JPH0890028A - Control method for tandem mill - Google Patents

Abstract

PURPOSE: To assure flatness of a product by controlling thickness and tension by means of a roll gap and successive velocity in the last stand and simultaneously controlling a rolling load with the thickness changed for the stand immediately before the last stand. CONSTITUTION: A command quantity S1 for correcting reduction position and the correction quantity V1 of roll speed are calculated from the output of a tension detector TC4 on the entrance side of the last stand 5. A command quantity S2 for correcting reduction position and the correction quantity V2 of roll speed are calculated from a thickness detector X5 on the exit side of the last stand 5. The reduction position is corrected only for the sum of the command values S1, S2 by the reduction position controller HC5 of the last stand 5. The roll speed is corrected only for the sum of the correction quantity V1, V2 by the roll speed controller DM of all stands except the last stand 5. The thickness on the exit side of a stand 4 is corrected by a thickness controller HC4 of the stand 4 on the upstream side, by means of the command value (h) for correcting thickness on the entrance side that is calculated from the output of a tension detector TM4 on the entrance side of the last stand 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem mill for rolling metal strips, which relates to a plate thickness control method capable of improving flatness while controlling product plate thickness to a constant level.

[0002]

2. Description of the Related Art In a tandem mill, plate thickness accuracy is an important control item for product quality, and various methods have been proposed in order to improve plate thickness control accuracy. Especially, the thickness control of the final stand is directly important because it is directly connected to the product.

As one of the methods for controlling the plate thickness of the final stand, there is a method disclosed in Japanese Patent Laid-Open No. 5-123727. FIG. 2 illustrates the configuration of the plate thickness control of the tandem mill according to this conventional method. In the drawings described below, ST represents the material to be rolled, #i represents the i-th stand of the tandem mill (for example, # 4 is the fourth stand), HSi is the rolling position control device of the i-th stand,
DMi is the mill drive motor of the i-th stand, Xi is the plate thickness detection device installed on the exit side of the i-th stand, and TMi is the i-th
1 to i-th stand tension detecting device, LCi represents a rolling load detecting device of the i-th stand. The feature of this method is that, as shown in FIG. 2, the rolling position of the final stand and all stands except the final stand, based on the plate thickness record of the upstream side of the final stand. The roll speed of the final stand is operated in a feed-forward manner, and at this time, the balance between the rolling position operation and the roll speed operation is also taken into consideration so as not to change the entrance side plate tension of the final stand.

Another conventional technique for controlling the plate thickness of the final stand is disclosed in Japanese Patent Laid-Open No. 2-92411. FIG. 3 illustrates the configuration of the plate thickness control of the tandem mill according to this conventional method. As shown in FIG. 3, the rolling position of the last stand is used to keep the rolling load constant, and the speed ratio between the last stand and the last stand one upstream is used to keep the tension between these stands constant. The characteristic feature is that the speed ratio between one stand upstream of the final stand and two upstream stands is used to keep the exit side plate thickness of the final stand constant.

[0005]

By the way, Japanese Unexamined Patent Publication No.
If the conventional method as proposed in the Japanese Patent No. 123727 is adopted, the following problem of load fluctuation occurs.
It is generally known that the fluctuation of rolling load greatly affects the flatness of the plate, but the flatness on the exit side of the final stand is the product flatness as it is, so the stability of the rolling load is better than that of other stands. , Especially important. That is, in the final stand, a control method that takes rolling load into consideration is required. However, in the above-mentioned conventional technique, the plate thickness and the tension are considered to be constant, but the stability of the rolling load is not considered at all. Therefore, it is difficult to manufacture a high-quality steel plate because the product flatness varies greatly.

Further, in the prior art as disclosed in Japanese Patent Application Laid-Open No. 2-92411, as described in the specification, the operating end of the plate thickness control is the final stand 1.
Since it is a stand on the upstream side, there is a large time delay until the plate thickness detection on the exit side of the final stand, and it is difficult to control the factors that cause plate thickness fluctuations that occur on the final stand. It is difficult to meet the requirements for thickness accuracy.

In view of the above-mentioned problems of the prior art, the present invention ensures a good product flatness by fully considering the rolling load stability of the final stand, while ensuring plate thickness controllability and tension controllability. It is an object to provide an excellent tandem mill final stand control method.

[0008]

Prior to the present invention, the inventor has conducted various studies on the control method of the final stand of a tandem mill in order to clarify the difference in characteristics between the final stand and intermediate stands other than the final stand. I did it.

First, an investigation and study were made to consider an automatic plate thickness control device (hereinafter referred to as AGC) for an intermediate stand.
The rolling characteristics of the intermediate stand will be described with reference to FIGS. 4 and 5.

FIG. 4A is a view showing the tandem mill with the i-1st stand and the i-th stand taken out. The plate thickness hi detected by the plate thickness detecting device Xi and the tension Ti-1 detected by the tension detecting device TMi-1 are the main control amounts. This is operated at the i-th stand roll gap Si and the i-1st stand with a successive speed Vi-1 (the speeds of all the stands upstream of the i-th stand are operated at the same ratio, or the speed of all the stands including the i-th stand is reduced to the downstream. Operate the speeds of all the stands at the same ratio (the same applies hereinafter), that is, the AGC of the intermediate stand is a 2-input 2-output system as shown in FIG. 4 (b). This will be described on the plate thickness-tension plane shown in FIG. In FIG. 5, the vertical axis represents the amount of change in the plate thickness hi and the horizontal axis represents the tension Ti-
This is a vector representation of how the plate thickness and tension change when the roll gap and the successive speed are manipulated by taking the amount of change of 1. From FIG. 5, the plate thickness-tension plane can be covered by the roll gap operation vector S and the successive velocity operation vector V. Therefore, if the roll gap and the successive velocity are sufficiently fast in response, the plate thickness deviation and the tension deviation are Both can be controlled independently with an appropriate combination of roll gap and successful speed, and the rolling point can be brought to the origin. Next, rolling characteristics investigated and studied for considering the final stand AGC will be described with reference to FIGS. 6 and 7. Figure 6 (a) shows the final 2 of the tandem mill.
In the figure with two stands, N is the final stand. It goes without saying that the plate thickness and the tension are also controlled variables in the final stand, but as described above, the rolling load is an important controlled variable. Plate thickness h detected by plate thickness detector XN
N, the tension TN-1 detected by the tension detector TMN-1, and the rolling load PN detected by the load detector LCN are the main control variables. The actuators that operate this are physically impossible to control with the Nth stand roll gap SN and the N-1st stand successive velocity VN-1. It is conceivable to introduce hN-1 as the third actuator, which can be controlled as the target of the stand outlet side plate thickness. That is, the AGC of the final stand has a 3-input 3-output system including one actuator having a slow response as shown in FIG. 6B. In the case of the final stand, the actuator characteristic evaluation corresponding to FIG. 5 needs to be performed in the plate thickness-tension-load space, and this is actually shown in FIGS. 7A to 7C. (A) ~
(C) shows the characteristics of the roll gap, the successive speed, and the entrance side plate thickness, respectively. Further, FIG. 8A shows a plane (plane A) which can be covered by the roll gap operation vector and the successful velocity vector having a fast response on the plate thickness-tension-load space.

In this plane, a control with a fast response (roll gap + successive speed) is performed to control the tension axis (plate thickness deviation and load deviation to 0) as a target (FIG. 8).
In (b), the points p1, p2, ... Are the targets, and the control with slow response (inlet plate thickness) allows this plane to pass through the origin so that the tension deviation is 0 (p1, p2, ... Are brought to the origin. )
This combination is the basis of the final stand AGC.

The present invention has been made based on the above-mentioned investigation and examination, and is a control method of the final stand for controlling the product plate thickness of the tandem mill at a constant level. To do.

(1) Final stand rolling load detection device, final stand entrance side tension detection device, final stand exit side plate thickness detection device, and plate thickness control device for one upstream side of the final stand, and rolling position control for each stand. In the case of a tandem mill equipped with a device, the load correction output amount is calculated from the output of the final stand rolling load detection device.

The load correction output amount is multiplied by the control gains Gs1 and Gv1 preset according to the rolling conditions to calculate the reduction position correction command amount S1 and the roll speed correction amount V1.

A plate thickness correction output amount is calculated from the output of the final stand outlet side plate thickness detecting device.

The sheet thickness correction output amount is multiplied by each control gain GS2, GV2 preset according to the rolling conditions to calculate the rolling position correction command amount S2 and the roll speed correction amount V2.

The rolling position is corrected by the rolling position control device of the final stand based on the sum of the rolling position correction command amount S1 and the rolling position correction command amount S2.

Based on the sum of the roll speed correction amount V1 and the roll speed correction amount V2, the roll speed is corrected by the roll speed control device of all stands except the final stand or the final stand.

A tension correction output amount is calculated from the output of the final stand entrance side tension detecting device.

An input side plate thickness correction command amount h is calculated by multiplying the tension correction output amount by a control gain G3 preset according to the rolling conditions.

Based on the input side plate thickness correction command amount h, the plate thickness control device for one upstream stand of the final stand corrects the output plate thickness of one upstream stand of the final stand.

(2) One of the final stands In the case of a tandem mill which does not have a plate thickness control device on the upstream stand,
The procedures up to are the same as in (1).

The tension correction output amount is multiplied by each control gain GS3, GV3 preset according to the rolling conditions to calculate the rolling position correction command amount S3 and the roll speed correction amount V3.

On the basis of the rolling position correction command amount S3, the rolling position is corrected by the rolling position control device of the upstream stand, which is one of the final stands.

Based on the roll speed correction command amount V3, the roll speed is corrected by the roll speed control device of all the stands except the last two stands or the last two stands.

[0026]

FIG. 1 shows the construction of a plate thickness control device for a tandem mill according to the method of the present invention, showing three stands in the latter stage of a five-stand mill.

The method of the present invention will be described in detail with reference to FIG. 1 by taking as an example the situation when the mill enters deceleration from the steady rolling state.

When the mill deceleration, that is, the rolling speed decreases, the rolling oil drawn between the roll and the material to be rolled decreases, so that the lubricity decreases and the friction coefficient increases. This appears in the form of an increase in rolling load and an increase in strip thickness. At this time, the plate thickness detecting device X5 detects a positive plate thickness deviation and
5 stand plate thickness controller HC5 corrects this,
Mainly, it outputs a command to V2 in the direction of successful speed deceleration. Further, the load detection device LC5 detects a positive load deviation, and the # 5 stand load control device PC corrects it. Therefore, a command for the roll gap opening direction is sent to S1 and V1.
The command for the slow speed deceleration direction is output to 1. With these, # 5 stand, while preventing the increase of rolling load,
5 It is possible to correct the stand-out side plate thickness to a target value. However, at this time, the tension between the # 4 and # 5 stands greatly increases. This is detected by the tension detecting device TM4, and the minus control of the entrance side plate thickness is output by the tension control device TC4. In response to this, the # 4 stand thickness control device HC4 closes the # 4 stand roll gap,
The 3-stand successive speed is corrected in the decelerating direction, and after the transfer time between the stands, the thickness of the # 5 stand entrance side plate is corrected thinly. At this time, the plate thickness detector X5 detects a slight negative plate thickness deviation, and the # 5 stand plate thickness controller HC
In order to correct this, 5 outputs a command for increasing the speed to V2 gently. This will reduce the tension between the # 4 and # 5 stands to the original level. Since the plate thickness controller HC5 and load controller PC are continuously controlled at a much higher speed (for example, the response time of HC5 and PC is about 0.5 seconds, TC4 is 5 seconds or more), the plate thickness and tension Does not fluctuate during this time.

Therefore, according to the method of the present invention, it is possible to control the final stand of the tandem mill while ensuring the flatness and excellent in the plate thickness controllability and the tension controllability.

[0030]

[Example] In a 5-stand tandem mill, a plate width of 1
A case where a base material having a thickness of 200 mm and a plate thickness of 2.3 mm is rolled to 0.5 mm will be described as an example.

FIG. 9 is a block diagram showing an embodiment of the plate thickness control method according to the present invention.

First, the load correction output c1 is obtained by performing a proportional integration operation on the # 5 stand rolling load deviation e1.
The plate thickness correction output c2 was obtained by performing a proportional integral calculation on the # 5 stand outlet side plate thickness deviation e2. By multiplying c1 by the control gain GS1 and multiplying c2 by the control gain GS2, and adding them, the # 5 stand pressing position correction command is obtained.
Also, c1 is multiplied by the control gain GV1, and c2 is multiplied by the control gain GV1.
By multiplying by V2 and adding, the # 1 to # 4 stand roll speed correction commands were obtained. If necessary, the roll speed command for another control device (for example, a rolling position command output from the load balance control device) can be added. Further, the tension correction output c3 is obtained by performing the proportional-plus-integral calculation on the tension deviation e3 between # 4 and # 5 stands.
This c3 was multiplied by the control gain G3 to obtain the # 4 stand exit side plate thickness correction command. This # 4 stand output side plate thickness correction command is added to the # 4 stand output side plate thickness deviation, and a proportional-plus-integral operation is performed on e4 to obtain the # 4 stand plate thickness correction output c4.
Then, this c4 was multiplied by the control gain GS4 to obtain the # 4 stand pressure reduction position correction command. Further, c4 is multiplied by the control gain GV4 to obtain the # 1 to # 3 stand roll speed correction commands.

FIG. 10 is a block diagram showing another embodiment of the plate thickness control method according to the present invention, which is an embodiment for claim 2 when the # 4 stand delivery side plate thickness control device is not provided.

The system of the # 5 stand rolling load deviation e1 and the # 5 stand exit side plate thickness deviation e2 is the same as in FIG. # 4
With respect to the # 5 stand tension deviation e3, a tension correction output c3 is obtained by performing a proportional integration calculation, and this c3 is multiplied by the control gain GS3 to obtain a # 4 stand pressure reduction position correction command. In addition, multiplying c3 by the control gain GV3 # 1
A roll speed correction command for the # 3 stand was obtained.

In any case, the control gain GS1,
For GV2, etc., an optimum value is calculated and set for each coil by a control gain calculation device.

Next, the method of the present invention and the above-mentioned FIG. 2 and FIG.
The results of comparison between the conventional method (2 method) typified by 1) and test rolling with an actual rolling mill are shown. Regarding the average thickness fluctuation range and load fluctuation range during acceleration / deceleration, those with large fluctuations are 1.
It is understood that the method according to the present invention is remarkably excellent.

Inventive Method Conventional Method 1 (FIG. 2) Conventional Method 2 (FIG. 3) Plate Thickness Fluctuation Range 0.32 0.37 1.00 Load Fluctuation Range 0.08 1.00 0.13

[0038]

As a result, as will be described later, it is possible to control the final stand of the tandem mill, which is excellent in plate thickness controllability and tension controllability, while guaranteeing product flatness.

[Brief description of drawings]

FIG. 1 shows a configuration of a plate thickness control system of a tandem mill for carrying out the method of the present invention, showing three stands after the five-stand mill.

FIG. 2 illustrates a configuration of a plate thickness control example (method 1) of a tandem mill final stand according to a conventional method.

FIG. 3 illustrates a configuration of a plate thickness control example (method 2) of a tandem mill final stand according to a conventional method.

FIG. 4 is an explanatory view showing an i-1th stand and an i-th stand of the tandem mill.

[FIG. 5] The vertical axis represents the amount of change in the plate thickness hi, and the horizontal axis represents the tension Ti-1.
FIG. 5 is an explanatory diagram expressing in vector how the plate thickness and the tension change when the roll gap and the successive speed are manipulated by taking the change amount of

FIG. 6 is an explanatory view showing the last two stands of the tandem mill, where N is the last stand.

FIG. 7 is an explanatory diagram corresponding to FIG. 5 for evaluating actuator characteristics of a roll gap, a successive speed, and an entrance side plate thickness in a plate thickness-tension-load space.

FIG. 8 is an explanatory diagram of a plane (plane A) that can be covered with a roll gap operation vector and a successful velocity vector.

FIG. 9 is a block diagram of an embodiment of a plate thickness control method according to the present invention.

FIG. 10 is a block diagram of an embodiment according to claim 2 of the plate thickness control method according to the present invention when there is no final stand exit side plate thickness control device.

[Explanation of symbols]

 ST: material to be rolled HSi: rolling position control device for the i-th stand DMi: mill drive motor for the i-th stand Xi: plate thickness detection device installed on the delivery side of the i-th stand TMi: between the i-th and i-th stands Tension detection device LCi: Rolling load detection device for the i-th stand HCi: Plate thickness control device for the i-th stand TCi: Tension control device for the i-th stand PC: Load control devices S1, S2: Reduction position correction command amounts V1, V2, V3: Roll speed correction amount h: Input side plate thickness correction command amount

Claims (2)

[Claims] 1. A final stand rolling load detection device, a final stand entrance side tension detection device, a final stand exit side plate thickness detection device, a plate thickness control device for one upstream stand of the final stand, and a rolling position installed in each stand. In a tandem mill control method equipped with a control device, a reduction position correction command amount S1 and a roll speed correction amount V1 are calculated from the output of the final stand rolling load detection device, and the reduction position correction is performed from the output of the final stand delivery side plate thickness detection device. The command amount S2 and the roll speed correction amount V2 are calculated, and the rolling position correction command amount S1 is calculated.
And the rolling position correction command amount S2, the rolling position is corrected by the rolling position control device of the final stand.
Further, based on the sum of the roll speed correction amount V1 and the roll speed correction amount V2, the roll speed is corrected by the roll speed control device of all stands except the final stand or the final stand, and the final stand entrance side tension detection is performed. Calculate the input side plate thickness correction command amount h from the output of the device,
A method for controlling a tandem mill, which corrects the outgoing plate thickness of one upstream stand of the final stands by a plate thickness control device of one upstream stand of the final stand based on the input plate thickness correction command amount h. . 2. A tandem mill control method comprising a final stand rolling load detection device, a final stand entrance side tension detection device, a final stand exit side plate thickness detection device, and a rolling position control device installed in each stand. The rolling position correction command amount S1 and the roll speed correction amount V1 are calculated from the output of the rolling load detection device, and the rolling position correction command amount S2 and the roll speed correction amount V2 are calculated from the output of the final stand exit side plate thickness detection device. Reduction position correction command amount S1
And the rolling position correction command amount S2, the rolling position is corrected by the rolling position control device of the final stand.
Further, based on the sum of the roll speed correction amount V1 and the roll speed correction amount V2, the roll speed is corrected by the roll speed control device of all stands except the final stand or the final stand, and the final stand entrance side tension detection is performed. A rolling position correction command amount S3 and a roll speed correction amount V3 are calculated from the output of the apparatus, and the rolling position is corrected by the rolling position control device of one upstream side stand of the final stand based on the rolling position correction command amount S3. A method for controlling a tandem mill, characterized in that the roll speed is corrected by a roll speed controller of all the stands except the last two stands or the last two stands based on the roll speed correction command amount V3.