KR101400041B1 - Device for estimating carbon-increasing of molten steel and method thereof - Google Patents

Abstract

The present invention relates to a ladle furnace comprising a storage section for storing a ladle slag amount, a ladle residual amount and a carbon concentration in the ladle slag present in a ladle, and a ladle slag storing section for dividing the ladle slag amount stored in the storage section by the ladle residual amount, And a central processing unit for obtaining a slag carbon incorporation ratio (SCI) by multiplying the slag carbon incorporation ratio (SCI) by the slag carbon incorporation ratio (SCI) and substituting the slag carbon incorporation ratio (SCI) into the following relationship to predict a carbon pick- .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for predicting carbon increase in molten steel,

More particularly, the present invention relates to an apparatus and method for predicting carbon increase in molten steel during ladle replacement for predicting contamination in a tundish during a reduction in ladle residue during a performance process.

The continuous casting machine is a machine that is produced in the steel making furnace, receives the molten steel transferred to the ladle by the tundish, and supplies it to the mold for the continuous casting machine to produce the cast steel of a certain size.

The continuous casting machine includes a ladle for storing molten steel, a casting mold for forming a tundish and a molten steel that is guided in the tundish first to form a cast slab having a predetermined shape, and a casting member connected to the mold, A plurality of pinch rolls.

In other words, molten steel introduced from the ladle and the tundish is formed into a cast slab having a predetermined width, thickness and shape in the mold and is transported through the pinch roll, and the slab transferred through the pinch roll is cut by a cutter A slab having a predetermined shape or a cast such as a bloom or a billet.

Related prior art is Korean Patent Publication No. 2005-21961 (published on Mar. 03, 2005, entitled " Method of manufacturing ultra-low carbon steel slab).

The present invention provides an apparatus and method for predicting carbon increase in molten steel for predicting the carbon increase (carbon pickup) of molten steel in a tundish due to reduction in ladle residue during a performance process using ultra-low carbon steel.

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems.

According to an aspect of the present invention, there is provided an apparatus for predicting carbon increase in molten steel, comprising: a storage unit for storing a ladle slag amount, a ladle residual amount, and a carbon concentration in the ladle slag present in the ladle; (SCI) is obtained by dividing the slag carbon content (SCI) by the amount of the ladle residue, and multiplying the carbon concentration in the ladle slag by the carbon concentration in the ladle slag to calculate the slag carbon incorporation ratio (SCI) And a central processing unit.

Relation

Where alpha is a value between 2.8 and 2.9 and beta is a value between 7.7 and 7.8.

Specifically, the slag carbon incorporation ratio (SCI) can be calculated by the following relational expression.

Relation

The method for predicting carbon increase in molten steel according to the present invention for realizing the above object comprises the steps of measuring a ladle slag amount, a ladle residual amount and a ladle slag component existing in a ladle, , Calculating slag carbon incorporation ratio (SCI) by multiplying the carbon concentration of the ladle slag by the carbon concentration of the ladle slag, and estimating carbon uptake (C pick-up) by substituting the slag carbon incorporation ratio (SCI) Step < / RTI >

Relation

Where α and β can be constants of the relationship between C pick-up and SCI.

Specifically, the molten steel may be an extremely low carbon steel containing more than 0 to 30 ppm of carbon.

Alpha of the above relational expression may be a value between 2.8 and 2.9 and beta may be a value between 7.7 and 7.8.

The slag carbon incorporation ratio (SCI) can be calculated by the following relational expression.

Relation

As described above, according to the present invention, the carbon content of the molten steel in the tundish (carbon pick-up) can be easily predicted and coped with beforehand due to the reduction of the ladle residue in the performance process, .

Further, according to the present invention, it is possible to improve the quality of the cast steel produced in extremely low carbon steel.

1 is a conceptual view showing a continuous casting machine according to an embodiment of the present invention, focusing on the flow of molten steel.
2 is a diagram showing a prediction apparatus according to an embodiment of the present invention.
FIG. 3 is a graph showing the carbon increase amount of the cast steel produced at the time of ladle exchange.
FIG. 4 is a flowchart illustrating a process of predicting a carbon increase amount using a slag carbon incorporation ratio (SCI) according to an embodiment of the present invention.
5 is a graph showing the relationship between the slag carbon incorporation ratio (SCI) of the present invention and the carbon increase amount.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference symbols whenever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

1 is a conceptual view showing a continuous casting machine according to an embodiment of the present invention, focusing on the flow of molten steel.

Continuous casting is a casting method in which molten metal is continuously cast (P) or steel ingot while solidifying in a mold without mold (Mold) (30). Continuous casting is used to manufacture slabs, blooms and billets, which are mainly rolled materials, and long products of simple cross-section such as square, rectangle, and circle.

The shape of a continuous casting machine is classified into a vertical type and a vertical bending type. In Fig. 1, a vertical bending type is illustrated.

1, a continuous casting machine may include a ladle 10 and a tundish 20, a mold 30, a secondary cooling stand, and a pinch roll 70. [

A tundish 20 is a container for receiving molten metal from a ladle 10 and supplying molten metal to a mold 30. In the tundish 20, the supply rate of the molten metal flowing into the mold 30 is controlled, the molten metal is distributed to each mold 30, the molten metal is stored, and the slag and the nonmetallic inclusions are separated.

Mold 30 is typically made of water-cooled copper and allows the molten steel taken to be first cooled. The mold 30 has a pair of structurally opposed faces open to form a hollow portion for receiving molten steel. In the case of manufacturing the slab, the mold 30 includes a pair of barriers and a pair of end walls connecting the barriers. Here, the end wall has a smaller area than the barrier. The walls, mainly the walls, of the mold 30 may be rotated to be away from or close to each other to have a certain level of taper. This taper is set to compensate for the shrinkage due to the solidification of the molten steel M in the mold 30. The degree of solidification of the molten steel (M) varies depending on the carbon content according to the steel type, the kind of the powder (strong cold type Vs and cold type), the casting speed and the like.

The mold 30 is formed of a solidified shell 81 or a solidified shell 81 that retains the shape of the casting 80 pulled out of the mold 30, And the like. The water-cooling structure includes a method using a copper tube, a method of water-cooling the copper block, and a method of assembling a copper tube having a water-cooling groove.

The mold 30 is oscillated by the oscillator 40 to prevent the molten steel from sticking to the wall surface of the mold 30. A lubricant is used to reduce the friction between the mold 30 and the solidification shell 81 during oscillation and to prevent burning. As the lubricant, there is oil to be sprayed and powder added to the molten metal surface in the mold 30. A powder feeder 50 is installed to feed the powder into the mold 30. The portion of the powder feeder 50 for discharging the powder is directed to the inlet of the mold 30.

The secondary cooling zone further cools the molten steel primarily cooled in the mold (30). The primary cooled molten steel is directly cooled by the spraying means 65 for spraying water while being maintained by the support roll 60 so that the coagulation angle is not deformed. Most of the solidification of the cast slab 80 is achieved by the secondary cooling.

The pulling device employs a multi-drive type or the like which uses several pairs of pinch rolls 70 so that the casting piece 80 can be pulled out without slipping. The pinch roll 70 pulls the solidified tip portion 83 of the molten steel in the casting direction so that molten steel passing through the mold 30 can be continuously moved in the casting direction.

In the continuous casting machine constructed as described above, the molten steel M contained in the ladle 10 flows into the tundish 20. For this flow, the ladle 10 is provided with a shroud nozzle 15 extending toward the tundish 20. The shroud nozzle 15 extends into the molten steel in the tundish 20 so that the molten steel M is not exposed to the air to be oxidized and nitrided.

The molten steel M in the tundish 20 is caused to flow into the mold 30 by the submerged entry nozzle 25 extending into the mold 30. The immersion nozzle 25 is disposed at the center of the mold 30 so that the flow of the molten steel M discharged from both the discharge ports of the immersion nozzle 25 can be made symmetrical. The start, the discharge speed and the interruption of the discharge of the molten steel M through the immersion nozzle 25 are determined by a stopper 21 provided on the tundish 20 in correspondence with the immersion nozzle 25. Specifically, the stopper 21 can be vertically moved along the same line as that of the immersion nozzle 25 so as to open and close the inlet of the immersion nozzle 25. The control of the flow of the molten steel M through the immersion nozzle 25 may use a slide gate method 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 plate material slides horizontally in the tundish (20).

Molten steel (M) in the mold (30) starts to solidify from a portion in contact with the wall surface of the mold (30). This is because the periphery of the molten steel M is liable to lose heat by the water-cooled mold 30. The rear portion along the casting direction of the cast slab 80 is formed into a shape in which the non-solidified molten steel 82 is wrapped in the solidifying shell 81 by the method in which the peripheral portion first coagulates.

The non-solidified molten steel 82 moves together with the solidification shell 81 in the casting direction as the pinch rolls (Figs. 1 and 70) pull the distal end portion 83 of the fully cast solidification casting 80. The non-solidified molten steel (82) is cooled by the spraying means (65) for spraying the cooling water in the up-shifting process. This causes the thickness of the non-solidified molten steel (82) to gradually decrease in the cast steel (80). When the cast slab 80 reaches one point, the cast slab 80 is filled with the solidified shell 81 as a whole. The solidification casting 80 having been solidified is cut to a predetermined size at the cutting point 91 and is divided into a slab P such as a slab or the like.

FIG. 2 is a conceptual view showing a tapping pattern of a forecasting device 100 and ladle 10 of the invention. The predicting device 100 includes a measuring unit 110, an input unit 120, a storage unit 130, A processing unit 150, and a display unit 170.

The measuring unit 110 is immersed in the slag at the upper end of the molten steel in the ladle 10 to measure the thickness of the slag layer, the height from the lower end of the ladle 10, and the components of the slag. The slag amount in the ladle 10 can be calculated using the fact that the slag amount in the ladle 10 is proportional to the measured thickness of the slag layer and the width of the ladle 10. [ In addition, in the measuring section 110, the residual amount in the ladle 10 can be calculated in comparison with the height of the slag layer in which the residual amount in the ladle 10 is measured and the total ladle 10 size. In addition, the carbon content in the slag measured by the measuring unit 110 can be analyzed to calculate the carbon concentration in the slag.

In addition, the input unit 120 is configured to receive various operation commands and setting reference values from the outside in the form of a keypad, a touch screen, or the like, and transmit the operation commands and setting reference values to the storage unit 130. In particular, an arbitrary amount of ladle slag, an amount of residual ladle, and a carbon concentration in slag can be directly input to immediately check the processing result under the condition.

In general, the remaining amount of the ladle may be calculated by measuring the weight by the load cell in addition to the method of calculating by the measuring unit 110, and calculating the amount of outflow on the basis of the tapping speed at the initial laden amount of the ladle 10 The input unit 120 may be required to input an amount of remaining ladle residue by the measuring unit 110 and store the amount.

The amount of ladle slag is also calculated by using the slag thickness information in the measuring unit 110, and the amount of slag generated by the amount of slag set material is calculated and used. Therefore, an input device capable of inputting an arbitrary value The input unit 120 is requested.

The carbon concentration in the slag may be measured by using the value analyzed by the measuring unit 110, or by directly inputting the carbon component value in the molten steel after the RH (vacuum degassing) treatment for manufacturing the ultra low carbon steel through the input unit 120 It is possible.

The thus determined ladle slag amount, ladle remaining amount, and carbon concentration in the slag are transferred to the storage unit 130.

The storage unit 130 stores the amount of ladle slag, the remaining amount of ladle, and the carbon concentration in the slag transferred through the input unit 120, and transfers the stored concentration to the central processing unit 150. In the storage unit 130, a relational expression for predicting the C increase (C pick-up), a calculation value thereof, and the like may be stored under the control of the central processing unit 150.

The central processing unit 150 calculates the slag carbon incorporation ratio (SCI) based on the amount of ladle slag transferred from the storage unit 130 and the remaining amount of ladle, predicts a C pick-up amount using the slag carbon incorporation ratio (SCI) And outputs it to the display unit 170.

Here, the slag carbon incorporation ratio (SCI) is calculated according to the following relational expression (1).

Relationship 1

Specifically, the slag carbon incorporation ratio (SCI) is calculated by multiplying the value obtained by dividing the amount of ladle slag by the amount of residual ladle and the carbon concentration in the slag.

The carbon increase amount (C pick-up) is obtained by substituting the calculated slag carbon incorporation ratio (SCI) into the following expression (2).

Relation 2

Here, α and β are calculated by the relationship between the slag carbon incorporation ratio (SCI) and the carbon increase amount (C pick-up) as a relation constant, which will be described later in the description of FIG. Specifically,? May be a value between 2.8 and 2.9, and? May be a value between 7.7 and 7.8.

In addition, the display unit 170 displays the amount of ladle slag stored in the storage unit 130, the amount of remaining ladle, the carbon concentration in the slag, the slag carbon incorporation ratio (SCI), the predicted carbon increase amount (C pick-up) And display it in a character or a graph under the control of the control unit 150.

Generally, in the case of automobile shell plates, it is possible to produce solidified alloying elements, especially carbon with extremely few extremely low carbon steel of less than 30 ppm in order to achieve high-quality formation. Therefore, carbon is removed through RH (vacuum degassing) process during steel refining process. In order to prevent increase of carbon even during continuous casting, carbon content of subsidiary material such as flux and mold powder in tundish is as low as 5% . However, as shown in part A of FIG. 2, when the ladle residue is reduced during casting, the ladle slag may flow into the tundish 20 due to a vortex formed in the bath surface portion, and the carbon content of the molten steel in the tundish 20 may increase .

On the other hand, in order to prevent the ladle slag from flowing into the molten steel, the molten steel in the ladle 10 is not completely introduced into the ladle 10 and the ladle 10 is stopped . At this ladle changing point, as described above, carbon inflow occurs in the molten steel due to the generation of vortex in the ladle 10 hot water surface portion. As a result, as shown in FIG. 3, It can be confirmed that it has increased rapidly.

In addition, as the carbon content in the molten steel increases, the plate material (hot-rolled coil) having reduced formability causes a problem that a part of the product tears during the molding of the final product. When the carbon content exceeds the allowable limit value The subsequent processing such as rolling of slabs increases unnecessary machining cost and increases the defective processing cost at the same time.

In the present invention, by easily anticipating and coping with the carbon increase (carbon pickup) of the molten steel in the tundish due to the reduction of the ladle residue during the performance process using the ultra-low carbon steel, the manufacture of the slab exceeding the carbon tolerance limit value and the unnecessary subsequent process And to prevent waste of productivity and cost due to progress.

FIG. 4 is a flowchart illustrating a process of predicting a carbon increase amount using a slag carbon incorporation ratio (SCI) according to an embodiment of the present invention, and will be described with reference to the accompanying drawings.

First, molten steel produced through a secondary refining process of an electric furnace and a ladle furnace is supplied to a continuous casting machine, and in the continuous casting machine as shown in FIG. 1, the supplied molten steel is manufactured into a slab-like casting piece P.

On the other hand, at the time when the molten steel is transferred from the ladle 10 to the tundish 20, the amount of ladle slag, remaining amount of the ladle, and slag components present in the ladle during casting are measured. (S10) The amount of slag, the amount of remaining ladle, and the carbon content of the slag are transferred directly or through the input unit 120 and stored in the storage unit 130 under the control of the central processing unit 150.

Subsequently, the central processing unit 150 calculates the slag carbon incorporation ratio (SCI) by dividing the amount of ladle slag stored in the storage unit 130 by the amount of residual ladle and multiplying the carbon concentration in the slag. (S20) Slag carbon incorporation ratio SCI ) Is calculated by the following equation (1).

Relationship 1

In detail, as the reaction rate index is a value obtained by dividing the amount of ladle slag by the amount of remaining ladle as a reaction rate index, that is, the greater the ratio of the ladle slag amount, the higher the probability that the slag impurities will flow into the molten steel. Lt; / RTI > In addition, the higher the carbon concentration in the slag, the higher the probability that the carbon content of the slag will flow into the slag.

For example, if the amount of ladle slag is 3 tons, the amount of remaining ladle is 5 tons, and the carbon concentration in the slag is 450 ppm, the slag carbon incorporation ratio (SCI) will be '270'.

The thus calculated slag carbon incorporation ratio (SCI) is stored in the storage unit 130.

Thereafter, the central processing unit 150 predicts a carbon pick-up amount (C pick-up) using the slag carbon incorporation ratio (SCI). (S30) Here, the carbon pick-up amount Can be calculated.

Relation 2

Here, α and β are relation constants calculated by the relationship between the slag carbon incorporation ratio (SCI) and the carbon increase amount (C pick-up) shown in FIG. 5, α is a value between 2.8 and 2.9, 7.7 to 7.8. The relationship between the slag carbon incorporation ratio (SCI) and the carbon increase amount (C pick-up) is shown in the graph of FIG. 5, -up) can be confirmed to have a roughly proportional relationship under the same conditions of other operating conditions.

Ladle residue
(ton) SCI
(ppm) Forecasted Carbon Growth
(ppm) Actual carbon increment
(ppm) Example 1 5 0.60 8.4 7.9 Example 2 10 0.30 6.4 6.9 Example 3 15 0.20 5.3 5.8 Example 4 20 0.15 4.4 4.7 Example 5 25 0.12 3.8 3.7 Example 6 30 0.10 3.3 2.6

In FIG. 5, the dots are actually measured data (Examples 1 to 6) of the carbon increase amount (C pick-up) according to the slag carbon incorporation ratio (SCI), and the solid line is the predicted model (R ² = 0.9363), indicating that the actual and predicted models are somewhat coincident.

Here, the first constant? According to the correlation between the slag carbon incorporation ratio (SCI) and the carbon increase amount (C pick-up) may preferably be 2.8957 and the second constant? '7.7663'.

When the C pick-up is calculated, the central processing unit 150 can calculate the final carbon content by adding the calculated C pick-up to the carbon content in the initial molten steel. The carbon content in the initial molten steel is the carbon content of the molten steel after RH (vacuum degassing) treatment at the time when molten steel is spouted from the ladle 10 to the tundish 20 or when the ultra low carbon steel is produced, It is within the range of extremely low carbon steel of 30 ppm or less.

Then, the central processing unit 150 compares the calculated final carbon content with the set reference carbon amount, and determines whether the final carbon amount exceeds the reference carbon amount. The reference carbon amount can be cut according to the steel grade or the specification, and the reference carbon amount in the case of the automobile exterior plate can be up to about 24 ppm.

When the predicted final carbon amount exceeds the set reference carbon amount, the central processing unit 150 outputs a warning message or the like to the display unit 170. At the same time, the steel strip P produced at the time point is output to a subsequent process such as rolling , And waits for reanalysis of the carbon content of the cast steel (P). This is to prevent unnecessary process waste such as the failure cast P proceeding to a subsequent process. Of course, when the final carbon amount predicted does not exceed the set reference carbon amount, the central processing unit 150 causes the cast P to be put into a subsequent process such as rolling.

In addition, during reanalysis of the carbon content of the cast steel, the reamer is moved back to the casting machine, and the molten steel that is in the waiting state is spouted to advance the casting performance.

Therefore, it is possible to easily predict the carbon increase amount (carbon pickup) of the molten steel in the tundish due to the reduction of the ladle residue in the performance process, and cope with it in advance, so that the carbon content of the molten steel in the tundish can be kept constant.

The apparatus for predicting the carbon increase in molten steel and the method thereof are not limited to the construction and the manner of operation of the embodiments described above. The embodiments may be configured so that all or some of the embodiments may be selectively combined so that various modifications may be made.

10: Ladle 15: Shroud nozzle
20: tundish 21: stopper
25: immersion nozzle 30: mold
40: Mold oscillator 50: Powder feeder
60: Support roll 65: Spray means
70: pinch roll 80: performance cast
81: Solidification shell 82: Non-solidified molten steel
83: tip portion 85: solidified point
87: Oscillation mark 91: Cutting point
100: prediction device 110:
120: input unit 130: storage unit
150: central processing unit 170:
S: ladle slag M: molten steel (ladle residue)

Claims (6)

A storage unit for storing the amount of ladle slag present in the ladle, the amount of ladle remaining amount, and the carbon concentration in the ladle slag; And
The slag carbon incorporation ratio (SCI) is obtained by substituting the amount of ladle slag, the amount of ladle residue, and the carbon concentration stored in the storage unit into the following relational expression 1, and the slag carbon incorporation ratio SCI is substituted into the following expression And a central processing unit for predicting carbon uptake (C pick-up).
Relationship 1

Relation 2

Where alpha is a value between 2.8 and 2.9 and beta is between 7.7 and 7.8.
delete Measuring the amount of ladle slag present in the ladle, the amount of ladle residue, and the component of the ladle slag;
Calculating a slag carbon incorporation ratio (SCI) by substituting the amount of the ladle slag, the amount of the ladle residue, and the carbon concentration of the ladle slag component into the following relationship (1 ); And
And estimating a carbon increase amount (C pick-up) by substituting the slag carbon incorporation ratio (SCI) into the following equation (2).
Relationship 1

Relation 2

Where alpha is a value between 2.8 and 2.9 and beta is between 7.7 and 7.8.
The method of claim 3,
Wherein the molten steel contains carbon of more than 0 to 30 ppm carbon.
delete delete

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