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 in a form of "reverse trumpet deformation" and improving an entire width shape of a longitudinal end portion.SOLUTION: In finish rolling of a hat shape steel sheet pile which has a web portion, a flange portion, an arm portion, an elbow portion which are junctions of the flange portion and the arm portion, and a joint portion, cooling is performed on one of the flange portion and the elbow portion, or both the flange portion and the elbow portion. At this time, a cooling condition for material to be rolled in the finish rolling may be determined based on the 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 position other than the longitudinal direction end portion, or based on temperature difference ΔT between the joint portion and the flange portion after the finish rolling.SELECTED DRAWING: Figure 5

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 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 end deformation in the form of ``reverse trumpet 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] In the finish rolling of a hat-shaped steel sheet pile having a web portion, a flange portion, an arm portion, an elbow portion which is a joint portion of the flange portion and the arm portion, A method for manufacturing a hat-shaped steel sheet pile, characterized in that a cooling treatment is performed on one of a flange portion and an elbow portion, or on both the flange portion and the elbow portion. [2] A manufacturing method of a hat-shaped steel sheet pile according to the item [1], characterized in that cooling conditions for the material to be rolled during finish rolling are determined based on an 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, predicted from rolling results, and the cooling treatment is performed based on the cooling conditions. [3] A manufacturing method of a hat-shaped steel sheet pile according to [1], characterized in that cooling conditions for the material to be rolled during finish rolling are determined 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 records, and the cooling treatment is performed based on the cooling conditions. [4] 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, an elbow portion which is a joint portion between the flange portion and the 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, The manufacturing equipment for hat-type steel sheet piles is characterized in that a cooling device capable of cooling either the flange portion or the elbow portion, or both the flange portion and the elbow portion, is provided in a guide attached to the finishing rolling mill during hot rolling. [5] A calculation device is provided for predicting an overall width difference ΔW, which is the difference between the overall width of the end portion of 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 of the longitudinal direction, based on the rolling results; The manufacturing equipment of the hat-shaped steel sheet pile according to [4], further comprising a means for determining cooling conditions of the cooling device for the material to be rolled during finish rolling based on the predicted overall width difference ΔW. [6] A calculation device is provided that predicts the temperature difference ΔT between the joint portion and the flange portion after finish rolling of the rolling target material based on rolling results, The manufacturing equipment of the hat-shaped steel sheet pile according to [4], further comprising a means for determining cooling conditions of the cooling device for the material to be rolled during finish rolling based on the predicted temperature difference ΔT.

[0012] The "total width difference, 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 joint portion and the flange 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, it is possible to prevent end deformation in the form of "reverse horn deformation" and obtain a hat-shaped steel sheet pile having a good overall width shape at the longitudinal end. [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 5] 1A and 1B are schematic diagrams showing a method for cooling a flange and / or elbow according to the present invention, where (a) shows cooling from the outer surface side of the flange, and (b) shows cooling from the inner surface side of the flange. [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 value obtained by dividing the amount of cooling water by the conveying speed 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 of its width, a pair of flanges 12 on both sides of the web, a pair of arm sections 13 on both sides of the web, and a pair of joint sections 14 whose cross-sectional shape is almost point-symmetric on the left and right. The joint between the flange sections 12 and the arm sections 13 is called an elbow section 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 is equipped with a guide, and an injection device 21, which will be described later with reference to Figure 5 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 so-called "horn deformation," in which the left and right joint parts 14 bend outward at the longitudinal end parts. Figure 4(b) shows "reverse horn deformation," in which the left and right joint parts 14 bend inward at the longitudinal end parts.

[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)> FIG. 5(a) is a front view, seen from the rolling direction, of 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. 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. In the upper guide 20a, sprayers 21a, 21b, 21c, and 21d that spray a refrigerant are disposed as components of the cooling device. The sprayer 21a is composed of a cooling header 22a and a cooling nozzle 23a. Similarly, the sprayers 21b, 21c, and 21d are each composed of a cooling header and a cooling nozzle 23. (In the drawing, of the sprayers 21a, 21b, 21c, and 21d, only the cooling header 22a and the cooling nozzle 23a of the sprayer 21a are labeled.)

[0035] Injection devices 21a and 21b shown on one side of the hat-shaped steel sheet pile in the overall width direction in Figure 5(a) are schematic diagrams of the case where refrigerant is injected vertically downward from above the hat-shaped steel sheet pile (outer surface side), with 21a cooling the elbow portion of the hat-shaped steel sheet pile and 21b cooling the flange portion of the hat-shaped steel sheet pile.

[0036] The injection devices 21c and 21d shown on the other side of the hat-shaped steel sheet pile in Figure 5(a) in the overall width direction are schematic diagrams of the case where the installation angle of the injection device is changed so that the injection direction of the refrigerant is inclined relative to the vertical direction.

[0037] As shown in Figure 5(a), one method is to install separate injectors 21b and 21c for cooling the flanges and injectors 21a and 21d for cooling the elbows, and select one or more injection positions by opening and closing valves 24a, 24b, 24c, and 24d. Alternatively, the system may be configured with only an injector for cooling the flanges or only an injector for cooling the elbows, or with a single injector for cooling both the flanges and elbows.

[0038] The coolant used for cooling may be water or compressed air, but the present invention is not limited to these.

[0039] When water is used as a coolant, the amount of cooling water (m 3 The cooling water flow rate (m / s) is preferably in the range of 0.5 to 5.5 times the conveying speed (m / s), although it depends on the size and manufacturing conditions of the hat-shaped steel sheet pile. When both the flange and elbow are cooled, the cooling water flow rate for the elbow is preferably set to 0.2 to 0.7 times the cooling water flow rate for the flange, although it depends on the size and manufacturing conditions of the hat-shaped steel sheet pile.

[0040] In Fig. 5(a), the spray device 21 is disposed on the upper guide 20a and cools the flange portion 12 and elbow portion 15 from above (from the outer surface side of the flange). However, as shown schematically in Fig. 5(b), spray devices 21e, 21f, 21g, and 21h may be disposed on the lower guide 20b and cool the flange portion 12 and 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 guide on the rear side of the K1 hole or on the guides on the front and rear sides of the K2 hole.

[0041] The injection devices shown in Figures 5(a) and 5(b) may be used in combination. Also, a plurality of the injection devices shown in Figures 5(a) and 5(b) may be arranged and installed along the longitudinal direction of the rolling guide.

[0042] In addition to the sprayers for cooling the flanges and elbows, sprayers for cooling the webs may also be provided. Also, a cooling device for cooling the flanges and / or elbows of the hat-type steel sheet pile according to the present invention may be installed on the front side of the rolling mill, and a cooling device capable of cooling the joints of the hat-type steel sheet pile may be installed on the rear side of the rolling mill, and these cooling facilities may be selected and used depending on the temperature distribution and overall width difference records of the hat-type steel sheet pile.

[0043] <Cooling condition settings> Figure 6 shows an example of an equipment configuration according to the present invention, which includes a cooling device (injection device 21), 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 full 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).

[0044] The temperature data measured by the thermometer is transmitted to the calculation device 25, which calculates, for example, the cooling conditions of the hat-shaped steel sheet piles from the next material onwards (for example, how much to cool the flanges and elbows). Then, based on the calculation results, the decision means (decision means (not shown)) decides the cooling conditions of the cooling device, and can give a command to the cooling device via the control means (control means (not shown)).

[0045] There are several ways to set and change the cooling conditions: (1) 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 (2) 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:

[0046] <How to determine cooling conditions> The following is an example of a method for determining the cooling conditions for the flange and elbow based on the temperature distribution in the entire width direction measured by the thermometer 8.

[0047] <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.

[0048] 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.

[0049] <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.

[0050] 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.

[0051] 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.

[0052] 8, the appropriate temperature difference ΔT at which the overall width difference ΔW becomes 0 mm is approximately −15° C. Therefore, in this example, it is preferable to set the cooling conditions so that ΔT approaches −15° C.

[0053] Figure 9 shows the results of investigating the temperature difference ΔT for a 45H hat-type steel sheet pile under three conditions: (1) no cooling, (2) cooling the elbow (24a open), and (3) cooling the flange (24b open) in a finishing rolling facility equipped with the cooling device shown on one side (left side) of the full width direction in Figure 5(b). The material conveying speed was 3 m / s, the cooling water flow rate was 5 liters / s, and cooling was performed on the front side of the rolling mill (K1 groove). Figure 9 shows that in this example, the conditions (1) no cooling, (2) cooling the elbow, and (3) cooling the flange meet the cooling conditions mentioned above for ΔT approaching -15°C.

[0054] <Variations in cooling condition selection> As described above, the cooling conditions for the flange or elbow can be appropriately modified or changed to cool the flange or elbow so that ΔT is appropriate.

[0055] When the 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 cooling conditions for each injection device may be the same or different. Also, the cooling conditions for the flange or elbow can be set separately for the left and right sides of the hat-type steel sheet pile.

[0056] In this way, 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 determination means (means for determining) can determine the cooling conditions of the cooling device for the material to be rolled during finish rolling based on the predicted temperature difference ΔT. By performing the cooling treatment according to the determined cooling conditions, the injection position of the coolant by the cooling device (injection device) can be adjusted, and end deformation in the form of "reverse horn deformation" can be suppressed.

[0057] <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 of the flange and elbow portions during finish rolling can be changed.

[0058] Figure 10 shows the results of an investigation into the relationship between the amount of cooling water used as a coolant and the conveying speed of the material being rolled during cooling, for a hat-shaped steel sheet pile 50H with a web thickness of 17 mm and an effective height H of 370 mm, using a cooling device 21 with an injector shown on one side (right side) of the hat-shaped steel sheet pile in Figure 5(a) in the overall width direction. In Figure 10, the amount of water used to cool the flange and the elbow is the same, and the sum of the two is used as the cooling water amount data. Cooling is performed on the front side of the rolling mill (K1 groove type).

[0059] From Figure 10, it can be seen that increasing the value obtained by dividing the cooling water volume (liters / second) by the transport speed (m / second) and strengthening the cooling of the flange and elbow sections tends to increase the overall width difference ΔW. In the example of Figure 10, although there is some variation, the relationship between the cooling water volume / transport speed and the overall width difference can be approximated by a linear relationship, and it can be seen that the value of cooling water volume / transport speed at which the overall width difference is 0 mm is around 3.

[0060] Therefore, it is possible to control the following: the gradient of the data on the total width difference relative to the cooling water amount / conveying speed is set to K, and at the start of the rolling chance, the cooling water amount / conveying speed is set to 3, and then, depending on the actual total width difference ΔW of that rolling chance, for the next material after that rolling chance, the left and right positions of the injection device are sequentially corrected so that they are proportional to ΔW / K (mm).

[0061] In this way, 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 determination means (means for determining) can determine the cooling conditions of the cooling device for the material to be rolled during finish rolling based on the predicted overall width difference ΔW. By performing the cooling process according to the determined cooling conditions, the injection position of the coolant by the cooling device (injection device) can be adjusted, making it possible to prevent end deformation in the form of "reverse horn deformation."

[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> Using the hat-type steel sheet pile rolling production line and production equipment shown in Figures 2, 3, 5(a), and 6, we manufactured a hat-type 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 (left side) of the overall width of the hat-type steel sheet pile in Figure 5(a), the cooling device includes an injector 21a for cooling the elbow portion, which is the joint between the flange and the arm portion, an injector 21b for cooling the flange portion, and associated valves 24a and 24b. 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, six materials were rolled. These materials were SYW295 steel grades with a yield stress of 295 MPa or higher at room temperature. Rollings 1 to 3 were finish-rolled with a K1 groove and no cooling was performed. Rollings 1 to 3 are comparative examples performed for comparison. In contrast, rollings 4 to 6 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 8 and 9. The rolling speed for all of these materials with a K1 groove was 3 m / s.

[0065] For the fourth piece, the cooling water volume for the flange was 5 liters / second and none for the elbow, but 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 -10°C, which was slightly higher than the target of -15°C. Therefore, 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 adjusted according to the actual temperature difference of the previous material, and the cooling water volume for the flange was set at 3.3 liters / second and the cooling water volume for the elbow at 1.7 liters / second.

[0066] 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.

[0067] [Table 1]

[0068] Under the conditions without joint water cooling (1st to 3rd rolls), the overall width difference could not be kept within the target range of -4mm to +4mm. In contrast, for rolls 4 to 6, which are compatible examples of the present application, the overall width difference was kept within the target range of -4mm to +4mm. 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.

[0069] <Example 2 50H> Using the hat-shaped steel sheet pile rolling production line and production equipment shown in Figures 2, 3, 5(a), 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. The cooling device, shown on one side (right side) of the overall width direction of the hat-shaped steel sheet pile in Figure 5(a), has an injector 21d for cooling the flange and an injector 21c for cooling the elbow. 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 clamps the product's longitudinal end and the overall width at a position 1 m from the end from both sides like a vernier caliper.

[0070] In this example, six blanks were rolled. These blanks were SYW295 steel, which has a yield stress of 295 MPa or higher at room temperature. The first and second blanks were finish-rolled with a K1 groove and no cooling was performed. These first and second blanks are comparative examples conducted for comparison. In contrast, the third to sixth blanks were adapted examples in which the cooling water volume and conveying speed were appropriately set and adjusted based on the data shown in Figure 10 for the cooling of the front side of the roll during finish-rolling with a K1 groove. In this example, the cooling water flow rate at the flange and elbow was the same. Furthermore, the upper limit of the cooling water volume for this cooling device was 7.0 liters / second. This limit was reached during the fourth blank. Therefore, for the fourth and subsequent blanks, the conveying speed was reduced to enhance cooling.

[0071] For the third roll, the cooling water volume was 5.0 liters / second and the conveying speed was 3.0 m / s, 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 cooling water volume / conveying speed values ​​were sequentially changed based on the ΔW of the previous roll. This change ΔV was calculated using equation (2).

[0072] ΔV=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=2.0.

[0073] The results of these cooling conditions (left and right positions of the injector) and overall width difference are summarized in Table 2.

[0074] [Table 2]

[0075] Under conditions without joint water cooling (1st and 2nd rolls), the overall width difference could not be kept within the target range of -4mm to +4mm. In contrast, in the conforming example of the present application, the overall width difference was kept within the target range of -4mm to +4mm. In particular, it can be seen that the overall width difference gradually approached the ideal 0mm in the 4th to 6th rolls, in which the cooling conditions were corrected based on the actual overall width difference of the 3rd roll. Thus, the present invention made it possible to obtain a product with a particularly good overall width shape at the longitudinal end.

[0076] 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 rolling conditions. [Explanation of symbols]

[0077] 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: Injection device (comprising a cooling header 22 and a cooling nozzle 23) 22a Cooling Header 23a Cooling nozzle 24a, 24b, 24c, 24d valves 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 The slope of the data in Figure 10 H Effective height

Claims

1. In finish rolling of a hat-shaped steel sheet pile having a web portion, a flange portion, an arm portion, an elbow portion which is a joint portion of the flange portion and the arm portion, A method for manufacturing a hat-shaped steel sheet pile, characterized in that a cooling treatment is performed on one of a flange portion and an elbow portion, or on both the flange portion and the elbow portion.

2. 2. The method for manufacturing a hat-shaped steel sheet pile according to claim 1, wherein cooling conditions for the material to be rolled during finish rolling are determined based on an 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, predicted from rolling results, and the cooling treatment is performed based on the cooling conditions.

3. 2. The method for manufacturing a hat-shaped steel sheet pile according to claim 1, wherein cooling conditions for the material to be rolled during finish rolling are determined 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 records, and the cooling treatment is performed based on the cooling conditions.

4. 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, an elbow portion which is a joint portion of the flange portion and the 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, The manufacturing equipment for hat-type steel sheet piles is characterized in that a cooling device capable of cooling either the flange portion or the elbow portion, or both the flange portion and the elbow portion, is provided in a guide attached to the finishing rolling mill during hot rolling.

5. 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; The manufacturing facility of the hat-shaped steel sheet pile according to claim 4, further comprising a means for determining cooling conditions of the cooling device for the material to be rolled during finish rolling based on the predicted overall width difference ΔW.

6. 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, The manufacturing facility of the hat-shaped steel sheet pile according to claim 4, further comprising a means for determining cooling conditions of the cooling device for the material to be rolled during finish rolling based on the predicted temperature difference ΔT.

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