Width pressing device and slab width pressing method

Abstract

To provide a width press device and a slab width press method.SOLUTION: A width press device according to the present invention comprises a thermometer, a width press machine, and a width press control unit. The width press control unit comprises: a slab temperature measurement part which measures a slab surface temperature of a slab after heating furnace extraction by using the thermometer arranged on an inlet side of the width press machine; a width press load calculation part which calculates a width press load prediction value on the basis of the measured slab surface temperature; a width press determination part which determines propriety of the width press of the slab according to the calculated width press load prediction value; a contact length control part which controls a contact length to be variable by correcting the contact length between the slab and a width press mold of the width press machine by a slab feeding amount correction value; a strain rate control part which controls a strain rate in the time of width press by correcting a crank rate of the width press machine by the slab feeding amount correction value and reducing the crank rate; and a width press execution part which executes the width press of the slab on the basis of the width press load prediction value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a width press device that width-presses a slab before hot rolling in the production of hot-rolled steel sheet, and a width-pressing method for a slab used in the width press device. [Background technology]

[0002] Generally, from the standpoint of improving productivity, in the production of hot-rolled steel sheets, slabs are often cast in the steelmaking process with the same width, making it difficult to vary the width of the slab to suit the final product.

[0003] Therefore, in order to accommodate various product widths, in the hot rolling process after casting, the slab is heated and then width-pressed using a width press device. In the width press device, the slab is intermittently pressed in the width direction by a pair of width press dies installed opposite each other in the width direction. This makes it possible to adjust the width of the slab to suit various product widths, making it possible to manufacture steel products with the desired product width.

[0004] However, since the amount of pressing of the slab varies depending on the product width, the width press load generated when pressing the slab in width may exceed the allowable load of the width press device, in which case there is a concern that the width press device may be damaged.

[0005] Patent Document 1, which is related to the edge load of a roughing mill in hot rolling, discloses a technique for adjusting the edge load of each rolling pass. Specifically, when a material to be rolled is rolled with a horizontal roll and a vertical roll installed immediately before the horizontal roll, the width of the material to be rolled is controlled by changing the target width of the material before width rolling with the vertical roll according to the rolling temperature of the material before rolling. This makes it possible to apply an appropriate edge load in each rolling pass. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-166018 Summary of the Invention [Problem to be solved by the invention]

[0007] The technology of Patent Document 1 makes it possible to change the target plate width value depending on the temperature (rolling temperature) of the material to be rolled. However, Patent Document 1 is intended for rolling using a rough rolling mill or the like, and there is a problem in that no measures are taken when the temperature is too low for width pressing. Therefore, the technology of Patent Document 1 cannot be applied to width pressing of a slab performed before rough rolling, which is the subject of the present invention.

[0008] Furthermore, if the slab temperature (slab surface temperature) after heating is in a low temperature range that is not suitable for width pressing, if the low-temperature extracted slab is directly introduced into the width pressing device and pressed down, the width pressing load will exceed the allowable load value of the width pressing device, leading to damage to the width pressing device. To prevent this, it is possible to reduce the width pressing load during width pressing by increasing the slab heating temperature to reduce the deformation resistance of the slab. However, extracting the slab by overheating also leads to a deterioration in the fuel consumption rate when the slab is heated.

[0009] On the other hand, even if the slab temperature after heating is within the temperature range where width pressing is possible, if the feed rate of the slab in the width pressing device is too large during large width reduction, the contact length between the width pressing die and the slab becomes long, resulting in a problem of a large width pressing load. Conversely, if the feed rate of the slab is too small, the contact length becomes short, resulting in a problem of the slab slipping.

[0010] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a width press device and a slab width press method that are capable of variably controlling the slab feed amount during width pressing of a slab before hot rolling and suppressing the application of excessive width press loads. [Means for solving the problem]

[0011] The present inventors have intensively studied width pressing technology that can prevent problems such as the above-mentioned damage to the width pressing device. They have focused on factors that cause the width pressing load generated when pressing a slab in width to exceed the allowable load of the width pressing device. They have also focused on the fact that even if the slab is heated to a temperature range in which width pressing is possible, the width pressing load may become excessive or the slab may slip during width pressing. As a result, they have found that these problems can be solved by appropriately controlling the contact length between the slab and the width pressing die in the width pressing device based on the slab temperature (slab surface temperature) after extraction from the heating furnace.

[0012] The present invention has been made based on these findings, and the gist of the present invention is as follows. [1] A width press device for width pressing a slab in a hot rolling line, comprising: The apparatus includes a thermometer, a width press machine for width pressing a slab, and a width press control unit for controlling the width press machine, The width press control section is a slab temperature measuring unit that measures the surface temperature of the slab after it is removed from the heating furnace using the thermometer disposed on the inlet side of the width press; A width press load calculation unit that calculates a width press load prediction value based on the measured slab surface temperature; A width press determination unit that determines whether or not the width press of the slab is possible depending on the calculated width press load prediction value; a contact length control unit that variably controls the contact length between the slab and the width press die of the width press machine by correcting the contact length with a slab feed correction value determined based on a table setting value in a process computer; a strain rate control unit that corrects a crank speed of the width press machine with the slab feed correction value and reduces the crank speed to control a strain rate during width press; a width press execution unit that executes width press of the slab based on the width press load prediction value; A width press device comprising: [2] In the width press determination unit, When it is determined that the width press load prediction value is equal to or less than an allowable load value of the width press machine, the width press execution unit performs width pressing of the slab; The width press device described in [1] is characterized in that when it is determined that the width press load prediction value exceeds the device allowable load value, correction is made by the contact length control unit, or by both the contact length control unit and the strain rate control unit, and then the width press of the slab is performed by the width press implementation unit. [3] A method for width pressing a slab in a hot rolling line, comprising: a slab temperature measuring step of measuring the surface temperature of the slab after removal from the heating furnace with a thermometer disposed on the inlet side of a width press; A width press load calculation step of calculating a width press load prediction value based on the measured slab surface temperature; A width press determination step of determining whether or not the width press of the slab can be performed based on the calculated width press load prediction value; A contact length control process for variably controlling the contact length between the slab and the width press die of the width press machine by correcting the contact length with a slab feed correction value determined based on a table setting value in a process computer; a strain rate control step of correcting a crank speed of the width press machine with the slab feed correction value to reduce the crank speed, thereby controlling the strain rate during width press; A width press performing step of performing a width press of the slab based on the width press load prediction value; A method for width pressing a slab, comprising the steps of: [4] In the width pressing judgment step, When it is determined that the width press load prediction value is equal to or less than the device allowable load value of the width press machine, the width press of the slab is performed by the width press performing step; The slab width pressing method described in [3], characterized in that when it is determined that the width press load prediction value exceeds the device allowable load value, correction is made by the contact length control process, or by both the contact length control process and the strain rate control process, and then the slab width is pressed by the width press implementation process. Effect of the Invention

[0013] According to the present invention, it is possible to provide a width press device and a method for width pressing a slab, which are capable of variably controlling the slab feed rate and suppressing the application of an excessive width press load during width pressing of a slab before hot rolling. This makes it possible to perform appropriate width pressing without exceeding the allowable load of the width press device, and also makes it possible to prevent damage to the width press device. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a hot rolling line to which a width press device according to an embodiment of the present invention is applied. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration of a width press device according to one embodiment of the present invention. [Diagram 3] FIG. 3 is a flow chart illustrating a method for width pressing a slab according to an embodiment of the present invention. [Figure 4] FIG. 4 is a graph showing the difference between the calculated extraction temperature (calculated SRT) of the slab and the actually measured temperature. [Diagram 5] FIG. 5 is a graph showing the relationship between the width press amount and the width press load for each slab feed amount. [Figure 6] FIG. 6 is a graph of FEM (finite element method) data showing the variation of width press load with time due to crank speed. [Figure 7] FIG. 7 is a graph showing steady-state average width press load versus crank speed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The width pressing device and the width pressing method of the present invention will be described below, although the present invention is not limited to this embodiment.

[0016] First, the width press device of the present invention will be described with reference to Figures 1 and 2. Here, as an example, the width press device of the present invention is applied to a hot rolling line in the manufacture of hot-rolled steel sheets.

[0017] Fig. 1 is a side view illustrating a configuration example of a hot rolling line 10 to which a width press device 3 of the present invention is applied. Fig. 2 is a diagram illustrating the configuration of the width press device 3 shown in Fig. 1. The thick arrows shown in Figs. 1 and 2 indicate the transport direction of slabs, etc.

[0018] The hot rolling line 10 shown in Fig. 1 includes, in order from the upstream side in the conveying direction of the slab S, a heating furnace 1, an HSB (Hydro Scale Breaker) device 2, a width press device 3, a roughing mill 5, a finishing mill 6, a run-out table 7, a water cooling device 8, and a coiler 9. These are controlled by respective control devices (not shown). These control devices control the operation of each piece of equipment according to commands from a process computer (not shown) that manages the operation of the hot rolling line.

[0019] As shown in FIG. 1, in a hot rolling line 10, after a slab S is heated in a heating furnace 1, scale formed on the surface of the slab S is removed by an HSB device 2, and then the slab S is width-pressed by a width press device 3. The width-pressed slab (rolled material) (see symbol S' in FIG. 1) is rolled (roughly rolled) to a predetermined thickness by a roughing mill 5, and then rolled (finish rolling) to a desired thickness (product thickness) by a finishing mill 6. The rolled material after the finish rolling is water-cooled by a water-cooling device 8 while passing through a run-out table 7, and then wound into a coil by a coiler 9. Although not shown, the coiled rolled material (hot-rolled steel strip in the example shown in FIG. 1) is cooled to room temperature in a coil yard.

[0020] In the manufacture of steel products, as described above, in order to accommodate various product widths, the slab width is changed to match various product widths by width pressing in the hot rolling process after casting. A typical hot rolling line includes, for example, a hot rolling line in which a heating furnace, a thermometer, an HSB device, a width press device, a rough rolling mill, and the like are arranged in this order from the upstream side in the slab transport direction. When width pressing of a slab is performed in this typical hot rolling line, there is a risk that the width press load when width pressing the slab exceeds the allowable load of the width press device. The present inventors consider the reason as follows.

[0021] In this general hot rolling line, the slab temperature (slab surface temperature) used during width pressing is the calculated extraction temperature (hereinafter referred to as the "calculated SRT"). The calculated SRT is a temperature calculated based on the heating pattern and material furnace time in the heating furnace. In other words, the calculated SRT and the actual slab temperature may deviate. Furthermore, the temperature of the slab may be further lower than the calculated SRT due to contact between the slab and air during transportation from the time the slab is extracted from the heating furnace until it is width pressed, and due to the injection of high-pressure water, etc. in the HSB device for removing scale. In that case, the deformation resistance of the slab increases.

[0022] If the width press load generated during width pressing exceeds the allowable load of the width press device, the width press device may be damaged. In order to reduce the deformation resistance of the slab, it is possible to solve the problem by increasing the slab heating temperature in the heating furnace, but this is not preferable because there is a concern that the fuel cost for heating the slab may increase.

[0023] In addition, overheating of the slab can cause sagging of the slab, which can result in deterioration of the product shape and a corresponding decrease in product yield. For this reason, it is not desirable to heat the slab to a temperature higher than that specified for the steel type.

[0024] On the other hand, even if the surface temperature of the slab after heating is within the temperature range where width pressing is possible, if the slab feed rate is too large compared to the amount of reduction in width pressing, the contact length between the width pressing die and the slab will be long. If this causes the width pressing load to increase, there is a risk of equipment damage as described above. On the other hand, if the slab feed rate is too small, the contact length will be short, but there is a risk of the slab slipping or the slab not being able to be reduced with an appropriate width pressing load.

[0025] Therefore, the inventors of the present invention focused on the temperature (slab surface temperature) used during width pressing. This will be explained with reference to FIG.

[0026] In general, the temperature of the slab after extraction from the heating furnace is measured to predict the reduction amount and press load value in the width press device. However, when the temperature is measured around the exit side of the heating furnace, the deformation resistance during width press cannot be correctly grasped. Therefore, the inventors found that there is an appropriate temperature measurement position and conducted various studies. As a result, they found that by installing a thermometer on the entry side of the press device to measure the temperature, the surface temperature of the slab just before width press can be measured, and this makes it possible to predict the deformation resistance more accurately than before.

[0027] Figure 4 shows a graph showing the difference between the calculated SRT and the actually measured temperature of a slab. In Figure 4, the vertical axis shows temperature (°C) and the horizontal axis shows the N number. As an example, a low-carbon steel slab was heated in a heating furnace, and the surface temperature of the slab was measured at a position just before width pressing. The measured value is shown as the temperature measurement result in Figure 4. The N number was 5. As shown in Figure 4, there is a difference between the calculated SRT and the actually measured temperature at a position after removal from the heating furnace and just before width pressing, but the amount of change in temperature was measured in the same way. This shows that measurement using a dual-wavelength pyrometer at a position just before width pressing is useful.

[0028] As described above, even if the slab is heated to a temperature range where width pressing is possible, it may be difficult to reduce the width pressing load and prevent the slab from slipping. The present inventors further focused on the relationship between the reduction amount in width pressing (width pressing amount), the width pressing load, and the slab feed amount. This will be explained with reference to FIG. 5.

[0029] Here, as in Fig. 4, low carbon steel slabs were used as the target for width pressing under various conditions. Fig. 5 plots the relationship between the width pressing amount and the width pressing load for each slab feed amount during width pressing. In Fig. 5, the vertical axis is the width pressing load (kN), and the horizontal axis is the width pressing amount (mm). The width pressing load is the value of the load cell sum load. The width pressing amount was measured as "slab width - cold dimension width of coil (width after cooling of coil)". As shown in Fig. 5, by reducing the slab feed amount from 386 mm to 330 mm, the width pressing load at a width pressing amount of 250 mm was reduced by 10% from 20000 kN to 18000 kN. In this way, it was found that by setting an appropriate slab feed amount, the width pressing load can be reduced and the risk of damage to the width pressing device can be reduced.

[0030] Next, the width press device 3 of the present invention, which has been made based on the above findings, will be described in detail. FIG 2 shows a part of the hot rolling line 10 shown in FIG .

[0031] The width press device 3 of the present invention is a device that reduces (width reduces) the slab S transported along the transport path of the hot rolling line 10 shown in Fig. 1. The width press device 3 is disposed on the outlet side of the HSB device 2 disposed downstream of the heating furnace 1 and on the inlet side of the roughing mill 5. As shown in Fig. 2, the width press device 3 of the present invention includes a thermometer 3a, a width press machine 3b, and a width press control unit 4.

[0032] The thermometer 3a measures the surface temperature of the slab after it is removed from the heating furnace at the inlet side of the width press machine 3b. The measurement point of the slab S is preferably the center position of the width of the slab. Examples of the thermometer 3a include a radiation thermometer and a two-wavelength thermometer. In the present invention, the thermometer 3a is preferably a two-wavelength thermometer. With the two-wavelength thermometer, the temperature of the slab is derived using the relationship between the radiant light emitted from the slab and the absolute temperature.

[0033] When the slab is left in the furnace for a long time, scale may form on the surface of the slab, and after the slab is removed from the heating furnace, the atmosphere near the slab surface may be steam, water may ride on the slab surface, etc., making it difficult to accurately measure the temperature. For these reasons, in the present invention, it is preferable to use a two-wavelength thermometer using two short wavelengths that are not absorbed by water films as the thermometer 3a.

[0034] As explained in FIG. 4 above, in order to take into consideration the difference between the calculated SRT and the actual temperature and to calculate the width press load more accurately, the thermometer 3a is placed on the exit side of the HSB device 2 and on the entry side of the width press machine 3b. For example, the thermometer 3a is preferably placed on the conveying path and in a position that can cover the entire slab length toward the HSB device 2 side with the entry side of the width press machine 3b as the reference point. More preferably, the thermometer 3a is placed in an area within 5 to 10 m from the entry side of the width press machine 3b toward the HSB device 2 side. In addition, the thermometer 3a is preferably placed above the surface of the slab S.

[0035] Although not shown, the width press machine 3b has a pair of width press dies installed facing each other in the plate width direction, and a die drive unit that controls the operation of the width press dies. The die drive unit causes the pair of width press dies to reciprocate symmetrically in the slab width direction. This reciprocating motion is controlled based on a width press amount (reduction amount) that is determined according to the final product width of the slab that is the subject of width pressing. The width press amount of the width press machine 3b is calculated by a width press control unit 4 that will be described later. The control of the die drive unit is managed by the width press control unit 4.

[0036] The width press control unit 4 has a slab temperature measurement unit 4a, a width press load calculation unit 4b, a width press judgment unit 4c, a contact length control unit 4d, a strain rate control unit 4e, and a width press execution unit 4f. The width press control unit 4 uses the slab temperature measurement unit 4a, the width press load calculation unit 4b, the width press judgment unit 4c, the contact length control unit 4d, the strain rate control unit 4e, and the width press execution unit 4f to obtain an appropriate width press load value, and an appropriate contact length and crank speed between the slab S and the width press die as necessary, and controls the operation of the width press machine 3b based on the obtained appropriate width press conditions. The control of the width press control unit 4 is managed by a process computer.

[0037] The slab temperature measuring unit 4a measures the surface temperature of the slab after it is removed from the heating furnace at the inlet side of the width press machine 3b using the thermometer 3a disposed on the inlet side of the width press device. The measured slab surface temperature data is passed by the width press control unit 4 to the subsequent width press load calculation unit 4b and contact length control unit 4d.

[0038] The width press load calculation unit 4b calculates the value of the width press load (predicted width press load value) based on the slab surface temperature measured by the slab temperature measurement unit 4a. The calculated predicted width press load value is passed to the subsequent width press determination unit 4b by the width press control unit 4.

[0039] The width press determination unit 4c determines whether or not the width press of the slab is possible, depending on the width press load prediction value calculated by the width press load calculation unit 4b. Specifically, the calculated width press load prediction value is compared with a set allowable value (equipment allowable load value) set in the equipment of the width press machine 3b, and a determination is made as to whether or not the width press is to be stopped or performed (i.e., whether or not the width press is possible). This equipment allowable load value is a set threshold value.

[0040] The contact length control unit 4d is a processing unit that is performed as necessary. The contact length control unit 4d controls the contact length between the slab and the width press die of the width press machine 3b. The contact length control unit 4d adjusts the length of the contact length so that the width press load prediction value does not become an excessive load with respect to the device allowable load value of the width press machine 3b and so that the slab does not slip. Specifically, the contact length control unit 4d variably controls the contact length by correcting the contact length with a slab feed amount value (slab feed amount correction value) determined based on a table setting value (slab feed amount setting value set based on the slab temperature) in a pre-set process computer.

[0041] Here, the "slab feed amount" refers to the distance that the slab is advanced in the line advance direction (transport direction) when the slab is width-pressed once by the width press die.

[0042] The strain rate control unit 4e is also a processing unit that is performed as needed. The strain rate control unit 4e corrects the crank speed of the width press machine 3b with the slab feed correction value determined by the contact length control unit 4d, and controls the crank speed to be reduced, thereby reducing the strain rate during width pressing.

[0043] The width press execution section 4f executes width press of the slab based on the obtained appropriate width press load predicted value.

[0044] If the width press determination unit 4c determines that the width press load prediction value is equal to or less than the device allowable load value (width press possible), the width press of the slab is performed by the width press implementation unit 4f. On the other hand, if the width press load prediction value is determined to be greater than the device allowable load value (width press impossible), correction is performed by the contact length control unit 4d, or by the contact length control unit 4d and the strain rate control unit 4e. After that, if it is determined again by the width press possibility judgment that the width press is possible, the width press of the slab is performed by the width press implementation unit 4c.

[0045] As described above, even if the slab is heated to a temperature range where width pressing is possible, it may be difficult to reduce the width press load or prevent the slab from slipping. In such cases, the contact length control 4d and the strain rate control unit 4e can be used to correct the slab feed rate and crank speed to an appropriate level to reduce the width press load, thereby reducing the risk of damage to the width press device.

[0046] In the present invention, it is important that the width press control unit 4 having the above-mentioned processing units judges whether to perform or stop the width press, and based on the judgment result, the feed rate of the slab S is appropriately adjusted so that the width press load prediction value in the width press machine 3b does not exceed the device allowable load value, thereby controlling the contact length between the slab and the width press die. Note that the specific processing by the width press control unit 4 will be described later with reference to FIG. 3, so it will not be described here.

[0047] When it is determined that width pressing can be performed in the width press device 3 of the present invention having the above-mentioned configuration, the die drive unit operates a pair of width press dies facing each other in the plate width direction based on the width press load, slab feed amount (i.e., contact length), and crank speed determined by the width press control unit 4, thereby intermittently pressing down the slab S in the plate width direction.

[0048] Next, the width pressing method for a slab of the present invention will be described with reference to Fig. 3. Fig. 3 shows a flow chart for explaining an example of the width pressing method for a slab of the present invention.

[0049] The slab width pressing method of the present invention is applicable to the width pressing device 3 (see FIG. 2) of the present invention having the above-mentioned configuration. Here, as an example, the present invention is applied to a hot rolling line in the manufacture of hot-rolled steel sheets. Therefore, the contents overlapping with the description of the width pressing device 3 will be omitted.

[0050] In the width pressing method for a slab according to the present invention, the width pressing control unit 4 in the width pressing device 3 shown in Fig. 2 sequentially executes each process (processing of steps s1 to s6) described below. Step s1 is started when the slab S enters the measurement range of the thermometer 3a of the width pressing device 3 after the slab S is extracted from the heating furnace 1 and then descaled in the HSB device 2.

[0051] (Step s1) As shown in FIG. 3, first, in step s1, the slab temperature measuring unit 4a measures the slab surface temperature of the slab S after being removed from the heating furnace using a thermometer 3a arranged on the exit side of the HSB device 2 and the entry side of the width press machine 3b shown in FIG. 2 (slab temperature measurement process).

[0052] For example, the temperature of the slab surface at the width center position is measured by a two-wavelength thermometer at the inlet side of the width press machine 3b. The slab temperature measurement unit 4a sends the measured slab surface temperature (measured slab surface temperature value) to the width press load calculation unit 4b and the contact length control unit 4d.

[0053] (Step s2) After processing of step s1, in step s2, the width press load calculation unit 4b calculates a predicted value of the width press load that will occur when width pressing (width reducing) the slab S based on the slab surface temperature measurement value measured in step s1 (width press load calculation process).

[0054] For example, the predicted width press load is calculated based on the slab surface temperature measured with a two-wavelength thermometer, using geometric conditions such as the width press die and slab thickness, as well as the deformation resistance of the slab and the press force function. The predicted width press load can be calculated using a process computer. Here, "geometric conditions" refers to the plate thickness and die shape.

[0055] Specifically, the width press load prediction value is calculated using the following model formula. P PR =K m Q p L dP '·H s / 1000 …(1) Here, P in formula (1) PR :Press load prediction value [kN], K m : Average press deformation resistance [MPa], Q p : Press force function, L dP ': Press contact arc length' [mm], H s : Slab thickness [mm].

[0056] The width press load calculation unit 4b sends the calculated width press load prediction value to the width press determination unit 4c.

[0057] (Step s3) After the process of step s2, in step s3, the width press determination unit 4c determines whether or not the width press of the slab S is possible, depending on the width press load prediction value calculated in step s2 (width press determination step).

[0058] Specifically, it is determined whether the width press load prediction value is equal to or less than the device allowable load value of the width press machine 3b. The device allowable load value is an allowable load value determined by the performance of the width press machine 3b. For example, the device allowable load value of the width press machine 3b can be preset in a table that stores data held by the width press control unit 4.

[0059] Here, if the result of the determination in step s3 is "width pressing possible" (if the process proceeds to the arrow below step s3 shown in FIG. 3), the process in step s6 described below is performed. Note that "if the result of the determination in step s3 is "width pressing possible"" refers to the case where it is determined that the width pressing load prediction value is equal to or less than the device allowable load value of the width pressing machine.

[0060] On the other hand, if the result of the determination in step s3 is "width pressing not possible" (proceeding to the arrow on the right side of step s3 in FIG. 3), continuing width pressing may lead to damage to the press machine 3b. Therefore, by carrying out the process in step s4 described later, the press load is reduced by changing the slab feed amount, and the contact length between the width press die and the slab is shortened to further reduce the press load.

[0061] (Step s4) In step s4, the contact length control unit 4d variably controls the contact length between the slab and the width press die by correcting the contact length with a slab feed amount correction value determined based on a table setting value (slab feed amount setting value) in the process computer (contact length control process).

[0062] Specifically, the contact length control unit 4d determines an appropriate contact length value (contact length correction value) between the slab S and the width press die in the width press machine 3b by adjusting (correcting) the slab feed amount of the slab S so that the predicted width press load value does not exceed the allowable load value of the width press machine 3b (i.e., so as to prevent excessive load).

[0063] If the slab feed amount is large, the contact length between the width press die and the slab becomes long, and the width press load becomes large. On the other hand, if the slab feed amount is small, the contact length between the width press die and the slab becomes short, resulting in point contact, which causes the slab to slip and cause hot rolling troubles. Therefore, it is necessary to set in advance the range of the slab feed amount that will result in surface contact for each width press die. In addition, the slab feed amount differs depending on the steel type, composition, and slab temperature of the slab. For these reasons, it is preferable to set the set value of the slab feed amount for each steel type measured in advance (slab feed amount set value) in advance in the table set value in the process computer.

[0064] Thereafter, the contact length control unit 4d corrects the width press load prediction value based on the determined contact length correction value.

[0065] (Step s41) After step s4, the contact length control unit 4d performs a width pressing possibility determination (step s41). If it is determined in step s41 that "width pressing is possible," the process of step s6 described below is performed, whereas if it is determined that "width pressing is not possible," the process of step s5 described below is further performed. Here, the "width pressing possibility determination" in step s41 is the same determination process as in step s3 described above, that is, a process of determining whether the corrected width pressing load prediction value is equal to or smaller than the device allowable load value.

[0066] The contact length control unit 4 d sends the contact length correction value and the corrected width press load prediction value to the width press control unit 4 .

[0067] (Step s5) In step s5, the strain rate control unit 4e corrects the crank speed of the width press machine 3b with the slab feed correction value, and reduces the crank speed, thereby controlling to reduce the strain rate during width pressing (strain rate control step). The strain rate can be controlled by changing the crank speed.

[0068] Specifically, the strain rate control unit 4e determines an appropriate crank speed value (crank speed correction value) for the width press die of the width press machine 3b so that the width press load predicted value does not exceed the device allowable load value of the width press machine 3b.

[0069] Even after the process of step s4 is performed, if the determination in step s41 is still "width pressing impossible," the strain rate control unit 4e performs the process of step s5 to reduce the strain rate during width pressing of the slab. This reduces the deformation resistance of the slab during width pressing, thereby making it possible to reduce the width pressing load. As a result, the equipment load can be reduced even in the case of large reduction in rolling.

[0070] Thereafter, the strain rate control unit 4e corrects the width press load prediction value based on the determined crank speed correction value.

[0071] Specifically, the reduction in the crank speed in the strain rate control process is determined by correcting the crank speed correction value determined based on the crank speed setting value so that the width press load prediction value does not exceed the upper limit.

[0072] (Steps s51 and s52) After step s5, the strain rate control unit 4e performs a width pressing feasibility determination (step s51). If it is determined in step s51 that "width pressing is possible," the process of step s6 described below is performed. On the other hand, if it is determined that "width pressing is not possible," the process of step s52 described below is further performed. Here, the "width pressing feasibility determination" in step s51 is the same determination process as in step s3 described above, that is, a process of determining whether the corrected width pressing load prediction value is equal to or less than the device allowable load value. The strain rate control unit 4e sends the corrected crank speed value and the corrected width press load predicted value to the width press control unit 4.

[0073] On the other hand, if it is determined in step s51 that "width pressing is not possible" even after the process in step s5 is performed, the process in step s52 is performed. In the process in step s52, the width pressing is stopped by returning the slab S.

[0074] For example, when it is determined in step s51 that the width pressing load exceeds the allowable load value of the equipment due to the low surface temperature of the slab resulting from low extraction temperature of the slab, the slab is returned before the width pressing and the width pressing is stopped. This makes it possible to prevent a large reduction in the width of a slab with a low extraction temperature, which is one of the causes of equipment trouble.

[0075] (Step s6) When it is determined in any one of steps s3, s41, and s51 that "width pressing is possible," step s6 is carried out.

[0076] In step s6, the width press of the slab S is performed based on the width press load prediction value (including the corrected width press load prediction value) determined by the width press control unit 4 (width press process). If necessary, when step s4 or both step s4 and step s5 are performed, the width press of the slab S is performed under width press conditions controlled based on the width press load prediction value, the contact length correction value obtained in the contact length control process, and the crank speed correction value obtained in the strain rate control process.

[0077] As described above, according to the present invention, after the slab is extracted from the heating furnace, the temperature of the slab surface is measured by a thermometer installed on the inlet side of the width press machine, the width press load is calculated based on the measured slab surface temperature, and the calculated width press load value is used to determine whether or not the slab can be pressed. If it is determined that the width press is impossible, the slab feed amount is adjusted so as not to exceed the load allowable value for equipment damage, and the contact length between the slab and the width press die is controlled. If the width press load allowable value is exceeded by adjusting the slab feed amount alone, the strain rate is further reduced by reducing the crank speed to reduce the width press load. Width pressing can be performed based on the controlled contact length and crank speed.

[0078] That is, by appropriately controlling the width press load, the slab feed amount can be changed so that the width press load does not exceed the allowable load value of the device even when performing width press, which makes it possible to prevent damage to the width press device. Since the slab feed amount can be variably controlled, it is also possible to prevent the slab from slipping and causing hot rolling trouble.

[0079] In addition, in the past, the press load was predicted based on the extraction temperature at the exit of the heating furnace, so the heating temperature of the slab was set too high to reduce the deformation resistance of the slab, taking into account the error in the load prediction during width pressing. However, according to the present invention, it is possible to obtain an accurate prediction value of the width press load by accurately measuring the slab surface temperature at the entry side of the width press machine. This makes it possible to prevent a large reduction in the width of a low extraction temperature slab, and also reduces the fuel consumption. EXAMPLES

[0080] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0081] In this embodiment, the width press device 3 of the present invention shown in Fig. 2 was installed in the hot rolling line 10 shown in Fig. 1, and the width press of the slab was performed. The width press method of the slab of the present invention was applied to the width press device 3, and the above-mentioned processes (steps s1 to s6) were performed in sequence. The number of N was 2910.

[0082] Specifically, the temperature of the slab is measured with a two-wavelength thermometer at the press entry side, and the press load for each steel type is calculated using the measured temperature by a process computer to determine whether or not the slab can enter the width press machine.

[0083] First, the relationship between the width reduction amount and width reduction load for each press feed amount was verified using the results measured during width pressing (actual values ​​of width press load and width press amount). Note that the conditions are the same as those explained in Figure 5 above, so they are omitted. The results are shown in Figure 5. Figure 5 plots the relationship between the width press amount and width press load for each slab feed amount. The width press load was the sum of the load cell loads. The press amount was measured as "slab width - cold coil width".

[0084] As shown in Fig. 5, by reducing the press feed amount from 386 mm to 330 mm, the width reduction load at a width press amount of 250 mm was reduced by 10%. In this way, it was found that by setting an appropriate feed amount, the load can be reduced and the risk of equipment damage can be reduced.

[0085] Next, the change in width press load over time due to the crank speed was examined. Here, the FEM analysis was performed under the conditions of width: 1200 mm, width press amount: 350 mm. The results are shown in Figures 6 and 7.

[0086] The graph in Figure 6 shows FEM data indicating the relationship between the width press load and the crank speed. In Figure 6, the vertical axis is the width press load (tf) and the horizontal axis is time (s). The graph in Figure 7 shows the steady-state average width reduction load for each crank speed. In Figure 7, the vertical axis is the width press load (tf) and the horizontal axis is the crank speed (rpm).

[0087] It was found that the load decreased by reducing the crank speed, as shown in Fig. 6. In addition, it was found that the average width press load in the steady part of the slab could be reduced by 11% by halving the crank speed, as shown in Fig. 7. [Explanation of symbols]

[0088] 1 Furnace 2 HSB device 3 Width press device 3a thermometer 3b Width press machine 4 Width press control section 5 Roughing mill 6 Finishing rolling mill 7 Runout Table 8 Water cooling device 9. Coiler 10. Hot Rolling Line S slab S´ Slab (rolled material) that has been width-reduced

Claims

1. A width press device for width pressing a slab in a hot rolling line, comprising: The apparatus includes a thermometer, a width press machine for width pressing a slab, and a width press control unit for controlling the width press machine, The width press control section is a slab temperature measuring unit that measures the surface temperature of the slab after it is removed from the heating furnace using the thermometer disposed on the inlet side of the width press; A width press load calculation unit that calculates a width press load prediction value based on the measured slab surface temperature; A width press determination unit that determines whether or not the width press of the slab is possible depending on the calculated width press load prediction value; a contact length control unit that variably controls the contact length between the slab and the width press die of the width press machine by correcting the contact length with a slab feed correction value determined based on a table setting value in a process computer; a strain rate control unit that corrects a crank speed of the width press machine with the slab feed correction value and reduces the crank speed to control a strain rate during width press; a width press execution unit that executes width press of the slab based on the width press load prediction value; A width press device comprising:

2. In the width pressing determination unit, When it is determined that the width press load prediction value is equal to or less than an allowable load value of the width press machine, the width press execution unit performs width pressing of the slab; 2. The width press device according to claim 1, characterized in that, when it is determined that the width press load prediction value exceeds the device allowable load value, a correction is made by the contact length control unit, or by both the contact length control unit and the strain rate control unit, and then the width press of the slab is performed by the width press implementation unit.

3. A method for width pressing a slab in a hot rolling line, comprising: a slab temperature measuring step of measuring the surface temperature of the slab after removal from the heating furnace with a thermometer disposed on the inlet side of a width press; A width press load calculation step of calculating a width press load prediction value based on the measured slab surface temperature; A width press determination step of determining whether or not the width press of the slab can be performed based on the calculated width press load prediction value; A contact length control process for variably controlling the contact length between the slab and the width press die of the width press machine by correcting the contact length with a slab feed correction value determined based on a table setting value in a process computer; a strain rate control step of correcting a crank speed of the width press machine with the slab feed correction value to reduce the crank speed, thereby controlling the strain rate during width press; A width press performing step of performing a width press of the slab based on the width press load prediction value; A method for width pressing a slab, comprising the steps of:

4. In the width pressing determination step, When it is determined that the width press load prediction value is equal to or less than the device allowable load value of the width press machine, the width press of the slab is performed by the width press performing step; 4. A method for width pressing a slab as described in claim 3, characterized in that, when it is determined that the width press load prediction value exceeds the device allowable load value, correction is performed by the contact length control process, or by both the contact length control process and the strain rate control process, and then width pressing of the slab is performed by the width press implementation process.

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