Roll cooling control system

Abstract

The present invention provides a roll cooling control device that can cool the roll without adversely affecting the controllability of the plate thickness. [Solution] The rolling / idling prediction unit predicts the time it will take for the next rolled material to reach the roll at the transition point when the machine transitions from rolling to idling. The cooling water volume monitor unit acquires the amount of cooling water supplied to the nozzle at the transition point. The roll thermal expansion amount prediction unit uses the time predicted by the rolling / idling prediction unit as the prediction period and predicts the amount of thermal expansion of the roll at the prediction period and at the transition point, respectively. The cooling water volume reduction calculation unit works in conjunction with the roll thermal expansion amount prediction unit to calculate the amount of cooling water to be reduced within the prediction period so that the difference between the amount of thermal expansion at the transition point and the amount of thermal expansion during the prediction period falls within a predetermined range. The variable flow valve adjustment unit adjusts the opening of the variable flow valve to reduce the amount of cooling water by the amount calculated by the cooling water volume reduction calculation unit.

Description

[Technical Field]

[0001] This disclosure relates to a roll cooling control device for cooling the rolls of a rolling mill, and more particularly to a device suitably applied to a hot rolling mill for rolling metal materials. [Background technology]

[0002] Among the rolling equipment installed on a rolling line is a hot rolling mill (hereinafter also referred to as "rolling mill") that rolls rolled material heated in a heating furnace. A rolling mill is equipped with one or more stands. Each stand is equipped with a pair of upper and lower work rolls (hereinafter referred to as "rolls"), and the thickness of the sheet metal at the exit of the rolling mill is controlled to the target thickness by appropriately calculating and controlling the roll gap and roll rotation speed.

[0003] Incidentally, the rolls expand due to heat input from the rolled material and heat generated by friction between the rolls and the material. To prevent excessive thermal expansion, cooling water is sprayed onto the rolls to cool them and keep their temperature within a predetermined range. When cooling the rolls, the cooling water is sprayed with a certain amount of pressure to enhance the cooling effect. For this reason, it is common to drive multiple pumps and supply water at a higher pressure than other water supply systems, and the pumps and the electric motors that drive them have large capacities.

[0004] Patent Document 1 below discloses a thermal crown control method for suppressing thermal crown (change in roll profile) caused by thermal expansion of the roll. This method achieves energy-saving operation during idle (non-rolling) by controlling the pump with VVVF (Variable Voltage Variable Frequency). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2006-272354 [Overview of the project]

Problems to be Solved by the Invention

[0006] The method disclosed in Patent Document 1 aims to suppress the thermal crown (thermal expansion) of a roll, and does not consider controlling the thermal expansion of the roll in a direction to increase or grow it. From the perspective of the sheet thickness controllability of a rolling mill, it is not always desirable to reduce the thermal expansion of the roll, and it is desired not to excessively reduce the thermal expansion of the roll. In other words, if the thermal expansion of the roll is excessively reduced, it will become a disturbance to the calculation and control of the roll gap and roll rotation speed, and may conversely have an adverse effect on the sheet thickness controllability.

[0007] The present disclosure has been made to solve the above problems, and an object thereof is to provide a roll cooling control device capable of cooling a roll without adversely affecting the sheet thickness controllability.

Means for Solving the Problems

[0008] The first aspect of this disclosure relates to a roll cooling control device for cooling the rolls of a rolling mill. The rolling mill includes nozzles for injecting cooling water onto the rolls, one or more pumps for supplying cooling water to the nozzles, and a variable flow valve capable of changing the flow rate of cooling water supplied from the pumps to the nozzles. The roll cooling control device includes a rolling / idling prediction unit, a cooling water volume monitor unit, a roll thermal expansion amount prediction unit, a cooling water volume reduction calculation unit, and a variable flow valve adjustment unit. The rolling / idling prediction unit takes the time at which the rolling mill transitions from rolling to an idling state as the transition time and predicts the time it will take for the next rolled material to reach the rolls at the transition time. The cooling water volume monitor unit obtains the amount of cooling water supplied to the nozzles at the transition time. The roll thermal expansion amount prediction unit takes the time predicted by the rolling / idling prediction unit as the prediction period and predicts the amount of thermal expansion of the rolls at the prediction period and at the transition time, respectively. The cooling water volume reduction calculation unit works in conjunction with the roll thermal expansion prediction unit to calculate the amount of cooling water to be reduced during the prediction period so that the difference between the thermal expansion amount at the transition point and the thermal expansion amount during the prediction period falls within a predetermined range. The variable flow valve adjustment unit adjusts the opening of the variable flow valve to reduce the amount of cooling water by the amount calculated by the cooling water volume reduction calculation unit.

[0009] A second aspect of this disclosure relates to a roll cooling control device for cooling the rolls of a rolling mill. The rolling mill includes nozzles for injecting cooling water onto the rolls, one or more pumps for supplying cooling water to the nozzles, and a variable flow valve capable of changing the flow rate of cooling water supplied from the pumps to the nozzles. The roll cooling control device includes a rolling / idling prediction unit, a roll thermal expansion prediction unit, a cooling water amount reduction calculation unit, and a variable flow valve adjustment unit. The rolling / idling prediction unit uses rolling information to predict the rolling period and idling period in a predetermined prediction period. The roll thermal expansion prediction unit predicts the amount of thermal expansion of the rolls in the prediction period. The cooling water amount reduction calculation unit works in conjunction with the roll thermal expansion prediction unit to calculate the amount of cooling water to be reduced during the prediction period, using the maximum thermal expansion of the rolls maintained when the maximum amount of cooling water is supplied to the nozzles as the thermal expansion target value, so that the difference between the thermal expansion target value and the amount of thermal expansion during the prediction period falls within a predetermined range. The variable flow valve adjustment unit adjusts the opening degree of the variable flow valve so as to reduce the amount of cooling water by the amount calculated by the cooling water volume reduction calculation unit.

[0010] The third aspect, in addition to the first or second aspect, further has the following features: The pump includes a variable speed pump. The roll cooling control device further comprises a variable speed pump adjustment unit. The variable speed pump adjustment unit adjusts the rotational speed of the variable speed pump according to the opening degree of the variable flow valve adjusted by the variable flow valve adjustment unit.

[0011] The fourth aspect, in addition to the first or second aspect, further has the following features: A drain valve is provided between the pump and the variable flow valve. The roll cooling control device further includes a drain valve adjustment unit. The drain valve adjustment unit adjusts the opening of the drain valve so as to reduce the amount of cooling water by the amount calculated by the cooling water amount reduction calculation unit, while the opening of the variable flow valve is adjusted by the variable flow valve adjustment unit.

[0012] The fifth aspect, in addition to the first aspect, has the following further features: The variable flow valve adjustment unit is configured to adjust the opening of the variable flow valve to the minimum opening when the difference between the amount of thermal expansion at the transition point and the amount of thermal expansion during the predicted period falls outside a predetermined range.

[0013] The sixth aspect, in addition to the first aspect, has the following further characteristics: The rolling mill performs rolling continuously with an idling state shorter than a predetermined time in between. The rolling / idling prediction unit is configured to predict rolling and idling during a second prediction period that is longer than the first prediction period. The cooling water amount reduction calculation unit is configured to calculate the amount of cooling water to be reduced during the second prediction period, using the maximum thermal expansion amount of the roll maintained when the maximum amount of cooling water is supplied to the nozzle during continuous rolling as the thermal expansion amount target value, so that the difference between the thermal expansion amount target value and the thermal expansion amount during the prediction period falls within a predetermined range. [Effects of the Invention]

[0014] According to the first aspect of this disclosure, the opening of the variable flow valve is adjusted so that the difference between the amount of thermal expansion of the roll at the transition point from rolling to idling and the amount of thermal expansion of the roll during the predicted period until the next rolled material reaches the roll falls within a predetermined range. This appropriately controls the amount of cooling water supplied to the roll, preventing the amount of thermal expansion of the roll from decreasing excessively during idling. Therefore, the roll can be cooled without adversely affecting the plate thickness controllability.

[0015] According to a second aspect of this disclosure, the amount of thermal expansion of the roll during a predicted period, including multiple rolling cycles and idling, is predicted, and the opening of the variable flow valve is adjusted so that the difference between the predicted amount of thermal expansion and the target amount of thermal expansion falls within a predetermined range. This appropriately controls the amount of cooling water supplied to the roll, allowing the amount of thermal expansion to reach the target value as quickly as possible. Therefore, the roll can be cooled without adversely affecting the plate thickness controllability. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram illustrating the configuration of a rolling line to which the roll cooling control device according to the embodiment is applied. [Figure 2] This is a schematic diagram illustrating the configuration of a process control computer, which is a roll cooling control device according to an embodiment. [Figure 3] This diagram illustrates the concept of calculating the thermal expansion of a roll. [Figure 4] This figure shows an example of the growth in the thermal expansion of a roll during hot rolling. [Figure 5] This figure shows an example of a sequence of opening degree command values ​​for a variable flow valve. [Figure 6] This figure shows an example of controlling the amount of roll thermal expansion according to the first embodiment. [Figure 7] This is a flowchart illustrating the procedure for roll cooling control according to the first embodiment. [Figure 8] This figure shows an example of controlling the amount of roll thermal expansion according to the second embodiment. [Figure 9] This figure shows an example of a pre-calculation of the average roll temperature rise. [Figure 10] Figure 9 shows an example of the effect of the amount of roll cooling water on the average roll temperature rise. [Figure 11] This figure shows an example of the hardware configuration of a process control computer. [Modes for carrying out the invention]

[0017] The embodiments of this disclosure will be described below with reference to the drawings, using the application to a hot rolling mill as an example. In each drawing, elements common to all parts are denoted by the same reference numerals, and redundant explanations are omitted.

[0018] Figure 1 is a schematic diagram illustrating the configuration of a rolling line to which the roll cooling control device according to the embodiment is applied. As shown in Figure 1, the rolling line RL includes a rolling mill 1. A heating furnace (not shown) is provided upstream of the rolling mill 1 in the conveying direction. The rolling mill 1 uses steel or other metal material as the rolling material M, and rolls the rolling material M, which has been heated to a predetermined temperature in the heating furnace, to a predetermined target product plate thickness.

[0019] The rolling mill 1 is equipped with one or more stands (one in the example shown in Figure 1), each stand comprising a pair of upper and lower work rolls 11, a pair of upper and lower backup rolls 12, and an electric motor (not shown) for rotating the rolls. Although not shown, the backup rolls 12 are provided with a reduction device, and the roll gap between the upper and lower work rolls 11 is controlled by adjusting the reduction opening of the reduction device. In this embodiment, the work rolls 11 are the rolls to be cooled. Hereafter, the work rolls 11 will also be simply referred to as rolls 11.

[0020] The rolling mill 1 includes a plurality of nozzles 13 (four in the example shown in Figure 1) for injecting cooling water onto the rolls 11, a plurality of pumps 14 (14a to 14n) for supplying cooling water to the nozzles 13, and a variable flow valve 15 that can change the flow rate of cooling water supplied from the pumps 14 to the nozzles 13. Each pump 14 is electrically coupled to an electric motor 141 for driving the pump 14. At least one pump 14n has an electric motor 141n electrically coupled to a variable speed drive 142n, thereby configuring the pump 14n as a variable speed pump capable of changing its rotational speed. The number of pumps 14, including the variable speed pump 14n, can be appropriately set according to the water supply capacity to the nozzles 13 and, consequently, the rolls 11. It is preferable to provide a check valve 16 on the nozzle 13 side (discharge side) of each pump 14. In addition, a drain valve 17 is interposed in a branch passage 172 that branches off from the cooling water supply passage 171 between the pumps 14 and the variable flow valve 15. The drain valve 17 constitutes part of the drainage mechanism and includes, for example, a bypass valve and an overflow valve. Although not shown, other drain valves may be provided in branch lines that branch off from the cooling water supply line between the pump 14 and the check valve 16. These other drain valves also constitute part of the drainage mechanism.

[0021] The rolling line RL is operated by a computer-based control system. The computer system includes a higher-level computer 2 and a process control computer 3, which are connected to each other via a network. The lower-level process control computer 3 is connected via the network to an interface screen 4, which is the operator's control screen. The operator can perform operations such as inputting control conditions on the interface screen 4.

[0022] The process control computer 3 performs setting calculations and control of the controlled objects in a series of rolling processes based on the rolling information (including the operation plan and rolling schedule) received from the higher-level computer 2. The target product thickness of the rolled material M is input to the process control computer 3 from the higher-level computer 2. The process control computer 3 appropriately controls each piece of equipment based on the target product thickness and control conditions given from the interface screen 4. The process control computer 3 calculates the settings for each piece of equipment that can achieve the target product thickness and operates the actuators of each piece of equipment based on these settings. While each piece of equipment is in operation, the process control computer 3 corrects the operation of the actuators according to the values ​​obtained from various measuring instruments (not shown). The process control computer 3 operates the reduction device of the stand and adjusts the roll gap so that the actual thickness of the rolled material M becomes the target product thickness (i.e., cancels out the thickness deviation).

[0023] Figure 2 is a schematic diagram illustrating the configuration of a process control computer 3, which is a roll cooling control device according to an embodiment. The roll cooling control device 3 includes a roll thermal expansion prediction unit 31, a rolling / idling prediction unit 32, a cooling water volume monitor unit 33, a cooling water volume reduction calculation unit 34, a variable flow valve adjustment unit 35, and a variable speed pump adjustment unit 36.

[0024] The roll thermal expansion prediction unit 31 calculates the amount of thermal expansion of the roll 11 (hereinafter also referred to as "roll thermal expansion") using the thermal expansion model of the roll 11 and the heat inflow and outflow to the roll 11. As shown in an enlarged view in Figure 1, the heat inflow and outflow to the work roll 11 includes heat input from the rolled material M (heat of the material, frictional heat generation, processing heat generation), heat removal by cooling water sprayed from the nozzle 13 (see dashed line in the figure), heat removal to the backup roll 12, and heat removal by air cooling. Figure 3 is a diagram illustrating the concept of calculating the amount of thermal expansion of the roll 11. In the roll thermal expansion model, the temperature of each node 110, shown as a black circle in Figure 3, is calculated using the finite difference method. The amount of heat input from the rolled material M and heat removal to other sources are calculated, and the conduction of that heat into the roll 11 is described by a physical model. The thermal expansion amount based on the roll radius or diameter is calculated by calculating the temperature of each node 110 inside the roll 11, calculating the amount of thermal expansion of each node 110 due to that temperature, and accumulating the amounts of thermal expansion of each node 110. Alternatively, the temperature of each node 110 inside the roll 11 may be calculated, the average temperature of the roll 11 may be calculated from the temperatures of each node 110, and the amount of thermal expansion may be calculated from the relationship between the average temperature and the amount of thermal expansion. Note that the calculation using the difference method shown in Figure 3 may take time depending on the number of nodes 110, and if real-time calculations or repeated interactions with the cooling water volume reduction calculation unit 34 described later are required, the computer load may become high. Therefore, it is also possible to pre-determine conditions, perform calculations, store the calculation results, and retrieve them as needed. Pre-determined conditions include, for example, the thickness, width, hardness, and temperature of the rolled material M, and calculate how much thermal expansion will occur when the roll 11 is rolled for a certain number of seconds under those conditions. Linear interpolation can be used to retrieve the calculation results if the conditions do not perfectly match. Alternatively, the average temperature in the diametrical direction, which serves as the basis for calculating the amount of thermal expansion, can be calculated in advance. Figure 4 shows an example of the growth (increase) of the amount of thermal expansion of the roll 11 during hot rolling. During rolling, the heat input to the roll 11 is greater than the heat extraction, so the amount of thermal expansion increases. During non-rolling (idling), the heat extraction from the roll 11 is greater than the heat input, so the amount of thermal expansion decreases. As rolling and non-rolling are repeated, the amount of thermal expansion gradually saturates and settles to a certain value, as shown by the approximation curve Ac indicated by the dashed line in the figure.If you need to calculate the roll thermal expansion amount in advance, you may also calculate the approximate curve Ac shown in Figure 4.

[0025] The rolling / idling prediction unit 32 predicts, from the rolling information received from the higher-level computer 2, the timing of rolling the rolled material M by the roll 11 (including the rolling start time t0), the rolling period (time during rolling), the timing of when the rolled material M leaves the roll 11 and transitions to an idling state (non-rolling state), the idling period (time in the idling state), the timing (future time) when the next rolled material (also called "next material") M reaches the roll 11, and the rolling period of the next material. Since the heat balance to the roll 11 changes significantly depending on whether it is rolling or not, it is important for the rolling / idling prediction unit 32 to accurately predict the rolling / rolling timing and the rolling period / idling period.

[0026] The cooling water volume monitor unit 33 acquires the flow rate of cooling water supplied to the nozzle 13 and, consequently, the roll 11 (hereinafter also referred to as "roll cooling water volume" or "cooling water volume"). The cooling water volume monitor unit 33 acquires the opening degree and on / off (on / off) information of various valves 15, 16, and 17 installed in the rolling mill 1, and acquires information regarding whether the cooling water is being effectively used to cool the roll 11, and / or whether the cooling water is being drained by the drainage mechanism.

[0027] The cooling water volume reduction calculation unit 34 virtually changes the roll cooling water volume and, in cooperation with (exchanging information with) the roll thermal expansion volume prediction unit 31, obtains the roll thermal expansion volume and calculates the roll cooling water volume so that the roll thermal expansion volume remains as constant as possible. The reason for keeping the roll thermal expansion volume as constant as possible is that if the roll thermal expansion volume changes excessively, the state of the roll 11 changes, which negatively affects rolling control and presets that ensure product quality, such as plate thickness control, plate crown control, and flatness control. In addition to exchanging information with the roll thermal expansion volume prediction unit 31, the cooling water volume reduction calculation unit 34 uses information from the rolling / idling prediction unit 32 to determine when and how much to open the variable flow valve 15 and what the rotation speed of the pump (including the variable speed pump 14n) 14 should be, and uses information from the cooling water volume monitoring unit 33 to obtain the roll cooling water volume and the state of the drain valves (bypass valves and overflow valves) 17 of the drainage mechanism. Based on this information, a sequence of variable flow valve opening command values ​​that conserves pump power is provided to the variable flow valve adjustment unit 35, and a sequence of pump output command values ​​is provided to the variable speed pump adjustment unit 36. Here, a sequence of command values ​​refers to command values ​​arranged in chronological order. Figure 5 shows an example of a sequence of variable flow valve opening command values. The format of the sequence of command values ​​is not limited to that shown in Figure 5; any information that specifies which command value to output at which time is acceptable.

[0028] The variable flow valve adjustment unit 35 receives a sequence of variable flow valve opening command values ​​sent from the cooling water volume reduction calculation unit 34 and sends a predetermined command value to the variable flow valve 15 at a predetermined time. The sequence of command values ​​is in the form of a vector or matrix, and the command value is a scalar (a single value). Here, if the change in the command value to the variable flow valve 15 is rapid, the variable flow valve adjustment unit 35 can apply a filter to slow down the change in the command value, or it is possible to make the command value slope like a ramp, as shown in Figure 6 which will be described later.

[0029] Similarly, the variable speed pump adjustment unit 36 ​​receives a sequence of pump output command values ​​sent from the cooling water volume reduction calculation unit 34 and sends a predetermined command value to the variable speed drive 142n at a predetermined time. Here, if the change in the command value to the variable speed drive 142n is rapid, the variable speed pump adjustment unit 36 ​​can apply a filter to slow down the change in the command value or make the command value a ramp. Note that during operation of the pump 14, if the pump 14 and the water flow resonate, the pump 14 may be damaged. Therefore, the cooling water volume reduction calculation unit 34 or the variable speed pump adjustment unit 36 ​​should be configured to avoid operation near the resonant frequency.

[0030] Next, the roll cooling control according to the first embodiment of this model will be described. Figure 6 is a diagram illustrating the control of the roll cooling water amount according to the first embodiment. In the first embodiment, the change in the amount of roll thermal expansion is predicted by a model, and the amount of roll cooling water is set to appropriately maintain the amount of roll thermal expansion during the non-rolling (idling) period between rolling and rolling, that is, at the time of transition from rolling to the idling state (time t1), until time t2 when the next rolled material M arrives at the roll 11.

[0031] When rolling operations run relatively smoothly, with short intervals between rolling cycles and shorter idling periods than predetermined, the heat input from the rolled material M to the roll 11 and the heat dissipation to the cooling water sprayed onto the roll 11 are in a near-equal state, and the roll's thermal expansion does not increase or decrease significantly. As a result, the roll diameter, including thermal expansion and wear, remains almost constant and does not significantly affect the rolling preset or control. Here, the wear of the roll 11 does not change abruptly but progresses gradually, making it easier to manage than changes in thermal expansion.

[0032] If the idling period (the period from time t1 to time t2) becomes longer for some reason, the heat input from the rolled material M to the roll 11 will cease. In this case, the amount of roll cooling water W during rolling occurs at the time when the machine transitions from rolling to idling (time t1). RC0If this is maintained, the heat dissipation to the cooling water will not change, and the amount of roll thermal expansion will gradually decrease as shown by the dashed line in Figure 6. At time t2 when the next rolled material M arrives at roll 11, roll 11 is excessively contracted, which can disturb the preset and control of the next rolled material M. Also, if roll 11 is excessively cooled by the roll cooling water, the amount of thermal expansion will increase rapidly during the rolling of the next rolled material M due to the heat input of the next rolled material M, which can also disturb the control. Therefore, if the interval between rolling operations is expected to be long, that is, if the idling period is expected to be long, the amount of roll cooling water W RC0 ΔW RC Reduce only W RC0,new This ensures that the amount of thermal expansion of the roll is not excessively reduced.

[0033] Figure 7 is a flowchart illustrating the procedure for roll cooling control according to the first embodiment. In the routine shown in Figure 7, it is first determined whether or not the machine has transitioned from rolling to an idling state (non-rolling) (step S1). If the machine has not transitioned to an idling state, i.e., if it is still rolling, the routine is terminated.

[0034] When the rolling process transitions to an idling state, the rolling / idling prediction unit 32 uses the rolling information to calculate the time T until the next rolled material M reaches the position of the roll (cooling target roll) 11 (step S2). The time T calculated in step S2 is also called the "prediction period". The rolling information includes the position and length of the rolled material M on the rolling line RL, the transport speed of the rolled material M, the steel type and size (thickness, width, etc.) of the rolled material M, and the temperature of the rolled material M. As the temperature of the rolled material M, the measured value of a temperature sensor (not shown) can be used. For example, if there are multiple stands with rolls 11 arranged in parallel, i.e., if there are multiple rolls 11 to be cooled, the time (prediction period) T should be the time until the next rolled material M reaches the roll 11 furthest upstream (closest to the leading edge of the subsequent rolled material M).

[0035] Next, the time T calculated in step S2 is the threshold T THDetermine whether it is as above (step S3). If the time T is shorter than the threshold value T TH , proceed to step S12. On the other hand, if the time T is greater than or equal to the threshold value T TH , proceed to step S4.

[0036] In step S4, the roll cooling water amount monitoring unit 33 records the roll cooling water amount W RC0 at the time of transition from the rolling state to the idling state (non-rolling).

[0037] Next, the cooling water amount reduction calculation unit 34 calculates the cooling water amount that can be reduced within the prediction target period T while cooperating with the roll thermal expansion amount prediction unit 31 (while exchanging information). Specifically, first, the roll thermal expansion amount reduction ΔR RC0 when the cooling water amount W TH recorded in step S4 above is continued for the time T is calculated (step S5). Next, it is determined whether the roll thermal expansion amount reduction ΔR TH calculated in step S5 is greater than or equal to the threshold value ΔR TH,MIN (ΔR TH,MIN ≦0) (step S6). When the roll thermal expansion amount reduction ΔR TH is smaller than the threshold value ΔR TH,MIN , it is determined that the roll cooling water amount W RC0 is continued during the time T. That is, it is determined that even if the roll cooling water amount W RC0 is continued for the time T, the roll 11 will not be excessively cooled (the roll thermal expansion amount will not change excessively) until the next rolling. In this case, the opening command value sequence of the variable flow valve 15 when the roll cooling water amount W RC0 is continued is calculated (step S7), and the process proceeds to step S11.

[0038] When the roll thermal expansion amount reduction ΔR TH calculated in step S5 above is greater than or equal to the threshold value ΔR TH,MIN , the roll cooling water amount W RC0If this continues for time T, it is determined that the roll 11 will be excessively cooled (the amount of thermal expansion of the roll will change excessively) by the next rolling time (time t2). In this case, the process proceeds to step S8. In step S8, the amount of roll cooling water W RC0 ΔW RC The amount reduced by W RC0,new Calculate as follows, and in the same manner as in step S5 above, the reduced amount of cooling water W RC0,new The decrease in roll thermal expansion ΔR when this is continued for time T. TH Next, calculate the decrease in roll thermal expansion ΔR calculated in step S8. TH The above threshold ΔR TH,MIN Determine whether it is smaller than or equal to (Step S9). Roll thermal expansion reduction ΔR TH The threshold ΔR TH,MIN If it is smaller, return to step S8. In step S8, for example, the amount of coolant W RC0,new By further reducing this, the appropriate reduction in roll thermal expansion ΔR can be achieved. TH This is calculated.

[0039] ΔR calculated in step S8 TH The above threshold ΔR TH,MIN If smaller, the amount of roll cooling water W is reduced for a period of time T. RC,new It is decided to continue. In this case, the roll cooling water volume W has been reduced. RC,new The sequence of opening command values ​​for the variable flow valve 15 when this is continued for time T (see Figure 5) is calculated (step S10), and the process proceeds to step S11.

[0040] In step S11, the sequence of opening degree command values ​​for the variable flow valve 15 calculated in step S10 or step S7 is set. For example, at each time specified in the sequence of opening degree command values ​​shown in Figure 5, the opening degree command value specified for each time is output to the variable flow valve 15, and the opening degree of the variable flow valve 15 is controlled.

[0041] In step S12, the output command value sequence of the variable speed pump 14n over time T is calculated, corresponding to the opening command value sequence of the variable flow valve 15. Here, the roll cooling water volume W RC0If this is to be continued, the rotation speed of the variable speed pump 14n will be kept at the current rotation speed. Meanwhile, the roll cooling water volume W RC0 to W RC0,new When reducing to ΔW, the reduction amount is ΔW. RC This is converted to the rotational speed of the variable speed pump 14n. That is, the decrease ΔW RC The rotational speed of the variable-speed pump 14n is calculated accordingly. The output command value sequence of the variable-speed pump 14n calculated in this way is set to the variable-speed drive 142n of the variable-speed pump 14n. Although not shown in the diagram, at each time specified in the output command value sequence, the pump command value specified for each time is output to the variable-speed drive 142n of the variable-speed pump 14n, and the rotational speed of the variable-speed pump 14n is controlled. During time T, the decrease is ΔW. RC This allows the rotation speed of the variable-speed pump 14n to be reduced, thus saving energy.

[0042] Furthermore, if the prediction period T is long, the roll cooling water volume W RC0 Even if reduced to the lower limit (e.g., 0%), the decrease in roll thermal expansion ΔR TH A certain threshold ΔR TH,MIN In some cases, it may not be possible to maintain the above. In this case, by adjusting the opening of the variable flow valve 15 to the minimum opening, the roll cooling water volume W RC0 The configuration should be such that it is reduced to the lower limit.

[0043] Based on the above, the difference ΔR between the amount of thermal expansion of the roll at the transition point from rolling to idling (non-rolling) and the amount of thermal expansion of the roll during the predicted period T until the next rolled material M reaches the roll 11 is... TH is within a predetermined range (threshold ΔR TH,MIN The opening of the variable flow valve 15 is adjusted so that it falls within a range smaller than the specified value. This appropriately controls the amount of cooling water supplied to the roll 11, preventing the amount of thermal expansion of the roll 11 from decreasing excessively during idling. Therefore, the roll 11 can be cooled without adversely affecting the plate thickness controllability.

[0044] Next, roll cooling control according to a second aspect of this embodiment will be described. Figure 8 shows an example of roll thermal expansion control according to the second aspect. In the second aspect, the prediction period T2 shown in Figure 8 includes multiple rolling periods and idling periods (non-rolling periods), and is longer than the prediction period T of the first aspect. The second aspect is suitably applied to continuous rolling in which rolling is carried out continuously with idling periods shorter than a predetermined time in between.

[0045] In the second embodiment, the amount of roll thermal expansion within a prediction period T from the current time (e.g., the rolling start time) t0 to the future is predicted at regular time intervals, and the amount of roll cooling water that minimizes the change in the predicted amount of roll thermal expansion is calculated. The prediction period T2 in the second embodiment also corresponds to the "second prediction period" in the claims. In Figure 8, the approximation curve Ac1 shown by the dashed line shows an example of the change in the amount of roll thermal expansion when the amount of roll cooling water is fixed at 100% (maximum flow rate). The approximation curve Ac2 shown by the solid line shows the amount of roll thermal expansion, with the target value R shown by the dashed line representing the amount of roll thermal expansion. TG This shows an example of the change in roll thermal expansion when the roll cooling water flow rate is set to saturate the roll as quickly as possible. Target value of thermal expansion: R TG This can be set to the maximum thermal expansion amount of the roll 11 that is maintained when the maximum amount of cooling water is supplied to the nozzle 13 via the variable flow valve 15 during continuous rolling.

[0046] To realize the above approximate curve Ac2, the rolling / idling prediction unit 32 uses rolling information to predict a future time t from the current time (e.g., rolling start time) t0. END The time until the roll 11 is defined as the forecast period T2, and a time schedule is created for rolling and non-rolling of roll 11 within the forecast period T2.

[0047] The roll thermal expansion prediction unit 31 calculates the roll thermal expansion amount assuming that cooling water is injected into the roll 11 at a constant flow rate during rolling and non-rolling. The cooling water amount reduction calculation unit 34 works in conjunction with the roll thermal expansion prediction unit 31 to calculate the thermal expansion amount and set the target value R TGThe amount of roll cooling water is determined to approximate the target. In this case, if the minimum flow rate during rolling is predetermined in order to prevent seizing between the rolled material M and the roll 11, the lower limit of the amount of roll cooling water during rolling shall be in accordance with the minimum flow rate. Similarly, if the minimum flow rate during non-rolling is predetermined, the lower limit of the amount of roll cooling water during non-rolling shall be in accordance with the minimum flow rate.

[0048] From the roll cooling water volume determined in this manner, a sequence of opening command values ​​for the variable flow valve 15 (see Figure 5) is calculated, similar to the first embodiment described above, and the calculated sequence of opening command values ​​is set in the variable flow valve 15. Next, similar to the first embodiment described above, in order to save energy, the reduction in roll cooling water volume ΔW is calculated. RC This is converted to the rotational speed of the variable speed pump 14n. That is, the decrease ΔW RC The rotational speed of the variable-speed pump 14n is calculated accordingly. The output command value sequence of the variable-speed pump 14n calculated in this way is set to the variable-speed drive 142n of the variable-speed pump 14n.

[0049] According to the second embodiment, the amount of thermal expansion of the roll 11 during the predicted period T2, which includes multiple rolling periods and idling periods, is predicted, and the predicted amount of thermal expansion and the target value R of thermal expansion are used. TG The opening of the variable flow valve 15 is adjusted so that the difference falls within a predetermined range. This appropriately controls the amount of cooling water supplied to the roll 11, and reduces the amount of thermal expansion to the target value R as quickly as possible. TG This allows the temperature to be reduced. Therefore, the roll 11 can be cooled without adversely affecting the plate thickness controllability.

[0050] By the way, if the prediction period T2 is long, the accuracy of the roll thermal expansion prediction decreases as it moves further away from the current time t0. Therefore, the above series of processes can be performed at regular intervals (for example, every 10 seconds). The sequence of opening command values ​​for the variable flow valve 15 and the sequence of pump output command values, once determined, are updated at regular intervals, so that the command values ​​at the same time are overwritten with new command values.

[0051] Here, the finite difference method calculation explained with reference to Figure 3 can be time-consuming, so it is also possible to use results calculated under predetermined conditions. These conditions include, for example, the thickness, width, hardness, and temperature of the rolled material M. Under these conditions, the amount of thermal expansion that occurs when rolling on roll 11 for a certain number of seconds is determined in advance through experimentation or simulation. If the conditions do not perfectly match, linear interpolation or other methods can be used to extract the determined amount of thermal expansion.

[0052] Furthermore, the average temperature in the radial direction (see Figure 3), which serves as the basis for calculating thermal expansion, may be calculated in advance. Figure 9 shows an example of a pre-calculation of the average roll temperature rise. Assuming a roll cooling water flow rate of 100% (maximum flow rate), the average roll temperature rise is calculated based on the average roll temperature at the start of rolling and the rolling time. Such calculations should be performed for each necessary category, such as steel grade classification and plate thickness classification, included in the rolling information. If the roll cooling water flow rate is not 100%, it is necessary to compensate with the cooling water flow rate. Figure 10 shows an example of the effect of the roll cooling water flow rate on the average roll temperature rise shown in Figure 9. The cooling water flow rate and the average roll temperature rise are not necessarily linearly related, and the degree of average temperature rise differs depending on the roll diameter. The maximum roll diameter is the roll diameter when the roll to be cooled is new, and the minimum roll diameter is the roll diameter when the roll to be cooled is used continuously until just before disposal. In Figures 9 and 10, it is difficult to calculate to cover all conditions, so discrete values ​​for representative conditions should be calculated in advance. The calculation results are stored as discrete values, and in areas that have not been calculated, various values ​​are extracted by linear interpolation between the calculated points or lines. This reduces the time required for the roll thermal expansion prediction unit 31 to calculate the average roll temperature and, consequently, the amount of thermal expansion.

[0053] Reducing the calculation time by the roll thermal expansion prediction unit 31 may decrease the accuracy of the thermal expansion prediction. Furthermore, the accuracy of the thermal expansion prediction by the roll thermal expansion prediction unit 31 may decrease due to disturbances. The cooling water volume W may decrease due to the accuracy of the thermal expansion prediction. RC0,newIf the accuracy of the variable flow valve 15 decreases, the amount of cooling water supplied to the nozzle 13 may become excessive even if the opening degree of the variable flow valve 15 is changed. In such cases, recalculating the roll thermal expansion amount, cooling water amount, and opening degree command value sequence would increase the computational load. Therefore, the amount of cooling water supplied to the nozzle 13 can be corrected by opening the drain valve 17 and adjusting its opening degree using the drain valve adjustment unit 37 shown in Figure 1. The opening degree of the drain valve 17 should be set to decrease by the amount of cooling water calculated by the cooling water amount reduction calculation unit 34. This is advantageous because it allows the use of the existing drain valve 17 without increasing the computational load.

[0054] There are no limitations on the specific structure of the process control computer 3, but as an example, it may be as follows. Figure 11 shows an example of the hardware configuration of the process control computer 3. The functions of the process control computer 3 can be realized by the processing circuit shown in Figure 11. This processing circuit may be dedicated hardware 30a. This processing circuit may also include a processor 30b and memory 30c. This processing circuit may be partially formed as dedicated hardware 30a and further include a processor 30b and memory 30c. In the example in Figure 11, part of the processing circuit is formed as dedicated hardware 30a, and the processing circuit also includes a processor 30b and memory 30c.

[0055] At least a portion of the processing circuit may be at least one dedicated hardware 30a. In this case, the processing circuit may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0056] The processing circuit may include at least one processor 30b and at least one memory 30c. In this case, each function of the process control computer 3 is realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 30c. The processor 30b realizes the functions of each part of the roll cooling control device 3 by reading and executing the programs stored in the memory 30c.

[0057] The processor 30b is also called a CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. Memory 30c includes non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, and EEPROM.

[0058] In this way, the processing circuit can realize each function of the process control computer 3 through hardware, software, firmware, or a combination thereof.

[0059] While embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above and can be implemented in various modified forms without departing from the spirit of this disclosure. When the number of elements, quantities, amounts, ranges, etc., are mentioned in the embodiments described above, this invention is not limited to the number mentioned unless it is specifically stated or clearly defined in principle. Furthermore, the structures, etc., described in the embodiments described above are not necessarily essential to this invention unless they are specifically stated or clearly defined in principle.

[0060] In the above embodiment, the case of cooling the work roll 11 was described as an example, but this disclosure can also be applied to the case of cooling the backup roll 12. Furthermore, in the above embodiment, a hot rolling mill was described as an example, but it is not limited to this. For example, since it is also necessary to cool the rolls in cold rolling mills, plate rolling mills, bar and wire rolling mills, this disclosure can also be applied to these rolling mills.

[0061] Furthermore, the first and second embodiments of the above-described model can be combined and implemented. According to this, the amount of thermal expansion of the roll 11 during the predicted period T, which includes multiple rolling periods and idling periods, is predicted, and the predicted amount of thermal expansion and the target value R of thermal expansion are compared. TG The opening of the variable flow valve 15 is adjusted so that the difference falls within a predetermined range. This appropriately controls the amount of cooling water supplied to the roll 11, and reduces the amount of thermal expansion to the target value R as quickly as possible. TG It can be achieved. Target value R for thermal expansion TG Once this point is reached, the amount of thermal expansion of the roll 11 is prevented from decreasing excessively during idling. Therefore, the roll 11 can be cooled without adversely affecting the plate thickness controllability. [Explanation of symbols]

[0062] 1...Rolling mill, 11...Work roll (roll), 12...Backup roll, 13...Nozzle, 14...Pump, 14n...Variable speed pump, 142n...Variable speed drive, 15...Variable flow valve, 17...Drain valve, 3...Roll cooling control device, process control computer, 31...Roll thermal expansion prediction unit, 32...Rolling / idling prediction unit, 33...Cooling water volume monitor unit, 34...Cooling water volume reduction calculation unit, 35...Variable flow valve adjustment unit, 36...Variable speed pump adjustment unit, 37...Drain valve adjustment unit, M...Rolled material, RL...Rolling line

Claims

1. A roll cooling control device for cooling the rolls of a rolling mill, The rolling mill comprises a nozzle for spraying cooling water onto the rolls, one or more pumps for supplying cooling water to the nozzle, and a variable flow valve capable of changing the flow rate of the cooling water supplied from the pump to the nozzle, A rolling / idling prediction unit that uses rolling information to predict the rolling period and idling period within a predetermined prediction target period, A roll thermal expansion prediction unit predicts the amount of thermal expansion of the roll during the predicted period, A cooling water reduction calculation unit, in cooperation with the roll thermal expansion prediction unit, sets the maximum thermal expansion amount of the roll maintained when the maximum amount of cooling water is supplied to the nozzle as the thermal expansion amount target value, and calculates the amount of cooling water to be reduced during the prediction period so that the difference between the thermal expansion amount target value and the thermal expansion amount during the prediction period falls within a predetermined range. A variable flow valve adjustment unit adjusts the opening degree of the variable flow valve so as to reduce the amount of cooling water by the amount calculated by the cooling water amount reduction calculation unit, A roll cooling control device equipped with a roll cooling control device.

2. A roll cooling control device according to claim 1, wherein the pump includes a variable speed pump, A roll cooling control device further comprising a variable speed pump adjustment unit that adjusts the rotational speed of the variable speed pump according to the opening degree of the variable flow valve adjusted by the variable flow valve adjustment unit.

3. A roll cooling control device according to claim 1, wherein a drain valve is provided between the pump and the variable flow valve, A roll cooling control device further comprising a drain valve adjustment unit that adjusts the opening degree of the drain valve so as to reduce the amount of cooling water by the amount calculated by the cooling water amount reduction calculation unit, while the opening degree of the variable flow valve is adjusted by the variable flow valve adjustment unit.

Images