JP2019177398A - Bending method of end of steel plate and device, and manufacturing method of steel pipe and equipment - Google Patents

Abstract

To acquire a predetermined end bent shape without adjusting a position of a mold.SOLUTION: In a bending method of an end of a steel plate, by using a steel plate end bending device 20 including a pair of molds 23, 24 arranged correspondingly to width direction end parts Sc, Sd of a steel plate S, and capable of relatively moving in an approaching or separating direction, the pair of molds 23, 24 are relatively moved in the approaching direction so that bending molding is performed on the width direction end parts Sc, Sd of the steel plate S. Among the pair of molds 23, 24, in the mold on a side contacting an outer surface of bending of the width direction end parts Sc, Sd of the steel plate S to be subjected to the bending molding, a pressing surface facing the other mold is formed of a flat surface inclined to a direction approaching to the other mold toward the width direction outside.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a steel plate end bending method and apparatus for bending a steel plate in a width direction end portion. Further, the present invention provides a steel pipe for manufacturing a steel pipe by forming a steel plate subjected to end bending into a cylindrical shape, butting the end portions in the width direction, and joining the end portions in the width direction of the joined steel plates by welding. The present invention relates to a manufacturing method and equipment.

  For the production of large-diameter steel pipes used for line pipes, etc., after forming a steel sheet having a predetermined length, width and thickness into a cylindrical shape with the longitudinal direction of the steel sheet as the pipe axis direction by pressing, A method is used in which the end portions in the width direction are butt-joined. In order to facilitate forming into a cylindrical shape and obtain an appropriate tube shape, end bending forming (C press) is performed to give a predetermined curvature to the widthwise end of the steel plate prior to forming into a cylindrical shape.

  This end bending is performed by a method in which a steel plate is pressed with a lower die onto an upper die having a curvature corresponding to the pipe diameter, and the steel plate is sequentially bent while being fed in the longitudinal direction.

  Patent Documents 1 to 3 disclose a method for obtaining a good shape at a butt portion. In patent document 1, the feed length b is prescribed | regulated according to the thickness and intensity | strength of a steel plate. In Patent Document 2, the length Lc of the bending region is defined according to the thickness and strength of the steel plate. In Patent Document 3, the radius R1 of the upper die, the horizontal distance u from the center of curvature of the upper die to the end of the steel plate, and the pressing force w are defined according to the thickness and strength of the steel plate. Patent Document 4 proposes a method for manufacturing a steel pipe with little variation in the shape of the butt portion based on the strength information of the steel sheet.

  Further, in Patent Document 5, when the lower mold is displaced in the vertical direction toward the fixed upper mold and bending is performed, the lower mold is also displaced in the horizontal direction. A bending method has been proposed in which the contact area is prevented from relative displacement.

  Furthermore, in Patent Document 6, various outer diameters are obtained using a concave lower mold having a curve in which the curve of the concave lower mold diverges with a larger slope than the convex curve of the upper mold and the machining interval gradually increases. There has been proposed a press using one lower die by changing the position of the lower die with respect to the upper die.

JP-A-8-294727 JP-A-10-2111520 JP 2008-119710 A JP 2009-6358 A JP 2011-173168 A JP-A-51-76158

  However, Patent Documents 1 to 5 do not discuss the mold shape. Moreover, in patent document 6, while it is necessary to move the position of a lower metal mold | die with respect to a different upper metal mold | die each time according to the outer diameter of the steel pipe to manufacture, it is in the position of the angle corresponding to the inclination of the outer edge of a steel plate. In order to achieve this, it is necessary to adjust the position, and there are problems that frequent adjustment work occurs and productivity is hindered, and when the adjustment is set incorrectly, a predetermined bending shape cannot be obtained. .

  An object of the present invention is to provide a steel plate end bending method and apparatus, and a steel pipe manufacturing method and equipment capable of solving the above-described problems of the prior art and obtaining a predetermined end bending shape without adjusting the position of a mold. There is.

  The inventors have investigated in detail the behavior at the time of end bending, particularly the contact state between the outer surface of the steel sheet and the mold, and have reached the present invention. The first aspect uses a steel plate end bending apparatus provided with a pair of molds that are arranged corresponding to the widthwise ends of the steel sheet and are relatively movable in the approaching / separating direction. Is an end bending method of a steel plate that bends the width direction end of the steel plate by relatively moving in the proximity direction, and of the pair of molds, In the mold on the side in contact with the surface to be bent outside, the pressing surface facing the other mold is formed of a flat surface inclined in a direction approaching the other mold as it goes outward in the width direction. It is the end bending method of the steel plate characterized by this.

  A second aspect is the steel sheet end bending method according to the first aspect, wherein the inclination of the pressing surface is equal to or greater than an end bending angle applied to the width direction end of the steel sheet.

  A 3rd aspect uses the end bending apparatus of the steel plate provided with a pair of metal mold | die arrange | positioned corresponding to the width direction edge part of a steel plate, and can move relatively in a proximity | contact / separation direction. The steel sheet is bent at both ends in the width direction by relatively moving in the proximity direction, and the steel sheet bent at both ends in the width direction is formed into a cylindrical shape. A method for manufacturing a steel pipe, comprising: a cylindrical forming step for abutting width direction end portions; and a joining step for welding the width direction end portions of the abutted steel plates; In the mold on the side in contact with the surface that is the outer side of the bending at the end in the width direction of the steel sheet to be pressed, the pressing surface facing the other mold approaches the other mold as it goes outward in the width direction. A method for manufacturing a steel pipe, characterized by comprising a flat surface inclined in a direction.

  A 4th aspect is a manufacturing method of the steel pipe characterized by the inclination of the said press surface being more than the end bending angle provided to the width direction edge part of a steel plate in the said 3rd aspect.

  A 5th aspect is equipped with a pair of metal mold | die arrange | positioned corresponding to the width direction edge part of a steel plate, and can move relatively in a proximity | contact / separation direction, This pair metal mold | die moves relatively in a proximity direction It is an end bending apparatus for a steel plate that performs bending on the width direction end of the steel sheet by making the surface of the pair of molds on the outer side of the bending of the width direction end of the steel plate to be bent. In the metal mold on the contact side, the pressing surface facing the other metal mold is formed of a flat surface inclined in a direction approaching the other metal mold toward the outside in the width direction. It is an end bending device.

  A sixth aspect is the steel sheet end bending apparatus according to the fifth aspect, wherein the inclination of the pressing surface is equal to or greater than an end bending angle applied to an end portion in the width direction of the steel sheet.

  The seventh aspect includes a pair of molds that are arranged corresponding to the widthwise ends of the steel sheet and that can move relatively in the approaching / separating direction, and the pair of molds move relatively in the approaching direction. Steel plate end bending device that bends the width direction end of the steel sheet, and the steel sheet bent at both width direction ends are formed into a cylindrical shape, and the width direction ends of the steel sheets are butted together A cylindrical pipe forming apparatus and a joining apparatus for welding the end portions in the width direction of the abutted steel sheets, and a steel pipe manufacturing facility comprising: In the mold on the side that is in contact with the surface that is the outer side of the bending, the pressing surface facing the other mold is a flat surface that is inclined in a direction approaching the other mold as it goes outward in the width direction. It is the manufacturing equipment of the steel pipe characterized by being comprised.

  An eighth aspect is the steel pipe manufacturing facility according to the seventh aspect, wherein the inclination of the pressing surface is equal to or greater than an end bending angle applied to the end portion in the width direction of the steel sheet.

  According to the present invention, of the pair of molds, the pressing surface facing the other mold is flat in the mold on the side in contact with the outer surface of the bending at the end in the width direction of the steel sheet to be bent. Since the surface is used, a predetermined end bending amount can be easily obtained. As a result, it has become possible to reduce defects in the shape of the butt portion when a steel pipe is manufactured using a steel plate bent at the end.

It is a figure explaining the outline of the manufacturing equipment and manufacturing method of a steel pipe of one embodiment of the present invention. It is a top view which shows an example of the steel plate used as the object of an end bending process. It is the schematic which shows the end bending apparatus of the steel plate of one Embodiment of this invention. It is sectional drawing in the width direction which shows the state before the end bending of the press mechanism in the end bending apparatus of the steel plate of FIG. It is sectional drawing in the width direction which shows the state at the time of the end bending of the press mechanism in the end bending apparatus of the steel plate of FIG. It is sectional drawing which showed a mode that the end bending process was performed as a comparison using the end bending apparatus of the steel plate which comprises the pressing surface of a lower metal mold | die by a concave curved surface. It is a graph which shows the relationship between an end bending width and an end bending angle in the end bending at the time of shape | molding the steel pipe of a predetermined dimension. It is a figure explaining a target bending angle. It is sectional drawing which shows a shaping | molding condition when an end bending process is performed using the bending apparatus of the steel plate comprised by the curved surface in which the pressing surface of a lower metal mold has the same curvature as the radius of the molding surface of an upper metal mold. It is sectional drawing which showed a mode that an end bending process was performed using the bending apparatus of the steel plate of one Embodiment of this invention by which the pressing surface of the lower mold was comprised by the flat surface. FIG. 10 is a cross-sectional view showing a state in which end bending is performed using a lower mold whose inclination of a pressing surface of the lower mold is smaller than that of FIG. 9. It is a figure explaining peaking. It is a figure explaining an end bending shape and peaking.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same components are denoted by the same reference numerals, and overlapping descriptions are omitted as appropriate. In the specification, “front” or “front” means “downstream side” or “direction from the upstream side to the downstream side” as viewed in the conveying direction of the steel sheet in the end bending apparatus described later, and “rear” or “ “Backward” is the opposite direction.

  FIG. 1 shows an outline of a method and equipment for manufacturing a steel pipe according to an embodiment of the present invention for manufacturing a steel pipe from a steel sheet cut into a predetermined dimension. First, the steel plate S cut to a predetermined size is subjected to groove processing on its side surface by the edge mirror 10 or the edge planar. In the illustrated example, the tab plate St is welded to the front end portion (longitudinal front end portion) Sa and the tail end portion (longitudinal rear end portion) Sb of the steel plate S. However, the tab plate St may not be provided. is there. Next, end bending is performed by the end bending apparatus (C press) 20 according to one embodiment of the present invention (end bending process), and a cylindrical shape is formed by the cylindrical forming apparatus 30 (cylindrical forming process). The cylindrical forming apparatus 30 is not limited to the one formed by the U press 30A for first forming the steel sheet S subjected to end bending forming into a U shape, and then the O press 30B for forming an O shape (cylindrical shape). It is also possible to use a bending press 30C that is provided with a feeding mechanism that feeds S in the width direction and that gradually forms a final cylindrical shape by performing three-point bending while sequentially feeding the steel plates S in the width direction. Next, after joining the width direction edge parts which faced as a result of cylindrical shaping | molding of the steel plate S with the joining apparatus 40 from an outer surface, it welds by the submerged arc welding method etc. from an inner surface and an outer surface, respectively (joining process). Thereafter, the steel pipe S 'is expanded in diameter by the mechanical expander 50, and residual stress is removed and finished to a predetermined outer diameter and dimensions (tube expansion process). In addition, it cannot be overemphasized that other processes, such as washing | cleaning, various inspections, and bead grinding, may be performed between each process or processes.

  A steel plate end bending apparatus 20 and a steel plate end bending method using the same according to an embodiment of the present invention will be described in more detail. FIG. 2 shows an example of the steel sheet S before end bending. The width of the steel sheet S ranges from 1200 mm to 5100 mm, for example, depending on the outer diameter of the product steel pipe. Further, the length of the steel plate is often about 12 m, which is the standard length of a line pipe. A tab plate St is welded to each end in the width direction of the longitudinal end portion Sa and the tail end portion Sb of the steel plate S to be the steel pipe body, but there may be no tab plate St.

  In FIG. 3, the schematic structure of the end bending apparatus 20 of a steel plate is shown. The steel sheet end bending apparatus 20 is configured to bend and deform the left width direction end Sc to a predetermined curvature with the transport mechanism 21 transporting the steel sheet S along the longitudinal direction as the transport direction and the downstream side in the transport direction as the front. The distance between the left and right press mechanisms 22A and 22B is set according to the width of the press mechanism 22A to be bent, the press mechanism 22B to bend and deform the right-side width direction end Sd to a predetermined curvature, and the steel sheet S to be end-bended. And an interval adjusting mechanism (not shown) for adjustment. The transport mechanism 21 includes a plurality of transport rolls 21a disposed before and after the press mechanisms 22A and 22B. Each transport roll 21a is arranged in a direction perpendicular to the transport direction of the steel sheet S, and is configured to rotate at a speed synchronized with each other by a motor and a transmission mechanism (not shown).

  FIG. 4 shows a cross-section in the width direction of the press mechanism 22B that bends and deforms the right-side width direction end Sd of the steel sheet S in the direction from the upstream side to the downstream side in the conveying direction of the steel sheet S. Note that the press mechanism 22A and the press mechanism 22B are symmetrical and have the same configuration, and thus the detailed illustration of the press mechanism 22A is omitted. The press mechanisms 22A and 22B push up the upper mold 23 and the lower mold 24 as a pair of molds opposed to each other in the vertical direction, and the lower mold 24 together with the tool holder 25 (a direction close to the upper mold 23). A hydraulic cylinder 26 as mold moving means for clamping with a predetermined pressing force, and a clamp mechanism 27 for releasably clamping the steel sheet S inside the upper mold 23 and the lower mold 24 in the width direction; It has. The length in the longitudinal direction of the steel plate S of the lower die 24 and the upper die 23 is shorter than the length of the steel plate S, and the steel plate S is shifted in the longitudinal direction by the transport mechanism 21 (intermittently feeding). However, the bending is performed a plurality of times, and end bending is applied to the width direction ends Sc and Sd of the steel sheet S over the entire length.

  In the end bending process, the lower mold 24 on the side in contact with the outer surface of the bending of the width direction ends Sc and Sd of the steel sheet S to be bent has a pressing surface 24 a facing the upper mold 23. The upper mold 23 has a convex curved surface 23a facing the pressing surface 24a and having a radius of curvature corresponding to the inner diameter of the steel pipe to be manufactured. The pressing surface 24a is configured by a flat surface that is inclined in a direction approaching the upper mold 23 as it goes outward in the width direction.

  FIG. 5 is a cross-sectional view in the width direction at the same position as FIG. 4, but shows a state where the lower mold 24 is pushed up by the hydraulic cylinder 26 and clamped. When the hydraulic cylinder 26 is advanced from the state before the end bending shown by the broken line, the lower mold 24 is pushed up to the position of the solid line, and the width direction ends Sc and Sd of the steel sheet S are arc-shaped of the upper mold 23. It is bent into a shape along the molding surface 23a. For this reason, the molding surface 23a of the upper mold 23 differs depending on the diameter of the steel pipe used as a product. The width at which end bending is performed varies depending on the width of the steel sheet S, but is generally about 100 mm to 400 mm. Here, the case where the clamp mechanism 27 for clamping the steel plate S during end bending is illustrated, but the present invention is not limited to the presence or absence of the clamp mechanism 27.

  In FIG. 6, as a reference example, the pressing surface 24a of the lower mold 24 is formed into a concave curved surface, and the curvature radii of the pressing surface 24a and the convex curved surface 23a are made equal to each other in the width direction end portion Sc of the steel sheet S. The case where Sd is bent is shown. Since the steel plate S has a thickness, the radius of the curve of the lower surface (surface to be bent outside) of the steel plate S after being bent is larger than the radius of the pressing surface 24a of the lower mold 24. The lower mold 24 is in contact with only the edge portion Se in the width direction of the steel plate S. Thus, it can be seen that in the end bending process, the lower mold 24 may have a shape that is in contact with the width direction edge portion Se of the steel sheet S.

FIG. 7 shows the relationship between the end bending width and the end bending angle for end bending to the steel sheet S when manufacturing a steel pipe having an outer diameter of 812.8 mm and a pipe thickness of 38.1 mm. The radius of the molding surface of the upper mold 23 is R250 mm. This is to make the radius of the bent portion of the steel sheet S in a spring-backed state after unloading equal to the diameter of the steel pipe used as a product. Further, as shown in FIG. 8, the target bending angle θ _{aim in} the graph of FIG. 7 is an angle corresponding to the ratio of the end-bent portion to the entire circumference of the steel pipe, and is expressed by the following equation (1). Is.

However, Lc is the actual processing width (width of the portion to bend), W 2 _O is the width of the steel plate after the groove processing, and is usually the diameter of the tube thickness center of the steel pipe (outer diameter OD−tube thickness t). And W _O = α (OD−t) × π from the correction coefficient α of the dimensional change due to the manufacturing process.

  As shown in FIG. 6, the steel plate S and the lower mold 24 are in contact only at the position of the width direction edge portion Se of the steel plate S. In order to prevent the steel sheet S from being crushed at the contact portion, as shown in FIG. 9, a flat portion Sf of the steel plate that is not bent is left outside the portion Sr to which the bending of the steel plate is applied. Is preferred. Therefore, in the example shown in FIG. 7, the actual processing width for setting the target bending angle is as large as 90% of the radius of the molding surface, such as 140 mm when R160 mm, 180 mm when R200 mm, and 240 mm when R250 mm. Value. In addition, it is preferable that the flat part Sf of the steel plate which is not bend-formed is in a range of about 1 to 2 times the plate thickness from the end in the width direction of the steel plate S to the inside in the width direction.

  FIG. 9 shows a molding condition when the pressing surface 24a of the lower mold 24 is a curved surface, the radius is 250 mm (R250) which is the same as the radius of the molding surface 23a of the upper mold 23, and the actual processing width is 150 mm. Since the arc of the pressing surface 24a of the lower mold 24 needs to be 150 mm from the center, the extension angle range β is increased and the height is also increased. For this reason, it may exceed the circular arc surface of the upper mold 23 at the end of molding. Further, the tangent angle at the contact point between the lower mold 24 and the steel sheet S at the end of molding increases, and the force acting on the lower mold 24 is in a direction perpendicular to the push-up direction (rightward in the figure) as shown in the figure. The acting force increases. When the force in the direction orthogonal to the push-up direction is increased, the load on the end bending device 20 such as the attachment portion of the lower mold 24 is also increased.

  FIG. 10 shows a flat surface in which the pressing surface 24a of the lower mold 24 (the surface in contact with the surface that is the outer side of the bending of the steel plate S) is inclined toward the upper mold 23 toward the outer side in the width direction. It is sectional drawing which showed a mode that an end bending was performed using the end bending apparatus 20 of made embodiment. Although the height of the lower mold 24 is smaller than that in FIG. 9, the lower mold 24 is in contact with the width direction edge portion Se of the steel sheet S even at the end of end bending, and the pressing surface 24a of the lower mold 24 is. It can be seen that an end bending shape similar to that obtained when the surface is curved is obtained. Further, in the illustrated example, the tangential angle at the contact point between the steel sheet S and the pressing surface 24a of the lower mold 24 is also small, and it can be seen that the reaction force in the direction perpendicular to the pushing direction of the lower mold 24 is small. .

  11 shows an inclination of the pressing surface 24a of the lower mold 24 than that shown in FIG. 10 (when the direction perpendicular to the approaching / separating direction of the upper mold 23 and the lower mold 24 is a horizontal direction, the pressing surface This shows the situation during end bending when the angle 24a is small with respect to the horizontal direction. When the inclination of the pressing surface 24a is small, the range in which the end portion in the width direction of the steel plate S is not bent is widened, and the end bending angle is insufficient. For this reason, it is preferable that the inclination of the pressing surface 24a be greater than or equal to the end bending angle applied to the steel sheet S. When one lower mold 24 is also used for the upper mold 23 with different radii, the inclination of the pressing surface 24a may be set larger than the largest end bending angle among them. The “end bending angle” refers to the difference between the inclination angle in the 20 mm range of the plate end and the inclination angle at the center of the width.

  The inclination of the pressing surface 24a shows the target bending angle as an ideal case for obtaining a good shape for the butted portion of the final product, but it can be compensated by the shape of the other parts that are not end-bent. , What is necessary is just to be half or more of the target bending angle obtained by the above equation (1). Moreover, it is preferable that the inclination of the pressing surface 24a is 45 degrees or less so that the reaction force in the direction orthogonal to the push-up direction is equal to or less than the reaction force in the push-up direction equal to the press load.

  Thus, according to the end bending method and apparatus 20 and the steel pipe manufacturing method and equipment of the present embodiment, of the upper mold 23 and the lower mold 24, the end in the width direction of the steel sheet S to be bent. In the lower mold 24 on the side of the Sc and Sd that is in contact with the outer surface of the bend, the pressing surface 24a facing the upper mold 23 is configured as a flat surface, so that complicated adjustment work of the lower mold 24 is performed. It becomes possible to cope with the manufacture of steel pipes of various diameters without performing. In addition, since the same lower mold 24 can be used for a plurality of upper molds 23 having different molding radii, the introduction cost of the apparatus can be suppressed.

  Further, by setting the inclination of the pressing surface 24a to be equal to or greater than the end bending angle applied to the width direction ends Sc and Sd of the steel sheet S, an end bending shape having a desired end bending angle can be obtained more reliably.

  Although the embodiments of the present invention have been described based on the illustrated examples, the present invention is not limited to these embodiments, and can be appropriately changed, modified, added, and the like within the scope of the claims. For example, in the illustrated example, the case where the lower mold 24 is pushed up by the hydraulic cylinder 26 to press the width direction ends Sc and Sd of the steel sheet S against the upper mold 23 and bending is performed has been described. 24 may be configured to be bent in the same direction as the illustrated example by pressing down the upper mold 23 with the fixed mold 24 and the upper mold 23 as a movable mold. Further, as an arrangement in which the upper mold 23 is positioned outside the bend in the opposite direction to the illustrated example, the width direction ends Sc and Sd of the steel sheet S may be pressed against the lower mold 24 to perform bending. In this case, the pressing surface of the upper mold 23 located on the outer side of the bending and facing the lower mold 24 is constituted by an inclined flat surface. Alternatively, both the upper mold 23 and the lower mold 24 may be moved in the direction of approaching and separating from each other. In this case, the upper mold 23 and the lower mold 24 are located outside the bend. On the other hand, the pressing surface facing the other mold may be a flat inclined surface.

  In order to confirm the effect of the present invention, end bending of the steel sheet was performed under different conditions, and the end bending width, end bending angle, and peaking were investigated, which will be described below.

Example 1
A steel plate having a tensile strength of 550 MPa, a plate width of 1676 mm, a plate thickness of 25.4 mm and a length of 12 m was prepared, and a steel pipe having an outer diameter of 559 mm was produced. In the end bending apparatus, the upper limit of the contact angle between the lower mold and the steel plate is set to 45 degrees. Using an upper mold having a molding surface with a curvature radius of 200 mm, the bending angle was measured after the end bending was performed by changing the end bending width and the shape of the lower mold. Here, the bending angle was obtained from the difference between the inclination angle of the plate end portion 20 mm range and the width center portion measured with an inclinometer. Subsequently, U-press and O-press were applied to form a cylindrical shape, but the widthwise ends of the steel plates were butted together, then the butted portions were welded to form a steel pipe, and the peaking of the steel pipe was measured. Peaking is an index of the sharp shape of the butt portion, and is the difference between the actual outer diameter of the steel pipe (ie, a virtual perfect circle) and the actual steel pipe shape as shown in FIG. As shown in FIG. 13, when the end bend amount is large, the butt portion of the steel pipe enters the inside (minus peaking), and when the end bend amount is small, the butt portion of the steel pipe projects to the outside (plus peaking). ).

  Table 1 shows the forming results together with the end bending conditions and the target bending angle. In the table, the case where the pressing surface of the lower mold is configured by a straight flat surface is described as “straight line”, and the case where the pressing surface of the lower mold is configured by a concave curved surface is described as “arc”. In the table, the column of “angle (degree) or R (mm)” indicates the inclination (degree) when the pressing surface of the lower mold is a flat surface, and extends the pressing surface of the lower mold. When the existing angle range β (see FIG. 9) is a concave curved surface of 45 degrees, the radius of curvature (mm) is indicated. Under conditions 1 to 4 (invention example) where the pressing surface of the lower mold is a linear flat surface, the end bending angle can be increased, and the peaking is 1.3 mm or less, with a tolerance of ± 3.2 mm required by the API standard. It became 1/2 or less. In condition 3 in which the inclination of the pressing surface of the lower mold was reduced, the inclination of the pressing surface of the lower mold was equal to the target end bending angle, so the end bending angle was smaller than the target bending angle, and peaking was performed under conditions 1, 2, 4 It became larger than On the other hand, in condition 5 (comparative example) in which the pressing surface of the lower mold is a concave curved surface, the curvature radius r of the lower mold is 200 mm, and the extension angle range β is 45 degrees. The width W (see FIG. 9) is about 141 mm from r · sin β. Here, the end bending width is set to 130 mm from the upper limit in terms of manufacturing technology, but the end bending angle is small and the peaking is larger than those in conditions 1 to 4. became.

(Example 2)
A steel plate having a tensile strength of 680 MPa, a plate width of 2753 mm, a plate thickness of 38.1 mm, and a length of 12 m was prepared to produce a steel pipe having an outer diameter of 914 mm. The end bending device is the same as that of the first embodiment, but the upper mold is replaced with one having a molding surface with a curvature radius of 335 mm, and the lower mold is formed of a flat surface having an inclined pressing surface as in the first embodiment. Two types were used (shown as “straight line” in the table) and those composed of concave curved surfaces (shown as “arc” in the table). Using this end bending apparatus, the end bending width and the shape of the lower mold were changed, and then the bending angle was measured. Here, the bending angle was obtained from the difference between the inclination angle of the plate end portion 20 mm range and the width center portion measured with an inclinometer. Subsequently, the steel sheet was formed into a cylindrical shape by a press bend method using a bending press and the width direction end portions of the steel plates were butted together, and the butted portions were welded to form a steel pipe, and the peaking of the steel pipe was measured. Table 2 shows the end bending conditions and the molding results. Conditions 1 to 4 (invention example) in which the pressing surface of the lower mold is a flat surface can increase the end bending angle, and the peaking is 1.6 mm or less, which is 1/2 of the tolerance ± 3.2 mm required by the API standard. It became the following. In condition 3 in which the inclination of the pressing surface of the lower mold was reduced, the inclination of the lower mold pressing surface was smaller than the target end bending angle, so the end bending angle was smaller than the target bending angle, and peaking was performed under conditions 1, 2, 4 It became larger than On the other hand, under condition 5 (comparative example) in which the pressing surface of the lower mold has a concave curved surface with an extension angle range β (see FIG. 9) of 45 degrees, the curvature radius r of the lower mold is 200 mm, and the extension angle range β By setting the angle to 45 degrees, the width W (see FIG. 9) of the lower mold in plan view is about 141 mm from r · sin β, and the end bending width is 130 mm from the upper limit in terms of manufacturing technology. The angle was small and the peaking was also large compared to Conditions 1-4.

  According to the present invention, a predetermined end bending shape can be obtained without adjusting the position of the mold.

DESCRIPTION OF SYMBOLS 10 Edge mirror 20 End bending apparatus of steel plate 30 Cylindrical forming apparatus 30A U press 30B O press 30C Bending press 40 Joining apparatus 50 Mechanical expander 21 Conveyance mechanism 21a Conveyance roll 22A, 22B Press mechanism 23 Upper die 23a Molding surface 24 Lower metal Mold 24a Pressing surface S Steel plate Sa Tip portion Sb Tail end portion Sc, Sd Width direction end portion Sr The portion where the bending of the steel plate is applied Sf The flat portion of the steel plate St Tab plate

Claims (8)

Using a steel plate end bending apparatus provided with a pair of molds that are arranged corresponding to the widthwise ends of the steel sheet and are relatively movable in the approaching / separating direction, the pair of molds are relatively moved in the approaching direction. It is an end bending method of a steel plate that performs bending on the width direction end of the steel plate by moving it,
Of the pair of molds, in the mold on the side in contact with the outer surface of the bending at the end in the width direction of the steel sheet to be bent, the pressing surface facing the other mold is directed outward in the width direction. A method of bending an end of a steel sheet, comprising a flat surface inclined in a direction approaching the other mold.   The method of bending an end of a steel sheet according to claim 1, wherein the inclination of the pressing surface is equal to or greater than an end bending angle applied to an end in the width direction of the steel sheet. Using a steel plate end bending apparatus provided with a pair of molds that are arranged corresponding to the widthwise ends of the steel sheet and are relatively movable in the approaching / separating direction, the pair of molds are relatively moved in the approaching direction. An end bending process of the steel sheet that performs bending on the widthwise end of the steel sheet by moving the steel sheet;
A cylindrical forming step of forming a steel sheet bent at both ends in the width direction into a cylindrical shape and abutting the width direction ends of the steel sheets,
A joining step of welding end portions in the width direction of the butted steel sheets, and a method of manufacturing a steel pipe,
Of the pair of molds, in the mold on the side in contact with the outer surface of the bending at the end in the width direction of the steel sheet to be bent, the pressing surface facing the other mold is directed outward in the width direction. A method of manufacturing a steel pipe, characterized by comprising a flat surface inclined in a direction approaching the other mold.   The method for manufacturing a steel pipe according to claim 3, wherein the inclination of the pressing surface is equal to or greater than an end bending angle applied to an end portion in the width direction of the steel plate. A pair of molds arranged corresponding to the width direction end of the steel sheet and relatively movable in the approaching / separating direction are provided, and the width of the steel sheet is moved by relatively moving the pair of molds in the proximity direction. An end bending apparatus for a steel plate that performs bending at a direction end,
Of the pair of molds, in the mold on the side in contact with the outer surface of the bending at the end in the width direction of the steel sheet to be bent, the pressing surface facing the other mold is directed outward in the width direction. An end bending apparatus for a steel sheet, comprising a flat surface inclined in a direction approaching the other mold.   The steel sheet end bending apparatus according to claim 5, wherein the inclination of the pressing surface is equal to or greater than an end bending angle applied to an end portion in the width direction of the steel sheet. A pair of molds arranged corresponding to the width direction end of the steel sheet and relatively movable in the approaching / separating direction are provided, and the width of the steel sheet is moved by relatively moving the pair of molds in the proximity direction. An end bending apparatus for a steel plate that performs bending at the direction end; and
A cylindrical forming apparatus that forms a steel plate that is bent at both ends in the width direction into a cylindrical shape, and abuts the end portions in the width direction of the steel plate;
A steel pipe manufacturing facility comprising: a joining device that welds the widthwise ends of the abutted steel sheets;
Of the pair of molds, in the mold on the side in contact with the outer surface of the bending at the end in the width direction of the steel sheet to be bent, the pressing surface facing the other mold is directed outward in the width direction. A steel pipe manufacturing facility comprising a flat surface inclined in a direction approaching the other mold.   The steel pipe manufacturing equipment according to claim 7, wherein the inclination of the pressing surface is equal to or greater than an end bending angle applied to an end portion in the width direction of the steel plate.