Method for manufacturing cylindrical body

Abstract

In this invention, by a bending step, a roll is operated so as to bend and raise an end part of a workpiece (1) in the out-of-plane direction, and a bent and raised part in which the end part is bent and raised in the out-of-plane direction is formed. Thereafter, in a thickening step, the roll is operated so as to push the bent and raised part in the in-plane direction, and a thickened part in which the end part is deformed in the out-of-plane direction is formed. As a result, material spreads in the out-of-plane direction in a range in the in-plane direction corresponding to the bent and raised part, thereby forming the thickened part.

Description

Method for manufacturing a cylindrical body

[0001] The present invention relates to a method for manufacturing a cylindrical body.

[0002] Roll forming is known in which a metal plate material is passed between a plurality of rolls and subjected to multi-stage forming to process it into a final shape. By bending the plate material so that the ends thereof abut against each other by roll forming and joining the abutting portions formed by the abutment of the ends, a cylindrical body can be manufactured. In roll forming, in order to prepare a long plate material, for example, cutting by a slitter is performed. Since the plate material cut by the slitter has cutting sag or undulation on the end face, a gap will occur between the end faces abutted by roll forming. Thus, when joining is performed in a state where a gap exists in the abutting portion, the material corresponding to the gap will be insufficient, so thinning will occur in the joined portion after joining, or a perforation defect will occur in the joined portion, resulting in a deterioration of the joining quality.

[0003] Therefore, in order to improve the joining quality of the abutting portion, a technique of thickening (thickening) the ends of the plate materials to be abutted is adopted. For example, in Patent Document 1, there is described a roll forming technique including a rolling roll that rotates while rolling a region excluding both side edges of a strip material, and a pair of side edge processing rolls that rotate while crushing both side edges of the strip material protruding from both sides of the rolling roll toward the rolling roll. According to Patent Document 1, it is described that since the side end faces of the thickened portions are flattened by the side edge processing rolls, there is an advantage that a gap is less likely to occur between the thickened portions when the side end faces of the thickened portions are abutted against each other.

[0004] Japanese Patent Application Laid-Open No. 2000-288626

[0005] In the case of the roll forming technique described in Patent Document 1, the side end faces can be flattened by crushing both side edges of the strip material with the side edge processing rolls. However, in the technique described in Patent Document 1, the range of both side edges that are deformed by being crushed is not limited to the end positions and spreads in the in-plane direction, and the amount of thickening of the side end faces may be insufficient.

[0006] The present invention aims to provide a method for manufacturing a cylindrical body that offers excellent joint quality at the butt joint, by enabling the formation of a thickened portion specifically at the end when joining the butt joints of long workpieces by roll forming.

[0007] [1]: A manufacturing method for producing a cylindrical body by joining the butt joints where the ends on the long sides of a long workpiece made of aluminum or an aluminum alloy are joined together, comprising a forming step of forming the butt joint by deforming the workpiece so that the ends on the long side of the workpiece are joined together by performing roll forming on the workpiece, wherein in the forming step, the workpiece is sandwiched between an outer roll positioned on the outer surface side of the workpiece and an inner roll positioned on the inner surface side of the workpiece to process the ends of the workpiece, and the forming step comprises a bending step of sandwiching the workpiece from both sides by a first outer roll and a first inner roll, and acting the first outer roll or the first inner roll to bend the ends of the workpiece out of the plane, thereby forming a curved portion where the ends are deformed so that they are bent out of the plane, A method for manufacturing a cylindrical body, comprising: a thickness-increasing step, in which the workpiece is sandwiched from both sides by a second outer roll and a second inner roll, and the second outer roll or the second inner roll is applied to push the curved portion in the in-plane direction, thereby forming a thickened portion in which the end is deformed so that it is thickened in the out-of-plane direction.

[0008] [2]: In the bending step, a gap equal to the thickness of the workpiece is provided between the first outer roll and the first inner roll, the first outer roll contacts the outer surface of the workpiece, and the first inner roll contacts the inner surface of the workpiece, thereby sandwiching the workpiece, and the first outer roll or the first inner roll is applied to the end of the workpiece by either (1) or (2) below: (1) At the end, the first inner roll is in a positional relationship where it enters into a virtual inner surface formed when the inner surface near the end is extended in the in-plane direction, and the first outer roll is in a positional relationship where it is separated from the virtual outer surface formed when the outer surface near the end is extended in the in-plane direction, and the first outer roll is in a positional relationship where it is separated from the virtual outer surface formed when the outer surface near the end is extended in the in-plane direction, and the first outer roll is in a positional relationship where it enters into a virtual outer surface formed when the outer surface near the end is extended in the in-plane direction, The method for manufacturing a cylindrical body according to [1], wherein at the end, the first inner roll faces the first outer roll in a positional relationship that is away from a virtual inner surface formed when the inner surface near the end is extended in the in-plane direction.

[0009] [3]: In the bending step, the first outer roll or the first inner roll is applied to the end of the workpiece by either (1) in the case of (1) of [2] above or (2) in the case of (2) above, by either (1) below: (1) The first inner roll has, in a cross-sectional view through the rotation axis of the first inner roll, a first inner surface (F31) that is in contact with the workpiece and has a width shorter than the width of the inner surface in the long side direction of the workpiece, and a first inner second surface (F32) that is inclined outward from the first inner surface; The first outer roll has, in a cross-sectional view through the rotation axis of the first outer roll, a first outer surface (F21) that is in contact with the workpiece and has a width shorter than the width of the outer surface in the long side direction of the workpiece, (2) The first inner roll has a first outer surface (F21) and a first outer second surface (F22) that slopes outward from the first outer surface (F21), and in the bending step, the first outer surface (F21) contacts the outside of the workpiece, and the first inner surface (F31) contacts the inside of the workpiece, thereby sandwiching the workpiece, and the first inner second surface (F32) contacts the end of the workpiece from the inner surface side, and the first outer second surface (F22) contacts the end that has been deformed to be bent outward in the out-of-plane direction, (2) The first inner roll has, in a cross-sectional view through the rotation axis of the first inner roll, a first inner surface (F71) that is in contact with the workpiece and has a width shorter than the width of the inner surface in the long side direction of the workpiece, and a first inner second surface (F72) that slopes inward from the first inner surface, The first outer roll, in a cross-sectional view through the rotation axis of the first outer roll, has a first outer surface (F61) that, when in contact with the workpiece, has a width shorter than the width of the outer surface in the long side direction of the workpiece, and a first outer second surface (F62) that slopes inward from the first outer surface.In the bending step, the first outer surface (F61) contacts the outside of the workpiece, the first inner surface (F71) contacts the inside of the workpiece, thereby sandwiching the workpiece, and the first outer second surface (F62) contacts the end of the workpiece from the side of the outer surface, and the first inner second surface (F72) contacts the end that has been deformed to be bent inward in the out-of-plane direction, as described in [2].

[0010] [4]: In the bending step, with respect to the plate thickness Tw of the workpiece, the width Ww11i of the inner surface in the long side direction of the workpiece, the width Ww21o of the outer surface in the long side direction of the workpiece, the width Wr11i of the first inner surface (F31), and the width Wr21o of the first outer surface (F61), either (1) below in the case of (1) of [3] above, or (2) below in the case of (2) of [3] above, (1) 0.5 × Tw ≤ (Ww11i - Wr11i) / 2 ≤ 2 × Tw (2) 0.5 × Tw ≤ (Ww21o - Wr21o) / 2 ≤ 2 × Tw The method for manufacturing a cylindrical body as described in [3].

[0011] [5]: In the bending step, in the case of [3](1) above, either (1) below or in the case of [3](2) above, (2) below is satisfied: (1) When the first inner roll acts on the end from the inner surface side of the workpiece to form the curved portion in which the end is deformed toward the outer surface side, the angle between the first inner surface (F31) and the first inner surface (F32) is 40° or more and 70° or less. (2) When the first outer roll acts on the end from the outer surface side of the workpiece to form the curved portion in which the end is deformed toward the inner surface side, the angle between the first outer surface (F61) and the first outer surface (F62) is 40° or more and 70° or less. The method for manufacturing a cylindrical body as described in [3].

[0012] [6]: In the thickness-increasing step, a gap equal to the thickness of the workpiece is provided between the second outer roll and the second inner roll, the second outer roll contacts the outer surface of the workpiece, and the second inner roll contacts the inner surface of the workpiece, thereby sandwiching the workpiece, and the second outer roll or the second inner roll is applied to the end of the workpiece by either (1) or (2) below: (1) At the end, the second inner roll is in contact with the curved portion from the end face side of the workpiece in a positional relationship that allows it to enter the workpiece at the end, and At the end, the second outer roll is opposite the second inner roll in a positional relationship that allows it to move away from the virtual outer surface formed when the outer surface near the end is extended in the in-plane direction. (2) At the end, the second inner roll is in contact with the curved portion from the end face side of the workpiece in a positional relationship in which it enters into the workpiece at the end, and is in a positional relationship in which it faces the second outer roll, away from the virtual inner surface formed when the inner surface near the end is extended in the in-plane direction, and at the end, the second outer roll is in a positional relationship in which it contacts the outer surface near the end, the method for manufacturing a cylindrical body according to [1].

[0013] [7]: In the thickening step, the second outer roll or the second inner roll is applied to the end of the workpiece by either (1) below in the case of (1) of [6] or (2) below in the case of (2) of [6], (1) The second inner roll has, in a cross-sectional view through the rotation axis of the second inner roll, a second inner first surface (F51) that is in contact with the workpiece and has a width shorter than the width of the inner surface in the long side direction of the workpiece, and a second inner second surface (F52) that rises substantially perpendicularly from the second inner first surface, and the second outer roll has, in a cross-sectional view through the rotation axis of the second outer roll, a second outer first surface (F41) that is in contact with the workpiece and has a width shorter than the width of the outer surface in the long side direction of the workpiece, and a second outer second surface (F42) that slopes outward from the second outer first surface, In the thickening step, the second outer first surface (F41) contacts the outside of the workpiece, and the second inner first surface (F51) contacts the inside of the workpiece, thereby sandwiching the workpiece, and the second inner second surface (F52) contacts the curved portion from the end face side of the workpiece, and the second outer second surface (F42) contacts the end that has been deformed to be thickened outward in the out-of-plane direction, (2) The second inner roll, in a cross-sectional view passing through the rotation axis of the second inner roll, has, with the rotation axis of the second inner roll as the center, a second inner first surface (F91) that contacts the inside of the workpiece, a second inner second surface (F92) that slopes inward and extends from the second inner first surface, and a second inner third surface (F93) that is substantially perpendicular to the second inner first surface, With the second inner first surface (F91) in contact with the workpiece, the second inner first surface (F91) and the second inner second surface (F92) have a width shorter than the width of the inner surface in the long side direction of the workpiece, and the second outer roll has, in a cross-sectional view through the rotation axis of the second outer roll, a second outer first surface (F81) that, in contact with the workpiece, has a width shorter than the width of the outer surface in the long side direction of the workpiece, with respect to the rotation axis of the second outer roll.In the thickening step, the second outer first surface (F81) contacts the outside of the workpiece, the second inner first surface (F91) contacts the inside of the workpiece, thereby sandwiching the workpiece, the second inner third surface (F93) contacts the curved portion from the end face side of the workpiece, and the second inner second surface (F92) faces the end portion which has been deformed to thicken inward in the out-of-plane direction, as described in [6].

[0014] [8]: In the thickness-increasing step, in the case of (1) of [7], the second outer roll or the second inner roll is applied to the end of the workpiece by the following (1): (1) The second inner roll has a second inner corner portion formed by the second inner first surface (F51) and the second inner second surface (F52), and the radius of curvature Rc12i of the second inner corner portion and the plate thickness Tw of the workpiece satisfy the following formula: Tw × 1 / 4 ≤ Rc12i ≤ Tw × 1 / 2 The second inner corner portion contacts the end portion which has been deformed to increase thickness inward in the out-of-plane direction, the method for manufacturing a cylindrical body according to [7].

[0015] [9]: In the thickness-increasing step, in the case of (1) of [7], the second outer roll or the second inner roll is applied to the end of the workpiece by the following (1): (1) The second outer roll has a second outer corner portion formed by the second outer first surface (F41) and the second outer second surface (F42), and the radius of curvature Rc12o of the second outer corner portion and the plate thickness Tw of the workpiece satisfy the following formula: Tw × 0.6 ≤ Rc12o ≤ Tw × 0.9 The second outer corner portion contacts the end on the out-of-plane side, the method for manufacturing a cylindrical body according to [7].

[0016]

[10] : In the thickening step, with respect to the plate thickness Tw of the workpiece, the widths Ww12i, Ww22i of the inner surface in the long side direction of the workpiece, the width Wr12i of the second inner first surface (F51), and the widths Wr22i of the second inner first surface (F91) and the second inner second surface (F92), either (1) below in the case of (1) of [7] or (2) below in the case of (2) of [7] is satisfied: (1) 0.2 × Tw ≤ (Ww12i - Wr12i) / 2 ≤ 2 × Tw (2) 0.2 × Tw ≤ (Ww22i - Wr22i) / 2 ≤ 2 × Tw The method for manufacturing a cylindrical body as described in [7].

[0017]

[11] : In the thickening step, with respect to the plate thickness Tw of the workpiece, the height Hr2i of the second inner second surface (F52), and the height Hr3i of the second inner third surface (F93), either (1) below in the case of (1) of [7] or (2) below in the case of (2) of [7] must satisfy the following conditions: (1) 1.05 × Tw ≤ Hr2i ≤ 2 × Tw (2) 1.05 × Tw ≤ Hr3i ≤ 2 × Tw The method for manufacturing a cylindrical body according to [7].

[0018]

[12] : In the thickness-increasing step, the second outer roll or the second inner roll is applied to the end of the workpiece by either (1) below in the case of (1) of [7] or (2) below in the case of (2) of [7], (1) the angle θ12i between the second inner second surface (F52) and the rotation axis of the second inner roll satisfies the following equation: -10° ≤ θ12i ≤ 10° (2) the angle θ22i between the second inner third surface (F93) and the rotation axis of the second inner roll satisfies the following equation: -10° ≤ θ22i ≤ 10° The method for manufacturing a cylindrical body as described in [7].

[0019]

[13] : The method for manufacturing a cylindrical body according to

[11] , wherein the forming process involves bending the workpiece in each step to form the butt joint from a flat workpiece through multiple stages, and the angle of the end in the state before bending is set to 0°, and the angle of the end in the state after the butt joint is formed changes to α°, such that the angle θb of the end after the bending step satisfies the following equation: α × (5 / 20) ≤ θb ≤ α × (7 / 20)

[0020]

[14] : The method for manufacturing a cylindrical body according to [1], wherein in the molding step, the workpiece is deformed so that the ends on which the thickened portions are formed abut against each other to form the abutting portion, and the manufacturing method further comprises a joining step of joining the abutting portions.

[0021]

[15] : The method for manufacturing a cylindrical body according to

[14] , wherein the joining step is performed by at least one selected from the group consisting of laser joining, arc joining, ultrasonic joining, high-frequency welding, resistance seam welding, and friction stir welding.

[0022] According to the present invention, when joining the butt joints where the ends of elongated workpieces are joined together by roll forming, it is possible to form a thickened portion specifically at the ends, thereby providing a method for manufacturing a cylindrical body with excellent joining quality at the butt joints.

[0023] This is a perspective view of a cylindrical body according to the first embodiment. This is an end view of a cylindrical body according to the first embodiment. This is an end view of a welded portion of a cylindrical body according to the first embodiment. This is an explanatory diagram of a method for manufacturing a cylindrical body according to the first embodiment. This is a cross-sectional view of a roll and workpiece used in a bending step according to the first embodiment. This is a cross-sectional view of a roll and workpiece used in a thickness-increasing step according to the first embodiment. This is an explanatory diagram of a roll flower according to the first embodiment. This is a cross-sectional view of a roll used in a bending step according to the first embodiment. This is an enlarged view of Figure 8. This is an explanatory diagram of the positional relationship between the roll and workpiece used in a bending step according to the first embodiment. This is an explanatory diagram of the bending and straightening of the end of a workpiece by a bending step according to the first embodiment, where (a) is a side view of the end of the workpiece before bending and straightening, and (b) is a side view of the end of the workpiece after bending and straightening. (a) is a cross-sectional view of a roll used in a thickness-increasing step according to the first embodiment, and (b) is an explanatory diagram of the angle between the face of the roll and the axis of rotation of the roll. This is an enlarged view of Figure 12(a). This is an explanatory diagram of the positional relationship between the roll and workpiece used in a thickness-increasing step according to the first embodiment. This is an explanatory diagram of the thickening step according to the first embodiment, where (a) is a side view of the workpiece before thickening and (b) is a side view of the workpiece after thickening. This is an end view of the workpiece after the molding process is completed according to the first embodiment. This is an enlarged view of Figure 16. This is an explanatory diagram of the joining process according to the first embodiment. This is an explanatory diagram of beam welding according to the first embodiment. This is a cross-sectional view (1 / 4) of the butt joint of a conventional workpiece. This is a cross-sectional view (2 / 4) of the butt joint of a conventional workpiece. This is a cross-sectional view of the welded part of a conventional workpiece. This is an explanatory diagram (3 / 4) of the butt joint of a conventional workpiece. This is an explanatory diagram (4 / 4) of the butt joint of a conventional workpiece. This is a cross-sectional view of the roll and workpiece used in the bending step according to the second embodiment. This is a cross-sectional view of the roll and workpiece used in the thickening step according to the second embodiment. This is an explanatory diagram of the roll flower according to the second embodiment. This is a cross-sectional view of the roll used in the bending step according to the second embodiment. This is an enlarged view of Figure 28. This is an explanatory diagram of the positional relationship between the roll and workpiece used in the bending step according to the second embodiment. This is an explanatory diagram of the bending step according to the second embodiment, where (a) is a side view of the workpiece before bending and (b) is a side view of the workpiece after bending and straightening.(a) is a cross-sectional view of the roll used in the thickening step according to the second embodiment, and (b) is an explanatory diagram of the angle between the face of the roll and the axis of rotation of the roll. This is an enlarged view of Figure 32(a). This is an explanatory diagram of the positional relationship between the roll and the workpiece used in the thickening step according to the second embodiment. This is an explanatory diagram of the thickening step according to the second embodiment, where (a) is a side view of the workpiece before thickening, and (b) is a side view of the workpiece after thickening. This is an end view of the workpiece after the molding process is completed according to the second embodiment. This is an enlarged view of Figure 36. This is an explanatory diagram of the joining process according to the second embodiment. This is an explanatory diagram of beam welding according to the first modified example. This is an explanatory diagram of a welded part by tandem beam welding according to the first modified example. This is an explanatory diagram of beam welding according to the second modified example. (a) is a side cross-sectional view when performing ring beam welding, and (b) is a schematic diagram showing the profiles of the ring beam and core beam when performing ring beam welding. This is an explanatory diagram of a welded part by ring beam welding according to the second modified example. This is an explanatory diagram of a tensile test of a cylindrical body according to this embodiment.

[0024] Embodiments of the present invention will be described with reference to the drawings as appropriate. The present invention is not limited to the following embodiments. Furthermore, some or all of the components in the embodiments and modifications can be combined as appropriate. Note that each drawing is a schematic illustration and does not necessarily correspond to the actual length, width, thickness, dimensional ratio, etc. Note that the term "parallel" includes the meaning of approximately parallel. The term "perpendicular" includes the meaning of approximately perpendicular.

[0025] [1. First Embodiment] [Cylindrical Body] Figure 1 is a perspective view of a cylindrical body according to the first embodiment. Figure 2 is an end view of the cylindrical body according to the first embodiment. The cylindrical body 100 is a manufactured product produced by roll forming and laser welding. The cylindrical body 100 has a rectangular shape in axial view and rounded corners. The cylindrical body 100 is made of a metal including aluminum or an aluminum alloy. A welded portion 101 is formed on the upper part of the cylindrical body 100. The welded portion 101 is a weld bead parallel to the axial direction (x direction) at the upper center of the cylindrical body 100.

[0026] Figure 3 is an end view of the welded portion of a cylindrical body according to the first embodiment. Figure 3 corresponds to an enlarged view of the upper center of the cylindrical body 100. As shown in Figure 3, in the welded portion 101, a weld bead 102 is formed that rises outward from the outer surface of the upper part of the cylindrical body 100. In addition, in the welded portion 101, a back bead 103 is formed that rises inward from the inner surface of the upper part of the cylindrical body 100.

[0027] [Manufacturing Method] Figure 4 is an explanatory diagram of a manufacturing method for a cylindrical body according to the first embodiment. As shown in Figure 4, when manufacturing the cylindrical body 100, a long workpiece 1 is used. The workpiece 1 is made of metal, including aluminum or an aluminum alloy. In the manufacturing method of the first embodiment, the butt joints are formed when the ends on the long sides of the workpiece 1 are joined together.

[0028] The manufacturing method comprises a molding process and a joining process. The molding process involves using rolls 104 and 105 that grip the workpiece 1 being transported to perform roll forming on the workpiece 1, thereby deforming the workpiece 1 so that its long edges abut against each other and forming a joint. The joining process involves joining the abutted joint by performing laser welding (laser joining) using a laser beam 106 emitted by a welding device (not shown).

[0029] Note that the direction of the longer side of workpiece 1 is the same as the transport direction (x direction) of workpiece 1 in roll forming. "Ends in the direction of the longer side" refers to the ends in the width direction perpendicular to the length direction of the elongated workpiece 1.

[0030] In roll forming, a pair of rolls that sandwich the workpiece are arranged in multiple stages in the conveying direction to form it. However, for the sake of illustration, Figure 4 shows only one stage of the pair of rolls 104 and 105, and the other rolls are omitted from the illustration. Also, in roll forming, the workpiece is formed over multiple stages by multiple stages of rolls that sandwich it. However, for the sake of illustration, Figure 4 shows only one stage of forming, and the forming by the other rolls is omitted from the illustration. The rolls arranged in each stage can be divided into outer rolls and inner rolls. In the forming process, the workpiece 1 is sandwiched between the outer rolls positioned on the outer surface side of the workpiece 1 and the inner rolls positioned on the inner surface side of the workpiece 1, and the end of the workpiece 1 is processed (end processing).

[0031] The "outer side" refers to the side of the roll that contacts the outside of the workpiece 1, which will ultimately become a cylindrical body 100. In the initial stages of roll forming, the outer roll contacts and deforms the workpiece 1 from below, but from the middle stages onward, it also contacts and deforms the workpiece 1 from above. The "inner side" refers to the side of the roll that contacts the inside of the workpiece 1, which will ultimately become a cylindrical body 100. In the initial stages of roll forming, the inner roll contacts and deforms the workpiece 1 from above.

[0032] Additionally, if necessary, in the latter half of the roll forming process, the workpiece 1 may be deformed using an upper roll that contacts and deforms it from the upper outside, and a lower roll that contacts and deforms it from the lower outside.

[0033] The molding process can be broken down into multiple n-th stage molding processes, where n is the number of pairs of rolls arranged in multiple stages in the conveying direction. Molding is performed step by step from the first stage by roll forming, and finally molding is performed up to the nth stage, thereby forming the butt joint.

[0034] [Rolls] Figure 5 is a cross-sectional view of the rolls and workpiece used in the bending step according to the first embodiment. The bending step corresponds to the second forming step. In the second forming step, the outer roll 2 and the inner roll 3, which are rolls used in roll forming, act on the workpiece 1. The outer roll 2 (first outer roll) is a roll positioned on the outer surface so (bottom surface) (see Figure 10) side of the workpiece 1. The outer roll 2 rotates around a rotation axis 21 that extends horizontally (y direction) and processes the workpiece 1. The inner roll 3 (first inner roll) is a roll positioned on the inner surface si (top surface) (see Figure 10) side of the workpiece 1. The inner roll 3 rotates around a rotation axis 31 that extends horizontally and processes the workpiece 1. As shown in Figure 5, when the outer roll 2 is viewed in cross-section on a plane including the rotation axis 21, it has a symmetrical shape centered on a plane perpendicular to the rotation axis 21 at a central position along the direction of the rotation axis 21. As shown in Figure 6, when the inner roll 3 is viewed in cross-section on a plane containing the rotation axis 31, it has a symmetrical shape centered on a plane perpendicular to the rotation axis 31 at a central position along the direction of the rotation axis 31.

[0035] In the second molding process, the workpiece 1 is sandwiched from both sides by the outer roll 2 and the inner roll 3, and the outer roll 2 or the inner roll 3 is applied to bend the end portion E11 of the workpiece 1 (see Figure 11(a)) out of the plane. As a result, a curved portion B11 (see Figure 11(b)) is formed, which is deformed so that the end portion E11 of the workpiece 1 is bent out of the plane.

[0036] Figure 6 is a cross-sectional view of the rolls and workpiece used in the thickness-increasing step according to the first embodiment. The thickness-increasing step corresponds to the third forming step. In the third forming step, the outer roll 4 and the inner roll 5, which are rolls used in roll forming, act on the workpiece 1. The outer roll 4 (second outer roll) is a roll positioned on the outer surface so (bottom surface) side of the workpiece 1. The outer roll 4 rotates around a rotation axis 41 that extends horizontally (y direction) and processes the workpiece 1. The inner roll 5 (second inner roll) is a roll positioned on the inner surface si (top surface) side of the workpiece 1. The inner roll 5 rotates around a rotation axis 51 that extends horizontally and processes the workpiece 1. As shown in Figure 6, when the outer roll 4 is viewed in cross-section on a plane including the rotation axis 41, it has a symmetrical shape centered on a plane perpendicular to the rotation axis 41 at a central position along the direction of the rotation axis 41. As shown in Figure 6, when the inner roll 5 is viewed in cross-section on a plane containing the rotation axis 51, it has a symmetrical shape centered on a plane perpendicular to the rotation axis 51 at a central position along the direction of the rotation axis 51.

[0037] In the third forming stage, the workpiece 1 is sandwiched from both sides by the outer roll 4 and the inner roll 5, and the outer roll 4 or the inner roll 5 is applied to push the curved portion B11 formed in the second forming stage in the in-plane direction. As a result, a thickened portion B12 (see Figure 15(b)) is formed in which the end portion E12 (see Figure 15(a)) of the workpiece 1 is deformed to increase in thickness in the out-of-plane direction.

[0038] Figure 7 is an explanatory diagram of the roll flower according to the first embodiment. The roll flower shows the superimposed cross-sections of the workpiece formed by the outer roll and inner roll in each of the n-th stage forming processes. The numerical value in Figure 7 is the value of n. The roll flower can be used to show how the workpiece is gradually formed into a three-dimensional shape. In Figure 7 and Figure 27, which will be described later, the shapes of the workpiece in the first to third stages and the nth stage are shown, and the shapes of the workpiece in the remaining stages are omitted.

[0039] [Bending Step] Figure 8 is a cross-sectional view of the roll used in the bending step according to the first embodiment. Figure 9 is an enlarged view of Figure 8. Figure 10 is an explanatory diagram of the positional relationship between the roll and the workpiece used in the bending step according to the first embodiment. For convenience of illustration, the workpiece 1 is not shown in Figures 8 and 9. Figure 10 corresponds to Figure 9, with the workpiece 1 shown after the bending step and before end forming added.

[0040] As shown in Figures 8 and 9, in the bending step, a gap equal to the thickness of the workpiece 1 is provided between the outer roll 2 and the inner roll 3. As shown in Figure 10, in the bending step, the outer roll 2 contacts the outer surface so (bottom surface) of the workpiece 1, and the inner roll 3 contacts the inner surface si (top surface) of the workpiece 1, thereby sandwiching the workpiece 1.

[0041] Furthermore, by clamping the workpiece 1, bending is performed at a predetermined position spaced apart from the end of the workpiece 1 toward the center in the width direction. This bending process forms a rounded corner between the upper and side portions of the cylindrical body 100. For the sake of explanation, the bending process that forms the rounded corner of the cylindrical body 100 is sometimes referred to as "corner processing."

[0042] As shown in Figure 10, in the bending step, the outer roll 2 or the inner roll 3 is applied to the end of the workpiece 1 in the following manner A1. <Manner A1> At the end E11 of the workpiece 1, the inner roll 3 is in contact with the end E11 from the inner surface si side of the workpiece 1, in a positional relationship in which it enters the interior of the virtual inner surface vi11 (first virtual inner surface) that is formed when the inner surface si near the end is extended in the in-plane direction. Also at the end E11 of the workpiece 1, the outer roll 2 is in a positional relationship in which it faces the inner roll 3, away from the virtual outer surface vo11 (first virtual outer surface) that is formed when the outer surface so near the end is extended in the in-plane direction.

[0043] Except for the end E11 of workpiece 1, the distance between the outer roll 2 and the inner roll 3 is approximately the same as the thickness of workpiece 1, with the outer roll 2 and the inner roll 3 sandwiching workpiece 1.

[0044] At the end E11 of the workpiece 1, the outer roll 2 faces the inner roll 3 in a positional relationship away from the virtual outer surface vo11, so a clearance is provided between the outer roll 2 and the virtual outer surface vo11. Also, the inner roll 3 contacts the end E11 from the inner surface si side of the workpiece 1 in a positional relationship where the inner roll 3 enters inside the virtual inner surface vi11, so a force directed outward in the out-of-plane direction is applied to the end E11. At this time, the end E11 in contact with the inner roll 3 is deformed so as to escape into the clearance between the outer roll 2 and the virtual outer surface vo11, and thus the end E11 is deformed so as to be bent outward in the out-of-plane direction.

[0045] More specifically, as shown in FIGS. 8 to 10, in the bending step, the outer roll 2 or the inner roll 3 is applied to the end E11 of the workpiece 1 according to the following aspect A2. <Aspect A2> In a cross-sectional view passing through the rotation axis 31 of the inner roll 3, the inner roll 3 has a first inner first surface F31 having a width shorter than the width of the inner surface si in the long side direction of the workpiece 1 in a state of contacting the workpiece 1 around the rotation axis 31 of the inner roll 3, and a first inner second surface F32 that slopes outward and expands from the first inner first surface F31. The outer roll 2 has a first outer first surface F21 having a width shorter than the width of the outer surface so in the long side direction of the workpiece 1 in a state of contacting the workpiece 1 around the rotation axis 21 of the outer roll 2 in a cross-sectional view passing through the rotation axis 21 of the outer roll 2, and a first outer second surface F22 that slopes outward and expands from the first outer first surface F21. In the bending step, the first outer first surface F21 contacts the outside of the workpiece 1, and the first inner first surface F31 contacts the inside of the workpiece 1, sandwiching the workpiece 1. The first inner second surface F32 contacts the end E11 from the side of the inner surface si of the workpiece 1. The first outer second surface F22 contacts the end E11 deformed so as to be bent outward in the out-of-plane direction.

[0046] As shown in FIGS. 5 and 9, the "first inner first surface F31" is a surface extended by rotating a line segment connecting points 3b, 3b prepared on the surface of the inner roll 3 along the surface of the inner roll 3 about the rotation axis 31. The width Wr11i of the first inner first surface F31 is shorter than the width Ww11i of the inner surface si in the long side direction of the work 1 (see FIGS. 5, 9, and 10).

[0047] Point 3a is a point on the boundary of the partial surface of the inner roll 3 that forms the corner of the work 1 by corner processing. Point 3b is a point on the boundary of the first inner first surface F31 and is located at both ends of the first inner first surface F31. The position of point 3b is set so that the width Wr11i of the first inner first surface F31 is shorter than the width Ww11i of the inner surface si in the long side direction of the work 1. Point 3b is arranged symmetrically from the center of the inner roll. Point 3b is also a point on the boundary of the first inner second surface F32.

[0048] As shown in FIG. 9, the "first inner second surface F32" is a surface extended by rotating a line segment connecting points 3b, 3c prepared on the surface of the inner roll 3 along the surface of the inner roll 3 about the rotation axis 31. Point 3c is a boundary point on the opposite side of point 3b with respect to the first inner second surface F32 among the boundary points of the first inner second surface F32.

[0049] As shown in FIGS. 5 and 9, the "first outer first surface F21" is a surface extended by rotating a line segment connecting points 2b, 2b prepared on the surface of the outer roll 2 along the surface of the outer roll 2 about the rotation axis 21. The width Wr11o of the first outer first surface F21 is shorter than the width Ww11o of the outer surface so in the long side direction of the work 1.

[0050] Point 2a is a point on the boundary of the partial surface of the outer roll 2, which forms the corner of the workpiece 1 by corner machining. Point 2b is a point on the boundary of the first outer surface F21, located at both ends of the first outer surface F21. The position of point 2b is set such that the width Wr11o of the first outer surface F21 is shorter than the width Ww11o of the outer surface so in the long side direction of the workpiece 1. Point 2b is positioned symmetrically from the center of the inner roll. Point 2b is also a point on the boundary of the first outer surface F22.

[0051] As shown in Figure 9, the "first outer second surface F22" is a surface extended by rotating a line segment connecting points 2b and 2c, which are prepared on the surface of the outer roll 2, along the surface of the outer roll 2, around the rotation axis 21. Point 2c is a point on the boundary of the first outer second surface F22 that is on the opposite side of the boundary from point 2b with respect to the first outer second surface F22.

[0052] Figure 11 is an explanatory diagram of the bending and straightening of the end of a workpiece by a bending step according to the first embodiment, where (a) is a side view of the end of the workpiece before bending and straightening, and (b) is a side view of the end of the workpiece after bending and straightening. Figure 11(b) shows the shape of the curved portion formed by the bending step.

[0053] As shown in Figures 8 to 11, the bending step satisfies the following embodiment A3. <Embodiment A3> The thickness Tw of workpiece 1, the width Ww11i of the inner surface si in the long side direction of workpiece 1, and the width Wr11i of the first inner surface F31 satisfy the following equation (1-1): 0.5 × Tw ≤ (Ww11i - Wr11i) / 2 ≤ 2 × Tw Equation (1-1)

[0054] Note that Ww11i corresponds to the width dimension of the upper surface of workpiece 1 (along the width of the first inner surface F31) when workpiece 1, which has not undergone end processing, is in contact with the inner roll 3. Ww11o corresponds to the width dimension of the lower surface of workpiece 1 (along the width of the first outer surface F21) when workpiece 1, which has not undergone end processing, is in contact with the outer roll 2. Wr11i corresponds to the length of the line segment connecting points 3b, 3b in Figures 5 and 9 along the surface of the first inner surface F31. Wr11o corresponds to the length of the line segment connecting points 2b, 2b in Figures 5 and 9 along the surface of the first outer surface F21. (Ww11i - Wr11i) / 2 is the value obtained by subtracting the length of the first inner surface F31 Wr11i from the width dimension of the upper surface of workpiece 1 in contact with the inner roll 3, and then dividing by 2. The width Ww11i of the inner surface si of workpiece 1 in contact with the inner roll 3 is longer than the length Wr11i of the first inner surface F31 by (Ww11i - Wr11i), and both ends E11, E11 of workpiece 1 extend in the width direction beyond the first inner surface F31. In this case, (Ww11i - Wr11i) / 2 corresponds to the length at one end of how much longer the width Ww11i of the inner surface si of workpiece 1 is compared to the length Wr11i of the first inner surface F31. The length of the curved portion B11 and the height of the thickened portion B12 will change according to the length of (Ww11i - Wr11i) / 2. Note that Wr11i is a specific example of Wr1i. Wr11o is a specific example of Wr1o.

[0055] The lower limit of (Ww11i - Wr11i) / 2 is preferably 0.7 × Tw or more, more preferably 0.8 × Tw or more, and even more preferably 0.9 × Tw or more. The upper limit of (Ww11i - Wr11i) / 2 is preferably 1.5 × Tw or less, more preferably 1.2 × Tw or less, even more preferably 1.0 × Tw or less, and even more preferably less than 1.0 × Tw. Above the lower limit, it is easy to make the thickened portion B12 appropriately large in the subsequent thickening step. Below the upper limit, it is easy to compress and deform the curved portion B11 so that it collapses without bending in the subsequent thickening step, thereby forming the thickened portion B12. In other words, a thickened portion B12 of an appropriate size can be formed.

[0056] Furthermore, as shown in Figure 11, the in-plane length Lb1 of the curved portion B11 formed in the bending step, and the plate thickness Tw of the workpiece 1 satisfy the following equation (1-2): 0.5 × Tw ≤ Lb1 ≤ 2 × Tw Equation (1-2)

[0057] "Length Lb1 in the in-plane direction of the curved portion B11" does not refer to the length along the in-plane direction (along the curved surface), but rather the length along the virtual inner surface vi11 formed when the inner surface si near the end E11 of the workpiece 1 is extended in the in-plane direction. Specifically, as shown in Figure 11, if points 1a and 1b are prepared on the surface of the workpiece 1, and point 1c is prepared on the virtual inner surface vi11, then Lb1 is the length of the line segment connecting point 1a and point 1c. Point 1a is a point on the boundary between the inner surface si (plane) near the end E11 of the workpiece 1 and the surface of the curved portion B11 of the workpiece 1. Point 1b is the outermost point on the surface of the curved portion B11 of the workpiece 1, toward the end of the workpiece 1. Point 1c is the point obtained by projecting point 1b perpendicularly onto the virtual inner surface vi11. Lb1 corresponds to the length of the bent portion B11 formed by bending the end E11 (bend length).

[0058] The lower limit of Lb1 is preferably 0.7 × Tw or more, more preferably 0.8 × Tw or more, and even more preferably 0.9 × Tw or more. The upper limit of Lb1 is preferably 1.5 × Tw or less, more preferably 1.2 × Tw or less, even more preferably 1.0 × Tw or less, and even more preferably less than 1.0 × Tw. Above the lower limit, it is easy to make the thickened portion B12 appropriately large in the subsequent thickening step. Below the upper limit, in the subsequent thickening step, the curved portion B11 is compressed and deformed so as to be crushed rather than bent, making it easier to form the thickened portion B12.

[0059] Furthermore, the bending step satisfies the following embodiment A4. <Embodiment A4> When the inner roll 3 acts on the end E11 from the inner surface si side of the workpiece 1, forming a curved portion B11 in which the end E11 deforms toward the outer surface so side, the angle θ(41) between the first inner surface F31 and the first inner surface F32 is 40° or more and 70° or less. The angle θ(41) represents the inclination angle of the first inner surface F32 with respect to the first inner surface F31, which is an inclined surface that acts on the end E11 to form the curved portion B11. More specifically, as shown in Figure 9, the angle θ(41) represents the angle between the surface of the first inner surface F31 near the end that is connected to the first inner surface F32, and the first inner surface F32. Hereafter, the same relationship will be assumed for the relationships between surfaces on the roll described in this specification.

[0060] The lower limit of the angle θ(41) is preferably 45° or more, more preferably 50° or more. The upper limit of the angle θ(41) is preferably 65° or less, more preferably 60° or less. Above the lower limit, it becomes easier to limit the formation range of the thickened portion B12 without the deformation range widening in the subsequent thickening step. Below the upper limit, it becomes easier to form the thickened portion B12 by compressing and deforming the curved portion B11 so that it collapses rather than bending in the subsequent thickening step.

[0061] The angle θ(42) between the first outer surface F21 and the first outer surface F22 is between 40° and 70°. The angle θ(42) represents the inclination angle of the first outer surface F22 with respect to the first outer surface F21.

[0062] Furthermore, as shown in Figure 11, the curved portion B11 formed in the bending step satisfies the following embodiment A5. <Embodiment A5> When the inner roll 3 acts on the end portion E11 from the inner surface si side of the workpiece 1, and the end portion E11 deforms toward the outer surface so side to form a curved portion B11, the angle θ(51) between the virtual inner surface vi11 formed when the inner surface si near the end portion E11 is extended in the in-plane direction and the curved portion B11 is 40° or more and 70° or less.

[0063] As shown in Figure 11, the "angle between the virtual inner surface vi11 and the curved portion B11" is the angle θ(51) (acute angle) between the virtual inner surface vi11 and the inner surface si (plane) of the curved portion B11 that abuts the first inner second surface F32. The angle θ(51) corresponds to the angle of bending (bending angle) of the curved portion B11 formed by bending the end E11.

[0064] [Thickening Step] Figure 12 (a) is a cross-sectional view of the roll used in the thickening step according to the first embodiment, and (b) is an explanatory diagram of the angle between the surface of the roll and the axis of rotation of the roll. Figure 13 is an enlarged view of Figure 12(a). Figure 14 is an explanatory diagram of the positional relationship between the roll and the workpiece used in the thickening step according to the first embodiment. For convenience of illustration, the workpiece 1 is not shown in Figures 12 and 13. Figure 14 corresponds to Figure 13 with the workpiece 1 shown after the thickening step and before end forming added.

[0065] As shown in Figures 12 and 13, in the thickness-increasing step, a gap equal to the thickness of the workpiece 1 is provided between the outer roll 4 and the inner roll 5. As shown in Figure 14, in the thickness-increasing step, the outer roll 4 contacts the outer surface so (bottom surface) of the workpiece 1, and the inner roll 5 contacts the inner surface si (top surface) of the workpiece 1, thereby sandwiching the workpiece 1.

[0066] As shown in Figure 14, in the thickening step, the outer roll 4 or the inner roll 5 is applied to the end E12 of the workpiece 1 in the following manner A6. <Manner A6> At the end E12 of the workpiece 1, the inner roll 5 is in contact with the curved portion B11 from the end face side of the workpiece 1 in a positional relationship in which it enters into the workpiece 1 at the end E12. Also, at the end E12 of the workpiece 1, the outer roll 4 is in a positional relationship in which it faces the inner roll 5, away from the virtual outer surface vo12 (second virtual outer surface) that is formed when the outer surface so near the end E12 is extended in the in-plane direction.

[0067] At the end E12 of the workpiece 1, the inner roll 5 is positioned opposite the outer roll 4 in a way that it contacts a virtual inner surface vi12 (a second virtual inner surface) that is formed when the inner surface si near the end E12 is extended in the in-plane direction. Outside of the end E12 of the workpiece 1, the distance between the outer roll 4 and the inner roll 5 is approximately the same as the thickness of the workpiece 1, with the outer roll 4 and the inner roll 5 sandwiching the workpiece 1.

[0068] At the end E12 of workpiece 1, the outer roll 4 is positioned away from the virtual outer surface vo12 and faces the inner roll 5, creating a clearance between the outer roll 4 and the virtual outer surface vo12. Furthermore, the inner roll 5 enters into workpiece 1 and contacts the curved portion B11 from the end face side of workpiece 1, applying an outward force in the out-of-plane direction to the curved portion B11. At this time, the curved portion B11 that has come into contact with the inner roll 5 deforms to escape into the clearance between the outer roll 4 and the virtual outer surface vo12, causing the end E12 to be deformed so that it is thickened outward in the out-of-plane direction, forming the thickened portion B12. Moreover, in embodiment A6 in which the thickened portion B12 is formed on the outside, the reaction force from the workpiece to the action from the inner roll 5 toward the curved portion B11 can be made to act in the direction toward the rotation axis 51 of the inner roll 5. In other words, the force from the workpiece generated when forming the thickened portion B12 can be received by the rotation axis 51 of the inner roll 5. Furthermore, because the inner roll 5 is positioned opposite the outer roll 4 in a positional relationship where it contacts the second virtual inner surface vi12, it is possible to suppress deformation such that the deformed curved portion B11 becomes thicker on the inner roll 5 side.

[0069] More specifically, as shown in Figures 12 to 14, in the thickening step, the outer roll 4 or the inner roll 5 is applied to the end E12 of the workpiece 1 according to the following embodiment A7. <Embodiment A7> The inner roll 5 has, in a cross-sectional view through the rotation axis 51 of the inner roll 5, a second inner first surface F51 that is in contact with the workpiece 1 and has a width shorter than the width of the inner surface si in the long side direction of the workpiece 1, and a second inner second surface F52 that rises substantially perpendicularly from the second inner first surface F51. The outer roll 4 has, in a cross-sectional view through the rotation axis 41 of the outer roll 4, a second outer first surface F41 that is in contact with the workpiece 1 and has a width shorter than the width of the outer surface so in the long side direction of the workpiece 1, and a second outer second surface F42 that slopes outward from the second outer first surface F41. In the thickening step, the second outer first surface F41 contacts the outside of the workpiece 1, and the second inner first surface F51 contacts the inside of the workpiece 1, thereby sandwiching the workpiece 1. The second inner second surface F52 contacts the curved portion B11 from the end face side of the workpiece 1. The second outer second surface F42 contacts the end portion E12 which has been deformed to thicken outwards in the out-of-plane direction.

[0070] As shown in Figures 6 and 13, the "second inner first surface F51" is a surface extended by rotating a line segment connecting points 5c, 5c prepared on the surface of the inner roll 5 along the surface of the inner roll 5, around the rotation axis 51. The width Wr12i of the second inner first surface F51 is shorter than the "width Ww12i of the inner surface si in the long side direction of the workpiece 1".

[0071] Point 5a is a point on the boundary of the partial surface of the inner roll 5, which forms the corner of the workpiece 1 by corner machining. Point 5b is also a point on the boundary of the second inner corner portion 52, which is rounded. The second inner corner portion 52 is a surface that extends by rotating a line segment connecting points 5b and 5c, which are prepared on the surface of the inner roll 5, along the surface of the inner roll 5, around the rotation axis 51. The second inner corner portion 52 is sandwiched between the second inner first surface F51 and the second inner second surface F52.

[0072] As shown in Figure 13, the "second inner second surface F52" is a surface that extends by rotating a line segment connecting points 5c and 5d prepared on the surface of the inner roll 5 along the surface of the inner roll 5, around the rotation axis 51.

[0073] Point 5c is a point on the boundary of the second inner first surface F51, and is located at both ends of the second inner first surface F51. The position of point 5c is set such that the width Wr12i of the second inner first surface F51 is shorter than the width Ww12i of the inner surface si in the long side direction of the workpiece 1. Point 5c is positioned symmetrically from the center of the inner roll. Point 5c is also a point on the boundary of the second inner second surface F52. Point 5c is also a point on the boundary opposite to point 5b with respect to the second inner corner portion 52. Point 5d is a point on the boundary of the second inner second surface F52, and is a point on the boundary opposite to point 5c with respect to the second inner second surface F52.

[0074] As shown in Figures 6 and 13, the "second outer first surface F41" is a surface that extends by rotating a line segment connecting points 4b, 4b prepared on the surface of the outer roll 4 along the surface of the outer roll 4, around the rotation axis 41. The width Wr12o of the second outer first surface F41 is shorter than the "width Ww12o of the outer surface so in the long side direction of the workpiece 1".

[0075] Point 4a is a point on the boundary of the partial surface of the outer roll 4, which forms the corner of the workpiece 1 by corner machining. Point 4b is a point on the boundary of the second outer first surface F41, and is located at both ends of the second outer first surface F41. The position of point 4b is set such that the width Wr12o of the second outer first surface F41 is shorter than the width Ww12o of the outer surface so in the long side direction of the workpiece 1. Point 4b is positioned symmetrically from the center of the outer roll. Point 4b is a point on the boundary of the second outer first surface F41. Point 4b is also a point on the boundary of the rounded second outer corner portion 42. The second outer corner portion 42 is a surface extended by rotating a line segment connecting points 4b and 4c, which are prepared on the surface of the outer roll 2, along the surface of the outer roll 4, around the rotation axis 21. The second outer corner portion 42 is sandwiched between the second outer first surface F41 and the second outer second surface F42.

[0076] As shown in Figure 13, the "second outer surface F42" is a surface that extends by rotating a line segment connecting points 4c and 4d prepared on the surface of the outer roll 4 along the surface of the outer roll 4, around the rotation axis 41.

[0077] Point 4c is a point on the boundary of the second outer second surface F42. Point 4c is also a point on the boundary opposite to point 4b with respect to the second outer corner portion 42. Point 4d is a point on the boundary of the second outer second surface F42 that is opposite to point 4c with respect to the second outer second surface F42.

[0078] As shown in Figure 13, in the thickening step, the inner roll 5 is applied to the end E12 of the workpiece 1 in the following manner A8. <Manner A8> The inner roll 5 has a second inner corner portion 52 formed by a second inner first surface F51 and a second inner second surface F52, and the following equation (1-3) is satisfied for the radius of curvature Rc12i of the second inner corner portion 52 and the thickness Tw of the workpiece. Tw × 1 / 4 ≤ Rc12i ≤ Tw × 1 / 2 Equation (1-3) The second inner corner portion 52 contacts the end E12 which has been deformed to be thickened inward in the out-of-plane direction.

[0079] The lower limit of Rc12i is preferably Tw × (11 / 40) or more, more preferably Tw × (12 / 40) or more. The upper limit of Rc12i is preferably Tw × (18 / 40) or less, more preferably Tw × (16 / 40) or less. Above the lower limit, the cutting accuracy of the formation of the second inner corner portion 52 can be maintained at a predetermined level or higher. However, when manufacturing from a viewpoint other than industrial considerations, the lower limit does not need to be particularly limited. Below the upper limit, when the end portions E12 are butted together, the thinning caused by the gap created by the rounded portion provided in the thickened portion B12 can be suppressed.

[0080] Figure 15 is an explanatory diagram of the thickening step according to the first embodiment, where (a) is a side view of the workpiece before thickening and (b) is a side view of the workpiece after thickening. Figure 15(a) shows the shape of the curved portion. Figure 15(b) shows the shape of the thickened portion formed by the thickening step.

[0081] As shown in Figure 15(b), the thickened portion B12 formed in the thickening step satisfies the following embodiment A9. <Embodiment A9> When the inner roll 5 acts on the end E12 from the inner surface si side of the workpiece 1, and the end E12 thickens to form a thickened portion B12 on the outer surface so side, an inner corner portion 11 is formed on the inner surface si side of the thickened portion B12 by the inner surface si and the end face of the thickened portion B12, and the radius of curvature Rt1 of the inner corner portion 11 of the thickened portion B12 and the plate thickness Tw of the workpiece 1 satisfy the following equation (1-4). Tw × 1 / 4 ≤ Rt1 ≤ Tw × 1 / 2 Equation (1-4)

[0082] The lower limit of Rt1 is preferably Tw × (11 / 40) or more, more preferably Tw × (12 / 40) or more. The upper limit of Rt1 is preferably Tw × (18 / 40) or less, more preferably Tw × (16 / 40) or less.

[0083] In the thickening step, the outer roll 4 is applied to the end E12 of the workpiece 1 in the following manner A10. <Manner A10> The outer roll 4 has a second outer corner portion 42 formed by a second outer first surface F41 and a second outer second surface F42, and the following equation (1-5) is satisfied for the radius of curvature Rc12o of the second outer corner portion 42 and the plate thickness Tw of the workpiece 1. Tw × 0.6 ≤ Rc12o ≤ Tw × 0.9 Equation (1-5) The second outer corner portion 42 contacts the end E12 of the workpiece 1 on the outward side in the out-of-plane direction.

[0084] The lower limit of Rc12o is preferably Tw × (65 / 100) or more, more preferably Tw × (70 / 100) or more. The upper limit of Rc12o is preferably Tw × (85 / 100) or less, more preferably Tw × (80 / 100) or less. Above the lower limit, it becomes easier to form the thickened portion B12. Below the upper limit, it becomes easier to secure the in-plane thickness (volume) of the thickened portion B12.

[0085] As shown in Figure 15(b), the thickened portion B12 formed in the thickening step satisfies the following embodiment A11. <Embodiment A11> When the outer roll 4 acts on the end E12 from the outer surface so side of the workpiece 1, and the end E12 forms a thickened portion B12 on the outer surface so side, an outer corner portion 12 is formed on the outer surface so side of the thickened portion B12 by the outer surface so and the slope of the thickened portion B12, and the radius of curvature Rtt1 of the outer corner portion 12 of the thickened portion B12 and the plate thickness Tw of the workpiece 1 satisfy the following equation (1-6). Tw × 0.5 ≤ Rtt1 ≤ Tw × 1.0 Equation (1-6)

[0086] The lower limit of Rtt1 is preferably Tw × (6 / 10) or more, more preferably Tw × (7 / 10) or more. The upper limit of Rtt1 is preferably Tw × (9 / 10) or less, more preferably Tw × (8 / 10) or less.

[0087] As shown in Figures 12 to 15, the following embodiment A12 is satisfied in the thickening step. <Embodiment A12> The following equation (1-7) is satisfied for the thickness Tw of workpiece 1, the width Ww12i of the inner surface si in the long side direction of workpiece 1, and the width Wr12i of the second inner first surface F51. 0.2 × Tw ≤ (Ww12i - Wr12i) / 2 ≤ 2 × Tw Equation (1-7)

[0088] Note that Ww12i corresponds to the width dimension of the upper surface of workpiece 1 (along the direction of the second inner first surface F51) when workpiece 1, which has not undergone end processing, is in contact with the inner roll 5. Ww12o corresponds to the width dimension of the lower surface of workpiece 1 (along the direction of the second outer first surface F41) when workpiece 1, which has not undergone end processing, is in contact with the outer roll 4. Wr12i corresponds to the length of the line segment connecting points 5c, 5c in Figures 6 and 13 along the surface of the second inner first surface F51. Wr12o corresponds to the length of the line segment connecting points 4b, 4b in Figures 6 and 13 along the surface of the second outer first surface. (Ww12i - Wr12i) / 2 is the value obtained by subtracting the length Wr12i of the second inner first surface F51 from the width dimension Ww12i of the upper surface of workpiece 1 when it is in contact with the inner roll 5, and then dividing by 2. The width Ww12i of the inner surface si of workpiece 1 in contact with the inner roll 5 is longer than the length Wr12i of the second inner first surface F51 by (Ww12i - Wr12i), and both ends E12, E12 of workpiece 1 extend in the width direction beyond the second inner first surface F51. In this case, (Ww12i - Wr12i) / 2 corresponds to the length at one end of how much longer the width Ww12i of the inner surface si of workpiece 1 is compared to the length Wr12i of the second inner first surface F51. The length of the curved portion B11 and the height of the thickened portion B12 will change according to the length of (Ww12i - Wr12i) / 2. Note that Wr12i is a specific example of Wr2i. Wr12o is a specific example of Wr2o.

[0089] The lower limit of (Ww12i - Wr12i) / 2 is preferably 0.3 × Tw or more, more preferably 0.4 × Tw or more. The upper limit of (Ww12i - Wr12i) / 2 is preferably 0.6 × Tw or less, more preferably 0.5 × Tw or less. Above the lower limit, the in-plane length of the thickened portion B12 increases, and the volume of the thickened portion B12 becomes sufficient, resulting in good joining quality. Below the upper limit, it becomes easier to suppress the formation of excessive thickened portions B12 that do not contribute much to the welding quality.

[0090] Furthermore, as shown in Figure 15, the in-plane length Lt1 of the thickened portion B12 formed in the thickening step, and the plate thickness Tw of the workpiece 1 satisfy the following equation (1-8): 0.5 × Tw ≤ Lt1 ≤ 2 × Tw Equation (1-8)

[0091] "Length Lt1 of the thickened portion B12 in the in-plane direction" refers to the length of the thickened portion B12 that extends outward from the outer surface so near the end E12 of workpiece 1, in the in-plane direction near the end E12 of workpiece 1. Specifically, as shown in Figure 15, if point 1d is prepared on the surface of the workpiece and point 1e is prepared on the end face of the thickened portion B12, then Lt1 is the length of the line segment connecting point 1d and point 1e. Point 1d is a point on the boundary between the outer surface so (plane) near the end E12 of workpiece 1 and the surface of the thickened portion B12 of workpiece 1. Point 1e is a point on the end face of the thickened portion B12 of workpiece 1 that intersects with a line along the in-plane direction of the outer surface so near the end E12 of workpiece 1.

[0092] The lower limit of Lt1 is preferably 0.7 × Tw or more, more preferably 0.8 × Tw or more, and even more preferably 0.9 × Tw or more. The upper limit of Lt1 is preferably 1.5 × Tw or less, more preferably 1.2 × Tw or less, even more preferably 1.0 × Tw or less, and even more preferably less than 1.0 × Tw.

[0093] Furthermore, in the thickness-increasing step, the following embodiment A13 is satisfied. <Embodiment A13>: The plate thickness Tw of workpiece 1 and the height Hr2i of the second inner surface F52 satisfy the following equation (1-9): 1.05 × Tw ≤ Hr2i ≤ 2 × Tw Equation (1-9)

[0094] The "height Hr2i of the second inner surface F52" is the rise width of the second inner surface F52, which rises almost perpendicularly from the second inner surface F51. Specifically, as shown in Figure 13, it is the length of the perpendicular (line segment) drawn from point 5d to the second inner surface F51 including point 5b. Hr2i determines the height dimension of the clearance of the inner roll for forming the thickened section B12. The out-of-plane height of the thickened section B12 will change according to Hr2i.

[0095] The lower limit of Hr2i is preferably 1.2 × Tw or more, more preferably 1.4 × Tw or more. The upper limit of Hr2i is preferably 1.8 × Tw or less, more preferably 1.6 × Tw or less. Above the lower limit, the out-of-plane height of the thickened portion B12 increases, and the volume of the thickened portion B12 becomes sufficient, resulting in good joining quality. Below the upper limit, it becomes easier to suppress the formation of excessive thickened portion B12, which has little contribution to welding quality.

[0096] As shown in Figure 15(b), the out-of-plane height Ht1 of the thickened portion B12 formed in the thickening step, and the plate thickness Tw of the workpiece 1 satisfy the following equation (1-10): 1.05 × Tw ≤ Ht1 ≤ 1.5 × Tw Equation (1-10)

[0097] The "out-of-plane height Ht1 of the thickened portion B12" is the length in the approximately perpendicular direction (z-direction) of the end face portion of the thickened portion B12 that abuts against the second inner surface F52 of the inner roll 5 (see Figure 7). The out-of-plane height Ht1 of the thickened portion B12 is smaller than the height Hr2i of the second inner surface F52 of the inner roll 5. This is because the formed thickened portion B12 is smaller than the clearance provided by the roll (inner roll 5).

[0098] The lower limit of Ht1 is preferably 1.15 × Tw or more, more preferably 1.25 × Tw or more. The upper limit of Ht1 is preferably 1.45 × Tw or less, more preferably 1.35 × Tw or less. Above the lower limit, the out-of-plane height of the thickened portion B12 increases, and the volume of the thickened portion B12 becomes sufficient, resulting in good joining quality. Below the upper limit, it becomes easier to suppress the formation of excessive thickened portion B12, which has little contribution to welding quality.

[0099] For example, in the thickening step, the inner roll 5 is applied to the end E12 of the workpiece 1 according to the following embodiment A14: <Embodiment A14> The angle θ12i between the second inner surface F52 and the rotation axis 51 of the inner roll 5 satisfies the following equation (1-11): -10° ≤ θ12i ≤ 10° Equation (1-11) θ12i corresponds to the angle between the rotation axis 51 of the inner roll 5 and the second inner surface F52 of the inner roll 5, which receives the reaction force from the workpiece 1 to the action from the inner roll 5 toward the bending portion B11 when the second inner surface F52 of the inner roll 5 acts toward the bending portion B11 from the end face side in the in-plane direction (see Figure 12(b)).

[0100] The lower limit of θ12i is preferably -7° or more, more preferably -5° or more. The upper limit of θ12i is preferably 7° or less, more preferably 5° or less. By having θ12i within the above range, the force applied from the end E12 of the workpiece 1 to the second inner second surface F52 can be received in a direction substantially perpendicular to the rotation axis 51 of the inner roll 5. That is, the force from the workpiece 1 generated when forming the thickened portion B12 is received by the rotation axis 51 of the inner roll 5, and the deformation of the thickened portion B12 can be efficiently carried out by the compressive force applied to the workpiece 1 from the second surface of the inner roll 5 in a direction substantially perpendicular to the rotation axis 51. Furthermore, as will be described later, in this embodiment, the angle of the end E12 with respect to the horizontal plane P1 when performing the thickening step is θa1 = 90°. In this case, as long as θ12i is within the above range, in the thickening step, when the second inner surface F52 of the inner roll 5 acts in the in-plane direction from the end face side on the curved portion B11, the direction in which the compressive force acting perpendicular to the rotation axis 51 of the inner roll 5 acts (compression direction) and the in-plane direction of the workpiece end are parallel (0°). As a result, the compressive force applied from the roll deforms the curved portion B11 by crushing it, thereby forming the thickened portion B12. On the other hand, if the compression direction of the roll and the in-plane direction are not parallel, the compressive force applied to the curved portion B11 is converted into a bending force, causing the curved portion B11 to undergo bending deformation, making it difficult to form a good thickened portion B12.

[0101] The angle θ(43) between the second inner first surface F51 and the second inner second surface F52 is between 80° and 100°. Angle θ(43) represents the inclination angle of the second inner second surface F52 with respect to the second inner first surface F51. The angle θ(44) between the second outer first surface F41 and the second outer second surface F42 is between 35° and 55°. Angle θ(44) represents the inclination angle of the second outer second surface F42 with respect to the second outer first surface F41.

[0102] [Timing of Bending Step and Thickening Step] As shown in Figure 7, in the first embodiment, the bending step is performed in the second forming process and the thickening step is performed in the third forming process. However, the bending step and thickening step can be performed as appropriate during the stepwise forming process by roll forming (roll flower).

[0103] For example, in the molding process, the workpiece 1 is bent in stages to form a butt joint T from a flat workpiece 1 through multiple stages. If the angle θ of the end E11 with respect to the horizontal plane P1 in the state before bending is 0°, and the angle θ of the end with respect to the horizontal plane P1 in the state after the butt joint T is formed changes up to α°, then it is desirable that the angle θa1 of the end with respect to the horizontal plane P1 in the state after the thickness-increasing step satisfies the following equation (1-12): α × (9 / 20) ≤ θa1 ≤ α × (11 / 20) Equation (1-12) θa1 can also be considered as the angle of the end E12 with respect to the horizontal plane P1 when the thickness-increasing step is performed.

[0104] In the first embodiment, the angle of the end portion E11 with respect to the horizontal plane P1 is 0° at the beginning of the molding process, and is eventually bent to α = 180°. After the thickness-increasing step, the angle of the end portion with respect to the horizontal plane P1 is θa1 = 90°.

[0105] In roll forming, the workpiece 1 is bent in stages. During bending, the inner surface si of the workpiece 1 shrinks, and the outer surface so of the workpiece 1 stretches. Therefore, even if the end faces of the workpiece 1 are perpendicular to the plane of the workpiece 1 during bending, each time bending is performed, stress is applied to the gap between the end faces in a direction that closes on the inner surface si side and opens on the outer surface so side. In addition, the shape of the end E11 is also deformed each time bending is performed.

[0106] According to the above formula (1-12), the angle of the end portion E12 reaches about 50% of the final angle at the time of the thickening step, which suppresses the deformation that occurs in the thickened portion B12 due to subsequent bending, and thus reduces the impact that occurs when the thickened portions B12 are finally joined together.

[0107] The lower limit of θa1 is preferably α × (47 / 100) or more, more preferably α × (49 / 100) or more. The upper limit of θa1 is preferably α × (53 / 100) or less, more preferably α × (51 / 100) or less.

[0108] For example, in the molding process, a butt joint T is formed from a flat workpiece 1 through multiple stages by bending the workpiece 1 step by step. If the angle of the end E11 with respect to the horizontal plane P1 in the state before bending is set to 0°, and the angle of the end with respect to the horizontal plane P1 in the state after the butt joint T is formed changes up to α°, then it is desirable that the angle θb1 of the end with respect to the horizontal plane P1 in the state after the bending step satisfies the following equation (1-13): α × (5 / 20) ≤ θb1 ≤ α × (7 / 20) Equation (1-13) θb1 can also be considered as the angle of the end E12 with respect to the horizontal plane P1 when the bending step is performed.

[0109] In the first embodiment, the angle θb1 of the end portion E12 after the bending step is 55°. In this case, θb1 ≈ α × 0.31. According to the above formula (1-13), the angle of the end portion E12 reaches about 30% of the final angle (about 60% of the angle in the thickening step) at the time of the bending step, which suppresses the deformation that occurs in the thickened portion B12 when transitioning from the bending step to the thickening step.

[0110] The lower limit of θb1 is preferably α × (27 / 100) or more, more preferably α × (29 / 100) or more. The upper limit of θb1 is preferably α × (33 / 100) or less, more preferably α × (31 / 100) or less. Note that θb1 is a specific example of θb.

[0111] Figure 16 is an end view of the workpiece 1 after the molding process is completed according to the first embodiment. Figure 17 is an enlarged view of Figure 16. As shown in Figures 16 and 17, when the molding process is completed, a butt joint T is formed where the ends of the workpiece 1 are joined together. According to the roll forming of this embodiment, the thickness of the reinforced portion B12 provided in the butt joint T can be increased.

[0112] [Joining Process] In the manufacturing method of the cylindrical body according to the first embodiment, the workpiece is deformed in the molding process so that the ends on which the thickened portion B12 is formed abut against each other to form a butt joint T. The manufacturing method further includes a joining process for joining the butt joint T. Figure 18 is an explanatory diagram of the joining process according to the first embodiment. As shown in Figure 18, a laser beam 106 can be irradiated onto the ends on which the convex thickened portion B12 is formed, which constitute the butt joint T. After manufacturing the cylindrical body, a container can be manufactured by joining the parts to seal the opening of the cylindrical body.

[0113] Figure 19 is an explanatory diagram of beam welding according to the first embodiment. The beam welding shown in Figure 19 is single-beam welding. The white arrows in Figure 19 indicate the welding direction, which is the direction opposite to the transport direction (x direction) of the workpiece 1.

[0114] When the laser beam 106 is irradiated onto the transported workpiece 1, the metal at the irradiated area melts, forming a hole-shaped keyhole 107. A high-temperature molten pool 108 is also formed around the keyhole 107. As the irradiated area moves due to the transport of the workpiece 1, the molten pool 108 cools, forming a rapidly solidified area 109. Through this state transition, a weld bead is formed.

[0115] In the first embodiment, laser bonding is performed in the bonding process. However, bonding can be performed in the bonding process by at least one selected from the group consisting of laser bonding, arc bonding, ultrasonic bonding, high-frequency welding, resistance seam welding, and friction stir welding.

[0116] [Conventional Example] Figure 20 is a cross-sectional view (1 / 2) of the butt joint of a conventional workpiece. Figure 21 is a cross-sectional view (2 / 2) of the butt joint of a conventional workpiece. Workpiece 1A shown in Figures 20 and 21 shows the end face shape when a sheet of metal containing aluminum or an aluminum alloy is cut on both sides in the width direction with a slitter and stretched, and then formed into a cylindrical body by roll forming, with the unprocessed ends butted together. As shown in Figure 20, when the ends are unprocessed, there is a tendency for cut sag 20-1, gaps 20-2, waviness 20-3, etc. to occur between the end faces. Also, as shown in Figure 21, when the ends are unprocessed, the end faces of each end tend to be non-parallel, and the groove surface accuracy tends to decrease. Due to these tendencies, there is a high possibility of perforation defects occurring during laser welding.

[0117] Figure 22 is a cross-sectional view of a welded portion of a conventional workpiece. In the workpiece 1A shown in Figure 22, a welded portion 1Aa is formed by laser welding to a butt joint where two unprocessed ends are joined together. As shown in Figure 22, the welded portion 1Aa is significantly thinner than the original plate thickness of workpiece 1A. When the ends are unprocessed, thinning of the material in the gap at the end face inevitably occurs, which is highly likely to lead to a decrease in the quality of the joint.

[0118] Figure 23 is an explanatory diagram (3 / 4) of the butt joint of a conventional workpiece. As shown in Figure 23, in Patent Document 1, thickened sections are formed on both sides of the plate material. When the end faces on which such thickened sections are formed are butted together to form a butt joint and join them, beads will be formed on both sides due to the material of the thickened sections provided on both sides. Here, for example, if it is desired to avoid interference between the contents and the beads, there is a need to form the beads on the front convex side. If it is desired to avoid interference with a part on the outside of a cylindrical part, there is a need to form the beads on the back convex side.

[0119] Figure 24 is an explanatory diagram (4 / 4) of the butt joint of a conventional workpiece. When forming a cylindrical body by roll forming, in order to form a thickened portion at each of the butt ends of workpiece 1B, the roll is applied in a way that pushes the end of the workpiece in the in-plane direction, thereby deforming the material at the end of the workpiece to spread outwards. In this case, as the deformation of the material at the end of the workpiece is transmitted from the end face inwards, the area where the thickness is increased expands inwards, and the thickness of the increased thickness decreases.

[0120] [Effects] According to the manufacturing method of the cylindrical body according to the first embodiment, a roll is applied to bend the end out of the plane in a bending step to form a bent portion B11 where the end is bent out of the plane, and then a roll is applied to push the bent portion B11 in the in-plane direction to form a thickened portion B12 where the end is deformed out of the plane. As a result, the thickened portion B12 is formed by the material expanding out of the plane in the in-plane range corresponding to the bent portion B11. In this way, by limiting the in-plane range in which the thickened portion B12 is formed to the range of the bent portion B11, the deformation of the material does not spread in the in-plane direction, but the deformation of the material in the out-of-plane direction occurs only within the range corresponding to the bent portion B11, so the thickness of the thickened portion B12 can be increased. In addition, the tendency for cutting sag, gaps, and waviness to occur between the abutted end faces can be suppressed, and the decrease in the accuracy of the bevel surface of each end face can be suppressed. Therefore, it is possible to manufacture a cylindrical body with excellent joint quality in which the weld bead formed in the weld is sound and fracture occurs in the heat-affected zone (HAZ) when a fracture test is performed. Examples of a sound weld bead include having sufficient throat thickness, reducing the thinned area, reducing the number of holes, and forming excess weld material in the joint.

[0121] Furthermore, according to the first embodiment, a thickened portion B12 can be provided on each of the butted ends of the workpiece 1 such that the outer surface so side (outside) is convex (Figure 17). In this way, since the thickened portion B12 can be formed on one side of the workpiece 1, the convex direction of the bead after joining can be controlled.

[0122] [2. Second Embodiment] In the second embodiment, we will mainly explain the differences from the first embodiment, and explain any overlapping points as appropriate. In the first embodiment, the end of the workpiece 1 was bent outwards (upper surface), the outer surface (upper surface) was thickened, and the butt joint was joined, so the area of ​​thickening was limited to the end. In the second embodiment, the end of the workpiece 1 was bent outwards (lower surface), the inner surface (lower surface) was thickened, and the butt joint was joined, so the area of ​​thickening is limited to the end.

[0123] [Rolls] Figure 25 is a cross-sectional view of the rolls and workpiece used in the bending step according to the second embodiment. The bending step according to the second embodiment corresponds to the second forming process. In the second forming process, the outer roll 6 and the inner roll 7 of the rolls used in roll forming act on the workpiece 1 (see Figure 30). The outer roll 6 (first outer roll) is a roll positioned on the outer surface so (bottom surface) side of the workpiece 1. The outer roll 6 rotates around a rotation axis 61 that extends horizontally (y direction) and processes the workpiece 1. The inner roll 7 (first inner roll) is a roll positioned on the inner surface si (top surface) side of the workpiece 1. The inner roll 7 rotates around a rotation axis 71 that extends horizontally and processes the workpiece 1.

[0124] In the second molding process, the workpiece 1 is sandwiched from both sides by the outer roll 6 and the inner roll 7, and the outer roll 6 or the inner roll 7 is applied to bend the end portion E21 of the workpiece 1 (see Figure 31(a)) out of the plane. As a result, a curved portion B21 (see Figure 31(b)) is formed, which is deformed so that the end portion E21 of the workpiece 1 is bent out of the plane.

[0125] Figure 26 is a cross-sectional view of the rolls and workpiece used in the thickness-increasing step according to the second embodiment. The thickness-increasing step according to the second embodiment corresponds to the third forming step. In the third forming step, the outer roll 8 and the inner roll 9, which are rolls used in roll forming, act on the workpiece 1 (see Figure 34). The outer roll 8 (second outer roll) is a roll positioned on the outer surface so (bottom surface) side of the workpiece 1. The outer roll 8 rotates around a rotation axis 81 that extends horizontally (y direction) and processes the workpiece 1. The inner roll 9 (first inner roll) is a roll positioned on the inner surface si (top surface) side of the workpiece 1. The inner roll 9 rotates around a rotation axis 91 that extends horizontally and processes the workpiece 1.

[0126] In the third forming stage, the workpiece 1 is sandwiched from both sides by the outer roll 8 and the inner roll 9, and the outer roll 8 or the inner roll 9 is applied to push the curved portion B21 formed in the second forming stage in the in-plane direction. As a result, a thickened portion B22 (see Figure 35(b)) is formed in which the end portion E22 (see Figure 35(a)) of the workpiece 1 is deformed to increase in thickness in the out-of-plane direction.

[0127] Figure 27 is an explanatory diagram of a roll flower according to the second embodiment. The roll flower shows the superimposed cross-sections of the workpiece formed by the outer roll and the inner roll in each of the n-th stage forming processes. The numbers in Figure 27 represent the value of n. The roll flower can be used to show how the workpiece is gradually formed into a three-dimensional shape.

[0128] [Bending Step] Figure 28 is a cross-sectional view of the roll used in the bending step according to the second embodiment. Figure 29 is an enlarged view of Figure 28. Figure 30 is an explanatory diagram of the positional relationship between the roll and the workpiece used in the bending step according to the second embodiment. For convenience of illustration, the workpiece 1 is not shown in Figures 28 and 29. Figure 30 corresponds to Figure 29 with the workpiece 1 shown after the bending step and before end forming added.

[0129] As shown in Figure 29, in the bending step, a gap equal to the thickness of the workpiece 1 is provided between the outer roll 6 and the inner roll 7. As shown in Figure 30, in the bending step, the outer roll 6 contacts the outer surface so (bottom surface) of the workpiece 1, and the inner roll 7 contacts the inner surface si (top surface) of the workpiece 1, thereby sandwiching the workpiece 1.

[0130] As shown in Figure 30, in the bending step, the outer roll 6 or the inner roll 7 is applied to the end of the workpiece 1 in the following manner B1. <Manner B1> At the end E21 of the workpiece 1, the outer roll 6 is in contact with the end E21 from the outer surface so side of the workpiece, in a positional relationship in which it enters the interior of the virtual outer surface vo21 (first virtual outer surface) formed when the outer surface so near the end is extended in the in-plane direction. Also at the end E21 of the workpiece 1, the inner roll 7 is in a positional relationship in which it is away from the virtual inner surface vi21 (first virtual outer surface) formed when the inner surface si near the end is extended in the in-plane direction, and is facing the outer roll 6.

[0131] Except for the end E21 of workpiece 1, the distance between the outer roll 6 and the inner roll 7 is approximately the same as the thickness of workpiece 1, with the outer roll 6 and the inner roll 7 sandwiching workpiece 1.

[0132] At the end E21 of workpiece 1, the inner roll 7 is positioned away from the virtual inner surface vi21 and faces the outer roll 6, creating a clearance between the inner roll 7 and the virtual inner surface vi21. Furthermore, the outer roll 6 contacts the end E21 from the outer surface so side of workpiece 1 in a position where it enters the interior of the virtual outer surface vo21, applying an inward force to the end E21 in the out-of-plane direction. At this time, the end E21 that has come into contact with the outer roll 6 deforms to escape into the clearance between the inner roll 7 and the virtual inner surface vi21, causing the end E21 to bend inward in the out-of-plane direction.

[0133] More specifically, as shown in Figures 29 and 30, in the bending step, the outer roll 6 or the inner roll 7 is applied to the end E21 of the workpiece 1 according to the following embodiment B2. <Embodiment B2> The inner roll 7 has, in a cross-sectional view through the rotation axis 71 of the inner roll 7, a first inner surface F71 that is in contact with the workpiece 1 and has a width shorter than the width of the inner surface si in the long side direction of the workpiece 1, and a first inner second surface F72 that slopes inward and widens from the first inner surface F71. The outer roll 6 has, in a cross-sectional view through the rotation axis 61 of the outer roll 6, a first outer surface F61 that is in contact with the workpiece 1 and has a width shorter than the width of the outer surface so in the long side direction of the workpiece 1, and a first outer second surface F62 that slopes inward and widens from the first outer surface F61. In the bending step, the first outer surface F61 contacts the outside of the workpiece 1, and the first inner surface F71 contacts the inside of the workpiece 1, thereby sandwiching the workpiece 1. The first outer second surface F62 contacts the end E21 from the side of the outer surface so of the workpiece 1. The first inner second surface F72 contacts the end E21, which has been deformed to be bent inward in the out-of-plane direction.

[0134] As shown in Figures 25 and 29, the "first inner surface F71" is a surface extended by rotating a line segment connecting points 7b, 7b prepared on the surface of the inner roll 7 along the surface of the inner roll 7, around the rotation axis 71 in the transport direction (x direction) of the workpiece 1. The width Wr21i of the first inner surface F71 is shorter than the "width Ww21i of the inner surface si in the long side direction of the workpiece 1" (see Figures 25, 29, and 30).

[0135] Point 7a is a point on the boundary of the partial surface of the inner roll 7, which forms the corner of the workpiece 1 by corner machining. Point 7b is a point on the boundary of the first inner surface F71, located at both ends of the first inner surface F71. The position of point 7b is set such that the width Wr21i of the first inner surface F71 is shorter than the width Ww21i of the inner surface si in the long side direction of the workpiece 1. Point 7b is positioned symmetrically from the center of the inner roll. Point 7b is also a point on the boundary of the first inner surface F72.

[0136] As shown in Figure 29, the "first inner second surface F72" is a surface extended by rotating a line segment connecting points 7b and 7c, which are prepared on the surface of the inner roll 7, along the surface of the inner roll 7, around the rotation axis 71. Point 7c is a point on the boundary of the first inner second surface F72 that is on the opposite side of the boundary from point 7b with respect to the first inner second surface F72.

[0137] As shown in Figures 25 and 29, the "first outer surface F61" is a surface extended by rotating a line segment connecting points 6b, 6b prepared on the surface of the outer roll 6 along the surface of the outer roll 6, around the rotation axis 61. The width Wr21o of the first outer surface F61 is shorter than the "width Ww21o of the outer surface so in the long side direction of the workpiece 1".

[0138] Point 6a is a point on the boundary of the partial surface of the outer roll 6, which forms the corner of the workpiece 1 by corner machining. Point 6b is a point on the boundary of the first outer surface F61, located at both ends of the first outer surface F61. The position of point 6b is set such that the width Wr21o of the first outer surface F61 is shorter than the width Ww21o of the outer surface so in the long side direction of the workpiece 1. Point 6b is positioned symmetrically from the center of the inner roll. Point 6b is also a point on the boundary of the first outer surface F62.

[0139] As shown in Figure 29, the "first outer second surface F62" is a surface extended by rotating a line segment connecting points 6b and 6c, which are prepared on the surface of the outer roll 6, along the surface of the outer roll 6, around the rotation axis 61. Point 6c is a point on the boundary of the first outer second surface F62 that is on the opposite side of the boundary from point 6b with respect to the first outer second surface F62.

[0140] Figure 31 is an explanatory diagram of the bending step according to the second embodiment, where (a) is a side view of the workpiece before bending and (b) is a side view of the workpiece after bending. Figure 31(b) shows the shape of the curved portion formed by the bending step. As shown in Figures 29 to 31, the bending step satisfies the following embodiment B3. <Embodiment B3> The plate thickness Tw of the workpiece 1, the width Ww21o of the outer surface so in the long side direction of the workpiece 1, and the width Wr21o of the first outer surface F61 satisfy the following equation (2-1). 0.5 × Tw ≤ (Ww21o - Wr21o) / 2 ≤ 2 × Tw Equation (2-1)

[0141] Note that Ww21i corresponds to the width dimension of the upper surface of workpiece 1 (along the first inner surface F71) when workpiece 1, which has not undergone end processing, is in contact with the inner roll 7. Ww21o corresponds to the width dimension of the lower surface of workpiece 1 (along the first outer surface F61) when workpiece 1, which has not undergone end processing, is in contact with the outer roll 6. Wr21i corresponds to the length of the line segment connecting points 7b, 7b in Figures 25 and 29 along the surface of the first inner surface F71. Wr21o corresponds to the length of the line segment connecting points 6b, 6b in Figures 25 and 29 along the surface of the first outer surface F61. (Ww21o - Wr21o) / 2 is the value obtained by subtracting the length of the first outer surface Wr21o from the width dimension of the lower surface Ww21o when workpiece 1 is in contact with the outer roll, and then dividing by 2. The width Ww21o of the outer surface so of workpiece 1 in contact with the outer roll is longer than the length Wr21o of the first outer surface by (Ww21o - Wr21o), and both ends E21, E21 of workpiece 1 extend in the width direction beyond the first outer surface. In this case, (Ww21o - Wr21o) / 2 corresponds to the length at one end of how much longer the width Ww21o of the outer surface so of workpiece 1 is compared to the length Wr21o of the first outer surface. The length of the curved portion B21 and the height of the thickened portion B22 will change according to the length of (Ww21o - Wr21o) / 2. Note that Wr21i is a specific example of Wr1i, and Wr21o is a specific example of Wr1o.

[0142] The lower limit of (Ww210 - Wr210) / 2 is preferably 0.7 × Tw or more, more preferably 0.8 × Tw or more, and even more preferably 0.9 × Tw or more. The upper limit of (Ww210 - Wr210) / 2 is preferably 1.5 × Tw or less, more preferably 1.2 × Tw or less, even more preferably 1.0 × Tw or less, and even more preferably less than 1.0 × Tw. Above the lower limit, it is easy to make the thickened portion B22 appropriately large in the subsequent thickening step. Below the upper limit, it is easy to compress and deform the curved portion B21 so that it collapses without bending in the subsequent thickening step, thereby forming the thickened portion B22. In other words, it is possible to form a thickened portion B22 of an appropriate size.

[0143] Furthermore, as shown in Figure 31, the in-plane length Lb2 of the bent portion B21 formed in the bending step, and the plate thickness Tw of the workpiece 1 satisfy the following equation (2-2): 0.5 × Tw ≤ Lb2 ≤ 2 × Tw Equation (2-2)

[0144] "Length Lb2 in the in-plane direction of the curved portion B21" does not refer to the length along the in-plane direction (along the curved surface), but rather the length along the virtual outer surface vo21 formed when the outer surface so near the end E21 of the workpiece 1 is extended in the in-plane direction. Specifically, as shown in Figure 31, if points 1f and 1g are prepared on the surface of the workpiece 1, and point 1h is prepared on the virtual outer surface vo21, then Lb2 is the length of the line segment connecting point 1f and point 1h. Point 1f is a point on the boundary between the outer surface so (plane) near the end E21 of the workpiece 1 and the surface of the curved portion B21 of the workpiece 1. Point 1g is the outermost point on the surface of the curved portion B21 of the workpiece 1, towards the end of the workpiece 1. Point 1h is the point obtained by projecting point 1g perpendicularly onto the virtual outer surface vo21. Lb1 corresponds to the length of the bent portion B21 formed by bending the end E21 (bend length).

[0145] The lower limit of Lb2 is preferably 0.7 × Tw or more, more preferably 0.8 × Tw or more, and even more preferably 0.9 × Tw or more. The upper limit of Lb2 is preferably 1.5 × Tw or less, more preferably 1.2 × Tw or less, even more preferably 1.0 × Tw or less, and even more preferably less than 1.0 × Tw. Above the lower limit, it is easy to make the thickened portion B22 appropriately large in the subsequent thickening step. Below the upper limit, in the subsequent thickening step, the curved portion B21 is compressed and deformed so as to be crushed without bending, making it easier to form the thickened portion B22.

[0146] Furthermore, the bending step satisfies the following embodiment B4. <Embodiment B4> When the outer roll 6 acts on the end E21 from the outer surface so side of the workpiece 1, forming a curved portion B21 in which the end E21 deforms toward the inner surface si side, the angle θ(45) between the first outer surface F61 and the first outer surface F62 is 40° or more and 80° or less. The angle θ(45) represents the inclination angle of the first outer surface F62 with respect to the first outer surface F61, which is an inclined surface that contacts the end E21 and forms the curved portion B21.

[0147] The lower limit of the angle θ(45) is preferably 45° or more, more preferably 50° or more. The upper limit of the angle θ(45) is preferably 65° or less, more preferably 60° or less. Above the lower limit, in the subsequent thickening step, it becomes easier to limit the formation range of the thickened portion B22 without the deformation range expanding. Below the upper limit, in the subsequent thickening step, the curved portion B21 is compressed and deformed in a way that crushes it, rather than bending, making it easier to form the thickened portion B22.

[0148] The angle θ(46) between the first inner surface F71 and the first inner surface F72 is between 40° and 80°. The angle θ(46) represents the inclination angle of the first inner surface F72 with respect to the first inner surface F71.

[0149] Furthermore, as shown in Figure 31, the bent portion B21 formed in the bending step satisfies the following embodiment B5. <Embodiment B5> When the outer roll 6 acts on the end portion E21 from the outer surface so side of the workpiece 1, forming a bent portion B21 in which the end portion E21 deforms toward the inner surface si side, the angle θ(52) between the virtual outer surface vo21 formed when the outer surface so near the end portion E21 is extended in the in-plane direction and the bent portion B21 is 40° or more and 70° or less. The angle θ(52) corresponds to the angle at which the bent portion B21 formed by bending the end portion E21 is straightened (bending angle).

[0150] As shown in Figure 31, the "angle between the virtual outer surface vo21 and the curved portion B21" is the angle θ(52) (acute angle) between the virtual outer surface vo21 and the outer surface so (plane) of the curved portion B21 that abuts the first outer second surface F62.

[0151] [Thickening Step] Figure 32 (a) is a cross-sectional view of the roll used in the thickening step according to the second embodiment, and (b) is an explanatory diagram of the angle between the surface of the roll and the axis of rotation of the roll. Figure 33 is an enlarged view of Figure 32(a). Figure 34 is an explanatory diagram of the positional relationship between the roll and the workpiece used in the thickening step according to the second embodiment. For convenience of illustration, the workpiece 1 is not shown in Figures 32 and 33. Figure 34 corresponds to Figure 33 with the workpiece 1 shown after the thickening step and before end forming added.

[0152] As shown in Figure 33, in the thickness-increasing step, a gap equal to the thickness of the workpiece 1 is provided between the outer roll 8 and the inner roll 9. As shown in Figure 34, in the thickness-increasing step, the outer roll 8 contacts the outer surface so (bottom surface) of the workpiece 1, and the inner roll 9 contacts the inner surface si (top surface) of the workpiece 1, thereby sandwiching the workpiece 1.

[0153] As shown in Figure 34, in the thickening step, the outer roll 8 or the inner roll 9 is applied to the end E22 of the workpiece 1 in the following manner B6. <Manner B6> At the end E22 of the workpiece 1, the inner roll 9 is positioned so as to enter into the workpiece 1 at the end E22, contacting the curved portion B21 from the end face side of the workpiece 1, and is positioned away from the virtual inner surface vi22 (second virtual inner surface) that is formed when the inner surface si near the end E22 is extended in the in-plane direction, and is facing the second outer roll. Also, at the end E22 of the workpiece 1, the outer roll 8 is positioned so as to contact the outer surface so near the end E22, and is facing the inner roll 9.

[0154] Except for the end E22 of workpiece 1, the distance between the outer roll 8 and the inner roll 9 is approximately the same as the thickness of workpiece 1, with the outer roll 8 and the inner roll 9 sandwiching workpiece 1.

[0155] At the end E22 of workpiece 1, the inner roll 9 is positioned away from the virtual inner surface vi22 and faces the outer roll 8, creating a clearance between the inner roll 9 and the virtual inner surface vi22. Furthermore, the inner roll 9 enters the workpiece 1 and contacts the curved portion B21 from the end face side of workpiece 1, applying an inward force to the curved portion B21 in the out-of-plane direction. At this time, the curved portion B21 that has come into contact with the inner roll 9 deforms to escape into the clearance between the inner roll 9 and the virtual inner surface vi22, causing the end E22 to be deformed inward in the out-of-plane direction, thereby forming the thickened portion B22. In addition, in embodiment B6 in which the thickened portion B22 is formed on the inside, the reaction force from the workpiece to the action from the inner roll 9 toward the curved portion B21 can be made to act in the direction toward the rotation axis 91 of the inner roll 9. That is, the force from the workpiece generated when forming the thickened portion B22 can be received by the rotation axis 91 of the inner roll 9.

[0156] More specifically, as shown in Figures 33 and 34, in the thickening step, the outer roll 8 or the inner roll 9 is applied to the end E22 of the workpiece 1 according to the following embodiment B7. <Embodiment B7> In a cross-sectional view through the rotation axis 91 of the inner roll 9, the inner roll 9 has a second inner first surface F91 that contacts the inside of the workpiece 1, a second inner second surface F92 that slopes inward and extends from the second inner first surface F91, and a second inner third surface F93 that is substantially perpendicular to the second inner first surface F91. With the second inner first surface F91 in contact with the workpiece 1, the second inner first surface F91 and the second inner second surface F92 have a width shorter than the width of the inner surface si in the long side direction of the workpiece 1. In a cross-sectional view through the rotation axis 81 of the outer roll 8, the outer roll 8 has a second outer first surface F81 that, when in contact with the workpiece 1, has a width shorter than the width of the outer surface so in the long-side direction of the workpiece 1, with the rotation axis 81 of the outer roll 8 as the center. In a cross-sectional view through the rotation axis 81 of the outer roll 8, the outer roll 8 has a second outer second surface F82 that, when in contact with the workpiece 1, has a width greater than or equal to the width of the outer surface so in the long-side direction of the workpiece 1, with the rotation axis 81 of the outer roll 8 as the center. In the thickening step, the second outer first surface F81 contacts the outside of the workpiece 1, and the second inner first surface F91 contacts the inside of the workpiece 1, thereby sandwiching the workpiece 1. The second inner third surface F93 contacts the curved portion B21 from the end face side of the workpiece 1. The second inner second surface F92 faces the end portion E22 which has been deformed to thicken inward in the out-of-plane direction.

[0157] As shown in Figures 26 and 33, the "second inner first surface F91" is a surface extended by rotating a line segment connecting points 9b, 9b prepared on the surface of the inner roll 9 along the surface of the inner roll 9, around the rotation axis 91. The width Wr22i of the second inner first surface F91 is shorter than the "width Ww22i of the inner surface si in the long side direction of the workpiece 1".

[0158] Point 9a is a point on the boundary of the partial surface of the inner roll 9, which forms the corner of the workpiece 1 by corner machining. Point 9b is a point on the boundary of the second inner first surface F91, and is located at both ends of the second inner first surface F91. The position of point 4b is set so that clearance is secured to form the thickened portion B22 between the virtual inner surface vi22 and the second inner second surface F92. Point 9b is positioned symmetrically from the center of the outer roll. Point 9b is a point on the boundary of the second inner first surface F91. Point 9b is also a point on the boundary of the rounded second inner corner portion 92. The second inner corner portion 92 is a surface extended by rotating a line segment connecting points 9b and 9c, which are prepared on the surface of the inner roll 9, along the surface of the inner roll 9, around the rotation axis 91. The second inner corner portion 92 is sandwiched between the second inner first surface F91 and the second inner second surface F92.

[0159] As shown in Figure 33, the "second inner second surface F92" is a surface extended by rotating a line segment connecting points 9c and 9d, which are prepared on the surface of the inner roll 9, along the surface of the inner roll 9, around the rotation axis 91. Point 9c is a point on the boundary of the second inner second surface F92, and is on the boundary opposite to point 9b with respect to the second inner corner portion 92. Point 9d is a point on the boundary of the second inner second surface F92, and is on the boundary opposite to point 9c with respect to the second inner second surface F92.

[0160] As shown in Figure 33, the "second inner third surface F93" is a surface extended by rotating a line segment connecting points 9e and 9f prepared on the surface of the inner roll 9 along the surface of the inner roll 9, around the rotation axis 91. Point 9e is a point on the boundary of the second inner first surface F91, and is located at both ends of the second inner first surface F91. The position of point 9e is set such that the width Wr22i of the second inner first surface F91 and the second inner second surface F92 is shorter than the width Ww22i of the inner surface si in the long side direction of the workpiece 1. In other words, the position of point 9e is set such that the width Wr22i, which is the sum of the widths of the second inner first surface F91 and the second inner second surface F92, is shorter than the width Ww22i of the inner surface si in the long side direction of the workpiece 1. Point 9e is positioned symmetrically from the center of the inner roll. Point 9e is also a point on the boundary of the second inner third surface F93. Point 9e is also a point on the boundary opposite to point 9d with respect to the second inner corner portion 93. Note that the lengths of the second inner corner portion 92 and the second inner corner portion 93 are sufficiently smaller than the lengths of the second inner first surface F91 and the second inner second surface F92. Therefore, when referring to the width Wr22i of the second inner first surface F91 and the second inner second surface F92, it refers to the length between points 9e, 9e. Point 9f is a point on the boundary of the second inner third surface F93, and is a point on the boundary opposite to point 9e with respect to the second inner third surface F93.

[0161] As shown in Figures 26 and 33, the "second outer first surface F81" is a surface extended by rotating a line segment connecting points 8b, 8b prepared on the surface of the outer roll 8 along the surface of the outer roll 8, around the rotation axis 81. The width Wr22o of the second outer first surface F81 is shorter than the "width Ww22o of the outer surface so in the long side direction of the workpiece 1".

[0162] Point 8a is a point on the boundary of the partial surface of the outer roll 8, which forms the corner of the workpiece 1 by corner machining. Point 8b is a point on the intersection line of the second outer first surface F81 and the virtual surface extending from the second inner third surface F93. The position of point 8b is set such that the width Wr22o of the second outer first surface F81 between points 8b, 8b is shorter than the width Ww22o of the outer surface so in the long-side direction of the workpiece 1. Point 8b is positioned symmetrically from the center of the outer roll. Point 8c is a point on the boundary of the second outer second surface F82, located at both ends of the second outer second surface F82. The position of point 8c is set such that the width Wr23o of the second outer second surface F82 is greater than or equal to the width Ww22o of the outer surface so in the long-side direction of the workpiece 1. Point 8c is positioned symmetrically from the center of the outer roll. Point 8c is located on the surface of the outer roll 8, in the direction from point 8a toward point 8b.

[0163] As shown in Figure 33, the "second outer second surface F82" is a surface that extends by rotating a line segment connecting points 8c, 8c prepared on the surface of the outer roll 8 along the surface of the outer roll 8, around the rotation axis 81. The width Wr23o of the second outer second surface F82 is greater than or equal to the "width Ww22o of the outer surface so in the long side direction of the workpiece 1".

[0164] Figure 35 is an explanatory diagram of the thickening step according to the second embodiment, where (a) is a side view of the workpiece before thickening and (b) is a side view of the workpiece after thickening. Figure 35(a) shows the shape of the curved portion. Figure 35(b) shows the shape of the thickened portion formed by the thickening step.

[0165] As shown in Figure 35(b), the thickened portion B22 formed in the thickening step satisfies the following embodiment B9. <Embodiment B9> When the outer roll 8 acts on the end E22 from the outer surface so side of the workpiece 1, and the end E22 thickens on the inner surface si side, an outer corner portion 13 is formed on the outer surface so side of the thickened portion B22 by the outer surface so and the end face of the thickened portion B22, and the radius of curvature Rt2 of the outer corner portion 13 of the thickened portion B22 and the thickness Tw of the workpiece satisfy the following equation (2-4). Tw × 1 / 4 ≤ Rt2 ≤ Tw × 1 / 2 Equation (2-4)

[0166] The lower limit of Rt2 is preferably Tw × (11 / 40) or more, more preferably Tw × (12 / 40) or more. The upper limit of Rt2 is preferably Tw × (19 / 40) or less, more preferably Tw × (18 / 40) or less.

[0167] In the thickening step, the inner roll 9 is applied to the end E22 of the workpiece 1 in the following manner B10. <Manner B10> The inner roll 9 has a second inner corner portion 92 formed by a second inner first surface F91 and a second inner second surface F92, and the following equation (2-5) is satisfied for the radius of curvature Rc22i of the second inner corner portion 92 and the plate thickness Tw of the workpiece 1. Tw × 0.6 ≤ Rc22i ≤ Tw × 0.9 Equation (2-5) The second inner corner portion 92 faces the end E22 of the workpiece 1 on the inside in the out-of-plane direction.

[0168] The lower limit of Rc22i is preferably Tw × (65 / 100) or more, more preferably Tw × (70 / 100) or more. The upper limit of Rc22i is preferably Tw × (85 / 100) or less, more preferably Tw × (80 / 100) or less. Above the lower limit, it becomes easier to form the thickened portion B22. Below the upper limit, it becomes easier to secure the in-plane thickness (volume) of the thickened portion B22.

[0169] As shown in Figure 35(b), the thickened portion B22 formed in the thickening step satisfies the following embodiment B11. <Embodiment B11> When the inner roll 9 acts on the end E22 from the inner surface si side of the workpiece 1, and the end E22 forms a thickened portion B22 on the inner surface si side, an inner corner portion 14 is formed on the inner surface si side of the thickened portion B22 by the inner surface si and the slope of the thickened portion B22, and the radius of curvature Rtt2 of the inner corner portion 14 of the thickened portion B22 and the plate thickness Tw of the workpiece 1 satisfy the following equation (2-6). Tw × 0.5 ≤ Rtt2 ≤ Tw × 1.0 Equation (2-6)

[0170] The lower limit of Rtt2 is preferably Tw × (6 / 10) or more, more preferably Tw × (7 / 10) or more. The upper limit of Rtt2 is preferably Tw × (9 / 10) or less, more preferably Tw × (8 / 10) or less.

[0171] As shown in Figures 33 to 35, the following embodiment B12a is satisfied in the thickness-increasing step. <Embodiment B12a> The following equation (2-7a) is satisfied for the thickness Tw of workpiece 1, the width Ww22i of the inner surface si in the long side direction of workpiece 1, and the widths Wr22i of the second inner surface F91 and the second inner surface F92 of the second workpiece 1. 0.2 × Tw ≤ (Ww22i - Wr22i) / 2 ≤ 2 × Tw Equation (2-7a)

[0172] Note that Ww22i corresponds to the width dimension (along the direction of the second inner first surface F91) of the upper surface of workpiece 1 when workpiece 1, which has not undergone end processing, is in contact with the inner roll 9. Wr22i corresponds to the length of the line segment connecting points 9e, 9e in Figures 26 and 33 along the surface of the second inner first surface F91. (Ww22i - Wr22i) / 2 is the value obtained by subtracting the length Wr22i of the second inner first surface F91 and the second inner second surface F92 from the width dimension Ww22i of the upper surface of workpiece 1 in contact with the inner roll 9, and then dividing by 2. The width Ww22i of the inner surface si of workpiece 1 in contact with the inner roll 9 is longer than the length Wr22i of the second inner first surface F91 and the second inner second surface F92 by (Ww22i - Wr22i), and the ends E22, E22 of workpiece 1 extend in the width direction more than the second inner first surface F91 and the second inner second surface F92. In this case, (Ww22i - Wr22i) / 2 corresponds to the length at one end of how much longer the width Ww22i of the inner surface si of workpiece 1 is compared to the length Wr22i of the second inner first surface F91 and the second inner second surface F92. The length of the curved portion B21 and the height of the thickened portion B22 will change according to the length of (Ww22i - Wr22i) / 2. Note that Wr22i is a specific example of Wr2i.

[0173] The lower limit of (Ww22i - Wr22i) / 2 is preferably 0.3 × Tw or more, more preferably 0.4 × Tw or more. The upper limit of (Ww22i - Wr22i) / 2 is preferably 0.6 × Tw or less, more preferably 0.5 × Tw or less. Above the lower limit, the in-plane length of the thickened portion B22 increases, and the volume of the thickened portion B22 becomes sufficient, resulting in good joining quality. Below the upper limit, it becomes easier to suppress the formation of excessive thickened portion B22, which has little contribution to welding quality.

[0174] As shown in Figures 33 to 35, the following embodiment B12b is satisfied in the thickening step. <Embodiment B12b> The following equation (2-7b) is satisfied for the plate thickness Tw of workpiece 1, the width Ww22o of the outer surface so in the long side direction of workpiece 1, and the width Wr22o of the second outer first surface F81. 0.2 × Tw ≤ (Ww22o - Wr22o) / 2 ≤ 2 × Tw Equation (2-7b)

[0175] Note that Ww22o corresponds to the width dimension of the lower surface of workpiece 1 (along the direction of the second outer first surface F81) when workpiece 1, which has not undergone end processing, is in contact with the outer roll 8. Wr22o corresponds to the length of the line segment connecting points 8b, 8b in Figures 26 and 33 along the surface of the second outer first surface F81. (Ww22o - Wr22o) / 2 is the value obtained by subtracting the length Wr22o of the second outer first surface F81 from the width dimension Ww22o of the lower surface of workpiece 1 in contact with the outer roll 8, and then dividing by 2. The width Ww22o of the outer surface so of workpiece 1 in contact with the outer roll 8 is longer than the length Wr22o of the second outer first surface F81 by (Ww22o - Wr22o), and the ends E22, E22 of workpiece 1 extend in the width direction beyond the second outer first surface F81 in a relative relationship. In this case, (Ww22o - Wr22o) / 2 corresponds to the length at one end of the width Ww22o of the outer surface so of workpiece 1 relative to the length Wr22o of the second outer surface F81. The length of the curved portion B21 and the height of the thickened portion B22 will change according to the length of (Ww22o - Wr22o) / 2. Note that Wr22o is a specific example of Wr2o.

[0176] The lower limit of (Ww22o - Wr22o) / 2 is preferably 0.3 × Tw or more, more preferably 0.4 × Tw or more. The upper limit of (Ww22o - Wr22o) / 2 is preferably 0.6 × Tw or less, more preferably 0.5 × Tw or less. Above the lower limit, the in-plane length of the thickened portion B22 increases, and the volume of the thickened portion B22 becomes sufficient, resulting in good joining quality. Below the upper limit, it becomes easier to suppress the formation of excessive thickened portion B22, which has little contribution to welding quality.

[0177] Furthermore, as shown in Figure 35, the in-plane length Lt2 of the thickened portion B22 formed in the thickening step, and the plate thickness Tw of the workpiece 1 satisfy the following equation (2-8): 0.5 × Tw ≤ Lt2 ≤ 2 × Tw Equation (2-8)

[0178] "Length Lt2 of the thickened portion B22 in the in-plane direction" refers to the length of the thickened portion B22, which is thickened inward from the inner surface si near the end E22 of workpiece 1, in the in-plane direction near the end E22 of workpiece 1. Specifically, as shown in Figure 35, if point 1i is prepared on the surface of the workpiece and point 1j is prepared on the end face of the thickened portion B22, then Lt2 is the length of the line segment connecting point 1i and point 1j. Point 1i is a point on the boundary between the inner surface si (plane) near the end E22 of workpiece 1 and the surface of the thickened portion B22 of workpiece 1. Point 1j is a point on the end face of the thickened portion B22 of workpiece 1 that intersects with a line along the in-plane direction of the inner surface si near the end E22 of workpiece 1.

[0179] The lower limit of Lt2 is preferably 0.7 × Tw or more, more preferably 0.8 × Tw or more, and even more preferably 0.9 × Tw or more. The upper limit of Lt2 is preferably 1.5 × Tw or less, more preferably 1.2 × Tw or less, even more preferably 1.0 × Tw or less, and even more preferably less than 1.0 × Tw.

[0180] Furthermore, in the thickness-increasing step, the following embodiment B13 is satisfied. <Embodiment B13> The plate thickness Tw of workpiece 1 and the height Hr3i of the second inner third surface F93 satisfy the following equation (2-9): 1.05 × Tw ≤ Hr3i ≤ 2 × Tw Equation (2-9)

[0181] The "height Hr3i of the second inner third surface F93" is the width of the second inner third surface F93, which is approximately perpendicular to the second inner first surface F91. Specifically, as shown in Figure 33, it is the length of the line segment connecting points 9e and 9f. Hr3i determines the height dimension of the clearance of the inner roll for forming the thickened portion B22. The out-of-plane height of the thickened portion B22 will change according to Hr3i.

[0182] The lower limit of Hr3i is preferably 1.2 × Tw or more, more preferably 1.4 × Tw or more. The upper limit of Hr3i is preferably 1.8 × Tw or less, more preferably 1.6 × Tw or less. Above the lower limit, the out-of-plane height of the thickened portion B22 increases, and the volume of the thickened portion B22 becomes sufficient, resulting in good joining quality. Below the upper limit, it becomes easier to suppress the formation of excessive thickened portion B22, which has little contribution to welding quality.

[0183] As shown in Figure 35(b), the out-of-plane height Ht2 of the thickened portion B22 formed in the thickening step, and the plate thickness Tw of the workpiece 1 satisfy the following equation (2-10): 1.05 × Tw ≤ Ht2 ≤ 1.5 × Tw Equation (2-10)

[0184] The "out-of-plane height Ht2 of the thickened portion B22" is the length in the approximately perpendicular direction (z-direction) of the end face portion of the thickened portion B22 that abuts against the second inner third surface F93 of the inner roll 9 (see Figure 37). The out-of-plane height Ht2 of the thickened portion B22 is approximately the same as or smaller than the height Hr3i of the second inner third surface F93 of the inner roll. This is because the formed thickened portion B22 is smaller than the clearance provided by the roll (inner roll 9).

[0185] The lower limit of Ht2 is preferably 1.15 × Tw or more, more preferably 1.25 × Tw or more. The upper limit of Ht2 is preferably 1.45 × Tw or less, more preferably 1.35 × Tw or less. Above the lower limit, the out-of-plane height of the thickened portion B22 increases, and the volume of the thickened portion B22 becomes sufficient, resulting in good joining quality. Below the upper limit, it becomes easier to suppress the formation of unnecessary thickened portion B22 that does not affect welding quality.

[0186] For example, in the thickening step, the inner roll 9 is applied to the end E22 of the workpiece 1 according to the following embodiment B14: <Embodiment B14> The angle θ22i between the second inner third surface F93 and the rotation axis 91 of the inner roll 9 satisfies the following equation (2-11): -10° ≤ θ22i ≤ 10° Equation (2-11) θ22i corresponds to the angle between the rotation axis 91 of the inner roll 9 and the second inner third surface F93 of the inner roll 9, which receives the reaction force from the workpiece 1 to the action from the inner roll 9 toward the bending portion B21 when the second inner third surface F93 of the inner roll 9 acts toward the bending portion B21 from the end face side in the in-plane direction (see Figure 32(b)).

[0187] According to embodiment B14, when a compressive force is applied perpendicular to the rotation axis of the roll (the rotation axis 91 of the inner roll 9), deformation can be efficiently carried out by the compressive force applied from the roll to the workpiece 1. In the thickening step, when the second surface of the roll (the second inner third surface F93) acts in the in-plane direction from the end face side on the curved portion B21, if the direction in which the compressive force applied perpendicular to the rotation axis of the roll acts (compression direction) is parallel (0°) to the in-plane direction, the compressive force applied from the roll can deform the curved portion B21 by crushing it, thereby forming the thickened portion B22. On the other hand, if the compression direction of the roll and the in-plane direction are not parallel, the compressive force applied to the curved portion B21 is converted into a bending force, resulting in bending deformation, and a good thickened portion B22 cannot be formed.

[0188] The lower limit of θ22i is preferably -7° or more, more preferably -5° or more. The upper limit of θ22i is preferably 7° or less, more preferably 5° or less. By having θ22i within the above range, the force applied from the end E22 of the workpiece 1 to the second inner third surface F93 can be received in a direction substantially perpendicular to the rotation axis 91 of the inner roll 9. That is, the force from the workpiece 1 generated when forming the thickened portion B22 is received by the rotation axis 91 of the inner roll 9, and the deformation of the thickened portion B22 can be efficiently carried out by the compressive force applied to the workpiece 1 from the second surface of the inner roll 9 in a direction substantially perpendicular to the rotation axis 91. Furthermore, as will be described later, in this embodiment, the angle of the end E22 with respect to the horizontal plane P2 when performing the thickening step is θa2 = 90°. In this case, because θ22i is within the above range, in the thickening step, when the second inner third surface F93 of the inner roll 9 acts in the in-plane direction on the curved portion B21 from the end face side, the direction in which the compressive force acting perpendicular to the rotation axis 91 of the inner roll 9 acts (compression direction) and the in-plane direction of the workpiece end are parallel (0°), so that the compressive force applied from the roll deforms the curved portion B21 by crushing it, thereby forming the thickened portion B22.

[0189] The angle θ(47) between the second outer first surface F81 and the second inner third surface F93 is between 80° and 100°. Angle θ(47) represents the inclination angle of the second inner third surface F93 with respect to the second outer first surface F81. The angle θ(48) between the second inner first surface F91 and the second inner second surface F92 is between 150° and 170°. Angle θ(48) represents the inclination angle of the second inner second surface F92 with respect to the second inner first surface F91. The angle θ(49) between the second inner second surface F92 and the second inner third surface F93 is between 60° and 80°. Angle θ(49) represents the inclination angle of the second inner third surface F93 with respect to the second inner second surface F92.

[0190] [Timing of Bending Step and Thickening Step] As shown in Figure 27, in the second embodiment, the bending step is performed in the second forming process and the thickening step is performed in the third forming process. However, the bending step and thickening step can be performed as appropriate during the stepwise forming process by roll forming (roll flower).

[0191] Furthermore, in the first embodiment, a more detailed explanation is provided regarding the angle θa1 of the end with respect to the horizontal plane P1 after the thickening step, and the angle θb1 of the end with respect to the horizontal plane P1 after the bending step. This detailed explanation also applies to the angle θa2 of the end with respect to the horizontal plane P2 after the thickening step, and the angle θb2 of the end E22 with respect to the horizontal plane P2 after the bending step, in the second embodiment. Note that θb2 is a specific example of θb.

[0192] Figure 36 is an end view of the workpiece 1 after the molding process is completed according to the second embodiment. Figure 37 is an enlarged view of Figure 36. As shown in Figures 36 and 37, when the molding process is completed, a butt joint T is formed where the ends of the workpiece 1 are joined together. According to the roll forming of this embodiment, the thickness of the reinforced portion B22 provided in the butt joint T can be increased.

[0193] [Joining Process] The description of the joining process in the first embodiment also applies to the second embodiment. Figure 38 is an explanatory diagram of the joining process according to the second embodiment. As shown in Figure 38, a laser beam 106 can be irradiated onto the end portion where the back-convex thickened portion B22, which constitutes the butt joint T, is formed. After manufacturing the cylindrical body, the container can be manufactured by joining the parts to seal the opening of the cylindrical body.

[0194] [Effects] The method for manufacturing a cylindrical body according to the second embodiment provides the same effects as the first embodiment. Furthermore, according to the second embodiment, a thickened portion B22 can be provided for each of the butted ends of the workpiece 1 such that the inner surface si side (inner side) is convex (Figure 37).

[0195] [3. First Modification] Figure 39 is an explanatory diagram of beam welding according to the first modification. In the first modification, a first laser beam and a second laser beam are irradiated onto the butt joint T where the reinforced portions B12 are joined together to perform tandem beam welding. Here, we will explain the case in which the modification is applied to the first embodiment in which the reinforced portion B12 is provided so that the outer surface so side is convex, but it can also be applied to the second embodiment in which the reinforced portion B22 is provided so that the inner surface si side is convex.

[0196] Figure 39 schematically shows a cross-sectional view taken from the side parallel to the direction of travel during tandem beam welding. The white arrows in Figure 39 indicate the welding direction, which is opposite to the transport direction (x direction) of the workpiece 1. As shown in Figure 39, the irradiation position of the first pass of laser beam 106a (first laser beam) is followed by the irradiation position of the second pass of laser beam 106b (second laser beam), and the first pass of laser beam 106a and the second pass of laser beam 106b are irradiated continuously with an interval between them. When the low-power first pass of laser beam 106a is irradiated onto the thickened portion B12 of the transported workpiece 1, the metal at the irradiated area partially melts, and a shallow, hole-like first keyhole 107a is formed. In addition, a small, high-temperature first molten pool 108a is formed around the first keyhole 107a. This causes partial penetration of the workpiece 1. A high-power second pass of laser light 106b is irradiated after a predetermined time has elapsed since the irradiation of the first pass of laser light 106a. During the predetermined time, the first molten pool 108a cools, and the first rapidly solidified portion 109a (solidified portion) is formed. As a result, a shallow joint is made. When the second pass of laser light 106b, which has a higher output than the first pass, is irradiated, the metal at the irradiated area melts completely, and a deep, hole-like second keyhole 107b is formed. In addition, a large and high-temperature second molten pool 108b is formed around the second keyhole 107b. This results in complete penetration in the thickness direction of the workpiece 1. When the irradiated area moves due to the transport of the workpiece 1, the second molten pool 108b cools, and a second rapidly solidified portion 109b (welded portion) is formed.

[0197] Figure 40 is an explanatory diagram of a weld made by tandem beam welding according to the first modified example. Figure 40 schematically shows a cross-sectional view in a plane perpendicular to the direction of travel when performing tandem beam welding. The upper part of Figure 40 shows the butt joint T in its initial state. The middle part of Figure 40 shows the first rapidly solidified portion 109a (first weld) 109a after irradiation with the first pass of laser light 106a. The lower part of Figure 40 shows the second rapidly solidified portion (second weld) 109b after irradiation with the second pass of laser light 106b. Through such state transitions, a weld bead is formed. According to the joining method of this example, by causing partial penetration by irradiating the butt joint T with laser light 106a in the first pass and forming the first rapidly solidified portion 109a, the ends with the thickened portion B12 can be leveled. Furthermore, by irradiating the first rapidly solidified portion 109a with laser light 106b in the second pass, the abutment portion T can be melted to a deeper position, thereby forming a second rapidly solidified portion 109b that joins the entire thickness of the abutment portion T1.

[0198] According to the first modified example, by tandem beam welding, the first pass of laser light 106a is irradiated onto the thickened portion B12 of the butt joint T to form a first rapidly solidified portion 109a, and the second pass of laser light 106b is irradiated onto this first rapidly solidified portion 109a to form a second rapidly solidified portion 109b (welded portion). In this way, by irradiating with two passes of laser light, laser light 106a and laser light 106b, with a time difference, the joining quality can be improved compared to single-beam welding.

[0199] In the first modified example, it is preferable that the output of the second pass of laser light 106b is higher than the output of the first pass of laser light 106a. This allows the first pass of laser light 106a to form a first rapidly solidified portion 109a that shallowly joins and solidifies the abutment portion T, and then the second pass of laser light 106b to form a second rapidly solidified portion 109b that joins to a deeper position in the abutment portion T1.

[0200] [4. Second Modification] Figure 41 is an explanatory diagram of beam welding according to the second modification. In the second modification, the first laser beam and the second laser beam are irradiated onto the butt joint T where the reinforced portions B12 are joined together to perform ring beam welding. Here, we will explain the case in which the modification is applied to the first embodiment in which the reinforced portion B12 is provided so that the outer surface so side is convex, but it can also be applied to the second embodiment in which the reinforced portion B22 is provided so that the inner surface si side is convex.

[0201] Figure 41(a) shows a cross-sectional view taken from the side parallel to the direction of travel during ring beam welding. The white arrow in Figure 41(a) indicates the welding direction, which is opposite to the transport direction (x direction) of the workpiece 1. As shown in Figure 41(a), the irradiation range of the ring beam 106c (first laser beam) and the irradiation range of the core beam 106d (second laser beam) overlap, and the ring beam 106c and core beam 106d are irradiated almost simultaneously. Figure 41(b) schematically shows the profile of the first irradiation region 106e irradiated by the ring beam 106c and the profile of the second irradiation region 106f irradiated by the core beam 106d during ring beam welding. The first irradiation region 106e irradiated by the ring beam 106c includes the area in front of the direction of travel of the core beam 106d and surrounds the second irradiation region 106f irradiated by the core beam 106d. Specifically, as shown in Figure 41(b), a second irradiation area 106f is irradiated by the core beam 106d, and a first irradiation area 106e is irradiated by the ring beam 106c surrounding the second irradiation area 106f. In this example, the second irradiation area 106f is circular in shape, and the first irradiation area 106e is annular in shape. As shown in Figures 41(a) and (b), when the annular ring beam 106c and the core beam 106d (drawn as dots) are irradiated onto the thickened portion B12 of the transported workpiece 1, the metal at the irradiated area melts, and a hole-shaped keyhole 107c is formed. In addition, a molten pool 108c is formed around the keyhole 107c. The ring beam 106c has a wide irradiation range, which allows the molten pool 108c to spread shallowly forward in the welding direction. The core beam 106d has a narrow irradiation range, which allows the molten pool 108c to deepen, and the metal at the irradiated area to melt completely. The ring beam 106c and core beam 106d allow the keyhole 107c and molten pool 108c to be expanded in the welding direction. Furthermore, as the irradiation point moves due to the transport of the workpiece 1, the molten pool 108c cools and a rapidly solidified portion 109c (welded area) is formed. Compared to single-beam welding, ring beam welding allows for a larger spread of the molten pool 108c, resulting in faster cooling of the molten pool 108c and better formation of the rapidly solidified portion 109c.

[0202] Figure 42 is an explanatory diagram of a weld made by ring beam welding according to a second modified example. Figure 42 schematically shows a cross-sectional view in a plane perpendicular to the direction of travel when performing ring beam welding. The upper part of Figure 42 shows the butt joint T in its initial state. The middle part of Figure 42 shows the front portion of the molten pool 108c being irradiated by the ring beam 106c. The lower part of Figure 41 shows the rapidly cooled and solidified portion (welded portion) 109c behind the molten pool 108c after irradiation with the ring beam 106c and core beam 106d. A weld bead is formed by such a state transition. According to the joining method of this example, by irradiating the butt joint T with the ring beam 106c, partial penetration occurs in the front and a molten pool 108c is formed, making it possible to level the ends where the thickened portion B12 is provided. Furthermore, by irradiating the molten pool 108c with the core beam 106d, the butt joint T can be melted to a deeper position, thereby forming a rapidly solidified portion 109c that joins the entire thickness of the butt joint T1.

[0203] According to the second modified example, by ring beam welding, a molten pool 108c is formed by irradiating a first irradiation region 106e, which includes the region in front of the direction of travel of the core beam 106d and surrounds the second irradiation region 106f by the core beam 106d, with the ring beam 106c. Then, by irradiating this molten pool 108c with the core beam 106d, a rapidly solidified portion 109c (welded portion) is formed. In this way, by irradiating with laser light from two passes, one from the ring beam 106c and the other from the core beam 106d, which have different irradiation regions, the joining quality can be improved compared to single-beam welding.

[0204] In the second modified example, a shallow molten pool 108c is formed in the butt joint T by the first irradiation region 106e of the ring beam 106c, and then a rapidly solidified portion 109c that joins to a deeper position in the butt joint T1 is formed by the second irradiation region 106f of the core beam 106d. The output of the ring beam 106c and the core beam 106d can be appropriately changed according to the shape of the workpiece and the desired properties of the weld.

[0205] [5. Others] (a) The metal used for the workpiece is not limited to aluminum or an aluminum alloy; for example, the present invention can be applied to metals other than aluminum. (b) It is also possible to realize a technology that appropriately combines the various technologies described in this embodiment. (c) The shape, material, function, etc. of the members described in this embodiment can be changed as appropriate. (d) In addition, the components of the present invention can be changed as appropriate without departing from the spirit of the present invention.

[0206] [6. Addendum] The following addendum is disclosed in relation to the above description. [1]: A manufacturing method for producing a cylindrical body by joining abutting portion where the ends on the long sides of a long workpiece made of aluminum or an aluminum alloy are joined together, comprising a forming step of forming the abutting portion by deforming the workpiece so that the ends on the long side of the workpiece are joined together by performing roll forming on the workpiece, wherein in the forming step, the workpiece is sandwiched between an outer roll positioned on the outer surface side of the workpiece and an inner roll positioned on the inner surface side of the workpiece to process the ends of the workpiece, and the forming step is performed by the first outer roll and the first inner roll A method for manufacturing a cylindrical body, comprising: a bending step of sandwiching the workpiece from both sides of the workpiece and applying the first outer roll or the first inner roll to bend the end of the workpiece out of the plane, thereby forming a curved portion that is deformed so that the end is bent out of the plane; and a thickening step of sandwiching the workpiece from both sides of the workpiece with the second outer roll and the second inner roll and applying the second outer roll or the second inner roll to push the curved portion in the in-plane direction, thereby forming a thickened portion that is deformed so that the end is thickened out of the plane. [2]: A method for manufacturing a cylindrical body according to [1], wherein in the molding step, the workpiece is deformed so that the ends on which the thickened portions are formed abut against each other to form a butt joint, and the manufacturing method further comprises a joining step of joining the butt joint. [3]: A method for manufacturing a cylindrical body according to [2], wherein in the joining step, the butt joint is joined by laser joining, in the joining step, a first laser beam and a second laser beam are irradiated onto the butt joint where the thickened portions are joined together, the first laser beam is irradiated onto the thickened portions to melt the joined thickened portions and form a solidified portion by solidifying the molten thickened portions together, and the second laser beam is irradiated onto the solidified portion to melt the butt joint including the solidified portion and form a welded portion by solidifying the molten butt joint.[4]: The method for manufacturing a cylindrical body according to [2], wherein in the joining step, the butt joint is joined by laser joining, and in the joining step, a first laser beam and a second laser beam are irradiated onto the butt joint where the thickened portions are butted together, the first irradiation area irradiated by the first laser beam includes an area in front of the direction of travel of the second laser beam with respect to the second irradiation area irradiated by the second laser beam, and is the area surrounding the second irradiation area, the first laser beam is irradiated onto the thickened portions to melt the butted portions and form a molten pool, the second laser beam is irradiated onto the molten pool to melt the butt joint including the molten pool, and a weld is formed by the solidification of the molten butt joint.

[0207] Examples of the present invention will be described in comparison with comparative examples.

[0208] [Evaluation Method] <Test Specimen> Figure 43 is an explanatory diagram of the tensile test of a cylindrical body according to this embodiment. The test specimen 200 is a cylindrical body manufactured according to the first and second embodiments. A welded portion 201 is formed on the upper surface of the test specimen 200 along the axial direction. The total length of the test specimen 200 in the axial direction is 900 mm. The plate thickness Tw of the test specimen 200 is Tw = 0.65 mm. The width of the test specimen 200 (short side of the rectangular annular end face) is 26.5 mm. The height of the test specimen 200 (long side of the rectangular annular end face) is 85 mm. The radius of curvature of the outer radius of the four corners of the test specimen 200 is 3 mm. Multiple test pieces 202 can be obtained by cutting the test specimen 200 perpendicular to the axial direction at predetermined positions in the axial direction. For example, as shown in Figure 43, five test pieces 202A to 202E were obtained, cut out along the axial direction at intervals of approximately 210 mm from the start point to the end point of the laser welding joint.

[0209] <Visual Inspection (Perforation Evaluation)> The number and size of holes visible in the welded joint 201 of the test specimen 200 before cutting were evaluated by visual inspection. If there were no holes (0), it was evaluated as "Excellent (◎)". If there were 1 to 3 holes, it was evaluated as "Good (○)". If there were 4 or more holes, it was evaluated as "Unacceptable (×)".

[0210] <Cross-section of the welded joint> Test piece 202 was embedded in epoxy resin with the excess removed, leaving the area near the joint intact. After rough polishing with emery paper (#80, #300, #600), it was polished with diamond paste (particle size 6 μm, 3 μm), then polished with alumina (particle size 1 μm), and finally mirror-finished with magnesium oxide powder to prepare a sample for cross-sectional observation of the welded joint. Subsequently, the sample for cross-sectional observation of the welded joint was etched with 5% hydrofluoric acid for 30 seconds. The cylindrical welded joint and its surrounding area were then observed in cross-section using an optical microscope, ECLIPSE MA200 manufactured by Nikon Solutions Inc., at a magnification of 50x.

[0211] <Tensile Test> Tensile tests were performed on the obtained test specimens 202 (202A to 202E). Specifically, a 20mm wide strip of test specimen 202 was cut along the joining direction, and then the center of the bottom surface of the cut test specimen 202 was cut along the axial direction, and the four corners of the rectangle were unfolded onto a plane. After that, the unfolded plate-shaped test specimen 202 was pulled using a tensile testing machine. The longitudinal dimension of the unfolded test specimen 202 (the same as the circumference of the end face of the test specimen 200) was 140mm. The short-side dimension of the unfolded test specimen 202 (the same as the axial direction of the test specimen 200) was 20mm. When pulled by the tensile testing machine, the weld 203 formed in the center of the test specimen 202 and / or the base material near the weld 203 fractured. Tensile tests were performed on five samples obtained from test specimens 202A to 202E, and the joint strength was obtained by calculating the average value of the five measured values.

[0212] Furthermore, the standard used for tensile testing was the tensile testing method for metallic materials (JIS Z 2241). In addition, the tensile testing machine used was the universal tensile testing machine (REH-30) manufactured by Shimadzu Corporation.

[0213] The quality of the 200 test specimens was evaluated by assessing the fracture of the welded joint through tensile testing. The specific evaluation items were (1) fracture location and (2) joint efficiency.

[0214] (1) Regarding the fracture location, the location and cross-sectional shape of fractures occurring inside the weld 204, and the location and cross-sectional shape of fractures occurring in the base metal near the weld 204, i.e., fractures in the heat-affected zone of the base metal (hereinafter sometimes referred to as "HAZ" (Heat-Affected Zone)), were observed and evaluated. If the fracture occurred inside the weld of the cylindrical body, it was evaluated as "weld metal". If the fracture occurred in the heat-affected zone of the base metal, it was evaluated as "HAZ". If the fracture occurred both inside the weld of the cylindrical body and in the heat-affected zone of the base metal, it was evaluated as "weld metal + HAZ".

[0215] (2) The joint efficiency was evaluated using the formula: "Joint efficiency (%) = (Joint strength [MPa] / Base material strength [MPa]) × 100". Five plate-shaped test pieces of the same size and material as the test piece used for the tensile test after forming the weld 201 were prepared, and tensile tests were performed under the same conditions. The base material strength was obtained by calculating the average of the five measured values. The base material strength was set to 159 [MPa] and the joint efficiency value was calculated.

[0216] [Example 1 (Condition C)] A workpiece 1 with a total length of 900 mm, a width of 223 mm, and a thickness of 0.65 mm was prepared by cutting a sheet material made of A3003 H14 using a slitter. A test specimen 200 of Example 1 was obtained by performing a forming process using a roll forming device and a joining process using a laser welding device on this workpiece 1.

[0217] In the roll forming apparatus of Example 1, the end of the workpiece 1 was processed to form a thickened portion B12 at the end E12, and the workpiece 1 was deformed so that the ends of the workpiece 1 butted together to form a butt portion T. In the roll forming apparatus of Example 1, the thickened portion B12 was formed on the outside (front side) of the workpiece 1 so as to be convex, using the method described in the first embodiment. In Example 1, the increase in the thickness of the workpiece 1 from the plate thickness Tw of the workpiece 1 before processing due to the thickened portion B12 formed by the end processing (end processing height) is 0.10 mm. In the second forming step of the roll forming apparatus of Example 1, as described with reference to Figures 8 to 11, a bending step was performed using the first outer roll (outer roll 2) and the first inner roll (inner roll 3). In the third forming step of the roll forming apparatus of Example 1, as described with reference to Figures 12 to 15, a thickening step was performed using the second outer roll (outer roll 4) and the second inner roll (inner roll 5). In the roll forming apparatus of Example 1, the relationship between the angle θα of the end E12 with respect to the horizontal plane P1 when the butt joint T is formed and the angle θa1 of the end E12 with respect to the horizontal plane P1 after the thickness-increasing step was α = 180° and θa1 = 90°. In this case, θa1 = α × (1 / 2). In the roll forming apparatus of Example 1, the relationship between the angle α of the end E12 with respect to the horizontal plane P1 when the butt joint T is formed and the angle θb1 of the end E12 with respect to the horizontal plane P1 after the bending step was θb1 = 55°. In this case, θb1 ≈ α × 0.31.

[0218] In Example 1, the relationship between the thickness Tw of the workpiece 1, the width Ww11i of the inner surface in the long-side direction of the workpiece 1, and the width Wr11i of the first inner surface F31 of the first inner roll (inner roll 3) was (Ww11i - Wr11i) / 2 = 0.6 mm. In this case, (Ww11i - Wr11i) / 2 ≈ 0.92 × Tw. In Example 1, the angle θ(41) between the first inner surface F31 and the first inner surface F32 of the first inner roll (inner roll 3) was 55°. In Example 1, the relationship between the in-plane length Lb1 of the curved portion B11 and the thickness Tw of the workpiece 1 was Lb1 = 0.6 mm. In this case, Lb1 = 0.92 × Tw. In Example 1, the bending angle θ(51) of the curved portion B11 was 55°.

[0219] In Example 1, for the second inner roll (inner roll 5), the relationship between the radius of curvature Rc12i of the second inner corner portion 52 and the thickness Tw of the workpiece 1 was Rc12i = 0.2 mm. In this case, Rc12i ≈ Tw × 0.31. In Example 1, for the second outer roll (outer roll 4), the relationship between the radius of curvature Rc12o of the second outer corner portion 42 and the thickness Tw of the workpiece 1 was Rc12o = 0.5 mm. In this case, Rc12o ≈ Tw × 0.77. In Example 1, for the second inner roll (inner roll 5), the relationship between the thickness Tw of the workpiece 1, the width Ww12i of the inner surface in the long side direction of the workpiece 1, and the width Wr12i of the second inner first surface F51 was (Ww12i - Wr12i) / 2 = 0.3 mm. In this case, (Ww12i - Wr12i) / 2 ≈ 0.46 × Tw. For the second inner roll (inner roll 5) in Example 1, the relationship between the plate thickness Tw of the workpiece 1 and the height Hr2i of the second inner surface F52 was Hr2i = 1.01 mm. In this case, Hr2i ≈ 1.6 × Tw. For the second inner roll (inner roll 5) in Example 1, the angle θ12i = 0° between the second inner surface F52 and the rotation axis 51 of the inner roll 5. In Example 1, the relationship between the radius of curvature Rt1 of the inner corner portion 11 of the thickened portion B12 and the plate thickness Tw of the workpiece 1 was Rt1 = 0.2 mm. In this case, Rt1 ≈ Tw × 0.31. In Example 1, the relationship between the radius of curvature Rtt1 of the outer corner portion 12 of the thickened portion B12 and the plate thickness Tw of the workpiece 1 was Rtt1 = 0.5 mm. In this case, Rtt1 ≈ Tw × 0.77. In Example 1, the relationship between the in-plane length Lt1 of the thickened portion B12 and the plate thickness Tw of the workpiece 1 was Lt1 = 0.6 mm. In this case, Lt1 ≈ 0.92 × Tw. In Example 1, the relationship between the out-of-plane height Ht1 of the thickened portion B12 and the plate thickness Tw of the workpiece 1 was Ht1 = 0.75 mm. In this case, Ht1 ≈ 1.15 × Tw.

[0220] In the joining process, laser joining was performed using the following single-mode joining conditions. The conditions and results are shown in Tables 1 and 2. <Joining Conditions> ・Equipment used: YLS-10000 (manufactured by IPG PHOTONICS) ・Welding method: Single ・Welding speed: 20 m / min ・Beam mode: Multimode laser ・Laser wavelength: 1070 nm ・Laser focal diameter: 400 μm ・Shielding gas type: Ar ・Laser incidence angle: 15° backward ・Laser output: 4200 W ・Shielding gas flow rate: 20 L / mm In the joining conditions, "laser incidence angle" represents the angle from the vertical line of the irradiated beam. "15° backward" means that the laser was incident at an angle of 15° backward from the vertical axis in the welding direction. "Shielding gas flow rate" represents the flow rate value of Ar.

[0221]

[0222]

[0223] [Example 2 (Condition D)] Workpiece 1 was prepared in the same manner as in Example 1, and a molding process using a roll forming device and a joining process using a laser welding device were performed on this workpiece 1 to obtain the test specimen 200 of Example 2.

[0224] In the roll forming apparatus of Example 2, the end of the workpiece 1 was processed to form a thickened portion B22 at the end E22, and the workpiece 1 was deformed so that the ends of the workpiece 1 butted together to form a butt joint T. In the roll forming apparatus of Example 2, the thickened portion B22 was formed on the inside (back side) of the workpiece 1 so as to be convex, using the method described in the second embodiment. In Example 2, the end processing height is 0.10 mm. In the second forming step of the roll forming apparatus of Example 2, as described with reference to Figures 28, 29, and 30, a bending step was performed using the first outer roll (outer roll 6) and the first inner roll (inner roll 7). In the third forming step of the roll forming apparatus of Example 2, as described with reference to Figures 32, 33, and 34, a thickening step was performed using the second outer roll (outer roll 8) and the second inner roll (inner roll 9). In the roll forming apparatus of Example 2, the relationship between the angle θ of the end E22 with respect to the horizontal plane P2 when the butt joint T is formed (α) and the angle θa2 of the end E22 with respect to the horizontal plane P2 after the thickness-increasing step was α = 180° and θa2 = 90°. In this case, θa2 = α × (1 / 2). In the roll forming apparatus of Example 2, the relationship between the angle α of the end E22 with respect to the horizontal plane P2 when the butt joint T is formed and the angle θb2 of the end E22 with respect to the horizontal plane P2 after the bending step was θb2 = 55°. In this case, θb2 ≈ α × 0.31.

[0225] In Example 2, the relationship between the thickness Tw of the workpiece 1, the width Ww21o of the inner surface in the long-side direction of the workpiece 1, and the width Wr21o of the first inner surface F71 of the first inner roll (inner roll 7) was (Ww21o - Wr21o) / 2 = 0.6 mm. In this case, (Ww21o - Wr21o) / 2 ≈ 0.92 × Tw. In Example 2, the angle between the first inner surface F71 and the second inner surface F72 of the first inner roll (inner roll 7) was 55°. In Example 2, the relationship between the in-plane length Lb2 of the curved portion B21 and the thickness Tw of the workpiece 1 was Lb2 = 0.6 mm. In this case, Lb2 = 0.92 × Tw. In Example 2, the bending angle θ(52) of the curved portion B21 was 55°.

[0226] In Example 2, for the second inner roll (inner roll 9), the relationship between the radius of curvature Rc22i of the second inner corner portion 92 and the thickness Tw of the workpiece 1 was Rc22i = 0.5 mm. In this case, Rc22i ≈ Tw × 0.77. In Example 2, for the second outer roll (outer roll 8), the relationship between the thickness Tw of the workpiece 1, the width Ww22o of the outer surface in the long side direction of the workpiece 1, and the width Wr22o of the second outer first surface F81 was (Ww22o - Wr22o) / 2 = 0.3 mm. In this case, (Ww22o - Wr22o) / 2 ≈ 0.46 × Tw. In Example 2, for the second inner roll (inner roll 9), the relationship between the thickness Tw of the workpiece 1 and the height Hr3i of the second inner third surface F93 was Hr3i = 1.01 mm. In this case, Hr3i ≈ 1.55 × Tw. In Example 2, the second inner roll (inner roll 9) had an angle θ22i = 0° between the second inner third surface F93 and the rotation axis 91 of the inner roll 9. In Example 2, the relationship between the radius of curvature Rt2 of the outer corner portion 13 of the thickened portion B22 and the plate thickness Tw of the workpiece 1 was Rt2 = 0.2 mm. In this case, Rt2 ≈ Tw × 0.31. In Example 2, the relationship between the radius of curvature Rtt2 of the inner corner portion 14 of the thickened portion B22 and the plate thickness Tw of the workpiece 1 was Rtt2 = 0.5 mm. In this case, Rtt2 ≈ Tw × 0.77. In Example 2, the relationship between the in-plane length Lt2 of the thickened portion B22 and the plate thickness Tw of the workpiece 1 was Lt2 = 0.6 mm. In this case, Lt1 ≈ 0.92 × Tw. In Example 2, the relationship between the out-of-plane height Ht2 of the thickened portion B22 and the plate thickness Tw of the workpiece 1 was Ht2 = 0.75 mm. In this case, Ht2 ≈ 1.15 × Tw.

[0227] In the bonding process, laser bonding was performed using the same single-type bonding conditions as in Example 1, except that the laser output was changed to 4100W. The conditions and results are shown in Tables 1 and 2.

[0228] [Example 3 (Condition E)] Workpiece 1 was prepared in the same manner as in Example 1, and a molding process using a roll forming device and a joining process using a laser welding device were performed on this workpiece 1 to obtain the test specimen 200 of Example 3.

[0229] In the forming process, the process was carried out in the same manner as in Example 1, except that the first outer roll (outer roll 2) and the first inner roll (inner roll 3), and the second outer roll (outer roll 4) and the second inner roll (inner roll 5) were changed so that the end processing height was lower than that of Example 1. The thickened portion B12 was formed on the outside (front side) of the workpiece 1 so that it was convex, and the workpiece 1 was deformed to form the butt joint T. In Example 3, the end processing height is 0.05 mm. In the joining process, laser joining was performed under the same conditions as in Example 1, except that the method was changed to a tandem method in which a first pass of laser with a laser output of 2800 W and a second pass of laser with a laser output of 4200 W were continuously irradiated. The conditions and results are shown in Tables 1 and 2.

[0230] [Example 4 (Condition F)] Workpiece 1 was prepared in the same manner as in Example 1, and a molding process using a roll forming device and a joining process using a laser welding device were performed on this workpiece 1 to obtain the test specimen 200 of Example 4.

[0231] In the molding process, a thickened portion B12 was formed on the outer (front) side of the workpiece 1 in the same manner as in Example 1, and the workpiece 1 was deformed to form a butt joint T. In Example 4, the end processing height was 0.10 mm. In the joining process, the equipment used was changed to TruDisk6001 (manufactured by TRUMP), the method was changed to a ring system that simultaneously irradiates with a ring laser with a laser output of 2520 W and a core laser with a laser output of 630 W, the laser incidence angle was changed to a retracted 10°, and the shielding gas flow rate was changed to 30 L / min. Laser joining was performed under the same conditions as the joining process in Example 1. The conditions and results are shown in Tables 1 and 2.

[0232] [Comparative Example 1 (Condition A)] A workpiece was prepared in the same manner as in Example 1, and a molding process using a roll forming device and a joining process using a laser welding device were performed on this workpiece to obtain the test specimen 200 of Comparative Example 1.

[0233] In the forming process, the workpieces were deformed to butt together to form a joint, in the same manner as in Example 1, except that end processing to form a thickened portion after cutting with a slitter was not performed. In Comparative Example 1, the end processing height was 0 mm. In the joining process, laser joining was performed using the same single-type joining conditions as in Example 1, except that the laser output was changed to 3000 W. The conditions and results are shown in Tables 1 and 2.

[0234] [Comparative Example 2 (Condition B)] A workpiece was prepared in the same manner as in Example 1, and a molding process using a roll forming device and a joining process using a laser welding device were performed on this workpiece to obtain the test specimen 200 of Comparative Example 2.

[0235] In the forming process, the workpieces were deformed to butt together to form a joint, in the same manner as in Example 1, except that end processing to form a thickened portion after cutting with a slitter was not performed. In Comparative Example 2, the end processing height was 0 mm. In the joining process, laser joining was performed under the same single-pass joining conditions as in Example 1, except that the method was changed to a tandem method in which a first pass of laser with a laser output of 2800 W and a second pass of laser with a laser output of 3400 W were continuously irradiated. The conditions and results are shown in Tables 1 and 2.

[0236] [Results] Table 3 shows the external view of the welded portion of the cylindrical body according to Comparative Example 1 under condition A, and the external view of the welded portion of the cylindrical body according to this embodiment 3 under condition E. As shown in Table 3, perforation was confirmed in the welded portion 201A of the cylindrical body 200A of Comparative Example 1. The perforation of the cylindrical body 200A of Comparative Example 1 is considered to be due to the low accuracy of the groove surface at the end of the workpiece used in the manufacture of the cylindrical body 200A of the comparative example, resulting in poor airtightness of the welded portion 201A.

[0237]

[0238] On the other hand, it was confirmed that there were no holes in the welded portion 201 of the test specimen 200 of Example 3 under condition E. The absence of holes suggests that the groove surface accuracy of the end of the workpiece used in the manufacture of the test specimen 200 was high, and the airtightness of the welded portion 201 was good.

[0239] Table 1 is a summary table of the results for each joining condition for the welded joints of the cylindrical bodies in the comparative example and this embodiment. Table 2 is a summary table of the welding conditions for the workpieces before manufacturing the cylindrical bodies in the comparative example and this embodiment.

[0240] In Comparative Example 1, the cylindrical body under condition A, the tensile test results showed that the fracture location was in the "weld metal," the joint efficiency (%) was "74% (joint strength: 118 MPa)," and perforation was "×." A cross-section of the weld revealed poor penetration, poor fusion, and insufficient weld reinforcement height in the cylindrical body under condition A. In Comparative Example 2, the cylindrical body under condition B, the tensile test results showed that the fracture location was in the "weld metal + HAZ," the joint efficiency (%) was "84% (joint strength: 134 MPa)," and perforation was "◎." A cross-section of the weld revealed poor fusion and insufficient weld reinforcement height in the cylindrical body under condition B.

[0241] In Example 1, the cylindrical body under condition name C showed the following results in a tensile test: the fracture location was "HAZ", the joint efficiency (%) was "82% (joint strength: 130 MPa)", and the perforation was "○". In Example 2, the cylindrical body under condition name D showed the following results in a tensile test: the fracture location was "HAZ", the joint efficiency (%) was "80% (joint strength: 125 MPa)", and the perforation was "○". In Example 3, the cylindrical body under condition name E showed the following results in a tensile test: the fracture location was "HAZ", the joint efficiency (%) was "82% (joint strength: 130 MPa)", and the perforation was "◎". In Example 4, the cylindrical body under condition name F underwent a tensile test, and the results showed that the fracture location was "HAZ", the joint efficiency (%) was "85% (joint strength: 134 MPa)", and the perforation was "◎".

[0242] [Study] The following findings were obtained from the results shown in Tables 1, 2, and 3. ・In Comparative Examples 1 and 2, where end processing of the present invention was not performed, neither weld bead nor back bead was formed in the weld, resulting in variations in joint strength and fracture location, and a decrease in the strength of the weld itself. In contrast, in Examples 1 to 4, where end processing of the present invention was performed, the end was thickened, allowing for good formation of weld bead or back bead in the weld. Furthermore, the joint efficiency exceeded the target value of 80%. The fracture location was limited to the heat-affected zone of the base material. Therefore, the strength of the weld itself could be increased to a predetermined level or higher. As a result, the yield when manufacturing cylindrical bodies or, for example, aluminum battery containers can be improved. ・In Comparative Example 1, where end processing of the present invention was not performed and single-beam welding was performed, many holes occurred in the weld. This phenomenon can be attributed to a decrease in the accuracy of the groove surface between the ends, resulting in a decrease in the airtightness of the weld. ・In Comparative Example 2, where end processing of the present invention was not performed and tandem beam welding was performed, the number of holes in the weld was significantly reduced. This phenomenon can be attributed to the fact that the dimensional variations of the groove surfaces at the ends are leveled out, stabilizing the absorption rate of the laser beam and improving the airtightness of the weld. The same reasoning can be applied to ring beam welding as well as tandem beam welding. In other words, it was found that even with tandem beam welding, which has relatively high welding accuracy, joint defects occur if the end processing of the present invention is not performed. In Examples 1 and 2, in which the end processing of the present invention was performed and single beam welding was performed, the perforation of the weld was reduced to some extent. This phenomenon can be attributed to the fact that the thickness of the end was increased, allowing for good formation of weld bead or back bead in the weld, thus avoiding thinning of the weld. Furthermore, Examples 1 and 2 confirmed that joint efficiency can be improved even without performing two-beam welding such as tandem beam or ring beam welding. In Example 3, in which the end processing of the present invention was performed and tandem beam welding was performed, and in Example 4, in which ring beam welding was performed, the perforation of the weld was significantly reduced.This phenomenon can be attributed to the fact that the dimensional variation of the groove surfaces at the ends is leveled out by two-beam welding, stabilizing the absorption rate of the laser beam and improving the airtightness of the weld, and that the thickness of the ends is increased, allowing for good formation of weld bead or back bead, thus avoiding thinning of the weld. ・Tandem beam welding is disclosed, for example, in Reference 1 (Japanese Patent Publication No. 2013-103259). However, the usefulness of performing tandem beam welding on the ends of workpieces processed by the roll forming method of the present invention has been confirmed. ・Ring beam welding is disclosed, for example, in Reference 2 (Japanese Patent Publication No. 2021-112774). However, the usefulness of performing ring beam welding on the ends of workpieces processed by the roll forming method of the present invention has been confirmed.

[0243] 100: Cylindrical body 101: Welded part 200: Test specimen 1: Workpiece 11, 14: Inner corner section 12, 13: Outer corner section 2: Outer roll (first outer roll) 21: Rotation axis (of outer roll 2) 3: Inner roll (first inner roll) 31: Rotation axis (of inner roll 3) 4: Outer roll (second outer roll) 41: Rotation axis (of outer roll 4) 42: Second outer corner section 5: Inner roll (second inner roll) 51: Rotation axis (of inner roll 5) 52: Second inner corner section 6: Outer roll (first outer roll) 61: Rotation axis (of outer roll 6) 7: Inner roll (first inner roll) 71: Rotation axis (of inner roll 7) 8: Outer roll (second outer roll) 81: Rotation axis (of outer roll 8) 9: Inner roll (first inner roll) 91: Rotation axis (of inner roll 9) 92, 93: Second inner corner T: Butt joint so: Outer surface si: Inner surface E11, E12, E21, E22: End B11, B21: Curved section B12, B22: Thickened section P1, P2: Horizontal surface F21: First outer surface F22: First outer surface F31: First inner surface F32: First inner surface F41: Second outer surface F42: Second outer surface F51: Second inner surface F52: Second inner surface F61: First outer surface F62: First outer surface F71: First inner surface F72: First inner surface F81: Second outer surface F82: Second outer surface F91: Second inner surface F92: Second inner surface F93: Second inner surface vi11, vi12, vi21, vi22: virtual interior; vo11, vo12, vo21, vo22: virtual exterior

Claims

1. A manufacturing method for producing a cylindrical body by joining the butt joints where the long sides of a long workpiece made of aluminum or an aluminum alloy are joined together, comprising a forming step of forming the butt joint by roll forming the workpiece to deform the workpiece so that the long sides of the workpiece butt joints together, wherein in the forming step, the workpiece is sandwiched between an outer roll positioned on the outer surface side of the workpiece and an inner roll positioned on the inner surface side of the workpiece to process the ends of the workpiece, wherein the forming step comprises a bending step of sandwiching the workpiece from both sides between a first outer roll and a first inner roll, and applying the first outer roll or the first inner roll to bend the ends of the workpiece out of the plane, thereby forming a curved portion where the ends are deformed so that they are bent out of the plane, A method for manufacturing a cylindrical body, comprising: a thickness-increasing step, in which the workpiece is sandwiched from both sides by a second outer roll and a second inner roll, and the second outer roll or the second inner roll is applied to push the curved portion in the in-plane direction, thereby forming a thickened portion in which the end is deformed so that it is thickened in the out-of-plane direction.

2. In the bending step, a gap equal to the thickness of the workpiece is provided between the first outer roll and the first inner roll, the first outer roll contacts the outer surface of the workpiece, and the first inner roll contacts the inner surface of the workpiece, thereby sandwiching the workpiece, and the first outer roll or the first inner roll is applied to the end of the workpiece by either (1) or (2) below: (1) At the end, the first inner roll is in a positional relationship where it enters into a virtual inner surface formed when the inner surface near the end is extended in the in-plane direction, and the first outer roll is in a positional relationship where it is away from a virtual outer surface formed when the outer surface near the end is extended in the in-plane direction, and the first outer roll is facing the first inner roll at the end, and the first outer roll is in a positional relationship where it is away from a virtual outer surface formed when the outer surface near the end is extended in the in-plane direction, and the first outer roll is in a positional relationship where it enters into a virtual outer surface formed when the outer surface near the end is extended in the in-plane direction, The method for manufacturing a cylindrical body according to claim 1, wherein at the end, the first inner roll faces the first outer roll in a positional relationship that is away from a virtual inner surface formed when the inner surface near the end is extended in the in-plane direction.

3. In the bending step, the first outer roll or the first inner roll is applied to the end of the workpiece by either (1) below in the case of claim 2 (1) or (2) below in the case of claim 2 (2): (1) The first inner roll has, in a cross-sectional view through the rotation axis of the first inner roll, a first inner surface (F31) that is in contact with the workpiece and has a width shorter than the width of the inner surface in the long side direction of the workpiece, and a first inner second surface (F32) that slopes outward from the first inner surface; The first outer roll has, in a cross-sectional view through the rotation axis of the first outer roll, a first outer surface (F21) that is in contact with the workpiece and has a width shorter than the width of the outer surface in the long side direction of the workpiece, and a first outer second surface (F22) that slopes outward from the first outer surface (F21); In the bending step, the first outer surface (F21) contacts the outside of the workpiece, the first inner surface (F31) contacts the inside of the workpiece, thereby clamping the workpiece, the first inner second surface (F32) contacts the end from the inner surface side of the workpiece, and the first outer second surface (F22) contacts the end that has been deformed to be bent outward in the out-of-plane direction. (2) The first inner roll, in a cross-sectional view through the rotation axis of the first inner roll, has, with the rotation axis of the first inner roll as the center, a first inner surface (F71) that, in contact with the workpiece, has a width shorter than the width of the inner surface in the long side direction of the workpiece, and a first inner second surface (F72) that slopes inward from the first inner surface. The first outer roll, in a cross-sectional view through the rotation axis of the first outer roll, has, with the rotation axis of the first outer roll as the center, It has a first outer surface (F61) that, when in contact with the workpiece, has a width shorter than the width of the outer surface in the long side direction of the workpiece, and a first outer second surface (F62) that slopes inward from the first outer surface.In the bending step, the first outer surface (F61) contacts the outside of the workpiece, the first inner surface (F71) contacts the inside of the workpiece, thereby sandwiching the workpiece, and the first outer second surface (F62) contacts the end of the workpiece from the side of the outer surface, and the first inner second surface (F72) contacts the end that has been deformed to be bent inward in the out-of-plane direction, the method for manufacturing a cylindrical body according to claim 2.

4. In the bending step, with respect to the plate thickness Tw of the workpiece, the width Ww11i of the inner surface in the long side direction of the workpiece, the width Ww21o of the outer surface in the long side direction of the workpiece, the width Wr11i of the first inner surface (F31), and the width Wr21o of the first outer surface (F61), in the case of claim 3 (1), either (1) below or in the case of claim 3 (2), the following conditions are met: (1) 0.5 × Tw ≤ (Ww11i - Wr11i) / 2 ≤ 2 × Tw (2) 0.5 × Tw ≤ (Ww21o - Wr21o) / 2 ≤ 2 × Tw The method for manufacturing a cylindrical body according to claim 3.

5. In the bending step, in the case of claim 3 (1), either (1) below or in the case of claim 3 (2), either (1) or (2) below is satisfied: (1) When the first inner roll acts on the end from the inner surface side of the workpiece to form the curved portion in which the end is deformed toward the outer surface side, the angle between the first inner surface (F31) and the first inner surface (F32) is 40° or more and 70° or less. (2) When the first outer roll acts on the end from the outer surface side of the workpiece to form the curved portion in which the end is deformed toward the inner surface side, the angle between the first outer surface (F61) and the first outer surface (F62) is 40° or more and 70° or less. The method for manufacturing a cylindrical body according to claim 3.

6. In the thickness-increasing step, a gap equal to the thickness of the workpiece is provided between the second outer roll and the second inner roll, the second outer roll contacts the outer surface of the workpiece, and the second inner roll contacts the inner surface of the workpiece, thereby sandwiching the workpiece, and the second outer roll or the second inner roll is applied to the end of the workpiece by either (1) or (2) below: (1) At the end, the second inner roll is in contact with the curved portion from the end face side of the workpiece in a positional relationship that allows it to enter the workpiece at the end, and (2) At the end, the second outer roll is opposite the second inner roll in a positional relationship that allows it to move away from the virtual outer surface formed when the outer surface near the end is extended in the in-plane direction. (2) At the end, the second inner roll is positioned such that it enters into the workpiece at the end, contacting the curved portion from the end face side of the workpiece, and is positioned opposite the second outer roll such that it is separated from the virtual inner surface formed when the inner surface near the end is extended in the in-plane direction, and at the end, the second outer roll is positioned such that it contacts the outer surface near the end, the method for manufacturing a cylindrical body according to claim 1.

7. In the thickening step, the second outer roll or the second inner roll is applied to the end of the workpiece by either (1) below in the case of claim 6 (1) or (2) below in the case of claim 6 (2): (1) The second inner roll has, in a cross-sectional view through the rotation axis of the second inner roll, a second inner first surface (F51) that is in contact with the workpiece and has a width shorter than the width of the inner surface in the long side direction of the workpiece, and a second inner second surface (F52) that rises substantially perpendicularly from the second inner first surface; The second outer roll has, in a cross-sectional view through the rotation axis of the second outer roll, a second outer first surface (F41) that is in contact with the workpiece and has a width shorter than the width of the outer surface in the long side direction of the workpiece, and a second outer second surface (F42) that slopes outward from the second outer first surface; In the thickening step, the second outer first surface (F41) contacts the outside of the workpiece, and the second inner first surface (F51) contacts the inside of the workpiece, thereby sandwiching the workpiece, and the second inner second surface (F52) contacts the curved portion from the end face side of the workpiece, and the second outer second surface (F42) contacts the end that has been deformed to be thickened outward in the out-of-plane direction, (2) The second inner roll, in a cross-sectional view passing through the rotation axis of the second inner roll, has, with the rotation axis of the second inner roll as the center, a second inner first surface (F91) that contacts the inside of the workpiece, a second inner second surface (F92) that slopes inward and extends from the second inner first surface, and a second inner third surface (F93) that is substantially perpendicular to the second inner first surface, With the second inner first surface (F91) in contact with the workpiece, the second inner first surface (F91) and the second inner second surface (F92) have a width shorter than the width of the inner surface in the long side direction of the workpiece, and the second outer roll has, in a cross-sectional view through the rotation axis of the second outer roll, a second outer first surface (F81) that, in contact with the workpiece, has a width shorter than the width of the outer surface in the long side direction of the workpiece, with respect to the rotation axis of the second outer roll.In the thickening step, the second outer first surface (F81) contacts the outside of the workpiece, the second inner first surface (F91) contacts the inside of the workpiece, thereby sandwiching the workpiece, the second inner third surface (F93) contacts the curved portion from the end face side of the workpiece, and the second inner second surface (F92) faces the end portion which has been deformed to thicken inward in the out-of-plane direction, the method for manufacturing a cylindrical body according to claim 6.

8. In the thickness-increasing step, in the case of claim 7 (1), the second outer roll or the second inner roll is applied to the end of the workpiece by the following (1): (1) The second inner roll has a second inner corner portion formed by the second inner first surface (F51) and the second inner second surface (F52), and the radius of curvature Rc12i of the second inner corner portion and the plate thickness Tw of the workpiece satisfy the following formula: Tw × 1 / 4 ≤ Rc12i ≤ Tw × 1 / 2 The second inner corner portion contacts the end portion which has been deformed to increase thickness inward in the out-of-plane direction, the method for manufacturing a cylindrical body according to claim 7.

9. In the thickness-increasing step, in the case of claim 7 (1), the second outer roll or the second inner roll is applied to the end of the workpiece by the following (1): (1) The second outer roll has a second outer corner portion formed by the second outer first surface (F41) and the second outer second surface (F42), and the radius of curvature Rc12o of the second outer corner portion and the plate thickness Tw of the workpiece satisfy the following formula: Tw × 0.6 ≤ Rc12o ≤ Tw × 0.9 The second outer corner portion contacts the end on the out-of-plane side, the method for manufacturing a cylindrical body according to claim 7.

10. In the thickness-increasing step, with respect to the plate thickness Tw of the workpiece, the widths Ww12i, Ww22i of the inner surfaces in the long side direction of the workpiece, the width Wr12i of the second inner first surface (F51), and the widths Wr22i of the second inner first surface (F91) and the second inner second surface (F92), either (1) below in the case of claim 7 (1) or (2) below in the case of claim 7 (2) is satisfied: (1) 0.2 × Tw ≤ (Ww12i - Wr12i) / 2 ≤ 2 × Tw (2) 0.2 × Tw ≤ (Ww22i - Wr22i) / 2 ≤ 2 × Tw The method for manufacturing a cylindrical body according to claim 7.

11. In the thickness-increasing step, with respect to the plate thickness Tw of the workpiece, the height Hr2i of the second inner second surface (F52), and the height Hr3i of the second inner third surface (F93), either (1) below in the case of claim 7 (1) or (2) below in the case of claim 7 (2) must be satisfied: (1) 1.05 × Tw ≤ Hr2i ≤ 2 × Tw (2) 1.05 × Tw ≤ Hr3i ≤ 2 × Tw The method for manufacturing a cylindrical body according to claim 7.

12. In the thickness-increasing step, the second outer roll or the second inner roll is applied to the end of the workpiece by either (1) below in the case of claim 7 (1) or (2) below in the case of claim 7 (2): (1) The angle θ12i between the second inner second surface (F52) and the rotation axis of the second inner roll satisfies the following equation: -10° ≤ θ12i ≤ 10° (2) The angle θ22i between the second inner third surface (F93) and the rotation axis of the second inner roll satisfies the following equation: -10° ≤ θ22i ≤ 10° The method for manufacturing a cylindrical body according to claim 7.

13. The molding process involves bending the workpiece in each step to form the butt joint from a flat workpiece through multiple stages, with the angle of the end in the state before bending being 0°, and when the angle of the end in the state after the butt joint is formed changes to α°, the angle θb of the end after the bending step satisfies the following equation: α × (5 / 20) ≤ θb ≤ α × (7 / 20). The method for manufacturing a cylindrical body according to claim 11.

14. The method for manufacturing a cylindrical body according to claim 1, wherein in the molding step, the workpiece is deformed so that the ends on which the thickened portions are formed abut against each other to form the abutting portion, and the manufacturing method further comprises a joining step of joining the abutting portions.

15. The method for manufacturing a cylindrical body according to claim 14, wherein the joining step is performed by at least one selected from the group consisting of laser joining, arc joining, ultrasonic joining, high-frequency welding, resistance seam welding, and friction stir welding.

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