RU2741916C1 - Method and device for bending edges of thick steel sheet and method and installation for producing steel pipe - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to a method and apparatus for bending the edges of a thick steel sheet, in which the bending of the Sc and Sd edges of a thick steel sheet S across the width is performed several times by means of a pair of die parts 23 and 24 with periodic feeding of a thick steel sheet S by means of a transport mechanism 21, so that the widthwise edges Sc and Sd of the thick steel sheet S are bent along the entire length. The lower die portion 24, which contacts the surface located on the outside of the bending edges Sc and Sd of the thick steel sheet S in the width to be bent, between the pair of die portions 23 and 24, has a flat portion 24a that contacts the surface located on the outer side of the bending edges, and edge bending is performed on the widthwise edges Sc and Sd of the thick steel sheet S with the center of the flat portion in the conveying direction 1 offset to the feeding side 3 in the conveying direction 1 with respect to the center of the pressure force generated by the actuator in the conveying direction 1. EFFECT: vibrations are reduced along the entire length of the thick steel sheet during bending.

10 cl, 5 tbl, 5 ex, 15 dwg

Description

The technical field to which the invention relates

The present invention relates to a method and apparatus for bending the widthwise edges of a thick steel sheet several times separately in the longitudinal direction of the thick steel sheet. In addition, the present invention relates to a method and apparatus for manufacturing a steel pipe by shaping a thick steel sheet that is subjected to bending edges to a cylindrical shape, joining the edges in width to each other, and joining the butted edges of the thick steel sheet in width by welding.

State of the art

For making large diameter steel pipe for pipeline, etc. a method is used in which a thick steel sheet having a predetermined length, width and thickness is formed into a cylindrical shape by pressure treatment having a pipe axis direction in the longitudinal direction of the thick steel sheet, and then the edges of the thick steel sheet are abutted with each other in width. For the convenience of giving a cylindrical shape and a corresponding shape of the pipe, bending of the edges (folding), which imparts a predetermined curvature to the edges of the thick steel sheet in width, is performed before shaping the thick steel sheet into a cylindrical shape.

Such bending of the edges is performed as follows: a thick steel sheet is placed between the lower part of the stamp and the upper part of the stamp, which have a curvature depending on the diameter of the pipe, and the lower part of the stamp is lifted by a hydraulic cylinder so that the edges of the thick steel sheet are pressed in width against the upper part of the stamp ... However, since the length of the thick steel sheet is longer than the effective length of the die portions, the thick steel sheet cannot be pressurized along its entire length in one pressure forming operation. For this reason, a method has been introduced in which bending at the edges of a thick steel sheet in width is performed several times (for example, three to four times), periodically feeding the thick steel sheet in the longitudinal direction to perform bending along the entire length.

In Patent Literatures 1 to 3, a method for obtaining a preferred shape in a mated area is described. Patent Literature 1 defines the feed length b depending on the thickness or strength of the thick steel sheet. Patent Literature 2 defines the length Lc of the region to be bent depending on the thickness or strength of the thick steel sheet. Patent Literature 3 defines the radius of curvature R1 of the upper part of the stamp, the horizontal distance u from the center of curvature of the upper part of the stamp to the edge of the thick steel sheet, and the pressure force w depending on the thickness or strength of the thick steel sheet. Patent Literature 4 proposes a method for manufacturing a steel pipe in which the shape fluctuation of the abutting portion is small based on the strength information of the thick steel sheet. Patent Literature 5 proposes a method for continuously performing edge bending.

Patent Literature 6 describes a method including a process of U-shape of a thick steel sheet using a press to bend the thick steel sheet along the entire length simultaneously in the process of making a steel pipe, in which a transition portion tapering towards the edge of the contact surface with the thick steel formed at both ends in the direction of the pipe axis of the lower die holder in contact with the outer side surface of the thick steel sheet to prevent local contact with the deformation-causing portion of the hole in the longitudinal end portion.

Citation list

Patent Literature

Patent Literature 1: JP-H08-294727 A

Patent Literature 2: JP-H10-211520 A

Patent Literature 3: JP-2008-119710 A

Patent Literature 4: JP-2009-6358 A

Patent Literature 5: JP-H07-32049 A

Patent Literature 6: JP-2007-245218 A

Disclosure of the essence of the invention

Technical problem

However, all of Patent Literatures 1 to 4 are intended to optimize the shape of a certain section of the thick steel sheet and does not take into account the longitudinal oscillation of the bending shape of the edges of the thick steel sheet. In particular, in the case of a thick steel sheet having a large thickness and high strength, the bending shape of the edges is sometimes uneven in the longitudinal direction of the thick steel sheet, which leads to welding defects in the butted portion or shape defects in the joined portion of the steel pipe. In addition, in the method described in Patent Literature 5, it is not clear that the head end, in front of which there are no steel sheets, or the tail end, behind which there are no steel sheets, is flexible as in the middle section in the longitudinal direction. In addition, the introduction of new equipment is required. The method described in Patent Literature 6 relates to a method for inhibiting deformation of a hole and does not take into account the case where a part of a steel pipe in the longitudinal direction is repeatedly bent with intermittent feeding of a thick steel sheet in the longitudinal direction.

The object of the present invention is to solve the problems associated with the above conventional methods and to provide a bend shape of the edges of a thick steel sheet with less oscillation along the entire length without introducing new equipment.

Problem solving tools

The inventors have studied the shape fluctuation of the bending edges in the longitudinal direction of a thick steel sheet to find out its cause, and as a result have developed the present invention. The first aspect is a method for bending edges of a thick steel sheet using a device for bending edges of a thick steel sheet, comprising: a pair of die portions adapted to be positioned corresponding to an edge of the thick steel sheet in width; an actuator configured to clamp a pair of die parts with a predetermined pressure force; and a conveying mechanism configured to transport the thick steel sheet in the direction of the longitudinal direction of the thick steel sheet as a conveying direction, in which an edge of the thick steel sheet in width is subjected to edge bending along the entire length by performing bending of the edge of the thick steel sheet in width several times by pairs of die parts, while the thick steel sheet is periodically transported by the conveying mechanism, and one of the pair of die parts that contacts the surface located on the outside of the bending side of the width of the thick steel sheet to be bent has a flat part that contacts surface located on the outer side of the bending, and bending of the edges is performed on the edge of the thick steel sheet in width with the center of the flat part in the conveying direction, offset to the feeding side in the conveying direction with respect to the center of the pressure force generated and the executive body in the direction of transportation.

A second aspect is a method for bending edges of a thick steel sheet according to a first aspect, in which a die portion that contacts a surface located on the outside of the bending edges comprises a transition portion formed with a curved surface and provided adjacent to the flat portion at least on the feeding side in the conveying direction, and the flat part and the transition part are connected in such a way that they have a common tangent line.

A third aspect is a method for bending the edges of a thick steel sheet according to the first or second aspect, in which the head end of the thick steel sheet in the conveying direction is in a position that corresponds to the front end of the flat portion in the first bending pass of the thick steel sheet edge in width.

A fourth aspect is a method for bending the edges of a thick steel sheet according to one of the first to third aspects, in which the tail end of the thick steel sheet in the conveying direction is at a position that corresponds to the trailing end of the flat portion in the final bending passage of the thick steel sheet edge in width.

A fifth aspect is a method for manufacturing a steel pipe, including: a process for bending edges of a thick steel sheet using a device for bending edges of a thick steel sheet, comprising a pair of die portions adapted to be positioned corresponding to an edge of the thick steel sheet in width, an actuator made with the possibility of clamping a pair of die parts with a predetermined pressure force, and a conveying mechanism configured to transport the thick steel sheet in the direction of the longitudinal direction of the thick steel sheet as a conveying direction, in which the edge of the thick steel sheet in width is subjected to edge bending along the entire length by performing bending the edges of the thick steel sheet in width several times with a pair of die parts, while the thick steel sheet is periodically transported by the conveying mechanism; a cylinder forming process in which a thick steel sheet with the widthwise edges subjected to edge bending is formed into a cylindrical shape and the widthwise edges of the thick steel sheet abut with each other; and a joining process in which the butted widthwise edges of the thick steel sheet are welded, and one of a pair of die portions that contacts a surface located on the outside of the bending side of the widthwise thick steel sheet edge to be bent has a flat portion that contacts the surface located on the outer side of the bending edges, and bending the edges is performed on the edge of the thick steel sheet in width with the center of the flat part in the conveying direction, offset to the feeding side in the conveying direction relative to the center of the pressure force generated by the actuator in the conveying direction.

A sixth aspect is an apparatus for bending edges of a thick steel sheet, comprising: a pair of die portions adapted to be positioned corresponding to an edge of the thick steel sheet in width; an actuator configured to clamp a pair of die parts with a predetermined pressure force; and a conveying mechanism configured to transport the thick steel sheet in the direction of the longitudinal direction of the thick steel sheet as a conveying direction, in which an edge of the thick steel sheet in width is subjected to edge bending along the entire length by performing bending of the edge of the thick steel sheet in width several times by pairs of die parts, while the thick steel sheet is periodically transported by the conveying mechanism, and one of the pair of die parts that contacts the surface located on the outside of the bending side of the width of the thick steel sheet to be bent has a flat part that contacts a surface located on the outer side of the bending edges, and the center of the flat part in the conveying direction is displaced towards the supply side in the conveying direction with respect to the center of the pressure force generated by the actuator in the conveying direction.

A seventh aspect is an apparatus for bending edges of a thick steel sheet according to a sixth aspect, in which a die portion that contacts a surface located on an outer side of the bending edges comprises a transition portion formed with a curved surface and provided adjacent to a flat portion at least on the supply side in the conveying direction, and the flat part and the transition part are connected in such a way that they have a common tangent line.

An eighth aspect is an apparatus for manufacturing a steel pipe, comprising: a device for bending the edges of a thick steel sheet comprising a pair of die portions adapted to be positioned corresponding to an edge of the thick steel sheet in width, an actuator configured to grip the pair of die portions with a predetermined force pressure, and a conveying mechanism configured to transport the thick steel sheet in the longitudinal direction of the thick steel sheet as a conveying direction in which an edge of the thick steel sheet in width is subjected to edge bending along the entire length by performing bending of the edge of the thick steel sheet in width several times with the help of a pair of die pieces, while the thick steel sheet is periodically transported by the transport mechanism; a cylinder-forming apparatus configured to cylindrically shape a thick steel sheet with edge-bending edges and join the width-wise edges of the thick steel sheet to each other; and a connecting device adapted to weld the butted edges of the thick steel sheet in width, and one of a pair of die parts that contacts the surface located on the outside of the bending side of the width of the thick steel sheet to be bent has a flat portion that contacts a surface located on the outer side of the bending edges, and the center of the flat part in the conveying direction is displaced towards the supply side in the conveying direction with respect to the center of the pressure force generated by the actuator in the conveying direction.

A ninth aspect is an apparatus for manufacturing a steel pipe according to an eighth aspect, in which a die portion that contacts a surface located on an outer side of the bending edges comprises a transition portion formed with a curved surface and provided adjacent to the flat portion at least on the side flow in the direction of transport, and the flat part and the transition part are connected in such a way that they have a common tangent line.

Effect of invention

According to the present invention, one of a pair of die parts that contacts a surface located on the outside of the bending side of the width of the thick steel sheet to be bent contains a flat portion that contacts the surface located on the outside of the bending edges, and the bending of the edges is performed on the edge of the thick steel sheet in width with the center of the flat part in the conveying direction, offset to the feeding side in the conveying direction with respect to the center of the pressure force generated by the actuator in the conveying direction, as a result of which the center of the bending deformation force moves closer to the center of the pressure force. As a result, the tilt of the die during bending of the edges can be suppressed, and fluctuation in the amount of bending deformation of the edges of the thick steel sheet along the width in the longitudinal direction can be reduced.

Brief Description of Drawings

FIG. 1 is a schematic diagram of an apparatus and method for manufacturing a steel pipe according to an embodiment of the present invention;

fig. 2 is a top plan view of an example of a thick steel sheet that is subjected to edge bending;

fig. 3 is a schematic view of a thick steel sheet edge bending apparatus according to an embodiment of the present invention;

fig. 4 is a width sectional view showing the state in front of the bending edge by the punching mechanism of the thick steel sheet edge bending device of FIG. 3;

fig. 5 is a width sectional view showing a state at the time of edge bending by the punching mechanism of the thick steel sheet edge bending apparatus of FIG. 3;

fig. 6 (a) is a sectional view in the conveying direction showing the punching mechanism of a conventional thick steel sheet edge bending apparatus in a state in front of bending edges, and FIG. 6 (b) - in a state during edge bending;

fig. 7 is a graph of the change in the shape of a thick steel sheet as a result of bending edges;

fig. 8 (a) shows the relative position of the center of pressure force, the center of the flat portion and the center of bending deformation force in the case of the first edge bending using the conventional thick steel sheet edge bending apparatus shown in FIG. 6, and FIG. 8 (b) is a schematic diagram of a state in which the bottom of the die is tilted as a result of the relative position of the center of the pressure force, the center of the flat part and the center of the bending force;

fig. 9 (a) shows the relationship between the center of pressure force, the center of the flat portion and the center of bending deformation force in the case of the second edge bending using the conventional thick steel sheet edge bending apparatus shown in FIG. 6, and FIG. 9 (b) is a schematic diagram of a state in which the bottom of the punch is tilted as a result of the relative position of the center of the pressure force, the center of the flat portion and the center of the bending force;

fig. 10 illustrates the positional relationship of the center of pressure force, the center of the flat portion, and the center of bending deformation force in the case of the first edge bending using the thick steel sheet edge bending apparatus according to an embodiment of the present invention;

fig. 11 illustrates the relationship between the center of pressure force, the center of the flat portion and the center of bending deformation force in the case of a second edge bending using the thick steel sheet edge bending apparatus according to an embodiment of the present invention;

fig. 12 (a) shows the relative position of a center of pressure force, a center of a flat portion, and a center of bending deformation force in the case of final edge bending using the thick steel sheet edge bending apparatus according to an embodiment of the present invention, and FIG. 12 (b) is a schematic view showing a state in which the bottom of the die is tilted in the opposite direction due to the relative position of the center of the pressure force, the center of the flat part and the center of the bending force;

fig. 13 is a sectional view in the conveying direction showing the lower part of the die from another example, where the transition part, which can be preferably used in the present invention, is located adjacent to the flat part;

fig. 14 is a view showing the peak value;

fig. 15 is a view showing an edge bend shape and a peak value.

Implementation of the invention

Below is a detailed description of an embodiment of the present invention with reference to the drawings. Similar constituent elements are identified with the same reference numbers and are not described in detail as the case may be. It should be noted that in the description, the terms "front" or "front side" mean "feeding side" or "direction from the inlet side to the loading side" in the direction of conveying the thick steel sheet in the edge bending device described below, and the terms "rear" or "backside" means the opposite direction.

FIG. 1 is a schematic diagram of a method and apparatus for manufacturing a steel pipe according to an embodiment of the present invention for manufacturing a steel pipe from a thick steel sheet that is cut to a predetermined size. First, a thick steel sheet S, cut to a predetermined size, is trimmed on the side surface using an edge cutter 10 or an edge planer. In the example shown, protruding plates St. are welded to the head end (front end in the longitudinal direction) Sa and the tail end (trailing end in the longitudinal direction) Sb of the thick steel sheet S. However, the protruding plates St may not be provided. Next, edge bending is performed with the edge bending (folding) device 20 according to the embodiment of the present invention (edge bending process), and the thick sheet is formed into a cylindrical shape by the cylinder forming device 30 (cylinder forming process). The cylinder forming apparatus 30 is not limited to devices including a U-shape press 30A, which first forms a U-shape on the edge-bent thick steel sheet S, and an O-shape press 30B. shape, which then gives the thick steel sheet S an O-shape (cylindrical shape). The cylinder forming apparatus 30 may be a press brake 30C including a feed mechanism that feeds the thick steel sheet S in the width direction and gradually shapes the thick steel sheet S into a cylindrical shape as a final shape by sequentially feeding the thick steel sheet S in the width direction and performing three-point bending. Further, the edges of the thick steel sheet S in the width direction, which abut with each other by forming the thick sheet into a cylindrical shape, are temporarily welded on the outer surface side and then welded by submerged arc welding or the like. from the side of the inner surface and the outer surface using the connecting device 40 (connection process). Next, the diameter of the steel pipe S 'is expanded with a mechanical expander 50 to relieve residual stresses, and the steel pipe S' is finally processed to have a predetermined outer diameter and size (pipe expansion process). It should be noted that during each process or between processes, other processing may be performed, such as cleaning, various types of inspection and grinding of the weld bead.

The following is a detailed description of an apparatus 20 for bending thick steel sheet edges according to an embodiment of the present invention and a method for bending thick steel sheet edges using said apparatus. FIG. 2 shows an example of a thick steel sheet S in front of flexible edges. Thick steel sheet width S has a wide range of 1200 - 5100 mm depending on the outer diameter of the steel pipe. In addition, the thick steel sheet is often about 12 m long, which is the standard length of the piping pipe. The protruding plates St are welded to each edge in the width direction of the head end Sa and the tail end Sb of the thick steel sheet S, which becomes the body of the steel pipe in the longitudinal direction. However, protruding St plates may not be present.

FIG. 3 schematically shows a configuration of a device 20 for bending edges of a thick steel sheet. The device 20 for bending the edges of the thick steel sheet includes a conveying mechanism 21 that conveys the thick steel sheet S in the longitudinal direction, namely, in the conveying direction 1, a punching mechanism 22A that performs the bending of the edge Sc in the width direction, which is located on the left side, when the feeding side 3 in the conveying direction is the front side to give it a predetermined curvature, a punching mechanism 22B that bends the edge Sd in the width direction, which is located on the right side, to give it a predetermined curvature, and a distance adjustment mechanism, which is not shown and adjusts the distance between the right and left stamping mechanisms 22A and 22B depending on the width of the thick steel sheet S on which the edge bending is performed. The conveying mechanism 21 includes a plurality of conveying rollers 21a, which are located before and after the stamping mechanisms 22A and 22B. The shafts of the conveying rollers 21a are disposed in a direction perpendicular to the conveying direction of the thick steel sheet S and are configured to rotate at a rotational speed synchronized with the rotational speed of the engine and the transmission, which are not shown.

FIG. 4 is a cross-sectional view in the width direction of the stamping mechanism 22A which shows the bending of the left edge Sc in the width direction of the thick steel sheet S as viewed from the direction from the inlet side 2 to the feeding side 3 in the conveying direction 1 of the thick steel sheet S. Note that the stamping mechanism 22A and the stamping mechanism 22B are bilaterally symmetrical and have the same structural design, therefore, the sectional view of the stamping mechanism 22B is not shown. The stamping mechanisms 22A and 22B comprise an upper die 23 and a lower die 24, which are a pair of die parts opposite each other in a vertical direction, a hydraulic cylinder 26, which is an actuator and lifts the lower die 24 together with the tool holder 25 and performs clamping with a predetermined compressive force, and a holding mechanism 27 that releasably holds the thick steel sheet S on each inner side in the width direction of the upper die portion 23 and the lower die portion 24. It should be noted that the length of the lower die part 24 and the upper die part 23 in the longitudinal direction of the thick steel sheet S is less than the length of the thick steel sheet S. Edge bending is performed several times as the thick steel sheet S moves (intermittent feeding) in the longitudinal direction by the conveying mechanism 21 to ensure that the edges Sc and Sd of the thick steel sheet S bend along their entire length.

FIG. 5 is a sectional view in the width direction in the same position as in FIG. 4, showing a state in which the lower die portion 24 is clamped during lifting by the hydraulic cylinder 26. When the hydraulic cylinder 26 moves forward from the state in front of the flexible edge shown by the dashed line, the lower die portion 24 is lifted and brought to the position shown by the solid line. The edges Sc and Sd along the width of the thick steel sheet S are bent and shaped to match the arcuate machining surface of the upper die 23. The width at which the bending of the edges is performed varies depending on the width of the thick steel sheet S and is generally approximately 100 to 400 mm. Here is an example where a holding mechanism 27 is provided for holding the thick steel sheet S during bending of the edges without limiting the presence or absence of the holding mechanism 27.

FIG. 6 is a cross-sectional view in the conveyance direction 1 showing a state in which the edges Sc and Sd of the thick steel sheet S in width are subjected to edge bending. The thick steel sheet S moves from the left side of the drawing to the right side. The bottom part 24 of the die contains a flat part 24a, which mainly allows the edge to be flexible. Within the portion facing the upper die portion 23, the flat portion 24a denotes a portion that extends linearly in the conveying direction 1 and is flat in section in the conveying direction 1, but is not flat in cross section across the sheet width. The shape of the flat portion 24a in cross-sectional width of the sheet is not particularly limited, and may be an arcuate shape that is inclined toward the surface inwardly in the width direction. To reduce the number of bending edges, the effective length of the lower die portion 24, i. E. the length of the flat portion 24a is set to be greater than the width that the edge is bent. For example, the flat portion 24a has a length of 3 to 5 m, which is approximately 10 times the width that the edge is bent. Thus, in the conveying direction 1, a plurality of hydraulic cylinders 26 are disposed for lifting the lower die portion 24. In this case, in general, a combination of a piston-type hydraulic cylinder 26 which generates axial force in two directions, upper and lower, and a plunger-type hydraulic cylinder 26, which generates axial force only during upward movement, is used. In the example shown, the piston type hydraulic cylinder 26 is disposed centrally in the conveying direction 1, and the plunger type hydraulic cylinders 26 are located upstream and downstream of the piston type hydraulic cylinder 26. In order to uniformly apply the pressure force P, the flat portion 24a of the lower die portion 24 is designed such that the center C1 of the flat portion 24a in the feeding direction 1 corresponds to the center C2 of the pressure force P applied by the hydraulic cylinders 26.

FIG. 6 (a) shows a state in which the widthwise edges Sc and Sd of the thick steel sheet S are bent by the punching mechanisms 22A and 22B, and then the thick steel sheet S is conveyed to a predetermined conveying distance by the conveying mechanism 21. This conveying distance is thus set. to be shorter than the length of the flat portion 24a of the lower die portion 24. Thus, the trailing end of the already bent edge portion is located on the flat portion 24a of the lower die portion 24, and the transition between the already formed portion and the unformed portion is permanently bent in the next fold step. The thick steel sheet S is disposed such that the rear end of the already bent edge portion is disposed on the flat part 24a, as shown by the broken line in FIG. 6 (b), and the hydraulic cylinders 26 raise the die bottom 24 to bend the widthwise edges Sc and Sd of the thick steel sheet S as shown by the solid line. At this stage, the portion that was bent during the previous operation is bent again by the amount of its springback, while the bent occurs in the portion on the entry side 2 (left side in the drawing) of the thick steel sheet S that is not located on the flat portion 24a of the lower part 24 of the stamp. In the example of FIG. 7 shows the results obtained by performing edge bending in a range of 170 mm on the edges of a thick steel sheet S in width having a width of 2755 mm and a thickness of 28.9 mm, followed by a shape check. The flat portion 24a of the lower die portion 24 has a length of 3 m, and the edge bending angle is measured while performing edge bending with respect to a range of 2.8 mm from the head end of the thick steel sheet. Then, the thick steel sheet was transported 2 m, and the edge bending angle was measured again while performing the second edge bending. Here, the bending angle of the edges is determined from the difference between the angle of inclination in the range of 20 mm at the edge in the width and the angle of inclination of the middle portion in the width, measured with a tilt angle meter. FIG. 7, the bending angle of the edges in the first bending of the edges is denoted as •, and the angle of bending of the edges at the second bending of the edges is denoted as ▲. In addition, the range of the flat die bottom portion 24a in the first edge bending is designated Ra1, and the range of the flat die bottom portion 24a in the second edge bending is designated Ra2. In the first bending of the edges, the bending angle of the edges is large (Da) at the head end Sa of the thick steel sheet S, and bending is also performed in the portion that is not in contact with the flat portion 24a on the upstream side 2, over a length of approximately 0.6 m. bending of the edges, bending is also performed in a portion that was bent in the first bending of the edges, and the angle of bending of the edges becomes larger in the direction of the feed side 3 (Dc). On the upstream side 2, the edge bending angle is slightly larger near the end of the flat portion 24a. Similarly, with the first flexible edges, the bending is also performed in the portion that does not contact the flat portion 24a over a length of approximately 0.6 m. At this stage, the lift amount of the lower die portion 24 is 2 mm larger on the feed side 3. It is envisaged that during the bending of the edges, an inclination of 0.04 degrees is formed, so that the side of the head portion is inclined upward (rotation in the skew direction).

Further investigation is carried out to determine the cause of this slope. FIG. 8 (a) is a schematic diagram showing the deformation of the thick steel sheet S and the distribution of the bending deformation force Df (force opposing the pressure force P; hereinafter also referred to simply as “deformation force”) in the first edge bending step. The deformation force Df is absent on the feeding side 3 where there is no thick steel sheet S, while the deformation force Df occurs at the inlet side 2, even in a portion that is not located on the flat portion 24a. Therefore, the center C3 of the deformation force Df is at a position offset to the upstream side 2 with respect to the center C1 of the flat portion 24a in the conveying direction 1. FIG. 9 (a) shows the case of the second edge bending. Since the thick steel sheet S is on the feeding side 3, a deformation force Df also occurs on the feeding side 3. However, the amount of deformation is small compared to the amount of springback, and the center C3 of the deformation force Df is in a position offset to the upstream side 2 with respect to the center C1 of the flat portion 24a. When the center C1 of the flat portion 24a corresponds to the center C2 of the pressure force P applied by the hydraulic cylinders 26 as shown in FIG. 8 (b) and 9 (b), a force that rotates the head end side in the upward direction (skew) is applied to the lower die portion 24 so that the lifting amount of the lower die portion 24 becomes larger on the feed side 3.

FIG. 10 and 11 schematically show the deformation of the thick steel sheet S and the distribution of the deformation force Df in the case where the center C1 of the flat portion 24a of the lower die portion 24 is displaced only by the amount d toward the feed side 3 with respect to the center C2 of the pressure force P of the present invention. FIG. 10 shows a first edge bend and FIG. 11 shows a second edge bend. It can be seen that the deformation force Df on the inlet side 2 is small, and the center C3 of the deformation force Df is located near the center C2 of the pressure force P. Thus, inclination (skewing) of the bottom die portion 24 when the head end is inclined upward during edge bending can be eliminated by shifting the center C1 of the flat portion 24a toward the feed side 3 with respect to the center C2 of the pressure force P.

The preferred offset value d of the center C1 of the flat portion 24a relative to the center C2 of the pressure force P can be determined as described below. As shown in FIG. 8 to 11, in the case where the bending deformation force Df that occurs on the entrance side 2 of the flat portion 24a varies substantially linearly, the sum is half the deformation force Df that occurs in the flat portion 24a. In other words, the deformation force Df is applied to the upstream side 2 at a position of half of the bending deformation length L from the rear end of the flat portion 24a. When the displacement amount d of the center C1 of the flat portion 24a is a quarter of the deformation length L of the bend on the upstream side 2 with respect to the rear end of the flat portion 24a, the hydraulic cylinders 26 apply a symmetrical force about the center C2 of the pressure force P, so that the inclination of the lower die portion 24 can be reduced to minimum.

However, the length L of the bending deformation occurring on the entry side 2 with respect to the rear end of the flat portion 24a varies depending on the amount of bending of the edges. When the pipe to be manufactured has a small outer diameter, the width of the thick steel sheet is also small. Therefore, the bending angle of the edges (the difference between the angle of inclination in the range of 20 mm in the edge portion of the width and the angle of inclination of the middle section in the width) becomes large, and the length L at which the bending deformation occurs on the entrance side 2 becomes large. When the thick steel sheet shown in FIG. 7 has a width of 2755 mm, the length L at which the deformation of the bend on the entry side 2 occurs is approximately 0.6 m, and a value of 150 mm, which is a quarter of 0.6 m, is the optimum displacement d. However, when the thick steel sheet has a width of 1200 mm, the length L at which the bending deformation occurs on the entry side 2 is approximately 1.0 m, and a value of 250 mm, which is a quarter of 1.0 m, is the optimal displacement amount d. ... Accordingly, it is preferable that the displacement amount d of the center C1 of the flat portion 24a from the center C2 of the pressure force P is set appropriately depending on the width of the thick steel sheet to be edge bent. In particular, it is preferable that the displacement amount d is large as the bending angle of the edges increases.

The deformation force Df applied on the feed side 3 increases with increasing displacement amount d. In this case, the amount of lift on the inlet side increases, so that the amount of bending of the edges on the inlet side 2 is increased. Therefore, it is preferable that the displacement amount d is not more than half the length L at which deformation of the bend occurs on the entrance side 2. FIG. 12 shows the deformation of the thick steel sheet S and the distribution of the deformation force Df in the case where the edges Sc and Sd of the tail end Sb of the thick steel sheet S in width undergo edge bending with the center C1 of the flat portion 24a offset to the feed side 3 with respect to the center C2 of the pressure force P ... In this case, the center C3 of the deformation force Df is located away from the center C2 of the pressure force P (displaced to the feed side 3) as compared with the case in FIG. 10 and 11, and a rotational force of the front side of the lower die portion 24 in the downward direction (skew) is applied to increase the lift amount of the upstream side 2. Accordingly, it is desirable that the upper limit value of the offset amount d be determined such that the bending of the edges does not become excessively large on the tail end side Sb of the thick steel sheet S.

Thus, in the apparatus 20 for bending thick steel sheet edges of the present embodiment and the method for bending thick steel sheet edges using the apparatus, the lower portion 24 of the pair of die portions 23 and 24 that contacts the surface located on the outside of the bending edges Sc and The width Sd of the thick steel sheet S to be edge-bent has a flat portion 24a that contacts the surface located on the outside of the bending edges Sc and Sd of the thick steel sheet S during bending, and the edges Sc and Sd of the thick steel sheet S in the width bend the edges with the center C1 of the flat portion 24a in the conveying direction 1, offset to the feeding side 3 in the conveying direction 1 relative to the center C2 of the pressure force P generated by the hydraulic cylinders 26 in the conveying direction 1, so that the center C3 of the deformation force Df moves closer to the center C2 force P pressure. As a result, it is possible to suppress the inclination of the lower die portion 24 at the time of edge bending and to reduce the fluctuation in the bending amount of the bending deformation of the edges Sc and Sd of the thick steel sheet S in the longitudinal direction. In addition, the displacement of the center C1 of the flat part 24a relative to the center C2 of the pressure force P can be achieved without the use of new equipment, for example, by displacing the lower die part 24 towards the feed side 3 in the transport direction 1 with respect to the tool holder 25 and the hydraulic cylinders 26 or by displacing of the hydraulic cylinders 26 to the inlet side 2 in the transport direction 1 with respect to the lower die part 24 in the existing installation.

The following is a description of the positional relationship of the head end (front end in the longitudinal direction) Sa and the tail end (rear end in the longitudinal direction) Sb of the thick steel sheet S and the flat portion 24a of the lower die portion 24. It should be noted that the head end Sa and the tail end Sb of the thick steel sheet S are portions that become the longitudinal ends of the steel pipe excluding the protruding plates St if present, and correspond to the ends Sa and Sb in FIG. 2. As shown in FIG. 10, when the head end Sa of the thick steel sheet S is located behind the head end of the flat portion 24a in the first edge bending (first pass), the bending deformation force Df does not occur on the feeding side 3 with respect to the head end Sa of the thick steel sheet S. Therefore, the force center C3 Df deformation is offset to the side 2 of the entrance relative to the center C2 of the pressure force P. When the head end Sa of the thick steel sheet S is moved closer to the head end of the flat portion 24a, the amount of displacement between the center C3 of the deformation force Df and the center C2 of the pressure force P becomes small, and it is possible to suppress fluctuation in the amount of bending of the edges. In this step, when the head end Sa of the thick steel sheet S lies on the feeding side 3 with respect to the head end of the flat portion 24a, the portions where the protruding plates St are welded are not sufficiently bent, and the welding is discontinuous at the transition from the protruding plates St to the thick steel sheet S. Therefore, it is preferable that the position of the head end Sa of the thick steel sheet S in place does not exceed the position of the head end of the flat portion 24a. Similarly, as shown in FIG. 12, when the tail end Sb of the thick steel sheet S is disposed in front of the rear end of the flat portion 24a during the final bending of the edges (final pass), the bending deformation force Df does not occur on the upstream side 2 with respect to the tail end Sb of the thick steel S. Therefore, the center C3 the deformation force Df is biased towards the feed side 3 relative to the center C2 of the pressure force P. When the tail end Sb of the thick steel sheet S moves closer to the rear end of the flat portion 24a, the amount of displacement between the center C3 of the deformation force Df and the center C2 of the pressure force P becomes small, and it is possible to suppress fluctuation in the amount of bending of the edges. In this case, when the tail end Sb of the thick steel sheet S is located on the upstream side 2 with respect to the rear end of the flat portion 24a, the portions where the protruding plates St are welded are not sufficiently bent, and the welding is discontinuous at the transition from the protruding plates St to the thick steel sheet S. Therefore, it is preferable that the position of the tail end Sb of the thick steel sheet S in place does not exceed the position of the rear end of the flat portion 24a.

The following is a description of another preferred die bottom that can be used in the present invention. As shown in FIG. 9, when there is a portion that has already been subjected to edge bending on the feeding side 3, the bending deformation force Df is absent in this area at the beginning of the next edge bending, and the bending deformation force Df becomes large at the entry side 2. As a result, the lower die portion 24 is not in contact with the thick steel sheet S on the feed side 3, and the center C3 of the bending deformation force Df is displaced toward the upstream side 2 with respect to the center C2 of the pressure force P. Therefore, as long as the bending deformation occurs on the feeding side 3, a rotational force of the head end of the lower die portion 24 in the upward direction is applied, and the lift amount on the feeding side 3 is large, so that the edge bending is performed with the inclined lower die portion 24 ... As a result, there is a problem that the feed-side portion of the flat portion 24a contacts a portion that has already been edge-bent, and as shown in FIG. 7, the portion of the thick steel sheet that contacts the portion on the supply side is deformed in the second edge bending and thus forms a large step relative to the portion that was subjected to the first edge bend on the supply side 3. Excessive change in shape results in interrupted welding in the corresponding area, thereby causing a defect or termination of welding. Therefore, it is desirable that the change in the bending angle of the edges is smooth (small).

Thus, according to a method and apparatus for bending edges of a thick steel sheet according to another embodiment of the present invention and a method and apparatus for manufacturing a steel pipe as shown in FIG. 13, the lower die portion 24, which is one of a pair of die portions, may have a transition portion 24b formed in a curved surface adjacent to the flat portion 24a on the entry side 3 in the transport direction 1. In this case, it is preferable that the flat portion 24a and the transition part 24b was connected using a common tangent line. When such a curved surface-shaped transition portion 24b is provided on the feeding side 3, which continues continuously with the flat portion 24a, it is possible to provide a smooth step between the portion of the thick steel sheet S subjected to edge bending in the previous pass and the portion bent in the next pass. ... At this point, the step becomes smoother when the change in the angle of the transition portion 24b is small, i.e. the change in curvature is continuous like an involute. However, it is necessary that the feed-side portion of the lower die portion 24 does not come into contact with the portion that has already been edge-bent. Likewise, a transition portion 24c can be provided on the inlet side 2. In this case, a transition portion 24c is necessary such that the bending deformation length L (see, for example, FIG. 10) on the rear side of the rear end of the flat portion 24a does not become large. Varying the length and angle of the transition portion 24c is preferable to set corresponding values in consideration of the above factors and the amount of bending of the edges that vary depending on the width of the thick steel sheet S. As an indication, the length or angle of the transition portion 24c may be changed so that the range, in which the transition portion 24c contacts the thick steel sheet S does not become more than half the length L at which the bending deformation occurs on the entry side 2.

The embodiment of the present invention has been described above based on the illustrated examples, but the present invention is not limited thereto. Changes, corrections, additions, etc. can be made within the scope of the claims. For example, in the illustrated examples, descriptions are given of a case where the edge bending is performed such that the lower die portion 24 is lifted by the hydraulic cylinders 26 and the widthwise edges Sc and Sd of the thick steel sheet S are pressed against the upper die portion 23. However, the lower die portion 24 may be stationary and the upper die portion 23 may be movable, so that the upper die portion 23 moves downward and the widthwise edges Sc and Sd of the thick steel sheet S are pressed against the lower die portion 24 to bend sheet in the same direction as shown in the example. In addition, the bending can be performed by interchanging the upper die portion 23 and the lower die portion 24 so that the surface of the upper side of the thick steel sheet is located on the outside of the bend, as opposed to the example shown. In this case, the center C1 of the flat portion of the upper die portion 23 in the conveying direction, which is located on the outside of the bending side, is displaced toward the feeding side 3 with respect to the center C2 of the pressure force P in the conveying direction 1. Alternatively, both the upper die portion 23 and the lower die portion 24 may be movable in directions in which they can approach each other or move away from each other. In this case, the center C1 of the flat portion in the conveying direction of any of the die portions that is located on the outside of the bending, i. E. the upper die part 23 or the lower die part 24 is displaced towards the feeding side 3 in the conveying direction 1 with respect to the center C2 of the pressure force P. In addition, the number of hydraulic cylinders 26 that clamp the upper die 23 and the lower die 24 is not limited. Clamping can be performed using one, two, or three or more hydraulic cylinders 26. In addition, the actuator that grips the upper die 23 and the lower die 24 is not limited to the hydraulic cylinders 26, and mechanical type actuators can be used clamping is performed by converting the rotational motion of the engine to the reciprocating motion of the crank mechanism and the like.

Example

In order to establish the effect of the present invention, a description will be made below with reference to the results of a study of longitudinal edge bending vibration performed under various conditions and the effect of vibration on the subsequent welding process.

Example 1

A thick steel sheet with a tensile strength of 500 MPa, 1676 mm wide × 25.4 mm thick × 12 m long, having a protruding plate 400 mm long × 100 mm wide attached to the head end and tail end was prepared, and a steel pipe with an outer diameter of 559 mm. For edge bending, an edge bending device was used that lifts the bottom of the die with three hydraulic cylinders (actuators) spaced 1000 mm apart. The central hydraulic cylinder is a piston type hydraulic cylinder and the other two hydraulic cylinders are plunger type hydraulic cylinders. The power of the central hydraulic cylinder is half that of each of the other two hydraulic cylinders, and the power of the three hydraulic cylinders is 15MN in total.

The top of the die used for bending the edges has a machining surface with a radius of curvature of 200 mm. The flat part of the lower part of the stamp has a straight shape, forming an angle of 40 degrees relative to the horizontal surface in cross-section along the width. The upper part of the stamp has the same cross-section along its entire length. Three types of die lower parts are used: the first, in which the flat part has a length of 3000 mm, and both its ends in the longitudinal direction have a bevel R25 mm (hereinafter referred to as "part A of the die"); a second having a smooth transition portion R1600 mm formed continuously from the flat portion and having a length of 3000 mm on the feeding side 3 (hereinafter referred to as "die B portion"); and a third having a smooth transition portion R1600 mm formed continuously from the flat portion and having a length of 3000 mm on both the inlet side 2 and the supply side 3 (hereinafter referred to as “die portion C”).

To ensure the bending angle of the edges (the difference between the angle of inclination in the range of 20 mm between the angle of inclination in the range of 20 mm at the edge in the width and the angle of inclination of the middle section in the width) 33 degrees for the range of 155 mm at the edges of the thick steel sheet in the width thick steel sheet bend the edges four times at a feed rate of 2600 mm each, and then do the fifth bend, so that the tail end of the thick steel sheet stops at a predetermined position. After bending the edges, the bending angle of the edges is measured in increments of 0.1 m in the longitudinal direction. The difference between the maximum and minimum values in the range of 10 m in the middle in the longitudinal direction is determined as the oscillation in a constant section, and the difference between the maximum and minimum values along the entire length is determined as the vibration along the entire length, and the angular difference in the stepped section where the difference is greatest are rated as steepness. The bending angle of the edges is determined from the difference between the angle of inclination in the range of 20 mm at the edge in width and the angle of inclination of the middle section along the width, measured with a tilt angle meter. Next, the sheet is U-shaped and O-shaped to form a cylindrical shape by means of presses, and the widthwise edges of the thick steel sheet subjected to edge bending are butted, and the butted widthwise edges are welded to make a steel pipe. The peak Dp of the steel pipe is measured in 0.1 m increments in the longitudinal direction. The peak Dp is an indication of the sharpened shape of the butt portion and is the difference between the outer diameter of a regular steel pipe (i.e., an imaginary ideal circle Se) and the actual shape Sp of the steel pipe, as shown in FIG. 14. As shown in FIG. 15, when the bending amount of the edges is excessively large, the abutting portion of the steel pipe has a recessed shape (minus peak value Dp-), and if the amount of bending of the edges is excessively small, the abutting portion of the steel pipe has a protruding shape (plus peak value Dp +). It should be noted that, similarly to the bending angle of the edges in relation to the peak value Dp, the difference between the maximum and minimum values in the range of 10 m in the middle in the longitudinal direction is determined as the oscillation in the constant section, and the difference between the maximum and minimum values along the entire length is defined as vibrations along the entire length.

The conditions for bending the edges and the results of the formation of the pipe are presented in table. 1. The column “Stop position of the head / tail end (stop position of the head end and tail end of thick steel plate) indicates“ Thick steel plate ”when the boundary between the steel plate and the protruding plate is at the end of the flat part of the bottom of the die on the feed side when the first bending of the edges, and also when the border between the steel sheet and the protruding plate is located at the end of the flat part of the lower part of the stamp on the entry side at the fifth bending of the edges. In addition, "Protrusion" is indicated when the entire length of the protruding plate is enclosed in the flat portion of the bottom of the die, and the end of the thick steel sheet is located 400 mm inward from the flat portion of the bottom of the stamp.

As shown in table. 1, under conditions 1 to 6 (examples of the invention), in which it is set that the center C1 of the flat portion 24a of the lower die portion in the conveying direction 1 is displaced by 150 mm (the amount of displacement d) to the feeding side 3 in the conveying direction relative to the center of the central hydraulic cylinder , i.e. center C2 of the pressure force P, the fluctuation Dc of the bending angle and the fluctuation of the peak value of the constant portion are attenuated to about half of the fluctuation under conditions 7 and 8 (comparative samples), in which it is set that the center C1 of the flat portion 24a of the lower die corresponds to the center C2 cylinder.

In addition, under conditions 3 and 4, in which the die part B having a smooth transition part on the feeding side 3 is used, and under conditions 5 and 6, in which the die part C having a smooth transition part on the inlet side and the feeding side is used, the infeed limit can hardly be recognized by eye, and the angular difference between adjacent portions is approximately half the variation in the bending angle of the edges of the constant portion. Meanwhile, under conditions 1, 2, 7 and 8 in which the die part A is used, the feed edge is clearly recognizable, and the angular difference between adjacent portions is the same as the fluctuation of the bending angle of the edges of the constant portion, and the bending angle of the edges changes abruptly. compared to the case where part B or C of the stamp is used. When comparing conditions 1, 3 and 5 and conditions 2, 4 and 6, in which only the used parts of the die are different, there are slight differences in the fluctuation of the bending angle of the edges, although the fluctuation will be less in some cases when using the part C of the die, and you can see, that the transition part can be formed at least on the supply side 3.

In addition, under conditions 1, 3, 5, and 7, in which the longitudinal end of the thick steel sheet stops to be located at the end of the flat portion, the fluctuation of the bending angle of the edges of the constant portion is the same as the fluctuation of the bending angle of the edges along the entire length. , and the fluctuation of the peak value of the constant section is the same as the fluctuation of the peak section along the entire length, and the amount of bending of the edges is the same along the entire length. Meanwhile, under conditions 2, 4, 6, and 8, in which the longitudinal end of the thick steel sheet is located on the inner side of the flat portion of the bottom of the die, the bending amount of the edges is large at the end, and a large fluctuation is observed along the entire length. Specifically, under condition 3, which uses the "die part B" and the longitudinal end of the thick steel sheet stops at a position at the end of the flat portion, and condition 5, which uses the "die part C" and the longitudinal end of the thick steel sheet stops at the end of the flat end, the peak value fluctuation is 0.9 - 1.0 mm, which does not exceed one-sixth ± 3.2 mm of the peak value tolerance required by API standards, and it can be taken into account that this the shape is of the highest quality.

Under conditions 7 and 8, which do not satisfy the conditions of the present invention, the fluctuations in the peak value and the bending angle of the edges are large compared to the samples of the invention. In particular, a large difference in the bending angles of the edges indicates that there is an abrupt step change at the feed edge. Since the abrupt change exceeds the profiling limit of the welding torch, welding stops immediately.

Example 2

A thick steel sheet with a tensile strength of 550 MPa, 2753 mm wide × 38.1 mm thick × 12 m long, having a protruding plate 400 mm long × 100 mm wide attached to the head end and the tail end was prepared, and a steel pipe with an outer diameter of 914 mm. The upper part of the die used for bending the edges has a machining surface with a radius of curvature of 335 mm. The bending of the edges is performed to obtain a bending angle of 24 degrees in the range of 180 mm at the edges of the thick steel sheet in width. Other edge bending conditions such as edge bending device, die bottom and thick steel sheet feed amount are the same as those in Example 1. The edge bending angle is measured after edge bending, and then the thick steel sheet is formed into a cylindrical shape by the method, using a press brake followed by welding to make a steel pipe.

The conditions for bending the edges and the results of the formation of the pipe are presented in table. 2. Sections in tab. 2 and descriptions are the same as in Example 1. As shown in table. 2, under conditions 1 to 6 (examples of the invention), in which it is set that the center C1 of the flat portion 24a of the lower die portion in the conveying direction is displaced by 150 mm (displacement amount d) to the feeding side 3 in the conveying direction 1 relative to the center of the central hydraulic cylinder , i.e. center C2 of the pressure force P, the fluctuation of the bending angle of the edges and the fluctuation of the peak value of the constant portion are attenuated to about half of the fluctuation under conditions 7 and 8 (comparative examples), in which it is set that the center C1 of the flat portion 24a of the bottom of the die corresponds to the center C2 of the central hydraulic cylinder ...

In addition, under conditions 3 and 4, in which the die part B having a smooth transition part on the feeding side 3 is used, and under conditions 5 and 6, in which the die part C having a smooth transition part on the inlet side and the feeding side is used, the infeed limit can hardly be recognized by eye, and the angular difference between adjacent portions is approximately half the variation in the bending angle of the edges of the constant portion. Meanwhile, under conditions 1, 2, 7 and 8 in which the die part A is used, the feed edge is clearly recognizable, and the angular difference between adjacent portions is the same as the fluctuation of the bending angle of the edges of the constant portion, and the bending angle of the edges changes abruptly. compared to the case where part B or C of the stamp is used.

When comparing conditions 1, 3 and 5 and conditions 2, 4 and 6, in which only the used parts of the die are different, there are slight differences in the fluctuation of the bending angle of the edges, although the fluctuation will be less in some cases when using the part C of the die, and you can see, that the transition part can be formed at least on the supply side 3.

In addition, under conditions 1, 3, 5, and 7, in which the longitudinal end of the thick steel sheet stops to be located at the end of the flat portion, the fluctuation of the bending angle of the edges of the constant portion is the same as the fluctuation of the bending angle of the edges along the entire length. , and the fluctuation of the peak value of the constant section is the same as the fluctuation of the peak section along the entire length, and the amount of bending of the edges is the same along the entire length. Meanwhile, under conditions 2, 4, 6, and 8, in which the longitudinal end of the thick steel sheet is located on the inner side of the flat portion of the bottom of the die, the bending amount of the edges is large at the end, and a large fluctuation is observed along the entire length. Specifically, under condition 3, which uses the "die part B" and the longitudinal end of the thick steel sheet stops at a position at the end of the flat portion, and condition 5, which uses the "die part C" and the longitudinal end of the thick steel sheet stops at the end of the flat part, the peak value fluctuation is 0.8 - 0.9 mm, which does not exceed one-seventh ± 3.2 mm of the peak value tolerance as required by API standards, and it can be taken into account that this the shape is of the highest quality.

Under conditions 7 and 8, which do not satisfy the conditions of the present invention, the fluctuations in the peak value and the bending angle of the edges are large compared to the samples of the invention. In particular, a large difference in the bending angles of the edges indicates that there is an abrupt step change at the feed edge. Since the abrupt change exceeds the profiling limit of the welding torch, welding stops immediately.

Example 3

A thick steel sheet with a tensile strength of 500 MPa, 3232 mm wide × 38.1 mm thick × 12 m long, having a protruding plate 400 mm long × 100 mm wide attached to the head end and tail end was prepared, and a steel pipe with an outer diameter of 1067 mm. The upper part of the die used for bending the edges has a machining surface with a radius of curvature of 400 mm. The bending of the edges is performed to obtain a bending angle of 22 degrees in the range of 195 mm at the edges of the thick steel sheet in width. Other edge bending conditions such as edge bending device, die bottom and thick steel sheet feed amount are the same as those in Example 1. The edge bending angle is measured after edge bending, and then the thick steel sheet is formed into a cylindrical shape by the method, using a press brake to make the U-shaped sheet and a press brake to make the O-shaped sheet, followed by welding to make a steel pipe.

The conditions for bending the edges and the results of the formation of the pipe are presented in table. 3. Sections in tab. 3 and descriptions are the same as in Example 1. As shown in table. 3, under conditions 1 to 6 (examples of the invention), in which it is set that the center C1 of the flat portion of the lower die portion in the conveying direction is displaced by 150 mm (the amount of displacement d) towards the feeding side 3 in the conveying direction with respect to the center C2 of the central hydraulic cylinder, the fluctuation of the bending angle of the edges and the fluctuation of the peak value of the constant portion are attenuated to about half of the fluctuation under conditions 7 and 8 (comparative examples), in which it is set that the center C1 of the flat part of the bottom of the stamp corresponds to the center C2 of the central hydraulic cylinder.

In addition, under conditions 3 and 4, which uses the die part B having a smooth transition part on the feed side 3, and under conditions 5 and 6, which uses the die part C having a smooth transition part on the inlet side 2 and 3 feed, the feed limit can hardly be recognized by eye, and the angular difference between adjacent portions is approximately half the variation in the bending angle of the edges of the constant portion. Meanwhile, under conditions 1, 2, 7 and 8 in which the die part A is used, the feed edge is clearly recognizable, and the angular difference between adjacent portions is the same as the fluctuation of the bending angle of the edges of the constant portion, and the bending angle of the edges changes abruptly. compared to the case where part B or C of the stamp is used. When comparing conditions 1, 3 and 5 and conditions 2, 4 and 6, in which only the used parts of the die are different, there are slight differences in the fluctuation of the bending angle of the edges, although the fluctuation will be less in some cases when using the part C of the die, and you can see, that the transition part can be formed at least on the supply side 3.

In addition, under conditions 1, 3, 5, and 7, in which the longitudinal end of the thick steel sheet stops to be located at the end of the flat portion, the fluctuation of the bending angle of the edges of the constant portion is the same as the fluctuation of the bending angle of the edges along the entire length. , and the fluctuation of the peak value of the constant section is the same as the fluctuation of the peak section along the entire length, and the amount of bending of the edges is the same along the entire length. Meanwhile, under conditions 2, 4, 6, and 8, in which the longitudinal end of the thick steel sheet is located on the inner side of the flat portion of the bottom of the die, the bending amount of the edges is large at the end, and a large fluctuation is observed along the entire length. Specifically, under condition 3, which uses the "die part B" and the longitudinal end of the thick steel sheet stops at a position at the end of the flat portion, and condition 5, which uses the "die part C" and the longitudinal end of the thick steel sheet stops at the end of the flat portion, the peak value fluctuation is 0.7 - 0.8 mm, which does not exceed one eighth ± 3.2 mm of the peak value tolerance as required by API standards, and it can be taken into account that this the shape is of the highest quality.

Under conditions 7 and 8, which do not satisfy the conditions of the present invention, the fluctuations in the peak value and the bending angle of the edges are large compared to the samples of the invention. In particular, a large difference in the bending angles of the edges indicates that there is an abrupt step change at the feed edge. Since the abrupt change exceeds the profiling limit of the welding torch, welding stops immediately.

Example 4

In a similar manner to Example 2, a thick steel plate with a tensile strength of 550 MPa, 2753 mm wide × 38.1 mm thick × 12 m long was prepared, having a protruding plate 400 mm long × 100 mm wide attached to the head end and tail end. , and a steel pipe with an outer diameter of 914 mm was manufactured. The upper part of the die used for bending the edges has a working surface with a radius of curvature of 335 mm, and the flat part of the lower part of the die has a working surface with a radius of curvature of 335 mm and corresponds to the upper part of the die. The upper part of the stamp has the same cross-section along its entire length. Edge bending is performed to obtain a bending angle of 24 degrees in the range of 180 mm at the edges of a thick steel sheet in width, using the lower parts of the dies of three types: the first, in which the flat part is 3000 mm long, and its both ends are longitudinally bevel C25 mm (hereinafter referred to as "part A of the stamp"); a second having a smooth transition portion R1200 mm formed continuously from the flat portion and having a length of 3000 mm on the feeding side 3 (hereinafter referred to as "die B portion"); and a third having a smooth transition portion R1200 mm formed continuously from the flat portion and having a length of 3000 mm on both the inlet side 2 and the supply side 3 (hereinafter referred to as “die portion C”).

Other edge bending conditions such as an edge bending device and a thick steel sheet feed amount are the same as those in Example 2. The edge bend angle is measured after the edge bending, and then the thick steel sheet is cylindrically shaped using a press brake method. followed by welding to make a steel pipe. The conditions for bending the edges and the results of the formation of the pipe are presented in table. 4. Sections in tab. 4 and descriptions are the same as in Example 1.

As shown in table. 4, under conditions 1 to 6 (examples of the invention), in which it is set that the center C1 of the flat portion 24a of the lower die portion in the conveying direction 1 is displaced by 150 mm (displacement amount d) to the feeding side 3 in the conveying direction 1 with respect to the center of the central hydraulic cylinder, i.e. center C2 of the pressure force P, the fluctuation of the bending angle of the edges and the fluctuation of the peak value of the constant portion are attenuated to about half of the fluctuation under conditions 7 and 8 (comparative examples), in which it is set that the center C1 of the flat portion 24a of the bottom of the die corresponds to the center C2 of the central hydraulic cylinder ...

In addition, under conditions 3 and 4, which uses the die part B having a smooth transition part on the feed side 3, and under conditions 5 and 6, which uses the die part C having a smooth transition part on the inlet side 2 and 3 feed, the feed limit can hardly be recognized by eye, and the angular difference between adjacent portions is approximately half the variation in the bending angle of the edges of the constant portion. Meanwhile, under conditions 1, 2, 7 and 8 in which the die part A is used, the feed edge is clearly recognizable, and the angular difference between adjacent portions is the same as the fluctuation of the bending angle of the edges of the constant portion, and the bending angle of the edges changes abruptly. compared to the case where part B or C of the stamp is used. When comparing conditions 1, 3 and 5 and conditions 2, 4 and 6, in which only the used parts of the die are different, there are slight differences in the fluctuation of the bending angle of the edges, although the fluctuation will be less in some cases when using the part C of the die, and you can see, that the transition part can be formed at least on the supply side 3.

In addition, under conditions 1, 3, 5, and 7, in which the longitudinal end of the thick steel sheet stops to be located at the end of the flat portion, the fluctuation of the bending angle of the edges of the constant section is almost the same as the fluctuation of the bending angle of the edges throughout length, and the fluctuation of the peak value of the constant section is almost the same as the fluctuation of the peak section along the entire length, and the amount of bending of the edges is almost the same along the entire length. Meanwhile, under conditions 2, 4, 6, and 8, in which the longitudinal end of the thick steel sheet is located on the inner side of the flat portion of the bottom of the die, the bending amount of the edges is large at the end, and a large fluctuation is observed along the entire length. Specifically, under condition 3, which uses the "die part B" and the longitudinal end of the thick steel sheet stops at a position at the end of the flat portion, and condition 5, which uses the "die part C" and the longitudinal end of the thick steel sheet stops at the end of the flat part, the peak value fluctuation is 0.7 - 0.9 mm, which does not exceed one-seventh ± 3.2 mm of the peak value tolerance as required by API standards, and it can be appreciated that this the shape is of the highest quality.

Under conditions 7 and 8, which do not satisfy the conditions of the present invention, the fluctuations in the peak value and the bending angle of the edges are large compared to the samples of the invention. In particular, a large difference in the bending angles of the edges indicates that there is an abrupt step change at the feed edge. Since the abrupt change exceeds the profiling limit of the welding torch, welding stops immediately.

Example 5

Similarly to Example 3, a thick steel sheet with a tensile strength of 500 MPa, 3232 mm wide × 38.1 mm thick × 12 m long was prepared, having a protruding plate 400 mm long × 100 mm wide attached to the head end and tail end. , and a steel pipe with an outer diameter of 1067 mm was manufactured. The upper part of the die used for bending the edges has a machining surface with a radius of curvature of 400 mm, and the flat part of the lower part of the die has a machining surface with a radius of curvature of 400 mm and corresponds to the upper part of the die. The upper part of the stamp has the same cross-section along its entire length. Edge bending is carried out to obtain a bending angle of 22 degrees in the range of 195 mm at the edges of thick steel sheet in width using the lower parts of the dies of three types: the first in which the flat part is 3000 mm long and both its ends in the longitudinal direction are bevel C25 mm (hereinafter referred to as "part A of the stamp"); a second having a smooth transition portion R1200 mm formed continuously from the flat portion and having a length of 3000 mm on the feeding side 3 (hereinafter referred to as "die B portion"); and a third having a smooth transition portion R1200 mm formed continuously from the flat portion and having a length of 3000 mm on both the inlet side 2 and the supply side 3 (hereinafter referred to as “die portion C”).

Other edge bending conditions such as an edge bending device and a thick steel sheet feed amount are the same as those in Example 3. The edge bend angle is measured after the edge bend, and then the thick steel sheet is cylindrically shaped using a press brake method. followed by welding to make a steel pipe. The conditions for bending the edges and the results of the formation of the pipe are presented in table. 5. Sections in tab. 5 and descriptions are the same as in Example 1.

Under conditions 1 to 6 (examples of the invention), in which it is specified that the center C1 of the flat portion of the lower die portion in the conveying direction is displaced by 150 mm (the amount of displacement d) to the feeding side 3 in the conveying direction relative to the center C of the central hydraulic cylinder, i.e. e. the center C2 of the pressure force P, the fluctuation of the bending angle and the fluctuation of the peak value of the constant portion are attenuated to about half of the fluctuation under conditions 7 and 8 (comparative examples), in which it is set that the center C1 of the flat part of the bottom of the die corresponds to the center C2 of the central hydraulic cylinder.

In addition, under conditions 3 and 4, which uses the die part B having a smooth transition part on the feed side 3, and under conditions 5 and 6, which uses the die part C having a smooth transition part on the inlet side 2 and 3 feed, the feed limit can hardly be recognized by eye, and the angular difference between adjacent portions is approximately half the variation in the bending angle of the edges of the constant portion. Meanwhile, under conditions 1, 2, 7 and 8 in which the die part A is used, the feed edge is clearly recognizable, and the angular difference between adjacent portions is the same as the fluctuation of the bending angle of the edges of the constant portion, and the bending angle of the edges changes abruptly. compared to the case where part B or C of the stamp is used. When comparing conditions 1, 3 and 5 and conditions 2, 4 and 6, in which only the used parts of the die are different, there are slight differences in the fluctuation of the bending angle of the edges, although the fluctuation will be less in some cases when using the part C of the die, and you can see, that the transition part can be formed at least on the supply side 3.

In addition, under conditions 1, 3, 5, and 7, in which the longitudinal end of the thick steel sheet stops to be located at the end of the flat portion, the fluctuation of the bending angle of the edges of the constant section is almost the same as the fluctuation of the bending angle of the edges throughout length, and the fluctuation of the peak value of the constant section is almost the same as the fluctuation of the peak section along the entire length, and the amount of bending of the edges is almost the same along the entire length. Meanwhile, under conditions 2, 4, 6, and 8, in which the longitudinal end of the thick steel sheet is located on the inner side of the flat portion of the bottom of the die, the bending amount of the edges is large at the end, and a large fluctuation is observed along the entire length. Specifically, under condition 3, which uses the "die part B" and the longitudinal end of the thick steel sheet stops at a position at the end of the flat portion, and condition 5, which uses the "die part C" and the longitudinal end of the thick steel sheet stops at the end of the flat part, the peak value fluctuation is 0.7 - 0.9 mm, which does not exceed one-seventh ± 3.2 mm of the peak value tolerance as required by API standards, and it can be appreciated that this the shape is of the highest quality.

Under conditions 7 and 8, which do not satisfy the conditions of the present invention, the fluctuations in the peak value and the bending angle of the edges are large compared to the samples of the invention. In particular, a large difference in the bending angles of the edges indicates that there is an abrupt step change at the feed edge. Since the abrupt change exceeds the profiling limit of the welding torch, welding stops immediately.

Industrial applicability

According to the present invention, it is possible to obtain the shape of the bending edges with less fluctuation along the entire length without introducing new equipment.

List of item numbers

1 - direction of transportation

2 - entrance side (front side in the direction of transportation)

3 - supply side (back side in the direction of transportation)

10 - cutter for processing edges

20 - device for bending the edges of thick steel sheet

21 - transporting mechanism

21a - transport roller

22A, 22B - stamping mechanism

23 - upper part of the stamp

24 - the bottom of the stamp

24a - flat part

24b, 24c - transition part

26 - hydraulic cylinder

30 - device for forming a cylinder

30A - U-shape thick steel plate press

30B - O-shaped thick steel plate press

30C - press brake

40 - connecting device

50 - mechanical expander

S - thick steel sheet

Sa - head end

Sb - tail end

Sc, Sd - edge by sheet width

St - protruding plate

Sp - pipe shape

Se - imaginary ideal circle

Ra1 is the range of the flat part 24a of the lower part of the die during the first bending

Ra2 - the range of the flat part 24a of the lower part of the die during the second bending

Da - angle fluctuation at the edge of a thick steel sheet in width

Dc - angle fluctuation on a constant section

Df - deformation force

P - hydraulic pressure (pressure force)

Dp - peak value

Dp- - minus peak value

Dp + is the positive peak value.

Claims (42)

1. A method for bending the edges of a thick steel sheet by means of a device for bending edges of a thick steel sheet containing a pair of die parts made with the possibility of their placement in a position corresponding to the edge of the thick steel sheet in width, an actuator configured to grip a pair of die parts with a predetermined pressure force, and a conveying mechanism configured to convey the thick steel sheet in the longitudinal direction of the thick steel sheet as a conveying direction, in which an edge of the thick steel sheet is bent along the entire length by performing the bending of the edge of the thick steel sheet in width several times with a pair of die parts while periodically conveying the thick steel sheet by the conveying mechanism, characterized in that one of a pair of die parts that contacts a surface located on the outside of the bendable edge of the widthwise bendable edge of the thick steel sheet has a flat part that contacts said surface located on the outside of the bendable edge, while bending the edge of the thick steel sheet the width is made in such a way that the center of the flat part is offset relative to the center of the pressure force generated by the actuator in the direction of conveying the thick steel sheet to the feeding side. 2. A method according to claim 1, wherein the part of the die that contacts said surface located on the outside of the foldable edge comprises a transition part formed by a curved surface and located adjacent to the flat part, at least on the feeding side in the direction of transportation , wherein the flat part and the transition part are connected in such a way that they have a common tangent line. 3. A method according to claim 1, wherein the head end of the thick steel sheet in the transport direction is at a position that corresponds to the front end of the flat portion in the first bending pass of the thick steel sheet widthwise. 4. A method according to claim 2, wherein the head end of the thick steel sheet in the conveying direction is in a position that corresponds to the front end of the flat portion in the first bending pass of the thick steel sheet widthwise. 5. The method according to any one of claims. 1-4, in which the tail end of the thick steel sheet in the conveying direction is in a position that corresponds to the rear end of the flat portion in the final bending passage of the thick steel sheet edge in width. 6. A method of manufacturing a steel pipe, including the process of bending the edges of a thick steel sheet by means of a device for bending the edges of a thick steel sheet containing a pair of die parts made with the possibility of their placement in a position corresponding to the edge of the thick steel sheet in width, an actuator configured to grip a pair of die parts with a predetermined pressure force, and a conveying mechanism configured to convey the thick steel sheet in the longitudinal direction of the thick steel sheet as a conveying direction, in which an edge of the thick steel sheet is bent along the entire length by performing the bending of the edge of the thick steel sheet in width several times with a pair of die parts while periodically conveying the thick steel sheet by the conveying mechanism, a cylinder-forming process in which a thick steel sheet with the widthwise bent edges is formed into a cylindrical shape and the edges of the thick steel sheet are abutted with each other in width, and a joining process in which the butted edges of a thick steel sheet are welded across the width, characterized in that one of a pair of die parts that contacts a surface located on the outside of the bendable edge of the widthwise bendable edge of the thick steel sheet has a flat part that contacts said surface located on the outside of the bendable edge, the bending of the edges of the thick steel sheet in width is performed in such a way that the center of the flat part is displaced relative to the center of the pressure force generated by the actuator in the direction of conveying the thick steel sheet to the feeding side. 7. Device for bending the edges of thick steel sheet, containing a pair of die parts made with the possibility of their placement in a position corresponding to the edge of the thick steel sheet in width, an actuator configured to grip a pair of die parts with a predetermined pressure force, and a conveying mechanism configured to convey the thick steel sheet in the longitudinal direction of the thick steel sheet as a conveying direction, in which an edge of the thick steel sheet is bent along the entire length by performing the bending of the edge of the thick steel sheet in width several times with a pair of die parts while periodically conveying the thick steel sheet by the conveying mechanism, characterized in that one of a pair of die parts that contacts a surface located on the outside of the bendable edge of the widthwise bendable edge of the thick steel sheet has a flat part that contacts said surface located on the outside of the bendable edge, the center of the flat part is displaced relative to the center of the pressure force generated by the actuator in the direction of transporting the thick steel sheet to the feeding side. 8. The apparatus of claim. 7, wherein the die portion that contacts said surface located on the outer side of the foldable edge comprises a transition portion formed by a curved surface and located adjacent to the flat portion, at least on the feed side in the conveying direction , wherein the flat part and the transition part are connected in such a way that they have a common tangent line. 9. Installation for the manufacture of steel pipe, containing a device for bending the edges of a thick steel sheet containing a pair of die parts made with the possibility of their placement in a position corresponding to the edge of the thick steel sheet in width, an actuator configured to grip a pair of die parts with a predetermined pressure force, and a conveying mechanism configured to convey the thick steel sheet in the longitudinal direction of the thick steel sheet as a conveying direction in which the width edge of the thick steel sheet is bent along the entire length by performing the width edge bending of the thick steel sheet several times with a pair of parts a stamp during periodic transportation of a thick steel sheet by a transport mechanism, a cylinder forming device configured to cylindrically shape a thick steel sheet with edge-bending edges and to join the width-wise edges of the thick steel sheet to each other, and a connecting device adapted to weld butted edges of a thick steel sheet in width, characterized in that one of a pair of die parts that contacts a surface located on the outside of the bendable edge of the widthwise bendable edge of the thick steel sheet has a flat part that contacts said surface located on the outside of the bendable edge, the center of the flat part is displaced relative to the center of the pressure force generated by the actuator in the direction of transporting the thick steel sheet to the feeding side. 10. The apparatus of claim 9, wherein the die portion that contacts said surface located on the outside of the foldable edge comprises a transition portion formed by a curved surface and located adjacent to the flat portion at least on the feeding side in the conveying direction , wherein the flat part and the transition part are connected in such a way that they have a common tangent line.

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