Steel sheet pile manufacturing method

Abstract

To suppress dimensional variation in a longitudinal direction of a rolled material without impairing centering property even when engagement deviation occurs at a tip of the rolled material by a bending molding machine.SOLUTION: There is provided a method for manufacturing a steel sheet pile, wherein the rolled material is composed of a web correspondence part, a flange correspondence part, an arm correspondence part and a joint correspondence part, a bending molding machine for performing bending is composed of one or a plurality of stands, a caliber is formed in the one stand or plurality of stands, and in at least first bending in the one or plurality of stands, bending is performed so that a relation between a bending angle Δθ of the flange correspondence part and an inclination angle θ1 of the flange correspondence part before bending satisfies Expression (1) or Expression (2). Expression (1): Δθ≤-0.30×θ1+32.0 (θ1≥40°). Expression (2): Δθ≤0.20×θ1+12.0 (θ1<40°).SELECTED DRAWING: Figure 9

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] Steel sheet piles having joints at both ends, such as hat-shaped steel sheet piles and U-shaped steel sheet piles, 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 to a predetermined temperature in a heating furnace and then roll it in order using a roughing mill, an intermediate mill, and a finishing mill each equipped with a groove.

[0003] Furthermore, particularly when manufacturing large, asymmetric products such as hat-shaped steel sheet piles, manufacturing them using the roughing mill, intermediate rolling mill, and finishing rolling mill requires a large number of grooves, necessitating large-scale equipment, and the shaping method becomes complicated, making it more likely that the shapes of the products will vary or be defective. Furthermore, a large number of rolls are required to manufacture steel sheet piles of different shapes. In response to this, as shown in Patent Document 2, a technology is known in which a steel sheet pile is rolled and manufactured by hot rolling, and then bent by cold working using roll forming (hereinafter also referred to as bending forming), to manufacture steel sheet piles with a width and a cross-sectional height that exceed the width of the rolling equipment.

[0004] Furthermore, Non-Patent Document 1 discloses a technology for manufacturing lightweight steel sheet piles by using multiple cold forming machines to bend steel plates. This technology has the advantage that the plate thickness is thinner than that of hot-rolled steel plates, making it easier to form, and since the steel plates are bent almost symmetrically, there is almost no difference in the shape of the cropped parts on the left and right, making it less likely to cause misalignment (misalignment of the bite). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-192905 [Patent Document 2] Patent No. 4012407 [Non-patent literature]

[0006] [Non-Patent Document 1] "Roll Forming", edited by the Japan Society for Technology of Plasticity, Corona Publishing, pp. 111-113 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 grooves in the intermediate rolling process to the finish rolling process. This limits the total elongation of the rolled material depending on the number of grooves used, 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 groove shifting, and unbalanced elongation of each part in the cross section during reverse rolling, resulting in warpage and variations in wire length within the cross section. Furthermore, when large steel sheet pile products are manufactured using the conventional groove rolling method, the number of grooves that can be arranged on one roll is reduced, which raises concerns about a decrease in manufacturing efficiency. Another problem is that the large difference in peripheral speed between each roll increases friction between the rolled material and the roll, resulting in defects.

[0008] Furthermore, in the manufacturing method of steel sheet piles as exemplified in Patent Document 2, bending is performed by cold working, and furthermore, the corners of the rolled material are not directly pressed down using support rolls, which are flat rolls. Therefore, there are problems such as the difficulty of applying plastic deformation directly to the corners, making it difficult to perform effective bending, and the cold working method making it easy for springback to increase after forming. Furthermore, when the web and flange are formed at different times using multiple forming rolls (support rolls), there is also the problem that the fulcrum is shifted in the longitudinal direction of the rolled material, reducing the efficiency of bending.

[0009] In addition, in the manufacturing method of steel sheet piles described in Patent Document 2, the temperature when bending by cold working is set to a temperature below the A1 transformation temperature or a temperature below the recrystallization temperature. Bending in such a temperature range imposes a large processing load, and problems such as deterioration of the material, such as a decrease in elongation and toughness, and an increase in residual stress may occur. Therefore, in order to solve these problems, it becomes necessary to arrange a large number of forming rolls, which leads to problems such as an increase in the size of the equipment and a complex structure.

[0010] Furthermore, the technology described in Non-Patent Document 1 is a cold bending technology and does not take into consideration slippage. That is, cold bending is performed without crops, whereas when bending is performed continuously with hot rolling, asymmetric crops are likely to be formed in the rolled material, which is likely to cause slippage. Therefore, there is a problem that it is difficult to apply the technology described in Non-Patent Document 1 to bending of large steel sheet piles that is performed continuously with hot rolling.

[0011] In view of the above problems, the present invention aims to provide a method for manufacturing a steel sheet pile product efficiently by bending the rolled material after hot finish rolling. That is, the present invention aims to provide a method for manufacturing a steel sheet pile that can suppress the longitudinal dimensional fluctuation of the rolled material without impairing the centering ability, even when asymmetric crops are formed on the rolled material during the rolling process due to asymmetry of the product shape, temperature deviation, lateral deviation of the rolling state, etc., and the leading edge of the rolled material is misaligned and caught in the bending machine. [Means for solving the problem]

[0012] In order to achieve the above object, according to the present invention, there is provided a method for manufacturing a steel sheet pile, in which a rolled material is subjected to rough rolling, intermediate rolling, and finish rolling by hot rolling, and then bent, wherein the rolled material is composed of a web corresponding portion, a flange corresponding portion, an arm corresponding portion, and a joint corresponding portion, a bending machine for performing the bending is composed of one stand or a plurality of stands, a groove is formed in the one stand or the plurality of stands, and in at least a first bending in the one stand or the plurality of stands, 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 formula (1) or formula (2). After the finish rolling, the cropped portion of the rolled material is not cut off. A method for manufacturing a steel sheet pile is provided, which includes bending. Δθ≦-0.30×θ1+32.0 (θ1≧40°) (1) Δθ≦0.20×θ1+12.0 (θ1<40°) (2) Here, "hot" refers to the temperature before the transformation of the rolled material is completed after hot rolling.

[0013] The bending machine that performs the bending is composed of upper and lower perforated rolls, and during bending, the roll gap in the portions of the upper and lower perforated rolls that face the web corresponding portion and the flange corresponding portion may be larger than the thickness of the web corresponding portion and the flange corresponding portion.

[0014] In the bending process, only one of the upper and lower grooved rolls may be driven.

[0015] The bending machine for performing the bending and the finish rolling machine for performing the finish rolling may be arranged in tandem.

[0016] The steel sheet pile may be a hat-shaped steel sheet pile. [Effects of the Invention]

[0017] The present invention provides a method for efficiently manufacturing steel sheet pile products by bending a rolled material after hot finish rolling. That is, even if an asymmetric crop is formed on the rolled material during the rolling process due to asymmetry in the product shape, temperature deviation, or lateral deviation in the rolling state, and the leading edge of the rolled material is misaligned and caught in the bending machine, the method can suppress longitudinal dimensional fluctuations of the rolled material without impairing centering ability. [Brief explanation of the drawings]

[0018] [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 the material being formed in the first stand, and (c) shows the material being formed in the second stand. [Figure 7] FIG. 1 is a schematic explanatory diagram showing a state in which asymmetric crop portions are formed on a rolled material. [Figure 8] A schematic cross-sectional view showing the state in which the tip of the finishing material is bitten into the bending machine with the tip being shifted to the maximum in the width direction. [Figure 9] 1 is a graph showing the relationship between the flange angle θ1 before forming and the forming angle Δθ. DETAILED DESCRIPTION OF THE INVENTION

[0019] 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.

[0020] <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.

[0021] 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 finishing mill 19, and a bending 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.

[0022] 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 19, and are further hot shaped by the bending machine 20 to become final products. For the sake of explanation, the material to be rolled rolled by the roughing mill 10 will be referred to as a rough material, the material to be rolled by the first intermediate rolling mill 13 to the second intermediate rolling mill 16 will be referred to as an intermediate material, and the material to be rolled by the finishing mill 19 will be referred to as a finished material 19a. That is, the finished material 19a is shaped (cross-section changed) by the bending machine 20 to become a final product (i.e., a hat-shaped or U-shaped steel sheet pile product).

[0023] Here, the roughing mill 10, the first intermediate mill 13, the second intermediate mill 16, the finishing mill 19 arranged in the rolling line L, and the associated edger mills 14 and 17 are common equipment that has been used conventionally in the manufacture of steel sheet piles, and therefore detailed explanations of their device configurations, etc. will be omitted in this specification.

[0024] <Configuration of bending machine> Next, the detailed configuration of the bending machine 20 will be described with reference to the drawings. Fig. 2 is a schematic side cross-sectional view of the bending machine 20, and Fig. 3 is a schematic front view of the bending machine 20. The bending machine 20 shown in Figs. 2 and 3 bends a finished material 19a that has been finish-rolled in a finishing mill 19. Fig. 3 also shows a schematic front view of a first stand 22 provided in the bending machine 20, which will be described below. Here, in this embodiment, the bending machine 20 is described as being composed of two forming stands (forming stands 22 and 23, which will be described below), but the bending machine 20 may be composed of a single stand or any number of stands.

[0025] As shown in Fig. 2, the bending machine 20 according to this embodiment includes 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 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.

[0026] 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 finished material 19a in the state before being formed by the bending machine 20, and Fig. 5 shows, by a dashed dotted line, the cross-sectional shape of the finished material 19a' in the 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 upward-open position (with the web corresponding portion described below positioned downward and the arm corresponding portion positioned upward).

[0027] 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 finishing material 19a (i.e., the flange-corresponding part) and the part corresponding to the web of the finishing material 19a (i.e., the web-corresponding part), and the angle formed between the part corresponding to the arm of the finishing material 19a (i.e., the arm-corresponding part), respectively, and bends and shapes the height and width of the finishing material 19a 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 finished material 19a) is rolled in a shape with a low height in the roughing mill 10 to the finishing mill 19, and the material to be rolled is bent in the bending machine 20 so as to increase the height of the material to a desired product height. This makes it possible to manufacture a large-sized hat-shaped steel sheet pile product.

[0028] 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 groove 55. This groove 55 has a shape close to the desired product shape, and changes the angle between the part corresponding to the flange formed in the first stand 22 of the bending machine 20 (i.e., the flange corresponding part) and the part corresponding to the web of the finishing material 19a (i.e., the web corresponding part), and the angle between the part corresponding to the arm (i.e., the arm corresponding part), respectively, to form the flange shape, arm shape, and joint shape into a predetermined shape (i.e., the product shape). That is, in this second stand 23, the inclination angle of the flange corresponding part, which was insufficient for the product shape in the forming in the first stand 22, is changed to an angle corresponding to the product shape.

[0029] Here, 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 finishing material 19a. That is, in the bending machine 20, the thickness of the finishing material 19a is not reduced, and the grooved rolls of the first stand 22 and the second stand 23 and the finishing material 19a come into contact only at some predetermined locations to perform bending.

[0030] Furthermore, during bending, the grooved rolls of the first stand 22 and the second stand 23 and the finishing material 19a may be in contact with each other at some predetermined locations and may also be pressed down. In this specification, "contact" refers to a state in the bending machine 20 where only one of the upper and lower surfaces of a specific location of the finishing material 19a is in contact with the peripheral surface of the grooved roll. In contrast, "pressing down" refers to a state in the bending machine 20 where both the upper and lower surfaces of a specific location of the finishing material 19a are in contact with the grooved roll and a force is applied to reduce the thickness.

[0031] For example, the roll gap at the portions facing the web and flange portions is preferably about 0.5 mm to 3 mm larger than the thickness of the flange and web portions of the finishing material 19a. Additionally, the roll gap at the locations of the grooves 45 and 55 that correspond to the arm portions of the finishing material 19a may be configured to be larger than the thickness of the arm portions over the entire cross section. If the roll gap allowance range is smaller than 0.5 mm, the thickness of the finishing material 19a may be reduced due to variations in thickness, increasing the load on the bending machine 20. If the allowance range is larger than 3 mm, the inclination angle of the flange portions may not be adjusted to the target angle.

[0032] Note that the bending in the present invention may be performed using either one or both of the first stand 22 and the second stand 23 shown in the figure. That is, the bending may be performed using a single stand or multiple stands. For example, this includes cases where one or multiple bendings are performed using only the first stand 22, and cases where multiple bendings are performed using both the first stand 22 and the second stand 23. In either case, the first bending performed in the bending machine 20 may be referred to as the "first bending."

[0033] <Bending of rolled materials> Next, the forming of the rolled material in the above-mentioned stands 22 and 23 will be described. Figure 6 is an explanatory diagram of the shape change of the rolled material (finishing material 19a) being bent in the first stand 22 and the second stand 23, with (a) showing a schematic cross-sectional view before forming in the first stand 22, (b) showing the material being formed in the first stand 22, and (c) showing the material being formed in the second stand 23. As shown in Figure 6(a), the finishing material 19a has a generally hat-shaped shape and is composed of a generally 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 that are different from the connection side with the web corresponding portion, and joint corresponding portions 68 and 69 formed at the tips of the arm corresponding portions 65 and 66. Furthermore, the finishing material 19a has a thickness that is approximately the same as the thickness of the finished product due to rolling in the finishing rolling mill 19, and the shapes of the joint corresponding parts 68, 69 are also approximately the shape of the joint of the finished product.

[0034] Here, the thickness of the corner portion 70 (hereinafter also referred to as the web-flange corner portion 70) 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, the finishing mill 19, etc. (see FIG. 1).

[0035] Similarly, the thickness of the corner portion 71 (hereinafter also referred to as the flange-arm corner portion 71) 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, the finishing mill 19, etc. (see FIG. 1).

[0036] The finishing material 19a 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 finishing material 19a 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 finishing material 19a becomes large.

[0037] Next, as shown in FIG. 6(c), the finishing material 19a is bent in the groove 55 of the second stand 23 into a shape substantially similar to the product shape.

[0038] <Cropped area generation> The manufacturing process using bending of hat-shaped steel sheet pile products has been described above with reference to Figs. 1 to 6. However, in hot rolling of hat-shaped steel sheet piles and the like, asymmetric crop portions are likely to be formed in the material to be rolled. When the material to be rolled (finishing material 19a) is transported from the finishing rolling mill 19 to the bending machine 20, if the crop portion is formed in the bending machine 20 without being cut with a hot saw or the like, misalignment (misalignment of the bite) is likely to occur in the bending machine 20, which becomes a problem. Fig. 7 is a schematic explanatory diagram showing a state in which asymmetric crop portions are formed in the material to be rolled (finishing material 19a).

[0039] 7, when an asymmetrical crop is formed at the tip of the finishing material 19a, the leading flange is caught first in the bending machine 20, resulting in uneven engagement. As a result, the finishing material 19a cannot be centered accurately in the bending machine 20, resulting in poor material passing and resulting defects in the product shape.

[0040] Therefore, the inventors conducted extensive research into the relationship between the widthwise misalignment amount and the forming angle when the finishing material 19a is bitten in the bending machine 20. They found that even when misalignment occurs in the bending machine 20, that is, even when the amount of misalignment becomes large, material passing problems do not occur by setting the relationship between the inclination angle of the flange corresponding portion before bending and the forming angle of the groove 45 to a predetermined value. This finding will be explained below with reference to the drawings. The amount of misalignment is the horizontal length of the misalignment between the connecting portions (hereinafter also referred to as corner portions) of the web corresponding portion 60 of the finishing material 19a and the flange corresponding portions 62, 63 and the corner portions of the groove 45 corresponding to these connecting portions.

[0041] <Relationship between bending angle and deviation amount> FIG. 8 is a schematic cross-sectional view showing the state in which the tip of the finishing material 19a is engaged in the bending machine 20 (i.e., the groove 45 of the first stand 22) with its tip displaced to the maximum in the width direction. The finishing material 19a can be displaced to the maximum extent that the connecting portion between one of the flange-corresponding portions and the arm-corresponding portion coincides with the groove 45 or 55 and the finishing material 19a. In this case, the flange on the right side (lower side in FIG. 7) is shown to be engaged in the bending machine 20 first. For the sake of explanation, as shown in FIG. 8, the inclination angle of the flange-corresponding portion of the finishing material 19a before forming relative to the horizontal direction (hereinafter simply referred to as the flange angle) is θ1, and the angle of the inclined portion of the groove 45 (the portion corresponding to the flange-corresponding portion on the groove 45) relative 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. Strictly speaking, the angle of the inclined portion of the groove 45 projected onto a vertical plane at the position where one flange is bitten between the upper and lower rolls shown in Figure 8 is θ2', but here it is represented by the above θ2. Also, the horizontal projection length of the flange corresponding portion 63 before forming (hereinafter also simply referred to as the horizontal projection length) is W, and the above maximum deviation amount is X (hereinafter also simply referred to as the deviation amount X). In reality, a corner R is given to the corner portion, so it is sufficient to consider the intersection of the respective straight portions of the web corresponding portion and the flange corresponding portion as the basis.

[0042] The inventors have investigated the relationship between the flange angle θ1 before forming and the flange bending angle Δθ (hereinafter simply referred to as the forming angle Δθ) under various conditions. As a result, they have found that it is possible to indicate suitable forming conditions based on the following equations (1) and (2), which are the relationship between the forming angle Δθ and the flange angle θ1 of the finishing material 19a before forming. This finding will be explained below with reference to FIG. 9. Δθ≦-0.30×θ1+32.0 (θ1≧40°) (1) Δθ≦0.20×θ1+12.0 (θ1<40°) (2)

[0043] When an asymmetric crop as shown in Figure 7 is formed on the rolled material and misalignment occurs as shown in Figure 8, the relationship between the flange angle θ1 before forming and the flange bending angle Δθ is plotted in the graph shown in Figure 9.

[0044] <Relationship between flange angle θ1 and bending angle Δθ> Figure 9 is a graph showing the relationship between the flange angle θ1 before forming of the finished material 19a before forming and the forming angle Δθ. In Figure 9, the symbol ◯ indicates good material passing, the symbol △ indicates poor material passing only at the tip, and the symbol × indicates poor material passing. Specifically, the symbol ◯ indicates that centering is achieved immediately when the flange-corresponding portion on the retreating side in the longitudinal direction engages with the forming roll (grooved roll), with no impact on the region with a good cross-sectional shape (the region before forming). The symbol △ indicates that after the rolled material is engaged, any misalignment is corrected within a few meters (e.g., within 2 to 3 meters in actual equipment) and centering is achieved, resulting in a good product by cutting a small area at the tip. The symbol × indicates that misalignment occurs, resulting in inaccurate centering and an unsatisfactory product.

[0045] 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.

[0046] 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. Δθ≦-0.30×θ1+32.0 (θ1≧40°) (1) Δθ≦0.20×θ1+12.0 (θ1<40°) (2)

[0047] As explained above with reference to Figure 9, in order to prevent material passing defects, it is sufficient to determine the forming angle in the bending machine 20 so that the relationship between the flange angle θ1 before forming and the forming angle Δθ satisfies the above formula (1) or formula (2).

[0048] Note that, for example, if the bending angle Δθ is set to less than 12°, the stability of the material passing through the bending machine is ensured. However, because the bending angle per stand is small, multiple stands are required to perform bending at a predetermined angle, which is inefficient in terms of equipment costs. That is, the preferred bending angle for the first stand is, for example, 12° or greater, within the range indicated by the above formulas (1) and (2). Furthermore, if the bending machine 20 is configured with multiple stands, satisfying the above bending conditions (the conditions indicated by formula (1) or (2)) in all stands will prevent material passing problems. Furthermore, the bending conditions described here are particularly suitable when the corner thickness of the finished material 19a is 10 mm or greater. Furthermore, it is desirable to set the bending angle Δθ to approximately 14° to 18° for the stability and efficiency of bending.

[0049] <Action and effect> As described above, a steel sheet pile product is manufactured under forming conditions that can avoid the occurrence of material passing defects during bending, i.e., conditions that satisfy the above formula (1) or (2). As a result, even if, for example, an asymmetric crop portion is formed during finish rolling and the tip of the rolled material becomes misaligned and jammed in the bending machine 20, it is possible to suppress longitudinal dimensional fluctuations without impairing the centering ability of the rolled material. Furthermore, as described above, the roll gap immediately below the rolls of the groove 45 during bending is configured to be larger (e.g., approximately 0.5 mm to 3 mm) than the thicknesses of the flange-corresponding portions and web-corresponding portions of the finishing material 19a. Furthermore, it is preferable that the roll gap immediately below the rolls of the groove 45 during bending be larger than the thicknesses of the arm-corresponding portions and corner portions of the finishing material 19a (the connecting portions between the web-corresponding portions and the flange-corresponding portions, and the connecting portions between the flange-corresponding portions and the arm-corresponding portions). This allows for easy centering by correcting the misalignment when the flange-corresponding portions 62 and 63 become misaligned and jammed during bending. This improves productivity and yield.

[0050] 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.

[0051] In the above embodiment, the bending machine 20 is illustrated and described as being composed of a first stand 22 and a second stand 23. However, the scope of application of the present invention is not limited to this. For example, the bending machine 20 may be a single stand (one stand) or may be composed of any number of multiple stands. When the bending machine 20 is composed of multiple stands, bending can be performed by sharing the bending work among the stands. When the bending machine 20 is composed of multiple stands, it is desirable that each of the multiple stands satisfy the appropriate forming conditions to prevent material passing defects. However, when multiple stands are arranged in tandem, the first stand (i.e., the first stand) that begins to bite the rolled material must have predetermined forming conditions. In this case, since the first stand can restrain the rolled material in a stably centered state under the predetermined forming conditions, the second stand can also adopt a forming angle outside the range determined by the above formulas (1) and (2). 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 about 20° to 30°, the two-stand configuration described in the above embodiment is suitable.

[0052] In the above embodiment, the upper and lower grooved rolls of the bending machine 20 can also be configured so that only one of the upper and lower grooved rolls is driven, and the other is not. Driving only one of the upper and lower grooved rolls makes it easier to balance the speed of the sheet when bending is performed in tandem with multiple stands. This also reduces tension in the rolled material due to speed imbalances between multiple stands, stabilizing the sheet threading and preventing unnecessary deformation of the rolled material. Additionally, the drive mechanisms, such as motors, spindles, and gears, for driving the rolls can be simplified, thereby achieving equipment miniaturization and reduced equipment costs. Furthermore, by arranging the finishing rolling mill and the bending machine in tandem and pushing the rolled material from the finishing rolling mill into the bending machine, the amount of misalignment is reduced and centering is stabilized, even when an asymmetric crop is caught.

[0053] In addition, in the above-mentioned embodiment and its modified examples, the case where a hat-shaped steel sheet pile product is manufactured in an upward opening position (with the arm corresponding portion on the upper side relative to the web corresponding portion) has been described as an example. However, the present invention can also be applied to the case where a hat-shaped steel sheet pile product is manufactured in the opposite downward opening position (with the arm corresponding portion on the lower side relative to the web corresponding portion). In this case, it is sufficient to consider that the orientation of the joints and the arrangement of the upper and lower slotted rolls are reversed to those in the above-mentioned embodiment. Furthermore, in the explanation of the above-mentioned embodiment and its modified examples, the case where a hat-shaped steel sheet pile is manufactured as a final product has been described as an example, 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. [Example]

[0054] As an example of the present invention, a bending experiment was carried out on an aluminum material having a hat-shaped steel sheet pile shape based on the manufacturing method of the steel sheet pile according to the present invention. The bending according to this example was carried out under the conditions shown in Conditions 1 to 6 in Table 1 below. The numerical values of each dimension in Table 1 are converted to values in an actual machine. In addition, the difference between the left and right crop lengths of the material to be rolled in this example was set to 300 mm.

[0055] Here, "good" in Table 1 refers to a case where the rolled material is centered immediately after being inserted into the bending machine, and a good shape is obtained for the rolled material except for the cropped portion. "Poor tip" in Table 1 refers to a case where the misalignment is corrected and centered within a few meters (e.g., within 2 to 3 meters in actual machine equivalent) after the rolled material is inserted into the bending machine, and a good shape is obtained by cutting off a small area at the tip. "Large defect" in Table 1 refers to a case where the rolled material is not properly centered when inserted into the bending machine, and the defective shape extends over a wide area (e.g., over 3 meters in actual machine equivalent). In other words, "good" and "poor tip" in Table 1 refer to a case where the defective shape portion (the portion to be cut) is within 3 meters from the tip in actual machine equivalent, and the centering ability and post-forming shape are maintained good (or within an acceptable range).

[0056] [Table 1]

[0057] Under condition 1, only the first stand of the bending machine was used, and the first bending was performed at a bending angle Δθ (17°) that satisfied the above formula (1). As a result, the centering ability and post-forming shape of the rolled material were good.

[0058] In addition, under condition 2, the first and second stands of the bending machine were used, and the first and second bending were performed at each stand. At that time, the bending angle Δθ (first bending: 16°, second bending: 13°) was set to satisfy the above formula (1). As a result, the centering ability and post-forming shape of the rolled material were good.

[0059] Under condition 3, the first and second stands of the bending machine were used, and the first and second bending were performed at each stand. The bending angle Δθ (first bending: 20°, second bending: 9°) was set to satisfy the above formula (1). As a result, the centering of the rolled material was ensured within a range of about 2 m from the tip, and a good shape was obtained by cutting a small area at the tip.

[0060] Furthermore, under condition 4, the first and second stands of the bending machine were used, and the first and second bending were performed at each stand. In the first bending, the forming angle Δθ (20°) was set, which does not satisfy the above formula (2), and in the second bending, the forming angle Δθ (13°) was set, which satisfies the above formula (1). As a result, the centering of the rolled material was not performed properly in the first bending, and the shape after forming was defective in a range of more than 5 m from the tip, or in some cases the material could not be passed through.

[0061] Under condition 5, the first and second stands of the bending machine were used, and the first and second bending were performed at each stand. At that time, the bending angles Δθ (first bending: 16°, second bending: 17°) were set to satisfy the above formulas (1) and (2). As a result, the centering ability and post-forming shape of the rolled material were good.

[0062] Furthermore, under condition 6, the first and second stands of the bending machine were used, and the first and second bending were performed at each stand. The first bending was performed at a bending angle Δθ (12°) that satisfied the above formula (2), while the second bending was performed at a bending angle Δθ (21°) that did not satisfy the above formula (1). As a result, the centering ability of the rolled material and the shape after bending were good in the first bending. On the other hand, although the second bending did not satisfy formula (1), the amount of deviation was kept small because the second bending was performed while the rolled material was restrained by the first bending. As a result, the centering ability and the shape after bending were good.

[0063] According to conditions 1 to 3 and 5 shown in Table 1, by performing bending under conditions that satisfy formula (1) or formula (2) described in the above embodiment, the centering ability and the post-forming shape of the rolled material are good and are fully acceptable as a product. Furthermore, according to condition 4, if formula (1) or formula (2) is not satisfied in the first bending, centering is not performed properly and the post-forming shape is poor. On the other hand, according to condition 6, even if formula (2) is satisfied in the first bending and formula (1) is not satisfied in the second bending, the centering ability and the post-forming shape are good. This shows that when bending is performed in tandem, such as first bending and second bending, it is possible to achieve good centering ability and post-forming shape by performing at least the first bending under the conditions described in the above embodiment (i.e., the conditions shown in formula (1) or formula (2)). [Industrial Applicability]

[0064] 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]

[0065] 10...Roughing mill 13...First intermediate rolling mill 14...Edger rolling mill 16...Second intermediate rolling mill 17...Edger rolling mill 19...Finishing rolling mill 19a...Finishing material 20...Bending machine 22...1st Stand 23...Second Stand 40...Upper perforated roll 41...Pre-hole type roll 44…Case 45...hole type 45a...Web section 45b...flange part 50...Upper perforated roll 51...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 L...Rolling line

Claims

1. A manufacturing method of a steel sheet pile, in which a rolled material is subjected to rough rolling, intermediate rolling, and finish rolling by hot rolling, and then bent, The rolled material is composed of a web corresponding portion, a flange corresponding portion, an arm corresponding portion, and a joint corresponding portion, The bending machine for performing the bending is composed of one stand or multiple stands, A groove is formed in the one or more stands, In at least a first bending process in the one stand or the plurality of stands, bending is performed without cutting a crop portion of the rolled material after the finish rolling 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 formula (1) or formula (2). Δθ≦−0.30×θ1+32.0 (θ1≧40°) (1) Δθ≦0.20×θ1+12.0 (θ1<40°)...(2)

2. The bending machine for performing the bending is composed of upper and lower grooved rolls, 2. The method for manufacturing a steel sheet pile according to claim 1, wherein, during bending, a roll gap between the upper and lower grooved rolls and the flange corresponding portions is larger than a thickness of the web corresponding portion and the flange corresponding portion.

3. The method for manufacturing a steel sheet pile according to claim 2 , wherein only one of the upper and lower grooved rolls is driven in the bending.

4. The manufacturing method of the steel sheet pile according to any one of claims 1 to 3, characterized in that a bending machine that performs the bending and a finishing rolling machine that performs the finish rolling are arranged in tandem.

5. The method for manufacturing a steel sheet pile according to any one of claims 1 to 4, wherein the steel sheet pile is a hat-shaped steel sheet pile.

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