RU2745056C1 - Method and device for bending edges of thick steel sheet and method and installation for producing steel pipe - Google Patents

Abstract

FIELD: steel sheets.

SUBSTANCE: invention relates to a method for bending the edges of a thick steel sheet. The bending of the edges and of the thick steel sheet in width is carried out several times with a pair of parts and dies, with periodic feeding of the thick steel sheet by means of a conveying mechanism, so that the edges of the thick steel sheet in width are bent along the entire length. The bending of the edges is carried out by means of a pair and parts of a stamp, wherein the part of the stamp that contacts the surface located on the outer side of the bending of the edges and the thick steel sheet along the width to be bending has a flat part that contacts the surface located on the outer side of the bending, and a transition part formed with a curved surface and provided adjacent to the flat portion on the feed side in the conveying direction. The flat part and the transition part are connected in such a way that they have a common tangent line.

EFFECT: as a result, the fluctuation of the bending angle of the edges between adjacent portions at the feed boundary of the thick steel sheet is reduced.

9 cl, 15 dwg, 5 tbl, 5 ex

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. using a method 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 the bending is performed at the edges of the thick steel sheet in width several times (for example, three to four times), intermittently feeding the thick steel sheet in the longitudinal direction to perform edge bending along the entire length.

Patent Literatures 1 to 3 describe a method for obtaining a preferred shape in a mated area. Patent Literature 1 specifies the feeding length b depending on the thickness or strength of the thick steel sheet. Patent Literature 2 specifies 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 variation in the shape 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 with a press to bend the thick steel sheet along the entire length simultaneously in a steel pipe manufacturing process, in which a transition portion tapering towards the edge of the contact surface with the steel sheet 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 a portion causing deformation 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 fluctuation of the bending angle of the edges between adjacent portions at the feeding boundary of the thick steel sheet. 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 reduce the fluctuation of the bending angle of the edges between adjacent portions at the feeding boundary of the thick steel sheet.

Solution to the problem

The inventors have studied the fluctuation of the bending angle of the edges between adjacent portions at the feeding boundary of the thick steel sheet to find out the cause, and as a result have developed the present invention. A first aspect is a method for bending edges of a thick steel sheet using a thick steel sheet edge bending apparatus, comprising: a pair of die portions adapted to be positioned corresponding to a widthwise edge of the thick steel sheet; 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 the edge of the thick steel sheet in the width is subjected to edge bending along the entire length by performing the bending of the edge of the thick steel sheet in the 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 edge of the thick steel sheet to be bent has a flat part that contacts surface located on the outer side of the bending, and a transition part formed with a curved surface and provided next to the flat part 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 then they have a common tangent line.

A second aspect is a method for bending the edges of a thick steel sheet according to the first aspect, in which the bending of the edge of the thick steel sheet in width is performed with the center of the flat portion 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.

A third aspect is a method for bending the edges of a thick steel sheet according to the first or second aspect, wherein the head end of the thick steel sheet in the conveying direction is set at 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 it is specified that the tail end of the thick steel sheet in the conveying direction is at a position corresponding to the rear end of the flat portion in the final bending passage of the thick steel sheet edge along width.

A fifth aspect is a method for manufacturing a steel pipe, including:

a thick steel sheet edge bending process using a thick steel sheet edge bending apparatus comprising a pair of die portions configured to be positioned corresponding to the width of the thick steel sheet edge, an actuator configured to grip the pair of die portions with a predetermined pressure force, 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 the edge of the thick steel sheet in the width is subjected to edge bending along the entire length by performing the bending of the edge of the thick steel sheet in the width several times with a pair parts of the stamp, while the thick steel sheet is periodically transported by the transport 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 each other; and a joining process in which the butted edges of the thick steel sheet are welded across the width, and the method for bending the edges of the thick steel sheet according to any one of the first to fourth aspects is used as a process for bending the edges.

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 a widthwise edge of the thick steel sheet; 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 the edge of the thick steel sheet in the width is subjected to edge bending along the entire length by performing the bending of the edge of the thick steel sheet in the 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 edge of the thick steel sheet to be bent has a flat part that contacts surface located on the outer side of the bending, and a transition part formed with a curved surface and provided next to the flat part 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 then they have a common tangent line.

A seventh aspect is an apparatus for bending edges of a thick steel sheet according to a sixth aspect, in which the center of a flat portion in a conveying direction in one of a pair of die portions that contacts a surface located on an outer side of the bending edges is displaced toward a feeding side in a conveying direction relative to the center the pressure force generated by the actuator in the direction of transportation.

The eighth aspect is a steel pipe manufacturing plant comprising:

a device for bending the edges of a thick steel sheet, comprising a pair of die parts configured to be positioned corresponding to the edge of a thick steel sheet in width, an actuator configured to clamp a pair of die parts with a predetermined pressure force, and a transport mechanism configured to transport a thick of the steel sheet in 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 the bending of the edge of the thick steel sheet in the width several times with a pair of die portions while the thick the steel sheet is periodically transported by the transport mechanism; a device for forming a cylinder, configured to give a cylindrical shape to the thick steel sheet with the edges in width subjected to the bending of the edges, and to join the edges of the thick steel sheet in width with each other; and a connecting device configured to weld butted edges of a thick steel sheet in width, and the steel pipe manufacturing apparatus includes a thick steel sheet edge bending apparatus in a sixth or seventh aspect as a thick steel sheet edge bending apparatus.

Effect of invention

According to the present invention, the thick steel sheet is edge-bent by a pair of die portions configured such that one of the pair of die portions that contacts the surface located on the outside of the bending side of the width of the thick steel sheet contains a flat portion that contacts surface located on the outer side of the bending, and a transition part formed with a curved surface and provided next to the flat part, at least on the supply side in the transport direction, and the flat part and the transition part are connected in such a way that they have a common tangent line ... Thus, the fluctuation of the bending angle of the edges between adjacent portions at the feeding boundary of the thick steel sheet can be reduced. As a result, it is possible to manufacture a steel pipe with fewer weld defects or shape defects in the butt portion.

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 cross-sectional view in width 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 bending of the edges;

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 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 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 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. 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 lower part of the punch is tilted due to the relative position of the center of the pressure force, the center of the flat part and the center of the deformation force of the bending;

fig. 10 is a sectional view in the conveying direction showing the bottom of the die of the thick steel sheet edge bending apparatus according to an embodiment of the present invention;

fig. 11 illustrates 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 a first edge bending using a thick steel sheet edge bending apparatus according to a preferred aspect of an embodiment of the present invention;

fig. 12 illustrates the positional relationship of a center of pressure force, a center of a flat portion, and a center of bending deformation force in the case of a second edge bending using a thick steel sheet edge bending apparatus according to a preferred aspect of an embodiment of the present invention;

fig. 13 (a) shows the relative position of the center of pressure force, center of flat portion and center of bending deformation force in the case of first edge bending using a thick steel sheet edge bending apparatus according to a preferred aspect of an embodiment of the present invention, and FIG. 13 (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. 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 apparatus 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 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 apparatus including a U-shaped sheet press 30A that first forms a U-shape on a thick steel sheet S subjected to edge bending, and an O-shape press 30B. which then gives the thick steel sheet S an O-shape (cylindrical shape), and may be a press brake 30C including a feed mechanism that feeds the thick steel sheet S in the width direction and gradually gives the thick steel sheet S a cylindrical shape as the final shape by sequentially feeding the thick steel sheet S in the width direction and performing three-point bending. Next, the edges of the thick steel sheet S in the width direction, which abut with each other by forming the 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 the 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, the protruding St plates may not be present.

FIG. 3 shows an embodiment of a device 20 for bending the 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 arranged 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 mechanism, 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 symmetric and have the same structural design, therefore, the sectional view of the stamping mechanism 22B is omitted. 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 the 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. The 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 carried out 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 conveying direction 1 showing a state in which the edges Sc and Sd of the thick steel sheet S across the width are subjected to edge bending. The thick steel sheet S moves from the left side of the drawing to the right side. The lower die portion 24 includes a flat portion 24a that generally allows the edge to bend. 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 cross 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 to raise 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 conveying direction 1 corresponds to the center C2 of the pressure force 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 stamping 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. so that it is less 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 bending 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, which 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 the range of 170 mm at 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 the portion that was bent in the first bending of the edges, and the angle of the 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. Likewise, with the first flexible edges, bending is also performed in the area that is not in contact with 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) schematically shows 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 in 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.

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 steel sheet S on the feeding 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 the 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 deforms 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. In other words, the bending angle of the edges varies between portions adjacent to each other at the feed boundary of the thick steel sheet S. Excessive shape change results in interrupted welding in the corresponding portion, thereby causing a defect or termination of welding. Therefore, it is desirable that the change in the bending angle of the edges in the longitudinal direction is smooth (small).

Thus, according to a method and apparatus for bending edges of a thick steel sheet and a method and an apparatus for manufacturing a steel pipe of the present invention, there is provided a lower die portion 24 which contacts a surface located on the outside of the bending of a thick steel sheet to be bent and has a transition a portion 24b formed as a curved surface adjacent to the flat portion 24a on the upstream side 3, and the flat portion 24a and the transition portion 24b are connected by a common tangent line as shown in FIG. 10. When on the supply side 3, there is provided such a transition portion 24b in the form of a curved surface that continues continuously with the flat portion 24a, a step between the portion of the thick steel sheet S which was edge-bent in the previous pass and the portion bent in the next pass ( the difference in bending angles of the edges between sections located next to each other on the infeed boundary) can be reduced. 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 a portion that has already been edge-bent. Similarly, on the entrance side 2 of the flat portion 24a, a transition portion 24c formed as a curved surface may be provided, and the flat portion 24a and the transition portion 24c may be connected by a common tangent line. At this stage, a transition portion 24c is necessary such that the bending deformation length L (see, for example, FIG. 11) 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 appropriate values in consideration of the above factors and the bending amount 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 varied such that the range, in which the transition portion 24c contacts the steel sheet S does not become more than half the length L at which the bending deformation occurs on the entry side 2.

The difference in edge bending angles between the portions adjacent to each other on the feed boundary can be further reduced by decreasing the inclination of the lower die portion 24 during the bending of the edges, as well as by forming transition portions 24b and 24c continuously with the flat portion 24a on the side 3 feed and side 2 entrance. Therefore, in a method and apparatus for bending edges of a thick steel sheet and a method and apparatus for manufacturing a steel pipe of the present embodiment, the center C1 of the flat portion 24a of the lower die portion 24 is preferably displaced toward the feeding side 3 with respect to the center C2 of the pressure force P. FIG. 11 and 12 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 bottom die 24 is displaced only by an amount d toward the feed side 3 with respect to the center C2 of the pressure force P. FIG. 11 shows a first edge bend, and FIG. 12 shows a second edge bend. It can be taken into account 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, tilting (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 following is a method for determining the preferred amount of displacement d of the center C1 of the flat portion 24a relative to the center C2 of the pressure force P. As shown in FIG. 8, 9, 11 and 12, 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 entry side 2 at a position of half the bending deformation length L from the rear end of the flat portion 24a (see FIGS. 11 and 12). 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, so that the inclination of the lower die portion 24 can be minimized. ...

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 portion 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 entrance 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 relative to 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 offset value 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 2 is increased, 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 of the length L at which deformation of the bend occurs on the entrance side 2. FIG. 13 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 (final pass) with the center C1 of the flat portion 24a offset to the feeding side 3 from the center C2 force P pressure. 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. 11 and 12, and a rotational force of the front side of the lower die portion 24 in the downward direction (skew) is applied to increase the lifting amount of the upstream side 2. Accordingly, it is desirable that the upper limit value of the offset amount d be determined so 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 a preferred aspect of a method and apparatus for bending thick steel sheet and a method and apparatus for manufacturing a steel pipe of the present invention, the lower die portion 24 of the pair of die portions 23 and 24 has a flat die portion 24a that contacts a surface located on the outside of the bending the edges Sc and Sd of the thick steel sheet S in the width to be edge bent and the edges Sc and Sd of the thick steel sheet S in the width to be bent 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 with respect 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 of the pressure force P. 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 strain Df of the edges Sc and Sd of the thick steel sheet S along the width 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 bottom 24 of the die 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 are portions of the thick steel sheet S 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. 11, 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 The deformation Df is biased towards the side 2 of the inlet 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 intermittent 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. Likewise, 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 entry side 2 with respect to the tail end Sb of the thick steel S. Therefore, the center C3 of 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 is moved closer to the rear end of the flat portion 24a, as shown in FIG. 13, 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 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 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 downwardly and the widthwise edges Sc and Sd of the thick steel sheet S are pressed against the lower die portion 24 to bend the sheet in the same direction as shown in the example. In addition, bending can be performed by interchanging the upper die part 23 and the lower die part 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 transition part is provided adjacent to the flat part of the upper die part 23, which is located on the outer side of the bending on the entrance side 2 and the feeding side 3 in the conveying direction. 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 transition part is provided adjacent to the flat part on the inlet side 2 and the feeding side 3 in the conveying direction 1 of any of the die parts that are located on the outside of the bending, i. E. the upper part 23 of the stamp or the lower part 24 of the stamp. 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 by 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 motor into 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 carried out under various conditions and the effect of the 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 at 1000 mm intervals. 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 equal to half the power of each of the other two hydraulic cylinders, and the power of the three hydraulic cylinders is 15 MN in total.

The upper part 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 with respect to the horizontal surface in cross-section across 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 ends thereof in the longitudinal direction have a bevel of C25 mm (hereinafter referred to as "die part A"); 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").

In order 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 time, 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 toughness. 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. Then, 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 then the butted widthwise edges are welded to make a steel pipe. The peak value Dp of the steel pipe is measured in 0.1 m increments in the longitudinal direction. The peak value Dp is an indication of the sharpened shape of the butt portion and is the difference between the outer diameter of the regular steel pipe (i.e., the 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 bending conditions of the edges and the results of forming the pipe are shown in Table 1. In the column “Stop position of the head / tail end (stop position of the head end and tail end of the thick steel sheet), indicate“ Thick steel sheet ”when the boundary between the steel sheet and the protruding plate is located at the end of the flat part of the lower part of the die on the feeding side in the first bending of the edges, and also when the boundary between the steel sheet and the protruding plate is located at the end of the flat part of the lower part of the die on the entry side in 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 lower portion of the stamp, and the end of the thick steel sheet is located 400 mm inward from the flat portion of the lower portion of the stamp.

As shown in Table 1, under conditions 1 to 4 in which die part B having a smooth transition part on the feed side 3 is used, and under conditions 5 to 8 in which a die part C having a smooth transition part on the inlet side 2 is used and the feeding side 3, the feeding border can hardly be recognized by eye, and the angular difference between adjacent portions is approximately half the variation of the bending angle of the edges of the constant portion. Meanwhile, under conditions 9 and 10, 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 and 5, conditions 2 and 6, conditions 3 and 7, and conditions 4 and 8, 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 part C die, and it can be seen that the transition part can be formed at least on the supply side 3.

In addition, under conditions 1, 2, 5 and 6, 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 (displacement amount d) to the feeding side 3 in conveying direction 1 with respect to the center of the central hydraulic cylinder , i.e. the 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 no more than half of the fluctuation under conditions 3, 4, 7, 8, 9, and 10, in which it is set that the center C1 of the flat portion of the bottom of the stamp corresponds to the center of the central hydraulic cylinder.

In addition, under conditions 1, 3, 5, 7, and 9, 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, 8, and 10, 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 1, in which the “die part B” is used, and the longitudinal end of the thick steel sheet is stopped at a position at the end of the flat portion, and the center C1 of the flat portion is displaced toward the feeding side 3 in the conveying direction with respect to the center C2 of the pressure force P, and under condition 5, in which the "die part C" is used, and the longitudinal end of the thick steel sheet stops at the position at the end of the flat portion, and the center C1 of the flat portion is displaced toward the feeding side 3 in the conveying direction with respect to the center C2 of the pressure force P, the fluctuation of the peak values are 0.9 - 1.0 mm, which does not exceed one-sixth ± 3.2 mm of the tolerance per peak as required by API standards, and it can be considered that this shape is of the highest quality.

Under conditions 9 and 10, 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 according to the invention. In particular, a large difference in the bending angles of the edges indicates that there is an abrupt step change at the infeed boundary. 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 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. 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 forming the pipe are shown in Table 2. The sections in Table 2 and descriptions are the same as in Example 1.

As shown in Table 2, under conditions 1 to 4, which uses the die part B having a smooth transition part on the feed side 3, and under conditions 5 through 8, which uses the die part C having a smooth transition part on the inlet side 2 and the feeding side 3, the feeding border can hardly be recognized by eye, and the angular difference between adjacent portions is approximately half the variation of the bending angle of the edges of the constant portion. Meanwhile, under conditions 9 and 10, 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 and 5, conditions 2 and 6, conditions 3 and 7, and conditions 4 and 8, 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 part C die, and it can be seen that the transition part can be formed at least on the supply side 3.

In addition, under conditions 1, 2, 5 and 6, 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 (displacement amount d) to the feeding side 3 in conveying direction 1 with respect to the center of the central hydraulic cylinder , i.e. the 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 no more than half of the fluctuation under conditions 3, 4, 7, 8, 9, and 10, in which it is set that the center C1 of the flat portion of the bottom of the stamp corresponds to the center of the central hydraulic cylinder.

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 throughout 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 1, in which the “die part B” is used, and the longitudinal end of the thick steel sheet is stopped at a position at the end of the flat portion, and the center C1 of the flat portion is shifted toward the feeding side 3 in the conveying direction with respect to the center C2 of the pressure force P, and under condition 5, in which the "die part C" is used, and the longitudinal end of the thick steel sheet stops at the position at the end of the flat portion, and the center C1 of the flat portion is displaced toward the feeding side 3 in the conveying direction with respect to the center C2 of the pressure force P, fluctuation values are 0.8-0.9 mm, which does not exceed one-seventh ± 3.2 mm of the tolerance per peak as required by API standards, and it can be taken into account that this shape is of the highest quality.

Under conditions 9 and 10, 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 according to the invention. In particular, a large difference in the bending angles of the edges indicates that there is an abrupt step change at the infeed boundary. 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 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. 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 sheet U-shaped and a press brake to make the sheet O-shaped, followed by welding to make a steel pipe. The conditions for bending the edges and the results of forming the pipe are presented in Table 3

Under conditions 1 to 4, which uses the die part B having a smooth transition part on the feed side 3, and under conditions 5 to 8, which uses the die part C having a smooth transition part on the inlet side and the feed side, the feed limit can be difficult to recognize by eye, and the angular difference between adjacent sections is approximately half the variation in the bending angle of the edges of the permanent section. Meanwhile, under conditions 9 and 10, 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 of the stamp is used. When comparing conditions 1 and 5, conditions 2 and 6, conditions 3 and 7, and conditions 4 and 8, 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 part C die, and it can be seen that the transition part can be formed at least on the supply side 3.

In addition, under conditions 1, 2, 5 and 6, in which it is set that the center C1 of the flat part of the bottom of the die in the conveying direction is displaced by 150 mm (displacement amount d) to the feeding side 3 in the conveying direction 1 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 section are attenuated to about half of the fluctuations under conditions 3, 4, 7, 8, 9 and 10, in which it is set that the center of the flat part C1 of the lower part of the die corresponds to the center cylinder.

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 throughout 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 1, in which the “die part B” is used, and the longitudinal end of the thick steel sheet is stopped at a position at the end of the flat portion, and the center C1 of the flat portion is displaced toward the feeding side 3 in the conveying direction with respect to the center C2 of the pressure force P, and under condition 5, in which the "die part C" is used, and the longitudinal end of the thick steel sheet stops at the position at the end of the flat portion, and the center C1 of the flat portion is displaced toward the feeding side 3 in the conveying direction with respect to the center C2 of the pressure force P, the fluctuation of the peak values are 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 shape is of the highest quality.

Under conditions 9 and 10, 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 according to the invention. In particular, a large difference in the bending angles of the edges indicates that there is an abrupt step change at the infeed boundary. Since the abrupt change exceeds the profiling limit of the welding torch, welding stops immediately.

Example 4

Similarly to Example 2, a thick steel sheet with a tensile strength of 500 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 treatment surface with a radius of curvature of 335 mm, and the flat part of the lower part of the die has a treatment surface with a radius of curvature of 335 mm and corresponds to the upper part of the stamp. 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 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 beveled 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 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 forming the pipe are shown in Table 4. The sections in Table 4 and descriptions are the same as in Example 1.

As shown in Table 4, under conditions 1 to 4 in which die part B having a smooth transition part on the feed side 3 is used, and under conditions 5 to 8 in which a die part C having a smooth transition part on the inlet side 2 is used and the feeding side 3, the feeding border can hardly be recognized by eye, and the angular difference between adjacent portions is approximately half the variation of the bending angle of the edges of the constant portion. Meanwhile, under conditions 9 and 10, 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 and 5, conditions 2 and 6, conditions 3 and 7, and conditions 4 and 8, 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 part C die, and it can be seen that the transition part can be formed at least on the supply side 3.

In addition, under conditions 1, 2, 5 and 6, 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 (displacement amount d) to the feeding side 3 in conveying direction 1 with respect to the center of the central hydraulic cylinder , i.e. relative to the 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 no more than half of the fluctuation under conditions 3, 4, 7, 8, 9 and 10, in which it is set that the center C1 of the flat portion of the lower portion of the stamp corresponds to the center of the central hydraulic cylinder.

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 throughout 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 1, in which the “die part B” is used, and the longitudinal end of the thick steel sheet is stopped at a position at the end of the flat portion, and the center C1 of the flat portion is displaced toward the feeding side 3 in the conveying direction with respect to the center C2 of the pressure force P, and under condition 5, in which the "die part C" is used, and the longitudinal end of the thick steel sheet stops at the position at the end of the flat portion, and the center C1 of the flat portion is displaced toward the feeding side 3 in the conveying direction with respect to the center C2 of the pressure force P, the fluctuation of the peak values are 0.7 - 0.8 mm, which does not exceed one-seventh ± 3.2 mm of the tolerance per peak as required by API standards, and it can be taken into account that this shape is of the highest quality.

Under conditions 9 and 10, 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 according to the invention. In particular, a large difference in the bending angles of the edges indicates that there is an abrupt step change at the infeed boundary. Since the abrupt change exceeds the profiling limit of the welding torch, welding stops immediately.

Example 5

In a similar manner 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 performed 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 for the manufacture of a steel pipe. The conditions for bending the edges and the results of forming the pipe are shown in Table 5. The sections in Table 5 and descriptions are the same as in Example 1.

As shown in Table 5, under conditions 1 to 4, which uses die part B having a smooth transition part on the feed side 3, and under conditions 5 through 8, which uses a die part C having a smooth transition part on the inlet side 2 and the feeding side 3, the feeding border can hardly be recognized by eye, and the angular difference between adjacent portions is approximately half the variation of the bending angle of the edges of the constant portion. Meanwhile, under conditions 9 and 10, 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 and 5, conditions 2 and 6, conditions 3 and 7, and conditions 4 and 8, 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 part C die, and it can be seen that the transition part can be formed at least on the supply side 3.

In addition, under conditions 1, 2, 5 and 6, 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 (displacement amount d) to the feeding side 3 in conveying direction 1 with respect to the center of the central hydraulic cylinder , i.e. relative to the 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 no more than half of the fluctuation under conditions 3, 4, 7, 8, 9 and 10, in which it is set that the center C1 of the flat portion of the lower portion of the stamp corresponds to the center of the central hydraulic cylinder.

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 throughout 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 1, in which the “die part B” is used, and the longitudinal end of the thick steel sheet is stopped at a position at the end of the flat portion, and the center C1 of the flat portion is displaced toward the feeding side 3 in the conveying direction with respect to the center C2 of the pressure force P, and under condition 5, in which the "die part C" is used, and the longitudinal end of the thick steel sheet stops at the position at the end of the flat portion, and the center C1 of the flat portion is displaced toward the feeding side 3 in the conveying direction with respect to the center C2 of the pressure force P, the fluctuation of the peak values are 0.6 - 0.7 mm, which does not exceed one eighth ± 3.2 mm of the peak value tolerance required by API standards, and it can be taken into account that this shape is of the highest quality.

Under conditions 9 and 10, 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 according to the invention. In particular, a large difference in the bending angles of the edges indicates that there is an abrupt step change at the infeed boundary. 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 reduce the fluctuation of the bending angle of the edges between adjacent portions at the feeding boundary of the thick steel sheet.

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 along the width of the sheet

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 at the first bending

Ra2 is 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 + - positive peak value

Claims (39)

1. A method of bending the edges of a thick steel sheet by means of a device for bending edges of a thick steel sheet, comprising: 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 direction of 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 transporting the thick steel sheet by the conveying mechanism, characterized in that one of a pair of die parts that contacts the surface located on the outside of the bend of the edge of the thick steel sheet in width, contains a flat part that contacts the specified surface located on the outside of the bend, and a transition part formed by the curved surface and located next to a flat part, at least on the supply side in the direction of transport, the flat part and the transition part are connected in such a way that they have a common tangent line. 2. A method according to claim 1, wherein the bending of the widthwise edges of the thick steel sheet is performed such that the center of the flat portion is offset from the center of the pressure force generated by the actuator in the direction of conveying the thick steel sheet towards the feeding side. 3. A method according to claim 1, wherein the head end of the thick steel sheet in the transport 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. 4. A method according to claim 2, wherein the head end of the thick steel sheet in the transport 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. 5. A 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: bending the edges of the thick steel sheet by means of a device for bending the edges of the 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 direction of 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 transporting the thick steel sheet by the conveying mechanism, forming a cylinder 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 abut each other in width, and a joint in which the butted edges of a thick steel sheet are welded across the width, characterized in that the bending of the edges of the thick steel sheet is carried out by the method of bending the edges of the thick steel sheet according to any one of paragraphs. 1-5. 7. 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 direction of the longitudinal direction of the thick steel sheet as a conveying direction, and configured to bend the widthwise edges of the thick steel sheet along the entire length by performing bending the widthwise edges of the thick steel sheet several times with a pair of die pieces while periodically transporting the thick steel sheet by the transport mechanism, characterized in that one of a pair of die parts that contacts the surface located on the outside of the bend of the edge of the thick steel sheet in width, contains a flat part that contacts the specified surface located on the outside of the bend, and a transition part formed by the curved surface and located next to a flat part, at least on the supply side in the direction of transport, the flat part and the transition part are connected in such a way that they have a common tangent line. 8. The apparatus of claim 7, wherein the center of the flat portion of one of the pair of die portions contacting a surface located on the outer side of the edge bend is offset from the center of the pressure force generated by the actuator in the direction of transporting the thick steel sheet towards the feed side. 9. Installation for the manufacture of steel pipes, 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 direction of the longitudinal direction of the thick steel sheet as a conveying direction, which is adapted to bend the edges of the thick steel sheet along the width along the entire length by performing the bending of the edges of the thick steel sheet in the width several times with a pair of die parts while periodically transporting the thick steel sheet by the transport mechanism, a device for forming a cylinder, configured to give a cylindrical shape to a thick steel sheet with edges in width subjected to edge bending, and to join the edges of a thick steel sheet in width with each other, and a connecting device adapted to weld the butted edges of the thick steel sheet across the width, characterized in that As a device for bending the edges of a thick steel sheet, a device for bending the edges of a thick steel sheet according to claim 7 or 8 is used.

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