DE1602321A1 - Process and system for the production of welded steel pipes with homogeneous cross-sections - Google Patents

Description

Patent attorney v Dip! .- lng.W.Meissn «r

Dipl.-Ing. H. Tischer
1 Berlin 33 (Grunewald)

December 5, 1967 M 553 1602321

Mannesmann Aktiengesellschaft sea, Mönchengladbach, Karmannsstr _o 29 *

Process and system for the production of homogeneous cross-sections,

welded steel pipes

and a plant

The invention preferably relates to a method / for production of longitudinally welded pipes, the weld seams of which are remunerated through further treatment «

It is well known that welded steel pipes are becoming increasingly popular manufactured according to processes which consist of the application of longitudinal seam welding machines in combination with multi-stand stretch-reducing mills exist·

In such systems, steel strip is used, which becomes a collar is wound up, initially through a multi-stand rolling mill shaped into a tubular slotted tube. The edges of the slotted tube are made by suitable welding devices preheated to welding heat and pressed together so strongly by calibrated welding rollers that a perfect weld the edges of the slotted tube enters

The edges can be heated by various means. The use of induction welding with high-frequency currents is particularly advantageous, with multi-wind induction pods being placed around the slotted tube to be welded without contact.

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They induced currents bring the edges in unusually short Time and for very short distances to welding heat, whereby the depth of penetration of the heat is very small and therefore the heating zone at the edges is rather narrow «

Because the high frequency welding heads with induction coils are a very allow high energy concentration, there is the possibility of welding very thick-walled slotted tubes perfectly can. When drilling, which must meet special quality regulations, the heat-affected welding zones have a very disruptive effect, which is especially true for pipes, the dynamic stresses is subject to, because with such pipes the physical data must be constant over the entire cross-section.

This door exposure can only be achieved by heat treatment not reach

In contrast, it is known from the strip rolling process that when processing thick-walled plates welded to one another on one greatly reduced strength such a deformation occurs that eliminates the weld seam in its cast structure and thus creates a homogenized cross-section that the original seam does not reveals more and no difference in strength shows. Transferring this knowledge according to the invention to the production of welded pipes, forms the possibility of the to meet special quality specifications for dynamically stressed pipes.

In order to be able to carry out this powerful cold or hot deformation during pipe production, welded blanks with special

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A thick wall is required, and one encounters the difficulty that lobes with a relatively small diameter and Wall was previously not available because of a certain ratio in the manufacture of slotted pipes on rolling tools the outer diameter must not be below the wall thickness. Rolling in a slotted tube of e.g. "65 mm outer diameter with a wall of 8 mm is difficult, while a slotted tube of 160 mm outer diameter with 8 mm wall is still can be perfectly formed into a slotted tube and then welded,

XIm the complete homogenization of the pipe cross-section of welded The task, the prerequisite, arises to be able to carry out steel pipes by strong 'deformation of the pipe wall to create tube semi-finished products with a correspondingly thick wall in an economical manner and also to create a system to be provided by rolling machines, which guarantee a powerful hot or cold deformation of the wall in an economical production

According to the invention, this object is achieved by a method whereby preferably a hot-rolled strip is used accordingly Dimensions in a known manner a welded billet of such a size is produced by the ratio of the required HaJxseugwand thickness to the outer diameter without difficulty the Slotted tube formation allows to then in multiple lengths and after reheating in a Reduaierwalzwerk the outer diameter the shell to the desired tube diameter without changing the wall thickness to reduce, so that after dividing into the desired lengths and heating the finished semi-finished product by hot

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roll over the stopper or a rod, the wall of the semi-finished product is vigorously deformed so that a reduction of the wall to at least $ 50 of the original wall is made, what is known per se Rolling mills are provided which, in their arrangement, apart from the Eandverformungs- and welding system behind a Heating furnace provides a multi-stand stretch-reducing mill, what about a separation system and a heating device connect two Diescher rolling mills for reasons of economy

Of course, a plug rolling mill or a continuous rolling mill or some other method for Extending wall can be chosen

In order to avoid the rolling in of the scale, they have to be reheated Furnace designs are used with certainty Exclude scaling of the inner surfaces, for which purpose induction heating under protective gas is advantageously proposed.

With the method according to the invention, first of all to manufacture a thick-walled welded billet with a larger diameter in order to make it then to change on the stretch-reducing mill to semi-finished tubular products and now subject this semi-finished product to severe deformation to be able to, not only the prerequisite for the creation of the necessary semi-finished products has been created, but also at the same time the possibility of manufacturing welded pipes with homogenized cross-section that meet the quality requirements.

Due to the inventive arrangement of the rolling mill selection, with a stretch-reducing mill behind a welding mill for the first time

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is only used for rolling semi-finished products is also It has been achieved that, in addition to a high hourly output, an improvement in quality can also be demonstrated, that of quality Seamless pipes are no longer inferior, whereby the economy is compared with the pricing of the finished products seamless pipes is advantageous.

- patent claims -

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Claims (2)

Claims 1, a process for the production of welded steel pipes with homogeneous cross-sections, characterized in that hot-rolled strip of the appropriate dimensions is deformed and welded in a "known manner" to form a welded bobbin of such a size that, due to the ratio of the required semi-finished product wall thickness to the outer diameter, the slotted tube can be formed without difficulty that then, in multiple lengths and after reheating, the outer diameter of the shell is reduced to the diameter of the semi-finished product without changing the wall, and that finally, after dividing into desired lengths and reheating the semi-finished product, the wall of the semi-finished product is vigorously deformed by hot rolling over plugs or rods that the wall is reduced to at least 50 # of the original wall 2. Plant for carrying out the method according to claim 1, characterized by one behind the other in the direction of deformation arranged band deformation and welding devices, a Heating furnace, a multi-stand stretch-reducing mill, a ! Separation plant, a warning device and two Diescher rolling mills 009819/0231