JPS6044163A - Method for predicting breakout in continuous casting - Google Patents

Abstract

PURPOSE:To decrease erroneous judgement of breakout and to judge exactly the breakout with a method for predicting the breakout from the value detected by plural temp. detecting ends embedded into the side wall of a casting mold by judging abnormality when the detected values deviate specifically. CONSTITUTION:Plural pieces of temp. detecting ends 2 are embedded like A-C in the copper plate wall 1 of a casting mold in the moving direction of a billet. When a molten steel 4 forms a solidified shell 5 of a billet and the broken part 6 of the shell 5 owing to the seizure or the like between the shell 5 and the wall 1 which is the cause for breakout, the broke part 6 moves downward on progressing of casting and when said part deviates from the bottom end of the mold 1, breakout arises. The values detected by the ends A-C in this stage transfer from A to B and from B to C in temp. rise with the delay time proportional to the casting speed. The breakout is thus predicted and judged from the deviation of the >=2 consecutive values detected by the detecting ends to the high temp. side from a stationary level in succession.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for predicting breakouts occurring in a continuous casting method.

[Prior art]

In continuous casting methods, breakouts are a major factor that hinders operations. If a breakout occurs, operations will be interrupted and productivity will be extremely reduced.

Particularly in the type of continuous casting-rolling line that has recently been developed, the reduction in productivity has a large impact on the rolling line.

Furthermore, in terms of equipment, not only the continuous casting mold is damaged, but also the roll group below the mold is damaged due to the sticking of base metal due to breakout, which has a very large impact. Conventionally, preventing breakout is important for stable operation in continuous casting methods, and attempts have been made to predict breakout.

For example, JP-A-51-151624, JP-A-56-
In No. 95461, one of the temperature detection values detected by multiple temperature detection terminals embedded in the copper plate wall of the side wall of the mold rose above the steady state, indicating that the solidified slab shell, which is one of the causes of breakout. Mold Copper Plate - It was assumed that the phenomenon of solidified slab shell breakage caused by seizing occurred within the mold, and the occurrence of breakout was predicted. As mentioned above, in the conventional method, if the detected temperature value rises above the steady level even in one place, it is judged as a breakout prediction, but due to fluctuations in casting operations, such as the casting speed or the level of molten metal in the mold, etc. When the temperature changes, the detected temperature value may temporarily rise, and it has been found that there are two cases in which the conventional method incorrectly determines that a breakout has been predicted.

FIG. 1 shows an example of temperature detection values measured when the molten metal level changes using the conventional method disclosed in Japanese Patent Application Laid-Open No. 51-151624. FIG. 1(a) shows one side of the mold, in which eight temperature detection ends 2 are embedded in a row in the copper plate wall 1 of the mold in the direction of movement of the slab. 31 and 32 indicate the molten metal level in the mold, and the change in the detected temperature value when the molten metal level rises from 1 to 32 is shown in Figure 1).

In Fig. 1(b), when the molten metal level in the mold is at 31, the temperature detection value distribution is 41, and when the molten metal level in the mold rises to 32, the temperature detection value distribution is 41 to 42.43. and move on. When the temperature detection value distribution is 42, the steady distribution is 41
Compared to , the number of maximum temperature distribution points is increased by 1 to 2.
Although the detected value increased in only one place compared to the steady level υ, it was actually only due to a change in the level of the molten metal in the mold. As described above, the conventional method has the disadvantage of incorrectly predicting a breakout even though the solidified slab shell fracture, etc., which is the cause of a breakout, does not occur.

Further, FIG. 2 shows an example of erroneous judgment caused by the conventional method disclosed in Japanese Unexamined Patent Publication No. 56-95461. FIG. 2(a) shows the configuration of the conventional method, in which a temperature sensing end 2 is attached to a molded copper plate 1 in the width direction.
Bury it in nine places at appropriate intervals in the row. In this method, once the casting speed is increased and then returned to the original speed, the second
Temperature detection values as shown in figure (b) are A, B of temperature detection end 2,
For 0 points, each is obtained. Therefore, Japanese Patent Application Publication No. 1983-
In the conventional method of 95461, similar to the conventional method described above, when one of the detected temperature values deviates to the high temperature side, it is incorrectly predicted that a breakout will occur, even though no breakout of the solidified slab shell actually occurs. There is a drawback of storing it away.

As described above, the conventional method simply detects a temperature rise in one location to determine breakout prediction, and therefore has the drawback of many false positives. On the other hand, in actual operation, the best means to avoid breakout is to stop or extremely reduce the casting speed and remove the broken part of the solidified slab shell in the mold, since it has been determined that a breakout has been predicted. After waiting for normality to return, casting is continued again. However, this process requires the casting speed to be stopped or extremely reduced, resulting in quality abnormalities such as step joints of slabs, producing important high-temperature slabs in processes such as continuous casting and direct rolling, and the process of each process. It has a very bad effect on matching.

Although the adverse effects caused by erroneous judgments in the conventional method are less severe than the effects of breakouts, they are by no means insignificant if they occur frequently.

[Structure 0 Effects of the Invention] The present invention aims to reduce the erroneous judgments that are the drawbacks of the above-mentioned prior art, and to accurately predict breakout, and to reduce the erroneous judgments that occur due to the erroneous judgments. This reduces the negative effects on the quality of slabs, as well as on the production of high-temperature slabs, process matching, etc.

Therefore, the gist of the present invention is to embed a plurality of temperature detection ends in the side wall of a continuous casting mold in the direction of slab movement, and to detect the detection values of at least two consecutive temperature detection ends in succession over time. This is a breakout prediction method for continuous casting, which is characterized in that an abnormality is determined when the temperature shifts from a steady level to the high temperature side.

Hereinafter, the present invention will be explained in detail based on experimental examples shown in the drawings.

FIG. 3 shows an embodiment in which a plurality of temperature detection ends 2 (three shown in the figure) are embedded in the mold copper plate wall 1 in the direction of slab movement, and FIG. 4 shows a cross section of the temperature detection ends 2. In this cross-sectional view, temperature detection ends 2 (for example, thermocouples, etc.) embedded in the mold copper plate 1 are installed at appropriate intervals as indicated by A, B, and 0 in the direction of movement of the slab. 4 is molten steel and 5 is a solidified slab shell. In addition, 6 indicates a broken part of the solidified slab shell, which is caused by the burning of the solidified slab shell and the wall of the copper plate of the mold, which is the cause of the breakout.

It is known that this slab solidified shell fracture portion 6 moves downward as casting progresses. The progress is shown in Figure 5. Figure 5(a) shows how the slab solidified shell fracture part 6 occurs.
FIGS. 5(b) and 5(C) show that the broken part 6 of the slab solidified shell also moves downward as casting progresses, and in FIG. 5(d), the broken part 6 of the solidified slab solidified shell moves further downward. 5, which shows how the lower end of the mold was removed and breakout occurred.
The transition of the temperature detection values at A, B, and 0 of the temperature detection terminal 2 multiplied by Figure K is shown in Figure @6. Figure 6 shows that the temperature rise point moves from A to B and from B to C with a delay time proportional to the casting speed.

In the present invention, as shown in FIG. 6, the detected values of at least two successive temperature detection ends of the plurality of temperature detection ends buried in the direction of movement of the slab change due to the movement of the fractured part of the solidified slab shell due to the baking. A breakout is predicted based on a subsequent shift from the steady level to the high temperature side over time. Therefore, if the values of a plurality of temperature detection ends buried in the slab movement direction simultaneously deviate toward the high temperature side, it is not determined that a breakout is predicted. The simultaneous deviation is mainly due to operational fluctuations (casting speed fluctuations,
Breakouts do not occur due to fluctuations in molten metal level, etc.).

According to this experiment, the temperature detection ends should be placed below the molten metal meniscus in the mold, at least 100m below the meniscus, and the number of temperature detection ends should be two or more in the moving direction of one piece, with an interval of 5o. It has been found through experiments by the inventors that it is preferable to set the distance above the fin in order to accurately grasp the movement of the broken part of the slab #a.

In addition, by arranging the slab in the same manner in the width direction, it is possible to quickly eliminate the occurrence of fractures in the solidified slab shell at any location in the width direction.
And can be predicted accurately. The arrangement of the temperature detection ends in the width direction is determined by the size of the mold, but according to the experiments of the present inventors, if the arrangement interval in the width direction is set to about 100 m to 300 W, breakout prediction can be properly performed over the entire mold surface. It has been found that it is possible to make accurate judgments, and that the number of temperature detection terminals buried is the minimum required, making it the most convenient practice.

〔Example〕

Examples will be described below.

FIG. 7 shows the method of the present invention in which a thermocouple 12 is embedded as a temperature detection end in an 870 m long mold for casting a slab having a width T of 1300 F+ and a thickness W of 250 m. An explanatory diagram of the slab to be treated with sea bream is shown. Two thermocouples 12 were installed in the direction of movement of the cast slab shown in FIG. 7, and these positions were 200 m and 3001 below the meniscus 30. In addition, in the width direction, one row is placed in the center on the short side, and seven rows are placed on the long side, with viRt approximately 200 m from the center in the width direction. Buried deep. When casting was carried out using this mold at a standard casting speed of 1.5 yrL/-, the temperature changes at A and B of the thermocouple arrays (A) arranged on the long side wall of the mold were as shown in FIG.

(a) of FIG. 8 shows the fluctuations in the temperature detection values of thermocouples A and B when the casting speed fluctuates, and (b) shows the fluctuation of the temperature detection values of thermocouples A and B when the molten metal level in the mold fluctuates. As shown in Figures (a) and (b), when the detected values fluctuate almost simultaneously, a breakout prediction is not made and the casting is continued without a breakout occurring. (C) in Figure 8 is a case where the temperature change at the time of rupture of the solidified slab shell is shown in the detected values of thermocouples A and H. In this case, a breakout prediction is determined and an alarm is issued. It was possible to prevent breakout by reducing the casting speed.

〔effect〕

As is clear from the explanation of the above experimental examples and examples, according to the present invention, breakout prediction can be accurately determined, and therefore, it is possible to prevent deterioration in slab quality due to operational response due to misjudgment. Slab temperature decreases.

Also, there are no adverse effects such as poor matching with subsequent processes, and the effect is very large.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing an overview of judgments made using the conventional method, Figure 3 is a diagram of the mold configuration of the experiment of the present invention, and Figure 4
5 is a diagram showing the movement of a slab that breaks out in the mold in an experiment of the present invention, and FIG. 6 shows the detected temperature values at each temperature detection end in the case of FIG. 5. FIG. 7 shows the configuration of an embodiment of the present invention, and FIG. 8 shows an example of temperature detection values measured in the embodiment of the present invention. 1...-Mold copper plate wall, 2...Temperature detection end, 31.32
... Molten metal level in the mold, 4... Molten steel, 5... Solidified slab shell, 41.42.43... Temperature detection value distribution. Left Figure 1 (e) Bank Figure 2 Kataotsu Figure (6) (C) (d3 Figure 25

Claims (1)

[Claims] (1) A plurality of temperature detection ends are embedded in the side wall of the continuous casting mold in the direction of slab movement, and the detected values of at least two consecutive temperature detection ends are temporally higher than the steady level. A method for predicting a breakout in continuous casting, characterized in that it is determined that an abnormality occurs when the deviation occurs.