JPH0628764B2 - Plate thickness control method using reduction device of tandem rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a metal tandem rolling mill which does not include a device for mechanically operating the inter-stand tension between stands such as a tandem cold rolling mill. The present invention relates to a plate thickness control method using a reduction device.

[Conventional technology]

Conventional tandem rolling mills such as cold tandem rolling mills do not have mechanical inter-stand tension operating positions between stands.
Stands other than the No. stand (hereinafter called the intermediate stand)
It was common knowledge that the stand outlet side plate thickness hardly changed even if the rolling device was operated to open and close the gaps of the rolling rolls. The reason will be described with reference to FIGS. In FIG. 3, 1 is a No. 1 stand rolling roll, 2 and 3 are No. 2 and 3 stand rolling rolls, which are so-called intermediate stand rolling rolls. Reference numerals 9, 10, and 11 are reduction devices for the first to third stands ST1 to ST3, respectively. Further, 31 is a strip, and H _1e , H _2e and H _3e are 1, 2, 3
No. stand entrance side plate thickness, H _1d , H _2d , H _3d is 1,
Nos. 2 and 3 stand outlet side plate thicknesses, V _1e , V _2e , and V _{3e are} strip speeds on the inlet side of Nos. 1, 2 and 3 stands, V _1d ,
V _2d and V _3d are strip speeds on the outlet side of the No. 1, 2 and 3 stands, T ₀₁ is strip tension on the inlet side of the No. 1 stand, T
₁₂ and T ₂₃ are strip tensions between the 1st and 2nd stands and between the 2nd and 3rd stands, L is the distance between the stands, and V ₁ and V
₂ , V ₃ indicates the peripheral speed of No. 1, ₂ , ₃ rolling rolls. Fourth
The figure shows the mill elastic curves a and b and strip plasticity curves C1 to C3 in the No. 3 stand ST3. Now, assuming that the No. 3 stand entrance side plate thickness H _3e and the roll gap of the No. 3 stand in the state where the strip is not attached are S ₃ , the mill elastic curve is a, and the strip plasticity curve is C1, and the intersection K is balanced. The thickness of the No. 3 stand exit side plate is H _3d .
Here, the No. 3 stand _pressing- down device 11 in FIG. 3 is operated to tighten the No. 3 stand outlet side plate thickness to _H3dn (tightening).
When the roll void is changed from S ₃ to S _3n , the mill elastic curve is b
_Therefore , the _board thickness on the _delivery side of the No. 3 stand determined by the intersection of the curve C1 and the curve b seems to be _H3dn . But the third
In the figure, the law of constant mass flow (equation (1) below) before tightening the reduction device must be satisfied even after tightening.

H _3d · V _3d = H _3e · V _3e …… (1) H _3e and V _3d remain the same after tightening, so if the speed on the No. 3 stand entry side after tightening is V _3en , then H _3dn · V _3d = Since H _3e · V _3en (2) and H _3d > H _3dn, V _3d > V _3en .

Despite the fact that the speed at the No. 3 stand entrance side has decreased, the speed at the No. 2 stand exit side V _2d does not change, and the tension T ₂₃ between the No. 2 and No. 3 stands becomes loose. That is, the inter-stand tension changes from T _{23 of the following} formula (3) to T _23n of the following formula (4).

The change in the tension between the No. 2 and No. 3 stands causes the slope of the strip plasticity curve in FIG. 4 to change from the curve C1 to the curve C2. As a result, the No. 3 stand output side plate thickness is curve b and curve C2.
The plate thickness is determined by the intersection point A of. Furthermore, as a result of the loose tension between the No. 2 and 3 stands, the No. 2 stand's delivery side plate thickness also becomes thicker. When this thickened portion reaches the No. 3 stand entry side, H _{3e in} FIG. 3 becomes thicker. H as shown in FIG.
_{If 3e} changes to _H'3e , the mill elastic curve moves from the curve C2 to the curve C3, the plate thickness on the delivery side of the No. 3 stand becomes _H'3d determined by the intersection of the curve b and the curve 3, and the No. 3 stand reduction device. Despite the operation of, the thickness of the No. 3 stand exit side plate does not change.

As described above, since it is said that the stand outlet side plate thickness does not change even if the pressure reduction of the intermediate stand is operated, the automatic plate thickness control (AGC) device was configured on the premise of this.

According to FIG. 5, in a 4-stand tandem cold rolling mill, for example, JP-A Nos. 52-123360 and 52-11676.
The configuration of a typical conventional AGC device shown by No. 1 or the like will be described. No. 1 stand entrance side plate thickness deviation detection device 3
5, the plate thickness deviation signal ΔH _1e (the plate thickness reference is given to the device 35 in advance) is input to the No. 1 stand reduction feedforward AGC device 27, and at the same time, the No. 1 stand entry side plate is made by the plate speed meter 39. The speed is detected and this is input to the AGC device 27. The AGC device 27 calculates to which position the strip having the plate thickness obtained by the detecting device 35 is moving according to the plate speed, and when the position reaches the No. 1 stand roll bite, the rolling position change command value Δ SR ₁ is given to the reduction control device 23. 23 to 26 may be the rolling position control device or the rolling force control device (in the case of the rolling force control device, ΔSR ₁ is the rolling force change command value ΔPR ₁
In this example, the case of the rolling position control device will be described. First, the calculation method of the command value ΔSR ₁ will be described. Generally, the plate thickness variation ΔH _1d on the mill exit side is calculated as follows:
_When expressed by _1e and the rolling position fluctuation ΔS, it is expressed by the following equation.

Where M is the mill elastic deformation coefficient and Q is the strip plastic deformation coefficient.

In order to make _{ΔH 1d} zero even if _{ΔH 1e} changes in the equation (5), ΔH _1d may be set to zero and ΔS may be operated according to the following equation.

Therefore, ΔSR ₁ is represented by the following equation according to _{ΔH 1e} .

The roll-down control device 23 in FIG. 5 moves the roll-down device 9 according to ΔSR ₁ to adjust the roll gap, thereby making the No. 1 stand output side plate thickness deviation to be zero based on the No. 1 stand input side plate thickness variation. The No. 2 stand entrance side plate thickness deviation ΔH _2e is detected by the detection device 36 and input to the No. 2 stand speed feedforward AGC device 17. 2 in AGC device 17
No. stand input side plate speed is obtained from the plate speed meter 40 to detect it.
The part of the strip with the thickness deviation detected by
No. 1 stand roll speed controller 13 according to ΔH _2e depending on the timing of arrival at the No. stand roll bite
Give a roll speed change command ΔV1R. ΔV1R is calculated as follows. Figure 3 in _{H 2e} is △ _{H 2e} only _{H 2d} when the changes are not changed _{V 2d} so as not to change to the _{V 2e} is changed _{V 2e} - △ _{V 2e}
And it is necessary to keep the mass flow constant, therefore
Equation (6) ′ holds.

(H _2e + ΔH _2e ) (V _2e −ΔV _2e ) = H _2d V
_2d ...... (6) is omitted 'constant mass flow law _{H 2e ·} V 2e ₌ a _{H 2d V} 2d (6) in the state of FIG. 3' is substituted into equation secondary small term △ _{H 2e} △ _{V 2e} ( 7) 'becomes.

Since V _2e is approximately equal to one No. roll peripheral speed V ₁ (7) 'equation is (8).

Therefore, the No. 1 stand roll speed change command ΔVIR can be expressed by the following equation.

According to this ΔVIR, the speed control device 13 of FIG. 5 changes the rotation speed of the roll driving electric motor 5 to make the No. 2 stand output side plate thickness variation due to the No. 2 stand input side plate thickness variation zero. Similarly, in FIG. 5, the thickness deviation of the No. 3 stand entering side is detected by the detecting device 37 and input to the AGC device 18.
In the AGC device 18, the timing is adjusted by the plate speed on the No. 3 stand entrance side (detected by 41), and the No. 2 stand roll speed change command ΔV2R is given to the roll speed control device 14, and the device 14 follows the rotation speed of the electric motor 6 according to ΔV2R. By changing the rotation speed of the roll 2
No. 3 stand exit side plate thickness fluctuation due to No. stand entrance side plate thickness fluctuation. The AGC device 18 also gives a speed change command to the roll speed control device 13 to keep the speed ratio of the rolls 1 and 2 so that the tension between No. 1 and No. 2 stands does not change because the speed of the roll 2 is changed. Change the speed of roll 1 as well. Similarly, in the No. 4 stand, the signals of the plate thickness deviation detection device 38 and the plate speed meter 42 are input to the AGC device 19, and the AGC device 19 makes the No. 4 stand output side plate thickness variation to zero based on the No. 4 stand input side plate thickness variation. No. 3 stand roll speed change command ΔV3R is given and the roll speed controller 1
3 and 14 are given roll speed change commands so that the No. 1, No. 2 and No. 3 stand roll speed ratios do not change depending on ΔV3R.

As described above, the No. 1 stand output side plate thickness variation operates the No. 1 stand reduction device, the No. 2 stand output side plate thickness variation changes the No. 1 stand roll speed, and the No. 3 stand output side plate thickness variation is No. 1 and 2. In the conventional AGC, the stand roll speed is changed and the No. 4 stand output side plate thickness variation is changed to zero by changing the No. 1, 2 and 3 stand roll speeds.

[Problems to be solved by the invention]

The conventional AGC has a limit in its controllability and cannot provide sufficient plate thickness accuracy. The reason is that the roll speed control devices 13 to 16 shown in FIG. 5 have a slow response speed. Normally, in a speed control system for large rolling rolls such as a rolling roll driving device of a tandem cold rolling mill, the response speed is at most about 2Hz because the moment of inertia of the rolls and the electric motor is large. The phase shift and the decrease in gain increase. On the other hand, it is known that there is a frequency component of 0 to 10 Hz when a frequency analysis is performed on the thickness variation of each of the stand entrance and exit sides. It is considered that the sheet thickness variation of 1 Hz to 10 Hz is the sheet thickness variation printed by the eccentricity of the rolling roll in the previous process (hot rolling). Roll eccentricity in tandem cold rolling is also considered to be caused by plate thickness fluctuation of 1 to 10 Hz, which is supported by the fact that the plate thickness fluctuation frequency is the roll rotation frequency of hot rolling and cold rolling and its harmonics. To be
In the conventional AGC, except that the No. 1 stand exit side plate thickness is controlled by the No. 1 stand pressure reduction control, the stand exit side plate thickness after No. 2 stand is controlled by operating each stand roll speed. Up to 2 Hz, which is the response speed of the roll speed control device, cannot be removed among the fluctuations in the plate thickness that have not been removed and the plate thickness fluctuations caused by the eccentricity of each roll of the rolling mill. Thickness variation of 2Hz or more is within ± 1% of strip thickness, which was within the range of tolerance in the past. However, as the automation of the manufacturing process using metal strip becomes faster, the requirement for strip thickness accuracy is increased. Became difficult, and the conventional AGC could not meet the demand.

The present invention aims to eliminate the plate thickness variation in the entire frequency range contained in the rolled material of the tandem rolling mill that could not be removed by the conventional plate thickness control device. It is intended to provide a control device.

[Means for solving problems]

In order to further enhance the application effect of the present invention, a condition that the metal strip rolling mill should have is that the response speed of the reduction control device is faster than the response speed of the roll speed control device. For example, the pressure reducing device may be a hydraulic pressure reducing device, and the roll driving device may be a thyristor Leonard apparatus using a DC motor. As described above, the response frequency of the roll speed control device is about 2 Hz, whereas the response frequency of the hydraulic pressure reduction control device is about 20 Hz, which is remarkably fast.

In the conventional tandem cold rolling, the eye of the present invention was thought to have little change in the stand-out side plate thickness by the operation of the rolling-down device of the intermediate stand, but in reality, it is 1 Hz to 2 Hz.
It is a fact that the output plate thickness can be changed by operating at a relatively high frequency of Hz. 2nd in 4 tandem cold rolling
The curve A1 shown by the solid line in FIG. 6 shows the variation of the outlet plate thickness when the stand pressing device is operated at various frequencies.
Is. Vertical axis is gain = variation in plate thickness at the stand exit side /
Indicates the amount of instruction to change the rolling position and shows the degree of change in the stand outlet side plate thickness due to the rolling operation. The horizontal axis is frequency and is shown on a logarithmic scale. The degree of influence of the reduction operation on the thickness variation is 2
The maximum is 4 Hz, and the response of the pressure reducing device deteriorates in a frequency higher than this region, and the reduction device itself does not move in spite of the instruction to change the reduction position, so the gain decreases.

The reason why the gain drops in the low frequency region is as follows. In Fig. 4, the gap between the No. 3 stand rolls is changed from S ₃ to S
_{Even if} changed to _3n1 , the mill elastic curve moves from C1 to C2 and then to C3. As a result, the No. 3 stand _delivery side plate thickness changes slightly from H _3d to H ′ _3d, and hardly changes. However, C1 moves to C2 only when the mill elastic curve shifts from a to b and then the tension between stands 1 and 2 (T _{12 in} FIG. 3) changes. This takes about 0.2 seconds. The phenomenon of going from C2 to C3 in Fig. 4 tension _{T 12}
Changes and the No. 2 stand stand-out side plate thickness H _2d changes, and the changed strip is transferred to the No. 3 stand roll and reaches H _3e , which only occurs. The strip transfer time is 0.5 seconds when the distance between stands (L in FIG. 3) is 5 m and V _2d in FIG. 3 is 600 mpm (10 mps). Therefore, the movement from C1 to C3 in FIG. 4 takes 0.7 seconds, and the rolling fluctuation having a period longer than that does not appear as the fluctuation to the stand outlet side plate thickness, resulting in the characteristic of FIG. On the contrary, fluctuations in the rolling position with a period of 0.7 seconds or more can change the plate thickness on the stand-out side.

Here, in FIG. 4, when the strip plasticity curve does not move from C1 to C2 and C3 even when the curve a shifts to the curve b by the rolling down operation, the dotted curve A2 in FIG. The side plate thickness changes. The present invention prevents the movement from C1 to C2, C3 in FIG. 4 by the operation of the reduction device of the stand and the upstream stand or eliminates the effect of the movement, and uses a reduction device having a higher response than the roll speed control device. Is to control the plate thickness with high accuracy.

The principle of the method of the present invention will be described with reference to FIG. Same figure a
No. 3 stand exit side plate thickness H _3d is determined by the intersection K of C1 and C1. Here, the No. 3 stand rolling-down device is operated to change the No. 3 stand roll gap from S ₃ to S _3n (required roll gap when there is no change in tension) in _order to make the No. 3 stand exit side plate thickness H _3dn. change. However, first, the tension T _{23 in} FIG. 3 changes and then shifts from C1 to C2 in FIG.
The intersection A with and determines the No. 3 delivery side plate thickness. Therefore, the No. 3 stand roll gap is moved to S _{3r in} FIG. 7 according to the change in tension. By moving from S _3n to S _3r (the plasticity curve moves from b to C), the tension T _{23 in} FIG. 3 further changes, and C 2 in FIG. 7 moves to C 3, but this is also taken into consideration. The S _3r is determined _so that the plate thickness on the _delivery side of the No. 3 stand determined by the intersection B of C becomes H _3dn . Also, the No. 2 stand roll-down device is operated to change the No. 2 stand roll gap so that the plastic curve does not move from C3 to C4 in FIG. Move from C3 to C4 are caused by the stand entry side thickness No. 3 is changed from H _3e to H _'3e, which tension T by the operation of the screw down device 11 of FIG. 3
₂₃ changes, which causes a change in the plate thickness H _2d (H '
_2d ), which is what happens when the No. 3 stand roll is reached. In order to prevent this, the No. 2 roll void may be changed at the same time as the No. 3 stand roll void is changed. Phenomenon caused by changing the No. 2 stand roll gap is 3
The _{H 3d H 2d,} the _{H 3e H} 2e, _{'the 3e H' H} 2e, the _{S 3} and _{S 2, S 3r} varied every a _{S 2r} in Figure 7 the same as the time of the roll gap changes No. Stand And good. For H _2d prevent the move to _{H '3e} from the value of _{H 3e} may be changed from _{S 2} to _{S 2r.} Since the tension T _{12 of} FIG. 3 is changed by changing the No. 2 stand roll gap, it is also necessary to operate the No. 1 stand roll gap to cancel the effect.

As mentioned above, the number of stand rolls for No. 3 is changed to 3
In order to set the No. stand stand-out plate thickness to the target value, move the No. 3 stand roll void operation amount more than the amount to be changed if it is considered that the tension between No. 2 and No. 3 stands does not change, and further move No. 2 and 1 This can be achieved by changing the roll gap of the number stand.

An application example of the plate thickness control method of the present invention based on the above principle will be described with reference to FIG. In this figure as well as FIG. 5, 1 to 4 are rolling rolls of the No. 1 to 4 stands, 9 to 12 are the same rolling reduction devices, 23 to 26 are rolling reduction control devices, and 27 to 30 are plate thickness control devices (rolling reduction devices). Feedforward AGC device),
35 to 38 are plate thickness deviation detecting devices, and 39 to 42 are plate speed gauges. Plate thickness control device for No. 1 stand (9 in Fig. 1,
23, 27, 35, 39) is exactly the same as that of FIG. 5 (composed of 9, 3, 27, 35, 39). Detecting the thickness deviation remaining on the No. 1 stand and the thickness deviation caused by the No. 1 stand roll eccentricity, etc.
It is detected in 6 and input to the plate thickness control device 28. The device 28
In (7) will be calculated according to equation 2 No. Stand plate thickness changing command △ SR ₂ Strip plastic deformation coefficient Q ₂ in No. 2 stand for between No. 1 and No. 2 stand tension changes by △ Q ₂ (which Is measured in advance), and is given by the following equation. However, M ₂ is the No. 2 stand mill plasticity coefficient.

(However, ΔH ₂ is the reduction amount H _2e − at the No. 2 stand.
H _2d ) The second term on the right side of the equation (10) will be described with reference to FIG. C1 and a
Of No. 2 stand delivery side thickness H _2Dn determined by the intersection strip plastic coefficient Q ₂ in No. 2 stand Q _{2 +} △ be varied to Q ₂ the variation of the roll gap to be changed in order to keep the same △ If S ₂ ′, ΔP _{2 in} FIG. 7 is − {(Q ₂ + ΔQ ₂ ) ΔH ₂ −Q ₂ ΔH ₂ } = − Δ for both M ₂ ΔS ₂ ′.
Also expressed as Q ₂ · ΔH ₂ . Therefore, M ₂ ΔS ₂ ′ = −Δ
Q ₂ ΔH ₂ , that is, The plate thickness control device 28 shown in FIG.
At the same time as giving the reduction position change command represented by the equation (0), the reduction controller 23 also operates the reduction of the No. 2 stand, so that the tension between the No. 1 and No. 2 stands changes, and as a result, the strip plasticity coefficient Q _{1 at the} No. 1 stand is changed. A No. 1 reduction position change command ΔSR ₁ ′ which should prevent the No. 1 stand output side plate thickness variation due to the change to Q ₁ + ΔQ ₁ is output according to the following equation. This idea is the same as in Eq. (11).

(However, M ₁ is the elastic modulus of the No. 1 stand mill, ΔH ₁ is the reduction amount at the No. 1 stand) The sheet thickness deviation remaining at the No. 2 stand and the sheet thickness deviation occurring at the No. 2 stand are the detection devices of FIG. It is detected by 37 and inputted to the plate thickness control device 29. In the device 29, the plate speed meter 41 measures the timing and outputs the No. 3 stand roll gap change command to the rolling-down control unit 25, and at the same time, the No. 3 stand roll gap In order not to change the No. 2 stand stand-out side plate thickness by the change, the No. 2 stand roll gap change amount command is given to the controller 24, and by changing this No. 2 stand roll gap, the No. 1 stand stand-out side plate thickness is not changed. A No. 1 stand roll gap change command is output to the control device 23. Similarly, in the No. 4 stand, the plate thickness control device 30 outputs roll gap change commands to the reduction control devices 26, 25, and 2423 using the measurement values of the plate thickness deviation detection device 38 and the plate speed meter 42, respectively. Rolling down control device 2 which received roll gap change command
3 to 26 operate the reduction devices 9 to 12 respectively to 1 to 4
Change the No. stand roll gap as instructed to eliminate the thickness variation of each stand outlet side.

As described above, conventionally, after the No. 2 stand, the plate speed was controlled by using the roll speed control device having a low response speed.
By using the plate thickness control method of the present invention, it is possible to remove high-frequency plate thickness deviation that cannot be removed by the conventional method. Of course, this method can be used in combination with the plate thickness control method using the conventional roll speed control device.

In addition, although it has been observed experimentally that the tension on the outlet side of the stand that has undergone the rolling operation also changes slightly, it is also possible to operate the rolling down device of the stand downstream from the stand, as shown by the broken line in Fig. 1. It is effective for improvement.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2, FIG. 4, FIG. 6 and FIG. 7 are graphs for explaining the operation, and FIG. 3 is an explanatory view of the tandem mill, FIG. FIG. 4 is a block diagram illustrating a conventional device. In the drawings, 1 to 4 are rolls of a rolling stand of 1 to 4, 9 to 1
2 is a rolling down device, 23 to 26 are rolling down control devices, 31 is a metal strip steel, and 35 to 38 are plate thickness deviation detecting devices.

Claims (1)

[Claims] 1. A metal strip having a plurality of rolling stands, comprising a rolling down control device for controlling the rolling down position or rolling force by operating the rolling down position, and not including a mechanical device for operating the inter-stand tension such as a looper between the stands. In a steel tandem rolling mill, the input side plate thickness or the output side plate thickness of at least one stand other than the first stand is detected directly or by calculation, and the plate thickness signal is input to the reduction control device,
By operating the reduction device of the stand according to the deviation between the plate thickness signal and its target value, the fluctuation of the strip tension caused by this operation is controlled by operating the reduction device of the upstream stand and / or the downstream stand, and And / or a strip thickness control method for a tandem rolling mill, characterized in that it also prevents variation in strip thickness at the downstream stand.