WO2019031661A1

WO2019031661A1 - Casting facility and casting method

Info

Publication number: WO2019031661A1
Application number: PCT/KR2017/015035
Authority: WO
Inventors: 김성줄; 김욱; 이영주; 김용환; 김성연
Original assignee: 주식회사 포스코
Priority date: 2017-08-08
Filing date: 2017-12-19
Publication date: 2019-02-14
Also published as: KR101969111B1; EP3666416A4; JP2020530399A; KR20190016345A; CN111107953A; EP3666416A1

Abstract

A method for casting slabs, according to the present invention, comprises the steps of: respectively positioning, at the upper part of a tundish and the outside of the tundish, ladles having molten steel accommodated therein; carrying out casting by supplying, to the tundish, the molten steel of the ladle arranged at the casting position of the upper part of the tundish; and blowing an inert gas into the ladle arranged at the casting position. Therefore, according to an embodiment of the present invention, the inert gas is blown when the ladle is in a stand-by position on a turret apparatus and during casting in which molten steel is supplied to the tundish. Thus, inclusions can be more reduced than those in a conventional casting method, and clean steel can be manufactured. That is, the generation of inclusions in the air can be reduced by carrying out micro-bubbling after opening the ladle when the ladle is in the stand-by position. In addition, the inclusions of the molten steel within the ladle during casting can be reduced by blowing the inert gas into the ladle (L) during casting.

Description

Casting equipment and casting method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting facility and a casting method, and more particularly, to a casting facility and a casting method capable of producing a clean steel.

In general, inclusions such as alumina (Al ₂ O ₃ ) are produced in the ladle by the reaction between aluminum (Al) and oxygen (O ₂ ) in the steel making process. The inclusions solidify together with the molten steel during the casting of the cast steel, which causes the occurrence of product defects during rolling.

In order to generate or remove inclusions such as alumina (Al ₂ O ₃ ) in the molten steel in the ladle, a vacuum degassing facility (Reinstahl Huten Werke Heraus, RH), a Ladle Furnace (LF) An inert gas such as Ar gas is blown into molten steel to remove inclusions.

On the other hand, ladders containing molten steel whose temperature was raised by refining using a vacuum degassing facility (Reinstahl Huten Werke Heraus, RH) or ladle furnace (LF) were supported by a ladle turret, . That is, the ladle turret is provided with support portions on both sides of the swing tower on which the rabbles can be seated, and the rabbles are supported by the support portions. Then, by the rotation operation of the swing tower, the two ladders are alternately transferred to the upper portion of the turn-off display. Here, among the two ladders, the ladders located on the top of the turn-off are the ladders participating in the casting, and the ladders located outside the turndish are the ladders waiting for the next casting.

However, even when Ar gas is blown in refining using a vacuum degassing apparatus (Reinstahl Huten Werke Heraus, RH), heating operation using a ladle furnace (LF) or turning-off, or when the ladle is being air- Inclusions are generated, and defects due to inclusions still occur.

For this purpose, Korean Utility Model Publication No. 1998-033102 discloses that Ar gas is supplied to ladles that are not in standby or in casting. This method can promote the separation of the inclusions present in the molten steel. However, there is a problem in that the generation of the molten metal is increased in the molten steel bath surface, and thus the generation of the re-inclusive inclusions is promoted.

Further, since Ar gas is not blown during the casting, there is a problem that inclusions are still generated in the ladle molten steel participating in the casting.

(Patent Document 1) Korean Registered Utility Model Publication No. KR0332894Y1

The present invention provides a casting facility and a casting method capable of reducing inclusions.

The present invention provides a casting facility and a casting method for reducing the generation of inclusions by blowing gas into the ladle in air or casting the turret.

The present invention provides a casting facility and a casting method for suppressing or preventing the generation of cracks.

A casting method according to the present invention is a process for casting ladle containing molten steel on the upper side of the turn-over side and the outside of the turn-side die, respectively. Supplying the molten steel of the ladle disposed at the casting position on the upper side of the turn-off to the turn-dish to perform casting; And injecting an inert gas into the ladle disposed at the casting position.

The step of blowing the inert gas into the ladle disposed at the casting position includes the steps of opening the ladle of the casting position by blowing an inert gas at a first flow rate into the ladle disposed at the casting position; And bubbling the inert gas at a lower flow rate than the first flow rate when casting for supplying molten steel with turning dicing is started after the ladle of the casting position is opened.

In order to bubble the ladle of the casting position, the inert gas blowing flow rate is decreased in accordance with the decrease of the molten steel height in the ladle of the casting position.

(L ₁ ) with respect to the initial molten steel height (L ₀ ) before the molten steel in the casting position ladle is supplied to the turn-off state in order to reduce the inert gas blowing flow rate in accordance with the decrease in the molten steel in the ladle at the casting position, And the flow rate m ₁ calculated by the equation (1) using the initial gas injection flow rate (m ₀ ) at the time of starting to supply the casting position ladle to the tundish.

[Equation 1]

It is preferable that the initial gas injection flow amount (m ₀ ) is 1 LPM or more and 20 LPM or less.

And injecting an inert gas into the ladle disposed at the standby position outside the turn-off time.

Wherein the step of introducing the inert gas into the ladle disposed at the standby position includes the steps of opening the ladle of the standby position by blowing inert gas at a first flow rate into the ladle disposed at the standby position; And bubbling the inert gas at a second flow rate lower than the first flow rate when casting for supplying the molten steel with the turn-by-turn is started after the ladle is opened at the standby position.

Preferably, the first flow rate is 80 LPM or more and 200 LPM or less, and the second flow rate is 1 LPM or more and 20 LPM or less.

The casting facility according to the present invention is a casting facility comprising: a tundish for temporarily storing molten steel; And a pair of supports for respectively supporting a pair of rails in which molten steel are accommodated, wherein the pair of supports are arranged alternately at a casting position on the upper side of the turn-indicator and a standby position outside the turn- ; A mold positioned below the tundish to solidify the molten steel supplied from the tundish; A ladle in the standby position and a ladle in the casting position, respectively, so that an inert gas is blown into each of the ladle supported at the standby position and the ladle supported at the casting position on the turret device.

The gas inlet device comprising: a first blow line connected to the ladle supported at the standby position; A second blow line connected to the ladle supported at said casting position; And a first supply line connected to the first blowing line for selectively supplying an inert gas to the first blowing line at a first flow rate for opening the ladle of the standby position and at a second flow rate smaller than the first flow rate, ; And a second supply part connected to the second blowing line for selectively supplying an inert gas to the second blowing line at a first flow rate for opening the ladle of the casting position and at a flow rate smaller than the first flow rate do.

The inert gas is supplied to the first blowing line at a first flow rate of 80 LPM or more and 200 LPM or less so that the inlet of the ladle of the standby position is opened, The inert gas is supplied to the line at a second flow rate of 1 LPM or more and 20 LPM or less to bubble the ladle in the standby position.

Wherein the second supply unit supplies an inert gas to the second blowing line at a first flow rate of 80 LPM or more and 200 LPM or less so that the inlet of the ladle of the casting position is opened, When the molten steel in the ladle of the casting position starts to be supplied to the turn-dish, the inert gas is supplied to the second blowing line at a flow rate lower than the first flow rate, Reduce blowing flow.

According to the embodiment of the present invention, inert gas is blown when the ladle is in the standby position on the turret apparatus and at the time of casting to supply molten steel in turn-off. As a result, inclusions can be reduced compared with the prior art, and a clean steel can be produced. That is, when the lugs are in the waiting position, fine bubbling is performed after opening the ladle to reduce the occurrence of atmospheric inclusions. In addition, by injecting inert gas into the ladle (L) during casting, it is possible to reduce inclusions in molten steel in the ladle during casting.

Further, by reducing the gas blowing flow rate in accordance with the falling of the molten steel during casting, it is possible to bubble at an appropriate amount, and occurrence of the breakage due to the inert gas can be suppressed or prevented. That is, if the gas is blown at an excessively large flow rate relative to the amount of molten steel or the molten steel, it is possible to generate a noxious space in the slag of the bath surface due to the generation of vortex due to the gas blowing. In the embodiment of the present invention, L), it is possible to suppress or prevent the generation of a crack due to the gas blowing by adjusting the gas blowing flow rate to correspond to the decrease in the molten steel height.

1 is a view showing a main part of a casting installation according to an embodiment of the present invention;

Figure 2 is a diagram illustrating ladders according to an embodiment of the present invention.

3 is a schematic view showing a gas inlet apparatus according to an embodiment of the present invention;

4 is a graph showing a method of blowing gas according to an embodiment of the present invention in a waiting ladle

5 is a graph showing a method for injecting gas according to an embodiment of the present invention into a casting ladle

FIG. 6 is a graph showing the results of bubbling occurring during bubbling by the method according to the comparative example in ladders during casting

7 is a graph showing the amount of interposition at each operation step as an inclusion index

Hereinafter, embodiments of the present invention will be described in detail. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of other various forms of implementation, and that these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know completely.

The present invention provides a casting facility for reducing or suppressing inclusions and occurrence of slag by blowing gas into a ladle in air and casting in a turret device, and a casting method using the same.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a casting facility according to an embodiment of the present invention; FIG. 2 is a view illustrating ladders according to an embodiment of the present invention. 3 is a schematic view showing a gas-inserting apparatus according to an embodiment of the present invention. Figure 4 is a graph illustrating a method for injecting gas into an idler ladle according to an embodiment of the present invention. 5 is a graph illustrating a method for blowing gas in accordance with an embodiment of the present invention to a ladle under casting.

1 and 3, a casting installation according to an embodiment of the present invention includes a casting facility for supporting a pair of ladles L containing molten steel, a turret for moving a pair of ladles L by a rotating operation, The apparatus 100 is provided with a tundish T for temporarily storing molten steel received from the ladle L moved upward and temporarily storing molten steel temporarily stored in the tundish T, A plurality of segments 20 provided at a lower portion of the mold M for performing initial solidification of the cast steel and performing a series of molding operations while secondarily cooling the cast steel that has been primarily cooled, And a gas introducing device 200 for introducing an inert gas into each of the ladle L positioned in correspondence with the upper side and the ladle L standing outside the turn dice T, respectively. The shroud nozzle SN for supplying the molten steel of the ladle L in a turn-off state, the gate for controlling the communication between the ladle L and the shroud nozzle SN, And a nozzle mounting unit 30 connecting the nozzle and the shroud nozzle.

The ladle (L), the turret device (100), the turndish (T), the mold (M) and the segment (20) are similar to or the same as those of a general continuous casting facility, and a detailed description thereof will be omitted or briefly explained .

The turret apparatus 100 includes a swing tower 110 that is driven to rotate and a swing arm 110 that is extended in both directions around the swing tower 110 or disposed on both sides of the swing tower 110, The ladle (L) includes a pair of supports 120 that can be supported or settled. According to the turret apparatus 100, the pair of supporters 120 are alternately moved to the upper side of the turn-off direction by the rotation of the swing tower 110. That is, by the rotation of the swing tower 110, one support portion 120 of the pair of support portions 120 and the ladle L supported by the support portion 120 are positioned on the upper side of the turndisse T, The other support portion 120 and the ladle L supported by the support portion 120 are located outside the turndisse T. [

The turret device 100 is not limited to the above-described embodiment, but can be applied to various configurations capable of supporting a pair of ladle L and alternately moving the turret device 100 to the upper side and the standby position of the turn- .

The ladle L forms an outer appearance and has an inner space capable of accommodating molten steel and has an opening (hereinafter referred to as a louver 321) capable of discharging molten steel at a lower portion thereof, And a top nozzle TN installed in the main body 310 so as to communicate with the inlet port 321. The main body 310 is provided with an opening (not shown) The body 310 may further include a plug 330 inserted into the body 310 to communicate with the body 310.

In the embodiment of the present invention, the inert gas is blown into each of the pair of ladles (L) supported by the turret device (100), thereby reducing or suppressing the generation of scum and inclusions as compared with the conventional art. That is, molten steel is supplied to the ladle (L) or the turn dish (T) supported on the support portion (120) corresponding to the upper side of the turn disc (T) among the pair of the support portions (120) of the turret device An inert gas is blown into each of the ladle (L) participating in the casting and the ladle (L) supported on the support (120) positioned outside the turn-dish (T). This will be described in terms of one ladle L. When the one turn disc T is supported by the turret device 100 and is standing outside the turn dish T, And then the ladle L moves upward of the turn-over T to blow the inert gas into the ladle L when the molten steel is supplied into the turn-dish T (i.e., casting).

In the embodiment, after the intake port 322 of the ladle L is opened to blow the inert gas into the waiting ladle L, inert gas is blown in a relatively small amount to reduce the generation of slag and inclusions, . When the casting is started after the ladle L is opened to blow the inert gas into the casting ladle, the inert gas flow rate is decreased while the molten steel is lowered or the bath surface is lowered, .

To this end, a gas-filling device 200 is provided for blowing an inert gas into the waiting ladle (L) that is seated in the turret device (100) and the ladle (L) participating in casting, and controls the gas flow rate.

3, the gas-filling apparatus 200 includes a first blowing line 210a connectable to a ladle L supported at a standby position, a second blowing line 210b connected to a ladle L supported at a casting position, A first gas storage part 220a for providing a high pressure inert gas, a second gas storage part 220b for providing a low pressure inert gas, first and second

gas storage parts

220a and 220b, A first supplying part 230a connecting the first blowing line 210a to the first blowing line 210a and supplying the inert gas of each of the first and second

gas storing parts

220a and 220b to the first blowing line 210a, A second blowing line 210b for supplying an inert gas of each of the first and second

gas storing units

220a and 220b to the second blowing line 210b by connecting the

gas storing units

220a and 220b and the second blowing line 210b, And a supply unit 230b.

Here, the first blowing line 210a is connectable and detachable to the ladle L take-in port 322 disposed at the standby position outside the turn-off T, and the second blowing line 210b is connected to the turn- ) To the ladle (L) take-in port 322 disposed at the upper casting position. Each of the first and

second blowing lines

210a and 210b may be in the form of a pipe capable of moving inert gas.

A first blowing valve 211a is provided on the extension path of the first blowing line 210a and a second blowing valve 211b is provided on the extension path of the second blowing line 210b.

The first supply part 230a according to the embodiment includes a first supply line 231a having one end connected to the first gas storage part 220a and a second supply line 231b having one end connected to the second gas storage part 220b, A first supply valve 232a and a first flow rate control unit 233a provided on the extension path of the first supply line 231a and a second supply line 234b connected to the second supply line 234a, And a second supply valve 235a and a second flow rate control unit 236a provided on the extension path. Here, the other end of the first supply line 231a may be connected to the second supply line 234a so as to be located at the front end of the second supply valve 235a.

Each of the first and

second supply lines

231a and 234a may be in the form of a pipe capable of moving inert gas.

The first supply valve 232a according to the embodiment may be, for example, a motor valve. The first flow rate controller 233a is connected to the rear end of the first supply valve 232a. The second flow rate controller 236a is connected to the second supply valve 232a. It is preferable to be provided so as to be located at the rear end of the second opening 235b.

The second supply part 230b according to the embodiment includes a third supply line 231b having one end connected to the first gas storage part 220a and one end connected to the second gas storage part 220b, The third supply valve 232b and the third flow rate control unit 233b provided on the extension path of the third supply line 231b and the fourth supply line 234b connected to the fourth supply line 234b connected to the fourth supply line 234b, And a fourth supply valve 235b and a fourth flow rate control unit 236b provided on the extension path. Here, the other end of the third supply line 231b may be connected to the fourth supply line 234b so as to be located at the front end of the fourth supply valve 235b.

Each of the third and

fourth supply lines

231b and 234b may be in the form of a pipe capable of movement of an inert gas.

The third flow rate control section 233b is connected to the rear end of the third supply valve 232b and the fourth flow rate control section 236b is connected to the fourth supply valve 232b, It is preferable to be provided so as to be located at the rear end of the second opening 235b.

In the embodiment, an inert gas, for example, Ar gas is blown in both the atmosphere and the casting position while the ladle L is supported by the turret device by using the gas-introducing apparatus 200 as described above, Reduce or suppress the occurrence.

The gas introducing apparatus 200 is not limited to the above-described configuration, and can be changed into various configurations capable of supplying inert gas by adjusting the pressure and the flow rate to the first and

second blowing lines

210a and 210b, respectively.

3 to 5, a casting method including a process of blowing an inert gas into each ladle L in the atmospheric and casting positions on the turret apparatus using the gas inlet apparatus 200 will be described. At this time, Ar gas is described as an inert gas by way of example.

The casting method according to an embodiment of the present invention includes the steps of placing rails accommodating molten steel on the upper side of the turn-over side and the outer side of the turn-over side, supplying the molten steel in the turn- And introducing the inert gas into the ladle disposed in the casting position.

Hereinafter, the casting method according to the embodiment will be described in more detail.

First, the ladle (L) containing molten steel is supported on the pair of supports 120 of the turret apparatus 100, respectively. The ladle L corresponding to the upper side of the turn-dish T among the pair of the support parts 120 supplies the molten steel with the turn dish T to participate in the casting, (T), waiting for casting of the subsequent charge.

First, with reference to FIG. 4, a method of injecting an inert gas such as Ar gas into the waiting ladle L will be described in detail.

In blowing the Ar gas into the waiting ladle, the Ar gas is first taken in at the first flow rate for the opening of the ladle (L). The opening of the ladle L means that the gas is supplied into the ladle through the main body 310 or the plug 330 of the ladle L. After the ladle L is opened, It is possible to blow the gas into the ladle L.

The opening of the ladle L proceeds for a predetermined time from the start of gas blowing, for example, within 10 seconds from the time of gas blowing, and this section may be called an initial blowing section.

In the embodiment, in blowing the inert gas at the first flow rate into the waiting ladle L, the gas is blown at a first flow rate of 80 LPM or more and 200 LMP or less (5 to 5 Nm ³ / h) The opening 322 is opened.

When the inert gas is blown into the ladle (L) or at the first flow rate, the gas pressure is controlled to be higher than 10 bar and lower than 20 bar, and is relatively higher than the pressure of the gas introduced after the opening To be supplied.

On the other hand, if the first flow rate is less than 80 LPM, for example, the intake port 322 may not be opened and Ar gas may not flow into the ladle L. Conversely, if the flow rate of the initial inert gas exceeds 200 LPM, the ladle (L) intake port 322 is opened but causes instability of the molten steel bath surface of the ladle L, which may lead to operational instability, There is a problem that the area where the hot water is generated increases.

When the ladle (L) is opened, inert gas is taken in at a second flow rate for reducing the inclusion of the molten steel and the occurrence of nagging. At this time, the gas flow rate is relatively small compared to the first flow rate at the time of opening the ladle (L).

In the embodiment, when the ladle (L) in the standby state is opened, the gas is blown at a second flow rate of 1 LPM or more and 20 LMP or less to reduce inclusions while bubbling the molten steel.

At this time, the pressure of the gas is supplied at a lower pressure than that of the ladle (L). In the embodiment, the pressure is not less than 2 bar and not more than 10 bar.

On the other hand, when the second flow rate blown after the ladle (L) is opened is less than 1 LPM, the effect of reducing the inclusions by the inert gas bubbling may be low or not manifested. On the other hand, when the second flow rate blown after the ladle (L) is opened exceeds 10 LPM, there is a problem that the inhibition of the generation of the scalding on the molten steel bath surface is not effected, or the scavenging area becomes large. In the case where the nutflow area is large, the inclusions are mixed into the molten steel through the slag, which makes it difficult to manufacture the clean steel.

As described above, the description will be made using the gas drawing apparatus 200 of FIG. 3 for drawing gas into the ladle L in the standby position as follows. First, when the first supply valve (for example, the motor valve) 232a and the first intake valve 211a are opened with the second supply valve 235a closed to open the ladle L, The gas in the first inlet line 220a moves through the first supply line 231a, the second supply line 234a and the first blowing line 210a to be blown into the inlet port 322 of the ladle L in the stand- do. At this time, when the motor valve is opened, a gas having a high pressure exceeding 10 bar and less than 20 bar flows instantaneously along the first supply line 231a and the first flow rate control unit 233a is adjusted so that the gas of 80 LPM or more and 200 LPM or less . Therefore, the Ar gas is supplied to the waiting ladle (L) at a flow rate of not less than 10 bar and not more than 20 bar, not less than 80 LPM and not more than 200 LPM, and the ladle (L) is opened.

When the ladle L is opened, the first supply valve 232a is closed and the operation of the first flow rate controller 233a is stopped. The second supply valve 235a is opened and the second flow rate controller 236a is operated to supply Ar gas having a pressure of 2 bar or more and 10 bar or less and a flow rate of 1 LPM or more and 20 LPM or less to the second supply Line 234a and the first blowing line 210a to blow the Ar gas into the waiting ladle L. [ By injecting such Ar gas, the molten steel in the waiting ladle L is finely bubbled, whereby the inclusions in the molten steel in the waiting ladle can be reduced, and the generation of the slag can be suppressed.

Thus, while bubbling the molten steel in the ladle L of the standby position, the ladle L in the casting position continuously feeds the molten steel into the turn-dish T to participate in the casting.

When casting is completed at the casting position, the swing tower 110 of the turret apparatus 100 is rotated to move the ladle bubbled at the standby position to the upper side of the turn D, that is, to the standby position .

Thereafter, the top nozzle TN of the ladle L and the shroud nozzle SN are fastened together, and the top nozzle TN and the shroud nozzle SN are communicated through the operation of the gate. The molten steel in the ladle L is supplied to the turn-dish through the shroud nozzle SN and the nozzle (immersion nozzle 40) of the turn-dish T is transferred to the mold M and solidified, The castle is cast.

When the molten steel in the ladle L located on the upper side of the turn-dish T is supplied to the turn-dish T for casting, the ladle L participating in the casting, that is, the ladle L ) To bubbles molten steel.

To this end, the second blowing line 210b is connected to the inlet of the ladle L moved to the casting position. Thereafter, Ar gas is supplied at a first flow rate for the opening of the ladle (L). The opening of the ladle L proceeds for a predetermined time from the start of gas blowing, for example, it may be within 10 seconds from the gas blowing point.

In the embodiment, in blowing the inert gas at the first flow rate into the ladle L of the casting position, the first flow rate may be 80 LPM or more and 200 LMP or less (5 to 5 Nm ³ / h) L is opened.

When the gas is blown at the first flow rate, it is preferable that the gas pressure is more than 10 bar and not more than 20 bar so that it is supplied at a relatively higher pressure than the pressure of the gas introduced after the opening.

On the other hand, for example, when the first flow rate to be introduced into the ladle L in the casting position is less than 80 LPM, the intake port 322 may not be opened and the Ar gas may not flow into the ladle L. On the contrary, when the first flow rate exceeds 200 LPM, the ladle (L) intake port 322 is opened but causes instability of the molten steel bath surface of the ladle L, which may lead to operational instability, There is an increasing problem.

When the casting position ladle (L) is opened, an inert gas is blown in order to reduce the inclusion of the molten steel and the occurrence of nagging. At this time, the gas blowing flow rate is a flow rate relatively smaller than the first flow rate when the ladle (L) is opened.

In the embodiment, when the ladle L in the casting position is opened, the gas is blown at a flow rate lower than the blowing flow rate at the time of opening, and the inclusions are reduced while the molten steel is being bubbled to suppress the generation of breakage.

On the other hand, when molten steel in the ladle L at the casting position is started to be fed by the turn-on time T, the molten steel in the ladle L is continuously supplied to the turn- The internal steels decrease in height as the casting time elapses. Therefore, in the embodiment, in blowing the inert gas into the ladle L from the start of casting, the Ar gas blowing flow rate is varied in accordance with the decrease in the height of the molten steel in the ladle L or the height of the molten steel bath surface. More specifically, when the ladle L of the casting position is opened and the molten steel in the ladle L starts to be supplied in turn, the inert gas is blown into the ladle. At this time, (m ₀ ) '. Then, the embodiment, while reducing to a low flow rate ₍₁ m) compared to the initial flow rate of the blown gas initially blown gas flow rate (m ₀₎ in accordance with a reduction in height of the liquid steel casting proceeds accepts the gas. That is, molten steel height at the start of casting (hereinafter referred to as the first molten steel height (L ₀₎₎ based on the real time current molten steel height or the height (L ₁₎ in accordance with the molten steel of the present time the initial gas inlet flow rate (m ₀₎ compared to the low flow rate (m ₁ ). The equation (1) is expressed by the following equation (1).

[Equation 1]

Here, the current molten steel height L ₁ in the ladle can be calculated in real time through the molten steel discharge preheating height, that is, the initial molten steel height L ₀ , and the molten steel discharge speed. When starting to supply molten steel in the ladle at the casting position, the initial gas injection flow rate m ₀ to be supplied to the ladle may be 1 LPM or more and 20 LPM or less, the pressure in the ladle L may be 2 bar or more To 10 bar or less.

On the other hand, if the initial gas blowing flow rate (m ₀ ) exceeds 20 LPM, the molten steel in the ladle may be generated at the start of casting.

Further, when the inert gas is blown at a constant flow rate irrespective of the decrease in the molten steel height during casting, there is a problem that the effect of reducing the inclusions is not obtained, the generation of the slag is not suppressed, or the slag is formed to a large extent. That is, if Ar gas is blown in a small amount of the molten steel in the ladle L, that is, the molten steel height (L ₁ ) of the current point, there is no effect of reducing the inclusions by the inert gas. On the other hand, if Ar gas is blown in at a large flow rate relative to the current molten steel height (L ₁ ), a large amount of gas blown may cause the molten steel bath surface to be clogged or the retention area may increase.

As described above, the description will be made using the gas-filling apparatus 200 of FIG. 3 in blowing gas into the ladle L at the casting position as follows.

First, in order to open the ladle L of the casting position, when the third supply valve (for example, the motor valve) 232b and the second intake valve 211b are opened with the fourth supply valve 235b closed, The gas in the gas storage portion 220a moves through the third supply line 231b, the fourth supply line 234b and the second blowing line 210a to move to the inlet port 322 of the ladle L in the casting position ). At this time, when the motor valve is opened, a high-pressure gas of more than 10 bar and less than 20 bar flows instantaneously along the third supply line 231b, and the third flow rate controller 233b is controlled so that the gas of 80 LPM or more and 200 LPM or less . Therefore, the ladle L is opened by introducing Ar gas at a flow rate of 80 LPM or more and 200 LPM or less at a pressure of 10 bar or more and 20 bar or less to the ladle L at the casting position.

When the ladle (L) is opened, the molten steel of the ladle (L) at the casting position is started to be supplied to the turndisse (T). At this time, the third supply valve 232b is closed and the operation of the third flow rate control part 233b is stopped. The fourth supply valve 235b is opened and the fourth flow rate controller 236b is operated to supply Ar gas having a pressure of 2 bar or more and 10 bar or less and 20 LPM or less to the fourth supply line 234b, And the second blowing line 210b to blow Ar gas into the ladle L at the casting position.

At this time, the flow rate of the gas supplied to the ladle L is adjusted in accordance with the change in the height of the molten steel in the ladle L from the start of casting to the end of the casting using the fourth flow rate controller 236b. That is, as shown in Equations (1) and (5), the gas is blown while decreasing the flow rate with respect to the initial gas blowing flow rate according to the real time current molten steel height based on the molten steel height at the start of casting.

By injecting such Ar gas, the molten steel in the waiting ladle L is finely bubbled, whereby the inclusions in the molten steel in the waiting ladle can be reduced, and the generation of the slag can be suppressed.

Hereinafter, with reference to FIG. 6 and FIG. 7, results of ladle ingot treatment using the molten steel treatment method according to the comparative example and the embodiment of the present invention will be described.

FIG. 6 is a graph showing the results of bubbling occurring during bubbling by the method according to the comparative example in ladders during casting. In the case of the ladle shown in Fig. 6, one draw-in opening is provided, and two lobes are provided. When the ladle shown in Fig. 6 is positioned on the upper side of the turn-off direction, the molten steel is discharged from the two ladle openings in turn, and the Ar gas is blown into one plug. In the comparative example of FIG. 6, a certain amount of Ar gas was supplied irrespective of the decrease in the molten steel height. FIG. 6A shows a result obtained by blowing at a flow rate of 10 Nm ³ / h and FIG. 6B shows a result obtained at a flow rate of 5 Nm ³ / The results are shown in Fig.

6A and 6B, it can be seen that the slag between the slag on the molten steel bath surface is generated.

According to the embodiment of the present invention, in blowing the Ar gas into the ladle participating in the casting or in the casting position, an appropriate amount of Ar gas is blown in accordance with the decrease in the molten steel height. Thus, there is an effect that the generation of scattering is suppressed as compared with the conventional art.

7 is a graph showing the interposition quantity in each operation step as an inclusion index. Here, the amount of intervening material is calculated by the total oxygen content in the molten steel, and the results are compared with each other.

FIG. 7 is a graph showing the inclusion index in molten steel during molten steel treatment according to Comparative Examples and Examples. FIG.

The comparative example includes deoxidizing in a vacuum degassing facility, bubbling and bubbling the Ar gas into the ladle while raising the molten steel in the ladle furnace after deoxidization, waiting the ladle in which the molten steel is contained in the waiting position of the turret device, The ladle was moved to the upper side of the turn, and molten steel was supplied by turning to start the casting. During the casting, Ar gas was blown into the immersion nozzle while bubbling, and the molten steel in the turn-off was supplied to the mold, and inclusions were measured in the molten steel in the mold.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: FIG. At the bubbling stage where the Ar gas is blown into the ladle, the ladle in the standby position is positioned on the upper side of the turn-off side, and the molten steel is moved by turning to start the casting. During the casting, Ar gas was blown into the immersion nozzle while bubbling, and the molten steel in the turn-off was supplied to the mold, and inclusions were measured in the molten steel in the mold.

The amount of intervening material in the molten steel was measured at each step of the operation according to the comparative example and the example. 7 shows the amount of intervening material in the molten steel in the turn-off time in which no bubbling is performed.

The amount of intervening material in each operation stage was calculated by the total oxygen content in the molten steel. In calculating the inclusion index, the inclusion index was calculated based on the amount of the inclusion in the molten steel in the vacuum degassing facility.

Referring to FIG. 7, in the case of the first to third embodiments, it can be seen that the inclusion index decreases compared to the first and second comparative examples. More specifically, when the amount of interposition in the molten steel in the mold was compared, the amount of interposition in the examples was reduced by 30% as compared with the comparative example. That is, in the case of the comparative example and the example, bubbling was performed at the elevated temperature using the ladle furnace and bubbling was performed at the immersion nozzle. However, in the case of the embodiment in which ladle bubbling was performed in the atmosphere and casting in the turret apparatus, The amount of intervening material is smaller than that of the example. Therefore, in the case of using the casting method according to the embodiment, it is possible to cast clean steel with less occurrence of cracks due to inclusions, compared with the comparative example.

As described above, in the case of the casting method according to the embodiment of the present invention, when the ladle L is in the standby position on the turret apparatus 100 and when the molten steel is fed by the turn-dish T, do. As a result, inclusions can be reduced compared with the prior art, and a clean steel can be produced. That is, when the ladle L is in the standby position, fine bubbling is performed to reduce the generation of inclusions in the atmosphere. In addition, inclusion of molten steel in the ladle (L) during casting can be reduced by blowing inert gas into the ladle (L) during casting.

Claims

Placing the ladle in which the molten steel is accommodated in the upper side of the turn-over side and the outer side of the turn-around side, respectively;

Supplying the molten steel of the ladle disposed at the casting position on the upper side of the turn-off to the turn-dish to perform casting; And

Injecting an inert gas into the ladle disposed at the casting position;

.
The method according to claim 1,

The process for blowing the inert gas into the ladle disposed at the casting position comprises:

Blowing an inert gas at a first flow rate into the ladle disposed at the casting position to open the ladle of the casting position;

Bubbling the inert gas at a lower flow rate than the first flow rate when the casting for supplying molten steel with turning dicing is started after the ladle of the casting position is opened;

.
The method of claim 2,

In bubbling the ladle of the casting position,

Wherein the flow rate of the inert gas blowing is reduced in accordance with a decrease in the molten steel in the ladle at the casting position.
The method of claim 3,

In order to reduce the inert gas blow-in flow rate in accordance with the decrease in the molten steel height in the ladle of the casting position,

The ratio of the current molten steel height (L 1 ) to the initial molten steel height (L 0 ) before the molten steel in the casting position ladle is supplied to the turndisse and the initial gas blown flow rate m < 2 >) using the equation ( 1 ).

[Equation 1]
The method of claim 4,

Wherein the initial gas blowing flow amount (m 0 ) is 1 LPM or more and 20 LPM or less.
The method according to claim 1,

And injecting an inert gas into the ladle disposed at a standby position outside the turn-off time.
The method of claim 6,

The process of injecting an inert gas into the ladle disposed at the standby position comprises:

Drawing an inert gas at a first flow rate into the ladle disposed at the standby position to open the ladle of the standby position;

Bubbling the inert gas at a second flow rate lower than the first flow rate when casting for supplying molten steel with turning dicing is started after the ladle of the standby position is opened;

Casting method
The method of claim 7,

Wherein the first flow rate is 80 LPM or more and 200 LPM or less,

Wherein the second flow rate is 1 LPM or more and 20 LPM or less.
A turn-off for temporarily storing molten steel;

And a pair of supports for respectively supporting a pair of rails in which molten steel are accommodated, wherein the pair of supports are arranged alternately at a casting position on the upper side of the turn-indicator and a standby position outside the turn- ;

A mold positioned below the tundish to solidify the molten steel supplied from the tundish;

A gas inlet device connected to the ladle in the standby position and the ladle in the casting position, respectively, so that an inert gas is blown into each of the ladle supported at the standby position and the ladle supported at the casting position on the turret device;

. &Lt; / RTI >
The method of claim 9,

The gas-

A first blow line connected to the ladle supported at said stand-by position;

A second blow line connected to the ladle supported at said casting position; And

A first supply portion connected to the first blowing line for selectively supplying an inert gas to the first blowing line at a first flow rate for opening the ladle of the standby position and a second flow rate smaller than the first flow rate;

A second supply portion connected to the second blowing line for selectively supplying an inert gas to the second blowing line at a first flow rate for opening the ladle of the casting position and at a flow rate smaller than the first flow rate;

. &Lt; / RTI >
The method of claim 10,

Wherein the first supply unit includes:

An inert gas is supplied to the first blowing line at a first flow rate of 80 LPM or more and 200 LPM or less so that the inlet of the ladle of the standby position is opened,

And supplying an inert gas to the first blowing line at a second flow rate of 1 LPM or more and 20 LPM or less after the ladle of the standby position is opened to bubble the ladle of the standby position.
The method of claim 10,

Wherein the second supply unit

Supplying an inert gas to the second blowing line at a first flow rate of 80 LPM or more and 200 LPM or less so that the inlet of the ladle of the casting position is opened,

When the molten steel in the ladle of the casting position starts to be supplied to the turn-dish after the ladle of the casting position is opened, in the flow rate range lower than the first flow rate to the second blowing line, Wherein the inert gas blowing flow rate is reduced as the molten steel is lowered.