JPWO1995007776A1 - Meandering control method and tandem plate rolling mill equipment train - Google Patents

Abstract

(57) [Abstract] A meandering control method and a tandem rolling mill line as a prerequisite for ensuring stable threading of rolled material, including when rolling the head and tail ends, in tandem rolling operations of metal plates are disclosed. The meandering control method for a tandem plate rolling mill is equipped with two or more rolling mills and, between the rolling mills, a strip tension measuring device having independent tension detectors on the work side and the drive side, and a strip width direction threading position measuring device. The strip width direction threading position at the position of the strip tension measuring device is directly detected or estimated from the output of the strip width direction threading position measuring device. The difference between the work side and the drive side tension measuring device in the tension actually acting on the rolled material at the position of the strip tension measuring device is calculated from this and the outputs of the work side and drive side detectors of the strip tension measuring device. The difference between the work side and the drive side of the tension measuring device is controlled with the goal of reducing the tension difference to zero.

Description

[Detailed Description of the Invention] Meandering Control Method and Tandem Plate Rolling Mill Equipment Train Technical Field The present invention relates to an operation control method for ensuring stable threading of rolled material during tandem rolling operations of metal plates, and the tandem rolling mill equipment that serves as the basis for this control.

BACKGROUND ART Tandem rolling of metal sheets is a process capable of mass-producing high-precision sheet metal. The ability to apply tension to the rolled material between each mill in the tandem rolling mill train allows for highly stable rolling operations. When tension is applied to the rolled material, even if there is a certain degree of deviation from the optimal value in the difference in the setting values of the work-side and drive-side screw leveling devices (hereinafter referred to as "leveling"), this does not directly result in a difference in elongation. Rather, the difference in elongation between the work side and drive side is suppressed by the redistribution of tension, and therefore, threading accidents are rarely directly linked.

However, because rear or front tension cannot be applied to the leading or trailing edge of the rolled material, the stabilizing effect of tension is halved, making the strip more susceptible to threading accidents. Rear tension has a particularly large effect, so when the rear end passes, rear tension is released, and a strip threading accident known as tail squeezing often occurs. Therefore, conventional methods of controlling the roll pressure, known as meandering control or tail squeezing control, are used. In the following explanation, the working and driving sides are often referred to as "left and right" for brevity.

In the present invention, the term "snake" refers to the rolling material passing while being shifted in the width direction from the mill center.

The primary cause of tail squeezing is thought to be material meandering, resulting from differences in elongation between the left and right sides near the rear end of the rolled material. Conventional methods for controlling meandering control involve controlling the difference in the left-right roll reduction settings of the rolling mill, i.e., leveling control, from the point at which tail squeezing begins to occur—that is, when the rear end of the rolled material leaves the previous rolling mill. The detection elements used in this process include the difference in the rolling load between the left and right sides of the rolling mill and the signal from a meandering sensor detecting the amount of off-center movement of the plate.

Conventional meandering control methods such as those described above essentially begin control as soon as the rear end of the rolled material leaves the previous rolling mill, resulting in a short operating time that may not be sufficient to prevent tail squeezing. Furthermore, if the roll leveling of the rolling mill deviates from the optimal value, the rear tension that had been acting until then disappears as soon as the rear end of the rolled material leaves the previous rolling mill, eliminating the compensating effect of the tension difference between the left and right sides, and causing rapid meandering. Initiating roll leveling control after the symptoms appear is often too late.

DISCLOSURE OF THE INVENTION In this invention, we disclose a method and a tandem rolling mill train for optimizing the roll leveling of each mill in a tandem rolling mill train during steady-state rolling before the rear end of the rolled material reaches the mill, rather than starting control when the rear end of the rolled material leaves the previous mill.

The most significant change that occurs when the rear end of the rolled material leaves the previous rolling mill is, of course, the disappearance of rear tension. Therefore, if sudden meandering begins at this point, it is likely that the roll leveling of that rolling mill is not optimal, and this is being compensated for by the difference in rear tension between the left and right sides. Therefore, it is believed that the key to preventing tail squeezing accidents is to keep the difference in left and right tension acting on the rolled material between each rolling mill as close to zero as possible during the steady-state rolling state before the rear end of the rolled material arrives. To do this, it is sufficient to detect the difference in left and right tension acting on the rolled material between each rolling mill and perform operations to bring it close to zero.

As a meandering control method for achieving this, the first invention discloses a meandering control method for a tandem plate rolling mill equipped with two or more rolling mills and, between the rolling mills, a strip tension measuring device and a strip width-direction threading position measuring device, each having independent tension detectors on the work side and drive side. The meandering control method directly detects or estimates the strip width-direction threading position at the location of the strip tension measuring device from the output of the strip width-direction threading position measuring device, and, based on this and the outputs of the work-side and drive-side detectors on the strip tension measuring device, calculates the difference in the tension actually acting on the strip between the work side and drive side at the location of the strip tension measuring device. The meandering control method controls the difference in the set pressure reduction between the work side and drive side of each rolling mill with the goal of reducing this tension difference to zero.

Furthermore, as examples of tandem plate rolling mill trains capable of effectively implementing such meandering control, the second invention discloses a tandem plate rolling mill train comprising four or more rolling mills and a rolled material tension measuring device and a rolled material width direction threading position measuring device disposed between at least two rolling mills in front of the most downstream rolling mill, the rolled material tension measuring device having independent tension detectors on the work side and the drive side. The third invention discloses a tandem plate rolling mill train comprising two or more rolling mills and a rolled material tension measuring device having independent tension detectors on the work side and the drive side at at least one location between each rolling mill, and a detector capable of measuring the rolled material width direction threading position upstream and downstream of the rolled material tension measuring device disposed between the rolling mills.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram showing the algorithm for a meandering control method according to one embodiment of the present invention; Figure 2 is a schematic diagram of a looper-type tension detection device, an example of a rolled material tension measurement device having independent tension detectors on the work side and drive side, which is one of the essential requirements of the present invention; Figure 3 is a schematic diagram of a semi-fixed tension detection device, an example of a rolled material tension measurement device having independent tension detectors on the work side and drive side, which is one of the essential requirements of the present invention; Figure 4 is a schematic diagram showing an example of a tandem plate rolling mill line according to another embodiment of the present invention; Figure 5 is a schematic diagram showing an example of a tandem plate rolling mill line according to yet another embodiment of the present invention; Figure 6 is a schematic diagram showing an example of a tandem plate rolling mill line according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 is a flowchart of a meandering control method according to one embodiment of the present invention. In step 1000, the widthwise threading position of the rolled material at the position of a rolled material tension measuring device installed between the rolling mills is directly detected or estimated by interpolation from the output of a widthwise threading position measuring device installed to measure the widthwise threading position of the rolled material between the rolling mills. In step 1002, the difference in tension actually acting on the rolled material between the left and right sides is calculated from the outputs of the work-side and drive-side detectors of the rolled material tension measuring device and the widthwise threading position. In step 1004, it is determined whether the calculated left-right tension difference is within a tolerance. If it is within the tolerance, the process returns to step 1000. If it is not within the tolerance, in step 1006, the difference in the left-right tension setting of each rolling mill is controlled with the goal of reducing the left-right tension difference to zero, and the process returns to step 1000.

Examples of rolled material tension measuring devices include a vertically movable looper device, as shown in FIG. 2, primarily used in hot rolling, and a substantially fixed tension detection roll, as shown in FIG. 3, primarily used in cold rolling. The force applied to the driven roll 7 due to the tension acting on the rolled material 4 is detected by torsion bar load cells 9a, 9b or load cells 11a, 11b. The present invention assumes that the load cells are independently located on the work side and the drive side, as shown in FIG. 2 or 3. By observing the difference in output between these two, the left-right asymmetric component of the force acting on the rolled material tension measuring device can be extracted. To convert this load cell output to tension acting on the rolled material, the angle between the rolled material 4 and the horizontal plane is calculated from the position of the driven roll 7 of the tension measuring device and the position of the work rolls of the rolling mill, and then the force vector is calculated based on the geometric equilibrium condition. Furthermore, the most practical device for measuring the width direction threading position of a rolled material is an optical type.

Now, taking the relationship between an arbitrary rolling mill No. i and No. i+1 rolling mill as the subject of consideration, a more detailed explanation will be given using an example of a looper type tension measuring device as shown in Figure 2. When the load cell load of the rolling material tension measuring device is converted into a vertical load taking into account the looper angle and the difference between the work side and the drive side is taken as _Rdfi , _Rdfi includes not only the tension difference _σdfi acting on the rolled material but also the influence of the threading position of the rolled material in the width direction, _i.e. , the material off-center amount _xci , and the following relational expression is established:

R _dfi = [{b ² / (6a _Li )} σ _dfi + (2 / a _Li )σ _i bx _ci ] (sin θ _bi + sin θ _fi ) h _i ... (1) Here, a _Li is the distance between the supports of the looper rolls, θ _bi and θ _fi are the angles formed by the horizontal plane by the rolled sheet surfaces on the i-th and (i+1)-th stands, separated by the looper roll, h _i is the sheet thickness on the delivery side of the i-th stand, x _ci is the amount of material off-center at the looper position, σ _i is the tension per unit cross-sectional area of the rolled sheet (hereinafter referred to as unit tension), and b is the sheet width of the rolled sheet.

According to formula (1), even if R _dfi is measured, if the material off-center amount x _ci at the looper position is unknown, it is impossible to accurately determine the tension acting on the rolled material from formula (1). Generally, rolling operations are carried out with the goal of making x _ci zero, but in reality, an error of about 10 to 20 mm exists, which has a non-negligible effect on the estimation accuracy of the tension σ _dfi acting on the rolled material. For example, when x _ci = 10 mm, a _Li = 2000 mm, and b = 1000 mm, an evaluation of the terms in [ ] on the right-hand side of formula (1) reveals that if the tension difference σ _dfi is estimated while ignoring the effect of x _ci , an error of 12% of the unit tension σ _i will occur. When roll leveling control is performed to make the difference in tension between the left and right sides σ _dfi zero, the material off-center amount x _ci also normally changes, but if control is performed without detecting this change at all, in the above example, this control will include an essential error of ±0.12σ _i from the target value σ _dfi , and it will be impossible to perform sufficient meandering control to eliminate tail squeezing accidents. This is because it is clear that the important thing to prevent strip threading accidents is not to make R _dfi = 0, but to make σ _dfi = 0.

As explained above, in order to accurately detect σ _dfi and to carry out control to make σ _dfi = 0, it is clear that it is essential to detect the difference in the load applied to the left and right tension measuring devices using a tension measuring device having tension detectors independently on the work side and the drive side, and to directly detect or estimate the width direction threading position of the rolled material at the position of the tension measuring device.

Next, we will explain the rolling mill equipment used to implement the meandering control described above. In tandem rolling mills, tail squeezing accidents generally occur in the rolling mill downstream of the tandem rolling mill. This can be explained by the fact that as the plate thickness decreases, if there is an error from the optimal value in the leveling, the effect of this error on the difference in elongation strain between the left and right sides becomes relatively large. Furthermore, as the rolling speed increases, there is less time available for conventional control or operator operation, which operates leveling after the rear end of the rolled material has passed the front stand.

Therefore, in a tandem plate rolling mill line according to another embodiment of the present invention, a tandem plate rolling mill is provided with four or more rolling mills and a rolled material tension measuring device and a rolled material width direction threading position measuring device arranged between the rolling mills in front of at least two rolling mills in succession from the most downstream rolling mill, and the rolled material tension measuring device has independent tension detectors on the work side and the drive side. The reason for having the rolling material tension measuring devices in front of the two rolling mills in front of the most downstream rolling mill is that, in addition to the susceptibility to tail squeezing accidents as mentioned above, in rolling further upstream than this, the plate thickness is quite large, so it is possible to forcibly restrain the material off-center amount to some extent by the guides in front of the rolling mills, and therefore it is possible to prevent a large error from occurring even if _xci is assumed to be zero in equation (1). That is, as shown in FIG. 4, by providing rolled material tension measuring devices 2a, 2b and width direction threading position measuring devices 3a, 3b for the rolled material between at least two rolling mills 1a, 1b in front of the most downstream rolling mill, it becomes possible to carry out substantially effective meandering control.

The process computer 12 receives the outputs of the rolling material tension measuring devices 2a, 2b and the width direction threading position measuring devices 3a, 3b, performs the above-mentioned calculations, calculates the tension differences acting on the rolling material between the rolling mills, and controls the difference in the set reduction between the work side and drive side of the rolling mills 1a, 1b, 1c, and 1d so that these differences become zero.

When directly measuring the widthwise threading position of the rolled material at the position of the tension measuring device, the edge of the rolled material must be detected at the position where it contacts the driven roll 7 (Figures 2 and 3). However, when optically detecting this, it is often difficult to separate the driven roll itself from the edge of the rolled material. Therefore, in the example shown in Figure 4, the widthwise threading position of the rolled material at a position slightly downstream of the tension measuring device is measured, and the widthwise threading position at the tension measuring device is estimated. However, this method inevitably introduces some degree of error into the widthwise threading position.

Therefore, in a tandem plate rolling mill line according to yet another embodiment of the present invention, as shown in FIG. 5, width-direction plate threading position measuring devices 3a', 3a", 3b', 3b", 3c', 3c" are arranged upstream and downstream of the rolled material tension measuring devices 2a, 2b, 2c. By arranging the width-direction plate threading position measuring devices upstream and downstream of the rolled material tension measuring devices in this manner, the width-direction plate threading position at the position of the rolled material tension measuring device, which is difficult to measure directly, can be estimated with high accuracy by interpolating the outputs of the width-direction plate threading position measuring devices before and after it. As a result, the accuracy of estimating the tension difference acting on the rolled material is improved, enabling the meandering control of the first aspect of the present invention to be implemented with higher accuracy.

Snake path control was performed using a seven-stand tandem mill as shown in FIG. 6, in which strip tension measuring devices 2a-2f having independent tension detectors on the work side and drive side are installed between all stands, and detectors 3a', 3a", 3b', 3b", 3c', 3c" capable of measuring the strip width direction threading position downstream and upstream of the strip tension measuring devices are installed between the front stands of the three rolling mills in front of the most downstream rolling mill.

Initially, the difference in tension σ _dfi acting on the rolled material between stands was estimated using only the output of the rolled material tension measuring device, assuming that the material off-center amount was always zero, and leveling control was carried out with the target of σ _dfi = 0, but the threading condition at the rear end of the rolled material was _not completely stabilized.

Next, the amount of material off-center immediately below the rolling mill was estimated by solving a system of equations that expresses the tandem rolling phenomenon using data from the load cell of the rolling mill, the set value of reduction, etc., in addition to the output of the rolling material tension measuring device, and the amount of material off-center x _ci at the position of the rolling material tension measuring device was calculated as an interpolated value, and the tension difference σ _dfi acting on the rolled material was estimated using equation (1), and reduction leveling control was carried out with the target of σ _dfi = 0. As a result, there was an improvement over the control in which the amount of material off-center was assumed to be zero, but the threading state at the rear end of the rolled material, particularly in the rolling mill on the downstream side, was not completely stabilized.

Finally, the amount of material off-center was directly detected using detectors 3a', 3a", 3b', 3b", 3c', 3c" capable of measuring the threading position in the width direction of the rolled material downstream and upstream of the above-mentioned rolled material tension measuring device, and the amount of material off-center at the position of the rolled material tension measuring device was calculated as an interpolated value of the outputs of the detectors between the respective stands. The tension difference σ _dfi acting on the rolled material was estimated using this value and equation (1), and roll leveling control was carried out for each rolling mill with the target of σ _dfi = 0. As a result, the accuracy of estimating the tension difference acting on the rolled material was dramatically improved, particularly in the downstream rolling mill where tail squeezing is a problem, and it was possible to almost completely stabilize the threading of the rear end of the rolled material.

By using the meandering control method and tandem plate rolling mill train of the present invention, it is possible to control the difference in tension acting on the rolled material between the respective mills of the tandem rolling mill train during steady-state rolling to nearly zero. As a result, accidents during threading, including during rear end rolling, are almost completely eliminated, making it possible to greatly improve work efficiency and yield.

Claims in the Amendment [Received by the International Bureau on February 21, 1995 (21.02.95): Original claims 4 and 8 have been withdrawn; original claims 1, 5-7, and 9 have been amended; other claims remain unchanged.

(Page 3) 1. (Amended) A meandering control method for a tandem plate rolling mill having two or more rolling mills and, between the rolling mills, a strip tension measuring device having independent tension detectors on the work side and drive side, and a strip width-threading position measuring device, characterized in that the strip width-threading position at the location of the strip tension measuring device is directly detected or estimated from the output of the strip width-threading position measuring device, and the difference between the work side and drive side tensions actually acting on the strip at the location of the strip tension measuring device is calculated from this and the outputs of the work side and drive side detectors of the strip tension measuring device, and the difference between the work side and drive side pressure reduction settings of at least each rolling mill upstream and downstream of the strip tension measuring device is controlled with the goal of zeroing this tension difference, regardless of the strip width-threading position.

2. A tandem plate rolling mill line comprising four or more rolling mills and at least two rolling mills in succession from the most downstream rolling mill, wherein a rolled material tension measuring device and a rolled material width direction threading position measuring device are provided between the front rolling mills, and wherein the rolled material tension measuring device has independent tension detectors on both the work side and the drive side.

3. A tandem plate rolling mill line comprising two or more rolling mills, a rolling material tension measuring device having independent tension detectors on the work side and drive side at at least one location between each rolling mill, and a detector capable of measuring the widthwise threading position of the rolling material upstream and downstream of the rolling material tension measuring device between the rolling mills.

4. (Deleted) 5. (Amended) A meandering control method comprising the steps of: a) providing a strip tension measuring device having work-side and drive-side detectors between at least one mill of a tandem plate rolling mill; b) determining the strip threading position in the width direction at the position of the strip tension measuring device; c) calculating the difference between the work side and drive side tension acting on the strip between the mills from the outputs of the work-side and drive-side detectors of the strip tension measuring device and the strip threading position; d) controlling the difference between the work side and drive side setpoints of each rolling mill upstream and downstream of the strip tension measuring device so that the tension difference becomes zero regardless of the strip threading position in the width direction.

6. The method according to claim 5, wherein in step b) (after correction), the threading position in the width direction of the rolled material is determined by detecting the threading position using a width direction threading position measuring device provided in the vicinity of the rolled material tension measuring device.

7. The method of claim 5, wherein in step b) (after correction), the strip threading position in the width direction of the rolled material is determined by interpolating the strip threading positions detected by width direction strip threading position measuring devices provided upstream and downstream of the rolled material tension measuring device.

8. (Deleted) 9. (Amended) A meandering control device provided between at least one rolling mill of a tandem plate rolling mill, comprising: a rolling material tension measuring device having work-side and drive-side detectors; means for determining the widthwise threading position of the rolling material at the position of the rolling material tension measuring device; means for calculating the difference between the work-side and drive-side tensions acting on the rolling material between the rolling mills based on the outputs of the work-side and drive-side detectors of the rolling material tension measuring device and the widthwise threading position; and means for controlling the difference between the work-side and drive-side setpoints of each rolling mill upstream and downstream of the rolling material tension measuring device so that the tension difference becomes zero regardless of the widthwise threading position.

Explanation under Article 19 of the Convention: A comparison of the claims contained in the replacement sheet with those originally submitted is as follows:

(1) Claims 1, 5, 6, 7 and 9 were amended.

(2) Claims 4 and 8 have been deleted.

(3) Claims 2, 3, 10 and 11 are not amended.

───────────────────────────────────────────────────── Continued from the front page (72) Inventor: Hiroshi Omi 2-6-3 Otemachi, Chiyoda-ku, Tokyo Nippon Steel Corporation (72) Inventor: Takehiro Nakamoto 1 Nishinosu, Oita City, Oita Prefecture Nippon Steel Corporation, Oita Works (Note) This publication is based on the publication published internationally by the International Bureau of Patents (WIPO). The effect of the international publication of the Japanese patent application (Japanese utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act) and is unrelated to this publication.

Claims (11)

[Claims] 1. A meandering control method for a tandem plate rolling mill having two or more rolling mills and, between the rolling mills, a strip tension measuring device having independent tension detectors on the work side and drive side, and a strip width direction threading position measuring device, wherein the strip width direction threading position at the position of the strip tension measuring device is directly detected or estimated from the output of the strip width direction threading position measuring device, and the difference between the work side and drive side tensions actually acting on the strip at the position of the strip tension measuring device is calculated from this and the outputs of the work side and drive side detectors of the strip tension measuring device, and the difference between the work side and drive side set pressures of each rolling mill is controlled with the goal of reducing the tension difference to zero. 2. A tandem plate rolling mill line comprising four or more rolling mills and at least two rolling mills in succession from the most downstream rolling mill, wherein a rolled material tension measuring device and a rolled material width direction threading position measuring device are provided between the front rolling mills, and wherein the rolled material tension measuring device has independent tension detectors on both the work side and the drive side. 3. A tandem plate rolling mill line comprising two or more rolling mills, a rolling material tension measuring device having independent tension detectors on the work side and drive side at at least one location between each rolling mill, and a detector capable of measuring the widthwise threading position of the rolling material upstream and downstream of the rolling material tension measuring device between the rolling mills. 4. A meandering control method comprising the steps of: a) determining the difference in tension acting on the work side and drive side of the rolling mill between the rolling mills; and b) controlling the difference in the set reduction values between the work side and drive side of the rolling mill so that the tension difference becomes zero. 5. The method of claim 4, wherein step a) includes the substeps of: i) providing a strip tension measuring device having work-side and drive-side detectors between the rolling mills; ii) determining the strip threading position in the width direction of the strip at the position of the strip tension measuring device; and iii) determining the tension difference by calculating the tension difference from the outputs of the work-side and drive-side detectors of the strip tension measuring device and the strip threading position. 6. The method according to claim 5, wherein in substep ii), the threading position of the rolled material in the width direction is determined by detecting the threading position using a width direction threading position measuring device provided near the rolled material tension measuring device. 7. The method of claim 5, wherein in substep ii), the strip threading position in the width direction of the rolled material is determined by interpolating the strip threading positions detected by width direction strip threading position measuring devices provided upstream and downstream of the rolled material tension measuring device. 8. A meandering control device comprising: means for determining the difference in tension acting on the work side and drive side of the rolling mill between the rolling mills; and means for controlling the difference in the set reduction between the work side and drive side of the rolling mill so that the tension difference becomes zero. 9. The tension difference determining means according to claim 8 comprises: a rolled material tension measuring device provided between the rolling mills and having work-side and drive-side detectors; a means for determining the strip threading position in the width direction of the rolled material at the position of the rolled material tension measuring device; and a means for determining the tension difference by calculating the tension difference from the outputs of the work-side and drive-side detectors of the rolled material tension measuring device and the strip threading position. 10. The apparatus according to claim 9, wherein said strip threading position determining means includes a width direction strip threading position measuring device provided in the vicinity of said rolled material tension measuring device. 11. The apparatus according to claim 9, wherein said strip threading position determining means comprises widthwise strip threading position measuring devices provided upstream and downstream of said rolled material tension measuring device, and means for interpolating the strip threading positions detected by said widthwise strip threading position measuring devices.