Manufacturing method of hat-shaped steel sheet pile and manufacturing equipment of hat-shaped steel sheet pile

Abstract

To provide a manufacturing method and a manufacturing facility of a hat shape steel sheet pile capable of suppressing end portion deformation of two forms of "wrapper deformation" and "reverse wrapper deformation" and improving an entire width shape of a longitudinal end portion.SOLUTION: An injection position of a refrigerant to material to be rolled in finish rolling is controlled between a flange portion and a joint portion, based on overall width difference ΔW which is difference between overall width of a longitudinal direction end portion of the material to be rolled after the finish rolling, which is predicted from a rolling result, and overall width at a preset position other than the longitudinal direction end portion in hot-rolling of a hat shape steel sheet pile which has a web portion, the flange portion, an arm portion, and the joint portion, or based on temperature difference ΔT between the joint portion and the flange portion after finish rolling of the material to be rolled, which is predicted from the rolling result.SELECTED DRAWING: Figure 5A

Description

[Technical Field]

[0001] The present invention relates to a manufacturing method and manufacturing equipment for a hat-shaped steel sheet pile having an arm portion in addition to a web portion, a flange portion, and a joint portion. [Background technology]

[0002] Hat-shaped steel sheet piles, which are used as earth retaining members in civil engineering works, have been generally manufactured by a groove rolling method. A typical process of the groove rolling method involves first heating a steel material (rectangular material) to a predetermined temperature in a heating furnace, and then hot rolling it in succession using a roughing mill, an intermediate mill, and a finishing mill equipped with grooves. The hot rolling by the roughing mill, the intermediate mill, and the finishing mill is also called rough rolling, intermediate rolling, and finishing rolling, respectively, and these hot rolling processes are also collectively called shaping rolling.

[0003] The hat-shaped steel sheet pile 1 thus hot-rolled has a cross-sectional shape as shown in Fig. 1, and is composed of a web portion 11, a pair of flange portions 12 on the left and right, a pair of arm portions 13 on the left and right, and a pair of joint portions 14 whose cross-sectional shape is almost point-symmetric on the left and right. The joint portion between the flange portions 12 and the arm portions 13 is sometimes called an elbow portion 15.

[0004] In this way, hat-shaped steel sheet piles manufactured by hot rolling may have shape defects such as warping or bending of joints after cooling due to uneven temperature distribution in the cross section caused by thickness differences in each part of the cross section and differences in cooling conditions. Furthermore, when the product is hot sawn after hot rolling, residual stress generated in the cross section due to temperature differences is released at the hot sawn part, which may cause deformation of the product's longitudinal ends such as "horn deformation" and "reverse horn deformation" described below.

[0005] When deformation occurs at the longitudinal end of a steel sheet pile, it is necessary to correct the end shape after sawing. Leveler straightening, which is commonly performed in the manufacture of steel sheet piles, can be performed online during the manufacturing process, but it is difficult to correct the end shape because it is not possible to apply pressure reduction to the longitudinal end with leveler straightening. On the other hand, press straightening, which is performed offline, can correct the end shape, but it reduces production efficiency.

[0006] Therefore, as a method for controlling the end shape of a hat-shaped steel sheet pile, Patent Document 1 discloses a manufacturing method of a hat-shaped steel sheet pile, in which the difference between the minimum temperature Tf of the flange portion and the maximum temperature Tg of the joint portion or the arm portion at the same time point during the period from the end of hot rolling until the temperature of the web portion drops to 500°C is defined as a temperature difference ΔT (=Tg-Tf), the relationship between the temperature difference ΔT and the amount of bending of the cut surface end portion after hot sawing is determined, and the joint portion is cooled during hot rolling in the final groove of the finishing rolling mill so as to obtain a range of ΔT that allows the amount of bending to be within an allowable value based on this relationship (see Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-038035 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the above-mentioned conventional techniques still have the following problems to be solved.

[0009] The manufacturing method of the hat-shaped steel sheet pile exemplified in the above Patent Document 1 was an effective technique only for "horn deformation" in which the overall width of the end portion after hot rolling is wider than that of the steady portion. In other words, even under the condition that the joint portion is not cooled by the finish rolling, when "reverse horn deformation" occurs in which the overall width of the end portion after hot rolling is narrower than that of the steady portion, there was a problem that the "reverse horn deformation" could not be suppressed because appropriate joint cooling conditions or appropriate temperature conditions could not be achieved.

[0010] The present invention has been made in consideration of the above circumstances, and its purpose is to propose a manufacturing method and manufacturing equipment for hat-shaped steel sheet piles that can suppress two types of end deformation, namely "trumpet deformation" and "reverse horn deformation," of hat-shaped steel sheet piles and have a good overall width shape at the longitudinal end. [Means for solving the problem]

[0011] [1] A manufacturing method of a hat-shaped steel sheet pile, characterized in that in hot rolling of a hat-shaped steel sheet pile having a web portion, a flange portion, an arm portion and a joint portion, the injection position of a coolant onto the material to be rolled during finish rolling is controlled between the flange portion and the joint portion based on an overall width difference ΔW, which is the difference between the overall width of the longitudinal end portion of the material to be rolled after finish rolling and the overall width at a predetermined position other than the longitudinal end portion, as predicted from rolling results. [2] A manufacturing method of a hat-shaped steel sheet pile, characterized in that, in hot rolling of a hat-shaped steel sheet pile having a web portion, a flange portion, an arm portion and a joint portion, the injection position of a coolant onto the material to be rolled during finish rolling is controlled between the flange portion and the joint portion based on the temperature difference ΔT between the joint portion and the flange portion after finish rolling of the material to be rolled, which is predicted from rolling results. [3] The method for manufacturing a hat-shaped steel sheet pile according to [1] or [2], characterized in that the control of the injection position is performed by at least one of moving an injection device that injects the coolant along the entire width direction of the material to be rolled, and changing the injection direction of the coolant. [4] The method for manufacturing a hat-shaped steel sheet pile according to [1] or [2], characterized in that the control of the injection position is performed by installing a plurality of injection devices for injecting refrigerant from the flange portion to the joint portion and selecting any one or more injection devices from the plurality of injection devices. [5] A manufacturing facility for a hat-shaped steel sheet pile, comprising: a hot rolling mill for hot-rolling a hat-shaped steel sheet pile having a web portion, a flange portion, an arm portion, and a joint portion into the shape of the hat-shaped steel sheet pile; and a sawing device for cutting the hat-shaped steel sheet pile obtained by the hot rolling in the width direction, a cooling device capable of selectively cooling the joint portion and the flange portion is provided within a guide attached to the finishing rolling mill during the hot rolling; A calculation device is provided for predicting an overall width difference ΔW, which is the difference between the overall width of the end portion in the longitudinal direction of the material to be rolled after finish rolling and the overall width at a position other than the end portion in the longitudinal direction, based on rolling results; A manufacturing facility for a hat-shaped steel sheet pile, characterized by comprising a means for controlling a coolant injection position with respect to the material to be rolled during finish rolling between the flange portion and the joint portion based on the predicted overall width difference ΔW. [6] A manufacturing facility for a hat-shaped steel sheet pile, comprising: a hot rolling mill for hot-rolling a hat-shaped steel sheet pile having a web portion, a flange portion, an arm portion, and a joint portion into the shape of the hat-shaped steel sheet pile; and a sawing device for cutting the hat-shaped steel sheet pile obtained by the hot rolling in the width direction, a cooling device capable of selectively cooling the joint portion and the flange portion is provided within a guide attached to the finishing rolling mill during the hot rolling; A calculation device is provided for predicting a temperature difference ΔT between the joint portion and the flange portion after finish rolling of the rolling target material based on rolling results, A manufacturing facility for a hat-shaped steel sheet pile, characterized by comprising a means for controlling the injection position of a coolant onto the material to be rolled during finish rolling between the flange portion and the joint portion based on the predicted temperature difference ΔT.

[0012] The "total width difference ΔW, which is the difference between the total width of the longitudinal end of the material to be rolled after finish rolling, predicted from rolling results, and the total width at a predetermined position other than the longitudinal end," can take the following values:

[0013] In the rolling production of shaped steel, hot rolling of the same steel type using the same groove set is repeated for multiple materials. The rolling conditions for these multiple materials usually do not vary significantly between materials. Therefore, the actual results of the overall width difference for the same steel type that has been hot rolled using the same groove set can be used as a predicted value for the overall width difference after hot rolling of that material. Alternatively, a model for predicting the overall width difference from the rolling conditions and cooling conditions can be created based on the actual results of the rolling conditions, cooling conditions, and overall width difference, and this model can be used to calculate a predicted value for the overall width difference after hot rolling of that material from the rolling conditions used for that material.

[0014] Furthermore, the "temperature difference ΔT between the flange portion and the joint portion after finish rolling of the material to be rolled, predicted from rolling records," can take the following values.

[0015] That is, the actual temperature difference of the same steel material that has been hot rolled using the same groove set can be used as the predicted value of the temperature difference after hot rolling of that material. Alternatively, a model that predicts the temperature difference from the rolling conditions and cooling conditions can be created based on the actual rolling conditions, cooling conditions, and temperature difference so far, and this model can be used to calculate the predicted value of the temperature difference after hot rolling of that material from the rolling conditions used for that material. [Effects of the Invention]

[0016] According to the present invention, both types of end deformation, namely "horn deformation" and "reverse horn deformation", can be suppressed, and a hat-shaped steel sheet pile with a good overall width shape of the longitudinal end can be obtained. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing the cross-sectional shape of a hat-shaped steel sheet pile. [Figure 2] FIG. 1 is a schematic diagram showing an example of an arrangement of equipment used in rolling production of steel sheet piles. [Figure 3] 1A and 1B are schematic diagrams showing examples of roll groove shapes used in hot rolling of hat-shaped steel sheet piles, where (a) shows the groove shape for rough rolling, (b) shows the groove shape for intermediate rolling, and (c) shows the groove shape for finish rolling. [Figure 4] Schematic diagrams showing the shape defects at the longitudinal end of a hat-shaped steel sheet pile, where (a) shows trumpet deformation and (b) shows reverse trumpet deformation. [Figure 5A] 1 is a schematic diagram showing a cooling method in which the injection position is variable according to the present invention; [Figure 5B] 1 is a schematic diagram showing a cooling method for selecting an injection position according to the present invention; [Figure 5C] FIG. 1 is a schematic diagram showing a method for cooling a hat-shaped steel sheet pile from the inner surface side of a flange according to the present invention. [Figure 6] 1 is a schematic diagram showing an example of the configuration of a cooling control device according to the present invention; [Figure 7] 10 is a graph showing the temperature distribution after finish rolling of a hat-shaped steel sheet pile. [Figure 8] 10 is a graph showing the relationship between the temperature difference and the total width difference of a hat-shaped steel sheet pile. [Figure 9] 10 is a graph showing the temperature difference of a hat-shaped steel sheet pile at each cooling point. [Figure 10] 10 is a graph showing the relationship between the left and right movement amount of the injection device and the overall width difference of the hat-shaped steel sheet pile. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a hat-shaped rolled material is described as being rolled in a position where the web portion is located above the flange portion (a so-called inverted U position or hat position), but the scope of application of the present invention naturally extends to rolling in other positions (for example, a U position).

[0019] <Hat-shaped steel sheet pile> The cross-sectional shape of a hat-shaped steel sheet pile is shown in Figure 1. The hat-shaped steel sheet pile 1 has a web 11 at the center in the overall width direction, a pair of flanges 12 on both sides of the web, a pair of arm portions 13 on both sides of the flanges, and a pair of joint portions 14 whose cross-sectional shape is almost point-symmetric on the left and right. The joint between the flange portions 12 and the arm portions 13 is also called an elbow portion 15.

[0020] <Rolling line> Next, we will explain the outline of the rolling line L, which is the basic configuration of the manufacturing facility 2 that produces hat-shaped steel sheet piles. Figure 2 is an arrangement diagram of the rolling facility for hat-shaped steel sheet piles. In Figure 2, the rolling progress direction of the rolling line L, that is, the transport direction of the material to be rolled, is the direction indicated by the arrow. Steel slabs, etc., which are materials heated in the heating furnace 3, are rolled in succession in the hot rolling mills, which are the roughing mill 4, intermediate mill 5, and finishing mill 6. The hot rolling performed by the roughing mill 4, intermediate mill 5, and finishing mill 6 are also called roughing, intermediate rolling, and finishing rolling, respectively, and these hot rolling processes are also collectively called shaping rolling. The finishing mill 6 is equipped with a guide, and an injection device 21, which will be described later with reference to Figures 5A, 5B, 5C, etc., is installed within this guide.

[0021] A sawing device 7 that cuts the shaped rolled product to a predetermined length is provided downstream of the finishing rolling mill 6. Furthermore, a thermometer 8 for measuring the surface temperature of the hat-shaped steel sheet pile is provided downstream of the finishing rolling mill 6 (between the finishing rolling mill 6 and the sawing device 7). A shape meter 9 that measures the overall width shape of the hat-shaped steel sheet pile is provided downstream of the sawing device 7.

[0022] The thermometer 8 for measuring the surface temperature of the steel sheet pile is not particularly limited, and for example, a two-dimensional radiation thermometer may be used to measure the temperature distribution in the width direction of the hat-shaped steel sheet pile. Alternatively, a one-dimensional line scan type thermometer that can measure the temperature distribution on a line may be used to measure the temperature distribution in the width direction of the hat-shaped steel sheet pile. Alternatively, instead of these thermometers, a plurality of spot radiation thermometers that can measure one point may be arranged in the width direction of the hat-shaped steel sheet pile so that the temperature at each point in the width direction can be measured.

[0023] The shape meter 9 for measuring the overall width shape after cooling is not particularly limited. For example, a contact measurement method may be used in which the outer edges of the left and right joints are clamped from the left and right, as with a vernier caliper, to measure the overall width at the longitudinal end and at a position a certain distance away from the longitudinal end, or a method may be used in which the hat-shaped steel sheet pile is photographed from above, the longitudinal outline of the joints is extracted by image processing, and the overall width shape is calculated from the outline shape. In addition to the overall width shape, the "bending" and "warping" shapes along the longitudinal direction may also be measured.

[0024] <Rough rolling> Figure 3(a) shows an example of roll grooves used in rough rolling. In this example, a rectangular cross-section slab is used as the material, and the slab is first width-reduced using a box groove, then bent into a hat shape using a K8 groove. Next, the slab is rolled to a specified thickness using a K7 groove, and the material after rough rolling, i.e., a rough billet, is formed.

[0025] <Intermediate rolling> Figure 3(b) shows an example of grooves in the intermediate rolling mill 5a (see Figure 2 again), where two grooves, K6 groove and K3 groove, are engraved on a pair of upper and lower rolls. Also, the other intermediate rolling mill 5b (see Figure 2 again), which is not shown in Figure 3, has two grooves, K5 groove and K4 groove.

[0026] In this example, the first pass of intermediate rolling is performed with a K6 groove (K5 rolling is a dummy with no reduction), and the second pass, which is rolling in the opposite direction to the first pass, is performed with tandem rolling using K6 and K5 grooves. Furthermore, the third pass is performed with tandem rolling using K4 and K3 grooves.

[0027] <Finishing rolling> After intermediate rolling, the material is transported to the finishing mill where it is finished. Figure 3(c) is an example of a groove used in finish rolling. In this example, the first pass of finish rolling uses a K2 groove to finish the material to its final thickness, and the second pass, which is rolling in the reverse direction, uses a K1 groove to perform claw bending. The third pass is rolling in the forward direction through the K1 groove, but is a dummy roll in which no reduction or claw bending is performed.

[0028] In this finish rolling, the second pass may be used as a dummy rolling, and the third pass may be used to perform finger bending with the K1 groove. Also, two passes of rolling may be performed with K1.

[0029] <Explanation of overall width defects (trumpet, reverse trumpet)> Figure 4 is a schematic diagram of deformation occurring at the end of a hat-shaped steel sheet pile 1. Figure 4(a) shows the so-called "horn-shaped deformation" in which the left and right joint parts 14 are bent outward at their longitudinal ends. Figure 4(b) shows the "reverse horn-shaped deformation" in which the left and right joint parts 14 are bent inward at their longitudinal ends. In some cases, one of the left and right joint parts 14 may be deformed into a "horn-shaped deformation" shape, while the other deforms into a "reverse horn-shaped deformation" shape.

[0030] In this specification, the total width of the hat-shaped steel sheet pile 1 at its longitudinal end is defined as W, the total width at a position 1 m longitudinally from the longitudinal end is defined as W', and the total width difference ΔW is defined as shown in equation (1).

[0031] ΔW=W-W' (1) When the sign of ΔW is positive, it is a trumpet deformation, and when it is negative, it is an inverse trumpet deformation.

[0032] In this embodiment, W' is the overall width at a position 1 m from the end in the longitudinal direction, but the object to be compared with the overall width W is not limited to the position 1 m from the end, and any position other than the end in the longitudinal direction may be set in advance. For example, it can be a length position from the end that is 0.5 to 5 times the overall width W.

[0033] Since steel sheet piles are used by fitting the joints of adjacent steel sheet piles together, a control range is usually set for the overall width difference ΔW. For example, the overall width at a position 1 m from the end is set as W', and a control range of -4 mm to +4 mm is set for the overall width difference ΔW. If the overall width difference ΔW falls outside this control range, offline press straightening is performed, and if the overall width difference ΔW is still not within the control range after press straightening, the product is rejected.

[0034] <Cooling method (nozzle installation)> 5A is an example of a schematic diagram showing a front guide 20 installed in front of the K1 hole mold and a cooling device installed in the front guide 20, and is a front view seen from the rolling direction. The front guide 20 has an upper guide 20a and a lower guide 20b that guide the web portion 11, flange portion 12, and arm portion 13 of the hat-shaped steel sheet pile. Injection devices 21a and 21b that inject a refrigerant are arranged in the upper guide 20a as devices that constitute the cooling device. These injection devices 21a and 21b are composed of cooling headers 22a and 22b and cooling nozzles 23a and 23b.

[0035] The spray device 21a shown on one side of the hat-shaped steel sheet pile in the full width direction of Fig. 5A can move in the full width direction of the hat-shaped steel sheet pile (hereinafter also referred to as the left-right direction in this specification), and by adjusting the position in the left-right direction, it is possible to spray the coolant to any location from the joint part to the flange part of the hat-shaped steel sheet pile. As a mechanism for adjusting the position in the left-right direction, for example, an electric slider can be used.

[0036] The refrigerant used for cooling includes, but is not limited to, water and compressed air.

[0037] The injector 21b shown on the other side of the hat-shaped steel sheet pile in Fig. 5A can inject refrigerant to any position from the flange to the joint of the hat-shaped steel sheet pile by changing its installation angle and changing the injection direction of the refrigerant. As an adjustment mechanism for the installation angle, for example, a method of setting the rotation angle with a stepping motor is available.

[0038] As shown in FIG. 5B, there is also a method in which a plurality of injectors are installed in advance at positions where injection is desired, and one or more injection positions are selected by opening and closing valves 24c, 24d, 24e, 24f, 24g, and 24h.

[0039] 5A and 5B, the spray device 21 is disposed on the upper guide 20a and cools the flange portion 12, the joint portion 14, and the elbow portion 15 from above (from the outer surface side of the flange). However, as shown in FIG. 5C, spray devices 21i, 21j, 21k, 21l, 21m, and 21n may be disposed on the lower guide 20b and cool the flange portion 12, the joint portion 14, and the elbow portion 15 from below (from the inner surface side of the flange). When cooling from above, the refrigerant may flow down from the flange portion 12 to the elbow portion 15 or the arm portion 13, causing an unintended temperature drop. However, when cooling from below, this risk is reduced. Furthermore, to increase the amount of cooling, spray devices 21 may also be provided on the rear guide of the K1 hole or the front and rear guides of the K2 hole.

[0040] A plurality of the injection devices shown in Figures 5A, 5B, and 5C are arranged and installed along the longitudinal direction of the rolling guide. The injection devices shown in Figures 5A, 5B, and 5C may be used in combination.

[0041] In addition to the spray device for cooling the joint portion to the flange portion, a spray device for cooling the web portion may be provided.

[0042] <Cooling condition settings> Figure 6 shows an example of an equipment configuration according to the present invention, which includes cooling devices (injectors 21a, 21b), a thermometer 8, and a computing device 25 that controls them and a shapemeter 9. In this example, the cooling devices are installed on the front and rear surfaces of the K1 caliber, which is the final groove for finish rolling. Downstream of the finish rolling mill, a thermometer 8 is installed to measure the temperature distribution in the entire width direction of the hat-shaped steel sheet pile, which is the material that has been subjected to final forming and rolling in the K1 caliber. Also installed downstream of this are a sawing device 7 and a shapemeter 9 (see Figure 2 again).

[0043] The temperature data measured by the thermometer is transmitted to the calculation device 25, which calculates the cooling conditions for the hat-shaped steel sheet pile from the next material onwards (for example, how much to cool the flange part or the joint part), and issues commands to the cooling device via a control means (control means (not shown)).

[0044] There are several ways to set and change the cooling conditions: (1) Changing the position of the injectors 21a and 21b to select cooling of the joint or flange. (2) Changing the injection device to be used by selecting whether or not the valve 24 is open (3) Adjusting the opening of the valve 24 that adjusts the flow rate of the refrigerant supplied to each injection device or adjusting the supply pressure of the refrigerant by the cooling pump 27 (4) Adjustment of the conveying speed during cooling of the hat-shaped steel sheet pile by adjusting the rotation speed of the main motor 26 that drives the rolling rolls and the table roller 28 Examples include:

[0045] <How to determine cooling conditions> The following is an example of a method for determining the cooling conditions for the flange and joint portions based on the temperature distribution in the entire width direction measured by the thermometer 8.

[0046] <How to calculate the representative temperature and temperature difference ΔT between the flange and joint> Figure 7 shows an example of the temperature distribution in the width direction after finish rolling measured by thermometer 8 for one series of hat-type steel sheet pile, 45H (web thickness is 15 mm, and effective height H shown in Figure 1 is 368 mm). From this temperature distribution, the representative temperature Tg of the joint and the representative temperature Tf of the flange are calculated, and the temperature difference ΔT (= Tg - Tf) is calculated.

[0047] There are no particular regulations for determining the representative temperatures of the flange portion and the joint, but there are methods such as using the average temperature value of the range that will become the flange portion as the representative temperature of the flange portion and the average temperature value of the range that will become the joint portion as the representative temperature of the joint, or using the minimum temperature value of the range that will become the flange portion as the representative temperature of the flange portion and the maximum temperature value of the range that will become the joint portion as the representative temperature of the joint.

[0048] <Mechanism for changing overall width difference> Here, we qualitatively explain the mechanism by which the temperature difference ΔT between the joint and the flange changes the overall width difference ΔW. If the temperature of the joint is higher than that of the flange during finish rolling, the amount of thermal contraction in the longitudinal direction when cooled to room temperature will be greater at the joint than at the flange. In reality, the joint and flange are joined via the arm, and they affect each other's deformation. As a result, when the temperature of the joint becomes higher than that of the flange, the joint at the longitudinal end tends to bend in the width direction, which is known as "horn deformation." Conversely, when the temperature of the joint becomes lower than that of the flange, the joint at the longitudinal end tends to bend in the width direction, which is known as "reverse horn deformation." Note that the trends described here are qualitative, and the appropriate temperature difference that can suppress the overall width deviation will vary depending on the finish rolling conditions and steel type of the hat-type steel sheet pile.

[0049] Figure 8 shows an example of the relationship between the temperature difference ΔT and the overall width difference ΔW, which was investigated for 45H, a series of hat-type steel sheet piles. This data was obtained by variously changing the cooling conditions for the flange and joint parts using a cooling device installed in front of the rolling mill during rolling of K1 grooves.

[0050] In Fig. 8, the joint temperature Tg is the maximum temperature in the 0-7% width direction section on the drive side (DS side in Fig. 7), and the maximum temperature in the 93-100% width direction section on the work side (WS side).The flange temperature Tf is the average temperature in the 20-30% width direction section on the DS side, and the average temperature in the 70-80% width direction section on the WS side.Here, the temperature difference ΔT is the average temperature between the left and right sides of the hat-shaped steel sheet pile.

[0051] In addition, in Figure 8, SYW295 steel, which has a room temperature yield stress of 295 MPa or more, is plotted with a circle, and SYW390 steel, which has a room temperature yield stress of 390 MPa or more, is plotted with a triangle. In the example of Figure 8, for SYW295 steel, the appropriate temperature difference ΔT at which the overall width difference ΔW is 0 mm is approximately -15°C. In contrast, for SYW390 steel, the appropriate temperature difference ΔT at which the overall width difference ΔW is 0 mm is approximately -35°C. Therefore, in this example, it is preferable to set cooling conditions for SYW295 steel so that ΔT approaches -15°C, and for SYW390 steel so that ΔT approaches -35°C.

[0052] Figure 9 shows the results of investigating the temperature difference ΔT for a hat-type steel sheet pile 45H when cooling the joint (open 24c), the elbow (where the flange and arm join) (open 24d), and the flange (open 24e) independently using the cooling device shown on one side of the overall width in Figure 5B. The material transport speed was 3 m / s, the cooling water flow rate was 300 liters / min, and cooling was performed on the front side of the rolling mill (K1 groove). Figure 9 shows that the flange cooling conditions were optimal for SYW295 steel, and the joint cooling conditions were optimal for SYW390 steel.

[0053] In this example of 45H, the temperature distribution after finish rolling shows that the temperature at the joint is generally lower than that at the flange, but this tendency may vary depending on the size and steel grade of the hat-type steel sheet pile. For example, in the case of 10H, which is shorter in height and thinner in each part than 45H, the joint is often hotter than the flange. The difference in temperature distribution is thought to be due to differences in the cross-sectional dimensions and the number of passes in each rolling mill. In any case, it is possible to improve the overall width difference of the hat-type steel sheet pile by appropriately setting or changing the cooling conditions according to the target and actual temperature difference ΔT after finish rolling.

[0054] <Variations for selecting cooling positions> As described above, the cooling positions of the joints and flanges can be selected and cooled so that ΔT is appropriate. Also, the flow rate of the coolant at the selected positions can be adjusted.

[0055] If injection devices are installed on both the front and rear sides of the K1 hole, or on the inlet and outlet sides of the K2 hole, the locations cooled by each injection device may be the same or different. For example, if the temperatures of the flange and joint are higher overall than the conventionally optimum conditions, with the flange temperature being particularly high, it is possible to cool both the joint and flange on the K1 inlet side and to cool the flange intensively on the K1 outlet side, thereby lowering the overall temperature and controlling ΔT within the optimum range.

[0056] In addition, the cooling conditions for the flange and joint parts can be set separately for the left and right sides of the hat-shaped steel sheet pile.

[0057] As described above, the calculation device 25 predicts the temperature difference ΔT between the joint portion and the flange portion after finish rolling of the material to be rolled from the rolling record, and the control means (controlling means) can control the injection position of the coolant onto the material to be rolled during finish rolling, between the flange portion and the joint portion, based on the predicted temperature difference ΔT. Therefore, the injection position of the coolant by the cooling device (injection device) can be adjusted, and both types of end deformation, namely "horn deformation" and "reverse horn deformation", can be suppressed.

[0058] <Method of determining or changing cooling conditions based on overall width difference> Instead of measuring the temperature, the overall width W of the longitudinal end of the hat-shaped steel sheet pile product sawn to a predetermined length after finish rolling and the overall width W' at a predetermined longitudinal position from the end can be measured using a shape meter 9, and based on this, the cooling conditions for the flange portion to the joint portion during finish rolling can be changed.

[0059] Figure 10 shows the results of an investigation into the relationship between the difference in overall width after rolling and the lateral position P (mm) of the injector, which is shown on one side of the hat-shaped steel sheet pile (50H) with a web thickness of 17 mm and an effective height H of 370 mm, was performed using a cooling device 21 that moves the injector in the overall width direction of the hat-shaped steel sheet pile (Figure 5A). In Figure 10, when the lateral position P = 0 mm, the cooling core of the refrigerant is located at the center of the joint, and when P = 210 mm, the cooling core of the refrigerant is located at the center of the flange. The cooling conditions in Figure 10 were a material conveying speed of 3 m / s and a cooling water flow rate of 300 liters / min. Cooling was performed on the front side of the rolling mill (K1-type).

[0060] Figure 10 shows that as the horizontal position P increases, the overall width difference ΔW tends to increase. In Figure 10, the slope of the linear approximation of the relationship between the horizontal position P and the overall width difference ΔW is K. Based on this survey data, the optimal horizontal position P for achieving an overall width difference of 0 mm is approximately P = 175 mm for SYW295 steel (plotted with circles) and P = 65 mm for SYW390 steel (plotted with triangles). Based on this data, for example, for 50H SYW295 steel, the horizontal position of the injector at the start of the rolling chance can be set to P = 175 mm, and for SYW390 steel, P = 65 mm. Alternatively, the horizontal position of the injector can be adjusted proportionally to ΔW / K (mm) for subsequent rolling chances, depending on the actual overall width difference ΔW for that rolling chance.

[0061] As described above, the calculation device 25 predicts, from the rolling results, the overall width difference ΔW, which is the difference between the overall width of the longitudinal end of the material to be rolled after finish rolling and the overall width at a predetermined position other than the longitudinal end from the end, and the control means (controlling means) can control the injection position of the coolant onto the material to be rolled during finish rolling between the flange portion and the joint portion based on the predicted overall width difference ΔW. Therefore, the injection position of the coolant by the cooling device (injection device) can be adjusted, and both types of end deformation, "horn deformation" and "reverse horn deformation", can be suppressed.

[0062] The following method is an even more advanced version of this cooling control. As shown in Figure 2, the temperature is measured by thermometer 8 before sawing, while the overall width difference is measured by shape meter 9 after sawing. Therefore, the cooling conditions can be changed based on the temperature measurement by thermometer 8, and then adjusted based on the subsequent measurement of the overall width difference by shape meter 9. This further improves the shape of the product's longitudinal ends, mainly the joints. [Example]

[0063] <Example 1 45H, FIG. 5B, Valve opening adjustment according to temperature difference> Using the hat-shaped steel sheet pile rolling production line and production equipment shown in Figures 2, 3, 5B, and 6, we manufactured a hat-shaped steel sheet pile 45H with a standard overall width of 936 mm, a web thickness of 15 mm, and an effective height of 368 mm. As shown on one side of the overall width of the hat-shaped steel sheet pile in Figure 5B, the cooling system includes an injector 21c for cooling the joint, an injector 21d for cooling the elbow portion (the joint between the flange and the arm), and an injector 21e for cooling the flange, as well as associated valves 24c, 24d, and 24e. The refrigerant used in this example was water. A one-dimensional line-scan type thermometer was used as the thermometer 8 to measure the temperature distribution after finish rolling.

[0064] In this example, nine raw materials were rolled. Rolls 1 to 6 were SYW295 steel grades with a room temperature yield stress of 295 MPa or more, and rolls 7 to 9 were SYW390 steel grades with a room temperature yield stress of 390 MPa or more. Rolls 1 to 3 were finish-rolled with a K1 groove and no cooling was performed. Rolls 1 to 3 are comparative examples performed for comparison. In contrast, rolls 4 to 9 are conforming examples in which cooling was performed on the front side of the rolling from the flange to the elbow during finish-rolling with a K1 groove, based on the data shown in Figures 7 and 8. The rolling speed for all of these raw materials with a K1 groove was 3 m / s.

[0065] For the fourth piece, the cooling water volume for the flange was set to 300 liters / minute, and for the elbow, there was no cooling water volume. However, since the actual temperature difference ΔT after rolling (ΔT is the average value for the left and right parts of the hat-shaped steel sheet pile) was slightly higher than the target, for the fifth and sixth pieces, the balance between the amount of water cooling the elbow and the amount of water cooling the flange was corrected according to the actual temperature difference of the previous material, and the cooling water volume for the flange was set to 200 liters / minute, and for the elbow, there was no cooling water volume.

[0066] Next, the seventh to ninth examples are for the SYW390 steel type, and are based on the data shown in Figures 7 and 8. During finish rolling with a K1 groove, the joint was cooled with cooling water at a rate of 300 liters per minute on the front side of the rolling.

[0067] These cooling conditions and the results of the temperature difference and overall width difference are shown in Table 1. The shape meter 9 used to measure the overall width shape of the product end is a type that clamps the outer edge of the joint from both sides like a vernier caliper to measure the longitudinal end of the product and the overall width at a position 1 m from the end.

[0068] [Table 1]

[0069] For 45H SYW295 steel, under conditions without joint water cooling (1st to 3rd rolls), the overall width difference could not be kept within the target range of -4 mm to +4 mm. In contrast, for the conforming examples of this application, the overall width difference was able to be kept within the target range of -4 mm to +4 mm for both SYW295 steel and SYW390 steel. In particular, for the 5th and 6th rolls, in which the cooling conditions were modified based on the temperature results of the 4th roll, the absolute value of the overall width difference was very small, and a product with a particularly good overall width shape at the longitudinal end was obtained.

[0070] <Example 2 50H, FIG. 5A, slide position adjustment according to overall width difference> Using the hat-shaped steel sheet pile rolling production line and production equipment shown in Figures 2, 3, 5A, and 6, we manufactured a hat-shaped steel sheet pile 50H with a standard overall width of 938 mm, a web thickness of 17 mm, and an effective height of 370 mm. As shown in Figure 5A, the cooling device is an injection device consisting of a cooling header 22a, a cooling nozzle 23a, and a valve 24a, which moves left and right, on one side of the overall width of the hat-shaped steel sheet pile. The cooling refrigerant used in this example was water. The shape meter 9 used to measure the overall width shape of the product end is a type that measures the overall width of the product by clamping it from both sides like a vernier caliper, at the longitudinal end of the product and at a position 1 m from the end.

[0071] In this example, 10 raw materials were rolled. Rolls 1 to 6 were SYW295 steel grades with a room temperature yield stress of 295 MPa or more, while rolls 7 to 10 were SYW390 steel grades with a room temperature yield stress of 390 MPa or more. Rolls 1 and 2 were finish-rolled with a K1 groove and no cooling was performed. These rolls are comparative examples performed for comparison. In contrast, rolls 3 to 10 are adapted examples in which cooling was performed on the front side of the roll during finish-rolling with a K1 groove by appropriately setting and adjusting the left and right positions P of the injection device based on the data shown in Figure 10. The rolling speed for all of these raw materials with a K1 groove was 3 m / s.

[0072] For the third roll, the left-right position P of the injector was set to 175 mm, but the overall width difference ΔW measured after rolling was -3 mm, which was within the target range but slightly small. Therefore, for the fourth roll and onwards, the left-right position P of the injector was changed sequentially based on the actual ΔW of the previous roll. This change ΔP was calculated using equation (2).

[0073] ΔP=-α·ΔW / K ‥‥(2) In equation (2), α is a sensitivity coefficient for control, and its value is set to 0.5 here. Also, K=0.057.

[0074] Next, for the seventh roll, SYW390 steel, the left-right position P of the injector was set to 65 mm, but the overall width difference ΔW measured after rolling was +3 mm, which was within the target range but slightly large. Therefore, for the eighth roll and beyond, the left-right position P of the injector was sequentially changed based on the actual ΔW of the previous roll. To calculate the amount of change at this time, equation (2) was used, just as for SYW295 steel, because the slope of the data shown in Figure 10 is nearly the same for SYW390 and SYW295 steel.

[0075] The results of these cooling conditions (left and right positions of the injector) and overall width difference are summarized in Table 2.

[0076] [Table 2]

[0077] For the 50H SYW295 steel, under conditions without joint water cooling (the first and second rolls), the overall width difference was not within the target range of -4 mm to +4 mm. In contrast, for the conforming examples of the present application, the overall width difference was within the target range of -4 mm to +4 mm for both SYW295 and SYW390 steel. In particular, the overall width difference approached the ideal 0 mm for the fourth to sixth rolls, in which the left and right positions of the injector were corrected based on the overall width difference measured for the third roll, and for the eighth to tenth rolls, in which the left and right positions of the injector were corrected based on the overall width difference measured for the seventh roll. Thus, the present invention enabled the production of products with particularly excellent overall width shapes at the longitudinal ends.

[0078] In this way, according to the present invention, appropriate positions from the joint portion to the flange portion can be cooled under appropriate conditions, so that a hat-shaped steel sheet pile with a small overall width difference and a good overall width shape at the longitudinal end can be obtained regardless of changes in the steel type or rolling conditions. [Explanation of symbols]

[0079] 1 Hat-shaped steel sheet pile 11 Web Department 12 Flange 13 Arm 14 Joint 15 Elbow 2. Hat-type steel sheet pile manufacturing equipment 3 Heating furnace 4 Roughing mill (hot rolling mill) 5. Intermediate rolling mill (hot rolling mill) 6 Finishing rolling mill (hot rolling mill) 7 Saw cutting device 8 Thermometer 9 Shape meter 20 K1 hole type front guide 20a upper guide 20b Lower guide 21a, 21b, 21c, 21d, 21e, 21f, 21g, 21h, 21i, 21j, 21k, 21l, 21m, 21n Injection device (consisting of a cooling header 22 and a cooling nozzle 23) 22a Cooling header (sliding type) 22b Cooling header (swing type) 23a Cooling nozzle (slide type) 23b Cooling nozzle (swing type) 24a Valve (for slide type) 24b Valve (for swing type) 24c valve (for joint) 24d Valve (for elbow) 24e Valve (for flange) 24f valve (for joint) 24g valve (for elbow) 24h valve (for flange) 25 Arithmetic unit 26 Rolling mill main motor 27 Refrigerant supply pump 28 Table Roller 41 Upper roll of roughing mill 42 Lower roll of roughing mill 51 Upper roll of intermediate rolling mill 52 Lower roll of intermediate rolling mill 61 Upper roll of finishing mill 62 Finishing mill bottom roll W Overall width at end W' Overall width at 1m from the end ΔW Overall width difference = W-W' Tf Representative temperature of flange Tg Representative temperature of joint ΔT temperature difference=Tg-Tf P Left and right movement of the injection device K Slope of the data in Figure 10 (total width difference / movement amount) H Effective height

Claims

1. A method for manufacturing a hat-shaped steel sheet pile, characterized in that, in hot rolling of a hat-shaped steel sheet pile having a web portion, a flange portion, an arm portion and a joint portion, the injection position of a coolant onto the material to be rolled during finish rolling is controlled between the flange portion and the joint portion based on an overall width difference ΔW, which is the difference between the overall width of the longitudinal end portion of the material to be rolled after finish rolling and the overall width at a predetermined position other than the longitudinal end portion, as predicted from rolling results.

2. A method for manufacturing a hat-shaped steel sheet pile, characterized in that, in hot rolling of a hat-shaped steel sheet pile having a web portion, a flange portion, an arm portion and a joint portion, the injection position of a coolant onto the material to be rolled during finish rolling is controlled between the flange portion and the joint portion based on a temperature difference ΔT between the joint portion and the flange portion after finish rolling of the material to be rolled, which is predicted from rolling results.

3. 3. The method for manufacturing a hat-shaped steel sheet pile according to claim 1, wherein the control of the injection position is performed by at least one of moving an injection device that injects the coolant along the entire width direction of the material to be rolled and changing the injection direction of the coolant.

4. 3. The method for manufacturing a hat-shaped steel sheet pile according to claim 1, wherein the control of the injection position is performed by installing a plurality of injection devices for injecting refrigerant from the flange portion to the joint portion and selecting one or more injection devices from the plurality of injection devices.

5. A manufacturing facility for a hat-shaped steel sheet pile, the manufacturing facility comprising: a hot rolling mill for hot-rolling a hat-shaped steel sheet pile having a web portion, a flange portion, an arm portion, and a joint portion into the shape of the hat-shaped steel sheet pile; and a sawing device for cutting the hat-shaped steel sheet pile obtained by the hot rolling in a width direction, a cooling device capable of selectively cooling the joint portion and the flange portion is provided within a guide attached to the finishing rolling mill during the hot rolling; a calculation device for predicting an overall width difference ΔW, which is the difference between the overall width of the end portion in the longitudinal direction of the material to be rolled after finish rolling and the overall width at a predetermined position other than the end portion in the longitudinal direction from the end portion, based on rolling results; A manufacturing facility for a hat-shaped steel sheet pile, comprising: a means for controlling a coolant injection position with respect to the material to be rolled during finish rolling between the flange portion and the joint portion based on a predicted overall width difference ΔW.

6. A manufacturing facility for a hat-shaped steel sheet pile, the manufacturing facility comprising: a hot rolling mill for hot-rolling a hat-shaped steel sheet pile having a web portion, a flange portion, an arm portion, and a joint portion into the shape of the hat-shaped steel sheet pile; and a sawing device for cutting the hat-shaped steel sheet pile obtained by the hot rolling in a width direction, a cooling device capable of selectively cooling the joint portion and the flange portion is provided within a guide attached to the finishing rolling mill during the hot rolling; a calculation device that predicts a temperature difference ΔT between the joint portion and the flange portion after finish rolling of the rolling target material based on rolling results, A manufacturing facility for a hat-shaped steel sheet pile, characterized by comprising a means for controlling a coolant injection position with respect to the material to be rolled during finish rolling between the flange portion and the joint portion based on the predicted temperature difference ΔT.

Images