Manufacturing method of hat-shaped steel sheet pile

Abstract

To efficiently manufacture a group of many kinds of products different in flange angle and / or thickness when manufacturing a hat-shaped steel sheet pile by performing hot bending forming to a material to be rolled after finish rolling is performed by using a role hole type of an identical finishing mill.SOLUTION: In a material to be rolled, corner parts are formed at a connection between a web corresponding part and a flange corresponding part and a connection between the flange corresponding part and an arm corresponding part. In bending forming, a part of a vertical hole type roll is brought into hot contact with an inside of the corner parts and the corner parts are bent, so that a group of products composed of many kinds of hat-shaped steel sheet piles different in flange angle and / or thickness are produced from the material to be rolled that are finish-rolled by the same roll are manufactured individually.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a hat-shaped steel sheet pile.

Background Art

[0002] The manufacture of steel sheet piles having joints at both ends, such as hat-shaped steel sheet piles and U-shaped steel sheet piles, is performed by, for example, a pass rolling method as shown in Patent Document 1. Specifically, as a general process of the pass rolling method, it is known that a rectangular material heated to a predetermined temperature in a heating furnace is first rolled in order by a roughing mill, an intermediate mill, and a finishing mill equipped with passes.

[0003] Further, particularly when manufacturing large and asymmetric products such as hat-shaped steel sheet piles, in order to manufacture them with the above-mentioned roughing mill, intermediate mill, and finishing mill, a large number of passes are required, large-scale equipment is required, the shaping method becomes complicated, and shape variations and shape defects of the products are likely to occur. Furthermore, a large number of rolls are required to manufacture steel sheet piles of different shapes. On the other hand, as shown in Patent Document 2, after rolling and manufacturing a steel sheet pile by hot rolling, bending (hereinafter also referred to as bending forming) is performed by cold working by roll forming, and a steel sheet pile having a width wider than that of the rolling equipment and a steel sheet pile having a high cross-sectional height are manufactured. A technique is known. Also, as shown in Patent Document 3, a technique is known in which the rolling process and the bending process are separated, and a universal mill and a double mill are used in the bending process.

[0004] In Non-Patent Document 1, a technique for manufacturing a lightweight steel sheet pile is disclosed in which a plurality of forming machines are used cold with a thin steel sheet having a thickness of about 4 to 7 mm as a material, and bending forming is performed on the steel sheet. In this technique, since the thickness is thinner than that of a hot-rolled steel sheet pile, forming is easy, and there is an advantage that shape defects are less likely to occur because bending is performed using a large number of rolls from the steel sheet.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In order to manufacture products of hot-rolled hat-shaped steel sheeting (hereinafter, also simply referred to as hat-shaped steel sheeting) with different section moduli, it is effective to change the height of the product. However, for example, when trying to manufacture multiple types of hat-shaped steel sheeting products with different heights by the method disclosed in Patent Document 1, it is necessary to use a dedicated pass die for each product of each dimension. That is, there are concerns about a decrease in productivity, such as an increase in the cost of preparing the pass die rolls and a decrease in work efficiency due to roll changeover. Also, depending on the equipment, there is a problem that it is difficult to manufacture products with a large section modulus (i.e., a large product height) due to restrictions on the roll diameter.

[0008] On the other hand, for example, Patent Document 2 discloses a technique for manufacturing various types of hat-shaped steel sheeting by performing bending forming by cold working after hot rolling. However, in bending forming by cold working, there is a concern that the residual stress of the material will increase. Also, in cold working, there are problems such as a high processing load and the need for large-scale production equipment.

[0009] In addition, Non-Patent Document 1 describes the concept of roll design in the manufacture of lightweight steel sheeting with a plate thickness of 4 mm to 7 mm by bending a steel plate. However, hat-shaped steel sheeting, which has an asymmetrical shape on the left and right and generally has a plate thickness of 8 mm or more, requires a high degree of fitting due to its complex joint shape and high-precision shaping, and the thickness of the corner part, which is the connection part between each part such as the web, flange, and arm, is different. Therefore, the manufacturing technology of lightweight steel sheeting cannot necessarily be applied. Further, Non-Patent Document 1 describes various methods as the bending method of profiles by roll forming, and the change in the bending radius and arc length of the bent part in each method is described. However, Non-Patent Document 1 does not explain any appropriate bending method for hat-shaped steel sheeting, and of course, there is no specific explanation about the sizing technology of hat-shaped steel sheeting and the appropriate range of the bending radius and arc length of the bent part at that time.

[0010] Based on the above problems, the inventors have intensively studied a technique for efficiently manufacturing a plurality of types of products with different section moduli by performing hot bending on the rolled material after finish rolling with the rolls of the same finishing rolling mill (so-called finish rolling rolls) and changing the flange angle.

[0011] In view of the above circumstances, an object of the present invention is to efficiently manufacture a plurality of product groups with different flange angles and / or plate thicknesses when manufacturing hat-shaped steel sheeting by performing hot bending on the rolled material after finish rolling using the rolls of the same finishing rolling mill, and to provide a manufacturing method for hat-shaped steel sheeting.

Means for Solving the Problems

[0012] In order to achieve the above object, according to the present invention, there is provided a method for manufacturing a hat-shaped steel sheet pile in which rough rolling, intermediate rolling, and finish rolling are performed on a material to be rolled by hot rolling, and then bending is performed. The material to be rolled is composed of a web corresponding portion, a flange corresponding portion, an arm corresponding portion, and a joint corresponding portion. Corner portions are formed at the connection locations between the web corresponding portion and the flange corresponding portion, and between the flange corresponding portion and the arm corresponding portion of the material to be rolled. After finish rolling, the angle formed between the web corresponding portion and the flange corresponding portion of the material to be rolled is wider than that of the product, and at least the portion excluding the corner portion has the same thickness as the product. The bending is performed at one or more forming stands, In the bending, the roll gaps of the upper and lower pass rolls that perform the bending at the portions facing the web corresponding portion, the flange corresponding portion, and the arm corresponding portion are each larger than the thicknesses of the web corresponding portion, the flange corresponding portion, and the arm corresponding portion. In the bending, a part of the upper and lower pass rolls is brought into contact with the inside of the corner portion while it is hot. so as to reduce the angle formed between the web corresponding portion and the flange corresponding portion, and the angle formed between the flange corresponding portion and the arm corresponding portion. to bend the corner portion At the final stand of the forming stand, the bending is performed such that the ratio of the inner arc length of the corner portion at the final stand to the inner arc length of the corner portion before forming at the final stand is 1.15 or less. There is provided a method for manufacturing a hat-shaped steel sheet pile, characterized in that a product group composed of a plurality of types of hat-shaped steel sheet piles having different flange angles and / or plate thicknesses is sorted from the material to be rolled finish-rolled by the same roll by bending the corner portion. Here, "hot" means the temperature before the transformation of the material to be rolled is completed after hot rolling.

[0013] In the finish rolling, the roll gap is changed according to the thickness of the product in the product group. In the bending, the roll design is performed such that the roll gap of the portion of the upper and lower pass rolls facing the flange corresponding portion is increased with respect to the maximum flange thickness in the product group. It is also possible to sort a product group composed of a plurality of types of hat-shaped steel sheet piles by changing the roll gap of the upper and lower pass rolls for the materials to be rolled having different thicknesses sorted in the finish rolling.

[0014] In the final rolling, the roll gap corresponding to the center of the corner portion for the product with the largest ratio of the center thickness to the web thickness among the product group may be set to be equal to or greater than the center thickness of the corner portion of the product with the largest ratio of the center thickness to the web thickness among the product group.

[0015] The final rolling roll for performing the final rolling may be designed such that the ratio of the radius of curvature of the roll corresponding to the inner side of the corner portion to the radius of curvature of the roll corresponding to the outer side of the corner portion is larger than the ratio of the radius of curvature of the inner side of the corner portion to the radius of curvature of the outer side of the corner portion for all products in the product group.

[0016] In the bending forming, the thickness of the corner portion may be reduced by the upper and lower pass rolls.

[0018] In the final stand of the forming stand, bending forming may be performed such that the ratio of the arc length of the inner side of the corner portion in the final stand to the arc length of the inner side of the corner portion before forming in the final stand is less than 1.0.

[0019] The bending forming is performed at one or more forming stands, and at each stand of the forming stand, the arm corresponding portion and the joint corresponding portion of the material to be rolled may be formed horizontally.

[0020] The bending forming is performed at one or more forming stands, and upper and lower pass rolls having a shape corresponding to the flange angle of the product group may be arranged at the forming stand.

[0021] In the bending forming, a pass roll facing the web corresponding portion may be brought into contact with the outside of the web corresponding portion, and a pass roll facing the arm corresponding portion may be brought into contact with the outer surface of the arm corresponding portion.

[0022] In the bending forming, a pass roll facing the joint corresponding portion may be brought into contact with the outer surface of the joint corresponding portion such that the joint corresponding portion becomes substantially horizontal.

[0023] The bending machine for performing the bending forming and the finishing rolling machine for performing the finishing rolling may be tandem.

Advantages of the Invention

[0024] According to the present invention, when manufacturing a hat-shaped steel sheet pile by performing hot bending forming on a rolled material after performing finishing rolling using the rolls of the same finishing rolling machine, it is possible to efficiently manufacture a plurality of product groups having different flange angles and / or plate thicknesses.

Brief Description of the Drawings

[0025]

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Embodiments for Carrying Out the Invention

[0026] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0027] <Rolling Line of Hat-Shaped Steel Sheet Pile> FIG. 1 is an explanatory view of a rolling line L (dashed-dotted line in the figure) for manufacturing a hat-shaped steel sheet pile according to an embodiment of the present invention, and rolling mills and the like provided on the rolling line L. In FIG. 1, the rolling progress direction of the rolling line L is the direction indicated by the arrow, the material to be rolled flows in that direction, and rolling and bending forming are performed on each rolling mill and bending forming machine on the line, and the product is shaped. Also, in FIG. 1, a rolling method (so-called multi-pass rolling) in which the material to be rolled is reciprocated a plurality of times in the same rolling mill is also described by a dashed-dotted line.

[0028] As shown in FIG. 1, on the rolling line L, a rough rolling mill 10, a first intermediate rolling mill 13, a second intermediate rolling mill 16, a finishing rolling mill 19, and a bending forming machine 20 are arranged in order from the upstream. Also, an edger rolling mill 14 is arranged adjacent to the upstream side of the first intermediate rolling mill 13, and an edger rolling mill 17 is arranged adjacent to the downstream side of the second intermediate rolling mill 16.

[0029] In the rolling line L, a rectangular material (material to be rolled) heated in a heating furnace (not shown) is sequentially hot-rolled in the rough rolling mill 10 to the finishing rolling mill 19, and further formed by the bending forming machine 20 in the hot state to become the final product. Hereinafter, for the sake of explanation, the material to be rolled rolled by the rough rolling mill 10 is also called a rough-shaped material, the material to be rolled rolled by the first intermediate rolling mill 13 to the second intermediate rolling mill 16 is called an intermediate material, and the material to be rolled rolled by the finishing rolling mill 19 is also called a finishing material 19a. That is, the one obtained by forming (changing the cross-section) the finishing material 19a by the bending forming machine 20 becomes the final product (that is, a hat-shaped steel sheet pile product).

[0030] Here, since the rough rolling mill 10, the first intermediate rolling mill 13, the second intermediate rolling mill 16, the finishing rolling mill 19 arranged on the rolling line L, and the edger rolling mills 14 and 17 arranged therewith are general facilities conventionally used in the manufacture of steel roof sheets, the description of their device configurations and the like is omitted in this specification.

[0031] <Bending and forming machine> Next, the detailed configuration of the bending and forming machine 20 will be described with reference to the drawings. FIG. 2 is a schematic side sectional view of the bending and forming machine 20, and FIG. 3 is a schematic front view of the bending and forming machine 20. The bending and forming machine 20 shown in FIGS. 2 and 3 bends and forms the finished material 19a finish-rolled by the finishing rolling mill 19. Note that FIG. 3 shows a schematic front view of the first stand 22 included in the bending and forming machine 20 described below. Here, in the present embodiment, the case where the bending and forming machine 20 is composed of two forming stands (the forming stands 22 and 23 described below) is illustrated and described, but the bending and forming machine 20 may be composed of a single stand or any plurality of stands.

[0032] As shown in FIG. 2, the bending and forming machine 20 according to the present embodiment includes two forming stands 22 and 23 (hereinafter also referred to as the upstream first stand 22 and the downstream second stand 23) arranged adjacent to each other in series. Further, as shown in FIG. 3, forming passes (passes 45 and 55 described below) composed of an upper pass roll and a lower pass roll are engraved on each of the stands 22 and 23, and the pass shapes are different between the first stand 22 and the second stand 23.

[0033] Here, the roll configurations and pass shapes of the first stand 22 and the second stand 23 will be described. FIG. 4 is a schematic enlarged front view showing the pass shape of the first stand 22, and FIG. 5 is a schematic enlarged front view showing the pass shape of the second stand 23. In FIG. 4, the cross-sectional shape of the finish material 19a in the state before forming by the bending machine 20 is illustrated by a dashed line, and in FIG. 5, the cross-sectional shape of the finish material 19a' in the state before forming at the second stand 23 is illustrated by a dashed line. Further, hereinafter, the case of bending and forming a rolled material having a substantially hat-shaped shape in an upward-opening posture (with the web corresponding portion described later being downward and the arm corresponding portion being upward) will be exemplified and described.

[0034] As shown in FIGS. 3 and 4, in the first stand 22, an upper pass roll 40 and a lower pass roll 41 are provided supported by a housing 44, and a pass 45 is formed by the upper pass roll 40 and the lower pass roll 41. The shape of the pass 45 from the portion corresponding to the flange to the portion corresponding to the joint is a shape one step before that of a hat-shaped steel sheet pile product (i.e., a substantially hat-shaped steel sheet pile product shape). The pass 45 changes the angles formed by the portion corresponding to the flange of the finish material 19a (i.e., the flange corresponding portion), the portion corresponding to the web of the finish material 19a (i.e., the web corresponding portion), and the portion corresponding to the arm of the finish material 19a (i.e., the arm corresponding portion), respectively, and bends and forms the height and width of the finish material 19a into a predetermined shape (i.e., a cross-sectional shape approximated to the product). When manufacturing a hat-shaped steel sheet pile, the rolled material (rough material to finish material 19a) is rolled in a shape with a low height in the roughing mill 10 to the finishing mill 19, and a method is adopted in which the bending machine 20 performs bending and forming to increase the height of the rolled material to the desired product height. Thereby, it becomes possible to manufacture large-sized hat-shaped steel sheet pile products.

[0035] Further, as shown in FIG. 5, in the second stand 23, an upper pass roll 50 and a lower pass roll 51 are provided and supported by a housing 54, and a pass 55 is formed by the upper pass roll 50 and the lower pass roll 51. This pass 55 has a shape close to a desired product shape, and changes the angles formed by the portion corresponding to the flange formed at the first stand 22 of the bending machine 20 (i.e., the flange corresponding portion), the portion corresponding to the web of the finishing material 19a (i.e., the web corresponding portion), and the portion corresponding to the arm (i.e., the arm corresponding portion), respectively, to form the flange shape, the arm shape, and the joint shape into a predetermined shape (i.e., the shape of the product). That is, in this second stand 23, forming is performed to deform the inclination angle of the flange corresponding portion, which was insufficient with respect to the product shape in the forming at the first stand 22, to an angle corresponding to the product shape.

[0036] Note that, in at least one of the first stand 22 and the second stand 23, bending may be performed to make the arm corresponding portion and the joint corresponding portion of the material to be rolled horizontal.

[0037] Here, the roll gaps in the above-mentioned passes 45 and 55 during bending (the roll gap between the upper pass roll 40 and the lower pass roll 41 and the roll gap between the upper pass roll 50 and the lower pass roll 51) are configured to be larger than the thicknesses of the flange corresponding portion and the web corresponding portion of the finishing material 19a. That is, in the bending machine 20, thickness reduction of the finishing material 19a is not performed, and the pass rolls of the first stand 22 and the second stand 23 and the finishing material 19a are configured to be in contact and perform bending only at some predetermined locations described later.

[0038] Also, as described later, during bending forming, the pass rolls of the first stand 22 and the second stand 23 and the finishing material 19a may be subjected to pressing in addition to contact at some predetermined locations. "Contact" as used in this specification refers to a state in which only one of the upper surface or the lower surface of a specific location of the finishing material 19a abuts against the circumferential surface of the pass roll in the bending forming machine 20. On the other hand, "pressing" refers to a state in which both the upper surface and the lower surface of a specific location of the finishing material 19a abut against the pass roll and a force is applied to reduce the thickness in the bending forming machine 20.

[0039] <Bending forming> Subsequently, the forming of the material to be rolled in the above-described forming stands 22 and 23 will be described. FIG. 6 is an explanatory view of the shape change of the material to be rolled (finishing material 19a) bent and formed in the first stand 22 and the second stand 23. (a) is a schematic cross-sectional view before processing in the first stand 22, (b) is a schematic cross-sectional view during processing in the first stand 22, and (c) is a schematic cross-sectional view during processing in the second stand 23. As shown in FIG. 6(a), the finishing material 19a has a substantially hat shape and includes a web corresponding portion 60 that is substantially horizontal, flange corresponding portions 62 and 63 connected by corner portions 70 at both ends of the web corresponding portion 60 at a predetermined angle (shown as angle α in the figure) larger than the product shape, and arm corresponding portions 65 and 66 connected to different ends of each flange corresponding portion 62 and 63 via corner portions 71 on the side different from the connection side with the web corresponding portion, and joint corresponding portions 68 and 69 formed at the tips of the arm corresponding portions 65 and 66. Further, the thickness of the finishing material 19a has become substantially the thickness of the product by rolling in the finishing rolling mill 19, and the shapes of the joint corresponding portions 68 and 69 have also become substantially the product joint shapes.

[0040] Here, the plate thickness of the corner portion 70 (hereinafter also referred to as the web-flange corner portion 70) may be dimensioned to be thicker than the product plate thickness. The plate thickness of the web-flange corner portion 70 can be rolled to a desired plate thickness according to the rolling conditions and rolling design in hot rolling performed by the rough rolling mill 10, the first intermediate rolling mill 13, the second intermediate rolling mill 16, the finishing rolling mill 19, etc. (see FIG. 1).

[0041] Similarly, the plate thickness of the corner portion 71 (hereinafter also referred to as the flange-arm corner portion 71) may be dimensioned to be thicker than the product plate thickness. The plate thickness of the flange-arm corner portion 71 can be rolled to a desired plate thickness according to the rolling conditions and rolling design in hot rolling performed by the roughing mill 10, the first intermediate rolling mill 13, the second intermediate rolling mill 16, the finishing rolling mill 19, etc. (see FIG. 1).

[0042] The finished material 19a shown in FIG. 6(a) is bent and formed so that the angle α formed by the web corresponding portion 60 and the flange corresponding portions 62, 63 in the pass 45 of the first stand 22 becomes smaller (becomes the angle α' shown in FIG. 6(b)), and has a desired height as shown in FIG. 6(b). That is, in the first stand 22, bending is performed so that the height of the finished material 19a increases.

[0043] Next, as shown in FIG. 6(c), in the pass 55 of the second stand 23, it is bent and formed so that the angle α' formed by the web corresponding portion 60 and the flange corresponding portions 62, 63 becomes smaller (the angle α'' shown in FIG. 6(c)). Thereby, the finished material 19a is bent and formed into a substantially product shape. Note that in at least one of the first stand 22 and the second stand 23, bending may be performed so that the arm corresponding portions 65, 66 and the joint corresponding portions 68, 69 are horizontal.

[0044] <Contact location between roll and material to be rolled in bending> FIG. 7 is an explanatory view of the contact portions of the finished material 19a in the bending machine 20, and FIGS. 7(a) to 7(d) each show an example of the contact portion. In FIG. 7, the contact portions are shown by thick lines. In the hole patterns 45 of the first stand 22 and the hole pattern 55 of the second stand 23, each hole pattern roll and the finished material 19a are in contact only at a part of a predetermined location, and no reduction in plate thickness is performed. The specific contact locations between the hole pattern roll and the finished material 19a are, for example, as shown in FIG. 7(a), the inner sides 70a, 70b of the corner portions at the boundaries between the web corresponding portion 60 and the flange corresponding portions 62, 63, and the inner sides 71a, 71b of the corner portions at the boundaries between the flange corresponding portions 62, 63 and the arm corresponding portions 65, 66. Here, "contact" means that at least the material and the hole pattern roll are in contact, and it may also be in a state where a force for pressing the material is applied.

[0045] As described in FIG. 7(a), the contact portions 70a, 70b are inside the corner portions 70 at the boundaries between the web corresponding portion 60 and the flange corresponding portions 62, 63. On the other hand, the contact portions 71a and 71b are inside the corner portions 71 at the boundaries between the flange corresponding portions 62, 63 and the arm corresponding portions 65, 66. At the contact portions 71a and 71b, reaction forces are generated in directions that balance the reaction forces at 70a and 70b, respectively.

[0046] Here, by bringing the central portion 60a on the lower surface (outer side) of the web corresponding portion 60 shown in FIG. 7(b) into contact with the lower hole pattern rolls 41, 51 facing it, the bending of the angle formed by the flange corresponding portions 62, 63 and the web corresponding portion 60 can be efficiently performed. During bending, since the web corresponding portion 60 tends to bend downward in the figure, by bringing the lower hole pattern rolls into contact with the central portion 60a on the lower surface that is away from both sides (corner portions 70) of the web corresponding portion 60, a bending moment can be effectively applied to both ends of the web corresponding portion 60.

[0047] Also, at least in the second stand 23 which is the final stand, the upper surfaces (outer surfaces) 65a, 66a of the arm corresponding parts 65, 66 become the contact portions in order to make the arm corresponding parts 65, 66 substantially horizontal. In addition, as shown in FIG. 7(c), in the hole die 45 of the first stand 22 and the hole die 55 of the second stand 23, the upper inner portions 62a, 63a of the flange corresponding parts 62, 63 of the finishing material 19a are brought into contact with the upper hole die rolls 40, 50, and the lower outer portions 62b, 63b of the flange corresponding parts 62, 63 are brought into contact with the lower hole die rolls 41, 51. By bringing the portions shown in FIG. 7(c) into contact, it is possible to perform highly accurate bending forming by causing three-point bending due to the hole die roll shape at the corner portions 70, 71.

[0048] Also, as shown in FIG. 7(d), in addition to the portions described in FIGS. 7(a) to 7(c) above, the upper surfaces (outer surfaces) 68a, 69a of the joint corresponding parts 68, 69 may be brought into contact with the upper hole die rolls 40, 50. By bringing the portions shown in FIG. 7(d) into contact, it is possible to perform forming such that the joint corresponding parts 68, 69 also become substantially horizontal, and further perform highly accurate bending forming.

[0049] Although the suitable contact portions for the finishing material 19a in the bending forming have been described with reference to FIGS. 7(a) to 7(d), as shown in FIG. 7, each portion that comes into contact in the bending forming is not configured to press down the plate thickness of the finishing material 19a. Specifically, a specific portion of the finishing material 19a is not configured to be pressed (i.e., pressed down) from both sides by both the upper and lower hole die rolls, and the roll gap of the upper and lower hole die rolls is also configured to be larger than the plate thickness of the finishing material 19a, so the plate thickness is not pressed down. If the web corresponding part 60 and the flange corresponding parts 62, 63 are not pressed down, it is not necessary to unnecessarily increase the pressing reaction force.

[0050] In addition, when sorting multiple types of products from the rolled material to be finish-rolled (finished material 19a) finish-rolled by the same finish-rolling roll as described later, rolling reduction of the corner portions 70 and 71 may be performed. When the bending machine 20 is composed of a plurality of stands, rolling reduction of the corner portions 70 and 71 may be performed at all stands, but if rolling reduction of the corner portions 70 and 71 is performed at least at the final stand (the second stand 23 in this embodiment), the effect of reducing the springback after forming can be enjoyed.

[0051] <Sorting of multiple types of products from the same finish-rolling roll> Next, in the rolling line L configured as described above, by using the same upper and lower rolls provided in the finish-rolling mill 19 as the finish-rolling roll, and preferably determining the design of the finish-rolling roll, the forming pass dies (pass dies 45 and 55) provided in the bending machine 20, and the relationship between the designs of both of them, a method for sorting a product group composed of a plurality of types of hat-shaped steel sheeting with different flange angles and / or plate thicknesses from the rolled material to be finish-rolled (finished material 19a) finish-rolled by the same finish-rolling roll will be described.

[0052] FIGS. 8(a) and (b) are schematic explanatory views showing the cross-sectional shapes of two types of hat-shaped steel sheeting products made through bending from the rolled material to be finish-rolled (finished material 19a) finish-rolled by the same finish-rolling roll, and (b) shows the one with a larger flange angle (flange inclination angle) compared to (a). Also, in sorting these two types of hat-shaped steel sheeting products, the plate thickness may be changed in combination with the change in the flange angle. Here, FIG. 8(a) is defined as the first hat-shaped steel sheeting 90, and (b) is defined as the second hat-shaped steel sheeting 92.

[0053] FIG. 9 is a schematic explanatory view showing a cross-sectional shape of a work roll (work material 19a) work-rolled by a finishing roll. FIGS. 10(a) and (b) are schematic cross-sectional views of bending forming when bending forming is performed on the work roll shown in FIG. 9, where (a) shows the case where bending forming is performed only at the first stand, and (b) shows the case where bending forming is performed at the second stand following the bending forming at the first stand. Here, regarding the product group shown in FIG. 8, the angle α' after forming at the first stand shown in FIG. 6(b) corresponds to the angle α1 of the first hat-shaped steel sheet pile 90, and the angle α'' after forming at the second stand shown in FIG. 6(c) corresponds to the angle α2 of the second hat-shaped steel sheet pile 92. In FIG. 10, mainly the pass shape is illustrated, and only a part of the work roll (arm corresponding parts 65, 66 and joint corresponding parts 68, 69) is illustrated.

[0054] As shown in FIG. 9, the work material 19a is rolled by a finishing roll 100 (upper finishing roll 100a, lower finishing roll 100b). By performing bending forming with different conditions on this work material 19a, hat-shaped steel sheet pile products 90, 92 having a plurality of types (here, two types) of cross-sectional performances as shown in FIGS. 8(a) and (b) are manufactured. The shape (curvature) of each corner part 70, 71 of the work material 19a shown in FIG. 9 is determined according to the curvature radius and arc length of the inner corner part and the outer corner part of the corner part 70 (hereinafter, also referred to as the web-flange corner part 70) and the corner part 71 (hereinafter, also referred to as the flange-arm corner part 71) of the desired product dimensions.

[0055] Here, the "inner corner part" refers to the inside of the part having a bent shape in the cross-section of the work roll. For example, the curvature radius (Ri in the figure) of the part facing the web-flange corner part 70 in the upper finishing roll 100a and the curvature radius (R'i in the figure) of the part facing the flange-arm corner part 71 in the lower finishing roll 100b are the "curvature radii of the inner corner parts" in each corner part 70, 71.

[0056] Additionally, the "outside corner" refers to the outside of the portion having a bent shape in the cross section of the rolled material. For example, the radius of curvature (Ro in the figure) of the portion of the bottom finishing roll 100b facing the web-flange corner 70 and the radius of curvature (R'o in the figure) of the portion of the top finishing roll 100a facing the flange-arm corner 71 are the "radius of curvature of the outside corner" of each corner 70, 71.

[0057] The thickness of each corner portion 70, 71 of the finishing material 19a is set to be equal to or greater than the thickness of the corner portion 70, 71 of a desired product (e.g., the first hat-shaped steel sheet pile 90 or the second hat-shaped steel sheet pile 92). On the other hand, the portions of the finishing material 19a excluding the corner portions 70, 71 are set to be the same thickness as the desired product. Note that the thickness of the corner portions 70, 71 is defined as the distance between the intersections of the bisector of the web-to-flange angle and the flange-to-arm angle on the line passing through the center of the thickness of the web corresponding portion 60, the flange corresponding portions 62, 63, and the arm corresponding portions 65, 66, as shown by the dashed lines in Figures 8 and 9 (tr1, tr2, tr'1, tr'2 in Figure 8, tr, tr' in Figure 9), and is hereinafter also referred to as the corner center thickness. Similarly, for the roll gaps at the center of the corner portions 70 and 71, as shown by the dashed lines in Figure 10, the distances between the bisectors of the web-flange angle and flange-arm angle and the intersection points on the inside and outside of each corner portion 70 and 71 are defined as gr1, gr2, gr'1, and gr'2 in Figure 10 on a straight line passing through the center of the roll gaps in the portions facing the web corresponding portion, flange corresponding portion, and arm corresponding portion.

[0058] As described above, the roll gap of the upper and lower grooved rolls of the bending machine 20 is configured to be larger than the plate thickness of the finishing material 19a in principle. Therefore, when producing a plurality of types of hat-shaped steel sheet piles as shown in Figures 8 and 10, the plate thickness of each product in the product group is determined by the roll gap of the finishing rolling rolls 100. That is, the thickness ratio of the web corresponding part 60 or arm corresponding parts 65, 66 to the flange corresponding parts 62, 63 of each product in the product group is approximately constant.

[0059] Here, when the roll gap of the bending machine 20 is adjusted by the same amount as the roll gap of the finishing rolling machine 19, the flange angles θ1 and θ2 (see FIG. 10) in the bending machine 20 are larger than the flange angle θ (see FIG. 9) of the finishing rolling machine 19. Therefore, the amount of change in the roll gap in the thickness direction of the flange corresponding portion in the bending machine 20 becomes smaller than the amount of change in the roll gap in the thickness direction of the flange corresponding portion in the finishing rolling machine 19. As a result, there is a risk that the thickness of the finished material 19a may be reduced by the upper and lower pass rolls (the portions facing the flange corresponding portion) of the bending machine 20. Therefore, roll design is performed so that the roll gap of the portion of the upper and lower pass rolls of the bending machine 20 facing the flange corresponding portion becomes larger with respect to the maximum flange thickness in the product group, and for the rolled materials with different thicknesses made separately in the finishing rolling, the flange thickness is not reduced, and the product group consisting of multiple types of hat-shaped steel sheeting may be sorted.

[0060] On the other hand, the thickness (corner center thickness) of the corner portions 70 and 71 may be determined by the roll gap of the finishing rolling roll 100, or the individual corner center thickness may be designed for each product in the product group. When manufacturing a plurality of types of product groups and setting the corner center thickness individually, for the product in the product group with the largest ratio of the corner center thickness to the web thickness, roll design may be performed so that the roll gap at the corner center of the finishing rolling roll 100 is equal to or greater than the corner center thickness of that product. When the corner center thickness of the rolled material after finishing rolling is designed to be thicker than the thickness of the desired product, the corner center thickness may be set to the desired value by reducing the thickness of the corner portions 70 and 71 by bending.

[0061] <Occurrence of Twisting and Its Suppression Method> In the method for manufacturing hat-shaped steel sheeting using the bending machine 20 described above, the cross-sectional shape of the hat-shaped steel sheeting is asymmetric about the left and right, and the contact state between the rolled material and the roll in the bending process is also asymmetric about the left and right. In particular, the left and right joint shapes are significantly different, and due to this asymmetric cross-sectional shape about the left and right, the rolled material after bending is likely to twist. The inventors of the present invention have intensively studied the amount of twist generated in the bending process (hereinafter, also simply referred to as the twist amount).

[0062] As an example, a study was conducted on the case where bending was performed using a bending machine 20 equipped with two forming stands (first stand 22 and second stand 23) according to this embodiment. Specifically, when manufacturing a hat-shaped steel sheet pile product with a web thickness of 14.7 mm and a flange thickness of 11.4 mm, the flange angle of the rolled material after finish rolling was set to 40°, the inclination angle of the flange-facing portion of the grooved roll of the first stand was set to 53° or 56°, and the inclination angle of the flange-facing portion of the grooved roll of the second stand was set to 67°, and the combination of the curvature radii of the corner portions of the grooved rolls of the first stand 22 and the second stand 23 was changed, and the influence on the hat-shaped steel sheet pile product after bending was investigated.

[0063] Fig. 11 is a graph in which the horizontal axis represents the ratio of the inner arc length of the corner portion during bending in the second stand 23, which is the final stand of the bending machine 20, to the inner arc length of the corner portion during bending in the first stand 22, which is the stand immediately preceding it (i.e., second stand inner arc length / first stand inner arc length), and the vertical axis represents the amount of twist that occurs after bending. That is, Fig. 11 is a graph showing the relationship between the corner portion inner arc length ratio and the amount of twist. Note that the inner arc length of the corner portion in this embodiment will be described as the length of a circular arc.

[0064] Here, the "inner arc length of the corner portion" is defined as "radius of curvature × flange angle × π / 180" at the inner corner portion of the grooved roll that contacts the inside of each corner portion 70, 71 of the rolled material. Also, the "inner arc length ratio of the corner portion" may be the ratio between the inner arc length of the corner portion during bending in the final stand of the bending machine 20 and the inner arc length of the corner portion before bending in the final stand. For example, when bending is performed in a single stand, the single stand is the final stand, and the ratio is defined by the inner arc length of the corner portion during bending and the inner arc length of the corner portion before bending.

[0065] Furthermore, the "amount of twist" was defined as the difference in height between the left and right joint-corresponding portions 68, 69, with a state in which there was no twist being defined as zero. Twist is particularly likely to occur at the longitudinal tip of the rolled material. Therefore, the amount of twist was defined in a state in which the material was placed on a table (transport table) with its rear end horizontal and a length of 10 m, excluding a 1 m cropped portion at the tip after bending. That is, in a cross section perpendicular to the longitudinal direction when placed on the table, the maximum longitudinal difference in height between the left and right joint-corresponding portions 68, 69 was defined as the amount of twist. Note that because the shapes of the left and right joint-corresponding portions 68, 69 are asymmetrical, the difference in joint height in a state without twist was corrected to zero.

[0066] As shown in Figure 11, when the corner inner arc length ratio is less than 1.0, the amount of twist is low and nearly constant. Furthermore, when the corner inner arc length ratio is 1.0 or greater, the amount of twist increases significantly. In particular, when the corner inner arc length ratio exceeds 1.15, the amount of twist exceeds 12 mm. Although the JIS does not specify the tolerance for twist in hat-shaped steel sheet pile products, based on the tolerance for bending (length × 0.12% or less), when the corner inner arc length ratio exceeds 1.15, the amount of twist exceeds 0.12% of the length, i.e., 12 mm. In other words, to keep the amount of twist to 0.12% or less of the length, it is desirable to set the corner inner arc length ratio to 1.15 or less. More preferably, the amount of twist can be kept low by setting the corner inner arc length ratio to less than 1.0.

[0067] The reason why the amount of twist increases when the corner inner arc length ratio is 1.0 or more is that the pressure from the inside of the corner portions 70, 71 becomes smaller during bending, resulting in less plastic deformation of the corner portions 70, 71. The reason why the amount of twist does not become 0 even when the corner inner arc length ratio is less than 1.0 is because the cross-sectional shape of the hat-shaped steel sheet pile is asymmetrical and the roll gap is made larger than the thickness of the material to be rolled during bending.

[0068] Fig. 12 is a graph showing the load (load ratio) of the second stand versus each corner inside arc length ratio, where the load of the second stand for a corner inside arc length ratio of 1.2 is set to 1. As shown in Fig. 12, it is known that the load on the final stand (second stand 23) of the bending machine 20 increases as the corner inside arc length ratio decreases. Similarly, torque also tends to increase, and the lower limit of the corner inside arc length ratio can be determined based on the equipment specifications for forming load and torque.

[0069] <Effects of the present invention> According to the manufacturing method of the hat-shaped steel sheet pile of this embodiment described above, it is possible to efficiently manufacture a group of multiple types of products (for example, the first hat-shaped steel sheet pile 90 and the second hat-shaped steel sheet pile 92) with different flange angles and / or plate thicknesses from the rolled material (finishing material 19a) that has been finish-rolled by the same finishing rolling rolls.

[0070] In addition, due to the cross-sectional shape of hat-shaped steel sheet piles being asymmetrical, there is an issue that twisting is likely to occur in the rolled material after bending.In response to this issue, by optimizing the inner arc length ratio of the corner section (for example, 1.15 or less) in the final stand where bending is performed, it is possible to suppress the occurrence of twisting and reduce the amount of twisting.

[0071] While one embodiment of the present invention has been described above, the present invention is not limited to the illustrated embodiment. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0072] For example, in the above embodiment, the case where the bending machine 20 is composed of the first stand 22 and the second stand 23 has been illustrated and described, but the present invention is not limited thereto. For example, the bending machine 20 may be a single stand, or may be composed of any number of multiple stands. In addition, the "final stand" in this specification refers to the forming stand that performs the final bending during the manufacture of the product to be manufactured. For example, in the case of a single stand, the final stand of the bending machine 20 refers to the single stand. Also, when manufacturing the second hat-shaped steel sheet pile 92 shown in FIG. 8, if the relationship between the thickness, radius of curvature, and arc length of the aforementioned corner portion is satisfied, the first stand does not necessarily have to be the same pass roll as the first hat-shaped steel sheet pile 90, and it may be changed to a pass roll with an arbitrary angle α1'.

[0073] Also, in the above embodiment, the pass roll shapes of the forming stands 22 and 23 of the bending machine 20 may be pass roll shapes corresponding to the dimensional shapes of the respective products in the product group to be manufactured. The pass roll shape corresponding to the dimensional shape of the product in this case includes a pass roll shape in which, when the flange angle does not become the same as the inclination angle of the flange opposing portion of the pass due to deformation after bending, the error due to the deformation is considered. Regarding the radius of curvature of each corner portion, it also includes the error between the shape of the product and the shape of the pass roll for performing the bending.

[0074] Also, in the above embodiment, the bending machine 20 and the finishing rolling mill 19 may perform material passing in a tandem state. By adopting the tandem state configuration, the tip of the material to be rolled can be pushed into the bending machine 20 by the finishing rolling mill 19, and the biting stability of the material to be rolled in the bending machine 20 can be achieved. In this case, it is preferable that the height of the upper surface of the table roller of the finishing rolling mill 19 and the height of the upper surface of the web corresponding portion of the lower pass roll in the bending machine 20 are substantially the same.

[0075] In the above embodiment, the case where a hat-shaped steel sheet pile product is manufactured in an upward opening position (with the arm corresponding portion above the web corresponding portion) has been described as an example, but the present invention can also be applied to the case where a hat-shaped steel sheet pile product is manufactured in the opposite downward opening position (with the arm corresponding portion below the web corresponding portion). In this case, the orientation of the joints and the upper and lower hole type rolls can be considered to be reversed. [Example]

[0076] Example 1 As Example 1 of the present invention, three types of hat-shaped steel sheet pile products (size 1, size 2, and size 3) shown in Table 1 below were manufactured using the same finishing rolls. Table 1 below shows the dimensional design at the product stage, the dimensional design at the finish rolling stage, the dimensional design at the first stand of bending, and the dimensional design at the second stand of this example. However, for sizes 1 and 2, bending was performed using only the first stand, and the dimensional design of only the first stand is also shown in Table 1.

[0077] [Table 1]

[0078] In the design example in Table 1, the finish rolling rolls were designed based on the product thickness (web thickness, flange thickness) of size 1, and the same finish rolling rolls were used for sizes 2 and 3, but the roll gap was changed for production. The radii of curvature of the inside corners and outside corners of the rolled material after finish rolling were determined so that the corner center thickness of the rolled material after finish rolling would be the same as that of products of sizes 1 and 2. The radii of curvature of the inside corners and outside corners of products of size 3 were also determined so that the corner center thickness of the rolled material after finish rolling would be the same as that of the products of size 3 when the roll gap of the finish rolling rolls was set to a thickness that matched that of size 3.

[0079] In the design examples in Table 1, the finish rolling rolls in finish rolling are designed so that the ratio of the radius of curvature of the corner portion (inner corner portion) of the roll corresponding to the inside of the corner portion of the rolled material to the radius of curvature of the corner portion (outer corner portion) of the roll corresponding to the outside of the corner portion of the rolled material is larger than the ratio of the radius of curvature of the inner corner portion (inner corner portion) to the outer corner portion (outer corner portion) of all products (sizes 1, 2, 3).

[0080] Furthermore, bending is performed in the first stand for all products (sizes 1, 2, and 3) using the same upper and lower grooved rolls with different roll gaps. As shown in Table 1, the corner inner arc length ratio in bending in the final stand is 0.92 for sizes 1 and 2, and 0.99 for size 3, conditions that keep the amount of twist low for all products.

[0081] According to each design example of Example 1, it was confirmed that three types of hat-type steel sheet pile products, sizes 1, 2, and 3, can be manufactured using the same finishing rolls. It was also confirmed that the amount of twist occurring during manufacturing can be kept low in all products.

[0082] <Example 2> As Example 2 of the present invention, three types of hat-shaped steel sheet pile products (size 1, size 2, and size 3) shown in Table 2 below were manufactured using the same finishing rolls. Table 2 below shows the dimensional design at the product stage, the dimensional design at the finish rolling stage, the dimensional design at the first stand of bending, and the dimensional design at the second stand of this example. However, for sizes 1 and 2, bending was performed using only the first stand, and the dimensional design of only the first stand is also shown in Table 2.

[0083] [Table 2]

[0084] In the design example in Table 2, the roll gap of the finishing rolls is determined based on the corner center thickness of size 3, which has the largest ratio of corner center thickness to web thickness among the three types of hat-shaped steel sheet pile products (size 1, size 2, size 3). Accordingly, the radius of curvature of the corner portion (inner corner portion) of the finish rolling roll that corresponds to the inside of the corner portion of the rolled material, and the radius of curvature of the corner portion (outer corner portion) of the roll that corresponds to the outside of the corner portion of the rolled material are determined.

[0085] In the design example in Table 2, the roll gap of the finish rolling rolls was determined based on the corner center thickness of size 3, which has the largest ratio of corner center thickness to web thickness. Therefore, for sizes 1 and 2, the corner center thickness after finish rolling is designed to be thicker than the final product. Therefore, for the top and bottom groove rolls in the first stand of bending, the radius of curvature of the corner (inner corner) of the roll corresponding to the inside of the corner of the rolled material and the radius of curvature of the corner (outer corner) of the roll corresponding to the outside of the corner of the rolled material are appropriately designed, and the thickness of the corners is reduced during bending. This allows three types of hat-shaped steel sheet pile products (sizes 1, 2, and 3) to be manufactured with the appropriate product dimensions.

[0086] As shown in Table 2, the corner inner arc length ratio during bending in the final stand was 0.78 for sizes 1 and 2, and 1.13 for size 3, which is a condition that ensures that the amount of twist is within the allowable range for all products.

[0087] According to each design example of Example 2, it was confirmed that three types of hat-type steel sheet pile products, sizes 1, 2, and 3, can be manufactured using the same finishing rolls. It was also confirmed that the amount of twist occurring during manufacturing can be kept within the allowable range for all products.

[0088] Example 3 As Example 3 of the present invention, a product (size 3 in Table 3) having the same thickness as the product of size 3 in Example 2 above but with a smaller radius of curvature at the corners was produced using the same finish rolling rolls as in Example 2. Table 3 below shows the dimensional design at the product stage, the dimensional design at the finish rolling stage, the dimensional design at the first stand of bending, and the dimensional design at the second stand of this example.

[0089] [Table 3]

[0090] As shown in Table 3, in this design example, to manufacture a product with a small radius of curvature at the corners, the radius of curvature of the corners (inner corners) of the rolls corresponding to the inside of the corners of the rolled material and the radius of curvature of the corners (outer corners) of the rolls corresponding to the outside of the corners of the rolled material are appropriately designed for the top and bottom groove rolls of the second stand. In this design example, the inner arc length ratio of the corners in the bending of the final stand is 0.85, which is a condition for keeping the amount of twist low.

[0091] It was confirmed that the design example of Example 3 can produce a product having the same thickness as the product of size 3 of Example 2 and a small radius of curvature at the corners using the same finishing rolls. It was also confirmed that the amount of twist that occurs during production can be kept low.

[0092] <Comparative Example> As a comparative example of the present invention, a product having the same thickness as the product of size 3 in Example 2 above but with a large radius of curvature at the corners (corresponding to sizes 1 and 2 in Table 2) was produced using the same finish rolling rolls. Table 4 below shows the dimensional design at the product stage, the dimensional design at the finish rolling stage, the dimensional design at the first stand of bending, and the dimensional design at the second stand for this comparative example.

[0093] [Table 4]

[0094] As shown in Table 4, in this design example, to manufacture a product with a large radius of curvature at the corners, the top and bottom groove rolls of the second stand are designed under the condition that the radius of curvature of the corners (inner corners) of the rolls corresponding to the inside of the corners of the rolled material and the radius of curvature of the corners (outer corners) of the rolls corresponding to the outside of the corners of the rolled material are large. In this design example, the inner arc length ratio of the corners in the bending of the final stand is 1.31, which may result in a large amount of twist.

[0095] According to the design example of this comparative example, when hat-shaped steel sheet pile products with different curvature radii at the corners are manufactured using the same finishing rolls, twisting occurs during bending depending on the design conditions. From this, it was confirmed that when manufacturing multiple types of hat-shaped steel sheet pile products, it is necessary to optimize the inner arc length ratio of the corners in the final stand where bending is performed. [Industrial Applicability]

[0096] The present invention can be applied to, for example, a method for manufacturing a hat-shaped steel sheet pile. [Explanation of symbols]

[0097] 10...Roughing mill 13...First intermediate rolling mill 14...Edger rolling mill 16...Second intermediate rolling mill 17...Edger rolling mill 19...Finishing rolling mill 19a...Finishing material 20...Bending machine 22...1st Stand 23...Second Stand 40...Upper perforated roll 41...Pre-hole type roll 44…Case 45...hole type 45a...Web section 45b...flange part 50...Upper perforated roll 51... Lower pass roll 54... Housing 55... Pass 60... Web corresponding part 62, 63... Flange corresponding part 65, 66... Arm corresponding part 68, 69... Joint corresponding part 70... Corner part 70a, 70b... Inner side of corner part 70c, 70d... Outer side of corner part 71... Corner part 71a, 71b... Inner side of corner part 71c, 71d... Outer side of corner part 90... First hat-shaped steel sheet pile 92... Second hat-shaped steel sheet pile 100... Finishing rolling roll L... Rolling line

Claims

1. A manufacturing method of a hat-shaped steel sheet pile, in which a rolled material is subjected to rough rolling, intermediate rolling, and finish rolling by hot rolling, and then bent, The rolled material is composed of a web corresponding portion, a flange corresponding portion, an arm corresponding portion, and a joint corresponding portion, Corner portions are formed in the rolled material at connection points between the web corresponding portion and the flange corresponding portion and at connection points between the flange corresponding portion and the arm corresponding portion, the rolled material after the finish rolling has an angle between the web corresponding portion and the flange corresponding portion wider than that of the product, and at least a portion excluding the corner portion has the same thickness as the product; The bending is performed in one or more forming stands, In the bending, the roll gaps of the upper and lower hole type rolls that perform the bending at the portions facing the web corresponding portion, the flange corresponding portion, and the arm corresponding portion are larger than the thicknesses of the web corresponding portion, the flange corresponding portion, and the arm corresponding portion, respectively, In the bending, a part of the upper and lower grooved roll is brought into contact with the inside of the corner portion in a hot state, and the corner portion is bent so as to reduce the angle between the web corresponding portion and the flange corresponding portion, and the angle between the flange corresponding portion and the arm corresponding portion, and in the final stand of the forming stands, bending is performed so that the ratio of the inner arc length of the corner portion in the final stand to the inner arc length of the corner portion before forming in the final stand is 1.15 or less, thereby producing a group of products consisting of multiple types of hat-shaped steel sheet piles with different flange angles and / or plate thicknesses from the rolled material finish-rolled by the same rolls.

2. In the finish rolling, the roll gap is changed according to the thickness of the product in the product group, In the bending process, the rolls are designed so that the roll gap at the portion facing the flange corresponding portion of the upper and lower grooved rolls is large relative to the maximum flange thickness in the product group, 2. The method for manufacturing a hat-shaped steel sheet pile according to claim 1, characterized in that a group of products consisting of a plurality of types of hat-shaped steel sheet piles is produced by changing the roll gap of the upper and lower grooved rolls for rolled materials of different thicknesses produced in the finish rolling.

3. 3. The method for manufacturing a hat-shaped steel sheet pile according to claim 1, wherein in the finish rolling, a roll gap corresponding to a center of a corner portion of a product having a maximum ratio of center thickness of a corner portion to a web thickness among the product group is set to be equal to or larger than the center thickness of the corner portion of a product having a maximum ratio of center thickness of a corner portion to a web thickness among the product group.

4. The method for manufacturing a hat-shaped steel sheet pile according to any one of claims 1 to 3, characterized in that the finish rolling rolls that perform the finish rolling are designed so that a ratio of a radius of curvature of a roll corresponding to an inside of the corner portion to a radius of curvature of a roll corresponding to an outside of the corner portion is larger than a ratio of a radius of curvature of an inside of the corner portion to a radius of curvature of an outside of the corner portion of all products in the product group.

5. The manufacturing method of any one of claims 1 to 4, characterized in that in the bending, a thickness of the corner portion is reduced by the upper and lower slotted rolls.

6. A method for manufacturing a hat-shaped steel sheet pile as described in claim 1, characterized in that in the final stand of the forming stand, bending forming is performed with the ratio of the inner arc length of the corner portion in the final stand to the inner arc length of the corner portion before forming of the final stand being less than 1.

0.

7. The bending is performed in one or more forming stands, The manufacturing method of a hat-shaped steel sheet pile according to any one of claims 1 to 6, characterized in that, in the forming stand, the arm corresponding portion and the joint corresponding portion of the rolled material are formed horizontally.

8. The bending is performed in one or more forming stands, The manufacturing method of any one of claims 1 to 7, characterized in that an upper and lower hole type roll having a shape corresponding to the flange angle of the product group is arranged in the forming stand.

9. In the bending process, a grooved roll facing the web corresponding portion is brought into contact with the web corresponding portion on the outside thereof, The manufacturing method of a hat-shaped steel sheet pile according to any one of claims 1 to 8, characterized in that a grooved roll facing the arm corresponding portion is brought into contact with an outer surface of the arm corresponding portion.

10. A method for manufacturing a hat-shaped steel sheet pile as described in Claim 9, characterized in that during the bending, a grooved roll facing the joint corresponding portion is brought into contact with the outer surface of the joint corresponding portion so that the joint corresponding portion is approximately horizontal.

11. A method for manufacturing a steel sheet pile described in any one of claims 1 to 10, characterized in that a bending machine that performs the bending and a finishing rolling machine that performs the finishing rolling are arranged in tandem.

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