JP7810157B2 - 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 - Google Patents

Description

The present invention relates to a method for determining whether or not a thickness change can be performed while on the move, a method for changing thickness while on the move, a device for determining whether or not a thickness change can be performed while on the move, and a program for determining whether or not a thickness change can be performed while on the move.

In the cold rolling process, the preceding material to be rolled (hereafter referred to as "preceding material") and the succeeding material to be rolled (hereafter referred to as "successing material") are joined (typically by welding) at the entry side of a tandem rolling mill, and the preceding and succeeding materials are then cold rolled in the tandem rolling mill as a continuous metal strip. The cold-rolled metal strip is then cut at the exit side of the tandem rolling mill at the product unit position, and the cut metal strip is sequentially wound on a tension reel. Furthermore, when cold rolling the metal strip, if any of the hardness, base thickness, or finished thickness differs between the preceding and succeeding material, a "flying thickness change" is performed. "Flying thickness change" refers to a process of changing the rolling conditions before and after the joining point (also known as the joining point) during continuous rolling in order to improve yield without stopping the line.

If rolling conditions change significantly before and after the weld when changing the thickness of a running strip, the amount of tension fluctuation increases as the weld passes through each rolling stand, which can lead to breakage or squeezing of the metal strip. If breakage or squeezing of the metal strip occurs, the operating efficiency of the tandem rolling mill decreases. Therefore, a technology has been proposed that predicts the amount of tension fluctuation as the weld passes through each rolling stand of the tandem rolling mill, and if the predicted amount of tension fluctuation is large, changes the operating conditions of the tandem rolling mill. Specifically, Patent Document 1 describes a method that includes a prediction means for predicting the amount of tension fluctuation that occurs during a running strip thickness change, and optimizes the time for running strip thickness change so that the predicted amount of tension fluctuation falls within an allowable range. In the method described in Patent Document 1, the prediction means uses a tension generation model with first-order lag characteristics and a correction term that learns the actual amount of tension fluctuation. Patent Document 1 also describes that a prediction means trained by a neural network using actual values of tension fluctuation as training data can be used as the prediction means.

Patent Document 2 also describes a method for predicting tension fluctuations during on-the-fly thickness changes, using a prediction model trained by machine learning to predict the amount of tension fluctuation when a joining point passes through a rolling stand. The prediction model described in Patent Document 2 takes the rolling operation parameters of the preceding material and the rolling operation parameter change amount representing the difference between the rolling operation parameters of the preceding material and the following material as input data, and outputs tension fluctuation information when the joining point passes through the rolling stand. Meanwhile, Patent Document 3 describes a method for calculating the actuator change amount at the timing when the joining point passes through the 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 from the actuator change amount in rolling schedule calculations, without the need to use a highly accurate tension fluctuation prediction model.

Japanese Patent Application Publication No. 10-249423 Japanese Patent Application Laid-Open No. 2022-21794 JP 2019-111568 A

However, the method described in Patent Document 1 provides low accuracy in predicting tension fluctuations. Specifically, a flying strip thickness change is performed when the base strip thickness, finish thickness, or deformation resistance differs between the preceding and following strips. 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 flying strip thickness changes. For this reason, 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 a tension generation model is used, it is difficult to accurately calculate tension fluctuations in an unsteady state where the roll gap and roll peripheral speed change at the junction of the preceding and following strips, resulting in sudden changes in base strip thickness, finish thickness, deformation resistance, and other factors.

Furthermore, the prediction model trained by machine learning described in Patent Document 2 also exhibits reduced prediction accuracy for tension fluctuations when a combination of preceding and following strips 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 and following strips. 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 that is 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.

The present invention was made to solve the above-mentioned problems, and its purpose is to provide a method, device, and program for determining whether or not to change the thickness while on the run that can accurately predict the amount of tension fluctuation when changing the thickness while on the run, even under conditions where there is little past operational experience for the combination of preceding and following material, and can determine whether or not to change the thickness while on the run appropriately. Another purpose of the present invention is to provide a method for changing the thickness while on the run that can prevent breakage, squeezing, etc. of the metal strip, and enable the metal strip to be rolled with a good yield.

The method for determining whether or not a flying thickness change is possible according to the present invention is a method for determining whether or not a flying thickness change is possible 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. The method includes: a setting value acquisition step for acquiring the roll gap and roll circumferential speed settings of the rolling stand for the preceding material before starting to change the roll gap and roll circumferential speed settings 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 roll gap and roll circumferential speed settings for the preceding material; and a determination step for determining whether or not the flying thickness change is possible based on the tension fluctuation calculated in the tension fluctuation calculation step.

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

When changing the thickness while traveling, it is preferable to set the start point of the change in the roll gap and roll peripheral speed to the position of the preceding material, and the end point of the change in the roll gap and roll peripheral speed to the position of the following material.

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.

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 if it is determined that the thickness can be changed on the fly in all rolling stands of the tandem rolling mill, and if 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.

The device for determining whether or not a flying thickness change is possible according to the present invention is a device for determining whether or not a flying thickness change is possible 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. It comprises: a set 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 flying thickness change is possible based on the tension fluctuation calculated by the tension fluctuation calculation means.

The program for determining whether or not a flying thickness change is possible according to the present invention is a program for determining whether or not a flying thickness change is possible 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. The program causes a computer to function as: a setting value acquisition means for acquiring the roll gap and roll circumferential speed settings of the rolling stand for the preceding material before starting to change the roll gap and roll circumferential speed settings 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 roll gap and roll circumferential speed settings for the preceding material; and a determination means for determining whether or not the flying thickness change is possible based on the tension fluctuation calculated by the tension fluctuation calculation means.

The method, device, and program for determining whether or not to change the thickness while on the run according to the present invention can accurately predict the amount of tension fluctuation that occurs when changing the thickness while on the run, even when there is little past operational experience with the combination of preceding and succeeding strips, and can perform an appropriate determination as to whether or not to change the thickness while on the run. Furthermore, the method for changing the thickness while on the run according to the present invention can prevent breakage, narrowing, etc. of the metal strip, thereby enabling the metal strip to be rolled with a high yield.

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. FIG. 2 is a diagram showing the relationship between the delivery thickness of the rolled material and the roll gap. FIG. 3 is a diagram showing the relationship between the delivery thickness of the rolled material and the roll gap. FIG. 4 is a flowchart showing the flow of setting calculations for the succeeding strip during rolling of the preceding strip. FIG. 5 is a diagram for explaining the start and end points of the change in thickness while running. FIG. 6 is a diagram for explaining a method for calculating the tension fluctuation index. 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. FIG. 8 is a diagram for explaining the two-stage on-the-fly thickness change. FIG. 9 is a diagram for explaining the start and end points of the two-stage on-the-fly thickness change. FIG. 10 is a diagram showing fluctuations in unit tension of the rolled material. FIG. 11 is a diagram showing the relationship between the tension fluctuation index and the actual value of tension fluctuation.

The following describes, with reference to the drawings, one embodiment of the present invention: a method for determining whether a thickness change can be performed while on the run, a method for changing thickness while on the run, a device for determining whether a thickness change can be performed while on the run, and a program for determining whether a thickness change can be performed while on the run.

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

Figure 1 is a schematic diagram showing an example of the configuration of a continuous cold rolling mill to which the present invention is applied. In Figure 1, other devices associated with the continuous cold rolling mill (for example, a rewinder, welding machine, and looper installed on the entry side, and devices such as a cutter and winder installed on the exit side) are not shown. As shown in Figure 1, the continuous cold rolling mill 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 mill 1 including the rolling control controller 3.

The tandem rolling mill 2 is a continuous cold tandem rolling mill having, in order from the entry side in the direction of the rolling material 5, the first rolling stand 2A to the fifth rolling stand 2E. Each rolling stand is equipped with a work roll 21, a roll peripheral speed control device 22 (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. Each rolling stand is also equipped with a rolling load detector 24 (a load cell) below the lower backup roll. Each rolling stand is also equipped with a roll gap position detector 25 that detects the roll gap position. Between each rolling stand, a tension gauge 26 is installed to detect the tension of the rolled material 5. Furthermore, a thickness gauge 27 is installed at the exit side of the first rolling stand 2A and the exit side of the fifth rolling stand 2E to detect the thickness (plate thickness) of the rolled material 5.

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 it to the control computer 4. The rolling controller 3 also executes processing to control the roll peripheral speed control device 22 and the roll gap control device 23 of each rolling stand based on the values acquired from the control computer 4. The rolling controller 3 also has the function of tracking the junction point between the preceding and succeeding materials, as well as tracking a specified position on the material to be rolled 5. This allows the rolling controller 3 to output command values for changing specified settings to control devices such as the roll peripheral speed control device 22 and the roll gap control device 23 when a predetermined position of the material to be rolled 5, including the junction point, passes through each rolling stand of the tandem rolling mill 2.

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

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

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 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).

Next, referring to Figure 3, we will explain the relationship between the delivery thickness h and the roll gap S during a running thickness change. 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 hard (the slope of the plastic characteristic curve is steep) and the following material is soft (the slope of the plastic characteristic curve is shallow). 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, the delivery thickness of the following material changes to hc when the joining point passes through the rolling stand. On the other hand, when the roll gap for the following material is changed to the second roll gap S2, the intersection between the elastic characteristic curve and the plastic characteristic curve shifts from intersection b to intersection c, the delivery thickness of the following material becomes the target thickness h2, and the running thickness change is complete.

When changing thickness while traveling, a command to change the roll gap is typically issued to coincide with the arrival of the junction at the rolling stand. However, because changing the roll gap takes a certain amount of time, the passage through the junction usually occurs before the roll gap change (from the first roll gap S1 to the second roll gap S2) is complete. Therefore, the thickness fluctuation before and after passing through the junction transiently follows a path close 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 on either side of the junction, 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.

[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.

The control computer 4 calculates the roll gap and roll peripheral speed settings by setting a pass schedule for the material to be rolled based on information such as base material dimensions and target product dimensions provided by a higher-level computer, calculating the rolling load for each rolling stand, and calculating the corresponding roll gap and roll peripheral speed settings. The pass schedule refers to the target value for the outlet thickness of each rolling stand of a tandem rolling mill.

Specifically, in the calculation of the roll gap S for 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 to be calculated from the pass schedule of the material to be rolled (the target value of the delivery thickness h), and then uses two-dimensional rolling theory to determine a predicted value of the rolling load P using, for example, the following formula (1): where, in formula (1), P is the rolling load (kN), _km is the average deformation resistance (MPa) of the material to be rolled, R' is the flattened roll radius (mm), H is the entry thickness of the material to be rolled (mm), h is the delivery thickness of the material to be rolled (mm), b is the width of the material to be rolled (mm), _QP is a rolling force function, μ is a friction coefficient, _qb is the entry tension (MPa), and _qf is the delivery tension (MPa). The flattening roll radius R' is determined by applying Hitchcock's roll flattening equation and by a simultaneous solution with load calculation based on two-dimensional rolling theory.

Next, the control computer 4 uses the predicted value of the rolling load P on the rolled material calculated in this way to determine the set value S of the roll gap S, for example, using the following formula (2): In formula (2), K is the 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.

The control computer 4 performs 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 any rolling stand is represented as S, but the roll gap setting value for each rolling stand is represented as S(i), which indicates the roll gap for the i-th rolling stand.

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 represents the peripheral speed of the work rolls of a tandem rolling mill. Specifically, the control computer 4 calculates a predicted value of the forward slip ratio _fs of each rolling stand using the following mathematical formula (3) based on the two-dimensional rolling theory and the pass schedule of the material to be rolled. The forward slip ratio can be found, for example, from the Bland & Ford forward slip ratio formula.

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

Here, in formula (4), i is the rolling stand number, h ⁽ⁱ⁾ is the delivery thickness (mm) of the rolled material in the i-th rolling stand, and _fs ⁽ⁱ⁾ is the forward slip (-) of the i-th rolling stand. This means that once the roll peripheral speed of an arbitrary rolling stand is determined, the roll peripheral speeds of the other rolling stands are determined by formula (4). Normally, the rolling speed when changing the running thickness is preset at the roll peripheral speed of the final rolling stand in the range of approximately 100 to 400 m/min, 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 to be continuously rolled in the tandem rolling mill.

Next, referring to Figure 4, we will explain the flow of setting calculations when changing the running thickness on a tandem rolling mill.

FIG. 4 is a flowchart showing the flow of setting calculations for the following strip while the preceding strip is being rolled. The roll gap and roll peripheral speed settings for the following strip have already been determined during rolling of the preceding strip. Therefore, the roll gap and roll peripheral speed settings for the following strip are calculated, and the roll gap change amount and roll peripheral speed change amount (difference command value) are obtained as command values for changing the thickness while traveling. Below, the roll gap for the preceding strip will be denoted as S1, and the roll peripheral speed as V _R1 . The entry thickness of the rolling stand for the preceding strip will be denoted as H1, the exit thickness as h1, the rolling load as P1, the forward slip as f _s 1, and the deformation resistance of the following strip as _km 1. Similarly, the roll gap for the following strip will be denoted as S2, the roll peripheral speed as V _R 2, the entry thickness as H2, the exit thickness as h2, the rolling load as P2, the forward slip as f _s 2, and the deformation resistance of the following strip as _km 2. In other words, at the time when the setting calculation for the following material shown in Figure 4 is started, the roll gap S1, roll peripheral speed V _R 1, entry side plate thickness H1, delivery side plate thickness h1, deformation resistance _km 1, rolling load P1, and forward slip f _s 1 for the preceding material are specified by the control computer 4 and are stored in the memory device within the control computer 4.

In the setting calculation for the following material shown in Figure 4, the control computer 4 sets the pass schedule for the following material (target value for delivery thickness h2) according to information such as the base material dimensions of the following material and the target product dimensions provided 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 the forward slip _fs2 of each rolling stand using the above formula (3). Then, the control computer 4 calculates the set value of the roll gap S2 for the following material using formula (2) and calculates the set value of the roll peripheral speed V _R2 for the following material using formula (4) (step ST2). This specifies the set values of the roll gap S2 and roll peripheral speed V _R2 for the following material. Here, the setting calculations for the roll gap S1 and roll peripheral speed V _R1 for the preceding material have already been completed. Therefore, the roll gap and roll peripheral speed difference command values are specified (step ST3) by acquiring the set values of the roll gap S1 and roll peripheral speed V _R 1 of the preceding material from the storage device in the control computer 4. The roll gap change amount ΔS, which is the roll gap difference command value, is calculated by the following formula (5).

Similarly, the change amount ΔV _R of the roll peripheral speed, which is the command value of the difference in the roll peripheral speed, is calculated by the following formula (6).

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 junction point. The calculations up to this point are performed before the start of the running strip thickness changing process. Note that the set values of the roll gap S1 and roll peripheral speed V _R1 of the preceding strip stored in the storage device within the control computer 4 may use values calculated in the setting calculation for the preceding strip. Also, the rolling controller 3 may collect actual values of the roll gap and roll peripheral speed during rolling of the preceding strip (called lock-on), and store these values in the storage device again as the roll gap S1 and roll peripheral speed V _R1 . This makes it possible to obtain set values that reflect the latest rolling state of the preceding strip.

[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.

The starting point for the on-the-fly thickness change is set near the joint (joint point) W between the preceding and following materials, 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.

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 roll gap and roll peripheral speed change has begun but before the change is completed. Therefore, as the intersection of the elastic characteristic curve and the plastic characteristic curve shown in Figure 3 transitions 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 roll gap and roll peripheral speed change has completed. Therefore, the intersection of the elastic characteristic curve and the plastic characteristic curve shown in Figure 3 transitions 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 roll gap and roll peripheral speed change begins. Therefore, the intersection of 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.

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 relative positions of the start point FS, end point FE, and junction point W, and the corresponding fluctuations in mass flow cause complex changes in the tension at the entry and exit sides of the rolling stand.

The on-the-fly thickness change time required to change the roll gap and roll peripheral speed to execute a on-the-fly thickness change is determined, for example, as follows. The roll gap change speed for each rolling stand varies depending on whether the reduction device is hydraulic or electric, but is set, for example, at 0.5 to 2 mm/s for hydraulic reduction and 0.2 to 0.8 mm/s for electric reduction. The time required to change the roll gap for 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, because 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 used. On an actual tandem rolling mill, the on-the-fly thickness change time is typically approximately 0.2 to 2.5 seconds. The running thickness change time may be determined for each rolling condition of the preceding and succeeding strips, or may be preset as a fixed value in the control computer 4.

Once the running thickness change time is determined, it can be converted into the length of the material being rolled based on the conveying speed at the entry side of the rolling mill, and this can be identified as the running thickness change section. The length of the joint (length in the conveying 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 conveying speed at the entry side of the tandem rolling mill is 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, because the length of the joint is shorter than the running thickness change section, the length of the joint can be ignored for practical purposes and referred to as the joint "point."

[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.

The set value acquisition step acquires set values for the roll gap and roll peripheral speed for the preceding material before the start point of the running thickness change reaches the rolling stand that performs the running thickness change. As the set values for the roll gap and roll peripheral speed, the set values for the roll gap S1 and roll peripheral speed V _R1 of the preceding material that are stored in the storage device in the control computer 4 can be used. Also, the rolling controller 3 may collect actual values of the roll gap and roll peripheral speed during rolling of the preceding material, and acquire these values as the roll gap S1 and roll peripheral speed V _R1 that are newly stored in the storage device.

The tension fluctuation calculation step calculates the tension fluctuation when the junction point W passes through the rolling stand while maintaining the set values of the roll gap S1 and roll peripheral speed V _R1 for the preceding strip. As described above, in a flying thickness change, when the junction point W passes through the rolling stand, the roll gap and roll peripheral speed are changed in accordance with the command of the difference amount set in the setting calculation. However, in the tension fluctuation calculation step, the tension fluctuation is calculated for a virtual state in which the junction point W passes through the rolling stand while maintaining the set values of the roll gap S1 and roll peripheral speed V _R1 for the preceding strip. The tension fluctuation calculated in this manner is hereinafter referred to as the tension fluctuation index. Although the tension fluctuation index is not calculated by accurately simulating an actual flying thickness change, it is an index that has a high correlation with the tension fluctuation that occurs in an actual flying thickness change when there is a difference in the thickness or deformation resistance at the entry side of the rolling stand between the preceding and following strips. Therefore, the feasibility of a flying thickness change can be accurately determined based on the tension fluctuation index. The method for calculating the tension fluctuation index will be described later.

The determination step determines whether or not the thickness can be changed while on the run based on the tension fluctuation index calculated in the tension fluctuation amount calculation step. The tension fluctuation index has a high correlation with the amount of tension fluctuation when the roll gap and roll peripheral speed are changed according to a set difference amount during a thickness change while on the run. This makes it possible to determine whether the tension fluctuation amount will become excessive before the joining point passes the rolling stand, thereby preventing operational problems caused by tension fluctuation. The determination of whether or not the thickness can be changed while on the run in the determination step can be made, for example, by setting a threshold value for the tension fluctuation index in advance, and determining that the thickness can be changed while on the run 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 thickness cannot be changed while on the run if it exceeds the threshold value.

[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.

Figure 6 shows a schematic diagram of three adjacent rolling stands that make up a tandem rolling mill. Figure 6 shows the state when the junction point W reaches between the N-1 stand and the N stand and then passes through the N stand. In other words, in the N stand and the N+1 stand, rolling is performed with the roll gap S1 and roll peripheral speed V _R 1 that are set for the preceding material, and in the N-1 stand, rolling is performed with the roll gap S2 and roll peripheral speed V _R 2 that are set for the succeeding material.

In this embodiment, the tension fluctuation index is calculated by, for example, calculating the amount of tension fluctuation that occurs on the entry side or exit side of the N stand when the junction point W passes through the N stand while maintaining the set values of the roll gap S1 and the roll peripheral speed V _R 1 relative to the preceding material. In this case, the amount of tension fluctuation that occurs when the junction point W passes through the N stand is greater on the entry side than on the exit side of the N stand, so the tension fluctuation index may be the amount of tension fluctuation that occurs on the entry side of the N stand (between the N-1 stand and the N stand).

A physical model for determining the tension q (MPa) at the entrance of stand N can generally be expressed by the following equation (7): In equation (7), L is the distance between rolling stands (m), E is the Young's modulus of the rolled material (MPa), v _in,N (m/s) is the material speed of the rolled material at the entrance of stand N, v _out,N-1 (m/s) is the material speed of the rolled material at the exit of stand N-1, and t is time (s).

In other words, the tension q on the entrance side of stand N can be calculated by integrating with time 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 elastic strain between the rolling stands. In this case, if rolling is carried out in stand N-1 at the roll gap S2 and roll peripheral speed V _R 2 set for the succeeding material, the material speed v _out,N- 1 of the rolled material at the exit side of stand N-1 is considered to be roughly constant, so the change dq in tension q on the entrance side of stand N can be expressed as in the following equation (8).

Here, the change in material speed dv _in,N of the rolled material at the entry side of the N stand in equation (8) changes in response to changes in the rolling state at the N stand. In other words, the thickness and deformation resistance of the rolled material change when the junction point W passes through the N stand, 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 settings of the roll gap and roll peripheral speed as well as the behavior of the junction point as it passes through the rolling stands.

In contrast to this, the tension fluctuation index used in this embodiment calculates the amount of fluctuation in tension q that occurs at the entry side of the N stand when the junction W passes through the N stand while maintaining the set values of the roll gap S1 and the roll circumferential speed V _R1 for the preceding material. Therefore, it is not necessary to constantly calculate the amount of change dv _in,N in the material speed of the rolled material at the entry side of the N stand that accompanies changes in the roll gap and roll circumferential speed. Furthermore, because the time it takes for the junction W to pass through the N stand is extremely short, about 0.01 seconds, as mentioned above, the time step dt in equation (8) can be replaced with a calculation of one step (time step Δt), and the amount of change Δq in tension q at the entry side of the N stand can be expressed as in equation (9) shown below. Here, in equation (9), Δv _in,N means the difference between the material speed _v1 of the material to be rolled on the inlet side of the N stand when a preceding material is rolled with the set values of roll gap S1 and _roll peripheral speed V R 1, and the material speed _v2 of the material to be rolled on the inlet side of the N stand when a succeeding material is rolled with the set values of roll gap and roll peripheral speed S1 and V _R 1. The change amount Δq in tension q calculated in this way becomes the tension fluctuation index in this embodiment.

The delivery thickness h1 at N stand when rolling the preceding material with the set values of roll gap S1 and roll peripheral speed V _R1 is found in the setting calculation from the intersection a of the elastic characteristic curve of N stand and the plastic characteristic curve of the preceding material (Figure 3). The setting calculation also calculates the corresponding forward slip _f1 . Therefore, the material speed _v1 of the rolled material at the entrance of N stand when rolling the preceding material with the set values of roll gap S1 and roll peripheral speed V _R1 can be found by the following formula (10).

On the other hand, the delivery thickness hc at N stand when rolling a subsequent material while maintaining the set values of the roll gap S1 and the roll peripheral speed V _R1 can be calculated as a simultaneous solution of the rolling load calculated from equation (1) using the entry thickness H2 and deformation resistance _km2 of the N stand and equation (2) representing the elastic characteristic curve of the N stand. That is, it can be obtained from intersection b in Figure 3. The corresponding forward slip f _c can also be calculated by applying equation (3). Therefore, the material speed _v2 of the rolled material at the entrance of N stand when rolling a subsequent material while maintaining the set values of the roll gap S1 and the roll peripheral speed V _R1 can be obtained from equation (11) shown below.

From the above, Δv _in,N in Equation (9) can be calculated using the material speed _v1 and material speed _v2 of the rolled material at the inlet side of the N stand. 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 with the length of the junction point W between the preceding and following strips within a constant range and the rolling speed at which running thickness changes are performed is approximately constant, then even if Δt is set to an arbitrary value, it can be used as an index for evaluating the magnitude of tension fluctuation when the junction point W passes through the rolling stand. On the other hand, Δt may be set as a function inversely proportional to the material speed v ₁ or the roll peripheral speed V _R 1 in the N stand, assuming that the length of the joining point W is constant, and applied to Equation (9).

As described above, the tension fluctuation index in this embodiment can be found from the entry material speed _v1 when a preceding material is rolled in N stands of a tandem rolling mill with the roll gap S1 and the roll peripheral speed V _R 1, and the entry material speed v2 when it is assumed that a succeeding material is rolled while maintaining the roll gap _S1 and the roll peripheral speed V R _1. This makes it possible to find an index representative of tension fluctuations extremely easily compared to methods of predicting tension fluctuations that perform integral calculations every short time, such as the method of performing a numerical simulation using equations (7) and (8).

In the tension fluctuation calculation step of this embodiment, as described above, it is preferable to calculate the tension fluctuation when the joining point W passes through the N stand while maintaining the set values of the roll gap S1 and the roll peripheral speed V _R1 for the preceding material, using the set values of the roll gap S1 and the roll peripheral speed V _R1 of the rolling stand for the preceding material acquired in the set value acquisition step, and the entry thickness H2 and deformation resistance _km2 set for the succeeding material passing through the N stand.

Flying thickness change in this embodiment is preferably applied when, in at least one rolling stand (N stand) of a tandem rolling mill, the start point of the roll gap and roll peripheral speed change (flying thickness change start point FS) is set for the preceding material, and the end point of the roll gap and roll peripheral speed change (flying thickness change end point FE) is set for the following material. That is, it is preferably applied when the junction point W passes through the N stand in the flying thickness change section, as shown in Figure 5(a). In the embodiment of flying thickness change shown in Figure 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 Figure 3, a transition occurs from the plastic characteristic curve of the preceding material to the plastic characteristic curve of the following material, 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.

Furthermore, the method for determining whether or not a running thickness change is possible according to the above embodiment is preferably applied when the difference between the deformation resistance _km1 of the preceding strip and the deformation resistance _km2 of the following strip is 80 MPa or more. The greater the difference in deformation resistance between the preceding and following strips, the greater the divergence of the plastic characteristic curves shown in FIG. 3 between the preceding and following strips, resulting in greater actual tension fluctuations. Therefore, a method using numerical simulation to calculate 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 strip and the deformation resistance of the following strip is large. Therefore, it is difficult to obtain a sufficient number of actual data, and prediction 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.

Here, we will explain the causes of tension fluctuations when the junction point passes through a rolling stand during a flying thickness change. The causes of tension fluctuations during a flying thickness change can be broadly classified into two categories. The first cause is due to tracking errors at the junction point and response delays in the roll gap and roll peripheral speed. Tracking errors at the junction point and response delays in the roll gap and roll peripheral speed cause a discrepancy between the theoretically expected 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 the roll gap and 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 junction point. The rolling condition of N stand changes drastically the moment the junction point reaches N stand. For example, when a soft preceding material is shifted to a harder succeeding material, the rolling load at the N stand increases sharply, 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. This causes the inlet speed v _in,N of the N stand to increase, and the tension between the N-1 stand and the N stand to increase sharply. In other words, tension fluctuations occur when passing through a joining point, even without changing the settings of the roll gap or roll peripheral speed.

The tension fluctuation index of this embodiment focuses on the second cause. In other words, considering the first cause requires a numerical simulation that calculates 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 becomes relatively smaller than the second cause as the performance of the control equipment for tandem rolling mills improves. In particular, when the difference in deformation resistance between the preceding and following strips is large, the influence of the first cause is smaller than that of the second cause. Therefore, under these 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.

[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.

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 the 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 setting calculations for the following strip and calculates set values for the roll gap S2 and roll peripheral speed V _R 2 for the following strip. When the junction point detection device detects the junction point, the rolling controller 3 starts tracking the junction point in the tandem rolling mill 2 based on the detected signal. Meanwhile, the control computer 4 performs setting calculations for the following strip and also performs calculations for executing the method for determining whether or not the thickness of a flying strip can be changed. 7 for all rolling stands 2A to 2E. If it is determined that on-the-fly thickness changes are possible in all rolling stands 2A to 2E, the control computer 4 changes the on-the-fly thickness in accordance with the differential command amounts ΔS and ΔV _R specified by the setting calculation. On the other hand, if it is determined in the determination step that on-the-fly thickness changes are 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 from the preset conditions (roll gap S2, roll peripheral speed V _R 2) before the junction point reaches the first rolling stand 2A of the tandem rolling mill, and causes the strip to pass the junction point in accordance with the changed conditions.

If the judgment step determines that a running thickness change is not possible in at least one rolling stand of the tandem rolling mill, the conditions to be changed are conditions that reduce tension fluctuations as the joining point passes through the rolling stands. Specifically, a gap opening plate may be implemented, which opens the roll gaps of all rolling stands of the tandem rolling mill and allows the joining point to pass without rolling the joining point. Also, the pass schedule for the following material may be changed from the preset one to allow the material to pass through the joining point.

[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.

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 personal computer, and is communicably connected to the 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 the determination result of 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 material 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 material. 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.

The above-mentioned method for determining whether or not a running thickness change is possible can also be implemented by a computer executing a program. Furthermore, a computer-readable recording medium on which the program is recorded 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.

The program for determining whether or not a thickness can be changed while on the fly in this embodiment may be configured to execute the steps of the method for determining whether or not a thickness can be changed while on the fly on a computer. In this case, by executing the program for determining whether or not a thickness can be changed while on the fly on a general-purpose computer such as a workstation or personal computer, the general-purpose computer functions as a device for determining whether or not a thickness can be changed while on the fly. Furthermore, by installing the program for determining whether or not a thickness can be changed 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 can be changed while on the fly.

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

As shown in Figure 8, in two-stage on-the-fly thickness change, the roll gap S is first set to the first roll gap S1 for the preceding material so that the target delivery thickness h1 is obtained, and the second roll gap S2 is set for the following material 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 maintenance process) in which rolling is performed with roll gaps different from the first roll gap S1 and the second roll gap S2 during the transition from the preceding material to the rolling of the following material. The process of transitioning from rolling the preceding material 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 material 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.

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 between the elastic characteristic curve and the plastic characteristic curve to transition from intersection a to intersection b. As a result, the strip thickness at the exit of the rolling stand changes from h1 to hc1. Furthermore, when the junction point passes through the rolling stand in this state, the plastic characteristic curve changes before and after the junction point, causing the intersection between the elastic characteristic curve and the plastic characteristic curve to transition from intersection b to intersection c. As a result, the strip thickness at the exit of the rolling stand changes from hc1 to hc2. Thereafter, when the second running thickness change process is performed, the roll gap is changed (Sc → S2), causing the intersection between the elastic characteristic curve and the plastic characteristic curve to transition from intersection c to intersection d. As a result, the strip thickness at the exit of the rolling stand changes from hc2 to h2, completing the running thickness change.

In a two-stage on-the-fly thickness change, the transient thickness change at the rolling stand delivery side 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 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 this two-stage on-the-fly thickness change. The start and end points of a two-stage on-the-fly thickness change are explained below with reference to Figures 9(a) and (b).

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 flying thickness changes are possible in this embodiment to the first flying thickness changing process. When determining whether flying thickness changes are possible in the first flying thickness changing process, the parameters (S2, V _R2 , h2) of the following strip B used in the above-mentioned one-stage flying thickness change determination can be calculated by replacing them with the parameters (Sc, V _R c, hc2) of the intermediate step. In this case, the deformation resistance _km2 of the following material B is used as the deformation resistance of the material to be rolled in the intermediate step. Specifically, before the first flying thickness changing process is started, the set values of the roll gap S1 and the roll peripheral speed _VR1 for the preceding material A are acquired in a set value acquisition step. Next, in a tension fluctuation calculation step, the tension fluctuation amount when the joining point W passes through the rolling stand while maintaining the set values of the roll gap S1 and the roll peripheral speed _VR1 for the preceding material A is calculated using the intermediate step parameters Sc, _VRC , and hc2. Based on the tension fluctuation amount calculated in this way, a determination step is executed to determine whether or not the flying thickness can be changed.

On the other hand, as shown in Figure 9 (b), the determination of whether or not to perform on-the-fly thickness changes 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, 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 changes of this embodiment to the second on-the-fly thickness change process. When determining whether or not to perform on-the-fly thickness changes of the second on-the-fly thickness change process, the tension fluctuation index can be calculated by replacing the parameters of the preceding material (S1, V _R1 , h1) used in the above-mentioned one-stage on-the-fly thickness change determination with the parameters of the intermediate step (Sc, V _R c, hc2). In this case, the deformation resistance _km1 of the preceding material A is used as the deformation resistance of the rolled material in the intermediate step. Specifically, before the second flying thickness changing process is started, the set values of the roll gap Sc and the roll peripheral speed _VRC for the intermediate step are acquired in the set value acquisition step. Next, in the tension fluctuation calculation step, the tension fluctuation amount when the joining point W passes through the rolling stand while maintaining the set values of the roll gap Sc and the roll peripheral speed _VRC for the intermediate step is calculated using the parameters S2, _VRC , and h2 of the following material B. Based on the tension fluctuation amount calculated in this way, a judgment step is executed to judge whether or not flying thickness changing is possible. As described above, the magnitude of tension fluctuation in two-stage flying thickness changing can be appropriately judged.

An example of the present invention will now be described. In this example, a determination was made as to whether or not a one-stage on-the-fly thickness change was possible using a tandem rolling mill 2, which is a tandem rolling mill having five rolling stands as shown in Figure 1. The specifications of the tandem rolling mill 2 are as follows. The rolling load detector 24, reduction position detector 25, tension meter 26, and thickness meter 27 were positioned as shown in Figure 1.

- Maximum line speed: 2000 mpm (m/min)
・Work roll diameter: 500 to 600 mmφ
・Backup roll diameter: 1300 to 1400 mmφ
・Distance between stands: 4600mm

First, we compared the tension fluctuation index of the present invention with actual tension fluctuations due to changes in running thickness. The tension fluctuation index evaluated tension fluctuations occurring between the first rolling stand 2A and the second rolling stand 2B when the junction point W passes through the second rolling stand 2B of the tandem rolling mill 2. The rolled materials for which tension fluctuations were 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 rolled materials had widths ranging from 760 to 1900 mm, ranging from low-carbon steel grades to high-strength steel plates with tensile strengths of 1180 MPa in cold-rolled steel products. The difference in deformation resistance between the preceding and following materials ranged from -200 to +200 MPa. When 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 obtained in the set value acquisition step were set values held by the control computer 4. Meanwhile, the actual value of tension fluctuation due to on-the-fly thickness change was obtained by acquiring the tension fluctuation amount (amplitude of tension fluctuation) measured during the on-the-fly thickness change process of the second rolling stand 2B from the fluctuations in 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 width at the inlet side of the second rolling stand 2B.

Figure 11 shows the results of comparing the tension fluctuation index calculated using the above method with the actual tension fluctuation caused by a change in thickness during travel. 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, it 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 suppressed to 2.1 MPa. From the above, it was confirmed that the tension fluctuation index calculated using the above method has a high correlation, especially when there is a large difference in deformation resistance between the preceding and following materials.

Next, we will explain the results of a determination of whether or not a running thickness change is possible using the above-mentioned tandem rolling mill 2. In this example, the dimensions of the rolled material were a base thickness of 2.4 to 3.6 mm, a thickness at the exit of the final rolling stand of 0.9 to 2.0 mm, and a width of 700 to 1400 mm. Here, a determination of whether or not a running thickness change is possible was made when the leading and trailing materials were a combination of high-strength steel plates with tensile strengths of 590 MPa and 1180 MPa, respectively. Conventionally, with these combinations of leading and trailing materials, excessive tension fluctuations were likely to cause the rolled material to break, so 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.

In the example, a determination was made at all rolling stands as to whether or not a running thickness change was possible. If the determination step determined that a running thickness change was possible at all rolling stands, a running thickness change was carried out. If it was 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, a running thickness change was determined to be possible; if it exceeded 30%, a running thickness change was determined to be impossible. As a result, for the above combination of preceding and following strip, gap opening was conventionally performed 20 times per month, but in the example, this was reduced to 15 times. This improved the operating rate of the tandem rolling mill.

The above describes an embodiment of the invention developed by the inventors, but the present invention is not limited to the descriptions and drawings that form part of the disclosure of the present invention according to this embodiment. In other words, all other embodiments, examples, and operational techniques that are developed by those skilled in the art based on this embodiment are included within the scope of the present invention.

REFERENCE SIGNS LIST 1 Continuous cold rolling equipment 2 Tandem rolling mill 3 Rolling control 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 Rolling position detector 26 Tension meter 27 Plate thickness meter W Joint point

Claims (7)

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: 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 when the joint passes through the rolling stand while maintaining the roll gap and roll peripheral speed settings for the preceding material, using the roll gap and roll peripheral speed settings of the rolling stand for the preceding material acquired in the setting value acquisition step, and the thickness and deformation resistance set for the succeeding material passing through the rolling stand. A method for determining whether or not a flying strip thickness change is possible, as described in claim 1, wherein, in the flying strip thickness change, the start point of the change in the roll gap and roll peripheral speed is set to the position of the preceding material, and the end point of the change in the roll gap and roll peripheral speed is set to the position of the following material. A method for determining whether or not a running thickness change is possible, as described in claim 1, wherein the difference between the deformation resistance of the preceding material and the deformation resistance of the following material is 80 MPa or more. A method for changing the thickness of a running strip, using the method for determining whether or not a running strip thickness change is possible as described in any one of claims 1 to 4, to change the thickness of a running strip when it is determined that a running strip thickness change is possible in all rolling stands of the tandem rolling mill, and to change the set values of the roll gap and roll peripheral speed of the rolling stand for the following strip when it is determined that a running strip thickness change is not possible in at least one rolling stand of the tandem rolling mill. 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. 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.