EP2903757B1 - Method for the high-speed production of a multi-layered tube - Google Patents

Description

The present invention relates to a method for the rapid production of a multilayer pipe. Multilayer pipes are preferably used in case of high requirements against corrosion or abrasion.

Corrosion-resistant pressure vessels or pressure lines can be produced more cost-effectively by using multilayer pipes than solid versions made of appropriate materials. This is achieved by the load sharing on a thin, corrosion-resistant inner layer (e.g., stainless and acid resistant steel) and a high strength, pressure resistant outer layer (eg, fine-block steel). As a result, overall steel consumption can be significantly reduced and much of the remaining steel consumption can be shifted to low-cost materials.

Abrasion-resistant pipes are made possible by the design as a multilayer pipe (such as mechanical bond, see below) in certain grades in the first place, because materials (eg high-strength steels with high hardness) can be used as an inner layer, which alone or only very difficult can be processed into tubes.

Other combinations of materials are possible in a great variety, in principle, the ability to combine materials is limited only by the relevant candidate processing techniques.

• vollflächiger metallurgischer Bindung (diese erfordert plattiertes Blech als Ausgangshalbzeug), und
• rein mechanischer Bindung (etwa einer Reibbindung) zwischen Innen- und Außenrohr - vorzugsweise Innen- und Außenblech und ihrer Verschweißung an den Blechkanten -.

When constructing the pipe jacket, a distinction is made between

• full-surface metallurgical bond (this requires plated sheet metal as a starting semi-finished product), and
• purely mechanical bond (such as a friction bond) between inner and outer tube - preferably inner and outer sheet and their welding at the sheet edges -.

For multi-layer pipes with metallurgical bond between the layers - such as multi-layer pipes made of metal sheets, preferably steel sheets - is used as a starting semi-finished a clad composite sheet of two different (steel) materials use.

The disadvantage of this method according to the prior art is firstly the high cost of the starting semifinished product and thus also of the end product, but on the other hand also a lack of sufficient availability of this semifinished product due to extremely limited production capacity for this purpose in the world. Furthermore, the number of materials that can be processed in this way, limited. For example, certain abrasion-resistant steels can not be used as the inner layer if they are difficult or impossible to weld because of their high carbon content.

• Zwei fertige Rohre werden aus den zu kombinierenden Werkstoffen passgenau gefertigt und ohne Reibung ineinander geschoben, wobei das äußere Rohr eine höhere Streckgrenze aufweisen muß als das innere.
• Durch Expandieren (mechanisch - etwa vermittels eines Expansionsstempels - oder durch Flüssigkeitsdruck, wobei im letzten Falle die ineinander liegenden Rohre in ein das Außenrohr umfassendes Gesenk gepreßt werden) wird das Innenrohr unter elastischer Aufweitung auch des Außenrohrs in das Außenrohr gedrückt. Nach Wegfallen der Expansionskräfte legt sich das Außenrohr wegen der höheren elastischen Rückfederung kraftschlüssig um das Innenrohr.
• Abschließend werden die beiden Werkstoffe an den Stirnseiten verschweißt.

In multi-layer pipes with mechanical bonding found in the older art as a starting semi-finished more - preferably two - finished pipes use. The method will be explained below with reference to the example of two tubes (in the case of further layers, the statements are to be understood accordingly):

• Two finished tubes are made of the materials to be combined accurately and pushed into each other without friction, the outer tube must have a higher yield strength than the inner.
• By expanding (mechanically - such as by means of an expansion punch - or by fluid pressure, in the latter case, the nested tubes are pressed into a comprehensive comprehensive the outer tube die) the inner tube is pressed under elastic expansion of the outer tube and into the outer tube. After elimination of the expansion forces, the outer tube sets because of the higher elastic resilience frictionally around the inner tube.
• Finally, the two materials are welded at the ends.

The disadvantage of this method according to the prior art is due to the fact that the outer tube must have a higher yield strength than the inner, otherwise the lack of adhesion to the inner tube causing and therefore required elastic resilience of the outer tube. This is particularly disadvantageous because high-strength materials - such as particularly high-strength steels - as they are preferably for abrasion-resistant pipelines are particularly advantageous in the interior of the tube, have high or even very high yield strengths and thus are not suitable for this production process.

• einzelne zum Mehrlagenrohr zu kombinierende Werkstofflagen aufeinandergelegt, und
• der so gebildete Mehrlagen-Werkstoff mit Hilfe der Biegewalze zu einem Mehrlagenrohr geformt, wobei in der Endphase der Rohrformung in der Biegewalze eine jeweilig als Innenrohr fungierende Werkstofflage kraftschlüssig in eine jeweilig als Außenrohr fungierende Werkstofflage gepresst wird.

Meanwhile, however, other procedures from the WO 2006/066814 A1 known, which do not have these disadvantages and are used to produce a multilayer pipe with mechanical bond between the material layers by means of a bending roll. Here are

• individual layers of material to be combined with the multi-layer pipe stacked on top of one another, and
• the multilayer material thus formed is formed into a multilayer pipe with the aid of the bending roll, wherein in the final phase of pipe forming in the bending roll, a respective material layer functioning as an inner pipe is pressed non-positively into a material layer acting as an outer pipe.

With the help of this method multilayer pipes can be produced, which do not require rolling and / or blast-plated semi-finished products, but on the other hand are not subject to the restrictions that brings the production of multi-layer pipes according to the aforementioned prior art with frictional mechanical bonding of layers with each other.

The use of rolled and / or blast-plated semifinished product is avoided by first creating a first joint between the layers of material, such as a weld, and thereafter the respective layer of material acting as an inner tube during tube forming in the bending roll by attaching it after a certain deformation progress - Pressed further connection between the material layers frictionally in the respective functioning as an outer tube material layer and is held in this way frictionally in each outer tube, without having to expand the multilayer tube and thus the above Expansion methods mentioned.

Nevertheless, this method has the technical production disadvantage that it is necessary to create a further connection between the material layers during the tube forming in the bending roll after a certain deformation progress, which is usually done by welding. For this connection, it is therefore necessary to interrupt the tube forming in order to connect the two material layers together at this further point. For this purpose, the still unfinished pipe must be removed from the bending roll and then created the connection, so in general, the weld can be applied. Alternatively It can also be welded in the bending roll, which blocks it during this time. Then, the tube blank (also called slot tube) can be re-introduced into the bending roll to continue the local manufacturing process. Such a procedure is extremely time-consuming and therefore represents a significant production cost disadvantage.

• einzelne zum Mehrlagenrohr zu kombinierende Werkstofflagen aufeinandergelegt werden, wobei eine als jeweiliges Außenrohr fungierende Werkstofflage ein Grundblech bildet, das in etwa entlang seiner beiden Längskanten oder in etwa parallel hierzu jeweils eine, vorzugsweise aufgeschweißte, Anschlagkante aufweist und die aufliegende Werkstofflage lose zwischen diese Anschlagkanten zu liegen kommt, und
• der so gebildete Mehrlagen-Werkstoff mit Hilfe der Biegewalze zu einem Mehrlagenrohr geformt wird, wobei die jeweilige als Innenrohr fungierende Werkstofflage zwischen die Anschlagkanten geklemmt und in der Endphase der Rohrformung in der Biegewalze die jeweilige als Innenrohr fungierende Werkstofflage hierdurch kraftschlüssig in die jeweilig als Außenrohr fungierende Werkstofflage gepreßt wird.

The WO 2006/066814 A1 However, it also teaches a method in which

• individual material layers to be combined to form multilayer pipe are stacked, wherein a material layer acting as a respective outer tube forms a base plate, which has a stop edge preferably approximately along its two longitudinal edges or approximately parallel thereto, and the resting material layer lies loosely between these stop edges comes, and
• the multilayer material formed in this way is formed into a multilayer pipe with the aid of the bending roll, the respective material layer acting as inner pipe being clamped between the abutment edges and in the final phase of tube forming in the bending roll, the respective material layer acting as inner tube thereby frictionally engaging in the respective outer tube Material layer is pressed.

According to this embodiment of the WO 2006/066814 A1 Thus, as the respective inner layer, it is also possible to use materials such as particularly high-strength steels which are difficult or impossible to weld. Again, the functioning as an inner tube material layer is pressed during the Rohrfomung in the bending roller frictionally in the respective acting as an outer tube material layer and so frictionally held in the respective outer tube and without that it requires a connection, such as a weld to be created. Therefore, a time- and cost-intensive interruption of the tube forming process in the bending roll is also not required here. However, this manufacturing process in turn has the disadvantage that in this case the pipe inner layer is not completely closed inwardly, since a part of the pipe inner circumference is formed by the on the respective base plate, so the respective outer material layer, attached stop edges, which leads to here the beneficial effects of the tube inner layer, such as corrosion or abrasion resistance can not occur. This disadvantage can not be solved simply by a build-up welding in this area, as a welded joint between the material of the stop edge and the inner layer in this process, which wants to avoid welding between outer and inner layer, just out of the question.

• einzelne zum Mehrlagenrohr zu kombinierende Werkstofflagen aufeinandergelegt, wobei zumindest eine der Werkstofflagen aus mehr als einem aufgelegten Element besteht,
• hiernach dann eine jeweils erste Verbindung zwischen den randseitigen Elementen der aufliegenden Werkstofflage und der benachbarten Werkstofflage geschaffen wird,
• der so gebildete Mehrlagen-Werkstoff zum Rohr geformt wird und bei der Verformung die noch frei gegeneinander verschiebbaren Kanten der Elemente der aufliegenden Werkstofflage aufgrund der unterschiedlichen Umfangslängen von Innenrohr und Außenrohr sich entsprechend dem Verformungsfortschritt frei aufeinander zu bewegen,
• dann diese sich aufeinander zu bewegenden Kanten der Elemente der aufliegenden Werkstofflage nach einem bestimmten Verformungsfortschritt aneinander stoßen, und
• sodann das Mehrlagenrohr mit Hilfe der Blechumformmaschine zu Ende geformt wird, wobei sich nun während dieser Endformung die Kanten der Elemente der aufliegenden Werkstofflage nun nicht weiter frei aufeinander zu bewegen können, wodurch die jeweilige als Innenrohr fungierende Werkstofflage kraftschlüssig in die jeweilig als Außenrohr fungierende Werkstofflage gepreßt wird.

Meanwhile, however, an optimized process of WO 2010/145680 A1 known, which requires neither an interruption of the tube forming process for material layer connection nor a subsequent incorporation of material parts. Here are

• individual layers of material to be combined to form the multi-layer tube, wherein at least one of the material layers consists of more than one applied element,
• Thereafter, a respective first connection between the edge-side elements of the overlying material layer and the adjacent material layer is created,
• the multilayer material formed in this way is formed into a tube and during the deformation the edges of the elements of the overlying material layer that are still freely displaceable relative to one another move freely towards each other due to the different circumferential lengths of inner tube and outer tube according to the deformation progress,
• then these mutually moving edges of the elements of the overlying material layer abut each other after a certain deformation progress, and
• Then the multi-layer pipe is formed with the help of Blechumformmaschine to the end, now now can not move freely towards each other during this final molding, the edges of the elements of the overlying material layer, whereby the respective working as an inner tube material layer pressed non-positively in each acting as an outer tube material layer becomes.

In this method according to the prior art, the interruption of the tube forming process in the sheet metal forming - ie in the bending roll - avoided by at least two elements that later form the inner layer, initially, ie before the tube forming process, edge laterally with the later the outer layer forming material layer, that is usually welded to this, be. During the tube forming process, So eg in the bending roll, then move the free ends of these elements due to the different bending radii (or circumferential lengths, which means the same) of inner and outer tube to each other and eventually encounter each other. Since at this time already a curvature of the sheet has been used to a pipe, the edges of the abutting layers do not jump from each other, but remain abutting, but they - assuming a smooth edge shaped - a, with increasing deformation progress increasing strength exert on the material inner layer, with which this is pressed against the outer layer. Such is an interruption of the molding process. - For example, for further welding of the material layers - to form a full-surface inner layer of material from the material provided inside the pipe no longer required.

However, this approach has the disadvantage that here a downstream processing step, namely for welding the then located inside the pipe abutting edge is required. Also arises after this process so an additional third weld - namely at the abutting edge - inside the tube, which is an additional source of error.

It is therefore - starting from the WO 2010/145680 A1 - Object of the present invention to provide a method for producing multilayer pipes, in which an additional weld in the tube interior of the multilayer pipe is avoided, however, the production technical advantages of the method according to the WO 2010/145680 A1 remain preserved, so neither an interruption of the tube forming process for material layer connection still a subsequent incorporation of material parts of the parts is required.

• die benachbarte Werkstofflage zumindest leicht gebogen wird, , - (wobei hier unter ,gebogen' sowohl eine elastische, wie auch eine plastische Verformung zu verstehen ist) -,
• die zum Mehrlagenrohr zu kombinierenden Werkstofflagen aufeinandergelegt werden, wobei die erste Werkstofflage als aufliegende Werkstofflage auf der benachbarten Werkstofflage positioniert wird,
• eine erste Verbindung zwischen der - nach der Rohrformung als Innenrohr fungierenden - aufliegenden Werkstofflagen und der - nach der Rohrformung als Außenrohr fungierenden - benachbarten Werkstofflage dadurch geschaffen wird, daß die aufliegende Werkstofflage mit der benachbarten Werkstofflage - vorzugsweise in etwa - entlang einer ersten Kante der aufliegenden Werkstofflage oder - vorzugsweise in etwa - entlang einer Linie parallel hierzu verbunden wird,
• eine zweite Verbindung zwischen der aufliegenden Werkstofflage und der benachbarten Werkstofflage dadurch geschaffen wird, daß die aufliegende Werkstofflage mit der benachbarten Werkstofflage - vorzugsweise in etwa - entlang einer der ersten Kante gegenüberliegenden zweiten Kante der aufliegenden Werkstofflage oder - vorzugsweise in etwa - entlang einer Linie parallel hierzu verbunden wird, und danach
• der so gebildete Mehrlagen-Werkstoff mit Hilfe der Blechumformmaschine zum Mehrlagenrohr geformt wird, wobei
  während dieser Formung ab einem gewissen Verformungsgrad die jeweilige aufliegende und sodann als Innenrohr fungierende einteilig ausgeführte Werkstofflage zwischen den beiden Werkstofflagenverbindungen in (Teil-)Kreisumfangsrichtung gestaucht und somit in die jeweilige benachbarte und sodann als Außenrohr fungierende Werkstofflage gepreßt wird.

This object is achieved by a method for the rapid production of a multilayer pipe using a Blechumformmachine according to claim 1. Advantageous embodiments will be apparent from the dependent claims. In the method according to the present invention, the multilayer pipe at least a first material layer and a material layer adjacent to the first material layer, wherein

• the adjacent material layer is bent at least slightly, - (in which case "bent" means both an elastic and a plastic deformation) -
• the material layers to be combined with the multilayer pipe are stacked on one another, wherein the first material layer is positioned as a resting material layer on the adjacent material layer,
• a first connection between the - after tube forming acting as an inner tube - resting material layers and - after tube forming acting as an outer tube - adjacent material layer created by the fact that the overlying material layer with the adjacent material layer - preferably approximately - along a first edge of the lying Material layer or - preferably in about - along a line parallel thereto,
• a second connection between the overlying material layer and the adjacent material layer is created by the material layer resting on it with the adjacent material layer, preferably approximately along a second edge of the overlying material layer opposite the first edge, or preferably along a line parallel thereto is connected, and after
• the thus formed multilayer material is formed by means of the sheet metal forming machine for multilayer pipe, wherein
  During this shaping from a certain degree of deformation, the respective resting and then acting as an inner tube integrally running material layer between the two material layer compounds in the (part) circumferential direction compressed and thus pressed into the respective adjacent and then acting as an outer tube material layer.

It should be emphasized that the aforementioned method steps by the order of their listing in the above text by no means require the same order in the execution of the method according to the invention. In the execution of the method - apart from technical necessities in the sequence, such as the last-mentioned process step of tube forming by means of sheet metal forming machine, which indeed requires the previous formation (production) of the multilayer material - it does not necessarily on this order. For example, the two material layer connections (preferably approximately) can be created simultaneously instead of successively. It is essential to first make the bend, and then create the second connection between the material layers.

The bending of the adjacent - preferably below - and after the (multilayer) pipe forming the outer layer of the multilayer pipe forming material layer brings their edges - seen in the pipe cross-section closer together. In the method according to the present invention, therefore, the interruption of the tube forming process in the sheet metal forming machine and an additional weld in the tube interior is avoided because here neither a break in the forming process in the sheet metal forming machine for connecting the material layers nor to form a full-surface material inner layer of the space provided here Material inside the tube and no further (third) weld is required because the material inner layer is carried out in one piece and on the other a bending of the adjacent material layer, so as a 'tempering' of the material takes place, which the connection of the two material layers together before the (further) tube forming process allowed in the sheet metal forming machine. The bonding of the material layers can thus happen before the actual tube forming process in the sheet metal forming machine (tube forming machine) and therefore does not interfere with this process further.

Any bending of the adjacent material layer along (about one or both) of its edges preferably according to the present invention already on the end radius of the multilayer tube to be manufactured, as this avoids a subsequent, often with manufacturing problems such as edge pinching, connected processing. Such bending on the end radius can be about preferably with a bending press for metal sheets, as shown in the WO 2010/118759 A2 is known.

In a preferred embodiment of the method for the rapid production of a multilayer pipe by means of a sheet metal forming machine according to the present invention, individual material layers to be combined with the multilayer pipe are stacked on top of each other, and then a first connection between the overlying material layer and the adjacent material layer is created by the overlying material layer is connected to the adjacent material layer approximately endang the first edge of the overlying material layer or approximately endang a line parallel thereto,
whereupon the thus formed multilayer material - and thus also the adjacent material layer - in the area in which the material layers approximately along the edge or endang a Line are connected approximately parallel thereto by the first connection, at least slightly bent (for the concept of bending as plastic or elastic deformation see above, there to the adjacent material layer),
the second still free edge of the overlying material layer is positioned relative to the adjacent material layer in the direction of a still free edge of the adjacent material layer, and
Then the second connection between the overlying material layer and the adjacent material layer is created by that
the resting material layer is connected to the adjacent material layer approximately along the second, until then free edge of the overlying material layer or approximately along a line parallel thereto, and
the thus formed multilayer material is formed by means of the sheet metal forming machine for multilayer pipe, wherein
During this shaping from a certain degree of deformation, the respective resting and then functioning as an inner tube material layer between the two material layer compounds in (part) circumferential direction compressed and thus pressed into the respective adjacent and then acting as an outer tube material layer.

mit

B_i

als der im Rohrquerschnitt betrachteten (Teil-)Kreisumfangslänge (Breite vor Rohrformung) der jeweilig als Innenrohr fungierenden Werkstofflage zwischen den beiden Verbindungen zwischen den Werkstofflagen etwa in mm angegeben,

L_nfa

der im Rohrquerschnitt gesehenen Kreisumfangslänge (Breite vor Rohrformung) der jeweilig als Außenrohr fungierenden Werkstofflage etwa in mm angegeben,

SA

der Wanddicke der jeweilig als Außenrohr fungierenden Werkstofflage etwa in mm angegeben,

SI

als der Wanddicke des jeweilig als Innenrohr fungierenden Werkstofflage etwa in mm angegeben, und

d₁

als dem Abstand der ersten Verbindung entlang der ersten Kante der aufliegenden Werkstofflage oder entlang einer Linie parallel hierzu von der entsprechenden ersten Kante der benachbarten Werkstofflage zum Zeitpunkt der Schaffung der ersten Verbindung zwischen den Werkstofflagen etwa in mm angegeben, und

d₂

als dem Abstand der zweiten Verbindung entlang der zweiten Kante der aufliegenden Werkstofflage oder entlang einer Linie parallel hierzu von der entsprechenden Kante der benachbarten Werkstofflage zum Zeitpunkt der Schaffung der zweiten Verbindung zwischen den Werkstofflagen etwa in mm angegeben.

In the above-described embodiment of the method according to the present invention, therefore, once again the interruption of the tube forming process in the sheet metal forming machine and also an additional weld in the tube interior is avoided, since neither an interruption of the molding process for the connection of the material layers, nor the formation of a full-surface material inner layer of the material provided inside the pipe inside and no further (third) weld is required because this by the 'biasing' of the multilayer material by means of the first one-sided bonding of the layers, the elastic or plastic bending in this area, the 'moving over' , Preferably 'pulling over' towards the other end and finally the fixing of this 'bias' at this other end by local re-connecting eliminated. This embodiment of the production according to the invention described above is advantageous because it does not require any initial (initial) deformation - be it plastic or elastic - of the adjacent material layer. Rather, this bend is only in the course of the execution of the manufacturing method according to the invention, namely by the positioning, preferably 'pulling over' the overlying material layer achieved simultaneously with this step of the method. Preferably, the circumference length (width) considered in the pipe cross-section of the material layer B _i acting between each of the two connections of the material layers as the inner pipe is chosen such that $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)-\left({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{1}}+{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{2}}\right)\mathrm{is}.$$

With

B _i

as the (partial) circumference length considered in the tube cross-section (width before tube forming) of the respective material layer acting as inner tube between the two connections between the material layers is given in mm,

L _nfa

the circumference length seen in the pipe cross-section (width before pipe forming) of the material layer acting in each case as the outer pipe is given approximately in mm,

SA

the wall thickness of the respective material layer acting as outer tube is given in mm,

SI

indicated as the wall thickness of the material layer acting respectively as an inner tube in approximately mm, and

d ₁

as the distance of the first connection along the first edge of the overlying material layer or along a line parallel thereto from the corresponding first edge of the adjacent material layer at the time of creating the first connection between the material layers approximately in mm, and

d ₂

as the distance of the second connection along the second edge of the overlying material layer or along a line parallel thereto from the corresponding edge of the adjacent material layer at the time of creation of the second connection between the material layers approximately in mm.

The latter condition is equivalent to the fact that in the tube cross-section considered (partial) circumference of the later acting as an inner tube material layers between the two material layer connections is greater than - also considered in the tube cross-section (partial) circumference length of an inner layer, which in the case of two (in a tube formed according to the present inventive method) stress-free (between the two material layer connections) of mutually lying material layers would result. This compared to the above conditions larger (partial) circumference length between the two material layer connections then leads to a compression of the inner layer in the circumferential direction and thus to a radial compression of the inner to the outer layer.

• Hierzu finden - vorzugsweise ausgehend von zwei Lagen, also einer aufliegenden Werkstofflage, die nach der Rohrformung die Innenlage, also das spätere Innenrohr, bildet, und einer benachbarten Werktofflage, die nach der Rohrformung die Außenlage, also das spätere Außenrohr, bildet - neben den bereits eingeführten Größen, auch die folgenden Größen Verwendung:

  σ_I

  als Streckgrenze (welche in der Regel in etwa der Stauchgrenze insbesondere bei gewalzten Metallen - entspricht) der aufliegenden Werkstofflage (Innenlage), also des (späteren) Innenrohres - etwa in N/mm²,

  E

  als Elastizitätsmodul (E-Modul) der aufliegenden Werkstofflage (Innenlage), also des (späteren) Innenrohres - etwa in N/mm².

According to those already in the WO 2006/066814 A1 mentioned geometric relationships are - depending on the desired pressing force - the size of the elements of the overlying material layer (ie the later inner layer) and the position of the connections between the overlying material layer (ie the material layer, which later forms the inner layer [or the inner tube]) and the In order to explain the mode of action here, in particular the formation of the pressing force which presses the respective inner layer of material against the respective outer material layer, the following representation of the geometric relationships is used:

• To find this - preferably starting from two layers, so an overlying material layer, which forms the inner layer, ie the later inner tube after tube forming, and an adjacent Werkofflage after the tube forming the outer layer, so the later outer tube, forms - in addition to the already introduced sizes, also the following sizes use:

  σ _I

  as yield strength (which usually corresponds approximately to the compression limit, in particular for rolled metals) of the overlying material layer (inner layer), ie of the (later) inner tube - approximately in N / mm ² ,

  e

  as modulus of elasticity (modulus of elasticity) of the overlying material layer (inner layer), ie of the (later) inner tube - approximately in N / mm ² .

was der mittleren (im Rohrquerschnitt betrachteten) Kreisumfangslänge - hier des (späteren) Außenrohres - (und damit auch der Breite der jeweilig als Außenrohr fungierenden Werkstofflage) entspricht. Wollte man das Innenrohr ohne jede Stauchung in das Außenrohr einpassen, so würde die Länge seiner neutralen Faser (ohne Stauchung der Innenlage) - hier L_nfiOS genannt - aufgrund der unterschiedlichen Biegeradien $${\mathrm{L}}_{\mathrm{nfiOS}}=\left(\mathrm{DA}-\mathrm{2}\cdot \mathrm{SA}-\mathrm{SI}\right)\cdot \mathrm{\pi },$$

was ebenfalls der mittleren Umfangslänge - hier jedoch des Innenrohres - entspricht, betragen.The length of the neutral fiber - in a circular bent state - of the (later) outer tube - here called L _nfa - is: $${\mathrm{L}}_{\mathrm{nfa}}=\left(\mathrm{THERE}-\mathrm{SA}\right)\cdot \mathrm{\pi }$$

which corresponds to the average circumference length (considered in the tube cross-section) - here the (later) outer tube - (and thus also the width of the respective material layer acting as the outer tube). Did you want to fit the inner tube without any compression in the outer tube, so the length of the neutral fiber would (without compression of the inner layer) - here called L _nfiOS - due to the different bending radii $${\mathrm{L}}_{\mathrm{nfiOS}}=\left(\mathrm{THERE}-\mathrm{2}\cdot \mathrm{SA}-\mathrm{SI}\right)\cdot \mathrm{\pi }.$$

which also corresponds to the mean circumferential length - here, however, the inner tube - amount.

Thus, if one uses a material _layer of width L _nfiOS as the inner _layer and a material _layer of width L _nfa as the outer layer, the inner layer can exactly fit into the outer layer during tube forming, which means that the respective longitudinal edges of the outer as well as the inner layer with the completion of the tube forming process - a geometrically ideal running tube forming process, ie the ideal formation of a circle (seen in the tube cross section) once assumed - at the same time abut each other. In this case, the inner tube would be pressed against the outer layer only by its built-up during the forming process spring-back force. A compression of the inner tube, which would open due to the built-up in the material pressure and its curvature outwards against the respective outer material layer out in an additional pressing force of the inner tube against the outer tube, however, would not take place.

However, such a method would just produce the method according to the invention. This raises the question of what - viewed in cross-section of the molded tube - (partial) circumference length (= width of the overlying material layer prior to forming) must have the inner layer, so that there is such a desired compression of the circumferential length of the inner layer of material (B _i ) or, what is the same, the width of the overlying material layer in the tube forming process.

und damit $${\mathrm{L}}_{\mathrm{fv}}=\left(\mathrm{DA}-\mathrm{SA}\right)\cdot \mathrm{\pi }-\left(\mathrm{DA}-\mathrm{2}\cdot \mathrm{SA}-\mathrm{SI}\right)\cdot \mathrm{\pi }$$

was äquivalent zu $${\mathrm{L}}_{\mathrm{fv}}=\left(\mathrm{SA}+\mathrm{SI}\right)\cdot \mathrm{\pi }$$

ist, womit klar wird, daß grundsätzlich immer dann eine Stauchung der jeweilig als Innenrohr fungierenden Werkstofflage eintritt, wenn dieses breiter ist, als die jeweilig als Außenrohr fungierende Werkstofflage abzüglich der Summe der Dicke beider benachbarter Werkstofflagen multipliziert mit der Kreiszahl π, wenn also für die Breite B_i des als Innenrohr fungierenden Werkstofflage gilt $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)\mathrm{.}$$

Wird aber die jeweilig als Innenrohr fungierende Werkstofflage bei der Rohrformung in der Breite - nämlich durch die beiden nach dem erfindungsgemäßen Verfahren geschaffenen Verbindungen zwischen den Werkstofflagen - gestaucht, so wird die jeweilig als Innenrohr fungierende Werkstofflage dadurch auch in die jeweilige äußere (also vom Rohmnnenraum gesehen nach außen benachbarte) Werkstofflage gepreßt. Dabei läßt sich diese Preßkraft bis zur Streckgrenze (respektive Stauchgrenze, die in der Regel - insbesondere bei gewalzten Metallblechen, in etwa gleich der Streckgrenze ist -) steigern. In Fällen, in denen keine ausgeprägte Streckoder Stauchgrenze vorliegt, kann anstelle dieser auch die sogenannte technische Streckgrenze (auch Dehngrenze als Betrag der Spannung einer plastischen bleibenden Dehnung unter einer bestimmten Krafteinwirkung genannt) oder technische Stauchgrenze genannt, treten. Oberhalb der Zone der sogenannten 'Hook' schen Geraden', also etwa im Bereich der plastischen Dehnung (z.B. im Bereich der sogenannten 'Lüderskurve') hingegen läßt sich diese Kraft nicht mehr wesentlich (zumindest nicht mehr proportional) steigern. Will man also vor diesem Hintergrund über die o.a. Bedingung $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right),$$

• die grundsätzlich überhaupt eine Stauchung sicherstellt - hinaus eine maximale Stauchung und damit auch eine maximale Preßkraft erreichen, so ist folgendes zu bedenken:
  • Der Stauchungsgrad der Innenwerkstofflage zum Erreichen der Stauchgrenze - hier ε_St genannt - ergibt sich nach dem Hook'schen Gesetz zu: $${\mathrm{\epsilon }}_{\mathrm{St}}=\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{E}}$$
    

According to the above explanations, the length over which the edges of the inner layer can move freely relative to those of the outer layer in the circumferential direction during tube forming: $${\mathrm{L}}_{\mathrm{fv}}={\mathrm{L}}_{\mathrm{nfa}}-{\mathrm{L}}_{\mathrm{nfiOS}}$$

and thus $${\mathrm{L}}_{\mathrm{fv}}=\left(\mathrm{THERE}-\mathrm{SA}\right)\cdot \mathrm{\pi }-\left(\mathrm{THERE}-\mathrm{2}\cdot \mathrm{SA}-\mathrm{SI}\right)\cdot \mathrm{\pi }$$

which is equivalent to $${\mathrm{L}}_{\mathrm{fv}}=\left(\mathrm{SA}+\mathrm{SI}\right)\cdot \mathrm{\pi }$$

is, which is clear that in principle always occurs a compression of each functioning as an inner tube material layer, if this is wider than the respective acting as an outer tube material layer minus the sum of the thickness of both adjacent material layers multiplied by the circle number π, so if for Width B _{i of} the material layer acting as inner tube applies $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)\mathrm{,}$$

However, if the respective material layer acting as an inner tube is compressed in the tube formation in the width - namely by the two connections between the material layers created by the method according to the invention - the material layer acting as the inner tube is thereby also seen in the respective outer (ie from the basic internal space outwardly adjacent) material layer pressed. This pressing force can be up to the yield strength (respectively compression limit, which is usually - especially in rolled metal sheets, approximately equal to the yield strength -) increase. In cases in which there is no pronounced yield or compression limit, the so-called technical yield strength (also referred to as yield strength as the amount of stress of a plastic permanent elongation under a certain force) or technical compression limit may be used instead. On the other hand, above the zone of the so-called 'hook' straight line, ie in the area of plastic strain (eg in the area of the so-called 'Lüders curve'), this force can no longer be significantly increased (at least not proportionally). So if you want against this background on the above condition $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right).$$

• which basically ensures compression at all - in addition to achieve maximum compression and thus a maximum compressive force, the following should be considered:
  • The degree of compression of the inner material layer to reach the compression limit - here called ε _St - results according to Hooke's law: $${\mathrm{\epsilon }}_{\mathrm{St}}=\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}$$
    

Accordingly, in the case that the maximum pressing force of the inner material layer against the outer material layer is just to be achieved: $${\mathrm{B}}_{\mathrm{i}}-{\mathrm{B}}_{\mathrm{i}}\cdot {\mathrm{\epsilon }}_{\mathrm{St}}={\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\cdot \left(\mathrm{SA}+\mathrm{SI}\right)$$

wobei für den maximal erreichbaren Stauchungsgrad $\mathrm{0}<\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{E}}<\mathrm{1}$

gilt.With regard to the width which results for the inner material layer in this case, then: $$\begin{array}{cc}{\mathrm{B}}_{\mathrm{i}}& =\frac{{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)}{\mathrm{1}-{\mathrm{\epsilon }}_{\mathrm{St}}}\\ & =\frac{{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)}{\mathrm{1}-\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{{\rm E}}}}\end{array}$$

where for the maximum achievable degree of compression $\mathrm{0}<\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}<\mathrm{1}$

applies.

For practical purposes it should be considered that - if one wants to achieve the maximum pressing force of the inner against the outer layer as reliably as possible, in any case approximately, it must be ensured that the compression limit (≈ yield strength) is actually reached. This can be achieved by giving the maximum degree of compression, as it results from the material constants ( σ _I , E), a certain - quite generous - surcharge - preferably up to 800% of the maximum degree of compression, more preferably of up to 600% or even up to 300% or up to 200% or even up to 100% of the maximum degree of compression - there.

Preferably, therefore, in the inventive method for the production of multi-layer pipes for the width of acting as an inner tube material layer strip in terms of the achievement of the highest possible compressive force of the inner against the outer layer for practical purposes are required, that: $${\mathrm{B}}_{\mathrm{i}}\ge \frac{{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)}{\mathrm{1}-\frac{{\mathrm{\sigma }}_{\mathrm{Ί}}}{\mathrm{e}}}.\mathrm{With}\mathrm{0}<\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}<\mathrm{1}$$

If the width of the inner layer is chosen to be greater than the right of the equation term, a possible compression allowance (see above) is taken into account, which can compensate for the production inaccuracies - such as in position and / or leadership of the material material bands to each other so that the desired maximum pressing force of the inner tube against the outer tube - at least in some - safely achieved.

Due to the compression allowance also an elastic expansion of the outer tube due to the radially acting compressive force of the inner tube to the outer tube and influences on the process by a pipe forming after the possible not exactly sheet-thick central layer of the neutral fiber of the respective material layer are collected.

However, the above statements assume that the compression of the inner layer is provided by the two connections between the material layers, wherein the - seen in the (later) pipe cross section - respective two corresponding edges of the adjacent material layers at the time of creation of the first and the second connection between the material layers in each case - preferably approximately - lie flush against each other and the respective connection also - preferably approximately - along the respective edge - preferably by a weld along the edge - takes place. However, if, for example, the second initially free edge of the overlying material layer (inner layer) is not pulled so far in the direction of the still free edge of the adjacent material layer (outer layer) that they lie flush against each other before - according to this embodiment of the present invention - the second compound is created, so is the resulting distance d ₂ between the second - along or parallel to the still free (second) edge of the overlying material layer running - material layer connection and the corresponding (second) edge of the adjacent material layer to be considered. The same applies correspondingly to the distance d _{1 of} the first material layer connection extending along or parallel to the other (first) edge of the resting material layer from the corresponding (first) edge of the adjacent material layer.

und damit: $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)-\left({\mathrm{d}}_{\mathrm{1}}+{\mathrm{d}}_{\mathrm{2}}\right),$$

als Bedingung für eine Stauchung. Will man eine maximale Stauchung erreichen, so ergibt sich für Bi dementsprechend: $${\mathrm{B}}_{\mathrm{i}}\ge \frac{{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)-\left({\mathrm{d}}_{\mathrm{1}}+{\mathrm{d}}_{\mathrm{2}}\right)}{\mathrm{1}-\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{E}}},\mathrm{mit}\mathrm{0}<\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{E}}<\mathrm{1.}$$

However, taking this into account, it follows $${\mathrm{L}}_{\mathrm{fv}}=\left(\mathrm{SA}+\mathrm{SI}\right)\cdot \mathrm{\pi }-\left({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{1}}+{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{2}}\right)$$

and thus: $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)-\left({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{1}}+{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{2}}\right).$$

as a condition for compression. If you want to achieve a maximum compression, Bi results accordingly: $${\mathrm{B}}_{\mathrm{i}}\ge \frac{{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)-\left({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{1}}+{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{2}}\right)}{\mathrm{1}-\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}}.\mathrm{With}\mathrm{0}<\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}<\mathrm{1.}$$

Preferably, the method for producing a multi-layer tube according to the present invention is characterized in that the first connection between the material layers is created by this - preferably approximately - along one of the longitudinal or transverse edges of the overlying material layer or - preferably along - along a line parallel thereto but also along or parallel to the future pipe seam. The laid-up (n) material layer (s) may or may therefore lie with its longitudinal edge parallel to the longitudinal edge of the adjacent (about underlying) material layer, but need not or must not. So it is also possible that they come to lie with their longitudinal edge transverse thereto or come. However, the connection with the adjacent (approximately below) material layer is preferably carried out along or parallel to the future pipe longitudinal seam.

In this connection, it should be noted that when this text is used herein to refer to a connection along an edge or along a (preferably imaginary) line only, it means any type of connection along the edge or line, whether or not it is Connection along the entire edge or line or only in sections along the edge or line or even in single points (such as spot welds), for instance at two points - preferably at the end points of the edge or line - or even at a single point at the point Edge or on the line.

Also, the functioning as an inner tube material layer in the finished multilayer tube in cross section form a circle, which can be achieved in that the elements of the overlying material layer, which later form the Rohrmnenlage cover only a portion of the surface of the material layer, which later forms the outer layer.

Preferably, the material layer functioning as an inner tube and forming a partial circle in cross-section in the finished multilayer tube forms a groove at the foot of the multilayer tube.

After completion of the slot tube, so after completion of - preferably essential - tube forming process, such as in the bending roll, then preferably in the inventive method for rapid production of a multilayer tube, the multilayer tube can be closed by welding the outer tube along the pipe seam. Also, this is preferably carried out a surfacing of the inner tube along the pipe seam. Preferably, the multilayer tubular body is thus completed.

Furthermore, the material layers can be connected to the front sides of the tube, such as there to prevent the ingress of moisture between the metallurgically yes not fully connected material layers.

A preferred application of the method according to the present invention is the production of double-layer tubes, however, the invention is not limited thereto, also three-, four- and more multi-layer tubes of the invention are hereby basically produced.

In a further particularly preferred embodiment of the present invention find sheets, preferably metal sheets and more preferably steel sheets, as a material layer or elements of the material layer use.

Also, in the method for producing a multilayer pipe according to the present invention, at least one of the joints of the material layers is preferably used as a weld, which is particularly suitable for the aforementioned metal sheets, preferably steel sheets.

As sheet metal forming machine is about a bending roll, for example, a three-roll bending machine, but also a press / die assembly, such as in the context of known from the prior art UOE (U- forms, O- forms, expand) -Rohrformungsverfahrens (see, for example, the UOE method: Hiersig, Heinz M., Encyclopedia Mechanical Engineering, Heidelberg 1997, p. 704f. to the keyword "Longitudinal seam-large pipe production It should, however, be borne in mind that according to the process of the present invention, depending on the combination of materials, it may be necessary to dispense with the last step of expansion if, owing to the yield ratio, the Materials from respective inner to outer layer the compression of the material layers against each other again would be too deteriorated.

In the JCO process, the pipe is formed by first placing the sheet in a press by means of a sword in the shape of a recumbent 'J' and then in that of a recumbent 'C' . After that, it is then - as in the case of the UOE method - bent into the O'- shape.

Fig. 1-6

eine perspektivisch skizzierte Ansicht einzelner Schritte des erfindungsgemäßen Verfahrens zur schnellen Herstellung eines Mehrlagenrohres mit Hilfe einer Blechumformmachine, wobei diese einzelnen Schritte nicht notwendigerweise alle denselben Formungsprozeß derselben Werkstofflagen wiedergeben, sondern vielmehr in schematischer Weise charakteristische Schritte oder Stationen des Formungsprozesses zeigen und die einzelnen Werkstofflagen von Schritt zu Schritt bzw. von Station zu Station durchaus andere sein können, als sie in den vorangehenden oder folgenden Schritten oder Stationen zu sehen sind, um so verschiedene Varianten des erfindungsgemäßen Verfahrens anhand einer Serie von Darstellungen in den Fig. 1 bis 6 zeigen zu können,

Fig. 7

einen perspektivischen Querschnitt durch ein fertiggestelltes Mehrlagenrohr mit Innenlage (etwa auch Innenrohr, Innenrohrleitung, Innenblech etc. genannt) und Außenlage (etwa auch Außenrohr, Außenrohrleitung, Grundblech etc. genannt),

Fig. 8

einen perspektivischen Querschnitt durch ein Mehrlagenrohr nach Fig. 7 mit Innenlage und Außenlage in Detailansicht im Bereich der (Schweiß-)Verbindungen in der Nähe des Rohtlängsnahtschweißung,

Fig. 9

eine Situation bei dem erfindungsgemäßen Verfahren, wenn die Blechformung vermittels einer UO(E)-Pressen-/Gesenkanordnung ausgeführt wird,

Fig. 10

sodann den Formungsschritt der ein 'U' formt,

Fig. 11

sodann den Formungsschritt, der ein 'O', also ein Schlitzrohr ausformt, und

Fig. 12

ein exemplarisches Spannungs-Dehnungsdiagramm zur Erläuterung, wie die angestrebte maximale Preßkraft durch Stauchung der Innenlage dem Umfang nach erreicht wird.

In the following non-limiting exemplary embodiments will be discussed with reference to the drawings. In this show:

Fig. 1-6

a perspective outlined view of individual steps of the inventive method for rapid production of a multilayer pipe using a Blechumformmachine, these individual steps do not necessarily reflect all the same molding process of the same material layers, but rather schematically show characteristic steps or stations of the molding process and the individual material layers of step to step or from station to station may be quite different than they can be seen in the preceding or following steps or stations, so as to different variants of the inventive method based on a series of representations in the Fig. 1 to 6 to be able to show

Fig. 7

a perspective cross-section through a finished multi-layer pipe with inner layer (also called inner tube, inner tube, inner plate, etc.) and outer layer (also called outer tube, outer tube, base plate, etc.),

Fig. 8

a perspective cross section through a multilayer pipe after Fig. 7 with inner layer and outer layer in detail view in the area of the (weld) connections in the vicinity of the raw longitudinal seam weld,

Fig. 9

a situation in the method according to the invention when the sheet metal forming is carried out by means of a UO (E) press / die arrangement,

Fig. 10

then the forming step which forms a 'U' ,

Fig. 11

then the forming step, which forms an 'O', ie a slot tube, and

Fig. 12

an exemplary stress-strain diagram for explaining how the desired maximum pressing force is achieved by compression of the inner layer in the scope.

Fig. 1 shows a first and second step of an embodiment of the method according to the invention for the rapid production of a multilayer pipe by means of a Blechumformmachine in perspective view (the sheet metal forming machine is not seen here).

In a first step, individual material layers to be combined to form the multilayer pipe, namely an overlying material layer 1 and an adjacent material layer 2, are stacked on top of each other.

In a second step, a first connection 3a - preferably a welded connection - between the overlying material layer 1 and the adjacent material layer 2 created by the fact that the overlying material layer 1 with the adjacent material layer 2 - preferably approximately - along a first edge 4a of the lying Material layer 1 connected - preferably welded - is. The first edge 4a of the overlying material layer 1 corresponding (first) edge 6a of the adjacent material layer 2 here lies on the first link 3a of the two to be seen material layers 1, 2 by the distance d ₁ - with respect to the overlying material layer 1 and the first Edge 4a - offset to the outside. The first connection 3a of the material layers 1, 2 is therefore also of the first edge 4a of the overlying material layer 1 corresponding (first) edge 6a of the adjacent material layer 2 by the distance d ₁ - in view of the adjacent (here below) material layer. 2 and its first edge 6a - offset inwards.

Fig. 2 then shows a third step of the method according to the Fig. 1 to 6 Where the formed by the preceding steps multi-layer material in the area in which the material layers 1, 2 along the edge 4a through the first connection 3a connected to each other are, is bent, which can be done about by means of a bending roll, for example a three-roll bending machine or by means of a press, such as a press brake, but also by means of any other suitable machine or any other suitable tool (possibly also manually). Here, the first edge 4a of the overlying material layer 1 and the corresponding edge 6a of the adjacent material layer 1 are flush with each other. The in Fig. 1 mentioned distance d ₁ between the first compound 3a of the material layers 1 and 2 and the edge 6a of the adjacent material layer 2, which runs along the two adjacent edges 4a and 6a here , is therefore zero in the material layers 1, 2 to be seen here ,

Fig. 3 then shows a fourth step of the method according to the present invention according to the Fig. 1 to 6 , in which case the still free edge 4b of the resting material layer 1 is moved relative to the adjacent material layer 2 in the direction 10 of its likewise free (second) edge 6b . This is preferably done so that this edge 4b approximately by means of a gripping device (not seen here) is detected, for example by a pair of pliers, which engages the overlying material layer 1 by means of one or more jaws (not seen here) and then - about by means of Gripping device - in the direction 10 of the yes also still free (second) edge 6b of the adjacent material layer 2 is pulled. However, this can also be done by means of any other suitable machine and / or a tool suitable for this purpose (if appropriate, but also manually). In principle, it is also possible to achieve the movement of the material layers 1, 2 and their respective still free (second) edges 4b, 6b which are provided according to the invention in such a way that the material layer 2 adjacent to the material layer 1, preferably below, adjoins the material layer 2 in the direction the (second) edge 4b of the resting material layer 1 is displaced. Likewise, both edges 4b, 6b can be moved against each other. It is crucial that there is a relative movement of the still free (second) edge 4b of the overlying material layer 1 to the still free (second) edge 6b of the adjacent material layer 2 , the distance between these two still free (respective second) edges 4b, 6b to each other - preferably up to a distance of zero, so therefore no remaining distance more - reduced. Then, a second connection 3b between the material layers 1, 2 take place here along the (second) still free edge 4b of the overlying material layer 1 - preferably as a welded joint, - runs approximately as a weld. The distance d ₂ between this (second) connection 3b of the material layers to each other to the (second) edge 6b of the adjacent (down here) Material layer is also marked here. The second edges 4b of the overlying material layer 1 corresponding (second) edge 6b of the adjacent material layer 2 here lies on the second link 3b of the two to be seen material layers 1, 2 by the distance d ₂ - with respect to the overlying material layer 1 and the second Edge 4b - offset to the outside. The second connection 3b of the material layers 1, 2 is thus also of the second edge 4b of the overlying material layer 1 corresponding (second) edge 6b of the adjacent material layer 2 by the distance d ₂ - with respect to the adjacent (here below) material layer. 2 and its second edge 6b - offset inwards.

Fig. 4 shows, for the first, a fifth step of the method according to the Fig. 1 to 6 , Are to be seen in the two material layers 1, 2, after previously still free edge 4b of the overlying material layer 1 relative to the adjacent material layer 2 in the direction 10 which is also previously still free edge 6b is moved - preferably drawn - has been and is, from this Movement finally resulting position of the material layers 1, 2 to each other a second connection 3b - preferably a welded joint, such as a weld - between the overlying material layer 1 and the adjacent material layer 2 was created. A first connection 3a had previously been created along the first edge 4a of the overlying material layer 1 . In the embodiment which can be seen here, moreover, the respectively corresponding edges 4a, 6a on the one hand and 4b and 6b on the other hand lie flush (approximately) flush with each other on the material layers 1 and 2 , namely on the line along which the two material layer connections also follow 3a on the one hand and 3b on the other. According to the embodiment, as can be seen here, thereby moving the previously free edge 4b of the overlying material layer 1 in the direction 10 of the previously still free edge 6b of - here below - adjacent material layer 2 and the subsequent second connection 3b the two material layers 1, 2 along the previously free edge 4b of the overlying material layer 1 already caused a curvature of the entire future tubular body.

To the other shows Fig. 4 but also the first step of another embodiment of the method according to the present invention, namely First, the adjacent material layer 2 was bent, such as by means of bending press for metal sheets, as they are known from WO 2010/118759 A2 is known and which makes it possible to reach in the region of the edges 6a and 6b of the adjacent material layer 2 already the end radius of the multilayer tube to be produced. However, the bending of the adjacent material layer 2 can also be achieved approximately in that this layer 2 is pressed into a correspondingly shaped die or even placed where it undergoes a bend due to the pressure or its own weight.

The material layers 1, 2 to be combined to form the multilayer pipe were then stacked on one another, the first material layer 1 being positioned as a resting material layer 1 on the adjacent material layer 2 .

Also, a first connection 3a between the overlying material layer 1 and the adjacent material layer 2 was created by connecting the overlying material layer 1 to the adjacent material layer 2 approximately along a first edge 4a of the overlying material layer 1 . A second connection 3b between the overlying material layer 1 and the adjacent material layer 2 has also been created and approximately along a second edge 4b of the overlying material layer 1, these compounds both sequentially, but also - preferably approximately - can be created simultaneously. A (approximately) simultaneous creation of both compounds is approximately possible if the resting material layer 1 immediately - for example by means of a suitable conveyor - in the correct position on the adjacent - then already bent - material layer 2 is positioned.

The thus-formed multi-ply material 1, 2 may then by means of the sheet metal forming machine (not shown here) to the multi-layer pipe 5 are formed, wherein 3a during this molding from a certain degree of deformation of the respective overlying and then acting as an internal pipe material layer 1 between the two material layer compounds , 3b in - seen in the cross section of the (later) (multi-layer) pipe - (partial) circumferential direction and thus compressed in the adjacent and then acting as an outer tube material layer 2 is pressed.

The Fig. 5 and 6 finally show the last step of a preferred embodiment of the method according to the present invention according to the Fig. 1 to 6 Where the formed by preceding steps of multilayer material with the aid of the sheet metal forming machine (not shown here) to the pipe 5 (more precisely to the slotted tube) is formed, namely to the multi-layer pipe (more precisely multi-layer slotted tube), wherein during this molding, the material layers 1, 2 - due to the previously made connections 3a, 3b with each other - (preferably from a certain deformation progress) between the two compounds 3a and 3b in - seen in the cross section of the (later) (multilayer) pipe - (partial) circumferential direction compressed be, whereby the respective functioning as an inner tube material layer 1 - preferably non-positively - is pressed into each functioning as an outer tube material layer 2 .

Fig. 7 then shows a perspective cross-section through a finished multilayer pipe 5 with inner layer (about also inner material layer, inner layer of material, inner tube, inner tube, inner plate or the like called) 1 and outer layer (as well as outer material layer, material outer layer, outer tube, outer tube, base plate or the like called ) 2, wherein the multilayer pipe 5 was preferably closed by a weld 7 of the outer tube 2 along a Rorhmaht 8 . Preferably, a contract weld 9 of the inner tube 1 can be made to close the tube, which can be seen here. However, such build-up welding 9 is not mandatory. The first (welding) connection 3a and the second (welding) connection 3b between the resting material layer 1 and the adjacent material layer 2 are also shown.

Fig. 8 shows a perspective cross section through a multilayer pipe after Fig. 7 with inner layer 1 and outer layer 2 in a detailed view in the area of the (welded) connections (such as welds) 3a, 3b and the welds (such as welds or build-up welds) 7 and 9.

Fig. 9 shows a situation of the inventive method, when the sheet metal forming is carried out approximately by means of a UO (E) -Pressen- / Gesenkanordnung. The later outer material layer 2 is here below and the subsequent inner layer 1 above. The upper layer 1 was with her - after welding the first compound 3a with the adjacent layer 2 - still free edge 4b in the direction 10 of the still free edge 6b of the adjacent (here below lying) material layer 2 pulled to the distance between both edges 4b and 6b was zero (the edges 4b and 6b thus abut one another directly) and in this position the edges 4b and 6b are welded to one another at the edges along the edge 4b adjacent to the adjacent material layer 2 below, whereby a second connection 3b between the material layers 1, 2 has emerged. The pulling over of the first still free edge 4b of the overlying material layer 1 in the direction 10 of the first also still free edge 6b of the adjacent (Here below) material layer 2 has here at the same time also a bending (be it a plastic bending, be it an elastic bending) at the other end of the material layers 1, 2, namely caused in the region of the first compound 3a , which again shows that bending does not necessarily have to be carried out as a first method step.

Fig. 10 then shows the forming step of a , U ' shaped by means of a press (not shown here), which drives a correspondingly shaped punch 11 down, where the material layers 1 and 2 together in a die (not here also not seen) to be driven. Here, the functioning as an inner tube material layer 1 - preferably from a certain deformation progress - (with a corresponding width of the inner layer 1) between the two compounds 3a, 3b of the material layers 1, 2 compressed and (non-positively) pressed into the outer layer acting as material layer 2.

Fig. 11 then shows the forming step, which forms an 'O', ie a slot tube by means of a press (not shown here), the two formed as a half round punch 12, 13 drives against the tubular body to be formed, where the material layers 1 and 2 in turn together to one - seen in cross-section - round shaped. Here, too, the inner material layer 1 is compressed with a corresponding width between the two material layer connections 3a and 3b and pressed there into the outer layer 2 . As a result of the curvature, which also results in other Blechutnformmaschinen for tube forming or tube forming tools or tube forming methods, such as in tube forming by means of a bending roll, such as a three-roll bending machine, the inner layer 1 does not jump from the outer layer 2, but hangs up the outer layer 2 at.

It should be noted that the method according to the invention can be carried out in a similar manner by means of a press / die arrangement designed for the so-called 'JCO' method. Here is then proceeded according to the JCO method, but this modified so that in turn two layers of material 1 and 2, as in the present invention modified UO (E) method are formed. Again, the overlying material layer 1 is connected to the later outer layer forming material layer 2 at least by two compounds 3a, 3b and then formed a slot tube by the JCO method. Here again, the desired effect of the invention occurs at the (preferably from a given shaping progress) compression of the inner layer 1 - with a corresponding width - between enters the two material layer connections 3a and 3b and so the inner layer 1 is pressed into the outer layer 2 .

In all cases, that is to say in particular in the modified UO (E) method according to the invention, as well as in the JCO method modified according to the invention, the connections 3a and 3b of the two material layers 1 and 2 can be produced by means of a weld, for example a weld.

Fig. 12 shows an exemplary stress-strain diagram for explaining how the desired maximum pressing force is achieved by compression of the inner layer in the extent.

The aim of the present invention is to compress the inner layer material of the multilayer pipe so far that you get into the area S of the here seen stress-strain diagram, so as to achieve the maximum possible compression of the inner to the outer layer by the compression, which to ensure a firm fit of the inner tube in the outer tube.

If the respective material layer functioning as an inner tube in the tube forming in the width - such as by the first and second connection of the two material layers together with a corresponding sufficient width B _{i of} the inner layer - compressed, so the respectively functioning as an inner tube material layer is thereby also in the respective outer (So seen from the pipe interior to the outside adjacent) pressed material layer. This pressing force can be up to the yield strength σ _I (respectively compression limit, which is usually - especially in rolled metal sheets, approximately equal to the yield strength -) increase. In cases in which there is no pronounced yield or compression limit, the so-called technical yield strength (also referred to as yield strength as the amount of stress of a plastic permanent elongation under a certain force) or technical compression limit can be cited instead. Above the zone of the so-called 'hook' straight line '- here in the figure the area H -, so approximately in the area of plastic strain (eg in the area of the so-called' Lüderskurve ') - here, the area S - but this force can be not significantly (at least not proportionally) increase.

bzw. die Bedingung $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)-\left({\mathrm{d}}_{\mathrm{1}}+{\mathrm{d}}_{\mathrm{2}}\right),$$

wenn man die Verpressung zwischen den beiden Werkstofflagenverbindungen berücksichtigt, die im Abstand von d₁ bzw. d₂ zu den jeweiligen Kanten der benachbarten Werkstofflage vorzugsweise nach innen (d.h. zur Mitte der benachbarten Werkstofflage) hin liegen (Erfolgt die Verbindung entlang der jeweiligen Kante der aufliegenden Werkstofflage und kommen diese hierzu auch noch jeweils bündig zu ihrer entsprechenden Kante der benachbarten Werkstofflage zu liegen, so wird der Term d₁ + d₂ = 0!), stellt zunächst überhaupt eine Stauchung sicher. Will man darüber hinaus eine maximale Stauchung und damit auch eine maximale Preßkraft (infolge dieser Stauchung) erreichen, so ist folgendes zu bedenken:The condition $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right).$$

or the condition $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)-\left({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{1}}+{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{2}}\right).$$

if one considers the compression between the two material layer connections, which are at the distance of d ₁ or d ₂ to the respective edges of the adjacent material layer preferably inwardly (ie to the center of the adjacent material layer) out (If the connection along the respective edge of the overlying Material layer and this come to be flush with their respective edge of the adjacent material layer, the term d ₁ + d ₂ = 0!), First ensures a compression at all. If you also want to achieve maximum compression and thus a maximum compressive force (as a result of this compression), the following should be considered:

wobei E die Steigung der sogenannten Hook'schen Geraden im Bereich H ist, wenn es eine solche (ausgeprägte Hook'sche Gerade) für das Material gibt. Demnach gilt für den Fall, daß die maximale Preßkraft der Innenwerkstofflage gegen die Außenwerkstofflage gerade eben erreicht werden soll: $${\mathrm{B}}_{\mathrm{i}}-{\mathrm{B}}_{\mathrm{i}}\cdot {\mathrm{\epsilon }}_{\mathrm{St}}={\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\cdot \left(\mathrm{SA}+\mathrm{SI}\right)$$

The degree of compression of the inner material layer to reach the compression limit - here ε _St - results according to Hooke's law: $${\mathrm{\epsilon }}_{\mathrm{St}}=\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}.$$

where E is the slope of the so-called Hook's line in the area H , if there is such a (pronounced Hook's line) for the material. Accordingly, in the case that the maximum pressing force of the inner material layer against the outer material layer is just to be achieved: $${\mathrm{B}}_{\mathrm{i}}-{\mathrm{B}}_{\mathrm{i}}\cdot {\mathrm{\epsilon }}_{\mathrm{St}}={\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\cdot \left(\mathrm{SA}+\mathrm{SI}\right)$$

wobei für den maximal erreichbaren Stauchungsgrad $\mathrm{0}<\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{E}}<\mathrm{1}$

gilt.With regard to the width which results for the band of the inner material layer in this case, then: $$\begin{array}{cc}{\mathrm{B}}_{\mathrm{i}}& =\frac{{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)}{\mathrm{1}-{\mathrm{\epsilon }}_{\mathrm{St}}}\\ & =\frac{{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)}{\mathrm{1}-\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{{\rm E}}}}\end{array}$$

where for the maximum achievable degree of compression $\mathrm{0}<\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}<\mathrm{1}$

applies.

For practical purposes it should be considered that - if one wants to achieve the maximum pressing force of the inner against the outer layer as reliably as possible, in any case approximately, it must be ensured that the compression limit σ _I (≈ yield strength) is actually reached. This can be achieved by adding to the maximum degree of compression, as it results from the material constants σ _I and E, still a certain surcharge - preferably up to 800% of the maximum compression ratio, more preferably up to 600% or up to 300% or up to 200% or up to 100% of the maximum degree of compression ε _St - gives.

Therefore, in the method according to the invention for the production of multilayer pipes for the width of the material layer strip acting as an inner tube, it is possible with regard to the achievement of the highest possible compressive force of the inner layer against the outer layer for practical purposes that $${\mathrm{B}}_{\mathrm{i}}\ge \frac{{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)}{\mathrm{1}-\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}}.\mathrm{With}\mathrm{0}<\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}<\mathrm{1}$$

Due to the fact that the width of the inner layer is chosen to be greater than the right of the equation term, a compression allowance is taken into account, which can compensate for the manufacturing inaccuracies - such as position and / or leadership of the material material tapes - so that the desired maximum pressing force of Inner tube against the outer tube - at least in about - safely achieved. In this way, it is safe for the material of the inner layer thus reaches the area S, where the desired maximum pressing force of the inner tube against the outer tube is guaranteed, as seen from here - in approximately - always the maximum return spring force of the inner tube acts. Compression surcharges of 100%, 200% and 300% are included in the diagram for illustration purposes. Likewise, the Rückfederweg R from 300% compression surcharge starting is entered as an example in the diagram. It follows that the resulting from the compression of the inner layer pressing force in the area S no longer, at least not significantly, increases.

so man eine maximale Preßkraft der Innen- gegen die Außenlage im Bereich zwischen den beiden Werkstofflagenverbindungen erreichen will. Für den Stauchungszuschlag gilt auch hier das bereits vorstehend Gesagte.Taking into account, in turn, the compression of the material layers against each other in the area between the two material layer connections, which at a distance of d ₁ and d ₂ to the respective Preferably, edges of the adjacent material layer lie inwards (ie towards the center of the adjacent material layer), the result for B _i being the width of the inner layer between the two material layer connections: $${\mathrm{B}}_{\mathrm{i}}\ge \frac{{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)-\left({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{1}}+{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{2}}\right)}{\mathrm{1}-\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}}.\mathrm{With}\mathrm{0}<\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{e}}<\mathrm{1}$$

so you want to achieve a maximum pressing force of the inner against the outer layer in the area between the two material layer connections. For the compression surcharge applies here also the above.

Claims (21)

1. Method for the high-speed production of a multi-layer tube (5) by means of a sheet metal forming machine, characterized in that the multi-layer tube (5) comprises at least one first material layer (1) and a material layer (2) adjacent to the first material layer (1), wherein - not necessarily in the following order -

   - the adjacent material layer (2) is at least slightly bent,

   - the material layers (1,2) to be combined into the multi-layer tube (5) are laid on top of each other, wherein the first material layer (1) is positioned as an overlying material layer (1) on the adjacent material layer (2),

   - a first connection (3a) between the overlying material layer (1) and the adjacent material layer (2) is created by
   connecting the overlying material layer (1) with the adjacent material layer (2) approximately along a first edge (4a) of the overlying material layer (1) or approximately along a line parallel thereto, and

   - after the adjacent material layer (2) has been at least slightly bent,
   a second connection (3b) between the overlying material layer (1) and the adjacent material layer (2) is created by
   connecting the overlying material layer (1) with the adjacent material layer (2) approximately along a second edge (4b), lying opposite the first edge (4a), of the overlying material layer (1) or approximately along a line parallel thereto,
   and after that

   - the thus formed multi-layer material (1,2) is shaped into the multi-layer tube (5) by means of the sheet metal forming machine, wherein during this shaping process, after a certain degree of shaping, the respective overlying material layer (1) formed as a single layer which then serves as inner tube is compressed between the two material layer connections (3a, 3b) in (partly) circumferential direction and is thus pressed into the respective adjacent material layer (2) which then serves as outer tube.
2. Method for the high-speed production of a multi-layer tube (5) according to claim 1, characterized in that the bending of the adjacent material layer (2) along at least one of its edges is carried out already to the end radius of the multi-layer tube (5) to be produced.
3. Method for the high-speed production of a multi-layer tube (5) according to claim 1 or 2, characterized in that

   - firstly, the adjacent material layer (2) is bent,

   - then the material layers (1,2) to be combined into the multi-layer tube (5) are laid on top of each other, wherein the first material layer (1) is positioned as an overlying material layer (1) on the adjacent material layer (2), and then - consecutively or simultaneously -

   - a first connection (3a) between the overlying material layer (1) and the adjacent material layer (2) is created by
   connecting the overlying material layer (1) with the adjacent material layer (2) approximately along a first edge (4a) of the overlying material layer (1) or approximately along a line parallel thereto,

   - a second connection (3b) between the overlying material layer (1) and the adjacent material layer (2) is created by
   connecting the overlying material layer (1) with the adjacent material layer (2) approximately along a second edge (4b) of the overlying material layer (1) or approximately along a line parallel thereto,
   and after that

   - the thus formed multi-layer material (1, 2) is shaped into the multi-layer tube (5) by means of the sheet metal forming machine,
   wherein during this shaping process, after a certain degree of shaping, the respective overlying material layer (1) which then serves as inner tube is compressed between the two material layer connections (3a, 3b) in (partly) circumferential direction and is thus pressed into the respective adjacent material layer (2) which then serves as outer tube.
4. Method for the high-speed production of a multi-layer tube (5) according to claim 1 or 2, characterized in that

   - the material layers (1,2) to be combined into the multi-layer tube (5) are laid on top of each other,

   - then a first connection (3a) between the overlying material layer (1) and the adjacent material layer (2) is created by connecting the overlying material layer (1) with the adjacent material layer (2) approximately along the first edge (4a) of the overlying material layer (1) or approximately along a line parallel thereto,

   - whereupon the thus formed multi-layer material is at least slightly bent in the area in which the material layers (1,2) are connected by means of the first connection (3a) approximately along the edge (4a) or along a line approximately parallel thereto, and after that

   - the second still free edge (4b) of the overlying material layer (1) is moved relative to the adjacent material layer (2) in a direction of an also still free edge (6b) of the adjacent material layer (2),

   - after that the second connection (3b) between the overlying material layer (1) and the adjacent material layer (2) is created by connecting the overlying material layer (1) with the adjacent material layer (2) approximately along the second still free edge (4b) of the overlying material layer (1) or approximately along a line parallel thereto, and after that

   - the thus formed multi-layer material is shaped into the multi-layer tube (5) by means of the sheet metal forming machine, wherein
   during this shaping process, after a certain degree of shaping, the respective overlying material layer (1) which then serves as inner tube is compressed between the two material layer connections (3a, 3b) in (partly) circumferential direction and is thus pressed into the respective adjacent material layer (2) which then serves as outer tube.
5. Method for the high-speed production of a multi-layer tube (5) according to one of claims 1 to 4, characterized in that the width before the tube shaping B_i, of the respective material layer (1) which serves as inner tube, in the region between the two connections (3a and 3b) of the material layers (1, 2), is selected such that $${\mathrm{B}}_{\mathrm{i}}>{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)-\left({\mathrm{d}}_{\mathrm{1}}+{\mathrm{d}}_{\mathrm{2}}\right),$$

   

   with B_i being the (partial) circumference, i.e. width before the tube shaping, of the respective material layer (1) which serves as inner tube, as seen in the cross-section of the tube, in the region between the two connections (3a,3b) between the material layers (1,2), preferably given in mm,

   L_nfa being the circumference, i.e. width before the tube shaping, of the respective material layer (2) which serves as outer tube, as seen in the cross-section of the tube, preferably given in mm,

   SA being the wall thickness of the respective material layer (2) which serves as outer tube, preferably given in mm,

   SI being the wall thickness of the respective material layer (1) which serves as inner tube, preferably given in mm, and

   d₁ being the distance of the first connection (3a), along the first edge (4a) of the overlying material layer (1) or along a line parallel thereto, from the corresponding first edge (6a) of the adjacent material layer (2) at the time of creation of the first connection (3a) between the material layers (1,2), preferably given in mm, and

   d₂ being the distance of the second connection (3b), along the second edge (4b) of the overlying material layer (1) or along a line parallel thereto, from the corresponding second edge (6b) of the adjacent material layer (2) at the time of creation of the second connection (3b) between the material layers (1,2), preferably given in mm.
6. Method for the high-speed production of a multi-layer tube (5) according to claims 1 to 5, characterized in that the width before the tube shaping Bi, of the respective material layer (1) which serves as inner tube, in the region between the two connections (3a and 3b) of the material layers (1, 2) is selected such that $${\mathrm{B}}_{\mathrm{i}}\ge \frac{{\mathrm{L}}_{\mathrm{nfa}}-\mathrm{\pi }\left(\mathrm{SA}+\mathrm{SI}\right)-\left({\mathrm{d}}_{\mathrm{1}}+{\mathrm{d}}_{\mathrm{2}}\right)}{\mathrm{1}-\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{E}}},$$

   

   with $$\mathrm{0}<\frac{{\mathrm{\sigma }}_{\mathrm{I}}}{\mathrm{E}}<\mathrm{1}$$

   

   with B₁ being the (partial) circumference, i.e. width before the tube shaping, of the respective material layer (1) which serves as inner tube, as seen in the cross-section of the tube, in the region between the two connections (3a, 3b) between the material layers (1, 2), preferably given in mm,

   L_nfa being the circumference, i.e. width before the tube shaping, of the respective material layer (2) which serves as outer tube, as seen in the cross-section of the tube, preferably given in mm,

   SA being the wall thickness of the respective material layer (2) which serves as outer tube, preferably given in mm,

   SI being the wall thickness of the respective material layer (1) which serves as inner tube, preferably given in mm,

   σ_I being the tensile yield point or compression yield point of the overlying material layer, i.e. the inner layer (1), i.e. of the later inner tube, preferably given in N/mm², and with

   E being the modulus of elasticity (Youngs's modulus) of the overlying material layer, i.e. the inner layer (1), i.e. of the later inner tube, preferably in N/mm², and

   d₁ being the distance of the first connection (3a), along the first edge (4a) of the overlying material layer (1) or along a line parallel thereto, from the corresponding first edge (6a) of the adjacent material layer (2) at the time of creation of the first connection (3a) between the material layers (1, 2), preferably given in mm, and

   d₂ being the distance of the second connection (3b), along the second edge (4b) of the overlying material layer (1) or along a line parallel thereto, from the corresponding second edge (6b) of the adjacent material layer (2) at the time of creation of the second connection (3b) between the material layers (1, 2), preferably given in mm.
7. Method for the high-speed production of a multi-layer tube (5) according to claim 4 or one of claims 5 or 6 insofar as they refer back to claim 4, characterized in that the relative movement of the second still free edge (4b) of the overlying material layer (1) to the adjacent material layer (2) in the direction of the also still free edge (6b) of the adjacent material layer (1) is provided by dragging of the overlying material layer (1) on its second still free edge (4b) in the direction of the also still free edge (6b) of the adjacent material layer (2).
8. Method for the high-speed production of a multi-layer tube (5) according to one of claims 1 to 7, characterized in that the first connection (3a) between the material layers (1, 2) is created by connecting the material layers (1, 2) approximately along one of the longitudinal or transverse edges of the overlying material layer (1) or parallel thereto and approximately along or parallel to the future longitudinal tube seam (8).
9. Method for the high-speed production of a multi-layer tube (5) according to one of claims 1 to 8, characterized in that the second connection (3b) between the material layers (1, 2) is created by connecting the material layers (1, 2) approximately along one of the longitudinal or transverse edges of the overlying material layer (1) or parallel thereto and approximately along or parallel to the future longitudinal tube seam (8).
10. Method for the high-speed production of a multi-layer tube (5) according to one of claims 1 to 9, characterized in that the material layer (1) which serves as inner tube in the finished multi-layer tube (5) forms part of a circle as seen in cross-section.
11. Method for the high-speed production of a multi-layer tube (5) according to claim 10, characterized in that the material layer (1) which serves as inner tube and forms part of a circle in the finished multi-layer tube (5), as seen in cross-section, forms a groove at the foot of the multi-layer tube.
12. Method for the production of a multi-layer tube (5) according to one of claims 1 to 11, characterized in that a welding is provided as first (3a) or second connection (3b) between the mutually overlying material layers (1, 2).
13. Method for the production of a multi-layer tube (5) according to one of claims 1 to 12, characterized in that the multi-layer tube (5) is closed by a welding (7) of the outer tube (2) along the tube seam (8).
14. Method for the production of a multi-layer tube (5) according to claim 13, characterized in that in addition there is a deposition welding (9) of the inner tube (1) along the tube seam (8), carried out from the inside.
15. Method for the production of a multi-layer tube (5) according to one of claims 1 to 14, characterized in that the material layers (1, 2) are connected at the end faces of the tube (5) - preferably by welding.
16. Method for the production of a multi-layer tube (5) according to one of claims 1 to 15, characterized in that a double-layer tube is manufactured as the multi-layer tube (5).
17. Method for the production of a multi-layer tube (5) according to one of claims 1 to 16, characterized in that sheets, preferably metal sheets, and more preferably steel sheets, are used as the material layer (1, 2).
18. Method for the production of a multi-layer tube (5) according to one of claims 1 to 17, characterized in that a bending roller is used as sheet metal forming machine.
19. Method for the production of a multi-layer tube (5) according to claim 18, characterized in that a three-roll-bending machine is used as bending roller.
20. Method for the production of a multi-layer tube (5) according to one of claims 1 to 17, characterized in that a UO (E) press / die arrangement (13, 14, 15) is used as sheet metal forming machine.
21. Method for the production of a multi-layer tube (5) according to one of claims 1 to 17, characterized in that a JCO press / die arrangement is used as sheet metal forming machine.

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