Method for manufacturing slit tube

Abstract

The present invention relates to a method for manufacturing a slit pipe (1) from a metal flat plate product (2), in particular a metal sheet, in which the flat plate product (2) is gradually deformed in a plurality of individual bending steps in the circumferential direction of the slit pipe (1) to be formed using at least one bending tool (3) and at least one lower tool (4) located on the outside, in which the positions of the individual bending steps and the penetration depth of the bending tool (3) are first pre-calculated, and then the metal flat plate product (2) is gradually deformed to form the slit pipe (1) based on the pre-calculation. In the method, after each of a plurality of bending steps, a target-actual distance adjustment is performed at a position arranged along the longitudinal extension of the metal flat plate product (2), at least one position between both edges (6a, 6b) of the metal flat plate product (2) and / or between one of the edges (6a) and the axial center line (7), and if there is a deviation, a correction value for the subsequent bending step is determined using a correction algorithm, and the penetration depth for the bending tool (3) in the bending step is then adjusted by the correction value.

Description

[Technical field]

[0001] The present invention relates to a method for producing a slit tube by deforming a flat metal product, in particular a sheet metal product, in which the flat metal product is gradually deformed in a number of separate bending steps in the circumferential direction of the slit tube to be formed using at least one bending tool and at least one lower tool located on the outside, and to a slit tube produced by the method according to the invention.

[0002] The production of thick-walled pipes, e.g. for pipeline applications, is usually carried out by progressive deformation of flat products to form so-called slit tubes, which are first deformed over their entire length to form slit tubes, also called pipe blanks, and then welded by introducing a longitudinal seam.

[0003] The deformation of flat products is usually carried out in two steps. The first deformation results in a semi-finished product with a polygonal contour. The approximately circular contour of the cross section is then achieved in a second step by means of an expander. However, with thick-walled tubes, the expander tool is subjected to excessive loads.

[0004] Using the bending tool and two opposing supports or lower tools, for example in the form of bottom bars, the flat product is locally deformed in the first deformation step described above, and by succession of a number of such deformation operations the desired shape of the workpiece is finally obtained.

[0005] Such deformation is typically performed on the basis of empirical values ​​and mathematical considerations of empirical values. Since each metal plate product has locally different strengths and therefore correspondingly different deformation characteristics, the industrial production of such slit tubes is a very complicated process based on various disturbances such as sheet metal thickness variations and batch variations.

[0006] It would therefore be desirable to further automate such complex deformation processes, thereby making it possible to produce tube cross-sections having the desired contour, preferably the desired shape over their entire length, with as little deviation as possible from the roundness of the cross-section.

[0007] An apparatus and a method for deforming a flat workpiece to form a slit tube or a tube semi-finished product are known, for example, from DE 10 2011 009 660 A1. The apparatus has at least one inner deforming tool for deforming the flat workpiece at least gradually in the circumferential direction of the cross section of the slit tube or tube semi-finished product to be formed and at least one outer deforming tool for deforming the flat workpiece from the outside, at least one light source and at least one receiver for measuring the inner contour of at least the slit tube or tube semi-finished product are connected to the at least one inner deforming tool. By continuously tracking the results of the individual deformation steps based on the contour measurement, such an apparatus makes it possible to compensate for deviations much more quickly and accurately, to carry out the method efficiently so that deformed sheet metal structures can be produced significantly more reliably and more accurately, and to control the deformation of the starting material to form a slit tube with a defined contour or shape. However, this kind of closed-loop control presupposes knowledge of the current tube contour, which is detected via an optical measuring system, which has to be accommodated in the respective tool in a laborious manner.

[0008] Furthermore, CN110102607 discloses a method for manufacturing slit tubes by the so-called JCO method, in which a sequence with multiple bending steps is determined for the tube, and each individual step of the multiple bending steps is repeated multiple times starting from a "sure" indentation depth until a pre-calculated distance of the step center to a given point in the vicinity of the edge is reached or until the used measuring bridge indicates a pre-calculated radius. Then, based on this sequence, all subsequent slit tubes are manufactured.

[0009] Starting from this, it is the object of the present invention to provide a method for producing a slit tube which is improved over the prior art, in particular to provide a method for producing a slit tube which allows closed-loop control over the entire circumference.

[0010] This problem is solved according to the invention by a method having the features of claim 1.

[0011] According to the method of the present invention for producing a slit tube from a flat metal product, in particular from a thin metal sheet, it is provided that the flat metal product is gradually deformed in a number of individual bending steps in the circumferential direction of the slit tube to be formed using at least one bending tool and at least one lower tool located on the outside, in which the positions of the individual bending steps and the penetration depth of the bending tool are first pre-calculated, and then, based on this pre-calculation, the flat metal product is gradually deformed to form the slit tube.

[0012] The method is characterized in that after each of a number of bending steps, a target-actual-distance adjustment is performed at at least one position located along the longitudinal extension of the metal flat product, between both edges of the metal flat product and / or between one of the edges and the axial centerline, and in case of deviation, a correction value for the subsequent bending step is determined using a correction algorithm and then the penetration depth for the bending tool is adjusted by this correction value.

[0013] According to the method according to the invention, the entire inner contour or a part of it is not detected, as is usual in the prior art, but the edge distance of the two edges of the metal flat product and / or the distance between one of the two edges and the axial center line is determined after each of the bending steps, so that the edge properties of the metal flat product are gradually controlled during the forming process into a slit tube. For this purpose, it is advantageous to use a laser sensor system with a laser source and a laser detector and / or a computer-aided camera, which performs the distance measurement via a suitable evaluation program. Additionally and / or alternatively, the edge distance of the two edges of the metal flat product and / or the distance between one of the two edges and the axial center line can be determined by ultrasound after each of the bending steps. By precalculating the positions of the individual bending steps and the respective required penetration depths, a target distance value for the entire forming process can be determined. Based on this target position and the then determined actual position, in the event of deviations, a correction value for the subsequent bending step can be determined by means of a correction algorithm, and the required penetration depth for the bending tool is then adjusted by this correction value. Another advantage of the method according to the invention is that the correction can be carried out already after the first bending step carried out by the bending tool and therefore earlier than in the methods known from the prior art. Overall, this allows for a step-by-step real-time control, which ensures a particularly high contour accuracy all around. The high contour accuracy has a particularly favorable effect on the ovality, which can be kept within a particularly narrow parameter window due to the continuous process control.

[0014] Here, by enabling contour accuracy around the entire circumference of the slit tube, the load can be applied more uniformly to the expander tool, reducing the risk of overloading the expander tool, especially in the case of thick-walled tubes having a wall thickness of at least 6.0 mm, preferably at least 15.0 mm, and more preferably at least 20.0 mm or more.

[0015] Furthermore, due to the high contour accuracy over the entire circumference, repetition of individual bending steps is not necessary, and it is therefore advantageously provided that each of the bending steps is carried out only once, which allows particularly high cycle times during production.

[0016] Further advantageous configurations of the invention are recited in several dependent claims. The features recited individually in these dependent claims can be combined with one another in a technically significant manner to define further configurations of the invention. Furthermore, the features recited in the claims are more particularly set out and described in the specification and in this case form further preferred configurations of the invention.

[0017] By the term edge, within the meaning of the present invention, is understood an end surface of a flat metal product which extends along the longitudinal extension of the flat metal product.

[0018] At least one edge, preferably both edges, of the metal flat product may be formed as an essentially straight edge, which is understood to be an end face formed perpendicular to one of the two peripheral faces of the metal flat product, and furthermore, such an edge has two edge points that can be detected by a sensor.

[0019] However, in an advantageous embodiment, it is provided that at least one edge, more preferably both edges, of the metal flat product have a geometry optimized for the subsequent welding process, which geometry comprises two, three or n partial end faces, each of two adjacent partial end faces forming a predefined angle. Furthermore, the edges thus formed have at least three, four or n edge points that can be detected by a sensor system to determine the distance between the edges of the metal flat product and / or the distance between one of the edges and the axial centerline. Which of these edge points are next observed relative to each other may change step by step depending on the accessibility or recognizability of these edge points by the laser sensor system and / or the computer-aided camera unit.

[0020] The method according to the invention is particularly suitable for a wide production range, so that advantageously the metal plate products have a width of 0.2 to 10 m, more preferably 0.8 to 8 m, most preferably 1.0 to 6.0 m, and a thickness of 5.0 to 100 mm, more preferably 6.0 to 50 mm.

[0021] The term width is understood within the meaning of the present invention to be the radial extension of the metal flat product which is formed by multiple bending steps along the slit tube to be produced.

[0022] In one preferred implementation variant, the target-actual-gap adjustment is performed at at least two, more preferably at least three and even more preferably at more positions arranged along the longitudinal extension of the metal flat product, between both edges of the metal flat product and / or between one of the edges and the axial centerline of the metal flat product, so that independent closed-loop control is partially possible over the axial length of the slit tube to be formed.

[0023] Advantageously, it is provided that the measurement results of the actual value-distance between the two edges of the metal flat product and / or between one of the two edges and the axial center line are transmitted to a control unit, which then performs a setpoint-actual value-distance adjustment and, in the event of deviations, determines correction values ​​for the subsequent bending step using a correction algorithm, so that the control unit controls (open-loop control) and adjusts (closed-loop control) the fully automatic deformation of the metal flat product to form a slit tube.

[0024] Particularly preferably, the actual value-distance between the two edges and / or between one of the two edges and the axial center line is carried out by means of a laser sensor system and / or a computer-aided camera unit, which is particularly preferably connected in signal technology to the control unit.

[0025] In another aspect, the present invention further relates to a slit tube manufactured by the method according to the present invention.

[0026] The present invention and the technical environment are described in detail below with reference to the figures and examples. It should be noted that the present invention is not limited by the examples shown. In particular, unless expressly stated otherwise, it is also possible to extract parts of the described entities in the figures and / or examples and combine them with other components and knowledge of the description and / or figures. It should be noted in particular that the figures or examples and in particular the illustrated size ratios are merely schematic. Identical objects are provided with the same reference signs, whereby a description based on another figure can be considered supplementarily, if necessary. [Brief description of the drawings]

[0027] [Figure 1] 5A to 5H are diagrams illustrating the individual work steps of the deformation process for manufacturing the slit tube. [Diagram 2] FIG. 2 shows the measurement principle according to the invention in a first embodiment variant. [Diagram 3]FIG. 2 shows the measurement principle according to the invention in a second implementation variant. [Figure 4] FIGS. 1A-C show the geometrical results under ideal assumptions for a metal sheet with a predefined wall thickness and a predefined yield strength, which are assumed to be constant. [Diagram 5] 11A to 11C are diagrams showing results from a first practical example.

[0028] 1a-1h the basic principle for producing a slit tube 1 from a metal flat product 2 is shown in eight separate working or bending steps. The metal flat product 2 is gradually deformed in the circumferential direction of the slit tube 1 to be formed by a number of separate bending steps with at least one bending tool 3 and two outer lower tools 4.

[0029] In step a), a flat plate product 2 is shown with edge regions 5a, 5b that have already been pre-deformed. The edge regions 5a, 5b are generally preformed by a deforming press (not shown). As shown in step b), the deformation process begins with the insertion of the metal flat plate product 2 between the two counter-bearings 4a, 4b of the lower tool 4 and the bending tool 3, which comprises a shaft 3a and a bending ram 3b. The bending tool 3 can be moved between the two counter-bearings 4a, 4b to make a stroke in a substantially vertical direction towards the flat plate product 2. Then, in cooperation with the counter-bearings 4a, 4b and the bending ram 3b, a local deformation of the flat plate product 2 takes place. In the working steps a)-d), a deformation of a first side of the flat plate product 2 takes place to form a slit tube cross section, whereas in steps e)-h), the right side of the flat plate product 2 is gradually deformed to form the slit tube 1. Both deformation processes are typically carried out as a sequence of local deformation steps performed inwards from the lateral edges 5a, 5b.

[0030] One implementation variant of the measurement principle is shown in Fig. 2. As can be seen from the drawing, after each bending step performed as shown in Fig. 1, a measurement is performed via a laser sensor system 8, by which the actual distance between the two edges 6a, 6b of the metal flat product 2 and / or between one of the two edges 6a and the axial center line 7 is determined. The laser sensor system 8 detects here a respective detectable edge point 9a, 9b of each edge 6a, 6b.

[0031] In Fig. 3, another embodiment of the measuring principle is shown. In contrast to the first embodiment, each of the edges 6a, 6b of the metal flat-plate product has a number of partial end faces 10a, 10b. As can be seen from this drawing, two adjacent partial end faces 10a, 10b are at an angle and each form an edge point 9a, 9b. These edge points 9a, 9b can be detected by the laser sensor system 8, so that the actual distance between the two edges 6a, 6b of the metal flat-plate product 2 and / or between one of the two edges 6a and the axial center line 7 can be determined.

[0032] example Comparative Example: To manufacture a slit tube with an outer diameter of 813 mm, a wall thickness of 12.7 mm and a length of 10 m, a sheet metal with dimensions of 10000x2554x12.7 mm (LxBxH) was provided, with a yield strength of 600 MPa. As a bending ram, a universal bending ram with a radius of 120 mm was used.

[0033] Based on the material dimensions, yield strength, radius of the bending ram used as well as the lower tool, lower tool distance and elastic modulus parameters, the number of individual bending steps and the corresponding penetration depth (Figure 4a) were pre-calculated. For a slit tube with a target slit width of 200.3 mm, 17 bending steps were determined.

[0034] The edge regions were then first formed in the conventional manner by a forming press. The sheet metal was then inserted between the bending tool and a lower tool with two counter-supports, and then the individual bending steps 1 to 17 (FIG. 3a) were performed as calculated. Since the sheet metal was not ideal across the surface, as assumed in the pre-calculation, neither in terms of material thickness nor in terms of yield strength, the entire forming process in the comparative example resulted in a deviation in the slit width of more than 3%.

[0035] Example according to the present invention: In contrast to the comparative example, a target-actual distance adjustment was already carried out after the first bending step (see FIG. 5a), which was carried out based on a precalculated penetration depth of 18 mm. For this purpose, the distances between the two edge points 9a, 9b and additionally between one edge point 9a and the center line 7 were determined by a laser sensor system as shown in FIGS. 2 and 3. The determined distances were compared with the precalculated target distances, after which a correction value for the subsequent second bending step was determined using a correction algorithm (see FIG. 5a). The penetration depth of the second bending process was then adjusted by the correction value, as shown in FIG. 5a. The subsequent bending steps 3 to 17 were carried out in the same way.

[0036] The results based on the comparative example and the example according to the invention are shown in the following table 1 against the background of theoretically calculated values. As can be seen from table 1, the favorable influence of the method according to the invention on the contour of the slit tube can be clearly seen.

[0037] [Table 1] [Explanation of symbols]

[0038] 1 Slit tube 2 Flat plate products 3 Bending tools 3a Shaft 4 Lower tool 4a Opposite reception 4b Opposite receiver 5a Edge Area 5b Edge Area 6a Edge 6b Edge 7 Center line 8 Laser Sensor System 9a Edge points 9b Edge points 10a Partial end face 10b Partial end face

Claims

1. A method for manufacturing a slit tube (1) from a metal flat plate product (2), comprising the steps of: gradually deforming the flat plate product (2) in a plurality of individual bending steps in a circumferential direction of the slit tube (1) to be formed using at least one bending tool (3) and at least one lower tool (4) located on the outside; firstly, pre-calculating the positions of the plurality of individual bending steps and the penetration depth of the bending tool (3); and then, based on the pre-calculation, gradually deforming the metal flat plate product (2) to form the slit tube (1); 13. A method for bending a metal flat-plate product according to claim 12, further comprising the steps of: determining a correction value for a subsequent bending step using a correction algorithm, and then adjusting a penetration depth for the bending tool by the correction value, if there is a deviation between a target value and an actual value for at least one of the distances between the edges (6a, 6b) and / or the distance between one of the edges (6a) and an axial centerline (7) of the metal flat-plate product (2) at positions arranged along the longitudinal extension of the metal flat-plate product (2), At least one of the edges (6a, 6b) has at least three edge points (9a, 9b), and the adjustment of the at least one distance is performed based on the edge points (9a, 9b).

2. 2. The method of claim 1, wherein said at least one edge (6a, 6b) has at least four edge points (9a, 9b).

3. 3. The method according to claim 1 or 2, characterized in that the adjustment of at least two distances along the longitudinal extension of the metal flat product (2) is performed: the distance between the two edges (6a, 6b) of the metal flat product (2) and / or the distance between one of the edges (6a) and the axial centerline (7).

4. 4. The method according to claim 1, further comprising the steps of: transmitting the measurement result of the distance between the two edges (6a, 6b) of the metal flat product (2) and / or the distance between one of the edges (6a) and the axial center line (7) to a control unit, which then performs an adjustment of the at least one distance and, in the event of a deviation, determines a correction value for the subsequent bending step using the correction algorithm, whereby the control unit controls and regulates the fully automatic deformation of the metal flat product into the slit tube (1).

5. 5. The method according to claim 1, wherein the measurement of the distance between the two edges (6a, 6b) and / or between one of the edges (6a) and the axial center line is performed by a laser sensor system (8) and / or a computer-aided camera.

6. The method according to claim 5, wherein the laser sensor system (8) and / or the camera are signal-technically connected to a control unit.

7. The method of claim 1 , wherein each of the bending steps is performed only once.

8. The method according to any one of claims 1 to 7, wherein the metal flat product (2) has a width of 0.2 to 10 m and a thickness of 6.0 to 100 mm.

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