JP3348538B2 - Control method of tandem 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 controlling a thickness of a tandem mill for rolling a metal strip, which can control the thickness of a product and improve the flatness thereof.

[0002]

2. Description of the Related Art In a tandem mill, the thickness accuracy is an important management item of product quality, and various methods have been conventionally proposed to improve the accuracy of thickness control. In particular, controlling the thickness of the final stand is directly important to the product as it is, and is therefore of great importance.

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

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

[0005]

SUMMARY OF THE INVENTION Incidentally, Japanese Patent Application Laid-Open No.
When the conventional method proposed in JP-A-123727 is adopted, the following problem of load fluctuation occurs.
It is generally known that fluctuations in the rolling load greatly affect the flatness of the plate, but the flatness on the exit side of the final stand becomes the product flatness as it is, so the stability of the rolling load is lower than that of other stands. Of particular importance. That is, in the final stand, a control method that takes into account the rolling load is required. However, in the above-mentioned prior art, the constant thickness and the constant tension are considered, but the stability of the rolling load is not considered at all. For this reason, the flatness of the product fluctuates greatly, making it difficult to produce a high-quality steel sheet.

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 one of the final stands.
Since the stand is located on the upstream side, there is a large delay in detecting the thickness of the sheet on the exit side of the final stand. It is difficult to meet the requirements for thickness accuracy.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention takes into consideration the rolling load stability of the final stand to ensure high quality product flatness while improving the thickness controllability and tension controllability. An object of the present invention is to provide an excellent control method for a tandem mill final stand.

[0008]

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

At first, an investigation was conducted to consider an automatic thickness control device for an intermediate stand (hereinafter, referred to as AGC).
The rolling characteristics of the intermediate stand will be described with reference to FIGS.

FIG. 4 (a) is a view showing the i-1st stand and the i-th stand of the tandem mill. 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 operation is performed by using the i-th stand roll gap Si and the (i-1) -th stand progressive velocity Vi-1 (operating the speeds of all the stands on the upstream side of the i-th stand at the same ratio, or including the i-th stand, and Operate the speeds of all the stands on the same side in the same ratio. The same applies to the following.) That is, the AGC of the intermediate stand has a two-input two-output system as shown in FIG. This will be described on a plate thickness-tensile plane shown in FIG. FIG. 5 shows the variation of the plate thickness hi on the vertical axis and the tension Ti− on the horizontal axis.
This is a vector representation of how the thickness and tension change when the roll gap and the succesive speed are manipulated by taking the amount of change of 1. From FIG. 5, the thickness-tension plane can be covered by the roll gap operation vector S and the succesive speed operation vector V. Therefore, if both the responsiveness of the roll gap and the succesive speed are sufficiently fast, the thickness deviation and the tension deviation can be reduced. Any of them can be controlled independently by an appropriate combination of the roll gap and the progressive speed, and the rolling point can be brought to the origin. Next, rolling characteristics investigated and studied in order to consider the final stand AGC will be described with reference to FIGS. Fig. 6 (a) shows the final 2 of the tandem mill.
In this figure, N stands for the last stand. In the final stand, the plate thickness and the tension are, of course, control amounts, but the rolling load is an important control amount as described above. The thickness h detected by the 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. Since it is physically impossible to control the two actuators, the N-th stand roll gap SN and the (N-1) -th stand continuous velocity VN-1, the input side plate thickness (one upstream of the last stand). It is conceivable to introduce hN-1 as a third actuator. That is, the AGC of the last stand has a three-input three-output system including one actuator with a slow response as shown in FIG. 6B. In the case of the final stand, it is necessary to perform the actuator characteristic evaluation corresponding to FIG. 5 in the thickness-tension-load space, and FIGS. 7A to 7C actually illustrate this. (A) ~
(C) shows the characteristics of the roll gap, the succesive speed, and the thickness of the entry side plate, respectively. FIG. 8A shows a plane (plane A) that can be covered by a roll gap operation vector and a responsive velocity vector with a fast response on the plate thickness-tension-load space.

In this plane, control is performed with the target of the load axis (the thickness deviation and the tension deviation are set to 0) by the control having a fast response (roll gap + successive speed) (FIG. 8).
In (b), the points p1, p2,... Are the targets), and the control is performed with a slow response (the thickness of the inlet side) so that this plane passes through the origin and the load deviation is set to 0 (p1, p2,. )
Is the basis of the final stand AGC.

The present invention has been made based on the above-mentioned investigation and study, and is a control method of a final stand for controlling a product thickness of a tandem mill to be constant. I do.

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

A reduction position correction command amount S1 and a roll speed correction amount V1 are calculated by multiplying the tension correction output amount by control gains Gs1 and Gv1 preset in accordance with rolling conditions.

A thickness correction output amount is calculated from the output of the final stand exit side thickness detection device.

The rolling position correction command amount S2 and the roll speed correction amount V2 are calculated by multiplying the plate thickness correction output amount by the control gains GS2 and GV2 preset according to the rolling conditions.

The rolling position of the final stand is corrected by the rolling position control device of the last 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 last stand or the last stand.

A load correction output amount is calculated from the output of the final stand rolling load detecting device.

An input side thickness correction command amount h is calculated by multiplying the load correction output amount by a control gain G3 set in advance according to the rolling conditions.

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

(2) In the case of a tandem mill in which one of the final stands has no thickness control device on the upstream stand,
Is the same procedure as in (1).

The rolling correction amount S3 and the roll speed correction amount V3 are calculated by multiplying the load correction output amount by the control gains GS3 and GV3 preset according to the rolling conditions.

The roll-down position of the upstream stand of the last stand is corrected by the roll-down position control device based on the roll-down position correction command amount S3.

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

[0026]

FIG. 1 shows a configuration of a plate thickness control device of a tandem mill according to the method of the present invention, showing three stands after a five-stand mill.

With reference to FIG. 1, the method of the present invention will be described in detail by taking as an example a situation when the mill starts to decelerate from the steady rolling state.

When the speed of the mill is reduced, that is, the rolling speed is reduced, the amount of rolling oil drawn between the roll and the material to be rolled is reduced, so that the lubricity is reduced and the coefficient of friction is increased. This appears in the form of an increase in rolling load and an increase in sheet thickness. At this time, the thickness detector X5 detects a positive thickness deviation, and
The 5-stand thickness control unit HC5 corrects this,
A command for the direction of closing the roll gap is output as S2, and a command for the decelerating speed is output as V2. This allows
The thickness of the exit side of the # 5 stand can be thinly corrected to the target value without changing the tension between the # 4 and # 5 stands. However, at this time, the rolling load of the # 5 stand is greatly increased. This is detected by the rolling load detector LC5,
The load control device PC outputs a minus correction of the entry side plate thickness. In response to this, the # 4 stand thickness controller HC4 corrects the # 4 stand roll gap in the closing direction and the # 3 stand successive speed in the deceleration direction. Thin correction. At this time, the thickness detector X5 detects a slight negative thickness deviation, and the # 5 stand thickness controller HC5 corrects the deviation.
As V2, a command in the direction of increasing the progressive speed is gently output. As a result, the load of the # 5 stand is reduced to the original level. Since the thickness control device HC5 and the tension control device TC4 are continuously controlled at a much higher speed (for example, the response time of HC5 and TC4 is about 0.5 seconds,
PC5 is more than 5 seconds), and the thickness and tension do not fluctuate during this period.

Thus, according to the method of the present invention, it is possible to control the final stand of the tandem mill which has excellent flatness control and excellent thickness controllability and tension controllability.

[0030]

[Embodiment] In a tandem mill with five stands, a sheet width of 1
A case where a base material having a thickness of 200 mm and a thickness of 2.3 mm is rolled to 0.5 mm will be described as an example.

FIG. 9 is a block diagram showing one embodiment of the method for controlling the thickness of a sheet according to the present invention.

First, a tension deviation e1 between # 4 and # 5 stands
Is subjected to a proportional integral operation to obtain a tension corrected output c1, and a proportional thickness integral output c2 is obtained by performing a proportional integral operation to the # 5 stand exit side sheet thickness deviation e2. The c1 is multiplied by the control gain GS1 and the c2 is multiplied by the control gain GS2 and added to obtain a # 5 stand pressure reduction position correction command. Further, by multiplying c1 by the control gain GV1 and multiplying c2 by the control gain GV2 and adding them, # 1 to # 4 stand roll speed correction commands were obtained. If necessary, a roll speed command of another control device (for example, a rolling position command output from a load balance control device or the like) can be further added. Further, a load correction output c3 is obtained by performing a proportional integral operation on the # 5 stand rolling load deviation e3.
The c3 was multiplied by the control gain G3 to obtain a # 4 stand exit side thickness correction command. The # 4 stand thickness correction output c4 is obtained by performing a proportional integral operation on e4 obtained by adding the # 4 stand exit thickness correction command to the # 4 stand exit thickness deviation.
The c4 is multiplied by the control gain GS4 to obtain a # 4 stand pressure lowering position correction command. Further, c4 is multiplied by the control gain GV4 to obtain # 1 to # 3 stand roll speed correction commands.

FIG. 10 is a block diagram showing another embodiment of the sheet thickness control method according to the present invention, which is an embodiment corresponding to claim 2 in the case where the apparatus for controlling the sheet thickness on the exit side of the # 4 stand is not provided.

# 4- # 5 Tension deviation e1 between stands e1, # 5
The system of the stand exit side thickness deviation e2 is the same as in FIG.
For the # 5 stand rolling load deviation e3, a load correction output c3 was obtained by performing a proportional integral operation, and this c3 was multiplied by a control gain GS3 to obtain a # 4 stand rolling position correction command. Also, c3 is multiplied by the control gain GV3 to # 1 to # 3.
A command to correct the roll speed of the # 3 stand was obtained.

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

Next, the method of the present invention and the aforementioned FIGS.
The following shows the results of test rolling with a conventional method (two methods) represented by Table 1 using an actual rolling mill and comparison. Regarding the average thickness variation width and load variation width during acceleration and deceleration,
The results of the relative comparison were set to 00, and it is found that the method according to the present invention is significantly superior.

Method of the Present Invention Conventional Method 1 (FIG. 2) Conventional Method 2 (FIG. 3) Thickness fluctuation width 0.34 0.37 1.00 Load fluctuation width 0.12 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 the thickness controllability and the tension controllability while guaranteeing the product flatness.

[Brief description of the drawings]

FIG. 1 shows the configuration of a tandem mill thickness control system that implements the method of the present invention, and shows three stands after a five-stand mill.

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

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

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

FIG. 5 is a graph showing the variation of the plate thickness hi on the vertical axis and the tension Ti-1 on the horizontal axis.
FIG. 4 is an explanatory diagram in which how the plate thickness and the tension change when the roll gap and the succesive speed are manipulated by taking the change amount of the change.

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 succesive speed, and an entry-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 by a roll gap operation vector and a successive velocity vector.

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

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

[Description of Signs] ST: Rolled material HSi: Rolling position control device for i-th stand DMi: Mill drive motor for i-th stand Xi: Plate thickness detecting device installed on the exit side of i-th stand TMi: i-1 To i-th stand tension detecting device LCi: rolling load detecting device for the i-th stand HCi: plate thickness controlling device for the i-th stand TCi: tension controlling device for the i-th stand PC: load controlling device S1, S2: rolling position correction command Amount V1, V2, V3: Roll speed correction amount h: Input side thickness correction command amount

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B21B 37/00-37/78

Claims (2)

(57) [Claims] 1. A final stand rolling load detection device, a final stand entry side tension detection device, a final stand exit side plate thickness detection device, a plate thickness control device of one of the final stands, an upstream stand, and a pressing position installed on each stand. In the control method of the tandem mill provided with the control device, the reduction position correction command amount S1 and the roll speed correction amount V1 are calculated from the output of the final stand entrance side tension detecting device, and the reduction position is calculated from the output of the final stand exit side plate thickness detection device. A correction command amount S2 and a roll speed correction amount V2 are calculated, and the roll-down position correction command amount S1 is calculated.
And the lowering position control device of the final stand corrects the lowering position based on the sum of the lowering position correction command amount S2 and
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 last stand or the final stand, and further, the final stand rolling load detecting device Calculate the input thickness correction command amount h from the output of
A control method for a tandem mill, wherein the thickness control device for one upstream stand of the final stand corrects the exit thickness of one upstream stand of the final stand based on the input thickness correction command amount h. . 2. A method for controlling a tandem mill comprising a final stand rolling load detection device, a final stand entry side tension detection device, a final stand exit side plate thickness detection device, and a rolling position control device installed in each stand. Calculate the reduction position correction command amount S1 and the roll speed correction amount V1 from the output of the entrance side tension detection device, calculate the reduction position correction command amount S2 and the roll speed correction amount V2 from the output of the final stand exit side plate thickness detection device, The rolling position correction command amount S1
And the lowering position control device of the final stand corrects the lowering position based on the sum of the lowering position correction command amount S2 and
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 last stand or the final stand, and further, the final stand rolling load detecting device From the output of the above, the roll-down position correction command amount S3 and the roll speed correction amount V3 are calculated. A control method for a tandem mill, wherein the roll speed is corrected by a roll speed control device of all stands except the last two stands or the last two stands based on the roll speed correction command amount V3.