JP3299161B2 - Tension control method and control device for 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 a control device for a tandem rolling mill, and more particularly to a tension control method from the time of zero start for stably starting a tandem rolling plant.

[0002]

2. Description of the Related Art In a tandem rolling mill in which rolling mills are continuously arranged, it is necessary to start the rolling machine stably without breaking at the time of starting and to smoothly shift to controlling the thickness. Conventionally, the drooping characteristic of the motor, which reduces the speed when a load is applied at startup, is used.The amount of correction of the drooping characteristic is increased at startup, and the drooping characteristic is adjusted according to the speed after startup so as not to become a disturbance in thickness control. While reducing the correction amount of
A method is used in which the tension between the stands is started stably, and the process shifts to plate thickness control. Alternatively, a method is used in which tension control for correcting the speed of the upstream stand with an absolute value is performed, the amount corrected by the tension control is reset to zero at a certain speed or more, and the process shifts to sheet thickness control.

[0003]

In the conventional tension control method that utilizes the drooping characteristics of an electric motor, the amount of speed correction changes according to the load applied to the rolling mill, and the amount of drooping characteristics changes according to the speed. In this case, the thickness of the delivery side changes due to the constant law of mass flow, which causes disturbance to the thickness control, and the accuracy of the thickness cannot be improved despite the thickness control. Also, when using the method of correcting the speed of the upstream stand with the absolute value at the time of startup, when the amount corrected by the tension control is reset to zero at a certain speed or more, it interferes with the thickness control, and as described above, It was difficult to improve the accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to control the tension stably immediately after the zero start of the tandem rolling mill, and to smoothly shift to the control of the sheet thickness while preventing the sheet from being broken due to the abnormal tension. It is to provide a tension control method and a control device.

[0005]

SUMMARY OF THE INVENTION The present invention is characterized in that the following three stages are switched with respect to the entrance side tension control of each stand in a tandem rolling mill when the line is started from zero start.

In the first stage, in order to remove the slack of the plate at the time of starting from the zero start, the speed of the upstream stand (i-1) is corrected by an absolute value to control the entrance tension of the stand (i). Do.

In the second stage, when the rolling phenomenon is established after the tension is stabilized after the start-up, the speed of the upstream stand is set to the reference speed of the setup based on a model of the rolling phenomenon that causes a change in the thickness just below the roll. Switch to tension control that controls with a relative value. At that time, the speed correction amount corrected by the absolute value in the first stage is converted into a relative value with respect to the speed at the time of switching, and the tension control is started using the value as an initial value to correct the upstream stand speed with the relative value. I do.

In the third stage, when the thickness control for correcting the speed of the tandem rolling mill by a relative value is started, the system shifts to a method of performing the entrance tension control by correcting the roll gap of the stand. At this time, in order to make the reference value of the speed used in the thickness control normal, the speed correction amount corrected by the relative value in the second stage is reset to zero. At this time, a roll that can assume a constant tension, estimate the thickness change amount corresponding to the speed correction amount from the relationship of the constant mass flow law, and cancel the same when the thickness change amount is also assumed to be constant tension. A gap correction amount is obtained from a rolling load type and a gauge meter type, and the roll gap is changed to the roll gap correction amount in coordination with zero reset of the speed correction amount.

The change rate for coordination is the minimum of the speed change rate limited by the current margin of the electric motor driving the rolling mill and the roll gap change rate limited by the opening and closing speed of the roll gap of the rolling mill. Using the value, the margin is determined in consideration of other control margins.

According to the present invention, it is possible to prevent sheet breakage or the like caused by abnormal tension at the time of starting a line in a tandem rolling mill, and to suppress occurrence of sheet thickness fluctuation which becomes a disturbance when shifting to sheet thickness control for correcting speed. As a result, the thickness control becomes effective immediately, greatly improving the accuracy of the thickness, stabilizing the start of the line and reducing the length of the off gauge.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below using an example applied to a Sendzimir tandem rolling mill. FIG. 1 shows a configuration diagram of a control system of a four-stand Sendzimir tandem rolling mill. The tandem rolling mill 100 includes a plurality of stands 101-1 to 10-4. Rolled material 2
00 is prepared as an entrance coil, and upper and lower work rolls 110-1 to 110-1 of each stand 101 are arranged from the entrance of the tandem rolling mill.
4 and rolled.

Each of the stands 101 of the tandem rolling mills # 1 to # 4 has a speed control device 120 for controlling the work roll speed to match the command value, and the roll gap between the work rolls to match the command value. Is provided with a pressure reduction control device 121 for controlling the pressure. Further, between each stand, a thickness gauge 125 for detecting the exit side plate thickness and a tension meter 126 for detecting the tension between the stands (inter-stand tension) are provided.

As the rolling control device, the rolling control device 1 is set so that the actual tension value measured by the tension meter 126 becomes a set value.
The rolling tension control unit 123 that controls the roll gap of the stand via the control unit 21, the speed correction control unit 140 that supplies a speed correction amount to the speed command circuit 124 to control the roll speed of the preceding stand, The speed control circuit 124 is given a speed correction amount so that the actual thickness value measured by the thickness gauge 125 becomes the set value, and the roll speed of the preceding stand is changed. Are respectively provided.

The speed command circuit 124 corrects the line speed command reference value using the speed correction amount from the speed tension control and the speed correction amount from the plate thickness control, and the speed control device 120 controls the entire tandem rolling mill. Control is performed while coordinating the roll speed. In addition, the setup control unit 130 calculates the schedule based on the rolling model 131 based on the information on the input coil of the material to be rolled and the product specifications, and calculates the output plate thickness and input of each stand to stably and efficiently produce the product. The target value of the side / outside tension is determined, and the thickness control unit 12
2. Output to the rolling tension control unit 123 and the speed tension control unit 140.

FIG. 2 is a configuration diagram of a rolling control device according to one embodiment. Here, the components of the tension control and its output switching circuit are shown. This rolling control device has a tension control output switching circuit section 150, and an absolute value speed tension control section 14
1. Relative value speed tension control unit 142 and rolling tension control unit 1
It is characterized in that the control calculation and the output of 23 are switched and controlled. Hereinafter, the configurations and operations of these units will be described in detail.

The rolling tension control unit 123 calculates the deviation between the actual entry-side tension value Tb measured by the tension meter 126 installed on the entrance side of each stand and the target entrance-side tension value TbREF sent from the setup control unit 130. The integral control is performed so as to remove ΔTb (= Tb−TbREF). The control output is calculated by the equation (3) using the relational expression of the equation (2) derived from the rolling phenomenon of the equation (1) and considering the control gain so that the performance of the control system is the same regardless of the rolled material. .

[0017]

(Equation 1)

Here, ΔH: change in thickness of the entry side, Δh: change in thickness of the exit side, ΔTb: change in the tension on the entry side, ΔTf: change in the tension on the exit side, ΔS: change in the roll gap, K: mill spring constant,
In each parenthesis is the influence coefficient in the rolling phenomenon. In addition,
The expression (1) is called a simple rolling load expression, and the expression (2) is called a gauge meter type.

[0019]

(Equation 2)

However, it is referred to as a delivery side plate thickness deformation type (3).
In the equation, the change in the thickness of the inlet side ΔH and the change in the output side tension ΔTf are ignored, and the change in the outlet side thickness Δh is performed by the thickness control.
Since ΔH = ΔTf = Δh = 0, ΔTb and ΔTb
The relationship of S is represented by equation (4).

Therefore, the control output ΔSTR of the rolling tension control unit 123 is considered with respect to the control gain in consideration of the relational expression of Expression 2.
EF is calculated by Equation 3.

[0022]

(Equation 3)

Here, KG: integral gain, Δt: control sampling period.

The speed tension controller 140 controls the tension until the rolling load is applied by removing the slack of the plate at the start of the zero start, and the tension control after the line operation, which is established as rolling and can be controlled using the rolling theory. For performing each of them, an absolute value speed tension control unit 141 and a relative value speed tension control unit 142 are configured.

First, the absolute value speed tension controller 141 will be described. The tension at the start of the zero start is a time when the rolling phenomenon has not been established, and basically occurs according to Equation 4.

[0026]

(Equation 4)

Here, E: Young's modulus, B: Width of rolled material,
H: Rolled material sheet thickness, Δl: Elongation of rolled material (change in sheet speed ΔVE
, L: distance between stands.

As is apparent from this tension generation formula, the entrance tension Tb can be directly controlled by changing the entrance speed VE of the stand i with the absolute value of the speed command of the upstream stand i-1. Therefore, the absolute value speed tension control unit 141 performs the proportional control, and calculates the control output ΔVREF by Expression 5.

[0029]

(Equation 5)

Here, KSA is a proportional gain.

Next, the relative value speed tension controller 142 will be described. The switching to the relative value control is a time when the rolling is established, and the rolling phenomenon of Expression 1 is established. That is, when the upstream stand speed VRi-1 is changed, the inlet speed VE changes, and the tension Tb also changes, but at the same time, the outlet plate thickness h immediately below the roll of the rolling mill also changes due to the constant law of mass flow, which is a result. Settle to tension. The simplified relational expression is expressed by the above-described exit side plate thickness deformation equation (3) and the equation (8) of the constant mass flow law deviation equation.

[0032]

(Equation 6)

Here, ignoring the entrance side plate thickness change ΔH, the exit side tension change ΔTf, and the exit side speed change ΔVD, ΔH = ΔVD
= ΔTf = 0, and if the reduction operation is ignored, (ΔS =
0), the entry-side speed tension relational expression (9) of Expression 7 is obtained from the above two expressions.

[0034]

(Equation 7)

In other words, the entry speed VE (substantially the same as the upstream stand roll speed VRi-1 if changes in the advance rate and the reverse rate due to tension are ignored) is changed relative to the reference speed from the setup controller 130. By doing so, it is possible to change the entry-side tension.

Therefore, the relative value speed tension control calculates the control output% ΔVREFi-1 according to Expression 8 as integral control.

[0037]

(Equation 8)

Here, KSR is an integral gain.

Next, the tension control output switching circuit section 150 will be described. When the speed tension control is switched from the absolute value method to the relative value method at the stage when the rolling phenomenon is established, it is necessary to convert the correction amount ΔVREFi-1 to a relative value% ΔVREFi-1 and give it as an initial value.

For this reason, the correction amount converter 151 converts the absolute value speed correction amount into the relative value speed correction amount according to Expression 9, and sets the relative value tension control initial value% ΔVREFi-10.

[0041]

(Equation 9)

Here, ΔVREFi-1f: the final value of the absolute value tension control output, and VREFi-10: the reference speed at the time of switching.

Next, switching from speed tension control to rolling tension control will be described. In the control of the tandem rolling mill, when the line speed becomes equal to or higher than a certain value, the upstream stand speed is changed, and the thickness control is performed based on the constant law of mass flow. At this time, it is necessary to switch from the speed tension control to the rolling tension control in order to prevent interference between the tension control and the plate thickness control.

However, the correction amount% ΔVRE of the speed tension control
When the thickness control is started with the Fi-1 remaining, originally, the setup control unit 130 starts by shifting by a correction amount from the speed reference value that is optimally calculated to obtain a predetermined product thickness, It takes time to remove the thickness deviation by the thickness control, and the correction amount also increases. For this reason, the correction amount by the speed tension control is reset to zero, but at the same time, the roll gap change amount calculation unit 152 calculates the roll gap change amount ΔSTREF0 as follows so as to minimize the plate thickness fluctuation caused by the zero reset. I do.

First, by using the above-mentioned outgoing side plate thickness deformation formula (3) and the constant mass flow law deviation formula (8), the incoming side thickness change ΔH,
Disregarding the exit side tension change ΔTf and the exit side speed change ΔVD (ΔH =
ΔVD = ΔTf = 0), and on the condition that the entrance-side tension ΔTb is constant and does not change, the entry-side speed roll gap relational expression (12) is obtained, and the roll gap change amount ΔSTR
A calculation formula (13) for EF0 is derived.

[0046]

(Equation 10)

Here, KTFF: changed gain,% ΔVREFi−
1f: Speed tension control correction amount final value.

The roll gap correction amount ΔSTREF0 needs to be changed in synchronization with the zero reset of the thickness correction amount in order to minimize the thickness variation at the time of transition. Therefore, the roll gap correction amount output unit 153 determines the roll gap change speed Vg and the roll speed change rate dVs / dt as shown in Expression 11 in consideration of the changing capabilities of the speed control device 120 and the rolling reduction control device 121.

[0049]

[Equation 11]

Here, VPUMAX: maximum value of the opening / closing speed of the pressure reduction control device, ΔI: current margin of the drive motor on the speed change direction side, Δφ: torque coefficient of the drive motor, R: drive roll radius, GR: gear ratio, J: The moment of inertia. In addition,
The roll gap change rate and the roll speed change rate are halved in consideration of the rolling tension control and the sheet thickness control, respectively.

Next, the roll gap change amount ΔSTREF0,
The roll gap change time tg and the roll speed change time ts are calculated from the speed change amount% ΔVREFi-1f, and the cooperative change time tc is determined at the maximum time, and the roll gap change rate αg and the roll speed change rate αs are calculated. , Change in coordination with that rate.

[0052]

(Equation 12)

The speed at each control cycle Δt and the change step width of the output of the change amount of the roll gap are calculated based on the above change rate, and the output amount of the control output at each control cycle is maintained until the roll gap reaches a predetermined target value. Change control output ΔSTREF
Is Expression 13 and the roll speed change control output% ΔVREFi-1 is Expression 14.
Is calculated as follows.

[0054]

(Equation 13)

However, the integration stops at ΔSTREF0.

[0056]

[Equation 14]

However, the integration stops at 0.

Next, the switching timing will be described. FIG. 3 shows a control switching time chart. The switching timing creation unit 154 performs the above-described 3 according to the rolling state.
The control method of the step is switched.

First, the absolute value speed tension control starts from the time t0 when the line is started, and ends at the time t1 when the tension deviation becomes stable below a certain value. Relative value speed tension control is t
The process starts from 1 and ends at a speed plate thickness control start time t2 when the line speed is equal to or more than a constant value. The rolling tension control starts at time t2.

As described above, according to the present embodiment, the tension control based on the absolute value speed when the rolling at the start of the line is unstable, the tension control based on the relative value speed according to the rolling model after the tension is stabilized, and the change of the plate thickness At the start of the control, a three-stage tension control is performed to the rolling tension control, and a plate thickness control with a small off-gauge length can be realized while avoiding a plate breakage or the like.

In particular, when shifting from the speed tension control to the rolling tension control, the speed correction amount for the tension control is changed to the roll gap correction amount in synchronization with resetting the speed correction amount for the tension control. Since the thickness variation at the time of transition is minimized, the thickness control becomes effective immediately. Furthermore, the roll gap change rate and the roll speed change rate are determined in consideration of the responsiveness of the speed control device and the rolling reduction device, and both are changed in cooperation with each other. Transition is possible.

[0062]

According to the present invention, from the start of a line in a tandem rolling mill, a transition to a tension control based on an absolute value speed, a tension control based on a relative value speed, and a tension control based on rolling down;
Since the thickness control based on the speed is started after the three-stage tension control, it is possible to avoid the plate breakage or the like due to the abnormal tension and realize the stable thickness control.

Further, when shifting from the speed tension control to the rolling tension control, the speed correction amount for the tension control is changed to the roll gap correction amount so as to minimize the thickness variation. Since the thickness variation can be prevented and the thickness control is immediately effective, the length of the off gauge is small, and the thickness accuracy at the time of starting the line can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a rolling control system according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a tension control unit according to one embodiment.

FIG. 3 is a time chart showing switching timing of tension control according to the present invention.

[Description of Signs] 100: Tandem rolling equipment, 101-1 to 4 ... # 1 to #
4 stands, 110-1 to 4 ... Vertical work rolls, 120
... speed control device, 121 ... reduction control device, 122 ... thickness control unit, 123 ... reduction tension control unit, 124 ... speed command circuit unit, 125 ... thickness gauge, 126 ... tension meter, 130 ... setup control unit, 131 ... rolling model, 140 ... speed tension control unit, 141 ... absolute value speed tension control unit, 142 ...
Relative value speed tension control section, 150: tension control output switching circuit section, 151: correction amount conversion section, 152: roll gap change amount calculation section, 153: roll gap correction amount output section,
154: Switching timing creation unit, 200: Rolled material.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B21B 37/12 112A (72) Inventor Toshihide Shinoda 5-2-1 Omikacho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Omika Plant (72) Invention Person Shinichi Ikeda 4976 Nomura Minamicho, Shinnanyo City, Yamaguchi Prefecture Nisshin Steel Co., Ltd., Shunan Steelworks (72) Inventor Norio Komatsu 4976 Nomura Minamicho, Shinnanyo City, Yamaguchi Prefecture Nisshin Steel Corporation, Shunan Steelworks (56) References JP-A-10-128421 (JP, A) JP-A-62-286615 (JP, A) JP-A-60-3910 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21B 37 / 00-37/78

Claims (4)

(57) [Claims] 1. A tension control method for a tandem rolling mill in which a thickness control is performed in all stands, wherein a proportional control is obtained based on an actual value of an entrance side tension of the stand when the line speed is started from a zero start. Entry-side tension control is performed by correcting the absolute value of the upstream stand speed, and then when the actual value of the tension becomes stable, the entrance-side tension control is corrected by correcting the upstream stand speed with a relative value to the reference speed. A tension control for a tandem rolling mill, wherein the control is shifted to a sheet thickness control for correcting the roll speed of the upstream stand and an entry-side tension control for correcting the roll gap of the stand after the line speed becomes equal to or higher than a predetermined value. Method. 2. The equation of a constant mass flow rule according to claim 1, wherein when shifting from the tension control for correcting the speed of the upstream stand to the tension control for correcting the roll gap of the stand, the tension is constant. Using a rolling load formula and a gauge meter formula, the speed correction amount used for tension control is converted into a roll gap correction amount for keeping the plate thickness constant, and the speed correction amount of the upstream stand is coordinated with the zero reset of the speed correction amount. A tension control method for a tandem rolling mill, wherein an entrance tension control for changing a roll gap to a roll gap correction amount is performed. 3. The tension of a tandem rolling mill according to claim 2, wherein the rate of zero resetting of the speed is determined by a changeable rate of the speed or a changeable rate of the roll gap restricted by the capacity of the equipment. Control method. 4. A control device for a tandem rolling mill, comprising: a thickness gauge for detecting an exit side thickness of each stand; a tension meter for detecting a tension between the stands; and a thickness control means for all stands. Absolute value speed tension control means that performs entry-side tension control with the speed correction amount of the absolute value of the upstream stand speed obtained based on the actual value of the side tension, and the input side with the speed correction amount of the relative value of the upstream stand speed to the reference speed A relative value speed tension control means for performing tension control, a rolling tension control means for performing entrance-side tension control using a roll gap correction amount converted from a speed correction amount at the time of resetting the relative value to zero as an initial value; A control device for a tandem rolling mill, comprising a tension control output switching means for switching between start and end of control.