Method for manufacturing rectangular pipe-shaped curved long material and method for forming curved channel material

Abstract

To provide a practical curve molding method for long-sized material.SOLUTION: For example, when a channel material 14 is curved as a long-sized material, the channel material is curved by repeating a bending process of pressing, with some lengthwise part 16 of a channel material supported with a patch metal 20 and a part 22 more on one end side than the part held, a part 24 more on the other end side than the part while shifting the part supported with the patch metal. Namely, the channel material is bent to a radius of curvature smaller than a radius of curvature of the curving a plurality of times while the position of the curving is shifted. When a bender is used, a dedicated roll die matching the curving is required, but the present curve molding method does not require the dedicated roll die. The method is specially effective in manufacturing a small number of curved long-sized materials.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for producing a curved elongated material having a cross section in the shape of a square pipe, and a method for bending a channel material, which is an elongated material having a web and a pair of flanges on both sides of the web. [Background technology]

[0002] When producing a curved elongated material (hereinafter sometimes referred to as a "curved elongated material"), it is common to curve a straight elongated material using a bender, as described in the following patent document, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-162557 Summary of the Invention [Problem to be solved by the invention]

[0004] In the bending process using a bender as described in the above patent documents, a roll die (inner die) to be placed inside the curved portion must be prepared according to the radius of curvature of the curve. Therefore, when only a small number of molded products (small batches) are to be produced, the cost of producing the roll die becomes relatively high. Furthermore, for molded products having curved portions with different radii of curvature, the cost of producing the roll die becomes significantly high. Therefore, a practical method for producing a small number of curved long materials is desired. The present invention has been made in consideration of such circumstances, and aims to provide a highly practical method for producing curved long materials having a square pipe cross section, and a highly practical method for bending long channel materials. [Means for solving the problem]

[0005] In order to solve the above problems, the method for manufacturing a rectangular pipe-shaped curved long material of the present invention comprises the steps of: A method for producing a curved elongated material having a square pipe cross section, comprising: a channel member preparing step of preparing a pair of straight channel members, each of which is an elongated member having a web and a pair of flanges on both sides of the web; a channel material bending process in which the pair of channel materials are arranged facing each other with the flanges overlapping each other, and a certain portion in the longitudinal direction is supported by a metal abutment, and while holding a portion on one end side from the aforementioned portion, a portion on the other end side from the aforementioned portion is pushed to bend the pair of channel materials at the portion supported by the metal abutment, and this bending process is repeated while shifting the portion supported by the metal abutment, thereby bending the pair of channel materials together; a welding step of welding flanges of the pair of curved channel members together; The present invention is characterized by comprising: Further, the method for forming a curved channel member of the present invention includes the steps of: A method for forming a channel material, which is a long material having a web and a pair of flanges on both sides of the web, into a curved shape, comprising: a bending step in which a certain point in the longitudinal direction of the channel material is supported by a metal backing and a portion on one end side of the point is held, and a portion on the other end side of the point is pressed to bend the channel material at the point supported by the metal backing; A channel material other than the channel material is used, and the channel material and the other channel material are arranged facing each other so that the flanges overlap each other, and then the channel material and the other channel material are curved; and The method is characterized in that the channel material is curved by repeatedly shifting the position where the abutment is supported. The channel material bending method of the present invention can be considered as a method having a higher concept than the channel material bending step in the square pipe-shaped curved long material manufacturing method of the present invention. 、2 One of the two channel materials may be a dummy channel (cover channel) that serves as a support to allow the other to be appropriately curved. [Effects of the Invention]

[0006] In the method for manufacturing a curved elongated material in the shape of a square pipe of the present invention, specifically the channel material bending step thereof, and the channel material bending method of the present invention, the channel material, which is a long material, is curved by repeatedly bending the material. Specifically, bends with a smaller radius of curvature than the radius of curvature of the original curve are applied while shifting the position of the bend. In other words, the channel material is shaped into an approximate curve by connecting bends with small radii of curvature at a distance. According to the method for manufacturing a curved elongated material in the shape of a square pipe of the present invention, it is possible to easily manufacture even a small number of curved elongated materials without the need to prepare a relatively expensive roll mold to match the curve. Similarly, according to the method for bending a channel material of the present invention, it is possible to easily curve even a small number of channel materials without the need to prepare an expensive roll mold to match the curve. Aspects of the Invention

[0007] The method for manufacturing a curved elongated material in the shape of a square pipe and the method for forming a curved channel material according to the present invention can be widely applied to elongated materials made of general metallic materials that undergo plastic deformation, such as steel and aluminum alloys.

[0008] The channel material preparation step in the method for manufacturing a curved elongated material in the shape of a square pipe of the present invention (hereinafter, sometimes simply referred to as the "method for manufacturing a curved elongated material") may be a step in which a channel material of a planned shape and dimensions is purchased, or may be a step in which a plate material is cut to a predetermined size by shearing or the like, and the cut piece is bent by a brake press or the like.

[0009] In the channel bending step (hereinafter sometimes simply referred to as the "bending step") of the method for producing a curved elongated member of the present invention, and in the channel bending method (hereinafter sometimes simply referred to as the "bending method") of the present invention in which a channel other than the channel is bent together with the channel while facing each other with its flanges overlapping, when two channels are faced each other, both of the pair of flanges of one of the two channels may be inside the pair of flanges of the other channel, or one of the pair of flanges of one of the two channels may be inside one of the pair of flanges of the other channel, and the other of the pair of flanges of the other of the two channels may be inside the other of the pair of flanges of the first channel. Simply put, one of the two channels may be placed over the other, or the two channels may be combined alternately.

[0010] Furthermore, the direction of curvature in the curving step of the curved elongated material manufacturing method of the present invention and the curved elongated material manufacturing method of the present invention is not particularly limited, but may be, for example, a direction in which the web of the channel material is on the inside of the curve and the tips of the pair of flanges are on the outside of the curve, or a direction in which the web of the channel material is on the outside of the curve and the tips of the pair of flanges are on the inside of the curve. The curve may be so-called "horizontal." On the other hand, the curve may be so-called "vertical" in which one of the pair of flanges is on the inside of the curve and the other is on the outside of the curve.

[0011] The bending step of the curved elongated material manufacturing method of the present invention and the bending method of the present invention can be performed, for example, using a jig having two side plates arranged to sandwich the channel material and a backing metal provided between the side plates. The channel material is set in the jig, and the bending step can be performed by pressing a location a predetermined distance longitudinally from the backing metal with, for example, a hydraulic piston. By appropriately setting the location supported by the backing metal and the pressing amount (pressing stroke) by a plunger, etc., it is possible to bend the channel material into a curved shape that approximates a curved shape with a desired radius of curvature.

[0012] For example, when a channel member is bent in the vertical direction, the flange on the outer side of the bend is relatively deeply concave, while the flange on the inner side of the bend develops wavy wrinkles. To mitigate this phenomenon as much as possible, in the bending step of the curved elongated member manufacturing method of the present invention and in the bending method of the present invention in which two channel members are bent facing each other, an object functioning as a core (which can also be called a "mandrel") may be filled into the space surrounded by the two channel members at the bent portion. That is, the core filling step can be performed before the bending step. For example, hard urethane rubber or a laminate of flexible plate materials can be used as this filling object. Alternatively, the two channel members facing each other may be covered with another channel member before the bending step of the curved elongated member manufacturing method of the present invention and the bending method of the present invention. The object functioning as the core may be removed, for example, by separating the two channel members after bending them. That is, the core bar removing step may be carried out after the bending step.

[0013] In the method for manufacturing a curved elongated member of the present invention, after the bending step, the flanges of a pair of curved channel members are welded together. This welding can be performed by fillet welding, stopper welding, etc. when the flanges are overlapped, or by butt welding, etc. when the flange tips are butted together. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating a side member of an automobile chassis frame, which is a curved long material to which the method for manufacturing a curved long material in the shape of a square pipe of an embodiment is applied. FIG. [Figure 2] 1A to 1C are diagrams for explaining a cross section of a side member to be manufactured and a manner in which the side member is divided and manufactured. [Figure 3] 1A and 1B are diagrams showing a designed curved elongated member to be produced and an actually produced curved elongated member. [Figure 4] FIG. 10 is a schematic perspective view showing how a channel material, which is a long material, is bent at a certain location when the channel material is formed into a curve. [Figure 5] FIG. 10 is a diagram showing how the channel material is curved by repeatedly bending the bent portion while shifting the bent portion. [Figure 6] FIG. 1 is a diagram showing a curve forming device used when curving a long material. [Figure 7] FIG. 10 is a diagram showing a state in which two channel members are placed opposite each other during bending, and a state in which a means for preventing deformation of the curved portion of the core metal or the like is provided. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following describes in detail, with reference to the drawings, the method for manufacturing a curved elongated member in the shape of a square pipe, which is an embodiment of the present invention, and the method for forming a curved channel member included therein. In addition to the following embodiment, the present invention can be embodied in various forms, including those described in the above section "Modes of the Invention," with various modifications and improvements made based on the knowledge of those skilled in the art. [Example]

[0016] [A] Curved long material to be produced The curved elongated members fabricated by the method for fabricating a curved elongated member in the shape of a square pipe according to the embodiment are left and right side members 10R, 10L that constitute the chassis frame of an automobile, as shown in FIG. 1(a). The left and right side members 10R, 10L are symmetrical, and the fabrication methods for each of them differ only due to this symmetry. In light of this, the following description will focus only on the right side member 10R, which is representative of the side members 10R, 10L. In the following description, the side members 10R, 10L may sometimes be collectively referred to as side member 10.

[0017] As shown in the front view of Fig. 1(b), the side member 10 has curved portions 12f1, 12f2, 12r1, and 12r2 on the front and rear sides that are curved in the up-down direction, in other words, curved portions that are vertically curved. Furthermore, as shown in the plan view of Fig. 1(c), the side member 10 has two curved portions 12c1 and 12c2 in the center in the front-to-rear direction that are curved in the vehicle width direction, in other words, curved portions that are horizontally curved. The curved portions 12f1, 12f2, 12r1, 12r2, 12c1, and 12c2 may be collectively referred to as curved portion 12 when there is no need to distinguish them from one another.

[0018] The side member 10 has a cross section generally in the shape of a square pipe. It may be produced by bending a long piece of square pipe using a pipe bender. However, since this chassis frame is a prototype and only a small number of side members 10 need to be produced, taking into consideration the manufacturing cost of the roll mold of the pipe bender and the difficulty of dealing with deformation (dents, wrinkles, etc.) of the curved portion when bending using a core metal or the like, the side member 10 is produced by joining two long channel members 14, as shown in the cross-sectional view of FIG. 2( a). One of the two channel members 14 is an outer channel member 14o located on the outside of the vehicle, and the other is an inner channel member 14i located on the inside of the vehicle. When there is no need to distinguish between them, they will be collectively referred to as channel members 14.

[0019] The outer channel member 14o and the inner channel member 14i are made of the same type of steel material, but have different thicknesses as shown in FIG. 2(a). o , the thickness of the inner channel is t i Then, the outer channel 14o is made thicker than the inner channel 14i. o >t i The outer channel 14o and the inner channel 14i each have a web 14w and a pair of flanges 14f on both sides of the web 14w. The outer channel 14o and the inner channel 14i are joined together with the flanges 14f overlapping each other, specifically with the inner surface of each of the pair of flanges 14f of the outer channel 14o in contact with the outer surface of each of the pair of flanges 14f of the inner channel 14i. More specifically, the tip of each of the pair of flanges 14f of the outer channel 14o is joined to the outer surface of each of the pair of flanges 14f of the inner channel 14i by fillet welds W.

[0020] As shown in Fig. 2(b), the side member 10 is made by fabricating three pieces and joining the three pieces in the longitudinal direction. The three pieces can be called, from the front of the vehicle, the front piece 10f, the center piece 10c, and the rear piece 10r. The front piece 10f includes the curved portions 12f1 and 12f2, the center piece 10c includes the curved portions 12c1 and 12c2, and the rear piece 10r includes the curved portions 12r1 and 12r2.

[0021] As can be seen from FIG. 2(b), at the joint between the front piece 10f and the center piece 10c, the outer channel member 14o of the front piece 10f extends longitudinally from the inner channel member 14i, and the inner channel member 14i of the center piece 10c extends longitudinally from the outer channel member 14o. Similarly, at the joint between the rear piece 10r and the center piece 10c, the outer channel member 14o of the rear piece 10f extends longitudinally from the inner channel member 14i, and the inner channel member 14i of the center piece 10c extends longitudinally from the outer channel member 14o. In other words, to improve the joint strength, the outer channel members 14o and the inner channel members 14i are joined alternately at the joint. Note that at the joint, the outer channel members 14o and the inner channel members 14i are joined together by butt welding.

[0022] [B] How to make curved long pieces As explained above, the side member 10 is produced by separately preparing the front piece 10f, the center piece 10c, and the rear piece 10r and joining them together. Each of the front piece 10f, the center piece 10c, and the rear piece 10r can be considered a curved elongated member. Hereinafter, the front piece 10f, the center piece 10c, and the rear piece 10r will be collectively referred to as the curved elongated member 10T, and a method for producing the curved elongated member 10T will be explained. In the following explanation, the channel members themselves constituting the curved elongated member 10T may be referred to as the channel member 14, the outer channel member 14o, and the inner channel member 14i.

[0023] The production of the curved elongated member 10T generally includes a channel member preparation step of preparing a pair of straight channels 14, namely, an outer channel member 14o and an inner channel member 14i, a channel member curving step of curving the outer channel member 14o and the inner channel member 14i together, and a welding step of welding the flanges 14f of the curved outer channel member 14o and the inner channel member 14i together. These steps will be described in detail below.

[0024] (a) Channel material preparation process If at least one of the outer channel 14o and the inner channel 14i has a commercially available shape and size, for example, it is sufficient to purchase that one. However, if either the outer channel 14o or the inner channel 14i is not commercially available, in other words, if it is not a commonly available standard size, the channel 14 itself can be fabricated. Specifically, a sheet material having a thickness t required for the channel 14 to be fabricated is cut to the desired dimensions by shearing or the like, and the cut sheet material is then bent by a brake press or the like to obtain a straight channel 14 having the desired web width and flange width. The method for fabricating this channel 14 is a common method in sheet metal processing, so a detailed description thereof will be omitted.

[0025] (b) Channel material curve forming process i) Basic method This channel bending process is a process for bending the outer channel 14o and the inner channel 14i together, but it can also be performed for only one channel 14. Therefore, a basic technique for the channel bending process will be described by taking the bending of one channel 14 as an example. Note that this channel bending process is an example of a channel bending method.

[0026] The curved long material 10T to be manufactured in the design is the standard curved long material 10T * Then, the standard curved long material is 10T * As shown in FIG. 3(a), the channel member 14 has one curved portion 12 in which three curved regions, A, B, and C, are connected. Each of the curved regions A, B, and C is curved in such a direction that one of a pair of flanges 14f of the channel member 14 is on the inside of the curve and the other is on the outside of the curve. In other words, it is curved in the vertical direction. The curved regions A and B are curved in the same direction, and the radius of curvature (the radius of curvature of the outer surface of the inner flange 14f) R of the curved region A is R A, the curved region B is R B (>R A On the other hand, the curved region C is curved in the opposite direction to the curved regions A and B, and has a radius of curvature R C is the radius of curvature R of the curved region B B Incidentally, the curved region A, curved region B, and curved region C each have an angle range of θ A ,θ B ,θ C It is as follows.

[0027] Referring to FIG. 3(b), the present channel material bending process is carried out by forming a standard curved long material 10T. * Radius of curvature R A ,R B ,R C By bending the material with a smaller radius of curvature R, the basic radius of curvature R0, multiple times at intervals, the standard curved long material 10T can be achieved. * The above-mentioned "bending" has a smaller radius of curvature R than "curving", and to distinguish it from curving, it will be called "bending" hereinafter. In short, this channel material curvature forming process can be considered as a process of curving the channel material 14 by repeatedly performing a bending process of bending the channel material 14 at a basic radius of curvature R0.

[0028] In Figure 3(b), the bending portions 16, which are the portions that are bent in each bending process, are numbered in the order in which the bending processes are performed, and the straight portions 18, which are the portions that are not bent, are shown shaded between the bending portions 16.

[0029] As shown schematically in Figure 4, the bending process is performed by supporting the portion that will become the bent portion 16 from below with abutment 20, holding the portion on one end side of the supported portion with a receiving metal 22, and pressing down the portion on the other end side with a piston. More specifically, to bend the channel member 14 in the vertical direction, one of the pair of flanges 14f of the channel member 14 is supported by the abutment 20, the other is held by the receiving metal 22, and the other is pressed down by the piston. Note that only the pressing head 24 attached to the tip of the piston is shown in the figure.

[0030] In the bending process as described above, forces as shown in the figure act on the push-down head 24 of the piston, the backing plate 20, and the receiving plate 22, so that the channel material 14 is bent at the bending portion 16. Note that the holding by the receiving plate 22 only prevents one end side from jumping up from the portion that will become the bending portion 16 when pushed down by the piston, but it may also be configured to prohibit movement of the channel material 14 in the longitudinal direction. Note that, in consideration of springback of the channel material 14, the backing plate 20 has an upper surface that is a partial cylindrical side surface having a radius that is somewhat smaller than the basic radius of curvature R0.

[0031] By fixing the contact metal pressing head distance L0, which is the distance between the contact metal 20 and the pressing head 24 of the piston in the longitudinal direction, and appropriately setting the contact metal channel end distance L, which is the distance in the longitudinal direction between one end of the channel material 14 and the contact metal 20, the pressing amount S of the pressing head 24, and the pressing force F of the pressing head 24, it is possible to bend the channel material 14 by any amount at any position. Note that it is desirable to set the pressing amount S and the pressing force F while taking into consideration the springback of the channel material. Furthermore, instead of the pressing force F, a force acting on the receiving metal 22 or the contact metal 20 may be used.

[0032] Then, by repeating the bending process while feeding the channel material 14 in the feeding direction shown in the figure, in other words, while shifting the bent portion 16, which is the portion supported by the backing metal 20, toward one end, the channel material 14 can be curved appropriately. The curved elongated material 10T shown in FIG. 3(b) can be curved by performing the bending process ten times, as shown in FIG. 5. The process numbers in FIG. 5 correspond to the numbers of the bent portion 16 in FIG. 3(b). As can be seen from the figure, the channel material 14 is turned upside down between the seventh and eighth processes.

[0033] Here, the basic method for bending one channel member 14 has been described. However, as described above, this channel member bending process is a process for each of the front piece 10f, the center piece 10c, and the rear piece 10r, and is a process for bending the outer channel member 14o and the inner channel member 14i together.

[0034] ii) Channel material bending device The channel material bending process is performed using a channel material bending device (hereinafter, sometimes simply referred to as the "bending device") as shown in a perspective view in Fig. 6(a). This bending device includes a jig 32 having a pair of base plates 30 arranged at a distance from each other, and a hydraulic cylinder 34 attached to the jig 32.

[0035] 6(b), which is a front view, the jig 32 can adjust the spacing between the pair of substrates 30 by replacing the spacers 36. This changes the spacing between the front piece 10f and the rear piece 10r, which are curved vertically, and the center piece 10c, which is curved horizontally. When bending the front piece 10f and the rear piece 10r, the overlap between the flanges 14f of the outer channel member 14o and the inner channel member 14i is greater than that shown in FIG. 2(a). Therefore, the spacing between the pair of substrates 30 is set based on the width of the flange 14f of the outer channel member 14o. When bending the center piece 10c, the spacing between the pair of substrates 30 is set based on the width of the web 14w of the outer channel member 14o.

[0036] The backing metal 20 is placed between the pair of base plates 30, and a rod-shaped receiving metal 22 is placed so as to penetrate the pair of base plates 30. The pressing head 24 is detachably attached to the tip of a piston 38 of a hydraulic cylinder 34. Pressurized hydraulic oil is supplied to the hydraulic cylinder 34 from a hydraulic unit (not shown). The backing metal 20 and pressing head 24 are placed and attached in a manner that corresponds to the distance between the pair of base plates 30.

[0037] Furthermore, the bending device may be provided with, for example, a laser displacement meter 40 to grasp the above-mentioned pushing amount S, a stopper device 44 that moves a stopper 42 by servo control to manage the above-mentioned distance L between the backing channel ends, and a load sensor 46 having a strain gauge, a load cell, or the like may be provided on the piston 38 to measure the above-mentioned pushing force F. By utilizing data related to the bending process obtained by the displacement meter 40, the stopper device 44, the load sensor 46, etc., it becomes possible to repeatedly perform bending of the channel material 14 with high accuracy.

[0038] iii) Dealing with deformation of curved parts When a long material is bent, deformation occurs at the curved portion. Specifically, for example, a depression occurs on the outer side of the curve, and a wavy, i.e., wrinkles, occurs on the inner side. When the long material is a channel material, it is not symmetrical in either the left-right or the top-bottom direction, and therefore deformations specific to channel materials, such as changes in the angle between the flange and the web, may occur. Taking this into consideration, the channel material bending process is performed by arranging a pair of channel materials 14, i.e., an outer channel material 14o and an inner channel material 14i, facing each other so that their flanges 14f overlap, as shown in FIG. 7(a). In other words, the two channel materials 14 are bent simultaneously not only to improve productivity by simultaneously bending the two channel materials 14, but also to obtain the advantage of one of the pair of channel materials 14 acting as a support for the other and vice versa.

[0039] Furthermore, in this channel member bending process, as shown in FIG. 7(b), a dummy channel (cover channel) 50 functioning as a supporter is placed on the outside of the outer channel member 14o, and a mandrel 52 (hereinafter simply referred to as the "mandrel") is filled in the space surrounded by the outer channel member 14o and the inner channel member 14i at the curved portion. The mandrel 52 shown in FIG. 7(b) is made of hard urethane. Alternatively, as shown in FIG. 7(c), the mandrel 52 may be formed by stacking plates 52p according to the curved direction. The action of the dummy channel 50 and mandrel 52 effectively suppresses the deformation of the curved portion 12 of the curved elongated member 10T.

[0040] The mandrel 52 may be filled before the bending process is started. In other words, the mandrel filling process may be performed before the bending process. The mandrel 52 may be removed after the bending process is completed, by separating the curved outer channel 14o and inner channel 14i from each other. In other words, the mandrel removing process may be performed after the bending process. When bending a long rectangular pipe, designing, setting, adjusting, etc., of an appropriate mandrel is relatively difficult and troublesome. However, in this channel bending process, the mandrel 52 can be easily filled when the outer channel 14o and the inner channel 14i are brought face to face with each other, and the mandrel 52 can be easily removed by separating the outer channel 14o and the inner channel 14i, even though the outer channel 14o and the inner channel 14i are curved.

[0041] (c) Welding process In the welding process, first, the outer channel member 14o and the inner channel member 14i, which have been curved through the channel member curving process, are set using an appropriate jig so as to be in the state shown in FIG. 2(a). In this set state, the flanges 14f are fillet welded together as shown in the figure. This fillet welding does not need to be performed continuously over the entire length of the curved elongated member 10T as long as an appropriate strength is obtained; for example, it may be performed so as to form tack welds with an appropriate pitch. The welding may be performed by an appropriate method, such as CO2 arc welding or TIG welding, depending on the material of the curved elongated member 10T. Since this welding process is a common process, a detailed description will be omitted. [Explanation of symbols]

[0042] 10: Side member (long curved member) 10T: Long curved member 10T *: Standard curved long material 12: Curved portion 14: Channel material 14o: Outer channel material 14i: Inner channel material 14w: Web 14f: Flange 16: Bent portion 18: Straight portion 20: Contact metal 22: Receiving metal 24: Press-down head 30: Base plate 32: Jig 34: Hydraulic cylinder 38: Piston 40: Displacement meter 42: Stopper 44: Stopper device 46: Load sensor 50: Cover channel 52: Object functioning as core metal 52p: Plate

Claims

1. A method for producing a curved elongated material having a square pipe cross section, comprising: a channel member preparing step of preparing a pair of straight channel members, each of which is an elongated member having a web and a pair of flanges on both sides of the web; a channel material bending process in which the pair of channel materials are arranged facing each other with the flanges overlapping each other, and a certain portion in the longitudinal direction is supported by a metal abutment, and while holding a portion on one end side from the aforementioned portion, a portion on the other end side from the aforementioned portion is pushed to bend the pair of channel materials at the portion supported by the metal abutment, and this bending process is repeated while shifting the portion supported by the metal abutment, thereby bending the pair of channel materials together; a welding step of welding flanges of the pair of curved channel members together; A method for manufacturing a curved elongated material in a square pipe shape, comprising:

2. 2. The method for manufacturing a curved elongated member in the shape of a square pipe according to claim 1, wherein in the channel member bending step, each of the pair of channel members is bent in a direction such that one of the pair of flanges of each of the pair of channel members is on the inside of the curve and the other is on the outside.

3. Before the bending step, a core metal filling step is performed in which a space surrounded by the pair of channel materials is filled with an object functioning as a core metal in a portion to be bent, the space being surrounded by the pair of channel materials with the flanges overlapping each other; 3. A method for manufacturing a curved elongated material in the shape of a square pipe according to claim 1 or claim 2, further comprising the step of separating the pair of curved channel members from each other after the bending step is completed, and then performing a core bar removal step to remove the object that has functioned as the core bar.

4. 4. The method for manufacturing a curved elongated member in the shape of a square pipe according to claim 1, wherein the channel member curving step is performed by covering a pair of channel members facing each other with another channel member.

5. A method for forming a channel material, which is a long material having a web and a pair of flanges on both sides of the web, into a curved shape, comprising: a bending step in which a certain point in the longitudinal direction of the channel material is supported by a metal backing and a portion on one end side of the point is held, and a portion on the other end side of the point is pressed to bend the channel material at the point supported by the metal backing; The channel material bending method uses a channel material different from the channel material, and bends the channel material by placing the channel material and the other channel material opposite each other so that the flanges overlap each other, and repeating this while shifting the positions supported by the abutments, thereby bending the channel material.

6. 6. The method for forming a curved channel member according to claim 5, wherein the bending step is performed by supporting one of a pair of flanges of the channel member by the abutment and pressing the other flange, thereby bending the channel member so that one of the pair of flanges of the channel member is on the inside of the curve and the other flange is on the outside.

7. a step of filling a body functioning as a core metal into a space surrounded by the channel material and the other channel material in a portion to be bent, the space being formed by arranging the channel material and the other channel material so that the flanges overlap each other, before the bending step; 7. The method for forming a curved channel member according to claim 5 or 6, further comprising the step of separating the curved channel member and the other channel member from each other after the bending step is completed, and taking out an object that has functioned as the mandrel.

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