Steel sheet pile manufacturing method

Abstract

To efficiently manufacture a large-sized steel sheet pile with excellent dimension accuracy when the steel sheet pile is manufactured.SOLUTION: Provided is a manufacturing method of a steel sheet pile including performing rough rolling, intermediate rolling, and bending on a rolled material. The rolled material after the intermediate rolling includes at least: a web corresponding part; two flange corresponding parts having one end portion connected to both end portions of the web corresponding portions and having an angle wider than a product; and a corner part being a connection part between the web corresponding part and each of the flange corresponding parts. In the bending, the corner part is bent while using an upper and lower hole type roll to bring the upper and lower hole type roll into contact with the inside of the corner part or press the corner part.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a steel sheet pile such as a hat-shaped steel sheet pile or a U-shaped steel sheet pile. [Background technology]

[0002] For example, it is known that hat-shaped steel sheet piles, U-shaped steel sheet piles, etc. are manufactured by a groove rolling method as shown in Patent Document 1. Specifically, it is known that a general process of the groove rolling method is to first heat a rectangular material (such as a slab) to a predetermined temperature in a heating furnace and then roll it using a roughing mill, an intermediate mill, and a finishing mill each equipped with a groove.

[0003] For example, when manufacturing a large, asymmetrical product such as a hat-shaped steel sheet pile, a groove shape that matches the flange angle of the product is used in order to manufacture the product using a roughing mill, an intermediate rolling mill, and a finishing rolling mill, and therefore, due to the constraints of the roll diameter, it is difficult to manufacture a product with a large height and a large cross section.

[0004] Therefore, for example, Patent Document 2 discloses a technology in which intermediate rolling and finish rolling are performed at a height lower than the product, and then the corner portions (the connection portions between the flange portions and the web portions) are bent and formed in a hot state to produce a product with a target height and width.

[0005] Furthermore, for example, Patent Document 3 discloses a technology for manufacturing a tall product by performing intermediate rolling so that the flange portion is curved or bent outward, and then performing bending shaping in finish rolling so that the flange portion is curved or bent inward or in a straight line. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-192905 [Patent Document 2] International Publication No. 2021 / 182528 [Patent Document 3] International Publication No. 2021 / 140728 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the conventional groove rolling method exemplified in Patent Document 1, one pass of rolling is performed with one groove while shifting the groove in the intermediate rolling process to the finish rolling process, so that the total elongation of the rolled material is restricted depending on the number of grooves used in rolling, resulting in a small elongation length of the product. Furthermore, particularly when the plate thickness is thin, there are problems such as deformation of the end shape due to shifting the groove, and an imbalance in the elongation of each part in the cross section during reverse rolling, resulting in warpage and changes in wire length in the cross section.

[0008] Furthermore, with the technology disclosed in Patent Document 2, bending can cause changes in the joint shape, which can lead to dimensional changes in the longitudinal direction of the product (particularly at the longitudinal ends).Furthermore, when cutting to the product length, the cut ends are more likely to widen than when manufacturing without bending, which raises concerns that the amount of processing required in the subsequent straightening process can be increased.

[0009] Furthermore, in the technology disclosed in Patent Document 3, the flanges are curved or bent from the middle, and the rolling height cannot be lowered significantly during intermediate rolling, which limits the dimensions of large products that can be manufactured. Furthermore, since the flange angle changes midway through the flanges, differences in plate thickness occur in the flange width direction during reverse rolling, and when multi-pass rolling is performed with the same groove, changes in cross-sectional line length are likely to occur, which limits the number of passes and raises concerns about an increase in the number of grooves. In addition, there is a problem that it is difficult to manufacture products of different thicknesses by changing the roll gap with the same groove.

[0010] In view of the above circumstances, an object of the present invention is to efficiently manufacture large steel sheet piles with excellent dimensional accuracy when manufacturing steel sheet piles. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, according to the present invention, there is provided a method for manufacturing a steel sheet pile, in which a material to be rolled is subjected to rough rolling, intermediate rolling, and bending, and then finish rolling, wherein the material to be rolled after the intermediate rolling has at least a web corresponding portion, two flange corresponding portions having one end connected to both ends of the web corresponding portion and having an angle wider than that of the product, and corner portions which are connection portions between the web corresponding portion and each of the flange corresponding portions, and wherein the bending is performed by using upper and lower grooved rolls to bend the corner portions while contacting the inside of the corner portions with the upper and lower grooved rolls or while pressing down the corner portions.

[0012] The rolled material after the intermediate rolling has an arm corresponding portion that connects to the other end of the flange corresponding portion, and a corner portion that is the connection portion between the flange corresponding portion and each of the arm corresponding portions, and in the bending forming, the corner portion may be bent using an upper and lower hole type roll while contacting the upper and lower hole type roll with the inside of the corner portion or while pressing down the corner portion.

[0013] The bending may be performed using a single-hole or multiple-hole mold, and at least in the first bending, the bending may be performed so that the relationship between the bending angle Δθ of the flange corresponding portion and the inclination angle θ1 of the flange corresponding portion before bending satisfies the following formula (1) or formula (2). Δθ≦-0.30×θ1+32.0 (θ1≧40°) (1) Δθ≦0.20×θ1+12.0 (θ1<40°) (2)

[0014] During the bending, the roll gaps of the upper and lower hole type rolls at the portions facing the web corresponding portion and the flange corresponding portion are larger than the thicknesses of the web corresponding portion and the flange corresponding portion, respectively, and the corner portion may be bent while a portion of the upper and lower hole type rolls is in contact with the inside of the corner portion or while pressing down the corner portion.

[0015] In the rolled material before being bent, the angle formed between the flange corresponding portion and the arm corresponding portion may be smaller than the angle formed between the web corresponding portion and the flange corresponding portion.

[0016] The bending is performed by a bending machine consisting of one or more stands including a first stand, and the bending machine is provided with a web restraint guide that restrains the upper surface of the web corresponding portion of the rolled material, at least upstream of the first stand of the bending machine, and the outer width of the web restraint guide may be configured to be narrower than the inner distance between the left and right flanges of the pre-deformed portion of the rolled material in a steady state at the installation position of the web restraint guide.

[0017] The groove used for the finish rolling may be provided with a stopper that restrains the joint corresponding portion of the rolled material, and during the finish rolling, the joint corresponding portion may be restrained by the stopper, and bending shaping may be performed while the joint corresponding portion is clamped between upper and lower rolls.

[0018] The final groove for performing the intermediate rolling and the groove for performing the bending may be arranged in tandem, or the groove for performing the bending and the first groove for performing the finish rolling may be arranged in tandem, and only one of the upper and lower groove rolls for performing the bending may be driven.

[0019] The bending may be performed by a stand-shift type bending machine, and the bending machine may be retracted from the rolling line until the final pass of the intermediate rolling, and bending may be performed only in the final pass.

[0020] The groove for performing the bending may be provided in a finish rolling mill for performing the finish rolling. [Effects of the Invention]

[0021] According to the present invention, when manufacturing a steel sheet pile, a large steel sheet pile with excellent dimensional accuracy can be efficiently manufactured. [Brief explanation of the drawings]

[0022] [Figure 1]1 is a schematic explanatory diagram of a rolling line according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic side cross-sectional view of a bending machine. [Figure 3] FIG. 2 is a schematic front view of the bending machine. [Figure 4] FIG. 4 is a schematic enlarged front view showing the groove shape of the first stand. [Figure 5] FIG. 10 is a schematic enlarged front view showing the groove shape of the second stand. [Figure 6] 1A and 1B are explanatory diagrams illustrating the shape change of the rolled material as it is bent in the first stand and the second stand, where (a) shows a schematic cross-sectional view before forming in the first stand, (b) shows a schematic cross-sectional view during forming in the first stand, and (c) shows a schematic cross-sectional view during forming in the second stand. [Figure 7] 10 is an explanatory diagram of contact points of an intermediate material in a bending machine. FIG. [Figure 8] 10 is a schematic cross-sectional view showing a state in which the tip of the intermediate material is bitten into the bending machine in a state where it is shifted in the width direction. FIG. [Figure 9] 1 is a graph showing the relationship between the flange angle of the intermediate material before forming and the forming angle. [Figure 10] FIG. 2 is a schematic explanatory diagram illustrating an example of a guide device. [Figure 11] FIG. 2 is a schematic explanatory view showing an example of a groove shape for performing finish rolling. [Figure 12] 10A and 10B are schematic explanatory views showing other cross-sectional shapes of intermediate materials. [Figure 13] FIG. 2 is a schematic diagram of an intermediate rolling mill. [Figure 14] FIG. 1 is a schematic diagram of an edger rolling mill. DETAILED DESCRIPTION OF THE INVENTION

[0023] 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 configurations are designated by the same reference numerals, and redundant description will be omitted. In this embodiment, a case where a hat-shaped steel sheet pile is manufactured as a steel sheet pile product will be described.

[0024] <Rolling line configuration> FIG. 1 is an explanatory diagram of a rolling line L (indicated by a dashed line in the drawing) 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 direction of the rolling line L is indicated by an arrow, and the material to be rolled flows in this direction, and is rolled and bent in each rolling mill and bending machine on the line to form a product. In FIG. 1, a rolling method in which the material to be rolled goes back and forth multiple times in the same rolling mill (so-called multi-pass rolling) is also shown by a dashed line.

[0025] As shown in Fig. 1, in the rolling line L, a roughing mill 10, a first intermediate rolling mill 13, a second intermediate rolling mill 16, a bending mill 19, and a finishing rolling mill 20 are arranged in this order from the upstream side. In addition, 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.

[0026] In the rolling line L, rectangular materials (materials to be rolled) heated in a heating furnace (not shown) are hot rolled in succession in the roughing mill 10 to the finishing mill 20. After intermediate rolling, the materials are hot bent by a bending machine 19. For the sake of explanation, the materials to be rolled rolled by the roughing mill 10 are also referred to as rough materials, and the materials to be rolled by the first intermediate rolling mill 13 to the second intermediate rolling mill 16 are also referred to as intermediate materials (the materials to be rolled after intermediate rolling are collectively referred to as M). That is, the intermediate materials M are shaped (cross-section changed) by the bending machine 19, and then finish-rolled to become final products (i.e., hat-shaped or U-shaped steel sheet pile products).

[0027] Here, the roughing mill 10, the first intermediate mill 13, the second intermediate mill 16, the finishing mill 20 arranged in the rolling line L, and the associated edger mills 14 and 17 are general equipment that has been conventionally used in the manufacture of steel sheet piles. Below, the configuration of the second intermediate mill 16 will be briefly described as an example of the configuration of an intermediate mill, and the configuration of the associated edger mill 17 will be briefly described as an example of the configuration of an edger mill.

[0028] Fig. 13 is a schematic diagram of the second intermediate rolling mill 16, and Fig. 14 is a schematic diagram of the edger rolling mill 17. For reference, the shape of the material to be rolled after several passes is shown by a dashed line in the figures. As shown in Fig. 13, the second intermediate rolling mill 16 is provided with a housing 200, an upper grooved roll 205 supported by the housing 200 via a roll shaft 202, and a lower grooved roll 208 supported by the housing 200 via a roll shaft 206. The second intermediate rolling mill 16 is provided with a groove 209 composed of the upper grooved roll 205 and the lower grooved roll 208, and thickness reduction (intermediate rolling) is performed on the entire rolled material by groove rolling in this groove 209. 14, the edger rolling mill 17 is provided with a housing 210, an upper grooved roll 215 supported by the housing 210 via a roll shaft 212, and a lower grooved roll 218 supported by the housing 210 via a roll shaft 216. The edger rolling mill 17 is provided with a grooved die 219 composed of the upper grooved roll 215 and the lower grooved roll 218, and this grooved die 219 is used to perform rolling, for example, to align the height of the claws of the material to a fixed dimension.

[0029] <Bending machine> Next, the detailed configuration of the bending machine 19 will be described with reference to the drawings. Fig. 2 is a schematic side cross-sectional view of the bending machine 19, and Fig. 3 is a schematic front view of the bending machine 19. The bending machine 19 shown in Figs. 2 and 3 bends an intermediate material M after intermediate rolling. Fig. 3 also shows a schematic front view of a first stand 22 provided in the bending machine 19, which will be described below. Here, in this embodiment, the bending machine 19 is described as being composed of two forming stands (forming stands 22 and 23, which will be described below), but the bending machine 19 may be composed of a single stand or any number of stands.

[0030] As shown in Fig. 2, the bending machine 19 according to this embodiment has two forming stands 22, 23 (hereinafter also referred to as the first stand 22 on the upstream side and the second stand 23 on the downstream side) arranged adjacent to each other in tandem in series. Also, as shown in Fig. 3, each of the stands 22, 23 is provided with a forming groove (groove dies 45, 55 described below) consisting of an upper groove roll and a lower groove roll, and the groove shapes of the first stand 22 and the second stand 23 are different.

[0031] <Bending machine groove> Here, the roll configuration and caliber shape of the first stand 22 and the second stand 23 will be described. Fig. 4 is a schematic enlarged front view showing the caliber shape of the first stand 22, and Fig. 5 is a schematic enlarged front view showing the caliber shape of the second stand 23. Note that Fig. 4 shows, by a dashed dotted line, the cross-sectional shape of the intermediate material M in a state before being formed by the bending machine 19, and Fig. 5 shows, by a dashed dotted line, the cross-sectional shape of the intermediate material M in a state before being formed by the second stand 23. In the following, an example will be described in which a rolled material having a substantially hat shape is bent in an upwardly open position (with a web corresponding portion, described later, positioned downward and an arm corresponding portion positioned upward).

[0032] 3 and 4, the first stand 22 is provided with an upper perforated roll 40 and a lower perforated roll 41 supported by a housing 44, and the upper perforated roll 40 and the lower perforated roll 41 form a perforated roll 45. The perforated roll 45 has a shape just short of a hat-shaped steel sheet pile product (i.e., a shape similar to a hat-shaped steel sheet pile product) from the part corresponding to the flange to the part corresponding to the joint. The perforated roll 45 changes the angle formed between the part corresponding to the flange of the intermediate material M (i.e., the flange-corresponding part) and the part corresponding to the web of the intermediate material M (i.e., the web-corresponding part), and the angle formed between the part corresponding to the arm of the intermediate material M (i.e., the arm-corresponding part), respectively, and bends and forms the height and width of the intermediate material M into a predetermined shape (i.e., a cross-sectional shape similar to that of the product). In particular, when manufacturing a hat-shaped steel sheet pile, a method is adopted in which the material to be rolled (raw material to intermediate material M) is rolled in a shape with a low height in the roughing mill 10 to the second intermediate rolling mill 16, the material to be rolled is bent in the bending mill 19 so as to increase the height of the material to a desired product height, and the material is made into a final product shape in the finishing mill 20. This makes it possible to manufacture a large-sized hat-shaped steel sheet pile product.

[0033] 5, the second stand 23 has an upper perforated roll 50 and a lower perforated roll 51 supported by a housing 54, and the upper perforated roll 50 and the lower perforated roll 51 form a perforated mold 55. The angle between the portion corresponding to the flange formed in the first stand 22 of the bending machine 19 (i.e., the flange corresponding portion) and the portion corresponding to the web (i.e., the web corresponding portion), and the angle between the flange corresponding portion and the portion corresponding to the arm (i.e., the arm corresponding portion) are changed, respectively, to form the flange shape, arm shape, and joint shape into predetermined shapes. That is, in this second stand 23, the inclination angle of the flange corresponding portion, which was insufficient for the product shape in the forming in the first stand 22, is deformed to a predetermined angle according to the product shape.

[0034] The roll gaps in the grooved dies 45 and grooved dies 55 during bending (the roll gap between the upper grooved roll 40 and the lower grooved roll 41 and the roll gap between the upper grooved roll 50 and the lower grooved roll 51) are configured to be larger than the thickness of the flange corresponding portion and the web corresponding portion of the intermediate material M. In other words, in the bending machine 19, the thickness of the intermediate material M is not reduced, and bending is performed while the grooved rolls of the first stand 22 and the second stand 23 and the intermediate material M are in contact only at some predetermined locations described below.

[0035] As will be described later, during bending, the grooved rolls of the first stand 22 and the second stand 23 and the intermediate material M may be lightly pressed down at some predetermined locations. In this specification, "contact" refers to a state in which only one of the upper surface or the lower surface of a specific location of the intermediate material M abuts against the peripheral surface of the grooved roll in the bending machine 19. In contrast, "pressing down" refers to a state in which both the upper and lower surfaces of a specific location of the intermediate material M abut against the grooved roll in the bending machine 19, and a force is applied to reduce the thickness.

[0036] The roll gap at the portions facing the web corresponding portion and the flange corresponding portion is preferably approximately 0.5 mm to 3 mm larger than the thickness of the flange corresponding portion and the web corresponding portion of the intermediate material M. In addition, even at the portions of the grooves 45 and 55 that overlap the arm corresponding portion of the intermediate material M, the roll gap may be configured to be larger than the thickness of the arm corresponding portion over the entire cross section. If the roll gap allowance range is smaller than 0.5 mm, when the thickness of the intermediate material M is thick due to manufacturing variations, a small roll gap will result in the intermediate material M being pressed down. Therefore, the reaction force (pressing reaction force) generated during pressing down increases the load on the bending machine 19. If the roll gap allowance range is larger than 3 mm, there is a possibility that the inclination angle of the flange corresponding portion cannot be formed to the target angle.

[0037] <Shape changes during bending> The shaping of the rolled material in the above-mentioned stands 22 and 23 will now be described. Figure 6 is an explanatory diagram of the shape change of the rolled material (intermediate material M) being bent in the first stand 22 and the second stand 23, with (a) showing a schematic cross-sectional view before shaping in the first stand 22, (b) showing shaping in the first stand 22, and (c) showing shaping in the second stand 23. As shown in Figure 6(a), the intermediate material M has a substantially hat-shaped shape and is composed of a substantially horizontal web corresponding portion 60, flange corresponding portions 62 and 63 connected to both ends of the web corresponding portion 60 by corner portions 70 at a predetermined angle (shown as angle α in the figure) larger than the product shape, arm corresponding portions 65 and 66 connected via corner portions 71 to the ends of each flange corresponding portion 62 and 63 opposite the connection side with the web corresponding portion 60, and joint corresponding portions 68 and 69 formed at the tips of the arm corresponding portions 65 and 66. In the intermediate material M after intermediate rolling, the claws at the tips of the joint corresponding portions 68, 69 are shaped to open outward.

[0038] The thickness of the corner portion 70 (hereinafter also referred to as the web-flange corner portion 70), which is the connection portion between the web corresponding portion 60 and the flange corresponding portions 62, 63, may be designed to be thicker than the product thickness. The thickness of the web-flange corner portion 70 can be rolled to a desired thickness by adjusting the rolling conditions and rolling design in hot rolling performed in the roughing mill 10, the first intermediate rolling mill 13, the second intermediate rolling mill 16, etc. (see FIG. 1).

[0039] Similarly, the thickness of the corner portion 71 (hereinafter also referred to as the flange-arm corner portion 71), which is the connection portion between the flange counterparts 62, 63 and the arm counterparts 65, 66, may be designed to be thicker than the product thickness. The thickness of the flange-arm corner portion 71 can be rolled to a desired thickness by the rolling conditions and rolling design in hot rolling performed in the roughing mill 10, the first intermediate rolling mill 13, the second intermediate rolling mill 16, etc. (see Figure 1).

[0040] The intermediate material M shown in Fig. 6(a) is bent in the groove 45 of the first stand 22 so that the angle α between the web corresponding portion 60 and the flange corresponding portions 62, 63 becomes small (becoming the angle α1 shown in Fig. 6(b)), and the intermediate material M reaches the desired height as shown in Fig. 6(b). That is, in the first stand 22, bending is performed so that the height of the intermediate material M becomes large.

[0041] Next, as shown in FIG. 6(c), the intermediate material M is bent in the groove 55 of the second stand 23 so as to have a shape similar to the shape of the product.

[0042] <Contact points with rolls during bending> 7A to 7D are explanatory diagrams of contact points between the intermediate material M and the grooved rolls in the bending machine 19, and (a) to (d) each show an example of the contact point. In FIG. 7, the contact points are shown by thick lines. In the grooved rolls 45 of the first stand 22 and the grooved rolls 55 of the second stand 23, the grooved rolls and the intermediate material M contact each other only at certain predetermined points, and no reduction in thickness is performed.

[0043] Specific contact points between the grooved roll and the intermediate material M may be, for example, the inside corners 70a, 70b of the boundary between the web corresponding portion 60 and the flange corresponding portions 62, 63, and the inside corners 71a, 71b of the boundary between the flange corresponding portions 62, 63 and the arm corresponding portions 65, 66, as shown in Figure 7(a).

[0044] As shown in Figure 7(a), contact points 70a and 70b are located inside corner portion 70 at the boundary between web corresponding portion 60 and flange corresponding portions 62 and 63. On the other hand, contact points 71a and 71b are located inside corner portion 71 at the boundary between flange corresponding portions 62 and 63 and arm corresponding portions 65 and 66. At contact points 71a and 71b, reaction forces are generated in directions that balance the reaction forces at 70a and 70b, respectively.

[0045] As shown in Figure 7(b), the central portion 60a of the underside (outside) of the web corresponding portion 60 may be brought into contact with the opposing pre-perforated rolls 41, 51. This allows efficient bending of the corners formed by the flange corresponding portions 62, 63 and the web corresponding portion 60. During bending, the web corresponding portion 60 tends to warp downward in the figure, so by bringing the pre-perforated rolls into contact with the central portion 60a of the underside 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.

[0046] Furthermore, at least in the second stand 23, which is the final stand, the upper surfaces (outer surfaces) 65a, 66a of the arm corresponding portions 65, 66 may be included in the contact points in order to make the arm corresponding portions 65, 66 approximately horizontal. In addition, as shown in Figure 7(c), in the grooved mold 45 of the first stand 22 and the grooved mold 55 of the second stand 23, the inner upper portions 62a, 63a of the flange corresponding portions 62, 63 of the intermediate material M may be brought into contact with the upper grooved rolls 40, 50, and the outer lower portions 62b, 63b of the flange corresponding portions 62, 63 may be brought into contact with the lower grooved rolls 41, 51. By bringing the points shown in Figure 7(c) into contact, three-point bending is generated at the corner portions 70, 71 due to the grooved roll shape, making it possible to perform highly accurate bending.

[0047] 7(d), in addition to the locations described in Figures 7(a) to 7(c), the upper surfaces (outer surfaces) 68a, 69a of the joint corresponding portions 68, 69 may be brought into contact with the upper perforated rolls 40, 50. By bringing the locations shown in Figure 7(d) into contact, the joint corresponding portions 68, 69 can also be formed to be approximately horizontal, enabling bending with even higher precision.

[0048] 7(a) to 7(d) have been described regarding suitable contact points with respect to the intermediate material M during bending, but these contact points are not positioned and configured to reduce the thickness of the intermediate material M. Specifically, the configuration is such that a specific point of the intermediate material M is not pressed from both sides by both the upper and lower grooved rolls (i.e., reduced), and the roll gap between the upper and lower grooved rolls is configured to be larger than the thickness of the intermediate material M, so that the thickness is not reduced. If the web corresponding portion 60 and the flange corresponding portions 62, 63 are not reduced, there is no need to unnecessarily increase the reduction reaction force.

[0049] 7 illustrates an example of a configuration in which a portion of each grooved roll contacts each corner portion 70, 71, but the contact points of each grooved roll in the present invention are not limited to this. That is, in addition to the contact points described above with reference to FIG. 7, further contact points may be provided. In the above description, a configuration in which the plate thickness is not reduced is described. However, as long as the increase in the above-mentioned reduction reaction force is within an acceptable range, the corner portions 70, 71 may be reduced. By reducing the corner portions 70, 71, the difference in the thickness direction of the stress generated at the corners by bending is alleviated. Furthermore, the plate thickness of the web corresponding portion 60, the flange corresponding portions 62, 63, and the arm corresponding portions 65, 66 may be reduced to some extent. In this case, it is preferable that the reduction rate be 20% or less when reducing only the corner portions, and that the reduction amount (reduction in plate thickness) be 0.5 mm or less when reducing the entire plate.

[0050] <Bending angle and material passing ability> In processes involving bending, there is a concern that the intermediate material M may not be centered accurately in the bending machine 19, resulting in poor material passing and resulting poor product shape. Figure 8 is a schematic cross-sectional view showing the state in which the tip of the intermediate material M is bitten into the bending machine 19 (the groove 45 of the first stand 22) with its tip misaligned in the width direction. As shown in Figure 8, the inclination angle of the flange-corresponding portion of the intermediate material M before forming with respect to the horizontal direction (hereinafter also simply referred to as the flange angle) is θ1, and the angle of the inclined portion of the groove 45 (the portion of the groove 45 corresponding to the flange-corresponding portion) with respect to the horizontal direction is θ2. The difference between angles θ1 and θ2 (i.e., θ2 - θ1) is the forming angle Δθ in the groove 45.

[0051] Figure 9 is a graph showing the relationship between the flange angle θ1 before forming of the intermediate material M before forming and the forming angle Δθ. Here, the symbol ◯ in Figure 9 indicates good material passing, the symbol △ indicates poor material passing only at the tip, and the symbol × indicates poor material passing. Specifically, the condition indicated by the symbol ◯ is when the flange-corresponding portion on the retreating side in the longitudinal direction is immediately centered as soon as it engages with the forming roll (grooved roll), and there is no impact whatsoever on the region with a good cross-sectional shape (the region before forming). The condition indicated by the symbol △ is when the misalignment is corrected and centering is achieved within a few meters (e.g., within 2 to 3 meters in actual equipment) after the rolled material is engaged, and a good product can be obtained by cutting a small area at the tip. The condition indicated by the symbol × is when misalignment occurs, resulting in inaccurate centering and an unsatisfactory product.

[0052] As shown in Figure 9, the limiting flange angle θ1 before forming is θ1 = 40°, and the limiting flange forming angle tends to become smaller regardless of whether the flange angle θ1 is large or small. This is for the following reason: When the flange angle θ1 is greater than 40°, even if the forming angle Δθ is the same, the larger the flange angle θ1, the larger the displacement X when the preceding flange corresponding part is engaged, and the smaller the horizontal projection length W, making the passing material more unstable. On the other hand, when the flange angle θ1 is smaller than 40°, the influence of friction with the forming roll becomes greater, and when the preceding flange contacts the lower roll, the rolled material is more likely to ride up on the lower roll rather than move laterally (widthwise), causing twisting and making the passing material unstable.

[0053] From the graph in Fig. 9, it is possible to extrapolate the flange angle θ1 before bending within a predetermined angle range, such as 30° to 56°, or within a range slightly wider than that angle range. Using an approximation line for the relationship between the flange angle θ1 and the forming angle Δθ based on the data in Fig. 9, it can be seen that material passing defects can be avoided by setting the range expressed by the following formulas (1) and (2). Note that the upper limits of the following formulas (1) and (2) are indicated by dashed lines in Fig. 9.

[0054] That is, in order to ensure centering of the rolled material during bending and perform stable bending, it is preferable that the following formulas (1) and (2) be satisfied at least during bending in the first stand 22. Δθ≦-0.30×θ1+32.0 (θ1≧40°) (1) Δθ≦0.20×θ1+12.0 (θ1<40°) (2)

[0055] <Guide device for bending machine> In a process involving bending, there is a concern that the intermediate material M may not be centered accurately in the bending machine 19, resulting in poor material passing and an associated defective product shape, and from this perspective, a guide device may be provided. For example, an inner guide and a lower guide extending in the rolling direction (the direction in which the material to be rolled passes) in a region including the upstream side of the first stand 22 may be provided as web restraining guides. Here, a configuration in which an inner guide 110 and a lower guide 112 are provided in the first stand 22 as web restraining guides will be described.

[0056] 10A and 10B are schematic explanatory diagrams showing an example of a guide device, in which (a) is a schematic explanatory diagram of an inner guide 110 and a lower guide 112 provided on a first stand 22 as seen from the side, and (b) is a schematic explanatory diagram of the inner guide 110, the lower guide 112, and the outer guide 80 as seen from the front. Note that FIG. 10A shows some of the transport rollers 95, and FIG. 10B omits components other than the inner guide 110, the lower guide 112, and the outer guide 80 for simplification. In FIG. 10, components having the same functional configuration as those described in the above embodiment are designated by the same reference numerals, and their description may be omitted.

[0057] As shown in Figure 10(a), the inner guide 110 and the lower guide 112 extend in the rolling direction from upstream to downstream of the first stand 22, and are composed of inner guides 110a, 110b and lower guides 112a, 112b arranged on the upstream and downstream sides of the first stand 22 in the vicinity of the first stand 22. That is, during bending, the intermediate material M is guided (restrained) from both above and below by the inner guide 110a, the conveying roller 95, and the lower guide 112a on the upstream side of the stand, and is then bitten into the first stand 22. Note that Figure 10 illustrates the vicinity of the first stand 22, and describes the inner guides 110a, 110b and the lower guides 112a, 112b, but an inner guide and a lower guide may also be provided downstream of the second stand 23.

[0058] 10(b), the inner guide 110a has a shape that protrudes downward from above the rolling line T, and its shape is similar to the shape of the intermediate material M. In other words, the lower surface of the inner guide 110a is shaped to fit along the upper surface of the web of the intermediate material M, which is approximately hat-shaped. Similarly, the shape of the inner guide 110b installed downstream of the stands may also be designed to match the shape of the intermediate material M to be bent in the second stand 23.

[0059] On the other hand, the lower guide 112a has a substantially flat plate shape and is arranged so as to follow the lower surface of the web of the intermediate material M when it is bitten. In this way, the intermediate material M is bitten into the first stand 22 with its upper and lower surfaces guided by the inner guide 110a, the conveying roller, and the lower guide 112a.

[0060] If the outer width of the web restraint guide is configured to be narrower than the inner distance between the left and right flanges of the pre-deformation portion of the intermediate material M in a steady state when the web restraint guide is installed, the pre-deformation during bending is not impaired and the guided engagement can be improved. In other words, by providing such a guide device, the intermediate material M can be accurately centered in the bending machine 19. Note that the shapes and arrangements of the guides described here are merely examples, and the present invention is not limited to these. For example, the cross-sectional shape of the inner guide 110a can be configured to continuously change from a shape that approximates the cross-sectional shape of the intermediate material M immediately after intermediate rolling to a shape immediately before bending, thereby achieving stable engagement.

[0061] <Joint shaping during finish rolling> As explained with reference to Fig. 1, in the rolling line L, the material to be rolled that has been bent by the bending machine 19 is finish-rolled by the finishing mill 20 to become a product. The shape of the groove used for finish rolling is arbitrary and is not limited, but as an example, it may be a groove shape for shaping the joint corresponding portions 68, 69. Fig. 11 is a schematic explanatory diagram showing an example of a groove shape used for finish rolling, where (a) shows a groove cross section and (b) shows a cross section including the material to be rolled.

[0062] As shown in FIG. 11 , left and right stoppers 120 (120a, 120b) for restraining the joint corresponding portions 68, 69 (particularly their tips) may be provided in the groove used for finish rolling. During finish rolling, the joint corresponding portions 68, 69 are restrained by the stoppers 120, and bending is performed while the joint corresponding portions 68, 69 are sandwiched between the upper and lower rolls. Here, "sandwiching" in this specification refers to a state in which the upper and lower grooved rolls sandwich the joint bottom and joint tip of the joint corresponding portions from the top or bottom in the finish rolling mill 20. This reduces the difference in left and right joint dimensions and the variation in joint shape in the longitudinal direction that occur in the bending machine 19, enabling the production of products with good dimensional accuracy. By reducing the thickness of the entire rolled material (plate thickness reduction) even slightly during finish rolling, stress in the cross section generated during bending can be alleviated, the spread of the cut end portion after cutting can be suppressed, and the correction work can be reduced.

[0063] <Action and effect> According to the manufacturing method of the steel sheet pile according to the present embodiment described above, bending is performed using the bending machine 19 configured as described above, and then finish rolling is performed. This makes it possible to efficiently manufacture a steel sheet pile product with good dimensional accuracy in hot working without using a mill with a large and complicated mechanism or a large number of mills.

[0064] 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.

[0065] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0066] For example, in the above embodiment, the bending machine 19 is illustrated and described as being composed of a first stand 22 and a second stand 23, but the present invention is not limited to this. For example, the bending machine 19 may be a single stand, or may be composed of any number of multiple stands. When the bending machine 19 is composed of multiple stands, each stand can share the bending work, making it possible to reduce changes in the shape of the joint corresponding portions 68, 69 that occur during bending. The number of stands is suitably determined based on the balance between the bending angle and capital investment; for example, if the bending angle is approximately 20° to 30°, two stands are suitable.

[0067] In the above embodiment, bending may be performed in a hot state. For example, the second intermediate rolling mill 16 and the bending machine 19 may be arranged in tandem, or the bending machine 19 and the finishing rolling mill 20 may be arranged in tandem. When multiple grooves are arranged in a rolling mill, the final groove of the second intermediate rolling mill 16 and the groove of the bending machine 19 may be arranged in tandem, or the groove of the bending machine 19 and the first groove of the finishing rolling mill 20 may be arranged in tandem. By performing intermediate rolling and bending successively in a hot state, the temperature drop of the rolled material is reduced and productivity is increased. Here, hot rolling and bending refers to rolling and forming at a temperature before the transformation of the rolled material is complete. By performing bending under these conditions, the forming load on the bending machine 19, material deterioration such as reduction in elongation and toughness due to bending, and residual stress can be reduced compared to conventional cold bending. In addition, when intermediate rolling in the second intermediate rolling mill 16 is performed by reverse rolling, the bending machine 19 may be of a stand shift type, and the bending machine 19 may be retracted from the rolling line L until the final pass of intermediate rolling, and bending may be performed only in the final pass.

[0068] The upper and lower slotted rolls of the bending machine 19 can also be configured so that only one of the upper and lower slotted rolls is driven, and the other is not. By configuring so that only one of the upper and lower slotted rolls is driven, it becomes easier to balance the speed of the material being passed when bending is performed in tandem with multiple stands, and the generation of tension in the material being rolled due to speed imbalance between multiple stands is suppressed, stabilizing the material being passed and suppressing unnecessary shape changes in the material being rolled. In addition, the drive mechanisms such as motors, spindles, and gears for driving the rolls can be simplified, thereby realizing downsizing of the equipment and reducing equipment costs.

[0069] Furthermore, in the above embodiment, the shaping of the joint corresponding portions 68, 69 of the rolled material is described as being performed by the finish rolling mill 20, but this is not limited to this. For example, a joint shaping groove may be provided in the edger rolling mill 17 arranged downstream of the second intermediate rolling mill 16. This joint shaping groove may be used to roll shaping the joint corresponding portions 68, 69, and then bending may be performed by the bending forming machine 19, and then bending shaping of the joint corresponding portions 68, 69 may be performed by the finish rolling mill 20. Alternatively, bending may be performed by the bending forming machine 19, and then rolling shaping of the joint corresponding portions 68, 69 may be performed by the joint shaping groove, and then bending shaping of the joint corresponding portions 68, 69 may be performed by the finish rolling mill 20. In other words, the process order in the rolling line L may be designed arbitrarily, and may be performed in an optimal order depending on the configuration of the rolling mills, etc.

[0070] Furthermore, in the above embodiment, the grooves 45, 55 for performing bending have been illustrated and described as being provided in the bending machine 19 arranged alone in the rolling line L, but the locations where these grooves 45, 55 are arranged are not limited to this. For example, the grooves 45, 55 as bending grooves may be provided in the second intermediate rolling mill 16, the edger rolling mill 17, and the finishing rolling mill 20. This allows for a reduction in equipment.

[0071] Furthermore, in the above embodiment, the intermediate material M is illustrated and described as having a substantially hat shape and the arm corresponding portions 65, 66 being substantially horizontal, but the cross-sectional shape of the intermediate material M is not limited to this. Fig. 12 is a schematic explanatory diagram showing another embodiment of the cross-sectional shape of the intermediate material M. As shown in Fig. 12, in the cross-sectional shape of the intermediate material M, the angle β formed between the flange corresponding portions 62, 63 and the arm corresponding portions 65, 66 may be smaller than the angle α formed between the web corresponding portion 60 and the flange corresponding portions 62, 63. In other words, by tilting the arm corresponding portions 65, 66 as shown in the figure, it is possible to suppress changes in the shape of the joint during bending.

[0072] In the above description of the embodiments, a 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 exemplified, but the present invention can also be applied to a 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 that case, it is sufficient to consider that the orientation of the joints and the upper and lower hole type rolls are reversed. Furthermore, in the above description of the embodiments, a case where a hat-shaped steel sheet pile is manufactured as a final product has been exemplified, but the present invention is not limited to this and can also be applied to the manufacture of steel sheet pile products such as U-shaped steel sheet piles, for example.

[0073] The following configuration examples also fall within the technical scope of the present invention. (1) A manufacturing method of a steel sheet pile in which a rolling material is subjected to rough rolling, intermediate rolling, and bending, and then finish rolling, The rolled material after the intermediate rolling comprises at least a web corresponding portion, two flange corresponding portions each having one end connected to both end portions of the web corresponding portion and having an angle wider than that of the product, and corner portions which are connection portions between the web corresponding portion and each of the flange corresponding portions, The method for manufacturing a steel sheet pile, characterized in that, in the bending, the corner portion is bent using an upper and lower grooved roll while contacting the upper and lower grooved roll with the inside of the corner portion or while pressing down the corner portion. (2) The rolled material after the intermediate rolling has an arm corresponding portion connected to the other end of the flange corresponding portion, and a corner portion which is a connection portion between the flange corresponding portion and the arm corresponding portion, The manufacturing method of the steel sheet pile according to (1), characterized in that in the bending, the corner portion is bent by using an upper and lower grooved roll while contacting the upper and lower grooved roll with the inside of the corner portion or while pressing down the corner portion. (3) The method for manufacturing a steel sheet pile according to (1) or (2), wherein the bending is performed using a single-hole or multiple-hole mold, and at least in the first bending, the bending is performed so that the relationship between the bending angle Δθ of the flange corresponding portion and the inclination angle θ1 of the flange corresponding portion before bending satisfies the following formula (1) or formula (2): Δθ≦-0.30×θ1+32.0 (θ1≧40°) (1) Δθ≦0.20×θ1+12.0 (θ1<40°) (2) (4) A method for manufacturing a steel sheet pile according to any one of (1) to (3), characterized in that during the bending, the roll gaps of the upper and lower slotted rolls facing the web corresponding portion and the flange corresponding portion are larger than the thicknesses of the web corresponding portion and the flange corresponding portion, respectively, and the corner portion is bent while a part of the upper and lower slotted rolls is in contact with the inside of the corner portion or while pressing down the corner portion. (5) A method for manufacturing a steel sheet pile according to (2), characterized in that in the rolled material before the bending forming, the angle between the flange corresponding portion and the arm corresponding portion is made smaller than the angle between the web corresponding portion and the flange corresponding portion. (6) The bending is performed by a bending machine having one or more stands including a first stand, The bending machine includes a web restraining guide that restrains an upper surface of a web corresponding portion of the rolled material, at least upstream of a first stand of the bending machine, A method for manufacturing a steel sheet pile according to any one of (1) to (5), characterized in that the outer width of the web restraint guide is configured to be narrower than the inner distance between the left and right flanges of the pre-deformation portion of the rolled material in a steady state at the installation position of the web restraint guide. (7) The groove for performing the finish rolling is provided with a stopper for restraining the joint corresponding portion of the rolled material, The method for manufacturing a steel sheet pile according to any one of (1) to (6), characterized in that in the finish rolling, the joint corresponding portion is restrained by the stopper, and the joint corresponding portion is bent and shaped while being clamped by upper and lower rolls. (8) The final groove for performing the intermediate rolling and the groove for performing the bending are arranged in tandem, or the groove for performing the bending and the first groove for performing the finish rolling are arranged in tandem, The method for manufacturing a steel sheet pile according to any one of (1) to (7), characterized in that only one of the upper and lower grooved rolls that perform the bending is driven. (9) A method for manufacturing a steel sheet pile according to any one of (1) to (8), characterized in that the bending is performed by a stand-shift type bending machine, the bending machine is withdrawn from the rolling line until the final pass of the intermediate rolling, and bending is performed only in the final pass. (10) The method for manufacturing a steel sheet pile according to any one of (1) to (5), characterized in that a groove for performing the bending is provided in a finishing rolling mill for performing the finish rolling. [Industrial Applicability]

[0074] The present invention can be applied to a method for manufacturing steel sheet piles such as hat-shaped steel sheet piles and U-shaped steel sheet piles. [Explanation of symbols]

[0075] 10...Roughing mill 13...First intermediate rolling mill 14...Edger rolling mill 16...Second intermediate rolling mill 17...Edger rolling mill 19...Bending machine 20...Finishing rolling mill 22...1st Stand 23...Second Stand 40...Upper perforated roll 41...Pre-hole type roll 44…Case 45…hole type 50...Upper perforated roll 51...Pre-hole type roll 54...Housing 55…hole type 60...Web Support Department 62, 63...Flange corresponding parts 65, 66...Arm corresponding parts 68, 69...Joint compatible parts 70...Corner section 71...Corner section 110...Inner guide 112...Lower guide 120...Stopper M…Intermediate material L...Rolling line

Claims

1. A manufacturing method of a steel sheet pile in which a rolling material is subjected to rough rolling, intermediate rolling, and bending, and then finish rolling, The rolled material after the intermediate rolling comprises at least a web corresponding portion, two flange corresponding portions each having one end connected to both end portions of the web corresponding portion and having an angle wider than that of the product, and corner portions which are connection portions between the web corresponding portion and each of the flange corresponding portions, The method for manufacturing a steel sheet pile, characterized in that, in the bending, the corner portion is bent using an upper and lower grooved roll while contacting the upper and lower grooved roll with the inside of the corner portion or while pressing down the corner portion.

2. The rolled material after the intermediate rolling comprises an arm corresponding portion connected to the other end of the flange corresponding portion, and a corner portion which is a connection portion between the flange corresponding portion and the arm corresponding portion, 2. The method for manufacturing a steel sheet pile according to claim 1, wherein the bending step includes using an upper and lower grooved roll to bend the corner portion while contacting the upper and lower grooved roll with the inside of the corner portion or while pressing down the corner portion.

3. 3. The method for manufacturing a steel sheet pile according to claim 1, wherein the bending is performed using a single-hole or multiple-hole type, and in at least a first bending, the bending is performed so that a relationship between a bending angle Δθ of the flange corresponding portion and an inclination angle θ1 of the flange corresponding portion before bending satisfies the following formula (1) or formula (2): Δθ≦−0.30×θ1+32.0 (θ1≧40°) (1) Δθ≦0.20×θ1+12.0 (θ1<40°)...(2)

4. 3. The method for manufacturing a steel sheet pile according to claim 1, wherein during the bending, roll gaps of the upper and lower grooved rolls facing the web corresponding portion and the flange corresponding portion are larger than the thicknesses of the web corresponding portion and the flange corresponding portion, respectively, and the corner portion is bent while a part of the upper and lower grooved rolls is in contact with the inside of the corner portion or while pressing down the corner portion.

5. 3. The method for manufacturing a steel sheet pile according to claim 2, wherein, in the rolled material before bending, an angle formed between the flange corresponding portion and the arm corresponding portion is smaller than an angle formed between the web corresponding portion and the flange corresponding portion.

6. The bending is performed by a bending machine having one or more stands including a first stand, the bending machine includes a web restraining guide that restrains an upper surface of a web corresponding portion of the rolled material, at least upstream of a first stand of the bending machine; 3. The method for manufacturing a steel sheet pile according to claim 1, wherein the outer width of the web restraint guide is configured to be narrower than the inner distance between the left and right flanges of the pre-deformed portion of the rolled material in a steady state at the installation position of the web restraint guide.

7. The groove for performing the finish rolling is provided with a stopper for restraining a joint corresponding portion of the rolled material, The method for manufacturing a steel sheet pile according to claim 1 or 2, characterized in that, in the finish rolling, bending shaping is performed while the joint corresponding portion is clamped by upper and lower rolls while the joint corresponding portion is restrained by the stopper.

8. A final groove for performing the intermediate rolling and a groove for performing the bending are arranged in tandem, or a groove for performing the bending and a first groove for performing the finish rolling are arranged in tandem, The method for manufacturing a steel sheet pile according to claim 1 or 2, characterized in that only one of the upper and lower grooved rolls for performing the bending is driven.

9. 3. The method for manufacturing a steel sheet pile according to claim 1, wherein the bending is performed by a stand-shift type bending machine, and the bending machine is retracted from the rolling line until the final pass of the intermediate rolling, and the bending is performed only in the final pass.

10. The method for manufacturing a steel sheet pile according to claim 1 or 2, wherein a groove for performing the bending is provided in a finishing rolling mill for performing the finish rolling.

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