JP2018183787A - Method of manufacturing steel pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a steel pipe capable of improving roundness of a cross section of a pipe end without enlarging only a pipe end part, concerning a steel pipe obtained by forming a steel sheet tubularly by UOE, JCOE, a bending roll, a spiral or the like.SOLUTION: In a method of manufacturing a steel pipe having a step for forming a steel sheet tubularly, a seam-welding step and a tube expansion step, a pipe end shaping step for shaping a cross-sectional shape of a pipe end part Se into a desired shape is performed, at the pipe end part Se in a longer direction of a steel pipe S4 formed in the seam-welding step, between the seam-welding step and the tube expansion step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a welded steel pipe in which a steel sheet is formed into a tubular shape by UOE, JCOE, bending roll, spiral or the like.

  In the manufacture of steel pipes used as pipelines for transporting natural gas, generally, after thick steel plates are formed into a tubular shape by processes such as UO, JCO, bending rolls, and spirals, the ends of the steel plates are joined together. The seam part is welded by arc welding. For example, steel pipes by the UOE method are manufactured by respective processes of forming steel plates by C press, U press, O press, seam welding, and pipe expansion. That is, as shown in FIG. 4, a C-press is applied in which bending is performed on both edges in the width direction of the steel sheet S (FIG. 4A) (FIG. 4B), and the U-press is formed into a U-shape. (FIG. 4 (c)), and after forming into a tubular shape in the O-pressing process (FIG. 4 (d)), both edges of the plate material are welded (FIG. 4 (e)) to form a steel pipe closed in the circumferential direction. To do. Thereafter, in order to improve the roundness of the steel pipe and obtain a desired cross-sectional shape, the pipe is expanded (FIG. 4 (f)).

  However, in the manufacture of such UOE steel pipes, only in the pipe expansion process in which the outer peripheral side of the steel pipe is free and expanded from the inside, if any direction of the cross section is long, the cross-sectional shape after the pipe expansion becomes elliptical. As such, there is a problem that the shape before the tube expansion process remains, and it is difficult to form a perfect circle. If the pipe end is not a shape close to a perfect circle, circumferential welding is likely to be poor when steel pipes are welded on site.

  Therefore, for example, Patent Literature 1 and Non-Patent Literature 1 disclose a pipe material correcting device for making the cross section of the tube end portion a shape close to a perfect circle, and Patent Literature 2 discloses tube ends using the pipe material correcting device. The joining method is disclosed.

JP2012-223817A JP 2012-223819 A

Tetsuya Kishiguchi and five others, “Development of a submarine pipeline / steel pipe end rounding and shaping machine -to improve the quality of on-site welds-”, Nippon Steel & Sumikin Engineering Technical Report, 2013 Vol. 4, p. 39-45

  However, the above-described pipe end straightening device has been conventionally used on the site where a pipeline is laid or on a trolley for pipeline laying. That is, after transporting a steel pipe manufactured as a UOE steel pipe to the site, the pipe end was shaped on the site, and then the steel pipe was attached to perform circumferential welding. However, when the UOE steel pipe product is subjected to pipe end shaping at the site, only the cross section of the pipe end portion is expanded with respect to the steel pipe main body, and the final shape of the steel pipe becomes a rough shape. On the other hand, since the cross section of the pipe end portion does not widen, it is difficult in terms of the process to prevent the pipe end portion from being expanded only in the pipe expansion process during the manufacture of the UOE steel pipe.

  Therefore, the present invention relates to a steel pipe that can form a steel plate into a tubular shape by UOE, JCOE, bending roll, spiral, or the like. An object is to provide a manufacturing method.

In order to solve the above problems, the present invention is a method of manufacturing a steel pipe having a step of forming a steel plate into a tubular shape, a seam welding step, and a pipe expanding step,
Between the seam welding process and the pipe expansion process, a pipe end shaping process is performed for shaping the cross-sectional shape of the pipe end to a desired shape at the pipe end in the longitudinal direction of the steel pipe formed by the seam welding process. A method for manufacturing a steel pipe is provided.

  The tube end shaping step is arranged so as to face the outer peripheral surface of the tube end portion, and contacts a ring-shaped casing that restricts deformation of the tube end portion toward the outer peripheral side, and an inner peripheral surface of the tube end portion. A shaping device provided with a shaping roll that is arranged in contact with each other and presses a side surface of the tube end portion toward the casing to plastically deform the tube end portion; and a rotating means that rotates the steel pipe around a central axis. It may be done.

  The pipe end may be in a range of 0 mm to 200 mm from both longitudinal ends of the steel pipe.

  ADVANTAGE OF THE INVENTION According to this invention, the roundness of the cross section of a pipe end can be improved, without expanding only the pipe end part of a steel pipe.

It is explanatory drawing which shows the manufacturing process of the UOE steel pipe concerning embodiment of this invention. It is sectional drawing which shows the example of the pipe end shaping process concerning embodiment of this invention. It is sectional drawing which shows the example of a pipe expansion process. It is explanatory drawing which shows the manufacturing process of the conventional UOE steel pipe.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, manufacture of a UOE steel pipe will be described as an example of a steel pipe formed by forming a steel plate into a tubular shape.

  The manufacture of a UOE steel pipe according to an embodiment of the present invention includes steps of steel plate C press, U press, O press, seam welding, pipe end shaping, and pipe expansion. FIG. 1 is a diagram for explaining processing by each process, and is a cross-sectional view as seen from the front direction of a steel plate (steel pipe). First, after performing groove processing on both edges in the width direction of a thick steel plate S0 (FIG. 1 (a)), a C press is applied to both ends in the width direction of the steel plate S0 by a punch 11 and a die 12. A process is performed (FIG. 1B). The C-pressed steel sheet S1 is further formed into a U-shaped steel sheet S2 in a U-press process (FIG. 1 (c)). Thereafter, the steel plate S3 is formed into a tubular steel plate S3 by an O-pressing process in which a compressive force is applied from the outside (FIG. 1 (d)), and both edges where the grooves of the steel plate S3 formed into a tubular shape face each other are seamed in the welding process. Welding is performed (FIG. 1 (e)). At this stage, the steel pipe S4 closed in the circumferential direction is formed.

  In the present invention, a pipe end shaping process is first performed on the steel pipe S4 after seam welding as shown in FIG. The pipe end shaping step is shaping performed so that the cross-sectional shape of the pipe end portion in the length direction of the steel pipe S4 is close to a perfect circle, and is disclosed in, for example, the above-mentioned Patent Document 1, Non-Patent Document 1, and the like. This is done using a shaping machine. In the present embodiment, the shaping machine 21 is disposed so as to face the outer peripheral surface of the pipe end portion Se of the steel pipe S4 as shown in FIG. 1 (f) viewed from the front direction and FIG. 2 viewed from the side direction. A ring-shaped casing 22 that restricts deformation of the end portion Se to the outer peripheral side and a tubular end portion 22 that is in contact with the inner peripheral surface of the pipe end portion Se are disposed, and the side surface of the pipe end portion Se is pressed toward the casing 22 to A shaping roll 23 for plastically deforming the end portion Se and a rotating means (not shown) for rotating the steel pipe S4 around the central axis are provided. Further, a receiving roll 24 that supports the casing 22 from below is provided. The pipe end Se of the steel pipe S4 is inserted into the casing 22 of the shaping machine 21, and the shaping roll 23 is pressed from the inner wall side of the steel pipe S4 to the casing 22 side in a state where the outer peripheral side of the steel pipe S4 is appropriately constrained within the range. By rotating the steel pipe S4, the pipe end Se of the steel pipe S4 is plastically deformed along the inner surface of the casing 22, and the cross-sectional shape of the pipe end Se becomes close to a perfect circle. It is preferable that the pipe end shaping step is performed on a range of at least 0 mm to 200 mm from both ends in the longitudinal direction of the steel pipe S4. That is, in order to secure the most important end shape, the tube end shaping step is preferably performed from the position of the tube end 0 mm. If the range is too narrow, the influence of the unshaped roundness shape defective portion will be affected. Since the end receives and the effect of improving the roundness is weakened, it is preferable to carry out within a range from the pipe end to 200 mm. The tube end shaping may be performed in a wider range, but if the range is too wide, the production efficiency is reduced due to the tube end shaping, and therefore the range may be determined as appropriate according to the required accuracy. Further, the apparatus for performing pipe end shaping according to the present invention is not limited to the shaping machine 21 shown in FIGS.

  After the pipe end shaping process, in order to further improve the roundness of the entire length of the steel pipe S4 and obtain a desired pipe shape, a pipe expanding process is performed in which a tensile force is applied from the inside by a pipe expanding device (FIG. 1 (g)). ). FIG. 3 is a cross-sectional view showing a state where the steel pipe S4 is expanded in the pipe expansion process, viewed from the side surface direction of the steel pipe S4. The pipe expanding device 31 is inserted into the steel pipe S4 after the pipe end shaping process, and pushes the steel pipe S4 from the inside by a plurality of segments 33 arranged so as to be in contact with the outer peripheral side surface of the truncated pyramid cone 32. The segment 33 is divided into a plurality of, for example, 8 or 12 segments in the circumferential direction. As shown in FIG. 3, the cone 32 is connected to a pull rod 34, and a boom 35 is provided on the outer periphery of the pull rod 34. By operating the pull rod 34 in the axial direction, the entire outer diameter of the plurality of segments 33 changes. When the segment 33 is inserted to the expanded position of the steel pipe S4 and the pull rod 34 is pulled in the axial direction, each segment 33 expands radially and is pressed against the inner peripheral surface of the steel pipe S4. Arrange the shape. The length of the segment 33 in contact with the inside of the steel pipe S4 in the axial direction is about 400 mm to 1000 mm. For example, the steel pipe S4 having a length of about 12 m is sequentially expanded one stroke at a time.

  The steel pipe S4 thus formed is then subjected to heat coating or the like according to the application, and is transported to the site as a pipeline UOE steel pipe.

  According to the present invention, since the cross-sectional shape of the pipe end portion of the steel pipe S4, which becomes the joint portion when forming the pipeline, is formed close to a perfect circle, the displacement of the pipe ends in the joint portion is prevented, Welding can be performed satisfactorily. In addition, by performing the tube expansion process over the entire length after performing the tube end shaping, only the tube end portion Se does not become a flaky shape, and a steel pipe having a uniform diameter over the entire length can be obtained.

  Furthermore, according to the present invention, it is not necessary to install a shaping machine at the pipeline construction site and perform pipe end shaping, and the process at the site can be simplified.

  Conventionally, when a UOE steel pipe is manufactured, if the mold of the O press is worn, the shape after the O press becomes unstable, and the shape becomes unstable by performing the tube expansion process as it is. It was necessary to replace the mold. However, according to the present invention, even if the mold in the O-pressing process is worn and the forming accuracy by the O-press is lowered, the tube end section is shaped into a desired shape by the tube-end shaping process which is the next process. And since the roundness of the pipe | tube edge part of a UOE steel pipe can be hold | maintained, the frequency of the die | dye exchange of O press can be reduced.

  Furthermore, by shaping the tube end portion and expanding the tube end section after becoming close to a perfect circle, it is possible to prevent cracking of the tube end portion at the start of the tube expansion process, which was easy to occur in the past. . In addition, it has been found from experiments by the present inventors that when the tube expansion step is performed after the tube end shaping step, the cross-sectional shape that is close to a perfect circle is hardly broken by the tube end shaping.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this example. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  The present invention is applicable not only to UOE steel pipes but also to steel pipes formed into a tubular shape by JCO, bending rolls, spirals, and the like.

21 Shaping machine 22 Casing 23 Shaping roll 24 Receiving roll S1, S2, S3 Steel plate S4 Steel pipe Se Pipe end

Claims (3)

A method of manufacturing a steel pipe having a step of forming a steel plate into a tubular shape, a seam welding step, and a pipe expanding step,
Between the seam welding process and the pipe expansion process, a pipe end shaping process is performed for shaping the cross-sectional shape of the pipe end to a desired shape at the pipe end in the longitudinal direction of the steel pipe formed by the seam welding process. The manufacturing method of the steel pipe characterized by the above-mentioned. The tube end shaping step includes
A ring-shaped casing that is disposed to face the outer peripheral surface of the tube end, restricts deformation of the tube end to the outer peripheral side, and is disposed in contact with the inner peripheral surface of the tube end; It is performed by a shaping device provided with a shaping roll for pressing the side surface of the pipe end portion toward the casing and plastically deforming the pipe end portion, and a rotating means for rotating the steel pipe around a central axis. The manufacturing method of the steel pipe of Claim 1.   The said pipe end part is the range from 0 mm-200 mm from the longitudinal direction both ends of the said steel pipe, The manufacturing method of the steel pipe as described in any one of Claim 1 or 2 characterized by the above-mentioned.

Images