JP5262746B2 - Pipe end shape correction method for UOE metal pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of correcting the shape of a pipe end by which the roundness in a pipe end part of a UOE metallic pipe is sufficiently improved. <P>SOLUTION: The method of correcting the shape of pipe end of the UOE metallic pipe by correcting the shape of the pipe end parts by expanding the metallic pipe which is formed through a pressing stage is characterized in that the shape of the pipe end part of the metallic pipe is preliminarily corrected after the pressing stage and before expanding the pipe. In this preliminary correcting method, the preliminary correction is performed by pressurizing the pipe end part of the metallic pipe with a lower die which has an upper surface having a circular-arcuate cross section and an upper die which has an under surface having a circular-arcuate cross section. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for correcting the shape of a tube end by expanding the tube end in order to improve the roundness of the tube end of a UOE metal tube.

  In general, a UOE metal pipe such as a UOE steel pipe for line pipes is laid by joining the pipe ends of the UOE metal pipe by circumferential welding at a laying place (site). When carrying out circumferential welding, it is necessary to abut the groove surface formed at the pipe end of the UOE metal pipe with high accuracy. If this matching accuracy is poor, there may be a problem that the UOE metal tubes cannot be joined together.

  The accuracy of butting the groove surfaces can be improved by improving the roundness of the tube end portion of the UOE metal tube. Therefore, conventionally, various methods for improving the roundness of the pipe end portion of the UOE metal pipe have been proposed in the manufacturing process of the UOE metal pipe (see, for example, Patent Document 1).

  In general, in the manufacturing process of a UOE metal tube, first, a metal plate is formed into an O shape by C press processing, U press processing, and then O press processing. Then, a metal tube is formed by welding the end surface of the metal plate shape | molded in the O shape. Finally, it corrects by expanding the pipe end part of the metal pipe using a pipe expanding apparatus, and a UOE metal pipe with high roundness is produced.

  In the correction method described in Patent Document 1, first, the outer diameter of the UOE steel pipe manufactured as described above is measured by an outer diameter measuring device. Further, the roundness of the UOE steel pipe is calculated by the calculation unit based on the measurement result. If the calculated roundness is outside the specified range, the shape of the tube end is corrected again by the corrector.

JP 2006-272365 A

  However, the conventional straightening method as described above may not be able to sufficiently improve the roundness of the tube end.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a tube end shape correction method capable of sufficiently improving the roundness of the tube end portion of a UOE metal tube. is there.

  The present inventors have repeatedly studied to provide a tube end shape correction method capable of sufficiently improving the roundness of the tube end portion of the UOE metal tube manufactured as described above. As a result, the following knowledge was obtained.

  (A) As described above, generally in the production of a UOE metal tube, the roundness is improved by producing a metal tube by pressing and welding and then expanding the tube end. However, local bending may be formed in the metal tube by press working. This local bent portion cannot be sufficiently extended in the tube expansion process, and is maintained in the metal tube after the tube expansion. Further, since the metal tube is work-hardened by expanding the tube, the method of correcting the shape of the tube end portion after expanding the tube as in the conventional correction method cannot sufficiently extend the local bent portion. Therefore, the roundness of the UOE metal tube cannot be improved. Further, when the shape of the tube end is corrected after the metal tube has been work-hardened, there is a possibility that cracking may occur during the correction.

  (B) Therefore, the shape of the pipe end of the metal pipe may be preliminarily corrected before the pipe expansion. In this case, since the shape of the tube end can be preliminarily corrected before the metal tube is work hardened, the bent portion can be sufficiently extended. Thereby, it can prevent that a bending part is maintained after a pipe expansion. As a result, the roundness of the UOE metal tube can be improved. Further, it is possible to sufficiently prevent the metal pipe from being cracked during shape correction.

(C) It is preferable to preliminarily correct the shape of the tube end of the metal tube by applying pressure with a lower die having an upper surface with an arcuate cross section and an upper die with a lower surface having an arcuate cross section. If the target radius R of the metal tube, the radius of curvature R1 of the upper surface of the lower die, and the radius of curvature R2 of the lower surface of the upper die satisfy the following formula (1) or (2), The roundness of the tube end of the tube can be sufficiently improved. Thereby, the roundness of the UOE metal tube can be further improved.
R ≧ R1> 0.80R (1)
R ≧ R2> 0.80R (2)

(D) When the target radius R of the metal tube, the radius of curvature R1 of the upper surface of the lower die, and the radius of curvature R2 of the lower surface of the upper die satisfy the following formula (3) or (4), the metal tube The roundness of the pipe end can be further improved.
R ≧ R1 ≧ 0.90R (3)
R ≧ R2 ≧ 0.90R (4)

  (E) When pressurizing the tube end of the metal tube, a lower die having an upper surface with an arc-shaped cross section is placed on the inner surface side of the tube end of the metal tube, and an upper die having a lower surface with an arc-shaped cross section After installation on the outer surface side of the tube end of the metal tube, the upper die may be lowered, the lower die may be raised, or both dies may be lowered and raised. In order to move the upper die and the lower die up and down, for example, a hydraulic cylinder may be connected to the upper die and / or the lower die.

  The present invention has been made based on the above findings, and the gist thereof is the following (1) to (6) UOE metal tube end shape correction method. Hereinafter, the present invention is collectively referred to as the present invention.

(1) A pipe end shape correction method for a UOE metal pipe, in which a metal pipe formed through a pressing process is tack welded, and then the inner end and the outer end are welded, and then the end of the pipe is corrected by expanding the pipe. Because
A tube end shape correcting method, wherein the shape of the tube end portion of the metal tube is preliminarily corrected after the tack welding and before the pipe expansion.

  (2) The pipe according to (1), wherein the pipe end is preliminarily corrected by pressurizing with a lower die having an upper surface having an arcuate cross section and an upper die having a lower surface having an arcuate cross section. Edge shape correction method.

(3) Preliminary correction so that the radius of curvature R of the target shape of the metal tube and the radius of curvature R1 of the upper surface of the lower die satisfy the following formula (1): Tube end shape correction method.
R ≧ R1> 0.80R (1)

(4) The above-described (2), wherein preliminary correction is performed so that the curvature radius R of the target shape of the metal tube and the curvature radius R1 of the upper surface of the lower die satisfy the following formula (2): Tube end shape correction method.
R ≧ R1 ≧ 0.90R (2)

(5) Preliminary correction is performed so that the radius of curvature R of the target shape of the metal tube and the radius of curvature R2 of the lower surface of the upper die satisfy the following formula (3): (4) The tube end shape correction method according to any one of
R ≧ R2> 0.80R (3)

(6) Preliminary correction is performed so that the curvature radius R of the target shape of the metal tube and the curvature radius R2 of the lower surface of the upper die satisfy the following formula (2): (4) The tube end shape correcting method according to any one of (4).
R ≧ R2 ≧ 0.90R (4)

  The tube end shape correcting method according to the present invention can sufficiently improve the roundness of the tube end portion of the UOE metal tube, and can prevent the occurrence of cracks during roundness correction.

It is a flowchart which shows an example of the manufacturing process of a UOE metal tube. It is a front view which shows an example of a preliminary correction apparatus. It is a side view of the preliminary correction apparatus of FIG. It is a figure which shows an example of the shape of the pipe end part of the metal pipe before preliminary correction. It is a figure which shows an example of the state of the preliminary correction apparatus at the time of preliminary correction. It is a figure which shows the other example of the state of the preliminary correction apparatus at the time of preliminary correction. It is a figure which shows an example of the shape of the pipe end part of the metal pipe after preliminary correction. It is a figure which shows the shape after the pipe expansion of the metal pipe of the comparative example 1. It is a graph which shows the roundness before the pipe expansion of Examples 1-4 and Comparative Example 1.

  Hereinafter, a tube end shape correcting method according to an embodiment of the present invention will be described with reference to the accompanying drawings.

1. Manufacturing Process of UOE Metal Pipe FIG. 1 is a flowchart showing an example of a manufacturing process of a UOE metal pipe using the present invention. In addition, as a material of a UOE metal tube, various metal materials, such as carbon steel, stainless steel, or alloy steel, can be used.

  As shown in FIG. 1, in the manufacturing process of a UOE metal tube, first, C press processing, U press processing, and O press processing are performed on a metal plate cut to a predetermined size (steps S1 to S3). Next, temporary welding is performed with respect to the metal plate after O press work (step S4). As a result, the metal plate is formed into a tubular shape.

  Next, the shape of the tube end portion of the metal tube produced in step S4 is preliminarily corrected by the preliminarily correcting device (step S5). The preliminary correction device and the preliminary correction method will be described later. Next, inner surface welding and outer surface welding are performed (steps S6 and S7).

  Thereafter, the metal tube is expanded to a predetermined size by the tube expansion device, thereby correcting the shape (step S8). Thereby, a UOE metal tube with improved roundness is produced. Actually, the manufacturing process of the UOE metal tube includes various inspection processes and a water pressure test, but is omitted in FIG. 1 for the sake of simplicity. In the above example, the shape of the pipe end of the metal pipe is preliminarily corrected after the tack welding. However, the precorrection of the pipe end may be performed before the pipe expansion, and is performed after the inner surface welding or the outer surface welding. May be.

2. Preliminary Straightening Device and Tube End Shape Correction Method Next, the preliminary correction device used in the tube end shape correction method (step S5 in FIG. 1) according to the present embodiment and the tube end shape preliminary correction using the preliminary correction device. A method will be described. First, the preliminary correction device will be described.

  2 and 3 are diagrams illustrating an example of the preliminary correction device. FIG. 2 is a front view of the preliminary correction device, and FIG. 3 is a side view of the preliminary correction device.

  As shown in FIGS. 2 and 3, the preliminary correction device 10 according to the present embodiment has a box-shaped frame 11 having an opening at the front. A lower die 12 is formed at the lower portion of the frame 11 so as to protrude forward, and a ceiling portion 13 having a reverse concave shape is formed at the upper portion of the frame 11 so as to cover the upper portion of the lower die 12. . The lower die 12 has an upper surface 12a having an arcuate cross section (hereinafter referred to as an arc surface 12a).

  A hydraulic cylinder 14 is fixed to the center of the ceiling portion 13. The hydraulic cylinder 14 has a piston 15 (FIG. 2) provided so as to be movable up and down. The tip of the piston 15 (FIG. 2) is connected to the upper die 16. The upper die 16 is provided in the ceiling portion 13 so as to be movable up and down. The upper die 16 has a lower surface 16a (hereinafter referred to as an arc surface 16a) having a circular arc cross section. A hydraulic pressure generator 17 (for example, a hydraulic pump) is connected to the hydraulic cylinder 14. In the present embodiment, the hydraulic pressure in the hydraulic cylinder 14 is adjusted by the hydraulic pressure generator 17. Thereby, the movement amount of the piston 15 (FIG. 2) is adjusted, and the position of the upper die 16 is adjusted. In addition, the vertex of the arc surface 16a is located immediately above the vertex of the arc surface 12a.

  A support column 18 is fixed to the back side of the frame 11. The support 18 is provided with an adjusting mechanism 19 for moving the support 18 up and down. The adjustment mechanism 19 can be configured using, for example, a pressure pump or an electric motor, but may be a manual type. In the present embodiment, the position of the lower die 12 in the vertical direction can be adjusted by moving the support column 18 up and down by the adjusting mechanism 19.

  Next, a pipe tube shape preliminary correction method using the preliminary correction apparatus 10 will be described with reference to the drawings.

  FIG. 4 is a diagram showing an example of the shape of the end of the metal tube before preliminary correction (for example, after tack welding). FIGS. 5 and 6 show the state of the preliminary correction device 10 during preliminary correction. It is a figure which shows an example. Moreover, FIG. 7 is a figure which shows the other example of the shape of the pipe end part of the metal pipe after preliminary correction.

  In the manufacturing process of the UOE metal tube, a local bent portion is formed on the metal plate (metal tube) by pressing such as C pressing. Therefore, in the present embodiment, before expanding the tube, first, a portion whose shape is to be preliminarily corrected (hereinafter referred to as a preliminarily correcting portion) is determined by visual observation or measurement. In the metal tube 20 shown in FIG. 4, there are local bent portions 20a and 20b formed at the time of the C press working. Therefore, in this metal tube 20, a region including the bent portions 20a and 20b becomes a preliminary correction portion.

  Next, as shown in FIG. 5, the tube ends of the metal tube 20 are positioned so that the bent portions 20 a and 20 b (preliminary correction portions) are located between the lower die 12 and the upper die 16 of the preliminary correction device 10. It is inserted between the lower die 12 and the upper die 16. In this state, as shown in FIG. 6, the upper die 16 is lowered. Thereby, the pipe end part of the metal pipe 20 is pressed, and the bent parts 20a and 20b (see FIG. 5) are extended in an arc shape along the arc surfaces 12a and 16a. As a result, as shown in FIG. 7, the pressed portion of the metal tube 20 has an arc-shaped smooth shape.

The radius of curvature of the arc surface 16a is preferably set larger than the radius of curvature of the arc surface 12a in consideration of the thickness of the metal tube 20. Further, the curvature radii of the arc surfaces 12a and 16a are determined in consideration of the influence of the spring back of the metal tube 20 (hereinafter referred to as the target radius) of the target shape of the metal tube 20 (the arc 21 indicated by a broken line in FIG. 6). It is preferable to set to the following values. Specifically, the radius of curvature of the circular arc surface 12a preferably satisfies the following formula (1), and more preferably satisfies the following formula (2). Moreover, it is preferable that the curvature radius of the circular arc surface 16a satisfy | fills following formula (3), and it is more preferable to satisfy | fill following formula (4). In the following formulas (1) to (4), R represents the target radius of the metal tube 20, R1 represents the radius of curvature of the arc surface 12a, and R2 represents the radius of curvature of the arc surface 16a.
R ≧ R1> 0.80R (1)
R ≧ R1 ≧ 0.90R (2)
R ≧ R2> 0.80R (3)
R ≧ R2 ≧ 0.90R (4)

3. As described above, in the present embodiment, the shape of the metal tube 20 is preliminarily corrected before the pipe expansion, that is, before the metal tube 20 is work-hardened. In this case, even if a local bent portion is formed in the metal tube 20 in the pressing step, the bent portion can be easily and sufficiently extended. Thereby, it can prevent that a bending part exists in the metal pipe 20 after pipe expansion. As a result, the roundness of the UOE metal tube can be improved. Further, it is possible to sufficiently prevent the metal tube 20 from cracking during preliminary correction.

4). Other Embodiments In the above embodiment, the pipe end of the metal tube 20 is pressurized by lowering the upper die 16, but the pipe end of the metal tube 20 is lowered by raising the lower die 12. You may pressurize. Alternatively, both the lower die 12 and the upper die 16 may be moved to pressurize the tube end portion of the metal tube 20.

  Five metal tubes with a target outer diameter (nominal diameter) of 609.6 mm (24 inches) are obtained by performing C press processing, U press processing, O press processing and tack welding on a metal plate having a thickness of 22 mm. Produced. For the four of the five metal tubes, the tube end shape preliminary correction method (the method described in the above embodiment) according to the present invention is performed under different conditions (Examples 1 to 4). The shape of the other one pipe end was not preliminarily corrected (Comparative Example 1). And the metal pipe of Examples 1-4 to which this invention was applied, and the metal pipe of the comparative example 1 to which this invention was not applied were expanded by the pipe expansion apparatus. Then, the shape of each metal tube was compared.

  Note that a 2000 kN press was used as the preliminary correction device 10 (see FIG. 2). In the first embodiment, dies 12, 16 (see FIG. 1) in which the radius of curvature of the arcuate surfaces 12a, 16a (see FIG. 1) is 0.80 times the target radius (304.8 mm) of the metal tube are used. In the second embodiment, the dies 12 and 16 whose radius of curvature of the circular arc surfaces 12a and 16a is 0.90 times the target radius are used, and in the third embodiment, the radius of curvature of the circular arc surfaces 12a and 16a is the target radius. The dies 12 and 16 having 0.95 times were used, and in the fourth embodiment, the dies 12 and 16 having the radius of curvature of the circular arc surfaces 12a and 16a being 1.0 times the target radius were used.

  As a result, in the metal pipes of Examples 1 to 4, the bent portions (see the bent portions 20a and 20b in FIG. 4) formed by pressing could be sufficiently extended. Thereby, the bent part did not exist in the metal tube after the tube expansion. On the other hand, as shown in FIG. 8, in the metal tube 30 of Comparative Example 1, the bent portions 30a and 30b were maintained even after the tube was expanded.

Moreover, in the metal tube 30 after the pipe expansion of the comparative example 1, the outer diameter was large in the portion where the bent portions 30a and 30b exist. Therefore, the roundness shown by the following formula (5) could not be sufficiently improved. On the other hand, in the metal pipe after the pipe expansion in Examples 1 to 4, since the bent portion does not exist, the roundness shown by the following formula (5) is sufficiently improved. Specifically, the roundness of the metal tube after the expansion of Examples 1 to 4 was 0.75%, 0.50%, 0.39%, and 0.48%, respectively. Thus, when this invention is applied, roundness can be improved to such an extent that the shape correction after pipe expansion becomes unnecessary.
Roundness = (maximum outer diameter of metal tube-minimum outer diameter of metal tube) / target outer diameter (5)

  Moreover, as shown in FIG. 9, especially in the metal pipes of Examples 2 to 4, the roundness before the pipe expansion could be sufficiently improved. Specifically, in the metal pipe of Example 3, the roundness before pipe expansion was improved to about 0.8%. From this, it was found that when the curvature radii of the arc surfaces 12a and 16a satisfy the above-described formulas (2) and (4), the roundness of the metal tube is sufficiently improved even before the pipe expansion. In this case, it is possible to easily improve the roundness of the metal tube when expanding the tube.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to fully improve the roundness of the pipe end part of a UOE metal pipe, the pipe end shape correction method which can prevent generation | occurrence | production of the crack at the time of shape correction can be provided. .

10 Preliminary straightening device 11 Frame 12 Lower die 12a Arc surface 12a
DESCRIPTION OF SYMBOLS 13 Ceiling part 14 Hydraulic cylinder 15 Piston 16 Upper die 16a Circular surface 17 Hydraulic pressure generator 18 Support | pillar 19 Adjustment mechanism 20 Metal pipe 20a, 20b Bending part 21 Target shape of metal pipe 30 Metal pipe 30a, 30b Bending part

Claims (6)

A pipe end shape correction method for a UOE metal pipe, in which a metal pipe formed through a pressing process is tack welded, and then the inner end and outer face are welded, and then the end of the pipe is corrected by expanding the pipe. ,
A tube end shape correcting method, wherein the shape of the tube end portion of the metal tube is preliminarily corrected after the tack welding and before the pipe expansion.   2. The pipe end shape correcting method according to claim 1, wherein the pipe end shape is preliminarily corrected by pressing with a lower die having an upper surface having an arcuate cross section and an upper die having a lower surface having an arcuate cross section. . The pipe end shape according to claim 2, wherein the radius of curvature R of the target shape of the metal tube and the radius of curvature R1 of the upper surface of the lower die are preliminarily corrected so as to satisfy the following formula (1). Correction method.
R ≧ R1> 0.80R (1) The pipe end shape according to claim 2, wherein the radius R of the target shape of the metal tube and the radius of curvature R1 of the upper surface of the lower die are preliminarily corrected so as to satisfy the following formula (2). Correction method.
R ≧ R1 ≧ 0.90R (2) The preliminary correction is performed so that the curvature radius R of the target shape of the metal pipe and the curvature radius R2 of the lower surface of the upper die satisfy the following formula (3). The tube end shape correction method described in 1.
R ≧ R2> 0.80R (3) The preliminary correction is performed so that the curvature radius R of the target shape of the metal tube and the curvature radius R2 of the lower surface of the upper die satisfy the following formula (4): 5. The tube end shape correction method described in 1.
R ≧ R2 ≧ 0.90R (4)

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