Plate thickness control method for rolling mill, and, plate thickness control device for rolling mill

Abstract

To suppress the occurrence of such a problem that an outlet side plate thickness deviation continuously changes to the minus side.SOLUTION: In a command calculation step, a command (ΔS) of the gap of a pair of rolling rolls 21,21, which is such a command (ΔS) that an outlet side plate thickness deviation Δh is brought close to zero, by means of integral control based on the outlet side plate thickness deviation Δh, is calculated. Also in the command calculation step, when in the outlet side plate thickness deviation Δh detected in the outlet side plate thickness deviation detection step is changed to the minus side, and when gap between the rolling rolls is controlled in such a manner as to increase, and when rolling load detected in a rolling load detection step increase, it is determined that thermal crown occurs in the rolling roll 21, and an integral time T in an integral control is shortened.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a rolling mill plate thickness control method and rolling mill plate thickness control device for controlling the plate thickness of a rolled material rolled by a rolling mill. [Background technology]

[0002] For example, Patent Document 1 describes a rolling mill that rolls a rolled material. In the technology described in this document, integral control is performed so that the deviation of the detected value (delivery thickness deviation) of the thickness of the rolled material rolled by the rolling mill from a target value becomes zero (see, for example,

[0032] of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-114541 Summary of the Invention [Problem to be solved by the invention]

[0004] When heat flows into the rolling rolls that roll the rolled material, the rolls expand thermally, causing thermal crown. If the thermal crown expands suddenly, the integral control may not be able to keep up with this change. This may cause the delivery thickness deviation, which should be controlled to zero, to continue to change negatively (details will be explained later).

[0005] Therefore, the present invention aims to provide a rolling mill thickness control method and a rolling mill thickness control device that can suppress the problem of the delivery thickness deviation continuing to change to the negative side. [Means for solving the problem]

[0006] The thickness control method for a rolling mill comprises a rolling load detection step, an outlet thickness deviation detection step, a command calculation step, and an opening / closing control step. The rolling load detection step detects the rolling load applied to a rolled material being rolled by a pair of rolls of the rolling mill. The outlet thickness deviation detection step detects the outlet thickness deviation of the rolled material after being rolled by the pair of rolls. The command calculation step calculates a roll gap command, which is the gap between the pair of rolls, by integral control based on the outlet thickness deviation detected in the outlet thickness deviation detection step, such that the outlet thickness deviation approaches zero. The opening / closing control step controls the opening and closing of the pair of rolls so that the gap between the pair of rolls becomes the roll gap calculated in the command calculation step. The command calculation step determines that a rapidly expanding thermal crown has occurred in the roll when the delivery thickness deviation detected in the delivery thickness deviation detection step has changed to the negative side, the roll gap has been controlled to increase in the opening / closing control step, and the rolling load detected in the rolling load detection step has increased. When it is determined that a rapidly expanding thermal crown has occurred in the roll, the command calculation step shortens the integral time in the integral control.

[0007] The rolling mill thickness control device comprises a rolling mill, a rolling load detection unit, an exit thickness deviation detection unit, a command calculation unit, and an opening / closing control unit. The rolling mill has a pair of rolls that roll a rolled material. The rolling load detection unit detects the rolling load applied to the rolled material. The exit thickness deviation detection unit detects the exit thickness deviation of the rolled material after it has been rolled by the pair of rolls. The command calculation unit calculates a roll gap command, which is the gap between the pair of rolls, by integral control based on the exit thickness deviation detected by the exit thickness deviation detection unit, such that the exit thickness deviation approaches zero. The opening / closing control unit controls the opening and closing of the pair of rolls so that the gap between the pair of rolls becomes the roll gap calculated by the command calculation unit. The command calculation unit determines that a rapidly expanding thermal crown has occurred in the roll when the delivery thickness deviation detected by the delivery thickness deviation detection unit has changed to the negative side, the opening / closing control unit is controlling the roll gap to increase, and the rolling load detected by the rolling load detection unit is increasing. When the command calculation unit determines that a rapidly expanding thermal crown has occurred in the roll, it shortens the integral time in the integral control. [Effects of the Invention]

[0008] The above rolling mill thickness control method and rolling mill thickness control device each make it possible to suppress the problem of the delivery thickness deviation continuing to change to the negative side. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram of a rolling system 1. [Figure 2] FIG. 2 is a block diagram of integral control performed by a controller 40 shown in FIG. [Figure 3] 3 is a graph showing a measured value PV and a manipulated variable MV of integral control when the integral time T shown in FIG. 2 is changed. [Figure 4]2 is a graph showing the delivery thickness deviation Δh and the like when the thermal crown does not suddenly expand on the rolling roll 21 shown in FIG. 1. [Figure 5] 2 is a graph showing the delivery thickness deviation Δh and the like when a rapidly expanding thermal crown occurs in the rolling roll 21 shown in FIG. 1 and the integral time T is not reduced. [Figure 6] 2 is a graph showing the delivery thickness deviation Δh and the like when a rapidly expanding thermal crown occurs in the rolling roll 21 shown in FIG. 1 and the integral time T is reduced. [Figure 7] 2 is a flowchart showing the control of a controller 40 shown in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] The rolling system 1 (rolling mill thickness control device and rolling mill thickness control method) will be described with reference to FIGS. 1 to 7.

[0011] As shown in FIG. 1, the rolling system 1 is a system for rolling a rolled material W. The rolled material W is a workpiece that is rolled by the rolling system 1. The rolled material W is rolled by a pair of rolling rolls 21, which will be described later. The rolled material W is in the form of a plate. The rolled material W is, for example, a metal. The rolling system 1 is configured to be able to automatically control the thickness of the rolled material W (as will be described later). The rolling system 1 includes rolling equipment 10 and a controller 40.

[0012] The rolling equipment 10 is equipment that rolls a rolled material W. The rolling equipment 10 includes a first reel 11, a second reel 12, a direction change unit 15, a rolling mill 20, an entry-side thickness detection unit 31, an exit-side thickness detection unit 32 (exit-side thickness deviation detection unit), a temperature detection unit 35, and a rolling load detection unit 37.

[0013] The first reel 11 and the second reel 12 are reels on which the rolled material W is wound. The first reel 11 and the second reel 12 are tension reels that apply tension to the rolled material W. The first reel 11 and the second reel 12 are arranged on both sides of the rolling mill 20 (on both sides of the rolling mill 20 in the direction of movement of the rolled material W). One of the first reel 11 and the second reel 12 is an unwinding reel (rewinding machine) that unwinds the rolled material W. The other of the first reel 11 and the second reel 12 (the one different from the unwinding reel) is a winding reel (winding machine) that winds the rolled material W. [Rolling Example 1] The rolled material W may be unwound from the first reel 11, rolled by the rolling mill 20, and wound up by the second reel 12. [Rolling Example 2] The rolled material W may be unwound from the second reel 12, rolled by the rolling mill 20, and wound up on the first reel 11. Both of the above [Rolling Example 1] and [Rolling Example 2] may be performed alternately (the rolling equipment 10 may be of a reverse type), or only one of them may be performed. Below, the above [Rolling Example 1] will mainly be described.

[0014] The direction change unit 15 is a deflector that changes the moving direction (path direction) of the rolled material W. In the example shown in Fig. 1, the direction change unit 15 is provided between the first reel 11 and the rolling mill 20 (in the path of the rolled material W) and between the second reel 12 and the rolling mill 20. The direction change unit 15 is a cylindrical or columnar member (deflector roll).

[0015] The rolling mill 20 is a device that rolls the rolled material W. The rolling mill 20 is equipped with a plurality of rolls (rolling rolls 21, which will be described later, and backup rolls 23). Each of the plurality of rolls of the rolling mill 20 is a cylindrical or columnar member. The rolls are rotatably supported on a frame (e.g., a housing), not shown. The rolls are rotatable around central axes extending in the longitudinal direction of the rolls. One of the plurality of rolls is a drive roll. The drive roll is driven by a drive device (e.g., a drive motor, not shown) that drives the roll.

[0016] The number of stages (the number of rolls) of this rolling mill 20 can be set in various ways. In the example shown in FIG. 1, the rolling mill 20 is a four-high rolling mill. The number of stages of the rolling mill 20 may be more than four. The rolling mill 20 may be a cluster rolling mill in which a plurality of rolls are arranged in a cluster shape (like a bunch of grapes) when viewed from the direction in which the rotation axes of the rolls extend. The rolling mill 20 may be a six-high rolling mill, a twelve-high rolling mill, a fourteen-high rolling mill, or the like. The rolling mill 20 includes rolling rolls 21, backup rolls 23, and a reduction device 25.

[0017] The rolling rolls 21 (work rolls) come into contact with the rolled material W and sandwich the rolled material W. The rolling rolls 21 are provided in pairs (two rolls) on both sides in the thickness direction of the rolled material W. The direction in which the pair of rolling rolls 21 sandwich the rolled material W (i.e., the thickness direction of the rolled material W) is, for example, the vertical direction.

[0018] The backup rolls 23 (support rolls) rotatably support the rolling rolls 21 from the roll back side (the side opposite the rolled material W). The backup rolls 23 are provided on both sides in the thickness direction of the rolled material W (for example, in a pair, upper and lower). The outer circumferential surfaces of the backup rolls 23 contact the roll back side portion of the outer circumferential surface of the rolling roll 21. The backup rolls 23 rotate while contacting the rolling roll 21.

[0019] Intermediate rolls may be provided between the rolling roll 21 and the backup roll 23. The intermediate rolls are provided on both sides in the thickness direction of the rolled material W (for example, in a pair, upper and lower), and rotatably support the rolling roll 21 from the roll back side. When intermediate rolls are provided, the backup rolls 23 rotatably support the intermediate rolls from the roll back side. In this case, the backup rolls 23 rotatably support the rolling roll 21 from the roll back side via the intermediate roll.

[0020] The reduction device 25 is a device that reduces (applies load to) the rolling rolls 21. The reduction device 25 presses the rolled material W against the rolling rolls 21. The reduction device 25 is a reduction control device that adjusts the roll gap. The "roll gap" is the gap between a pair of rolling rolls 21, 21, and is the gap through which the rolled material W passes.

[0021] The entry-side thickness detection unit 31 (entry-side thickness gauge) detects the thickness of the rolled material W (at the entry side) before it is rolled by the pair of rolls 21. The entry-side thickness detection unit 31 may detect the thickness of the rolled material W in a non-contact manner (may be a non-contact type), or may detect the thickness of the rolled material W by, for example, electromagnetic waves (specifically, laser light, X-rays, etc.) (the same applies to the delivery-side thickness detection unit 32). The entry-side thickness detection unit 31 may detect the thickness of the rolled material W by coming into contact with the rolled material W (may be a contact type) (the same applies to the delivery-side thickness detection unit 32).

[0022] The delivery thickness detection unit 32 (delivery thickness deviation detection unit) (delivery thickness gauge) detects the thickness of the rolled material W (at the delivery side) after it has been rolled by the pair of rolls 21. The delivery thickness detection unit 32 detects the delivery thickness deviation Δh (delivery thickness deviation detection step). The delivery thickness deviation Δh is the difference between the actual (detected) value of the delivery thickness of the rolled material W (delivery thickness) and a target value. For example, the controller 40 may calculate the delivery thickness deviation Δh based on the delivery thickness detected by the delivery thickness detection unit 32 and the target value set in the controller 40 (this calculation is included in detection). In this case, the delivery thickness deviation detection unit is the delivery thickness detection unit 32 and the controller 40. When the rolling equipment 10 is of a reverse type, the delivery-side thickness detecting unit 32 also functions as the entry-side thickness detecting unit 31, and the entry-side thickness detecting unit 31 also functions as the delivery-side thickness detecting unit 32.

[0023] The temperature detection unit 35 (roll temperature detector) detects the temperature (roll temperature) of the reduction roll 21 (temperature detection step). The temperature detection unit 35 may detect the temperature of the reduction roll 21 directly or indirectly. For example, the temperature detection unit 35 may detect the roll temperature by detecting the temperature of a cooling medium (e.g., coolant oil) for the reduction roll 21.

[0024] The rolling load detection unit 37 (rolling load detection device) detects the rolling load P applied to the rolled material W (rolling load detection step). The rolling load detection unit 37 detects the rolling load P by detecting the load (reaction force of the rolling load P) that the rolling rolls 21 receive from the rolled material W. For example, the rolling load detection unit 37 detects the load transmitted from the rolled material W to the backup rolls 23 via the rolling rolls 21.

[0025] The controller 40 is a computer that inputs and outputs signals, performs calculations (processing), stores information, etc. For example, the functions of the controller 40 are realized by executing a program stored in a memory unit of the controller 40 in a calculation unit. The controller 40 may be provided inside (inside) the rolling equipment 10, or may be provided outside (for example, in a control room, etc.) the rolling equipment 10. The controller 40 may be a personal computer or may be provided on a control panel. The controller 40 has the function of a thickness control controller that controls the thickness of the rolled material W. The functions of the controller 40 include a command calculation unit 41 and an opening / closing control unit 43.

[0026] The command calculation unit 41 calculates a rolling roll gap command ΔS (roll gap command, monitor AGC command) (command calculation step) which will be described later. The rolling roll gap command ΔS is a command for the gap between a pair of rolling rolls 21, 21 (rolling roll gap, gap width). The command calculation unit 41 calculates the rolling roll gap command ΔS (details will be described later) so as to bring the delivery strip thickness deviation Δh closer to zero (to control it so as to bring it closer to zero).

[0027] The opening / closing control unit 43 controls the opening and closing of the pair of rolls 21 (opening / closing control step). The opening / closing control unit 43 controls the reduction device 25 so that the actual gap between the pair of rolls 21 becomes the roll gap calculated by the command calculation unit 41. Specifically, the opening / closing control unit 43 outputs (commands) the roll gap command ΔS calculated by the command calculation unit 41 to the reduction device 25.

[0028] (Activated) The rolling system 1 is configured to operate as follows.

[0029] (Operation of rolling equipment 10) The rolling equipment 10 operates as follows: A drive device (not shown) drives a drive roll (e.g., a backup roll 23), thereby driving the rolling roll 21. The rolling material W is transported between the first reel 11 and the second reel 12 and is rolled by the rolling roll 21.

[0030] The controller 40 controls the rolling of the rolled material W by the rolling mill 20. The controller 40 may also control the shape of the rolled material W. The controller 40 controls the thickness of the rolled material W. The controller 40 controls the gap between a pair of rolls 21 (rolling roll gap) to control the thickness of the rolled material W.

[0031] (automatic thickness control) The controller 40 automatically controls the thickness of the rolled material W (performs automatic thickness control). The controller 40 has a monitor AGC (Automatic Gauge Control) function. Specifically, the controller 40 calculates a roll gap command ΔS based on the delivery thickness deviation Δh detected by the delivery thickness detection unit 32. Based on the delivery thickness deviation Δh, the controller 40 calculates a roll gap command (roll gap command ΔS) such that the delivery thickness deviation Δh approaches zero. The controller 40 outputs the calculated roll gap command ΔS to the reduction device 25. The controller 40 controls the opening and closing of the pair of rolls 21 so that the gap between the pair of rolls 21 becomes the calculated roll gap.

[0032] (integral control) The controller 40 performs this automatic thickness control by integral control (see FIG. 2). The controller 40 calculates a rolling roll gap command ΔS by integral control. Integral control is a control method that accumulates (integrates) the deviation between a target value and a detected value (current value) over time, and adds a value proportional to the accumulated value to the manipulated variable, thereby controlling the deviation to zero. In this embodiment, the controller 40 controls the delivery thickness deviation Δh to approach zero by adding a value proportional to the value obtained by integrating the delivery thickness deviation Δh over time to the rolling roll gap command ΔS (manipulated variable).

[0033] The controller 40 performs integral control based on a predetermined integral time T. Specifically, the controller 40 calculates a roll gap command ΔS using the following equation 1.

[0034] ΔS={(M+m) / M}×(1 / T)×∫Δhdt (Equation 1) where: ΔS: Roll gap command (units are, for example, micrometers) M: Mill constant of the rolling mill 20 (unit: for example, ton / millimeter) m: Plastic constant of rolled material W (unit: ton / mm, for example) T: Integration time (unit: seconds, for example) (see below) Δh: Outlet thickness deviation (unit: micrometers, for example) is.

[0035] Figure 2 shows the theoretical formula and block diagram of integral control. The "operating variable MV" in the theoretical formula is the operating variable derived from the rolling roll gap command ΔS in the above (Equation 1). "e" in the theoretical formula is the deviation of the measured value PV from the target value, which in the above (Equation 1) is the delivery thickness deviation Δh. The integral control coefficient ("(M+m) / M" in the above (Equation 1)) is omitted in the theoretical formula. As shown in the block diagram in Figure 2, the controlled objects include dead time (e.g., 1 second) and first-order lag. Note that the formulas for "integral gain" and "first-order lag" in the block diagram are transfer functions, "s" is a variable in the Laplace transform, and "τ" in the formula for first-order lag is a time constant (e.g., 3).

[0036] 3 shows the time change of the measured value PV (delivery thickness in this embodiment) and the time change of the manipulated variable MV (roll gap command ΔS in this embodiment) when the target value changes from 0 to a predetermined value greater than 0 (when a step input is given as the target value). From the graph of the measured value PV, it can be confirmed that the measured value PV matches the target value due to integral control (integral action).

[0037] (When integral time T is changed) "T" in Equation 1 above is integral time (the same applies to "T" in the theoretical equation in Figure 2). The integral time T is the following: Assuming that a control system performs proportional control and integral control and a step input is given as the target value, the integral time T is the time it takes for the manipulated variable (MV) to equalize with the manipulated variable (MV) through proportional action (proportional control action). If the control system performs only integral action and not proportional action and the target value is a step input of 1, the integral time T is the time it takes for the measured value (PV) to reach the target value (i.e., 1). Figure 3 shows graphs of the time change in the measured value (PV) and the time change in the manipulated variable (MV) when the integral time T is changed. In this example, the graphs show the cases where the integral time T is set to 5, 7.5, and 10. This graph shows that the responsiveness slows as the integral time T increases. Specifically, the shorter the integral time T, the larger the manipulated variable (MV) becomes in a shorter time, resulting in faster control responsiveness. The longer the integral time T, the longer it takes for the manipulated variable MV to increase, and the slower the response of the control becomes.

[0038] The controller 40 shown in Fig. 1 performs at least integral control in the automatic thickness control. The controller 40 may perform proportional control. Specifically, the controller 40 may calculate a rolling roll gap command ΔS based on a value proportional to the delivery thickness deviation Δh. The controller 40 may perform differential control. Specifically, the controller 40 may calculate a rolling roll gap command ΔS based on a value proportional to a value obtained by differentiating the delivery thickness deviation Δh with respect to time.

[0039] (About Thermal Crown) Thermal crown occurs in the rolling roll 21. More specifically, when heat flows into the rolling roll 21 from the rolled material W, the rolling roll 21 thermally expands. At this time, the axial center of the rolling roll 21 expands compared to both axial ends of the rolling roll 21. The "axial direction" of the rolling roll 21 is the direction in which the rotation axis of the rolling roll 21 extends. When thermal crown occurs in the rolling roll 21, the thickness of the central portion in the width direction of the rolled material W after being rolled by the rolling roll 21 (exit side, after processing) becomes thinner than the thickness of the outer portions in the width direction of the rolled material W. As a result, the exit thickness detected by the exit thickness detection unit 32 becomes smaller (thinner). The exit thickness detection unit 32 detects the thickness of the rolled material W at a specific position in the width direction of the rolled material W (for example, the center position in the width direction).

[0040] 4, 5, and 6 are graphs showing the time variations of the roll gap command ΔS, the rolling load P, and the delivery thickness deviation Δh when thermal crown occurs in the roll 21. Below, the components of the rolling system 1 and the rolled material W will be described with reference to FIG. 1. FIG. 4 is a graph showing the case where thermal crown does not suddenly increase (described later). As shown in this graph, when thermal crown occurs in the roll 21 and the delivery thickness detected by the delivery thickness detection unit 32 decreases, the controller 40 changes the roll gap command ΔS in the direction of increasing the width. This keeps the actual gap between the pair of rolls 21 approximately constant. In this case, the rolling load P (rolling load detection value) detected by the rolling load detection unit 37 is also kept approximately constant. In this example, the roll gap command ΔS is controlled to an appropriate value, and the actual gap between the pair of rolls 21 is controlled to an appropriate size, so the delivery thickness deviation Δh is kept approximately zero (±0 μm).

[0041] On the other hand, when rolling is started with the rolls 21 at a low temperature and the temperature of the rolls 21 rises, the rolls 21 suddenly expand, causing a sudden increase in the thermal crown of the rolls 21 (a rapidly expanding thermal crown occurs in the rolls 21). In this case, as shown in FIG. 5, a problem occurs in which the delivery thickness deviation Δh continues to change to the negative side (is not maintained at approximately zero). More specifically, when a rapidly expanding thermal crown occurs in the rolls 21, the controller 40 changes the roll gap command ΔS in the direction of increasing the roll gap. However, when the thermal crown suddenly increases, the automatic thickness control cannot adequately follow the sudden increase in the thermal crown (response is slow). Specifically, when the rate at which the thermal crown increases is greater than the rate at which the gap between the rolls 21 is increased by the automatic thickness control, the rolling load P continues to increase, and the delivery thickness deviation Δh continues to change to the negative side.

[0042] Therefore, when a rapidly expanding thermal crown occurs in the reduction roll 21, the controller 40 shortens (reduces or decreases) the integral time T. This speeds up the response of the automatic thickness control.

[0043] FIG. 6 shows graphs representing the time variations of the roll gap command ΔS, the rolling load P, and the delivery thickness deviation Δh when the controller 40 performs a process to shorten the integral time T in the event of a rapidly expanding thermal crown occurring in the roll 21. As can be seen from this graph, the delivery thickness deviation Δh is maintained at approximately zero (±0 μm), improving the situation shown in FIG. 5 . Specifically, when performing a process to shorten the integral time T, the controller 40 changes the roll gap command ΔS to a larger value compared to when the process to shorten the integral time T is not performed. By increasing the roll gap command ΔS, the amount of narrowing of the actual gap between the pair of rolls 21 (the amount of narrowing of the gap due to the expansion of the thermal crown) is offset. Specifically, the roll gap command ΔS when the process to shorten the integral time T is performed (FIG. 6) is approximately twice as large in the direction of widening the gap as compared to the roll gap command ΔS when the process to shorten the integral time T is not performed (FIG. 5). As a result, the rolling load P becomes substantially constant, and the delivery thickness deviation Δh is maintained at substantially zero (±0 μm). Note that the shapes of the graphs shown in Figs. 4 to 6 are merely examples.

[0044] (Specific example of processing by the controller 40) A specific example of the processing of the controller 40 will be described with reference to the flowchart shown in FIG. 7. In the following, unless otherwise specified, the processing will be described in the order of the processing. Note that the order of the processing can be changed in various ways. As described above, each component of the rolling system 1 and the rolled material W shown in FIG. 1 will be described with reference to FIG. 1. Furthermore, each step shown in FIG. 7 will be described with reference to FIG. 7.

[0045] In step S1, the controller 40 reads the integral time T. Specifically, the controller 40 reads the integral time T (for example, the initial value, normal setting) when the integral time T has not been shortened (step S3).

[0046] In steps S2 and S3, the controller 40 determines (judges) whether a rapidly expanding thermal crown will occur in the reduction roll 21. In step S2, the controller 40 determines whether a rapidly expanding thermal crown is likely to occur in the reduction roll 21, and then determines whether to make the determination in step S3. The controller 40 determines whether a rapidly expanding thermal crown is likely to occur in the reduction roll 21 based on the temperature of the reduction roll 21 (roll temperature). Specifically, the controller 40 determines whether the roll temperature is equal to or lower than a predetermined temperature. The roll temperature is a temperature detected by the temperature detection unit 35, such as the temperature of the coolant oil in the reduction roll 21 (see above). The "predetermined temperature" is a temperature that is set in advance in the controller 40 (before step S2). The "predetermined temperature" is, for example, 40°C.

[0047] If the roll temperature is equal to or lower than the predetermined temperature (YES in step S2), the controller 40 determines that there is a possibility that a rapidly expanding thermal crown has occurred in the reduction roll 21. In this case, the controller 40 determines whether or not a rapidly expanding thermal crown has occurred in the reduction roll 21 (step S3). In this case, the controller 40 causes the processing flow to proceed to step S3. If the roll temperature exceeds the predetermined temperature (NO in step S2), the controller 40 determines that there is no possibility that a rapidly expanding thermal crown has occurred in the reduction roll 21. In this case, the controller 40 does not determine whether or not a rapidly expanding thermal crown has occurred in the reduction roll 21 (step S3). In this case, the controller 40 causes the processing flow to proceed to step S5. Note that the processing in step S2 may be omitted.

[0048] In step S3, the controller 40 determines whether or not a rapidly expanding thermal crown has occurred in the reduction roll 21. The controller 40 determines whether or not to perform a process for shortening the integral time T (step S4). Here, the "rapidly expanding thermal crown" is a thermal crown that expands (expands) at such a rate of change that the delivery thickness deviation Δh cannot be maintained at approximately zero (±0 μm) when the integral time T is set (for example, at a normal setting) without the shortening of the integral time T (step S4).

[0049] Specifically, the controller 40 determines that a rapidly expanding thermal crown has occurred in the roll 21 when all of the following conditions, [Condition A], [Condition B], and [Condition C], are satisfied (satisfied simultaneously): [Condition A] The delivery thickness deviation Δh detected by the delivery thickness detection unit 32 (delivery thickness deviation detection unit) has changed to the negative side (see Figure 5). [Condition B] The controller 40 is controlled (opening / closing control) so that the gap between the pair of rolls 21 (roll gap) increases. Specifically, the controller 40 changes the roll gap command ΔS to the opening side (see Figure 5). [Condition C] The rolling load P detected by the rolling load detection unit 37 has increased (see Figure 5).

[0050] The controller 40 may determine whether each of the above conditions has "changed" or "increased" within a predetermined time range, and may make the determination based on, for example, an average value within the predetermined time range. Specifically, in the example shown in Fig. 5, the delivery thickness deviation Δh fluctuates both positively and negatively when viewed over a short period of time, but decreases when viewed over a certain time range (a relatively long time range rather than a short period of time). In this case, the controller 40 determines that the delivery thickness deviation Δh has changed to the negative side (satisfies the above [Condition A]). The controller 40 may also determine the conditions of the roll gap command ΔS and the rolling load P within a predetermined time range, in the same way as the delivery thickness deviation Δh.

[0051] If all of the above conditions ([Condition A], [Condition B], and [Condition C]) are satisfied (YES in step S3), the controller 40 determines that a rapidly expanding thermal crown has occurred in the reduction roll 21. In this case, the controller 40 advances the processing flow to step S4. If any one of the above conditions is not satisfied (NO in step S3), the controller 40 determines that a rapidly expanding thermal crown has not occurred in the reduction roll 21. In this case, the controller 40 advances the processing flow to step S5. Note that the order in which the determinations of whether or not the above [Condition A] is satisfied, whether or not the above [Condition B] is satisfied, and whether or not the above [Condition C] is satisfied are made (the order of calculation) may be any order.

[0052] The conditions for determining that a rapidly expanding thermal crown has occurred in the reduction roll 21 may be different from the above conditions. For example, the controller 40 may determine that a rapidly expanding thermal crown has occurred in the reduction roll 21 when all of the above conditions are satisfied and a condition different from the above conditions is also satisfied.

[0053] In step S4, the controller 40 shortens (reduces or decreases) the integral time T. More specifically, when the controller 40 determines that a rapidly expanding thermal crown has occurred in the reduction roll 21, it shortens the integral time T in the integral control. The controller 40 sets a value smaller than the currently set integral time T as the new integral time T. This speeds up the response time of the integral control. As a result, the delivery thickness deviation Δh can be maintained at approximately zero (±0 μm).

[0054] Specifically, the controller 40 shortens the integral time T, for example, as follows. For example, the controller 40 may set the new integral time T to a value (T - ΔT) obtained by subtracting the subtractive integral time ΔT from the current integral time T. The "subtractive integral time ΔT" may be a constant value set in advance (before step S4) in the controller 40. The controller 40 may also set the new integral time T to a value that is 1 / a times (e.g., 1 / 3 times) the current integral time T. The "a" is a value greater than 1 and does not have to be an integer. The controller 40 may also change the degree to which the integral time T is shortened (e.g., the above ΔT, a, etc.) depending on some condition (e.g., the delivery thickness deviation Δh, etc.). Specifically, if the integral time T (e.g., the normal setting) before the shortening of the integral time T (step S4) is 10 seconds, the new integral time T is 3 seconds, for example. The numerical values ​​"10 seconds" and "3 seconds" are merely examples to make it easier to understand the process of shortening the integration time T.

[0055] This process of shortening the integral time T (step S4) may be performed multiple times. Specifically, after the integral time T is shortened in step S4, if the answers are YES in step S7, YES in step S2, and YES in step S3, the integral time T may be further shortened in step S4. Also, the process of shortening the integral time T (step S4) may be performed only once. After step S4, the controller 40 advances the process flow to step S6.

[0056] In step S5, the controller 40 does not shorten the integral time T. The controller 40 sets the integral time T in the current process to the integral time T in the previous process (previous value). Note that, when the thermal crown of the reduction roll 21 is no longer rapidly expanding, the controller 40 may return the integral time T to the integral time T (for example, the normal setting, initial value) that was used when the integral time T was never shortened (step S4). After step S5, the controller 40 advances the process flow to step S6.

[0057] In step S6, the controller 40 performs automatic thickness control. Specifically, the controller 40 calculates a rolling roll gap command ΔS by integral control using the integral time T determined in step S4 or step S5, and outputs the calculated rolling roll gap command ΔS to the screw down device 25.

[0058] In step S7, the controller 40 determines whether or not to continue the calculation. If the calculation is to be continued (YES in step S7), the controller 40 returns the process flow to step S1. If the calculation is not to be continued (NO in step S7), the controller 40 ends the calculation. For example, if the controller 40 receives a command to end the calculation, it determines not to continue the calculation. For example, the controller 40 may determine not to continue the calculation if it determines to end rolling or if it determines that the shape of the thermal crown has transitioned to a steady state.

[0059] (Effects of the first invention) The effects of the thickness control method for the rolling mill 20 shown in Figure 1 are as follows. The thickness control method comprises a rolling load detection step, an exit thickness deviation detection step, a command calculation step, and an opening / closing control step. The rolling load detection step detects the rolling load P applied to the rolled material W being rolled by the pair of rolls 21 of the rolling mill 20. The exit thickness detection step detects the exit thickness deviation Δh of the rolled material W after being rolled by the pair of rolls 21. The command calculation step calculates a command (roll gap command ΔS) by integral control based on the exit thickness deviation Δh detected in the exit thickness deviation detection step. The above command is a command that brings the exit thickness deviation Δh closer to zero, and is a command for the roll gap, which is the gap between the pair of rolls 21. The opening / closing control step controls the opening / closing of the pair of rolls 21 so that the gap between the pair of rolls 21 becomes the gap between the rolls calculated in the command calculation step.

[0060] [Configuration 1-1] The command calculation step determines that a rapidly expanding thermal crown has occurred in the rolling roll 21 when the following [Condition 1A] is satisfied, and also when the following [Condition 1B] is satisfied, and also when the following [Condition 1C] is satisfied (Step S3 in Figure 7). [Condition 1A] The delivery side thickness deviation Δh detected in the delivery side thickness deviation detection step has changed to the negative side (see Figure 5). [Condition 1B] The opening / closing control step is controlling so that the roll gap increases (see Figure 5). [Condition 1C] The rolling load P detected in the rolling load detection step has increased (see Figure 5).

[0061] [Configuration 1-2] In the command calculation step, if it is determined that a rapidly expanding thermal crown has occurred in the reduction roll 21 (YES in step S3 in FIG. 7), the integral time T in the integral control is shortened (step S4 in FIG. 7).

[0062] When the above-mentioned [Condition 1A], [Condition 1B], and [Condition 1C] of [Configuration 1-1] are satisfied, it is considered that the thermal crown of the rolling roll 21 is rapidly expanding. More specifically, when the thermal crown of the rolling roll 21 rapidly expands, the actual gap between the pair of rolling rolls 21 narrows, the thickness of the rolled material W becomes thinner, and the delivery thickness deviation Δh changes to the negative side. At this time, the rolling roll gap is controlled to increase (widen) by integral control that brings the delivery thickness deviation Δh closer to zero based on the delivery thickness deviation Δh (the above-mentioned [Condition 1B] is satisfied). However, when the thermal crown of the rolling roll 21 rapidly expands, this control cannot follow the change in thermal crown, and the increase in the actual gap between the pair of rolling rolls 21 becomes insufficient. As a result, the delivery thickness becomes narrower than the target, that is, the delivery thickness deviation Δh changes to the negative side (the above [Condition 1A] is satisfied), and the rolling load P increases (the above [Condition 1C] is satisfied).

[0063] Therefore, when the above [Condition 1A], [Condition 1B], and [Condition 1C] are satisfied, it is determined that "a rapidly expanding thermal crown has occurred in the rolling roll 21." In this case, the above [Configuration 1-2] shortens the integral time T in the integral control. This speeds up the response of the integral control. As a result, the integral control can follow the negative change in the delivery thickness deviation Δh, and the roll gap command ΔS can follow, allowing the actual gap between the pair of rolls 21 to be appropriately increased. This prevents the problem of the delivery thickness deviation Δh continuing to change negatively. This allows the thickness of the rolled material W to approach the target value. As a result, the quality of the rolled material W can be improved.

[0064] (Effects of the second invention) [Configuration 2] In the command calculation step, if the temperature of the roll 21 is equal to or lower than a predetermined temperature (YES in step S2 in FIG. 7), it is determined whether or not a rapidly expanding thermal crown has occurred in the roll 21 (step S3). In the command calculation step, if the temperature of the roll 21 exceeds a predetermined temperature (NO in step S2 in FIG. 7), it is not determined whether or not a rapidly expanding thermal crown has occurred in the roll 21 (does not proceed to step S3 in FIG. 7).

[0065] The above-mentioned [Configuration 2] provides the following effect. When the temperature of the rolling roll 21 changes from a low temperature (below a predetermined temperature) to a high temperature, the rolling roll 21 may suddenly expand, and a rapidly expanding thermal crown may occur in the rolling roll 21. This may cause a problem in that the integral control cannot follow the change in the thermal crown of the rolling roll 21, and the delivery thickness deviation Δh continues to change to the negative side. Therefore, in the above-mentioned [Configuration 2], when the temperature of the rolling roll 21 is below a predetermined temperature (YES in step S2), it is determined whether a rapidly expanding thermal crown has occurred in the rolling roll 21 (step S3). As a result, the problem of the delivery thickness deviation Δh continuing to change to the negative side can be suppressed.

[0066] On the other hand, when the temperature of the rolling roll 21 is high (above a predetermined temperature), sudden expansion of the rolling roll 21 does not occur or is unlikely to occur. Therefore, integral control can follow changes in the thermal crown of the rolling roll 21, and the delivery thickness deviation Δh is maintained at approximately zero. Therefore, in the above [Configuration 2], when the temperature of the rolling roll 21 exceeds a predetermined temperature (NO in step S2 of FIG. 7), it is not determined whether a sudden expansion of the thermal crown has occurred in the rolling roll 21. Therefore, the calculation load on the computer (specifically, the command calculation unit 41) that makes this determination can be reduced.

[0067] (Effect of the third invention) The rolling system 1 (rolling mill thickness control device) comprises a rolling mill 20, a rolling load detection unit 37, an exit thickness detection unit 32 (exit thickness deviation detection unit), and a command calculation unit 41. The rolling mill 20 has a pair of rolls 21 that roll the rolled material W. The rolling load detection unit 37 detects the rolling load P applied to the rolled material W. The exit thickness detection unit 32 detects the exit thickness deviation Δh of the rolled material W after it has been rolled by the pair of rolls 21. The command calculation unit 41 calculates a command (roll gap command ΔS) by integral control based on the exit thickness deviation Δh detected by the exit thickness detection unit 32. The above command is a command that brings the exit thickness deviation Δh closer to zero, and is a command for the roll gap, which is the gap between the pair of rolls 21. The opening / closing control unit 43 controls the opening and closing of the pair of rolls 21 so that the gap between the pair of rolls 21 becomes the gap between the rolls calculated by the command calculation unit 41 .

[0068] [Configuration 3-1] The command calculation unit 41 determines that a rapidly expanding thermal crown has occurred in the rolling roll 21 when the following [Condition 3A] is satisfied, and also when the following [Condition 3B] is satisfied, and also when the following [Condition 3C] is satisfied (Step S3 in FIG. 7). [Condition 3A] The delivery side thickness deviation Δh detected in the delivery side thickness deviation detection step has changed to the negative side (see FIG. 5). [Condition 3B] The rolling roll gap is controlled to increase in the opening / closing control step (see FIG. 5). [Condition 3C] The rolling load P detected in the rolling load detection step has increased (see FIG. 5).

[0069] [Configuration 3-2] When it is determined that a rapidly expanding thermal crown has occurred in the reduction roll 21, the command calculation unit 41 shortens the integral time T in the integral control (step S4 in FIG. 7).

[0070] The above [Configuration 3-1] and [Configuration 3-2] can suppress the problem of the delivery thickness deviation Δh continuing to change to the negative side, similar to the effects obtained by the above [Configuration 1-1] and [Configuration 1-2].

[0071] (Effect of the fourth invention) [Configuration 4] When the temperature of the roll 21 is equal to or lower than a predetermined temperature (YES in step S2), the command calculation unit 41 determines whether or not a rapidly expanding thermal crown has occurred in the roll 21 (step S3 in FIG. 7). When the temperature of the roll 21 exceeds a predetermined temperature (NO in step S2 in FIG. 7), the command calculation unit 41 does not determine whether or not a rapidly expanding thermal crown has occurred in the roll 21 (does not proceed to step S3 in FIG. 7).

[0072] The above [Configuration 4] can reduce the calculation load on the command calculation unit 41, similar to the effect obtained by the above [Configuration 2].

[0073] (Variation) The above-described embodiments (including modified examples within the embodiments (the same applies hereinafter)) may be modified in various ways. For example, the number of components in the above-described embodiments may be changed, or some of the components may not be provided. For example, the inclusion relationships between the components may be changed in various ways. For example, a component described as a lower-level component included in a higher-level component may not be included in this higher-level component, but may be included in another component. For example, what is described as multiple different elements may be combined into a single element. For example, what is described as a single element may be provided as multiple different elements. For example, the order of the steps in the flowchart shown in FIG. 7 may be changed, or some of the steps may not be performed. For example, various pieces of information (values, ranges, etc.) may be set in the controller 40 in advance, or may be set by being read into the controller 40 from a storage device external to the controller 40. The various pieces of information may be set directly by manual operation by an operator, or may be set in the controller 40 based on information set by manual operation by an operator. The various pieces of information may be set in the controller 40 based on information detected by a detection unit (e.g., the delivery thickness detection unit 32, etc.). For example, the various pieces of information may not be changeable, may be changeable by manual operation, or may be automatically changed by the controller 40 in response to certain conditions. For example, the controller 40 may perform substantially the same processing (calculation, determination, etc.) as the processing of the above-described embodiment. For example, the mathematical formulas, processing procedures, information used in the processing, etc. may be changed in various ways. Specifically, the controller 40 may perform processing using information that can be converted into the various pieces of information used in the above-described embodiment. The processing performed by the controller 40 may be combined in various ways. For example, each component may have only a part of its characteristics (function, arrangement, shape, operation, etc.).

[0074] The rolling system 1 is configured to perform each of the above operations. A thickness control program may be set that causes a computer (controller 40) to execute processing to perform each of the above operations. Each of the above operations may be defined as a "step" in a thickness control method and a thickness control program. [Explanation of symbols]

[0075] 1. Rolling system (rolling mill thickness control device) 20. Rolling Mill 21 Rolling mill 32 Exit thickness detector 37 Rolling load detection unit 41 Command calculation section 43 Opening and closing control section P rolling load T integration time W rolled material Δh Output thickness deviation

Claims

1. a rolling load detection step of detecting a rolling load applied to a rolled material being rolled by a pair of rolls of a rolling mill; An outlet thickness deviation detection step of detecting an outlet thickness deviation of the rolled material after being rolled by the pair of rolling rolls; A command calculation step of calculating a roll gap command, which is a command to bring the delivery thickness deviation closer to zero by integral control based on the delivery thickness deviation detected in the delivery thickness deviation detection step, and is a gap command between the pair of rolling rolls; an opening / closing control step of controlling opening and closing of the pair of rolls so that the gap between the pair of rolls becomes the roll gap calculated in the command calculation step; Equipped with The command calculation step determines that a rapidly expanding thermal crown has occurred in the rolling roll when the delivery thickness deviation detected in the delivery thickness deviation detection step has changed to the negative side, the opening / closing control step has controlled the roll gap to increase, and the rolling load detected in the rolling load detection step has increased, the command calculation step shortens an integral time in the integral control when it is determined that a rapidly expanding thermal crown has occurred in the reduction roll. A method for controlling thickness in a rolling mill.

2. The method for controlling a thickness of a rolling mill according to claim 1, The command calculation step includes: determining whether or not a thermal crown that rapidly expands occurs in the rolling roll when the rolling roll is at or below a predetermined temperature; When the temperature of the rolling roll exceeds the predetermined temperature, it is not determined whether a rapidly expanding thermal crown has occurred in the rolling roll. A method for controlling thickness in a rolling mill.

3. a rolling mill having a pair of rolling rolls for rolling the rolled material; a rolling load detection unit that detects a rolling load applied to the rolled material; An outlet thickness deviation detection unit that detects an outlet thickness deviation of the rolled material after being rolled by the pair of rolling rolls; A command calculation unit that calculates a roll gap command, which is a gap between the pair of rolling rolls, by integral control based on the delivery thickness deviation detected by the delivery thickness deviation detection unit to bring the delivery thickness deviation closer to zero; an opening / closing control unit that controls opening and closing of the pair of rolls so that the gap between the pair of rolls becomes the roll gap calculated by the command calculation unit; Equipped with the command calculation unit determines that a rapidly expanding thermal crown has occurred in the rolling roll when the delivery thickness deviation detected by the delivery thickness deviation detection unit has changed to the negative side, the opening / closing control unit is controlled to increase the roll gap, and the rolling load detected by the rolling load detection unit has increased, the command calculation unit shortens an integral time in the integral control when it determines that a rapidly expanding thermal crown has occurred in the reduction roll. Rolling mill thickness control device.

4. The rolling mill thickness control device according to claim 3, The command calculation unit determining whether or not a thermal crown that rapidly expands occurs in the rolling roll when the rolling roll is at or below a predetermined temperature; When the temperature of the rolling roll exceeds the predetermined temperature, it is not determined whether a rapidly expanding thermal crown has occurred in the rolling roll. Rolling mill thickness control device.

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