KR20090073495A - Break out monitoring system and its method in continuous casting process - Google Patents

Abstract

A system and a method for monitoring break out in a continuous casting process are provided to estimate the defect location and extent of a solidified shell quantitatively based on the inflow and discharge temperature of the cooling water. A system for monitoring break out in a continuous casting process comprises a mold body(10) including a plurality of cooling water slits(20) arranged along the long width, and a temperature sensor(100) which is installed on the outlet of the cooling water slit for measuring the temperature of the cooling water ejected through the cooling water slit.

Description

Break out monitoring system and its method in continuous casting process

The present invention relates to an apparatus for predicting breakout in a continuous casting process and a method using the same, and more particularly, a change value of an inlet temperature and an outlet temperature of cooling water supplied to cool molten steel in a mold during a continuous casting process of steel. The present invention relates to an apparatus for predicting breakout in a continuous casting process for predicting a defect occurring in a solidification shell by comparing with a change value during normal operation, and a method using the same.

In general, the continuous casting process of steel is performed by a continuous casting apparatus, that is, when the molten steel of the Turdish flows into the mold through the immersion nozzle, the solidification shell is formed by the initial solidification shell formed by the cooling water flowing inside the mold. Begins.

The slab playing mold consists of four sides, two sides are long and two sides are short, and the inner space has a rectangular parallelepiped shape with the upper and lower portions open. The material of the mold is copper with excellent thermal conductivity, and cooling water is supplied inside the mold to cool the mold.

The length of the mold is typically around 1000 mm, and the molten steel cools toward the mold at the point of contact with the mold to form a solidified shell. The coagulation shell is drawn continuously by guide rolls and pinch rolls under the mold.

The molten steel still exists inside the drawn solidification shell, and the remaining molten steel is gradually solidified while moving downward by the cooling water sprayed from the bottom of the mold, and then solidification is completed to produce slabs.

In the mold, the solidification shell is formed to a normal thickness on four sides and then drawn to the bottom of the mold to continuously produce a normal casting. However, sometimes the solidification shell is attached to the mold wall and separated from the lower solidification shell, so that a so-called stiching breakout occurs in which molten steel flows out to the bottom of the mold. In addition, a so-called coagulation delay breakout occurs, in which the solidification shell does not grow in contact with the mold, especially at the corners, and cannot overcome the iron static pressure when it leaves the mold thin.

1 is a block diagram showing defects occurring in the solidification shell, as shown in FIG. 1, the solidification shell 2 is deformed as it cools during growth in the mold 10 and does not come into contact with the mold 10. When the so-called depression (4), which is lifted up from the mold (10) in a pressed form, also occurs, the solidification shell (2) does not grow or cracks, and when the mold (10) leaves the thin solidification shell As (2) cannot withstand iron static pressure, coagulation delay breakout occurs.

In the drawings, reference numeral 1 denotes molten steel in the mold, 3 denotes a mold flux film, and 20 denotes a cooling water slit in the mold.

In addition, if a large amount of flux introduced into the upper part of the mold is introduced in an uneven amount at a specific site for the purpose of reducing friction between the mold and the solidification shell, the growth of the solidification shell is delayed in the same manner as the solidification shell shown in FIG. 1. As a result, coagulation delay breakout occurs.

In order to predict such breakout, a thermocouple is installed in a mold main body, and the detected temperature distribution is analyzed to detect sticking occurring in the mold, poor contact between the edge solidification shell and the mold, and depression. Therefore, if such a phenomenon is detected and breakout is expected, breakout occurs as the coagulation shell is drawn out, that is, the casting speed is reduced to allow the coagulation shell to grow further inside the mold, and then the casting speed is increased again to operate. Prevented.

Among the various factors that cause breakout as described above, when sticking occurs, the area is easily detected by the thermocouple since the area covers a large area. However, defects in contact between the coagulation shell and the mold and depression at the edges are not distributed over a wide area as in sticking, but are long in the shape of the mold. The temperature must be measured, and there was a problem in that the temperature of several places were simultaneously measured in the longitudinal direction. For example, if the width is 20mm when the depression occurs and the gap between the thermocouples is 150mm, it is easy to see the temperature change of the mold when the band of depression is close to the thermocouple. Is not easy and it is not possible to estimate the exact location and size of the depression. When such quantitative determination becomes difficult, errors in breakout prediction increase, and small and unnecessary fluctuations of the casting speed are inevitable, resulting in unstable operation and deterioration of cast quality.

In order to solve this problem, the installation interval of the thermocouple should be narrowed, but it was difficult to increase the number of thermocouples due to the structural characteristics of the mold and the operation of the stable equipment.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is used to predict breakout in a continuous casting process in which the temperature change of the mold is densely measured using the structural characteristics of the mold to detect the change value. The purpose is to provide a device.

In addition, by densely detecting the temperature change of the mold, the contact failure between the coagulation shell and the mold occurs or the deformation occurs when the coagulation shell grows and contracts. Another object is to provide a breakout prediction method in a continuous casting process that can minimize the

Apparatus for predicting the breakout in the continuous casting process according to the present invention for achieving the above object comprises a mold body having a plurality of coolant slits spaced apart in the long width direction; And a temperature sensor installed at an outlet side of the coolant slit to measure a temperature of the coolant discharged from the coolant slit.

Long slots are formed in one of the upper and lower surfaces of the mold main body in the longitudinal direction of the mold main body, and a plurality of grooves are formed in the long slots at positions corresponding to the positions of the coolant slits. An installation hole communicating with an outlet of the cooling water slit is formed, and the temperature sensor is inserted into each of the installation holes.

The groove is provided with a packing member for fixing the temperature sensor, O-ring is further provided between the packing member and the groove.

The long slot may further include a cover for opening and closing an upper portion thereof, and a cable connected to the temperature sensor may be disposed therein.

The connector is inserted into any one of the upper surface, the lower surface, or the side surface of the mold body, and the cable is connected to the connector.

An end of the temperature sensor is exposed to the outlet of the coolant slit.

The cooling water slit is characterized in that it is provided at intervals of 10 ~ 150mm in the long width direction of the mold body.

In addition, the method of predicting breakout in the continuous casting process according to the present invention is a method of predicting breakouts generated during the continuous casting process, wherein the casting body flows into each cooling water slit provided with a plurality at equal intervals in the mold body. Measuring the temperature of each coolant; And measuring a temperature of each of the cooling water discharged from each of the cooling water slit outlets, and calculating a change value of inflow and discharge temperature of each of the cooling water supplied to each cooling water slit, and It is characterized by determining the position.

The method may further include defining normal change values of inflow and discharge temperatures of the cooling water during normal operation of the continuous casting process, and calculating change values of inflow and discharge temperature of each of the cooling water in the continuous casting process. Characterized in that it is determined that the abnormality of the solidification shell occurs at the point where the coolant slit where the change value and the difference occurs.

At this time, the abnormality level of the solidification shell is characterized in that determined by the following equation (1).

According to the present invention, a temperature sensor capable of measuring the discharge temperature of the cooling water is provided in the cooling water slit which is densely spaced in the long width direction of the mold body, and based on the change value of the cooling water inlet temperature and the discharge temperature. There is an effect that can quantitatively predict the location and level of severity of solidification shell defects occurring in.

As the location and severity of solidification shell defects can be known in real time, casting conditions can be adjusted in real time, thereby preventing equipment accidents such as breakouts.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention in more detail.

First, the inventors of the present invention are based on the fact that when the depression occurs in the solidification shell, the temperature of the mold body decreases, as well as the amount of increase in the coolant temperature of the coolant slit passing through the depression portion decreases. Completed.

However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you.

FIG. 2 is a perspective view showing an apparatus for predicting breakout in a continuous casting process according to the present invention, and FIG. 3 is a cross-sectional view of main parts of the apparatus for predicting breakout in a continuous casting process according to the present invention.

As shown in the figure, an apparatus for predicting breakout in a continuous casting process according to the present invention has a mold body 10 used in a continuous casting apparatus, for example, has a long width, and has a plurality of coolant slits ( 20 and the mold main body 10 which are closely spaced in the long width direction; It is installed on the outlet side of the coolant slit 20 includes a temperature sensor 100 for measuring the temperature of the coolant discharged from the coolant slit 20.

Cooling water slits 20 provided at equal intervals on the mold main body 10 are provided along the up and down direction of the mold main body 10 at a pitch of less than 50 mm and a small size of 10 mm on the back surface of the mold. Preferably it is provided at intervals of 10 ~ 150mm it is preferable to measure the temperature change of the mold main body 10 at a tight interval.

A long slot 200 is formed in a longitudinal direction of the mold main body 10 on a surface of the upper and lower surfaces of the mold main body 10 where the outlet of the cooling water slit 20 is located, and the cooling water is formed in the long slot 200. A plurality of grooves 201 are formed at the point where the slit 20 is located.

In addition, each recess 201 is provided with an installation hole 210 which communicates with the outlet of the coolant slit 20, and the temperature sensor 100 is inserted into each installation hole 210. At this time, it is preferable that the end of the temperature sensor 100 is exposed to the outlet of the cooling water slit 20 to be in contact with the cooling water.

The groove 201 is provided with a packing member 220 for fixing the temperature sensor 100, and an O-ring 230 is further provided between the packing member 220 and the groove 201 so that the coolant has a groove 201. Is discharged through).

As the temperature sensor 100, a RTD (Resistance Temperature Detect) having a higher detection rate is used instead of a thermocouple for measuring a normal mold temperature. At this time, the distance that the RTD protrudes to the outlet of the cooling water slit 20 is preferably 10 mm or less so as not to interfere with the flow of the cooling water.

In addition, the cable 300 connected from the temperature sensor 100 is disposed along the long-term long slot 200.

The connector 400 is inserted into any one of an upper surface, a lower surface, or a side surface of the mold body 10, and the cable 300 is connected to the connector 400. Thus, the temperature value measured by the temperature sensor 100 can be transmitted to a controller (not shown) that controls the continuous casting device.

The long slot 200 further includes a cover 240 that opens and closes an upper portion thereof, and protects the cable 300 and the temperature sensor 100 disposed in the long slot 200.

At this time, it is obvious that the coolant supplied to the coolant slit 20 measures the inlet temperature of the coolant before flowing into the coolant slit 20. At this time, the inlet temperature of the cooling water supplied to the plurality of cooling water slits 20 is the same. Thus, the inlet temperature of the coolant may be measured anywhere in the inlet of the coolant slit 20, the supply device for supplying the coolant, and the supply line.

A breakout prediction method in a continuous casting process according to the present invention using the apparatus configured as described above will be described with reference to the drawings.

During normal operation of the continuous casting process, the inlet temperature and the outlet temperature of each cooling water supplied to each cooling water slit 20 provided in the mold main body 10 are measured to calculate a change value between the two temperatures, and thus the normal change value (ΔT1). ).

Then, the temperature of each of the cooling water flowing into the cooling water slit 20 of the mold body 10 during casting is measured. Then, the temperature of each of the cooling water discharged from the outlet of each cooling water slit 20 is measured. Thus, the change in inlet temperature and discharge temperature (ΔT2, hereinafter referred to as "calculated change value") of each coolant supplied to each coolant slit 20 is calculated and compared with the normal change value of the solidified shell. Judgment of the abnormality and its position.

Therefore, it is determined that the solidification shell is abnormal at the point where the coolant slit 20 is located where the difference between the normal change value and the calculated change value is located.

And the abnormality level of the solidification shell in which abnormality generate | occur | produced is defined by following formula (1).

The principle of the breakout prediction method in the continuous casting process for explaining in detail the breakout prediction method in the continuous casting process as described above is as follows.

4 is an explanatory diagram illustrating a principle of predicting a defect occurring in a solidification shell.

When the outlet temperature of the coolant is measured at the outlet of the coolant slit 20 provided at close intervals in the mold body 10 by using the apparatus as described above, near the inlet of the coolant of the mold body 10 or in a continuous casting apparatus The amount of temperature change ΔT in each cooling water slit 20 is obtained using the operating cooling water inlet temperature. If the solidification shell 2 in all positions grows to the same thickness, the temperature change amount ΔT in all the coolant slits 20 will have the same value.

However, if depression 4 occurs in the solidification shell 2 of a specific site, an air gap occurs between the solidification shell 2 and the mold main body 10 so that the solidification shell 2 does not grow. In addition, the heat transfer to the mold main body 10 is greatly reduced, so that the temperature of the mold main body 10 is reduced, thereby reducing the amount of heat transfer to the cooling water. As a result, the temperature measured at the outlet of the coolant slit 20 is also lower than the temperature measured at the outlet of the coolant slit 20 at other sites. The decrease in temperature is greatest in the middle of the depression (4), and the decrease decreases gradually toward the point where the normal solidification shell (2) is located.

For example, if the temperature sensor 100 is installed in all the coolant slits A through I as shown in FIG. 4, the difference between the temperature and the normal change amount obtained by the temperature sensor 100 during the passage of the depression 4 is Maximum in the coolant slit (E), both tend to decrease toward the left and right. It can be seen that the cooling water slit E is the center of the depression 4 because it shows a maximum difference from the normal temperature change amount. Further, if the temperature change amount ΔT in the steady state was 16 ° C. but the minimum temperature change amount ΔT when the depression 4 passed was 8 ° C., the level of the depression 4 was expressed by Equation (1). -8) / 16) × 100 = 50%.

Next, an experiment was conducted to compare the breakout prediction method using a conventional thermocouple and the breakout prediction method according to the present invention.

5 is a view showing the temperature and the coolant temperature measurement position of the mold by the thermocouple,

As illustrated in FIG. 5, seven thermocouples were installed along the casting direction at the center of the long side of the mold for the thin slab player, and the temperature of the mold was measured. The longitudinal coordinates of the left side were 175 mm, 305 mm, 435mm etc. The cooling water slits 20 were provided with nine temperature sensors 100 each at the center and at the left and right sides at 20 mm intervals. In the mold main body 10, since the coolant flows from the upper portion of the cooling water slit 20 and flows out to the lower portion, the temperature sensor 100 is installed at the lower outlet side of the cooling water slit 20.

In this way, two castings were performed in a state in which a temperature sensor was installed at the outlet side of the thermocouple and the cooling water slit, and the results of the temperature measurement are shown in FIGS. 6A to 7B. At this time, the casting speed was 5.0 m / min.

Figures 6a and 7a is a graph showing the temperature of the mold measured in the thermocouple, Figures 6a and 7b is a graph showing the result of measuring the coolant temperature.

First, FIG. 6A is compared with FIG. 6B.

According to the graph value of FIG. 6A, the first depression occurred at a position of 565 mm from the upper part of the mold at about 7230 seconds, the maximum severity was reached at 7250 seconds, and the peak point of 435 mm moved downward in accordance with the solidification shell movement speed. It can be seen. At this time, it can be seen that the same tendency appears in the temperature change of the cooling water also by the graph value of 6b. The maximum drop width of the temperature change value was the N1 point, and the width direction position was almost the same as the mold temperature measurement position. Then, the width of the temperature change gradually decreased toward N2 and N3, and the width of the drop decreased while going toward the opposite directions S1 and S2. This means that there is a center of depression at the N1 point. In this case, since the center of the depression is located directly at the position where the thermocouple of the mold is arranged, the position and severity of the depression can be directly determined only by temperature measurement using a conventional thermocouple.

However, in comparison with FIGS. 7A and 7B, the temperature reduction phenomenon of the mold was not detected in FIG. 7A. However, according to FIG. 7B, the drop width of the temperature change value at the point S5 at 3820 seconds showed the largest value compared to the surroundings, and also decreased in S4 and S6. Therefore, it can be detected that the depression occurred around the S5 point. In addition, since the drop width of the temperature change value is about half of that of FIG. 6B, the degree of depression severity was determined to be about half. As can be seen from the comparison of FIG. 7A and FIG. 7B, the detection of depression by the thermocouple is not performed at the point except the center of the mold in which the thermocouple is installed, but the temperature of the cooling water is provided by the temperature sensor provided in the coolant slit which is provided with a relatively compact density. According to the present invention for detecting the amount of temperature change, it was confirmed that the detection of depression is possible.

Therefore, according to the method of the present invention, not only the position of the occurrence of depression can be accurately known, but also the severity of the depression can be quantitatively determined in comparison with the conventional method of measuring the temperature change of the mold by the thermocouple. It was confirmed.

1 is a block diagram showing a defect occurring in the solidification shell,

2 is a perspective view showing an apparatus for predicting breakout in a continuous casting process according to the present invention;

3 is a cross-sectional view of main parts of an apparatus for predicting breakout in a continuous casting process according to the present invention;

4 is an explanatory diagram illustrating a principle of predicting a defect occurring in a solidification shell;

5 is a view showing the temperature and the coolant temperature measurement position of the mold by the thermocouple,

6A, 6B, 7A, and 7B are graphs showing the results of measuring the mold temperature and the coolant temperature.

<Explanation of symbols for the main parts of the drawings>

10: mold body 20: coolant slit

100: temperature sensor 200: long slot

201: groove 210: installer

220: packing member 230: O-ring

240: cover 300: cable

400: connector

Claims (10)

A mold body provided with a plurality of cooling water slits spaced apart in a long width direction; And a temperature sensor installed at an outlet side of the coolant slit for measuring a temperature of the coolant discharged from the coolant slit. The method of claim 1, Long slots are formed in one of the upper and lower surfaces of the mold main body in the longitudinal direction of the mold main body, The long slot is formed with a plurality of grooves in a position corresponding to the position of the cooling water slit, Each of the grooves is provided with an installation hole in communication with the outlet of the cooling water slit, And the temperature sensor is inserted into each of the installation holes. The method of claim 2, The groove is provided with a packing member for fixing the temperature sensor, the device for predicting the breakout in the continuous casting process, characterized in that the O-ring is further provided between the packing member and the groove. The method of claim 2, The long slot is further provided with a cover for opening and closing the upper portion, An apparatus for predicting breakout in a continuous casting process, wherein a cable connected to the temperature sensor is disposed therein. The method of claim 4, wherein An apparatus for predicting breakout in a continuous casting process, characterized in that the connector is inserted into one of the upper, lower or side surfaces of the mold body and the cable is connected to the connector. The method of claim 1, And an end of the temperature sensor is exposed to an outlet of the coolant slit. The method of claim 1, The coolant slit is an apparatus for predicting breakout in the continuous casting process, characterized in that provided in the long width direction of the mold body 10 to 150mm intervals. In the method for predicting the breakout occurring during the continuous casting process, Measuring the temperature of each coolant flowing into each coolant slit provided with a plurality at equal intervals in the mold body at the time of casting; Measuring a temperature of each of the cooling water discharged from each of the cooling water slit outlets, The breakout prediction method of the continuous casting process, characterized in that the presence and absence of the solidification shell and determine the position by calculating the change in the inlet temperature and discharge temperature of each of the cooling water supplied to the cooling water slit. The method of claim 8, Defining a normal change in inlet and outlet temperature of each of said cooling water during normal operation of a continuous casting process; In the continuous casting process, the inlet temperature and the discharge temperature change value of each of the cooling water is calculated by determining the point where the abnormality of the solidification shell occurred at the point where the coolant slit where the difference between the normal change value is located Breakout Prediction Method in Casting Process. The method of claim 9, The abnormality level of the solidification shell is determined by the following equation (1) breakout prediction method in the continuous casting process. (Equation 1) Abnormal level (%) of solidification shell = ((normal change value (ΔT1) -calculated change value (ΔT2)) / normal change value (ΔT1))

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