JPH037461B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a curved continuous casting machine that continuously casts slabs with a curved guide rail of a continuous body following a mold, and in particular a curved continuous casting machine that continuously casts slabs by straightening at bending points. This invention relates to a roll speed control device for compression continuous casting that performs casting while applying compressive force to a slab in order to prevent internal cracks and surface cracks in the slab due to tensile force.

<Prior art> In a curved continuous casting machine as shown in FIGS. 1a and 2a, a slab is pulled out by a push drive roll in a curved part, a braking force is applied by a group of speed reference rolls in a horizontal part, Alternatively, compression continuous casting is performed in which the slab is pulled out by a group of speed reference rolls, a braking force is applied by brake rolls, and compressive force is applied in the longitudinal direction of the slab to improve the quality of the slab.

In such compression continuous casting, if the pushing force (braking force in the case of the system shown in Figure 2 a) applied to the slab becomes excessive, it will cause damage between the slab and the pushing roll (braking roll in Figure 2 a). Slips occur, which cause slip defects on the surface of the slab and impair the surface quality of the slab.At the same time, the level of the molten steel in the mold fluctuates rapidly due to rapid fluctuations in the speed of the slab. poses a great danger to foundry operations. Furthermore, when such a situation occurs, it goes without saying that the desired compressive force cannot be achieved and the effect of improving slab quality is reduced.

In conventional compression continuous casting control, the pushing force of the push roll or the braking force of the brake roll is controlled only for each roll group consisting of multiple push rolls or brake rolls, which prevents the occurrence of slips. In order to do this, either the pushing force or braking of all pushing rolls or braking roll groups is reduced to reduce the pushing force or braking force as a whole, or the pushing (braking) rolls of all pushing rolls or braking rolls of the pushing roll group or braking roll group are reduced. The only option was to increase the force and apply excessive pressure to the slab. However, all of these methods either reduce the improvement effect on slab quality or
Otherwise, the quality of the slab was adversely affected.

<Problems to be solved by this invention> As a solution to these problems, it is possible to individually control the drive motors of the push roll or brake roll,
One possible method is to suppress the slip by reducing the pushing force or braking force of only the roll where the slip has occurred, thereby minimizing the amount of decrease in the pushing force or braking force. Furthermore, it is also conceivable to make the pressing force of the push roll or the brake roll individually adjustable, and increase the pressing force of only the roll where the slip has occurred to suppress the slip and minimize the adverse effect on the slab.

However, among these methods, in the method of adjusting the pressing force of a push roll or a brake roll, there is an optimum pressure for pressing the slab, so it is not desirable in terms of the quality of the slab to significantly increase or decrease this value. Moreover, the pressing device such as a hydraulic device also becomes large-sized, resulting in a large equipment cost.

For this reason, a method of adjusting the pushing force or braking force generated by the drive roll is adopted, but a slip detector is installed on each drive roll or on a representative drive roll to detect when slip has occurred on the drive roll. Therefore, there are methods of emitting a signal to automatically or manually reduce the pushing force or braking force of the drive roll, or of intentionally increasing the pushing force or braking force of the drive roll to cause slip. A method is also used in which a detector detects the pushing force or braking force immediately before slipping, and this value is used as the compression force set value.

However, these conventional methods require a slip detector to detect slips, making them complicated and expensive. Furthermore, since the measures were taken after slips occurred, they did not fundamentally solve the problems caused by slip flaws at the time slips occurred, deterioration in the surface quality of the slab, and fluctuations in casting speed.

Therefore, the present invention solves the problems of the conventional roll speed control method as described above, prevents the occurrence of slip, truly stabilizes the slab speed, maintains the desired compression force, and reduces equipment costs. An object of the present invention is to provide a roll speed control device for a curved continuous casting machine that can improve the quality of slabs at low cost.

<Means for Solving the Problems> The present invention provides a roll speed control device for a curved continuous casting machine that continuously casts slabs with a curved guide rail of a continuous body following a mold, in which the rollers constituting the guide rail are Each motor driving the group is provided with an independent speed control power supply device which has a speed detector and uses a speed signal from the speed detector as a negative feedback loop, and a predetermined one of the mutually independent speed control power supply devices is provided. a minute speed setting that provides the speed control power supply driving the rollers in the section with an incremental or decrement speed setting that is small relative to the desired casting speed and sufficient to saturate a speed control amplifier in the speed control power supply; The present invention is characterized in that a pushing force or braking force limiter is provided which allows the saturation value of the speed control amplifier to be changed from the outside.

With this configuration, if a small increase is set for the casting speed setting, the actual casting speed will not increase, so the deviation of the speed control amplifier will increase, and this will cause the limit value of the pushing force limiter to increase. This limit value becomes the pushing force setting, and the desired compression force is applied. When a slip is about to occur, the load on the drive roll decreases, the rotation speed of the drive roll increases, and the deviation of the speed control amplifier becomes smaller because the increased setting is minute, and the output of the speed control amplifier becomes smaller than the limit value. The occurrence of slips is automatically suppressed. These actions are performed for each drive roll to maintain the desired compressive force while preventing the occurrence of slip.

<Example> Hereinafter, the present invention will be explained using the illustrated example. FIG. 1a shows a schematic diagram of a curved continuous casting apparatus, FIG. 1b shows a block diagram of a push roll drive motor control device, and FIG. 1c shows a block diagram of a speed-based roll drive motor control device.

In this curved continuous casting device, a push roll 3' is arranged at the curved part, and drive rolls (indicated by black circles) provided for a predetermined number of push rolls 3' each have independent push rolls. A pushing force is applied to the slab 2 under the control of the roll drive motor control device 3 .

Furthermore, a speed reference roll 4' is provided in the straight line downstream of the curved part, and each drive roll (indicated by a black circle) provided at a predetermined number is controlled by an independent speed reference roll drive motor. The casting speed is controlled by the device 4 in order to maintain the casting speed stably.

The push roll drive motor control device 3 shown in FIG. 1b is equipped with a speed control amplifier SC, and an addition/subtraction point 8 is provided upstream of the speed control amplifier SC.

To this addition/subtraction point 8, the casting speed setting V and the slight increase in casting speed ΔV are added, and further a speed feedback signal _VFB from a speed detector TG, which will be described later, is subtracted.

The output of the addition/subtraction point 8 is amplified by the speed control amplifier SC and then input to the addition/subtraction unit 9 provided at the next stage. A current detection value signal from a current detector CD, which will be described later, is input to the adder/subtractor 9, and the value is subtracted from the output signal of the speed control amplifier SC and input to the current control amplifier CC.

A power converter 7 is installed on the output side of the current control amplifier CC.
is connected, and this power converter 7 outputs power from the power source to the drive motor M in accordance with the output signal from the current control amplifier CC. This power converter 7
A current detector CD is provided between the drive motor M and the drive motor M, and detects the current value actually supplied to the drive motor M and feeds it back to the addition/subtraction point 9.

Further, a speed detector TG is attached to the drive motor M, and supplies a speed feed back signal to the addition/subtraction point 8.

Further, a pushing force limiter 6 is installed across the input end and output end of the speed control amplifier SC. The pushing force setting P value from the pushing force setting device 5 is input to this pushing force limiter 6.
Limit the output of the speed control amplifier SC according to the value.

The speed reference roll drive motor control device 4 shown in FIG. 1c includes a speed control amplifier SC and a current control amplifier.
Equipped with CC, the casting speed is automatically controlled so that the actual casting speed V _FB matches the casting speed setting V, and the casting speed is maintained stably.

These push roll drive motor control device 3 and speed reference roll drive motor control device 4 are provided for each push roll 3' and speed reference roll 4', but one roll drive motor control device 3 and speed reference roll drive motor control device 4 are provided for each push roll 3' and speed reference roll 4', Although it is possible to perform automatic control using the control devices 3 and 4, the control devices 3 and 4 are provided for each roll 3' and 4' for reasons explained in detail later.

Here, if the casting speed setting V is input to the speed control amplifier SC from the addition/subtraction point 8 in the push roll drive motor control device 3, the drive motor M operates as a speed reference roll, but if the casting speed slight increment setting ΔV is further input. The rotational speed of the drive motor M tends to increase by a minute amount. Here, since the slab 2 is engaged with the speed reference roll 4' as described above, the actual casting speed does not increase, and the speed control amplifier SC
deviation becomes larger.

Since the speed control amplifier SC amplifies this by its own amplification degree, the current command, which is the output of the speed control amplifier SC, becomes large and reaches the limit value of the pushing force limiter 6.

Therefore, the pushing force setting P, which is the limit value, becomes the current setting, that is, the compression force setting, and this compression force can be set by the pushing force setting device 5 provided externally.

Here, the greater the amplification degree of the speed control amplifier SC, the more effective it is, and the casting speed minute increase setting ΔV
Even if the input amount is small, it still applies to the limit value, so even if a slip occurs between the slab 2 and the push roll 3', it will not adversely affect the casting speed. That is, when the load on the push roll 3' decreases and the rotational speed of the drive motor M increases, the deviation of the speed control amplifier SC becomes smaller, and the output becomes smaller than the limit value, thereby suppressing the occurrence of slip.

Therefore, the smaller the casting speed minute increment setting ΔV and the higher the amplification degree of the speed control amplifier SC, the higher the quick response in the event of a slip and the higher the ability to prevent slip, and the drive motor of the push roll 3' It is preferable to install a push roll drive motor control device 3 for each drive roll drive motor as an independent control device because the amplification degree of the automatic control system, especially the speed control amplifier, can be increased.

This can be similarly applied to the speed reference roll drive motor control device 4 that controls the drive roll of the speed reference roll 4'.

In this example, the amplification degree of the speed control amplifier SC is
It is set to about 40 times, and the casting speed slight increase setting ΔV is input about 1 to 3% of the casting speed setting V. Therefore, even if the pushing force setting P is set too high and slip occurs, the rotation of the drive roll of the pushing roll 3' will only increase by 3% at most. However, in reality, the drive roll does not completely separate from the slab 2, so the speed is controlled with almost no slippage, and the casting speed is not varied.

If you lower the limit value of the speed control amplifier SC output, the pushing force will also decrease accordingly, but if it exceeds the normal upper limit value, slips will occur, so the slab width, slab thickness,
The pushing force setting device 5 is used to set the pushing force so as not to exceed the limit pushing force calculated from the temperature, the pushing force of the driving roll, the coefficient of friction between the driving roll and the slab, and the specific gravity of the molten steel.

Another embodiment of the present invention is shown in FIGS. 2a, b, and c, in which a speed reference roll 4' is provided at a curved portion of the slab 2 conveyance line. Then, the brake roll 1 is applied over a predetermined section from the end of the curved part.
0' is arranged, and a speed reference roll 4' is arranged downstream of the line again. Therefore, in the continuous casting machine shown in FIGS. 2a, b, and c, a braking force is applied to the slab 2 from the braking roll 10' as a compressive force.

The control block diagram of the brake roll drive motor control device 10 that controls the drive roll of the brake roll 10' is shown in FIG. 2b, and is compared with the push roll drive motor control device 3 shown in FIG. 1b. The configuration is such that the pushing force setting device 5 and the pushing force limiter 6 are replaced with a braking force setting device 11 and a braking force limiter 12, respectively.

Further, the casting speed minute decrease setting ΔV inputted to the addition/subtraction point 8 is given a negative sign.

The control block diagram of the speed reference roll drive motor control device 4 shown in FIG. 2c has the same configuration as the control block diagram shown in FIG. 1c, and the actual casting speed V _FB matches the casting speed setting V. Automatically control.

Normally, the slab width, slab thickness, temperature, pressing force, etc. change depending on various conditions, so the pressing force setting device 5 and the braking force setting device 11 are configured with a microcomputer to detect the various conditions. It is also possible to have an arithmetic function to automatically set the compression force.

Alternatively, the purpose can be achieved by creating a table of compression force settings by hand calculation or the like, and allowing the operator to manually set the table.

The settings of the compression force, including the pushing force and braking force, are within the rated operating range of the drive motor to prevent overload of the drive motor.

The device of the present invention can be installed on almost all existing continuous casting machines, has low equipment costs, and can be installed on all push and brake roll drive motor control devices to set the compression force for each drive roll. , it is possible to perform compression according to the conditions of the continuous casting machine.

In addition, by setting the casting speed slight increase and decrease to completely zero, it is possible to use a speed-based roll drive motor, or by setting the compression force to an extremely small value,
If the compression force is set to a value that compensates only for the mechanical loss consumed by the drive rolls, it is possible to create a group of unstrained rolls, and it is possible to smoothly perform compression continuous casting and non-compression continuous casting while performing continuous casting. can be switched.

Furthermore, as shown in FIGS. 2a, b, and c, the compression force can be adjusted by the braking force simply by changing the polarity of ΔV. Therefore, as mentioned above, it is possible to easily switch between the speed reference roll, push drive roll, and brake drive roll.
It is possible to switch between push drive, brake drive, and speed reference roll during continuous casting.

<Effects of the Invention> The embodiments of the roll speed control device for a continuous casting machine according to the present invention are as described above, and can provide the following effects.

A desired compressive force can be applied while preventing the occurrence of slips, and the quality of the slab can be improved.

Using a control device having the same configuration, it is possible to freely select a casting method for adjusting the roll speed of normal casting, compression casting, and no-load casting depending on operating conditions and the like.

Further, abnormal rotation of the drive roll can be detected, and occurrence of abnormal current, power supply trip, and casting trip at the time of abnormal rotation can be prevented.

Furthermore, a complicated central processing unit is not required, and a simple controller for each motor is sufficient.

[Brief explanation of the drawing]

FIGS. 1a, b, and c are schematic diagrams and control block diagrams showing an embodiment of the present invention, and FIGS. 2a, b, and c are schematic diagrams and control block diagrams showing another embodiment. 1... Mold, 2... Slab, 3... Push roll drive motor control device, 3'... Push roll, 4...
Speed reference roll drive motor control device, 4'... Speed reference roll, 5... Pushing force setter, 6... Pushing force limiter, 7... Power converter, 8, 9... Addition/subtraction point, 10... Brake roll drive motor control device, 1
0'...Brake roll, 11...Brake force setting device, 1
2... Braking force limiter.

Claims (1)

[Scope of Claims] 1. In a roll speed control device for a curved continuous casting machine that continuously casts slabs on a curved guide rail of a continuous body following a mold, for each roller drive motor of a group of rollers constituting the guide rail. is provided with mutually independent speed control power supply devices each having a speed detector and using a speed signal from the speed detector as a negative feedback loop, and driving the rollers in a predetermined section of the mutually independent speed control power supply devices. Speed control power supply,
A minute speed setting device is provided that provides a speed setting that is minute increment or decrement relative to the desired casting speed and is sufficient to saturate the speed control amplifier in the speed control power supply, and the saturation value of the speed control amplifier is set to A roll speed control device for a curved continuous casting machine, characterized by being provided with a pushing force or braking force limiter whose settings can be changed from the outside.