JP3506120B2 - Method of changing rolling load distribution of tandem 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 rolling load distribution control and work roll bender pressure change control in plate thickness control of a tandem rolling mill having a plurality of stands in series.

[0002]

2. Description of the Related Art In a hot continuous rolling mill composed of a plurality of rolling mill stands, a combination of a lock-on AGC and an X-ray monitor AGC is generally used as an automatic sheet thickness controller (AGC). . Of these, the lock-on AGC has a function of holding the plate thickness when the rolled material is bitten into the rolling mill, and the actual plate thickness is calculated by using the roll gap (reduction position) and the rolling load. Has been done.

The X-ray monitor ACC measures the plate thickness of the rolled material to be the product by an X-ray plate thickness gauge provided on the exit side of the final stand, and operates the roll gap of the final stand so as to keep it constant. However, as a result of this operation, you can also change the roll gap of the stand in front of the final stand so that the load is not concentrated on the final stand or the load on the final stand is not too light. Has been done.

The lock-on AGC itself did not originally have the function of keeping the absolute value of the plate thickness at the target value.
A so-called absolute value AGC, which calculates a plate thickness at each stand by a computer and operates a roll gap so as to maintain the value at a target value, is also widely used.

However, it is the X-ray monitor AGC that controls the final plate thickness. Therefore,
If the speed setup of each rolling mill and main machine (motor for driving the rolls of the rolling mill) performed before the start of rolling is improper and, as a result, the strip thickness at the leading end deviates greatly from the target value, the strip thickness X-ray monitor AG
C operates the roll gap of the final stand largely. As a result, the load of the final stand increases or becomes too small, which causes a problem that the plate shape is disturbed and the passage stability is impaired.

With respect to such a problem, Japanese Patent Laid-Open No. 5-17
In the 7223 publication, under the condition that the delivery side plate thickness is constant, the running schedule is changed to adjust all or part of the plate thickness, speed ratio, rolling position, and tension of each stand, and each stand is changed. There is disclosed a technique for changing the rolling reduction balance of No. 1, which makes it possible to automate the operation normally performed by manual intervention of an operator and prevent the plate shape from being disturbed and the running stability to be reduced.

In a cold tandem rolling mill, X
Mass flow AGC is used to change the main machine speed ratio of each stand so that the plate thickness measured by the wire plate thickness gauge is maintained at the target value. Even in the hot continuous rolling mill, rolling material with thick thickness is rolled. In some cases, mass flow AGC is used.

[0008]

However, in the technique disclosed in Japanese Patent Laid-Open No. 5-177223, the rolling load fluctuation is not adjusted in the course of changing the running plate thickness, so that the rolling material is especially used in the stand at the latter stage. However, there is a problem in that it is impossible to prevent problems such as adversely affecting the shape of, and inducing bending of the tip. A similar problem occurs when using the mass flow AGC.

Further, when the thickness of the running plate is changed, the rolling-down device is directly driven, so that a normal lock-on AGC or X-ray monitor A is used.
Since it is necessary to temporarily stop the GC, it is difficult to guarantee the plate thickness during the change of the running plate thickness, and at the same time, the AGC is stopped at the start of the changing of the running plate thickness and the AGC after the completion of the changing of running plate thickness. However, there was a problem in that complicated sequences such as the restart of the control system are involved and the load and capacity of the control system such as the sequencer become high.

In order to solve these problems of the prior art, the inventors of the present invention deteriorate the shape of the rolled material and bend the tip of the rolling material even when the initial setting of the rolling mill is not appropriate. A method for changing the load distribution of a tandem rolling mill that can bring the state of the rolling mill into a proper state without inducing has been developed, and a patent application has been filed as Japanese Patent Application No. 2000-145765 (hereinafter referred to as "prior invention").

The contents are characterized in that, in a tandem rolling mill having a plurality of stands, at least one of a speed ratio of each stand and a roll gap of each stand is determined so as to keep a rolling load of each stand at a predetermined ratio. This is a method of changing the load distribution of the tandem rolling mill. That is, when the initial setting (setup) calculation of the rolling mill is inappropriate and the desired plate thickness cannot be obtained, or the load distribution of each stand is disturbed and the shape of the rolled material deteriorates. In addition, by changing at least one of the speed ratio of each stand and the roll gap of each stand to change the plate thickness and the load distribution of each stand to an appropriate one, at this time, the rolling load of each stand is adjusted to a predetermined ratio. Determine the manipulated variable so that Therefore, since the rolling load distribution of each stand is corrected to an appropriate one, it is possible to prevent the shape of the rolled material from being deteriorated and to prevent the strip passing property from being deteriorated.

However, in the prior invention, the load ratio between the stands is taken into consideration, but the balance between the rolling load and the work roll bender pressure in each stand is not taken into consideration. That is, since the rolling load at each stand changes due to the change of the load ratio, the balance between the load and the work roll bender pressure may be lost and the output side plate crown may fluctuate. In particular, in the case of thin rolling or when the fluctuation of the rolling load is large, there is a problem that the fluctuation of the outgoing side plate crown not only adversely affects the plate shape, but also disturbs the running stability of the plate.

The present invention has been made in view of the above circumstances, and is an improvement of the prior invention, in which the final stand outlet plate thickness is the target value and the rolling load balance of each stand is the target value. It is an object of the present invention to provide a rolling load distribution control method for a tandem rolling mill capable of appropriately controlling the plate crown by appropriately controlling the roll bender even when the rolling schedule is changed to .

[0014]

A first means for solving the above problems is to provide a tandem rolling mill consisting of a plurality of stands having work roll benders, while controlling the finishing delivery side plate thickness as desired. By changing the stand-out plate thickness and roll speed ratio, the rolling load of each stand is changed to a predetermined ratio, and at the same time, the work roll bender pressure of each stand is changed so that the stand-out plate crown of each stand becomes a target. A rolling load distribution changing method (claim 1) of a tandem rolling mill characterized by the above.

In this means, the rolling load of each stand is changed by changing the delivery side plate thickness and the roll speed ratio of each stand while controlling the finishing delivery side plate thickness which is achieved by the prior invention. In accordance with the function of changing to a predetermined ratio, the work roll bender pressure of each stand is changed so that the output side plate crown of each stand becomes a target. Therefore, even if the rolling load of each stand is changed to a predetermined ratio by changing the delivery side plate thickness and roll speed ratio of each stand, the delivery side plate shape of each stand is not disturbed.

In the claims and the means for solving the problem, "each stand" means that the rolling load ratio with other stands is set to a predetermined value by changing the delivery side plate thickness and the roll speed ratio. The stand that is the target of the control to be kept at, and does not necessarily mean all the stands.

The second means for solving the above-mentioned problems is as follows.
The first means is characterized in that the work roll bender pressure of each stand is changed so as to correct the plate crown change caused by the load change of each stand under the rolling load ratio change control (claim 2). ).

In this means, the work roll bender pressure of each stand is changed so as to correct the plate crown change caused by the load change of each stand by the rolling load ratio change control. Distortion of the plate crown does not occur.

A third means for solving the above-mentioned problems is as follows.
The first means or the second means, characterized in that the work roll bender pressure is changed at the same timing as the change of the outlet plate thickness and the roll speed ratio of each stand in the rolling load ratio change control. (Claim 3)

In this means, since the work roll bender pressure is changed at the same timing as the changing of the outlet plate thickness and the roll speed ratio of each stand in the rolling load ratio change control, the turbulence of the plate crown is almost completely eliminated. Can be compensated.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Before showing specific embodiments of the present invention, first, the configuration and calculation method of a rolling load distribution control system of a tandem rolling mill according to the present invention will be described. FIG. 1 is a block diagram showing the configuration of a load distribution control system by changing the running plate thickness applied in the present invention. The figure shows four stands of the latter stage of the finishing continuous rolling mill consisting of seven stands. Block 1 in FIG. 1 is a performance collection device that detects the rolling condition when the plate front end leaves the final stand, and block 2 in FIG. 1 is a plate thickness change amount that achieves the target load distribution of each stand. , A running plate thickness change setting calculation device for obtaining the speed ratio change amount.

Block 3 in FIG. 1 is a tracking / online target value changing device (running plate thickness changing device) for performing online tracking and changing the plate thickness and the target value of the speed ratio. Block 4 in FIG. 1 is the work roll bender pressure changing device of the present invention.

The actual result collecting apparatus 1 detects the actual plate thickness and the actual rolling load of each stand at the time when the leading end of the plate leaves the final stand, and grasps the rolling situation. Regarding the actual thickness detection method, a thickness gauge may be placed between each stand,
A mass flow plate thickness calculated by a known method may be used. As for the load record detection method for each stand, since a load meter is usually arranged for each stand, it may be used. Although the present invention does not limit the method of detecting the achievement,
It is assumed that the achievement collecting device can be used to know the plate thicknesses of all the stand-out sides and the rolling loads of all the stands at the moment when the plate tip end leaves the final stand.

The running plate thickness change setting calculation device 2 for changing the load distribution is based on the plate thickness actual results and the load actual results observed by the actual result collecting device 1 and each stand for realizing a predetermined target load distribution. The plate thickness change amount and the speed ratio change amount of are calculated. The tracking / online target value changing device 3 manages the tracking of the plate thickness change point online and outputs a change command of the plate thickness and the speed ratio target value.

In the work roll bender pressure changing device 4,
First, the target plate thickness change amount data is acquired from the setting calculation device 2, and the outgoing side plate crown caused by the load fluctuation due to the load distribution change is estimated. Next, a vendor pressure change amount for correcting the estimated crown fluctuation amount is calculated. During online control,
A vendor pressure change command is output to the work roll vendor control device in accordance with the plate thickness change progress rate obtained by the tracking / online target value change device 3.

In the present invention, the load distribution change in the plate thickness control is not limited to the stand or the method to be executed,
Any method will do. Regarding the change of the work roll bender pressure, the target crown preset in the setup calculation before rolling may be set, or the plate crown before and after the load distribution may not be changed. Hereinafter, the work roll bender pressure changing method of the present invention will be described by taking the load ratio changing method by changing the running plate thickness in the F5, F6 and F7 stands as an example so that the plate crown before and after load distribution does not change. The load distribution control method disclosed in the prior invention will be described.

The following example is an example in which only the rolling load distribution from the F5 stand to the F7 stand (final stand) is changed to the target distribution (rolling load ratio). First, set the rolling loads of F5, F6, and F7 obtained by the setup calculation before the start of rolling to the setup rolling loads.

[0028]

[Equation 1]

Then, when the tip of the plate comes out of F7, F5,
The actual rolling load of F6 and F7

[0030]

[Equation 2]

It is assumed that At this time, the plate thickness deviation amount corrected by the monitor AGC at F7 is set to Δh7, and F5, F6, and F7 are set.
F is such that the rolling load of is the setup rolling load ratio
5, the plate thickness change amounts Δh5 and Δh6 of F6 may be obtained. now,

[0032]

[Equation 3]

When the rolling load of each stand is realized after changing the plate thickness, the following relationship is approximately established.

[0034]

[Equation 4]

Here,

[0036]

[Equation 5]

Is the coefficient of influence of the rolling load at each stand on the change of the outgoing side plate thickness, and the coefficient of influence on the change of the incoming side plate thickness.

In addition,

[0039]

[Equation 6]

Set the ratio of [Calculation result]

[0041]

[Equation 7]

Since it is desired to make it the same as the ratio of,

[0043]

[Equation 8]

Can be described as follows.

[0045]

[Equation 9]

When these are combined

[0047]

[Equation 10]

It becomes The variables in this equation are Δh5, Δh6 and

[0049]

[Equation 11]

Since there are three, calculation becomes possible. Therefore,
Δh5 and Δh6 can be calculated by solving the following linear equation

[0051]

[Equation 12]

By using these Δh5 and Δh6, the target rolling load distribution (ratio) can be achieved. Note that this relationship holds even if the number of stands is expanded to the most upstream stand (F1), so any stand may be the starting point.

An example of the work roll vendor control method, which is a feature of the present invention, will be described below.

The outgoing plate thickness of each stand is set to Δh ₅ , Δh ₆ ,
The load of each stand after changing only Δh ₇ is as follows.

[0055]

[Equation 13]

The amount of change in load is as follows.

[0057]

[Equation 14]

The change of the outgoing side plate crown caused by this load variation can be calculated by the following formula.

[0059]

[Equation 15]

Here,

[0061]

[Equation 16]

(I = 5 to 7) is the coefficient of influence of the fluctuation of the outgoing side plate crown due to load fluctuation, and KC _i (i = 5 to 6) is the coefficient of influence of the plate crown of one upstream stand on the stand plate crown. is there.

Work roll vendor pressure before load distribution

[0064]

[Equation 17]

Assuming that is changed only by ΔP _B5 , ΔP _B6 , and ΔP _B7 , the plate crown fluctuation amount after load distribution is as follows.

[0066]

[Equation 18]

Here,

[0068]

[Formula 19]

Is a variation coefficient of the output side plate crown variation due to work roll bender pressure variation.

In order to prevent the plate crown on the delivery side of each stand from changing, the target of the change amount of the work roll bender pressure of each stand can be calculated by the following formula.

[0071]

[Equation 20]

In the method of changing the work roll bender pressure, it is necessary to change the work roll bender pressure in accordance with the change of the load (that is, the change of the plate thickness) in order to maintain the plate crown during the change of the load distribution. In the present invention, the work roll bender pressure is changed by using the same method as changing the delivery side plate thickness and roll speed ratio of each stand in the load ratio changing control, for example, changing the running plate thickness.

The running plate thickness change execution device (block 3 in FIG. 1) manages the tracking of the plate thickness change points online, and when the plate thickness change section extends over a plurality of stands, the plate thickness change for each stand is performed. A parameter (progress rate) ratio _i for managing the progress of is introduced, and it is obtained by what percentage of the running variation length L _FGC determined by the F7 outgoing rolling length. That is, ratio _i = {L ₇ (t) -L _i (0)} / L _FGC (i = 5 to 7) L ₇ (t) is the exit rolling length of the F7 stand at time t, and L _i ( 0) is the F7 stand exit side existing rolled length at the start time of changing the strip running thickness of each stand.

The work roll bender pressure change command is calculated by the following equation. ΔP _Brefi = ΔP _Bi · ratio _i

[0075]

[Examples] The method of the present invention is applied below to finish plate thickness 1.
3 mm, finishing plate width 1237 mm, F5, F6, F7 An example is shown in which the load of the stand is changed to the target load distribution and the bender pressure of the work roll is changed at the same time. The rolling conditions are given as follows. Target load ratio: [P5: P6: P7] = [1.35: 1.44: 1.00] Set vendor pressure (TON): P _B5 = 26
5, P _B6 = 279, P _B7 = 217 Crown / load influence coefficient:

[0076]

[Equation 21]

Crown / Vendor Influence Coefficient:

[0078]

[Equation 22]

FIG. 2 shows the results obtained by changing the load by changing the plate thickness of the F5, F6, and F7 stands by the conventional method when the plate thickness at the plate tip end deviated from the target during rolling. In the conventional method,
By changing the running plate thickness, the load of each stand was changed, and the actual load ratio in this case was (1.38: 1.48: 1.00), which was able to maintain the load balance as desired. Since the rolling load record of each stand has changed,
The output plate crown fluctuates by several tens of μm.

The result of applying the method of the present invention is shown in FIG. In the present invention, the load load is changed by changing the plate thickness, and at the same time, the bender pressure of the work roll is also changed (Fig. 3).
Bottom right). As a result, the output side plate thickness control and the load balance maintenance control can be performed, and at the same time, the work roll bender pressure is changed according to the change in the load. Stable rolling mill load distribution control with good crown accuracy was achieved. The horizontal axes of FIGS. 2 and 3 are seconds.

[0081]

As described above, according to the present invention, even if the load distribution of each stand at the initial stage is different from the target, it is possible to change the load distribution to an appropriate one. The work roll bender pressure is changed at the same time as the distribution control is performed, so that the fluctuation of the outgoing side plate crown of each stand can be suppressed, and it becomes possible to manufacture a steel plate having excellent plate thickness and plate crown precision. As a result, in addition to improving the yield, improving the surface shape and properties, the plate running stability during rolling is guaranteed, and it is effective in reducing the workload of operators.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a load distribution and vendor pressure change control system by changing a running plate thickness, which is applied in an example of an embodiment of the present invention.

FIG. 2 is a diagram showing a load distribution control result of a conventional method in which only the running plate thickness is changed.

FIG. 3 is a diagram showing a result of load distribution control in which the method of the present invention is implemented.

[Explanation of symbols]

1… Achievement collection device 2 ... Running thickness change setting calculator 3 Tracking / online target value changing device 4 ... Work roll bender pressure change device

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shomasa Kido 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Steel Pipe Co., Ltd. (56) Reference JP-A-60-152316 (JP, A) JP-A Sho 61-88910 (JP, A) JP 2001-321813 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 37/00-37/78

Claims (3)

(57) [Claims] 1. A tandem rolling mill comprising a plurality of stands having a work roll bender, while controlling the finishing delivery side plate thickness as desired while changing the delivery side plate thickness and roll speed ratio of each stand. A rolling load distribution changing method for a tandem rolling mill, which comprises changing the rolling load to a predetermined ratio and changing the work roll bender pressure of each stand so that the output side plate crown of each stand becomes a target. 2. The load distribution changing method for a tandem rolling mill according to claim 1, wherein the work roll bender of each stand is adapted to correct a plate crown change caused by a load change of each stand due to rolling load ratio change control. A method for changing the load distribution of a tandem rolling mill, which is characterized by changing the pressure. 3. The load distribution changing method for a tandem rolling mill according to claim 1 or 2, wherein the work is carried out at the same timing as the change of the outlet plate thickness and the roll speed ratio of each stand in the rolling load ratio change control. A load distribution changing method for a tandem rolling mill, which is characterized by changing a roll bender pressure.