KR20120075252A - Pipe making method and pipe making device - Google Patents

Abstract

PURPOSE: A method and an apparatus for making pipes are provided to stably make steel pipes by using high strength steel sheets of which yield strength is more than 830MPa. CONSTITUTION: An apparatus for making pipes makes steel sheets to pipes with one or more molding machines. The apparatus for making pipes comprises a C-molding machine and a U-molding machine. The C-molding machine comprises an upper molding unit(110) and a lower molding unit(120). Steel sheets placed on the lower molding unit are pressed by the upper molding unit. The curvature radius of the upper molding unit is gradually increased as inwardly heading to a lateral direction of the steel sheets.

Description

PIPE MAKING METHOD AND PIPE MAKING DEVICE

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a steel pipe for use in a line pipe or the like, or a device for piping a pipe, and more particularly, to a pipe manufacturing method and a pipe forming device capable of manufacturing a large diameter steel pipe using a high strength steel sheet.

More specifically, the present invention relates to an apparatus and a method for piping a steel pipe with a high strength steel sheet having a yield strength of 830 MPa or more.

With the increase in global energy demand, the transportation method using line pipe is the most efficient method for long-distance oil or gas transportation. Such a line pipe can maximize its efficiency by increasing the transport pressure of the fluid, ie, crude oil or gas, in the pipe. However, in order to increase the transport pressure of the fluid, it is necessary to increase the strength of the pipe base material.

Currently, line pipes of X70 grade or less are mainly used, but line pipe construction cost is reduced by reducing the weight of steel used by reducing the diameter and thickness of the line pipe, as well as improving the transportation efficiency due to the increase in the transportation pressure. By reducing the thickness of the pipe, it is possible to reduce the construction time of the circumferential welding (pipe-pipe welding), which takes up a large part of the cost of the line pipe.

The procedure of the conventional UOE tubing method is shown in FIG. First, C-forming is performed by pressing both ends of the plate P to the upper molding machine 11 and the lower molding machine 12 of the C-molding machine. Then, U-press is performed to deform the plate P into a U-shape through the main molding portion 21 and the jig 22 of the alphabet U-forming machine.

The U-shaped plate which has been finished to U molding is O-shaped which is pressed between the upper molding machine 31 and the lower molding machine 32 of the O molding machine each having a semi-circular face and deformed into an alphabet O shape. The O-shaped steel pipe is subjected to tack welding to fix the pipe that is caused by the spring back phenomenon for pipe welding, and then piped by submerged arc welding. The pipe manufacturing is completed by welding the pipe and expanding the pipe for the purpose of improving the roundness and reducing the residual stress during molding.

The UOE pipe making method is used in most pipeline construction because it is possible to mass-produce a pipe having a length of 12m by forming in a short time, and includes a pipe expansion process so that the quality of the pipe being piped is excellent.

At present, the yield strength of high-strength line pipe steel is developed to over 830MPa. However, when the tube of such a high strength steel, there are the following problems.

First, as the yield strength of the steel increases, the required pipe diameter decreases, and as the strength increases and the pipe diameter decreases, it becomes difficult to uniformly form the plate during the pipe making, thus making it difficult to secure the roundness of the pipe. Here, roundness means the ratio of the width to the length of the pipe.

In addition, as the strength of the steel increases, the spring back phenomenon is increased after the pipe is piped, and the residual stress acting on the weld portion increases, thereby increasing the possibility of cracking during welding. In this regard, a conventional C-molding machine is shown in FIG. 2. As shown in Fig. 2, the conventional C-molding machine is to pre-form the end of the plate with a curvature corresponding to the target radius, so that the radius a is set to one radius according to the target radius. That is, because of having a curvature for each aperture, the section (a) to be molded for the small diameter is short, and the section (a) to be molded for the large diameter is long.

Even if the end of the plate is formed in advance according to the target radius with a conventional C-molding machine, the shape is returned to the spring back after the pipe is piped as the strength of the steel increases, and when welding in the state that the spring back occurs Is welded as shown in FIG. 3.

In order to weld high strength steel pipes, a weld metal part 40 having a higher strength than that of a steel pipe base material is provided. In this welding process, a modified part is generated due to heat input of a weld around the weld part. As shown in FIG. 3 (b), the welding heat affected part 41 has a lower strength than the surroundings, and in the case where the residual stress in the steel pipe is large, cracks are generated in the weld heat affected part 41. Pipe expansion can lead to pipe failure.

In addition, if the spring back is severe after the U molding, as shown in Figure 4 it is impossible to put into the O molding machine, there is a problem that the steel pipe forming itself becomes difficult.

 The present invention has been invented to solve the above problems, the present invention is an object of manufacturing a UOE steel pipe using a high strength steel sheet with a yield strength of 830MPa or more.

 In addition, an object of the present invention is to provide a steel pipe having a roundness close to 1 and having a large picking angle despite high springback of a high strength steel.

In addition, an object of the present invention is to provide a UOE tubing method that can be stably steel pipes.

The present invention, in order to achieve the above object, as one or more piping device for pipe joints to the molding machine, the molding machine provides a piping device including a pressing surface formed with a curved surface of which the radius of curvature continuously changes.

In addition, the tube manufacturing apparatus of the present invention includes a C-forming machine and a U-forming machine, wherein the C-forming machine includes an upper molding machine and a lower molding machine, and presses the plate placed on the lower molding machine to the upper molding machine to form a plate. The upper molding machine may be configured to continuously increase the radius of curvature toward the width direction of the plate.

In addition, when the upper molding machine of the C-molding machine is divided into a plurality of curved portions 111, 112, 113, and 114, the width of the increase in the radius of curvature at each curved portion may increase inward.

The U-molding machine includes a main molding part, a fixing part for fixing the position of the plate at the lower part of the main molding part when the plate is pressed by the main molding part, and a jig for pushing both side plates when the main molding part presses the steel sheet. The forming portion includes a central portion having a radius of curvature R _u and a side portion connected to the central portion and having a radius of curvature r _u smaller than the central portion, wherein the radius of curvature R _u of the central portion is 0.65R < It can be configured such that R _u <0.82 R, where R is the radius of the target tube.

Further, the curvature radius r _u of the side part may be configured to be in a range of 0.04R <r _u <0.2R.

On the other hand, the present invention includes the step of manifolding the plate into one or more forming step, the forming step may provide a tube forming method comprising a C forming step of forming a part of the plate into a curved surface in which the radius of curvature continuously changes have.

In addition, in the forming step C, both ends of the width direction of the plate are formed into the C forming part, and when the C forming part is divided into a plurality of curved parts 111, 112, 113, and 114, the radius of curvature of each curved part is the width of the plate. It can grow larger in the direction.

Further, the radius of curvature R _c1 of the edge-side curved portion of the sheet of the curved portion may be 0.7R <R _c1 <1.2R (where R is the target radius).

In addition, the molding step includes a U molding step performed after the C molding step, wherein the U molding step forms a part including the center of the plate into a U molding part, and a radius of curvature R _u of the central part of the U molding part is It can be molded so as to be in the range of 0.65R <R _u <0.82R, where R is the target radius.

In the U molding step, the radius of curvature r _u of both sides of the U-shaped part may be molded to be within a range of 0.04R <r _u <0.2R.

In the manufacturing method and manufacturing apparatus of the present invention, the plate may be applied to a high strength steel sheet having a yield strength of 830 MPa or more, and the plate may be a steel plate having a thickness of 16 mm or more. It is preferable that the manufacturing method and manufacturing apparatus of the present invention be applied to a high strength steel sheet having a springback effect of 16 mm or more and a yield strength of 830 MPa or more.

In addition, the present invention may be to produce a steel pipe having a radius of 18 inches or more.

The present invention, through the above configuration, it is possible to provide a device for pipe and tube steel pipe using a high strength steel sheet with a yield strength of 830MPa or more.

 In addition, the present invention is capable of providing a steel pipe having a roundness close to 1 and having a large picking angle in spite of the high springback of the high strength steel.

In addition, the present invention can provide a piping method that can be stably welded steel pipe.

1 is a schematic diagram of a conventional UOE piping method and a tube apparatus.
2 is a partial cross-sectional view of a C-molding machine of the conventional UOE tube manufacturing apparatus.
Fig. 3 (a) is a cross section of a welded portion of a UOE steel pipe formed by a conventional UOE pipe making method, and Fig. 3 (b) is a graph showing the strength at some surface of Fig. 3 (a).
4 is a state diagram when the high-strength steel is piped with an O molding machine by a conventional UOE pipe forming method.
5 is a partial cross-sectional view of the C-molding machine of the UOE piping system of the present invention.
Fig. 6 is a front view of the U-molding machine of the UOE tubular apparatus of the present invention.
7 is a cross sectional view of a UOE steel pipe molded by a conventional UOE pipe forming apparatus and a UOE steel pipe molded by the present invention.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail.

The material of the steel pipe processed in the embodiment of the present invention uses the material of Patent Application No. 2006-107917, and the welding material of Patent Application No. 2007-81137 is used as the welding material. The present invention includes the contents of both documents.

Also, in the present invention, since the C-molding machine 100 and the O-molding machine except for the U-molding machine 200 are the same as the conventional UOE method, the description thereof will be omitted.

5 is a partial cross-sectional view of the C-molding machine 100 of the present invention. As shown in FIG. 5, the C-molding machine 100 is pressurized between the upper molding machine 110 and the lower molding machine 120 so that the plate material P is pressed to form curved portions 111, 112, 113, and 114 of the upper molding machine 110. Along the end of the plate is deformed. Although only a part is shown in FIG. 5, a configuration symmetrical to this is disposed at the other end in the width direction of the plate.

The upper molder 110 of the C-molding machine 100 of the present invention includes a curved portion 111, 112, 113, 114 that the curvature radius is continuously increased, the curved surface (deformation) The radii of curvature at 111, 112, 113, and 114 are called Rc1, Rc2, Rc3, and Rc4.

In the present invention, the curved portions 111, 112, 113, and 114 continuously increase in radius of curvature from the edge to the inside. That is, the radius of curvature Rc1 of the curved portion 111 is smaller than the radius of curvature Rc2 of the curved portion 112, and the radius of curvature Rc2 of the curved portion 112 is smaller than the radius of curvature Rc3 of the curved portion 113. The radius of curvature Rc3 of the curved portion 113 is smaller than the radius of curvature Rc4 of the curved portion 114.

In addition, it is preferable that the radius of curvature of the curved portions 111, 112, 113, and 114 be formed such that the increasing width increases inward. That is, the radius of curvature increases faster from the curved portion 111 to the curved portion 114. The radius of curvature (Rc1) at the beginning of the valley portion 111 is 0.7R <R _c1 <1.2R preferably in the (R is the radius of the steel tube to target) range.

If the radius of curvature Rc1 of the initial curvature 111 is smaller than 0.7R, even if springback occurs, the end of the sheet is excessively bent, which may adversely affect roundness and picking angle, and the initial curvature 111 than 1.2R. If the radius of curvature Rc1) is large, spring back occurs even when molding, so that the end of the sheet is unmolded, which may adversely affect the roundness and the picking angle.

In the present invention, the radius of curvature of the curved portions 111, 112, 113, and 114 is continuously increased, thereby initially having a radius of curvature smaller than the target radius, but having a radius of curvature larger than the initial target radius.

Therefore, the C-molding machine of the present invention will form a wide width while the end of the plate is molded to a radius smaller than the target radius (R). Accordingly, even in the springback effect due to the rigidity of the high strength steel sheet, the end portion of the plate can be molded to the target radius level.

When forming high strength steel, the springback phenomenon of the steel itself is so severe that if the section subjected to deformation is short, it is present as a straight section without deformation after C-forming. As shown in Figure 7 when the small diameter pipe of the high-strength steel pipe (a) is the overall deformation lengthened as in the case of large diameter and guide the deformation to occur well, by designing the end of the plate to the desired pipe diameter After completion of the tubing, the curvature of the plate end will be improved compared to before.

On the other hand, Figure 6 schematically shows the U-forming machine of the present invention. The U-forming machine of the present invention is the same as the conventional U-forming machine except for the shape of the main molding part 210.

As shown in FIG. 6, the U-molding machine 210 is a plate (P) to the jig 220 of the side, while the C molding plate (P) is pressed down between the fixing portion 230 and the main molding portion (210) The side of is pushed back. Accordingly, the plate is molded according to the curved shape of the U-forming machine 210, and both sides are pressed along the side of the U-forming machine 210, thereby making it easy to feed into the continuously O-forming machine. .

U- shape of the molding machine 210 includes a central portion 211. In doedaga formed as a curved surface having a curvature radius (R _u) smaller radius of curvature than the side portion 212 in the radius of curvature (R _u) of the central portion 211 (r _u) It is formed as a curved surface having a.

The radius of curvature R _u of the center portion 211 is configured to be within the range of 0.65R <R _u <0.82R, and the radius of curvature r _u of the side portion is configured to be within the range of 0.04R <r _u <0.2R.

The radius of curvature R _u of the central portion 211 should be greater than 0.65R, so that the roundness and the picking angle are secured after the piping, so that no fracture occurs when expanding. For example, when the target radius is 18 inches, the radius of curvature R _u must be at least 297 mm to ensure roundness and picking angle after the piping.

In addition, the radius of curvature R _u of the central portion 211 should be smaller than 0.82 to enable O molding after U molding. For example, when the target radius is 18 inches, when the radius of curvature Ru of the center portion 211 is formed to be 380 mm exceeding 374 mm, the molding width by the center portion 211 is large and O molding is impossible.

When molded with the U-forming machine 200 designed by the present invention, the radius of curvature (R _u ) of the central portion 211 is large, the portion deformed into the deformed section is wide, the overall U-shaped vertical. In addition, the small radius of curvature r _{u at} both sides of the U-molding machine 200 is 0.04R <r _u. By applying 25mm in the range of <0.2R, for example, 36 inches in diameter, it has a substantially U-shape close to the vertical, so that the next step of O-molding machine is good.

As such, when the small curvature r _{u on} both sides of the U-forming machine 200 is smaller than 0.04R, more deformation may be received, but the pipe may be locally bent due to the too small radius of curvature to cause scratches on the pipe surface. If the radius of curvature is greater than 0.2R, the deformation becomes difficult to have a U-shape to be opened, so that the subsequent O-molding machine is impossible or stable O-molding is impossible even if it is introduced.

Figure 7 shows the shape of the steel pipe after the tubing by the conventional C-forming machine, U-forming machine, and the C-forming machine 100, U-forming machine 200 developed by the present invention.

In case of applying the existing molding machine, as shown in the dotted line in the photo, the deformed length during U-molding is short, so it is not deformed even after O-molding, and it shows the oval-shaped pipe as a whole, and the end of the plate where welding is applied is almost straight. have.

On the other hand, the pipe formed by the C-molding machine 100 and the U-molding machine 200 designed by the present invention exhibits a good circular shape overall, and the deformed area is long during U-molding, thus perfect during O-molding. It can be seen that the deformation is in contact with the molding machine.

The change of picking angle and roundness before and after this invention is shown in [Table 1]. Inventive Examples 1 to 6 have a radius of curvature that continuously increases the radius of curvature of the C-molding machine 100, and fixes the radius of curvature r _u of both sides of the main molding part 210 of the U-forming machine 200 to 25 mm. In the case of changing only the central radius (R _u ) of the main molding portion 210 of the U-forming machine 200 shows the change in roundness and picking angle.

As the central radius R _u of the U-shaped molding machine 200 increases, the roundness increases, but in the case of 320 mm, the roundness is larger than 1, that is, the shape is slightly distorted to the side. That is, when the radius is more than 320mm, the pipe is pressed sideways by excessive deformation rather than the diameter of the target pipe, so the picking angle is good but the roundness tends to decrease. However, the expansion unit was possible and could be expanded.

However, in the case of 380 mm (approximately 0.83 R) as in Comparative Example 9, the pipe was pressed excessively to the side, and after the U-molding, it was impossible to insert the O-molding machine so that the pipe was impossible.

As a case where the fixing to a large radius of fame 7-8 times U- shaper 200 to 320mm, and change only the radius (r _u) of the side of the U- molding machine 200, a significant relation to changes in the radius (r _u) It can be seen that the roundness and peaking angle are constant without.

However, when the radius (r _u ) is larger than 0.2R at 100mm (about 0.21R), O-forming is impossible due to the plate unfolding after U-forming as in Comparative Example 11, and the radius (r as in Comparative Example 10). _{When u} ) is 18 mm (about 0.39 R), which is smaller than 0.04 R, local deformation occurs due to excessive deformation, and a flaw occurs in the plate.

Comparative Examples 12 to 13 are C-molded with a C-molding machine having a fixed curvature radius for each pipe diameter, which is a conventional C-molding method, and a U-molding machine also has a smaller radius of curvature (R _{u for} more than 36 inches in diameter). It shows the case where 186mm is applied. At this time, the radius of curvature r _{u of} both sides of the main molding part of the U-molding machine was applied to 1/2 of the radius of curvature R _u of the central part of the U-molding machine.

As a result, the roundness was decreased, the section deformed by the radius of curvature of the fixed C-molding machine, or the peaking angle was small due to the application of a large radius of curvature, resulting in fracture at the weld.

Finally, in the case of Comparative Example 14, the invention was applied to the C-molding machine 100, and the existing U-molding machine was applied. The picking angle was good, but the roundness was reduced and the weld fracture occurred when the tube was expanded.

As a result, it can be seen that not only the picking angle but also the roundness must be improved to achieve the expansion of the high strength pipe. Specifically, the picking angle is greater than 80 ° and the roundness should be within the range of 1 ± 0.5.

100: C-molding machine 110: upper molding machine
120: lower molding machine 111, 112, 113, 114: curved portion
200: U-forming machine 210: main molding part
220: jig 230: fixed part

Claims (13)

An apparatus for piping a sheet of material into one or more molding machines,
The molding machine includes a pressing surface formed with a curved surface of which the radius of curvature continuously changes. The method of claim 1,
C-forming machine, U-forming machine,
The C-molding machine includes an upper molding machine and a lower molding machine, and presses the plate placed on the lower molding machine to the upper molding machine to form a plate,
And the upper molding machine is configured to continuously increase the radius of curvature toward the width direction of the plate. The method of claim 2,
When the upper molding machine of the C-molding machine is divided into a plurality of curved portions (111, 112, 113, 114), the width of the increase in the radius of curvature at each curved portion becomes larger toward the inside. The method of claim 2,
The U-molding machine includes a main molding part, a fixing part for fixing the position of the plate at the lower part of the main molding part when the plate is pressed by the main molding part, and a jig for pushing both side plates when the main molding part presses the steel sheet,
The main molding part includes a center part having a radius of curvature R _u , and a side part connected to the center part and having a radius of curvature r _u smaller than the center part.
And said radius of curvature (R _u ) of said central portion is configured to be within the range of 0.65R < R _u < 0.82R (where R is the radius of the target tube). The method of claim 4, wherein
The curvature radius (r _u ) of the side portion is configured to be in the range 0.04R <r _u <0.2R. Comprising the step of aligning the plate into one or more molding steps,
The forming step comprises a C-forming step of forming a portion of the sheet material to the curved surface of the curvature radius continuously changes. The method according to claim 6,
In the forming C step, the widthwise both ends of the sheet are molded into the forming part C,
When the C-shaped portion is divided into a plurality of curved portions (111, 112, 113, 114), the curvature radius of each curved portion becomes larger toward the inner side in the width direction of the plate. The method of claim 7, wherein
The radius of curvature (R _c1 ) of the edge curved portion of the plate of the curved portion is 0.7R <R _c1 <1.2R (where R is the target radius). The method of claim 7, wherein
The forming step includes a U forming step performed after the C forming step,
The U molding step forms a portion including the center of the sheet into a U molding portion, and forms a center curvature radius R _u of the U molding portion to be within a range of 0.65R <R _u <0.82R (where R is a target radius). An article method characterized in that the. The method of claim 9,
In the U-forming step, the radius of curvature (r _u ) of the both sides of the U-shaped portion is molded, characterized in that formed in the range 0.04R <r _u <0.2R. The method according to any one of claims 6 to 10, wherein the sheet is a high strength steel sheet having a yield strength of 830 MPa or more. The method according to any one of claims 6 to 10, wherein the plate is a steel sheet having a thickness of 16 mm or more. The method according to any one of claims 6 to 10, wherein a steel pipe having a radius of 18 inches or more is produced.

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