JPH0618655B2 - Method of avoiding abnormal tension drop in temper rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is designed to restrain strips on the inlet side and the outlet side of a mill by bridle rolls and mechanically connect these bridle rolls to drive them to improve the elongation. The present invention relates to strip tension control of a temper rolling mill of a type in which the strip tension on the mill entrance side and the strip tension on the mill exit side are controlled by controlling and operating the mill reduction position and the mill speed.

[Conventional technology]

The strip is constrained by the bridle rolls on the mill input side and the output side, these bridle rolls are mechanically linked and driven to control the elongation, and the mill reduction position and mill speed are controlled to control the mill input side. An elongation control system and a strip tension control system for a temper rolling mill that controls the strip tension and the strip tension on the delivery side of the mill (JP-A-59-12).
7917 gazette) is shown in FIG.

Bridle rolls 5 and 6 on the inlet and outlet sides of the mill 4
Are mechanically connected and driven by one motor 1. Further, by adjusting the number of rotations of the motor 3 given through the differential gear 2, it is possible to give an arbitrary speed difference [%] (= elongation rate) between the entrance-side and exit-side bride rolls 5-6. it can.

Generally, the rolling reduction (= elongation) in temper rolling is around 1%, and if the number of rotations of the motor 3 corresponding to this is set according to the line speed, the set elongation will be ± 0.1%. It is possible to achieve rates.

However, the elongation control, which is performed by mechanically connecting and driving the bridle rolls, is a control system irrelevant to the strip tension between the bridle rolls, that is, the strip tension on the mill entrance side and the mill exit side. It is necessary to control the strip tension on the inlet and outlet sides to an appropriate value, and the following strip tension control system is configured.

The strip tension control system is composed of two control systems. One is a sum tension control system 7 and the other is a difference tension control system 8.

The total tension control system 7 is a system for controlling the sum (Te + Td) of the strip tension Te on the mill entrance side and the strip tension Td on the mill exit side to a target value (Te ^* + Td ^* ) with the mill reduction as the operation end. It is composed of a tensiometer 9, an exit tensiometer 10, a controller 11, a reduction cylinder 12, and the like.

The differential tension control system 8 is a system for controlling the difference (Td-Te) between the strip tension Te on the mill entrance side and the strip tension Td on the mill exit side to a target value (Td ^* -Te ^* ) with the mill speed as the operating end. The input side tensiometer 9, the output side tensiometer 10, the controller 13, the mill motor 14, and the like.

In addition to this, as the strip tension control of this type, a method of controlling the strip tension on the mill entrance side and controlling the strip tension on the mill exit side at the mill speed (see FIG. 5) or the strip tension on the mill entrance side is used. Controlled by mill speed,
There is a method of controlling the strip tension on the outlet side of the mill under the pressure of the mill (see FIG. 6).

[Problems to be Solved by the Invention]

The bridle rolls 5 and 6 are devices that firmly restrain the strip 15 and generate tension in the strip between the bridle rolls, but in recent years, the friction coefficient μ between the bridle roll and the strip has decreased due to the following three reasons.
Slip tends to occur. That is, due to the demand for high productivity, speeding up of the line is remarkable. As the line speed increases, the friction coefficient μ between the bridle roll and the strip decreases as shown in FIG. Further, in the case of wet temper rolling, as the line speed increases, the amount of rolling oil carried out to the mill exit side increases. That is, the friction coefficient μ between the mill exit bridle roll and the strip tends to decrease. From the demand for high image clarity on the strip surface, there is a tendency to reduce the roughness of the strip surface,
Therefore, the friction coefficient μ between the bridle roll and the strip tends to decrease.

As a measure against these, it is possible to increase the roughness of the bridle roll to improve the friction coefficient μ between the bridle roll and the strip, but in reality, the roughness of the bridle roll is not so high from the viewpoint of ensuring the surface quality of the strip. It can't be raised and is therefore less effective.

Now, what happens when a strip occurs between the bridle roll and the strip will be described below.

The temper rolling mill strip tension control system taken up here is a sum tension control system 7 and a differential tension control system 8 shown in FIG.
It shall consist of two control systems.

First, a case where a strip occurs between the bridle roll 5 and the strip 15 on the mill entrance side will be described.

At this time, the strip tension Te on the mill entry side decreases.
Due to the above, a deviation occurs in the differential tension control system 8, and the control operation is performed in the direction of increasing the mill speed. At the same timing as described above, a deviation occurs in the total tension control system 7, a control operation is performed in the direction of releasing the reduction, and the reverse speed ratio is reduced.
Due to the above and, the strip speed on the mill entry side is increased. Here, since the speed of the mill entrance side bridle roll 5 is constant, the slip speed between the mill entrance side bridle roll 5 and the strip 15 tends to increase.

On the other hand, the bridle roll 6 and the strip 15 on the mill exit side
If a slip occurs during this, the strip tension Td on the mill side decreases. Due to the above, a deviation occurs in the differential tension control system 8, and the control operation is performed in the direction of decreasing the mill speed. At the same timing as above, a deviation occurs in the sum tension control system 7, and the control operation is performed in the direction to release the reduction.
The advanced rate decreases. Due to the above and, the strip speed on the exit side of the mill is reduced. Here, since the speed of the mill exit side bridle roll 6 is constant, the slip speed between the mill exit side bridle roll 6 and the strip tends to increase.

Fig. 8 shows the strip tension on the mill input side, the strip tension on the mill outlet side, each strip tension control operation amount (strip tension control signal), and the slip speed between the bridle roll and the strip when slip occurs between the bridle roll and the strip. Shows the change state of.

As can be seen from this figure, when the slip speed between the bridle roll and the strip is below a certain level, there is almost no decrease in the strip tension on the mill inlet / outlet side and changes in the strip tension control manipulated variables. Therefore, even if a slip occurs between the bridle roll and the strip, the friction coefficient μ between the bridle roll and the strip decreases little in the region where the slip speed is small (A in FIG. 8), It is thought that sufficient grip is working.

However, when the slip speed exceeds a certain level, a sudden drop in strip tension and a change in each strip tension control operation amount begin to occur. In other words, this means that the grip force between them has dropped sharply, that is, the friction coefficient μ
Is considered to have dropped sharply. From this, it is assumed that the relationship between the slip speed between the bridle roll and the strip and the friction coefficient μ is as shown in FIG.

Therefore, even if slip occurs, the slip speed is set to A in FIG.
It can be said that an abnormally low tension will not be reached if the value is kept within the range.

However, if the strip tension control is still activated when the slip occurs between the bridle roll and the strip, the strip tension control increases the slip speed between the two as described above, and the lost tension is reduced due to the decrease in grip force. As a result, the condition is promoted.

In addition, the above is a method of controlling the strip tension on the mill entry side under pressure and controlling the strip tension on the mill exit side at the mill speed (see Fig. 5) or by controlling the strip tension on the mill entry side at the mill speed. Also, the strip tension control method of the temper rolling mill of the method (see FIG. 6) of controlling the strip tension on the outlet side of the mill under the pressure of the mill is applicable.

First, a strip tension control method in which the strip tension on the mill entrance side is controlled under pressure and the strip tension on the mill exit side is controlled according to the mill speed will be described. (See FIG. 5) When slip occurs between the bridle roll 5 on the mill entry side and the strip 15, the strip tension on the mill entry side decreases. Due to the above, a deviation occurs in the strip tension control system 16 on the mill entrance side, and the control operation is performed in the direction of releasing the reduction. When the reduction is operated in the opening direction, the advance rate decreases and the strip speed on the mill exit side decreases,
The tension on the outlet side of the mill increases. On the other hand, the mill exit-side strip tension control system 17 controls the mill so that the mill speed increases. On the other hand, if the reduction is operated in the opening direction, the reverse rate decreases. Due to the above and, the strip speed on the mill entry side is increased. Since the speed of the mill entrance side bridle roll 5 is constant, that is, the slip speed between the mill entrance side bridle roll 5 and the strip 15 increases.

On the other hand, when slip occurs between the bridle roll 6 on the mill exit side and the strip, the strip tension on the mill exit side decreases. Due to the above, a deviation occurs in the strip tension control system 17 on the outlet side of the mill, and the control operation is performed in the direction of decreasing the mill speed. As a result, the strip tension on the mill entry side is reduced. On the other hand, the mill entrance side strip tension control system 16 is operated, and the control operation is performed in the direction to release the reduction, so that the advance rate is reduced. Due to the above and, the strip speed on the exit side of the mill is reduced.
Here, since the speed of the mill exit side bridle roll 6 is constant, that is, the slip speed between the mill exit side bridle roll 6 and the slip 15 increases.

Next, a strip tension control method will be described in which the strip tension on the mill entrance side is controlled by the mill speed and the strip tension on the mill exit side is controlled under pressure. (See Fig. 6)
When slip occurs between the bridle roll 5 and the strip 15 on the mill entry side, the strip tension on the mill entry side decreases. Due to the above, a deviation occurs in the strip tension control system 16 on the mill entrance side, and the control operation is performed in the direction of increasing the mill speed. Due to the above, the strip tension on the exit side of the mill is reduced. In response to the above, the mill outlet strip tension control system 17 is operated, and the control operation is performed in the direction to release the reduction, so that the reverse travel ratio is reduced. Due to the above and, the strip speed on the mill entry side is increased. Here, since the speed of the mill entrance side bridle roll 5 is constant, that is, the slip speed of the mill entrance side bridle roll 5 and the strip 15 increases.

On the other hand, the bridle roll 6 and the strip 15 on the mill exit side
If slip occurs in the meantime, the strip tension on the exit side of the mill decreases. A deviation occurs in the mill exit side strip tension control system 17 as described above, and the control operation is performed in the direction to release the reduction. If the reduction is operated in the opening direction, the backward movement rate decreases, the strip speed on the mill entry side increases, and the tension on the mill entry side increases. On the other hand, the mill entry strip tension control system 16 controls the mill speed in the direction of decreasing the mill speed. On the other hand, when the reduction is operated in the opening direction, the advance rate decreases. Due to the above and, the strip speed on the exit side of the mill is reduced. Here, the speed of the mill exit side bridle roll 6 is constant, that is, the slip speed between the mill exit side bridle roll 6 and the strip 15 increases.

As described above, an increase in the slip speed between the bridle roll and the strip leads to an abnormally reduced strip tension.

In the worst case, abnormal reduction in strip tension causes narrowing and breaking of the strip. In addition, even if it does not reach the point of narrowing or breaking, as described above, since the operation of releasing the strip is performed as the operation of the strip tension control, as a result, the strip shape is disturbed, the strip surface roughness is poor, and the elongation is poor. Was occurring.

[Means and Examples for Solving the Problems]

In order to solve the above-mentioned problems, the present invention detects the slip speed between the bridle roll and the strip, and holds the strip tension control signal when the slip speed exceeds a certain level. It is prevented that the slip is increased due to the adverse effect and the strip tension abnormally lowered state is reached.

FIG. 1 is an explanatory diagram of an apparatus according to an embodiment of the present invention.

Note that FIG. 1 omits the drawing of the elongation control system and the tension control system of FIG.

18 and 20 are pulse generators attached to the non-driving roll,
Numerals 19 and 21 are pulse oscillators attached to the driving roll. Here, pulse generators 18 and 1 generated in a unit time
9 is the slip speed Se between the mill entrance side bridle roll 5 and the strip 15, and similarly the difference between the pulse numbers of the pulse transmitters 20 and 21 generated in a unit time is the mill exit side bridle roll 6 and the strip. The slip speed Sd of 15 is detected. Furthermore, slip speeds Se and S
The one with the larger absolute value of d is always selected and designated as S.

Next, a level determination is made for the slip speed S. When S greater than the constant absolute value level Sa is detected, it is determined that slip has occurred, and the strip tension control signal is held.

Here, Sa is within the range of B in FIG. 8 and is a value larger than the measurement noise.

After the strip tension control signal is held, if S becomes smaller than a certain absolute value level Sb, the strip tension control signal is released and the normal control is resumed.

Here, Sb is a value smaller than Sa. It is desirable to determine Sa and Sb based on actual data.

FIG. 2 shows the results of implementation by the apparatus of the above embodiment. As is apparent from this figure, when the slip speed is equal to or higher than Sa, the strip tension control signal is held to prevent the slip increase due to the adverse effect of the strip tension control and prevent the abnormal reduction of the strip tension. it is obvious.

It is also clear that the slip will automatically decrease.

Further, by adding the method described below, it is possible to speed up the elimination of the slip after holding the strip tension control signal.

This will be described with reference to FIG. The switch SW1 operates under the following conditions. ON when S> Sa, OFF when S <Sb. That is, the switch SW1 is turned ON only when it is determined that the slip has occurred in the bridle roll on either the input side or the output side and the strip tension control signal is held.

Further, the slip SW2 is switched depending on which bridle roll has caused the slip. When slippage occurs on the entrance side bridle roll, SW2 is switched to the P2 side, and when slippage occurs on the exit side bridle roll, SW2 is switched to the P1 side. When there is no slip, SW2 is at the neutral point.

First, a case where slippage occurs on the entrance-side bridle roll 5 will be described. At this time, as described above, the switch SW1 is turned on, the slip speed of the entrance-side bridle roll 5 is input to the operational amplifier 22, and as a result, the mill reduction is operated through the reduction cylinder 12 in the tightening direction.

When the mill reduction is tightened, the reverse speed increases, that is, the strip speed on the mill entry side decreases, so the slip speed of the entry side bridle roll 5 and the strip 15 decreases, and the entry side bridle roll 5 and The slip between the strips 15 is eliminated, and the grip force is restored.

Here, if the mill reduction is operated in the tightening direction, the advance rate also increases, so the strip tension on the mill exit side will decrease if this is the case, but at this time, as described above, the switch SW
2 is switched, and in this example, the slip is generated on the entrance side bridle roll, so the switch is switched to the P2 side,
A system 10, SW2, 23, 14 for controlling the mill outlet strip tension to the outlet strip tension set value or the outlet strip allowable lower limit value 25 at the mill speed is configured to reduce the mill outlet strip tension. To prevent. Further, at this time, the mill speed is operated in the direction of decreasing, but this operation is in the direction of decreasing the mill entrance side strip speed, and the direction of assisting the early recovery by the grip force between the bridle roll and the strip.

Next, a case where slippage occurs on the exit side bridle roll 6 will be described. At this time, similarly, the switch SW1 is turned on, the slip speed of the outgoing bridle roll is input to the operational amplifier 22, and as a result, the pressure reducing cylinder 1
Mill reduction is operated via 2 in the tightening direction.

When the mill reduction is tightened, the advance rate increases, that is, the strip speed on the outlet side of the mill increases, so the slip speed of the outlet bridle roll 6 and the strip 15 decreases, and the outlet bridle roll and the strip move quickly. The slip between them is eliminated and the grip power is restored.

Here, if the mill pressure reduction is operated in the tightening direction, the backward movement rate also increases, and the mill entry side strip tension decreases as it is, but at this time, as described above, the switch SW is used.
2 switches to the P1 side, and controls the mill entrance strip tension at the mill speed so as to reach the entry strip tension setting value or the entry strip tension allowable lower limit value 24, S
W2, 2314 is configured to prevent the strip tension on the mill entry side from decreasing. Further, at this time, the mill speed is operated in the direction of increasing, but this operation is in the direction of increasing the mill exit strip speed, and is in the direction of assisting the early recovery of the grip force between the bridle roll and the strip.

The above is the method of eliminating the slip early after holding the strip tension control signal. In addition, it goes without saying that upper and lower limit values are set for the mill pressure reduction operation amount and the mill speed operation amount for safety in this method.

When the slip is eliminated, the switches SW1,
Both SW2 are turned off, and normal strip tension control is performed.

〔The invention's effect〕

As described above, according to the method for avoiding abnormal reduction in tension of the temper rolling mill of the present invention, even if slip occurs on the bridle roll on the mill entrance side or the exit side, the slip is increased due to the adverse effect of the strip tension control. Therefore, it is possible to prevent the tension from being lowered abnormally.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of an embodiment of the method of the present invention, FIG. 2 is an example of a chart showing the effect of the present invention, and FIG. 3 is an implementation of a method for speeding up slip elimination. Example explanatory drawing, FIG. 4 is explanatory drawing of the structure of the elongation control system and strip tension control system of a temper rolling mill, FIG. 5, FIG. 6 is explanatory drawing of the modification of a strip tension control system, FIG. Is a relationship diagram between the friction coefficient between the bridle rolls and strips and the bridle roll rotation speed. FIG. 8 is a diagram showing a general chart example when an abnormally low tension of the temper rolling mill occurs, and FIG. 9 is a bridle roll and strip. FIG. 6 is an estimated diagram of a relationship between a slip speed and a friction coefficient between the two. 1 ... motor, 2 ... differential gear, 3 ... motor, 4 ... mill (temper rolling mill), 5 ... mill entry side bridle roll, 6 ...
Mill exit side bridle roll, 7 ... Sum tension control system, 8 ... Differential tension control system, 9 ... Input tension meter, 10 ... Exit side tension meter, 11 ... Controller, 12 ... Reduction cylinder, 13 ... Controller,
14 ... Mill motor, 15 ... Strip, 16 ... Inlet tension control system, 17 ... Outlet tension control system, 22, 23 ... Operational amplifier, 24 ... Inlet strip tension setting value or Inlet strip tension allowable lower limit value, 25 … Output strip tension setting value or output strip tension allowable lower limit value.

Claims (1)

[Claims] 1. A strip is constrained by a bridle roll on the inlet side and the outlet side of the mill, and these bridle rolls are mechanically connected and driven to control the elongation and to control the mill reduction position and the mill speed. In a temper rolling mill that controls the strip tension on the entry side and the strip tension on the mill side by providing a slip detector on the bridle roll on the mill entry side and the mill exit side bridle roll, either the mill entry side or the exit side When a slip occurs between the bridle roll and the strip, it is detected and the strip tension control signal is held to suppress the increase of the slip and prevent the abnormal tension drop caused by the slip between the bridle roll and the strip. A method for avoiding abnormal tension reduction of a temper rolling mill, characterized by: