JP7723261B2 - Steel sheet pile manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing steel sheet piles, such as hat-shaped steel sheet piles and U-shaped steel sheet piles.

Hat-shaped steel sheet piles, U-shaped steel sheet piles, and other steel sheet piles with joints at both ends are manufactured using a groove rolling method, as shown in Patent Document 1, for example. Specifically, a typical process for the groove rolling method involves first heating a rectangular material to a predetermined temperature in a heating furnace, and then rolling it sequentially through a roughing mill, an intermediate rolling mill, and a finishing rolling mill equipped with grooves.

In particular, when manufacturing large, asymmetrical products such as hat-shaped steel sheet piles, manufacturing them using the roughing mill, intermediate mill, and finishing mill requires a large number of grooves, necessitating large-scale equipment. Not only does this complicate the shaping method, it also increases the likelihood of product shape variations and defects. Furthermore, manufacturing steel sheet piles of different shapes requires a large number of rolls. In response to this, as shown in Patent Document 2, a technology is known in which steel sheet piles are rolled and manufactured by hot rolling, and then bent by cold working using roll forming (hereinafter also referred to as bending), to manufacture steel sheet piles with widths and cross-sectional heights that exceed the widths of rolling equipment.

Non-Patent Document 1 also discloses a technology for manufacturing lightweight steel sheet piles by using multiple cold forming machines to bend steel plate. This technology has the advantage that the plate is easier to form because it is thinner than hot-rolled steel plate, and since it is bent almost symmetrically from steel plate, there is almost no difference in the shape of the left and right cropped portions, making it less likely to cause misalignment (misalignment of the plate).

Japanese Unexamined Patent Publication No. 10-192905 Patent No. 4012407

"Roll Forming," edited by the Japan Society for Technology of Plasticity, Corona Publishing, pp. 111-113

However, with the conventional groove rolling method exemplified in Patent Document 1, rolling is performed in one pass with one groove while groove shifting is performed from the intermediate rolling process to the finish rolling process. This means that the total elongation of the rolled material is limited 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 an imbalance in the elongation of each part within the cross section during reverse rolling, resulting in warping and changes in wire length within the cross section. Furthermore, when large steel sheet pile products are manufactured using conventional groove rolling methods, the number of grooves that can be placed on one roll is reduced, raising concerns about reduced 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.

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 flat support rolls. This makes it difficult to apply plastic deformation directly to the corners, making it difficult to perform effective bending. Furthermore, the cold working process makes 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 misaligned in the longitudinal direction of the rolled material, reducing the efficiency of bending.

In addition, in the steel sheet pile manufacturing method described in Patent Document 2, the temperature during cold bending is set to a temperature below the A1 transformation temperature or the recrystallization temperature. Bending in these temperature ranges imposes a heavy processing load, which can lead to problems such as material degradation (e.g., reduced elongation and toughness) and increased residual stress. Therefore, to address these issues, it becomes necessary to install a large number of forming rolls, which leads to problems such as larger equipment and more complex structures.

Furthermore, the technology described in Non-Patent Document 1 is a cold bending technology and does not take into account misalignment. In other words, cold bending is performed without crops, whereas when bending is performed consecutively with hot rolling, asymmetric crops tend to form on the rolled material, which can easily cause misalignment. As a result, there is a problem in that it is difficult to apply the technology described in Non-Patent Document 1 to bending large steel sheet piles consecutively with hot rolling.

In consideration of the above problems, the object of the present invention is to provide a method for highly efficiently manufacturing steel sheet pile products by bending the rolled material after hot finish rolling. In other words, the present invention provides a method for manufacturing steel sheet piles that can suppress longitudinal dimensional fluctuations in the rolled material without impairing centering, even when asymmetric crops are formed in the rolled material during the rolling process due to asymmetry in the product shape, temperature deviations, or left-right misalignment in the rolling state, causing the leading edge of the rolled material to become misaligned and jammed in the bending machine.

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 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 multiple stands, and a groove is formed in the one stand or multiple stands, and in at least a first bending in the one stand or multiple stands, bending is performed without cutting a crop portion of the rolled material after the finish rolling 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 formula (1) or formula (2).
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.

The bending machine that performs the bending is composed of upper and lower perforated rolls, and during bending, the roll gap between the upper and lower perforated rolls facing 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.

During the bending process, only one of the upper and lower slotted rolls may be driven.

The bending machine that performs the bending and the finishing rolling machine that performs the finishing rolling may be arranged in tandem.

The steel sheet piles may be hat-shaped steel sheet piles.

The present invention provides a method for highly efficient manufacturing of steel sheet pile products by bending the rolled material after hot finish rolling. In other words, even if asymmetric crops are 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, causing misalignment and jamming of the leading edge of the rolled material in the bending machine, it is possible to suppress longitudinal dimensional fluctuations of the rolled material without impairing centering.

1 is a schematic explanatory diagram of a rolling line according to an embodiment of the present invention. FIG. 2 is a schematic side cross-sectional view of a bending machine. FIG. 2 is a schematic front view of the bending machine. FIG. 10 is a schematic enlarged front view showing the groove shape of the first stand. FIG. 10 is a schematic enlarged front view showing the groove shape of the second stand. 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. FIG. 1 is a schematic explanatory diagram showing a state in which asymmetric crop portions are formed on a rolled material. 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. 1 is a graph showing the relationship between the flange angle θ1 before forming and the forming angle Δθ.

Embodiments of the present invention will be described below with reference to the drawings. Note that in this specification and drawings, components having substantially the same functional configuration will be assigned the same reference numerals, and redundant explanations will be omitted. Note that in this embodiment, a case will be described in which hat-shaped steel sheet piles are manufactured as steel sheet pile products.

<Rolling line configuration>
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 rolled material 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 rolled material is reciprocated multiple times in the same rolling mill (so-called multi-pass rolling) is also shown by a dashed line.

As shown in Figure 1, the rolling line L is arranged, in order from upstream, with 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. Furthermore, 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.

In the rolling line L, rectangular materials (rolled materials) heated in a heating furnace (not shown) are hot-rolled sequentially in the roughing mill 10 to the finishing mill 19, and then hot-shaped by the bending machine 20 to become the final product. For the sake of explanation, the rolled materials rolled by the roughing mill 10 will be referred to as rough material, the rolled materials rolled by the first intermediate rolling mill 13 to the second intermediate rolling mill 16 will be referred to as intermediate material, and the rolled materials rolled by the finishing mill 19 will be referred to as finished material 19a. In other words, the finished material 19a is shaped (cross-section changed) by the bending machine 20 to become the final product (i.e., hat-shaped or U-shaped steel sheet pile products).

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

<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.

As shown in Figure 2, the bending machine 20 of this embodiment has two forming stands 22, 23 (hereinafter also referred to as the upstream first stand 22 and the downstream second stand 23) arranged adjacent to each other in series. Furthermore, as shown in Figure 3, each stand 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 differ between the first stand 22 and the second stand 23.

The roll configuration and groove shape of the first stand 22 and the second stand 23 will now be described. Figure 4 is a schematic enlarged front view showing the groove shape of the first stand 22, and Figure 5 is a schematic enlarged front view showing the groove shape of the second stand 23. Note that Figure 4 uses a dashed line to show the cross-sectional shape of the finished material 19a before it is formed by the bending machine 20, and Figure 5 uses a dashed line to show the cross-sectional shape of the finished material 19a' before it is formed by the second stand 23. The following description will be given, as an example, of bending a rolled material having a generally hat-like shape in an upwardly open position (with the web-corresponding portion, described below, positioned downward and the arm-corresponding portion positioned upward).

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 shape of this perforated roll 45 from the portion corresponding to the flange to the portion corresponding to the joint is a shape just short of a hat-shaped steel sheet pile product (i.e., approximately the shape of a hat-shaped steel sheet pile product). The perforated roll 45 changes the angle between the portion corresponding to the flange of the finishing material 19a (i.e., the flange-corresponding portion) and the portion corresponding to the web of the finishing material 19a (i.e., the web-corresponding portion), as well as the angle between the portion corresponding to the arm of the finishing material 19a (i.e., the arm-corresponding portion), thereby bending and forming the height and width of the finishing material 19a into a predetermined shape (i.e., a cross-sectional shape similar to the product). In particular, when manufacturing hat-shaped steel sheet piles, the method used is to roll the rolled material (rough material to finished material 19a) to a low height in the roughing mill 10 to the finishing mill 19, and then bend the rolled material in the bending machine 20 to raise its height to the desired product height. This makes it possible to manufacture large-sized hat-shaped steel sheet pile products.

Also, as shown in FIG. 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. This perforated mold 55 has a shape similar to the desired product shape, and changes the angle between the portion corresponding to the flange formed in the first stand 22 of the bending machine 20 (i.e., the flange-corresponding portion) and the portion corresponding to the web of the finishing material 19a (i.e., the web-corresponding portion), as well as the angle between the portion corresponding to the arm (i.e., the arm-corresponding portion), thereby forming the flange shape, arm shape, and joint shape into the desired shape (i.e., the product shape). In other words, in this second stand 23, the inclination angle of the flange-corresponding portion, which was insufficient for the product shape when formed in the first stand 22, is changed to an angle appropriate for the product shape.

Here, the roll gaps in the grooved dies 45 and 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. In other words, the bending machine 20 does not reduce the thickness of the finishing material 19a, and the grooved rolls of the first stand 22 and the second stand 23 and the finishing material 19a come into contact only at certain predetermined locations to perform bending.

Furthermore, during bending, the grooved rolls of the first stand 22 and the second stand 23 and the finishing material 19a may not only be in contact with each other at certain specified locations, but may also be pressed down. In this specification, "contact" refers to a state in the bending machine 20 where only one of the upper or 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.

For example, 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 finishing material 19a. Additionally, at the portions of the grooves 45 and 55 that overlap the arm corresponding portion of the finishing material 19a, 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, there is a possibility that the thickness will be reduced due to variations in the thickness of the finishing material 19a, increasing the load on the bending machine 20. If it 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.

Note that bending in the present invention may be performed using either or both of the first stand 22 and second stand 23 shown in the figure. That is, bending may be performed using a single stand or multiple stands. For example, this includes cases where bending is performed once or multiple times using only the first stand 22, and cases where bending is performed multiple times 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."

<Bending of rolled material>
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 (finished 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 finished 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.

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 the desired thickness by adjusting the rolling conditions and rolling design during hot rolling performed in the roughing mill 10, first intermediate rolling mill 13, second intermediate rolling mill 16, finishing mill 19, etc. (see Figure 1).

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 the desired thickness by adjusting the rolling conditions and rolling design during hot rolling performed in the roughing mill 10, first intermediate rolling mill 13, second intermediate rolling mill 16, finishing mill 19, etc. (see Figure 1).

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). In other words, in the first stand 22, bending is performed so that the height of the finishing material 19a becomes large.

Next, as shown in Figure 6(c), the finishing material 19a is bent into approximately the shape of the product in the groove 55 of the second stand 23.

<Cropped area generation>
The manufacturing process using bending of hat-shaped steel sheet pile products has been described above with reference to Figures 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 rolled material. When the rolled material (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 is a problem. Figure 7 is a schematic explanatory diagram showing a state in which asymmetric crop portions are formed in the rolled material (finishing material 19a).

As shown in Figure 7, if an asymmetric crop portion is formed at the tip of the finishing material 19a, the leading flange will be caught first in the bending machine 20, and the engagement will not occur evenly. As a result, the finishing material 19a will not be centered accurately in the bending machine 20, resulting in material passing problems and resulting product shape defects.

The inventors therefore conducted extensive research into the relationship between the widthwise misalignment amount and the forming angle when the finishing material 19a is engaged in the bending machine 20. They discovered that even when misalignment occurs in the bending machine 20, i.e., when the amount of misalignment becomes large, material passing problems can be prevented by maintaining a specific relationship between the inclination angle of the flange-corresponding portion before bending and the forming angle of the groove 45. This discovery is explained below with reference to the drawings. The above-mentioned misalignment amount refers to 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 that correspond to these connecting portions.

<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 the maximum widthwise displacement. The finishing material 19a can be displaced to the maximum extent that the connection between one of the flange-corresponding portions and the arm-corresponding portion of the groove 45 or 55 coincides with 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 of 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 will be 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 reference.

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)

When an asymmetric crop portion 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 during material passing is plotted, resulting in the graph shown in Figure 9.

<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 condition indicated by the symbol ◯ is 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 condition indicated by the symbol △ is 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 condition indicated by the symbol × is that misalignment occurs, resulting in inaccurate centering and no good product.

As shown in Figure 9, the limiting condition for the flange angle θ1 before forming is θ1 = 40°, and the limiting angle for the flange forming angle tends to become smaller 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 greater the flange angle θ1, the greater the amount of deviation X when the preceding flange corresponding portion is engaged, and the smaller the horizontal projection length W, making the passing of material more likely to become 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 of material unstable.

From the graph in Figure 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. It can be seen that material passing problems can be avoided by using an approximation line for the relationship between the flange angle θ1 and the forming angle Δθ based on the data in Figure 9 and setting the range expressed by the following equations (1) and (2). Note that the upper limits of the following equations (1) and (2) are indicated by dashed lines in Figure 9.
Δθ≦−0.30×θ1+32.0 (θ1≧40°) (1)
Δθ≦0.20×θ1+12.0 (θ1<40°)...(2)

As explained above with reference to Figure 9, in order to prevent material passing defects, the forming angle in the bending machine 20 should be determined so that the relationship between the flange angle θ1 before forming and the forming angle Δθ satisfies the above formula (1) or (2).

Note that if the bending angle Δθ is set to, for example, less than 12°, the stability of material passage is ensured, but because the bending angle per stand is small, multiple stands are required to bend at a specified angle, which is inefficient in terms of equipment costs, etc. In other words, the ideal bending angle for the first stand is, for example, 12° or greater, in the range shown in equations (1) and (2) above. Furthermore, if the bending machine 20 is composed of multiple stands, ensuring that the above bending conditions (conditions shown in equations (1) and (2)) are met in all stands prevents material passage problems. Furthermore, the bending conditions described here are particularly suitable when the corner thickness of the finished material 19a is 10 mm or greater, for example. Furthermore, it is desirable to set the bending angle Δθ to approximately 14° to 18° for the stability and efficiency of bending.

<Action and effect>
As described above, steel sheet pile products are manufactured under forming conditions that can avoid 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 and web-corresponding portions of the finishing material 19a. Furthermore, it is preferable to configure the roll gap immediately below the rolls of the groove 45 during bending to 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, 63 become misaligned and jammed during bending. This improves productivity and yield.

The above describes one example of an embodiment of the present invention, but the present invention is not limited to the illustrated form. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

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 each stand. 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 problems. However, when multiple stands are arranged in tandem, it is necessary to set the predetermined forming conditions, especially for the first stand (i.e., the first stand) that begins to bite the rolled material. In this case, since the first stand can restrain the rolled material in a stably centered state under the predetermined forming conditions, it is also possible to use a forming angle outside the range determined by the above formulas (1) and (2) in the second stand. The number of stands is determined based on the balance between the bending angle and capital investment; for example, if the bending angle is approximately 20° to 30°, the two-stand configuration described in the above embodiment is suitable.

In addition, in the above-described embodiment, the upper and lower slotted rolls of the bending machine 20 can be configured so that only one of the upper and lower slotted rolls is driven, and the other is not. By configuring only one of the upper and lower slotted rolls to be driven, it becomes easier to balance the speed of the sheet metal when bending is performed in tandem with multiple stands. This also reduces the generation of tension in the rolled material due to speed imbalances between multiple stands, stabilizing sheet metal threading and preventing unnecessary deformation of the rolled material. Additionally, the drive mechanisms, such as the motor, spindle, and gears used to drive the rolls, can be simplified, resulting in smaller equipment and reduced equipment costs. Furthermore, by arranging the finishing rolling mill and bending machine in tandem and pushing the rolled material from the finishing rolling mill into the bending machine, the amount of misalignment is reduced, even when an asymmetric crop is caught, resulting in stable centering.

Furthermore, in the above embodiment and its modified examples, 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 described as an example. However, the present invention can also be applied to manufacturing in the opposite downward-opening position (with the arm corresponding portion below the web corresponding portion). In that case, the orientation of the joints and the upper and lower slotted rolls can be considered to be in the opposite position to the above embodiment. Furthermore, in the explanation of the above embodiment and its modified examples, a case where a hat-shaped steel sheet pile is manufactured as the final product has been described as an example, but the present invention is not limited to this and can also be applied to the manufacturing of steel sheet pile products such as U-shaped steel sheet piles, for example.

As an example of the present invention, a bending experiment was conducted on aluminum material in the shape of a hat-shaped steel sheet pile, based on the steel sheet pile manufacturing method according to the present invention. The bending in this example was performed under the conditions shown in Conditions 1 to 6 in Table 1 below. Note that the numerical values for each dimension in Table 1 are converted to actual equipment values. In addition, the difference in left and right crop lengths of the rolled material in this example was set to 300 mm.

In Table 1, "good" refers to a situation where the rolled material is centered immediately after being inserted into the bending machine, resulting in a good rolled material shape excluding the cropped area. "Poor tip" refers to a situation where the rolled material is centered and corrected within a few meters (e.g., within 2 to 3 meters in actual equipment) after being inserted into the bending machine, and a good shape can be achieved by cutting a small area at the tip. "Large defect" refers to a situation where the rolled material is not properly centered when inserted into the bending machine, resulting in a wide area of defective shape (e.g., more than 3 meters in actual equipment). In other words, "good" and "poor tip" in Table 1 refer to situations where the defective shape (the area to be cut) is within 3 meters of the tip in actual equipment, and the centering and post-forming shape are maintained good (or within an acceptable range).

Under condition 1, only the first stand of the bending machine was used, and the first bending was performed at a forming 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.

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. 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 excellent.

Under condition 3, the first and second stands of the bending machine were used, and the first and second bending processes 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, centering of the rolled material was ensured within a range of approximately 2 m from the tip, and a good shape was obtained by cutting a small area from the tip.

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

Furthermore, 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. The bending angle Δθ (first bending: 16°, second bending: 17°) was set to satisfy the above formulas (1) and (2). As a result, the centering ability and post-forming shape of the rolled material were excellent.

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

According to conditions 1 to 3 and 5 in Table 1, by performing bending under conditions that satisfy formula (1) or (2) described in the above embodiment, the centering ability and 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 (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 but formula (1) is not satisfied in the second bending, the centering ability and post-forming shape are good. This demonstrates that when bending is performed in tandem, such as first bending and second bending, performing at least the first bending under the conditions described in the above embodiment (i.e., the conditions shown in formula (1) or (2)) can improve the centering ability and post-forming shape.

The present invention can be applied to manufacturing methods for steel sheet piles, such as hat-shaped steel sheet piles and U-shaped steel sheet piles.

DESCRIPTION OF SYMBOLS 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... First stand 23... Second stand 40... Upper groove type roll 41... Lower groove type roll 44... Housing 45... Groove 45a... Web portion 45b... Flange portion 50... Upper groove type roll 51... Lower groove type roll 54... Housing 55... Groove 60... Web corresponding portion 62, 63... Flange corresponding portion 65, 66... Arm corresponding portion 68, 69... Joint corresponding portion 70... Corner portion 71... Corner portion L... Rolling line

Claims (5)

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) 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 web corresponding portion and the flange corresponding portion is larger than a thickness of the web corresponding portion and the flange corresponding portion. A method for manufacturing a steel sheet pile according to claim 2, wherein only one of the upper and lower slotted rolls is driven during the bending process. A method for manufacturing a steel sheet pile according to any one of claims 1 to 3, characterized in that the bending machine that performs the bending and the finishing rolling machine that performs the finishing rolling are arranged in tandem. 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.