JPS6335328B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant tension control method and apparatus in a continuous rolling mill.

Conventionally, constant tension control in a continuous rolling mill, for example, no-tension control, has been performed by controlling the load current or rolling load of the drive device in each rolling stand of the continuous rolling mill.
Alternatively, the ratio of rolling torque to rolling load was detected at the time of biting, and the detected value was used as a command value to output a speed change command to the drive device so as to maintain the same value even during rolling. For example, in a continuous rolling mill consisting of two rolling stands, a torque detector 29 for detecting the rolling torque of the first stand and a rolling load detector 14 for detecting the rolling load are installed as shown in FIG. and torque detector 2
a calculation device 15 for calculating the ratio between the output signal of 9 and the output signal of the rolling load detector 14;
A storage device 16 that stores the value when the rolled material is bitten.
was provided, and controlled so as to output a speed change command to the speed control device 13 so that the difference between the output signal of the arithmetic unit 30 during rolling and the output signal of the storage device 16 was made zero.

However, such conventional control has the disadvantage that tension or compression force is generated when a temperature drop in the rolled material, skid marks, a change in base material thickness, or other disturbances occur during rolling. In other words, as is clear from the block diagram in Figure 1, since each stand is simply controlled independently, disturbances that cannot be ignored as time passes (for example, various disturbances due to temperature changes in the rolled material, etc.) It has drawbacks that cannot be compensated for.

In addition, in the case of a rolling mill consisting of three or more stands, conventional control will prevent the rolled material between the i-th stand and the (i+1)-th stand from being bitten by the (i+2)-th stand. If the constant tension state is not reached, or if the stand is caught in the next stage before the tension caused by the disturbance is compensated for, perfect constant tension control cannot be achieved in either case.

In other words, constant tension control after the rolled material is bitten by the (i+2)th stand is first performed by controlling the rolling load P(i+1) of the (i+1)th stand immediately after the rolled material is bitten by the (i+1)th stand. ), or rolling torque G(i+1), or their ratio G(i
+1)/P(i+1), then use the stored value as a reference value, compare it with the value at the (i+1)th stand after biting into the corresponding (i+2)th stand, and calculate the (i+1)th stand. i+1) It is based on the principle of deciding the speed command value of the stand.

However, the measured value immediately after the (i+1)th stand is bitten is affected by the tension generated by the impact drop effect, and if there is tension between the (i+1)th stand and the i-th stand, the tension Because of this, the rotational speed of the i-th stand changes, so tension is generated between the i-th stand and the (i+1)-th stand, and its influence is also included.

Therefore, the value immediately after biting into the (i+1)th stand, which is adopted as the value in the no-tension state, is inaccurate as a reference value for subsequent constant tension rolling control.

Therefore, it is necessary to engage the (i+1)th stand in a state where no tension fluctuation occurs between the (i-1)th stand and the i-th stand.

For this reason, for example, in continuous (tandem) rolling, when high-speed operation including acceleration and deceleration is desired, placing constraints on the acceleration and deceleration before the stand engages will increase the speed in order to prevent the generation of tension due to acceleration and deceleration before the stand engages. This has the disadvantage of interfering with the

The present invention has been made to eliminate the above-mentioned drawbacks, and its purpose is to provide a method and apparatus for controlling tension in a continuous rolling mill with high precision.

To help understand the present invention, the principle of the present invention will first be explained using theoretical formulas. As will be clear from the following explanation, the present invention is applied to a continuous rolling mill having two or more rolling stands, but for the sake of simplicity, two stands as shown in FIG. The following describes a rolling stand consisting of:

First, the thickness at the entrance of the first stand is H, the thickness at the exit side is hm, the thickness at the exit side of the second stand is h, the detected values of rolling torque and rolling load in the first stand, and the radius of the work roll are G ₁ , respectively. Assuming that P ₁ , R ₁ , those of the second stand are G ₂ , P ₂ , R ₂ , and the inter-stand tension is T, the relationships of equations (1) and (2) are established between these.

G ₁ =2λ ₁・P ₁・l ₁ −R ₁ T ……(1) G ₂ =2λ ₂・P ₂・l ₂ +R ₂ T ……(2) However, l ₁ and l ₂ are each stand 1 and the contact arc length of 2, λ ₁ is the torque arm coefficient. The product λ ₁ ·l ₁ is called the torque arm.

By transforming equations (1) and (2), it can be seen that equation (3) holds true at any time during rolling.

(R ₁ /P ₁ +R ₂ /P ₂ )T=(2λ ₁・l ₁ −2λ ₂・l ₂ ) −(G ₁ /P ₁ −G ₂ /P ₂ ) ………(3) The above equation The first term on the right side is expressed as a function of the contact arc length of both stands.

The contact arc lengths l ₁ and l ₂ themselves are a function of the reduction amount and decrease as the temperature of the rolled material decreases, but since the contact arc lengths of both stands change with temperature to the same degree, the first term on the right side Changes due to temperature are canceled. In other words, the temporal change in the first term on the right side during rolling is smaller than the change in the contact arc length itself. Therefore, if the first term on the right side is determined at a certain timing, the influence of temperature changes in the rolled material during subsequent rolling on the tension can be ignored.

Next, a method for determining the value of the first term on the right side will be explained.

In equation (1) above, before the rolled material is bitten by the second stand, the tension T between the stands is zero, so if we express the state at that time with a subscript ₀ , the torque arm λ ₁₀ at the first stand - l ₁₀ can be expressed as in equation (4) using the torque detection signal G ₁₀ and the rolling load signal P ₁₀ .

2λ ₁₀・l ₁₀ = (G ₁ /P ₁ ) ₀ ...(4) Also, if we add the subscript b to indicate the state of tension generated immediately after the rolled material is bitten by the second stand, (5) ,
The relationship is as shown in equation (6).

G ₁ b＝2・λ ₁ b・P ₁ b・l ₁ b−R ₁・Tb …(5) G ₂ b＝2・λ ₂ b・P ₂ b・l ₂ b＋R ₂・Tb …(6) If Tb is eliminated from these two equations, the torque arm λ ₂ b·l ₂ b at the second stand satisfies equation (7).

2λ ₂ b・l ₂ b=(G ₂ /P ₂ )b+R ₁ /R ₂ (P ₁ /P ₂ )b {(G ₁
/P ₁ )b −2λ ₁ b・l ₁ b} …(7) Here, the torque arm of the first stand λ ₁₀・l ₁₀
If calculated just before the rolled material is bitten into the second stand, the torque arm λ ₁ b·l ₁ b immediately after biting becomes approximately equal to λ ₁₀ ·l ₁₀ . That is, 2λ ₁ b·l ₁ b2λ ₁₀ ·l ₁₀ = (G ₁ /P ₁ ) ₀ holds true.

At this time, if formula (7) is defined as (G ₂ /P ₂ ) ₀ , (G ₂ /P ₂ ) ₀ ≡2λ ₂ b・l ₂ b = (G ₂ /P ₂ )b−R ₂ /R ₁ (P ₁ /P ₂ )b・{(G ₁ /P ₁ )
₀ − (G ₁ /P ₁ ) b} …(8) As mentioned above, if the changes in the contact arc length of both stands during rolling are equal, the torque arm in the first term on the right side of equation (3) above is The difference between is expressed as follows.

2λ ₁・l ₁ −2λ ₂・l ₂ = 2λ ₁ b・l ₁ b−2λ ₂ b・l ₂ b = (G ₁ /P ₁ ) ₀ − (G ₂ /P ₂ ) Summarize the results of ₀ or more and (3) can be expressed as the following equation (9).

(R ₁ /P ₁ +R ₂ /P ₂ )T= {(G ₁ /P ₁ ) ₀ − (G ₂ /P ₂ ) ₀ } − {(G ₁ /P ₁ )−(
G ₂ /P ₂ )}...(9) Here, (G ₁ /P ₁ ) ₀ is the ratio of the rolling torque and rolling load of the first stand before the second stand bites, and (G ₂ /P ₂ ) ₀ is given by equation (10).

(G ₂ / P ₂ ) ₀ = (G ₂ / P ₂ ) b − R ₂ / P ₁ (P ₁ / P ₂ ) b {(G ₁ / P ₁ ) ₀ − (G ₁ / P ₁ ) b
}...(10) In the above equation (9), the difference between the ratio of rolling torque and rolling load in the two stands (G ₁ /P ₁ ) - (G ₂ /P ₂
) is controlled to be equal to (G ₁ /P ₁ ) ₀ − (G ₂ /P ₂ ) ₀ , constant control with zero tension can be achieved. That is,
Since the right side of equation (9) corresponds to the tension T, constant control with zero tension can be achieved by adjusting the speed of the drive motor of the rolling stand so as to make this value zero. By controlling the motor speed so that the value on the right side becomes a predetermined target tension, so-called constant tension control can be realized.

In order to further clarify the features of the present invention, a case will be described in which the control principle of constant tension control described above is applied to a continuous rolling mill having three rolling stands.

FIG. 3 schematically shows three stands. In addition, G, P, and R in the figure are rolling torques, respectively.
It shows the rolling load and roll radius, and the subscript matches the number attached to the corresponding stand.

First, if there is a tension T ₁ between the first stand and the second stand, and a tension T ₂ between the second stand and the third stand, then equations (11), (12), and (13) are applied. holds true.

G ₁ =2λ ₁・P ₁・l ₁ −R ₁・T ₁ …(11) G ₂ =2λ ₂・P ₂・l ₂ +R ₂・T ₁ −R ₂・T ₂ …(12) G ₃ =2λ ₃・P ₃・l ₃ +R ₃・T ₂ ...(13) Here, 2λ ₁
Define the value of l ₁ as (G ₁ /P ₁ ) ₀ , and further (14),
Define it as shown in equation (15).

(G ₂ /P ₂ ) ₀ ≡ (G ₂ /P ₂ )(2)/b− R ₂ /R ₁・(P ₁ /P ₂ )(2)/b・{(G ₁ /P ₁ ) ₀ −(G ₁ /
P ₁ )(2)/b} ………(14) (G ₃ /P ₃ ) ₀ ≡ (G ₃ /P ₃ )(3)/b− R ₃ /R ₂・(P ₂ /P ₃ ) (3)/0・{(G ₂ /P ₂ ) ₀ −(G
₂ /P ₂ ) (3) / b} ... (15) Here, 〓 ⁽ⁱ⁾ _b indicates the actual value immediately after the i-th stand is caught. Note that (G ₁ /P ₁ ) ₀ corresponds to the torque arm in an apparent tension-free state. Strictly speaking, it is twice the value of the torque arm in the apparent tension-free state at the i-th stand (see equation (4)).

At this time, from equations (11) to (13), (2λ ₁・l ₁ −
2λ ₂・l ₂ ) and (2λ ₂・l ₂ −2λ ₃・l ₃ ) and eliminate them in the same way as in the case of 2 stands, (16)
(17) The formula stands.

(R ₁・R ₂ /P ₁・P ₂ +R ₂・R ₃ /P ₂・P ₃ +R ₃・R ₁ /P ₃・P ₁ )
T ₁ = (R ₂ /P ₂ + R ₃ /P ₃ )x + R ₂ /P ₂ y ... (16) (R ₁・R ₂ /P ₁・P ₂ +R ₂・R ₃ /P ₂・P ₃ +R ₃・R ₁ /P ₃・P ₁ )
T ₂ = R ₂ /P ₂ x+ (R ₁ /P ₁ +R ₂ /P ₂ )y (17) Here, x and y are each (18),
It is shown by equation (19).

x={(G ₁ /P ₁ ) ₀ −(G ₂ /P ₂ ) ₀ }−{G ₁ /P ₁ −G ₂ /P ₂
}……(18) y={(G ₂ /P ₂ ) ₀ −(G ₃ /P ₃ ) ₀ }−{G ₂ /P ₂ −G ₃ /P ₃
} ......(19) From both formulas (16) and (17), the tension between the stands T ₁ ,
To make T ₂ zero, x and y should be made zero at the same time. In other words, in order to perform constant tension control with zero tension, the difference between the torque arms of adjacent stands (G _i /P _i ) - (G _i /P _{i+1 ) is calculated from equations (18) and (19} ). G _i /P _i ) ₀
−(G _i+1 /P _i+1 ) The speeds of adjacent stands should be corrected so that they are always equal to ₀ .

As a result of the above, the speed change amount of the i-th stand (ΔN/
N) When the second stand is used as a key stand, i is (ΔN/N) _1i = α・X ………(20) (ΔN/N) ₃ = β・Y……(21) Here where α and β are the gains of dimension change.

Generally, to perform constant tension control, the torque arm difference between adjacent stands is controlled to a value commensurate with the target tension.

FIG. 4 is a control block diagram explaining the tension control of the present invention. Each stand has a load cell LC for detecting the rolling load P, and the rolling rolls are linked with a motor having an automatic speed control ASR system.

The detected values of the rolling load of the adjacent stand and the motor load torque are respectively sent to the control system HTFC,
A command value that makes the tension between the stands zero is output to the ASR system from the aforementioned equations (14) to (19).

Hereinafter, the specific configuration of the control device will be explained using FIG. 5.

In FIG. 5, 1, 2, and 3 are numbers attached to the stands in the rolling direction, and 4 is a thyristor device, which converts the alternating voltage of the AC power supply (not shown in the figure) into DC voltage. 5 is an electric motor for driving the rolling roller of each rolling stand, 6 is a speed generator that detects the rotation speed of the driving electric motor 5, 7 is a current detector that detects the main circuit current flowing through the electric motor 5, and 8 is a field current.
A field current detector that detects IF; 9 is a function generator that inputs the output IF of the field current detector 8 and outputs the field strength φ; 10 is the output of the function generator 9 and a current detector a multiplier for calculating the product with the output of 7; 11;
12 is a conversion gain device that inputs the output of the differentiator 11 and converts it into acceleration torque, and subtracts this output from the output of the multiplier 10. and the rolling torque G is obtained. 13 is a speed control device that outputs a firing angle command to the thyristor device 4 for controlling the speed of the driving electric motor 5; 14 is a load cell that detects the rolling load of each stand; 15 is the ratio of rolling torque to rolling load ( G/P) divider, 16
a is a storage device that stores the output of the divider 15 after the first stand is engaged, and 16b is a storage device that stores the apparent tension-free rolling torque calculated by equation (14) immediately after the second stand is engaged. A memory device 16c stores the ratio of the rolling torque to the rolling load, 16c stores the ratio of the rolling torque in the no-tension state to the rolling load calculated by equation (15) immediately after the third stand is bitten, and 17a stores the ratio of the rolling torque to the rolling load. The one-shot relay 17b is switched on before the stand is engaged, the one-shot relay 17b operates immediately after the rolled material is engaged in the second stand, and the one-shot relay 18 is operated immediately after the third stand is engaged.

19 is a divider that calculates the ratio of the rolling loads of adjacent stands; 20 is a gain device that multiplies the output of the divider 19 by the ratio of the roll diameters of the same pair of stands;
1 is a multiplier that calculates the product of the difference in the rolling load ratio G/P of the rolling torque immediately after biting and before biting and the output of the gain device 20, and 22 is a multiplier that calculates the product of the above-mentioned equations (18) and (19).
A conversion gain device 23 is an integrator that converts the amount corresponding to the right-hand side of into a speed change amount. Also 25, 26
is an arithmetic circuit that calculates the speed change amount expressed by equation (20) or (21) from the outputs of the dividers 15 and 19. This arithmetic circuit is the control system HTFC mentioned above.
It is.

This embodiment is an example using the control method according to the above-mentioned equations (14) to (19). First, the rolled material is bitten by the first stand, and before it is bitten by the second stand, the rolling torque and rolling load related to the first stand are detected, their ratio is calculated by the divider 15, and the storage device 16a to be memorized. After the one-shot relay 17 is operated in conjunction and 17a is opened, the rolled material is bitten into the second stand. At this time, the divider 15 regarding the rolling stand 1
The torque arm equivalent amount (G ₂ /P ₂ ) ₀ for the second stand is calculated from the output of the storage device 16a and the output of the divider 19, and is stored in the storage device 16b. Until the rolled material is sucked into the third stand, the output of the divider 15 of the first stand and the second
The difference between the dividers 15 of the stands is taken, and the difference between the outputs of the storage devices 16a and 16b is calculated, and the speed of the first stand is controlled so that the difference between the two becomes zero. Furthermore, immediately after the third stand is engaged, the one-shot relay 18 is activated, the above-mentioned equation (15) is calculated, and the torque arm equivalent amount (G ₃ /P ₃ ) ₀ is stored in the storage device 16c. .
The operation during rolling after the third stand is bitten is
The rolling of the first rolling stand is performed so that the value obtained by subtracting the difference between the outputs of the storage devices 16a and 16b from the difference between the output of the divider 15 of the stand and the output of the divider 15 of the second stand is zero. The storage device 16b controls the speed and at the same time calculates the difference between the output of the divider 15 of the second stand and the output of the divider 15 of the third stand.
The rolling speed of the third stand is controlled so that the value obtained by subtracting the difference between the outputs of and 16c becomes zero. This control makes it possible to realize tension-free control that does not generate tension between the rolling stands.

The above-mentioned embodiment of the present invention shows an example in which the present invention is implemented in a continuous rolling mill having three rolling stands, but as is clear from the above explanation of the principle, the present invention can Needless to say, it can also be applied to a continuous rolling mill having a FIG. 6 shows an example in which the present invention is implemented in a continuous rolling mill having three rolling stands, and in this embodiment, the key stand is selected as the first stand. Then, the speed commands are changed by the two control systems HTFC for the second stand and the third stand. In this case, succession is required to prevent speed modifications of one pair of stands from creating tension in the other pair of stands.

The example shown in FIG. 6 is the same as the example shown in FIG. 5 except that a succession is provided between the second and third stands.

In a continuous rolling mill with three or more stands, in order to improve product accuracy, it is necessary to use the last stand as a key stand and provide inter-stand succession for all stands except the last stand. Therefore, the example of FIG. 6 can be easily extended to a continuous rolling mill with three or more stands.

Further, in explaining the present invention, an example applied to strip steel rolling has been described, but it is clear from the description of the present invention that the present invention can be easily applied to steel bar rolling, shape steel rolling, etc.

FIG. 7 is an example in which the principle of the present invention is applied to tension control, and shows an apparatus for applying arbitrary tension to a rolled material when rolling is performed in a rolling mill consisting of two stands.

Note that although the circuit for detecting rolling torque and rolling load is omitted in this figure, it is omitted because the same circuit as the detection circuit shown in FIG. 5 etc. can be used. Further, the control system HTFC 25 is composed of the same circuit as the control system 25 shown surrounded by broken lines in FIG.

Here, if the set value of tension is T and the amount of variation in tension caused by disturbance is ΔT, the following relationship is established according to the above-mentioned equation (9).

(R ₁ /P ₁ +R ₂ /P ₂ ) (+ΔT) = {(G ₁ /P ₁ ) ₀ − (G ₂ /P ₂ ) ₀ } − {(G ₁ /P ₁ ) −
(G ₂ /P ₂ )} ………(22) ∴(R ₁ /P ₁ +R ₂ /P ₂ )ΔT={(G ₁ /P ₁ ) ₀ − (G ₂ /P ₂ )
₀ } −{(G ₁ /P ₁ )−(G ₂ /P ₂ )}−(R ₁ /P ₁ +R ₂ /P ₂ )
......(23) The tension ΔT caused by disturbance changes the plate thickness, so the right side is controlled to make it zero. Since the difference between the first and second terms on the right side is the output of the control system HTFC, a block diagram is constructed in which the third term is subtracted from the output.

Clearly, in the case of FIG. 7, any constant tension can be generated. Therefore, by arbitrarily selecting the tension setting value, the inter-stand tension can be controlled to an arbitrary constant value.

As an example of controlling the tension to a constant value, we have shown an example in the case of two stands, but in the case of rolling with three or more stands, by giving a target value for the tension between each stand, it is possible to control the tension to a constant value. Similarly, constant tension control is possible.

In addition, the tensionless rolling control of three stands (20),
When performing this based on equation (21), the tension T ₁ does not necessarily need to be zero when the third stand is engaged. That is, (G ₃ /P ₃ ) ₀ to be memorized is
It can be obtained by calculation using the detected value at the time of biting in (14). Furthermore, in the conventional method, as described above, TT ₁ is required to be zero.
When performing high-speed rolling, the rolled material may be accelerated by both the first and second stands before the third stand bites. Therefore, the tension T 1 is not necessarily zero when the third stand bites, and the tension T ₁ is not necessarily zero when the third stand bites. The method includes
There were restrictions on increasing speed. In the example described above,
Since this drawback has been overcome, productivity can be expected to improve.

As described in detail above, according to the present invention, since the temperature drop of the rolled material and disturbances caused by skid marks etc. are canceled out by adjacent stands, highly accurate constant tension control can be realized. It can be understood from the following that the tension control according to the present invention is much more precise than the conventional one. Regarding the conventional method of controlling the ratio of rolling torque and rolling load in a single stand to a constant level,
According to calculations, the change in the torque arm was approximately 1 mm. At this time, the rolling load at the leading end of the rolled material was approximately 950 [ton], the rolling load at the rear end was approximately 1150 [ton], and the mill constant was 400 [ton/mm]. The difference in load between the leading and trailing ends of the rolled material was approximately 200 tons, and this is thought to be due to the temperature drop. When the change in torque arm Δl ₁ is 1 [mm], the amount of unit tension change Δt _E is calculated as follows.

Δt _E = Δl ₁ /R ₁ /P ₁ /S = Δl ₁・P ₁ /R ₁・S = 1 [mm] ・1150 [ton] / 350 [mm] ・20000 [m
m ² ] ≒0.16 [Kg/mm ² ] where R is the roll diameter and S is the cross-sectional area of the rolled material.

In the tension control according to the present invention, since the changes in the torque arm are canceled out in the adjacent stands as shown in equation (3), Δl ₁ and Δl ₂ are approximately 1 [mm] as described above.
If there is, the change will be a value of Δl ₁ −Δl ₂ and will be canceled to a value close to zero. Δl ₁ =
1 [mm] and Δl ₂ =0.9 [mm], and when the control of the present invention is performed using the same rolling mill as described above, the tension fluctuation is estimated as follows.

Δt _E = Δl ₁ −Δl ₂ /R ₁ /P ₁ +R ₂ /P ₂ )/S = 1.0 [mm] - 0.9 [mm] / 350 [mm] / 1150 [ton] +
350 [mm] / 1050 [ton] / 20000 [mm] ² ≒0.008 [Kg/mm ² ] However, R ₁ = R ₂ = 350 [mm] Generally, between the first and second stands of a hot finishing mill Since the target tension is about 0.20 [Kg/mm ² ], it is clear that the tension fluctuation of about 0.20±0.16 [Kg/mm ² ] caused by the conventional method poses a problem. In the tension control according to the present invention, the error is at least one order of magnitude smaller than that of the conventional method, so there is almost no effect on the plate thickness, shape, etc. due to tension fluctuations.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of a tensionless control device in a conventional continuous rolling mill, Figures 2 and 3
The figure is an explanatory block diagram for explaining the control principle of the present invention, FIG. 4 is a block diagram showing one embodiment of the present invention, FIG. 5 is a block diagram showing some details of FIG. 4, and FIG. 7 are block diagrams showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... First rolling stand, 2... Second rolling stand, 3... Third rolling stand, 4... Thyristor device, 5... Roller drive electric motor, 6... Speed generator,
7... Current detector, 8... Field current detector, 9... Function generator, 10, 21... Multiplier, 11... Differentiator, 1
2, 20...gain device, 13...speed control device, 1
4... Rolling load detector, 15, 19... Divider, 16
...Storage device, 17,18...One-shot relay,
22...Conversion gain device, 23...Integrator, 25,
26...Control circuit.

Claims (1)

[Scope of Claims] 1. At least two or more rolling stands, a drive device including an automatic speed control device for an electric motor for driving the rolling rolls of the rolling stands, and a rolling load for detecting the rolling load of the rolling stands. In a method for controlling inter-stand tension of a rolled material rolled in a continuous rolling mill having a detector, the electric motor in the i-th stand before the rolled material is bitten by the (i+1)-th stand counting in the rolling direction. Calculate the rolling torque of the i-th stand from the voltage, current, and speed detection signals, and detect the rolling load at the same time as the detection of the voltage, etc. using a rolling load detector, and when the i-th stand is the first stand, The ratio of the calculated rolling torque and the detected rolling load is stored as the reference value of the ratio [(G _i /P _i ) ₀ ], and when the i-th stand is the second stand or a subsequent rolling stand. is the rolling torque/load ratio [(G _i /P _i )] of the i-th stand, the roll radius ratio and rolling load ratio of the i-th stand and the (i-1)-th stand, and the (i-1)-th stand. Rolling torque corrected from the difference between the rolling torque/load ratio stored as the standard value of the stand and the rolling torque/load ratio of the i-th stand before the rolled material is bitten by the (i+1)-th stand・The load ratio is stored as the reference value of the ratio of the i-th stand [(G _i /P _i ) ₀ ], and the difference in rolling torque/load ratio between the (i-1)th stand and the i-th stand [(G _i-1 /P _i-1 ) - (G _i /P _i )]
is the difference in rolling torque/load ratio stored as the reference value of the i-th stand and the (i-1)th stand [(G _i-1 /P _i-1 ) ₀ − (G _i /P _i ) ₀ ] so that the i-th
1. A tension control method for a continuous rolling mill, characterized in that the tension of a rolled material is controlled by correcting the speed of a drive motor of a stand or the (i-1)th stand. 2. A continuous rolling mill comprising at least two or more rolling stands, a drive device including an automatic speed control device for an electric motor for driving the rolling rolls of the rolling stands, and a rolling load detector for detecting the rolling load of the rolling stands. In a tension control device that controls the inter-stand tension of a rolled material rolled in a rolling mill, the voltage and current of the motor at the i-th stand before the rolled material is bitten by the (i+1)th stand counting in the rolling direction. and a calculation means that calculates the rolling torque of the i-th stand from the speed detection signal, a rolling load detector that detects the rolling load at the same time as the detection of the voltage, etc., and when the i-th stand is the first stand, the i-th stand is the first stand. a storage means for storing the ratio of the calculated rolling torque and the detected rolling load as a reference value [(G _i /P _i ) ₀ ]; and when the i-th stand is a second stand or a subsequent rolling stand; The rolling torque/load ratio [(G _i /P _i )] of the i-th stand is the roll radius ratio and rolling load ratio of the i-th stand and the (i-1)-th stand, and the (i-1)-th stand means for performing a correction calculation from the difference between the rolling torque/load ratio stored as a reference value for the rolling material and the rolling torque/load ratio of the i-th stand before the rolled material is bitten by the (i+1)-th stand; a storage means for storing the corrected rolling torque/load ratio as a reference value [(G _i /P _i ) ₀ ] of the i-th stand; and rolling torque/load of the (i-1)-th stand and the i-th stand. Difference in ratio [(G _i-1 /P _i-1 )−(G _i /P _i )]
is the difference in rolling torque/load ratio stored as the reference value between the i-th stand and the (i-1)th stand [(G _i-1 /P _i-1 ) ₀ − (G _i /P _i ) ₀ ] so that the i-th
A continuous rolling mill comprising: a speed control device that corrects the speed of a drive motor of a stand or the (i-1)th stand and controls the speed according to the corrected speed; and controls the tension of a rolled material. tension control device.