Method for determining whether thickness can be changed while on the move, method for changing thickness while on the move, device for determining whether thickness can be changed while on the move, and program for determining whether thickness can be changed while on the move

Abstract

To provide a method for determining whether to allow proper flying thickness change, a device for determining whether to allow flying thickness change and a program for determining whether to allow flying thickness change, which can accurately predict tension fluctuation during flying thickness change, even in a condition in which a material to be milled in which a preceding material and a succeeding material combined with each other have been actually operated less frequently in the past.SOLUTION: A method for determining whether to allow flying thickness change, which determines whether to allow flying thickness change when a tandem mill continuously mills a material to be milled in which a preceding material is joined to a succeeding material through a joint part, includes: a set value obtaining step of obtaining set values of a roll gap and a roll circumferential velocity at a milling stand with respect to the preceding material, before starting to change the set values of the roll gap and the roll circumferential velocity on at least one milling stand of the tandem mill; a tension fluctuation calculating step of calculating tension fluctuation when the joint part passes on the milling stand while maintaining the set values of the roll gap and the roll circumferential velocity with respect to the preceding material; and a determining step of determining whether to allow flying thickness change on the basis of the tension fluctuation calculated in the tension fluctuation calculating step.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a method for determining whether or not a thickness change while on the fly is possible, a method for changing the thickness while on the fly, an apparatus for determining whether or not a thickness change while on the fly is possible, and a program for determining whether or not a thickness change while on the fly is possible. [Background technology]

[0002] In the cold rolling process, a preceding material to be rolled (hereinafter referred to as "preceding material") and a succeeding material to be rolled (hereinafter referred to as "successive material") are joined (typically by welding) at the entry side of a tandem rolling mill, and the preceding and succeeding materials are cold rolled in the tandem rolling mill as a continuous metal strip. The metal strip that has completed cold rolling is then cut at the exit side of the tandem rolling mill at the position of each product, and the cut metal strips are sequentially wound on tension reels. Furthermore, when cold rolling a metal strip, if any of the hardness, base thickness, and finished thickness of the preceding and succeeding material differ, "flying thickness change" is performed. "Flying thickness change" refers to a process of changing the rolling conditions before and after the joining part (also called the joining point) during continuous rolling in order to improve yield without stopping the line.

[0003] If rolling conditions change significantly before and after the welded section during on-the-fly thickness change, the tension fluctuations increase as the welded section passes through each rolling stand, potentially causing strip breakage or narrowing. If strip breakage or narrowing occurs, the operating efficiency of the tandem rolling mill decreases. To address this issue, a technology has been proposed that predicts the tension fluctuations as the welded section passes through each rolling stand of the tandem rolling mill, and if the predicted tension fluctuations are large, changes the operating conditions of the tandem rolling mill. Specifically, Patent Document 1 describes a method that includes a prediction unit for predicting the tension fluctuations that occur during on-the-fly thickness change and optimizes the on-the-fly thickness change time so that the predicted tension fluctuations fall within an allowable range. In the method described in Patent Document 1, the prediction unit uses a tension generation model with first-order lag characteristics and a correction term that learns the actual tension fluctuations. Patent Document 1 also describes that a prediction unit trained by a neural network using actual tension fluctuation values ​​as training data can be used as the prediction unit.

[0004] Furthermore, Patent Document 2 describes a method for predicting tension fluctuations during on-the-fly thickness changes, in which a prediction model trained by machine learning is used to predict the amount of tension fluctuation when a joining point passes through a rolling stand. The prediction model described in Patent Document 2 uses rolling operation parameters of a preceding strip and rolling operation parameter change amounts representing the difference between the rolling operation parameters of the preceding strip and the succeeding strip as input data, and tension fluctuation information when the joining point passes through a rolling stand as output data. Meanwhile, Patent Document 3 describes a method for calculating an actuator change amount at the timing when the joining point passes through a rolling stand and determining whether or not to change the on-the-fly thickness based on the calculated actuator change amount and a predetermined threshold value. Patent Document 3 also describes that it is possible to easily determine whether or not to change the on-the-fly thickness based on the actuator change amount in a rolling schedule calculation, without the need to use a highly accurate tension fluctuation prediction model. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-249423 [Patent Document 2] Japanese Patent Publication No. 2022-21794 [Patent Document 3] Japanese Patent Application Publication No. 2019-111568 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 provides low accuracy in predicting tension fluctuations. Specifically, a running gauge change is performed when the base material thickness, finish thickness, or deformation resistance of the preceding and following strips differs. However, there are various combinations of these changes for the preceding and following strips for each rolling stand. Furthermore, the combination of the preceding and following strips is set according to the production schedule of the tandem rolling mill and is not necessarily set to reduce tension fluctuations during running gauge change. Therefore, even if a prediction method trained by a neural network using actual tension fluctuation values ​​as training data is used, the prediction accuracy of tension fluctuations decreases when a combination of preceding and following strips with no past operating history is set. Meanwhile, Patent Document 1 describes the use of a tension generation model determined based on a physical model for the prediction method. However, when using a tension generation model, it is difficult to accurately calculate tension fluctuations in an unsteady state where the roll gap and roll peripheral speed change at the junction point between the preceding and following strips, resulting in sudden changes in base material thickness, finish thickness, deformation resistance, etc.

[0007] Similarly, the prediction model trained by machine learning described in Patent Document 2 also has a reduced prediction accuracy for tension fluctuations when a combination of a preceding strip and a following strip with no past operational history is set. This is because there are many combinations of the rolling operation parameters of the preceding strip and the rolling operation parameter change amount representing the difference between the rolling operation parameters of the preceding strip and the following strip. On the other hand, the method described in Patent Document 3 is a method for determining whether or not a running thickness change is possible based on an actuator change amount correlated with tension fluctuations, but it does not predict the amount of tension fluctuation that occurs when a running thickness change is made. For this reason, depending on the threshold value used to determine whether or not a running thickness change is possible, it may not always be possible to make an appropriate determination.

[0008] The present invention has been made to solve the above problems, and its object is to provide a method, an apparatus, and a program for determining whether or not a thickness change while on the run can be performed, which can accurately predict the amount of tension fluctuation that occurs when a thickness change while on the run is performed, even under conditions where the combination of preceding and succeeding strips has little past operational experience. Another object of the present invention is to provide a method for changing the thickness while on the run, which can prevent breakage or narrowing of the metal strip and enable the metal strip to be rolled with a high yield. [Means for solving the problem]

[0009] The method for determining whether or not the thickness can be changed while on the run according to the present invention is a method for determining whether or not the thickness can be changed while on the run when a rolled material in which a preceding material and a following material are joined via a joint is continuously rolled by a tandem rolling mill, and includes the following steps: a setting value acquisition step for acquiring the set values ​​of the roll gap and roll circumferential speed of the rolling stand for the preceding material before starting to change the set values ​​of the roll gap and roll circumferential speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation step for calculating the amount of tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material; and a determination step for determining whether or not the thickness can be changed while on the run based on the tension fluctuation calculated in the tension fluctuation calculation step.

[0010] The tension fluctuation calculation step preferably calculates the tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material, using the set values ​​of the roll gap and roll circumferential speed of the rolling stand for the preceding material acquired in the set value acquisition step, and the plate thickness and deformation resistance set for the succeeding material passing through the rolling stand.

[0011] In the above-mentioned change of the thickness while traveling, it is preferable that the change start point of the roll gap and the roll peripheral speed is set at the position of the preceding material, and the change end point of the roll gap and the roll peripheral speed is set at the position of the following material.

[0012] It is preferable that the difference between the deformation resistance of the preceding material and the deformation resistance of the following material be 80 MPa or more.

[0013] The method for changing the thickness on the fly according to the present invention uses the method for determining whether or not the thickness can be changed on the fly according to the present invention to perform a thickness change on the fly when it is determined that the thickness can be changed on the fly in all rolling stands of the tandem rolling mill, and when it is determined that the thickness cannot be changed on the fly in at least one rolling stand of the tandem rolling mill, it changes the set values ​​of the roll gap and roll peripheral speed of the rolling stand for the following material.

[0014] The device for determining whether or not the thickness can be changed while on the run according to the present invention is a device for determining whether or not the thickness can be changed while on the run when a rolled material in which a preceding material and a following material are joined via a joint is continuously rolled by a tandem rolling mill, and is equipped with: a setting value acquisition means for acquiring the set values ​​of the roll gap and roll circumferential speed of the rolling stand for the preceding material before starting to change the set values ​​of the roll gap and roll circumferential speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation means for calculating the amount of tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material; and a determination means for determining whether or not the thickness can be changed while on the run based on the tension fluctuation calculated by the tension fluctuation calculation means.

[0015] The program for determining whether or not the thickness can be changed while on the run according to the present invention is a program for determining whether or not the thickness can be changed while on the run when a rolled material in which a preceding material and a following material are joined via a joint is continuously rolled by a tandem rolling mill, and causes a computer to function as: a setting value acquisition means for acquiring the set values ​​of the roll gap and roll circumferential speed of the rolling stand for the preceding material before starting to change the set values ​​of the roll gap and roll circumferential speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation means for calculating the amount of tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material; and a determination means for determining whether or not the thickness can be changed while on the run based on the tension fluctuation calculated by the tension fluctuation calculation means. [Effects of the Invention]

[0016] According to the method, device, and program for determining whether or not a thickness change can be performed while on the fly, it is possible to accurately predict the amount of tension fluctuation that occurs when a thickness change is performed while on the fly, even under conditions where the combination of preceding and succeeding strips has little past operational experience, and to determine whether or not an appropriate thickness change can be performed while on the fly. Furthermore, according to the method for changing the thickness while on the fly, it is possible to suppress the occurrence of breakage, squeezing, etc. in the metal strip, and to roll the metal strip with a high yield. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of continuous cold rolling equipment to which the present invention is applied. [Figure 2] FIG. 2 is a diagram showing the relationship between the delivery thickness of the rolled material and the roll gap. [Figure 3] FIG. 3 is a diagram showing the relationship between the delivery thickness of the rolled material and the roll gap. [Figure 4] FIG. 4 is a flowchart showing the flow of setting calculations for the succeeding material during rolling of the preceding material. [Figure 5] FIG. 5 is a diagram for explaining the start and end points of the change in thickness while running. [Figure 6] FIG. 6 is a diagram for explaining a method for calculating the tension fluctuation index. [Figure 7] FIG. 7 is a flowchart showing the flow of a method for determining whether or not the running gauge can be changed, according to one embodiment of the present invention. [Figure 8] FIG. 8 is a diagram for explaining the two-stage on-the-fly thickness change. [Figure 9] FIG. 9 is a diagram for explaining the start and end points of the two-stage on-the-fly thickness change. [Figure 10] FIG. 10 is a diagram showing fluctuations in unit tension of the material to be rolled. [Figure 11] FIG. 11 is a diagram showing the relationship between the tension fluctuation index and the actual value of tension fluctuation. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, with reference to the drawings, an embodiment of the present invention will be described, which relates to a method for determining whether or not a thickness can be changed while on the move, a method for changing thickness while on the move, an apparatus for determining whether or not a thickness can be changed while on the move, and a program for determining whether or not a thickness can be changed while on the move.

[0019] [Configuration of continuous cold rolling equipment] First, with reference to FIG. 1, an example of the configuration of continuous cold rolling equipment to which the present invention is applied will be described.

[0020] Fig. 1 is a schematic diagram showing an example of the configuration of a continuous cold rolling facility to which the present invention is applied. In Fig. 1, other devices incidental to the continuous cold rolling facility (for example, a rewinder, a welding machine, and a looper installed on the entry side, and devices such as a cutter and a winder installed on the exit side) are not shown. As shown in Fig. 1, the continuous cold rolling facility 1 to which the present invention is applied includes a tandem rolling mill 2, a rolling control controller (PLC) 3 that controls the tandem rolling mill 2, and a control computer (process computer) 4 that manages the continuous cold rolling facility 1 including the rolling control controller 3.

[0021] The tandem rolling mill 2 is a continuous cold tandem rolling mill having a first rolling stand 2A to a fifth rolling stand 2E, arranged in order from the entry side in the direction of the rolling material 5. Each rolling stand is equipped with a work roll 21, a roll peripheral speed control device 22, which is an electric motor that changes the roll peripheral speed of the work roll 21, and a roll gap control device 23 that changes the roll gap between the upper and lower work rolls 21. A rolling load detector 24, consisting of a load cell, is also installed below the lower backup roll of each rolling stand. Each rolling stand is also equipped with a roll gap position detector 25 that detects the roll gap position. A tension meter 26 that detects the tension of the rolled material 5 is also installed between each rolling stand. A thickness meter 27 that detects the thickness (plate thickness) of the rolled material 5 is also installed at the exit side of the first rolling stand 2A and the exit side of the fifth rolling stand 2E.

[0022] The rolling controller 3 collects rolling operation data such as the rolling load detected by the rolling load detector 24 and the tension detected by the tension meter 26 at a predetermined sampling period and outputs the data to the control computer 4. The rolling controller 3 also executes processing to control the roll peripheral speed control device 22 and the screw-down control device 23 of each rolling stand based on the values ​​acquired from the control computer 4. The rolling controller 3 also has a function to track the junction point of the preceding material and the succeeding material, as well as to track a specified position on the material to be rolled 5. This allows the rolling controller 3 to output command values ​​for changing predetermined set values ​​to control devices such as the roll peripheral speed control device 22 and the screw-down control device 23, at the timing when a preset position of the material to be rolled 5, including the junction point, passes through each rolling stand of the tandem rolling mill 2.

[0023] The control computer 4 sets the rolling schedule and the on-the-fly thickness change unit (described later), and generates command values ​​for changing the set values ​​of the roll gap and roll peripheral speed of each rolling stand corresponding to the on-the-fly thickness change unit. The command values ​​for changing the set values ​​of the roll gap and roll peripheral speed often use the difference between the set values ​​for the preceding and succeeding strips, which are called differential command values. In addition, the control computer 4 calculates the pass schedules for the preceding and succeeding strips, predicted values ​​of the rolling force and forward ratio of each rolling stand, and set values ​​of the roll gap and roll peripheral speed according to information such as the base strip dimensions and target product dimensions given by the upper computer. The control computer 4 then sets these calculated values ​​in the lower-level rolling controller 3.

[0024] [Relationship between roll gap and plate thickness] Next, the process of changing the setting of the roll gap from the preceding material to the following material will be described with reference to FIGS.

[0025] First, referring to Figure 2, we will explain the general relationship between the roll gap of a rolling mill and the thickness of the rolled material. In a rolling mill, the reaction force of the rolling load applied to the rolled material causes the entire mill to deform vertically, widening the preset roll gap. Therefore, to obtain a rolled material of a specified thickness, the roll gap must be set taking into account the rolling load and the amount of deformation of the rolling mill. Figure 2 shows the relationship between the roll gap S and the exit thickness h of the rolled material when rolling a rolled material with an entry thickness H of the rolling mill. As shown in Figure 2, because the deformation of the rolling mill is elastic, the roll gap S increases approximately linearly with the rolling load P. This characteristic is called the elastic characteristic curve of the rolling mill. On the other hand, a curve connecting the rolling load P calculated from two-dimensional rolling theory assuming various exit thicknesses h is called the plastic characteristic curve of the rolled material. In actual rolling, the exit thickness h of the rolled material is determined based on the condition where the rolling loads P are balanced (the intersection of the curves shown in Figure 2).

[0026] Next, referring to Figure 3, the relationship between the delivery thickness h and the roll gap S during a running thickness change will be explained. Figure 3 shows the relationship between the delivery thickness of the rolled material and the roll gap when the entry thickness of the preceding material is H1, the entry thickness of the following material is H2, and the preceding material is a hard material (with a steeper slope of the plastic characteristic curve) and the following material is a soft material (with a shallower slope of the plastic characteristic curve). As shown in Figure 3, during a running thickness change, the roll gap S is set to the first roll gap S1 for the preceding material so that the target delivery thickness h1 is obtained. Then, when the joining point passes through the rolling stand, the plastic characteristic curve transitions from that of the preceding material (hard material) to that of the following material (soft material). As a result, when the roll gap S1 is maintained, the intersection point between the elastic characteristic curve and the plastic characteristic curve transitions from intersection point a to intersection point b. As a result, when the joining point passes through the rolling stand, the delivery thickness of the following material changes to hc. On the other hand, when the roll gap for the following strip is changed to the second roll gap S2, the intersection of the elastic characteristic curve and the plastic characteristic curve shifts from intersection b to intersection c, the outlet thickness of the following strip becomes the target thickness h2, and the on-the-fly thickness change is completed.

[0027] In a running thickness change, a roll gap change command is usually issued when the joining point reaches the rolling stand. However, because changing the roll gap takes a certain amount of time, the passage through the joining point is usually completed before the roll gap change (from the first roll gap S1 to the second roll gap S2) is completed. Therefore, the thickness fluctuation before and after passing through the joining point transiently follows a path similar to h1 → hc → h2. This transient thickness fluctuation changes the mass flow balance in each rolling stand, causing large tension fluctuations. In particular, when the plastic characteristic curve changes significantly across the joining point, the thickness fluctuation (h1 → hc) becomes significant. This is why large tension fluctuations occur when the deformation resistance of the preceding and following strips is different.

[0028] [Calculation of roll gap and roll peripheral speed settings] Next, a method for calculating the roll gap and roll peripheral speed for the material to be rolled in a tandem rolling mill will be described.

[0029] The calculations for setting the roll gap and roll peripheral speed are carried out by the control computer 4, which sets a pass schedule for the material to be rolled in accordance with information such as base material dimensions and target product dimensions given by a higher-level computer, calculates the rolling load for each rolling stand, and calculates the corresponding set values ​​for the roll gap and roll peripheral speed. The pass schedule refers to the target value for the delivery thickness of each rolling stand of a tandem rolling mill.

[0030] Specifically, in the calculation of the roll gap S of the material to be rolled in a tandem rolling mill, the control computer 4 first obtains the entry thickness H and delivery thickness h of the material to be rolled in the rolling stand being calculated from the pass schedule of the material to be rolled (target value of delivery thickness h), and then calculates the predicted value of the rolling force P using two-dimensional rolling theory, for example, using the following formula (1). In formula (1), P is the rolling force (kN), k m is the average deformation resistance of the rolled material (MPa), R' is the radius of the flat roll (mm), H is the entry thickness of the rolled material (mm), h is the exit thickness of the rolled material (mm), b is the width of the rolled material (mm), Q P is the rolling force function, μ is the friction coefficient, q b is the entry tension (MPa), q f indicates the tension at the delivery side (MPa). The flattening roll radius R' is calculated by applying Hitchcock's roll flattening equation and is obtained from a simultaneous solution with load calculations based on two-dimensional rolling theory.

[0031]

number

[0032] Next, the control computer 4 uses the predicted value of the rolling load P on the material to be rolled calculated in this way to determine the set value S of the roll gap S, for example, by the following formula (2): Here, in formula (2), K is a mill constant (kN / mm) that represents the slope of the elastic characteristic curve of the tandem rolling mill, and δ is a constant set for each tandem rolling mill.

[0033]

number

[0034] The control computer 4 executes the above calculations for all rolling stands of the tandem rolling mill to determine the roll gap setting value S for each rolling stand. Note that the roll gap setting value for an arbitrary rolling stand is represented as S, but the roll gap setting value for each rolling stand is represented as S(i) to indicate the roll gap in the ith rolling stand.

[0035] Next, the flow of calculation for setting the roll peripheral speed of each rolling stand will be explained. The calculation for setting the roll peripheral speed is executed at the same timing as the calculation for setting the roll gap. The roll peripheral speed indicates the peripheral speed of the work rolls of a tandem rolling mill. Specifically, the control computer 4 calculates the forward slip ratio f of each rolling stand using two-dimensional rolling theory based on the pass schedule of the material to be rolled. s The predicted value of is calculated using the following formula (3): The forward advance rate can be calculated, for example, from the Bland & Ford forward advance rate formula.

[0036]

number

[0037] At this time, the roll peripheral speed V of each rolling stand R (i) (mm / s) satisfies the law of constant mass flow shown in the following formula (4) in a steady state.

[0038]

number

[0039] In equation (4), i is the rolling stand number, h (i) is the delivery thickness of the rolled material in the i-th rolling stand (mm), f s (i)indicates the forward slip (-) of the i-th rolling stand. This means that once the roll peripheral speed of any rolling stand is determined, the roll peripheral speeds of the other rolling stands are determined by equation (4). Normally, the rolling speed when changing the thickness on the fly is preset in the range of approximately 100 to 400 m / min as the roll peripheral speed of the final rolling stand, and the roll peripheral speeds of the other rolling stands are also determined based on this. The above setting calculations are performed for each rolled material that is being continuously rolled in a tandem rolling mill.

[0040] Next, with reference to FIG. 4, a flow of setting calculations when changing the running strip thickness in a tandem rolling mill will be described.

[0041] Figure 4 is a flowchart showing the flow of setting calculations for the following material while the preceding material is being rolled. During the rolling of the preceding material, the set values ​​of the roll gap and roll peripheral speed for the preceding material have already been determined. Therefore, the set values ​​of the roll gap and roll peripheral speed for the following material are calculated, and the change amounts of the roll gap and roll peripheral speed (difference command values) are obtained as command values ​​when changing the thickness of the traveling strip. In the following, the roll gap for the preceding material is set to S1, and the roll peripheral speed is set to V R 1. In addition, the entry thickness of the target rolling stand for the preceding material is H1, the delivery thickness is h1, the rolling load is P1, and the forward slip is f s 1. The deformation resistance of the preceding material is k m Similarly, the roll gap for the following material is expressed as S2, and the roll peripheral speed is expressed as V R 2, the entry thickness is H2, the exit thickness is h2, the rolling load is P2, and the forward slip is f s 2. The deformation resistance of the following material is k m In other words, at the time of starting the setting calculation for the following material shown in Figure 4, the roll gap S1 and roll peripheral speed V R 1, entry plate thickness H1, exit plate thickness h1, deformation resistance k m 1, rolling load P1, and forward force f s 1 is specified in the control computer 4 and is stored in a storage device within the control computer 4.

[0042] In the setting calculation for the succeeding strip shown in Figure 4, the control computer 4 sets the pass schedule (target value of delivery thickness h2) for the succeeding strip in accordance with information such as the base strip dimensions of the succeeding strip and the target product dimensions given by the host computer (step ST1). Next, the control computer 4 calculates the rolling load P2 of each rolling stand using the above formula (1), and calculates the forward slip f of each rolling stand using the above formula (3). s Then, the control computer 4 calculates the set value of the roll gap S2 for the following material using the formula (2), and calculates the roll peripheral speed V for the following material using the formula (4). R 2 (Step ST2). As a result, the roll gap S2 and roll peripheral speed V R The set values ​​of roll gap S1 and roll peripheral speed V2 are specified. R The setting calculation of 1 has already been completed. Therefore, the roll gap S1 and roll peripheral speed V of the preceding material are stored in the storage device of the control computer 4. R By acquiring the set value of 1, the roll gap and roll peripheral speed difference command values ​​are specified (step ST3). The roll gap change amount ΔS, which is the roll gap difference command value, is calculated by the following formula (5).

[0043]

number

[0044] Similarly, the roll peripheral speed change amount ΔV R is calculated using the following formula (6).

[0045]

number

[0046] The command values ​​for the difference between the roll gap and the roll peripheral speed calculated as described above are sent to the rolling controller 3 based on the tracking information of the joining point. The calculations up to this point are executed before the start of the running thickness changing process. The roll gap S1 and roll peripheral speed V of the preceding material stored in the storage device in the control computer 4 are also sent to the rolling controller 3. R The set value of S1 may be the value calculated in the setting calculation of the preceding material. Also, during the rolling of the preceding material, the rolling control controller 3 collects the actual values ​​of the roll gap S1 and the roll peripheral speed V (called lock-on), and uses these values ​​as the roll gap S1 and the roll peripheral speed V R In some cases, the setting value is stored in the storage device as 1. This makes it possible to obtain a setting value that reflects the latest rolling state of the preceding material.

[0047] [Start and end points of thickness change during flight] Next, the start and end points of the change in thickness while running will be described with reference to FIGS. 5(a) to 5(c).

[0048] The starting point for the on-the-fly thickness change is set near the joint (joint point) W between the preceding and following strips, and is the starting point for changing the roll gap and roll peripheral speed. Changing the roll gap and roll peripheral speed takes a certain amount of time, and the time from the start to the end of the roll gap and roll peripheral speed change in each rolling stand is called the on-the-fly thickness change time. The on-the-fly thickness change time is often set to be the same for all rolling stands. The position where the change in the roll gap and roll peripheral speed in the longitudinal direction of the rolled material is completed corresponding to the on-the-fly thickness change time is the end point of the on-the-fly thickness change, and the section from the start point to the end point of the on-the-fly thickness change is sometimes called the on-the-fly thickness change section.

[0049] Figure 5(a) shows an example in which the start point FS is set near the tail end of the preceding material A and upstream of the junction point W, and the end point FE is located at the front end of the following material B. In this case, the junction point W passes through the rolling stand after the start of the change in the roll gap and roll peripheral speed but before the change is completed. Therefore, while the intersection of the elastic characteristic curve and the plastic characteristic curve shown in Figure 3 is transitioning from point a to point d, a transition occurs from the plastic characteristic curve of the preceding material A to the plastic characteristic curve of the following material B. Figure 5(b) shows an example in which the start point FS and the end point FE are both set near the tail end of the preceding material A. In this case, the junction point W passes through the rolling stand after the change in the roll gap and roll peripheral speed is completed. Therefore, the intersection of the elastic characteristic curve and the plastic characteristic curve shown in Figure 3 is transitioning from point a to point d, and then from point d to point c. Figure 5(c) shows an example in which the start point FS and the end point FE are both set near the front end of the following material B. In this case, the junction point W passes through the rolling stand before the start of changes in the roll gap and roll peripheral speed. Therefore, the intersection point between the elastic characteristic curve and the plastic characteristic curve shown in Figure 3 transitions from point a to point b, and then from point b to point c.

[0050] As described above, when changing the thickness while traveling, the behavior of the transition of the intersection of the elastic characteristic curve and the plastic characteristic curve changes depending on the positional relationship between the start point FS and the end point FE and the junction point W, and the corresponding fluctuation in mass flow causes complex changes in the tensions at the entry and exit of the rolling stand.

[0051] The on-the-fly thickness change time required to change the roll gap and roll peripheral speed to execute on-the-fly thickness change is determined, for example, as follows. The roll gap change speed of each rolling stand varies depending on whether the reduction device is hydraulic or electric, but is set, for example, to 0.5 to 2 mm / s for hydraulic reduction and 0.2 to 0.8 mm / s for electric reduction. In this case, the time required to change the roll gap of each rolling stand can be calculated by dividing the absolute value of the roll gap change amount ΔS by the roll gap change speed (|ΔS| ÷ roll gap change speed). However, since tension fluctuations can be reduced by standardizing the on-the-fly thickness change time across all rolling stands, the longest on-the-fly thickness change time required for each rolling stand is adopted. In actual tandem rolling mills, the on-the-fly thickness change time is usually about 0.2 to 2.5 seconds. The running thickness change time may be determined for each rolling condition of the preceding and succeeding strips, but may also be preset in the control computer 4 as a fixed value.

[0052] Once the on-the-fly thickness change time is determined, the on-the-fly thickness change time can be converted into the length of the material being rolled from the conveyance speed at the entry side of the rolling mill, and this can be identified as the on-the-fly thickness change section. The length of the joint (length in the conveyance direction) at the entry side of the tandem rolling mill is approximately 1 to 100 mm. For example, if the length of the joint is 10 mm and the conveyance speed at the entry side of the tandem rolling mill is assumed to be 60 m / min, the time it takes for the joint to pass through the first rolling stand 2A is an extremely short 0.01 seconds. In other words, since the length of the joint is shorter than the on-the-fly thickness change section, the length of the joint is ignored for practical purposes and is referred to as the joint "point."

[0053] [Method for determining whether or not to change thickness while running] A method for determining whether or not a running thickness change is possible, which is one embodiment of the present invention, includes a setting value acquisition step of acquiring set values ​​for the roll gap and roll circumferential speed for the preceding material before starting to change the settings of the roll gap and roll circumferential speed in at least one rolling stand of a tandem rolling mill; a tension fluctuation calculation step of calculating the amount of tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll circumferential speed for the preceding material; and a determination step of determining whether or not a running thickness change is possible based on the tension fluctuation amount calculated in the tension fluctuation calculation step.

[0054] The set value acquisition step acquires the set values ​​of the roll gap and roll peripheral speed for the preceding material before the start point of the running thickness change reaches the rolling stand where the running thickness change is performed. The set values ​​of the roll gap and roll peripheral speed are the roll gap S1 and roll peripheral speed V of the preceding material stored in the storage device in the control computer 4. R The set values ​​of roll gap S1 and roll peripheral speed V1 can be used. In addition, the rolling controller 3 collects actual values ​​of the roll gap S1 and roll peripheral speed V2 during rolling of the preceding material, and calculates these values ​​as the roll gap S1 and roll peripheral speed V3. R Alternatively, the value stored in the storage device may be set as 1 and acquired again.

[0055] The tension fluctuation calculation step is to calculate the roll gap S1 and roll peripheral speed V R The tension fluctuation amount is calculated when the junction point W passes through the rolling stand while maintaining the set value of 1. As mentioned above, in the running thickness change, when the junction point W passes through the rolling stand, the roll gap and roll peripheral speed are changed according to the command of the difference amount set in the setting calculation. However, in the tension fluctuation calculation step, the roll gap S1 and roll peripheral speed V for the preceding material are changed. RThe tension fluctuation amount is calculated for a hypothetical situation in which the joining point W passes through the rolling stand while maintaining the set value of 1. The tension fluctuation amount calculated in this way is hereinafter referred to as the tension fluctuation index. The tension fluctuation index is not calculated by accurately simulating an actual on-the-fly thickness change, but it is an index that has a high correlation with the tension fluctuation that occurs during an actual on-the-fly thickness change when there is a difference in thickness or deformation resistance at the entry side of the rolling stand between the preceding and following strips. Therefore, it is possible to accurately determine whether or not to change the on-the-fly thickness based on the tension fluctuation index. The method for calculating the tension fluctuation index will be described later.

[0056] The determination step determines whether or not the on-the-fly thickness change is possible based on the tension fluctuation index calculated in the tension fluctuation amount calculation step. The tension fluctuation index has a high correlation with the tension fluctuation amount when the roll gap and roll peripheral speed are changed according to a set difference amount during on-the-fly thickness change. Therefore, it is possible to determine whether or not the tension fluctuation amount will become excessive before the joining point passes through the rolling stand, and to prevent operational problems caused by tension fluctuation. The determination of whether or not the on-the-fly thickness change is possible in the determination step may be made, for example, by setting a threshold value for the tension fluctuation index in advance, and determining that the on-the-fly thickness change is possible if the tension fluctuation index calculated in the tension fluctuation amount calculation step is equal to or less than the threshold value, and determining that the on-the-fly thickness change is not possible if the tension fluctuation index exceeds the threshold value.

[0057] [Tension fluctuation index] The tension fluctuation index calculated in the tension fluctuation calculation step can be calculated by applying basic equations used in continuous rolling theory using a physical model in which physical phenomena are modeled by differential equations or the like. In this case, if the roll gap and roll peripheral speed change according to a set difference amount along with the behavior of the junction passing through the rolling stand, a numerical simulation is required to solve the differential equation at every minute time. However, if the roll gap and roll peripheral speed are constant, the tension fluctuation amount can be easily found.

[0058] Figure 6 shows a schematic representation of three adjacent rolling stands among those that make up a tandem rolling mill. Figure 6 shows the state when the junction point W passes through the N stand after arriving between the N-1 stand and the N stand. In other words, the roll gap S1 and roll peripheral speed V set for the preceding material in the N stand and the N+1 stand are R Rolling is performed at stand N-1, and the roll gap S2 and roll peripheral speed V are set for the succeeding material at stand N-1. R Rolling is taking place at 2.

[0059] In this embodiment, the tension fluctuation index is, for example, the roll gap S1 and the roll peripheral speed V R Calculate the amount of tension fluctuation that occurs on the entry or exit side of N stand when junction point W passes through N stand while maintaining the set value of 1. In this case, the amount of tension fluctuation that occurs when junction point W passes through N stand is greater on the entry side than on the exit side of N stand, so the tension fluctuation index can be taken as the amount of tension fluctuation that occurs on the entry side of N stand (between N-1 stand and N stand).

[0060] The physical model for determining the tension q (MPa) at the entry side of the N stand can generally be expressed by the following formula (7): where L is the distance between the rolling stands (m), E is the Young's modulus of the rolled material (MPa), and v in,N (m / s) is the material speed of the rolled material at the entrance of the N stand, v out,N-1 (m / s) represents the material speed of the rolled material at the exit of stand N-1, and t represents time (s).

[0061]

number

[0062] In other words, the tension q at the entrance of stand N can be calculated by integrating the difference between the speed of the rolled material being carried out from the upstream rolling stand and the speed of the rolled material flowing into the downstream rolling stand, and converting this into the elastic strain between the rolling stands. In this case, the roll gap S2 and roll peripheral speed V set for the following material in stand N-1 are R When rolling is performed at stand N-1, the material speed of the rolled material at the exit side is v out,N-1 is considered to be roughly constant, the change dq in the tension q at the entrance side of the N stand can be expressed as the following formula (8).

[0063]

number

[0064] Here, the change in material speed of the rolled material at the inlet side of the N stand in equation (8) is dv in,N changes according to changes in the rolling condition at the N stand. In other words, when the junction point W passes through the N stand, the thickness and deformation resistance of the rolled material change, and it also changes as the roll gap and roll peripheral speed of the N stand change. Therefore, to accurately determine the amount of tension fluctuation between rolling stands, a numerical simulation is required to solve a differential equation at every minute time interval in response to changes in the roll gap and roll peripheral speed settings, as well as the behavior of the junction point as it passes through the rolling stands.

[0065] In contrast, the tension fluctuation index used in this embodiment is the roll gap S1 and roll peripheral speed V R Calculate the amount of change in tension q that occurs at the entry side of N stand when joining point W passes through N stand while maintaining the set value of 1. For this purpose, calculate the amount of change in material speed dv of the rolled material at the entry side of N stand due to the change in the roll gap and roll peripheral speed settings. in,NIt is not necessary to calculate it at any time. Also, since the time it takes for the joining point W to pass through the N stand is extremely short, about 0.01 seconds as mentioned above, the time step dt in formula (8) can be replaced with a calculation of one step (time step Δt), and the change Δq in the tension q on the N stand entrance side can be expressed as formula (9) shown below. Here, in formula (9), Δv in,N is the roll gap S1 and roll peripheral speed V R The set values ​​for roll gap and roll peripheral speed are S1, V1, and V2. R 1 means the difference in material speed v2 of the material to be rolled on the inlet side of the N stand when rolling the following material. The amount of change Δq in tension q calculated in this way becomes the tension fluctuation index in this embodiment.

[0066]

number

[0067] Roll gap S1 and roll peripheral speed V R When rolling the preceding material with the set value of 1, the delivery thickness h1 at the N stand is calculated from the intersection a of the elastic characteristic curve of the N stand and the plastic characteristic curve of the preceding material (Fig. 3). The corresponding forward slip ratio f1 is also calculated in the calculation. Therefore, the roll gap S1 and the roll peripheral speed V R The material speed v1 of the material to be rolled at the entrance of N stand when the preceding material is rolled with the set value of 1 can be calculated by the following formula (10).

[0068]

number

[0069] On the other hand, the roll gap S1 and roll peripheral speed V R When rolling the following material while maintaining the set value of 1, the exit thickness hc at N stand is calculated by the entry thickness H2 of N stand, the deformation resistance k m2, the rolling load calculated from equation (1) and equation (2) representing the elastic characteristic curve of N stand can be calculated as a simultaneous solution. In other words, it can be found from the intersection point b in Figure 3. The corresponding forward ratio f c can also be calculated by applying formula (3). Therefore, the roll gap S1 and the roll peripheral speed V R When rolling a succeeding material while maintaining the set value of 1, the material speed v2 of the rolled material at the entrance of N stand can be calculated by the following formula (11).

[0070]

number

[0071] From the above, using the material speed v1 and material speed v2 of the rolled material at the inlet side of N stand, Δv in equation (9) in,N can be obtained. Note that Δt in Equation (9) is a value representing the time it takes for the junction point W to pass through the N stand, and can be calculated using the length of the junction point W and the material speed of the rolled material passing through the rolling stand. However, in practice, Δt in Equation (9) may be set arbitrarily within the range of 0.005 to 0.050 seconds. Even if the time step Δt used in Equation (9) differs from the actual time it takes for the junction point W to pass through the N stand, it can be used as an index reflecting the magnitude of tension fluctuation. For example, if operation is performed within a constant range of the length of the junction point W between the preceding and succeeding strips, and the rolling speed at which the thickness change is performed while running is roughly constant, then even if Δt is set to an arbitrarily set value, it can be used as an index to evaluate the magnitude of tension fluctuation when the junction point W passes through the rolling stand. On the other hand, Δt can be calculated by assuming that the length of the junction point W is constant and using the material speed v1 and roll peripheral speed V in the N stand. R It is also possible to set it as a function inversely proportional to 1 and apply this to Equation (9).

[0072] As described above, the tension fluctuation index in this embodiment is the roll gap S1 and the roll peripheral speed V R When rolling the preceding material by 1, the inlet material speed v1, the roll gap S1 and the roll peripheral speed VR and the inlet material speed v2 when it is assumed that the succeeding material is rolled while maintaining 1. This makes it possible to obtain an index that represents tension fluctuations extremely easily compared to prediction methods of tension fluctuations that perform integral calculations at short time intervals, such as the method of performing numerical simulations using equations (7) and (8).

[0073] In the tension fluctuation calculation step of this embodiment, as described above, the roll gap S1 and roll peripheral speed V of the rolling stand for the preceding material acquired in the setting value acquisition step are R The set value of 1, and the entry thickness H2 and deformation resistance k set for the succeeding strip passing through N stand m 2, the roll gap S1 and roll peripheral speed V R It is preferable to calculate the amount of tension fluctuation when the joining point W passes through the N stand while maintaining the set value of 1.

[0074] Furthermore, the on-the-fly thickness change of this embodiment is preferably applied when, in at least one rolling stand (N stand) of a tandem rolling mill, the start point of the change in roll gap and roll peripheral speed (start point FS of on-the-fly thickness change) is set for the preceding strip, and the end point of the change in roll gap and roll peripheral speed (end point FE of on-the-fly thickness change) is set for the following strip. That is, it is preferably applied when the junction point W passes through the N stand in the on-the-fly thickness change section, as shown in FIG. 5(a). In the on-the-fly thickness change embodiment shown in FIG. 5(a), as the intersection of the elastic characteristic curve and the plastic characteristic curve transitions from point a to point d, as shown in FIG. 3, a transition occurs from the plastic characteristic curve of the preceding strip to the plastic characteristic curve of the following strip, making the actual tension fluctuation behavior complex. However, even in such a case, the magnitude of tension fluctuation can be estimated using a simple method.

[0075] Furthermore, the method for determining whether or not the thickness of a running strip can be changed according to the above embodiment is based on the deformation resistance k m 1 and the deformation resistance k of the succeeding material m2 is preferably applied when the difference between the preceding and following strips is 80 MPa or more. The greater the difference in deformation resistance between the preceding and following strips, the greater the divergence between the plastic characteristic curves shown in Figure 3 between the preceding and following strips, resulting in greater actual tension fluctuations. Therefore, a numerical simulation method that calculates tension fluctuations at short time intervals requires finely setting time steps, which increases the calculation time. Furthermore, in actual operations, running thickness changes are rarely performed under conditions where the difference between the deformation resistance of the preceding and following strips is large. Therefore, it is difficult to obtain a sufficient number of actual data, and predictions of tension fluctuations using machine learning cannot achieve high accuracy. In contrast, the tension fluctuation index according to this embodiment can ensure relatively high estimation accuracy of tension fluctuations using a simple method.

[0076] Here, we will explain the causes of tension fluctuations when the joining point passes through the rolling stand during a flying thickness change. The causes of tension fluctuations that occur during a flying thickness change can be broadly divided into two categories. The first cause is due to tracking errors at the joining point and delayed response of the roll gap and roll peripheral speed. Tracking errors at the joining point and delayed response of the roll gap and roll peripheral speed cause a discrepancy between the theoretically predicted speed of the rolled material and the actual speed. This causes fluctuations in the mass flow of the rolled material, resulting in tension fluctuations. Therefore, the greater the change in roll gap or roll peripheral speed (difference command value) during a flying thickness change, the greater the tension fluctuations. The second cause is tension fluctuations resulting from differences in the entry thickness and deformation resistance of the preceding and following strips in the rolling stands before and after the joining point. The rolling condition of N stand changes drastically the moment the joining point reaches N stand. For example, when a soft preceding material is shifted to a hard succeeding material, the rolling load in the N stand increases rapidly, and the actual roll gap opens due to the elastic deformation of the rolling mill, causing the outlet thickness of the N stand to increase. in,N increases, and the tension between stand N-1 and stand N increases sharply. In other words, tension fluctuations occur when passing through the joining point, even without changing the roll gap or roll peripheral speed settings.

[0077] The tension fluctuation index of this embodiment focuses on the second cause. In other words, considering the first cause requires a numerical simulation to calculate an integral formula every minute, whereas the tension fluctuation for the second cause can be calculated using a very simple method. As a result, the tension fluctuation index of this embodiment can be calculated by simply adding a single hypothetical setting calculation for the following strip. On the other hand, the tension fluctuation index of this embodiment does not consider the first cause. However, the first cause is caused by tracking errors at the joining point and response delays in the roll gap and roll peripheral speed, and as the performance of the control equipment for tandem rolling mills improves, it becomes relatively smaller than the second cause. In particular, when the difference in deformation resistance between the preceding and following strips is large, the influence of the first cause becomes smaller than the influence of the second cause. Therefore, under such conditions, the magnitude of tension fluctuation during a running thickness change can be appropriately determined even if the tension fluctuation is estimated based on the second cause.

[0078] [Method of changing plate thickness while running] The method for changing the thickness on the fly of this embodiment is a method for continuous rolling of rolled material that applies the above-mentioned method for determining whether the thickness can be changed on the fly, and if the determination step determines that the thickness can be changed on the fly in all rolling stands of the tandem rolling mill, the method executes the change of the thickness on the fly, and if the determination step determines that the thickness cannot be changed on the fly in at least one rolling stand of the tandem rolling mill, the set values ​​of the roll gap and roll peripheral speed of the rolling stand for the succeeding material are changed.

[0079] The method for changing the thickness of a flying strip according to this embodiment will be described with reference to Fig. 1. In the method for changing the thickness of a flying strip according to this embodiment, a determination is made as to whether or not the thickness of a flying strip can be changed while the preceding strip is being rolled in all rolling stands 2A to 2E of the tandem rolling mill 2. For example, when the junction point between the preceding strip and the following strip reaches a junction point detection device (not shown) provided upstream of the tandem rolling mill 2, the control computer 4 performs calculations to set the roll gap S2 and roll peripheral speed V for the following strip. R2. When the joining point detection device detects the joining point, the rolling control controller 3 starts tracking of the joining point in the tandem rolling mill 2 based on the detected signal. Meanwhile, the control computer 4 performs setting calculations for the succeeding strip, and also performs calculations for executing the above-mentioned method for determining whether or not the running strip thickness can be changed. Specifically, the control computer 4 performs setting value acquisition step ST11, tension fluctuation amount calculation step ST12, and determination step ST13 shown in Fig. 7 for all rolling stands 2A to 2E. Then, when it is determined that the running strip thickness can be changed in all rolling stands 2A to 2E, the control computer 4 calculates the differential command amounts ΔS, ΔV specified by the setting calculations. R On the other hand, if it is determined in the determination step that the running thickness change is not possible in at least one rolling stand of the tandem rolling mill, the control computer 4 changes the rolling conditions for the succeeding strip to the preset conditions (roll gap S2, roll peripheral speed V R 2) and pass the junction according to the changed conditions.

[0080] The conditions to be changed when it is determined in the determination step that the running thickness change is not possible in at least one rolling stand of the tandem rolling mill are conditions that reduce tension fluctuations when the joining point passes through the rolling stands. Specifically, a gap opening plate may be implemented in which the roll gaps of all rolling stands of the tandem rolling mill are opened to allow the joining point to pass without rolling the joining point. Also, the pass schedule for the following material may be changed from a preset one to allow the following material to pass through the joining point.

[0081] [Device and program for determining whether or not to change thickness while traveling] Next, a device and a program for determining whether or not the above-mentioned thickness change while on the run is possible will be described.

[0082] The device for determining whether or not a running thickness change is possible in this embodiment is composed of a general-purpose computer such as a workstation or a personal computer, and is communicably connected to a control computer 4. The device for determining whether or not a running thickness change is possible acquires information necessary for processing from the control computer 4 and outputs a determination result regarding whether or not a running thickness change is possible to the control computer 4. The device for determining whether or not a running thickness change is possible comprises a set value acquisition means, a tension fluctuation calculation means, and a determination means. The set value acquisition means acquires the set values ​​of the roll gap and roll peripheral speed of the rolling stand for the preceding strip from the control computer 4 before starting to change the set values ​​of the roll gap and roll peripheral speed in at least one rolling stand of the tandem rolling mill. The tension fluctuation calculation means calculates the tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll peripheral speed for the preceding strip. The determination means determines whether or not a running thickness change is possible based on the tension fluctuation calculated by the tension fluctuation calculation means, and outputs the determination result to the control computer 4.

[0083] The method for determining whether or not the running thickness can be changed can also be realized by a computer executing a program. A computer-readable recording medium having the program recorded thereon and a computer program product of the program can also be applied as embodiments of the present invention. Examples of recording media that can be used include flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, magnetic tapes, non-volatile memory cards, and ROMs.

[0084] The program for determining whether or not a thickness change is possible while on the fly according to this embodiment may be configured to execute the steps of the method for determining whether or not a thickness change is possible while on the fly on a computer. In this case, by executing the program for determining whether or not a thickness change is possible while on the fly on a general-purpose computer such as a workstation or a personal computer, the general-purpose computer functions as a device for determining whether or not a thickness change is possible while on the fly. Furthermore, by loading the program for determining whether or not a thickness change is possible while on the fly on the control computer 4, the control computer 4 can execute the processing of the method for determining whether or not a thickness change is possible while on the fly on the control computer 4.

[0085] [Other embodiments of thickness change during running] The above-mentioned method for determining whether or not a thickness change is possible on the fly and the method for changing the thickness on the fly can also be applied to two-stage thickness change on the fly, in which two-stage thickness changes are made on rolled materials joined via a joining point. Two-stage thickness change on the fly refers to a thickness change on the fly that transitions from rolling the preceding material to rolling the succeeding material via an intermediate step in a tandem rolling mill that rolls rolled materials that have a joining point between the preceding and succeeding materials. Two-stage thickness change on the fly will be explained using Figure 8.

[0086] As shown in Figure 8, in two-stage on-the-fly thickness change, first, the roll gap S is set to the first roll gap S1 for the preceding strip so that the target delivery thickness h1 is obtained, and the second roll gap S2 is set for the following strip so that the target delivery thickness h2 is obtained. In two-stage on-the-fly thickness change, an intermediate roll gap Sc is also set in the intermediate step. The intermediate step refers to a process (roll gap holding process) in which rolling is performed with roll gaps different from the first roll gap S1 and the second roll gap S2 during the process of transitioning from the preceding strip to the rolling of the following strip. The process of transitioning from rolling the preceding strip to the intermediate step is referred to as the first on-the-fly thickness change process, and the process of transitioning from the intermediate step to rolling the following strip is referred to as the second on-the-fly thickness change process. When two-stage on-the-fly thickness change is performed, the control computer 4 calculates the intermediate roll gap Sc and intermediate roll peripheral speed Vc corresponding to the delivery thickness hc at the intermediate step before the joining point reaches the rolling stand.

[0087] In the example shown in Figure 8, when the first running thickness change process is performed while the preceding strip is being rolled, the roll gap is changed (S1 → Sc), causing the intersection of the elastic characteristic curve and the plastic characteristic curve to transition from intersection a to intersection b. As a result, the thickness at the delivery end of the rolling stand changes from h1 to hc1. Furthermore, when the junction passes through the rolling stand in this state, the plastic characteristic curve changes before and after the junction, causing the intersection of the elastic characteristic curve and the plastic characteristic curve to transition from intersection b to intersection c. As a result, the thickness at the delivery end of the rolling stand changes from hc1 to hc2. After that, when the second running thickness change process is performed, the roll gap is changed (Sc → S2), causing the intersection of the elastic characteristic curve and the plastic characteristic curve to transition from intersection c to intersection d. As a result, the thickness at the delivery end of the rolling stand changes from hc2 to h2, completing the running thickness change.

[0088] In a two-stage on-the-fly thickness change, the transient thickness change at the delivery side of the rolling stand is h1 → hc1 → hc2 → h2. Compared to the transient thickness change h1 → hc' → h2 in a one-stage on-the-fly thickness change without an intermediate step, the thickness change during the transition process is smaller, and mass flow fluctuations are suppressed. As a result, tension fluctuations are alleviated. In this embodiment, the feasibility of on-the-fly thickness change is determined based on such a two-stage on-the-fly thickness change. Below, the start and end points of the two-stage on-the-fly thickness change will be explained with reference to Figures 9(a) and 9(b).

[0089] FIG. 9(a) shows an example in which the start point FS1 of the first flying thickness changing process is set to the preceding strip A, and the end point FE1 of the first flying thickness changing process is set to the following strip B. The start point FS2 and end point FE2 of the second flying thickness changing process are both set to the following strip B. In this case, tension fluctuations become large in the first flying thickness changing process in which the roll gap and roll peripheral speed settings are changed via the joining point W, so it is preferable to apply the determination of whether or not the flying thickness can be changed in this embodiment to the first flying thickness changing process. When determining whether or not the flying thickness can be changed in the first flying thickness changing process, the parameters (S2, V R 2, h2) as the intermediate step parameters (Sc, V Rc, hc2) to calculate the tension fluctuation index. In this case, the deformation resistance of the rolled material in the intermediate step is calculated by replacing the deformation resistance k m Specifically, before starting the first running thickness change process, the roll gap S1 and roll peripheral speed V for the preceding material A are set in the setting value acquisition step. R Next, in the tension fluctuation calculation step, the roll gap S1 and roll peripheral speed V for the preceding material A are calculated. R The tension fluctuation amount when the joining point W passes through the rolling stand while maintaining the set value of 1 is calculated as the intermediate step parameters Sc and V. R c and hc2 are used for calculation. Based on the tension fluctuation amount calculated in this way, a determination step is executed to determine whether or not the running thickness can be changed.

[0090] On the other hand, as shown in FIG. 9(b), the determination of whether or not to perform on-the-fly thickness change of this embodiment can also be applied to a two-stage on-the-fly thickness change in which the start point FS1 of the first on-the-fly thickness change process, the end point FE1 of the first on-the-fly thickness change process, and the start point FS2 of the second on-the-fly thickness change process are set to the preceding material A, and the end point FE2 of the second on-the-fly thickness change process is set to the following material B. In this case, since tension fluctuations become large in the second on-the-fly thickness change process in which the roll gap and roll peripheral speed settings are changed via the junction point W, it is preferable to apply the determination of whether or not to perform on-the-fly thickness change of this embodiment to the second on-the-fly thickness change process. When determining whether or not to perform on-the-fly thickness change for the second on-the-fly thickness change process, the parameters (S1, V) of the preceding material used in the above-mentioned one-stage on-the-fly thickness change determination are used. R 1, h1) to the parameters of the intermediate step (Sc, V R c, hc2) to calculate the tension fluctuation index. In this case, the deformation resistance of the rolled material in the intermediate step is calculated by replacing the deformation resistance k m Specifically, before starting the second running thickness change process, the roll gap Sc and roll peripheral speed V for the intermediate step are obtained in the setting value acquisition step. R Next, in the tension fluctuation calculation step, the roll gap Sc and roll peripheral speed V for the intermediate step are calculated. RThe tension fluctuation when the joining point W passes through the rolling stand while maintaining the set value of c is calculated by the parameters S2 and V of the succeeding material B. R 2, h2 are used for calculation. A determination step is then executed to determine whether or not to change the thickness while on the run based on the tension fluctuation amount calculated in this way. As a result, the magnitude of tension fluctuation during two-stage thickness change while on the run can be appropriately determined. [Example]

[0091] An example of the present invention will be described. In this example, a determination was made as to whether or not a flying thickness change is possible for a single stage of flying thickness change using a tandem rolling mill 2, which is a tandem rolling mill having five rolling stands as shown in FIG. 1. The specifications of the tandem rolling mill 2 are as follows. The rolling load detector 24, the reduction position detector 25, the tension meter 26, and the thickness meter 27 were arranged at the positions shown in FIG. 1.

[0092] Maximum line speed: 2000mpm (m / min) Work roll diameter: 500-600mmφ Backup roll diameter: 1300~1400mmφ Stand distance: 4600mm

[0093] First, the tension fluctuation index of the present invention was compared with the actual tension fluctuation due to changes in running thickness. The tension fluctuation index was evaluated based on the tension fluctuation that occurred between the first rolling stand 2A and the second rolling stand 2B when the junction point W passed through the second rolling stand 2B of the tandem rolling mill 2. The rolled material for which tension fluctuation was evaluated had a base thickness of 2.4 to 7.0 mm and a thickness of 0.5 to 3.6 mm at the exit of the final rolling stand. The width of the rolled material ranged from 760 to 1900 mm, and included steel grades ranging from low-carbon steel to high-strength steel sheets with a tensile strength of 1180 MPa in cold-rolled steel sheet products. The difference in deformation resistance between the preceding and succeeding materials was in the range of -200 to +200 MPa. In calculating the tension fluctuation index, the time step Δt used in Equation (9) was set to 0.023 s based on the length of the junction point W. Furthermore, the roll gap and roll peripheral speed of the second rolling stand 2B for the preceding strip, which were acquired in the set value acquisition step, were set values ​​held by the control computer 4. On the other hand, the actual value of tension fluctuation due to the on-the-fly strip thickness change was obtained by acquiring the tension fluctuation amount (amplitude of tension fluctuation) measured during the on-the-fly strip thickness change process of the second rolling stand 2B from the fluctuations in the tension per unit cross-sectional area (unit tension) of the rolled strip shown in Figure 10. The unit tension was calculated from the total tension using the strip thickness and strip width at the inlet side of the second rolling stand 2B.

[0094] Figure 11 shows the results of comparing the tension fluctuation index calculated using the above method with the actual tension fluctuation caused by a running thickness change. As shown in Figure 11, there is a high correlation between the tension fluctuation index calculated in the tension fluctuation calculation step and the actual tension fluctuation. In this case, the correlation coefficient between the tension fluctuation index and the actual tension fluctuation was 0.67, and the root mean square error (RMSE) was 1.7 MPa. Furthermore, when only combinations of leading and trailing strips where the absolute difference in deformation resistance between the leading and trailing strips was 80 MPa or greater were extracted from the data shown in Figure 11 and the correlation coefficient was recalculated, the result was 0.92. Furthermore, for combinations of leading and trailing strips where the absolute difference in deformation resistance between the leading and trailing strips was 80 MPa or greater, tension fluctuation was large, but the RMSE was kept to 2.1 MPa. From these results, it was confirmed that the tension fluctuation index calculated using the above method exhibits a high correlation, especially when the difference in deformation resistance between the leading and trailing strips is large.

[0095] Next, the results of determining whether or not the running thickness can be changed using the tandem rolling mill 2 will be described. In this example, the dimensions of the rolled material were a base thickness of 2.4 to 3.6 mm, a thickness at the outlet of the final rolling stand of 0.9 to 2.0 mm, and a width of 700 to 1400 mm. Here, a determination was made as to whether or not the running thickness can be changed when the preceding and succeeding materials were high-strength steel plates with tensile strengths of 590 MPa and 1180 MPa, respectively. Conventionally, with these combinations of preceding and succeeding materials, excessive tension fluctuations were likely to cause a high risk of breakage of the rolled material. Therefore, a gap-opening method was used, in which the roll gaps of all rolling stands were opened and the material passed through without rolling the joint.

[0096] In the example, a determination was made at all rolling stands as to whether a running thickness change was possible. If the determination step determined that a running thickness change was possible at all rolling stands, the running thickness change was carried out. If the determination step determined that a running thickness change was not possible at at least one rolling stand, a gap opening was carried out. In the determination step of this example, if the tension fluctuation index calculated in the tension fluctuation calculation step was 30% or less of the interstand tension set for the preceding strip, it was determined that a running thickness change was possible. If it exceeded 30%, it was determined that a running thickness change was not possible. As a result, for the above combination of preceding and following strips, gap opening was reduced from 20 times per month in the past to 15 times in the example. This improved the operating rate of the tandem rolling mill.

[0097] Although the present invention has been described above as an embodiment, the present invention is not limited to the descriptions and drawings that form part of the disclosure of the present invention. In other words, other embodiments, examples, and operational techniques that can be made by those skilled in the art based on the present invention are all included in the scope of the present invention. [Explanation of symbols]

[0098] 1. Continuous cold rolling equipment 2 Tandem rolling mill 3 Rolling controller 4 Control computer 5 Rolled material 21 Work Roll 22 Roll peripheral speed control device 23 Rolling control device 24 Rolling load detector 25 Roll position detector 26 Tension meter 27 Thickness gauge W Junction

Claims

1. A method for determining whether or not a running thickness change is possible when a rolling target material in which a preceding material and a succeeding material are joined via a joining portion is continuously rolled by a tandem rolling mill, comprising: a setting value acquisition step of acquiring the setting values ​​of the roll gap and the roll peripheral speed of the rolling stand for the preceding material before starting to change the setting values ​​of the roll gap and the roll peripheral speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation step of calculating a tension fluctuation amount when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and the roll peripheral speed for the preceding material; a determination step of determining whether or not the running thickness can be changed based on the tension fluctuation amount calculated in the tension fluctuation amount calculation step; A method for determining whether or not a running thickness change is possible, including:

2. 2. The method for determining whether or not a running thickness can be changed according to claim 1, wherein the tension fluctuation calculation step calculates the tension fluctuation amount when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll peripheral speed for the preceding material, using the set values ​​of the roll gap and roll peripheral speed of the rolling stand for the preceding material acquired in the set value acquisition step, and the thickness and deformation resistance set for the succeeding material passing through the rolling stand.

3. 2. The method for determining whether or not a running thickness change is possible according to claim 1, wherein, in the running thickness change, a start point for changing the roll gap and the roll peripheral speed is set to the position of the preceding material, and an end point for changing the roll gap and the roll peripheral speed is set to the position of the following material.

4. 2. The method for determining whether or not a running thickness change is possible according to claim 1, wherein a difference between the deformation resistance of the preceding material and the deformation resistance of the following material is 80 MPa or more.

5. A method for changing a thickness on the fly, comprising: using the method for determining whether a thickness change on the fly is possible according to any one of claims 1 to 4; executing a thickness change on the fly when it is determined that a thickness change on the fly is possible in all rolling stands of the tandem rolling mill; and changing the set values ​​of the roll gap and roll peripheral speed of the rolling stand for the succeeding material when it is determined that a thickness change on the fly is not possible in at least one rolling stand of the tandem rolling mill.

6. A device for determining whether or not a running thickness change is possible when a rolling target material in which a preceding material and a succeeding material are joined via a joining portion is continuously rolled by a tandem rolling mill, a set value acquisition means for acquiring the set values ​​of the roll gap and the roll peripheral speed of the rolling stand for the preceding material before starting to change the set values ​​of the roll gap and the roll peripheral speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation means for calculating a tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll peripheral speed for the preceding material; a determination means for determining whether or not the running thickness can be changed based on the tension fluctuation calculated by the tension fluctuation calculation means; A device for determining whether or not a running plate thickness change is possible.

7. A program for determining whether or not a running thickness change is possible when a rolling target material in which a preceding material and a succeeding material are joined via a joining portion is continuously rolled by a tandem rolling mill, Computer, a set value acquisition means for acquiring the set values ​​of the roll gap and the roll peripheral speed of the rolling stand for the preceding material before starting to change the set values ​​of the roll gap and the roll peripheral speed in at least one rolling stand of the tandem rolling mill; a tension fluctuation calculation means for calculating a tension fluctuation when the joint passes through the rolling stand while maintaining the set values ​​of the roll gap and roll peripheral speed for the preceding material; a determination means for determining whether or not the running thickness can be changed based on the tension fluctuation calculated by the tension fluctuation calculation means; This is a program that determines whether or not to change the thickness while running.

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