Method of manufacturing hat-shaped steel sheet pile

Abstract

To provide a method of manufacturing a hat-shaped steel sheet pile that prevents a change in the position of an intersection of a flange and an arm when bending back a rolled material after rolling it with its height made smaller than a product.SOLUTION: A method of manufacturing a hat-shaped steel sheet pile includes the steps of: performing rolling under a condition that a height Hf1 of a flange corresponding part is smaller than a flange height Hf0 of a product by bending a web corresponding part; and performing rolling so as to bend back the bent web corresponding part in a linear shape and return the height of the flange corresponding part to the flange height Hf0 of the product. For the steps of performing such rolling, rolling conditions are determined so as to satisfy the expressions (9), (10), and (12): θf1=sin-1{(1-(Hf0-Hf1) / Hf0)sinθf0} ...(9); θw1=cos-1[α{cosθw0+Lf0 / Lw0(cosθf0-cosθf1)}] ...(10); 1≤α≤λw / λf...(12).SELECTED DRAWING: Figure 12

Description

[Technical field]

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

[0002] A hat-shaped steel sheet pile having a central web (also referred to as a web portion), flanges (also referred to as flange portions) connected to both sides of the central web, and a pair of arms (also referred to as arm portions) and joints (also referred to as joint portions) connected to both sides, which are the other ends of the flanges, is generally manufactured by a groove rolling method. As a process of this groove rolling method, it is known that a rectangular cross-section material such as a slab or bloom heated to a predetermined temperature in a heating furnace is first rolled in sequence by a roughing mill, an intermediate rolling mill, and a finishing rolling mill equipped with grooves.

[0003] In the groove rolling method, rolling is performed using grooves provided on a pair of upper and lower grooved rolls provided in a roughing mill, an intermediate rolling mill, and a finishing rolling mill. Since the grooved rolls wear with use, the roll diameter is reduced by roll grinding, and the effective use range of the roll is enlarged while maintaining the groove shape, so that the rolls can be used for a long period of time.

[0004] When using a grooved roll, it must have a minimum diameter to ensure roll strength, and even when the diameter is reduced by roll grinding, it is required that the smallest diameter part has a minimum diameter. For this reason, when rolling a steel sheet pile by a grooved rolling method, if the difference in diameter between the small diameter part and the large diameter part is small, the part where the necessary roll strength is ensured is large even if the diameter of the grooved roll is reduced, and the roll can be used effectively. Therefore, a method is known in which the rolling height is made lower than the product height when rolling a steel sheet pile by the grooved rolling method. For example, Patent Document 1 discloses a technology in which a groove whose height is smaller than the product height is used in intermediate rolling, and the shape of the rolled material after intermediate rolling is rolled to a first shape in which the flange part is curved or bent outward, thereby increasing the usage allowance (effective usage range) of the roll.

[0005] In addition, when manufacturing steel sheet piles by the groove rolling method, it is required to optimize the balance between flange stretching and web stretching and perform rolling efficiently from the viewpoint of improving manufacturing efficiency and suppressing roll wear. For example, Patent Document 2 discloses a technology that determines the inclination angles of the flange portion and the web portion so as to balance the flange stretching and the web stretching, and uses a groove configuration designed based on this. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7031788 [Patent Document 2] Japanese Patent Application Publication No. 60-44101 Summary of the Invention [Problem to be solved by the invention]

[0007] In the technology described in Patent Document 1, the line length of the flange is constant, and the inclination angle of the flange is made larger than that of the product (see Figures 6 to 10 of Patent Document 1, etc.) to make the height of the rolled material smaller than that of the product, and then the material is rolled, and in a downstream process, the inclination angle of the flange is bent back to the same angle as the product. Figure 1 is a schematic explanatory diagram of such conventional bending back. The dashed line in Figure 1 indicates the material before bending back, and the solid line indicates the material after bending back.

[0008] As shown in Figure 1, in conventional bending back forming, the position of the intersection point P2 between the flange and the arm changes in order to maintain the horizontal position of the intersection point P1 between the web and the flange (see the arrow in Figure 1). In this way, in bending back forming, since the positions of the arms and joints change, it is difficult to press down the relevant points, and bending back forming must be performed in a state where they are released from the groove. Therefore, it is necessary to provide a dedicated groove for bending back forming, and an increase in the number of grooves becomes a problem.

[0009] In addition, the technology described in the above Patent Document 2 discloses conditions for balancing flange stretching and web stretching, but does not mention anything about a rolling process in which the height of the rolled material is made smaller than the product, rolling is performed, and then bending back the material, nor does it mention any appropriate conditions for bending back the material.

[0010] In view of the above circumstances, an object of the present invention is to provide a manufacturing method for a hat-shaped steel sheet pile in which the height of the rolled material is made smaller than that of the product, rolling is performed, and then bending back the material, without changing the position of the intersection between the flange and the arm. [Means for solving the problem]

[0011] In consideration of the above object, according to the present invention, there is provided a method for manufacturing a hat-shaped steel sheet pile, comprising: a step of rolling a rolled material including a web corresponding portion, a flange corresponding portion, an arm corresponding portion, and a joint corresponding portion under a condition that the web corresponding portion is bent so that a height Hf1 of the flange corresponding portion is smaller than a flange height Hf0 of a product; and a step of rolling the bent web corresponding portion back into a straight shape so that the height of the flange corresponding portion is returned to the flange height Hf1 of the product, characterized in that the rolling steps are performed under rolling conditions that satisfy the following formulas (9), (10), and (12). θf1=sin -1 {(1-(Hf0-Hf1) / Hf0)sinθf0} ···(9) θw1=cos -1 [α{cosθw0+Lf0 / Lw0(cosθf0-cosθf1)}] ···(10) 1≦α≦λw / λf (12) Here, θf0: flange inclination angle after unbending, θw0: web inclination angle after unbending, θf1: flange inclination angle before unbending, θw1: web inclination angle before unbending, Lf0: flange line length after unbending, Lw1: 1 / 2 of the web line length before unbending, Lw0: 1 / 2 of the web line length after unbending, λw=tw1 / tw0 λf=tf1 / tf0 α=Lw0 / Lw1 where tw1 is the web thickness before unbending, tw0 is the web thickness after unbending, tf1 is the flange thickness before unbending, and tf0 is the flange thickness after unbending. Effect of the Invention

[0012] According to the present invention, a manufacturing method for a hat-shaped steel sheet pile is provided in which the height of the rolled material is made smaller than that of the product, and then the rolling is performed, so that the position of the intersection between the flange and the arm does not change when bending back the material. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic explanatory diagram of conventional bending back forming. [Diagram 2] FIG. 2 is a schematic explanatory diagram of a cross-sectional shape of a hat-shaped steel sheet pile. [Diagram 3] FIG. 1 is a schematic diagram of a process for manufacturing a hat-shaped steel sheet pile. [Figure 4] FIG. 1 is a schematic explanatory diagram illustrating the change in shape of a rolled material, including the groove, in a conventional rolling process. [Diagram 5] FIG. 1 is a schematic explanatory diagram illustrating the change in shape of a rolled material, including the groove, in a conventional rolling process. [Figure 6] FIG. 1 is a schematic explanatory diagram illustrating a change in the shape of a rolled material, including a groove, in a conventional rolling process. [Figure 7] FIG. 1 is a schematic explanatory diagram illustrating a change in the shape of a rolled material, including a groove, in a conventional rolling process. [Figure 8] FIG. 2 is a schematic explanatory diagram illustrating the change in shape of a rolled material, including the groove, in the rolling process according to the present invention. [Figure 9] FIG. 2 is a schematic explanatory diagram illustrating the change in shape of a rolled material, including the groove, in the rolling process according to the present invention. [Figure 10] FIG. 2 is a schematic explanatory diagram illustrating the change in shape of a rolled material, including the groove, in the rolling process according to the present invention. [Figure 11]FIG. 2 is a schematic explanatory diagram illustrating the change in shape of a rolled material, including the groove, in the rolling process according to the present invention. [Figure 12] FIG. 2 is a schematic explanatory diagram of rolling conditions in bending back. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment 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 may be denoted by the same reference numerals to avoid repetitive description. The hat-shaped steel sheet pile to which the present invention is directed is a hat-shaped steel sheet pile having a central web portion, flange portions connected to both sides of the central web portion, and a pair of arm portions and joint portions connected to both sides, which are the other ends of the flange portions.

[0015] In this embodiment, for convenience of explanation, the rolled material having a substantially hat-shaped cross-sectional shape during rolling may be collectively referred to as "rolled material A". In addition, each part of the rolled material A may be described by a different name described below based on the shape of the hat-shaped steel sheet pile product. FIG. 2 is a schematic explanatory diagram of the cross-sectional shape of a hat-shaped steel sheet pile. The rolled material A is composed of a web corresponding part 3 corresponding to the web part of the hat-shaped steel sheet pile product, flange corresponding parts 4 and 5 corresponding to the flange parts connected to both ends of the web corresponding part 3, arm corresponding parts 6 and 7 corresponding to the arm parts formed at the respective tips of the flange corresponding parts 4 and 5, and joint corresponding parts 8 and 9 corresponding to the joint parts formed at the tips of the arm corresponding parts 6 and 7. In addition, claw corresponding parts 8a and 9a are formed at the tips of the joint corresponding parts 8 and 9.

[0016] <Rolling line configuration> Fig. 3 is a schematic diagram of a process for manufacturing a hat-shaped steel sheet pile according to an embodiment of the present invention, and is an explanatory diagram of a rolling mill provided in a rolling line L. In Fig. 3, the rolling proceeding direction of the rolling line L is the direction indicated by the arrow, and the material to be rolled flows in the direction, and is rolled in each rolling mill on the line to manufacture a product. In Fig. 3, a rolling method in which the material to be rolled is made to go back and forth multiple times in the same rolling mill (so-called multi-pass rolling) is illustrated by a solid line as an example.

[0017] As shown in FIG. 3, in the rolling line L, a roughing mill 10, a first intermediate rolling mill 12, a second intermediate rolling mill 14, a third intermediate rolling mill 16, and a finishing rolling mill 18 are arranged in this order from upstream.

[0018] In this rolling line L, a rectangular cross-section material such as a slab or bloom heated in a heating furnace (not shown) located further upstream is hot-rolled in sequence in a roughing mill 10, a first intermediate rolling mill 12, a second intermediate rolling mill 14, a third intermediate rolling mill 16, and a finishing rolling mill 18 to produce a final product (a hat-shaped steel sheet pile product). Each rolling mill is provided with one or more rolling grooves, and rolling is performed in one or more passes in each groove. As an example, as shown in FIG. 3, multi-pass rolling may be performed in the roughing mill 10 and the first intermediate rolling mill 12, and single-pass rolling may be performed in the second intermediate rolling mill 14, the third intermediate rolling mill 16, and the finishing rolling mill 18.

[0019] <Shape of rolled material in conventional rolling process> As described above, the material A to be rolled is rolled by the grooves provided in each rolling mill, such as the roughing mill 10, the first intermediate rolling mill 12, the second intermediate rolling mill 14, the third intermediate rolling mill 16, and the finishing rolling mill 18. The shape of the grooves provided in each rolling mill is different depending on the shape of the material A to be rolled at each rolling stage. In addition, the shape of each groove can be arbitrarily changed depending on the process design. First, the shape of the material A to be rolled by the grooves in the conventional rolling process will be described below with reference to the drawings.

[0020] 4 to 7 are schematic explanatory diagrams illustrating the change in the shape of the material A to be rolled in a conventional rolling process, including the grooves. The grooves described below with reference to FIG. 4 to FIG. 7 are provided in each rolling mill from the roughing mill 10 to the finishing mill 18, but which rolling mill each groove described below is provided in is optional, and can be changed appropriately depending on conditions such as equipment status and product dimensions, usually taking into consideration productivity (efficiency and yield) and workability. In FIG. 4 to FIG. 7, the solid lines in the figures indicate the groove shape, and show the shapes before and after narrowing the roll gap (i.e., before and after rolling down). In FIG. 4 and FIG. 5, the direction in which the roll gap is narrowed is shown by an arrow. In addition, the dashed lines in the figures show the shape of the material A to be rolled before rolling with the groove. In addition, in FIG. 6 and FIG. 7, for the purpose of explanation, an enlarged view of the vicinity of one of the jaws is shown.

[0021] In each groove described below, the rolling of the material A may be performed in one pass, or may be performed in multiple passes of reverse rolling (reversible rolling). For example, in the rough rolling process, due to constraints on biting and load characteristics, multiple passes of reverse rolling may be performed, and the number of passes can be set arbitrarily depending on the rolling mill characteristics, etc.

[0022] In a conventional rolling process, first, a rolled material A having a substantially rectangular cross section is introduced into the groove 30 provided on upper and lower rolls 30a, 30b shown in Fig. 4. Then, the roll gap is narrowed (see the arrows in the figure) to roll down the rolled material A. As a result, a web corresponding portion 3 corresponding to the future web portion and flange corresponding portions 4, 5 corresponding to the future flange portions are roughly formed in the rolled material A, giving it a substantially hat-shaped cross section.

[0023] The material A to be rolled that has been rolled by the groove 30 is introduced into the groove 40 provided on the upper and lower rolls 40a, 40b shown in Fig. 5. The roll gap is then narrowed (see the arrow in the figure) to further reduce the material A to be rolled. As a result, the material A to be rolled has a substantially hat-shaped cross-sectional shape that is closer to the product shape.

[0024] The material A to be rolled that has been rolled by the groove 40 is introduced into the groove 50 provided on the upper and lower rolls 50a, 50b shown in Fig. 6. In the groove 50, the thickness of the material A to be rolled is reduced as a whole, and the thickness of the claw corresponding parts 8a, 9a that correspond to the rear claw parts is reduced. The thickness reduction of the claw corresponding parts 8a, 9a is performed by the groove 50 whose claw tips are open (see the enlarged view in the figure).

[0025] The material A to be rolled that has been rolled by the groove 50 is introduced into the groove 60 provided on the upper and lower rolls 60a, 60b shown in Fig. 7. In the groove 60, the material A to be rolled is reduced in thickness overall, and the height of the claw corresponding parts 8a, 9a corresponding to the rear claw parts is adjusted. The height adjustment of the claw corresponding parts 8a, 9a is performed by the groove 60, the claw tips of which are closed (see the enlarged view in the figure).

[0026] Through the rolling process as described above with reference to Fig. 4 to Fig. 7, a hat-shaped steel sheet pile is manufactured as a final product. The shape of the rolled material A during rolling is a so-called approximately hat-shaped cross-sectional shape, and the shape approaches the product shape the further downstream. Note that the approximately hat-shaped cross-sectional shape refers to a cross-sectional shape that has been rolled down to a degree that the boundaries of each part, such as the web corresponding part 3, the flange corresponding parts 4, 5, the arm corresponding parts 6, 7, and the joint corresponding parts 8, 9, are clear, and does not necessarily refer to a cross-sectional shape that has been formed into fine shapes such as a joint shape.

[0027] The above-mentioned grooves 30 to 60 are part of the grooves provided in each rolling mill, such as the roughing mill 10, the first intermediate rolling mill 12, the second intermediate rolling mill 14, the third intermediate rolling mill 16, and the finishing mill 18, and are provided in an arbitrary configuration and distributed in each rolling mill. As an example, the groove 30 may be provided in the roughing mill 10, the groove 40 in the first intermediate rolling mill 12, the groove 50 in the second intermediate rolling mill 14, and the groove 60 in the third intermediate rolling mill 16.

[0028] <Shape of the material to be rolled in the rolling process of the present invention> In the rolling process using the conventional groove configuration described with reference to Figures 4 to 7, it is not assumed that the height of the rolled material A is made smaller than that of the product by making the inclination angle of the flange corresponding parts 4, 5 larger than that of the product and performing rolling. Since the inventors performed diameter reduction by roll grinding and tried to enlarge the effective use range of the roll, it was not possible to do so sufficiently, they conducted extensive research into groove shapes and rolling conditions that would make the inclination angle of the flange corresponding parts 4, 5 larger than that of the product during the rolling of the rolled material A and would not change the position of the intersection (intersection P2 described in Figure 1) between the flange corresponding parts 4, 5 and the arm corresponding parts 6, 7.

[0029] The following describes the caliber shape devised by the inventors and the rolling process using the same. Figures 8 to 11 are schematic explanatory diagrams illustrating the change in shape of the rolled material A in the rolling process according to the present invention, including the caliber. In Figures 8 to 11, components having the same functional configuration as the conventional caliber configuration described in Figures 4 to 7 are illustrated with the same reference numerals, and their description may be omitted.

[0030] The grooves described below with reference to Figs. 8 to 11 are provided in each of the rolling mills from the roughing mill 10 to the finishing mill 18, and it is optional which rolling mill each groove described below is provided in, and usually, it can be appropriately changed according to conditions such as equipment status and product dimensions, taking into consideration productivity (efficiency and yield) and workability. In Figs. 8 to 11, the solid lines in the figures indicate the groove shape, and show the shape before and after narrowing the roll gap (i.e., before and after rolling down). In Figs. 8 and 9, the arrows show the direction in which the roll gap is narrowed. In addition, the dashed lines in the figures show the shape of the rolled material A before rolling with the groove. In Figs. 10 and 11, for the purpose of explanation, an enlarged view of the vicinity of one of the jaws is shown.

[0031] First, the rolled material A having a substantially rectangular cross section is introduced into the groove 80 provided on the upper and lower rolls 80a, 80b shown in Fig. 8. Then, the roll gap is narrowed (see the arrows in the figure) to roll down the rolled material A. As a result, the rolled material A is roughly formed with a web corresponding portion 3 corresponding to the future web portion and flange corresponding portions 4, 5 corresponding to the future flange portions. Here, the groove 80 is configured to form a bent portion approximately at the center of the web corresponding portion 3, and after rolling, a bent portion 82 is formed approximately at the center in the width direction of the web corresponding portion 3 (see Fig. 9).

[0032] Then, the material A to be rolled that has been rolled by the above-mentioned groove 80 is introduced into the groove 90 provided on the upper and lower rolls 90a, 90b shown in Fig. 9. The roll gap is then narrowed (see the arrow in the figure) to further reduce the material A to be rolled. At this time, a bent portion 82 is formed in the center of the web corresponding portion 3 in the material A to be rolled, and reduction proceeds in this state.

[0033] Then, the material A to be rolled that has been rolled by the above-mentioned groove 90 is introduced into the groove 100 provided on the upper and lower rolls 100a, 100b shown in Fig. 10. In the groove 100, the thickness of the material A to be rolled is reduced as a whole, and the thickness of the claw corresponding parts 8a, 9a that correspond to the rear claw parts is reduced. The thickness of the claw corresponding parts 8a, 9a is reduced by the groove 100 whose claw tips are open (see the enlarged view in the figure). At this time, in the material A to be rolled, a bent part 82 is formed in the center of the web corresponding part 3, and reduction proceeds in this state.

[0034] Then, the material A to be rolled that has been rolled by the above-mentioned groove 100 is introduced into the groove 110 provided on the upper and lower rolls 110a, 110b shown in FIG. 11. In the groove 110, the entire thickness of the material A to be rolled is reduced, and the height of the claw corresponding parts 8a, 9a corresponding to the rear claw parts is adjusted. The height adjustment of the claw corresponding parts 8a, 9a is performed by the groove 110 whose claw tips are closed (see the enlarged view in the figure). In this groove 110, the groove part corresponding to the web corresponding part 3 is configured in an approximately straight line, and the bent part 82 formed in the web corresponding part 3 is bent back to an approximately straight line to proceed with the reduction.

[0035] The rolling process according to the present invention uses the grooves 80 to 110 described with reference to Figures 8 to 11. That is, the process includes a step of bending the web corresponding portion 3 shown in Figures 8 to 10 and performing rolling under conditions in which the height of the flange corresponding portions 4, 5 is smaller than the flange height of the product, and a step of bending the bent web corresponding portion 3 shown in Figure 11 back into a straight shape and performing rolling so as to return the height of the flange corresponding portions 4, 5 to the flange height of the product.

[0036] <Rolling conditions for bending back> Next, the inventors geometrically studied rolling conditions for performing the bending back so as not to change the position of the intersection (intersection P2 described in FIG. 1) between the flange corresponding parts 4, 5 and the arm corresponding parts 6, 7 when performing the rolling process described with reference to FIG. 8 to FIG. 11. The rolling conditions will be described below with reference to FIG.

[0037] Fig. 12 is a schematic explanatory diagram of the rolling conditions for bending back. In Fig. 12, the shape of the rolled material A is represented typically by a straight line, the state before bending back is shown by a dashed line, and the state after bending back is shown by a solid line. First, as shown in Fig. 12, in defining the rolling conditions, each value is defined as follows. Note that the "inclination angle" here refers to the inclination angle with respect to a horizontal line.

[0038] θf0: flange inclination angle after bending back, θw0: Web inclination angle after bending back, θf1: flange inclination angle before bending back, θw1: web inclination angle before unbending, Lf0: flange line length after bending back, Lf1: flange line length before bending back, Lw0: 1 / 2 of the web length after unbending, Lw1: 1 / 2 of the web length before bending back, tw0: web thickness after unbending, tw1: web thickness before unbending, tf0: flange thickness after bending back, tf1: flange thickness before bending back, Hf0: flange height after bending back (= flange height of product), Hf1: flange height before bending back, Let us assume that.

[0039] In addition, if the reduction ratio of the web corresponding portion 3 is λw and the reduction ratio of the flange corresponding portions 4 and 5 is λf, then λw=tw1 / tw0 and λf=tf1 / tf0. Note that, as shown in the figure, θf0>θf1 and θw0<θw1.

[0040] First, the line length of the flange corresponding parts 4, 5 (hereinafter also referred to as the flange line length) Lf0 is calculated by the following formula (1). Lf0 = Hf0 / sinθf0 (1) In order to reduce the flange height to Hf1 while keeping the flange line length Lf0 constant, the flange inclination angle θf1 before unbending can be determined according to the following formulas (2) and (3). Hf0-Hf1=Lf0(sinθf0-sinθf1) (2) sinθf1=sinθf0-(Hf0-Hf1) / Lf0=(1-(Hf0-Hf1) / Hf0)sinθf0...(3)

[0041] Here, the intersection of the flange corresponding parts 4, 5 and the arm corresponding parts 6, 7 is used as a reference, and the amount of movement dx of the intersection of the flange corresponding parts 4, 5 and the web corresponding part 3 towards the web center is calculated by the following formula (4). dx=Lf0(cosθf0-cosθf1) ···(4) If the following formula (5) is satisfied, bending back can be performed without changing the positions of the intersections between the flange corresponding parts 4, 5 and the arm corresponding parts 6, 7. dx=Lw0cosθw0-Lw1cosθw1 ···(5)

[0042] Furthermore, if Lw0=αLw1 (that is, α=Lw0 / Lw1), the following equation (6) is derived. dx=Lw0(cosθw0-cosθw1 / α) ···(6) Then, equation (7) is derived from equations (4) and (6) as follows: Let Lf0(cosθf0-cosθf1)=Lw0(cosθw0-cosθw1 / α), and then transform this to cosθw1=α{cosθw0+Lf0 / Lw0(cosθf0-cosθf1)} ···(7)

[0043] Here, if α<1, the line length of the web corresponding portion 3 will be reduced during unbending, and there is a risk of web curvature or web buckling during unbending, so α must be ≥ 1. On the other hand, in order to increase the line length of the web corresponding portion 3, the apparent web cross-sectional elongation must be equal to or greater than the flange cross-sectional elongation, so the relationship shown in the following formula (8) must be satisfied. (Lf1×tf1) / (Lf0×tf0)≦(Lw1×tw1) / (Lw0×tw0)=tw1 / tw0 / α ···(8) From Lf1=Lf0, λw=tw1 / tw0, and λf=tf1 / tf0, λf≦λw / α holds, and by modifying this, the following equation (8)′ is derived. α≦λw / λf (8)'

[0044] From the above calculation results, it can be seen that when rolling is performed under conditions where the web corresponding portion 3 is bent and the height Hf1 of the flange corresponding portions 4, 5 is smaller than the flange height Hf0 of the product, and then the flange corresponding portions 4, 5 are bent back to return to the flange height Hf0 of the product, the flange inclination angle θf1 before unbending and the web inclination angle θw1 before unbending can be given by the following equations (9) and (10). θf1=sin -1 {(1-(Hf0-Hf1) / Hf0)sinθf0} ···(9) θw1=cos -1 [α{cosθw0+Lf0 / Lw0(cosθf0-cosθf1)}] ···(10)

[0045] The above formula (10) can also be expressed as the following formula (11). α=cosθw1 / {cosθw0+Lf0 / Lw0(cosθf0-cosθf1)} ···(11)

[0046] In addition, α must be equal to or greater than 1, and from the above formula (8)′, the following formula (12) must be satisfied. 1≦α≦λw / λf (12)

[0047] As described above, when rolling is performed under conditions in which the web corresponding portion 3 is bent so that the height Hf1 of the flange corresponding portions 4, 5 is smaller than the flange height Hf0 of the product, and then the flange corresponding portions 4, 5 are bent back to return to the flange height Hf0 of the product, the rolling conditions should be determined so as to satisfy the above formulas (9), (10), and (12).

[0048] <Action and effect> According to the manufacturing method of the hat-shaped steel sheet pile of the present invention described above, when the web corresponding portion 3 is bent to roll under conditions where the height Hf1 of the flange corresponding portions 4, 5 is smaller than the flange height Hf0 of the product, and then the process of bending back the height of the flange corresponding portions 4, 5 to return them to the flange height Hf0 of the product is performed, the bending back can be performed without changing the position of the intersection between the flange corresponding portions 4, 5 and the arm corresponding portions 6, 7.

[0049] In other words, a process design is realized that can sufficiently secure the usage allowance (effective usage range) of the rolls without providing an additional groove for bending back, making it possible to efficiently manufacture hat-shaped steel sheet piles.

[0050] Although an example of an 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 come up with various modified or revised examples within the scope of the ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention.

[0051] In addition, the effects described in this specification are merely explanatory or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to a person skilled in the art from the description of this specification in addition to or in place of the above effects. EXAMPLES

[0052] As examples of the present invention, hat-shaped steel sheet piles were manufactured using equipment including the groove configuration described in the above embodiment with reference to Figures 8 to 11. In Example 1, the rolling conditions according to the present invention were satisfied, and in Comparative Examples 1 to 3, the rolling conditions according to the present invention were not satisfied, and the rolling results under each condition were confirmed.

[0053] The dimensional conditions were web line length 2Lw0 = 270 mm, flange height Hf0 = 180 mm, flange inclination angle θf0 = 70°, web thickness tw0 = 13.3 mm, flange thickness tf0 = 8.5 mm, web inclination angle θw0 = 0°, and the flange height was reduced by 10 mm before rolling and then bending back. At this time, the flange line length Lf0 is 191.55 mm based on the above formula (1).

[0054] Further, based on the calculation method described in the above embodiment, the flange inclination angle before unbending is θf1=62.56°, and the movement amount dx of the intersection point between the flange corresponding part and the web corresponding part toward the web center is dx=22.8 mm.

[0055] In the specific rolling process, a bent portion was formed in the web corresponding portion, followed by rolling and then bending back as shown in Figures 8 to 11. At that time, rolling was performed in a state in which the flange height was reduced by 10 mm before bending back, and bending back was performed without changing the position of the intersection between the flange corresponding portion and the arm corresponding portion.

[0056] The following Table 1 shows the values ​​of the web thickness tw1, flange thickness tf1, web inclination angle θw1, and draw ratios λw / λf and α before unbending among the rolling conditions of Example 1 and Comparative Examples 1 to 3. Table 1 also shows the rolling results of Example 1 and Comparative Examples 1 to 3. [Table 1]

[0057] As shown in Table 1, in Example 1, rolling and bending back were performed under conditions that satisfied formula (12), and no particular problems occurred.

[0058] On the other hand, in Comparative Examples 1 and 3, α>λw / λf, which does not satisfy formula (12), and therefore, shrinkage (phenomenon in which the thickness is reduced beyond the roll gap) occurred in the web corresponding portion, and good rolling was not achieved. Also, in Comparative Example 2, 1>α, which does not satisfy formula (12), vibrations thought to be due to the curvature of the web corresponding portion occurred during unbending, and good rolling was not achieved. [Industrial Applicability]

[0059] The present invention can be applied to a manufacturing method of a hat-shaped steel sheet pile. [Explanation of symbols]

[0060] 3. Web Support Department 4, 5...Flange corresponding part 6, 7…Arm corresponding parts 8, 9...Joint compatible parts 10...Roughing mill 12…First intermediate rolling mill 14…Second intermediate rolling mill 16…Third intermediate rolling mill 18...Finishing rolling mill 30, 40, 50, 60...(conventional) hole type 80, 90, 100, 110...(invention) groove 82…Bend A: Rolled material L…Rolling line

Claims

[Claim 1] A manufacturing method of a hat-shaped steel sheet pile, a step of rolling a rolled material including a web corresponding portion, a flange corresponding portion, an arm corresponding portion, and a joint corresponding portion under a condition that the web corresponding portion is bent and a height Hf1 of the flange corresponding portion is smaller than a flange height Hf0 of a product; and a rolling step of bending the bent web corresponding portion back into a straight shape and rolling the flange corresponding portion back to a flange height Hf0 of the product. The manufacturing method of the hat-shaped steel sheet pile is characterized in that the rolling conditions in the rolling steps are determined so as to satisfy the following formulas (9), (10), and (12). θf1=sin －１ {(1-(Hf0-Hf1) / Hf0)sinθf0} ・・・(9) θυ1=cos －１ [α{cosθw0+Lf0 / Lw0(cosθf0-cosθf1)}} ・・・(10) 1≦α≦λw / λf...(12) Here, θf0: flange inclination angle after unbending, θw0: web inclination angle after unbending, θf1: flange inclination angle before unbending, θw1: web inclination angle before unbending, Lf0: flange line length after unbending, Lw1: 1 / 2 of the web line length before unbending, Lw0: 1 / 2 of the web line length after unbending, λw=tw1 / tw0 λf=tf1 / tf0 α=Lw0 / Lw1 where tw1 is the web thickness before unbending, tw0 is the web thickness after unbending, tf1 is the flange thickness before unbending, and tf0 is the flange thickness after unbending.

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