JPS6243763B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling tension applied to a rolled material caught between rolling stands of a tandem rolling mill.

Tandem rolling mills require various conditions to be kept constant in order to roll the rolled material into a uniform thickness, width, and shape from the tip to the tail.

In particular, fluctuations in tension between stands have an important effect on thickness, width, shape, etc., and controlling this tension to a constant level is essential for stable rolling operations.

In hot rolling, in which the rolled material is heated to a high temperature to facilitate plastic deformation, a slight variation in tension greatly affects the dimensions and quality of the rolled product. Moreover, this tension fluctuation causes accidents such as plate breakage.

Therefore, in order to carry out stable rolling operations, it is necessary for the rolling equipment to include tension control means. For example, a hot finish rolling mill that performs plate rolling is provided with a mechanical tension control means called a looper. Tension control using this looper is performed as follows. In other words, after the tip of the rolled material reaches the i-th stand of the rolling mill, the next i+1-th stand
When the stand is engaged, the looper provided between the stands rises up, and thereafter the looper is controlled to form a loop until the end of rolling to prevent the generation of excessive tension. However, in systems using such a looper, there is a problem in that excessive tension is generated when the looper rises, resulting in a decrease in plate thickness accuracy.
This system also handles various external disturbances during rolling, such as temperature drop in the longitudinal direction of the rolled material (thermal
Rundown), skid marks, etc. may cause unstable operation, resulting in excessive tension or damage to the rolled material. Furthermore, the environment in which the looper is used is extremely hot and humid, making it difficult to maintain its performance.

In addition, such a system can only be used for plate rolling, and cannot be used for rolling shaped steel, steel bars, or the like.

In order to solve these problems, methods have been proposed for electrically non-contact detection and control of tension. For example, in US Pat. No. 3,940,960, tension control is performed using the ratio of rolling torque to rolling load. The operation of this US patent is as follows. After the rolled material is bitten by the first stand and before it is bitten by the subsequent adjacent second stand,
The rolling load P ₁₀ and rolling torque G ₁₀ of the first stand are detected, and the ratio G ₁₀ /P ₁₀ is stored. This is the first
The exit side of the stand shows the torque arm in a non-tensioned state. After that, the rolling loads P _1B , P _2B and rolling torques G 1B , G _2B of the first stand and the second stand, respectively, immediately after the rolled material is bitten by the second stand are detected, and from these detected values, the _first stand is determined. Calculate the second stand torque arm G ₂₀ /P ₂₀ when the two stands are in a non-tensioned state.
After that, the difference (G 10 /P 10 ) - (G ₁ /P ₁ ) between the torque and load ratio G 1 /P 1 during rolling in the first stand and the stored value of the first stand, and the difference (G ₁₀ /P ₁₀ ) - (G ₁ /P ₁ ) in the second stand The difference between the torque and load ratio G ₂ /P ₂ during rolling and the stored value of the second stand (G ₂₀ /P ₂₀ ) - (G 2 /P ₂ ) is adjusted so that the difference (G ₂₀ /P 20 ) - (G 2 /P 2 ) is equal. Control speed. This controls the tension to be constant.

Such electrical tension control is employed in rolling equipment for steel shapes and bars, as well as hot rough rolling mills, and greatly contributes to the realization of stable operations.
In many cases, in these rolling operations, automatic adjustment of the roll opening degree to control dimensions is not performed.
On the other hand, in hot finish rolling, the roll opening degree is actively changed in order to control the plate thickness with high precision. In hot finish rolling, it has become clear that fluctuations in tension appear when the tension is controlled by the method described above in which the difference in the torque-load ratio of adjacent stands is controlled to be constant. . Therefore, a problem arises when this technique is applied to a hot rolling mill that involves changing the roll opening. especially,
In finish rolling, since the thickness of the rolled material is becoming thinner, such slight tension fluctuations have a considerable effect.

An object of the present invention is to provide a tension control method with high control accuracy in a tandem rolling mill.

Another object of the present invention is to provide a tension control method suitable for rolling with a hot finish tandem rolling mill.

Another object of the present invention is to detect tension in a non-contact manner;
An object of the present invention is to provide a tension control method and device that can realize tension control with high precision.

Another object of the present invention is to provide a tension control method that has a simple configuration and can control tension with fairly high accuracy.

Other objects of the invention will become apparent from the following description of the drawings and embodiments of the invention.

In the present invention, in a hot rolling mill that involves changing the roll opening degree, tension is determined using a relational expression between rolling load, rolling torque, and torque arm, and the tension is controlled so that the difference from the target tension becomes zero. In other words, the torque arm included in this equation is changed from time to time. The tension is calculated directly based on the detected values of two of the parameters: entry side plate thickness, exit side plate thickness, roll opening rolling load, and using the calculated torque arm, rolling load, and rolling torque, Control is performed so that there is no difference from the target tension. In addition, in the present invention, the torque arm is determined as the sum of the torque arm when no tension is applied and the amount of change in the torque arm thereafter, and the tension is determined from the determined torque arm, rolling load, and rolling torque, and the difference from the target tension is determined. control so that it becomes zero. Note that the amount of change in the torque arm is calculated from two detected values among the amount of change in the inlet side plate thickness, the amount of change in the outlet side plate thickness, the amount of change in the roll opening degree, and the amount of change in the rolling load.

Other features of the invention will become apparent from the description below.

Hereinafter, the present invention will be explained in detail using the drawings.

First, before describing specific embodiments of the present invention,
The basic principle of the present invention will be explained. In this explanation, a tandem rolling mill having two stands shown in FIG. 1 will be taken as an example. However, the present invention
The present invention is not limited to a tandem rolling mill configured with two stands, but can also be applied to a tandem rolling mill configured with three or more stands.

Now, in FIG. 1, numeral 1 indicates the rolled material being rolled, 21 and 22 the back-up rolls of the respective rolling stands, 31 and 32 the work rolls, and 4
1 and 42 are main motors that drive the work rolls 31 and 32, respectively; 51 and 52 are load detectors (for example, load cells) that detect the rolling loads of the respective stands; and 61 and 62 are the work roll opening degrees of the respective stands. A roll opening degree detector is used to detect the roll opening degree, 7 is a plate thickness detector (for example, meray) that detects the plate thickness on the entrance side of the rolling stand, and 20 is a rolling torque calculation device that calculates rolling torque using a formula described later. Here, of the equipment shown in FIG. 1, all except 20 are equipment included in a normal rolling mill, and are not specially provided for the present invention.

As is well known, according to rolling theory, the rolling torques G ₁ and G ₂ of the first stand and the second stand are expressed by the following equations.

However, l ₁ , l ₂ : torque arm, R ₁ , R ₂ : roll radius, P ₁ , P ₂ : rolling load, T : tension between stands.
Represents a stand.

The rolling torque G ₁ in equations (1) and (2) is obtained using the following equation, which is well known in the rolling torque calculation device 20.

G ₁ =V ₁・I ₁ /ω ₁ −J ₁ dω ₁ /dτ−G _LOSS (ω
₁ )(3) However, I ₁ : Motor main circuit current V ₁ : Motor terminal voltage ω ₁ : Motor angular speed τ: Time J ₁ : Moment of inertia G _LOSS ω ₁ : Motor rotation loss torque (This is the motor angular speed ω ₁ and is measured in advance.) The first term on the right side of equation (3) represents the motor torque, and the second term
The term represents the acceleration torque of the motor. The rolling loads P ₁ and P ₂ in equations (1) and (2) can be detected by load cells 51 and 52.

Using equations (1) and (2), the tension T can be expressed in various ways.

An example of the tension equation is expressed as follows using equations (1) and (2).

Further, another tension equation can be expressed as follows from equation (1).

T=2l ₁ P ₁ −G ₁ /R (5) Rolling torque G ₁ and rolling load P ₁ in equations (4) and (5)
can be known by calculation or direct detection, so if the torque arms l ₁ and l ₂ are known, the tension can also be found from equation (4) or (5).

In US Pat. No. 3,940,960 described in the conventional example, tension is detected and controlled using the approximation equation (4) described above. That is, this U.S. patent no.
In No. 3940960, when there is no tension (i.e. when biting)
It is assumed that the torque arm difference (l ₁₀ - l ₂₀ ) and the subsequent torque arm difference (l ₁ - l ₂ ) are almost the same. In other words, the influence of this torque arm is ignored when determining the tension deviation by setting (l ₁₀ −l ₂₀ )−(l ₁ −l ₂ )≈0. For this reason, in reality, hot rolling that involves changing the roll opening degree includes detection errors, resulting in a decrease in control accuracy.

It is known that this torque arm l _i is expressed as follows.

However, λ: Torque arm coefficient (λ〓0.4) H _i : Plate thickness at the entrance of the i-th stand h _i : Plate thickness at the exit of the i-th stand c: Hitsuchikoku constant (0.000214) b: Average plate width Also, the gauge meter equation h _i By substituting =S _i +P _i /K _i into equation (6), l _i can also be obtained from equation (7).

However, K _i is the spring constant of the mill. Therefore, if the inlet plate thickness H _i or the outlet plate thickness h _i changes, or by automatic plate thickness control, the roll opening degree S _i
It can be seen that when moving , the value of torque arm l _i also changes. As can be seen from equation (7), H
The value of the torque arm is determined from the detected values of _i , h _i and S _i . S _i can be detected by the roll opening measuring device 61. Furthermore, by expressing the outlet plate thickness h _i using the above-mentioned gauge meter equation, the torque arm l _i can also be obtained as in the following equation.

Further, the inlet plate thickness H _i can be detected by the plate thickness detector 7 in the first stand, and the outlet plate thickness of the first stand (gauge meter type h _i =S _i
+P _i /K _i ) which is synchronized with the inter-stand tracking of the rolled material gives the plate thickness H ₂ at the entrance of the second stand.

In this way, the torque arm can be directly determined from equations (6) to (8). Therefore, the torque arm obtained in this way may be applied to the above equations (4) and (5). However, H _i , h _i , S _i , obtained using this method,
P _i includes various errors. For example, if the zero point of the rolling position changes due to roll wear, heat crown, etc., an error will be included in the opening degree S. If the opening degree S includes an error, H _i and h _i determined by the gauge meter method also include an error. It also includes detector drift errors.

Next, a torque arm calculation method with little measurement error will be described.

The torque arm of the i-th stand, l _i, is expressed by the following equation.

l _i =l _i0 +Δl _i (9) Here, l _i0 represents a torque arm reference value which will be explained below, and Δl _i represents the amount of torque arm change after l _i0 calculation. The torque arm reference value l _i0 of the first stand is determined before rolling starts on the second stand. For example, just before rolling starts on the second stand, no tension has been generated in the rolled material yet, so equation (1) shows that T
By setting = 0, it can be obtained from the following equation.

2l ₁₀ =G ₁₀ /P ₁₀ (10) However, the subscript "0" for the rolling torque and rolling load indicates that the data is when calculating the torque arm reference value l ₁₀ . The torque arm l ₂ in the case of the second stand is expressed as follows from equations (1) and (2).

2l ₂ =G ₂ /P ₂ -R ₁ /R ₂ P ₂ /P ₁ (2l ₁ -G ₁
/P ₁ }(11) The torque arm l ₂ immediately after the second stand engages is set as the torque arm reference value of the second stand. In other words, the subscript B is added to the data immediately after the second stand bites.
2l ₂₀ = G _2B /P _2B - R ₁ /R ₂ P _2B /P _1B {
2l _1B −G _1B /P _1B }(12) Here, the torque arm l _1B in the first stand when the rolled material bites into the second stand is (10)
It is considered to be equal to l ₁₀ obtained by Eq. In other words, l ₁₀ is obtained from the detected value at the time after the first stand is engaged, and the time up to immediately after the second stand is engaged is extremely short, and it is thought that there is no change in the torque arm during that time.

Therefore, equation (12) can be written as equation (13).

2l ₂₀ =G _2B /P _2B -R ₁ /R ₂ P _2B /P _1B (
G ₁₀ /P ₁₀ −G _1B /P _1B ) (13) Therefore, l ₁₀ and l ₂₀ can be determined using equations (10) and (13).

Next, how to obtain the amount of change Δl _i in the torque arm will be described.

From equation (6), the amount of change Δl in the torque arm when H, h, and S change by ΔH, Δh, and ΔS is expressed by the following equation.

Δl=∂l/∂HΔH+∂l/∂hΔh+∂l/∂S
ΔS = λ ² R/2l ₀ {ΔH+(c/bK-1)Δh-
c/bKΔS} (14) Also, if we write the gauge meter equation in the form of deviation, Δh=
Since ΔS+ΔP/K is obtained, when this is applied to equation (14), the following equation holds true.

Δl=λ ² R/2l ₀ {ΔH+(c/b-1/K)Δ
P−ΔS} (14′) Δl=λ ² R/2l ₀ {ΔH+c/bΔP−Δh}(
14'') Since ΔH, Δh, ΔS, and ΔP are in the form of deviations, the measurement errors mentioned above are canceled.
Therefore, the influence of detection error on Δl is extremely small.

Therefore, it is clear that the torque arm l _i expressed by equation (9) can be determined with high accuracy by determining the amount of change Δl _i .

The above can be summarized as follows.
The torque arm l at each point during rolling is determined by the standard torque arm of the stand and the amount of change in the torque arm obtained using the detected values of the inlet side plate thickness, outlet side plate thickness, roll opening degree, and rolling load of the stand. required from. In this invention, focusing on this point, the inter-stand tension is calculated using the torque arm at each time point obtained, the rolling load and the rolling torque detected at that time, and the tension between the stands is calculated using the torque arm at each time point obtained. Tension adjustment means such as motor speed and reduction position are adjusted to zero the deviation between the tension and the target tension.

An embodiment of the present invention based on such a principle will be described. Figures 2a to 2c show an example in which the present invention is applied to a two-stand tandem rolling mill. In FIG. 2, the same numbers as in FIG. 1 indicate devices having the same functions.

In FIG. 2a, 81 is a motor speed control device, and the speed of the motor 41 is changed according to its output. The motor speed control device 81 actually consists of an automatic speed control system (ASR), an automatic current control system (ACR) based on the output of the ASR, and an automatic pulse system that controls the firing angle of the thyristor power supply based on the output of the ACR. It includes a phase shifter and a thyristor power supply for driving the motor. 20a and 20b are rolling torque detectors that detect the rolling torque G; 11 is a dead time device that delays the input signal by the time the rolled material travels between the plate thickness detector 7 and the first stand; 1;
1' is a dead time device that delays the input signal by the time the rolled material travels between the first stand and the second stand, and 100 is a plate thickness calculator that calculates the plate thickness at the exit side of the first stand from a gauge meter type. Since the output of 100 is delayed by 11' by the inter-stand transfer time, the output of 11' becomes the thickness of the plate on the entrance side of the second stand. 1000 is a computer that calculates and outputs the tension control signal ΔωP ₁ .

FIG. 2b is a diagram illustrating the contents of the computer 1000 of FIG. 2a in terms of circuitry. In FIG. 2b, 30a and 30b are torque arm calculation units that calculate the torque arm, 9 is a tension calculation unit that calculates tension, and 10 is a control signal calculation unit that calculates a control signal according to tension deviation.

The torque arm calculation unit 30a of the first stand is
After the rolled material 1 is bitten by the first stand and before it is bitten by the second stand, a torque arm reference value _l10 is calculated according to equation (10). At the same time, the inlet plate thickness H ₁ given by the dead time device 11 which delays the output of the plate thickness detector 7 by the transfer time, the output S ₁ of the roll opening degree detector 61 and the output P ₁ of the load cell 51 are set as reference values. Stored as H ₁₀ , S ₁₀ , P ₁₀ together with l ₁₀ . Similarly, in the device 30b of the second stand, the torque arm reference value _l20 is calculated and stored using equation (13) immediately after the second stand is engaged. 1 at the same time
The detected values of the output H ₂ of 1', the output S ₂ of 62, and the output P ₂ of 52 are stored as reference values H ₂₀ , S ₂₀ , and P ₂₀ . Although the detection of the rolling material being caught in each stand and the bottom falling out is not shown, it is recognized by a sudden change in the output of the load cell of each stand. Torque arm calculation section 3
For 0a and 30b, torque arm reference values l ₁₀ and l ₂₀
After calculation, rolling stand 1 is set based on these memorized values.
The torque arm l _i is calculated until the rolling is completed. That is, first, the detected values H _i , S _i , and P _i of the plate thickness, roll opening degree, and rolling load are input, and the following deviation is calculated.

ΔH _i =H _i -H _i0 (15) ΔS _i =S _i -S _i0 (16) ΔP _i =P _i -P _i0 (17) In this case, since there are 2 stands, i = 1 or 2. 30a and 30b are By substituting the value of into equation (14'), Δl _i is determined. 30a and 30b respectively express this Δl _i and the stored reference value l _i0 as (9)
By substituting into the equation, the torque arm length l _i during rolling is calculated.

The tension calculation unit 9 receives the outputs G ₁ and G ₂ of the torque calculation units 20 of the first stand and the second stand, the detection values P ₁ and P ₂ of the rolling load, and the outputs l ₁ and l ₂ of the torque arm calculation unit 30. This is input and substituted into equation (4) along with the set values of the work roll radii R ₁ and R ₂ to determine the inter-stand tension T. It is determined by the following equation of tension per unit area.

〓=T/h _i・b (18) Here, b is the set value of the average plate thickness, h _i is the exit plate thickness of the first stand, and the value calculated using h ₁ = S ₁ + P ₁ /K ₁ It is. Of course, a directly detected value of h ₁ may be used.

Furthermore, the deviation between the output 〓 of the tension calculation unit 9 and the target tension t ₀ is determined and input to the control signal calculation unit 10 . The calculation unit 10 compensates for the tension deviation by proportional integration or the like, and determines a correction value Δω _P of the speed command of the motor 41. Specifically, it is calculated using the following equation, for example.

Δω _P = L {K _H (1+1/T _N P _L ) L ^-1 (t-t _P )} (19) Here, L is the Laplace transform symbol, K _H is the proportional gain, T _H is the integral time constant, and P _L indicates Laplace variable. By adding this compensation signal Δω _P to the control signal ωP ₁ of the speed control device 81, the speed of the motor 41 is adjusted, and highly accurate inter-stand tension control can be performed. Furthermore, since no looper is used, the effort required for looper maintenance can be reduced.

The operation shown in FIG. 2b can be expressed as a flowchart as shown in FIG. 2c. Since the operation is substantially the same as that shown in FIG. 2b, the explanation of this flowchart will be omitted.

Next, an example will be described in which the tension is calculated using equation (5) of the tension calculation formula. Figure 3 a is (5)
FIG. 3 is a tension control block diagram when tension calculation is performed using a formula. In this example, a 3-stand tandem mill will be used. In FIG. 3a, the same numbers and symbols as in FIG. 2 indicate the same things. In this figure, 23 is the backup roll of the third stand, 33 is the work roll of the third stand, 43 is the main motor of the third stand, 5
3 is the load cell of the third stand, 63 is the roll opening degree detector of the third stand, 14a to c are the lowering devices of each stand, and 12 is the plate thickness on the exit side of the first stand.
Dead time device for delaying h ₁ by the material transfer time to make the plate thickness H ₂ at the entrance of the second stand, 13a ~
9a and 9c are tension calculation devices, 10a and 10b are control compensation devices, and 82 and 83 are motor speed control devices. 1000' is a computer.

The torque detector 20a constantly detects the rolling torque _G1 during rolling. Torque arm calculation section 30a
is the reference value of the torque arm l ₁₀ by substituting the detected value of the rolling load P ₁ and the output G ₁ of the detector 20a into equation (10) before the tip of the rolled material is bitten by the second stand.
Calculate. At the same time, the inlet plate thickness H ₁ obtained through the dead time device 11, the output S ₁ of the roll opening measuring device 6, and the output P ₁ of the load cell 5 are set as reference values.
Stored as H ₁₀ , S ₁₀ , P ₁₀ together with l ₁₀ . Furthermore, after storing, the next torque arm calculation is performed while rolling is being performed in the first stand. That is, first, the input values of the inlet plate thickness H ₁ obtained via the dead time device 11, the output S ₁ of the roll opening degree detector 61, and the output P ₁ of the load cell 51, and their stored values
Calculate the deviation from H ₁₀ , S ₁₀ , and P ₁₀ .

ΔH ₁ =H ₁ −H ₁₀ (20) ΔS ₁ =S ₁ −S ₁₀ (21) ΔP ₁ =P ₁ −P ₁₀ (22) Substitute these values into equation (14') to calculate the torque arm deviation Δl Find ₁ . The torque arm is determined as the sum of this and the torque arm reference value.

When the rolled material is bitten by the second stand, the tension calculating section 9a starts calculating the tension.

That is, the tension T ₁ is calculated from equation (5) using the detected value P ₁ of the rolling load, the output l ₁ of the torque arm calculation section 30a, the output G ₁ of the torque detector 20a, etc.
Furthermore, calculate the unit tension 〓 from this.

〓=T ₁ /h ₁ b (23) Here, the board width b is the set value, and h ₁ is determined from the gauge meter formula.

In order to optimize the response of this tension control system to the deviation between the output 〓 ₁ of the tension calculation section 9a and the target tension _t01 , the control signal calculation section 10a performs compensation such as proportional integration. The output ΔωP ₁ of the calculation unit 10a is given as a correction value of the motor speed command ωP ₁ . The motor speed is changed according to the magnitude of this correction value ΔωP ₁ , and the tension between the first stand and the second stand is controlled to the target value. The tension between the second stand and the third stand is controlled in exactly the same manner.

The operation of the embodiment shown in FIG. 3a is shown in a flowchart as shown in FIG. 3b.

Next, a method for applying the present invention to N tandem rolling mills will be described. The following torque equation holds true for N rolling mills.

By transforming this, the following relational expression is obtained.

here, The torque arm of equation (28) can be obtained by using equations (9), (14'), etc., as in the embodiment shown in FIG. Since the rolling torques G _i , G _i+1 and rolling loads P _i , P _i+1 in equations (26) to (28) can also be calculated or detected, the elements of the matrix on the left side of equation (25) and the elements on the right side of equation (25) All vector element values can be known. Therefore, the tensions T ₁ , T ₂ , . . . , T _N-1 can be obtained by solving the matrix equation (25). The determined tension between each stand T _i
is converted into unit tension t ₁ by dividing by the cross-sectional area of the rolled material between the stands, and the deviation from the target unit tension t ₁₀ can be determined. This deviation is amplified and the motor speed of the i-th stand or the motor speed of the i+1-th stand is corrected. By performing the above control, it is possible to perform highly accurate tension control without using a looper in a rolling system made up of arbitrary stands.

Next, another method for determining the torque arm change amount Δl will be explained. By taking the deviation of the gauge meter equation h=S+P/K, the following equation is obtained.

Δh=ΔS+ΔP/K (29) When ΔS is eliminated from equation (14) using equation, the following equation holds true.

Δl=λ ² R/2l ₀ {ΔH+c/bΔP−Δh}(
30) Here, due to the effect of AGC, the change in outlet plate thickness Δh
If can be regarded as zero, the following equation holds true.

Δl=λ ² R/2l ₀ {ΔH+c/bΔP} (31) In this case, the torque arm Δl can be calculated using only the variation ΔH in the inlet plate thickness and the variation ΔP in the rolling load.

Furthermore, if the outlet plate thickness of the upstream stand can be considered to be almost constant due to the AGC effect of that stand, the variation ΔH in the inlet plate thickness of the downstream stand can also be regarded as zero. Therefore, in equation (31), Δ
Assuming H=0, the following equation is obtained.

Δl=λ ² R/2l ₀ c/bΔP (32) In this case, instead of formula (14) or (14'),
The amount of change in the torque arm can be determined only from the amount of change in rolling load.

Furthermore, depending on the rolling conditions, plate thickness fluctuations ΔH, Δh
In some cases, the variation ΔP in rolling load can be considered to be small compared to , and in this case, the following equation holds from equation (30).

Δl=λ ² R/2l ₀ {ΔH−Δh} (33) ≒λ ² R/2l ₀ {ΔH−ΔS} (33′) In this case, ΔH and Δh or ΔH and ΔS
The amount of change in the torque arm can be calculated from

If Δl is determined using any of the various calculation methods for torque arm fluctuation amount Δl described above, torque arm l can be determined from equation (9) and tension control can be performed. In all of the above embodiments, the motor speed command value was corrected in accordance with the tension deviation, but this means that the mass flow of the rolled material in the correction stand was corrected. Another method for modifying this mass flow is to modify the roll opening degree. Therefore, instead of the previous embodiment, it is also possible to control the tension by correcting the reduction command value according to the tension deviation.

As described above, by implementing the present invention, it becomes possible to perform non-contact tension control with high precision.

Particularly, by implementing the present invention, even if the plate thickness varies greatly during rolling and the rolling reduction amount is changed even during tension control, the tension can be controlled with high precision.

[Brief explanation of the drawing]

Figure 1 is a drawing drawn to explain the principle of the present invention, and shows the state of rolling in a tandem rolling mill consisting of two stands;
Figures a and b are block diagrams showing an embodiment of the present invention applied to a tandem rolling mill consisting of two stands, Figure 2c is a flowchart of its operation, and Figure 3a is a block diagram showing an embodiment of the present invention applied to a tandem rolling mill consisting of two stands. FIG. 3b is a block diagram showing an embodiment implemented in a tandem rolling mill consisting of three stands, and is a flowchart of its operation. 41, 42... Motor, 51, 52... Load detector, 61, 62... Roll opening degree detector, 7...
...Plate thickness detector, 20a, 20b...Rolling torque detector, 11, 11'...Dead time device, 100...
...Plate thickness calculator, 1000...Calculator, 30a, 3
0b... Torque arm calculation section, 9... Tension calculation section, 10... Control signal calculation section.

Claims (1)

[Claims] 1. A tension control method for a tandem rolling mill in which the inter-stand tension of a rolled material caught in the tandem rolling mill is controlled by a tension control signal according to the difference between the calculated tension and the target tension. , detecting the rolling torque and rolling load of the i-th stand during the period from when the rolled material is bitten by the i-th stand until it is bitten by the (i+1)th stand,
The ratio is stored as a reference torque arm, and one or more of the physical quantities of the inlet side plate thickness, roll opening degree, outlet side plate thickness, and rolling load of the i-th stand at the time when the detection is performed is set as the i-th stand reference value. Then, during the period when the rolled material is bitten by the i-th and (i+1)-th stands, the amount of change from the reference value of the i-th stand is calculated, and the amount of change in the torque arm is calculated from this amount of change. Calculate the torque arm using the torque arm change amount and the reference torque arm of the i-th stand, and calculate the inter-stand tension from the calculated torque arm and the rolling torque and rolling load of the i-th stand at that time. A tension control method for a tandem rolling mill, comprising: calculating the inter-stand tension based on a deviation between the calculated inter-stand tension and a target tension. 2 The inter-stand tension of the rolled material caught in the tandem rolling mill is controlled by a step of calculating the tension from the detected values of the rolling load and rolling torque at the i-th stand (i is an integer that is at least 1 smaller than the total number of stands). , a step of calculating a difference between the calculated tension and a target tension, and adjusting the tension using a tension control signal according to the difference, wherein the rolled material is in the i-th stand. I've been bitten by
The rolling torque and rolling load of the i-th stand are detected during the period until it is bitten by the +1 stand, and the ratio is stored as the reference torque arm of the i-th stand. Detect and store one or more physical quantities of the side plate thickness, roll opening degree, exit side plate thickness, and rolling load as the i-th stand reference value, and immediately after the rolled material is bitten in the i+1-th stand, the i+1-th stand Detect the rolling torque and rolling load, use the ratio to calculate and store the standard torque arm at the i+1st stand, and calculate the entrance plate thickness, roll opening, and exit plate thickness at the time when the detection regarding the i+1st stand is performed. One or more physical quantities of the side plate thickness and rolling load are detected and stored as the i+1st stand reference value, and then during the period when the rolled material is bitten in the i+1st stand, the ith and i+1st stands are Calculate the amount of change from the reference value of , calculate the torque arm using the amount of change and the reference torque arm of the i-th and i+1th stands, and calculate the amount of change from the reference torque arm of the i-th,
A method for controlling tension in a tandem rolling mill, comprising calculating an inter-stand tension from the rolling torque and rolling load of the i+1-th stand, and controlling the inter-stand tension using the calculated inter-stand tension.