WO2024042601A1

WO2024042601A1 - Hot rolling mill plate thickness control device

Info

Publication number: WO2024042601A1
Application number: PCT/JP2022/031680
Authority: WO
Inventors: 稔橘
Original assignee: 東芝三菱電機産業システム株式会社
Priority date: 2022-08-23
Filing date: 2022-08-23
Publication date: 2024-02-29

Abstract

The present disclosure provides a hot rolling mill plate thickness control device capable of reliably threading a tip end portion of material being rolled, without increasing equipment costs, even if the material being rolled is being rolled to be extremely thin. The hot rolling mill plate thickness control device comprises: a plate thickness gauge installed on an exit side of a final rolling stand in a row-arrangement direction; a gap calculating unit for calculating a gap between rolls of each rolling stand, said gap being greater than a product target plate thickness of the material being rolled and corresponding to a threadable plate thickness with which the tip end portion of the material being rolled can be stably threaded; a gap setting unit for setting the gap calculated by the gap calculating unit for each rolling stand; an automatic plate thickness control unit for executing automatic plate thickness control to minimize a plate-thickness deviation between a plate thickness measured value from the plate thickness gauge and the threadable plate thickness; and a target plate thickness changing unit for changing the threadable plate thickness to the product target plate thickness by adding a plate-thickness bias to the plate-thickness deviation with a predetermined ramp rate, after the tip end portion of the material being rolled has been threaded through the final rolling stand.

Description

Plate thickness control device for hot rolling mill

The present disclosure relates to a plate thickness control device for a hot rolling mill in which a plurality of rolling stands are arranged in parallel and a material to be rolled, such as a heated steel plate, is sequentially rolled by the plurality of rolling stands, and in particular, the present disclosure relates to a plate thickness control device for a hot rolling mill in which a plurality of rolling stands are arranged in parallel and a material to be rolled, such as a heated steel plate, is sequentially rolled by the plurality of rolling stands. The present invention relates to a product suitable for manufacturing ultra-thin hot-rolled steel strips having a thickness of 1.0 mm or less.

Generally, hot-rolled steel strip is produced by heating a slab, which is the material to be rolled, to a predetermined temperature in a heating furnace, and then rough-rolling the heated slab to a thickness of about 30 mm in a rough rolling mill to obtain a rough bar. The rough bar is rolled into a hot-rolled steel strip with a predetermined thickness by, for example, a finishing mill with seven rolling stands installed in parallel, and this hot-rolled steel strip is cooled on a run-out table and then rolled. It is manufactured by winding it with a coiler.

The reduction in finishing temperature at the tip of the hot-rolled steel strip increases as the thickness of the hot-rolled steel strip becomes thinner. For this reason, the thinner the hot-rolled steel strip is, the more difficult it is to ensure the finishing temperature at the tip, and furthermore, since the rolling speed is high, there is a problem in that it is difficult to thread the tip. In order to solve this problem, in the conventional method, a plurality of rough bars are connected to each other, and the connected bars are passed through a finishing mill at high speed, thereby making finishing rolling continuous. However, this method requires installation of a joining device such as a welding device, which increases equipment costs.

In the method disclosed in Patent Document 1 below, in order to improve the dimensional accuracy of plate profile, plate shape, plate width, plate thickness, etc., the thickness of the rough bar is set to less than 20 mm, and a rough rolling mill and a finishing rolling mill are used. By installing a coil box or online heating device between the bar and the bar, the temperature drop in the rough bar is compensated for. However, the method of Patent Document 1 focuses on improving the precision of product dimensions, and it is important to ensure the finishing temperature of the tip of the steel strip, especially the temperature at the entry side of the finishing mill, and especially to prevent scale surface defects. No consideration has been given to countermeasures for the surface properties of the product. Furthermore, if the thickness of the rough bar is less than 20 mm, the temperature drop during the rough rolling process will be significantly large, and in order to compensate for this temperature drop, it is necessary to install an extremely high-output online heating device as described above. Equipment costs will rise.

In addition, increasing the thickness of the rough bar is effective when the product plate thickness is thick because it can secure the finishing temperature, but when the product plate thickness is thin, the load and power of the finishing mill etc. This is difficult to realize due to constraints on the rolling schedule.

In addition, in the method disclosed in Patent Document 2 below, the thickness of the rough bar is within the range of 20 to 30 mm, and the rough bar is heated using an online heating device installed at the entrance side of a finishing mill. The bar is heated so that the finishing input temperature falls within the range of 1000 to 1150°C, and the rough bar heated to this temperature is finished rolled. However, even with the method of Patent Document 2, it is necessary to install an online heating device, which increases the equipment cost.

Japanese Patent Publication No. 2-165802 Japanese Patent Publication No. 9-300004

In this way, the shape of the tip of the rolled material deteriorates due to the temperature drop, and since the material is rolled at high speed, the tip of the rolled material is warped or meandered, making it difficult to thread the tip of the rolled material. difficult. In order to suppress the temperature drop at the tip, the above-mentioned prior art proposes a rolling schedule in which the plate thickness is increased on the outlet side of the roughing mill, and the installation of a heating device on the inlet side of the finishing mill to prevent the temperature of the rolled material from dropping. However, there are limitations such as equipment cost and rolling schedule.

The present disclosure has been made in order to solve the above-mentioned problems, and even when rolling the material to be extremely thin, it is possible to reliably pass the tip of the material to be rolled without increasing the equipment cost. An object of the present invention is to provide a plate thickness control device for a hot rolling mill that can control the thickness of a hot rolling mill.

The first aspect relates to a plate thickness control device for a hot rolling mill in which a plurality of rolling stands are arranged in parallel and a heated material to be rolled is sequentially rolled by the plurality of rolling stands. The plate thickness control device is installed on the exit side of the final rolling stand in the side-by-side direction, and includes a plate thickness gauge that measures the thickness of the rolled material and a plate thickness that is larger than the product target thickness of the rolled material. A gap calculation unit that calculates the gap between the rolls of each rolling stand corresponding to the thickness of the plate that can stably pass the tip of the sheet, and sets the gap calculated by the gap calculation unit to each rolling stand. A gap setting section, an automatic thickness control section that performs automatic thickness control to minimize the deviation between the thickness measured by the thickness gauge and the passable thickness, and After the tip of the plate is threaded, a target plate thickness changing unit is provided that changes the passable plate thickness to the product target plate thickness by adding a plate thickness bias to the plate thickness deviation at a predetermined ramp rate.

In addition to the first aspect, the second aspect further has the following characteristics. The target thickness change section adds a thickness bias at a predetermined ramp rate to the thickness deviation before the tail end of the rolled material is passed through the first rolling stand in the parallel direction. It is configured to change the target plate thickness to a plate thickness that allows the plate to pass through.

According to the first viewpoint, even when rolling the material to be rolled extremely thin, by setting the gap to correspond to the thickness of the material that can be passed through, the tip of the material to be rolled can be reliably passed through the hot rolling mill. It can be made into a board. Therefore, unlike the prior art, there is no need to install a heating device on the inlet side of the hot rolling mill, and an increase in equipment costs can be prevented. Furthermore, after the tip of the rolled material is passed through the final rolling stand, a thickness bias is added to the thickness deviation between the measured thickness value and the passable thickness. By executing automatic plate thickness control using the plate thickness deviation, the portion of the material to be rolled after the tip end is rolled to an ultra-thin product target thickness. Moreover, since the plate thickness bias is gradually added to the plate thickness deviation, the passable plate thickness is gradually changed to the product target plate thickness. Thereby, the material to be rolled can be stably rolled into an extremely thin material.

According to the second viewpoint, prior to rolling the tail end of the material to be rolled, the product target thickness is changed to a passable thickness. That is, automatic plate thickness control is performed for the tail end of the material to be rolled using the plate thickness deviation between the plate thickness measurement value and the passable plate thickness. This makes it possible to suppress the occurrence of tail end meandering and tail end squeezing of the rolled material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining the configuration of a rolling plant including a plate thickness control device for a hot rolling mill according to an embodiment. FIG. 2 is a block diagram for explaining the configuration of main parts of the plate thickness control device. It is a diagram showing an example of the hardware configuration of a process computer included in a rolling plant. It is a timing chart for explaining the flow of plate thickness control using the plate thickness control device. It is a flow chart for explaining the flow of plate thickness control using a plate thickness control device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that common elements in each figure are given the same reference numerals and redundant explanations will be omitted.

FIG. 1 is a schematic diagram showing the configuration of a rolling plant 1 equipped with a plate thickness control device for a hot rolling mill according to an embodiment. The rolling plant 1 uses steel or other metal materials as a material to be rolled M, and hot-rolls the material to be rolled into a plate shape.

The rolling plant 1 is equipped with a heating furnace 2, a rough rolling mill 3, a crop shear 4, a finishing mill 5 as a hot rolling mill, a cooling device 6, and a winding machine 7. In the present embodiment, a case will be described as an example in which the plate thickness at the outlet side of the finishing rolling mill 5 as a hot rolling mill is controlled to an extremely thin (for example, 1.0 mm or less) product target plate thickness.

The heating furnace 2 is configured to heat a slab as the material to be rolled M to a predetermined temperature. The rough rolling mill 3 has at least one rolling stand and is configured to roll the material M to be rolled heated in the heating furnace 2 .

The crop shear 4 is configured to use upper and lower blades to cut a shape-defective portion at the tail end of the rolled material M based on the shape measured by a shape detector 81, which will be described later.

The finishing rolling mill 5 is a tandem rolling mill equipped with a plurality of rolling stands Fi (1≦i≦N) arranged in parallel in the conveying direction of the material M to be rolled. In this embodiment, an example will be explained in which seven rolling stands F1 to F7 are arranged in parallel. Each of the rolling stands F1 to F7 includes two upper and lower work rolls 51, two upper and lower backup rolls 52, and an electric motor 53 for rotating the rolls. The backup roll 52 is provided with a rolling down device 54, and is configured such that the gap between the upper and lower work rolls 51 can be adjusted by the rolling down device 54.

The cooling device 6 is configured to be able to cool the rolled material M by injecting water into the rolled material M using a cooling bank. The cooled rolled material M is wound up by a winding machine 7. This results in a coiled product.

Various sensors as measuring instruments are installed at important points in the rolling plant 1. Important points of the rolling plant 1 include, for example, the outlet side of the heating furnace 2, the outlet side of the rough rolling mill 3, the outlet side of the finishing mill 5, and the inlet side of the winder 7. Various sensors may also be provided between the rolling stands F1 to F7 of the finishing rolling mill 5. The various sensors include a shape detector 81 that can measure the shape of the rolled material M on the exit side of the rough rolling mill 3, a thermometer 82 that measures the surface temperature of the rolled material M on the entry side of the finishing mill 5, A thermometer 83 that measures the surface temperature of the rolled material M on the exit side of the finishing rolling mill 5, a plate thickness gauge 84 that measures the plate thickness Ta of the rolled material M on the exit side of the finishing rolling mill 5, and It includes a rolling load sensor 85 that measures the rolling load at stands F1 to F5. Various sensors sequentially measure the condition of the rolled material M and each device.

The rolling plant 1 is operated (operated) by a control system using a computer. The computer includes a host computer 10 and a process computer 11 that are connected to each other via a network. An interface screen 12, which is an operation screen, and a database 13 are connected to the process computer 11 via a network. Past rolling data is sequentially stored in the database 13. The past rolling data includes actual values of the inter-roller gap (hereinafter sometimes abbreviated as "gap") of each rolling stand F1 to F7. The actual value of the gap is classified by steel type and product target plate thickness Tt. In addition, the database 23 contains the actual value of the gap in which the tip of the material to be rolled M is stably passed through without any trouble at the tip, that is, the sheet thickness at that time (described later as " (corresponding to the "thickness that can be passed through the plate").

The plate thickness control device 20 of the present embodiment uses not only the product target plate thickness Tt but also the passable plate thickness Ts that allows the tip of the rolled material M to be stably passed through. It is configured to control the plate thickness. FIG. 2 is a block diagram for explaining the configuration of main parts of the plate pressure control device 20. As shown in FIG.

The plate thickness control device 20 includes the plate thickness meter 84, a gap calculation section 21, a gap setting section 22, a thickness deviation calculation section 23, an automatic thickness control section 24, and a target thickness change section 25. .

When the target product thickness Tt is input from the host computer 11, the gap calculation unit 21 determines a thickness that is larger than the target product thickness Tt and that allows the tip of the rolled material M to be stably passed through. It is configured to calculate the gap between the work rolls 51 of each rolling stand F1 to F7 corresponding to Ts. For example, the gap calculation unit 21 acquires the passable plate thickness Ts stored in the database 23 in association with the product target plate thickness Tt, and uses each rolling stand F1 to realize the obtained passable plate thickness Ts. ~F7 gaps are calculated respectively. Note that the gaps between the rolling stands F1 to F7 are calculated such that they become smaller in the order from the first rolling stand F1 to the last rolling stand F7 in the juxtaposed direction.

The gap setting unit 22 is configured to set a gap in each of the rolling stands F1 to F7 by controlling the rolling device 54 of each of the rolling stands F1 to F7 in accordance with the gap calculated by the gap calculating unit 21. ing.

The plate thickness deviation calculation unit 23 calculates the plate thickness deviation FBK1 (=Ta−Ts) by subtracting the passable plate thickness Ts from the plate thickness measurement value (actual plate thickness) Ta measured by the plate thickness meter 84. calculate. The automatic board thickness control unit 24 controls the board so that the board thickness deviation FBK1 calculated by the board thickness deviation calculation unit 23 becomes the minimum, or the board to which a board thickness bias Tb, which will be described later, is added (added) to the board thickness deviation FBK1. The rolling device 54 of each rolling stand F1 to F7 is controlled so that the thickness deviation FBK2 is minimized. The control by the automatic plate thickness control section 24 corresponds to AGC (Auto Gain Control) control. Further, the plate thickness deviations FBK1 and FBK2 being minimized means that the plate thickness deviations FBK1 and FBK2 converge to zero, for example.

The target plate thickness changing unit 25 includes a ramp 251, a timer 252, a bias amount 253 that is input to the ramp 251 when triggered by the timer 252, and a ramp rate 254 that is input to the ramp 251. The bias amount 253, that is, the difference between the passable plate thickness Ts and the product target plate thickness Tt, can be set depending on the steel type of the material to be rolled M, and can be set to 300 μm, for example. The target plate thickness changing unit 25 can output (change) the plate thickness bias Tb added to the plate thickness deviation FBK1 at a predetermined ramp rate. The plate thickness deviation FBK2 obtained by adding the plate thickness bias Tb is positive, and the automatic plate thickness control unit 24 performs AGC control to converge the plate thickness deviation FBK2 to zero, so each rolling stand F1 to F7 The gap is gradually changed in the tightening direction.

Here, the timer 252 sets the trigger signal to SET after a predetermined time TD1 has elapsed from the time (F7_In) when the tip of the material to be rolled M passed through the final rolling stand F7. As a result, the plate thickness bias Tb output from the target plate thickness changing unit 25 gradually increases at a predetermined ramp rate. By performing AGC control using the plate thickness deviation FBK2 to which the plate thickness bias Tb is applied, the gaps between the rolling stands F1 to F7 are gradually changed in the tightening direction. As a result, the thickness of the rolled material M after the tip end is gradually changed from the passable thickness Ts to the product target thickness Tt.

Further, the timer 252 sets the trigger signal to RESET after the tail end of the rolled material M is cut by the crop shear 4. As a result, the plate thickness bias Tb output from the target plate thickness changing unit 25 gradually decreases at a predetermined ramp rate. By performing AGC control using the plate thickness deviation FBK2 to which the plate thickness bias Tb is applied, the gaps of the rolling stands F1 to F7 are gradually changed in the loosening direction. As a result, the plate thickness at the tail end of the rolled material M is gradually changed from the product target plate thickness Tt to the passable plate thickness Ts.

Although there is no limitation to the specific structure of the plate pressure control device 20, the following may be used as an example. FIG. 3 is a diagram showing an example of the hardware configuration of the plate pressure control device 20. As shown in FIG. The functions of the plate pressure control device 20 can be realized by a processing circuit shown in FIG. This processing circuit may be dedicated hardware 20a. This processing circuit may include a processor 20b and a memory 20c. This processing circuit may be partially formed as dedicated hardware 20a and further include a processor 20b and a memory 20c. In the example of FIG. 3, part of the processing circuit is formed as dedicated hardware 20a, and the processing circuit also includes a processor 20b and a memory 20c.

At least a portion of the processing circuitry may be at least one piece of dedicated hardware 20a. In this case, the processing circuit can be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

The processing circuit may include at least one processor 20b and at least one memory 20c. In this case, each function of the process computer 11 is realized by software, firmware, or a combination of software and firmware. Software and firmware are written as programs and stored in the memory 20c. The processor 20b realizes the functions of each section by reading and executing programs stored in the memory 20c.

The processor 20b is also called a CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. The memory 20c is, for example, a nonvolatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, EEPROM, or the like. Note that it is also possible to configure the memory 20c to also serve as the database 13.

In this way, the processing circuit can realize each function of the plate pressure control device 20 using hardware, software, firmware, or a combination thereof.

In the rolling plant 1, the material to be rolled M is heated in the heating furnace 2 and then extracted onto a roller table (not shown) of the rolling line. The material M to be rolled at this stage is, for example, a steel billet. When the rolled material M reaches the rough rolling mill 3, it is repeatedly rolled while changing the rolling direction. The material to be rolled M at this stage is a bar having a thickness of, for example, several tens of millimeters. A shape detector 81 on the exit side of the rough rolling mill 3 measures the shape of the material to be rolled M, and based on the measurement results, a portion of the tail end of the material to be rolled M having a defective shape is cut off by the crop shear 4. The material to be rolled M is rolled while being sequentially bitten by the rolling stands F1 to F7 of the finishing mill 5, and is controlled to a desired product target thickness Tt.

Next, a method of controlling plate thickness using the plate thickness control device 20 of the finishing rolling mill 5 will be described. FIG. 4 is a timing chart for explaining the flow of plate thickness control using the plate thickness control device 20. FIG. 5 is a flowchart for explaining the flow of plate thickness control using the plate thickness control device 20.

When the target product thickness Tt is input from the host computer 11 to the process computer 12 before the routine shown in FIG. Obtain the passable plate thickness Ts that allows the tip of the rolled material M to be stably passed through. The gap calculation unit 21 calculates the gap of each of the rolling stands F1 to F7 corresponding to the obtained passable plate thickness Ts. The gap setting unit 22 sets a gap in each of the rolling stands F1 to F7 by controlling the rolling device 54 of each of the rolling stands F1 to F7 according to the gap calculated by the gap calculating unit 21.

When the routine shown in FIG. 5 is started, it is determined whether F7_In is ON, that is, whether the tip of the material to be rolled M has passed through the final rolling stand F7 (step S1).

Before time t1, F7_In is OFF, so the thickness bias Tb output from the target thickness changing unit 25 is zero (that is, the thickness bias Tb added to the thickness deviation FBK1 is zero). be). In this case, the automatic plate thickness control unit 24 performs AGC control on the rolling devices 54 of each of the rolling stands F1 to F7, respectively, so that the plate thickness deviation FBK1 is minimized (for example, zero) (step S2). As a result, the gap between each of the rolling stands F1 to F7 is controlled to be large in order to ensure that the tip of the material M to be rolled passes through the plate.

Here, when F7_In is turned ON at time t1 after a predetermined time has elapsed from the time when the tip of the material to be rolled M was detected by the shape detector 81, the process moves to step S3.

In step S3, it is determined whether time TD1 has elapsed. The time TD1 corresponds to a time delay. If the time TD1 has not elapsed, the trigger signal from the timer 252 is OFF, so the thickness bias Tb output from the target thickness changing unit 25 is zero (that is, the thickness bias Tb that is added to the thickness deviation FBK1 thickness bias Tb is zero). In this case as well, the automatic plate thickness control section 24 performs AGC control on the rolling devices 54 of each of the rolling stands F1 to F7, respectively, so that the plate thickness deviation FBK1 is minimized (for example, zero) (step S4). In step S4 as well, the gaps between the rolling stands F1 to F7 are controlled to be large in order to ensure that the tip of the material to be rolled M passes through the plate. After that, the process returns to step S3.

At time t2 when time TD1 has elapsed from time t1, when the trigger signal from the timer 252 becomes SET, it is determined that the threading of the tip of the material to be rolled M has been completed, and the thickness bias is changed from the target thickness changing unit 25. Tb is output. The output plate thickness bias Tb is added to the plate thickness deviation FBK1, and becomes the plate thickness deviation FBK2. Here, when the bias amount of the plate thickness bias Tb is, for example, 300 μm, the plate thickness bias Tb output from the target plate thickness changing unit 25 increases at a predetermined ramp rate during the time from time t2 to time t3. When the plate thickness bias Tb reaches 300 μm, FBK2=Ta−Ts+300 μm. The automatic plate thickness control unit 24 performs AGC control on the rolling devices 54 of each of the rolling stands F1 to F7, respectively, so that the positive plate thickness deviation FBK2 to which the plate thickness bias Tb is added is minimized (for example, zero) (step S5). During the period from time t2 to time t3, the gaps of each of the rolling stands F1 to F7 are controlled to be gradually smaller (the gaps are gradually tightened) by AGC control. Thereby, the plate thickness of the portion behind the tip of the rolled material M can be controlled to the extremely thin product target plate thickness Tt.

Here, when the tail end of the rolled material M becomes extremely thin, the tail end meandering and tail end narrowing of the rolled material M are likely to occur. As a result, the tail end of the material to be rolled M is likely to become entangled with the work rolls 51 of each of the rolling stands F1 to F7, and there is a possibility that the number of replacements of the work rolls 51 will increase.

Therefore, in this embodiment, the following control is executed. That is, it is determined whether CS_TCut is ON, that is, whether the defective shape portion of the tail end of the rolled material M has been cut by the crop shear 4 (step S6). If CS_TCut is OFF, the process returns to step S5.

When CS_TCut turns ON at time t4, that is, when cutting is performed by the crop shear 4, the process moves to step S7. In step S7, it is determined whether time TD2 has elapsed. The time TD2 corresponds to a time delay. The time TD2 is set so that the tail end of the material to be rolled M is not passed through the first rolling stand F1 after cutting by the crop shear 4. Time TD2 is usually different from time TD1. Until the time TD2 elapses, AGC control is continued to be performed at the product target thickness Tt, where Tb=300 μm, as in step S5 (step S8).

At time t5 when time TD2 has elapsed from time t4, when the trigger from timer 252 becomes RESET, plate thickness bias Tb output from target plate thickness changing unit 25 gradually decreases from 300 μm to 0 μm at a predetermined ramp rate. Therefore, the automatic plate thickness control unit 24 performs AGC control on the rolling devices 54 of the rolling stands F1 to F7, respectively, so that the plate thickness deviation FBK2 becomes the minimum (eg, zero) (step S8). As a result, from time t5 to time t6, the gaps of each rolling stand F1 to F7 are gradually changed to a larger value by each AGC control. As a result, the thickness of the tail end of the rolled material M is gradually changed from the product target thickness Tt to the passable thickness Ts. In addition, the occurrence of tail end meandering and tail end squeezing of the rolled material M can be suppressed. This makes it difficult for the tail end of the rolled material M to get entangled with the work rolls 51 of the rolling stands F1 to F7, and it is possible to suppress an increase in the number of replacements of the work rolls 51.

As explained above, according to the present embodiment, even when rolling the material M to be rolled to an ultra-thin product target thickness Tt, the gap between each rolling stand F1 to F7 corresponds to the thickness Ts that allows the material to pass through. By setting the gap to such a gap, it is possible to ensure that the finishing mill 5 passes the tip of the material M to be rolled. Therefore, unlike the prior art, there is no need to install a heating device on the entry side of the finishing rolling mill 5, and an increase in equipment costs can be prevented. Moreover, after the tip of the material to be rolled M is passed through the material M, AGC control is performed using the thickness deviation FBK2, which is obtained by gradually adding the thickness bias Tb to the thickness deviation FBK1, so that each rolling stand F1 to The gap F7 is gradually changed to a gap corresponding to the target product thickness Tt. This, together with the fact that the gaps between the rolling stands F1 to F7 are not changed suddenly, makes it possible to stably roll the material M to be rolled into an extremely thin sheet.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be implemented with various modifications without departing from the spirit of the present invention. In the embodiments described above, when the number, amount, amount, range, etc. of each element is referred to, unless it is specifically specified or it is clearly specified to the number in principle, the mentioned number does not apply. This invention is not limited. Furthermore, the structures described in the above-described embodiments are not necessarily essential to the present invention, unless explicitly stated or clearly specified in principle.

5... Finishing rolling mill (hot rolling mill), 20... Plate thickness control device, 21... Gap calculation section, 22... Gap setting section, 23... Plate thickness deviation calculation section, 24... Automatic plate thickness control section, 25... Target Plate thickness change section, 84... Plate thickness gauge, F1 to F7... Rolling stand, F1... First rolling stand, F7... Final rolling stand, FBK1, FBK2... Plate thickness deviation, M... Material to be rolled, Ta... Plate thickness Measured value, Tb...Thickness bias, Ts...Thickness that can be passed through, Tt...Product target thickness

Claims

In a plate thickness control device for a hot rolling mill in which a plurality of rolling stands are arranged in parallel and a heated material to be rolled is sequentially rolled by the plurality of rolling stands,
a plate thickness gauge installed on the exit side of the final rolling stand in the parallel arrangement direction and measuring the plate thickness of the rolled material;
a gap calculation unit that calculates a gap between the rolls of each rolling stand that is larger than the product target thickness of the material to be rolled and corresponds to a passable thickness that allows the tip of the material to be rolled to pass stably;
a gap setting unit that sets the gap calculated by the gap calculation unit to each rolling stand;
an automatic plate thickness control unit that executes automatic plate thickness control that minimizes a plate thickness deviation between a plate thickness measurement value of the plate thickness meter and the passable plate thickness;
After the tip of the material to be rolled is passed through the final rolling stand, a thickness bias is added to the thickness deviation at a predetermined ramp rate, thereby changing the passable thickness to the product target thickness. A plate thickness control device for a hot rolling mill equipped with a target plate thickness changing section that changes the target plate thickness.
The target plate thickness changing unit adds a plate thickness bias to the plate thickness deviation at a predetermined ramp rate before the tail end of the material to be rolled is passed through the first rolling stand in the juxtaposition direction. The plate thickness control device for a hot rolling mill according to claim 1, wherein the device is configured to change the product target plate thickness to the passable plate thickness.