Steel sheet pile manufacturing method

Abstract

To improve productivity by suppressing a shape defect of a claw matching part liable to occur in a rough rolling process in the manufacture of a steel sheet pile.SOLUTION: A method for manufacturing a steel sheet pile by drafting the material of a rectangular cross section has a rough rolling step, an intermediate rolling step, and a finish rolling step. A rolling machine is provided with a caliber that elongates the thickness center line length of the material to perform a flexure rolling for roll-molding the material from the rectangular cross-sectional shape to an almost steel sheet pile shape, where the flexure rolling includes light draft rolling in which a draft volume to a predetermined section is smaller than a draft volume to a part other than the predetermined section. The flexure rolling is performed through a plurality of paths, and rolling by the plurality of paths is divided into a pre-stage in which a claw matching part of the material is not drafted and a post-stage in which a claw matching part of the material, and the light draft rolling is applied to a path in the pre-stage of the plurality of paths.SELECTED DRAWING: Figure 11

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] Conventionally, steel sheet piles having joints at both ends, such as hat-shaped or U-shaped ones, have been manufactured by a groove rolling method. A general process of this groove rolling method is known in which a material heated to a predetermined temperature in a heating furnace is first rolled in sequence by a roughing mill, an intermediate mill, and a finishing mill, each equipped with a groove.

[0003] According to the above-mentioned general groove rolling method, steel sheet pile products currently manufactured in Japan can be manufactured from materials with rectangular cross sections. Specifically, for example, if the moment of inertia per 1 m of wall width is 1.0 (10 4 cm 4 / m), and the hat-shaped steel sheet pile product called 10H product, and the moment of inertia per 1m of wall width is 2.5 (10 4 cm 4 Hat-shaped steel sheet pile products, which are 25H products and have a diameter of 1 / m, are manufactured by the conventionally known groove rolling method.

[0004] When manufacturing steel sheet piles from rectangular cross-section materials, it is known that various shape defects occur in the rolled material during the rolling process, and solutions have been devised. For example, Patent Document 1 discloses a technique for applying a strong reduction to the biting end to prevent the occurrence of a biting shape in the end flange of the rolled material during rolling shaping. Furthermore, Patent Document 2 discloses a technique for preventing the occurrence of crops by forming a tip portion in the rolled material before rough rolling in the production of shaped steel. Furthermore, Patent Document 3 discloses a technique for giving a pre-formed shape to the end of the rolled material in order to reduce crops.

[0005] Furthermore, when a steel sheet pile is manufactured from a rectangular cross-section material using a groove rolling method, the thicknesses of the web and flange portions are equal at the rectangular cross-section material stage, and then, in the bending rolling stage where the boundary between the web and flange portions is formed, the flange portions are shear-deformed to bring the thickness ratio between the web and flange portions closer to that of the product. In this method, shear deformation is unlikely to occur at the biting end of the rolled material during bending rolling, which raises concerns about the occurrence of shape defects due to the thickened flange portions. Therefore, Patent Document 4 discloses a technology for suppressing the occurrence of shape defects by performing so-called light reduction rolling in the bending rolling stage, where a predetermined section of the biting end of the material is rolled with a smaller reduction amount than other sections. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 55-50902 [Patent Document 2] Japanese Patent Application Publication No. 01-178301 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-192490 [Patent Document 4] Patent No. 6590087 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, the techniques of Patent Documents 1 to 3 do not take into consideration the occurrence of defective shapes due to the increased thickness of the flange portion caused by the difficulty in shear deformation occurring at the biting end of the rolled material during bending rolling of the material. In contrast, Patent Document 4 proposes performing so-called light reduction rolling in a state where the amount of reduction in a predetermined section of the biting end of the material is smaller than in other sections.

[0008] However, when the present inventors manufactured a steel sheet pile by applying the rolling technology disclosed in Patent Document 4, they found that there was a risk of a shape defect occurring in the portion of the material (raw material) that corresponds to the claw (hereinafter also referred to as the claw corresponding portion). It has been found that such a shape defect in the claw corresponding portion may not only cause a defect in the claw shape of the steel sheet pile, but also cause a defect in the subsequent rolling roll.

[0009] In view of these circumstances, the object of the present invention is to provide a method for manufacturing a steel sheet pile that can suppress the defective shape of the claw corresponding portion that may occur during the bending rolling stage of the rough rolling process in the manufacture of a steel sheet pile, thereby improving productivity. [Means for solving the problem]

[0010] In order to achieve the above object, according to the present invention, there is provided a manufacturing method for manufacturing a steel sheet pile by rolling down a raw material having a rectangular cross section, the method comprising a rough rolling process, an intermediate rolling process, and a finish rolling process, wherein a rolling mill performing the rough rolling process is provided with a groove for performing bending rolling to extend a thickness centerline length of the raw material and roll the raw material from a rectangular cross section shape to a substantially steel sheet pile cross section shape, and in the bending rolling, a light reduction rolling is performed on a predetermined section of a biting end of the raw material, the light reduction rolling being a rolling process in which an amount of reduction for the predetermined section is smaller than an amount of reduction for a portion other than the predetermined section, and the bending rolling is performed in a plurality of passes, and the rolling by the plurality of passes is divided into an earlier stage in which a claw-corresponding portion of the raw material is not reduced, and a later stage in which the claw-corresponding portion of the raw material is reduced, and the light reduction rolling is applied to a pass in the earlier stage among the plurality of passes. The predetermined section of the biting end of the material is set to a section of 0.75 m or more from the biting end in the longitudinal direction of the material. A method for manufacturing a steel sheet pile is provided.

[0012] The steel sheet pile may be a U-shaped steel sheet pile.

[0013] The steel sheet pile may be a hat-shaped steel sheet pile. [Effects of the Invention]

[0014] According to the present invention, in the manufacture of steel sheet piles, it is possible to suppress the occurrence of defective shapes of claw corresponding portions that may occur in the bending rolling stage of the rough rolling process, thereby improving productivity. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic explanatory diagram of a rolling line according to an embodiment of the present invention. [Figure 2] FIG. 3 is a schematic explanatory view of the shape of a first cavity. [Figure 3] FIG. 4 is a schematic explanatory view of the shape of the second cavity. [Figure 4] FIG. 10 is a schematic explanatory view of the shape of a third hole. [Figure 5] FIG. 10 is a schematic explanatory view of the shape of a fourth hole. [Figure 6] FIG. 10 is a schematic explanatory view of the shape of a fifth hole. [Figure 7] FIG. 10 is a schematic explanatory view of the shape of a sixth hole. [Figure 8] FIG. 10 is a schematic explanatory view of the shape of a seventh hole. [Figure 9] FIG. 10 is a schematic explanatory diagram of the shape of an eighth hole. [Figure 10] FIG. 10 is a schematic explanatory view of bending rolling in a second caliber. [Figure 11] 10 is a graph showing the transition of the difference in elongation between the top and bottom in each pass when bending rolling is performed in multiple passes using a second caliber. [Figure 12] FIG. 2 is a schematic explanatory diagram showing the elongation amounts of the upper claw and the lower claw in a raw material (≒ material to be rolled). [Figure 13] FIG. 3 is a schematic explanatory view showing the shape of a second grooved roll for performing bending rolling. [Figure 14] FIG. 2 is a schematic explanatory diagram of the effect of the difference in peripheral speed between upper and lower grooved rolls and shear stress in bending rolling. [Figure 15] FIG. 2 is a schematic explanatory view of soft rolling of the biting end portion. DETAILED DESCRIPTION OF THE INVENTION

[0016] 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 the following, a case where a hat-shaped steel sheet pile is manufactured will be described as an example of a steel sheet pile product.

[0017] In this embodiment, for convenience of explanation, a material having a rectangular cross section will be referred to as stock material B, and a rolled material obtained by rolling stock B to have an approximately hat-shaped cross section will be referred to as rolled material A. In other words, steel materials with an approximately hat-shaped cross section passing through the rolling line L will be collectively referred to as rolled material A, and each part of rolled material A will be referred to by a different name as described below. Here, rolled material A is composed of a web-corresponding portion 3 corresponding to the web of the hat-shaped steel sheet pile product, flange-corresponding portions 4 and 5 connected to both ends of web-corresponding portion 3, arm-corresponding portions 6 and 7 formed at the tips of flange-corresponding portions 4 and 5, respectively, and joint-corresponding portions 8 and 9 formed at the tips of arm-corresponding portions 6 and 7. Furthermore, claw-corresponding portions 8a and 9a are formed at the tips of joint-corresponding portions 8 and 9.

[0018] <Rolling line configuration> FIG. 1 is an explanatory diagram of a rolling line L that produces hat-shaped steel sheet piles, which is a rolling facility according to an embodiment of the present invention, and the rolling mills provided in the rolling line L. As shown in FIG. 1, the rolling line L includes a roughing mill (BD) 11, a first intermediate rolling mill (R1) 12, a second intermediate rolling mill (R2) 13, and a finishing rolling mill (F) 14, which are arranged in this order. The rolling line L is composed of multiple lines L1 to L3, with line L1 adjacent to line L2 and line L2 adjacent to line L3. The lines L1 to L3 are connected in series with some of them overlapping each other, and the material A to be rolled moves parallel to the width direction from L1 to L2 or from L2 to L3 to advance through the rolling line L.

[0019] As shown in Fig. 1, a roughing mill 11 is arranged on line L1, a first intermediate rolling mill 12 is arranged on line L2, and a second intermediate rolling mill 13 and a finishing rolling mill 14 are arranged on line L3. Each of lines L1 to L3 can carry a different material A to be rolled and perform rolling, and the rolling line L is configured to be able to roll a plurality of materials A to be rolled simultaneously in parallel.

[0020] In the rolling line L shown in Fig. 1, a material having a rectangular cross section (material B, material A to be rolled later) heated in a heating furnace (not shown) is rolled in succession in a roughing mill 11 to a finishing mill 14 to become a hat-shaped steel sheet pile, which is the final product. That is, the final product is manufactured by subjecting material B (material A to be rolled) to a roughing rolling process, an intermediate rolling process, and a finishing rolling process in this order.

[0021] <Configuration of the groove provided in the rolling mill> Below, the configuration of the grooves provided in the roughing mill 11, first intermediate rolling mill 12, second intermediate rolling mill 13, and finishing mill 14 (hereinafter, multiple rolling mills may be abbreviated as roughing mill 11 to finishing mill 14) arranged in the rolling line L will be briefly explained in order from the upstream of the rolling line L with reference to the drawings. Note that the roughing mill 11, first intermediate rolling mill 12, second intermediate rolling mill 13, and finishing mill 14 are general equipment that has been used conventionally, so in the following description in this specification, attention will be focused on the explanation of the groove configuration, and explanation of the detailed equipment configuration of each rolling mill will be omitted.

[0022] 2 to 9 are provided in each rolling mill from the roughing mill 11 to the finishing mill 14, but which rolling mill each groove described below is provided in can be changed as appropriate depending on conditions such as equipment status and product dimensions, usually taking productivity (efficiency and yield) and workability into consideration. Therefore, in this embodiment, these grooves are referred to as the first groove K1 to the eighth groove K8, and the grooves will be described as being provided in order from the upstream side of the rolling line L. For reference, in FIGS. 3 to 9, the shapes of the material B and the material A to be rolled that are reduced and shaped by each groove are shown by dashed lines.

[0023] However, the configurations of the first caliber K1 to the eighth caliber K8 according to the present embodiment described below are not limited to the illustrated form, and for example, the arrangement of the adjustment calibers for various calibers can be changed as appropriate depending on conditions such as equipment conditions and product dimensions. Note that in the first caliber K1 to the eighth caliber K8 described below, it is preferable that the rolling shaping of the rolled material is performed by multiple pass reverse rolling (reversible rolling), and the number of passes can be set as desired.

[0024] FIG. 2 is a schematic diagram illustrating the groove shape of the first groove K1. As shown in FIG. 2, the first groove K1 is a box groove composed of an upper groove roll 20a and a lower groove roll 20b, and the bottom of the box groove has a predetermined tapered shape. This first groove K1 imparts a tapered shape to the short sides of the widthwise end of the rectangular cross-sectional material B and lightly reduces the width (so-called edging rolling) in the upright state (with the width direction of the steel sheet pile vertical) in order to achieve a uniform width dimension in the longitudinal direction. The tapered shape is imparted to the widthwise end of the rectangular cross-sectional material B so that it can be suitably engaged with the groove shape of the second groove K2 (described later), thereby stably performing the desired reduction and forming claws with the desired thickness at both ends. The first groove K1 shown in FIG. 2 is a groove used for so-called edging rolling, and this first groove K1 is referred to as an "edging groove."

[0025] 3 is a schematic explanatory diagram of the groove shape of the second groove K2. As shown in FIG. 3, the second groove K2 is composed of an upper grooved roll 30a as a protruding roll and a lower grooved roll 30b as a grooved roll, and this second groove K2 performs rolling on the entire material B (≒ material A to be rolled) having a rectangular cross-sectional shape that has been edge-rolled in the first groove K1. Here, the material B is in an upright position during rolling in the first groove K1, but then the material B is rotated 90° or 270°, and in the second groove K2, the material B is rolled with its width direction horizontal (with its width direction of the steel sheet pile horizontal), and rolling is performed to form a cross section that is an intermediate shape between a rectangular cross-sectional shape and a substantially hat-shaped cross-sectional shape. In this specification, rolling in the second groove K2 is also referred to as "bending rolling."

[0026] The upper perforated roll 30a is composed of a web facing portion 32 facing the upper surface of the web corresponding portion 3 of the material B, flange facing portions 34 and 35 facing the upper surfaces of the flange corresponding portions 4 and 5, and arm facing portions 37 and 38 facing the upper surfaces of the arm corresponding portions 6 and 7. On the other hand, the lower perforated roll 30b is composed of a web facing portion 42 facing the lower surface of the web corresponding portion 3 of the material B, flange facing portions 44 and 45 facing the lower surfaces of the flange corresponding portions 4 and 5, and arm facing portions 47 and 48 facing the lower surfaces of the arm corresponding portions 6 and 7. Furthermore, the flange facing portions 44 and 45 are composed of multiple portions with different inclinations, and are composed of gently sloping flange facing portions 44a and 45a connected to the web facing portion 42, and steeply sloping flange facing portions 44b and 45b connected to the arm facing portions 47 and 48.

[0027] 4 is a schematic explanatory diagram of the groove shape of the third caliber K3. As shown in Fig. 4, the third caliber K3 is composed of an upper caliber roll 50a as a protruding roll and a lower caliber roll 50b as a groove roll, and in this third caliber K3, further reduction is applied to the material B (≒ material A to be rolled) shaped in the second caliber K2, and reduction is applied to the entire material B so that the cross-sectional shape changes from an intermediate shape (an intermediate shape between a rectangular cross-sectional shape and an approximately hat-shaped cross-sectional shape) to an approximately hat-shaped cross-sectional shape.

[0028] It should be noted that the term "approximately hat-shaped cross-sectional shape" used herein refers to a cross-sectional shape in which material B has been compressed to such an extent that the boundaries between the portion corresponding to the web (web corresponding portion 3), the portion corresponding to the flange (flange corresponding portions 4 and 5), and the portion corresponding to the arm (arm corresponding portions 6 and 7) are clearly defined, and does not necessarily refer to a cross-sectional shape that has been formed down to the finest details such as a joint shape.

[0029] The upper perforated roll 50a is composed of a web facing portion 52 facing the upper surface of the web corresponding portion 3 of the material B, flange facing portions 54 and 55 facing the upper surfaces of the flange corresponding portions 4 and 5, and arm facing portions 57 and 58 facing the upper surfaces of the arm corresponding portions 6 and 7. The lower perforated roll 50b is composed of a web facing portion 62 facing the lower surface of the web corresponding portion 3 of the material B, flange facing portions 64 and 65 facing the lower surfaces of the flange corresponding portions 4 and 5, and arm facing portions 67 and 68 facing the lower surfaces of the arm corresponding portions 6 and 7.

[0030] Fig. 5 is a schematic explanatory diagram of the groove shape of the fourth groove K4. As shown in Fig. 5, the fourth groove K4 is composed of an upper grooved roll 70a as a protruding roll and a lower grooved roll 70b as a grooved roll, and this fourth groove K4 forms a claw corresponding portion and performs thickness reduction and shaping (thickness elongation rolling) on ​​the entire rolled material A, resulting in a shape closer to that of a hat-shaped steel sheet pile product.

[0031] FIG. 6 is a schematic explanatory diagram of the groove shape of the fifth groove K5. As shown in FIG. 6, the fifth groove K5 is composed of an upper grooved roll 80a as a protruding roll and a lower grooved roll 80b as a grooved roll, and this fifth groove K5 performs thickness reduction and shaping of the entire rolled material A. Specifically, claw height shaping, in which the heights of the two claw corresponding parts 8a, 9a are aligned by adjusting the heights (height h1 in the vertical direction in the figure), and thickness reduction of the entire rolled material A are performed simultaneously. Note that shaping, in which the heights of the claw corresponding parts 8a, 9a are aligned, such as with this fifth groove K5, is referred to as the claw shaping process, and the groove that performs the claw shaping process is referred to as the claw shaping groove.

[0032] Fig. 7 is a schematic explanatory diagram of the groove shape of the sixth groove K6. As shown in Fig. 7, the sixth groove K6 is composed of an upper grooved roll 90a as a protruding roll and a lower grooved roll 90b as a grooved roll, and this sixth groove K6 performs thickness reduction and forming (thickness elongation rolling) on ​​the entire rolled material A.

[0033] Figure 8 is a schematic explanatory diagram of the groove shape of the seventh groove K7. As shown in Figure 8, the seventh groove K7 is composed of an upper grooved roll 100a as a protruding roll and a lower grooved roll 100b as a grooved roll, and this seventh groove K7 performs thickness reduction and shaping of the entire rolled material A, and in particular, performs claw height shaping by adjusting the height of the claw corresponding parts 8a, 9a (height h2 in the vertical direction in the figure) to align the heights of the two claw corresponding parts 8a, 9a. However, the seventh groove K7 has a smaller thickness reduction amount than the sixth groove K6, which actively reduces the thickness of the entire rolled material A.

[0034] FIG. 9 is a schematic explanatory diagram of the groove shape of the eighth groove K8. As shown in FIG. 9, the eighth groove K8 is composed of an upper grooved roll 110a as a protruding roll and a lower grooved roll 110b as a grooved roll. This eighth groove K8 bends and shapes the joint corresponding portions 8 and 9 of the rolled material A and shapes the entire rolled material A by light rolling. Specifically, joint forming is performed by bending the entire joint corresponding portions 8 and 9, including the claw corresponding portions 8a and 9a, so that they form the joint shape of the product. As a result, the eighth groove K8 shapes the rolled material A to the shape of the hat-shaped steel sheet pile product. Note that grooves that bend and shape the entire joint corresponding portions 8 and 9, such as this eighth groove K8, are called finishing grooves.

[0035] The groove shapes and functions of the first groove K1 to the eighth groove K8 have been described above with reference to Figures 2 to 9. As described above, the groove rolling method for hat-shaped steel sheet piles consists of a rough rolling process, an intermediate rolling process, and a finish rolling process. For example, the rough rolling process and the intermediate rolling process are performed sequentially in the grooves from the first groove K1 to the seventh groove K7, and the finish rolling process is performed in the eighth groove K8. Here, the groove shapes of the fourth groove K4 to the eighth groove K8 are all approximately hat-shaped cross-sectional shapes, but the shapes of the grooves in the later stages are closer to the product shape. In other words, the shape of the eighth groove K8, which is used for the final process of finish rolling, is the approximately hat-shaped steel sheet pile product shape.

[0036] In this embodiment, the rolling line L is assumed to be arranged in this order with a roughing mill (BD) 11, a first intermediate rolling mill (R1) 12, a second intermediate rolling mill (R2) 13, and a finishing mill (F) 14 (see FIG. 1 ), but the first caliber K1 to the eighth caliber K8 are provided in any distributed configuration in each rolling mill. As an example, the roughing mill 11 is provided with the first caliber K1 to the third caliber K3, the first intermediate rolling mill 12 is provided with the fourth caliber K4 and the fifth caliber K5, the second intermediate rolling mill 13 is provided with the sixth caliber K6 and the seventh caliber K7, and the finishing mill 14 is provided with the eighth caliber K8. However, the caliber configuration in the present invention is not limited to this configuration.

[0037] <Problems in bending rolling> The present inventors have discovered that when the rolling technique disclosed in Patent Document 4, for example, is applied to the forming process (bending rolling) using the second caliber K2 in the rough rolling process for forming a substantially hat-shaped cross-sectional shape from a material B having a rectangular cross-sectional shape, and a method of performing so-called light reduction rolling with a smaller reduction amount in a predetermined section of the biting end of the material compared to other sections is used, the following problems arise. Specifically, the inventors have discovered that the cross-sectional shape of material B (≒ material A to be rolled) changes with bending rolling, resulting in a difference in the elongation amount of the upper claw and the lower claw (upper and lower elongation difference) particularly in the portions corresponding to the claws (later claw corresponding portions 8a, 9a). This discovery will be described below with reference to the drawings. Note that, in the following description, the claw corresponding portions 8a, 9a of material B (≒ material A to be rolled) may also be referred to as the claw corresponding portions.

[0038] Figure 10 is a schematic explanatory diagram of bending rolling in the second caliber K2, and (a) to (d) sequentially show the process of bending rolling performed in multiple passes. As shown in Figure 10(a), the upper caliber roll 30a and the lower caliber roll 30b come into contact with the top and bottom surfaces of the material B that has been edging-rolled in the first caliber K1. Thereafter, bending rolling proceeds in the order shown in Figure 10(b), (c), and (d).

[0039] 10 is performed by passing the material B (≒ material A to be rolled) through the same second groove K2 multiple times, gradually narrowing the roll gap. At this time, the contact points between the material B (≒ material A to be rolled) and the upper grooved roll 30a and the lower grooved roll 30b may differ for each pass.

[0040] The inventors focused on the difference in elongation between the upper and lower claws (hereinafter also referred to as the "upper and lower elongation difference") that occurs in the areas corresponding to the claws (rear claw corresponding portions 8a, 9a), and investigated the upper and lower elongation difference during bending and rolling with multiple passes. FIG. 11 is a graph showing the transition of the upper and lower elongation difference during each pass when bending and rolling is performed with multiple passes (a total of 14 passes in this case) using the second caliber K2. FIG. 12 is a schematic explanatory diagram showing the upper and lower claw elongation amounts for material B (≒ material A to be rolled). FIG. 11 shows a case where a so-called light reduction rolling method is used in which a predetermined section of the biting end of material B is subjected to a smaller reduction amount than other sections (hereinafter also referred to as "single-pass rolling"), and a case where material B is subjected to bending and rolling with a constant reduction amount throughout the entire section for each pass (hereinafter also referred to as "normal rolling"). For the sake of explanation, FIG. 12 also shows a schematic enlarged view of one side of the cross section of material B.

[0041] As shown in Figure 11, when comparing normal rolling and single pass rolling, no clear difference is seen in the transition of the difference in top and bottom elongation up to the 7th pass. On the other hand, from the 8th pass onwards, in normal rolling, elongation on the top jaw side (hereinafter also referred to as top elongation) and elongation on the bottom jaw side (hereinafter also referred to as bottom elongation) are repeated, and eventually the difference in top and bottom elongation is almost eliminated, whereas in single pass rolling, the difference in top and bottom elongation increases significantly.

[0042] If the difference in elongation between the top and bottom becomes large in this way during bending rolling, defects in shape such as upper and lower splits may occur in the claw-matching portions 8a, 9a of the material B (≒ material A to be rolled) in the subsequent rolling process (for example, intermediate rolling process), and further, the split claw-matching portions 8a, 9a may become double-bited. This may cause problems such as defects in the rolling rolls used in the intermediate rolling process.

[0043] <Mechanism of difference in vertical expansion> Based on the verification results shown in Fig. 11, the inventors investigated the contact state of the portions corresponding to the claws (shown as claw corresponding portions 8a and 9a in Fig. 10) with the grooved roll. As a result of the investigation, it was found that in the single-pass rolling related to this verification, the eighth pass is the pass in which the upper portions of the claw corresponding portions 8a and 9a (the broken line portions in Fig. 10(c)) start to come into contact with the upper grooved roll 30a (see Fig. 10(c)). That is, of the total 14 passes, in the bending rolling in the second groove K2, the first pass to the seventh pass correspond to the rolling state shown in Figs. 10(a) to (b), and the eighth pass to the fourteenth pass correspond to the rolling state shown in Figs. 10(c) to (d).

[0044] It is estimated that the reason why the difference in elongation between the top and bottom during bending rolling widens is that the reduction of the claw corresponding portions 8a, 9a begins from the eighth pass. Figure 13 is a schematic explanatory diagram showing the shape of the grooved roll of the second groove K2 used for bending rolling, with (a) being a schematic front view and (b) being a schematic side view. As shown in Figure 13, the upper grooved roll 30a is a protruding roll and the lower grooved roll 30b is a grooved roll. Therefore, the diameters of the rolls vary depending on the location, and the diameter of the lower roll is larger than the diameter of the upper roll at the positions facing the claw corresponding portions 8a, 9a. In other words, the peripheral speed of the lower grooved roll 30b is faster than the peripheral speed of the upper grooved roll 30a at the positions facing the claw corresponding portions 8a, 9a.

[0045] Figure 14 is a schematic explanatory diagram of the difference in peripheral speed between upper and lower grooved rolls and the effect of shear stress in bending rolling, and is an enlarged side view of the rolling state at the trailing edge of the pass. As shown in Figure 14, when bending rolling is performed on material B (≒ material A to be rolled), in passes after the rolling of the claw corresponding parts 8a, 9a has started (here, the 8th pass and onwards), it is thought that shear stress acts on the upper claw part 8a-1 (9a-1) in a direction that moves material B forward, and shear stress acts on the lower claw part 8a-2 (9a-2) in a direction that moves material B backward (see arrows in Figure 14).

[0046] <Application of single pass rolling in bending rolling> In view of the problems and mechanisms involved in bending rolling described above, the present inventors have devised a technology for suppressing the occurrence of differential elongation between the top and bottom of the claw corresponding portions 8a, 9a by limiting the range of application to a suitable range of passes when single-pass rolling is applied to bending rolling performed in multiple passes.

[0047] Specifically, when performing bending rolling in multiple passes, the process is divided into a pre-stage pass (non-reduction pass) where reduction of the claw corresponding portions 8a, 9a begins, and a post-stage pass (reduction pass) where reduction of the claw corresponding portions 8a, 9a is performed, and single-pass rolling is applied only to the non-reduction pass. This prevents defects in the shape of the claw corresponding portions 8a, 9a in the post-process due to a large difference in elongation between the top and bottom during single-pass rolling, making it possible to perform good bending rolling.

[0048] FIG. 15 is a schematic explanatory diagram of soft reduction rolling (so-called single-pass rolling) of the biting end of material B (≒ material A to be rolled). Specifically, it is an explanatory diagram of the case where the roll gap is opened by rolling with the second groove K2 (upper and lower groove rolls 30a, 30b) and soft reduction rolling is performed on the biting end, and is a schematic side view. For the purpose of explanation, FIG. 15 shows material B before rolling in an arbitrary pass (left side of the figure), from the start of rolling in that pass to the middle of rolling in that pass (center of the figure), and after rolling in that pass is completed (right side of the figure). Also, FIG. 15 shows the roll trajectory when viewed with the steel material fixed, using a dashed line.

[0049] As shown in Fig. 15, in the second caliber K2, it is desirable to open the roll gap at the start of shaping compared to the roll gap during rolling of the steady portion, and after the material B passes through the caliber rolls only in a predetermined section P of the biting end, to narrow the roll gap and perform rolling shaping of the steady portion. Also, the roll gap is narrowed at the maximum speed of the equipment performance, and the upper and lower rolls do not necessarily have to be narrowed equally, and only the upper roll or the lower roll may be narrowed. In bending rolling performed in this way, bending rolling is performed in a state where the amount of reduction is smaller (i.e., light reduction) in the predetermined section P of the biting end compared to the steady portion.

[0050] The predetermined section P is preferably the range of the biting end in the longitudinal direction of the rolled material, excluding the range known as the steady portion, but this range can be set arbitrarily as appropriate. Note that, as in Patent Document 1, this predetermined section P may be set to a section of 0.75 m or more from the biting end in the longitudinal direction of the material.

[0051] In order to carry out the above-described soft reduction rolling, it is desirable that the rolling mill provided with the second grooves K2 is configured to include a mechanism for changing the roll gap of the grooved rolls. As such a mechanism, for example, a hydraulic reduction mechanism can be mentioned.

[0052] <Action and effect> According to the manufacturing method of the steel sheet pile according to the present embodiment described above, in the bending rolling in multiple passes, so-called single-pass rolling is performed in which the predetermined section P of the biting end is subjected to a smaller reduction amount than other sections. The multiple passes are divided into a pre-stage pass (non-reduction pass) in which reduction of the claw corresponding sections 8a, 9a is started, and a post-stage pass (reduction pass) in which reduction of the claw corresponding sections 8a, 9a is performed, and single-pass rolling is applied only to the non-reduction pass. This makes it possible to suppress the occurrence of differential elongation between the top and bottom of the claw corresponding sections 8a, 9a during bending rolling. Furthermore, this suppresses the occurrence of defective shapes of the claw corresponding sections 8a, 9a in subsequent processes due to the large differential elongation between the top and bottom during single-pass rolling, enabling good bending rolling to be performed.

[0053] Note that the technique of applying light reduction rolling in the bending rolling described above may be applied to the biting end of the material B in each pass when the bending rolling is performed in multiple passes and the material B is reversed. This prevents the shape of the claw corresponding portions 8a, 9a at both longitudinal ends of the material B from being deformed, making it possible to perform good bending rolling.

[0054] By suppressing the defects in the shape of the claw corresponding parts 8a, 9a, the occurrence of defects in the claw shape in the final steel sheet pile product is suppressed, and problems such as defects occurring in the subsequent rolling rolls are eliminated, thereby improving productivity.

[0055] 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.

[0056] For example, in the above embodiment, the manufacturing of a hat-shaped steel sheet pile product is illustrated and described as an example, but the scope of application of the present invention is not limited to this. Specifically, if the present invention is applied to manufacturing methods of various steel sheet pile products manufactured using rectangular cross-sectional materials, it is possible to suppress shape defects at the biting end. For example, the present invention can also be applied to manufacturing methods of U-shaped steel sheet piles. However, hat-shaped steel sheet piles are characterized by their large cross-sectional structure. Due to this characteristic, they are tall after second-gauge rolling, in which they are bent and rolled to approximately the cross-sectional shape of the steel sheet pile, and the amount of deformation in the wire length is larger than that of ordinary steel sheet piles. Therefore, the technology of the present invention is particularly useful in manufacturing hat-shaped steel sheet piles.

[0057] 3 to 10, the hat-shaped steel sheet pile is rolled in a configuration in which the protruding rolls of a series of groove rows are arranged as upper groove rolls and the grooved rolls are arranged as lower groove rolls, i.e., in a so-called U-position rolling. However, the hat-shaped steel sheet pile may be rolled in a configuration in which the protruding rolls are arranged as lower groove rolls and the grooved rolls are arranged as upper groove rolls, i.e., in an inverted U-position rolling, for some or all of such a series of groove rows. [Industrial Applicability]

[0058] 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]

[0059] 3. Web Support Department 4, 5...Flange compatible parts 6, 7...Arm-compatible parts 8, 9...Joint compatible parts 8a, 9a...claw corresponding parts 11...Roughing mill 12...First intermediate rolling mill 13...Second intermediate rolling mill 14...Finishing rolling mill 30a...(Second-hole type) upper-hole type roll 30b...(Second-hole type) lower-hole type roll 32, 42...(Second hole type) web facing portion 34, 35, 44, 45... (Second hole type) flange facing portion 37, 38, 47, 48... (Second hole type) arm facing parts 52, 62...(third hole type) web facing portion 54, 55, 64, 65... (third hole type) flange facing part 57, 58, 67, 68... (third hole type) arm facing parts A: Rolled material B...Material O...(material) thickness centerline K1~K8...1st hole type~8th hole type L (L1~L3)...Rolling line

Claims

1. A manufacturing method for manufacturing a steel sheet pile by pressing a rectangular cross-section material, It has a rough rolling process, an intermediate rolling process, and a finish rolling process, The rolling mill that performs the rough rolling step is provided with a groove that performs bending rolling to extend the thickness center line length of the material and roll the material from a rectangular cross-sectional shape to a substantially steel sheet pile cross-sectional shape, In the bending rolling, light reduction rolling is performed on a predetermined section of the biting end of the material, in which the reduction amount for the predetermined section is smaller than the reduction amount for a portion other than the predetermined section, The bending rolling is performed in multiple passes, The rolling by the multiple passes is divided into an earlier stage in which the claw corresponding portions of the material are not pressed down, and a later stage in which the claw corresponding portions of the material are pressed down, The soft reduction rolling is applied to an earlier pass among the plurality of passes, A method for manufacturing a steel sheet pile, characterized in that the predetermined section of the biting end of the material is set to a section of 0.75 m or more from the biting end in the longitudinal direction of the material.

2. A method for manufacturing a steel sheet pile as described in claim 1, characterized in that the steel sheet pile is a U-shaped steel sheet pile.

3. A method for manufacturing a steel sheet pile as described in claim 1, characterized in that the steel sheet pile is a hat-shaped steel sheet pile.

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