WO2012030151A2

WO2012030151A2 - Method for predicting contamination range of molten steel when switching ladles

Info

Publication number: WO2012030151A2
Application number: PCT/KR2011/006422
Authority: WO
Inventors: 안재환; 김경수; 문홍길
Original assignee: 현대제철 주식회사
Priority date: 2010-08-30
Filing date: 2011-08-30
Publication date: 2012-03-08
Also published as: WO2012030151A3

Abstract

The present invention relates to a method for predicting the contamination range of molten steel when switching ladles, comprising the following steps: setting a casting amount (Q) after a first ladle has finished and the remaining molten steel amount (Qrm) of a tundish when starting a second ladle, respectively; calculating the casting amount (Qplug) when the contamination concentration becomes a set first reference value and the casting amount (Qpeak) when the contamination concentration becomes a set second reference value from the finishing point of the first ladle, respectively, using the remaining molten steel amount (Qrm) and the first proportional coefficient or the second proportional coefficient; obtaining the degree of contamination with respect to a specific casting amount by substituting the obtained casting amounts (Q, Qplug, Qpeak) and the remaining molten steel amount (Qrm) into a set linear and exponential function; and comparing the degrees of contamination obtained by the linear function and the exponential function to determine the smaller value as the degree of contamination by the specific casting amount.

Description

Prediction Method of Molten Steel Contamination Range in Ladle Change

The present invention relates to a method for predicting a molten steel contamination range in ladle exchange for predicting molten steel contamination in a tundish upon ladle exchange.

In general, a continuous casting machine is a facility for producing cast steel of a certain size by receiving a molten steel produced in a steelmaking furnace and transferred to a ladle (Tundish) and then supplied to a continuous casting machine mold.

The continuous casting machine includes a ladle for storing molten steel, a playing mold for cooling the tundish and the molten steel discharged from the tundish for the first time to form a casting cast having a predetermined shape, and the casting cast formed in the mold connected to the mold. It includes a plurality of pinch rolls.

In other words, the molten steel tapping out of the ladle and tundish is formed as a cast piece having a predetermined width, thickness and shape in a mold and is transferred through a pinch roll, and the cast piece transferred through the pinch roll is cut by a cutter. It is made of slabs (Slab), Bloom (Bloom), Billet (Billet) and the like having a predetermined shape.

In the case of the ladle is composed of a plurality of ladle, if the molten steel of the first ladle is all supplied to the tundish, the molten steel is supplied again to the tundish in the second ladle successively.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for predicting a pollution range of molten steel during ladle exchange, which predicts and analyzes a pollution degree and a range thereof generated at the end of casting of the first ladle and the beginning of casting of the second ladle according to operating variables.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

In the molten steel pollution prediction method of the present invention for realizing the above object, a first step in which the casting amount (Q) after the end of the first ladle and the remaining molten steel amount (Qrm) of the tundish at the start of the second ladle are respectively designated; ; Casting when the pollution concentration becomes the set first reference value from the end of the first ladle and the set second reference value using the Qrm and the set first or second proportional coefficient A second step of calculating quantities Qpeak respectively; A third step of substituting the values obtained in the first step and the second step into the set linear function and the exponential function, respectively, to obtain a degree of contamination for a specific casting amount; And a fourth step of comparing the pollution degree obtained by the linear function and the exponential function with each other, and determining a smaller value of the pollution degree according to a specific casting amount.

In the second step, the first reference value is 0.01, the second reference value is a value when the pollution concentration is maximum, the Qplug is obtained by multiplying Qrm by the first proportional coefficient (g), and the Qpeak is Qrm and the second Obtained by multiplying the proportional coefficient h, the first proportional coefficient g is determined between 0 and 0.3, and the second proportional coefficient h is determined between 0.1 and 0.4.

Comprehensive molten steel pollution degree is calculated by adding the pollution degree of the fourth stage obtained by applying the first proportional coefficient and the pollution degree of the fourth stage obtained by applying the second proportional coefficient, respectively. And comparing the pollution degree and "0" with each other to select a larger value of the two to determine the final pollution degree.

As described above, according to the present invention, by predicting and analyzing the pollution degree generated at the end of the first ladle and the initial casting of the second ladle according to the operating variables, the estimation of the occurrence time for the molten steel contaminant that best represents the cast failure rate is It is possible to focus on the management of the source of contamination at the start of the second ladle and have the advantage of minimizing or eliminating the poor quality of the cast.

1 is a side view showing a continuous casting machine according to an embodiment of the present invention.

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.

3 is a perspective view from above of the tundish of FIG. 2;

Figure 4 is a flow chart showing a molten steel pollution prediction process in the tundish according to an embodiment of the present invention

5 is a view showing the final casting situation of the first ladle.

6 is a view showing the initial casting situation of the second ladle.

7 and 8 are graphs showing the molten steel pollution degree at ladle exchange, respectively.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention. Like elements in the figures are denoted by the same reference numerals wherever possible. In addition, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

Referring to this drawing, the continuous casting machine may include a tundish 20, a mold 30, secondary cooling tables 60 and 65, a pinch roll 70, and a cutter 90.

The tundish 20 is a container that receives molten metal from the ladle 10 and supplies molten metal to the mold 30. Ladle 10 is provided with a pair of first ladle 11 and the second ladle 12, and alternately receives the molten steel to be supplied to the tundish 20 alternately. In the tundish 20, the supply rate of molten metal flowing into the mold 30 is adjusted, distribution of molten metal into each mold 30, storage of molten metal, separation of slag and nonmetallic inclusions, and the like are performed.

The mold 30 is typically made of water-cooled copper and allows the molten steel to be primary cooled. The mold 30 forms a hollow portion in which molten steel is accommodated as a pair of structurally facing surfaces are opened. In the case of manufacturing a slab, the mold 30 includes a pair of barriers and a pair of end walls connecting the barriers. Here, the short wall has a smaller area than the barrier. The walls of the mold 30, mainly short walls, may be rotated away from or close to each other to have a certain level of taper. This taper is set to compensate for shrinkage caused by solidification of the molten steel M in the mold 30. The degree of solidification of the molten steel (M) will vary depending on the carbon content, the type of powder (steel cold Vs slow cooling), casting speed and the like depending on the steel type.

The mold 30 is formed such that the cast steel drawn out from the mold 30 maintains its shape, and a strong solidification angle or solidifying shell (see FIG. 2) is formed so that molten metal, which is still less solidified, does not flow out. It plays a role. The water cooling structure includes a method of using a copper pipe, a method of drilling a water cooling groove in the copper block, and a method of assembling a copper pipe having a water cooling groove.

The mold 30 is oscillated by the oscillator 40 to prevent the molten steel from sticking to the wall of the mold. Lubricant is used to reduce the friction between the mold 30 and the cast steel during the oscillation and to prevent burning. Lubricants include splattered flat oil and powder added to the molten metal surface in the mold 30. The powder is added to the molten metal in the mold 30 to become slag, as well as the lubrication of the mold 30 and the cast steel, as well as the oxidation and nitriding prevention and thermal insulation of the molten metal in the mold 30, and the non-metallic inclusions on the surface of the molten metal. It also performs the function of absorption. In order to inject the powder into the mold 30, a powder feeder 50 is installed. The part for discharging the powder of the powder feeder 50 faces the inlet of the mold 30.

The

secondary cooling zones

60 and 65 further cool the molten steel primarily cooled in the mold 30. The primary cooled molten steel is directly cooled by the spray means 65 for spraying water while maintaining the solidification angle by the support roll 60 not to be deformed. The solidification of the cast steel is mostly made by the secondary cooling.

The drawing device adopts a multidrive method using a few sets of pinch rolls 70 and the like so as to pull out the cast pieces without slipping. The pinch roll 70 pulls the solidified tip of the molten steel in the casting direction, thereby allowing the molten steel passing through the mold 30 to continuously move in the casting direction.

The cutter 90 is formed to cut a continuously produced cast piece to a certain size. As the cutting machine 90, a gas torch, a hydraulic shear, or the like may be employed.

Referring to this figure, the molten steel (M) is to flow to the tundish 20 in the state accommodated in the ladle (10). For this flow, the ladle 10 is provided with a shroud nozzle 15 extending toward the tundish 20. The shroud nozzle 15 extends to submerge in the molten steel in the tundish 20 so that the molten steel M is not exposed to air and oxidized and nitrided. The case where molten steel M is exposed to air due to breakage of shroud nozzle 15 is referred to as open casting.

The molten steel M in the tundish 20 flows into the mold 30 by a submerged entry nozzle 25 extending into the mold 30. The immersion nozzle 25 is disposed in the center of the mold 30 so that the flow of molten steel M discharged from both discharge ports of the immersion nozzle 25 can be symmetrical. The start, discharge speed, and stop of the discharge of the molten steel M through the immersion nozzle 25 are determined by a stopper 21 installed in the tundish 20 corresponding to the immersion nozzle 25. Specifically, the stopper 21 may be vertically moved along the same line as the immersion nozzle 25 to open and close the inlet of the immersion nozzle 25. Control of the flow of the molten steel M through the immersion nozzle 25 may use a slide gate method, which is different from the stopper method. The slide gate controls the discharge flow rate of the molten steel M through the immersion nozzle 25 while the sheet material slides in the horizontal direction in the tundish 20.

The molten steel M in the mold 30 starts to solidify from the part in contact with the wall surface forming the mold 30. This is because heat is more likely to be lost by the mold 30 in which the periphery is cooled rather than the center of the molten steel M. By the way that the periphery is first solidified, the back portion along the casting direction of the cast steel 80 forms a shape in which the unsolidified molten steel 82 is wrapped in the solidified shell 81 on which the molten steel M is solidified.

As the pinch rolls 70 (FIG. 1) pull the front end portion 83 of the completely cast solid cast piece 80, the unsolidified molten steel 82 moves together with the solidified shell 81 in the casting direction. The uncondensed molten steel 82 is cooled by the spray means 65 for spraying the cooling water in the above movement process. This causes the thickness of the non-solidified molten steel 82 in the playing cast 80 to gradually decrease. When the cast steel 80 reaches a point 85, the cast steel 80 is filled with the solidification shell 81 of the entire thickness. The solidified cast piece 80 is cut to a certain size at the cutting point 91 is divided into slabs (P) such as slabs.

3 is a perspective view from above of the tundish of FIG. 2;

Referring to this figure, the tundish 20 has a body 22 that is open at the top to receive the molten steel (M) that is stepped out of the ladle (10). The body 22 may include an iron shell disposed outside and a refractory layer disposed inside the iron shell.

The shape of the body 22 may be a variety of forms, for example, straight, etc., in this embodiment illustrates the body 22 of the 'T' shape.

A portion 23 of the body 22 is formed with a pouring portion 23. The pouring portion 23 is a portion where the molten steel M flowing through the shroud nozzle 15 of the ladle 10 falls. The pouring portion 23 may communicate with the tapping portion 24 having a larger area.

The tapping part 24 is a part for guiding the molten steel M received through the pouring part 23 to the mold 30. A plurality of tapping holes 24a may be opened in the tapping part 24. An immersion nozzle 25 is connected to each tap 24a, and the immersion nozzle 25 guides the molten steel M of the tundish 20 to flow into the mold 30.

FIG. 4 is a flowchart illustrating a process of predicting molten steel pollution degree in a tundish according to an embodiment of the present invention, with reference to the accompanying drawings.

First, molten steel is contaminated much at the end of casting of the first ladle 11 and at the beginning of casting of the second ladle 12 when the ladle 10 is replaced.

In the final casting of the first ladle 11 as shown in Figure 5, since the slag of the ladle is supplied to the mold through the tundish 20, the quality defect rate of the slab at the end of the ladle is increased.

In addition, as shown in FIG. 6, during the initial casting of the second ladle 12, the filler of the second ladle 12 may be mixed in the molten steel, or the molten steel height of the tundish 20 may be temporarily lower than that of the shroud nozzle 15. The situation arises that the molten steel is re-produced at 20 so that molten steel is reoxidized or the slag of the tundish 20 is incorporated into the mold. This problem increases the defective rate of cast steel.

Therefore, it is necessary to quantitatively evaluate the extent of molten steel contamination and to predict the degree of molten steel pollution during ladle exchange.

As a result of experimenting the molten steel pollution degree through a water model, the result as shown in FIG. 7 was obtained. That is, the molten steel pollution degree tends to increase linearly with the passage of time (casting amount) at the end of the first ladle 11 or the initial casting of the second ladle 12, and then decreases exponentially when the maximum pollution degree is reached. And it was found. That is, the concentration of the contaminant during ladle exchange increases linearly from "1" to "peak" from Qplug to Qpeak, and then decreases exponentially to approach "0". FIG. 7 shows the molten steel contamination at the mold inlet side, which is injected into the mold 30 through the immersion nozzle 25 in the tundish 20, and then sets it linearly.

Hereinafter, the procedure for obtaining the molten steel contamination at the end of the first ladle 11 generated in the situation as shown in FIG. 5 and the molten steel contamination at the start of the second ladle 12 generated in the situation shown in FIG. 6 will be described.

First, the process of obtaining the molten steel pollution degree at the end of the first ladle 11 will be described. As shown in FIG. 4, the pollution prediction system (not shown) includes a molten steel amount, that is, an amount of casting Q, which flows into the mold through the tundish 20 after the end of the first ladle 11, which is an operating variable. At the start of the second ladle 12, the remaining molten steel Qrm remaining in the tundish 20 is set by the user as shown in FIG. 6 (S11). The residual molten steel Qrm may be obtained by subtracting the intrinsic weight of the tundish 20 from the total weight of the tundish 20 and the molten steel at the start of the second ladle 12. Although not shown, the contamination prediction system includes an input means for inputting various variables and parameters, a control unit for calculating contamination levels according to arithmetic algorithms and various variables and parameters stored in a memory, and the calculated contamination levels by a controller. It may be configured as a computer including a display unit for displaying.

Then, the pollution prediction system sets the pollution concentration from the end of the first ladle 11 by using the tundish residual molten steel Qrm at the start of the ladle second ladle 12 and the set first proportional coefficient. The casting amount Qplug when it becomes a 1st reference value and the casting amount Qpeak when it becomes a set 2nd reference value are respectively calculated by following relational formula 1 (S12, S13).

Relationship 1

Here, Qrm is the amount of remaining tundish molten steel at the start of the ladle second ladle, Qplug is the casting amount when the pollution concentration becomes 0.01 from the end of the first ladle, and Qpeak is the source concentration. A casting amount when " 1 ", g is a first proportional coefficient, and h is a second proportional coefficient.

For example, in FIG. 7, the minimum pollution concentration is "0" and the maximum pollution concentration is "1". The amount of casting when the pollution concentration becomes 0.01 from the end of the first ladle 11 is defined as Qplug. Qplug refers to the amount of casting required for the ladle slag introduced from the ladle to be injected into the mold through the shortest path in the tundish 20 and has a proportional relationship with the remaining molten steel Qrm of the tundish at the time of inflow. The first proportional factor g is a measure of how much plug flow characteristics the molten steel flow in the tundish 20 has, and is 0 to 0.2 depending on the shape of the tundish 20, that is, the plug flow characteristic. It can have a value between

And Qpeak is defined as the casting amount when the source concentration is "1". The Qpeak value is a value determined by the flow characteristics in the tundish 20 and has a proportional relationship with the tundish residual molten steel Qrm at the inflow point. The second proportional coefficient h has a value between 0.1 and 0.3. Can be.

Thus, after calculating Qplug and Qpeak respectively, based on the calculated Qplug and Qpeak and the set values, the pollution degree according to the linear function and the exponential function is calculated. The straight line function and the exponential function are as shown in Equations 2 and 3 below (S14).

Relation 2

Here, Q is the casting amount (ton) after the end of the first ladle, Qrm is the remaining tundish molten steel (ton) at the start of the second ladle, Qplug is a pollution concentration of 0.01 from the end of the first ladle Is the casting amount at the time of ton and Qpeak is the casting amount when the source concentration is "1".

Relationship 3

Where f is a third proportional coefficient.

Contaminant concentration by the ladle slag increases linearly to "1" from when the casting amount is Qplug to Qpeak as shown in FIG. 7, and then decreases exponentially to approach "0". Here, the degree of exponential decrease is proportional to the ratio (Q / Qrm) of Qrm at the time when the ladle slag enters the tundish 20 and the casting amount cast thereafter, and the third proportional coefficient f is 3 It can have a value between.

Thus, each pollution degree obtained by the linear function and the exponential function is compared with each other, and the smaller of the two values is determined first as the molten steel pollution degree at the end of the first ladle 11 according to the specific casting amount (S15). Here, the reason for selecting the smaller of the two, the pollution degree between Qplug and Qpeak in the graph of Figure 8 appears in the form of a linear function (㉮), where the value of the linear function (㉮) is an exponential function (㉯) This is because it is smaller than the value of. In addition, the pollution degree is expressed in exponential form in the section above Qpeak, because the exponential function is smaller than the value of the linear function.

Subsequently, the above-described pollution degree and "0" are compared with each other, and the larger of the two values is finally determined as the molten steel pollution degree at the end of the first ladle 11 (S16 and S17). Here, the reason why the larger of the two values are selected by comparing the pollution degree with "0" is that the pollution degree cannot have a negative value (-).

Meanwhile, the process of obtaining the molten steel pollution degree at the start of the second ladle 12 will be described. The contamination prediction system (not shown) also includes the amount of molten steel flowing out of the mold through the tundish 20 after the end of the first ladle 11, that is, the casting amount Q and the start of the second ladle 12. As shown in FIG. 6, the remaining molten steel quantity Qrm remaining in the tundish 20 is set by the user (S11).

Subsequently, the contamination prediction system uses the tundish residual molten steel Qrm at the start of the second ladle 12 and the set secondary proportional coefficients g and h to contaminate from the end point of the first ladle 11. The casting amount Qplug when the concentration becomes the set first reference value and the casting amount Qpeak when the concentration becomes the set second reference value are respectively calculated by the above relationship 1 (S12 and S18). The second proportional coefficient is the same parameter as the above-described first proportional coefficient, and its value may be different.

For example, in FIG. 7, the minimum pollution concentration is "0" and the maximum pollution concentration is "1". The casting amount when the contamination concentration becomes 0.01 from the end of the first ladle 11 is defined as Qplug, and Qplug is calculated by the above relation 1

Can be Qplug refers to the amount of casting required for the ladle slag introduced from the ladle to be injected into the mold through the shortest path in the tundish 20 and has a proportional relationship with the remaining molten steel Qrm of the tundish at the time of inflow. The first proportional coefficient (g) is a measure of how plug flow is characterized in that the molten steel flow in the tundish 20 is 0.1, depending on the shape of the tundish 20, that is, the plug flow characteristic. It can have a value between 0.3.

And, Qpeak is defined as the amount of casting when the pollutant concentration is "1", Qpeak is calculated by the relationship 1

Can be The Qpeak value is a value determined by the flow characteristics in the tundish 20 and has a proportional relationship with the remaining molten amount Qrm of the tundish at the inflow point. The second proportional coefficient h has a value between 0.2 and 0.4. Can have

As described above, after calculating Qplug and Qpeak, respectively, the pollution degree according to the linear function and the exponential function is calculated based on the calculated Qplug and Qpeak and the set values (S19). The linear function and the exponential function are the same as the relations 2 and 3.

Contaminant concentration by filler and tundish slag and molten steel reoxidation of the ladle increases linearly to "1" from the time of Qplug to Qpeak as shown in FIG. 7, and then decreases exponentially to "0". Close to. Here, the degree of exponential decrease is proportional to the ratio of Qrm at the time when the ladle slag is introduced and the casting amount (Q / Qrm) cast thereafter, and the third proportional coefficient f is a value between 3 and 8. Can have. The tundish remaining molten steel quantity Qrm becomes a minimum amount immediately before the opening of the second ladle 12 and rises until it becomes a normal molten steel after the opening of the second ladle 12. The third proportional coefficient f is larger in the range 3 to 8 as the amount of molten steel in the tundish immediately before the opening of the second ladle 12 becomes larger, and is until the normal amount of molten steel after opening of the second ladle 12. The larger the amount of molten steel per minute supplied from the second ladle 12 to the tundish 30, the larger the range is.

Thus, each pollution degree obtained by the linear function and the exponential function is compared with each other, and the smaller of the two is first determined as the molten steel pollution degree at the start of the second ladle 12 according to the specific casting amount (S20).

Subsequently, the above-described pollution degree and "0" are compared with each other, and the larger of the two values is finally determined as the molten steel pollution level at the start of the second ladle 12 (S21 and S22).

As described above, the molten steel contamination at the end of the first ladle 11 and the molten steel pollution at the start of the second ladle 12 may include the first proportional coefficient g, the second proportional coefficient h, and the third proportional coefficient ( Only the values of f) are different and are calculated using the same relations and procedures.

Thus, the process of obtaining the molten steel pollution degree (C1) at the end of the first ladle 11 and the molten steel pollution degree (C2) at the start of the second ladle 12 is shown as the following equations 4 and 5. In other words, the method for obtaining the molten steel pollution degree (C1, C2) is to select a smaller value by comparing the linear function and the exponential function determined as in relations 4 and 5, and then select the larger value by comparing the selected value with "0". To determine the degree of contamination according to the specific casting amount (Q).

Relationship 4

Relationship 5

Then, the pollution prediction system determines the pollution degree C1 at the end of the first ladle 11 obtained by applying the first proportional coefficient and the pollution degree C2 at the start of the second ladle 12 obtained by applying the second proportional coefficient. Each addition is calculated to calculate the total molten steel pollution degree (Tc) as shown in Equation 6 below (S23).

Relationship 6

Here, C1 is a pollution degree at the end of the first ladle 11, C2 is a pollution degree at the start of the second ladle 12, A is a weight.

The weight A may be a value between 0.2 and 0.4, since the influence of the source at the end of the first ladle 11 is about 30% and the influence of the source at the start of the ladle is about 70%. As for (A), about 0.3 are preferable.

Thus, through the contamination prediction process, it is possible to estimate the occurrence time for the molten steel contaminant that best represents the failure rate of the cast steel according to the operation variables (Q, Qrm) and the shape of the tundish 20 to change the position of cutting the cast steel By adjusting, the quality defect of the cast steel can be minimized, and the quality defect of the cast steel can be minimized or eliminated by focusing on the management of the pollution source at the start of the second ladle 12.

The present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention pertains to the detailed description of the present invention and other forms of embodiments within the essential technical scope of the present invention. Could be. Here, the essential technical scope of the present invention is shown in the claims, and all differences within the equivalent range will be construed as being included in the present invention.

Claims

A first step in which, after the end of the first ladle, the casting amount Q and the remaining molten steel Qrm of the tundish at the start of the second ladle are respectively designated;

The amount of casting Qplug and the set second reference value when the contamination concentration becomes the set first reference value from the end of the first ladle using the residual molten steel Qrm and the set first proportional coefficient or the second proportional coefficient A second step of calculating the amount of casting Qpeak at each time;

A third step of substituting the obtained casting amount (Q, Qplug, Qpeak) and the remaining molten steel amount (Qrm) into the set linear function and the exponential function, respectively, to obtain the pollution degree for the specific casting amount; And

And comparing a contamination degree obtained by the linear function and the exponential function with each other, and determining a smaller value of the contamination degree according to a specific casting amount. 4.
The method according to claim 1,

In the second step, the first reference value is 0.01, and the second reference value is the value when the contamination concentration is the maximum molten steel pollution range prediction method during ladle exchange.
The method according to claim 1,

The Qplug is obtained by multiplying the remaining molten steel Qrm of the tundish by the first proportional coefficient g, and the Qpeak is the ladle exchange obtained by multiplying the remaining molten steel Qrm of the tundish by the second proportional coefficient h. Method of Predicting Pollution Range of Municipal Steel.
The method according to claim 3,

The first proportional coefficient (g) is determined between 0 and 0.3, and the second proportional coefficient (h) is determined between 0.1 to 0.4.
       The method according to claim 3,

      The first proportional coefficient (g) is determined between 0 and 0.2 in the first proportional coefficient, and determined between 0.1 and 0.3 in the second proportional coefficient,

      The second proportional coefficient (h) is determined between 0.1 to 0.3 in the first proportional coefficient, the molten steel pollution range prediction method during ladle exchange is determined between 0.2 to 0.4 in the second proportional coefficient.
The method according to claim 1,

The pollution degree (C) for the specific casting amount in the third step is calculated by the linear function of the following equation 1 and the exponential function of the following equation 2, respectively.

Relationship 1

Relation 2

Here, Q is the casting amount (ton) after the end of the first ladle, Qrm is the remaining tundish molten steel (ton) at the start of the second ladle, Qplug is a pollution concentration of 0.01 from the end of the first ladle Is the casting amount (ton) at the time, Qpeak is the casting amount (ton) when the source concentration is 1, and f is the third proportional coefficient.
The method according to claim 6,

The third proportional coefficient f is determined between 3 to 8 molten steel pollution range prediction method during ladle exchange.
The method according to claim 1,

A method of predicting the molten steel pollution range during ladle exchange by adding the pollution degree in the fourth step obtained by applying the first proportional coefficient and the pollution degree in the fourth step obtained by applying the second proportional coefficient to calculate a comprehensive molten steel pollution degree (Tc). .
The method according to claim 8,

The comprehensive molten steel pollution degree (Tc) is a method of predicting the molten steel pollution range when ladle exchange is calculated by the following equation (3).

Relationship 3

Here, C1 is a pollution degree obtained by applying the first proportional coefficient at the end of the first ladle, C2 is a pollution degree obtained by applying the second proportional coefficient at the start of the second ladle, A is a weight.
The method according to claim 9,

The weight (A) is a value between 0.25 to 0.35 molten steel pollution range prediction method during ladle exchange.
The method according to claim 1,

And comparing the pollution degree determined in the fourth step with "0" and selecting a larger value of the two to determine a final pollution degree.