WO2003004200A1

WO2003004200A1 - System for controlling a billet cutting machine in continuous casting process

Info

Publication number: WO2003004200A1
Application number: PCT/KR2001/001709
Authority: WO
Inventors: Hyun-Suk Choi
Original assignee: Satec Co,. Ltd
Priority date: 2001-07-07
Filing date: 2001-10-11
Publication date: 2003-01-16
Also published as: KR200250256Y1

Abstract

Disclosed is a system for controlling a billet cutting machine (105) in a continuous casting process capable of exactly cutting a billet (104) in a desired length. The controlling system of the billet cutting machine (105) includes a noncontact type laser speed meter capable of measuring a speed of the billet in the continuous casting process, a speed signal generator for converting the measured value of the laser speed meter (221) into speed value, a noncontact type laser range meter (311) for measuring a distance of the cutting machine (105) cutting the billet (104) while moving on the billet (104), a camera (421) for capturing a head part (104a) of the billet (104) in a fixed position, an image processor (422) receiving image data of the camera (421) and calculating position, and an arithmetically operating part (400) for comparing and calculating the measured values.

Description

System for controlling a billet cutting machine in continuous casting process

Technical Fie ld

The present invention relates to a system for controlling a billet cutting machine in a continuous casting process, which can exactly control a casting speed by accurately measuring a speed of a billet and exactly cut the billet in a desired length in a process of making molten steel into the billet.

The present invention relates to a system for controlling a billet cutting machine in a continuous casting process, and more particularly, to a system for controlling a billet cutting machine in a continuous casting process, which can accurately measure casting speed and length of the billet using a laser speed meter, a laser range meter and an image processor and more exactly cut the billet by compensating the measured value in real time, in the billet cutting machine that cuts the billet at regular intervals for the purpose of use in a process that the molten steel is continuously imprinted into the billet.

Background Art

In general, as shown in FIG. 1 , a continuous casting process is to continuously cast a billet by putting molten steel in a tundish 101 and molding the billet 1 04 in a mold 1 02. In the early stage of the continuous casting, a lower end portion of the mold 1 02 is stopped with a dummy bar and a horizontal vibration is applied to the mold to slip the billets from the mold smoothly. When the mold is cooled after the molten steel is poured into the mold 1 02, the molten steel is hardened from an outer part, thereby being maintained in a prescribed solid condition. After that, the billet 1 04 is imprinted through a pinch roll 1 03 while the dummy bar stopping the lower end portion of the mold 1 02 is moved toward a lower end part slowly according to a casting speed.

Through the above steps, the molten steel is continuously cast into the billet and the billet is continuously drawn out. After that, the continuously cast billet 1 04 is cut in a desired length according to the purpose of use and according to a consumers demand and conveyed .

As shown in FIG . 3, a pulse encoder is attached on the pinch roll 1 03. The pulse encoder attached on the pinch roll 1 03 measures a rotational length of the pinch roll generated when the billet is imprinted in the mold, and casting speed and length of the billet using signal of a pulse encoder, which is attached on a conveying roller, generated according to the movement of the billet and the rotation of the roll. Also, another pulse encoder is attached on a cutting machine wheel located at an upper end of the conveying roller to measure how far the cutting machine moves from a home position. The cutting machine 105 is moved into the cutting position and starts to cut the billet in consideration of a seating period of time of the cutting machine when the cutting position enters a cutting area after the measurement of the position of the cutting machine 1 04. At this time, to measure the length of the billet 104, which is cast continuously, the pulse encoder calculates the rotation of the roll into a distance. However, error in the length of the billet 1 04 occurs due to slip generated by irregular friction between the roll and the billet, reduction in length of a roll circumference due to abrasion of the roll, and locking of the roll. Moreover, also error in movement distance occurs due to a slip or abrasion of an encoder wheel attached on the cutting machine wheel and locking of the encoder wheel. The cutting machine is set at zero point using a limit when entering the home position to compensate the errors. At this time, backlash occurs due to the movement speed of the cutting machine, thereby causing error in the zero point position of the cutting machine.

To solve the above problems somewhat, a technology for exactly measuring the casting speed and length of the billet using a noncontact type laser speed meter, without using the above pulse encoder has been developed and used.

The technology solves the error occurring due to the roll slip, abrasion and locking phenomenon, but also has several problems that a reflection angle between a laser speed meter 221 and the billet must be kept at an angle of 90 degrees, a distance between the laser speed meter 221 and the billet 104 must be kept in a fixed interval, and- the noncontact type laser speed meter 221 has a lim it in the range of installation . Thereby, the prior art causes various disturbances due to the above poor surroundings.

Furthermore, laser beam is scattered due to vapor of cooling water sprayed for cooling the billet, intense heat generated from the billet and metallic dust, and the reflection angle and distance between the laser speed meter 221 and the billet 1 04 cannot be kept due to vibration of the continuous casting machine. Speed signal and casting length signal measured in the above bad conditions has poor precision even though the disturbances are removed through a filter.

That is, the conventional methods have various errors when the movement speed and the casting length of the billet are measured using the pulse encoder attached on the roll or the laser speed meter. Also, the method for measuring the position of the cutting machine by attaching the pulse encoder on the wheel has error in position signal of the cutting machine.

In the drawings, the reference numeral 210 designates a measuring position moving part, 21 1 designates a cylinder, 21 2 designates a motor, 21 3 designates a cylinder actuator, 220 designates a speed meter part, 222 designates a speed signal generator, 223 designates a filter, 224 designates a speed operating part, 225 designates a computer for control, and 230 designates a vibration measuring part.

As described above, if the casting length of the billet and the position of the cutting machine are not accurate, because the billet must be cut with a prescribed clearance, casting materials as mush as the clearance amount of the billet are wasted, thereby causing a rise of manufacturing cost. Moreover, if data of the length of the billet 1 04 is not correct, it results in error in the next process.

Additionally, if the movement speed of the billet is not exact, it is not guaranteed to accurately control the casting speed . Also, if the control of the casting speed is not accurate, a level of the molten steel in the mold is not uniform and foreign matters may enter the mold, thereby influencing on the quality of products. Furthermore, the ununiform level of the molten steel causes uneven cooling of the billet, and thereby a thickness of coagulated cell of the billet is not even and the billet becomes swollen.

Because the above problems prevent a high speed casting, it is impossible to improve castability and reduce the manufacturing cost.

Disc losure of Invention

Therefore, it is an object of the present invention to provide a system for controlling a billet cutting machine in a continuous casting process capable of measuring an absolute position of a head part of a billet even in poor surroundings (especially, vapor) of the continuous casting process.

It is another object of the present invention to provide a system for controlling a billet cutting machine in a continuous casting process capable of calculating the time when the cutting machine is seated on the billet by exactly measuring a movement speed of the billet.

It is a further object of the present invention to provide a system for controlling a billet cutting machine in a continuous casting process capable of exactly cutting the billet without any influence even in a position where the absolute position of the head part of the billet is not measured, thereby exactly measuring the movement speed and a casting length of the billet.

It is a still further object of the present invention to provide a system for controlling a billet cutting machine in a continuous casting process capable of cutting the billet in an exact length using the cutting machine seating on the moving billet by exactly measuring the position o the cutting machine.

The system for controlling a billet cutting machine according to the present invention can exactly measure the casting speed and length of the billet and the absolute position of the cutting machine, thereby more accurately controlling the cutting machine. Furthermore, because the controlling system puts the cutting machine on the exact cutting position of the billet, the billet can be exactly cut, thereby reducing the manufacturing cost without any clearance in the length of the billet, improving the quality of products by guaranteeing the exact length of the billet, and exactly controlling the casting speed through feedback because the casting speed of the billet is accurate.

The accurate control of the casting speed can prevent entrance of foreign matters by making a level of molten steel uniform in a mold, prevent the billet from being swollen because the billet is cooled uniformly, improve productivity by the high speed casting in the continuous casting process, and considerably reduce the manufacturing cost.

The present invention can be changed, converted, replaced and substituted within a range of the business model, technical method and system and is not restricted in the above. Brief Description of the Drawings

Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawing in which:

FIG. 1 illustrates an exemplary view of a conventional continuous casting process;

FIG . 2 illustrates a plan view of FIG. 1 ;

FIG. 3 illustrates a brief view of a conventional system for controlling cutting of a billet; and

FIG. 4 illustrates a brief view of a billet cutting machine according to a preferred embodiment of the present invention.

Best Mode for Carrying Out the Invention

The present invention will now be described in detail in connection with preferred em bodiments with reference to the accompanying drawings. For reference, like reference characters designate corresponding parts throughout several views.

As shown in FIG. 4, in a continuous casting process for continuously imprinting a billet 104, which is cast in a mold, through a pinch roll 103, a system for controlling a billet cutting machine measuring casting length and speed of the billet 104, measuring a position of the cutting machine 1 05, and exactly cutting the billet 1 04 in a desired length includes a speed meter part 200 for measuring a transport speed of the billet 104 using a laser speed meter 221 , a billet head measuring part 400 for measuring an absolute position of the billet head, a cutting machine measuring part 300 for measuring an absolute position of the cutting machine, and an arithmetically operating part 400 receiving signals from the speed meter part 200, the billet head measuring part 400 and the cutting machine measuring part 300 and controlling the cutting machine.

The speed meter part 200 includes the laser speed meter 221 emitting laser beam on the cast and moving billet and converting reflected laser beam into digital signal, and a speed signal generator 222 for operating the converted signal into speed and converting the speed into speed signal.

The billet head measuring part 400 includes a camera for capturing a head 1 04a of the billet 1 04 and an image processor 422 for calculating the absolute position of the billet head 1 04a.

The cutting machine measuring part 300 includes a laser range meter 31 1 for emitting laser beam on the cutting machine 105 and converting the emitted laser beam into distance signal and a reflection plate 31 2 for reflecting the emitted laser beam .

The arithmetically operating part 400 includes an arithmetic operator 51 1 and a cutting controller 521 for controlling the cutting machine 1 05. The arithmetic operator 51 1 performs control operation of the cutting machine using movement speed signal and casting length signal of the billet 1 04 received from the speed meter part 200, absolute signal of the billet head received from the billet head measuring part 400, and absolute signal of the cutting machine received from the cutting machine measuring part 300. Embodiment

A preferred embodiment of the system for controlling the billet cutting machine according to the present invention will be described in more detail as follows.

As described above, the continuous casting process is to continuously cast the billet after inserting molten steel into the mold. The billet cast through the mold is imprinted by the pinch roll and cast and drawn out to a cutting area through a cooling process. The cast billet is cut in a required length and conveyed to the next step.

When the continuous casting process is started, the laser range meter 31 1 measures the position of the cutting machine 1 05 standing by in the home position, measures movement speed signal of the initially cast billet 1 04 using the laser speed meter 221 , and sends the measured signal to the arithmetic operator 51 1 .

When the movement speed of the billet 1 04 is measured and the position of the head part 1 04a enters the cutting area, the laser speed meter 221 calculates the position of the billet head 1 04a in the arithmetic operator 51 1 based on the measured movement speed signal of the billet 1 04. The cutting machine 1 05 is seated near the billet head 1 04 to cut head crap, which is not cast as desired at the time of the initial casting, and then cuts the head crap. The laser range meter 31 1 measures the position by time zone of the cutting machine 1 05, which moves with the billet 1 04, and sends signal to the arithmetic operator 51 1 .

After the cutting of the head crap, when the billet head 104a enters a head recognizing area 1 07, the fixed camera 421 captures the head part 1 04a, and the image processor 422 calculates signal of the position of the head 1 04a into absolute position by time zone and sends the calculated value to the arithmetic operator 51 1 .

The arithmetic operator first compensates signals of the casting speed and length of the billet 1 04 measured in the speed meter part 200 using signals of the casting speed and length measured in the cutting machine measuring part 300, and second com pensates the signals of the casting speed and length of the billet 1 04 using signals of the casting speed and length of the billet 1 04 calculated by measuring the absolute position of the billet head 104a in the head measuring part 400. The casting speed and length accurately calculated through the second com pensation and the position signal of the cutting machine 1 05 measured in the cutting machine measuring part 300 are sent to the cutting machine controller 521 .

The cutting machine controller 521 receiving the signals calculates the casting speed and length of the billet 1 04 and the position signal of the cutting machine 105 received from the arithmetic operator 51 1 . After that, the cutting machine controller 521 moves the cutting machine 1 05 into an exact position to cut the billet in the desired length and seats the cutting machine 1 05 on the billet 1 04 and starts the cutting .

At this time, even when the cutting machine measuring part 300 is in a standing by state after cutting the billet 1 04 or located in the home position 1 06, or the head 1 04a of the billet does not enter the head recognizing area 1 07 due to a short length of the billet 1 04, the cutting work of the billet 1 04 may be performed.

Because the laser speed meter 221 always measures the casting speed and length of the billet 1 04 and com pensates signal of the laser speed meter 221 in real time using signals received from the cutting machine measuring part 300 and the head measuring part 400, there is no problem in exactly cutting the billet 104 because of good casting speed and length of the billet 104.

As described above, the billet 1 04 is imprinted through the pinch roll 1 03, cooled and conveyed into the cutting position, and the laser speed meter 221 is installed in front of the absolute position, i.e., at the center of a width direction of the billet 1 04, to emit laser beam at an angle of 90 degrees. Thereby, the laser speed meter 221 is to emit laser on the billet even though the width of the billet 104 is increased or decreased.

Furthermore, the laser speed meter 221 maintains the laser emitting angle at 90 degrees to collect the most laser beam since detecting the speed using laser beam returning after the laser beam is emitted .

When the head 1 04a of the billet 1 04 reaches a measuring area of the laser speed meter 221 at the initial time of the continuous casting process, the laser speed meter 221 emits laser beam on the billet 1 04, and a beam collecting part of the laser speed meter 1 04 receives reflected laser, converts it into digital signal and sends digital signal to the speed signal generator 222. The speed signal generator converts the signal into speed signal and sends the speed signal to the arithmetic operator 51 1 located in the arithmetically operating part 500.

The billet cast and moved continuously is variable in its length. Therefore, the camera 421 is fixed on the head measuring part 400 in such a manner that the camera can capture the billet head 1 04a even though the billet is cut in any length.

The camera 421 provided on the head measuring part 400 captures the billet head 1 04a when the billet 1 04 is moved into the head recognizing area 107 and sends captured image to the image processor 422. The image processor 422 finds the head part from the image consisting of various dots and colors and calculates the position of the head part to find the absolute position, and sends the position signal to the arithmetic operator 51 1 .

As described above, when the initial billet 1 04 is cast and enters the measuring area of the laser speed meter 221 , laser beam is emitted on the cast billet 1 04. The laser beam collecting part receives reflected laser beam of the laser speed meter 221 , converts it into digital signal and sends digital signal to the speed signal generator 22.

The speed signal generator 222 converts the. digital signal into speed signal and sends the speed signal to the arithmetic operator 51 1 of the arithmetically operating part 500 for measurement and control. The arithmetic operator 51 1 calculates speed signal by removing signal beyond a prescribed range and by using only effective signal, and applies measuring time to each speed signal.

The camera 421 calculates the absolute position of the billet head 1 04a, and then, sends the value of the absolute position to the arithmetic operator 51 1 .

Using the value of the absolute position, the arithmetic operator 51 1 carries out the following steps of:

1 . calculating the casting speed measured by the laser speed meter 221 into a standard casting speed;

2. finding the absolute position using the image processor 422 and calculating a standard casting speed by comparing with the measuring period of time that the laser speed meter 221 measured the initial casting speed;

3. calculating error parameter of the laser speed meter 221 by comparing the standard casting speed of the image processor 422 with the standard casting speed of the laser speed meter 221 ; and

4. second compensating the casting speed by applying the error parameter.

Meanwhile, the cutting machine 1 05 is put and moved on an upper portion of the billet 1 04 to cut the billet 1 04. At this time, the laser range meter 31 1 measures the absolute position of the cutting machine 1 05 and sends the measured value to the arithmetic operator.

In this case, the arithmetic operator 51 1 carries out the following steps of:

1 . converting the measured absolute position by time zone into the casting speed;

2. calculating error parameter by comparing the casting speed with the first compensated casting speed; and

3. second compensating the first compensated casting speed by applying the error parameter.

Through the above process, the casting speed is continuously compensated in real time to obtain an exact casting speed.

Therefore, even though errors occur due to disturbances continuously or temporarily in the casting speed measured by the laser speed meter 221 , the laser range meter 31 1 and the image processor 422, the casting speed can be measured stably and exactly.

Meanwhile, the arithmetic operator 51 1 calculates the position of the cutting machine 1 05 measured by the laser range meter 31 1 and a distance from an end part of the billet 104 to a stop position of the cutting machine, and sends the calculated value to the cutting machine controller 521 with the casting speed in real time.

The cutting machine controller 521 calculates a proper time for seating the cutting machine 1 05 on the billet 1 04 in consideration of the casting speed when a desired cutting length point of the billet 1 04 reaches the stop position of the cutting machine 1 05, and sends seating signal. The cutting machine 1 05 cuts the billet while moving with the billet 1 04 after seated on the billet 104. Therefore, the billet can be accurately cut in the desired length or in very small error.

Industrial App licability

While the present invention has been described with reference to the particular illustrative em bodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention .

Claims

What Is C laimed Is :

1 . A system for controlling a billet cutting machine in a continuous casting process capable of accurately cutting a billet, which is cast in a continuous casting process, in a desired length, the system comprising: a speed measuring part for measuring casting length and speed of the billet using a noncontact type laser speed meter; a cutting machine measuring part for measuring a position of the cutting machine in real time, the cutting machine measuring part measuring the casting length and speed of the billet using a real time change of distance of the cutting machine which is seated and moves on the billet; a head measuring part for measuring an absolute position of the billet and the casting length and speed of the billet by measuring a position of a billet head in an image processor in real time using image of a fixed camera; and an arithmetically operating part for calculating pure casting speed and length of the billet by com pensating signals of the casting speed and length of the billet measured by the speed meter part, the cutting machine measuring part and the head measuring part, the arithmetically operating part controlling the cutting machine using position signal of the cutting machine.

2. The system according to claim 1 , wherein the cutting machine measuring part includes a reflection plate disposed at a side of the cutting machine and a laser range meter located at a position corresponding to the reflection plate in a prescribed interval from the reflection plate.

3. The system according to claim 1 , wherein the head measuring part includes the camera fixed on an upper portion of a cutting area and the image processor mounted at a side thereof, the camera having a head recognizing area.

4. The system according to claim 1 , wherein the arithmetically operating part includes an arithmetic operator connected with the speed signal generator, the laser range meter and the image processor through wires, and a cutting controller connected with the cutting machine through wires at a side of the arithmetic operator.