JP2003136207A - System for monitoring casting state of continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system for monitoring the casting state of continuous casting which serues for monitoring by an operator by showing the casting state of molten steel into a mold on a monitor screen, in a continuous casting line. SOLUTION: This system is provided with a process, in which information on the molten steel is obtained from a host computer, a process in which the state of the mold is obtained from a sensor arranged in the inner part of and/or near the mold, a process in which the casting state of the molten steel in the mold is simulated based on the information of the molten steel and the state of the mold, and a process in which the fluidized state of the molten steel is pseudomorphically shown on the monitor screen based on the simulation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting condition monitoring system for an operator to monitor the casting condition of continuous casting.

[0002]

2. Description of the Related Art First, a continuous casting line in a steelmaking process will be described with reference to FIG. Molten steel refined in a converter and other refining equipment (not shown) is cast into a mold 4 from a tundish 3 via a ladle (ladle) 2. Then, the shell portion of the surface layer is solidified by the mold 4 and is pulled out downward. Immediately below the mold 4, the drawn continuous cast material 1 remains molten steel inside with only the shell portion solidified, and is constrained by a number of pinch rolls 5 arranged side by side and drawn out. Then, while being spray-cooled with cooling water, the inside is solidified. The continuous cast material 1 that has been solidified to the inside is straightened by a straightening device (not shown) on the downstream side and cut into a desired length to form a cast piece (slab).

By the way, when a continuous cast material is cast in the above continuous casting line, a phenomenon may occur in which molten steel flows out from the solidified shell. In an extreme case, the solidified shell is completely broken and a large amount of molten steel flows out, resulting in a breakout.
Further, in the case of a slight amount, minute crevices are generated on the surface of the continuous cast material, and bleeding occurs in which a small amount of molten steel is ejected. When such a breakout or bleed occurs, the molten steel ejected adheres to the roll of the continuous casting machine and scratches the continuous casting material due to the adhered material, so it is necessary to stop the line,
This may cause a large number of defects.

Further, the mold is subjected to periodic vibration in order to prevent seizure during casting. From this, an uneven pattern called an oscillation mark may occur on the surface of the cast continuous cast material. This oscillation mark is also one of the serious defects. There are the following three types of oscillation marks. A continuous cast material (slab after cutting) whose surface is concave. This anomaly is an indented mark caused by the fact that the shell tip is deformed by the vibration of the mold when it is cast in a state where the molten metal level in the mold is stable. Cylindrical shape with an abnormal tissue of about a few mm bent like a nail inside. It is estimated that this abnormal structure occurs due to uneven solidification below the surface of the continuous cast material when there is a change in the molten metal surface. A claw-shaped abnormal tissue bent in the opposite direction.
It is presumed that this abnormal structure occurs when the solidified shell is deformed to the inside of the unsolidified molten steel and the interface tension between the molten steel and powder is lost and overflows.

In addition, there are cases in which various defects such as sticking may occur due to changes in the casting level due to fluctuations in the molten metal level in the mold, fluctuations in temperature, and the like. On the other hand, on the other hand, there is a problem that non-metallic inclusions existing in the continuous cast material become actual defects on the surface at the stage of becoming the rolled sheet material and become serious defects. Furthermore, there may be a crack or pinhole defect during processing such as assembly at the customer's site.

The existence of such non-metallic inclusions has been studied for many years. In particular, non-metallic inclusions consisting mainly of alumina in the surface layer of continuous cast materials, which has been a major problem in the past, lack sufficient cleanliness during molten steel, oxidation by air, reaction with refractories and slag, molding It is known to be generated due to fluctuations in the molten steel inside the mold, mutual relationships with powder and flux that are put into the mold, and it has been confirmed that this will be a serious product defect. The generation factor of such non-metallic inclusions has been confirmed in each process or facility unit, and by optimizing and stabilizing the continuous casting operation, it has been suppressed to minimize the generation. ing.

Defects caused by non-metallic inclusions are caused by high-strength steel plates for press-forming in complicated shapes and steel plates for cans, which give priority to the design of outer panels for automobiles (members painted and finished on the vehicle body). As described above, this is a particularly serious problem in a steel sheet such as a thin steel sheet having a high tensile strength and a thinner thickness in order to realize weight reduction. These steel sheets satisfy T
Ultra low carbon aluminum killed steel (extra lo) with addition of carbides such as i, Nb, B, nitride forming elements, and grain boundary strength increasing elements.
wC Al-killed steel) is processed by the continuous annealing method.

For steel plates for cans, high-strength, ultra-thin steel plates made by continuous annealing of low-carbon aluminum killed steel are used for 3-piece cans, and ultra-low carbon aluminum killed steels are used for 2-piece cans. There is. The quality of steel sheets has been improving year by year due to the completeness of inspection equipment and improvement of operation technology for both manufacturers and customers, and the rate of defective contamination such as defects has been greatly reduced.

[0009] As described above, the defects, which can be said to have become extremely low in frequency of occurrence, become a very serious problem if they are found after the steel sheet is processed and assembled into a product at the customer. For example, in the case of small things such as cans, the defective products that have the defect will be discarded, and in the case of large objects such as the car body of automobiles, it will be a large-scale situation of dismantling and replacing defective parts. .

[0010]

Therefore, the customer side is now required to completely eliminate the outflow of defects including these non-metallic inclusion defects to the customer's destination. . In order to meet this demand, it is necessary to take measures in each line of the steel production line. For example, in a converter for refining ultra-low carbon steel, if the blow-stop C amount is reduced, the C-O equilibrium relationship will result. The amount of oxygen in the molten steel increases, and the oxygen reacts with Al added in the subsequent step to form non-metallic inclusions, so it is necessary to strictly control the amount of blow-stop C. It is also necessary to completely prevent the outflow of slag to the ladle during tapping. Furthermore, in ultra low carbon steel, since trace elements such as Ti, Nb, and B are added, the element ore is added and adjusted while stirring the molten steel in a vacuum degassing treatment device, resulting in a lower molten steel temperature. , Viscosity also rises and hinders the floating separation of non-metallic inclusions.

Further, in each of the vacuum degassing process, the ladle, and the tundish, the details are omitted, but the device for suppressing the generation and growth of the nonmetallic inclusions has been devised, and the device has been devised so as not to flow to the next process. ing. On the other hand, even in continuous casting lines, various measures have been taken to suppress the formation of non-metallic inclusions, but they have not been sufficient, and due to fluctuations in the molten metal level in the mold, temperature fluctuations, etc. Under the present circumstances, there is a possibility that the flow state of unsolidified molten steel may change and cause the formation of non-metallic inclusions.

In the casting process into the mold, it is necessary to pay the same attention to other serious defects such as breakouts and oscillation marks. INDUSTRIAL APPLICABILITY The present invention improves the casting status monitoring screen monitored by the operator of the continuous casting line, enables the operator to be visually alerted in real time, and enables the operator to accurately grasp the abnormal condition. This makes it possible to quickly respond to workers and, as a result, to manufacture defect-free steel sheets.

[0013]

The present invention has solved the above-mentioned problems by a casting condition monitoring system for continuous casting described in the following items. In a continuous casting line, it is a casting status monitoring system of continuous casting that displays the casting status of molten steel in the mold on the monitor screen and is used for worker's monitoring, and obtains information on the molten steel from a host computer And the step of obtaining the condition of the mold from a sensor provided inside and / or in the vicinity of the mold, and based on the information of the molten steel and the condition of the mold, simulate the molten steel casting condition in the mold. A casting condition monitoring system for continuous casting, comprising: a process; and a process of displaying a molten steel flow condition based on the simulation on a monitor screen in a pseudo manner. The information of the molten steel includes information accumulating the defect detection record of the steel sheet material manufactured in the downstream process from the slab cast by the molten steel of the same composition in the past, and the information accumulating the defect detection record is described above. The casting condition monitoring system for continuous casting according to the above, characterized in that it is used as one of simulation parameters. The casting condition monitoring system for continuous casting according to the above item 1 or 2, wherein the simulation is a simulation based on the finite element method, and the flow condition of the molten steel is displayed on the screen as a vector display with an arrow. Any of the above items, wherein the sensor for acquiring the mold condition is at least one of a molten steel surface level meter in a mold, a mold thermometer, an oscillation mark detector, and a breakout detector. A continuous casting condition monitoring system according to Crab.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION First, referring to FIG.
The states of the molten steel 13 and the solidified shell 14 inside will be described. The mold 4 is a mold made of metal such as copper, and is cooled by passing cooling water 4a inside. Here, the molten steel flow 13a discharged from the immersion nozzle 3a in the lower part of the tundish (not shown)
Collides with the solidified shell 14 on the short side surface of the mold 4 and splits into an upflow and a downflow as shown. This rising flow causes a fluctuation in the molten metal surface near the short side in the mold 4, causing the slag composed of the molten flux 12 and the powder 11 on the molten metal surface to be caught in the molten steel. On the other hand, the non-metallic inclusions (not shown because they are minute) riding on the descending flow penetrate deeply and are captured by the solidification surface to become non-metallic inclusion defects. Where 15
Is a powder film formed of powder, 16 is
A gap with the mold 4 is shown. Further, 17 indicates the casting direction of the continuous cast material.

Such a dynamic change of molten steel flow, temperature, etc. in the mold can be simulated by using various simulation techniques. The finite element method (FEM) can be cited as the most typical technique for simulating the solidification of a mold and the flow of molten steel. However, the present invention does not limit the simulation technique to this.

The most typical method of displaying the flow of molten steel in the mold by the finite element method is to express the direction and speed of the molten steel as a vector with arrows, and change the vector at each point in the mold. Is to be displayed in a static manner. Similarly, it is also possible to simulate temperature fluctuations in the mold and to display the difference in molten steel temperature in color. Next, the continuous casting casting condition monitoring system of the present invention will be described with reference to FIG. The same members as those already described with reference to FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted.

In the present invention, in the continuous casting line shown in FIG. 1, the monitor screen 25 shows the state of casting the molten steel 13 into the mold 4.
It is a casting condition monitoring system of continuous casting, which is displayed above and used for monitoring of workers. In particular, in the present invention, the process of obtaining the information of the molten steel 13 being cast from the host computer 32 and the condition of the mold 4 being cast are measured by the sensors 21 to 21 provided inside and / or in the vicinity of the mold 4. Based on the process obtained from 24, the information of the molten steel 13 and the situation of the mold 4, the casting situation of the molten steel 13 in the mold 4 is simulated by applying, for example, the finite element method in the control computer 20. The process includes a process and a process of displaying a molten steel flow state based on the simulation in a pseudo screen display section 27 of the casting state provided on the screen of the monitor screen 25 in a pseudo manner. Here, the casting status data display unit 26 may be appropriately provided on the monitor screen 25, and the pseudo display screen inside the mold based on the simulation may be full screen display. .

By the way, the information on the molten steel includes information accumulated in the past about the defect detection results of the thin steel sheet material manufactured in the downstream process using a slab (not shown) cast from the molten steel having the same composition. It is assumed that the accumulated information of the defect detection records is accumulated in the host computer 32 via another line computer 31b, 31c in the downstream process, and the information is received,
It is preferable to use one of the parameters of the above simulation. By doing so, the simulation accuracy can be further improved. Further, it is preferable that the simulation is displayed on the screen as a simulation based on the finite element method, and the flow state of the molten steel is displayed as a vector display with an arrow. By doing so, it is possible to improve the visibility of the displayed operator.

In addition, the casting results of the slab in which a defect is found in the downstream process, or a part of the slab, is accumulated,
When casting molten steel of the same composition, if a screen similar to that when casting a material slab of thin steel sheet in which a defect was detected in the downstream process appears, a caution buzzer sound is emitted and it can be realistically optimized. Purify. Here, an example schematically showing a pseudo screen to be displayed is shown in FIG.
It shows in (c). FIG. 1B is an example of a pseudo screen showing an example of a normal flow state, and FIG. 1C is an example of a pseudo screen showing an example of a flow state in an abnormal state when a breakout occurs.

The sensor provided inside and / or in the vicinity of the mold is a molten steel surface level meter in the mold,
It is preferable to use at least one of a mold thermometer, an oscillation mark detector, and a breakout detector. By using these sensors in appropriate combination, the simulation can be realized with high accuracy.

The molten steel level meter in the mold can be realized by applying a laser range finder, for example. The mold thermometer can be realized by embedding a thermometer such as a thermocouple in the mold, and preferably, two-dimensionally embedding a large number in the mold. By doing so, the accuracy of the simulation can be improved. Oscillation mark detectors and breakout detectors are visible or infrared IT
This can be easily realized by applying a V (industrial camera), a CCD camera, or the like and processing the acquired image.

With the practical application of the present invention, the system described below can be constructed. First, the casting condition monitoring system for continuous casting according to the present invention is applied, the casting condition in the mold is monitored, and the abnormality is accumulated together with the position information of the continuous casting material. Then, the coil flaw detection after rolling in the post-process is carried out by an automatic surface flaw detector, and the detected defect signal is accumulated as defect existing position information including the front and back of the coil, the width direction, and the longitudinal direction. The non-metallic inclusion information detected by the automatic metal inclusion sensor is stored as defect location information including the front and back of the coil, the width direction, and the longitudinal direction.

Then, by associating the above-mentioned three accumulated data accumulated in the superordinate computer which controls the continuous casting process and the downstream process, the occurrence of the non-metallic inclusion defect can be predicted in advance. Further, it is possible to construct a pseudo monitoring system for molten steel in a mold that does not cause defects.

[0024]

According to the present invention, the operator of a continuous casting line can visually display the status of molten steel in the mold in real time, and the operator can accurately grasp the abnormal condition. , To speed up the response of workers,
As a result, it was possible to manufacture a steel sheet without defects.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a casting condition monitoring system (a) of the present invention, and a pseudo screen example (b) in a normal state and a pseudo screen example (c) in an abnormal state.

FIG. 2 is a schematic diagram showing a casting condition in a continuous casting mold.

FIG. 3 is a partial schematic view of continuous casting equipment.

[Explanation of symbols]

1 continuous cast material 2 ladle 3 tundish 3a immersion nozzle 4 mold 4a cooling water 5 pinch rolls 11 powder 12 Molten flux 13 Molten steel 13a molten steel flow 14 Solidified shell 15 powder film 16 gap 17 Casting direction 20 Control computer 21 Molten Steel Surface Level Meter in Mold 22 Mold thermometer 23 Oscillation mark detector 24 breakout detector 25 Operator monitoring screen display 26 Casting status data display 27 Pseudo status display screen 27a, 27b Pseudo screen display example of casting status 31a Continuous casting line calculator 31b, 31c (for other lines) Line calculator 32 host computer

Continued front page    (72) Inventor Tadahiro Yusa             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. (72) Inventor Toshimitsu Nagaya             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. (72) Inventor Hideo Minato             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. (72) Inventor Makoto Araya             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. (72) Inventor Atsushi Ogino             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. (72) Inventor Nobuaki Nomura             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. (72) Inventor N. Tomura             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. (72) Inventor Ichiro Maeda             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. (72) Inventor Kazari Hoshi             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. (72) Inventor Ken Shiraishi             1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture             In Homu System Co., Ltd. (72) Inventor Taisuke Kogure             1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture             In Homu System Co., Ltd. F-term (reference) 4E004 MD10

Claims (4)

[Claims] 1. A continuous casting pouring status monitoring system for displaying the status of molten steel casting into a mold on a monitor screen in a continuous casting line, for use by a worker to monitor the molten steel information. From the host computer, the step of obtaining the status of the mold from a sensor provided inside and / or in the vicinity of the mold, and based on the information of the molten steel and the status of the mold, the status of the molten steel in the mold A casting status monitoring system for continuous casting, comprising: a step of simulating a casting status; and a step of pseudo-displaying a molten steel flow status based on the simulation on a monitor screen. 2. The molten steel information includes information accumulating defect detection results of a steel sheet material manufactured in a downstream process from a slab cast from molten steel having the same composition in the past. The casting condition monitoring system for continuous casting according to claim 1, wherein the accumulated information is used as one of the parameters of the simulation. 3. The continuous casting according to claim 1, wherein the simulation is a simulation based on the finite element method, and the flow status of the molten steel is displayed on the screen as a vector display with an arrow. Casting condition monitoring system. 4. The sensor for acquiring the mold condition is at least one of a molten steel surface level meter in a mold, a mold thermometer, an oscillation mark detector, and a breakout detector. Claim 1
The casting condition monitoring system for continuous casting according to any one of 3 to 3.