KR101755948B1 - Dc electric furnace - Google Patents

Abstract

An electric furnace using a direct current electrode, comprising: a main body having a bottom surface on which a slit is formed, the main body providing an internal space in which scrap is charged; A lower electrode mounted on a bottom surface of the main body; And a deodorizing means provided on a bottom surface on which interference with the lower electrode does not occur to blow gas into the inner space of the body.

Description

DC electric furnace {DC ELECTRIC FURNACE}

The present invention relates to a DC electric furnace which does not cause interference with a lower electrode and which has a lowering means disposed at a position spaced apart from a refractory of a main body, thereby securing an engaging force of the molten steel and solving the stability problem.

Generally, the electric furnace has a problem that the agitating force of the molten steel is weak as compared with the converter. Due to the weak agitating force, there is a problem that the equilibrium value of [C] * [O] is high and the oxygen concentration at the end point is high, and the T-Fe in the slag is high.

The high T.Fe in the high end oxygen and slag increased the intrinsic loading of Al as a deoxidizer and acted as a major cause of increased quality defects and increased cost due to Al ₂ O ₃ inclusions generated in the deoxidation process.

In addition, there is no separate stirring method other than stirring by dropping the molten steel in the electric arc furnace operation, so that nitrogen is picked up by excessive stirring of the steel in a ladle furnace, adversely affecting the quality of the product, .

In the case of AC electric furnace in the electric furnace, when there is no molten steel agitation force other than the heat flow type, considering the electric furnace characteristics of the upper heating type, the thermal agitation is also weak. Recently, attempts have been made to introduce and operate the low- However, the DC electric furnace has relatively high aging force due to the electromagnetic and arc penetration power compared to the AC electric furnace, and the facility stability due to the large bottom electrode installed under the DC electric furnace may be a problem There was no attempt to operate the brewing equipment.

It should be understood that the foregoing description of the background art is merely for the purpose of promoting an understanding of the background of the present invention and is not to be construed as an admission that the prior art is known to those skilled in the art.

KR 10-2013-0107713 A

It is an object of the present invention to provide a DC electric furnace which does not cause interference with a lower electrode and disposes a low-drawing means at a position spaced apart from a refractory of a main body, thereby securing an engaging force of molten steel and solving the problem of stability.

According to an aspect of the present invention, there is provided an electric furnace using a DC electrode, the electric furnace comprising: a main body having a bottom surface on which a slit is formed, A lower electrode mounted on the bottom surface of the main body; And R is a distance from the center of the lower electrode to (5/8) * R to (7/8) * R, where R is the distance from the center of the lower electrode to the inner wall of the body nearest to the center, And a plurality of lower electrodes disposed on the lower surface of the lower electrode to prevent gas from interfering with the lower electrode and to blow gas into the inner space of the body, At least one or more than one placement is made at a position where a first virtual line which is a reference of the lapping area and the running area is placed for mixing with the subsidiary material, And at least one second sloping portion disposed at the same distance from the center of the lower electrode and on the both sides of the second imaginary line connecting the center of the slab and the slit, Taken is divided into a unit.
The lowering means may be disposed at a position spaced apart from the lower electrode by a predetermined distance.
The bottom surface of the main body is formed to be inclined from the inner wall toward the lower electrode at the central portion, and the gas blowing direction of the lowering means may be perpendicular to the inclined portion.
The flow rate supplied from the above-mentioned deodorizing means may be changed according to the operating point of time.

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According to the DC electric furnace of the present invention as described above, there is an effect of reducing the power intensity by increasing the agitation force of the molten steel due to the gas introduced from the reducing means. In addition, there is an effect that the running error rate is increased due to the downward effect of the end point oxygen.

It is possible to reduce the input amount of Al, and it is possible to produce high-grade steel by improving the cleanliness of molten steel.

1 shows a DC electric furnace according to an embodiment of the present invention.
Figure 2 shows a virtual model of a DC electric furnace for an experiment.
3 shows a virtual model of a DC electric furnace for an experiment;
FIG. 4 is a graph showing the Maximum UDS, Minimum UDS, and Delta UDS and Mix UDS, which are differences between the maximum value and the minimum value, according to the time of each case in the experiment.
FIG. 5 is a graph showing absolute values and relative values according to time of each case for an experiment. FIG.
FIG. 6 is a graph showing absolute values and relative values according to time of each case for an experiment. FIG.
FIG. 7 is a graph showing absolute values and relative values according to time of each case for an experiment. FIG.
8 is a graph showing an absolute value and a relative value according to time of each case for an experiment.
FIG. 9 is a graph showing absolute values and relative values according to time of each case for an experiment. FIG.
FIG. 10 is a graph showing absolute values and relative values according to time of each case for an experiment. FIG.
11 is a graph showing an absolute value and a relative value of each case with respect to time according to an experiment.
12 is a graph showing a minimum UDS according to time of each case for an experiment.
FIG. 13 is a view showing a cut in a direction perpendicular to a first imaginary line on the basis of a deodorizing means of a DC electric furnace according to an embodiment of the present invention; FIG.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

The electric furnace using the direct current electrode according to the present invention includes a main body 100 having a bottom surface on which the louver 110 is formed as shown in FIG. 1 and providing an internal space in which scrap is charged; A lower electrode (200) mounted on the bottom surface; And a lowering means 300 provided on a bottom surface of the lower electrode 200 where interference does not occur to blow gas into the inner space of the main body 100.

The main body 100 constitutes a DC electric furnace and has an inner wall and a bottom surface. Scrap is charged into the inner space formed by the inner side wall and the bottom side. A refractory is formed on the inner sidewall to protect the main body 100 from a high temperature. On the other hand, the ladle 110 is formed on the bottom surface, and the scrap is melted according to the operation steps, and after the heat is heated, the ladle is led through the ladle 110.

A lower electrode 200 is mounted on the center of the bottom surface. The lower electrode 200 dissolves the scrap by forming arc heat with the electrode rod mounted on the upper part of the DC electric furnace with the scrap interposed therebetween. As mentioned above, in the case of a DC electric furnace, there has been no attempt to operate a low-temperature stirring apparatus in connection with the safety problem due to the presence of the lower electrode 200.

The lowering means 300 is provided at a position where interference with the lower electrode 200 of the bottom surface does not occur for stirring the low-purity air to blow gas into the internal space of the main body 100 from below. A direct porous plug can be used as the deodorization means 300 for blowing gas. Further, argon (Ar) gas or nitrogen (N ₂ ) gas or the like may be used as the gas taken in from the deodorization means 300.

The effect of lowering the temperature by means of the lowering means 300 as compared with the case where the lowering is not performed can be confirmed by the following Table 1.

Power unit level
(kWh / ton-steel) End point oxygen
ppm Al Basic Unit
(kg / ton-steel) Running error rate
(%) Not sterilized
(320 times) 478 827 3.7 89.1 Deodorant application
(380 times) 454 711 3.3 89.6

As can be seen from the above Table 1, it is possible to operate the apparatus without abnormality for 380 times even if the apparatus 300 is mounted at a position according to the present invention to reduce the power consumption. This resulted in a savings of about 24 kWh / tonne. In addition, the end point oxygen was also 116 ppm or lower and Al (aluminum) was used less, resulting in a savings of about 0.4 kg per ton.

The running error rate could be increased by about 0.5% compared to the case of not using the low value.

Preferably, in the case of the DC electric furnace according to the present invention, a plurality of the reduction means 300 are provided and may be disposed at a position spaced apart from the lower electrode 200 by a predetermined distance.

First, an optimal position at which interference with the lower electrode 200 does not occur due to a certain distance from the lower electrode 200 is derived, and the lowering means 300 is disposed at the corresponding position, thereby ensuring the stability of the equipment. When the stability is ensured, a plurality of the down-sizing means 300 are disposed at the optimum positions derived to maximize the engaging force of the molten steel. Once the stability is secured, the more the deodorization means 300 is disposed, the more effective it is to increase the stirring force of the molten steel.

More preferably, when the distance from the center of the lower electrode 200 to the inner wall of the main body 100 at the nearest side is R, the lowering means 300 is disposed at a distance of 5/8 from the center of the lower electrode 200, * R ~ (7/8) * R.

The lowering means 300 may be separated from the lower electrode 200 since the lowering means 300 should not interfere with the lower electrode 200 at the bottom surface of the main body 100 having a limited area, It is appropriate that the refractory material is spaced apart from the refractory material by a certain distance because it may damage the refractory material by the gas injected from the deodorizing means 300. [

Therefore, the lowering means 300 is disposed at a position (5/8) * R ~ (7/8) * R from the center of the lower electrode 200 with reference to the distance R from the center of the lower electrode 200 to the inner wall. . When the lowering means 300 is disposed at a position less than the distance from the center of the lower electrode 200 to a distance of (5/8) * R, the lowering means 300 approaches the lower electrode 200, ) May be damaged.

On the other hand, when the deodorization means 300 is disposed at a position exceeding the distance from the center of the lower electrode 200 to (7/8) * R, the deodorization means 300 approaches the refractory formed on the inner wall, It can cause damage. Therefore, it is appropriate to dispose the deodorizing means 300 at a position (5/8) * R to (7/8) * R from the center of the lower electrode 200.

In the DC electric furnace according to the present invention, the bottom surface is divided into a running area formed on the lower electrode 200 and a running area formed on the opposite side of the running area 110, At least one or more than one can be disposed at a position where the first imaginary line 10 serving as a reference of the lap area and the artificial area is placed.

In the artificial region, oxygen is taken in and the deodorizing means 300 is also disposed, so that when the gas is taken in together, the damage to the refractory occurs rapidly, which may cause a serious problem in durability. Therefore, the deodorizing means 300 is disposed at a position spaced apart from the center of the lower electrode 200 by a predetermined distance, and is arranged at the lapping region side where the lobes 110 are present.

The deodorization means 300 may be disposed at a position passing through the first imaginary line 10 dividing the excitation region and the excitation region in a state of being separated from the lower electrode 200 by a certain distance. The above positions on the bottom of the main body 100 are formed in two places. The deodorizing means may be disposed in at least one of the two locations.

The reason for disposing the deodorization means 300 at a position spaced apart from the lower electrode 200 by a predetermined distance and passing through the first imaginary line 10 is as follows. In the course of the operation through the electric furnace, it can be seen that the cold zone is formed at such a position when the result of the computer simulation is examined. In this case, the cold zone is formed at a position where no sufficient stirring is performed, and the quality of the molten steel is deteriorated as a result. In addition, since the subsidiary material such as burnt lime corresponds to the drop position, it is necessary to secure an agitating force so that such sub ingredient can be sufficiently mixed with molten steel.

Therefore, by arranging the deodorization means 300 at a position spaced apart from the lower electrode 200 by a distance of the first imaginary line 10, an agitating force is ensured to suppress the formation of a cold zone, Whereby the quality of molten steel can be improved.

In the DC electric furnace according to the present invention, the second virtual line 20 connecting the center of the lower electrode 200 and the louver 110 is referred to as a second imaginary line 20, At least one or more of them may be disposed at the same distance apart from each other.

In order to determine the position for disposing the deodorization means 300, the deodorization means 300 is disposed around the lobes 110. The deodorization means 300 is arranged around the lobes 110, At least one or more than two virtual lines 20 may be disposed on both sides of the second imaginary line 20 with respect to the imaginary line 20.

The reason why the deodorization means 300 is disposed at the same distance from both sides of the second imaginary line 20 is as follows. As a result of the computer simulation, it can be seen that a cold zone is formed at such a position. In this case, the cold zone is formed at a position where no sufficient stirring is performed, and the quality of the molten steel is deteriorated as a result. In addition, there is a risk that the slag will flow out through the ladle 110 during the ladle launch, and a certain amount of gas is blown through the ladle 300 disposed near the ladle 110 during ladle operation, It is possible to prevent the leakage together.

Therefore, the quality of the molten steel can be improved and the leakage of the slag can be prevented by disposing the deodorization means 300 at the same distance from both sides of the second imaginary line 20.

In the following, we will confirm the effect of securing the traction force according to the deodorant at a specific position through the test results.

As shown in FIG. 2 and FIG. 3, a virtual model of the DC electric furnace is generated, and time for stirring is measured by measuring the time of diffusion through the concentration of UDS (User Defined Scholar) volume over time.

Specifically, the internal temperature of the virtual model is set to about 1750K, and the heat flux of heat per unit area is set to about 9.27 MW / m ^{2. The} upper electrode is set to 0 V and the lower electrode 200 is set to 700 V. The diffusion time of the UDS volume having a diffusion rate of 0.004 kg / ms under the above environment is measured.

The positions where the deodorizing means 300 for reducing the argon (Ar) gas are disposed are the positions where the above-mentioned first imaginary line 10 passes A and B and the same distance C and D were measured at different positions, and the test was performed with different arrangement of the deodorizing means 300 as shown in Table 2. [

Low flow rate Bogey location Case 1 No savings - Case 2 Low (80 NL / min) C Case 3 Low (80 NL / min) A, B, C Case 4 Low (80 NL / min) A, C Case 5 Low (80 NL / min) C, D Case 6 Low (80 NL / min) B, C Case 7 Low (80 NL / min) B, C, D Case 8 Low (150 NL / min) C, D Case 9 Low (150 NL / min) B, C, D Case 10 Low (150 NL / min) A, B, C Case 11 Low (300 NL / min) C, D Case 12 Low (300 NL / min) B, C, D Case 13 Low (300 NL / min) A, B, D

When the numerical value representing the concentration is set as 3977, and the numerical value representing the total concentration in the virtual model reaches 3977, the UDS volume is considered to be completely diffused.

------------------------------ 식 (1)First, Fig. 4 compares Csae1, Case2, Case3, Case4, Case5, Case6, and Case7, and the first graph shows the time taken until the minimum value of the value representing the concentration in the virtual model reaches 3977 And the second graph is a graph showing the time taken until the maximum value of the value representing the concentration in the virtual model reaches 3977. The third graph is a graph showing the time required for the difference between the maximum value and the minimum value of the concentration value to reach 0,

------------------------------ Equation (1)

(I _i : a value indicating a specific concentration, I _mean : a value indicating an average concentration)

Is a graph showing the time taken until the mixing coefficient defined by equation (1) reaches zero.

As can be seen from the graph, Case 7 shows the best result.

FIGS. 5 and 6 are graphs showing relative values of a graph obtained by comparing the absolute values of the respective cases when the flow rate of the low-drawn gas is 80 NL / min. In the case of absolute value, the spreading speed is faster as the time to reach 0 is shorter, and the spreading speed is faster as the relative value moves from 1 to the time as the reference is based on Case 1.

Similarly, in FIG. 7, the absolute value and the relative value of each case are shown when the low flow rate is 150 NL / min. In the case of FIG. 8, when the low flow rate is 300 NL / min, .

9 is a graph showing a comparison between a relative value of a case 5, a case 8, and a case 11 in which the deodorizing means 300 is disposed at C and D, FIG. 10 is a graph showing a comparison between the absolute value and the relative value of Case 7, Case 9, and Case 12 in which the deodorizing means 300 is disposed at B, C, and D, FIG. 11 is a graph in which the relative values of the case 3, the case 10, and the case 13 in which the deodorizing means 300 is disposed at A, B,

The graph of FIG. 12 is a graph comparing the times at which stirring occurs under each condition by comparing the time at which the minimum value transition of the numerical value indicating the concentration reaches 95% (3778.2) of the reference value 3977. The time at which the minimum value for each case reaches 95% of the reference value is shown in Table 3.

The time at which the minimum value reaches 95% of the average (sec) Case 1 448 Case 2 446 Case 3 334 Case 4 334 Case 5 332 Case 6 384 Case 7 330 Case 8 328 Case 9 272 Case 10 248 Case 11 324 Case 12 270 Case 13 246

As can be seen from the above Table 3, it was confirmed that the increase of the stirring effect was insignificant when the value of the low-flow rate was increased from 150 NL / min to 300 NL / min. Further, it can be seen that the number of the deodorizing means 300 is higher than that in the two places, and the stirring effect is high. Comparing Case 4, Case 5 and Case 6, it can be seen that placing the low-devise means 300 in two locations is most efficient to place them in positions C and D, respectively.

In the case of disposing the deodorizing means 300 at three places, the effect of stirring is higher than that of arranging the deodorizing means 300 at B, C and D at A, B and C at a low flow rate of 80 NL / min However, when the low flow rate values were 150 NL / min and 300 NL / min, the effect of agitation was higher when the low-load means (300) were arranged in A, B and C.

13, the bottom surface of the main body 100 is formed so as to be inclined from the inner wall to the lower electrode 200 at the central portion, as shown in FIG. 13, May be perpendicular to the inclined portion.

In the inclined portion, since the gas blowing direction of the deodorization means 300 is formed vertically, the gas can be injected toward the center of the inner space of the main body 100, so that the whole stirring effect of the molten steel can be expected. Further, since the gas blowing direction is formed in a direction away from the inner wall of the main body 100, there is less possibility that the gas is directly injected into the refractory, and damage to the refractory due to low workability can be prevented.

In the DC electric furnace according to the present invention, the flow rate supplied from the deodorization means 300 may be changed at the time of operation.

The operation of the electric furnace can be divided into a primary dissolver that dissolves iron resources such as scrap, a secondary dissolver, a boiler that raises the temperature of molten steel, a boiler that boils molten steel, and a waiting boiler. As shown in Table 4, an appropriate low flow rate is set for each operation time and supplied through the reduction means 300.

Point Flow rate (NL / min)
Primary dissolver
~ Power input amount 5000kWh 40 ~ Power input capacity 10000kWh 40 ~ Power input 30000kWh 40
Secondary dissolver
~ Power input amount 5000kWh 40 ~ Power input capacity 10000kWh 60 ~ Input power 70000kWh 80
Opening wins
~ Power input 3000kWh 100 ~ Input power 20000kWh 150 ~ Power input 30000kWh 150
When lecturing
~ 2 minutes 40 Completed 60 ~ After completion of the course 40
When waiting for operation
~ 1 hour 40 ~ 2 hours 60 ~ 40

As described above, by varying the flow rate of the low-concentration gas at each point of time, it is possible to reduce the production amount while securing the agitating force through efficient deodorization.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims It will be apparent to those of ordinary skill in the art.

10: first imaginary line 20: second imaginary line
100: main body 110:
200: lower electrode 300:

Claims (7)

As an electric furnace using a DC electrode,
A main body having a bottom surface formed with a louver and providing an internal space in which scrap is charged;
A lower electrode mounted on the bottom surface of the main body; And
(5/8) * R to (7/8) * R from the center of the lower electrode when the distance from the center of the lower electrode to the inner wall of the main body nearest to the center of the lower electrode is R, A lower electrode provided on the bottom surface of the lower electrode and not interfering with the lower electrode to blow gas into the inner space of the body,
Wherein the bottom surface is divided into a running area on the opposite side to the running area in which the lug opening is formed with respect to the center of the lower electrode,
The above-
A first lowering means disposed at least one position where the first imaginary line which is a reference of the running area and the running area is to be placed for mixing with the subsidiary material, And second lowering means disposed at least one position spaced at the same distance from both sides of the second imaginary line connecting the louver. The method according to claim 1,
Wherein the lowering means is disposed at a position spaced apart from the lower electrode by a predetermined distance. delete delete delete The method according to claim 1,
Wherein the bottom surface of the main body is inclined from the inner wall toward the lower electrode at a central portion thereof,
Wherein a direction in which the gas is blown by the deodorizing means is perpendicular to an inclined portion. The method according to claim 1,
And the flow rate supplied from the low-temperature de- vice means is changed according to a time point of operation.

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