JPH0446621A - Method for controlling speed of tandem rolling mill - Google Patents

Abstract

PURPOSE:To realize the stable tandem rolling by measuring the speed change of the stand which speed is reduced with electric-controlling caused on the over load, and reducing the speed of the other all stands only by the rate of this speed change. CONSTITUTION:For example, if the over load is generated on the 2nd stand and the speed control device 8 controls the electric current of the motor 7, the speed command being powered finally from the speed control device 8 to the motor 7, the signal of the contact point A to close with the current control to the motor 7, and the present rolling speed outputting from the pulse generator 18 are transmitted to the MRH correcting circuit 17. So, the MRH correcting circuit 17 searches the rate of the speed change generated based on the above electric wave control with the speed control 8 at each stand, controls for reducing the speed of the other all stands with the above rate of speed change till that the value of electric current of the motor 7 of this electric current controlled stand is stabilized within the regular max. electric current (concretely 90% of the max. electric current). Therefore, the stable tandem rolling can be executed if the speed change is generated on the electric current control stand.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a speed control method for a tandem rolling mill, and particularly to a technique for preventing troubles when overload occurs for a short period of time.

[Prior art] In a tandem rolling mill, the same material is rolled in multiple stands as described in "2nd edition, Recent hot strip manufacturing technology in Japan" (p. 97) (Japan Iron and Steel Institute, 1986). Since they are being rolled at the same time, the speed is controlled as shown in FIG.

That is, FIG. 2 mainly describes the second stand, or the rolled material 1 is rolled by a pair of work rolls W.

Here, in order to prevent the tension acting between the stands from becoming too small due to fluctuations in mass flow (volume velocity) and causing the rolled material 1 to fall down and get caught in the next stand, or to prevent the tension from becoming excessive and breaking, each stand is A looper 2 is disposed between them to control tension. The looper 2 is rotated by a looper motor (or cylinder) 3 as shown by the arrow in FIG.
A speed correction signal Δvt is output to.

Further, the fluctuation in mass flow, which is one of the causes of excess or deficiency of the tension, also occurs due to plate thickness deviation. AGC
(Automatic plate thickness control calculator) 5 constantly calculates plate thickness in order to perform plate thickness control based on information from the rolling down device 4, load cell 15, and the like. If the plate thickness is constant, the mass flow will be almost constant, so the excess or deficiency in tension will be small, but
In reality, thickness deviations that cannot be controlled occur and the mass flow changes. Therefore, the speed correction signal Δvh is outputted from the AGC 5 to the speed correction circuit 9.

The manual speed correction signal ΔvM from the manual speed corrector 10 is also output to the speed correction circuit 9, but this is to prevent the operating personnel from over or under tension due to sudden disturbances.

Further, the total speed correction amount ΔvT is output from the speed correction circuit 9R of the subsequent stand (here, the third stand) to the speed correction circuit 9 of the own stand, and similarly, the total speed correction amount ΔvT is output from the speed correction circuit 9 of the own stand. ΔvT is output to the speed correction circuit 9F of the front stage stand. For example, when insufficient tension occurs between the third stand and the fourth stand, a phenomenon called "double" occurs at the manufacturing site, and the above-mentioned correction circuit adjusts the speed of the third stand. This is because if the speed of the second stand is left unchanged, the above-mentioned "double" will occur between the second stand and the third stand, which is not preferable.

In addition, in the tandem rolling mill, the basic speed setting is calculated by the host computer 16 based on the planned plate thickness, advance rate, finishing temperature, etc., and is set at MRH (main speed setting circuit) 14.5.
It is output to the SRH (stand speed ratio setting circuit) 13.

Then, the set value of the MRH 14 and the set value of the 5SRH 13 are multiplied by a multiplier and outputted to the speed control device 8 of each stand.

By the way, all of the speed corrections of each stand are reflected on the front stand, but the first problem is the magnitude of the correction amount. That is, when a correction signal is output to the rear stand side, since the sheet passing speed becomes faster toward the rear stage, the minute correction amount at the front stage is expanded, making it difficult to perform stable control. The second point is that it is undesirable for the speed of the final stand to change from moment to moment in terms of controlling the winding device (not shown). Therefore, essentially, the speed correction signal is output in one direction, to the front stage stand.

[Invention or problem to be solved] However, in each stand, the capacity (rated maximum current) of the motor 7 is not infinite but has a limit, and it is designed to be compatible with the material that generates the maximum rolling load. be.

Therefore, if the motor 7 requires a torque exceeding its capacity due to setting errors (plate thickness, rolling load, etc.) or sudden disturbances, it is necessary to protect the motor 7 by limiting the current to the motor power supply. . At this time, if you continue rolling,
Only the current limiting stand will be slowed down.

As a result, considering the second stand in Fig. 2, either the tension is too small between the first stand and the second stand, or the speed of the first stand is reduced through the looper 2 so that there is no problem. Either there is an excessive tension between the 2nd stand and the 3rd stand, and the speed of the 2nd stand is increased through the looper 2, or the 2nd stand is already under current limit and cannot be sped up. However, as a result of excessive tension, the board may break in the worst case scenario.

This is the problem with the prior art, and if a speed change occurs due to current limitation to the electric motor in any of the stands, stable tandem rolling cannot be achieved.

The present invention is applicable to cases in which when an overload occurs in a certain stand due to a setting error in plate thickness, rolling load, etc. or a sudden disturbance, a current limit is applied to the electric motor of the stand, and as a result, a speed change occurs in the current control stand. The purpose is to realize stable tandem rolling.

[Means for Solving the Problems] The present invention provides a speed control method for a tandem rolling mill in which the rolling rolls of each stand are driven by an electric motor. Limit the current of the motor and find the speed change ratio that occurs based on the current limit at the current limit stand, or until the current value of the motor at the current limit stand stabilizes within the rated maximum current using a unique constant. , the speeds of all other stands are controlled to be decelerated at the speed change ratio described above.

[Function] According to the present invention, the speed change of the stand whose speed has decreased due to current restriction to cope with overload is measured, and the speed of all other stands is calculated by the speed change ratio of the current-limiting stand. Or lower it by a unique constant. Therefore, when the current is limited, the speed fluctuation that occurs in the current limiting stand can be reflected in all other stands, and as a result, the tension between each stand can be controlled to just the right amount.
Avoiding troubles such as sheet breakage and realizing stable tandem rolling.

[Example] FIG. 1 is a block diagram showing a tandem rolling mill to which the present invention is applied.

In the tandem rolling mill, an electric motor 7 drives the rolling rolls of each of the first to fourth stands. In each stand, the electric motor 7 is controlled by a speed control device 8 as described later.

In addition, each stand is equipped with the work roll W for rolling the rolling material 1, and the backup roll B which supports the work roll W.

A looper 2 is arranged between each stand. The looper 2 is operated by a looper electric motor (or cylinder) 3.
It rotates as shown by the arrow in the figure and performs tension control.As a result, due to fluctuations in mass flow, the tension acting between the stands becomes too small, causing the rolled material 1 to fall down and get caught in the next stand, or become too large. Breaking is prevented.

Here, since the tension control range by the looper 2 is theoretically narrow, each stand is provided with a tension control calculator 6. The tension control calculator 6 operates upon receiving the drive signal for the looper 2, and outputs a speed correction signal Δvt to the speed correction circuit 9 for the speed control device W8.

In addition, each stand is equipped with an AGC (automatic plate thickness control calculator) 5.
Or is provided. The AGC 5 constantly calculates the plate thickness for controlling the plate thickness based on information from the rolling down device 4 and the load cell 15.

Here, the variation in mass flow, which is one of the causes of excess or deficiency in tension, also occurs due to plate thickness deviation. However, if the thickness of the plate is kept constant by AGC5, the mass flow will be almost constant and the excess or deficiency of tension will be slight, but in reality, deviations in the thickness of the plate that cannot be controlled will occur and the mass flow will change. , AGC5 outputs a speed correction signal Δvh to the speed correction circuit 9.

Each stand is equipped with a manual speed compensator 10. The manual speed compensator 10 sends a manual speed compensation signal to the speed compensation circuit 9 in order to prevent operating personnel from over- or under-tensioning the tension due to sudden disturbances. Output ΔvM.

In addition, in a tandem rolling mill, the total speed correction amount ΔvT is output from the speed correction circuit 9R of the stage stand (in this case, the third stand) to the speed correction circuit 9 of the own stand, and the speed of the own stand is similarly adjusted. The correction circuit 9 is configured to output the total speed correction amount ΔvT to the speed correction circuit 9F of the front stage stand. For example, when insufficient tension occurs between the third stand and the fourth stand, a phenomenon called "double" occurs at the manufacturing site, and the above-mentioned correction circuit reduces the speed of the third stand. This is because if the speed of the second stand is left unchanged, the above-mentioned "double" will occur between the second stand and the third stand, which is not preferable.

In addition, in a tandem rolling mill, the basic speed setting is calculated by the host computer 16 based on the planned plate thickness, advance rate, finishing temperature, etc., and the MRH (main speed setting circuit) 14.5
It is output to the SRH (stand speed ratio setting circuit) 13.

Then, the set value of the MRH 14 and the set value of the 5SRH 13 are multiplied by a multiplier and outputted to the speed control device 8 of each stand.

The above is the conventional speed control method,
The set speed V1 (1 indicates the stand) by the speed control device 8 is expressed by the following equation (1). However, V (is the maximum speed, MRH is the setting value of MRH14 (7), and 5SRH is the setting value of 5SRH13.

vi= ViX MRHX SSR old × (1+ΔV
ti + △Vh1 + △VMI + △v r t + l)
(i) In each stand, when a torque exceeding the rated maximum current of the motor 7 is generated, the speed control device 8 limits the current of the motor 7 to protect the motor 7.

However, in the present invention, an MRH correction circuit 17 is added to each stand.

The MRH correction circuit 17 adjusts the speed command finally output from the speed control device 8 to the electric motor 7, the signal of the contact A which is closed by limiting the current to the electric motor 7, and the current rolling speed output from the pulse generator 18. be transferred.

Thereby, the MRH correction circuit 17 calculates the speed change ratio that occurs based on the above-mentioned current limitation by the speed control device 8 of each stand, and
Until the current value becomes stable within the rated maximum current (specifically, 90% of the maximum current), the speeds of all other stands are decelerated at the speed change ratio described above.

That is, the MRH correction circuit 17 calculates the speed change ratio described above, and sends a correction signal based on this speed change ratio to the MRH 14.
The MRH command from the MRH command is multiplied by a calculator, and the input value to the speed control device 8 of each stand is corrected.

By the way, in this embodiment, the MRH correction circuit 17 calculates the above-mentioned speed change ratio R using the following equation (2).

However, vact is the current speed, and ■ is the speed command.

Incidentally, when the contact A is open, the MRH correction circuit 17 performs the following:
It outputs R=1.0.

Incidentally, since the output of the MRH correction circuit 17 changes due to switching, a rate circuit 17A is provided to protect the motor.

In addition, in Fig. 1, MRH
Although the correction circuit 17 is provided only in the second stand, it is natural that it would be better to provide it in all stands.

Further, for example, a speed control circuit may be configured to output a correction signal based on the speed change ratio of the MRH correction circuit 17 provided in each stand to each speed correction circuit 9 of the front stage stand and the rear stage stand. In the end, the speed control circuit becomes unnecessarily complicated, and as a result, the speeds of all the stands are changed as in the present embodiment. Therefore, MRH
The correction signal based on the speed change ratio of the correction circuit 17 is M
It is extremely useful in implementing the present invention to adopt the above-mentioned simple circuit configuration in which the MRH command from the RH 14 is multiplied by a calculator.

In addition, the MRH correction circuit 17 uses a method of "setting JrR to a fixed value only by opening and closing contact A" which indicates current limitation, if it is difficult to "sequentially calculate" the speed change ratio described above. Alternatively, the speed command (MRH) of all the stands may be uniquely lowered by R% (R is a fixed value) by the current limit signal of any of the stands.

According to the above embodiment, the speed change of the star whose speed has decreased due to current restriction to cope with an overload is measured, and the speed of all other stands is calculated as the speed change ratio of the current limit stand, Or lower the bone height by a unique constant. Therefore, when the current is limited, the speed fluctuation that occurs in the current limiting stand can be reflected in all other stands, and as a result, the tension between each stand can be controlled to just the right amount, and troubles such as board breakage can be avoided. , stable tandem rolling can be achieved.

Note that the present invention can be applied to all cases in tandem rolling mills.

[Effects of the Invention] As described above, according to the present invention, when an overload occurs in a certain stand due to a setting error in plate thickness, rolling load, etc. or sudden disturbance, the current limit is applied to the electric motor of the stand. , stable tandem rolling can be achieved when speed changes occur in the current control stand.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a tandem rolling mill to which the present invention is applied, and FIG. 2 is a block diagram showing a conventional example. 7... Electric motor, 8... Speed control device, 9... Speed correction circuit, 17... MRH correction circuit. Agent Patent Attorney Osamu Shiokawa

Claims (1)

[Claims] (1) In a speed control method for a tandem rolling mill in which the rolling rolls of each stand are driven by an electric motor, when a torque exceeding the rated maximum current of the electric motor of that stand is generated in a certain stand, the current of the electric motor is limited, and the current of the electric motor is Find the rate of speed change that occurs based on the current limit at the limit stand,
Alternatively, a tandem rolling mill characterized in that the speeds of all other stands are decelerated at the speed change ratio described above until the current value of the motor of the current limiting stand is stabilized within the rated maximum current by a unique constant. Speed control method.