High cross-section or wall thickness reductions of over 80% can be achieved. A distinction is made between warm and cold pilgrims.

Warm pilgrimage

The warm pilgrimage process is one of the oldest processes for stretching hollow blocks to form tube blanks . Today, pipes for power plants, the petrochemical industry and the construction sector are mainly produced on hot pilgrims' facilities.

The hollow blocks are produced by cross- rolling mills or piercing presses with a downstream elongator. For rolling in the pilger mill, the hollow block is pushed over a cylindrical, smooth mandrel, the diameter of which corresponds approximately to the inner diameter of the pipe to be manufactured, and then fed to the pilger rollers by the feed device. The pilgrim's mouth grips the hollow block, presses off a wave of material, which is then stretched out by the smoothing caliber on the pilgrim mandrel to the desired wall thickness. With a step-by-step rolling process (pilgrim step movement), the hollow block is stretched out into a hollow.

After leaving the pilger mill, a hot saw cuts off the remainder of the hollow, the so-called pilgrim's head, and possibly the unevenly deformed front end of the hollow. Then the lobes are z. B. heated an induction furnace before they are calibrated in a sizing mill to the desired outer diameter. Both the seamless tube and the pilgrim step method were developed by the brothers Max and Reinhard Mannesmann between 1885 and 1890.

Cold pilgrimage

Cold pilger rolling is a special forming process that is cost-effective and indispensable for numerous applications - especially with long pipe lengths. Large reductions in cross-section (diameter and wall thickness) can be achieved. At the same time, there is a significant reduction in eccentricity due to the homogenization of the material flow during forming and the desired micro-structures in the material are set.

The cold pilgrimage eliminates the need for additional, time-consuming and costly process steps such as cleaning, annealing, pickling, cutting and straightening. The high number of forming steps improves the roundness, the homogeneity and the surface quality of the seamless tubes. No other cold forming process for tubes offers as many advantages as cold pilgrimage.

Production of diaphragm walls

When building diaphragm walls , the alternating digging of the slots is known as the pilgrim step method. First the primary slots are produced and then the secondary lamellas between the primary slots follow in a second work step. This enables the simultaneous production of several lamellas and thus a faster construction process.

Securing the ground with a shotcrete wall

A method known as the pilgrim step method is also used to secure the ground by means of nailed shotcrete walls. Excavations are carried out in sections that are 2 to 3 m wide and 1.50 to 1.60 m deep.

Manufacture of concrete walls

When creating long, oversized concrete walls, the use of the pilgrim step method has structural and logistical advantages. The wall is divided into individual blocks. First every second block is created. Recesses are provided on the connecting sides, which are used for later interlocking with the gap elements that are subsequently concreted in. The heat of hydration generated when the concrete sets can flow away more evenly. In the next step, the gaps are filled with concrete. The blocks that have already been created make the side formwork superfluous. If there is enough staff, several blocks can be pulled up at the same time, which simplifies work processes.

Manufacture of road slabs

Concreting the reinforced concrete deck slabs of composite steel bridges is often carried out in sections using the pilgrimage method. The carriageway slab is not produced continuously in successive sections. Only after the road slab has been concreted in the field area is the previously omitted section in the support area produced. This construction process reduces the tensile stresses in the concrete and thus the risk of cracking in the support area above the pillars.

literature

  • K. Neuhoff: The tube production according to the cross-rolling and pilgrim step process. Publishing house advisory center f. Steel use 1954.
  • Theodoros Triantafyllidis: Planning and construction in special civil engineering: diaphragm wall and cut-off wall technology . Berlin 2004. p. 38 ff. ISBN 3-433-02859-1

Web links

Individual evidence

  1. ↑ Stahlrohre.de: Manufacturing process for steel pipes . P. 8 (pdf). Retrieved March 22, 2020
  2. ↑ sms-group.com: Warm pilger rolling mills . Retrieved March 22, 2020
  3. ↑ sms-group.com: cold pilger rolling mills . Retrieved March 22, 2020
  4. ↑ Geobau.it: Pilgrim step method . Retrieved March 22, 2020
  5. ↑ TEC21, Peter Seitz: Refined Elixir . Block by block in the pilgrimage. Article dated May 12, 2017. Retrieved March 6, 2020