KR20140082517A - Pipe making method and c crimping device - Google Patents

Abstract

Provided is a C crimping device capable of bending both edges of a sheet in a width direction in order to secure the roundness without affecting the performance of a steel pipe, including an upper forming unit having a pair of C-forming portions having a curved surface at a position corresponding to both edges of the sheet in the width direction, and a center forming portion disposed between the C-forming portions and having a protruding curved surface facing the bottom surface; and a lower forming unit having a curved surface corresponding to the shape of the C-shaping portions and the center shaping portion.

Description

TECHNICAL FIELD [0001] The present invention relates to a PIPE MAKING METHOD AND CCRIMPING DEVICE,

The present invention relates to a method for manufacturing a steel pipe used for a line pipe or the like, or a molding machine used for a tube making method, and more particularly to a tube making method and a C-molding machine capable of sufficiently deforming a high strength steel plate.

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

Currently, steels for line pipe of X70 grade or less are mainly used. However, by reducing the diameter and thickness of the line pipe and reducing the weight of the steel used, it is possible to improve the transportation efficiency by increasing the transportation pressure, (Pipe-to-pipe welding), which occupies a large part of the line pipe construction cost due to the reduction in the thickness of the pipe.

The procedure of the conventional UOE tube making method is shown in Fig. First, the upper and lower forming portions 11 and 12 of the C-molding machine bending both ends of the plate material P are pressed to perform C-crimping. Thereafter, U-molding is performed to deform the plate material P in a U-shape through the main die 21 and the jig 22 of the alphabet U-molding machine.

The U-shaped plate material that has undergone the U-shaping is O-shaped in which it is pressed between the upper molding portion 31 and the lower molding portion 32 of the O molding machine having the semicircular surfaces and deformed into an alphabet O shape. The O-shaped steel pipe is subjected to a tack welding process for fixing the pipe caused by a spring back phenomenon for pipe welding, and is then subjected to a submerged arc welding process, And pipe manufacturing is completed by expanding for the purpose of improving the roundness and reducing the residual stress at the time of molding.

Such a UOE pipe making method is capable of mass production of a pipe having a length of 12 m by molding in a short time, and it is used for most pipeline construction because it includes an expanding process and thus the quality of the pipe is excellent.

However, in the case of using a high-strength steel, it is difficult to make a shape of a true circle even after the tube is spanned by the spring back of the plate material, which is severe in the case of a high-strength thin plate.

Therefore, there has been an attempt to make a press shape in the shape of an apple at the time of the O-molding, excessive strain by the additional press at the upper part, or a uniform roundness by rotating the steel pipe during the O-molding.

However, there is a problem that the end portion of the plate material is displaced during excessive molding, resulting in unstable O-molding. In addition, there is a problem that the productivity is extremely low because the steel pipe is rotated, so that realization is not feasible.

Disclosure of the Invention The present invention has been made in order to solve the above problems, and it is an object of the present invention to secure the roundness without affecting the performance of a steel pipe in manufacturing a UOE steel pipe using a high strength steel plate, in particular, a high strength thin plate.

In addition, the present invention aims to improve the shape of a steel pipe without increasing the number of processes by improving the C molding machine in manufacturing a high strength steel pipe.

In order to accomplish the above object, the present invention provides a method of making a trowel and a molding machine as described below.

The present invention relates to a C molding machine for bending both edges in a width direction of a plate material, comprising: a pair of C molding portions each having a curved surface at a position corresponding to both widthwise edges of the plate material; An upper molding machine including a central forming part having a curved surface; And a lower molding machine having a curved surface corresponding to the shape of the C molding part and the center molding part.

At this time, the pair of C forming portions and the central forming portion may be continuously formed as a single member.

In the present invention, the radius of curvature (r) of the curved surface of the central forming part preferably satisfies the relation of r ≥ πR - Cr relationship between the radius R of the steel pipe to be formed and the curvature (Cr) of the C molding part.

In the present invention, the central forming part includes a first curved part on the side of the C molding part and a second curved part between the first curved part, and the first curved part and the second curved part may have different curvatures .

The present invention provides a method of manufacturing a steel sheet, comprising: a C molding step of bending both widthwise edges of a plate material; A positive deformation forming step of forming a plate material into a U shape before forming the U by molding a curved surface between the forming section of the C forming step and the widthwise middle part of the plate material at the same time as the C forming step; A U forming step of bending the plate material with respect to the widthwise center portion of the plate material; There is provided a gauzing method including an O shaping step of putting a plate material into a O type molding machine to form a circular shape and a welding step of welding both ends of the circularly formed plate material.

In the present invention, the radius of curvature r in the normal deformation step can satisfy the relationship between the radius R of the steel pipe to be gutted and the curvature Cr in the C molding step to satisfy the relationship r ≥ πR - Cr.

Further, in the present invention, it is preferable that the forming depth H to be formed in the constant deformation forming step is smaller than the radius of curvature in the U-forming step so that normal deformation can be repeatedly processed.

The present invention can provide a C molding machine and a construction method capable of securing a roundness without affecting the performance of a steel pipe in manufacturing a UOE steel pipe using a high strength steel plate, in particular, a high strength thin plate.

In addition, the present invention can produce a high strength steel pipe by performing the regular deformation step together with the C molding machine or the C molding step to increase the strength by repeated work hardening and to reduce the YS (yield strength) .

In addition, since the deforming step is performed together with the C forming step, not only the load can be reduced in the O molding step subsequent to the C forming step, but also the influence of the spring back largely acting on the article making can be reduced.

In addition, due to the increase in roundness, it is possible to prevent low-temperature cracks due to residual stress in the case of welded welding and to prevent the shape of the weld around the welded portion during the spreading.

FIG. 1 is a schematic view of a conventional UOE sewing method and sewing apparatus.
2 is a cross-sectional view showing the appearance of the tube after UOE molding.
3 is a sectional view of a conventional C molding machine.
Fig. 4 is a cross-sectional view of a C molding machine according to an embodiment of the present invention, Fig. 4A is a sectional view before a C molding machine forms a plate, and Fig.
5 is a cross-sectional view of the plate material molded by the C molding machine of FIG.
6 is a cross-sectional view of a plate material molded by a C molding machine according to another embodiment of the present invention.

Hereinafter, a specific embodiment of the present invention will be described with reference to the accompanying drawings.

2 is a sectional view of a steel pipe formed by a conventional UOE method. As shown in Fig. 2, in the UOE molding, the A region is formed in the C molding, the C region is formed in the U molding, and the entire region is formed in the O molding. Since the B region is not molded other than the O molding, Due to the bag, the overall shape is destroyed (roundness decline).

3 shows a conventional C molding machine. The C molding machine shown in Fig. 3 is the same as that shown in Fig. 1, and only the end portion of the plate P is molded through the upper molding portion 11 and the lower molding portion 12, and the B region is not molded.

The inventors of the present invention have found out that the reason why the B region does not have a sufficient curvature is that molding can not be performed except for O molding, and therefore, it is necessary to make the B region have curvature before O molding. In addition, the present invention has been made to provide a curvature for the B region but not to have a separate process in addition to the conventional UOE molding.

4 shows a cross section of the C molding machine of the present invention. 4A is a cross-sectional view of the C molding machine 100 according to the present invention before the plate P is molded. FIG. 4B shows a C molding machine 100 according to the present invention forming the plate P Are shown in this cross-sectional view.

In the present invention, the C molding machine 100 will be mainly described, and the remaining U molding and O molding are described in the prior art and are well known, so that a detailed description thereof will be omitted in the present invention.

4, the C molding machine 100 of the present invention includes an upper molding part 110 and a lower molding part 120, and a plate material is placed between the upper molding part 110 and the lower molding part 120 The upper forming part 110 is pressed by the lower forming part 120 to form the plate material P. [

The upper forming unit 110 includes a pair of C forming units 111 located at both ends of the upper forming unit 110 and a central forming unit 115 disposed between the C forming units 111 to form both ends of the plate material. ).

C forming part 111 includes a curved part 112 formed so that the end of the plate has a predetermined curvature Cr and the central forming part 115 includes a curved part 116 having a predetermined curvature R, . Since the C forming portion 111 and the central forming portion 115 are integrally formed in the upper forming portion 110, the upper forming portion 110 moves so that the pair of C forming portions 111 and the center The forming part 115 moves together.

The curved surface portion 116 having the predetermined radius r of the central forming portion 115 is protruded from the C forming portion 111. [ Therefore, when the upper shaping part 110 moves integrally, the central shaping part 115 can form a portion between the parts to be C-shaped in the sheet material with a radius r.

In the case of the lower molding part 120, the C corresponding part 121 and the center corresponding part 115 are formed to have a shape corresponding to the C molding part 111 and the central molding part 115 of the upper molding part 110, (Not shown).

At this time, the curvature radius r of the curved surface of the central forming part 115 satisfies the following relationship with the radius R of the steel pipe to be gouged.

r ≥ πR - Cr

When the curvature radius r of the curved surface of the central forming part 115 is smaller than? R - Cr, the end part of the plate material enters the inside of the steel pipe when entering the O forming process, .

In addition, the depth H to be formed by the central forming portion 115 must be smaller than the radius of the main forming portion 21 in the subsequent U molding machine (see Fig. 1) so that molding can be smoothly performed in the subsequent U molding , An increase in strength due to repeated working and curing can be expected.

5 shows a state of the sheet material P formed by the upper forming part 110 in which the sheet material P is placed between the upper forming part 110 and the lower forming part 120. As shown in FIG.

5, the plate material P is formed by the central forming portion 115 and the C forming portion 111, and is formed to correspond to the C forming portion 111 and the central forming portion 115. As shown in FIG. Therefore, the C molding machine 110 performs C molding of a small radius (Cr) on the end portion of the plate material P and molding of a large radius r on the remaining central portion, To perform a primary operation. Therefore, as described above, since the unformed region (B in Fig. 2) prior to the O-shaping is primarily formed, the load in the O-shaping is not only reduced but also the roundness is increased.

Further, since repetitive machining is performed, it is possible to increase the strength (press hardening) by repeated machining.

Therefore, the present invention can achieve the above effect by not only increasing the roundness by giving curvature to the previous unformed region while minimizing the springback of the article, but also adding a central forming portion to the C molding machine without any additional process .

Table 1 below shows an embodiment related to forming after molding with the C molding machine of the present invention and a comparative example relating to the molding after molding with a conventional C molding machine such as Fig. 1 or Fig. Other U molding and O molding except C molding machine were carried out by the same molding machine.

Herein, the roundness is the roundness after the spot welding, the width / diameter, and the yield ratio means the yield strength (YS) / tensile strength (TS).

As can be seen from the above table, it can be confirmed that the roundness of the embodiment of the present invention is close to 1 and the yield ratio is improved as compared with the comparative example. That is, the increase in roundness facilitates the welding performance, and the yield strength is increased by the work hardening phenomenon due to the repeated molding in the tube direction.

In addition, it can be confirmed that the effect of increasing the yield strength is superior to the case where the thickness of the steel pipe is thin.

On the other hand, FIG. 6 shows another embodiment of the present invention. 6 does not show a molding machine, in forming the plate material P, the central forming part 115 (see FIG. 4A) may be formed of a curved surface 116 (see FIG. 4A) having a plurality of curvature radii. That is, the curved surface 116 includes the second curved surface portion between the first curved surface portion and the first curved surface portion on the side of the C molding portion so that the central forming portion 115 is formed like the plate material P shown in Fig. 6 Lt; / RTI >

At this time, the first curved portion and the second curved portion may have different curvatures. For example, as shown in FIG. 6, the radius of the second hollow portion R2 may be larger than the radius R1 of the first curved portion.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention.

100: C molding machine 110: upper molding part
111: C molding section 115: central forming section
120: Lower molding part
P: plate r: radius of curvature of the central forming part
Cr: C radius of curvature of forming part

Claims (7)

A C molding machine for bending both widthwise edges of a plate material,
An upper molding machine including a pair of C molding portions each having a curved surface at a position corresponding to both widthwise edges of the plate material and a central molding portion disposed between the C molding portions and having a protruding curved surface along the lower surface thereof; And
And a lower molding machine having a curved surface corresponding to the shape of the C molding part and the central molding part.
The method according to claim 1,
Wherein the pair of C forming portions and the central forming portion are continuously formed as a single member.
The method according to claim 1,
Wherein the curvature radius (r) of the curved surface of the central forming part satisfies the following relationship with the radius R of the steel pipe to be gutted and the curvature (Cr) of the C molding part.
r ≥ πR - Cr
The method of claim 3,
The central forming portion includes a first curved portion on the side of the C molding portion and a second curved portion between the first curved portion,
Wherein the first curved portion and the second curved portion have different curvatures.
A C molding step of bending both widthwise edges of the plate material;
A positive deformation forming step of forming a plate material into a U shape before forming the U by molding a curved surface between the forming section of the C forming step and the widthwise middle part of the plate material at the same time as the C forming step;
A U forming step of bending the plate material with respect to the widthwise center portion of the plate material;
An O molding step in which the sheet material is put into an O type molding machine and molded into a circular shape; and
And a welding step of welding both ends of the circularly formed plate material.
The method according to claim 1,
Wherein the radius of curvature r in the normal deformation step satisfies the following relationship with the radius R of the steel pipe to be gutted and the curvature Cr in the C molding step.
r ≥ πR - Cr
6. The method of claim 5,
Wherein the forming depth (H) to be formed in the regular deformation forming step is smaller than the radius of curvature in the U forming step so that normal deformation can be repeatedly performed.

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