KR100271205B1 - Casting speed control device for continuous casting process using laser speed meter - Google Patents

Abstract

In the present invention, in the continuous casting process in which the molten steel injected into the mold 22 through the nozzle 20 is molded into the cast steel 26 and drawn by the pinch roll 24, the feed speed of the cast steel 26 is accurately measured. The feedback control using such a measurement value is intended to enable precise casting speed control, and the casting speed control system according to the present invention provides a laser speedometer 102 for non-contact measurement of the feed speed of the cast steel 26. And a speed signal generator 104 for generating a time signal for each time zone from the measured value of the laser tachometer 102, and a time signal for each time zone output from the speed signal generator 104 to filter only components within a predetermined frequency band. The filter 106 to pass through, the position detector 202 for detecting the position of the mold 22, and the output values of the position detector 202 are filtered to pass only components within a predetermined frequency band The key is driven by a filter 204, a speed converter 206 for generating a time-phase speed increase signal from the filtered detection signal, and a motor 114 to determine the position of the laser tachometer 102 relative to the slab 26. A cylinder 116 configured to be variable, and a motor controller 112 for controlling the motor 110 according to the thickness information supplied from the control computer 28.

Description

Casting Speed Control Device for Continuous Casting Process Using Laser Speedometer

The present invention relates to a casting speed control system for a continuous casting process using a laser tachometer, and more particularly, to precisely measure the feed speed of a cast in a continuous casting process and to feed it back to a control value for obtaining a reference value of a set casting speed. A casting speed control system for a continuous casting process that enables casting speed control.

In general, rolling products of metal are manufactured through the process of melting → ingot → homogeneous heating → ingot → heating → rolling, but ingot of the above process by continuously casting billet which is directly rolled from molten metal → Homogeneous heating → disintegration process can be omitted. This is called continuous casting, and its advantages include ① cost savings due to the simplification of the process, ② economic advantages due to improved casting yield, and ③ good surface and interior quality of the resulting billet. There is this.

1 is a block diagram showing a casting speed control system in the conventional continuous casting process as described above. In such continuous casting, the molten steel injected into the mold 22 through the nozzle 20 exits below the mold 22 and goes through a cooling process by cooling means (not shown). Drawn through and subsequently formed into slabs 26. In continuous casting, the mold 22 reciprocates in the horizontal direction, i.e., vibrates to ensure the molding of the slab 26.

In such continuous casting process, casting speed is a basic variable that must be controlled. The actual value of such casting speed was recognized by the conveying speed of the slab 26 measured by the rotational speed of the pinch rolls 24 in contact with the slab 26 and conveying the slab 26. Therefore, this measuring method is called a contact measuring method. The rotation speed of the pinch roll 24 is calculated by counting the number of pulses detected by the pulse encoder 34 at the rear end of the pinch roll 24 as the pinch roll 24 rotates. The position of the pinch rolls to be measured varies depending on the continuous casting plant, but is mainly the last pinch roll 24, and may be compared with each other by measuring the speed of other pinch rolls.

However, such a conventional casting speed control system is controlled by an open loop control method that controls the casting speed according to a reference value input from a programmable logic controller (PLC) 28 regardless of the actual value of the casting speed. did. This is because the conveyance speed of the slab 26 cannot be measured accurately by the contact measuring method. That is, due to the high heat radiated from the slab 26, the environment is poor, there is a mechanical backlash in the pinch roll 24, the surface of the slab 26 is not smooth, and the pinch roll 24 and There were many error factors, such as slip with the slab 26.

According to this open loop control method, the pinch rolls 24 are driven by the motor 32 controlled by the PLC 28 via the motor driver 30 according to the reference value of the casting speed input from the PLC 28. . The actual value of the casting speed due to the feed rate of the measured slab 26 is displayed on the display via the PLC 28. If the actual value of the casting speed indicated on the display is different from the reference value of the set casting speed, the operator must adjust the input value in the PLC 28.

Therefore, in the open loop control method using the conventional casting speed control system, precise casting speed control cannot be expected, and when the precise casting speed is not controlled, the level of the molten metal in the mold 22 is constant. Because of this, the inclusion of inclusions occurs, adversely affecting the quality of the product. In addition, when the casting speed is not constant, since the cooling speed of the cast steel 26 is not constant, the thickness of the solidification shell (shell) of the cast steel 26 is uneven, causing bulging (bulging phenomenon). There is a problem. In addition, high speed casting in the continuous casting process is essential for improving productivity and reducing manufacturing cost, and precise casting speed should be measured for high speed casting.

The present invention is to solve the above problems in the conventional casting speed control system for the continuous casting process, by precisely measuring the feed speed of the cast steel to maintain a precise level of molten metal in the mold by controlling the casting speed While trying to maintain a constant casting speed.

The present invention also seeks to eliminate disturbances in the measured feed rate of the cast and to obtain the true feed rate of the cast.

The present invention is also intended to reduce the measurement error even if the width of the cast steel changes by allowing the measuring position to be varied according to the actual value of the width of the cast steel.

1-A block diagram showing a casting speed control system for a conventional continuous casting process

2-block diagram showing a casting speed control system using a laser speedometer in a continuous casting process according to the present invention

3-2 is a graph showing the feed rate of the cast steel for each time zone measured by the laser speedometer of the casting speed control system shown in FIG.

4 to 3 are graphs showing the feed rate of the cast steel according to time zones after filtering the measured velocity component.

5-2 is a graph showing the speed increase and decrease by time due to vibration of the mold measured by the position detector of the casting speed control system shown in FIG.

6 to 4 are graphs showing the feed rate of the cast steel at each time zone after subtracting the speed increment shown in FIG. 5 from the speed component shown in FIG.

Explanation of symbols on the main parts of the drawings

22: mold, 26: cast,

28: PLC (control computer) 30: motor driver,

32: motor, 34: pulse encoder,

100: speed measurement unit, 102: laser speed meter,

104: speed signal generator, 106: filter,

110: measuring position moving part, 112: cylinder driver,

114: motor, 116: cylinder,

200: vibration measuring unit, 202: position detector,

204: filter, 206: speed converter,

300: net speed calculating unit.

According to the present invention for achieving the above object, in the continuous casting process in which the molten steel injected into the mold through the nozzle is formed into a cast steel and drawn by the pinch roll, the feed rate of the cast steel is accurately measured and using such measured values A feedback speed control system is provided which enables precise casting speed control by feedback control. The casting speed control system includes a speed measuring unit for measuring the feed speed of the cast steel in a non-contact manner, a vibration measuring unit for measuring the vibration of the mold, and the vibration measuring unit from the feed speed of the cast steel measured by the speed measuring unit. Net speed operation unit for removing the change factors due to the vibration of the mold measured by the pinch, the pinch roll control unit for controlling the rotational speed of the pinch roll for drawing the cast, and the pinch roll in accordance with the net speed input from the net speed operation unit The control computer which changes the control value input to a control part is included.

In addition, the speed measuring unit may include a measuring position moving unit capable of moving the position for measuring the feed rate of the cast steel according to the actual value of the width of the cast steel.

EXAMPLE

Hereinafter, a preferred embodiment of a casting speed control system for a continuous casting process according to the present invention will be described in detail with reference to the accompanying drawings.

The casting speed control system shown in FIG. 2 includes a speed measuring unit 100 for measuring the feed speed of the cast steel 26 in a non-contact manner, a vibration measuring unit 200 for measuring the vibration of the mold 22, and Net speed calculation unit 300 and cast steel to remove the change factor caused by the vibration of the mold 22 measured by the vibration measuring unit 200 from the feed speed of the slab 26 measured by the speed measuring unit 100 Pinch roll control unit for controlling the rotational speed of the pinch roll 24 for drawing (26), and PLC (28) for changing the control value input to the pinch roll control unit in accordance with the net speed input from the net speed operation unit 300 ).

The speed measuring unit 100 includes a laser tachometer 102 for measuring the feed speed of the slab 26 in a non-contact manner, and a speed signal generator for generating a speed signal for each time zone from the measured value of the laser tachometer 102 ( 104 and a filter 106 for filtering the time-specific speed signal output from the speed signal generator 104 to pass only components within a predetermined frequency band.

The vibration measuring unit 200 includes a position detector 202 for detecting a position of a mold, a filter 204 for filtering only an output value of the position detector 202 and passing a component within a predetermined frequency band, and a filtered detection signal. It includes a speed converter 206 for generating a time-dependent speed increase signal from.

The forward speed calculating unit 300 subtracts the speed increase or decrease according to the vibration of the mold input from the vibration measuring unit 200 from the feed speed of the slab 26 input from the speed measuring unit 100 of the cast steel 26. Obtain the net velocity component.

The net velocity component of the cast steel 26 thus obtained is input to the PLC 28 and compared with the reference value of the set casting speed, and the PLC 28 rotates the pinch roll 24 input to the pinch roll control unit according to the comparison result. Increase or decrease the control value for controlling the speed.

The pinch roll control unit of the casting speed control system according to this embodiment shown in FIG. 2 is similar to the pinch roll 24, the PLC 28, the motor driver 30, and the same as in the conventional casting speed control system shown in FIG. 1. It consists of a motor 32 and a pulse encoder 34.

On the other hand, the speed measuring unit 100 includes a measuring position moving unit 110 to move the position for measuring the feed rate of the slab 26 according to the actual value of the width of the slab 26. The measuring position moving unit 110 is a motor 114, a cylinder 116 configured to be driven by the motor 114 to vary the position of the laser tachometer 102 relative to the slab 26, and the PLC 28 And a motor controller 112 for controlling the motor 114 according to the thickness information supplied from the forward speed calculating unit 300.

In the following, a method of controlling the casting speed of the continuous casting process by using the casting speed control system according to this embodiment shown in FIG.

As in the prior art described above, the molten steel injected into the mold 22 through the nozzle 20 is formed into a slab 26 is drawn by the pinch roll 24. At this time, the rotation speed of the pinch roll 24 is determined according to the reference value of the set control speed. That is, the PLC 28 controls the rotational speed of the pinch roll 24 by setting a control value according to the reference value of the control speed, and inputting the control value to the motor driver 30 to control the speed of the motor 32. The slab 26 is conveyed at a speed corresponding to the rotational speed of the pinch roll 24.

On the other hand, the laser tachometer 102 of the speed measuring unit 100 emits a laser beam to the slab 26 to be transferred, and analyzes the reflected laser beam to obtain a signal corresponding to the feed speed of the slab 26. The signal obtained by the laser tachometer 102 is input to the speed signal generator 104 and converted into a speed signal representing the feed speed of the cast steel for each time zone. The time-specific feed rate thus obtained is shown in FIG. 3. As shown in Fig. 3, the speed signal not only includes the change factor due to the vibration of the mold 22, but also includes various disturbance factors such as the disturbance factor due to the rough surface of the slab 26. This velocity signal passes through the filter 106, and filters out components outside the predetermined frequency band, thereby eliminating disturbance factors. The velocity signal after filtering is as shown in FIG. 4, and the velocity signal is input to the forward velocity calculator 300. However, the change factor due to the vibration of the mold 22 still remains in the velocity signal after filtering.

In addition, the position detector 202 of the vibration measuring unit 200 detects the reciprocating motion, that is, the position of the vibrating mold. The detected position signal is input to the filter 204 to filter out signals outside the predetermined frequency band. The filtered position signal is input to the speed converter 206 and converted into a signal representing the increase and decrease of the feed speed of the slab 26 according to the vibration of the mold 22. This signal is as shown in FIG. 5, and this signal is also input to the forward speed calculator 300.

The forward speed calculating unit 300 subtracts the signal input from the vibration measuring unit 200 as shown in FIG. 5 from the signal input from the speed measuring unit 100 as shown in FIG. 4. The subtracted signal is as shown in Fig. 6, which represents the net velocity of the reliable cast. The average value of the net velocity of the cast steel is about 1.3 mpm, as shown in FIG.

The net speed of the cast steel as described above is compared to the reference value of the set casting speed is input to the PLC 28, the PLC 28 changes the control value input to the motor driver 30 in accordance with the comparison result. The motor driver 30 changes the rotational speed of the pinch roll 24 by increasing or decreasing the rotational speed of the motor 32 in accordance with the change of the control value.

As described above, in the casting speed control system according to the present invention, it is possible to precisely control the casting speed of the continuous casting process by feeding back the net speed of the accurately measured slab 26 and changing the control value in real time.

On the other hand, when the thickness of the slab 26 changes, the distance between the surface of the slab 26 and the laser tachometer 102 may change, causing measurement errors. In order to prevent this, the PLC 28 inputs the actual value of the thickness of the slab 26 measured by the thickness measuring means such as the pinch roll 24 to the motor controller 112. The motor controller 112 keeps the relative distance between the slab 28 and the laser tachometer 102 constant by appropriately controlling the motor 114 in accordance with the actual value of the input slab thickness.

Although the configuration and operation of the casting speed control system according to the present invention have been described by the preferred embodiments above, the present invention is not limited to such embodiments.

As described above, according to the present invention, the net speed of the cast steel can be measured accurately, the casting speed can be precisely controlled by the feedback control using the cast steel, and the casting speed can be kept constant. Therefore, the level of the molten metal is kept constant in the mold, there is less possibility that inclusions are mixed, and a high quality cast without bulging can be obtained. In addition, high-speed casting in the continuous casting process can be performed, whereby an improvement in productivity and a reduction in manufacturing cost can be expected.

Claims (2)

In the continuous casting process in which molten steel injected into a mold through a nozzle is formed into a cast steel and drawn out by a pinch roll, casting is precisely measured and the feed rate is controlled by using the measured value to enable precise casting speed control. In a speed control system, A speed measuring unit 100 for measuring the feed speed of the cast steel 26 in a non-contact manner, Vibration measuring unit 200 for measuring the vibration of the mold 22, A net speed calculating part 300 for removing a change factor due to vibration of the mold 22 measured by the vibration measuring part 200 from the feed speed of the slab 26 measured by the speed measuring part 100, Pinch roll control unit for controlling the rotational speed of the pinch roll 24 for drawing the cast piece 26, It includes a control computer 28 for changing the control value input to the pinch roll control unit in accordance with the net speed input from the forward speed operation unit 300, The speed measuring unit 100 includes a laser tachometer 102 for measuring the feed speed of the slab 26 in a non-contact manner, and a speed signal generator for generating a speed signal for each time zone from the measured value of the laser tachometer 102 ( 104) and a filter 106 for filtering the time-specific speed signal output from the speed signal generator 104 to pass only components within a predetermined frequency band, The vibration measuring unit 200 includes a position detector 202 for detecting the position of the mold 22, a filter 204 for filtering only the output value of the position detector 202, and a component within a predetermined frequency band, and filtering. Casting speed control system for a continuous casting process comprising a speed converter (206) for generating a time-dependent speed increase signal from the detected detection signal. The method of claim 1, The speed measuring part 100 additionally includes a measuring position moving part 110 capable of moving a position for measuring a feed speed of the slab 26 according to the actual value of the width of the slab 26. The measurement position moving unit 110 is a motor 114, a cylinder 116 configured to be driven by the motor 114 to vary the position of the laser tachometer 102 relative to the slab 26, and the control computer ( 28. A casting speed control system for a continuous casting process, characterized in that it comprises a motor controller (112) for controlling the motor (114) in accordance with the thickness information supplied from.