JPH0586295B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a metal tandem rolling mill that is not equipped with a device for mechanically controlling the strip tension between the stands, such as a tandem cold rolling mill. The present invention relates to a highly accurate plate thickness control method.

[Conventional technology]

It is common knowledge that in conventional cold tandem rolling mills, even if the rolling device of the stands other than the No. 1 stand (hereinafter referred to as intermediate stand) is operated to open or close the gap in the rolling rolls, the plate thickness at the exit side of the stand will hardly change. It was hot. The reason for this will be explained qualitatively with reference to FIG. 1 is a No. 1 stand roll, and 2 and 3 are No. 2 and 3 stand roll rolls. Stands 2 and 3 correspond to so-called intermediate stands. 9 to 11 are the rolling down devices of stands No. 1 to 3. It is now assumed that the roll gap of the stand is narrowed by the No. 2 stand lowering device 5. Before narrowing, the entrance plate thickness of No. 2 stand is H ₁ ′, the exit plate thickness is H ₂ , the entrance speed is v ₁ ′, the exit speed is v ₂ , 1
Let the exit speed of the stand be v ₁ . At that time, the following equation holds between these quantities due to the constant mass flow law.

H ₁ ′V ₁ ′＝H ₂ v ₂ ……(1) H ₂ when the roll gap of No. 2 stand is narrowed
Assuming that becomes smaller and the change is set as ΔH ₂ , the thickness of the exit side of the No. 2 stand will be H ₂ − ΔH ₂ .
Each stand roll circumferential speed V ₁ , V ₂ , in FIG.
V ₃ does not change. For example, No. 2 roll peripheral speed V ₂ and 2
There is a relationship as shown in equation (2) with the plate thickness on the exit side v ₂ (where λ ₂ is the advance rate of the No. 2 stand, usually several %).

v ₂ = (1+λ ₂ )V ₂ (2) Since λ ₂ hardly changes due to the operation of No. 2 reduction device 5, v ₂ does not change. Since H ₁ ′ also does not change, v ₁ ′ changes in equation (1), and if we set the amount of change as Δv ₁ , equation (1) becomes (1′).

H ₁ ′(v ₁ ′−Δv ₁ ′)=(H ₂ −ΔH ₂ )v ₂ ……(1′) Here, the tension between stand No. 1 and stand No. 2 T ₁₂
is expressed by the following equation.

T ₁₂ = K∫ ^t ₀ (v ₁ ′−v ₁ ) dt ……(3) (However, t = distance between stands / v ₁ k = proportionality constant) From formula (1′), No. 2 stand after tightening down The entrance speed v ₁ −Δv ₁ ' is given by the following formula.

v ₁ ′−Δv ₁ ′=H ₂ −ΔH ₂ /H ₁ ′v ₂ ……(1″) In other words, the tension T ₁₂ between the 1st and 2nd stands in equation (3) is K∫ ^t ₀ (H ₂ /H ₁ ′v ₂ −v ₁ )dt (from equations (1) and (3)) to K∫ ^t ₀ (H ₂ −ΔH ₂ /H ₁ ′v ₂ −v ₁ )dt ((1″), (3) (from the formula). When the tension T ₁₂ decreases, the thickness of the exit side of the No. 2 stand mainly increases. As a result, even though the rolling down device of the No. 2 stand was tightened, the thickness of the plate on the exit side of the No. 2 stand remained almost unchanged. Expressed in another way, if the thickness of the plate on the exit side of the No. 1 stand is H ₁ and the thickness of the plate on the inlet side of the No. 1 stand is constant, the relationship H ₁ v ₁ = H ₂ v ₂ holds true.

v ₁ = V ₁ (1 + λ ₁ ), v ₂ = V ₂ (1 + λ ₂ ) ...(3)' (However, λ ₁ and λ ₂ are the advance rates of No. 1 and No. 2 stands), so V ₁ ( 1+λ ₁ )H ₁ =V ₂ (1+λ ₂ )H ₂ . That is, it is expressed as H ₂ =V ₁ (1+λ ₁ )H ₁ /V ₂ (1+λ ₂ ) (4). Even if you operate the lowering of the No. 2 stand
Since V ₁ , V ₂ , H ₁ , λ ₁ , and λ ₂ hardly change, the No. 2 outlet side plate thickness hardly changes as a result. Strictly speaking, H ₁ and λ ₂ will be slightly larger, and λ ₁
becomes slightly smaller, and as a result, H ₂ hardly changes. To explain this using the mill elasticity curve and strip plasticity curve according to Figure 2, if the mill elasticity curve before the No. 2 stand is rolled down and tightened is C1, and the strip plasticity curve is C3, then the thickness of the plate on the exit side of the No. 2 stand is C1 where the rolling force required to elongate the mill and the rolling force required to compress the strip match.
It is determined by the intersection of and C3, resulting in H ₂ . At this point, tighten the pressure of the No. 2 stand, and the mill elastic curve becomes C1.
If it moves from to C2, the thickness of the exit side of the No. 2 stand will be H ₂ − ΔH ₂ determined by the intersection of C2 and C3, but
As mentioned above, for this reason, the tension between the No. 1 and No. 2 stands becomes small. As a result, the strip plasticity curve moves from C3 to C4, and eventually the thickness of the exit side of the No. 2 stand returns to approximately _H2 . Strictly speaking, even if the tension between stands 1 and 2 is loosened, it will not completely move from C3 to C4, but will only move to C5, but 1,
Because the tension between the No. 2 stands is relaxed, H ₁ becomes thicker, and as a result, H ₁ ′ becomes larger, H ₁ ′ + ΔH ₁ ′
As a result, the thickness of the exit side of the No. 2 stand returns to _H2 .

As described above, it has been conventionally said that even if the intermediate stand is lowered, the plate thickness at the exit side of the stand does not change, and automatic plate thickness control (AGC) devices have been constructed on this premise.

For example, in a four-stand tandem cold rolling mill according to FIG.
We will explain the configuration of a typical conventional AGC as shown in the following issue. The plate thickness signal (ΔH ₀ ′) detected by the plate thickness deviation detection device 35 on the entrance side of the No. 1 stand (the plate thickness reference is given to the plate thickness deviation detector 35) is input to the No. 1 stand reduction feed forward AGC device 27. At the same time, the board speed at the entrance of the No. 1 stand is detected by the board speed meter 39 and input into the device 27.
The AGC device 27 calculates to which position the strip having the thickness obtained by the detection device 35 is moving based on the plate speed, and when the position reaches the No. 1 stand roll bite, the reduction position change command value ΔSR ₁ is given to the reduction control device 23. 23-26
may be a rolling position control device or a rolling force control device (in the case of a rolling force control device, ΔSR ₁ becomes the rolling force change command value ΔPR ₁ ), but in this example, the case of a rolling force control device will be explained. The method for calculating ΔSR ₁ will be described. In general, when plate thickness variation ΔH ₁ on the mill exit side is expressed by plate thickness variation ΔH ₀ ′ on the mill entrance side and rolling position variation ΔS, it is expressed by the following equation.

ΔH ₁ =Q/M+QΔH ₀ '+M/M+QΔS...(5) where M is the mill elastic deformation coefficient and Q is the strip plastic deformation coefficient.

In order to make ΔH ₁ zero even if ΔH ₀ ' changes in equation (5), ΔH ₁ should be set to zero and ΔS should be operated according to the following equation.

ΔS=-Q/MΔH ₀ '...(6) Therefore, ΔSR ₁ is expressed by the following equation according to ΔH ₀ '.

ΔSR ₁ = -Q/MΔH ₀ ′ ...(7) The rolling down control device 23 in Fig. 3 moves the rolling down device 9 according to ΔSR ₁ and adjusts the roll gap to control the change in thickness at the entrance of No. 1 stand. Zero the plate thickness deviation on the exit side of No. 1 stand. The plate thickness deviation ΔH ₁ ′ on the entrance side of No. 2 stand is detected by the detection device 36.
The signal is input to the AGC device 17. In the AGC device 17, the No. 2 inlet side plate speed is obtained from the plate speed meter 40, and the detection device 3
A roll speed change command ΔV1R is given to the No. 1 stand roll speed control device 13 in accordance with ΔH ₁ ' to determine the timing at which the portion of the strip having the plate thickness deviation detected by No. 6 arrives at the No. 2 roll bite. ΔV1R is calculated as follows. In FIG. 5, when H ₁ ' changes by ΔH ₁ ', in order for H ₂ to remain unchanged, the roll circumferential speed V must change to become V - ΔV, assuming that the plate speed v remains unchanged. Therefore
Equation (1) becomes equation (1″).

(H ₁ ′+ΔH ₁ ′) (v ₁ ′−Δv ₁ ′)=H ₂ v ₂ ...(1″) Substituting (1) into (1″) and omitting the second-order minute terms ΔH and ΔV, we get It becomes equation (8).

Δv ₁ ′=v ₁ ′／H ₁ ′ΔH ₁ ′ ...(8) However, according to equation (3), there is a relationship of v ₁ = V ₁ (1+λ ₁ ), so Δv ₁ = ΔV ₁・(1+λ ₁ )( However, ΔV ₁ is the variation of V ₁ ). Since v ₁ is approximately equal to v ₁ ′
v ₁ ′=V ₁ (1+λ ₁ ) and Δv ₁ ′=ΔV ₁ (1+λ ₁ ), and when these are substituted into equation (8), the following equation is obtained.

ΔV ₁ =V ₁ /H ₁ ′ΔH ₁ ′ (9) Based on equation (9), the speed change command ΔV1R to the roll speed control device 13 in FIG. 3 is expressed as follows.

ΔV1R=V ₁ /H ₁ ′ΔH ₁ ′ ...(10) According to this ΔV1R, the roll speed control device 13 shown in FIG. The thickness variation on the exit side of the No. 2 stand based on this will be reduced to zero. Similarly, in Fig. 3, the device 37 detects the plate thickness deviation on the entrance side of No.
is detected and input to the AGC device 18. AGC device 1
8, the timing is adjusted according to the plate speed on the entrance side of the No. 3 stand, and a No. 2 stand roll speed change command ΔV2R is given to the roll speed control device 14, and the roll speed control device 14 changes the rotational speed of the roll drive electric motor 6 according to ΔV2R. By changing the rotational speed of the rolling roll 2, the variation in the plate thickness on the exit side of the No. 3 stand, which is based on the variation in the plate thickness on the input side of the No. 3 stand, is made zero. Also, the AGC device 18 is a roll speed control device 13.
A speed change command was given to the rolling roll 2 so that the speed ratio of the rolling rolls 1 and 2 was kept constant so that the tension between stands 1 and 2 did not change due to changing the speed of the rolling roll 2. Change the roll speed of 1.
Similarly, for the No. 4 stand, the signals from the entrance plate thickness deviation detection device 38 and the plate speed meter 42 are input to the AGC device 19.
The AGC device 19 gives the No. 3 roll speed change command ΔV3R to zero the No. 4 stand exit side plate thickness variation based on the No. 4 stand entrance side plate thickness variation, and also gives the No. 3 roll speed change command ΔV3R to the roll speed control devices 13 and 14 for Nos. 1, 2, Give each roll speed change command so that the No. 3 roll speed ratio does not change due to ΔV3R.

As mentioned above, changes in plate thickness on the exit side of the No. 1 stand are achieved by operating the No. 1 rolling down device, changes in the plate thickness on the exit side of No. 2 are changed by changing the speed of the No. 1 roll, and changes in plate thickness on the exit side of the No. 3 stand are controlled by changing the speed of the No. 1 and 2 rolls. In conventional AGC, the thickness variation on the exit side of No. 4 is reduced to zero by changing the speed of No. 1, 2, and 3 rolls.

[Problem that the invention seeks to solve]

Conventional AGC has limits to its control ability,
Sufficient plate thickness accuracy cannot be achieved. The reason for this is that the response speed of the roll speed control devices 13 to 15 shown in FIG. 3 is slow. Normally, in the speed control system of large rolling rolls such as the rolling roll drive device of a tandem cold rolling mill, the moment of inertia of the rolls and electric motor is large, so the response speed is at most about 2 Hz, and for frequencies higher than this, In this case, the phase shift and gain decrease will be large. On the other hand, frequency analysis of plate thickness fluctuations at the entrance and exit sides of each stand reveals that there is a frequency component between 0 and 10 Hz. It is believed that the plate thickness variation of 1 Hz to 10 Hz is the plate thickness variation printed by the eccentricity of the rolling roll in the previous process (hot rolling). Also, the roll eccentricity in tandem cold rolling is 1~
This is believed to be the cause of the 10 Hz plate thickness variation, and this is supported by the fact that the plate thickness variation frequency is the frequency of roll rotation in hot rolling and cold rolling and its harmonics. In conventional AGC, except for controlling the thickness of the No. 1 outlet side under the No. 1 pressure, each stand roll speed is controlled to control the thickness of the stand exit side from the No. 2 stand onwards, so the thickness is not removed until the No. 2 inlet side. Of the remaining sheet thickness fluctuations and sheet thickness fluctuations caused by the eccentricity of each roll of the rolling mill, those over 2 Hz, which is the response speed of the roll speed control device, cannot be removed. Thickness fluctuations of 2 Hz or more were approximately ±1% of the strip thickness, which was within the allowable error range, but as manufacturing processes using metal strips become more automated and faster, demands for strip thickness accuracy are increasing. As the demands became more severe, conventional AGC was no longer able to meet these demands.

The present invention provides plate thickness control in a metal tandem rolling mill, with the purpose of eliminating plate thickness fluctuations in the entire frequency range included in the rolled material of the tandem rolling mill, which could not be removed by conventional plate thickness control devices. It is related to the device.

[Means for solving problems]

A condition that a metal strip rolling mill, which is a premise of the present invention, must have is that the response speed of the rolling reduction control device is faster than the response speed of the roll speed control device. For example, the rolling down device may be a hydraulic rolling device, and the roll driving device may be a thyristor Leonard device using a DC motor. As mentioned above, the response frequency of the roll speed control device is approximately 2 Hz, whereas the response frequency of the hydraulic pressure reduction control device is about 20 Hz, which is much faster.

The focus of the present invention is that, in conventional tandem cold rolling, it was thought that there would be almost no change in the plate thickness at the exit side of the stand due to the operation of the rolling device of the intermediate stand, but in reality, the operation is performed at a relatively high frequency of 1Hz to 20Hz. The fact is that it is possible to change the plate thickness on the exit side. The curve shown by the fourth solid line shows the variation in the exit plate thickness when the rolling device of the second stand is operated at various frequencies in 4-tandem cold rolling.
It is A1. The vertical axis indicates gain=amount of change in plate thickness on the exit side of the stand/amount of change in the rolling position, and indicates the degree of change in plate thickness on the exit side of the stand due to the rolling operation. The horizontal axis is frequency, expressed on a logarithmic scale. The degree of influence of the rolling operation on plate thickness fluctuation is maximum at 2 to 4 Hz, and at frequencies higher than this range, the response of the rolling device becomes poor, and the rolling device itself stops moving despite instructions to change the rolling position, so the gain decreases. . 2-4
The reason why the gain decreases in a frequency range lower than Hz will be explained based on FIG. 2.

As already mentioned, the plate thickness is determined from the intersection of curves C1 and C3.
H ₂ has been decided. When changing the pressure position and changing C1 to C2, the change in pressure changes the pressure from C3 to C5.
However, according to experiments, there is a difference between the downward movement amount ΔS ₂ and the back tension fluctuation amount ΔT ₁₂ as follows: ΔT ₁₂ = K ₁₂ /1 + t ₁₂ ·sΔS ₂ (s: Laplace's operator, t ₁₂ : time constant) Usually about
0.2 seconds), and it takes time for the change to occur. Also, when back tension fluctuation occurs, the thickness of the exit side of No. 1 stand H ₁
A change occurs and the stage moves from C5 to C6, but the timing of the shift is when the strip whose thickness has changed reaches the No. 2 stand. The strip of No. 1 stand roll bite reaches the No. 2 inlet side when the distance between No. 1 and No. 2 stands (L in Figure 5) is 5 m, and the exit speed of No. 1 stand (v ₁ in Figure 5) is 300 mpm. , about 1
Seconds later. In other words, after operating the reduction, the thickness of the exit side of the No. 2 stand will eventually return to the value before the operation.
After 1.2 seconds, the light temporarily becomes thinner. In other words, the plate thickness does not change if the rolling operation is performed at a period longer than 1.2 seconds, but the plate thickness changes if the rolling operation is performed at a period shorter than 1.2 seconds. Figure 4 shows this quantitatively. This fact was not useful for plate thickness control in the days when the rolling mill's rolling machine was an electric rolling machine, and the rolling machine could only be operated slowly.
A hydraulic reduction device that can achieve a response speed of about 20 Hz can be effectively used as a plate thickness control device.

However, as you can see from what I said above, the period is 1.2.
If the rolling is performed at a speed of less than a second (frequency 1/1.2 Hz), only the tension will fluctuate, although the thickness of the plate on the outlet side of the stand will hardly change, which will be harmful in terms of threadability. Therefore, the plate thickness control according to the present invention removes only the high frequency component of the plate thickness variation by rolling down, and removes the low frequency component by changing the roll speed ratio. It is a device.

Next, an example of application of the present invention will be explained based on FIG. 3, 1 to 4 are the rolling rolls of stands 1 to 4, 5 to 8 are the electric motors for driving the rolls, 9 to 12 are the same rolling devices, 13 to 16 are the same roll speed control devices, 17 -19 are low frequency AGC devices for stands 2-4. 20-22 is 2-4
Low pass filter for stand low frequency AGC, 2
3 to 26 are the reduction control devices for stands No. 1 to 4, 2
7 is No. 1 stand reduction feed forward AGC
Equipment, 28-30 are No. 2-4 stand high frequency
AGC device, 31 is metal strip, 32-34
are high-pass filters for high-frequency AGC in stands No. 1 to No. 4, numerals 35 to 38 are entry-side plate thickness deviation detection devices of stands No. 1 to No. 4, and numerals 39 to 42 are plate speed meters.
The portion surrounded by a dashed line in FIG. 1 is a portion added according to the present invention to the conventional AGC shown in FIG. 3. Device 35 for detecting plate thickness deviation on the entrance side of No. 1 stand
is detected and input to the AGC device 27. The AGC device 27 determines the timing based on the plate speed from the plate speed meter 39, and outputs a rolling position change reference ΔSR ₁ according to equation (7), which is applied to the rolling control device 23, which controls the rolling device 9. By moving the roll gap by ΔSR ₁ , the variation in the plate thickness on the exit side of the No. 1 stand based on the variation in the plate thickness on the entrance side of the No. 1 stand will be made zero. The plate thickness deviation remaining in the No. 1 stand and the plate thickness deviation caused by the roll eccentricity of the No. 1 stand are detected by the detection device 36 and input to the filter 32. The filter 32 extracts only the high frequency component (ΔH′ _1h ) of approximately 1 Hz or more from the plate thickness deviation signal and supplies it to the AGC device 28 . The AGC device 28 measures the timing at which the strip having the thickness deviation measured by the detection device 36 reaches the roll bite of the roll 2 based on the signal from the plate speed meter 40, and at the time of arrival, according to equation (7). (However, ΔH ₀ ′ in equation (7) becomes ΔH′ _1h ) Outputs the reduction position change standard ΔSR ₂ ,
The device 24 moves the rolling device 10 and moves the roll gap by ΔSR ₂ , thereby controlling the change in thickness at the entrance side of No. 2 stand by 1 Hz.
An attempt is made to reduce the thickness variation on the outlet side of No. 2 stand to zero based on the above components. Similarly, high frequency components of 1 Hz or more of plate thickness fluctuations that could not be completely removed by stand No. 2 and plate thickness fluctuations of 1 Hz or more caused by roll eccentricity of stand No. 2 are transferred to the high frequency component of stand No. 3.
Remove with AGC. Their roles are: the detection device 37 is the same 36, the plate speed meter 41 is the same 40, the filter 33 is the same 32, the AGC device 29 is the same 28, the reduction control device 25 is the same 24, and the reduction device 11 is the same 10. and,
Roll 3 is the same as roll 2. Similarly, the component of 1Hz or more on the entrance side of stand No. 4 is the high frequency of stand No. 4.
Remove with AGC. Here, the No. 1 stand reduction feed forward AGC device 27 is different from the No. 2 to No. 4 stand high-frequency AGC devices, and can also remove plate thickness fluctuations at low frequencies of 1 Hz or less. This is because the tension of the strip on the entry side of the No. 1 roll is generally kept constant by some means, so even if the strip thickness on the exit side of the No. 1 stand changes by operating the No. 1 stand roll-down device 9, the tension is kept constant by some means. This is because the tension on the entrance side of the No. stand does not change, so the characteristic does not become as shown in FIG. 4 A1, but as shown in the curve A2 shown by the broken line in the same figure.

The plate thickness variation signal detected by the detection device 36 in FIG. 1 is also input to the filter 20. 20 is a low-pass filter, which filters only the frequency components lower than 1 Hz of the signal obtained by the detection device 36 (ΔH′ _1l ).
is passed through and given to the AGC device 17. The device 1
In step 7, the timing at which the strip with the thickness deviation obtained by the detection device 36 reaches the roll bite of the roll 2 is measured using the plate speed signal detected by the plate speed meter 40, and at the time of reaching the roll bite of the roll 2, the equation (10) is calculated. A No. 1 roll speed change command ΔSR ₁ is given to the roll speed control device 13 according to the following (however, H ₁ ′ in equation (10) uses the No. 2 inlet side plate thickness reference, and ΔH ₁ ′ is ΔH′ _1l ). The device 13 changes the rotational speed of the roll drive electric motor 5, and attempts to make the plate thickness variation on the outlet side of the No. 2 stand zero based on the component of 1 Hz or less of the plate thickness variation of the No. 2 stand. Similarly 3
The component of 1 Hz or less of the plate thickness variation on the entrance side of the No. 3 stand is removed by the No. 3 stand low frequency AGC. Its role is that of the entrance side plate thickness deviation detection device 37 and the plate speed meter 41.
corresponds to 40, the filter 21 corresponds to 20, the AGC device 18 corresponds to 17, the roll speed control device 14 corresponds to 13, the roll drive motor 6 corresponds to 5, and the roll 2 corresponds to 1. However, 18 is 14 and 1 at the same time.
A speed change command is also given to roll 3 to keep the speed ratio of rolls 1 and 2 constant. Similarly, the component of 1 Hz or less of the plate thickness variation on the entrance side of the No. 4 stand is removed by the No. 4 stand low frequency AGC.

Among the constituent functions of low frequency AGC, Figure 1 20, 21,
22 low-pass filters can be omitted. The reason for this is, for example, in terms of one stand, Figure 1 1, 5,
The response speed of the roll speed control system consisting of 13 is approximately 2 Hz or less, and the AGC device 1
This is because even if a speed change command of 0 to 20 Hz is given to the roll speed control device 13 through No. 7, the actual No. 1 roll speed does not respond at 2 Hz or higher. However, in that case, in the 1 to 2 Hz region, it interferes with the high frequency AGC and the gain cannot be increased sufficiently, so the filter 20
-22, the effect of the present invention can be fully exhibited. Also, among the components of high frequency AGC, Fig. 132,
The high-pass filters indicated by 33 and 34 can also be omitted if the magnitude of tension fluctuations and the decrease in gain due to interference with low-frequency AGC do not pose too much of a problem in operation, but a sufficient effect cannot be expected unless they are present.

The main component of the present invention is that, in a metal tandem rolling mill that is not equipped with a mechanical device for controlling tension between stands, a rolling device including at least one stand other than the first stand is provided with a roll speed control device that controls plate thickness fluctuations. The objective is to have the roll speed control device, which has a slow response speed, take charge of removing high-frequency components relative to the response speed, and to remove plate thickness fluctuations of relatively low-frequency components. Therefore, embodiments of the present invention need not be limited to the method shown in FIG.
may be a gauge meter AGC.

〔Effect of the invention〕

The present invention is as described above, and according to the present invention, it is possible to remove plate thickness fluctuations in the entire frequency range included in the rolled material of a tandem rolling mill, which could not be removed by conventional plate thickness control devices. This makes it possible to achieve highly accurate plate thickness control in cases where the stands are not equipped with a device for mechanically manipulating the strip tension between the stands, such as in a tandem rolling mill.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a schematic diagram showing a conventional rolling process, Fig. 3 is a block diagram showing AGC of a conventional tandem cold rolling mill, and Fig. 4 is a schematic diagram showing the rolling situation of a conventional tandem cold rolling mill. In order to explain the present invention, FIG.
A graph showing plate thickness fluctuations when operating the rolling down device of a specific stand at various frequencies in AGC,
FIG. 5 is an explanatory diagram showing the rolling situation of the conventional method. In the drawings, 1 to 4 are rolling rolls of the first to fourth stands, 5 to 8 are roll drive electric motors, and 13 to 1 are rolling rolls of the first to fourth stands.
6 is a roll speed control device, 9 to 12 are rolling devices,
23 to 26 are reduction control devices, and 36 to 38 are entrance side plate thickness deviation detection devices.

Claims (1)

[Claims] 1 Equipped with a roll speed control device that controls the rotational speed of the rolls on the stands, and a roll-down control device that controls the roll-down position or rolling force by operating the roll-down device, and roll-down control based on the response speed of the roll speed control device. In a tandem rolling mill for metal strip steel that is constructed with equipment that has a faster response speed and is not equipped with a mechanical device for controlling inter-stand tension such as a looper between the stands, the entrance plate of at least one stand other than the first stand The thickness or exit side plate thickness is detected directly or by calculation, and the plate thickness signal is input to the rolling down control device and the speed control device, and the response speed of the roll speed control device is calculated based on the deviation between the plate thickness signal and its target value. The lowering device of the stand is operated according to the plate thickness deviation signal with a relatively high frequency component compared to the above, and the roll down device of the stand is operated in accordance with the plate thickness deviation signal of other frequency components. A method for controlling plate thickness of a tandem rolling mill, characterized in that the plate thickness at the outlet of the stand is made constant by controlling the speed.