DE102016105902B4 - Process for the production of a tube made of metal with different wall thicknesses - Google Patents

Abstract

Method (1) for producing a tube (2) made of metal with an essentially circular cross-section and with at least two sections (3a, 3b) lying one behind the other in the axial direction of the tube (2) and having different wall thicknesses, an outer tube (4) and a Inner tube (5) are provided (100), the outer diameter of the inner tube (5) being smaller than the inner diameter of the outer tube (4), the inner tube (5) being introduced (110) into the outer tube (4) at a desired position, and wherein the outer tube (4) is reduced in diameter (130) at least at the point of the target position of the inner tube (5) by the action of external force, characterized by the use of the inner tube (5) or the outer tube (4) in such a way that at least the inner tube (5 ) or the outer tube (4) in the force-free state has such a shape deviation from the ideal circular cross-section that the inner tube (5) is held in the outer tube (4) at its desired position by frictional connection en (120) is because the outer wall of the inner tube (5) and the inner wall of the outer tube (4) are in contact with one another at the desired position and are connected to one another by a force fit.

Description

The invention relates to a method according to the preamble of claim 1 for producing a pipe made of metal with a substantially circular cross-section and with at least two sections with different wall thicknesses lying one behind the other in the axial direction of the pipe.

Processes for producing metal pipes with wall thicknesses that vary over their length are known from the prior art in very different ways. The desire to change the wall thickness of a metal pipe can have different technical reasons. A wall thickness that changes over the length of the pipe is often due to a change in mechanical stress on the pipe over its length. With a variable wall thickness, the pipe is equipped with strength properties that can be varied over its length. Another reason for variable wall thicknesses may also be a variable thermal load.

A large number of methods are known from the prior art for producing pipes with variable wall thicknesses. From the DE 10 2007 032 267 A1 For example, it is known to manufacture a pipe for an exhaust system with variable wall thickness by inserting an inner pipe in the form of a sleeve into an outer pipe, which inner pipe is connected to the outer pipe by means of a soldered seam. Apart from the fact that there has to be a sufficiently large distance between the sleeve and the outer tube in order to be able to reliably take up the solder, a large-area heat treatment is always required in order to establish a connection here, especially when using a high-temperature solder . The generic method is known from the publications U.S. 2,102,325 A , U.S. 5,007,667 A as U.S. 6,484,384 B1 . The DE 101 09 112 A1 shows the welding of an inner pipe to an outer pipe.

From the DE 197 50 959 A1 It is known that a metallic pipe with a wall-reinforced end region is produced in that the reinforcement is connected in one piece to the pipe wall, in that it consists of a pipe section that is turned inside out and rests against the pipe wall. The technique is limited to reinforcing end areas.

The object of the present invention is to provide a method for producing a metal pipe with an essentially circular cross-section and with at least two sections with different wall thicknesses lying one behind the other in the axial direction of the pipe, in which a local variation of the wall thickness even without that from the prior art known disadvantages can be produced.

The object derived and shown above is achieved according to the invention with the features of patent claim 1.

Overall, it is therefore provided that an outer tube and an inner tube are provided, the outer diameter of the inner tube being smaller than the inner diameter of the outer tube, so that the inner tube is introduced into the outer tube at a desired position. The inner tube or the outer tube are selected according to the invention so that at least the inner tube or the outer tube in the force-free state has such a shape deviation from the ideal circular cross-section that the inner tube is held in the outer tube at its target position by a frictional connection. Finally, the outer tube is then reduced in diameter at least at the point of the target position of the inner tube by the action of external forces.

The method according to the invention has a number of advantages. When it is said here that a process for the production of a metal pipe with an essentially circular cross-section is involved, then it means that the pipe should ideally have a circular cross-section, which in technical reality - in the mathematical sense - of course does not achieve becomes. According to the invention, it is provided that the inner tube, the outer tube or both tubes, i.e. the inner tube and the outer tube, have a shape deviation from the ideal circular cross-section in the force-free state, so that the inner tube is held in the outer tube at its intended target position by frictional connection becomes. This means that the outer wall of the inner tube and the inner wall of the outer tube are in contact with one another at the desired position and are connected to one another by a force fit. For this it may be necessary to push the inner tube into the outer tube by overcoming a certain feed force.

When it is said that the described form deviation is present in the force-free state, this means that no external force acts on the respective pipe, i.e. the pipe has such a form deviation without the action of an external force. One advantage of this procedure is that the inner tube and the outer tube are fixed to one another in the target position, so it is easily possible to subject the outer tube and the inner tube located at the target position to further processing steps without There is a risk that the positioning of the inner tube and outer tube will be lost.

In the subsequent process step, the diameter reduction of the outer pipe - this means a permanent, i.e. plastic diameter reduction of the outer pipe - a further intensification of the contact between the outer pipe and the inner pipe is effected without further measures - such as brazing or welding, for example - need.

According to a preferred embodiment of the method, it is provided that at least the outer tube or the inner tube is plastically reshaped in preparation so that in the force-free state such a shape deviation from the ideal circular cross section is achieved that the inner tube after being inserted into the outer tube in the outer tube Target position is held by frictional connection. This means that the outer pipe or the inner pipe - or also the outer pipe and the inner pipe - before the inner pipe is introduced to a target position in the outer pipe is or will be plastically deformed in a way that deviates from the ideal circular cross-section, so that there are significant deviations from the circular cross-section can be achieved and the cross-section of the inner tube and the cross-section of the outer tube cannot be superimposed without overlapping in the force-free state. It is therefore necessary to bring about at least an elastic deformation when the inner pipe is brought into one another in the outer pipe. In this process step, shape deviations are thus achieved that lie outside the range of manufacturing-related deviations from the ideal circular cross-section. In this way, a specific holding force of the inner tube in the outer tube can be set in a targeted manner at the target position of the inner tube. This production of the form deviation from the ideal circular cross section is thus achieved before the outer tube and inner tube are brought into one another and thus also before the diameter of at least the outer tube is reduced.

According to a further advantageous embodiment of the method, it is provided that at least the plastically deformed inner pipe or the plastically deformed outer pipe is elastically deformed to an ideally round opening when inserted into one another at the end by a gripping means, with which the inner pipe is introduced into the outer pipe or the Outer tube is passed over the inner tube. This process step serves to facilitate the insertion of the inner pipe into the outer pipe or of the outer pipe via the inner pipe, so that the inner pipe can be inserted into the outer pipe with a reduced mechanical resistance.

According to a special embodiment of this method, a first variant provides that the gripping means is designed as an inner expansion means and is guided into the inner tube or into the outer tube and the tube wall is elastically deformed by forces directed radially outward. This inner expansion means is preferably introduced into the respective pipe without mechanical resistance - for example with a kind of lance - and then enlarged in its diameter, for example by setting up metallic wings. Said inner expansion means is in particular expanded uniformly in terms of its diameter over its entire circumference, so that the respective tube into which the inner expansion means has been inserted is also uniformly deformed in the direction of a round opening.

As an alternative or in addition to this, it is provided that the gripping means - or an additional gripping means - is designed as external gripping means and is guided around the inner pipe or around the outer pipe and the pipe wall is elastically deformed by forces directed radially inward. Particularly through the interaction of such measures, that is to say by deforming one end of the inner tube and the outer tube, that is to say those ends that are to be brought into one another, a particularly problem-free insertion of the inner tube and the outer tube is ensured.

When reducing the diameter of the outer pipe, the question arises as to how far the diameter of the outer pipe should be reduced in order to achieve a desired strength or desired flow properties within the pipe produced. According to one embodiment of the method, it is provided here that the outer tube is plastically reduced in diameter to the outer diameter of the inner tube by the action of external forces at least at the point of the target position of the inner tube - with the inner tube inserted at the target position. This measure alone already ensures that the inner pipe is firmly positioned and fixed in the outer pipe, since the deformed inner pipe is also elastically deformed, possibly even plastically deformed beyond its elastic limit and so in any case is in full contact with the outer pipe . This measure alone largely avoids gaps between the inner pipe and the outer pipe.

In a further process step, the outer pipe and the inner pipe are both jointly reduced in plastic diameter at least at the point of the target position of the inner pipe by the action of external forces, whereby an even more intensive connection between the outer pipe and the inner pipe is achieved. There is no need to, take additional connection measures between the outer pipe and the inner pipe.

In the event of particular loads, in a further process step after the diameter of the outer tube has been reduced in the area of the inner tube, the outer tube is welded to the inner tube. Two circumferential weld seams at the ends of the inner tube are particularly advantageous here. It is particularly advantageous here if the outer tube is welded to the inner tube from the outside by laser welding, in particular by an orbitally rotating laser. There are practically no seams that protrude into the flow cross-section of the resulting metallic pipe. The pipe achieved is almost ideal also in terms of fluid mechanics.

• 1 schematisch den grundlegenden Herstellungsprozess für ein wandstärkenveränderliches Metallrohr,
• 2 anhand eines Ablaufdiagramms in einem Schema das Herstellungsverfahren für wandstärkenveränderliche Metallrohre,
• 3 schematisch einen Verfahrensschritt unter Verwendung eines Greifwerkzeuges und
• 4 ein Metallrohr gemäß den vorherigen Verfahrensschritten mit zusätzlicher Schweißnaht.

In detail, there are now a large number of possibilities for designing and developing the method according to the invention for producing a tube made of metal. For this, reference is made to the patent claim on the one hand 1 subordinate claims, on the other hand to the following description of exemplary embodiments in conjunction with the drawing. Show in the drawing

• 1 schematically the basic manufacturing process for a metal pipe with variable wall thickness,
• 2 Using a flow chart in a scheme, the manufacturing process for metal pipes with variable wall thicknesses,
• 3 schematically a process step using a gripping tool and
• 4th a metal pipe according to the previous process steps with an additional weld seam.

In 1 is shown schematically a process 1 for the production of a pipe 2 made of metal with a substantially circular cross-section and with at least two in the axial direction of the tube 2 successive sections 3a, 3b with different wall thicknesses. Such a metal pipe is in 1 shown at the very bottom, as a result of the procedure 1 . To carry out the procedure 1 are first an outer tube 4th and an inner tube 5 provided 100 .

Below is the inner tube 5 to a target position in the outer tube 4th brought in 110 . What is not shown here in detail is the fact that the inner tube 5 or / and the outer tube 4th in the force-free state have such a shape deviation from the ideal circular cross-section that the inner tube 5 in the outer tube 4th held at a target position by frictional connection 120 becomes. After the introduction 110 of the inner tube 5 into the outer tube 4th , touch the outer wall of the inner tube 5 and the inner wall of the outer tube 4th therefore partially, so that the outer tube 4th and the inner tube 5 are fixed to each other.

Finally the outer tube 4th at least at the point of the target position of the inner tube 5 Diameter reduced by an external force F 130. Due to the reduction 130 of diameter - in 1 indicated by rolling 6th - becomes the contact between the outer tube 4th and the inner tube 5 reinforced so that the outer tube 4th and the inner tube 5 are practically no longer separable from each other. Depending on the degree of diameter reduction 130 can result from the frictional connection between the outer tube 4th and inner tube 5 there is also a form fit.

The whole process 1 is in 2 once again shown schematically as a flow chart. Providing 100 of outer tube 4th and inner tube 5 a preparatory plastic forming process goes here 90 ahead, in which it is consciously ensured that the outer pipe 4th or the inner tube 5 In the force-free state - i.e. without external force - such a form deviation from the ideal circular cross-section is given that the inner tube 5 after introduction 110 into the outer tube 4th in the outer tube 4th is held at its target position by frictional connection. So here it is not only trusted that the deviation from the ideal circular cross-section that is always present in real pipes is sufficient to ensure sufficient contact between the outer pipe 4th and inner tube 5 to achieve in the target position, rather is in the forming step 90 a sufficient ovality of the pipe parts to be brought into one another is deliberately ensured.

In 3 is shown that in the process 1 Another process step is added, namely deformation 140 one end of the inner tube 5 and also the outer tube 4th by a gripping means 7th towards an ideally round opening. This procedural step 140 serves to bring them together 110 of the inner tube 5 into the outer tube 4th to simplify. With the outer tube 4th is the means of gripping 7th as an internal spreading agent 7a formed and into the inner tube 5 introduced. The internal spreading agent 7a is in the end area of the outer tube 4th spread open, so that a force F acting radially outwards ensures that the inner tube 5 facing end of the outer tube 4th is elastically deformed towards an ideally round opening. The opposite is true for the inner tube 5 the gripping means 7th as external gripping means 7b formed and around the inner tube 5 guided. Here a force F acts radially inwards in order to bring about the desired elastic deformation.

The in 1 metal pipe shown below 2 is the diameter reduction 130 so strong that both the outer tube 4th as well as the inner tube 5 have been jointly reduced in plastic diameter 130.

4th shows that after the diameter reduction 130 of the outer tube 4th in the area of the inner tube 5 the outer tube 4th with the inner tube 5 is additionally welded 150. In the present case, result from the welding process 150 two at the ends of the inner tube 5 circumferential weld seams 8th . In the illustrated embodiment, the welds are 8th produced externally by an orbital laser.

List of reference symbols

1.

Process for the production of a metal pipe

2.

Metal pipe

3.

Sections of the pipe

4th

Outer tube

5.

Inner tube

6th

Rollers

7th

Gripping means

7a.

Internal spreading agent

7b.

External gripping means

8th.

Weld

90.

Creation of a form deviation from the circular cross-section

100.

Provision of outer pipe and inner pipe

110.

Insertion of inner pipe into outer pipe

120.

Holding the inner tube in the outer tube by means of a force fit

130

Diameter reduction

140

Deformation of a pipe opening towards the ideal circular cross-section

150.

welding

Claims (9)

Method (1) for producing a tube (2) made of metal with an essentially circular cross-section and with at least two sections (3a, 3b) lying one behind the other in the axial direction of the tube (2) and having different wall thicknesses, an outer tube (4) and a Inner tube (5) are provided (100), the outer diameter of the inner tube (5) being smaller than the inner diameter of the outer tube (4), the inner tube (5) being introduced (110) into the outer tube (4) at a desired position, and wherein the outer tube (4) is reduced in diameter (130) at least at the point of the set position of the inner tube (5) by the action of external force, characterized by the use of the inner tube (5) or the outer tube (4) in such a way that at least the inner tube (5 ) or the outer tube (4) in the force-free state has such a shape deviation from the ideal circular cross-section that the inner tube (5) is held in the outer tube (4) at its desired position by frictional connection en (120) because the outer wall of the inner tube (5) and the inner wall of the outer tube (4) are in contact with one another at the desired position and are connected to one another by a force fit. Procedure (1) according to Claim 1 , characterized in that at least the outer tube (4) or the inner tube (5) is preliminarily plastically deformed (90) in such a way that in the force-free state such a shape deviation from the ideal circular cross-section is achieved that the inner tube (5) after insertion ( 110) in the outer tube (4) is held in the outer tube (4) at its desired position by a frictional connection. Procedure (1) according to Claim 1 or 2 , characterized in that at least the plastically deformed inner pipe (5) or the plastically deformed outer pipe (5) is elastically deformed at the end by a gripping means (7) to an ideally round opening, with which the inner pipe (5) is introduced (110) into the outer tube (4) or the outer tube (4) is guided (110) over the inner tube (5). Procedure (1) according to Claim 3 , characterized in that the gripping means (7) is designed as an inner expansion means (7a) and is guided (110) into the inner tube (5) or into the outer tube (4) and the tube wall is elastically deformed by forces (F) directed radially outwards (140). Procedure (1) according to Claim 3 or 4th , characterized in that the gripping means (7) is designed as external gripping means (7b) and is guided around the inner pipe (5) or around the outer pipe (4) and the pipe wall is elastically deformed (140) by forces (F) directed radially inward. . Method (1) according to one of the Claims 1 to 5 , characterized in that the outer tube (4) is plastically reduced (130) in diameter to the outer diameter of the inner tube (5) at least at the point of the desired position of the inner tube (5) by the action of external force (F). Method (1) according to one of the Claims 1 to 6th , characterized in that the outer tube (4) and the inner tube (5) are jointly reduced in plastic diameter (130) at least at the point of the target position of the inner tube (5) by the action of external force (F). Method (1) according to one of the Claims 1 to 7th , characterized in that after the diameter reduction (130) of the outer tube (4) in the area of the inner tube (5), the outer tube (4) is welded (150) to the inner tube (5), in particular by two at the ends of the inner tube (5) ) circumferential weld seams (8). Procedure (1) according to Claim 8 , characterized in that the outer tube (4) is welded (150) to the inner tube (5) from the outside by laser welding, in particular by an orbitally rotating laser.

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