JPS5820360A - Continuous casting method for steel - Google Patents

Abstract

PURPOSE:To cast steel continuously and stably without slipping, over-pushing, etc. by controlling the torque of motors for respectively plural pieces of driving rolls for pushing and reference driving rolls with a command controller in accordance with the signals for the decrease in pushing force. CONSTITUTION:When the signal indicating the generation of a slip in any of the driving rolls 4' for pushing of, for example, No.1 block of forcing rolls 4 is fed from a device 14 for detecting slips to a device 16 for generating the signal for decrease in pushing force, the prescribed rate of the decrease in pushing force is operated with the device 16. Such a signal for the decrease in pushing force which regulates the pushing force by the rolls 2 to the operated pushing force is fed to a command controller 13, then the rolls 4' are controlled to the prescribed torque by the device 13 and the slip between the rolls 4' and an ingot 2 is eliminated. When a slip is generated in the reference driving roll 6' of speed reference rolls 6, the rolls 4' of the No.1 and No.2 blocks are controlled of torque. Even when the signal from a device 15 for detecting unstability is fed to the device 16, the rolls 4' are controlled of torque in the same way as mentioned above.

Description

[Detailed description of the invention] The present invention relates to a continuous casting method for steel.

In the continuous casting method, when the slab is straightened at multiple slab straightening points in the slab guide track following the mold, the tensile force generated during straightening the slab at the straightening points causes internal cracks in the slab. or surface cracks may occur.

As a casting method to prevent this, there is a so-called compression casting method in which casting is performed while applying compressive force to the slab.

To give an overview of the compression casting method, in continuous casting equipment where multiple slab straightening points are provided on the slab guide track following the mold, multiple slab pushing rolls are installed upstream of the final straightening point. A plurality of speed standard rolls for drawing the slab are installed downstream of the final straightening tube, and by setting the torque of the pushing roll to be larger than the torque of the speed standard roll, casting is performed while applying compressive force to the slab. This is a casting method that performs The drive rolls of the push roll and the speed reference roll have cylinders, and a slab pressing force is applied to them in order to prevent slippage occurring between them and the slab.

However, when performing operations such as changing the ladle, changing the tundish, changing the mold, or casting different steel types in succession during the above-mentioned compression casting, it is necessary to reduce the slab withdrawal speed during the above operations, but the casting speed When the cooling conditions of the slab decrease, the position of the crater end moves to the upstream side if the cooling conditions of the slab remain the same. As a result, the balance between the bulging force (the force that pushes the shell outward due to the static pressure of the molten steel) and the slab pressing force by the push roll and/or the speed reference roll is lost.
Slip occurs between the slab and each of the rolls.

Further, if the torque of the push roll is increased excessively in order to increase the compressive force applied to the slab by the push roll, slippage occurs between the slab and the push roll.

Furthermore, when the above-mentioned slip occurs, the set through compression force is not applied to the slab.

If the above situation occurs, the slab cannot be cast properly.

This invention was made to solve the above-mentioned problems.

A plurality of slab straightening points are provided on the slab guide track following the mold, and a plurality of slab pushing rolls are installed upstream of the final pressure point.
A plurality of speed reference rolls for drawing slabs are provided downstream of the final straightening point, and the plurality of slab pushing rolls apply compressive force to the slab while casting the continuous steel. In the casting method.

The plurality of push rolls are divided into at least two blocks, and the rotational speed and current value of the push drive roll motor of the plurality of push rolls and the reference drive motor of the plurality of speed reference rolls are determined by the motor. Based on each detection signal, the slip detection device individually detects each detection signal.
Generating a slip occurrence signal indicating that slip has occurred in any of the blocks or the plurality of speed reference rolls, and detecting a total current flowing through the plurality of motors in each block for each block. Then, the instability detection device compares the detected total current value with a preset total current value to be applied to the plurality of motors in each of the blocks.

If the detected total current is larger than a predetermined value, an instability occurrence signal is generated, and at the same time, the instability detection device causes the rotational speed of the reference drive roll motor to be set in advance. Compared with the slab drawing speed,
If the rotational speed is greater than a predetermined value, an instability occurrence signal is generated, and then either the slip occurrence signal or the instability occurrence signal is generated by the pushing force reduction signal generating device.

or 7. Generate a pushing force reduction signal based on the signals, and based on the pushing force reduction signal, the command control device:
Controlling the torque of the plurality of pushing drive roll motors and the plurality of reference drive roll motors, and thus,
It is characterized by stable casting without slipping, over-indentation, etc.

An embodiment of the method of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic explanatory diagram showing the configuration of the continuous casting method of the present invention.

In FIG. 1, l is a mold, 2 is a slab continuously pulled out from the mold l by each roll described later, and 3 is a support roll consisting of a plurality of rolls provided directly below the mold l. The reed is a roll that guides the slab 2 pulled out from the mold l to a push roll to be described later. Reference numeral 4 denotes a push roll consisting of a plurality of rolls provided on the downstream side of the support roll 3, a push drive roll 4' having a cylinder 5, and a non-drive roll 4'. The push roll 4 has the function of horizontally straightening the slab 2 and applying compressive force to the slab 2. The compressive force is applied to the pushing drive roll 4'
This can be obtained by increasing the torque of the reference drive roll of the speed reference roll, which will be described later. The cylinder 5 presses the pushing drive roll 4' against the slab 2 in order to prevent slippage occurring between the pushing drive roll 4' and the slab 2 when applying compressive force to the slab 2. act. The push roll 4 is divided into several blocks,
(In the example shown in Fig. 1, it is divided into two blocks, 1111 and N12.) The pushing drive roll 4' and cylinder 5 of each block are connected to a motor control device and a cylinder control device, which will be described later for each block. They are each controlled by Reference numeral 6 denotes a speed reference roll consisting of a plurality of rolls, which is provided on the downstream side of the push roll 4, and includes a reference drive roll 6' having a cylinder γ and a non-drive roll 6.
′ is there. The cylinder 7 functions to press the standard drive roll 6' against the slab 2 in order to prevent slippage between the slab 2 and the standard drive roll C. The reference drive roll 6' and the cylinder 7 are controlled by a motor control device and a cylinder control device, respectively, which will be described later. Reference numeral 8 denotes a motor control device for controlling the torque of the pushing drive roll 4' for each block and controlling the torque of the reference drive roll C.
a current detector 9 that determines the total current flowing through the motors for the plurality of pushing drive rolls 4' in each block; and the motors for the plurality of pushing drive rolls 4' in each block and the speed reference roll. 6, and a current detector 10 that individually measures the current flowing through the motor for a plurality of reference drive rolls 6', and the pushing drive rolls 4' are torque-controlled by a command control device to be described later for each block. .

11 is a motor for the pushing drive roll 4' and a reference drive port, -
The next tachogenerator, 1, is directly connected to the motor for
2 is a cylinder control device for controlling the pressing force of the cylinder 5 of the pushing drive roll 4' for each block and controlling the pressing force of the cylinder 7 of the reference driving roll 6';
13 is a command control device that sends control command signals to the motor control device 8 and the cylinder control device 9; 14 is a slip detection device; ' and a plurality of reference drive rolls 6' motors, and a motor rotation speed signal from a tachogenerator 11 directly connected to each of the motors. death,
If the values of these signals both exceed predetermined values, the speed reference roll 6 is
This serves to send a slip occurrence signal indicating that a slip has occurred to a pushing force reduction signal generating device, which will be described later. Reference numeral 15 denotes an instability detection device, which detects the total current value flowing through the motors for the drive rolls 4' in each block of the push roll 4, detected by the current detector 10, and the output from the command control device 13. , compare the set slab valve's pushing force by the pushing drive roll 4', that is, the set current value of the motor for the pushing drive roll 4', and determine that the difference is the unstable fluctuation tolerance value, that is, the pushing drive roll 4'. If it exceeds a predetermined slab pushing force to be applied to the slab 2, the pushing force reduction signal generating device generates an instability occurrence signal indicating that the slab pushing force by the pushing roll 4 has become unstable. It has the effect of sending the Regarding the speed reference roll 6, the reference drive roll 6
Compare the rotational speed of ' and the set casting speed, and check that the difference exceeds the unstable fluctuation tolerance, that is, the predetermined slab drawing speed by the standard-driven roll 6') f, the standard speed roll 6
An instability occurrence signal indicating that the slab withdrawal speed has become unstable is sent to the pushing force reduction signal generator. 16
is a pushing force reduction signal generating device, which sends a pushing force reduction signal to the command control device 13 based on a signal ζ2 from either or both of the slip detection device 14 and the instability detection device 15. be.

Next, a slip detection method using the slip detection device 14 will be explained with reference to FIG. 2.

The slip phenomenon is a phenomenon that causes a relative difference between the moving speed of the slab 2 and the circumferential speed of the drive rolls (pushing drive roll 4' and reference drive roll 6'), and when the slip phenomenon occurs, the drive roll motor As the rotational speed of the drive roll changes greatly, the drive roll becomes unloaded. For this reason, the current flowing through the drive roll motor 1 also changes greatly. Therefore, it is determined whether or not a snap crab has occurred by checking whether the rotational speed and current of the motor both exceed allowable values or whether the strain force is greater than or equal to the allowable value. That is, as shown in Figure 2 (a) l, a motor speed reference value is created for each motor, and the difference between the speed reference value and the motor's actual rotational speed determines the speed fluctuation tolerance value (εB?). surpassed, and moreover, the second
As shown in Figure (b), the difference between the motor current reference value and the actual current flowing through the motor is the current fluctuation tolerance i value (a, ,
), it is determined that a slip has occurred between the drive roll and the slab, and a slip occurrence signal is sent to the pushing force reduction signal generator 16.

The speed reference value is determined by averaging a plurality of pieces of data sampled at a constant period α. time t
When determining the speed reference value V, Gt) based on three pieces of data, it is determined by the following formula.

Similarly, the current reference value is determined by the following equation.

In FIGS. 2(a) and 2(b), the case where the speed reference value and the current reference value exceed the allowable values ε8V and εBi, that is, the slip occurrence period is indicated by T8.

The advantage of creating standard values for individual motors in this way is that if a common standard value is set for all motors, the rotational speed of the motors will vary due to machine manufacturing errors such as reduction gears, so all motors It is necessary to strictly adjust the speed of each motor so that the rotational speed of each motor is constant, which takes a lot of time and effort, but this time and effort can be saved.

Next, the pushing force reduction signal generating device 16 will be further explained with reference to FIG. 3.

When the slip detection device 14 or instability detection device 15 sends a slip occurrence signal or instability occurrence signal to the pushing force reduction signal generating device 16, the device 16 calculates the required pushing force after slip or instability occurs according to the following formula. The force is calculated, and a pushing force reduction signal corresponding to this pushing force is sent to the command control device 13.

b=α−□ However, (a) the pushing force before slippage or instability occurs; b After slippage or instability occurs pushing force, C: Minimum required to pull out the slab the power of, N: Number of times the pushing force is decreased.

Even after the pushing force is applied to the slab 2 by the pushing roll 4 for a certain period of time ('ro) due to the pushing force mentioned above, a slip or instability occurrence signal is still generated by the pushing force reduction signal generator 16.
If the pushing force is sent, the pushing force is set by subtracting the pushing force (Δy=-;) that was decreased the first time from the pushing force after the decrease. In this way, the pushing force is gradually reduced until the signal no longer occurs. Incidentally, even when the slip occurrence signal and the instability occurrence signal are sent to the pushing force reduction signal generating device 16 at the same time, the pushing force is reduced stepwise in the same way as in the case described above.

Since it consists of the above configuration, 1, for example, the hidden 1 of the push roll 4.
When a slip occurrence signal indicating that slip has occurred in any of the pushing drive rolls 4' of the block is sent from the slip detection device 14 to the pushing force reduction signal generating device 16, the device 16 detects a predetermined amount of pushing force reduction. The calculation is made, and a pushing force reduction signal is sent to the command control device 13 so that the pushing force of the slab by the pushing roll 4 becomes the calculated pushing force. Said 1
The 1 ml block pushing drive roll 4' is controlled to a predetermined torque according to a command from the command control device 13.

As a result, the slip between the pushing drive roll 4' and the slab 2 is eliminated, and when the slip detection device 14 no longer sends the slip occurrence signal to the pushing force reduction signal generating device 16, casting continues in this state. If the slip occurrence signal is still issued even after reducing the pushing force, a signal to further reduce the pushing force is sent from the pushing force reduction signal generator 16 to the command control device 13. This operation continues until the slip occurrence signal is no longer issued.

The above explanation is for the case where a slip occurs in any of the pushing drive rolls 4' of the N11L1 block of the pushing rolls 4, but if slip occurs in any of the pushing drive rolls 4' of the Taki 2 block, , N12 push drive roll 4' is torque controlled in the same manner as described above. on the other hand,
A slip occurrence signal indicating that slip has occurred on the reference drive roll 6' of the speed reference roll 6 is detected by the slip detection device 1.
4 to the pushing force reduction signal generating device 16, the device 16 sends a signal to the command control device 13 to reduce the pushing force by the pushing drive rolls 4' of the Il & L1 and floor 2 blocks, and Block pushing drive roll 4'
is torque controlled.

Even when an instability occurrence signal is sent from the unstable ball ejection device 15 to the pushing force reduction signal generator device 16, the pushing drive roll 4' is torque-controlled in the same way as in the case of slip occurrence described above.

In the method of the present invention, the pressing pressure of the cylinders 5 and 7 is set to such a level that the driving force from the drive roll during casting can be transmitted to the slab without causing internal cracks due to slipping or over-pressing. Adjustment is made by the cylinder control device 12.

As explained above, according to the present invention, there are cases in which slip occurs between the drive roll and the slab during compression casting, and cases in which the pushing force from the pushing hole exceeds the allowable value of the set pushing force. ,
Alternatively, if the slab drawing speed by the speed standard roll exceeds the allowable value of the speed setting value, the pushing force of the pushing roll can be reduced step by step until the above phenomenon disappears, so that slips and This brings about the extremely useful effect of being able to perform stable compression casting without over-indentation.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing the configuration of the continuous casting method of the present invention, FIG. 2 is an explanatory diagram showing the slip detection method, and FIG.
The figure is an explanatory diagram showing a state in which the pushing force is reduced. In the drawings, l...Mold 2...Slab 3...Support roll 4...Pushing roll 4'...Pushing drive roll 4'...Non-drive roll 5...Cylinder
6...Speed reference roll 6'...Reference drive roll 6'...Non-drive roll 7...Cylinder
8... Motor control device 9.10... Current detector 11... Tacho generator 12... Cylinder control device 13... Command control device 14... Slip detection device 15... Unstable detection Device 16,...
Applicant for the device that initiates the state of reduced pushing force: Agent for Nippon Kokan Co., Ltd. Keitabe Tsutsumi (and one other person) Figure 3 Time-

Claims (1)

[Claims] A plurality of slab straightening points are provided on the slab guide track following the mold, and a plurality of slab pushing rolls are provided upstream of the final straightening point.
A plurality of speed standard rolls for drawing slabs are provided downstream of the final straightening point. In the continuous steel casting method, the casting is performed while applying compressive force to the slab through the plurality of slab pushing ports. The plurality of push rolls are divided into at least two blocks, and the rotational speed and current value of the push drive roll motor of the plurality of push rolls and the reference drive motor of the plurality of speed reference rolls are set to 1. Detecting each motor individually, and using a slip detection device to generate a slip occurrence signal indicating that slip has occurred in any of the 4-blocks or the plurality of speed reference rolls based on each of the detection signals, On the other hand, the total current flowing through the plurality of motors in each of the blocks is detected for each block, and the instability detection device combines the detected total current value with the preset value of the current in each block. Compare the total current value that should flow to multiple motors. If the detected total current is larger than a predetermined value, an instability occurrence signal is generated, and at the same time, the instability detection device detects the rotational speed of the reference drive roll motor and a preset value. Compared with the slab drawing speed,
If the rotational speed is greater than a predetermined value, an instability occurrence signal is generated, and then either one or both of the slip occurrence signal and the instability occurrence signal is generated by the pushing force reduction signal generator. A pushing force reduction signal is generated based on the signal, and the torque of the plurality of pushing drive roll motors and the plurality of reference drive roll motors is controlled by the command control device based on the pushing force reduction signal. A continuous casting method for steel, which is characterized in that stable casting is performed without slippage, over-indentation, etc.