JP3433581B2 - Meandering control method in continuous hot rolling mill - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing meandering of a material to be rolled which can reliably prevent the material to be rolled from being narrowed in continuous hot finish rolling.

[0002]

2. Description of the Related Art In recent years, in the field of hot continuous rolling and the like, various crown control mills such as HC-MILL have been put into practical use, and as a result, flat steel plates without plate crowns can be stably manufactured. Came. However, as the plate crown becomes smaller, the plate is more likely to meander during rolling, and especially when the tail end of the material to be rolled (hereinafter simply referred to as “strip”) slips out, the material to be rolled is guided by the side guide. There was a new problem that the so-called narrowing occurred, that is, the steel sheet collided with the steel sheet and fell and rolled.

On the other hand, conventionally, as a strip meandering control technique for preventing such an accident, a method for controlling the parallel rigidity of a rolling mill, which is expressed by the following formula (1), has been proposed ("Hitachi Review" Vol. , 65 No. 2 (1983) 25).

[ _Equation 1] S _df = −α · ΔP _df / M (1) where S _df : Leveling correction amount α: Control gain ΔP _df : After the tail end of the strip exits the stand immediately before the stand. , Deviation of load difference between driving side and operating side in the stand M: parallel rigidity

According to this method, when the strip meanders during rolling, the deviation ΔP _{df of the} load difference between the driving side and the operating side of the stand.
If the parallel rigidity value of the rolling mill is M, the difference between the driving side and the operating side of the roll opening is ΔP _df / M. Therefore, it is a method of controlling the strip meandering by correcting the difference between the rolling positions of the driving side and the operating side, that is, the leveling so as to compensate for the difference in the roll opening.

[0005]

The above-mentioned prior art is the meandering control only by the proportional control. According to this method, the control can be performed quickly, and the stripping can be performed by increasing the control gain to near 1. It is possible to suppress the meandering of with a good accuracy. However, in this conventional technique, when the control gain is increased, although the effect of suppressing the meandering of the strip is large, it is rather overcorrected in many cases, which causes the strip meandering on the driving side to meander to the operating side. In the end, there was a problem that narrowing down could not be completely prevented. The object of the present invention is to solve the problems of the above-mentioned conventional techniques, and the tail end of the strip is controlled by controlling the meandering so that the strip always passes near the roll center of the stand. The object is to propose a meandering control technology that can surely prevent the narrowing of.

[0006]

Means for Solving the Problems As a means for achieving the above object, the present invention provides a leveling of an arbitrary stand of a continuous hot rolling mill based on a load difference between a driving side and an operating side of the stand. When the meandering control of the rolled material is performed by changing, the tail end of the strip reaches the stand until the tail end of the strip passes through the stand immediately before the stand and reaches the stand. A meandering control method in continuous hot rolling, characterized in that a control gain α in the following equation is changed according to a time or a distance after leaving the immediately preceding stand, S _df = −α · ΔP _df / M Here Then, S _df : Leveling correction amount α: Control gain ΔP _df : Deviation of load difference between driving side and operating side in the stand M: Propose parallel rigidity. In the present invention, when the control gain α is set according to the time or the distance after leaving the front stand, it is preferable to determine the control gain α according to the following formula. α = a (1 + b (1-t / t ₀ )) where a and b are constants t ₀ : time from when the material to be rolled leaves the preceding stand until it reaches the stand (passing time between stands) ) T: Time after the rolled material passes through the stand in the preceding stage, and in setting the control gain, immediately after the tail end of the strip passes through the stand immediately before the stand, the control gain α is a value larger than 1. It is a preferred embodiment that when reaching the stand, the value is greater than 0 and equal to or less than 1.

[0007]

The present invention will be described in detail below with reference to the drawings.
FIG. 1 shows a control system used when the method of the present invention is applied. The work rolls 7, 7'are provided at any stand of the continuous hot rolling mill, for example, the i-th stand.
4 shows a state in which the material to be rolled 6 is rolled by a four-high rolling mill consisting of the reinforcing rolls 8 and 8 '. Illustrated controller 5
Is the output difference P _df between the load meter 2 on the driving side and the load meter 1 on the operating side in this i stand, based on the output difference immediately after the tail end of the strip passes through the immediately preceding stand (i-1). Then, the deviation ΔP _df is divided by the parallel rigidity value M ₁ to calculate the difference between the roll opening degrees on the driving side and the operating side, and this is multiplied by the control gain α to calculate the leveling correction amount S _df. The leveling correction amount S _df is output to the driving-side reduction position control device 4 and / or the operation-side reduction position control device 3. Based on the result, the driving-side reduction position control device 4 and / or the operation-side reduction position control device 3 corrects the difference between the driving-side and operation-side reduction positions, that is, the leveling S _df to change the reduction position. To do. In addition, 1 and 2 of illustration are load cells.

What is important here is how to set the control gain α. For example, according to the place shown in FIG. 2, the rolling material is changed so as to be gradually reduced in accordance with the time or the distance from the time when the rolled material leaves the former stand until it reaches the stand. A method can be considered. This way of thinking
This is due to the following research results conducted by the inventors. This is because the control gain α is set to a constant value irrespective of the time after the rolled material passes through the front stand and the meandering control is performed based on various control gains α, as shown in FIG. This is because it was found that the situation would meander as shown. In this figure, the meandering amount is represented based on the deviation (off-center amount) from the center of the width center of the material to be rolled directly under the stand with respect to the center of the housing.

That is, as shown in FIG. 3, when the control gain α is less than 1, the larger the value (the closer α is to 1), the smaller the meandering amount of the material to be rolled after it has passed through the front stand. However, the plate cannot be returned to the center, and the meandering itself is still outstanding, and stable plate passing has not been completed. Further, when the control gain α is set to be larger than 1, the material to be rolled after passing through the front stand is
Although it is possible to turn from the meandering direction and return it to the center, after that, meandering in the opposite direction, the amount increases rather, and in this case also it is possible to realize stable threading. I found it difficult.

FIG. 4 is a graph showing the relationship between the control gain α and the time from the exit of the preceding stand to the reversal of the meandering direction, based on FIG. As shown in this figure, it can be seen that the larger the control gain α is, the shorter the time taken for the rolled material to pass through the front stand and the faster the direction of so-called meandering is reversed.

From the above-mentioned various findings, in the present invention, the control gain α is set in accordance with the time after leaving the front stand, and, if possible, as shown in FIG.
It is possible to always give the maximum control gain α if it is set so as to gradually decrease with respect to (t / t ₀ ). in this case,
For example, the control gain α can be determined according to the equation (2).

[Formula 2] α = a · (1 + b · (1−t / t ₀ )) (2) where a and b: constant t ₀ : the material to be rolled arrives at the stand after passing through the preceding stand. Time (passing time between stands) t: time after the rolled material leaves the former stand

As a method of gradually decreasing the control gain α, not only the linear decreasing method shown in the above equation (2) but also
You may make it gradually reduce based on a multi-order function, an exp function, etc.

Specifically, as an example of the meandering control, the control gain α is set to a value larger than 1 immediately after the tail end of the strip leaves the stand immediately before the stand, and the stand is reached. Meandering control, which is sometimes greater than 0 and less than or equal to 1, is a preferred embodiment of the invention.

The operation and effect of the present invention is not limited to the above-described control method, that is, the method of determining the tail end of the material to be rolled according to the time elapsed after passing through the front stand, but also the material to be rolled. Even if the control gain α is set in accordance with the distance after the tail end of the vehicle has passed through the front stand, the same result can be obtained, and this case can be regarded as an embodiment of the present invention.

[0015]

[Example] A low carbon steel having a finish plate thickness of 1.6 mm and a plate width of 1600 mm was used.
Rolling was performed by a hot finish rolling mill including a stand, and meandering control based on the load difference was performed at the seventh stand in accordance with the following (A) to (D). The implemented control is (a) no control (comparative example), (b) control using a fixed control gain of 0.6 (conventional method 1), (c) control using a fixed control gain of 1.4. (Conventional method 2), (d) Set the control gain to 1.4 according to the above equation (2).
When the control is performed while sequentially changing from 0 to 0.6 (invention method), for each of the above (a) to (d), the off-center amount of the seventh stand in the steady state is set to 10 mm on the drive side and rolling is performed. Was carried out.

According to the execution results, as shown in FIG. 5, which shows the relationship between the time t after the tail end of the strip passes through the sixth stand and the off-center amount of the strip on the exit side of the seventh stand, as shown in FIG. Example (a) and conventional method 1
In (b), although the meandering speeds are different, the meandering amount is too large and the aperture is generated in both cases. Further, in the conventional method 2 (c), the off-center amount reverses from the driving side to the operating side, the meandering amount increases on the operating side, and the aperture is generated. On the other hand, in the method of the present invention, the conventional method 2
Although the off-center amount increases at a slow speed similar to (c), the off-center amount does not become negative (off-center to the operating side), and slipping out is completed in a stable state. .

[0017]

As described above, according to the present invention, the control gain α is set according to the time after the strip has passed through the front stand, so that the control gain is increased at the beginning of meandering when the strip has passed through the front stand. Since it is possible to make the control gradually smaller thereafter, it is possible to effectively and stably perform rolling without meandering to the opposite side. Therefore, it is possible to reliably prevent the strip from being narrowed down, and it is possible to stabilize the quality of the rolled steel sheet.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a rolling mill used for implementing the present invention and its control system.

FIG. 2 is a diagram showing how to set a control gain in the present invention.

FIG. 3 is a diagram showing a meandering situation when a control gain is changed.

FIG. 4 is a diagram showing a relationship between a control gain and a position at which meandering is reversed.

FIG. 5 is a diagram showing a change situation of the off-center amount of the seventh stand in the example.

[Explanation of symbols]

1, 2 load cell 3, 4 Rolling position control Ca 5 control device 6 Rolled material 7, 7'work roll 8, 8'reinforcing roll

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-6-182417 (JP, A) JP-A-5-285520 (JP, A) JP-A-3-216207 (JP, A) JP-A-8- 267117 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 37/00-37/78

Claims (3)

(57) [Claims] 1. In an arbitrary stand of a continuous hot rolling mill, when the leveling of the stand is changed based on the load difference between the driving side and the operating side of the stand to control the meandering of the material to be rolled, the strip tail is controlled. Depending on the time or distance after the tail end of the strip has passed through the stand immediately before the stand from the time when the end passes through the stand immediately before the stand until it reaches the stand, the following formula 3. A meandering control method in continuous hot rolling, which is characterized by changing a control gain α in. Note S _df = −α · ΔP _df / M where S _df : Leveling correction amount α: Control gain ΔP _df : Deviation of load difference between driving side and operating side in the stand M: Parallel rigidity 2. The control gain α is determined according to the following equation when the control gain α is set according to the time or distance after leaving the front stand.
The method of controlling meandering according to. α = a (1 + b (1-t / t ₀ )) where a and b are constants t ₀ : time from when the material to be rolled leaves the preceding stand until it reaches the stand (passing time between stands) ) T: Time after the rolled material passes through the front stand 3. When setting the control gain, the control gain α is set to a value larger than 1 immediately after the tail end of the strip leaves the stand immediately before the stand, and is set to a value larger than 0 when the stand is reached. The meandering control method according to claim 1 or 2, wherein the meandering control value is large and 1 or less.