Rolling method for steel sheet piles

Abstract

This invention provides a method for rolling steel sheet piles that can improve productivity by avoiding mis-rolls in the rolled material during rolling, or by shortening the mis-roll processing time by processing them upstream of the rolling line. [Solution] A method for rolling steel sheet piles using multiple passes in at least one rolling mill, wherein the reduction amount and roll gap settings for each pass are calculated before rolling, and the rolling load P is applied to the downstream passes i+1 to k, with reference to the i-pass upstream of the final pass of the multiple passes. i+1~k Rolling torque G i+1~k , and the final exit plate thickness tk of the rolled material is calculated, and the rolling load P i+1~k , the rolling torque G i+1~k , Rolling load Pmax of the rolling mill equipment limit i+1~k The rolling torque Gmax of the rolling mill is the equipment limit. i+1~k Based on the final exit thickness tk of the rolled material and the tolerance of the final exit thickness, rolling is performed according to conditions 1 and 2.

Description

[Technical Field]

[0001] The present invention relates to a method for rolling steel sheet piles, such as hat-shaped steel sheet piles and U-shaped steel sheet piles. [Background technology]

[0002] The hole-type rolling method is known as a method for manufacturing steel sheet piles, such as hat-shaped steel sheet piles and U-shaped steel sheet piles, which include a web, a pair of flanges at both ends to which one end connects to the web, and joints to which the other end of the flanges connects. A general procedure for the hole-type rolling method is to first heat a rectangular material (such as a slab) to a predetermined temperature in a heating furnace, and then sequentially roll it using a roughing mill equipped with a hole-type, an intermediate rolling mill, and a finishing rolling mill.

[0003] In the manufacture of steel sheet piles using the die-cut rolling method, multiple die-cuts are placed in a single rolling mill and rolled sequentially. After finish rolling, the rolled material is cut to product length while still hot and then transported to the next process, such as cooling and finishing. In this process, the lateral movement of the rolled material between die-cuts is generally performed manually by the operator, and even when manufacturing products of the same dimensions, there is a risk of variations in rolling time for each rolled material. Furthermore, correcting issues such as poor material passage may also be done manually by the operator, which can also cause variations in rolling time. Such variations in rolling time can lead to increased rolling time and a decrease in the temperature of the rolled material, potentially increasing the load on the rolling mill. If the load on the rolling mill increases and there is insufficient margin in the rolling load and torque relative to the equipment specifications, there is a risk of equipment damage or misrolls (rolling interruption) due to mill trips.

[0004] If a misroll occurs during the rolling process, it becomes necessary to gas-cut and lift the rolled material on the rolling line, which can result in a rolling stoppage of several hours. Furthermore, since multiple rolled materials are typically being rolled on the same rolling line, there is a risk of misrolls occurring in subsequent rolled materials as well.

[0005] On the other hand, even if the product dimensions fall outside tolerances, if the rolled material can be hot-sawed after the finish rolling is complete, there will be little to no interruption in the rolling process, and the rolling of subsequent rolled materials can continue. Furthermore, if it becomes clear that rolling cannot be completed to the finish rolling of downstream materials, and the rolling process can be stopped upstream at that stage when the rolled material is still short, the processing time will be shortened, and the impact on subsequent rolled materials will be minimized. Rolling lines for steel sheet piles and structural steel are generally equipped with sawing machines to cut the crop (unsteady portion) of the rolled material during the rolling process. If rolling is abandoned at the stage where cutting with this sawing machine is possible, the above-mentioned methods such as gas cutting become unnecessary, and the processing time can be shortened.

[0006] Thus, in the rolling of structural steel and steel sheet piles, there is a demand for increased efficiency in the rolling schedule and improved productivity, and various technologies have been devised. For example, Patent Document 1 discloses a rolling control method that determines the deformation resistance for each pass based on the load performance for each pass of the preceding rolled material, and corrects the pre-set rolling schedule if there is a difference with the set deformation resistance of the next material, or corrects the rolling schedule so that all passes are within the load specifications if the load of the next material exceeds the equipment specifications. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2-84208 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, in the technology described in Patent Document 1, the roll gap correction is applied to subsequent materials, which means that the currently rolling material (the material in question) may experience mis-rolls due to deviations from dimensional tolerances or increased load. If mis-rolls occur, as described above, rolling will be stopped for several hours, raising concerns about a significant decrease in productivity.

[0009] Furthermore, in rolling lines for structural steel and steel sheet piles, the systematization of process changes such as determining whether rolling can continue in the event of a delay or controlling the load on downstream mills within equipment specifications has not yet been established, and in reality, it is left to the judgment of the operator. While it is possible to systematize this by creating a model equation in advance for the temperature changes of the rolled material during rolling and the resulting changes in load and torque, accurately grasping the temperature of the rolled material online is extremely difficult. This is because, for example, in steel sheet piles, the thickness differs from part to part within the cross-section, and the temperature during rolling also differs from part to part. To accurately grasp the temperature of the rolled material, it is necessary to measure the temperature of the entire cross-section, but because the cross-section has an asymmetrical shape and the position of the material passing through changes depending on the rolling conditions, it is a complex process that requires measurement over a wide area and is not practical.

[0010] Furthermore, even if temperature distribution data for the entire cross-section of the rolled material is obtained, there is no established method for selecting the cross-sectional temperature range to be used for load prediction. This necessitates the systematization of process changes such as determining whether rolling can continue and controlling the load on downstream mills within equipment specifications.

[0011] Therefore, in view of the above circumstances, the object of the present invention is to provide a method for rolling steel sheet piles that can improve productivity by avoiding the occurrence of mis-rolls with respect to the rolled material during rolling, or by shortening the mis-roll processing time by processing them upstream of the rolling line. [Means for solving the problem]

[0012] To achieve the above objective, the present invention provides a method for rolling steel sheet piles using multiple passes in at least one rolling mill, wherein the reduction amount and roll gap of each pass are calculated before rolling, and the rolling load P is applied to the downstream passes i+1 to k, with reference to the i pass upstream of the final pass of the multiple passes. i+1~k Rolling torque G i+1~k , and the final exit plate thickness tk of the rolled material is calculated, and the rolling load Pi+1~k and the rolling torque G i+1~k the rolling load Pmax at the equipment limit of the rolling mill i+1~k the rolling torque Gmax at the equipment limit of the rolling mill i+1~k A method for rolling steel roof sheets is provided, characterized in that rolling is performed according to the following Conditions 1 and 2 based on the final exit side plate thickness tk of the material to be rolled and the tolerance of the final exit side plate thickness. (Condition 1) Rolling load P i+1~k and rolling torque G i+1~k are both smaller than the rolling load Pmax at the equipment limit of the rolling mill i+1~k and the rolling torque Gmax at the equipment limit of the rolling mill i+1~k When this is the case, rolling is performed as in the following Conditions 1-1 and 1-2. (Condition 1-1) When the final exit side plate thickness tk of the material to be rolled is within the tolerance, rolling is continued with the reduction per pass and the roll gap for each pass based on the setting calculation performed before rolling. (Condition 1-2) When the final exit side plate thickness tk of the material to be rolled is outside the tolerance, the reduction per pass and the roll gap for each pass are recalculated so as to be within the tolerance, and the roll gap is changed to continue rolling. (Condition 2) Rolling load P i+1~k and rolling torque G i+1~k at least one of which is greater than the rolling load Pmax at the equipment limit of the rolling mill i+1~k and the rolling torque Gmax at the equipment limit of the rolling mill i+1~k When this is the case, rolling is performed as in the following Conditions 2-1 and 2-2. Here, the corresponding pass is referred to as the j-th pass below. (Condition 2-1) In the j-th pass, the roll gap is recalculated, and for the j+1 to k-th passes, the roll gap is recalculated and calculated so as not to change from the reduction per pass before the recalculation of the roll gap in the j-th pass. As a result, when the final exit side plate thickness tk of the material to be rolled is within the tolerance, rolling is continued with the reduction per pass and the roll gap for each pass for which the recalculation has been performed. (Condition 2-2) In the j-pass, the reduction amount and roll gap are recalculated. For the j+1 to N passes, the roll gap is recalculated so that it does not change from the reduction amount before the recalculation of the roll gap in the j-pass. If, as a result, the final exit plate thickness tk of the rolled material falls outside the tolerance, the following methods under conditions 2-2-1, 2-2-2, and 2-2-3 are adopted. (Condition 2-2-1) If the conditions exist that the load is within the equipment specifications and the final exit thickness tk of the rolled material is within tolerance, the reduction amount and roll gap are recalculated for passes j+1 to k so that the load is within the equipment specifications and the final exit thickness tk of the rolled material is within tolerance, and then rolling is performed. (Condition 2-2-2) If the conditions do not exist in which the load is within the equipment specifications and the final exit plate thickness tk of the rolled material is within tolerance, the reduction amount and roll gap will be recalculated for passes j+1 to k to bring the load within the equipment specifications, and rolling will be performed. (Condition 2-2-3) If, after recalculating under conditions 2-2-1 and 2-2-2 above, the roll clearance exceeds the equipment's limits, rolling will be impossible and the rolling process will be stopped.

[0013] During rolling, the rolling load of the i-pass (Pobs) i The rolling load Poms was measured and measured. i Using the rolling load model and deformation resistance model, the average cross-sectional temperature T of the rolled material of i-pass is determined. i The mean cross-sectional temperature T of the rolled material in the i-pass is calculated. i And using a cooling model, the mean cross-sectional temperature T of the rolled material from the downstream i+1 pass to the final k pass is determined. i+1~k The average cross-sectional temperature T is calculated, i+1~k Using the rolling load model and the rolling torque model, the rolling load P i+1~k and the rolling torque G i+1~k The rolling load P is calculated, i+1~k and the rolling torque G i+1~k The final exit plate thickness tk of the rolled material can also be calculated from this.

[0014] The final exit plate thickness may be the final exit plate thickness at the joint bottom of the steel sheet pile. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a method for rolling steel sheet piles that can improve productivity by avoiding the occurrence of mis-rolls in the rolled material during rolling, or by shortening the mis-roll processing time by processing them upstream of the rolling line. [Brief explanation of the drawing]

[0016] [Figure 1] This is an explanatory diagram showing an example of the shape of a U-shaped steel sheet pile. [Figure 2] This is a schematic diagram illustrating the rolling mills that make up a rolling line. [Figure 3] This is an explanatory diagram showing an example of a general configuration of a hole type. [Figure 4] This graph shows the results of numerical analysis performed using FEM. [Figure 5] This is a graph showing the relationship between the amount of pressure reduction and the load. [Figure 6] This is an explanatory diagram showing an example of a general configuration of a hole type. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described below with reference to the drawings. In this specification and the drawings, components having substantially the same functional configuration may be denoted by the same reference numerals, and redundant explanations may be omitted. In this specification, when describing hole shapes and the like, the case in which U-shaped steel sheet piles are manufactured as steel sheet pile products will be illustrated and explained as an example.

[0018] <Examples of steel sheet pile shapes to be targeted> In the steel sheet pile rolling method according to this embodiment, the steel sheet pile to be rolled is, for example, a U-shaped steel sheet pile. Figure 1 is an explanatory diagram showing an example of the shape of a U-shaped steel sheet pile.

[0019] As shown in Figure 1, the U-shaped steel sheet pile 10 includes a substantially horizontal web 11, a pair of flanges 12 (12a, 12b) with one end connected to each end of the web 11, and joint portions 15 (15a, 15b) connected to the other end (outer end) of each flange 12a, 12b. Both joint portions 15a and 15b are configured to open downwards, and their joint bottoms 13 (13a, 13b) are configured to be substantially parallel to the web 11. The joint bottoms 13 are also called throats.

[0020] <Outline configuration of the rolling line> Figure 2 is a schematic diagram illustrating the rolling mills that make up the rolling line L1 used for manufacturing steel sheet piles. In Figure 2, the rolling direction is indicated by the arrows, and the material to be rolled flows in this direction and is rolled by each rolling mill on the line. In Figure 2, as an example of the process, a rolling method in which the material to be rolled is passed back and forth multiple times in the same rolling mill (so-called reverse rolling) is illustrated with a solid line.

[0021] As shown in Figure 2, the rolling line L1 is arranged in the following order from upstream: a heating furnace 30, a roughing mill 32, a group of intermediate rolling mills 34, and a group of finishing rolling mills 36. Between the roughing mill 32 and the group of intermediate rolling mills 34, a saw cutter 33 is positioned to cut the crop (unsteady portion) of the material to be rolled. In this rolling line L1, the material to be rolled, such as a slab, heated in the heating furnace 30 is sequentially hot-rolled in the roughing mill 32, the group of intermediate rolling mills 34, and the group of finishing rolling mills 36.

[0022] Each of the roughing mill 32, the rolling mills included in the intermediate rolling mill group 34, and the rolling mills included in the finishing rolling mill group 36 are equipped with a pair of upper and lower rolling rolls for rolling the material to be rolled, and rolling is performed using multiple holes provided on the rolls of each rolling mill. The number, shape, and configuration of the holes provided in each rolling mill are arbitrary and may differ depending on the rolling equipment. Below, an example of the configuration of the holes provided in the roughing mill 32, the intermediate rolling mill group 34, and the finishing rolling mill group 36 will be described.

[0023] <Outline configuration of the pore type> Figure 3 is an explanatory diagram showing an example of the schematic configuration of the hole molds provided in the roughing mill 32, the intermediate rolling mill group 34, and the finishing rolling mill group 36. The arrows in the figure indicate that rolling in the hole molds proceeds in this order. Note that the hole mold configuration shown is an example for manufacturing U-shaped steel sheet piles as steel sheet pile products, and the shape and configuration of the hole molds are not limited to this example.

[0024] The rolling mills on which hole types K9 to K1 are provided in the figure are arbitrary. For example, hole types K9 to K7 may be provided in the roughing mill 32, hole types K6 to K4 in the intermediate rolling mill group 34, and hole types K3 to K1 in the finishing rolling mill group 36.

[0025] In the hole molds K9 to K7 shown in Figure 3, for example, in hole mold K9, the rolled material, which is a slab with a rectangular cross-section, is rolled in an upright position (with the width direction of the steel sheet pile as the vertical direction). Then, the rolled material is rotated by 90° or 270°, and rough rolling is performed in hole molds K8 and K7 to form a split corresponding to the boundary between the web 11 and the flange 12, and a split corresponding to the boundary between the flange 12 and the joint portion 15.

[0026] Next, in hole types K6 to K4, rolling is performed with the width direction horizontal (the width direction of the steel sheet pile is horizontal). In this rolling, for example, intermediate rolling is performed so that the cross-section of the rolled material becomes an intermediate shape (approximately U-shaped cross-section) between the shape of a slab (rectangular cross-section) and a U-shaped cross-section. In this intermediate rolling, in addition to reducing the thickness of the rolled material, edging of the tip of the joint portion 15 (i.e., the tip of the claw) may also be performed. Furthermore, a roughly U-shaped cross-section refers to a cross-section where the boundaries of the web 11, flange 12, and joint 15 are clearly defined and reduced to a certain extent, and does not necessarily refer to a cross-section that has been formed down to the finer details of the joint shape, etc.

[0027] Next, in hole types K3 to K1, rolling is performed with the width direction horizontal (the width direction of the steel sheet pile is horizontal), similar to the intermediate rolling. In this rolling, for example, finish rolling is performed so that the cross-sectional shape of the rolled material changes from a roughly U-shaped cross-section to a U-shaped cross-section. This produces U-shaped steel sheet pile products. In this finish rolling, the tip of the joint portion 15 (i.e., the tip of the claw) may be bent.

[0028] <Estimation of average cross-sectional temperature from rolling load> The inventors of the present invention aimed to estimate the temperature of the rolled material from the rolling load (hereinafter also simply referred to as load) in the rolling of steel sheet piles, since the rolling load can be stably measured. Furthermore, they considered that although the thickness of the rolled material differs from part to part within its cross-section during the manufacturing of steel sheet piles, and the temperature during rolling also differs from part to part, it would be easier to estimate the average temperature of the cross-section by using the deformation resistance calculated from the average temperature within the cross-section.

[0029] The inventors first investigated the effect of temperature distribution on load. If F is the value obtained by dividing the load of a reference rolled material (hereinafter also referred to as the reference rolled material) by the deformation resistance, Tave is the average cross-sectional temperature of a rolled material (hereinafter also referred to as the average temperature) whose temperature has changed from that of the reference rolled material, Pobs is the measured load, and K is the deformation resistance, then the following relationship (1) holds. Pobs=K(Tave, ε, ε', C)×F ···(1) Here, ε is the strain, ε' is the strain rate, and C is the carbon content. Furthermore, the deformation resistance K is expressed by the following equation (2). K = Pobs / F ···(2)

[0030] By determining the deformation resistance K from the measured load value Pobs, it is possible to inversely calculate the average cross-sectional temperature Tab. Therefore, in order to investigate the effect of the temperature conditions within the cross-section of the rolled material on the load, the load at the cross-sectional distribution temperature, where the temperature was applied to each unit divided into the web 11, flange 12, joint bottom 13, and joint section 15, and the load at the average temperature, which was calculated by converting the cross-sectional distribution temperature to a uniform temperature within the cross-section, were estimated and compared using numerical analysis with FEM. Here, the average temperature was calculated as the temperature corresponding to the average deformation resistance, which is the area average of the deformation resistance of the temperature of each part.

[0031] If we consider the distributed temperature as follows: web temperature Tw, flange temperature Tf, joint bottom and joint temperature Ta, average temperature Tave, web cross-sectional area Vw, flange cross-sectional area Vf, and joint bottom and joint cross-sectional area Va, then the average temperature Tave can be calculated from the following equation (3). K(Tave)={K(Tw)×Vw+K(Tf)×Vf+K(Ta)×Va} / (Vw+Vf+Va) ···(3)

[0032] The target of the numerical analysis using FEM was a U-shaped steel sheet pile (see Figure 1) with an effective width of 500 mm, a height of 225 mm, a web thickness of 27.6 mm, and a joint bottom thickness of 10.0 mm (hereinafter referred to as size A steel sheet pile), specifically hole types K6 to K4 and K3 to K1 of the rolling line L1 shown in Figures 2 and 3.

[0033] The analysis conditions are as shown in Table 1 below. In Table 1, "arm" refers collectively to the joint base 13 and the joint section 15.

[0034] [Table 1]

[0035] Figure 4 is a graph showing the results of numerical analysis performed by FEM under the analysis conditions in Table 1, where (a) shows the relationship between the load at the cross-sectional temperature distribution and the load at the average temperature, (b) shows the relationship between the motor torque at the cross-sectional temperature distribution and the motor torque at the average temperature, (c) shows the relationship between the upper spindle torque at the cross-sectional temperature distribution and the upper spindle torque at the average temperature, and (d) shows the relationship between the lower spindle torque at the cross-sectional temperature distribution and the lower spindle torque at the average temperature.

[0036] As shown in Figure 4(a), the difference in load between the cross-sectional temperature distribution and the average temperature is small, approximately ±3%, indicating that the effect of temperature distribution on the load is small. Similarly, as shown in Figures 4(b) to (d), the same applies to the sum of vertical torques and each vertical torque, indicating that the effect of temperature distribution is small. In other words, it is possible to estimate the cross-sectional average temperature from the load, and it was confirmed that the error is small when estimating the load and torque using the estimated cross-sectional average temperature.

[0037] <Estimation of load and torque> Based on the above findings, we diligently investigated methods for estimating the temperature of the rolled material from the measured rolling load, and then estimating the load and torque based on this. Figure 5 is a graph showing the relationship between reduction amount and load, and as an example, it shows the relationship between web reduction amount and load in hole type K3 of a steel sheet pile of size A. Figure 5(a) shows the relationship between web reduction amount and load, and Figure 5(b) shows the relationship between web reduction amount and the sum of vertical torques.

[0038] As shown in Figure 5, the reduction amount and load (load and torque) tend to change linearly with respect to the reduction amount. Therefore, the value P / K obtained by dividing the load by the deformation resistance, and the value G / K obtained by dividing the torque by the deformation resistance, also tend to change linearly with respect to the reduction amount. Thus, as shown in equations (4) and (5) below, if we determine the slopes Cp and Cg of P / K and G / K with respect to the reduction amount, and the values ​​Dp and Dg of P / K and G / K at a reduction amount of 0 for each pass, we can estimate the load P for the i-pass. i Estimated Torque G iThese can be calculated from equations (4) and (5). Note that Cp, Cg, Dp, and Dg change depending on the temperature, so they may also be calculated based on the assumed temperature of each pass. P i / K i =Dp i +Cp i ×Δt i ...(4) G i / K i =Dg i +Cg i ×Δt i ...(5) Here, K i : i-pass transform resistor, Δt i : i-pass pressure reduction amount, Cp i : The slope of the load / deformation resistance of the i-path with respect to the reduction amount, Dp i :i-pass load / deformation resistance value at reduction amount 0, Cg i : The slope of the torque / deformation resistance of the i-pass with respect to the reduction amount, Dg i :i is the value of the torque / deformation resistance of the pass when the reduction amount is 0. Note that Δt i When this is the amount of web reduction, Δt i Even if the web reduction amount is 0, load and torque will still be generated if reduction is occurring in other parts, so Dp and Dg are not necessarily always 0.

[0039] In this embodiment, the "i-pass" described may be any pass upstream of the final pass when rolling the material in multiple passes. Also, in the rolling line L1 shown in Figure 2, the "i-pass" may be the first pass at the uppermost rolling mill of the intermediate rolling mill group 34. Furthermore, the "i-pass" may be the pass immediately preceding the uppermost pass among the passes in which, based on prediction calculations or operational experience, at least one of the rolling load and rolling torque (hereinafter also simply referred to as torque) is predicted to exceed the equipment limit of the rolling mill, in the passes after the first pass at the uppermost rolling mill of the intermediate rolling mill group 34.

[0040] And the thickness of the iPass i , the thickness of the i-1 path i-1 Therefore, the following equation (6) holds true. Δt i =t i-1 -t i ={S i-1 +(P i-1 -p0 i-1 ) / M i-1}-{S i +(P i -p0 i ) / M i} ···(6) Here, S i-1 :i-1 pass roll gap, p0 i-1 : Zero load on i-1 path, M i-1 :i-1 pass mill stiffness, S i :i Pass role gap, p0 i :i path zero load, M i Let's define this as the mill stiffness of the i-pass.

[0041] iPass measured load is Pobs i In this case, from equation (4), the deformation resistance K i It can be expressed by the following equation (7). K i =Pos i / (Dp i +Cp i ×Δt i ) ···(7)

[0042] And then, the deformation resistor K i The average cross-sectional temperature T of the rolled material from iPass i We will find the following. As a deformation resistance formula, Misaka's formula (Japan Society for Technology of Plasticity, "Plastic Processing", vol. 8, No. 79, 1967, p. 414) is known and can be expressed by the following formula (8). Kfm=1.15exp{0.126-1.75C+0.594C 2 +(2851+2968C-1120C 2 ) / (T+273)}×ε 0.21 ×ε' 0.13 ...(8) Then, the average cross-sectional temperature Ti of the rolled material, calculated inversely from the deformation resistance Ki based on equation (8) above, can be determined by the following equation (9). Ti = (2851 + 2968C - 1120C) 2) / log[1.15exp{0.126 - 1.75C + 0.594C 2}×ε 0.21 ×ε’ 0.13 -273 ···(9) Thus, using the rolling load model and the flow stress model, the cross-sectional average temperature T of the rolled material in the i-th pass i is calculated.

[0043] Then, based on the previously obtained temperature drop curve and the inter-pass time without delay, using the cross-sectional average temperature T of the rolled material in the i-th pass i and the cooling model, the cross-sectional average temperature T of the rolled material from the downstream (i + 1)-th pass to the final k-th pass n (n = i + 1, i + 2 ··· k) is calculated.

[0044] Then, using the cross-sectional average temperature T of the rolled material from the downstream (i + 1)-th pass to the final k-th pass n (n = i + 1, i + 2 ··· k), the rolling load model and the rolling torque model, based on the above formulas (4), (6), the load P n is estimated, and based on the above formula (5), the torque G n is estimated.

[0045] <Method for Rolling Steel Sheet Piles> The inventors of the present invention have, in addition to the load P n and the torque G n estimated as described above, from the relationships among the rolling load Pmax at the equipment limit (upper limit of equipment specifications) of the rolling mill n [[ID= for]] the rolling torque Gmax at the equipment limit (upper limit of equipment specifications) of the rolling mill n the final exit side plate thickness tk of the rolled material, and the tolerance of the final exit side plate thickness, devised a method for performing rolling by determining the following conditions.

[0046] That is, in the downstream passes i + 1 to k with respect to the above "i-th pass", the rolling load P i+1~k the rolling torque G i+1~k and the final exit side plate thickness tk of the rolled material are calculated, and the rolling load P i+1~k the rolling torque G i+1~k the rolling load Pmax at the equipment limit of the rolling mill i+1~k, Rolling torque Gmax at the equipment limit of the rolling mill i+1~k , From the final exit side plate thickness tk of the material to be rolled and the tolerance of the final exit side plate thickness, rolling is performed according to the following conditions 1 and 2. Here, the "tolerance of the final exit side plate thickness" refers to the allowable thickness range of the steel corrugated sheet as a product, and is appropriately determined according to the product size, required dimensional accuracy, etc. Here, within the allowable thickness range is "within the tolerance", and outside the thickness range is "outside the tolerance".

[0047] First, before rolling, the reduction per pass and the setting calculation of the roll gap for each pass are performed. Then, rolling is carried out in accordance with the following conditions.

[0048] (Condition 1) Rolling load P i+1~k , Rolling torque G i+1~k are both less than the rolling load Pmax at the equipment limit of the rolling mill i+1~k , and the rolling torque Gmax at the equipment limit of the rolling mill i+1~k , when it is smaller, rolling is performed as follows. (Condition 1-1) When the final exit side plate thickness tk of the material to be rolled is within the tolerance, rolling is continued with the reduction per pass and the roll gap for each pass based on the setting calculation performed before rolling. (Condition 1-2) When the final exit side plate thickness tk of the material to be rolled is outside the tolerance, the reduction per pass and the roll gap for each pass are recalculated so that it is within the tolerance, and the roll gap is changed to continue rolling.

[0049] The specific recalculation method in the above Condition 1-2 is as follows. The reduction adjustment amount from the (i + 1)-th pass to the final pass required to be within the tolerance is Δt tOt ', and it is distributed according to the maximum reduction within the range not exceeding the upper limit of the equipment specifications for each pass. The rolling load at the upper limit of the equipment specifications for each pass is Pmax n , the rolling torque at the upper limit of the equipment specifications for each pass is Gmax n , the maximum reduction is Δtmax n , then from the above formulas (4) and (5), the following formula (10) holds. Δtmax n = min{(Pmaxn / K n -Dp n ) / Cp n , (Gmax n / K n -Dg n ) / Cg n} ···(10) Recalculated reduction amount Δt for each pass n ' becomes the following equation (11). Δt n '=Δt n +Δt tOt '×(Δtmax n -Δt n ) / Σ k n=i+1 (Δtmax n -Δt n ) ···(11) Recalculated reduction amount Δt n 'satisfying roll gap S' n Using equations (4) and (6) above, we obtain the following equation (12). S' n =( t' n-1 -Δt' n )-(P' n -p0 n ) / M n ...(12)

[0050] (Condition 2) Rolling load P i+1~k Rolling torque G i+1~k At least one of the rolling loads Pmax of the rolling mill is the equipment limit of the rolling mill. i+1~k The rolling torque Gmax of the rolling mill is the equipment limit. i+1~k If the size exceeds this, rolling is performed as follows. This relevant pass will be referred to as the j-pass below. (Condition 2-1) In the j-pass, the roll gap is recalculated, and for the j+1 to k-passes, the roll gap is recalculated so that it does not change from the reduction amount before the recalculation of the j-pass. If the final exit thickness tk of the rolled material is within tolerance as a result, rolling is continued with the recalculated reduction amount and roll gap for each pass.

[0051] The specific recalculation method for condition 2-1 above is as follows: For the J-pass, the reduction amount Δtmax will be within the equipment specifications for load and torque. j The result is given by the following equation (14). Δtmax j =min{(Pmax j / K j -Dp j ) / Cp j , (Gmax j / K j -Dg j ) / Cg j} ···(14) Regarding J-Pass, reduction amount Δtmax j The roll gap S' that satisfies the conditions j The answer can be found using the following formula (15). S' j =( t' j-1 -Δtmax j )-(P' j -p0 j ) / M j ...(15) For passes from j+1 onward, the roll gap S' is set so that the reduction amount Δtn remains unchanged. n Recalculate using the following formula (16). S' n =( t' n-1 -Δt n )-(P n -p0 n ) / M n ...(16)

[0052] (Condition 2-2) In the j-pass, the reduction amount and roll gap are recalculated. For the j+1 to N passes, the roll gap is recalculated so that it does not change from the reduction amount before the recalculation of the roll gap in the j-pass. If, as a result, the final exit plate thickness tk of the rolled material falls outside the tolerance, the following method is adopted. (Condition 2-2-1) If the conditions exist that the load is within the equipment specifications and the final exit thickness tk of the rolled material is within tolerance, the reduction amount and roll gap are recalculated for passes j+1 to k so that the load is within the equipment specifications and the final exit thickness tk of the rolled material is within tolerance, and rolling is performed. This recalculation is performed based on the above equations (10) to (12). (Condition 2-2-2) If the conditions for the load to be within the equipment specifications and the final exit thickness tk of the rolled material to be within tolerance do not exist, the reduction amount and roll gap are recalculated for passes j+1 to k to bring the load within the equipment specifications, and rolling is performed. This recalculation is performed based on equations (14) to (16) above. Here, the condition that the conditions for the load to be within the equipment specifications and the final exit thickness tk of the rolled material to be within tolerance do not exist is when the following equation (17) is satisfied. Σ k n=i+1 (Δtmax n -Δt n )<Δt tOt ' ···(17) (Condition 2-2-3) If, after recalculating under conditions 2-2-1 and 2-2-2 above, the roll gap exceeds the equipment's limits, rolling becomes impossible and is therefore stopped. This is because, even when recalculating and widening the roll gap, it cannot be widened indefinitely. For example, widening the roll gap beyond a certain point may cause problems such as reduced guidance of the entry guide of the rolling mill or interference with the exit guide or the entry guide of the next pass. This acceptable roll gap can be predetermined for each hole type. If rolling is possible within the allowable roll gap range so that the load is within the equipment specifications, rolling is performed as per conditions 2-2-1 and 2-2-2 above. If rolling is not possible, rolling is stopped as per condition 2-2-3. It is preferable to decide to stop rolling as early as possible, for example, when it is possible to cut the rolled material with the saw cutter 33 (see Figure 2), which is located upstream of the rolling line L1 and installed between the roughing mill 32 and the intermediate rolling mill group 34.

[0053] In the steel sheet pile rolling method described above, the final exit plate thickness tk of the rolled material is used as a parameter. However, the plate thickness of any part of the steel sheet pile to be rolled can be used as the final exit plate thickness tk of the rolled material. That is, in the case of a U-shaped steel sheet pile, the plate thickness of the web 11, flange 12, joint bottom 13, or joint section 15 may be used. In the case of a U-shaped steel sheet pile, the joint bottom 13 is the part that requires the highest dimensional accuracy in plate thickness, so it is preferable to use the final exit plate thickness of the joint bottom 13 as the parameter.

[0054] <Effects and Effects> According to the steel sheet pile rolling method of this embodiment described above, with respect to the material currently being rolled, it is possible to predict whether the final exit plate thickness tk of the material being rolled is within tolerance and whether the load in the downstream pass exceeds the equipment specifications. By classifying the cases as described in conditions 1 and 2 above, if rolling can be continued, rolling can be continued until the final pass of the finishing rolling mill group 36 by changing the roll gap. If the change in the roll gap exceeds the equipment limit, rolling becomes impossible and rolling can be stopped.

[0055] This makes it possible to avoid misrolls when rolling can be continued. Furthermore, if rolling is impossible, deciding to stop rolling as early as possible allows for processing upstream of the rolling line L1, thus shortening the misroll processing time. In other words, productivity is improved compared to conventional steel sheet pile manufacturing methods.

[0056] Although an example of an embodiment of the present invention has been described above, the present invention is not limited to the illustrated form. It will be clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the idea described in the claims, and these will naturally also fall within the technical scope of the present invention.

[0057] Furthermore, the effects described herein are merely descriptive or illustrative and not limiting. In other words, the technology relating to this disclosure may produce other effects that will be apparent to those skilled in the art from the description herein, in addition to or instead of the effects described herein.

[0058] For example, in the above embodiment, the case in which a U-shaped steel sheet pile is manufactured by rolling was illustrated and explained, but the scope of application of the present invention is not limited to this. For example, it can be applied to various steel sheet pile products, and in addition to U-shaped steel sheet piles, it can also be applied to hat-shaped steel sheet piles. [Examples]

[0059] To verify the effects of the present invention, the process applying the present invention and the conventional process (conventional method: judgment by the rolling operator) were performed under the conditions of Examples 1 to 6 below when manufacturing U-shaped steel sheet piles of size A and U-shaped steel sheet piles with an effective width of 600 mm, a height of 210 mm, a web thickness of 18.0 mm, and a joint bottom thickness (hereinafter also referred to as throat thickness) of 9.3 mm (hereinafter referred to as steel sheet pile of size B) on the rolling line L1 shown in Figure 2. The hole configuration for manufacturing U-shaped steel sheet piles of size A is shown in Figure 3, and the hole configuration for manufacturing U-shaped steel sheet piles of size B is shown in Figure 6. The tolerance for the throat thickness of U-shaped steel sheet piles of size A is a lower limit of 8.8 mm and an upper limit of 11.2 mm, and the tolerance for the throat thickness of U-shaped steel sheet piles of size B is a lower limit of 8.1 mm and an upper limit of 10.5 mm.

[0060] Table 2 below shows the rolling conditions (assumed rolling time, assumed temperature, roll gap), load estimation formula (rolling load influence coefficient, reference state load, reduction amount torque influence coefficient, reference state torque), estimated values ​​(load, torque, throat thickness), and equipment specifications of the rolling mill (mill stiffness, zero-adjustment load, load equipment upper limit, torque equipment upper limit, allowable upper limit roll gap) for each pass from hole type K6 to K1 to which the present invention is applicable.

[0061] [Table 2]

[0062] In the following embodiments, when deviations occurred from the assumed rolling time and temperature shown in Table 2, the present invention was applied by estimating the load, torque, and throat thickness using the load performance of the first pass (1P) of hole type K6 and the temperature of the downstream pass obtained from the temperature drop curve. By changing the roll gap to keep the load within the upper limit of the equipment specifications, the aim was to avoid mis-rolls caused by overload, or to efficiently complete rolling and shorten the processing time. Here, the passes to which the roll gap was changed were selected from hole type K4 onwards, taking into account the time required for estimating the load, torque, and throat thickness using the temperature of the downstream pass, as well as for recalculating and changing the roll gap.

[0063] Table 3 below shows the temperature, load, torque, throat depth, and roll gap for each pass for each actual load when the present invention is applied in each of the following Examples 1 to 6. Changes made when applying the present invention are indicated as "after modification". Table 3 also includes the judgment results, which are explained in Examples 1 to 6 below.

[0064] [Table 3]

[0065] <Example 1> In the manufacturing of U-shaped steel sheet piles of size B, as shown in Table 3, when the actual load at 1P of hole type K6 was 420 tonf, the load and torque in the downstream pass were expected to be within the equipment specifications, and the final exit plate thickness of the rolled material was also expected to be within tolerance. Therefore, when the present invention was applied, the above condition 1-1 was met, and the finish rolling was completed without changing the roll gap.

[0066] On the other hand, according to the conventional method, the actual load of 420 tonf at hole type K6 1P was higher than the estimated load of 390 tonf shown in Table 2. Therefore, the rolling operator determined that a misroll occurred after rolling at hole type K6 2P in order to avoid equipment damage due to overload. The rolled material was then moved to the sawing machine for cutting and other processing, resulting in a 40-minute rolling stop.

[0067] <Example 2> In the manufacturing of U-shaped steel sheet piles of size A, as shown in Table 3, when the actual load at 1P of hole type K6 was 634 tonf, although the load and torque in the downstream pass were within the equipment specifications, it was anticipated that the final exit plate thickness of the rolled material (=11.3 mm) would be outside the tolerance (upper limit 11.2 mm). Therefore, when the present invention was applied, the above conditions 1-2 were met, and the reduction amount and roll gap of each pass were recalculated, the roll gap was changed, and rolling was continued until finish rolling was completed.

[0068] On the other hand, according to the conventional method, the actual load of 634 tonf at 1P of hole type K6 was higher than the estimated load of 516 tonf shown in Table 2. However, the rolling operator continued rolling without interrupting the rolling process or changing the roll gap, resulting in the product being out of tolerance. As a result, a spare roll was added, extending the rolling time by 12 minutes.

[0069] <Example 3> In the manufacturing of U-shaped steel sheet piles of size B, as shown in Table 3, when the actual load at 1P of hole type K6 was 448 tonf, it was expected that the load and torque in the downstream passes would exceed the equipment specifications in some cases, while the final exit plate thickness of the rolled material would be within tolerance. Therefore, when the present invention was applied, the above condition 2-1 was met, and rolling was continued with recalculated reduction amounts and roll gaps for each pass to keep the load and torque within the equipment specifications and the final exit plate thickness of the rolled material within tolerance, until finish rolling was completed.

[0070] On the other hand, according to the conventional method, the actual load of 448 tonf at hole type K6 1P was higher than the estimated load of 390 tonf shown in Table 2. Therefore, the rolling operator determined that a misroll occurred after rolling at hole type K6 2P in order to avoid equipment damage due to overload. The rolled material was then moved to the sawing machine for cutting and other processing, resulting in a 40-minute rolling stop.

[0071] <Example 4> In the manufacturing of U-shaped steel sheet piles of size A, as shown in Table 3, when the actual load at 1P of hole type K6 was 669 tonf, it was anticipated that the load and torque in the downstream passes would exceed some of the equipment specifications, and that the final exit plate thickness of the rolled material (=11.6 mm) would be outside the tolerance (upper limit 11.2 mm). Therefore, when the present invention was applied, the above condition 2-2-1 was met, and the reduction amount and roll gap of each pass were recalculated, the roll gap was changed, and rolling was continued until finish rolling was completed.

[0072] On the other hand, according to the conventional method, the actual load of 669 tonf at 1P of hole type K6 was higher than the estimated load of 516 tonf shown in Table 2. However, the rolling operator continued rolling without interrupting the rolling process or changing the roll gap, resulting in a mis-roll due to torque overload at hole type K2 causing the rolled material to jam. This required gas cutting of the rolled material, resulting in a 180-minute rolling stop.

[0073] <Example 5> In the manufacturing of U-shaped steel sheet piles of size A, as shown in Table 3, when the actual load at 1P of hole type K6 was 690 tonf, it was anticipated that the load and torque in the downstream pass would exceed the equipment specifications, and the final exit plate thickness of the rolled material (=11.8 mm) would be outside the tolerance (upper limit 11.2 mm). Therefore, when the present invention was applied, the above condition 2-2-2 was met, and the reduction amount and roll gap of each pass were recalculated, and the roll gap was changed with priority given to keeping the load within the equipment specifications. As a result, although the final exit plate thickness of the rolled material (=12.4 mm) was outside the tolerance, the load and torque remained within the equipment specifications and the finishing rolling was completed.

[0074] On the other hand, according to the conventional method, the actual load of 690 tonf at 1P of hole K6 was higher than the estimated load of 516 tonf shown in Table 2. Therefore, to avoid equipment damage due to overload, the rolling operator widened the roll gap by 1.0 mm in each pass from hole K4 to K1 and continued rolling. However, a mis-roll occurred at hole K2 due to torque overload causing the rolled material to jam. This required gas cutting of the rolled material, resulting in a 180-minute rolling stop.

[0075] <Example 6> In the manufacturing of U-shaped steel sheet piles of size A, as shown in Table 3, when the actual load at hole type K6, 1P was 730 tonf, it was anticipated that the load and torque in the downstream pass would exceed the equipment specifications, and the final exit plate thickness of the rolled material (=12.3 mm) would be outside the tolerance (upper limit 11.2 mm). Therefore, when the present invention was applied, the above condition 2-2-3 was met, and although the reduction amount and roll gap of each pass were recalculated and a change in the roll gap was considered, the upper limit of the allowable roll gap was exceeded, so the roll gap was not changed, and rolling was immediately stopped at the next pass (hole type K6, 2P). The rolled material was then moved to the sawing machine for cutting and other processing, resulting in a 40-minute rolling pause.

[0076] On the other hand, according to the conventional method, the actual load of 730 tonf at 1P of hole K6 was higher than the estimated load of 516 tonf shown in Table 2. Therefore, to avoid equipment damage due to overload, the rolling operator modified the roll gaps in each pass from hole K4 to K1 to the maximum allowable limit and continued rolling. However, a misroll occurred at hole K2 due to torque overload causing the rolled material to jam. This required gas cutting of the rolled material, resulting in a 180-minute rolling stop.

[0077] As described above, in all of the conditions of Examples 1 to 6, it was confirmed that by applying the present invention, mis-rolls can be avoided or the processing time can be shortened by processing upstream of the rolling line, compared to the conventional method. [Industrial applicability]

[0078] The present invention can be applied to rolling methods for steel sheet piles, such as hat-shaped steel sheet piles and U-shaped steel sheet piles. [Explanation of symbols]

[0079] 10…U-shaped steel sheet piles 11…Web (of U-shaped steel sheet piles) 12…Flange (of a U-shaped sheet pile) 13…Arms (of U-shaped steel sheet piles) 15…Joint section (of U-shaped steel sheet piles) 30...Heating furnace 32…Roughing mill 34…Intermediate rolling mill group 36…Finishing Rolling Mills L1...Rolling line

Claims

1. A method for rolling steel sheet piles, comprising performing multi-pass rolling in at least one rolling mill, Before rolling, the reduction amount for each pass and the roll gap settings for each pass are calculated. When the upstream path i is taken as the reference point from the final path of the aforementioned multiple paths, in the downstream paths i+1 to k, the rolling load P ｉ＋１～ｋ Rolling Torque G ｉ＋１～ｋ , and calculate the final exit plate thickness tk of the rolled material. The rolling load P ｉ＋１～ｋ , the rolling torque G ｉ＋１～ｋ , Rolling load Pmax of the rolling mill equipment limit ｉ＋１～ｋ The rolling torque Gmax of the rolling mill's equipment limit ｉ＋１～ｋ A method for rolling steel sheet piles, characterized in that rolling is performed according to the following conditions 1 and 2 based on the final exit plate thickness tk of the rolled material and the tolerance of the final exit plate thickness. (Condition 1) Rolling load P ｉ＋１～ｋ , rolling torque G ｉ＋１～ｋ are both less than the rolling load Pmax at the equipment limit of the rolling mill ｉ＋１～ｋ , the rolling torque Gmax at the equipment limit of the rolling mill ｉ＋１～ｋ , when it is smaller, rolling is performed as in the following conditions 1-1 and 1-2. (Condition 1-1) If the final exit thickness tk of the rolled material is within tolerance, rolling continues with the reduction amount and roll gap for each pass based on the setting calculations performed before rolling. (Condition 1-2) If the final exit thickness tk of the rolled material falls outside the tolerance, the reduction amount for each pass and the roll gap for each pass are recalculated to bring them within the tolerance, and the roll gap is changed to continue rolling. (Condition 2) Rolling load P ｉ＋１～ｋ Rolling Torque G ｉ＋１～ｋ At least one of the rolling loads Pmax of the rolling mill is the equipment limit of the rolling mill. ｉ＋１～ｋ The rolling torque Gmax of the rolling mill's equipment limit ｉ＋１～ｋ If the size exceeds this, rolling shall be carried out according to the following conditions 2-1 and 2-2. This relevant pass will be referred to as the j-pass below. (Condition 2-1) In the j-pass, the roll gap is recalculated, and for the j+1 to k-passes, the roll gap is recalculated and calculated so that it does not change from the reduction amount before the recalculation of the j-pass roll gap. If the final exit thickness tk of the rolled material is within tolerance as a result, rolling is continued with the recalculated reduction amount and roll gap for each pass. (Condition 2-2) In the j-pass, the reduction amount and roll gap are recalculated, and for the j+1 to N passes, the roll gap is recalculated so that it does not change from the reduction amount before the recalculation of the roll gap in the j-pass. If, as a result, the final exit plate thickness tk of the rolled material falls outside the tolerance, the following methods such as those described in conditions 2-2-1, 2-2-2, and 2-2-3 are adopted. (Condition 2-2-1) If the conditions exist that the load is within the equipment specifications and the final exit plate thickness tk of the rolled material is within tolerance, the reduction amount and roll gap are recalculated for passes j+1 to k so that the load is within the equipment specifications and the final exit plate thickness tk of the rolled material is within tolerance, and then rolling is performed. (Condition 2-2-2) If the conditions do not exist in which the load is within the equipment specifications and the final exit plate thickness tk of the rolled material is within tolerance, the reduction amount and roll gap are recalculated for passes j+1 to k to bring the load within the equipment specifications, and rolling is performed. (Condition 2-2-3) If, after recalculating under conditions 2-2-1 and 2-2-2 above, the roll gap exceeds the equipment's limits, rolling will be impossible and the rolling process will be stopped.

2. During rolling, the iPass rolling load Pobs ｉ We measured it, The rolling load Pobs ｉ Using the rolling load model and deformation resistance model, the average cross-sectional temperature T of the rolled material of iPass is determined. ｉ Calculate, The average cross-sectional temperature T of the rolled material of the i-pass ｉ And using a cooling model, the average cross-sectional temperature T of the rolled material from the downstream i+1 pass to the final k pass is determined. ｉ＋１～ｋ Calculate, Said section average temperature T ｉ＋１～ｋ Using the rolling load model and the rolling torque model, the rolling load P ｉ＋１～ｋ and the rolling torque G ｉ＋１～ｋ Calculate, The rolling load P ｉ＋１～ｋ and the rolling torque G ｉ＋１～ｋ A method for rolling steel sheet piles according to claim 1, characterized in that the final exit plate thickness tk of the rolled material is calculated from the final exit plate thickness tk.

3. The method for rolling steel sheet piles according to claim 1 or 2, characterized in that the final exit plate thickness is the final exit plate thickness of the joint bottom in the steel sheet pile.

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