JPS6057404B2 - Tension control method and device for continuous rolling mill - Google Patents

Description

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

Conventionally, for constant tension control in a continuous rolling mill, for example, tensionless control, the load current or rolling load of the drive device in each rolling stand of the continuous rolling mill, or the ratio of rolling torque to rolling load, is detected at the time of biting, and the detected value is A speed change command was output to the drive device so as to keep the speed constant during rolling using the command value as the command value.

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. In addition, a calculation device 15 for calculating the ratio between the output signal of the torque detector 29 and the output signal of the rolling load detector 14, and a storage device 16 for storing the value of the calculation device 15 when the rolled material is bitten are provided. Control was performed such that a speed change command was output to the speed control device 13 so that the difference between the output signal of the arithmetic device 30 and the output signal of the storage device 16 was made zero. However, such conventional control
When rolling material temperature drops during rolling, skid marks, base material thickness changes, or other disturbances occur, tension or compression forces are generated.

In other words, as is clear from the block diagram in Figure 1,
Since each stand is simply controlled independently, it has the disadvantage that it cannot compensate for disturbances that cannot be ignored over time (for example, various disturbances caused by temperature changes in the rolled material). In addition, in the case of a rolling mill consisting of three or more stands, in conventional control, by the time the rolled material is bitten by the (1+2) stand, the first stand and the (1+1)
) If the rolled material between the stands does not reach a constant tension state,
Alternatively, 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, the constant tension control after the rolled material is bitten by the (1+2) stand is based on the rolling load P( 1+1) stand or rolling torque G(1
+1) or their ratio G(1+1)/P(1+1), then use the memorized value as the reference value, and at the (1+1) stand after biting into the corresponding (1+2) stand. It is based on the principle that the speed command value of the (1+1)th stand is determined by comparing the value of However, the measured value immediately after the (1+1) stand is bitten is affected by the tension generated by the effect of the impact drop, and if there is tension in the (1-1) stand and the first stand, the Since the rotation speed of the first stand changes due to the tension, tension is generated between the first stand and the (1+1) stand, and its influence is also included.

Therefore, the (1+
1) The value immediately after biting into the stand is inaccurate as a reference value for subsequent constant tension rolling control.

Therefore, it is necessary to engage the (1+1)th stand in a state where no tension fluctuation occurs between the (1-1)th stand and the first 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 was 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, set the thickness of the entrance side of the first stand to H
1 Thickness on the exit side is Hml. Thickness on the exit side of the 2nd stand is h1. Detected values of rolling torque and rolling load in the 1st stand and radius of the work roll are Gl, Pl, Rl respectively. Those of the 2nd stand are G2, P2. , R2, and the inter-stand tension is T, the relationships of equations (1) and (2) hold between these. However, El,'2 is the contact arc length of stands 1 and 2, respectively, and λ1 is the torque arm coefficient.

The product λ1·f1 is called the torque arm. When formulas (1) and (2) are transformed, it can be seen that formula (3) holds true at any time during rolling. The first term on the right side of the above equation is expressed as a function of the contact arc length of both stands.

The contact arc length '1f2 itself decreases due to the temperature drop of the rolled material as a function of the rolling reduction amount, but since the contact arc lengths of both stands show the same degree of change due to temperature, the first term on the right side shows the change due to temperature. is canceled.

In other words, the temporal change in the first term on the right side during rolling is much 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 effect on the tension of the rolled material due to temperature changes during subsequent rolling 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, the tension T between the stands is zero before the rolled material is bitten by the second stand, so the state at that time is subscripted. The torque arm λ10-ElO at the first stand can be expressed as in equation (4) using the torque detection signal GlO and the rolling load signal PlO. When the state of tension generation is indicated with the subscript b, (5
), the relationship is as shown in equation (6). From these two equations, if Tb is eliminated, the torque arm λ2b◆'2b at the second stand
satisfies equation (7).

Here, if the torque arm λ10・'10 of the first stand is calculated just before the rolled material bites into the second stand, the torque arm λ1b-'1b immediately after biting is λ10-Fl
approximately equal to O.

That is, 2λ1b-Elb72λ10-ElO=(G
1/P1). holds true. At this time, we convert equation (7) to (G2
/P2).

, then υJ

■t As mentioned above, if the changes in the contact arc length of both stands during rolling are equal, the difference in torque arm in the first term on the right side of equation (3) above can be expressed as follows. In summary, equation (3) can be expressed as equation (9) below. Here, (G1/P1).

is the value of the ratio of the rolling torque to the rolling load of the first stand before the second stand bites, and is (G2/P2). is (10)
It is given by Eq. In the above equation (9), the difference (straddle) between the ratio of rolling torque and rolling load in the two stands is (?).

-(?). By controlling the tension to be equal to , constant control with zero tension can be realized. That is, since the right side of equation (9) corresponds to the tension T, constant control with zero tension can be achieved by modifying the drive motor speed of the rolling stand so as to make this value zero. If the motor speed is controlled 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 the figure, G, P, and R indicate rolling torque, rolling load, and roll radius, respectively, and the subscripts correspond to the numbers attached to the corresponding stands. First, when the tension T1 is applied between the first stand and the second stand, and the tension T2 is applied between the second stand and the third stand, (11), (12), (1
3) The formula holds true.

Here, the value of 2λ1·'1 after the rolled material is bitten by the first stand in the same manner as in the case of two stands described above is (G1/P1).

and furthermore. It is defined as in equations (14) and (15). Here, ( ) indicates the actual value measured immediately after the first stand was caught.

In addition, (G1/P1-). corresponds to the torque arm in an apparent tension-free state. Strictly speaking, the torque arm 2 in the apparent no-tension state in the first stand
The value is doubled (see equation (4)). At this time, equation (11)
~(13) to (2λ1 ・f1−2λ2・E2) and (
2λ2·E2−2λ3·E3) and eliminate it in the same way as in the case of 2 stands, formulas (16) and (17) are obtained.

Here, X and y are shown by equations (18) and (19), respectively. From both formulas (16) and (17), the tension between the stands T
In order to make l and T2 zero, it is sufficient to make X and y zero at the same time.

That is, in order to perform constant tension control with zero tension, equation (18
), (19), the difference in torque arms of adjacent stands (
G1/P1) - (G1+1/Pi+1) (G1/P,
). One (Gj+, /Pj+,). All you have to do is modify the speeds of adjacent stands so that they are always equal to . From the above, the speed change amount (ΔN/N)i of the first stand is, when the second stand is used as a key stand, where α and β are 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.

Figures 4 to 6 are control block diagrams explaining the control device as a premise of the tension control of the present invention, each stand has a load cell (1) for detecting the rolling load P, and the rolling roll has an automatic speed control. It is linked to a motor that has a control ASR system.

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

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 an alternating current power source (not shown) into direct current voltage.

5 is a motor for driving the rolling roller of each rolling stand; 6 is a speed generator that detects the number of revolutions of the drive motor 5; 7 is a current detector that detects the main circuit current flowing through the motor 5; 8 is a field current IE; 9 is a function generator that inputs the output 1F of the field current detector 8 and outputs the field strength φ; 10 is the output of the function generator 9 and the current detector 7;
11 is a differentiator that performs time differentiation of the output of the current detector 6 and outputs acceleration. 12 is a conversion gain device that inputs the output of the differentiator 11 and converts it into acceleration torque. Then, by subtracting this output from the output of the multiplier 10, 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 drive motor 5; 14;
1 is a load cell that detects the rolling load of each stand, 15 is a divider that calculates the ratio of rolling torque to -rolling load (G/P), and 16a is a memory that stores the output of the divider 15 after the first stand is engaged. A storage device 16b stores the ratio of rolling torque to rolling load in an apparent no-tension state calculated by equation (14) immediately after the second stand is engaged. The storage device 16c for storing data is expressed by formula (15) immediately after the third stand is inserted.
17a is a one-shot relay that is switched before the second stand is engaged; 17b is a storage device that stores the ratio of the rolling torque in the no-tension state to the rolling load calculated by 17b; The one-shot relay 18 is activated immediately after the second stand is engaged, and the one-shot relay 18 is activated immediately after the third stand is engaged.

19 is a divider that calculates the ratio of rolling loads of adjacent stands; 2
0 is a gain installation that multiplies the output of the divider 19 by the ratio of the roll diameter of the same stern pair, and 21 is a gain device 20 that is the difference between the rolling load ratio G/P of the rolling torque immediately after biting and before biting. 22 is a conversion gain device that converts the amount corresponding to the right side of equations (18) and (19) into a speed change amount, and 23 is an integrator.

Further, 25 and 26 are calculated from the outputs of the dividers 15 and 19 by formula (20
) or (21) is an arithmetic circuit that calculates the speed change amount expressed. This arithmetic circuit is the control system HTF'C
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, and the ratio thereof is calculated by the divider 15 and stored. The information is stored in the device 16a. 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 output of the divider 15 regarding the rolling stand 1 is converted to the torque arm equivalent amount (G2/P2) regarding the second stand from the output of the storage device 16a and the output of the divider 19. is calculated,
It is stored in the storage device 16b. Until the rolled material is bitten by the third stand, the difference between the output of the divider 15 of the first stand and the divider 15 of the second stand is taken, and the difference between the outputs of the storage devices 16a and 16b is determined. 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 and the above-mentioned equation (15) is calculated, and the torque arm equivalent amount (G3/P3) is calculated. is stored in the storage device 16c. The operation during rolling after the third stand is engaged is based on the difference between the output force of the divider 15 of the first stand and the output force of the divider 15 of the second stand. The rolling speed of the first rolling stand is controlled so that the subtracted value is zero, and at the same time the rolling speed of the second rolling stand is controlled so that the subtracted value becomes zero.
The output of the divider 15 on the stand and the divider 1 on 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 the storage devices 16b and 16c from the difference between the outputs of the storage devices 16b and 16c becomes zero. This control makes it possible to realize tension-free control that does not generate tension between the rolling stands. FIG. 6 shows another example of controlling a continuous rolling mill having three rolling stands; in this example, the key stand is selected as the first stand.

Then, the speed commands are changed by the two control system HTFCs for the second stand and the third stand. In this case, successiveness is required to prevent speed modification 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 stand and the third stand.

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 to provide succession between stands on 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 tension control which is the premise of the present invention, an example applied to band shaping rolling has been described, but it is clear that it can be easily applied to bar shaping rolling, shape shaping rolling, etc.

FIG. 7 is an example of a block diagram of only the essential parts of an embodiment of the present invention, and shows an apparatus for applying arbitrary tension to a rolled material when rolling is performed using 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 enclosed by a broken line in FIG. Here, if the set value of tension is 〒 and the amount of variation in tension caused by disturbance is ΔT, then the following relationship is established according to the above-mentioned equation (9).

Since the tension ΔT caused by the disturbance changes the plate thickness, the right side is controlled so as 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. Note that when the tensionless rolling control of three stands is performed based on equations (20) and (21), the tension T1 does not necessarily need to be zero when the third stand is engaged.

That is, it should be stored (G3/P3). is (14)
It can be determined by calculation using the detected value at the time of biting. Further, in the conventional method, as described above, T1 is required to be zero. In the case of high-speed rolling, the rolled material may be accelerated by both the first and second stands before the third stand bites. Therefore, the tension T1 is not necessarily zero when the third stand bites, and the tension T1 is not necessarily zero when the third stand bites. However, there were limitations to speeding up the process. The above-mentioned embodiment overcomes this drawback, so it can be expected to improve productivity. As described above in detail, 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. In the conventional method of controlling the ratio of rolling torque and rolling load in a single stand to a constant value, the change in a-torque arm is calculated to be about 1[? ] It was about . 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 40
0ct0n/Tnln]. The difference in load between the leading and trailing ends of the rolled material was about 200 [TOn], and this is thought to be due to the temperature drop. When the torque arm change Δe1 is 1 [sono], how much unit tension change ΔTO is calculated is as follows. be.

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), Δe1 and Δ'2 are approximately 1 [? ] If there is, the change will be a value of Δe1-ΔE2, which will be canceled and become a value close to zero.

If Δe1 = 1 (in order) and ΔE2 = 0.9 (in order) and the rolling mill is controlled according to the present invention in the same manner as described above, the tension fluctuation is estimated as follows. However, R1=R2=350C
Tm] Generally, the target tension between the first and second stands of a rolling mill during hot finishing is about 0.20 [K9/i], so the tension by the conventional method is 0.20±0.16 [K9/d]. ] It is clear that tension fluctuations of this magnitude pose 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 drawings]

FIG. 1 is a block diagram showing an embodiment of a tensionless control device in a conventional continuous rolling mill, FIGS. 2 and 3 are explanatory block diagrams for explaining the control principle of the present invention, and FIGS. FIG. 6 is a block diagram for explaining a control device that is a prerequisite for tension control of the present invention, and FIG. 7 is a block diagram showing an embodiment of the present invention. 1...First rolling stand, 2...Rolling stand, 3...Rolling stand, 4...
・Thyristor device, 5...Roller drive motor, 6...Speed generator, 7...Current detector, 8...Field current detector , 9...function generator, 10,21...multiplier, 11...
Differentiator, 12, 20...Gain device, 13...
... Speed control device, 14 ... Rolling load detector, 15, 19 ... Divider, 16 ... Memory device, 17, 18 ... One shot relay, 22
... Conversion gain device, 23 ... Integrator, 25, 26 ... Control circuit.

Claims (1)

[Claims] 1. At least two or more n rolling stands, a drive device including an automatic speed control device for an electric motor for driving rolling rolls of the rolling stands, and a rolling load of the rolling stands is detected. In the device for controlling inter-stand tension of a rolled material rolled in a continuous rolling mill having a rolling load detector, the electric motor at the i-th stand before the rolled material is bitten by the i+1-th stand counting in the rolling direction. Detects and stores rolling torque from voltage, current and speed signals,
The rolling load is detected and stored from the signal of the rolling load detector at the same time, and each detection and storage is performed each time the rolled material bites into each stand.The rolling load and rolling torque during rolling are detected and stored for each stand. The rolling load and rolling torque during rolling in the own stand and the stand one stand before the own stand, the stored torque arm equivalent amount in the no-tension state of the i stand, and the torque arm equivalent amount in the no-tension state of the (i+1) stand The difference between ({(Gi/P
i)_0-(Gi+1/Pi+1)_0}) and the difference between the torque arm of the i stand and the (i+1) stand ({(G
i/Pi) - (Gi+1/Pi+1)}), the sum of the ratios of the work roll radius and load of the stand and the (i+1) stand and the set tension between the i stand and the (i+1) stand ((@T@) Continuous rolling characterized in that a speed correction amount according to tension variation with respect to the set tension is calculated from the value obtained by subtracting the value of the product of Tension control method for a machine. 2 At least two or more n rolling stands, a drive device having an automatic speed control device for an electric motor for driving the rolling rolls of the rolling stands, and a voltage, current and speed signal of the electric motor. A continuous rolling mill having a torque detector for detecting the rolling torque of the rolling stand and a rolling load detector for detecting the rolling load of the rolling stand. first and second means for detecting and storing the rolling load and rolling torque at the i-th stand before the rolled material is bitten by the i+1-th stand, and for setting the tension of the rolling mill; In addition, each stand is provided with a torque arm equivalent amount in the non-tension state of the i-stand, which is stored as the rolling load and rolling torque during rolling in the own stand and the stand immediately before the own stand, respectively. The difference ({(Gi/Pi)_0-(
Gi+1/Pi+1)_0}) and i stand and (i+1
) Difference from the torque arm of the stand ({(Gi/Pi)-
(Gi+1/Pi+1)}), the sum of the ratios of the work roll radius and load of the i-stand and the (i+1) stand, and the set tension between the i-stand and the (i+1) stand ( @T@) product (R_1/P_1)
+R_2/P_2)@T@), and a sixth calculating means for calculating a target speed correction signal to the automatic speed control device of the electric motor from the output signals of the fourth and fifth calculating means. 1. A tension control device for a continuous rolling mill, characterized in that a calculation means is provided.