KR101193850B1 - Method for detecting dropping alien substance of submerged entry nozzle and continuous casting method using the same - Google Patents
Method for detecting dropping alien substance of submerged entry nozzle and continuous casting method using the same Download PDFInfo
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- KR101193850B1 KR101193850B1 KR20100062405A KR20100062405A KR101193850B1 KR 101193850 B1 KR101193850 B1 KR 101193850B1 KR 20100062405 A KR20100062405 A KR 20100062405A KR 20100062405 A KR20100062405 A KR 20100062405A KR 101193850 B1 KR101193850 B1 KR 101193850B1
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Abstract
The present invention includes the steps of obtaining a first height of the stopper for the amount of molten steel discharged through the immersion nozzle in the steady state in the tundish; Acquiring a second height which is a height of a stopper for discharging the molten steel in the state in which the immersion nozzle is blocked; Obtaining a blockage index of the immersion nozzle using the first height and the second height; Obtaining a difference value obtained by subtracting the blockage index of the second time point from the blockage index of the first time point, wherein the first time point is earlier than the second time point; When the difference value is a positive real number greater than a predetermined value, it relates to a method for detecting inclusion dropout of the immersion nozzle, and a continuous casting method related thereto comprising the step of determining that the inclusion of the immersion nozzle has dropped.
Description
The present invention relates to a method for detecting inclusion dropout of an immersion nozzle in a continuous casting and a continuous casting method relating thereto.
In general, a continuous casting machine is a facility for producing slabs of a constant size by receiving a molten steel produced in a steelmaking furnace and transferred to a ladle in a tundish and then supplying it as a mold for a continuous casting machine.
The continuous casting machine includes a ladle for storing molten steel, a continuous casting machine mold for cooling the tundish and the molten steel discharged from the tundish to form a casting having a predetermined shape, and a casting formed in the mold connected to the mold. It includes a plurality of pinch roller to move.
In other words, the molten steel tapping out of the ladle and tundish is formed of a slab (Slab) or bloom (Bloom), billet (Billet) having a predetermined width and thickness in the mold and is transferred through the pinch roller.
The present invention is to propose a method for increasing the productivity of continuous casting by detecting the dropping point of inclusions formed in the immersion nozzle in continuous casting.
In order to solve the above problems, an embodiment of the present invention, the inclusion drop detection method of the immersion nozzle, obtaining a first height of the stopper for the amount of molten steel discharged through the immersion nozzle in the steady state in the tundish; Acquiring a second height which is a height of a stopper for discharging the molten steel in the state in which the immersion nozzle is blocked; Using the first height and the second height, obtaining a blockage index of the immersion nozzle by the following formula; Obtaining a difference value obtained by subtracting the blockage index of the second time point detected after a predetermined time has elapsed from the blockage index of the first time point; And determining that the inclusion of the immersion nozzle is dropped if the difference is a positive number greater than a predetermined value, wherein the predetermined value may be 0.1 or more and 1.0.
[Equation 2]
C (blocking index) = 1-H 0 / H
H 0 : 1st height (mm)
H: 2nd height (mm)
According to an aspect of an embodiment of the present invention, the first height may be obtained by the following [Formula 1].
[Equation 1]
H 0 [mm] = discharge rate [ton / min] × a + b
H 0 is the first height, a is a constant set to 7.01 and b to 3.74.
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According to one embodiment of the present invention, the blockage index difference value can be obtained by the following [Equation 3].
[Formula 3]
Blockage Index Difference = Cl n -Min (Cl n +1 : Cl n +90 )
Cl n : Blockage index value at n seconds
Min (Cl n +1 : Cl n +90 ): Minimum blockage index between n + 1 and n + 90 seconds
n: seconds (sec)
Cl: blockage index
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In another embodiment of the present invention, a continuous casting method includes: obtaining a first blockage index indicating a degree of blockage at a first time point with respect to an immersion nozzle used in a continuous casting process; Obtaining a second blockage index indicating a degree of blockage of the immersion nozzle at a second time point, which is a set time point after the first time point; And if the difference value obtained by subtracting the second blockage index from the first blockage index is a positive number greater than a predetermined value, determining that the inclusions of the immersion nozzle have been dropped, and scarfing or downgrading the slab accordingly. The predetermined value is 0.1 or more and 1.0, and the first blockage index and the second blockage index can be obtained by the following equation.
[Equation 2]
C (blocking index) = 1-H 0 / H
H 0 : 1st height (mm)
H: 2nd height (mm)
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According to one embodiment of the present invention, in the continuous casting, when the molten steel is discharged into the mold, it is possible to detect the dropping time of the inclusions formed in the immersion nozzle. At this time, the slab manufactured is able to prevent the process cost and defects that may occur due to the input into the post-process, it is possible to expect cost reduction and quality improvement effect.
1 is a side view showing a continuous casting machine according to an embodiment of the present invention.
Figure 2 is a conceptual diagram for explaining the continuous caster of Figure 1 centered on the flow of molten steel (M).
Figure 3 is a graph showing the relationship between the height of the stopper and the discharge amount of the molten steel in the steady state associated with one embodiment of the present invention.
Figure 4 is a graph showing the weight of the ladle, the weight of the tundish, the casting speed, the blockage index, and the blockage change rate ratio over time associated with one embodiment of the present invention.
5 is a flowchart illustrating a inclusion drop detection method of an immersion nozzle according to an embodiment of the present invention.
6 is a flowchart illustrating a continuous casting method using the inclusion drop detection method of the immersion nozzle according to an embodiment of the present invention.
Hereinafter, the inclusion drop detection method and the continuous casting method of the immersion nozzle according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the present specification, different embodiments are given the same or similar reference numerals for the same or similar configurations, and the description is replaced with the first description.
Continuous casting is a casting method in which a casting or steel ingot is continuously extracted while solidifying molten metal in a mold without a bottom. Continuous casting is used to manufacture simple products such as squares, rectangles, circles, and other simple cross-sections, and slab, bloom and billets, which are mainly for rolling.
The type of continuous casting machine is classified into vertical type, vertical bending type, vertical axis difference bending type, curved type and horizontal type. 1 and 2 illustrate a curved shape.
1 is a side view showing a continuous casting machine related to an embodiment of the present invention.
Referring to this drawing, the continuous casting machine may include a tundish 20, a
The tundish 20 is a container that receives molten metal from the
The
The
The
The
The drawing device adopts a multidrive method using a plurality of sets of pinch rolls 70 and the like so that the casting can be taken out without slipping. The
The
FIG. 2 is a conceptual view illustrating the continuous casting machine of FIG. 1 based on the flow of molten steel M. Referring to FIG.
Referring to this figure, the molten steel (M) is to flow to the
The molten steel M in the
The molten steel M in the
As the pinch roll 70 (FIG. 1) pulls the
Here, when the height of the
By using this principle, the reference height of the
In this detailed description, for the sake of simplicity, a method of obtaining a blockage index according to the stopper height will be described in detail with reference to FIG. 3. It is to be understood that the present invention is not limited thereto and that the blockage index of the immersion nozzle can be obtained by various methods as described above. That is, the blockage index may be obtained based on the amount of argon gas Ar introduced into the immersion nozzle.
Hereinafter, a method of obtaining the blockage index through the stopper height will be described in detail with reference to FIGS. 3 and 4.
3 is a graph of the discharge amount and the height of the stopper in the immersion nozzle in the steady state. The vertical axis is the height of the stopper (mm), and the horizontal axis is the discharge amount per minute (ton / min) of the molten steel (M). As shown, the height of the
[Equation 1]
H 0 = Discharge amount × a + b
H 0 : Stopper height in steady state immersion nozzle (mm), a and b are constants, a is 7.01 and b is 3.74.
Discharge amount: ton / min
If nozzle clogging occurs under a constant molten steel discharge amount, the height of the stopper is raised to compensate for the decrease in the opening area of the
[Equation 2]
Cl (blocking index) = 1-H 0 / H
H 0 : Height of the stopper in the normal immersion nozzle (mm)
H: Height of stopper in immersion nozzle in blocked state (mm)
The blockage index thus obtained is obtained over time, and the dropping point of the inclusions formed in the immersion nozzle can be detected through the distribution of the blockage index. That is, if the blockage index at the first time point and the blockage index at the second time point are obtained, and the difference value is a positive real number larger than a predetermined value, it is determined that the inclusions of the immersion nozzle are dropped. Here, the difference value may be obtained by
[Equation 3]
Blockage Index Difference = Cl n -Min (Cl n +1 : Cl n +90 )
Cl n : Blockage index value at n seconds (blockage index at the first time point)
Min (Cl n +1 : Cl n +90 ): The lowest blockage index between n + 1 and n + 90 seconds (blockage index at the second time point)
n: seconds (sec)
4 is a graph showing the weight of the ladle, the weight of the tundish, the casting speed, the blockage index, and the blockage change rate ratio over time.
In Fig. 4, reference numeral (a) denotes a line for the amount of molten steel of the ladle over time, reference numeral (b) denotes a line for the amount of molten steel of the tundish over time, and reference numeral (c) corresponds to the time It is a line about casting speed (that is, the meaning of discharge amount of molten steel), and (D) is a line about the blockage index with time.
As shown, the clogging index of the immersion nozzle generally rises over time. However, at some point A, the value of the blockage index rapidly decreases. This point is when the inclusion of the immersion nozzle is dropped. Therefore, it can be seen that after this point, the address speed returns to normal speed again (see line (c)).
5 is a flowchart illustrating a method for detecting inclusions of an immersion nozzle according to an embodiment of the present invention.
As shown, first, the first height of the stopper with respect to the amount of molten steel discharged through the immersion nozzle in the steady state in the tundish is obtained (S1). Since the first height acquisition has been described with reference to FIG. 3, description thereof will be omitted. Then, the continuous casting process is actually carried out to obtain a second height which is the height of the stopper for discharging the molten steel amount during the actual process, that is, the immersion nozzle is blocked (S3). Using the first height and the second height, the blockage index of the immersion nozzle is obtained by [Equation 2] (S5). Since the blockage index has been described above, detailed description thereof will be omitted. A difference value obtained by subtracting the blockage index at the second time point detected after a predetermined time has elapsed from the blockage index at the first time point is obtained. The first time point is earlier than the second time point (S7). If the difference is a positive real number larger than a predetermined value, it is determined that the inclusions of the immersion nozzle are dropped (S9). The predetermined value is 0.1 or more and 1.0 here. That is, as shown in Figure 4, even if there is no dropout of the inclusions, the difference value of the blockage index may be a positive real number at a fine value according to the discharge degree of the molten steel. In order to prevent such an error, the predetermined value is preferably 0.1 or more. In addition, the difference value may not be greater than 1.0. Therefore, the predetermined value is limited from 0.1 to 1.0.
According to one embodiment of the present invention having the above-described configuration, it is possible to detect the dropping point of the inclusions formed in the immersion nozzle. At this time, the slab manufactured is able to prevent the process cost and defects that may occur due to the input into the post-process, it is possible to expect cost reduction and quality improvement effect.
6 is a flowchart illustrating a continuous casting method using the inclusion drop detection method of the immersion nozzle according to an embodiment of the present invention.
As shown in FIG. 6, first, a first blockage index indicating a blockage degree at a first time point is obtained for the immersion nozzle used in the continuous casting process (S11). Next, a second blockage index indicating a degree of blockage of the immersion nozzle at a second point in time after the first point in time is obtained (S13). As described above, the blockage indices are represented by
According to one embodiment of the present invention, in the continuous casting, when the molten steel is discharged into the mold, the dropping point of the inclusions formed in the immersion nozzle is detected and, accordingly, the slab containing the inclusions is scarfed or down. By graded, process costs and defects can be prevented in advance, resulting in cost reduction and quality improvement.
10: ladle 15: shroud nozzle
20: tundish 25: immersion nozzle
30: mold 40: mold oscillator
50: powder feeder 51: powder layer
52: liquid fluidized bed 53: lubricating layer
60: support roll 65: spray
70: pinch roll 80: strand
81: solidified shell 82: unsolidified molten steel
83: tip 85: solidification completion point
87: oscillation mark 88: bulging area
Claims (8)
Acquiring a second height which is a height of a stopper for discharging the molten steel in the state in which the immersion nozzle is blocked;
Using the first height and the second height, obtaining a blockage index of the immersion nozzle by the following formula;
Obtaining a difference value obtained by subtracting the blockage index of the second time point detected after a predetermined time has elapsed from the blockage index of the first time point; And
And determining that the inclusions of the immersion nozzle are dropped if the difference value is a positive real number greater than a predetermined value, wherein the predetermined value is 0.1 or more to 1.0.
Equation
C (blocking index) = 1-H 0 / H
H 0 : 1st height (mm)
H: 2nd height (mm)
And the first height is obtained by the following equation.
H 0 [mm] = discharge amount [ton / min] × a + b
H 0 is the first height, a is a constant set to 7.01 and b to 3.74.
The clogging index difference value is obtained by the following equation, the inclusion drop detection method of the immersion nozzle.
Blockage Index Difference = Cl n -Min (Cl n + 1 : Cl n + 90 )
Cl n : Blockage index value at n seconds
Min (Cl n + 1 : Cl n + 90 ): Minimum blockage index between n + 1 and n + 90 seconds
n: seconds (sec).
Cl: blockage index
Obtaining a second blockage index indicating a degree of blockage of the immersion nozzle at a second time point, which is a set time point after the first time point; And
If the difference between the first blockage index minus the second blockage index is a positive real number larger than the predetermined value, the inclusion of the immersion nozzle is determined to fall off, and thus the step of scarfing or downgrading the slab accordingly, The predetermined value is 0.1 or more and 1.0, wherein the first blockage index and the second blockage index is obtained by the following formula.
Equation
C (blocking index) = 1-H 0 / H
H 0 : 1st height (mm)
H: 2nd height (mm)
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KR101505156B1 (en) * | 2013-04-30 | 2015-03-23 | 현대제철 주식회사 | Continuous casting method |
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KR101400035B1 (en) * | 2012-01-31 | 2014-06-27 | 현대제철 주식회사 | Method for producing high quality slab |
KR101400042B1 (en) * | 2012-04-26 | 2014-05-30 | 현대제철 주식회사 | Method for producing high quality slab |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
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JPS6224848A (en) | 1985-07-23 | 1987-02-02 | Kawasaki Steel Corp | Automatic stopping method for continuous casting machine |
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Patent Citations (1)
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JPS6224848A (en) | 1985-07-23 | 1987-02-02 | Kawasaki Steel Corp | Automatic stopping method for continuous casting machine |
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KR101505156B1 (en) * | 2013-04-30 | 2015-03-23 | 현대제철 주식회사 | Continuous casting method |
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