JPH08300026A - Method for controlling tension of rolling stock - Google Patents

Abstract

PURPOSE: To provide a tension control method uninfluenced by the nonuniformity in the temperature especially due to a skid mark of a rolling stock, in a current memory method whose cost for equipment is low. CONSTITUTION: In the tension control method of a rolling stock 3 between the tandem stands of which a distance between the first stand 1 and the second stand 2 is longer than the length of the rolling stock 3 and of which, after the second stand 2, a distance between the stands is made shorter than the same; measurement is made on the load current of a nontensile rolling mill in the first stand 1 over the entire length of the rolling stock and, on the basis of the measured value, a position of the rolling stock is determined at which change in the load current occurs by the change in rolling temperature. The determined position is tracked until it arrives at the rolling mill on the downstream side, so that no tension control is performed while this position is passing the rolling mills on the downstream side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tension control method for rolled material.

[0002]

2. Description of the Related Art As a tension control method for a rolled material between tandem stands, a current memory method and a torque arm method are known. The current memory method is a method of estimating a change in tension during rolling based on a change in a current value of a drive motor (this current value corresponds to load torque).

That is, the current value I ₀ of the drive motor of the first stand when the rolled material is rolled only by the first stand is stored in memory. The rolled material is caught in the second stand,
The current value I ₁ of the drive motor of the first stand when the first stand and the second stand are simultaneously rolling is compared with the stored current value I ₀ .

If I ₁ > I ₀ , the first stand and the second stand
Since the compression force acts between the stands, the speed of the first stand is reduced. When I ₁ <I ₀ , tension is applied between the first stand and the second stand, so the speed of the first stand is increased. In this way, the _first so that I ₁ = I ₀
Adjust the speed of the stands to keep the first and second stands tensionless.

On the other hand, in the torque arm memory system, as described in Japanese Patent Publication No. 1-57961, tensionless control is performed by obtaining a torque arm which is a ratio of rolling torque and rolling load.

[0006]

In the current memory method, the current value (load torque) of the drive motor is not limited to the tension between the rolling stands, but the temperature distribution of the rolled material (temperature unevenness of the heating furnace skid part, etc.). ) Also greatly changes. Therefore, when the temperature distribution of the rolled material is large, the speed of the first stand is adjusted even when the tension is not working.
On the contrary, the tension between stands may increase.

For example, when the skid portion is rolled by the first stand, the temperature of the rolled material is low, so that the drive motor current of the first stand becomes large and a compressive force acts between the first and second stands. Therefore, the tension is applied between the first and second stands because the speed of the first stand is controlled to be decreased. That is, in this current memory system,
There is a problem that the change in current due to temperature change and the change in current due to tension cannot be distinguished, and accurate tensionless control cannot be performed.

On the other hand, in the torque arm memory system, even if there is a temperature distribution in the material, this gives fluctuations in both rolling torque and rolling load. Therefore, the torque arm, which is the ratio of rolling torque to rolling load, is It is not affected by the fluctuation and changes mainly by the tension component. Therefore, this torque arm memory system is most often used as a more accurate tensionless control system than the current memory system.

However, in the torque arm memory system, since it is necessary to measure the rolling load, it is necessary to attach a load cell to the rolling mill, and there is a problem that the rolling mill costs higher. Therefore, it is an object of the present invention to provide a tension control method which is not affected by temperature unevenness of a rolled material, particularly temperature unevenness due to skid marks in a current memory method which is inexpensive in terms of equipment.

[0010]

In order to achieve the above object, the present invention takes the following measures. That is, the feature of the first aspect of the present invention is that the distance between the first stand and the second stand is longer than the rolled material length, and after the second stand, the distance between the respective stands is shorter than the rolled material length. In the method of controlling the tension of rolled material between tandem stands,
The load current of the rolling mill in a tensionless state is measured at the first stand over the entire length of the rolled material, and the position of the rolled material at which the load current change due to the temperature change of the rolled material occurs is determined based on the measured value. It is a point that the tension control is not performed while the arrival at the side rolling mill is tracked and the position is passing through the downstream side rolling mill.

The second aspect of the present invention is that in the method for controlling the tension of rolled material between tandem stands in which the distance between the stands is shorter than the rolled material length, the load current of the first stand is Measured over the entire length of the rolled material, the time from the start of the rolled material passing through the first stand to the change in the load current value by a predetermined value or more and the time during which the change continued are stored as a change start time and a change duration time, respectively, and rolled. When the change start time elapses after the material starts passing through the downstream stand, tension control is not performed for the change continuation time.

[0012]

According to the present invention, since the portion where the load current increases due to the temperature change of the rolled material is specified and the tension control is not performed at that portion, it is possible to perform the accurate tension control corresponding to only the tension fluctuation.

[0013]

Embodiments of the present invention will be described below. As the tandem stand, as shown in FIG. 5, there are cases where the distance between the first stand 1 and the second stand 2 is longer than the length of the rolled material 3 and cases where the distance is short (not shown). Therefore, description will be made below for different cases. [When the distance between the first stand 1 and the second stand 2 is wide and the material 3 between the stands 1 and 2 is free (in the case shown in FIG. 5)] In such a case, each stand after the second stand 2 In the meantime, the above-mentioned current memory type tension control is performed.

Prior to the tension control of the current memory system, the load current i is first measured in the first stand 1 over the entire length of the rolled material 3. As shown in FIG. 4, the load current value i shows a constant value i ₁ in the portion where the temperature of the rolled material 3 is constant. When the rolled material 3 has a temperature distribution, the load current value i changes greatly in the low temperature portions 4 and 5. Conversely, it can be determined that the portion where the current change has changed by a predetermined value or more, for example, the portion where i ≧ i ₁ × 1.02, is the low temperature portion 4,5.

Therefore, if the tension control is set to "off" when the low temperature parts 4 and 5 arrive at the stand on the downstream side, when the tension control is performed by the current memory system, the influence of temperature unevenness may occur. Disappear. Therefore, it is necessary to know when these low temperature parts 4 and 5 arrive at the downstream stand 2. That is, it is necessary to track the movement of the rolled material 3. Hereinafter, a method for tracking the movement of the low temperature parts 4 and 5 will be described.

When the rolled material is free between the first stand and the second stand, the mass flow is constant (A ₁ · V ₁ = A ₂
· V _2, A: cross-sectional area, V: velocity) and so not, the rolling speed ratio, can not identify the location in the rolling time. Therefore,
The position is specified by using the stretch ratio. First, the length of the rolled material 3 from when the tip of the rolled material 3 is bitten by the first stand 1 to when the load current changes by 2% or more from a certain value is
Store as ₁₁ and the continuing length of the current change as l ₁₂ . If there are a plurality of such changed portions, the length of the rolled material from the time of biting to the start of the change is sequentially stored as l ₁₃ , and the continuous length thereof is stored as l ₁₄ ...

Next, the above-mentioned l ₁₁ , l in the second stand 2
_The positions corresponding to ₁₂ , l ₁₃ and l ₁₄ are determined by the stretching ratio.
That is, the length of the rolled material 3 after passing the first stand 1 is l ₁ and its cross-sectional area is A _1, and the length of the rolled material 3 after passing the i-th stand 2 is l _i and its cross-sectional area is If A _i ,
Stretching ratio L becomes _{L = l i / l 1 =} A 1 / A i.

The positions l _i1 , l _i2 , l _i3 corresponding to the above l ₁₁ , l ₁₂ , l ₁₃ and l ₁₄ after passing through the i-th stand 2 are
l _i4 is: l _i1 = L × l ₁₁ , l _i2 = L × l ₁₂ , l _i3 = L × l ₁₃ , l
_It is obtained as _i4 = L × l ₁₄ . Therefore, the l in the second stand 2
Positions l ₂₁ , l ₂₂ corresponding to ₁₁ , l ₁₂ , l ₁₃ , l ₁₄
l ₂₃ and l ₂₄ are: l ₂₁ = L × l ₁₁ , l ₂₂ = L × l ₁₂ , l ₂₃ = L × l ₁₃ , l
_It is calculated as ₂₄ = L × l ₁₄ .

Therefore, when the rolled material 3 passes through the second stand 2 and the length l of the rolled material 3 is within the following range,
The cold parts 4 and 5 are passing through the second stand 2. l ₂₁ <l <l ₂₁ + l ₂₂ l ₂₃ <l <l ₂₃ + l _{24 While} this low temperature part 4,5 is passing through the second stand 2, the tension control between the second stand 2 and the third stand is “turned off”.
To Except for the above range, the tension control is set to "ON".

The rolled material lengths l ₁₁ , l ₁₂ , ... Are measured as follows. First, as shown in FIG. 4, the change in the load current value of the rolling mill motor is measured to detect when the rolled material is caught in the first stand and when there is a change of a predetermined value or more. Based on the detection, the rotation speed N of the rolling roll from a certain detection to a certain detection is detected.
The roll speed N is detected by a pulse generator attached to the motor. Then, the length l of the rolled material is calculated by the following formula. However, D _W is an effective roll diameter.

1 = πD _W N A flowchart of the above control is shown in FIG. [When Each Stand Interval is Shorter than Rolled Material Length] FIG. 2 is a flowchart showing the control in this case. First, the time when the load current of the first stand 1 changes by 2% or more from the constant value after the tip of the rolled material 3 is bitten into the first stand 1 is stored as t ₁₁ . Then, the duration of this change is stored as t ₁₂ . If there are a plurality of such changed portions, the change start time from the time of biting is t ₁₃ , the duration is sequentially stored as t _14, ...

Next, it is judged whether or not the rolled material 3 is caught in the second stand 2, and when it is caught, the second stand 2 is held.
2 The elapsed time t ₂ from the time of biting is measured. When the measurement time t ₂ is within the following range, the low temperature parts 4,5 are passing through the second stand 2. t ₁₁ ≤t ₂ ≤t ₁₁ + t ₁₂ t ₁₃ ≤t ₂ ≤t ₁₃ + t ₁₄ Within the above range, rolled material 3 passing through the second stand 2
Is the low temperature portion 4 or 5, so the tension control between the first and second stands is turned off. In the other parts, the tension control is set to the "ON" state.

The tail end of the rolled material 3 is the first stand 1
After passing, the tension control between the first and second stands is terminated. Note that, in the control in the flow of FIG. 2, when the rolled material is simultaneously rolled by the first stand and the second stand, and when the load current value is measured by the first stand, the change in the current value is the temperature change. The determination as to whether it is due to a change, a change in tension or other disturbance is
When the load current changes by 2% or more from a certain value, it is considered that the temperature changes, and the change below that is caused by the tension change or the like.

FIG. 3 shows the control between the No.i and No.i + 1 stands after the rolled material 3 is bitten into the No.i + 1 stand. When the rolled material 3 is bitten into the No. i stand, the time t _i is measured from the biting, and when the time t _i is within the following range, the low temperature parts 4,5 are passing through the i-th stand. It will be.

T ₁₁ ≤t _i ≤t ₁₁ + t ₁₂ t ₁₃ ≤t _i ≤t ₁₃ + t _{14 In the} above range, the rolled material 3 passing through the i-th stand is the low temperature portion 4 or 5, so the i-th ~ Turn off the tension control between the (i + 1) th stand. In the other parts, the tension control is set to the "ON" state.

When the tail end of the rolled material 3 passes through the i-th stand, the tension control between the i-th stand and the (i + 1) th stand is terminated. The control of FIG. 3 is applied to the control of FIGS. 1 and 2. In the above-described embodiment, the stand for changing the rotation speed when controlling the tension is the first stand between the first and second stands and the i-th stand between the i-th and (i + 1) th stands.

The present invention is not limited to the above embodiment. Further, the temperature of the rolled material is actually measured, the start time of the portion where the temperature change of the rolled material becomes equal to or greater than the set temperature change is stored as t _1i , and its duration is stored as t _1j , and the portion passes through the downstream stand. At this time, the tension control can be turned off.

[0028]

According to the present invention, the portion where the load current increases due to the temperature change of the rolled material is specified, and the tension control is not performed at that portion, so that the accurate tension control corresponding to only the tension fluctuation can be realized.

[Brief description of drawings]

FIG. 1 is a flowchart showing a first embodiment of the present invention.

FIG. 2 is a flow chart showing a second embodiment of the present invention.

FIG. 3 is a flowchart showing a third embodiment of the present invention.

FIG. 4 is a drawing showing the relationship between changes in load current and the position of rolled material.

FIG. 5 is a plan view showing a space between stands.

[Explanation of symbols]

 1 1st stand 2 2nd stand 3 Rolled material

Claims (2)

[Claims] 1. The tension of the rolled material between the tandem stands in which the distance between the first stand and the second stand is longer than the rolled material length, and the distance between the respective stands is shorter than the rolled material length after the second stand. In the control method, the load current of a rolling mill in a tension-free state is measured on the first stand over the entire length of the rolled material, and based on the measured value, the position of the rolled material at which the load current change due to the temperature change of the rolled material occurs is determined. A method for controlling tension of a rolled material, characterized in that the tension control is not performed while the position reaches the downstream rolling mill and the position is passing through the downstream rolling mill. 2. A method for controlling the tension of a rolled material between tandem stands in which the distance between the stands is shorter than the length of the rolled material, wherein the load current of the first stand is measured over the entire length of the rolled material, The time from the start of the stand passage to the change of the load current value by a predetermined value or more and the duration of the change are stored as a change start time and a change duration, respectively. The tension control method for a rolled material is characterized in that the tension control is not performed for the above-mentioned change duration time.